SJEEE STUDENTS JOURNAL OF ELECTRICAL & ELECTRONICS ENGINEERING

Volume 1, Issue 1, July2015

Published by

Research Cell-EEE (Accredited by NBA) DEPARTMENT OF EEE, SARANATHAN COLLEGE OF ENGINEERING [email protected]

EDITOR IN CHIEF: Dr.M.Arutchelvi, Professor & Head, Saranathan college of Engineering, Tiruchirappalli. Email ID : [email protected] PUBLISHERS: Dr.S.Vijayalakshmi, Assistant Professor, Saranathan college of Engineering, Tiruchirappalli. Email ID : [email protected] Mobile No: 9842138779 Ms. N.Shobana, Assistant Professor, Saranathan college of Engineering, Tiruchirappalli. Email ID : [email protected] Mobile No: 9750393734 REVIEWERS: Dr.D.Kalyana kumar, Professor, Saranathan college of Engineering, Tiruchirappalli. Email ID : [email protected] Mr.B.Paranthagan, Associate Professor, Saranathan college of Engineering, Tiruchirappalli. Email ID : [email protected] Mr.S.Ramprasath, Assistant Professor, Saranathan college of Engineering, Tiruchirappalli. Email ID : [email protected] Ms.C.Pearline kamalini, Assistant Professor, Saranathan college of Engineering, Tiruchirappalli. Email ID : [email protected] Mr.S.Lenin prakash, Assistant Professor, Saranathan college of Engineering, Tiruchirappalli. Email ID : [email protected]

July 29

Students Journal of Electrical and Electronics Engineering Publishing a paper in a journal or conference is a consequence of several actions and efforts taken over a period of time and not an action by itself

Editor’s Note It is widely observed that students who participate in symposiums, conferences etc have a practice of presenting papers without traversing the necessary path. Normally most of the students indulge in copy paste work and inculcate the practice of plagiarism knowingly or unknowingly in their very beginning stage without realizing the serious implications of such acts. The research cell of department of EEE intends to make the student realize that, publishing a paper is a consequence of several actions and efforts taken over a period of time and not an action by itself. Also it is desired to inculcate the best practices of engineers among the students in their very beginning stage. In this perspective, the research cell of department of EEE has taken an initiative to publish a new ejournal exclusively for students with the following objectives. We are glad to release the first issue of this journal consequence to the initiatives taken last year. Objectives: ∑ To provide a platform for the students to submit papers based on their original work ∑ To cultivate interest in students to execute simple projects relevant to their curriculum and appreciate their significance ∑ Encourage students to develop their indigenous capability as well as enhance their technical writing skills ∑ To eradicate plagiarism in the very initial stage of one’s career ∑ Expose students with an well defined path for getting a publication All the students are encouraged to read the first issue and also submit your original article based on your analytical/simulation/hardware work in the area of electrical and electronics engineering.

-

Research Cell Department of Electrical and Electronics Engineering

Dr.M.Arutchelvi

Volume 1 , Issue 1 , July 2015

S.N O

TITLE

AUTHOR

PAGE.NO

1

AUTOMATIC CHANGEOVER OF DG SUPPLY

RAGA BRINTHA.S MANOCHITRA.J KANIMOZHI.G

2

DESIGN AND IMPLEMENTATION OF DOUBLE FREQUENCY BOOST CONVERTER

SHANMUGAPRIYA. G ARTHIKA. E

12

3

LOW COST POWER QUALITY ANALYZER FOR ACADEMIC APPLICATIONS

JANANI .R , DHIVYALAKSHMI .A JAYASRI .RS , DEEPA .G

20

4

ENERGY MAXIMIZER FOR PV FED DC-DC BOOST CONVERTER

N.SANGEETHA, PAVITHRA. A, DIVYA .S, AKILANDESWARI .A

28

5

AUTOMATIC CONTROL OF ALTERNATOR PARAMETERS IN A POWER STATION USING PLC

SUBRAMANIAN .RV M.GOWTHAMAN R.EZHAMPARITHI

32

6

SINGLE PHASE SINE WAVE PWM INVERTER

BALAMUGUNTHAN .E VIMALRASU .M MURUGANANDAM .M KADAR BASHA .M.A

37

7

POWER CONTROL UNIT OF A HYBRID PV-UTILITY SOLAR PUMP

SRINVAS.R , ARUNKUMAR.A SARAVANAKRISHNAN .D ARAVINTH VIGNESH .G

40

8

FUZZY OBSERVER BASED FLOW CONTROL OF INDUCTION MOTOR PUMP

RUBAN .A , KAMALAHASAN .C VIJAYAPRABAKARAN.M SENTHI KUMAR .R

45

9

DESIGN AND IMPLEMENTATION OF AN PID CONTROLLED EFFICIENT BUCK-BOOST CONVERTER USING INTERLEAVED TOPOLOGY

SANTHANAGOPALAN.A

49

10

DESIGN OF MOTOR CONTROLLED AIR BREAK DISCONNECTOR

ARAVINTH VIGNESH .G SRINVAS.R , ARUNKUMAR.A SARAVANAKRISHNAN .D

57

11

MODELING AND SIMULATION OF INTERLEAVED BUCK-BOOST CONVERTER WITH PID CONTROLLER

ARTHIKA.E SHANMUGAPRIYA. G

63

12

LITERATURE SURVEY ON MPPT SCHEMES FOR STAND ALONE AND GRID CONNECTED PHOTOVOLTAIC SYSTEM

SHARANMONIKA.A STEPHY SHARON.S

68

13

SIMULATION OF MPPT FOR SINGLE STAGE PV GRID CONNECTED SYSTEM

STEPHY SHARON.S SHARANMONIKA.A

72

1

Student Journal of Electrical and Electronics Engineering Issue No. 1, Vol. 1, 2015

AUTOMATIC CHANGEOVER OF DG SUPPLY Raga Brintha.S, Manochitra.J, Kanimozhi.G Final year EEE, Saranathan college of Engineering, Panchapur, Trichy -12 [email protected] ABSTRACT 1

The process plants are continuously operating round the clock. Any power supply interruption will result in process stoppage leading to severe productivity loss and financial implications. In the event of any failure of TANGEDCO main supply, the standby power should come in line without much time delay. For meeting this requirement an Automatic Mains Failure(AMF) arrangement is required for automatically changing over from utility supply to DG supply in the event of utility supply failure.In this project work,an AMF arrangement is fabricated, wired up, interfaced with laboratory three -phase Alternator and was tested for different sequences. Also a real time AMF circuit was studied for interlocks and various sequences of operation. The connected load details in the college campus were collected and sizing of cables was analyzed from the perspectives of generator operation. Based on the load details collected, the generator was adequately sized, neutral arrangement were all examined and proper sizing is arrived to ensure reliable operation of Diesel Generator for standby mode of operation. The present continuous mode of DG sets along with TANGEDCO supply is compared with the ongoing HT conversion mode of operation. The economics Diesel consumption/TANGEDCO tariff is estimated based on comparative analysis.The location of proposed DG set is also optimized for better flexibility of operation to feed the campus loads without any interruption and also to ensure efficient operation of DG set.Complete role of DG set is investigated by properly taking into consideration all the aspects namely AMF, economics, flexibility of operation etc.

Keywords –Automatic changeover, Generator, Optimum Location, Power supply, Single phase preventer 1.

INTRODUCTION

The main idea of this project work is to highlight the economical impact of excessive diesel consumption of Diesel Generators (DGs), reliability issues, lack of flexibility of operation, inadequate sizing of DGs, overworking of Diesel Generators (DG) owing to the negligent attitude of the electricians, improper location of DGs in the

electrical layouts, operation with load limitation as constraints and in turn develop an amicable solution to resolve such issues. The complete analysis and design are from our college campus perspectives. These critical problems are addressed in this project by designing an Automatic Mains Failure scheme (AMF) for practical implementation with proper sizing of DG taking into consideration the present connected loads, optimum location for DG with due considerations for connected loads, short circuit rating, rated thermal rating and neutral sizing of all cables and conductors associated with this captive power plant. An extensive work is carried out to study the connected loads in order to arrive at proper sizing of the DG set in order to totally remove the load constraints and to ensure economical, reliable and uninterrupted operation of the Generator. Presently, the DG sets are manually switched on in the event of Mains failure. Number of Generators and capacity of the Generator need to be manually brought into operation will have to be based on prevailing load requirements at the instant of power failure. Once the main power restores, the electricians on duty must switch off the DG at once to avoid fuel wastage. Most of the time this is not happening. Hence the need for an AMF for implementation. First phase of our project is oriented towards the development of an AMF circuit and fabrication of a demo unit as per the designed AMF circuit. Subsequently the AMF unit is put into operation by interfacing with a laboratory alternator and utility mains supply. The sequence of various operations is practically tested at the laboratory level. As a second phase, a practical circuit is developed for real time interfacing with Circuit Breaker panels of captive power plant and utility supply. The third phase is to study and incorporate an overall real time practical circuit, for automatic starting of DG set, monitoring all the required mechanical parameters of associated Diesel Engine with necessary interlocks, in this project work. This project ensures the removal of stress on manual switching of Generators when the mains supply fails. In section -2 of this paper Generator sizing is done through the analysis of connected loads in the college campus. We have brought out the economics of Generator operation in section-3. Design of Power cables fed from generator is

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Automatic changeover of DG supply

shown in section-4.The design of Diesel Engine Flue gas chimney requirements as per pollution control norms are explained in section-5. Section-6 explains the optimum location of DG set with regard to various loads.AMF design is indicated in section-7.Results are discussed in section-8. Earlier work carried out in this area of AMF incorporate different types of circuits. To cite few of our references indicated in this paper, [1] incorporates Schmitt trigger in their design, [2] needs additional protections and [3] talks about power sensor design using microcontroller. In our work we have made a simple design using electromagnetic contactors, electronic timers and single phase preventers. 2.

GENERATOR SIZING

2.1 Generator Size Variations With the latest advancements in the field of electrical engineering, generators are now available in a wide range of sizes. Generators with power supply capacities of 5kW to 50kW are readily available in the personal and home use markets, while industrial generators are anywhere from 50kW to over 3 Megawatts. Handy and portable generator sets are available for homes; RV's and small offices, but larger businesses, buildings, plants, and industrial applications need to use the much larger sized industrial generators to meet their higher power requirements. In Our College have four generators. 125KVA 140KVA 625KVA 40KVA 2.1.1

Generator Sizing

Many people believe smaller generators can be used for standby electric power because they are not running all the time. This is not only a myth but can actually be very detrimental. Unfortunately, generator under sizing is one of the most common mistakes committed by buyers. Not only does it involve the risks of damaging the new asset (the generator), but it can also damage other assets connected to it, create hazardous situations, and even limit overall productivity of the unit and/or the business relying on it. If nothing else, the key thing to remember here is that more is always better than less. 2.1.2

Details of 625KVA

Rating – 625KVA Power Factor – 0.8 Ambient Temperature – 40 Degree Celsius

Degree of Protection - IP23 Voltage – 415V, Three Phase,Star connected Speed – 1500rpm Diesel tank capacity – 1000L 2.1.3

Generator Sizing 62KVA generator

calculation

for

Connected load in College = 805KW+ (43.365HP)+38.80KVA = 805KW+(43.365*0.746)+(38.80*0.9) = 805KW +32KW + 35KW = 872KW Maximum Demand = Connected Load/Diversity Factor = 872KW/2.18(from Appendix A) = 400KW = 400KW/0.9 = 444KVA % Loading = 80 % = 625KVA*0.8 = 500KVA 625KVA maximum loading is 500KVA.Our maximum demand is 444KVA.So that 625KVA generator is selected. 2.1.4

Advantages of choosing the right size generator

- No unexpected system failures - No shutdowns due to capacity overload - Increased longevity of the generator - Guaranteed performance - Smoother hassle-free maintenance - Increased system life span - Assured personal safety - Much smaller chance of asset dam 3.

ECONOMICS OF GENERATOR OPERATION

Diesel Consumption Calculation of 125KVA Generator: Full load running=125*0.8 Running for 7hrs=100*7=700units Working duration for each DG/year=9 months=1890hrs For one day energy consumption=700units For 9 months energy consumption=9*30*700 No of units consumption by 125KVA DG/annum=1, 89,000units L = Litre Diesel consumption/hr. at full load = 28 L/hr. Total diesel consumption/annum = 28*1890 = 52,920 L/annum Cost of diesel/L = Rs.53 Total cost of diesel consumption for 125KVA DG / Annum = Rs.28, 04,760 Cost/unit for EB supply = Rs.7.33 Cost/unit through captive power plant = Rs.14.84 Units generated/L of the Diesel consumption=700/ (7*28) =3L/hr. Diesel consumption Generator:

calculation

Published by Research Cell, Department of EEE, Saranathan College of Engineering

of

140KVA

Page 2

Raga Brintha S, Manochitra J, Kanimozhi G

Full load running = 140*0.8 =112KW Running for 7hrs = 112*7 =784units Working duration for each DG/year = 9 months =1890 hrs. Table 3.1.Consumed Unit and amount details for 12 months (By using Appendix F) Consumed unit 21830.8

Bill amount in RS 178638

17706 14519.2

146155 115058

18058.0

128846

16097.6 20784.4

115466 147454

20113.2 18589.6

142873 132474

18014.4 36427.6

128548 254218

17097.6

122291

18710.8

133301

For one day energy consumption=784units For 9 months energy consumption=9*30*784 No of units consumption by 140KVA DG/Annum=2, 11,680 units Diesel consumption /hr. at full load=33L/hr. Total Diesel consumption /Annum =33*1890 =62,370L/Annum Cost of diesel/L=Rs.53 Total cost of diesel consumption for 140KVA DG set/Annum=Rs.33, 05,610 Cost/unit through Captive Power Plant=Rs.15.6 Unit generated/L of the Diesel Consumption=784/ (7*33) = 3L/hr. Diesel consumption calculation of 625KVA Generator: Full load running=625*0.8=500KW Running for 7hrs=500*7=3,500 units Working duration for each DG/Year=9 months =1890hrs For one day energy consumption =3500 units For 9 months energy consumption=9*30*3500 No of units consumption by 625KVA DG/Annum = 9, 45,000units Diesel consumption /hr. at full load=110L/hr. Total diesel consumption /Annum=2, 07,900L/Annum Total cost of diesel consumption for 625KVA DG/Annum=Rs.1, 10, 18,700 Units generated /L of the Diesel consumption=3500/ (7*110) = 4.5 L/hr. Total consumed unit = 237949.2

Average consumed unit = 237949.2/12 = 19829.1 Total bill amount = Rs.17, 45,322 AverageBill/month = Rs.17,45,322/12 = Rs. 145443.5 Consumed unit

Bill amount in Rs.

13440

111839

14170

104261

12320

89084

10550

77004

13390

96387

15730

112357

Total consumed unit = 79600 Average unit/month = 79600/12 = 6633 units Total bill amount = Rs.590932 Average cost/month = Rs.590932/12 = Rs.49, 244 LT bill calculation: LT charges/month = EB cost of college/month + EB cost of hostel/month + Diesel consumption cost of 125KVA and 140KVAGenerator/month = Rs.1, 45,443 + Rs.49, 244 + Rs.678930 = Rs.8, 73,617 HT bill calculation: Demand charges = Rs.350/KVA Unit charges = Rs.8.50/unit Meter rent = Rs.2000 Tax = 5% HTCharge = (Maximum Demand*350/KVA) + (Unit charges*8.50) = (500*350) + (((1, 89,000+2, 11,680)/9) +26462.1)*(8.50) = (1, 75,000) + (44,520 + 26462.1)*(8.50) = (1, 75,000) + (6, 03,347) = Rs.7, 78,347 HT EB bill/month = (𝐻𝑇𝑐ℎ𝑎𝑟𝑔𝑒𝑠 + 2000(𝐻𝑇𝑐ℎ𝑎𝑟𝑔𝑒𝑠 2000)(5%) = 7, 78,347 + 2000 + (7, 78,347 2000) (0.05) = 7, 80,347 + 38,917 = 𝑅𝑠. 8, 19,264 4. DESIGN OF POWER CABLES The proper sizing of an electrical (load bearing) cable is important to ensure that the cable can: 1. Operate continuously under full load without being damaged. 2. Withstand the worst short circuits currents flowing through the cable. 3. Provide the load with a suitable voltage (and avoid excessive voltage drops). 4. Ensure operation of protective devices during an earth fault.

Published by Research Cell, Department of EEE, Saranathan College of Enginering

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Automatic changeover of DG supply

4.1

Cable Construction

The basic characteristics of the cable's physical construction, which includes:      

Conductor material - normally copper or aluminium Conductor shape - e.g. circular or shaped Conductor type - e.g. stranded or solid Conductor surface coating - e.g. plain (no coating), tinned, silver or nickel Insulation type - e.g. PVC, XLPE, EPR Number of cores - single core or multicore (e.g. 2C, 3C or 4C)

conductor, PVC insulated, etc.) and a base set of installation conditions (e.g. ambient temperature, installation method, etc.). It is important to note that the current ratings are only valid for the quoted types of cables and base installation conditions. 4.3 Voltage Drop A cable's conductor can be seen as impedance and therefore whenever current flows through a cable, there will be a voltage drop across it. The voltage drop will depend on two things:  

Installation Conditions     

Ambient or soil temperature of the installation site Cable bunching, i.e. the number of cables that are bunched together Cable spacing, i.e. whether cables are installed touching or spaced Soil thermal resistivity (for underground cables) Depth of laying (for underground cables)

4.2 Cable Selection Based on Current Rating Current flowing through a cable generates heat through the resistive losses in the conductors, dielectric losses through the insulation and resistive losses from current flowing through any cable screens / shields and armouring. The component parts that make up the cable (e.g. conductors, insulation, bedding, sheath, armour, etc.) must be capable of withstanding the temperature rise and heat emanating from the cable. The current carrying capacity of a cable is the maximum current that can flow continuously through a cable without damaging the cable's insulation and other components (e.g. bedding, sheath, etc.). It is sometimes also referred to as the continuous current rating or capacity of a cable. Cables with larger conductor cross-sectional areas (i.e. more copper or aluminium) have lower resistive losses and are able to dissipate the heat better than smaller cables. Therefore a 16 sq.mm cable will have a higher current carrying capacity than a 4 sq.mm cable. 4.2.1

Base Current Ratings

International standards and manufacturers of cables will quote base current ratings of different types of cables in tables such as shown on the Appendix B. Each of these tables pertain to a specific type of cable construction (e.g. aluminium

4.4

Current flow through the cable – the higher the current flow, the higher the voltage drop Impedance of the conductor – the larger the impedance, the higher the voltage drop. Cable Impedances

The impedance of the cable is a function of the cable size (cross-sectional area) and the length of the cable. Most cable manufacturers will quote a cable’s resistance and reactance in Ω/km 4.5 Short Circuit Temperature Rise During a short circuit, a high amount of current can flow through a cable for a short time. This surge in current flow causes a temperature rise within the cable. High temperatures can trigger unwanted reactions in the cable insulation, sheath materials and other components, which can prematurely degrade the condition of the cable. As the cross-sectional area of the cable increases, it can dissipate higher fault currents for a given temperature rise. Therefore, cables should be sized to withstand the largest short circuit current. 4.6 Calculation 120sq.mm cable (from New MV panel to Hostel): Current Rating Cable size from New panel to Hostel = 120sq.mm Current withstand capacity of 120sq.mm cable (by using Appendix B) = 180A Maximum load in Hostel = 50KW Rated Current in A = 50*1000/ (1.732*400*0.9) = 77.2A Current withstand capacity of 120sq.mm cable is more than the rated current. Voltage drop calculation Voltage drop of 120sq.mm = 0.31*10^-3 volt/ampere/meter (By using Appendix B) Length of Cable from New MV panel to Hostel = 200m = 0.31*10^-3*80*200 = 4.96V Percentage of Voltage drop = (4.96*100)/240 = 2.06%

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Raga Brintha S, Manochitra J, Kanimozhi G

Percentage Voltage drop should not exceed 6% (by using Appendix B).So that 120sq.mm cable is suitable for Hostel . Short circuit fault level estimation Sub-transient reactance of 625KVA generator = 0.06 ohm Short circuit current of 625KVA generator = 625*10^3 /(0.06*1.732*415) = 15KA Distance from New MV panel to hostel = 200m Impedance of 120sq.mm cable = ((0.30*0.2) ^2+ (0.087*0.2)^2)^1/2 (by using Appendix G) = 6.24 m Short circuit current rating 625 ∗10^3 = = 7KA 0.06+0.0624 ∗ 3 ∗415

Short circuit current withstand Capacity of 120sq.mm = 9KA (By using Appendix D) 9KA is more than the 7KA.So that 120sq.mm is very safety. 400sq.mm cable :( From New MV panel to MV1 panel) Current rating: Connected load in MV1= KS block load + Mechanical lab load = 89.2KW+42KW = 131.2KW Full load current rating 131.2*10^3 = = 202.8A 3*415*0.9

Total current withstand capacity of 400sq.mm = 335A (by using Appendix B) The current capacity of 400sq.mm is greater than the full load current rating of MV1 panel. So that 400sq.mm cable is applicable. Voltage drop Distance from new MV panel to MV1 panel = 50m Voltage drop = 0.12*10^-3*202.8*50 = 1.2168V Percentage of Voltage drop = (1.2168*100)/240 = 0.507% This value is not exceeded 6% as per in the rule in the Appendix B.

This value is more than the 7KA.So that 400sq.mm cable is used. 400sq.mm cable: (From 625KVA generator output to new MV panel) 625KVA has three cables. Each cable size is 400sq.mm. Current Rating Full load current =

625*10^3

= 869A 3*415 Current flows through the each cable = 289A 400sq.mm cable withstand capacity is 335A.This value is more than the current flows through the each cable. Voltage drop Voltage drop = 0.12*10^-3*289*50 = 1.734 Percentage of Voltage drop = (1.734*100)/240 = 0.72% < 6% Short circuit current Impedance of 400sq.mm cable = ((0.09*0.05) ^2 + ((0.086*0.05)^2)^1/2)= 6.2m 625*10^3 Short circuit current = 0.06+0.062 3*415 = 7KA Short circuit current withstand capacity of 400sq.mm cable is 30KA (by using Appendix D).This value is more than the 7KA.So that 400sq.mm cable is used. 4.7 Generator Neutral Sizing Neutral earth fault current = 15KA/1.732 = 8.66KA Neutral has two cables. Each cable size is 240sq.mm.(by using Appendix C) Current capacity of 240sq.mm cable is 35KA (by using Appendix E).This value is more than the neutral earth fault current. So that 240sq.mm cable is applicable. 5. EMISSION NORM 5.1 Diesel Generator Sets: Stack Height The minimum height of stack to be provided with each generator set can be worked out using the following formula:

Short circuit current Impedance of 400sq.mm cable = ((0.09*0.05) ^2 + ((0.086*0.05)^2)^1/2) = 6.2m (From Appendix G) 625*10^3 Short circuit current = 0.06+0.062 3*415 = 7KA

H = h + 0.2 √ (capacity of DG in KVA.) H = Total height of stack in metre h = Height of the building in metres where the generator set is installed KVA = Total generator capacity of the set in KVA Based on the above formula the minimum stack height to be provided with different range of generator sets maybe categorised as follows:

Short circuit current withstand capacity of 400sq.mm cable is 30KA (by using Appendix D).

For Generator Sets Total Height of stack in metre 50 KVA Ht. of the building + 1.5 metre

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Automatic changeover of DG supply

50-100 KVA Ht. of the building + 2.0 metre 100-150 KVA Ht. of the building + 2.5 metre 150-200 KVA Ht. of the building + 3.0 metre 200-250 KVA Ht. of the building + 3.5 metre 250-300 KVA Ht. of the building + 3.5 metre

supply to KS Block,Mechanical Laband RV CS Lab. It has two bus bars, one is EBbus bar and another one is Generator bus bar.It is a two lock one key system.If EB supply is off,the panel is running by the generator bus by interchanging the key. MV2Panel

Fig.3. MV2 Panel Fig. 1. Flue Gas Emission Outlet (Control Pollution Control Board Norms) Similarly for higher KVA ratings a stack height can be worked out using the above formula. For 625 KVA Diesel Generator the stack height will be H = h + 0.2 √ (capacity of DG in KVA.) H= 10 + 0.2 √625 H=15 m (refer Fig.1.)

Its operation similar to that of MV Panel1.It gives the supply to RV Block,MCA Block,Street light,Machines lab.It gets the supply from MV Panel1 through the 240sq.mm cable. Changeover Panel

6. OPTIMUM LOCATION Existing Layout MV1 (Medium Voltage) Panel

Fig.4. Change Over Panel The changeover panel has two generator busbars, one is 125KVA and another one is 140KVA.By considering the load, particular generators are selected. Drawbacks of Existing layout

Fig.2. MV1 Panel The output of step down transformer is connected to MV1 panel through the 185sq.mm cable.It consists of six feeders.MV1panel gives the

1. If EB supply is available, any one of the generator or both the generators are running. So that more amount of diesel is wasted. 2. Power circuit and lighting circuit are mixed up in the existing layout. For example Power circuits use 15A fuse. ButLighting circuits use only 5A fuse. So if power circuit gets fault means, the lighting circuit is affected. To avoid that situation, power and lighting circuits are separated. New MV Panel

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Raga Brintha S, Manochitra J, Kanimozhi G

625KVA generator is used for maximum load operation. 7. AUTOMATIC CHANGEOVER A Prototype model of control and power circuit was developed for carrying out from three phase alternator to utility TANGEDCO and vice versa. Fig.5. New MV Panel

Power Circuit:

It has two busbars.ie.generator bus and EB bus. In the new panel has two generators.ie 125KVA and 140KVA.It has Bus coupler. It is a three lock two key system. Lighting Panel

Fig.8. Power Circuit Detailed Setup Fig.6. Lighting Panel All the lighting connections are connected to this panel. 625KVA Generator

The complete setup after fabrication and wiring was tested after interfacing with a three phase, 5KVA salient pole alternator. The 415V utility TANGEDCO power supply as well as three phase alternator power supply were connected to the fabricated automatic change over power circuit. Single Phase Preventer (SPP) Two numbers of single phase preventers are provided in the circuit one for alternator and another one for utility supply control. These single phase preventers are doing a vital function of enabling auto change over, in the event of abnormal conditions like reverse phase sequence, under voltage, over voltage and open phase conditions. In addition to the main three phase input power supply, two phase 415V supply is looped out to provide auxiliary power supply for the function of the preventer. In the event of operation of the preventer for abnormal conditions stated above, a 1 NO (Normally Open), 1 NC (Normally Close) change over contactors will switch over from NO to NC and vice versa. These contactors are wired up in the control circuit to disable or enable the required control function for AMF (Auto Mains Failure) operation. Electromagnetic Contactors (MC1, MC2)

Fig.7. 625KVA Generator

Two numbers of electromagnetic contactors are employed, one for alternator power and another

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Automatic changeover of DG supply

one for utility power. The coils of the contactors are rated at 415V AC, 50Hz.Each contactor has the configuration of 4NO (main contactor), 1 NO and 1NC (auxiliary contactor). In the event of failure of TANGEDCO supply this contactor will de energize and its NC contact (under de energized condition) will initiate the operation for automatic change over to captive power through an auto manual change over switch (switch kept in auto mode).

Testing the circuit

While the alternator is in operation, if utility supply rest source, the utility contactor (MC1) will energize, its contact will open and alternator supply is cut off. Electronic Timers Two numbers of electronic timers are provided with adjustable time setting variable from 0.3s to 30hr.The timer is energized by 230V AC. The time of operation can be set according to the requirement. The alternator supply will be connected to the load after the set time delay. Once the timer is energized its contact will change over from NO to NC and this NC contact will facilitate the energization of the concerned electromagnetic contactor MC2 provided the automatic switch is in auto mode. Push buttons Two sets of push buttons (one for OFF, one for ON) are provided, one set for each power supply. The NO contacts are used in the ON push button and the NC contacts are used in the OFF push button. By selecting the auto manual switch is in the manual mode, ON and OFF push button operations are enabled. However, the OFF push button can be operated both in auto and manual modes.

Fig.10. Testing the Circuit

INTERFACING THE CIRCUIT WITH ALTERNATOR

Fig.11. Interfacing the Circuit with Alternator 8.RESULTS AND DISCUSSION The AMF was interfaced with TANGEDCO utility supply and the following sequences were checked: 

Miniature Circuit Breaker The MCBs are used to provide protection against short circuits and also isolating the power supplies.



Control Circuit: 



 Fig.9. Control Circuit

The utility supply was switched off and AMF unit was found automatically cut in and power supply was restarted to the connected load, through alternator. The utility supply phase sequence was reversed and AMF unit was found automatically cut in and power supply was restarted to the connected load with correct phase sequence, through alternator. The utility supply voltage magnitude was lowered below the “SPP”, AMF unit was found automatically cut in and three phase power was restarted to the connected load, through alternator. The utility supply voltage fuses were removed one after one in all the phase and AMF unit was found automatically cut in and power supply was restarted in all the phases, through alternator. While alternator is in operation, through AMF the TANGEDCO supply was switching over to alternator supply.

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Raga Brintha S, Manochitra J, Kanimozhi G





 



The sizing of cable connected to the load, through alternator was checked for short circuit withstand, thermal rated withstand and voltage regulation to ensure reliable operation during automatic changeover. The voltage regulation was found in all the cables well below 6%(acceptable limit in low voltage distribution on per IEEE Rule). The actual short circuit current expected in the cables in the field were found to be lesser than the withstanding capability of the cable(estimated value or theoretically calculated value). A chimney height of the 625KVA DG set was calculated based on CPCP norms and was taken up the height of 15m. Generator neutral connection are suitably sized to share the generator earth fault current by using two numbers of 40*6mm copper flats. AMF operation was checked in the laboratory at various settings of electronic timers.

Appendix A

9. CONCLUSION This project work is instrumental in providing knowledge and wide technical data to understand more about the economics of DG operation, sizing of DG set for the given load condition, the requirements of AMF operation etc. AMF panels are highly demanded in apartments, foundations, textile, sugar and chemical industries. The AMF will ensure automatic battery charging of DG set while operating in utility supply mode, automatic starting or stopping of engine, automatic shutdown on faults like over speed, under speed, high temperature, low oil pressure, etc. Automation will avoid excessive diesel consumption and ensure high degree of reliability.

Appendix B

10. REFERENCES [1] Jonathan Gana Kolo,“Design and Construction of an Automatic Power Changeover Switch”, Department of Electrical and Computer Engineering, Federal University of Technology,Minna, Nigeria. [2] L.S. Ezema, B.U. Peter, O.O.Harris,”Design of automatic changeover with generator control mechanism”, Electrical Power and Electronic Development Department, Projects Development Institute (PRODA), Enugu, NIGERIA. [3] The Art of Gbenga, Daniel Obikoya, “Design and Implementation of a Generator Power Sensor and Shutdown Timer”, Department of Electrical and Electronics Engineering, Federal University Oye-Ekiti, Nigeria.

NOTE: As per rule 54 of IER’s 1956, the voltage variation for M.V/L.V installations should not exceed 6%. This variation should be could from the transformer secondary side to the tail and load (i.e.) the worst condition.

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Automatic changeover of DG supply

Appendix C Appendix E Thermal Short-Circuit Current rating Copper Conductor XLPE Insulation

Appendix D Thermal Short-Circuit Current Rating Aluminium Conductor PVC 70 Degree Celsius Insulation Appendix F

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Raga Brintha S, Manochitra J, Kanimozhi G

Appendix G :

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Student Journal of Electrical & Electronics Engineering Issue No. 1, Vol. 1, 2015

DESIGN AND IMPLEMENTATION OF DOUBLE FREQUENCY BOOST CONVERTER Shanmugapriya. G, Arthika. E Second year M.E PED / EEE, Saranathan College of Engineering, Panchapur, Trichy-12 [email protected], [email protected]

Abstract- Improving the efficiency and dynamics of power converters is concerned tradeoff in power electronics. The increase of switching frequency can improve the dynamics of power electronics, but the efficiency may be degraded.A double frequency Boost converter is proposed to address this concern. This converter is comprised of two Boost cells: one works at high frequency, and another works at low frequency. To operate at high frequency, converter performance is improved and at low frequency, efficiency is improved. So both converter performance and efficiency is improved by a double frequency Boost converter. . It operates in a way that current in the high-frequency switch is diverted through the low-frequency switch. Thus the converter can operate at very high frequency without adding the switching loss of the converter remains small. Simulation results demonstrate that the proposed converter greatly improves the efficiency and exhibits nearly the same dynamics as the conventional high frequency Boost converter. Key words - Boost, Double frequency Boost, Efficiency 1. INTRODUCTION In order to improve the transient and steady state performance of power converters and to enhance power density, high switching frequency is an effective method. However, switching frequency rise causes higher switching losses and greater electromagnetic interference. This in turn, limits the increase of switching frequency and hinders the improvement of system performance. Active and passive soft-switching techniques have been introduced to reduce switching losses. Switching losses are more in DC-DC converter. To reduce the Switching losses, Switching techniques are used. There are two types of Switching techniques1.Hard Switching 2.Soft Switching. Soft Switching namely Zero Voltage Switching and Zero Current Switching[1-2]. The major disadvantage of ZVS and ZCS is that they require variable-frequency control to regulate the output. This is undesirable since it complicates the control circuit and generates unwanted EMI harmonics, especially under wide load variations.

Interleaved Converter is only option to reduce the harmonics, and to achieve higher efficiency [3]. The major disadvantage of Interleaving technique is Circulating current problem. To overcome the Circulating current problem, a newly proposed converter namely Double frequency Boost Converter is introduced. This paper proposes a novel converter topology to achieve high dynamics response and high efficiency of Boost converter. This topology consists of a high frequency Boost cell and a low frequency Boost cell; and call it the “Double Frequency Boost converter” (DF Boost). Double frequency Boost converter consists of two Boost cells: one works at high frequency, and another works at low frequency. To operate at high frequency, converter performance can be improved and at low frequency efficiency can be improved. Both efficiency and converter performancecan be improved by Double Frequency Boost converter.It operates in a way that current in the high-frequency switch is diverted through the low-frequency switch. On the other hand, high frequency switching converter in parallel with low frequency converter enhances the output voltage response. The interleaved operation employs N converters to operate in parallel with interleaved clocks, so the total dynamics can reach higher performance. Multi converter paralleling method, which employs low power converters in parallel to enhance the power rating, has been proposed to enhance the power processing capability. Moreover, the parallel structure brings about the circulating current problem[4-5].Additional current sharing control is need to overcome this problem.

Fig.1. Schematic diagram of Boost converter

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G. Shanmuga priya, E. Arthika

2, PROPOSED DOUBLE FREQUENCY BOOST CONVERTER

corresponding switching period is𝑇𝑠𝑙 . Assume that the high frequency is an integer multiples of the low frequency, i.e.

𝑓ℎ =M𝑓𝑙

(2)

At each low-frequency cycle, four switching states exist. Table I lists the switching states according to the status of switches S1 and S2.

Mode 1 2 3 4 Fig. 2. Schematic diagram of Double Frequency Boost converter The topology of a conventional Boost converter is shown inFig. 1. In the steady state,the input (𝑉𝑆 ) and the output (𝑉𝑂 ) of the converter are governed by 𝑉

𝑆 𝑉0= 1−𝑑

(1)

Where, dis the duty ratio.From the above relation(1), we can find the output voltage of double frequency Boost converter. It is same as a boost converter. If the Boost converter works in the continuous conduction mode, then the inductor current 𝐼𝐿 can be regarded as a current source. In each switching cycle, both the current flowing through the switch and the voltage across the diode is averaged. In this paper, the proposed converter is called the DF Boost converter, because these Boost cells work at two different frequencies. The cell containing L1, S1 and D1 works at higher frequency, and is called the high-frequency Boost cell. Another cell containing L2, S2 and D2 works at lower frequency, and is called the low frequency Boost cell. The high frequency Boost cell is used to enhance the output performance, and the lowfrequency Boost cell to improve the converter efficiency. An active switch, instead of a diode as in the conventional unidirectional Boost converter, is employed to realize D1 in the high-frequency Boost cell. This active switch transfers the energy stored in the low-frequency cell to the source during the transient stage of load step-down. It works complementarily with high-frequency cell switch S1, and improves the transient response. The switch S1is controlled to operate at the high frequency𝑓ℎ , and the corresponding switching period is 𝑇𝑠ℎ . On the other hand, the switch S2is controlled to work at a low frequency𝑓𝑙 , and the

Table 1, Switching States S1 S2 ON ON ON OFF ON ON OFF ON

2.1 Mode 1: S1 ON, and S2 ON The circuit operation of Double Frequency Boost converter is split up into four modes of operation is depicted in Table 1. In mode 1 operation, both switches S1 and S2 are ON and diodes D1 and D2 are OFF. The voltage and current equations are expressed in equations (3)(5). 𝑉𝑠= 𝑉𝐿1 𝑉𝑆= 𝑉𝐿2 - 𝑖𝑐= 𝑖𝑜

(3) (4) (5)

Fig. 3. Mode 1 circuit for DF Boost converter In this state, the voltage 𝑉𝐿1 across the inductor L1 is positive, hence the current 𝐼𝐿1 flowing through L1rises, and the current 𝐼𝐿2 flowing through L2 does not change. 2.2 Mode 2:S1 ON, and S2 OFF

Fig. 4. Mode 2 circuit for DF Boost converter

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Design and implementation of Double Frequency Boost Converter

The mode 2 diagram of Double Frequency Boost converter is shown in Fig. 4. The voltage and current equations for mode2 is expressed in equations (6)-(8). 𝑉𝑆= 𝑉𝐿1 𝑉𝐿2= 𝑉𝑆 − 𝑉0 𝑖𝑐 = 𝑖𝐿2 − 𝑖𝑜

(6) (7)

(8)

In the mode 2 operation, the Switch 𝑆1 ON and 𝑆2 OFF and diode 𝐷1 OFF and 𝐷2 ON. The voltage across the inductor 𝐿1 is equal to the supply voltage. The voltage across the inductor 𝐿2 is equal to the supply voltage minus the load voltage.The voltage 𝑉𝐿1 across 𝐿1 is positive, so the current 𝐼𝐿1 rises. Since the voltage 𝑉𝐿2 across 𝐿2 is negative, the current 𝐼𝐿2 through 𝐿2 decreases. The current across the capacitor is equal to the current across the inductor 𝐿2 minus the load current. 2.3 Mode 3: S1 ON, and S2 ON In mode 3 operation, both switches S1 and S2 are ON and diodes D1 and D2 are OFF. The voltage and current equations for mode 3 is expressed in equations (9)-(11). The equivalent circuit equations are derived as 𝑉𝑆= 𝑉𝐿1 𝑉𝑆= 𝑉𝐿2 −𝑖𝑐 = 𝑖𝑜

(9) (10) (11)

In this state, the voltage 𝑉𝐿1 across the inductor L1 is positive, hence the current 𝐼𝐿1 flowing through L1 rises, and the current 𝐼𝐿2 flowing through L2 does not change.

Fig. 5. Mode 3 circuit for DF Boost converter 2.4 Mode 4: S1 OFF, and S2 ON

Fig. 6. Mode 4 circuit for DF Boost converter

Finally,In the mode 4 operation, the Switch 𝑆1 OFF and 𝑆2 ON and diode 𝐷1 ON and 𝐷2 OFF. The voltage across the inductor 𝐿1 is equal to the supply voltage minus the load voltage. The voltage across the inductor 𝐿2 is equal to the supply voltage. The current across the capacitor isequal to the current across the inductor 𝐿1 minus the load current. 𝑉𝑆= 𝑉𝐿2 𝑉𝐿1= 𝑉𝑆− 𝑉0 𝑖𝑐 = 𝑖𝐿1 − 𝑖0

(12) (13) (14)

The designed Double Frequency Boost converter is described in Table 2. Table 2, Design parameters

Parameter

Values

Input voltage(𝑉𝑠 )

8V

Output voltage(𝑉0 ) Output power(𝑃0 ) Ripple voltage (Δ𝑉𝑐 ) Ripple current(Δ𝐼𝑙 ) High frequency inductor (L1) for 𝐹ℎ =100KHZ Low frequency inductor (L2) for 𝐹𝑙 =10KHZ Output capacitance Resistance(𝑅0 )

16V 10W 0.070 0.95 42.10µH

3. DESIGN OF DOUBLE BOOST CONVERTER

421µH 44µF 26Ὡ

FREQUENCY

Simulink diagram of Double Frequency Boost converter using Matlabis depicted as shown in Fig. 7. A DF Boost, a single high-frequency Boost converter whoseswitching frequency is the same as the higher frequency of DF Boost, and a single low-frequency Boost converter whose switching frequency is equal to the lower frequency of DF Boost. Table 3, Performance parameters of the open loop boost converters Boost Settling Peak Rise Converter Time Over- Time (ms) shoot (ms) (%) Double 12 60 1 frequency High 5 80 0.05 Frequency Low 24 79 3 frequency

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Steady State Error (V) 0.02

Output Ripple Voltage (V) 0

0.05

less

0.04

more

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G. Shanmuga priya, E. Arthika

Fig. 7. Simulink diagram of Double Frequency Boost converter The Double Frequency Boost converter is modeled using state space averaging technique in which the design is carried out in time domain based on their performance indices. This method is highly significant for this kind of converters since the PWM converters are the special type of nonlinear systems which is switched in between two or more nonlinear circuits depending upon the duty ratio .The unique feature of this method is that the design can be carried out for a class of inputs such as impulse, step or sinusoidal function in which the initial conditions are also incorporates.The state vector of Double Frequency Boost Converter is given Fig. 8. Output voltage waveform of Boost converters Fig. 8 shows the comparison of output voltage for Double Frequency Boost, high frequency Boost and low frequency Boost converter. In high frequency Boost converter,a peakovershoot is about 80% and its settling time is about 5ms.In low frequency Boost converter,a peakovershoot is about 79% and its settling time is about 24ms.In double frequency Boost converter,a peakovershoot is about 60% and its settling time is about 12ms. Table III shows the performance parameters of the DF Boost, high frequency Boost, and low frequency Boost are shown in Table III. The table III proves that the Double Frequency Boost performance is better than all other Boost converter. 3

MODELLING OF DOUBLE FREQUENCY BOOST CONVERTER

𝒊𝑳𝟏 𝒙(𝒕) = 𝒊𝑳𝟐 (15) 𝒗𝒄 whereiL1and iL2 are the current through an inductor L1and L2 respectively; Vc is the voltage across the capacitor C. For the given duty cycle d(k) for the kth period, the systems are illustrated by the following set of state space equations in continuous time domain : 𝑿 = 𝑨𝒙 + 𝑩𝑽𝒔 (16) Where x is the state vector matrix, A is the state coefficient matrix and B is the source coefficient matrix, and d is a duty cycle is a function of x and Vs in a feedback system. State model of an Double Frequency Boost converter is derived and is discussed below. High power densities are possible only for continuous conduction mode (CCM) of operation. Diode Dl and D2 are always in a complementary state with the switches S1and S2 respectively. When S1 ON, D1 - OFF and vice versa and S2 - ON, D2 -

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Design and Implementation of Double Frequency Boost converter

OFF vice versa. For the continuous conduction mode of operation, four modes of operations are possible, and state equations are Mode 1: S1 is ON and S2 is ON (17)

Mode 2: S1 is ON and S2 is OFF 𝒙 = 𝑨𝟐 𝒙 + 𝑩𝟐 𝑽𝟏

(18)

Mode 3: S1 is ON and S2 is ON 𝒙 = 𝑨𝟑 𝒙 + 𝑩𝟑 𝑽𝟏

(19)

Mode 4: S1 is OFF and S2 is ON 𝒙 = 𝑨𝟒 𝒙 + 𝑩𝟒 𝑽𝟏 0 0 0

0 𝐴2 = 0 0

0 0 1/𝐶

0 A 3 = A1 = 0 0 𝐴4 =

0 0 1/𝐶

0 0 0

0 0 ; 𝐵1 = −1/RC

(20) 1 L1 1 L2

0 1

0 −1/𝐿2 ; 𝐵2 = −1/𝑅𝐶 0 0 0

0 0 ; −1/RC

−1/𝐿1 0 ; 𝐵4 = −1/𝑅𝐶

L1 1 𝐿2

0

𝐵3 = 1

1 L1 1

𝑠 3 +1.923𝑒 5 𝑠 2 +1.485 𝑒 8 𝑠+1.674 𝑒 −5

CLOSED LOOP OF DOUBLE FREQUENCY BOOST CONVERTER

In closed-loop control systems the difference between the actual output and the desired output is fed back to the controller to meet desired system output. Often this difference, known as the error signal is amplified and fed into the controller. 4.1 PID Controller A proportional integral derivative controller (PID controller) is a control loop feedback mechanism widely used in industrial control systems. A PID controller calculates an error value as the difference between a measured process variable and a desired set point. PID Controllers are also known as three term controllersProportional,Integral and Derivative. Proportional action: responds quickly to changes in error deviation.Integral action: is slower but removes offsets between the plant’s output and the reference.Derivative action: Speeds up the system response by adding in control action proportional to the rate of change of the feedback error.

0

L1 1 𝐿2

0 (21)

𝐵 = 𝐵1 𝑑1 + 𝐵2 𝑑2 + 𝐵3 𝑑3 + 𝐵4 𝑑4

(22)

𝑢 = 𝑉1

(23) .

Where d is the duty cycle ratio. d1, d2, d3,& d4 are the duty cycle of Mode 1, Mode 2, Mode 3 & Mode 4 respectively. For the continuous conduction mode of operation, we have 𝑑1 = 𝑑3 ; 𝑑2 = 𝑑4 ; 𝑑1 + 𝑑2 = 0.5 ;𝑑1 + 𝑑2 + 𝑑3 = 𝐷; 𝑑4 = 1 − 𝐷 Hence

𝐴= 0

5.821 𝑒 −11 𝑠 2 +2.969𝑒 8 𝑠−0.0001217

L2

Where 𝐴 = 𝐴1 𝑑1 + 𝐴2 𝑑2 + 𝐴3 𝑑3 + 𝐴4 𝑑4

0

= 4

𝒙 = 𝑨𝟏 𝒙 + 𝑩𝟏 𝑽𝟏

0 A1 = 0 0

By using A and B matrices, we have to find transfer function. Transfer function G(s)

0 0

−𝑑 2 𝐿1 −𝑑 2

𝑑2

𝑑2

𝐿2 −2𝑑 1 −2𝑑 2

𝐶

𝐶

𝑅𝐶

2𝑑 1 +2𝑑 2

;𝐵 =

𝐿1 2𝑑 1 +2𝑑 2 𝐿2

0

Fig. 9. Control Logic Of PID Controller The proportional, integral and derivative term is given by: 𝑢 𝑡 = 𝐾𝑝 𝑒 𝑡 + 𝐾𝑑

𝑑 𝑑𝑡

𝑒 𝑡 + 𝐾𝑖

𝑡 0

𝑒 𝑡 𝑑𝑡

(24)

By using PID Controller, overshoot of the system is reduced and it improves the stability of the system. 5

Tuning Methods

Tuning a PID controller is setting the 𝐾𝑝 , 𝐾𝑖 , and 𝐾𝑑 tuning constants so that the weighted sum of the proportional, integral, and derivative terms produces a controller output that steadily drives the process variable in the direction required to

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G. Shanmuga Priya, E. Arthika

eliminate the error. The process of selecting the controller parameters to meet given performance specifications is known as controller tuning. Ziegler and Nichols method used for tuning PID controllers (for determining values of𝐾𝑝 , 𝑇𝑖 and 𝑇𝑑 ) based on the transient response characteristics of a given plant. 6

Ziegler-Nichols Closed Loop Tuning

At the controller, select Proportional-only control, i.e. set 𝐾𝑝 to the lowest value and 𝑇𝑖 to infinity and 𝑇𝑑 to zero.Adjust the controlled system manually to the desired operating point.Set the manipulated variable of the controller to the manually adjusted value and switch to automatic operating mode. Continue to gradually increase 𝐾𝑝 until the controlled variable encounters harmonic oscillation. If possible, small step changes in the set point should be made during the 𝐾𝑝 adjustment to cause the control loop to oscillate.Take down the adjusted 𝐾𝑝 value as critical Proportional-action coefficient𝐾𝑐𝑟 .

can be calculated as, 𝐾𝑑 = 𝐾𝑝 . 𝑇𝑑 .After finding 𝐾𝑝 , 𝐾𝑖 , 𝐾𝑑 , substitute these values in PID controller for control the output voltage. The cell containing𝐿1 ,𝑆1 and 𝐷1 works at higher frequency, and is called the high-frequency boost cell. Another cell containing𝐿2 , 𝑆2 and 𝐷2 works at lower frequency, and is called the low frequency boost cell. The input Voltage is 8V.𝐿1 acts as a high-frequency inductor.𝐿2 acts as a low frequency inductor. Two switches are connected in parallel and it is connected to a capacitance of 44µF and it is given to load resistance of 26Ὼ.The output voltage obtained is 16V.In the closed loop of Double Frequency Boost Converter,the variation in load, and the input parameters, but the output voltage is maintained to be constant. The simulation circuit of closed loop of Double Frequency Boost Converter is shown in Fig.10

Fig. 11. Closed Loop output voltage response of Double Frequency Boost Converter 7. EFFICIENCY ANALYSIS Fig. 10. Closed Loop Circuit Of Double Frequency Boost Converter

Determine the time span for one oscillation amplitude as 𝑃𝑐𝑟 , if necessary by taking the time of several oscillations and calculating their average. 2𝜋 𝑃𝑐𝑟 = , 𝜔is the crossover frequency. Once the 𝜔 value for 𝐾𝑐𝑟 and 𝑃𝑐𝑟 are obtained, the PID parameter can be calculated.𝐾𝑝 = 0.6𝐾𝑐𝑟 , 𝑇𝑖 =0.5𝑃𝑐𝑟 , 𝑇𝑑 =0.125𝑃𝑐𝑟 .After finding𝐾𝑝 ,𝑇𝑖 , 𝑇𝑑 then we have to calculate the values of derivative gain Constant 𝐾𝑑 and integral gain constant 𝐾𝑖 .The integral gain constant can be 𝐾 calculated as, 𝐾𝑖 = 𝑝 .The derivative gain constant 𝑇𝑖

In order to analyze the efficiency improvement of the proposed DF Boost converter, the efficiency expression is analyzedin this section. The analysis is also applied to the single highfrequencyBoost and low-frequency Boost converters. Variousloss estimation methods have been proposed in the literaturebased on different assumptions [11-12] A simple loss modelis adopted here [13] in that want to show the efficiency relationship between the DF Boost and single high-frequencyBoost, not to develop a new loss model. In the analysis, the following assumptions are made. 1) The conduction losses of active switch and diode areestimated, respectively, according to their conductionvoltages 𝑉𝑜𝑛 and𝑉𝐹 .

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Design and Implementation of Double Frequency Boost converter

2) The switching transient processes are assumed to satisfythe linear current and voltage waveforms. Moreover, theturn-on time 𝑡𝑜𝑛 is the same for all switches and diodes,so is the turn-off time𝑡𝑜𝑓𝑓 . 3) Since the switching loss usually dominates the total loss,losses of the output capacitor and output inductor are not calculated here. Efficiency= Pin - (PSWITCH+PINDUCTOR+PDIODE) Pin PSWITCH = RNMOS × D× (IOUT/1 – D)2 PINDUCTOR = RL × (IOUT/1 – D)2 PDIODE = RD ×IOUT2 + VF× IOUT

(25) (26) (27) (28)

In a single-frequency Boost converter, the total loss 𝑃𝑆𝐹 comes from four parts, the conduction loss𝑃𝑠𝑐𝑜𝑛 and switchingloss 𝑃𝑆𝑆 of the active switch S, and the conduction loss 𝑃𝑑𝑐𝑜𝑛 and switching loss 𝑃𝑠𝑑 of the diode. When the input voltage is 𝑉𝑖𝑛 , duty ratio is d, the inductor average current is𝐼𝐿 , and theswitching frequency is 𝑓𝑠 , the losses can be estimated accordingto the following equations [13]. 𝑃𝑠𝑐𝑜𝑛 = 𝑑𝑉𝑜𝑛 𝐼𝐿 𝑃𝑑𝑐𝑜𝑛 = 1 − 𝑑 𝑉𝐹 𝐼𝐿 1 𝑃𝑠𝑠 = 𝑓𝑠 𝑉𝑖𝑛 𝐼𝐿 𝑡𝑜𝑛 + 𝑡𝑜𝑓𝑓

(29) (30) (31)

𝑃𝑠𝑑 = 𝑓𝑠 𝑉𝑖𝑛 𝐼𝐿 𝑡𝑜𝑛 + 𝑡𝑜𝑓𝑓

(32)

2 1 2

Total switching losses 𝑃𝑠𝐷𝐹 ≈ 𝑓1 𝑉𝑖𝑛 𝐼𝐿 (𝑡𝑜𝑛 + 𝑡𝑜𝑓𝑓 )

(42)

It follows from (33)–(42) that the total conduction loss of DF boost converter is the same as the single frequency boost converter. This result also can be reasoned from the fact that the total currents flowing through the DF boost switches and diodes are the same as that through a single-frequency boost. On the other hand, the total switching loss is nearly the same as the single low-frequency boost, and is much smaller than that of the single highfrequency boost. Hence, the DF boost converter improves the efficiency by current diversion to the low-frequency boost cell. The efficiency of the Double Frequency Boost, low frequency Boost and high frequency Boost are illustrated in Fig. 12. From the graph one can understand that the high frequency Boost converter has less efficiency than the other two Boost converters. The efficiency of the low frequency Boost and double frequency Boost are almost same.

The losses in high frequency cell 𝑃𝑠𝑐𝑜𝑛𝐻 = 0.5𝐷. 𝑉𝑜𝑛 𝐼𝐿ℎ 𝑃𝑑𝑐𝑜𝑛𝐻 = 0.5(1 − 𝐷). 𝑉𝐹 𝐼𝐿ℎ 1 𝑃𝑠𝑠𝐻 = 𝑓ℎ 𝑉𝑖𝑛 𝐼𝐿ℎ 𝑡𝑜𝑛 + 𝑡𝑜𝑓𝑓

(33) (34) (35)

𝑃𝑠𝑑𝐻 = 𝑓ℎ 𝑉𝑖𝑛 𝐼𝐿ℎ 𝑡𝑜𝑛 + 𝑡𝑜𝑓𝑓

(36)

4 1 4

The losses in low frequency cell 𝑃𝑠𝑐𝑜𝑛𝐿 = 𝐷. 𝑉𝑜𝑛 𝐼𝐿 − 0.5𝐼𝐿𝑙 𝑃𝑑𝑐𝑜𝑛𝐿 = (1 − 𝐷). 𝑉𝐹 𝐼𝐿 − 0.5𝐼𝐿𝑙 1 𝑃𝑠𝑠𝐿 = 𝑓1 𝑉𝑖𝑛 𝐼𝐿 − 0.5𝐼𝐿𝑙 𝑡𝑜𝑛 + 𝑡𝑜𝑓𝑓

(37) (38) (39)

𝑃𝑠𝑑𝐿 = 𝑓1 𝑉𝑖𝑛 𝐼𝐿 − 0.5𝐼𝐿𝑙 𝑡𝑜𝑛 + 𝑡𝑜𝑓𝑓

(40)

2 1 2

Then from(29)-(40),the total conduction loss PconDFin the DF boost is approximately the same as that in the single frequency boost converter Total conduction loss in Double Frequency Boost converter. 𝑃𝑐𝑜𝑛𝐷𝐹 ≈ 𝑃𝑠𝑐𝑜𝑛 + 𝑃𝑑𝑐𝑜𝑛

(41)

In the case the low-frequency inductor current is small with reference to the inductor average current, the total switching loss PsDF can be approximated as

Fig.12. Efficiency of the Boost converters From the above results, the Double Frequency Boost converter not only improve the performance of the Boost converter and also improve the efficiency of the Boost converter is evident. 8.

CONCLUSION

This paper has presented a novel topology of Double Frequency Boost converter. Analytical results have demonstrated that the DF Boost converter not only exhibits the same steady state and transient performance but also improves the efficiency of conventional Boost converters. The proposed converter does not need the load transient change information for accurate current control and does not have the current circulating problem and it

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G. Shanmuga Priya, E. Arthika

is used for high power applications. Extension to double-frequency switch-inductor three-terminal network has also been described. Future work will investigate whether the proposed Boost converter is applicable for Electric Vehicle and PV cell applications

REFERENCES [1] C. M. Wang, “New family of zero-currentswitching PWM converters using a new zerocurrent-switching PWM auxiliary circuit,” IEEE Trans.Ind. Electron., vol. 53, no. 3, pp. 768–777, Jun. 2006. [2] W. Chen and X. Ruan, “Zero-voltageswitching PWM hybrid full-bridge three-level converter with secondary-voltage clamping scheme,” IEEETrans. Ind. Electron., vol. 55, no. 2, pp. 644–654, Feb. 2008. [3] Yao-Ching Hsieh, Te-Chin Hsueh, and HauChen Yen,”An Interleaved Boost Converter With Zero-Voltage Transition” IEEE Trans. Power Electron.,vol. 24, no. 4, Apr 2009. [4] Z. Ye, P. K. Jain, and P. C. Sen, “Circulating current minimization in high-frequency AC power distribution architecture with multiple inverter modules operated in parallel,” IEEE Trans. Ind. Electron., vol. 54, no. 5,pp. 2673– 2687, Oct. 2007. [5] C.-T. Pan and Y.-H. Liao, “Modeling and coordinate control of circulating currents in parallel three-phase boost rectifiers,” IEEE Trans. Ind.Electron., vol. 54, no. 2, pp. 825– 838, Apr. 2007. [6] J. Marcos Alonso, Juan Viña, David Gacio Vaquero, Gilberto Martínez, and René Osorio“Analysis and Design of the Integrated Double Buck–Boost Converter as a HighPower-Factor Driver for Power-LED Lamps”, IEEE Trans. power electron., vol. 59, no. 4, Apr 2012.

[7] Jingquan Chen, Dragan, Maksimovic,and Robert W. Erickson,”Analysis and Design of a Low-Stress Buck-Boost Converter in Universal-Input PFC Applications” IEEE Trans. power electron., vol. 21, no. 2, Mar 2006 [8] Xiong Du, Luowei Zhou, and Heng-Ming Tai, “Double Frequency BuckConverter”IEEE Trans. power electron., vol. 56, no. 5, May 2009 [9] H. Mao, F. C. Lee, D. Boroyevich, and S. Hiti, “Review of high performance three-phase power-factor correction circuit,” IEEE Trans.Ind. Appl., vol. 44, no. 4, pp. 437–446, Aug. 1997. [10] U. Borup, F. Blaabjerg, and P. Enjeti, “Sharing of nonlinear load in parallelconnected three-phase converters,” IEEE Trans. Ind. Appl., vol. 37, no. 6, pp. 18171823, Nov./Dec. 2001. [11] Y. Suh, J. K. Steinke, and P. K. Steimer, “Efficiency comparison of voltage-source and current-source drive systems for mediumvoltage applications,”IEEE Trans. Ind. Electron., vol. 54, no. 5, pp. 2521–2531,Oct. 2007. [12] S. Saggini, W. Stefanutti, P. Mattavelli, and A. Carrera, “Efficiency estimation in digitally-controlled dc–dc buck converters based on single current sensing,” in Proc. IEEE PESC, 2008, pp. 3581–3586. [13] N. Mohan, T. M. Undeland, and W. P. Robbins, Power Electronics:Converters, Applications, and Design, 3rd ed. New York: Wiley, 2003. [14] Z. Ye, D. Boroyevich, J. Y. Choi, and F. C. Lee, “Control of circulating current in two parallel three-phase boost rectifiers,” IEEE Trans. PowerElectron., vol. 17, no. 5, pp. 609–615, Sep. 2002.

1

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Student Journal of Electrical and Electronics Engineering, Issue No. 1, Vol. 1, 2015

LOW COST POWER QUALITY ANALYZER FOR ACADEMIC APPLICATIONS Janani R, Jayasri RS, Deepa G, Dhivyalakshmi A

Final year EEE, Saranathan college of Engineering, Trichy-12 [email protected], [email protected], [email protected], [email protected] Abstract - This work presents a low cost power quality analyzer (LCPQA) using Texas Instruments microcontroller TMS320F28027 with a product cost less than 200 USD that will be capable of measuring and displaying all the power quality parameters displayed by a high end power quality analyzer available in the market. The LCPQA is developed exclusively for academic laboratory applications, which doesn’t need to survive the stringent industrial conditions, which enables the low cost. The LCPQA will serve as tool for an enhanced study of power quality issues created by various Nonlinear loads. The algorithm for measurement of various Power quality parameters which includes, true rms, fundamental, harmonics, symmetrical comp, real, reactive and apparent power etc. is implemented using classical instantaneous p-q theory and instantaneous symmetrical components. The LCPQA is built using current and voltage sensors and the control circuit includes a C2000 launch-pad, signal conditioning board and Sharp Memory LCD Booster Pack for display of parameters. The LCPQA is validated and benchmarked using a FLUKE 434-II power quality analyzer and the results are presented in this paper.

The Instantaneous Reactive Power (IRP) p-q Theory [1] is based on the Clarke Transform of voltages and currents in three-phase systems into α and β orthogonal coordinates. Its development was a response to “...the demand to instantaneously compensate the reactive power...” Originally, this theory was formulated by Akagi, Kanazawa and Nabae for the active power filter control. Power properties of three-phase systems are described by the IRP p-q Theory in two orthogonal α and β coordinates in terms of two, p and q instantaneous powers. They are referred to as the instantaneous real and the imaginary powers or more commonly, as the instantaneous active and reactive powers. According to “The instantaneous reactive power, q was introduced on the same basis as the conventional real power, p in three- phase circuits and then the instantaneous reactive power in each phase was defined with the focus on the physical meaning and the reason for naming” Because of it, the IRP p-q Theory has become a very attractive theoretical tool not only for the active power filter control, but also for analysis and identification of power properties of three-phase systems with non-sinusoidal voltages and currents.

Keywords— power quality, harmonics, true rms

Power properties of three-phase systems are expressed by the IRP p-q Theory in terms of only two, active and reactive, p and q, powers, while power properties of such systems, even without any harmonic distortion, depend on three independent phenomena. The IRP p-q Theory has been developed for three-phase systems with nonsinusoidal voltages and currents.

1.

INTRODUCTION

The main motivation behind the development of LCPQA is our interest towards power quality. The FLUKE Power quality meter available within the institution is capable of measuring all power quality parameters such as three phase currents, voltages, real, reactive and apparent power, powerfactor, symmetrical comp etc. which can be stored and retrived later. The cost of this high end power quality analyser is very high. For acadamics such costly metres are not necessary so we framed our goal in such a way that the power quality metre which we develop, 1. 2. 3.

Willserve as a experimental facility that will serve multiple branch of students will act as a huge supplement to the theoretical course will be cost effective and maintains good efficiency

Fig.1. Power circuit diagram

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R. Janani, R.S. Jayasri, G. Deepa, and A. Dhivyalakshmi

2. 1.

2.

3.

4. 5. 6.

PROPOSED SOLUTION

The three phase voltages and currents of the nonlinear loads are sensed using voltage and current sensors as shown in Fig. 1 The sensed outputs are interfaced with ADC of TMS320F28027 using a signal conditioning board The digital algorithms are developed for the processor to implement the equations shown below based on p-q theory and instantaneous symmetrical components. The calculated parameters will be displayed in an LCD display. The functional block diagram of the control unit of the proposed LCPQA is shown in Fig. 2 Functional features of LCPQA– Measure and display True rms, fundamental, harmonics, % THD, unbalancing, power(real, reactive and apparent), power factor, symmetrical components, frequency

Formulas based on generalized instantaneous pq theory [2] a). Real power , 𝒑 = 𝒗. 𝒊 𝒐𝒓 𝒑 = 𝒗𝒂 𝒊𝒂 + 𝒗𝒃 𝒊𝒃 + 𝒗𝒄 𝒊𝒄 ……….1 𝒒𝒂 b). Reactive Power , 𝒒 = 𝒗 × 𝒊 = 𝒒𝒃 = 𝒒𝒄 𝒗𝒂 𝒗𝒄 𝒊𝒂 𝒊𝒄 𝒗𝒄 𝒗𝒂 𝒐𝒓 𝒒 = 𝒒 ………………………2 𝒊𝒄 𝒊𝒂 𝒗𝒂 𝒗𝒃 𝒊𝒂 𝒊𝒃 𝒒=

𝒒𝟐𝒂 + 𝒒𝟐𝒃 + 𝒒𝟐𝒄

c). Apparent Power , 𝒔 ≝ 𝒗𝒊…………………….3 where 𝒗 = 𝒗 =

𝒗𝟐𝒂 + 𝒗𝟐𝒃 + 𝒗𝟐𝒄 and

𝒊= 𝒊 =

𝒊𝟐𝒂 + 𝒊𝟐𝒃 + 𝒊𝟐𝒄

𝒑

d). P𝒐𝒘𝒆𝒓 𝑭𝒂𝒄𝒕𝒐𝒓 , 𝝀 ≝ ………………..…….4 𝒔

e).𝑻𝑯𝑫 =

𝑰𝒓𝒎𝒔 −𝑰𝑯𝒓𝒎𝒔 𝑰𝑯𝒓𝒎𝒔

………………………..….5

3. IMPLEMENTATION 3.1 Hardware Implementation

Fig.2. Functional block diagram

Description for Sub-Systems 1.

2.

3. 4. 5.

6.

Voltage & Current Sensor:Two voltage and two current sensors are used to sense the three phase balanced system. Signal Conditioning Unit:Two Signal Conditioning circuits (Unipolar) each have two channels C2000 Launch Pad:Evaluation Module from Texas Instruments is used as a controller LCD Display:Sharp Memory LCD Booster pack for displaying output parameters. Power Supply:It supplies a. Signal conditioner (±5V) b. Current Sensor (±15V) c. LCD (+5V) Load: Three cases of load are considered a. Three phase wye connected Resistive load b. Three phase Inductive load c. Three phase diode bridge rectifier fed Resistive load.

Voltage SensorIncoming AC voltage is stepped down using potential transformer (230V/3V) and is sent to signal conditioning circuits. In fig.3 we have a normal potential transformer which is used as the voltage sensor.

Using the above equations 1, 2, 3, 4 and 5 the various power and power factor are calculated. These are the formulas used in the code composer studio to do the calculations and displays the results.

Fig.3. Potential Transformer

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Low Cost Power Quality Analyzer for Academic Applications

Current SensorsLA 25P 711290 Current transducer is used as the current sensor. The current transducer steps down the current in the ratio 1000:1. The stepped down current in terms of voltage is measured across a resistor. In fig.4 is the general current transducer which is being used as the current sensor.

Fig.6. Block diagram of signal conditioning circuit

Fig.4. Current Transducer

LA -25 P

LEM

M O/P

-

+

R -15V

+15V

Fig.5. Current Sensor circuit

In fig.5 we can see that a dual supply of 15V is given to the current transducer. Then across the resistor the output is taken. The resistor employed here is 100ohm. Advantages of current transducer1. Excellent accuracy 2. Very good linearity 3. Low temperature drift 4. Optimize response time 5. No insertion loss Signal Conditioning UnitOutputs of Voltage and Current sensors are sent to signal conditioning unit where Bipolar Signals are transformed to unipolar signal using a clamper circuit. Two non-inverting amplifiers are used to limit the gain of the signal. Amplifier and clamper circuits are made using Texas Instruments Operational amplifier LM2902. The signal conditioning output is fed to ADC unit of C2000 micro-controller. In the fig.6 gives us the general block diagram of the signal conditioning circuit which consist of an amplifier to amplify the input signal and clamper to clamp the signal when it goes beyond the desired value the signal is also shifted to make it unipolar and then buffer is used to maintain the given signal.

Fig.7 .Signal Conditioning Circuit

Fig. 7. gives the circuit diagram of the signal conditioner in which we use LM2902 quad op-amp, resistors of 10Kohm & 470ohm, pre-set value pot of 50Kohm and 4.7Kohm, 1N4007 diodes, capacitor of 1uF and LED. Features of LM2902:     

Internally frequency compensated for unity gain. Large DC voltage gain 100dB. Wide Bandwidth (1Mhz). Very low supply drain current Low input biasing current

Advantages of LM2902:    

Four internally compensated op-amps in a single package. Power drain suitable for battery operation. Vout goes to GND Direct sensing near GND etc

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R. Janani, R.S. Jayasri, G. Deepa, and A. Dhivyalakshmi

C2000 Launch Pad 1. 2. 3. 4.

5. 6. 7. 8.

High-Efficiency - Three 32-Bit CPU timers a. 60 MHz (16.67-ns Cycle Time) Low Cost 48-Pin PT : Low-Profile Quad Flatpack (LQFP) Serial Port Peripherals a. SCI (UART) Module b. SPI Module c. Inter-Integrated-Circuit (I2C) Bus Peripheral Interrupt Expansion (PIE) Independent 16-Bit Timer in Each ePWMmodule Code-Security Module : 128-Bit Security Key/Lock Analog-to-Digital Converter (ADC)

6.

and supports ratio-metric VREFHI/VREFLO references. The ADC interface has been optimized for low overhead and latency.

LoadThree cases of load are considered Three phase wye connected Resistive load

a.

In fig.8 we have the c2000 launch pad microcontroller which is the heart of the LCPQA. The coding’s embedded in the processor using Code Composing Studio software.

Fig.9. Resistive load

b.

Three phase Inductive load

c.

Three phase diode bridge rectifier fed Resistive load.

Fig.8. C2000 Microcontroller

Features of C2000 Launch Pad – 1. 2.

3.

4.

5.

The F2802x Piccolo family of microcontrollers provides the power of the C28x™ core coupled with highly integrated control peripherals in low pin-count devices. This family is code-compatible with previous C28x- based code, as well as providing a high level of analog integration. An internal voltage regulator allows for singlerail operation. Enhancements have been made to the HRPWM module to allow for dual-edge control (frequency modulation). Analog comparators with internal 10-bit references have been added and can be routed directly to control the PWM outputs. The ADC converts from 0 to 3.3-V fixed full-scale range

For load we have considered three cases here fig.9, fig.10, Fig.11 are the various loads. These loads are connected and the power quality is monitored. B. Software Implementation

Fig.12. Simple Three-Phase Diode Bridge Rectifier – RLoad

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Low Cost Power Quality Analyzer for Academic Applications

Above in fig.12 we have the simple threephase diode bridge rectifier which is used for simulation purpose.

The algorithm for the development of LCPQA is derived from instantaneous PQ theory and is simulated using Matlab/ Simulink environment. And fig.13 gives the complete circuit model of three-phase diode bridge rectifier fed R-Load. ADC Flowchart: Features & Functions of the ADC module . The core of the ADC contains a single 12-bit converter fed by two sample-and-hold circuits. The sample-and-hold circuits can be sampled simultaneously or sequentially. It consists of 13 analog input channels. The converter can be configured to run with an internal band-gap reference to create true-voltage based conversions (or) a pair of external voltage references (VREFHI/VREFLO) to create radiometric-based conversions. The basic principle of operation is centered on the configurations of individual conversions, called SOCs .Full range analog input: 0 V to 3.3 V fixed.

Fig.13.Matlab Simulink model of three-phase diode bridge rectifier

The digital value of the input analog voltage is derived by

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R. Janani, R.S. Jayasri, G. Deepa, and A. Dhivyalakshmi

1.

Internal Reference (VREFLO = VSSA. VREFHI must not exceed VDDA when using either internal or external reference modes.)

trends or cycles. The threshold between short-term and long-term depends on the application, and the parameters of the moving average will be set accordingly. Viewed simplistically it can be regarded as smoothing the data. Moving Window rmsFlowchart:

2. External Reference (VREFHI/VREFLO connected to external references. VREFHI must not exceed VDDA when using either internal or external reference modes.)

Moving Average Flowchart:

The root mean square is calculated using a moving window. It is calculated for each window of data according to the equation 5: 1

1

2

𝑆 2 RMS = 𝑓 (𝑆) …………………………….5 𝑆 1 WhereRMS - Root Mean Square, S - Window Length (Points), f(s) - Data within the Window According to the equation, the root mean square calculation consists of three steps:

1. 2. 3. A moving average (rolling average or running average) is a calculation to analyze data points by creating a series of averages of different subsets of the full data set. It is also called a moving mean (mm) or rolling mean and is a type of finite impulse response filter. Variations include: simple, and cumulative, or weightedforms moving average is commonly used with time series data to smooth out short-term fluctuations and highlight longer-term

Square all of the values in the window Determine the mean of the resultant values Take the square root of the result

ADC Interrupt Service Routine pseudo code: 4.

5.

ADC Interrupt Service Routine: a. After every ADC conversion an interrupt is being generated and enters the ADC_ISR routine. Various parameters of power quality are being computed in this routine.

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Low Cost Power Quality Analyzer for Academic Applications

6.

7. 8.

Moving average of Voltage, Current, real, reactive and apparent powers are being computed. Moving window RMS of voltage, fundamental current and harmonic current are also computed. About 100 samples per cycle of waveform are being taken and ADC trigger is given by PWM pulses. 4.

Here fig.15 gives the complete setup of LCPQA which consist of two voltage sensors, two current sensors, two signal conditioning circuits and c2000 microprocessor.

RESULTS

The proposed concept has been well validated using simulation in Matlab/Simulink.

Fig.16. Complete set up of LCPQA with FLUKE and other loads

In the above fig.16 we can see the complete set of LCPQA with other loads and gives the respective readings which can be viewed in the watch window of Code Composer Studio Software. VALIDATION OF LCPQA WITH FLUKE 434-II Benchmarking/Performance Analysis Fig.14.Simulated Waveforms of instantaneous values of extracted components of voltage, current and power using Instantaneous pq theory

Thus, fig.14 gives the simulated results of three-phase diode bridge rectifier fed R load which is done using matlab software

Table 1: Voltage and Current readings shown in LCPQA and FLUKE (for RL load)

Fig.15. Experimental setup of LCPQA

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R. Janani, R.S. Jayasri, G. Deepa, and A. Dhivyalakshmi

Fig.17. (c) Fig.17.(a). Various Powers and Power Factor Readings of FLUKE (b).Voltage and Current Readings of FLUKE (c).Corresponding Readings Shown in LCPQA Table 2: Real and Reactive Power readings shown in LCPQA and FLUKE (for RL load)

Fig.18. Graph showing the accuracy of the meter at various % of nominal parameters Table 3: Apparent Power and Power Factor readings shown in LCPQA and FLUKE (for RL load)

From the above Table 1, Table 2 and Table 3 we can see the various readings of LCPQA vs. FLUKE.

5.

CONCLUSION

The proposed LPQA is expected to meet the high accuracy standards existing market available at a low cost customized to meet the academic needs excluding the waveform display features and data logging features. It is intended to restrict the product cost within 200 USD. For a large scale manufacturing the product cost could be further reduced. Also the LPQA will be calibrated using Fluke 434-II and field tested. A well-defined process will be developed in the due course to convert this prototype to a product. REFERENCE

Fig.17. (a)

[1] H. Akagi, Y. Kanazawa and A. Nabae, “Instantaneous reactive power compensators comprising switching devices without energy storage components,” IEEE Trans. Ind. AppL, vol. 20, pp. 625-630, May/June 1984. [2] Z. P. Peng, G. W. Ott, and D. J. Adams, “Harmonic and reactive power compensation based on the generalized instantaneous reactive power theory for three-phase four-wire systems,” IEEE Trans. on Power Electronics, vol.13, no. 3, pp. 1174-1181, July 1998.

Fig.17. (b)

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Student Journal of Electrical and Electronics Engineering, Issue No. 1, Vol. 1, 2015

Energy Maximizer for PV fed DC-DC Boost Converter N. Sangeetha, A. Pavithra, S. Divya, and A. Akilandeswari Final year EEE, Saranathan College of Engineering [email protected] Abstract — This work presents a novel energy maximizing unit (EMU) using Texas Instruments microcontroller TMS320F28027 for a stand-alone or grid connected PV plant. One of the essential requirements in any PV plant is to extract the maximum power from the PV arrays under varying weather conditions for which normally an MPPT (Maximum Power point tracking) controller is employed. The MPPT controller is employed at a system level or macro level which is spread across huge area. Under such conditions, shading and mismatching of different panels prohibits the MPPT to extract the maximum power. Hence the upcoming trend is to employ the MPPT controller at micro level for each panel or a small group of panels which eliminates shading and mismatch losses. The product presented in this paper works at micro level for a small group of panel. In such applications the controller requires to extract the maximum power as well maintain the voltage within a desired range. This feature has been demonstrated and validated. The validation and field results are presented in this paper.

accurate tracking performance and reduce the oscillations around MPP. Each algorithm can be categorized based on the type of the control variable it uses: 1) voltage; 2) current; or 3) duty cycle. Among different algorithms, much focus has been on perturb and observe (P&O). The P&O method involves a perturbation in the operating voltage of the solar array. This MPPT algorithm is implemented in boost converter. Control of output voltage is done by the TMS320F28027 piccolo device. It provides the fast and flexible control. The various quantity can be programmed and controlled to it’s specify limit range. 2.   

Keywords—PV, MPPT 1.

INTRODUCTION

Solar power generation is currently considered as one of the most useful renewable energy sources, as it is relatively less polluted and maintenance free. The main hindrance of solar energy going widespread is the initial high capital cost of solar modules. The disadvantage of solar energy production is that the power generation is not constant throughout the day, as it changes with weather conditions. Furthermore, the efficiency of solar energy conversion to electrical energy is very low, which is only in the range of 9–17% in low irradiation regions. This means that a fairly vast amount of surface area is required to produce high power. Therefore, maximum power point tracking is an essential part of the photovoltaic system to ensure that the power converters operate at the maximum power point (MPP) of the solar array. Various MPPT algorithms have been developed. These algorithms differ from each other in terms of number of the sensors used, complexity, and cost to implement the algorithm. The main objectives of all these MPPT algorithms are to achieve faster and



PROPOSED SOLUTION

The EMU is proposed to replace eliminate the problem of partial shading and mismatching losses. The EMU addresses both maximum power extraction as well as voltage regulation of the PV fed boost converter. The power circuit of the proposed solution is shown in Fig. 1a and the functional block diagram of the EMU is shown in Fig. 1b. Functional features of EMU – 1.Provide output voltage regulation 2. MPPT of PV at micro level.

Experimental Setup :

Fig.1a. Power Circuit Diagram of EMU Fig.1a. shows the experimental setup of the project with all parts is described in more detail later in this report. The testing of different components in this setup was carried out with the use of a power supply, a signal generator, a multimeter and an oscilloscope in the Laboratories of the college.

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Energy Maximizer for PV fed DC-DC Boost Converter

1b) is configured and given as the input to the driver circuit of boost converter. 3.2.Voltage sensor: The voltage sensor LA 20-P is a simple voltage divider that steps down the voltage that can be fed into one of the analog inputs of TMS320F28027 piccolo device. 3.3. Current sensor: Fig.1b. Functional Block Diagram of the EMU

3.

IMPLEMENTATION

3.1 Hardware Implementation Data sheets for all hardware components give operational data as well as limitations of the products and best conditions at which the product operates. The data sheets were very important reference to ensure circuits were being setup correctly.

The LA 55-P current sensor is used in our project. This will measure the current provided by the solar panel.This voltage from measure pin is then fed into an analog pin of TMS320F28027 piccolo device. The +15V and -15V supply is supplied from the power source 47247 ta 60/B. 3.4. Design of boost converter:

3.1.1. TMS320F28027 Processor:

Vo = 48V ; Vin = 25-35V ; Power P =125W ; Duty Cycle D= 50 % ; Assume Vin = 25 V ; Io = P/ Vo= 2.6 A Vo/ Vin = Iin/ Io ; Iin= 5A ; Iin = IL IL = 5A ; IL = 4.5 to 5.5 A ; Δ IL = 1 A ΔVrip = 48 x 0.02 =0.96V L = ( Vin x D)/(Fs x Δ IL) = 3.5mH The output capacitor is designed for 1% output voltage ripple (ΔVrip) C= (Io x D)/(Fs x ΔVrip) = 135µF The practical value of capacitance available to support the output voltage of 50V is 220μF, 200V. Fig. 1. LAUNCHXL – F28027 Board Overview LAUNCHXL-F28027 Piccolo texas device is used to control the output voltage of the EMU. Among the 16 ADC channels of the F28027 device, A4 and A2 channels is configured for voltage sensor and current sensor respectively. The sampling period of ADC is taken as 0.2ms (1/5000Hz). With this sampling period, SOC is configured and ADC process starts. Then the digital value is converted into the respective analog value of voltage and current. This value is fed as the input to the P&O algorithm. As the output of the algorithm the compare register value of ePWM is configured. Among the 4 channels of ePWM module of Piccolo device the first channel (1a &

Fig. 2b. Experimental setup of Boost Converter For low power application MOSFET is a suitable device and also for frequency 5 kHz, switching losses in MOSFET is not much higher.

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N. Sangeetha, A. Pavithra, S. Divya, A, and Akilandeswari

3.5 Software Implementation Code Composer Studio version 5 is used to develop the firmware for the processor All the system simulations have been performed using MATLAB.

4.

RESULTS

Simulation Results : Simulation of boost converter with calculated values of inductor and capacitor to get output voltage of 48V is carried out using MATLAB. The results are shown in Fig .3a & 3b.

Fig.3a Output Voltage

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Energy Maximizer for PV fed DC-DC Boost Converter

Fig.4b. Output Voltage-Validation Result-2 5.

CONCLUSION

Fig.3b. Inductor Current

Open loop test of power circuit:

This EMU is employed at micro level for each panel which Eliminates shading and mismatch losses. The proposed EMU will increase the power output of a PV plant and hence it will reduce the break even period of the investment in PV plants, this will in turn improve the availability of power in remote areas where PV is employed due to non availability of utility grid.

Input PV voltage

Duty cycle (%)

21

10

Boost converter output voltage 34

26

20

33

REFERENCES:

22

30

32

16 10

40 50

46 20

[1] O. Honorati, G. L. Bianco, F. Mezzetti, and L. Solero, “Power electronic interface for combined wind/PV isolated generating system,” in Proc. European UnionWind Energy Conf., Goteborg, Sweden, 1996, pp. 321–324. [2] B. S. Borowy and Z. M. Salameh, “Dynamic response of a stand-alone wind energy conversion system with battery energy storage to a wind gust,” IEEE Trans. Energy Conversion, vol. 12, pp. 73–78, Mar. 1997. [3] S. Kim, C. Kim, J. Song, G. Yu, and Y. Jung, “Load sharing operation of a 14 kW photovoltaic/wind hybrid power system,” in Proc. 26th IEEE Photovoltaic Specialists Conf., 1997, pp. 1325–1328. [4] K. Kurosumi et al., “A hybrid system composed of a wind power and a photovoltaic system at NTT kume-jima radio relay station,” in Proc.20th Int. Telecommun. Energy Conf., 1998, pp. 785–789. [5] C. Grantham, D. Sutanto, and B. Mismail, “Steady-state and transient analysis of self-excited induction generators,” Proc. Inst. Elec. Eng. B, vol. 136, no. 2, pp. 61–68, 1989. [6] R. Leidhold, G. Garcia, and M. I. Valla, “Field-oriented controlled induction generator with loss minimization,” IEEE Trans. Ind. Electron., vol. 49, pp. 147–155, Feb. 2002. [7] S. Arul Daniel and N. Ammasai Gounden, “A Novel Hybrid Isolated Generating System Based on PV Fed Inverter-Assisted Wind-Driven Induction Generators”, Ieee Transactions on Energy Conversion, VOL. 19, NO. 2, Jun 2004 [8] M. Arutchelvi and S. Arul Daniel, “Voltage control of autonomous hybrid generation scheme based on PV array and wind-driven induction generators”, Electric power components and systems, Vol. 34, No.7, pp.759-773, July 2006. [9] Brian G. Finan, “Maximum Power Point Tracking for Solar Power Applications with Partial Shading”, National University of Ireland, April 2013.

. The above table shows the output voltage of the power circuit under open loop control.

Fig.4a. Output Voltage-Validation Result-1 The above figures show the constant output voltage of the power circuit irrespective to PV input voltage variation.

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Students Journal of Electrical and Electronics Engineering, Issue No. 1, Vol. 1, 2015

AUTOMATIC CONTROL OF ALTERNATOR PARAMETERS IN A POWER STATION USING PLC RV Subramanian, M. Gowthaman and R. Ezhamparithi Saranathan college of engineering, Tiruchirappalli, Tamil Nadu, India. Abstract—The objective of our dissertation is to control generator parameters using Programmable Logic Controllers (PLC) in thermal power stations. In most of the old power stations and captive power stations the control of alternator parameters is presently done by relay logics or controlled manually. In such cases , the control of generator parameters can be done by using PROGRAMMABLE LOGIC CONTROLLERS ( PLC ). GENERATOR PARAMETERS which are controlled under closed loop are 1)Stator current 2)Stator voltage 3)Rotor current 4)Rotor voltage 5)Rotor temperature 6)Stator Cu temperature 7)Cooling gas temperature 8)Seal oil drain temperature 9)Seal oil pressure 10)Active load 11)Reactive load 12)Power factor. The system which is in existence to control the generator parameters in Thermal power stations is Distributed Digital Control system (DDC) which houses microprocessors. However DDC cannot be used in captive power plants and other small power stations due to cost constraints. 1. INTRODUCTION The alternators work on the principle of electromagnetic induction. When there is a relative motion between the conductors and the flux, emf gets induced in the conductors. Synchronous machines are principally used as alternating current (AC) generators. The generators used in the Thermal Power Plant are synchronous generators. They supply the electric power used by all sectors of modern societies viz industrial, commercial, agricultural, and domestic. Synchronous generators usually operate together (or in parallel), forming a large power system supplying electrical energy to the loads or consumers. Synchronous generator converts mechanical power to ac electric power. The source of mechanical power, the prime mover here is a steam turbine. The main generators used in the thermal power stations are separately excited generators. For this purpose another synchronous generator is installed on the same shaft of the turbine and the main generator which is called exciter. The exciter is a self excited synchronous generator. In the initial start-up the DC supply is

given to the field winding of the exciter by the DC batteries for 4 seconds. After that the DC batteries are cut-off and the DC supply is given to the field of the exciter by its own generator supply after the rectification. The AC supply generated by the exciter is also given to the field winding for its excitation after the rectification. The AC produced by the exciter is sent to the rectifier room where it is converted into controlled DC supply by thyristor. The firing angles of thyristor are controlled by AVR(Automatic Voltage Regulator) and hence the excitation of the generator is controlled.

S. NO 1. 2. 3. 4. 5. 6.

Table 1. Generator Particulars PARTICULARS 50 MW 100 MW Max continuous KVA rating Max continuous KW Rated terminal

9.

Rated stator current Power factor Excitation current at MCR condition Slip ring voltage at MCR condition Efficiency at MCR condition Rated speed

10.

Rated frequency

7. 8.

62500K VA 50000K W 10500+ _5%V 3440A 0.8 640A

117500 KVA 100000 KW 10500+_5 %V 6475A 0.85 1600A

224V

240V

98.4%

98.4%

3000 rpm 50Hz

3000 rpm 50Hz

2. STATIC EXCITATION SYSTEM The static excitation equipment is one which supplies the required excitation current to the generator rotor field and which regulates the generator voltage by direct influence on the excitation current controlled rectifiers replaces the old usual exciter machines. The required excitation power is supplied by a 3.3 KV/ 380 V, 3-phase, star-delta transformer to the thyristor and from the thyristor, the rectified power is delivered to the generator slip rings through field breaker. The system is normally fed from the generator terminals, but in our station, it is fed from the 3.3KV unit section of the respective units.

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Automatic control of alternator parameters in a power station using PLC

DESIGN FEATURES 

  







The excitation system controls the field voltage the generator in such a way that the transient change in the voltage in the regulated voltage are effectively suppressed and sustained. Oscillations in the regulated voltage are not produced by the excitation system during steady state load condition. The generator terminal voltage is maintained constant within +/-0.5% of the present value over the entire load range of the machine. The excitation system is capable of providing field forcing for the maximum duration of 10seconds. The response of the excitation system is such that 90% of ceiling voltage emerges in 40milliseconds, at 5% drop in generator terminal voltage. The system incorporates a device for controlling volt/frequency ratio, which enables the regulation to be proportional to the frequency below a pre-determined cut-off frequency. The thyristor converter is based on (n-1) principle i.e. if one parallel bridge goes out; the remaining bridges are rated to meet the nominal excitation and field forcing excitation requirements of the generator without exceeding permissible operating temperature. The AVR measurement circuit suitable for 5A or 1A CT secondary and 110V PT secondary.

 Frequency range of operation: 48.5 to 51.5 Hz  Accuracy with which generator voltage is held: better than +/-0.5%  % of transformer drop compensation: 0 to 15%  Maximum change in generator voltage: <0.5%  When AVR is changed from ‘Auto’ to ‘Manual’ under all condition of excitation.  Manual control range: 0-105% of generator terminal.  Response time: <50milliseconds. 3. SIGNIFICANCE OF EACH PARAMETER Generator Current: Generator current (Ig) depends on the active load, the stator current should never be allowed to go beyond the full load current for a 50 MW alternator. At 10.5 KV GTV, the full load generator current is 3440 A and for 100 MW generator the full load stator current is 6500 A. There are chances in some instant that the generator current may go beyond this full load limit due to excessive steam input. Generator Terminal Voltage (GTV): As the turbine is spinning at 3000 rpm, the generator rotor coupled to the turbine will also spin at 3000 rpm. When DC voltage is injected into rotor circuit, voltage in induced across the stator terminals of the stator winding. For the alternator in thermal power station-1 of NLC, the GTV is 10.5 KV. The GTV may also be in range of 11 KV or 15 KV etc. The GTV depends on the rotor voltage. When the machine is loaded, the GTV leads to fall and the excitation level has to be increased to maintain the GTV at constant level. Similarly when the load on the machine suddenly drops down, the GTV leads to rise and the excitation will be decreased and so maintain the GTV. Rotor Voltage:

Fig. 1. Single line diagram of stator exciter control panel AVR parameters  Range of voltage level adjustment: in all modes of operation of generator.

+/-10%

For a 50 MW machine the rotor voltage will be in the range of 140-160 V DC and for a 100 MW machine, the rotor voltage will be in the range of 220-240 V. When the rotor voltage is increased or decreased the active load on the machine increases or decreases. The static excitation system always maintains the GTV constant irrespective of the load condition by varying the rotor voltage or current. Rotor Current The rotor current is otherwise known as field current (If). The rotor current varies upon the active

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RV Subramanian, M. Gowthaman and R. Ezhamparithi

load on the machine. The rotor current is equally shared by the converter bridges in the SEE system. When there is any problem converter bridge will get overloaded. Action has to be taken to rectify the fault converter bridge. The exciter in the excitation system automatically takes action in the case of any abnormal rotor current. Hydrogen Pressure Another vital parameter controlled in the alternator is hydrogen pressure. Hydrogen is used for cooling purpose inside the alternator. Thermal conductivity of the hydrogen increases with increase in hydrogen pressure. Hydrogen is locked up inside the alternator in pressurized condition.

low/high is monitored with an alarm system and is acted upon manually by the engineer inside the control room. Hot Gas Temperature This the temperature of the hydrogen gas at the outlet of the generator. The cold gas as it enters the generator it is made to circulate inside the alternator. The hydrogen gas takes away the heat from the winding and it gets heated up and its temperature rises. The maximum allowable hot gas temperature increases, it has to be ensured whether the cooling condensate flow is proper or not. Load reduction has to be done as a last measure. Seal Oil Temperature

For a 50 MW machine, the hydrogen pressure inside the alternator is 1.0 KAC and for a 100 MW machine, the hydrogen pressure is 2.0 KAC. Hydrogen pressure low/high is acted upon manually by the engineer inside the control room. Copper Temperature When the load on the machine increases copper temperature tends to go high. The copper temperature should not be allowed to go beyond a preset limit. Alternators are provided with "class F" insulation and hence the maximum permissible temperature is 130 deg Celsius. In the stator side the temperature is restricted to 110 deg Celsius. The copper temperature of a machine increases on the following occasions:  When the active load on the machine increases.  When the reactive load on the machine increases.  When the cooling condensate pressure decreases.  When the cooling condensate flow decreases.  When the H2 pressure decreases.  When the H2 purity decreases. Iron Temperature Iron temperature of the alternator should be maintained within prescribed limit. Iron temperature may also tend to rise when the load on the machine goes beyond the limit. The iron temperature is recorded at various points of the alternator and they are monitored continuously. Cooling Gas Temperature This is the temperature of the hydrogen gas at the inlet of the generator. The safe limit of the cold gas temperature is 45 deg Celsius. The cold gas temperature may rise when the cooling condensate water/pressure/flow decreases. The temperature

Another generator parameter of generator to be considered is seal oil temperature. The generator seals are provided at both ends of the generator in order to prevent hydrogen from escaping. The generator seals are provided with seal liners and the seal liners are made up of special alloy " Babbitt metal ". The Babbitt metal can withstand temperature up to 70 deg Celsius. So the seal oil temperature has to be maintained well below this value. The seal oil temperature should be maintained in the range of 50 to 55 deg Celsius. When then seal oil temperature increases, steps have to be taken to increase the flow and pressure, to bring down the temperature. This can be done by adjusting automatic pressure regulator. Seal Oil Pressure As already discussed, the seals are provided for sealing the hydrogen gas in the generator. The seal oil pressure maintained depends on the hydrogen pressure inside the generator. Seal oil pressure maintained for a 50 MW generator is 1.5 KSC and for 100 MW it is 2.15 KSC. The seal oil pressure is adjusted automatically by the pressure regulator so as to maintain a constant pressure difference of 0.5 KSC. When the seal oil pressure reduces below a certain limit, seal oil pressure low annunciation will come into control room. When the pressure rises, seal oil pressure annunciation will come, pressure intercool is provided for starting the reserve oil pumps when the seal oil pressure drops below normal limit. When the seal oil pressure becomes very low, then the hydrogen will start escaping from the generator which is very dangerous. When the oil pressure becomes high, oil enters the generator

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Automatic control of alternator parameters in a power station using PLC

which is also highly dangerous. Hence seal oil pressure has to be maintained always. PRACTICAL DIFFERENCE BETWEEN PLC AND DCS:

PLC

DCS

1. Flexible: It is possible to use just one model of a PLC to run and control 'n' no. of machines.

1. 15 machines might require 15 different controllers.

2. When a PLC program circuit or sequence design change is made, the PLC program can be changed from the keyboard sequence in a matter of minutes. 3. A PLC program change cannot be made unless the PLC is properly unlocked and programmed.

2. With a wired relay panel, any program alternations require time for rewiring of panels and devices.

4. The PLC is made of solid state components with very high reliable rates.

4. Mechanical system or relays are less reliable compared to PLC.

5. PLC control is a singlehouse type controller where in all the control is made available under one roof.

5. DCS deploys a wide spread control system, there is a threat of damage in communication system.

3. Relay panels tend to undergo undocumented changes.

instruments in the field. The inputs and outputs can be either analog signal which are continuously changing or digital signals which are 2 state either on or off .

Fig. 2. Flow chart representation of various parameter control In other words it acts as a Human Machine Interface (HMI). The input/output devices (I/O) can be integral with the controller or located remotely via a field network. DCSs are usually designed with redundant processors to enhance the reliability of the control system. Most systems come with displays and configuration software that enable the end-user to configure the control system without the need for performing low-level programming, allowing the user also to better focus on the application rather than the equipment.

4. THE PRESENT SYSTEM OF PARAMETER CONTROL

5. PARAMETER CONTROL USING PLC

A Distributed Digital Control Management Information System (DDC MIS) is a control system for a process or plant, wherein control elements are distributed throughout the system. This is in contrast to non-distributed systems, which use a single controller at a central location. In a DCS, a hierarchy of controllers is connected by communication networks for monitoring and controlling.

Each different electronically controlled production machine required its own controller. 15 machines might require 15 different controllers. Now it is possible to use just one model of a PLC to run anyone of the 15 machine. Furthermore we probably need fewer than 15 controllers, because one PLC can easily run many machines. Each of the 15 machines under PLC control would have its own distinct program.

A DCS typically uses custom designed processors as controllers and uses both proprietary interconnections and standard communications protocol for communication. Input and output modules form component parts of the DCS. The processor receives information from input modules and sends information to output modules. The input modules receive information from input instruments in the process (or field) and the output modules transmit instructions to the output

With a wired relay panel, any program alternations require time for rewiring of panels and devices. When a PLC program circuit or sequence design change is made, the PLC program can be changed from the keyboard sequence in a matter of minutes. No wiring is required for a PLC controlled system. Also if a programming error has to be corrected in a PLC control ladder diagram, a change can be typed in quickly.

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RV Subramanian, M. Gowthaman and R. Ezhamparithi

respect to the reaction time set on the timer. As soon as the memory M0 picks up after time delay T0, Q0 i.e. Excitation is reduce signal is generated. On the other hand if the Field current stays abnormal for too long timer T 2 trips the unit. The action sequence is as follows M0-M4-M6-T2.

Fig. 3. Block diagram representation of DDC MIS in power plants Relays can take an unacceptable amount of time to actuate. The operational speed for the PLC program is very fast. The speed for the PLC logic operation is determined by the scan time, which is a matter of milliseconds. Below given figure (fig. 4) shows the ladder logic for PLC operation of parameter control. 1. I0 – Rotor or Field current 2. I1 – Rotor or Field voltage >160V 3. I2 – Rotor voltage < 140V 4. I3 – Copper and Iron temperature 5. I4 – Hydrogen gas pressure 6. I5 – Cooling condensate flow and pressure 7. I6 – Generator current > Full load current 8. I6 – Generator current > Full load current 9. I7 – Generator current > Full load current + 10% 10. I9 – [(Machine voltage) – (Grid voltage)] < or = 0 11. Q0 – Decrease excitation 12. Q1 – Increase excitation 13. Q2 – Charge hydrogen 14. Q3 – Unit tripped due to abnormal generator parameter 15. Q4 – Reduce load 16. Q5 – All parameters in normal condition 17. Q6 – All parameters in abnormal condition The hydrogen cooling system for instance, PLC has multiple inputs and multiple output arrangement. Hence, the inputs of PLC can be connected to sensors to keep track the value of hydrogen pressure, hydrogen purity and hydrogen temperature. A brief explanation on how Rotor current I0 control can be employed with this logic. Whenever the rotor current value goes below the specific reference value the switch I0 closes and the memory M0 picks up. Parallel operation takes place with

Fig. 4. PLC Ladder logic 6. CONCLUSION In the project , effort has been made to demonstrate what are all the alternator parameters, how they are controlled in power stations by Distributed Digital Controls and Management Information System (DDCMIS) . The significance of each parameter is also dealt with. A few suggestive measures to improve the existing system by introducing a PLC is also discussed. Moreover the suggested model will be useful in captive power plants where distributed Digital Controls and Management Information System (DDCMIS) is not available. REFERENCES 1. 2. 3.

Power system model and control by A.J.Calvaer. Programmable logic controllers by Webb John W, Reis Ronald A. Programmable logic controllers 5th edition by George Bolton.

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Students Journal of Electrical and Electronics Engineering, Issue No. 1, Vol. 1, 2015

SINGLE PHASE SINE WAVE PWM INVERTER E.Balamugunthan, M.A.Kadar Basha, M.Muruganandam, M.Vimalrasu Final year EEE, Saranathan College of Engineering [email protected], [email protected], [email protected], [email protected] ABSTRACT - This project thesis is about the brief overview of Single Phase Sine Wave PWM inverter. The main advantage of PWM is that power loss in the switching devices is very low. This project deals with studying the basic theory of a Sinusoidal Pulse Width Modulated Inverter (SPWM), it’s simulink modelling, estimating various design parameters and the hardware implementation of the inverter and a transformer for its practical application. The project will be commenced by a basic understanding of the circuitry of the SPWM inverter, the components used in its design and the reason for choosing such components in this circuitry.

R2=2R1.The R value is calculated by using the formula, f = 1 / (2*3.14*R*C) R= 1 / (2*3.14*50*1x10^-6) R= 3.3x10^3 ohmR2=2R1 R2=1.5x10^3 ohm, R1=860 ohm

Keywords-SPWM, Inverter, Transformer 1.

INTRODUCTION

The main objective of this project is to construct a prototype of practical inverter circuit. For that,first we have to design and implement the SPWM generator for control of Inverter and then to design and implement transformer for inverter. A survey of different PWM techniques is performed considering the efficiency,type of inverter used and the type of switch used in the inverter.Based on the survey Sine Wave PWM technique is chosen since it is more advantageous than other techniques(driver circuit is not required).The half bridge inverter is chosen

Fig 2. Sine Wave Generator

Fig 3. Sine Wave output Fig 1. Block diagram of Sine Wave PWM Inverter 1.1 Sine Wave Generator: The single phase sine wave is generated with the help of Wein Bridge oscillator. To get the desired frequency of 50Hz and peak-peak voltage of 12V it is assumed to take C=1uF and

1.2 Triangle Wave Generator: The triangular wave is generated using Triangular Wave generator circuit. Two LM324N ICs are used to generate the triangle wave with the frequency of 1 KHz and peak-peak voltage of 20V. Output Voltage Vo= (2R3/R2) Vsat Where Vsat=15 V, Vo=20 V 20=2(15)(R3/R2) 2R3=R2

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Single Phase Sine Wave PWM Inverter

To get the desired frequency of 1 KHz, Let us assume, C1=1uF, R3=10x10^3 ohm fo=4 / (R1*C1*R3) 1KHz=16x10^3 / (4*R1*1x10^-6*10x10^3) R1=400 ohm

load. Sine wave PWM signals are given to the gates of the MOSFET switches.

Fig 4. Triangle Wave Generator Fig 6. Comparator circuit

Fig 7. Inversion of gate pulses

Fig 5. Triangle Wave Output 1.3 PWM generation: The gating pulses required for turning ON the MOSFET switch is generated by comparing the Sine Wave with the Triangular wave. Depending upon the Modulation Index chosen the width of the pulse is varied. The LM324N IC is used as comparator. To turn ON the switches alternatively it is necessary to produce two gating pulses. The gate pulses generated for the first switch is inverted and it is given to the second switch. Inverter Overview: A single phase half bridge inverter with two MOSFET switches are used to convert the 12V DC into 230V AC.Two switches S1 and S2 are used to chop the DC supply and a transformer converts this pulsating 12V DC into 230V AC. The inverter output power 500W is given to a resistive

Fig 8. Gate pulses The MOSFET turns ON and OFF depending upon the Gate pulse and the duration of ON and OFF are determined by the width of SPWM. When S1 is ON: When switch S1 is ON the current flows through the upper half of the centre tapped

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E.Balamugunthan, M.A.Kadar Basha, M.Muruganandam, M.Vimalrasu

transformer. Hence flux linkage is established at the secondary. During this switch S2 is maintained in OFF state. When S2 is ON: When the switch S2 is ON the current flows through the lower half of the centre tapped transformer. Hence flux linkage is established at the secondary. During this switch S1 is maintained in OFF state.

Circular mil for secondary = 2.17 X 700 = 1519 circular mils d = √A = 38.97 mils 38.97 mils = 38.97/1000 = 0.038 inch SWG = 20 Core geometry: Selected core is ETD44 so Ae = 175 mm2 taken from core data book. Assume Bmax = 1500 G E = 4.44fФmN = 4fBmAeN N1/2 = E/ (4fBmAe) = E/ (4fBmAeX10^-8) N1/2 = 12X10^8/ (4X1000X1500X1.75) = 114.286 = 115 N1= 230 turns N2= 3120 turns 1.5 Hardware Setup:

Fig 9. Schematic of Inverter 1.4 Transformer design: Assume the worst case efficiency of transformer is 80% Po = 500Wtransformer efficiency Ƞ = Po / Pin Pin = 500 / 0.8 Pin = 625W Secondary current, I rms-s = output power/output voltage I rms-s = 500 / 230 I rms-s = 2.17 A Primary current, I m = Pin / Vin = 625/12 = 52.08 A I rms-p = Im / √2 = 36.82 A 1.5 Wire gauge: It is chosen based on the value of current density. Usually 500 to 1000 circular mils/Amp. Now multiply this with current to get circular mil. Circular mil for primary = 52.08 X 700 = 36456 circular mill 𝜋𝑟 2 = 36456 A = d2 d = √A = 160.54 mils 1 inch = 1000 mils 1 mil = 1/1000 inch 160.54 mils = 160.54/1000 = 0.16inch SWG = 8

Conclusion: Thus the single phase sine wave PWM inverter has been simulated in Multisim software and implemented practically. In future a LC filter circuit can be added to reduce the harmonics at the output side. Reference: [1] Linear Integrated Circuit by Dr. ROY CHOUDRY. [2] Power Electronics: circuits, devices and applications by M.H.Rashid. [3] Power Electronics: converters applications and design by Mohan, Undeland and Robbins. [4] Design of transformers by Indragit Dasgupta.

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Student Journal of Electrical and Electronics Engineering Issue No. 1, Vol. 1, 2015

POWER CONTROL UNIT OF A HYBRID PV-UTILITY SOLAR PUMP G.AravinthVignesh, A.ArunKumar, D.SaravanaKrishnan, R.Srinivas Final year EEE, Saranathan College of Engineering, Trichy -12 [email protected] Abstract:— This work proposes to develop a novel power control unit (PCU) using Texas Instruments microcontroller TMS320F28027 for a hybrid PVutility solar pump that employs a squirrel cage induction motor (SCIM) replacing the Permanent magnet DC motor (PMDCM)which is normally used in the most of the existing solar pump applications . The cost of SCIM is several times cheaper than that of PMDCM. The power circuit consists of a single stage inverter whose output drives the three phase SCIM. The Inverter is controlled in such a fashion by the PCU, so that the frequency of the inverter is modified based on the available DC link voltage which is fed from PV array. The PCU will provide a output voltage such that v/f remains constant despite of the variations in PV voltage caused due to change in irradiation. The unique feature of the proposed PCU is, it is possible to operate the pump with utility supply also whenever the PV voltage fails due to low irradiation or during nights. The priority is given to PV mode of operation which is decided by the controller. The power circuit of the PCU includes a three phase inverter and a parallel three phase AC voltage controller circuit using back-back scr’s in each phase, while the control circuit includes a C2000 launch-pad, DAP signal conditioning board, Hall effect Voltage sensors and 430BOOSTSHARP96 - Sharp Memory LCD Booster Pack for display of parameters. The proposed PCU will be validated using a 2.4 kW PV panels available with the institution.

of same operating range. Squirrel Cage Induction Motor (SCIM) is one of the most robust motor and it doesn’t need frequent maintenance. Hence we replaced DC motor by Induction motor. The main disadvantage of solar pump is we can’t use it during night time, rainy season and cloudy days. In order to overcome this we’ve decided to implement automatic changeover between PV and Utility. For implementing this we’ve designed a hybrid controller using Texas Instruments microcontroller TMS320F28027. Our ultimate aim is to help our farmers by designing a controller for the energy efficient operation of solar pump driven by existing Induction motors for cultivating crops throughout the year. As a result our nation’s productivity and GDP will be improved.

Keywords—PWM, PV, LCD, PCU, DAP, SCIM, PMDCM, ADC and EPWM.

Fig. 1 Power Circuit of a Pump

1.

2. PROPOSED SOLUTION

INTRODUCTION

The main reason for the reduction in food materials production is lack of water supply. Even though we have Motor-Pump set for irrigation it can work for 3 hours per day in summer because of power crisis. In Tamil Nadu we are receiving solar energy throughout the year. So if we replace Utility operated Motor Pump with Solar operated water pump we can supply water from morning to evening. At the same time we can reduce the major part of our utility demand which further enhances the power quality by providing uninterrupted power supply. This thought made us to work on Solar operated water pumps. The Solar pumps available in markets were driven by DC motors. Since motors have to be placed in open space DC motors need frequent maintenance. Also the costs of DC motors are much higher than Induction motors

Fig. 2 Functional Block Diagram of PCU

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G.AravinthVignesh, A.ArunKumar, D.SaravanaKrishnan, R.Srinivas

The SCIM is proposed to replace the PMDCM used in the present solar pump, which will reduce the cost. The power circuit of the proposed solution is shown in Fig. 1. The pump is fed by a three phase inverter which in turn if fed by the PV arrays. The functional block diagram of the PCU (power control unit) of the proposed hybrid solar pump is shown in Fig. 2.Functional features of PCU – 1.Provide variable frequency variable voltage output by maintaining v/f constant which will improve the efficiency of motor 2. Once the irradiation falls below a certain level, automatic changeover to utility 3. Maximize the frequency of SCIM by maintaining v/f constant. 2.1 Description for Sub-Systems:

Hardware implementation for the same setup could be explained in implementation Section. 3. IMPLEMENTATION 3.1 Hardware Implementation 3.1.1 Voltage Sensor:

Fig.3 Voltage Sensor

PV Array- 2.4 kW 3 Phase Inverter: Rating of the Inverter is 7kVA SCIM: Power rating of Squirrel Cage Induction Generator is 5HP Voltage Sensor: Sensor used here is a Hall Effect Sensor, for sensing dc link voltage of inverter Signal Conditioning Unit: one DAP Signal Conditioning Board (Unipolar) is used to interface the sensor signals with ADC of the TMS320F28027. C2000 Launch Pad: Evaluation Module from Texas Instruments is used as a controller LCD Display: Sharp Memory LCD Booster pack for displaying various parameters HMI: Human Machine Interface unit for operating the pump Driver Circuit: It boosts the Microcontroller output voltage of 3.3V to 15V and given to the gates of IGBT’s Power Supply: Power supply is designed from Webench tool from Texas. It supplies i. LCD Display (+5V), ii. Voltage & Current Sensor (±15V), iii. C2000 Launch Pad (5V), iv. Driver Circuit (+5V, +15V)

The implementation V/f control for the energy efficient operation of induction motor is done. Since the PV voltage varies from time to time we are using voltage sensor for sensing the variation in PV voltage.

In the functional block diagram of PCU, the voltage sensor senses the voltage accordingly to the voltage from PV solar panel, which is given to the Signal Conditioning Unit. The purpose of SCU is convert bipolar to unipolar signal. The power supply unit is made for the functioning of SCU, C2000 Launchpad, LCD display, driver circuits and level shifters. The level shifters shifts the 5v to 15v.Human Machine Interface acts as a interface between user and controller to provide inputs.

3.1.3 C2000 Launchpad:

The Power Circuit holds the responsible for powering of pump. The input from PCU’s fed to the inverter, which takes supply from solar PV panel, if the solar power is available. Otherwise, the supply would be taken from 3 phase 440v supply. The operation of motor is being controlled by C2000 Launchpad by means of ADC and ePWM Signals.

3.1.2 Signal Conditioning Circuit:

Fig.4 Signal Conditioning Circuit The purpose of signal conditioner is to convert bi polar signal into unipolar signal. It performs both clipping and clamping operations to maintain the input to processor within limit.

Fig. 5 C2000 Piccolo Launchpad Processors

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Power Control Unit of a Hybrid PV-utility Solar pump

For implementing V/f control and to produce sinusoidal PWM pulse for gate we’ve used C2000 Launchpad from TEXAS INSTRUMENTS. 3.1.4 Level Shifter:

sensed by voltage sensor for which, frequency changes by C2000 processor. ADC signal is given to A2 pin of the C2000 processor.

Start Initialize the header files Initialize the global variable

Fig. 6 Level shifter Circuit The magnitude of output pulse from controller is 3.3V. To trigger the gate we need 15V. In order to shift the level from 3.3V to 15V we use level shifter IC CD4504BE from TEXAS INSTRUMENTS.

Select internal oscillator as clock source Initialize the header CPU,CLK,GPIO,ADC,PW M&PIE Setup PLL as 50MHz Setup debug vector table Register interrupt into PIE

3.1.5 LCD Display:

Configure ADC Setup PWM 1 for ADC SOC Define ADC interrupt

A

Set timer period=5.5KHz Fig.7 LCD Display To display the measured digital values we are using 430BOOST-SHARP96 - Sharp Memory LCD Booster Pack from TEXAS INSTRUMENTS. 3.2. Software Implementation The flow chart (a) and (b) inserted in proposed solutions. Initializations of the software implementation starts with initialize the header files and global variables. Select internal oscillator as clock pulse. Set Phase Lock Loop as 50MHZ. To save a memory we select a interrupt that store a values in temporary registers to avoid congestions. Triggering of ADC is done by PWM signal.PWM signal is given to A4 pin of c2000 processors. Here we use PWM module 1.Time period we taken is 5.5KHZ.To generate triangle wave we had used a UPDOWN counter. These blocks fed into the compare registers. We draw another flowchart (b) that fed in compare register in flowchart (a).In flowchart (b) it shows the changing voltage corresponding to frequency. Voltage value is

Setup TBCLK=50MHz Setup UPDOWN counter Setup compare register

B

Set action qualifiers Setup the dead band End

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G.AravinthVignesh, A.ArunKumar, D.SaravanaKrishnan, R.Srinivas

A Configure ADC (A2) for the voltage sensor

Vactual= voltage sensor gain

Values are compared using cmp variable corresponding to voltage These compared values of cmp is given to flowchart (a).Here we got the voltage corresponding to frequency was done.

List of Formulae:

Fo=ma *conversion factor*vactual

If (i>1)

Where, Vdc = DC input voltage F=frequency V01_line_line_rms = Line to line output rms voltage.

Cmp A=ma*TBPRD*Sine A(i) cmp B=ma*TBPRD*Sine B(i) cmp C=ma*TBPRD*Sine C(i)J=F/10

If(i>=105)

i=1

Fig. 8b conversion involved in implementing V/f control in MATLAB Simulink.

Update compare register values Goto (B) MATLAB Simulation:

Fig. 8c shows producing sinusoidal PWM in MATLAB Simulink model. 4. RESULTS

Fig. 8a MATLAB/Simulink Model for inverter fed induction motor supplied by a variable voltage source.

The simulation is done using MATLAB/Simulink of a PV fed inverter fed induction motor. The operation of the induction motor based pump has been depicted in Fig. 2, which shows the different variables like motor voltage, frequency, V/F ratio, PV voltage under varying conditions of Irradiation. From below Fig.1 it can be observed the speed (and hence the power and flow) of

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Power Control Unit of a Hybrid PV-utility Solar pump

the pump varies with change in irradiation. The change in irradiation causes the PV voltage and hence the inverter voltage fed to the motor changes. The controller in the PCU automatically changes the frequency of the inverter in order to maintain v/f constant as shown in below Fig. Maintaining v/f and hence flux of the SCIM constant, the efficiency is increased. This figure shows the variation of frequency corresponding to voltage.

5. CONCLUSIONS The present solar pumps driven by DC motors are very costlier and they need proper maintenance. By replacing the DC motors with Induction motor we can reduce the cost. Some solar pumps driven by AC motors need special construction and normal motors can’t be used during night time. All these problems can be rectified by replacing DC motors with Induction motors and converting the system into a Hybrid one by adding provision for operating it with utility service. REFERENCES O. Honorati, G. L. Bianco, F. Mezzetti, and L. Solero, “Power electronic interface for combined wind/PV isolated generating system,” in Proc. European Union Wind Energy Conf., Goteborg, Sweden, 1996, pp. 321–324. 2. B. S. Borowy and Z. M. Salameh, “Dynamic response of a stand-alone wind energy conversion system with battery energy storage to a wind gust,” IEEE Trans. Energy Conversion, vol. 12, pp. 73–78, Mar. 1997. 3. S. Kim, C. Kim, J. Song, G. Yu, and Y. Jung, “Load sharing operation of a 14 kW photovoltaic/wind hybrid power system,” in Proc. 26th IEEE Photovoltaic Specialists Conf., 1997, pp. 1325–1328. 4. K. Kurosumi et al., “A hybrid system composed of a wind power and a photovoltaic system at NTT kume-jima radio relay station,” in Proc.20th Int. Telecomm. Energy Conf., 1998, pp. 785–789. 5. C. Grantham, D. Sutanto, and B. Mismail, “Steady-state and transient analysis of selfexcited induction generators,” Proc. Inst. Elec. Eng. B, vol. 136, no. 2, pp. 61–68, 1989. 6. R. Lei hold, G. Garcia, and M. I. Valla, “Fieldoriented controlled induction generator with loss minimization,” IEEE Trans. Ind. Electron., vol. 49, pp. 147–155, Feb. 2002. 7. S. Arul Daniel and N. Ammasai Gounden, “A Novel Hybrid Isolated Generating System Based on PV Fed Inverter-Assisted WindDriven Induction Generators”, Ieee Transactions on Energy Conversion, VOL. 19, NO. 2, Jun 2004 8. M. Arutchelvi and S. Arul Daniel, “Voltage control of autonomous hybrid generation scheme based on PV array and wind-driven induction generators”, Electric power components and systems, Vol. 34, No.7, pp.759773, July 2006. 9. M. Arutchelvi and S. Arul Daniel, “Composite controller for a hybrid power plant based on PV array fed wind-driven induction generator with battery storage”, International Journal of Energy Research, Vol.31, pp.515–524, April 2007. 10. Roger Dugan, Marc F.Mcgranaghan, “Electrical Power Systems Quality” 1.

.

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Student Journal of Electrical and Electronics Engineering Issue No. 1, Vol. 1, 2015

FUZZY OBSERVER BASED FLOW CONTROL OF INDUCTION MOTOR PUMP A.Ruban, R.Senthil kumar, M.Vijayaprabakaran, and C.Kamalahasan Final year EEE, Saranathan College of Engineering, Venkateswara Nagar, Tiruchirapalli-620012 [email protected],[email protected] Abstract—This work proposes to develop a novel power control unit (PCU) using Texas Instruments microcontroller TMS320F28027 for a fuzzy observer based flow controller of a pump. The proposed fuzzy observer based control unit is very much essential and finds application where the motor shaft is not accessible as in case of a liquid transfer pump. Flow of liquid like transmission of petroleum products and water over a long distance could be controlled by using the closed loop v/f control method based on fuzzy observer approach. This type of electrical flow control provides better energy conservation with smooth control of liquid flow. The unique feature of the proposed PCU doesn’t uses any speed sensor for sensing the speed of the pump and hence the flow. Also the proposed PCU founds application for speed control of induction motor where the speed sensing is not feasible by either a contact or a non-contact type speed sensor. The power circuit of the PCU includes a three phase inverter and three phase induction motor, while the control circuit includes a C2000 launch-pad, DAP signal conditioning board, Hall effect Voltage and current sensors and 430BOOSTSHARP96 - Sharp Memory LCD Booster Pack for display of parameters. The proposed PCU will be validated using a 5 kW water pumping station present in the institution. Keywords— fuzzy observer, v/f control. Pump. 1. INTRODUCTION The analysis is made considering the different ratings of VFD used, applications, price and features of the products. It is observed from the analysis, most of the flow controller uses a open loop VFD drive, where speed sensing is not possible and hence the dynamic performance is compromised. The proposed PCU overcomes this issue and intend to provide a closed loop control and enhanced dynamic performance without sensing speed.VFD drives combined with fuzzy logic provide closed loop control of induction motor pump. Fuzzy logic used where ever a system cannot modeled by mathematical analysis.FLC based on fuzzy logic provides a means of converting a linguistic control strategy based on expert knowledge into an automatic control strategy .Using TMS320F28027 the expected pulse can be given to the inverter.

1.1.1Technical Background The fuzzy logic Controllers are basically put to use when the system is highly non-linear thereby, making the mathematical modeling of the system very arduous. The analytical form of the system is not provided, instead a linguistic form is provided. The precise identification of the system parameters is needed. The system behavior has a vague characteristic under precisely defined conditions. The conditions themselves are vague. The Fuzzy Logic Controller used in this simulation has some drawbacks along with is advantages. But these disadvantages, viz. (i) achievement of only near to exact reference speed. After change in reference speed and (ii) high rise time, can be reduced by refining the membership functions. In this simulation we have taken hybrid of trapezoidal and triangular membership functions for the inputs and triangular membership functions for the output. We can choose Gaussian membership functions for refining the control. Also the membership functions near the zero region can be made narrower and those towards the outside can be made comparatively wider. The tuning of the control will be taken up as the next step for the project. The modified design of the Fuzzy Logic Controller was found to have a decent performance. The steady state error was found to be zero. Whenever the induction machine was loaded the speed of the machine fell, but only to a very little extent. The rise time and the settling time of the system were not affected much, but the peak overshoot of the system was found to have reduced as compared to the earlier design. Hence, this controller can now be used in other applications. But now the system has to be optimized so as to achieve an optimum value for the rise time, settling time and peak overshoot. 1.1 PROPOSED SOLUTION Power circuit

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Fuzzy observer based flow control of Induction Motor Pump

In this block diagram explains power circuit to the inverter. Here three phase input is given to the three phase rectifier. in order to filter the harmonics ,the coupling capacitor is added between rectifier and three phase inverter. Rectifier converts AC input into DC output. This DC source input given to the inverter. Six gate pulse given to the inverter gate terminal from power control unit. Power Control Unit

conditioning unit is given to microcontroller. In microcontroller contains ADC section. Enhancement PWM is one of SOC to start the ADC conversion. Actual speed can be estimated by actual voltage and current values. for implementing the fuzzy algorithm, we need a corresponding information from the pump. The linguistic form of speed data of pump configured from expert knowledge .the various speed corresponding to a Voltage and current values tabulated from the experiment. From the tabulated values the expression of speed is derived with a values of voltage and current values. from the professional curve fitting software expression of the speed is derived from voltage and current values. 1.2 MICROCONTROLLER:

This block diagram includes LV25-P voltage sensor and LA25-P current sensor, signal conditioning unit, C2000 launch-pad microcontroller driver circuit, LCD display, three phase inverter. In this, actual speed is measured from combination of sensors ,signal conditioning unit and microcontroller Voltage and current measured by sensors .The measured voltage and current is given to the signal conditioning unit .signal conditioning unit is used for range matching, amplification and used to clamping and clipping .controller input should be positive values, so signal conditioning unit gives positive amplitude of voltage and current to microcontroller. Micro controller having four important sections used. That includes ADC, e-pwm signal, HMI, LCD display. The analog voltage and current value is given to the microcontroller. In this ADC will convert analog values into digital.LCD display used to display the digital values. Voltage sensor- Closed loop (compensated) voltage transducer using the Hall effect ·Insulated plastic case recognized according to UL 94-V0.low thermal drift, high bandwidth, high immunity to external interference. it having galvanic isolation between primary circuit(high voltage)and secondary circuit(electronic circuit).This voltage sensor used to measure up to 600V.current sensorlow temperature drift, optimized response time, current overload capability. This current sensor using the Hall Effect principle and measure up to 25A.signal conditioning unit-In this unit, gain magnitude is set by first two pot and required output adjusted by another two pot. this pots used for clipping and clamping operation.10V supply is given to signal conditioning unit. The input of signal conditioning unit is ac supply. This unit is used to clamp the input to positive values. the maximum value of output is 3.3V.The output of sensors is given to the signal conditioning unit. The output of signal

Launchxl-f280x microcontroller used for analog to digital conversion in the fuzzy observer concept. The speed can be displayed using analog to digital conversion. The corresponding rms Voltage and rms current noted. From the current and Voltage sensor data fed to the microcontroller. so microcontroller is very much needed for this specific application. 2. IMPLEMENTATION 2.1 Hardware Implementation Signal conditioning unit: its implemented using lm324 Ics .This signal conditioning unit having two channel input and output. one channel used for voltage sensor and another channel used for current sensor. first two amplifier used to adjust the gain magnitude and another two amplifier used for clipping and clamping action take place, DC compensating voltage given to the amplifier. pots used to adjust the gain magnitude and output voltage . 2.2 Schematic for SCB:

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A.Ruban, R.Senthil kumar, M.Vijayaprabakaran, and C.Kamalahasan

4. FLOW CHART FOR ADC

Voltage sensor: LV25-P voltage sensor used to sense up to 600V.voltage is measured between measuring point. Conversion ratio is 2500:1000.voltage between 100ohm resistors measured. Current sensor: LA25-p current sensor used to sense up to 25A.current is measured. 3. SOFTWARE IMPLEMENTATION 3.1 Professional curve fitting software: The experiment is conducted in a 5kw, 3phase induction motor. The motor is loaded continuously; the RMS value of current is noted. The corresponding voltage and speed is noted. Using the professional curve fitting software these values are tabulated. From this the speed in terms of voltage and current expression is obtained. The expression is, Y=a+bx1+cx2+dx12+cx22+fx12+gx22+hx1x2+ix12x2+jx1 x22 Y-speed, x1-rms voltage, x2-rms current. Here, a=8.3071e+02, b=4.4310e+00, c=-7.4884e+02, d=-6.9815e-03, e=1.8784e+02, f=1.1684e-05, g=-1.7203e+01, h=3.7648e-01, i=-2.3435e-04, j=-1.4815e-02 3.1 Code composer studio 5.5 This software is used to display the speed using the Vrms and Irms values.TMS28027 microcontroller used. This is very much used for analyzing the data. From this software we write a coding. In this coding Vrms and Irms for the motor values converted into digital form by using ADC in the microcontroller. By using this Vrms,Irms values corresponding speed is obtained by using the speed expression into that.

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Fuzzy observer based flow control of Induction Motor Pump

4. RESULTS In this fuzzy observer based flow controller, it is observed that speed of the induction motor pump mostly equal to the actual speed. The speed changed relatively change in the Voltage and Current.

Signal conditioning output: In this signal conditioning unit up to 2.45V output is pure sinusoidal and positive peak. Above that input voltage output is clipped.

5. CONCLUSIONS

Curve fitting software output graph:

The proposed project develop a low cost IMPump set using 1.Fuzzy observer based closed loop v/f control (enhance the dynamic response) 2.The problems associated with the speed sensing is overcome by using the fuzzy observer (without contact or non contact type sensors).The PCU for the proposed system constructed using the low cost TMS320F28027 processor. The prototype once developed has a clear potential for getting converted to a product with all the features mentioned above. A well defined methodology adopted for development cycle that will ensure a prototype confirming to its performance specification. REFERENCES [1]

[2]

[3]

[4]

[5]

[6]

Jamoussi K et al,” Robust fuzzy sliding mode observer for sensor less field oriented control of induction motor”, 6th International MultiConference on Systems Signals and Devices, 2009. SSD '09, 23-26 March 2009,pp.1-7. Benharir, N.; Zerikat, M et al,”Design and Analysis of a New Fuzzy Sliding Mode Observer for Speed Sensorless Control of Induction Motor Drive”, International Review of Electrical Engineering;Sep/Oct2012, Vol. 7 Issue 5, p5557 Xiao-Jun Ma et al,”Analysis And Design Of Fuzzy Controller And Fuzzy Observer” , IEEE Transactions on Fuzzy Systems ,Vol:6 , Issue: 1,Feb 1998,pp.41-51. Yimin Li,”Indirect adaptive fuzzy observer and controller design based on interval type-2 T–S fuzzy model”, Applied Mathematical Modelling,vol.36.issue:4, April 2012, PP 1558– 1569 Oudghiri M,” Lateral vehicle velocity estimation using fuzzy sliding mode observer”, Mediterranean Conference on Control & Automation, 2007. MED '07, 27-29 June 2007,pp.1-6 Xiaogang Feng et al,”Fuzzy-controlled DC drive system with load observer”, 4th International Workshop on Advanced Motion Control, 1996 18-21 Mar 1996,pp354-358.

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Student Journal of Electrical and Electronics Engineering Issue No. 1, Vol. 1, 2015

DESIGN AND IMPLEMENTATION OF AN PID CONTROLLED EFFICIENT BUCK-BOOST CONVERTER USING INTERLEAVED TOPOLOGY Santhanagopalan.A, Final year EEE, Saranathan College of Engg, Venkateswara Nagar, Trichy – 12. [email protected] the converter is improved than the conventional Abstract—A DC-DC converter is of great importance in the buck-boost converters. field of sustainable energy. This paper deals with the BuckBoost converter which converts a DC voltage to a higher value (step up) and also to a lower value (step down). But 2. BUCK-BOOST CONVERTER due to various switching losses, conduction losses across the passive elements, there is a reduction in efficiency which deteriorates the converter performance. Thus to avoid a Interleaved topology is employed. Where two buck-boost converters operate in parallel and reduce the switching stress and reduce the ripple content of the input current as the switches operate 180o out of phase. Thus this paper analyses the efficiency and the output values of both Buck-Boost and Interleaved Buck-Boost converter and the Fig. 1 Schematic diagram of Buck-Boost results are simulated with the help of MATLAB / Converter SIMULINK environment. Keywords: Buck-Boost converter; Interleaved Buck-Boost converter; Efficiency; Ripple cancellation. 1. INTRODUCTION A suitable DC-DC converter is required for designing high efficiency power systems. Among the various topologies, Interleaved buck-boost converter is considered as a better solution for high power systems due to improved electrical performance, reduced weight and size. Detailed analysis has been done to investigate the benefits of interleaved buck-boost converter compared to the conventional buck-boost converter topologies. Due to the current handling limitation of single switch, the output power is small, typically tens of watts. At a higher current, the size of these components increases, with increased component losses, and the efficiency decreases. The simplest way of describing a interleaved converter is to see it as consisting of several power stages (converter “phases”) with inputs parallel and drive signals shifted to ensure uniform distribution over a switching period . In pratical case there will be formation of harmonics and current ripples and voltage losses along the passive elements of the power converter. Hence the pratical values will be lesser than the calculated one.These losses can be reduced by using interleaved topology. Where the gate pulses to the transistors in parallel with the inductors are 180o out of phase with each other with the same frequency thus the ripples in the input inductor current will get reduced. And thus the efficiency of

Buck-Boost converter belongs to the family of basic power conversion topologies (the other two being buck and buck-boost derivative). The schematic diagram of buck-boost converter is shown in Fig. 1. Buck-Boost converters are probably the most versatile paths to sustainable energy power converters today. It is typically used when output voltage can be made either higher or lower than the input voltage. It uses only one switch, employing only one stage conversion, and requires inductors and capacitors for energy transfer. It provides output voltage of reverse polarity. Hence care must be taken by switching the terminals while using the converted power for practical applications. The relationship between the input voltage and the output voltage is (1) Where

is the duty cycle ratio. T on is the

ON time of the semiconductor switch and T is the switching period. In continuous current mode of conduction the selected value of inductance should be greater than the critical value of the inductance Lc. The value of inductance L and capacitance C can be found by [1]: (2) (3) Where I is the ripple current, Vc is the ripple voltage, f is the switching frequency, L is the filter inductance and C is the filter capacitance of the circuit.

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Design and implementation of an PID controlled efficient Buck-Boost converter using Interleaved topology

3. INTERLEAVED BUCK-BOOST CONVERTER

Hence the pratical values will be lesser than the calculated one. These losses can be reduced by using interleaved topology.The inductor and capacitor values of the interleaved buck-boost converter is derived from equation (2) and (3). 4. SIMULATION RESULTS AND DISCUSSION

Fig. 2 Schematic diagram of Interleaved Buck-Boost Converter Due to the current handling limitation of single switch, the output power is small, typically tens of watts. At a higher current, the size of these components increases, with increased component losses, and the efficiency decreases. The simplest way of describing a Interleaved converter is to see it as consisting of several power stages (converter “phases”) with inputs and outputs connected in parallel and drive signals shifted to ensure uniform distribution over a switching period . 4. DESIGN CONSIDERATIONS For designing the interleaved buck-boost power converter we must choose the appriopriate value for the inductor and capacitive filter used whose value is given by, (4) (5)

Table 1. Design parameters of Interleaved Buck-Boost Converter Parameter Input voltage( )

Values 10 V

Output voltage( ) Output power( Ripple voltage (Δ Ripple current(Δ ) Inductor (L1= L2) Output capacitance Resistance ) Duty ratio (d)

15 V 25 W 0.017 4.645 52µH 2.5 mF 9Ὡ 60 %

In pratical case there will be formation of harmonics and current ripples and voltage losses along the passive elements of the power converter.

Fig. 3. MatLAB / Simulink diagram of BuckBoost converter The proposed interleaved buck-boost converter is simulated using MATLAB / SIMULINK is shown in Fig. 3. The ultimate aim is to achieve a ripple free high efficiency buck-boost converter operation. Where the gate pulses to the transistors in parallel are 180º out of phase with each other with the same frequency thus the ripples in the input inductor current will get reduced. The interleaved buck-boost converter is designed using Table II. The designed DC-DC converter simulated using Matlab is depicted in Fig. 3. Input inductor current L1 and L2 are given in Fig. 4. The MOSFETs are operated by 180º out of phase, the ripple present in the current are eliminated. The current from the inductors are out of phase with each other, hence 3rd order harmonics present in the current is eliminated. Hence the small value of capacitor is enough to eliminate the rest of the harmonics present in the load current. The output voltage response of the buck-boost converter and interleaved buck-boost converter are given in Fig. 5. Both the circuits are simulated with the input voltage of 10 V and the duty cycle of the pulse given to the switches is 60 %. The obtained output voltage of the buck-boost converter is only 13.6 V, but the output voltage of the interleaved buck-boost converter is 15.05 V. Similarly the Output Current for the Buck-Boost converter is only 1.51A but it is 1.66 A in the case of an

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A. Santanagopalan

Interleaved Buck Boost converter, which shows that there is an improved efficiency.

The conduction loss (PSC) and switching loss (Pss) of the MOSFET are PSC = Rs× d × (Ia/1 – d)2

(7) (8)

PS = PSC + Psd

(9)

Where, Rs is MOSFET ON resistance, ton is the ON time of the switch, toff is the OFF time of the switch, d is the duty ratio, and IL is the current through an inductor. The conduction loss in the inductor (Pl)

Fig. 4 Input Inductive current ripple cancellation

Pl =RL× (Ia/1 – δ)2

(10)

The conduction loss (Pd) and switching loss (Psd) of the diode Pcd = RD ×Ia2 + VF× Ia

(11) (12)

Pd = Pcd + Psd

(13)

Where, VF is the forward ON Voltage, RD is the Diode resistance, and Ia is the output current. Thus the input power PIN = Pout+Ps+Pl+Pd

Fig. 5. Output Voltage and Output current of the Buck-Boost and Interleaved Buck-Boost Converter Both the converter output consists of peak overshoot. This ripple cancellation helps to reduce the voltage drop and increase the output voltages in the conventional and interleaved Buck-Boost converter. 5. EFFICIENCY ANALYSIS The efficiency calculation of the Buck-Boost and the interleaved Buck-Boost converter are given below: The equations corresponding to the calculations are, Efficiency =

(6)

(14)

Fig. 6 Efficiency graph for buck-boost and interleaved buck-boost converter Efficiency graph for buck-boost and interleaved buck-boost converter is portrayed in Fig. 10. The efficiency of both the converters are calculated using the equation (14) to (22). The load resistance is varied from 1 Ohm to 9 Ohm; the corresponding efficiency values are plotted. For every load resistance value efficiency of the interleaved buck-boost converter is higher than the conventional buck-boost converter. Thus it is evident from the above graph that the interleaving technique improves the efficiency of the BuckBoost converter by 2% to 6%. As it reduces the ripple and reduces the heat dissipation of the inductor used.

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Design and implementation of an PID controlled efficient Buck-Boost converter using Interleaved topology .6. DESIGNING OF CLOSED LOOP PID CONTROLLER FOR INTERLEAVED BUCKBOOST CONVERTER For designing the closed loop PID controller for the converter state space modelling is done to determine the transfer function of the system and then by using Ziger Nicholas chart and Routh stability criterion the values proportional, Integral and Differential gains are determined and the stability of the controller is determined through MATLAB programs from which the closed loop is simulated by SIMULINK.

(17) The state space parameters for mode 1 are given by,

(18)

5.1 .State Space Modelling There are four modes of operation for an interleaved buck-boost converter based on the ON/OFF state of the switches. Since this design deals only with two switches there are four states of operation which are tabulated below

(19)

5.1.2.Mode 2: Q1 OFF, and Q2 ON

Table 2. Modes Of Operation Of Interleaved Buck-Boost Converter Mode 1 2 3 4

Q1 ON OFF ON OFF

Q2 ON ON OFF OFF

5.1.1 .Mode 1: Q1 and Q2 ON In mode 1 operation, both transistors Q1 and Q2 are ON and diodes D1 and D2 are reverse biased. The inductor stores the supplied energy (1/2 LI2 ).

Fig. 8 Mode 2 Interleaved Buck-Boost Converter In mode 2 the transistor Q1 is OFF and Q2 is ON and the diode D1 is forward biased and D2 is reversed biased. Thus L1 discharges to the capacitor C1.The governing equations of mode 2 can be described by: (19)

(20)

Fig. 7 Mode 1 Interleaved Buck-Boost Converter The governing equations of mode 1 is expressed as

(21) The state space parameters for mode 2 are given by,

(15)

(16)

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A. Santanagopalan

(22)

(23)

5.1.3

Fig. 10 Mode 4 Interleaved Buck-Boost Converter

Mode 3: Q1 ON, and Q2 OFF

Finally, during the Mode 4 operation, the transistors Q1 and Q2are OFF and the diodes D1 and D2 are forward biased Thus both the inductors L1 and L2 discharges to the capacitor C1. The equations of mode 4 are

(29) Fig. 9 Mode 3 Interleaved Buck-Boost Converter (30) In the mode 3 operation, the transistors Q1 ON and Q2 OFF and diode D1 reverse biased and D2 forward biased. Thus L2 discharges to the capacitor C1 The equivalent circuit equations are derived as

(24)

(31) The state space parameters for mode 4 are given by,

(25)

(32)

(26) The state space parameters for mode 3 are given by,

(27)

(33)

Thus the state space equation for the entire system is given by, A=A1*d1+ A2*d2+ A3*d3+ A4*d4 Therefore,

(34)

(28)

5.1.4.MODE 4: Q1 OFF and Q2 OFF

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Design and implementation of an PID controlled efficient Buck-Boost converter using Interleaved topology

6.679e-013 s^2 - 3.692e006 s + 7.824e-008 ------------------------------------------------------- (39) s^3 + 44.44 s^2 + 2.462e006 s + 2.708e-008 (35) The step response of the transfer function is given below. The Characteristics equation is given by, Similarly, B = B1*d1+ B2*d2+ B3*d3+ B4*d4

1+G(s).H(s) = 0 (35)

(36)

(40)

Now, by using Routh stability criterion and Ziger Nicolas chart the values of proportional, Integral and Differential gains are determined which are given by, Kp=1 ; Ki=7e10 ; Kd=1e6

And, As the controller is based on output voltage sensing, C=[ 0 0 1] ; D=[0] Thus the state space model is given by, X‟=AX+BU ; and Y=CX‟+DU. Where,

(37)

(38)

Fig 12. Step response of PID controller

Thus from the above response the system seems to be stable at an settling time of 1.6 feta secs. 7. SIMULATION AND RESULTS OF CLOSED LOOP PID CONTROLLED INTERLEAVED BUCK-BOOST CONVERTER The calculated values are simulated SIMULINK and the result are shown,

using

Fig 11. step response of the transfer function Thus from the derived state space model we can get the transfer function and its response given by,

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A. Santanagopalan

The above figure shows the output when the reference is 5V which is the buck configuration. 7. .HARDWARE IMPLEMENTATION This project deals with the Open loop Configuration of Interleaved Buck-Boost Converter alone for hardware implementation. For the hardware the converter prototype is designed for 1Watt.The corresponding PCB (Printed Circuit Board) are fabricated which involves the following components

Fig 13. SIMULINK diagram of PID Controller The above figure shows the SIMULINK diagram of PID closed loop simulation the results of the simulations are shown below.

1. Mosfet-2 Pieces-IRF840 2. Inductor 1.5H -2 Pieces 3. Capacitor 10µF -1 Piece 4. Mosfet Driver IC- TLP250- 2 Pieces 5. The Mosfet Driver is used to amplify the gate pulse voltage to the Mosfet threshold needs by push pull amplification. The schematic of TLP250is shown below,

Fig 16. Schematic of TLP250 Mosfet driver

Fig 14. Output Boost Configuration The above figure shows the output when the reference is 15V which is the boost configuration.

It should be noted that the Vcc bust be between 12V to 20V which is the operating range of the driver. A capacitor is connected across the supply pins to filter the ripples in the supply. Pins 2 and 3 forms the input and Pin 6 is the output pin which is connected to the gate of the mosfet. The hardware is implemented and the results are shown below.

Fig 15. Output Buck Configuration Fig 17. Boost operation 60% duty cycle

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Design and implementation of an PID controlled efficient Buck-Boost converter using Interleaved topology

[8]

[9]

[10] Fig 18. Buck operation 40% duty cycle

REFERENCES [1]

[2]

[3]

[4]

[5]

[6]

[7]

D.Lakshmi M.Tech , S.Zabiullah M.Tech, Dr. Venu gopal.N M.E,PhD., Improved Step down Conversion in Interleaved Buck Converter and Low Switching Losses, Research Inventy: International Journal Of Engineering And Science Vol.4, Issue 3(March 2014), PP 15-24 Farag. S. Alargt “Analysis and Simulation of Interleaved Boost Converter for Automotive Applications International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 11, May 2013 Il-Oun Lee, Student Member, IEEE, ShinYoung Cho, Student Member, IEEE, and Gun-Woo Moon, Member, IEEE, Interleaved Buck Converter Having Low Switching Losses and Improved Step-Down Conversion Ratio, IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 27, NO. 8, AUGUST 2012. Interleaved Buck Converter using Low Voltage and High Current Application, International Journal of Applied Engineering Research, ISSN 0973-4562, Vol. 8, No. 19 (2013). M.H. Rashid, „Power Electronics: Circuits, Devices and Applications‟, Pearson Education, PHI Third edition, NewDelhi 2004. M.Shanmuga Priya, P.Parthasarathy,R.Saran RajPG Scholar, Department of EEE, Saranathan College of Engineering , Periyar Maniammai University, M.I.E.T College of Engineering, Trichy , India, Multi Device Interleaved Boost Converter for Water Pumping System, IJIRSET. M.Vellaiyaras, K. Esakki Shenbaga Logaand J. Jasper Gnana Chandran. Interleaved Buck-Boost Converter Fed DC Motor, International Journal of Electrical

[11]

[12] [13]

Engineering. ISSN 0974-2158 Volume 6, Number 3 (2013), pp. 301-309 Milan Ilic and Dragan Maksimovic, Senior Member, IEEE. ,Interleaved Zero-CurrentTransition Buck Converter IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 43, NO. 6, NOVEMBER/DECEMBER 2007 1619 Suman Dwari, Student Member, IEEE, and Leila Parsa, Member, An Efficient HighStep-Up Interleaved DC–DC Converter With a Common Active ClampIEEE, IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 26, NO. 1, JANUARY 2011 Shenbaga Lakshmi, Sree Renga Raja, Observer-based controller for current mode control of an interleaved boostconverter by. Turk J Elec Eng & Comp Sci (2014) 22: 341352 S. Sugumar, E.M. Saravanan, E. Dinesh, D. Elangovan and Dr. R. Saravanakumar.,Interleaved BuckConverter using Low Voltage and High Current Application, International Journal of Applied Engineering Research, ISSN 0973-4562, Vol. 8, No. 19 (2013) Texas Instruments, An Interleaved PFC Preregulator for High-Power Converters Vijayalakshmi, S and Sree Renga Raja T, Time Domain Based Digital Controller for Buck-Boost Converter by J Electr Eng Technol Vol. 9, No. 5: 1551 -1561 , 2014.

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Student Journal of Electrical and Electronics Engineering Issue No. 1, Vol. 1, 2015

DESIGN OF MOTOR CONTROLLED AIR BREAK DISCONNECTOR G.AravinthVignesh, A.ArunKumar, D.SaravanaKrishnan, and R.Srinivas Final year EEE, Saranathan college of Engineering, Panchapur, Trichy -12, [email protected]

Abstract: Air break disconnectors are widely used in all the substations and PowerStation in conjunction with circuit breakers primarily for isolation purpose and for enabling Safe maintenance work in this project, we have fabricated a small prototype motor operated horizontal air break disconnector.This disconnector was tested as per the standards requirement. We have incorporated a novel feature of disconnector operation through variable frequency drive in order to eliminate sturdier gearboxes leading to lot of transmission losses.Further, to this prototype development, we have brought out complete technical data design information on disconnectors for Indian substation voltage level right from low voltage to extra high voltage level.Through this project we gained adequate confidence to design air break disconnector independently for any power project. 1. INTRODUCTION When carrying out inspection or repair in a sub-station installation, it is essential to disconnect reliably the unit or the section , on which the work is to be done, from all other live parts on the installation in order to ensure complete safety of the working staff. To guard against mistakes, it is desirable that this should be done by an apparatus which makes visible break in the circuit. Such an apparatus is the isolating switch (or isolator). It may be defined as a device used to open (or close) a circuit either when negligible current is interrupted (or established) or when no significant change in the voltage across the terminals of each pole of isolator will result from the operation. 1. 2. 3. 4. 5. 6. 7. 8.

Operating handles Base Channel Insulators Arcing horns Female contacts Make before break after contact Terminal Pad Rotating arm with male contact

9. Stop for rotating arms 10. Earthing blades 11. Female contact for earthing switch

Fig. 1 The location of an isolating switch in the substation is shown above:

Fig. 2 The isolating switches can be broadly classified into three categories based on the functions as 1. Bus isolator 2. Line isolator cum earthing switch 3. Transformer isolating switch

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Design of Motor Controlled Air Break disconnector

Based on operation, isolators can be classified as, 1. Centre break isolators

Type of insulator

Pantograph Disconnect or series RP Vertical break Disconnect or series RV Centre break Disconnect or series RC

Rated voltage in kV

Rated curre nt in A

245 420 525 765 245 420 525 765

3150 3150 3150 3150 3150 3150 4000 4000

Rated short time current in KA 40 50 50 40 60 60 60 60

Rated peak short circuit current in KA 100 125 125 100 150 150 150 150

123 3150 60 150 145 3150 60 150 245 3150 60 150 420 3150 60 150 525 3150 60 150 Double 72.5 3150 40 100 break 123 3150 40 100 Disconnect 145 3150 40 100 or series 245 3150 40 100 RD 420 4000 60 150 525 4000 60 150 2. Double break isolators 3. Pantograph isolators 4. Vertical break isolators The BS: 3078-1959 on isolators distinguishes between “offload” and “on load” isolators. OFF load isolator is an isolator which is operated in a circuit either when the isolator is already disconnected from all sources of supply or when the isolator is already disconnected from the supply. ON load isolator is an isolator which is operated in a circuit where there is a parallel path of low impedance so thatno significant change in the terminals of each pole occurs when it is operated.

Particulars

Contact pressure(Kg) Contact area Motor rating(H.P) Max. starting current(A) Max. full load current(A) Max. weight of motor(Kg) R.P.M of motor Operation Max. torque required(Kg m) Weight of Disconnector metallic without insulators(Kg ) Max. weight of electrical operating mechanism Motor type No.of operations without deterioration Safety factor Max.chargin g current that can be interrupted Bearing type

Centre break 245kV/ 420kV 9/9

Double break 245kV/ 420kV 9/9

Pantograp h

Line contact 0.5/0.5

Line contact 0.5/1

Point contact 1

4/4

4/8

8

1/1

1/2

2

9/9

9/14

14

1370/137 0 3pole/ 1pole 30/20

1370/140 0 3pole/ 1pole 40/45

1400

140/400

150/420

250

130/130

130/130

175

40

1 pole 65

Squirrel cage 1000

1.5 to 2 0.7A

Ball bearing

2.2 Disconnector Drives: 2. TECHNICAL PRE QUALIFICATION The technical pre qualifications for an isolator are, i) Disconnector Ratings ii) Technical Specifications iii) Disconnector Drives iv) Terminal Connectors v) Test Reports 2.1 Technical Specifications:

The operating mechanism of disconnectors can be broadly classified into three types as 1) 2) 3) 4) Manual method

Manual operated Manual winch operated Pneumatic operated Motor operated operated and manual winch operated needs our human effort to operate an

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G.AravinthVignesh, A.ArunKumar, D.SaravanaKrishnan, and R.Srinivas

isolator switch. Hence they can’t be used for systems above 245kV. The operating cabinet is suitably designed and gasketed for protection against water and dust. If the system voltage is 11kv or above, high torque is required to operate the disconnectors hence it is very difficult to operate manually. In such cases manual winch type operating mechanism is used. This mechanism uses gear assembly to reduce human efforts.

3. FABRICATION OF ISOLATOR For making the prototype of air break disconnector we have replaced the insulator in original assembly with wood. We have used 25*3mm aluminium flat for moving contact. The isolator contacts in the closed and positions are shown below.

The pneumatic operating mechanisms are of single cylinder double acting piston construction actuating a rack and pinion arrangement for developing required torques. The linear piston movement is transmitted to the pinion which is engaged to the rack causing the output shaft to rotate. The main disadvantage of pneumatic operating mechanism is it needs more attention. Small leakages in pipe lead to mal operation of disconnectors. Motor operated disconnectoruses squirrel cage induction motors for rotating the shaft to which the moving contacts are connected. Upto 245kV single motor can be used to operate all the three poles of an isolator after that we have to use separate motor for each pole of isolator. 2.3Terminal Connectors: In order to connect the transmission lines to the terminals of isolators terminal connectors are used. It should have sufficient mechanical strength to withstand the weight of transmission lines. The connector is cast with aluminium alloy to grade LM6 of specification BS1490. It should have good corrosion resistance. For 220kV and 400kV systems corona free connectors are designed so that under fair weather operating conditions the voltage gradients at the connector surface will be at a level that will not cause corona.

The three moving isolators are connected by means of wooden stick so that they can open and close at the same time.Motor shaft is connected to the middle isolator so that the load can be equally divided. The entire arrangement with the motor is shown below.

Once the contacts have completely closed or opened, motor should be automatically turned off. For this purpose two limit switches are used. The limit switch arrangements are shown below.

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Design of Motor Controlled Air Break disconnector

At present, gear boxes are used to reduce the speed of motor in motor controlled air break disconnector. We have replaced the gear box with a Variable Frequency Drive which is also a energy efficient practice. The control circuit for operating the motor in both forward and reverse direction, indication lamps and motor protection are shown below.

hence motor rotates in normal direction. Once the isolator switch is closed in will press the limit switch close and RED lamp glows to indicate that the isolator is in operation. If OFF push button is pressed then Open Contact coil (O.C) gets energised. This will actuate the O.C in power circuit and phase sequence to the motor is changed. As a result the motor rotates in reverse direction. If the contact is opened completely it will press the limit switch open and GREEN lamp glows to indicate that the isolator is open. If the motor is overloaded overload relay will get actuated and motor is turned OFF. YELLOW lamp glows to indicate the abnormal condition. Testing: The commonly used tests for analysing the performance of isolators are, (i)

(ii)

(iii) (iv) (v) (vi) (vii) (viii)

Fig. 3 The power circuit for isolator operation is shown below.

Power frequency tests (a) Dry and Wet Flashover Tests (b) Wet and Dry Withstand Tests (One Minute) Impulse test (a) Impulse Withstand Voltage Tests. (b) Impulse Flashover Test Dielectric tests Temperature rise tests Mechanical endurance tests Short circuit tests Milli volt drop tests Operation tests

Special Tests: There are certain special tests that are performed mainly on the demand of the customers and the location where it has to be operated. Some of the special tests are 1. 2.

Pollution tests Seismic tests

We have done some tests which can be performed with the resources available in our college. 4. TEST TABULATIONS 4.1 Milli volt drop test To close the isolator ON push button is pressed and Close Contact coil (C.C) gets energised. This will close the C.C contact in power circuit and

Before heat run test:

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G.AravinthVignesh, A.ArunKumar, D.SaravanaKrishnan, and R.Srinivas

Bill of materials: Equipment’s

0.5hp 3phase motor Variable Frequency drive Power Contactor Auxillary contacts Push button Indicating Lamp Over Load Relay Limit switch

quantity

Cost per equipment (rupees)

Total cost (rupees)

1

6050

6050

1

14450

14450

S. no

Curr ent ( A)

1 2 3 4 5

0.2 0.4 0.6 0.8 1

Voltage drop (mV)

2

914

1828

2

150

300

3

36

108

R 0.9 2.1 3.2 3.8 4.2 Average

3

30

90

5. RESULTS

1

500

500

2

232

464

Circuit breaker

1 900 Design cost Total amount After heat run test:

900 4000 28690

Y B 1.1 1.0 1.8 1.8 2.5 3.1 3.7 4.2 5.2 4.6 resistance

Phase Insulation value(MΩ) connection 25% 50% 75% 100% R Y+B+E 125 80 50 40 Y R+B+E 110 60 40 30 B R+Y+E 250 200 160 100 R R 600 500 400 300 Y Y 130 100 80 70 B B 1100 800 700 200 4.3 INSULATION TEST: R Y B R Y B

Y+B+E R+B+E R+Y+E r Y B

150MΩ 125MΩ 350MΩ 800MΩ 150MΩ 1500MΩ

Y 5.5 4.5 4.17 4.63 5.2 4.8

B 5 4.5 5.17 5.25 4.6 4.90

Resistance (MΩ) R Y 3.5 4

B 2.5

Cur rent (A)

1

0.2

Voltage drop (mV) R Y B 0.7 0.8 0.5

2

0.4

1.7

1.8

1.6

4.25

4.5

4

3

0.6

2.5

2.6

2.2

4.16

4.33

3.67

4

0.8

4.7

4.6

4.3

5.87

5.75

5.37

1

5.5

6.3

5.9

5.5

6.3

5.9

4.65

4.97

4.3

Average resistance

4.2 POLLUTION TEST:

R 4.5 5.25 5.33 4.75 4.2 4.806

S. no

5

Fig. 4

Resistance (MΩ)

1) The millivolt drop test was performed and the contact resistance was measured in all three poles through DC current injection. 2) The heat run test was conducted by injecting an AC current of 20Amperes in all three poles simultaneously. The maximum temperature stabilise at 63oC.Ambient temperature was from around 31oC.Temperature rise was from 32oC.As per standards, for aluminium maximum allowable temperature is 75oC. 3) The physical condition of moving and fixed contacts were after temperature rise test ,the resistance measurement has revealed the same 4.6 milliohm. 4)The insulation measurements was carried out for the poles using 5KV insulation test.The maximum and minimum values were observed to be 125 MΩ and 1500MΩ which is quite adequate for 415V. 5) An artificial pollution test has been taken,minimum value of insulation was 40MΩ which is adequate for 415V. 6) Few mechanical open/close operation were made using Variable Frequency Drive. About 300

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Design of Motor Controlled Air Break disconnector

operations were made we couldn’t observe any wear and tear at the main current contacts.

6. CONCLUSIONS Air Break Disconnectors are the heart of any substation they are basically OFF load device they can be interrupt line charging current to the level of 0.7A.The design of this device is very critical from radio interference and corona discharge point of view. Also the clearance between isolator busbar junction and earth is very significant for avoiding flash over the contact profile, interlocks, creepage distance across isolator distance are all important in the design of air break disconnector to ensure reliable operation. Then is plenty of scope to introduce vertical break and pantograph isolators in power/substation. Such isolation will occupy lesser area of substation. Since, land cost is huge constraints for a power station we must explore the feasibility of using more and more vertical break/Pantograph isolators exact control design is critical and trouble free operation. Operation specification of isolator is equally important we could also explain the economic feasibility of VFD instead of mechanical gearbox in the future from every energy conservation point of view.

during discussions on Mr. Yves Porcheron's paper. 11) HVT 32S(S) 865/72 12) Rosenthal Technik-Technical disadvantages of multicone and hollow Post type insulators in comparison with solid core post type insulators. 13) NGK Technical note no.TN 7007R1 comments on Multicone type post insulators. 14) NGK Technical note no.TN 80073 Excellent features of NGKSolidcore station post insulators. 15) TVA (USA) 500KV tenders for Roanesub station for Solid core Posts only.

REFERENCES 1.

Substation Design and Equipment by P.S. Satnam, P.V. Gupta. 2. IEE Conference Publication No.15, Session 8 Discussion Insulators, Bushings, etc. 3. How the results of dielectric tests on External insulation in natural conditions may be predicted from indoor laboratory tests. Electrical insulation conference. 4. Cement "Basolit" oil pour scellementd'isolateurs. 5. Flashover of Polluted HV insulators in a variety of wetting conditions. IEE Colloquium on Breakdown and Discharge phenomena on insulating surfaces in gas media and in Vacuum. 6. A new insulation system for HV, EHV and UHV applications. Southwestern IEEE Conference San Antonio, Texas. 7. MULTICONE Stacks tested in MartiquesEdF Testing stand. 8. CESI REPORT: AT 1323 Dt.11.10.67. 9. Support isolant "Multicone" Th.Kaldor Electro Porcelain. 10. International Symposium on Pollution Performance of insulation and surge diverters Feb.26, 27 1981. Comments of Dr.M.P.Verma

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Student Journal of Electrical and Electronics Engineering Issue No. 1, Vol. 1, 2015

MODELING AND SIMULATION OF INTERLEAVED BUCK-BOOST CONVERTER WITH PID CONTROLLER E. Arthika, and G. Shanmuga Priya Second year M.E PED, Saranathan college of Engineering, Panchapur, Trichy -12 [email protected], [email protected] Abstract— In this paper, the analysis and

modeling of interleaved Buck- boost converter with PID controller is discussed. Nowadays, Buck-boost power converter is widely used in many applications and power capability demands [1]. The applications of Buck-boost power converter may be seen in electric vehicles [2], photovoltaic (PV) system, uninterruptable power supplies (UPS), and fuel cell power system [4]. Converters are controlled by interleaved switching signals, [5] which have the same switching frequency but shifted in phase. By paralleling the converters, the input current can be shared among the inductors so that high reliability and efficiency in power electronic systems can be obtained and ripples also reduced [2], the converter performance can be improved [3]. The control circuit of this converter is controlled by using the PID controller [3]. The simulation of interleaved buck-boost converter results with PID controller has been presented in detail. Index Terms—Interleaved Buck-Boost Converter, PID Controller, Buck-Boost Converter, Ziegler Nichol Tuning Method

1. INTRODUCTION Interleaving also called as multi phasing is a technique which is useful for reducing the size of filter component [8] . In a interleaved circuit there will more than one power switch. The phase difference for two switches is 180º[2]. Interleaving technique is a strategic interconnection of multiple switching cells that will increase the effective pulse frequency by synchronizing several smaller sources and operating them with relative phase shift [10]. Interleaved method is used in order to improve converter performance in the aspects of efficiency, size, and conducted electromagnetic emission. Interleaved also has benefits such as high power capability, modularity, and improved reliability [3]. But, having interleaved may cost on additional inductors, power switching devices, and output rectifiers. When the size of inductor increases, the power loss in a magnetic component will decrease although both the low power loss and small volume are required.In the power electronic s[4], application of interleaving technique can be found back to early days especially in high power application. The voltage and current stress can

easily go beyond the range that power device can handle in high power application. One solution to this problem is by connecting multiple power devices in parallel or in series. But, instead of paralleling power devices, it is better to parallel the power converters [2]. By paralleling the power converters, the interleaving technique will comes naturally. Interleaving can cancel the harmonics, increase the efficiency, better thermal performance and the high power density can be obtained. Paralleling of converter [1] power stages is a well known technique that is often used in high-power applications to achieve the desired output power with smaller size power transformers and inductor [3]. In addition to physically distributing the magnetic and their power losses and thermal stresses, paralleling also distributes power losses and thermal stresses of the semiconductors due to a smaller power processed through the individual paralleled power stages. As a result, paralleling is a popular approach to eliminating “hotspots” in power supplies [8]. Besides, the switching frequencies of paralleled lower power stages may be higher than the switching frequency of the corresponding single high-power processing stage because lower power faster semiconductor switches can be used in implementing the individual power stages. Consequently, paralleling also offers an opportunity to reduce the size of the magnetic components. The control objective in the design of PID controller is to drive the Interleaved Buck converter switch with a duty cycle [10] so that the dc component of the output voltage is equal to the reference voltage [6]. The regulation should be maintained constant in spite of variations in the input voltage or in the load [4]. Furthermore, the constraints in the design of controller results due to the duty cycle which is bounded between zero and one. This problem can be solved by modeling the Interleaved Buck-Boost converter using state space averaging technique. 2. BLOCK DIAGRAM OF INTERLEAVED BUCKBOOST CONVERTER

The Fig.1 shows that the overall block diagram of Interleaved Buck-boost Converter with PID

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Modeling and Simulation of Interleaved Buck-Boost Converter with PID Controller Controller [8] The DC supply is given to the interleaved buck-boost converter. In Interleaved Buck-boost Converter two switches are connected in parallel. By using paralleling the current can be divided through two switches. So the current stresses can be reduced.

Where 𝑉0 is the output voltage,𝛼 is the duty ratio, f is the switching frequency,∆𝑉𝐶 is the capacitor ripple voltage, ∆𝐼𝐿 the inductor ripple current, L and C are inductor, capacitor respectively,𝑅𝑂 is the load resistance,𝜂 is the efficiency,𝑃𝑜𝑢𝑡 , 𝑃𝑖𝑛 is the output and input power.

The output of the interleaved buck-boost converter is given as a input to the load [3]. Here PID controller is used. The control circuit of the converter is controlled by the PID. The DC supply is given to the PID controller. In PID Controller the Ziegler-Nichols tuning Method is used. By using this PID controller oscillations and ripples can be reduced. Then the reduced ripple voltage is given to the converter, then it is given to the load.

3.2 Interleaved Buck-boost Converter Interleaved buck-boost converter consists of „n‟ single boost converters that are connected in parallel. For the interleaved with two switch, the switching signals operate 180º phase shift between them [8]. The interleaved is formed by two independent buck- boost switching units [4]. For each boost switch unit, there are two switching stages which are switch close and switch open stages [7]. When the switch is closed, the current in the inductor start to rise while the diode is blocking. The inductor starts charging. When the switch is opened, the inductor starts to discharge and transfer the current through diode to the load .

Fig. 1 Block diagram of Interleaved Buck-boost Converter 3. DESIGN OF INTERLEAVED BUCK-BOOST CONVERTER Fig.3 Interleaved Buck-boost Converter

3.1 Design of Buck-boost Converter The Buck-boost converter provides an output voltage can be either higher or lower than the input voltage [2]. The output voltage polarity is opposite to that of the supply voltage. It is also called as inverting regulator [4]. The advantage of Buckboost converter is the increased efficiency. The L and C values can be calculated by

The L and C values of this converter is calculated by 𝑉 𝐿1 = 𝐿2 = 𝑆𝛼 (6) 𝐶1 = 𝐶 =

∆𝐼𝑓 𝐼0 𝛼

(7)

∆𝑉 𝐶 𝑓

From equation (6),(7) it is observed that L and C values are same as that of the Buck-boost converter. Table 1. Overall system parameters S.NO 1 2

Fig.2 Circuit Diagram of Buck-boost Converter 𝑉0 = − 𝐿= 𝐶=

𝑉𝑆 𝛼 1−𝛼

𝑉 𝑆𝛼

∆𝐼𝑓 𝐼0 𝛼 ∆𝑉 𝐶 𝑓

𝑅𝑂 = 𝑉 𝐼 𝑃 𝜂 = 𝑜𝑢𝑡 𝑃 𝑖𝑛

(2)

3 4 5 6

(3)

7

(1)

(4) (5)

8 9

Prameters Input Voltage Switching frequency Inductor Capacitor Resistor Capacitor ripple voltage Inductor ripple current Output Voltage Output Power

Symbol 𝑉𝑖𝑛 (𝑉) 𝑓𝑠 (𝐻𝑍 )

Value 12 25

𝐿1, 𝐿2 (µ𝐻) 𝐶(µ𝐹) 𝑅(Ω) ∆𝑉𝐶

1.4 7.2 12 0.05

∆𝐼𝐿

0.2

𝑉0 (𝑉) 𝑃0 (𝑊)

−18 27

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E. Arthika, and G. Shanmuga Priya The calculated design values of Interleaved Buck-boost Converter are shown in Table I.

Mode 2: S1 is ON and S2 is OFF

4. MODELING OF INTERLEAVED BUCK-BOOST CONVERTER

𝒙 = 𝑨𝟐 𝒙 + 𝑩𝟐 𝑽𝟏

(11)

Mode 3: S1 is ON and S2 is ON The ZCS interleaved buck converter is modeled using state space averaging technique in which the design is carried out in time domain based on their performance indices [6]. This method is highly significant for this kind of converters since the PWM converters are the special type of non linear systems which is switched in between two or more non linear circuits depending upon the duty ratio .The unique feature of this method is that the design can be carried out for a class of inputs such as impulse [7], step or sinusoidal function in which the initial conditions are also incorporated. As a general case state space averaging method for two switched basic PWM converters is discussed now [4]. The switches S1, S2 is driven by a pulse sequence with a constant switching frequency f. The state vector for an Interleaved Buck-boost Converter is given 𝒊𝑳𝟏 𝒙(𝒕) = 𝒊𝑳𝟐 𝒗𝒄 (8) whereiL1and iL2 are the current through an inductor L1and L2 respectively; Vc is the voltage across the capacitor C. For the given duty cycle d(k) for the kth period, the systems are illustrated by the following set of state space equations in continuous time domain 𝑿 = 𝑨𝒙 + 𝑩𝑽𝒔 (9)

𝒙 = 𝑨𝟑 𝒙 + 𝑩𝟑 𝑽𝟏 Mode 4: S1 is OFF and S2 is ON 𝒙 = 𝑨𝟒 𝒙 + 𝑩𝟒 𝑽𝟏 0 A1 = 0 0

Mode 1: S1 is ON and S2 is ON 𝒙 = 𝑨𝟏 𝒙 + 𝑩𝟏 𝑽𝟏 (10)

0 0 0

0 0 ;𝐵1 = −1/RC

0 0 𝐴2 = −1/𝐶

0 0 0

0 A 3 = A1 = 0 0

0 0 0

A4 =

0 0 −1/C

0 0 0

(13) 1 L1 1

(14)

L2

0

1 0 𝐿1 1/𝐿2 ;𝐵2 = 0 −1/𝑅𝐶 0

0 0 ;𝐵3 = −1/RC 1/L1 0 ; B4= −1/RC

(15)

1 L1 1

(16)

L2

0 0 1 L2

(17)

0

Where 𝐴 = 𝐴1 𝑑1 + 𝐴2 𝑑2 + 𝐴3 𝑑3 + 𝐴4 𝑑4

(18)

𝐵 = 𝐵1 𝑑1 + 𝐵2 𝑑2 + 𝐵3 𝑑3 + 𝐵4 𝑑4

(19)

𝑢 = 𝑉1

(20)

Where d is the duty cycle ratio. d1, d2, d3,& d4 are the duty cycle of Mode 1, Mode 2, Mode 3 & Mode 4 respectively.

Where x is the state vector matrix, A is the state coefficient matrix and B is the source coefficient matrix, and d is a duty cycle is a function of x and Vs in a feedback system. State model of an Interleaved Buck-Boost converter is derived and is discussed below. High power densities are possible only for continuous conduction mode (CCM) of operation. Diode Dl and D2 are always in a complementary state with the switches S1and S2 respectively. When S1 ON, D1 - OFF and vice versa and S2 - ON, D2 OFF vice versa. For the continuous conduction mode of operation, four modes of operations are possible, and state equations are

(12)

d1 + d2 + d3 + d4 = 1 ; d1 + d2 + d3 = d ; d1 = d3 ; d2 = d4 ;

(21) (22) (23) (24)

Hence A=

0 0 −d2 /C

0 0 −d2 /C

d2 /L1 d2/L2 (25) −2d1 /RC − 2d2 /RC

2d 1 +d 2

B=

L1 2d 1 +d 2

(26)

L2

0 𝑌= 0

0

1

𝑖𝐿1 𝑖𝐿2 𝑉𝑐

(27)

Find the transfer function G(s) of the IBC using state space model equation (19) and (27).Finally

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Modeling and Simulation of Interleaved Buck-Boost Converter with PID Controller

G S =

−6.821 e −13 −4.762e 005 s+8.223 e −010 s 3 +115 .7s 2 +3.175 e 005 s−3.092e −009

(28)

5.CLOSED LOOP CONTROL OF INTERLEAVED BUCK-BOOST CONVERTER The closed loop control system for the Interleaved Buck converter with PID controller feedback is shown in Fig.4

controller respectively . Kp, Ti and Td are calculated according to Ziegler – Nichols tuning rules. This method is an accurate heuristic method for determining good settings of PID controllers. This method is based on the empirical knowledge of the 2𝜋 ultimate critical gain Pcr , which is given by 𝜔 where ω is the natural frequency of oscillation of the converter under consideration. The Ziegler – Nichols tuning formulae is illustrated in the Table II. TABLE II. ZIEGLER-NICHOL TUNING METHOD Type of Controller P PI

Kp

Ti

Td

0.5Kcr 0.45 Kcr

0 0

PID

0.6 Kcr

∞ 1 1.2𝑃𝑐𝑟 0.5Pcr

0.125Pcr

6. SIMULATION RESULTS OF INTERLEAVED BUCK-BOOST CONVERTER

𝑢 𝑠 = [𝐾𝑃 + 𝐾𝑖 + 𝐾𝑑 𝑠]𝑒(𝑠)

(30)

12 11

0 0.1 0.2 0.3 Interleaved 0.4 0.5 Buck-Boost 0.6 0.7 Fig.5.Simulink Model of Converter 200

Output Voltage (V)

𝑑𝑡

Where u(t) is the control output, k is the derivative time and e(t) is the error between the Vref and Vo.The transfer function is given as

13

100 0 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

20 0 -20 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Output Current (A)

𝑇𝑖

The circuit for the interleaved Buck-Boost converter with PID [3] controller is shown in the fig.5.using MATLAB Simulink. A DC voltage source 𝑉𝑖𝑛 =12V is used. The switch S1,S2 have the same duty ratio of 0.6at a switching frequency of 25KHZ.Output voltage 𝑉0 = 18 V

Input Voltage (V)

The ultimate aim in designing the controller is to minimize the error between 𝑉0 and 𝑉𝑟𝑒𝑓 from the Figure 3, the important functional blocks that are evident are: PID Controller, PWM(Pulse Width Modulation) and dc-dc converter [3]. The PID Controller acts as a compensator and generates the control signal by compensating the error signal (Ve).PWM block is for the generation of driver signal obtained from the compensator[8]. The error (Ve) between the output voltage (Vo) and reference voltage (Vref) is processed by the compensator block with PID Controller algorithm to generate control signal [7]. The control signal significantly affects the converter characteristics and therefore effective tuning of the controller is one of the desired aspects of the control system [9]. The fine tuned PID controller generates the duty cycle command corresponding to the error signal which is then converted as switching pulses using the PWM functional block.The typical closed loop system using PID controller is shown in the time PID controller can be expressed as, 1 𝑡 𝑑 𝑢 𝑡 = 𝐾𝑃 𝑒(𝑡)+ 0 𝑒 𝑡 𝑑𝑡 + 𝑇𝑑 𝑒(𝑡) (29)

The proposed closed loop response of the Interleaved Buck-Boost converter is simulated using MATLAB / SIMULINK. The ultimate aim is to achieve a robust controller in spite of uncertainty and large load disturbances.

Input Current (A)

Fig.4 Block diagram of PID Controller

2 0 -2 0

Time (sec)

Where 𝐾𝑝 , 𝐾𝑖 =

𝐾𝑝 𝑇𝑖

,𝐾𝑑 = 𝐾𝑝 𝑇𝑑

are the

proportional, integral and derivative gains of the

Fig. 6 Output Waveform of the Interleaved Buck- Boost Converter

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E. Arthika, and G. Shanmuga Priya

Efficiency

Transaction on Industry Applications, Vol.48,No.1, January/February 2012 100 [3] Chien-Ming Lee, Yao-Lun Liu, Hong-Wei Shie, “LabVIEW Implementation of an Autotuning PID Regulator via Grey-predictor,”In 95 Proceedings of IEEE International Conference on Computer Intelligent System, 90 Bangkok : IEEE Press, 2006,1-5. [4] C.M. Lee, Y.L. Liu, H.W. Shieh, C.C. Tong, “LabVIEW Implementation of an AutoProposed 85 tuning PID Regulator via Conventional Greypredictor”,IEEE Conference on Cybernetics and Intelligent Systems, 2006, 80 pp. 1-5. [5] Femia, N.; Spagnuolo, G.; Tucci, V. State75 space models and order reduction for DC-DC switching converters in discontinuous modes. 50 100 150 200 250 IEEE Transaction on Power Electronics.,Vol. Change in Resistance 10, 640–650. 1995. [6] G. Caledron-Lopez, A.J. Forsyth, “HighFig. 7 Comparison of Efficiency power dual-interleaved ZVS boost converter with inter phase transformer for electric The efficiency of the ordinary Buck-boost vehicles,” IEEE Applied Power Electronics Converter, Interleaved Buck-Boost converter are determined [7] and are shown against the load Conference, 2009, pp. 1078-1083. Resistance in Figure 7. The efficiency of the [7] Jos´e M. Blanes, Roberto Guti´errez, Ausi`as interleaved Buck-boost Converter is high when Garrig´os, Jos´e Lu´ıs Liz´an, and Jes´us compared to the Buck-Boost Converter. Mart´ınez Cuadrado, “Electric Vehicle Battery Life Extension Using Ultra capacitors and an FPGA Controlled Interleaved Buck– 7. CONCLUSION Boost Converter”,IEEE Transaction on In this Paper, a new Interleaved Buck-Boost Power Electronics,Vol.28,No.12,December converter has been proposed with PID controller. 2013. The simulation results thus obtained using [8] Jingquan Chen, Member, IEEE, Dragan MATLAB Simulink is with the mathematical Maksimovic´, Member, IEEE, and Robert W. calculations. The mathematical analysis, simulation Erickson, “ Analysis and Design of a Lowstudy and the experimental study show that the Stress Buck-Boost Converter in Universal controller thus designed to achieves tight output Input PFC Applications”, IEEE Transactions voltage regulation and good dynamic performances on Power Electronics, vol. 21, No. 2,March and higher efficiency. It can be conclude that, by 2006. using the interleaved Buck-Boost converter, the [9] Kosai, H.,UES Inc.; McNeal, S., Jordan, B., output voltage ripples can be reduced and Scofield, J., Collier, J., Air Force Research efficiency can be improved. Most importantly, the Laboratory; Ray, B., Bloomsburg University input current has no ripple. By using two switches of Pennsylvania; “Design and implementation on the circuit, it can reduce the switching losses of a Compact Interleaved Boost Converter”. because it can alternate the turning on and off [10] Lakshmi D, Zabiullah S, “Improved Step between these two switches. down conversion in Interleaved Buck Converter and Low Switching Losses”, International Journal Of Engineering And REFERENCES Science, Vol.4, 2014, PP 15-24.z [1] Bor-Ren Lin and Chien-Lan Huang, „Interleaved ZVS Converter with RippleCurrent Cancellation‟, IEEE Transaction on Industrial Electronics, 55,(2008), 4, pp. 15761585. [2] Ching-Ming Lai, Ching-Tsai Pan and MingChieh Cheng, “ High-Efficiency Modular High Step-Up Interleaved Boost Converter for DC-Microgrid Applications”, IEEE

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Student Journal of Electrical and Electronics Engineering Issue No. 1, Vol. 1, 2015

LITERATURE SURVEY ON MPPT SCHEMES FOR STAND ALONE AND GRID CONNECTED PHOTOVOLTAIC SYSTEM A. SharanMonika, and S.Stephy Sharon Final year ME-PED, EEE, Saranathan College of Engineering,Panchapur,Tiruchirapalli [email protected], [email protected] Abstract—Solar energy which is trapped by Photovoltaic (PV) array has witnessed a tremendous growth in the past decade. Along with this the need for energy efficient and reliable system has boosted the researchers to develop Maximum Power Point Tracking (MPPT) schemes for PV systems.The Energy Utilization Efficiency of a PV standalone system can be significantly improved by using MPPT controllers.But the problem arises with selecting the proper MPPT as each MPPT has its own merits and demerits. This paper presents a comprehensive review of major MPPT techniquesused for standalone and grid connected systems. Key Words —Maximum Power Point Tracking (MPPT), Perturb and Observe (PO),Incremental Conductance (INC),standalone PV systems.

disadvantage of these systems is the increased power density. The use of power optimization mechanisms called the Maximum Power Point Tracking (MPPT) algorithms has led to the increase in the efficiency of operation of the solar modules and thus is effective in the field of utilization of renewable sources of energy. In this paper a comprehensive review of major MPPT techniques used in the PV standalone system are presented. Section II explains the principle of standalone and grid connected PV system. Section III gives a brief explanation of Maximum power point tracking. Section IV gives a detailed review on various MPPT techniques used in the literature. Simulation of a PV standalone system with both the MPPT schemes and the results of simulation are presented in section V.

1. INTRODUCTION

Solar energy is abundantly available that has made it possible to harvest it and utilize it properly. Solar energy can be a standalone generating unit or can be a grid connected generating unit depending on the availability of a grid nearby. Thus it can be used to power rural areas where the availability of grids is very low. Another advantage of using solar energy is the portable operation whenever and wherever necessary. In order to tackle the present energy crisis one has to develop an efficient method in which maximum power has to be extracted from the incoming solar radiation. The power conversion mechanisms have been greatly reduced in size in the past few years. The development in power electronics and renewable energy systems has helped engineers to come up with very small but powerful systems to withstand the high power demand. But the

No.of Papers

20 15 10 5 0 1995

2000

2005

2010

2015

Year

Fig.1. Graph on the Number of papers on Standalone PV systems versus Year of publication No of Papers

The main concern in the power sector is the dayto-day increasing power demand and the unavailability of enough resources to meet the power demand using the conventional energy sources. Demand has increased for renewable sources of energy to be utilized along with conventional systems to meet the energy demand. Renewable sources like wind energy and solar energy are the prime energy sources which are being utilized in this regard. The continuous use of fossil fuels has caused the fossil fuel deposit to be reduced and has drastically affected the environment depleting the biosphere and cumulatively adding to global warming.

60 40 20 0 2010

2011

2012

2013

No. of… Year

2014 (Till May)

Fig.2. Graph on the Number of papers on grid connected PV systems versus year of publication 2. STANDALONE AND GRID CONNECTED PV SYSTEMS A system feeding a load or connected to a load and which is not connected to the grid is called a Standalone or Isolated system. When a system is connected to the grid or if it feeds the grid then the

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A. Sharonmonica, and S. Stephy sharon

system is said to be grid connected. Standalone system requires a battery in some cases but with grid connected system battery is not needed as the deficit power could be obtained from the grid itself. Both standalone and grid connected photovoltaic systems use Maximum Power Point Tracking to obtain the maximum possible output power from the PV array. The basic schematic of PV standalone and grid connected system is shown in Fig.3

4. REVIEW OF MPPT TECHNIQUES From the literature survey done it is observed from Fig.1 and Fig.2 that the research in PV system is greatly increasing in the past decade. Maximum Power Point Tracking of a PV array has become an essential part of any PV system. Various MPP tracking methods have been discussed, developed and implemented in the literature. The following different MPPT techniques were observed in the standalone PV and grid connected system as shown in Fig.3

No. of

20

0

No. of Papers

Types of MPPT used

Fig.3.Block schematic of a PV standalone system and grid connected system 3. MAXIMUM POWER POINT TRACKING

Fig. 4 Block schematic of a PV standalone system and grid connected systems Maximum Power point tracking is a technique used to obtain the maximum possible power output from the PV source. MPPT can be used in both in standalone and grid connected systems. MPPT algorithm can be implemented using two different configurations- Duty cycle MPPT algorithm and Voltage based MPPT algorithm as shown in Fig.4

5

2

1

MPPT Techniques 2 1 1 4 8

20

1

Fig.5. Graph on the Number of papers versus MPPT methods used in standalone and grid connected systems Perturb and Observe(PO) algorithm- It is the most popular algorithm belonging to the class of the direct MPPT techniques. It is characterized by the injection of a small perturbation into the system and the resulting effects are used to drive the operating point toward the MPP. The PV operating point is perturbed periodically by changing the voltage at PV source terminals, and after each perturbation, the control algorithm compares the values of the power fed by the PV source before and after the perturbation. If after the perturbation the PV power has increased, this means that the operating point has been moved toward the MPP; consequently, the subsequent perturbation imposed to the voltage will have the same sign as the previous one as shown in Table I. If after a voltage perturbation the power drawn from the PV array decreases, this means that the operating point has been moved away from the MPP as shown in Fig.6. Table 1. P&O APPROACH Perturbation Change in Next Power Perturbation Positive Positive Positive Positive Negative Negative Negative Positive Negative Negative Negative Positive

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1

Literature Survey on MPPT schemes for Stand alone and Grid Connected Photovoltaic system be adjusted in order to move the array terminal voltage towards the MPP voltage.

Fig.6. PV Curve In recent times this method has been widely used to achieve the maximum amount of power from a solar panel. Huang et al proposed a modular self controlled photovoltaic (PV) charger with P&O MPPT. Usually in battery charging applications the P&O responds in a slower manner. Here the author has given a new idea of a fast MPPT method by narrowing the charging period [6]. Mohammed et al gives a complete assessment of P&O algorithm implementation techniques. A detailed assessment on the reference voltage perturbation and direct duty ratio perturbation is simulated, implemented, and analyzed and concludes with the advantage and disadvantages of both methods. The paper also describes the advantages of P&O that it is a simple algorithm and it is easy to implement. [2]Kun Ding et al proposed a complete MATLAB / Simulink based PV module with the P&O technique and have analyzed the results for both the conditions of uniform and non-uniform irradiance [3]. T.Esram and Patrick served with a convenient reference with the comparison on different MPPT techniques and it is mentioned that P&O technique is the most used MPPT control technique due to its simplicity and ease to implement. It is also given that the main drawback in P&O is the efficiency of the MPPT decreases under rapidly changing irradiance. [4] Incremental Conductance MPPT-The basic idea of the Incremental Conductance algorithm is that, at the MPP, the derivative of the power with respect to the voltage or current becomes zero because the MPP is the maximum point of the power curve as shown in fig.6.Here the output characteristics of power and voltage are analyzed. We note that in the left side of the MPP the power increases with voltage, i.e. dP / dV>0 and it decreases with voltage at the right side of the MPP, i.e. dP / dV<0. The algorithm of INC starts its cycle by obtaining the present values of I(k) and V(k), then using the corresponding values stored at the end of the preceding cycle, I(k-1) and V(k-1), the incremental change is approximated as: dI ≈ I(k) – I(k-1), and dV ≈ V(k) –V(k-1).The main check is carried out by comparing dI / dV against -I/V, and according to the result of this check, the duty ratio will

Qianget al have proposed a modified variable step size Incremental conductance method .The INC method usually works under fixed iteration step size. In some of the literature variable step size INC is used. However the dynamics of MPPT is affected greatly due to when the irradiance changes quickly. In order to overcome this limitation this modified variable step size INC was proposed. [5]Mohammed et al compares INC with other hill climbing methods such as Perturb and observe (PO) and Constant Voltage MPPT method and concludes that INC is less confused by noise and it has got higher energy utilization efficiency. The limitation of INC is also mentioned that implementing it with analog circuits becomes complex and costly. [6]Kok and Saad proposed a modified IncCond algorithm based on multifaceted duty cycle control method which utilizes the PV curve under partial shaded conditions effectively and the tracking speed is also increased than the conventional INC method [7]. Particle Swarm Optimization-In case of shaded PV system the PV curve possess multiple peaks and convergence to MPP becomes essential. In order to overcome this many biologically inspired optimization methods were implemented. One such optimization method is called Particle Swarm Optimization where the individual module voltage is determined. Mohammed et al have used this algorithm for switching power converters which used multi-junction solar cells. Thus only a single PSO based controller has been used thereby reducing the cost and complexity. [2]K. L. Lianet al proposed a hybrid model of Perturb & Observe (PO) and PSO method. The PO method was used to initially identify the nearest local maximum then the PSO method is followed. The advantage of this hybrid method is the search space is reduced with very fast MPP tracking [8]. Fuzzy Logic based MPPT method-This method comes under the Artificial Neural Network (ANN) type of MPPT as classified by Bidyadhar and Brassware. [13] Ahmad and Rached have proposed a new DSP controlled dual-MPPT scheme based on fuzzy logic control (FLC). The first MPPT controller is an astronomical two-axis sun tracker that keeps maximum radiation on the panel throughout the day. The second controller implements a new fuzzy-based MPPT technique to adaptively change the P&O perturbation step size depending on the PV system operating point and the current step size. The proposed control scheme achieves stable operation in the entire region of the PV panel and eliminates therefore the resulting oscillations around the maximum power operating point [14].

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Extremum Seeking control MPPT method- In order to deal with the varying shading conditions Peng et al proposed a sequential Extremum Seeking Control(ESC).This method deals with segmental search of MPP with consistent definition of searching range in order to achieve better computational efficiency. In this method the accumulative variation of in determining the initial search voltage is avoided [10]. Xiao et al classifies the MPPT methods as static and dynamic where the Extremum Seeking Control comes under dynamic category of MPPT and these are the methods which improve the transient performance. They have also brought some stability and performance issues of the normal ESC MPPT methods. In order to overcome such limitations they have proposed an Adaptive Extremum Seeking Control (AESC) which has some modifications in the previous ESC method [12]. DSP based MPPT method-In the research of MummadiVeerachary a voltage-based power tracking for nonlinear PV sources using coupled inductor SEPIC converter was proposed and demonstrated. Here a DSP based MPPT with a separate mathematical algorithm is explained.The main advantage of this method is the reduced ripple in the array current and the converter efficiency has improved. [11] 5. CONCLUSION The review and analysis of various MPPT technique used in the literature for both standalone and grid connected systems has been discussed. The advantages and disadvantages for each MPPT method can be understood from the survey. From this paper appropriate MPPT method can be selected and implemented as per the requirement. REFERENCES [1] Huang-Jen Chiu, Yu-Kang Lo, Chun-Jen Yao, Ting-Peng Lee, Jian-Min Wang, and Jian-Xing Lee,( March 2011) “A Modular Self-Controlled Photovoltaic Charger With InterIntegrated Circuit (I2C) Interface”, IEEE Transactions on Energy Conversion, Vol. 26, No. 1. [2] Mohammed A. Elgendy, Bashar Zahawi, and David J. Atkinson, (January 2012)“Assessment of Perturb and Observe MPPT Algorithm Implementation Techniques for PV Pumping Applications”, IEEE Transactions on Sustainable Energy, Vol. 3, No. 1. [3] Kun Ding, XinGaoBian, HaiHao Liu, and Tao Peng (December 2012) “A MATLAB-SimulinkBased PV Module Model and Its Application Under Conditions of Nonuniform Irradiance”, IEEE Transactions on Energy Conversion, Vol. 27, No. 4.

[4] TrishanEsram, and Patrick L. Chapman(June 2007), “Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques”, IEEE Transactions on Energy Conversion, Vol. 22, No. 2. [5] Qiang Mei, Mingwei Shan, Liying Liu, and Josep M. Guerrero (June 2011), “A Novel Improved Variable Step-Size IncrementalResistance MPPT Method for PV Systems”, IEEE Transactions on Industrial Electronics, Vol. 58, No. 6. [6] Mohamed O. Badawy, Ahmet S. Yilmaz, Yilmaz Sozer, and Iqbal Husain, “Parallel Power Processing Topology for Solar PV Applications”, IEEE Transactions on Industry Applications, Vol. 50, No. 2, March/April 2014 [7] Kok Soon Tey and SaadMekhilef (October 2014) “Modified Incremental Conductance Algorithm for Photovoltaic System Under Partial Shading Conditions and Load Variation”, IEEE Transactions on Industrial Electronics, Vol. 61, No. 10. [8] K. L. Lian, J. H. Jhang, and I. S. Tian,( March 2014) “A Maximum Power Point Tracking Method Based on Perturb-and-Observe Combined With Particle Swarm Optimization”, IEEE Journal of Photovoltaics, Vol. 4, No. 2. [9] Ahmad Al Nabulsi and RachedDhaouadi (August 2012), “Efficiency Optimization of a DSP-Based Standalone PV System Using Fuzzy Logic and Dual-MPPT Control”, IEEE Transactions on Industrial Informatics, Vol. 8, No. 3. [10] Peng Lei, Yaoyu Li, and John E. Seem (July 2011), “Sequential ESC-Based Global MPPT Control for Photovoltaic Array With Variable Shading”, IEEE Transactions on Sustainable Energy, Vol. 2, No. 3. [11] MummadiVeerachary (July 2005), “Power Tracking for Nonlinear PV Sources with coupled Inductor SEPIC Converter”, IEEE Transactions on Aerospace and Electronic Systems Vol. 41, No. 3. [12] Xiao Li, Yaoyu Li, and John E. Seem, “Maximum Power Point Tracking for Photovoltaic SystemUsing Adaptive Extremum Seeking Control” [13] BidyadharSubudhi and Raseswari Pradhan (January 2013), “A Comparative Study on maximum Power Point Tracking Techniques for Photovoltaic Power Systems”, IEEE Transactions on Sustainable energy, Vol. 4, No. 1. [14] Ahmad Al Nabulsi and RachedDhaouadi (August 2012), “Efficiency Optimization of a DSP-Based Standalone PV System Using Fuzzy Logic and Dual-MPPT Control”, IEEE Transactions on Industrial Informatics, Vol. 8, No. 3.

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Student Journal of Electrical and Electronics Engineering Issue No. 1, Vol. 1, 2015

SIMULATION OF MPPT FOR SINGLE STAGE PV GRID CONNECTED SYSTEM S. Stephy Sharon, A. Sharan Monika Second year MEPED, Saranathan College of Engineering, Tiruchirapalli [email protected], [email protected]

1. INTRODUCTION Grid-connected Photovoltaic systems usually employs two stages, the first stage is a dc-dc boost converter for boosting the PV voltage, and achieving MPPT, and the second stage is a dc-ac inverter for conditioning the output power and synchronizing with the power grid. However, such systems have drawbacks as complexity in control, lower efficiency, lower reliability, higher cost, and larger size. On the other hand, single-stage grid-connected systems provide many advantages such as simple topology, high efficiency, high power density, and lower cost. However, achieving MPPT, while conditioning the output power and synchronizing with the power grid, is a big challenge in such systems [1]. The inverters must guarantee that the PV module is operated at the MPP, which is the operating point where the maximum energy is captured. MPPT is an essential part of any PV system. Many Maximum Power Point tracking (MPPT) methods have been developed and implemented. The methods vary in performance indices, complexity, input sensors, convergence speed, cost, range of effectiveness, implementation complexity, and in other aspects.

The paper is organized as follows, section II presents literature survey, the theoretical frameworks are described in Section III. Section IV describes Incremental Conductance MPPT scheme for grid connected PV Systems. Finally, conclusion and future work have been presented in Section V. 2. LITERATURE SURVEY About 135 IEEE Journal Papers have been studied to make a survey on the basis of the MPPT schemes employed in standalone and grid connected PV Systems. It is majorly segregated as grid connected system and standalone applications. Further, classified based on the topology used in the paper i.e. Single Stage and Double Stage. Figure 1 shows number of papers in the literature about MPPT schemes employed in grid connected PV systems.

Statistics 50 0

2010 2011 2012 2013 201…

Index Terms—MPPT, Single Stage, Load angle(delta), Photovoltaics, Incremental Conductance.

The general requirements for MPPT are simplicity, low cost, quick tracking under changing conditions, and small output power fluctuation. Efficient methods to solve this problem become crucially important. This paper presents a MPPT controller that enables an efficient power control using a single-stage voltage source inverter (VSI)[2].

No of Papers

Abstract— This paper presents a Simulation of Maximum Power Point Tracking (MPPT) control for Grid connected PV systems. The topology considered in this project is single stage system. The Single stage system consists of PV array fed to three phase Inverter synchronized with three phase Grid. Different MPPT algorithms reported in literature have been classified based on topology of Grid interface. In this work, Modified Incremental Conductance with δ control has been employed. Simulation of this single stage Grid tied PV Inverter is done using MATLAB/ Simulink. Different cases have been considered for simulation and validation under varying irradiation and temperature conditions. Also the MPPT control under varying grid parameters has also been analyzed. The Simulation results have been presented in detail and the results depicts that δ(delta) control modified Incremental conductance MPPT works for different values of Irradiations, Temperature and grid parameters variation and are presented in this work.

No. of papers

Year

Fig. 1 No. of PV Grid Connected system Papers Using a solar panel or an array of panels without a controller that can perform Maximum Power Point Tracking (MPPT) will often result in wasted power, which ultimately results in the need to install more panels for the same power requirement [3]. In short term, not using an MPPT controller will result in a higher installation cost. Based on the topologies used, that is single stage or double stage, the converter on which the MPPT is implemented is differs. In case of a double-stage conversion system, the MPPT technique is used to control the DC/DC converter, while in case of single-stage conversion system the

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S. Stephy Sharon, and A. Sharon Monica

MPPT is included in the DC/AC converter control [4]. This survey gives a clear idea about the existing MPPT schemes employed in grid interfaced PV systems. Figure 2 shows the different types of MPPT schemes.

places only when there is some load angle difference in the voltages. Let load angle be δ (delta). δ ranges from 0° to 180°. 𝑉 𝑉

P = 3 1 2 sin δ 𝑋 P- Maximum Power Delivered (W)

(1)

Fig. 3 Two Ideal sources in series Fig.2 Types of MPPT used in Grid Connected PV systems The main MPPT methods can be classified as Perturb and Observe (P&O), Incremental Conductance (INC). These algorithms are called “hill-climbing” methods. The P&O is one of the most used MPPT methods, because it can be easily implemented. But the advantage of Incremental conductance method is the fast and accurate tracking of the MPP without oscillations around the MPP, otherwise the complexity is increased, and hence it requires more computational time. In this paper, incremental conductance algorithm is employed In the incremental conductance method [1], the controller must measure the incremental changes in array current and voltage to predict the effect of a voltage change. This method requires more computation in the controller, but can track changing conditions more rapidly than perturb and observe method (P&O) [5]. Like the P&O algorithm, it can produce oscillations in power output. This method utilizes the incremental conductance (dI/dV) of the photovoltaic array to compute the sign of the change in power with respect to voltage (dP/dV).

PV Voltage, Vpv=V1=230 V∠δ°, Load angle-δ Grid Voltage, Vg=V2= 230 V∠0°, Frequency-f (Hz) Reactance, X= 2ΠfL (L=30mH) From equation (1), we know that the maximum power is a function of δ (load angle). Hence, Power can be controlled by varying the value of δ. The block schematic of single stage PV tied grid connected system is shown in figure 4. A set of PV array is connected in combination of series and parallel, which is interfaced with a three phase inverter through a dc link capacitor across it. The value of dc link capacitor is chosen appropriately. The output of the inverter is synchronized with three phase grid/utility. A line reactance is kept in between in the inverter and grid (L=30mH). Here, the inverter is controlled by Sine PWM technique in which δ is introduced in the three phase sine reference signal for power control.

POWER TRANSFER BETWEEN TWO SOURCES The primary objective of this PV fed Inverter synchronized with grid is to inject power from solar modules to grid. It is nothing but the power transfer between two sources. Circuit shown in fig.3 can be used to study the power transfer between two sources. The circuit consists of two ideal single phase sources of same magnitude and difference in phase angle connected in series along with a reactance. According to the Maximum Power Transfer theorem [2], it is clear that the power flow takes

Fig 4. Block Diagram of Single Stage PV Grid Connected Systems A. δ -Control The load angle (δ) usually has a small value. In such band of angles, the sine function has a sharp slope, and the cosine function has a flat slope. Therefore, the active power (Pg) is deeply affected by changing δ than by changing the generator output voltage [6].

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Simulation of MPPT for Single Stage PV Grid Connected System

The above principle is usually used in case of conventional power generation systems. Moreover, it is applicable to grid connected PV systems [1]. This principle is applied to maximize the power produced by a grid connected PV system; as presented in [7]. Their investigations concluded that tracking with δ exhibits steady state oscillations around the MPP. Moreover, tracking with δ is made to be stable when it reaches state performance. On the other hand, the latter has a poor dynamic performance. B. Simulation Of Single Phase PV Fed Grid with δ Control The single stage PV grid connected system, is simulated in MATLAB/Simulink. The various simulation parameters are indicated in Table III (System Parameters). The maximum power delivered by the PV panels is Powermax (Pm). Pm is given as the reference to calculate the value of δ (using Eqn. 2). Thus, the calculated δ is given to the sine PWM module to generate pulses to the inverter and the reference power is the maximum power, delivered to the grid. This is validated through calculations and the circuit is simulated for different values of irradiations (Q)(kW/m2) temperature (T)(°C). δ = sin−1

P X

(2)

3V 1 V 2

The above table is taken by simulating the circuit shown in figure.6. The values of Real Power P, Reactive Power Q, Apparent Power S, Power factor (pf) are taken are the varying values of δ. Here, for analysis, δ has been considered from 15° to 180°. Because for 0 value of δ, the power flow will become zero. Hence it is omitted.

Power Vs δ 20000 10000 0 -10000

15° 30° 45° 60° 90° 120° 150° 180° Real power

Reactive power

Apparent Power Fig 6. Power (P,Q,S) characteristics with respect to δ From the above Figure 6, the characteristics of Real power, Reactive Power and Apparent Power are shown. For Real Power P, the value increases from its minimum value to maximum value till it reaches it maximum value at 90°. Beyond 90°, the value of real power decreases and also reaches negative value of power. Which means, the flow of power is reversed. That is the power flows from source-2 to source-1. B. Simulation

Fig .5 Array Power Vs Array Voltage By varying the value of δ, which ranges from (0° to 180°), and the magnitude of the voltage kept constant. Table. 1 Power for different Values of δ δ 15°

Irms 6.327

P 1449

Q 189

S 1462

0.9915

30°

12.58

2799

747

2897

0.9661

45°

18.62

3961

1636

4285

0.9243

60°

24.3

4846

2793

5594

0.8664

90°

34.36

5593

5587

7906

0.7075

120°

42.09

4838

8383

9679

0.4999

150°

46.43

2776

10420

10780

0.257

180°

48.72

-20.17

11210

11210

0.0018

pf

Fig 7 Block diagram single stage PV grid connected system The load angle (δ) usually has a small value. In such band of angles, the sine function has a sharp slope, and the cosine function has a flat slope. Therefore, the active power (Pg) is deeply affected by changing δ than by changing the generator output voltage. In fig 7, the block diagram of single stage grid connected system is shown .The above principle is usually used in case of conventional power generation systems. Moreover, it is applicable to grid connected PV systems. This principle is applied to maximize the power produced by a grid connected PV system. Their investigations concluded that tracking with δ exhibits steady state oscillations around the MPP. Moreover, tracking with δ is made

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S. Stephy Sharon, and A. Sharon Monica

to be stable when it reaches state performance. On the other hand, the latter has a poor dynamic performance.

6

No. of strings in parallel

7

7

No. of panels in series

35

Vg

400

Grid Parameters

300

Grid Voltage (V)

200

8

Grid Voltage

Vg(V)

415V, 3 φ

9

Line Inductance

L(mH)

30mH

10

Switching Frequency

fs (Hz)

1050Hz

11

Modulation Index

Mi

1

100 0 -100

PWM

-200 -300 -400 0

0.005

0.01

0.015

0.02 Time (sec)

0.025

0.03

0.035

0.04

(a) ig

40

CONCLUSION

30

A delta control MPPT is presented for single stage grid connected PV Inverters. It employs load angle control to deliver maximum power. Power is very sensitive to the change in load angle(δ). (Power is a function of Load angle, δ). The simulation results proved its efficient performance and applicability to track the MPP in a grid connected PV energy systems.

Grid Current Ig (A)

20 10 0 -10 -20 -30 -40 1

1.005

1.01

1.015

1.02 Time (sec)

1.025

1.03

1.035

1.04

(b) Fig 8. Grid voltage and grid current using delta control MPPT The different values of irradiation and temperature used for the simulation of PV fed grid. The simulation reaches its steady state at 0.2 seconds for each change in value of Q and T. In fig 8, the grid voltages and currents are shown. As irradiation reduces, power delivered reduces. Array power with respect to array voltage is shown in Figure 5. For each change in value of irradiance and temperature, the power delivered varies accordingly. Different maximum power point of different values of irradiations are indicated in the graph above. (Fig.5). Table II gives the specifications considered for the simulation. Table. 2 System Parameters S.No

Parameter

Symbol

Value

P(W)

80W

2

Maximum Power of a Module Standard Temperature

T(°C)

25°C

3

Standard Irradiance

Q(kW/m2)

1 kW/m2

4

Open Circuit Voltage

Voc(V)

21.29V

5

Short Circuit Current

Isc(A)

4.72A

PV Parameters 1

REFERENCES Gamal M. Dousoky, Masahito Shoyama, and Haitham Abu‐Rub, “Dual-Mode Controller for MPPT in Single-Stage Grid-Connected Photovoltaic Inverter” 2013 IEEE Gamal M. Dousoky, Emad M. Ahmed, Masahito Shoyama” MPPT Schemes for Single-Stage Three-Phase Grid-Connected Photovoltaic Voltage-Source Inverters” IEEE International Conference on Industrial Technology Mihnea Rosu-Hamzescu, Sergiu Oprea,Microchip Technology Inc. “Practical Guide to Implementing Solar Panel MPPT Algorithms” Enrique romer o-cadaval,Giovanni spagnuolo, Leopoldo g. Franquelo, Carlos-andrés ramospaja, Te uvo suntio, and Weidong-michael xiao “Grid-Connected Photovoltaic Generation Plants” IEEE industrial electronics magazine September 2013. Sreeraj E. S., Kishore Chatterjee, Member, IEEE, and Santanu Bandyopadhyay One-Cycle-Controlled Single-Stage Single-Phase Voltage-Sensorless Grid-Connected PV System” IEEE Transactions On Industrial Electronics, Vol. 60, No. 3, March 2013 Rashid, “Power Electronics: Circuits, Devices and Applications”, Pearson Education India, 2003 [7] Søren Bækhøj Kjær, Member, IEEE “Evaluation of the “Hill Climbing” and the “Incremental Conductance” Maximum Power Point Trackers for Photovoltaic Power Systems” IEEE Transactions On Energy Conversion, Vol. 27, No. 4, December 2012.

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