Bidirectional Converter For Renewable Energy Application.

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

FACULTY OF ELECTRICAL ENGINEERING

LAPORAN PROJEK SARJANA MUDA

BIDIRECTIONAL CONVERTER FOR RENEWABLE ENERGY APPLICANTION

CHONG MAN YUEN

“I hereby declare that I have read through this report entitle “Bidirectional converter for renewable energy application” and found that it has comply the partial fulfillment for awarding the degree of Bachelor of Electrical Engineering (Industrial Power)”

Signature : ...

Supervisor’s Name : ... Date : ...

BIDIRECTIONAL CONVERTER FOR RENEWABLE ENERGY APPLICATION

CHONG MAN YUEN

A report submitted in partial fulfillment of the requirements for the degree of Electrical Engineering(Industrial Power)

Faculty of Electrical Engineering

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

I declare that this report entitle “Bidirectional converter for renewable energy application” is the result of my own research except as cited in the references. The report has not been accepted for any degree and is not concurrently submitted in candidature of any other degree.

Signature : ... Name : ... Date : ...

Special dedicated to my beloved parent and family

For my supervisor, Mr. Azhan Bin Ab. Rahman Universiti Teknikal Malaysia Melaka

And lastly to my beloved friends and who encouraged, guided and inspired me throughout my journey in education

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ACKNOWLEDGEMENT

First of all, I would like to express my deepest thankful and gratitude to my family which give me fully support during my deepest concentrations. In particular, I wish to express my sincere appreciation to my main project supervisor, En. Azhan Bin Ab. Rahman for encouragement, guidance critics and friendship. Without his continued support and interest, this project would not have been same as presented here.

Secondly, it is difficult to name all the people who directly and indirectly help me in this project; an idea here and there may have appeared insignificant at the time but may have had a significant casual effect. In addition, deeply acknowledge who involve directly and indirectly for their never ending encouragement, moral support and patient during the duration of final year project. For all your advice and encouragement, this thesis is gratefully dedicated to my family and my friends. Thank you very much for your continuous support toward this the publication of this thesis.

Last but not least, I take this opportunity to dedicate this thesis for all electrical engineering students. All suggestions for further improvement of this thesis are welcome and will be gratefully acknowledged.

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ABSTRACT

The Project is aimed to design a battery system that consists of a bidirectional converter for renewable energy application. In order to determine the most applicable bidirectional converter circuit which meets the set of requirements, three or four types of the circuits will be simulated with the aid of PSCAD software. The battery is supposed to be energized when there is excessive supply of power available. Besides that, the battery is also supposed to release its energy when supply of power is low. The chosen circuit will then be constructed so that analysis can be performed in order to compare the simulation and experiment result.

vii

ABSTRAK

Projek ini adalah bermatlamat untuk merekabentuk satu sistem bateri yang mengandungi sebuah penukar dwiarah untuk mengaplikasikan penggunaan tenaga boleh baharu. Untuk menentukan litar penukar dwiarah yang memenuhi syarat-syarat tertentu, tiga atau empat jenis litar penukar dwiarah akan disimulasikan dengan menggunakan perisian PSCAD. Bateri sepatutnaya dicaskan apabila terdapat bekalan kuasa yang belebihan. Selain itu, bateri juga mengeluarkan tenaganya apabila bekalan kuasa adalah rendah. Litar penukar dwiarah terpilih akan dibina dan analisis dengan tujuan membandingkan keputusan simulasi dan eksperimen.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

ACKNOWLEDGEMENT v

ABSTRACT vi

TABLE OF CONTENTS viii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF ABBREVIATIONS xiv

LIST OF APPENDICES xv

1 INTRODUCTION 1

1.1 Problem Statement 1 1.2 Project Objective 2 1.3 Project Scope 2

2 LITERATURE REVIEW 3

2.1 Renewable energy 3 2.2 Switch-mode power supply (SMPS) 6 2.2.1 Rectifier 6 2.2.2 Smoothing 9 2.2.3 Inverter 10 2.3 Bidirectional converter 11 2.3.1 Buck converter 13 2.3.2 Buck-boost converter 15 2.3.3 Bidirectional converter circuit diagram 17

ix

CHAPTER TITLE PAGE

2.3.4 Diode 18 2.3.5 Insulated gate bipolar transistor (IGBT) 19 2.4 Feedback control system 20 2.5 Optocoupler 21

3 PROJECT METHODOLOGY 23

3.1 Project flow chart 23 3.2 PSCAD 24 3.3 Parts of simulation circuit 27 3.3.1 Simplified power line circuit 27 3.3.2 Feedback control circuit 28 3.3.3 Bidirectional converter circuit 29 3.3.3.1 Circuit one 29 3.3.3.2 Circuit two 30 3.3.3.3 Circuit three 31 3.3.3.4 Circuit four 32 3.4 Simulation for suitable bidirectional 33

converter circuit

3.4.1 Circuit one 33 3.4.2 Circuit two 34 3.4.3 Circuit three 35 3.4.4 Circuit four 36

4 SIMULATION RESULT AND DISCUSSION 37

4.1 Simulation result of circuit one 37 4.2 Simulation result of circuit two 39 4.3 Simulation result of circuit three 41 4.4 Simulation result of circuit four 43

x

4.5 Summary of simulation result 45 4.5 Performance test for circuit four 47

4.5.1 Test one 47 4.5.2 Test two 49

5 Conclusion 51

5.1 Conclusion 51 5.2 Recommendation 52 5.3 Contribution 52

CHAPTER TITLE PAGE

REFERENCES 53

xi

LIST OF TABLES

TABLE TITLE PAGE

4.1 Waveform of Vs, Is,Vcap, Icap, Vbat, Ibat and Icon for 37

circuit one

4.2 Waveform of Vs, Is,Vcap, Icap, Vbat, Ibat and Icon for 39

circuit two

4.3 Waveform of Vs, Is,Vcap, Icap, Vbat, Ibat and Icon for 41

circuit three

4.4 Waveform of Vs, Is,Vcap, Icap, Vbat, Ibat and Icon for 43

circuit four

4.5 Capacitor voltage and battery current of circuit one 45 4.6 Capacitor voltage and battery current of circuit two 45 4.7 Capacitor voltage and battery current of circuit three 46 4.8 Capacitor voltage and battery current of circuit four 46 4.9 Waveform of Vs, Is,Vcap, Icap, Vbat, Ibat and Icon 48

xii

LIST OF FIGURES

FIGURE TITLE PAGE

2.1 Cost of generating electricity in UK[3] 4 2.2 Wind power technology development[7] 5 2.3 Conventional configuration for renewable 6

energy power generation[4]

2.4 Half-wave rectifier and waveform[15] 7 2.5 Half-wave rectifier with transformer-coupled 7

input voltage[15]

2.6 Half-wave rectifier operation and waveform[15] 7 2.7 Full wave rectifier and waveform[15] 8 2.8 Center-tapped full wave rectifier[15] 8 2.9 Full-wave rectifier operation and waveform[15] 9 2.10 Waveform after smoothing[4] 10 2.11 Bridge inverter configuration[6] 11 2.12 Renewable energy generation configuration with 11

back-up supply and bidirectional converter

2.13 Current from line flow into battery while 12 excessive of power available

2.14 Current flow out from battery and supply to load 12 while supply is low

2.15 Buck converter circuit diagram[5] 13 2.16 Switch-on for time duration DT[5] 14 2.17 Switch-off for a time duration (1-D)T[5] 14 2.18 Buck converter waveform in continuous mode[5] 14

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FIGURE TITLE PAGE

2.19 Buck-boost circuit diagram[16] 15 2.20 Buck-boost converter waveform in continuous 16

mode[17]

2.21 Bidirectional converter circuit diagram[8] 17 2.22 Example and circuit symbol of diode[11] 18 2.23 I-V characteristic for P-N junction diode[10] 18 2.24 Cross section and circuit symbol of IGBT[12] 19 2.25 Feedback control system block diagram[14] 20 2.26 Schematic diagram of a very simple optocoupler[25] 22 3.1 Project flow chart 23 3.2 Open the file 24 3.3 Set the file as active 25 3.4 Select “Edit Definition” to open a module 25 3.5 Select “Save As” to save the circuit in specific file 26 3.6 Click “Run” to run simulation 26 3.7 Simulation result show on graph frame 27 3.8 Simplified power line 28 3.9 Feedback control circuit 28 3.10 Circuit one 29 3.11 Circuit two 30 3.12 Circuit three 31 3.13 Circuit four 32 3.14 Circuit one 33 3.15 Circuit two 34 3.16 Circuit three 35 3.17 Circuit four 36 4.1 Circuit four with breaker and additional load 47

xiv

LIST OF ABBREVATIONS

V - Voltage I - Current A - Ampere

IEEE - Institute of Electrical and Electronic Engineers SMPS - Switch-mode power supply

IGBT - Insulated gate bipolar transistor L - Inductor

C - Capacitor R - Resistor DC - Direct Current AC - Alternating Current Vs - Supply voltage

Vcap - Capacitor voltage

Vbat - Battery voltage

Is - Supply voltage

Icap - Capacitor current

Ibat - Battery current

xv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Project Planning 56 B A new topology of a battery energy storage system 58 C Efficient, High-Temperature Bidirectional Dc/Dc

Converter for Plug-in-Hybrid Electric Vehicle(PHEV) 65 using SiC Devices

D Analysis and Control of Bidirectional DC/DC 73 Converter for PEM Fuel Cell Applications

E Parallel Bidirectional DC/DC Converter Topology 81 for Energy Storage Systems in Wind Applications

F Performance Comparison of Bidirectional Converter 89 Designs for Renewable Power Generation

CHAPTER 1

INTRODUCTION

1.1 Problem Statement

Although switch-mode power supply (SMPS) is commonly use in renewable energy generation industry but renewable energy generation supply is inconsistent due to renewable energy relies on the weather for its source of power. To solve this problem, battery and bidirectional converter is needed to perform bidirectional power flow. Besides that, Bidirectional converter that use in the renewable energy generation industrial is complex and expensive.

This project is focused on the design of bidirectional converter. The Bidirectional converter to be designed has to meet the requirement of:

1. Enable to perform basic bidirectional power flow 2. Simple design

2

1.2 Project Objective

The objectives of this project are:

1. To design a battery system which consist of a bidirectional converter for a renewable energy application.

2. The battery is supposed to be energized when there is excessive supply of power available.

3. The battery is also supposed to release its energy when supply of power is low.

1.3 Project Scope

The target of this project is on the design of bidirectional converter. Simulation will be performed only on the four chosen bidirectional converter circuits by using PSCAD. From the simulation result, the battery is supposed to be energized when there is excessive supply of power available. The battery is also supposed to release its energy when supply of power is low. Besides, the four chosen bidirectional converter circuits have to meet three criteria which is the bidirectional circuit can performed basic dual power flow, simple design and inexpensive to construct.

CHAPTER 2

LITERATURE REVIEW

2.1 Renewable energy

Nowadays, many energy sources include oil, nature gas, and coal that are extremely limited in supply and they will exhaust soon. So in an effort to find alternative forms of energy, the world has turned to renewable energy sources as the solution.

Renewable energy is the energy generated from natural sources such as sunlight, wind, tides and geothermal heat which are naturally replenished. We can capture some of this energy and put it to use in our homes and businesses with the help of special collectors. As long as sunlight, water and wind continue to flow and trees and other plants continue to grow, we have access to a ready of supply of energy.

The most common advantage with the use of renewable energy is that they are renewable and cannot be depleted. Besides that, Renewable energy is produces little or no waste products such as carbon dioxide or other chemical pollutants, so they don’t pollute environment and don’t contribute to global warming or greenhouse effect. Since renewable energy is natural, the cost of operations is reduced. By then, renewable energy facilities generally require less maintenance than traditional generators. This is because traditional generator will produce waste after some process, so more maintenance requires.[1] Furthermore, Renewable energy projects can also bring economic benefits to many regional areas, as most projects are located away from large urban centers and suburbs of the capital cities. The most significant effect is bringing working opportunities to residents

4

in that area.[1]

It is easy to recognize the environmental advantages of utilizing the alternative and renewable forms of energy but we must also be aware of the disadvantages. One of the disadvantages with renewable energy is difficult to generate the quantities of electricity that are as large as those produced by traditional fossil fuel generators. This may mean that we need to reduce the amount of energy we use or simply build more energy facilities.[2] Another disadvantage of renewable energy sources is the reliability of supply. Renewable energy often relies on the weather for its source of power, for example, hydro generators need rain to fill dams to supply flowing water, Wind turbines need wind to turn the blades and solar collectors need clear skies and sunshine to collect heat and make electricity. When unsuitable weather condition happens, renewable energy plant cannot supply enough energy to us. This mean renewable energy is unpredictable and inconsistent.[1] Besides that, the current cost of renewable energy technology is also far in excess of traditional fossil fuel generation. This is because it is a new technology and as such has extremely large capital cost.[2]

5

Figure 2.1 shows the cost of generating electricity with no cost of CO2 emissions included in UK. The first six elements is traditional generation and last four is renewable energy generation. From here show that cost of generating electricity by renewable energy are more expensive than traditional generation.[3]

Renewable energy generation will improve because of power electronics. Once renewable energy generation establish and stable, it will much cheaper if compare to traditional generation.[7]

Figure 2.2: Wind power technology development.[7]

Figure 2.2 shows wind power technology development. From this figure, we can see that it predicts that future, cost will much cheaper.[7] Switch-mode power supply (SMPS) commonly uses in renewable energy generation industry. Basic SMPS included rectifier and inverter. Section 1.1 below will describe move on SMPS.

6

2.2 Switch-mode power supply (SMPS)

Figure 2.3 : Conventional configuration for renewable energy power generation[4]

Figure 2.3 shows conventional configuration for renewable energy power generation. First, renewable energy output pass rectifier and convert to DC output. After that, DC output from rectifier will pass a capacitor to smooth the ripple of DC output. Next, the DC output will pass inverter and convert to AC output. Last, AC output from inverter will go in to grid line and supply to consumer.

2.2.1 Rectifier

A basic rectifier is a circuit that converts AC input power to DC output power. The input supply may be a single phase or a multi-phase supply. The output is DC voltage and current with certain amount of ripple components. There are two types of rectifier, namely half wave and full wave. Each type can either be uncontrolled, half-controlled or fully controlled. An uncontrolled rectifier uses diodes, while a full-controlled rectifier uses thyristor or popularly known as Silicon Controlled Rectifier (SCR). A half controlled is a mix of diodes and thyristors. The thyristors need to be turned on using a special triggering circuit.[7]

7

In practice, the half-wave rectifier is used most often in low-power applications because the average current in the supply will not be zero. This may cause problems in transformer performance. While practical applications of half wave rectifier are limited, the analysis is important because it will enable us to understand more complicated circuits such as full wave-and three-phase rectifiers.

Figure 2.4: Half-wave rectifier and waveform[15]

Figure 2.5: Half-wave rectifier with transformer-coupled input voltage[15]

8

Figure 2.4 shows the half-wave rectifier and waveform. Next, Figure 2.5 shows the half-wave rectifier with transformer-coupled input voltage. Last, Figure 2.6 shows half-wave rectifier operation and waveform. Like half-wave, the objective of a full-wave rectifier is to produce a voltage or current which is purely DC or has some specified dc component. While the purpose of the full wave rectifier is basically the same as that of the half-wave rectifiers have some fundamental advantages. The average current in the ac source is zero in the full-wave rectifier, thus avoiding problems associated with nonzero average source currents. The average DC output voltage is higher than half-wave. The output of the full-wave is inherently less ripple that the half-wave rectifier.[7]

Figure 2.7: Full wave rectifier and waveform[15]

CHAPTER 2

LITERATURE REVIEW

2.1 Renewable energy

Nowadays, many energy sources include oil, nature gas, and coal that are extremely limited in supply and they will exhaust soon. So in an effort to find alternative forms of energy, the world has turned to renewable energy sources as the solution.

Renewable energy is the energy generated from natural sources such as sunlight, wind, tides and geothermal heat which are naturally replenished. We can capture some of this energy and put it to use in our homes and businesses with the help of special collectors. As long as sunlight, water and wind continue to flow and trees and other plants continue to grow, we have access to a ready of supply of energy.

The most common advantage with the use of renewable energy is that they are renewable and cannot be depleted. Besides that, Renewable energy is produces little or no waste products such as carbon dioxide or other chemical pollutants, so they don’t pollute environment and don’t contribute to global warming or greenhouse effect. Since renewable energy is natural, the cost of operations is reduced. By then, renewable energy facilities generally require less maintenance than traditional generators. This is because traditional generator will produce waste after some process, so more maintenance requires.[1] Furthermore, Renewable energy projects can also bring economic benefits to many regional areas, as most projects are located away from large urban centers and suburbs of the capital cities. The most significant effect is bringing working opportunities to residents

in that area.[1]

It is easy to recognize the environmental advantages of utilizing the alternative and renewable forms of energy but we must also be aware of the disadvantages. One of the disadvantages with renewable energy is difficult to generate the quantities of electricity that are as large as those produced by traditional fossil fuel generators. This may mean that we need to reduce the amount of energy we use or simply build more energy facilities.[2] Another disadvantage of renewable energy sources is the reliability of supply. Renewable energy often relies on the weather for its source of power, for example, hydro generators need rain to fill dams to supply flowing water, Wind turbines need wind to turn the blades and solar collectors need clear skies and sunshine to collect heat and make electricity. When unsuitable weather condition happens, renewable energy plant cannot supply enough energy to us. This mean renewable energy is unpredictable and inconsistent.[1] Besides that, the current cost of renewable energy technology is also far in excess of traditional fossil fuel generation. This is because it is a new technology and as such has extremely large capital cost.[2]

Figure 2.1 shows the cost of generating electricity with no cost of CO2 emissions included in UK. The first six elements is traditional generation and last four is renewable energy generation. From here show that cost of generating electricity by renewable energy are more expensive than traditional generation.[3]

Renewable energy generation will improve because of power electronics. Once renewable energy generation establish and stable, it will much cheaper if compare to traditional generation.[7]

Figure 2.2: Wind power technology development.[7]

Figure 2.2 shows wind power technology development. From this figure, we can see that it predicts that future, cost will much cheaper.[7] Switch-mode power supply (SMPS) commonly uses in renewable energy generation industry. Basic SMPS included rectifier and inverter. Section 1.1 below will describe move on SMPS.

2.2 Switch-mode power supply (SMPS)

Figure 2.3 : Conventional configuration for renewable energy power generation[4]

Figure 2.3 shows conventional configuration for renewable energy power generation. First, renewable energy output pass rectifier and convert to DC output. After that, DC output from rectifier will pass a capacitor to smooth the ripple of DC output. Next, the DC output will pass inverter and convert to AC output. Last, AC output from inverter will go in to grid line and supply to consumer.

2.2.1 Rectifier

A basic rectifier is a circuit that converts AC input power to DC output power. The input supply may be a single phase or a multi-phase supply. The output is DC voltage and current with certain amount of ripple components. There are two types of rectifier, namely half wave and full wave. Each type can either be uncontrolled, half-controlled or fully controlled. An uncontrolled rectifier uses diodes, while a full-controlled rectifier uses thyristor or popularly known as Silicon Controlled Rectifier (SCR). A half controlled is a mix of diodes and thyristors. The thyristors need to be turned on using a special triggering circuit.[7]

In practice, the half-wave rectifier is used most often in low-power applications because the average current in the supply will not be zero. This may cause problems in transformer performance. While practical applications of half wave rectifier are limited, the analysis is important because it will enable us to understand more complicated circuits such as full wave-and three-phase rectifiers.

Figure 2.4: Half-wave rectifier and waveform[15]

Figure 2.5: Half-wave rectifier with transformer-coupled input voltage[15]

Figure 2.4 shows the half-wave rectifier and waveform. Next, Figure 2.5 shows the half-wave rectifier with transformer-coupled input voltage. Last, Figure 2.6 shows half-wave rectifier operation and waveform. Like half-wave, the objective of a full-wave rectifier is to produce a voltage or current which is purely DC or has some specified dc component. While the purpose of the full wave rectifier is basically the same as that of the half-wave rectifiers have some fundamental advantages. The average current in the ac source is zero in the full-wave rectifier, thus avoiding problems associated with nonzero average source currents. The average DC output voltage is higher than half-wave. The output of the full-wave is inherently less ripple that the half-wave rectifier.[7]

Figure 2.7: Full wave rectifier and waveform[15]