Power Electronic Converters for Microgrids E-Book

Suleiman M. Sharkh

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Wiley - IEEE
• Sprache: Englisch

Seitenzahl: 415

Veröffentlichungsjahr: 2014

Beschreibung

As concerns about climate change, energy prices, and energy security loom, regulatory and research communities have shown growing interest in alternative energy sources and their integration into distributed energy systems. However, many of the candidate microgeneration and associated storage systems cannot be readily interfaced to the 50/60 Hz grid. In Power Electronic Converters for Microgrids, Sharkh and Abu-Sara introduce the basics and practical concerns of analyzing and designing such micro-generation grid interface systems. Readers will become familiar with methods for stably feeding the larger grid, importing from the grid to charge on-site storage, disconnecting from the grid in case of grid failure, as well as connect multiple microgrids while sharing their loads appropriately. Sharkh and Abu-Sara introduce not only the larger context of the technology, but also present potential future applications, along with detailed case studies and tutorials to help the reader effectively engineer microgrid systems.

Leseprobe

Table of Contents

Cover

Title Page

Copyright

About the Authors

Preface

Acknowledgments

Chapter 1: Introduction

1.1 Modes of Operation of Microgrid Converters

1.2 Converter Topologies

1.3 Modulation Strategies

1.4 Control and System Issues

1.5 Future Challenges and Solutions

References

Chapter 2: Converter Topologies

2.1 Topologies

2.2 Pulse Width Modulation Strategies

2.3 Modeling

References

Chapter 3: DC-Link Capacitor Current and Sizing in NPC and CHB Inverters

3.1 Introduction

3.2 Inverter DC-Link Capacitor Sizing

3.3 Analytical Derivation of DC-Link Capacitor Current RMS Expressions

3.4 Analytical Derivation of DC-Link Capacitor Current Harmonics

3.5 Numerical Derivation of DC-Link Capacitor Current RMS Value and Voltage Ripple Amplitude

3.6 Simulation Results

3.7 Discussion

3.8 Conclusion

References

Chapter 4: Loss Comparison of Two- and Three-Level Inverter Topologies

4.1 Introduction

4.2 Selection of IGBT-Diode Modules

4.3 Switching Losses

4.4 Conduction Losses

4.5 DC-Link Capacitor RMS Current

4.6 Results

4.7 Conclusion

References

Chapter 5: Minimization of Low-Frequency Neutral-Point Voltage Oscillations in NPC Converters

5.1 Introduction

5.2 NPC Converter Modulation Strategies

5.3 Minimum NP Ripple Achievable by NV Strategies

5.4 Proposed Band-NV Strategies

5.5 Performance of Band-NV Strategies

5.6 Simulation of Band-NV Strategies

5.7 Hybrid Modulation Strategies

5.8 Conclusions

References

Chapter 6: Digital Control of a Three-Phase Two-Level Grid-Connected Inverter

6.1 Introduction

6.2 Control Strategy

6.3 Digital Sampling Strategy

6.4 Effect of Time Delay on Stability

6.5 Capacitor Current Observer

6.6 Design of Feedback Controllers

6.7 Simulation Results

6.8 Experimental Results

6.9 Conclusions

References

Chapter 7: Design and Control of a Grid-Connected Interleaved Inverter

7.1 Introduction

7.2 Ripple Cancellation

7.3 Hardware Design

7.4 Controller Structure

7.5 System Analysis

7.6 Controller Design

7.7 Simulation and Practical Results

7.8 Conclusions

References

Chapter 8: Repetitive Current Control of an Interleaved Grid-Connected Inverter

8.1 Introduction

8.2 Proposed Controller and System Modeling

8.3 System Analysis and Controller Design

8.4 Simulation Results

8.5 Experimental Results

8.6 Conclusions

References

Chapter 9: Line Interactive UPS

9.1 Introduction

9.2 System Overview

9.3 Core Controller

9.4 Power Flow Controller

9.5 DC Link Voltage Controller

9.6 Experimental Results

9.7 Conclusions

References

Chapter 10: Microgrid Protection

10.1 Introduction

10.2 Key Protection Challenges

10.3 Possible Solutions to Key Protection Challenges

10.4 Case Study

10.5 Conclusions

References

Chapter 11: An Adaptive Relaying Scheme for Fuse Saving

11.1 Introduction

11.2 Case Study

11.3 Simulation Results and Discussion

11.4 Fuse Saving Strategy

11.5 How Reclosing Will Be Applied

11.6 Observations

11.7 Conclusions

References

Appendix A: SVM for the NPC Converter–MATLAB®-Simulink Models

A.1 Calculation of Duty Cycles for Nearest Space Vectors

A.2 Symmetric Modulation Strategy

A.3 MATLAB

®

-Simulink Models

References

Appendix B: DC-Link Capacitor Current Numerical Calculation

Index

End User License Agreement

Pages

xi

xii

xii

xiv

xv

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

154

153

155

156

157

158

159

160

161

162

163

167

164

165

166

168

169

171

172

173

174

175

176

177

178

179

180

181

182

183

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

204

203

205

211

206

207

208

209

210

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

239

240

241

242

244

243

245

246

247

248

249

250

251

253

252

254

255

256

257

258

259

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

285

286

287

288

289

290

291

292

293

Guide

Table of Contents

List of Illustrations

Figure 1.1

Figure 1.2

Figure 1.3

Figure 1.4

Figure 1.5

Figure 1.6

Figure 2.1

Figure 2.2

Figure 2.3

Figure 2.4

Figure 2.5

Figure 2.6

Figure 2.7

Figure 2.8

Figure 2.9

Figure 2.10

Figure 2.11

Figure 2.12

Figure 2.13

Figure 2.14

Figure 2.16

Figure 3.1

Figure 3.2

Figure 3.3

Figure 3.4

Figure 3.5

Figure 3.6

Figure 3.7

Figure 3.8

Figure 3.9

Figure 3.10

Figure 4.1

Figure 4.2

Figure 4.3

Figure 4.4

Figure 4.5

Figure 5.1

Figure 5.2

Figure 5.3

Figure 5.7

Figure 5.4

Figure 5.5

Figure 5.6

Figure 5.8

Figure 5.9

Figure 5.10

Figure 5.11

Figure 5.12

Figure 5.13

Figure 5.14

Figure 5.15

Figure 5.16

Figure 5.17

Figure 5.18

Figure 5.19

Figure 5.20

Figure 5.21

Figure 6.1

Figure 6.2

Figure 6.3

Figure 6.4

Figure 6.5

Figure 6.6

Figure 6.7

Figure 6.8

Figure 6.9

Figure 6.10

Figure 6.11

Figure 6.12

Figure 6.13

Figure 6.14

Figure 6.15

Figure 6.16

Figure 7.1

Figure 7.2

Figure 7.3

Figure 7.4

Figure 7.5

Figure 7.6

Figure 7.7

Figure 7.8

Figure 7.9

Figure 7.10

Figure 7.11

Figure 7.12

Figure 7.13

Figure 7.14

Figure 7.15

Figure 7.16

Figure 7.17

Figure 7.18

Figure 7.19

Figure 7.20

Figure 7.21

Figure 7.22

Figure 7.23

Figure 7.24

Figure 7.25

Figure 7.26

Figure 7.27

Figure 7.28

Figure 7.29

Figure 7.30

Figure 7.31

Figure 7.32

Figure 7.33

Figure 7.34

Figure 7.35

Figure 7.36

Figure 8.1

Figure 8.2

Figure 8.3

Figure 8.4

Figure 8.5

Figure 8.6

Figure 8.7

Figure 8.8

Figure 8.9

Figure 8.10

Figure 8.11

Figure 8.12

Figure 8.13

Figure 8.14

Figure 9.1

Figure 9.2

Figure 9.3

Figure 9.4

Figure 9.5

Figure 9.6

Figure 9.7

Figure 9.8

Figure 9.9

Figure 9.10

Figure 9.11

Figure 9.12

Figure 9.13

Figure 9.14

Figure 9.15

Figure 9.16

Figure 9.17

Figure 9.18

Figure 9.19

Figure 9.20

Figure 9.21

Figure 9.22

Figure 9.23

Figure 9.24

Figure 9.25

Figure 9.26

Figure 9.27

Figure 10.1

Figure 10.2

Figure 10.3

Figure 10.4

Figure 10.5

Figure 10.6

Figure 10.7

Figure 10.8

Figure 11.1

Figure 11.2

Figure 11.3

Figure 11.4

Figure 11.5

Figure 11.6

Figure 11.7

Figure 11.8

Figure 11.9

Figure 11.10

Figure A.1

Figure A.2

Figure A.3

Figure A.4

Figure A.5

List of Tables

Table 2.1

Table 3.1

Table 3.2

Table 3.3

Table 3.4

Table 3.5

Table 4.1

Table 4.2

Table 4.3

Table 4.4

Table 4.5

Table 4.6

Table 4.7

Table 5.1

Table 6.1

Table 7.1

Table 7.2

Table 7.3

Table 7.4

Table 7.5

Table 8.1

Table 9.1

Table 9.2

Table 9.3

Table 10.1

Table 10.2

Table 10.3

Table 11.1

Table A.1

POWER ELECTRONIC CONVERTERS FOR MICROGRIDS

Suleiman M. Sharkh

University of Southampton, United Kingdom

Mohammad A. Abusara

University of Exeter, United Kingdom

Georgios I. Orfanoudakis

University of Southampton, United Kingdom

Babar Hussain

Pakistan Institute of Engineering and Applied Sciences, Pakistan

This edition first published 2014

© 2014 John Wiley & Sons Singapore Pte. Ltd.

Registered office

John Wiley & Sons Singapore Pte. Ltd., 1 Fusionopolis Walk, #07-01 Solaris South Tower, Singapore 138628.

For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as expressly permitted by law, without either the prior written permission of the Publisher, or authorization through payment of the appropriate photocopy fee to the Copyright Clearance Center. Requests for permission should be addressed to the Publisher, John Wiley & Sons Singapore Pte. Ltd., 1 Fusionopolis Walk, #07-01 Solaris South Tower, Singapore 138628, tel: [phone], fax: [phone], email: [email protected].

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The Publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the Publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought.

MATLAB® is a trademark of The MathWorks, Inc. and is used with permission. The MathWorks does not warrant the accuracy of the text or exercises in this book. This book's use or discussion of MATLAB® software or related products does not constitute endorsement or sponsorship by The MathWorks of a particular pedagogical approach or particular use of the MATLAB® software.

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom. If professional advice or other expert assistance is required, the services of a competent professional should be sought.

Library of Congress Cataloging-in-Publication Data has been applied for.

A catalogue record for this book is available from the British Library.

ISBN 978-0-470-82403-0

About the Authors

Suleiman M. Sharkh obtained his BEng and PhD degrees in Electrical Engineering from the University of Southampton in 1990 and 1994, respectively. He is currently the Head of the Electro-Mechanical Research Group at the University of Southampton. He is also the Managing Director of HiT Systems Ltd, and a visiting Professor at the Beijing Institute of Technology and Beijing Jiaotong University.

He has 20 years research experience in the field of electrical and electromagnetic systems, including electric switches, power electronics, electrical machines, control systems, and characterization and management of advanced batteries. To date he has published about 150 publications. He has obtained research grant income of about £2M from the Research Councils and industry since 1998. He has supervised 11 PhD students to completion and is currently supervising 5 PhD students. He is an established doctoral external examiner in the UK and abroad, including Europe, China, and Australia. His research has contributed to the development of a number of commercial products, including rim driven marine thrusters (TSL Technology Ltd), down-hole submersible motors for drilling and pumping oil wells (TSL Technology Ltd), sensorless brushless DC motor controllers (TSL Technology), power electronic converters for microgrids (Bowman Power Systems and TSL Technology), high-speed PM alternators for Rankine cycle and gas microturbine energy recovery systems (TSL Technology, Bowman Power Systems, and Freepower), and battery management systems (Reap Systems Ltd).

He was the winner of The Engineer Energy Innovation and Technology Award that was presented at the Royal Society London in October 2008 for his work on novel rim driven marine thrusters and turbine generators, which are produced commercially under licence by TSL Technology Ltd. He was also awarded the Faraday SPARKS award in 2002. He is a past committee member of the UK Magnetics Society, a member of the IET and a Chartered Engineer.

Mohammad A. Abusara received the BEng degree from Birzeit University, Palestine, in 2000, and the PhD degree from the University of Southampton, UK, in 2004, both in electrical engineering. From 2003 to 2010, he was with Bowman Power Group, Southampton, UK, responsible for research and development of digital control of power electronics for distributed energy resources, hybrid vehicles, and machines and drives. He is currently a Senior Lecturer in Renewable Energy at the University of Exeter, UK.

Georgios I. Orfanoudakis received his MEng in Electrical Engineering and Computer Science from the National Technical University of Athens (NTUA), Greece, in 2007, and his MSc in Sustainable Energy Technologies from the University of Southampton, UK, in 2008. He then joined the Electro-Mechanical Research Group at the University of Southampton and obtained his PhD in 2013. His research focused on the modulation and DC-link capacitor sizing of three-level inverters. Since October 2012 he is working as a Research Associate in a Knowledge Transfer Partnership (KTP) with the University of Southampton and TSL technology Ltd., performing R&D work on inverters for motor drive applications. Dr Orfanoudakis is a member of the IEEE Power Electronics Society.

Babar Hussain received the BSc degree in electrical engineering from the University of Engineering and Technology, Taxila, Pakistan, in 1995 and the PhD degree in electrical engineering from the University of Southampton, Southampton, UK, in 2011. He has more than 10 years experience in the electric power sector. His major research interests include protection of distribution networks with distributed generation, power quality, and control of grid-connected inverters.

Preface

Microgrids and distributed generation (DG), including renewable sources and energy storage, can help overcome power system capacity limitations, improve efficiency, reduce emissions, and manage the variability of renewable sources. A key component of such a system is the power electronic interface between a generator or an energy storage system, and the grid. Such an interface needs to be capable of performing several functions, including injection of high quality current into the grid to meet national standards; charging and discharging energy storage systems in a controlled manner; anti-islanding protection to disconnect from the grid when the mains are lost; and continuing to supply critical loads when the grid is lost.

The aim of this book is to provide an in-depth coverage of specific topics related to power electronic converters for microgrids, focusing on three-phase converters in the range 50–250 kW. It also discusses the important problem of protection of distribution networks, including microgrids and DG. The book is intended as a textbook for graduating students with an electrical engineering background who wish to work or do research in this field.

Chapter 1 presents a review of the state of the art and future challenges of power electronic converters used in microgrids. Chapter 2 describes the structure and modulation strategies of the conventional two-level and three-level neutral point clamped (NPC) and cascaded H-Bridge (CHB) converter topologies. Chapter 3 discusses the sizing of DC-link capacitors in two-level and three-level inverters, based on expressions for the rms values and the harmonic spectrum of the capacitor current. Chapter 4 investigates semiconductor and DC-link capacitor losses in two-level and three-level inverters, and presents a comparison between the different topologies. Chapter 5 investigates the problem of low-frequency voltage oscillations that appear at the neutral point of an NPC converter, and proposes an algorithm for minimizing these oscillations. Chapter 6 discusses the design and practical implementation of a digital current controller for a three-phase two-level voltage source grid-connected inverter with an LCL output filter. Chapter 7 discusses the design and control of a three-phase voltage source grid-connected interleaved inverter and describes its practical implementation. Chapter 8 discusses the design and practical implementation of a repetitive controller for an interleaved grid-connected inverter. Chapter 9 discusses the design and practical implementation of a line interactive UPS (uninterruptible power supply) system capable of seamlessly transferring between grid-connected to stand-alone modes in parallel with other sources, as well as managing the charging and discharging of the battery. Chapter 10 discusses protection issues and challenges arising from the integration of microgrids and DG into the grid. Chapter 11 discusses the problem of recloser–fuse coordination in a distribution network including microgrids and DG, and proposes an adaptive fuse saving scheme that takes into account the status of the DG. There are also two appendices. Appendix A gives some background material on SVM (space vector modulation) for NPC converters and describes the MATLAB®/Simulink models and programs used to carry out the simulations in Chapter 5. Appendix B includes the MATLAB® code used to numerically calculate the DC-link capacitor rms current and voltage ripple.

Acknowledgments

The authors would like to thank and acknowledge the valuable support of TSL Technology Ltd and Bowman Power Group Ltd who funded some of the research included in this book. In particular they wish to thank Dr Mike Yuratich at TSL and Mr John Lyons at Bowman for their support and help over the last 15 years. They also wish to acknowledge the contributions of Dr Zahrul Faizi Hussain and Dr Mohsin Jamil to some of the material presented in this book. Thanks are also due to the UK Engineering and Physical Science Research Council (EPSRC) for supporting Dr Orfanoudakis's PhD. We wish also to express special appreciation to the staff at Wiley, especially James Murphy, Clarissa Lim, and Shelley Chow for their support, patience, and trust in this project.

Chapter 1Introduction

Fossil fuels are running out and current centralized power generation plants using these fuels are inefficient with a significant amount of energy lost as heat to the environment. These plants also produce harmful emissions and greenhouse gases. Furthermore, existing power systems, especially in developing countries, suffer from several limitations, such as the high cost of expansion and efficiency improvement limits within the existing grid infrastructure. Renewable energy sources can help address these issues, but their variable nature poses challenges to their integration within the grid.

Distributed generators (DGs), including renewable sources, within microgrids can help overcome power system capacity limitations, improve efficiency, reduce emissions, and manage the variability of renewable sources. A microgrid, a relatively new concept, is a zone within the main grid where a cluster of electrical loads and small microgeneration systems, such as solar cells, fuel cells, wind turbine, and small combined heat and power (CHP) systems, exist together under an embedded management and control system, with the option of energy storage. Other benefits of generating power close to electrical loads include the use of waste heat locally, saving the cost of upgrading the grid to supply more power from central plants, reducing transmission losses, and creating opportunities for increasing competition in the sector, which can stimulate innovation and reduce consumer prices [1, 2].