Distributed power generation is a technology that could help to enable efficient, renewable energy production both in the developed and developing world. It includes all use of small electric power generators, whether located on the utility system, at the site of a utility customer, or at an isolated site not connected to the power grid. Induction generator (IG) is the most commonly used and cheapest technology, compatible with renewable energy resources. Permanent magnet (PM) generators have traditionally been avoided due to high fabrication costs; however, compared with IGs they are more reliable and productive.

Distributed Generation thoroughly examines the principles, possibilities and limitations of creating energy with both IGs and PM generators. It takes an electrical engineering approach in the analysis and testing of these generators, and includes diagrams and extensive case study examples to better demonstrate how the integration of energy sources can be accomplished. The book also provides the practical tools needed to model and implement new techniques for generating energy through isolated or grid-connected systems.

Besides a chapter introducing the technical, economic and environmental impacts of distributed generation, this book includes:

• an examination of various phase-balancing schemes for a three-phase IG operating on a single-phase power system;
• a coupled circuit 2-D finite element analysis of a grid-connected IG, with Steinmetz connection;
• a study of self-excited induction generator (SEIG) schemes for autonomous power systems, and the voltage and frequency control of SEIG with a slip-ring machine (SESRIG);
• a report on a PM synchronous generator with inset rotor for achieving a reduced voltage regulation when supplying an autonomous power system, and an analysis of its performance using a two-axis model and finite element method;
• experimental work on various IG and SEIG schemes.

This book is a must-read for engineers, consultants, regulators, and environmentalists involved in energy production and delivery, helping them to evaluate renewable energy sources and to integrate these into an efficient energy delivery system. It is also a superior reference for undergraduates and postgraduates. Designers, operators, and planners will appreciate its unique contribution to the literature in this field.

Loi Lei Lai graduated from Aston University in Birmingham with a BSc and a PhD. He was awarded a DSc by City University London. He is also an honrorary graduate of City University. In 1984, he was appointed Senior Lecturer at Staffordshire Polytechnic. From 1986 to 1987, he was a Royal Academy of Engineering Industrial Fellow to both GEC Alsthom Turbine Generators Ltd and the Engineering research Centre. He is currently Head of Energy Systems Group and Chair in Electrical Engineering at City University London. In the last decade, Professor Lai has authored/co-authored 200 technical publications. He has also written a book entitled Intelligent System Applications in Power Engineering - Evolutionary Programming and Neural Networks and, in 2001, edited the book Power System Restructuring and Deregulation - Trading, Performance and Information Technology, both published by John Wiley & Sons, Ltd. He was award the IEEE Third Millennium Medal and won the IEEE Power Engineering Society, United Kingdom and Republic of Ireland (UKRI), chapter, Outstanding Engineer Award in 2003. In 1995, he received a high-quality paper prize from the International Association of Desalination, USA and in 2006 he was awarded a Prize paper by the IEEE Power Generation Committee. He is a Fellow of the IEEE and the IET (Institution of Engineering and Technology).

Among his professional activities, he is a Founder and was the Conference Chairman of the international Conference on Power Utility Deregulation, Restructuring man of the International Conference on Power Utility Deregulation, Restructuring and Power Technologies (DRPT) 2000, co-sponsored by the IEEE (now IET) and Power Technologies (DRPT) 2000, co-sponsored by the IEE (now IET) and IEEE. He reviews grant proposals regularly for the EPSRC, Australian Research Council and Hong Kong research Grant Council. In 2001, he was invited by the Hong Kong Institution of Engineers to be Chairman of an Accreditation Visit Team to accredit the BEng (Hons) degree in Electrical Engineering. Since 2005, Professor Lai has been invited as a judge for the Power/Energy Category in the IET Innovation in Engineering Awards. He was also Student Recruitment Office of the IEEE UKRI Section Executive Committee. He is a member of the Intelligent Systems Subcommittee in Power System Analysis, Computing and Economic Committee, IEEE Power Engineering Society; a Member of the Executive Team of the Power Trading and Control Technical and Professional Network, IET; an Editor of the IEE Proceedings - Generation, Distribution and Generation (now IET Generation, Distribution and Generation); an Editorial Board Member of the International Journal of Electrical Power & Energy Systems published by Elsevier Science Ltd, UK; International Advisor, Hong Kong Institution of Engineers (HKIE) Transactions and an Editorial Board Member of the European Transactions on Electrical Power published by John Wiley & Sons, Ltd. He was a research Professor at Tokyo Metropolitan University, is also Visiting professor at Southeast University Nanjing and Guest Professor at Fudan University, Shanghai. He has also been invited to deliver keynote addresses and plenary speeches to several major international conferences sponsored by the IET and IEEE.

Tze Fun Chan received his BSc (Eng) and MPhil degrees in electrical engineering from the University of Hong Kong in 1974and 1980, respectively. He received his PhD in electrical engineering from City University London in 2005. Currently, Dr Chan is an Associate Professor in the Department of Electrical Engineering, Hong Kong Polytechnic University, where he has been since 1978. His research interests are self-excited AC generators, brushless AC generators and permanent magnet machines. In June 2006, he was awarded a Prize Paper by the IEEE Power Engineering Society Energy Development and Power Generation Committee.

Foreword xi

Preface xiii

Acknowledgements xvii

About the Authors xix

1 Distributed Generation 1

1.1 Introduction 1

1.2 Reasons for DG 1

1.3 Technical Impacts of DG 3

1.3.1 DG Technologies 3

1.3.2 Thermal Issues 5

1.3.3 Voltage Profile Issues 5

1.3.4 Fault-Level Contributions 7

1.3.5 Harmonics and Interactions with Loads 7

1.3.6 Interactions Between Generating Units 8

1.3.7 Protection Issues 8

1.4 Economic Impact of DG 9

1.5 Barriers to DG Development 10

1.6 Renewable Sources of Energy 11

1.7 Renewable Energy Economics 12

1.8 Interconnection 15

1.8.1 Interconnection Standardization 15

1.8.2 Rate Design 15

1.9 Recommendations and Guidelines for DG Planning 16

1.10 Summary 18

2 Generators 21

2.1 Introduction 21

2.2 Synchronous Generator 21

2.2.1 Permanent Magnet Materials 22

2.2.2 Permanent Magnet Generator 23

2.3 Induction Generator 28

2.3.1 Three-Phase IGs and SEIGs 29

2.3.2 Single-Phase IGs and SEIGs 30

2.4 Doubly Fed Induction Generator 31

2.4.1 Operation 31

2.4.2 Recent Work 33

2.5 Summary 34

3 Three-Phase IG Operating on a Single-Phase Power System 41

3.1 Introduction 41

3.2 Phase Balancing using Passive Circuit Elements 41

3.2.1 Analysis of IG with Phase Converters 41

3.2.2 Phase Balancing Schemes 43

3.2.3 Case Study 45