Flexible AC Transmission Systems (FACTS)

523 Pages·2008·25.63 MB·English

by  Yong Hua Song

IET Power and Energy Series, Volume 30 
Flexible Ac
Transmission
Systems (FAcTS)

Edited by Yong Hua Song
and Allan T. Johns
The Institution of Engineering and Technology
Published by The Institution of Engineering and Technology, London, United Kingdom
First edition © 1999 The Institution of Electrical Engineers
New cover © 2008 The Institution of Engineering and Technology
First published 1999
Reprinted with new cover 2008
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British Library Cataloguing in Publication Data
A CIP catalogue record for this book is available from the British Library
ISBN (10 digit) 0 85296 771 3
ISBN (13 digit) 978-0-85296-771-3
First printed in the UK by TJ International Ltd, Padstow, Cornwall
Reprinted in the UK by Lightning Source UK Ltd, Milton Keynes
Preface
The rapid development of power electronics technology provides exciting opportunities
to develop new power system equipment for better utilization of existing systems.
During the last decade, a number of control devices under the term "Flexible AC
Transmission Systems" (FACTS) technology have been proposed and implemented.
FACTS devices can be effectively used for power flow control, loop-flow control, load
sharing among parallel corridors, voltage regulation, enhancement of transient stability
and mitigation of system oscillations. A large number of papers and reports have been
published on these subjects. In this respect, it is timely to edit a book with an aim to
report on the state of the art development, internationally, in this area. By covering all
the major aspects in research and development of FACTS technologies, the book
intends to provide a comprehensive guide, which can serve as a reference text for a
wide range of readers.
Chapter 1 focuses on the fundamentals of ac power transmission to provide a
necessary technical background for understanding the problems of present power
systems and the power electronics-based solutions the Flexible AC Transmission
System (FACTS,) offers. In Chapter 2 the principles of power electronic converters are
introduced, covering the basics of power electronics systems as well as structures
suitable for the design of high power converters for transmission level voltages and
currents. Although the inclusion of high voltage dc transmission (HVdc) in this book
seems to be a contradiction to some people, the boundaries between HVdc and FACTS
will gradually become 'blurred'. For example, the back-to-back dc link may also be
considered as a FACTS device. Thus an introduction to HVdc technology is given in
Chapter 3.
The principles and applications of shunt, series, phase shifter and unified
compensations are discussed in Chapters 4, 5, 6 and 7 respectively. Chapter 4
describes the principles, configuration and control of two major types of shunt static
compensations - static var compensator (SVC) and Static Synchronous Compensator
(STATCOM). Their practical applications are also reported, including recent
relocatable SVC applications in the UK system. Chapter 5 examines the Thyristor-
Controlled Series Capacitor (TCSC) and the Static Synchronous Series Compensator
(SSSC) and their applications for damping of electromechnical oscillations and for
xvi Flexible ac transmission systems
mitigation of subsynchronous resonance. The main objectives of Chapter 6 are to
describe the principles of operation, operational characteristics, technical merits and
limitations and potential applications of phase shifters. More recently, one of the
potentially most versatile class of FACTS device - the Unified Power Flow Controller
(UPFC) was proposed. This device, with its unique combination of fast shunt and
series compensation, offers a versatile device for the relief of transmission constraints.
Chapter 7 contains an in-depth look at the basic operating principles, characteristics,
control and dynamic performance of the UPFC. The first UPFC installation is also
reported.
Chapters 8, 9, 10, 11 and 12 address the system aspects of FACTS applications.
Various models, suitable for different studies including electromagnetic transient
studies, steady-state and dynamic analysis, are presented. Effective control strategies
for power flow and stability control, and novel protection schemes are proposed in
these chapters. A review of FACTS development in Japan is reported in Chapter 13.
Applications of power electronics in distribution systems are summarized in Chapter
14.
Finally, we, the editors, are very grateful to authors for their cooperation and
patience. We wish to thank Sarah Daniels of the IEE for her help in the production of
the book. We would also like to thank Xing Wang for re-setting the style o fthe whole
book by overcoming incompatible word processing format.
Yong Hua Song, Brunei University
Allan T Johns, The University of Bath
October 1999
Contents
Preface xv
Contributors xvii
1 Power transmission control:
basic theory; problems and needs; FACTS solutions 1
Laszlo Gyugi
1.1 Introduction 1
1.2 Fundamentals of ac power transmission 2
1.2.1 Basic relationships 3
1.2.2 Steady-state limits of power transmission 9
1.2.3 Traditional transmission line compensation and power flow control 10
1.2.4 Dynamic limitations of power transmission 19
1.2.5 Dynamic compensation for stability enhancement 20
1.3Transmission problems and needs: the emergence of FACTS 26
1.3.1 Historical background 27
1.3.2 Recent developments and problems 27
1.3.3 Challenges of deregulation 29
1.3.4 The objectives of FACTS 30
1.4 FACTS controllers 32
1.4.1 Thyristor controlled FACTS controllers 32
1.4.2 Converter-based FACTS controllers 39
1.5 FACTS control considerations 61
1.5.1 Functional control of a single FACTS controller 62
1.5.2 FACTS area control: possibilities and issues 65
1.6 Summary 68
1.7 Acknowledgements 70
1.8 References 71
2 Power electronics: fundamentals 73
Geza Joos
2.1 Introduction 73
vi Flexible ac transmission systems
2.2 Basic functions of power electronics 74
2.2.1 Basic functions and connections of power converters 74
2.2.2 Applications of reactive power compensation 75
2.3 Power semiconductor devices for high power converters 78
2.3.1 Classification of devices 78
2.3.2 Device types and features 79
2.4 Static power converter structures 80
2.4.1 General principles 80
2.4.2 Basic ac/dc converter topologies 83
2.4.3 Converter power circuit configurations 86
2.4.4 Power flow control 87
2.4.5 Switch gating requirements 89
2.5 AC controller-based structures 89
2.5.1 Thyristor-controlled reactor 89
2.5.2 Thyristor-controlled series capacitor 90
2.5.3 Thyristor-controlled phase-shifting transformer 90
2.5.4 Force-commutated ac controller structures 90
2.6 DC link converter topologies 91
2.6.1 Current source based structures 91
2.6.2 Synchronous voltage source structures 94
2.6.3 Other compensator structures 98
2.6.4 High voltage dc transmission 99
2.7 Converter output and harmonic control 100
2.7.1 Converter switching 100
2.7.2 Principles of harmonic mitigation 101
2.7.3 Output control 105
2.7.4 Multi-stepped converters 108
2.8 Power converter control issues 111
2.8.1 General control requirements 111
2.8.2 Line synchronization 112
2.8.3 Voltage and current control 112
2.8.4 Supplementary controls 112
2.8.5 Operation under non-ideal conditions 113
2.9 Summary 113
2.10 References 114
3 High voltage dc transmission technology 117
/. Arrillaga
3.1 Introduction 117
3.2 Ac versus dc interconnection 118
Contents vii
3.3 The HVdc converter 118
3.3.1 Rectifier operation 120
3.3.2 Inverter operation 123
3.3.3 Power factor active and reactive power 123
3.4 HVdc system control 125
3.4.1 Valve firing control 125
3.4.2 Control characteristics and direction of power flow 127
3.4.3 Modifications to the basic characteristics 130
3.5 Converter circuits and components 131
3.5.1 The high voltage thyristor valve 134
3.5.2 HVdc configurations 135
3.5.3 Back-to-back configurations 136
3.6 Power system analysis involving HVDC converters 138
3.7 Applications and modern trends 141
3.8 Summary 144
3.9 References 144
4 Shunt compensation: SVC and STATCOM 146
H. L Thanawala, D. J. Young, andM. H. Baker
4.1 Introduction: principles and prior experience of shunt static var
compensation 146
4.2 Principles of operation, configuration and control of SVC 151
4.2.1 Thyristor Controlled Reactor (TCR) 151
4.2.2 Thyristor Switched Capacitor (TSC) 155
4.2.3 Combined TCR/TSC 158
4.3 STATCOM configuration and control 159
4.3.1 Basic concepts 159
4.3.2 Voltage-sourced converters 161
4.3.3 Three-phase converter 166
4.3.4 Reduction of harmonic distortion 167
4.3.5 Source voltage ripple 174
4.3.6 Snubber circuits 174
4.3.7 Some practical implications 175
4.3.8 STATCOM operating characteristics 175
4.3.9 Transient response 178
4.3.10 STATCOM losses 180
4.3.11 Other types of STATCOM source 182
4.4 Applications 183
4.4.1 Some practical SVC applications 183
4.4.2 Recent relocatable SVC applications in UK practice 187
viii Flexible ac transmission systems
4A3 STATCOM applications 191
4.5 Summary 195
4.6 Acknowledgment 196
4.7 References 197
5 Series compensation 199
M. Noroozian, L. Angquist and G. Ingestrdm
5.1 Introduction 199
5.1.1 Steady state voltage regulation and prevention of voltage collapse 199
5.1.2 Improving transient rotor angle stability 200
5.1.4 Power flow control 200
5.1.5 Series compensation schemes 201
5.2 Principle of operation 202
5.2.1 Blocking mode 203
5.2.2 Bypass mode 204
5.2.3 Capacitive boost mode 205
5.2.4 Inductive boost mode 208
5.2.5 Harmonics 209
5.2.6 Boost control systems 210
5.3 Application of TCSC for damping of electromechanical oscillations 214
5.3.1 Model 215
5.3.2 TCSC damping characteristics 216
5.3.3 Damping of power swings by TCSC 217
5.3.4 POD controller model 218
5.3.5 Choice of POD regulator parameters 219
5.3.6 Numerical examples 220
5.4 Application of TCSC for mitigation of subsynchronous resonance 223
5.4.1 The subsynchronous resonance (SSR) phenomena related to series
compensation 224
5.4.2 Apparent impedance of TCSC 227
5.4.3 Application example 230
5.5 TCSC layout and protection 232
5.5.1 TCSC reactor 233
5.5.2 Bypass breakers 233
5.5.3 Capacitor overvoltage protection 234
5.5.4 Thyristor valve 234
5.5.5 Measuring system 235
5.5.6 Capacitor voltage boost 235
5.5.7 Fault handling 236
5.6 Static synchronous series compensator (SSSC) 237
Contents ix
5.6.1 Principle of operation 238
5.6.2 SSSC model for load flow and stability analysis 238
5.6.3 Power interchange 241
5.6.4 Applications 241
5.7 References 241
6 Phase shifter 243
M.R. Iravani
6.1 Introduction 243
6.2 Principles of operation of a phase shifter 244
6.3 Steady-state model of a Static Phase Shifter (SPS) 246
6.4 Steady-state operational characteristics of SPS 249
6.5 Power circuit configurations for SPS 251
6.5.1 Substitution of mechanical tap-changer by electronic switches 251
6.5.2 AC controller 253
6.5.3 Single-phase ac-ac bridge converter 255
6.5.4 PWM voltage source converter (VSC) 260
6.5.5 PWM current source converter (CSC) 261
6.5.6 Other SPS circuit configurations 262
6.6 SPS applications 262
6.6.1 Steady-state 262
6.6.2 Small-signal dynamics 263
6.6.3 Large-signal dynamics 263
6.7 Summary 264
6.8 References 264
7 The unified power flow controller 268
Laszlo Gyugyi and Colin D. Schauder
7.1 Introduction 268
7.2 Basic operating principles and characteristics 269
7.2.1 Conventional transmission control capabilities 271
7.2.2 Independent real and reactive power flow control 275
7.2.3 Comparison of the UPFC to the controlled series compensators and
phase shifters 278
7.3 Control and dynamic performance 286
7.3.1 Functional operating and control modes 288
7.3.2 Basic control system for P and Q control 290
7.3.3 Dynamic performance 293
7.4 The first UPFC installation 302
7.4.1 Application background 303
x Flexible ac transmission systems
7.4.2 Power circuit structure 304
7.4.3 Control system 306
7.4.4 Commissioning test results 307
7.5 Summary 317
7.6 References 317
8 Electromagnetic transient simulation studies 319
J.Y.Liu and Y.H. Song
8.1 Introduction 319
8.2 Principles of the UPFC based on SPWM inverters 321
8.3 EMTP/ATP simulation 324
8.3.1 The EMTP/ATP program 324
8.3.2 SPWM scheme generated by EMTP/ATP TACS 326
8.3.3 EMTP model development for systems with UPFC 328
8.4 Open-loop simulation 335
8.4.1 Simulation of SPWM UPFC regulation performance 335
8.4.2 Results of the power flow and voltage support under control of SPWM
UPFC 339
8.4.3 Operating envelope of UPFC 340
8.5 Close-loop simulation 341
8.6 Conclusions 348
8.7 Acknowledgment 348
8.8 References 349
9 Steady-state analysis and control 350
Y.H. Song and J.Y.Liu
9.1 Introduction 350
9.2 Steady-state UPFC model for power flow studies 352
9.2.1 Principles of UPFC 352
9.2.2 Steady-state UPFC representation 352
9.2.3 Power injection model of UPFC 352
9.3 Representation of UPFC for power flow 355
9.3.1 UPFC modified Jacobian matrix elements 355
9.3.2 Normal (open-loop) and controlled (close-loop) power flow with
UPFC 357
9.4 Implementation of UPFC in power flow studies 357
9.4.1 Difficulties with implementation of UPFC in power flow 357
9.4.2 Optimal multiplier power flow algorithm 358
9.4.3 Power flow procedure with UPFC 360
9.5 Power injection based power flow control method 360