FACTS Controllers in Power Transmission and Distribution by K.R.Padiyar PDF

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NEW AGE FACTS CONTROLLERS IN POWER TRANSMISSION AND DISTRIBUTION ~ NEW AGE INTERNATIONAL PUBLISHERS FACTS CONTROLLERS IN POWER TRANSMISSION AND DISTRIBUTION This page intentionally left blank FACTS CONTROLLERS IN POWER TRANSMISSION AND DISTRIBUTION K. R. Padiyar Department of Electrical Engineering ...

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NEW AGE

FACTS CONTROLLERS IN POWER TRANSMISSION AND DISTRIBUTION

~

NEW AGE INTERNATIONAL PUBLISHERS

FACTS CONTROLLERS IN POWER TRANSMISSION AND DISTRIBUTION

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FACTS CONTROLLERS IN POWER TRANSMISSION AND DISTRIBUTION

K. R. Padiyar Department of Electrical Engineering Indian Institute of Science Bangalore-560 012 India

PUBUSHING FOR ONE WORLD

NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS New Delhi· Bangalore • Chennai • Cochin • Guwahati • Hyderabad lalandhar • Kolkata • Lucknow • Mumbai • Ranchi Visit us at www.newagepublishers.com

Copyright © 2007, New Age International (P) Ltd., Publishers Published by New Age International (P) Ltd., Publishers All rights reserved. No part of this ebook may be reproduced in any form, by photostat, microfilm, xerography, or any other means, or incorporated into any information retrieval system, electronic or mechanical, without the written permission of the publisher. All inquiries should be emailed to [email protected]

ISBN (13) : 978-81-224-2541-3

PUBLISHING FOR ONE WORLD

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This book is dedicated to

Dr.....1. G. HI.I....I who pioneered the concepts of Flexible AC Transmission Systems (FACTS) and Custom Pcwer

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Preface

Modern power systems are highly complex and are expected to fulfill the growing demands of power wherever required, with acceptable quality and costs. The economic and environmental factors necessitate the location of generation at places away from load centres. The restructuring of power utilities has increased the uncertainties in system operation. The regulatory constraints on the expansion of the transmission network has resulted in reduction of stability margins and increased the risks of cascading outages and blackouts. This problem can be effectively tackled by the introduction of high power electronic controllers for the regulation of power flows and voltages in AC transmission networks. This allows ’flexible’ operation of AC transmission systems whereby the changes can be accommodated easily without stressing the system. Power electronic based systems and other static equipment that provide controllability of power flow and voltage are termed as FACTS Controllers. It is to be noted that power electronic controllers were first introduced in HVDC transmission for not only regulation of power flow in HVDC links, but also for modulation to improve system stability (both angle and voltage). The technology of thyristor valves and digital controls was initially extended to the development of Static Var Compensator (SVC) for load compensation and voltage regulation in long transmission lines. In 1988,Dr.Narain G. Hingorani introduced the concept of Flexible AC Transmission Systems (FACTS) by incorporating power electronic controllers to enhance power transfer in existing AC transmission lines, improve voltage regulation and system security without adding new lines. The FACTS controllers can also be used to regulate power flow in critical lines and hence, ease congestion in electrical networks. FACTS does not refer to any single device, but a host of controllers such as SVC, Thyristor Controlled Series Capacitor (TCSC), Static Phase Shifting Transformer (SPST), and newer controllers based on Voltage Source Converters (VSC)-Static synchronous Compensator (STATCOM), Static Synchronous Series Compensator (SSSC), Unified Power Flow Controller (UPFC), Interline Power Flow Controller (IPFC) etc. The advent of FACTS controllers has already made a major impact on the planning and operation of power delivery systems. The concept of Custom Power introduced by Dr.Hingorani in 1995 has extended the application of FACTS controllers for distribution systems with the objective of improving power quality. An understanding of the working of individual FACTS controllers and issues that affect their operation under various conditions is essential for both students and engineers (in industry) who are interested in the subject. This book aims to provide detailed information for students, researchers, and development and application engineers in industry. It contains

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FACTS Controllers in Power Transmission and Distribution

comprehensive and up-to-date coverage of the FACTS controllers that have been proposed and developed both for transmission and distribution. It is hoped that this book will complement the excellent book on ”Understanding FACTS-Concepts and Technology of Flexible AC Transmission Systems” by the pioneers, Dr. Narain G. Hingorani and Dr.Laszlo Gyugyi. The present book covers many analytical issues that affect the design of FACTS Controllers, which are of interest to academics and application engineers. It can be used as a text or reference for a course on FACTS Controllers. The author has been working in the area of HVDC and FACTS Controllers over many years. He has taught a course on FACTS for graduate students at Indian Institute of Science and has guided several Masters and PhD students who have worked on various aspects of different FACTS controllers. He has delivered many lectures in short- term intensive courses attended by teachers from engineering colleges and engineers from industry. He is the author of a book on HVDC Power Transmission Systems (published by Wiley Eastern and John Wiley in 1991), which is widely used. Hence, it was natural to attempt this book based on the expertise and experience gained. The book is organized into 14 chapters and 4 appendices. The first chapter introduces FACTS controllers and their application in transmission and distribution networks in the context of operational problems of modern power systems involving transmission congestion, loop flows, system security and power quality issues. The second chapter reviews the modeling and steady state characteristics of AC transmission lines. It also covers the analysis of how an individual FACTS controller can modify the power flow and voltage profile in a line. Chapters 3 to 9 cover the various FACTS controllers -SVC, TCSC and GCSC, Static PST, STATCOM, SSSC, UPFC, IPFC, CSC, IPC and other devices such as Fault Current Limiter (FCL), Thyristor Controlled Braking Resistor (TCBR), NGH Damping and Thyristor Controlled Voltage Limiter (TCVL). In each case, the function of the FACTS device is explained with the description of power circuit, associated controllers and operating modes. The modeling of each FACTS Controller is derived from first principles and simplifications where appropriate are discussed. The applications and control interactions involving Subsynchronous Resonance (SSR), electromagnetic interactions and harmonic interactions are also discussed in some detail wherever required. A major function of a FACTS Controller is power oscillation damping involving low frequency oscillations that threaten system security under peak power flow conditions. Chapter 10 covers the analysis of this problem with solutions involving control strategies for voltage and power modulation. Illustrative examples are included to explain the techniques. Another important control function is the improvement of transient stability using bang-bang control technique. This is also termed as discrete control. The analysis and control strategies for this function are discussed in detail in chapter 11 with the help of case studies. Chapter 12 introduces the power quality issues involving voltage fluctuations, flicker, sags and swells, momentary interruptions, unbalance and harmonics. The measures for power quality are described and introduction to Custom Power Devices (CPD) is presented. Chapter 13 deals with load

Preface

ix

compensation and application of distribution STATCOM (DSTATCOM) for fast voltage regulation or reactive power compensation, balancing of source currents and active filtering. Chapter 14 covers series power quality conditioner involving dynamic voltage restoration and harmonic isolation. The Unified Power Quality Conditioner (UPQC), which includes both shunt and series compensators is also described. In all cases considered, the operation of the individual device is described along with modeling, control algorithms and simulation of the system to evaluate the performance. The case studies are presented to illustrate the analysis. The Appendix A describes the modeling of synchronous machines for both stability and transient analysis. The mechanical system of rotor masses and shafts is also modeled. The major Pulse Width Modulation (PWM) techniques such as Sine PWM and Space Vector modulation are discussed in Appendix B. The per unit system for a STATCOM is discussed in Appendix C. The Appendix D lists the abbreviations used. It is assumed that the reader has an exposure to elementary power electronics, power systems and basic control theory. Hence, topics on power semiconductor devices and converters have been deliberately left out. Still, the book contains more material than what can be covered in a one-semester course.

Acknowledgements I would like to acknowledge with gratitude the contributions of several individuals in the preparation of this book. First and foremost, I wish to acknowledge the encouragement and help received from Dr.Narain Hingorani who pioneered the concepts of FACTS and Custom Power. Drs. John Vithayathil (who explained the RANI concept), R.Mohan Mathur, R.S.Thallam, Rambabu Adapa, Rajiv Varma and Subhashish Bhattacharya have helped in getting information and literature on FACTS. I acknowledge the research work carried out by my graduate students on FACTS. Starting with Dr.Rajiv Varma, other PhD students who contributed are: Drs. Vijayan Immanuel, K. Uma Rao, M.K. Geetha, Anil Kulkarni, Sujatha Subhash, Parthasarathy Sensarma, S.Krishna, H.V.Saikumar and Nagesh Prabhu. There are many Masters Students who have worked on FACTS. In particular, I wish to acknowledge the contributions of Lakshmi Devi, Sreekumar, Jayati, Sriram, Sreekantha, Dhiman, Renuka, Sandeep, Anjali, Rajesh Kumar, Manmayjyoti, Mohanraj, Mahesh Sitaram, Swayam Prakash, Venkatesh, Dhananjay and Anand Kumar. I thank Dr. S. Krishna for assisting in proof reading and the preparation of CRC. Thanks are also due to Dr. Nagesh Prabhu and Mr. Anand Kumar for their help in the preparation of the final manuscript and Mr. Kiran Kumar for the drawings. Dr. Kalyani Gopal made available the Latex style file used. I thank Mr. Saumya Gupta of New Age International Publishers for his keen interest and help in publishing this book on time. This book was catalyzed and supported by the Department of Science and Technology (DST), Government of India under its Utilization of Scientific Expertise of Retired Scientists (USERS) scheme. The DST has

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FACTS Controllers in Power Transmission and Distribution

also supported research schemes during the period from 1994 to 2003. The author also wishes to gratefully acknowledge the financial assistance from All India Council of Technical Education (AICTE) under the Emeritus Fellowship Scheme during the period (August 1,2003-June 30,2006). Finally, I am deeply indebted to Indian Institute of Science for permitting me to pursue academic activities as an Honorary Professor from May 2003. Last, but not the least, I thank my wife Usha for her patience and quiet support during the long hours of working on this book. K.R.Padiyar

Contents

Preface

vii

1 Introduction 1.1 1.2

1 . . . . . . . . . . . . . .

1

. . . . . . . . . . . . . .

1

. . . . . . . . . . . . . .

4

. . . . . . . . . . . . . . in Distribution Systems

7 16

2 AC Transmission Line and Reactive Power Compensation

19

1.3 1.4 1.5

General . . . . . . . . . . . . . . . Basics of Power Transmission Networks . . . . . . . . . . . . . . Control of Power Flow in AC Transmission Line . . . . . . . . . Flexible AC Transmission System Controllers . . . . . . . . . . . . . Application of FACTS Controllers

2.1

Analysis of Uncompensated AC Line . . . . . . . . . . . .

19

2.2

Passive Reactive Power Compensation . . . . . . . . . . .

29

2.3

Compensation by a Series Capacitor Connected at the Midpoint of the Line . . . . . . . . . . . . . . . . . . . . . . .

32

2.4

Shunt Compensation Connected at the Midpoint of the Line . . . . . . . . . . . . . . . . . . .

34

2.5

Comparison between Series and Shunt Capacitor

. . . . .

36

2.6

Compensation by STATCOM and SSSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some Representative Examples . . . . . . . . . . . . . . .

38 42

2.7

3 Static Var Compensator

51

3.1

Analysis of SVC . . . . . . . . . . . . . . . . . . . . . . . .

51

3.2

Configuration of SVC . . . . . . . . . . . . . . . . . . . . .

58

3.3 3.4

68

3.5

SVC Controller . . . . . Voltage Regulator Design Issues . . . . . . . . . . . Harmonics and Filtering

. . . . . . . . . . . . . . . . . . . – Some . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

75 83

3.6

Protection Aspects . . . . . . . . . . . . . . . . . . . . . .

91

FACTS Controllers in Power Transmission and Distribution 3.7

Modelling of SVC . .

96

3.8

Applications of SVC

99

4 Thyristor and GTO Controlled Series Capacitor

105

4.1 4.2

Introduction . . . . . . . . . . . . . . . . . . . . . Basic Concepts of Controlled Series Compensation

105 106

4.3

Operation of TCSC

110

4.4

Analysis of TCSC .

112

4.5 4.6

Control of TCSC Modelling of TCSC for Stability Studies . . . . . . . . . . . . . . GTO Thyristor Controlled Series Capacitor (GCSC) . . . . . . . .

118

4.7 4.8 4.9

Mitigation of Subsynchronous Resonance with TCSC and GCSC . Applications of TCSC. . . . . . .

5 Static Phase Shifting Transformer

122 125 128 150

157

5.1 5.2

General.......... Basic Principle of a PST

157 157

5.3

Configurations of SPST .

161

5.4

Improvement of Transient Stability Using SPST . . . . . . . . . . . . .

166

Damping of Low Frequency Power Oscillations . . . . . Applications of SPST . . . . . . . .

168 170

5.5 5.6

6 Static Synchronous Compensator (STATCOM)

173

6.1 6.2

Introduction . . . . . . . . . . . . . . Principle of Operation of STATCOM

173 174

6.3 6.4

A Simplified Analysis of a Three Phase Six Pulse STATCOM . . . . . Analysis of a Six Pulse VSC Using Switching Functions.

177 184

6.5

Multi-pulse Converters . . . .

188

6.6

Control of Type 2 Converters

192

6.7

Control of Type 1 Converter.

197

6.8

Multilevel Voltage Source Converters

200

6.9 6.10

Harmonic Transfer and Resonance in VSC Applications of STATCOM . . . . . . . . .

209 213

Contents 7 Static Synchronous Series Compensator

217

7.1 7.2

Introduction...................... Operation of SSSC and the Control of Power Flow

217 217

7.3

Modelling and Control of SSSC

225

7.4

SSSC with an Energy Source .

229

7.5

Analysis of SSR with a SSSC

237

7.6

Applications of SSSC . . . . .

240

8 Unif]ed Power Flow Controller and other Multi-Converter DeVIces 243 8.1 8.2

Introduction...... Operation of a UPFC .

243 246

8.3 8.4 8.5 8.6

Control of UPFC . . . Protection of UPFC . . Interline Power Flow Controller Convertible Static Compensator

257 262 263 265

8.7

Modelling of UPFC, IPFC and other Multi-Converter FACTS

266

8.8 8.9

SSR Characteristics of UPFC Applications of UPFC . . . . . . . . . . . . . . . . . . . .

269 269

9 Interphase Power Controller and other FACTS Devices

273

9.1

Interphase Power Controller (IPC)

273

9.2

NGH SSR Damping Scheme .

286

9.3

Thyristor Controlled Braking Resistor (TCBR) . . . . . . .

291

9.4

Fault Current Limiter (FCL) .

293

9.5

Thyristor Controlled Voltage Limiter (TCVL)

296

10 Power Oscillation Damping 10.1 10.2

10.3

Introduction . . . . . . . Basic Issues in the Damping of Low Frequency Oscillations in Large Power Systems. . . . . . . . . . . .

301 301

302

System Modelling for Small Signal Stability . . . . . . . . . . . . .

305

10.4

Design of Damping Controllers.

316

10.5

Modal 'fransformation of Swing Equations . . . . . . . . . . . .

322

FACTS Controllers in Power Transmission and Distribution 10.6 10.7 10.8

Damping of Power Oscillations Using Series FACTS Controllers

325

Damping of Power Oscillations Using Shunt FACTS Controllers

334

A Case Study of Damping Controllers in UPFC

340

11 Improvement of Transient Stability

349

11.1 11.2

Introduction . . . . . . . . . . . . . . . . . . . Transient Stability of a Two Machine System

349 350

11.3

Extension to Multimachine Power Systems . . . . . . . . . . . . . . . . . . . . .

352

11.4

Potential Energy Function for SVC, SSSC and UPFC

361

11.5

A New Control Algorithm for Improving Transient Stability and Damping of Oscillations .

366

Case Studies of Discrete Control for Stability Improvement . . . . . . .

374

11.6

12 Power Quality and Introduction to Custom Power Devices 383 12.1 12.2 12.3 12.4 12.5 12.6

General . . . . . Electromagnetic Phenomena and Power Quality . . . . . . . . .

383

Custom Power Devices . . . . . . Definitions of Reactive Power .. Reactive Power Compensation in Single Phase Circuits . . . . . . .

394 403

Reactive Power Compensation in Three Phase Circuits

420

13 Load Compensation and Distribution STATCOM

384

412

433

13.1 13.2

Introduction . . . . . . . . . . . . Three Phase Three Wire Systems

433 434

13.3

Three Phase Four Wire Systems.

443

13.4

A Case Study . . . . . . . . . . .

448<...