CONCEPT OF FACTS

FLEXIBLE AC TRANSMISSION SYSTEM

CONCEPT OF F A C T SFLEXIBLE AC TRANSMISSION SYSTEM

Er. P. SURESHB.E., M.E.

Lecturer, Department of EEE TCET Vandavasi

Tamilnadu

Dr. KABILAN RAMACHANDRANB.E., M.E., (PhD)

Associate Professor, Department of EEET.J. Institute of Technology, Karapakkam

ChennaiTamilnadu

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CONCEPT OF FACTS FLEXIBLE AC TRANSMISSION SYSTEM

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vi CONCEPT OF FACTS—FLEXIBLE AC TRANSMISSION SYSTEM

CONTENTS vii

PREFACE It is a pleasant endeavour to bring out this textbook, viz., “CONCEPT OF FACTS” for Anna University affiliated college students of Electrical and Electronics Engineering. Each unit of this book has been prepared in a lucid and comprehensible language with neat diagrams. It will help the students to know the concepts of FACTS controllers in such a way, as if a teacher is in front of them discussing the subject in an easy way. The ultimate aim of this book is to cover the Anna University affiliated-college-syllabus. We are thankful to all the authors and publishers of the other books referred to in this book.

Suggestions for improvement of this book are welcome.

—Authors

viii CONCEPT OF FACTS—FLEXIBLE AC TRANSMISSION SYSTEM

CONTENTS ix

CONTENTS

Preface vii

Chapter 1 : Introduction 11.1 Series Compensation 1

1.2 Shunt Compensation 2

1.3 Theory 3

1.4 Examples 4

Chapter 2 : Static Var Compensator (SVC) and Applications 6

2.1 Voltage Control by The SVC 6

2.2 Advantages of the Slope in the SVC Dynamic Characteristic 7

2.3 Reduction of the SVC Rating 8

2.4 Prevention of Frequent Operation at Reactive-Power Limits 8

2.5 Load Sharing Between Parallel-Connected SVCs 9

2.6 Influence of the SVC on The System Voltage 10

2.6.1 Coupling Transformer Ignored 10

2.6.2 Coupling Transformer Considered 11

2.6.3 The System Gain 12

2.7 Enhancement of Transient Stability 14

2.8 Power-Angle Curves 14

2.9 Synchronizing Torque 15

2.10 Uncompensated System 16

2.10.1 SVC-Compensated System 16

2.11 Increase in Steady-State Power-Transfer Capacity 20

2.12 Augmentation of Power-System Damping 23

2.13 Principle of the SVC Auxiliary Control 24

2.14 Prevention of Voltage Instability 26

x CONCEPT OF FACTS—FLEXIBLE AC TRANSMISSION SYSTEM

2.15 Principles of SVC Control 26

2.15.1 A Case Study 44

2.16 Configuration and Design of the SVC Controller 28

2.17 Rating of an SVC 29

Chapter 3 : The Thyristor-controlled Series Capacitor (TCSC) 313.1 Series Compensation 31

3.1.1 Fixed-Series Compensation 31

3.1.2 The Need For Variable-Series Compensation 31

3.1.3 Advantages of the TCSC 31

3.2 The TCSC Controller 32

3.3 Operation of the TCSC 34

3.3.1 Basic Principle 34

3.3.2 Modes of TCSC Operation 34

3.4 Modeling of The TCSC 37

3.4.1 Variable-Reactance Model 37

3.5 An Advanced Transient-Stability Studies Model 44

3.6 TCSC Controller Optimization and TCSC Response-Time compensation: 443.7 Discrete and Phasor Models 46

3.8 Modeling for Subsynchronous Resonance (SSR) Studies 46

3.9 Improvement of the System-Stability Limit 47

3.10 Enhancement of System Damping 48

3.11 Voltage-Collapse Prevention 50

Chapter 4 : Emerging FACTS Controllers 534.1 The STATCOM 53

4.2 The Principle of Operation 54

4.3 The V-I Characteristic 564.4 The UPFC 58

4.2.1 The Principle of Operation 58

4.5 Applications 62

Chapter 5 : FACTS Controller 63

5.1 Controller Interactions 63

5.2 Coordination of Facts Controllers 63

5.2.1 Steady-State Interactions 63

CONTENTS xi

5.2.2 Electromechanical-Oscillation Interactions 63

5.2.3 Control or Small-Signal Oscillations 64

5.2.4 Sub Synchronous Resonance (SSR) Interactions 64

5.2.5 High-Frequency Interactions 65

5.2.6 The Frequency Response of Facts Controllers 65

5.3 SVC–SVC Interaction 68

5.3.1 The Effect of Electrical Coupling and Short-Circuit Levels 68

5.4 Coordination of Multiple Controllers Using linear-Control Techniques 70

5.4.1 The Basic Procedure for Controller Design 70

5.4.2 Controller Coordination for Damping Enhancement 71

5.4.3 Linear Quadratic Regulator (LQR)-Based Technique 73

5.4.4 Constrained Optimization 73

5.4.5 Nonlinear-Constrained Optimization of aSelective-Modal-Performance Index 74

5.4.6 Global Coordination Using Nonlinear-Constrained Optimization 75

5.4.7 Control Coordination Using Genetic Algorithms 75

Index 77

FACTS—AN INTRODUCTION 1

1

Chapter 1

A Flexible Alternating Current Transmission System (FACTS) is a system composed ofstatic equipment used for the AC transmission of electrical energy. It is meant to enhancecontrollability and increase power transfer capability of the network. It is generally apower electronics-based system technology.

Fig. 1.1: Transmission on a no-loss line.

1.1 SERIES COMPENSATION

In series compensation, the FACTS is connected in series with the power system. It worksas a controllable voltage source. Series inductance exists in all AC transmission lines. Onlong lines, when a large current flows, this causes a large voltage drop. To compensate,series capacitors are connected, decreasing the effect of the inductance.

FACTS—AN INTRODUCTION

2 CONCEPT OF FACTS—FLEXIBLE AC TRANSMISSION SYSTEM

VrVsX

I

XC

j XI – j XcI

Vs Vrδ

j (X–Xc) I j XI– j XcI

Fig. 1.2: Series compensation.

1.2 SHUNT COMPENSATION

In shunt compensation, power system is connected in shunt (parallel) with the FACTS.It works as a controllable current source. Shunt compensation is of two types:

I

VrVs

X/2

Vs Vr

Vm

X/2

Ic

δ/2 δ/2

Vs=Vm=Vr=V

Vm

Fig. 1.3: Shunt compensation.

1.2.1 Shunt Capacitive CompensationThis method is used to improve the power factor. Whenever an inductive load is connectedto the transmission line, power factor lags because of lagging load current. To compensate,a shunt capacitor is connected which draws current leading the source voltage. The netresult is improvement in power factor.

1.2.2 Shunt Inductive CompensationThis method is used either when charging the transmission line, or, when there is verylow load at the receiving end. Due to very low, or no load — very low current flows

Concepts Of Facts Flexible ACTransmission System

Publisher : Laxmi Publications ISBN : 9789384872298Author : Dr KabilanRamachandran, Er P.Suresh

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