Understanding FACTS

About the Authors...Narain G. Hingorani is credited with originating the concepts ofFACTS and Custom Power. He is a retired vice president ofElectrical Systems at EPRI and provides consulting services thathelp utilities plan and purchase power electronics technology. Dr.Hingorani has published widely on HVDC and ac transmission and iscoauthor of High Voltage Direct Current Power Transmission (GarawayLtd., 1960). Dr. Hingorani is the recipient of the 1985 Uno LammMedal of the IEEE Power Engineering Society for outstandingcontributions to High Voltage Direct Current Technology and the1995 IEEE Lamme Medal for leadership and pioneering contributionsto the transmission and distribution of electric power. He is aFellow of the IEEE and in 1988 he was elected to the NationalAcademy of Engineering.Laszlo Gyugyi is technical director at Siemens FACTS & PowerQuality Division in Orlando, Florida. His research covers a broadrange of power electronic circuits and systems. In collaborationwith B. R. Pelly, Dr. Gyugyi established the theoreticalfoundations of ac to ac switching converters in Static PowerFrequency Changers (John Wiley & Sons, 1976). Subsequently, hehas focused on the development of new power electronic technologiesfor electric transmission and distribution systems, and haspioneered the converter-based approach for FACTS. Dr. Gyugyi haspublished more than 50 papers in the field and holds 76 U.S.patents. He is the recipient of the 1992 Westinghouse Order ofMerit, the 1994 William E. Newell Power Electronics Award of theIEEE Power Electronics Society, and the first Flexible ACTransmission System (FACTS) Award given by the IEEE PowerEngineering Society in 1999. He is a Fellow of the IEE.

• PREFACE xiiiACKNOWLEDGMENTS xviiCHAPTER 1 FACTS Concept and General System Considerations 11.1 Transmission Interconnections 11.1.1 Why We Need Transmission Interconnections 11.1.2 Opportunities for FACTS 21.2 Flow of Power in an AC System 31.2.1 Power Flow in Parallel Paths 41.2.2 Power Flow in Meshed System 41.3 What Limits the Loading Capability? 71.4 Power Flow and Dynamic Stability Considerations of a Transmission Interconnection 91.5 Relative Importance of Controllable Parameters 121.6 Basic Types of FACTS Controllers 131.6.1 Relative Importance of Different Types of Controllers 141.7 Brief Description and Definitions of FACTS Controllers 161.7.1 Shunt Connected Controllers 181.7.2 Series Connected Controllers 201.7.3 Combined Shunt and Series Connected Controllers 231.7.4 Other Controllers 241.8 Checklist of Possible Benefits from FACTS Technology 251.9 In Perspective: HVDC or FACTS 26CHAPTER 2 Power Semiconductor Devices 372.1 Perspective on Power Devices 372.1.1 Types of High-Power Devices 402.2 Principal High-Power Device Characteristics and Requirements 412.2.1 Voltage and Current Ratings 412.2.2 Losses and Speed of Switching 422.2.3 Parameter Trade-Off of Devices 442.3 Power Device Material 452.4 Diode (Pn Junction) 462.5 Transistor 482.5.1 MOSFET 512.6 Thyristor (without Turn-Off Capability) 522.7 Gate Turn-Off Thyristor (GTO) 542.7.1 Turn-On and Turn-Off Process 562.8 MOS Turn-Off Thyristor (MTO) 582.9 Emitter Turn-Off Thyristor 602.10 Integrated Gate-Commutated Thyristor (GCT and IGCT) 612.11 Insulated Gate Bipolar Transistor (IGBT) 632.12 MOS-Controlled Thyristor (MCT) 64CHAPTER 3 Voltage-Sourced Converters 673.1 Basic Concept of Voltage-Sourced Converters 673.2 Single-Phase Full-Wave Bridge Converter Operation 693.3 Single Phase-Leg Operation 723.4 Square-Wave Voltage Harmonics for a Single-Phase Bridge 733.5 Three-Phase Full-Wave Bridge Converter 743.5.1 Converter Operation 743.5.2 Fundamental and Harmonics for a Three-Phase Bridge Converter 773.6 Sequence of Valve Conduction Process in Each Phase-Leg 803.7 Transformer Connections for 12-Pulse Operation 833.8 24- and 48-Pulse Operation 853.9 Three-Level Voltage-Sourced Converter 873.9.1 Operation of Three-Level Converter 873.9.2 Fundamental and Harmonic Voltages for a Three-Level Converter 883.9.3 Three-Level Converter with Parallel Legs 913.10 Pulse-Width Modulation (PWM) Converter 913.11 Generalized Technique of Harmonic Elimination and Voltage Control 953.12 Converter Rating—General Comments 97CHAPTER 4 Self- and Line-Commutated Current-Sourced Converters 1034.1 Basic Concept of Current-Sourced Converters 1034.2 Three-Phase Full-Wave Diode Rectifier 1064.3 Thyristor-Based Converter (With Gate Turn-On but Without Gate Turn-Off) 1104.3.1 Rectifier Operation 1104.3.2 Inverter Operation 1134.3.3 Valve Voltage 1164.3.4 Commutation Failures 1184.3.5 AC Current Harmonics 1204.3.6 DC Voltage Harmonics 1264.4 Current-Sourced Converter with Turn-Off Devices (Current Stiff Converter) 1294.5 Current-Sourced Versus Voltage-Sourced Converters 132CHAPTER 5 Static Shunt Compensators: SVC and STATCOM 1355.1 Objectives of Shunt Compensation 1355.1.1 Midpoint Voltage Regulation for Line Segmentation 1355.1.2 End of Line Voltage Support to Prevent Voltage Instability 1385.1.3 Improvement of Transient Stability 1385.1.4 Power Oscillation Damping 1425.1.5 Summary of Compensator Requirements 1435.2 Methods of Controllable Var Generation 1445.2.1 Variable Impedance Type Static Var Generators 1455.2.2 Switching Converter Type Var Generators 1645.2.3 Hybrid Var Generators: Switching Converter with TSC and TCR 1775.2.4 Summary of Static Var Generators 1785.3 Static Var Compensators: SVC and STATCOM 1795.3.1 The Regulation Slope 1835.3.2 Transfer Function and Dynamic Performance 1845.3.3 Transient Stability Enhancement and Power Oscillation Damping 1885.3.4 Var Reserve (Operating Point) Control 1935.3.5 Summary of Compensator Control 1955.4 Comparison Between STATCOM and SVC 1975.4.1 V-I and V-Q Characteristics 1975.4.2 Transient Stability 1995.4.3 Response Time 2015.4.4 Capability to Exchange Real Power 2015.4.5 Operation With Unbalanced AC System 2025.4.6 Loss Versus Var Output Characteristic 2045.4.7 Physical Size and Installation 2045.4.8 Merits of Hybrid Compensator 2055.5 Static Var Systems 205CHAPTER 6 Static Series Compensators: GCSC, TSSC, TCSC, and SSSC 2096.1 Objectives of Series Compensation 2096.1.1 Concept of Series Capacitive Compensation 2106.1.2 Voltage Stability 2116.1.3 Improvement of Transient Stability 2126.1.4 Power Oscillation Damping 2136.1.5 Subsynchronous Oscillation Damping 2146.1.6 Summary of Functional Requirements 2156.1.7 Approaches to Controlled Series Compensation 2166.2 Variable Impedance Type Series Compensators 2166.2.1 GTO Thyristor-Controlled Series Capacitor (GCSC) 2166.2.2 Thyristor-Switched Series Capacitor (TSSC) 2236.2.3 Thyristor-Controlled Series Capacitor (TCSC) 2256.2.4 Subsynchronous Characteristics 2366.2.5 Basic Operating Control Schemes for GCSC, TSSC, and TCSC 2396.3 Switching Converter Type Series Compensators 2436.3.1 The Static Synchronous Series Compensator (SSSC) 2446.3.2 Transmitted Power Versus Transmission Angle Characteristic 2456.3.3 Control Range and VA Rating 2486.3.4 Capability to Provide Real Power Compensation 2506.3.5 Immunity to Subsynchronous Resonance 2546.3.6 Internal Control 2576.4 External (System) Control for Series Reactive Compensators 2596.5 Summary of Characteristics and Features 261CHAPTER 7 Static Voltage and Phase Angle Regulators: TCVR and TCPAR 2677.1 Objectives of Voltage and Phase Angle Regulators 2677.1.1 Voltage and Phase Angle Regulation 2697.1.2 Power Flow Control by Phase Angle Regulators 2707.1.3 Real and Reactive Loop Power Flow Control 2727.1.4 Improvement of Transient Stability with Phase Angle Regulators 2747.1.5 Power Oscillation Damping with Phase Angle Regulators 2767.1.6 Summary of Functional Requirements 2777.2 Approaches to Thyristor-Controlled Voltage and Phase Angle Regulators (TCVRs and TCPARs) 2777.2.1 Continuously Controllable Thyristor Tap Changers 2807.2.2 Thyristor Tap Changer with Discrete Level Control 2867.2.3 Thyristor Tap Changer Valve Rating Considerations 2897.3 Switching Converter-Based Voltage and Phase Angle Regulators 2907.4 Hybrid Phase Angle Regulators 293CHAPTER 8 Combined Compensators: Unified Power Flow Controller (UPFC) and Interline Power Flow Controller (IPFC) 2978.1 Introduction 2978.2 The Unified Power Flow Controller 2998.2.1 Basic Operating Principles 3008.2.2 Conventional Transmission Control Capabilities 3018.2.3 Independent Real and Reactive Power Flow Control 3058.2.4 Comparison of UPFC to Series Compensators and Phase Angle Regulators 3088.2.5 Control Structure 3158.2.6 Basic Control System for P and Q Control 3198.2.7 Dynamic Performance 3228.2.8 Hybrid Arrangements: UPFC with a Phase Shifting Transformer 3298.3 The Interline Power Flow Controller (IPFC) 3338.3.1 Basic Operating Principles and Characteristics 3348.3.2 Control Structure 3438.3.3 Computer Simulation 3448.3.4 Practical and Application Considerations 3468.4 Generalized and Multifunctional FACTS Controllers 348CHAPTER 9 Special Purpose Facts Controllers: NGH-SSR Damping Scheme and Thyristor-Controlled Braking Resistor 3539.1 Subsynchronous Resonance 3539.2 NGH-SSR Damping Scheme 3589.2.1 Basic Concept 3589.2.2. Design and Operation Aspects 3619.3 Thyristor-Controlled Braking Resistor (TCBR) 3629.3.1 Basic Concept 3629.3.2 Design and Operation Aspects 364CHAPTER 10 Application Examples 37310.1 WAPA's Kayenta Advanced Series Capacitor (ASC) 37310.1.1 Introduction and Planning Aspects 37310.1.2 Functional Specification 37610.1.3 Design and Operational Aspects 37710.1.4 Results of the Project 38010.2 BPA's Slatt Thyristor-Controlled Series Capacitor (TCSC) 38210.2.1 Introduction and Planning Aspects 38210.2.2 Functional Specifications 38410.2.3 Design and Operational Aspects 38710.2.4 Results of the Project 39210.3 TVA's Sullivan Static Synchronous Compensator (STATCOM) 39410.3.1 Introduction and Planning Aspects 39410.3.2 STATCOM Design Summary 39610.3.3 Steady-State Performance 40010.3.4 Dynamic Performance 40110.3.5 Results of the Project 40710.4 AEP's Inez Unified Power Flow Controller (UPFC) 40710.4.1 Introduction and Planning Aspects 40710.4.2 Description of the UPFC 41110.4.3 Operating Performance 41410.4.4 Results of the Project 423INDEX 425ABOUT THE AUTHORS 431