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This comprehensive reference guides the reader through all HVDC technologies, including LCC (Line Commutated Converter), 2-level VSC and VSC HVDC based on modular multilevel converters (MMC) for an in-depth understanding of converters, system level design, operating principles and modeling. Written in a tutorial style, the book also describes the key principles of design, control, protection and operation of DC transmission grids, which will be substantially different from the practice with AC transmission grids.
The first dedicated reference to the latest HVDC technologies and DC grid developments; this is an essential resource for graduate students and researchers as well as engineers and professionals working on the design, modeling and operation of DC grids and HVDC.

Key features:

Provides comprehensive coverage of LCC, VSC and (half and full bridge) MMC-based VSC technologies and DC transmission grids.
Presents phasor and dynamic analytical models for each HVDC technology and DC grids.
Includes HVDC protection, studies of DC and AC faults, as well as system-level studies of AC-DC interactions and impact on AC grids for each HVDC technology.
Companion website hosts SIMULINK SimPowerSystems models with examples for all HVDC topologies.



Table of Contents

Contents

Preface xi

Part I HVDC with Current Source Converters 1

1 Introduction to Line-Commutated HVDC 3

1.1 HVDC Applications 3

1.2 Line-Commutated HVDC Components 5

1.3 DC Cables and Overhead Lines 6

1.4 LCC HVDC Topologies 7

1.5 Losses in LCC HVDC Systems 9

1.6 Conversion of AC Lines to DC 10

1.7 Ultra-High Voltage HVDC 10

2 Thyristors 12

2.1 Operating Characteristics 12

2.2 Switching Characteristic 13

2.3 Losses in HVDC Thyristors 17

2.4 Valve Structure and Thyristor Snubbers 20

2.5 Thyristor Rating Selection and Overload Capability 22

3 Six-Pulse Diode and Thyristor Converter 23

3.1 Three-Phase Uncontrolled Bridge 23

3.2 Three-Phase Thyristor Rectifier 25

3.3 Analysis of Commutation Overlap in a Thyristor Converter 26

3.4 Active and Reactive Power in a Three-Phase Thyristor Converter 30

3.5 Inverter Operation 31

4 HVDC Rectifier Station Modelling, Control and Synchronization with AC Systems 35

4.1 HVDC Rectifier Controller 35

4.2 Phase-Locked Loop (PLL) 36

5 HVDC Inverter Station Modelling and Control 40

5.1 Inverter Controller 40

5.2 Commutation Failure 42

6 HVDC System V-I Diagrams and Operating Modes 45

6.1 HVDC-Equivalent Circuit 45

6.2 HVDC V-I Operating Diagram 45

6.3 HVDC Power Reversal 48

7 HVDC Analytical Modelling and Stability 53

7.1 Introduction to Converters and HVDC Modelling 53

7.2 HVDC Analytical Model 54

7.3 CIGRE HVDC Benchmark Model 56

7.4 Converter Modelling, Linearization and Gain Scheduling 56

7.5 AC System Modelling for HVDC Stability Studies 58

7.6 LCC Converter Transformer Model 62

7.7 DC System Model 63

7.8 HVDC-HVAC System Model 65

7.9 Analytical Dynamic Model Verification 65

7.10 Basic HVDC Dynamic Analysis 66

7.11 HVDC Second Harmonic Instability 70

7.12 Oscillations of 100 Hz on the DC Side 71

8 HVDC Phasor Modelling and Interactions with AC System 72

8.1 Converter and DC System Phasor Model 72

8.2 Phasor AC System Model and Interaction with the DC System 73

8.3 Inverter AC Voltage and Power Profile as DC Current is Increasing 75

8.4 Influence of Converter Extinction Angle 76

8.5 Influence of Shunt Reactive Power Compensation 78

8.6 Influence of Load at the Converter Terminals 78

8.7 Influence of Operating Mode (DC Voltage Control Mode) 78

8.8 Rectifier Operating Mode 80

9 HVDC Operation with Weak AC Systems 82

9.1 Introduction 82

9.2 Short-Circuit Ratio and Equivalent Short-Circuit Ratio 82

9.3 Power Transfer between Two AC Systems 85

9.4 Phasor Study of Converter Interactions with Weak AC Systems 89

9.5 System Dynamics (Small Signal Stability) with Low SCR 90

9.6 Control and Main Circuit Solutions for Weak AC Grids 90

9.7 LCC HVDC with SVC (Static VAR Compensator) 91

9.8 Capacitor-Commutated Converters for HVDC 93

9.9 AC System with Low Inertia 93

10 Fault Management and HVDC System Protection 98

10.1 Introduction 98

10.2 DC Line Faults 98

10.3 AC System Faults 101

10.4 System Reconfiguration for Permanent DC Faults 103

10.5 Overvoltage Protection 106

11 LCC HVDC System Harmonics 107

11.1 Harmonic Performance Criteria 107

11.2 Harmonic Limits 108

11.3 Thyristor Converter Harmonics 109

11.4 Harmonic Filters 110

11.5 Noncharacteristic Harmonic Reduction Using HVDC Controls 118

Bibliography Part I Line Commutated Converter HVDC 119

Part II HVDC with Voltage Source Converters 121

12 VSC HVDC Applications and Topologies, Performance and Cost Comparison with LCC HVDC 123

12.1 Voltage Source Converters (VSC) 123

12.2 Comparison with Line-Commutated Converter (LCC) HVDC 125

12.3 Overhead and Subsea/Underground VSC HVDC Transmission 126

12.4 DC Cable Types with VSC HVDC 129

12.5 Monopolar and Bipolar VSC HVDC Systems 129

12.6 VSC HVDC Converter Topologies 130

12.7 VSC HVDC Station Components 135

12.8 AC Reactors 139

12.9 DC Reactors 139

13 IGBT Switches and VSC Converter Losses 141

13.1 Introduction to IGBT and IGCT 141

13.2 General VSC Converter Switch Requirements 142

13.3 IGBT Technology 142

13.4 Development of High Power IGBT Devices 147

13.5 IEGT Technology 148

13.6 Losses Calculation 148

13.7 Balancing Challenges in Series IGBT Chains 154

13.8 Snubbers Circuits 155

14 Single-Phase and Three-Phase Two-Level VSC Converters 156

14.1 Introduction 156

14.2 Single-Phase Voltage Source Converter 156

14.3 Three-Phase Voltage Source Converter 159

14.4 Square-Wave, Six-Pulse Operation 159

15 Two-Level PWM VSC Converters 167

15.1 Introduction 167

15.2 PWM Modulation 167

15.3 Sinusoidal Pulse-Width Modulation (SPWM) 168

15.4 Third Harmonic Injection (THI) 171

15.5 Selective Harmonic Elimination Modulation (SHE) 172

15.6 Converter Losses for Two-Level SPWM VSC 173

15.7 Harmonics with Pulse-Width Modulation (PWM) 175

15.8 Comparison of PWM Modulation Techniques 178

16 Multilevel VSC Converters 180

16.1 Introduction 180

16.2 Modulation Techniques for Multilevel Converters 182

16.3 Neutral Point Clamped Multilevel Converter 183

16.4 Flying Capacitor Multilevel Converter 185

16.5 H-Bridge Cascaded Converter 186

16.6 Half Bridge Modular Multilevel Converter (MMC) 187

16.7 MMC Based on Full Bridge Topology 200

16.8 Comparison of Multilevel Topologies 208

17 Two-Level PWM VSC HVDC Modelling, Control and Dynamics 209

17.1 PWM Two-Level Converter Average Model 209

17.2 Two-Level PWM Converter Model in DQ Frame 210

17.3 VSC Converter Transformer Model 212

17.4 Two-Level VSC Converter and AC Grid Model in ABC Frame 21