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High Voltage Direct Current Transmission: Converters, Systems and DC Grids

High Voltage Direct Current Transmission: Converters, Systems and DC Grids

Dragan Jovcic, Khaled Ahmed

ISBN: 978-1-118-84668-1

Jul 2015

440 pages

$104.99

Description

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.

Related Resources

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 213

17.5 Two-Level VSC Converter and AC Grid Model in DQ Rotating Coordinate Frame 213

17.6 VSC Converter Control Principles 214

17.7 The Inner Current Controller Design 215

17.8 Outer Controller Design 218

17.9 Complete VSC Converter Controller 221

17.10 Small-Signal Linearized VSC HVDC Model 224

17.11 Small-Signal Dynamic Studies 224

18 Two-Level VSC HVDC Phasor-Domain Interaction with AC Systems and PQ Operating Diagrams 226

18.1 Power Exchange between Two AC Voltage Sources 226

18.2 Converter Phasor Model and Power Exchange with an AC System 230

18.3 Phasor Study of VSC Converter Interaction with AC System 232

18.4 Operating Limits 234

18.5 Design Point Selection 236

18.6 Influence of AC System Strength 239

18.7 Influence of Transformer Reactance 243

18.8 Operation with Very Weak AC Systems 247

19 Half Bridge MMC Converter: Modelling, Control and Operating PQ Diagrams 254

19.1 Half Bridge MMC Converter Average Model in ABC Frame 254

19.2 Half-Bridge MMC Converter-Static DQ Frame and Phasor Model 257

19.3 Differential Current at Second Harmonic 262

19.4 Complete MMC Converter DQ Model in Matrix Form 263

19.5 Second Harmonic Circulating Current Suppression Controller 264

19.6 DQ Frame Model of MMC with Circulating Current Controller 267

19.7 Phasor Model of MMC with Circulating Current Suppression Controller 269

19.8 Dynamic MMC Model Using Equivalent Series Capacitor CMMC 270

19.9 Full Dynamic Analytical MMC Model 273

19.10 MMC Converter Controller 275

19.11 MMC Total Series Reactance in the Phasor Model 275

19.12 MMC VSC Interaction with AC System and PQ Operating Diagrams 277

20 VSC HVDC under AC and DC Fault Conditions 280

20.1 Introduction 280

20.2 Faults on the AC System 280

20.3 DC Faults with Two-Level VSC 281

20.4 Influence of DC Capacitors 286

20.5 VSC Converter Modelling under DC Faults and VSC Diode Bridge 287

20.6 Converter-Mode Transitions as DC Voltage Reduces 294

20.7 DC Faults with Half-Bridge Modular Multilevel Converter 294

20.8 DC Faults with Full-Bridge Modular Multilevel Converter 298

21 VSC HVDC Application for AC Grid Support and Operation with Passive AC Systems 302

21.1 VSC HVDC High-Level Controls and AC Grid Support 302

21.2 HVDC Embedded inside an AC Grid 303

21.3 HVDC Connecting Two Separate AC Grids 304

21.4 HVDC in Parallel with AC 304

21.5 Operation with a Passive AC System and Black Start Capability 305

21.6 VSC HVDC Operation with Offshore Wind Farms 305

21.7 VSC HVDC Supplying Power Offshore and Driving a MW-Size Variable-Speed Motor 307

Bibliography Part II Voltage Source Converter HVDC 309

Part III DC Transmission Grids 311

22 Introduction to DC Grids 313

22.1 DC versus AC Transmission 313

22.2 Terminology 314

22.3 DC Grid Planning, Topology and Power-Transfer Security 314

22.4 Technical Challenges 315

22.5 DC Grid Building by Multiple Manufacturers 316

22.6 Economic Aspects 316

23 DC Grids with Line-Commutated Converters 317

23.1 Multiterminal HVDC 317

23.2 Italy–Corsica–Sardinia Multiterminal HVDC Link 318

23.3 Connecting LCC Converter to a DC Grid 319

23.4 Control of LCC Converters in DC Grids 321

23.5 Control of LCC DC Grids through DC Voltage Droop Feedback 321

23.6 Managing LCC DC Grid Faults 323

23.7 Reactive Power Issues 325

23.8 Large LCC Rectifier Stations in DC Grids 325

24 DC Grids with Voltage Source Converters and Power-Flow Model 326

24.1 Connecting a VSC Converter to a DC Grid 326

24.2 DC Grid Power Flow Model 327

24.3 DC Grid Power Flow under DC Faults 331

25 DC Grid Control 334

25.1 Introduction 334

25.2 Fast Local VSC Converter Control in DC Grids 334

25.3 DC Grid Dispatcher with Remote Communication 336

25.4 Primary, Secondary and Tertiary DC Grid Control 337

25.5 DC Voltage Droop Control for VSC Converters in DC Grids 338

25.6 Three-Level Control for VSC Converters with Dispatcher Droop 339

25.7 Power Flow Algorithm When DC Powers are Regulated 340

25.8 Power Flow and Control Study of CIGRE DC Grid-Test System 344

26 DC Grid Fault Management and DC Circuit Breakers 349

26.1 Introduction 349

26.2 Fault Current Components in DC Grids 350

26.3 DC System Protection Coordination with AC System Protection 352

26.4 Mechanical DC Circuit Breaker 352

26.5 Semiconductor Based DC Circuit Breaker 355

26.6 Hybrid DC Circuit Breaker 359

26.7 DC Grid-Protection System Development 361

26.8 DC Grid Selective Protection System Based on Current Derivative or Travelling Wave Identification 362

26.9 Differential DC Grid Protection Strategy 363

26.10 DC Grid Selective Protection System Based on Local Signals 364

26.11 DC Grids with DC Fault-Tolerant VSC Converters 365

27 High Power DC/DC Converters and DC Power-Flow Controlling Devices 372

27.1 Introduction 372

27.2 Power Flow Control Using Series Resistors 373

27.3 Low Stepping-Ratio DC/DC Converters 376

27.4 High Stepping Ratio Isolated DC/DC Converter 383

27.5 High Stepping Ratio LCL DC/DC Converter 383

27.6 Building DC Grids with DC/DC Converters 385

27.7 DC Hubs 387

27.8 Developing DC Grids Using DC Hubs 390

27.9 North Sea DC Grid Topologies 390

Bibliography Part III DC Transmission Grids 394

Appendix A Variable Notations 396

Appendix B Analytical Background for Rotating DQ Frame 398

Appendix C System Modelling Using Complex Numbers and Phasors 409

Appendix D Simulink Examples 411

Index 000