High voltage direct current transmission : converters, systems and DC grids

Content: 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