Voltage-Sourced Converters in Power Systems: Modeling, Control, and Applications / Edition 1

by Amirnaser Yazdani, Reza Iravani

Overview

Presents Fundamentals of Modeling, Analysis, and Control of Electric Power Converters for Power System Applications

Electronic (static) power conversion has gained widespread acceptance in power systems applications; electronic power converters are increasingly employed for power conversion and conditioning, compensation, and active filtering. This book presents the fundamentals for analysis and control of a specific class of high-power electronic converters—the three-phase voltage-sourced converter (VSC). Voltage-Sourced Converters in Power Systems provides a necessary and unprecedented link between the principles of operation and the applications of voltage-sourced converters. The book:

• Describes various functions that the VSC can perform in electric power systems
• Covers a wide range of applications of the VSC in electric power systems—including wind power conversion systems
• Adopts a systematic approach to the modeling and control design problems
• Illustrates the control design procedures and expected performance based on a comprehensive set of examples and digital computer time-domain simulation studies

This comprehensive text presents effective techniques for mathematical modeling and control design, and helps readers understand the procedures and analysis steps. Detailed simulation case studies are included to highlight the salient points and verify the designs.

Voltage-Sourced Converters in Power Systems is an ideal reference for senior undergraduate and graduate students in power engineering programs, practicing engineers who deal with grid integration and operation of distributed energy resource units, design engineers, and researchers in the area of electric power generation, transmission, distribution, and utilization.

Product Details

ISBN-13:	9780470521564
Publisher:	Wiley
Publication date:	02/15/2010
Series:	IEEE Press
Pages:	464
Product dimensions:	6.40(w) x 9.30(h) x 1.20(d)

About the Author

Amirnaser Yazdani, PhD, is an assistant professor in the Department of Electrical and Computer Engineering at the University of Western Ontario. Formerly, he was with Digital Predictive Systems (DPS) Inc., Mississauga, Ontario, active in the design and production of power converters for wind energy systems. Dr. Yazdani has more than ten years of industry experience in the design, modeling, and analysis of switching power converters and railway signaling systems. He is a Senior Member of the IEEE and a professional engineer in the province of Ontario, Canada.

Reza Iravani, PhD, is a professor in the Department of Electrical and Computer Engineering at the University of Toronto. Dr. Iravani is a Fellow of the IEEE and a professional engineer in the province of Ontario, Canada.

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Table of Contents

Preface xv

Acknowledgments xvii

Acronyms xix

1 Electronic Power Conversion 1

1.1 Introduction 1

1.2 Power-Electronic Converters and Converter Systems 1

1.3 Applications of Electronic Converters in Power Systems 3

1.4 Power-Electronic Switches 4

1.4.1 Switch Classification 5

1.4.2 Switch Characteristics 8

1.5 Classification of Converters 8

1.5.1 Classification Based on Commutation Process 8

1.5.2 Classification Based on Terminal Voltage and Current Waveforms 9

1.6 Voltage-Sourced Converter (VSC) 10

1.7 Basic Configurations 10

1.7.1 Multimodule VSC Systems 11

1.7.2 Multilevel VSC Systems 14

1.8 Scope of the Book 20

Part I Fundamentals 21

2 DC/AC Half-Bridge Converter 23

2.1 Introduction 23

2.2 Converter Structure 23

2.3 Principles of Operation 25

2.3.1 Pulse-Width Modulation (PWM) 25

2.3.2 Converter Waveforms 26

2.4 Converter Switched Model 27

2.5 Converter Averaged Model 32

2.6 Nonideal Half-Bridge Converter 38

2.6.1 Analysis of Nonideal Half-Bridge Converter: Positive AC-Side Current 38

2.6.2 Analysis of Nonideal Converter: Negative AC-Side Current 43

2.6.3 Averaged Model of Nonideal Half-Bridge Converter 45

3 Control of Half-Bridge Converter 48

3.1 Introduction 48

3.2 AC-Side Control Model of Half-Bridge Converter 48

3.3 Control of Half-Bridge Converter 50

3.4 Feed-Forward Compensation 53

3.4.1 Impact on Start-Up Transient 53

3.4.2 Impact on Dynamic Coupling Between Converter System and AC System 54

3.4.3 Impact on Disturbance Rejection Capability 57

3.5 Sinusoidal Command Following 59

4 Space Phasors and Two-Dimensional Frames 69

4.1 Introduction 69

4.2 Space-Phasor Representation of a Balanced Three-Phase Function 70

4.2.1 Definition of Space Phasor 70

4.2.2 Changing the Amplitude and Phase Angle of a Three-phase Signal 73

4.2.3 Generating a Controllable-Amplitude/Controllable-Frequency Three-Phase Signal 78

4.2.4 Space-Phasor Representation of Harmonics 81

4.3 Space-Phasor Representation of Three-Phase Systems 82

4.3.1 Decoupled Symmetrical Three-Phase Systems 83

4.3.2 Coupled Symmetrical Three-Phase Systems 87

4.3.3 Asymmetrical Three-Phase Systems 88

4.4 Power in Three-Wire Three-Phase Systems 88

4.5 αβ-Frame Representation and Control of Three-Phase Signals and Systems 91

4.5.1 αβ-Frame Representation of a Space Phasor 91

4.5.2 Realization of Signal Generators/Conditioners in αβ-Frame 94

4.5.3 Formulation of Power in or αβ-Frame 95

4.5.4 Control in αβ-Frame 96

4.5.5 Representation of Systems in αβ-Frame 98

4.6 dq-Frame Representation and Control of Three-Phase Systems 101

4.6.1 dq-Frame Representation of a Space Phasor 101

4.6.2 Formulation of Power in dq-Frame 105

4.6.3 Control in dq-Frame 105

4.6.4 Representation of Systems in dq-Frame 107

5 Two-Level, Three-Phase Voltage-Sourced Converter 115

5.1 Introduction 115

5.2 Two-Level Voltage-Sourced Converter 115

5.2.1 Circuit Structure 115

5.2.2 Principles of Operation 116

5.2.3 Power Loss of Nonideal Two-Level VSC 118

5.3 Models and Control of Two-Level VSC 119

5.3.1 Averaged Model of Two-Level VSC 119

5.3.2 Model of Two-Level VSC in αβ-Frame 121

5.3.3 Model and Control of Two-Level VSC in dq-Frame 124

5.4 Classification of VSC Systems 125

6 Three-Level, Three-Phase, Neutral-Point Clamped, Voltage-Sourced Converter 127

6.1 Introduction 127

6.2 Three-Level Half-Bridge NPC 128

6.2.1 Generating Positive AC-Side Voltages 128

6.2.2 Generating Negative AC-Side Voltages 129

6.3 PWM Scheme For Three-Level Half-Bridge NPC 130

6.4 Switched Model of Three-Level Half-Bridge NPC 133

6.4.1 Switched AC-Side Terminal Voltage 133

6.4.2 Switched DC-Side Terminal Currents 133

6.5 Averaged Model of Three-Level Half-Bridge NPC 135

6.5.1 Averaged AC-Side Terminal Voltage 135

6.5.2 Averaged DC-Side Terminal Currents 135

6.6 Three-Level NPC 136

6.6.1 Circuit Structure 136

6.6.2 Principles of Operation 136

6.6.3 Midpoint Current 138

6.6.4 Three-Level NPC with Impressed DC-Side Voltages 143

6.7 Three-Level NPC with Capacitive DC-Side Voltage Divider 144

6.7.1 Partial DC-Side Voltage Drift Phenomenon 145

6.7.2 DC-Side Voltage Equalization 146

6.7.3 Derivation of DC-Side Currents 152

6.7.4 Unified Models of Three-Level NPC and Two-Level VSC 153

6.7.5 Impact of DC Capacitors Voltage Ripple on AC-Side Harmonics 155

7 Grid-Imposed Frequency VSC System: Control in αβ-Frame 160

7.1 Introduction 160

7.2 Structure of Grid-Imposed Frequency VSC System 160

7.3 Real/Reaetive-Power Controller 161

7.3.1 Current-Mode Versus Voltage-Mode Control 162

7.3.2 Dynamic Model of Real-/Reactive-Power Controller 163

7.3.3 Current-Mode Control of Real-/Reactive-Power Controller 165

7.3.4 Selection of DC-Bus Voltage Level 168

7.3.5 Trade-Offs and Practical Considerations 173

7.3.6 PWM with Third-Harmonic Injection 174

7.4 Real-/Reactive-Power Controller Based on Three-Level NPC 181

7.4.1 Midpoint Current of Three-level NPC Based on Third-Harmonic Injected PWM 188

7.5 Controlled DC-Voltage Power Port 189

7.5.1 Model of Controlled DC-Voltage Power Port 191

7.5.2 DC-Bus Voltage Control in Controlled DC-Voltage Power Port 195

7.5.3 Simplified and Accurate Models 200

8 Grid-Imposed Frequency VSC System: Control in dq-Frame 204

8.1 Introduction 204

8.2 Structure of Grid-Imposed Frequency VSC System 205

8.3 Real-/Reactive-Power Controller 206

8.3.1 Current-Mode Versus Voltage-Mode Control 206

8.3.2 Representation of Space Phasors in dq-Frame 208

8.3.3 Dynamic Model of Real/Reactive Power Controller 208

8.3.4 Phase-Locked Loop (PLL) 211

8.3.5 Compensator Design for PLL 213

8.4 Current-Mode Control of Real-/Reactive-Power Controller 217

8.4.1 VSC Current Control 219

8.4.2 Selection of DC-Bus Voltage Level 224

8.4.3 AC-Side Equivalent Circuit 226

8.4.4 PWM with Third-Harmonic Injection 231

8.5 Real-/Reactive-Power Controller Based on Three-Level NPC 232

8.6 Controlled DC-Voltage Power Port 234

8.6.1 Model of Controlled DC-Voltage Power Port 235

8.6.2 Control of Controlled DC-Voltage Power Port 237

8.6.3 Simplified and Accurate Models 242

9 Controlled-Frequency VSC System 245

9.1 Introduction 245

9.2 Structure of Controlled-Frequency VSC System 246

9.3 Model of Controlled-Frequency VSC System 247

9.4 Voltage Control 253

9.4.1 Autonomous Operation 262

10 Variable-Frequency VSC System 270

10.1 Introduction 270

10.2 Structure of Variable-Frequency VSC System 270

10.3 Control of Variable-Frequency VSC System 273

10.3.1 Asynchronous Machine 274

10.3.2 Doubly-Fed Asynchronous Machine 288

10.3.3 Permanent-Magnet Synchronous Machine 307

Part II Applications 311

11 Static Compensator (STATCOM) 313

11.1 Introduction 313

11.2 Controlled DC-Voltage Power Port 313

11.3 STATCOM Structure 314

11.4 Dynamic Model for PCC Voltage Control 315

11.4.1 Large-Signal Model of PCC Voltage Dynamics 315

11.4.2 Small-Signal Model of PCC Voltage Dynamics 318

11.4.3 Steady-State Operating Point 320

11.5 Approximate Model of PCC Voltage Dynamics 321

11.6 STATCOM Control 322

11.7 Compensator Design for PCC Voltage Controller 324

11.8 Model Evaluation 324

12 Back-to-Rack HVDC Conversion System 334

12.1 Introduction 334

12.2 HVDC System Structure 334

12.3 HVDC System Model 336

12.3.1 Grid and Interface Transformer Models 336

12.3.2 Back-to-Back Converter System Model 338

12.4 HVDC System Control 342

12.4.1 Phase-Locked Loop (PLL) 342

12.4.2 dq-Frame Current-Control Scheme 345

12.4.3 PWM Gating Signal Generator 348

12.4.4 Partial DC-Side Voltage Equalization 349

12.4.5 Power Flow Control 350

12.4.6 DC-Bus Voltage Regulation 331

12.5 HVDC System Performance Under an Asymmetrical Fault 353

12.5.1 PCC Voltage Under an Asymmetrical Fault 354

12.5.2 Performance of PLL Under an Asymmetrical Fault 357

12.5.3 Performance of dq-Frame Current-Control Scheme Under an Asymmetrical Fault 358

12.5.4 Dynamics of DC-Bus Voltage Under an Asymmetrical Fault 360

12.5.5 Generation of Low-Order Harmonics Under Asymmetrical Fault 365

12.5.6 Steady-State Power-Flow Under an Asymmetrical Fault 369

12.5.7 DC-Bus Voltage Control Under an Asymmetrical Fault 371

13 Variable-Speed Wind-Power System 385

13.1 Introduction 385

13.2 Constant-Speed and Variable-Speed Wind-Power Systems 385

13.2.1 Constant-Speed Wind-Power Systems 385

13.2.2 Variable-Speed Wind-Power Systems 386

13.3 Wind Turbine Characteristics 388

13.4 Maximum Power Extraction from A Variable-Speed Wind-Power System 390

13.5 Variable-Speed Wind-Power System Based on Doubly-Fed Asynchronous Machine 393

13.5.1 Structure of the Doubly-Fed Asynchronous Machine-Based Wind-Power System 393

13.5.2 Machine Torque Control by Variable-Frequency VSC System 395

13.5.3 DC-Bus Voltage Regulation by Controlled DC-Voltage Power Port 397

13.5.4 Compensator Design for Controlled DC-Voltage Power Port 401

Appendix A Space-Phasor Representation of Symmetrical Three-Phase Electric Machines 413

A.1 Introduction 413

A.2 Structure of Symmetrical Three-Phase Machine 413

A.3 Machine Electrical Model 414

A.3.1 Terminal Voltage/Current Equations 415

A.3.2 Stator Flux Space Phasor 415

A.3.3 Rotor Flux Space Phasor 417

A.3.4 Machine Electrical Torque 418

A.4 Machine Equivalent Circuit 418

A.4.1 Machine Dynamic Equivalent Circuit 418

A.4.2 Machine Steady-State Equivalent Circuit 420

A.5 Permanent-Magnet Synchronous Machine (PMSM) 421

A.5.1 PMSM Electrical Model 421

A.5.2 PMSM Steady-State Equivalent Circuit 424

Appendix B Per-Unit Values for VSC Systems 426

B.1 Introduction 426

B.1.1 Base Values for AC-Side Quantities 426

B.1.2 Base Values for DC-Side Quantities 426

References 431

Index 439