As the first book of its kind for power electronics-enabled autonomous power systems, it
• introduces a holistic architecture applicable to both large and small power systems, including aircraft power systems, ship power systems, microgrids, and supergrids
• provides latest research to address the unprecedented challenges faced by power systems and to enhance grid stability, reliability, security, resiliency, and sustainability
• demonstrates how future power systems achieve harmonious interaction, prevent local faults from cascading into wide-area blackouts, and operate autonomously with minimized cyber-attacks
• highlights the significance of the SYNDEM concept for power systems and beyond
Power Electronics-Enabled Autonomous Power Systems is an excellent book for researchers, engineers, and students involved in energy and power systems, electrical and control engineering, and power electronics. The SYNDEM theoretical framework chapter is also suitable for policy makers, legislators, entrepreneurs, commissioners of utility commissions, energy and environmental agency staff, utility personnel, investors, consultants, and attorneys.
Table of Contents
List of Figures xix
List of Tables xxxiii
Foreword xxxv
Preface xxxvii
Acknowledgments xxxix
About the Author xli
List of Abbreviations xliii
1 Introduction 1
1.1 Motivation and Purpose 1
1.2 Outline of the Book 3
1.3 Evolution of Power Systems 7
1.3.1 Today’s Grids 8
1.3.2 Smart Grids 8
1.3.3 Next-Generation Smart Grids 8
1.4 Summary 10
Part I Theoretical Framework 11
2 Synchronized and Democratized (SYNDEM) Smart Grid 13
2.1 The SYNDEM Concept 13
2.2 SYNDEM Rule of Law - Synchronization Mechanism of Synchronous Machines 15
2.3 SYNDEM Legal Equality - Homogenizing Heterogeneous Players as Virtual Synchronous Machines (VSM) 18
2.4 SYNDEM Grid Architecture 19
2.4.1 Architecture of Electrical Systems 19
2.4.2 Overall Architecture 22
2.4.3 Typical Scenarios 23
2.5 Potential Benefits 24
2.6 Brief Description of Technical Routes 28
2.6.1 The First-Generation (1G) VSM 28
2.6.2 The Second-Generation (2G) VSM 29
2.6.3 The Third-Generation (3G) VSM 29
2.7 Primary Frequency Response (PFR) in a SYNDEM Smart Grid 30
2.7.1 PFR from both Generators and Loads 31
2.7.2 Droop 31
2.7.3 Fast Action Without Delay 31
2.7.4 Reconfigurable Virtual Inertia 31
2.7.5 Continuous PFR 32
2.8 SYNDEM Roots 32
2.8.1 SYNDEM and Taoism 32
2.8.2 SYNDEM and Chinese History 33
2.9 Summary 34
3 Ghost Power Theory 35
3.1 Introduction 35
3.2 Ghost Operator, Ghost Signal, and Ghost System 36
3.2.1 The Ghost Operator 36
3.2.2 The Ghost Signal 37
3.2.3 The Ghost System 39
3.3 Physical Meaning of Reactive Power in Electrical Systems 41
3.4 Extension to Complete the Electrical-Mechanical Analogy 43
3.5 Generalization to Other Energy Systems 46
3.6 Summary and Discussions 47
Part II 1G VSM: Synchronverters 49
4 Synchronverter Based Generation 51
4.1 Mathematical Model of Synchronous Generatorss 51
4.1.1 The Electrical Part 51
4.1.2 The Mechanical Part 53
4.1.3 Presence of a Neutral Line 54
4.2 Implementation of a Synchronverter 55
4.2.1 The Power Part 56
4.2.2 The Electronic Part 56
4.3 Operation of a Synchronverter 57
4.3.1 Regulation of Real Power and Frequency Droop Control 57
4.3.2 Regulation of Reactive Power and Voltage Droop Control 58
4.4 Simulation Results 59
4.4.1 Under Different Grid Frequencies 60
4.4.2 Under Different Load Conditions 62
4.5 Experimental Results 62
4.5.1 Grid-connected Set Mode 63
4.5.2 Grid-connected Droop Mode 63
4.5.3 Grid-connected Parallel Operation 63
4.5.4 Seamless Transfer of the Operation Mode 64
4.6 Summary 67
5 Synchronverter Based Loads 69
5.1 Introduction 69
5.2 Modeling of a Synchronous Motor 70
5.3 Operation of a PWM Rectifier as a VSM 71
5.3.1 Controlling the Power 72
5.3.2 Controlling the DC-bus Voltage 73
5.4 Simulation Results 74
5.4.1 Controlling the Power 74
5.4.2 Controlling the DC-bus Voltage 76
5.5 Experimental Results 77
5.5.1 Controlling the Power 77
5.5.2 Controlling the DC-bus Voltage 77
5.6 Summary 79
6 Control of Permanent Magnet Synchronous Generator (PMSG) Based Wind Turbines 81
6.1 Introduction 81
6.2 PMSG Based Wind Turbines 83
6.3 Control of the Rotor-Side Converter 83
6.4 Control of the Grid-Side Converter 85
6.5 Real-time Simulation Results 86
6.5.1 Under Normal Grid Conditions 87
6.5.2 Under Grid Faults 89
6.6 Summary 90
7 Synchronverter Based AC Ward Leonard Drive Systems 91
7.1 Introduction 91
7.2 Ward Leonard Drive Systems 93
7.3 Model of a Synchronous Generator 95
7.4 Control Scheme with a Speed Sensor 96
7.4.1 Control Structure 96
7.4.2 System Analysis and Parameter Selection 97
7.5 Control Scheme without a Speed Sensor 98
7.5.1 Control Structure 98
7.5.2 System Analysis and Parameter Selection 99
7.6 Experimental Results 100
7.6.1 Case 1: With a Speed Sensor for Feedback 101
7.6.2 Case 2: Without a Speed Sensor for Feedback 104
7.7 Summary 106
8 Synchronverter without a Dedicated Synchronization Unit 107
8.1 Introduction 107
8.2 Interaction of a Synchronous Generator (SG) with an Infinite Bus 109
8.3 Controller for a Self-synchronized Synchronverter 110
8.3.1 Operation after Connection to the Grid 112
8.3.2 Synchronization before Connection to the Grid 113
8.4 Simulation Results 114
8.4.1 Normal Operation 114
8.4.2 Operation under Grid Faults 118
8.5 Experimental Results 119
8.5.1 Case 1: With the Grid Frequency Below 50 Hz 119
8.5.2 Case 2: With the Grid Frequency Above 50 Hz 123
8.6 Benefits of Removing the Synchronization Unit 123
8.7 Summary 124
9 Synchronverter Based Loads without a Dedicated Synchronisation Unit 125
9.1 Controlling the DC-bus Voltage 125
9.1.1 Self-synchronization 125
9.1.2 Normal Operation 126
9.2 Controlling the Power 127
9.3 Simulation Results 127
9.3.1 Controlling the DC-bus Voltage 128
9.3.2 Controlling the Power 130
9.4 Experimental Results 131
9.4.1 Controlling the DC-bus Voltage 132
9.4.2 Controlling the Power 132
9.5 Summary 134
10 Control of a DFIG Based Wind Turbine as a VSG (DFIG-VSG) 135
10.1 Introduction 135
10.2 DFIG Based Wind Turbines 137
10.3 Differential Gears and Ancient Chinese South-pointing Chariots 138
10.4 Analogy between a DFIG and Differential Gears 139
10.5 Control of a Grid-side Converter 140
10.5.1 DC-bus Voltage Control 141
10.5.2 Unity Power Factor Control 141
10.5.3 Self-synchronization 142
10.6 Control of the Rotor-Side Converter 142
10.6.1 Frequency Control 143
10.6.2 Voltage Control 143
10.6.3 Self-synchronization 144
10.7 Regulation of System Frequency and Voltage 145
10.8 Simulation Results 146
10.9 Experimental Results 150
10.10 Summary 153
11 Synchronverter Based Transformerless Photovoltaic Systems 155
11.1 Introduction 155
11.2 Leakage Currents and Grounding of Grid-tied Converters 156
11.2.1 Ground, Grounding, and Grounded Systems 156
11.2.2 Leakage Currents in a Grid-tied Converter 158
11.2.3 Benefits of Providing a Common AC and DC Ground 159
11.3 Operation of a Conventional Half-bridge Inverter 160
11.3.1 Reduction of Leakage Currents 161
11.3.2 Output Voltage Range 161
11.4 A Transformerless PV Inverter 161
11.4.1 Topology 161
11.4.2 Control of the Neutral Leg 161
11.4.3 Control of the Inversion Leg as a VSM 164
11.5 Real-time Simulation Results 165
11.6 Summary 167
12 Synchronverter Based STATCOM without an Dedicated Synchronization Unit 169
12.1 Introduction 169
12.2 Conventional Control of STATCOM 170
12.2.1 Operational Principles 171
12.2.2 Typical Control Strategy 172
12.3 Synchronverter Based Control 173
12.3.1 Regulation of the DC-bus Voltage and Synchronization with the Grid 173
12.3.2 Operation in the Q-mode to Regulate the Reactive Power 175
12.3.3 Operation in the V-mode to Regulate the PCC Voltage 176
12.3.4 Operation in the VD-mode to Droop the Voltage 176
12.4 Simulation Results 177
12.4.1 System Description 177
12.4.2 Connection to the Grid 179
12.4.3 Normal Operation in Different Modes 180
12.4.4 Operation under Extreme Conditions 181
12.5 Summary 185
13 Synchronverters with Bounded Frequency and Voltage 187
13.1 Introduction 187
13.2 Model of the Original Synchronverter 188
13.3 Achieving Bounded Frequency and Voltage 189
13.3.1 Control Design 190
13.3.2 Existence of a Unique Equilibrium 193
13.3.3 Convergence to the Equilibrium 197
13.4 Real-time Simulation Results 199
13.5 Summary 202
14 Virtual Inertia, Virtual Damping, and Fault Ride-through 203
14.1 Introduction 203
14.2 Inertia, the Inertia Time Constant, and the Inertia Constant 204
14.3 Limitation of the Inertia of a Synchronverter 206
14.4 Reconfiguration of the Inertia Time Constant 210
14.4.1 Design and Outcome 210
14.4.2 What is the Catch? 211
14.5 Reconfiguration of the Virtual Damping 212
14.5.1 Through Impedance Scaling with an Inner-loop Voltage Controller 213
14.5.2 Through Impedance Insertion with an Inner-loop Current Controller 214
14.6 Fault Ride-through 214
14.6.1 Analysis 214
14.6.2 Recommended Design 215
14.7 Simulation Results 215
14.7.1 A Single VSM 216
14.7.2 Two VSMs in Parallel Operation 217
14.8 Experimental Results 221
14.8.1 A Single VSM 221
14.8.2 Two VSMs in Parallel Operation 222
14.9 Summary 225
Part III 2G VSM: Robust Droop Controller 227
15 Synchronization Mechanism of Droop Control 229
15.1 Brief Review of Phase-Locked Loops (PLLs) 229
15.1.1 Basic PLL 229
15.1.2 Enhanced PLL (EPLL) 230
15.2 Brief Review of Droop Control 232
15.3 Structural Resemblance between Droop Control and PLL 234
15.3.1 When the Impedance is Inductive 234
15.3.2 When the Impedance is Resistive 236
15.4 Operation of a Droop Controller as a Synchronization Unit 238
15.5 Experimental Results 239
15.5.1 Synchronization with the Grid 239
15.5.2 Connection to the Grid 240
15.5.3 Operation in the Droop Mode 241
15.5.4 Robustness of Synchronization 241
15.5.5 Change in the Operation Mode 242
15.6 Summary 243
16 Robust Droop Control 245
16.1 Control of Inverter Output Impedance 245
16.1.1 Inverters with Inductive Output Impedances (L-inverters) 245
16.1.2 Inverters with Resistive Output Impedances (R-inverters) 246
16.1.3 Inverters with Capacitive Output Impedances (C-inverters) 247
16.2 Inherent Limitations of Conventional Droop Control 248
16.2.1 Basic Principle 248
16.2.2 Experimental Phenomena 250
16.2.3 Real Power Sharing 251
16.2.4 Reactive Power Sharing 252
16.3 Robust Droop Control of R-inverters 252
16.3.1 Control Strategy 252
16.3.2 Error due to Inaccurate Voltage Measurements 253
16.3.3 Voltage Regulation 254
16.3.4 Error due to the Global Settings for E∗ and 𝜔∗ 254
16.3.5 Experimental Results 255
16.4 Robust Droop Control of C-inverters 261
16.4.1 Control Strategy 261
16.4.2 Experimental Results 262
16.5 Robust Droop Control of L-inverters 262
16.5.1 Control Strategy 262
16.5.2 Experimental Results 265
16.6 Summary 268
17 Universal Droop Control 269
17.1 Introduction 269
17.2 Further Insights into Droop Control 270
17.2.1 Parallel Operation of Inverters with the Same Type of Impedance 271
17.2.2 Parallel Operation of L-, R-, and RL-inverters 272
17.2.3 Parallel Operation of RC-, R-, and C-inverters 273
17.3 Universal Droop Controller 275
17.3.1 Basic Principle 275
17.3.2 Implementation 276
17.4 Real-time Simulation Results 277
17.5 Experimental Results 277
17.5.1 Case I: Parallel Operation of L- and C-inverters 277
17.5.2 Case II: Parallel Operation of L-, C-, and R-inverters 279
17.6 Summary 281
18 Self-synchronized Universal Droop Controller 283
18.1 Description of the Controller 283
18.2 Operation of the Controller 285
18.2.1 Self-synchronization Mode 285
18.2.2 Set Mode (P-mode and Q-mode) 286
18.2.3 Droop Mode (PD-mode and QD-mode) 286
18.3 Experimental Results 287
18.3.1 R-inverter with Self-synchronized Universal Droop Control 288
18.3.2 L-inverter with Self-synchronized Universal Droop Control 290
18.3.3 L-inverter with Self-synchronized Robust Droop Control 294
18.4 Real-time Simulation Results from a Microgrid 297
18.5 Summary 300
19 Droop-Controlled Loads for Continuous Demand Response 301
19.1 Introduction 301
19.2 Control Framework with a Three-port Converter 302
19.2.1 Generation of the Real Power Reference 302
19.2.2 Regulation of the Power Drawn from the Grid 304
19.2.3 Analysis of the Operation Modes 305
19.2.4 Determination of the Capacitance for Grid Support 306
19.3 An Illustrative Implementation with the 𝜃-converter 308
19.3.1 Brief Description about the 𝜃-converter 309
19.3.2 Control of the Neutral Leg 310
19.3.3 Control of the Conversion Leg 311
19.4 Experimental Results 311
19.4.1 Design of the Experimental System 311
19.4.2 Steady-state Performance 312
19.4.3 Transient Performance 315
19.4.4 Capacity Potential 317
19.4.5 Comparative Study 318
19.5 Summary 319
20 Current-limiting Universal Droop Controller 321
20.1 Introduction 321
20.2 System Modeling 322
20.3 Control Design 323
20.3.1 Structure 323
20.3.2 Implementation 323
20.4 System Analysis 326
20.4.1 Current-limiting Property 326
20.4.2 Closed-loop Stability 327
20.4.3 Selection of Control Parameters 328
20.5 Practical Implementation 329
20.6 Operation under Grid Variations and Faults 330
20.7 Experimental Results 331
20.7.1 Operation under Normal Conditions 332
20.7.2 Operation under Grid Faults 334
20.8 Summary 338
Part IV 3G VSM: Cybersync Machines 339
21 Cybersync Machines 341
21.1 Introduction 341
21.2 Passivity and Port-Hamiltonian Systems 343
21.2.1 Passive Systems 343
21.2.2 Port-Hamiltonian Systems 343
21.2.3 Passivity of Interconnected Passive Systems 345
21.3 System Modeling 346
21.4 Control Framework 348
21.4.1 The Engendering Block Σe 349
21.4.2 Generation of the Desired Frequency 𝜔d and Flux 𝜑d 350
21.4.3 Design of Σ𝜔 and Σ𝜑 to Obtain a Passive ΣC 351
21.5 Passivity of the Controller 352
21.5.1 Losslessness of the Interconnection Block ΣI 352
21.5.2 Passivity of the Cascade of ΣC and ΣI 354
21.6 Passivity of the Closed-loop System 355
21.7 Sample Implementations for Blocks Σ𝜔 and Σ𝜑 355
21.7.1 Using the Standard Integral Controller (IC) 355
21.7.2 Using a Static Controller 356
21.8 Self-Synchronization and Power Regulation 357
21.9 Simulation Results 358
21.9.1 Self-synchronization 360
21.9.2 Operation after Connection to the Grid 360
21.10 Experimental Results 362
21.10.1 Self-synchronization 362
21.10.2 Operation after Connection to the Grid 363
21.11 Summary 364
Part V Case Studies 365
22 A Single-node System 367
22.1 SYNDEM Smart Grid Research and Educational Kit 367
22.1.1 Overview 367
22.1.2 Hardware Structure 368
22.1.3 Sample Conversion Topologies Attainable 369
22.2 Details of the Single-Node SYNDEM System 375
22.2.1 Description of the System 375
22.2.2 Experimental Results 377
22.3 Summary 378
23 A 100% Power Electronics Based SYNDEM Smart Grid Testbed 379
23.1 Description of the Testbed 379
23.1.1 Overall Structure 379
23.1.2 VSM Topologies Adopted 379
23.1.3 Individual Nodes 382
23.2 Experimental Results 384
23.2.1 Operation of Energy Bridges 384
23.2.2 Operation of Solar Power Nodes 384
23.2.3 Operation of Wind Power Nodes 386
23.2.4 Operation of the DC-Load Node 388
23.2.5 Operation of the AC-Load Node 389
23.2.6 Operation of the Whole Testbed 391
23.3 Summary 393
24 A Home Grid 395
24.1 Description of the Home Grid 395
24.2 Results from Field Operations 396
24.2.1 Black start and Grid forming 396
24.2.2 From Islanded to Grid-tied Operation 399
24.2.3 Seamless Mode Change when the Public Grid is Lost and Recovered 400
24.2.4 Voltage/Frequency Regulation and Power Sharing 400
24.3 Unexpected Problems Emerged During the Field Trial 402
24.4 Summary 404
25 Texas Panhandle Wind Power System 405
25.1 Geographical Description 405
25.2 System Structure 406
25.3 Main Challenges 407
25.4 Overview of Control Strategies Compared 407
25.4.1 VSM Control 408
25.4.2 DQ Control 410
25.5 Simulation Results 411
25.5.1 VSM Control 412
25.5.2 DQ Control 415
25.6 Summary and Conclusions 416
Bibliography 417
Index 441
