Integrating renewable energy and other distributed energy sources into smart grids, often via power inverters, is arguably the largest “new frontier” for smart grid advancements. Inverters should be controlled properly so that their integration does not jeopardize the stability and performance of power systems and a solid technical backbone is formed to facilitate other functions and services of smart grids.
This unique reference offers systematic treatment of important control problems in power inverters, and different general converter theories. Starting at a basic level, it presents conventional power conversion methodologies and then ‘non-conventional’ methods, with a highly accessible summary of the latest developments in power inverters as well as insight into the grid connection of renewable power.
Consisting of four parts – Power Quality Control, Neutral Line Provision, Power Flow Control, and Synchronisation – this book fully demonstrates the integration of control and power electronics.
Key features include:
- the fundamentals of power processing and hardware design
- innovative control strategies to systematically treat the control of power inverters
- extensive experimental results for most of the control strategies presented
- the pioneering work on “synchronverters” which has gained IET Highly Commended Innovation Award
Engineers working on inverter design and those at power system utilities can learn how advanced control strategies could improve system performance and work in practice. The book is a useful reference for researchers who are interested in the area of control engineering, power electronics, renewable energy and distributed generation, smart grids, flexible AC transmission systems, and power systems for more-electric aircraft and all-electric ships. This is also a handy text for graduate students and university professors in the areas of electrical power engineering, advanced control engineering, power electronics, renewable energy and smart grid integration.
Table of Contents
Preface xvii
Acknowledgments xix
About the Authors xxi
List of Abbreviations xxiii
1 Introduction 1
1.1 Outline of the Book 1
1.2 Basics of Power Processing 4
1.3 Hardware Issues 24
1.4 Wind Power Systems 44
1.5 Solar Power Systems 53
1.6 Smart Grid Integration 55
2 Preliminaries 63
2.1 Power Quality Issues 63
2.2 Repetitive Control 67
2.3 Reference Frames 71
PART I POWER QUALITY CONTROL
3 Current H∞ Repetitive Control 81
3.1 System Description 81
3.2 Controller Design 82
3.3 Design Example 87
3.4 Experimental Results 88
3.5 Summary 91
4 Voltage and Current H∞ Repetitive Control 93
4.1 System Description 93
4.2 Modelling of an Inverter 94
4.3 Controller Design 96
4.4 Design Example 100
4.5 Simulation Results 102
4.6 Summary 107
5 Voltage H∞ Repetitive Control with a Frequency-adaptive Mechanism 109
5.1 System Description 109
5.2 Controller Design 110
5.3 Design Example 116
5.4 Experimental Results 117
5.5 Summary 126
6 Cascaded Current-Voltage H∞ Repetitive Control 127
6.1 Operation Modes in Microgrids 127
6.2 Control Scheme 129
6.3 Design of the Voltage Controller 131
6.4 Design of the Current Controller 133
6.5 Design Example 134
6.6 Experimental Results 136
6.7 Summary 147
7 Control of Inverter Output Impedance 149
7.1 Inverters with Inductive Output Impedances (L-inverters) 149
7.2 Inverters with Resistive Output Impedances (R-inverters) 150
7.3 Inverters with Capacitive Output Impedances (C-inverters) 152
7.4 Design of C-inverters to Improve the Voltage THD 153
7.5 Simulation Results for R-, L- and C-inverters 157
7.6 Experimental Results for R-, L- and C-inverters 159
7.7 Impact of the Filter Capacitor 162
7.8 Summary 163
8 Bypassing Harmonic Current Components 165
8.1 Controller Design 165
8.2 Physical Interpretation of the Controller 167
8.3 Stability Analysis 169
8.4 Experimental Results 171
8.5 Summary 172
9 Power Quality Issues in Traction Power Systems 173
9.1 Introduction 173
9.2 Description of the Topology 175
9.3 Compensation of Negative-sequence Currents, Reactive Power and Harmonic Currents 175
9.4 Special Case: cos θ = 1 180
9.5 Simulation Results 181
9.6 Summary 184
PART II NEUTRAL LINE PROVISION
10 Topology of a Neutral Leg 187
10.1 Introduction 187
10.2 Split DC Link 188
10.3 Conventional Neutral Leg 189
10.4 Independently-controlled Neutral Leg 190
10.5 Summary 191
11 Classical Control of a Neutral Leg 193
11.1 Mathematical Modelling 193
11.2 Controller Design 195
11.3 Performance Evaluation 199
11.4 Selection of the Components 201
11.5 Simulation Results 202
11.6 Summary 205
12 H∞ Voltage-Current Control of a Neutral Leg 207
12.1 Mathematical Modelling 207
12.2 Controller Design 210
12.3 Selection of Weighting Functions 214
12.4 Design Example 215
12.5 Simulation Results 216
12.6 Summary 217
13 Parallel PI Voltage-H∞ Current Control of a Neutral Leg 219
13.1 Description of the Neutral Leg 219
13.2 Design of an
13.3 Addition of a Voltage Control Loop 226
13.4 Experimental Results 226
13.5 Summary 230
14 Applications in Single-phase to Three-phase Conversion 233
14.1 Introduction 233
14.2 The Topology under Consideration 236
14.3 Basic Analysis 237
14.4 Controller Design 239
14.5 Simulation Results 244
14.6 Summary 248
PART III POWER FLOW CONTROL
15 Current Proportional–Integral Control 251
15.1 Control Structure 251
15.2 Controller Implementation 254
15.3 Experimental Results 254
15.4 Summary 258
16 Current Proportional-Resonant Control 259
16.1 Proportional-resonant Controller 259
16.2 Control Structure 260
16.3 Controller Design 261
16.4 Experimental Results 263
16.5 Summary 268
17 Current Deadbeat Predictive Control 269
17.1 Control Structure 269
17.2 Controller Design 269
17.3 Experimental Results 271
17.4 Summary 275
18 Synchronverters: Grid-friendly Inverters that Mimic Synchronous Generators 277
18.1 Mathematical Model of Synchronous Generators 278
18.2 Implementation of a Synchronverter 282
18.3 Operation of a Synchronverter 284
18.4 Simulation Results 287
18.5 Experimental Results 290
18.6 Summary 296
19 Parallel Operation of Inverters 297
19.1 Introduction 297
19.2 Problem Description 299
19.3 Power Delivered to a Voltage Source 300
19.4 Conventional Droop Control 301
19.5 Inherent Limitations of Conventional Droop Control 304
19.6 Robust Droop Control of R-inverters 309
19.7 Robust Droop Control of C-inverters 319
19.8 Robust Droop Control of L-inverters 326
19.9 Summary 330
20 Robust Droop Control with Improved Voltage Quality 335
20.1 Control Strategy 335
20.2 Experimental Results 337
20.3 Summary 346
21 Harmonic Droop Controller to Improve Voltage Quality 347
21.1 Model of an Inverter System 347
21.2 Power Delivered to a Current Source 349
21.3 Reduction of Harmonics in the Output Voltage 351
21.4 Simulation Results 353
21.5 Experimental Results 355
21.6 Summary 358
PART IV SYNCHRONISATION
22 Conventional Synchronisation Techniques 361
22.1 Introduction 361
22.2 Zero-crossing Method 362
22.3 Basic Phase-locked Loops (PLL) 363
22.4 PLL in the Synchronously Rotating Reference Frame (SRF-PLL) 364
22.5 Second-order Generalised Integrator-based PLL (SOGI-PLL) 366
22.6 Sinusoidal Tracking Algorithm (STA) 368
22.7 Simulation Results with SOGI-PLL and STA 369
22.8 Experimental Results with SOGI-PLL and STA 372
22.9 Summary 378
23 Sinusoid-locked Loops 379
23.1 Single-phase Synchronous Machine (SSM) Connected to the Grid 379
23.2 Structure of a Sinusoid-locked Loop (SLL) 380
23.3 Tracking of the Frequency and the Phase 382
23.4 Tracking of the Voltage Amplitude 382
23.5 Tuning of the Parameters 382
23.6 Equivalent Structure 383
23.7 Simulation Results 384
23.8 Experimental Results 386
23.9 Summary 390
References 393
Index 407
