Smart Solar PV Inverters with Advanced Grid Support Functionalities
1. Auflage Januar 2022
512 Seiten, Hardcover
Wiley & Sons Ltd
ISBN:
978-1-119-21418-2
John Wiley & Sons
Learn the fundamentals of smart photovoltaic (PV) inverter technology with this insightful one-stop resource
Smart Solar PV Inverters with Advanced Grid Support Functionalities presents a comprehensive coverage of smart PV inverter technologies in alleviating grid integration challenges of solar PV systems and for additionally enhancing grid reliability. Accomplished author Rajiv Varma systematically integrates information from the wealth of knowledge on smart inverters available from EPRI, NREL, NERC, SIWG, EU-PVSEC, CIGRE, IEEE publications; and utility experiences worldwide. The book further presents a novel, author-developed and patented smart inverter technology for utilizing solar PV plants both in the night and day as a Flexible AC Transmission System (FACTS) Controller STATCOM, named PV-STATCOM. Replete with case studies, this book includes over 600 references and 280 illustrations.
Smart Solar PV Inverters with Advanced Grid Support Functionalities' features include:
* Concepts of active and reactive power control; description of different smart inverter functions, and modeling of smart PV inverter systems
* Distribution system applications of PV-STATCOM for dynamic voltage control, enhancing connectivity of solar PV and wind farms, and stabilization of critical motors
* Transmission system applications of PV-STATCOM for improving power transfer capacity, power oscillation damping (POD), suppression of subsynchronous oscillations, mitigation of fault induced delayed voltage recovery (FIDVR), and fast frequency response (FFR) with POD
* Hosting capacity for solar PV systems, its enhancement through effective settings of different smart inverter functions; and control coordination of smart PV inverters
* Emerging smart inverter grid support functions and their pioneering field demonstrations worldwide, including Canada, USA, UK, Chile, China, and India.
Perfect for system planners and system operators, utility engineers, inverter manufacturers and solar farm developers, this book will prove to be an important resource for academics and graduate students involved in electrical power and renewable energy systems.
About the Author xxiii
Foreword xxv
Preface xxvii
Acknowledgments xxxi
List of Abbreviations xxxiii
1 Impacts of High Penetration of Solar PV Systems and Smart Inverter Developments 1
1.1 Concepts of Reactive and Active Power Control 1
1.1.1 Reactive Power Control 1
1.1.1.1 Voltage Control 1
1.1.1.2 Frequency Control 3
1.1.2 Active Power Control 4
1.1.2.1 Voltage Control 4
1.1.2.2 Frequency Control 5
1.1.3 Frequency Response with Synchronous Machines 5
1.1.3.1 Rate of Change of Frequency 6
1.1.3.2 Factors Impacting ROCOF 7
1.1.3.3 System Inertia 7
1.1.3.4 Critical Inertia 8
1.1.3.5 Size of Largest Contingency 8
1.1.4 Fast Frequency Response 8
1.2 Challenges of High Penetration of Solar PV Systems 10
1.2.1 Steady-state Overvoltage 10
1.2.2 Voltage Fluctuations 11
1.2.3 Reverse Power Flow 11
1.2.4 Transient Overvoltage 13
1.2.5 Voltage Unbalance 14
1.2.6 Decrease in Voltage Support Capability of Power Systems 14
1.2.7 Interaction with Conventional Voltage Regulation Equipment 15
1.2.8 Variability of Power Output 15
1.2.9 Balancing Supply and Demand 15
1.2.10 Changes in Active Power Flow in Feeders 16
1.2.11 Change in Reactive Power Flow in Feeders 17
1.2.12 Line Losses 17
1.2.13 Harmonic Injections 17
1.2.14 Low Short Circuit Levels 20
1.2.15 Protection and Control Issues 20
1.2.16 Short Circuit Current Issues 20
1.2.17 Unintentional Islanding 22
1.2.18 Frequency Regulation Issues due to Reduced Inertia 23
1.2.18.1 Under Frequency Response 23
1.2.18.2 Over Frequency Response 26
1.2.19 Angular Stability Issues due to Reduced Inertia 26
1.3 Development of Smart Inverters 28
1.3.1 Developments in Germany 29
1.3.2 Developments in the USA 29
1.3.3 Development in Canada of Night and Day Control of Solar PV Farms as STATCOM (PV-STATCOM) 29
1.4 Conclusions 30
References 30
2 Smart Inverter Functions 35
2.1 Capability Characteristics of Distributed Energy Resource (DER) 35
2.2 General Considerations in Implementation of Smart Inverter Functions 37
2.2.1 Performance Categories 38
2.2.1.1 Normal Performance 39
2.2.1.2 Abnormal Performance 39
2.2.2 Reactive Power Capability of DERs 39
2.2.2.1 Active Power (Watt) Precedence Mode 40
2.2.2.2 Reactive Power (Var) Precedence Mode 41
2.3 Smart Inverter Functions for Reactive Power and Voltage Control 41
2.3.1 Constant Power Factor Function 41
2.3.2 Constant Reactive Power Function 41
2.3.3 Voltage-Reactive Power (Volt-Var) Function 41
2.3.4 Active Power-Reactive Power (Watt-Var or P-Q) Function 42
2.3.5 Dynamic Voltage Support Function 44
2.3.5.1 Dynamic Network Support Function 44
2.3.5.2 Dynamic Reactive Current Support Function 45
2.4 Smart Inverter Function for Voltage and Active Power Control 46
2.4.1 Voltage-Active Power (Volt-Watt) Function 46
2.4.2 Coordination with Volt-Var Function 48
2.4.3 Dynamic Volt-Watt Function 48
2.5 Low/High Voltage Ride-Through (L/H VRT) Function 50
2.5.1 IEEE Standard 1547-2018 51
2.5.2 North American Electric Reliability Corporation (NERC) Standard PRC-024 53
2.6 Frequency-Watt Function 54
2.6.1 Frequency-Watt Function 1 55
2.6.2 Frequency-Watt Function 2 56
2.6.3 Frequency Droop Function 56
2.6.4 Frequency-Watt Function with Energy Storage 56
2.7 Low/High Frequency Ride-Through (L/H FRT) Function 57
2.7.1 IEEE Standard 1547-2018 58
2.7.2 North American Electric Reliability Corporation (NERC) Standard PRC-024 59
2.8 Ramp Rate 59
2.9 Fast Frequency Response 61
2.10 Smart Inverter Functions Related to DERs Based on Energy Storage Systems 61
2.10.1 Direct Charge/Discharge Function 61
2.10.2 Price-Based Charge/Discharge Function 62
2.10.3 Coordinated Charge/Discharge Management Function 62
2.10.3.1 Time-Based Charging Model 63
2.10.3.2 Duration at Maximum Charging and Discharging Rates 63
2.11 Limit Maximum Active Power Function 64
2.11.1 Without Energy Storage 64
2.11.2 With Energy Storage System 65
2.12 Set Active Power Mode 65
2.13 Active Power Smoothing Mode 65
2.14 Active Power Following Function 65
2.15 Prioritization of Different Functions 65
2.15.1 Active Power-related Functions 66
2.15.1.1 Functions Affecting Operating Boundaries 66
2.15.1.2 Dynamic Functions 66
2.15.1.3 Steady-State Functions Managing Watt Input/Output 66
2.15.2 Reactive Power-Related Functions 66
2.15.2.1 Dynamic Functions 66
2.15.2.2 Steady-State Functions 66
2.15.3 Smart Inverter Functions Under Abnormal Conditions 66
2.16 Emerging Functions 67
2.16.1 PV-STATCOM: Control of PV inverters as STATCOM during Night and Day 67
2.16.2 Reactive Power at No Active Power Output 67
2.17 Summary 68
References 68
3 Modeling and Control of Three-Phase Smart PV Inverters 73
3.1 Power Flow from a Smart Inverter System 73
3.1.1 Active Power Flow 75
3.1.1.1 Magnitude of Active Power Flow 75
3.1.1.2 Direction of Active Power Flow 75
3.1.2 Reactive Power Flow 75
3.1.2.1 Magnitude of Reactive Power Flow 75
3.1.2.2 Direction of Reactive Power Flow 76
3.1.3 Implementation of Smart Inverter Functions 76
3.2 Smart PV Inverter System 77
3.3 Power Circuit Constituents of Smart Inverter System 79
3.3.1 PV Panels 79
3.3.2 Maximum Power Point Tracking (MPPT) Scheme 82
3.3.3 Non-MPP Voltage Control 82
3.3.4 Voltage Source Converter (VSC) 83
3.3.4.1 DC-Link Capacitor 84
3.3.4.2 AC Filter 84
3.3.4.3 Isolation Transformer 86
3.4 Control Circuit Constituents of Smart Inverter System 86
3.4.1 Measurement Filters 86
3.4.2 abc-dq Transformation 87
3.4.2.1 Concept 87
3.4.2.2 Theoretical Basis 88
3.4.2.3 Power in abc and dq Reference Frame 91
3.4.3 Pulse Width Modulation (PWM) 92
3.4.4 Phase Locked Loop (PLL) 94
3.4.5 Current Controller 97
3.4.6 DC-Link Voltage Controller 99
3.5 Smart Inverter Voltage Controllers 100
3.5.1 Volt-Var Control 101
3.5.2 Closed-Loop Voltage Controller 101
3.6 PV Plant Control 102
3.7 Modeling Guidelines 104
3.8 Summary 104
References 104
4 PV-STATCOM: A New Smart PV Inverter and a New FACTS Controller 107
4.1 Flexible AC Transmission System (FACTS) 107
4.2 Static Var Compensator (SVC) 109
4.3 Synchronous Condenser 111
4.4 Static Synchronous Compensator (STATCOM) 113
4.5 Control Modes of SVC and STATCOM 118
4.5.1 Dynamic Voltage Regulation 118
4.5.1.1 Power Transfer Without Midpoint Voltage Regulation 119
4.5.1.2 Power Transfer with Midpoint Voltage Regulation 119
4.5.2 Modulation of Bus Voltage in Response to System Oscillations 121
4.5.3 Load Compensation 122
4.6 Photovoltaic-Static Synchronous Compensator (PV-STATCOM) 122
4.7 Operating Modes of PV-STATCOM 124
4.7.1 Nighttime 124
4.7.2 Daytime with Active Power Priority 124
4.7.3 Daytime with Reactive Power Priority 125
4.7.3.1 Reactive Power Modulation After Full Active Power Curtailment 125
4.7.3.2 Reactive Power Modulation After Partial Active Power Curtailment 126
4.7.3.3 Simultaneous Active and Reactive Power Modulation After Partial Active Power Curtailment 126
4.7.3.4 Simultaneous Active and Reactive Power Modulation with Pre-existing Active Power Curtailment 127
4.7.4 Methodology of Modulation of Active Power 127
4.8 Functions of PV-STATCOM 128
4.8.1 A New Smart Inverter 128
4.8.2 A New FACTS Controller 129
4.9 Cost of Transforming an Existing Solar PV System into PV-STATCOM 129
4.9.1 Constituents of a PV System 130
4.9.2 Costing of PV-STATCOM 130
4.9.2.1 Cost of 5 Mvar PV-STATCOM 131
4.9.2.2 Cost of 100 Mvar PV-STATCOM 132
4.9.3 Cost of a STATCOM 133
4.9.3.1 Equipment Cost 133
4.9.3.2 Infrastructure Costs 133
4.10 Cost of Operating a PV-STATCOM 135
4.10.1 Nighttime Operating Costs 135
4.10.2 Daytime Operating Costs 135
4.10.3 Additional Costs 135
4.10.4 Technical Considerations of PV-STATCOM and STATCOM 136
4.10.4.1 Number of Inverters 136
4.10.4.2 Ability to Provide Full Reactive Power at Nighttime 136
4.10.4.3 Transient Overvoltage and Overcurrent Rating 136
4.10.4.4 Low Voltage Ride-through 136
4.10.5 Potential of PV-STATCOM 137
4.11 Summary 138
References 139
5 PV-STATCOM Applications in Distribution Systems 145
5.1 Nighttime Application of PV Solar Farm as STATCOM to Regulate Grid Voltage 145
5.1.1 Modeling of Solar PV System 146
5.1.2 Solar Farm Inverter Control 146
5.1.3 Simulation Study 147
5.1.4 Summary 149
5.2 Increasing Wind Farm Connectivity with PV-STATCOM 149
5.2.1 Study System 150
5.2.2 Control System 150
5.2.3 Model of Wind Farm 151
5.2.4 Simulation Studies 151
5.2.4.1 Mitigation of Steady-state Voltage Rise 151
5.2.4.2 Control of Transient Overvoltage 153
5.2.4.3 PV-STATCOM Reactive Power Requirement 153
5.2.4.4 Effect of Distance of PV-STATCOM from Wind Farm 153
5.2.4.5 Increase in Wind Farm Connectivity 155
5.2.5 Summary 155
5.3 Dynamic Voltage Control by PV-STATCOM 156
5.3.1 Study System 156
5.3.2 Control System 157
5.3.2.1 DC-link Voltage Control 157
5.3.2.2 AC Voltage Control 157
5.3.2.3 Power Factor Control (PFC) 157
5.3.3 Operation Mode Selector 157
5.3.4 PSCAD Simulation Studies 159
5.3.4.1 Full STATCOM Mode - Daytime 159
5.3.4.2 Full STATCOM Mode - Nighttime 161
5.3.4.3 Low-voltage Ride-through (LVRT) 163
5.3.5 Summary 163
5.4 Enhancement of Solar Farm Connectivity by PV-STATCOM 165
5.4.1 Study System 165
5.4.2 System Modeling 166
5.4.3 Control System 166
5.4.3.1 Operation Mode Selector 168
5.4.3.2 PCC Voltage Control 169
5.4.3.3 TOV Detection Block 169
5.4.4 Simulation Studies 171
5.4.4.1 Conventional PV System (Without PV-STATCOM Control) 171
5.4.4.2 PV-STATCOM and Two Conventional Solar PV Systems 171
5.4.5 Summary 175
5.5 Reduction of Line Losses by PV-STATCOM 175
5.5.1 Concept of PV-STATCOM Voltage Control for Line Loss Reduction 175
5.5.1.1 Determination of Optimal Voltage Setpoints 178
5.5.1.2 Inverter Operating Losses 178
5.5.2 Simulation Studies 179
5.5.2.1 Case Study 1: Two Bus Radial System with Constant Load 179
5.5.2.2 Case Study II: IEEE 33 Bus System with Variable Load 181
5.5.2.3 Improvement in Loss Reduction with PV-STATCOM 181
5.5.3 Summary 184
5.6 Stabilization of a Remotely Located Critical Motor by PV-STATCOM 186
5.6.1 Study Systems 187
5.6.1.1 Study System 1 187
5.6.1.2 Study System 2 188
5.6.2 Study System with PV-STATCOM Control 189
5.6.2.1 Grid-Connected Solar PV Plant 189
5.6.2.2 Conventional PV Inverter Control 190
5.6.2.3 PV-STATCOM Controller 190
5.6.3 Simulation Studies on Study System 1 193
5.6.3.1 Performance of the Proposed PV-STATCOM Controller 194
5.6.3.2 Comparison of PV-STATCOM and STATCOM Operation 196
5.6.4 Field Validation Tests on Utility Solar PV System 196
5.6.4.1 PV Solar Plant Without PV-STATCOM Control 197
5.6.4.2 PV Solar System Operation According to German Grid Code 197
5.6.4.3 PV Solar System Operating as PV-STATCOM at Night 198
5.6.5 Simulation Studies on Study System 2 199
5.6.6 Summary 199
5.7 Conclusions 199
References 200
6 PV-STATCOM Applications in Transmission Systems 205
6.1 Increasing Power Transmission Capacity by PV-STATCOM 205
6.1.1 Study Systems 206
6.1.2 System Model 206
6.1.3 Control System 209
6.1.3.1 Conventional Reactive Power Control 209
6.1.3.2 PCC Voltage Control 209
6.1.3.3 Damping Control 209
6.1.4 Power Transfer Studies for Study System I 210
6.1.4.1 Nighttime Operation of Solar PV System as PV-STATCOM 210
6.1.4.2 Daytime Operation of Solar PV System as PV-STATCOM 211
6.1.5 Power Transfer Studies for Study System II 216
6.1.5.1 Nighttime Operation of Solar DG and Wind DG as STATCOM 216
6.1.5.2 Daytime Operation of Solar DG and Wind DG as STATCOM 216
6.1.6 Summary 219
6.2 Power Oscillation Damping by PV-STATCOM 219
6.2.1 Study System 220
6.2.2 PV-STATCOM Control System 220
6.2.2.1 DC Voltage Controller 220
6.2.2.2 Conventional PV Controller 222
6.2.2.3 Q-POD Controller 222
6.2.2.4 Oscillation Detection Unit (ODU) 222
6.2.2.5 PV Active Power Controllers 222
6.2.2.6 Design of POD Controller 224
6.2.2.7 Small Signal Studies of the POD Control 224
6.2.3 Simulations Studies 225
6.2.3.1 Power Transfer without PV-STATCOM Control 225
6.2.3.2 Power Transfer with Full STATCOM Damping Control and Power Restoration in Normal Ramped Manner 225
6.2.3.3 Power Transfer with Full STATCOM Damping Control and
Ramped Power Restoration with POD Control Active in Partial STATCOM Mode 226
6.2.3.4 Nighttime Power Transfer Enhancement with Full STATCOM POD Control 226
6.2.3.5 Effect of PV-STATCOM Control on System Frequency 228
6.2.4 Summary 228
6.3 Power Oscillation Damping with Combined Active and Reactive Power Modulation Control of PV-STATCOM 228
6.3.1 Modes of PV-STATCOM Control 229
6.3.1.1 Partial STATCOM 229
6.3.1.2 Full STATCOM 229
6.3.2 Study System 230
6.3.3 PV-STATCOM Control System 230
6.3.4 PV Reactive Power Controllers 230
6.3.4.1 Conventional Reactive Power Control 230
6.3.4.2 Q-POD Controller 230
6.3.5 PV-Active Power Controllers 232
6.3.5.1 Conventional Active Power Control 232
6.3.5.2 P-POD Controller 232
6.3.5.3 PQ-POD Controller 232
6.3.5.4 Active Power Restoration Controller 232
6.3.6 Small Signal PV-STATCOM Modeling 232
6.3.7 Selection of PV-STATCOM Controller Mode 233
6.3.8 Design of POD Controllers 234
6.3.9 Effect of PV-STATCOM Placement on Effectiveness of POD Techniques 234
6.3.9.1 Residue Analysis for PV-STATCOM with Q-POD 234
6.3.9.2 Residue Analysis for PV-STATCOM with P-POD 234
6.3.10 Simulation Studies 235
6.3.10.1 POD by PV-STATCOM 236
6.3.10.2 Effect of POD Controllers on System Frequency 239
6.3.10.3 Effect of PV Active Power Output on POD Controls 239
6.3.10.4 POD by PV-STATCOM Connected at Other Buses 239
6.3.11 Summary 240
6.4 Mitigation of Subsynchronous Resonance (SSR) in Synchronous Generator by PV-STATCOM 240
6.4.1 Study System 241
6.4.2 Control System 241
6.4.3 SSR Damping Controller 243
6.4.4 DC Voltage Controller 243
6.4.5 Simulation Studies 245
6.4.5.1 Damping of Critical Mode 1 (67% Series Compensation) 247
6.4.5.2 Ramp Up without PV-STATCOM Control 247
6.4.5.3 Damping of Critical Mode 2 (54% Series Compensation) 250
6.4.5.4 Damping of Critical Mode 3 (41% Series Compensation) 250
6.4.5.5 Damping of Critical Mode 4 (26% Series Compensation) 251
6.4.6 Potential of Utilizing Large Solar Farms for Damping SSR 251
6.4.7 Summary 253
6.5 Alleviation of Subsynchronous Oscillations (SSOs) in Induction-Generator-Based Wind Farm by PV-STATCOM 254
6.5.1 Study System 254
6.5.2 Control System 256
6.5.2.1 Current Controller 256
6.5.2.2 Damping Controller 256
6.5.2.3 DC Voltage Controller 257
6.5.3 Simulation Studies 257
6.5.3.1 Daytime Case Study: PV System Connected at Wind Farm Terminal 257
6.5.3.2 Daytime Case Study: PV System Connected at Line Midpoint 259
6.5.3.3 Nighttime Case Study: SSO Alleviation by PV-STATCOM 260
6.5.4 Potential of Utilizing Large Solar Farms for Alleviating SSO in Wind Farms 262
6.5.5 Summary 262
6.6 Mitigation of Fault-Induced Delayed Voltage Recovery (FIDVR) by PV-STATCOM 263
6.6.1 Study System 264
6.6.2 Structure of a Large Utility-Scale Solar PV Plant 265
6.6.3 Proposed PV-STATCOM Control 265
6.6.3.1 Mode Selector 267
6.6.3.2 Sensitivity Calculator 268
6.6.3.3 Current Reference Calculator 270
6.6.4 Design of PV-STATCOM Controllers 271
6.6.5 Simulation Studies 271
6.6.5.1 Response of IMs for LLL-G Fault with no PV Plant Control 271
6.6.5.2 Performance of Proposed PV-STATCOM Controller 271
6.6.5.3 Advantage of Enhanced Voltage Support up to TOV Limit 274
6.6.5.4 Comparison of Proposed PV STATCOM Controller and Other Smart Inverter Controls 274
6.6.5.5 Comparison of PV STATCOM Controller and STATCOM 275
6.6.5.6 PV-STATCOM Impact on System Frequency 276
6.6.5.7 Nighttime Performance of PV-STATCOM Controller 277
6.6.5.8 Compliance with IEEE Standard 1547-2018 277
6.6.6 Summary 278
6.7 Simultaneous Fast Frequency Control and Power Oscillation Damping by PV-STATCOM 279
6.7.1 Study System 280
6.7.2 System Modeling 281
6.7.2.1 PV Plant Model 281
6.7.2.2 Combined FFR and POD Controller 281
6.7.3 Simulation Scenarios 283
6.7.4 Over-Frequency Control 284
6.7.4.1 25 MW Load Trip in Area 1 (Pavailable = 100 MW, Kcurt = 0); (Power Imbalance less than PV Plant Capacity) 284
6.7.4.2 200 MW Load Trip in Area 1 (Pavailable = 100 MW, Kcurt = 0); (Power Imbalance more than PV Plant Capacity) 286
6.7.5 Under Frequency Control 286
6.7.5.1 25 MW Load Connection in Area 1 (Pavailable = 100 MW, Kcurt = 50%); (Power Imbalance less than PV Plant Capacity) 286
6.7.5.2 100 MWLoad Connection in Area 1 (Pavailable = 100 MW, Kcurt = 50%); (Power Imbalance more than PV Plant Capacity) 288
6.7.6 Performance Comparison of Proposed FFR + POD Control with Conventional Frequency Control 290
6.7.7 Summary 291
6.8 Conclusions 292
References 292
7 Increasing Hosting Capacity by Smart Inverters - Concepts and Applications 301
7.1 Hosting Capacity of Distribution Feeders 301
7.1.1 Voltage 302
7.1.2 Thermal Overloading 302
7.2 Hosting Capacity Based on Voltage Violations 302
7.3 Increasing Hosting Capacity with Non Smart Inverter Techniques 304
7.3.1 Active Power Curtailment (APC) 305
7.3.2 Change in Orientation of PV Panels 306
7.3.3 Correlation between Load and PV Systems 306
7.3.4 Demand Side Management (DSM) 306
7.3.5 On Load Tap Changer (OLTC) Transformers, Voltage Regulators, and Switched Capacitors 306
7.3.6 Application of Decentralized Energy Storage Systems 306
7.3.7 Energy Storage Requirements for Achieving 50% Solar PV Energy Penetration in California 307
7.3.8 Comparative Evaluation of Different Techniques for Increasing Hosting Capacity 307
7.3.8.1 Active Power Curtailment 308
7.3.8.2 Different PV System Orientations 308
7.3.8.3 Correlation with Load 309
7.3.8.4 Demand Side Management (DSM) Approach 310
7.3.8.5 On Load Tap Changer Transformer (OLTC) 311
7.3.8.6 Storage 311
7.3.8.7 Reactive Power Control (RPC) 311
7.3.9 Summary 311
7.4 Characteristics of Different Smart Inverter Functions 312
7.4.1 Constant Power Factor 312
7.4.1.1 Advantages 312
7.4.1.2 Potential Issues 313
7.4.2 Volt-Var Function 314
7.4.2.1 Advantages 314
7.4.2.2 Potential Issues 314
7.4.3 Volt-Watt Control 314
7.4.3.1 Advantages 314
7.4.3.2 Potential Issues 315
7.4.4 Active Power Limit 315
7.4.4.1 Advantages 315
7.4.4.2 Potential Issues 315
7.5 Factors Affecting Hosting Capacity of Distribution Feeders 315
7.5.1 Size and Location of DER 315
7.5.2 Physical Characteristics of Distribution System 316
7.5.3 DER Technology 316
7.5.4 PV Hosting Capacity Estimation 316
7.5.4.1 Impact of Feeder Characteristics 316
7.5.4.2 Impact of Smart Inverter Functions 319
7.6 Determination of Settings of Constant Power Factor Function 320
7.6.1 Single DER System 320
7.6.2 Multiple DERs 321
7.6.2.1 Median Feeder X/R Ratio 321
7.6.2.2 Weighted Average X/R Ratio 321
7.6.2.3 Sensitivity Analysis Based Technique 321
7.6.2.4 Performance Comparison of the Three Methods 322
7.7 Impact of DER Interconnection Transformer 322
7.8 Determination of Smart Inverter Function Settings from Quasi-Static Time-Series (QSTS) Analysis 323
7.8.1 Development of Detailed Feeder Model 325
7.8.1.1 Distribution System 325
7.8.1.2 Conventional Voltage Regulation Equipment 325
7.8.1.3 PV Systems with Smart Inverter Controls 325
7.8.1.4 Type of Smart Inverter Control 326
7.8.1.5 Performance Criteria 326
7.8.2 Simulation of Quasi-Static Time-Series Model 327
7.8.2.1 Characterization of Solar Conditions 327
7.8.2.2 Characterization of Load Conditions 328
7.8.2.3 Simulation Studies 328
7.8.3 Analysis of Results 328
7.8.4 Selection of Appropriate Setting 329
7.9 Guidelines for Selection of Smart Inverter Settings 330
7.9.1 Autonomous Default Settings 330
7.9.2 Non-optimized Settings 330
7.9.3 Optimized Settings 331
7.10 Determination of Sites for Implementing DERs with Smart Inverter Functions 331
7.11 Mitigation Methods for Increasing Hosting Capacity 333
7.12 Increasing Hosting Capacity in Thermally Constrained Distribution Networks 334
7.13 Utility Simulation Studies of Smart Inverters for Increasing Hosting Capacity 334
7.13.1 Voltage Control in a Distribution Feeder with High PV Penetration 334
7.13.2 Smart Inverter Functions for Increasing Hosting Capacity in New York Distribution Systems 335
7.13.3 Impact of Different Smart Inverter Functions in Increasing Hosting Capacity in Hawaii 337
7.13.4 Smart Inverter Impacts on California Distribution Feeders with Increasing PV Penetration 339
7.13.4.1 Methodology 340
7.13.4.2 Voltage Profile Along Feeder 340
7.13.4.3 Maximum Voltage 340
7.13.4.4 Minimum Voltage 341
7.13.4.5 Tap Operations 342
7.13.4.6 Line Losses 342
7.13.4.7 Voltage Fluctuations 342
7.13.5 Mitigation Methods to Increase Feeder Hosting Capacity 343
7.13.5.1 Assessment of Base Feeder 343
7.13.5.2 Integration Solution Assessment 344
7.13.5.3 Volt-Watt Function 344
7.13.5.4 Volt-Var Function 346
7.13.5.5 Watt-Power Factor Function 346
7.13.5.6 Fixed Power Factor Function 349
7.13.6 Impact of Smart Inverter Functions in Increasing Hosting Capacity in Five California Distribution Feeders 349
7.13.6.1 Volt-Var Control 352
7.13.6.2 Volt-Watt Control 353
7.13.6.3 Limiting Maximum Real Power (LMRP) Output Function 353
7.13.6.4 Selection of the Smart Inverter Settings 354
7.13.7 Hosting Capacity Experience in Utah 354
7.13.7.1 Constant Power Factor Function 354
7.13.7.2 Volt-Var Function 354
7.14 Field Implementation of Smart Inverters for Increasing Hosting Capacity 355
7.14.1 Voltage Control by Constant Power Factor Function in a Distribution Feeder in Fontana, USA 355
7.14.2 Smart Inverter Demonstration in Porterville Feeder in California 356
7.14.3 Improvement in Feeder Hosting Capacity Through Smart Inverter Controls in Upper Austria 358
7.14.4 Demonstration of Smart Inverter Controls under the META PV Project Funded by the European Commission 359
7.14.5 Arizona Public Service Solar Partner Program 359
7.14.6 Increasing Renewables Hosting Capacity in the Czech Republic 361
7.14.6.1 Use Case 1: Increasing DER Hosting Capacity of LV Distribution Networks 361
7.14.6.2 Use Case 2: Increasing DER Hosting Capacity in MV Networks 362
7.14.7 Hosting Capacity Experience in Salt River Project 363
7.15 Conclusions 364
References 365
8 Control Coordination of Smart PV Inverters 369
8.1 Concepts of Control Coordination 369
8.1.1 Need for Coordination 369
8.1.2 Frequency Range of Control Interactions 370
8.1.2.1 Steady-State Interactions 370
8.1.2.2 Electromechanical Oscillation Interactions 370
8.1.2.3 Control System Interactions 371
8.1.2.4 Subsynchronous Oscillation (SSO) Interactions 371
8.1.2.5 High-frequency Interactions 371
8.1.3 Principle of Coordination 372
8.2 Coordination of Smart Inverters with Conventional Voltage Controllers 372
8.2.1 European IGREENGrid Project 372
8.2.2 Interaction of Smart Inverters with Load Tap Changing Transformers 373
8.2.2.1 System Modeling 375
8.2.2.2 Simulation Studies 376
8.2.3 Coordination of Smart Inverters with Distribution Voltage Control Strategies 377
8.2.3.1 System Modeling 377
8.2.3.2 Simulation Studies 378
8.2.4 Coordination of Transformer On-Load Tap Changer and PV Smart Inverters for Voltage Control of Distribution Feeders 380
8.3 Control Interactions - Lessons Learned from Coordination of FACTS Controllers for Voltage Control 381
8.3.1 Controller Interaction Among Static Var Compensators in a Test System 383
8.3.2 Controller Interaction Among Multiple Static Var Compensators in Hydro-Quebec System 384
8.4 Control Interactions Among Smart PV Inverters and their Mitigation 385
8.4.1 Concepts of Control Stability with Volt-Var Control in a Single Smart PV Inverter 387
8.4.2 Concepts of Control Stability with Volt-Var Control with Multiple Smart PV Inverters 392
8.4.3 Control Interactions Within a Smart Inverter 392
8.4.4 Smart Inverters with Volt-Var Functions 393
8.4.5 Control Interaction Between Volt-Var Controls of Smart Inverters 396
8.4.6 Oscillations Due to Voltage Control by Smart Inverter 398
8.4.7 Control Interactions of Volt-Var Controllers 400
8.4.8 Controller Interaction Between Volt-Var and Volt-Watt Controllers 402
8.5 Study of Smart Inverter Controller Interactions 404
8.6 Case Study of Controller Coordination of Smart Inverters in a Realistic Distribution System 405
8.6.1 Study System 406
8.6.2 Small Signal Modeling of Study System 407
8.6.2.1 Network 407
8.6.2.2 PV Plant 407
8.6.2.3 Overall Study System Model 410
8.6.3 Small Signal Studies 410
8.6.3.1 Impact of Delay 410
8.6.3.2 Impact of Response Time 411
8.6.4 Time Domain Simulation Studies 411
8.6.4.1 Impact of Delay 412
8.6.4.2 Impact of Response Time 412
8.6.5 Summary 413
8.7 Control Coordination of PV-STATCOM and DFIG Wind Farm for Mitigation of Subsynchronous Oscillations 413
8.7.1 Study System 414
8.7.2 Control System of DFIG 415
8.7.3 Control System of PV-STATCOM 416
8.7.4 Optimization of Subsynchronous Damping Controllers 416
8.7.5 System Response with No Subsynchronous Damping Controls 416
8.7.6 Independently Optimized SSDC of DFIG Converter 419
8.7.7 Independently Optimized SSDC of PV-STATCOM 419
8.7.8 Uncoordinated SSDCs of PV-STATCOM and DFIG Converter 420
8.7.9 Coordinated SSDCs of PV-STATCOM and DFIG Converter 420
8.8 Control Interactions Among Plants of Inverter Based Resources and FACTS/HVDC Controllers 424
8.9 Conclusions 424
References 425
9 Emerging Trends with Smart Solar PV Inverters 431
9.1 Combination of Smart PV Inverters with Battery Energy Storage Systems (BESS) 431
9.1.1 Increasing Hosting Capacity 431
9.1.2 Capacity Firming 434
9.1.3 Preventing Curtailment of Wind/Solar Plant Outputs and Managing Ramp Rates 434
9.2 Combination of Smart PV Inverters with Electric Vehicle Charging Systems 435
9.3 Combination of Smart PV Inverters with Battery Energy Storage Systems (BESS) and EV Charging Systems 437
9.4 Grid Forming Inverter Technology 440
9.4.1 Grid Following Inverters 441
9.4.2 Grid Forming Inverters 441
9.4.3 Considerations in the Application of Grid Forming Inverters 441
9.5 Field Demonstrations of Smart Solar PV Inverters 441
9.5.1 Reactive Power Control by Solar PV Plant in China 442
9.5.2 Active Power Controls by a PV Plant in Puerto Rico Island Grid, USA 442
9.5.3 Reliability Services by a 300 MW Solar PV Plant in California, USA 443
9.5.3.1 Automatic Generation Control (AGC) Test 443
9.5.3.2 Droop Test During Underfrequency Event 444
9.5.3.3 Droop Test During Overfrequency Event 445
9.5.3.4 Power Factor Control Test 446
9.5.4 Night and Day PV-STATCOM Operation by a Solar PV Plant in Ontario, Canada 448
9.5.4.1 Study System 448
9.5.4.2 PV-STATCOM Controller 449
9.5.4.3 Response of Conventional PV Inverter to a Large Disturbance During Daytime 451
9.5.4.4 Response of PV-STATCOM to a Large Disturbance During Daytime 452
9.5.4.5 Response of Conventional Inverter to a Large Disturbance During Nighttime 452
9.5.4.6 Response of PV-STATCOM to a Large Disturbance During Nighttime 454
9.5.4.7 Summary 456
9.5.5 Nighttime Reactive Power Support from a Solar PV Plant in UK 456
9.5.6 Commercial Ancillary Grid Services by Solar PV Plant in Chile 456
9.5.7 Nighttime Reactive Power Control by a Solar PV Plant in India 457
9.6 Potential of New Revenue Making Opportunities for Smart Solar PV Inverters 457
9.6.1 Providing Ancillary Services Without Curtailing PV Power Output 457
9.6.2 Providing Ancillary Services by Curtailing PV Power Output 457
9.6.2.1 Fast Frequency Response and Frequency Regulation Services 457
9.6.2.2 Flexible Solar Operation 458
9.6.3 Providing Reactive Power Support at Night 458
9.6.4 Providing STATCOM Functionalities 459
9.7 Conclusions 461
References 461
Index 465
Foreword xxv
Preface xxvii
Acknowledgments xxxi
List of Abbreviations xxxiii
1 Impacts of High Penetration of Solar PV Systems and Smart Inverter Developments 1
1.1 Concepts of Reactive and Active Power Control 1
1.1.1 Reactive Power Control 1
1.1.1.1 Voltage Control 1
1.1.1.2 Frequency Control 3
1.1.2 Active Power Control 4
1.1.2.1 Voltage Control 4
1.1.2.2 Frequency Control 5
1.1.3 Frequency Response with Synchronous Machines 5
1.1.3.1 Rate of Change of Frequency 6
1.1.3.2 Factors Impacting ROCOF 7
1.1.3.3 System Inertia 7
1.1.3.4 Critical Inertia 8
1.1.3.5 Size of Largest Contingency 8
1.1.4 Fast Frequency Response 8
1.2 Challenges of High Penetration of Solar PV Systems 10
1.2.1 Steady-state Overvoltage 10
1.2.2 Voltage Fluctuations 11
1.2.3 Reverse Power Flow 11
1.2.4 Transient Overvoltage 13
1.2.5 Voltage Unbalance 14
1.2.6 Decrease in Voltage Support Capability of Power Systems 14
1.2.7 Interaction with Conventional Voltage Regulation Equipment 15
1.2.8 Variability of Power Output 15
1.2.9 Balancing Supply and Demand 15
1.2.10 Changes in Active Power Flow in Feeders 16
1.2.11 Change in Reactive Power Flow in Feeders 17
1.2.12 Line Losses 17
1.2.13 Harmonic Injections 17
1.2.14 Low Short Circuit Levels 20
1.2.15 Protection and Control Issues 20
1.2.16 Short Circuit Current Issues 20
1.2.17 Unintentional Islanding 22
1.2.18 Frequency Regulation Issues due to Reduced Inertia 23
1.2.18.1 Under Frequency Response 23
1.2.18.2 Over Frequency Response 26
1.2.19 Angular Stability Issues due to Reduced Inertia 26
1.3 Development of Smart Inverters 28
1.3.1 Developments in Germany 29
1.3.2 Developments in the USA 29
1.3.3 Development in Canada of Night and Day Control of Solar PV Farms as STATCOM (PV-STATCOM) 29
1.4 Conclusions 30
References 30
2 Smart Inverter Functions 35
2.1 Capability Characteristics of Distributed Energy Resource (DER) 35
2.2 General Considerations in Implementation of Smart Inverter Functions 37
2.2.1 Performance Categories 38
2.2.1.1 Normal Performance 39
2.2.1.2 Abnormal Performance 39
2.2.2 Reactive Power Capability of DERs 39
2.2.2.1 Active Power (Watt) Precedence Mode 40
2.2.2.2 Reactive Power (Var) Precedence Mode 41
2.3 Smart Inverter Functions for Reactive Power and Voltage Control 41
2.3.1 Constant Power Factor Function 41
2.3.2 Constant Reactive Power Function 41
2.3.3 Voltage-Reactive Power (Volt-Var) Function 41
2.3.4 Active Power-Reactive Power (Watt-Var or P-Q) Function 42
2.3.5 Dynamic Voltage Support Function 44
2.3.5.1 Dynamic Network Support Function 44
2.3.5.2 Dynamic Reactive Current Support Function 45
2.4 Smart Inverter Function for Voltage and Active Power Control 46
2.4.1 Voltage-Active Power (Volt-Watt) Function 46
2.4.2 Coordination with Volt-Var Function 48
2.4.3 Dynamic Volt-Watt Function 48
2.5 Low/High Voltage Ride-Through (L/H VRT) Function 50
2.5.1 IEEE Standard 1547-2018 51
2.5.2 North American Electric Reliability Corporation (NERC) Standard PRC-024 53
2.6 Frequency-Watt Function 54
2.6.1 Frequency-Watt Function 1 55
2.6.2 Frequency-Watt Function 2 56
2.6.3 Frequency Droop Function 56
2.6.4 Frequency-Watt Function with Energy Storage 56
2.7 Low/High Frequency Ride-Through (L/H FRT) Function 57
2.7.1 IEEE Standard 1547-2018 58
2.7.2 North American Electric Reliability Corporation (NERC) Standard PRC-024 59
2.8 Ramp Rate 59
2.9 Fast Frequency Response 61
2.10 Smart Inverter Functions Related to DERs Based on Energy Storage Systems 61
2.10.1 Direct Charge/Discharge Function 61
2.10.2 Price-Based Charge/Discharge Function 62
2.10.3 Coordinated Charge/Discharge Management Function 62
2.10.3.1 Time-Based Charging Model 63
2.10.3.2 Duration at Maximum Charging and Discharging Rates 63
2.11 Limit Maximum Active Power Function 64
2.11.1 Without Energy Storage 64
2.11.2 With Energy Storage System 65
2.12 Set Active Power Mode 65
2.13 Active Power Smoothing Mode 65
2.14 Active Power Following Function 65
2.15 Prioritization of Different Functions 65
2.15.1 Active Power-related Functions 66
2.15.1.1 Functions Affecting Operating Boundaries 66
2.15.1.2 Dynamic Functions 66
2.15.1.3 Steady-State Functions Managing Watt Input/Output 66
2.15.2 Reactive Power-Related Functions 66
2.15.2.1 Dynamic Functions 66
2.15.2.2 Steady-State Functions 66
2.15.3 Smart Inverter Functions Under Abnormal Conditions 66
2.16 Emerging Functions 67
2.16.1 PV-STATCOM: Control of PV inverters as STATCOM during Night and Day 67
2.16.2 Reactive Power at No Active Power Output 67
2.17 Summary 68
References 68
3 Modeling and Control of Three-Phase Smart PV Inverters 73
3.1 Power Flow from a Smart Inverter System 73
3.1.1 Active Power Flow 75
3.1.1.1 Magnitude of Active Power Flow 75
3.1.1.2 Direction of Active Power Flow 75
3.1.2 Reactive Power Flow 75
3.1.2.1 Magnitude of Reactive Power Flow 75
3.1.2.2 Direction of Reactive Power Flow 76
3.1.3 Implementation of Smart Inverter Functions 76
3.2 Smart PV Inverter System 77
3.3 Power Circuit Constituents of Smart Inverter System 79
3.3.1 PV Panels 79
3.3.2 Maximum Power Point Tracking (MPPT) Scheme 82
3.3.3 Non-MPP Voltage Control 82
3.3.4 Voltage Source Converter (VSC) 83
3.3.4.1 DC-Link Capacitor 84
3.3.4.2 AC Filter 84
3.3.4.3 Isolation Transformer 86
3.4 Control Circuit Constituents of Smart Inverter System 86
3.4.1 Measurement Filters 86
3.4.2 abc-dq Transformation 87
3.4.2.1 Concept 87
3.4.2.2 Theoretical Basis 88
3.4.2.3 Power in abc and dq Reference Frame 91
3.4.3 Pulse Width Modulation (PWM) 92
3.4.4 Phase Locked Loop (PLL) 94
3.4.5 Current Controller 97
3.4.6 DC-Link Voltage Controller 99
3.5 Smart Inverter Voltage Controllers 100
3.5.1 Volt-Var Control 101
3.5.2 Closed-Loop Voltage Controller 101
3.6 PV Plant Control 102
3.7 Modeling Guidelines 104
3.8 Summary 104
References 104
4 PV-STATCOM: A New Smart PV Inverter and a New FACTS Controller 107
4.1 Flexible AC Transmission System (FACTS) 107
4.2 Static Var Compensator (SVC) 109
4.3 Synchronous Condenser 111
4.4 Static Synchronous Compensator (STATCOM) 113
4.5 Control Modes of SVC and STATCOM 118
4.5.1 Dynamic Voltage Regulation 118
4.5.1.1 Power Transfer Without Midpoint Voltage Regulation 119
4.5.1.2 Power Transfer with Midpoint Voltage Regulation 119
4.5.2 Modulation of Bus Voltage in Response to System Oscillations 121
4.5.3 Load Compensation 122
4.6 Photovoltaic-Static Synchronous Compensator (PV-STATCOM) 122
4.7 Operating Modes of PV-STATCOM 124
4.7.1 Nighttime 124
4.7.2 Daytime with Active Power Priority 124
4.7.3 Daytime with Reactive Power Priority 125
4.7.3.1 Reactive Power Modulation After Full Active Power Curtailment 125
4.7.3.2 Reactive Power Modulation After Partial Active Power Curtailment 126
4.7.3.3 Simultaneous Active and Reactive Power Modulation After Partial Active Power Curtailment 126
4.7.3.4 Simultaneous Active and Reactive Power Modulation with Pre-existing Active Power Curtailment 127
4.7.4 Methodology of Modulation of Active Power 127
4.8 Functions of PV-STATCOM 128
4.8.1 A New Smart Inverter 128
4.8.2 A New FACTS Controller 129
4.9 Cost of Transforming an Existing Solar PV System into PV-STATCOM 129
4.9.1 Constituents of a PV System 130
4.9.2 Costing of PV-STATCOM 130
4.9.2.1 Cost of 5 Mvar PV-STATCOM 131
4.9.2.2 Cost of 100 Mvar PV-STATCOM 132
4.9.3 Cost of a STATCOM 133
4.9.3.1 Equipment Cost 133
4.9.3.2 Infrastructure Costs 133
4.10 Cost of Operating a PV-STATCOM 135
4.10.1 Nighttime Operating Costs 135
4.10.2 Daytime Operating Costs 135
4.10.3 Additional Costs 135
4.10.4 Technical Considerations of PV-STATCOM and STATCOM 136
4.10.4.1 Number of Inverters 136
4.10.4.2 Ability to Provide Full Reactive Power at Nighttime 136
4.10.4.3 Transient Overvoltage and Overcurrent Rating 136
4.10.4.4 Low Voltage Ride-through 136
4.10.5 Potential of PV-STATCOM 137
4.11 Summary 138
References 139
5 PV-STATCOM Applications in Distribution Systems 145
5.1 Nighttime Application of PV Solar Farm as STATCOM to Regulate Grid Voltage 145
5.1.1 Modeling of Solar PV System 146
5.1.2 Solar Farm Inverter Control 146
5.1.3 Simulation Study 147
5.1.4 Summary 149
5.2 Increasing Wind Farm Connectivity with PV-STATCOM 149
5.2.1 Study System 150
5.2.2 Control System 150
5.2.3 Model of Wind Farm 151
5.2.4 Simulation Studies 151
5.2.4.1 Mitigation of Steady-state Voltage Rise 151
5.2.4.2 Control of Transient Overvoltage 153
5.2.4.3 PV-STATCOM Reactive Power Requirement 153
5.2.4.4 Effect of Distance of PV-STATCOM from Wind Farm 153
5.2.4.5 Increase in Wind Farm Connectivity 155
5.2.5 Summary 155
5.3 Dynamic Voltage Control by PV-STATCOM 156
5.3.1 Study System 156
5.3.2 Control System 157
5.3.2.1 DC-link Voltage Control 157
5.3.2.2 AC Voltage Control 157
5.3.2.3 Power Factor Control (PFC) 157
5.3.3 Operation Mode Selector 157
5.3.4 PSCAD Simulation Studies 159
5.3.4.1 Full STATCOM Mode - Daytime 159
5.3.4.2 Full STATCOM Mode - Nighttime 161
5.3.4.3 Low-voltage Ride-through (LVRT) 163
5.3.5 Summary 163
5.4 Enhancement of Solar Farm Connectivity by PV-STATCOM 165
5.4.1 Study System 165
5.4.2 System Modeling 166
5.4.3 Control System 166
5.4.3.1 Operation Mode Selector 168
5.4.3.2 PCC Voltage Control 169
5.4.3.3 TOV Detection Block 169
5.4.4 Simulation Studies 171
5.4.4.1 Conventional PV System (Without PV-STATCOM Control) 171
5.4.4.2 PV-STATCOM and Two Conventional Solar PV Systems 171
5.4.5 Summary 175
5.5 Reduction of Line Losses by PV-STATCOM 175
5.5.1 Concept of PV-STATCOM Voltage Control for Line Loss Reduction 175
5.5.1.1 Determination of Optimal Voltage Setpoints 178
5.5.1.2 Inverter Operating Losses 178
5.5.2 Simulation Studies 179
5.5.2.1 Case Study 1: Two Bus Radial System with Constant Load 179
5.5.2.2 Case Study II: IEEE 33 Bus System with Variable Load 181
5.5.2.3 Improvement in Loss Reduction with PV-STATCOM 181
5.5.3 Summary 184
5.6 Stabilization of a Remotely Located Critical Motor by PV-STATCOM 186
5.6.1 Study Systems 187
5.6.1.1 Study System 1 187
5.6.1.2 Study System 2 188
5.6.2 Study System with PV-STATCOM Control 189
5.6.2.1 Grid-Connected Solar PV Plant 189
5.6.2.2 Conventional PV Inverter Control 190
5.6.2.3 PV-STATCOM Controller 190
5.6.3 Simulation Studies on Study System 1 193
5.6.3.1 Performance of the Proposed PV-STATCOM Controller 194
5.6.3.2 Comparison of PV-STATCOM and STATCOM Operation 196
5.6.4 Field Validation Tests on Utility Solar PV System 196
5.6.4.1 PV Solar Plant Without PV-STATCOM Control 197
5.6.4.2 PV Solar System Operation According to German Grid Code 197
5.6.4.3 PV Solar System Operating as PV-STATCOM at Night 198
5.6.5 Simulation Studies on Study System 2 199
5.6.6 Summary 199
5.7 Conclusions 199
References 200
6 PV-STATCOM Applications in Transmission Systems 205
6.1 Increasing Power Transmission Capacity by PV-STATCOM 205
6.1.1 Study Systems 206
6.1.2 System Model 206
6.1.3 Control System 209
6.1.3.1 Conventional Reactive Power Control 209
6.1.3.2 PCC Voltage Control 209
6.1.3.3 Damping Control 209
6.1.4 Power Transfer Studies for Study System I 210
6.1.4.1 Nighttime Operation of Solar PV System as PV-STATCOM 210
6.1.4.2 Daytime Operation of Solar PV System as PV-STATCOM 211
6.1.5 Power Transfer Studies for Study System II 216
6.1.5.1 Nighttime Operation of Solar DG and Wind DG as STATCOM 216
6.1.5.2 Daytime Operation of Solar DG and Wind DG as STATCOM 216
6.1.6 Summary 219
6.2 Power Oscillation Damping by PV-STATCOM 219
6.2.1 Study System 220
6.2.2 PV-STATCOM Control System 220
6.2.2.1 DC Voltage Controller 220
6.2.2.2 Conventional PV Controller 222
6.2.2.3 Q-POD Controller 222
6.2.2.4 Oscillation Detection Unit (ODU) 222
6.2.2.5 PV Active Power Controllers 222
6.2.2.6 Design of POD Controller 224
6.2.2.7 Small Signal Studies of the POD Control 224
6.2.3 Simulations Studies 225
6.2.3.1 Power Transfer without PV-STATCOM Control 225
6.2.3.2 Power Transfer with Full STATCOM Damping Control and Power Restoration in Normal Ramped Manner 225
6.2.3.3 Power Transfer with Full STATCOM Damping Control and
Ramped Power Restoration with POD Control Active in Partial STATCOM Mode 226
6.2.3.4 Nighttime Power Transfer Enhancement with Full STATCOM POD Control 226
6.2.3.5 Effect of PV-STATCOM Control on System Frequency 228
6.2.4 Summary 228
6.3 Power Oscillation Damping with Combined Active and Reactive Power Modulation Control of PV-STATCOM 228
6.3.1 Modes of PV-STATCOM Control 229
6.3.1.1 Partial STATCOM 229
6.3.1.2 Full STATCOM 229
6.3.2 Study System 230
6.3.3 PV-STATCOM Control System 230
6.3.4 PV Reactive Power Controllers 230
6.3.4.1 Conventional Reactive Power Control 230
6.3.4.2 Q-POD Controller 230
6.3.5 PV-Active Power Controllers 232
6.3.5.1 Conventional Active Power Control 232
6.3.5.2 P-POD Controller 232
6.3.5.3 PQ-POD Controller 232
6.3.5.4 Active Power Restoration Controller 232
6.3.6 Small Signal PV-STATCOM Modeling 232
6.3.7 Selection of PV-STATCOM Controller Mode 233
6.3.8 Design of POD Controllers 234
6.3.9 Effect of PV-STATCOM Placement on Effectiveness of POD Techniques 234
6.3.9.1 Residue Analysis for PV-STATCOM with Q-POD 234
6.3.9.2 Residue Analysis for PV-STATCOM with P-POD 234
6.3.10 Simulation Studies 235
6.3.10.1 POD by PV-STATCOM 236
6.3.10.2 Effect of POD Controllers on System Frequency 239
6.3.10.3 Effect of PV Active Power Output on POD Controls 239
6.3.10.4 POD by PV-STATCOM Connected at Other Buses 239
6.3.11 Summary 240
6.4 Mitigation of Subsynchronous Resonance (SSR) in Synchronous Generator by PV-STATCOM 240
6.4.1 Study System 241
6.4.2 Control System 241
6.4.3 SSR Damping Controller 243
6.4.4 DC Voltage Controller 243
6.4.5 Simulation Studies 245
6.4.5.1 Damping of Critical Mode 1 (67% Series Compensation) 247
6.4.5.2 Ramp Up without PV-STATCOM Control 247
6.4.5.3 Damping of Critical Mode 2 (54% Series Compensation) 250
6.4.5.4 Damping of Critical Mode 3 (41% Series Compensation) 250
6.4.5.5 Damping of Critical Mode 4 (26% Series Compensation) 251
6.4.6 Potential of Utilizing Large Solar Farms for Damping SSR 251
6.4.7 Summary 253
6.5 Alleviation of Subsynchronous Oscillations (SSOs) in Induction-Generator-Based Wind Farm by PV-STATCOM 254
6.5.1 Study System 254
6.5.2 Control System 256
6.5.2.1 Current Controller 256
6.5.2.2 Damping Controller 256
6.5.2.3 DC Voltage Controller 257
6.5.3 Simulation Studies 257
6.5.3.1 Daytime Case Study: PV System Connected at Wind Farm Terminal 257
6.5.3.2 Daytime Case Study: PV System Connected at Line Midpoint 259
6.5.3.3 Nighttime Case Study: SSO Alleviation by PV-STATCOM 260
6.5.4 Potential of Utilizing Large Solar Farms for Alleviating SSO in Wind Farms 262
6.5.5 Summary 262
6.6 Mitigation of Fault-Induced Delayed Voltage Recovery (FIDVR) by PV-STATCOM 263
6.6.1 Study System 264
6.6.2 Structure of a Large Utility-Scale Solar PV Plant 265
6.6.3 Proposed PV-STATCOM Control 265
6.6.3.1 Mode Selector 267
6.6.3.2 Sensitivity Calculator 268
6.6.3.3 Current Reference Calculator 270
6.6.4 Design of PV-STATCOM Controllers 271
6.6.5 Simulation Studies 271
6.6.5.1 Response of IMs for LLL-G Fault with no PV Plant Control 271
6.6.5.2 Performance of Proposed PV-STATCOM Controller 271
6.6.5.3 Advantage of Enhanced Voltage Support up to TOV Limit 274
6.6.5.4 Comparison of Proposed PV STATCOM Controller and Other Smart Inverter Controls 274
6.6.5.5 Comparison of PV STATCOM Controller and STATCOM 275
6.6.5.6 PV-STATCOM Impact on System Frequency 276
6.6.5.7 Nighttime Performance of PV-STATCOM Controller 277
6.6.5.8 Compliance with IEEE Standard 1547-2018 277
6.6.6 Summary 278
6.7 Simultaneous Fast Frequency Control and Power Oscillation Damping by PV-STATCOM 279
6.7.1 Study System 280
6.7.2 System Modeling 281
6.7.2.1 PV Plant Model 281
6.7.2.2 Combined FFR and POD Controller 281
6.7.3 Simulation Scenarios 283
6.7.4 Over-Frequency Control 284
6.7.4.1 25 MW Load Trip in Area 1 (Pavailable = 100 MW, Kcurt = 0); (Power Imbalance less than PV Plant Capacity) 284
6.7.4.2 200 MW Load Trip in Area 1 (Pavailable = 100 MW, Kcurt = 0); (Power Imbalance more than PV Plant Capacity) 286
6.7.5 Under Frequency Control 286
6.7.5.1 25 MW Load Connection in Area 1 (Pavailable = 100 MW, Kcurt = 50%); (Power Imbalance less than PV Plant Capacity) 286
6.7.5.2 100 MWLoad Connection in Area 1 (Pavailable = 100 MW, Kcurt = 50%); (Power Imbalance more than PV Plant Capacity) 288
6.7.6 Performance Comparison of Proposed FFR + POD Control with Conventional Frequency Control 290
6.7.7 Summary 291
6.8 Conclusions 292
References 292
7 Increasing Hosting Capacity by Smart Inverters - Concepts and Applications 301
7.1 Hosting Capacity of Distribution Feeders 301
7.1.1 Voltage 302
7.1.2 Thermal Overloading 302
7.2 Hosting Capacity Based on Voltage Violations 302
7.3 Increasing Hosting Capacity with Non Smart Inverter Techniques 304
7.3.1 Active Power Curtailment (APC) 305
7.3.2 Change in Orientation of PV Panels 306
7.3.3 Correlation between Load and PV Systems 306
7.3.4 Demand Side Management (DSM) 306
7.3.5 On Load Tap Changer (OLTC) Transformers, Voltage Regulators, and Switched Capacitors 306
7.3.6 Application of Decentralized Energy Storage Systems 306
7.3.7 Energy Storage Requirements for Achieving 50% Solar PV Energy Penetration in California 307
7.3.8 Comparative Evaluation of Different Techniques for Increasing Hosting Capacity 307
7.3.8.1 Active Power Curtailment 308
7.3.8.2 Different PV System Orientations 308
7.3.8.3 Correlation with Load 309
7.3.8.4 Demand Side Management (DSM) Approach 310
7.3.8.5 On Load Tap Changer Transformer (OLTC) 311
7.3.8.6 Storage 311
7.3.8.7 Reactive Power Control (RPC) 311
7.3.9 Summary 311
7.4 Characteristics of Different Smart Inverter Functions 312
7.4.1 Constant Power Factor 312
7.4.1.1 Advantages 312
7.4.1.2 Potential Issues 313
7.4.2 Volt-Var Function 314
7.4.2.1 Advantages 314
7.4.2.2 Potential Issues 314
7.4.3 Volt-Watt Control 314
7.4.3.1 Advantages 314
7.4.3.2 Potential Issues 315
7.4.4 Active Power Limit 315
7.4.4.1 Advantages 315
7.4.4.2 Potential Issues 315
7.5 Factors Affecting Hosting Capacity of Distribution Feeders 315
7.5.1 Size and Location of DER 315
7.5.2 Physical Characteristics of Distribution System 316
7.5.3 DER Technology 316
7.5.4 PV Hosting Capacity Estimation 316
7.5.4.1 Impact of Feeder Characteristics 316
7.5.4.2 Impact of Smart Inverter Functions 319
7.6 Determination of Settings of Constant Power Factor Function 320
7.6.1 Single DER System 320
7.6.2 Multiple DERs 321
7.6.2.1 Median Feeder X/R Ratio 321
7.6.2.2 Weighted Average X/R Ratio 321
7.6.2.3 Sensitivity Analysis Based Technique 321
7.6.2.4 Performance Comparison of the Three Methods 322
7.7 Impact of DER Interconnection Transformer 322
7.8 Determination of Smart Inverter Function Settings from Quasi-Static Time-Series (QSTS) Analysis 323
7.8.1 Development of Detailed Feeder Model 325
7.8.1.1 Distribution System 325
7.8.1.2 Conventional Voltage Regulation Equipment 325
7.8.1.3 PV Systems with Smart Inverter Controls 325
7.8.1.4 Type of Smart Inverter Control 326
7.8.1.5 Performance Criteria 326
7.8.2 Simulation of Quasi-Static Time-Series Model 327
7.8.2.1 Characterization of Solar Conditions 327
7.8.2.2 Characterization of Load Conditions 328
7.8.2.3 Simulation Studies 328
7.8.3 Analysis of Results 328
7.8.4 Selection of Appropriate Setting 329
7.9 Guidelines for Selection of Smart Inverter Settings 330
7.9.1 Autonomous Default Settings 330
7.9.2 Non-optimized Settings 330
7.9.3 Optimized Settings 331
7.10 Determination of Sites for Implementing DERs with Smart Inverter Functions 331
7.11 Mitigation Methods for Increasing Hosting Capacity 333
7.12 Increasing Hosting Capacity in Thermally Constrained Distribution Networks 334
7.13 Utility Simulation Studies of Smart Inverters for Increasing Hosting Capacity 334
7.13.1 Voltage Control in a Distribution Feeder with High PV Penetration 334
7.13.2 Smart Inverter Functions for Increasing Hosting Capacity in New York Distribution Systems 335
7.13.3 Impact of Different Smart Inverter Functions in Increasing Hosting Capacity in Hawaii 337
7.13.4 Smart Inverter Impacts on California Distribution Feeders with Increasing PV Penetration 339
7.13.4.1 Methodology 340
7.13.4.2 Voltage Profile Along Feeder 340
7.13.4.3 Maximum Voltage 340
7.13.4.4 Minimum Voltage 341
7.13.4.5 Tap Operations 342
7.13.4.6 Line Losses 342
7.13.4.7 Voltage Fluctuations 342
7.13.5 Mitigation Methods to Increase Feeder Hosting Capacity 343
7.13.5.1 Assessment of Base Feeder 343
7.13.5.2 Integration Solution Assessment 344
7.13.5.3 Volt-Watt Function 344
7.13.5.4 Volt-Var Function 346
7.13.5.5 Watt-Power Factor Function 346
7.13.5.6 Fixed Power Factor Function 349
7.13.6 Impact of Smart Inverter Functions in Increasing Hosting Capacity in Five California Distribution Feeders 349
7.13.6.1 Volt-Var Control 352
7.13.6.2 Volt-Watt Control 353
7.13.6.3 Limiting Maximum Real Power (LMRP) Output Function 353
7.13.6.4 Selection of the Smart Inverter Settings 354
7.13.7 Hosting Capacity Experience in Utah 354
7.13.7.1 Constant Power Factor Function 354
7.13.7.2 Volt-Var Function 354
7.14 Field Implementation of Smart Inverters for Increasing Hosting Capacity 355
7.14.1 Voltage Control by Constant Power Factor Function in a Distribution Feeder in Fontana, USA 355
7.14.2 Smart Inverter Demonstration in Porterville Feeder in California 356
7.14.3 Improvement in Feeder Hosting Capacity Through Smart Inverter Controls in Upper Austria 358
7.14.4 Demonstration of Smart Inverter Controls under the META PV Project Funded by the European Commission 359
7.14.5 Arizona Public Service Solar Partner Program 359
7.14.6 Increasing Renewables Hosting Capacity in the Czech Republic 361
7.14.6.1 Use Case 1: Increasing DER Hosting Capacity of LV Distribution Networks 361
7.14.6.2 Use Case 2: Increasing DER Hosting Capacity in MV Networks 362
7.14.7 Hosting Capacity Experience in Salt River Project 363
7.15 Conclusions 364
References 365
8 Control Coordination of Smart PV Inverters 369
8.1 Concepts of Control Coordination 369
8.1.1 Need for Coordination 369
8.1.2 Frequency Range of Control Interactions 370
8.1.2.1 Steady-State Interactions 370
8.1.2.2 Electromechanical Oscillation Interactions 370
8.1.2.3 Control System Interactions 371
8.1.2.4 Subsynchronous Oscillation (SSO) Interactions 371
8.1.2.5 High-frequency Interactions 371
8.1.3 Principle of Coordination 372
8.2 Coordination of Smart Inverters with Conventional Voltage Controllers 372
8.2.1 European IGREENGrid Project 372
8.2.2 Interaction of Smart Inverters with Load Tap Changing Transformers 373
8.2.2.1 System Modeling 375
8.2.2.2 Simulation Studies 376
8.2.3 Coordination of Smart Inverters with Distribution Voltage Control Strategies 377
8.2.3.1 System Modeling 377
8.2.3.2 Simulation Studies 378
8.2.4 Coordination of Transformer On-Load Tap Changer and PV Smart Inverters for Voltage Control of Distribution Feeders 380
8.3 Control Interactions - Lessons Learned from Coordination of FACTS Controllers for Voltage Control 381
8.3.1 Controller Interaction Among Static Var Compensators in a Test System 383
8.3.2 Controller Interaction Among Multiple Static Var Compensators in Hydro-Quebec System 384
8.4 Control Interactions Among Smart PV Inverters and their Mitigation 385
8.4.1 Concepts of Control Stability with Volt-Var Control in a Single Smart PV Inverter 387
8.4.2 Concepts of Control Stability with Volt-Var Control with Multiple Smart PV Inverters 392
8.4.3 Control Interactions Within a Smart Inverter 392
8.4.4 Smart Inverters with Volt-Var Functions 393
8.4.5 Control Interaction Between Volt-Var Controls of Smart Inverters 396
8.4.6 Oscillations Due to Voltage Control by Smart Inverter 398
8.4.7 Control Interactions of Volt-Var Controllers 400
8.4.8 Controller Interaction Between Volt-Var and Volt-Watt Controllers 402
8.5 Study of Smart Inverter Controller Interactions 404
8.6 Case Study of Controller Coordination of Smart Inverters in a Realistic Distribution System 405
8.6.1 Study System 406
8.6.2 Small Signal Modeling of Study System 407
8.6.2.1 Network 407
8.6.2.2 PV Plant 407
8.6.2.3 Overall Study System Model 410
8.6.3 Small Signal Studies 410
8.6.3.1 Impact of Delay 410
8.6.3.2 Impact of Response Time 411
8.6.4 Time Domain Simulation Studies 411
8.6.4.1 Impact of Delay 412
8.6.4.2 Impact of Response Time 412
8.6.5 Summary 413
8.7 Control Coordination of PV-STATCOM and DFIG Wind Farm for Mitigation of Subsynchronous Oscillations 413
8.7.1 Study System 414
8.7.2 Control System of DFIG 415
8.7.3 Control System of PV-STATCOM 416
8.7.4 Optimization of Subsynchronous Damping Controllers 416
8.7.5 System Response with No Subsynchronous Damping Controls 416
8.7.6 Independently Optimized SSDC of DFIG Converter 419
8.7.7 Independently Optimized SSDC of PV-STATCOM 419
8.7.8 Uncoordinated SSDCs of PV-STATCOM and DFIG Converter 420
8.7.9 Coordinated SSDCs of PV-STATCOM and DFIG Converter 420
8.8 Control Interactions Among Plants of Inverter Based Resources and FACTS/HVDC Controllers 424
8.9 Conclusions 424
References 425
9 Emerging Trends with Smart Solar PV Inverters 431
9.1 Combination of Smart PV Inverters with Battery Energy Storage Systems (BESS) 431
9.1.1 Increasing Hosting Capacity 431
9.1.2 Capacity Firming 434
9.1.3 Preventing Curtailment of Wind/Solar Plant Outputs and Managing Ramp Rates 434
9.2 Combination of Smart PV Inverters with Electric Vehicle Charging Systems 435
9.3 Combination of Smart PV Inverters with Battery Energy Storage Systems (BESS) and EV Charging Systems 437
9.4 Grid Forming Inverter Technology 440
9.4.1 Grid Following Inverters 441
9.4.2 Grid Forming Inverters 441
9.4.3 Considerations in the Application of Grid Forming Inverters 441
9.5 Field Demonstrations of Smart Solar PV Inverters 441
9.5.1 Reactive Power Control by Solar PV Plant in China 442
9.5.2 Active Power Controls by a PV Plant in Puerto Rico Island Grid, USA 442
9.5.3 Reliability Services by a 300 MW Solar PV Plant in California, USA 443
9.5.3.1 Automatic Generation Control (AGC) Test 443
9.5.3.2 Droop Test During Underfrequency Event 444
9.5.3.3 Droop Test During Overfrequency Event 445
9.5.3.4 Power Factor Control Test 446
9.5.4 Night and Day PV-STATCOM Operation by a Solar PV Plant in Ontario, Canada 448
9.5.4.1 Study System 448
9.5.4.2 PV-STATCOM Controller 449
9.5.4.3 Response of Conventional PV Inverter to a Large Disturbance During Daytime 451
9.5.4.4 Response of PV-STATCOM to a Large Disturbance During Daytime 452
9.5.4.5 Response of Conventional Inverter to a Large Disturbance During Nighttime 452
9.5.4.6 Response of PV-STATCOM to a Large Disturbance During Nighttime 454
9.5.4.7 Summary 456
9.5.5 Nighttime Reactive Power Support from a Solar PV Plant in UK 456
9.5.6 Commercial Ancillary Grid Services by Solar PV Plant in Chile 456
9.5.7 Nighttime Reactive Power Control by a Solar PV Plant in India 457
9.6 Potential of New Revenue Making Opportunities for Smart Solar PV Inverters 457
9.6.1 Providing Ancillary Services Without Curtailing PV Power Output 457
9.6.2 Providing Ancillary Services by Curtailing PV Power Output 457
9.6.2.1 Fast Frequency Response and Frequency Regulation Services 457
9.6.2.2 Flexible Solar Operation 458
9.6.3 Providing Reactive Power Support at Night 458
9.6.4 Providing STATCOM Functionalities 459
9.7 Conclusions 461
References 461
Index 465
Rajiv K. Varma is Professor in Electrical and Computer Engineering at the University of Western Ontario in London, ON, Canada. He is an internationally renowned researcher in FACTS and grid integration of solar PV and wind power systems. He received the prestigious IEEE PES Nari Hingorani FACTS Award in 2021 "for advancing FACTS controllers application in education, research, and professional society, and for developing an innovative STATCOM technology utilizing PV solar farms." He became a Fellow of the Canadian Academy of Engineering in 2021 with the citation, "...Among his pioneering contributions has been a major ground-breaking utility-implemented award-winning technology, PV-STATCOM, that enables solar PV plants to provide FACTS functionalities at one-tenth cost of FACTS themselves..."
