Power Electronics-Enabled Autonomous Power Systems

QING-CHANG ZHONG, PhD, FELLOW of IEEE and IET, is the Max McGraw Endowed Chair Professor in Energy and Power Engineering and Management at Illinois Institute of Technology, Chicago, USA, and the Founder and CEO of Syndem LLC, Chicago, USA. He served(s) as a Distinguished Lecturer of IEEE Power and Energy Society, IEEE Control Systems Society, and IEEE Power Electronics Society, an Associate Editor of several leading journals in control and power engineering including IEEE Transactions on Automatic Control, IEEE Transactions on Industrial Electronics, IEEE Transactions on Power Electronics, and IEEE Transactions on Control Systems Technology, a Senior Research Fellow of Royal Academy of Engineering, U.K., the U.K. Representative to European Control Association, a Steering Committee Member of IEEE Smart Grid, and a Vice-Chair of IFAC Technical Committee on Power and Energy Systems. He delivered over 200 plenary/invited talks in over 20 countries.

• List of Figures xixList of Tables xxxiiiForeword xxxvPreface xxxviiAcknowledgments xxxixAbout the Author xliList of Abbreviations xliii1 Introduction 11.1 Motivation and Purpose 11.2 Outline of the Book 31.3 Evolution of Power Systems 71.3.1 Today’s Grids 81.3.2 Smart Grids 81.3.3 Next-Generation Smart Grids 81.4 Summary 10Part I Theoretical Framework 112 Synchronized and Democratized (SYNDEM) Smart Grid 132.1 The SYNDEM Concept 132.2 SYNDEM Rule of Law – Synchronization Mechanism of Synchronous Machines 152.3 SYNDEM Legal Equality – Homogenizing Heterogeneous Players as Virtual Synchronous Machines (VSM) 182.4 SYNDEM Grid Architecture 192.4.1 Architecture of Electrical Systems 192.4.2 Overall Architecture 222.4.3 Typical Scenarios 232.5 Potential Benefits 242.6 Brief Description of Technical Routes 282.6.1 The First-Generation (1G) VSM 282.6.2 The Second-Generation (2G) VSM 292.6.3 The Third-Generation (3G) VSM 292.7 Primary Frequency Response (PFR) in a SYNDEM Smart Grid 302.7.1 PFR from both Generators and Loads 312.7.2 Droop 312.7.3 Fast Action Without Delay 312.7.4 Reconfigurable Virtual Inertia 312.7.5 Continuous PFR 322.8 SYNDEM Roots 322.8.1 SYNDEM and Taoism 322.8.2 SYNDEM and Chinese History 332.9 Summary 343 Ghost Power Theory 353.1 Introduction 353.2 Ghost Operator, Ghost Signal, and Ghost System 363.2.1 The Ghost Operator 363.2.2 The Ghost Signal 373.2.3 The Ghost System 393.3 Physical Meaning of Reactive Power in Electrical Systems 413.4 Extension to Complete the Electrical-Mechanical Analogy 433.5 Generalization to Other Energy Systems 463.6 Summary and Discussions 47Part II 1G VSM: Synchronverters 494 Synchronverter Based Generation 514.1 Mathematical Model of Synchronous Generatorss 514.1.1 The Electrical Part 514.1.2 The Mechanical Part 534.1.3 Presence of a Neutral Line 544.2 Implementation of a Synchronverter 554.2.1 The Power Part 564.2.2 The Electronic Part 564.3 Operation of a Synchronverter 574.3.1 Regulation of Real Power and Frequency Droop Control 574.3.2 Regulation of Reactive Power and Voltage Droop Control 584.4 Simulation Results 594.4.1 Under Different Grid Frequencies 604.4.2 Under Different Load Conditions 624.5 Experimental Results 624.5.1 Grid-connected Set Mode 634.5.2 Grid-connected Droop Mode 634.5.3 Grid-connected Parallel Operation 634.5.4 Seamless Transfer of the Operation Mode 644.6 Summary 675 Synchronverter Based Loads 695.1 Introduction 695.2 Modeling of a Synchronous Motor 705.3 Operation of a PWM Rectifier as a VSM 715.3.1 Controlling the Power 725.3.2 Controlling the DC-bus Voltage 735.4 Simulation Results 745.4.1 Controlling the Power 745.4.2 Controlling the DC-bus Voltage 765.5 Experimental Results 775.5.1 Controlling the Power 775.5.2 Controlling the DC-bus Voltage 775.6 Summary 796 Control of Permanent Magnet Synchronous Generator (PMSG) Based Wind Turbines 816.1 Introduction 816.2 PMSG Based Wind Turbines 836.3 Control of the Rotor-Side Converter 836.4 Control of the Grid-Side Converter 856.5 Real-time Simulation Results 866.5.1 Under Normal Grid Conditions 876.5.2 Under Grid Faults 896.6 Summary 907 Synchronverter Based AC Ward Leonard Drive Systems 917.1 Introduction 917.2 Ward Leonard Drive Systems 937.3 Model of a Synchronous Generator 957.4 Control Scheme with a Speed Sensor 967.4.1 Control Structure 967.4.2 System Analysis and Parameter Selection 977.5 Control Scheme without a Speed Sensor 987.5.1 Control Structure 987.5.2 System Analysis and Parameter Selection 997.6 Experimental Results 1007.6.1 Case 1: With a Speed Sensor for Feedback 1017.6.2 Case 2: Without a Speed Sensor for Feedback 1047.7 Summary 1068 Synchronverter without a Dedicated Synchronization Unit 1078.1 Introduction 1078.2 Interaction of a Synchronous Generator (SG) with an Infinite Bus 1098.3 Controller for a Self-synchronized Synchronverter 1108.3.1 Operation after Connection to the Grid 1128.3.2 Synchronization before Connection to the Grid 1138.4 Simulation Results 1148.4.1 Normal Operation 1148.4.2 Operation under Grid Faults 1188.5 Experimental Results 1198.5.1 Case 1: With the Grid Frequency Below 50 Hz 1198.5.2 Case 2: With the Grid Frequency Above 50 Hz 1238.6 Benefits of Removing the Synchronization Unit 1238.7 Summary 1249 Synchronverter Based Loads without a Dedicated Synchronisation Unit 1259.1 Controlling the DC-bus Voltage 1259.1.1 Self-synchronization 1259.1.2 Normal Operation 1269.2 Controlling the Power 1279.3 Simulation Results 1279.3.1 Controlling the DC-bus Voltage 1289.3.2 Controlling the Power 1309.4 Experimental Results 1319.4.1 Controlling the DC-bus Voltage 1329.4.2 Controlling the Power 1329.5 Summary 13410 Control of a DFIG Based Wind Turbine as a VSG (DFIG-VSG) 13510.1 Introduction 13510.2 DFIG Based Wind Turbines 13710.3 Differential Gears and Ancient Chinese South-pointing Chariots 13810.4 Analogy between a DFIG and Differential Gears 13910.5 Control of a Grid-side Converter 14010.5.1 DC-bus Voltage Control 14110.5.2 Unity Power Factor Control 14110.5.3 Self-synchronization 14210.6 Control of the Rotor-Side Converter 14210.6.1 Frequency Control 14310.6.2 Voltage Control 14310.6.3 Self-synchronization 14410.7 Regulation of System Frequency and Voltage 14510.8 Simulation Results 14610.9 Experimental Results 15010.10 Summary 15311 Synchronverter Based Transformerless Photovoltaic Systems 15511.1 Introduction 15511.2 Leakage Currents and Grounding of Grid-tied Converters 15611.2.1 Ground, Grounding, and Grounded Systems 15611.2.2 Leakage Currents in a Grid-tied Converter 15811.2.3 Benefits of Providing a Common AC and DC Ground 15911.3 Operation of a Conventional Half-bridge Inverter 16011.3.1 Reduction of Leakage Currents 16111.3.2 Output Voltage Range 16111.4 A Transformerless PV Inverter 16111.4.1 Topology 16111.4.2 Control of the Neutral Leg 16111.4.3 Control of the Inversion Leg as a VSM 16411.5 Real-time Simulation Results 16511.6 Summary 16712 Synchronverter Based STATCOM without an Dedicated Synchronization Unit 16912.1 Introduction 16912.2 Conventional Control of STATCOM 17012.2.1 Operational Principles 17112.2.2 Typical Control Strategy 17212.3 Synchronverter Based Control 17312.3.1 Regulation of the DC-bus Voltage and Synchronization with the Grid 17312.3.2 Operation in the Q-mode to Regulate the Reactive Power 17512.3.3 Operation in the V-mode to Regulate the PCC Voltage 17612.3.4 Operation in the VD-mode to Droop the Voltage 17612.4 Simulation Results 17712.4.1 System Description 17712.4.2 Connection to the Grid 17912.4.3 Normal Operation in Different Modes 18012.4.4 Operation under Extreme Conditions 18112.5 Summary 18513 Synchronverters with Bounded Frequency and Voltage 18713.1 Introduction 18713.2 Model of the Original Synchronverter 18813.3 Achieving Bounded Frequency and Voltage 18913.3.1 Control Design 19013.3.2 Existence of a Unique Equilibrium 19313.3.3 Convergence to the Equilibrium 19713.4 Real-time Simulation Results 19913.5 Summary 20214 Virtual Inertia, Virtual Damping, and Fault Ride-through 20314.1 Introduction 20314.2 Inertia, the Inertia Time Constant, and the Inertia Constant 20414.3 Limitation of the Inertia of a Synchronverter 20614.4 Reconfiguration of the Inertia Time Constant 21014.4.1 Design and Outcome 21014.4.2 What is the Catch? 21114.5 Reconfiguration of the Virtual Damping 21214.5.1 Through Impedance Scaling with an Inner-loop Voltage Controller 21314.5.2 Through Impedance Insertion with an Inner-loop Current Controller 21414.6 Fault Ride-through 21414.6.1 Analysis 21414.6.2 Recommended Design 21514.7 Simulation Results 21514.7.1 A Single VSM 21614.7.2 Two VSMs in Parallel Operation 21714.8 Experimental Results 22114.8.1 A Single VSM 22114.8.2 Two VSMs in Parallel Operation 22214.9 Summary 225Part III 2G VSM: Robust Droop Controller 22715 Synchronization Mechanism of Droop Control 22915.1 Brief Review of Phase-Locked Loops (PLLs) 22915.1.1 Basic PLL 22915.1.2 Enhanced PLL (EPLL) 23015.2 Brief Review of Droop Control 23215.3 Structural Resemblance between Droop Control and PLL 23415.3.1 When the Impedance is Inductive 23415.3.2 When the Impedance is Resistive 23615.4 Operation of a Droop Controller as a Synchronization Unit 23815.5 Experimental Results 23915.5.1 Synchronization with the Grid 23915.5.2 Connection to the Grid 24015.5.3 Operation in the Droop Mode 24115.5.4 Robustness of Synchronization 24115.5.5 Change in the Operation Mode 24215.6 Summary 24316 Robust Droop Control 24516.1 Control of Inverter Output Impedance 24516.1.1 Inverters with Inductive Output Impedances (L-inverters) 24516.1.2 Inverters with Resistive Output Impedances (R-inverters) 24616.1.3 Inverters with Capacitive Output Impedances (C-inverters) 24716.2 Inherent Limitations of Conventional Droop Control 24816.2.1 Basic Principle 24816.2.2 Experimental Phenomena 25016.2.3 Real Power Sharing 25116.2.4 Reactive Power Sharing 25216.3 Robust Droop Control of R-inverters 25216.3.1 Control Strategy 25216.3.2 Error due to Inaccurate Voltage Measurements 25316.3.3 Voltage Regulation 25416.3.4 Error due to the Global Settings for E∗ and 𝜔∗ 25416.3.5 Experimental Results 25516.4 Robust Droop Control of C-inverters 26116.4.1 Control Strategy 26116.4.2 Experimental Results 26216.5 Robust Droop Control of L-inverters 26216.5.1 Control Strategy 26216.5.2 Experimental Results 26516.6 Summary 26817 Universal Droop Control 26917.1 Introduction 26917.2 Further Insights into Droop Control 27017.2.1 Parallel Operation of Inverters with the Same Type of Impedance 27117.2.2 Parallel Operation of L-, R-, and RL-inverters 27217.2.3 Parallel Operation of RC-, R-, and C-inverters 27317.3 Universal Droop Controller 27517.3.1 Basic Principle 27517.3.2 Implementation 27617.4 Real-time Simulation Results 27717.5 Experimental Results 27717.5.1 Case I: Parallel Operation of L- and C-inverters 27717.5.2 Case II: Parallel Operation of L-, C-, and R-inverters 27917.6 Summary 28118 Self-synchronized Universal Droop Controller 28318.1 Description of the Controller 28318.2 Operation of the Controller 28518.2.1 Self-synchronization Mode 28518.2.2 Set Mode (P-mode and Q-mode) 28618.2.3 Droop Mode (PD-mode and QD-mode) 28618.3 Experimental Results 28718.3.1 R-inverter with Self-synchronized Universal Droop Control 28818.3.2 L-inverter with Self-synchronized Universal Droop Control 29018.3.3 L-inverter with Self-synchronized Robust Droop Control 29418.4 Real-time Simulation Results from a Microgrid 29718.5 Summary 30019 Droop-Controlled Loads for Continuous Demand Response 30119.1 Introduction 30119.2 Control Framework with a Three-port Converter 30219.2.1 Generation of the Real Power Reference 30219.2.2 Regulation of the Power Drawn from the Grid 30419.2.3 Analysis of the Operation Modes 30519.2.4 Determination of the Capacitance for Grid Support 30619.3 An Illustrative Implementation with the 𝜃-converter 30819.3.1 Brief Description about the 𝜃-converter 30919.3.2 Control of the Neutral Leg 31019.3.3 Control of the Conversion Leg 31119.4 Experimental Results 31119.4.1 Design of the Experimental System 31119.4.2 Steady-state Performance 31219.4.3 Transient Performance 31519.4.4 Capacity Potential 31719.4.5 Comparative Study 31819.5 Summary 31920 Current-limiting Universal Droop Controller 32120.1 Introduction 32120.2 System Modeling 32220.3 Control Design 32320.3.1 Structure 32320.3.2 Implementation 32320.4 System Analysis 32620.4.1 Current-limiting Property 32620.4.2 Closed-loop Stability 32720.4.3 Selection of Control Parameters 32820.5 Practical Implementation 32920.6 Operation under Grid Variations and Faults 33020.7 Experimental Results 33120.7.1 Operation under Normal Conditions 33220.7.2 Operation under Grid Faults 33420.8 Summary 338Part IV 3G VSM: Cybersync Machines 33921 Cybersync Machines 34121.1 Introduction 34121.2 Passivity and Port-Hamiltonian Systems 34321.2.1 Passive Systems 34321.2.2 Port-Hamiltonian Systems 34321.2.3 Passivity of Interconnected Passive Systems 34521.3 System Modeling 34621.4 Control Framework 34821.4.1 The Engendering Block Σe 34921.4.2 Generation of the Desired Frequency 𝜔d and Flux 𝜑d 35021.4.3 Design of Σ𝜔 and Σ𝜑 to Obtain a Passive ΣC 35121.5 Passivity of the Controller 35221.5.1 Losslessness of the Interconnection Block ΣI 35221.5.2 Passivity of the Cascade of ΣC and ΣI 35421.6 Passivity of the Closed-loop System 35521.7 Sample Implementations for Blocks Σ𝜔 and Σ𝜑 35521.7.1 Using the Standard Integral Controller (IC) 35521.7.2 Using a Static Controller 35621.8 Self-Synchronization and Power Regulation 35721.9 Simulation Results 35821.9.1 Self-synchronization 36021.9.2 Operation after Connection to the Grid 36021.10 Experimental Results 36221.10.1 Self-synchronization 36221.10.2 Operation after Connection to the Grid 36321.11 Summary 364Part V Case Studies 36522 A Single-node System 36722.1 SYNDEM Smart Grid Research and Educational Kit 36722.1.1 Overview 36722.1.2 Hardware Structure 36822.1.3 Sample Conversion Topologies Attainable 36922.2 Details of the Single-Node SYNDEM System 37522.2.1 Description of the System 37522.2.2 Experimental Results 37722.3 Summary 37823 A 100% Power Electronics Based SYNDEM Smart Grid Testbed 37923.1 Description of the Testbed 37923.1.1 Overall Structure 37923.1.2 VSM Topologies Adopted 37923.1.3 Individual Nodes 38223.2 Experimental Results 38423.2.1 Operation of Energy Bridges 38423.2.2 Operation of Solar Power Nodes 38423.2.3 Operation of Wind Power Nodes 38623.2.4 Operation of the DC-Load Node 38823.2.5 Operation of the AC-Load Node 38923.2.6 Operation of the Whole Testbed 39123.3 Summary 39324 A Home Grid 39524.1 Description of the Home Grid 39524.2 Results from Field Operations 39624.2.1 Black start and Grid forming 39624.2.2 From Islanded to Grid-tied Operation 39924.2.3 Seamless Mode Change when the Public Grid is Lost and Recovered 40024.2.4 Voltage/Frequency Regulation and Power Sharing 40024.3 Unexpected Problems Emerged During the Field Trial 40224.4 Summary 40425 Texas Panhandle Wind Power System 40525.1 Geographical Description 40525.2 System Structure 40625.3 Main Challenges 40725.4 Overview of Control Strategies Compared 40725.4.1 VSM Control 40825.4.2 DQ Control 41025.5 Simulation Results 41125.5.1 VSM Control 41225.5.2 DQ Control 41525.6 Summary and Conclusions 416Bibliography 417Index 441