Microgrids

Qobad Shafiee is an Associate Professor at the University of Kurdistan, Faculty of Engineering. He earned his PhD in Electrical Engineering from Aalborg University in 2014 and is an IEEE Senior Member. Mobin Naderi received his PhD in Control of Modern Power Systems from the University of Kurdistan in 2019, where he is currently a postdoctoral scholar. Hassan Bevrani is a Professor and Head of Smart/Micro Grids Research Center at the University of Kurdistan.

• About the Authors xvPreface xviiAcknowledgments xixAcronyms xxi1 Introduction 11.1 Overview 11.2 Microgrid Concept and Capabilities 21.3 Microgrid Structure 21.4 Microgrids in the Future Smart Grids 51.5 Microgrids-Integrated Power Grids 71.6 Current Trends and Future Directions 81.6.1 Dynamic Behavior of MGs and Their Impacts on Power Grids 91.6.2 Microgrid-Based Ancillary Services 101.6.3 Dynamic Modeling and Control 101.7 The Book Content and Organization 10References 12Part I Individual Microgrids 152 Microgrid Dynamic Modeling: Concepts and Fundamentals 172.1 Introduction 172.2 Dynamics and Modeling 192.3 Fundamental Analysis Tools and Requirements 202.3.1 State-Space (Small-Signal) Modeling 212.3.1.1 Finding Differential Equations 212.3.1.2 Park and Clark Transformations 222.3.1.3 Linearization 232.3.1.4 State-Space Representation 242.3.1.5 Interconnecting Modules 252.3.2 Detailed Modeling 282.3.3 Simplification Methods 282.3.3.1 Truncation (Regular Perturbation) 292.3.3.2 Residualization (Singular Perturbation) 302.3.3.3 Aggregation 302.3.3.4 Sensitivity Analysis 322.3.4 Prony Analysis 332.3.5 Large-Signal Modeling 352.4 Small-Signal Modeling of Microgrid Components 352.4.1 DC–AC Converter (Inverter) 362.4.2 AC–DC Converter (Rectifier) 362.4.3 DC–DC Converter (Chopper) 372.4.4 LC Filter 392.4.5 Power Network 392.4.5.1 Virtual Resistor Calculation 402.4.6 Loads 412.4.6.1 Constant RL Impedance Load 422.4.6.2 Constant Power Load (CPL) 432.4.6.3 Motor Load 442.4.6.4 Active Load 442.4.7 Energy Resources and Storages 462.4.7.1 Wind Generation Unit 462.4.7.2 Photovoltaic Generation Unit 502.4.7.3 Battery 522.4.7.4 Super-Capacitor 552.5 Small-Signal Modeling of Microgrid Controllers 582.5.1 Primary Control Strategies 582.5.1.1 Grid-Forming Strategy 592.5.1.2 Grid-Following Strategy 652.5.2 Secondary Control 682.5.3 Higher Control Levels 702.6 Large-Signal Modeling: An Example 702.6.1 Governing Equations on Synchronverter 702.6.2 Nonlinear State-Space Representation 722.7 Summary 72References 733 Microgrid Dynamic Modeling: Overall Modeling and Case Studies 793.1 Introduction 793.2 Overall Microgrid Dynamic Modeling 803.2.1 Common Reference Frame 803.2.2 Microgrid General State-Space Model 813.2.3 Grid Model 813.3 Small-Signal Modeling of DC and AC Microgrids 823.3.1 A Grid-Connected PV 823.3.2 Grid-Connected AC Microgrids 843.3.3 Islanded AC Microgrids: The Detailed Model 853.3.4 Islanded AC Microgrids: A Sensitivity Analysis-Based Simplified Model 863.3.4.1 Removing/Reconfiguration Process of Modules 863.3.4.2 DLFMs Comparison of the Detailed and Simplified Models 883.3.4.3 The Oscillatory DLFM Comparison 893.3.5 Islanded AC Microgrids: Aggregated Single-Order Model 903.3.5.1 General Steps of Modeling 903.3.5.2 Virtual Swing Equation-Based Single-Order Model 913.3.6 Islanded DC Microgrid 933.4 Large-Signal Modeling of Microgrids 963.4.1 Model Validation 963.4.2 Time-Domain Simulations 983.5 Summary 99References 1004 Microgrids Stability 1034.1 Introduction 1034.2 Stability Definition and Classification 1044.3 Basic Requirements 1064.3.1 Eigenvalue Analysis 1064.3.2 Participation Matrix 1074.3.3 Sensitivity Analysis 1084.4 Small-Signal Stability Analysis 1094.4.1 Grid-Connected PV 1094.4.1.1 Sensitivity Analysis: LC Filter Parameters 1114.4.1.2 Sensitivity Analysis: Coupling/Grid Line Length 1114.4.1.3 Sensitivity Analysis: PLL Gains 1124.4.1.4 Sensitivity Analysis: Current Control Gains 1134.4.1.5 Sensitivity Analysis: DC Voltage Control gains 1134.4.2 Grid-Connected AC Microgrids 1144.4.2.1 Sensitivity Analysis: Grid Strength Study 1154.4.2.2 Sensitivity Analysis: Interaction of GFL DERs 1164.4.3 Islanded AC Microgrids 1174.4.3.1 Sensitivity Analysis of Droop Gains 1174.4.3.2 Sensitivity Analysis of Virtual Impedance 1184.4.3.3 Stability Analysis of Secondary Control 1204.4.3.4 Sensitivity Analysis of GFL DER Parameters 1224.4.3.5 Weakness of AC Microgrids 1234.4.3.6 Relative Stability Improvement Using Grid-Supporting Control Strategy 1254.4.4 Islanded DC Microgrids 1294.5 Transient Stability 1314.5.1 Power Sharing Stability in AC Microgrids 1314.5.2 Synchronverter Stabilization 1344.5.2.1 Adaptive Backstepping Stabilizing Method 1344.5.2.2 Simulation Results 1364.6 Summary 137References 1395 Microgrid Control: Concepts and Fundamentals 1435.1 Introduction 1435.2 Fundamentals and Requirements 1435.2.1 Introduction to Control Systems 1435.2.2 Control Objectives and Challenges 1445.2.3 Control Architectures 1465.3 Control Strategies for Power Converters 1495.3.1 Introduction 1495.3.2 Grid-Following Power Converters 1505.3.2.1 Current Control 1515.3.2.2 Synchronization Algorithm 1535.3.3 Grid-Forming Power Converters 1535.4 Hierarchical Control 1555.4.1 The Control Hierarchy 1555.4.2 Control Layers 1565.5 Primary Control 1575.5.1 Droop Control 1605.5.1.1 Droop Control for Inductive Grids 1625.5.1.2 Droop Control for Resistive Grids 1635.5.1.3 Droop Control for Resistive–Inductive Grids 1635.5.1.4 Discussion on the Conventional Droop Control 1645.5.1.5 Droop Control for DC Grids 1675.5.2 Virtual Impedance 1685.5.3 A Simulation Study for Primary Control of AC Microgrids 1695.5.3.1 Case Study 1695.5.3.2 Simulation Results 1695.6 Secondary Control 1735.6.1 Secondary Control Functions and Strategies 1735.6.1.1 Secondary Control Functions 1735.6.1.2 Secondary Control Strategies 1755.6.2 Centralized Secondary Control 1755.6.3 Distributed Secondary Control 1765.6.3.1 Communication Network as a Graph 1765.6.3.2 Average-Based DISC 1775.6.3.3 Consensus-Based DISC 1775.6.3.4 Event-Triggered DISC 1785.6.4 Decentralized Secondary Control 1795.6.4.1 Washout Filter-Based DESC 1805.6.4.2 Local Variable-Based DESC 1805.6.4.3 Estimation-Based DESC 1805.6.5 A Simulation Study for Secondary Control of AC Microgrids 1825.6.5.1 Case Study and Controller Implementation 1825.6.5.2 Simulation Results 1825.7 Central Control 1855.8 Global Control 1865.9 Summary 186References 1876 Advances in Microgrid Control 1976.1 Introduction 1976.2 Advanced Control Synthesis 1986.2.1 Advanced Control Techniques 1986.2.1.1 Optimal Control 1996.2.1.2 Robust Control 2006.2.1.3 Nonlinear Control 2006.2.1.4 Intelligent Control 2006.2.2 Model Predictive Control 2016.2.2.1 MPC for Microgrids 2026.2.2.2 Finite Control Set Model Predictive Control 2036.2.3 Model Predictive Control of DC Microgrids with Constant Power Loads 2046.2.3.1 Case Study and Dynamic Modeling 2056.2.3.2 Design Methodology 2086.2.3.3 Real-Time Hardware in the Loop Results 2106.2.4 Hybrid Fuzzy Predictive Control for Smooth Transition of AC Microgrids 2106.2.4.1 Case Study and Dynamic Modeling 2136.2.4.2 Control System Design 2166.2.4.3 Simulation Results 2186.3 Virtual Dynamic Control 2216.3.1 Concept and Structure 2216.3.2 Virtual Synchronous Generator (VSG) 2236.3.2.1 VSG Applications 2256.3.3 Virtual Dynamic Control of DC Microgrids 2266.3.3.1 Dynamic Improvement of DC Microgrids Using Virtual Inertia Concept 2266.3.3.2 Case Study and Simulation Results 2286.4 Resilient and Cybersecure Control 2306.4.1 Microgrid as a Cyber-Physical System 2306.4.2 Communication Requirements 2326.4.3 Cybersecurity 2336.4.3.1 Network/Data Cyber Threats on Microgrids 2346.4.3.2 Distributed Secondary Control Under Network Cyber Attacks 2356.4.3.3 Cyberattack Detection 2366.4.3.4 Cyberattack Mitigation 2406.4.4 Event-Triggered Control 2406.4.4.1 Event-Triggered Secondary Control of AC Microgrids 2426.4.4.2 Physical and Control Layers 2426.4.4.3 Secondary Control Design 2436.4.4.4 Case Study and Simulation Results 2456.5 Summary 250References 250Part II Interconnected Microgrids 2637 Interconnected Microgrids: Opportunities and Challenges 2657.1 Introduction 2657.2 An Overview 2677.3 Architectures of Interconnected Microgrids 2697.4 Benefits, Challenges, and Research Fields 2717.5 Operation of Interconnected Microgrids 2727.6 Vacancies for Future Research 2737.6.1 IMG Dynamic Modeling 2737.6.2 IMG Stability Analysis 2737.6.3 IMG Control 2747.7 Summary 274References 2758 Modeling of Interconnected Microgrids 2858.1 Introduction 2858.2 Interconnection Method 2868.3 Module Modeling 2878.3.1 Microgrid Modeling 2898.3.1.1 Modeling of Secondary Control for CB-IMGs 2918.3.1.2 Other MG Modules 2948.3.1.3 Overall MG Model 2948.3.2 Interlinking Line Modeling 2958.3.3 Back-to-Back Converter Modeling 2968.3.3.1 AC Side of the BTBC 2978.3.3.2 DC Side of the BTBC 2978.3.3.3 Dependent Current and Voltage Sources 2988.3.3.4 BTBC Power Part Interconnection 2998.3.3.5 Power Controller 2998.3.3.6 DC Voltage Controller 3008.3.3.7 Synchronizing PLLs 3008.3.3.8 Complete Interconnection of BTBC Modules 3018.3.4 Circuit Breaker Modeling 3028.4 Overall IMG Modeling 3028.4.1 Comprehensive Modeling of CB-IMGs 3028.4.2 Comprehensive Modeling of BTBC-IMGs 3058.5 Model Validation 3058.5.1 Model Validation Procedure 3058.5.2 Real-Time Simulator 3078.5.3 Validation of CB-IMG Modeling 3088.5.3.1 Case Study Information 3088.5.3.2 Prony Analysis Results 3088.5.3.3 Comparison Results 3098.5.4 Validation of BTBC-IMG Modeling 3128.6 Reduced-Order Models 3128.6.1 Simplified Model Application in CB-IMG Frequency Control 3138.6.2 Simplified Model of MGs and CB-IMGs 3148.6.3 Comparing Detailed and Single-Order Models 3168.7 Summary 317References 3179 Stability of Interconnected Microgrids 3239.1 Introduction 3239.2 IMG Stability Review 3249.3 Small-Signal Stability Analysis 3249.3.1 Eigenvalue Analysis of CB-IMGs 3259.3.2 Frequency Stability of CB-IMGs 3269.3.2.1 Intermicrogrid Oscillatory Modes 3269.3.2.2 Frequency Response 3279.3.3 Eigenvalue Analysis of BTBC-IMGs 3289.4 Sensitivity Analysis 3319.4.1 CB-IMGs 3319.4.2 BTBC-IMGs 3329.4.2.1 DC Side and Voltage Controller of Back-to-Back Converter 3329.4.2.2 PLLs of Back-to-Back Converter 3339.4.2.3 ω − P Droop Characteristic 3349.4.2.4 Cutoff Frequency (ωc) of LPFs 3349.4.2.5 Initial DC Voltage (V2dc0) 3359.4.2.6 Comparison Between Two and Three Interconnected Microgrids 3369.4.2.7 Number of Interconnected Microgrids 3369.5 Transient Stability of BTBC-IMGs: BTBC DC Voltage 3379.5.1 Energy-Based Transient Stability Analysis 3379.5.2 Minimum Stabilizing DC Voltage Criterion 3389.5.2.1 Time Interval ΔTstab 3389.5.2.2 Capacitance of the cjdc 3399.5.2.3 Injected Power to the DC Link (Pjdc0) 3399.5.2.4 MSDVC Comparison with Common Transient Stability Criteria 3399.5.3 Grid Strength Impact 3409.5.4 BTBC Power Flow Direction 3419.5.5 Time-Domain Simulations 3419.5.5.1 Frequency Instability of BTBC-IMGs 3419.5.5.2 Voltage Instability of BTBC-IMGs 3429.5.5.3 Power Flow Direction 3439.5.5.4 Pre-charging Before Power Flow 3449.5.5.5 Initial Power Transfer Limit 3449.6 Summary 345References 34610 Control of Interconnected Microgrids 34910.1 Introduction 34910.2 Overview on IMG Control 35010.2.1 CB-IMGs 35210.2.2 BTBC-IMGs 35310.2.3 DC-IMGs 35510.3 Frequency Control for CB-IMGs 35610.3.1 Tuning of Secondary Control Gains 35610.3.2 Virtual Inertia Control 35810.4 Power Sharing Control for CB-IMGs 35910.5 Power Exchange Control for BTBC-IMGs 36110.5.1 Prerequisites of Individual Microgrid Control 36110.5.2 Interlinking Back-to-Back Converter Control 36410.5.3 Simulation Results for Planned BTBC-IMG Power Exchange 36510.5.3.1 Two BTBC-IMGs 36610.5.3.2 Multiple BTBC-IMGs 36810.6 Emergency Control for BTBC-IMGs 37010.6.1 Logical Control 37210.6.2 Generalized Droop Control 37510.6.3 Coordination of BTBC Emergency Controls 37610.6.4 Real-Time Simulation Results 37710.6.4.1 Bidirectional Power Flow Support 37710.6.4.2 Averaging Interval Impact on the Controller Performance 38010.6.4.3 DER Plug-and-Play 38010.6.4.4 Three Interconnected Microgrids 38210.7 Summary 382References 38311 Synchronization in Interconnected Microgrids 38911.1 Introduction 38911.2 Synchronization Control Requirements 39011.2.1 Basic Control of CB-IMGs 39011.2.2 Synchronization Control of CB-IMGs 39111.3 Inrush Power Analysis 39311.3.1 Modeling of Inrush Power 39311.3.2 Impact of PCC Voltage Parameters on the Inrush Power 39411.3.3 Impact of X/R Ratio and Impedance Value on the Inrush Power 39511.4 Small-Signal Modeling and Stability Analysis 39611.4.1 Small-Signal Modeling of IMGs 39611.4.1.1 Modeling of Sub-Systems 39611.4.1.2 Modeling of Synchronization Control Unit 39811.4.1.3 Modeling of Overall IMGs 39811.4.2 Small-Signal Stability Analysis 39811.4.2.1 Synchronization Control Parameter 39911.4.2.2 Secondary Control Parameters 39911.5 Transient Stability Assessment 39911.5.1 Transition During Synchronization 40011.5.2 Time-Domain Simulations 40111.5.2.1 Trade-Off Between Synchronization Control Objectives 40111.5.2.2 Constraints Impact on the Synchronization Transients 40311.5.2.3 Synchronization During High-Load MGs 40411.6 Summary 404References 405Index 409