Smart Hybrid AC/DC Microgrids
Description
Addresses the technical aspects and implementation challenges of smart hybrid AC/DC microgrids
Hybrid AC/DC Microgrids: Power Management, Energy Management, and Power Quality Control provides comprehensive coverage of interconnected smart hybrid microgrids, their different structures, and the technical issues associated with their control and implementation in the next generation of smart grids. This authoritative single-volume resource addresses smart hybrid microgrids power management, energy management, communications, power converter control, power quality, renewable generation integration, energy storage, and more.
The book contains both basic and advanced technical information about smart hybrid AC/DC microgrids, featuring a detailed discussion of microgrid structures, communication technologies, and various configurations of interfacing power converters and control strategies. Numerous case studies highlight effective solutions for critical issues in hybrid microgrid operation, control and power quality compensation throughout the text. Topics include control strategies of renewable energy and energy storage interfacing converters in hybrid microgrids, supervisory control strategies of interfacing power converters for microgrid power management and energy microgrid, and smart interfacing power converters for power quality control. This volume:
* Includes a thorough overview of hybrid AC/DC microgrid concepts, structures, and applications
* Discusses communication and security enhancement techniques for guarding against cyberattacks
* Provides detailed controls of smart interfacing power electronics converters from distributed generations and energy storage systems in hybrid AC/DC microgrids
* Provides details on transient and steady-state power management systems in microgrids
* Discusses energy management systems, hierarchical control, multi-agent control, and advanced distribution management control of smart microgrids
* Identifies opportunities to control power quality with smart interfacing power electronic converters
* Addresses power quality issues in the context of real-world applications in data centers, electric railway systems, and electric vehicle charging stations
Smart Hybrid AC/DC Microgrids: Power Management, Energy Management, and Power Quality Control is a valuable source of up-to-date information for senior undergraduate and graduate students as well as academic researchers and industry engineers in the areas of renewable energy, smart grids, microgrids, and power electronics.
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Persons
Yunwei Ryan Li, Ph.D., is a Professor at the University of Alberta, Canada. His research interests include distributed generation, microgrids, renewable energy, smart grids, high power converters, and electric motor drives. Dr. Li is a Fellow of IEEE and is recognized as a Highly Cited Researcher by the Web of Science Group. He serves as the Editor-in-Chief for IEEE Transactions on Power Electronics (TPEL) Letters.
Farzam Nejabatkhah, Ph.D., is a Senior Research and Development (R&D) Engineer at CYME International T&D, Eaton. His research interests include smart grids, hybrid AC/DC microgrids, power converters, and cyber-physical systems.
Hao Tian, Ph.D., is a Postdoctoral Research Fellow at the University of Alberta, Canada. His research interests include microgrids and high-power converters.
Content
Author Biographies xiii
Preface xv
Part I Smart Hybrid AC/DC Microgrids 1
1 Smart Hybrid AC/DC Microgrids 3
1.1 Introduction to Microgrids 3
1.1.1 Concept of Microgrids 3
1.1.2 Development of Microgrids 4
1.1.3 Features of Modern Microgrids 6
1.2 Smart Hybrid Microgrid Configurations 8
1.2.1 AC-coupled Hybrid Microgrid 8
1.2.2 DC-coupled Hybrid Microgrid 9
1.2.3 AC/DC-Coupled Hybrid Microgrid 10
1.2.4 Examples of Hybrid Microgrids 11
1.3 Smart Hybrid Microgrid Operations 14
1.3.1 Distributed Generation and Energy Storage Systems 14
1.3.2 Smart Interfacing Converters 16
1.3.3 Cyber Systems 16
1.3.4 Power Management and Energy Management Systems 17
1.3.5 Power Quality 17
1.4 Outline of the Book 18
References 20
2 Renewable Energy, Energy Storage, and Smart Interfacing Power Converters 21
2.1 Renewable-based Generation 21
2.1.1 Photovoltaic (PV) Power Systems 21
2.1.2 Wind Power Systems 29
2.2 Energy Storage Systems 37
2.2.1 Battery Energy Storage System 38
2.2.2 Flywheel Energy Storage System 43
2.2.3 Superconducting Magnet Energy Storage System 44
2.2.4 Hydrogen and Fuel Cell Energy Storage 45
2.3 Integration of Renewable Energy and Energy Storage 49
2.3.1 Structure of Smart Interfacing Converters (IFCs) 49
2.3.2 Operation and Coordination 52
2.4 Summary 54
References 54
3 Smart Microgrid Communications 55
3.1 Introduction 55
3.2 Communication Technique for Smart Microgrids 57
3.2.1 Basic Concepts of Communication Systems 57
3.2.2 Structures of Communication Networks in Smart Microgrids 59
3.2.3 Requirements of Communication in Smart Microgrids 61
3.2.4 Wired Communication Technologies in a Microgrid 62
3.2.5 Wireless Communication Technologies 65
3.3 Standards and Protocols in Smart Microgrids 67
3.3.1 Standards and Protocols for General Communication 67
3.3.2 Standards and Protocols for Substation Automation 70
3.3.3 Standards and Protocols for Control Center and Wide Area Monitoring 71
3.3.4 Standards and Protocols for Distributed Generation and Demand Response 72
3.3.5 Standards and Protocols for Metering 73
3.3.6 Standards and Protocols for Electric Vehicle Charging 74
3.4 Network Cyber-security 75
3.5 Summary 78
References 78
Part II Power Management Systems (PMSs) and Energy Management Systems (EMSs) 81
4 Smart Interfacing Power Electronics Converter Control 83
4.1 Primary Control of Power Electronics Converters 83
4.1.1 Basic Control Techniques in Power Converters 84
4.1.2 Current Control Method 90
4.1.3 Voltage Control Method 92
4.2 Virtual Impedance Control of Power Electronic Converters 93
4.2.1 Internal Virtual Impedance 94
4.2.2 External Virtual Impedance 96
4.2.3 Integration of both Internal and External Virtual Impedance 97
4.3 Droop Control of Power Electronics Converters 99
4.3.1 Frequency and Voltage Droop Control in an AC Subgrid 99
4.3.2 Voltage Droop Control in DC Subgrids 102
4.3.3 Unified Droop for Interlinking AC and DC Subgrids 102
4.3.4 Challenges of Droop Control and Solutions 105
4.4 Virtual Synchronous Generator (VSG) Control of Interfacing Power Electronics Converters 110
4.4.1 Principles of VSG Control 111
4.4.2 Implementation of VSG Control 112
4.4.3 Relationship Between Droop Control and VSG Control 115
4.5 Unified Control of Power Electronics Converters 116
4.6 Summary 118
References 118
5 Power Management System (PMS) in Smart Hybrid AC/DC Microgrids 121
5.1 Introduction 121
5.2 Hierarchical Control of Hybrid Microgrids 122
5.3 Power Management Systems (PMSs) in Different Structures of Hybrid Microgrids 125
5.3.1 PMS of an AC-coupled Hybrid Microgrid 125
5.3.2 PMS of a DC-coupled Hybrid Microgrid 128
5.3.3 PMS of an AC-DC-coupled Hybrid Microgrid 130
5.4 Power Management Strategies During Transitions and Different Loading Conditions 133
5.4.1 PMS During Transition Between Grid-Connected and Islanding Operation Modes 133
5.4.2 Power Management Strategies Under Different Loading Conditions 137
5.5 Implemented Examples of Power Management Systems in Hybrid Microgrids 137
5.5.1 PMS Example of an AC-coupled Hybrid Microgrid 137
5.5.2 PMS Example of a DC-coupled Hybrid Microgrid 140
5.5.3 PMS Example of an AC-DC-coupled Hybrid Microgrid 143
5.6 Black Start in Hybrid Microgrids 146
5.6.1 General Requirements of Black Start in Microgrids 147
5.6.2 Microgrid Black Start Scheme 147
5.6.3 Main Issues and Related Measures of Black Starts in Microgrids 152
5.7 Summary 153
References 153
6 Energy Management System (EMS) in Smart Hybrid Microgrids 155
6.1 Energy Management in Hierarchical Control of Microgrids 155
6.1.1 Hierarchical Control 155
6.1.2 Energy Management System 157
6.1.3 Communications in an Energy Management System 162
6.2 Multi-agent Control Strategy of Microgrids 162
6.3 Advance Distribution Management Systems (ADMSs) in Smart Hybrid Microgrids 165
6.3.1 Supervisory Control and Data Acquisition (SCADA) 165
6.3.2 Geographic Information Systems (GISs) 167
6.3.3 Distribution Management System (DMS) 167
6.3.4 Automated Meter Reading/Automatic Metering Infrastructure (amr/ami) 168
6.3.5 Outage Management Systems (OMSs) 168
6.3.6 Distributed Energy Resource Management System (DERMS) 169
6.4 Cyber-security in Smart Hybrid Microgrids 170
6.4.1 Different Types of Cyber-security Violations 170
6.4.2 Impacts of Cyber-security Violations on Smart Microgrids 172
6.4.3 Construction of Cyber-security Violations in Smart Microgrids 173
6.4.4 Defensive Strategies Against Cyber-attacks 174
6.4.5 Case Study Example: Cyber-security Violations in Power Electronics-intensive DC Microgrids 176
6.4.6 Future Trends of Microgrid Cyber-security 181
6.5 Summary 182
References 182
Part III Power Quality Issues and Control in Smart Hybrid Microgrids 185
7 Overview of Power Quality in Microgrids 187
7.1 Introduction 187
7.2 Classification of Power Quality Disturbances 188
7.2.1 Transients 188
7.2.2 Short Duration Variations 189
7.2.3 Long Duration Variations 191
7.2.4 Voltage Fluctuations 191
7.2.5 Voltage Imbalance 191
7.2.6 Power Frequency Variations 192
7.2.7 Waveform Distortion 192
7.3 Overview of Power Quality Standards 193
7.4 Mitigation Techniques of Power Quality Problems 198
7.4.1 Passive Mitigation Solutions 198
7.4.2 Active Mitigation Solutions 202
7.5 Power Quality Issues and Compensation in Microgrids 210
7.5.1 Power Quality Issues in an AC Microgrid 210
7.5.2 Power Quality in a Hybrid AC/DC Microgrid 213
7.6 Summary 216
References 216
8 Smart Microgrid Control During Grid Disturbances 219
8.1 Introduction 219
8.2 Islanding Detection 220
8.2.1 Local Islanding Detection Methods 221
8.2.2 Remote Islanding Detection Methods 225
8.2.3 Signal Processing Techniques Used in Islanding Detection 226
8.2.4 Intelligent Techniques Used in Islanding Detection 227
8.3 Fault Ride-through Capability 228
8.3.1 Fault Ride-through Requirement 229
8.3.2 Ride-through Enhancement 232
8.4 Fault Current Contribution and Protection Coordination 240
8.4.1 Impact of DG on Fuse-recloser Coordination 241
8.4.2 Impact of Reactive Power Injection on Fuse-recloser Coordination 244
8.4.3 Example of Inverter Current Control Strategy under RT 245
8.5 Summary 250
References 250
9 Unbalanced Voltage Compensation in Smart Hybrid Microgrids 253
9.1 Introduction 253
9.2 Control of Individual Three-phase IFCs for Unbalanced Voltage Compensation 254
9.2.1 Three-phase IFC Model under Unbalanced Voltage 255
9.2.2 Control of Unbalanced Voltage Adverse Effects on IFC Operation 259
9.2.3 Adjustable Unbalanced Voltage Compensation with IFC Active Power Oscillation Minimization 260
9.3 Control of Parallel Three-phase IFCs for Unbalance Voltage Compensation 262
9.3.1 Parallel Three-phase IFCs Model under Unbalanced Voltage 263
9.3.2 Parallel Three-phase IFCs Control under Unbalanced Voltage: Redundant IFC for ¿P Cancelation 267
9.3.3 Parallel Three-phase IFCs Control under Unbalanced Voltage: All Parallel IFCs Participate in ¿P Cancelation 271
9.4 Control of Single-phase IFCs for Three-phase System Unbalanced Voltage Compensation 276
9.4.1 System Model with Embedded Single-phase IFCs under Three-phase Unbalanced Voltage 276
9.4.2 Reactive Power Control of Single-phase IFCs for Three-phase AC Subgrid Unbalanced Voltage Compensation 280
9.5 Summary 288
References 289
10 Harmonic Compensation Control in Smart Hybrid Microgrids 291
10.1 Introduction 291
10.2 Control of Interfacing Power Converters for Harmonic Compensation in AC Subgrids 292
10.2.1 Harmonics Compensation with the Current Control Method (CCM) 296
10.2.2 Harmonics Compensation with the Voltage Control Method (VCM) 298
10.2.3 Harmonics Compensation with the Hybrid Control Method (HCM) 301
10.2.4 Comparison of Harmonics Compensation with the CCM, the VCM, and the HCM 305
10.3 Control of Low-switching Interfacing Power Converters for Harmonics Compensation in an AC Subgrid 308
10.3.1 Low-switching Interfacing Converters Sampling Methods 309
10.3.2 Control of Low-switching IFCs for Harmonics Compensation with Feed-forward Strategy 311
10.4 Control of Interfacing Power Converters for Harmonics Compensation in a DC Subgrid 317
10.4.1 Harmonics Compensation in a DC Subgrid Using DC/AC Interlinking Power Converters 319
10.4.2 Harmonics Compensation in a DC Subgrid Using DC/DC Interfacing Power Converters 320
10.5 Coordinated Control of Multiple Interfacing Power Converters for Harmonics Compensation 321
10.5.1 Autonomous Harmonic Control 322
10.5.2 Supervisory Harmonic Control 322
10.6 Summary 329
References 329
A Instantaneous Power Theory from Three-phase and Single-phase System Perspectives 331
A. 1 Introduction 331
A. 2 Principles of Instantaneous Power Theory 331
A. 3 Power Control Using Instantaneous Power Theory from a Three-phase System Perspective 333
A.3. 1 Reference Current Focusing on Unbalanced Condition Compensation 333
A.3. 2 Reference Current Focusing on Active and Reactive Power Oscillation Cancelation 335
A. 4 Power Control Using Instantaneous Power Theory from a Single-phase System Perspective 336
A. 5 Discussion 338
A.5. 1 Example 1: Only Positive Sequence Active Current Injection 338
A.5. 2 Example 2: Only Negative Sequence Active Current Injection 340
A. 6 Summary 340
References 341
B Peak Current of Interfacing Power Converters Under Unbalanced Voltage 343
B.1 Introduction 343
B.2 Peak Currents of Interfacing Converters 343
B.2.1 Individual Interfacing Converters 343
B.2.2 Parallel Interfacing Converters 346
B.3 Maximizing Power/Current Transfer Capability of Interfacing Converters 348
B.3.1 Individual IFCs Peak Currents in the Same Phase as the Collective Peak Current of Parallel IFCs 350
B.3.2 Individual IFCs Peak Currents In-phase with the Collective Peak Current of Parallel IFCs 357
B. 4 Summary 358
References 358
C case Study System Parameters 359
Index 367
1
Smart Hybrid AC/DC Microgrids: Structures and Technical Challenges
1.1 Introduction to Microgrids
1.1.1 Concept of Microgrids
"Microgrids" became jargon in the electrical engineering field at the beginning of the twenty-first century. After nearly two decades of development, the core of this concept keeps expanding and growing along with the development of many other fields, such as power electronics and smart grids. In general, a microgrid refers to a less complex form of an electrical grid, consisting of power generation, energy storage, and consumption as well as essential interfaces. Its functions, on the other hand, entail many more differences than conventional grids [1], e.g. (i) it can work in grid-connected or standalone operation modes; (ii) To the grid, it operates as a self-controlled entity; (iii) it normally features an advanced control strategy to optimally regulate the intermittence from renewable energies, providing high reliability and high power quality; (iv) it is typically located near the users as well as the power generators in a distributed manner, providing high flexibility and cost-effectiveness.
Another important concept closely related to microgrids is distributed generation (DG). DG mainly refers to power generation with distributed forms, differing from the traditional centralized power plant. DG technologies can use sources such as: (i) renewable energy resources such as wind, photovoltaic, micro-hydro, biomass, geothermal, ocean wave, and tides; (ii) clean alternative energy generation technologies such as fuel cells and microturbines; (iii) traditional fossil fuel and rotational machine technologies, such as diesel generators. Due to several benefits of these sources, such as cleanness and simple technologies, compounded with increasing demand for electrical energy and the exhaustible nature of fossil fuels, renewable and clean-energy-based DGs play an essential role in microgrids. Generally speaking, the microgrid is a key concept to broadly adopt DGs into the conventional electrical grid.
1.1.2 Development of Microgrids
The affix "micro" in "microgrid" indicates one iconic nature of this technique, which is its scale compared to the utility grid. However, the traditional grid used to be much smaller when the first power plant was constructed in the 1880s - the Manhattan Pearl Street Station. In terms of scale, it is indeed micro, and can essentially fall into the generalized category of microgrids. It was also operated as the very early combined heat and power (CHP) demonstration where steam was used to heat nearby buildings as well as power the generators.
During the dawn of the electrical grid, Thomas Edison's direct current (DC) grid configuration showed superior performance when supporting power at a short distance. By 1886, Edison's firm had installed 58 DC "microgrids." Things quickly changed after Nikola Tesla, with the Westinghouse company, patented an electric motor in 1888. It exploited the rotating field invented by Galileo Ferraris, showing the promising potential of the alternative current (AC) generator. Further enabled by AC transformer technologies, high voltage AC transmission with high efficiency became possible. In 1891, an experiment regarding such an AC-based transmission technique took place in Germany, where a 175 km long, 15 kV transmission line was implemented [2]. The success of this experiment soon gained commercial attention, resulting in the monopoly of AC-type utility grids until now.
During this early stage of the electrical system, power quality issues like harmonic voltages and currents also gained their engineering-perspective investigation rather than pure mathematical problems. The word "harmonic" firstly appeared in electrical research in 1894 by Houston and Kennelly's work entitled "The Harmonics of Alternating Current." The active compensation concept came later during the 1920s [3]: an AC-machine-based compensator was introduced by Boucherot and Kapp. It can adjust the reactive power produced by the machine which shares the similar methodology of modern static compensation equipment.
Alongside the rapid development of a centralized AC electrical system, electricity generation for remote areas (e.g. small islands, isolated mountain settlements, etc.) was challenging based on the traditional grid infrastructure with remote fuel-based power plants and long distance transmission. For those areas, small-scale AC off-grid systems or standalone-only microgrids provided electrical power utilizing techniques such as wind-diesel combinations in the early twentieth century, and even up until now. On the other hand, DC power systems, including DC microgrids, still exist and found their application in systems such as telecommunication systems.
During the last century, worldwide electrical grids experienced significant growth, driven by the everlasting demand for electricity generation. In 1924, the first event of the World Energy Congress was held in London. The concerns regarding limited sources of fossil fuels and dramatically increased energy demand embarked energy experts on exploring alternatives. Solar energy was described as a promising candidate in F. M. Jaeger's article published in Science in 1929 [4]. More detailed discussions of alternative energy forms covering water, wind, solar, and nuclear (at that time it was called atomic) were provided in C.C. Furnas's article published in Science in 1941 [5]. Similar discussions are scattered in historical publications but rarely conveyed into market driving forces toward sustainable energy eco-systems until the first energy crisis in the twentieth century. The 1973 Arab oil embargo, a turning point for the United States energy strategy, resulted in a chain reaction that soon spread out worldwide. One of the eventual reactions was the establishment of the International Energy Agency (IEA). Born from the oil security crisis, the IEA has evolved through the years, pursuing the enhancement of the reliability, affordability, and sustainability of energy. Another important point of progress in history was the 1992 Energy Policy Act in the United States, further strengthening the cost-competitiveness of renewable energy technologies.
In addition to utility-scale regulation, small scale distributed power generation was also taken care of by national policies, e.g. through the 1978 Public Utilities Regulatory Policy Act, the United States became the first country to establish fixed power buy-back rates (i.e. independent producers are allowed to connect to the grid and sell power). The rapid growth of electricity demand keeps pushing the electrical grids to their design limits. During the 1980s-1990s, the economic value of DG started to be recognized as a good complement to the monopoly of the traditional grid. In addition, DGs can support critical electrical needs in rural areas that are difficult to be covered by the centralized grid infrastructure.
At the end of the twentieth century, distributed-resources-based systems received dedicated research attention, which eventually spawned into the concept of modern microgrids, where power electronics serve as vital interfaces bridging renewable energy generation and the load and grid. In 1999, the United States microgrid research development and demonstration program was established under the Consortium for Electric Reliability Technology Solutions (CERTS). The 2005 Energy Policy Act was more energy legislation that was of great significance not only in the United States but also worldwide. It covers a wide scope of renewable energy forms, emphasizes research and development, and promotes the study of advanced energy technologies such as DG, integrated thermal systems, reliability of energy production, etc.
The following years witnessed intense research of microgrids. The trajectory of microgrid technology is shifting from technology demonstration pilot projects to commercial projects, which have grown into a multi-billion-dollar market. In addition to pure electrical power generation, microgrids with CHP applications brought significant opportunities by optimally regulating multiple energy forms for local customers to achieve much better overall efficiency. This is particularly true considering the much higher efficiency of transmitting electricity over a relatively long distance and the flexibility of DG locations. The concept of "district heating" presented in 1950 is a typical precedent that promoted the combination of thermal/electric stations to generate all the heat and power for a town [6]. In recent years, the philosophy of integration has been further extended to clusters of microgrids for a broader scope of energy generation, forming the virtual power plant (VPP) concept, which is not restricted to physical locations and can include assets connected to any part of the grid.
Moving forward to the third decade of the twenty-first century, a number of countries have announced pledges to achieve net-zero emissions in the future, e.g., IEA 2021 report "Net Zero by 2050" [7]. This is when microgrids as well as their...
