Preface

      The electric grid is on the threshold of a significant change. In the past few years, the picture of the grid has changed dramatically due to the introduction of renewable energy sources, advancements in power electronics, digitalization, and other factors. All these mega-trends are pointing toward a new electrical system based on Direct Current (DC). DC power systems have inherent advantages of no harmonics, no reactive power, and high efficiency, over conventional AC power systems. Hence, DC power systems have become an emerging and promising alternative in various emerging applications, which include distributed energy sources like wind, solar, and Energy Storage Systems (ESS); distribution networks; smart buildings, remote telecom systems; and transport electrification like electric vehicles (EVs) and shipboard. All these applications are designed at different voltages to meet their specific requirements individually because of the lack of standardization. Thus, the factors influencing the DC voltages and system operation needed to be surveyed and analyzed, which include voltage standards, architecture for existing and emerging applications, topologies and control strategies of power electronic interfaces, fault diagnosis and design of the protection system, optimal economical operation, and system reliability.

This groundbreaking new volume presents these topics and trends of DC microgrids, bridging the research gap on DC microgrid architectures, control, and protection challenges to enable wide-scale implementation of energy-efficient DC microgrids. Whether for the veteran engineer or the student, this is a must-have for any library. This book also presents a detailed analysis of DC electrical architectures and power management methods with their technological aspects. Since the late twentieth century, power electronics technology has progressively gained traction. This technology is now practically allowing DC to reclaim ground from AC power. Of course, standard inertia is a huge roadblock, and it may be a long time before DC overtakes AC, but it will happen eventually. DC power distribution is expected to play a vital role in the optimal use of renewable resources as well as the enhancement of electrical system resilience. DC will cause higher-performing smart grids that are more stable and efficient throughout their life cycle while conserving energy and raw materials. In this book, at various stages of power conversion, the authors give a variety of energy models, management tactics, and control rules. They concentrate on renewable energy conversion like solar, energy storage systems, backup generators, and, of course, smart microgrids. Furthermore, the numerous experimental results and associated simulations contribute significantly to the book’s high quality.

Chapter 1 discusses DC microgrid protection challenges, fault detection methods, and design criteria for an efficient protective system. DC micro-grid protection strategies and both line-to-ground and line-to-line faults, besides their impacts, are reviewed. Also, DC fault current interrupting devices are presented. Chapter 2 provides a comprehensive overview of different existing control schemes for DC microgrids, along with the motivation and challenges behind them. It covers the basic and multi-level control schemes in detail, along with the converter control scheme for solar, wind, battery, and fuel cell-based systems. Chapter 3 describes different basic fault detection, location, and islanding detection methods for DC microgrids, along with the advantages and disadvantages of the schemes. Chapter 4 proposes an optimized energy management system for a micro-grid consisting of solar and wind generation units, an energy storage system, and a diesel generator. An optimization model for the energy management system was developed to minimize the overall operating and maintenance costs for the real power flow in the microgrid. The optimization was done using genetic algorithms and pattern search algorithms and a comparison is made based on the total operating and maintenance costs for real power flow. Chapter 5 presents the literature review of various energy management strategies involving energy storage in a microgrid, and a case study is presented by optimizing the involved objective functions using the linear programming method for a residential microgrid. The optimal operating mode is decided hourly to get the optimal cost. Chapter 6 presents the design of a hybrid renewable energy system using parameters such as available solar radiation, available hydro potential, demand assessment, etc., for DC microgrid application. The present study developed a systematic approach for solar and hydro potential assessment for DC microgrid applications. Chapter 7 details the influence of line equivalent resistances on power-sharing and on average DC bus voltage errors caused by droop techniques, reviewing the secondary control methods proposed in the literature to correct such errors. Moreover, two secondary control techniques based on distributed control, proposed by the authors, are highlighted, as well as the design of the communication system. Chapter 8 discusses the improvement of power electronic interface performance using dynamic analysis. An improved pole clustering method is proposed for dynamic analysis of quadratic boost converters with switched inductor cells only to unravel the resolvent matrix and prove the methodology’s easiness. Additionally, a view of various controllers applied to DC-DC converters is given for researchers to have as a guide for their analytical study of mathematical modelling. Chapter 9 presents a detailed study of the matrix converter. The control of a multiphase matrix converter for multiphase drive applications is discussed to make the system more reliable. A brief description of each part of the drive system fed from the matrix converter is presented. Moreover, several issues associated with the matrix converter, such as modulation, control, and mitigating effects of non-idealities, are discussed. The different applications, especially in more electric aircraft applications, wind power conversion, and applications in electrical drives, are also discussed. Chapter 10 proposes an Active Neutral-Point Clamped Multilevel Inverter that has the advantages of both flying capacitors and neutral point-clamped multilevel inverters, such as flexibility of switching redundancy and robustness to produce multilevel voltages. The operation of the proposed Active Neutral-Point clamped multilevel inverter is explained in detail. Chapter 11 presents a quasi-Z-source network-based DC-DC converter with a quadratic voltage conversion ratio that applies to photovoltaic systems and DC microgrids. In Chapter 12, a typical multiterminal VSC DC microgrid for the study is proposed, with careful consideration of topology design and grounding mode selection. Then the DC fault characteristics of a multi-terminal DC microgrid are analyzed, including DC unipolar fault and DC bipolar fault, and are