This book provides an overview of recent research activities in the control, protection and architectural design of a number of different types of DC distribution systems and microgrids. Practical requirements and implementation details of several types of DC distribution systems used in real world industrial applications are also given.
This book presents intuitive explanations of the principles of microgrids, including their structure and operation and their applications. It also discusses the latest research on microgrid control and protection technologies and the essentials of microgrids as well as enhanced communication systems. The book provides solutions to microgrid operation and planning issues using various methodologies including planning and modelling; AC and DC hybrid microgrids; energy storage systems in microgrids; and optimal microgrid operational planning. Written by specialists, it is filled in innovative solutions and research related to microgrid operation, making it a valuable resource for those interested in developing updated approaches in electric power analysis, design and operational strategies. Thanks to its in-depth explanations and clear, three-part structure, it is useful for electrical engineering students, researchers and technicians.
This book focuses on the mitigation of the destabilizing effects introduced by constant power loads (CPLs) in various non-isolated DC/DC converters and island DC microgrids using a robust non-linear sliding mode control (SMC) approach. This book validates theoretical concepts using real-time simulation studies and hardware implementations. Novel sliding mode controllers are proposed to mitigate negative impedance instabilities in DC/DC boost, buck, buck-boost, bidirectional buck-boost converters, and islanded DC microgrids. In each case, the condition for the large-signal stability of the converter feeding a CPL is established. An SMC-based nonlinear control scheme for an islanded DC microgrid feeding CPL dominated load is proposed so as to mitigate the destabilizing effect of CPL and to ensure system stability under various operating conditions. A limit on CPL power is also established to ensure system stability. For all proposed solutions, simulation studies and hardware implementations are provided to validate the effectiveness of the proposed sliding mode controllers.
In light of the growing demand for electrical power around the globe, the need to increase electrical power generation in order to diminish total carbon emissions has led to the installation of renewable resources to replace traditional generators. Most of today's microgrids are AC microgrids, whose advantages and shortcomings with respect to control techniques and stability assessment have been demonstrated through extensive studies reported in the literature. These considerations have led to the recent proposal and investigation of DC microgrids, accompanied by the introduction of the hybrid AC/DC microgrid as a means of combining the advantages and benefits of both types of microgrid. However, since a hybrid microgrid is viewed as a weak system with low inertia, controlling and assessing the performance of a hybrid microgrid constitutes a high-priority issue that requires further investigation. The lack of inertia of power electronics converters, especially in an islanded hybrid microgrid, poses a threat to stability and control. For these reasons, effective stability analysis has become a necessity with respect to the implementation of hybrid microgrids. Because of these challenges, the emulation of synchronous machine (SM) inertia and damping is now viewed as necessary for enhancing the effect of a VSC on an active distribution system and for facilitating its participation in voltage and frequency support. Improving the stability and performance of a hybrid microgrid therefore requires the introduction of a form of inertia into a hybrid microgrid. This research first proposes the incorporation of a novel form of virtual inertia into a hybrid microgrid using virtual synchronous machine (VSM) control of the intertying converter (IC) controller. The second proposal of this research is to employ the VSM control to establish autonomous control of the IC. A first research component, a novel control strategy for the Intertying converter in hybrid AC/DC microgrid has been proposed to ensure the benefit of a virtual synchronous machine (VSM) control algorithm in the hybrid AC/DC microgrid. The VSM controller application in hybrid AC/DC microgrid is capable to enable an IC converter to support the AC-side voltage and frequency as well as the DC-side voltage. The proposed control application of the VSM is chosen based on a comprehensive assessment of VSM control algorithms that are exist in the literature. Moreover, proposing an autonomous operation control of the VSM intertying converter based on dual droop characteristics which is quite different compared to using only current controller. The autonomous operation of the intertying converter based on dual droop control is modified and proposed to be capable to feed the VSM controller (swing equation) to ensure accurate power exchange management between the AC and DC sub-subsystems. The most important portion for the hybrid microgrid system is the stability study due to that fact that the behavior of the system when it is subjected to a temporary disturbance is the main concern. In hybrid microgrid, the disturbances take place continuously because of the load changing endlessly. Satisfying the hybrid microgrid operation during the disturbances conditions must be achieved in order to supply the demand. Therefore, the second part of the research introduces a generic small-signal state space model of the hybrid AC/DC microgrid system, and built to carry out the stability analysis. The development of the small-signal state-space model for the entire hybrid AC/DC microgrid was developed to investigate the overall system stability under different operating points. The final part of this thesis reveals three serious issues of operating hybrid AC/DC microgrid; some of these issues are temporary take a place based on the system operating conditions. In hybrid AC/DC microgrid, an Intertying converter (IC) becomes harmonics voltage source due to the antiparallel diodes and the shunt capacitor at its DC side. The nonlinearity behavior of ICs introduces another operation issue that is circulating current in case of parallel ICs. Reconnecting an IC after abnormal operation condition or schedule maintenance requires an extra challenging synchronization control due the variation of the AC subgrid voltages and frequency; which is the third issue. This part proposes a solution for all these issues by developing a new control strategy that combines the VSM control concept with a dual based droop control. The developed VSM controller on the IC solves these issues. The test system used in this research, which is simulated in a PSCAD/EMTDC environment, consisted of simulated voltage source converters with two AC voltage levels; while the stability analysis is conducted in MATLAB environment.
Smart Power Distribution Systems: Control, Communication, and Optimization explains how diverse technologies work to build and maintain smart grids around the globe. Yang, Yang and Li present the most recent advances in the control, communication and optimization of smart grids and provide unique insight into power system control, sensing and communication, and optimization technologies. The book covers control challenges for renewable energy and smart grids, communication in smart power systems, and optimization challenges in smart power system operations. Each area discussed focuses on the scientific innovations relating to the approaches, methods and algorithmic solutions presented. Readers will develop sound knowledge and gain insights into the integration of renewable energy generation in smart power distribution systems. Presents the latest technological advances in electric power distribution networks, with a particular focus on methodologies, approaches and algorithms Provides insights into the most recent research and developments from expert contributors from across the world Presents a clear and methodical structure that guides the reader through discussion and analysis, providing unique insights and sound knowledge along the way
The Energy Internet: An Open Energy Platform to Transform Legacy Power Systems into Open Innovation and Global Economic Engines is an innovative concept that changes the way people generate, distribute and consume electrical energy. With the potential to transform the infrastructure of the electric grid, the book challenges existing power systems, presenting innovative and pioneering theories and technologies that will challenge existing norms on generation and consumption. Researchers, academics, engineers, consultants and policymakers will gain a thorough understanding of the Energy Internet that includes a thorough dissemination of case studies from the USA, China, Japan, Germany and the U.K. The book's editors provide analysis of various enabling technologies and technical solutions, such as control theory, communication, and the social and economic aspects that are central to obtaining a clear appreciation of the potential of this complex infrastructure. Presents the first complete resource on the innovative concept of the Energy Internet Provides a clear analysis of the architecture of the Energy Internet to ensure an understanding of the technologies behind generating, distributing and consuming electricity in this way Includes a variety of global case studies of real-world implementation and pilot projects to thoroughly demonstrate the theoretical, technological and economic considerations
This handbook gathers state-of-the-art research on optimization problems in power distribution systems, covering classical problems as well as the challenges introduced by distributed power generation and smart grid resources. It also presents recent models, solution techniques and computational tools to solve planning problems for power distribution systems and explains how to apply them in distributed and variable energy generation resources. As such, the book therefore is a valuable tool to leverage the expansion and operation planning of electricity distribution networks.
The integration of renewable energy resources (RES), as a type of distributed generation (OG) units, is increasing in distribution, systems. This integration, changes the topology, performance and the operational aspects of conventional distribution systems. Protection is one of the main issues that are affected after the high penetration of OGs. Therefore, new protection methods are necessary to guarantee the safety and the reliability of active distribution systems. On the other hand, most RESs are interfaced with the AC grids through power-electronic devices. These interfaces consist of at least one AC/DC conversion units. Hence, using OC distribution systems can contribute to the loss/cost reduction, as some power conversion stages are eliminated. Enhancement in system stability, reduction of power losses, and power quality 1 improvement are other advantages of OC networks. For these reasons as well as the simple integration of electronic loads that are supplied by OC power, the concept of OC distribution systems has attracted a considerable attention over the last years. In 1 fact, MVOC and LVDC grids can be an important part of the future distribution systems. Furthermore, AC and OC system can contribute to construct hybrid AC/DC distribution systems. According to these significant changes in the distribution systems, it is necessary to modify the algorithm of existing protection methods or to propose new protection schemes for both active AC and OC distribution systems. Moreover, in conventional distribution systems, loads are supplied by upstream grid, i.e. transmission lines; therefore, when a fault impacts the upstream grid and the faulty part disconnected by the protection system, all loads connected to distribution systems are disconnected as well. However, in active distribution systems, DGs can support the on-outage zones if the grid equipped with an appropriate fault management system. Therefore, automatic self-healing methods can increase the network reliability and power supply continuity. To provide the self-healing capability, distribution grids should be equipped with adequate algorithms that are able to guarantee the continuous and optima! operation for the isolated section of the grid. In this thesis, differences between protection issues in OC and AC systems are investigated and analyzed. Then, based on this analyze, effective protection and fault management methods are presented far OC distribution systems and microgrids. In the other part of this thesis, a fault management and self-healing algorithm is proposed far active distribution systems. The proposed methods have been evaluated by the hardware-in-the-loop approach using real-time simulators and suitable controllers.
This book discusses relevant microgrid technologies in the context of integrating renewable energy and also addresses challenging issues. The authors summarize long term academic and research outcomes and contributions. In addition, this book is influenced by the authors’ practical experiences on microgrids (MGs), electric network monitoring, and control and power electronic systems. A thorough discussion of the basic principles of the MG modeling and operating issues is provided. The MG structure, types, operating modes, modelling, dynamics, and control levels are covered. Recent advances in DC microgrids, virtual synchronousgenerators, MG planning and energy management are examined. The physical constraints and engineering aspects of the MGs are covered, and developed robust and intelligent control strategies are discussed using real time simulations and experimental studies.
Urban DC Microgrid: Intelligent Control and Power Flow Optimization focuses on microgrids for urban areas, particularly associated with building-integrated photovoltaic and renewable sources. This book describes the most important problems of DC microgrid application, with grid-connected and off-grid operating modes, aiming to supply DC building distribution networks. The book considers direct current (DC) microgrid to supply DC building distribution networks for positive energy buildings; dynamic interactions with the utility grid based on communication with the smart grid; supervisory control systems; and energy management. The global power system is exposed and the DC microgrid system is presented and analyzed with results and discussion, highlighting both the advantages and limitations of the concept. Coverage at the system level of microgrid control as well as the various technical aspects of the power system components make this a book interesting to academic researchers, industrial energy researchers, electrical power and power system professionals. Provides a strong overview of microgrid modelling Describes the most important problems of DC microgrid application, with grid-connected and off-grid operating modes, aiming to supply DC building distribution networks Offers experimental problem examples and results Includes supervisory control and energy management
Microgrid demonstrations and deployments are expanding in US power systems and around the world. Although goals are specific to each site, these microgrids have demonstrated the ability to provide higher reliability and higher power quality than utility power systems and improved energy utilization  . The vast majority of these microgrids are based on AC power transfer because this has been the traditionally dominant power delivery scheme. Independently, manufacturers, power system designers and researchers are demonstrating and deploying DC power distribution systems for applications where the end-use loads are natively DC , e.g., computers , solid-state lighting , and building networks . These early DC applications may provide higher efficiency, added flexibility, reduced capital costs over their AC counterparts. Further, when onsite renewable generation, electric vehicles and storage systems are present, DC-based microgrids may offer additional benefits . Early successes from these efforts raises a question--can a combination of microgrid concepts and DC distribution systems provide added benefits beyond what has been achieved individually?
The electric power delivery system that carries electricity from large central generators to customers could be severely damaged by a small number of well-informed attackers. The system is inherently vulnerable because transmission lines may span hundreds of miles, and many key facilities are unguarded. This vulnerability is exacerbated by the fact that the power grid, most of which was originally designed to meet the needs of individual vertically integrated utilities, is being used to move power between regions to support the needs of competitive markets for power generation. Primarily because of ambiguities introduced as a result of recent restricting the of the industry and cost pressures from consumers and regulators, investment to strengthen and upgrade the grid has lagged, with the result that many parts of the bulk high-voltage system are heavily stressed. Electric systems are not designed to withstand or quickly recover from damage inflicted simultaneously on multiple components. Such an attack could be carried out by knowledgeable attackers with little risk of detection or interdiction. Further well-planned and coordinated attacks by terrorists could leave the electric power system in a large region of the country at least partially disabled for a very long time. Although there are many examples of terrorist and military attacks on power systems elsewhere in the world, at the time of this study international terrorists have shown limited interest in attacking the U.S. power grid. However, that should not be a basis for complacency. Because all parts of the economy, as well as human health and welfare, depend on electricity, the results could be devastating. Terrorism and the Electric Power Delivery System focuses on measures that could make the power delivery system less vulnerable to attacks, restore power faster after an attack, and make critical services less vulnerable while the delivery of conventional electric power has been disrupted.
Risk-Based Energy Management: DC, AC and Hybrid AC-DC Microgrids defines the problems and challenges of DC, AC and hybrid AC-DC microgrids and considers the right tactics and risk-based scheduling to tackle them. The book looks at the intermittent nature of renewable generation, demand and market price with the risk to DC, AC and hybrid AC-DC microgrids, which makes it relevant for anyone in renewable energy demand and supply. As utilization of distributed energy resources and the intermittent nature of renewable generations, demand and market price can put the operation of DC, AC and hybrid AC-DC microgrids at risk, this book presents a timely resource. Discusses both the challenges and solutions surrounding DC, AC and hybrid AC-DC microgrids Proposes robust scheduling of DC, AC and hybrid AC-DC microgrids under uncertain environments Includes modeling upstream grid prices, renewable resources and intermittent load in the decision-making process of DC, AC and hybrid AC-DC microgrids
The use of distributed resources in the electric power system at the distribution level has opened new possibilities; among others, the overwhelming use of the DC microgrid in rural areas, electric vehicles, and ships. Most challenges associated with the DC microgrid in the protection system are related to ground fault. While low impedance ground fault can be detected through a high current surge, high impedance ground fault remains difficult due to a small current fault and a small reduction of the DC link voltage. The purpose of this project is to design a DC microgrid protection system capable of detecting and isolating ground faults impedance, both for a ring and radial bus configuration. To accomplish this goal, a new method has been developed for a DC ring bus while artificial neural network has been used for a DC radial bus configuration. Throughout the length of this document, their algorithms and performance will be discussed.
This paper discusses a brief history of electricity, specifically alternating current (AC) and direct current (DC), and how the current standard of AC distribution has been reached. DC power was first produced in 1800, but the shift to AC occurred in the 1880's with the advent of the transformer. Because the decisions for distribution were made over 100 years ago, it could be time to rethink the standards of power distribution. Compared to traditional AC distribution, DC microgrids are significantly more energy efficient when implemented with distributed generation. Distributed generation, or on-site generation from photovoltaic panels, wind turbines, fuel cells, or microturbines, is more efficient when the power is transmitted by DC. DC generation, paired with the growing DC load profile, increases energy savings by utilizing DC architecture and eliminating wasteful conversions. Energy savings would result from a lower grid strain and more efficient utilization of the utility grid. DC distribution results in a more reliable electrical service due to short transmission distances, high service reliability when paired with on-site generation, and efficient storage. Occupant safety is a perceived concern with DC microgrids due to the lack of knowledge and familiarity in regards to these systems. However, with proper regulation and design standards, building occupants never encounter voltage higher than 24VDC, which is significantly safer than existing 120VAC in the United States. DC Microgrids have several disadvantages such as higher initial cost due, in part, to unfamiliarity of the system as well as a general lack of code recognition and efficiency metric recognition leading to difficult certification and code compliance. Case studies are cited in this paper to demonstrate energy reduction possibilities due to the lack of modeling ability in current energy analysis programs and demonstrated energy savings of approximately 20%. It was concluded that continued advancement in code development will come from pressure to increase energy efficiency. This pressure, paired with the standardization of a 24VDC plug and socket, will cause substantial increases in DC microgrid usage in the next 10 years.
This book brings together emerging objectives and paradigms in the control of both AC and DC microgrids; further, it facilitates the integration of renewable-energy and distribution systems through localization of generation, storage and consumption. The control objectives in a microgrid are addressed through the hierarchical control structure. After providing a comprehensive survey on the state of the art in microgrid control, the book goes on to address the most recent control schemes for both AC and DC microgrids, which are based on the distributed cooperative control of multi-agent systems. The cooperative control structure discussed distributes the co-ordination and optimization tasks across all distributed generators. This does away with the need for a central controller, and the control system will not collapse in response to the outage of a single unit. This avoids adverse effects on system flexibility and configurability, as well as the reliability concerns in connection with single points of failure that arise in traditional, centralized microgrid control schemes. Rigorous proofs develop each control methodology covered in the book, and simulation examples are provided to justify all of the proposed algorithms. Given its extensive yet self-contained content, the book offers a comprehensive source of information for graduate students, academic researchers, and practicing engineers working in the field of microgrid control and optimization.
This book focuses on the challenges of rural electrification, particularly in poorer regions. It covers low voltage DC distribution system for various applications including charging of electric vehicles (EV).
This book presents comprehensive coverage of the means to integrate renewable power, namely wind and solar power. It looks at new approaches to meet the challenges, such as increasing interconnection capacity among geographical areas, hybridisation of different distributed energy resources and building up demand response capabilities.
This book covers power electronics, in depth, by presenting the basic principles and application details, which can be used both as a textbook and reference book. Introduces a new method to present power electronics converters called Power Blocks Geometry (PBG) Applicable for courses focusing on power electronics, power electronics converters, and advanced power converters Offers a comprehensive set of simulation results to help understand the circuits presented throughout the book
This book features extensive coverage of all Distributed Energy Generation technologies, highlighting the technical, environmental and economic aspects of distributed resource integration, such as line loss reduction, protection, control, storage, power electronics, reliability improvement, and voltage profile optimization. It explains how electric power system planners, developers, operators, designers, regulators and policy makers can derive many benefits with increased penetration of distributed generation units into smart distribution networks. It further demonstrates how to best realize these benefits via skillful integration of distributed energy sources, based upon an understanding of the characteristics of loads and network configuration.