Foreword
With energy and environment issues becoming increasingly prominent, developing low-carbon economy and promoting ecological progress to achieve sustainability has been widely recognized all over the world, and use of clean, renewable resources has become an important strategy. To coordinate macrogrids and distributed generation (DG), and maximize the strengths of DG for economy, energy, and environment, scholars put forward the concept of “microgrid.” It is a single controllable electric power system comprising DG, load, energy storage (ES), and control devices. It can reduce feeder loss, and enhance local power supply reliability and energy efficiency.
With the development of smart grid, microgrid and its key enabling technologies are becoming a heated topic around the world. In an effort to further promote microgrid technologies and provide guidance for construction of microgrids, the authors write this book based on their practices and experience. In this book, the basic concept, key technologies, related standards, and practical design methods and principles of microgrid are comprehensively and systematically discussed, and a typical design case is presented and analyzed.
This book is organized into 11 chapters, as detailed below: Chapter 1 “Overview of Microgrid” describes the history, current status, and trends of microgrids; Chapter 2 “Composition and Classification of the Microgrid” describes the composition, operation and control modes, integration voltage, and classification of microgrids; Chapter 3 “Microgrid and Distributed Generation” introduces types of DG commonly used in microgrids; Chapter 4 “Control and Operation of the Microgrid” introduces control of connection to and disconnection from grids, operation control (three-state control, inverter control), and operation processes in grid-connected mode and islanded mode respectively; Chapter 5 “Protection of the Microgrid” discusses impacts of connection of microgrids on distribution network relay protection, microgrid protection strategies, and configuration scheme of protection for microgrids connected to distribution networks; Chapter 6 “Monitoring and Energy Management of the Microgrid” introduces composition of microgrid monitoring system, energy management, and optimized control methods; Chapter 7 “Communication of the Microgrid” introduces special requirements, design principles, and schemes of microgrid communication system; Chapter 8 “Earthing of a Microgrid” introduces microgrid earthing schemes; Chapter 9 “Harmonic Control of the Microgrid” introduces harmonic control technologies; Chapter 10 “Related Standards and Specifications” presents standards and specifications related to microgrid in and outside China; Chapter 11 “A Practical Case” introduces engineering design and test schemes by taking a specific project as example.
Given the short history of microgrid, many technologies are still under study. This book sums up only existing study results and practices. With studies on this subject going deeper, many new technologies will definitely emerge in the future, and we will amend this book accordingly.
This book is coauthored by Li Fusheng (researcher), Li Ruisheng (professorate senior engineer), and Zhou Fengquan (doctor), and Li Xianwei, Ma Hongwei, Yang Huihong, Tang Yunlong, Zhang Zhiwei, and Wang Huijuan from Smart Grid Research Center of XJ Group contributed significantly to data sorting and diagrams of the book. We also give our special thanks to Dr. Song Xiaowei from Zhongyuan University of Technology who provided a large number of references for us before writing, and Professor Yao Qinglin from Hefei University of Technology who carefully reviewed Chapter 5 “Protection of Microgrid,” and gave valuable comments and suggestions. We are also sincerely grateful to the authors of books we referred to while writing this book.
Owing to our limited knowledge and time, there may be some flaws or even errors in this book. Your comments and corrections are highly appreciated.
The Authors
August 2014