Distribution Static Compensators and their Applications in Microgrids

Microgrids are clusters of distributed energy resources, energy storage systems and loads which are capable of operating in grid-connected as well as in offgrid modes. In the off-grid mode, the energy resources supply the demand while maintaining the voltage and frequency within acceptable limits whereas in the gridconnected mode, the energy resources supply the maximum or nominal power and the network voltage and frequency is maintained by the grid. This chapter first summarizes the structure and control principles of microgrids. It then briefly introduces the structures and control perspectives of distribution static compensators (DSTATCOMs). Finally, some applications of DSTATCOMs are discussed in microgrids. The introduced applications are power quality improvement due to the presence of nonlinear and unbalanced loads, voltage regulation and balancing, and interphase power circulation in the case of the presence of single-phase energy resources with unequal distribution amongst phases. Each application is illustrated by examples, realized in PSCAD/EMTDC.

Superconducting Magnetic Energy Storage, a Promising FACTS Device for Wind Energy Conversion Systems

The applications of FACTS devices have become popular in the last few decades. There are many types of FACTS devices that are currently used in power systems to improve system stability, power quality and the overall reliability of the power systems. Since the involvement of renewable energies based power plants such as wind and PV, problems related to power system stability and quality has become even more complex, therefore the deployment of FACTS devices has become a challenging task. In this chapter, a Superconducting Magnetic Energy Storage (SMES) Unit is applied to improve the performance of Doubly Fed Induction Generator (DFIG) based wind turbine during various disturbances such as voltage sag, short circuit faults and load variation, including problems related to internal faults within the DFIG converters.

Applications of Unified Power Flow Controller in Wind Energy Conversion System

Unified power flow controller (UPFC) is one of the Flexible ac Transmission System (FACTS) devices that possess the ability of modulating both active and reactive power at the point of common coupling in four quadrant operational modes. This chapter illustrates UPFC topology, controllers with some case studies for various applications of UPFC in the DFIG-based WECS. New applications for UPFC are proposed to improve the overall performance of a DFIG-based WECS during voltage sag and voltage swell events at the grid side.

Overview of Wind Energy Conversion Systems and Flexible AC Transmission Systems

Flexible AC transmission system (FACTS) is a technology that consists of a variety of power electronic devices which was developed with the aim of controlling both power and voltage at certain locations of the electricity grids during disturbances, improving the existing transmission line capacity and providing a controllable power flow for a selected transmission direction. This chapter provides a general overview for variable FACTS devices, concepts and topologies. It also provides brief information about various wind energy conversion systems.

Preface

Due to the continuous resources’ reduction and cost increase of conventional fossil fuel along with the global trend to decrease the greenhouse effect, clean energy production from renewable sources has been given a global great concern. Among renewable energy sources, wind energy conversion systems have received a worldwide notable attention. It is expected that more than 10% of the global electricity demand will to be generated by wind energy conversion systems by the year 2020. During their early implementation stage, wind turbines were to be disconnected during abnormal and fault conditions within the electricity grid it is connected to. Owing to the fact that current wind installations supply a significant portion of the load demand, disconnecting windfarms may lead to business interruption and discontinuity of power supply to the end user. As such, transmission line operators have developed strict grid codes that wind turbine generator must meet to maintain its connection to support the grid during various fault conditions. To comply with these codes, flexible AC transmission systems have been widely used with current wind energy conversion systems to modulate reactive and/or active power at the point of common coupling of the wind turbine generator and the grid. This book presents the applications of various flexible ac transmission system devices to wind energy conversion systems. Devices such as unified power flow controllers, superconducting magnetic energy storage and static synchronous compensator are covered in this book. Topologies, control systems along with case studies of the aforementioned devices are presented and discussed. This book will be useful for postgraduate research students, upper-division electrical engineering students and practicing engineers.