The rapid development of power electronics technology provides exciting opportunities to develop new power system equipment for better utilisation of existing systems. Deregulation of the supply industry worlwide, and the resulting competition, is forcing utilities to operate their facilities at ever higher efficiency, driving this trend. During the last decade, a number of control devices under the term flexible ac transmission systems (FACTS) technology have been proposed and implemented. This book provides a comprehensive guide to FACTS, covering all the major aspects in research and development of FACTS technologies. Various real-world applications are also included to demonstrate the issues and benefits of applying FACTS. Written by international experts in the field from both industry and academia, this book will be a useful reference for professional engineers involved in the operation and control of modern power systems. It will also be of value to postgraduate students and researchers.