Describes a variety of reasons justifying the use of DC transmission as well as the basic concepts and techniques involved in the AC-DC and DC-AC conversion processes. Since the first edition of this book in 1983, HVDC technology has continued to develop and few power systems can now escape its influence. Fully revised, updated and expanded, this second edition builds on its predecessor's coverage of HVDC systems and describes the variety of reasons justifying the use of DC transmission as well as the basic concepts and techniques involved in the AC-DC and DC-AC conversion processes. Updates include the main technical advances of the past 15 years, such as improvements in the ratings and reliability of thyristor valves and other semiconductor devices, more controllable solid state devices, cost reduction techniques and discussion of the widening applications of DC that continue to make HVDC a competitive technology.