Static var compensator is one of the valuable applications for power electronics technology. For ac power transmission and distribution system, various types of static reactive power compensator have been proposed. Shunt compensation is widely used to improve power factor and voltage stability. A static synchronous compensator (STATCOM) based on voltage source converter (VSC) can be said to be the most advanced shunt-type reactive power compensator. In contrast with thyristor-based reactive power compensators