At present, the power system plays a vital role in China's national economy, therefore, power indicator problem of the system attracting much attention, reactive power and voltage as one of the light elements give enough weight, the stability of the system is not to be neglected, static synchronous compensator (STATCOM) is a member that has high precision control, fast response time, dynamic reactive compensation ability in flexible exchange transmission system devices. At the same time, it has become a hot topic in the study of reactive power compensation devices and a growing number of widely applied to power system.

Flexible AC transmission technology (FACTS) is a new technology developed in recent years. It use power electronic technology and modern control technology to achieve fast control for AC transmission system parameter and structure [, to achieve the rational allocation of transmission power, reduce the power loss and the cost of power generation, greatly improve the stability and reliability of the system. STATCOM is based on the principle of reactive power compensation, using full-controlled switching devices to compose self-commutated inventer, complemented by small-capacity storage elements constitute reactive power compensation device. Its role in the power system is the compensation of reactive power, maintain the voltage of the connection point, improve system voltage stability, and improve the steady performance and dynamic performance of the system.