Analysis and Implement of Thyristor-based STATCOM

As an important member of FACTS family, STATCOM has got more and more widely application. However, conventional STATCOM is based on self-commutated devices, the price and unavailable homemade devices limit its application in China. Based on detailed analysis of commuting process of conventional STATCOM, the authors find that as STATCOM operated in the state of absorb reactive power, only turn-on signals is available, and turn-off signals have no effects. And when STATCOM generates reactive power, only turn-off signals are available. Hence, this paper proposed a new kind of STATCOM, where thyristors instead of self-commutated devices are used as switching devices. Simulation and experimental results show that such a thyristor-based VSC (voltage source converter) STATCOM can absorb inductive reactive power by adjusting its fire angle and has the same characteristics as ordinary STATCOM within its inductive operating range, so the thyristor- based STATCOM can be used for static var compensation in power systems.