Thyristor firing circuit synchronization techniques in Thyristor Controlled Series Capacitors

Thyristor Controlled Series Capacitors (TCSC)s are common circuits in static VAR control, FACTS, and some wind generator systems. The TCSC thyristors are fired with gate pulses, which are generated from the synchronization with the sinusoidal line current. However, the line current is not sinusoidal and contains large harmonics in some operating conditions. This paper discusses the possible thyristor firing techniques for TCSC. Simulation results show that the assumption of sinusoidal current is not valid for some operating modes of the TCSC. However, synchronization with the AC supply mains can replace the ordinary synchronization technique.