Dynamic Response of TCSC and Reactance Control Method Study

Reactance control is essential to the application of thyristor controlled series capacitor (TCSC). It has been recognized that the reactance response of TCSC to change in firing angle may exhibit strong non-linearity. Such non-linearity makes it difficult to design system control with conventional open loop reactance control of TCSC. This paper first puts an insight into the dynamic response of TCSC through time domain digital simulation of an example TCSC circuit. It is shown that if the firing angle is adjusted dynamically during the transient process the dynamic response might be improved. Consequently an improved closed loop reactance control method is proposed. The steady state effective reactance characteristics are used to correct the firing angle. Simulation results show that, compared with the open loop reactance control, the proposed method improves the dynamic response of TCSC greatly by making the response time much shorter and less dependent upon the operation condition.