Research on Impedance Characteristics of Thyristor Controlled Series Capacitor

The desired impedance of Thyristor Controlled Series Capacitor (TCSC) is usually obtained by adjusting the firing angle and it is of great importance to make clear the relationship between the two quantities. The relationship between firing angle and conduction angle is proposed in this paper considering the influence of the thyristor conduction characteristics and the equivalent resistance in the reactor branch. In the derivation of the fundamental-frequency impedance, it is found out that there are dual solutions corresponding to the same firing angle in most steady operation area of TCSC. One is inductive and the other is capacitive. This phenomenon is demonstrated by both digital simulation and dynamic emulation experiment. Some conclusions and experiment results can provide reference to engineering exploitation and bottom control design of TCSC.