Characteristics and firing control of thyristor controlled series compensation installations

Thyristor controlled series compensation (TCSC) is expected to provide various benefits to power systems, including transient stability improvement, subsynchronous resonance (SSR) mitigation, power swings damping, fault current reduction, etc. Grasping the characteristics of TCSC installations and ending effective firing control strategies are essential to implement these advantages. This paper studies two important aspects of TCSC characteristics, the time constant of TCSC dynamic response and impacts of reference signals for thyristor firing angles on TCSC dynamic response. Closed-loop impedance control is proposed to speed the dynamic response of TCSC. A "two-stage" firing control method is presented to accomplish smooth switching between the capacitive region and inductive region. Both digital simulations with EMTDC/PSCAD software and physical experiments are employed in the study.