A comparative study of damping subsynchronous resonance using TCSC and IMDU

Damping SSR oscillation has been a topic of great interest and research. The advent of series FACTS controllers, e.g. Thyristor Controlled Series Capacitor (TCSC) and Static Synchronous Series Compensator (SSSC) has made it possible not only for the fast control of power flow in a transmission line, but also for the mitigation of Subsynchronous Resonance (SSR) in the presence of fixed series capacitors. An idea is presented in this paper for damping of sub synchronous resonance with TCSC and its comparison with IMDU in which no controllers is needed. The IEEE First Benchmark Model for subsynchronous resonance studies is used to conduct eigenvalue analysis. The time domain simulation study under large disturbance condition is carried out with IMDU located at the HP turbine end of T-G shaft and TCSC connected along the transmission line. This paper presents a simple design for TCSC scheme in which constant firing angle model is used. This paper shows that damping characteristics obtained by using IMDU are better than TCSC; But TCSC can be used for damping SSR as well as controlling the active power flow. The results are obtained by modelling a linearized system in MATLAB.