A Comparative Study of Damping Subsynchronous Resonance Using SSSC and STATCOM

Application of series capacitor in long transmission line is a cost effective method to increase power transfer. But presence of series capacitor has sometimes been limited because of the concern for subsynchronous resonance phenomenon in transmission line. SSR is basically an electrical power system condition where the electrical network exchanges energy with the turbine generator at one or more of the natural frequencies of the combined system below the synchronous frequency of the system. Presence of SSR torque causes oscillation which causes shaft fatigue and possible damage or failure of shaft. Long transmission line needs series or shunt compensation for power flow control as well as for mitigating the SSR phenomenon. An idea of this paper is to damp SSR by adding static synchronous series compensator (SSSC, Series device) or Static compensator (STATCOM, Shunt device). This paper shows that damping characteristics obtained by SSSC is better than STATCOM for damping SSR phenomenon. The results are obtained by modelling a lineralized system in MATLAB and study is performed on the system adapted from the IEEE first bench mark model for Eigen value analysis.