A COMPARATIVE STUDY OF DAMPING SUBSYNCHRONOUS RESONANCE USING SSSC AND STATCOM

Abstract

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 introduces 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 thesis is to damp SSR by adding static synchronous series compensator (SSSC, Series device) or Static compensator (STATCOM, Shunt device). This thesis 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 Eigenvalue analysis for SSR study. SSSC is a series FACTS device, which could be used to completely replace traditional series capacitor with even more flexibility of series compensation. By including STATCOM in series compensated transmission line which do not change the SSR characteristics of network significantly. This thesis provides comparative study of damping SSR by using FACTS Devices SSSC and STATCOM which is series and shunt device respectively. It is found that SSSC a series FACTS device is more effective in damping SSR in comparison with STATCOM which is a shunt FACTS device.