Comparative study of proportional and TS fuzzy controlled GCSC for SSR mitigation

The subsynchronous resonance (SSR) is a potential problem in power systems having a steam turbine-generator connected to a series compensated transmission line. Flexible ac transmission systems (FACTS) controllers are widely applied to mitigate SSR. In this paper, two control ways for SSR damping for the gate-controlled series capacitor (GCSC) are presented. The first method is constant power control based on proportional (P) controller and the other one is based on Takagi-Sugeno (TS)-type fuzzy logic controller. The First IEEE Benchmark Model for the analysis of the SSR phenomenon is adopted. The actual possibility of controlling SSR was verified by MATLAB program. Three different GCSC ratings are evaluated. It will be shown that although the GCSC with the designed constant power control based on the P controller in the all considered GCSC ratings can damp SSR, it can not prepare a good dynamic response for the system. A comparative study between proportional and TS fuzzy controller is carried out showing that the performance of TS fuzzy controlled GCSC is better than that of P controlled GCSC, and SSR as well as electromechanical power oscillation can be properly damped by this method.