Application ofgate‐controlledseries capacitor to mitigate subsynchronous resonance in a thermal generation plant connected to aseries‐compensatedtransmission network

This paper demonstrates the functionality and control of the gate-controlled series capacitor (GCSC), a new FACTS device composing a pair of antiparallel GTOs in parallel with a fixed capacitor, to mitigate subsynchronous resonance (SSR) in a thermal generation plant connected to a series compensated transmission line. Firstly, by the use of both small-signal stability analysis and time-domain simulation, it is revealed that the studied system compensated by the series fixed capacitor is potentially unstable due to the first torsional mode. Then, in order to take benefits of series compensation without the risk of SSR, the fixed capacitor is replaced by GCSC. The capability and effectiveness of the GCSC to damp SSR are validated using modal analysis and time-domain simulation. Furthermore, GCSC is used in conjunction with a fixed series capacitor to minimize the overall cost of compensation. For this purpose, unlike previous studies, a linear controller is used to stabilize the system. In this study, the IEEE First Benchmark Model is considered as a case study, and MATLAB/Simulink is used as a tool for modeling and design of the control system. Also, time-domain simulations are done using PSCAD/EMTDC.