Damping of Power Oscillations in a Series Compensated Transmission Line Using Gate Controlled Series Capacitor

Torsional vibrations and resonance problems with synchronous machines are most frequently encountered in rotor systems with long shafts and large inertias constituting weakly damped mechanical resonator which exhibits a low resonance frequency. The subsynchronous resonance (SSR) phenomenon may occur when a steam turbine-generator is connected to a long transmission line with series compensation. The main purpose of this paper is to verify the capability of the gate controlled series capacitor (GCSC) to mitigate torsional oscillations that occur when a steam turbine generator (T-G) is connected to a long transmission line with series compensation. This investigation was done based on IEEE First Benchmark Model. Turnoff pulse generator with zero crossing detectors is used for GCSC. By using turnoff pulse generator capacitive reactance of transmission line can be controlled and hence torsional oscillations can be damped out. The simulation results show how the stresses on T-G Shaft reduce with application of GCSC.