Damping subsynchronous resonance using an improved NGH SSR damping scheme

This paper puts forward an improved NGH subsynchronous resonance (SSR) damping scheme and presents digital simulation results of the employment of the improved scheme on damping unstable torsional oscillations that occur in the IEEE First Benchmark Model, which contains a turbine-generator set connected to an infinite bus through a series compensated transmission line. The improved NGH scheme adds SSR detection and prefiring functions on the basis of the original NGH scheme invented by Narain G. Hingorani. The basic principle of the improved scheme is described as well as the fundamental concepts of the original scheme. The Electromagnetic Transient Program (EMTP) is employed to simulate the damping effects respectively contributed by the original and the improved NGH schemes. The simulation results show that the improved NGH scheme is more effective in improving both the transient torque and system stability forms of SSR problems as compared with the original scheme