Simulations of prefiring NGH damping scheme on suppressing torsional oscillations using EMTP

This paper presents the simulation results of the employment of both conventional firing and prefiring NGH damping schemes on damping unstable torsional oscillations occurring in the IEEE Second Benchmark Model, system-1 which contains a turbine-generator set connected to an infinite bus through two parallel transmission lines, one of which is series-capacitor compensated. The electromagnetic transient program (EMTP) is employed to simulate the damping effects respectively contributed by the two damping NGH schemes. The simulation results show that the NGH device is capable to damp out low level subsynchronous oscillations of the studied system much faster by prefiring at an advanced angle than by conventional firing scheme.