This paper presents the simulation results of the employment of both conventional firing (8.33ms) and prefiring NGH damping schemes (8.01 ms) on damping unstable torsional oscillations occurring in a standard power system. The studied system 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. Figures 1(a), (b), and (c) show the torque responses of the studied system subject to a three-phase to ground fault at the left-hand side of series capacitor bank for the system without NGH scheme, with conventional NGH scheme, and with prefiring NGH scheme, respectively. The response curve exponentially increases with time and exhibits unstable characteristics when the system has no NGH schemes. The response curve has nearly the same fixed amplitudes when the system uses the conventional firing NGH scheme. The response curve has gradually decreasing amplitudes when the system employs the prefiring NGH damping scheme. The specific conclusions of this paper are summarized as follows. (Figure Presented) Figure 7. Torque responses of the system under three-phase fault • The dynamic responses of the studied system using the conventional NGH scheme exhibit nearly fixed amplitudes of torsional torques under disturbance condition. On the other hand, with thyristor of the NGH scheme prefiring at 173ã, the torsional torques gradually decrease with time but they will take a long time to reach steady state. The analyzed results obtained by the EMTP show that the prefiring NGH scheme can provide better damping characteristics than the conventional firing NGH scheme in the studied system. • The prefiring NGH scheme has been verified under three-phase to ground fault, capacitor insertion, successful reclosures, and unsuccessful reclosures, etc. conditions. The simulation results have shown that the proposed damping NGH method can effectively stabilize unstable torsional oscillations of the studied system.
|期刊||IEEE Power Engineering Review|
|出版狀態||Published - 1997 十二月 1|
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering