Investigation of dynamic instability of torsional modes in power system compensated by SSSC and fixed capacitor

Abstract

The torsional mode is one of the power system problems which may lead to dynamic instability in them. In this paper, a static synchronous series compensator (SSSC) along with a fixed capacitor is used in order to avoid torsional mode instability in a series compensated transmission system. For this purpose, a 6-step harmonic neutralized inverter is used for realization of the SSSC. Also, the IEEE first benchmark model on SSR analysis is considered as the case study. The system dynamic stability is studied through EMTDC/PSCAD simulation studies. The presence of the fixed capacitor ensures increased damping of small signal oscillations. At higher levels of fixed capacitor compensation, a damping controller is required to stabilize the torsional modes of SSR. It is shown that the combination of the SSSC and the fixed capacitor improves the damping oscillations. © 2009 Praise Worthy Prize S.r.l. - All rights reserved.