Damping of subsynchronous oscillations using STATCOM-a FACTS device

Analysis and damping of torsional oscillations in series compensated power transmission systems is presented in this paper. The presence of series capacitors has given rise to the phenomena of subsynchronous resonance (SSR). Many countermeasures to the SSR problem have been reported in the literature, which makes use of signals available at the generator station. The use of flexible AC transmission system (FACTS) devices like the static compensator (STATCOM) is increasing in networks for enhancing power transfer, voltage stability and damping of power oscillations. In this paper, the damping of subsynchronous oscillations using a STATCOM, which is provided at the middle of the transmission line, is presented. A new auxiliary control signal designated as computed internal voltage (CIV) is proposed to control the STATCOM, which involves the computation of the internal voltage of the remotely located generator utilising locally measurable STATCOM bus voltage and transmission line current signals. The IEEE second benchmark model system-1 is considered for the analysis. It is demonstrated that the system is effectively damped under SSR conditions