Mitigation of subsynchronous oscillations in a series compensated wind farm with static var compensator

Subsynchronous resonance (SSR) is a potential problem in a series compensated power system. A wind farm employing self-excited induction generator (SEIG) connected to the grid through a series compensated transmission line may experience the same problem. This paper presents a study of subsynchronous oscillations resulting from torsional interactions as well as induction generator self-excitation effects in such a wind energy conversion system (WECS). It is shown that these two phenomena may cause system instability if proper preventive measures are not taken. A static var compensator (SVC) with a voltage controller has been employed at the induction generator terminal to damp the subsynchronous oscillations. It is also found that an auxiliary subsynchronous damping controller (SSDC) improves the damping of torsional oscillations. Extensive time domain simulations have been carried out using EMTDC/PSCAD to validate the performance of the SVC in preventing SSR