Investigation of the impact of SSSC on the stability of the power system connected to wind turbines based on SCIG and DFIG

The investment capacity in wind power generation is growing significantly. However, the increasing penetration of wind energy in the network may lead to instability of the system and this may have negative impacts on the power quality of the system. In recent years, the effects of wind turbines on the voltage stability of power systems have received much attention. In the past, wind turbines based on squirrel cage induction generator (SCIG) were usually used due to their low cost and simplicity. But in recent years, wind turbines based on doubly-fed induction generator (DFIG) are mostly used because they are more stable. Recent studies have shown that the performance of the grid-connected wind turbines can be improved by employing flexible ac transmission systems (FACTS) devices. In this paper, the performance of a 9 MW wind turbine based on SCIG and DFIG in the presence and absence of static synchronous series compensator (SSSC), at the point of common connection (PCC) is investigated, considering single-phase and two-phase short circuit faults. A voltage stability index (VSI) is used to evaluate the stability of the wind turbines. The simulation results show that in the case of a two-phase fault that the system variables experience some oscillations, SSSC helps to damp out the generated oscillations faster and improve system stability. In particular, in the presence of SSSC, oscillations for the wind turbine voltage, reactive power and active power are damped out about 0.3, 0.5 and 0.6 seconds faster, respectively. All simulations are performed in MATLAB/Simulink software.