A Comparative Small Signal Stability Analysis of PMSG and SCIG-Based Wind Farms

The increasing interest in exploiting renewable energy resources has introduced a new generation of energy conversion technologies including wind farms (WF) to the power systems. Previous studies of these WFs and their impacts on power systems have made new challenges emerge, which in turn, require detailed assessment for continuously increasing wind power penetration. Among these challenges, the power system transients and its small signal stability are from crucial importance. In this paper, the small signal stability assessment of increasing output power of WFs with fixed installed capacity is carried out. For a fixed capacity, the variations of wind speed leads to different levels of power injections from WFs, thus, considering the dispatching operation and unit commitment, leading to changes in power obtained from conventional synchronous machine-based plants. Permanent magnet synchronous generator (PMSG) and squirrel cage induction generator (SCIG)-based WFs are studied and compared. The results have shown that the impact of injected power from WFs on power system oscillations depends on several factors including wind speed, WF location in power system and the employed control strategies in WFs. Furthermore, it is shown that the contribution of the PMSGbased WFs on the oscillation damping is more effective than that of the SCIG-based one.