The impact of wind farms with doubly fed induction generators on power system electromechanical oscillations

Introduction of large amounts of new wind generation can affect the small signal stability of power systems with three mechanisms: displacing synchronous generators (SGs); reducing SGs power generation; and the dynamics of wind farms (WFs) interacting with the electromechanical mode of SGs. In this paper a novel approach is developed to investigate the impact of the latter mechanism on existing power systems oscillations. In this approach, the dynamic behavior of grid connected WFs is studied independent of the dynamic behavior of system SGs. This approach helps to identify the conditions in which the dynamics of WFs may interact with the electromechanical mode of SGs. Also it helps to foresee the impact of these probable interactions on the frequency and damping of system oscillations. By using this approach in a test system, it was shown that under some circumstances these dynamic interactions considerably decrease the damping of system oscillations but they barely change the frequency of system oscillations. The frequency of system oscillation and the operating point of WF are the two major parameters determine the severity of the decrease in oscillation damping. Comparison of the SG electromechanical eigenvalues calculated before and after the introduction of the WF in the test system, confirmed the prospects of the proposed approach.