Secondary voltage control applied to DFIG-based wind park and its effect on long-term voltage stability

Abstract

This paper investigates the use of secondary voltage control (SVC) in a wind park based on doubly fed induction generator (DFIG) and its effect on long-term voltage stability. The performance of the SVC applied to wind park is compared with the case when only the primary voltage control (PVC) is adopted. A detailed analysis is conducted with time-domain simulations, considering high and low wind speed regimes, control variable limits of wind generators, static and dynamic loads, and dynamic models of overexcitation limiter (OEL) and load tap changing (LTC) transformer. Based on the results, the use of secondary voltage control in a DFIG-based wind park can postpone long-term voltage instability. Further, some interesting findings were obtained showing that SVC can lead the grid-side converter (GSC) of DFIG to absorb a significant amount of reactive power and lose the capability of injecting additional reactive power. To address this problem, two novel auxiliary control strategies are presented, and the results indicate the effectiveness of the proposed strategies in postponing voltage instability.