Analytical assessment of subsynchronous resonance (SSR) impact on doubly fed induction generator wind turbine behavior and efficient suppression of SSR oscillations

Wind-farms are usually placed in remote areas, and thus high-voltage AC-based transmission systems with series capacitive compensation may be cost-effective approaches for connection of wind-farms to the grid over long transmission lines. However, the risk of subsynchronous resonance (SSR) is the main issue raised in series compensated transmission systems. This article first analytically investigates the effect of SSR phenomenon on the doubly fed induction generator (DFIG) dynamic behavior in a series compensated grid, and then proposes a proficient damping approach for complete suppression of SSR oscillations. The proposed damping approach is created by partial/full compensation of rotor back-emf voltages by modifying the rotor-side converter control. It is shown that under full compensation of rotor back-emf voltages: (a) the rotor, stator, and grid currents become independent of SSR and (b) the DFIG and rotor circuit do not contribute to the induction generator effect, and subsynchronous oscillations have vanished quickly. In this article by the modal analysis and simulation results, it is shown that the proposed approach has a satisfactory response under different values of short circuit ratio and different series compensation levels. Next, it is shown that the proposed approach has superior performance compared to the rotor virtual resistance emulation approach.