Damping subsynchronous resonance in series-compensated wind farms by adding notch filters to DFIG controllers

The interaction between controllers of doubly-fed induction generators (DFIGs) and fixed series compensation would induce subsynchronous resonance (SSR) problem. To address this issue, this paper proposes a novel control scheme to defuse such an interaction just by adding notch filters (NF) to DFIG controllers. Two specific schemes are developed. One is to embed a NF into its d-axis channel in the inner current loop of rotor-side converter (RSC) controller. The other is to add a NF to its q-axis channel. They are then applied to a practical series-compensated DFIG-based wind power system for performance verification. Eigenvalue analysis and time-domain simulation have been conducted to investigate their effectiveness. The results show that they both can significantly enhance the damping and guarantee SSR stability without affecting the normal operation of DFIGs. Moreover, it is discovered that the first scheme can provide better damping than the second one.