Optimal adaptive sub-synchronous resonance damping controller for a series-compensated doubly-fed induction generator-based wind farm

Using both modal analysis and time domain simulations, it is shown that sub-synchronous resonance (SSR) phenomena in a series-compensated DFIG wind farms may cause system instability. In order to damp the SSR, both the rotor-side converter (RSC) and grid-side converter (GSC) controllers of the doubly-fed induction generator (DFIG) are utilised. The objectives are to design an SSR damping controller (SSRDC) with an optimum input control signal (ICS), and to identify the optimum point within the RSC and GSC controllers where to introduce the SSRDC. The optimum ICS is identified using residue-based analysis and root-locus method. The criterion for choice of optimal ICS is that it should make the SSR mode stable without decreasing or destabilising the other system modes. Moreover, since the dynamics of the DFIG-based series compensated wind farm change with varying operating point conditions, the operation of the SSRDC is optimised using the adaptive gain-scheduling method.