H∞ mixed-sensitivity robust control design for damping low-frequency oscillations with DFIG wind power generation

This study presents a H∞ mixed-sensitivity robust control design to improve the overall damping performance of lowfrequency oscillations for power systems with doubly fed induction generator-based (DFIG) wind power generation. The supplementary damping controller is designed in the linear matrix inequality framework which allows the placement of the closed-loop poles inside a pre-defined region for improved stability. The damping signal is implemented at the reactive power modulation of the rotor-side converter of the DFIG wind turbine (DFIG-WT). The damping contribution of the power oscillator damper is compared with that provided by the power system stabiliser (PSS) of the synchronous generator (SG). State-space system analysis and time-domain simulations show the capability of DFIG-WT to enhance the overall damping of the oscillatory modes even if PSSs are not installed at SG s. Also, the designed controller shows a robust performance to wind speed variations. The performance evaluation is based on the revised two-area four machines system and the revised New England 39-bus system.