SSCI mitigation of grid-connected DFIG wind turbines with fractional-order sliding mode controller

To mitigate subsynchronous control interaction (SSCI) in doubly fed induction generator (DFIG)-based wind farm, this paper proposes a robust controller for rotor-side converter (RSC) using fractional-order sliding mode controller (FOSMC). The proposed FOSMC can improve robustness and convergence properties of the controlled system, thus achieving SSCI damping under various operating conditions. Impedance-based analysis and time-domain simulation are performed to check the capability of the designed FOSMC as compared with conventional sliding mode control (SMC) and subsynchronous damping control (SSDC). Simulation results demonstrate that FOSMC can mitigate SSCI within shorter time and effectively reduce the fluctuation range of system transient responses under various operating conditions of wind speeds and compensation levels. Moreover, FOSMC also improves system robustness against parameter uncertainties and external disturbances, which is important for safe operation of realistic wind farms.