Adaptive Second Order Sliding Mode Speed Control of Doubly Fed Induction Generator Wind Turbines

Accurate control of the wind turbine at its optimal rotational speed for a given wind speed is required to extract maximum power from the wind turbine generator system in the absence of aerodynamic pitch control. Due to inherent wind turbine nonlinearities and unpredictable wind speed fluctuations, precise control is a difficult task to undertake. This paper presents a sliding mode speed controller for doubly fed induction generator (DFIG) wind turbines. The strategy uses sliding mode control theory based on adaptive twisting algorithm, to achieve accurate tracking under the wind turbine's nonlinear dynamics. As such, robustness to unpredictable wind uncertainties is achieved. Simulation results for different situations highlight the performance of the proposed controller under various wind speed operating conditions.