Second‐order sliding mode control for power optimisation of DFIG‐based variable speed wind turbine

Abstract

Power optimisation is quite important for the doubly‐fed induction generator (DFIG)‐based variable speed wind turbine (VSWT) in the modern renewable power generation system. However, the VSWTs are generally non‐linear and uncertain systems. This study proposes a super‐twisting second‐order sliding mode (SOSM) control scheme to maximise the wind energy capture of a DFIG‐based VSWT system, and regulate the stator reactive power to follow the grid requirements. By regulating the generator rotor voltage, the designed SOSM controller makes the wind turbine rotor speed track the optimal speed to maximise the power generation, and controls the rotor current to follow the external reference to regulate the stator reactive power. A quadratic form Lyapunov function is adopted to determine the range of controller parameters and guarantee the finite time stability. Simulation results on a 1.5 MW DFIG‐based VSWT demonstrate the effectiveness of the proposed control strategy.