Robust quasi-continuous sliding-mode control of a variable-speed wind turbine

In this paper, a quasi-continuous sliding-mode strategy is done which solves the problem of power generation for variable speed wind turbine systems. The control objective is to maximize the extracted energy from the wind while mechanical loads are reduced. The properties of the proposed controller are robustness to parametric uncertainties of the turbine, robustness with respect to external disturbances, robustness to unmodeled dynamics and accuracy, with an accuracy of higher order and finite reaching time. The high-order sliding-mode controller is applied to reduce the effects of chattering in the generated torque that could lead to increased mechanical stress because of strong torque variations. We use a realistic model which takes into account the nonlinear dynamic aspect of the wind turbine and the turbulent nature of the wind. We assume that only the rotor speed and electric power are available from measurements on the wind turbine. In order to validate the mathematical model and evaluate the performance of proposed controller, we used the National Renewable Energy Laboratory aeroelastic wind turbine simulator FAST. Simulation and validation results show that the proposed control strategy has improvements in comparison with the existing controllers.