Designing a fuzzy PI^lambda controller to control the pitch angle in wind turbines under variant speed

One of the main tasks of the control systems in the wind turbines is to maintain the power of the wind when its wind speed proceed its nominal value. Because the failure to maintain the power in its nominal value in the region of the turbine curve damages the turbine and increases the mechanical stress. This object is obtained by controlling the pitch angle in the third region of the turbine curve. In this study, a fuzzy fractional-order PID controller is designed to regulate pitch angle in the wind turbines and its efficiency is compared with conventional PID and fractional-order PID controllers. The proposed control method is applied to a 100kW wind turbine under a variable wind speed. The simulations results show that the value of the root mean squre error for the proposed control method is less than the conventional PID and fractional order PID controllers, and also the proposed control scheme results in smoother and better control signals, output power and generator speed in third region of performance.