Bounded UDE based MPPT Control for Wind Turbines

Due to the randomness and intermittency of wind speed, the complexity of wind turbine operating environment and its own structure, the maximum power point tracking (MPPT) control of wind turbines is still a hot topic for control communities. In this study, a MPPT torque controller is designed for variable-speed wind turbines (VSWT) based on the bounded uncertainty and disturbance estimator (UDE). First, the optimal rotor speed is calculated according to the relationship between the wind turbine's power coefficient and the tip speed ratio. Based on the dynamic model of VSWT, a torque controller based on UDE, which can eliminate the control deviation caused by the uncertainties and disturbances, is designed. However, traditional UDE control have integral phenomenon, which will affect the tracking performance and even causes the system to run out of control. To deal with this, a bounded UDE torque controller along with a time-varying constraint coefficient is developed. It can avoid the integral windup issue caused by the input torque of the VSWT exceeding the maximum boundary of the actuator, and achieve a more stable optimal speed tracking performance. Finally, the effectiveness of the proposed MPPT torque controller is verified through the FAST (Fatigue, Aerodynamics, Structures, and Turbulence) platform.