A new pitch control method for large scale wind turbine based on ADRC

Above rated wind speed, pitch control system is the most important part of wind turbine to regulate the aerodynamic power and loads produced by the rotor so that the rotor speed is kept within its design limit. Large scale wind turbines usually adopt PI controller to adjust rotor speed in high winds. Since wind turbine system is a highorder nonlinear system, one set of PI parameters can´t achieve excellent control performance, especially when wind turbulence is very strong. In view of the shortcoming of conventional PI controller and nonlinear characteristics of wind turbines, a new pitch control method based on the active-disturbance-rejection control theory is researched in this paper. A linear model of the wind turbine is derived by linearising the aerodynamic torque equation around the rated operation point and the dynamic response of the drive train is transformed into a first-order linear system by compensating the disturbance which is estimated by the linear extended-state observer based on the feedback of rotor speed. Simulation of the new pitch control method has been carried out under turbulent winds. The results show that the proposed pitch control method produces good robustness and can effectively restrain the overshoot of wind turbine´s rotor speed.