Nonlinear feed forward pitch controller for wind turbine based on rotor's aerodynamic characteristic

Abstract

Large-scale variable pitch wind turbine generator (WTG) system usually uses the PID controller to maintain the output power unchanged above the rated wind speed. Because WTG has the characteristic of inertia and delay and the wind speed varies randomly, the simple feedback control method such as PID controller can hardly achieve satisfactory performance. This paper firstly analyzes the shortcomings of PID controller, and then a new pitch control method combined with nonlinear feed forward controller and PID controller is proposed. At high wind speed range, there is nonlinear relationship between pitch angle and wind speed due to the aerodynamic characteristic of the rotor. This paper obtains this relationship with numerical calculation and least square polynomial fit method. Then the nonlinear model is used to design the feed forward controller. Its input is wind speed and the output is the increasing feed forward reference pitch angle. The feed forward controller has achieved the dynamic feed forward compensation and improved the rapidness of control system. With the simulation of a 300kW wind turbine generator at different wind speed, the new pitch control strategy can effectively reduce system's overshoot and regulation time, and has a satisfactory control performance.