Anti-Windup Pitch Angle Control for Wind Turbines Based on Bounded Uncertainty and Disturbance Estimator

Abstract

Due to physical limitations and safety requirements, the rate and amplitude of change in wind turbines’ pitch angle are limited, which will bring integral saturation problems to the control system. This leads to the deterioration of the pitch control system’s performance or even an instability problem. This paper designs an anti-windup robust pitch angle control strategy to deal with pitch rate constraint issue to enhance the safety of the control system. First, to facilitate controller design, a filtered tracking-error technique is employed to transform the nonaffine form into an affine one. Subsequently, a feedback robust controller based on an uncertainty and disturbance estimator (UDE) is developed to handle the model’s uncertainty and external disturbances. To address the issue of integral saturation in the pitch system and guarantee its safety, an elliptical bounded constraint is integrated into the designed UDE strategy. This bounded UDE controller can improve the stability of power generation quality, reducing the mechanical loads on components. Finally, the effectiveness of the proposed scheme is verified on the Wind Turbine Blockset platform in Matlab/Simulink. It can achieve better performance than traditional methods.

Keywords

• variable speed wind turbine (VSWT)
• pitch angle control
• integral saturation
• bounded uncertainty and disturbance estimator (UDE)