Pitch angle controller of variable-speed wind turbine based on L1 adaptive control theory

In this paper, a pitch angle controller is designed based on L₁ adaptive control theory to guarantee steady generator power output while reducing the mechanical loads at above rated wind speed. Firstly, a non-affine model of the pitch regulated variable-speed wind turbine is built to formulate complicated aerodynamics. The L₁ adaptive pitch angle controller is then introduced to assure uniformly bounded transient response of wind energy conversion systems in the presence of rapidly changing wind speed, in addition to stable generator angle speed. Without the loss of robustness, the performance of the closed-loop system can be improved by increasing the adaptation rate. Simulation results on GH Bladed software package show that better performance on output power is obtained by the L₁ adaptive controller compared with the traditional pitch angle controller adopted in industries.