L₁ adaptive pitch angle controller of wind energy conversion systems

In conditions of above rated wind speed, the power output of a wind turbine should be maintained at rated power to prevent overheating of generators and power electronics systems. Furthermore, extreme wind conditions, such as wind gusts, can even lead to shut-downs. In this paper, a novel L₁ adaptive controller is designed for blade pitch control of wind energy conversion systems (WECS) to achieve stable output power and generator speed, in the presence of turbulent wind conditions. Firstly, the pitch regulated variable-speed wind turbine is modeled as a non-affine nonlinear system with uncertainties. Subsequently, the L₁ adaptive controller is introduced, which consists of three elements: state predictor, adaptive law, and control law. Without the requirement of exact system dynamics and wind speed measurement, uniformly bounded transient power response can be achieved. Compared with traditional methods adopted in industries, L₁ adaptive controller is more robust and can achieve better transient control performance. The feasibility of the proposed scheme is verified via extensive simulation studies on a professional GH Bladed software package.