Backstepping-based active fault tolerant control of wind turbine system using nonlinear fuzzy state observer

Reliability and robustness are two main goals in developing control systems for wind turbine  (WT) due to the existence of different sources, such as unknown malfunctions or faults. Their ignorance can significantly jeopardize the system  performance and even stability. This paper presents a new active fault tolerant control (FTC) for WT system considering the fault of pitch  system. The nonlinear model of WT is constructed in the form of strict-feedback in order to design an appropriate FTC-based backstepping control law. The mechanism of fault detection is based on a modified nonlinear fuzzy state observer, where the estimation of unknown terms is realized via fuzzy approximators, incorporated in the fuzzy observer. Accordingly, the rotor speed of the system can follow the desired reference in the presence of an actuator fault. The robust behavior, fast response, and acceptable tracking performance together with the model-free structure are the important properties of the proposed FTC-based controller. The stability of the overall closed-loop system, including the controller and the observer, is derived by the Lyapunov method. Simulation results highlight the superior performance of the proposed control method.