Abstract: In the process of wind energy conversion,a H_∞optimal fault-tolerant performance controller was designed to solve the problem of actuator failure and high cost of fault-tolerant control,and a PI observer was proposed to get the fault diagnosis. First,the deficiencies such as time delay,parameter uncertainty and actuator failure in wind power systems are expressed by the singular perturbed linear parameter varying（LPV）model. Second,a PI observer is designed for actuator fault reconstruction,under the dual constraints of H_∞performance index and cost performance index,the feedback gain of the optimal guaranteed cost fault-tolerant control law is wrought out by solving the convex optimization problem. Simulation results show that at low wind speed,the controller can effectively track the optimal rotor speed and achieve the maximum wind energy capture.