Active fault-tolerant linear parameter varying control for the pitch actuator of wind turbines

This paper proposes a fault-tolerant control method using the virtual actuator for the problem of the pitch actuator failure. The simplified second-order transfer function of the pitch actuator is transformed into the identification equation using the Euler transformation. For the purpose of fault estimation, a least-squares batch identification algorithm is adopted to estimate the time-varying natural frequency and damping ratio. Then, according to the convex decomposition theory, the nonlinear model of wind turbines is converted to a linear parameter variation model. The fault-tolerant control structure of the virtual actuator is obtained by applying the state feedback law. In the light of the polyhedral approximation theory, an infinite number of linear matrix inequalities can be transformed into a finite number of linear matrix inequalities. The feedback controller is obtained after solving finite linear matrix inequalities. Finally, the simulation results show that the fault-tolerant control method with the fault estimation is capable of handling the pitch actuator failure and maintaining a constant power output.