Abstract:

Wind turbines are generally installed in harsh environments, and their pitch actuators are prone to failure. In view of the pitch actuator failure of a type of wind turbine system with unknown but bounded interference and noise, a collective unknown input observer is designed to detect and separate the pitch actuator failure. The model of wind turbine system is established by using aerodynamic mechanism and modern identification principle and the disturbance is decoupled by optimizing the design of unknown input observer. The interval envelope without considering the fault is obtained by zonotopes, which is used as the upper and lower dynamic threshold of the residual estimation to realize the state estimation. Based on the proposed design, a fault diagnosis strategy using a bank of unknown input observers is presented. The simulation shows that the time and location of the sudden and slow time-varying faults in the 3rd and 5th order linear systems of the pitch actuators are accurately diagnosed by the designed set unknown input observer, which verifies the effectiveness of the proposed fault diagnosis strategy.

Key words: unknown but bounded, pitch actuators for wind turbines, identification theory, unknown input observer, disturbance decoupling, residual error threshold, zonotope, fault estimation and isolation