Actuator fault diagnosis and fault-tolerant control of wind turbines using a Takagi-Sugeno sliding mode observer

A Takagi-Sugeno sliding mode observer (TS SMO) is used to reconstruct actuator faults in wind turbines. Since the two control signals, the pitch angle and the generator torque, are of significantly different orders of magnitude, a TS SMO with a weighted switching action is used. For the nonlinear full-load region, a TS controller based on linear LQR control designs is used, where the stability is ensured by a negative derivative of the Lyapunov function. The actuator faults are directly reconstructed from the equivalent output injection signal of the TS SMO. The control inputs are then modified with the reconstructed fault signals to achieve fault-tolerant control in the presence of actuator faults with a similar behaviour to the fault-free case. The performance of the fault diagnosis and fault-tolerant control scheme is tested in simulations with the aero-elastic code FAST by NREL.