Uncertainty estimator-based dual layer adaptive fault-tolerant control for wind turbines

Abstract

Under the detrimental effects of sensor and actuator faults, the blade pitch system is found to be the least reliable subsystem. Therefore, to apprehend required level of reliability and efficiency, an efficient Fault Tolerant Control framework (FTC) seems crucial. This paper presents an Active FTC (AFTC) strategy to control the pitch angle of a wind turbine in the presence of actuator and sensor faults, uncertainties and exogenous disturbances. First, a lumped term consisting of model uncertainty and disturbance is estimated by a novel dual layer adaptive uncertainty estimator. Next, to achieve high accuracy in supplying the required power, a continuous adaptive time delay control is designed based on the estimated uncertainties. In the proposed controller, chattering caused by discontinuous control term is eliminated, and faults are accommodated. Stability of the closed-loop system is demonstrated by the Lyapunov theory. Furthermore, in order to verify the validity of the proposed strategy, the controller is implemented in FAST-MATLAB/Simulink for five different load cases generated using TurbSim. Results confirm the effectiveness and superiority of the proposed structure in the presence of sensor and actuator faults (bias, gain, performance degradation and actuator stuck) compared to Nonlinear PI (N-PI) control and Feedback Linearized Control (FLC) schemes.