Fault Estimation and Fault-Tolerant Control of Wind Turbines Using the SDW-LSI Algorithm

The dynamic response of the pitch angle slows down when the pitch actuator of wind turbines fails, and the fault leads to fluctuations in the generator speed and in the output power. According to identification and analytical theories, a fault-tolerant control combined with fault estimation is proposed to solve this problem. The simplified two-order transform function of the pitch actuator is transformed into the identification equation by means of the Euler transformation method. Next, the time-varying natural frequency and the damping ratio of pitch actuators are regarded as gradual change and abrupt change parameters; these two parameters are estimated using the proposed sliding data window least squares-based iterative (SDW-LSI) identification algorithm. The sliding data window length is adjusted when changes in the system parameters are detected. Then, according to analytical theory, a compensation equation is derived in the pitch actuator, and the estimated values are fed back to the compensation module to adjust the relations before and after fault occurrences in the pitch actuator to eliminate the effects caused by the pitch actuator failure. Finally, the feasibility of the SDW-LSI algorithm is validated by choosing the fault of high air content in the hydraulic oil.