Sliding mode control of pitch angle for direct driven PM Wind turbine

The power generated by wind turbines appears to be instable at high rate speed due to the stochastic nature of wind speed, system lagging and nonlinearities, and involving time-variable parameters. To improve the dynamic performance in the operation region of constant power output, a sliding mode variable structure controller based on the analysis of the features model of the variable pitch and the speed wind turbine generator system is proposed. Moreover, to eliminate the chattering problem caused by the sign function in the traditional controllers, a quasi-sliding mode controller within the boundary layer is introduced. The pitch control model of a 2MW permanent magnet direct-drive wind power system is built and simulated. The simulation results show that the sliding mode control with quasi sliding mode can cope with traditional chattering problems in variable structure systems, and has such advantages as strong robustness to changes in parameters and fast response.