Sensorless control for direct-drive PMSG wind turbines based on sliding mode observer

In order to obtain the accurate information of generator speed and angle, and alleviate the shortcomings of the speed sensor, this paper presents a sensorless vector control model of permanent magnet synchronous generator (PMSG) based on sliding mode observer (SMO) in the direct-drive permanent magnet wind power generation system. The proposed observer is easy to implement and less sensitive to parameter variations. But since it is the discontinuous control, the high frequency chattering problem would be produced in the conventional PMSG Bang-Bang control. In this paper, the saturation function is adopted to replace the discontinuous sign function and solve the problem successfully. The validity of the proposed estimation and control algorithms are shown by simulation studies on a 1MW PMSG wind turbine and are further demonstrated by experimental results on a 7.5KW practical PMSG wind turbine.