Improvement of sliding mode observer for PMSM sensorless control in renewable energy system

This paper proposes an improved sliding mode observer (SMO) for sensorless permanent magnet synchronous motors (PMSM) in renewable energy systems. In order to alleviate the chattering problem in the conventional SMO, the switching function is modified with a sinusoidal function in the sliding-surface neighborhood and the switching gain is regulated with rotor speed to expend the functional range. The phase locked loop (PLL) method is adopted to extract the rotor speed and position for further improvement of the chattering problem. The adaptive rule is obtained by the Lyapunov analysis, during which the stability superiority of the proposed method is demonstrated. Experimental results show the improved SMO is effective for speed and rotor position extraction and confirm its ability of chattering suppression and accuracy improvement.