Identification of load current influences on position estimation errors for sensorless SPMSM drives

For low-speed sensorless Surface mounted Permanent Magnet Synchronous Machine (SPMSM) drives, the position is often estimated based on the rotor magnet saliency. Magnetic field distortion caused by load current may change the orientation of the rotor magnet saliency and it is therefore no longer aligned with the rotor mechanical saliency. This paper analyzes the cross-saturation effects caused by load current influence on SPMSM sensorless drives with respect to position estimation error; a new method is proposed to reliably detect the saturation dependent position estimation error that may influence the performance of sensorless SPMSM drives. Motor parameters are not required in the proposed saturation dependent position estimation error detection method and there is no need to lock the rotor. The method is suitable to use at any initial rotor position without causing noticeable rotor movement. Experimental results are presented to validate the effectiveness of the proposed methods.