Initial Rotor Position Determination for Permanent Magnet Assisted Synchronous Reluctance Motor in Standstill Conditions Based on Adjustable Symmetrical Square-wave Pulses

Accurate initial angle information is necessary for Permanent Magnet Assisted Synchronous Reluctance Motor (PMa-SynRM) in some sensorless applications especially which do not allow for shaft movement. The initial angle identification will always be used repeatedly in sensorless startup mode. In some high load startup application, conventional d-q axis high current alignment methods may be applied to incorrect position, which may lead to irreversible demagnetization of the ferrite. To address these issues, an initial rotor position determination method based on adjustable α-β axis symmetrical square wave pulses have been proposed. Firstly, the current response of α-β axis symmetrical square wave pulses has been analyzed, which considers magnetic saturation and cross saturation of PMa-SynRM. The amplitude and durations of square wave pulses are selected to guarantee standstill operating and polar detection. Secondly, extra small high-frequency (HF) signals are superimposed onto applied square wave signals, allowing for the simultaneous acquisition of motor angle based on Saliency information. At last, the phase lock loop is applied to obtain the estimation angle. Validation was conducted on a 15 kW PMa-SynRM, and experimental results demonstrate that the method offers superior identification rates and accuracy.