A novel method for polarity detection of nonsalient PMSMs in initial position estimation

This paper proposes a novel method for magnetic polarity detection in pulsating current injection based self-sensing control of surface-mounted permanent-magnet synchronous motors (SPMSM). When a proper high frequency current is superimposed in d-axis, the flux linkage saturates which can lead to the distortion of the resulting voltage. With the Fourier analysis, the 2nd harmonic of the resulting voltage in estimated d-axis includes the magnetic polarity information. A demodulation mechanism is designed to detect the magnetic polarity. This method can achieve fast and accurate initial position estimation and is verified by the simulations and experiments.