Low-Noise Initial Position Detection Method for Sensorless Permanent Magnet Synchronous Motor Drives

Initial rotor position detection is important to ensure the start-up operation of sensorless permanent magnet synchronous motor (PMSM) drives. In order to suppress the annoying noise caused by the additional signal injection during the detection process in the existing methods, a pseudorandom high-frequency (HF) square-wave voltage injection based low-noise initial position detection method is proposed in this article. Two fixed HF square-wave voltage signals are injected into the estimated d-axis randomly. As the magnetic pole position is detected, the magnetic polarity can be identified at the same time, based on the accumulation of the induced random HF current peak pairs without any extra signal. In addition, a saturated peak current delay compensation strategy is proposed to reduce the digital delay effects on the magnetic polarity detection. The proposed method makes the entire detection process simpler and faster. Furthermore, power spectral density (PSD) analysis of random HF currents is adopted to provide the theoretical support for noise reduction. Finally, the proposed method is verified by experiments on a 2.2-kW interior PMSM drive platform.