Sensorless vector control of PMSM by new carrier frequency voltage injection method

This paper presents a new sensorless vector control method for permanent-magnet synchronous motors (PMSMs) that employs pulsating high frequency voltage injection. The frequency range of the injected voltage is almost the same as that of the pulse width modulation (PWM) carrier. This allows high-speed phase estimation that is indispensable for a high performance drive, and possibly low acoustic noise due to the injected voltage. The proposed method injects a pulsating high-frequency voltage for current modulation in the quasi-synchronous reference frame, demodulates the modulated current, and produces a phase estimate in the same reference frame. The demodulation and phase estimation are characterized by a small current sampling period, filter-less extraction of the modulated current, new polarity processing of the current difference, and a new function that improves the positive correlation region. In addition, no further phase compensation is required. The usefulness of the proposed method is verified through extensive experiments.