Position Sensorless Control Method at Zero-Speed Region for Permanent Magnet Synchronous Motors Using the Neutral Point Voltage of Stator Windings

A new sensorless control method that uses the neutral point voltage from stator windings is proposed. Each inductance of the three phase coils of the permanent magnet synchronous motor (PMSM) is slightly affected by the rotor magnet flux. As a result, the neutral point voltage also changes depending on the rotor position. The rotor position can be estimated by detecting the neutral point voltage even in the zero-speed regions based on this principle. In addition to this, this method can be applied to nonsaliency PMSMs. This paper presents the principle and the experimental results when using a small-capacity PMSM without saliency.