Radial Displacement Sensorless Control at Low Speed Based on High-Frequency Voltage Injection for Bearingless Permanent Magnet Vernier Motor With Special Winding

Abstract

To ensure stable suspension of rotor for bearingless motor, the rotor displacement information as a feedback signal must be obtained accurately. Traditional mechanical sensors increase the system cost and volume and are sensitive to environmental disturbance. When the motor starts at a low speed, the signal-to-noise ratio of flux linkage is so low that the rotor displacement information is difficult to extract. In this article, for bearingless permanent magnet Vernier motor (BPMVM) with dual-purpose-no-voltage (DPNV) winding, a specific radial displacement observer based on high-frequency voltage injection is proposed. Due to the particularity of DPNV winding structure, after injecting a high-frequency signal into the torque voltage, the difference between induced high-frequency voltages in symmetrical windings can be computed. High-frequency bias voltage whose amplitude is linear with radial displacement is included in the difference, and the radial displacement observer can be consequently designed. The topology of DPNV winding and the mathematical model considering rotor eccentricity are analyzed in detail. Also, the performance of the proposed observer is analyzed, proving that it has no theoretical error. The proposed radial displacement sensorless control method is carried out on a 1.1-kW BPMVM prototype to testify its stability, anti-disturbance, and parameter robustness.