An Accurate Full-Speed Position Estimation for Permanent Magnet Synchronous Motors With a DC-Bus Current Sensor

An accurate full-speed sensorless control of permanent magnet synchronous motors (PMSMs) with a single dc-bus current sensor is attractive for low-cost or compact motor drives and has not been solved completely. This article utilizes a recent proposed quasi edge aligned pulsewidth modulation (QEAPWM) method in the whole speed range to realize an accurate position estimation for PMSMs. The proposed full-speed sensorless control strategy combines a high-frequency square-wave voltage injection method and a sliding mode observer (SMO) in the
dq
-axis both based on the QEAPWM with a single dc-bus current sensor. The accuracy of reconstructed phase current, and position/speed estimation are all improved benefiting from two dc-current samplings with a fix and short time interval in one control cycle using the QEAPWM. Hence, a satisfactory sensorless control performance can be achieved during the full-speed range. Furthermore, the modulation region of the QEAPWM is analyzed. Finally, a comparison of sensorless control performance based on the conventional phase-shifting SVPWM and the QEAPWM has been studied on a 500-W PMSM drive. The experimental results demonstrate that the constructed phase current error can be reduced by 50%, and the position estimation accuracy, in terms of the bias error and error ripple, can be both reduced. Moreover, by adding a dead-time compensation, the lowest speed of the SMO in the
dq
-axis can be down to 3% of the rated speed with the rated load.