A Time-Delay Compensation Method for IPMSM Hybrid Sensorless Drives in Rail Transit Applications

Abstract

This paper proposes a hybrid sensorless control strategy for rail transit application employing interior permanent magnet synchronous machine (IPMSM), which works under low switching frequency. Due to a long system time delay, the convergence rate of estimated position in the sensorless dynamic region is reduced. As the speed increases, the dq axes currents coupling is more severe, and deteriorates the control performance. In order to solve these problems, the analysis of time-delay effect on the IPMSM sensorless drives is first derived. Then, using q-axis current error, a global time-delay compensation method is designed to eliminate the lag angle of estimated position. Furthermore, the effect of this compensation on audible noise reduction is also analyzed. Through a phase-locked loop, the hybrid estimated position is obtained from a normalized position error. Finally, a 3.7-kW IPMSM is tested to verify the feasibility of the proposed sensorless method.