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

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-axis 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 firstly 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 phaselocked loop (PLL), 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.