Parameters Compensation of Permanent Magnet Synchronous Motor in Flux-Weakening Region for Rail Transit

This article proposes a dual-parameters compensation control method to improve the torque accuracy of permanent magnet synchronous motor (PMSM) in flux-weakening region for rail transit. For the sake of the feature that six-step operation is the essential operation of rail transit and switching frequency is very low, the proposed method works on the single q-axis current regulator-variable voltage angle (SQCR-VVA) flux-weakening control strategy for PMSM operation. Based on SQCR-VVA flux-weakening control, impact of inaccurate parameters is analyzed in seven different conditions, and inaccurate parameters (d-axis inductance, q-axis inductance and permanent magnet flux linkage) result in the errors on d-axis current response and d-axis feed forward voltage. In order to eliminate the impact of the three parameters at the same time, dual compensation regulators are applied to the proposed method. Error of q-axis inductance is identified by the d-axis voltage regulator. The whole impact of inaccurate d-axis inductance and permanent magnet flux linkage is eliminated by the d-axis current regulator. The proposed method is subsequently tested on PMSM and shows quite good performance on the improvement of torque accuracy.