Torque-Preserving Flux-Weakening Control for IPMSM Based on q-Axis Current Compensation and Adaptive Voltage Regulation

A torque-preserving flux-weakening control strategy combining q-axis current compensation with a bandwidth-based speed-adaptive voltage regulator is proposed for interior permanent magnet synchronous motor (IPMSM) drives. The conventional negative d-axis current compensation method is first analyzed, showing that the associated current-vector variation can cause transient torque deviation during flux-weakening operation. A q-axis current compensation law is therefore derived based on the torque-preservation condition. In addition, a speed-dependent tuning law for the voltage closed-loop regulator is developed through frequency-domain analysis, with the voltage-loop bandwidth as the principal design parameter. Experimental results show that, compared with the conventional method, the proposed strategy reduces the torque-fluctuation amplitude from 2.35 N·m to 1.83 N·m, corresponding to a reduction of approximately 22.1%, and suppresses the approximately 9% q-axis current overshoot observed with the conventional method. Under a sudden-load condition, the maximum speed dip is reduced from 66 r/min to 61 r/min (7.6%), while the recovery time is shortened from 0.28 s to 0.25 s (10.7%). These results demonstrate improved transient torque stability and disturbance-rejection performance in the flux-weakening region.