Control Strategy of Open-End Winding Permanent Magnet Synchronous Motor for Performance Improvement in the Flux-Weakening Region

This study proposes a new control strategy to address voltage limitation and torque instability issues during the flux-weakening operation of open-end winding (OEW) permanent magnet synchronous motors. In the OEW structure, a zero-sequence current inevitably arises, affecting the effective fundamental voltage range and deteriorating the control performance at high speeds. Although the conventional method compensates for this variation by increasing the negative d-axis current, it fails to track the torque reference and increases the loss. This study overcomes these drawbacks by introducing a new concept called peak flux and incorporating it, as well as the torque reference into the current reference table. The proposed flux-weakening strategy optimizes the overall current components (dqn) to extend the flux-weakening operating region while satisfying the output quality conditions. Consequently, voltage utilization and current efficiency can improved simultaneously. The ability of the proposed method to extend the speed range by approximately 15.7% and reduce losses by 11.8% with respect to conventional methods was verified by experimental results.