Torque Ripple Suppression Strategy for Open-Winding PMSM With Zero-Sequence Loop Model-Free Control

To suppress the torque ripple caused by zero-sequence loop (ZSL) in open-winding permanent magnet synchronous motors, a
${q}$
-axis current injection strategy has been proposed. However, in this method, the torque ripple cannot be effectively suppressed and will even be augmented when the third flux linkage mismatch occurs. First, an extended state observer (ESO) based on the ultralocal model is established in this article to address the problem. In ESO, the future zero sequence current (ZSC) and ZSL back-electromotive force (EMF) can be estimated under complex conditions; then the injected
${q}$
-axis current can be calculated, which addresses the problem of one-step delay and aforementioned disturbance caused by third flux linkage mismatch. Second, the desired zero-sequence voltage (ZSV) can be calculated by ESO. Then zero voltage duration ratios are adjusted in space vector pulsewidth modulation to obtain the desired ZSV to suppress ZSC. Finally, comparative simulation and experimental results have been shown to prove the effectiveness of the proposed control method.