Optimal Vector Sequences for Simultaneous Reduction of the Switching Loss, Zero-Sequence Circulating Current, and Torque Ripple in Two Parallel Interleaved Inverter-Fed PMSM Drives

The two-parallel interleaved converters system is essentially a multilevel converter and introduces more vector redundancies than a single converter, leaving a large space for vector sequences optimization for the simultaneous optimization of crucial indicators. However, the vector redundancies have not been fully explored by previous studies to achieve multiple crucial indicators optimization. This article aims to obtain high efficiency and low torque ripples for the two-parallel interleaved converters-fed permanent-magnet synchronous motor (PMSM), which are dominantly affected by the switching loss, zero-sequence circulating current (ZSCC), and torque ripples. First, given the vector redundancies, this article explores the available vector sequences according to switching times, the minimal torque ripple, and ZSCC with a priority of the switching times. The resultant vector sequences split each 60° sector into eight subsectors, but each subsector has redundant vector sequences. Then, this article further quantitatively analyzes the torque ripple and ZSCC of the redundant vector sequences in the subsectors, based on which each subsector applies an optimal vector sequence. Despite the complexity of the divisions of the subsectors, this article proposes a simple carrier-based modulation scheme and the implementation of the proposed optimal vector sequences amounts to corresponding common-mode voltage (CMV) injections into the references, which only require a simple logic judgment. The theoretical analysis confirms that the proposed method yields smaller torque ripples, ZSCCs, and switching losses than existing pulsewidth modulation (PWM) schemes over the whole modulation indices. Finally, the experimental results further verify the theoretical analysis and the effectiveness of the proposed strategy.