Many reduced common mode voltage (CMV) modulation methods have been proposed for three-level inverters. However, most of them suffer from large current distortion because only part of the available base vectors is utilized. The interleaved paralleling can reduce both CMV and the output current distortion, though the CMV reduction is limited and large zero-sequence circulating current (ZSCC) is inevitably caused by the phase-shifted carriers. To further reduce the CMV while maintaining smaller current distortion and ZSCC, a five-level reduced CMV (RCMV) modulation method is proposed in this article, which treats the parallel inverters as a whole. Theoretical analysis reveals that the integrated modulation provides additional base vectors that contribute to smaller total harmonic distortion (THD) of the current, and the selected vectors ensure the nearest-three-vector synthesis and half-reduced CMV. The switching sequences design and neutral point balancing strategy are also developed for dual-parallel three-level inverters, ensuring that the average circulating current is zero and the neutral point voltage is balanced, which are both critical to the proper operation of parallel inverters. Superior performance in terms of CMV, THD, and ZSCC provided by the proposed method in comparison with conventional modulation is verified by comprehensive simulation and experimental results.

中文翻译：

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降低共模电压和环流的双并联三电平逆变器集成调制


已经针对三电平逆变器提出了许多降低共模电压（CMV）调制方法。然而，它们中的大多数都遭受大电流失真，因为仅利用了部分可用基向量。交错并联可以降低CMV和输出电流失真，尽管CMV的降低是有限的，并且相移载波不可避免地会引起大的零序环流（ZSCC）。为了进一步降低CMV，同时保持较小的电流失真和ZSCC，本文提出了一种五级降低CMV（RCMV）调制方法，该方法将并联逆变器视为一个整体。理论分析表明，集成调制提供了额外的基向量，有助于减小电流的总谐波失真（THD），并且所选向量确保了最近三向量合成和一半减少的CMV。还针对双并联三电平逆变器开发了开关时序设计和中性点平衡策略，确保平均环流为零和中性点电压平衡，这对于并联逆变器的正常运行至关重要。通过综合仿真和实验结果验证了所提出的方法与传统调制相比在 CMV、THD 和 ZSCC 方面的优越性能。