Conventional reduced common-mode voltage discontinuous pulsewidth modulation method for a three-level inverter can reduce the common-mode voltage and switching transitions compared with continuous modulation. However, it suffers from poor output current quality and cannot provide additional performance enhancements when applied directly on parallel three-level inverters. Based on the interactions between the parallel inverters, this article reveals that dual parallel three-level inverters could be analyzed and controlled as a single five-level inverter. Based on this idea, a novel five-level discontinuous modulation method is therefore proposed to further reduce the common-mode voltage of the system by half, in addition to dramatically improving the output current quality compared with conventional three-level method. The specific implementation process is explained in detail, and a unique switching sequence design is developed considering keeping zero average circulating current, which is crucial to the proper function of parallel operation. Furthermore, a neutral point voltage balancing strategy through alternatively applying charging and discharging switching sequences is proposed for the five-level modulation process, which can effectively restore the neutral point balance in case imbalance occurs. The effectiveness and advantages of the proposed method are verified by both simulation and experimental results.

中文翻译：

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在并联三电平逆变器上实现五电平 DPWM 以降低共模电压和交流电流纹波

与连续调制相比，传统的用于三电平逆变器的降低共模电压的不连续脉宽调制方法可以减少共模电压和开关转换。然而，它的输出电流质量较差，直接应用于并联三电平逆变器时，无法提供额外的性能增强。基于并联逆变器之间的相互作用，本文揭示了双并联三电平逆变器可以作为单个五电平逆变器进行分析和控制。基于这一思想，提出了一种新颖的五电平不连续调制方法，与传统的三电平方法相比，除了显着提高输出电流质量外，还可以将系统的共模电压进一步降低一半。详细解释了具体的实现过程，并在考虑保持零平均循环电流的情况下开发了独特的开关序列设计，这对于并联运行的正常功能至关重要。此外，针对五电平调制过程提出了交替应用充放电开关序列的中性点电压平衡策略，可以在发生不平衡的情况下有效恢复中性点平衡。仿真和实验结果验证了所提出方法的有效性和优势。针对五电平调制过程提出了交替应用充放电开关序列的中性点电压平衡策略，在发生不平衡时可有效恢复中性点平衡。仿真和实验结果验证了所提出方法的有效性和优势。针对五电平调制过程提出了交替应用充放电开关序列的中性点电压平衡策略，在发生不平衡时可有效恢复中性点平衡。仿真和实验结果验证了所提出方法的有效性和优势。