Cascaded multilevel inverter cells produce double-grid frequency ripples that require a large electrolytic capacitor bank for every cell, resulting in reduced system reliability and lifespan. This paper proposes a new generalized power-decoupling methodology that is applicable to any three-phase cascaded multilevel inverter topology. The proposed flux cancellation method is based on forcing a three-phase double-frequency ripple into the core of a three-phase transformer. The flux components from each phase, which are phase-shifted by 120°, cancel each other inside the core. Therefore, no power-decoupling capacitor is required in this method. A three-port bidirectional isolated converter is proposed to cancel the three-phase 120 Hz pulsating power in a single high-frequency (HF) core. High-leakage inductances and imbalances among the ports of a HF transformer are a topographical challenge. The imbalance in leakage inductances can be reduced by improving the winding schemes. However, increased leakage and imbalance among the three ports are unavoidable under high voltages because of the need for higher isolation. A universal solution involves the application of a phase shift-based controller to obtain balanced and reduced voltage ripples among the three DC links. This paper presents the dynamic analysis and controller design procedure. Results of the prototype hardware confirm the suitability of the proposed power-decoupling methods.

级联的多电平逆变器单元会产生双电网频率纹波，每个单元都需要一个大的电解电容器组，从而降低了系统的可靠性和使用寿命。本文提出了一种适用于任何三相级联多电平逆变器拓扑的新型通用功率去耦方法。所提出的磁通消除方法基于将三相双频纹波强加到三相变压器的铁心中。每个相的磁通分量相移了120°，它们在铁心内部相互抵消。因此，该方法不需要电源去耦电容器。提出了一种三端口双向隔离转换器，以消除单个高频（HF）铁芯中的三相120 Hz脉动功率。高频变压器端口之间的高泄漏电感和不平衡是一个地形挑战。可以通过改进绕组方案来减少漏感的不平衡。但是，由于需要更高的隔离度，因此在高压下三个端口之间的泄漏和不平衡的增加是不可避免的。通用解决方案涉及应用基于相移的控制器，以在三个直流链路之间获得平衡且降低的电压纹波。本文介绍了动态分析和控制器设计过程。原型硬件的结果证实了所提出的功率去耦方法的适用性。在高压下，三个端口之间不可避免的漏电和不平衡的增加是不可避免的，因为需要更高的隔离度。通用解决方案涉及应用基于相移的控制器，以在三个直流链路之间获得平衡且降低的电压纹波。本文介绍了动态分析和控制器设计过程。原型硬件的结果证实了所提出的功率去耦方法的适用性。在高压下，三个端口之间不可避免的漏电和不平衡的增加是不可避免的，因为需要更高的隔离度。通用解决方案包括应用基于相移的控制器，以在三个直流链路之间获得平衡且降低的电压纹波。本文介绍了动态分析和控制器设计过程。原型硬件的结果证实了所提出的功率去耦方法的适用性。