In applications such as ship propulsion and off-shore wind power generation, it is important to minimize the volume of medium voltage power converters. To make this possible, a novel five-level converter topology is proposed in this paper. This converter is realized by connecting two half-bridge (HB) cells with a three-level neutral point clamped (3L-NPC) unit. In each HB cell, the switches are directly clamped to DC side capacitors where the larger volume high-voltage flying capacitors are avoided. By adopting the 3L-NPC unit, the volume of the proposed converter is further reduced. A comprehensive comparison result shows that the volume of the proposed converter is more than 7% less than existing five-level converters. The operation principle and modulation method of this converter are also introduced. Based on the phase-shift pulse width modulation (PS-PWM) method, the capacitor voltages of the proposed converter can be self-balanced. Simulation and experiment results are shown to verify the performance of this converter and the validity of the theoretical analysis.

在船舶推进和海上风力发电等应用中，尽量减少中压功率转换器的体积非常重要。为此，本文提出了一种新颖的五电平转换器拓扑结构。该转换器是通过将两个半桥 (HB) 单元与一个三电平中性点钳位 (3L-NPC) 单元连接来实现的。在每个 HB 单元中，开关直接钳位到直流侧电容器，避免了较大体积的高压飞跨电容器。通过采用 3L-NPC 单元，所提出的转换器的体积进一步减小。综合比较结果表明，该变流器的体积比现有的五电平变流器减少了7%以上。还介绍了该转换器的工作原理和调制方法。基于相移脉冲宽度调制（PS-PWM）方法，所提出的转换器的电容器电压可以自平衡。仿真和实验结果验证了该转换器的性能和理论分析的有效性。