In this work, the general structure of a hybrid NPP/NPC seven-level inverter is derived from a dual-T-type inverter. Compared with the original structure, the general structure is more flexible as there are four specific circuit configurations to meet different applications. In addition to self-balanced capacitor voltages and boost capability, various commercial NPP and NPC modules can be used to speed up the design process. Circuit description, operation principle, modulation and simulation results are analyzed comparatively. Theoretical analysis and simulation comparison indicate that the four configurations of the hybrid NPP/NPC inverter have their own merits and demerits. Especially, except for a bidirectional switch, all switching components of the NPP + NPC configuration have the same voltage stress as the dc input voltage making it is better in the aspect of component selection, and it is more suitable for high voltage applications. The performance of the NPP + NPC inverter is experimentally demonstrated by an 1kW prototype and its efficiency is closed to 96%.

中文翻译：

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混合核电站与带开关电容的NPC七电平逆变器对比分析

在这项工作中，混合 NPP/NPC 七电平逆变器的一般结构源自双 T 型逆变器。与原来的结构相比，通用结构更加灵活，有四种具体的电路配置，以满足不同的应用。除了自平衡电容器电压和升压能力外，还可以使用各种商用 NPP 和 NPC 模块来加快设计过程。电路描述、工作原理、调制和仿真结果进行了比较分析。理论分析和仿真对比表明，混合NPP/NPC逆变器的四种配置各有优缺点。特别是，除了双向开关，NPP+NPC配置的所有开关元件都具有与直流输入电压相同的电压应力，使其在元件选择方面更好，更适合高压应用。NPP+NPC逆变器的性能通过1kW样机进行实验验证，其效率接近96%。