Comparative Analysis of Hybrid NPP and NPC Seven-Level Inverter With Switched-Capacitor

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%.