| Abstract |
This paper describes theoretical analysis of a power flow and a total stored energy in the capacitor of a neutral-point-clamped modular multilevel converter (NPC-MMC). The NPC-MMC consists of both a three-level structure with common DC capacitors and chopper cells. It requires only half of chopper cells compared to the conventional MMC.In this paper, at first, theoretical analysis reveals the NPC-MMC can supply the AC power from not only the cells but also common DC capacitors. The direct power flow between the DC capacitors and the AC side brings 48\% reduction of the total stored energy in the cell capacitors and the DC capacitors to the conventional MMC.Secondary, the 10-kVA experimental circuit using low-voltage MOSFETs validates the capacitor energy analysis. Measured efficiency reaches extremely high value of 99.3\%. Therefore, it requires neither heat sink nor cooling fans. These experimental results show that the NPC-MMC can realize both downsizing and very high efficiency conversion. |
