Half bridge NPC inverter and its three phase application with constant common mode voltage

摘要

In the transformerless grid connected photovoltaic system, the inverter is the main component. In order to improve the efficiency of the inversion system, several topologies have been applied, among which three level NPC inverter is a kind of popular application. Because the three level NPC inverter has the advantages of low switching losses, good common mode behavior and the small output distortion. This paper proposed a kind of novel three level half bridge NPC inverter which only applies four switches with a constant common mode voltage. Compared to the traditional half bridge NPC inverter, the proposed topology consumes less devices and has a lower conducting losses. The common mode model of the novel topology is analyzed which has verified the good common mode behavior. The three phase extended topology of the proposed inverter is also introduced with a novel modulation strategy. With the proposed modulation strategy, the three phase inverter has a constant common mode voltage. Finally, the simulation and experimental results illustrated the theoretical findings.