Analysis and reduction of power losses in PV converters for grid connection to low-voltage three-phase three-wire systems

This paper discusses analysis and reduction of power losses in PV converter systems using conventional Si-IGBTs as well as SiC-MOSFETs. The PV converter system discussed in this paper consists of a boost converter and two half-bridge PWM inverters, considering grid connection to three-phase three-wire low-voltage power systems in Japan. Power losses in Si-IGBTs and SiC-MOSFETs are measured and theoretically discussed from experimental result in a buck converter benchmark. The power losses in PV converters using Si-IGBTs and SiC-MOSFETs are also measured and separated into the components in each part. As a result, it is clarified that the dominant power loss occurs in the two half-bridge inverters, and their switching power losses are larger than the on-state losses. Moreover, application of SiC-MOSFETs to both boost converter and half-bridge inverters makes it possible to improve the overall power conversion efficiency from 93.5% to 95.5% in the Euro-eta definition.