Comparison of circuit topologies for active power decoupling toward high power density

Abstract

This paper discusses how to achieve high power density with high efficiency for single-phase AC connected inverter with active or passive power decoupling circuit. An inverter connected to a single-phase grid requires a power decoupling device to compensate power pulsation with twice the grid frequency. As the alternative to an electrolytic capacitor connected to DC-link, active buffer circuits with bi-directional chopper and a flying capacitor converter (FCC) with power decoupling capability have been evaluated in terms of long lifetime. In this paper, Pareto optimization is used to compare the character of the power decoupling circuits in terms of an efficiency and a power density. The volume of capacitors in the FCC with ceramic capacitors can be reduced by 54.6% compared to bulky electrolytic capacitors. As a result, when the 400-V SiC-MOSFETs are used for the FCC at 25 kHz, a maximum power density of 5.3 kW/dm3, which is 1.3 times higher than the power density of the passive topology, can be obtained. Furthermore, the total power loss is reduced by 10.5% in comparison with that of the conventional converter.