A performance comparison of SiC and Si devices in a bi-directional converter for distributed energy storage systems

Abstract

Due to its superior electrical characteristics resultant from material properties such as high critical electric field, larger bandgap and higher thermal conductivity in comparison to Silicon (Si), Silicon Carbide (SiC) devices are becoming increasingly popular in the power electronics industry. Many SiC device types have been commercialised during the past decade. In this paper, a performance comparison between SiC MOSFET, SiC BJT and SiC SJT based bi-directional converters, targeting energy storage applications, has been made along with a Si IGBT version. Conduction losses and switching losses have been calculated and compared with the aid of measured forward I–V curves and double-pulse testing in a clamped-inductive test configuration, respectively. In order to validate the continuous operation, the device performances when operating the bi-directional converter in DC/DC conversion mode have been compared. The efficiency of the converters have been assessed at 20 and 40 kHz switching frequencies and up to 6.6 kW output powers and 27 A input current levels per half-bridge. From the results discussed, it is clear that the SiC devices surpass Si IGBTs in switching performance. During 250 V to 500 V boost conversion at 20 kHz, a loss reduction of 50.8% has been observed at a 4.9 kW power output in SiC MOSFET converter, in comparison to the Si IGBTs. At 40 kHz, peak efficiencies of 98.8% and 98.6% have been demonstrated by SiC MOSFET and SiC BJT converters, respectively. The aim of this comparison is to identify and set a guideline as to the most appropriate circumstances for using each device technology.