Experimental analysis of phase shift modulation methods effects on EMI in dual active bridge DC-DC converter

Abstract

Dual active bridge DC-DC converters (DAB) are one of the bidirectional converters and mainly used in electric vehicles and micro grids. With the increasing number of electric vehicles in use, and the increasing amount of batteries in these vehicles and rapidly spanning micro grids, the importance of DAB converters has increased and they are expected to be smaller in size and operate at higher power levels. The reduction in size has increased the importance of power density and efficiency, which are two significant parameters of DAB circuits. One of the methods to increase efficiency and power density is to increase the switching frequency. However, with the increase at the switching frequency, electromagnetic interference (EMI) in the DAB circuit also increases.In this manuscript, the change in the EMI values emitted by conduction, according to the phase shift modulation methods at DAB converters are evaluated. Also the effect of type of MOSFETs on conducted EMI is examined. Prototypes of the DAB converters by using Si and SiC MOSFETs with power rating of 1 kW are designed and developed. Switching frequency of converter is 25 kHz and leakage inductance is determined 81uH and 75uH. Si based circuit is operated with %88.5 efficiency. SiC based circuit is also operated with %88 efficiency. The designed circuits are operated using the phase shift modulations SPS and DPS. Conducted emission noise emitted by these circuits are analyzed by dividing them into common mode and difference mode noises. It has been observed that the EMI value when using SPS method is 15–20 dBµV lower than the EMI when using DPS method. The relationship between the measured noises and the efficiency of the circuits was observed.