Analysis and suppression of electromagnetic interference caused by SiC-based dual active bridge converters

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 study, phase shift methods that can be applied on SiC MOSFET based DAB circuit and the effect of these methods on EMI changes are evaluated. A SiC-based DAB circuit prototype that can operate at 1000W power outputs has been designed and developed. The switching frequency was determined as 1kHz and the leakage inductance value was fixed as 25µH. After this point, the circuit was operated with the SPS method with certain phase shift ratios and the EMI results were separated into noise modes and recorded. Later, by changing the phase shift method, phase shifting methods were discovered among 1189 different methods, the efficiency of which did not change but yielding lower EMI results. It has been shown that when the circuit is operated with the DPS method, it emits with 7dBuV less conducted EMI than the SPS method, while operating at 90% efficiency as in the SPS method. Phase shift methods were examined with simulation programs and experimental system, and the results were shown. Therefore, it has been shown that the EMI values of the circuit are suppressed with the same efficiency by making software changes at the source without making any hardware additions.