Design and Characterization of a 500 kW 20 kHz Dual Active Bridge using 1.2 kV SiC MOSFETs

High power Silicon Carbide (SiC) semiconduc-tor enable an increase of the power level for the Dual Active Bridge (DAB). This paper presents a concept for a novel high power DAB up to 500 kW. 1200 V SiC MOSFETs are used as power semiconductors, which are operated with a switching frequency of 20 kHz. In order to investigate the feasibility of such high power DABs basic design rules are presented and the influence of parasitic components is deduced. It is shown that these parasitic effects become more and more important with increasing power and therefore cannot be neglected as in the case of lower power DABs. Using a calorimetric measurement setup a detailed loss distribution is presented. Measurements confirm the concept for the parasitic influence and design target of 500 k W

Time Domain Modeling of Zero Voltage Switching behavior considering Parasitic Capacitances for a Dual Active Bridge

To increase the switching frequency in DC/DC converters, soft switching is necessary to limit switching losses. In case of the Dual Active Bridge (DAB), Zero Voltage Switching (ZVS) is used to reduce switching losses. Since the ZVS behavior of the DAB depends on multiple parameters, an accurate model is necessary to ensure operation with minimal losses by applying ZVS. This paper presents an accurate capacitance based time domain (CTD) model for the resonant commutation which enables the calculation of the minimal necessary current, the optimal deadtime as well as the voltage error caused by the nonideal commutation. The parasitics and therefore nonideal behavior of the MOSFETs are considered to further increase accuracy. The model can be used for all operating points commonly applied in single (SPS) and triple phase shift (TPS) modulation. Measurement results obtained with a 500 kW DAB prototype proves the high accuracy of the model

Mirror Source based Overcurrent and Short Circuit Protection Method for High Power SiC MOSFETs

This paper presents a fast overcurrent and short circuit protection based on the mirror source detection method for 1200V/1200A Silicon Carbide (SiC) MOSFETs used in a high power Dual Active Bridge (DAB). It will be shown that this protection method is feasible for a low inductive short circuit caused by a half bridge shoot through, a high inductive short circuit based on a failure inside the load as well as short circuits of Type 1 or hard switching fault. Additionally, the short circuit behaviour is analyzed for different junction temperatures of the MOSFETs. Experimental results proof that using the investigated method always ensures the operation in the Short Circuit Safe operating Area (SCSOA) of the MOSFET after triggering short circuits