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

Abstract

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.