Abstract
The paper presents a novel modeling approach of the power flow in a bidirectional dual active bridge DC-DC converter. By using basic superposition principles, the mathematical distinction of cases is avoided in the modeling process of the high-frequency transformer currents for different types of modulation. The generalized model is used in the optimization of the converter losses of a 3.3kW electric vehicle battery charger with an input voltage of 400V and a battery voltage range from 280V to 420V. Besides the commonly used control variables such as the phase-shift and the clamping intervals, the variation in the switching frequency is also considered in the optimization process. The optimal modulation including the frequency variation leads to an increase in the converter efficiency up to 8.6% using IGBTs and 17.8% using MOSFETs at the most critical point compared to phase-shift modulation at a fixed switching frequency.
