Power Flow Characterization of a Bidirectional Galvanically Isolated High-Power DC/DC Converter Over a Wide Operating Range

This paper studies the power flow characterization of a bidirectional galvanically isolated high-power dual active bridge dc/dc converter. In experimental tests at the University of Michigan, we have observed three phenomena, which we term as internal power transfer, phase drift, and low system efficiency, that are present under certain operating conditions. These phenomena cannot be explained by conventional power transfer analysis. The authors develop a new model, based on a detailed analysis over a short time scale, that incorporates additional parameters, including the power semiconductor voltage loss and dead time. The new power flow model may be used to explain the observed phenomena and to characterize the power flow of the converter. The model may also be used to perform accurate power flow computations over a wide operating range, thereby supporting optimal hardware design, operating range selection, and power management strategy development. Experimental results are presented to illustrate the validity of the new model.