A Generic Modulation Approach to Suppress DC Bias in Dual Active Bridge Converters

In order to suppress the transient DC bias current in dual active bridge (DAB) converters, this study introduces a scheme of global modulation coupled with suppression. It may lead to a significant bias in transient current when the DAB state changes, which may lead to magnetic saturation and circuit damage. To address this problem, this paper explores a modulation strategy that integrates a global optimal modulation. This study found that the expression for the transient DC bias in DAB converters can be analyzed using an analytical equation derived from the initial current of the modulation process, rather than based on the current at each commutation. After analysis, it was found that the initial current expressions under each mode are the same, from which a new modulation strategy was derived. This strategy newly introduces three phase-shift values, and can suppress the bias current and achieve unity in any transition between two modes. which simplifies the size of the hardware and the complexity of the suppress scheme. To validate the proposed modulation scheme, the paper includes simulation results that confirm its effectiveness.