Active Thermal Management Method for Output-Parallel DAB DC–DC Converters Under Parameter Mismatches and Asymmetrical Modulation

In output-parallel dual active-bridge (OP-DAB) converters, the asymmetrical phase-shift modulation (PSM) and the mismatched parameters will result in the thermal imbalance, which leads to premature aging and failure. To suppress the thermal imbalance, an active thermal management consisted of an improved PSM and a reliability-based power divider (PD) is proposed. First, a losses model based on double-phase-shift control is established to analyze the power losses and estimate the junction temperature. Second, the reason for the unbalanced thermal distribution under the asymmetrical PSM is studied, and a modulation cycle instead of the switching cycle is adopted in the modulation process to make targeted improvements. Third, based on the estimated temperatures, the reliability-based PD is established by linking IGBT temperature and its failure rate, and the optimal power distribution coefficient is obtained to deal with the negative effect of the mismatched parameters. With the proposed active thermal management method, the thermal distribution becomes balanced and the converter reliability is increased. Besides, the proposed method does not bring a bad effect on the electrical performance. Finally, all theoretical analyses and conclusions are verified based on a simulation example and a prototypic experiment.