Comprehensive Analysis of Asymmetric Modulated Dual-Active-Bridge Converter and Its Hybrid Control Strategy

Dual active bridge (DAB) converter has been widely used in distributed power supply, new energy vehicles, energy storage systems, etc. Their modulation strategy is an important research direction. At present, the research on modulation strategy is basically symmetric phase shift, but it is not enough to generalize modulation strategy comprehensively. In this article, an asymmetric phase-shifting (APS) strategy is proposed to control the power flow by simultaneously adjusting the asymmetric duty cycle and the phase-shifting angle. With this modulation scheme, the current stress and cyclic power loss can be reduced by adjusting the modulation ratio of the inductor current waveform. As a result, the light-load efficiency can be improved compared with the conventional symmetric modulation scheme. The power characteristic, current stress, soft switching characteristic, and backflow power of this modulation strategy are analyzed and calculated comprehensively. Then, based on this asymmetric strategy, a hybrid modulation strategy that can achieve ZVS over the entire power range with low current stress, low return power, and minimum rms current at light load is proposed. Finally, a 100–50 V/300 W prototype is built to verify the analysis.