Research on Current Stress Optimization for Dual Active Bridge Converters

Dual active bridge (DAB) converter technologies are advanced DC/DC converter topologies widely adopted in solid-state transformers, DC microgrids, and other applications. However, the traditional design employs the conventional single-phase-shift (SPS) modulation that brings problems such as increased backflow power, rising current stress, and reduced efficiency when the voltage ratio deviates from one. Improved symmetry and asymmetry modulations have been proposed to solve these issues. This paper investigates the effects of dual-phase-shift (DPS) and unilateral asymmetric PWM modulation (UAPM) on the peak-to-peak current and zero voltage switching (ZVS) for DAB converters. The mathematical models of transmission power, peak-to-peak current, and ZVS ability of SPS, DPS, and UAPM were derived through detailed analysis of their operations. In addition, the optimization strategies and benefits achieved by DPS and UAPM through KKT conditions were compared. It was found that both DPS and UAPM significantly optimized the performance of peak-to-peak current and ZVS ability, where UAPM exhibited good performance under high voltage ratio and light load.