Active Saturation Mitigation in High-Density Dual-Active-Bridge DC–DC Converter for On-Board EV Charger Applications

This article presents a transformer saturation prevention algorithm (SPA) targeting dual-active-bridge (DAB) dc-dc converters utilized in bidirectional, two-stage electric vehicle (EV) on-board battery chargers. Saturation prevention is achieved by detecting the variation in transformer current slope near the boundary of saturation and applying duty-cycle offsets to the DAB converter full bridges. Compared to alternative methods of saturation mitigation, the proposed algorithm offers the following benefits: Lower transformer design safety margins which enable volume reduction with minimal harm to efficiency, and low-cost implementation using a single low-cost current sensor even at high converter switching speeds. Experiments on a custom 6.6-kW on-board EV charger confirm the controller functionality and initial converter analysis. A peak converter efficiency of 96.8% with a transformer volume of 80 cm³ is achieved, which is a 50% volume reduction in comparison to other academic works.