An Optimal Primary-Side Duty Modulation Scheme With Minimum Peak-to-Peak Current Stress for DAB-Based EV Applications

Dual active bridge (DAB) is a popular interface between energy sources and electric vehicle storage systems because of its galvanic separation, bidirectional power transmission, and extensive voltage adjustability. To overcome the drawbacks of conventional modulations, an optimal primary-side duty modulation (OPDM) is proposed in this article, which combines phase-shift modulation and asymmetrical duty modulation on the primary side to achieve a compromise between high efficiency performance and lower control complexity. To begin with, under traditional DAB modulations, modes attaining all devices zero voltage switching (ZVS) are frequently associated with high peak current stress or indirect power transfer, which can be avoided by OPDM. Second, under OPDM, all six typical operation modes can realize all semiconductors ZVS, where full-power-range ZVS can be realized simply to reduce switching loss. Third, under fixed transmission power, the minimum peak-to-peak current stress can be obtained through Lagrange multipler method. Peak current, rms current, and soft-switching characteristics under OPDM outperform conventional control methods. Eventually, a DAB prototype is established to verify the effectiveness of proposed OPDM method.