A Dual-Side Variable Duty Cycle Phase-Shift Modulation Strategy for DAB Converter With Minimal Current Stress

Nowadays, DAB converters are widely used due to the advantages of wide voltage regulation range, high efficiency, and easy realization of soft switching. In order to ensure the efficient operation of DAB, there are increasing studies on three degrees of freedom modulation schemes, but the problems of high current stress and narrow soft switching range especially in light load range still affect the performance of DAB. Therefore, a dual-side variable duty cycle phase-shift modulation (DVDM) is proposed in this paper, in which the duty cycles of the primary and secondary side switches of DAB change simultaneously. Lagrange multiplier method (LMM) and Karush-Kuhn-Tucker (KKT) conditions are utilized to optimize the peak-to-peak inductor current under DVDM control, and obtains a complete optimized modulation scheme. By comparing the RMS current and soft switching characteristics of DVDM control with existing three degrees of freedom modulation schemes, the advantages of the DVDM control can be proved. Finally, a 250 W experimental prototype with 50 V input and 25 V output is built under 100kHz switching frequency to verify the above analysis. The obtained peak efficiency is up to 95.48%.