A Fundamental Harmonic Analysis-Based Optimized Scheme for DAB Converters With Lower RMS Current and Wider ZVS Range

To improve the efficiency of the dual active bridge (DAB) converter working in the low- and medium-power ranges, this article proposes a new triple-phase shift (TPS) modulation scheme based on frequency-domain fundamental harmonic analysis (FDFHA) with lower root mean square (rms) current and wider zero-voltage switching (ZVS) range. The DAB converter's Fourier decomposition expression under TPS is generated, and the FDFHA expression is created using fundamental harmonic analysis (FHA). With the rms current as the optimization target, the operating point with the smallest rms current is found by solving for it using the extended global optimum condition (EGOC) that applies to the FDFHA expression. Based on this, a control strategy with a simple controller structure is established, which has excellent dynamic performance. In addition, when comparing the proposed scheme to other optimized schemes, the results show that the proposed scheme can drastically lower the rms current in the low- and medium-power ranges and achieve a wider ZVS range, notably in the low-power range to enable all switches to achieve ZVS. Finally, an experimental prototype with a peak efficiency of 95.95% was built to verify the effectiveness of the proposed scheme.