Multi-objective Optimization for Dual Active Bridge Converter Under Variable-Frequency Single-Phase-Shift Modulation

The dual active bridge (DAB) converter serves as a dc transformer in high-power applications. Efficiency and power density are significant optimization objectives for DAB converters, influenced by factors such as modulation strategy, converter parameter, magnetic components design, etc. Variable-frequency (VF) single-phase-shift (SPS) modulation has been employed to improve light load efficiency, which is suitable in scenarios where the input and output bus voltages remain constant. However, under this modulation strategy, converter parameters and magnetic components have received little optimization. This article presents a multi-objective optimization method for DAB converter under VF SPS modulation. To ensure rated power and light-load zero-voltage-switching (ZVS), the design range of inductance and switching frequency is determined while considering nonidealities. Pareto optimization is applied for magnetic components design under the specific modulation strategy, balancing efficiency and power density. Finally, the switching frequency is optimized under different loads for high efficiency. A 6.4 kW DAB prototype is developed for experiment, verifying the multi-objective optimization is reasonable. Compared with traditional SPS modulation, the measured efficiency of optimized VF SPS modulation increases by 1.7% and 1.2% under full load and 20% load conditions respectively, proving the effectiveness of the proposed optimization method.