Wide Voltage Range Efficiency Enhancement Scheme for Input-Parallel-Output-Series DAB Converters in 800 V DC Microgrids

Input-parallel-output-series dual-active-bridge (DAB) converter presents an appealing approach in energy storage integrated high-voltage dc microgrids. The wide voltage range of the energy storage battery introduces significant challenges to the optimal design of the DAB converter. To cope with this issue, this article proposes a hybrid modulation scheme to enhance the wide voltage range efficiency. It combines asymmetrical pulsewidth modulation (APWM), phase-shift modulation, and coupled inductor modulation, aimed at optimizing circulating currents and extending the zero-voltage-switching (ZVS) range across wide voltage and load ranges. APWM ensures that the primary and secondary voltages are aligned through the intermediary dc blocking capacitor. Meanwhile, the coupled inductor modulation achieves an adaptive equivalent series inductance. The operational modes of this modulation scheme are outlined, with a thorough analysis of the relationship between root-mean-square (rms) current, phase shift ratio, voltage gain, and output power. Based on these insights, a control strategy is developed to extend the ZVS range with reduced rms currents. To validate the concept, a 2-kW, 100-kHz prototype is designed and tested. The prototype interfaces a 200–400 V battery port to an 800 V dc bus. Recorded efficiencies peak at 98.3% in forward mode and 98.2% in backward mode, with consistently high performance maintained across wide voltage and load ranges.