The dual active bridge (DAB) converter is widely used for bidirectional DC–DC conversion due to its high efficiency and soft-switching capability. While traditionally applied to DC loads, its use in UPS systems faces challenges as the AC inverter introduces double-line-frequency pulsating power, leading to increased circulating current, a narrowed ZVS range, and efficiency degradation under conventional single-phase shift (SPS) control. This paper investigates triple phase shift (TPS) control for DAB converters to address these issues. By exploiting three-phase-shift variables, TPS reduces circulating energy, extends ZVS, and improves efficiency under AC load conditions. Finally, a 3 kW prototype with a 48-56 V battery input and a 120 VAC output is built to verify the theoretical analyses. The highest efficiency of 95% is achieved at 70% load.
