ZVS Soft Switching Operation Range Analysis of Three-Level Dual-Active Bridge DC–DC Converter Under Phase Shift Control Strategy

The switches of three-level dual active bridge (3L-DAB) dc-dc converter under phase shift control may operate with hard working especially when the voltage conversion ratio is not equal to one, which will lead to high power loss and low system efficiency. A comprehensive analysis of the ZVS soft switching operation range of 3L-DAB is presented for the first time. The power characteristics of 3L-DAB operating under phase shift control is analyzed. Then, the ZVS operation range of the switches in the primary and secondary sides varied with phase shift ratios and voltage conversion ratio is deduced. The ZVS operation range is obtained by using steady-state time domain analysis under two conditions, without and with considering the junction capacitance of the semiconductor, and the comparative analysis are carried out later. Finally, simulation and experimental results obtained from a 3L-DAB prototype verify the discussed theoretical analysis.