Output-Series Connected Dual Active Bridge Converters for Zero-Voltage Switching Throughout Full Load Range by Employing Auxiliary LC Networks

This paper presents an output-series connected dual active bridge (DAB) converter for efficient zero-voltage switching (ZVS) by employing dual auxiliary LC networks in high-output voltage applications. The dual auxiliary LC networks are integrated into the converter for ZVS throughout full load range. The gate signals of the output side switches can control the current in the LC networks. By analyzing the working modes of the converter, the modulation trajectory is designed in terms of the boundaries of the ZVS range. The conduction loss caused by the auxiliary LC networks is adjusted according to the voltage and load power. The modulation scheme can achieve seamless transition between the adjacent working modes. The conduction loss of the proposed converter is compared with the conventional output-series DAB converter. Although the conduction loss is increased under light loads, all the switches can achieve ZVS. The reduced switching loss can improve the overall efficiency. Finally, a 1.3 kW experimental prototype was built to verify the effectiveness of the proposed converter and the modulation scheme, which demonstrates the ZVS performance and efficiency improvement.