Dual-Transformer-Based DAB Converter with Wide ZVS Range for Wide Voltage Conversion Gain Application

A control strategy is proposed for the dual-transformer-based dual-active-bridge converter to achieve wide zero-voltage switching (ZVS) range for wide voltage conversion gain range application. The phase-shift control is adopted for the dual-transformer-based converter with minimum power switches employing half bridge output, and a control law is proposed to achieve wide ZVS range and reduce the current-related loss. With the proposed method, four switches of the converter can achieve full range of ZVS. The other two switches can achieve full-range ZVS under positive power flow, while a slightly reduced ZVS region under reverse power flow. Unlike the methods employing three control degrees of freedom, the proposed method only utilizes two decoupled control variables, making the controller easy to be implemented, more reliable, and independent of the converter parameters. In addition, the design of turns ratios for the two transformers is also optimized based on the control law and loss analysis. The effectiveness of the converter with the proposed control is verified by experimental results from a 1-kW prototype.