A high-efficiency variable modulation strategy for a dual-active-bridge converter with a wide operating range

This paper proposes a variable modulation strategy for a dual-active-bridge (DAB) converter with a wide operating range to achieve high efficiency. In the propose method, four voltage modulation strategies are automatically changed for efficiency optimization under the operating voltage and the output power. To do this, the boundary conditions of each modulation region are derived to minimize the power loss, and a seamless mode transition algorithm between each modulation strategy is introduced. A 3kW DAB converter whose primary voltage is 380V and the secondary voltage ranges from 100V to 500V has been built. The experimental results show that the DAB converter with the proposed modulation strategy achieves peak 98.9% peak efficiency under 400V output voltage condition.