Modulation strategy for improving the voltage gain of the dual-active-bridge converter

A novel modulation strategy for improving the voltage gain of a dual-active-bridge converter is proposed herein. Under the strategy, the converter performs a high-voltage gain under a low transformer turns ratio, thereby improving the transmission efficiency of the transformer because the large turns ratio typically results in large parasitic parameters, such as leakage inductance or distributed capacitance. In addition, voltage spikes can be avoided as the energy caused by leakage inductance is recycled to the output side. The operating principle of the proposed modulation strategy is discussed in detail herein. Moreover, the zero-voltage switching conditions in both buck and boost modes are analysed and derived. Finally, a prototype with a 350 V high voltage, 48 V low voltage, and 1 kW output power is established, and the conversion efficiencies of 94.2% in buck mode and 93.2% in boost mode are obtained. Experimental results verify the validity of the proposed modulation strategy.