Increase in Power Conversion Efficiency of Bidirectional DC-DC Converter Using 1: 1 Transformer and Pulse-Frequency Modulation Control

This paper proposes a circuit structure of bidirectional dc-dc converter. This structure uses two switches, two capacitors, a 1: 1 transformer, and a control circuit for pulse-frequency modulation. The windings of the transformer are connected in a series-aiding configuration to reduce current ripples and to increase power conversion efficiency eta(epsilon). The capacitors and the leakage inductance of the transformer provide soft-switching conditions. When the proposed converter was designed to operate at a switching frequency of 110-240 kHz, input/output voltages of 100-400 V, and output power P-o of 30-300 W, eta(epsilon) was >= 97% for P-o >= 90W and 93.5% at P-o = 30 W. Experimental results show that the proposed converter is suitable for use in photovoltaic power conversion systems and energy storage systems.