Bidirectional soft-switching dc-dc converter for battery energy storage systems

The study introduces a bidirectional dc-dc converter with current- and voltage-fed (VF) ports that features soft switching in both buck and boost operating modes. The converter can be used for integration of low-voltage DC sources, such as batteries into a dc bus of considerably higher voltage or a dc link of a grid side inverter. Zero current switching, assisted with the leakage inductance of the isolation transformer, can be achieved at the current-fed side along with zero voltage switching of the VF side, assisted by snubber or intrinsic capacitances of the transistors. Soft switching can be maintained over a wide range of voltage and power levels, regardless of the energy transfer direction. Converter operation is described and theoretical findings were verified with experimental results obtained by means of a 300W prototype operating at a switching frequency of 100kHz and designed for integration of a 24V battery into 400V dc bus. The converter proposed is compared in terms of efficiency to other competing soft-switching full-bridge topologies implemented with the same components.