Battery Energy Storage System With Interleaving Structure of Dual-Active-Bridge Converter and Non-Isolated DC-to-DC Converter With Wide Input and Output Voltage

We propose a circuit topology suitable as a battery charge/discharge tester with a DAB converter and a non-isolated dc-dc converter as a module structure. The module structure can be configured to have a wide input and output voltage range because it is easy to expand. DAB converters are used for bidirectional power transfer and galvanic isolation. By controlling the phase difference of the voltages across the DAB to be almost identical, the generation of circulating current due to the phase difference is minimized, and the ZVS is guaranteed. In addition, by switching at a phase angle that flattens the DAB switch current, the peak current is reduced to diminish the switch's conduction loss, lowering the switch current rating, and reducing the magnetic core size. The non-isolated dc-dc converter is used to control the battery output voltage. Through the interleaved structure, good dynamic characteristics and current ripple can be reduced, so the effect of improving the battery lifecycle can be expected. We present four series-parallel structures of the proposed converter and compare them with the case of generating an output voltage only with a DAB converter. Analyze the characteristics of automatic voltage balancing due to the difference between the input capacitors' initial voltage and capacitance connected in series. We analyze the features of the proposed system through simulation and verify the technical feasibility and excellence of the proposed battery charge/discharge tester through charge/discharge experiments using supercapacitors instead of batteries.