Bidirectional DC-DC Converter Utilizing Coupled Inductors for Energy Storage System

In future power systems, the influence of diverse renewable energy sources will lead to power supply imbalance and energy intermittency. Energy storage systems with bidirectional operation mechanisms are needed to address these challenges. This paper proposes a non-isolated bidirectional DC-DC converter for energy storage systems. On the battery side, two sets of coupled inductors are used to achieve high voltage gain and reduce current ripple on the low-voltage side. The DC bus side employs a three-level neutral-point clamped structure to mitigate the problem of high switch voltage ratings. Finite element simulation is conducted on the circuit's magnetic components, and an improved magnetic core with two materials and varied gap distributions is introduced. A comparative analysis of the losses in the two magnetic components is also provided. Finally, following the design process outlined in this paper, a converter with a low-voltage side of 60 V, a high-voltage side of 400 V, a rated power of 300 W, and a switching frequency of 100 kHz was developed and tested. Experimental results demonstrate the feasibility of the proposed bidirectional topology, achieving a maximum efficiency of 93.72% in step-up stage and 92.33% in step-down stage under the condition of a 300 W output power.