Abstract：Current-fed isolated bidirectional DC-DC converters (CF-IBDC) are suitable as the interfaces between the batteries and dc bus in the battery energy storage systems. To solve the problem of circulating currents between the CF-IBDCs connected at the DC bus together, a method for suppressing the circulating currents based on the capacitors at the DC bus ports was proposed. Firstly, general conditions for paralleled system’s stability and the balance of dc bus currents were derived based on the dc bus ports’ admittances of the CF-IBDCs. Secondly, the closed-loop admittance at the dc bus port of the CF-IBDCs was analyzed and derived according to the control block diagram of the droop control and the open-loop transfer functions based on the generalized average model. Thirdly, the LC resonance structure at the battery side of the CF-IBDC is found to be the cause of the circulating currents and the imbalance of the dc bus currents after substituting the admittance of the CF-IBDC into the derived general stability conditions. At last, the effects of the DC bus port capacitors on the admittances of the CF-IBDCs were analyzed. Simulations of the paralleled system were conducted, and the correctness of the circulating current suppression method is verified by the simulation results.
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2022, Vol. 37 
