Soft-switching and low conduction loss current-fed isolated bidirectional DC-DC converter with PWM plus dual phase-shift control

In battery energy storage systems, the battery and DC bus voltages vary greatly. This makes it difficult for the battery storage converter to maintain high efficiencies under all circumstances. A current-fed isolated bidirectional DC-DC converter is presented in this paper. This converter contains two series transformers, two conventional current-fed half-bridges at the battery side and two half-bridges at the DC bus side. PWM plus dual phase shift modulation with equal duty cycles and voltage-matched control is applied to ensure ZVS of all the switches and low conduction losses. The average and backflow power transmission equations and soft-switching conditions for all of the operation modes in the full operation range are analyzed comprehensively in this paper. Then six recommended modes are addressed based on the above analyses. Moreover, the control scheme and hardware design guidelines are addressed. Finally, the above theoretical analyses and control strategy are verified by experimental results.