A soft-switching current-fed isolated bidirectional dc-dc converter with low circulating power and easy-implemented control strategy

In the battery energy storage systems, the existing isolated bidirectional DC/DC converters fail to achieve high-efficiency because it is difficult to achieve soft-switching and low current stress simultaneously in the full operation range. A novel current-fed isolated bidirectional dc-dc converter with two transformers and two half bridges at the high voltage side is proposed to solve the problem. The PWM plus dual phase shift modulation (PPDPS) with voltage-match control is applied to keep peak and rms current of the transformers low. ZVS for most switches can be ensured by the control strategy, while practical ZVS for the rest switches is achieved by the magnetizing currents of the transformers. Therefore, low conduction losses and switching losses can be obtained in the proposed converter. The theoretical analysis and the soft-switching capability of the proposed converter are verified by the experimental results.