A Multilevel Current-Fed DAB Converter With Direct Power Transfer

Abstract

This paper proposes a novel modulation scheme for a multilevel Dual Active Bridge (DAB) DC–DC converter with direct power transfer capability in PV applications. The proposed modulation scheme has the ability to shape the high-frequency current waveforms, leading to lower peak/RMS values of current over a wide range of PV voltages. In addition, the multi-level structure allows for the use of low-voltage devices with significantly smaller channel resistance. The power circuit topology is based on a current-fed half-bridge (CF-HB) converter, with a coupled inductor, which facilitates the direct power transfer, resulting in significantly lower conduction losses. In summary, the proposed topology tackles both the conduction and switching losses through a multi-faceted approach by using the novel modulation scheme, the multi-level structure, the direct power transfer, and the inherent soft-switching. Detailed mathematical analysis and extensive experimental results demonstrate the superior performance of the proposed converter.

Keywords

• 4-level flying capacitor (4L-FC) DC–DC converter
• direct power transfer (DPT)
• dual active bridge (DAB)
• modulation scheme
• multilevel converter
• PV application