Single-Phase Operating Modes for DC–DC Three-Phase Dual-Active-Bridge With YΔ Transformer

Abstract

Dual-active-bridge (DAB) converter is a popular topology for bidirectional dc–dc isolated conversion. The features of this converter are simplicity of control, soft-switching capacity and high power density. The three-phase version (DAB3) shows a lower capacitive filter volume than the single-phase version. However, when DAB/DAB3 converters operate at light load or with a different gain ratio than the unit, it loses soft-switching capacity and increases the rms current, leading to efficiency degradation. The DAB3 converter with a star-delta windings ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Y}\Delta $ </tex-math></inline-formula> ) transformer can keep soft-switching even at light load for gain close to the unit. This work introduces two single-phase operating modes for the DAB3- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Y}\Delta $ </tex-math></inline-formula> converter. These single-phase modes have optimal operating points with different voltage values than the three-phase mode, allowing enhanced performance in applications where voltage variation is required, such as charging and discharging batteries. The work discusses the limits for each operating mode and brings experimental results showing efficiency gains up to 10%.