New Triple-Output Quad-Active-Bridge DC/DC Converter Employing a Four-Leg Inverter Input Stage

Charging stations for electric vehicles require electrical isolation between the charging ports. Therefore, this paper proposes a multi-port DC/DC converter structure that combines three conventional dual-active bridge converters (DABCs) where the primary side switching stages are integrated into a single four-leg inverter, and three individually isolated output ports (4L3) are provided. This quad-active bridge converter (QABC) structure features fewer semiconductor devices than three parallel connected single-phase DABCs with a six-leg inverter $(3\times 2\mathrm{L}3$, resulting in 6L3). The 4L3 QABC is also advantageous compared to a known variant where the primary side switching stages are integrated into a three-leg inverter (3L3), as the 4L3 QABC does not limit the duty cycles of the primary side transformer voltages. Therefore, the input voltage can be fully utilized, which allows lower transformer RMS currents compared to the conventional 3L3 QABC. Our analysis explains the operation and modulation and underscores the 4L3 QABC’s enhanced performance that consistently diminishes transformer current across all operational ranges, achieving a 20% reduction in the sum of squared transformer RMS currents at rated operation compared to the conventional 3L3 QABC. Furthermore, we show a virtual prototype with an integrated cooling system, which reaches a power conversion efficiency of 98.4% for 750V/400V primary/secondary voltages at 120kW and a power density of $10\mathrm{k}\mathrm{W}/\mathrm{d}\mathrm{m}^{3}$.