부산대학교 도서관

Multi-port converters have gained attention in the last decade due to developments in bipolar dc microgrids, hybrid energy storage systems, and emerging high-efficient grid-interactive buildings. Such buildings can be supplied from an active front-end (i-AFE) converter (ac-dc), which provides an interface between the ac grid and dc distribution inside homes or other small buildings. This application has specific requirements related to the voltage levels, protection zones, and isolation. Following the standard NPR9090, it is a general practice to provide isolation between ac part and dc, where commonly 350 $\mathrm{V}_{dc}$ are used for the power distribution. However, an additional isolation (dc-dc) stage is required when extra-low voltage dc (ELVDC) is necessary. To reduce the power processing stages for grid-interactive buildings, this paper proposes a multi-port i-AFE converter, adding a passive center-tapped rectifier port to a conventional dual-active bridge (DAB). In this topology, DAB converter is responsible to control the main dc port (350 $\mathrm{V}_{dc})$, while the extra-low voltage port (48–60 $\mathrm{V}_{dc})$ is supplied by the center-tapped rectifier. To evaluate this concept, a 5-kW prototype was built, and laboratory tested, resulting in a peak efficiency of 95.6% for the main port and 92.80 % for the ELVDC port.