On voltage standards for DC home microgrids energized by distributed sources

Abstract

Owing to the increasing prevalence for DC home appliances and distributed energy resources, the concept of a DC home microgrid is attracting considerable attention. This paper is to investigate voltage standards for DC home microgrids. First, a DC home microgrid configuration is proposed. All home loads are divided into five groups for separate connection to a common DC bus. An alternative path is designed to supply the high-power load groups through the public AC grid with less power conversion stages, when local sources are deficient. Second, voltage levels and wire cross-sections for different load groups are discussed, according to line thermal limits, power losses, and voltage drops. The results show that, if 120 volts is chosen for the DC bus, higher voltage standard over 120 volts could not bring loss savings for load groups. It can also be concluded that, 24 V DC could be a standard only for extra-low power appliances in a small house or single room, because of big losses; instead, 48 V DC may be better suitable for lighting and low-power appliances, especially when most of them could be working on 48 V DC in future.