Protection of Low-Voltage DC Micro-grids

LV dc microgrid is used to interconnect distributed resources and sensitive electronic loads. To ensure reliable operation of the LV dc microgrid, it is important to have a well-functioning protection system. When designing an LV dc microgrid protection system, knowledge from existing dc power systems can be used. However, in most cases, these systems use grid-connected rectifiers with current-limiting capability during dc faults. In contrast, an LV dc microgrid must be connected to an ac grid through converters with bidirectional power flow and, therefore, a different protection-system design is needed. In this paper, the operating principles and technical data of LV dc protection are presented. Furthermore, different fault-detection and grounding methods are discussed. The influence of the selected protection devices and grounding method on an LV dc microgrid is studied through simulations. The results show that it is possible to use available devices to protect such a system.