“…Generally speaking, GFUs should allow bidirectional power flow. Utility grid, external DC microgrids, external AC microgrids, and ESSs can all work as GFUs [7], [8] to support a specific DC microgrid with the assistance of power electronic devices and associated control strategies, and different types of ESSs can be used in DC microgrids, like batteries, supercapacitors (SCs), fuel cells, etc [9].…”