Bottom-up and recursive interconnection for multi-layer DC microgrids

We propose a recursively scalable DC infrastructure starting off from simple DC nanogrids (subsystem) that are interconnected via a DC power bus line to form a cluster. We have conceived a non-droop based procedure to exchange power from one subsystem to another in order to balance demand/generation fluctuations within the community without requiring any central monitoring or control. To scale the procedure to higher layers we further propose three approaches that could be used for managing power exchanges between clusters. The approaches are compared using analogies with the internet architecture i.e. circuit-switching, packet-switching and virtual switching. Each approach is analyzed in its ability to provide decoupling between analog and digital-centric goals as well as between infrastructures. Furthermore, we discuss whether the approaches could verify the four ground rules of the internet. The 2-layer architecture and the procedure for DC power exchange has been validated in practice on a full-scale 19 DC nanogrids installed in inhabited houses in Okinawa. The evaluation of the multi-layer exchange procedure is still ongoing.