Hybrid AC-DC microgrids with energy storages and progressive energy flow tuning

Modern distributed sources and loads can either be ac or dc. It is thus possible to have ac and dc sub-grids inter-tied to form hybrid microgrids with lesser power conversion and hence higher efficiency. However, operation of hybrid microgrids to gain these advantages is not trivial, and is so far limited. It is therefore the theme here to develop a control scheme for the hybrid microgrids so that they can operate efficiently with progressive energy flow tuning and no requirement for fast communication links. A plug-in scheme is also proposed for progressive and selective charging / discharging of storages, which are likely to be present in the hybrid microgrids for energy smoothing and ride-through purposes. The overall scheme has already been verified in experiment.