ELECTRICITY SUPPLY SYSTEM

A controller (70) for a DC microgrid (1) and associated renewable energy source, RES, units (60). The DC microgrid comprises energy storage, ES, units (20) and consumer units (40, 50) that are interconnected by a DC distribution network (10). The DC microgrid is connected to an AC grid (2) to allow power to flow between the DC microgrid and the AC grid. The controller has three levels: a first for controlling daily operations, a second for making optimizing adjustments to the first level control based on historical data and the weather forecast, and a third which is an analysis level for modelling how changes in provision of the number of RES units and ES units would affect the DC microgrid's dependency on power from the AC grid. The output of the third level thus enables incremental changes to be made to provision in order to reduce, ideally eliminate, the net power demand from the AC grid.