Equivalence of Primary Control Strategies for AC and DC Microgrids
administration (http://nordman.lbl. gov/docs/nano.pdf). It must have at least one load or sink of power—which could be electricity storage—and at least one gateway to the outside. Electricity sources aren’t part of the nanogrid, but a source often will be connected only to a single nanogrid. Figure 1 illustrates a simple nanogrid structure. All power flows are accompanied by communications— either wired or wireless. Interfaces to other power entities are through gateways within the nanogrid controller. Each nanogrid manages the power distributed to its loads. The controller uses price to mediate local electricity supply and demand, both within the nanogrid and in exchanges across gateways. The nanogrid controller receives requests for power, grants or revokes such requests, measures or estimates power, and sets the local price. Nanogrids implement power distribution only—they perform no functional for which it’s possible to estimate the replacement cost. With this increasing complexity at the “edge” of the grid, total central control becomes infeasible, making new system designs a necessity. In addition, many usage contexts lack grid connectivity, sometimes or always, but have the same, if not greater, need to match supply and demand. Energy price—and the ability to communicate this price among supply and demand units at all scales—is central to making intelligent choices regarding the timing and amount of energy used. Nanogrids can provide local operational management with lower costs and reduced energy use. Applying digital control to power distribution is a foundational example of green IT.