Below are the definition wordings from the U.S. DOE MEG and the CIGRE 6.22 WG.
- U.S. Department of Energy Microgrid Exchange Group:
- A microgrid is a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid. A microgrid can connect and disconnect from the grid to enable it to operate in both grid-connected or island-mode.
- CIGRÉ C6.22 Working Group, Microgrid Evolution Roadmap:
- Microgrids are electricity distribution systems containing loads and distributed energy resources, (such as distributed generators, storage devices, or controllable loads) that can be operated in a controlled, coordinated way either while connected to the main power network or while is landed.
- CIGRÉ C6.22 Definition Qualifiers:
- Generators covers all sources possible at the scales and within the context of a microgrid, e.g. fossil or biomass-fired small-scale combined heat and power (CHP), photovoltaic modules (PV), small wind turbines, mini-hydro, etc.
- Storage Devices includes all of electrical, pressure, gravitational, flywheel, and heat storage technologies. While the microgrid concept focuses on a power system, heat storage can be relevant to its operation whenever its existence affects operation of the microgrid. For example, the availability of heat storage will alter the desirable operating schedule of a CHP system as the electrical and heat loads are decoupled. Similarly, the pre-cooling or heating of buildings will alter the load shape of heating ventilation and air conditioning (HVAC) system, and therefore the requirement faced by electricity supply resources.
- Controlled loads, such as automatically dimmable lighting or delayed pumping, are particularly important to microgrids simply by virtue of their scale. Inevitably in small power systems, load variability will be more extreme than in utility-scale systems. The corollary is that load control can make a particularly valuable contribution to a microgrid.