Microgrid
A local group of generators, storage and loads with defined boundaries that can operate connected to the main grid or independently in island mode.
A microgrid is a localised power system, from a single building to a town, with its own generation, storage and control system, connected to the main grid at a point of common coupling. The US DOE definition stresses that it acts as a single controllable entity and can disconnect to operate in island mode.
Typical components include solar PV, batteries, diesel or gas gensets, CHP, a microgrid controller managing dispatch and protection, and a fast switch at the grid connection. In island mode at least one source must set voltage and frequency: traditionally a synchronous genset, increasingly a battery with a grid-forming inverter.
Applications:
- Resilience: hospitals, military bases, data centres and campuses that must ride through outages, for example after hurricanes in Puerto Rico.
- Remote and island systems: mines, Pacific and Caribbean islands and Alaskan villages, replacing diesel generation that often costs 0.30 to 1.00 USD/kWh.
- Energy access: solar mini-grids in sub-Saharan Africa and South Asia; the World Bank (ESMAP) estimates mini-grids are the least-cost option for several hundred million people still without electricity.
Hybrid PV-battery-diesel systems typically cut fuel use by 40 to 80%. Ta'u in American Samoa (1.4 MW PV, 6 MWh batteries, 2016) runs almost entirely on solar.
Related terms
All terms →- Grid-forming inverter
An inverter that sets its own voltage and frequency reference, behaving like a voltage source that can stabilise weak grids and provide synthetic inertia.
- Virtual power plant (VPP)
A software platform that aggregates many distributed resources, such as batteries, EVs, heat pumps and rooftop solar, and operates them as a single dispatchable unit.
- Black start
The process of restoring a power system after a total or partial blackout using units that can start without power from the grid.
- BESS (Battery Energy Storage System)
A complete grid- or site-connected battery installation, including cells, battery management, power conversion, thermal management and controls.
- Behind-the-meter
Equipment located on the customer's side of the utility meter, such as rooftop solar, home batteries or EV chargers, which primarily serves on-site load.
- Self-consumption
The share of on-site generation, typically rooftop solar, that is used directly by the producer rather than exported to the grid.