Glossary term
Microgrid
A local electric power system with defined boundaries and coordinated control that can operate with the main grid or in islanded mode.
Definition
systemA microgrid is a local electric power system with defined electrical boundaries and coordinated control that can operate connected to the main grid or, if designed for it, in islanded mode.
Microgrids combine local generation, storage, controllable loads, protection, communications, and control logic to serve a defined set of loads. They are used for resilience, remote power, renewable integration, peak management, critical facilities, campuses, industrial sites, and communities. Their design depends on operating modes, protection, voltage and frequency control, black start, load prioritization, and resynchronization.
A microgrid is a coordinated local power system. It may include solar generation, generators, batteries, fuel cells, controllable loads, switchgear, relays, inverters, communications, and a microgrid controller.
The key feature is a defined operating boundary. A microgrid can usually operate connected to the wider grid. Some microgrids can also separate and operate as an island, maintaining voltage and frequency internally.
Microgrids are designed for different objectives: resilience, remote electrification, lower energy cost, renewable integration, critical facility support, or distribution constraint management. The objective determines source sizing, storage reserve, protection philosophy, communications, and control logic.
Engineering use
An islandable microgrid needs an internal voltage and frequency reference. That may come from a synchronous generator, grid-forming inverter, battery energy storage system, or coordinated source group. Grid-following inverters alone usually cannot sustain an island without a reference source.
Design reviews must separate normal grid-connected operation from islanded, transition, black-start, resynchronization, and emergency modes. Each mode has different limits for fault current, load pickup, voltage regulation, frequency response, reactive power, protection selectivity, and load shedding.
Microgrid reliability depends on more than installed generation capacity. The design must prove that critical loads are prioritized, noncritical loads can be shed, fuel or state-of-charge reserves are sufficient, communications failures are handled, and maintenance bypasses do not defeat the resilience objective. Validation should include transition tests, black-start sequence, load steps, faults, communications loss, generator or inverter outage, and return-to-grid operation.
Common mistakes
A common mistake is assuming that onsite generation automatically creates a microgrid. Without coordinated control, protection, islanding logic, load priority, and validation, local generation may not support resilient operation during a grid outage. Another mistake is sizing sources for average load while ignoring motor starts, inrush, fault clearing, thermal limits, fuel constraints, battery reserve, and recovery after long outages. A strong microgrid review states boundary, operating modes, reference source, load priority, source dispatch, protection behavior, reserve policy, test evidence, and fallback state.