{"schemaVersion":1,"slug":"grid-forming-inverter","name":"Grid-forming inverter","kind":"symbol","abbreviation":"GFM","aliases":["GFM inverter","voltage-source mode inverter","virtual synchronous machine inverter"],"category":"microgrid-systems","drawingTypes":["SLD"],"referenceFamilies":["IEC","IEEE / ANSI"],"summary":"An inverter controlled as a voltage source that sets its own voltage and frequency, able to energise and hold up an island.","description":["A grid-forming inverter controls its output as a voltage source behind an impedance, setting voltage magnitude and frequency itself rather than measuring and following them. This lets it start a dead microgrid, share load with other sources through droop or virtual synchronous machine control, and respond instantly to load steps.","Single-line diagrams use the inverter symbol, a box with DC and AC marks, with a GFM label, a voltage-source note or a sine source mark to show the control mode. On microgrid drawings at least one grid-forming source must be available whenever the system is islanded.","Hardware alone does not decide grid-forming behaviour; many converters can switch modes in software. The symbol does not show current limits during faults, which are usually far lower than a synchronous machine, so protection based on fault current needs checking."],"readingNotes":["Look for GFM or voltage-source notes; the box itself is the same as any inverter.","Confirm that a grid-forming source is present in every islanded operating case."],"drawingChecklist":["State control mode and droop settings.","Show island and grid-connected switching.","Reference fault current capability."],"distinction":"A grid-forming inverter sets voltage and frequency; a grid-following inverter injects current synchronised to a voltage that something else provides.","facts":[{"label":"Control behaviour","value":"Voltage source"},{"label":"Islanding role","value":"Can energise and hold an island"},{"label":"Fault current","value":"Converter-limited"},{"label":"Preview","value":"Independent educational illustration; consult the applicable standard and project legend for the exact graphic"}],"references":[{"sourceId":"pub-object-victron-quattro","relevance":"Public inverter-charger documentation describing island operation."},{"sourceId":"s28-deif-hybrid-microgrid","relevance":"Public hybrid microgrid context in which a forming source sets voltage and frequency."}],"related":["grid-following-inverter","dc-to-ac-inverter","microgrid-controller","battery-power-conversion-system"],"artwork":"s28-grid-forming-inverter","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","plainEnglish":{"title":"What does Grid-forming inverter mean?","introduction":"A grid-forming inverter controls its output as a voltage source behind an impedance, setting voltage magnitude and frequency itself rather than measuring and following them. This lets it start a dead microgrid, share load with other sources through droop or virtual synchronous machine control, and respond instantly to load steps.","example":"Single-line diagrams use the inverter symbol, a box with DC and AC marks, with a GFM label, a voltage-source note or a sine source mark to show the control mode. On microgrid drawings at least one grid-forming source must be available whenever the system is islanded.","drawings":"Hardware alone does not decide grid-forming behaviour; many converters can switch modes in software. The symbol does not show current limits during faults, which are usually far lower than a synchronous machine, so protection based on fault current needs checking.","terms":[{"name":"DC","meaning":"Direct current: electricity flowing in one direction."},{"name":"AC","meaning":"Alternating current: electricity whose direction changes periodically."},{"name":"Signal","meaning":"Electrical information passed between devices, rather than necessarily the main power supply."}],"diagram":"flow","steps":["Identify the device and form","Read the connections and state","Check the equipment reference"],"caption":"A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.","sources":[{"label":"Quattro official product and documents","url":"https://www.victronenergy.com/inverters-chargers/quattro"},{"label":"Reliable hybrid power and microgrid solutions","url":"https://www.deif.com/applications/power-generation/reliable-hybrid-power-and-microgrid-solutions/"}],"detail":"An inverter controlled as a voltage source that sets its own voltage and frequency, able to energise and hold up an island. A grid-forming inverter sets voltage and frequency; a grid-following inverter injects current synchronised to a voltage that something else provides.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/grid-forming-inverter","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/grid-forming-inverter.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pub-object-victron-quattro","title":"Quattro official product and documents","publisher":"Victron Energy","url":"https://www.victronenergy.com/inverters-chargers/quattro","type":"manufacturer","scope":"Public product-family identity and official mechanical/document resources; no vendor geometry reproduced.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public inverter-charger documentation describing island operation."},{"id":"s28-deif-hybrid-microgrid","title":"Reliable hybrid power and microgrid solutions","publisher":"DEIF","url":"https://www.deif.com/applications/power-generation/reliable-hybrid-power-and-microgrid-solutions/","type":"manufacturer","scope":"Public hybrid and microgrid control context combining gensets, PV, storage and mains.","checkedOn":"2026-10-28","reuse":"link-only","relevance":"Public hybrid microgrid context in which a forming source sets voltage and frequency."}]}