# Grid-forming inverter

Canonical URL: https://eloragrid.ai/symbols/grid-forming-inverter
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: GFM
Drawing use: SLD
Reference families: IEC, IEEE / ANSI

An inverter controlled as a voltage source that sets its own voltage and frequency, able to energise and hold up an island.

## In plain English

### What does Grid-forming inverter mean?

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.

### A simple 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.

### What the drawings help you do

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.

### This particular reference

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.

### Terms

- DC: Direct current: electricity flowing in one direction.
- AC: Alternating current: electricity whose direction changes periodically.
- Signal: Electrical information passed between devices, rather than necessarily the main power supply.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [Quattro official product and documents](https://www.victronenergy.com/inverters-chargers/quattro)
- [Reliable hybrid power and microgrid solutions](https://www.deif.com/applications/power-generation/reliable-hybrid-power-and-microgrid-solutions/)


## What it represents

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.

## How to read it

- 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.

## Information to show or reference

- State control mode and droop settings.
- Show island and grid-connected switching.
- Reference fault current capability.

## Important distinction

A grid-forming inverter sets voltage and frequency; a grid-following inverter injects current synchronised to a voltage that something else provides.

## Facts

- Control behaviour: Voltage source
- Islanding role: Can energise and hold an island
- Fault current: Converter-limited
- Preview: Independent educational illustration; consult the applicable standard and project legend for the exact graphic

## Public references

- [Quattro official product and documents](https://www.victronenergy.com/inverters-chargers/quattro) — Victron Energy. Public inverter-charger documentation describing island operation.
- [Reliable hybrid power and microgrid solutions](https://www.deif.com/applications/power-generation/reliable-hybrid-power-and-microgrid-solutions/) — DEIF. Public hybrid microgrid context in which a forming source sets voltage and frequency.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.