Grid-Forming Inverter

The problem with grid-following inverters

Every solar inverter connected to the grid is a power electronics device that synthesises AC electricity. Conventional inverters are designed to synchronise to the grid - they track the grid’s voltage waveform and frequency (50 Hz in Australia) and match it exactly before injecting power. This is necessary to avoid damaging out-of-phase injection.

The consequence is that when the grid goes down, these inverters have nothing to follow. Anti-islanding protection - a safety requirement in AS/NZS 4777 - forces them to shut down within seconds of losing the grid reference. This protects linesmen working on downed wires who could otherwise encounter live household-injected power. But it also means your solar panels stop working in a blackout even if it’s a sunny day.

What grid-forming inverters do differently

A grid-forming inverter can create its own voltage and frequency reference independently. It doesn’t need the grid to exist as a reference - it can establish the AC waveform from scratch, like a small generator. This allows it to:

1. Keep supplying power to the home when the grid is down
2. Potentially support grid stability by providing a stable frequency anchor (unlike grid-following inverters, which follow whatever frequency the grid has - including if it’s unstable)

In islanded operation, the grid-forming inverter manages the local microgrid: it sets the frequency, regulates voltage, and coordinates with connected loads and other generation.

Current products with grid-forming capability

Enphase IQ8 microinverters are the most widely available residential grid-forming product in Australia. Each IQ8 unit can form its own grid island with the Enphase IQ System Controller, allowing a full solar + storage system to black-start and operate off-grid.

Some hybrid inverters (Growatt, SolarEdge, Fronius) include grid-forming capability for their EPS (Emergency Power Supply) output, though this is often limited to a single backup circuit rather than whole-home.

Utility-scale grid-forming storage is a major focus of AEMO’s grid stability planning, as synchronous generation (coal and gas) exits the NEM and the frequency-stabilising properties of spinning machines need to be replaced by inverter-based resources.