As solar, wind and battery energy storage systems (BESS) account for a growing share of electricity generation, the way power grids maintain stability is changing. One technology becoming increasingly important is the grid-forming inverter (GFM). Unlike conventional renewable energy inverters that generally follow an existing grid signal, grid-forming inverters can help establish and support that signal.
What Is a Grid-Forming Inverter?
A grid-forming inverter is a power electronic device designed to establish and regulate voltage and frequency. This allows it to perform some grid-support functions traditionally associated with synchronous generators.
Most conventional solar PV plants use grid-following (GFL) inverters. These inverters synchronise their output with the voltage waveform and frequency already present on the grid. Grid-forming inverters work differently: their control systems can establish a stable AC voltage waveform and respond dynamically when grid conditions change.
Grid-Following vs Grid-Forming Inverters
The simplest way to understand the difference is by looking at how each technology interacts with the grid.
| Grid-Following Inverter | Grid-Forming Inverter |
|---|---|
| Follows existing grid voltage and frequency | Can establish and regulate voltage and frequency |
| Requires a sufficiently stable grid reference | Can provide a voltage and frequency reference |
| Primarily injects power into the grid | Can actively contribute to grid stability |
| Common in conventional solar PV plants | Increasingly relevant for BESS and renewable-heavy grids |
In simple terms, a grid-following inverter “listens” to the grid and synchronises with it, while a grid-forming inverter can help “set the rhythm” that other connected resources follow.
How Does a Grid-Forming Inverter Work?
The key difference lies mainly in the inverter’s control system. A grid-forming inverter continuously regulates parameters such as voltage, frequency, active power and reactive power.
When a disturbance causes grid frequency or voltage to change, the inverter can rapidly adjust its output to support the network. Depending on its control strategy, it may also provide a response resembling the inertia traditionally supplied by rotating generators, often referred to as synthetic or virtual inertia.
For example, a grid-forming BESS can rapidly increase power output when frequency falls, subject to available stored energy and equipment limits.
Why Does It Matter for Renewable Energy?
Traditional power systems rely heavily on synchronous generators in coal, gas, hydro and nuclear plants. Their rotating machinery naturally contributes inertia and helps maintain stable voltage and frequency.
Solar PV, wind and battery systems increasingly connect through power electronics instead. As their share grows, maintaining grid strength and stability can become more challenging, particularly in weaker networks.
Grid-forming technology offers one way to address this transition. It can be deployed in BESS, solar-plus-storage plants, microgrids and other inverter-based resources.
Grid-forming inverters do not replace the need for careful grid planning and other stability resources. Instead, they represent an evolution in inverter technology—enabling renewable energy and storage assets to move beyond simply supplying electricity and take a more active role in supporting a stable power system.
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