Grid-Forming Inverter Virtual Inertia Margin
Quantify the inertia margin and approximate active power injection a grid-forming inverter can deliver for a target frequency deviation over a chosen support window.
Screening-only tool. Confirm controller settings and grid code compliance with full studies before deployment.
Examples
- 150 MVA inverter, H = 3.5 s, 50 Hz system, Δf = 0.2 Hz over 2 s ⇒ 1,050.00 MW·s inertia and 14.70 MW active power
- 90 MVA inverter, H = 2.2 s, 60 Hz system, Δf = 0.15 Hz over 1 s ⇒ 396.00 MW·s inertia and 2.18 MW active power
FAQ
Why is apparent power used instead of real power?
Grid-forming controllers size virtual inertia on the converter's apparent power capability, assuming unity power factor during transient support.
How should I pick the support window?
Use the time span over which you expect the controller to respond to the initial frequency ramp, commonly 1–2 seconds for primary response tuning.
Does this replace detailed EMT studies?
No. The calculation provides a screening estimate. Electromagnetic transient simulations are required to validate stability and protection interactions.
What happens if Δf is very small?
The active power term shrinks toward zero, while the inertia headroom stays constant because it is independent of the chosen event size.
Additional Information
- Inertia headroom equals 2 × H × S, where S approximates MW at unity power factor.
- Active power estimation treats the frequency swing over the support window as an approximate rate-of-change-of-frequency.
- Outputs round to two decimal places and clamp negative or missing inputs to zero.
- Use Δf as a magnitude; the calculator reports support capability irrespective of under- or over-frequency events.