How to Check an Energy Storage Inverter's Grid-Forming Capability: China's New GB/T 48211-2026 and GB/T 47968-2026, the Draft's Numeric Requirements (±60° Phase Jump, 2–20 s Inertia, SCR 1.1–10, 300% Overcurrent), and How NERC, AEMO, National Grid ESO and IEEE 2800 Frame It

Short answer. A grid-forming (GFM) storage converter behaves as a voltage source: it builds and holds its own internal voltage amplitude and frequency, whereas a grid-following (GFL) converter tracks the grid as a current source. China now has a dedicated national standard for electrochemical storage grid-forming PCS, shown as published under GB/T 48211-2026, plus a general grid-forming converter standard, GB/T 47968-2026, effective 1 November 2026. The numbers in this guide come from the August 2025 consultation draft, because the published text was not retrieved: ride-through of ±60° phase jumps, an inertia constant settable from 2 to 20 s, stable operation at short-circuit ratios from 1.1 to 10.0, and overcurrent of 300% for at least 10 s, among others. Outside China, NERC recommends that all new bulk-system batteries have GFM capability or be upgradable to it, AEMO publishes a voluntary specification and National Grid ESO has proposed a mandate for large plants. A buyer should test claims against the standard's clauses, not against a datasheet label.

1. What 'grid-forming' means in the Chinese texts

The draft standard defines a GFM PCS as one that autonomously builds and maintains the amplitude and frequency of its internal EMF and operates with voltage-source characteristics, and a GFL PCS as one that follows grid frequency and voltage with current-source characteristics. It covers electrochemical storage converters with an AC port of 35 kV and below.

The drafting explanation says grid-forming storage can emulate a generator's excitation and power-angle characteristics, giving active voltage support, inertia support and frequency response, improving damping and weak-grid short-circuit capability; that no Chinese standard for grid-forming storage converters existed, so type tests could not be run; that comparable international product standards were lacking; and that the standard was not based on an international standard.

NERC gives a similar functional description: most definitions agree that GFM controls tend to hold voltage magnitude and angle at the terminals constant immediately after a system event. AEMO says a GFM inverter should behave like a voltage source behind an impedance.

2. Status of the Chinese standards

• Storage GFM PCS standard. Plan 20243219-T-524 (recommended standard; plan issued 26 October 2024; TC550; China Electricity Council as competent body) is shown as published as GB/T 48211-2026. Drafters include CEPRI, State Grid, NR Electric, Sungrow and Huawei Digital Power. The platform record retrieved does not give its publication or effective date.
• General GFM converter standard. GB/T 47968-2026 was published on 30 July 2026 and takes effect on 1 November 2026.
• Related. The plan page also lists GB/T 48268-2026 on grid-forming wind grid connection.
• Policy. The 2025–2027 action plan for large-scale new-type storage calls for faster demonstration of grid-forming storage in high-renewable, weak and island grids.

3. The draft's numeric requirements

All values below are from the consultation draft (clause numbers in brackets); confirm against the published GB/T 48211-2026 before using them in a specification.

CNWattHub reading: the draft uses 宜 ('should') for the frequency dead band and the damping ratio, so those two are recommended settings rather than hard limits; the others are stated with 应 ('shall').

4. How other system operators frame it

• NERC (US, white paper, September 2023). Recommends that all new BESS connecting to the bulk power system have GFM capability or be upgradable, that transmission owners write this into interconnection requirements or PPAs, and that GFM be enabled only after study; it notes studies suggest GFM shares may need to exceed 30% (a system-specific answer) and that new BESS can add GFM at relatively low incremental controller and hardware cost. It also separates GFM from black start: GFM is a prerequisite for blackstart eligibility, but blackstart may need extra overcurrent, ride-through, energy or hardware and should be specified separately.
• AEMO (Australia, voluntary specification, May 2023). Voluntary and meant to inform future rule changes; 'core' capabilities are achievable mainly through software and control changes and the majority of them are expected of all GFM devices, while 'additional' capabilities may need hardware or operational changes.
• National Grid ESO (Great Britain, proposal slides, August 2024). GC0137 (February 2022) set the minimum GB grid-forming specification and GC0163 (July 2024) allowed real, virtual or combined impedance; ESO proposed mandating GFM capability from the end of 2025 on Type D modules (50 MW and above and/or 110 kV and above) and HVDC systems, with compliance by end-2028, not retrospective, and further evaluation of a 60-degree phase-jump withstand. This was a proposal when presented; check whether it was adopted.
• IEEE 2800-2022. Sets uniform minimum requirements for inverter-based resources on transmission systems, including ride-through, active and reactive power control, dynamic support, power quality, negative-sequence current and protection; an amendment project, P2800a, is listed.

CNWattHub reading: the Chinese draft's ±60° phase-jump ride-through matches the 60° figure ESO proposed to evaluate.

Reading table

Checklist

CNWattHub editorial method, not a sourced rule:

1. Ask which standard the PCS was type-tested to (GB/T 48211-2026, GB/T 47968-2026 or a draft) and for the test report, not only a certificate.
2. Check the phase-jump, inertia, frequency-response, damping, transient-impedance, SCR and overcurrent results against the published clauses.
3. Ask whether black start and GFM/GFL switching were tested, and at what power fluctuation.
4. Request electromechanical and EMT models matching the delivered firmware, and the tuning parameters used in the test.
5. For export projects, map the results to the target operator's document (for example NERC's recommendations, AEMO's core capabilities or the GB Grid Code) and to IEEE 2800 where it applies.
6. Write the GFM requirement and its acceptance tests into the supply contract.

Scope limits

One SAC plan page, one draft standard and its drafting explanation, one standard information page, one Chinese action plan, and NERC, AEMO, National Grid ESO and IEEE documents only. The published GB/T 48211-2026 and GB/T 47968-2026 texts were not read, so all numeric values are from the 2025 draft; no grid-company connection rule, test report or cost figure is quoted. Not engineering or procurement advice.