ERCOT FFR Dispatch Timeline

How a grid-following BESS turns an under-frequency trigger into delivered fast frequency response.

By Sergey Syrvachev — Director of Product Engineering, grid-scale BESS · 10+ GWh delivered

Part of: the ERCOT frequency ride-through envelope — the 57.0-61.8 Hz band this dispatch happens inside, with the clause it comes from.

GFL / ERCOT / FFR
speed
The FFR clock starts when frequency crosses 59.85 Hz. This example delivers full power in 180 ms, leaving 70 ms before the 0.25 s ERCOT limit.
elapsed-40ms
frequency60.00Hz
inverter P0%
ERCOT margin0/180
GFL dispatch on the ERCOT FFR trigger59.85 Hz / response timing
01 / GRID FREQUENCY (Hz)60.00 HzFFR trigger - 59.85 Hz60.059.8559.7002 / RESPONSE TIMELINEfallmeterPPCESCinvertersettle060100150240310full power0.25 s limitmeter → PPC → ESC → inverter03 / INVERTER POWER (%)0%050100%0100150240310400490time since grid event (ms)
-40 msPre-event: frequency is steady at 60.00 Hz.response clock 0 / 180 ms
Control visualization - autoplay the under-frequency event, scrub the timeline, and check whether full response lands inside the ERCOT 0.25 s FFR window.

Download the ERCOT FFR Dispatch Timeline diagram

ERCOT fast frequency response timeline: grid-following BESS detects 59.85 Hz under-frequency and ramps inverter to full power
An interactive ERCOT fast frequency response timeline showing how a grid-following BESS detects a 59.85 Hz under-frequency event and ramps its inverter to full power within the 0.25-second limit.

Free to download and reuse — including commercially — under CC BY 4.0, with credit to BESS.engineer. Licence & attribution →
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What it shows

The timeline follows an under-frequency event from the moment grid frequency crosses the FFR trigger through the command path — POI meter, plant controller (PPC), energy storage controller (ESC), inverter — to delivered active power. Each hop adds latency; the example delivers full power well inside the 0.25 s ERCOT limit, leaving margin.

Why it matters for BESS

Fast frequency response is a revenue-bearing ancillary service, but only if the full detection-to-delivery chain fits inside the market window. Mapping the latency budget across the command path is how engineers prove a plant can qualify — and where they find the milliseconds when it cannot.

Frequently asked

What is Fast Frequency Response (FFR)?
FFR is an ancillary service in which a resource injects active power within a fraction of a second of a frequency deviation to arrest decline — far faster than traditional primary frequency response. ERCOT requires delivery within 0.25 seconds.
Why is BESS well suited to FFR?
Batteries and inverters can move from zero to full power in tens of milliseconds, so the binding constraint is the measurement and command chain, not the hardware — which is exactly what this timeline makes visible.

References

Standards and authoritative sources this visual is built on:

  1. ERCOT Nodal Protocols — Responsive Reserve Service and the Fast Frequency Response (FFR) component (0.25 s deployment requirement) — ERCOT (Electric Reliability Council of Texas)
  2. IEEE Std 2800-2022 — Standard for Interconnection and Interoperability of Inverter-Based Resources (IBRs) Interconnecting with Associated Transmission Electric Power Systems (frequency response / fast frequency response requirements) — IEEE, 2022
  3. Reliability Standard BAL-003-2 — Frequency Response and Frequency Bias Setting — NERC (North American Electric Reliability Corporation), 2020
  4. Fast Frequency Response Concepts and Bulk Power System Reliability Needs — NERC Inverter-Based Resource Performance Task Force, 2020

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