IBR Oscillations

A grid collapsed in ninety seconds.

On April 28, 2025, the power grids of Spain and Portugal collapsed, cutting electricity to over 50 million people for up to 16 hours. The ENTSO-E final report confirmed the cause: cascading IBR oscillations and inverter-based generators that withdrew from the grid instead of stabilizing it. 1

Phase 1

Warning 30 minutes

• 12:03 First oscillations detected
  0.63 Hz forced oscillation traced to converter-driven instability at a photovoltaic plant in southern Spain.
• 12:07 First oscillation period ends
  Local oscillation affecting Spain and Portugal subsides. Grid appears stable.
• 12:16 Second oscillation begins
  0.2 Hz inter-area oscillation between Spain and Portugal. Operators observe but cannot identify the source or damp it.
• 12:22 Second oscillation mitigated
  Grid appears stable again. No oscillations detected for the next ten minutes.
• 10 min Silence. No oscillations detected. The grid reads normal.

Phase 2

Collapse 27 seconds

• 12:32:57 Generation trips begin
  Series of trips near Granada, Badajoz, Seville. 2,200 MW lost. Voltage surges. Inverters trip on overvoltage protection.
• 12:33:18 Frequency collapses below 48 Hz
  Automatic load shedding activated across the peninsula.
• 12:33:21 France–Spain interconnectors trip
  Iberian Peninsula isolated from Continental European grid.
• 12:33:24 Total blackout
  Entire Iberian grid collapses. 50 million people without power for up to 16 hours.

ENTSO-E concluded that high-quality, real-time measurement data is needed to reliably detect and localize oscillations. 1 2 The infrastructure existed in concept. It was not deployed at the resolution required.

Why it happens

Inverters don't stabilize the grid.

The traditional grid was built on synchronous generators, massive rotating machines that inherently stabilize frequency and voltage through physical inertia. As IBRs replace these machines, that stabilizing mass disappears.

IBRs connect to the grid through power electronics running complex control loops. These control loops interact with each other and with grid dynamics in ways that produce sub-synchronous oscillations: rapid power and voltage fluctuations at frequencies below the fundamental 60 Hz that the grid was designed around. When enough IBRs cluster in a region, their interactions can amplify oscillations to destructive levels.

Think of it as acoustic feedback in a stadium PA system: each speaker is working correctly, but their interactions produce a screech that no individual speaker intended.

This is not a deficiency in any single inverter. It is an emergent property of a grid whose physics are changing faster than its monitoring infrastructure. The oscillations are real. They are growing. At SCADA's 2 to 4 second scan rates, they are completely invisible.

These oscillations also do not arrive as discrete events. They wax and wane with load, weather, generation mix, and the control interactions of hundreds of inverters across the grid. Some persist for months at low amplitude before crossing into instability. Treating each as a moment to be detected misses the underlying behavior the utility actually needs to understand.

It is already happening here

NERC has documented a growing pattern.

The Iberian blackout was not a one-off. Each event below reveals the same systemic vulnerabilities on the North American grid. 3

Florida Forced Oscillation

January 11, 2019
A single steam turbine's 0.25 Hz oscillation interacted with a natural mode of the entire Eastern Interconnection and propagated across the grid for 18 minutes before the plant operator manually removed the unit from service.

• IBR share NERC report

San Fernando Disturbance

July 7, 2020 · Southern California
A routine fault triggered the loss of approximately 1,000 MW of solar PV across Southern California. Inverter tripping caused by instantaneous AC overcurrent that the inverter current controls failed to absorb.

• IBR share NERC report

CAISO Solar Disturbances

June to August 2021 · Four events
Four separate events. Solar PV resources tripped on normally cleared faults the grid is designed to ride through. Triggered by line faults, fires causing smoke-induced faults, and a tripped transformer.

• IBR share NERC report

Odessa Disturbance

May 9 & June 26, 2021 · Texas
A single-line-to-ground fault caused over 1,100 MW of solar PV and wind loss across a region up to 200 miles from the fault. First widespread IBR loss event in the Texas Interconnection.

• IBR share NERC report

California BESS Disturbances

March 9 & April 6, 2022
The first major events involving battery energy storage system facilities. Normally cleared faults caused unexpected BESS tripping. NERC concluded that BESS may have the same systemic performance problems as solar PV.

• IBR share NERC report

The pattern is consistent: as the share of generation supplied by IBRs increases, the consequences of each disturbance grow. The events in California and Texas occurred when IBRs were supplying 33 to 61% of regional demand. Those shares are rising every year.

FERC waited fourteen years to establish mandatory reliability standards for a known, potentially catastrophic risk.

Every one of these events involved oscillations that SCADA could not see.

The oscillations that collapsed the Iberian grid operated at 0.2 Hz and 0.63 Hz. The disturbances in California and Texas were driven by inverter control interactions at sub-second timescales. SCADA polls every 2 to 4 seconds. The grid is adding IBRs faster than it is adding the ability to see what they are doing.

The trajectory

Batteries make it worse.

Battery energy storage carries the same oscillation, tripping, and ride-through risks as solar and wind. The problem is not slowing down. It is accelerating.

• 11.6 GW battery storage installed in California alone
  EIA · End of 2024
• 21 GW planned across the Western Interconnection by 2033
  CAISO · 8x increase from 2022
• 2,600 GW of proposed generation in the U.S. queue. 95% is IBR.
  LBNL · 2024

The nationwide interconnection queue contains over 2,600 GW of proposed generation, roughly twice the entire existing U.S. generating capacity of approximately 1,300 GW. Solar, battery, and wind comprise over 95%. 4

Every one of these resources connects through inverters. NERC's 2022 BESS disturbance report made clear that batteries carry the same oscillation, tripping, and ride-through risks as solar and wind. 5

The architectural answer

Detection is not understanding.

PredictiveGrid helps utilities understand what their IBR fleets are actually doing. Not just whether an alarm should fire.

Most IBR monitoring watches the last few seconds of grid behavior. But oscillations are not discrete events. They are continuous dynamics that rise, fade, shift, and return as load, weather, generation mix, and inverter controls interact across hundreds of devices.

Root cause requires history: months of full-resolution synchrophasor data, time-aligned across substations and assets, queryable fast enough to compare today's instability against past behavior.

That is the foundation PredictiveGrid provides. Without it, mitigation is a bandaid on a symptom the utility never fully understood.

Detection tells you an oscillation is happening. It does not tell you why.

The inverter fleet is already here. The visibility isn't.

PingThings PredictiveGrid captures and time-aligns full-resolution synchrophasor data across substations and assets. Months of history, queryable in milliseconds. The foundation for understanding what your IBR fleet is actually doing.

References

1. ENTSO-E, "Grid Incident in Spain and Portugal on 28 April 2025, ICS Investigation Expert Panel Final Report," March 20, 2026.
2. Wikipedia, "2025 Iberian Peninsula blackout," citing ENTSO-E timeline and REE operational data. Timestamps from ENTSO-E preliminary and final reports.
3. NERC, IBR and DER Disturbances Overview and Resources advisory, June 2024; multiple NERC event analysis reports 2019 to 2024.
4. Lawrence Berkeley National Laboratory, interconnection queue data, 2024; EIA total U.S. net summer generating capacity approximately 1,300 GW.
5. NERC and WECC, BESS disturbance reports, March and April 2022 events.