In April 2025, large parts of Spain and Portugal were plunged into darkness by a cascade of failures that began with a small disturbance, and spiraled into a system-wide blackout. The scale and speed of the collapse shocked many, but for those of us involved in renewable system integration, it wasn’t entirely a surprise. In fact, it’s a glimpse into what can happen when a power system shifts to more decentralised generation without the operational guardrails in place.

As Britain’s energy system pushes towards net zero, we face the same structural challenge: how to run a grid dominated by inverter-based resources like wind and solar, which don’t behave like traditional rotating power stations. What we’ve learned was that Spain’s blackout wasn’t about green energy going wrong. It was about not adapting fast enough to the demands of a changing grid. The good news is that the organisations responsible for maintaining the UK electrical network have done a lot to head off exactly this type of scenario. The bad news is that we’re not done yet.

What went wrong in Spain?

The Spanish blackout was triggered by a voltage instability that knocked off more than 2 GW of generation in under a minute. Much of what tripped off was inverter-connected solar. That sudden loss of generation led to over-voltages, frequency dips, and further cascading failures. The grid became unstable faster than the system could react.

Critically, many of those generators disconnected because their protection settings were too sensitive to normal disturbances: things like short-term voltage rises, or frequency swings just outside their normal setpoints and operational ranges. This is an old problem, familiar to anyone who remembers the UK August 2019 blackout. Inverters designed to disconnect at the first sign of trouble can inadvertently make a bad situation worse, especially when they represent a large share of generation.

Spain’s report clearly ruled out cyberattacks or sabotage. What remained was a story of system fragility. The grid didn’t have enough inertia, not enough voltage control, and the inverters that should have helped instead made things worse by dropping offline when they were needed most.

Why inverter-based grids are so complex

Unlike traditional power stations that use turbines and rotating mass to generate electricity, inverter-based resources like solar and wind generation use power electronics. Mostly, these inverters take their cue from the grid (they’re ‘grid-following’) meaning they respond to the grid’s frequency and voltage, but don’t create or stabilise it.

That works fine when there’s plenty of inertia on the system for them to follow. However, as we retire thermal plant and ramp up renewables, the grid becomes lighter, it has less physical inertia to slow down sudden changes in frequency. Without that buffer, small issues can escalate quickly.

Moreover, grid following inverters often limit fault current and can’t provide the same voltage control unless specifically designed and configured to do so. During disturbances, some older inverters may drop offline due to outdated protection settings, or simply fail to help when their contribution is most needed. Modern systems must compensate for this by deploying rapid frequency containment and distributed reactive power control. This is what we are starting to see with updated Power Control Units (PCUs) on battery and renewable energy sites that are designed to be grid forming. We will see much more of this type of technology being implemented over the next few years.

To be clear, inverter-based generation can play a positive role in grid stability, but only if integrated properly. That means asking more of inverters: ride through faults, manage voltage, contribute fast frequency response, and avoid unnecessary trips. In short, we need smarter, more grid-aware power electronics.

How the UK responded: ALoMCP and the grid code shift

Here in the UK to an extent we saw this coming. After our 2019 blackout, where hundreds of megawatts of distributed solar and wind tripped off, the key organisations tasked with the operation of the grid undertook a review and, following that kicked off the Accelerated Loss of Mains Change Programme (ALoMCP). The premise was simply to stop distributed generators from tripping unnecessarily. In practice, that meant going out to thousands of sites and changing the settings on legacy grid relays and inverters, boosting their tolerance to frequency and voltage swings and removing over-sensitive “vector shift” triggers. New standard settings, such as an amended RoCoF trip threshold, were implemented to prevent nuisance trips.

Locogen was involved in this national effort, helping developers and asset owners across the UK to access funding, carry out protection studies, and update their systems. We worked on a wide range of wind and solar sites, some dating back over a decade, making sure they could ride through disturbances instead of bailing out at the first sign of trouble.

By the time ALoMCP closed in 2022, over 4,000 sites and more than 7 GW of capacity had been updated, these weren’t flashy projects, but they were essential. Without them, our grid would still be riddled with trip-happy generators ready to cut out during a minor bump. That legacy has laid the groundwork for a more resilient embedded generation fleet.

Beyond ALoMCP: A new grid model in practice

Fixing protection settings was just the start. The UK has since gone much further:

Fault Ride-Through (FRT) Requirements: Modern inverters must now stay connected during voltage dips and supply reactive power to support voltage recovery. These are mandated in the grid code and ensure devices don’t disappear just when we need them most.
Dynamic Containment and Fast Frequency Response: Battery storage systems are contracted to respond within 1 second, or even faster, to frequency drops. These assets inject power almost instantly to arrest frequency falls that would otherwise spiral.
Stability Pathfinder Projects: These have led to the deployment of synchronous condensers and grid-forming batteries, especially in Scotland and northern England, to provide virtual inertia, voltage stability, and fault-level support.
Grid-Forming Inverter Projects: Battery sites with advanced control systems are now being commissioned that can set the voltage and frequency reference themselves, effectively acting like traditional synchronous machines but without the emissions.
Greener Grid Parks: Delivered by companies like Statkraft, these projects combine synchronous condensers, STATCOMs, and battery storage to deliver site-specific stability support in weaker areas of the network.
Voltage optimisation schemes and flexible connection arrangements: Many new wind and solar projects are now being connected under ‘flexible connections’ where active power can be curtailed under certain conditions to maintain local voltage and thermal limits, often with support from local grid-enhancing technologies.

Together, these initiatives are delivering practical, distributed resilience, enabling high-renewable penetration even in parts of the network that weren’t built for it.

Could a Spanish-style blackout still happen here?

In short, yes it could, though the probability is now much lower. The UK has addressed many of the root causes that made Spain vulnerable. But under certain conditions, similar issues could still occur. For example:

An extremely low-inertia day, with high wind/solar output and minimal synchronous generation online. This is increasingly common in summer shoulder periods.
A sudden fault or voltage rise that trips a large cluster of embedded generators still running outdated settings. While ALoMCP tackled much of this, legacy rooftop solar and microgeneration sites may still pose a risk.
A failed fast frequency response event, where one or more contracted services are unavailable or delayed. This could allow frequency dips to breach safe operating thresholds.
A loss of interconnector capacity, such as during a storm or cable fault, creating a net export imbalance and a rapid over- or under-frequency excursion.
A control software bug or cyber issue, impacting the orchestration of rapid-response assets like batteries or demand flexibility providers.

These scenarios are edge cases, but they’re not impossible. And the more variable and inverter-heavy our grid becomes, the more these conditions could align by chance. That’s why investment in coordination, testing, and visibility is so important.

Engineering the future grid – not just hoping it works

It’s tempting to reduce these discussions to ideology, but the truth is this: renewables are here to stay, and they work brilliantly when the engineering keeps up. What Spain experienced in 2025 is the kind of failure that happens when controls, standards, and operational practice lag behind the energy mix. What we’ve done in the UK, from the nuts-and-bolts changes of ALoMCP to cutting-edge work on grid-forming inverters, is exactly the kind of proactive engineering response that keeps the lights on.

The future grid will be different: more decentralised, more variable, more reliant on digital controls. But if those controls are well-designed, and the devices on the system are robust, there’s no reason we can’t run a stable, reliable grid with 80% or more renewables. The path there is technical, not ideological. And the work is already well underway.

So next time someone questions whether the grid can cope with all this renewable energy, tell them: it can. But only because people (planners, engineers, consultants, and operators) have done the hard, often invisible work to make sure it does.

At Locogen, we’re proud to have been part of that effort, supporting wind and solar asset owners throughout the ALoMCP and beyond. In fact, as the system evolves, we’ll be right there, working to make sure tomorrow’s renewable grid is not just clean, but rock solid too.