alt Hacker NewsFor those who dont know why this is important:
The loads are slowing down the generators that are burning a well metered amount of fuel to stay at 60Hz. This is a delicate balance since the phase angle must also be spot on.
If a generator and the local line disagree on f, phase or V, you have a short circuit.
If you lose a large amount of load, your generator will spin up with the excess fuel until the control system re-establishes the right amount of fuel.
But now your generators are out of sync! No worry, for small disturbances the dissipative losses sync everything up like syncros on a manual transmission.
But the disturance cant be too big!
Rotating machines are big and heavy, so the first line of defense is their inertia. But this is a finite (and precious) resource.
Contrary to belief, renewables, or generally speaking DC, makes things this stability problem worse. They generate large amounts of power while providing no inertia.
You'd think it isn't a big deal since the DC-AC converter can just synthesize whatever is needed. Heck just keep it rigid at 60 Hz with no phase change.
Well the later doesn't work - the rest of the grid is no longer at that phase and frequency so you got yourself a short.
Furthermore, the DC-AC converter, despite their manufacturers' promise, has no good way to establish what f and phase it should be at during a disturbance (and these magic codes are closed source, believe it or not)
Anywho, a large enough loss of load causes the grid to enters into unstable oscillations, causing protective relays to trip causing a zipper effect where the grid goes down.
Now restart will take a few days depending on the energy mix (fastest for hydro heavy)
Long story short - this is not a trivial problem, and the data-centers can't be allowed to just dump load willy nilly.
EDIT: made it clear that the grid killing disturbance is not caused by renewables; not exclusively anyway. Everyone has to play nice or the grid goes down.
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The ELI5 version is you're arm-wrestling someone and they suddenly let their arm go limp, so your arm slams down on the table since you can't react that fast.
That’s a simplified and somewhat outdated version, there’s a huge range of technology to mitigate each of these issues but infrastructure generally isn’t free. A turbine does provides inertia for free where you need to pay for a flywheel or battery system.
In the end a renewable heavy grid can be extremely resilient due to all the batteries, but smart battery systems need to be incentivize or mandated because ‘dumb’ batteries are cheaper.
10+ MW voltage-source converters that can't do up to around 80% of their nominal capacity as mostly-reactive apparent power with stabilizing synthetic inertia scaled as desired/specified are a mostly software issue, stemming from lack of regulatory pressure incentivizing the engineering complexity of that.
Though if you want to do a smoothing action on real power flux you'll have to colocate battery capacity with the converter. Which to be clear is fairly cheap to do as long as you get compensated for the substantial frequency stabilization capacity this represents. I'm talking like 15~120 minutes at converter nominal AC power of battery capacity.
The first 10~20% of reactive power are almost free from the converter electronics, btw....
To add on to this overview, there are a new class of inverters in research called grid forming inverters which don't just follow the rest of the grid. One interesting technique is they can simulate the inertia of a traditional rotating machine/generator.
https://iten.ieee-ies.org/journal-featured-article/2025/grid...
Would demanding that large spikey users of energy like data centers implement some sort of demand ramping/isolation from the grid in the form of a massive capacitor bank or flywheel generator between them and the grid help reduce the risk here?
> Contrary to belief, renewables, or generally speaking DC, makes things this stability problem worse.
Is there such belief? My feel is that anybody to whom electrical grid stability has even crossed their minds know this.
When you say "short circuit" - is this when wires get hit and make and burn, or this is reference to some other stuff?
Some of us in Texas are all too familiar with the problem of balancing load with generation, the risk of a cascade failure causing a slow restart.
During winter storm Uri, they did a duty cycle where we only had power available for ~6-12 hours at a time on the days it was available. This was apparently to avoid that very problem.
So far as I know, the obvious mitigations like winterizing NG generation and/or peering with neighbor grids have not been performed.
Grid scale battery systems are also used to maintain proper synchronization.
Grid forming batteries and inverters are a thing. They can control the frequency on the grid. Just a matter of getting the right equipment.
The nice thing with data centers is that they are somewhat flexible. It's not a constant load. Data center operators can choose to reduce load. And if properly engineered, they could do so automatically based on signals from the grid.
The issue with outdated grids is that it relies on technology (spinning mass) that's at this point a century old. Which makes it brittle against outages like you describe. The solution is not more spinning mass but batteries and renewables to take the place of that spinning mass. A battery can respond to oscillations in milliseconds. If you then add flexible load that can spin up/down based on the amount of available power, you gain a lot of stability.