There are costly means to compensate for the lack of spinning baseload but actually building these devices have been neglected, to no ones surprise.
Looking at power generation reports it's the plants relying on inertia (like nuclear) which were disconnected and haven't been reconnected since:
In a control system when you have an actuator that is much more responsive than the load, you can get into instable operating regimes where. On a small scale, when you are setting up servo motors, there is an inertia matching ratio for stability. In some of the systems I set up it was 10:1 load inertia:motor inertia. If you exceed that, you end up with elasticity between the motor and load that the motor can locally be above set point, and the control tells the motor to slow down, while the load has not yet reached set point. The motor is then too slow, and the control tells it to go faster, and you get the motor oscillating around the speed of the load.
On the grid you can have similar elasticity. An inverter many km away can get too far ahead in the AC cycle, then when that signal reaches the local inverter, the local inverter slows down, but the remote inverter has already slowed down, and by the time that slower wave gets to the local inverter, it is already too slow, and so the local inverter starts to speed up. If you get the frequency "right" you can end up with a positive feedback loop. With a high inertia rotating generator, the system is damped and slow enough to respond you don't change set point faster than the signal can propagate.
At the start of solar and wind integration, it didn't matter. Large rotating generators were the main source on the grid, and provided stability. We're in a different world with an all-inverter grid control perspective-wise.
I think there is also still an information issue. The grid is definitely not point-to-point. It also isn't all generators. You also have loads switching on and off at indeterminate times. There is an overall predictability to it, but not at the phase governing resolution. If you have a local inverter and the phase slows down, you don't know if it is a remote inverter that has over-slowed, to which you shouldn't respond as it will fix itself, or a near-by load that suddenly switched on, to which you should respond as demand is now greater, and needs more supply. With big rotating generators, it doesn't really matter, as they are time averaging with the large inertia to stabilize the load/generator balance.
-react immediately
-use its full capacity all the time
Imagine you're trying to coordinate a choir of ten million singers that are scattered across a radius of a thousand kilometer, that all sing into their individual Ham radio. And you need it to come out in a perfect unison that sounds good for those who tune into the mixed broadcast.
"A problem of coordination" is perhaps correct, but it neglects the difficulties involved
Also we know the locations of the generators, so we can calculate the phase shift and control them accordingly. At thousand kilometres it's around 60 degrees anyway, so not catastrophically huge.
I'm pretty sure in grid terms, 60 degrees out of sync is catastrophic. I'm pretty sure you'll be disconnected by protection circuits before it gets that far out.
And even if we did have the superluminal grid sync signal the propagation of electricity itself is slower than C and you'll need to consider perceived phase synchronization over distance.
If I can sync ALL my [important] servers across the globe to the EXACT same time (under 2 microseconds variance in the last 7 days), and all that on the off-the-shelf hardware, surely a NATION can devise something better?
(also replaces the need for synchronous condensers where they would typically be sited for grid ancillary services)
https://www.abc.net.au/news/2021-05-26/queensland-blackout-c...
https://www.pscconsulting.com/australia-leans-in-on-syntheti...
https://aemo.com.au/-/media/files/initiatives/engineering-fr...
https://www.ercot.com/files/docs/2024/01/12/Tesla%20BESS%20G...
Our recent govt installation is reported at $1.6bn for 2000MWh, which is incredibly expensive, and can't scale to run the grid, simply smooth load/demand diurnal curves.
I'm not saying "at some point" batteries won't be viable as grid "storage", I'm just saying today they aren't.
You are still correct in the sense that storage is still incredibly expensive per hour of demand stored, but batteries may very well already be the cheapest option out there
https://en.m.wikipedia.org/wiki/Snowy_2.0_Pumped_Storage_Pow...
More importantly, according to the REE, PV played a mayor role in the current and successful black start.
If the power is out, do you imagine that all the load that is out there disappears too?
If I'm in a blackout and put my multimeter into the grid socket, will the measurement be something that my local inverter can drive an AC load through with no problems?
And if that's not possible, how do we get an AC wave out to my 5000 local solar panel neighbors? And if we don't get any carrier wave to synch it to, then how do all these thousands of individual inverters decide on the unison synchronization necessary to all start jumping together?
And if they try and fail, will all the connected load accept a graceful out of synch mixed power noise at 0-220v until things properly latch together?
The problem isn't like playing a sine tune of acoustic sound that's merely audible to your local neighbor, who can dial in his own tune, and then daisy chaining this until it matches on a grid sized level.
Then depending on how out-of-sync a given station is with the signal, they ramp production up or down accordingly.
Is the problem here that there is inadequate or slow feedback to the supply side regarding load and therefore you'd end up with under-voltage?
It's not about getting the generator to spin at 50hz, it's about getting it to spin at 50hz under dynamic load. Most generators are mostly fixed speed I think for the sake of efficiency, so the mechanism the grid has to regulate the frequency of power is largely by controlling the number of generators running at any given time, and how much of the grid is connected to them. Ramping up and down based on the current observed frequency of the grid is exactly how this all works. However it's more complicated because what if two or more power stations see a low frequency grid and decide to ramp up more generators? Well now the grid frequency is too high. If they them respond to that by ramping down, it'll go too low. Rinse and repeat and you get undesirable frequency oscillation, so there needs to be more communication across the grid than just responding to the locally observed frequency.
Connect a stopped, or sufficiently out of phase generator to a full scale power grid and the puny thousands of pounds of metal that make up a generator are going to get ripped apart by the sheer inertia of the power grid forcing it to match speed and phase in an instant. This is also a problem when attempting to connect two isolated grids, of they're too out of phase with each other, catastrophic physical damage will occur.
Any individual station that gets out of sync either works hard to catch up, or gets disconnected.
The problem, as I see it, is that the load signal is equal and equivalent to the sync signal and maybe they could be separated. (e.g. the FM modulated signal wouldn't have to be a sine wave, nor would it even have to be 50Hz)
> what if two or more power stations see a low frequency grid and decide to ramp up more generators?
Seems to me it would solve this problem - they both have a single invariant sync signal.
> Connect a stopped, or sufficiently out of phase generator to a full scale power grid and the puny thousands of pounds of metal that make up a generator are going to get ripped apart
Seems to me this problem is solvable with electronics, but I don't know enough to say how much out-of-phase is problematic. What if, as you say, some heavy load is switched on, the local nuclear turbines slow by a fraction for a few 10s of seconds, and so a home PV array starts leading by 0.01Hz (e.g. home PV at 50.00Hz, local power station at 49.99Hz, so after 10s the PV is fully 36º or 0.6rad ahead). Does this result in the inverter (or the small local windfarm) exploding? Is that a realistic scenario?
> there needs to be more communication across the grid than just responding to the locally observed frequency
Precisely - a grid-wide sync signal, modulated at high frequency.
A millisecond latency will cause a significant out of phase shift to the AC signal too.
The AC data you want is already codified in the power signal
Ooh, good point. But then, we have I think micro- or even nano-second clock sync over public internet now. Or use (reliable) GPS timestamps codified in the sync signal.
> The AC data you want is already codified in the power signal
You're right, but:
> there needs to be more communication across the grid than just responding to the locally observed frequency
Maybe large stations need a grid-wide sync signal that is independent of load, but small (e.g. domestic, community) suppliers just latch on the observed AC (which is easy for an inverter).
Thermal and hydro plants use synchronous rotating generators that have physical inertia, and the generator rotational speed is exactly locked to the electrical frequency. (proportional to the number of poles in the generator).
On-topic: Wind power brings in about 20% of Spain's electricity, and that one fluctuates a lot indeed. I hope they put out a detailed post-mortem, I'd be an enjoyable read.
Some even borrowed the essence of it, posted it elsewhere and still downvoted, ¯\_(ツ)_/¯.
(also we're a bit early for a proper postmortem, but that's an inevitable reality of social media, got to get the talking points in before the facts)
I agree as well. And I think the gp (or the ggp?) post noticed that there is a lack of "spinning mass" to do frequency damping would have agreed as well. They could be merely suggesting to add just spinning mass synchronizers. These could be independent units, doing just that or maybe even convert some old power plants: "just" decouple the turbine from the generator.
The solution in either case is the same. Put enough smarts in the inverter for it to have "synthetic inertia". If we didn't have the ability to do something like that in inverters, the solution would be something like flywheels to augment the chemical batteries.