[jacquesm]

'Too much electricity in the grid' is a wrong way of expressing it, just like you can't have 'too much fluid in a pipe'. What happens is that the line voltage creeps up because loads are lagging further behind compared to generation.

And like you wrote, that's controlled. Agreed with the rest of your comment, especially the bit that pricing is mostly controlled by the worst parties, not by the best. What we are simply finding out is that a grid designed mostly for baseline loads needs fast response generation (for instance: half of the UK putting their kettle on during half time requires so much extra power that pumped storage becomes a good alternative). And conversely, that if you change the mix considerably that you're going to have to have more control over the cumulative effect of many smaller generators.

But there are already standards for dealing with that even absent remote control of resources: as soon as the local grid voltage that the inverters in modern wind and solar plants see exceeds a very specific maximum for a proscribed period of time they fully autonomously back off their capacity until they are well below those maximums again, and then slowly ramp up to avoid causing grid instability due to oscillation.

What grid balancing is all about is to make this all financially optimal, it has relatively little to do with the safety of the grid, it is simply a way to extract maximum capacity without affecting that safety. A coarser mechanism would simply incur some more waste, but given the amounts of money involved it pays off to tune this.

[iTokio]

That’s very interesting, but as a counter point, it seems that the major spain blackout was partially caused by such a voltage increase that was not mitigated properly.

So yes there are mitigations but it still is a major cause of concern I think

[jacquesm]

Yes, but that voltage increase alone wasn't enough to have caused the outage. The bigger issue was the subsequent oscillations which were amplified by the fact that that part of the grid is relatively isolated. The larger lessons there are still being learned with the report on that outage due in October I believe, but this isn't the first and it certainly won't be the last power outage. The 2003 one in the USA and Canada was much larger and didn't have any renewables other than as instantly available recovery loads for a good chunk of the grid, whereas nuclear power (everybody's baseline stand-by) took much, much longer to recover.

I think for myself the main takeaway is that we have come to rely on always available grid power to a degree that we probably should not have. Unfortunately inverters and battery systems that are capable of running in off-grid mode are very hard to come by compared to the on-line variety. Automatic disconnect and synchronization hardware are present in pretty much all inverters but they are connected in ways that the house would not be isolated from the grid and the software does not support such a solution because of the certification requirements.

Interestingly, a large (house capacity, which is a considerable amount of power) UPS does have those capabilities, and charging UPS batteries through a different mechanism than the built in charger is easily doable.

As for that Spanish/Portuguese outage: I fully expect that there will be some regulatory demands made on grid operators, especially with respect to containment of such outages, and possibly a requirement for better interconnection to increase the amount of perceived inertia in the grid. That is the best protection against such issues. Another thing that needs to be studied better is the kind of 'thundering herd' scenario that seems to have been the cause here (that's very much preliminary, but that seems to be the most logical explanation), especially in grid regions with low internal inertia. Such inertia is basically tightly coupled to how much grid synchronized rotating mass there is in a particular section of the grid. The more mass like that the more inertia there is the harder it is to make the grid go into oscillations. This mass is present both on the production side (generators) and on the consumer side (industry, because the prevalence of electric motors). So areas where the are no traditional (non-renewable) sources and very little industry are more susceptible to such kind of problems, especially when they become more isolated.

I'm following this closely because I look at companies in this space with some regularity and it is in fact what I went to school for at some point, it has always been a field that has interested me.

[bradfa]

As the grid moves away from physical inertia sources and loads, do you think it would be realistic to distribute a grid-wide signal separate from the actual line voltage which could assist non-rotating power sources to stay in sync or at least help reduce the chances of oscillation?

The easiest is probably radio or satellite broadcasts but the topology of the grid, which does change, would also have to be considered. Probably not an easy problem to solve simply?

[jacquesm]

The grid itself is the best source for that. What I think we will see instead is custom superconductance based sink/source units that help with local grid stabilization. Those are already being deployed and they work quite well absent mechanical solutions, but they are still expensive and their capacity is still limited. A really dumb (but probably quite effective) way of doing this could also be by simply hooking up massive but slow flywheels.

Both have the same effect. Good distribution of generation and consumption in a geographical sense is something we never really gave much consideration in the past, it wasn't rare at all to have one side of a geographic region to be 'mostly producers' and another to be 'mostly consumers' and where the two sat next to each other it was usually to accommodate some really large consumer (for instance, a paper mill or a steel or aluminum plant). That also allowed for co-generation which is far more efficient. I think we will see more of this as well, and incentives to allow EVs to be used as sinks during times of excess power availability.

Other options are HVDC interconnects between geographically distant regions or to use these to create micro grids, each of which would be less stable than a much larger one but it would serve to isolate problems if and when they occur.

Interesting detail: wind power, while theoretically rotating grid synchronized mass is increasingly uncoupled and powering the grid using inverters. This is for efficiency reasons, the rotors have a much wider range that way, and you then only use furling of the blades to protect the installation from overspeeding and maximum efficiency the rest of the time even if that means rotating at a different speed than what would sync with the grid. This is optional, if the machine is synchronized it will still produce power, but not quite as much because blades are more efficient at higher RPM running flatter than at lower RPM running coarse, though coarse they do have more torque. So by sticking an inverter in the middle you can basically electronically do MPPT for the windmill rather than doing that mechanically.

Over the life of an installation the cost of that inverter is more than paid back in extra power but it has the downside of not having the mechanical mass of the wind turbine rotor and blades as extra inertia. Win some, lose something else...