Synchronous Condensers for Power Grid Stabilization

[bhobba]

I mentioned in a post some time ago now that, at present, the renewable energy debate here in Australia is mired in economic issues, not technical issues this forum is concerned with.

It still is, but a new twist has appeared - the need for synchronous condensers:
https://search.abb.com/library/Down...LanguageCode=en&DocumentPartId=&Action=Launch

All sides seem to agree they are needed, and the discussion is now around their economics.

The economics is not in this forum's ballywick, but what they are and how they work is.

I remember my father mentioned they were used a lot in the 1950s (he worked as an electrical estimator, primarily for power stations), but gradually grew out of favour.

I thought a discussion of what they are, why they went out of favour, and why they are important for renewable energy would be of value.

So over to the professionals. What, technically, are they and the reason for their comeback?

Thanks
Bill

 

[renormalize]

Your link gives me (in Windows 10, Google Chrome):
"404 Not Found. We can not find the page you are looking for."

 

[jrmichler]

I got the same, then cut and pasted just the https://www.pv-magazine-australia.com portion of the link. I clicked on the article, and cut and pasted the link of the article: https://www.pv-magazine-australia.c...o-play-key-role-in-system-security-says-aemo/. It worked when I tested it.

It's a general article about dealing with intermittent generation from solar. The only specific mention of synchronous condensers is: Key to AEMO’s plan is the timely delivery of synchronous condensers capable of providing both system strength and inertia.

That synchronous condensers link in the article leads to this quote: “Synchronous condensers are large spinning machines that mimic the grid-stabilising role of coal generators, enabling the NSW power system to more rapidly accommodate renewable energy generation, delivering cleaner and cheaper electricity to consumers,” the high-voltage grid operator said in a statement.

 

[bhobba]

Whoops.

I found a link to a paper that definitely works as a link and gives more detail. Original post updated.

Thanks
Bill

 

[Ken Fabian]

There is ongoing evaluation of batteries with grid forming inverters for providing synthetic inertia; Tesla Motors Australia (that does Tesla batteries) has been urging more use of batteries with GFI's for system strength and inertia, as well as support for a specific market ie payment for such services. They did the first trial and do in fact appear to be approved for providing such services - https://neoen.com/en/innovations/ne...ornsdale-power-reserve-big-battery-australia/ - sufficient for about 15% of total requirements for South Australia.

The grid operator AEMO has rejected creation of such a market at this time but is likely to revisit that decision. They are unwilling to bet system reliability on inverters emulating spinning inertia but are trialing them.

Syncons are a known quantity for dealing with big loads shifting in and out and for giving time to respond to faults and retrofitting 'clutch fitted' gas power plants to enable them to act as syncons when the gas plant is not producing power is already an option. But either way they are expensive with long wait times between ordering them and installation. If batteries can do the equivalent simply with updated inverter software (or with newer inverters) it makes sense to use them.

Synthetic inertia is still undergoing evaluation and adequate 'fault current' seems to be an issue not fully resolved, which Tesla Australia appears to think is not really a problem (I don't have the knowhow to evaluate this) but I expect any revealed shortcomings are going to be addressed by people smarter than me.

Given the first 'big battery' in Australia is only 8 years old and grid forming inverters are even newer technology than that and just 2 years since first trials of synthetic inertia it does seem likely they will displace the need for a lot more Synchronous Condensers and do so soon. A lot of battery capacity is being added in Australia and it will almost certainly include all their capabilities - frequency and voltage regulation and synthetic inertia and system strength included.

 

[nsaspook]

https://reneweconomy.com.au/was-the...ul-battery-too-much-for-crippled-transformer/

Some outside observers say the fact that all transformers were taken off line as a precaution, and problems found in a second unit, suggest that is one possibility.

These things are used to simulate rotational inertia energy reserves when RE energy is the main driver in the grid. Looks like they were pumping massive energy into the grid when it smoked.

https://www.wtc.com.au/our-company/...ransformer-for-waratah-super-battery-project/

On Saturday, the last of the three 350MVA 330/33/33kV power transformers started its epic journey out of Melbourne to its final destination in NSW, at the site of the former Munmorah coal-fired power station, in a complex 9-day operation. With a transport mass of 170 tonnes and being carried by a 477-tonne superload, the transformer makes for an unforgettable sight.
...
The project is being developed by Akaysha Energy. WTC is supplying 3 x 350MVA 330/33/33kV and 145 x 7.3MVA 33/0.77/0.77kV transformers (all made in Australia) to Consolidated Power Projects (CPP) and Akaysha Energy for the project.

https://transformers-magazine.com/t...nsformer-failure-halts-waratah-super-battery/

Despite the failure, Akaysha Energy confirmed that the facility continues to provide 350 MW and 700 MWh of capacity under the System Integrity Protection Scheme (SIPS), acting as a grid stabiliser for Sydney, Newcastle, and Wollongong.

 

[Fisherman199]

a strong system is a system which has capability of significant fault current contribution into nearly immediate voltage decay. The short-hand way of looking at that is the 3-p-g bolted fault at a system busbar and 1-p-g fault at the same system busbar. if they're similar in magnitude, the system is "strong". in better practice, the slower voltage decay happens (we're talking in 1/16s of a cycle delineations, here) the "stronger" the system is.

syncons provide inertia, which is to say, they can provide the sub-synchronous reactive/magnetic response to the system in faulted conditions in order to support fault MVA into collapsing voltage. This is necessary for system protective devices to plan and function correctly. This sub-synchronous inertia inverters are not able to provide. on PMW inverters which use park transform and DQ0 control, they can accept and reject MVAR from the system by modulating voltage on the AC and DC side. This mimics inertia on seconds scale, but not sub-synchronous scale, which is necessary.

I used to do a fair amount of economic generation planning and inertia is a "cost-able" metric in expansion plans and economic models. This has not traditionally been used in a time where all gens were rotating but, as you note, that's changing and the planners will need to change with it. Developing ways to place our heads around inertia cost will become subject of much discussion and papers in coming years/decades.