Industrial UPS

I work for a specialised blow moulding company. As a 24/7 business, we installed a 500kWp rooftop solar array and more recently a 640kVA generator to reduce our dependancy on Eskom power. Due to very irregular demand, we are struggling with sync errors on the generator, as well as under voltage and under frequency trips. A further issue is that we have very frequent but short mains power drop-outs. All of these sudden stops are wreaking havoc with our equipment and we require some kind of industrial UPS to integrate everything, remove power spikes and support the generator with sudden changes in demand. What are our options other than going full hybrid with 1500 or 2000kWh batteries?

Maybe you don’t need that big batteries… Basically a double-conversion UPS can be assembled from Victron parts.

Charge batteries with 3x Quattro from grid or generator, which should provide a pretty stable load for the generator. There’s a lot of tweaking options in the config for dealing with generators. This is the input stage and only provides power for the DC bus and batteries.

Then convert back to AC using another 3x MultiPlus (or Quattros). Power goes via DC bus with battery buffer, so that’s not efficient at all, but you’re fully in control of your output power quality then and your generator is effective decoupled from your load spikes.

Sounds like your PV is AC-coupled, so that can just go on output.

Essentially you’re running a microgrid from solar and battery, but with additional mains / generator battery chargers.

You could also bypass the chargers and use the grid directly into your output stage Multiplus / Quattro set, but that won’t cleanup the power. Could work well enough 80% of the time and when you’re fed up, you switch to double-conversion for the week?

@JacoDeJongh has experience with some pretty big systems, so should be able to design something good.

These things exist as off-the-shelf products too under traditional UPS labels.

Double-conversion vs Line-interactive: Double Conversion UPS – Benefits & Comparison | Mitsubishi Electric

Edit: This is massive though: Does anyone have a grid-tie system with no storage? - #10 by Scubadude

Victron tops out at 180kVA for 3-phase :grimacing:… Maybe do 5x, one per 100kW SolarEdge :expressionless: :

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Can this system run the critical plant without additional power?


See Does anyone have a grid-tie system with no storage? - #10 by Scubadude

It might make more business sense to look at a better generator that will be able to support your load, otherwise I would contact the likes of FreedomWon to get a recommendation for someone to quote on an ATESS + FW solution. That should guide you towards the correct generator solution :crazy_face:

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Its the only “Easy” option above 100kVA.
You don’t really want to work with a 48VDC bus at those power levels, just imagine, at 500KW if you pulled that power from a 48VDC bus you will pull around 10 000A!

I am also looking at a solution for a packhouse where there is currently 2x 450kVA Gennies with a AC Synchronizer.
And the only viable option I have seen thus far would be 4 x 150KW ATESS inverters.


Thanks … yeah, need a bigger solution than that.

Not at the moment … we are getting a SolarEdge technician (hopefully this week) to complete the solar - generator integration. But even when connected the solar is really only a diesel saver - it is too erratic to run any production equipment with.

When we planned the first we aimed to offset the effects of Stage 1 and 2 on a couple of key machines. But with September having had more loadshedding than all of 2021 combined we will be installing a second generator soon. Running on disels costs 4-5 times as much as running on Eskom power, but not running at all costs even more.

Thanks for the ideas …

The under voltage / under frequency issue was traced to a turbo boost pipe that worked loose. And the sync errors we will try to address by giving the Syncroscope a +/-2Hz tolerance. But we still have those Eskom drop-outs which are an absolute pain. I have spoken to three UPS experts, and all seem to have workable solutions provided you have deep pockets …

Just delivered for our house … joking.

It did make me think of your plight.

Picture from an email from Jennifer Jones

I’m no expert, but have heard about a huge smelter that use what was termed a “dip doctor”. Basically a massive flywheel buffer that can keep the voltage and frequency stable until the generator can kick in. Their equipment were extremely sensitive to voltage dips.

I don’t know who to contact w.r.t. this type of solution, but I can find out from the electrical engineer who was involved with the power delivery to smeltery. He told me about this “dip doctor”.

Something like this:

Spoke to the guys at EDS UPS about Piller rotary UPS which is an incredibly elegant Dip Doctor solution - the 3% efficiency loss is possibly offset by a reduction in peak demand tarriff, and it is virtually maintenance free. Deep pockets clause apply.

Eish, so the cost is a little prohibitive? I spoke to the person who told me about it and he said the one he saw was actually purchased secondhand. Maybe there’s something like that available… no idea where to start looking.

We have a “kinetic flywheel” UPS installed at work to carry the load on voltage sensitive machines for a short time while the generator starts up and get up to speed. Ours was supplied by Barlow World. It has the added benefit of also filtering spikes from the Eskom supply (when available). Not a cheap option, but very effective. Due to the clean power supplied, our maintenance cost on the control electronics of these machines was significantly reduced.


So we received two Freedom Won / Atess offers. Had the opportunity to visit the FW factory and it is quite incredible. Love the feverish activity of a fast-growing business!

With more frequent power spikes and a (deliberately) undersized generator, we are leaning heavily towards 2 x 600kVA Atess + 1600kWh FW. The payback comes in the form of a R5/kWh saving compared to diesel, and winter energy arbitrage in times of no loadshedding.

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