ceriw avatar image
ceriw asked

connecting generator to AC output of Quattro?

I have a parallel setup of Quattro 8000 and i would like to add a small 3.4kVA generator to my setup.

Being unable to use the AC inputs on the Quattros due to the current limiter being too high, i'm looking at another way to do it.

If I run the Quattros in inverter mode, and then connect the generator to the output through a hot bus synchroniser, this would frequency and phase match the generators output with the inverters before closing a solenoid to connect them.

I know this method works well for linking multiple generators together, but how does the Quattro respond to it? Will it just treat it like a AC coupled solar array?

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hans-schive avatar image hans-schive commented ·

Hi Ceri.w, did you give it a go? Any updates on this?

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ceriw avatar image ceriw hans-schive commented ·

Not yet. I've been having some teething issues getting the basic system to work so have not added anything to it yet. I have however done quite a few measurements on my generator and built an electronic throttle control as the mechanical one was not accurate enough.

Even with an electronic throttle control though, the generator is not stable enough that I would feel comfortable synchronizing it to anything - I think it is just too small to have the stability of the large flywheels on the bigger gen sets.

I have had a re-think though and have a new way to try. I'm building a 3.5kW active PFC to convert the generator output to DC, then I'm going to use a PV inverter to feed the power back into AC out of the Quattros.

I'll install a AC power meter on the output of the PV inverter. The only thing I have not yet figured out is how to get that to display as generator power on the VRM as there is currently no setting to show generator connected to AC out in the AC meters menu...

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hans-schive avatar image hans-schive ceriw commented ·

Thanks for sharing your thoughts, we'll be curious to follow your progression in this installation.

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3 Answers
Paul B avatar image
Paul B answered ·

Hi I have no idea, I Think you would just have to try this and see.

I suspect it would work but as its never been tested this would be all up to you

Sorry I cant be more helpfull

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

You can reduce the AC input current limit if you disable the power assist feature. I would recommend you do that instead if possible.

This and other suggestions to get troublesome generators working with Victron Equipment is suggested in the MultiPlus Generator FAQ.

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ceriw avatar image ceriw commented ·

Hi Guy, if I disable the power assist feature, would this then mean that the generator has to carry the full peak load of upto 14kVA plus the charging power?

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Ahh, yup, that won’t work for you then.

In that situation I would suggest a dedicated charger (like a skylla), and a BMV.

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Alistair Warburton avatar image
Alistair Warburton answered ·

If for some reason the generator will not work feeding the charger, as it should, noting the current limit Guy pointed out and up end up fiddling...

Use an external charge on the DC side of things. You were talking about rectifying the generator output anyway so re inverting that to feed into the AC is, well, complicated for little reason.

I ran a small led acid system for about 8 years before buying the Victron kit and used a cheap DC welder as a battery charger. All it needed was an external current control and a big choke to reduce the ripple.

Having said that... You probably have some of the best inverter charger kit on the planet and genertors are cheap in comparison. Once you have the correct settings it should be fine and if it isnt engeneering a custom solution will likely cost more than a generator... Fun possibly but likely not clever in the long run.

I run a 3.2 KVA inverter generator made by Champion. it feeds a 5KVA Multiplus with no issue at all. AC current limit is 12.5A, wide mains frq/volts is off because it decreeses PF when attempting to match things. There is another setting, week mains I think, that limits the charger ramp rate to give the generator time to react, which I have on because I keep the set in economy mode and it take time to ramp up.

It alll worked first time and hasnt let me down of had an issue once.

It is also probably worth mensioning that th genni is dual fuel and only ever run s on LPG so it wouldnt be capable of 3.2KVA even if I wanted to go there.

I am in no way affiliated with Champion and couldnt comment on more expensive systems but I have hammered my little unit way beyond its intended use for a couple of years now and when I finally ware it out, no sign of that yet, I will simply buy another one, without checking anything else, because its been so good.

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ceriw avatar image ceriw commented ·

Hi Alistair, thanks for sharing your experience. One of the reasons I was looking to re-invert back to AC is because after the active power factor correction stage I have 400-600 VDC. The difference in design and efficiency between a DC-DC converter and a DC-AC inverter is minimal. Using a welder, or any other linear power supply to charge batteries is going to have a power factor of 0.7 at best. That's a lot of circulating current for no good reason and is going to drop system efficiency.

I should probably explain a bit more about the sizing of my generator. It is part of a combined heat and power system that I have built. I can get 3.4kVA of power from it and 9kW of heat - it runs on natural gas so had in effect taken place of the house boiler. The output of the generator is stable, it just can not be expected to meet the minimum shore current requirements of my inverters (21A). If I was to up-size the generator to meet this then it would mean the heat output would be over 15kW, more than my current heating system could deal with, and also for a shorter period, so I would need to add a much larger thermal store to the system - something I'm not sure I have enough space for.

I've had to put this project on hold for a couple of weeks as work has been really busy but I'm hoping I can get back on to it soon - will keep you updated

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