AC Coupling offgrid with zero injection

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kyuketsuki asked Jan 2, '23

AC Coupling offgrid with zero injection

Hi, I have an off grid installation with a DC Coupling via Victron Smart Solar, Victron Multiplus and OPZS batteries. I want expand it via AC Coupling, but until April there aren't Fronius Primo on market, for this reason I bought a Solax inverter.

Multiplus communicates to Solax increasing frequency, but I'm afraid this increase may damage the appliances or may lead to a malfunction of these.

I have a Smart Meter Chint DDSU666-D 80A 1Ph, it's an export limiting meter.

I want install it between the AC Out Multiplus and the house loads, so that it regulates the Solax according to the loads and no energy is sent to the Multiplus.

There are any problem with this configuration?

Maybe I could set the Multiplus to very low frequencies such as 50.01 instead of 50.20 to start the Solax output reduction, 50.03 instead of 52.70 to minimize and 50.05 instead of 53Hz to stop the Solax?

If I don't configure the Solax it will be regulated by the Smart Meter regardless of the frequency sent by the Multiplus, right?

What will happen when the Multiplus detects that the Solax has not stopped?

With my DC Coupling system, now I can charge overnight consume and batteries stay on float almost all day.

I attach a simple diagram.

Thanks.

offgrid ac coupling

esquema-chint-2.jpg (70.7 KiB)

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Answer 1 · 2023-01-03T05:35:48Z

shaneyake answered · Jan 03, 2023 at 05:35 AM

What appliances do you have? Only motor heavy appliances may be affected but the 6 percent increase in speed is really not a problem for 99% of appliances.

Changing the Frequency shift window can make the system unstable best to leave at 51-52 with cut off at 53hz.

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Answer 2 · 2023-01-03T06:21:14Z

Phil Gavin answered · Jan 03, 2023 at 06:21 AM

I have been running an off-grid house (ac coupled) for several years.

It has all the typical domestic appliances, and I haven't had issues.

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Answer 3 · 2023-01-03T09:28:27Z

rvicev answered · Jan 03, 2023 at 09:28 AM

Inconvenience : electronic clocks may be affected (ovens, clock driven electric heating systems, etc, often still don have quartz clocks .....)

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Answer 4 · 2023-01-03T14:49:22Z

kyuketsuki answered · Jan 03, 2023 at 02:49 PM

My idea is the Multiplus know there is a grid inverter, but I must to give him some frequencies in this configuration, then I give it the command to reduce the production using frequencies very close to 50.00Hz.

I think that being the frequencies so close to each other could cause a Solax's malfunction, but I no configure the Solax to obey the Multiplus, I configure Solax to obey the Smart Meter, then this problem would disappear.

The theory is if Multiplus knows there is a grid inverter no have a problem when detects voltage in AC out.

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Answer 5 · 2023-04-27T17:51:58Z

kyuketsuki answered · Apr 27, 2023 at 05:51 PM

Hi, at last I make my project, and it works OK, on this wiring you don't need configure Multiplus, the Solax is working by himself and the smart meter prevents not overcharge the batteries, trough the Solax app you can decide haw many watts go to Multiplus, I configure it in 40W maximum becouse it's the Victron's Multiplus and MPPT consupmtion.

I attempt to control Solax by frequency, but I don't find the FreqSetPoint and FreqDropRate in the app menu.

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