question

chrish avatar image

AC-coupled Fronius trips out 3 parallel MPii's off-grid

14.4kWh Lithium

3 x MPii's in parallel set up using VE-Config3

Venus GX sees the Fronius via local link

Fronius Primo 5.0 set to country MG50

Primo ramps up to 2.5kW, batts are at 99%, MPiis then trip on overvoltage

I am measuring the microgrid AC frequency - I do not see it change from 50.00Hz during ramp up

I notice there is no mention in the Victron guides of setting any frequency set points in the Primo

I do know that the Primo can track a changing load via frequency/power control seamlessly/effortlessly as I have seen it done with an off-grid Tesla, via frequency control *only* (ie no data cable)

Is there a Victron ref for frequency settings that should be in the Primo?

I am very happy to change these - we do it with the Volt/Watt response for on-grid all the time.

I ASSUME - that I would set the zero-point in the Primo for (say) 51.5Hz

Please confirm or advise of any other refs?

Thanks ChrisH

AC PV CouplingFroniusovervoltage
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Are you running off-grid, or ESS?

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chrish answered ·

I missed stating the Assistant, sorry - its "PV Inverter Support". Installed using VE-Config3

The Fronius can track loads using frequency-shifting - I've seen it on a Tesla. It should therefore have no problem at all ramping down before the Victrons go over -voltage.

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Hi @chrish

Did you check in VRM if the Multi changes frequency as expected?

And if it does, does the PV inverter react to this?

chrish avatar image chrish Daniël Boekel (Victron Energy Staff) ♦♦ ·

No, we weren't able to see any change during testing. The grid-inverter was then taken off the MPii output.

I've just had a look at the history in VRM - Note that there is a second device charging the battery - I've just noticed that the MPii's swung to hard 52.7Hz from about 0730 to 1930 (ie roughly sunrise/sunset this time of year). This is the time when the other device charges the battery.

So it seems that the MPiis are either: now responding; OR are not responding fast enough for the Fronius (which is very odd IMHO)

I think I'd better re-visit the site and re-test.

chrish avatar image
chrish answered ·

It is off-grid.

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I think this happens as the battery reaches full state of charge, and then the fronius continues to produce full power which actually causes the battery voltage to overshoot. If this is so, it’s most likely a Victron setting, related to frequency shifting. Which assistants are you using in the Victron?