The best setup for Zero-feed-in 3-phase installation using Fronius inverters.

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jaro2k asked Mar 20, '24

The best setup for Zero-feed-in 3-phase installation using Fronius inverters.

Hi,

I would like to ask for your opinion. We have 3-phase power grid connectivity in our building and we are considering building a system based on Victron ESS using 3x Multiplus-II 5k in combination to Fronius inverters connected on the AC-in side. Since there is Zero-feed-in requirement from the energy provider I would like to ask what would be the best solution to eliminate energy feed-in on any of the given phases.

Sure, we plan to install energy-metering on the grid-input which will communicate this to Cebro-GX.

The alternatives are:

1/ using 1x Fronius Symo

2/ using 3x Fronius Primo (single Primo connected to each phase)

I have a feeling that second alternative could provide better results in terms of zero-feed-in requirements just because energy consumption in the building is asymmetric so if we set "Multiphase regulation" to "Individual Phase" then ESS logic will likely manage each Primo inverter independently based on consumption per each phase to keep Grid-setpoint Zero for each phase.

The first alternative on the other side may lead to ineffective use of Symo inverter since this device would distribute power across all 3-phases symmetrically regardless of asymmetric consumption which could result in lowering the power generation on Symo based on phase with lowest consumption.

What are your thoughts?

Thanks

ESS Fronius feed-in limit

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Answer 1 · 2024-03-20T17:50:34Z

duivert answered · Mar 20 at 05:50 PM

Hi, I dont think you can control zero feed in with fronius inverters on AC in side, only on AC out side of the multiplus

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max-payne commented · Mar 20 at 08:34 PM

That is not true in three ways.

First fronius support zero feed in via Fronius Smart Meter
Second fronius can be controlled via frequency shifting by multiplus-ii
Third a fronius can be controlled via lan by the cerbo GX

https://www.victronenergy.com/live/ac_coupling:fronius
https://www.fronius.com/~/downloads/Solar%20Energy/Technical%20Articles/SE_TEA_Quick_Guide_How_to_set_up_Export_Limiting_using_the_Fronius_Smart_Meter_EN_AU.pdf

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duivert max-payne commented · Mar 20 at 09:20 PM

Of course fronius support zero feed in, i did not state that :)

Yes, can be controlled by frequency shifting, but not on AC in!

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Answer 2 · 2024-03-20T20:32:35Z

max-payne answered · Mar 20 at 08:32 PM

In your system it would be recommended to put the controlled PV to the ac-out of the Multiplus. If that is not possible because of the 1:1 rule or cost - then the fronius side needs to control itself:
BOM: Fronius Smart Meter TS 65A-3

A real important point of your system is if your are grid parallel or grid serial with respect to the 3x Multiplus II.

I assume grid parallel now. This way frequency shifting cannot be used and you have to go LAN route. https://www.victronenergy.com/live/ac_coupling:fronius

IMO you invite a lot of headache by mixing this. You have two easier options:
Buy a fronius hybrid inverter and a matching battery and a TS 65A-3 OR
Buy 3 multiplus-ii and a (pylontech) battery and a Victron Smartsolar and a EM24.
Both ways support zero-feed-in

Better yet - make zero feed in go away and make money with excess

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Answer 3 · 2024-03-20T21:29:51Z

duivert answered · Mar 20 at 09:29 PM

There is more info here, part 2.1.3 and 4.3.14:

https://www.victronenergy.com/media/pg/Energy_Storage_System/en/index-en.html

Also why you cant use a fronius smart meter with ESS, see Q4 here:

https://www.victronenergy.com/live/ac_coupling:fronius

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Answer 4 · 2024-03-21T00:45:22Z

jaro2k answered · Mar 21 at 12:45 AM

Hmm.. right, frequency shifting will not work on AC-IN but I could control all Fronius inverters via Modbus-TCP.. so I believe I could still stay with Victron Cebro-GX and Victron compatible smart-metering on grid-input. Don't you think so?

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Answer 5 · 2024-03-21T05:54:35Z

duivert answered · Mar 21 at 05:54 AM

Yes it should work, but as @Max Payne said it will give you headache’s

Connecting them on ac out (if possible) is much easier and you will benefit from still working solar when grid is lost!

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