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chriss83 avatar image
chriss83 asked

Fronius on ESS without MG50?

Hi there,

since Fronius Support is taking some time to answer the question, I might as well post it here.

The local utilities require a specific cosPhi setting in the inverter, which - for my knowledge - requires a countrysetup other than MG50.

How does changing from MG50 to i.e. DE2U affect the behaviour of the inverter in an ESS?

Feed-in only needs to be limited to 70%, so no zero feed-in required.


As always, thanks for the help!

Chris

ESSFronius
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4 Answers
Rob Duthie avatar image
Rob Duthie answered ·

You only add the MG50 if you are using the Fronius on the AC output of the Victron, if on the input side of the Victron use your normal country code to comply with.

Regards

Rob D

NZ


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borisut avatar image borisut commented ·
I have this Situation attaching Fronius to the AC out. As I use the Bypass I would like to use the correct Grid code so that this works when the multiplus fails.

Question is what happens if the network fails. Is the multiplus still controlled by ethernet or the frequency shift?

I don't find any clear advise

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Rob Duthie avatar image Rob Duthie borisut commented ·
Hi

Yes it will still shut down as per grid code, as when doing the setups you install the country code then install the MG50 code next then all is well with grid protection etc.

Regards

Rob D

NZ

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alan avatar image
alan answered ·

In an ESS with a PV inverter Ac coupled to the multi output, the system is controlled by Modbus-Tcp.

Frequency control is only used if the grid has failed and the multi can control its output frequency.

In the ess while grid connected, the grid interaction is controlled by the multi and the grid code, with reactive power control set in the multi.

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chriss83 avatar image chriss83 commented ·

Perfect answer I was looking for, many thanks!

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baxter avatar image
baxter answered ·

Hi,


same issue here. My provider requieres the national grid code to be set in the Fronius on ACout of an 3~ ESS. No issue if grid is available, but whats in case of a grid failure?

Will that work in general and what are the drawbacks using the national grid code in the Fronius instead of MG50?


TIA

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·

The MultiPlus is the connection to the grid and will disconnect from it if something is wrong.

So there is no need for the Fronius to use the normal grid code.

If the Fronius is not set to MG50/60 it will most likely not start in case of a grid failure.

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baxter avatar image baxter Matthias Lange - DE ♦ commented ·

AT is different ;)

In case the Multi provides a grid within the reconnect range of the Fronius (47,5 - 50,05Hz) it should start?

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ baxter commented ·
The frequency is not the only thing. The Fronius is also checking the voltage and the grid impedance.

The correct grid impedance is the thing a MultiPlus can't match.

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baxter avatar image baxter Matthias Lange - DE ♦ commented ·
According to Fronius Dev Department it works with the national grid code. P(f) is not working as good with MG50 but sufficient. As it is an ESS that should be just fine
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borisut avatar image borisut Matthias Lange - DE ♦ commented ·
The issue above is the usage beind a Bypass that needs Fronius to be set on reginal grid code. MG50 would be not correct in this case. Is MG50 mandatory if the feiniua needs to be controlled behind ACout?
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baxter avatar image
baxter answered ·

Update: Fronius Symo off-grid with AT1E (grid code Austria) works fine.

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borisut avatar image borisut commented ·
Fine is nice but what happens if grid is off and the batteries are full?
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bytebang avatar image bytebang borisut commented ·
I have tested this today: symo 20.0-3m (reduced to 7kWp, GridCode AT1E) with 3x MP2 50/70 (same grid Code, with ~25 kWh LiFePo batteries)


As soon as the batteries are full, the frequency at the AC-OUT1 of the MP2 will start to rise. This forces the Symo to reduce its power until the frequency rises up to 51.5 Hz.


As soon as 51.5 Hz is hit, the Symo will instantly turn off (because of grid protection defined in AT1E settings). The victrons will switch from "charging the batteries" to "discharging the batteries" and you may notice a short flicker on the lights, but no power interruptions as such.

Since the Symo is not producing any pv power which has to be stored in the batteries, the frequency of the victrons decreases to 50 Hz again - which provides a stable (enough) grid to start the symo again.

After that the cycle starts again: The symo will power up and after approx 5 minutes it starts to produce pv power again - which forces the victron to rise the frequency - which forces the symo to disconnect, and so on.

This game is played until the battery is "empty enough" to store the incoming PV energy which is not used otherwise.

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bytebang avatar image bytebang bytebang commented ·

One more update: If you set the "frequency degradation rate" from 40%/Hz to 77%/Hz in the PROFI menu on the Fronius, then a stable grid is formed, where the Fronius does not go into frequency protection mode (even when operated in the AT1E grid code)

Background: AT1E says that frequency based degradation starts at 50.2 Hz, and the PV inverter should switch off at 51.5 Hz. With the standard settings this forces the Fronius to degrade its power output till the net reaches 51.5 Hz - and from there on it will just switch off. The standard degradation rate of 40%/Hz reduces therefore the power to (51.5-50.2)*40% = 1.3*40% ~52% before the Fronius is forced to shut down because it reaches the 51.5 Hz.

The updated "frequency degradation rate" value of 77% tells the Fronius to degrade its power faster. When the frequency reaches 51.5Hz then the generated PV power is already reduced by 100% - meaning that the Fronius is not delivering any power at all if the frequency reaches 51.5Hz.

This means that the Fronius has no reason to disconnect forcefully because the victrons limit the fronius more and more till the delivered power ist 0 W at 51.5 Hz.

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