question

bonzabuy avatar image
bonzabuy asked

Can Cerbo GX Limit Grid Feed in with Fronius without ET112? ESS

Looking at ESS system with Quattro 2: Cerbo already calculates the combined Fronius (AC) & Quattro (DC) combined import / export to the grid.

However when changing the ESS grid feed maximum in Cerbo settings, it doesn't seem to make a difference. The feed in goes above this max setting (Fronius can't produce more than this setting so it is not Fronius throttling issue)

Is this a known bug?

img-1130.png

Or does the Fronius need MG50? Surely not when AC coupled?

Manual of ESS / Cerbo / Fronius doesn't seem to clarify this (surely common) scenario...

ESS manual does state the below:

Fronius needs to be set: "Data export via Modbus to tcp."

Again this seems redundant when the Cerbo doesn't need to actually control it.

In some places, it seems that this may even need an ET112 meter (see below). Surely this isn't needed with Fronius on AC & communication with Cerbo?

screenshot-222764.jpg

Scenario:

5KW Fronius AC PV > connected to INPUT of Victron Quattro 2

Cerbo GX shows the output of the Fronius, it calculates the total going back to the grid from both Fronius and DC Victron.

Can it limit the Quattro feed in without controlling the Fronius AC PV?

The Fronius has maximum 5KW, so all Cerbo has to do is Feed in from the DC to make up to the 5KW when Fronius is under 5W.

(If the Fronius is already producing 5KW, the Cerbo just needs to throttle MPPT so there is no extra feed in).

This would surely be a very common set up in Australia as 5KW is the maximum feed in for many residences.

cerbo gxESSFroniusfeed-in limit
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1 Answer
matt1309 avatar image
matt1309 answered ·

Assuming you've got ET112 or similar to monitor grid input if Grid is on same side as PV input? As the diagram suggests (ie ET112 as a grid meter rather than a PV meter, as I believe you're correct in sayng you dont need ET112 for PV production of fronius as that's accessible via modbus but a meter would be needed for victron to know how much is coming/going to the grid)


One other thing to try may be enabling Frequency shifting to enable fronius throttling. I'm not sure why you'd need it given you've mentioned the AC coupled power is equal to the max export and you'd just need to throttle the AC coupled but maybe that's needed? Not a concrete answer but my best guess.

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bonzabuy avatar image bonzabuy commented ·
Sorry I never saw your reply.

Yes I ended up switching the Fronius to AC coupled and set ESS to frequency shift.

On the whole this system works much more efficiently now, however the system at times still does export more than the set 5KW. It does throttle, I am guessing it is a time issues due to varying loads / PV input.

I am doubtful the ET112 will make any difference now.

Thanks again

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matt1309 avatar image matt1309 bonzabuy commented ·

If it's close to 5kw then I imagine you're right and it's just taking a few seconds to ramp down/adjust frequency,

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