question

Pierre-Marie Baty avatar image
Pierre-Marie Baty asked

Multiplus-II GX throttling down PV inverter on grid loss

Hello all,

I have a grid-tied home ESS system with a MultiPlus-II GX, a PV array with a Fronius Primo inverter on AC OUT, and a BYD battery connected to the Multiplus.

Each time there's a grid loss (happens very often over here) all the PV power from the Fronius inverter is instantly throttled down to zero, even in case of full sun exposure. Consequently, for all the duration of the grid loss, all the backup power is provided by the battery only.

I have the feeling it's just a waste of solar power. Why can't the Multiplus allow the Fronius inverter to continue its operation in case of grid loss ? Its power added to the battery power could sustain much more loads than just the battery alone.

Is that a bug, is there a reason, or am I missing a hidden setting somewhere ?

Thanks everybody for your insights.


Multiplus-IIESSgridFroniusBYD
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2 Answers
netrange avatar image
netrange answered ·

Microgrid "50" or "60" is enabled with the Fronius ?

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Pierre-Marie Baty avatar image Pierre-Marie Baty commented ·

I can't find where this is set in the Fronius inverter config (logged in on the Fronius as "service", looked into all the tabs, but I couldn't find anything like that. "Dynamic power reduction" is "off"). Could you please tell me where to look ?

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netrange avatar image netrange Pierre-Marie Baty commented ·

There is a key combination for this

Look in youtube for the video ... Fronius Microgrid


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Pierre-Marie Baty avatar image Pierre-Marie Baty netrange commented ·

This one ? https://www.youtube.com/watch?v=qoRtQ3etNZw

Wait... I'm wondering why all this would be needed since the Fronius inverter is on the Multiplus' AC OUT. It doesn't "see" the grid loss, since the MPII instantly kicks the battery in as an AC backup source. Or am I mistaken ?

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netrange avatar image netrange Pierre-Marie Baty commented ·

However, it must "communicate" the feedback since it is now no longer led by the mains frequency.

It is only a guess but the microcrid should also be set up for normal operation so that the communication works.

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baxter avatar image baxter Pierre-Marie Baty commented ·
In case of a grid loss the Output power of the Fronius is controlled by the MP by ramping up the frequency.
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Pierre-Marie Baty avatar image Pierre-Marie Baty baxter commented ·

The MP already controls the output power of the Fronius, for example when the battery is full. I have disabled grid feed back so when there's a power excess, the MP throttles the Fronius down. This is already working alright. So what could be missing ?

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netrange avatar image netrange Pierre-Marie Baty commented ·

When "Microcrid" has been activated, it actually does it all by itself ... Trying out can not hurt anything

How do you do it at the moment? via pure frequency shifting

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Pierre-Marie Baty avatar image Pierre-Marie Baty netrange commented ·
Alright. I'll try to find out more about that. Do I have to endure the full 47 min of the webinar or is there a particular location where I should jump to ? :) Thanks
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baxter avatar image baxter Pierre-Marie Baty commented ·
When Grid is available it uses modbus TCP. When grid lost the frequency, two completly different methods. Pls read the ac coupling section of the ess document.
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Pierre-Marie Baty avatar image Pierre-Marie Baty baxter commented ·
@Baxter It all makes sense now ! Thank you, I'll read that (again).
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netrange avatar image netrange Pierre-Marie Baty commented ·

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

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Pierre-Marie Baty avatar image
Pierre-Marie Baty answered ·

Indeed I had naively commissioned my Fronius inverter with the local country code (FR) and not with "MG50". Accessing the hidden menu from the front panel and starting over allowed me to fix that.

I can now see the PV inverter supplying the loads along with the battery, when I switch off the mains. Switching the mains back on temporarily throttles the PV inverter off (I suspect this is intended and normal), then it starts supplying PV power again. That Multiplus is one smart machine.

Thanks !

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