jschz avatar image
jschz asked

DVCC Not working on an offgrid system

Hi everyone. My system setup is the following:

-Offgrid system.

-Three Quattro (10000 VA) as a three phase system (PV inverter support assistant)

-Pylontech batteries (US3000C) system (25 kW and 49 kWh in total).

-Cerbo GX

-Fronius symo 3.7 kW (In the future I will have a bigger one, for now I'm using this just for doing some tests).

I want to manage the control of the charge current of the batteries by using the DVCC, but it is not working. If I have, for example, 32 A of charging, and I limit the current, on the DVCC menu, at 20A, what my system do is to turn on and off the Fronius constantly, but it is not able to control the power of the solar inverter.

I don't know what I'm doing wrong. Any help would be very appreciate.

battery chargingoffgridDVCC
1 comment
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Alexandra avatar image Alexandra ♦ commented ·

I am going to start with the basics...

Is all the firmware (even on the Fronius) up to date?

Check what the batteries request when they are full and set the DVCC limit to that. Don't go under it.

The control over the fronius is a bit clunky Fronius have a solution for that but don't share it openly. Something called twilight settings or something. You have to contact them directly for it.

To be dead honest I replaced the fronius in our installs in favour of the RS 450 series. Never been happier. Way easier integration and control.

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1 Answer
snoobler avatar image
snoobler answered ·

This sounds like normal behavior.

A grid tie inverter does not regulate its output. It must have an infinite grid in which to dump its output.

Being AC coupled with the Quattro means, the only way to "regulate" the Fronius is to shift the frequency such that the Fronius disconnects.

As battery attains the "charged" voltage dictated by the BMS, the inverter shifts the frequency from 50/60Hz to something about 2Hz off to cause the Fronius to disconnect.

In other words...

If solar conditions are such that your Fronius outputs 30A, your Fronius MUST output either 30A while connected to the grid or grid-forming inverter or 0A by disconnecting.

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jschz avatar image jschz commented ·

Hi @snoobler thanks for answering.

The conclusion I get from your comment is that it is not posible to regulate the output of the solar inverter, but in this video (Smart Battery Charging Control with Victron DVCC. It actually works!), the guy is able to do it by using DVCC, and that is what I want to do.

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snoobler avatar image snoobler jschz commented ·

Andy is only using Victron MPPTs in that demonstration.

I suggest you start here:

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jeanmarie avatar image jeanmarie jschz commented ·
Yes, a fronius inverter is capable of modulate it's power but you must have followed the manual for that, have you (MG50/60 mode and other options, well described in Victron documentations ?)
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