question

What assistants are being used and are they installed on all 3 units

you do also need a PV assistant or ess assistant

I take it this is an off-grid installation.

I haven't tested what I will explain, but I think it may work.

One method to reset the AC coupling is to put a 50Hz supply onto the Quattros.

I think it is sufficient that only the master Quattro gets the 50Hz signal. The Quattros then reset from the 53Hz, back to 50 Hz in order to synchronize to the grid. Resetting the AC-coupling as a consequence.

I think a tiny 1ph 200W-ish off-grid inverter feeding 50Hz onto the Quattro AC input via a contact will do the trick. You can control the contact with whatever, manually, a 30 min timer, a SOC contact etc. that's just a detail.

although my setup is single phase this is my assistant setup, may help and then may not. good luck
also look at the order you have the assistants in as some assistants have to be the very first in the list, this is specified in there descriptions if its applicable.

Also my system is 99.9% always having ac1 in ignored so its always basically off grid.

HOWEVER

I have also placed a isolation contractor in the PV inverters output line, and I then use the generator auto start to turn this relay off when voltage reaches 56v and back on when it reaches lower than 55.0v for 10 min- this was done a long time ago when frequency shifting was not fast enough and I had battery overvoltages on maybe the bank was two small ( ie 12kw), so you maybe able to do something like this to get over the issue.

its a work around if nothing else works the voltages mentioned are examples only

Hello, my big problem is on the following video.
After input ignored the frequency keep shifting!!!!

@Daniël Boekel (Victron Energy Staff) ?
@mvader (Victron Energy) ?
any suggestions?

Config:
https://we.tl/t-ioc3xFOBJY

Video:

https://we.tl/t-RP1A3cNjpE

I am confused.

I interpret your problem as the high-frequency locking out of your AC-coupled inverters so that when you need them, they are unavailable. In other words, there is too much hysteresis before they reset.

The AC-coupled inverter does this once the batteries are charged and there is no alternative route for the power. This is the correct inverter response, but perhaps it can be reset sooner.

I'd like you to reframe your problem with the inverter's response, as I do not understand what you are trying to say is the issue.

Update:
Second system(multiplus 24/5000) with same issue!!

Some screenshots from VRM.

Multiplus 24/5000 (firmware 481, CC Gx 3.00):
Frequency stuck at 53hz all-day and night and system need restart to operate normal again.

Quattro 48/10000 (firmware 502, Cerbo 3.00):
Quattros still frequency shifting after grid charge battery and then ignored.
Need to disconnect grid and some times to restart to fix it.

Any idea to solve the problem please?

@Daniël Boekel (Victron Energy Staff)

Thank you

My setup that also uses ignore AC in has just started doing this issue. after a update of fw from 506 to 508, I finally solved it by moving the PV or ESS assistant to the BOTTOM of the assistant list. and so far thats solved my issue. and the freq stays at 50hz and moves up in increments on 0.1 hz as in my case the voltage rises above 56.3v NOTE my absorption is set at 55.8v as at Frequency shift start at .5 volt above absorption voltage, well that was my experience. Also I have noticed that if the Inverter/charger is working at MAX output and the inverter temp starts to get close to its overtemp point then this also triggers the hz to Increase, thus reducing the charge rate