Yes, indeed.
Fronius is set to MG50 with MODBUS control priority.
All firmwares are up to date.
Then I unfortunately don’t know. As far as I know this problem is catered for, if it does not work I cannot say why. You will have to consult an official support channel, which usually starts with your installer and goes up the chain. Or ask on community.
The trouble with the modbus route is that it is simply too slow, even if you were to attempt that. A Fronius inverter can take up to 5 seconds to fully respond to a modbus command.
If hackery is required, I would probably do it via the IO control feature of the Fronius (this would take highest priority then):
In this example, closing gpio4 pulls the inverter to 0% power. An assistant on the Multi can close a relay to do the job if the voltage exceeds some limit and AC-input is not in use. Although, I am getting way ahead of myself here, ideally such hackery should not be required.
Dear Plonkster,
Thank you for the help and advice. Much appreciated.
Sorry did not keep you in the loop.
I created a Question in the Victron community.