Whilst understanding that the 1:1 Rule applies when Fronius is connected on AC-Out so that a Multi/Quattro will control output of Fronius with frequency shifting, there appears to be a different approach when ESS is used.
In the document AC-coupled PV with Fronius PV Inverters (https://www.victronenergy.com/live/ac_coupling:fronius) it states:
2.5 Zero Feed-in
It is possible to make a Zero feed-in system with Victron & Fronius. The Venus device will the control
the Fronius output power. See the ESS manual, chapter 4.3.11 Fronius Zero feed-in for details.
This suggests the Multi/Quattro does NOT do frequency shift to control output of Fronius.
ESS manual 4.3.11 talks about setting the GX device & changing some parameters on the Fronius. The communication method between GX & Fronius must be TCP & both devices must be on the LAN.
So, this raises a question.
Given 2.5 Zero Feed-in suggests GX controls Fronius output (not Multi/Quattro), does the 1:1 Rule still apply?
Let us assume that a 3kva Victron with full batteries and a 5kva Fronius (on Victron AC-out) on a STC day and generating 5kva.
Suddenly, the only load of 4kva stops.
The Fronius must reduce its output by 2kva to 3kva.
The rationale of the 1:1 rule is that frequency shifting to reduce output is too slow to respond.
The intent of the question is does the GX device respond fast enough to communicate to the Fronius to reduce output by 2kva (and possibly does the Multi/Quattro have enough surge capacity and duration on AC-out) before 'bad things happen'.
If it can, the 1:1 rule is probably not necessary.
