I have an off-grid system with 3 Quattros (48/10000 230volt) in parallel (used to be in 3 phase) and a Fronius Primo 5KW AC coupled inverter connected to a 48v NiFe battery bank. The Batteries are charged by two Schneider MPPT 80/600 charge controllers and the Quattros are set to charge from excess power from the Fronius.
We use the grid as a UPS with an ATS to switch to the grid when the inverters shut down (usually due to low battery voltage).
This setup (minus the Fronius) worked great when it was in a 3Phase configuration.
Recently we added the AC coupled Fronius and reconfigured the whole system be be single phase parallel. The reason was mainly that we did not use any 3-phase equipment and need a larger load on one outlet so balancing between phases became a bit of an issue. By switching to a single phase the Inverters are more balanced.
However, since switching we have this issue occurring occasionally when the battery voltage is low and the inverters switch off;
VE.Bus Error: VE.Bus Error 18: AC Overvoltage on the output of a slave has occurred while already switched off
I am confused about what could be causing this. I did update the inverters to the latest firmware before making the config change. They are all on 2653496. The Fronius is also upgraded to the latest firmware before installation.
Any help is appreciated!
Iwan.
Some additional information.
(read 'grid' as the local off-grid power network, not the real grid)
It happens in about 50% of the cases when the system shuts down due to load battery voltage. It seems to be at times when the Fronius is actually pushing some power on the local grid.
Could it be the Victron is measuring the (over)voltage coming from the Fronius just before the Fronius switches off because it lost it's 'grid'?
Is there a way to tell the Victron to allow a short period of time where it might measure a voltage on the AC-Out even if it's switched off?
