I work in a hospital in Mulanje (Malawi). We have recently connected 6 Quattro (6x15kW) with 6 Fronius Symo (6x15kW) AC-coupled. We have 6 battery banks (29 batteries in total). Each bank has a BMV and battery capacity of 500Ah (5x100Ah). 1 bank is different with 400Ah (4x100Ah). It is in Malawi not allowed to feed back to the grid. The system is running pretty good but we are dealing with one issue.
When we have low voltage (<180v) the Victron will switch from grid to the battery. Then the frequency goes up briefly to 52,9Hz or 53,1Hz. The next thing is that the Fronius-inverters shut down because of high frequency (error state 105). We have the correct county-settings in the Fronius (MG50). I know that it happens when there is no place to store the energy. But it happens also when the battery is at 40% and the hospital load is 40-60kW. The Fronius-inverters try to start up again and again but gives error until the grid-voltage is good enough for the Victron to go back to the grid. Normally it happens, between 11-2, when the sun is very strong and we need the Fronius-inverters to charge the batteries for the night. In the ESS is the possibility to change the frequency range but the advice to leave it like it is. I added some pictures for clarification. What can we do to solve this issue?
Thanks in advance, Gerwin Habermehl