We live in Belgium and have a 3 x 230V delta grid connection. We have solar panels and have been looking for a way to store this solar energy in a battery so that we can use it in the evening. Also as a backup when the grid goes down, which happens quite regularly in our region.
At the moment, we have 2 inverters from Solaredge SE3500. SE1 is connected to phase A, and SE2 to phase B. Phase C only receives energy from the grid. And this combination works excellently.
We would of course like a full-fledged 3-phase system, but that does not exist for our grid. The ESS system with the Victron Multiplus comes closest to our wishes because the Victron Multiplus II can work together with the Solaredge inverters.
I have created a schematic diagram, and now my question is: can this work?
It is not the intention to have a complete 3-phase 230V delta, as I have already found that this would not be possible. But rather something that might work?
First, a bit of explanation about the diagram. FM1 is a phase monitor (like the Schneider RM22TR31). As long as all phases are at their normal voltage, the relay output of FM1 is ON, and thus the contacts of the relays CR1 and CR2 are closed. The Multiplus units can operate normally, charging the battery with solar power during sunny hours, etc., as described in the Victron documents.
If the grid goes down (or if one phase goes down), FM1 detects this and opens CR1 and CR2. Phases A and B receive energy from the battery via MP1 and MP2. Phase C does not receive voltage because CR2 is open. This is necessary to prevent ghost voltage on L1 and L3.
When the grid is restored, CR1 and CR2 turn back ON, but after a time delay. This time delay (ON Delay) is adjustable in FM1. I would set this to 20 seconds. When the grid comes back ON, it often happens that it goes down again within a few seconds. ON – OFF – ON – OFF… is not very healthy. Therefore, I would prefer to wait 20 seconds for a stable grid.
I would disable the Ground Relays in both Multiplus units.
What do you think about this? I hope there are specialists here who can help me ?
Thank you very much for this.