Hi everyone,
I’m hoping to get some technical insights on a specific fail-safe idea. I want to prevent my system from attempting to form a microgrid if the battery is unable to safely absorb the excess power from my AC-tied inverters during a sudden grid failure.
My Setup:
- 3-Phase ESS with 3x MultiPlus-II
- DIY 16kWh Battery
- MPPT RS 450
- Several AC-tied inverters (some on AC-IN, some on AC-OUT)
- The MP2s are installed inline (grid → MP2 → house) so they provide full off-grid backup.
Disclaimer: Yes, I am fully aware of the Factor 1.0 rule and its background. This question is strictly about an automated protective workaround.
The Logic:
I actively monitor my battery’s charging capability. If the battery is restricted (e.g., fully charged, low temperatures) and cannot absorb a sudden spike from the AC-tied inverters on AC-OUT, I need to protect the MP2s in case the grid drops at that exact moment.
Instead of proactively shutting down the entire PV production when the battery is full, my idea is to dynamically switch the MultiPlus-II units into “Charger Only” mode.
My Question:
If a sudden grid outage occurs while the MP2s are in “Charger Only” mode, will this reliably prevent them from forming an island/microgrid?
My goal in this specific scenario is that the house simply goes dark, the AC-tied inverters shut down due to the loss of the grid frequency, and the MultiPlus units are protected from being overloaded by the unabsorbable AC-coupled excess.
Does “Charger Only” physically/logically disable the islanding process in an inline setup?
Thanks in advance for your technical insights!
Jonny