We built a new single-phase installation recently with the following components:
- MultiPlus II 48/5000
- Cerbo GX
- 4x Pylontech US2000C
- PV inverter Fronius Primo 4.0
Grid is connected to MultiPlus AC in, all loads and the PV inverter are connected to AC out 1, like so:
Grid metering is done by the internal meter of the MultiPlus, Fronius is connected via ethernet (zero feed-in with ModBus via TCP).
Generally speaking, this setup works really great, now we're getting to the last 10% of optimization, and the current issue is the transition from grid-parallel to micro-grid, which causes the following:
- Error 105 on Fronius (AC frequency too high) when switching off the connection to the grid (Fronius restarts/recovers quite quickly though)
- Flickering lights at certain load constellations while operating on micro-grid (e.g. Fronius delivering 2.5 kW and loads around the same value (oven + small toaster)
The flickering can be described as brightness oscillation around 1-2 Hz, as if MultiPlus competed with Fronius for the voltage regulation. If useful, I can upload a video later.
Parameters are set as recommended by the documentation (MG50 on Fronius, Frequencies set in the ESS assistand according to https://www.victronenergy.com/live/ac_coupling:fronius). Native Fronius zero feed-in works fine also. The documentation mentions "Q5 How can I get the Fronius firmware that improves flickering?", but the Fronius is brand-new and all firmwares have been updated, so this shouldn't be the point.
Any ideas and help is much appreciated :-)