Some months ago I DIY installed a Victron system including a MultiPlus II 15000/48. The inverter is configured in ESS mode with PowerAssist and Spain’s grid code.
While in inverter mode, there are no problems whatsoever, but after a night where the configured minimum SoC has been reached, when battery starts getting charged in the morning by the solar charge controller, the inverter tries to start inverting but fails to do so for a period of time.
After checking with a multimeter, I think I have figured out what the problem seems to be: the grid is pretty soft (I’m quite far from the transformer and seems like the cabling has seen better days), therefore there is a substantial voltage drop when consuming from the grid.
When the inverter starts, grid consumption rapidly decreases, it sees a sudden voltage spike, aborts and starts again (at least that’s what seems to be the problem), which produces a very uncomfortable voltage flicker. After a few minutes it ends up starting successfully.
During this process, mains led is solid green, bulk led is solid yellow and inverter light blinks green.
I will try to get the line from the meter to my board replaced with a greater section, but that is as much as I can do, the voltage drop from the utility company is something I can’t control.
I have been trying to figure out which settings I need to change to solve this problem, but I’m a bit lost.
That is the sound of (besides a high impedance connection) a bad neutral and a probably a strange harmonic thrown in for good measure
Beides the grid line, they would need to make sure not trees/vegetation is touching the lines and chrck corroded connections.
If the grid side cant be solved, then use another inverter for the grid /charge and separate your inverter its the only other way to stop that.
I think that the bad neutral is also prompted by the high impedance of the line (when the voltage drops, the neutral “rises” increasing N-PE voltage). We could try to install a neutral reinforcement rod before the meter (I will probably have to ask the company for permission).
The lines are underground so a tree can’t be the problem. I will check my meter box to check for any corrosion.
Aren’t there any settings that can be tweaked in order for the inverter to start more softly and/or tolerate weaker grids (weak ac in, changing grid code, etc.).
The batteries are 9 pylontech us5000 (48v, 900Ah total).
The cables from the inverter to the lynx are 95mm2 (2 positive 2 negative) as victron indicates, not more than half a meter long. From the lynx to the batteries, the official pylontech 1,8m 25mm2 cables, 6 pairs in total (two per group of three batteries).