Hi,
I’m using two assistants: “ESS with Fronius” and “AC Ignore AC Input using the Generator Assistant.”
I’m facing an issue — when AC power is present, the inverter shows significant frequency fluctuations, changing from 49.99 Hz up to 53 Hz (see video). Because of this, the three-phase load is experiencing problems.
The system worked perfectly for about a year, but this issue started after a firmware update.
Has anyone encountered a similar problem or knows how to fix it?
Do you have ac pv on the output of the inverters?
yes, Fronius 15kW.
During the test, the Fronius was switched off, the test was carried out at night.
When AC Power is present, the inverter tries to stay in sync with the grid so that if it needs to switch to the grid, the switch will be instantaneous and without nasty spikes or transients.
But when it’s configured with AC PV Inverter support, it periodically spikes the frequency to 53 Hz for a short time. If there is a compatible PV Inverter on the AC Output, the inverter should treat this as a “temporary turn off” command.
In theory, when the ESS system is always connected to the grid, this oscillation should only happen for a few minutes.
It seems there is a bug in the inverter logic because it tries to synchronize to the grid and spike the frequency even if the AC Input voltage is out of range or when it should intentionally Ignore the AC input.
I’ve seen this behavior on my system (ESS with AC PV inverter) when the grid voltage is just a bit out of the valid range. It doesn’t switch to grid, but it also keeps trying to stay synchronized and turn off the AC PV inverter during the grid connection phase via the 53 Hz spike.
Do you know which (number) firmware haven’t this type of glitch?
No, sorry.