I have the same issue as the one described in the archived link below. Is it possible that this is a ‘bug’ in the Victron system? Does anybody know a solution for this other than the proposed Red-node work-around?
I have a grid connected 3-phase Victron ESS with a Fronius Symo Advanced inverter on the AC out of the Multiplus-II. When reconnecting after a grid failure the system does the following:
upon grid return the Multiplus-II immediately drops the Frequency on AC-out to 50Hz. However, the Multiplus-II waits about one minute before closing the grid relay (due to VDE grid code)
the Fronius inverter on AC out sees this frequency drop and starts producing at maximum capacity. As there is not yet a grid to ‘absorb’ this energy, the PV production is forced into the battery, triggering DC overvoltage alarms
settings:
ESS assistant is correctly configured in the Multiplus-II
Fronius is configured with Microgrid according to the recommended settings
The battery is dimensioned appropriately. As extra ‘margin’ I never charge the battery above 90%, When the grid fails (at the worst-case moment with the inverter producing at max capacity) the battery is able to absorb the excess PV power until the inverter has reduced it’s production. However, upon return the batteries don’t have the capacity remaining to absorb another minute of this excess power.
Modbus TCP between Victron and Fronius works fine.
Nothing the Multiplus could to different, in order to reconnect, it HAS to lower it’s frequency to 50 Hz.
That is the issue. The Multiplus will increase the frequency to the configured “disconnect-frequency” before attempting to reconnect to the grid. This should drive all AC-Inverters into a fault-state, waiting AT LEAST 1 minute before they start to produce again.
Apparently your Fronius is not doing that - and that may have one of two reasons:
1.) You are running the fronius with a unsuitable grid-profile making him not do that.
2.) You are using the MG-50 gridcode and are affected by fronius increasing the drop-off-frequency with a single mentioning in the version change logs:
Thus, if you still have configured your ESS-Assistant to use 53 HZ as disconnect Frequency, it just isn’t high enough (after that firmware change was applied to your fronius) to drive the fronius into an fault-state and wait 1 Minute before resuming production.
Can’t give you re-configure advice at this point, as we still haven’t heard anything if that really is what happened, or if this line in the changelogs means something different.
Is Victron discussing this issue with Fronius and will adapt the ESS assistant if necessary?
Or is there already an ESS assistant version which takes this into account?
Yes it is beeing discussed or let’s say, resolution is beeing awaited.
Actually, Fronius only wanted to defer the relay opening a bit, so the inverter goes into fault at 52.8Hz, but the relay remains closed upto 53.1, in order to avoid it switching too frequently.
But apparently their ramp-up delay is coupled to the relay closing, and therefore it now starts to ramp up without delay, unless it is forced into relay opening with now more than 53.1 Hz.
So, most likely a future firmware-update should restore delay-functionality at 52.8 Hz, but we don’t have any details about how or when that will be fixed.
@Dognose: thank you already for this information !
If I change the parameter in the ESS assistant as shown in the image: will that resolve the issue in our case? In other words: will the Multiplus-II then briefly push the frequency to 53.2Hz before dropping to 50Hz when reconnecting to the grid?
As long as the Issue on the Fronius side behaves as described, that should then force the Fronius into it’s grid-reconnect-delay, when frequency is lowered again.
You could test once at a soc < 100%, and watch the Fronius display.
If it still doesn’t work, your battery should catch that without overvoltage-issues, given you obeyed the Factor 1 Rule.
Since it is unclear what the final official settings will have to be, we updated our documentation with a hint about these “exceptional firmwares”:
1.5 Known frequency exceptions
Fronius bundles between fro35020 and fro36120 (at time of writing) contains a change that holds the inverter relay closed up to 53Hz for grid code MG50, or 63Hz for MG60. This sometimes causes problems when reconnecting to the grid. Please set the Disconnect frequency to 53.1Hz/63.1Hz for these versions.
Fronius increased to 53.1 right - so 53.1 should be “enough” to achieve the disconnect. Considering measurement imprecisions on both sides a higher value may make sence. Will ask our Fronius-Expert to review if that should be accounted for in the documentation, it may even be suspect to manufacturing / measurement tolerance on either side and individual units.
I increased the ‘converter disconnect frequency’ to 53.2Hz in the ESS assistant and tested on-site. The system now does what it has to do: the Fronius stops producing during the minute the Multiplus uses to reconnect to the grid.
