question

colj avatar image
colj asked

ESS and Fronius ethernet connected to Cerbo GX

This is a simplification of an earlier question:

In an ESS system, if the Fronius and Cerbo GX are ethernet connected, is all management of the Fronius PV output via the ethernet connection please (both when the Grid is active and in the event of a power failure with micro-grid)? In my system, frequency shifting will not work so I am hoping that when the Fronius is ethernet connected this will avoid it's use even in a micro-grid.

Colin

cerbo gxESSFroniusethernet
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1 Answer
anthony avatar image
anthony answered ·

Hi, To answer your question fully and accurately it would be necessary to know more details about how your system is connected, where the Fronius sits in the system and what country code your Fronius is set to? Is it set to MG50 for example? Is it on the output or input of the Muliplus/Quattro.

Also why frequeny shift does not work for your application?

The ethernet connection to the Fronius can only control the limit feed in to X amount or zero feed in function. The ethernet does not control whether or not the Fronius stays connected on the AC side. If there is an AC grid present on the line that the Fronius (Primo I assume) is connected to then the Fronius will stay connected to the AC grid assuming the voltage, frequency etc is within the range of the pre-selected county code. The ethernet connection also transmits solar generation data and inverter status to the GX device and in turn to the VRM portal of course.

But remember the Fronius (Primo I assume) is not a grid forming inverter so if there is no AC grid present from either the grid network or the Victron battery inverter then the Fronius with not output power. Anthony

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colj avatar image colj commented ·

Thanks Anthony. I don't yet have the Fronius but was thinking of replacing an old SMA inverter that was installed 12 years ago (so Grid attached, and not reconfigured) predating the Victron system installed this year. I'm trying to address a potential problem when the grid fails with my specific setup. The PV inverter is connected to AC1out (in normal operation) but is configured 'Grid attached' (UK, 50hz, G98/G99 compliant) The reason it's still configured Grid attached is that I have a bypass switch for the Victron system which 'reattaches' all my AC1out loads (including the PV) to the Grid and totally isolates the Victron system. So, if I did install the Fronius, it too would have to be installed as Grid attached (not MG50) for the same reason. I was hoping that the ethernet connected Fronius would obviate the need for frequency shifting to control the PV when the Grid fails. The main situation that I'm concerned about is during a grid failure, batteries full, excess PV being generated and frequency shifting not working (it's configured for Grid attached). I expect my system to go into some sort of overload and shutdown which I want to avoid! From what you are saying an ethernet attached Fronius isn't going to be any better?

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colj avatar image colj commented ·
... another thought. If zero feed in was configured, then the ethernet connection is enabling the PV output to be controlled such that there is no excess. What happens in the case of a Grid failure? Clearly there's no Grid to feed into, but even so the logic could still work to ensure that no excess PV is generated. In the event of Grid failure, the question would be does the system know that there is no real Grid and fallback to frequency shifting or does it continue to use the ethernet connection to manage the PV so that there is no excess?
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