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colj avatar image
colj asked

ESS and Victron management of Fronius PV inverter output

Hi All,

My system is an ESS setup: Quattro, Cerbo GX, Batteries, 3kW SMA inverter. The problem I have is that frequency shifting will not work for my setup since the SMA is configured for Grid attached (and needs to stay like that for the DNO) since I have a bypass switch that allows the Victron system to be bypassed and the SMA PV inverter to be physically grid attached. So, in the event of a Grid failure, with batteries full there is no control over the PV output. Thinking of upgrading to a Fronius inverter but it too would need to configured as 'grid attached' and so frequency shifting again wouldn't be an option. The question is whether connecting the cerbo GX and the Fronius via ethernet would allow the system to 'safely' control the Fronius PV output in the situation when there is a Grid failure, the batteries are full and excess PV is being generated? Note: When grid attached I'm not concerned about zero feed-in (DNO authorised for 3kW).

Colin

ESSoffgridFronius
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Michelle Konzack avatar image
Michelle Konzack answered ·

I do not understand Why your SMA/Fronius must be on the Grid side.


If you put in on AC1out and the Batteries are full, you can feed the 3kW over the MultiPlus-II into the grid.


If the batteries are not full and the grid fail, the MultiPlus-II goes into Inverter mode and continue charging the batteries from the SMA/Fronius. Once the batteries are full, the MultiPlus-II does the frequency shifting and stop the SMA/Fronius. Once the Grid is back, the MultiPlus-II goes back into pass-trough and the SMA/Fronius feed-in again.

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colj avatar image colj commented ·
The problem is the Victron by-pass switch. In normal operation the PV is attached to AC1out. The PV was installed many years ago before the Victron install and so has been configured for 'on-grid' and satisfying the DNO requirements for anti-islanding - in this mode frequency shifting doesn't work. If I didn't have the by-pass switch then I could get the SMA Inverter reconfigured to off-grid (needs authorised SMA engineer to make this change - not end-user changeable) and everything would work as you describe. But, because the bypass switch cuts out the Victron system and 'reconnects' the PV directly to the Grid, then the SMA inverter must remain configured as directly 'grid attached' (i.e. frequency shifting doesn't work). Hence the question. If I replaced the SMA inverter with a Fronius that is ethernet attached to the cerbo GX would that enable the Victron system to control the PV output directly (without using frequency shifting since the Fronius would also have to be configured as 'grid attached' - to satisfy DNO requirements when the bypass switch is in operation - and not as MicroGrid)


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