I am putting together a Multiplus with a SolarEdge inverter. The SolarEdge has more power than the Multiplus II so it will not follow the 1:0 rule. In the example below (notice where the SolarEdge power meter is), if the grid goes down the SolarEdge does not know how much power it is producing. In this case it will depend on the frequency adjustment driven by the Multiplus II to control its power generation. Please look:
Now, suppose I change the SolarEdge’s power meter positioning so it will know how much power it is producing towards the Multiplus II (micro grid). Please look:
In this specific approach, as the SolarEdge knows how much it is producing it may limit its power generation as it does on its normal operation, reacting like if it were connected to the grid.
Question: In this specific approach, does the 1:0 still apply?
I think that if a large load goes off, the SolarEdge will react like it normally does. By other hand, if the batteries on Multiplus II get full charged, then the frequency can be adjusted so the SolarEdge will stop producing.
It is not about how much it is producing (although that is part of it) so much as the load it is supporting.
If the inverter cannot support the load the ac pv is then don’t do it.
If the inverter (and by extension battery bank) cannot process the power being produced then don’t do it.
TLDR Don’t do it.
Aleays ask yourself what will happen if it all goes wrong?
As I understand from the 1:0 application note, when the PV inverter is producing a lot for a big load, if the load is switched off, then the PV inverter power has no place to go other then the Multiplus batteries as it takes a while for the Multiplus to raise the frequency telling the PV inverter to reduce its power production. So far, this is quite easy to understand.
Now, in Alternative Power Source (APS) mode, a SolarEdge inverter will “think” that the power source is a generator. So, to the maximum possible extent, it will try not to export any power. If the SolarEdge power meter is measuring what is being delivered to the Multiplus II, then it should be 0 (zero) or very close to it. Also, the SolarEdge inverter will adapt its power generation like it does when it is under normal operation, responding very quickly to load variations.
Charging the batteries is a quite slow process. If the Multiplus can not charge the batteries anymore (they are at full load) then I would expect that it raises the frequency so the SolarEdge will stop producing power.
In summary, an inverter that is controlling itself to avoid exporting should not trigger the event explained on the application note. Unless there are other factors that I do not know, then it should work ok.
It raises another question: As it may get outside of a standard design, how can we ask for Victron’s expert advise?
Their requirements are stated in the documents that is the official statement.
If the DC based inverter supporting the AC PV can’t support the entire load - It is a set up unsupported officially.
It is a lot less in your proposed scenario about control and more about the loads that you are wanting to support being an overload for the victron inverter.
I bought a MPPT 250/60 and I will migrate 2500W from the SolarEdge to the Victron. While the system will keep 2 inverters, with a total power of 16kW, in a single moment the maximum power out of them together will be about 9800W. This should solve the problem, right?
And yes, I think I got the message. I may need to split the load into critical/not critical to make sure when the grid goes off the load will not overload the Multiplus.
