question

paulcupine avatar image
paulcupine asked

Fronius on AC-in limitted with battery under 70% SoC

I have two MPii's 3kVA in a parallel setup with two Fronius inverters. I have a 2.5kW Galvo on the ACout of the Multi's and a 4.6kW Primo on the AC-in side. I also have DC coupled PV.

With the battery still under 70% SoC, the Primo's output is being cut back while the Galvo's is not. If I switch on "feed in excess AC coupled PV", the Primo ramps up to full output and the Multis ramp up charging to match so there is still no actual feed in happening.

Is this a bug or have I done something wrong with my setup? The behaviour I expect is that the Primo should only cut back if the battery is full or if the charge current limit is reached, neither of which is the case here.

Fronius
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
matt1309 avatar image
matt1309 answered ·

Hi @Paulcupine

I'm not too familiar with fronius inverters but sounds like the frequency shifting is coming on too early for the Primo. What settings have you got within VEConfig in terms of the frequency shifting, and similarly if you set them in the Primo what are they on that?


(ie what have you got for your settings equivalent to 1.4 section 4 in this link AC-coupled PV with Fronius PV Inverters [Victron Energy] )

10 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

paulcupine avatar image paulcupine commented ·
There can't be any frequency shifting going on because the grid is on.
0 Likes 0 ·
Alexandra avatar image Alexandra ♦ paulcupine commented ·
@Paulcupine

It can control the fronius over modbus/comms, so will have the dame effect as physically shifting the frequency.

Check in the advanced tab if they are being throttled. Load some widgets there.

I assume you have followed the instructions in the link from @matt1309 above

0 Likes 0 ·
paulcupine avatar image paulcupine Alexandra ♦ commented ·
It is being throttled, down to 20W or so. As soon as I switch on feedin excess AC (switching off the throttling), it jumps in output to the 1.5 or 2kW or whatever depending on conditions. All this while the Galvo on the ACout is working correctly.
0 Likes 0 ·
matt1309 avatar image matt1309 paulcupine commented ·
Ohh sorry I miss read.

That does seem odd, escially given its linked to Soc of battery. I've not seen that elsewhere.

My only other guess (and is very much a guess)

is maybe linked to the factor of 1 for ac coupling not working correctly I didn't think limitations were setup for that. But maybe primo being limited to 3kw? And maybe the multi is limiting fronius via coms somehow as victron system incorrectly thinks only 3kw can be passed through to battery.


Is it always spot on 70% Soc. And is there a particular number it seems to limit to?

0 Likes 0 ·
paulcupine avatar image paulcupine matt1309 commented ·

Sorry if I was unclear. The 70% SoC is not a fixed figure. At any time the battery is not at 100%, the Multis should not be limtting the solar from the Fronius. As I said above, as soon as I swtiched off the limtting (by enabling feed-in excess AC), the charger ramped up to consume the extra solar produced. Clearly no other charge limit or input current limit is a factor here.

0 Likes 0 ·
matt1309 avatar image matt1309 paulcupine commented ·

Not a solution but out of curiosity does the amount being produced by galvo seem to impact anything. Ie if galvo output is low does inverter on ac in output higher. Or is it always low/nil?


I only ask because like you said the behaviour is what you'd expect/want to happen if you were producing more power than can go into batteries but other than charge limit VE config and DVCC I csnt think what else could be causing the behaviour sorry.

My guess was maybe it being limited to charge current of one multi and not 2, which I'd guess would be a ve config issue but if galvo output doesn't impact anything then that disproves that idea

If you've setup per that link then I'm out of guesses sorry. Let me know if you solve it.

0 Likes 0 ·
paulcupine avatar image paulcupine matt1309 commented ·
Galvo output doesn't seem to impact the situation. I'm beginning to suspect it has something to do with the AC input cabling impedance. The two Multi's are different hardware revisions and I have had issues with this before.
0 Likes 0 ·
ponzoa avatar image ponzoa paulcupine commented ·
Do you have a meter between the 4.6kW Primo and the Multiplus? This, connected to the Cerbo, is needed so that the system knows if the power being input to the batteries from this inverter is coming from the grid or the inverter.


The AC In side does NOT need to restect the 1-0 rule. That aopplies only for the AC Out.


You also have your VE Configure settings to review;

Enable Battery Monitor

Set "State of charge when bulk finished" to what is required for your type of batteries. This is the percentage when the charge rate ramps down. Make sure the rest of the settings are correct and aligned with the battery brand and type and capacity as per the instructions which can be found on the Victron website.


Let us know how you go.

0 Likes 0 ·
Show more comments