Inconsistent frequency shifting documentation - correct Fronius defaults?

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richard-mori asked Mar 25, '20

Inconsistent frequency shifting documentation - correct Fronius defaults?

Hi,

When setting up an AC coupled system with a Fronius PV inverter, the instructions state that the default Victron configuration is the correct one. However, I have found conflicting defaults and self contradicting documentation, so would like to clear the air on this and get a definitive answer on the correct settings.

On the Victron website there is a guide for setting up a Fronius inverter: https://www.victronenergy.com/live/ac_coupling:fronius#setting_up_the_victron_multi_or_quattro . This mentions that it is not necessary to change the defaults, and shows a screenshot of the settings and also a table:

However, as can be seen above, the setting for 50Hz are inconsistent between the picture and the table, with different start frequencies.

When configuring the system, I have tried both the ESS assistant and the PV Inverter assistant, and noticed they both have different defaults:

So when we are told that the defaults are fine, and there are different defaults depending on the assistant, and the documentation contradicts itself, it can be a bit confusing.

For what its worth, I believe the defaults in the PV Inverter assistant are correct (51Hz start) based on my discussions with Fronius, but I just want to check this with Victron and draw attention to it so that the assistant defaults and documentation can be updated.

Thank you,

Richard

Fronius documentation

victron-help-page.png (57.7 KiB)

pv-inverter-assistant-defaults.png (51.3 KiB)

ess-defaults.png (52.1 KiB)

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richard-mori answered · Apr 09, 2020 at 12:13 PM

Documentation has now been updated, as have the default values of the PV Inverter assistant to make it the same as the ESS assistant:

The comment at the end is important: the specific start value isn't critical since the control isn't that precise, so there is wiggle room in the configuration. This question stemmed from trying to identify a fault in a system which turns out to lie with the Quattro inverter itself, not with the configuration. I believe the system would have been stable with either starting frequency if there wasn't this separate hardware fault.

1586434232533.png (172.0 KiB)

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Answer 1 · 2020-03-27T20:08:30Z

jbakuwel answered · Mar 27, 2020 at 08:08 PM

Hi Richard,

I tried to get some clarity about this from SMA a while ago. It seems not many of their support engineers are familiar with this, nor with the complete list of all the parameters that can be set/changed from their defaults.

I've settled for a linear reduction of PV power between 50.5 Hz and 52.5 Hz and explicitly programmed both Multi and SMA Sunny Boy's with these parameters. It might suffice to use a 1Hz band (ie. between 50.5 Hz and 51.5 Hz) and I guess the only way to find out is try.

It seems (to me) a bit arbitrary for off grid systems, ie. I think as long as both PV inverter and battery inverter are aligned, it should work.

For on-grid systems though, you may need to dig a bit deeper.

Hope this helps,
Jan

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