Hi,
On VRM I see a frequency difference between IN and OUT in advanced view.
Grid is present.
Can this difference be somehow explained?
Regards,
Marek
asked
IN - OUT frequency difference on VRM
Hi Marek,
"Can this difference be somehow explained? "
Short version: "measurement inaccuracy "
BR
Hi @Markus,
Possible, but why only on the AC out?
Also, is AC-in and AC-out physically connected when grid is present?
Regards,
Marek
It seems like, you will have to wait for someone coming by with the "long version" :o)
But in reality it doesn't really make a difference. What are you concerned of?
"Also, is AC-in and AC-out physically connected when grid is present? "
Yes
I noticed, you like to edit your Question/Comments after they get answered by someone else, which makes it sometimes difficult to keep up a straight conversation.
Hi @Markus,
My PV inverter is now connected to AC-out.
This inverter reacts to frequency change on the lower side of 50.
It lowers production when frequency is below 50Hz not like Fronius when FQ is higher than 50Hz.
Regards,
Marek
But as the grid (AC-IN) is physically connected to AC-Out, does your PV inverter lower production with 50.1 Hz present on AC-IN?
The frequency difference or shifting is an intentional thing as part of the program of ess as far as i know or understand. One of the mechanisms to do with the way feedback to grid is prevented.
You have awesome grid stability by the way! Our ess works hard the grid is always shifting frequency very unstable in bith voltage and frequency.
The other thought here is as mentioned in a previous comment, the Victron is not a lab measuring instrument and never claims to be, have you actually checked the input and output with an ocilloscope? That would rule out whether it is an actual problem or just a position of a sensor internally causing a slight difference.
Hi Alex,
when grid is present, the AC-in is physically connected to AC-out. So there can never be any difference in frequency as long as the grid is passed through the system.
BR
Hi Markus, Ess is a frequency shifting program it can shift frequency after the unit but not before, so by nature can cause a difference.
The other thing that can affect this is wiring issues usually with undersized cables.
Sorry, I have to disagree.
Look at the block diagram of a MP2:
Because there is a physical connection between AC-in and AC-out, the frequency can never be different on AC-out as long as the grid is present and passed through.
But I am open to discussions ;o)
Hi @Alexandra,
The ESS assistant is not present in my system.
For now it is just UPS for my home.
Regards,
Marek
Hi @MarekP
Then it will be LOM detection are you using Type A or Type B?
It uses frequency shifting as well. I have seen with higher impedance connection the shifting as well. And by this I am referring to guys who have not installed the victron but have an extension cable to and from the unit or have undersized cabling to and from it.
LOM detection trys to change the frequency of the grid.
As long as the grid is present, it cannot do that.
If you would see a influence of LOM to the frequency on AC-in you would see it on AC-out frequency too.
I do understand that it cannot change the grid, but if it does it disconnects.
I have graphs to show on grid failure the frequency change in ac in shortly before grid failure. There is an interesting change in the internal resistance of the unit that happens when it is pushing back against the grid to frequency shift it. If it is able to raise itself higher than the grid or shift the grid itself it disconnects.
But as from mareks next reply this is also not the issue. Maybe there is something deeper in the works than I know is still at play. In any case a LOM function of some kind would still need to be there in the programming so the feedback relay opens for safety.
Yes.
and no, we are going off track of Mareks questions :o)
But an additional claim I set up in regards to the original question:
If you manage somehow to have different frequencies on ac-in and ac-out when grid is present and passed through the Multi, the result will be fireworks or magic smoke. ;o)
Hi @Alexandra,
In my grid settings the transfer switch is controlled by AC-in voltage.
System accepts very wide FQ range.
Regards,
Marek
Hi @Alexandra,
My VEconfigure setting for Grid does not give mi LOM settings to choose.
Maybe I am missing it.
Regards,
Marek
Hi @Alexandra.
Unfortunately there is no ESS assistant in my system.
I have a second unit that measures the grid parameters and it measure the grid FQ.
Grid FQ oscillated in 49.98-50.00Hz range.
Regards,
Marek
That is interesting. Maybe because of its grid changing and the Victron always trying to do the synchronizing its always changing and all you seeing is its constant changing coming through?
I was just running over graphs from a few sites and there seems to be a 0.11 hz to a 0.15hz difference even with all the fluctuations we have in grid using the Victron VRM graphs
How is the difference for you? If it is constant maybe it is designed to be like that.
Hi @Alexandra,
You can see the difference MP-II reports in my first post.
There is slight ripple visible on the AC-out FQ VRM graph and there is noting on the AC-in FQ graph.
My grid parameters measuring system never shows more than 0.02Hz fluctuations of grid AC FQ.
Regards,
Marek
