Any idea why these dips happen to my solar readings, every half hour, ON the half hour? It almost looks like the inverter drops production or reboots (which takes 5+ minutes, so it’s not that)?
There are no dips on any other Sense readings, and these Solar CTs monitored dedicated circuit fine before moving to Solar…I really feel like the inverter is doing a recalculation or something…
I have something similar:
I have a string inverter with 2 x 5 panels in series on one mppt input and another 10 panels on the second mppt input.
On one row of these 5 panels I have an item in the way that casts a shadow on one of the panels and an hour later covers the next panel and so on
My dips are certainly not as deep as yours, but you should see if you can find something (air vent, antenna,chimney) that during those times might be casting a shadow on some of your panels.
And like lights in a Christmas tree, if one of the panels gets shaded, the whole strings produces way less (unless you use optimizers underneath each panel)
Most inverters have an MPPT scan time cycle and reset parameter. On mine this is adjustable. At the set time the inverter will reset the MPPT to maximize the Maximum Power Point Tracking. Lets say it is cloudy, the MPPT locks in. But the sun comes out full blast, when the cycle scan comes up it will lock into the brighter sun situation. Down side is the lower you set the scan time, then the more off line you are. But it would adapt to big billowy clouds better. Yours may not be settable. Take a look at the production before the scan cycle and then right after. Usually the solar production will be higher.
Lowell
Most inverters/charge controllers I have seen/ have experience with do not lock in at all.
They adjust all the time and multiple times per second.
This is technical paper with tracking times of 7 mS
https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/iet-pel.2013.0603
"As we can see that the tracking time is 2.5 ms, and the voltage and current waveforms fluctuations are decreased around MPP. "
Thanks, @lpistol , I think you may have found the solution. No, afaik, I cannot adjust this scan time, but it’s interesting to know about it, thank you.
You can see here where twice today it did just as you described.
What is the brand/model of your inverter?
Have you looked for newer available firmware ?
Sorry, I forgot to mention in my original post; I have Tesla panels, inverter, and PowerWall+. I think the system checks for updates regularly…?
As a side note, intermittent and partial shade is one of the big problems for more widespread solar usage. While not yet for rooftop solar, I did notice these guys the other day - they claim a much more shade tolerant solar solution, though mostly for off grid-applications.
I should have also noted that I don’t have shading issues, at least not with these consistent, repeating dips. I’m 99% sure they’re caused by the inverter (where Tesla houses the MPPT’s).
I wish I knew how my panels were wired; I know there are 2 strings; prob 1 for the 16 SW-facing panels and prob 1 for the 4 SW-facing panels.
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