Odd power generation graph

On two back-to-back dry, cloudless days in April, my system recorded the following power generation. The first graph is as expected for my 15kw system with two SolarEdge inverters. The second is like nothing I’ve seen before. While on many otherwise-sunny days there are sudden, brief declines in production due to a stray cloud, I’ve never seen a pattern like the second graph’s underlying smooth generation curve with sudden, brief spikes in production. If I were a betting person, I would say it indicates a problem with one of the two inverters. However, this happened on only one day and I’ve since seen no repeat of this pattern or anything else that would suggest such a problem. Has anyone seen a pattern like this before? Any insights or suggestions of how to proceed?

check your inverters for errors.
it does look like one has dropped out. perhaps due to over voltage? or they were both limited?

do you have each as a child system and then combine as a parent? to diagnose what one is having the issue.

Best bet is see if you can identify the error data on the inverters for that day and if its one or the other.

can you check the voltage for that day?

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Those are helpful questions, thank you. I don’t know enough yet to answer them, but now at least I have an idea what I need to figure out (what a child system is, how to find past error data for the inverters, what can trigger over voltage conditions).

child system is where you have each inverter as their own PVoutput system and then use a third to combine them together.

I’m not sure how to access it on the SolarEdge inverters but with the fronius inverters I just log into solarweb website and can view the errors in the GUI.

Over voltage is triggered when the street voltage is too high and the inverters are set to shut down or limit power once they hit a certain voltage.

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Thank you very much for those clear explanations. Contacted the company that installed my system and they report that their troubleshooting with SolarEdge identifies the cause as “grid conditions that they’re going to address by pushing a firmware update to my inverter.” Which I take to mean probably a grid overvoltage condition as you suspect. I assume the firmware update changes how the inverter responds to grid overvoltage. They said it would take a couple of days for the firmware update to become active, so I’ll keep a close eye going forward to verify that things have improved. I found this helpful as well: Overvoltage is impacting your Solar Systems • Dan the Solar Man.