FoxESS Community - Owners & Installers Forum

Hi all, Stupid question time again.

I've been noticing that at certain times the peak output from my inverter exceeds its rated capacity (see attached picture) with an immediate crash to a lower output and a later recovery.

I've been doing a bit of reading on this effect (I know that's dangerous, its sets the worry bit and suppresses the effect of the calm down it's not a problem bit) and I'm curious as to what measures may have been taken in the design of the Fox MPPTs to mitigate its effect.

My mindset on this - probably wrong, but it's a start:

The MPPT, in trying to limit the current due to this effect, raises the voltage and if too high my cause the inverter to shut down momentarily (I think this can be seen in the picture attached) to protect itself.

But, there's always a but, what exactly is going on with the cloud edge effect - is it a momentary increase in irradiance due to some lensing effect created by the cloud? Or is it something generated by the MPPT in responding changes in irradiance value.

Scientifically based explanations of this effect would be most appreciated.

Best regards from conundrum central.

Derrick.

Hello Derrick,

I think Dave answered this yesterday
viewtopic.php?p=16349#p16349

I also think that with cloud cover, the panels also cool down between clouds, and this amplifies the cloud edge effect even more before they heat up and efficiency takes a hit again.

Thanks MB.

I've read through Dave's responses and it doesn't quite do it for me - there's more to it given the complexity of the MPPT algorithms (I'm still reading through information on that particular gremlin).

I know a fair amount about clouds and their formation (decades of flying gliders and trying stay aloft does that to people) and I'm not entirely sold on the reflection from clouds explanation - one has to factor into it how the inverter's MPPT responds to the variation in irradiance. There are somewhat scientific explanations out there, but getting access to them is difficult because of the journal policies where they reside (demand for wonga).

I'll keep looking and report on what I find.

Best regards,

Derric.

You do love a good rabbit hole, my mind works similar, but I try not to go to deep on subjects.

Best of luck!