Stumped: Can't figure out these dips / fluctuations in power graph

[logslogs]

I have the following setup:
- 12x580watt Longi Hi-mo x6 panels (6960watt)
- Growatt 15kw On-Grid Inverter (export to grid with no limits)

I keep getting dips and fluctuations on graphs daily, while my friend who has the same inverter in the same area, does not get these dips and has a rather smooth graph.

Things I have tried:

- I ensured there's no shade of any kind at the time of dips (there's none, through the day as it's roof-top and highest point here).
- Ensured panels are clean. No dirt or debris.
- I installed 2 high-RPM fans, as I felt it was a bit warm, to ensure the inverter stays cool. Didn't help.
- It's a dual MPPT inverter, so I moved the string to MPPT2 from MPPT1. Nothing changed.
- I got the panels checked by a solar tech who charged heavily but couldn't find a fault with the panels. Although I still think something's wrong with panels.

Please see the attached graphs and let me know if you have any ideas what could be causing these dips.

 

[kommando]

Well you must get clouds from time to time. Just because your neighbour has smoother graphs does not mean much if the polling time between measurements is different.

 

[logslogs]

Well you must get clouds from time to time. Just because your neighbour has smoother graphs does not mean much if the polling time between measurements is different.

Thanks for the input. This was my concern too and ruled out clouds as a factor as first thing. He has the exactly same inverter and panels (except 12kw total panels in his case) and has same positioning of panels. Only difference is tilt. His is 15deg while mine's 25deg. Otherwise same direction.

 

[Brett V]

Those dips are clouds.

 

[kommando]

Well I would get double my output with graphs like yours, I have gone from 40kwh production one day to 5kwh production next day all down to clouds. What is the difference in daily total yields between your setup and his.

 

[HighTechLab]

Maybe a flock of birds landed on the array - there are many environmental factors at hand that can change an output graph.

 

[ThaiTaffy]

I have the following setup:
- 12x580watt Longi Hi-mo x6 panels (6960watt)
- Growatt 15kw On-Grid Inverter (export to grid with no limits)

I keep getting dips and fluctuations on graphs daily, while my friend who has the same inverter in the same area, does not get these dips and has a rather smooth graph.

Things I have tried:

- I ensured there's no shade of any kind at the time of dips (there's none, through the day as it's roof-top and highest point here).
- Ensured panels are clean. No dirt or debris.
- I installed 2 high-RPM fans, as I felt it was a bit warm, to ensure the inverter stays cool. Didn't help.
- It's a dual MPPT inverter, so I moved the string to MPPT2 from MPPT1. Nothing changed.
- I got the panels checked by a solar tech who charged heavily but couldn't find a fault with the panels. Although I still think something's wrong with panels.

Please see the attached graphs and let me know if you have any ideas what could be causing these dips.

Is this off-grid, are you charging you batteries during the dips, what loads are you using? There could be many reasons for the dips not just clouds your panels will only produce as much as you can load them, if your adamant that there's no clouds I'd put good money on your load dropping off during these dips.
Sorry just saw the on-grid part I'm a idiot

 

[logslogs]

Ok after weeks of research, I finally figured it out there's a hidden feature on the growatt web interface that can get me history data. I got the history data and could correlated it to DerateMode = 4 whenever power drops.

It appears whenever the grid frequency reaches 50.3+hz, the derating begins which is odd because High Grid Frequency Limit is set to 51hz in my inverter settings.

Any ideas how to change this internal limit of 50.3hz? I am assuming I would need to modify this via some hidden register. The online interface does allow to set or read values of registers via inverter settings but I can't figure out which register it would be.

I did find a manual here but it seems outdated: https://www.amosplanet.org/wp-conte...us-RTU-Protocol_II-V1_13_20190116-English.pdf

 

[kommando]

Which country grid code is your inverter set to. For the Netherlands they start the derating at 50.2htz, UK has no derating based on frequency. What is the Pakistani Grid code setting.