diy solar

diy solar

Intermittent power loss Growatt MIN TL XH US

1201 said:
@saenns

In the graphs the dropouts don't seem to be happening in the morning- I wonder if this could be temperature related.


Did this happen in winter?

It would also give some support to what @MajicDiver is thinking, maybe this only happens when the battery is full?
Click to expand...
I’m having some doubts about the battery possibility- but it’s been a long afternoon, been wiring up power to two new out buildings and looking at phone during rest time, high 90’s here today. I just realized his PV power is dropping, not just output ac power, which probably shoots down the battery possibility- but in a lifetime of trouble shooting I’ve learned that things you would never think of can and frequently happen.
 
Yesterday I disabled AFCI, changed the grid code from Rule 21 to IEEE and modified the FreqHighDerate: Point=60.05Hz and Slope=100%. Results below, problem persists. I found in the debug2 field what I suspect is the derated power, since it's normally 11400 (nominal power of the inverter) and it drops along with Ppv and the DeratingMode. It's the grey series in the chart above.

Screenshot 2024-06-24 at 7.32.29 AM.png
> In the graphs the dropouts don't seem to be happening in the morning- I wonder if this could be temperature related.

I plotted inverter temp below. The problem seems to get worse after around 2:00pm even as the temps return to morning levels, E.g at 5:27 it derates even though temp is just 42.8c, same as it was before 10AM. I would expect to see DeratingMode 5 or 6 (Tboost, Tinv) if temp were the problem but I don't. Although my PV modules are partially shaded at this time of day so that could be it too.

Screenshot 2024-06-24 at 7.39.17 AM.png

Today I will try the following:
* Disconnect battery completely
* Measure Fac with multimeter. Morning and afternoon.

If time allows I will also Install SolarAssistant in hopes that it can monitor Fac more precisely. What if I disable Frequency Watt completely? Seems like it would violate UL 1541? But if just for a day it could at least lead to a clear diagnosis.
 

Attachments

  • Screenshot 2024-06-24 at 7.21.20 AM.png
    Screenshot 2024-06-24 at 7.21.20 AM.png
    219.5 KB · Views: 1
saenns said:
Yesterday I disabled AFCI, changed the grid code from Rule 21 to IEEE and modified the FreqHighDerate: Point=60.05Hz and Slope=100%. Results below, problem persists. I found in the debug2 field what I suspect is the derated power, since it's normally 11400 (nominal power of the inverter) and it drops along with Ppv and the DeratingMode. It's the grey series in the chart above.

View attachment 224245
> In the graphs the dropouts don't seem to be happening in the morning- I wonder if this could be temperature related.

I plotted inverter temp below. The problem seems to get worse after around 2:00pm even as the temps return to morning levels, E.g at 5:27 it derates even though temp is just 42.8c, same as it was before 10AM. I would expect to see DeratingMode 5 or 6 (Tboost, Tinv) if temp were the problem but I don't. Although my PV modules are partially shaded at this time of day so that could be it too.

View attachment 224248

Today I will try the following:
* Disconnect battery completely
* Measure Fac with multimeter. Morning and afternoon.

If time allows I will also Install SolarAssistant in hopes that it can monitor Fac more precisely. What if I disable Frequency Watt completely? Seems like it would violate UL 1541? But if just for a day it could at least lead to a clear diagnosis.
Click to expand...
Thanks for posting the updates. Surprised non of those worked.

deactivating frequency watt completely for even a couple of hours would help to see if it's related to that or not.
 
OK I may try that too. I found some data from January, and although it's hard to tell because I had Export Limit enabled and there was more shade, it does seem to have been a problem then as well.

Screenshot 2024-06-24 at 8.02.22 AM.png
 
saenns said:
The power loss is weakly correlated with derating mode 4 (Fac) and derating mode 20 (not documented?). Inverter temps are getting well into the 60C+ but it's less correlated and I don't see any derating mode 5 or 6 (Tinv, Tboost) in the logs. Similarly, weak correlation with AFCI strength/status.

https://www.amosplanet.org/wp-conte...us-RTU-Protocol_II-V1_13_20190116-English.pdf
Click to expand...
That is a very, very old modbus list. Attached is a more recent list I was given by Growatt earlier this year. Page 73/74 are the derating modes for the MIN TL XH US. read page 3 for explanation of applicability.
Obviously, this May, 2022 modbus list is obsolete because it does not have mode 20 listed, but it has more than the achient document you posted here. I suggest calling Growatt and get an updated list and/or some other document that explains all the derates. and of course share......

Don't have time to look at your recent data, am interested and will get to it a day or so, just too busy.
 

Attachments

  • Growatt Inverter Modbus RTU Protocol_II V1_25-English (2)_Recieved-20240404.pdf
    1.8 MB · Views: 5
saenns said:
derating mode 20 (not documented?)
Click to expand...
I have downloaded data for both of my inverters for 1-June to 24-June. The only derating I get is Derating 4, which is only on the ac coupled inverter, which it should when the grid forming inverter increases frequency to reduce its power. no derating 20 whatsoever.
I also did some experimenting and found that if I unplug the RS485 from the power meter I get derating 14.
 
saenns said:
Installed in Bay Area, 90% shade, daytime highs have been around 80f.
Click to expand...
Can you send a picture of the installed location? If the inverter ever gets any direct sunlight, it can heat up very quickly. Your response seems to indicate that it is installed outside in "90% shade". Perhaps you are getting short periods where you have direct sunlight long enough to heat it up......
 
OK so yesterday I disconnected the battery at around 8AM. Then I spoke to Growatt tech support. They changed my FrequencyHighDerate settings remotely and explained that both DeratingMode 4 and 20 are frequency related. DeratingMode 4 disappeared after the change, but 20 persists. I suspect 20 may be due to low frequency, the settings for which they did not change. Yesterday afternoon was overcast so Ppv looks bad.

Sorry I've been busy so I haven't had a chance to answer all the questions. Will try to get to them by tomorrow.

Screenshot 2024-06-25 at 7.41.39 AM.png
Screenshot 2024-06-24 at 12.34.37 PM.png
 
saenns said:
OK so yesterday I disconnected the battery at around 8AM. Then I spoke to Growatt tech support. They changed my FrequencyHighDerate settings remotely and explained that both DeratingMode 4 and 20 are frequency related. DeratingMode 4 disappeared after the change, but 20 persists. I suspect 20 may be due to low frequency, the settings for which they did not change. Yesterday afternoon was overcast so Ppv looks bad.

Sorry I've been busy so I haven't had a chance to answer all the questions. Will try to get to them by tomorrow.

View attachment 224507
View attachment 224506
Click to expand...
If you disable derating temporarily we can know for sure if it's related to frequency.

I'm also curious to know how much your grid frequency fluctuates.
 
Last edited:
I'll disable high and low frequency tomorrow. I was also able to install solar assistant and it does report grid frequency more precisely:
Screenshot 2024-06-25 at 9.58.00 AM.png
 
1201 said:
That frequency drop around 5:40pm, does it correspond to a drop in output?
Click to expand...
There was a DeratingMode: 20 at that time, and although output was already low due to shade at that time, the debug field would suggest it was derated to 973W at that time.
 
saenns said:
There was a DeratingMode: 20 at that time, and although output was already low due to shade at that time, the debug field would suggest it was derated to 973W at that time.
Click to expand...
hmm. that's promising. then maybe it is an under frequency thing.
 
Sorry for the delay. I decreased Under Frequency Loading Point to be symmetric with the FrequencyHighDerate point, and since then the drops are nearly all gone and I have not seen a single derating mode > 0 all week, even with the daytime high breaking 100f. I also added back AFCI about a week ago. Thank you 1201 and MajicDiver for your help! Now I just need to remove a protected tree from my west facing array...

Screenshot 2024-07-06 at 6.15.26 PM.png
Screenshot 2024-07-06 at 6.17.17 PM.png
 
saenns said:
Sorry for the delay. I decreased Under Frequency Loading Point to be symmetric with the FrequencyHighDerate point, and since then the drops are nearly all gone and I have not seen a single derating mode > 0 all week, even with the daytime high breaking 100f. I also added back AFCI about a week ago. Thank you 1201 and MajicDiver for your help! Now I just need to remove a protected tree from my west facing array...

View attachment 226894
View attachment 226893
Click to expand...
That's awesome that you got it fixed and it was all due to grid frequency. I'm saving your post for future reference.

Thanks for coming back to update us.
 
You must log in or register to reply here.

diy solar

diy solar
Back
Top