Great and inexpensive monitoring system and a problem to solve.

[scrambler]

To Oregon_phil. I also have Arc fault detection; The DC production is reported both by Tigo and Darfon and the new monitoring reports the Darfon AC out and they all track;

*** At this point I will put this one to rest until I have forwarded all my findings to them, and they have had a chance to review the inverter internal data, and speak with Darfon. ***

Thanks all!

[oregon_phil]

Scrambler, I tried to piece together some of your data in the following .pdf.

I think it is reasonable to rule out the following potential causes:

8: Bad utility connection. Doesn't happen to Enphase
7. Bad Tigo: Happens on both MPPT channels. What is the probability of one bad TIGO on each string? low
6. Bad AC connection: Your installer checked this right?
4. Bad solar panel: Happens on both MPPT channels. What is the probability of one bad solar panel on each channel and that you left the two bad solar panels, one on each Darfon MPPT channel. Low

Can the following explain your problem?

5) DC connection: Possible. Lets say you do have a bad connection and you have several hundred volts across it. In my case, the Arc fault detection circuit picked up the noise from the bad connection and faulted the inverter. And generally the connection would keep getting worse and worse and worse until?

3) Bad data reporting from inverter: Maybe the inverter is working correctly except for the reporting function. Bad sensors/detectors? From the fried battery board incident? It's probably not just bad reporting because the sensors are the same.

2) Firmware not working properly: Possible. This can be proved by new firmware or new inverter.

1) bad inverter: maybe a sensor did get damaged during the battery board incident and is sensitive to thermals, etc. Other explanations?

[scrambler]

Okay, is the definition of "out of range" the same frequency as the frequency which determines when curtailment begins?

I honestly don't know, so I will add that to my list of things to find out.
I am going to first let them come up with some possible explanations though

[Ampster]

The inverter also has error codes for frequency out of range (up or down)

Okay, is the definition of "out of range" the same frequency as the frequency which determines when curtailment begins?

[DanS26]

Thermal or wind movement in wiring causing intermittent or high resistance connections.

[scrambler]

The voltage could be okay but the frequency may have increased enough to trigger some curtailment. Do you have a way to check both values? If you look at the 1741 spec it refers to frequency and, if I am correct, a certain amount of frequency increase will trigger the inverter to curtail output. I am guessing that we can rule out low voltage and/or lower frequency since those do not typically result in curtailment. That guess is just an assumption and until it can be checked is just a guess.
The observation is that output is being curtailed, which you have documented. The hypothesis or issue to be resolved is what is triggering that curtailment?

The inverter also has error codes for frequency out of range (up or down)

[Ampster]

........ the inverter is not throwing an under/over voltage error

The voltage could be okay but the frequency may have increased enough to trigger some curtailment. Do you have a way to check both values? If you look at the 1741 spec it refers to frequency and, if I am correct, a certain amount of frequency increase will trigger the inverter to curtail output. I am guessing that we can rule out low voltage and/or lower frequency since those do not typically result in curtailment. That guess is just an assumption and until it can be checked is just a guess.
The observation is that output is being curtailed, which you have documented. The hypothesis or issue to be resolved is what is triggering that curtailment?

[scrambler]

Just looking at the production graphs it appears the fluctuations start and end at the same production levels.......to me that points to voltage.

These are just tow examples, I have had several others where it is not the case.
And the inverter is not throwing an under/over voltage error

[DanS26]

Although the monitoring I installed measures Voltage, I cant download that data yet, it is a feature planned for the Future. I will check it manually on the next event though,

But the Integrator has access to the full inverter data monitoring, so that will be his job if they agree the problem is real and requires investigation (again, I have not forwarded my new dat yet...)

Just looking at the production graphs it appears the fluctuations start and end at the same production levels.......to me that points to voltage.

[oregon_phil]

Can you talk the integrator into gaining full installer access? You are smart enough not to change parameters that will harm your system and your installer should know that by now since they have been working with you. That amount of data that can be downloaded off of inverters is mind boggling.

I have full installer access on my system and I bet most people on this forum have installer access. I'm just guessing. Most people on this forum are very knowledgeable.

[scrambler]

If you could graph voltage over the same period you may find a correlation with the production curve anomalies.

Although the monitoring I installed measures Voltage, I cant download that data yet, it is a feature planned for the Future. I will check it manually on the next event though,

But the Integrator has access to the full inverter data monitoring, so that will be his job if they agree the problem is real and requires investigation (again, I have not forwarded my new dat yet...)

[scrambler]

I had originally asked about your inverter model to see if data could be extracted real time. Due to the short timeline, you could display your Darfon inverter real time variables on your PC and use your phone/camera to record the data. Maybe DC input values and AC output values. The power output discrepancies seem to happen every day so I don't think it would be a waste of time.

I don't have access to real time data of the inverter, I don't even have access to minute data. All I have is the Tigo Minute data of the DC drawn from the panels, and the AC output data using my new monitoring system.

This crashing event DOES NOT happen every day. On cloudy days where the production fluctuates all the time, so far the DArfon production tracks the Micro inverter perfectly.
On some sunny days, the Darfon also produces perfectly and its production curve tracks the one of the Micro inverters.
But on some sunny days, it will have these crashing period.

I am yet to establish a percentage of the days when the problem happens. I cant watch the system all the time as I have other aspiration for my time
But now that I have installed the Monitoring of the Micro Inverters output, I will be able to go back and check all the days where the problem happens, and I will be able to find out if these are a few exceptions or a large percentage of the sunny days.

[DanS26]

If you could graph voltage over the same period you may find a correlation with the production curve anomalies.

[oregon_phil]

I had originally asked about your inverter model to see if data could be extracted real time. Due to the short timeline, you could display your Darfon inverter real time variables on your PC and use your phone/camera to record the data. Maybe DC input values and AC output values. The power output discrepancies seem to happen every day so I don't think it would be a waste of time.

I believe your assumptions on Darfon strangeness from failure or FW bug seem to be on track. With 10 days of data they should agree with you. You have gone above and beyond most what most solar customers would do. Most solar customers probably wouldn't even know they had a problem. Just because Darfon has never seen the problem before doesn't mean that yours is the only case out there. You just happen to look at the data.

[scrambler]

That is the point of this whole thing

Something strange is happening with the Darfon that I cant explain with anything else than failure or FW bug so far

On some days (not all), when solar production is sustained, the Darfon will suddenly drop down the production significantly and fluctuates down there, with occasional ramp up to normal.
There are no external circumstances I can find so far to justify it other than malfunction as the Micro Inverters keep producing normally.