Solarisium
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Derating events since December:
It happened at 8:50 am on a December day too!
It’s always string A.
I have one pv array but paralleled it with MPpT B so technically both MPPTs are running together on the same feed
4kw system outputting 2.5kw. Why?
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It happened at 8:50 am on a December day too!
It’s always string A.
I have one pv array but paralleled it with MPpT B so technically both MPPTs are running together on the same feed
Hedges
I See Electromagnetic Fields!
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Yes but ... Sunny Boy and DMM both saw elevated frequency. While RMS voltage might be a single correct value, what does "frequency" even mean when there are many frequencies present? Zero crossings? Highest peak of FFT?
(I ask this often using FFT to study noise issues, and it isn't the way to actually determine precise frequency.)
Hedges
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Now that seems odd. Can you see output or voltage and current of MPPT A and MPPT B independently?
(I'm wondering if the paralleling isn't actually done, like an open wire, so only string (MPPT) A is involved.
Is two short strings, one per MPPT, convenient to try? (but paralleling has worked for others who had clipping or some sort of derating.)
And of course, try diddling with parameters as a test.
Got a scope or digitizer to see what waveform is showing up as 60.4 Hz?
Solarisium
New Member
Measured Frequency just now: 60.3 Hz and in a second reading it was 60.4 Hz. I am not making any changes to the parameters specially to the frequency limits.
Disable to power limit ? Which one is a safer experiment to do?
Hedges
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Safest is set to UL-1741. Oh, that will disconnect at 60.5 Hz.
If that happens, maybe increase that to 61 Hz. Similar effect to changing frequency limits of Rule-21.
I suppose neither is legal. But this is just a test to determine if frequency limits are causing the derating.
Another would be Island mode 60. That disables anti-islanding, not legal on-grid.
Yes, disable power limit is a possibility.
UL-1741-SA without Rule-21 should have a ride-through of some time above 60.5 Hz. Could be long enough to observe that it allows full power. That could be the "safest".
It doesn't make sense for grid frequency to be high. Especially during inclement weather when grid won't be requesting reduced power (unless there is lots of sun elsewhere in the state, and cool weather so no A/C running. We have heavy overcast and rain in the bay area.)
If that happens, maybe increase that to 61 Hz. Similar effect to changing frequency limits of Rule-21.
I suppose neither is legal. But this is just a test to determine if frequency limits are causing the derating.
Another would be Island mode 60. That disables anti-islanding, not legal on-grid.
Yes, disable power limit is a possibility.
UL-1741-SA without Rule-21 should have a ride-through of some time above 60.5 Hz. Could be long enough to observe that it allows full power. That could be the "safest".
It doesn't make sense for grid frequency to be high. Especially during inclement weather when grid won't be requesting reduced power (unless there is lots of sun elsewhere in the state, and cool weather so no A/C running. We have heavy overcast and rain in the bay area.)
Solarisium
New Member
One string of 9 panels. See previous post for photos. Basically one string feeds bith mppt s.
Voltage per string is 273…269… V (keeps changing, it’s a cloudy day today)
All instant values are exported attached
Hedges
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That does show power split evenly between A and B.
Power is low enough won't be a heat issue.
Voltage surprisingly low - I see closer to 125V most of the time. Maybe that is when PV producing. Or just a lightly loaded transformer.
Frequency 60.02 Hz, nothing odd right now.
Power is low enough won't be a heat issue.
Voltage surprisingly low - I see closer to 125V most of the time. Maybe that is when PV producing. Or just a lightly loaded transformer.
Frequency 60.02 Hz, nothing odd right now.
Solarisium
New Member
Two MPPTs are outputting values. Identical values. Picture.
I only have only spare panel. Voltage would be too low to be used as a string.
I suppose i can try it anyway. Away is installed on roof and modification isn’t possible immediately. Needs some work and help.
Don’t have a score or digitizer. Just a regular clamp voltmeter.
Hedges
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No need to split between MPPT now that you've confirmed power is divided 50/50.
And power level too low to derate for heat. Any chance airflow is entirely blocked?
The funny thing is elevated frequency. Some if your displays is was close enough to 60 Hz.
What fraction of time is this occurring, and what fraction of available power lost? If occasional maybe not a big deal.
Have to wonder if grid impedance and anti-islanding confuses frequency measurement. Maybe other loads, or a neighbor's PV.
You could try shutting off all breakers except the inverter, if you have any funny loads. Grasping at straws here, without anything to display voltage waveform.
60.4 Hz again! But a no-name voltmeter, with 1 significant digit after decimal place. I would trust Sunny Boy more.
And power level too low to derate for heat. Any chance airflow is entirely blocked?
The funny thing is elevated frequency. Some if your displays is was close enough to 60 Hz.
What fraction of time is this occurring, and what fraction of available power lost? If occasional maybe not a big deal.
Have to wonder if grid impedance and anti-islanding confuses frequency measurement. Maybe other loads, or a neighbor's PV.
You could try shutting off all breakers except the inverter, if you have any funny loads. Grasping at straws here, without anything to display voltage waveform.
60.4 Hz again! But a no-name voltmeter, with 1 significant digit after decimal place. I would trust Sunny Boy more.
wheisenburg
Independent Solar Consultant
Actually grid tied inverters will put the maximum available power back into the grid that is available, unless they have been somehow commanded to produce less. DC coupled inverters are different.
Solarisium
New Member
Airflow is not blocked. The inverter is installed exactly per manual. I will monitor the inverter radiator temperature for a couple of days i guess, just to confirm that going to use a smart temperature sensor.
I trust the inverter measurement too. My no name voltmeter isn’t accurate.
I watched the instant frequency value reported by the inverter for a while, and it seems it’s in the range of 59.97 to 60.04.
Also going to do some data digging. Hopefully data is logged somewhere so i can find out the grid frequency at the moment when Active Power Limit event and the derating event occurred.
I guess i don’t need to change the configuration mode to ul1741 anymore. But will find the power limit and turn it off….
wpns
Solar Joules are catch and release
Yabut IIRC 0.2 Hz something seriously wrong with the grid, like load or generation shedding before it all blows up, so it just feels really unlikely that the western US would be that far out and no-one noticed.
Solarisium
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Hedges
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I don't think there is any safety risk in turning active power limitation off. That just makes it behave like older versions of inverters, doesn't help maintain grid stability.
My DMM just said 60.02 Hz. Two counts in least significant digit might me measurement error, or real.
0.2 Hz delta would be a big amount.
If OP is only seeing 60.4 Hz on DMM, not on Sunny Boy, I would assume something else caused derating.
But wasn't the error message frequency related?
My DMM just said 60.02 Hz. Two counts in least significant digit might me measurement error, or real.
0.2 Hz delta would be a big amount.
If OP is only seeing 60.4 Hz on DMM, not on Sunny Boy, I would assume something else caused derating.
But wasn't the error message frequency related?
Solarisium
New Member
60.4 was inaccurate. It was taken using my no name digital voltmeter. The accurate frequency seems to be reported by the inverter which was 60.00 +- ~0.04
The event messages were two types:
| 507 | Active power limit AC frequency |
I don’t know why this event is thrown.
And the second event message
| 8006 | String A is in derating mode |
I placed a temperature sensor on top of the radiator at the back of the inverter. It’s reading 98 F. That is not hot. Derating is not caused by the heat.
A point to be noted is that derating lasts from few seconds to few minutes. I guess i can live with it song it os not lasting long periods.
And finally this test:
I turned off the active power limitation. After a couple of minutes this warning was thrown:
I had to revert the changes back. It interrupted the communication of the inverter to the sunny portal the EnnoxOS. That was odd!
Last edited:
Hedges
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I'm not real familiar with Event Log. I see a few for my SBS, the first unit I connect to by browser.
At some point, open a ticket with SMA. There shouldn't be derating if not hot and frequency not shifted.
I have this feeling SMA firmware and support isn't what it once was.
I first caught them on "backup" mode of 10000TL-US-12, which should have supported frequency-watts but didn't. Somebody didn't specify and verify required functionality. I've also heard that SI 6048US may be adjustable down to 50 Hz, but not everything functions correctly. Must have some hard-wired values instead of referencing user-adjustable parameters.
And now I'm trying to get SBS to behave correctly. For two weeks it has charged only every other day. Today it charged two days in a row, wonder if only due to last night's power failure. That function wouldn't be part of your SB -41, but other parts of the inverter seem similar.
At some point, open a ticket with SMA. There shouldn't be derating if not hot and frequency not shifted.
I have this feeling SMA firmware and support isn't what it once was.
I first caught them on "backup" mode of 10000TL-US-12, which should have supported frequency-watts but didn't. Somebody didn't specify and verify required functionality. I've also heard that SI 6048US may be adjustable down to 50 Hz, but not everything functions correctly. Must have some hard-wired values instead of referencing user-adjustable parameters.
And now I'm trying to get SBS to behave correctly. For two weeks it has charged only every other day. Today it charged two days in a row, wonder if only due to last night's power failure. That function wouldn't be part of your SB -41, but other parts of the inverter seem similar.
Solarisium
New Member
Just to share this information:
Graphed a sunny day generation with DC Current and DC Voltage (from MPPT A. the actual power of the system is double the power in the graph, since MPPT B is not included).
Clearly, except for a few moment, the MPPT sits on a pretty fixed DC voltage (~270VDC) and the DC Current is the variable. At 0745, the max power is at a lower voltage (212VDC) and not the higher voltage of 293VDC that was recorded at 0740. see graph.
This is my data digging to understand why my PV voltage is not at ~370VDC (9 x VMP=9x 41.51=~370VDC), instead it is steady at ~270VDC.
Graphed a sunny day generation with DC Current and DC Voltage (from MPPT A. the actual power of the system is double the power in the graph, since MPPT B is not included).
Clearly, except for a few moment, the MPPT sits on a pretty fixed DC voltage (~270VDC) and the DC Current is the variable. At 0745, the max power is at a lower voltage (212VDC) and not the higher voltage of 293VDC that was recorded at 0740. see graph.
This is my data digging to understand why my PV voltage is not at ~370VDC (9 x VMP=9x 41.51=~370VDC), instead it is steady at ~270VDC.
