Inverter on 12K residential solar system sporatically tripping off

[bdn2004]

The 12000 watt solar inverter will randomly see an error code (DC detected on the AC line) and shuts itself off for five minutes. When it restarts, sometimes will work fine, other times it will continue shutting down over and over. All the manufacturer will say is that it is “grid distortion” and that I should contact my utility. This may happen 2-15 times a day, usually after the output reaches at least the 5000 to 6000 watt range.

I have added a 20hp 5% line reactor (rated for 59 amps) to mitigate some harmonics and it seems to have helped some but has not removed the problem. Is a capacitor needed to work in conjunction with the reactor and if so, how would I size it?

Attached is a single line sketch of the system. Thanks for any help or suggestions!

 

[catserveng]

Your best solution would be to rent a power quality recorder, hang it on the line for a while and identify the actual root cause of the problem. I would run the recorder for a couple of days with the inverter active, and then a couple with the inverter off. If it really is a utility problem it will be there if the inverter is on or off, if it an inverter problem you should only see it when the inverter is on.

Once you know what the condition is causing the shutdown, then you can either approach the utility for a solution, or determine what you need on your end to prevent the problem from occuring again.

MikeL.

 

[jraef]

And no, adding a capacitor will likely make things worse. You can inadvertently create a tank circuit with the caps inside of your inverter, which will hopefully trip on an over voltage fault, or worse yet be damaged.

Rent the meter, but most likely what you will find is high harmonics on the utility side, likely from a nearby user who has added other inverters without mitigating their current distortion. That's what IEEE519 is all about. If you find greater than 5% THD voltage on the input without your inverter running, the utility must mitigate it. IEEE519 WORKS BOTH WAYS; users must mitigate their current distortion so as to not create greater than 5% VTHD at the PCC, but also the utilities must not deliver more than 5% to the users to begin with. That means they will go knocking on your neighbor's doors looking for causes, usually inverters. They will hook up a recording meter and look at the issue over a time period to help pinpoint any usage patterns that might be helpful in finding the culprit.

Just make sure YOU are not your own culprit!


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[bdn2004]

This is a follow up and what we found out and a question.

We connected a power meter recorder. The inverter appeared to be the culprit.

However one issue not described was a knocking sound at the inverter. After turning off the circuit breaker for the house LED lighting circuit, with about 20 lamps, that noise went away. We replaced the LEDs with incandescent lights and there has not been an issue with the inverter kicking off since. The LED lighting circuit also has dimmers.


Is there anything we can do to mitigate the harmonics caused by the LEDs?

Thanks for the help!

 

[itsmoked]

It's not clear in your, "house LED lighting circuit, with about 20 lamps" if these are all individual driver lights or all on a single big driver.

Larger LED drivers should always be "Power Factor Corrected" models. Cheaper or lower power ones often are not. You may have an issue with lots of little bitty uncorrected ones adding up to a lot of uncorrected distortion power factor. Distortion power factor is what's really being dealt with here, not the usual leading/lagging stuff. The PF corrected drivers are designed to keep their power consumption very close to sine-waves.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[bdn2004]

This is a residential installation with standard canned recessed fixtures and BR30 LED lamps. Is there a power factor corrected single lamp available? Or some other solution?

 

[davidbeach]

Cheap LED driver with half-wave rectification. Nasty stuff on any AC system, your inverter doesn't want to deal with it.