AC coupling - light flicker

Discussion about adding energy storage to grid-dependent inverters using OutBack Power technology
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AC coupling - light flicker

Post by sjsamuel »

Well, I’m super excited as I finally, after a lot of work, time and money, have my system up and running. Thanks to everyone here that has helped with my many questions so far.
Well, now the journey to get everything working smoothly starts, and I ran into my first significant issue that has me stumped. Here is my system in a nutshell: 2 Radian 8048a’s powered by a lithium battery bank and Grid Tied. PV is an Enphase IQ7 system that is AC coupled to the Radians.

Turned of the Grid yesterday and had a big grin on my face as my inverters didn’t miss a beat and powered the house without any delay. I left the PV on, and it too continued to function now operating on the local grid created by the Radians as it should. As my load requirements dropped however, I noticed a very apparent flicker in all my lights, LED and incandescent(yes I still have a couple :eek:). If I increased the load by turning in the dryer or something the flicker gets better, but still there. Finally in an attempt to trouble shoot, I turned of PV and the flicker is gone. I’m assuming there is some interaction between the Radians output and the PV it a phasing issue? What can I do to sort this out?

Oh and the Radian Battery Charger is off and still not difference

Thanks for the help in advance!

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Re: AC coupling - light flicker

Post by raysun »

I'm an all DC off-grid guy, so am speaking from no experience, but I'd think phase sync between AC coupled busses would be out-of-phase on occasion, on purpose.

One common method to modulate current admittance is to shift frequency. I believe it the method Outback uses. How nimbly the string inverters respond, or don't, may lead to interference waveforms in AC OUT.

I'm not saying that's your issue, but I'd think it might.
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