Flickering PV output when Solis inverter hits max cap

Gus75

I've had panels for a few days and when the sun is high, output flickers:

The array consists of

• 3 panels south at 27°
• 2 panels south at 15° with optimizers
• 3 panels west at 27°

South and West are on different connections to a Solis inverter.

I was told by installers that the optimizers on the flat roof panels will disconnect them when not helpful. Is that really what an optimizer does?

What might be causing the flicker?

Any chance to improve it?

UPDATE: Inverter is a S6-GR1P3K, max output rating is 3 kWh, so it just cannot cope with power levels > 3kW.

graememk

Id say it's just clouds. Unless you can guarantee that there wasn't a cloud in the sky at that particular time.

10-10-20

Not saying that there's an actual problem here and @graememk is probably right - but I wonder if it's undervolting the south MPPT input when the optimisers kick in. And maybe west is suffering from the same fate. What inverter and what panels were fitted?

Gus75

If it was clouds, the effect would spread across the day, but it clearly concentrates on the most sunny hours. It happened 2/3 days so far, where the other day was cloudy all along.
See a cloudy day for comparison:

I am not sure of the models, it is an Activ8 installation with Solis inverter and 435W panels…

Gus75

I found the inverter model, it is a S6-GR1P3K… Perhaps it cannot handle more than 3 kW!!!

bullit_dodger

Occams razor I would think. Clouds. What you are seeing is fairly standard for all of us. Sun is out, getting 5kw. Sun goes behind a cloud you get 1/2 power (on this specific day) and then back out from behind a cloud and your back to full power again

Note this was for June 26th and I'm in south Dublin city. You can note that after 3pm, the generation dropped off as it got overcast instead of broken clouds.

Gus75

Thanks for sharing that, same area and day here.

https://www.boards.ie/discussion/comment/122309964#Comment_122309964

Only I am very suspicious that my power output flickers like mad when over 3 kW, and I realize the inverter is rated at 3 kW.
I am calling for a replacement with the 3.6 kW model.

10-10-20

https://www.boards.ie/discussion/comment/122310106#Comment_122310106

That's not how it works. A 3kW inverter with 8x 424w panels (3,400w) will be limited to around 3000W and will simply drop or cap at that value and not provide more power to the grid. Over-sizing panels is a common design and isn't a technical design issue - it's actually beneficial to you as it keeps the cost lower.

bullit_dodger

Looking at the charts you've posted……they all look perfectly normal to me. You've 8 panels, but you didn't state what wattage they are. Assuming 400w, that's 3.2Kw in total.

Even with a 3kw inverter….it's only in May-July that you'll probably be hitting the max and at that only "clipping" maybe 200-300 watts for an hour or two….at most. Out of your production for the year, you (might) be losing 1%…..maybe and that's doubtful.

If it was me, I'd do nothing - everything you have is working pretty much about as good as it should be.

Also, you might define more what you mean by "flickering". Is it what you've shown in the charts above? If so, normal - but maybe you mean somehting else?

Gus75

Thanks for your analysis.

My panels are the new ones rated at 435W so the total rating is 3.48 kW

I may insist in getting the 3.6 kW inverter because that was implicit in the quote, which was originally for more panels.

After reading your notes and some research, a 3 KW inverter might not be a bad idea, but I want to hear the installer's explanation.

Buffman

https://www.boards.ie/discussion/comment/122309784#Comment_122309784

Are you using the last few days for your comparison? If so, I don't think the weather was good enough to rule out clouds. That 'cloudy' graph still has similar ups and downs as the 'sunny' graph, just not as pronounced as cloud thickness will obviously cause a far greater drop on a sunnier day. IMO you'd have to get a perfect condition day of zero clouds all day to get a good baseline before being able to rule out clouds.

https://www.boards.ie/discussion/comment/122309849#Comment_122309849

The S6-GR1P3K has a recommended max PV power of 4.5kW, rated apparent power of 3kW, and max output power of 3.3kW, so on the face of it would seem an OK fit for a 3.48kW system with split orientations.

However, if you paid for a S6-GR1P3.6K, that's what you should of got. I'm assuming you paid less than the original quote if the system size was reduced? Did they reissue you a quote when the system was redesigned or was it reflected on the invoice?

Cuddlesworth

Sunny day without clouds and sunny day with clouds. I had to go back 2 months to find the actual sunny day.

You usually don't match the power to the inverter exactly, it's a waste. Especially in Ireland where you rarely get sun.

10-10-20

https://www.boards.ie/discussion/comment/122316685#Comment_122316685

You'd actually get more of those wall-to-wall sunny days during Winter than you would during Summer!

Gus75

Thanks for the sunny day sample.

I've been discussing with Solis support and turns out the inverter power limit was set to 98%.

They remotely changed it to 110% to avoid the spikes, now this is the result today:

This looks great for a semi-cloudy day, resulting in the highest daily yield so far.

graememk

Power limit wouldn't have caused what you were experiencing,

It would just limit the output, not cause a drop in power.

This was today for me (it's 8.4 on a 6kW inverter)

Gus75

https://www.boards.ie/discussion/comment/122356570#Comment_122356570

I agree, power limit should not cause downward spikes, but whatever they tweaked seems to have made a positive impact so far.

I asked for a screenshot of the hidden settings but nothing else was really visible.

Fact remains that yesterday's was the best yield since installation two weeks ago.

@graememk, @Cuddlesworth, was yesterday the same for you?

graememk

https://www.boards.ie/discussion/comment/122358624#Comment_122358624

Id still say initial problem was high scattered cloud, ive seen it enough times.

My all year high was a month or so ago now, but still not a "perfect day"

Gus75

I meant to ask if yesterday was the best in the last 2 weeks or so.

Assuming your panels are not too far from Sallynoggin for comparison 🙂 (facing South-West)

https://www.boards.ie/discussion/comment/122358776#Comment_122358776

graememk

https://www.boards.ie/discussion/comment/122358827#Comment_122358827

NE/SW, very north of the country

Cuddlesworth

The 8th was the first really good day in a good while, so yeah mine looks similar. Some clouds towards the end of the day.

I wouldn't get too hung up on the graphs, they are a approximation of output over a period of time. Solis probably just changed the graph output to weight more towards average, not the inverter.

We have a lot of clouds in the summer. So your going see a lot of peaks/valley's. Even more so because the clouds allow the panels to cool down between the bursts of sun, meaning more power output in the short term.

As I said before, this is a standard sunny day in Ireland.