AFORE cliping max power

[Gobo]

Hello,
My first post here
I have 5kW AFORE inverter. Is this normal that it shows (quite often) output much above the max output? I even had 6.01kW. Such peaks above max appears when clouds move away and installation get full sun. What I've seen on other installation is clipping when power from panels exceed inverters max power.This is also reported on inverters display, not only on graph. What makes this more strange is that I have panels that give only 5.1kWp.
Zrzut ekranu 2021-05-30 224138.png

[Ampster]

I see clipping on my system all the time. On sunny days it just looks like a flat top on a typical solar generation curve. The above graph is what mine looks like when there are intermiitent clouds. If your panels are cold, it is possible that they could produce more than their STC (Standard Test Condition) rating.

[Gobo]

I thought that inverter can only convert 5kW, even if input power is higher. AFORE BNT005KTL has Nominal Output Power 5000W.There is no clipping on power above that. Is it cheating on the graph? Or is it showing input power instead of output?

If your panels are cold, it is possible that they could produce more than their STC (Standard Test Condition) rating.

How much (above STC) can cold panel produce? I have 5,1kWp but as I wrote, it shows 8-12% (once 18%) above STC. On graph above, last (>5kW) peak duration is 15min with max 5.59kW at the end of peak. I saw (on other instalations) up to 5% above STC but not as high as mine.

[nerdralph]

I thought that inverter can only convert 5kW, even if input power is higher. AFORE BNT005KTL has Nominal Output Power 5000W.There is no clipping on power above that. Is it cheating on the graph? Or is it showing input power instead of output?


How much (above STC) can cold panel produce? I have 5,1kWp but as I wrote, it shows 8-12% (once 18%) above STC. On graph above, last (>5kW) peak duration is 15min with max 5.59kW at the end of peak. I saw (on other instalations) up to 5% above STC but not as high as mine.

The temperature coefficient of mono panels is 0.35%/C, so at 10C, output would be 1.0035^15 == 5.38% higher.
If you are at high altitude, insolation can be much higher than STC, around 8% higher for 1km altitude.

[oregon_phil]

The 5kW AFORE inverter has a max output power of 5500 watts. This matches up with the max output shown in the line graph the OP provided.

[Gobo]

The temperature coefficient of mono panels is 0.35%/C, so at 10C, output would be 1.0035^15 == 5.38% higher.
If you are at high altitude, insolation can be much higher than STC, around 8% higher for 1km altitude.

What is the difference in nominal and max power? Max 5500W can be produced for 1, (5, 15, 20, ...) minutes and then drops to nominal power 5000W?
My location is 100 mamsl - rather standard Also location is "typical":North 50
On above graph 5,59kW lasting about 15minutes. Delta T= 35C?
Here are two other graphs:
6_01.png5_87.PNG
Especially the first one shows there was no sun, and suddenly peak 18% above STC. This means that according to the rule0.35%/C the temp. should be -25C.

[oregon_phil]

You have clouds then bright sun; perfect conditions for maximum power. When you get a full day with no clouds and full sun, I think any clipping questions will be answered.

[J.P.M.]

The temperature coefficient of mono panels is 0.35%/C, so at 10C, output would be 1.0035^15 == 5.38% higher.
If you are at high altitude, insolation can be much higher than STC, around 8% higher for 1km altitude.

This may seem inconsequential and it may be for this post, but the temp. coeff. - which is a negative number - actually expresses the change in power output as f(temp.). It's expressed as a % and that's too bad because doing so can get a bit confusing to the casual user astray and into errors. The change is mostly but not precisely linear.

So, if a 300 W STC panel has a temp. coeff. of power = -.0035/deg. C., panel power output will drop (0.0035*300) = ~ 1.05 W per deg. of cell temp. increase and drop ~ 1.05 W per degree C of cell temp. decrease. Your power function as you use it gives approximately correct answers only because -.0035 is relatively small number and the temp. diff. is slight.

As far as irradiance as f(alt.), the barometric press at 1,000 m above mean sea level is ~ 890 MB. But to say that irradiance is ~ 8 % greater at that altitude over simplifies the situation as doing so takes no account of the other variables that are direct and indirect functions to the altitude.

Anyway all this seems somewhat esoteric with respect to what the OP seems to be looking.

Gobo: As Oregon Phil suggests, a sunny day will clear up a lot of your questions. Wait for one of those days.
Start by assuming your array's output will rarely if ever exceed the STC rating of your panels. If your inverter is rated for less than that, it may well clip a bit 1X/awhile.

BTW< what's your zip and what's your array's orientation, tilt and azimuth ?

Also, ever hear of PVWatts ?

[Gobo]

I would like to move PV production to new thread. Here I would like to clear inverter matters. Having 5000W nominal power (and 5500W max - what ever it means) should I have clipping on power above it or not as graphs don't show such clipping.
I'm thinking about shutting down all fuses at home for a couple of hours and check what production will show inverter and what amount of energyi passed to network will show electric counter.
Instalation is ongrid, orientation 226deg (SW), and tilt about 30deg. I'm from Poland,
Below is graph. from yesterday. Max peak was 4.8kW

PS. I found online catalogue for my inverter, and indeed there is max AC power but it's 5350W (page 10). There is also max DC power rated 5500W.
https://pvgroup.pl/wp-content/upload...oltaiczne1.pdf

[oregon_phil]

You are right, the max AC power is 5350W for your 3 phase unit. I made the incorrect assumption earlier that you were single phase.

Your picture above shows "parameters". Can you select the parameters to graph? Are you displaying DC power into the inverter or AC power out of the inverter?

[nerdralph]

This may seem inconsequential and it may be for this post, but the temp. coeff. - which is a negative number - actually expresses the change in power output as f(temp.). It's expressed as a % and that's too bad because doing so can get a bit confusing to the casual user astray and into errors. The change is mostly but not precisely linear.

Good point. I shouldn't have used a power function. And while we are being pedantic, the mostly linear part is the voltage, not the power. The forward voltage of a PN junction drops about 2mV per degree. Silicon diodes are often used in electronics to measure temperature.
With the drop in voltage due to increased temperature, panel current increases slightly. Since P=I^2 * R, the increased current means increase power losses in the panel. Mathematically the formula would be quadratic, but can be approximated quite closely with a linear equation.

[bcroe]

What is the difference in nominal and max power? Max 5500W can be produced for 1, (5, 15, 20, ...) minutes and then drops to nominal power 5000W?
My location is 100 mamsl - rather standard Also location is "typical":North 50
On above graph 5,59kW lasting about 15minutes. Delta T= 35C?
Here are two other graphs:
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Especially the first one shows there was no sun, and suddenly peak 18% above STC. This means that according to the rule0.35%/C the temp. should be -25C.

That 6.01KW peak happened because the sun came out from behind a cloud. Its
base is made to look as broad as a couple data sampling periods. The truth is, the
electronics would have made adjustments in mili seconds. The actual peak was so
narrow as to be invisible on this scale, could be observed on a storage O scope.

Bruce Roe