Large ground array - series parallel theory

[Jinx]

For large ground array, just for example 10 strings (parallel) of 22 panels (series). A broken panel is bypassed. Now 9 strings of 22, 1 string of 21 panels.
How is this reflected in output?

[AlBargey]

Probably difficult to notice 1 missing out of 220 solar panels all on the same tracker! Vs variable shading throughout the day? But I guess it would drag the voltage down a bit.

[nowty]

The MPPT of the inverter will operate at a fraction down from the max power point on the 22 panel strings and will operate quite a bit higher than max power point on the single string of 21. The voltage point on all strings will be the same.

Total output will hardly change on that many panels and I reckon you still would get more output than taking the 21 panel string out completely.

I run multiple strings of slightly different panels and find that as long as the string voltages are not too far apart from each other its makes hardly any difference.

[Jinx]

Interesting, i came across this yesterday and found no current flowing in the 21 string. I thought perhaps the MPPT voltage the inverter selected was higher than the 21 could produce and in effect they became a load to the 22s, obviously the diodes preventing reverse current flow. This was in full blown sunlight (>900W/M2), albeit panels at 25degrees in Feb.

[sharpener]

Sounds like the MPPT is trying to earn its crust and has decided that the optimum PP with 9 x 22 is better than the one with 10 x 21.

Though thinking about the shape of the V-I curve I am somewhat surprised at this. If they were all working at the lower voltage the output power of the 9 good strings would be reduced (but by less than 1/22 as their current will rise a bit) but the total current will be 1/9 more, so surely a better result as @nowty proposes?

[nowty]

Interesting, i came across this yesterday and found no current flowing in the 21 string. I thought perhaps the MPPT voltage the inverter selected was higher than the 21 could produce and in effect they became a load to the 22s, obviously the diodes preventing reverse current flow. This was in full blown sunlight (>900W/M2), albeit panels at 25degrees in Feb.

If the MPPT voltage is higher than the Voc of the 21 panel string I would expect this but taking say a typical panel with Pmax of say 31V and Voc of 37V.

22 x 31 = 682V

21 x 37 = 777V

So I would expect some current from the 21 panel string unless any of the panels were shaded.
My strings only have a mismatch of around 5V but a whole panel loss is a bit higher.