string inverters and clouds...

[MikeInRialto]

Do string inverter systems get adversity affected if just a few panels are shaded by clouds?

[Panelmal]

A string is only as strong as it's weakest panel. Even one shaded panel could negatively affect the string, but I wouldn't worry about clouds.

[inetdog]

Do string inverter systems get adversity affected if just a few panels are shaded by clouds?

Panels contain bypass diodes which can conduct when the rest of the string tries to drive more current through the panel than it can sustain based on the lower level of light hitting it.
An optimizer or microinverter can get full (lower) output from a diffusely shaded panel, while the same panel in a string will produce zero power. But it will not choke down the current that the rest of the string is capable of.
As long as the string output voltage (figuring negative three volts for each shaded panel) is still within the MPPT tracking range of the inverter the results should be tolerable.

I do agree that partial cloud shading on that scale is likely to be very short lived and not worth worrying about in any case.

[bcroe]

Do string inverter systems get adversity affected if just a
few panels are shaded by clouds?

I would expect a cloud to affect all the panels, as opposed to a shadow (tree, etc) only
affecting a few. A string with an MPPT inverter can continue to produce from the
unshaded panels, at a lower voltage; the shaded cells will be bypassed. If strings are
paralleled, the MPPT will not be able to optimize for both. It might choose to run at
full voltage on the unshaded string. If so the shaded string won't be able to produce
much current at that voltage.

Ot the MPPT might choose to run at the reduced voltage of the shaded string with bypassed
cells. In that case the unshaded string will be pulled down to that voltage which is a loss,
but it will supply full current. In effect shading a panel in a string is equivalent to shading
a panel in all the paralleled strings. Bruce Roe