... Solar flares give V/km (volts per kilometre) induced voltages. ...
Thus I'd have thought that PV wouldn't even notice, but decent bypass and blocking diodes would ensure that any small voltages and currents induced would be likely dissipated safely.
Solar flares are a problem for power grids because the lines are many kilometres long. The induced voltage from the (slowly) moving mag field adds up over long distances to hysterical levels.
Your panels are small by comparison to the wavelengths involved and won't pick up any substantial voltage. Your wiring from the panels to the inverter may be long enough to pick up a few volts. But even if they pick up a couple hundred it's nothing compared to a surge from a nearby lightning strike.
The main problem with long distance power lines is that, if the central Y point of a three-phase transmission line's transformers are grounded at BOTH ends, a bad mag storm can induce enough common-mode current that it combines with the line current to saturate a transformer core at one peak of the current waveform. Then the inductance drops by maybe something over five orders of magnitude. Without the inductance to impede it, the current from the transmitted power climbs by a similar factor (and the unbalanced current may also lead to saturation of the other transformers in the group at both ends of the line). The heating of the coils goes up with the square of the current (TEN orders of magnitude, YIKE!) and the power from the grid fries the transformers almost instantly. Then the line is out until a half-dozen house-sized transformers are manufactured, shipped, and hooked up. With a large number of lines suffering the problem simultaneously it could take a year or more to bring the whole grid back up.
But that's a problem for long high-tension lines blowing up giant transformers in the substation. And if you're out in the country and your utility hooks up your "pole pig" transformers in Y rather than delta, you might just possibly have problems with the pole pigs that feeds your house, too, before the grid protects them by going down. But it's not an issue for the wiring from your panels to your inverter. (Even if your panels are on the hill behind your house rather than on it or beside it, and you also risked galvanic corrosion and lightning surge problems by grounding one of the feed wires from your panels at the panel end.)
For the grid the solution is to put a resistor in the grounding of the center of the Y on at least one end. But for the grid such a resistor is a big box, comparable in size to the transformers, very pricey and requiring maintenance. (I think they're actually full of water with electrodes it it...) And it only protects them from trouble every few decades and from disasters every couple centuries. So there haven't been many installed, and a lot of long lines are still unprotected.
Early telegraphs used the ground for one of the wires, and (as I understand it) were in place for the last giant magnetic storm. So there actually was an event with some damage back then - though it wasn't understood at the time.
Rural POTS telephones, with many miles of wire and a ringer circuit for party lines that does a return through ground, may have similar issues. (If the line is long enough that the voltage gets up to 80V or so, some party line bells might do a little oddball ringing - much like they do in severe electrical storms. B-) ) The old copper T1 (twisted pair) and T3 (coaxial) long distance cabling might also have had trouble. But it's pretty much all been replaced by fiber, which is immune, (and the copper sold off to pay for the fiber installation B-) ).
Edit: Posted all that before I saw that there was a second page where it was all answered already. Leaving it up just for the hell of it.