[stephen_g]

A phase-locked loop would fairly quickly come back into sync with the reference frequency - that’s exactly what they’re designed to do.

I’m pretty sure companies like Victron Energy already make these kinds of systems - combination solar inverters and battery chargers that have transfer switches to be able to seamlessly switch to UPS mode when the grid drops out but can still export excess energy when it’s up.

[zaarn]

Of course these systems are made but they're just very expensive and usually for customers of theirs that don't play around with a couple 100W panels because they want to save a buck or two in the summer.