If people are interested, the magic word is "islanding" and the key technology you want which makes this stuff safe to deploy is thus "anti-islanding protection".

If your device discovers it has become an "island", generating power with no real grid (maybe there are two similar panels next door but not a 10GW power grid) it switches off. This is not only safer for you, it's also critical for repair people who might be fixing some overhead line miles away and then a dozen stupid devices inject lethal power onto a circuit their operator has assured them is dead - because from their end it was dead.