I recall some noise a while back about PV systems having to power down when the grid was down if they were connected to the grid. I don't recall if there was some kind of exception if you had the correct isolation or not though.
Edit: https://thirdsunsolar.com/residential/does-solar-work-in-a-blackout-third-sun-solar/
However you can buy a more expensive inverter that can provide its' own 60 cycle reference signal and use a battery pack as a storage/modulator. The "Sunny Island" from SMA is an example of this. When grid power goes down they switch to the batteries and run a portion of your house like a large UPS.