If you want clean power no matter what is on the other side, there are three options:
1: As stated above, Victron has a converter/inverter which can run off two power supplies, so one can be on a generator, switch to shore power, and have no dropouts due to the batteries.
2: Magnum Energy has a 3000 watt hybrid inverter/converter that adds voltage if the incoming AC is not up to spec.
3: You can always add an online UPS (note, not standby, online.) Of course, the downside of this is that it comes with its own heavy batteries, and costs about the same as either #1 or #2. To boot, it generally assumes dirty power is an exception, rather a rule, so might autofry early.
My next rig, I'm looking at option #2. That way, it doesn't matter how dirty the shore power is, all the sensitive stuff gets clean voltage until the house batteries are discharged.
