From the comment I replied to: > Generally grid backfeed capability for these systems is predicated on the presence of a stable voltage and frequency already o

From the comment I replied to: > Generally grid backfeed capability for these systems is predicated on the presence of a stable voltage and frequency already on the grid. You are using the reference clock to know precisely how misaligned the grid is and you use the reference to make small corrections to the generator power or inverter phase to restore phase alignment. If you have an external stable reference clock (GPS) you know what the grid *phase* should be and it should be easier for network of multiple small inverters to keep the grid stable and to bring it up by themselves if there's a large blackout.