[PapaBear3625]

On the power grid's "infinite bus," an alternator that falls behind due to RPM drop becomes a motor, sucking energy from the grid. Thus the problem becomes one of phase control, really. Each alternator is a synchronous device that must be phase locked to within a very small amount (like a fraction of an electrical degree) of the grid at large.

We're starting to see a shift to high voltage DC (HVDC), with that being a big factor in favor of the switch

[Steely Tom]

Thanks for the link. Very interesting.