When I used to work on the AWAC it had eight generators, all could be (and usually were)connected to a synch bus. The unit controlling the synch bus (and the eight GCUs) is a BPCU (bus power control unit), one downside of having all the generators on a single bus is that of load sharing, so the bus is protected by both real and reactive load sharing circuits.
On older Boeing 707s and the like then the flight engineer could control the phase of each generator relative to each other before they were connected to the synch bus.
