The 777 can sync the AC buses when needed. For example, when you shutdown an engine, there is a light delay (250 ms if memory serves) before the fuel shutoff command goes to the engine. ELMS uses this delay to sync the AC bus before the engine spools down and the IDG drops off line (known as a 'breakless transfer'). So if everything is working correctly, on the 777 you don't get that annoying ~50 ms power interrupt when a generator comes on or drops off line that causes the displays to flicker on the 747-400/757/767/