You will have to use one of the side corridors (doesn't matter which one) leading to the upper level to get closer to the generators. Both of these objects are guarded by Comstock's men and by machine gun turrets.
The hallway on the first floor holds two additional turrets and a group of guards from the corridor you've ignored before.
Once you've eliminated all the guards use the stairs leading to one of the generators and pull a lever to turn it off.
Return to the lower floor where you'll be stopped by a Mechanized Patriot and a new group of guards.
Kill all enemy units and find the staircase leading to the remaining second generator. Turn off this generator and then get back to the operating room.