Voltages supplied by the 787 electrical system are as follows:
28VDC - Traditional, through the batteries and TRUs, which are powered by the 235VAC system.
110VAC - Supplied through solid state PSUs, powered by the 235VAC system or ground power when connected. The 28VDC and 110V/400hz PSUs provide for the majority of electrical loads on the aircraft.
+/- 270VDC - Supplied through TRUs, 3 wire system as Chu Chu posts. Mainly supplies large electric motor loads such as hydraulic pumps, cabin air compressors, and center tank fuel pumps.
235VAC - Frequency wild as Turin states, 360-800hz, according to engine gearbox speed. Supplies starter/generators, wing anti-ice, flight control actuators, cabin air recirculating fans among others. These buses can also be supplied from the GPU 110VAC current through dedicated PSUs.
The flight control system electronics are powered by 3 independent, dedicated generators, two on the left engine, one on the right. As a backup, 28VDC from the TRUs or aircraft main batteries can also provide power, as can, temporarily, dedicated batteries.