Patent ID: 7061139

Claim:
A power system ( 8 ) for providing uninterrupted AC electric power to a critical load ( 14 ), comprising: a. a first power source ( 18 ) comprising at least one fuel cell power plant ( 18 ), the first power source normally providing sufficient power to supply at least the critical load ( 14 ) and being normally substantially continuously connected and providing power to, the critical load ( 14 ); b. a second AC power source ( 10 ) comprising a utility power grid normally providing sufficient power to supply the critical load ( 14 ); c. high speed isolation switching means ( 19 ) for selectively connecting and disconnecting the second power source ( 10 ) to the first power source ( 18 ) and to the critical load ( 14 ); d. a switch controller ( 49 , 45 ) for controlling the state of the high speed isolation switching means ( 19 ) to connect the second power source ( 10 ) with the critical load ( 14 ) and the first power source ( 18 ) during normal operation of the second power source ( 10 ) whereby the first power source can provide any excess power to the second power source, and to rapidly disconnect the second power source ( 10 ) from the critical load ( 14 ) and the first power source ( 18 ) if and when operation of the second power source ( 10 ) deviates beyond a limit from normal; e. the at least one said fuel cell power plant ( 18 ) comprising a fuel cell ( 60 ) and a power conditioning system (PCS) ( 62 ) including an inverter ( 64 ), the fuel cell ( 60 ) being normally connected to supply DC power to the inverter ( 64 ) for conversion to AC power to supply the critical load ( 14 ), the power conditioning system (PCS) ( 62 ) operating to configure operation of the respective fuel cell ( 18 ) in a grid connected mode or in a grid independent mode in response to mode control signals (D 1 / 401 ′, D 2 / 402 ′); f. a site management controller ( 31 ) connected intermediate the switch controller ( 49 , 45 ) and the power conditioning system (PCS) ( 62 ) and being responsive to preliminary mode signals (M 1 / 401 , M 2 / 402 ) from the switch controller ( 49 , 45 ) for providing the mode control signals (D 1 / 401 ′, D 2 / 402 ′) to the fuel cell power conditioning system (PCS) ( 62 ) to rapidly transition operation of the fuel cell power plant ( 18 ) between the grid connected and the grid independent modes; and g. power assurance means ( 65 ; 10 ″, 66 , 64 , 70 ; 74 , 75 ) operatively connected to at least the inverter ( 64 ) of the PCS ( 62 ) of the fuel cell power plant ( 18 ) to provide an even and continuous supply of AC power to the critical load ( 14 ).