System for providing assured power to a critical load

Abstract

A power system ( 8 ) is provided for economically supplying uninterrupted electrical power to one or more critical loads ( 14 ). One or more fuel cell power plants ( 18 ) provide one substantially continuous source of power, and a utility grid ( 10 ) provides another source of power. The fuel cell power plants ( 18 ) are adapted to be, and are, normally substantially continuously connected and providing power to, the critical load(s) ( 14 ). A rapidly-acting static switch ( 19 ) selectively connects and disconnects and reconnects the grid power supply ( 10 ) to the critical load(s) ( 14 ) and with the fuel cell power plant(s) ( 18 ) for abnormal and normal grid operation, respectively. A switch controller ( 49, 45 ) controls the state of the static switch ( 19 ) to connect the grid power source ( 10 ) with the critical load(s) ( 14 ) and the rapidly ( less than 4 ms ) make the disconnections and the reconnections. The fuel cell power plant(s) ( 18 ) during normal operation of the grid ( 10 ), and to rapidly (less than 4 ms) disconnect the grid power source ( 10 ) from the load(s) ( 14 ) and the fuel cell power plant(s) ( 18 ) when operation of the grid ( 10 ) deviates from normal beyond a limit. each include power conditioning systems ( PCS ) indirectly controlled by the switch controller ( 49, 45 ) to in turn rapidly transition the ( PCSs ) of the fuel cell power plants ( 18 ) between grid connected and grid independent modes .

1. A power system ( 8 ) for providing uninterrupted electric power to a critical load ( 14 ), comprising:
 a. a first power source ( 10 ) providing sufficient power to supply the critical load ( 14 );  
 b. a second power source ( 18 ) comprising at least one fuel cell power plant ( 18 ), the second power source providing sufficient power to supply the critical load ( 14 ) and adapted to be normally substantially continuously connected and providing power to, the critical load ( 14 );  
 c. a static switch ( 19 ) for selectively connecting and disconnecting the first power source ( 10 ) to the second power source ( 18 ) and ( to)  the critical load ( 14 ); and  
 d. a switch controller ( 49 ,  45 ) for controlling the state of the static switch ( 19 ) to connect the first power source ( 10 ) with the critical load ( 14 ) and the second power source ( 18 ) during normal operation of the first power source ( 10 ) and to rapidly disconnect the first power source ( 10 ) from the critical load ( 14 ) and the second power source ( 18 ) if and when operation of the first power source ( 10 ) deviates beyond a limit from normal.  
 
     
     
       2. The power system ( 8 ) of  claim 1  wherein the switch controller ( 49 ,  45 ) additionally controls the state of the static switch ( 19 ) to rapidly reconnect the first power source ( 10 ) with the critical load ( 14 ) and the second power source ( 18 ) when the first power source ( 10 ) returns to normal operation. 
     
     
       3. The power system ( 8 ) of  claim 1  wherein the second power source ( 18 ) comprises only one or more fuel cell power plants ( 18 ). 
     
     
       4. The power system ( 8 ) of  claim 1  wherein the static switch ( 19 ) is a solid-state device. 
     
     
       5. The power system ( 8 ) of  claim 4  wherein the solid-state device is a thyristor ( 19 ). 
     
     
       6. The power system ( 8 ) of  claim 1  wherein the first power source ( 10 ) is a utility power grid and wherein each fuel cell power plant ( 18 ) includes a power conditioning system (PCS) for configuring 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 ′), and including a site management controller ( 31 ) connected intermediate the switch controller ( 49 ,  45 ) and the power conditioning system (PCS) and 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), whereby the fuel cell power plants ( 18 ) rapidly transition operation between the grid connected and the grid independent modes. 
     
     
       7. The power system of  claim 6  wherein the rapid disconnection of the first power source ( 10 ) from the critical load ( 14 ) and the second power source ( 18 ), and the rapid transitioning of operation of the at least one fuel cell ( 18 ) between the grid connected mode and the grid independent mode occurs within an interval of about 4 milliseconds. 
     
     
       8. The power system of  claim 1  wherein the rapid disconnection of the first power source ( 10 ) from the critical load ( 14 ) and the second power source ( 18 ) occurs within an interval of about 4 milliseconds. 
     
     
       9. A power system ( 8 ) for providing substantially continuous electric power to at least at critical load ( 14 ), comprising:
 a. a utility grid power source ( 10 ) providing sufficient power to supply the critical load ( 14 );  
 b. at least one fuel cell power plant ( 18 ) operating substantially continuously for providing at least sufficient power to supply the critical load ( 14 ), the at least one fuel cell power plant ( 18 ) including a power conditioning system (PCS) for configuring 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 ′), the at least one fuel cell power plant ( 18 ) being normally substantially continuously connected and providing power to, the critical load ( 14 );  
 c. a static switch ( 19 ) for selectively connecting and disconnecting the grid power source ( 10 ) to the at least one fuel cell power plant ( 18 ) and to the critical load ( 14 );  
 d. a switch controller ( 49 ,  45 ) for controlling the state of the static switch ( 19 ) to connect the grid power source ( 10 ) with the critical load ( 14 ) and the at least one fuel cell power plant ( 18 ) during normal operation of the grid power source ( 10 ) and to disconnect, within a 4 millisecond interval, the grid power source ( 10 ) from the critical load ( 14 ) and the at least one fuel cell power plant ( 18 ) when the grid power source deviates beyond a limit from normal, and  
 e. a site management controller ( 31 ) connected between the switch controller ( 49 ,  45 ) and the power conditioning system (PCS) and 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) to cause the at least one fuel cell power plant ( 18 ) to rapidly transition operation, within a 4 millisecond interval, between the grid connected mode and the grid independent mode.  
 
     
     
       10. A power system ( 8 ) for providing substantially continuous electric power to at least a critical load ( 14 ), comprising:
 a. a utility grid power source ( 10 ) providing sufficient power to supply the critical load ( 14 );  
 b. at least one fuel cell power plant ( 18 ) operating substantially continuously for providing at least sufficient power to supply the critical load ( 14 ), the at least one fuel cell power plant ( 18 ) including a power conditioning system (PCS) for configuring 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 ′), the at least one fuel cell power plant ( 18 ) being normally substantially continuously connected and providing power to, the critical load ( 14 );  
 c. a static switch ( 19 ) for selectively connecting and disconnecting the grid power source ( 10 ) to the at least one fuel cell power plant ( 18 ) and to the critical load ( 14 );  
 d. a switch controller ( 49 ,  45 ) for controlling the state of the static switch ( 19 ) to connect the grid power source ( 10 ) with the critical load ( 14 ) and the at least one fuel cell power plant ( 18 ) during normal operation of the grid power source ( 10 ) and to disconnect, within less than an 8.3 millisecond interval, the grid power source ( 10 ) from the critical load ( 14 ) and the at least one fuel cell power plant ( 18 ) when the grid power source deviates beyond a limit from normal; and  
 e. a site management controller ( 31 ) connected with the switch controller ( 49 ,  45 ) and the power conditioning system (PCS) and responsive to the switch controller ( 49 ,  45 ) for providing mode control signals (D 1 / 401 ′, D 2 / 402 ′) to the fuel cell power conditioning system (PCS) to cause the at least one fuel cell power plant ( 18 ) to rapidly transition operation, within less than an 8.3 millisecond interval, between the grid connected mode and the grid independent mode.  
 
     
     
       11. The power system ( 8 ) of  claim 10  wherein the at least one fuel cell power plant ( 18 ) is caused to rapidly transition operation between the grid connected mode and the grid independent mode in an interval of less than about 4 milliseconds. 
     
     
       12. A power system (   8   )  for providing uninterrupted electric power to a critical load  (   14   ) , comprising:      a. a first power source  (   10   )  providing sufficient power to supply the critical load  (   14   );      b. a second power source  (   18   ) , the second power source providing sufficient power to supply the critical load  (   14   )  and adapted to be normally substantially continuously connected and providing power to, the critical load  (   14   );      c. a static switch  (   19   )  for selectively connecting and disconnecting the first power source  (   10   )  to the second power source  (   18   )  and to the critical load  (   14   ) ; and        d. a switch controller  (   49 ,  45   )  for controlling the state of the static switch  (   19   )  to connect the first power source  (   10   )  with the critical load  (   14   )  and the second power source  (   18   )  during normal operation of the first power source  (   10   )  and to rapidly disconnect the first power source  (   10   )  from the critical load  (   14   )  and the second power source  (   18   )  if and when operation of the first power source  (   10   )  deviates beyond a limit from normal.     
     
     
       13. The power system (   8   )  of    claim 12    wherein the switch controller  (   49 ,  45   )  additionally controls the state of the static switch  (   19   )  to rapidly reconnect the first power source  (   10   )  with the critical load  (   14   )  and the second power source  (   18   )  when the first power source  (   10   )  returns to normal operation.   
     
     
       14. The power system (   8   )  of    claim 12    wherein the static switch  (   19   )  is a solid - state device.   
     
     
       15. The power system (   8   )  of    claim 14    wherein the solid - state device is a thyristor  (   19   ). 
     
     
       16. The power system (   8   )  of    claim 12    wherein the first power source  (   10   )  is a utility power grid and wherein the second power source  (   18   )  includes at least one power conditioning system  ( PCS )  for configuring operation of the second power source  (   18   )  in a grid connected mode or in a grid independent mode in response to mode control signals  ( D 1 / 401 ′, D 2 / 402 ′ ) , and including a site management controller  (   31   )  connected intermediate the switch controller  (   49 ,  45   )  and the power conditioning system  ( PCS )  and 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 second power source power conditioning system  ( PCS ) , whereby the second power source  (   18   )  rapidly transitions operation between the grid connected and the grid independent modes.   
     
     
       17. The power system of  claim 16  wherein the rapid disconnection of the first power source (   10   )  from the critical load  (   14   )  and the second power source  (   18   ) , and the rapid transitioning of operation of the second power source  (   18   )  between the grid connected mode and the grid independent mode occurs within an interval of about  4  milliseconds.   
     
     
       18. The power system of  claim 12  wherein the rapid disconnection of the first power source (   10   )  from the critical load  (   14   )  and the second power source  (   18   )  occurs within an interval of less than about  8 . 3  milliseconds.   
     
     
       19. The power source of  claim 18  wherein the rapid disconnection of the first power source (   10   )  from the critical load  (   14   )  and the second power source  (   18   )  occurs within an interval of about  4  milliseconds.