Power supply control for power generator

• US 7,880,334 B2
• Filed: 08/03/2007
• Issued: 02/01/2011
• Est. Priority Date: 08/04/2006
• Status: Active Grant

• Current Assignee: Ceres Intellectual Property Company Limited
• Original Assignee: Ceres Intellectual Property Company Limited
• Inventors: Evans, Christopher John, Elliott, Charles Richard, Watkins, Stephen James
• Primary Examiner(s): Fureman; Jared J
• Assistant Examiner(s): AMAYA, CARLOS DAVID
• Application Number:
  US11/833,791
• Publication Number:
  US 20080067869A1
• Time in Patent Office: 1,278 Days
• Field of Search: 307/66, 307/11, 307/18
• US Class Current: 307/66
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 5/00 Circuit arrangements for transfer of electric power between ac networks and dc networks H02J3/36 takes precedence
• CPC Class Codes: H02M 7/797 using semiconductor devices only

Abstract

A system (100) for connecting a fuel cell stack to an A.C. grid to provide power thereto is disclosed in which a voltage regulated D.C. bus (110) is provided to be coupled to the fuel cell stack, a bidirectional inverter (120) is coupled to the D.C. bus (110), and is to be coupled between the D.C. bus (110) and the A.C. grid. At least one D.C. auxiliary load (130) of the fuel cell stack is provided coupled to the D.C. bus (110). A D.C. to D.C. converter (140) is provided between the fuel cell stack and the D.C. bus (110).

Claims

1. A system for connecting a fuel cell stack to an A.C. grid to provide power thereto, comprising:

a D.C. to D.C. converter to be coupled to the fuel cell stack;

a voltage regulated D.C. bus coupled to the D.C. to D.C. converter;

a bidirectional inverter coupled to the D.C. bus, and to be coupled between the D.C. bus and the A.C. grid; and

at least one D.C. auxiliary load of the fuel cell stack coupled to the D.C. bus,

wherein the at least one D.C. auxiliary load of the fuel cell stack includes a load that is required for the fuel cell stack to operate,

wherein the D.C. to D.C. converter is unidirectional in order to provide power from the fuel cell stack to the D.C. bus, and

wherein the D.C. bus extends continuously from the D.C. to D.C. converter to the bidirectional inverter without interruption by a D.C. isolator in the D.C. bus.

2. A system according to claim 1, wherein the bidirectional inverter comprises an A.C. to D.C. converter.

3. A system according to claim 1, wherein the bidirectional inverter is arranged to regulate the voltage on the D.C. bus.

4. A system according to claim 1, wherein the bidirectional inverter is arranged to regulate the voltage on the D.C. bus when the system is connected to the A.C. grid.

5. A system according to claim 1, wherein the D.C. to D.C. converter is arranged to regulate the voltage on the D.C. bus.

6. A system according to claim 5, wherein the D.C. to D.C. converter is arranged to regulate the voltage on the D.C. bus when the system is not connected to the A.C. grid.

7. A system according to claim 1, further comprising at least one A.C. auxiliary load connected on the A.C. grid side of the bidirectional inverter.

8. A system according to claim 7, wherein the A.C. auxiliary load is an auxiliary load of the fuel cell stack.

9. A system according to claim 1, wherein the system is arranged to provide D.C. power to the at least one D.C. auxiliary load, via the D.C. bus, at least partially from the A.C. grid when the fuel cell stack is not providing sufficient power for the at least one D.C. auxiliary load.

10. A system according to claim 9, wherein the bidirectional inverter is adapted to provide active power factor correction to the D.C. auxiliary load when the D.C. auxiliary load is powered at least partially from the A.C. grid.

11. A system according to claim 1, wherein the system is arranged to provide power to the at least one D.C. auxiliary load, via the D.C. bus, from the fuel cell stack when the fuel cell stack is providing sufficient power for the at least one D.C. auxiliary load.

12. A system according to claim 1, further comprising at least one electrical energy storage device coupled to the D.C. bus.

13. A system according to claim 12, further comprising a further D.C. to D.C. converter, coupled between the D.C. bus and the electrical energy storage device.

14. A system according to claim 1, wherein a switch is provided that can be opened to isolate the system from the A.C. grid.

15. A system according to claim 14, wherein an A.C. auxiliary load is provided between the switch and the bidirectional inverter.

16. A method for controlling a power generation system including a fuel cell stack supplying an A.C. grid, the method comprising providing power to a voltage regulated D.C. bus, and at least one D.C. auxiliary load of the fuel cell stack connected to the D.C. bus, wherein:

the at least one D.C. auxiliary load of the fuel cell stack includes a load that is required for the fuel cell stack to operate,

in a first mode, voltage regulated D.C. power is provided to the at least one D.C. auxiliary load from the A.C. grid, via the voltage regulated D.C. bus; and

in a second mode, voltage regulated D.C. power is provided to the at least one D.C. auxiliary load from the fuel cell stack, via the voltage regulated D.C. bus,

wherein a unidirectional D.C. to D.C. converter is provided between the fuel cell stack and the D.C. bus in order to provide power from the fuel cell stack to the D.C. bus, and

wherein the D.C. bus is provided so as to extend continuously from the D.C. to D.C. converter to a bidirectional inverter without interruption by a D.C. isolator in the D.C. bus.

17. A method according to claim 16, wherein, in a first sub-mode of the first mode, power is provided to the at least one D.C. auxiliary load from the A.C. grid only.

18. A method according to claim 17, wherein, in a second sub-mode of the first mode, power is provided to the at least one D.C. auxiliary load from both the A.C. grid and fuel cell stack.

19. A method according to claim 18, wherein the second sub-mode of the first mode occurs when the fuel cell stack is producing less power than the at least one D.C. auxiliary load draws.

20. A method according to claim 17, wherein the first sub-mode of the first mode occurs when the fuel cell stack is not producing any power.

21. A method according to claim 16, wherein, in the first mode, the D.C. bus voltage is regulated by an A.C. to D.C. converter between the A.C. grid and the D.C. bus.

22. A method according to claim 16, wherein, in the second mode, the D.C. bus voltage is regulated by an A.C. to D.C. converter between the A.C. grid and the D.C. bus.

23. A method according to claim 16, wherein, in the second mode, power is provided to the A.C. grid from the fuel cell stack.

24. A method according to claim 16, wherein the second mode occurs when the fuel cell stack is producing more power than the at least one D.C. auxiliary load draws.

25. A method according to claim 16, further comprising a third mode in which the power generation system is isolated from the A.C. grid and the D.C. bus voltage is regulated by the D.C. to D.C. converter.

26. A method according to claim 25, wherein, in the third mode, a local A.C. grid is provided by an A.C. to D.C. converter between the local A.C. grid and the D.C. bus.

27. A method according to claim 16, further comprising a fourth mode in which no power is drawn from the fuel cell stack, no auxiliary loads are powered and power is provided to a system controller.

28. A method according to claim 27, wherein, in the fourth mode, power is also provided to at least one system A.C. auxiliary load.

29. A method according to claim 16, wherein the D.C. bus voltage is between 300 and 500 volts D.C.

30. A method according to claim 29, wherein the D.C. bus voltage is around 400 volts D.C.

31. A method according to claim 16, wherein a switch is provided that can be opened to isolate the system from the A.C. grid.

32. A method according to claim 31, wherein an A.C. auxiliary load is connected between the switch and the system.

33. A power generating device, comprising a system for connecting a fuel cell stack to an A.C. grid to provide power thereto, the system comprising:

a D.C. to D.C. converter to be coupled to the fuel cell stack;

a voltage regulated D.C. bus coupled to the D.C. to D.C. converter;

a bidirectional inverter coupled to the D.C. bus, and to be coupled between the D.C. bus and the A.C. grid; and

at least one D.C. auxiliary load of the fuel cell stack coupled to the D.C. bus,

wherein the at least one D.C. auxiliary load of the fuel cell stack includes a load that is required for the fuel cell stack to operate, wherein the D.C. to D.C. converter is unidirectional in order to provide power from the fuel cell stack to the D.C. bus, and

wherein the D.C. bus extends continuously from the D.C. to D.C. converter to the bidirectional inverter without interruption by a D.C. isolator in the D.C. bus.

34. A power generating device according to claim 33, the device being configured to produce useable heat.

35. A power generating device according to claim 33, wherein a switch is provided that can be opened to isolate the system from the A.C. grid.

36. A power generating device according to claim 35, wherein an A.C. auxiliary load is provided between the switch and the bidirectional inverter.