Vehicle power system with fuel cell auxiliary power unit (APU)

• US 8,602,141 B2
• Filed: 04/05/2011
• Issued: 12/10/2013
• Est. Priority Date: 04/05/2010
• Status: Active Grant

• Current Assignee: cellcentric GmbH & Co. KG
• Original Assignee: Daimler Trucks North America LLC (Mercedes-Benz Group AG)
• Inventors: Yee, Justin, Woolley, Mark S., Paun, Cristin, Duraiswamy, Shivkumar, Ziegler, Maik, Rotz, Derek James, Rogers, Matthew C. C.
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): GOLDMAN, RICHARD A
• Application Number:
  US13/080,210
• Publication Number:
  US 20110246013A1
• Time in Patent Office: 980 Days
• Field of Search: None
• US Class Current: 180/65.21
• CPC Class Codes: B60L 1/00 Supplying electric power to auxiliary equipment of vehicles circuit arrangements for charging batteries H02J7/00
• CPC Class Codes: B60L 2240/36 Temperature of vehicle components or parts
• CPC Class Codes: B60L 50/72 Constructional details of fuel cells specially adapted for electric vehicles
• CPC Class Codes: B60L 58/14 Preventing excessive discharging
• CPC Class Codes: B60L 58/30 for monitoring or controlling fuel cells
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 10/28 including control of fuel cells
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/10 Controlling the power contribution of each of the prime movers to meet required power demand
• CPC Class Codes: B60W 2510/244 Charge state
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

A power distribution system comprises at least one fuel cell that is selectively operated in response to conditions to provide power to electrical loads and/or to charge an electrical storage device such as a vehicle battery. One form of an alternator can be selectively engaged or disengaged to provide power to the electrical loads and/or to charge the electrical storage device. Either or both of the fuel cell and alternator can be operated to provide electrical power.

Claims

1. A vehicle power system comprising:

a plurality of electrical loads that consume electrical energy from the vehicle power system;

an energy storage device for storing electrical energy from the vehicle power system and providing stored electrical energy to the vehicle power system, the energy storage device having a state of charge;

an internal combustion engine;

an alternator, the alternator comprising a first power mode wherein the alternator is driven by the engine to convert mechanical energy from the engine into electrical energy that is provided to the vehicle power system, the alternator comprising a second non-power mode in which the alternator is not providing electrical energy to the vehicle power system;

a fuel cell having a plurality of fuel cell modes comprising a Power Mode wherein the fuel cell converts fuel into electrical energy that is at least selectively provided to the vehicle power system, and at least a second mode wherein the fuel cell does not provide electrical energy to the vehicle power system; and

a vehicle power system controller coupled to the alternator and to the fuel cell and operable to control the production and distribution of electrical energy in the vehicle power system, the controller being configured to, based upon the electrical energy consumption of the electrical loads and the state of charge of the energy storage device, shift the alternator between the first power mode and the second non-power mode and to shift the fuel cell between plural fuel cell modes.

2. The vehicle power system of claim 1 wherein the alternator is a field clutched alternator, wherein the alternator can be switched to the second non-power mode state by opening an external sense circuit and the alternator can be switched to the first power mode state by closing the external sense circuit.

3. The vehicle power system of claim 1 wherein the fuel cell is a solid oxide fuel cell.

4. The vehicle power system of claim 1, wherein the plurality of modes of the fuel cell comprise an Off Mode, a Startup Mode, a Power Mode, and a Shutdown Mode, and wherein the vehicle power system controller controls the shifting of the fuel cell at least from the Off Mode to the Startup Mode and from the Power Mode to the Shutdown Mode.

5. The vehicle power system of claim 1, wherein the engine is a diesel fueled engine and the fuel cell comprises a fuel reformer operable to convert diesel fuel into a hydrogen fuel for the fuel cell.

6. The vehicle power system of claim 1 wherein the system controller is responsive to a plurality of conditions including the state of an on/off signal to control the shifting of the fuel cell between the plurality of modes.

7. The vehicle power system of claim 1 wherein the vehicle power system controller selectively controls the production of energy from the fuel cell and from the alternator to be solely from the fuel cell under conditions wherein the state of charge of the energy storage device is at or above a threshold, wherein the fuel cell is in the Power Mode and has the capacity to supply the electrical energy requirements of all of the electrical loads, and wherein it is more efficient to provide electrical energy from the fuel cell than to provide electrical energy from the alternator.

8. The vehicle power system of claim 7 wherein the vehicle power system controller selectively controls the production of energy to be from both the fuel cell and the alternator under conditions wherein the state of charge of the energy storage device is at or above the threshold, the fuel cell is in the Power Mode, but the fuel cell lacks the capacity to meet the electrical energy requirements of all of the loads.

9. The vehicle power system of claim 1 wherein the vehicle system controller selectively controls the production of electrical energy to be solely from the alternator under conditions wherein the state of charge of the energy storage device is less than a threshold.

10. The vehicle power system of claim 1 wherein if the alternator is in the second non-power mode and the engine is running, the system controller shifts the alternator to the first power mode if at least one condition is met.

11. The vehicle power system of claim 10 wherein the at least one condition that is met comprises any one or more of the following conditions:

(a) the fuel cell is in a Startup Mode wherein the fuel cell is not producing electrical energy for distribution to the electrical loads; and

(b) the fuel cell is in the Power Mode and the state of charge of the electrical energy storage device is less than a threshold.

12. The vehicle power system of claim 11 wherein the at least one condition that is met further comprises (c) the fuel cell is in the Power Mode and one or more of the following conditions:

(i) the road grade is downhill and steeper than a downhill threshold, (ii) the vehicle has a service brake and the service brake is engaged, and (iii) the vehicle has an engine brake that is active to apply a braking force to the engine.

13. The vehicle power system of claim 1 wherein if the alternator is in the first power mode and the engine is running, the system controller shifts the alternator to the second non-power mode if at least one condition is met.

14. The vehicle power system of claim 13 wherein the at least one condition that is met comprises:

the fuel cell is in the power mode and the battery state of charge is greater than or equal to a threshold.

15. The vehicle power system of claim 14 wherein the at least one condition that is met further comprises that the alternator has been in the power mode for at least a minimum time period.

16. The vehicle power system of claim 1 wherein if the alternator is in the first power mode and the engine is running, the system controller shifts the alternator to the second non-power mode if the state of charge of the energy storage device is greater than a threshold and one or more of the following conditions are met:

the road grade is not a downhill grade that is steeper downhill than a threshold, the vehicle has a throttle and the throttle position is greater than a throttle position threshold.

17. The vehicle power system of claim 1 wherein if the alternator is in the first power mode and the engine is running, the system controller shifts the alternator to the second non-power mode if the state of charge of the energy storage device is greater than a threshold and one or more of the following conditions are met:

the road grade is not a downhill grade that is steeper downhill than a threshold, the vehicle has a throttle and the throttle position is greater than a throttle position threshold except that the system controller does not shift the alternator from the first power mode to the second non-power mode unless the alternator has been in the first power mode for a time that is at least a minimum time period.

18. The vehicle power system of claim 1 wherein if the alternator is in the second non-power mode and the engine is running, the system controller shifts the alternator to the first power mode if any one or more of the following conditions are met:

(a) the fuel cell is in a Startup Mode wherein the fuel cell is not producing electrical energy for distribution to the electrical loads; and

(b) the fuel cell is in the Power Mode and the state of charge of the electrical energy storage device is less than a threshold; and

(c) the fuel cell is in the Power Mode and one or more of the following conditions are met;

(i) the road grade is downhill and steeper than a downhill threshold;

the vehicle has a service brake and the service brake is engaged; and

(iii) the vehicle has an engine brake that is active to apply a braking force to the engine; and

wherein if the alternator is in the first power mode and the engine is running, the system controller shifts the alternator to the second non-power mode if at least one or more of the following conditions are met;

(a) the fuel cell is in the Power Mode and the battery state of charge is greater than or equal to a threshold and the alternator has been in the first power mode for at least a minimum time period; and

(b) if the state of charge of the energy storage device is greater than a threshold, the alternator has been in the first power mode for at least a minimum time period, and one or more of the following conditions are met;

the road grade is not a downhill grade that is steeper downhill than a threshold, the vehicle has a throttle and the throttle position is greater than a throttle position threshold.

38. A vehicle power system according to claim 1 wherein the system controller is operable to provide a fuel cell mode control signal to initiate shifting of the fuel cell from the Shutdown Mode to the Startup Mode if there is at least enough power in the energy storage device to start the engine from a stopped state, the engine is running, and the system controller receives a fuel cell on command.

19. A vehicle power system comprising:

an internal combustion engine;

a starter coupled to the internal combustion engine and that is operable to crank the engine in response to delivery of a crank engine current to the starter;

a switchable power output alternator that is operable in response to an alternator control signal to shift from a first power mode in which the alternator is driven by the engine to produce output power at an alternator output and a second non-power mode in which the alternator is not driven by the engine to produce output power;

an energy storage device coupled to the alternator output and to vehicle electrical loads;

a fuel cell coupled to the energy storage device and to the vehicle electrical loads;

a system controller coupled to the fuel cell and to the energy storage device, the system controller being operable to selectively provide alternator control signals to the alternator to control the shifting of the alternator from the first power mode to the second non-power mode and from the second non-power mode to the first power mode, the system controller also being operable to selectively provide an engine start signal to cause the engine to start, the system controller selectively controlling the shifting of the alternator to the first power mode and the starting of the engine so as to control the production of alternator output current, the fuel cell being operable to produce electrical power when the fuel cell is in a Power Mode, the system controller being operable to selectively control the delivery of power from the alternator, power from the fuel cell, and power from both the alternator and the fuel cell to the energy storage device and to the electrical loads.

20. A vehicle power system comprising:

an internal combustion engine;

a starter coupled to the internal combustion engine, the starter being operable to crank the engine to start the engine in response to the delivery of engine cranking electrical current to the starter;

an alternator coupled to the engine and operable to produce an alternator current output when driven by the engine;

an energy storage device that is coupled to the alternator output and to vehicle electrical loads;

a fuel cell that is coupled to the energy storage device and to the vehicle electrical loads, the fuel cell having an electrically powered fuel cell cooler that is selectively operable to cool the fuel cell, the fuel cell comprising an Off Mode in which the fuel cell is not producing output power;

a Startup Mode in which the fuel cell is shifted toward an operational state wherein the fuel cell produces output power, a Power Mode in which the fuel cell is at least selectively operable to produce output power; and

a Shutdown Mode in which the fuel cell is shifted toward the Off Mode, the fuel cell being responsive to fuel cell mode control signals to shift to selected fuel cell modes;

a system controller coupled to the fuel cell and to the energy storage device, the system controller being operable to provide the fuel cell mode control signals to the fuel cell to control the shifting in the fuel cell to the selected modes; and

wherein the system controller blocks the shifting of the fuel cell from the Off Mode to the Startup Mode under conditions comprising there is not at least enough power in the energy storage device to start the engine from a stopped state.

21. A vehicle power system according to claim 20 wherein the system controller blocks the shifting of the fuel cell from the Off Mode to the Startup Mode under conditions further comprising the engine is not running.

22. A vehicle power system according to claim 20 wherein the system controller is responsive to an on/off command with the system controller providing a fuel cell mode control signal that blocks the shifting of the fuel cell from the Off Mode to the Startup Mode in response to a fuel cell off command.

23. A vehicle power system according to claim 20 wherein the energy storage device comprises at least one battery and wherein the system controller provides a fuel cell mode control signal that blocks the shifting of the fuel cell from the Off Mode to the Startup Mode if the state of charge of the battery is less than a first threshold.

24. A vehicle power system according to claim 23 wherein the system controller provides a fuel cell mode control signal that causes the fuel cell to commence shifting from the Startup Mode to the Shutdown Mode if the state of charge of the battery reaches a second threshold that is less than the first threshold.

25. A vehicle power system according to claim 24 wherein the system controller provides a fuel cell mode control signal to maintain the fuel cell in the Startup Mode if the state of charge of the battery reaches a third threshold that is less than the first threshold and greater than the second threshold, the internal combustion engine is running and the alternator is delivering power to the energy storage device, and wherein the electrical loads comprise hotel loads at a first level with the system controller causing the disconnect of at least selected hotel loads to reduce the magnitude of the electrical loads from the first level.

26. A vehicle power system according to claim 25 wherein the system controller provides a fuel cell mode control signal to maintain the fuel cell in the Startup Mode if the state of charge of the battery reaches a fourth threshold that is less than the first threshold and greater than the second threshold, and the engine is not running, the system controller providing an engine start signal causing power to be delivered to the starter from the energy storage device to start the engine and cause the delivery of power from the alternator to the energy storage device with the fuel cell remaining in the Startup Mode.

27. A vehicle power system according to claim 26 wherein the third and fourth thresholds are the same.

28. A vehicle power system according to claim 27 wherein the system controller provides a fuel cell mode control signal to maintain the fuel cell in the Startup Mode if the battery state of charge reaches the fourth threshold, the engine is running, wherein the alternator comprises a switchable power output alternator that is operable in response to an alternator control signal to shift from a first power mode in which the alternator is driven by the engine to produce output power at an alternator output and a second non-power mode in which the alternator is not driven by the engine to produce output power, and wherein the system controller provides an alternator control signal to the alternator and causes the alternator to shift to the first power mode to provide alternator power, and with the fuel cell remaining in the Startup Mode.

29. A vehicle power system according to claim 28 wherein the system controller is responsive to an on/off command with the off command indicating the fuel cell should be turned off, wherein the system controller provides a fuel cell mode control signal to maintain the fuel cell in the Power Mode if the state of charge of the battery is at or below a fifth threshold even though the system controller has received a fuel cell off command.

30. A vehicle power system according to claim 29 wherein the fifth threshold is greater than the first threshold.

31. A vehicle power system according to claim 29 wherein the system controller provides a fuel cell mode control signal to maintain the fuel cell in the Power Mode if the state of charge of the battery is at or below a sixth threshold and the system controller disconnects at least selected electrical loads from receiving electrical power.

32. A vehicle power system according to claim 31 wherein the system controller provides an engine start signal to cause power to be delivered to the starter from the energy storage device to start the engine, the system controller also causing the delivery of power from the alternator to the energy storage device with the fuel cell remaining in the Power Mode.

33. A vehicle power system according to claim 31 wherein the sixth threshold is equal to the third threshold.

34. A vehicle power system according to claim 32 wherein the system controller causes the reconnecting of the disconnected electrical loads in the event the state of charge of the battery reaches or exceeds a seventh threshold.

35. A vehicle power system according to claim 32 wherein the seventh threshold is equal to the fifth threshold.

36. A vehicle power system according to claim 20 wherein the system controller provides a fuel cell mode control signal to initiate shifting of the fuel cell from the Power Mode to the Shutdown Mode if the state of charge of the battery reaches an eighth threshold level that is greater than the fifth threshold level.

37. A vehicle power system according to claim 36 wherein the eighth threshold level corresponds to a fully charged state of charge of the battery.

39. A vehicle power system according to claim 20 wherein the system controller is responsive to a fuel cell off command indicating that the fuel cell should be shut down, wherein the system controller provides a fuel cell mode control signal to initiate shifting of the fuel cell from the Power Mode to the Shutdown Mode in response to the fuel cell off command and if the battery state of charge is at or exceeds a threshold level that is greater than the fifth threshold level.

40. A vehicle power system according to claim 39 wherein the system controller is responsive to a low fuel signal to provide a fuel cell mode control signal to initiate shifting of the fuel cell from the Power Mode to the Shutdown Mode.

41. A vehicle power system according to claim 20 wherein the system controller is responsive to a low fuel signal to provide a fuel cell mode control signal to initiate shifting of the fuel cell from the Power Mode to the Shutdown Mode.

42. A vehicle power system according to claim 20 wherein the alternator comprises an alternator that is continuously driven by the engine to produce an alternator current output whenever the engine is running.

43. A vehicle power system according to claim 20 wherein the alternator comprises a switchable power output alternator that is operable in response to an alternator control signal to shift from a first power mode in which the alternator is driven by the engine to produce output power at an alternator output and a second non-power mode in which the alternator is not drivenly connected to the engine to produce output power, wherein the system controller is operable to selectively provide alternator control signals to the alternator to shift the alternator to the first power mode to control the alternator to produce an alternator output power and to shift the alternator to the non-power mode.

44. A vehicle power system according to claim 43 wherein the alternator comprises a clutched alternator.

45. A vehicle power system according to claim 44 wherein the alternator comprises a field clutched alternator.

46. A vehicle power system comprising:

an internal combustion engine;

a starter coupled to the internal combustion engine, the starter being operable to crank the engine to start the engine in response to the delivery of an engine cranking electrical current to the starter;

an alternator coupled to the engine and operable to produce power at an alternator output;

an energy storage device that is coupled to the alternator output and to vehicle electrical loads;

a fuel cell that is coupled to the energy storage device and to the vehicle electrical loads, the fuel cell having an electrically powered fuel cell cooler that is selectively operable to cool the fuel cell, the fuel cell comprising fuel cell modes comprising an Off Mode in which the fuel cell is not producing output power;

a Startup Mode in which the fuel cell is shifted toward an operational state wherein the fuel cell produces output power, a Power Mode in which the fuel cell is at least selectively operable to produce output power; and

a Shutdown Mode in which the fuel cell is shifted toward the Off Mode;

the fuel cell being responsive to fuel cell mode control signals to initiate or block shifting between fuel cell modes;

a system controller coupled to the fuel cell and to the energy storage device, the system controller being operable to provide the fuel cell mode control signals to the fuel cell to control the initiating of shifting and blocking of shifting of the fuel cell to at least selected modes of the fuel cell modes; and

wherein the system controller provides a fuel cell mode control signal to cause blocking of the shifting of the fuel cell from the Off Mode to the Startup Mode if the engine is not running.

47. A vehicle power system according to claim 46 wherein the system controller provides fuel cell mode control signals to cause blocking of the shifting of the fuel cell from Off Mode to the Startup Mode if any one or more of the following conditions exist:

the engine is not running, the charge of the energy storage device is not at least at a first threshold that is sufficient to start the engine from a stopped state, and a fuel cell “

on”

command is not received by the system controller.

48. A method of controlling a vehicle power system, the vehicle power system comprising a plurality of electrical loads, a battery having a state of charge (SOC), an internal combustion engine with an alternator, a fuel cell having at least an Off Mode, a Startup Mode, a Power Mode and a Shutdown Mode, and an input for receiving commands to switch the fuel cell to the Power Mode or the Off Mode, the method comprising:

when the fuel cell is in the Off Mode;

if a received command is to switch the fuel cell on Power Mode and the SOC is less than or equal to a first threshold value or the engine is not running, then leaving the fuel cell in the Off Mode;

if a received command is to switch the fuel cell on Power Mode, the engine is running, and the SOC is greater than the first threshold value , then switching the fuel cell to the Startup Mode;

when the fuel cell is in the Startup Mode;

if the SOC is less than or equal to a second threshold value, then switching the fuel cell to the Shutdown Mode;

if the SOC is less than or equal to a third threshold greater than the second threshold value and the engine is not running, then starting the engine;

if the SOC is less than or equal to the third threshold value and the engine is running and the electrical energy consumption of the electrical loads is greater than a first level, then reducing the electrical energy consumption of the electrical loads below the first level;

if the temperature of the fuel cell reaches a fuel cell operating temperature, then switching the fuel cell to the Power Mode;

when the fuel cell is in the Power Mode;

if the SOC is less than or equal to the third threshold value, then reducing the electrical energy consumption of the electrical loads until the SOC reaches a fourth threshold value that is greater than the first threshold value;

if a received command is to switch the fuel cell off and the SOC is less than or equal to a fifth threshold value, then leaving the fuel cell in the Power Mode;

if a received command is to switch the fuel cell Power Mode off and the SOC is greater than the fifth threshold value, then switching the fuel cell to the Shutdown Mode;

if the fuel level is less than a low fuel threshold level, then switching the fuel cell to the Shutdown Mode;

when the fuel cell is in the Shutdown Mode;

if the temperature of the fuel cell reaches a second temperature at which a fuel cell cooling mechanism can be turned off without damaging the fuel cell, then switching the fuel cell to the Off Mode; and

if the received command is to switch the fuel cell on, the SOC is greater than the first threshold, the engine is running and the fuel is not less than a low fuel level, switching the fuel cell to the Startup Mode.

49. The method of claim 48 wherein the second threshold value is based on the minimum SOC needed to start the engine and to cool the fuel cell to a level that avoids damage to the fuel cell.