Fuel cell system and related control method

• US 7,371,476 B2
• Filed: 09/26/2003
• Issued: 05/13/2008
• Est. Priority Date: 10/22/2002
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Aso, Takeshi
• Primary Examiner(s): Kalafut; Stephen
• Assistant Examiner(s): ANTHONY, JULIAN
• Application Number:
  US10/670,508
• Publication Number:
  US 20040076860A1
• Time in Patent Office: 1,691 Days
• Field of Search: 429/12, 429/23
• US Class Current: 429/429
• CPC Class Codes: B60L 2210/10 DC to DC converters
• CPC Class Codes: B60L 58/31 for starting of fuel cells
• CPC Class Codes: B60L 58/33 by cooling
• CPC Class Codes: B60L 58/34 by heating
• CPC Class Codes: H01M 2008/1095 Fuel cells with polymeric electrolytes
• CPC Class Codes: H01M 2250/20 Fuel cells in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: H01M 8/04007 related to heat exchange
• CPC Class Codes: H01M 8/04268 Heating of fuel cells during the start-up of the fuel cells
• CPC Class Codes: H01M 8/04298 Processes for controlling fuel cells or fuel cell systems
• CPC Class Codes: H01M 8/04328 of anode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04358 of the coolant
• CPC Class Codes: H01M 8/04388 of anode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04395 of cathode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04589 of fuel cell stacks
• CPC Class Codes: H01M 8/0494 of fuel cell stacks
• CPC Class Codes: H01M 8/04955 Shut-off or shut-down of fuel cells
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

A fuel cell system and a related control method are disclosed wherein, during start-up of a fuel cell stack 1, a controller 21 operates a DC/DC converter 13 in a voltage control mode to allow an electric power to be supplied from a secondary battery 7 to a load 6 at an output voltage managed by the DC/DC converter. Under such a condition, an electric power level appearing when a voltage level of the electric power to be supplied from the secondary battery to the load lies at a value greater than an open voltage level of the fuel cell stack 1. Next, the DC/DC converter 13 is operative in an electric power control mode to allow the electric power to be supplied from the secondary battery to the load at a managed electric power output. Then, a level of the electric power to be supplied to the load is detected with the DC/DC converter 13, which permits the electric power to be supplied from the secondary battery to the load at an electric power level less than a resulting detected electric power level.

Claims

1. A fuel cell system comprising:

a fuel cell stack supplied with fuel gas and oxidant gas to generate an electric power which is supplied through a diode to a load installed on a fuel cell powered vehicle;

a secondary battery by which an electric power is charged and discharged;

an electric power converter connected to the fuel cell stack through the diode to convert an electric power, charged in the secondary battery, and supply a converted electric power to the load; and

a controller that controls the electric power converter under two control modes during a start-up of the fuel cell stack, the two control modes including;

a first control mode to set a target voltage level of an electric power to be supplied to the load from the secondary battery equal to or greater than an open voltage level of the fuel cell stack; and

a second control mode to set a target electric power level of an electric power to be supplied to the load from the secondary battery equal to an electric power level of an electric power being supplied to the load from the secondary battery, to perform a reduction of the target electric power level at a given rate, and to interrupt the reduction of the target electric power level when one of the following conditions is satisfied;

(1) an output electric current level of the fuel cell stack increases beyond a first threshold; and

(2) an output voltage level of the fuel cell stack drops below a second threshold, the first and second thresholds being predetermined based on a voltage-current characteristic during the start-up of the fuel cell stack to a completion of the start-up.

2. The fuel cell system according to claim 1, wherein when a temperature of the fuel cell stack is less than a given value under the first control mode, the controller is adapted to control the electric power converter under the second control mode.

3. The fuel cell system according to claim 1, wherein the controller is adapted to measure an output voltage level of the fuel cell stack under the first control mode and control a timing of the reduction under the second control mode depending on rise-up condition of the output voltage level of the fuel cell stack.

4. The fuel cell system according to claim 3, wherein when the rise-up condition of a output voltage level of the fuel cell stack is slower than a predetermined rise-up condition, then the controller is adapted to delay the timing of the reduction under the second control mode, in order to stabilize the fuel cell stack.

5. The fuel cell system according to claim 1, wherein the controller is adapted to keep the fuel cell stack in a stand-by state when one of the conditions (1) and (2) is satisfied.

6. A fuel cell system comprising:

a fuel cell stack supplied with fuel gas and oxidant gas to generate an electric power which is supplied through a diode to a load installed on a fuel cell powered vehicle;

a secondary battery by which an electric power is charged and discharged;

electric power converting means connected to the fuel cell stack through the diode and converting an electric power charged in the secondary battery, supplying to the load; and

control means that controls the electric power converter means under two control modes during start up of the fuel cell stack, the two control modes including;

a first control mode to set a target voltage level of an electric power to be supplied to the load from the secondary battery equal to or greater than an open voltage level of the fuel cell stack; and

a second control mode to set a target electric power level of an electric power to be supplied to the load from the secondary battery equal to an electric power level of an electric power being supplied to the load from the secondary battery, to perform a reduction of an the target electric power level at a given rate. ,and to interrupt the reduction of the target electric power level when one of the following conditions is satisfied;

(1) an output electric current level of the fuel cell stack increases beyond a first threshold and (2) an output voltage level of the fuel cell stack drops below a second threshold ,the first and second thresholds being predetermined based on a voltage-current characteristic during the start-up of the fuel cell stack to a completion of the start-up.

7. A method of controlling a fuel cell system, which has a fuel cell stack supplied with fuel gas and oxidant gas to generate an electric power which is supplied through a diode to a load installed on a fuel cell powered vehicle, and a secondary battery by which an electric power is charged and discharged, the method comprising:

converting an electric power of the secondary battery to supply to the load ;

controlling the fuel cell system such that, when starting up the fuel cell stack, a voltage level of an electric power to be supplied from the secondary battery to the load is set at a value equal to or greater than an open voltage level of the fuel cell stack;

setting a target electric power level of an electric power to be supplied from the secondary battery to the load equal to an electric power level of an electric power being supplied from the secondary battery to the load;

controlling the fuel cell system to perform a reduction of the target electric power level at a given rate; and

interrupting the reduction of the target electric power level when one of the following conditions is satisfied;

(1) an output electric current of the fuel cell stack increases beyond a first threshold; and

(2) an output voltage of the fuel cell stack drops below a second threshold, the first and second thresholds being predetermined based on a voltage-current characteristic during the start-up of the fuel cell stack to a completion of the start-up.