Fuel cells system and method of controlling cells

• US 20040048119A1
• Filed: 09/11/2003
• Published: 03/11/2004
• Est. Priority Date: 06/25/1998
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Iwase, Masayoshi
• Granted Patent: US 7,476,457 B2
• Time in Patent Office: Days
• US Class Current: 429/22
• CPC Class Codes: B60L 2210/10 DC to DC converters
• CPC Class Codes: B60L 58/30 for monitoring or controlling fuel cells
• CPC Class Codes: B60L 58/40 for controlling a combination of batteries and fuel cells
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H01M 2250/20 Fuel cells in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: H01M 8/04089 of gaseous reactants
• 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 8/04626 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/04656 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/0488 of fuel cell stacks
• CPC Class Codes: H01M 8/0491 of fuel cell stacks
• CPC Class Codes: H01M 8/0494 of fuel cell stacks
• CPC Class Codes: H01M 8/04947 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• 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 system which enables fuel cells to be activated at a working point of high energy conversion efficiency. A control unit calculates a required output of an inverter from an input accelerator travel. The control unit specifies an output electric current-output voltage characteristic corresponding to a gas flow rate, obtains a point of highest energy conversion efficiency on the specified characteristic to specify the point as a working point of fuel cells, and computes an output electric power of the fuel cells at the specified working point. The control unit determines an output voltage required to a battery, based on a difference between the calculated required output of the inverter and the computed output electric power of the fuel cells and a state of charge of the battery. The control unit controls a DC-DC converter and regulates the output voltage of the DC-DC converter, so as to cause the battery to generate the output voltage thus determined. The control unit subsequently controls the inverter, so as to cause a motor to consume electric power corresponding to the required output.

Claims

1. A fuel cells system having fuel cells, which receive a supply of a gas and generate electric power, and supply the generated electric power to a load, said fuel cells system comprising:

a gas flow rate-relating quantity measurement unit configured to measure a gas flow rate-relating quantity, which relates to a flow rate of the gas supplied to said fuel cells; and

a control unit configured to specify a working point associated with an output electric current-output voltage characteristic of said fuel cells corresponding to the measured gas flow rate-relating quantity, and to regulate electric power to be taken out of said fuel cells, so as to cause said fuel cells to be activated at the specified working point.

2. A fuel cells system in accordance with claim 1, wherein said control unit specifies a point of highest energy conversion efficiency on the output electric current-output voltage characteristic as the specified working point.

3. A fuel cells system having fuel cells, which receive a supply of a gas and generate electric power, and a secondary battery, which accumulates electric power therein and outputs the accumulated electric power, said fuel cells system supplying at least one of the electric power generated by the fuel cells and the electric power output from the secondary battery to a load, said fuel cells system comprising:

a gas flow rate-relating quantity measurement unit configured to measure a gas flow rate-relating quantity, which relates to a flow rate of the gas supplied to said fuel cells; and

a control unit configured to specify a working point associated with an output electric current-output voltage characteristic of said fuel cells corresponding to the measured gas flow rate-relating quantity, to determine a first amount of electric power to be taken out of said fuel cells, which is required to activate said fuel cells at the specified working point, to determine a second amount of electric power to be supplied to the load, and to regulate at least one of the electric power to be output from the secondary battery and the electric power to be accumulated in said secondary battery, based on the first and second determined amounts of electric power.

4. A fuel cells system in accordance with claim 3, further comprising:

a state of charge sensor configured to measure a state of charge of said secondary battery,

wherein said control unit regulates at least one of the electric power to be output from said secondary battery and the electric power to be accumulated in said secondary battery, based on the measured state of charge in addition to the first and second determined amounts of electric power.

5. A fuel cells system in accordance with claim 3, wherein said control unit specifies a point of highest energy conversion efficiency on the output electric current-output voltage characteristic as the specified working point.

6. A fuel cells system in accordance with claim 4, wherein said control unit specifies a point of highest energy conversion efficiency on the output electric current-output voltage characteristic as the specified working point.

7. A fuel cells system, comprising:

fuel cells configured to a supply of a gaseous fuel and an oxidizing gas and to generate electric power through an electrochemical reaction of the gaseous fuel and the oxidizing gas;

a flow sensor configured to measure a flow rate of at least one of the gaseous fuel and the oxidizing gas supplied to said fuel cells;

a secondary battery configured to accumulate electric power therein and to output the accumulated electric power;

a state of charge sensor configured to measure a state of charge of said secondary battery;

an inverter configured to receive a supply of electric power from at least one of said fuel cells and said secondary battery to drive a motor;

a converter configured to vary a voltage output from said fuel cells and apply the varied voltage in parallel to said secondary battery and said inverter; and

a control unit configured to specify a working point associated with an output electric current-output voltage characteristic of said fuel cells corresponding to the measured flow rate, to determine a first amount of electric power to be taken out of said fuel cells, which is required to activate said fuel cells at the specified working point, to determine a second amount of electric power to be supplied to said inverter based on external information, and to regulate the voltage output from said converter, based on the first and second determined amounts of electric power and the measured state of charge.

8. A method of controlling fuel cells that receive a supply of a gas and generate electric power, said method comprising the steps of:

(a) measuring a gas flow rate-relating quantity, which relates to a flow rate of the gas supplied to said fuel cells;

(b) specifying a working point associated with an output electric current-output voltage characteristic of said fuel cells corresponding to the measured gas flow rate-relating quantity; and

(c) regulating electric power to be taken out of said fuel cells, so as to cause said fuel cells to be activated at the specified working point.

9. A method in accordance with claim 8, wherein said step (b) comprises the step of specifying a point of highest energy conversion efficiency on the output electric current-output voltage characteristic as the specified working point.

10. In a fuel cells system having fuel cells, which receive a supply of a gas and generate electric power, and a secondary battery, which accumulates electric power therein and outputs the accumulated electric power, and supplies at least one of the electric power generated by the fuel cells and the electric power output from the secondary battery to a load, a method of controlling the secondary battery, said method comprising the steps of:

(a) measuring a gas flow rate-relating quantity, which relates to a flow rate of the gas supplied to the fuel cells;

(b) specifying a working point associated with an output electric current-output voltage characteristic of the fuel cells corresponding to the measured gas flow rate-relating quantity;

(c) determining a first amount of electric power to be taken out of the fuel cells, which is required to activate the fuel cells at the specified working point, and determining a second amount of electric power to be supplied to the load; and

(d) regulating at least one of electric power to be output from the secondary battery and the electric power to be accumulated in the secondary battery, based on the first and second determined amounts of electric power.

11. A method in accordance with claim 10, said method further comprising the step of:

(e) measuring a state of charge of the secondary battery,

wherein said step (d) comprises the step of regulating at least one of the electric power to be output from the secondary battery and the electric power to be accumulated in the secondary battery, based on the observed state of charge in addition to the first and second determined amounts of electric power.

12. A method in accordance with claim 10, wherein said step (b) comprises the step of specifying a point of highest energy conversion efficiency on the output electric current-output voltage characteristic as the specified working point.

13. A method in accordance with claim 11, wherein said step (b) comprises the step of specifying a point of highest energy conversion efficiency on the output electric current-output voltage characteristic as the specified working point.

14. A fuel cells system having fuel cells, which receive a supply of a gas and generate electric power, and supply the generated electric power to a load, said fuel cells system comprising:

means for measuring a gas flow rate-relating quantity which relates to a flow rate of the gas supplied to said fuel cells; and

means for specifying a working point associated with an output electric current-output voltage characteristic of said fuel cells corresponding to the measured gas flow rate-relating quantity, and for regulating electric power to be taken out of said fuel cells for causing said fuel cells to be activated at the specified working point.

15. A fuel cells system in accordance with claim 14, wherein said means for specifying specifies a point of highest energy conversion efficiency on the output electric current-output voltage characteristic as the specified working point.

16. A fuel cells system having fuel cells, which receive a supply of a gas and generate electric power, and a secondary battery, which accumulates electric power therein and outputs the accumulated electric power, said fuel cells system supplying at least one of the electric power generated by the fuel cells and the electric power output from the secondary battery to a load, said fuel cells system comprising:

means for measuring a gas flow rate-relating quantity which relates to a flow rate of the gas supplied to said fuel cells; and

means for specifying a working point associated with an output electric current-output voltage characteristic of said fuel cells corresponding to the measured gas flow rate-relating quantity, for determining a first amount of electric power to be taken out of said fuel cells, which is required to activate said fuel cells at the specified working point, for determining a second amount of electric power to be supplied to the load, and for regulating at least one of the electric power to be output from the secondary battery and the electric power to be accumulated in said secondary battery, based on the first and second determined amounts of electric power.

17. A fuel cells system in accordance with claim 16, further comprising:

means for measuring a state of charge of said secondary battery,

wherein said means for specifying regulates at least one of the electric power to be output from said secondary battery and the electric power to be accumulated in said secondary battery, based on the measured state of charge in addition to the first and second determined amounts of electric power.

18. A fuel cells system in accordance with claim 16, wherein said means for specifying specifies a point of highest energy conversion efficiency on the output electric current-output voltage characteristic as the specified working point.

19. A fuel cells system in accordance with claim 17, wherein said means for specifying specifies a point of highest energy conversion efficiency on the output electric current-output voltage characteristic as the specified working point.

20. A fuel cells system, comprising:

fuel cell means for supplying a gaseous fuel and an oxidizing gas for generating electric power;

means for measuring a flow rate of at least one of the gaseous fuel and the oxidizing gas supplied to said fuel cell means;

battery means for accumulating electric power therein and for outputting the accumulated electric power;

means for measuring a state of charge of said battery means;

means for receiving a supply of electric power from at least one of said fuel cell means and said battery means to drive a motor;

means for varying a voltage output from said fuel cell means and for applying the varied voltage in parallel to said battery means and said means for receiving the supply of electric power; and

means for specifying a working point associated with an output electric current-output voltage characteristic of said fuel cell means corresponding to the measured flow rate, for determining a first amount of electric power to be taken out of said fuel cell means, which is required to activate said fuel cell means at the specified working point, for determining a second amount of electric power to be supplied to said means for receiving the supply of electric power based on external information, and for regulating the voltage output from said means for varying, based on the first and second determined amounts of electric power and the measured state of charge.