Fuel cells system and method of controlling cells

• US 7,476,457 B2
• Filed: 09/11/2003
• Issued: 01/13/2009
• Est. Priority Date: 06/25/1998
• Status: Expired due to Fees

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Iwase, Masayoshi
• Primary Examiner(s): Ryan; Patrick
• Assistant Examiner(s): Martin; Angela J.
• Application Number:
  US10/659,285
• Publication Number:
  US 20040048119A1
• Time in Patent Office: 1,951 Days
• Field of Search: 429/23, 429/22, 429/13, 429/21, 429/19
• US Class Current: 429/431
• 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 cell system having fuel cells, which receive a supply of a gas and generate electric power to satisfy a load, and a secondary battery, which accumulates electric power therein and outputs the accumulated electric power to satisfy the load, 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 at the specified working point, to determine a second amount of electric power to be supplied to the load, to compare said first and second determined amounts of electric power, 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 comparison of the first and second determined amounts of electric power.

2. A fuel cell system in accordance with claim 1, 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.

3. A fuel cell 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.

4. A fuel cell system in accordance with claim 2, 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.

5. A fuel cell system having fuel cells, which receive a supply of a gas and generate electric power to satisfy a load, and a secondary battery, which accumulates electric power therein and outputs the accumulated electric power to satisfy the load, 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;

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,

means for determining a first amount of electric power to be taken out of said fuel cells at the specified working point,

means for determining a second amount of electric power to be supplied to the load,

means for comparing said first and second determined amounts of electric power; and

means 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 comparison of the first and second determined amounts of electric power.

6. A fuel cell system in accordance with claim 5, 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.

7. A fuel cell system in accordance with claim 5, 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.

8. A fuel cell system in accordance with claim 6, 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.