Fuel cell internal state detection system and state detection method

Patent metadata

Field	Value
Publication number	US-10193174-B2
Application number	US-201515554497-A
Country	US
Kind code	B2
Filing date	Mar 3, 2015
Priority date	Mar 3, 2015
Publication date	Jan 29, 2019
Grant date	Jan 29, 2019

Abstract

A fuel cell internal state detection system includes estimation object state quantity setting unit for setting a suitable estimation object state quantity as an index of an internal state, an impedance value acquisition unit configured to obtain an impedance value of a fuel cell, an impedance usability judging unit configured to judge whether or not the obtained impedance value is usable for the calculation of the estimation object state quantity, estimation object state quantity calculation unit for calculating the estimation object state quantity set by the estimation object state quantity setting unit on the basis of the obtained impedance value when the impedance value is judged to be usable for the calculation of the estimation object state quantity by the impedance usability judging unit, and an unusable-scene process execution unit configured to perform an unusable-scene process when the impedance value is judged not to be usable for the calculation of the estimation object state quantity by the impedance usability judging unit.

First claim

The invention claimed is:

1. A fuel cell internal state detection system for detecting an internal state of a fuel cell on the basis of an impedance value of the fuel cell, comprising a controller programmed to:
set an estimation object state quantity as an index of the internal state;
obtain the impedance value of the fuel cell;
judge whether or not the obtained impedance value is usable for a calculation of the estimation object state quantity;
calculate the estimation object state quantity set by the controller on the basis of the obtained impedance value when the impedance value is judged to be usable for the calculation of the estimation object state quantity by the controller;
perform an unusable-scene process when the impedance value is judged not to be usable for the calculation of the estimation object state quantity by the controller;
obtain impedance values based on three or more frequencies; and
determine whether at least one of three or more obtained impedance values belongs to an arc region or to a non-arc region in an impedance curve on a complex plane and judging whether or not the impedance value is usable according to the determination result.

2. The fuel cell internal state detection system according to claim 1 , wherein:
the controller is further programmed to judge whether at least one of the impedance values obtained at the three or more frequencies belongs to the arc region or to the non-arc region in the impedance curve by comparing the values of intersections of two or more lines obtained from two or more impedance values selected from the impedance values obtained at the three or more frequencies and a real axis with each other.

3. The fuel cell internal state detection system according to claim 1 , wherein:
the controller is further programmed to judge whether at least one of the impedance values obtained at the three or more frequencies belongs to the arc region or to the non-arc region in the impedance curve by comparing two or more electrical double layer capacitance values obtained from two or more impedance values selected from the impedance values obtained at the three or more frequencies with each other.

4. The fuel cell internal state detection system according to claim 1 , wherein:
the controller is further programmed to judge whether at least one of the three or more impedance values belongs to the arc region or to the non-arc region in the impedance curve by comparing two or more reaction resistance values estimated from two or more impedance values selected from the impedance values obtained at the three or more frequencies with each other.

5. The fuel cell internal state detection system according to claim 1 , wherein:
the controller is further programmed to judge whether at least one of the three or more impedance values belongs to the arc region or to the non-arc region in the impedance curve by comparing the value of an intersection of a line obtained from two or more impedance values selected from the impedance values obtained at the three or more frequencies and a real axis with a high frequency impedance value obtained at a frequency in a high frequency band.

6. The fuel cell internal state detection system according to claim 1 , wherein the controller is further programmed to:
re-search a frequency, at which the impedance value should be obtained, and re-obtains an impedance value corresponding to the re-searched frequency; or
improve acquisition sensitivity of the controller and re-obtain the impedance value.

7. The fuel cell internal state detection system according to claim 1 , wherein:
the controller is further programmed to calculate a roughly estimated value as the estimation object state quantity.

8. The fuel cell internal state detection system according to claim 1 , wherein:
the controller is further programmed to give up the detection of the internal state.

9. The fuel cell internal state detection system according to claim 1 , wherein the controller is further programmed to:
set at least either one of a reaction resistance value of an anode electrode and an electrical double layer capacitance value as the estimation object state quantity when the internal state to be detected is a hydrogen amount;
set at least either one of an electrolyte membrane resistance value and an ionomer resistance value as the estimation object state quantity when the internal state to be detected is a degree of wetness; or
set a reaction resistance value of a cathode electrode as the estimation object state quantity when the internal state to be detected is an oxygen amount.

10. The fuel cell internal state detection system according to claim 1 , wherein:
the fuel cell is configured as a laminated battery; and
the fuel cell internal state detection system further comprises:
an alternating current power supply unit connected to the laminated battery, the alternating current power supply unit outputting an alternating current to the laminated battery;
an alternating current adjusting unit for adjusting the alternating current on the basis of a positive-electrode side alternating current potential difference and a negative-electrode side alternating current potential difference, the positive-electrode side alternating current potential difference being a potential difference obtained by subtracting a potential of an intermediate part of the laminated battery from a potential on a positive-electrode side of the laminated battery, the negative-electrode side alternating current potential difference being a potential difference obtained by subtracting the potential of the intermediate part from a potential on a negative-electrode side of the fuel cell; and
an impedance computation unit for computing the impedance value of the fuel cell on the basis of the adjusted alternating current and the positive-electrode side alternating current potential difference and the negative-electrode side alternating current potential difference.

11. A fuel cell internal state detection method for detecting an internal state of a fuel cell on the basis of an impedance value of the fuel cell, comprising:
an estimation object state quantity setting step of setting a suitable estimation object state quantity as an index of the internal state;
an impedance value acquisition step of obtaining the impedance value of the fuel cell;
an impedance usability judging step of judging whether or not the obtained impedance value is usable for the calculation of the estimation object state quantity;
an estimation object state quantity calculation step of calculating the estimation object state quantity set in the estimation object state quantity setting step on the basis of the obtained impedance value when the impedance value is judged to be usable for the calculation of the estimation object state quantity in the impedance usability judging step; and
an unusable-scene process execution step of performing an unusable-scene process when the impedance value is judged not to be usable for the calculation of the estimation object state quantity in the impedance usability judging step,
impedance values based on three or more frequencies being obtained in the impedance value acquisition step,
whether at least one of three or more obtained impedance values belongs to an arc region or to a non-are region in an impedance curve on a complex plane being determined and whether or not the impedance value is usable being judged according to the determination result in the impedance usability judging step.

Assignees

• Nissan Motor

Inventors

• Kotaka Toshikazu
• Aoki Tetsuya

Classifications

• H01M2250/20

  Fuel cells in motive systems, e.g. vehicle, ship, plane · CPC title

• H01M8/0485

  of the electrolyte · CPC title

• H01M8/04582

  of the individual fuel cell · CPC title

• H01M8/04552

  of the individual fuel cell · CPC title

• H01M8/04641 Primary

  of the individual fuel cell · CPC title