JP2009129760A - Fuel cell system and control method of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to determine accurately deterioration status of a fuel cell. <P>SOLUTION: The control part 30 carries out a purging operation to a fuel cell stack 1 at the shutdown process of the system. Then, the control part 30, corresponding to the purging operation, estimates the residual water amount in a catalyst layer of the fuel battery cells, and based on the estimation result, determines deterioration status of the fuel battery cells ( more concretely, catalyst layer). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a control method thereof.

  Conventionally, a fuel gas (for example, hydrogen) is supplied to the fuel electrode, and an oxidant gas (for example, air) is supplied to the oxidant electrode, and these gases are reacted electrochemically to generate power. There is known a fuel cell system including a fuel cell for performing the above. The fuel cell is mainly composed of a fuel cell structure in which a fuel electrode and an oxidant electrode are provided with a solid polymer electrolyte membrane interposed therebetween, and the power generation performance depends on the water content.

For example, Patent Document 1 discloses a technique for determining the wet state of an electrolyte membrane by measuring the electrical resistance of a fuel cell in time series and calculating a predetermined parameter value related to variations in these measured values. Has been.
JP 2006-252864 A

  By the way, according to the method of Patent Document 1, although it is disclosed that the wet state of the fuel cell is determined, the method for determining the deterioration state of the fuel cell is not disclosed.

  The present invention has been made in view of such circumstances, and an object thereof is to accurately determine the deterioration state of the fuel cell.

  In order to solve this problem, the present invention performs a purge operation on the fuel cell in the system stop process. Then, in response to the purge operation, the amount of residual water in the catalyst layer of the fuel cell is estimated, and the deterioration state of the fuel cell is determined based on the estimation result.

  According to the present invention, when the purge operation is executed, the discharge of the residual water in the catalyst layer is promoted. Nevertheless, the large amount of residual water in the catalyst layer is nonetheless that the catalyst layer deteriorates. Therefore, it can be determined that the water repellency is lowered. Therefore, it is possible to accurately determine the deterioration of the fuel cell (catalyst layer) by estimating the amount of residual water in the catalyst layer corresponding to the purge operation.

(First embodiment)
FIG. 1 is a block diagram showing the overall configuration of the fuel cell system according to the first embodiment of the present invention. The fuel cell system is mounted on, for example, a vehicle that is a moving body, and the vehicle is driven by electric power supplied from the fuel cell system.

  The fuel cell system includes a fuel cell stack 1. The fuel cell stack 1 is configured by stacking a plurality of fuel cells each functioning as a power generation element. Each fuel cell is provided with a catalyst (for example, platinum) layer on both sides of a solid polymer electrolyte membrane, and a fuel cell structure in which a fuel electrode and an oxidant electrode are opposed via this catalyst layer is sandwiched between separators. Configured. In the fuel cell stack 1, in each fuel cell, the fuel gas is supplied to the fuel electrode, and the oxidant gas is supplied to the oxidant electrode, whereby these reaction gases are caused to react electrochemically. Generate generated power. In this embodiment, a case where hydrogen is used as the fuel gas and air is used as the oxidant gas will be described.

  The fuel cell system further includes a hydrogen system for supplying hydrogen to the fuel cell stack 1 and an air system for supplying air to the fuel cell stack 1.

  In the hydrogen system, hydrogen, which is a fuel gas, is stored in a fuel tank 10 (for example, a high-pressure hydrogen cylinder), and is supplied from the fuel tank 10 to the fuel cell stack 1 via the hydrogen supply flow path L1. Specifically, a fuel tank original valve (not shown) is provided downstream of the fuel tank 10, and when the fuel tank original valve is opened, the high-pressure hydrogen gas from the fuel tank 10 flows downstream thereof. The pressure is mechanically reduced to a predetermined pressure by a pressure-reducing valve (not shown) provided in the. The depressurized hydrogen gas is further depressurized by a hydrogen pressure regulating valve 11 provided downstream of the depressurizing valve, and then supplied to the fuel cell stack 1. The hydrogen pressure supplied to the fuel cell stack 1 can be adjusted by controlling the opening of the hydrogen pressure regulating valve 11.

  Exhaust gas from the fuel electrode (gas containing unused hydrogen) is discharged from the fuel cell stack 1 to the hydrogen circulation passage L2. The other end of the hydrogen circulation flow path L2 is connected to the hydrogen supply flow path L1 on the downstream side of the hydrogen pressure regulating valve 11, and a gas such as a hydrogen circulation pump 12 is provided in the hydrogen circulation flow path L2. Circulation means are provided. By driving the hydrogen circulation pump 12, exhaust gas from the fuel electrode is circulated to the fuel cell stack 1.

  By the way, in the case of using air as the oxidant gas, since impurities in the air permeate from the oxidant electrode to the fuel electrode, the impurities in the hydrogen circulation passage L2 including the fuel electrode increase and the hydrogen partial pressure decreases. Tend to. Here, the impurity is a non-fuel gas component other than hydrogen which is a fuel gas, and a typical example is nitrogen. If the amount of nitrogen is excessively increased, the output from the fuel cell stack 1 is disadvantageously reduced. Therefore, it is necessary to manage the amount of nitrogen in the hydrogen circulation passage L2 including the fuel electrode. Therefore, the hydrogen circulation flow path L2 is provided with a purge flow path L3 for discharging the circulation gas to the outside. The purge flow path L3 is provided with a purge valve 13. By adjusting the opening amount of the purge valve 13, the amount of nitrogen discharged to the outside through the purge flow path L3 can be adjusted. Thereby, the nitrogen amount existing in the fuel electrode and the hydrogen circulation passage L2 is managed so that the power generation performance can be maintained. Further, a hydrogen combustor 14 is provided in the purge flow path L3, and hydrogen contained in the gas is combusted by the hydrogen combustor 14.

  In the air system, for example, when the air that is the oxidant gas is taken in by the compressor (oxidant gas supply means) 20, it is pressurized and supplied to the fuel cell stack 1 via the air supply flow path L4. Exhaust gas from the oxidant electrode (air in which oxygen has been consumed) is discharged to the outside through the air discharge flow path L5. In addition, an air pressure adjusting valve 21 that adjusts the pressure of the air supplied to the fuel cell stack 1 is provided in the air discharge flow path L5.

  A power extraction device 2 is connected to the fuel cell stack 1. The power take-out device 2 is controlled by a control unit 30 to be described later, and by taking out current from the fuel cell stack 1, electric power generated in the fuel cell stack 1 is converted into electric motors 3 and compressors 20 that drive the vehicle. Supply to auxiliary equipment.

  The control unit 30 has a function of controlling the entire system in an integrated manner, and controls the operating state of the fuel cell stack 1 by operating according to the control program. As the control unit 30, a microcomputer mainly composed of a CPU, a ROM, a RAM, and an I / O interface can be used. The control unit 30 performs various calculations based on the state of the system, outputs the calculation results to various actuators (not shown) as control signals, and supplies a hydrogen pressure regulating valve 11, a hydrogen circulation pump 12, a purge valve. 13, various elements such as the compressor 20, the air pressure adjustment valve 21, and the power extraction device 2 are controlled.

  Sensor signals from various sensors and the like are input to the control unit 30 in order to detect the state of the system. The impedance sensor 31 is a sensor that detects the impedance of the fuel cell stack 1 by applying an AC voltage. In this embodiment, the impedance sensor 31 detects the impedance of the fuel cell.

  In relation to the present embodiment, the control unit 30 has the following functions. First, the control unit 30 performs a purge operation for the fuel cell stack 1 by controlling the compressor 20 and supplying air to the oxidant electrode of the fuel cell stack 1 in a stop process executed on the premise of system stop. (Processing means). Secondly, the control unit 30 estimates the amount of residual water in the catalyst layer of the fuel cell corresponding to the purge operation (estimating means). Thirdly, the control unit 30 determines the deterioration state of the fuel cell stack 1 based on the estimation result of the residual water amount.

  Here, the purge operation is the generated water (hereinafter referred to as “residual water”) remaining in the flow path of the reaction gas in the fuel cell stack 1 (specifically, including the flow path itself, the catalyst layer, and the electrolyte membrane). Is a process performed for purging. This purge operation suppresses freezing of the fuel cell stack 1 by purging the residual water even when the environment is below freezing after the system is stopped, and thereby smoothly at the next start-up. It is executed from the viewpoint of being able to perform driving.

  FIG. 2 is a flowchart showing a control method of the fuel cell system according to the first embodiment of the present invention. The processing shown in this flowchart is invoked by the input of a trigger signal that instructs the system to stop, and is executed by the control unit 30.

  First, in step 1 (S1), it is determined whether or not to perform a purge operation. This purge operation is a process executed on the premise that the system is stopped. When the stop of the system is instructed, the execution of the purge operation is determined. If an affirmative determination is made in step 1, that is, if a purge operation is performed, the process proceeds to step 2 (S2) and subsequent steps. On the other hand, if a negative determination is made in step 1, that is, if the purge operation is not performed, this routine is terminated.

  In step 2, the purge is started. Specifically, the control unit 30 supplies air only to the oxidant electrode of the fuel cell stack 1 in a state where supply of hydrogen to the fuel electrode of the fuel cell stack 1 is stopped. The control unit 30 supplies air corresponding to the purge flow rate Q that defines the air flow rate in the purge operation as purge starts. Here, in consideration of the configuration of the system including the fuel cell stack 1, the reference value (reference purge flow) Qs of the purge flow rate Q is determined in advance through experiments and simulations so that the fuel cell can be purged appropriately. Initially, the reference purge flow rate Qs is set as the purge flow rate Q.

  In step 3 (S3), impedance detection is started. Specifically, the control unit 30 reads the detection signal from the impedance sensor 31 and specifies the impedance based on the detection signal. In addition, once the control unit 30 starts detecting impedance, it detects this in a predetermined cycle, and thereby the impedance is acquired in time series.

  In step 4 (S4), the time change rate α of impedance is calculated. Here, the time change rate α is a change in impedance per unit time.

  In step 5 (S5), it is determined whether the time change rate α is equal to or greater than the determination change rate αth. The time change rate α of the impedance has a correlation with the residual water amount in the catalyst layer, and there is a tendency that the time change rate decreases as the residual hydrogen amount increases. Therefore, by setting the determination change rate αth to an appropriate value in advance through experiments and simulations, the time change rate as shown in FIG. 3A is obtained from a comparison between the determination change rate αth and the time change rate α. It can be estimated that in a scene where α is large, the amount of residual water in the catalyst layer is small, or in a scene where the time change rate α is small as shown in FIG. If an affirmative determination is made in step 5, that is, if the time change rate α is greater than or equal to the determination change rate αth (α ≧ αth), the process proceeds to step 6 (S6). If a negative determination is made in step 5, that is, if the time change rate α is smaller than the determination change rate αth (α <αth), the process proceeds to step 9 (S9).

  In step 6 (S6), the purge time T is set (changed) to the shortened purge time Ta. The purge time T is a time that defines the duration of the purge process. In consideration of the configuration of the system including the fuel cell stack 1 and the like, the reference value (reference purge time) Ts of the purge time T is determined in advance through experiments and simulations so that the fuel cell can be purged appropriately. Initially, the reference purge time Ts is set as the purge time T. On the other hand, the shortened purge time Ta is a parameter for setting the purge time T to a time shorter than the reference purge time Ts. For example, the shortened purge time Ta is set to a value that shortens the reference purge time Ts by A (0 <A <100)%. It is set (for example, 10% shorter than the reference purge time Ts).

  In step 7 (S7), it is determined whether or not the elapsed time from the start of the purge has reached the purge time T. If an affirmative determination is made in step 7, that is, if the elapsed time reaches the purge time T, the process proceeds to step 8 (8). On the other hand, if a negative determination is made in step 7, that is, if the elapsed time has not reached the purge time T, the processing returns to step 3.

  In step 8, the purge is terminated. Specifically, the control unit 30 ends the air for the oxidant electrode of the fuel cell stack 1.

  In step 9, the purge time T is set (changed) to the increased purge time Tb. The increased purge time Tb is a parameter for setting the purge time T to a time longer than the reference purge time Ts, and is set, for example, as a value that increases the reference purge time Ts by B (0 <B <100)%. (For example, 20% increase).

  In step 10 (S10), it is determined whether the time change rate α is equal to or greater than the determination change rate αth. If an affirmative determination is made in step 9, that is, if the time change rate α is greater than or equal to the determination change rate αth (α ≧ αth), the process proceeds to step 7 (S7). If a negative determination is made in step 9, that is, if the time change rate α is smaller than the determination change rate αth (α <αth), the process proceeds to step 10 (S10).

  In step 10, the purge flow rate Q is set (changed) to the increased purge flow rate Qc. The increased purge flow rate Qc is a parameter for setting the purge flow rate Q to a time longer than the reference purge flow rate Qs, and is set, for example, as a value that increases the reference purge flow rate Qs by C (0 <C <100)%. (For example, 30% increase).

  Thus, in the present embodiment, the control unit 30 performs the purge operation for the fuel cell stack 1 in the system stop process. Then, the control unit 30 estimates the residual water amount in the catalyst layer of the fuel cell corresponding to the purge operation, and determines the deterioration state of the fuel cell (specifically, the catalyst layer) based on the estimation result. judge.

  In each fuel cell, when the catalyst layer is further deteriorated, the water repellency is lowered, and thus the generated water tends to remain. In addition, when purge is performed in the purge operation, discharge of residual water in the catalyst layer is promoted by the supplied air. Nevertheless, a large amount of residual water in the catalyst layer is It can be determined that the water repellency of the layer is reduced. Therefore, it is possible to accurately determine the deterioration of the fuel cell stack 1 by estimating the residual water amount in the catalyst layer corresponding to the purge operation.

  Moreover, the time change rate α of the impedance has a correlation with the amount of residual water in the catalyst layer, and the time change rate tends to decrease as the amount of residual hydrogen increases. Therefore, it is possible to accurately determine the deterioration of the fuel cell stack 1 from the time change rate α of the impedance.

  Further, according to the present embodiment, it is possible to determine the deterioration of the fuel cell stack 1 using the purge operation executed as the system stop process. As a result, both the purge operation contributing to the suppression of freezing and the like and the deterioration determination of the fuel cell stack 1 can be realized simultaneously.

  In the present embodiment, the control unit 30 changes the operation condition of the purge operation based on the result of the deterioration determination. Since the deterioration state of the fuel cell has a correlation with the residual water amount of the catalyst layer, in order to effectively purge this residual water by the purge operation, the operation condition of the purge operation is set according to the deterioration state of the fuel cell. Need to change. According to this embodiment, since the operating conditions are set according to the amount of residual water in the catalyst layer, it can be effectively purged, and the residual water in the catalyst layer can be reduced. Further, when the amount of residual water in the catalyst layer is reduced, the possibility of freezing is reduced even if the system is stopped during a low temperature environment. Thereby, since it becomes easy for a reactive gas to reach a catalyst layer at the time of starting, starting can be implemented smoothly.

  Specifically, the control unit 30 performs the purge operation by extending the time longer than the reference purge time Ts as the fuel cell deteriorates. Further, the control unit 30 performs the purge operation by increasing the flow rate from the reference purge flow rate Qs as the fuel cell deteriorates. According to this method, the residual water amount in the catalyst layer can be effectively purged.

(Second Embodiment)
FIG. 4 is a block diagram showing the overall configuration of the fuel cell system according to the second embodiment of the present invention. The fuel cell system according to the second embodiment is different from that of the first embodiment in that the amount of residual water in the catalyst layer is estimated based on the temperature of the fuel cell stack 1. In addition, the description regarding the structure which overlaps with 1st Embodiment shall be abbreviate | omitted, and a different point is demonstrated below.

  The fuel cell system according to the present embodiment detects a temperature sensor (temperature detection means) 32 instead of the impedance sensor 31 in the first embodiment. The temperature sensor 32 is a sensor that detects the temperature of the fuel cell stack 1. In this embodiment, the temperature sensor 32 detects the temperature of the fuel cell (hereinafter referred to as “cell temperature”). The cell temperature detected by the temperature sensor 32 is read by the control unit 30 as necessary.

  FIG. 5 is a flowchart showing a control method of the fuel cell system according to the second embodiment of the present invention. The processing shown in this flowchart is invoked by the input of a trigger signal that instructs the system to stop, and is executed by the control unit 30.

  First, in step 20 (S20), it is determined whether or not a purge operation is performed. If an affirmative determination is made in step 20, that is, if a purge operation is performed, the process proceeds to step 21 (S21) and subsequent steps. On the other hand, if a negative determination is made in step 20, that is, if the purge operation is not performed, this routine is terminated.

  In step 21, detection of the cell temperature is started. Specifically, the control unit 30 reads a detection signal from the temperature sensor 32 and specifies the cell temperature based on the detection signal. Further, once the detection of the cell temperature is started, the control unit 30 detects this at a predetermined cycle, and thereby the cell temperature is acquired in time series.

  In step 22 (S22), a purge process is performed. Specifically, the control unit 30 supplies air only to the oxidant electrode of the fuel cell stack 1 in a state where supply of hydrogen to the fuel electrode of the fuel cell stack 1 is stopped. This purge process includes a series of processes for starting the supply of air corresponding to the purge flow rate Q and stopping the supply of air on the condition that the elapsed time from the start timing has reached the purge time T. . As in the first embodiment, the purge time T and the purge flow rate Q are set to the reference purge time Ts and the reference purge flow rate Qs.

  In step 23 (S23), after calculating the time change rate β of the cell temperature, it is determined whether or not this time change rate β is equal to or less than the determination change rate βth.

Here, the time change rate β is a change in the cell temperature per unit time. The time change rate β of the cell temperature has a correlation with the residual water amount in the catalyst layer, and the time change rate β tends to increase as the residual hydrogen amount increases. Therefore, in the experiment or simulation, the determination change rate βth is set to an appropriate value in advance through the experiment or simulation, and the comparison between the determination change rate βth and the time change rate β is shown in FIG. It is estimated that the amount of residual water in the catalyst layer is large in a scene where the time change rate β is large as shown, or that the residual water amount in the catalyst layer is small in a scene where the time change rate β is small as shown in FIG. It can be carried out. If the determination in step 23 is affirmative, that is, if the time change rate β is equal to or less than the determination change rate βth (β ≦ βth), this routine ends. On the other hand, if a negative determination is made in step 23, that is, if the time change rate β is greater than the determination change rate βth (β> βth), the process proceeds to step 24 (S24).

  In step 24, a purge process is performed. Specifically, in this process, similarly to the process in step 22, the purge time T is set to the reference purge time Ts, and the purge flow rate Q is set to the reference purge flow rate Qs.

  In step 25 (S25), after calculating the time change rate β of the cell temperature, it is determined whether or not this time change rate β is equal to or less than the determination change rate βth. If the determination in step 35 is affirmative, that is, if the time change rate β is equal to or less than the determination change rate βth (β ≦ βth), this routine ends. On the other hand, if a negative determination is made in step 25, that is, if the time change rate β is larger than the determination change rate βth (β> βth), the process proceeds to step 26 (S26).

  In step 26, the reference purge flow rate Qs is set (changed) to a value increased by C% from the present.

  Thus, in the present embodiment, the control unit 30 performs the purge operation for the fuel cell stack 1 in the system stop process. Then, the control unit 30 estimates the residual water amount in the catalyst layer of the fuel cell corresponding to the purge operation, and determines the deterioration state of the fuel cell (specifically, the catalyst layer) based on the estimation result. judge.

  In each fuel cell, when the catalyst layer is further deteriorated, the water repellency is lowered, and thus the generated water tends to remain. In addition, the scene in which purge is executed in the purge operation is a scene in which discharge of residual water in the catalyst layer is promoted by the supplied air, but in spite of this, the amount of residual water in the catalyst layer is large. It can be determined that the water repellency of the catalyst layer is lowered. Therefore, it is possible to accurately determine the deterioration of the fuel cell stack 1 by estimating the residual water amount in the catalyst layer corresponding to the purge operation.

  Further, the time change rate β of the cell temperature is correlated with the amount of residual water in the catalyst layer, and the time change rate tends to increase as the amount of residual hydrogen increases. Therefore, the deterioration of the fuel cell stack 1 can be accurately determined from the time change rate β of the cell temperature.

  In the present embodiment, the control unit 30 changes the operation condition of the purge operation based on the result of the deterioration determination. Since the deterioration state of the fuel cell has a correlation with the residual water amount of the catalyst layer, in order to effectively purge this residual water by the purge operation, the operation condition of the purge operation is set according to the deterioration state of the fuel cell. Need to change. According to this embodiment, since the operating conditions are set according to the amount of residual water in the catalyst layer, it can be effectively purged, and the residual water in the catalyst layer can be reduced. Further, when the amount of residual water in the catalyst layer is reduced, the possibility of freezing is reduced even if the system is stopped during a low temperature environment. Thereby, since it becomes easy for a reactive gas to reach a catalyst layer at the time of starting, starting can be implemented smoothly.

  Specifically, by repeating the purge process, the control unit 30 performs the purge operation by extending the time longer than the reference purge time Ts as the fuel cell deteriorates. Further, the control unit 30 performs the purge operation by increasing the flow rate from the reference purge flow rate Qs as the fuel cell deteriorates. According to this method, the residual water amount in the catalyst layer can be effectively purged.

  In the present embodiment, the residual water amount in the catalyst layer is estimated based on the time change rate β of the cell temperature, but the present invention is not limited to this. The change in cell temperature over time correlates with the amount of residual water in the catalyst layer, and the larger the amount of residual hydrogen, the longer the time until the temperature changes within a predetermined range of temperature change, the greater the rate of change over time. Yes. Here, the temperature change width is determined in advance as a temperature range in which the temperature change can be regarded as constant. Even with such a configuration, it is possible to accurately determine the deterioration of the fuel cell stack 1 from the change in the cell temperature over time.

1 is a block diagram showing the overall configuration of a fuel cell system according to a first embodiment. The flowchart which shows the control method of the fuel cell system concerning a 1st embodiment. Illustration of impedance time change rate α The block diagram which shows the whole structure of the fuel cell system concerning 2nd Embodiment. The flowchart which shows the control method of the fuel cell system concerning 2nd Embodiment. Explanatory diagram of cell temperature change rate β

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Electric power take-out device 3 Electric motor 10 Fuel tank 11 Hydrogen pressure regulation valve 12 Hydrogen circulation pump 13 Purge valve 14 Hydrogen combustor 20 Compressor 21 Air pressure regulation valve 30 Control part 31 Impedance sensor 32 Temperature sensor

Claims (10)

In the fuel cell system,
A fuel cell structure in which a catalyst layer is provided on both surfaces of an electrolyte membrane, and a fuel electrode and an oxidant electrode are provided via the catalyst layer, a fuel gas supplied to the fuel electrode, and the oxidant electrode A fuel cell that generates electricity by electrochemically reacting with an oxidant gas supplied to the
An oxidant gas supply means for supplying an oxidant gas to the oxidant electrode;
In a stop process executed on the premise of system stop, a processing means for performing a purge operation on the fuel cell by controlling the oxidant gas supply means and supplying an oxidant gas to the fuel cell;
In response to the purge operation, estimating means for estimating the amount of residual water in the catalyst layer of the fuel cell;
A fuel cell system comprising: a determination unit that determines a deterioration state of the fuel cell based on an estimation result of the estimation unit.   2. The fuel cell system according to claim 1, wherein the determination unit determines that the fuel cell is deteriorated as the residual water amount estimated by the estimation unit increases. Further comprising impedance detection means for detecting the impedance of the fuel cell;
The estimation means calculates a temporal change rate of impedance detected by the impedance detection means in time series during the purge operation, and the smaller the calculated change rate, the larger the residual water amount. The fuel cell system according to claim 1, wherein the fuel cell system is estimated. Further comprising temperature detecting means for detecting the temperature of the fuel cell;
The estimation means calculates a temporal change rate of the temperature of the fuel cell detected in time series by the temperature detection means during the purge operation, and the larger the calculated change rate, the more the residual The fuel cell system according to claim 1 or 2, wherein the amount of water is estimated to be large. Further comprising temperature detecting means for detecting the temperature of the fuel cell;
The estimation means has a predetermined temperature change range in which the temperature change over time of the fuel cell detected in time series by the temperature detection means during the purge operation can be regarded as constant. 3. The fuel cell system according to claim 1, wherein the remaining water amount is estimated to increase as the time until it falls within the range.   The fuel cell system according to any one of claims 1 to 5, wherein the processing unit changes an operation condition of the purge operation based on a determination result of the determination unit.   The processing unit performs the purge operation by extending a time from a reference value of a purge time set in advance as a purge operation as the fuel cell is deteriorated. Fuel cell system.   The said processing means increases the flow rate from the reference value of the purge flow rate set in advance as the purge operation as the fuel cell is deteriorated, and performs the purge operation. Fuel cell system. In the fuel cell system,
A fuel cell structure in which a catalyst layer is provided on both surfaces of an electrolyte membrane, and a fuel electrode and an oxidant electrode are provided via the catalyst layer, a fuel gas supplied to the fuel electrode, and the oxidant electrode A fuel cell that generates electricity by electrochemically reacting with an oxidant gas supplied to the
An oxidant gas supply means for supplying an oxidant gas to the oxidant electrode;
In a stop process executed on the premise that the system is stopped, a processing unit that controls the oxidant gas supply unit to supply an oxidant gas to the fuel cell and performs a purge operation on the fuel cell;
Corresponding to the purge operation, and having an estimation means for estimating the amount of residual water in the catalyst layer of the fuel cell,
The fuel cell system, wherein the processing unit sets operating conditions for the purge operation in accordance with an estimation result of the estimation unit. In a control method of a fuel cell system provided with a fuel cell having a fuel cell structure in which a catalyst layer is provided on both surfaces of an electrolyte membrane, and a fuel electrode and an oxidant electrode are provided via the catalyst layer,
Supplying a fuel gas to the fuel electrode, and supplying an oxidant gas to the oxidant electrode, thereby generating electricity by electrochemically reacting the fuel gas and the oxidant gas; and
A second step of executing a stop process on the assumption that the system is stopped,
The second step includes
A third step of performing a purge operation on the fuel cell by supplying an oxidant gas to the fuel cell;
A fourth step of estimating a residual water amount in the catalyst layer of the fuel cell in response to the purge operation;
And a fifth step of determining a deterioration state of the fuel cell based on the estimation result in the fourth step.

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