Control device

Abstract

This control device (10) comprises: a determination unit (82) that determines, on the basis of a concentration allowable value and a concentration equivalent value of an anode gas in each exhaust gas of a plurality of fuel cells (22), whether the amount of hydrogen corresponding to the concentration of the anode gas contained in a merged exhaust gas flowing through an exhaust flow path (50) is greater than the total amount of hydrogen corresponding to the concentration allowable value in each of the plurality of fuel cells; and a supply control unit (84) that, when the amount of hydrogen corresponding to the concentration of the anode gas is greater than the total amount of hydrogen corresponding to the concentration allowable value, increases the amount of cathode gas supplied to at least one of the plurality of fuel cells.

Description

Control device

[0001] The present disclosure relates to a control device.

[0002] In recent years, research and development on fuel cells that contribute to energy efficiency has been carried out in order to ensure access to more people to affordable, reliable, sustainable and advanced energy. International Publication No. 2013 / 187514 discloses a fuel cell system that limits the cathode gas flow rate supplied by a compressor when the cathode gas flow rate supplied to a fuel cell stack is greater than or equal to a target flow rate.

[0003] The concentration of anode gas contained in the combined exhaust gas discharged from a plurality of fuel cells may increase significantly. In that case, it is necessary to reduce the concentration in order to discharge the combined exhaust gas into the atmosphere.

[0004] The present disclosure aims to solve the above-described problems and thus contributes to energy efficiency.

[0005] Aspects of the present disclosure relate to a control device for controlling a cathode gas supply device in a fuel cell system having a plurality of fuel cells, a cathode gas supply device for supplying cathode gas to the plurality of fuel cells, and an exhaust channel through which combined exhaust gas, discharged from each of the plurality of fuel cells, is combined and discharged into the atmosphere, the control device comprising: a concentration acquisition unit that acquires a concentration equivalent value corresponding to the concentration of anode gas in each of the exhaust gases discharged from each of the plurality of fuel cells, and a concentration tolerance value indicating the permissible upper limit of the concentration of anode gas in each of the exhaust gases, and the concentration acquisition unit that acquires the anode gas in each of the exhaust gases The control device comprises: a determination unit that determines, based on the aforementioned concentration tolerance value and the aforementioned concentration equivalent value, whether the amount of hydrogen corresponding to the concentration of the anode gas contained in the combined exhaust gas flowing through the discharge channel is greater than the total amount of hydrogen corresponding to the concentration tolerance value in each of the plurality of fuel cells; and a supply control unit that, if the amount of hydrogen corresponding to the concentration of the anode gas contained in the combined exhaust gas is greater than the total amount of hydrogen corresponding to the concentration tolerance value in each of the plurality of fuel cells, controls the cathode gas supply device to increase the supply amount of the cathode gas targeting at least one of the plurality of fuel cells.

[0006] According to this disclosure, the concentration of anode gas contained in combined exhaust gas emitted from multiple fuel cells can be reduced.

[0007] Figure 1 is a diagram illustrating a control device and a fuel cell system according to one embodiment. Figure 2 is a block diagram illustrating the configuration of the control device. Figure 3 is a diagram illustrating the equivalent concentration value and allowable concentration value of anode gas contained in combined exhaust gas. Figure 4 is a flowchart illustrating a processing procedure for reducing the concentration of anode gas contained in combined exhaust gas. Figure 5 is a flowchart illustrating a fuel cell to which the cathode gas supply amount is to be increased and a processing procedure for determining the said supply amount. Figure 6 is a flowchart illustrating a processing procedure for returning the cathode gas supply amount to its original level.

[0008] Large vehicles may be equipped with multiple fuel cells. When the combined exhaust gas, obtained by combining the exhaust gases emitted from each of the multiple fuel cells, is discharged into the atmosphere, the concentration of anode gas in the combined exhaust gas can be regulated to be below a predetermined concentration. The predetermined concentration is, for example, 4%, as will be described later. The equivalent concentration of anode gas in each exhaust gas emitted from each of the multiple fuel cells is normally maintained at a concentration well below the predetermined concentration. The equivalent concentration is, for example, 2%, as will be described later. Therefore, the concentration of anode gas in the combined exhaust gas is also normally maintained at a concentration well below the predetermined concentration.

[0009] Suppose a leak failure occurs in a fuel cell system containing multiple fuel cells, where anode gas leaks at one point. Conventionally, when a leak failure occurs, power generation from all multiple fuel cells is stopped. However, even if the concentration of anode gas in the combined exhaust gas increases due to the leak failure, it may be possible to keep the concentration below a predetermined level. In that case, it is preferable to continue power generation from the multiple fuel cells without stopping. Details will be explained using Figures 1 to 5.

[0010] Figure 1 illustrates a control device 10 and a fuel cell system 20 according to one embodiment. The fuel cell system 20 includes a plurality of fuel cells 22. In the example shown in Figure 1, the fuel cell system 20 includes four fuel cells 22A, 22B, 22C, and 22D. The fuel cell system 20 includes an anode gas supply device 24 and a cathode gas supply device 26 that supply anode gas and cathode gas to each of the plurality of fuel cells 22, respectively.

[0011] The anode gas is, for example, hydrogen gas. The anode gas supply device 24 is, for example, a hydrogen tank for storing hydrogen gas. The cathode gas is, for example, air. The cathode gas supply device 26 is, for example, an air pump. The fuel cell system 20 includes an anode gas supply path 28, which is a flow path for the anode gas supplied from the anode gas supply device 24 to each fuel cell 22. The fuel cell system 20 also includes a cathode gas supply path 30, which is a flow path for the cathode gas supplied from the cathode gas supply device 26 to each fuel cell 22.

[0012] Each fuel cell 22 has an electrolyte membrane 22m and an anode electrode 22e and a cathode electrode 22f facing each other across the electrolyte membrane 22m. Anode gas is supplied to the anode electrode 22e of each fuel cell 22. Cathode gas is supplied to the cathode electrode 22f of each fuel cell 22. The fuel cell 22 generates electricity by receiving the supply of anode gas to the anode electrode 22e and the supply of cathode gas to the cathode electrode 22f.

[0013] Specifically, the fuel cell 22 generates electricity through an oxidation-reduction reaction between hydrogen gas supplied to the anode electrode 22e and cathode gas supplied to the cathode electrode 22f. The fuel cell 22 outputs electricity and also produces water and oxygen. The fuel cell system 20 includes an anode gas discharge channel 32, a purge valve 34 provided in the anode gas discharge channel 32, and a cathode gas discharge channel 36.

[0014] Unreacted anode gas in fuel cell 22 is separated from the generated water in a gas-liquid separator (not shown), and most of it is supplied back to the anode electrode 22e. However, some of the anode gas is discharged into the anode gas discharge channel 32 when valve 34 is opened and purging is performed. Unreacted cathode gas, along with the generated oxygen, is discharged into the cathode gas discharge channel 36. The anode gas discharge channel 32 is connected to the cathode gas discharge channel 36. That is, cathode gas, oxygen, and anode gas flow through the cathode gas discharge channel 36 as exhaust gas discharged from each fuel cell 22.

[0015] The fuel cell system 20 includes an exhaust channel 50. The exhaust channel 50 carries combined exhaust gas, which is formed by the convergence of exhaust gases emitted from each of the multiple fuel cells 22 and discharged into the atmosphere. In the example shown in Figure 1, cathode gas exhaust channels 36A, 36B, 36C, and 36D are connected to a single exhaust channel 50. Exhaust gas from fuel cell 22A flows through cathode gas exhaust channel 36A. Exhaust gas from fuel cell 22B flows through cathode gas exhaust channel 36B. Exhaust gas from fuel cell 22C flows through cathode gas exhaust channel 36C. Exhaust gas from fuel cell 22D flows through cathode gas exhaust channel 36D.

[0016] The fuel cell system 20 includes a pressure sensor 38 for measuring the pressure of the anode gas supplied to the fuel cell 22, and a temperature sensor 40 for measuring the temperature of the fuel cell 22. The temperature of the fuel cell 22 measured by the temperature sensor 40 may be the temperature of the refrigerant that cools the inside of the fuel cell 22. The control device 10 controls each cathode gas supply device 26 in the fuel cell system 20.

[0017] The equivalent anode gas concentration in the exhaust gas emitted from each of the multiple fuel cells 22 is measured in advance by experiment and stored in the control device 10. The equivalent anode gas concentration includes the value under normal conditions when no malfunction occurs and the value when a malfunction occurs, as will be described later using Figure 3. In this embodiment, an internal leak malfunction is assumed in which the valve 34 provided in the anode gas discharge passage 32 of each fuel cell 22 remains fully open. In that case, the anode gas leaks into the cathode gas discharge passage 36 and the discharge passage 50.

[0018] However, other types of leak failures may also be considered. Other types of leak failures include, for example, a cross-leak failure in which anode gas leaks from the anode electrode 22e to the cathode electrode 22f of the fuel cell 22, and / or an external leak failure in which anode gas leaks to the outside of the fuel cell system 20. Of the anode gas concentration equivalent values, the values ​​at the time of failure are measured in advance for each type of leak failure and stored in the control device 10. When the control device 10 detects an anode gas leak, it reads out the values ​​at the time of failure as the anode gas concentration equivalent values ​​and uses them.

[0019] An anode gas concentration sensor may be provided in the cathode gas discharge channel 36. In that case, the anode gas concentration equivalent value does not need to be measured in advance and stored in the control device 10. When the control device 10 detects an anode gas leak, it uses the value measured by the concentration sensor as the anode gas concentration equivalent value.

[0020] The detection of anode gas leaks by the control device 10 will now be explained. When an anode gas leak occurs, the pressure of the anode gas supplied to the fuel cell 22 drops. The pressure drop of the anode gas can be detected by the pressure sensor 38. The anode gas pressure drop rate during a leak failure is measured in advance for each type of leak failure described above and stored in the control device 10. The control device 10 can detect anode gas leaks that occur during power generation by the fuel cell 22 by repeatedly acquiring the measured values ​​of the pressure sensor 38 and comparing them with the stored anode gas pressure drop rates.

[0021] In the example shown in Figure 1, suppose an internal leak failure occurs in which, for example, the valve 34 of fuel cell 22A remains fully open. In that case, assume that the anode gas concentration equivalent value in the exhaust gas discharged from fuel cell 22A and flowing through the cathode gas discharge channel 36A is 8%, the value at the time of the failure. Assume that the anode gas concentration equivalent values ​​in the exhaust gas discharged from fuel cells 22B, 22C, and 22D and flowing through the cathode gas discharge channels 36B, 36C, and 36D are all 2%, which is the normal value.

[0022] As will be described later using Figure 3, a concentration tolerance value indicating the permissible upper limit of the anode gas concentration in the exhaust gas discharged from each fuel cell 22 and flowing through each cathode gas discharge channel 36 is determined in advance by experimentation and stored in the control device 10. The concentration tolerance value is determined based on the pressure of the anode gas supplied to each of the multiple fuel cells 22, the temperature of each fuel cell 22, and a predetermined margin related to said pressure and said temperature. This makes it easier to suppress a large increase in the concentration of anode gas in the exhaust gas discharged from each fuel cell 22.

[0023] The pressure of the anode gas supplied to each fuel cell 22 can be measured by a pressure sensor 38 during the experiment. The temperature of each fuel cell 22 can be measured by a temperature sensor 40 during the experiment. The predetermined margin is determined taking into account the measurement errors of the pressure sensor 38 and the temperature sensor 40. The permissible concentration of anode gas in the exhaust gas discharged from each of the fuel cells 22A, 22B, 22C, and 22D and flowing through the cathode gas discharge channels 36A, 36B, 36C, and 36D is assumed to be 4% in all cases.

[0024] As described above, the combined exhaust gas obtained by combining the exhaust gases emitted from each of the multiple fuel cells 22 flows through the discharge channel 50 and is discharged into the atmosphere. Therefore, the concentration of anode gas contained in the combined exhaust gas flowing through the discharge channel 50 can be regulated to be below a predetermined concentration. The predetermined concentration is, for example, 4%. An anode gas concentration sensor may be provided in the discharge channel 50. Even if the concentration of anode gas contained in the combined exhaust gas increases, if the increase in concentration is not large, the concentration may remain below the predetermined concentration.

[0025] In other words, if the amount of hydrogen corresponding to the increment in concentration is less than or equal to the total amount in the multiple fuel cells 22 of the difference between the amount of hydrogen corresponding to each allowable concentration value and the amount of hydrogen corresponding to each equivalent concentration value, then the concentration may remain below the predetermined concentration. Therefore, it is sufficient to maintain the supply amount of cathode gas to each of the multiple fuel cells 22 without increasing it.

[0026] In the example described above, the equivalent concentration of anode gas in the exhaust gas emitted from fuel cell 22A and flowing through the cathode gas discharge channel 36A is 8% due to an internal leak failure in valve 34 of fuel cell 22A. This equivalent concentration is 6% higher than the normal equivalent concentration of 2%. The equivalent concentration of anode gas in the exhaust gas emitted from fuel cells 22A, 22B, 22C, and 22D and flowing through the cathode gas discharge channels 36A, 36B, 36C, and 36D is 2% under normal conditions. These equivalent concentrations are 2% lower than the permissible concentration limit of 4%.

[0027] Assume that fuel cells 22A, 22B, 22C, and 22D are all generating power equally. In this case, the amount of hydrogen corresponding to the increase in the concentration of anode gas contained in the combined exhaust gas is the amount of hydrogen corresponding to the 6% increase in concentration due to the internal leak failure in valve 34 of fuel cell 22A. The total amount of hydrogen across the four fuel cells 22, which is the difference between the amount of hydrogen corresponding to the allowable concentration of 4% and the amount of hydrogen corresponding to the equivalent concentration of 2% in the exhaust gas emitted from each fuel cell 22, is 8% of the total hydrogen amount.

[0028] Therefore, the amount of hydrogen corresponding to a 6% increase in the concentration of anode gas contained in the combined exhaust gas is less than or equal to the 8% total amount of hydrogen in the four fuel cells 22, which is the difference mentioned above. In this case, the supply of cathode gas to each of the four fuel cells 22 does not need to be increased and is maintained by the control device 10. This allows power generation in the fuel cell system 20 to continue, making it highly convenient.

[0029] Furthermore, if the power generation of fuel cell 22A is high, the amount of hydrogen corresponding to the increase in the concentration of anode gas contained in the combined exhaust gas may be greater than the total amount of the difference in the four fuel cells 22 as described above. In that case, the amount of cathode gas supplied to at least one of the four fuel cells 22 may be increased by the control device 10. This can reduce the concentration of anode gas contained in the combined exhaust gas emitted from multiple fuel cells 22. In addition, it is highly convenient because power generation in the fuel cell system 20 can be continued.

[0030] If the power generation of the fuel cell 22A is even greater, the cathode gas supply capacity of the cathode gas supply device 26 may reach its limit. Therefore, it may not be possible to increase the amount of cathode gas supplied to the extent necessary to reduce the concentration of anode gas contained in the combined exhaust gas to below the predetermined concentration mentioned above. In that case, the entire power generation in the fuel cell system 20 will stop.

[0031] Figure 2 is a block diagram illustrating the configuration of the control device 10. The control device 10 includes an arithmetic unit 70 and a storage unit 72. The arithmetic unit 70 is a computer and includes a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). In other words, the arithmetic unit 70 includes processing circuitry.

[0032] The storage unit 72 is a recording medium that can be read by a computer. The storage unit 72 includes volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory) or flash memory. The volatile memory is used as the working memory of the processor. The non-volatile memory stores the computer program executed by the processor, the equivalent concentration value and allowable concentration value of the anode gas, the pressure drop rate of the anode gas in the event of a leak failure, and other necessary data.

[0033] Computer programs (computer software) executed by a processor can also be called computer program products. Computer program products are not limited to computer programs stored on recording media, but also include computer programs transmitted, distributed, or downloaded via the internet, etc.

[0034] The calculation unit 70 includes a concentration acquisition unit 80, a determination unit 82, a supply control unit 84, a leak detection unit 86, and a target determination unit 88. The calculation unit 70 executes a computer program stored in the storage unit 72 to realize the concentration acquisition unit 80, the determination unit 82, the supply control unit 84, the leak detection unit 86, and the target determination unit 88.

[0035] At least a portion of the concentration acquisition unit 80, the determination unit 82, the supply control unit 84, the leak detection unit 86, and the target determination unit 88 may be implemented by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array), or by an electronic circuit including discrete devices.

[0036] The concentration acquisition unit 80 acquires a concentration equivalent value from the storage unit 72 that corresponds to the concentration of anode gas in each exhaust gas discharged from each of the multiple fuel cells 22. The concentration equivalent value acquired by the concentration acquisition unit 80 includes values ​​for normal operation when no malfunction occurs and values ​​for when a malfunction occurs. As values ​​for when a malfunction occurs, there are values ​​corresponding to each type of leak failure. If an anode gas concentration sensor is provided in the cathode gas discharge channel 36, the concentration acquisition unit 80 may acquire the measured value from the concentration sensor as the concentration equivalent value.

[0037] The concentration acquisition unit 80 further acquires a concentration tolerance value from the storage unit 72 that indicates the permissible upper limit of the anode gas concentration in each exhaust gas discharged from each of the multiple fuel cells 22.

[0038] When a leak of anode gas is detected by the leak detection unit 86, which will be described later, the determination unit 82 determines whether the first amount is greater than the second amount based on the concentration equivalent value and the concentration tolerance value obtained by the concentration acquisition unit 80. The first amount is the amount of hydrogen corresponding to the increment in the concentration of anode gas contained in the combined exhaust gas flowing through the discharge channel 50. Hereinafter, the first amount will also be referred to as the amount of hydrogen corresponding to the increment. The second amount is the total amount of the difference between the amount of hydrogen corresponding to the concentration tolerance value and the amount of hydrogen corresponding to the concentration equivalent value in the multiple fuel cells 22. Hereinafter, the second amount will also be referred to as the total amount of the difference.

[0039] The supply control unit 84 controls the cathode gas supply device 26 to supply cathode gas to each fuel cell 22. If the determination unit 82 determines that the amount of hydrogen corresponding to the above-mentioned increment is greater than the total amount of the above-mentioned difference, the supply control unit 84 controls the cathode gas supply device 26 to increase the amount of cathode gas supplied to at least one of the multiple fuel cells 22. The amount of increase in the amount of cathode gas supplied by the supply control unit 84 by controlling the cathode gas supply device 26 is an amount corresponding to the deviation between the amount of hydrogen corresponding to the above-mentioned increment and the total amount of the above-mentioned difference. This makes it possible to appropriately reduce the concentration of anode gas contained in the combined exhaust gas discharged from the multiple fuel cells 22.

[0040] However, because there are limitations to the cathode gas supply performance of the cathode gas supply device 26, it may not be possible to reduce the concentration of anode gas contained in the combined exhaust gas to below the predetermined concentration mentioned above. Before increasing the amount of cathode gas supplied by controlling the cathode gas supply device 26, the supply control unit 84 determines whether or not the concentration of anode gas contained in the combined exhaust gas can be reduced to below the predetermined concentration by increasing the amount of cathode gas supplied.

[0041] If the concentration of anode gas in the combined exhaust gas can be reduced to a predetermined concentration or lower, the supply control unit 84 controls the cathode gas supply device 26 to increase the amount of cathode gas supplied. If the concentration of anode gas in the combined exhaust gas cannot be reduced to a predetermined concentration or lower, power generation is stopped for all of the multiple fuel cells 22, and the supply control unit 84 stops all of the cathode gas supply devices 26.

[0042] If the determination unit 82 determines that the amount of hydrogen corresponding to the increment is less than or equal to the total amount of the difference, the supply control unit 84 controls the cathode gas supply device 26 to maintain the amount of cathode gas supplied to each of the multiple fuel cells 22.

[0043] The leak detection unit 86 detects leaks of the anode gas supplied to each of the plurality of fuel cells 22. As described above, the pressure drop rate of the anode gas during a leak failure is stored in the storage unit 72. The leak detection unit 86 repeatedly acquires the measured value of the pressure sensor 38 and compares it with the stored pressure drop rate of the anode gas, thereby detecting a leak of the anode gas generated during power generation of the fuel cell 22.

[0044] When a leak is detected by the leak detection unit 86, as described above, the determination unit 82 determines whether the amount of hydrogen corresponding to the above-described increment is greater than the total amount of the above-described difference. In the case of an affirmative determination, the supply amount of the cathode gas for at least one of the four fuel cells 22 can be increased by the supply control unit 84. Thereby, the concentration of the anode gas contained in the combined exhaust gas discharged from the plurality of fuel cells 22 can be reduced. Note that the determination unit 82 may make the above-described determination without being involved in the detection of the leak by the leak detection unit 86.

[0045] The target determination unit 88 determines the fuel cell 22 that is the target for the supply control unit 84 to control the cathode gas supply device 26 to increase the supply amount of the cathode gas. The target determination unit 88 determines, among the plurality of fuel cells 22, the fuel cell 22 with the smallest supply amount of the cathode gas by the cathode gas supply device 26 as the fuel cell 22 whose supply amount of the cathode gas is to be increased. Thereby, it becomes easier to equalize the supply loads of the cathode gas by the plurality of cathode gas supply devices 26.

[0046] Note that when the fuel cells 22A, 22B, 22C, and 22D, which are the plurality of fuel cells 22, are all generating power evenly, the supply amounts of the cathode gas by the cathode gas supply devices 26 for each of the plurality of fuel cells 22 are equal. Therefore, it is not possible to determine the fuel cell 22 with the smallest supply amount of the cathode gas by the cathode gas supply device 26.

[0047] In that case, the target determination unit 88 determines all of the plurality of fuel cells 22 as the target fuel cells 22 for which the supply control unit 84 controls the cathode gas supply device 26 to increase the supply amount of the cathode gas. The supply control unit 84 determines to equally increase the supply amount of the cathode gas to each of the plurality of fuel cells 22 based on the increase amount of the supply amount of the cathode gas determined according to the deviation described above.

[0048] That is, the supply control unit 84 controls the cathode gas supply device 26 to equally increase the supply amount of the cathode gas by the cathode gas supply device 26 to each of the plurality of fuel cells 22 determined by the target determination unit 88. Thereby, it becomes easier to equalize the supply load of the cathode gas by the plurality of cathode gas supply devices 26.

[0049] FIG. 3 is a diagram for explaining the concentration equivalent value and the concentration allowable value of the anode gas contained in the combined exhaust gas. When the measured value of the anode gas concentration sensor that can be provided in the cathode gas discharge passage 36 is not used, the concentration equivalent value is determined for each of the plurality of fuel cells 22. The concentration equivalent value includes the value in the normal state where no failure has occurred and the value at the time of failure occurrence. The value at the time of failure occurrence is determined for each type of leak failure.

[0050] Further, the concentration allowable value is also determined for each of the plurality of fuel cells 22. The concentration equivalent value and the concentration allowable value are determined by conducting experiments in advance for each fuel cell 22 and stored in the storage unit 72.

[0051] In the example shown in FIG. 3, the concentration equivalent value corresponding to each of the fuel cells 22A, 22B, 22C, and 22D is 2% in the normal state and 8% when a full - open failure of the valve 34 occurs. Only the full - open failure of the valve 34 is shown as an example of the leak failure. The concentration allowable value corresponding to each of the fuel cells 22A, 22B, 22C, and 22D is 4%. When each of the four fuel cells 22A, 22B, 22C, and 22D is generating power without failure, the concentration equivalent value is the normal value of 2%, and there is a margin with respect to the concentration allowable value of 4%.

[0052] This margin of concentration relative to the permissible concentration limit allows for compensation of the increase in anode gas concentration even if a leak occurs in some fuel cells 22 due to a valve 34 fully opening failure. Even if the increase in anode gas concentration cannot be fully compensated, the anode gas concentration can be reduced by increasing the supply amount of cathode gas to at least one of the four fuel cells 22A, 22B, 22C, and 22D. Therefore, a large increase in concentration can be suppressed.

[0053] Figure 4 is a flowchart illustrating a processing procedure for reducing the concentration of anode gas contained in combined exhaust gas. This processing procedure is performed by the calculation unit 70 executing a computer program stored in the memory unit 72 of the control device 10. When this processing procedure is started, in step S1, the leak detection unit 86 detects a leak in the anode gas supplied to each of the multiple fuel cells 22. If the answer in step S1 is YES, the processing procedure proceeds to step S2. If the answer in step S1 is NO, the processing procedure ends.

[0054] In step S2, the concentration acquisition unit 80 acquires the above-mentioned concentration equivalent value and concentration allowable value corresponding to each of the multiple fuel cells 22. In step S3, the determination unit 82 determines whether the amount of hydrogen corresponding to the increment in the concentration of anode gas contained in the combined exhaust gas is greater than the total amount of the difference between the amount of hydrogen corresponding to the concentration allowable value and the amount of hydrogen corresponding to the concentration equivalent value in the multiple fuel cells 22. If the result in step S3 is YES, the process proceeds to step S4. If the result in step S3 is NO, the process proceeds to step S21.

[0055] If the answer in step S3 is YES, in step S4 the supply control unit 84 determines whether the concentration of anode gas contained in the combined exhaust gas can be reduced to a predetermined concentration or less by increasing the supply amount of cathode gas. If the answer in step S4 is YES, the process proceeds to step S5. If the answer in step S4 is NO, the process proceeds to step S31.

[0056] If the answer in step S4 is YES, in step S5, the target determination unit 88 determines which fuel cell 22 will be targeted for increasing the cathode gas supply amount by controlling the cathode gas supply device 26 with the supply control unit 84. The supply control unit 84 also determines the amount of cathode gas to be increased. Details of the processing procedure performed in step S5 will be described later with reference to Figure 5.

[0057] When the processing procedure performed in step S5 is completed, in step S6, the supply control unit 84 increases the amount of cathode gas supplied to the fuel cell 22 as determined in step S5. When the processing in step S6 is completed, this processing procedure is terminated.

[0058] In step S21, the supply control unit 84 controls the cathode gas supply device 26 to maintain the amount of cathode gas supplied to each of the multiple fuel cells 22. Once the process in step S21 is completed, this processing procedure is terminated.

[0059] In step S31, power generation is stopped for all of the fuel cells 22. Therefore, the supply control unit 84 stops all cathode gas supply devices 26. Once the process in step S31 is completed, this procedure is terminated.

[0060] Figure 5 is a flowchart illustrating the fuel cell 22 to which the cathode gas supply amount is to be increased, and the processing procedure for determining the said supply amount. This processing procedure is performed by the calculation unit 70 executing a computer program stored in the storage unit 72 of the control device 10. As a result of this processing procedure, the process of step S5 shown in Figure 4 is performed.

[0061] When this processing procedure is initiated, in step S51, the supply control unit 84 obtains the amount of cathode gas to be supplied to each of the multiple fuel cells 22. If the cathode gas supply device 26 is an air pump, the supply control unit 84 can obtain the amount of cathode gas to be supplied using the command value or measured value of the rotational speed of the motor that drives the air pump.

[0062] In step S52, the supply control unit 84 determines whether the amount of cathode gas supplied to each of the multiple fuel cells 22 is equal, based on the result of obtaining the amount of cathode gas supplied in step S51. Alternatively, the determination in step S52 may be made based on the measured value of the power generation current of the multiple fuel cells 22 instead of the result of obtaining the amount of cathode gas supplied in step S51. If the result in step S52 is YES, the process proceeds to step S53. If the result in step S52 is NO, the process proceeds to step S61.

[0063] In step S53, the target determination unit 88 determines that all of the multiple fuel cells 22 are the fuel cells 22 for which the supply control unit 84 will increase the amount of cathode gas supplied. In step S54, the supply control unit 84 determines that the amount of cathode gas supplied to each of the multiple fuel cells 22 determined in step S53 will be increased equally. Once the processing in step S54 is completed, this processing procedure ends, and the processing procedure shown in Figure 4 continues from the stage when the processing in step S5 is completed.

[0064] In step S61, the target determination unit 88 determines that the fuel cell 22 with the lowest cathode gas supply among the multiple fuel cells 22 will be the fuel cell 22 for which the supply control unit 84 will increase the cathode gas supply. In step S62, the supply control unit 84 determines the amount of increase in the cathode gas supply to the fuel cell 22 determined in step S61. Once the processing in step S62 is completed, this processing procedure ends, and the processing procedure shown in Figure 4 continues from the point where the processing in step S5 is completed.

[0065] The embodiments described above may be modified as follows. In the following modifications, explanations that overlap with the embodiments described above will be omitted.

[0066] (Modification 1) In the embodiment described above, no processing is considered regarding the supply amount of cathode gas to at least one of the multiple fuel cells 22 after the supply amount of said supply has been increased. In this modification 1, a process to return the supply amount of cathode gas to its original amount may be performed. This modification will be explained with reference to Figure 6. Figure 6 is a flowchart illustrating the processing procedure when returning the supply amount of cathode gas to its original amount.

[0067] This processing procedure is performed by the calculation unit 70 executing a computer program stored in the memory unit 72 of the control device 10. This processing procedure may be performed, for example, after the supply control unit 84 has increased the supply amount of cathode gas to at least one of the multiple fuel cells 22 through the processing procedure shown in Figures 4 and 5.

[0068] When this processing procedure is started, the process in step S81 is performed. In step S81, the determination unit 82 determines whether the amount of hydrogen corresponding to the increment in the concentration of anode gas contained in the combined exhaust gas is less than or equal to the total amount in the multiple fuel cells 22 of the difference between the amount of hydrogen corresponding to the concentration tolerance value and the amount of hydrogen corresponding to the concentration equivalent value. If the result in step S81 is YES, this processing procedure proceeds to step S82. If the result in step S81 is NO, this processing procedure returns to step S81, and the process in step S81 is performed again.

[0069] In step S82, the determination unit 82 determines whether a predetermined time has elapsed since the processing in step S81 was performed. If the result in step S82 is YES, the process proceeds to step S83. If the result in step S82 is NO, the process returns to step S82, and the processing in step S82 is performed again.

[0070] In step S83, the determination unit 82, in the same manner as in step S81, determines again whether the amount of hydrogen corresponding to the above-mentioned increment is less than or equal to the total amount of the above-mentioned difference. If the result in step S83 is YES, the process proceeds to step S84. If the result in step S83 is NO, the process returns to step S81, and the process in step S81 is repeated.

[0071] In step S84, the supply control unit 84 returns the amount of cathode gas supplied to the fuel cell 22, which is subject to the cathode gas supply increase, back to the amount before the increase. Once the process in step S84 is completed, this processing procedure is terminated.

[0072] As described above, after the supply control unit 84 increases the amount of cathode gas supplied to the fuel cell 22 for which the cathode gas supply amount is to be increased, the processing procedure shown in Figure 6 is started. After the processing procedure is started, the amount of hydrogen corresponding to the above-mentioned increment becomes less than or equal to the total amount of the above-mentioned difference, and then a predetermined time is allowed to pass.

[0073] If the amount of hydrogen corresponding to the above-mentioned increment after a predetermined time has elapsed is again less than or equal to the total amount of the above-mentioned difference, the supply control unit 84 controls the cathode gas supply device 26. In this way, the supply control unit 84 controls the cathode gas supply device 26 to return the amount of cathode gas supplied to the fuel cell 22 to which the cathode gas supply amount is to be increased back to the amount before the supply amount was increased.

[0074] Even if the amount of hydrogen corresponding to the aforementioned increment falls below the total amount of the aforementioned difference, the cathode gas supply will not be immediately restored. Only after a predetermined period of time has elapsed and it has been confirmed that the amount of hydrogen corresponding to the aforementioned increment is again below the total amount of the aforementioned difference will the cathode gas supply be restored. By waiting for the predetermined period of time to elapse, repeated changes in the cathode gas supply can be avoided. In other words, the cathode gas supply can be changed stably.

[0075] (Modification 2) In the above-described embodiment, the determination unit 82 of the control device 10 determines whether the first amount is greater than the second amount based on the concentration equivalent value and the concentration tolerance value obtained by the concentration acquisition unit 80. The first amount is the amount of hydrogen corresponding to the increment in the concentration of anode gas contained in the combined exhaust gas flowing through the discharge channel 50. The second amount is the total amount in the multiple fuel cells 22 of the difference between the amount of hydrogen corresponding to the concentration tolerance value and the amount of hydrogen corresponding to the concentration equivalent value.

[0076] The first amount may be the amount of hydrogen corresponding to the concentration of anode gas contained in the combined exhaust gas flowing through the discharge channel 50. In that case, the second amount is the amount of hydrogen corresponding to the concentration allowable value in the multiple fuel cells 22. That is, in this modified example 2, the determination unit 82 determines whether the amount of hydrogen corresponding to the concentration of anode gas contained in the combined exhaust gas flowing through the discharge channel 50 is greater than the total amount of hydrogen corresponding to the concentration allowable value in each of the multiple fuel cells 22.

[0077] In the examples shown in Figures 1 and 3, suppose an internal leak failure occurs in which the valve 34 of fuel cell 22A remains fully open. In that case, the equivalent anode gas concentration in the exhaust gas discharged from fuel cell 22A and flowing through the cathode gas discharge channel 36A is 8%, which is the value at the time of the failure. The equivalent anode gas concentration in the exhaust gas discharged from fuel cells 22B, 22C, and 22D and flowing through the cathode gas discharge channels 36B, 36C, and 36D are all 2%, which is the normal value.

[0078] The permissible concentration of anode gas in the exhaust gas emitted from each of the fuel cells 22A, 22B, 22C, and 22D and flowing through the cathode gas exhaust channels 36A, 36B, 36C, and 36D is 4% for all of them. Assume that fuel cells 22A, 22B, 22C, and 22D are all generating electricity equally.

[0079] In that case, the amount of hydrogen corresponding to the concentration of anode gas contained in the combined exhaust gas corresponds to the sum of the anode gas concentration values ​​of 8%, 2%, 2%, and 2% in the exhaust gas flowing through cathode gas discharge channels 36A, 36B, 36C, and 36D, totaling 14%. The total amount of hydrogen corresponding to the concentration allowable value in each of the multiple fuel cells 22 corresponds to the sum of the anode gas concentration allowable values ​​of 4%, 4%, 4%, and 4% in the exhaust gas flowing through cathode gas discharge channels 36A, 36B, 36C, and 36D, totaling 16%.

[0080] Therefore, the 14% equivalent of hydrogen corresponding to the anode gas concentration in the combined exhaust gas is less than or equal to the 16% equivalent of the total amount of hydrogen corresponding to the allowable concentration in the multiple fuel cells 22. In this case, the supply amount of cathode gas to each of the four fuel cells 22 does not need to be increased and is maintained by the control device 10. This allows power generation in the fuel cell system 20 to continue, making it highly convenient.

[0081] Furthermore, the determination unit 82 may determine that the amount of hydrogen corresponding to the concentration of anode gas contained in the combined exhaust gas is greater than the total amount of hydrogen corresponding to the concentration tolerance values ​​in the multiple fuel cells 22. In that case, the supply control unit 84 controls the cathode gas supply device 26 to increase the amount of cathode gas supplied to at least one of the multiple fuel cells 22. The amount of increase in the cathode gas supply is an amount corresponding to the deviation between the amount of hydrogen corresponding to the concentration of anode gas contained in the combined exhaust gas and the total amount of hydrogen corresponding to the concentration tolerance values ​​in the multiple fuel cells 22. This makes it possible to appropriately reduce the concentration of anode gas contained in the combined exhaust gas emitted from the multiple fuel cells 22.

[0082] Furthermore, the determination result by the determination unit 82 in this modified example 2 is the same as the determination result by the determination unit 82 in the embodiment described above. Therefore, the determination by the determination unit 82 in this modified example 2 may be made based on the determination by the determination unit 82 in the embodiment described above.

[0083] With regard to the embodiments and modifications described above, the following additional information is disclosed.

[0084] (Note 1) The control device (10) of the present disclosure is a control device for controlling the cathode gas supply device in a fuel cell system (20) having a plurality of fuel cells (22), a cathode gas supply device (26) that supplies cathode gas to the plurality of fuel cells, and an exhaust flow path (50) through which combined exhaust gas, which is discharged into the atmosphere after the exhaust gases discharged from each of the plurality of fuel cells have merged, is discharged into the atmosphere, and comprises a concentration acquisition unit (80) that acquires a concentration equivalent value corresponding to the concentration of anode gas in each of the exhaust gases discharged from each of the plurality of fuel cells, and a concentration tolerance value indicating the allowable upper limit of the concentration of anode gas in each of the exhaust gases, and the exhaust gas acquired by the concentration acquisition unit The system includes a determination unit (82) that determines whether the amount of hydrogen corresponding to the concentration of the anode gas contained in the combined exhaust gas flowing through the discharge channel is greater than the total amount of hydrogen corresponding to the concentration allowable value in each of the multiple fuel cells, based on the concentration allowable value and the equivalent concentration value of the anode gas in the system, and a supply control unit (84) that controls the cathode gas supply device to increase the supply amount of cathode gas targeting at least one of the multiple fuel cells if the amount of hydrogen corresponding to the concentration of the anode gas contained in the combined exhaust gas is greater than the total amount of hydrogen corresponding to the concentration allowable value in each of the multiple fuel cells. With this configuration, the concentration of anode gas contained in the combined exhaust gas discharged from multiple fuel cells can be reduced.

[0085] (Note 2) In the control device described in Note 1, the amount of increase in the supply amount of cathode gas that the supply control unit controls and increases in the cathode gas supply device may be an amount corresponding to the deviation between the amount of hydrogen corresponding to the concentration of the anode gas contained in the combined exhaust gas and the total amount of hydrogen corresponding to the concentration tolerance value in the plurality of fuel cells. With such a configuration, the concentration of anode gas contained in the combined exhaust gas discharged from the plurality of fuel cells can be appropriately reduced.

[0086] (Note 3) In the control device described in Note 1, the determination by the determination unit may be made based on whether the amount of hydrogen corresponding to the increment in the concentration of the anode gas contained in the combined exhaust gas is greater than the total difference between the amount of hydrogen corresponding to the concentration tolerance value and the amount of hydrogen corresponding to the concentration equivalent value. With such a configuration, the concentration of anode gas contained in the combined exhaust gas discharged from multiple fuel cells can be reduced.

[0087] (Note 4) In the control device described in Note 3, the amount of increase in the supply amount of cathode gas that the supply control unit controls and increases in the cathode gas supply device may be an amount corresponding to the deviation between the amount of hydrogen corresponding to the increment and the total amount of the difference. With such a configuration, the concentration of anode gas contained in the combined exhaust gas discharged from multiple fuel cells can be appropriately reduced.

[0088] (Note 5) The control device described in Note 3 further comprises a leak detection unit (86) that detects leaks in the anode gas supplied to each of the plurality of fuel cells, and when the leak detection unit detects a leak, the determination unit makes a determination. This makes it possible to reduce the concentration of anode gas contained in the combined exhaust gas discharged from the plurality of fuel cells.

[0089] (Note 6) The control device described in Note 5 further comprises a target determination unit (88) which determines which fuel cell the supply control unit controls to increase the amount of cathode gas supplied by the cathode gas supply device, and the target determination unit may determine, among a plurality of fuel cells, the fuel cell with the smallest amount of cathode gas supplied by the cathode gas supply device as the fuel cell to which the supply control unit controls to increase the amount of cathode gas supplied by the cathode gas supply device. With such a configuration, it becomes easier to equalize the supply load of cathode gas by a plurality of cathode gas supply devices.

[0090] (Note 7) The control device described in Note 5 further comprises a target determination unit that determines which fuel cells are to which the supply control unit controls the cathode gas supply device to increase the amount of cathode gas supplied, and when the amount of cathode gas supplied by the cathode gas supply device to each of the plurality of fuel cells is equal, the target determination unit may determine all of the plurality of fuel cells as the fuel cells to which the supply control unit controls the cathode gas supply device to increase the amount of cathode gas supplied. With such a configuration, it becomes easier to equalize the supply load of cathode gas by the plurality of cathode gas supply devices.

[0091] (Note 8) In the control device described in Note 7, the supply control unit may control the cathode gas supply device to uniformly increase the amount of cathode gas supplied by the cathode gas supply device to each of the fuel cells determined by the target determination unit. With such a configuration, it becomes easier to equalize the supply load of cathode gas from multiple cathode gas supply devices.

[0092] (Note 9) A control device according to any one of Notes 3 to 8, wherein the concentration tolerance value may be determined based on the pressure of the anode gas supplied to each of the plurality of fuel cells, the temperature of the fuel cell, and a predetermined margin relating to the pressure and the temperature. With such a configuration, it becomes easier to suppress a large increase in the concentration of anode gas in the exhaust gas discharged from each fuel cell.

[0093] (Note 10) In the control device described in Note 9, if the amount of hydrogen corresponding to the increment is less than or equal to the total amount of the difference, the supply control unit may control the cathode gas supply device to maintain the amount of cathode gas supplied to each of the plurality of fuel cells. With such a configuration, power generation in the fuel cell system can be continued, which is highly convenient.

[0094] (Note 11) In the control device described in Note 10, if, after the supply control unit increases the supply amount of the cathode gas, the amount of hydrogen corresponding to the increment becomes less than or equal to the total difference, and then after a predetermined time has elapsed, the amount of hydrogen corresponding to the increment in the concentration is less than or equal to the total difference, the supply control unit may control the cathode gas supply device to return the supply amount of the cathode gas to the amount before the supply amount was increased. With such a configuration, the supply amount of cathode gas can be changed stably.

[0095] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

[0096] 10...Control device 20...Fuel cell system 22...Fuel cell 24...Anode gas supply device 26...Cathode gas supply device 28...Anode gas supply channel 30...Cathode gas supply channel 32...Anode gas discharge channel 34...Valve 36...Cathode gas discharge channel 38...Pressure sensor 40...Temperature sensor 50...Discharge channel 70...Calculation unit 72...Storage unit 80...Concentration acquisition unit 82...Determination unit 84...Supply control unit 86...Leak detection unit 88...Target determination unit

Claims

1. A control device (10) for controlling the cathode gas supply device in a fuel cell system having a plurality of fuel cells (22), a cathode gas supply device (26) that supplies cathode gas to the plurality of fuel cells, and an exhaust channel (50) through which combined exhaust gas, which is discharged into the atmosphere after the exhaust gases discharged from each of the plurality of fuel cells are combined, comprises: a concentration acquisition unit (80) that acquires a concentration equivalent value corresponding to the concentration of anode gas in each of the exhaust gases discharged from each of the plurality of fuel cells, and a concentration tolerance value indicating the upper limit of the permissible concentration of the anode gas in each of the exhaust gases; and a determination unit (82) that determines, based on the concentration tolerance value and the concentration equivalent value of the anode gas in each of the exhaust gases acquired by the concentration acquisition unit, whether the amount of hydrogen corresponding to the concentration of the anode gas contained in the combined exhaust gas flowing through the exhaust channel is greater than the total amount of hydrogen corresponding to the concentration tolerance value in each of the plurality of fuel cells. A control device comprising: a supply control unit (84) that controls the cathode gas supply device to increase the amount of cathode gas supplied to at least one of the multiple fuel cells when the amount of hydrogen corresponding to the concentration of the anode gas contained in the combined exhaust gas is greater than the total amount of hydrogen corresponding to the concentration allowable value in each of the multiple fuel cells; 2. A control device according to claim 1, wherein the amount of increase in the supply amount of cathode gas, which the supply control unit controls and increases by the cathode gas supply device, is an amount corresponding to the deviation between the amount of hydrogen corresponding to the concentration of the anode gas contained in the combined exhaust gas and the total amount of hydrogen corresponding to the concentration allowable value in the plurality of fuel cells.

3. A control device according to claim 1, wherein the determination by the determination unit is made based on whether the amount of hydrogen corresponding to the increment in the concentration of the anode gas contained in the combined exhaust gas is greater than the total difference between the amount of hydrogen corresponding to the concentration allowable value and the amount of hydrogen corresponding to the concentration equivalent value.

4. A control device according to claim 3, wherein the amount of increase in the supply amount of cathode gas, which the supply control unit controls and increases by the cathode gas supply device, is an amount corresponding to the deviation between the amount of hydrogen corresponding to the increment and the total amount of the difference.

5. A control device according to claim 3, further comprising a leak detection unit (86) for detecting a leak in the anode gas supplied to each of the plurality of fuel cells, wherein when the leak detection unit detects the leak, the determination unit makes a determination.

6. A control device according to claim 5, further comprising a target determination unit (88) which determines which fuel cell is the target of the supply control unit controlling the cathode gas supply device to increase the amount of cathode gas supplied, wherein the target determination unit determines, among a plurality of fuel cells, the fuel cell in which the amount of cathode gas supplied by the cathode gas supply device is the smallest as the target fuel cell for which the supply control unit controls the cathode gas supply device to increase the amount of cathode gas supplied.

7. A control device according to claim 5, further comprising a target determination unit which determines which fuel cells are to be targeted for increasing the amount of cathode gas supplied by the cathode gas supply device, wherein if the amount of cathode gas supplied by the cathode gas supply device to each of the plurality of fuel cells is equal, the target determination unit determines all of the plurality of fuel cells as fuel cells to be targeted for increasing the amount of cathode gas supplied by the supply control device.

8. A control device according to claim 7, wherein the supply control unit controls the cathode gas supply device to uniformly increase the amount of cathode gas supplied by the cathode gas supply device to each of the fuel cells determined by the target determination unit.

9. A control device according to any one of claims 3 to 8, wherein the allowable concentration is determined based on the pressure of the anode gas supplied to each of the plurality of fuel cells, the temperature of the fuel cell, and a predetermined margin relating to the pressure and the temperature.

10. A control device according to claim 9, wherein the supply control unit controls the cathode gas supply device to maintain the amount of cathode gas supplied to each of the plurality of fuel cells when the amount of hydrogen corresponding to the increment is less than or equal to the total amount of the difference.

11. A control device according to claim 10, wherein after the supply control unit increases the supply amount of the cathode gas, if the amount of hydrogen corresponding to the increment becomes less than or equal to the total difference, and then after a predetermined time has elapsed, the amount of hydrogen corresponding to the increment in the concentration is less than or equal to the total difference, the supply control unit controls the cathode gas supply device to return the supply amount of the cathode gas to the amount before the supply amount was increased.

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