Fuel cell system

Abstract

This fuel cell system includes a plurality of power generation units and a control unit. The power generation unit includes a fuel cell that generates electric power using fuel gas and air. The fuel gas is supplied from a first supply system to the fuel cell. The air is supplied from a second supply system to the fuel cell. When the difference between the voltages of each of a plurality of power generation units exceeds a difference threshold value, the control unit changes verification of the state of at least one of the first supply system and the second supply system to the power generation unit that has the maximum voltage and a power generation unit that is different from the aforementioned power generation unit.

Description

fuel cell system CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2024-057357, filed on March 29, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a fuel cell system.

[0003] 2. Description of the Related Art A fuel cell system in which a plurality of fuel cell stacks are connected in series is known (see Patent Document 1).

[0004] Patent No. 5062948

[0005] A fuel cell device according to a first aspect comprises a plurality of power generation units electrically connected in series, each including a fuel cell that generates electricity using fuel gas supplied from a first supply system and air supplied from a second supply system, and a control unit that, when the difference in voltage between each of the plurality of power generation units exceeds a difference threshold, checks the status of at least one of the first supply system and the second supply system by switching between the power generation unit with the highest voltage and a power generation unit other than the power generation unit.

[0006] It is a configuration diagram showing a schematic configuration of a fuel cell system according to the present embodiment. It is a configuration diagram showing a schematic configuration of a power generation unit of Fig. 1. It is a first flowchart for explaining a confirmation process executed by a control unit of Fig. 1. It is a second flowchart for explaining a confirmation process executed by the control unit of Fig. 1.

[0007] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same components are denoted by the same reference numerals.

[0008] As shown in FIG. 1 , a fuel cell system 10 according to an embodiment of the present disclosure includes a plurality of power generation units 11 and a control unit 12 .

[0009] The plurality of power generation units 11 are electrically connected in series. In Fig. 1, two power generation units 11 are illustrated as the plurality of power generation units 11, but the number is not limited to two. As shown in Fig. 2, the power generation unit 11 includes a fuel cell 13. The power generation unit 11 may further include a combustion unit 14, a reformer 15, and a voltage sensor 16.

[0010] The fuel cell 13 generates electricity through an electrochemical reaction using a fuel gas and air. The fuel gas may include, for example, hydrogen gas. Specifically, the fuel cell 13 performs an electrochemical reaction using oxygen gas in the air. The fuel cell 13 may include a fuel cell unit. The fuel cell 13 may include a plurality of fuel cell units. The plurality of fuel cell units may form a cell stack. The fuel cell unit may be a solid oxide fuel cell unit. In the fuel cell 13, not all of the fuel gas and oxygen gas in the air may undergo an electrochemical reaction, and unreacted fuel gas and oxygen gas may be discharged.

[0011] The combustion unit 14 may combust unreacted fuel gas in the fuel cell 13 using unreacted oxygen gas. The combustion unit 14 may heat the reformer 15 using heat generated by burning the unreacted fuel gas. The combustion unit 14 may heat the reformer 15 to provide energy for a steam reforming reaction in the reformer 15. The combustion unit 14 may be located in a direction opposite to the first direction from the reformer 15 to effectively heat the reformer 15. In the fuel cell system 10, the first direction is a direction that is assumed to be directed vertically upward when the fuel cell system 10 is installed. The combustion unit 14 may be, for example, a space in the first direction from the fuel cell 13. Unreacted fuel gas and unreacted oxygen gas injected from an outlet of the fuel cell 13 may be combusted in the space. Alternatively, the combustion unit 14 may be, for example, a burner located in the first direction from the fuel cell 13.

[0012] The reformer 15 may generate fuel gas by steam reforming raw fuel and water. The raw fuel may include, for example, light hydrocarbons such as methane, ethane, propane, and butane. The raw fuel may be, for example, city gas, LPG, or biogas containing the light hydrocarbons. The reformer 15 may contain a reforming catalyst. The reforming catalyst may generate fuel gas from the raw fuel and water. Steam may be supplied to the reformer 15 as liquid reforming water and vaporized into steam in an vaporization unit provided in the reformer 15.

[0013] The fuel cell 13 is supplied with fuel gas directly or indirectly from a first supply system 17. For example, the first supply system 17 may supply raw fuel to a reformer 15, thereby indirectly supplying the fuel gas to the fuel cell 13. In the following description, the fuel gas will be described as being supplied to the fuel cell 13 indirectly via the reformer 15.

[0014] 1 , the first supply system 17 may include a first supply path 18 and a first supply unit 19. The first supply path 18 may be a pipe through which the fuel gas and the raw fuel gas flow. The first supply unit 19 may cause the fuel gas to flow through the first supply path 18.

[0015] The first supply unit 19 may flow the fuel gas, for example, by increasing the pressure of the fuel gas or raw fuel. The first supply unit 19 may be capable of adjusting the flow rate of the fuel gas according to the operating intensity. The operating intensity is a variable value that contributes to the flow rate fluctuation by the first supply unit 19. The operating intensity may be, for example, the rotation speed in a configuration in which the first supply unit 19 is a turbo pump, or the current value of a motor that imparts torque to the turbo pump. The first supply unit 19 may be, for example, a pump with a variable duty ratio. The first supply unit 19 may typically receive a designated flow rate of the fuel gas or raw fuel from the control unit 12 as information, and perform, for example, feedback control to ensure that the designated flow rate is flowed.

[0016] The first supply unit 19 may be shared by multiple power generation units 11. In other words, one first supply unit 19 may cause the raw fuel gas to flow through the first supply paths 18 of multiple power generation units 11. The term "one first supply unit 19" does not mean a single unit for the entire fuel cell system 10, but rather means that one first supply unit 19, which is at least a part of the multiple first supply units 19 that make up the fuel cell system 10, causes the raw fuel gas to flow through the first supply paths 18 of multiple power generation units 11. Alternatively, the first supply unit 19 may be provided for each of the multiple power generation units 11. In the following description, the first supply unit 19 will be described as causing the raw fuel gas to flow through the first supply paths 18 of multiple power generation units 11.

[0017] Air is supplied to the fuel cell 13 from a second supply system 20. The second supply system 20 may include a second supply path 21 and a second supply unit 22. The second supply path 21 may be a conduit through which air flows. The second supply unit 22 may cause air to flow through the second supply path. The second supply unit 22 may cause air to flow, for example, by increasing the pressure of the air. The second supply unit 22 may be capable of adjusting the air flow rate according to the operating intensity. The operating intensity is a variable value that contributes to the flow rate fluctuation of the second supply unit 22. The operating intensity is, for example, the rotation speed in a configuration in which the second supply unit 22 is a centrifugal blower. The second supply unit 22 may be, for example, a centrifugal blower with a variable duty ratio. The second supply unit 22 may typically receive a designated air flow rate as information from the control unit 12 and perform, for example, feedback control to ensure that the designated air flow rate is maintained.

[0018] The second supply unit 22 may be provided for each of the plurality of power generation units 11. Alternatively, one second supply unit 22 may be shared by the plurality of power generation units 11. In the following description, the second supply unit 22 will be described as being provided for each of the plurality of power generation units 11.

[0019] Water may be supplied to the reformer 15 from a third supply system 23. The third supply system 23 may include a third supply path 24 and a third supply unit 25. The third supply path 24 may be a pipe through which water flows. The third supply unit 25 may pressurize the water to cause it to flow within the third supply path 24. The third supply unit 25 may be capable of adjusting the amount of water supplied. The third supply unit 25 may be, for example, a pump with a variable duty ratio. The third supply unit 25 may typically receive a designated water flow rate as information from the control unit 12 and perform, for example, feedback control to ensure that the designated water flow rate is maintained.

[0020] The third supply unit 25 may be provided for each of the plurality of power generation units 11. Alternatively, one third supply unit 25 may be shared by the plurality of power generation units 11. In the following description, the third supply unit 25 will be described as being provided for each of the plurality of power generation units 11.

[0021] 2, the voltage sensor 16 may detect the voltage of the fuel cell 13. The voltage sensor 16 may provide the detected voltage to the control unit 12 as information.

[0022] The control unit 12 is configured to include at least one processor, at least one dedicated circuit, or a combination thereof. The processor is a general-purpose processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), or a dedicated processor specialized for specific processing. The dedicated circuit may be, for example, an FPGA (Field-Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like. The control unit 12 may control the operation of the fuel cell system 10.

[0023] The control unit 12 may further include a storage unit. The storage unit may include any storage device, such as a RAM (Random Access Memory) or a ROM (Read Only Memory). The storage unit may store various programs that cause the control unit 12 to function and various information used by the control unit 12.

[0024] For example, the storage unit may store a difference threshold, a first voltage threshold, a second voltage threshold, an operating range of the first supply unit 19, and an operating range of the second supply unit 22, which will be described later.

[0025] The control unit 12 may acquire information about the voltages of the power generation units 11 from the voltage sensors 16 provided in each of the power generation units 11. The control unit 12 may calculate the difference between the voltages. The difference may be, for example, an absolute deviation using an average voltage value as a reference value, or the absolute value of the difference between two arbitrarily selected power generation units 11.

[0026] If the calculated voltage difference exceeds the difference threshold, the control unit 12 performs a status check. The status check is a check for the presence or absence of an abnormality in the amount of a substance that contributes to power generation in the power generation unit 11 in the supply system. The status check is, for example, a check for the occurrence of a blockage and a change in the concentration of a substance that contributes to power generation. Blockages and changes in the concentration of a substance can affect the amount available for power generation. The control unit 12 also performs a status check of at least one of the first supply system 17 and the second supply system 20, alternately checking the power generation unit 11 with the highest voltage and the power generation units 11 other than the power generation unit 11.

[0027] When the voltage of the power generation unit 11, which is the maximum voltage, exceeds a first voltage threshold, the control unit 12 may check the state of the power generation unit 11. The control unit 12 may check the state of one of the first supply system 17 and the second supply system 20 of the power generation unit 11. The control unit 12 may give priority to checking the state of the one of the systems. When the operating intensity of the one system whose state has been given priority for status check is within a predetermined operating range, the control unit 12 may determine that there is an abnormality in the other system.

[0028] The one whose state is checked may be the supply system 17, 20 that has the fewer number of shared supply units 19, 22, out of the first supply system 17 and the second supply system 20. In an example in which each power generation unit 11 is provided with a second supply unit 22, the one whose state is checked may be the second supply system 20.

[0029] When the operating intensity of the second supply unit 22 in the power generation unit 11, which has the maximum voltage, exceeds a predetermined operating range, the control unit 12 may determine that there is an abnormality in the second supply system 20. When the operating intensity of the second supply system 20, which has been given priority for status check as described above, is within the predetermined operating range, the control unit 12 may determine that there is an abnormality in the first supply system 17.

[0030] When the control unit 12 determines that there is an abnormality in the first supply system 17, it may determine whether the operating intensity of the first supply unit 17 of the power generation unit 11, which is the maximum voltage, exceeds a predetermined operating range. When the operating intensity exceeds the predetermined operating range, the control unit 12 may determine that there is an abnormality in at least one of the first supply path 18 and the first supply unit 19. Specifically, the control unit 12 may determine that there is a blockage in at least one of the first supply path 18 and the first supply unit 19. When the operating intensity is within the predetermined operating range, the control unit 12 may determine that there is an abnormality in the concentration of the fuel gas. The abnormality in the concentration of the fuel gas is caused by an abnormality in the concentration of light hydrocarbons such as methane in the raw fuel, such as biogas before reforming.

[0031] During or after performing a status check on the power generation unit 11 with the maximum voltage, the control unit 12 may perform a status check on the power generation unit 11 with a voltage less than the second voltage threshold, among the power generation units 11 other than the power generation unit 11 with the maximum voltage. If the operating intensity of the first supply unit 19 of the power generation unit 11 exceeds a predetermined operating range, the control unit 12 may determine that there is an abnormality in the first supply path 18. If the operating intensity of the first supply unit 19 of the power generation unit 11 falls within the predetermined operating range, the control unit 12 may determine that the power generation unit 11 has deteriorated.

[0032] When the control unit 12 determines that there is an abnormality in the first supply system 17, it may increase the operating intensity of the first supply unit 19 for a predetermined time. When the control unit 12 determines that there is an abnormality in the second supply system 20, it may increase the operating intensity of the second supply unit 22 for a predetermined time.

[0033] When the control unit 12 determines that there is an abnormality in at least one of the first supply system 17 and the second supply system 20, it notifies the user of the abnormality. The notification is made, for example, by issuing a notification instruction to an output device that communicates with the control unit 12, causing the output device to output information indicating that there is an abnormality. The output device is, for example, a display, a warning lamp, or a speaker.

[0034] Next, the confirmation process executed by the control unit 12 in this embodiment will be described with reference to the flowcharts of Figures 3 and 4. The confirmation process is started periodically, for example.

[0035] In step S100, the control unit 12 calculates the difference in voltage between the multiple power generation units 11. In the description of this flowchart, the voltage difference is an absolute deviation with the average value of the voltages of the multiple power generation units 11 as a reference value, but is not limited to this. After the calculation, the process proceeds to step S101.

[0036] In step S101, the control unit 12 determines whether or not there is a power generation unit 11 among the multiple power generation units 11 whose difference calculated in step S100 exceeds the difference threshold. If there is a power generation unit 11 whose difference exceeds the difference threshold, the process proceeds to step S102. If there is no power generation unit 11 whose difference exceeds the voltage threshold, the confirmation process ends.

[0037] In step S102, the control unit 12 determines whether the voltage of the power generation unit 11, which is the maximum voltage, exceeds a first voltage threshold. If the voltage exceeds the first voltage threshold, the process proceeds to step S103. If the voltage does not exceed the first voltage threshold, the process proceeds to step S109.

[0038] In step S103, the control unit 12 determines whether the operating intensity of the second supply unit 22 of the power generation unit 11, which is the maximum voltage, exceeds a predetermined operating range. If it does not exceed the predetermined operating range, the process proceeds to step S104. If it does exceed the predetermined operating range, the process proceeds to step S105.

[0039] In step S104, the control unit 12 determines that there is an abnormality in the second supply system 20. After the determination, the process proceeds to step S109.

[0040] In step S105, the control unit 12 determines that there is an abnormality in the first supply system 17. After the determination, the process proceeds to step S106.

[0041] In step S106, the control unit 12 determines whether the operating intensity of the first supply unit 19 exceeds a predetermined operating range. If it exceeds the predetermined operating range, the process proceeds to step S107. If it does not exceed the predetermined operating range, the process proceeds to step S108.

[0042] In step S107, the control unit 12 determines that there is an abnormality in the first supply path 18 and the first supply unit 19. After the determination, the process proceeds to step S109.

[0043] In step S108, the control unit 12 determines that there is an abnormality in the concentration of the fuel gas. After the determination, the process proceeds to step S109.

[0044] In step S109, the control unit 12 determines whether there are any other power generation units 11 among the multiple power generation units 11 whose voltage is less than the second voltage threshold. By other power generation units 11, we mean the power generation unit 11 with the highest voltage. If there is a power generation unit 11 whose voltage is less than the second voltage threshold, the process proceeds to step S110. If there is no power generation unit 11 whose voltage is less than the second voltage threshold, the process proceeds to step S113.

[0045] In step S110, the control unit 12 determines whether the operating intensity of the first supply unit 19 of the power generation unit 11, which is a voltage less than the second voltage threshold, exceeds a predetermined operating range. If the operating intensity does not exceed the predetermined operating range, the process proceeds to step S111. If the operating intensity exceeds the predetermined operating range, the process proceeds to step S112.

[0046] In step S111, the control unit 12 determines that there is deterioration in the power generation unit 11. After the determination, the process proceeds to step S113.

[0047] In step S112, the control unit 12 determines that there is an abnormality in the first supply path 18 of the power generation unit 11. After the determination, the process proceeds to step S113.

[0048] In step S113, the control unit 12 notifies the control unit 12 of an abnormality that is determined to have occurred in at least one of the power generation unit 11 whose voltage exceeds the first voltage threshold and the power generation unit 11 whose voltage is less than the second voltage threshold. The abnormalities that are determined to have occurred include an abnormality in the first supply path 17, an abnormality in the second supply path 20, an abnormality in the concentration of fuel gas, and deterioration of the power generation unit 11 whose voltage is less than the second voltage threshold. After the notification, the process proceeds to step S114.

[0049] In step S114, it is determined whether or not an abnormality has occurred in the first supply system 17 and the second supply system 20. If an abnormality has occurred, the process proceeds to step S115. If an abnormality has not occurred, the confirmation process ends.

[0050] In step S115, the control unit 12 increases the operating intensity of at least one of the first supply system 17 and the second supply system 20 of the power generation unit 11 that is determined to have an abnormality for a predetermined time. After the increase, the confirmation process ends.

[0051] The fuel cell system 10 of this embodiment, configured as described above, includes a plurality of power generation units 11 electrically connected in series, each including a fuel cell that generates electricity using fuel gas supplied from a first supply system 17 and air supplied from a second supply system 20, and a control unit 12 that, when the difference in voltage between the plurality of power generation units 11 exceeds a difference threshold, alternately checks the status of at least one of the first supply system 17 and the second supply system 20 between the power generation unit 11 with the highest voltage and the other power generation units 11. Malfunctions in the first supply system 17 and the second supply system 20 disrupt normal operation of the fuel cell 13. Therefore, it is desirable to appropriately check the status of the first supply system 17 and the second supply system 20. However, constantly checking the status is undesirable because it places unnecessary strain on the control unit 12, and reducing the frequency of status checks can lead to delayed detection of malfunctions. In response to such an event, the fuel cell system 10 having the above-described configuration checks the status based on an increase in the voltage difference that may occur when there is a malfunction in the first supply system 17 and the second supply system 20. Therefore, the fuel cell system 10 can appropriately check the occurrence of a malfunction. The control unit 12 may constantly check the status of at least one of the first supply system 17 and the second supply system 20. Furthermore, when there is a voltage difference, the cause of the malfunction may differ between the power generation unit 11 with a higher voltage and the other power generation unit 11. For example, in the power generation unit 11 with a higher voltage, it is assumed that the relative amount of fuel gas in the fuel cell 13 is higher than normal. The event of the relative amount of fuel gas in the fuel cell 13 being higher than normal may be due to a higher-than-normal concentration of the fuel gas flowing into the fuel cell 13. Furthermore, the event of the relative amount of fuel gas in the fuel cell 13 being higher than normal may be due to an excessive supply of fuel gas due to an abnormality in the first supply system 17. Furthermore, the phenomenon in which the relative amount of fuel gas in the fuel cell 13 is higher than normal may be due to an increase in the voltage of the fuel cell 13 caused by a rise in the power generation temperature, which may result in an increase in the amount of fuel gas supplied. Furthermore, the phenomenon in which the relative amount of fuel gas in the fuel cell 13 is higher than normal may be due to an abnormality in the second supply system 20 causing an insufficient amount of air to be supplied.On the other hand, in a power generation unit 11 with a low voltage, it is expected that the relative amount of fuel gas in the fuel cell 13 is lower than normal. The event of the relative amount of fuel gas in the fuel cell 13 being lower than normal may be due to a lower-than-normal concentration of the fuel gas flowing into the fuel cell 13. The event of the relative amount of fuel gas in the fuel cell 13 being lower than normal may be due to an abnormality in the first supply system 17 causing the supply of fuel gas to be insufficient. Furthermore, the event of the relative amount of fuel gas in the fuel cell 13 being lower than normal may be due to a drop in the voltage of the fuel cell 13 caused by a drop in the power generation temperature, resulting in a reduction in the supply of fuel gas. Furthermore, the event of the relative amount of fuel gas in the fuel cell 13 being lower than normal may be due to an excessive supply of air caused by an abnormality in the second supply system 20. In response to such events, the fuel cell system 10 having the above-described configuration can perform status checks on malfunctions with a high probability of occurrence or on areas where the impact of a malfunction is small, depending on whether the voltage is at the maximum voltage. Therefore, the fuel cell system 10 can appropriately check for the occurrence of a malfunction.

[0052] Furthermore, when the voltage of a power generation unit 11, which is the maximum voltage, exceeds a first voltage threshold, the fuel cell system 10 checks the state of that power generation unit 11. Even when the difference in voltage among multiple power generation units 11 exceeds the difference threshold, the voltage of the power generation unit 11 may be within the appropriate voltage range. In response to such an event, the fuel cell system 10 having the above-described configuration adds the condition for checking the state that the voltage exceeds the appropriate voltage, thereby more appropriately checking for the occurrence of a malfunction.

[0053] In the fuel cell system 10, the first supply system 17 includes a first supply path 18 and a first supply unit 19 that adjustably flows fuel gas through the first supply path 18 at a flow rate corresponding to the operating intensity, the second supply system 20 includes a second supply path 21 and a second supply unit 22 that adjustably flows air through the second supply path 21 at a flow rate corresponding to the operating intensity, and the control unit 12 checks the status of one of the first supply system 17 and the second supply system 18 of the power generation unit 11 that has the highest voltage. With this configuration, the fuel cell system 10 can check the status of the supply system, which is the easiest to estimate among the causes of voltage differences, and thus can easily analyze the cause. For example, as described above, in a configuration in which the second supply unit 22 is more unique than the first supply unit 19, even if there is an abnormality in the first supply system 17, it is necessary to check the status of the other power generation units 11 as well to determine whether the abnormality is in the power generation unit 11 whose status is being checked. On the other hand, in this configuration, an abnormality in the second supply system 20 can be determined to be an abnormality in the second supply system 20 itself in the power generation unit 11. In this way, the ease of analyzing the cause changes depending on the configurations of the first supply unit 17 and the second supply unit 22.

[0054] Furthermore, if the operating strength of the second supply unit 20 in the power generation unit 11, which is the maximum voltage, exceeds a predetermined operating range, the fuel cell system 10 determines that there is an abnormality in the second supply system 20. With this configuration, the fuel cell system 10 can easily make the above determinations regarding the second supply system 20 without using a flow meter or the like.

[0055] Furthermore, the fuel cell system 10 prioritizes checking the status of either the first supply system 17 or the second supply system 20. With this configuration, the fuel cell system 10 first checks the status of the supply system that is the easiest to estimate among the factors that cause a voltage difference, thereby reducing the need to perform unnecessary status checks.

[0056] Furthermore, when the operating strength of one of the first and second supply systems, which is prioritized for status check in the power generation unit 11 with the highest voltage, falls within a predetermined operating range, the fuel cell system 10 determines that there is an abnormality in the other supply system 17, 20. With this configuration, the fuel cell system 10 can easily check the status of one supply system 17, 20 by checking the status of the other supply system 17, 20.

[0057] Furthermore, when determining that there is an abnormality in the first supply system 17, if the operating strength of the first supply unit 17 of the power generation unit 11, which is the maximum voltage, exceeds a predetermined operating range, the fuel cell system 10 determines that there is an abnormality in at least one of the first supply path 18 and the first supply unit 19. With this configuration, the fuel cell system 10 can easily determine whether there is an abnormality in the structure of the first supply system 17 or in the fuel gas itself, based on the operating strengths of the first supply unit 19 and the second supply unit 22.

[0058] Furthermore, the fuel cell system 10 determines that there is an abnormality in the concentration of the fuel gas when the operating intensity of the first supply unit 19 of the power generation unit 11, which is the maximum voltage, falls within a predetermined operating range. With this configuration, the fuel cell system 10 can easily determine whether there is an abnormality in the structure of the first supply system 17 or in the fuel gas itself, based on the operating intensities of the first supply unit 19 and the second supply unit 22.

[0059] Furthermore, during or after the status check is being performed on the power generation unit 11 with the maximum voltage, the fuel cell system 10 performs a status check on the power generation units 11 other than the power generation unit 11 with a voltage below the second voltage threshold. With this configuration, the fuel cell system 10 adds the condition of being below the appropriate voltage to the conditions for performing a status check, thereby more appropriately checking for the occurrence of a malfunction.

[0060] Furthermore, when the operating strength of the first supply unit 19 of the power generation unit 11, which is a voltage less than the second voltage threshold, exceeds a predetermined operating range, the fuel cell system 10 determines that there is an abnormality in the first supply path 18. With this configuration, the fuel cell system 10 can easily determine whether there is an abnormality in the structure of the first supply system 17 or in the power generation unit 11, based on the operating strength of the first supply unit 19.

[0061] Furthermore, the fuel cell system 10 determines that the power generation unit 11 is degraded when the operating strength of the first supply unit 19 of the power generation unit 11, which is a voltage less than the second voltage threshold, falls within a predetermined operating range. With this configuration, the fuel cell system 10 can easily determine whether there is an abnormality in the structure of the first supply system 17 or in the power generation unit 11, based on the operating strength of the first supply unit 19.

[0062] Furthermore, when the fuel cell system 10 determines that there is an abnormality in the first supply system 17, it increases the operating intensity of the first supply unit 19 for a predetermined time, and when it determines that there is an abnormality in the second supply system 20, it increases the operating intensity of the second supply unit 22 for a predetermined time. A major cause of abnormalities in the first supply system 17 and the second supply system 20 can be clogging due to foreign matter or the like. In response to such an event, the fuel cell system 10 having the above-described configuration can blow away the foreign matter or the like by increasing the operating intensity. Therefore, the fuel cell system 10 can return the abnormal state of the first supply system 17 and the second supply system 20 to a normal state.

[0063] In one embodiment, (1) a fuel cell system includes a plurality of power generation units electrically connected in series, each including a fuel cell that generates electricity using fuel gas supplied from a first supply system and air supplied from a second supply system, and a control unit that, when a difference in voltage between each of the plurality of power generation units exceeds a difference threshold, checks the status of at least one of the first supply system and the second supply system by switching between the power generation unit with the highest voltage and a power generation unit other than the power generation unit.

[0064] (2) In the fuel cell system of (1) above, the control unit checks the state of the power generation unit when the voltage of the power generation unit, which is the maximum voltage, exceeds a first voltage threshold.

[0065] (3) In the fuel cell system of (2) above, the first supply system has a first supply path and a first supply unit that flows the fuel gas through the first supply path at an adjustable flow rate depending on the operating intensity, the second supply system has a second supply path and a second supply unit that flows the air through the second supply path at an adjustable flow rate depending on the operating intensity, and the control unit checks the state of one of the first supply system and the second supply system of the power generation unit that has the maximum voltage.

[0066] (4) In the fuel cell system of (3) above, the control unit determines that there is an abnormality in the second supply system when the operating intensity of the second supply unit in the power generation unit with the maximum voltage exceeds a predetermined operating range.

[0067] (5) In the fuel cell system of (3) or (4), the control unit checks the state of one of the first supply system and the second supply system with priority.

[0068] (6) In the fuel cell system of (5) above, when the operating strength of one of the first supply system and the second supply system, which is checked first in the power generation unit with the highest voltage, falls within a predetermined operating range, the control unit determines that there is an abnormality in the other one.

[0069] (7) In the fuel cell system of (6) above, when the control unit determines that there is an abnormality in the first supply system, if the operating strength of the first supply unit of the power generation unit, which is the maximum voltage, exceeds the predetermined operating range, it determines that there is an abnormality in at least one of the first supply path and the first supply unit itself.

[0070] (8) In the fuel cell system of (6) or (7) above, the control unit determines that there is an abnormality in the concentration of the fuel gas when the operating intensity of the first supply unit of the power generation unit with the maximum voltage is within the predetermined operating range.

[0071] (9) In any of the fuel cell systems (1) to (8) above, during or after the status check is performed on the power generation unit with the maximum voltage, the control unit performs the status check on the power generation unit other than the power generation unit with the maximum voltage that has a voltage less than a second voltage threshold.

[0072] (10) In the fuel cell system of (9) above, the control unit determines that there is an abnormality in the first supply path when the operating intensity of the first supply unit of the power generation unit, which has a voltage less than the second voltage threshold, exceeds a predetermined operating range.

[0073] (11) In the fuel cell system of (9) or (10) above, the control unit determines that there is an abnormality in the concentration of the fuel gas when the operating intensity of the first supply unit of the power generation unit with the maximum voltage is within the predetermined operating range.

[0074] (12) In any of the fuel cell systems (1) to (11) above, the control unit increases the operating intensity of the first supply unit for a predetermined time when it determines that there is an abnormality in the first supply system, and increases the operating intensity of the air supply unit for the predetermined time when it determines that there is an abnormality in the second supply system.

[0075] The above has described an embodiment of the fuel cell system 10, but the present disclosure can also be embodied as a method or program for implementing the device, as well as a storage medium on which a program is recorded (for example, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a magnetic tape, a hard disk, or a memory card).

[0076] Furthermore, the implementation form of the program is not limited to application programs such as object code compiled by a compiler or program code executed by an interpreter, but may also be in the form of a program module incorporated into an operating system. Furthermore, the program may or may not be configured so that all processing is performed solely by the CPU on the control board. The program may also be configured so that part or all of it is executed by another processing unit mounted on an expansion board or expansion unit added to the board as needed.

[0077] The drawings illustrating the embodiments of the present disclosure are schematic, and the dimensional ratios and the like in the drawings do not necessarily correspond to the actual ones.

[0078] Although the embodiments of the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art could make various modifications or alterations based on the present disclosure. Therefore, it should be noted that these modifications or alterations are included in the scope of the present disclosure. For example, the functions included in each component can be rearranged so as not to cause logical inconsistencies, and multiple components can be combined or divided into one.

[0079] All of the features described in this disclosure and / or all steps of all disclosed methods or processes may be combined in any combination except combinations in which these features are mutually exclusive. Furthermore, each feature described in this disclosure may be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless expressly denied. Thus, unless expressly denied, each disclosed feature is only one example of a generic series of identical or equivalent features.

[0080] Furthermore, embodiments of the present disclosure are not limited to the specific configurations of any of the above-described embodiments, but rather extend to any novel feature or combination thereof described herein, or any novel method or process step or combination thereof described herein.

[0081] In this disclosure, descriptions such as "first" and "second" are identifiers for distinguishing the configuration. In this disclosure, the configurations distinguished by descriptions such as "first" and "second" can have their numbers exchanged. For example, the first supply system can exchange the identifiers "first" and "second" with the second supply system. The exchange of identifiers is performed simultaneously. The configurations remain distinguished even after the identifier exchange. Identifiers may be deleted. A configuration from which an identifier has been deleted is distinguished by a symbol. The descriptions of identifiers such as "first" and "second" in this disclosure should not be used solely to interpret the order of the configurations or to justify the existence of an identifier with a smaller number.

[0082] REFERENCE SIGNS LIST 10 fuel cell system 11 power generation unit 12 control unit 13 fuel cell 14 combustion unit 15 reformer 16 voltage sensor 17 first supply system 18 first supply path 19 first supply unit 20 second supply system 21 second supply path 22 second supply unit 23 third supply system 24 third supply path 25 third supply unit

Claims

1. A fuel cell system comprising: a plurality of power generation units electrically connected in series, each including a fuel cell that generates electricity using fuel gas supplied from a first supply system and air supplied from a second supply system; and a control unit that, when the difference in voltage between each of the plurality of power generation units exceeds a difference threshold, checks the status of at least one of the first supply system and the second supply system by switching between the power generation unit with the highest voltage and a power generation unit other than the power generation unit.

2. A fuel cell system according to claim 1, wherein the control unit checks the state of the power generation unit when the voltage of the power generation unit, which is the maximum voltage, exceeds a first voltage threshold.

3. A fuel cell system as claimed in claim 2, wherein the first supply system has a first supply path and a first supply unit that flows the fuel gas through the first supply path at an adjustable flow rate according to the operating intensity, the second supply system has a second supply path and a second supply unit that flows the air through the second supply path at an adjustable flow rate according to the operating intensity, and the control unit checks the state of one of the first supply system and the second supply system of the power generation unit with the maximum voltage.

4. A fuel cell system according to claim 3, wherein the control unit determines that there is an abnormality in the second supply system when the operating strength of the second supply unit in the power generation unit with the maximum voltage exceeds a predetermined operating range.

5. A fuel cell system according to claim 3 or 4, wherein the control unit checks the state of one of the first supply system and the second supply system with priority.

6. A fuel cell system as claimed in claim 5, wherein the control unit determines that there is an abnormality in the other of the first and second supply systems when the operating strength of either the first or second supply system, which is given priority for status confirmation in the power generation unit with the maximum voltage, is within a predetermined operating range.

7. A fuel cell system according to claim 6, wherein the control unit determines that there is an abnormality in the first supply system when the operating strength of the first supply unit of the power generation unit, which is the maximum voltage, exceeds the predetermined operating range, and determines that there is an abnormality in at least one of the first supply path and the first supply unit itself.

8. A fuel cell system according to claim 6 or 7, wherein the control unit determines that there is an abnormality in the concentration of the fuel gas when the operating intensity of the first supply unit of the power generation unit with the maximum voltage is within the predetermined operating range.

9. A fuel cell system according to any one of claims 1 to 8, wherein the control unit, during or after the status check for the power generation unit with the maximum voltage, performs the status check for the power generation unit other than the power generation unit with the maximum voltage that has a voltage below a second voltage threshold.

10. A fuel cell system according to claim 9, wherein the control unit determines that there is an abnormality in the first supply path when the operating intensity of the first supply unit of the power generation unit, which has a voltage less than the second voltage threshold, exceeds a predetermined operating range.

11. A fuel cell system according to claim 9 or 10, wherein the control unit determines that the power generation unit has deteriorated when the operating intensity of the first supply unit of the power generation unit, which has a voltage less than the second voltage threshold, falls within a predetermined operating range.

12. A fuel cell system according to any one of claims 3 to 11, wherein the control unit increases the operating intensity of the first supply unit for a predetermined period of time when it determines that there is an abnormality in the first supply system, and increases the operating intensity of the second supply unit for the predetermined period of time when it determines that there is an abnormality in the second supply system.

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