Control device

Abstract

SOLUTION: To provide a control device 22 in which, when an excessively dry determining unit 156 determines that a power generating cell 28 is in an excessively dry state, a power generation control unit 150 limits the power generation of the power generating cell 28 at the start of the first power generation control.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device. [Background technology]

[0002] In recent years, research and development into fuel cells has been conducted to contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] A system equipped with a fuel cell stack is called a fuel cell system. A fuel cell stack includes multiple power generation cells. The power generation cells generate electricity through an electrochemical reaction between fuel gas (hydrogen-containing gas) and oxidant gas (oxygen-containing gas). When the power generation cells generate electricity, water is produced. Some of the produced water accumulates inside the fuel cell stack. If the operation of the fuel cell system is stopped in a low-temperature environment, there is a risk that the water accumulated inside the fuel cell stack will freeze. If water freezes in a fuel cell system, the flow of gas is obstructed, and the fuel cell stack will no longer be able to generate electricity.

[0004] Patent Document 1 discloses a method for shutting down a fuel cell system in which, when an ignition switch is turned off, a dry power generation process is performed and then a wastewater power generation process is performed in order to promote drying of a membrane electrode assembly (MEA) of a power generation cell. The amount of humidification of the oxidant gas supplied to the fuel cell stack during the dry power generation process is set to be less than the amount of humidification of the oxidant gas supplied to the fuel cell stack during the wastewater power generation process. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-058188 A Summary of the Invention [Problem to be solved by the invention]

[0006] There is a need for a technology that allows power generating cells to generate power efficiently.

[0007] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0008] An aspect of the present invention is a control device provided in a fuel cell system having a fuel cell stack including a power generation cell and a power generation control unit that controls power generation of the power generation cell, wherein the power generation control unit is capable of executing a first power generation control and a second power generation control different from the first power generation control, and the second power generation control is power generation control for drying an electrolyte membrane provided in the power generation cell after receiving a system stop command to stop the fuel cell system, and the control device further includes a temperature acquisition unit that acquires temperature information indicating a stack temperature, which is the temperature of the fuel cell stack, a history acquisition unit that acquires history information indicating that the second power generation control was performed after receiving the previous system stop command, and an over-dryness determination unit that determines whether the power generation cell is in an over-dry state based on the history information and the temperature information, and when the over-dryness determination unit determines that the power generation cell is in an over-dry state, the power generation control unit limits the power generation power of the power generation cell when the first power generation control is started. Effect of the Invention

[0009] According to the present invention, it is possible to cause the power generating cell to generate power satisfactorily. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a fuel cell system. [Diagram 2] FIG. 2 is a flowchart showing the procedure of the power limiting process. [Diagram 3] FIG. 3 is a schematic diagram of a fuel cell system according to the first modification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [1 Configuration of fuel cell system 10] 1 is a schematic diagram of a fuel cell system 10. The fuel cell system 10 is mounted on, for example, a vehicle (fuel cell vehicle). The fuel cell system 10 can also be mounted on moving objects such as ships, aircraft, and robots. The fuel cell system 10 can also be used as a stationary power source in facilities, homes, and the like.

[0012] In the fuel cell system 10, a fuel gas and an oxidant gas are used as reactant gases. The fuel gas is a hydrogen-containing gas. The oxidant gas is an oxygen-containing gas such as air. Each of the fuel gas and the oxidant gas is supplied to the fuel cell stack 12 and subjected to an electrochemical reaction. In this specification, the fuel gas discharged from the fuel cell stack 12 without being subjected to the electrochemical reaction is also referred to as fuel off-gas. In this specification, the oxidant gas discharged from the fuel cell stack 12 without being subjected to the electrochemical reaction is also referred to as oxidant off-gas.

[0013] The fuel cell system 10 includes a fuel cell stack 12, a tank 14, an anode system 16, a cathode system 18, a cooling system 20, and a control device 22. Electric power generated by the fuel cell stack 12 is supplied to a load 26. The load 26 includes a drive motor and a battery of a fuel cell vehicle. The tank 14 is filled with high-pressure fuel gas.

[0014] The fuel cell stack 12 includes a fuel gas supply port 12a that supplies fuel gas to the inside of the fuel cell stack 12, and a fuel gas discharge port 12b that discharges fuel off-gas from the inside of the fuel cell stack 12. The fuel cell stack 12 includes an oxidant gas supply port 12c that supplies oxidant gas to the inside of the fuel cell stack 12, and an oxidant gas discharge port 12d that discharges the oxidant off-gas from the inside of the fuel cell stack 12. The fuel cell stack 12 includes a refrigerant supply port 12e that supplies a refrigerant to the inside of the fuel cell stack 12, and a refrigerant discharge port 12f that discharges the refrigerant from the inside of the fuel cell stack 12.

[0015] The fuel cell stack 12 has a plurality of power generating cells 28. Each of the plurality of power generating cells 28 has the same configuration. Each power generating cell 28 includes a membrane electrode assembly 30, a first separator 32, and a second separator 34. The membrane electrode assembly 30 is sandwiched between the first separator 32 and the second separator 34. One of the plurality of power generating cells 28 is shown in FIG. 1.

[0016] The first separator 32 and the second separator 34 are formed of a metal sheet having a corrugated cross section. In two adjacent power generating cells 28, the first separator 32 of one power generating cell 28 and the second separator 34 of the other power generating cell 28 are joined to each other. A cell cooling flow path (not shown) is formed between the first separator 32 and the second separator 34. The cell cooling flow path communicates with the refrigerant supply port 12e and the refrigerant discharge port 12f.

[0017] The membrane electrode assembly 30 includes an electrolyte membrane 36, an anode electrode 38, and a cathode electrode 40. The electrolyte membrane 36 is interposed between the anode electrode 38 and the cathode electrode 40. An anode flow path 42 is formed between the first separator 32 and the anode electrode 38. A cathode flow path 44 is formed between the second separator 34 and the cathode electrode 40. The anode flow path 42 communicates with the fuel gas supply port 12a and the fuel gas discharge port 12b. The cathode flow path 44 communicates with the oxidant gas supply port 12c and the oxidant gas discharge port 12d.

[0018] A temperature sensor 46 is provided near the fuel gas discharge port 12b. For example, the temperature sensor 46 is provided in the fuel gas discharge channel 86 connected to the fuel gas discharge port 12b. The temperature sensor 46 detects the temperature of the fuel gas. The temperature sensor 46 may be provided near the oxidant gas discharge port 12d. For example, the temperature sensor 46 may be provided in the oxidant gas discharge channel 108 connected to the oxidant gas discharge port 12d. In this case, the temperature sensor 46 detects the temperature of the oxidant gas. The temperature of the fuel gas or oxidant gas (gas temperature) near the discharge port of the fuel cell stack 12 is the representative temperature of the fuel cell stack 12. In other words, the gas temperature corresponds to the temperature of the fuel cell stack 12 (stack temperature).

[0019] The anode system 16 includes a fuel gas supply passage 84, a fuel gas discharge passage 86, a circulation passage 88, and a drain passage 90. The anode system 16 also includes an injector 94, an ejector 96, a gas-liquid separator 98, and a drain valve 100.

[0020] The fuel gas supply path 84 is connected to the exhaust port of the tank 14 and the fuel gas supply port 12a of the fuel cell stack 12. An injector 94 and an ejector 96 are provided in the fuel gas supply path 84. The ejector 96 is disposed closer to the fuel cell stack 12 than the injector 94.

[0021] The fuel gas discharge path 86 is connected to the fuel gas discharge port 12b of the fuel cell stack 12 and a supply port of a gas-liquid separator 98. The circulation path 88 is connected to the exhaust port of the gas-liquid separator 98 and the ejector 96.

[0022] The drainage passage 90 is connected to the drain outlet of the gas-liquid separator 98 and to the inlet of a diluter 121. The outlet of the diluter 121 is connected to a discharge port provided in the vehicle. The drainage passage 90 is provided with a drain valve 100.

[0023] The cathode system 18 includes an oxidant gas supply channel 106, an oxidant gas discharge channel 108 (discharge channel), and a bypass channel 110. The cathode system 18 also includes a compressor 112 (oxidant gas supplier), a humidifier 114, a first shutoff valve 116, a second shutoff valve 118, and a bypass valve 119.

[0024] The oxidizing gas supply channel 106 is connected to an air intake port provided in the vehicle and the oxidizing gas supply port 12c of the fuel cell stack 12. The oxidizing gas supply channel 106 is provided with a compressor 112, a first sealing valve 116, and a humidifier supply channel 114A of the humidifier 114. A portion of the oxidizing gas supply channel 106 that is disposed upstream of the humidifier 114 is referred to as the oxidizing gas supply channel 106A. A portion of the oxidizing gas supply channel 106 that is disposed downstream of the humidifier 114 is referred to as the oxidizing gas supply channel 106B. The oxidizing gas supply channel 106A is provided with the compressor 112 and a first sealing valve 116. The first sealing valve 116 is disposed closer to the humidifier 114 than the compressor 112.

[0025] The oxidant gas discharge channel 108 is connected to the oxidant gas discharge port 12d of the fuel cell stack 12 and the inlet of the diluter 121. The oxidant gas discharge channel 108 is provided with a humidifier discharge channel 114B of the humidifier 114 and a second shutoff valve 118. A portion of the oxidant gas discharge channel 108 that is disposed upstream of the humidifier 114 is referred to as an oxidant gas discharge channel 108A. A portion of the oxidant gas discharge channel 108 that is disposed downstream of the humidifier 114 is referred to as an oxidant gas discharge channel 108B. The oxidant gas discharge channel 108B is provided with the second shutoff valve 118.

[0026] The bypass passage 110 is connected to the oxidizing gas supply passage 106A between the compressor 112 and the first shutoff valve 116, and to the oxidizing gas discharge passage 108B downstream of the second shutoff valve 118. The bypass passage 110 is provided with a bypass valve 119.

[0027] The cooling system 20 includes a coolant flow path 120. The cooling system 20 also includes a pump 126, a radiator 128, a temperature sensor 130, and a flow dividing valve 132.

[0028] The coolant flow path 120 circulates a coolant between the fuel cell stack 12 and the radiator 128. The coolant is, for example, water containing ethylene glycol. The coolant flow path 120 includes a coolant supply path 122, a coolant discharge path 124, and a branch path 125. The coolant supply path 122 connects a fluid discharge port of the radiator 128 to a coolant supply port 12e of the fuel cell stack 12. The coolant discharge path 124 connects a coolant discharge port 12f of the fuel cell stack 12 to a fluid supply port of the radiator 128. The branch path 125 branches off from the coolant discharge path 124 and merges with the coolant supply path 122.

[0029] The pump 126 is provided in the coolant supply path 122. The pump 126 may also be provided in the coolant discharge path 124. The radiator 128 is a heat dissipator that dissipates heat from the coolant in the coolant flow path 120. The radiator 128 may include a fan.

[0030] The temperature sensor 130 is provided in the coolant discharge path 124. The temperature sensor 130 may be provided in the coolant supply path 122. The temperature sensor 130 detects the temperature of the coolant (coolant temperature). The coolant temperature corresponds to the temperature inside the fuel cell stack 12 (stack temperature). The fuel cell system 10 further includes an outside air temperature sensor 140. The outside air temperature sensor 140 is provided, for example, in the body of the fuel cell vehicle. The outside air temperature sensor 140 detects the temperature in the air outside the fuel cell stack 12 (outside air temperature). A signal output from the outside air temperature sensor 140 is supplied to the control device 22.

[0031] The flow dividing valve 132 is provided at a junction where the branch passage 125 joins the refrigerant supply passage 122. The flow dividing valve 132 may be provided at a branch portion where the branch passage 125 branches off from the refrigerant discharge passage 124. The opening degree of the flow dividing valve 132 is adjustable. The amount of refrigerant supplied to the radiator 128 is adjusted according to the opening degree of the flow dividing valve 132. The opening degree of the flow dividing valve 132 is controlled by the control device 22.

[0032] The control device 22 may be configured by an ECU (Electronic Control Unit). The control device 22 includes a calculation unit 136 and a storage unit 138.

[0033] The calculation unit 136 is, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The calculation unit 136 includes a power generation control unit 150, a temperature acquisition unit 152, a history acquisition unit 154, an overdryness determination unit 156, and a warm-up determination unit 158. The power generation control unit 150, the temperature acquisition unit 152, the history acquisition unit 154, the overdryness determination unit 156, and the warm-up determination unit 158 ​​are operated by the calculation unit 136 executing a program stored in the memory unit 138.

[0034] At least one of the power generation control unit 150, the temperature acquisition unit 152, the history acquisition unit 154, the overdryness determination unit 156, and the warm-up determination unit 158 ​​may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). Alternatively, at least one of the power generation control unit 150, the temperature acquisition unit 152, the history acquisition unit 154, the overdryness determination unit 156, and the warm-up determination unit 158 ​​may be realized by an electronic circuit including a discrete device.

[0035] The storage unit 138 is a computer-readable storage medium, and includes a volatile memory and a non-volatile memory. The volatile memory is, for example, a random access memory (RAM). The non-volatile memory is, for example, a read only memory (ROM), a flash memory, etc. Data, for example, is stored in the volatile memory. Programs, tables, maps, etc. are stored in the non-volatile memory. At least a part of the storage unit 138 may be provided in the above-mentioned processor, integrated circuit, etc.

[0036] The power generation control unit 150 controls the operation of the injector 94, the compressor 112, the pump 126, the valves, etc. so that the fuel gas and the oxidant gas are supplied to the fuel cell stack 12. As a result, power generation is carried out in the power generation cells 28 inside the fuel cell stack 12.

[0037] The temperature acquisition unit 152 acquires temperature information indicating the stack temperature. The stack temperature is at least one of the temperature detected by the temperature sensor 46 and the temperature detected by the temperature sensor 130. The temperature acquisition unit 152 acquires temperature information indicating the outside air temperature. The outside air temperature is the temperature detected by the outside air temperature sensor 140.

[0038] The history acquisition unit 154 acquires history information 160 stored in the storage unit 138. The history information 160 is information indicating that power generation control (second power generation control) for drying the electrolyte membrane 36 included in the power generation cell 28 has been performed. The second power generation control will be described later.

[0039] The over-dryness determination unit 156 determines whether the power generating cell 28 is in an over-dry state based on the temperature information acquired by the temperature acquisition unit 152 and the history information 160 acquired by the history acquisition unit 154. An over-dry state is a state in which the water content of the electrolyte membrane 36 of the power generating cell 28 is insufficient and the cell is excessively dry.

[0040] The warm-up determination unit 158 ​​determines, based on the temperature information acquired by the temperature acquisition unit 152, whether or not the fuel cell stack 12 is being warmed up.

[0041] The storage unit 138 is configured by a volatile memory (not shown) and a non-volatile memory (not shown) which are computer-readable storage media. The volatile memory is, for example, a random access memory (RAM). The non-volatile memory is, for example, a read only memory (ROM) or a flash memory. Data and the like are stored, for example, in the volatile memory. Programs, tables, maps, and the like are stored, for example, in the non-volatile memory. At least a part of the storage unit 138 may be provided in the above-mentioned processor, integrated circuit, and the like. The storage unit 138 stores programs, history information 160, and the like. The history information 160 is erased from the storage unit 138 when the battery is removed.

[0042] [2 Fluid flow in fuel cell system 10] [2-1 Fluid flow in the anode system 16] The injector 94 is one of the supply devices that supplies reactant gas to the fuel cell stack 12. The injector 94 injects the fuel gas supplied from the tank 14 downstream of the fuel gas supply path 84. The fuel gas injected from the injector 94 is supplied to the fuel gas supply port 12a of the fuel cell stack 12 via the fuel gas supply path 84. The fuel gas that has not reacted inside the fuel cell stack 12 is discharged as fuel off-gas from the fuel gas discharge port 12b of the fuel cell stack 12. The fuel off-gas contains hydrogen that has not reacted with oxygen, nitrogen in the oxidant gas that has permeated the electrolyte membrane 36, and moisture produced by the reaction between oxygen and hydrogen.

[0043] The fuel off-gas is supplied to a gas-liquid separator 98 via a fuel gas discharge passage 86. The gas-liquid separator 98 separates the fuel off-gas into a gas component (fuel off-gas) and a liquid component (water). The fuel off-gas discharged from the gas-liquid separator 98 is supplied to an ejector 96 via a circulation passage 88. The fuel off-gas sucked from the gas-liquid separator 98 and the fuel gas injected from the injector 94 join together in the ejector 96.

[0044] [2-2 Fluid flow in the cathode system 18] The compressor 112 is one of the supply devices that supplies the reactant gas to the fuel cell stack 12. The compressor 112 discharges the oxidant gas (air) sucked in from outside the vehicle downstream of the oxidant gas supply passage 106. The oxidant gas discharged from the compressor 112 is supplied to the oxidant gas supply port 12c of the fuel cell stack 12 via the oxidant gas supply passage 106. The oxidant gas that has not reacted inside the fuel cell stack 12 is discharged as oxidant off-gas from the oxidant gas discharge port 12d of the fuel cell stack 12. The oxidant off-gas contains each component contained in the oxidant gas and moisture produced by the reaction of oxygen and hydrogen.

[0045] The oxidant off-gas is discharged to the diluter 121 through the oxidant gas discharge passage 108. The oxidant off-gas contains moisture. In the humidifier 114, a part of the moisture contained in the oxidant off-gas is used to humidify the oxidant gas flowing through the humidifier supply passage 114A.

[0046] [2-3 Fluid flow in cooling system 20] The pump 126 discharges the coolant toward the coolant supply port 12e of the fuel cell stack 12. The coolant discharged from the pump 126 is supplied to the coolant supply port 12e of the fuel cell stack 12 via the coolant supply path 122. The coolant that has circulated inside the fuel cell stack 12 is discharged from the coolant discharge port 12f of the fuel cell stack 12. The coolant discharged from the coolant discharge port 12f is supplied to the radiator 128 via the coolant discharge path 124. The coolant that has dissipated heat in the radiator 128 reaches the pump 126.

[0047] A part of the coolant discharged from the coolant discharge port 12f flows into the coolant supply path 122 via the branch path 125 without being supplied to the radiator 128. The amount of this flow-in is adjusted according to the opening degree of the branch valve 132.

[0048] [3 Power generation control] The power generation control unit 150 can execute a first power generation control and a second power generation control. The first power generation control is a power generation control for supplying power according to a request to the load 26. The second power generation control is a control for drying the electrolyte membrane 36 provided in the power generation cell 28.

[0049] The power generation control unit 150 executes the first power generation control when it receives a system start-up command, which is a command to start up the fuel cell system 10. The power generation control unit 150 ends the first power generation control when it receives a system stop command, which is a command to stop the fuel cell system 10.

[0050] If the stack temperature or the outside air temperature becomes equal to or lower than a predetermined temperature after receiving a system stop command and before receiving the next system start command, the power generation control unit 150 executes the second power generation control. In other words, if the stack temperature or the outside air temperature does not become equal to or lower than a predetermined temperature after receiving a system stop command and before receiving the next system start command, the second power generation control is not executed. The outside air temperature may be determined based on information acquired by the outside air temperature sensor 140 or the like, but is not limited thereto. The predetermined temperature is selected from a range of, for example, 0°C to 5°C. Note that, if the stack temperature or the outside air temperature is expected to become equal to or lower than a predetermined temperature after receiving a system stop command and before receiving the next system start command, the power generation control unit 150 may execute the second power generation control.

[0051] In the first power generation control, a warm-up process is executed at the time of cold start to warm up the fuel cell stack 12. That is, the warm-up process is executed at the start of the first power generation control when the stack temperature or the outside air temperature becomes equal to or lower than a predetermined temperature. In this case, the power generation control unit 150 controls the injector 94 and the compressor 112 based on the target power value so that the power generated by the power generation cell 28 becomes the target power value set for warming up the fuel cell stack 12.

[0052] When the stack temperature indicated by the temperature information acquired by the temperature acquisition unit 152 reaches or exceeds the target temperature, the power generation control unit 150 ends the warm-up process and executes the power supply process. In this case, the power generation control unit 150 controls the injector 94 and the compressor 112 based on the required power generation so that the power generated by the power generating cell 28 becomes the required power generation. The required power generation is calculated by the power generation control unit 150 based on, for example, the accelerator opening, the vehicle speed, the road gradient, etc.

[0053] If the stack temperature falls below the target temperature during the power supply process, the power generation control unit 150 may interrupt the power supply process and perform a warm-up process. In this case, when the stack temperature reaches or exceeds the target temperature, the power generation control unit 150 ends the warm-up process and resumes the power supply process.

[0054] In the second power generation control, the power generation control unit 150 controls the injector 94 and the compressor 112 so that the stoichiometric ratio of the oxidant gas supplied to the fuel cell stack 12 becomes relatively large (the amount of oxidant increases). That is, the power generation control unit 150 sets the stoichiometric ratio of the oxidant gas in the second power generation control to be larger than the stoichiometric ratio of the oxidant gas in the first power generation control. This makes it possible to increase the efficiency of discharging water retained inside the fuel cell stack 12 to the outside. As a result, the water content of the power generation cell 28 becomes lower. The stoichiometric ratio is the ratio of the oxidant gas to the fuel gas. A larger stoichiometric ratio means that the oxidant gas is increased and the ratio of the oxidant gas increases.

[0055] The humidification amount of the oxidant gas supplied to the fuel cell stack 12 during the second power generation control may be less than the humidification amount of the oxidant gas supplied to the fuel cell stack 12 during the first power generation control. In this case, a humidifier bypass flow path (not shown) is used. The humidifier bypass flow path is a flow path that branches off from the oxidant gas supply path 106A and merges with the oxidant gas supply path 106B without passing through the humidifier 114. During the second power generation control, the power generation control unit 150 controls valves and the like so that the oxidant gas is supplied to the fuel cell stack 12 via this humidifier bypass flow path. On the other hand, during the first power generation control, the power generation control unit 150 controls valves and the like so that the oxidant gas is supplied to the fuel cell stack 12 without passing through the humidifier bypass flow path.

[0056] The power generation control unit 150 ends the second power generation control, for example, when a predetermined time has elapsed since the second power generation control was started. In this case, the power generation control unit 150 stops the injector 94 and the compressor 112. The power generation control unit 150 also generates history information 160 indicating that the second power generation control was performed after receiving a system stop command, and stores the information in the storage unit 138. The history information 160 includes the date and time when the second power generation control was performed, the period, etc. The timing when the second power generation control is performed includes the period from when the system stop command is received until the fuel cell system 10 is stopped, or the period during which the fuel cell system 10 is stopped. In other words, the history information 160 indicates that the second power generation control was performed during the period from when the system stop command is received until the fuel cell system 10 is stopped, or the period during which the fuel cell system 10 is stopped.

[0057] [4 Power Limit Processing] The control device 22 executes a power limiting process in parallel with the first power generation control at the time of system startup (at the time of starting the first power generation control). Fig. 2 is a flowchart showing the procedure of the power limiting process.

[0058] When the control device 22 receives the system startup command, it starts the power limiting process.

[0059] In step S1, the control device 22 compares the stack temperature indicated by the temperature information acquired by the temperature acquisition unit 152 with a first temperature threshold. The first temperature threshold is set to a temperature that is a reference for determining whether or not the environment is a low temperature environment.

[0060] If the stack temperature is less than the first temperature threshold, the power limiting process ends. In this case, the power generation control unit 150 executes low-temperature power generation control (not shown) instead of the first power generation control. On the other hand, if the stack temperature is equal to or greater than the first temperature threshold, the power limiting process proceeds to step S2.

[0061] In step S2, the control device 22 accesses the storage unit 138. If the history information 160 indicating that the second power generation control was performed after the previous system stop command was received is not stored in the storage unit 138, the power limiting process ends. If the history information 160 indicating that the second power generation control was performed after the previous system stop command was received is stored in the storage unit 138, the control device 22 acquires the history information 160. If the history information 160 indicating that the second power generation control was performed after the previous system stop command was received is acquired, the power limiting process proceeds to step S3.

[0062] In step S3, the control device 22 determines that the power generating cell 28 is in an excessively dry state. After that, the power limiting process proceeds to step S4.

[0063] In step S4, the power generation control unit 150 compares the stack temperature with a second temperature threshold. The second temperature threshold is set to a temperature at which a stable state is reached at which rated output (maximum output) can be obtained from the power generation cell 28. The second temperature threshold is higher than the first temperature threshold.

[0064] If the stack temperature is equal to or higher than the second temperature threshold, the warming up of the fuel cell stack 12 by the power generation control unit 150 has been completed. Therefore, the electrolyte membrane 36 of the power generation cells 28 has been sufficiently humidified by the water generated by the reaction during warming up, and the over-dry state of the power generation cells 28 has been resolved. Therefore, the power limiting process ends. On the other hand, if the stack temperature is lower than the second temperature threshold, the warming up of the fuel cell stack 12 by the power generation control unit 150 has not been completed. In a state in which the warming up has not been completed, the electrolyte membrane 36 of the power generation cells 28 has not been sufficiently humidified by the water generated by the reaction during warming up, and the over-dry state of the power generation cells 28 has not been resolved. Therefore, the power limiting process proceeds to step S5.

[0065] In step S5, the control device 22 limits the power generated by the power generating cells 28. In this case, the power generation control unit 150 limits the supply (output) of the generated power to the load 26 to a predetermined power threshold or less. In other words, even if power exceeding the power threshold is requested, the power generation control unit 150 limits the power supplied to the load 26 to the power threshold or less. Thereafter, the power limiting process returns to step S4. Note that the control device 22 continues to limit the power generated by the power generating cells 28 until the stack temperature becomes equal to or higher than the second temperature threshold in step S4.

[0066] [5. Effects of the above embodiment] As described above, when the over-dryness determination unit 156 determines that the power generating cell 28 is in an over-dry state, the power generation control unit 150 limits the power generation power of the power generating cell 28 when the first power generation control is started. This makes it possible to stabilize the power generation of the power generating cell 28 even if the power generating cell 28 is in an over-dry state. As a result, it is possible to avoid constantly performing low-temperature power generation control when the system is started up immediately after the second power generation control is performed.

[0067] In the above embodiment, when the over-dryness determination unit 156 determines that the power generating cells 28 are in an over-dry state and the warm-up determination unit 158 ​​determines that the warm-up of the fuel cell stack 12 has not been completed, the power generation control unit 150 limits the power generation of the power generating cells 28 during warm-up. This makes it possible to prevent the limit on the power generation from being lifted even if the over-dryness of the power generating cells 28 has been resolved by water generated in response to power generation during warm-up. As a result, the power generation efficiency of the power generating cells 28 can be improved.

[0068] [6 Modifications of the above embodiment] The above embodiment may be modified as follows.

[0069] (Variation 1) Fig. 3 is a schematic diagram of a fuel cell system 10 according to Modification 1. In Fig. 3, the same components as those described in the embodiment are denoted by the same reference numerals. Note that in this modification, descriptions that overlap with the embodiment will be omitted.

[0070] In this modification, the control device 22 further includes an information acquisition unit 162. The information acquisition unit 162 acquires moisture information indicating a value corresponding to the moisture content of the power generating cell 28. The overdryness determination unit 156 determines whether the power generating cell 28 is in an overdry state based on the moisture information in addition to the history information 160 and temperature information. This can improve the accuracy of the determination compared to the case where whether the power generating cell 28 is in an overdry state is determined based only on the history information 160 and temperature information.

[0071] The value according to the water content of the power generating cells 28 is, for example, the impedance (AC impedance) of the entirety of the power generating cells 28 provided in the fuel cell stack 12, but is not limited to this.

[0072] When the value according to the water content of the power generating cell 28 is the AC impedance, the information acquiring unit 162 can acquire the AC impedance from an impedance sensor that detects the AC impedance.

[0073] When the AC impedance is a value corresponding to the moisture content of the power generating cells 28, the over-dryness determination unit 156 can determine whether or not the power generating cells 28 are in an over-dry state, for example, as follows. That is, when the stack temperature is less than the first temperature threshold or the history information 160 cannot be acquired from the storage unit 138, the control device 22 determines that the power generating cells 28 are not in an over-dry state. On the other hand, when the stack temperature is less than the first temperature threshold or the history information 160 cannot be acquired from the storage unit 138, the control device 22 compares the AC impedance indicated by the moisture information acquired by the information acquisition unit 162 with a predetermined impedance threshold.

[0074] There is a correlation between the AC impedance and the water content of the power generating cell 28. This correlation indicates that the greater the water content of the power generating cell 28, the lower the AC impedance.

[0075] When the AC impedance exceeds the impedance threshold, the over-dryness determining unit 156 determines that the power generating cell 28 is not in an over-dry state. On the other hand, when the AC impedance is equal to or less than the impedance threshold, the over-dryness determining unit 156 determines that the power generating cell 28 is in an over-dry state.

[0076] (Variation 2) The warm-up determination unit 158 ​​may determine whether or not the fuel cell stack 12 is being warmed up based on the time since receiving the system startup command. That is, if a predetermined time has not elapsed since receiving the system startup command, the warm-up determination unit 158 ​​determines that the fuel cell stack 12 is being warmed up. On the other hand, if a predetermined time has elapsed since receiving the system startup command, the warm-up determination unit 158 ​​determines that the fuel cell stack 12 is not being warmed up.

[0077] (Variation 3) When the control device 22 determines that the power generating cells 28 are in an excessively dry state, the control device 22 may limit the power generated by the power generating cells 28 without determining whether the fuel cell stack 12 is being warmed up.

[0078] (Variation 4) The power generation control unit 150 may vary the limit on the power generation of the power generating cells 28 based on the stack temperature. In this case, the power generation control unit 150 reduces the limit on the power generation as the stack temperature increases. In this way, the power generation efficiency of the power generating cells 28 can be improved.

[0079] [7 Notes] In addition to the above disclosure, the following notes are also disclosed.

[0080] (Appendix 1) The present disclosure relates to a control device (22) provided in a fuel cell system (10) having a fuel cell stack (12) including a power generation cell (28) and a power generation control unit (150) that controls power generation of the power generation cell, the power generation control unit being capable of executing a first power generation control and a second power generation control different from the first power generation control, the second power generation control being a power generation control for drying an electrolyte membrane (36) provided in the power generation cell after receiving a system stop command to stop the fuel cell system, the control device further comprising a temperature acquisition unit (152) that acquires temperature information indicating a stack temperature, which is the temperature of the fuel cell stack, a history acquisition unit (154) that acquires history information (160) indicating that the second power generation control was performed after receiving the previous system stop command, and an over-dryness determination unit (156) that determines whether the power generation cell is in an over-dry state based on the history information and the temperature information, and if it is determined by the over-dryness determination unit that the power generation cell is in an over-dry state, the power generation control unit limits the power generation power of the power generation cell when the first power generation control is started.

[0081] According to the above, power generation of the power generating cell can be stabilized even if the power generating cell is in an excessively dry state, and as a result, malfunction of the load caused by unstable output of the power generating cell can be prevented in advance.

[0082] (Appendix 2) In the control device described in Appendix 1, the first power generation control includes warming up the fuel cell stack, and the control device further includes a warm-up determination unit (158) that determines whether the warm-up has been completed, and when the over-dryness determination unit determines that the power generation cell is in an over-dry state and the warm-up determination unit determines that the warm-up has not been completed, the power generation control unit may limit the power generation power of the power generation cell during the warm-up.

[0083] According to the above, it is possible to prevent the generated power from being limited even though the excessively dry state of the power generating cells has been eliminated due to water produced in response to power generation during warm-up, thereby improving the power generation efficiency of the power generating cells.

[0084] (Appendix 3) In the control device described in Appendix 2, the over-dryness determination unit may determine that the power generation cell is in an over-dry state when the temperature information is equal to or greater than a predetermined first temperature threshold and the history acquisition unit has acquired the history information indicating that the second power generation control was performed after the previous system stop command was received, and the warm-up determination unit may determine that the warm-up has not been completed when the temperature information is less than a predetermined second temperature threshold.

[0085] (Appendix 4) In the control device described in Appendix 1, the first power generation control includes a warm-up process for warming up the fuel cell stack, and the control device further includes a warm-up determination unit that determines whether the temperature information has become equal to or higher than a predetermined temperature as a result of the warm-up process, and when the over-dryness determination unit determines that the power generation cell is in an over-dry state and the warm-up determination unit determines that the temperature information has not become equal to or higher than the predetermined temperature, the power generation control unit may limit the power generation power of the power generation cell during the warm-up.

[0086] According to the above, it is possible to prevent the generated power from being limited even though the excessively dry state of the power generating cells has been eliminated due to water produced in response to power generation during warm-up, thereby improving the power generation efficiency of the power generating cells.

[0087] (Appendix 5) In the control device described in Appendix 4, the over-dryness determination unit may determine that the power generation cell is in an over-dry state when the temperature information is equal to or greater than a predetermined first temperature threshold and the history acquisition unit has acquired the history information indicating that the second power generation control was performed during the period from when the previous system stop command was received until the fuel cell system was stopped or during the period when the fuel cell system is stopped, and the warm-up determination unit may determine that the warm-up has not been completed when the temperature information is less than a predetermined second temperature threshold.

[0088] (Appendix 6) In the control device described in any one of Supplementary Notes 1 to 5, the control device may further include an information acquisition unit (162) that acquires moisture information indicating a value corresponding to the moisture content of the power generating cell, and the over-dryness determination unit may determine whether or not the power generating cell is in an over-dry state based on the history information, the temperature information, and the moisture information.

[0089] Based on the above, it is possible to improve the accuracy of the determination as compared with the case where whether or not the state is excessively dry is determined based on the history information and the temperature information.

[0090] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention. [Explanation of symbols]

[0091] 10...Fuel cell system 12...Fuel cell stack 20...cooling system 22...control device 28...Power generation cell 36...Electrolyte membrane 150... power generation control unit 152... temperature acquisition unit 154... history acquisition unit 156... overdrying determination unit 158... Warm-up determination unit 160... History information 162…Information acquisition department

Claims

1. A control device provided in a fuel cell system having a fuel cell stack including a power generation cell and a power generation control unit that controls power generation of the power generation cell, the power generation control unit is capable of executing a first power generation control and a second power generation control different from the first power generation control, the second power generation control is power generation control for drying an electrolyte membrane provided in the power generation cell after receiving a system stop command for stopping the fuel cell system, The control device includes: a temperature acquisition unit that acquires temperature information indicating a stack temperature, which is the temperature of the fuel cell stack; a history acquisition unit that acquires history information indicating that the second power generation control has been performed after receiving the previous system stop command; an excessively dry determination unit that determines whether the power generating cell is in an excessively dry state based on the history information and the temperature information; Further comprising: A control device, wherein when the excessively dry determining unit determines that the power generating cell is in an excessively dry state, the power generation control unit limits the power generation electric power of the power generating cell at the start of the first power generation control.

2. The control device according to claim 1 , the first power generation control includes warming up the fuel cell stack, The control device further includes a warm-up determination unit that determines whether the warm-up has been completed, A control device, wherein when the over-dryness determination unit determines that the power generation cell is in an over-dry state and the warm-up determination unit determines that the warm-up has not been completed, the power generation control unit limits the power generation power of the power generation cell during the warm-up.

3. The control device according to claim 2, the excessively dry determination unit determines that the power generating cell is in an excessively dry state when the temperature information is equal to or greater than a predetermined first temperature threshold and the history acquisition unit has acquired the history information indicating that the second power generation control was performed after the previous system stop command was received, The warm-up determination unit determines that the warm-up has not been completed when the temperature information is less than a predetermined second temperature threshold.

4. The control device according to claim 1 , the first power generation control includes a warm-up process for warming up the fuel cell stack, The control device further includes a warm-up determination unit that determines whether the temperature information has become equal to or higher than a predetermined temperature as a result of the warm-up process, A control device, wherein when the over-dryness determination unit determines that the power generation cell is in an over-dry state and the warm-up determination unit determines that the temperature information is not above the specified temperature, the power generation control unit limits the power generation power of the power generation cell during the warm-up.

5. The control device according to claim 4, the over-dryness determination unit determines that the power generating cell is in an over-dry state when the temperature information is equal to or greater than a predetermined first temperature threshold and the history acquisition unit has acquired the history information indicating that the second power generation control was performed during the period from when the previous system stop command was received until the fuel cell system was stopped or during the period when the fuel cell system is stopped; The warm-up determination unit determines that the warm-up has not been completed when the temperature information is less than a predetermined second temperature threshold.

6. The control device according to any one of claims 1 to 5, the control device further includes an information acquisition unit that acquires moisture information indicating a value corresponding to a moisture content of the power generating cell, The over-dryness determining unit determines whether or not the power generating cell is in an over-dry state based on the history information, the temperature information, and the moisture information.

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