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 Art

[0002] In recent years, in order for more people to have access to affordable, reliable, sustainable, and advanced energy, research and development on fuel cells that contribute to energy efficiency have been carried out.

[0003] A system equipped with a fuel cell stack is called a fuel cell system. The fuel cell stack includes a plurality of power generation cells. The power generation cells generate electricity through an electrochemical reaction between a fuel gas (hydrogen-containing gas) and an oxidant gas (oxygen-containing gas). Water is generated during power generation by the power generation cells. A part of the generated water stays inside the fuel cell stack. When the operation of the fuel cell system is stopped in a low-temperature environment, the water staying inside the fuel cell stack may freeze. When water freezes in a fuel cell system or the like, the gas flow is obstructed, so that the fuel cell stack cannot generate electricity.

[0004] Patent Document 1 discloses a method for stopping a fuel cell system that, in order to promote drying of a membrane electrode assembly (MEA) of a power generation cell, after an ignition switch is turned off, performs a drainage power generation process after performing a drying power generation process. The amount of humidification of the oxidant gas supplied to the fuel cell stack during the drying power generation process is determined to be less than the amount of humidification of the oxidant gas supplied to the fuel cell stack during the drainage power generation process.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] There is a long-felt need for a technology that can enable a power generation cell to generate power well.

[0007] An object of the present invention is to solve the above-described problems.

Means for Solving the Problems

[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 performs power generation control of the power generation cell, wherein the power generation control unit can execute 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 a 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, and the control device further includes a temperature acquisition unit that acquires temperature information indicating a stack temperature that 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 the previous system stop command was received, and an overdrying determination unit that determines whether or not the power generation cell is in an overdried state based on the history information and the temperature information. When the overdrying determination unit determines that the power generation cell is in an overdried state, the power generation control unit restricts the power generation power of the power generation cell at the start of the first power generation control.

Advantages of the Invention

[0009] According to the present invention, it becomes possible to enable a power generation cell to generate power well.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] [Configuration of Fuel Cell System 10] FIG. 1 is a schematic configuration 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 bodies such as ships, aircraft, and robots. Further, the fuel cell system 10 can also be used as a stationary power source in facilities, homes, etc.

[0012] In the fuel cell system 10, a fuel gas and an oxidant gas are used as reaction 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 used for an electrochemical reaction. In this specification, the fuel gas discharged from the fuel cell stack 12 without being used for the electrochemical reaction is also referred to as fuel off-gas. Also, in this specification, the oxidant gas discharged from the fuel cell stack 12 without being used for 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. The 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 the 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 for supplying fuel gas to the inside of the fuel cell stack 12, and a fuel gas discharge port 12b for discharging fuel off-gas from the inside of the fuel cell stack 12. The fuel cell stack 12 includes an oxidant gas supply port 12c for supplying oxidant gas to the inside of the fuel cell stack 12, and an oxidant gas discharge port 12d for discharging oxidant off-gas from the inside of the fuel cell stack 12. The fuel cell stack 12 includes a refrigerant supply port 12e for supplying refrigerant to the inside of the fuel cell stack 12, and a refrigerant discharge port 12f for discharging refrigerant from the inside of the fuel cell stack 12.

[0015] The fuel cell stack 12 has a plurality of power generation cells 28. The plurality of power generation cells 28 each have an equivalent configuration. The power generation cell 28 includes an electrolyte membrane - electrode structure 30, a first separator 32, and a second separator 34. The electrolyte membrane - electrode structure 30 is sandwiched between the first separator 32 and the second separator 34. One of the plurality of power generation cells 28 is illustrated in FIG. 1.

[0016] The first separator 32 and the second separator 34 are formed of a corrugated thin metal plate. In two adjacent power generation cells 28, the first separator 32 of one power generation cell 28 and the second separator 34 of the other power generation 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 a refrigerant supply port 12e and a refrigerant discharge port 12f.

[0017] The electrolyte membrane - electrode structure 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 a fuel gas supply port 12a and a fuel gas discharge port 12b. The cathode flow path 44 communicates with an oxidant gas supply port 12c and an 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 a fuel gas discharge passage 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 an oxidant gas discharge passage 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 the oxidant gas (gas temperature) near the discharge port of the fuel cell stack 12 becomes the representative temperature of the fuel cell stack 12. That is, 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 drainage 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 passage 84 is connected to the discharge port of the tank 14 and the fuel gas supply port 12a of the fuel cell stack 12. The fuel gas supply passage 84 is provided with an injector 94 and an ejector 96. The ejector 96 is arranged closer to the fuel cell stack 12 than the injector 94.

[0021] The fuel gas discharge passage 86 is connected to the fuel gas discharge port 12b of the fuel cell stack 12 and the supply port of the gas-liquid separator 98. The circulation passage 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 drainage port of the gas-liquid separator 98 and the inlet of the diluter 121. The outlet of the diluter 121 is connected to an exhaust 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 passage 106, an oxidant gas discharge passage 108 (discharge passage), and a bypass passage 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 oxidant gas supply passage 106 is connected to an air intake port provided in the vehicle and an oxidant gas supply port 12c of the fuel cell stack 12. The oxidant gas supply passage 106 includes the compressor 112, the first shutoff valve 116, and a humidifier supply passage 114A of the humidifier 114. A portion of the oxidant gas supply passage 106 disposed upstream of the humidifier 114 is referred to as an oxidant gas supply passage 106A. A portion of the oxidant gas supply passage 106 disposed downstream of the humidifier 114 is referred to as an oxidant gas supply passage 106B. The oxidant gas supply passage 106A includes the compressor 112 and the first shutoff valve 116. The first shutoff valve 116 is disposed closer to the humidifier 114 than the compressor 112.

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

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

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

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

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

[0030] The temperature sensor 130 is provided in the refrigerant discharge path 124. The temperature sensor 130 may be provided in the refrigerant supply path 122. The temperature sensor 130 detects the temperature of the refrigerant (refrigerant temperature). The refrigerant 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, on the body of the fuel cell vehicle. The outside air temperature sensor 140 detects the temperature of 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 control valve 132 is provided at the confluence where the flow path 125 merges into the refrigerant supply path 122. Note that the flow control valve 132 may be provided at the branch where the flow path 125 branches off from the refrigerant discharge path 124. The flow control valve 132 is capable of adjusting its opening degree. The amount of refrigerant supplied to the radiator 128 is adjusted according to the opening degree of the flow control valve 132. The opening degree of the flow control valve 132 is controlled by the control device 22.

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

[0033] The arithmetic unit 136 is, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The arithmetic unit 136 includes a power generation control unit 150, a temperature acquisition unit 152, a history acquisition unit 154, an over-drying 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 over-drying determination unit 156, and the warm-up determination unit 158 operate when a program stored in the storage unit 138 is executed by the arithmetic unit 136.

[0034] Note that at least one of the power generation control unit 150, the temperature acquisition unit 152, the history acquisition unit 154, the over-drying 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 over-drying determination unit 156, and the warm-up determination unit 158 may be realized by an electronic circuit including discrete devices.

[0035] The storage unit 138 is a computer-readable storage medium, and the storage unit 138 includes a volatile memory and a non-volatile memory. The volatile memory is, for example, RAM (Random Access Memory) or the like. The non-volatile memory is, for example, ROM (Read Only Memory), flash memory, or the like. 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-described processor, integrated circuit, or the like.

[0036] The power generation control unit 150 controls the operations of the injector 94, the compressor 112, the pump 126, each valve, etc. so that the fuel gas and the oxidant gas are supplied to the fuel cell stack 12. Thereby, power generation is performed in the power generation cell 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 the 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 provided in the power generation cell 28 has been performed. The second power generation control will be described later.

[0039] The over-drying determination unit 156 determines whether or not the power generation cell 28 is in an over-dried 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. The over-dried state is a state in which the water content of the electrolyte membrane 36 of the power generation cell 28 is insufficient and the membrane is excessively dried.

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

[0041] The storage unit 138 is composed of 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 RAM (Random Access Memory) or the like. The non-volatile memory is, for example, a ROM (Read Only Memory), a flash memory, or the like. Data and the like are stored in the volatile memory, for example. Programs, tables, maps, and the like are stored in the non-volatile memory, for example. At least a part of the storage unit 138 may be provided in the above-described processor, integrated circuit, or the like. A program, history information 160, and the like are stored in the storage unit 138. The history information 160 is erased from the storage unit 138 when the battery is removed.

[0042] [Fluid flow in the fuel cell system 10] [Fluid flow in the anode system 16] The injector 94 is one of the supply devices that supply the reaction 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 passage 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 passage 84. The fuel gas that did not react 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 did not react with oxygen, nitrogen in the oxidant gas that permeated through the electrolyte membrane 36, and moisture generated by the reaction of oxygen and hydrogen.

[0043] The fuel off-gas is supplied to the gas-liquid separator 98 via the 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 the ejector 96 via the circulation passage 88. The fuel off-gas sucked from the gas-liquid separator 98 and the fuel gas injected from the injector 94 merge in the ejector 96.

[0044] [Fluid flow in the cathode system 18 of [2-2]] The compressor 112 is one of the supply devices that supplies the reaction gas to the fuel cell stack 12. The compressor 112 discharges the oxidant gas (air) sucked 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 generated by the reaction of oxygen and hydrogen.

[0045] The oxidant off-gas is discharged to the diluter 121 via 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] [Fluid flow in the cooling system 20 of [2-3]] The pump 126 discharges the refrigerant toward the refrigerant supply port 12e of the fuel cell stack 12. The refrigerant discharged from the pump 126 is supplied to the refrigerant supply port 12e of the fuel cell stack 12 via the refrigerant supply passage 122. The refrigerant that has flowed through the inside of the fuel cell stack 12 is discharged from the refrigerant discharge port 12f of the fuel cell stack 12. The refrigerant discharged from the refrigerant discharge port 12f is supplied to the radiator 128 via the refrigerant discharge passage 124. The refrigerant that has dissipated heat in the radiator 128 reaches the pump 126.

[0047] Note that a part of the refrigerant discharged from the refrigerant discharge port 12f flows into the refrigerant supply path 122 via the shunt path 125 without being supplied to the radiator 128. This inflow amount is adjusted according to the opening degree of the shunt valve 132.

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

[0049] When the power generation control unit 150 receives a system start command which is a command for starting the fuel cell system 10, it executes the first power generation control. When the power generation control unit 150 receives a system stop command which is a command for stopping the fuel cell system 10, it terminates the first power generation control.

[0050] After receiving the system stop command, when the stack temperature or the outside air temperature becomes equal to or lower than a predetermined temperature before receiving the next system start command, the power generation control unit 150 executes the second power generation control. In other words, after receiving the system stop command, if the stack temperature or the outside air temperature does not become equal to or lower than the predetermined temperature before receiving the next system start command, the second power generation control is not executed. The outside air temperature can be determined based on information obtained by the outside air temperature sensor 140 or the like, but is not limited thereto. The predetermined temperature is selected from, for example, the range of 0°C to 5°C. Note that when it is expected that the stack temperature or the outside air temperature will become equal to or lower than the predetermined temperature after receiving the 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 for warming up the fuel cell stack 12 is executed during cold start. 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 generation power of 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 becomes equal to or higher than 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 power so that the power generation power of the power generation cell 28 becomes the required power generation power. The required power generation power is calculated by the power generation control unit 150 based on, for example, the accelerator opening degree, the vehicle speed, the road gradient, etc.

[0053] Note that when the stack temperature becomes lower than the target temperature during the power supply process, the power generation control unit 150 may interrupt the power supply process and perform the warm-up process. In this case, when the stack temperature becomes equal to or higher than 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 oxidant increases). That is, the power generation control unit 150 sets the stoichiometric ratio of the oxidant gas during the second power generation control to be larger than the stoichiometric ratio of the oxidant gas during the first power generation control. Thereby, the efficiency of discharging the water remaining inside the fuel cell stack 12 to the outside can be increased. As a result, the water content of the power generation cell 28 becomes low. Note that the stoichiometric ratio is the ratio of the oxidant gas to the fuel gas. An increase in the stoichiometric ratio means an increase in the oxidant gas and an increase in the ratio of the oxidant gas.

[0055] Note that the amount of humidification of the oxidant gas supplied to the fuel cell stack 12 during the second power generation control may be less than the amount of humidification 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 from the oxidant gas supply path 106A and merges into the oxidant gas supply path 106B without passing through the humidifier 114. In the second power generation control, the power generation control unit 150 controls a valve or the like so that the oxidant gas is supplied to the fuel cell stack 12 through this humidifier bypass flow path. On the other hand, in the first power generation control, the power generation control unit 150 controls a valve or the like so that the oxidant gas is supplied to the fuel cell stack 12 without passing through the humidifier bypass flow path.

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

[0057] [4 Power Limitation Process] When the system is started (when the first power generation control is started), the control device 22 executes a power limitation process in parallel with the first power generation control. FIG. 2 is a flowchart showing the procedure of the power limitation process.

[0058] When the control device 22 receives a system start command, it starts the power limitation 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 serves as a criterion for whether it is a low-temperature environment or not.

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

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

[0062] In step S3, the control device 22 determines that the fuel cell 28 is in an over-dried state. Thereafter, the power limit 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 or the like when the fuel cell 28 reaches a stable state where it is possible to obtain the rated output (maximum output). The second temperature threshold is higher than the first temperature threshold.

[0064] When the stack temperature is equal to or higher than the second temperature threshold, the warm-up of the fuel cell stack 12 by the power generation control unit 150 is completed. Therefore, the electrolyte membrane 36 of the power generation cell 28 is sufficiently humidified by the reaction-generated water during warm-up, and the overdried state of the power generation cell 28 is eliminated. Accordingly, the power limit process ends. On the other hand, when the stack temperature is lower than the second temperature threshold, the warm-up of the fuel cell stack 12 by the power generation control unit 150 is not completed. In a state where the warm-up is not completed, the electrolyte membrane 36 of the power generation cell 28 is not sufficiently humidified by the reaction-generated water during warm-up, and the overdried state of the power generation cell 28 is not eliminated. Accordingly, the power limit process proceeds to step S5.

[0065] In step S5, the control device 22 restricts the power generation power of the power generation cell 28. In this case, the power generation control unit 150 suppresses the supply (output) of the power generation power to the load 26 to be equal to or lower than a predetermined power threshold. In other words, even if power exceeding the power threshold is requested, the power generation control unit 150 suppresses the power supplied to the load 26 to be equal to or lower than the power threshold. Thereafter, the power limit process returns to step S4. Note that the control device 22 continues to restrict the power generation power of the power generation cell 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 it is determined by the overdrying determination unit 156 that the power generation cell 28 is in an overdried state, the power generation control unit 150 restricts the power generation power of the power generation cell 28 at the start of the first power generation control. Thereby, even if the power generation cell 28 is in an overdried state, the power generation of the power generation cell 28 can be stabilized. As a result, it is possible to avoid always performing the low-temperature power generation control at the time of system startup immediately after the second power generation control is performed.

[0067] In the above embodiment, when it is determined by the overdrying determination unit 156 that the power generation cell 28 is in an overdried state and it is determined by the warm-up determination unit 158 that the warm-up of the fuel cell stack 12 has not been completed, the power generation control unit 150 restricts the power generation power of the power generation cell 28 during warm-up. Thereby, even though the overdried state of the power generation cell 28 has been eliminated by the water generated in response to power generation during warm-up, it is possible to suppress the release of the restriction on the power generation power. As a result, the power generation efficiency of the power generation cell 28 can be increased.

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

[0069] (Modification Example 1) FIG. 3 is a schematic configuration diagram of the fuel cell system 10 according to Modification Example 1. In FIG. 3, the same reference numerals are given to the configurations equivalent to those described in the embodiment. In this modification example, the description overlapping with the embodiment is omitted.

[0070] In this modification example, 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 water content of the power generation cell 28. The overdrying determination unit 156 determines whether or not the power generation cell 28 is in an overdried state based on the moisture information in addition to the history information 160 and the temperature information. Thereby, the determination accuracy can be improved as compared with the case where it is determined whether or not it is in an overdried state only based on the history information 160 and the temperature information.

[0071] Note that the value corresponding to the water content of the power generation cell 28 is, for example, the impedance (AC impedance) of the plurality of power generation cells 28 provided in the fuel cell stack 12, but is not limited thereto.

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

[0073] When the value corresponding to the water content of the power generation cell 28 is the AC impedance, the overdrying determination unit 156 can determine whether the power generation cell 28 is in an overdried 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 obtained from the storage unit 138, the control device 22 determines that the power generation cell 28 is not in an overdried state. On the other hand, when the stack temperature is less than the first temperature threshold or the history information 160 cannot be obtained 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 generation cell 28. This correlation is such that as the water content of the power generation cell 28 increases, the AC impedance decreases.

[0075] When the AC impedance exceeds the impedance threshold, the overdrying determination unit 156 determines that the power generation cell 28 is not in an overdried state. In contrast, when the AC impedance is less than or equal to the impedance threshold, the overdrying determination unit 156 determines that the power generation cell 28 is in an overdried state.

[0076] (Modification 2) The warm-up determination unit 158 may determine whether the fuel cell stack 12 is being warmed up based on the time elapsed since receiving the system startup command. That is, when the 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, when the 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] (Modification 3) When the control device 22 determines that the power generation cell 28 is in an overdried state, it may limit the power generation power of the power generation cell 28 without determining whether the fuel cell stack 12 is being warmed up.

[0078] (Modification 4) The power generation control unit 150 may vary the limit on the power generation amount of the power generation cell 28 based on the stack temperature. In this case, the higher the stack temperature, the smaller the limit on the power generation amount that the power generation control unit 150 sets. By doing so, the power generation efficiency of the power generation cell 28 can be increased.

[0079] [7 Addendum] Regarding the above disclosure, the following addendum is further disclosed.

[0080] (Addendum 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 the power generation of the power generation cell. The power generation control unit is capable of executing first power generation control and 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 (36) provided in the power generation cell after receiving a system stop command for stopping the fuel cell system. The control device further includes a temperature acquisition unit (152) that acquires temperature information indicating the stack temperature, which is the temperature of the fuel cell stack, and a history acquisition unit (154) that acquires history information (160) indicating that the second power generation control was performed after the previous system stop command was received. Based on the history information and the temperature information, the control device further includes an overdrying determination unit (156) that determines whether the power generation cell is in an overdried state. When the overdrying determination unit determines that the power generation cell is in an overdried state, the power generation control unit restricts the power generation amount of the power generation cell at the start of the first power generation control.

[0081] According to the above, even when the power generation cell is in an overdried state, the power generation of the power generation cell can be stabilized. As a result, it is possible to prevent a malfunction of a load due to unstable output of the power generation cell.

[0082] (Addendum 2) The control device according to Supplementary Note 1, wherein the first power generation control includes warm-up of the fuel cell stack, and the control device further includes a warm-up determination unit (158) that determines whether or not the warm-up has ended. When the dry-out determination unit determines that the power generation cell is in a state of over-drying and the warm-up determination unit determines that the warm-up has not ended, 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 suppress the power generation power from being limited even though the over-dried state of the power generation cell has been eliminated by the water generated in response to power generation during warm-up. As a result, the power generation efficiency of the power generation cell can be increased.

[0084] (Supplementary Note 3) The control device according to Supplementary Note 2, wherein the over-drying determination unit determines that the power generation cell is in an over-dried state when the temperature information is equal to or higher than a predetermined first temperature threshold value and the history acquisition unit acquires the history information indicating that the second power generation control has been performed after receiving the previous system stop command. The warm-up determination unit may determine that the warm-up has not ended when the temperature information is less than a predetermined second temperature threshold value.

[0085] (Supplementary Note 4) The control device according to Supplementary Note 1, wherein 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 or not the temperature information has reached a predetermined temperature by the warm-up process. When the dry-out determination unit determines that the power generation cell is in a state of over-drying and the warm-up determination unit determines that the temperature information has not reached 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 suppress the power generation power from being limited even though the over-dried state of the power generation cell has been eliminated by the water generated in response to power generation during warm-up. As a result, the power generation efficiency of the power generation cell can be increased.

[0087] (Appendix 5) The control device according to Appendix 4, wherein the over-drying determination unit determines that the temperature information is equal to or higher than a predetermined first temperature threshold value, and during the period from when the previous system stop command was received until the fuel cell system stops, or when the history information indicating that the second power generation control was performed during the period when the fuel cell system is stopped is acquired by the history acquisition unit, it is determined that the fuel cell is in an over-dried state, and the warm-up determination unit may determine that the warm-up has not ended when the temperature information is less than a predetermined second temperature threshold value.

[0088] (Appendix 6) The control device according to any one of Appendices 1 to 5, further comprising an information acquisition unit (162) that acquires moisture information indicating a value corresponding to the water content of the fuel cell, and the over-drying determination unit may determine whether the fuel cell is in an over-dried state based on the history information, the temperature information, and the moisture information.

[0089] According to the above, the determination accuracy can be improved compared to the case of determining whether it is in an over-dried state based on the history information and the temperature information.

[0090] Note that the present invention is not limited to the above-described disclosure, and various configurations can be adopted without departing from the gist of the present invention.

Explanation of Reference Numerals

[0091] 10... Fuel cell system 12... Fuel cell stack 20... Cooling system 22... Control device 28... Fuel cell 36... Electrolyte membrane 150... Power generation control unit 152... Temperature acquisition unit 154... History acquisition unit 156... Over-drying determination unit 158... Warm-up determination unit 160... History information 162... Information acquisition unit

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 performs power generation control of the power generation cell, wherein the power generation control unit is capable of executing first power generation control and 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 that 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, an overdrying determination unit that determines whether or not the power generation cell is in an overdried state based on the history information and the temperature information, and further includes, when it is determined by the overdrying determination unit that the power generation cell is in an overdried state, the power generation control unit restricts the power generation power of the power generation cell at the start of the first power generation control.

2. The control device according to claim 1, wherein 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 or not the warm-up has ended, when it is determined by the overdrying determination unit that the power generation cell is in an overdried state and it is determined by the warm-up determination unit that the warm-up has not ended, the power generation control unit restricts the power generation power of the power generation cell during the warm-up.

3. The control device according to claim 2, the overdrying determination unit determines that the power generation cell is in an overdried state when the temperature information is equal to or higher than a predetermined first temperature threshold value and the history information indicating that the second power generation control was performed after receiving the previous system stop command is acquired by the history acquisition unit, the warm-up determination unit determines that the warm-up has not ended when the temperature information is less than a predetermined second temperature threshold value.

4. The control device according to claim 1, wherein 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 or not the temperature information has become equal to or higher than a predetermined temperature by the warm-up process. When it is determined by the overdrying determination unit that the power generation cell is in an overdried state and it is determined by the warm-up determination unit that the temperature information is not equal to or higher than the predetermined temperature, the power generation control unit limits the power generation power of the power generation cell during warm-up. A control device.

5. The control device according to claim 4, wherein the overdrying determination unit determines that the power generation cell is in an overdried state when the temperature information is equal to or higher than a predetermined first temperature threshold and during the period from when the previous system stop command is received until the fuel cell system stops, or when the history information indicating that the second power generation control has been performed during the period when the fuel cell system is stopped is acquired by the history acquisition unit. The warm-up determination unit determines that the warm-up has not ended when the temperature information is less than a predetermined second temperature threshold. A control device.

6. The control device according to any one of claims 1 to 5, wherein the control device further includes an information acquisition unit that acquires moisture information indicating a value corresponding to the water content of the power generation cell. The overdrying determination unit determines whether or not the power generation cell is in an overdried state based on the history information, the temperature information, and the moisture information. A control device.

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