Control device

Abstract

The invention provides a control device. In a control device (22), when an over-dry determination unit (156) determines that a power generation battery (28) is in an over-dry state, a power generation control unit (150) limits the power generated by the power generation battery (28) when first power generation control is started. Therefore, the power generation battery can generate power efficiently.

Description

Technical Field

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

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

[0003] A system having a fuel cell stack is called a fuel cell system. A fuel cell stack has a plurality of power generation cells. The power generation cell generates electricity through an electrochemical reaction between a fuel gas (hydrogen-containing gas) and an oxidant gas (oxygen-containing gas). Water is generated when the power generation cell generates electricity. A portion of the generated water is retained inside the fuel cell stack. When the operation of the fuel cell system is stopped in a low temperature environment, the water retained inside the fuel cell stack may freeze. When water freezes in a fuel cell system, etc., the flow of gas is hindered, so that the fuel cell stack cannot generate electricity.

[0004] Japanese Patent Publication No. 2016-058188 discloses a method for stopping a fuel cell system, in which, in order to promote the drying of a membrane electrode assembly (MEA) of a power generation cell, a dry power generation process is performed when an ignition switch is turned off, and then a drain power generation process is performed. The humidification amount of the oxidant gas supplied to the fuel cell stack during the dry power generation process is set to be less than the humidification amount of the oxidant gas supplied to the fuel cell stack during the drain power generation process. Summary of the invention

[0005] A technology that enables power generation cells to generate electricity efficiently is desired.

[0006] The purpose of the present invention is to solve the above-mentioned technical problems.

[0007] The present invention is a control device, which is arranged in a fuel cell system, wherein the fuel cell system has a fuel cell stack and a power generation control unit, wherein the fuel cell stack includes a power generation cell; the power generation control unit performs power generation control 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, wherein the second power generation control is a power generation control for drying an electrolyte membrane possessed by the power generation cell after receiving a system stop command for stopping the fuel cell system, and the control device also has a temperature acquisition unit, a history acquisition unit, and an overdrying determination unit, wherein the temperature acquisition unit acquires temperature information indicating the temperature of the fuel cell stack, i.e., the stack temperature; the history acquisition unit acquires history information indicating that the second power generation control was performed after receiving the last system stop command; the overdrying determination unit determines whether the power generation cell is in an overdry state based on the history information and the temperature information, and when the overdrying determination unit determines that the power generation cell is in an overdry state, the power generation control unit limits the power generation power (power generation cell output power) of the power generation cell when the first power generation control is started.

[0008] According to the present invention, it is possible to enable a power generation cell to generate power efficiently.

[0009] The above-mentioned objects, features and advantages will be easily understood through the following description of the embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram of the fuel cell system.

[0011] Figure 2 This is a flowchart showing the procedure of the electric power limitation process.

[0012] Figure 3 This is a schematic structural diagram of a fuel cell system according to Modification 1. DETAILED DESCRIPTION

[0013] [1 Structure of the fuel cell system 10] Figure 1 1 is a schematic diagram of the structure of the fuel cell system 10. The fuel cell system 10 is installed in a vehicle (fuel cell vehicle), for example. The fuel cell system 10 can also be installed in a mobile object such as a ship, an airplane, or a robot. In addition, the fuel cell system 10 can also be used as a fixed power source in equipment, homes, etc.

[0014] In the fuel cell system 10, fuel gas and 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. The fuel gas and the oxidant gas are respectively supplied to the fuel cell stack 12 for electrochemical reaction. In addition, in this specification, the fuel gas that is not used for electrochemical reaction and is discharged from the fuel cell stack 12 is also referred to as fuel exhaust gas. In addition, in this specification, the oxidant gas that is not used for electrochemical reaction and is discharged from the fuel cell stack 12 is also referred to as oxidant exhaust gas.

[0015] The fuel cell system 10 includes a fuel cell stack 12, a storage 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 a fuel cell vehicle. The storage tank 14 is filled with a high-pressure fuel gas.

[0016] The fuel cell stack 12 has a fuel gas supply port 12a for supplying fuel gas to the interior of the fuel cell stack 12 and a fuel gas exhaust port 12b for exhausting fuel exhaust gas from the interior of the fuel cell stack 12. The fuel cell stack 12 has an oxidant gas supply port 12c for supplying oxidant gas to the interior of the fuel cell stack 12 and an oxidant gas exhaust port 12d for exhausting oxidant exhaust gas from the interior of the fuel cell stack 12. The fuel cell stack 12 has a refrigerant supply port 12e for supplying refrigerant to the interior of the fuel cell stack 12 and a refrigerant exhaust port 12f for exhausting refrigerant from the interior of the fuel cell stack 12.

[0017] The fuel cell stack 12 has a plurality of power generation cells 28. The plurality of power generation cells 28 have the same structure. The power generation cell 28 has an electrolyte membrane-electrode structure (membrane electrode assembly) 30, a first separator 32, and a second separator 34. The electrolyte membrane-electrode structure 30 is sandwiched by the first separator 32 and the second separator 34. Figure 1 The middle figure shows one power generation cell 28 among the plurality of power generation cells 28 .

[0018] The first separator 32 and the second separator 34 are formed of a metal thin plate having a corrugated cross section. 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 battery cooling flow path (not shown) is formed between the first separator 32 and the second separator 34. The battery cooling flow path is connected to the refrigerant supply port 12e and the refrigerant discharge port 12f.

[0019] 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 is connected to the fuel gas supply port 12a and the fuel gas exhaust port 12b. The cathode flow path 44 is connected to the oxidant gas supply port 12c and the oxidant gas exhaust port 12d.

[0020] A temperature sensor 46 is provided near the fuel gas outlet 12b. For example, a temperature sensor 46 is provided on the fuel gas outlet path 86 connected to the fuel gas outlet 12b. The temperature sensor 46 detects the temperature of the fuel gas. The temperature sensor 46 may be provided near the oxidant gas outlet 12d. For example, a temperature sensor 46 may be provided on the oxidant gas outlet path 108 connected to the oxidant gas outlet 12d. In this case, the temperature sensor 46 detects the temperature of the oxidant gas. The temperature of the fuel gas or oxidant gas near the outlet of the fuel cell stack 12 (gas temperature) becomes the representative temperature of the fuel cell stack 12. That is, the gas temperature is equivalent to the temperature of the fuel cell stack 12 (stack temperature).

[0021] The anode system 16 includes a fuel gas supply path 84 , a fuel gas discharge path 86 , a circulation path 88 , and a drain path 90 . The anode system 16 also includes an injector 94 , an ejector 96 , a gas-liquid separator 98 , and a drain valve 100 .

[0022] The fuel gas supply path 84 connects the discharge port of the tank 14 and the fuel gas supply port 12a of the fuel cell stack 12. The fuel gas supply path 84 includes an injector 94 and an ejector 96. The ejector 96 is disposed closer to the fuel cell stack 12 than the injector 94.

[0023] The fuel gas discharge path 86 is connected to the fuel gas discharge port 12 b of the fuel cell stack 12 and the supply port of the gas-liquid separator 98 . The circulation path 88 is connected to the exhaust port of the gas-liquid separator 98 and the ejector 96 .

[0024] The drainage path 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 a drainage port provided in the vehicle. The drainage path 90 is provided with a drainage valve 100.

[0025] The cathode system 18 has an oxidant gas supply path 106, an oxidant gas exhaust path 108 (exhaust path), and a bypass path 110. In addition, the cathode system 18 has a compressor 112 (oxidant gas supplier), a humidifier 114, a first sealing valve 116, a second sealing valve 118, and a bypass valve 119.

[0026] The oxidant gas supply path 106 is connected to the air intake port provided in the vehicle and the oxidant gas supply port 12c of the fuel cell stack 12. The oxidant gas supply path 106 includes a compressor 112, a first sealing valve 116, and a humidifier supply path 114A of the humidifier 114. The portion of the oxidant gas supply path 106 disposed upstream of the humidifier 114 is referred to as the oxidant gas supply path 106A. The portion of the oxidant gas supply path 106 disposed downstream of the humidifier 114 is referred to as the oxidant gas supply path 106B. The oxidant gas supply path 106A includes a compressor 112 and a first sealing valve 116. The first sealing valve 116 is disposed closer to the humidifier 114 than the compressor 112.

[0027] The oxidant gas discharge path 108 is connected to the oxidant gas discharge port 12d of the fuel cell stack 12 and the inlet of the diluter 121. The humidifier discharge path 114B of the humidifier 114 and the second sealing valve 118 are provided on the oxidant gas discharge path 108. The portion of the oxidant gas discharge path 108 disposed upstream of the humidifier 114 is referred to as the oxidant gas discharge path 108A. The portion of the oxidant gas discharge path 108 disposed downstream of the humidifier 114 is referred to as the oxidant gas discharge path 108B. The second sealing valve 118 is provided on the oxidant gas discharge path 108B.

[0028] The bypass path 110 is connected to the oxidant gas supply path 106A located between the compressor 112 and the first sealing valve 116 and the oxidant gas discharge path 108B located downstream of the second sealing valve 118. The bypass path 110 is provided with a bypass valve 119.

[0029] The cooling system 20 includes a refrigerant flow path 120 . In addition, the cooling system 20 includes a pump 126 , a radiator 128 , a temperature sensor 130 , and a flow dividing valve 132 .

[0030] The refrigerant flow path 120 circulates the 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 bypass 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 bypass path 125 branches from the refrigerant discharge path 124 and merges with the refrigerant supply path 122.

[0031] The pump 126 is provided in the refrigerant supply path 122. In addition, the pump 126 may be provided in the refrigerant discharge path 124. The radiator 128 is a heat dissipation device that dissipates heat from the refrigerant in the refrigerant flow path 120. The radiator 128 may include a fan.

[0032] 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 is equivalent to the temperature inside the fuel cell stack 12 (stack temperature). The fuel cell system 10 further includes an external air temperature sensor 140. The external air temperature sensor 140 is provided, for example, in the body of the fuel cell vehicle. The external air temperature sensor 140 detects the temperature of the air outside the fuel cell stack 12 (external air temperature). The signal output from the external air temperature sensor 140 is supplied to the control device 22.

[0033] The flow divider valve 132 is provided at a confluence portion where the flow divider path 125 and the refrigerant supply path 122 merge. In addition, the flow divider valve 132 may be provided at a branch portion where the flow divider path 125 branches from the refrigerant discharge path 124. The flow divider valve 132 is capable of adjusting the opening degree. The amount of refrigerant supplied to the radiator 128 is adjusted according to the opening degree of the flow divider valve 132. The opening degree of the flow divider valve 132 is controlled by the control device 22.

[0034] The control device 22 can be constituted by an ECU (Electronic Control Unit) and includes a calculation unit 136 and a storage unit 138 .

[0035] The computing unit 136 is, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The computing unit 136 includes a power generation control unit 150, a temperature acquisition unit 152, a history acquisition unit 154, an overdrying determination unit 156, and a preheating determination unit 158. The power generation control unit 150, the temperature acquisition unit 152, the history acquisition unit 154, the overdrying determination unit 156, and the preheating determination unit 158 ​​operate by executing a program stored in the storage unit 138 through the computing unit 136.

[0036] In addition, at least one of the power generation control unit 150, the temperature acquisition unit 152, the history acquisition unit 154, the overdrying determination unit 156, and the preheating determination unit 158 ​​may be implemented 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 overdrying determination unit 156, and the preheating determination unit 158 ​​may be implemented by an electronic circuit including discrete devices.

[0037] The power generation control unit 150 controls the operation of the ejector 94, the compressor 112, the pump 126, and various valves so as to supply fuel gas and oxidant gas to the fuel cell stack 12. As a result, the power generation cell 28 inside the fuel cell stack 12 generates power.

[0038] 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 .

[0039] The history acquisition unit 154 acquires the history information 160 stored in the storage unit 138. The history information 160 is information indicating that the power generation control (second power generation control) is performed to dry the electrolyte membrane 36 included in the power generation cell 28. The second power generation control will be described later.

[0040] The overdrying determination unit 156 determines whether the power generation cell 28 is in an overdry 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 overdry state means that the electrolyte membrane 36 of the power generation cell 28 has insufficient water content and is excessively dry.

[0041] The warm-up determination unit 158 ​​determines whether to warm up the fuel cell stack 12 based on the temperature information acquired by the temperature acquisition unit 152 .

[0042] The storage unit 138 is a computer-readable storage medium. It is composed of a volatile memory (not shown) and a non-volatile memory (not shown). Examples of volatile memory include RAM (Random Access Memory). Examples of non-volatile memory include ROM (Read Only Memory), flash memory, etc. Data, etc. are stored in the volatile memory. Programs, tables, mappings, etc. are stored in the non-volatile memory. At least a portion of the storage unit 138 may be provided in the above-mentioned processor, integrated circuit, etc. Programs, historical information 160, etc. are stored in the storage unit 138. The historical information 160 is deleted from the storage unit 138 when the battery is removed.

[0043] [2 Flow of Fluid in Fuel Cell System 10] [2-1 Flow of Fluid in Anode System 16] The injector 94 is a supply device for supplying a reaction gas to the fuel cell stack 12. The injector 94 injects the fuel gas supplied from the tank 14 to the 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 through the fuel gas supply path 84. The fuel gas that has not reacted inside the fuel cell stack 12 is discharged from the fuel gas outlet 12b of the fuel cell stack 12 as a fuel exhaust gas. The fuel exhaust gas contains hydrogen that has not reacted with oxygen, nitrogen in the oxidant gas that has permeated the electrolyte membrane 36, and moisture generated by the reaction of oxygen and hydrogen.

[0044] The fuel exhaust gas is supplied to the gas-liquid separator 98 through the fuel gas discharge path 86. The gas-liquid separator 98 separates the fuel exhaust gas into a gas component (fuel exhaust gas) and a liquid component (water). The fuel exhaust gas discharged from the gas-liquid separator 98 is supplied to the ejector 96 through the circulation path 88. The fuel exhaust gas discharged from the gas-liquid separator 98 and the fuel gas injected from the ejector 94 merge in the ejector 96.

[0045] [2-2 Flow of Fluid in Cathode System 18] The compressor 112 is a supply device for supplying a reaction gas to the fuel cell stack 12. The compressor 112 discharges the oxidant gas (air) sucked from the outside of the vehicle to the downstream of the oxidant gas supply path 106. The oxidant gas discharged from the compressor 112 is supplied to the oxidant gas supply port 12c of the fuel cell stack 12 through the oxidant gas supply path 106. The oxidant gas that has not reacted inside the fuel cell stack 12 is discharged from the oxidant gas discharge port 12d of the fuel cell stack 12 as an oxidant exhaust gas. The oxidant exhaust gas contains various components contained in the oxidant gas and moisture generated by the reaction of oxygen and hydrogen.

[0046] The oxidant off-gas is discharged to the diluter 121 through the oxidant gas discharge path 108. The oxidant off-gas contains moisture. In the humidifier 114, part of the moisture contained in the oxidant off-gas is used to humidify the oxidant gas flowing through the humidifier supply path 114A.

[0047] [2-3 Flow of Fluid in Cooling System 20] The pump 126 discharges the refrigerant to 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 through the refrigerant supply path 122. The refrigerant flowing inside 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 through the refrigerant discharge path 124. The refrigerant after heat dissipation by the radiator 128 reaches the pump 126.

[0048] In addition, part of the refrigerant discharged from the refrigerant discharge port 12f is not supplied to the radiator 128 but flows into the refrigerant supply path 122 through the bypass path 125. The inflow amount is adjusted by the opening degree of the bypass valve 132.

[0049] [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 electric power corresponding to a request to the load 26. The second power generation control is a control for drying the electrolyte membrane 36 included in the power generation cell 28.

[0050] The power generation control unit 150 executes the first power generation control when receiving a system start command as a command for starting the fuel cell system 10. The power generation control unit 150 terminates the first power generation control when receiving a system stop command as a command for stopping the fuel cell system 10.

[0051] After receiving the system stop command and before receiving the next system start command, when the stack temperature or the outside air temperature is below the specified temperature, the power generation control unit 150 performs the second power generation control. In other words, after receiving the system stop command and before receiving the next system start command, when the stack temperature or the outside air temperature is not below the specified temperature, the second power generation control is not performed. The outside air temperature can be determined based on information obtained by the outside air temperature sensor 140, etc., but is not limited to this. The specified temperature is selected from the range of 0°C to 5°C, for example. In addition, after receiving the system stop command and before receiving the next system start command, when it is predicted that the stack temperature or the outside air temperature is below the specified temperature, the power generation control unit 150 can perform the second power generation control.

[0052] In the first power generation control, at the time of low temperature start-up, a preheating process is performed for preheating the fuel cell stack 12. That is, the preheating process is performed at the start of the first power generation control when the stack temperature or the outside air temperature is below a predetermined temperature. In this case, the power generation control unit 150 controls the ejector 94 and the compressor 112 according to the target power value so that the power generated by the power generation cell 28 is the target power value set for preheating the fuel cell stack 12.

[0053] When the stack temperature indicated by the temperature information acquired by the temperature acquisition unit 152 is equal to or higher than the target temperature, the power generation control unit 150 ends the preheating process and executes the power supply process. In this case, the power generation control unit 150 controls the ejector 94 and the compressor 112 according to the required power generation in such a manner that the power generation of the power generation battery 28 is the required power generation. The required power generation is calculated by the power generation control unit 150 based on the accelerator opening, the vehicle speed, the road slope, etc., for example.

[0054] In addition, when the stack temperature is 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 preheating process. In this case, when the stack temperature is higher than the target temperature, the power generation control unit 150 terminates the preheating process and restarts the power supply process.

[0055] In the second power generation control, the power generation control unit 150 controls the ejector 94 and the compressor 112 in such a way 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. Accordingly, it is possible to improve the discharge efficiency of the water retained inside the fuel cell stack 12 to the outside. As a result, the water content of the power generation cell 28 is reduced. In addition, the stoichiometric ratio refers to the ratio of the oxidant gas to the fuel gas. The increase in the stoichiometric ratio means that the oxidant gas is increased, and the ratio of the oxidant gas is increased.

[0056] In addition, 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. In the second power generation control, the power generation control unit 150 controls valves and the like in such a manner that the oxidant gas is supplied to the fuel cell stack 12 through the humidifier bypass flow path. On the other hand, in the first power generation control, the power generation control unit 150 controls valves and the like in such a manner that the oxidant gas is supplied to the fuel cell stack 12 without passing through the humidifier bypass flow path.

[0057] The power generation control unit 150 ends the second power generation control, for example, when a specified time has passed since the start of the second power generation control. In this case, the power generation control unit 150 stops the injector 94 and the compressor 112. In addition, the power generation control unit 150 generates historical information 160 indicating that the second power generation control is performed after receiving the system stop command, and stores it in the storage unit 138. The historical information 160 includes the date and time, period, etc. when the second power generation control is executed. In addition, the time when the second power generation control is executed includes the period from the receipt of the system stop command until the fuel cell system 10 stops or the period during the fuel cell system 10 stops. In other words, the historical information 160 indicates that the second power generation control is performed from the receipt of the system stop command until the fuel cell system 10 stops or the period during the fuel cell system 10 stops.

[0058] [4 Electric power limitation processing] The control device 22 executes the electric power limitation process in parallel with the first power generation control at the time of system startup (at the time of startup of the first power generation control). Figure 2 This is a flowchart showing the procedure of the electric power limitation process.

[0059] The control device 22 starts the electric power limitation process when receiving the system startup command.

[0060] 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 as a temperature serving as a reference for determining whether the environment is a low temperature environment.

[0061] When the stack temperature is less than the first temperature threshold, the electric power limitation 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, when the stack temperature is greater than the first temperature threshold, the electric power limitation process moves to step S2.

[0062] In step S2, the control device 22 accesses the storage unit 138. Here, when the history information 160 indicating that the second power generation control is performed after the last system stop command is received is not stored in the storage unit 138, the electric power limitation process ends. When the history information 160 indicating that the second power generation control is performed after the last system stop command is received 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 is performed after the last system stop command is acquired, the electric power limitation process shifts to step S3.

[0063] In step S3, the control device 22 determines that the power generation cell 28 is in an over-dry state. Thereafter, the electric power limitation process moves to step S4.

[0064] In step S4, the power generation control unit 150 compares the stack temperature with the second temperature threshold. The second temperature threshold is set to a temperature at which the rated output (maximum output) can be obtained from the power generation cell 28 in a stable state. The second temperature threshold is higher than the first temperature threshold.

[0065] When the stack temperature is above the second temperature threshold, the preheating of the fuel cell stack 12 by the power generation control unit 150 is terminated. Therefore, the electrolyte membrane 36 of the power generation cell 28 is sufficiently humidified by the water generated by the reaction during preheating, and the over-dry state of the power generation cell 28 is eliminated. Therefore, the electric power limitation process is terminated. On the other hand, when the stack temperature is less than the second temperature threshold, the preheating of the fuel cell stack 12 by the power generation control unit 150 is not terminated. In a state where the preheating is not terminated, the electrolyte membrane 36 of the power generation cell 28 is not sufficiently humidified by the water generated by the reaction during preheating, and the over-dry state of the power generation cell 28 is not eliminated. Therefore, the electric power limitation process is transferred to step S5.

[0066] In step S5, the control device 22 limits the generated electric power of the power generation cell 28. In this case, the power generation control unit 150 suppresses the supply (output) of the generated electric power to the load 26 to be below the prescribed electric power threshold. In other words, even if the electric power greater than the electric power threshold is required, the power generation control unit 150 suppresses the electric power supplied to the load 26 to be below the electric power threshold. Thereafter, the electric power limitation process returns to step S4. In addition, the control device 22 continues to limit the generated electric power of the power generation cell 28 in step S4 until the stack temperature is above the second temperature threshold.

[0067] [5 Effects of the above-mentioned embodiments] In this way, when the overdrying determination unit 156 determines that the power generation cell 28 is in an overdry state, the power generation control unit 150 limits the power generation of the power generation cell 28 at the start of the first power generation control. According to this, even if the power generation cell 28 is in an overdry state, the power generation of the power generation cell 28 can be stabilized. As a result, it is possible to avoid always implementing the low-temperature power generation control when the system is started immediately after the second power generation control is performed.

[0068] In the above embodiment, when the overdrying determination unit 156 determines that the power generation cell 28 is in an overdry state and the preheating determination unit 158 ​​determines that the preheating of the fuel cell stack 12 has not yet been completed, the power generation control unit 150 limits the power generation of the power generation cell 28 during the preheating process. In this way, the power generation can be suppressed from being limited regardless of the overdrying state of the power generation cell 28 being eliminated by the water generated in response to the power generation during the preheating. As a result, the power generation efficiency of the power generation cell 28 can be improved.

[0069] [6 Variations of the above embodiment] The above-mentioned embodiment can be modified as follows.

[0070] (Variant 1) Figure 3 FIG. 1 is a schematic diagram of the structure of a fuel cell system 10 according to a first modification. Figure 3 In the embodiment, the same reference numerals are given to the same structures as those described in the embodiment. In addition, in this modification, the description overlapping with the embodiment is omitted.

[0071] 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 generation cell 28. The overdrying determination unit 156 determines whether the power generation cell 28 is in an overdry state based on the moisture information in addition to the history information 160 and the temperature information. Thus, the determination accuracy can be improved compared to the case where the overdry state is determined only based on the history information 160 and the temperature information.

[0072] The value corresponding to the water content of the power generation cell 28 is, for example, the impedance (AC impedance) of the entirety of the plurality of power generation cells 28 included in the fuel cell stack 12 , but is not limited thereto.

[0073] When the value corresponding to the water content of the power generation cell 28 is AC impedance, the information acquisition unit 162 can acquire the AC impedance from an impedance sensor that detects the AC impedance.

[0074] When the value corresponding to the water content of the power generation cell 28 is AC impedance, the overdrying determination unit 156 can determine whether the power generation cell 28 is in an overdry state, for example, as follows. That is, when the stack temperature is lower 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 generation cell 28 is not in an overdry state. On the other hand, when the stack temperature is lower 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.

[0075] There is a correlation between the AC impedance and the water content of the power generation cell 28. The AC impedance decreases as the water content of the power generation cell 28 increases.

[0076] When the AC impedance is greater than the impedance threshold, the overdryness determination unit 156 determines that the power generation cell 28 is not in an overdry state. On the other hand, when the AC impedance is less than the impedance threshold, the overdryness determination unit 156 determines that the power generation cell 28 is in an overdry state.

[0077] (Variant 2) The preheating determination unit 158 ​​can determine whether to preheat the fuel cell stack 12 based on the time from when the system startup command is received. That is, when the specified time has not passed since the system startup command was received, the preheating determination unit 158 ​​determines that the fuel cell stack 12 is preheated. On the other hand, when the specified time has passed since the system startup command was received, the preheating determination unit 158 ​​determines that the fuel cell stack 12 is not preheated.

[0078] (Variant 3) When the control device 22 determines that the power generation cell 28 is in an over-dry state, it may limit the power generated by the power generation cell 28 without determining whether to warm up the fuel cell stack 12 .

[0079] (Variant 4) The power generation control unit 150 may change the limit amount of the power generated by the power generation cell 28 according to the stack temperature. In this case, the power generation control unit 150 reduces the limit amount of the power generated as the stack temperature increases. In this way, the power generation efficiency of the power generation cell 28 can be improved.

[0080] [7 Notes] Regarding the above-mentioned technical solution, the following supplementary notes are also disclosed.

[0081] (Note 1) The technical solution is a control device (22) arranged in a fuel cell system (10), the fuel cell system having a fuel cell stack (12) and a power generation control unit (150), the fuel cell stack including a power generation cell (28); the power generation control unit performs power generation control 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, the second power generation control being a power generation control for drying an electrolyte membrane (36) possessed by the power generation cell after receiving a system stop command for stopping the fuel cell system, and the control device also having a temperature acquisition unit (150) 52), a history acquisition unit (154) and an over-dryness determination unit (156), wherein the temperature acquisition unit acquires temperature information indicating the temperature of the fuel cell stack, i.e., the stack temperature; the history acquisition unit acquires history information (160) indicating that the second power generation control was performed after receiving the last system stop command; the over-dryness determination unit 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.

[0082] This makes it possible to stabilize the power generation of the power generation cell even when the power generation cell is in an over-dry state. As a result, it is possible to suppress malfunction of the load due to unstable output of the power generation cell in advance.

[0083] (Note 2) In the control device described in Appendix 1, the first power generation control includes preheating of the fuel cell stack, and the control device also has a preheating determination unit (158) for determining whether the preheating is completed. When the over-dryness determination unit determines that the power generation cell is in an over-dry state and the preheating determination unit determines that the preheating is not completed, the power generation control unit limits the power generation power of the power generation cell during the preheating process.

[0084] This can prevent the power generation from being limited, regardless of the overdrying of the power generation cell by the water generated in response to power generation during preheating. As a result, the power generation efficiency of the power generation cell can be improved.

[0085] (Note 3) In the control device described in Note 2, the overdrying judgment unit may judge that the power generation cell is in an overdry state when the temperature information is above a prescribed first temperature threshold and the history information indicating that the second power generation control was performed after the last system stop command was received is obtained through the history acquisition unit, and the preheating judgment unit may judge that the preheating has not yet ended when the temperature information is less than a prescribed second temperature threshold.

[0086] (Note 4) In the control device described in Note 1, the first power generation control may include a preheating process for preheating the fuel cell stack, and the control device may also include a preheating determination unit for determining whether the temperature information has reached a specified temperature or above through the preheating process, and when the over-drying determination unit determines that the power generation cell is in an over-dry state and the preheating determination unit determines that the temperature information has not reached the specified temperature or above, the power generation control unit limits the power generation power of the power generation cell during the preheating process.

[0087] This can prevent the power generation from being limited, regardless of the overdrying of the power generation cell by the water generated in response to power generation during preheating. As a result, the power generation efficiency of the power generation cell can be improved.

[0088] (Note 5) In the control device described in Note 4, the overdrying determination unit may determine that the power generation cell is in an overdry state when the temperature information is above a prescribed first temperature threshold and the history acquisition unit obtains the history information indicating that the second power generation control was performed from the time the last system stop command was received until the fuel cell system was stopped or during the fuel cell system stop process, and the preheating determination unit may determine that the preheating has not yet ended when the temperature information is less than a prescribed second temperature threshold.

[0089] (Note 6) In the control device described in any one of Notes 1 to 5, the control device may also include an information acquisition unit (162) which acquires moisture information representing a value corresponding to the moisture content of the power generation cell, and the overdrying determination unit determines whether the power generation cell is in an overdry state based on the historical information, the temperature information and the moisture information.

[0090] This makes it possible to improve the determination accuracy compared to the case where whether or not the dry state is excessively present is determined based on history information and temperature information.

[0091] In addition, the present invention is not limited to the above-mentioned technical aspects, and various structures can be adopted within the scope not departing from the gist of the present invention.

Claims

1. A control device provided in a fuel cell system, the fuel cell system comprising a fuel cell stack and a power generation control unit, the fuel cell stack including a power generation cell; the power generation control unit controls power generation of the power generation cell, It is characterized in that 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 a power generation control for drying the electrolyte membrane of the power generation cell after receiving a system stop command for stopping the fuel cell system. The control device further comprises a temperature acquisition unit, a history acquisition unit and an over-drying determination unit, wherein: The temperature acquisition unit acquires temperature information indicating the temperature of the fuel cell stack, ie, the stack temperature; The history acquisition unit acquires history information indicating that the second power generation control was performed after receiving the last system stop command; The overdrying determination unit determines whether the power generation cell is in an overdry state based on the history information and the temperature information. When the overdrying determination unit determines that the power generation cell is in an overdry state, the power generation control unit limits the power generated by the power generation cell at the start of the first power generation control.

2. The control device according to claim 1, characterized in that: The first power generation control includes preheating the fuel cell stack. The control device further includes a preheating determination unit that determines whether the preheating is completed. When the overdrying determination unit determines that the power generation cell is in an overdry state and the preheating determination unit determines that the preheating has not yet been completed, the power generation control unit limits the power generation of the power generation cell during the preheating.

3. The control device according to claim 2, characterized in that: The overdrying determination unit determines that the power generation cell is in an overdry state when the temperature information is above a predetermined first temperature threshold and the history acquisition unit acquires the history information indicating that the second power generation control was performed after the last system stop instruction was received, The preheating determination unit determines that the preheating has not yet been completed when the temperature information is lower than a predetermined second temperature threshold.

4. The control device according to claim 1, characterized in that: The first power generation control includes performing a preheating process for preheating the fuel cell stack. The control device further includes a preheating determination unit configured to determine whether the temperature information has reached a predetermined temperature or above through the preheating process. When the overdrying determination unit determines that the power generation cell is in an overdry state and the preheating determination unit determines that the temperature information is not equal to or higher than the predetermined temperature, the power generation control unit limits the power generation of the power generation cell during the preheating process.

5. The control device according to claim 4, characterized in that: The overdrying determination unit determines that the power generation cell is in an overdry state when the temperature information is above a predetermined first temperature threshold value and the history acquisition unit acquires the history information indicating that the second power generation control was performed from the time the last system stop instruction was received until the fuel cell system was stopped or during the time when the fuel cell system was stopped, The preheating determination unit determines that the preheating has not yet been completed when the temperature information is lower than a predetermined second temperature threshold.

6. The control device according to any one of claims 1 to 5, characterized in that: The control device further includes an information acquisition unit that acquires moisture information indicating a value corresponding to the moisture content of the power generation cell. The overdrying determination unit determines whether the power generation cell is in an overdry state based on the history information, the temperature information, and the moisture information.

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