Control device, fuel cell system, and control method

Abstract

We provide technology to suppress the degradation of fuel cells. [Solution] The control device 16 of a fuel cell system having a fuel cell unit, a humidifier for humidifying the cathode gas supplied to the fuel cell unit, and a temperature control device for adjusting the temperature of the fuel cell unit comprises an estimation unit 54 that derives an estimated degradation rate Des of the fuel cell unit based on the temperature Tcg of the cathode gas introduced into the humidifier, and a temperature control unit 64 that controls the temperature control device to lower the temperature of the fuel cell unit when the estimated degradation rate is higher than the target degradation rate Dtgt of the fuel cell unit.

Description

Technical Field

[0001] The present disclosure relates to a control device, a fuel cell system, and a control method.

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 on fuel cells that contribute to energy efficiency have been carried out. For example, Japanese Patent Application Laid-Open No. 2010-129278 discloses a technology related to a fuel cell system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Recently, better technologies have been desired for suppressing the deterioration of fuel cells.

[0005] <~ The present disclosure aims to solve the above-described problems.

Means for Solving the Problems

[0006] A first aspect of the present disclosure is a control device for a fuel cell system including a fuel cell unit, a humidifier that humidifies a cathode gas supplied to the fuel cell unit, and a temperature control device that adjusts the temperature of the fuel cell unit, the control device including an estimation unit that derives an estimated deterioration rate of the fuel cell unit based on the temperature of the cathode gas introduced into the fuel cell unit, and a temperature control unit that controls the temperature control device to lower the temperature of the fuel cell unit when the estimated deterioration rate is higher than a target deterioration rate of the fuel cell unit.

[0007] A second aspect of this disclosure is a fuel cell system comprising a control device according to the first aspect of this disclosure, the fuel cell unit, the humidifier, and the temperature control device.

[0008] A third aspect of the present disclosure is a control method for a fuel cell system having a fuel cell unit, a humidifier for humidifying the cathode gas supplied to the fuel cell unit, and a temperature control device for adjusting the temperature of the fuel cell unit, the control method comprising: an estimation step of deriving an estimated degradation rate of the fuel cell unit based on the temperature of the cathode gas introduced into the fuel cell unit; and a temperature control step of controlling the temperature control device to lower the temperature of the fuel cell unit when the estimated degradation rate is higher than the target degradation rate of the fuel cell unit. [Effects of the Invention]

[0009] According to this disclosure, a better technology is provided for suppressing the degradation of fuel cells. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing a vehicle according to one embodiment. [Figure 2] Figure 2 is a diagram showing the configuration of the power generation system shown in Figure 1. [Figure 3] Figure 3 is a block diagram showing the configuration of the control device shown in Figure 1 in more detail. [Figure 4] Figure 4A is a causal relationship diagram showing the relationship between the temperature of the cathode gas supplied to the fuel cell, the amount of water vapor contained in the cathode gas, the temperature of the fuel cell, the relative humidity of the cathode gas, and the degradation rate (estimated degradation rate) of the fuel cell. Figure 4B is a simplified diagram showing the flow of the target cooling temperature determination process performed by the target temperature determination unit. [Figure 5] Figure 5 schematically shows the time-series changes of the cathode gas temperature, the relative humidity of the cathode gas, the estimated degradation rate of the fuel cell, and the temperature of the fuel cell. [Figure 6] Figure 6 is a flowchart of a control method according to one embodiment. [Modes for carrying out the invention]

[0011] According to Japanese Patent Publication No. 2010-129278, when the temperature of the fuel cell stack is higher than the temperature of the reaction gas, the fuel cell system reduces the flow rate of the refrigerant supplied to the fuel cell stack. This increases the temperature and humidity of the reaction gas discharged from the fuel cell stack.

[0012] Incidentally, in the technology related to fuel cell components, suppressing the degradation of the fuel cell is a challenge. However, conventional technologies, including those described in Japanese Patent Publication No. 2010-129278, do not always successfully suppress the degradation of fuel cells provided in fuel cell systems. For example, the higher the temperature of the fuel cell, the more likely it is that the water content of the fuel cell (the electrolyte membrane provided in the fuel cell) will decrease. Even if the humidity of the gas discharged from the fuel cell is increased by treatments such as reducing the flow rate of the refrigerant, if the water content of the electrolyte membrane of the fuel cell is excessively low, the degradation of the electrolyte membrane will ultimately be accelerated.

[0013] Based on the preliminary explanation above, one embodiment will be described below. In the following description, the term "program" (computer program, computer software) is also referred to as a "computer program product." A computer program product is not limited to programs stored on a storage medium (recording medium), but also includes programs transmitted, distributed, and downloaded via networks such as the Internet.

[0014] (One embodiment) Figure 1 is a schematic diagram showing a vehicle 10 according to one embodiment. Figure 2 is a configuration diagram of the power generation system 14 shown in Figure 1.

[0015] Vehicle 10 is, for example, a fuel cell vehicle. Vehicle 10 includes a fuel cell system 12. The fuel cell system 12 has a plurality of power generation systems 14 and a control device 16. In the present embodiment, a case where the number of the power generation systems 14 is two will be described, but the fuel cell system 12 may have three or more power generation systems 14. The plurality of power generation systems 14 may be arranged side by side in the front-rear direction DFB of the vehicle 10. The configurations (FIG. 2) of the plurality of power generation systems 14 may be common.

[0016] As shown in FIG. 2, each power generation system 14 (each of the plurality of power generation systems 14) includes a fuel cell unit 18, a cathode gas circuit 20, a temperature control device 22, and a plurality of temperature sensors 24.

[0017] The fuel cell unit 18 has a fuel cell. The fuel cell unit 18 may have a plurality of fuel cells. For example, the fuel cell unit 18 may be a fuel cell stack. A fuel cell is a device that generates electrical energy by chemically reacting oxygen contained in cathode gas and hydrogen contained in anode gas. The cathode gas is, for example, air. The anode gas is, for example, hydrogen gas. Although illustration is omitted, a fuel cell includes a cathode (cathode electrode part) to which cathode gas is supplied, an anode (anode electrode part) to which anode gas is supplied, and an electrolyte membrane disposed between the cathode and the anode. The electrolyte membrane is, for example, a solid polymer electrolyte membrane.

[0018] The cathode gas circuit 20 is a fluid circuit that supplies cathode gas to the fuel cell unit 18 and recovers cathode off-gas discharged from the fuel cell unit 18 from the fuel cell unit 18. The cathode gas circuit 20 includes a gas supply path 26, an air pump unit 28, a gas discharge path 30, a pressure regulating valve unit 32, a bypass path 34, a bypass valve unit 36, and a humidifier 38.

[0019] The gas supply passage 26 is a first gas flow passage connected to the fuel cell unit 18. The cathode gas is supplied to the fuel cell unit 18 through the gas supply passage 26. As described above, the cathode gas may be air. In that case, the air is taken into the vehicle 10 from the atmosphere through, for example, an air supply port 40 provided in the vehicle 10. In this case, a plurality of air supply ports 40 corresponding to each of the plurality of power generation systems 14 may be provided in the vehicle 10. The air taken into the vehicle 10 is supplied to the fuel cell unit 18 through the gas supply passage 26.

[0020] The air pump unit 28 is provided in the gas supply passage 26. The air pump unit 28 includes a device that promotes the flow of the cathode gas in the gas supply passage 26. For example, an air pump that sends air toward the fuel cell unit 18 is included in the air pump unit 28.

[0021] The gas discharge passage 30 is a second gas flow passage connected to the fuel cell unit 18. The cathode off-gas discharged from the fuel cell unit 18 flows into the gas discharge passage 30.

[0022] The pressure regulating valve unit 32 is provided in the gas discharge passage 30. The pressure regulating valve unit 32 has a valve that adjusts the gas flow pressure (gas flow rate). By adjusting the gas flow pressure in the gas discharge passage 30, the internal pressure of the fuel cell unit 18 is adjusted.

[0023] The bypass passage 34 is a third gas flow passage that connects the gas supply passage 26 and the gas discharge passage 30. A part of the cathode gas taken in from the air supply port 40 can flow into the gas discharge passage 30 through the bypass passage 34. As shown in FIG. 2, the bypass inflow portion 34a, which is the connection portion between the gas supply passage 26 and the bypass passage 34, may be located between the air pump unit 28 and the fuel cell unit 18. Further, the above-described pressure regulating valve unit 32 may be located between the bypass branch portion 34b, which is the connection portion between the gas discharge passage 30 and the bypass passage 34, and the fuel cell unit 18.

[0024] The bypass valve section 36 is provided in the bypass passage 34. The bypass valve section 36 has a valve that adjusts the gas flow pressure (gas flow rate) in the gas discharge passage 30.

[0025] The humidifier 38 is a device that humidifies the cathode gas. As shown in Figure 2, the humidifier 38 is installed between the fuel cell unit 18 and the bypass line 34, and is connected not only to the gas supply line 26 but also to the gas discharge line 30. In this case, the humidifier 38 humidifies the cathode gas by, for example, moving moisture contained in the cathode-off gas to the cathode gas.

[0026] The temperature control device 22 is a device for adjusting the temperature Tfc of the fuel cell section 18 using a refrigerant. The temperature control device 22 comprises a cooler 42, a refrigerant supply passage 44, a refrigerant recovery passage 46, and a refrigerant pump section 47.

[0027] The cooler 42 is a device that adjusts the temperature of the refrigerant. For example, a cooling device such as a radiator that cools the refrigerant is included in the cooler 42. The cooler 42 that adjusts the temperature of the refrigerant can effectively adjust the temperature Tfc of the fuel cell section 18 (electrolyte membrane).

[0028] The refrigerant supply path 44 and the refrigerant recovery path 46 are respective refrigerant pathways connecting the fuel cell unit 18 and the cooler 42. The refrigerant cooled by the cooler 42 is supplied to the fuel cell unit 18 via the refrigerant supply path 44. After the refrigerant supplied to the fuel cell unit 18 recovers heat from the fuel cell unit 18 (electrolyte membrane), it returns to the cooler 42 via the refrigerant recovery path 46. The refrigerant that returns to the cooler 42 is cooled by the cooler 42 and then supplied again to the fuel cell unit 18 via the refrigerant supply path 44.

[0029] The refrigerant pump unit 47 includes a device that adjusts the flow rate (flow velocity) of the refrigerant between the fuel cell unit 18 and the cooler 42. For example, a water pump may be included in the refrigerant pump unit 47. The refrigerant pump unit 47 is installed, for example, in the refrigerant supply path 44 (Figure 2), but it may also be installed in the refrigerant recovery path 46.

[0030] The multiple temperature sensors 24 include a gas temperature sensor 24A and an FC temperature sensor 24B.

[0031] The gas temperature sensor 24A is a temperature sensor (first temperature sensor) 24 provided in the gas supply line 26. For example, as shown in Figure 2, the gas temperature sensor 24A is installed between the bypass inlet 34a and the humidifier 38. The gas temperature sensor 24A outputs a detection signal corresponding to the temperature Tcg of the cathode gas introduced into the fuel cell unit 18.

[0032] The FC temperature sensor 24B is a temperature sensor (second temperature sensor) 24 that outputs a detection signal corresponding to the temperature of the fuel cell unit 18. The FC temperature sensor 24B is installed in the fuel cell unit 18, but may also be installed in the refrigerant recovery path 46 as shown in Figure 2. The refrigerant flowing through the refrigerant recovery path 46 has heat recovered from the fuel cell unit 18. The detection signal output from the FC temperature sensor 24B according to the temperature of the refrigerant having heat recovered from the fuel cell unit 18 is substantially a detection signal corresponding to the temperature of the fuel cell unit 18.

[0033] Although not shown in the diagram, the power generation system 14 may further include a fluid circuit (anode gas circuit) that supplies anode gas taken from a container such as a gas tank to the fuel cell unit 18. The power generation system 14 may further include a pump to promote the flow of refrigerant, an ion exchange resin to remove ions in the refrigerant, etc. The power generation system 14 may further include a pressure sensor for detecting the pressure of the cathode gas and a flow sensor for detecting the flow rate of the cathode gas.

[0034] Figure 3 is a block diagram showing the configuration of the control device 16 shown in Figure 1 in more detail.

[0035] The control device 16 is an electronic device provided in the fuel cell system 12. For example, a computer such as an ECU (Electronic Control Unit) is included in the control device 16. The control device 16 comprises a storage unit 48 and an arithmetic unit 50.

[0036] The storage unit 48 includes one or more memory devices. The storage unit 48 includes non-volatile memory such as ROM (Read Only Memory), flash memory, or magnetic disk. Non-volatile memory is a storage medium that stores programs, tables, maps, etc., on a non-temporary basis. At least a portion of the storage unit 48 may be implemented by a storage medium such as USB (Universal Serial Bus) memory, a memory card, or an optical disk. The storage unit 48 may also include volatile memory such as RAM (Random Access Memory).

[0037] The arithmetic unit 50 includes a processing circuit capable of performing arithmetic processing. This processing circuit may have one or more processors. For example, the processing circuit may have a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc. The processing circuit may have an IC (Integrated Circuit) or discrete devices.

[0038] The calculation unit 50 includes a temperature acquisition unit 52, an estimation unit 54, a statistical processing unit 56, a target degradation rate determination unit 58, a temperature control necessity determination unit 60, a target temperature determination unit 62, and a temperature control unit 64. The temperature acquisition unit 52, estimation unit 54, statistical processing unit 56, target degradation rate determination unit 58, temperature control necessity determination unit 60, target temperature determination unit 62, and temperature control unit 64 are realized by the processing circuit described above. For example, the temperature acquisition unit 52, estimation unit 54, statistical processing unit 56, target degradation rate determination unit 58, temperature control necessity determination unit 60, target temperature determination unit 62, and temperature control unit 64 are realized when a program stored in the storage unit 48 is executed by the processor of the calculation unit 50. At least one of the above-mentioned IC and discrete device may implement at least a part of the temperature acquisition unit 52, estimation unit 54, statistical processing unit 56, target degradation rate determination unit 58, temperature control necessity determination unit 60, target temperature determination unit 62, and temperature control unit 64.

[0039] The temperature acquisition unit 52 acquires temperature information based on the detection signal from the temperature sensor 24. For example, the temperature acquisition unit 52 acquires gas temperature information based on the detection signal from the gas temperature sensor 24A. The gas temperature information is temperature information indicating the temperature Tcg of the cathode gas introduced into the fuel cell unit 18. The temperature acquisition unit 52 also acquires FC temperature information based on the detection signal from the FC temperature sensor 24B. The FC temperature information is temperature information indicating the temperature of the fuel cell unit 18. The temperature acquisition unit 52 acquires gas temperature information and FC temperature information from each of the multiple power generation systems 14.

[0040] The estimation unit 54 performs degradation rate estimation processing. Degradation rate estimation processing is a process that derives the estimated degradation rate Des of the fuel cell unit 18 based on gas temperature information. The estimated degradation rate Des is an estimated value of the degradation rate of the fuel cell unit 18. More specifically, the estimated degradation rate Des is an estimated value of the degradation rate (stress amount) of the electrolyte membrane provided in the fuel cell unit 18. Since each of the multiple power generation systems 14 is provided with a fuel cell unit 18, the fuel cell system 12 as a whole has multiple fuel cell units 18. The estimation unit 54 derives the estimated degradation rate Des for each of the multiple fuel cell units 18. Regarding the degradation rate estimation processing, the estimation unit 54 has a humidity estimation unit 541 and a degradation rate estimation unit 542, which will be described below.

[0041] The humidity estimation unit 541 performs a first estimation process. The first estimation process estimates the relative humidity RHcg of the cathode gas at the stage when it reaches the fuel cell unit 18, based on the cathode gas temperature Tcg and the fuel cell unit 18 temperature Tfc. The relative humidity RHcg is the ratio of the amount of water vapor contained in the cathode gas to the saturated water vapor amount of the cathode gas. In this case, the cathode gas temperature Tcg is determined based on the gas temperature information described above. Also, in this case, the fuel cell unit 18 temperature Tfc is determined based on the FC temperature information described above.

[0042] The humidity estimation unit 541 may estimate the relative humidity RHcg of the cathode gas using a pre-prepared humidifier model and a relative humidity estimation model. The humidifier model is a mathematical model that estimates the amount of water vapor Wcg contained in the cathode gas after humidification by the humidifier 38, based on the temperature Tcg of the cathode gas. The relative humidity estimation model is a mathematical model that estimates the relative humidity RHcg based on the amount of water vapor Wcg contained in the cathode gas and the temperature Tfc of the fuel cell unit 18. The humidifier model and the relative humidity estimation model may each be a statistical model or a trained machine learning model.

[0043] Figure 4A is a causal relationship diagram showing the causal relationship between the temperature Tcg of the cathode gas supplied to the fuel cell unit 18, the amount of water vapor Wcg in the cathode gas, the temperature Tfc of the fuel cell unit 18, the relative humidity RHcg of the cathode gas, and the degradation rate of the fuel cell unit 18 (estimated degradation rate Des).

[0044] The change in the temperature Tcg of the cathode gas introduced into the humidifier 38 affects the amount of water vapor Wcg contained in the cathode gas after it has passed through the humidifier 38. Based on this causal relationship, the humidifier model described above is constructed. Furthermore, the saturated water vapor content of the cathode gas at the stage when it reaches the fuel cell unit 18 changes depending on the temperature of the cathode gas at that stage. This temperature changes depending on the temperature Tfc of the fuel cell unit 18. As the saturated water vapor content changes, the relative humidity RHcg changes. Looking at these factors as a whole, a causal relationship can be found between the change in the temperature Tfc of the fuel cell unit 18, the change in the amount of water vapor Wcg contained in the cathode gas, and the change in the relative humidity RHcg at the stage when it reaches the fuel cell unit 18. Based on this causal relationship, the relative humidity estimation model is constructed.

[0045] The input data for the humidifier model may further include design information for the humidifier 38. The design information for the humidifier 38 includes, for example, one or more parameters indicating the characteristics of the components provided in the humidifier 38 (porous hollow fiber membrane, module case, inner pipe, etc.). This allows the humidifier model to estimate the amount of water vapor Wcg contained in the cathode gas more accurately. As a result, the humidity estimation unit 541 can estimate the relative humidity RHcg of the cathode gas more accurately.

[0046] The input data for the humidifier model may also include information indicating the pressure and flow rate of the cathode gas. The pressure and flow rate of the cathode gas can be detected by the pressure sensor, flow rate sensor, etc., as described above. Furthermore, the pressure and flow rate of the cathode gas may already be set (known) as control parameters used to control power generation by the fuel cell unit 18. In that case, the humidity estimation unit 541 may include these control parameters in the input data for the humidifier model.

[0047] The degradation rate estimation unit 542 performs a second estimation process. The second estimation process is the process of estimating the estimated degradation rate Des of the fuel cell unit 18 (electrolyte membrane) based on the relative humidity RHcg of the cathode gas. In this case, the relative humidity RHcg of the cathode gas is shown by the result of the estimation by the humidity estimation unit 541. The degradation rate estimation unit 542 may also estimate the estimated degradation rate Des of the fuel cell unit 18 using a pre-prepared degradation rate estimation model. The degradation rate estimation model is a model (mathematical model) that outputs the estimated degradation rate Des in response to input data that includes information indicating the relative humidity RHcg of the cathode gas. The degradation rate estimation model may be a statistical model or a trained machine learning model. The input data of the degradation rate estimation model may further include information (data) other than information indicating the relative humidity RHcg of the cathode gas.

[0048] The lower the relative humidity RHcg of the cathode gas supplied to the fuel cell unit 18, the lower the chemical stability of the electrolyte membrane provided in the fuel cell unit 18. Therefore, the lower the relative humidity RHcg of the cathode gas, the faster the degradation of the fuel cell unit 18 is accelerated. In other words, there is a causal relationship between the relative humidity RHcg of the cathode gas and the degradation rate of the fuel cell unit 18, where a change in the relative humidity RHcg of the cathode gas affects a change in the degradation rate of the fuel cell unit 18 (see Figure 4A). The degradation rate estimation model described above is constructed based on this causal relationship.

[0049] The statistical processing unit 56 derives a representative value for each of the multiple estimated degradation rates Des estimated for each of the multiple fuel cell units 18. This representative value is, for example, the average value of the multiple estimated degradation rates Des, but is not limited to this. For example, the representative value for the multiple estimated degradation rates Des may be the median, mode, or the like.

[0050] The target degradation rate determination unit 58 determines the target degradation rate Dtgt (see also Figure 5) based on a representative value derived by the statistical processing unit 56. The target degradation rate Dtgt is the target value for the degradation rate of each of the multiple fuel cell units 18. A single target degradation rate Dtgt common to the multiple fuel cell units 18 may be determined by the target degradation rate determination unit 58. The target degradation rate determination unit 58 determines the above-mentioned representative value as the target degradation rate Dtgt, but is not limited to this. For example, the target degradation rate determination unit 58 may select one estimated degradation rate Des that is less than or equal to the representative value from among multiple estimated degradation rates Des, and determine that selected estimated degradation rate Des as the target degradation rate Dtgt. If multiple estimated degradation rates Des that are less than or equal to the representative value are identified, the target degradation rate determination unit 58 may select one of the multiple estimated degradation rates Des that are less than or equal to the representative value based on predetermined selection criteria. The target degradation rate determination unit 58 may randomly select one of several estimated degradation rates Des that are less than or equal to a representative value, or it may allow the user of the fuel cell system 12 (vehicle 10) to select one.

[0051] The temperature control necessity determination unit 60 determines whether temperature control, described later, is necessary for each of the multiple fuel cell units 18. More specifically, the temperature control necessity determination unit 60 compares multiple estimated degradation rates Des corresponding to each of the multiple fuel cell units 18 with a target degradation rate Dtgt to identify fuel cell units 18 whose estimated degradation rate Des is higher than the target degradation rate Dtgt. Fuel cell units 18 whose estimated degradation rate Des is higher than the target degradation rate Dtgt are determined to be fuel cell units 18 that require temperature control, described later.

[0052] Figure 4B is a simplified diagram showing the flow of the target cooling temperature determination process performed by the target temperature determination unit 62.

[0053] The target temperature determination unit 62 performs a target cooling temperature determination process based on the target degradation rate Dtgt and the causal relationship described above. The target cooling temperature determination process is a process for determining the target cooling temperature Ttgt (see also Figure 5) of the fuel cell unit 18. The target cooling temperature Ttgt of the fuel cell unit 18 is the target temperature of the fuel cell unit 18 that requires temperature control. Regarding the target cooling temperature determination process, the target temperature determination unit 62 has a target humidity determination unit 621 and a target cooling temperature determination unit 622, which will be described below.

[0054] The target humidity determination unit 621 executes a first determination process included in the target cooling temperature determination process. The first determination process is the process of determining the target relative humidity RHtgt of the cathode gas based on the target degradation rate Dtgt. The target relative humidity RHtgt is the target value of the relative humidity RHcg of the cathode gas at the stage when it reaches the fuel cell unit 18. As described above, there is a causal relationship between the relative humidity RHcg of the cathode gas and the degradation rate of the fuel cell unit 18. Based on this causal relationship, the target humidity determination unit 621 identifies the target value of the relative humidity RHcg of the cathode gas in order to bring the degradation rate of the fuel cell unit 18 closer to the target degradation rate Dtgt.

[0055] The target cooling temperature determination unit 622 executes a second determination process included in the target cooling temperature determination process. The second determination process determines the target cooling temperature Ttgt based on the amount of water vapor Wcg contained in the cathode gas and the target relative humidity RHtgt. As described above, there is a causal relationship between the temperature Tfc of the fuel cell unit 18, the change in the amount of water vapor Wcg contained in the cathode gas, and the change in relative humidity RHcg at the stage when it reaches the fuel cell unit 18. Based on this causal relationship, the target cooling temperature determination unit 622 identifies the target cooling temperature Ttgt that should be targeted in order to bring the relative humidity RHcg of the cathode gas closer to the target relative humidity RHtgt.

[0056] The target humidity determination unit 621 may perform the first determination process using a target humidity determination model. The target humidity determination model is a mathematical model that outputs a target relative humidity RHtgt of the cathode gas according to the target degradation rate Dtgt. The target cooling temperature determination unit 622 may also perform the second determination process using a target cooling temperature determination model. The target cooling temperature determination model is a mathematical model that outputs a target cooling temperature Ttgt according to the amount of water vapor Wcg contained in the cathode gas and the target relative humidity RHtgt. The target humidity determination model and the target cooling temperature determination model may each be statistical models or trained machine learning models.

[0057] The temperature control unit 64 performs temperature control. Temperature control includes the process of the temperature control unit 64 controlling the temperature control device 22 based on the target cooling temperature Ttgt to lower the temperature of the refrigerant. Temperature control may also include the process of controlling the refrigerant pump unit 47 based on the target cooling temperature Ttgt to increase the flow rate of the refrigerant. This lowers the temperature of the refrigerant. Temperature control may also include the process of controlling the cooler 42 based on the target cooling temperature Ttgt to lower its temperature.

[0058] As the temperature of the refrigerant decreases, the temperature Tfc of the fuel cell unit 18, which is cooled by the refrigerant, decreases. As the temperature Tfc of the fuel cell unit 18 decreases, the degradation rate of the fuel cell unit 18 approaches the target degradation rate Dtgt, based on the causal relationship described above. The temperature control unit 64 continues temperature control until the temperature Tfc of the fuel cell unit 18, which has been determined to require temperature control based on the result of the temperature control necessity determination unit 60, reaches the target cooling temperature Ttgt of the fuel cell unit 18. When the temperature Tfc of the fuel cell unit 18 reaches the target cooling temperature Ttgt, the temperature control unit 64 terminates temperature control for the fuel cell unit 18.

[0059] Figure 5 schematically shows the time-series changes of the cathode gas temperature Tcg, the cathode gas relative humidity RHcg, the estimated degradation rate Des of the fuel cell unit 18, and the temperature Tfc of the fuel cell unit 18.

[0060] Figure 5 shows the first time point t1. The first time point t1 is the point at which the cathode gas temperature Tcg begins to rise relatively significantly. For example, the cathode gas temperature Tcg rises when it is heated by a heat source provided in the vehicle 10. This heat source includes, for example, a power generation system 14 provided in the fuel cell system 12. For example, if multiple power generation systems 14 (141, 142) are arranged in the longitudinal direction of the vehicle 10 DFB (see also Figure 1), the waste heat from one power generation system 141 located at the front may heat the cathode gas supplied to another power generation system 142 located at the rear. Also, as mentioned above, the cathode gas may be taken in from the atmosphere. In this case, the cathode gas temperature Tcg may change depending on the external environment of the fuel cell system 12 (vehicle 10).

[0061] As the cathode gas temperature Tcg increases, the relative humidity RHcg of the cathode gas decreases. As a result, the degradation rate (estimated degradation rate Des) of the fuel cell unit 18 increases.

[0062] Furthermore, by restricting the operation of one of the power generation systems 141 mentioned above, the amount of waste heat from that power generation system 141 is reduced. This may lower the temperature Tcg of the cathode gas supplied to the other power generation systems 142. However, since this may limit the overall power generation of the fuel cell system, restricting the operation of each of the multiple power generation systems 14 is not necessarily desirable.

[0063] Figure 5 further shows a second time point t2. The second time point t2 is the point in time when the target cooling temperature Ttgt is determined by the target temperature determination unit 62 and temperature control by the temperature control unit 64 begins. After the second time point t2, the temperature Tfc of the fuel cell unit 18 is lowered by temperature control. As a result, the relative humidity RHcg of the cathode gas increases after the second time point t2, bringing the degradation rate of the fuel cell unit 18 closer to the target degradation rate Dtgt. By lowering the temperature of the refrigerant, the temperature Tfc of the fuel cell unit 18 is lowered. As a result, even if the temperature Tcg of the cathode gas cannot be lowered significantly, the relative humidity RHcg of the cathode gas increases, and the degradation rate of the fuel cell unit 18 is suppressed.

[0064] Figure 6 is a flowchart of a control method according to one embodiment.

[0065] The control device 16 (computer) can execute the control method shown in Figure 6, for example, based on the program described above. The control method in Figure 6 includes a temperature acquisition step S1, an estimation step S2, a statistical processing step S3, a target degradation rate determination step S4, a temperature control necessity determination step S5, a target temperature determination step S6, and a temperature control step S7.

[0066] In the temperature acquisition step S1, the temperature acquisition unit 52 acquires gas temperature information and FC temperature information.

[0067] In estimation step S2, the estimation unit 54 derives the estimated degradation rate Des for each of the multiple fuel cell units 18. More specifically, estimation step S2 includes humidity estimation step S21 and degradation rate estimation step S22.

[0068] In the humidity estimation step S21, the humidity estimation unit 541 estimates the relative humidity RHcg of the cathode gas based on the temperature Tcg of the cathode gas supplied to the fuel cell unit 18 and the temperature Tfc of the fuel cell unit 18. The temperature Tcg of the cathode gas is indicated by the temperature information obtained in the temperature acquisition step S1. The temperature Tfc of the fuel cell unit 18 is indicated by the FC temperature information obtained in the temperature acquisition step S1.

[0069] In the degradation rate estimation step S22, the degradation rate estimation unit 542 estimates the estimated degradation rate Des based on the relative humidity RHcg of the cathode gas. The relative humidity RHcg of the cathode gas is shown by the result of the humidity estimation step S21.

[0070] In the statistical processing step S3, the statistical processing unit 56 derives representative values ​​of multiple estimated degradation rates Des estimated for each of the multiple fuel cell units 18. In the target degradation rate determination step S4, the target degradation rate determination unit 58 determines the target degradation rate Dtgt based on the results of the statistical processing step S3. In the temperature control necessity determination step S5, the temperature control necessity determination unit 60 determines whether temperature control is necessary for each of the multiple fuel cell units 18.

[0071] In the target temperature determination step S6, the target temperature determination unit 62 performs the target cooling temperature determination process. More specifically, the target temperature determination step S6 includes the target humidity determination step S61 and the target cooling temperature determination step S62.

[0072] In the target humidity determination step S61, the target humidity determination unit 621 determines the target relative humidity RHtgt based on the target degradation rate Dtgt. In this case, the target degradation rate Dtgt is shown by the result of the target degradation rate determination step S4.

[0073] In the target cooling temperature determination step S62, the target cooling temperature determination unit 622 determines the target cooling temperature Ttgt based on the target relative humidity RHtgt. In the temperature control step S7, the temperature control unit 64 performs temperature control. In this case, the target relative humidity RHtgt is indicated by the result of the target humidity determination step S61. The cathode gas temperature Tcg is indicated by the temperature information obtained in the temperature acquisition step S1.

[0074] The control device 16, fuel cell system 12, vehicle 10, and control method described above will produce the effects and benefits described below, for example.

[0075] The control device 16 includes a temperature control unit 64. When the estimated degradation rate Des is higher than the target degradation rate Dtgt of the fuel cell unit 18, the temperature control unit 64 controls the cooler 42 to lower the temperature Tfc of the fuel cell unit 18. This increases the relative humidity RHcg of the cathode gas, bringing the degradation rate of the fuel cell unit 18 closer to the target degradation rate Dtgt (see also Figure 5). In other words, the degradation of the fuel cell unit 18 is suppressed.

[0076] Temperature control is performed on fuel cell units 18 whose estimated degradation rate Des is higher than the target degradation rate Dtgt among the multiple fuel cell units 18. By performing temperature control, the temperature control unit 64 brings the degradation rate of each of the multiple fuel cell units 18 closer to the common target degradation rate Dtgt for all of the multiple fuel cell units 18. This reduces the variation in degradation rates among the multiple fuel cell units 18.

[0077] The target degradation rate Dtgt may be determined based on representative values ​​(such as the mean) of multiple estimated degradation rates Des. This reduces the risk of setting an excessively small or excessively large target degradation rate Dtgt.

[0078] The target temperature determination unit 62 determines the target cooling temperature Ttgt of the fuel cell unit 18 based on the target degradation rate Dtgt. The temperature control unit 64 lowers the temperature Tfc of the fuel cell unit 18 until it reaches the target cooling temperature Ttgt. Once the temperature Tfc of the fuel cell unit 18 reaches the target cooling temperature Ttgt, the temperature control for that fuel cell unit 18 is terminated. This prevents an increase in the variation in degradation rates of multiple fuel cell units 18. It also prevents the fuel cell unit 18 from being overcooled by the temperature control.

[0079] The control device 16 (estimation unit 54) includes a humidity estimation unit 541 and a degradation rate estimation unit 542. The humidity estimation unit 541 estimates the relative humidity RHcg of the cathode gas supplied to the fuel cell unit 18 based on the temperature Tcg of the cathode gas. This allows the control device 16 to estimate the estimated degradation rate Des.

[0080] One embodiment may be modified as described below. In the following description, any descriptions that overlap with the first embodiment will be omitted as appropriate. Reference numerals used for drawing reference in one embodiment will also be used in the following description unless otherwise specified.

[0081] (Variation 1) The degradation rate estimation model may also include a relative humidity estimation model. For example, the degradation rate estimation model may output an estimated degradation rate Des based on input data including gas temperature information and FC temperature information.

[0082] (Modification 2) The humidity estimation unit 541 may estimate the relative humidity RHcg of the cathode gas using a pre-prepared humidity estimation table. The humidity estimation table is a table that shows the correspondence between the temperature Tcg of the cathode gas and the relative humidity RHcg. The humidity estimation table is created in advance, for example, based on experiments or simulations.

[0083] (Variation 3) The degradation rate estimation unit 542 may estimate the estimated degradation rate Des of the electrolyte membrane using a pre-prepared degradation rate estimation table. The degradation rate estimation table is a table that shows the correspondence between the relative humidity RHcg of the cathode gas and the estimated degradation rate Des of the fuel cell unit 18. The degradation rate estimation table is created in advance, for example, based on experiments, simulations, etc.

[0084] (Modification 4) The target degradation rate Dtgt may be a predetermined value. In this case, the target degradation rate Dtgt may be arbitrarily specified by the user of the fuel cell system 12 (vehicle 10), or it may be specified by the manufacturer that provides the fuel cell system 12 (vehicle 10) to the user.

[0085] (Variation 5) The target cooling temperature determination model may be a model that includes the target humidity determination model. That is, the target cooling temperature determination model may output a target cooling temperature Ttgt according to the target degradation rate Dtgt. In this case, the target temperature determination unit 62 can perform the first determination process and the second determination process using the target cooling temperature determination model.

[0086] (Experimental variation 6) The target temperature determination unit 62 may perform the first determination process using a target humidity determination table. The target humidity determination table is a table that shows the correspondence between the target degradation rate Dtgt and the target relative humidity RHtgt. The target humidity determination table is created in advance, for example, based on experiments, simulations, etc.

[0087] (Example 7) The target temperature determination unit 62 may perform a second determination process using a target cooling temperature determination table. The target cooling temperature determination table is a table that shows the correspondence between the target relative humidity RHtgt and the target cooling temperature Ttgt. The target cooling temperature determination table is created in advance, for example, based on experiments, simulations, etc.

[0088] (Variation 8) The gas temperature sensor 24A may sequentially output a detection signal corresponding to the cathode gas temperature Tcg. The FC temperature sensor 24B may also sequentially output a detection signal corresponding to the refrigerant temperature. In this case, the estimation unit 54 may sequentially derive the estimated degradation rate Des even while the temperature control step S7 is being executed. The temperature control unit 64 may lower the temperature Tfc of the fuel cell unit 18 until the estimated degradation rate Des sequentially derived by the estimation unit 54 reaches the target degradation rate Dtgt. This suppresses the degradation of the fuel cell unit 18.

[0089] (A combination of multiple variations) The various modifications described above may be combined as appropriate, within the bounds of consistency.

[0090] The following additional information is disclosed regarding the above embodiments.

[0091] (Note 1) The control device (16) according to this disclosure is a control device for a fuel cell system (12) having a fuel cell unit (18), a humidifier (38) for humidifying the cathode gas supplied to the fuel cell unit, and a temperature control device (22) for adjusting the temperature of the fuel cell unit, and comprises an estimation unit (54) for deriving an estimated degradation rate (Des) of the fuel cell unit based on the temperature (Tcg) of the cathode gas introduced into the fuel cell unit, and a temperature control unit (64) for controlling the temperature control device to lower the temperature of the fuel cell unit when the estimated degradation rate is higher than the target degradation rate (Dtgt) of the fuel cell unit. This suppresses the degradation of the fuel cell unit.

[0092] (Note 2) The control device described in Appendix 1, wherein the fuel cell system comprises a plurality of fuel cell units and a plurality of humidifiers corresponding to each of the plurality of fuel cell units, and the temperature control unit may lower the temperature of the fuel cell unit whose estimated degradation rate is higher than the target degradation rate. This reduces the variation in the degradation rates of the plurality of fuel cell units.

[0093] (Note 3) The control device described in Appendix 2 further comprises a statistical processing unit (56) that derives representative values ​​of a plurality of estimated degradation rates estimated for each of the plurality of fuel cell units, and the target degradation rate may be determined based on the representative values. This reduces the risk of setting an excessively small target degradation rate, an excessively large target degradation rate, etc.

[0094] (Note 4) The control device described in Appendix 3, wherein the representative value may be the average value of a plurality of estimated degradation rates.

[0095] (Note 5) In the control device described in Appendix 3, any one of the estimated degradation rates that is less than or equal to the representative value may be determined as the target degradation rate.

[0096] (Note 6) The control device described in Appendix 1 or 2, wherein the target degradation rate may be a value specified in advance.

[0097] (Note 7) A control device as described in any one of appendices 1 to 5, further comprising a target temperature determination unit (62) that determines a target cooling temperature (Ttgt) of the fuel cell section based on the target degradation rate, wherein if the estimated degradation rate is higher than the target degradation rate, the temperature control unit may lower the temperature of the fuel cell section until the temperature of the fuel cell section reaches the target cooling temperature. This prevents, for example, an increase in the variation in the degradation rates of multiple fuel cell sections.

[0098] (Note 8) A control device as described in any one of Appendix 1 to 5, wherein the estimation unit sequentially derives the estimated degradation rate, and the temperature control unit may lower the temperature of the fuel cell unit until the estimated degradation rate sequentially deriven by the estimation unit reaches the target degradation rate.

[0099] (Note 9) A control device according to any one of appendices 1 to 8, wherein the estimation unit may include a humidity estimation unit (541) that estimates the relative humidity (RHcg) of the cathode gas supplied to the fuel cell unit based on the temperature of the cathode gas, and a degradation rate estimation unit (542) that estimates the estimated degradation rate based on the relative humidity.

[0100] (Note 10) The control device described in Appendix 9 may increase the estimated degradation rate derived by the estimation unit as the relative humidity decreases.

[0101] (Note 11) The control device described in any one of the appendices 1 to 10, wherein the estimated degradation rate derived by the estimation unit increases as the temperature of the cathode gas increases.

[0102] (Note 12) The fuel cell system relating to this disclosure comprises a control device described in any one of appendices 1 to 11, the fuel cell unit, the humidifier, and the temperature control device.

[0103] (Note 13) The control method according to this disclosure is a control method for a fuel cell system (12) having a fuel cell unit (18), a humidifier (38) for humidifying the cathode gas supplied to the fuel cell unit, and a temperature control device (22) for adjusting the temperature of the fuel cell unit, comprising: an estimation step (S2) for deriving an estimated degradation rate (Des) of the fuel cell unit based on the temperature (Tcg) of the cathode gas introduced into the fuel cell unit; and a temperature control step (S7) for controlling the temperature control device to lower the temperature of the fuel cell unit when the estimated degradation rate is higher than the target degradation rate (Dtgt) of the fuel cell unit.

[0104] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of symbols]

[0105] 12…Fuel cell systems 16...Control device 18…Fuel cell section 22…Temperature control device 38…humidifier 54…Estimation part 56…Statistical Processing Section 62...Target temperature determination section 64...Temperature control unit 541...Humidity estimation section 542...Deterioration rate estimation section Dtgt…Target deterioration rate Ttgt…Target cooling temperature

Claims

1. A control device for a fuel cell system having a fuel cell unit, a humidifier for humidifying the cathode gas supplied to the fuel cell unit, and a temperature control device for adjusting the temperature of the fuel cell unit, An estimation unit that derives an estimated degradation rate of the fuel cell based on the temperature of the cathode gas introduced into the fuel cell unit, A temperature control unit controls the temperature control device to lower the temperature of the fuel cell when the estimated degradation rate is higher than the target degradation rate of the fuel cell unit, A control device equipped with the following features.

2. A control device according to claim 1, The fuel cell system comprises a plurality of fuel cell units and a plurality of humidifiers corresponding to each of the plurality of fuel cell units. The temperature control unit is a control device that lowers the temperature of the fuel cell section where the estimated degradation rate is higher than the target degradation rate.

3. A control device according to claim 2, The system further includes a statistical processing unit that derives representative values ​​of a plurality of estimated degradation rates, each of which is estimated to correspond to a plurality of fuel cell sections. A control device in which the target degradation rate is determined based on the aforementioned representative value.

4. A control device according to claim 3, The control device wherein the aforementioned representative value is the average value of a plurality of estimated degradation rates.

5. A control device according to claim 3, A control device in which one of the estimated degradation rates that is less than or equal to the aforementioned representative value is determined as the target degradation rate.

6. A control device according to claim 1 or 2, The control device wherein the aforementioned target degradation rate is a value specified in advance.

7. A control device according to any one of claims 1 to 5, The system further includes a target temperature determination unit that determines a target cooling temperature for the fuel cell section based on the target degradation rate, If the estimated degradation rate is higher than the target degradation rate, the temperature control unit lowers the temperature of the fuel cell unit until the temperature of the fuel cell unit reaches the target cooling temperature.

8. A control device according to any one of claims 1 to 5, The estimation unit sequentially derives the estimated degradation rate, The temperature control unit is a control device that lowers the temperature of the fuel cell unit until the estimated degradation rate, which is successively derived by the estimation unit, reaches the target degradation rate.

9. A control device according to any one of claims 1 to 5, The estimation unit, A humidity estimation unit that estimates the relative humidity of the cathode gas supplied to the fuel cell unit based on the temperature of the cathode gas, A degradation rate estimation unit that estimates the estimated degradation rate based on the relative humidity, A control device having

10. A control device according to claim 9, A control device wherein the lower the relative humidity, the greater the estimated degradation rate derived by the estimation unit.

11. A control device according to any one of claims 1 to 5, A control device wherein the estimated degradation rate derived by the estimation unit increases as the temperature of the cathode gas increases.

12. A control device according to any one of claims 1 to 5, The fuel cell unit, The humidifier and, The temperature control device and A fuel cell system having the following features.

13. A control method for a fuel cell system having a fuel cell unit, a humidifier for humidifying the cathode gas supplied to the fuel cell unit, and a temperature control device for adjusting the temperature of the fuel cell unit, An estimation step of deriving the estimated degradation rate of the fuel cell based on the temperature of the cathode gas introduced into the fuel cell section, If the estimated degradation rate is higher than the target degradation rate of the fuel cell section, the temperature control step involves controlling the temperature control device to lower the temperature of the fuel cell section. A control method having

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