fuel cell system

Abstract

To provide a fuel cell system that can accurately specify the estimated amount of change.SOLUTION: A fuel cell system includes a fuel cell stack, a fuel cell, a temperature sensor, and a control device 81. A cooling system circulates a coolant between the fuel cell stack and a heat exchanger by rotating a cooling water pump. The temperature sensor is provided downstream side of the fuel cell stack and detects the temperature of the coolant. The control device 81 controls the cooling system. The control device 81 calculates the estimated amount of change in the temperature of the coolant in a predetermined time on the basis of the amount of heat by the power generation of the fuel cell stack and the volume of the coolant passing through the fuel cell stack in the predetermined time, and determines that the operation of the cooling system is abnormal if the deviation between the amount of change and the estimated amount of change exceeds a predetermined threshold, on the basis of the estimated amount of change and the amount of change in the temperature of the coolant.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system. [Background technology]

[0002] In recent years, technology related to fuel cell systems equipped with cooling systems for maintaining a constant internal temperature of the fuel cell has become known. Generally, the cooling system includes a refrigerant pump, a heat exchanger, piping for circulating the refrigerant, and a temperature sensor for detecting the temperature of the refrigerant circulating through the fuel cell. The cooling system regards the refrigerant temperature as the internal temperature of the fuel cell and controls the refrigerant pump and heat exchanger fan based on the refrigerant temperature to maintain a constant internal temperature of the fuel cell.

[0003] On the other hand, if the temperature sensor cannot detect the temperature properly due to a malfunction or the like, it is difficult for the cooling system to maintain a constant internal temperature of the fuel cell. In response to this, there is known a technique for calculating an estimated temperature value in preparation for a malfunction of the temperature sensor, and using the calculated estimated temperature value to control the cooling system (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-14236 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the technology disclosed in Patent Document 1, various parameters are used to calculate the temperature estimate, which makes the process of calculating the temperature estimate complex and may increase the processing load related to controlling the cooling system. [Means for solving the problem]

[0006] A fuel cell system that achieves the above-mentioned objective comprises a fuel cell stack, a cooling system that circulates a coolant between the fuel cell stack and a heat exchanger by rotating a cooling water pump, a temperature sensor located downstream of the fuel cell stack that detects the temperature of the coolant, and a control unit that controls the cooling system, wherein the control unit calculates an estimated amount of change in the temperature of the coolant over a predetermined period of time based on the amount of heat generated by the power generation of the fuel cell stack and the volume of the coolant passing through the fuel cell stack over the predetermined period of time, and based on the amount of change in the temperature of the coolant over the predetermined period of time based on the detection result of the temperature sensor and the estimated amount of change, determines that the operation of the cooling system is abnormal if the deviation between the estimated amount of change and the amount of change exceeds a predetermined threshold.

[0007] With this configuration, the processing load related to the control of the cooling system can be reduced. In the above fuel cell system, the control unit may change the rotation speed of the cooling water pump based on the amount of power generated by the fuel cell stack.

[0008] The more electricity a fuel cell stack generates, the more heat it tends to generate. With this configuration, the cooling pump speed is controlled based on the amount of electricity generated by the fuel cell system, ensuring an appropriate flow rate of the coolant required to cool the fuel cell stack.

[0009] In the above fuel cell system, the cooling system may circulate the coolant using a circulation path, and the circulation path may not have a branch path and may directly connect the fuel cell stack and the heat exchanger.

[0010] According to this configuration, the estimated change amount can be determined with high accuracy. [Effects of the Invention]

[0011] According to the present invention, it is possible to reduce the processing load related to the control of the cooling system. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a fuel cell system. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a control device. [Figure 3] 4 is a flowchart showing an example of the operation of the control device. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Embodiment] An embodiment of a fuel cell system will be described below. <About the fuel cell system 40> 1, a vehicle 10 includes a load 11, a power conversion unit 12, a cooling system 21, and a fuel cell system 40. The vehicle 10 includes a passenger car and an industrial vehicle. The industrial vehicle is, for example, a forklift or a towing tractor.

[0014] The load 11 is a device driven by electric power. The load 11 is, for example, an electric motor driven by electric power. The vehicle 10 runs when driven by this electric motor. The power conversion unit 12 converts input electric power and outputs the converted power. The power conversion unit 12 includes a DC / DC converter and an inverter. The power output from the power conversion unit 12 is supplied to the load 11. This drives the load 11.

[0015] The fuel cell system 40 includes a fuel cell stack 41 , an air supply system 50 , a hydrogen supply system 61 , a water storage tank 71 , a water pipe 76 , a float sensor 77 , an opening / closing member 78 , and a control device 81 .

[0016] The fuel cell stack 41 generates electricity using hydrogen as a fuel gas and oxygen in the air as an oxidant gas. The fuel cell stack 41 is, for example, a polymer electrolyte fuel cell. The fuel cell stack 41 includes a plurality of fuel cell cells 42. Each fuel cell 42 includes an anode electrode to which a fuel gas is supplied, a cathode electrode to which an oxidant gas is supplied, and an electrolyte membrane disposed between the anode electrode and the cathode electrode. The electric power generated by the power generation in the fuel cell stack 41 is input to the power conversion unit 12. As a result, the load 11 is driven by the electric power generated by the fuel cell stack 41.

[0017] The cooling system 21 includes a circulation path 22, a fan 26, a cooling water pump 28, and a temperature sensor 29. The circulation path 22 includes a supply path 23, a discharge path 24, and a heat exchanger 25. The supply path 23 connects the fuel cell stack 41 and the heat exchanger 25. The discharge path 24 connects the fuel cell stack 41 and the heat exchanger 25. The heat exchanger 25 is, for example, a radiator. A refrigerant circulates through the circulation path 22. For example, water, antifreeze, or air is used as the refrigerant. Below, a case where the refrigerant is cooling water will be described.

[0018] The fan 26 blows air toward the heat exchanger 25. The fan 26 includes a fan motor 27. The fan 26 is driven by the fan motor 27. The air blown from the fan 26 cools the refrigerant inside the heat exchanger 25.

[0019] Cooling water pump 28 circulates the coolant through circulation path 22. Cooling water pump 28 causes the coolant to flow through supply path 23, fuel cell stack 41, discharge path 24, heat exchanger 25, and supply path 23 in this order. The coolant cooled in heat exchanger 25 is supplied to fuel cell stack 41 through supply path 23, thereby cooling fuel cell stack 41. After cooling the fuel cell stack 41, the coolant is supplied to heat exchanger 25 through discharge path 24, thereby cooling the coolant.

[0020] The temperature sensor 29 detects the temperature of the coolant. In this embodiment, the temperature sensor 29 is provided downstream of the fuel cell stack 41. More specifically, the temperature sensor 29 is provided in the discharge path 24 of the circulation path 22.

[0021] The air supply system 50 includes an electric compressor 51 and an inverter 53. The electric compressor 51 includes an electric motor 52. The electric compressor 51 is driven by the electric motor 52. The electric compressor 51 supplies air to the fuel cell stack 41. The amount of air supplied to the fuel cell stack 41 can be adjusted by controlling the rotation speed of the electric motor 52.

[0022] The inverter 53 converts input DC power into AC power and outputs it. The DC power input to the inverter 53 may be output from a battery mounted on the vehicle 10. The DC power input to the inverter 53 may be power obtained by power generation by the fuel cell stack 41 being stepped down by a step-down converter. The AC power output by the inverter 53 is supplied to the electric motor 52. The electric motor 52 is driven by the AC power output by the inverter 53.

[0023] The hydrogen supply system 61 includes a hydrogen tank 62, a pressure sensor 63, an injector 64, a hydrogen circulation pump 65, and a receptacle 66. The hydrogen tank 62 stores hydrogen.

[0024] The pressure sensor 63 detects the pressure in the hydrogen tank 62. The injector 64 is a component for adjusting the amount of hydrogen supplied from the hydrogen tank 62 to the fuel cell stack 41. The injector 64 is an electromagnetically driven on-off valve whose valve body is electromagnetically driven in accordance with the drive cycle and valve open time. The amount of hydrogen supplied to the fuel cell stack 41 can be adjusted by controlling the drive cycle and valve open time of the injector 64.

[0025] The hydrogen circulation pump 65 supplies unreacted hydrogen contained in the gas discharged from the fuel cell stack 41 back to the fuel cell stack 41. The receptacle 66 is a fill port for filling the hydrogen tank 62 with hydrogen. To fill the hydrogen tank 62 with hydrogen, the operator of the vehicle 10 drives the vehicle 10 to a hydrogen station. The hydrogen station is equipped with a hydrogen filling device. A fill nozzle of the hydrogen filling device is connected to the receptacle 66. The hydrogen filling device supplies hydrogen from the fill nozzle to the receptacle 66. Hydrogen is supplied to the hydrogen tank 62 via the receptacle 66. In this way, the hydrogen tank 62 is filled with hydrogen.

[0026] The water storage tank 71 stores water produced by the fuel cell stack 41. In the following description, the water produced by the fuel cell stack 41 may be referred to as produced water. As shown in FIG. 2, the water storage tank 71 has a water storage area A1 capable of storing the produced water. The water storage tank 71 also has a drain outlet 75. A water pipe 76 is connected to the drain outlet 75.

[0027] The float sensor 77 is provided in the water storage area A1. The float sensor 77 is a sensor used by the control device 81 to detect when the water storage tank 71 is full. The float sensor 77 is provided below the ceiling of the water storage area A1. Full water refers to a state in which the water level in the water storage area A1 reaches the float sensor 77. When the water level in the water storage area A1 rises and reaches the float sensor 77, the position of the float sensor 77 changes. The electrical signal output from the float sensor 77 changes as the position changes. The maximum amount of produced water that can be stored in the water storage tank 71 is the same as the volume of the water storage area A1.

[0028] The opening / closing member 78 is provided on the water distribution pipe 76. The opening / closing member 78 switches between an open state and a closed state. When the opening / closing member 78 is in the open state, the produced water is allowed to flow through the inside of the water distribution pipe 76, and the produced water in the water storage tank 71 is discharged to the outside of the water storage tank 71 via the water distribution pipe 76. When the opening / closing member 78 is in the closed state, the water distribution pipe 76 is blocked by the opening / closing member 78, and the produced water in the water storage tank 71 is not discharged from the water distribution pipe 76. The opening / closing member 78 may be an electromagnetic valve that can be electrically switched between an open state and a closed state. The opening / closing member 78 may be a plug that can be manually switched between an open state and a closed state.

[0029] The produced water is discharged from the water storage tank 71 at a hydrogen station. When filling the hydrogen tank 62 with hydrogen, the operator of the vehicle 10 can also discharge the produced water from the water storage tank 71. The produced water is discharged from the water storage tank 71 by opening the opening / closing member 78. After the produced water has been discharged from the water storage tank 71, the opening / closing member 78 is closed.

[0030] <Configuration of the control device 81> As shown in FIG. 2, the control device 81 includes a control unit 100 and a storage unit 200. The control unit 100 is realized by a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of these components may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware. The program may be stored in the storage unit 200, which includes a non-transitory storage medium such as an HDD (Hard Disk Drive) or flash memory.

[0031] The storage unit 200 may be realized by the above-mentioned various storage devices, or an EEPROM (Electrically Erasable Programmable Read Only Memory), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. In addition to the above-mentioned programs, the storage unit 200 stores threshold information 201. Details of the threshold information 201 will be described later.

[0032] The control unit 100 includes, for example, an acquisition unit 101, a fuel cell stack control unit 102, a calculation unit 103, and a determination unit 104. The acquisition unit 101 acquires various pieces of information from, for example, each unit included in the fuel cell system 40. More specifically, the acquisition unit 101 acquires information indicating the temperature of the refrigerant detected by the temperature sensor 29.

[0033] The fuel cell stack control unit 102 controls the power generation of the fuel cell stack 41. The fuel cell stack control unit 102 sets a target value for the amount of power generation of the fuel cell stack 41, i.e., a target value for the output of the fuel cell stack 41. The fuel cell stack control unit 102 can adjust the amount of air supplied to the fuel cell stack 41 by controlling the electric compressor 51. The fuel cell stack control unit 102 can adjust the amount of hydrogen supplied to the fuel cell stack 41 by controlling the injector 64. In this way, the fuel cell stack control unit 102 can control the output of the fuel cell stack 41. The fuel cell stack control unit 102 controls the output of the fuel cell stack 41 so that it follows the target value.

[0034] The fuel cell stack control unit 102 also detects the remaining amount of hydrogen, i.e., the amount of hydrogen stored in the hydrogen tank 62. The remaining amount of hydrogen can be detected from the pressure in the hydrogen tank 62 detected by the pressure sensor 63. There is a correlation between the remaining amount of hydrogen and the pressure in the hydrogen tank 62. For this reason, the fuel cell stack control unit 102 can detect the remaining amount of hydrogen by using a map that associates the hydrogen pressure with the remaining amount of hydrogen, or by using a relational expression between the hydrogen pressure and the remaining amount of hydrogen.

[0035] The fuel cell stack control unit 102 also detects whether the water storage tank 71 is full based on the detection result of the float sensor 77. As the amount of produced water stored in the water storage tank 71 increases, the water level in the water storage area A1 rises. When the water level in the water storage area A1 reaches the float sensor 77, the attitude of the float sensor 77 changes. The fuel cell stack control unit 102 can detect whether the water storage tank 71 is full based on the change in the electrical signal. The water storage tank 71 being full means that the produced water stored in the water storage tank 71 has reached a predetermined amount. In this embodiment, the amount of produced water when the water level in the water storage area A1 reaches the float sensor 77 is a predetermined amount. The amount of produced water when the water level in the water storage area A1 reaches the float sensor 77 is, for example, less than the maximum amount of produced water that can be stored in the water storage tank 71. The fuel cell stack control unit 102 issues a warning before the amount of produced water in the water storage tank 71 reaches the maximum amount that can be stored in the water storage tank 71.

[0036] The fuel cell stack control unit 102 also controls the cooling system 21. A target temperature is set for the temperature of the refrigerant in a steady state. The fuel cell stack control unit 102 controls the cooling system 21 so that the temperature of the refrigerant follows the target temperature. For example, the fuel cell stack control unit 102 monitors the temperature of the refrigerant using the temperature sensor 29 and controls the fan motor 27 to make the temperature of the refrigerant follow the target temperature. Here, when the amount of power generated by the fuel cell stack 41 is large, the temperature of the refrigerant increases. Therefore, the cooling system 21 cools the refrigerant more as the amount of power generated by the fuel cell stack 41 increases. To cool the refrigerant more, the cooling system 21 increases the rotation speed of the cooling water pump 28 and increases the flow rate of the refrigerant circulated through the circulation path 22 by the cooling water pump 28. In other words, the amount of power generated by the fuel cell stack 41 and the rotation speed of the cooling water pump 28 are correlated. For this reason, the fuel cell stack control unit 102 changes the rotation speed of the cooling water pump 28 based on the amount of power generated by the fuel cell stack 41. Specifically, the fuel cell stack control unit 102 controls the cooling water pump 28 so that the rotation speed increases as the amount of power generated by the fuel cell stack 41 increases.

[0037] The calculation unit 103 calculates an estimated amount of change ΔT in the temperature of the refrigerant over a predetermined time t based on the heat generation amount CV and the volume FV. The predetermined time t is a time interval approximately equal to the time interval at which the determination process of the determination unit 104 is performed, and is, for example, a time of several seconds to several hundred seconds. The heat generation amount CV is the amount of heat generated by the power generation of the fuel cell stack 41. The volume FV is the volume of the refrigerant passing through the fuel cell stack 41 over the predetermined time t. Details of the calculation process of the estimated amount of change ΔT by the calculation unit 103 will be described later.

[0038] Based on the estimated change ΔT calculated by the calculation unit 103 and the detection result of the temperature sensor 29, the determination unit 104 determines whether the discrepancy between the change ΔRT in the refrigerant temperature at a predetermined time t and the estimated change ΔT exceeds a threshold value TH1. The change ΔRT is, for example, a value obtained by subtracting a value indicating the refrigerant temperature detected by the temperature sensor 29 at a certain timing from a value indicating the refrigerant temperature detected by the temperature sensor 29 after the predetermined time t has elapsed from the certain timing. The determination unit 104 acquires information indicating the detection results from the temperature sensor 29 at the determination timing and at the timing when the predetermined time t has elapsed from the determination timing. The determination unit 104 identifies the change ΔRT based on the acquired information. If the absolute value of the value obtained by subtracting the change ΔRT from the estimated change ΔT exceeds the threshold value TH1, the determination unit 104 determines that the discrepancy between the change ΔRT and the estimated change ΔT exceeds the predetermined threshold value. The threshold value TH1 is indicated in, for example, the threshold value information 201, and the determination unit 104 refers to the threshold value information 201 when performing the determination process.

[0039] Here, when the cooling system 21 is operating properly, the amount of change ΔRT follows the estimated amount of change ΔT, and therefore the amount of change ΔRT does not diverge from the amount of change ΔRT. On the other hand, when the cooling system 21 is not operating properly, the amount of change ΔRT does not follow the estimated amount of change ΔT, and the divergence between the amount of change ΔRT and the estimated amount of change ΔT exceeds the threshold value TH1. Specifically, when the actual refrigerant temperature does not rise more than the estimated refrigerant temperature rise, or when the temperature sensor 29 is not properly detecting the refrigerant temperature, the divergence between the amount of change ΔRT and the estimated amount of change ΔT may exceed the threshold value TH1. In other words, when the divergence between the amount of change ΔRT and the estimated amount of change ΔT exceeds the threshold value TH1, the operation of the cooling system 21 is abnormal. Therefore, when the determination unit 104 determines that the divergence between the amount of change ΔRT and the estimated amount of change ΔT exceeds the threshold value TH1, the determination unit 104 determines that the operation of the cooling system 21 is abnormal. The fuel cell stack control unit 102 stops the operation of the fuel cell system 40 when the determining unit 104 determines that the operation of the cooling system 21 is abnormal.

[0040] [Calculation process for estimated change ΔT] The calculation process of the estimated change amount ΔT by the calculation unit 103 will be described in detail below. First, the calculation unit 103 calculates the calorific value CV based on the following equation (1). The lower heating value LHV used in calculating the calorific value CV can take a predetermined value based on the IV characteristics of the fuel cell system 40. Specifically, the lower heating value LHV is the amount of heat equivalent to the power generated when water generated when hydrogen is completely converted into electricity is in gas form. Specifically, the lower heating value LHV is the value obtained by subtracting the latent heat of condensation of water vapor from the higher heating value HHV. The higher heating value HHV is the amount of heat equivalent to the power generated when water generated when hydrogen is completely converted into electricity is in liquid form. Information indicating the lower heating value LHV may be acquired from another device capable of transmitting and receiving information to and from the control device 81, or may be pre-stored in the storage unit 200.

[0041] In the following description, the voltage generated by the fuel cell stack 41 will be referred to as a stack voltage Va, and the current flowing through the fuel cell stack 41 will be referred to as a stack current Ia. The number of fuel cell units 42 in the fuel cell stack 41 will be referred to as the cell number CN. The calculation unit 103 acquires information indicating the stack voltage Va as a measurement result from, for example, a measurement unit (not shown) that measures the stack voltage Va. The calculation unit 103 also acquires information indicating the stack current Ia as a measurement result from a measurement unit (not shown) that measures the stack current Ia. The information indicating the cell number CN is pre-stored in the memory unit 200.

[0042] CV = (LHV × CN - Va) × Ia…(1) CV: Heat output [W] LHV: Low Heat Value [V] CN: Cell number measurement Va: Stack voltage [V] Ia: Stack current [A] Next, the calculation unit 103 determines the volume FV. The calculation unit 103 determines the volume FV based on, for example, the flow rate of the cooling water pump 28 or the maximum flow rate of the refrigerant circulated by the cooling water pump 28 in a predetermined time t. Below, a case will be described in which the calculation unit 103 determines the maximum flow rate of the refrigerant circulated by the cooling water pump 28 in a predetermined time t as the volume FV. Next, the calculation unit 103 calculates the estimated change ΔT based on the following equation (2) using the calculated heat generation amount CV and the determined volume FV. The integrated heat generation amount CIV used to calculate the estimated change ΔT is a value obtained by multiplying the heat generation amount CV by the predetermined time t. Furthermore, the specific heat SF used to calculate the estimated change ΔT may take a predetermined value depending on the refrigerant used. Information indicating the specific heat SF may be acquired from another device capable of transmitting and receiving information to and from the control device 81, or may be pre-stored in the storage unit 200.

[0043] ΔT = CIV ÷ SF ÷ FV…(2) (CIV = CV × t) ΔT: Estimated change [℃] CIV: Heat generation integrated value [J] SF: specific heat [J / kg K] FV: Volume [L] CV: Heat output [W] t: Predetermined time [sec] As described above, the integrated heat generation value CIV is the value obtained by multiplying the heat generation amount CV by the predetermined time t. Therefore, the estimated change amount ΔT can be expressed as the following equation (3) based on equations (1) and (2).

[0044] ΔT=(LHV×CN-Va)×Ia×t÷SF÷FV…(3) ΔT: Estimated change [℃] LHV: Low Heat Value [V] CN: Number of cells [sheets] Va: Stack voltage [V] Ia: Stack current [A] t: Predetermined time [sec] SF: specific heat [J / kg K] FV: Volume [L] [Operation flow] An example of the operation of the control device 81 will be described below with reference to Fig. 3. The flowchart shown in Fig. 3 is executed, for example, at predetermined time intervals. The predetermined time intervals are time intervals at which it is preferable to determine whether the cooling system 21 is operating properly, and are, for example, intervals of several seconds to several hundred seconds. Furthermore, the fuel cell stack control unit 102 executes control related to power generation by the fuel cell stack 41 in parallel with the flowchart shown in Fig. 3.

[0045] First, the acquisition unit 101 acquires information indicating the refrigerant temperature detected by the temperature sensor 29 (step S100). The calculation unit 103 calculates an estimated amount of change ΔT in the refrigerant temperature over a predetermined time t based on the heat generation amount CV and the volume FV (step S102). More specifically, the calculation unit 103 calculates the estimated amount of change ΔT based on the heat generation amount CV, the stack current Ia, the predetermined time t, the specific heat SF, and the volume FV.

[0046] Based on the estimated change ΔT calculated by the calculation unit 103 and the detection result of the temperature sensor 29, the determination unit 104 determines whether the discrepancy between the change ΔRT in the refrigerant temperature at a predetermined time t and the estimated change ΔT exceeds a threshold value TH1 (step S104). Specifically, the determination unit 104 acquires information indicating the detection result from the temperature sensor 29 at the determination timing and at a timing when the predetermined time t has elapsed from the determination timing. The determination unit 104 identifies the change ΔRT based on the acquired information. If the value obtained by subtracting the change ΔRT from the estimated change ΔT exceeds the threshold value TH1, the determination unit 104 determines that the discrepancy between the change ΔRT and the estimated change ΔT exceeds the predetermined threshold value. If the determination unit 104 determines that the discrepancy between the change ΔRT and the estimated change ΔT does not exceed the threshold value TH1, the process ends. It is preferable to determine the deviation between the amount of change ΔRT and the estimated amount of change ΔT based on the absolute value of the difference between the amount of change ΔRT and the estimated amount of change ΔT.

[0047] If the judgment unit 104 determines that the deviation between the change amount ΔRT and the estimated change amount ΔT exceeds a predetermined threshold, the fuel cell stack control unit 102 determines that the operation of the cooling system 21 is abnormal and stops the operation of the fuel cell system 40 (step S106).

[0048] [Effects of the embodiment] According to the above embodiment, the following effects can be obtained. (1) The fuel cell system 40 includes a fuel cell stack 41, fuel cells 42, a temperature sensor 29, and a control device 81. The control device 81 includes a calculation unit 103 and a determination unit 104. The cooling system 21 circulates a coolant between the fuel cell stack 41 and the heat exchanger 25 by rotating a cooling water pump 28. The temperature sensor 29 is provided downstream of the fuel cell stack 41 and detects the temperature of the coolant. The control device 81 controls the cooling system 21. The control device 81 includes a calculation unit 103 and a determination unit 104. The calculation unit 103 calculates an estimated amount of change ΔT in the temperature of the coolant over a predetermined time t based on the amount of heat generated by the fuel cell stack 41 and the volume FV of the coolant passing through the fuel cell stack 41 over the predetermined time t. Based on the change amount ΔRT of the refrigerant temperature at a predetermined time t based on the detection result of the temperature sensor 29 and the estimated change amount ΔT, the judgment unit 104 judges that the operation of the cooling system 21 is abnormal if the deviation between the change amount ΔRT and the estimated change amount ΔT exceeds a predetermined threshold.

[0049] With this configuration, the determination unit 104 can determine whether or not the operation of the cooling system 21 is abnormal, based solely on the detection result of the temperature sensor 29. Therefore, the fuel cell system 40 can determine the state of the cooling system 21 through simple processing, based solely on the detection result of the temperature sensor 29, and can reduce the processing load related to the control of the cooling system 21.

[0050] (2) The cooling system 21 circulates the refrigerant using the circulation path 22, which does not have any branch paths and directly connects the fuel cells 42 and the heat exchanger 25. Here, if a branch path is provided in the circulation path 22, of the refrigerant circulated by the cooling system 21, the refrigerant flowing through the branch path does not pass through the heat exchanger 25 and is not cooled. In this case, the accuracy of the estimated change amount ΔT calculated by the calculation unit 103 decreases. With this configuration, the circulation path 22 does not have a branch path and directly connects the fuel cell 42 and the heat exchanger 25, so the calculation unit 103 can accurately calculate the estimated change amount ΔT.

[0051] The above-described embodiments may be modified as follows: The above-described embodiments and the following modifications may be combined with each other within the scope of technical compatibility. For example, the calculation unit 103 may determine the volume FV based on the flow rate of the refrigerant circulated by the coolant pump 28 in the predetermined time t, instead of the maximum flow rate of the refrigerant circulated by the coolant pump 28 in the predetermined time t. Here, the power consumption of the coolant pump 28 and the volume of the refrigerant circulated through the circulation path 22 by the coolant pump 28 in the predetermined time t are correlated. Specifically, the power consumption of the coolant pump 28 increases as the volume of the refrigerant circulated through the circulation path 22 by the coolant pump 28 in the predetermined time t increases. Therefore, the calculation unit 103 can uniquely determine the volume FV of the refrigerant circulated through the circulation path 22 based on the measurement results of a measurement unit that measures the power consumption of the coolant pump 28. When the calculation unit 103 calculates the estimated change ΔT using the maximum flow rate of the refrigerant circulated by the coolant pump 28 in the predetermined time t as the volume FV, the calculation unit 103 can set stricter determination conditions for the determination unit 104. On the other hand, when the calculation unit 103 calculates the estimated change amount ΔT using the volume FV as the flow rate of the refrigerant circulated by the cooling water pump 28 in a predetermined time t, the calculation unit 103 can cause the judgment unit 104 to perform the judgment process using judgment conditions that are more in line with the actual situation of the fuel cell system 40.

[0052] The calculation unit 103 may correct the estimated change ΔT based on, for example, the heat dissipation coefficient of the fuel cell system 40 or the cooling system 21. Furthermore, the determination unit 104 may correct the change ΔRT based on the heat dissipation coefficient of the fuel cell system 40 or the cooling system 21.

[0053] As described above, the power consumption of the cooling water pump 28 correlates with the volume of refrigerant that the cooling water pump 28 circulates through the circulation path 22 in a given time t. Furthermore, the rotation speed of the cooling water pump 28 corresponds to the power consumption of the cooling water pump 28. Specifically, as the rotation speed of the cooling water pump 28 increases, the power consumption of the cooling water pump 28 also increases, and as the rotation speed of the cooling water pump 28 decreases, the power consumption of the cooling water pump 28 also decreases. Furthermore, as described above, the amount of power generated by the fuel cell stack 41 correlates with the rotation speed of the cooling water pump 28. Therefore, the amount of power generated by the fuel cell stack 41 correlates with the volume of refrigerant that the cooling water pump 28 circulates through the circulation path 22 in a given time t. Therefore, the fuel cell stack control unit 102 may determine the volume of refrigerant that the cooling water pump 28 circulates through the circulation path 22 in a given time t based on the power generation amount of the fuel cell stack 41, and control the rotation speed of the cooling water pump 28 based on the determined volume.

[0054] Determination unit 104 may determine that the deviation between the change ΔRT and the estimated change ΔT exceeds a predetermined threshold when the value obtained by subtracting the change ΔRT from the estimated change ΔT is equal to or greater than threshold TH2. Threshold TH2 is a value corresponding to the deviation between the estimated change ΔT and the change ΔRT that can be expected when the refrigerant temperature is not properly detected due to a malfunction of temperature sensor 29, for example. In this case, threshold information 201 includes information indicating threshold TH2 instead of (or in addition to) threshold TH1. With this configuration, determination unit 104 can determine that the operation of cooling system 21 is abnormal when the refrigerant temperature is not properly detected due to a malfunction of temperature sensor 29 and a temperature lower than the actual refrigerant temperature is detected.

[0055] The determination unit 104 may determine that the deviation between the change ΔRT and the estimated change ΔT exceeds a predetermined threshold when the value obtained by subtracting the estimated change ΔT from the change ΔRT is less than a threshold TH3. The threshold TH3 is a value corresponding to the deviation between the expected change ΔRT and the estimated change ΔT when, for example, the amount of heat dissipated by the fuel cell system 40 or the cooling system 21 is greater than expected. In this case, the threshold information 201 includes information indicating the threshold TH3 instead of (or in addition to) the threshold TH1. With this configuration, the determination unit 104 can determine that the operation of the cooling system 21 is abnormal when the estimated change ΔT cannot be appropriately estimated because, for example, the amount of heat dissipated by the fuel cell system 40 or the cooling system 21 is different from expected, and a temperature higher than expected is detected.

[0056] Instead of (or in addition to) a configuration in which temperature sensor 29 outputs information indicative of the detection result of the refrigerant temperature to control device 81, temperature sensor 29 may output information indicative of the amount of change ΔRT to control device 81. Specifically, temperature sensor 29 subtracts a value indicative of the refrigerant temperature detected at a certain timing from a value indicative of the refrigerant temperature detected after a predetermined time t has elapsed from the certain timing, and outputs the resulting value as the amount of change ΔRT to control device 81 at intervals of predetermined time t. In this case, based on the amount of change ΔRT obtained from temperature sensor 29 and the estimated amount of change ΔT calculated by calculation unit 103, determination unit 104 determines whether the deviation between the amount of change ΔRT and the estimated amount of change ΔT exceeds a predetermined threshold.

[0057] The mobile object may be, for example, an aircraft or a train, as long as it is equipped with the fuel cell stack 41. [Explanation of symbols]

[0058] 10...vehicle, 11...load, 12...power conversion unit, 21...cooling system, 22...circulation path, 23...supply path, 24...discharge path, 25...heat exchanger, 26...fan, 27...fan motor, 28...cooling water pump, 29...temperature sensor, 40...fuel cell system, 41...fuel cell stack, 42...fuel cell, 50...air supply system, 51...electric compressor, 52...electric motor, 53...inverter, 61...hydrogen supply system, 62...hydrogen tank, 63...pressure sensor, 64...injector, 65...hydrogen circulation pump, 66...receptacle , 71...water storage tank, 75...drain outlet, 76...distribution pipe, 77...float sensor, 78...opening / closing member, 81...control device, 100...control unit, 101...acquisition unit, 102...fuel cell stack control unit, 103...calculation unit, 104...determination unit, 200...memory unit, CIV...accumulated heat value, CN...number of cells, CV...heat value, FV...volume, HHV...higher heat value, Ia...stack current, LHV...lower heat value, SF...specific heat, t...predetermined time, TH1, TH2, TH3...threshold value, Va...stack voltage, ΔRT...amount of change, ΔT...estimated amount of change.

Claims

1. a fuel cell stack; a cooling system that circulates a coolant between the fuel cell stack and a heat exchanger by rotating a cooling water pump; a temperature sensor provided downstream of the fuel cell stack for detecting the temperature of the coolant; a control unit that controls the cooling system, The control unit calculating an estimated amount of change in the temperature of the coolant over a predetermined time period based on the amount of heat generated by the fuel cell stack and the volume of the coolant passing through the fuel cell stack over the predetermined time period; and determining that the operation of the cooling system is abnormal when a deviation between the amount of change in the temperature of the refrigerant over the predetermined time period based on the detection result of the temperature sensor and the estimated amount of change exceeds a predetermined threshold. A fuel cell system characterized by:

2. the control unit changes the rotation speed of the cooling water pump based on the amount of power generated by the fuel cell stack.

2. The fuel cell system according to claim 1.

3. The cooling system circulates the refrigerant using a circulation path, the circulation path does not have a branch path and directly connects the fuel cell stack and the heat exchanger; 3. The fuel cell system according to claim 1 or 2.

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