fuel cell system

Abstract

To provide technology to effectively utilize a voltage converter that steps down an output voltage of a FC stack to supply electric power to an electric device.SOLUTION: A fuel cell system disclosed in the present specification includes: a fuel cell stack which generates electric power; a voltage converter which steps down an output voltage of the fuel cell stack by a circuit of a switching element; a cooler which includes a coolant to cool the voltage converter; and a controller which controls the voltage converter. The voltage converter can supply electric power to a plurality of electric devices. The controller determines an output upper limit of the voltage converter depending on a temperature of the switching element and a temperature of the coolant. In the fuel cell system, the voltage converter can be effectively utilized by adjusting the output upper limit depending on a state of the voltage converter.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a fuel cell system that generates electricity. Mu Regarding. [Background technology]

[0002] Patent Document 1 discloses an automobile (fuel cell vehicle) equipped with a fuel cell stack. The fuel cell vehicle is equipped with various electric devices. The fuel cell vehicle of Patent Document 1 is equipped with multiple voltage converters that step down the output voltage of the fuel cell stack. Power is supplied from the multiple voltage converters to multiple electric devices. The fuel cell vehicle of Patent Document 1 uses the multiple voltage converters appropriately depending on the magnitude of the load. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-090278 Summary of the Invention [Problem to be solved by the invention]

[0004] A voltage converter has a set output upper limit. The output upper limit of the voltage converter may change depending on the state of the voltage converter. One technique disclosed in this specification is to adjust the output upper limit according to the state of the voltage converter and make effective use of the voltage converter. Another technique disclosed in this specification is to adjust the output of the electric device being driven so that the output of the voltage converter does not exceed the output upper limit. [Means for solving the problem]

[0005] One aspect of the technology disclosed in this specification is embodied in a fuel cell system. This fuel cell system includes a fuel cell stack that generates electric power, a voltage converter that reduces the output voltage of the fuel cell stack using a switching element circuit, a cooler that includes a refrigerant that cools the voltage converter, and a controller that controls the voltage converter. The voltage converter can supply electric power to multiple electrical devices. The controller determines the upper limit of the output of the voltage converter based on the temperature of the switching element and the temperature of the refrigerant. This fuel cell system can effectively utilize the voltage converter by adjusting the upper limit of the output based on the state of the voltage converter (the temperature of the switching element and the refrigerant).

[0006] The controller may determine the output upper limit based on the temperature of the fuel cell stack and the state of the fuel cell stack in addition to the temperature of the switching element and the temperature of the coolant. By adjusting the output upper limit of the voltage converter based on many parameters, the voltage converter can be used more effectively.

[0007] Priorities may be assigned in advance to the multiple electrical devices receiving power from the voltage converter. In this case, the controller may reduce the output of the electrical device with the lowest priority among the currently operating electrical devices when the total power consumption of the currently operating electrical devices exceeds an output allowable value that is lower than the output upper limit. The output allowable value is a value obtained by subtracting a margin from the output upper limit. In other words, when the total power consumption approaches the output upper limit, the controller can reduce the output of the electrical device with the lowest priority so that the total power consumption does not exceed the output upper limit.

[0011] Details and further improvements of the technology disclosed in this specification are described in the following "Description of Embodiments of the Invention." [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram of a fuel cell system (fuel cell vehicle) of a first embodiment. [Figure 2]10 is a flowchart of an output upper limit determination process. [Figure 3] 10 is a flowchart of an output upper limit determination process (modification); [Figure 4] 10 is a flowchart of a process performed by a controller of a fuel cell vehicle according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] For ease of explanation, "fuel cell" may be abbreviated as "FC" below. "Fuel cell system," "fuel cell stack," and "fuel cell vehicle" will be abbreviated as "FC system," "FC stack," and "FC vehicle," respectively.

[0014] (First embodiment) Figure 1 shows a block diagram of an FC system of the first embodiment. The FC system of the first embodiment is an FC vehicle 2. The FC vehicle 2 includes an FC stack 10, voltage converters 4 and 20, an inverter 5, a driving motor 6, and a controller 30. The voltage converter 4 is a step-up converter, and the voltage converter 20 is a step-down converter. The power generated by the FC stack 10 is boosted by the voltage converter 4 and supplied to the inverter 5. The inverter 5 converts the boosted DC power into AC power suitable for driving the motor 6. The motor 6 is driven by the AC power output by the inverter 5. The output shaft of the motor 6 is linked to the wheels. The FC vehicle 2 travels due to the output torque of the motor 6. The FC stack 10, voltage converter 4, and inverter 5 are controlled by the controller 30.

[0015] As is well known, the FC stack 10 generates electricity by reacting air and hydrogen. The FC stack 10 is equipped with a temperature sensor 15, a status sensor 16, and a cooler (FC cooler 12). The temperature sensor 15 measures the temperature of the FC stack 10, and the status sensor 16 measures the status of the FC stack 10. Examples of the status of the FC stack 10 include, but are not limited to, the output current and output voltage of the FC stack 10. The controller 30 acquires the measured values ​​of the temperature sensor 15 and the status sensor 16 and uses this information to operate the FC stack 10. The FC stack 10 is equipped with many more devices, but these are not shown in the figure. Examples of electrical devices essential for operating the FC stack 10 include a compressor that sends air to the FC stack 10 and a hydrogen pump that sends hydrogen to the FC stack 10.

[0016] The FC cooler 12 cools the FC stack 10. The FC cooler 12 has a refrigerant flow path 13. The refrigerant flow path 13 passes through the FC stack 10. The FC cooler 12 uses a pump (not shown) to flow refrigerant into the refrigerant flow path 13, cooling the FC stack 10. A temperature sensor 14 is provided on the FC stack outlet side of the refrigerant flow path 13. The temperature sensor 14 measures the refrigerant temperature after cooling the FC stack 10. The measurement value of the temperature sensor 14 is an index of the performance of the FC cooler 12. If the measurement value of the temperature sensor 14 is high, the controller 30 increases the output of the pump of the FC cooler 12 and increases the refrigerant flow rate.

[0017] The controller 30 is connected to the FC vehicle 2's main switch 31, vehicle speed sensor 32, accelerator position sensor 33, and so on. The main switch 31 can be switched between three states: off, accessory on, and power on. "Off" means that all electrical devices of the FC vehicle 2 are stopped. "Accessory on" means that the driving system (inverter 5 and motor 6) remains stopped, but other electrical devices are available. In "accessory on" and "power on" states, the controller 30 operates the FC stack 10.

[0018] When the main switch 31 is in the "power on" state, the controller 30 obtains the vehicle speed from the vehicle speed sensor 32 and the accelerator opening from the accelerator opening sensor 33. The controller 30 determines the target output of the motor 6 from the vehicle speed and the accelerator opening, and controls the FC stack 10, the voltage converter 4, and the inverter 5 so that the output of the motor 6 follows the target output.

[0019] A voltage converter 20 is also connected to the power output terminal of the FC stack 10. The voltage converter 20 is a step-down converter that steps down the output voltage of the FC stack 10 using a circuit including a switching element 21. Voltage converter circuits using switching elements 21 are well known, so a detailed description of the circuit will be omitted here. An example of the output voltage of the FC stack 10 is 500-700 volts. An example of the output voltage of the voltage converter 20 is 200-400 volts.

[0020] The voltage converter 20 is equipped with a temperature sensor 25 and a cooler (DDC cooler 22). The temperature sensor 25 measures the temperature of the switching element 21. The DDC cooler 22 cools the voltage converter 20 (i.e., the switching element 21). The DDC cooler 22 has a coolant flow path 23. The coolant flow path 23 passes through the voltage converter 20. The DDC cooler 22 uses a pump (not shown) to circulate coolant through the coolant flow path 23, cooling the voltage converter 20 (i.e., the switching element 21). A temperature sensor 24 is provided on the voltage converter outlet side of the coolant flow path 23. The temperature sensor 24 measures the coolant temperature after cooling the voltage converter 20 (i.e., the switching element 21). The measurement value of the temperature sensor 24 is an indicator of the performance of the DDC cooler 22. If the measurement value of the temperature sensor 24 is high, the controller 30 increases the output of the pump of the DDC cooler 22 and increases the coolant flow rate.

[0021] The voltage converter 20 can supply power to a plurality of electric devices. A plurality of electric devices 41 (41a-41c), 42 (42a-42c), and 43 (43a-43c) are connected to the output terminal (low voltage terminal) of the voltage converter 20.

[0022] The electrical devices that receive power from the voltage converter 20 are divided into several categories (FC-essential devices 41, driving-essential devices 42, and optional devices 43). Electrical devices necessary for operating the FC stack 10 are collectively referred to as the FC-essential devices 41. Examples of the FC-essential devices 41 include a compressor 41a that sends air to the FC stack 10, a hydrogen pump 41b that sends fuel to the FC stack 10, and an FC heater 41c that heats the FC stack 10 when the temperature of the FC stack 10 is below the allowable range. The compressor 41a, hydrogen pump 41b, and FC heater 41c are examples of the FC-essential devices 41, and although there are multiple other FC-essential devices 41, illustrations and descriptions of these will be omitted.

[0023] The electrical devices required to run the FC vehicle 2 are collectively referred to as essential driving devices 42. Examples of essential driving devices 42 include a power steering motor 42a, a brake assist motor 42b, and a headlight 42c. The power steering motor 42a, the brake assist motor 42b, and the headlight 42c are examples of essential driving devices 42, and although there are multiple other essential driving devices 42, illustration and description of these will be omitted.

[0024] Electrical devices that do not belong to either the FC-essential devices 41 or the driving-essential devices 42 are collectively referred to as optional devices 43. Examples of optional devices 43 include an air conditioner 43a that adjusts the air temperature inside the vehicle cabin, a seat heater 43b, and an external power supply 43c. The external power supply 43c is an electrical device that supplies power to electrical devices outside the vehicle. An "external electrical device" refers to an electrical device that is not built into the FC vehicle 2. The external power supply 43c can convert the DC power output by the voltage converter 20 into AC power that drives general household electrical appliances (for example, lamps 44a, audio equipment 44b, etc.) and output the converted power. The air conditioner 43a, seat heater 43b, and external power supply 43c are examples of optional devices 43, and although there are multiple other optional devices 43, illustration and description of these will be omitted.

[0025] The controller 30 is capable of communicating with electrical devices that receive power from the voltage converter 20 (excluding electrical devices outside the vehicle that are connected to the external power supply 43c), and is able to determine the category of an electrical device that is operating with power supplied from the voltage converter 20. Optional devices 43 such as an air conditioner 43a are operated by the user, but the controller 30 can also adjust the output of the optional devices 43. The FC-required devices 41 and the driving-required devices 42 are controlled by the controller 30.

[0026] An upper output limit is set for the voltage converter 20. The upper output limit is set based on the temperature of the coolant in the DDC cooler 22 and the temperature of the switching element 21 of the voltage converter 20. For ease of explanation, the temperature of the coolant in the DDC cooler 22 is referred to as the DDC coolant temperature, and the temperature of the switching element 21 is referred to as the SW element temperature. The controller 30 stores a relationship for determining the upper output limit from the DDC coolant temperature and the SW element temperature. The relationship for determining the upper output limit from the DDC coolant temperature and the SW element temperature may be stored in the controller 30 in the form of a map (correspondence table) or as a mathematical formula. The upper output limit is set to decrease as the SW element temperature increases. The upper output limit is also set to decrease as the DDC coolant temperature increases. This is because the operating conditions of the switching element 21 become more severe as the SW element temperature and the DDC coolant temperature increase.

[0027] 2 shows a flowchart of the output upper limit determination process executed by the controller 30. The controller 30 acquires the SW element temperature and the DDC coolant temperature (step S2). As described above, the SW element temperature is measured by the temperature sensor 25. The DDC coolant temperature is acquired from the temperature sensor 24. The controller 30 determines the output upper limit of the voltage converter 20 from the acquired temperatures (SW element temperature and DDC coolant temperature) (step S3). The controller 30 periodically repeats the process of FIG. 2. The controller 30 controls the voltage converter 20 (i.e., the switching element 21) so that the output of the voltage converter 20 does not exceed the output upper limit.

[0028] The process of FIG. 2 enables the FC vehicle 2 to use the voltage converter 20 efficiently.

[0029] A modified example of the process for determining the upper output limit will be described. In the modified process, the controller 30 determines the upper output limit by taking into consideration the temperature of the FC stack 10 (FC temperature) and the state of the FC stack 10 (FC state) in addition to the SW element temperature and DDC coolant temperature. As described above, the FC temperature is measured by the temperature sensor 15. The FC state is measured by the state sensor 16. Examples of the FC state include the output current and output voltage of the FC stack 10.

[0030] In a modified example, when the total power consumption of the electric devices approaches the upper output limit of the voltage converter 20, the controller 30 reduces the output of the electric devices with lower priority.

[0031] A flowchart of the modified output upper limit determination process is shown in Fig. 3. The controller 30 periodically repeats the process of Fig. 3.

[0032] The controller 30 acquires the SW element temperature, DDC coolant temperature, FC temperature, and FC state (step S12). Next, the controller 30 determines the upper limit of output of the voltage converter 20 from the acquired information (step S13). The controller 30 stores in advance the relationship between the SW element temperature, DDC coolant temperature, FC temperature, FC state, and the upper limit of output. This relationship may be in the form of a map (correspondence table) or a relational expression. As described above, the controller 30 controls the voltage converter 20 so that the output of the voltage converter 20 does not exceed the upper limit of output.

[0033] The controller 30 communicates with the electric devices receiving power from the voltage converter 20 and acquires the power consumption of the operating electric devices (excluding external devices receiving power from the external power supply 43c). The controller 30 calculates the sum of the acquired power consumption (total power consumption) (step S14). Next, the controller 30 compares the total power consumption with the output allowable value (step S15). The output allowable value is set to a value slightly lower than the output upper limit. More specifically, the output allowable value is set to a value obtained by subtracting a margin from the output upper limit.

[0034] If the total power consumption is greater than the allowable output value, the controller 30 reduces the output of the electric device with the lowest priority among the electric devices that are in operation (step S15: YES, S16).

[0035] Priorities are assigned in advance to each of the optional devices 43 (excluding external devices connected to the external power supply 43c) that receive power from the voltage converter 20. The highest priority is assigned to the external power supply 43c. The air conditioner 43a is assigned the second highest priority after the external power supply 43c. The seat heater 43b is assigned the lowest priority. The priorities are stored in the controller 30.

[0036] If the total power consumption exceeds the output allowable value while the air conditioner 43a, the seat heater 43b, and the external power supply 43c are operating, the controller 30 reduces the output of the seat heater 43b, which has the lowest priority. The controller 30 reduces the output of the seat heater 43b by an amount equivalent to the total power consumption minus the output allowable value (excess power). If the current output of the seat heater 43b is less than the excess power, the controller 30 reduces the output of the seat heater 43b to zero. That is, the controller 30 stops the seat heater 43b. When the seat heater 43b is stopped, the air conditioner 43a becomes the lowest-priority optional device 43 that is operating. After stopping the seat heater 43b, the controller 30 executes the process of FIG. 3 again. If the total power consumption exceeds the output allowable value (step S15: YES), the controller 30 reduces the output of the air conditioner 43a by an amount equivalent to the excess power (= total power consumption - output allowable value) (step S16).

[0037] In this way, the controller 30 effectively supplies as much power as possible to the electric device without causing the output of the voltage converter 20 to exceed the upper output limit.

[0038] The controller 30 does not reduce the output of the FC-essential device 41 and the driving-essential device 42. The voltage converter 20 is designed to be able to output enough power to operate the FC-essential device 41 and the driving-essential device 42 even when the output upper limit is at its lowest. When the state of the main switch 31 of the FC vehicle 2 is "accessory on," the FC vehicle 2 cannot drive, and therefore the total power consumption of the driving-essential devices is zero.

[0039] (Second embodiment) An FC vehicle of the second embodiment will be described. The hardware configuration of the FC vehicle of the second embodiment is the same as that of the FC vehicle 2 shown in Figure 1. In the second embodiment, the processing for preventing the output of the voltage converter 20 from exceeding the output upper limit differs from that of the first embodiment.

[0040] 4 shows a flowchart of the processing performed by the controller 30 in the FC vehicle 2 of the second embodiment. The controller 30 repeatedly executes the processing of FIG. 4 at a predetermined interval.

[0041] The controller 30 calculates the total power consumption of the FC-required devices 41 (step S22). Next, the controller 30 calculates the surplus power (step S23). The surplus power is a value obtained by subtracting the total power consumption of the FC-required devices 41 from the output upper limit of the voltage converter 20. Next, the controller 30 compares the total power consumption of the operating optional devices 43 with the output allowable value of the voltage converter 20 (step S24). The output allowable value is set to a value lower than the surplus power. Specifically, the output allowable value is set to a value obtained by subtracting a margin from the surplus power.

[0042] If the total power consumption of the optional devices 43 exceeds the output allowable value, the controller 30 reduces the output of the optional device with the lowest priority among the operating optional devices 43 (step S24: YES, S25). The priority of each optional device is predetermined and stored in the controller 30.

[0043] The controller 30 reduces the output of the lowest-ranked optional device by an amount equivalent to the excess power (=total power consumption of optional devices−allowable output value).

[0044] The above process can prevent the output of voltage converter 20 from exceeding the output upper limit.

[0045] When the external power supply device 43c is switched on, the controller 30 changes the formula for calculating surplus power. A maximum supply power is set for the external power supply device 43c. When the switch of the external power supply device 43c is on, the controller 30 calculates the surplus power by subtracting the total power consumption of the FC required devices 41 and the maximum supply power (maximum supply power of the external power supply device 43c) from the output upper limit of the voltage converter 20. If the total power consumption of the operating optional devices 43 exceeds the output allowable value (= surplus power - margin), the controller 30 reduces the output of the optional device with the lowest priority among the operating optional devices 43 (steps S24: YES, S25).

[0046] The external power supply 43c is permitted to be used only when the FC vehicle 2 is not running. As mentioned above, the main switch 31 of the FC vehicle 2 can be switched between three states: off, accessory on, and power on. When the main switch 31 is in the "accessory on" state, the controller 30 keeps the driving system (inverter 5 and motor 6) stopped. In other words, when the main switch 31 is in the "accessory on" state, the driving-essential devices 42 do not operate. When the main switch 31 is in the "accessory on" state, the controller 30 permits the use of the external power supply 43c. When the external power supply 43c is available, the controller 30 calculates the surplus power without taking into account the power consumption of the driving-essential devices 42.

[0047] When the main switch 31 is in the "power on" state, the controller 30 activates the driving system (inverter 5 and motor 6). In other words, the FC vehicle 2 is able to drive. At this time, the controller 30 does not activate the external power supply 43c. In other words, the controller 30 keeps the external power supply 43c in a stopped state. This is because devices outside the vehicle cannot be connected when the FC vehicle 2 is driving. For ease of explanation, the state when the main switch 31 is in the "power on" state is referred to as "driving mode." In driving mode, the controller 30 does not activate the external power supply 43c. In driving mode, the external power supply 43c is unavailable.

[0048] When the FC vehicle 2 is in driving mode, the controller 30 calculates the surplus power by subtracting the total power consumption of the FC-essential devices 41 and the total power consumption of the driving-essential devices 42 from the upper output limit of the voltage converter 20. If the total power consumption of the operating optional devices 43 exceeds the output allowable value (= surplus power - margin), the controller 30 reduces the output of the optional device with the lowest priority among the operating optional devices 43 (steps S24: YES, S25).

[0049] As described above, the FC vehicle of the second embodiment can also prevent the output of voltage converter 20 from exceeding the output upper limit. Furthermore, the FC vehicle of the second embodiment can effectively distribute the power that voltage converter 20 can supply.

[0050] A few points to note regarding the technology described in the embodiment are described below. If the optional device with the lowest priority is a device that can only take two values, on and off, in step S25, the controller 30 stops the optional device with the lowest priority. Meanwhile, the power consumption of the air conditioner 43a varies depending on the set temperature. The power consumption of the seat heater 43b also varies depending on the set temperature. Therefore, in step S24, the controller 30 reduces the output of the optional device 43 with the lowest priority so that the total power consumption of the optional devices 43 does not exceed the surplus power. In step S24, the controller 30 may reduce the output of the optional device 43 to zero.

[0051] The total power consumption of the FC-required devices may be obtained by the controller 30 in real time, or may be a predetermined value. The total power consumption expected during operation of the FC stack 10 can be set in advance. Furthermore, the total power consumption required to operate the FC stack 10 depends on the outside air temperature and the output of the FC stack. The total power consumption of the FC-required devices may be determined depending on the outside air temperature and the output of the FC stack 10. The controller 30 may store a map that determines the total power consumption of the FC-required devices depending on the outside air temperature and the output of the FC stack 10.

[0052] The total power consumption of the travel-essential devices may also be acquired by the controller 30 in real time, or may be a predetermined value. The total power consumption of the travel-essential devices may be determined depending on the outside temperature and the type of road on which the vehicle is traveling (such as an urban road or a highway). The controller 30 may store a map that determines the total power consumption of the travel-essential devices depending on the outside temperature and the type of road.

[0053] When the outside temperature is below freezing, the controller 30 may prohibit activation of the external power supply device 43c even if the main switch 31 is in the "accessory on" state. This is because the power consumption of the external power supply device 43c may be large. On the other hand, when the outside temperature is below freezing, the total power consumption of the FC-required devices 41 increases, and the importance of the air conditioner 43a, which is an optional device, increases. Another aspect of the technology disclosed herein is embodied in a fuel cell vehicle. The fuel cell vehicle includes a fuel cell stack that generates electric power, a voltage converter that reduces the output voltage of the fuel cell stack, multiple electric devices that operate using the output power of the voltage converter, and a controller that controls the voltage converter and the electric devices. The multiple devices include FC-required devices necessary for operating the fuel cell stack and optional devices that are not necessary for operating the fuel cell stack. The optional devices are prioritized in advance. The controller calculates surplus power by subtracting the total power consumption of the FC-required devices from the output upper limit of the voltage converter. If the total power consumption of the optional devices exceeds an output allowable value that is lower than the surplus power, the controller reduces the output of the optional device with the lowest priority that is in operation. In the fuel cell system described above, the output upper limit of the voltage converter is adjusted. In the fuel cell vehicle disclosed herein, the controller first secures power to operate the FC-required devices. Then, the controller adjusts the output of the optional devices within the range of the surplus power of the voltage converter. This fuel cell vehicle can effectively utilize the output power of the voltage converter. The multiple electrical devices receiving power from the voltage converter may include an external power supply that supplies power to electrical devices outside the fuel cell vehicle (electrical devices not pre-installed on the fuel cell vehicle). The external power supply has a set maximum supply power. In this case, the controller may be configured to perform the following process: The controller calculates surplus power by subtracting the total power consumption of the FC-required devices and the aforementioned maximum supply power from the output upper limit of the voltage converter. If the total power consumption of the optional devices exceeds an output allowable value that is lower than the surplus power, the controller reduces the output of the optional device with the lowest priority that is in operation. The controller can prevent the output of the voltage converter from exceeding the output upper limit while guaranteeing the operation of the FC-required devices and the power supply to the outside. The electric devices may include essential driving devices required to drive the fuel cell vehicle. In this case, the controller may be configured to perform the following process. When an external power supply is being used, the controller keeps the essential driving devices stopped and calculates surplus power by subtracting the total power consumption of the FC-essential devices and the maximum supply power from the output upper limit of the voltage converter. When the fuel cell vehicle is able to drive, the controller keeps the external power supply stopped and calculates surplus power by subtracting the total power consumption of the FC-essential devices and the essential driving devices from the output upper limit of the voltage converter. Whether the external power supply is available or unavailable, the controller reduces the output of the lowest-ranked optional device so that the total power consumption of the optional devices does not exceed the surplus power. When the fuel cell vehicle is able to drive, the power required by the essential driving devices is guaranteed.

[0054] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives alone is technically useful. [Explanation of symbols]

[0055] 2: Fuel cell vehicle (fuel cell system) 4: Voltage converter 5: Inverter 6: Motor 10: FC stack 12: FC cooler 13, 23: Refrigerant flow path 14, 15, 24, 25: Temperature sensor 16: Status sensor 20: Voltage converter 21: Switching element 22: DDC cooler 30: Controller 31: Main switch 32: Vehicle speed sensor 33: Accelerator opening sensor 41: FC-essential device 42: Driving-essential device 43: Optional device 43c: External power supply

Claims

1. a fuel cell stack; a voltage converter that reduces the output voltage of the fuel cell stack using a circuit of switching elements, the voltage converter supplying power to a plurality of electrical devices; a cooler having a refrigerant for cooling the voltage converter; a controller for controlling the voltage converter; It is equipped with A priority order is assigned to the plurality of electrical devices; the controller determines an output upper limit of the voltage converter in accordance with the temperature of the switching element and the temperature of the coolant, and when the total power consumption of the electric devices currently operating exceeds an output allowable value that is lower than the output upper limit, stops the electric device having the lowest priority among the electric devices currently operating. Fuel cell system.

2. the controller determines the output upper limit based on the temperature of the switching element, the temperature of the coolant, the temperature of the fuel cell stack, and the state of the fuel cell stack. The fuel cell system according to claim 1 .

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