Fuel cell system

Abstract

To provide a fuel cell system that outputs the power required for a load and is smaller in size than a system equipped with a DC-DC converter.SOLUTION: A fuel cell system 30 includes a fuel cell stack 41, a switching unit 80, a power storage device 90, a current sensor 91, a voltage sensor 92, and a control device 100. The switching unit 80 electrically disconnects the fuel cell stack from a motor-generator 21 when the SoC of the power storage device 90 increases, and electrically connects the fuel cell stack to the motor-generator 21 when the SoC of the power storage device 90 decreases. An identification unit 112 identifies the IV characteristics of the fuel cell stack. An operation control unit 113 increases the amount of air to be compressed by an air compressor when the stack power is low. The operation control unit 113 decreases the amount of air to be compressed by the air compressor when the stack power is high.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, vehicles equipped with a fuel cell system (for example, industrial vehicles such as forklifts) are known (see, for example, Patent Document 1). In the fuel cell system of Patent Document 1, the output of the fuel cell stack is connected to a load via a DCDC converter. The DC power generated by the fuel cell stack is stepped down to a predetermined voltage by the DCDC converter and then output to the load.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in industrial vehicles such as forklifts, depending on the type of the mounted machine base, further miniaturization may be required compared to the fuel cell system of Patent Document 1. In the fuel cell system mounted on the vehicle disclosed in Patent Document 1, the size of the DCDC converter hinders miniaturization. Also, in the configuration of the fuel cell system mounted on the vehicle disclosed in Patent Document 1, it is difficult to output the power required for the load without providing a DCDC converter.

Means for Solving the Problems

[0005] A fuel cell system for achieving the above object includes a fuel cell stack, an air compressor for pumping an oxidant gas to the fuel cell stack, a load to which the power generated by the fuel cell stack is connectable for supply, a power storage device to which the load can be supplied with power and which can store the power generated by the fuel cell stack, a detection unit for detecting the voltage of the power storage device, and a switching unit for not electrically connecting the fuel cell stack and the load when the voltage of the power storage device rises to a first threshold value, and for electrically connecting the fuel cell stack and the load when the voltage of the power storage device decreases to a second threshold value lower than the first threshold value. When the voltage of the power storage device decreases to the second threshold value, a control device for controlling the operations of the fuel cell stack and the air compressor so as to cause the fuel cell stack to generate power is provided. The fuel cell stack is connected to the power storage device without passing through a power conversion circuit. The control device includes an acquisition unit for acquiring a target stack power to be supplied to the load, a specifying unit for specifying the IV characteristics of the fuel cell stack, and an operation control unit for controlling the operations of the fuel cell stack and the air compressor based on the IV characteristics, the first threshold value, and the second threshold value so that the stack power output by the fuel cell stack becomes the target stack power. The operation control unit increases the amount of the oxidant gas pumped to the air compressor compared to the normal control state when the stack power is lower than the target stack power, and decreases the amount of the oxidant gas pumped to the air compressor compared to the normal control state when the stack power is higher than the target stack power.

[0006] According to such a configuration, while outputting the power required for the load, the fuel cell system can be miniaturized as compared with a system including a DCDC converter. In the fuel cell system for achieving the above object, the switching unit is a diode. The anode of the diode is connected to the fuel cell stack, and the cathode of the diode is connected to the load and the power storage device. When the voltage of the power storage device reaches the first threshold value, the control device can charge the power storage device with the stack power generated by the fuel gas remaining in the fuel cell stack via the diode while stopping the power generation of the fuel cell stack. When the voltage of the power storage device reaches the second threshold value, the control device may supply the stack power to the load while starting the power generation of the fuel cell stack.

[0007] According to such a configuration, the connection state between the fuel cell stack and the load can be easily changed. In the fuel cell system for achieving the above object, when the stack power is lower than the target stack power based on the IV characteristics specified by the specifying unit, the operation control unit may increase the pressure of the oxidant gas pumped to the air compressor compared to the normal control state, or when the stack power is higher than the target stack power based on the IV characteristics specified by the specifying unit, the operation control unit may decrease the pressure of the oxidant gas pumped to the air compressor compared to the normal control state.

[0008] According to such a configuration, it is possible to more easily adjust the IV characteristics. In the fuel cell system for achieving the above object, the specifying unit may store information indicating the specified IV characteristics in the storage unit, and the operation control unit may execute various controls based on the most recent IV characteristics stored in the storage unit.

[0009] According to such a configuration, by reading the information indicating the IV characteristics stored in the storage unit, the labor involved in the process of specifying the IV characteristics can be reduced.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a fuel cell system that is miniaturized compared to a system including a DC-DC converter while outputting the power required for a load.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0012] <Embodiment> Hereinafter, an embodiment in which a fuel cell system is embodied will be described with reference to the drawings. [Overall Configuration] As shown in FIG. 1, an industrial vehicle 10 includes a traveling device 20 for traveling the industrial vehicle 10. The industrial vehicle 10 is, for example, a forklift. The traveling device 20 includes, for example, a motor generator 21, an inverter 22, a vehicle ECU (Electronic Control Unit) 23, and a fuel cell system 30.

[0013] The vehicle ECU 23 is an electronic control unit that controls the industrial vehicle 10. The vehicle ECU 23 includes, for example, a control unit 24 and a storage unit 25. The control unit 24 is realized, for example, by a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Also, some or all of these components may be realized by hardware (including circuitry such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), GPU (Graphics Processing Unit)), or may be realized by the cooperation of software and hardware. The program may be stored in a storage device (not shown) having a non-transitory storage medium such as an HDD (Hard Disk Drive) or a flash memory provided in advance by the storage unit 25. The storage unit 25 may be realized by the above various storage devices, or by an EEPROM (Electrically Erasable Programmable Read Only Memory), ROM (Read Only Memory), RAM (Random Access Memory), etc. The vehicle ECU 23 instructs the power to be output to the fuel cell system 30 according to the control state of each part of the industrial vehicle 10.

[0014] The fuel cell system 30 includes a power generation functional unit 40, a cathode system 50, an anode system 70, a switching unit 80, a power storage device 90, a current sensor 91, a voltage sensor 92, and a control device 100.

[0015] The power generation functional unit 40 includes a fuel cell stack 41 and other components. The fuel cell stack 41 is formed by stacking a plurality of fuel cells. The fuel cell is, for example, a polymer electrolyte fuel cell. The fuel cell stack 41 generates electricity through a chemical reaction between a fuel gas and an oxidant gas. In this embodiment, it is assumed that power generation is performed using hydrogen gas as the fuel gas and oxygen in the air as the oxidant gas. The fuel cell stack 41 is electrically connected to the motor generator 21 and the power storage device 90 via a switching unit 80. Specifically, one end of the switching unit 80 is connected to the fuel cell stack 41, and the other end of the switching unit 80 is connected to the motor generator 21 and the power storage device 90. The switching unit 80 is realized by a switch such as a relay, for example. In other words, the fuel cell stack 41 and the power storage device 90 are connected without passing through a power conversion circuit such as a DCDC converter.

[0016] [Detailed description of the fuel cell stack 41] As shown in FIG. 2, the power generation functional unit 40 includes a fuel cell stack 41 and a diluter 79, and is connected to a cathode system 50 and an anode system 70. The fuel cell stack 41 includes a plurality of fuel cells 42. The fuel cell 42 includes an anode electrode to which an anode gas is supplied, a cathode electrode to which a cathode gas is supplied, and an electrolyte membrane disposed between the anode electrode and the cathode electrode. The fuel cell 42 is sandwiched by separators.

[0017] The cathode system 50 supplies a cathode gas to the fuel cell stack 41. The cathode system 50 includes a cathode flow path 50a. The cathode flow path 50a includes a cathode internal flow path 43 that flows inside the fuel cell stack 41. A cathode gas flows through the cathode internal flow path 43. The cathode internal flow path 43 is provided, for example, in a separator facing the cathode electrode in the fuel cell stack 41. The cathode internal flow path 43 includes an inlet 44 and an outlet 45. The cathode gas flows into the cathode internal flow path 43 from the inlet 44 and flows out of the cathode internal flow path 43 from the outlet 45.

[0018] The anode system 70 supplies anode gas to the fuel cell stack 41. The anode system 70 includes an anode flow path 70a. The anode flow path 70a includes an anode internal flow path 46 that flows inside the fuel cell stack 41. Anode gas flows through the anode internal flow path 46. The anode internal flow path 46 is provided, for example, in a separator facing the anode electrode in the fuel cell stack 41. The anode internal flow path 46 includes an inlet 47 and an outlet 48. The anode gas flows into the anode internal flow path 46 from the inlet 47 and flows out of the anode internal flow path 46 from the outlet 48.

[0019] The fuel cell stack 41 generates electricity by the reaction between the anode gas flowing through the anode internal flow path 46 and the cathode gas flowing through the cathode internal flow path 43. In other words, the fuel cell stack 41 generates electricity by the reaction between hydrogen gas as the anode gas supplied to the anode flow path 70a and oxygen in the air as the cathode gas supplied to the cathode flow path 50a.

[0020] The anode system 70 includes a tank 71, an anode gas supply unit 72, a gas-liquid separator 75, a circulation pump 76, and an exhaust and drain valve 77. The anode flow path 70a includes a supply path 73 and a circulation path 74.

[0021] The tank 71 stores anode gas. Anode gas is supplied from the tank 71 to the anode gas supply unit 72. The anode gas supply unit 72 is a member for adjusting the amount of anode gas supplied to the fuel cell stack 41. The amount of anode gas supplied to the fuel cell stack 41 can be adjusted by controlling the anode gas supply unit 72. As the anode gas supply unit 72, for example, an electromagnetic valve such as an injector can be used.

[0022] The supply path 73 connects the anode gas supply unit 72 and the inlet 47 of the anode internal flow path 46. The anode gas injected from the anode gas supply unit 72 is supplied to the fuel cell stack 41 through the supply path 73.

[0023] The circulation path 74 connects the outlet 48 of the anode internal flow path 46 and the supply path 73. An anode exhaust gas flows through the circulation path 74. The anode exhaust gas contains unreacted anode gas and generated water. The generated water is water generated by power generation in the fuel cell stack 41. The circulation path 74 is a passage for returning the unreacted anode gas contained in the anode exhaust gas to the supply path 73.

[0024] The gas-liquid separator 75 is provided in the circulation path 74. The gas-liquid separator 75 separates the anode exhaust gas into anode gas and generated water. The generated water separated from the anode exhaust gas is stored in the gas-liquid separator 75.

[0025] The circulation pump 76 is provided in the circulation path 74. The circulation pump 76 supplies the anode gas separated from the anode exhaust gas by the gas-liquid separator 75 to the supply path 73. Thereby, the anode gas circulates.

[0026] The exhaust and drain valve 77 is connected to the gas-liquid separator 75. The exhaust and drain valve 77 can be switched between an open state and a closed state. When the exhaust and drain valve 77 is in the open state, the generated water is discharged from the gas-liquid separator 75. The exhaust and drain valve 77 may be switched from the closed state to the open state when the amount of the generated water stored in the gas-liquid separator 75 exceeds a threshold value. The exhaust and drain valve 77 may be switched from the closed state to the open state at predetermined time intervals.

[0027] The gas-liquid separator 75 is connected to the diluter 79. When the exhaust and drain valve 77 is in the open state, the generated water stored in the gas-liquid separator 75 and the anode exhaust gas are supplied to the diluter 79. The diluter 79 is open to the atmosphere and discharges the supplied anode exhaust gas. The cathode system 50 includes a cathode gas inlet 51, an air compressor 52, an intercooler 53, a sealing valve 60, and a pressure regulating valve 61. In other words, the power generation functional unit 40 has the pressure regulating valve 61. The cathode flow path 50a includes a cathode supply path 54 and a cathode discharge path 57.

[0028] The cathode gas inlet 51 is an inlet for sucking cathode gas into the power generation functional unit 40. When using oxygen in the air as the cathode gas, the cathode gas inlet 51 may be open to the atmosphere. The cathode gas inlet 51 may be connected to a gas cylinder for storing the cathode gas.

[0029] The air compressor 52 is driven by an electric motor. The air compressor 52 supplies cathode gas to the fuel cell stack 41. Specifically, the air compressor 52 compresses the cathode gas supplied from the cathode gas inlet 51 and supplies it to the fuel cell stack 41. The cathode gas may be supplied from the cathode gas inlet 51 to the air compressor 52 through an air cleaner (not shown). The cathode gas supplied from the air compressor 52 to the fuel cell stack 41 flows through the cathode internal flow path 43.

[0030] The intercooler 53 is supplied with the cathode gas discharged from the air compressor 52. The intercooler 53 cools the cathode gas supplied from the air compressor 52. The cathode gas supplied to the fuel cell stack 41 is the cathode gas cooled by the intercooler 53.

[0031] The cathode supply path 54 is a portion of the cathode flow path 50a that is located upstream of the fuel cell stack 41. The cathode supply path 54 connects the air compressor 52 and the inlet 44 of the cathode internal flow path 43. The cathode supply path 54 includes a first supply path 55 and a second supply path 56. The first supply path 55 connects the air compressor 52 and the intercooler 53. The second supply path 56 connects the intercooler 53 and the inlet 44 of the cathode internal flow path 43.

[0032] The cathode exhaust passage 57 is a portion of the cathode flow passage 50a that is located downstream of the fuel cell stack 41. The cathode exhaust passage 57 connects the outlet 45 of the cathode internal flow passage 43 and the diluter 79. The cathode exhaust passage 57 is a passage through which the cathode exhaust gas flows. The cathode exhaust gas is the cathode gas discharged from the fuel cell stack 41 and contains the generated water. The cathode exhaust gas is discharged from the cathode exhaust passage 57 to the diluter 79. The diluter 79 dilutes the anode exhaust gas supplied from the gas-liquid separator 75 with the cathode exhaust gas and discharges it into the atmosphere.

[0033] The shut-off valve 60 is provided in the cathode supply passage 54. In the present embodiment, the shut-off valve 60 is provided in the second supply passage 56. The shut-off valve 60 may be provided in the first supply passage 55. The shut-off valve 60 is, for example, a butterfly valve that shuts off the cathode supply passage 54. The shut-off valve 60 can be switched between an open state and a closed state. When the shut-off valve 60 is in the open state, the cathode gas is supplied to the cathode internal flow passage 43 through the cathode supply passage 54. When the shut-off valve 60 is in the closed state, the cathode supply passage 54 is shut off.

[0034] The pressure regulating valve 61 is provided in the cathode exhaust passage 57. Therefore, the pressure regulating valve 61 is provided downstream of the fuel cell stack 41 in the cathode flow passage 50a. The pressure regulating valve 61 is a butterfly valve. By adjusting the opening degree of the pressure regulating valve 61, the internal pressure of the fuel cell stack 41 is adjusted. The smaller the opening degree of the pressure regulating valve 61, the higher the internal pressure of the fuel cell stack 41. When the pressure regulating valve 61 is fully closed, the cathode exhaust passage 57 is shut off.

[0035] Returning to FIG. 1, the inverter 22 converts the DC power output from the fuel cell system 30 or the power storage device 90 into AC power and outputs it. The inverter 22 in the present embodiment is assumed to be a three-phase inverter that converts DC power into three-phase AC power.

[0036] The power storage device 90 is connected in parallel to the inverter 22. Specifically, the inverter 22 includes three-phase half-bridge circuits each having two switching elements connected in series to each other, and the power storage device 90 is connected in parallel to the half-bridge circuits. That is, the power storage device 90 can output DC power to the inverter 22 together with the fuel cell stack 41.

[0037] As the power storage device 90, a chargeable and dischargeable device is used. In the present embodiment, a lithium-ion capacitor is used as the power storage device 90. However, as the power storage device 90, capacitors other than lithium-ion capacitors, secondary batteries such as lithium-ion secondary batteries and nickel-metal hydride storage batteries can also be used. Note that as the power storage device 90, a single power storage device 90 may be used, or a modularized plurality of power storage devices 90 may be used.

[0038] The motor generator 21 is, for example, a three-phase AC rotating electric machine. The motor generator 21 is connected to the inverter 22. When power is supplied from the inverter 22, the motor generator 21 operates as an electric motor and generates a rotational driving force. The industrial vehicle 10 travels when this rotational driving force is transmitted to the drive wheels through the axle. The motor generator 21 is an example of a load.

[0039] The current sensor 91 is connected in series to the power storage device 90. The current sensor 91 detects the discharge current from the power storage device 90 and the charge current to the power storage device 90. The charge current includes the current flowing into the power storage device 90 due to the power generation of the fuel cell stack 41. In the following description, the discharge current and the charge current are collectively referred to as the charge / discharge current.

[0040] The voltage sensor 92 detects the inter-terminal voltage of the power storage device 90. When the power storage device 90 is a modularized plurality of power storage devices 90, it is preferable that the voltage sensor 92 can individually detect the inter-terminal voltages of the plurality of power storage devices 90. The voltage sensor 92 is an example of a detection unit.

[0041] The control device 100 includes, for example, a control unit 110 and a storage unit 200. The control unit 110 is realized, for example, by a hardware processor such as a CPU executing a program (software). Also, some or all of these components may be realized by hardware (including circuit parts) such as LSI, ASIC, FPGA, GPU, etc., or may be realized by the cooperation of software and hardware. The program may be stored in a storage device (not shown) having a non-transitory storage medium such as an HDD or a flash memory provided in the storage unit 200 in advance. The storage unit 200 may be realized by the above various storage devices, or by an EEPROM, ROM, RAM, etc. In addition to the program, IV characteristic information 201 is stored in the storage unit 200. Details of the IV characteristic information 201 will be described later.

[0042] The vehicle ECU 23 and the control device 100 are connected so as to be able to transmit and receive information, and communicate with each other using a communication protocol such as CAN (Controller Area Network) or LIN (Local Interconnect Network).

[0043] The control unit 110 includes, for example, an acquisition unit 111, a specification unit 112, and an operation control unit 113. The acquisition unit 111 acquires information indicating the target power supplied to the motor generator 21 from the vehicle ECU 23. In the following description, the power instructed by the vehicle ECU 23 is also referred to as "target stack power". Also, in the following description, the power output by the fuel cell stack 41 is also referred to as "stack power". Therefore, the acquisition unit 111 acquires information indicating the target stack power from the vehicle ECU 23.

[0044] The specification unit 112 specifies the current-voltage specification (hereinafter, IV characteristic) of the fuel cell stack 41. Details of the process in which the specification unit 112 specifies the IV characteristic of the fuel cell stack 41 will be described later. The specification unit 112 stores information indicating the specified current IV characteristic of the fuel cell stack 41 in the storage unit 200.

[0045] The operation control unit 113 controls the air compressor 52 based on the IV characteristics of the fuel cell stack 41 identified by the identification unit 112. Specifically, when the stack power is lower than the target stack power, the operation control unit 113 increases the amount of air pumped by the air compressor 52 and / or adjusts the opening degree of the pressure regulating valve 61 to increase the pressure of the air flowing through the cathode system 50. Further, when the stack power is higher than the target stack power, the operation control unit 113 decreases the amount of air pumped by the air compressor 52 and / or adjusts the opening degree of the pressure regulating valve 61 to decrease the pressure of the air flowing through the cathode system 50.

[0046] In addition, the operation control unit 113 controls the switching unit 80 to be in an open state or a closed state based on the voltage of the power storage device 90 detected by the voltage sensor 92. [Regarding the operation timing of the fuel cell stack 41] As shown in FIG. 3, the waveform W1 shows the change over time of the SoC (State of Charge) of the power storage device 90 based on the detection result of the voltage sensor 92. The SoC of the power storage device 90 is correlated with the voltage of the power storage device. In this embodiment, an example in which the SoC of the power storage device 90 is directly proportional to the voltage of the power storage device is schematically shown. Therefore, the vertical axis of the waveform W1 indicates the SoC of the power storage device 90 and the voltage of the power storage device 90. Further, the waveform W2 shows the change over time of the operation state of the power storage device 90. The waveform W3 shows the change over time of the operation state of the fuel cell stack 41.

[0047] The operation control unit 113 estimates the SoC of the power storage device 90 based on the detection result of the voltage sensor 92. While the estimated SoC of the power storage device 90 is in the first state, the operation control unit 113 controls the switching unit 80 to the open state and stops the power generation by the fuel cell stack 41. The first state is a state where the estimated SoC is decreasing and is equal to or higher than the lower limit value of the SoC. As shown by the waveform W1, the SoC of the power storage device 90 is in the first state between time 0 and time t1, between time t2 and time t3, and between time t4 and time t5. As shown by the waveform W3, since the fuel cell stack 41 is stopped in the first state, it does not output power. As described above, while the switching unit 80 is controlled to the open state in the first state and the fuel cell stack 41 is stopped. Therefore, in the first state, only the power storage device 90 supplies power to the motor generator 21. Thus, as shown by the waveform W2, in the first state, the power storage device 90 discharges the power stored in the power storage device 90.

[0048] While the estimated SoC of the power storage device 90 is in the second state, the operation control unit 113 controls the switching unit 80 to the closed state and performs power generation by the fuel cell stack 41. The second state is a state where the estimated SoC of the power storage device 90 is increasing and is equal to or lower than the upper limit value of the SoC of the power storage device 90. As shown by the waveform W1, the SoC of the power storage device 90 is in the second state between time t1 and time t2, between time t3 and time t4, and between time t5 and time t6. As shown by the waveform W3, since the fuel cell stack 41 is operating in the second state, it outputs power. As described above, while the switching unit 80 is controlled to the closed state in the second state and the fuel cell stack 41 is operating. Therefore, in the second state, the fuel cell stack 41 supplies power to the motor generator 21 and the power storage device 90. Thus, as shown by the waveform W2, in the second state, the power storage device 90 is charged by the power supplied by the fuel cell stack 41.

[0049] The upper limit value of the SoC is an example of the first threshold value TH1. The first threshold value TH1 is, for example, a value indicating 70 [%]. The lower limit value of the SoC is an example of the second threshold value TH2. The second threshold value TH2 is, for example, 30 [%]. Note that the values of the first threshold value TH1 and the second threshold value TH2 are just examples and are not limited to these.

[0050] [Regarding the IV characteristics of the fuel cell stack 41] Referring to FIG. 4, the IV characteristics of the fuel cell stack 41 will be described. The graph in FIG. 4 schematically shows the characteristics of the current and voltage of the fuel cell 42 in a state where sufficient hydrogen and oxidant gas are supplied to the fuel cell stack 41. The IV characteristics of the fuel cell stack 41 change as the fuel cell 42 deteriorates. Specifically, the fuel cell stack 41 outputs less power as the fuel cell 42 deteriorates. The waveform W4 shows, for example, the IV characteristics when the deterioration of the fuel cell stack 41 is small. Also, the waveform W6 shows, for example, the IV characteristics when the deterioration of the fuel cell stack 41 has progressed. Also, the waveform W5 shows, for example, the IV characteristics when the deterioration of the fuel cell stack 41 is at an intermediate level between the degrees of deterioration shown by the waveforms W4 and W6.

[0051] The IV characteristics of the fuel cell stack 41 are uniquely determined to a certain extent according to the degree of deterioration of the fuel cell 42. Specifically, if the voltage and current output by the fuel cell stack 41 are determined, it is possible to identify which mode of the IV characteristics the current IV characteristics of the fuel cell stack 41 are. Hereinafter, it is assumed that the IV characteristic information 201 includes information indicating the IV characteristics when the degree of deterioration is small like the waveform W4, information indicating the IV characteristics when the degree of deterioration is medium like the waveform W5, and information indicating the IV characteristics when the degree of deterioration is large like the waveform W6.

[0052] The specific unit 112 specifies the current IV characteristics of the current fuel cell stack 41 based on the detection result of the current sensor 91 and the detection result of the voltage sensor 92 when the switching unit 80 is in the closed state, and the IV characteristic information 201. Specifically, the specific unit 112 determines the coordinates (operating point of the fuel cell stack 41) connecting the detection result of the current sensor 91 and the detection result of the voltage sensor 92 when the switching unit 80 is in the closed state. Then, the determined coordinates are compared with the known IV characteristics, and the matching characteristics or approximate characteristics among the plurality of IV characteristics are specified as the IV characteristics of the current fuel cell stack 41.

[0053] Here, when the switching unit 80 is closed, the voltage output by the fuel cell stack 41 synchronizes with the voltage of the power storage device 90. Also, it is required that the SoC of the power storage device 90 be adjusted within a range less than the first threshold TH1 and greater than or equal to the second threshold TH2. Accordingly, the operation control unit 113 adjusts the amount of current flowing from the fuel cell stack 41 to the motor generator 21 so that the voltage output by the fuel cell stack 41 is within a range from the voltage corresponding to the second threshold TH2 to the voltage corresponding to the first threshold TH1. In other words, the operation control unit 113 adjusts the amount of current flowing from the fuel cell stack 41 to the motor generator 21 so that the voltage output by the fuel cell system 30 does not exceed the voltage corresponding to the upper limit value of the SoC. Further, the operation control unit 113 adjusts the amount of current flowing from the fuel cell stack 41 to the motor generator 21 so that the voltage output by the fuel cell system 30 does not fall below the voltage corresponding to the lower limit value of the SoC.

[0054] Specifically, when the current IV characteristic identified by the identification unit 112 is the waveform W4, the operation control unit 113 adjusts the current amount so that the voltage output by the fuel cell stack 41 is within the range of the coordinates P1 to P2 and the stack power becomes the target stack power. Also, when the current IV characteristic is the waveform W5, the operation control unit 113 adjusts the current amount so that the voltage output by the fuel cell stack 41 is within the range of the coordinates P3 to P4 and the stack power becomes the target stack power. Further, when the current IV characteristic is the waveform W6, the operation control unit 113 adjusts the current amount so that the voltage output by the fuel cell stack 41 is within the range of the coordinates P5 to P6 and the stack power becomes the target stack power.

[0055] Based on the current IV characteristic of the fuel cell stack 41, the operation control unit 113 specifies the supply amount of hydrogen gas and the supply amount of air so as to output the current amount when outputting the target stack power as the stack power at the synchronized voltage. Then, the operation control unit 113 controls each part of the fuel cell stack 41 to supply the specified supply amount of hydrogen gas and the supply amount of air.

[0056] [When the IV characteristic and the output power do not correspond] Here, in the normal control state, the stack power that can be output in the current IV characteristics of the fuel cell stack 41 may not correspond to the target stack power. Specifically, when the operation control unit 113 recognizes the target stack power from the vehicle ECU 23, the maximum value of the stack power that can be output in the current IV characteristics of the fuel cell stack 41 may be smaller than the target stack power. In this case, the operation control unit 113 improves the IV characteristics by increasing the flow rate of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state. Also, the operation control unit 113 improves the IV characteristics by increasing the pressure of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state. By these means, the operation control unit 113 makes the state in which an electrochemical reaction is likely to occur inside the fuel cell stack 41. Thereby, the operation control unit 113 can increase the stack power so as to correspond to the target stack power.

[0057] Also, the minimum value of the stack power that can be output in the current IV characteristics of the fuel cell stack 41 may be larger than the target stack power. In this case, the operation control unit 113 reduces the IV characteristics by decreasing the flow rate of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state. Also, the operation control unit 113 reduces the IV characteristics by decreasing the pressure of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state. Thereby, the operation control unit 113 can decrease the stack power so as to correspond to the target stack power.

[0058] [Regarding the operation of the control device 100] Hereinafter, with reference to FIGS. 5 and 6, the details of the processing executed in the control device 100 will be described. The processing of the flowcharts shown in FIGS. 5 and 6 is repeatedly executed at predetermined time intervals when the power supply of the fuel cell system 30 is turned on and activated.

[0059] First, the operation control unit 113 determines whether the SoC of the power storage device 90 has decreased and fallen below the lower limit value (i.e., the second threshold value TH2) (step S100). Until the SoC of the power storage device 90 falls to the second threshold value TH2 (step S100; NO), the operation control unit 113 does not control the power generation by the fuel cell stack 41, so the determination process in step S100 is repeatedly executed.

[0060] When the operation control unit 113 determines that the SoC of the power storage device 90 has decreased and then fallen to the second threshold value TH2 after the decrease (step S100; YES), it controls the switching unit 80 to the closed state (step S102). Next, the acquisition unit 111 acquires information indicating the target stack power from the vehicle ECU 23 (step S104). Next, the acquisition unit 111 acquires information indicating the detection results from the current sensor 91 and the voltage sensor 92, respectively (step S106).

[0061] The specifying unit 112 determines whether information indicating the IV characteristics of the most recent fuel cell stack 41 is stored in the storage unit 200 (step S108). The information indicating the IV characteristics of the most recent fuel cell stack 41 is stored in the storage unit 200 in the process of step S112 described later. Therefore, at the first operation, or during the operation after the reset of the storage unit 200, etc., the information indicating the IV characteristics of the most recent fuel cell stack 41 is not stored in the storage unit 200. When the specifying unit 112 determines that the information indicating the IV characteristics of the most recent fuel cell stack 41 is stored in the storage unit 200 (step S108; YES), the process proceeds to step S114. Here, it is preferable that the first operation described here is the case where the power supply of the fuel cell system 30 is turned on from off. Also, it is preferable that the reset of the storage unit 200 is performed when the power supply of the fuel cell system 30 is turned off from on.

[0062] When the specific unit 112 determines that the information indicating the IV characteristics of the most recent fuel cell stack 41 is not stored in the storage unit 200 (step S108; NO), it specifies the IV characteristics of the current fuel cell stack 41 (step S110). Specifically, the specific unit 112 specifies the IV characteristics of the current fuel cell stack 41 based on the detection results of the current sensor 91 and the voltage sensor 92 acquired by the acquisition unit 111 and the IV characteristic information 201 at the timing of step S106 immediately after the switching unit 80 is controlled to the closed state. The specific unit 112 stores the information indicating the specified current IV characteristics in the storage unit 200 as the information indicating the most recent IV characteristics (step S112).

[0063] Based on the information indicating the target stack power acquired by the acquisition unit 111 in step S104 and the IV characteristics of the fuel cell stack 41, the operation control unit 113 determines whether to lower the IV characteristics (step S114). When the minimum value of the power that can be output in the IV characteristics specified in step S110 or read from the storage unit 200 is greater than the target stack power, the operation control unit 113 determines to lower the IV characteristics.

[0064] When the operation control unit 113 determines to lower the IV characteristics (step S112; YES), it controls each part of the power generation function unit 40 and the cathode system 50 so as to reduce the flow rate of the air flowing through the cathode system 50 (step S116). Specifically, the operation control unit 113 controls the air compressor 52 to reduce the flow rate of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state. Then, the operation control unit 113 specifies the supply amounts of hydrogen gas and air so as to output the current amount when outputting the target stack power as the stack power at the synchronized voltage. The operation control unit 113 controls each part of the fuel cell stack 41 to supply the specified supply amounts of hydrogen gas and air. For example, after continuously executing the control associated with the process of step S116 for a predetermined time, the operation control unit 113 changes the air flow rate to the normal control state and executes the subsequent processes.

[0065] When the operation control unit 113 determines not to decrease the IV characteristics (step S114; NO), it determines whether to increase the IV characteristics (step S118). When the maximum value of the power that can be output in the IV characteristics specified in step S110 or read from the storage unit 200 is smaller than the target stack power, the operation control unit 113 determines to increase the IV characteristics. When the operation control unit 113 determines to increase the IV characteristics (step S118; YES), it controls each part of the fuel cell stack 41 to increase the flow rate of the air flowing through the cathode system 50 (step S120). Specifically, the operation control unit 113 controls the air compressor 52 to increase the flow rate of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state. Then, the operation control unit 113 specifies the supply amount of hydrogen gas and the supply amount of air so as to output the current amount when outputting the target stack power as the stack power at the synchronized voltage. The operation control unit 113 controls each part of the fuel cell stack 41 to supply the specified supply amount of hydrogen gas and the supply amount of air. For example, after continuously executing the control associated with the process of step S120 for a predetermined time, the operation control unit 113 changes the air flow rate to the normal control state and executes the subsequent process.

[0066] While determining not to decrease the IV characteristics (step S114; NO) and determining not to increase the IV characteristics (step S118; NO), the operation control unit 113 adjusts the stack power so as to output the target stack power (step S122). The case where the IV characteristics are not increased or decreased is, for example, the case where the power that can be output in the IV characteristics specified in step S110 or read from the storage unit 200 matches the target stack power. Specifically, it is the case where the target stack power is within the range from the minimum value to the maximum value of the power that can be output in the IV characteristics. The operation control unit 113 specifies the supply amount of hydrogen gas and the supply amount of air so as to output the current amount when outputting the target stack power as the stack power. While controlling each part of the fuel cell stack 41 to supply the specified supply amount of hydrogen gas and the supply amount of air, the operation control unit 113 advances the process to step S132.

[0067] The operation control unit 113 determines whether the stack power has sufficiently decreased and approached the target stack power through the process of step S116 (step S124). For example, the operation control unit 113 determines whether it is possible to adjust the stack power to the target stack power within the range from the first threshold TH1 to the second threshold TH2 of the IV characteristics decreased by the process of step S116. Here, when the target stack power is smaller than the minimum value of the stack power that can be output within the range from the first threshold TH1 to the second threshold TH2 of the decreased IV characteristics, the IV characteristics of the fuel cell stack 41 need to be further decreased. Therefore, when the target stack power is smaller than the minimum value of the stack power that can be output within the range from the first threshold TH1 to the second threshold TH2 of the decreased IV characteristics, the operation control unit 113 determines that it has not approached the target stack power.

[0068] When the operation control unit 113 determines that the stack power has sufficiently decreased and approached the target stack power (step S124; YES), the process proceeds to step S132. When the operation control unit 113 determines that the stack power has not sufficiently decreased and has not approached the target stack power (step S124; NO), it decreases the pressure of the air flowing through the cathode system 50 (step S126). Specifically, the operation control unit 113 increases the opening degree of the pressure regulating valve 61 to decrease the pressure of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state. Then, the operation control unit 113 specifies the supply amount of hydrogen gas and the supply amount of air so as to output the current amount when outputting the target stack power as the stack power at the synchronized voltage. The operation control unit 113 controls each part of the fuel cell stack 41 to supply the specified supply amount of hydrogen gas and the supply amount of air. For example, after continuously executing the control associated with the process of step S120 for a predetermined time, the operation control unit 113 changes the air flow rate to the normal control state and executes the subsequent process.

[0069] The operation control unit 113 determines whether the stack power has sufficiently increased and approached the target stack power through the process of step S120 (step S128). For example, the operation control unit 113 determines whether it is possible to adjust the stack power to the target stack power within the range from the first threshold TH1 to the second threshold TH2 of the improved IV characteristics by the process of step S120. Here, if the target stack power is greater than the maximum value of the stack power that can be output within the range from the first threshold TH1 to the second threshold TH2 of the improved IV characteristics, the IV characteristics of the fuel cell stack 41 need to be further improved. Therefore, when the target stack power is greater than the maximum value of the stack power that can be output within the range from the first threshold TH1 to the second threshold TH2 of the improved IV characteristics, the operation control unit 113 determines that it has not approached the target stack power.

[0070] When the operation control unit 113 determines that the stack power has sufficiently increased and approached the target stack power (step S128; YES), the process proceeds to step S132. When the operation control unit 113 determines that the stack power has not sufficiently increased and has not approached the target stack power (step S128; NO), it increases the pressure of the air flowing through the cathode system 50 (step S130). Specifically, the operation control unit 113 reduces the opening degree of the pressure regulating valve 61 to increase the pressure of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state. Then, the operation control unit 113 specifies the supply amounts of hydrogen gas and air so as to output the current amount when outputting the target stack power as the stack power at the synchronized voltage. The operation control unit 113 controls each part of the power generation function unit 40 and the cathode system 50 to supply the specified supply amounts of hydrogen gas and air. For example, after continuously executing the control associated with the process of step S124 for a predetermined time, the operation control unit 113 changes the air flow rate to the normal control state and executes the subsequent process.

[0071] The operation control unit 113 determines whether the SoC of the power storage device 90 has risen to the upper limit value (i.e., the first threshold value TH1) (step S132). For example, the operation control unit 113 estimates the SoC based on the detection result of the voltage sensor 92 acquired by the acquisition unit 111 at the timing when step S132 is executed. When the estimated SoC of the power storage device 90 is less than the first threshold value TH1 (step S132; NO), the operation control unit 113 repeatedly executes the processes from step S114 to S130.

[0072] When the operation control unit 113 determines that the SoC of the power storage device 90 has risen to the upper limit value (step S132; YES), it controls the switching unit 80 to the open state (step S134). Next, while executing the stop process of the fuel cell stack 41 (step S136), the operation control unit 113 ends the series of processes. The stop process is, for example, that the operation control unit 113 stops both the supply of hydrogen gas to the fuel cell stack 41 and the supply of air, or at least one of them. Accordingly, the fuel cell stack 41 stops generating power and the stack power decreases.

[0073] [Effects of the Embodiment] According to the above embodiment, the following effects can be obtained. (1) The fuel cell system 30 includes the motor generator 21, the fuel cell stack 41, the switching unit 80, the power storage device 90, the current sensor 91, the voltage sensor 92, and the control device 100. The fuel cell stack 41 included in the power generation functional unit 40 and the power storage device 90 are connected without passing through a power conversion circuit such as a DCDC converter. When the SoC of the power storage device 90 rises and reaches the first threshold value TH1, the switching unit 80 does not electrically connect the fuel cell stack 41 and the motor generator 21, and when the SoC of the power storage device 90 decreases and reaches the second threshold value TH2, the switching unit 80 electrically connects the fuel cell stack 41 and the motor generator 21.

[0074] When the SoC of the power storage device 90 decreases to the second threshold value TH2, the control device 100 controls the operations of the fuel cell stack 41 and the air compressor 52 so as to cause the fuel cell stack 41 to generate power. The control unit 110 of the control device 100 includes an acquisition unit 111, a specification unit 112, and an operation control unit 113. The acquisition unit 111 acquires the target stack power to be supplied to the motor generator 21. The specification unit 112 specifies the IV characteristics of the fuel cell stack 41. The operation control unit 113 controls the operations of the fuel cell stack 41 and the air compressor 52 based on the IV characteristics, the first threshold value TH1, and the second threshold value TH2 so that the stack power becomes the target stack power. Specifically, when the stack power is lower than the target stack power, the operation control unit 113 increases the amount of air to be pumped to the air compressor 52 as compared with the normal control state. Also, when the stack power is higher than the target stack power, the operation control unit 113 decreases the amount of air to be pumped to the air compressor 52 as compared with the normal control state.

[0075] Here, in a conventional fuel cell system, a DCDC converter has been used to convert the power output from the fuel cell stack into power that can be input to the motor generator. On the other hand, since it is difficult to miniaturize the DCDC converter, it has been difficult to miniaturize the conventional fuel cell system.

[0076] According to such a configuration, the fuel cell system 30 can widen the range of stack power that the fuel cell stack 41 can output by improving or deteriorating the IV characteristics. Therefore, the fuel cell system 30 can output the power required for the motor generator 21 by directly supplying power from the fuel cell stack 41 to the motor generator 21, and can be miniaturized by not including a DCDC converter.

[0077] In a conventional fuel cell system, the IV characteristics are uniquely determined in response to the deterioration of the fuel cell, and the adjustment of the IV characteristics as in the fuel cell system 30 of the present embodiment is not performed. In this case, in the conventional fuel cell system, as the fuel cell 42 deteriorates, the range of power that can be output becomes narrower, and sufficient power cannot be supplied. Therefore, in the conventional fuel cell system, the operating time of the system becomes the time corresponding to the deterioration of the fuel cell 42. On the other hand, the fuel cell system 30 adjusts the IV characteristics by varying the air flow rate compared to the normal control state. Therefore, according to such a configuration, the fuel cell system 30 can extend the operating time of the system by adjusting the IV characteristics compared to the case where the IV characteristics are uniquely determined.

[0078] (2) When the stack power is lower than the target stack power based on the IV characteristics identified by the identification unit 112, the operation control unit 113 increases the pressure of the air pumped to the air compressor 52 compared to the normal control state. Also, when the stack power is higher than the target stack power based on the IV characteristics identified by the identification unit 112, the operation control unit 113 decreases the pressure of the air pumped to the air compressor 52 compared to the normal control state. According to such a configuration, the fuel cell system 30 can more easily adjust the IV characteristics by adjusting the air pressure.

[0079] (3) The identification unit 112 causes the storage unit 200 to store information indicating the identified IV characteristics. The operation control unit 113 executes various controls based on the most recent IV characteristics stored in the storage unit 200. According to such a configuration, the operation control unit 113 can reduce the labor involved in the process of identifying the current IV characteristics by reading out the information indicating the most recent IV characteristics stored in the storage unit 200.

[0080] The above embodiments may be modified as follows. The above embodiments and the following separate examples may be combined with each other as long as they are not technically contradictory. ○ In the above description, the case where the fuel cell system 30 includes the switching unit 80 has been described, but it is not limited thereto. The fuel cell system 30 may include a diode instead of the switching unit 80. In this case, the fuel cell stack 41 is electrically connected to the motor generator 21 and the power storage device 90 via the diode. Specifically, the anode terminal of the diode is connected to the fuel cell stack 41, and the cathode terminal of the diode is connected to the motor generator 21 and the power storage device 90. In this case, among the processes shown in FIGS. 5 and 6, the processes of steps S102 and S134 are omitted.

[0081] When the SoC of the power storage device 90 increases to the first threshold value TH1, the power generation by the power generation functional unit 40 is stopped by the control device 100. However, due to the remaining hydrogen gas present inside the fuel cell stack 41, the power generation of the fuel cell stack 41 is temporarily continued. Accordingly, the power storage device 90 can be charged by the stack power. On the other hand, when the remaining hydrogen gas is consumed, the voltage of the fuel cell stack 41 decreases, and the potential of the cathode terminal side becomes higher than that of the anode terminal side. Therefore, the diode becomes an off state and does not electrically connect the fuel cell stack 41 to the motor generator 21 and the power storage device 90. Further, when the SoC of the power storage device 90 decreases and then becomes the second threshold value TH2, the power generation of the power generation functional unit 40 is started by the control device 100. At this time, since a current flows from the fuel cell stack 41 to the motor generator 21 and the power storage device 90, the potential of the cathode terminal side becomes lower than that of the anode terminal side. Therefore, the diode becomes an on state and electrically connects the fuel cell stack 41 to the motor generator 21. According to such a configuration, the fuel cell system 30 can easily change the connection state between the fuel cell stack 41 and the motor generator 21 by the diode.

[0082] ○In the above description, the case where there are three pieces of information indicating the IV characteristics included in the IV characteristic information 201 has been described, but it is not limited thereto. The IV characteristic information 201 may include two or less pieces of information indicating the IV characteristics that the fuel cell 42 can have, or may include four or more pieces of information.

[0083] ○In the above description, the case where the operation control unit 113 improves or degrades the IV characteristics by increasing or decreasing the flow rate of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state has been described, but it is not limited thereto. The operation control unit 113 may vary the flow rate of the air to be increased or decreased compared to the normal control state according to the degree of deviation between the stack power and the target stack power. For example, when the operation control unit 113 improves the IV characteristics and the deviation between the stack power and the target stack power is large, the amount of increase in the flow rate of the air flowing through the cathode system 50 is made larger compared to the case where the deviation is small. Also, for example, when the operation control unit 113 degrades the IV characteristics and the deviation between the stack power and the target stack power is large, the amount of decrease in the flow rate of the air flowing through the cathode system 50 is made larger compared to the case where the deviation is small.

[0084] ○In addition, in the above description, the case where the operation control unit 113 improves or degrades the IV characteristics by increasing or decreasing the pressure of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state has been described, but it is not limited thereto. The operation control unit 113 may vary the pressure of the air to be increased or decreased compared to the normal control state according to the degree of deviation between the stack power and the target stack power. For example, when the operation control unit 113 improves the IV characteristics and the deviation between the stack power and the target stack power is large, the amount of increase in the pressure of the air flowing through the cathode system 50 is made larger compared to the case where the deviation is small. Also, for example, when the operation control unit 113 degrades the IV characteristics and the deviation between the stack power and the target stack power is large, the amount of decrease in the pressure of the air flowing through the cathode system 50 is made larger compared to the case where the deviation is small.

[0085] ○ In the above description, the operation control unit 113 was described as continuing the process of increasing or decreasing the flow rate and pressure of the air flowing through the cathode system 50 by a predetermined amount for a predetermined time compared to the normal control state. However, this is not the only case. The operation control unit 113 may vary the time for which it continues the process of increasing or decreasing the flow rate and pressure of the air flowing through the cathode system 50 by a predetermined amount compared to the normal control state according to the degree of deviation between the stack power and the target stack power. For example, when the operation control unit 113 is improving the IV characteristics and the deviation between the stack power and the target stack power is large, it increases the time for which the flow rate and pressure of the air flowing through the cathode system 50 are increased compared to when the deviation is small. Also, for example, when the operation control unit 113 is degrading the IV characteristics and the deviation between the stack power and the target stack power is large, it increases the time for which the flow rate and pressure of the air flowing through the cathode system 50 are decreased compared to when the deviation is small.

[0086] ○ In the above description, the operation control unit 113 was described as adjusting the IV characteristics by increasing and decreasing both the flow rate and pressure of the air flowing through the cathode system 50. However, this is not the only case. The operation control unit 113 may adjust the IV characteristics by increasing or decreasing at least one of the flow rate and pressure of the air flowing through the cathode system 50.

[0087] ○ In the above description, the case where the specific unit 112 executes the process of step S110 when the information indicating the IV characteristics of the current fuel cell stack 41 is not stored in the storage unit 200 was described. However, this is not the only case. The specific unit 112 may execute the process of specifying the IV characteristics of the current fuel cell stack 41 each time. In this case, in the process shown in FIG. 5, the processes of step S108 and step S128 are omitted.

[0088] ○ The motor generator 21 may operate as a generator during braking of the industrial vehicle 10 or when reducing acceleration during downhill driving to perform regenerative power generation. In this case, the electric power generated by the motor generator 21 is supplied as regenerative power to the power storage device 90 through the inverter 22. Further, the charging current includes the current flowing into the power storage device 90 by the power generation of the fuel cell stack 41 and the current flowing into the power storage device 90 by the regeneration of the motor generator 21. In this case, the first threshold value TH1 is a value obtained by considering the regenerative power with respect to the upper limit value of the SoC of the power storage device 90, and the second threshold value TH2 is a value obtained by considering the regenerative power with respect to the lower limit value of the SoC of the power storage device 90.

[0089] ○ The fuel cell system 30 may be mounted on a passenger car, a ship, a railway, or the like. ○ The fuel cell system 30 may be used as a stationary power generation device. The technical idea that can be grasped from the above-described embodiments and modification examples will be described.

[0090] [Aspect 1] The fuel cell system includes a fuel cell stack, an air compressor that pumps an oxidant gas to the fuel cell stack, a load to which the power generated by the fuel cell stack is connectably supplied, a power storage device that can supply power to the load and can store the power generated by the fuel cell stack, a detection unit that detects the voltage of the power storage device, and a switching unit that, when the voltage of the power storage device rises to a first threshold value, does not electrically connect the fuel cell stack and the load, and when the voltage of the power storage device decreases to a second threshold value lower than the first threshold value, electrically connects the fuel cell stack and the load. When the voltage of the power storage device decreases to the second threshold value, a control device that controls the operations of the fuel cell stack and the air compressor so as to cause the fuel cell stack to generate power. The fuel cell stack is connected to the power storage device without passing through a power conversion circuit. The control device includes an acquisition unit that acquires a target stack power to be supplied to the load, a specifying unit that specifies the IV characteristics of the fuel cell stack, and an operation control unit that controls the operations of the fuel cell stack and the air compressor based on the IV characteristics, the first threshold value, and the second threshold value so that the stack power output by the fuel cell stack becomes the target stack power. When the stack power is lower than the target stack power, the operation control unit increases the amount of the oxidant gas pumped to the air compressor compared to the normal control state, and when the stack power is higher than the target stack power, the operation control unit decreases the amount of the oxidant gas pumped to the air compressor compared to the normal control state.

[0091] [Aspect 2] The switching unit is a diode. The anode of the diode is connected to the fuel cell stack, and the cathode of the diode is connected to the load and the power storage device. When the voltage of the power storage device reaches the first threshold value, the control device can charge the power storage device via the diode with the stack power generated by the fuel gas remaining in the fuel cell stack while stopping the power generation of the fuel cell stack. When the voltage of the power storage device reaches the second threshold value, the control device supplies the stack power to the load while starting the power generation of the fuel cell stack. The fuel cell system according to [Aspect 1].

[0092] [Aspect 3] Based on the IV characteristics specified by the specifying unit, when the stack power is lower than the target stack power, the operation control unit increases the pressure of the oxidant gas pumped to the air compressor compared to the normal control state, or based on the IV characteristics specified by the specifying unit, when the stack power is higher than the target stack power, the operation control unit decreases the pressure of the oxidant gas pumped to the air compressor compared to the normal control state. The fuel cell system according to [Aspect 1] or [Aspect 2].

[0093] [Aspect 4] The specifying unit causes the storage unit to store information indicating the specified IV characteristics, and the operation control unit executes various controls based on the most recent IV characteristics stored in the storage unit. The fuel cell system according to any one of [Aspect 1] to [Aspect 3].

Explanation of Signs

[0094] TH1... the first threshold value, TH2... the second threshold value, 10... an industrial vehicle, 20... a traveling device, 21... a motor generator, 22... an inverter, 23... a vehicle control device, 24, 110... control units, 25, 200... storage units, 30... a fuel cell system, 40... a power generation functional unit, 41... a fuel cell stack, 42... a fuel cell, 50... a cathode system, 52... an air compressor, 70... an anode system, 71... a tank, 80... a switching unit, 90... a power storage device, 91... a current sensor, 92... a voltage sensor, 100... a control device, 111... an acquisition unit, 112... a specifying unit, 113... an operation control unit, 201... IV characteristic information.

Claims

1. A fuel cell stack, an air compressor that pumps an oxidant gas to the fuel cell stack, a load to which the power generated by the fuel cell stack is connectably supplied, a power storage device that can supply power to the load and is connectably configured to store the power generated by the fuel cell stack, a detection unit that detects the voltage of the power storage device, a switching unit that, when the voltage of the power storage device rises to a first threshold value, does not electrically connect the fuel cell stack and the load, and when the voltage of the power storage device decreases to a second threshold value lower than the first threshold value, electrically connects the fuel cell stack and the load, a control device that controls the operations of the fuel cell stack and the air compressor so as to cause the fuel cell stack to generate power when the voltage of the power storage device decreases to the second threshold value, the fuel cell stack is connected to the power storage device without passing through a power conversion circuit, the control device, an acquisition unit that acquires a target stack power to be supplied to the load, a specifying unit that specifies the IV characteristics of the fuel cell stack, an operation control unit that controls the operations of the fuel cell stack and the air compressor such that the stack power output by the fuel cell stack becomes the target stack power based on the IV characteristics, the first threshold value, and the second threshold value, when the stack power is lower than the target stack power, the operation control unit increases the amount of the oxidant gas pumped to the air compressor compared to a normal control state, and when the stack power is higher than the target stack power, the operation control unit decreases the amount of the oxidant gas pumped to the air compressor compared to the normal control state, a fuel cell system.

2. the switching unit is a diode, the anode of the diode is connected to the fuel cell stack, the cathode of the diode is connected to the load and the power storage device, when the voltage of the power storage device reaches the first threshold value, the control device stops the power generation of the fuel cell stack and enables the stack power generated by the fuel gas remaining in the fuel cell stack to be charged to the power storage device via the diode, and when the voltage of the power storage device reaches the second threshold value, the control device starts the power generation of the fuel cell stack and supplies the stack power to the load, The fuel cell system according to claim 1.

3. When the stack power is lower than the target stack power based on the IV characteristics specified by the specifying unit, the operation control unit increases the pressure of the oxidant gas to be pumped to the air compressor as compared with the normal control state, or when the stack power is higher than the target stack power based on the IV characteristics specified by the specifying unit, the operation control unit decreases the pressure of the oxidant gas to be pumped to the air compressor as compared with the normal control state. The fuel cell system according to claim 1.

4. The specifying unit causes the storage unit to store information indicating the specified IV characteristics. The operation control unit executes various controls based on the most recent IV characteristics stored in the storage unit. The fuel cell system according to claim 1.

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