Fuel cell system and method for controlling charge / discharge of power storage device of fuel cell system

Abstract

To optimize the range of electric energy that can be charged and discharged by a power storage device in a fuel cell system.SOLUTION: A fuel cell system 10 includes an acceleration buffer in which a buffer 7 is set within the charge / discharge limit range of a power storage device 244, the buffer being the amount of power that the power storage device 244 can discharge to an air pump 112 when the air pump 112 is accelerated, and a control device 26 calculates the AP steady-state power consumption of the air pump 112 and sets the acceleration buffer on the basis of the calculated AP steady-state power consumption and the rated power of the air pump 112.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system and a method for controlling charging and discharging of a power storage device of a fuel cell system. [Background technology]

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

[0003] A power generation system equipped with a fuel cell stack is called a fuel cell system. A fuel cell stack includes multiple power generation cells. Each power generation cell generates electricity through an electrochemical reaction between fuel gas (hydrogen-containing gas) and oxidant gas (oxygen-containing gas) supplied from an air pump. The electricity generated by each power generation cell is supplied to a load and charged into a power storage device.

[0004] For example, Patent Document 1 discloses a fuel cell system in which a limit range is set for the amount of electric power charged and discharged from a power storage device.

[0005] This fuel cell system sets a buffer for the limited range of charge / discharge power amount and allocates the buffered amount of power to drive the air pump. When the temperature of the power storage device becomes low, the buffered amount of power is set to a small amount. This increases the amount of power that the power storage device can discharge to devices other than the air pump. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-152280 Summary of the Invention [Problem to be solved by the invention]

[0007] In a fuel cell system, it has been long awaited to optimize the range of charge / dischargeable power of an electrical storage device.

[0008] An object of the present invention is to solve the above-described problems.

Means for Solving the Problems

[0009] A first aspect of the present invention is a fuel cell system that generates power using a fuel gas and an oxidant gas, a pump that supplies the oxidant gas to the fuel cell, an electrical storage device capable of supplying power to the pump, and a control device that controls power generation of the fuel cell and charge / discharge of the electrical storage device. The control device sets a range of charge / dischargeable power for the electrical storage device, sets a buffer within the power range of the electrical storage device, and the buffer includes an acceleration buffer that is the amount of power that the electrical storage device can discharge to the pump when the pump is accelerating. The control device calculates the steady power consumption of the pump and sets the acceleration buffer based on the calculated steady power consumption and the rated power of the pump.

[0010] A second aspect of the present invention is a method for controlling charge / discharge of an electrical storage device in a fuel cell system that generates power using a fuel gas and an oxidant gas, a pump that supplies the oxidant gas to the fuel cell, an electrical storage device capable of supplying power to the pump, and a control device that controls power generation of the fuel cell and charge / discharge of the electrical storage device. The control device sets a range of charge / dischargeable power for the electrical storage device, sets a buffer within the power range of the electrical storage device, and the buffer includes an acceleration buffer that is the amount of power that the electrical storage device can discharge to the pump when the pump is accelerating. The control device calculates the steady power consumption of the pump and sets the acceleration buffer based on the calculated steady power consumption and the rated power of the pump.

Effects of the Invention

[0011] According to the present invention, in a fuel cell system, the power amount range in which the power storage device can be charged and discharged can be optimized.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0013] [First Embodiment] [Configuration of Fuel Cell System 10] FIG. 1 is a schematic configuration diagram of a fuel cell system 10 according to the first embodiment. Here, the configuration of the fuel cell system 10 mounted on the fuel cell vehicle 11 will be described. However, the fuel cell system 10 can also be mounted on a moving body other than a vehicle. For example, the fuel cell system 10 can be mounted on a ship, an aircraft, a robot, etc., and can also be used as a stationary power source in facilities, homes, etc.

[0014] In the fuel cell system 10, a fuel gas and an oxidant gas are used as reaction gases. The fuel gas is a hydrogen-containing gas. The oxidant gas is an oxygen-containing gas such as air. Each of the fuel gas and the oxidant gas is supplied to the fuel cell stack 12 and used for an electrochemical reaction. In this specification, the fuel gas discharged from the fuel cell stack 12 without being used for the electrochemical reaction is also referred to as fuel off-gas. Further, the oxidant gas discharged from the fuel cell stack 12 without being used for the electrochemical reaction is also referred to as oxidant off-gas.

[0015] The fuel cell system 10 includes a fuel cell stack 12, a tank 14, an anode system 16, a cathode system 18, a cooling system 20, a load 21, and a power supply system 27. The fuel cell system 10 also includes a control device 26.

[0016] The fuel cell stack 12 includes a positive electrode terminal 23a and a negative electrode terminal 23b. The electric power generated by the fuel cell stack 12 is supplied to the load 21 and the power supply system 27 via the positive electrode terminal 23a and the negative electrode terminal 23b.

[0017] The tank 14 is filled with high-pressure fuel gas.

[0018] The fuel cell stack 12 includes a fuel gas supply port 22a and a fuel gas discharge port 22b. The fuel gas supply port 22a supplies fuel gas to the inside of the fuel cell stack 12. The fuel gas discharge port 22b discharges fuel off-gas from the inside of the fuel cell stack 12.

[0019] The fuel cell stack 12 includes an oxidant gas supply port 22c and an oxidant gas discharge port 22d. The oxidant gas supply port 22c supplies oxidant gas into the fuel cell stack 12. The oxidant gas discharge port 22d discharges oxidant off-gas from inside the fuel cell stack 12.

[0020] The fuel cell stack 12 includes a cooling medium supply port 22e and a cooling medium discharge port 22f. The cooling medium supply port 22e supplies cooling medium into the fuel cell stack 12. The cooling medium discharge port 22f discharges cooling medium from inside the fuel cell stack 12.

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

[0022] The fuel gas supply passage 84 is connected to the discharge port of the tank 14 and the fuel gas supply port 22a of the fuel cell stack 12. The fuel gas supply passage 84 is provided with the injector 94 and the ejector 96. The inflow port of the ejector 96 is connected to the discharge port of the injector 94, and the discharge port of the ejector 96 is connected to the fuel gas supply port 22a. The ejector 96 is arranged between the injector 94 and the fuel gas supply port 22a.

[0023] The fuel gas discharge passage 86 is connected to the fuel gas discharge port 22b of the fuel cell stack 12 and the supply port of the gas-liquid separator 98. The circulation passage 88 is connected to the exhaust port of the gas-liquid separator 98 and the suction port of the ejector 96. The drain passage 90 is connected to the drain port of the gas-liquid separator 98 and the discharge passage 109. The discharge passage 109 communicates with the atmosphere through the discharge port 109p provided in the fuel cell vehicle 11. The drain passage 90 is provided with the drain valve 100.

[0024] The cathode system 18 includes an oxidant gas supply passage 106, an oxidant gas discharge passage 108 (discharge passage), and a bypass passage 110. The cathode system 18 includes an air cleaner 105, an air pump 112 (oxidant gas supplier, compressor, simply referred to as a pump), a humidifier 114, an inlet shutoff valve 116, an outlet shutoff valve 118 which is a backpressure valve, and a bypass valve 120.

[0025] The oxidant gas supply passage 106 is connected to an air intake port 106p provided in the fuel cell vehicle 11 and an oxidant gas supply port 22c of the fuel cell stack 12. The oxidant gas supply passage 106 is provided with an air cleaner 105, a flow rate sensor 107, an air pump 112, an inlet shutoff valve 116, and a humidifier supply passage 114A of the humidifier 114.

[0026] A portion of the oxidant gas supply passage 106 disposed upstream of the humidifier 114 is referred to as an oxidant gas supply passage 106A. A portion of the oxidant gas supply passage 106 disposed downstream of the humidifier 114 is referred to as an oxidant gas supply passage 106B.

[0027] The inlet shutoff valve 116 is disposed closer to the humidifier 114 than the air pump 112. An air cleaner 105, a flow rate sensor 107, a temperature sensor 104, and a pressure sensor 266 are attached to the oxidant gas supply passage 106A upstream of the air pump 112. The flow rate sensor 107 detects the flow rate Qo of the oxidant gas flowing through the air pump 112. The temperature sensor 104 detects the temperature (inlet temperature of the air pump 112) Tin of the oxidant gas at the intake port 300 of the air pump 112. The pressure sensor 266 detects the pressure (inlet pressure of the air pump 112) Pin on the intake port 300 side of the air pump 112. A pressure sensor 268 is attached to the oxidant gas supply passage 106A downstream of the air pump 112. The pressure sensor 268 detects the pressure (outlet pressure of the air pump 112) Pout on the discharge port 302 side of the air pump 112.

[0028] FIG. 2 is a schematic diagram of a turbo-type air pump 112 including an air bearing mechanism.

[0029] The air pump 112 has a rotor shaft 274, and an impeller 276 is fixed to one end of the rotor shaft 274. A plurality of magnets are axially embedded in the cylindrical side surface of the rotor shaft 274. In the casing of the air pump 112, stator coils 272 of U-phase, V-phase and W-phase are attached, and a bearing (also referred to as an air bearing) 292 is attached. The rotor shaft 274 is inserted through the bearing 292. In the casing of the air pump 112, a flow path for the oxidant gas is attached, and a supercharger 294 including the impeller 276 is provided.

[0030] When the impeller 276 rotates as the rotor shaft 274 rotates, compressed air is supplied between the rotor shaft 274 and the inner peripheral surface of the bearing 292 at a predetermined rotational speed or higher. Thereby, an air layer is formed between the rotor shaft 274 and the inner peripheral surface of the bearing 292, and the rotor shaft 274 can rotate stably at high speed without contacting the inner peripheral surface of the bearing 292. This is called the axial floating of the rotor shaft 274.

[0031] During the operation of the fuel cell system 10 (from the start of operation to the stop of operation), it is preferable that the axial floating of the rotor shaft 274 is maintained in order to timely respond to the power generation demand for the fuel cell stack 12. The rotational speed of the air pump 112 is basically controlled to a value equal to or higher than the rotational speed at which the axial floating of the rotor shaft 274 can be realized. That is, the rotational speed of the air pump 112 is controlled to a value equal to or higher than the minimum rotational speed at which the rotor shaft 274 can rotate without contacting the inner peripheral surface of the bearing 292.

[0032] Under such control, the air pump 112 sucks outside air through the intake port 300 and supercharges (pressurizes and compresses) it with the supercharger 294. The air supercharged by the supercharger 294 is the oxidant gas, and is discharged from the discharge port 302 to the oxidant gas supply path 106A.

[0033] Returning to FIG. 1, the oxidant gas discharge passage 108 is connected to the oxidant gas discharge port 22d of the fuel cell stack 12 and the discharge passage 109. The oxidant gas discharge passage 108 is provided with the humidifier discharge passage 114B of the humidifier 114 and the outlet shutoff valve 118.

[0034] Of the oxidant gas discharge passage 108, the portion disposed upstream of the humidifier 114 is referred to as the oxidant gas discharge passage 108A. Of the oxidant gas discharge passage 108, the portion disposed downstream of the humidifier 114 is referred to as the oxidant gas discharge passage 108B.

[0035] A hydrogen concentration sensor 111 is attached to the oxidant gas discharge passage 108A. The hydrogen concentration sensor 111 is attached near the oxidant gas discharge port 22d. The hydrogen concentration sensor 111 detects the hydrogen concentration Dh in the oxidant off-gas.

[0036] The bypass passage 110 is connected to the oxidant gas supply passage 106A between the air pump 112 and the inlet shutoff valve 116 and the oxidant gas discharge passage 108B downstream of the outlet shutoff valve 118. The bypass passage 110 is provided with a bypass valve 120.

[0037] The bypass valve 120 is a butterfly valve whose opening can be linearly adjusted. Similarly, the inlet shutoff valve 116 that opens and closes the oxidant gas supply passage 106B and the outlet shutoff valve 118 that opens and closes the oxidant gas discharge passage 108A are also butterfly valves whose opening can be linearly adjusted. Note that the inlet shutoff valve 116 and the outlet shutoff valve 118 may be valves that switch between on (opening 100%) / off (opening 0%) like solenoid valves.

[0038] The cooling system 20 includes a cooling medium supply passage 122 and a cooling medium discharge passage 124. The cooling system 20 includes a water pump 126 and a radiator 128. The cooling medium supply passage 122 is connected to the fluid discharge port of the radiator 128 and the cooling medium supply port 22e of the fuel cell stack 12. The cooling medium supply passage 122 is provided with a water pump 126.

[0039] The cooling medium discharge passage 124 is connected to the cooling medium discharge port 22f of the fuel cell stack 12 and the fluid supply port of the radiator 128. A temperature sensor 130 is attached to the cooling medium discharge passage 124. The temperature sensor 130 detects the temperature of the cooling medium flowing through the cooling medium discharge passage 124. The temperature of the cooling medium flowing through the cooling medium discharge passage 124 corresponds to the temperature inside the fuel cell stack 12 (stack temperature).

[0040] The fuel cell stack 12 is formed by stacking a plurality of power generation cells 24. The power generation cell 24 includes an electrolyte membrane - electrode structure 32 and separators 28 and 30 that sandwich the electrolyte membrane - electrode structure 32. The electrolyte membrane - electrode structure 32 includes an MEA (Membrane Electrode Assembly) 34 and a resin frame member (not shown) that surrounds the outer peripheral portion of the MEA.

[0041] The MEA 34 includes, for example, a thin film (solid polymer electrolyte membrane) 36 of perfluorosulfonic acid containing moisture, and a cathode electrode 40 and an anode electrode 38 that sandwich the thin film 36. The cathode electrode 40 and the anode electrode 38 each have an electrode catalyst layer (not shown) and a gas diffusion layer (not shown) made of carbon paper or the like. The electrode catalyst layer contains porous carbon particles with a platinum alloy supported on the surface. The porous carbon particles are uniformly coated on the surface of the gas diffusion layer together with an ion - conductive polymer binder. Thereby, the electrode catalyst layer is formed. This electrode catalyst layer is formed on both sides of the thin film (solid polymer electrolyte membrane) 36.

[0042] On the surface of one separator 28 facing the electrolyte membrane - electrode structure 32, a cathode flow path (oxidant gas flow path) 50 is formed. The cathode flow path 50 communicates the oxidant gas supply port 22c and the oxidant gas discharge port 22d. The pressure of the oxidant gas flowing through the cathode flow path 50 is controlled by the control device 26 adjusting the opening degree of the outlet sealing valve 118.

[0043] On the surface of the separator 30 of the other party facing the electrolyte membrane - electrode structure 32, an anode flow path (fuel gas flow path) 66 is formed. The anode flow path 66 communicates the fuel gas supply port 22a and the fuel gas discharge port 22b.

[0044] Fuel gas (hydrogen) is supplied to the anode electrode 38. At the anode electrode 38, hydrogen ions are generated from hydrogen molecules by an electrode reaction using a catalyst, and electrons are released from the hydrogen molecules. The hydrogen ions permeate through the MEA 34 and move to the cathode electrode 40, while the electrons released from the hydrogen molecules move from the separator 30 and the negative terminal 23b, through the load 21, and via the positive terminal 23a and the separator 28 to the cathode electrode 40.

[0045] Oxidant gas (oxygen) is supplied to the cathode electrode 40. At the cathode electrode 40, hydrogen ions, electrons, and oxygen contained in the supplied oxidant gas react under the action of a catalyst to generate water.

[0046] A cell voltage sensor 25 is attached to each power generation cell 24. The cell voltage sensor 25 detects the cell voltage Vcell, which is the voltage between the terminals of one power generation cell 24 (single cell).

[0047] The load 21 includes a motor 246 and an air pump (electric auxiliary machine) 112 as high - voltage loads, and a battery heater 251 and an air conditioner (not shown) as low - voltage loads. The motor 246 is a drive source of the fuel cell vehicle 11, and the fuel cell vehicle 11 travels by the driving force of the motor 246. The air pump 112 supplies oxidant gas to the fuel cell stack 12. The battery heater 251 warms the power storage device 244.

[0048] The power supply system 27 includes a power storage device (battery) 248, which is a low-voltage power supply that generates a low voltage Vl, and a power storage device (battery) 244, which is a high-voltage power supply that generates a high voltage Vh. Here, a lead-acid battery is used for the power supply 248. A lithium-ion secondary battery or the like may be used instead of the lead-acid battery. Here, a lithium-ion secondary battery is used for the power storage device 244. A capacitor or the like may be used instead of the lithium-ion secondary battery.

[0049] The power storage device 244 is configured to be able to charge and discharge electric power, and discharges the shortage of the generated power of the fuel cell stack 12 with respect to the actual power consumption of the motor 246 and the air pump 112 (hereinafter also referred to as the AP actual power consumption) during power running. The power storage device 244 charges the regenerative power of the motor 246 during regeneration. In addition, the power storage device 244 charges the excess of the generated power of the fuel cell stack 12 with respect to the AP actual power consumption of the air pump 112.

[0050] A temperature sensor (temperature measuring device) 250, a state-of-charge detection sensor (SOC sensor) 245, and a battery heater 251 are attached to the power storage device 244. The temperature sensor 250 detects the temperature Tbat of the power storage device 244 and outputs it to the control device 26.

[0051] The state-of-charge detection sensor 245 detects the SOC of the power storage device 244 {state of charge [%] = (current remaining capacity) ÷ (fully charged capacity) × 100} and outputs it to the control device 26. SOC [%] is the remaining capacity with respect to the fully charged capacity, and the state-of-charge detection sensor 245 calculates SOC [%] from the temperature Tbat, input / output current (charge / discharge current), and stored voltage of the power storage device 244.

[0052] The state-of-charge detection sensor 245 calculates a discharge limit value Dlim [kWh] and a charge limit value Clim [kWh] according to the calculated SOC. The discharge limit value Dlim is a threshold value that prohibits the power storage device 244 from being overdischarged, and the charge limit value Clim is a threshold value that prohibits the power storage device 244 from being overcharged.

[0053] The discharge limit value Dlim and the charge limit value Clim can be calculated based on, in addition to the SOC of the power storage device 244, the temperature Tbat of the power storage device 244, the input / output current (charge / discharge current) and the stored power voltage, the internal resistance of the power storage device 244, and the like. Note that the discharge limit value Dlim and the charge limit value Clim may be calculated by the control device 26 instead of being calculated by the charge amount detection sensor 245.

[0054] The charge amount detection sensor 245 notifies the control device 26 of the calculated discharge limit value Dlim and charge limit value Clim. The control device 26 prohibits the use of the range exceeding the discharge limit value Dlim and the charge limit value Clim via the buck-boost converter 243. In other words, the control device 26 uses the power storage device 244 within the charge / discharge limit range (power amount range) 68 from the discharge limit value Dlim to the charge limit value Clim.

[0055] FIG. 3 is an explanatory diagram for explaining the charge / discharge limit range 68 of the power storage device 244. The charge / discharge limit range 68 may have a variable overall power width according to the temperature Tbat of the power storage device 244. Generally, at low temperatures (including extremely low temperatures (for example, less than 0 degrees)), the power width of the charge / discharge limit range 68 is smaller than that at normal temperature. The charge amount detection sensor 245 monitors the charge / discharge limit range 68 at any time and notifies the control device 26.

[0056] As shown in FIG. 3, a buffer (also referred to as a margin) 70 for the air pump 112 is set in the charge / discharge limit range 68 of the power storage device 244. The buffer 70 includes an acceleration buffer (discharge margin) 72 set on the Dlim side of the discharge limit value and a deceleration buffer (charge margin) 74 set on the Clim side of the charge limit value.

[0057] The acceleration buffer 72 allows for sudden power consumption associated with the acceleration of the air pump 112, insufficient FC generated power, and transient power fluctuations. For example, when power shortage occurs in the air pump 112 in the power storage device 244, the power storage device 244 discharges the insufficient power to the air pump 112 within the range of the acceleration buffer 72. Note that the acceleration of the air pump 112 means that the rate of change of the rotational speed [rpm] of the air pump 112 with respect to time [rpm / sec] is positive.

[0058] On the other hand, the deceleration buffer 74 allows for sudden power surplus associated with the deceleration of the air pump 112, excess FC generated power, power surplus due to the regenerative power of the air pump 112 or the motor 246, and transient fluctuations in power. For example, when a power surplus occurs in the air pump 112, the power storage device 244 charges the surplus power within the range of the deceleration buffer 74. Note that the deceleration of the air pump 112 means that the rate of change of the rotational speed [rpm] of the air pump 112 with respect to time [rpm / sec] is negative.

[0059] Ultimately, the buffer 70 (acceleration buffer 72, deceleration buffer 74) absorbs sudden fluctuations in the actual AP power consumption during acceleration and deceleration of the air pump 112, and prevents over-discharge and over-charge of the power storage device 244.

[0060] The power range of the buffer 70 can be set based on, for example, the discharge limit value Dlim, the charge limit value Clim calculated by the charge amount detection sensor 245, and the temperature Tbat of the power storage device 244. The control device 26 may calculate the power range of the buffer 70 using a buffer calculation map (not shown) stored in advance in the storage unit 138 of the control device 26. Note that the power range of the buffer 70 is also simply referred to as the buffer range.

[0061] In the fuel cell system 10 according to the present embodiment, the power amount of the acceleration buffer 72 can be changed (variable) within the power range (buffer range) of the buffer 70. The minimum value (minimum required value) of the acceleration buffer 72 can be set based on, for example, the power amount required when the air pump 112 rotates at the minimum rotational speed (the minimum value of the rotational speed at which the rotor shaft 274 of the air pump 112 can be axially lifted). The maximum value (maximum required value) of the acceleration buffer 72 can be set based on, for example, the power amount required when the air pump 112 rotates at the maximum acceleration rate (the positive maximum value of the rate of change of the rotational speed with respect to time).

[0062] Similarly, the power amount of the deceleration buffer 74 can also be changed (variable) within the power width (buffer width) range of the buffer 70. The minimum value (minimum required value) of the deceleration buffer 74 can be set in consideration of variations such as the measurement error of the flow rate sensor 107 and the power error of the inverter 252. The maximum value (maximum required value) of the deceleration buffer 74 can be set based on, for example, the maximum deceleration rate (negative maximum value of the rate of change of the rotational speed over time) of the air pump 112 that can avoid drying of the fuel cell stack 12 when reducing the output of the fuel cell stack 12. Here, the predetermined rated current of the fuel cell stack 12 is a current value set from the I-V characteristics (current-voltage characteristics) of the fuel cell stack 12, and may be, for example, the maximum value of the current that the fuel cell stack 12 can stably output.

[0063] In the charge-discharge limit range 68 shown in FIG. 3, the range other than the acceleration buffer 72 and the deceleration buffer 74 is referred to as an energy management control range (EM control range) 76. The power width of the EM control range 76 is allocated to the charge and discharge of the load 21 other than the air pump 112. The load 21 other than the air pump 112 includes the motor 246, the battery heater 251, an air conditioner (not shown), and the like.

[0064] Returning to FIG. 1, the motor 246 is connected to the inverter 242. The inverter 242 is supplied with power of a high voltage Vh from the fuel cell stack 12 via the boost converter 240 and with power of the high voltage Vh from the power storage device 244 via the buck-boost converter 243. That is, the motor 246 is supplied with power from both or either of the fuel cell stack 12 and the power storage device 244. The inverter 242 converts the direct current of the high voltage Vh supplied from both or either of the fuel cell stack 12 and the power storage device 244 into a three-phase alternating current and drives the motor 246.

[0065] The power storage device 244 is charged by the generated energy generated by the fuel cell stack 12. The boost converter 240 boosts the generated voltage Vfc of the fuel cell stack 12 to the direct current high voltage Vh, and the boosted high voltage Vh is applied to the power storage device 244 via the buck-boost converter 243.

[0066] When the fuel cell vehicle 11 decelerates and the motor 246 regenerates, the motor 246 functions as a generator, and a three-phase alternating current is generated in the motor 246. The generated three-phase alternating current is converted into direct current high-voltage Vh power by the inverter 242 and supplied to the high-voltage terminal of the buck-boost converter 243. The regenerative power supplied to the high-voltage terminal is charged into the power storage device 244 through the low-voltage terminal of the buck-boost converter 243.

[0067] The low-voltage loads include the control device 26, various sensors, the battery heater 251, an air conditioner (not shown), an electric power steering device, a lighting device, etc. These low-voltage loads are supplied with direct current low-voltage Vl power from the power source 248. The high-voltage Vh power supplied from the power storage device 244 is stepped down to low-voltage Vl by the buck converter 247 and charged into the power source 248.

[0068] The air pump 112 is supplied with three-phase alternating current power from the inverter 252. The inverter 252 converts the direct current high-voltage Vh supplied from the power storage device 244 into a three-phase alternating current. The inverter 252 supplies the converted three-phase alternating current to the air pump 112 and drives the air pump 112 within the rated power range. The rated power of the air pump 112 is, for example, the maximum power that the air pump 112 can stably output and is preset according to the specifications of the air pump 112. Any two phases of the three-phase alternating current, here the U-phase alternating current Iu and the V-phase alternating current Iv, are respectively detected by the current sensors 253 and 254.

[0069] Note that when the air pump 112 is driven by the power generated by the fuel cell stack 12, the power generated by the fuel cell stack 12 is not directly supplied to the air pump 112. In this case, the power generated by the fuel cell stack 12 is charged into the power storage device 244 through the buck-boost converter 243 and then supplied from the power storage device 244 to the air pump 112 through the inverter 252.

[0070] A power switch (operation switch or ignition switch), not shown, is connected to the control device 26. The user instructs the fuel cell vehicle 11 (fuel cell system 10) to start operation (start power generation) and stop operation (stop power generation) via the power switch.

[0071] In the ON state, the power switch starts or continues the power generation operation of the fuel cell stack 12 to make the fuel cell vehicle 11 in a drivable state or a driving state. The drivable state of the fuel cell vehicle 11 means a state where the fuel cell stack 12 is in an idling power generation state with low power generation and the fuel cell vehicle 11 is stopped. In the OFF state, the power switch ends the power generation operation of the fuel cell stack 12 and makes the fuel cell vehicle 11 in a stopped state (soak state).

[0072] The control device 26 can be constituted by an ECU (Electronic Control Unit). The control device 26 includes an arithmetic unit 136 and a storage unit 138. The arithmetic unit 136 is a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), for example. That is, the arithmetic unit 136 can be constituted by a processing circuitry. The arithmetic unit 136 controls each device by executing computer-executable instructions (programs) stored in the storage unit 138. At least a part of the arithmetic unit 136 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). At least a part of the arithmetic unit 136 may be realized by an electronic circuit including discrete devices.

[0073] The arithmetic unit 136 includes an acquisition unit 140, a control unit 142, a timing unit (not shown), a determination unit 146, a buffer setting unit 150, and a current limit value setting unit 152. The acquisition unit 140 acquires information from electronic components (sensors, ECUs, etc.) other than the control device 26.

[0074] In addition to the cell voltage sensor 25, temperature sensor 104, flow rate sensor 107, hydrogen concentration sensor 111, temperature sensor 130, current sensor 253, current sensor 254, pressure sensor 266, pressure sensor 268, charge detection sensor 245, and temperature sensor 250 shown in FIG. 1, the sensor includes sensors not shown in the figure. For example, there are a voltage sensor for detecting the power generation voltage Vfc of the fuel cell stack 12, a current sensor for detecting the power generation current Ifc of the fuel cell stack 12, a voltage sensor for detecting the high voltage Vh of the power storage device 244, a voltage sensor for detecting the low voltage Vl of the power supply 248, a flow rate sensor for detecting the flow rate of the oxidant gas in the fuel cell stack 12, and the like.

[0075] The control unit 142 executes computer-executable instructions (programs) based on various signals acquired from the sensors through the acquisition unit 140. The control unit 142 controls the operations of the injector 94, air pump 112, water pump 126, motor 246, boost converter 240, inverter 242, inverter 252, buck-boost converter 243, buck converter 247, valve, and the like. The timing unit measures the execution time and the like using a timer (not shown). The determination unit 146 determines the suitability of the buffer 70 of the power storage device 244 and the like. The buffer setting unit 150 sets the buffer 70 of the power storage device 244. The current limit value setting unit 152 sets the upper limit value of the output current of the fuel cell stack 12 (hereinafter, also referred to as the FC current limit value).

[0076] The storage unit 138 is composed of a volatile memory (not shown) and a non-volatile memory (not shown), which are computer-readable storage media. At least a part of the storage unit 138 may be provided in the above-described processor, integrated circuit, and the like.

[0077] The volatile memory is, for example, RAM (Random Access Memory) or the like. Data and the like are recorded in the volatile memory, for example. Physical quantities acquired by the control device 26 from various sensors and calculated values including the discharge limit value Dlim and the charge limit value Clim are recorded in the volatile memory.

[0078] The non-volatile memory is, for example, a ROM (Read Only Memory), a flash memory, etc. Programs, tables, maps, etc. are recorded in the non-volatile memory, for example. In the non-volatile memory, a power calculation map 148 capable of calculating the steady power consumption (AP steady power consumption) of the air pump 112 is recorded. Also, in the non-volatile memory, a buffer calculation map (not shown) and an air pump system efficiency map (not shown) are recorded.

[0079] The AP steady power consumption of the air pump 112 is the power consumed in a state (steady state) where the air pump 112 rotates at a constant rotational speed [rpm] when the fuel cell stack 12 generates power with a stable power generation amount. In the power calculation map 148, the AP steady power consumption is recorded in advance for each constant rotational speed. The control unit 142 can acquire the rotational speed of the air pump 112, refer to the power calculation map 148 from the acquired rotational speed, and calculate the AP steady power consumption.

[0080] Also, the AP steady power consumption may be calculated from the theoretical thermodynamics work [w] of the compressor (air pump 112) and the air pump system efficiency [%]. The air pump system efficiency can be calculated from the air pump system efficiency map.

[0081] In the air pump system efficiency map, the air pump system efficiency [%] corresponding to the flow rate Qo of the oxidant gas and the pressure ratio of the air pump 112 is recorded in advance. The pressure ratio of the air pump 112 is calculated as the ratio of the inlet pressure Pin of the air pump 112 detected by the pressure sensor 266 and the outlet pressure Pout of the air pump 112 detected by the pressure sensor 268. The control unit 142 calculates the air pump system efficiency by referring to the air pump system efficiency map from the flow rate Qo of the oxidant gas and the pressure ratio of the air pump 112.

[0082] Regarding the flow rate Qo of the oxidizing agent gas, instead of the measured value of the flow rate sensor 107, a value obtained by correcting the measured value of the flow rate sensor 107 may be used. The control unit 142 can correct the measured value of the flow rate sensor 107 in consideration of, for example, the specifications of the air pump 112 and the pressure loss inside the air pump 112. When correcting the measured value of the flow rate sensor 107, the inlet temperature Tin of the air pump 112, the inlet pressure Pin of the air pump 112, or other values may be further considered.

[0083] The rotation speed of the air pump 112 can be calculated by the control unit 142 by the acquisition unit 140 acquiring the changes in the U-phase alternating current Iu and the V-phase alternating current Iv detected by the current sensors 253 and 254 by the control device 26.

[0084] The control device 26 performs feedback control by vector control on the three-phase alternating current supplied from the inverter 242 to the motor 246 based on the torque command value of the motor 246. Further, the control device 26 performs feedback control by vector control on the three-phase alternating currents Iu, Iv, and Iw supplied from the inverter 252 to the air pump 112 based on the torque command value of the motor 246.

[0085] The power actually consumed by the air pump 112 (AP actual power consumption) is calculated by the control device 26 from the DC terminal voltage of the air pump 112 and the three-phase alternating current detected by the current sensors 253 and 254.

[0086] [Difference between AP actual power consumption and AP steady-state power consumption] Here, the difference between the AP actual power consumption and the AP steady-state power consumption will be described. FIG. 4 is a timing chart showing an example of the relationship between the AP actual power consumption and the AP steady-state power consumption of the air pump 112.

[0087] The fuel cell system 10 basically supplies the power required by the load 21 of the fuel cell vehicle 11 with the power generated by the fuel cell stack 12. The control device 26 calculates the power consumed by the entire fuel cell vehicle 11. Hereinafter, the power consumed by the entire fuel cell vehicle 11 is referred to as the vehicle required power. The control device 26 calculates the target power generation power (FC power generation required power) of the FC according to this vehicle required power. The control device 26 calculates the target rotation speed of the air pump 112 from the flow rate Qo of the oxidant gas and the pressure ratio (the ratio of the inlet pressure Pin of the air pump 112 to the outlet pressure Pout of the air pump 112) corresponding to the FC power generation required power. The control device 26 refers to the power calculation map 148 from the target rotation speed and calculates the AP steady consumption power. The calculated AP steady consumption power is fed back as the power required for driving the air pump 112 to the calculation of the next vehicle required power.

[0088] From the time point t2 to the time point t3 in FIG. 4, the fuel cell stack 12 stably generates power at a constant power generation amount (FC power generation power), and the air pump 112 is driven at a constant rotation speed. In this case, the AP actual consumption power and the AP steady consumption power generally coincide.

[0089] However, a difference may occur between the AP actual consumption power and the AP steady consumption power during acceleration or deceleration of the air pump 112.

[0090] From the time point t1 to the time point t2 in FIG. 4 shows the acceleration of the air pump 112. The power generation amount (FC power generation power) of the fuel cell stack 12 increases, and the rotation speed of the air pump 112 rises. In this case, the increase in the power (AP steady consumption power) supplied by the fuel cell stack 12 to the air pump 112 cannot catch up with the increase in the AP actual consumption power, and the AP actual consumption power becomes larger than the AP steady consumption power. In this specification, the difference between the AP actual consumption power and the AP steady consumption power (= AP actual consumption power - AP steady consumption power) in such a transient operation of the air pump 112 is referred to as "ΔAP".

[0091] When the air pump 112 is accelerating, the power storage device 244 discharges power by an amount of ΔAP to compensate for the shortage of the FC generated power. By providing an acceleration buffer 72 that can be discharged within the charge-discharge limit range 68 in advance, the power storage device 244 can absorb the rapid power consumption and power shortage associated with the acceleration of the air pump 112.

[0092] The time period from time point t3 to time point t4 in FIG. 4 indicates the deceleration of the air pump 112. The power generation amount (FC generated power) of the fuel cell stack 12 decreases, and the rotational speed of the air pump 112 decreases. In this case, the decrease in the power (AP steady-state power consumption) supplied from the fuel cell stack 12 to the air pump 112 cannot catch up with the decrease in the actual AP power consumption, and the actual AP power consumption becomes smaller than the AP steady-state power consumption.

[0093] When the air pump 112 is decelerating, the power storage device 244 charges power by an amount of ΔAP to compensate for the excessive power generation of the FC generated power. By providing a deceleration buffer 74 that can be charged within the charge-discharge limit range 68 in advance, the power storage device 244 can absorb the rapid power excess and power surplus associated with the deceleration of the air pump 112.

[0094] [Fluid Flow in the Fuel Cell System 10] (1) Fluid Flow in the Anode System 16 The injector 94 injects the fuel gas supplied from the tank 14 downstream of the fuel gas supply path 84 under the pulse width modulation (PWM) control by the control device 26. The fuel gas injected from the injector 94 is supplied to the fuel gas supply port 22a of the fuel cell stack 12 via the fuel gas supply path 84. The fuel gas that did not react inside the fuel cell stack 12 is discharged as fuel off-gas from the fuel gas discharge port 22b of the fuel cell stack 12. The fuel off-gas contains hydrogen that did not react with oxygen and nitrogen in the oxidant gas that permeated through the thin film (solid polymer electrolyte membrane) 36.

[0095] At the cathode electrode 40, moisture is generated by the reaction between oxygen and hydrogen, and a part of the generated moisture permeates through the thin film (solid polymer electrolyte membrane) 36 and moves to the anode electrode 38 side. The fuel off-gas contains, in addition to hydrogen and nitrogen, the moisture that has permeated through the thin film (solid polymer electrolyte membrane) 36 and moved to the anode electrode 38 side.

[0096] The fuel off-gas is supplied to the gas-liquid separator 98 through the fuel gas discharge passage 86. The gas-liquid separator 98 separates the fuel off-gas into a gas component (fuel off-gas) and a liquid component (liquid water). The fuel off-gas discharged from the gas-liquid separator 98 is supplied to the ejector 96 through the circulation passage 88. In the ejector 96, the fuel off-gas sucked from the gas-liquid separator 98 and the fuel gas injected from the injector 94 merge.

[0097] (2) Flow of fluid in the cathode system 18 The air pump 112 compresses the oxidant gas (air) sucked from outside the fuel cell vehicle 11 and discharges it downstream of the oxidant gas supply passage 106. The oxidant gas discharged from the air pump 112 is supplied to the oxidant gas supply port 22c of the fuel cell stack 12 through the oxidant gas supply passage 106 provided with a cooler (not shown). The oxidant gas that has not reacted inside the fuel cell stack 12 is discharged as oxidant off-gas from the oxidant gas discharge port 22d of the fuel cell stack 12. The oxidant off-gas contains each component contained in the oxidant gas and the moisture generated by the reaction between oxygen and hydrogen.

[0098] The oxidant off-gas is discharged to the outside of the fuel cell vehicle 11 through the oxidant gas discharge passage 108. The oxidant off-gas contains moisture. A part of the moisture contained in the oxidant off-gas is used to humidify the oxidant gas flowing through the humidifier supply passage 114A in the humidifier 114.

[0099] In the cathode system 18, the inlet shutoff valve 116 may be fully closed and the bypass valve 120 may be fully opened. In this case, the oxidant gas discharged from the air pump 112 flows into the bypass passage 110 without flowing into the oxidant gas supply passage 106B. The oxidant gas that has flowed into the bypass passage 110 is discharged to the outside of the fuel cell vehicle 11 via the oxidant gas discharge passage 108.

[0100] (3) Flow of fluid in the cooling system 20 The water pump 126 discharges the cooling medium toward the cooling medium supply port 22e of the fuel cell stack 12. The cooling medium discharged from the water pump 126 is supplied to the cooling medium supply port 22e of the fuel cell stack 12 via the cooling medium supply passage 122. The cooling medium that has flowed through the inside of the fuel cell stack 12 is discharged from the cooling medium discharge port 22f of the fuel cell stack 12. The cooling medium discharged from the cooling medium discharge port 22f is supplied to the radiator 128 via the cooling medium discharge passage 124. The cooling medium that has dissipated heat in the radiator 128 is sucked into the water pump 126.

[0101] [Setting of the acceleration buffer] The fuel cell system 10 according to the first embodiment is basically configured as described above. Next, a flow in which the control device 26 sets the power amount of the acceleration buffer 72 of the power storage device 244 during acceleration of the air pump 112 will be described with reference to the flowchart of FIG. 5.

[0102] In the flowchart of FIG. 5, the ON state of the power switch is set as the initial state. The fuel cell stack 12 has started or is continuing the power generation operation, and the fuel cell vehicle 11 is in a drivable state or a driving state. The initial value of the acceleration buffer 72 is set to the maximum value (maximum required value).

[0103] As shown in FIG. 5, in step S1, the acquisition unit 140 of the control device 26 acquires the current acceleration buffer 72 from the charge amount detection sensor 245. In step S2, the determination unit 146 determines whether the acquired acceleration buffer 72 is equal to or greater than the minimum required value. Since the initial value of the acceleration buffer 72 is the maximum value (maximum required value), the determination unit 146 can determine that the acquired acceleration buffer 72 is equal to or greater than the minimum required value (step S2: YES). Therefore, the process proceeds to step S3.

[0104] Note that, for example, in a situation where the SOC of the power storage device 244 is very small, such as at low temperatures, the acceleration buffer 72 may be determined to be less than the minimum required value (step S2: NO). In this case, the process returns to step S1, and the temperature rise of the power storage device 244 and the recovery of the SOC are awaited.

[0105] In step S3, the calculation unit 136 calculates the AP steady power consumption from the rotation speed of the air pump 112 and the power calculation map 148. In step S4, the calculation unit 136 adds the acceleration buffer 72 and the AP steady power consumption. The determination unit 146 determines whether the value obtained by adding the acceleration buffer 72 and the AP steady power consumption (the sum of the acceleration buffer 72 and the AP steady power consumption) exceeds the rated power of the air pump 112.

[0106] In step S4, when the value obtained by adding the acceleration buffer 72 and the AP steady power consumption does not exceed the rated power of the air pump 112 (step S4: NO), the process returns to step S1 without correcting the acceleration buffer 72.

[0107] In step S4, when the value obtained by adding the acceleration buffer 72 and the AP steady power consumption exceeds the rated power of the air pump 112 (step S4: YES), there is a possibility that an acceleration buffer 72 larger than necessary is secured for the power storage device 244. This is because the air pump 112 is driven within the range of the rated power.

[0108] In step S5, the calculation unit 136 subtracts the AP steady power consumption from the rated power of the air pump 112, and the determination unit 146 determines whether the subtracted value is smaller than the acceleration buffer 72.

[0109] In step S5, when the value obtained by subtracting the AP steady-state power consumption from the rated power of the air pump 112 is equal to or greater than the acceleration buffer 72 (step S5: NO), the determination unit 146 determines that the acceleration buffer 72 is set within an appropriate range. The control device 26 returns to step S1 without correcting the acceleration buffer 72.

[0110] In step S5, when the value obtained by subtracting the AP steady-state power consumption from the rated power of the air pump 112 is less than the acceleration buffer 72 (step S5: YES), the process proceeds to step S6.

[0111] In step S6, the determination unit 146 determines whether the value obtained by subtracting the AP steady-state power consumption from the rated power is equal to or greater than the minimum required value of the acceleration buffer 72.

[0112] In step S6, when the value obtained by subtracting the AP steady-state power consumption from the rated power is equal to or greater than the minimum required value of the acceleration buffer 72 (step S6: YES), the process proceeds to step S7. In step S7, the buffer setting unit 150 corrects the acceleration buffer 72 and sets the value obtained by subtracting the AP steady-state power consumption from the rated power as the new acceleration buffer 72. Thereby, an appropriate amount of power is allocated to the acceleration buffer 72.

[0113] In step S6, when the value obtained by subtracting the AP steady-state power consumption from the rated power is less than the minimum required value of the acceleration buffer 72 (step S6: NO), the process proceeds to step S8. In step S8, the buffer setting unit 150 corrects the acceleration buffer 72 and sets the minimum required value of the acceleration buffer 72 as the new acceleration buffer 72.

[0114] [Operation Explanation Based on Timing Chart] An example of the operation described by the flowchart of FIG. 5 will be described with reference to the timing chart of FIG. 6 while omitting the repetition of the operation explanation.

[0115] Before the time point t0 in FIG. 6, the fuel cell system 10 (fuel cell stack 12) is generating power. In this initial state, the air pump 112 is rotating at the minimum rotational speed that allows the shaft of the rotor shaft 274 to float.

[0116] At the time point t0, the control device 26 receives the target power generation power (FC power command) of the fuel cell stack 12 (alternatively, the control device 26 itself calculates the target power generation power of the fuel cell stack 12). When the control device 26 instructs the air pump 112 to a target rotational speed, the air pump 112 starts to accelerate, and the actual power consumption of the AP and the steady power consumption of the AP begin to increase.

[0117] From the time point t0 to the time point t1, the acceleration buffer 72 is the maximum value (maximum required value) W1 and is equal to or greater than the minimum required value W2 (step S2: YES). The value obtained by adding the acceleration buffer W1 and the steady power consumption of the AP W3 does not exceed the rated power W4 of the air pump 112 (step S4: NO). Therefore, the control device 26 maintains the acceleration buffer W1 without correction.

[0118] From the time point t1 to the time point t3, as the steady power consumption of the AP W6 increases, the value obtained by adding the acceleration buffer W5 and the steady power consumption of the AP W6 exceeds the rated power W4 of the air pump 112 (step S4: YES). The value obtained by subtracting the steady power consumption of the AP W6 from the rated power W4 is smaller than the acceleration buffer W5 (step S5: YES). On the other hand, the value obtained by subtracting the steady power consumption of the AP W6 from the rated power W4 is equal to or greater than the minimum required value W2 of the acceleration buffer 72 (step S6: YES). The control device 26 corrects the acceleration buffer W5 and sets the value obtained by subtracting the steady power consumption of the AP W6 from the rated power W4 to the new acceleration buffer 72 (step S7). That is, from the time point t1 to the time point t3, the control device 26 decreases the acceleration buffer 72 in response to the increase in the steady power consumption of the AP.

[0119] In this way, the control device 26 sets the acceleration buffer 72 based on the AP steady-state power consumption and the rated power of the air pump 112. The control device 26 secures the acceleration buffer 72 within the range required for driving the air pump 112 with respect to the charge / discharge limit range 68 of the power storage device 244. On the other hand, the control device 26 does not secure an extra (unnecessary) power amount range that is not required by the air pump 112 as the acceleration buffer 72. For this reason, the energy management control range (EM control range shown in FIG. 3) 76 available to the loads 21 other than the air pump 112 can be expanded.

[0120] Also, the control device 26 controls so that the value obtained by adding the acceleration buffer 72 and the AP steady-state power consumption does not exceed the rated power of the air pump 112. For this reason, the control device 26 can accurately secure the acceleration buffer 72 required for driving the air pump 112 with respect to the charge / discharge limit range 68.

[0121] Note that at time t2, the AP actual power consumption reaches the rated power W4, and the AP actual power consumption substantially coincides with the rated power W4 between time t2 and time t3. At time t3, the acceleration buffer W7 reaches the minimum required value W2.

[0122] At time t3, the AP actual power consumption substantially coincides with the AP steady-state power consumption. As a result, after time t3, the fuel cell stack 12 generates power stably according to the FC power command. The air pump 112 rotates at a constant rotational speed at which the fuel cell stack 12 can output the target power generation power. That is, the air pump 112 reaches a steady state. In this case, the value obtained by adding the acceleration buffer W7 and the AP steady-state power consumption W8 does not exceed the rated power W4 of the air pump 112 (step S4: NO). The value obtained by subtracting the AP steady-state power consumption W8 from the rated power W4 is smaller than the acceleration buffer W7. The value obtained by subtracting the AP steady-state power consumption W8 from the rated power W4 substantially coincides with the minimum required value W2 of the acceleration buffer 72. The control device 26 maintains the minimum required value W2 as the acceleration buffer 72.

[0123] [Appendix] Regarding the above disclosure, Appendices 1 to 5 below are further disclosed.

[0124] (Appendix 1) A fuel cell system (10) includes a fuel cell (12) that generates electricity using a fuel gas and an oxidant gas, a pump (112) that supplies the oxidant gas to the fuel cell, a power storage device (244) capable of supplying power to the pump, and a control device (26) that controls the power generation of the fuel cell and the charge and discharge of the power storage device. The control device sets a power amount range (68) within which the power storage device can be charged and discharged, and sets a buffer (70) within the power amount range of the power storage device. The buffer includes an acceleration buffer (72) which is the power amount that the power storage device can discharge to the pump when the pump is accelerating. The fuel cell system is such that the control device calculates the steady power consumption (AP steady power consumption) of the pump, and sets the acceleration buffer based on the calculated steady power consumption and the rated power of the pump.

[0125] According to such a configuration, the control device 26 sets the acceleration buffer 72 based on the AP steady power consumption and the rated power of the air pump 112. The control device 26 secures the acceleration buffer 72 required for driving the air pump 112 within the charge and discharge limit range 68 of the power storage device 244. On the other hand, the control device 26 does not secure an extra (unnecessary) power amount that is not required from the air pump 112 as the acceleration buffer 72. For this reason, the energy management control range (EM control range) 76 available to loads 21 other than the air pump 112 can be expanded.

[0126] Thereby, the fuel cell system 10 can optimize the power amount range (charge and discharge limit range 68) within which the power storage device 244 can be charged and discharged.

[0127] (Appendix 2) In the fuel cell system according to Appendix 1, when the sum of the acceleration buffer and the steady power consumption exceeds the rated power of the pump, the control device may reduce the acceleration buffer according to the steady power consumption.

[0128] According to such a configuration, the control device 26 controls so that the value obtained by adding the acceleration buffer 72 and the AP steady power consumption does not exceed the rated power of the air pump 112. The control device 26 can accurately secure the acceleration buffer 72 necessary for driving the air pump 112 with respect to the charge / discharge limit range 68.

[0129] Therefore, the fuel cell system 10 can further optimize the power amount range (charge / discharge limit range 68) in which the power storage device 244 can be charged and discharged.

[0130] (Appendix 3) In the fuel cell system according to Appendix 1 or Appendix 2, the control device may cover the steady power consumption with the power generated by the fuel cell.

[0131] According to such a configuration, the power corresponding to the AP steady power consumption among the AP actual power consumption required during acceleration of the air pump 112 is covered with the power generated by the fuel cell stack 12. The power shortage occurring in the air pump 112 becomes at least the difference between the AP actual power consumption and the AP steady power consumption (ΔAP from time point t1 to time point t2 in FIG. 4). The power storage device 244 can compensate for the power shortage (ΔAP) of the air pump 112 within the range of the acceleration buffer 72. Thereby, the fuel cell system 10 can accurately optimize the power amount range (charge / discharge limit range 68) in which the power storage device 244 can be charged and discharged.

[0132] (Appendix 4) In the fuel cell system according to any one of Appendices 1 to 3, the control device may charge the power storage device with the power generated by the fuel cell and supply the power charged in the power storage device to the pump.

[0133] According to such a configuration, when the power storage device 244 supplies the power generated by the fuel cell stack 12 to the air pump 112, the power charged in the power storage device 244 in advance can be added and supplied.

[0134] (Appendix 5) A method for controlling charge and discharge of a power storage device (244) of a fuel cell system (10) includes a fuel cell (12) that generates power using a fuel gas and an oxidant gas, a pump (112) that supplies the oxidant gas to the fuel cell, a power storage device capable of supplying power to the pump, and a control device (26) that controls power generation of the fuel cell and charge and discharge of the power storage device. The control device sets a range of chargeable and dischargeable power (68) for the power storage device, sets a buffer (70) within the range of the power amount of the power storage device, and the buffer includes an acceleration buffer (72) that is the amount of power that the power storage device can discharge to the pump when the pump is accelerating. A method for controlling charge and discharge of a power storage device of a fuel cell system, wherein the control device calculates the steady power consumption (AP steady power consumption) of the pump and sets the acceleration buffer based on the calculated steady power consumption and the rated power of the pump.

[0135] According to such a configuration, the control device 26 sets the acceleration buffer 72 based on the AP steady power consumption and the rated power of the air pump 112. The control device 26 secures the acceleration buffer 72 required for driving the air pump 112 within the charge and discharge limit range 68 of the power storage device 244. On the other hand, the control device 26 does not secure an extra (unnecessary) amount of power that is not required from the air pump 112 as the acceleration buffer 72. Therefore, the energy management control range (EM control range) 76 available to loads 21 other than the air pump 112 can be expanded.

[0136] Thereby, the range of the amount of power (charge and discharge limit range 68) that the power storage device 244 can charge and discharge can be optimized.

[0137] Note that the AP steady power consumption does not necessarily have to be calculated based on the rotation speed of the air pump 112 and the power calculation map 148. It is sufficient to be able to calculate an estimated value of the power supplied by the fuel cell stack 12 to the air pump 112, and the calculation method can adopt a known method.

[0138] Further, the rated power of the air pump 112 can be replaced with other values. In the setting flow of the acceleration buffer 72, a value larger than the AP steady-state power consumption at the maximum rotation rate of the air pump 112 is sufficient. Depending on the specifications of the air pump 112, the fuel cell stack 12, etc., it may be replaced with a value larger or smaller than the rated power.

[0139] [Second Embodiment] Next, the fuel cell system 210 according to the second embodiment will be described. In the first embodiment, the charge / discharge limit range 68 of the power storage device 244 is optimized by assigning a buffer width that is necessary and sufficient for driving the air pump 112 to the acceleration buffer 72. On the other hand, the fuel cell system 210 according to the second embodiment relaxes the current limit of the fuel cell stack 12 due to the deceleration buffer 74, and optimizes the charge / discharge limit range 68 of the power storage device 244. Hereinafter, in the description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals. Redundant descriptions are omitted as appropriate.

[0140] [Current Limit Value of Fuel Cell Stack 12] The fuel cell system 210 according to the second embodiment sets an upper limit value for the generated current Ifc of the fuel cell stack 12 in order to control the generated current Ifc of the fuel cell stack 12. This upper limit value is referred to as the current limit value of the fuel cell stack 12, or simply the FC current limit value.

[0141] Normally, the rated current, which is the maximum output of the fuel cell stack 12, is set as the FC current limit value. However, when the deceleration buffer 74 is insufficient and the deceleration rate of the air pump 112 (the time change rate of the rotation speed during deceleration) cannot satisfy a predetermined condition, a small current during idling power generation may be set as the FC current limit value. In this specification, the predetermined condition that the deceleration rate of the air pump 112 should satisfy is referred to as the water content control condition of the fuel cell stack 12.

[0142] [Water Content Control Condition of Fuel Cell Stack 12] The water content control condition of the fuel cell stack 12 will be described with reference to FIGS. 7A to 7D.

[0143] FIG. 7A shows the change over time in the rotational speed (AP rotational speed) [rpm] of the air pump 112 during deceleration of the air pump 112, that is, the deceleration rate [rpm / sec] of the air pump 112. FIG. 7B shows the change over time in the opening degree [%] of the bypass valve 120, and FIG. 7C shows the change over time in the flow rate (stack air flow rate) [g / sec] of the oxidant gas flowing through the fuel cell stack 12. FIG. 7D shows the change over time in the dryness (stack dryness) inside the fuel cell stack 12.

[0144] In FIGS. 7A to 7D, the time point t30 is the initial state. In the initial state, the fuel cell stack 12 outputs a predetermined rated current, and the air pump 112 rotates at a rotational speed corresponding to the rated current of the fuel cell stack 12. In each figure, the time from the time point t30 to the time point t32 is referred to as the excess air allowable time.

[0145] The excess air allowable time is the time during which the flow of excess oxidant gas is allowed in the fuel cell stack 12 when the rotational speed of the air pump 112 is reduced to the rotational speed corresponding to the current during idling power generation.

[0146] The current during idling power generation is, for example, a small current that can drive the air pump 112 at the minimum rotational speed at which the rotor shaft 274 of the air pump 112 can be shaft-floated. Alternatively, the current during idling power generation may be a small current such that the power generated by the fuel cell stack 12 and the power consumed by the air pump 112 are substantially the same.

[0147] The excess air allowable time is set, for example, in the range of several seconds depending on the specifications of the fuel cell system 210 including the fuel cell stack 12.

[0148] When the rotational speed of the air pump 112 is reduced to the rotational speed corresponding to the current during idling power generation within the excess air allowable time, drying inside the fuel cell stack 12 is avoided. In this case, the deceleration rate satisfies the water content control condition. On the other hand, when the rotational speed of the air pump 112 is not reduced to the rotational speed corresponding to the current during idling power generation within the excess air allowable time, the inside of the fuel cell stack 12 dries out. In this case, the deceleration rate does not satisfy the water content control condition.

[0149] In the graph with a solid line in FIG. 7A, it is an example of a deceleration rate that satisfies the water content control condition. The rotational speed of the air pump 112 gradually decreases from time point t30 and reaches the rotational speed corresponding to the current during idling power generation at time point t31.

[0150] The graph with a solid line in FIG. 7B shows that the bypass valve 120 starts to be driven toward the fully open state (opening degree 100%) from time point t30. The bypass valve 120 reaches the fully open state before reaching time point t31.

[0151] The graph with a solid line in FIG. 7C shows that at time point t30, an oxidant gas with a flow rate corresponding to the rated current is flowing inside the fuel cell stack 12. The oxidant gas flowing inside the fuel cell stack 12 gradually decreases and reaches the flow rate corresponding to the current during idling power generation at time point t31. The flow rate of the oxidant gas flowing inside the fuel cell stack 12 is maintained at the flow rate corresponding to the current during idling power generation also after time point t31.

[0152] The graph with a solid line in FIG. 7D shows that the degree of dryness inside the fuel cell stack 12 is low at time point t30. When the air pump 112 starts to decelerate, the power generation amount of the fuel cell stack 12 decreases, and the amount of moisture generated inside the fuel cell stack 12 decreases. On the other hand, the oxidant gas continues to flow inside the fuel cell stack 12 after time point t30. The degree of dryness inside the fuel cell stack 12 gradually increases. However, the degree of dryness inside the fuel cell stack 12 is maintained at a value below the dryness threshold also after time point t31.

[0153] On the other hand, the dashed graphs in FIGS. 7A, 7C, and 7D show an example when the water content control conditions are not satisfied.

[0154] As shown in FIG. 7A, the deceleration rate when the water content control conditions are not satisfied is smaller than the deceleration rate when the water content control conditions are satisfied. For this reason, at time t32, the rotational speed of the air pump 112 exceeds the rotational speed corresponding to the current during idling power generation. At time t32 in FIG. 7C, the flow rate of the oxidant gas flowing through the fuel cell stack 12 exceeds the flow rate corresponding to the current during idling power generation. As a result, as shown at time t32 in FIG. 7D, the stack dryness exceeds the dryness threshold value. That is, when the deceleration rate does not satisfy the water content control conditions, drying of the fuel cell stack 12 is caused.

[0155] Thus, the fuel cell system 210 according to the second embodiment can be controlled to avoid drying in the fuel cell stack 12 when the air pump 112 decelerates, using the water content control conditions consisting of the rotational speed of the air pump 112 corresponding to the FC current limit value (usually the rated current), the rotational speed of the air pump 112 corresponding to the current during idling power generation, and the excess air allowable time.

[0156] Note that this fuel cell system 210 is noted for including the bypass valve 120. The rotational speed of the air pump 112 corresponding to the current during idling power generation can be changed according to the opening degree of the bypass valve 120. If the opening degree of the bypass valve 120 is increased, the flow rate of the oxidant gas directed to the fuel cell stack 12 decreases, so the rotational speed of the air pump 112 corresponding to the current during idling power generation may be a large value. In this case, the excess power ΔAP generated by the air pump 112 when the air pump 112 decelerates becomes small, and there is an advantage that it is sufficient to set a small buffer width for the deceleration buffer 74.

[0157] [Setting of Current Limit Value] Next, the flow in which the control device 26 sets the current limit value (FC current limit value) of the fuel cell stack 12 will be described with reference to the flowchart of FIG. 8.

[0158] In step S21, the control device 26 acquires the temperature Tbat of the power storage device (battery) 244 from the temperature sensor 250.

[0159] In step S22, the control device 26 compares the temperature Tbat with a threshold temperature Tthr1. The threshold temperature Tthr1 is a threshold between an extremely low temperature (e.g., less than 0 degrees Celsius) and a low temperature (e.g., 0 degrees Celsius or more and less than 5 degrees Celsius), and is set to, for example, 0 degrees Celsius.

[0160] When the temperature Tbat is less than the threshold temperature Tthr1 (step S22: YES), the control device 26 determines that there is not enough power margin in the charge / discharge limit range 68 of the power storage device 244. The control device 26 proceeds to step S23 without setting the buffer 70 (acceleration buffer 72, deceleration buffer 74).

[0161] In step S23, the control device 26 sets the current during idling power generation (idle current) to the FC current limit value. The control device 26 waits for the power storage device 244 to be heated for a predetermined time.

[0162] Returning to step S21, the control device 26 acquires the temperature Tbat of the power storage device (battery) 244 from the temperature sensor 250 again.

[0163] In step S22, the control device 26 compares the temperature Tbat with the threshold temperature Tthr1. When the temperature Tbat is equal to or higher than the threshold temperature Tthr1 (step S22: NO), the charge / discharge limit range 68 of the power storage device 244 is slightly expanded compared to the case of an extremely low temperature. The control device 26 determines that it is possible to set the buffer 70 (deceleration buffer 74, acceleration buffer 72) within the charge / discharge limit range 68 of the power storage device 244, and proceeds to step S24.

[0164] In step S24, the control device 26 compares the temperature Tbat with a threshold temperature Tthr2. The threshold temperature Tthr2 is a threshold between a low temperature (e.g., 0 degrees Celsius or more and less than 5 degrees Celsius) and a normal temperature (e.g., 5 degrees Celsius or more), and is, for example, 5 degrees Celsius.

[0165] When the temperature Tbat is less than the threshold temperature Tthr2 (step S24: YES), the control device 26 determines that the minimum buffer 70 (deceleration buffer 74, acceleration buffer 72) can be set within the charge / discharge limit range 68 of the power storage device 244, and proceeds to step S25.

[0166] In step S25, the control device 26 sets the minimum buffer width (minimum required value) in the deceleration buffer 74. The minimum buffer width of the deceleration buffer 74 may be, for example, the minimum amount of electric power necessary to absorb variations such as the measurement error of the flow rate sensor 107 and the power error of the inverter 252.

[0167] In step S25, when setting the deceleration buffer 74, the control device 26 also sets the acceleration buffer 72. For example, the minimum buffer width (minimum required value) is set in the acceleration buffer 72. The minimum buffer width of the acceleration buffer 72 may be, for example, the amount of electric power necessary for the air pump 112 to rotate at the minimum rotation speed (the minimum value of the rotation speed at which the rotor shaft 274 of the air pump 112 can float on the axis).

[0168] Next, in step S26, the control device 26 changes the FC current limit value to a value larger than the current during idling power generation (idle current) according to the temperature Tbat. The FC current limit value is set to an intermediate current value between the current during idling power generation and the rated current. This intermediate current value between the current during idling power generation and the rated current is hereinafter referred to as the intermediate current value.

[0169] When the FC current limit value is increased from the current during idling power generation to the intermediate current value, the fuel cell stack 12 can generate a current larger than the current during idling power generation. For example, if the generated power of the fuel cell stack 12 is supplied to the battery heater 251, the battery heater 251 can warm the power storage device 244. The control device 26 waits for the power storage device 244 to be warmed for a predetermined time.

[0170] When the temperature Tbat is equal to or higher than the threshold temperature Tthr2 (step S24: NO), the control device 26 determines that a large buffer 70 (deceleration buffer 74, acceleration buffer 72) can be set within the charge / discharge limit range 68 of the power storage device 244, and proceeds to step S27.

[0171] In step S27, the control device 26 sets the maximum buffer width (maximum required value) in the deceleration buffer 74. The maximum buffer width of the deceleration buffer 74 may be calculated based on the deceleration rate when the output of the fuel cell stack 12 is reduced from the rated current to the current during idling power generation within the excess air allowable time.

[0172] When setting the deceleration buffer 74, the control device 26 changes the buffer width of the acceleration buffer 72 according to the temperature Tbat. The buffer width of the acceleration buffer 72 may be set based on the amount of power required when the air pump 112 rotates at the maximum acceleration rate.

[0173] Next, in step S28, the control device 26 changes the FC current limit value from the intermediate current value to the rated current. As a result, the fuel cell stack 12 can generate power at the rated current, and power can be supplied not only to low-voltage loads such as the battery heater 251 but also to high-voltage loads such as the motor 246.

[0174] [Operation Explanation Based on Timing Chart] An example of the operation described by the flowchart of FIG. 8 will be described with reference to the timing chart of FIG. 9 while omitting the repetition of the operation explanation.

[0175] FIG. 9 is a timing chart showing an example of the transition of the actual AP power consumption and the steady AP power consumption of the air pump 112 at low temperature and normal temperature.

[0176] At time t40, it is determined that the temperature Tbat of the power storage device 244 is low (step S24: YES). A minimum buffer width is set for the deceleration buffer 74, and a minimum buffer width is also set for the acceleration buffer 72 (step S25). An intermediate current value is set for the FC current limit value (step S26). At this time, the upper limit of the FC power (FC power limit value) is limited to the FC power upper limit value based on the intermediate current value.

[0177] Also, at time t40, the control device 26 receives the target power generation power (FC power command) of the fuel cell stack 12. When the control device 26 instructs the air pump 112 to rotate at a target speed, the air pump 112 starts to accelerate, and the AP actual power consumption and the AP steady power consumption begin to increase.

[0178] From time t40 to time t41, the AP steady power consumption is assigned to the deceleration buffer 74, and the deceleration buffer 74 rises slightly. After time t41, the upper limit of the deceleration buffer 74 is maintained at the minimum buffer width set in step S25.

[0179] At time t42, the acceleration of the air pump 112 ends, and the air pump 112 enters a steady state. At this time, the AP actual power consumption and the AP steady power consumption substantially coincide. The fuel cell stack 12 can supply power to a low-voltage load such as the battery heater 251.

[0180] At time t43, the air pump 112 starts to decelerate. The minimum value is set for the deceleration buffer 74. Here, the control device 26 decelerates the air pump 112 at a deceleration rate at which no surplus power (the difference between the AP actual power consumption and the AP steady power consumption) ΔAP is generated in the air pump 112. At time t44, the deceleration of the air pump 112 ends.

[0181] At time t45, it is determined that the temperature Tbat of the power storage device 244 is normal temperature (step S24: NO). The maximum buffer width is set for the deceleration buffer 74 (step S27), and an appropriate buffer width is also set for the acceleration buffer 72. The control device 26 changes the FC current limit value from the intermediate current value to the rated current (step S28). At this time, the upper limit value (FC power limit value) of the FC power generation power is released up to the upper limit value based on the FC rated current.

[0182] At time t45, the control device 26 receives the target power generation power (FC power command) of the fuel cell stack 12. When the control device 26 instructs the air pump 112 to rotate at a target speed, the air pump 112 starts to accelerate, and the AP actual power consumption and the AP steady power consumption begin to increase.

[0183] Between time t45 and time t46, the AP steady power consumption is allocated to the deceleration buffer 74, and the upper limit of the deceleration buffer 74 maintains the maximum buffer width set in step S27.

[0184] At time t47, the air pump 112 starts to decelerate. Since the maximum required value is set for the deceleration buffer 74 (step S27), the power storage device 244 can charge the surplus power ΔAP generated between the AP actual power consumption and the AP steady power consumption. At time t48, the deceleration of the air pump 112 ends.

[0185] [Comparative Example] FIG. 10 is an explanatory diagram showing an example of the FC current limit value according to the temperature Tbat of the power storage device 244.

[0186] The broken line in FIG. 10 shows a comparative example. In the comparative example, at extremely low temperatures and low temperatures, the FC current limit value is fixed to the current during idling power generation. When the temperature Tbat of the power storage device 244 reaches the threshold between low temperature and normal temperature (threshold temperature Tthr2), the FC current limit value is first raised to the rated current.

[0187] In this comparative example, since the rotational speed of the air pump 112 corresponding to the current during idling power generation is low, the deceleration rate that satisfies the water content control condition becomes large. When the air pump 112 decelerates, a large surplus power ΔAP may be generated. Therefore, it is necessary to secure a large buffer width corresponding to the deceleration rate in the deceleration buffer 74. Accordingly, in this comparative example, the FC current limit value is not raised to the rated current until the necessary buffer width for the deceleration buffer 74 can be secured, and the FC current limit value is fixed at the current during idling power generation.

[0188] The solid line in FIG. 10 shows an example of the FC current limit value in the fuel cell system 210. In the fuel cell system 210, when the temperature Tbat of the power storage device 244 is extremely low, the current during idling power generation is set as the FC current limit value (step S23). When the temperature Tbat of the power storage device 244 reaches the threshold between extremely low temperature and low temperature (threshold temperature Tthr1), the FC current limit value is switched to an intermediate current value (step S26). When the temperature Tbat of the power storage device 244 reaches the threshold between low temperature and normal temperature (threshold temperature Tthr2), the FC current limit value is raised to the rated current (step S28).

[0189] Thus, even when the fuel cell system 210 according to the second embodiment cannot secure a sufficient deceleration buffer 74 in the power storage device 244 at low temperatures, the FC current limit value is switched from the current during idling power generation to an intermediate current value to generate power from the fuel cell stack 12. For example, power can be supplied to a low-voltage load such as the battery heater 251, and the power storage device 244 can be heated using the battery heater 251. Thereby, a moving body such as the fuel cell vehicle 11 equipped with the fuel cell stack 12 can be shifted to a travelable state (operable state) at an early stage.

[0190] Regarding the above disclosure, the following Appendices 6 to 9 are further disclosed.

[0191] (Appendix 6) A fuel cell system (210) includes a fuel cell (12) that generates electricity using a fuel gas and an oxidant gas, a pump (112) that supplies the oxidant gas to the fuel cell, a power storage device (244) capable of supplying power to the pump, a control device (26) that controls power generation of the fuel cell and charge / discharge of the power storage device, and a temperature measurement device (250) that measures the temperature (Tbat) of the power storage device. The control device sets a power amount range (68) in which charge / discharge is possible for the power storage device, sets a buffer (70) within the power amount range of the power storage device, and the buffer includes a deceleration buffer (74) that is an amount of power with which surplus power (ΔAP) generated during deceleration of the pump can be charged to the power storage device. The control device changes the buffer width of the deceleration buffer according to the temperature of the power storage device, and changes the current limit value (FC current limit value) of the fuel cell based on the buffer width of the deceleration buffer, and generates power from the fuel cell using the current limit value (intermediate current value) after the change.

[0192] According to such a configuration, even when it is not possible to secure a sufficient deceleration buffer 74, for example, at low temperatures, the FC current limit value of the fuel cell stack 12 is changed to an intermediate current value to generate power from the fuel cell.

[0193] Thereby, power can be supplied to a low-voltage load such as a battery heater 251, for example, and the power storage device 244 can be heated using the battery heater 251. Heating of the power storage device 244 expands the charge / discharge limit range 68 in which charge / discharge is possible, and optimizes the power amount range in which the power storage device 244 can be charged / discharged. Thereby, a moving body such as a fuel cell vehicle 11 equipped with the fuel cell stack 12 can be shifted to a travelable state (operable state) earlier. Further, when the outside air temperature is low, the occupant of the fuel cell vehicle 11 can use the air conditioner. The occupant can also use power inside the fuel cell vehicle 11.

[0194] (Appendix 7) In the fuel cell system described in Supplementary Note 6, the control device may change the current limit value of the fuel cell based on the buffer width of the deceleration buffer and the rate of change of the rotational speed of the pump over time, and cause the fuel cell to generate power with the changed current limit value.

[0195] According to such a configuration, in addition to the buffer width of the deceleration buffer 74, the rate of change of the rotational speed (deceleration rate) of the air pump 112 is taken into account to change the FC current limit value. As a result, for example, power can be supplied to a low-voltage load such as the battery heater 251 at an early stage.

[0196] (Supplementary Note 8) In the fuel cell system described in Supplementary Note 6 or Supplementary Note 7, an oxidant gas supply passage (106) for supplying the oxidant gas to the fuel cell, an inlet shutoff valve (116) provided between the pump and the fuel cell in the oxidant gas supply passage, an exhaust passage (109) for exhausting the oxidant gas discharged from the fuel cell to the outside, a bypass passage (110) for allowing the oxidant gas supplied to the oxidant gas supply passage to flow from the upstream side of the inlet shutoff valve to the exhaust passage, and a bypass valve (120) provided between the oxidant gas supply passage and the exhaust passage in the bypass passage. The control device may change the current limit value of the fuel cell based on the buffer width of the deceleration buffer and the opening degree of the bypass valve, and cause the fuel cell to generate power with the changed current limit value.

[0197] According to such a configuration, in addition to the buffer width of the deceleration buffer 74, the opening degree of the bypass valve 120 is taken into account to change the FC current limit value. As a result, for example, power can be supplied to a low-voltage load such as the battery heater 251 at an early stage.

[0198] (Supplementary Note 9) A control method for a fuel cell system (210) includes a fuel cell (12) that generates electricity using a fuel gas and an oxidant gas, a pump (112) that supplies the oxidant gas to the fuel cell, a power storage device (244) capable of supplying power to the pump, a control device (26) that controls power generation of the fuel cell and charge / discharge of the power storage device, and a temperature measurement device (250) that measures the temperature (Tbat) of the power storage device. The control device sets a power amount range (68) in which the power storage device can be charged and discharged, and sets a buffer (70) within the power amount range of the power storage device. The buffer includes a deceleration buffer (74) that is an amount of power with which surplus power (ΔAP) generated during deceleration of the pump can be charged to the power storage device. A control method for a fuel cell system includes changing a buffer width of the deceleration buffer according to the temperature of the power storage device (steps S25, S27), changing a current limit value of the fuel cell based on the buffer width of the deceleration buffer (steps S23, S26, S28), and generating power from the fuel cell with the changed current limit value.

[0199] According to such a configuration, even when it is not possible to secure a sufficient deceleration buffer 74, for example, at low temperatures, the FC current limit value of the fuel cell stack 12 is changed to an intermediate current value to generate power from the fuel cell.

[0200] Thereby, power can be supplied to a low-voltage load such as a battery heater 251, and the power storage device 244 can be heated using the battery heater 251. Heating of the power storage device 244 expands the power amount range in which charge and discharge are possible (charge / discharge limit range 68), and the power amount range in which the power storage device 244 can be charged and discharged is optimized. Thereby, a moving body such as a fuel cell vehicle 11 equipped with the fuel cell stack 12 can be shifted to a travelable state (operable state) at an early stage. Further, when the outside air temperature is low, the occupant of the fuel cell vehicle 11 can use the air conditioner. The occupant can also use power inside the fuel cell vehicle 11.

[0201] Note that the present invention is not limited to the above-described disclosure, and various configurations can be adopted without departing from the gist of the present invention.

[0202] For example, the opening degree of the bypass valve 120 is not limited to the example shown in FIG. 7B. The opening degree of the bypass valve 120 does not have to be in the fully open state (opening degree 100%). The opening degree of the bypass valve 120 can be changed as appropriate. In addition to the bypass valve 120, the inlet shut-off valve 116 and the outlet shut-off valve 118 may be controlled to adjust the flow rate of the oxidant gas flowing through the fuel cell stack 12.

[0203] For example, the intermediate current value shown in FIG. 10 is an example, and a plurality of intermediate current values may be set between the rated current and the current during idling power generation. The intermediate current value may be set so that the graph in FIG. 10 monotonically increases in a stepwise, staircase, or curved manner according to the temperature Tbat of the power storage device 244.

Explanation of Reference Numerals

[0204] 10... Fuel cell system 12... Fuel cell stack (fuel cell) 26... Control device 68... Charge / discharge limit range (electric energy range) 70... Buffer 72... Acceleration buffer 74... Deceleration buffer 112... Air pump (pump) 244... Power storage device 250... Temperature sensor (temperature measurement device)

Claims

1. A fuel cell system that generates electricity using a fuel gas and an oxidant gas, a pump that supplies the oxidant gas to the fuel cell, a power storage device capable of supplying power to the pump, a control device that controls the power generation of the fuel cell and the charge and discharge of the power storage device, and is provided with the control device sets a power amount range in which the power storage device can be charged and discharged, and sets a buffer within the power amount range of the power storage device, the buffer includes an acceleration buffer that is the amount of power that the power storage device can discharge to the pump when the pump is accelerating a fuel cell system, the control device calculates the steady power consumption of the pump, and sets the acceleration buffer based on the calculated steady power consumption and the rated power of the pump A fuel cell system.

2. In the fuel cell system according to Claim 1, the control device when the sum of the acceleration buffer and the steady power consumption exceeds the rated power of the pump, reduces the acceleration buffer according to the steady power consumption A fuel cell system.

3. In the fuel cell system according to Claim 2, the control device covers the steady power consumption with the power generated by the fuel cell A fuel cell system.

4. In the fuel cell system according to Claim 3, the control device charges the power storage device with the power generated by the fuel cell, and supplies the power charged in the power storage device to the pump A fuel cell system.

5. A fuel cell system that generates electricity using a fuel gas and an oxidant gas, a pump that supplies the oxidant gas to the fuel cell, a power storage device capable of supplying power to the pump, a control device that controls the power generation of the fuel cell and the charge and discharge of the power storage device, and is provided with the control device sets a power amount range in which the power storage device can be charged and discharged, and sets a buffer within the power amount range of the power storage device, the buffer includes an acceleration buffer that is the amount of power that the power storage device can discharge to the pump when the pump is accelerating A method for controlling the charge and discharge of a power storage device in a fuel cell system, the control device calculates the steady power consumption of the pump, and sets the acceleration buffer based on the calculated steady power consumption and the rated power of the pump A method for controlling the charge and discharge of a power storage device in a fuel cell system.

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