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, there is a demand for optimizing the range of electric energy that can be charged and discharged by a power storage device.

[0008] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0009] A first aspect of the present invention is a fuel cell system comprising: a fuel cell that generates electricity using a fuel gas and an oxidant gas; a pump that supplies the oxidant gas to the fuel cell; an electric storage device that can supply electric power to the pump; and a control device that controls the power generation of the fuel cell and the charging and discharging of the electric storage device, wherein the control device sets a range of electric power that can be charged and discharged to the electric storage device and sets a buffer within the electric power range of the electric storage device, the buffer including an acceleration buffer that is the amount of electric power that can be discharged from the electric storage device to the pump when the pump is accelerating, and the control device calculates the steady-state power consumption of the pump and sets the acceleration buffer based on the calculated steady-state power consumption and the rated power of the pump.

[0010] A second aspect of the present invention is a method for controlling the charging and discharging of a power storage device in a fuel cell system, the method comprising: a fuel cell that generates power using a fuel gas and an oxidant gas; a pump that supplies the oxidant gas to the fuel cell; a power storage device that can supply power to the pump; and a control device that controls the power generation of the fuel cell and the charging and discharging of the power storage device, wherein the control device sets a range of power amounts that can be charged and discharged to the power storage device and sets a buffer within the power amount range of the power storage device, the buffer including an acceleration buffer that is the amount of power that can be discharged by the power storage device to the pump when the pump is accelerated, and the control device calculates the steady-state power consumption of the pump, and sets the acceleration buffer based on the calculated steady-state power consumption and the rated power of the pump. [Effects of the Invention]

[0011] According to the present invention, the range of electric energy that can be charged and discharged by the power storage device in a fuel cell system can be optimized. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a fuel cell system according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram of a turbo air pump equipped with an air bearing mechanism. [Figure 3] FIG. 3 is an explanatory diagram for explaining the charge / discharge limit range of the power storage device. [Figure 4] FIG. 4 is a timing chart showing an example of the relationship between the actual AP power consumption and the steady-state AP power consumption of the air pump. [Figure 5] FIG. 5 is a flowchart illustrating a flow for setting the acceleration buffer. [Figure 6] FIG. 6 is a timing chart showing an example of the transition of the actual power consumption and the steady-state power consumption of the AP when the air pump is accelerating. [Figure 7] Fig. 7A is an explanatory diagram showing the change in the rotation speed of the air pump over time, Fig. 7B is an explanatory diagram showing the change in the opening degree of the bypass valve over time, Fig. 7C is an explanatory diagram showing the change in the flow rate of the oxidant gas over time, and Fig. 7D is an explanatory diagram showing the change in the dryness level inside the fuel cell stack over time. [Figure 8] FIG. 8 is a flowchart showing the flow of setting the current limit value of the fuel cell stack. [Figure 9] FIG. 9 is a timing chart showing an example of the transition of the actual AP power consumption and the steady-state AP power consumption of the air pump at low temperature and at normal temperature. [Figure 10] FIG. 10 is an explanatory diagram showing an example of the FC current limit value according to the temperature of the power storage device. DETAILED DESCRIPTION OF THE INVENTION

[0013] [First embodiment] [Configuration of fuel cell system 10] FIG. 1 is a schematic diagram of a fuel cell system 10 according to a first embodiment. Here, the configuration of the fuel cell system 10 mounted on a fuel cell automobile 11 is described. However, the fuel cell system 10 can also be mounted on moving objects other than vehicles. For example, the fuel cell system 10 can also be mounted on ships, aircraft, robots, 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 reactant 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 subjected to an electrochemical reaction. In this specification, the fuel gas discharged from the fuel cell stack 12 without being subjected to the electrochemical reaction is also referred to as fuel off-gas. The oxidant gas discharged from the fuel cell stack 12 without being subjected to 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 controller .

[0016] The fuel cell stack 12 has 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 oxidizing gas supply port 22c and an oxidizing gas discharge port 22d. The oxidizing gas supply port 22c supplies oxidizing gas to the inside of the fuel cell stack 12. The oxidizing gas discharge port 22d discharges oxidizing off-gas from the inside of the fuel cell stack 12.

[0020] The fuel cell stack 12 has a coolant supply port 22e and a coolant discharge port 22f. The coolant supply port 22e supplies a coolant to the inside of the fuel cell stack 12. The coolant discharge port 22f discharges the coolant from the inside of the fuel cell stack 12.

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

[0022] The fuel gas supply path 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 path 84 is provided with an injector 94 and an ejector 96. The inlet 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 disposed between the injector 94 and the fuel gas supply port 22a.

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

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

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

[0026] The portion of the oxidizing gas supply channel 106 that is disposed upstream of the humidifier 114 is referred to as the oxidizing gas supply channel 106A. The portion of the oxidizing gas supply channel 106 that is disposed downstream of the humidifier 114 is referred to as the oxidizing gas supply channel 106B.

[0027] The inlet seal 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 oxidizing gas supply path 106A upstream of the air pump 112. The flow rate sensor 107 detects the flow rate Qo of the oxidizing gas flowing through the air pump 112. The temperature sensor 104 detects the temperature Tin of the oxidizing gas at the intake port 300 of the air pump 112 (the inlet temperature of the air pump 112). The pressure sensor 266 detects the pressure Pin on the intake port 300 side of the air pump 112 (the inlet pressure of the air pump 112). A pressure sensor 268 is attached to the oxidizing gas supply path 106A downstream of the air pump 112. The pressure sensor 268 detects the pressure Pout on the discharge port 302 side of the air pump 112 (the outlet pressure of the air pump 112).

[0028] FIG. 2 is a schematic diagram of a turbo air pump 112 equipped with 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 embedded in the axial direction on the cylindrical side surface of the rotor shaft 274. U-phase, V-phase, and W-phase stator coils 272 are attached to the casing of the air pump 112, and a bearing (also referred to as an air bearing) 292 is also attached. The rotor shaft 274 is inserted through the bearing 292. A flow path for oxidant gas is attached to the casing of the air pump 112, and a supercharger 294 including the impeller 276 is provided.

[0030] When the impeller 276 rotates in accordance with the rotation of the rotor shaft 274, compressed air is supplied between the rotor shaft 274 and the inner circumferential surface of the bearing 292 at a predetermined rotation speed or higher. This forms an air layer between the rotor shaft 274 and the inner circumferential surface of the bearing 292, allowing the rotor shaft 274 to rotate stably at high speed without coming into contact with the inner circumferential surface of the bearing 292. This is called axial levitation of the rotor shaft 274.

[0031] During operation of the fuel cell system 10 (from start-up to shutdown), it is preferable to maintain axial levitation of the rotor shaft 274 in order to respond in a timely manner to a power generation request to the fuel cell stack 12. The rotation speed of the air pump 112 is basically controlled to a value equal to or greater than the rotation speed at which axial levitation of the rotor shaft 274 can be achieved. In other words, the rotation speed of the air pump 112 is controlled to a value equal to or greater than the minimum rotation speed at which the rotor shaft 274 can rotate without coming into contact with the inner circumferential surface of the bearing 292.

[0032] Under such control, the air pump 112 draws in outside air via the intake port 300 and supercharges (compresses and compresses) it in the supercharger 294. The air supercharged by the supercharger 294 is an oxidizing gas, and is discharged from the discharge port 302 to the oxidizing gas supply channel 106A.

[0033] 1, the oxidizing gas discharge channel 108 is connected to the oxidizing gas discharge port 22d of the fuel cell stack 12 and to a discharge channel 109. The oxidizing gas discharge channel 108 is provided with a humidifier discharge channel 114B of the humidifier 114 and an outlet seal valve 118.

[0034] Of the oxidizing gas discharge channel 108, a portion disposed upstream of the humidifier 114 is referred to as an oxidizing gas discharge channel 108A. Of the oxidizing gas discharge channel 108, a portion disposed downstream of the humidifier 114 is referred to as an oxidizing gas discharge channel 108B.

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

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

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

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

[0039] The cooling medium discharge path 124 is connected to a cooling medium discharge port 22f of the fuel cell stack 12 and a fluid supply port of the radiator 128. A temperature sensor 130 is attached to the cooling medium discharge path 124. The temperature sensor 130 detects the temperature of the cooling medium flowing through the cooling medium discharge path 124. The temperature of the cooling medium flowing through the cooling medium discharge path 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. Each power generation cell 24 includes a membrane electrode assembly 32 and separators 28 and 30 that sandwich the membrane electrode assembly 32. The membrane electrode assembly 32 includes an MEA (Membrane Electrode Assembly) 34 and a resin frame member (not shown) that surrounds the outer periphery of the MEA.

[0041] The MEA 34 includes, for example, a thin film (solid polymer electrolyte membrane) 36 of water-containing perfluorosulfonic acid, 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 includes porous carbon particles having a platinum alloy supported on their surfaces. The porous carbon particles are uniformly coated on the surface of the gas diffusion layer together with an ion-conductive polymer binder, thereby forming an electrode catalyst layer. The electrode catalyst layers are formed on both sides of the thin film (solid polymer electrolyte membrane) 36.

[0042] A cathode flow path (oxidant gas flow path) 50 is formed on the surface of one separator 28 facing the membrane electrode assembly 32. The cathode flow path 50 connects 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 of the outlet seal valve 118.

[0043] An anode flow channel (fuel gas flow channel) 66 is formed on the surface of the other separator 30 facing the membrane electrode assembly 32. The anode flow channel 66 connects 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, a catalytic electrode reaction generates hydrogen ions from hydrogen molecules, and electrons are released from the hydrogen molecules. The hydrogen ions permeate 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 electrode terminal 23b through the load 21, via the positive electrode terminal 23a and the separator 28, to the cathode electrode 40.

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

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

[0047] The load 21 includes a motor 246 and an air pump (electric accessory) 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 for the fuel cell vehicle 11, and the fuel cell vehicle 11 runs using the driving force of the motor 246. The air pump 112 supplies oxidant gas to the fuel cell stack 12. The battery heater 251 heats 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. A lead-acid battery is used as the power supply 248 here. A lithium-ion secondary battery or the like may be used instead of the lead-acid battery. A lithium-ion secondary battery is used as the power storage device 244 here. 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 power, and during power running, discharges the shortfall in the power generated by the fuel cell stack 12 relative to the actual power consumption of the motor 246 and the air pump 112 (hereinafter also referred to as AP actual power consumption). During regeneration, the power storage device 244 is charged with regenerated power from the motor 246. In addition, the power storage device 244 is charged with the excess of the power generated by the fuel cell stack 12 relative to the AP actual power consumption of the air pump 112.

[0050] The power storage device 244 is equipped with a temperature sensor (temperature measurement device) 250, a charge amount detection sensor (SOC sensor) 245, and a battery heater 251. The temperature sensor 250 detects the temperature Tbat of the power storage device 244 and outputs it to the control device .

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

[0052] The charge amount 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 over-discharged, and the charge limit value Clim is a threshold value that prohibits the power storage device 244 from being over-charged.

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

[0054] The charge amount detection sensor 245 notifies the calculated discharge limit value Dlim and charge limit value Clim to the control device 26. The control device 26 prohibits use in a range exceeding the discharge limit value Dlim and the charge limit value Clim via the step-up / step-down converter 243. In other words, the control device 26 uses the power storage device 244 in a charge / discharge limit range (power amount range) 68 between the discharge limit value Dlim and the charge limit value Clim.

[0055] 3 is an explanatory diagram for explaining the charge / discharge limit range 68 of the power storage device 244. The entire power range of the charge / discharge limit range 68 can change depending on the temperature Tbat of the power storage device 244. In general, the power range of the charge / discharge limit range 68 is smaller at low temperatures (including extremely low temperatures (e.g., below 0 degrees)) than at normal temperatures. The charge amount detection sensor 245 constantly monitors the charge / discharge limit range 68 and notifies the control device 26 of the result.

[0056] 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 discharge limit value Dlim side, and a deceleration buffer (charge margin) 74 set on the charge limit value Clim side.

[0057] Acceleration buffer 72 tolerates sudden power consumption, a shortage of FC-generated power, and transient power fluctuations that accompany the acceleration of air pump 112. For example, if a power shortage occurs in air pump 112, power storage device 244 discharges the shortage of power to air pump 112 within the range of acceleration buffer 72. Note that acceleration of air pump 112 means that the rate of change over time [rpm / sec] of the rotation speed [rpm] of air pump 112 is positive.

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

[0059] Ultimately, buffer 70 (acceleration buffer 72, deceleration buffer 74) absorbs sudden fluctuations in the actual power consumption of the AP when air pump 112 accelerates and decelerates, and prevents power storage device 244 from being overcharged or overdischarged.

[0060] The power width of the buffer 70 may be set based on, for example, the discharge limit value Dlim and 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 width of the buffer 70 using a buffer calculation map (not shown) that is stored in advance in the storage unit 138 of the control device 26. The power width of the buffer 70 may also be simply referred to as the buffer width.

[0061] In the fuel cell system 10 according to this embodiment, the amount of power in the acceleration buffer 72 is changeable (variable) within the range of the power width (buffer width) of the buffer 70. The minimum value (minimum required value) of the acceleration buffer 72 can be set, for example, based on the amount of power required when the air pump 112 rotates at a minimum rotation speed (the minimum rotation speed at which the rotor shaft 274 of the air pump 112 can float). The maximum value (maximum required value) of the acceleration buffer 72 can be set, for example, based on the amount of power required when the air pump 112 rotates at a maximum acceleration rate (the maximum positive value of the rate of change in the rotation speed over time).

[0062] Similarly, the amount of power in the deceleration buffer 74 is also changeable (variable) within the range of the power width (buffer width) of the buffer 70. The minimum value (minimum required value) of the deceleration buffer 74 can be set taking into account variations in, for example, the measurement error of the flow rate sensor 107 or 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 (maximum negative value of the rate of change in rotation speed over time) of the air pump 112 that can prevent the fuel cell stack 12 from drying out 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 IV characteristics (current-voltage characteristics) of the fuel cell stack 12, and may be, for example, the maximum current that the fuel cell stack 12 can stably output.

[0063] 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 charging and discharging the loads 21 other than the air pump 112. The loads 21 other than the air pump 112 include the motor 246, the battery heater 251, an air conditioner (not shown), etc.

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

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

[0066] When the fuel cell vehicle 11 is decelerating and the motor 246 is regenerating, the motor 246 operates as a generator. Capable R .stomach Converter 242 is the regenerative voltage of the motor 246. DC high voltage V h conversion The DC high voltage Vh is , at the high voltage end of the buck-boost converter 243 application The regenerative power supplied to the high voltage end is charged into the power storage device 244 through the low voltage end of the step-up / step-down converter 243.

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

[0068] Three-phase AC power is supplied to air pump 112 from inverter 252. Inverter 252 converts high DC voltage Vh supplied from power storage device 244 into three-phase AC current. Inverter 252 supplies the converted three-phase AC current to air pump 112, causing air pump 112 to operate within a rated power range. The rated power of air pump 112 is, for example, the maximum power that air pump 112 can stably output, and is set in advance according to the specifications of air pump 112. Any two phases of the three-phase AC, in this case U-phase AC current Iu and V-phase AC current Iv, are detected by current sensors 253 and 254, respectively.

[0069] It should be noted 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 via the step-up / step-down converter 243, and then supplied from the power storage device 244 to the air pump 112 via the inverter 252.

[0070] A power switch (operation switch or ignition switch) (not shown) is connected to the control device 26. A 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] When the power switch is in the ON state, it starts or continues the power generation operation of the fuel cell stack 12, putting the fuel cell vehicle 11 into a state where it is ready to run or in a running state. The state where the fuel cell vehicle 11 is ready to run means that the fuel cell stack 12 is in an idling power generation state with a small amount of generated power, and the fuel cell vehicle 11 is not running. When the power switch is in the OFF state, it ends the power generation operation of the fuel cell stack 12, putting the fuel cell vehicle 11 into a stopped state (soak state).

[0072] The control device 26 may be configured by an ECU (Electronic Control Unit). The control device 26 includes a calculation unit 136 and a storage unit 138. The calculation unit 136 is, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). That is, the calculation unit 136 may be configured by processing circuitry. The calculation unit 136 controls each device by executing computer-executable instructions (programs) stored in the storage unit 138. At least a portion of the calculation 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 portion of the calculation unit 136 may be realized by an electronic circuit including discrete devices.

[0073] The calculation unit 136 includes an acquisition unit 140, a control unit 142, a timer (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 other than the control device 26 (sensors, ECUs, etc.).

[0074] 1 , the sensors include 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 amount detection sensor 245, and temperature sensor 250, as well as other sensors not shown in the figures. For example, there are a voltage sensor that detects the power generation voltage Vfc of the fuel cell stack 12, a current sensor that detects the power generation current Ifc of the fuel cell stack 12, a voltage sensor that detects the high voltage Vh of the power storage device 244, a voltage sensor that detects the low voltage Vl of the power source 248, a flow rate sensor that detects the flow rate of the oxidant gas in the fuel cell stack 12, and the like.

[0075] The control unit 142 executes computer-executable commands (programs) based on various signals acquired from sensors via 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, boost / buck converter 243, buck converter 247, valves, etc. The timing unit measures execution time, etc. using a timer (not shown). The determination unit 146 determines whether the buffer 70 of the power storage device 244 is appropriate, etc. The buffer setting unit 150 sets the buffer 70 of the power storage device 244. The current limit value setting unit 152 sets an upper limit value of the output current of the fuel cell stack 12 (hereinafter also referred to as an FC current limit value).

[0076] The storage unit 138 is configured with a volatile memory (not shown) and a non-volatile memory (not shown) that are computer-readable storage media. At least a part of the storage unit 138 may be included in the above-mentioned processor, integrated circuit, etc.

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

[0078] The nonvolatile memory is, for example, a ROM (Read Only Memory), a flash memory, etc. Programs, tables, maps, etc. are recorded in, for example, the nonvolatile memory. The nonvolatile memory stores a power calculation map 148 that can calculate the steady-state power consumption (AP steady-state power consumption) of the air pump 112. The nonvolatile memory also stores a buffer calculation map (not shown) and an air pump system efficiency map (not shown).

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

[0080] In addition, the AP steady-state power consumption is calculated by the theoretical thermodynamic work of the compressor (air pump 112) [ W ] and air pump system efficiency [%]. The air pump system efficiency may be calculated from an air pump system efficiency map.

[0081] The air pump system efficiency map stores in advance the air pump system efficiency [%] corresponding to the oxidant gas flow rate Qo and the pressure ratio of the air pump 112. The pressure ratio of the air pump 112 is calculated as the ratio between 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 oxidant gas flow rate Qo and the pressure ratio of the air pump 112.

[0082] It should be noted that, with regard to the flow rate Qo of the oxidant gas, a value obtained by correcting the measurement value of the flow rate sensor 107 may be used instead of the measurement value of the flow rate sensor 107. The control unit 142 may correct the measurement value of the flow rate sensor 107, for example, taking into consideration the specifications of the air pump 112 and pressure loss inside the air pump 112. When correcting the measurement 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 also be taken into consideration.

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

[0084] The control device 26 performs feedback control by vector control on the three-phase AC currents supplied from the inverter 242 to the motor 246 based on the torque command value of the motor 246. The control device 26 also performs feedback control by vector control on the three-phase AC 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 air pump 112 (AP actual power consumption) is calculated by control device 26 from the DC terminal voltage of air pump 112 and the three-phase AC current detected by current sensors 253 and 254.

[0086] [Difference between actual AP power consumption and AP steady-state power consumption] Here, the difference between the actual power consumption of the AP and the steady power consumption of the AP will be described.

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

[0088] 4, the fuel cell stack 12 stably generates a constant amount of power (FC generated power), and the air pump 112 is driven at a constant rotation speed. In this case, the actual power consumption of the AP and the steady-state power consumption of the AP are approximately the same.

[0089] However, when the air pump 112 is accelerating or decelerating, a difference may occur between the actual power consumption of the AP and the steady power consumption of the AP.

[0090] 4, the period from time t1 to time t2 indicates the acceleration of the air pump 112. The amount of power generated by the fuel cell stack 12 (FC generated power) increases, and the rotation speed of the air pump 112 rises. In this case, the increase in the power supplied by the fuel cell stack 12 to the air pump 112 (AP steady power consumption) does not keep up with the increase in the actual AP power consumption, and the actual AP power consumption becomes greater than the AP steady power consumption. In this specification, the difference between the actual AP power consumption and the AP steady power consumption during such transient operation of the air pump 112 (=AP actual power consumption - AP steady power consumption) is referred to as "ΔAP."

[0091] When air pump 112 accelerates, power storage device 244 discharges power equivalent to ΔAP to compensate for the shortage of FC-generated power. By providing acceleration buffer 72 that can discharge within charge / discharge limit range 68 in advance, power storage device 244 can absorb the sudden power consumption and power shortage that accompanies the acceleration of air pump 112.

[0092] 4 shows the period from time t3 to time t4 when the air pump 112 is decelerating. The amount of power generated by the fuel cell stack 12 (FC generated power) decreases, and the rotation speed of the air pump 112 decreases. In this case, the decrease in the power supplied by the fuel cell stack 12 to the air pump 112 (AP steady power consumption) does not keep up with the decrease in the AP actual power consumption, and the AP actual power consumption becomes smaller than the AP steady power consumption.

[0093] When air pump 112 decelerates, power storage device 244 is charged with power equivalent to ΔAP to compensate for the excess power generated by the FC. By providing deceleration buffer 74 that can be charged within charge / discharge limit range 68 in advance, power storage device 244 can absorb the sudden excess or surplus power that accompanies deceleration of air pump 112.

[0094] [Fluid flow in 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 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 has not reacted 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 has not reacted with oxygen and nitrogen in the oxidant gas that has permeated the thin film (solid polymer electrolyte membrane) 36.

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

[0096] The fuel off-gas is supplied to a gas-liquid separator 98 via a fuel gas discharge path 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 an ejector 96 via a circulation path 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 join together.

[0097] (2) Fluid flow in the cathode system 18 The air pump 112 compresses oxidant gas (air) drawn in from outside the fuel cell vehicle 11 and discharges it downstream of the oxidant gas supply channel 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 via the oxidant gas supply channel 106, which is equipped 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 the components contained in the oxidant gas and moisture produced by the reaction of oxygen and hydrogen.

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

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

[0100] (3) Fluid flow 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 path 122. The cooling medium that has circulated inside 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 path 124. The cooling medium that has dissipated heat in the radiator 128 is drawn into the water pump 126.

[0101] [Acceleration buffer settings] 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 amount of power in the acceleration buffer 72 of the power storage device 244 when the air pump 112 is accelerated will be described with reference to the flowchart in FIG.

[0102] 5, the ON state of the power switch is the initial state. The fuel cell stack 12 has started or is continuing power generation operation, and the fuel cell vehicle 11 is in a state where it can run or is running. The initial value of the acceleration buffer 72 is set to the maximum value (maximum required value).

[0103] 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. Because 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] In addition, under circumstances where the SOC of the power storage device 244 is very low, such as at low temperatures, it may be determined that the acceleration buffer 72 is less than the minimum required value (step S2: NO). In this case, the process returns to step S1, and the process waits for the temperature of the power storage device 244 to rise and for the SOC to recover.

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

[0106] In step S4, if the sum of acceleration buffer 72 and AP steady power consumption does not exceed the rated power of air pump 112 (step S4: NO), acceleration buffer 72 is not corrected and the process returns to step S1.

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

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

[0110] In step S5, if the value obtained by subtracting the AP steady power consumption from the rated power of air pump 112 is smaller than 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 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, if the value obtained by subtracting the AP steady power consumption from the rated power is equal to or greater than the minimum required value for 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 power consumption from the rated power as the new acceleration buffer 72. As a result, an amount of power that is neither excessive nor insufficient is allocated to the acceleration buffer 72.

[0113] In step S6, if the value obtained by subtracting the AP steady-state power consumption from the rated power is smaller 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 to the new acceleration buffer 72.

[0114] [Operation explanation using timing chart] An example of the operation described with reference to the flowchart in FIG. 5 will be described with reference to the timing chart in FIG. 6, while omitting repetition of the operation description.

[0115] 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 rotation speed that allows the rotor shaft 274 to float.

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

[0117] From time t0 to time t1, the acceleration buffer 72 is at the maximum value (maximum required value) W1, which is equal to or greater than the minimum required value W2 (step S2: YES). The sum of the acceleration buffer W1 and the AP steady power consumption 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 correcting it.

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

[0119] In this way, 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 reserves the acceleration buffer 72 within the range necessary to drive the air pump 112, relative to the charge / discharge limit range 68 of the power storage device 244. On the other hand, the control device 26 does not reserve an excess (unnecessary) power amount range that is not required by the air pump 112 as the acceleration buffer 72. This makes it possible to expand the energy management control range (EM control range shown in FIG. 3) 76 that can be used by the load 21 other than the air pump 112.

[0120] Furthermore, the control device 26 controls the sum of the acceleration buffer 72 and the AP steady power consumption so that it does not exceed the rated power of the air pump 112. Therefore, the control device 26 can accurately ensure the acceleration buffer 72 required to drive the air pump 112 for the charge / discharge limit range 68.

[0121] At time t2, the actual power consumption of the AP reaches the rated power W4, and the actual power consumption of the AP is approximately equal to the rated power W4 between time t2 and time t3. 72 reaches the minimum required value W2.

[0122] At time t3, the actual AP power consumption is approximately equal to the AP steady power consumption. As a result, from time t3 onwards, the fuel cell stack 12 generates power stably in accordance with the FC power command. The air pump 112 rotates at a constant rotation speed at which the fuel cell stack 12 can output the target power generation. In other words, the air pump 112 reaches a steady state. In this case, the sum of the acceleration buffer W7 and the AP steady 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 power consumption W8 from the rated power W4 is the acceleration buffer W7. Acceleration buffer W7 is approximately equal to 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] [Note] In addition to the above disclosure, the following Supplementary Notes 1 to 5 are disclosed.

[0124] (Appendix 1) The fuel cell system (10) comprises a fuel cell (12) that generates electricity using fuel gas and oxidant gas, a pump (112) that supplies the oxidant gas to the fuel cell, an electric storage device (244) that can supply electric power to the pump, and a control device (26) that controls the power generation of the fuel cell and the charging and discharging of the electric storage device, wherein the control device sets a range (68) of electric energy that can be charged and discharged to the electric storage device and sets a buffer (70) within the range of electric energy of the electric storage device, the buffer including an acceleration buffer (72) that is the amount of electric energy that can be discharged from the electric storage device to the pump when the pump accelerates, and the control device calculates the steady-state power consumption of the pump (AP steady-state power consumption) and sets the acceleration buffer based on the calculated steady-state power consumption and the rated power of the pump.

[0125] With this configuration, control device 26 sets acceleration buffer 72 based on the AP steady power consumption and the rated power of air pump 112. Control device 26 secures acceleration buffer 72 necessary for driving air pump 112 within charge / discharge limit range 68 of power storage device 244. On the other hand, control device 26 does not secure, as acceleration buffer 72, an excess (unnecessary) amount of power that is not requested by air pump 112. This makes it possible to expand energy management control range (EM control range) 76 that can be used by load 21 other than air pump 112.

[0126] This allows the fuel cell system 10 to optimize the range of the amount of electric power that the power storage device 244 can charge and discharge (charge and discharge limit range 68).

[0127] (Appendix 2) In the fuel cell system described in Appendix 1, the control device may be configured to reduce the acceleration buffer in accordance with the steady-state power consumption when the sum of the acceleration buffer and the steady-state power consumption exceeds the rated power of the pump.

[0128] With this configuration, the control device 26 controls the acceleration buffer 72 so that the sum of 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 ensure the acceleration buffer 72 required to drive the air pump 112 within the charge / discharge limit range 68.

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

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

[0131] With this configuration, the power equivalent to the AP steady-state power consumption, out of the AP actual power consumption required when accelerating the air pump 112, is supplied by the power generated by the fuel cell stack 12. The power shortage that occurs in the air pump 112 is at least the difference between the AP actual power consumption and the AP steady-state power consumption (ΔAP from time t1 to time 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. This allows the fuel cell system 10 to accurately optimize the range of power that the power storage device 244 can charge and discharge (charge / discharge limit range 68).

[0132] (Appendix 4) In the fuel cell system described in any one of Supplementary Notes 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] With this configuration, when the power storage device 244 supplies the air pump 112 with electric power generated by the fuel cell stack 12, the power storage device 244 can supply the electric power together with the electric power that has been previously stored in the power storage device 244.

[0134] (Appendix 5) A method for controlling charging and discharging of an electric storage device (244) of a fuel cell system (10) includes a fuel cell (12) that generates electric power from a fuel gas and an oxidant gas, a pump (112) that supplies the oxidant gas to the fuel cell, an electric storage device that can supply electric power to the pump, and a control device (26) that controls the power generation of the fuel cell and the charging and discharging of the electric storage device, wherein the control device sets a range of electric power that can be charged and discharged to the electric storage device and sets a buffer (70) within the range of electric power that can be charged and discharged to the electric storage device, and the buffer includes an acceleration buffer (72) that is an amount of electric power that can be discharged by the electric storage device to the pump when the pump is accelerated, and the control device calculates steady-state power consumption of the pump (AP steady-state power consumption) and sets the acceleration buffer based on the calculated steady-state power consumption and the rated power of the pump.

[0135] With this configuration, control device 26 sets acceleration buffer 72 based on the AP steady power consumption and the rated power of air pump 112. Control device 26 secures acceleration buffer 72 necessary for driving air pump 112 within charge / discharge limit range 68 of power storage device 244. On the other hand, control device 26 does not secure, as acceleration buffer 72, an excess (unnecessary) amount of power that is not requested by air pump 112. This makes it possible to expand energy management control range (EM control range) 76 that can be used by load 21 other than air pump 112.

[0136] This makes it possible to optimize the range of the amount of power that can be charged and discharged by the power storage device 244 (charge and discharge limit range 68).

[0137] The AP steady-state power consumption does not 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 from the fuel cell stack 12 to the air pump 112, and any known calculation method can be used.

[0138] The rated power of the air pump 112 may be replaced with another value. In the setting flow of the acceleration buffer 72, it is sufficient if the value is greater than the AP steady-state power consumption at the maximum rotation speed rate of the air pump 112. Depending on the specifications of the air pump 112 and the fuel cell stack 12, the rated power may be replaced with a value greater or smaller than the rated power.

[0139] [Second embodiment] Next, a fuel cell system 210 according to a second embodiment will be described. In the first embodiment, the charge / discharge limit range 68 of the power storage device 244 is optimized by allocating to the acceleration buffer 72 a buffer width that is necessary for driving the air pump 112 and that is neither too much nor too little. In contrast, the fuel cell system 210 according to the second embodiment optimizes the charge / discharge limit range 68 of the power storage device 244 by relaxing the current limit on the fuel cell stack 12 caused by the deceleration buffer 74. In the following description of the second embodiment, the same components as those in the first embodiment will be assigned the same reference numerals. Duplicate descriptions will be omitted where 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 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 as the FC current limit value.

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

[0142] [Water content control conditions for fuel cell stack 12] The moisture content control conditions for 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 rotation speed (AP rotation speed) [rpm] of the air pump 112 when the air pump 112 is decelerating, i.e., the deceleration rate [rpm / sec] of the air pump 112. Fig. 7B shows the change over time in the opening [%] 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 circulating within the fuel cell stack 12. Fig. 7D shows the change over time in the dryness within the fuel cell stack 12 (stack dryness).

[0144] 7A to 7D, time t30 indicates 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 rotation speed corresponding to the rated current of the fuel cell stack 12. In each figure, the time from time t30 to time t32 is referred to as the excess air allowable time.

[0145] The excess air allowable time is the time during which excess oxidant gas is allowed to flow in the fuel cell stack 12 when the rotation speed of the air pump 112 is reduced to a rotation speed equivalent 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 rotation speed that allows the rotor shaft 274 of the air pump 112 to float. Alternatively, the current during idling power generation may be a small current that causes the power generated by the fuel cell stack 12 and the power consumed by the air pump 112 to approximately match.

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

[0148] If the rotation speed of the air pump 112 is reduced to a rotation speed equivalent to the current during idling power generation within the excess air allowable time, drying out of the fuel cell stack 12 is avoided. In this case, the deceleration rate satisfies the moisture control condition. On the other hand, if the rotation speed of the air pump 112 is not reduced to a rotation speed equivalent to the current during idling power generation within the excess air allowable time, the inside of the fuel cell stack 12 will dry out. In this case, the deceleration rate does not satisfy the moisture control condition.

[0149] 7A is an example of a deceleration rate that satisfies the moisture control condition. The rotation speed of the air pump 112 gradually decreases from time t30, and reaches a rotation speed equivalent to the current during idling power generation at time t31.

[0150] 7B indicates that the bypass valve 120 starts to be driven toward the fully open state (opening degree 100%) from time t30. The bypass valve 120 reaches the fully open state before time t31.

[0151] The solid line graph in Figure 7C indicates that at time t30, the oxidant gas is flowing through the fuel cell stack 12 at a flow rate equivalent to the rated current. The oxidant gas flowing through the fuel cell stack 12 gradually decreases, and at time t31, reaches a flow rate equivalent to the current during idling power generation. The flow rate of the oxidant gas flowing through the fuel cell stack 12 is maintained at a flow rate equivalent to the current during idling power generation even after time t31.

[0152] The solid line graph in FIG. 7D indicates that the dryness level within the fuel cell stack 12 is low at time t30. When the air pump 112 begins to decelerate, the amount of power generated by the fuel cell stack 12 decreases, and the amount of water produced within the fuel cell stack 12 also decreases. Meanwhile, the oxidant gas continues to flow through the fuel cell stack 12 after time t30. The dryness level within the fuel cell stack 12 gradually increases. However, the dryness level within the fuel cell stack 12 remains below the dryness threshold even after time t31.

[0153] On the other hand, the broken line graphs in each of FIGS. 7A, 7C, and 7D show examples of cases where the moisture control conditions are not met.

[0154] As shown in FIG. 7A, the deceleration rate when the moisture control condition is not satisfied is smaller than the deceleration rate when the moisture control condition is satisfied. Therefore, at time t32, the rotation speed of the air pump 112 exceeds the rotation 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. In other words, if the deceleration rate does not satisfy the moisture control condition, the fuel cell stack 12 will dry out.

[0155] In this way, the fuel cell system 210 according to the second embodiment can be controlled to avoid drying out of the fuel cell stack 12 when the air pump 112 is decelerating, using a moisture control condition consisting of the relationship between the rotation speed of the air pump 112 corresponding to the FC current limit value (usually the rated current), the rotation speed of the air pump 112 corresponding to the current during idling power generation, and the allowable excess air time.

[0156] It should be noted that this fuel cell system 210 is equipped with a bypass valve 120. The rotation speed of the air pump 112, which corresponds to the current during idling power generation, can be changed depending on the opening of the bypass valve 120. If the opening of the bypass valve 120 is increased, the flow rate of oxidant gas toward the fuel cell stack 12 decreases, so the rotation speed of the air pump 112, which corresponds to the current during idling power generation, may be set to a large value. In this case, there is an advantage that the surplus power ΔAP generated by the air pump 112 when the air pump 112 decelerates becomes small, and it is sufficient to set a small buffer width for the deceleration buffer 74.

[0157] [Current limit setting] Next, the flow of how 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.

[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 (for example, less than 0 degrees Celsius) and a low temperature (for example, equal to or greater than 0 degrees Celsius and less than 5 degrees Celsius), and is set to, for example, 0 degrees Celsius.

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

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

[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. If 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 wider than that at an extremely low temperature. The control device 26 determines that the buffers 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 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 value between low temperature (for example, 0 degrees Celsius or higher and lower than 5 degrees Celsius) and normal temperature (for example, 5 degrees Celsius or higher), for example, 5 degrees Celsius.

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

[0166] In step S25, the control device 26 sets a minimum buffer width (minimum required value) for the deceleration buffer 74. The minimum buffer width of the deceleration buffer 74 may be the minimum amount of power required to absorb variations such as measurement errors of the flow rate sensor 107 and power errors 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, a minimum buffer width (minimum required value) is set for the acceleration buffer 72. The minimum buffer width of the acceleration buffer 72 may be, for example, the amount of power required for the air pump 112 to rotate at a minimum rotation speed (the minimum value of the rotation speed at which the rotor shaft 274 of the air pump 112 can be lifted).

[0168] Next, in step S26, the control device 26 changes the FC current limit value to a value greater than the current during idling power generation (idle current) according to the temperature Tbat. The FC current limit value is set to a current value intermediate between the current during idling power generation and the rated current. This current value intermediate 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 greater than the current during idling power generation. For example, if the power generated by the fuel cell stack 12 is supplied to the battery heater 251, the battery heater 251 can heat the power storage device 244. The control device 26 waits for a predetermined time for the power storage device 244 to be heated.

[0170] If 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 a maximum buffer width (maximum required value) for 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 period.

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

[0173] Next, in step S28, the control device 26 switches the FC current limit value from the intermediate current value to the rated current, which enables the fuel cell stack 12 to generate power at the rated current and supply power to high-voltage loads such as the motor 246 in addition to low-voltage loads such as the battery heater 251.

[0174] [Operation explanation using timing chart] An example of the operation described with reference to the flowchart in FIG. 8 will be described with reference to the timing chart in FIG. 9, while omitting repetition of the operation description.

[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 at 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). The intermediate current value is set as 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) for the fuel cell stack 12. When the control device 26 instructs the air pump 112 to set a target rotation speed, the air pump 112 starts to accelerate, and the AP actual power consumption and AP steady power consumption start to increase.

[0178] From time t40 to time t41, the AP steady power consumption is allocated to the deceleration buffer 74, slightly increasing the deceleration buffer 74. 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 actual power consumption of the AP and the steady power consumption of the AP are approximately equal. The fuel cell stack 12 can supply power to a low-voltage load such as a battery heater 251.

[0180] At time t43, the air pump 112 begins to decelerate. A minimum value is set in the deceleration buffer 74. Here, the control device 26 decelerates the air pump 112 at a deceleration rate that does not generate excess power ΔAP (the difference between the actual power consumption of the AP and the steady-state power consumption of the AP) 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 room 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 switches the FC current limit value from the intermediate current value to the rated current (step S28). At this time, the upper limit value of the FC generated power (FC power limit value) is increased to an upper limit value based on the FC rated current.

[0182] At time t45, the control device 26 receives the target power generation (FC power command) for the fuel cell stack 12. When the control device 26 instructs the air pump 112 to set a target rotation speed, the air pump 112 starts to accelerate, and the AP actual power consumption and AP steady power consumption start 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 is maintained at the maximum buffer width set in step S27.

[0184] At time t47, air pump 112 begins to decelerate. Because the maximum required value is set in deceleration buffer 74 (step S27), power storage device 244 can store surplus power ΔAP that occurs between the actual AP power consumption and the AP steady-state power consumption. At time t48, deceleration of 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. In FIG.

[0186] The dashed line in Fig. 10 indicates a comparative example. In the comparative example, the FC current limit value is fixed to the current during idling power generation at extremely low and low temperatures. The FC current limit value is raised to the rated current only when the temperature Tbat of the power storage device 244 reaches the threshold value for low and normal temperatures (threshold temperature Tthr2).

[0187] In this comparative example, the rotation speed of the air pump 112, which corresponds to the current during idling power generation, is small, so the deceleration rate that satisfies the moisture control condition is large. A large surplus power ΔAP may be generated when the air pump 112 decelerates. For this reason, it is necessary to ensure that the deceleration buffer 74 has a large buffer width that corresponds to the deceleration rate. Therefore, in this comparative example, the FC current limit value is not increased to the rated current until the necessary buffer width can be ensured for the deceleration buffer 74, and the FC current limit value is fixed to 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 an extremely low temperature, the FC current limit value is set to the current during idling power generation (step S23). When the temperature Tbat of the power storage device 244 reaches the threshold value between an extremely low temperature and a 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 value between a low temperature and a normal temperature (threshold temperature Tthr2), the FC current limit value is increased to the rated current (step S28).

[0189] In this way, even when a sufficient deceleration buffer 74 cannot be secured in the power storage device 244 at low temperatures, the fuel cell system 210 according to the second embodiment switches the FC current limit value from the current during idling power generation to an intermediate current value to cause the fuel cell stack 12 to generate power. For example, power can be supplied to a low-voltage load such as a battery heater 251, and the battery heater 251 can be used to heat the power storage device 244. This allows a mobile object such as a fuel cell automobile 11 equipped with the fuel cell stack 12 to quickly transition to a state where it can run (a state where it can operate).

[0190] In addition to the above disclosure, the following Supplementary Notes 6 to 9 are disclosed.

[0191] (Appendix 6) The fuel cell system (210) includes a fuel cell (12) that generates electricity using fuel gas and oxidant gas, a pump (112) that supplies the oxidant gas to the fuel cell, an electric storage device (244) that can supply electric power to the pump, a control device (26) that controls the power generation of the fuel cell and the charging and discharging of the electric storage device, and a temperature measurement device (250) that measures the temperature (Tbat) of the electric storage device, wherein the control device sets a range (68) of electric energy that can be charged and discharged to the electric storage device and sets a buffer (70) within the range of electric energy of the electric storage device, the buffer including a deceleration buffer (74) that is an amount of electric energy that can charge surplus electric power (ΔAP) generated when the pump decelerates, into the electric storage device, and the control device changes a buffer width of the deceleration buffer in accordance with the temperature of the electric storage device, switches a current limit value (FC current limit value) of the fuel cell based on the buffer width of the deceleration buffer, and causes the fuel cell to generate electricity using the switched current limit value (intermediate current value).

[0192] With this configuration, even if a sufficient deceleration buffer 74 cannot be ensured at low temperatures, for example, the FC current limit value of the fuel cell stack 12 is changed to the intermediate current value to cause the fuel cell to generate electricity.

[0193] This allows power to be supplied to a low-voltage load such as a battery heater 251, and the battery heater 251 can be used to heat the power storage device 244. Heating the power storage device 244 expands the charge / discharge limit range 68 within which charging and discharging is possible, and the range of electric energy that the power storage device 244 can charge and discharge is optimized. This allows a mobile object such as a fuel cell vehicle 11 equipped with a fuel cell stack 12 to quickly transition to a state in which it can run (a state in which it can operate). Furthermore, when the outside temperature is low, the passengers of the fuel cell vehicle 11 can use the air conditioner. The passengers can also use electric power inside the fuel cell vehicle 11.

[0194] (Appendix 7) In the fuel cell system described in Appendix 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 time rate of change of the rotation speed of the pump, and cause the fuel cell to generate power using the current limit value after the change.

[0195] With this configuration, the FC current limit value is changed taking into account the time rate of change (deceleration rate) of the rotation speed of the air pump 112 in addition to the buffer width of the deceleration buffer 74. This allows power to be supplied quickly to a low-voltage load such as the battery heater 251.

[0196] (Appendix 8) The fuel cell system according to Supplementary Note 6 or Supplementary Note 7 may further include an oxidant gas supply channel (106) that supplies the oxidant gas to the fuel cell, an inlet seal valve (116) provided in the oxidant gas supply channel between the pump and the fuel cell, a discharge channel (109) that discharges the oxidant gas discharged from the fuel cell to the outside, a bypass flow channel (110) that circulates the oxidant gas supplied to the oxidant gas supply channel from the upstream side of the inlet seal valve to the discharge channel, and a bypass valve (120) provided in the bypass flow channel between the oxidant gas supply channel and the discharge channel, and the control device may change a current limit value of the fuel cell based on the buffer width of the deceleration buffer and an opening degree of the bypass valve, and cause the fuel cell to generate power using the changed current limit value.

[0197] According to this configuration, the FC current limit value is changed taking into account the opening degree of the bypass valve 120 in addition to the buffer width of the deceleration buffer 74. This allows power to be supplied early to low-voltage loads such as the battery heater 251, for example.

[0198] (Appendix 9) A method for controlling 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, an electricity storage device (244) that can supply power to the pump, a control device (26) that controls the power generation of the fuel cell and the charging and discharging of the electricity storage device, and a temperature measurement device (250) that measures the temperature (Tbat) of the electricity storage device, wherein the control device sets a range (68) of electric energy that can be charged and discharged to the electricity storage device, and provides a buffer (70) within the range of electric energy of the electricity storage device. ) and the buffer is an amount of power that can charge the power storage device with surplus power (ΔAP) generated when the pump decelerates, the method for controlling a fuel cell system including a deceleration buffer (74), the method including the steps of changing a buffer width of the deceleration buffer in accordance with 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 causing the fuel cell to generate power using the current limit value after the change.

[0199] With this configuration, even if a sufficient deceleration buffer 74 cannot be ensured at low temperatures, for example, the FC current limit value of the fuel cell stack 12 is changed to the intermediate current value to cause the fuel cell to generate electricity.

[0200] This allows power to be supplied to a low-voltage load such as a battery heater 251, and the battery heater 251 can be used to heat the power storage device 244. Heating the power storage device 244 expands the range of power that can be charged and discharged (charge and discharge limit range 68), optimizing the range of power that can be charged and discharged by the power storage device 244. This allows a mobile object such as a fuel cell vehicle 11 equipped with a fuel cell stack 12 to quickly transition to a state where it can run (a state where it can operate). Furthermore, when the outside temperature is low, the passengers of the fuel cell vehicle 11 can use the air conditioner. The passengers can also use power inside the fuel cell vehicle 11.

[0201] The present invention is not limited to the above 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 fully open (100% opening). The opening degree of the bypass valve 120 can be changed as appropriate. In addition to the bypass valve 120, the inlet seal valve 116 and the outlet seal 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 values ​​shown in Fig. 10 are merely examples, and multiple intermediate current values ​​may be set between the rated current and the current during idling power generation. The intermediate current values ​​may be set in accordance with the temperature Tbat of the power storage device 244 so that the graph in Fig. 10 increases in a step-like manner, a staircase-like manner, or a curved line. [Explanation of symbols]

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

Claims

1. a fuel cell that generates electricity using a fuel gas and an oxidant gas; a pump for supplying the oxidant gas to the fuel cell; an electricity storage device capable of supplying power to the pump; a control device that controls power generation by the fuel cell and charging / discharging of the power storage device; Equipped with the control device sets a range of the amount of power that can be charged and discharged to the power storage device, and sets a buffer within the range of the amount of power that can be charged and discharged to the power storage device; The buffer includes an acceleration buffer that is an amount of power that the power storage device can discharge to the pump when the pump is accelerating.

1. A fuel cell system, comprising: The control device Estimating steady-state power consumption that is steadily consumed by the pump when the pump is rotating at a constant rotation speed; setting the acceleration buffer based on the estimated steady-state power consumption and the rated power of the pump; When the sum of the acceleration buffer and the steady-state power consumption exceeds the rated power of the pump, the acceleration buffer is reduced in accordance with an increase in the steady-state power consumption. Fuel cell system.

2. 2. The fuel cell system according to claim 1, The control device When the sum of the acceleration buffer and the steady-state power consumption exceeds the rated power of the pump, when reducing the acceleration buffer in response to an increase in the steady-state power consumption, the acceleration buffer is corrected to a value obtained by subtracting the steady-state power consumption of the pump from the rated power of the pump. Fuel cell system.

3. 3. The fuel cell system according to claim 1, The control device The steady-state power consumption is covered by the power generated by the fuel cell. Fuel cell system.

4. 4. The fuel cell system according to claim 3, The control device The power generated by the fuel cell is charged into the power storage device, and the power charged in the power storage device is supplied to the pump. Fuel cell system.

5. a fuel cell that generates electricity using a fuel gas and an oxidant gas; a pump for supplying the oxidant gas to the fuel cell; an electricity storage device capable of supplying power to the pump; a control device that controls power generation by the fuel cell and charging / discharging of the power storage device; Equipped with the control device sets a range of the amount of power that can be charged and discharged to the power storage device, and sets a buffer within the range of the amount of power that can be charged and discharged to the power storage device; The buffer includes an acceleration buffer that is an amount of power that the power storage device can discharge to the pump when the pump is accelerating. A method for controlling charging and discharging of a power storage device in a fuel cell system, comprising: The control device Estimating steady-state power consumption that is steadily consumed by the pump when the pump is rotating at a constant rotation speed; setting the acceleration buffer based on the estimated steady-state power consumption and the rated power of the pump; When the sum of the acceleration buffer and the steady-state power consumption exceeds the rated power of the pump, the acceleration buffer is reduced in accordance with an increase in the steady-state power consumption. A method for controlling charging and discharging of a power storage device in a fuel cell system.

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