WO2013128609A1 - 燃料電池システム - Google Patents
燃料電池システム Download PDFInfo
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- WO2013128609A1 WO2013128609A1 PCT/JP2012/055191 JP2012055191W WO2013128609A1 WO 2013128609 A1 WO2013128609 A1 WO 2013128609A1 JP 2012055191 W JP2012055191 W JP 2012055191W WO 2013128609 A1 WO2013128609 A1 WO 2013128609A1
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- fuel cell
- voltage
- output
- cell system
- oxide film
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04858—Electric variables
- H01M8/04865—Voltage
- H01M8/0488—Voltage of fuel cell stacks
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04992—Processes for controlling fuel cells or fuel cell systems characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
- H01M8/04238—Depolarisation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
- H01M8/04537—Electric variables
- H01M8/04544—Voltage
- H01M8/04559—Voltage of fuel cell stacks
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
- H01M8/04537—Electric variables
- H01M8/04574—Current
- H01M8/04589—Current of fuel cell stacks
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04746—Pressure; Flow
- H01M8/04753—Pressure; Flow of fuel cell reactants
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M2008/1095—Fuel cells with polymeric electrolytes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2250/00—Fuel cells for particular applications; Specific features of fuel cell system
- H01M2250/20—Fuel cells in motive systems, e.g. vehicle, ship, plane
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02T90/40—Application of hydrogen technology to transportation, e.g. using fuel cells
Definitions
- the present invention relates to a fuel cell system having a catalyst activation function.
- a fuel cell stack is a power generation system that directly converts energy released during an oxidation reaction into electrical energy by oxidizing fuel by an electrochemical process.
- the fuel cell stack has a membrane-electrode assembly in which both side surfaces of a polymer electrolyte membrane for selectively transporting hydrogen ions are sandwiched by a pair of electrodes made of a porous material.
- Each of the pair of electrodes is mainly composed of a carbon powder carrying a platinum-based metal catalyst, and is formed on the surface of the catalyst layer in contact with the polymer electrolyte membrane and a gas having both air permeability and electronic conductivity. And a diffusion layer.
- Patent Document 1 discloses that when the required power for the fuel cell is less than a predetermined value, the supply of air (oxidizing gas) to the fuel cell stack is stopped and the output voltage of the fuel cell stack is set to DC. / DC converter forcibly lowers the cell voltage to a reduction voltage (for example, 0.6 V or less), thereby removing the oxide film from the platinum catalyst surface and recovering the performance of the catalyst layer (hereinafter referred to as refresh process) Is referred to).
- a reduction voltage for example, 0.6 V or less
- the document also mentions that the fuel cell vehicle using the fuel cell system as an in-vehicle power source prohibits the refresh process when the travel speed of the fuel cell vehicle is traveling above a predetermined value.
- the reduction voltage capable of removing the oxide film exists not only in one stage but also in two or more stages.
- the output voltage of the fuel cell stack is reduced to a reduction voltage as referred to in Patent Document 1 (hereinafter referred to as a first reduction voltage).
- a film that can be removed hereinafter referred to as an I-type oxide film
- a film that cannot be removed without lowering to a second reduction voltage lower than the first reduction voltage hereinafter referred to as a II-type oxide film
- the catalyst layer can be sufficiently recovered, but the first reduction is possible. Since the cell voltage is further reduced as compared with the case where the voltage is lowered to the voltage, the responsiveness to a high load request (output increase request) may be significantly reduced. For example, in a fuel cell vehicle, if the cell voltage is extremely lowered, an output that follows the accelerator response at the time of a high load request may not be obtained, and drivability (maneuvering performance) is significantly reduced. There is a fear.
- an object of the present invention is to propose a fuel cell system capable of maximizing recovery of the performance of the catalyst layer while minimizing the influence on the responsiveness to the output increase request.
- the fuel cell system of the present invention comprises: A fuel cell comprising a membrane-electrode assembly in which electrodes having a catalyst layer are disposed on both sides of a polymer electrolyte membrane; A controller for performing a performance recovery process of the catalyst layer by reducing the output voltage of the fuel cell to a predetermined voltage, The control device predicts the timing of an output increase request to the fuel cell, and determines the necessity and content of the performance recovery processing based on the prediction result.
- the necessity of the performance recovery process and the content (degree) of the performance recovery process to be executed can be determined according to the predicted output increase request timing. It is possible to achieve both the minimization of the catalyst and the maximum recovery of the performance of the catalyst layer.
- the oxide film formed on the catalyst layer during power generation of the fuel cell can be removed by lowering the output voltage of the fuel cell to a first film removal voltage; and
- the control device may change the predetermined voltage to be reduced according to the prediction result when it is determined that the performance recovery process is necessary.
- the control device predicts that the output increase request timing for the fuel cell is earlier than the elapse of the first predetermined time, the control device only increases the output voltage of the fuel cell to the first film removal voltage.
- the output increase request timing to the fuel cell is predicted to be after the first predetermined time has elapsed or after the second predetermined time longer than the first predetermined time.
- the output voltage of the fuel cell may be lowered to the second film removal voltage.
- the output request to the fuel cell is equal to or less than a predetermined value (for example, the idling operation when the fuel cell system is mounted on the vehicle corresponds to this case).
- the output voltage of the fuel cell may be lowered to the second film removal voltage.
- the control device may predict the output increase request timing for the fuel cell based on the brake opening.
- FIG. 1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. It is a disassembled perspective view of the cell which comprises a fuel cell stack. It is a timing chart which shows an example of the operation control of a fuel cell system. It is a flowchart which shows the procedure which implements a refresh process on condition that the brake opening exceeded a predetermined threshold value. It is a flowchart which shows the procedure which implements the refresh process according to brake opening when a brake opening exceeds a predetermined threshold value.
- FIG. 6 is an example of a refresh process corresponding to the brake opening degree in FIG. 5, and is a table showing the relationship between the brake opening degree and the refresh voltage.
- FIG. 6 is an example of a refresh process corresponding to the brake opening degree in FIG.
- FIG. 5 is a table showing the relationship between the brake opening degree and the refresh time.
- FIG. 3 is a diagram showing that each ratio of type I oxide film to type III oxide film in the oxide film formed on the catalyst layer changes with time when the output voltage of the fuel cell stack is maintained at a constant value. . It shows that each ratio of type I oxide film and type II oxide film in the oxide film formed on the catalyst layer changes as the number of times the output voltage of the fuel cell stack crosses the predetermined boundary voltage up and down FIG.
- FIG. 1 shows a system configuration of a fuel cell system 10 according to the first embodiment.
- the fuel cell system 10 functions as an in-vehicle power supply system mounted on a fuel cell vehicle.
- the fuel cell stack 20 generates electric power by receiving supply of reaction gas (fuel gas, oxidant gas), and air as oxidant gas.
- a system 50 and a controller 60 that performs overall control of the entire system are provided.
- the fuel cell stack 20 is a solid polymer electrolyte cell stack formed by stacking a large number of cells in series.
- the oxidation reaction of the formula (1) occurs at the anode electrode
- the reduction reaction of the equation (2) occurs at the cathode electrode.
- the fuel cell stack 20 as a whole undergoes an electromotive reaction of the formula (3).
- the fuel cell stack 20 is provided with a voltage sensor 71 for detecting the output voltage (FC voltage) of the fuel cell stack 20 and a current sensor 72 for detecting the output current (FC current).
- the oxidizing gas supply system 30 has an oxidizing gas passage 33 through which oxidizing gas supplied to the cathode electrode of the fuel cell stack 20 flows and an oxidizing off gas passage 34 through which oxidizing off gas discharged from the fuel cell stack 20 flows. .
- an air compressor 32 that takes in the oxidizing gas from the atmosphere via the filter 31, a humidifier 35 for humidifying the oxidizing gas pressurized by the air compressor 32, and the fuel cell stack 20 are connected.
- a shutoff valve A1 for shutting off the oxidizing gas supply is provided.
- a shutoff valve A2 for shutting off the oxidizing off gas discharge from the fuel cell stack 20
- a back pressure adjusting valve A3 for adjusting the oxidizing gas supply pressure, oxidizing gas (dry gas) and oxidizing A humidifier 35 is provided for exchanging moisture with off-gas (wet gas).
- the fuel gas supply system 40 includes a fuel gas supply source 41, a fuel gas passage 43 through which fuel gas supplied from the fuel gas supply source 41 to the anode electrode of the fuel cell stack 20 flows, and fuel discharged from the fuel cell stack 20.
- a circulation passage 44 for returning off-gas to the fuel gas passage 43, a circulation pump 45 for pressure-feeding the fuel off-gas in the circulation passage 44 to the fuel gas passage 43, and an exhaust / drain passage 46 branched and connected to the circulation passage 44 Have.
- the fuel gas supply source 41 is composed of, for example, a high-pressure hydrogen tank or a hydrogen storage alloy, and stores high-pressure (for example, 35 MPa to 70 MPa) hydrogen gas.
- high-pressure hydrogen gas for example, 35 MPa to 70 MPa
- the shut-off valve H1 When the shut-off valve H1 is opened, the fuel gas flows out from the fuel gas supply source 41 into the fuel gas passage 43.
- the fuel gas is decompressed to about 200 kPa, for example, by the regulator H2 and the injector 42, and supplied to the fuel cell stack 20.
- the circulation passage 44 is connected to a shutoff valve H4 for shutting off the fuel off-gas discharge from the fuel cell stack 20 and an exhaust drainage passage 46 branched from the circulation passage 44.
- An exhaust / drain valve H5 is disposed in the exhaust / drain passage 46.
- the exhaust / drain valve H ⁇ b> 5 is operated according to a command from the controller 60, thereby discharging the fuel off-gas containing impurities in the circulation passage 44 and moisture to the outside.
- the fuel off-gas discharged through the exhaust / drain valve H5 is mixed with the oxidizing off-gas flowing through the oxidizing off-gas passage 34 and diluted by a diluter (not shown).
- the circulation pump 45 circulates and supplies the fuel off gas in the circulation system to the fuel cell stack 20 by driving the motor.
- the power system 50 includes a DC / DC converter 51, a battery 52, a traction inverter 53, a traction motor 54, and auxiliary machinery 55.
- the DC / DC converter 51 boosts the DC voltage supplied from the battery 52 and outputs it to the traction inverter 53, and the DC power generated by the fuel cell stack 20, or the regenerative power collected by the traction motor 54 by regenerative braking. And a function of charging the battery 52 by stepping down the voltage.
- the battery 52 functions as a surplus power storage source, a regenerative energy storage source at the time of regenerative braking, and an energy buffer at the time of load fluctuation accompanying acceleration or deceleration of the fuel cell vehicle.
- a secondary battery such as a nickel / cadmium storage battery, a nickel / hydrogen storage battery, or a lithium secondary battery is suitable.
- the battery 52 is attached with an SOC sensor for detecting SOC (State of charge) which is the remaining capacity.
- the traction inverter 53 is, for example, a PWM inverter driven by a pulse width modulation method, and converts a DC voltage output from the fuel cell stack 20 or the battery 52 into a three-phase AC voltage in accordance with a control command from the controller 60.
- the rotational torque of the traction motor 54 is controlled.
- the traction motor 54 is a three-phase AC motor, for example, and constitutes a power source of the fuel cell vehicle.
- Auxiliary machines 55 are motors (for example, power sources such as pumps) arranged in each part in the fuel cell system 10, inverters for driving these motors, and various on-vehicle auxiliary machines. (For example, an air compressor, an injector, a cooling water circulation pump, a radiator, etc.) is a general term.
- the controller 60 is a computer system including a CPU, a ROM, a RAM, and an input / output interface, and controls each part of the fuel cell system 10. For example, when the controller 60 receives the start signal IG output from the ignition switch, the controller 60 starts the operation of the fuel cell system 10, and the accelerator opening signal ACC output from the accelerator sensor or the vehicle speed signal output from the vehicle speed sensor.
- the required power of the entire system is obtained based on VC or the like.
- the required power of the entire system is the total value of the vehicle running power and the auxiliary machine power.
- Auxiliary power includes power consumed by in-vehicle accessories (humidifiers, air compressors, hydrogen pumps, cooling water circulation pumps, etc.), and equipment required for vehicle travel (transmissions, wheel control devices, steering devices, and Power consumed by a suspension device or the like, and power consumed by a device (such as an air conditioner, a lighting fixture, or audio) disposed in the passenger space.
- in-vehicle accessories humidity, air compressors, hydrogen pumps, cooling water circulation pumps, etc.
- equipment required for vehicle travel transmissions, wheel control devices, steering devices, and Power consumed by a suspension device or the like
- power consumed by a device such as an air conditioner, a lighting fixture, or audio
- the controller 60 determines the distribution of the output power of each of the fuel cell stack 20 and the battery 52, and the oxidizing gas supply system 30 and the fuel gas supply system 40 so that the power generation amount of the fuel cell stack 20 matches the target power. And the DC / DC converter 51 to adjust the output voltage of the fuel cell stack 20, thereby controlling the operation point (output voltage, output current) of the fuel cell stack 20.
- FIG. 2 is an exploded perspective view of the cells 21 constituting the fuel cell stack 20.
- the cell 21 includes a polymer electrolyte membrane 22, an anode electrode 23, a cathode electrode 24, and separators 26 and 27.
- the anode electrode 23 and the cathode electrode 24 are diffusion electrodes having a sandwich structure with the polymer electrolyte membrane 22 sandwiched from both sides.
- Separators 26 and 27 made of a gas-impermeable conductive member form fuel gas and oxidizing gas flow paths between the anode electrode 23 and the cathode electrode 24 while sandwiching the sandwich structure from both sides.
- the separator 26 is formed with a rib 26a having a concave cross section.
- the separator 27 is formed with a rib 27a having a concave cross section.
- the opening of the rib 27a is closed and an oxidizing gas flow path is formed.
- the anode electrode 23 is mainly composed of carbon powder supporting a platinum-based metal catalyst (Pt, Pt—Fe, Pt—Cr, Pt—Ni, Pt—Ru, etc.), and a catalyst layer 23 a in contact with the polymer electrolyte membrane 22. And a gas diffusion layer 23b formed on the surface of the catalyst layer 23a and having both air permeability and electronic conductivity.
- the cathode electrode 24 has a catalyst layer 24a and a gas diffusion layer 24b.
- the catalyst layers 23a and 24a are made by dispersing carbon powder carrying platinum or an alloy made of platinum and another metal in an appropriate organic solvent, adding an appropriate amount of an electrolyte solution to form a paste, and forming a polymer electrolyte. Screen-printed on the film 22.
- the gas diffusion layers 23b and 24b are formed of carbon cloth, carbon paper, or carbon felt woven with carbon fiber yarns.
- the polymer electrolyte membrane 22 is a proton conductive ion exchange membrane formed of a solid polymer material, for example, a fluorine resin, and exhibits good electrical conductivity in a wet state.
- a membrane-electrode assembly 25 is formed by the polymer electrolyte membrane 22, the anode electrode 23, and the cathode electrode 24.
- FIG. 3 is a timing chart showing operation control of the fuel cell system 10.
- the fuel cell system 10 improves power generation efficiency by switching the operation mode of the fuel cell stack 20 according to the operation load.
- the fuel cell system 10 controls the operation by setting the power generation command value of the fuel cell stack 20 to zero in the low load region where the power generation efficiency is low (the operation region where the power generation request is less than a predetermined value).
- An intermittent operation is performed in which the power required from the battery 52 is provided by the power required for system operation. Note that if the cell voltage is low when there is a high load request (output increase request) during intermittent operation, the drivability deteriorates, so the cell voltage during intermittent operation is kept high.
- the power generation command value of the fuel cell stack 20 is calculated based on the accelerator opening, the vehicle speed, etc.
- the normal load operation is performed in which the power required for system operation and the power necessary for system operation are covered only by the power generated by the fuel cell stack 20 or by the power generated by the fuel cell stack 20 and the power from the battery 52.
- the fuel cell system 10 depresses the brake when parked or stopped immediately after startup or when waiting for a signal, in other words, when the shift lever is in the P range or N range, or in the D range.
- the fuel cell stack 20 When the vehicle speed is zero, the fuel cell stack 20 generates power at the power generation voltage necessary for ensuring drivability, and the idle operation for charging the generated power to the battery 52 is performed.
- the platinum catalyst of the catalyst layer 24a may be eluted.
- High potential avoidance control (OC avoidance operation) is performed to control the fuel cell stack 20 so as to maintain the durability of the fuel cell stack 20 by controlling it to the use upper limit voltage V1 or lower.
- the use upper limit voltage V1 is set so that the voltage is about 0.9 V per cell, for example.
- FIG. 4 is a flowchart showing a procedure for performing the refresh process on condition that the brake opening exceeds a predetermined threshold.
- FIG. 3 shows an example of determining whether or not the refresh process is necessary during idle operation after normal load operation (for example, when waiting for a signal). An example of determining whether or not the refresh process is necessary will be described.
- the controller 60 determines whether or not the refresh process is necessary at a predetermined cycle during the normal load operation (step S1) (step S3).
- the necessity of the refresh process is based on, for example, experiments and simulation results in which the oxide film formation amount (surface area of the formed oxide film) is estimated by time integration based on the elapsed time from the time when the previous refresh process was performed. Whether the estimated oxide film formation amount exceeds the specified threshold by estimating the oxide film formation amount with reference to the map created in the above, estimated by theoretical calculation, or estimated from the output tendency during high potential avoidance control Judgment by
- the oxide film is reduced by lowering the cell voltage to a reduction voltage (hereinafter sometimes referred to as refresh voltage) for a predetermined time (hereinafter sometimes referred to as refresh time), and the oxide film is removed from the catalyst surface. It is a removal process. More specifically, the output current is increased by dropping the voltage of each cell, that is, the output voltage of the fuel cell stack 20 for a predetermined time, and the electrochemical reaction in the catalyst layer 24a is transitioned from the oxidation reaction region to the reduction reaction region. To recover the catalytic activity.
- refresh voltage a reduction voltage
- refresh time a predetermined time
- step S3 NO
- the process returns to the normal load operation (step S1), and when the estimated oxide film formation amount exceeds the predetermined threshold value (step S3: YES).
- step S5 Based on the brake opening signal output from the brake sensor, it is determined whether or not the brake opening exceeds the threshold value ⁇ (step S5).
- the threshold ⁇ is set to 5% to 10%, for example.
- step S5 If the brake opening does not exceed the threshold value ⁇ (step S5: NO), that is, if the brake is not depressed more than a certain level, the process returns to step S1.
- the brake opening degree exceeds the threshold value ⁇ (step S5: YES), for example, when the operation mode of the fuel cell stack 20 is idle operation and the brake opening degree is fully open due to a signal waiting or the like, a refresh process is performed (step S7). ).
- the refresh process according to the present embodiment is performed at a constant refresh voltage (reduction voltage) and refresh time (reduction voltage holding time) regardless of the brake opening.
- the refresh voltage at this time is preferably a low voltage capable of removing the later-described II-type oxide film or III-type oxide film from the viewpoint of maximizing the performance recovery of the catalyst layer 24a.
- the oxide film formation amount exceeds a predetermined threshold
- the brake opening degree is predetermined. It is necessary to satisfy two conditions of exceeding the threshold value ⁇ . In other words, even if the oxide film formation amount exceeds the predetermined threshold value, the execution of the refresh process is prohibited unless the brake opening degree exceeds the predetermined threshold value ⁇ .
- the case where the brake opening exceeds the threshold value ⁇ is a case where the amount of depression of the brake pedal is large. Therefore, it is unlikely that a high load request is commanded from this state.
- the performance recovery of the catalyst layer 24a is maximized while the influence on drivability is minimized.
- FIG. 5 is a flowchart showing a procedure for performing a refresh process according to the brake opening when the brake opening exceeds a predetermined threshold.
- 6 and 7 are examples of the refresh process according to the brake opening degree of FIG. 5,
- FIG. 6 is a table showing the relationship between the brake opening degree and the refresh voltage, and
- FIG. It is a table
- Steps S1 to S5 in FIG. 5 have the same processing contents as steps S1 to S5 in FIG. 4, and therefore the same step numbers will be assigned and description thereof will be omitted.
- the processing content of step S17 following step S5 will be described in detail.
- the refresh voltage and the refresh time are set to constant values regardless of the brake opening, but in the refresh process performed in step S17 in FIG.
- the refresh voltage or / and the refresh time are switched according to the brake opening.
- the refresh voltage is 0.4 V (hereinafter referred to as pattern V2). With this refresh process, the later-described II-type oxide film can be removed. is there. Further, when 50% ⁇ brake opening degree, the refresh voltage is 0.05 V (hereinafter referred to as pattern V3). According to this refresh process, the later-described type III oxide film can be removed.
- the I-type oxide film, the II-type oxide film, and the III-type oxide film can be mixed in one oxide film.
- the output voltage of the fuel cell stack 20 is constant.
- the ratio in the oxide film gradually changes as the retention time increases, and the size of each reduction voltage satisfies the following relationship: , Is known.
- Type I oxide film eg, 0.65 V to 0.9 V
- Type II oxide film eg, 0.4 V to 0.6 V
- Type III oxide film eg, 0.05 V to 0.4 V
- the I-type oxide film, the II-type oxide film, and the III-type oxide film for example, as shown in FIG. 9 (however, the III-type oxide film is not shown)
- the output voltage of the fuel cell stack 20 has a predetermined boundary. It is also known that the ratio in the oxide film gradually changes with an increase in the number of times (eg, the number of cycles) over which a voltage (for example, 0.8 V) is straddled up and down.
- the refresh voltage is switched according to the degree of brake opening, in other words, depending on the possibility that the accelerator pedal will be depressed soon and the required power generation amount for the fuel cell stack 20 will increase.
- the degree of brake opening in other words, depending on the possibility that the accelerator pedal will be depressed soon and the required power generation amount for the fuel cell stack 20 will increase.
- the refresh voltage is set to the highest voltage, and only the I-type oxide film is removed.
- the possibility that the accelerator pedal is depressed is lower than in the case of the pattern V1, but not as low as in the case of the pattern V3. Therefore, the influence on drivability and the performance recovery of the catalyst layer 24a are achieved.
- the refresh time when the brake opening ⁇ 10% is 0.5 seconds (hereinafter referred to as pattern T1), and the refresh when 10% ⁇ brake opening ⁇ 30%.
- the time is 1 second (hereinafter referred to as pattern T2), and the refresh time when 30% ⁇ brake opening is 3 seconds.
- the refresh time is switched according to the degree of the brake opening, in other words, depending on the possibility that the accelerator pedal will be depressed soon and the required power generation amount for the fuel cell stack 20 will increase.
- the degree of the brake opening in other words, depending on the possibility that the accelerator pedal will be depressed soon and the required power generation amount for the fuel cell stack 20 will increase.
- the refresh time is set as shortest as possible.
- the refresh time is set to be the longest in consideration of maximizing the performance recovery of the catalyst layer 24a.
- the refresh time is set to the time between the pattern T1 and the pattern T2 in order to balance the above and the highest possible dimension.
- the removal amount of the oxide film increases in the order of the pattern T1, the pattern T2, and the pattern T3.
- priority is given to drivability by shortening the time during which the cell voltage is reduced as much as possible, and in a situation where deterioration of drivability is not a concern (pattern T2). Since the time during which the cell voltage is lowered may be long, priority is given to maximization of the oxide film removal amount.
- the refresh voltage and refresh time when the brake opening ⁇ 10% are 0.6 V and 0.5 seconds, respectively, and the refresh voltage and refresh time when 10% ⁇ brake opening ⁇ 25% are 0.6 V and The refresh voltage and refresh time when 1 second, 25% ⁇ brake opening ⁇ 30% are 0.4V and 1 second, respectively, and the refresh voltage and refresh time when 30% ⁇ brake opening ⁇ 50% are 0.
- the refresh voltage and the refresh time may be set to 0.05 V and 3 seconds, respectively, and the refresh process may be performed.
- a mode of predicting from a brake opening degree in a fuel cell vehicle on which the fuel cell system 10 is mounted is illustrated.
- the form of predicting the timing of the output increase request for 20 is not limited to this example.
- the timing of the output increase request may be predicted assuming that the brake opening degree is 100%.
- the usage form in which the fuel cell system 10 is used as the in-vehicle power supply system is illustrated, but the usage form of the fuel cell system 10 is not limited to this example.
- the fuel cell system 10 may be mounted as a power source of a mobile body (robot, ship, aircraft, etc.) other than the fuel cell vehicle.
- the fuel cell system 10 according to the present embodiment may be used as a power generation facility (stationary power generation system) such as a house or a building.
Abstract
Description
触媒層を有する電極が高分子電解質膜の両面に配置されてなる膜-電極アセンブリを備えた燃料電池と、
前記燃料電池の出力電圧を所定電圧まで低下させることにより前記触媒層の性能回復処理を実施する制御装置と、を備え、
前記制御装置は、前記燃料電池に対する出力増加要求のタイミングを予測し、その予測結果に基づいて前記性能回復処理の要否及び内容を決定するものである。
前記制御装置は、前記性能回復処理が必要と判定した場合に、前記予測結果に応じて前記低下させる所定電圧を変更するようにしてもよい。
前記制御装置は、前記燃料電池に対する出力増加要求のタイミングをブレーキ開度に基づいて予測するようにしてもよい。
12 燃料電池
24a 触媒層
25 膜-電極アセンブリ
60 コントローラ(制御装置)
図1は実施形態1に係わる燃料電池システム10のシステム構成を示す。
燃料電池システム10は、燃料電池車両に搭載される車載電源システムとして機能するものであり、反応ガス(燃料ガス、酸化ガス)の供給を受けて発電する燃料電池スタック20と、酸化ガスとしての空気を燃料電池スタック20に供給するための酸化ガス供給系30と、燃料ガスとしての水素ガスを燃料電池スタック20に供給するための燃料ガス供給系40と、電力の充放電を制御するための電力系50と、システム全体を統括制御するコントローラ60とを備えている。
H2 → 2H++2e- …(1)
(1/2)O2+2H++2e- → H2O …(2)
H2+(1/2)O2 → H2O …(3)
セル21は、高分子電解質膜22と、アノード極23と、カソード極24と、セパレータ26,27とから構成されている。アノード極23及びカソード極24は、高分子電解質膜22を両側から挟んでサンドイッチ構造を成す拡散電極である。
燃料電池システム10は、運転負荷に応じて、燃料電池スタック20の運転モードを切り替えることにより発電効率の向上を図る。
なお、先の図3には、通常負荷運転後のアイドル運転時(例えば、信号待ちの際)にリフレッシュ処理の要否を判定する例が記載されているが、図4では、通常負荷運転中にリフレッシュ処理の要否を判定する例について説明する。
ブレーキ開度が閾値αを超えている場合(ステップS5:YES)、例えば信号待ち等で燃料電池スタック20の運転モードがアイドル運転中でブレーキ開度が全開のときには、リフレッシュ処理を行なう(ステップS7)。
このときのリフレッシュ電圧は、触媒層24aの性能回復の最大化という観点にたてば、後述のII型酸化皮膜又はIII型酸化皮膜を除去できる低さの電圧であることが好ましい。
図5は、ブレーキ開度が所定の閾値を超えたときにブレーキ開度に応じたリフレッシュ処理を実施する手順を示すフローチャートである。
また、図6,7は、図5のブレーキ開度に応じたリフレッシュ処理の一例であり、図6はブレーキ開度とリフレッシュ電圧との関係を示す表であり、図7はブレーキ開度とリフレッシュ時間との関係を示す表である。
例えば、図6に示すように、ブレーキ開度≦25%の場合のリフレッシュ電圧は0.6Vであり(以下、パターンV1と称する。)、このリフレッシュ処理によれば、後述のI型酸化皮膜の除去が可能である。
I型酸化皮膜(例えば、0.65V~0.9V)>II型酸化皮膜(例えば、0.4V~0.6V)>III型酸化皮膜(例えば、0.05V~0.4V)
また、I型酸化皮膜、II型酸化皮膜、及びIII型酸化皮膜は、例えば図9に示すように(ただし、III型酸化皮膜については図示略)、燃料電池スタック20の出力電圧が所定の境界電圧(例えば、0.8V)を上下に跨いだ回数(以下、サイクル数)の増大に伴い酸化皮膜中の割合が徐々に変化するものとしても知られている。
例えば、図7に示すように、ブレーキ開度≦10%の場合のリフレッシュ時間は0.5秒であり(以下、パターンT1と称する。)、10%<ブレーキ開度≦30%の場合のリフレッシュ時間は1秒であり(以下、パターンT2と称する。)、30%<ブレーキ開度の場合のリフレッシュ時間は3秒である。
例えば、ブレーキ開度≦10%の場合のリフレッシュ電圧及びリフレッシュ時間はそれぞれ0.6V及び0.5秒、10%<ブレーキ開度≦25%の場合のリフレッシュ電圧及びリフレッシュ時間はそれぞれ0.6V及び1秒、25%<ブレーキ開度≦30%の場合のリフレッシュ電圧及びリフレッシュ時間はそれぞれ0.4V及び1秒、30%<ブレーキ開度≦50%の場合のリフレッシュ電圧及びリフレッシュ時間はそれぞれ0.4V及び3秒、50%<ブレーキ開度の場合のリフレッシュ電圧及びリフレッシュ時間はそれぞれ0.05V及び3秒に設定して、リフレッシュ処理を実施してもよい。
Claims (5)
- 触媒層を有する電極が高分子電解質膜の両面に配置されてなる膜-電極アセンブリを備えた燃料電池と、
前記燃料電池の出力電圧を所定電圧まで低下させることにより前記触媒層の性能回復処理を実施する制御装置と、を備え、
前記制御装置は、前記燃料電池に対する出力増加要求のタイミングを予測し、その予測結果に基づいて前記性能回復処理の要否及び内容を決定する、燃料電池システム。 - 請求項1に記載の燃料電池システムにおいて、
前記燃料電池の発電中に前記触媒層に形成される酸化皮膜が、前記燃料電池の出力電圧を第1の皮膜除去電圧まで低下させることにより除去できる第1の酸化皮膜と、前記燃料電池の出力電圧を前記第1の皮膜除去電圧よりも低い第2の皮膜除去電圧まで低下させないと除去できない第2の酸化皮膜とが混在したものであり、
前記制御装置は、前記性能回復処理が必要と判定した場合に、前記予測結果に応じて前記低下させる所定電圧を変更する、燃料電池システム。 - 請求項2に記載の燃料電池システムにおいて、
前記制御装置は、前記燃料電池に対する出力増加要求のタイミングが第1の所定時間の経過よりも前と予測した場合には、前記燃料電池の出力電圧を前記第1の皮膜除去電圧までしか下げないが、前記燃料電池に対する出力増加要求のタイミングが前記第1の所定時間の経過よりも後、或いは前記第1の所定時間よりも長い第2の所定時間の経過よりも後と予測した場合には、前記燃料電池の出力電圧を前記第2の皮膜除去電圧まで下げる、燃料電池システム。 - 請求項3に記載の燃料電池システムにおいて、
前記制御装置は、前記燃料電池に対する出力要求が所定値以下であるときに前記燃料電池の出力電圧を前記第2の皮膜除去電圧まで下げる、燃料電池システム。 - 車載電源として燃料電池車両に搭載された請求項1に記載の燃料電池システムにおいて、
前記制御装置は、前記燃料電池に対する出力増加要求のタイミングをブレーキ開度に基づいて予測する、燃料電池システム。
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CA2866010A CA2866010C (en) | 2012-03-01 | 2012-03-01 | Predictive fuel cell system |
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CN201280071044.2A CN104137315B (zh) | 2012-03-01 | 2012-03-01 | 燃料电池系统 |
DE112012005964.6T DE112012005964B4 (de) | 2012-03-01 | 2012-03-01 | Brennstoffzellensystem mit Katalysatoraktivierungsfunktion |
PCT/JP2012/055191 WO2013128609A1 (ja) | 2012-03-01 | 2012-03-01 | 燃料電池システム |
US14/382,079 US9786938B2 (en) | 2012-03-01 | 2012-03-01 | Fuel cell system |
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JP6943170B2 (ja) * | 2017-12-19 | 2021-09-29 | トヨタ自動車株式会社 | 燃料電池システム |
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JP7302528B2 (ja) * | 2020-05-15 | 2023-07-04 | トヨタ自動車株式会社 | 燃料電池システム |
DE102020114626A1 (de) | 2020-06-02 | 2021-12-02 | Audi Aktiengesellschaft | Verfahren zum Betreiben eines Hybrid-Fahrzeuges sowie Hybrid-Fahrzeug |
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