Method for controlling a fuel cell system

Abstract

The present invention relates to a method for controlling a fuel cell system. The method for controlling a fuel cell system of the present invention is as follows: a method for controlling a fuel cell system, the method comprising: a measurement process, in which a power generation voltage at a predetermined current density of a fuel cell unit is measured; a first calculation process, in which the poisoning rate of the electrode catalyst at the power generation voltage measured in the measurement process is calculated from a predetermined relationship between the poisoning rate of the electrode catalyst of the fuel cell unit and the power generation voltage at the predetermined current density; and a second calculation process, in which the generation rate of hydrogen peroxide at the poisoning rate of the electrode catalyst calculated in the first calculation process is calculated from a predetermined relationship between the generation rate of hydrogen peroxide of the fuel cell unit and the poisoning rate of the electrode catalyst.

Description

Technical Field

[0001] The invention relates to a method for controlling a fuel cell system. Background Art

[0002] In a fuel cell, during power generation, in addition to the main reaction (2H + +2e - +(1 / 2)O2→H2O), the side reaction (2H + +O2+2e - →H2O2) also occurs. The hydrogen peroxide (H2O2) generated during this side reaction reacts with Fe that has flowed into the membrane electrode assembly (MEA) as an impurity to generate free radicals. The free radicals attack the electrolyte membrane, and the electrolyte material is destroyed. As a result, due to the protons (H + ) is reduced, and performance may deteriorate. In addition, due to excessive damage to the electrolyte material, holes may be formed in the electrolyte membrane, and hydrogen may leak from the anode to the cathode, which leads to reduced fuel consumption. In the worst case, the vehicle may stop running. In order to avoid these problems, various inventions have been proposed.

[0003] For example, Japanese Unexamined Patent Application Publication No. 2007-12375 (JP 2007-12375 A) describes a method in which Ti(SO4)2 is pre-added to an electrolyte material and thereby adheres to hydrogen peroxide, complexes with it and removes hydrogen peroxide from a fuel cell cell. In addition, Japanese Unexamined Patent Application Publication No. 2008-218100 (JP 2008-218100 A) describes a method in which a portion of an edge of an electrolyte membrane whose surface is not covered with an electrode is covered with a sealing member and a peroxide decomposition catalyst is added to at least a portion of the sealing member covering the electrolyte membrane.

[0004] In the methods described in JP 2007-12375 A, JP 2008-218100 A, etc., after hydrogen peroxide is produced in a fuel cell monomer, hydrogen peroxide is supplemented and removed from the monomer, or hydrogen peroxide is decomposed, which makes hydrogen peroxide harmless. However, all of these methods involve taking measures after hydrogen peroxide is produced, and do not involve taking measures before hydrogen peroxide is produced. In addition, because it is necessary to use special additives in the monomer to detoxify hydrogen peroxide, it is necessary to fully consider the adverse effects of its addition on cost and performance. In addition, when more hydrogen peroxide than expected is produced, because the amount of hydrogen peroxide produced cannot be diagnosed from the outside, it is unclear whether the amount of the additive added before the fuel cell operation is suitable as the amount required to fully detoxify hydrogen peroxide.

[0005] On the other hand, Japanese Unexamined Patent Application Publication No. 2020-181665 (JP 2020-181665 A) describes a method for controlling a fuel cell system, wherein, in a fuel cell monomer, two findings are used: 1) when the poisoning rate of the electrode catalyst is less than a threshold value γ, the production rate of hydrogen peroxide is low; and 2) by a potential fluctuation operation in which the potential of the fuel cell monomer repeatedly fluctuates between a high potential and a low potential, the poisoning rate of the electrode catalyst can be reduced, and the production of hydrogen peroxide itself is minimized. In this method, the poisoning rate of the electrode catalyst is estimated from the curves of the reduction wave and the oxidation wave obtained by cyclic voltammetry, and when the poisoning rate of the electrode catalyst is a threshold value or more, it is estimated that the production rate of hydrogen peroxide will have reached a specified value or more and will increase sharply. Therefore, in this case, a potential fluctuation operation in which the potential of the fuel cell monomer repeatedly fluctuates between a high potential and a low potential is performed, the poisoning rate of the electrode catalyst is reduced, and therefore the production rate of hydrogen peroxide of the electrode catalyst is reduced. Summary of the invention

[0006] However, in the method for controlling a fuel cell system described in JP 2020-181665 A, for example, at the time of vehicle shipment and at the time of vehicle testing, it is necessary to connect an external measuring machine to the fuel cell monomer, and then use the external measuring machine to diagnose the poisoning rate of the electrode catalyst of the fuel cell monomer measured by cyclic voltammetry. This operation of diagnosing the poisoning rate is complicated and particularly troublesome at the time of vehicle shipment. Therefore, a method for more easily estimating the generation rate of hydrogen peroxide is needed.

[0007] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of controlling a fuel cell system in which the generation rate of hydrogen peroxide can be estimated more easily.

[0008] In order to solve the above problems, a method for controlling a fuel cell system of the present invention is provided, which is a method for controlling a fuel cell system as follows, which includes: a measurement process, in which the power generation voltage at a predetermined current density of a fuel cell cell is measured; a first calculation process, in which the poisoning rate of the electrode catalyst at the power generation voltage measured in the measurement process is calculated from a predetermined relationship between the poisoning rate of the electrode catalyst of the fuel cell cell and the power generation voltage at the predetermined current density; and a second calculation process, in which the generation rate of hydrogen peroxide at the poisoning rate of the electrode catalyst calculated in the first calculation process is calculated from a predetermined relationship between the generation rate of hydrogen peroxide of the fuel cell cell and the poisoning rate of the electrode catalyst.

[0009] According to the fuel cell system of the present invention, the generation rate of hydrogen peroxide can be estimated more easily.

[0010] In the fuel cell system, the method may further include a potential fluctuation operation process, in which, when the generation rate of hydrogen peroxide calculated in the second calculation process is a specified value α or greater, a potential fluctuation operation is performed in which the potential of the fuel cell monomer repeatedly fluctuates between a high potential and a low potential.

[0011] According to the present invention, the generation rate of hydrogen peroxide can be estimated more easily. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like symbols represent like elements, and in which:

[0013] Figure 1 is a diagram showing a schematic configuration of a fuel cell system that executes a method of controlling a fuel cell system according to an embodiment;

[0014] Figure 2 is a graph showing a poisoning rate of an electrode catalyst of a fuel cell unit according to one embodiment;

[0015] Figure 3 is a flow chart illustrating a method of controlling a fuel cell system according to one embodiment;

[0016] Figure 4 is a graph showing an example of a predetermined relationship between a power generation voltage at a predetermined current density and a poisoning rate of an electrode catalyst in a predetermined operating state of a fuel cell cell according to one embodiment;

[0017] Figure 5 is a graph showing an example of a predetermined relationship between a poisoning rate of an electrode catalyst and a generation rate of hydrogen peroxide at a predetermined current density in a predetermined operating state of a fuel cell cell according to one embodiment;

[0018] Figure 6 is a graph showing potential fluctuation of a fuel cell cell in a potential fluctuation operation according to one embodiment; and

[0019] Figure 7 is a graph showing an example of the relationship between the number of cycles of potential fluctuation and the poisoning rate of an electrode catalyst in a fuel cell according to one embodiment. DETAILED DESCRIPTION

[0020] Hereinafter, a method of controlling a fuel cell system according to an embodiment of the present invention will be described.

[0021] A method for controlling a fuel cell system according to an embodiment is a method for controlling a fuel cell system, the method comprising: a measurement process, in which a power generation voltage at a predetermined current density of a fuel cell cell is measured; a first calculation process, in which the poisoning rate of the electrode catalyst at the power generation voltage measured in the measurement process is calculated from a predetermined relationship between the poisoning rate of the electrode catalyst of the fuel cell cell and the power generation voltage at the predetermined current density; and a second calculation process, in which the generation rate of hydrogen peroxide at the poisoning rate of the electrode catalyst calculated in the first calculation process is calculated from a predetermined relationship between the generation rate of hydrogen peroxide of the fuel cell cell and the poisoning rate of the electrode catalyst.

[0022] First, an outline of a method of controlling a fuel cell system according to the embodiment will be described by illustrating one embodiment.

[0023] (Fuel Cell System)

[0024] Before describing a method of controlling a fuel cell system according to one embodiment, a fuel cell system that performs the control method will be described. Figure 1 is a diagram schematically illustrating a configuration of a fuel cell system for executing a method of controlling the fuel cell system according to an embodiment.

[0025] As in Figure 1 As shown in , a fuel cell system 10 according to one embodiment includes a fuel cell 100 , a fuel cell converter 200 , a secondary battery 300 , a secondary battery converter 400 , a DC / AC inverter 500 , a drive motor 600 , and a control unit 700 .

[0026] The fuel cell system 10 further includes a fuel cell wire EW1, a secondary battery wire EW2, and a DC wire EW3. The fuel cell wire EW1 electrically connects the fuel cell 100 and the fuel cell converter 200. The secondary battery wire EW2 electrically connects the secondary battery 300 and the secondary battery converter 400. The DC wire EW3 connects the fuel cell converter 200 and the secondary battery converter 400 in parallel with the DC / AC inverter 500.

[0027] The fuel cell 100 is a solid polymer fuel cell and generates DC power. The fuel cell 100 generates power by reacting hydrogen gas and oxygen gas supplied from the outside in the fuel cell monomer 110 according to an electrochemical reaction. The power generated by the fuel cell 100 is input to the fuel cell converter 200, the secondary battery converter 400 and the DC / AC inverter 500 via the fuel cell wire EW1. Here, although not shown, the fuel cell system 10 further includes a gas supply unit that supplies hydrogen gas to the fuel cell monomer 110 from the outside and can adjust the amount of the supplied hydrogen gas, and a gas supply unit that supplies oxygen gas to the fuel cell monomer 110 from the outside and can adjust the amount of the supplied oxygen gas.

[0028] The fuel cell 100 has a stacked structure in which a plurality of identical fuel cell monomers 110 as unit modules for power generation are stacked. Each fuel cell monomer 110 has an electrolyte membrane composed of a polymer ion exchange membrane. Each fuel cell monomer 110 has, for example, an anode electrode on one side of the electrolyte membrane and a cathode electrode on the other side of the electrolyte membrane. The anode electrode is a reaction field in which an electrode reaction on the anode side is carried out and contains a catalyst that promotes the electrode reaction near the contact surface with the electrolyte membrane. The cathode electrode is a reaction field in which an electrode reaction on the cathode side is carried out and contains a catalyst near the contact surface with the electrolyte membrane as in the anode electrode. Here, the "electrode catalyst" is a catalyst of the cathode electrode.

[0029] The fuel cell converter 200 is a boost converter that boosts the voltage input from the fuel cell 100 to a target voltage and outputs it. The fuel cell converter 200 is electrically connected to the DC / AC inverter 500 via a DC wire EW3.

[0030] The secondary battery 300 is functionally used as a power source of the fuel cell system 10 together with the fuel cell 100. The secondary battery 300 charges the power generated by the fuel cell 100. In addition, the secondary battery 300 inputs the charged power into the drive motor 600. The secondary battery 300 is composed of a lithium ion battery. The secondary battery 300 can be another type of battery such as a lead storage battery, a nickel-cadmium battery, and a nickel metal hydride battery.

[0031] The secondary battery converter 400 is a lifting and lowering converter device and has a configuration similar to the fuel cell converter 200. The secondary battery converter 400 adjusts the voltage of the secondary battery wire EW2 and controls the charging and discharging of the secondary battery 300. When the output power of the fuel cell converter 200 is insufficient relative to the target, the secondary battery converter 400 discharges the secondary battery 300. On the other hand, when the drive motor 600 generates regenerative power, the secondary battery converter 400 charges the secondary battery 300 with the regenerative power. Here, the secondary battery converter 400 may have a configuration different from that of the fuel cell converter 200.

[0032] The DC / AC inverter 500 converts the DC power supplied from the fuel cell 100 and the secondary battery 300 via the DC wire EW3 into three-phase AC power. The DC / AC inverter 500 is electrically connected to the drive motor 600 via the AC wire and supplies the three-phase AC power to the drive motor 600. In addition, the DC / AC inverter 500 converts the regenerative power generated by the drive motor 600 into DC power according to the instruction from the control unit 700 and then inputs the result to the secondary battery 300 via the DC wire EW3.

[0033] The drive motor 600 constitutes a main power source of the fuel cell system 10. The drive motor 600 is an electric motor that converts three-phase AC power supplied from the DC / AC inverter 500 into rotational power.

[0034] The fuel cell system 10 further includes a first voltage measuring unit VM1, a current measuring unit IM, and a second voltage measuring unit VM2. The first voltage measuring unit VM1 and the current measuring unit IM are installed in the fuel cell wire EW1. The second voltage measuring unit VM2 is installed in the DC wire EW3. The first voltage measuring unit VM1 measures the output voltage of the fuel cell 100 and inputs the measured output voltage as a signal to the control unit 700. The current measuring unit IM measures the output current of the fuel cell 100 and inputs the measured output current as a signal to the control unit 700. The second voltage measuring unit VM2 measures the output voltage of the fuel cell converter 200 and inputs the measured output voltage as a signal to the control unit 700.

[0035] The control unit 700 controls each component of the fuel cell system 10. The control unit 700 includes a poisoning countermeasure processing unit 710 as a functional unit for controlling each component of the fuel cell system 10. In the method of controlling the fuel cell system to be described below, the poisoning countermeasure processing unit 710 of the control unit 700 calculates the poisoning rate of the electrode catalyst based on the output voltage of the fuel cell 100. The poisoning countermeasure processing unit 710 calculates the generation rate of hydrogen peroxide based on the calculated poisoning rate of the electrode catalyst. The poisoning countermeasure processing unit 710 performs a determination for determining whether to perform a potential fluctuation operation based on the calculated generation rate of hydrogen peroxide. The poisoning countermeasure processing unit 710 performs a potential fluctuation operation based on the output voltage and output current of the fuel cell 100 depending on the determination result.

[0036] (Poisoning rate of electrode catalyst of fuel cell monomer)

[0037] Next, a poisoning rate of an electrode catalyst of a fuel cell cell 110 according to one embodiment will be described. Figure 2 is a graph showing a poisoning rate of an electrode catalyst of a fuel cell cell according to one embodiment.

[0038] Figure 2 The figure shows the change in current density when the potential of a fuel cell measured by cyclic voltammetry is swept. Figure 2 , La1 and La2 are curves showing current density when the electrode catalyst of the fuel cell monomer 110 is poisoned by a substance that can cause poisoning such as an organic component, La1 shows a reduction wave generated when the potential of the fuel cell monomer 110 is swept from a high potential to a low potential, and La2 shows an oxidation wave generated when the potential of the fuel cell monomer 110 is swept from a low potential to a high potential. On the other hand, Lb1 and Lb2 are curves showing current density when the electrode catalyst of the fuel cell monomer 110 is not poisoned, Lb1 shows a reduction wave generated when the potential of the fuel cell monomer 110 is swept from a high potential to a low potential, and Lb2 shows an oxidation wave generated when the potential of the fuel cell monomer 110 is swept from a low potential to a high potential.

[0039] As in Figure 2As shown in , in Lb1, when the potential of the fuel cell cell 110 is about 0.9V, the current density reaches a maximum. The potential when the current density is maximum is a potential that maximizes the adsorption rate of oxygen required for power generation relative to the electrode catalyst of the fuel cell cell 110. When the electrode catalyst of the fuel cell cell 110 is poisoned by a substance that can cause poisoning, such as an organic component, the adsorption of oxygen to the electrode catalyst is suppressed. Thus, in La1, as compared with Lb1, as indicated by arrow A, the current density decreases when the potential of the fuel cell cell 110 is 0.9V. The poisoning rate of the electrode catalyst of the fuel cell cell 110 can be estimated based on the amount of reduction in current density indicated by arrow A. On the other hand, in La1 and Lb1, when the potential of the fuel cell cell 110 is about 0.4V, the adsorption rate of oxygen relative to the electrode catalyst of the fuel cell cell 110 is the smallest.

[0040] Here, a state in which the electrode catalyst of the fuel cell cell 110 is not poisoned is a state in which the current density is saturated when the potential fluctuation operation to be described below is performed from a state in which the electrode catalyst of the fuel cell cell 110 is poisoned (such as a state in which the poisoning rate of the electrode catalyst is 70% as described below), when the potential fluctuation is repeated until the number of cycles reaches 100 and when the potential of the fuel cell cell 110 is approximately 0.9V.

[0041] As described above, when Pa is the current density when the potential at La1 is 0.9 V, Pa0 is the current density when the potential at La1 is 0.4 V, Pb is the current density when the potential at Lb1 is 0.9 V, and Pb0 is the current density when the potential at Lb1 is 0.4 V, the poisoning rate of the electrode catalyst of the fuel cell monomer 110 is defined by formula (1).

[0042] Electrode catalyst poisoning rate = (1-(Pa-Pa0) / (Pb-Pb0))×100(1)

[0043] Pa0 and Pb0 are determined by the characteristics of the electrode catalyst of the fuel cell unit 110 itself, and are constant regardless of whether the electrode catalyst is poisoned. In addition, Pb is constant because it is the current density when the electrode catalyst of the fuel cell unit 110 is not poisoned. On the other hand, as the poisoning of the electrode catalyst of the fuel cell unit 110 progresses, Pa decreases relative to Pb. Therefore, when the difference (Pb-Pb0) obtained by subtracting Pb0 from Pb is constant, the difference (Pa-Pa0) obtained by subtracting Pa0 from Pa decreases as the poisoning of the electrode catalyst of the fuel cell unit 110 progresses. Therefore, the poisoning rate of the electrode catalyst defined by formula (1) is 0% when the electrode catalyst of the fuel cell unit 110 is not poisoned, and increases as the poisoning of the electrode catalyst progresses.

[0044] Here, Pa and Pb are not particularly limited as long as they are current densities that enable the poisoning rate of the electrode catalyst to be specified, and may be current densities that make the potential at La1 and Lb1 approximately 0.9 V, and thus may be current densities when the potential is a value other than 0.9 V (e.g., 0.85 V). Similarly, Pa0 and Pb0 are not particularly limited as long as they are current densities that enable the poisoning rate of the electrode catalyst to be specified, and may be current densities when the potential at La1 and Lb1 is approximately 0.4 V, and thus may be current densities when the potential is a value other than 0.4 V (e.g., 0.3 V).

[0045] (Method of controlling fuel cell system)

[0046] Next, a method of controlling a fuel cell system according to one embodiment will be described. Figure 3 is a flow chart illustrating a method of controlling a fuel cell system according to one embodiment.

[0047] In a method of controlling a fuel cell system according to one embodiment, first, as in Figure 3 As shown in FIG. 1 , the current density (e.g., 2.0 A / cm ) of the fuel cell monomer 110 is measured in an online manner in a predetermined operating state. 2 ) under the power generation voltage (measurement process S10).

[0048] Specifically, in the measurement process S10, the poisoning countermeasure processing unit 710 of the control unit 700 controls the fuel cell system 10 in response to the output request, and adjusts the amount of hydrogen gas and oxygen gas supplied to the fuel cell cells 110, and thus the current density of the output current of the fuel cell 100 measured by the current measuring unit 114 is swept to a predetermined current density, and in this case, the power generation voltage of the fuel cell cells 110 is determined from the output voltage of the fuel cell 100 measured by the first voltage measuring unit VM1. In this case, the power generation voltage of the fuel cell cells 110 is calculated by the poisoning countermeasure processing unit 710 by dividing the output voltage of the fuel cell 100 by the number of stacked fuel cell cells 110.

[0049] Then, as in Figure 3 As shown in , the poisoning rate of the electrode catalyst at the power generation voltage measured in the measurement process S10 is calculated from a predetermined relationship between the power generation voltage at a predetermined current density in a predetermined operation state of the fuel cell cell 110 and the poisoning rate of the electrode catalyst (first calculation process S20).

[0050] Specifically, the poisoning countermeasure processing unit 710 of the control unit 700 pre-stores the relationship between the power generation voltage at a predetermined current density and the poisoning rate of the electrode catalyst in a predetermined operating state of the fuel cell monomer 110 as the first control information. In the first calculation process S20, the poisoning countermeasure processing unit 710 calculates the poisoning rate of the electrode catalyst at the power generation voltage measured in the measurement process S10 from the first control information.

[0051] here, Figure 4 is a graph showing an example of a predetermined relationship between a power generation voltage at a predetermined current density and a poisoning rate of an electrode catalyst in a predetermined operating state of a fuel cell cell according to one embodiment. Figure 4 The fuel cell unit 110 is shown in the operating state at 0.2 A / cm 2 and 2.0A / cm 2A predetermined relationship between the power generation voltage and the poisoning rate of the electrode catalyst at a current density of a certain value. The relationship between the power generation voltage and the poisoning rate of the electrode catalyst has a very good correlation. The relationship between the poisoning rate of the electrode catalyst of the fuel cell monomer 110 and the power generation voltage at a predetermined current density changes depending on the material, relative humidity and temperature of the fuel cell monomer 110 and the operating state determined by conditions such as the configuration of the fuel cell system 10. Therefore, the poisoning countermeasure processing unit 710 of the control unit 700 pre-stores the first control information (the relationship between the poisoning rate of the electrode catalyst of the fuel cell monomer 110 and the power generation voltage at a predetermined current density) for each operating state, and is therefore able to appropriately select and use the first control information according to the operating state.

[0052] Then, as in Figure 3 As shown in FIG. 1 , the generation rate of hydrogen peroxide at the poisoning rate of the electrode catalyst calculated in the first calculation process S20 is calculated from a predetermined relationship between the poisoning rate of the electrode catalyst of the fuel cell cell 110 and the generation rate of hydrogen peroxide (H 2 O 2 ) (second calculation process S30 ).

[0053] Specifically, the poisoning countermeasure processing unit 710 of the control unit 700 pre-stores the relationship between the poisoning rate of the electrode catalyst and the generation rate of hydrogen peroxide at a predetermined current density in a predetermined operating state of the fuel cell monomer 110 as the second control information. In the second calculation process S30, the poisoning countermeasure processing unit 710 calculates the generation rate of hydrogen peroxide at the poisoning rate of the electrode catalyst calculated in the first calculation process S20 from the second control information.

[0054] Here, the “generation rate of hydrogen peroxide” is a value [%] obtained by multiplying a result obtained by dividing the amount of generated hydrogen peroxide [mol] by the sum of the amount of water [mol] generated by electric power generation and the amount of generated hydrogen peroxide [mol] by 100.

[0055] here, Figure 5 is a graph showing an example of a predetermined relationship between a poisoning rate of an electrode catalyst and a generation rate of hydrogen peroxide at a predetermined current density in a predetermined operating state of a fuel cell cell according to one embodiment. Figure 5 The fuel cell unit 110 is shown in the operating state at 0.2 A / cm 2A predetermined relationship between the poisoning rate of the electrode catalyst and the generation rate of hydrogen peroxide at a predetermined current density of the fuel cell cell 110. The relationship between the poisoning rate of the electrode catalyst and the generation rate of hydrogen peroxide at a predetermined current density of the fuel cell cell 110 changes depending on the operating state of the fuel cell cell 110. Therefore, the poisoning countermeasure processing unit 710 of the control unit 700 pre-stores the second control information (the relationship between the poisoning rate of the electrode catalyst and the generation rate of hydrogen peroxide at a predetermined current density of the fuel cell cell 110) for each operating state, and is therefore able to appropriately select and use the second control information according to the operating state.

[0056] According to one embodiment, for example, in the inspection at the time of vehicle shipment and at the time of vehicle testing, since the generation rate of hydrogen peroxide of the fuel cell cell 110 can be estimated from the power generation voltage of the fuel cell cell 110 which can be measured in an online manner as described above, the generation rate of hydrogen peroxide of the fuel cell cell 110 can be estimated more easily (effect 1). In addition, for example, at a voltage such as 0.2 A / cm 2 Up to 2.0A / cm 2 In a wide range of current densities, because the relationship between the power generation voltage of the fuel cell monomer 110 and the poisoning rate of the electrode catalyst has a very good correlation, the generation rate of hydrogen peroxide can be estimated in a wide range of current density, and the vehicle inspection process can be simplified (effect 2).

[0057] In a control method according to one embodiment, then, as in Figure 3 As shown in , it is determined whether the generation rate of hydrogen peroxide calculated in the second calculation process S30 is a predetermined prescribed value α or more (determination process S40). Specifically, the poisoning countermeasure processing unit 710 of the control unit 700 stores the prescribed value α in advance. The poisoning countermeasure processing unit 710 determines whether the generation rate of hydrogen peroxide calculated in the second calculation process S30 is a prescribed value α or more.

[0058] Here, the predetermined prescribed value α for the generation rate of hydrogen peroxide of the fuel cell unit 110 will be described. Figure 5As shown in the example, when the poisoning rate of the electrode catalyst is less than the threshold value γ, the generation rate of hydrogen peroxide is small. On the other hand, when the poisoning rate of the electrode catalyst is the threshold value γ or more, as the poisoning rate of the electrode catalyst increases, the generation rate of hydrogen peroxide increases sharply. The prescribed value α is the value of the generation rate of hydrogen peroxide when the poisoning rate of the electrode catalyst is the threshold value γ. The prescribed value α changes depending on the current density and operating state of the fuel cell monomer 110. Therefore, the poisoning countermeasure processing unit 710 of the control unit 700 stores the prescribed value α for each current density and operating state in advance, and can appropriately select and use the prescribed value α depending on the current density and operating state of the fuel cell 100.

[0059] Then, as in Figure 3 As shown in , when the generation rate of hydrogen peroxide calculated in the second calculation process S30 is a prescribed value α or more, a potential fluctuation operation (potential fluctuation operation process S50) is performed in which the potential of the fuel cell monomer 110 repeatedly fluctuates between a high potential and a low potential. Here, the "potential of the fuel cell monomer" is the potential of the cathode electrode of the fuel cell monomer relative to the anode electrode.

[0060] Specifically, in the potential fluctuation operation process S50, when it is determined in the determination process S40 that the generation rate of hydrogen peroxide is the prescribed value α or more, the poisoning countermeasure processing unit 710 of the control unit 700 performs the potential fluctuation operation. After the potential fluctuation operation process S50, the poisoning countermeasure processing unit 710 performs the measurement process S10 again. On the other hand, as in Figure 3 As shown in , when it is determined in the determination process S40 that the generation rate of hydrogen peroxide is not the prescribed value α or more, the poisoning countermeasure processing unit 710 ends the control of the fuel cell system.

[0061] Hereinafter, a potential fluctuation operation according to one embodiment will be described. Figure 6 is a graph showing potential fluctuation of a fuel cell cell in a potential fluctuation operation according to one embodiment.

[0062] In the potential fluctuation operation, the potential of the fuel cell monomer 110 repeatedly fluctuates between a high potential and a low potential. Specifically, the poisoning countermeasure processing unit 710 of the control unit 700 controls the fuel cell system 10 and adjusts the amount of hydrogen gas and oxygen gas supplied to the fuel cell monomer 110, and thus causes the output current and output voltage of the fuel cell 100 measured by the current measuring unit IM and the first voltage measuring unit VM1 to fluctuate so that the potential of the fuel cell monomer 110 is between a high potential (e.g., 0.9V) and a low potential (e.g., 0.1V) and as in Figure 6As shown in , it fluctuates repeatedly. Thus, when the potential of the fuel cell monomer 110 is high, substances such as organic components that can cause poisoning that are bonded to the electrode catalyst are oxidized and removed, and when the potential of the fuel cell monomer 110 is low, the bonding force of the substances that can cause poisoning relative to the electrode catalyst is reduced, the current output from the fuel cell monomer 110 increases, the amount of water generated in the fuel cell monomer 110 increases, and as a result, the effect of washing away the substances that can cause poisoning with the generated water is improved. Therefore, the poisoning rate of the electrode catalyst of the fuel cell monomer 110 can be reduced. As a result, the generation rate of hydrogen peroxide of the fuel cell monomer 110 can be reduced. Thus, damage to the electrolyte membrane can be reduced.

[0063] The high potential of the potential fluctuation of the fuel cell monomer 110 is not particularly limited, as long as the effect of removing substances that can cause poisoning, such as organic components, is obtained, and preferably, for example, in the range of 0.8V or more and 1.0V or less. This is because, when the high potential is equal to or higher than the lower limit of this range, the poisoning rate of the electrode catalyst can be effectively reduced. This is because, when the high potential is equal to or less than the upper limit of this range, the degradation of the electrode catalyst can be alleviated. The low potential when the potential of the fuel cell monomer 110 fluctuates repeatedly is not particularly limited, as long as the effect of removing substances that can cause poisoning, such as organic components, is obtained, and preferably, for example, in the range of 0.1V or more and 0.2V or less. This is because, when the low potential is equal to or higher than the lower limit of this range, the amount of water produced can be prevented from becoming excessive. This is because, when the low potential is equal to or less than the upper limit of this range, the effect of washing away substances that can cause poisoning with the produced water can be effectively improved.

[0064] here, Figure 7 is a graph showing an example of the relationship between the poisoning rate of an electrode catalyst of a fuel cell cell and the number of cycles of potential fluctuation according to one embodiment. Figure 7 The relationship between the number of cycles of potential fluctuation of the fuel cell cell 110 and the poisoning rate of the electrode catalyst from the initial state in which the poisoning rate of the electrode catalyst of the fuel cell cell 110 is 70% is shown.

[0065] As in Figure 7 As shown in , the poisoning rate of the electrode catalyst of the fuel cell unit 110 decreases inversely proportional to the number of cycles of potential fluctuation. Then, when the number of cycles of potential fluctuation is 100, the poisoning rate of the electrode catalyst of the fuel cell unit 110 decreases to 0%. In addition, from Figure 7 The relationship shown shows that it is necessary to set the number of cycles of potential fluctuation of the fuel cell unit 110 to 20 in order to reduce the poisoning rate of the electrode catalyst of the fuel cell unit 110 from 37% to 20% (20% is less than the threshold value γ).

[0066] The time of one cycle of potential fluctuation in which the potential of the fuel cell monomer 110 repeatedly fluctuates is not particularly limited as long as the effect of removing substances that may cause poisoning, such as organic components, is obtained, and is preferably, for example, in the range of 3 seconds or longer and 10 seconds or shorter. This is because when the time of one cycle of potential fluctuation is within this range, the effect of removing substances that may cause poisoning becomes effective.

[0067] Although the method of controlling a fuel cell system according to an embodiment of the present invention has been described above in detail, the present invention is not limited to the embodiment, and various design modifications can be made thereto without departing from the spirit and scope of the present invention described in the claims.

Claims

1. A method for controlling a fuel cell system, comprising: The measurement process is to measure the power generation voltage at a predetermined current density of the fuel cell monomer, wherein the predetermined current density is 0.2A / cm 2 Up to 2.0A / cm 2 in the range of; a first calculation process in which a poisoning rate of the electrode catalyst at the power generation voltage measured in the measurement process is calculated from a predetermined relationship between a poisoning rate of the electrode catalyst of the fuel cell monomer and the power generation voltage at the predetermined current density; as well as A second calculation process in which the generation rate of hydrogen peroxide at the poisoning rate of the electrode catalyst calculated in the first calculation process is calculated from a predetermined relationship between the generation rate of hydrogen peroxide of the fuel cell unit and the poisoning rate of the electrode catalyst.

2. The method for controlling a fuel cell system according to claim 1, further comprising: A potential fluctuation operation process in which, when the generation rate of hydrogen peroxide calculated in the second calculation process is a prescribed value α or more, a potential fluctuation operation is performed in which the potential of the fuel cell unit repeatedly fluctuates between a high potential and a low potential.

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