Diagnostic device, electrochemical reaction system

Abstract

To provide a diagnostic device and an electrochemical reaction system, each enabling appropriate evaluation of gas transport characteristics of at least one of an anode and a cathode.SOLUTION: A diagnosis device 30 includes: an impedance measurement part 32 that measures an internal impedance of a fuel cell FC; a storage part M in which an equivalent circuit model of the fuel cell FC is stored; and a parameter identification part 34 that identifies a plurality of parameters constituting the equivalent circuit model. The diagnosis device 30 includes a state diagnosis part 36 that diagnoses an internal state of the fuel cell FC based on the equivalent circuit model. The equivalent circuit model includes one or more anode diffusion resistances and one or more anode diffusion capacities as parameters indicative of a gas transport property of the anode of the fuel cell FC. The parameter identification part 34 identifies a parameter including an anode diffusion resistance and an anode diffusion capacity based on a physical quantity having a correlation with a gas diffusion rate in the anode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a diagnostic device and an electrochemical reaction system including the diagnostic device. [Background technology]

[0002] Conventionally, a method and apparatus for evaluating gas transport characteristics at an anode by incorporating an anode diffusion impedance, which is formed by connecting a resistor and a capacitor in parallel, into an equivalent circuit model of a fuel cell is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-66589 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the frequency response frequency band of the gas transport characteristics at the anode is close to that at the cathode, making it difficult to distinguish between the gas transport characteristics at the anode and the gas transport characteristics at the cathode based on the internal impedance. Therefore, even if a diffusion impedance formed by connecting a resistor and a capacitor in parallel is simply incorporated into an equivalent circuit model of a fuel cell, it is difficult to appropriately evaluate the gas transport characteristics at the anode or the cathode. This is true not only for fuel cells, but also for reaction devices such as electrolysis devices that generate fuel by electrolysis of gases such as water vapor.

[0005] An object of the present disclosure is to provide a diagnostic device and an electrochemical reaction system that are capable of appropriately evaluating the gas transport characteristics of at least one of an anode and a cathode. [Means for solving the problem]

[0006] The present inventors have conducted extensive research into solutions to the above problems. As a result of this research, they have discovered that the gas diffusion speeds at the anode and cathode are different. The present disclosure was devised based on this finding.

[0007] The invention described in claim 1 is A diagnostic device for diagnosing a reaction device (FC, EC) that outputs electric energy by an electrochemical reaction of a first gas that serves as an oxidant and a second gas that serves as a reductant, or that receives as input a first gas that serves as a reductant and a second gas that serves as an oxidant, and electrolyzes the second gas using electric energy to output fuel, an impedance measuring unit (32, 32A) for measuring the internal impedance of the reaction device based on an AC signal including a plurality of frequencies output from the reaction device; a memory unit (M) in which an equivalent circuit model simulating the electrochemical characteristics of the reaction device is stored; a parameter identification unit (34, 34A) that compares the internal impedance measured by the impedance measurement unit with the equivalent circuit model to identify a plurality of parameters that constitute the equivalent circuit model; a state diagnosis unit (36, 36A) that diagnoses an internal state of the reaction equipment based on an equivalent circuit model in which the parameters identified by the parameter identification unit are reflected, The equivalent circuit model includes one or more anode diffusion resistances and one or more anode diffusion capacitances as parameters representing gas transport characteristics of the anode of the reactor; The parameter identification unit identifies parameters including the anode diffusion resistance and the anode diffusion capacitance based on physical quantities that have a correlation with the gas diffusion rate in the anode.

[0008] In this way, if the configuration is such that parameters including the anode diffusion resistance and the anode diffusion capacitance are identified based on physical quantities correlated with the gas diffusion rate at the anode, the difference in the gas diffusion rates at the anode and cathode is reflected in the equivalent circuit model. Use of such an equivalent circuit model makes it easier to understand the gas transport characteristics at the anode separately from the gas transport characteristics at the cathode, thereby enabling appropriate evaluation of the gas transport characteristics at the anode.

[0009] The invention described in claim 2 is A diagnostic device for diagnosing a reaction device (FC, EC) that outputs electric energy by an electrochemical reaction of a first gas that serves as an oxidant and a second gas that serves as a reductant, or that receives as input a first gas that serves as a reductant and a second gas that serves as an oxidant, and electrolyzes the second gas using electric energy to output fuel, an impedance measuring unit (32, 32A) for measuring the internal impedance of the reaction device based on an AC signal including a plurality of frequencies output from the reaction device; a memory unit (M) in which an equivalent circuit model simulating the electrochemical characteristics of the reaction device is stored; a parameter identification unit (34, 34A) that compares the internal impedance measured by the impedance measurement unit with the equivalent circuit model to identify a plurality of parameters that constitute the equivalent circuit model; a state diagnosis unit (36, 36A) that diagnoses an internal state of the reaction equipment based on an equivalent circuit model in which the parameters identified by the parameter identification unit are reflected, The equivalent circuit model includes one or more cathode diffusion resistances and one or more cathode diffusion capacitances as parameters representing the gas transport characteristics of the cathode of the reactor; The parameter identification unit identifies parameters including the cathode diffusion resistance and the cathode diffusion capacitance based on physical quantities that have a correlation with the gas diffusion rate in the cathode.

[0010] In this way, if the configuration is such that parameters including the cathode diffusion resistance and the cathode diffusion capacitance are identified based on physical quantities correlated with the gas diffusion rate in the cathode, the difference in gas diffusion rate between the anode and the cathode is reflected in the equivalent circuit model. Use of such an equivalent circuit model makes it easier to understand the gas transport characteristics in the cathode separately from the gas transport characteristics in the anode, thereby enabling appropriate evaluation of the gas transport characteristics in the cathode.

[0011] The invention described in claim 3 is A diagnostic device for diagnosing a reaction device (FC, EC) that outputs electric energy by an electrochemical reaction of a first gas that serves as an oxidant and a second gas that serves as a reductant, or that receives as input a first gas that serves as a reductant and a second gas that serves as an oxidant, and electrolyzes the second gas using electric energy to output fuel, an impedance measuring unit (32, 32A) for measuring the internal impedance of the reaction device based on an AC signal including a plurality of frequencies output from the reaction device; a memory unit (M) in which an equivalent circuit model simulating the electrochemical characteristics of the reaction device is stored; a parameter identification unit (34, 34A) that compares the internal impedance measured by the impedance measurement unit with the equivalent circuit model to identify a plurality of parameters that constitute the equivalent circuit model; a state diagnosis unit (36, 36A) that diagnoses an internal state of the reaction equipment based on an equivalent circuit model in which the parameters identified by the parameter identification unit are reflected, the equivalent circuit model includes one or more anode diffusion resistances and one or more anode diffusion capacitances as parameters representing gas transport characteristics of the anode of the reactor, and includes one or more cathode diffusion resistances and one or more cathode diffusion capacitances as parameters representing gas transport characteristics of the cathode of the reactor; The parameter identifying unit identifies the parameter based on a first physical quantity that has a correlation with the gas diffusion rate in the anode and a second physical quantity that has a correlation with the gas diffusion rate in the cathode.

[0012] This makes it easier to understand the gas transport characteristics at the anode and the gas transport characteristics at the cathode separately, and therefore makes it possible to appropriately evaluate the gas transport characteristics at the anode and the cathode, respectively.

[0013] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram of a fuel cell system according to a first embodiment. [Figure 2] FIG. 2 is an explanatory diagram for explaining an equivalent circuit model of the reaction device according to the first embodiment. [Figure 3] FIG. 1 is a Cole-Cole plot of the internal impedance obtained when an AC current is superimposed on a reactor. [Figure 4] FIG. 3 is an explanatory diagram for explaining the gas diffusion characteristics of a fuel gas and an oxidant gas. [Figure 5] 4 is a flowchart showing the flow of diagnostic processing executed by the diagnostic device. [Figure 6] FIG. 2 is an explanatory diagram for explaining an anode diffusion resistor and a cathode diffusion resistor. [Figure 7] 4 is a flowchart showing the flow of an abnormality countermeasure process executed by a control unit of the fuel cell system. [Figure 8] FIG. 2 is an explanatory diagram for explaining an equivalent circuit model of a reaction device according to a first modified example of the first embodiment. [Figure 9] FIG. 10 is an explanatory diagram for explaining an equivalent circuit model of a reaction device according to a second modified example of the first embodiment. [Figure 10] FIG. 10 is an explanatory diagram for explaining an equivalent circuit model of a reaction device according to a third modified example of the first embodiment. [Figure 11] 10 is a flowchart showing the flow of diagnostic processing executed by a control unit of a fuel cell system according to a second embodiment. [Figure 12]FIG. 10 is a schematic diagram of a water electrolysis system according to a third embodiment. [Figure 13] 4 is a flowchart showing the flow of an abnormality countermeasure process executed by a control unit of the water electrolysis system. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same as or equivalent to those described in the preceding embodiments will be given the same reference numerals, and their description may be omitted. Furthermore, in the embodiments, when only some of the components are described, the components described in the preceding embodiments can be applied to the remaining components. The following embodiments can be partially combined with each other, even if not specifically stated, as long as there is no particular problem with the combination.

[0016] (First embodiment) This embodiment will be described with reference to Figures 1 to 7. In this embodiment, an example will be described in which a diagnostic device 30 and an electrochemical reaction system according to the present disclosure are applied to a diagnostic device 30 for a fuel cell FC and a fuel cell system 1, as shown in Figure 1.

[0017] The fuel cell system 1 is configured as a system to be mounted on a mobile object such as a vehicle. As shown in Fig. 1, the fuel cell system 1 includes a fuel cell FC, an air supply unit SAP, a fuel supply unit SFP, and a control device 10 for the fuel cell FC.

[0018] The fuel cell FC outputs electrical energy through an electrochemical reaction of a fuel gas containing air as an oxidant and hydrogen as a reducing agent. The fuel cell FC of this embodiment outputs electrical energy through an electrochemical reaction between hydrogen and oxygen. In this embodiment, the fuel cell FC corresponds to the "reaction device." Also, in this embodiment, air corresponds to the "first gas" as an oxidant, and the fuel gas corresponds to the "second gas" as a reducing agent.

[0019] Specifically, the fuel cell FC is configured as a cell stack CS in which a plurality of solid polymer type battery cells C are stacked one on top of the other. The solid polymer type battery cells C are also called PEFC (short for Polymer Electrolyte Fuel Cell).

[0020] As shown in the lower part of Fig. 2, the battery cell C is composed of an electrolyte membrane EM, a hydrogen electrode AN constituting the anode, an oxygen electrode CA constituting the cathode, and a separator SP forming an air flow path and a fuel flow path. The battery cell C outputs electrical energy to an external circuit (not shown) through the electrochemical reaction of hydrogen and oxygen shown in the following reaction formulas F1 and F2. The power output from each battery cell C is supplied to a load device or a battery via a power converter such as an inverter (not shown).

[0021] (Fuel electrode) 2H2→4H + +4e - …(F1) (Oxygen electrode) 4H + +O2+4e - →2H2O …(F2)

[0022] An air supply unit SAP including an air flow path and a fuel supply unit SFP including a fuel gas flow path are connected to the fuel cell FC. Air, which serves as an oxidizing agent, and hydrogen, which serves as a reducing agent, are supplied to the fuel cell FC through the air supply unit SAP and the fuel supply unit SFP.

[0023] The air supply unit SAP uses atmospheric air as a supply source and supplies the air from the supply source to the fuel cell FC using a blower or the like (not shown). The air supply unit SAP constitutes a "first gas supply unit" that controls the supply amount of the first gas, which serves as an oxidant, to the fuel cell FC, which is a reaction device.

[0024] The fuel supply unit SFP uses a hydrogen tank or the like as a fuel gas supply source, and supplies hydrogen from the supply source to the fuel cell FC using a blower or the like (not shown). The fuel supply unit SFP constitutes a "second gas supply unit" that controls the supply amount of the second gas, which serves as a reducing agent, to the fuel cell FC, which is the reaction device.

[0025] In a fuel cell FC, water produced by the electrochemical reaction between hydrogen and oxygen is discharged as off-gas. This off-gas may contain unreacted hydrogen in addition to water. For this reason, the fuel cell system 1 is designed to reduce the hydrogen concentration in the off-gas by recycling or using a catalyst before discharging it to the outside.

[0026] The control device 10 of the fuel cell FC is configured by a computer including a processor and a memory unit M. The memory unit M includes not only ROM and RAM but also auxiliary storage devices, etc. The memory unit M is a non-transitory tangible storage medium.

[0027] The control device 10 includes a control unit 20 that controls various devices in the fuel cell system 1 and a diagnostic device 30 that diagnoses the internal state of the fuel cell FC. The control unit 20 and the diagnostic device 30 may be configured using common hardware, or may be configured using separate hardware.

[0028] The control unit 20 outputs control signals to various controlled devices such as the air supply unit SAP and the fuel supply unit SFP, thereby controlling the operation of the various controlled devices. Furthermore, when the diagnosis result of the internal state of the fuel cell FC by the diagnostic device 30, which will be described later, indicates an abnormal state, the control unit 20 performs recovery processing to recover from the abnormal state. The control unit 20 includes, as functional units for realizing various functions, a device control unit 21 that controls the operation of the various controlled devices, and a recovery execution unit 22 that executes recovery processing.

[0029] The diagnostic device 30 measures the internal impedance of the fuel cell FC and diagnoses the internal state of the fuel cell FC using an equivalent circuit model based on the measured internal impedance. The diagnostic device 30 includes an impedance measurement unit 32, a parameter identification unit 34, and a state diagnosis unit 36 ​​as functional units for realizing various functions.

[0030] The impedance measurement unit 32 measures the internal impedance of the fuel cell FC based on an electrochemical impedance method. Specifically, the impedance measurement unit 32 superimposes an AC current of a predetermined frequency on the fuel cell FC, and measures the internal impedance of the fuel cell FC based on an AC signal including multiple frequencies output from the fuel cell FC at this time. The internal impedance measured by the impedance measurement unit 32 is used for fitting parameters of an equivalent circuit model ECM stored in the memory unit M. Note that the impedance measurement unit 32 may also be configured to superimpose an AC current of a predetermined frequency on each battery cell C, and measure the internal impedance of each battery cell C based on the AC signal output from each battery cell C at this time. In this case, the internal impedance of each battery cell C corresponds to the internal impedance of the fuel cell FC.

[0031] Here, the equivalent circuit model ECM is a circuit model that simulates the fuel cell FC, and is stored in advance in the storage unit M. The equivalent circuit model ECM includes parameters that indicate the gas transport characteristics of the anode and cathode of the fuel cell FC.

[0032] In the memory unit M of this embodiment, a circuit model is stored as an equivalent circuit model ECM, in which a membrane resistance Romh, a gas reaction component GR, an anode diffusion component AD, and a cathode diffusion component CD are connected in series, as shown in Fig. 2. The gas reaction component GR is a parameter that indicates the reaction characteristics of the reaction gas in the catalyst, and is configured as a series circuit in which a reaction resistance Ract and a reaction capacity Cact are connected in parallel. The anode diffusion component AD is a parameter that indicates the gas diffusion characteristics in the anode, and the anode diffusion resistance R H and anode diffusion capacitance C HThe cathode diffusion component CD is a parameter that indicates the gas diffusion characteristics in the cathode, and the cathode diffusion resistance R O and cathode diffusion capacitance C O and are configured as a series circuit connected in parallel.

[0033] The parameter identification unit 34 compares the internal impedance measured by the impedance measurement unit 32 with the equivalent circuit model ECM to identify a plurality of parameters that constitute the equivalent circuit model ECM. Upon completion of the parameter identification, the parameter identification unit 34 stores the equivalent circuit model ECM reflecting the parameters in the memory unit M.

[0034] Figure 3 is a Cole-Cole plot showing the behavior of the internal impedance of a fuel cell FC on a complex plane, measured using electrochemical impedance spectroscopy. In Figure 3, the solid line shows the behavior of the internal impedance when the gas transport properties inside the fuel cell FC are normal. Also in Figure 3, the dashed-dotted line shows the behavior of the internal impedance when the gas transport properties at the anode deteriorate, and the dashed-two-dotted line shows the behavior of the internal impedance when the gas transport properties at the cathode deteriorate.

[0035] As shown in Figure 3, when the gas transport characteristics at the anode and cathode deteriorate, the internal impedance curve becomes larger on the right side of the complex plane compared to when the gas transport characteristics are normal. However, the frequency response band of the gas transport characteristics at the anode is close to that of the gas transport characteristics at the cathode, making it difficult to distinguish between the gas transport characteristics at the anode and the gas transport characteristics at the cathode based on the internal impedance.

[0036] Therefore, even if a diffusion impedance, which is a parallel connection of a resistance component and a capacitance component, is simply incorporated into the equivalent circuit model ECM of the fuel cell FC, it is difficult to appropriately evaluate the gas transport characteristics at the anode or cathode. Note that the diffusion impedance corresponds to the anode diffusion component AD and the cathode diffusion component CD.

[0037] In a fuel cell FC, the gas diffusion rate at the anode differs from the gas diffusion rate at the cathode. Specifically, as shown in Figure 4, the gas diffusion rate at the anode tends to be about four times faster than the gas diffusion rate at the cathode. This difference in diffusion rate is manifested as a difference in the cutoff frequency of the anode diffusion component AD and the cathode diffusion component CD.

[0038] Taking these factors into consideration, the parameter identification unit 34 is configured to identify parameters constituting the equivalent circuit model ECM based on a first physical quantity correlated with the gas diffusion rate in the anode and a second physical quantity correlated with the gas diffusion rate in the cathode. The parameter identification is performed by, for example, complex nonlinear least squares analysis, DRT analysis, or the like. DRT is an abbreviation for Distribution of Relaxation Times.

[0039] The parameter identifying unit 34 of this embodiment determines the cutoff frequency of the anode diffusion component AD as a first physical quantity having a correlation with the gas diffusion rate at the anode. The parameter identifying unit 34 also determines the cutoff frequency of the cathode diffusion component CD as a second physical quantity having a correlation with the gas diffusion rate at the cathode. The parameter identifying unit 34 determines the cutoff frequency of the cathode diffusion component CD as a second physical quantity having a correlation with the gas diffusion rate at the cathode, for example, by using the formula "1 / (2π*R H *C H )” is calculated as the cutoff frequency of the anodic diffusion component AD, and “1 / (2π*R O *C O )” is calculated as the cutoff frequency of the cathode diffusion component CD. Note that, hereinafter, the cutoff frequency of the anode diffusion component AD may be referred to as “CF1”, and the cutoff frequency of the cathode diffusion component CD may be referred to as “CF2”.

[0040] Then, the parameter identifying unit 34 identifies the parameters that configure the equivalent circuit model ECM based on CF1 and CF2. Specifically, the parameter identifying unit 34 sets predetermined constraint conditions for CF1 and CF2, and identifies each parameter so that the constraint conditions are met.

[0041] As the constraint, for example, at least one of the following conditions [LC1] to [LC6] is adopted.

[0042] [LC1] CF1 ≧ first threshold, CF2 ≧ second threshold (however, first threshold > second threshold) [LC2] CF1 is within the first range, and CF2 is within the second range (however, the first range > the second range) [LC3]CF1-CF2≧predetermined threshold [LC4]CF1-CF2 is within the specified range [LC5]CF1 / CF2≧predetermined threshold [LC6]CF1 / CF2 is within the specified range

[0043] The above-mentioned constraint conditions are defined, for example, as relational expressions, functions, etc. Note that the constraint conditions are merely examples and may be different from those described above. Furthermore, the threshold values ​​and ranges in the constraint conditions are set based on CF1 and CF2 obtained through simulation, experiments, on-board learning, etc. However, it is desirable that the threshold values ​​and ranges in the constraint conditions be changed according to the battery temperature, battery voltage, battery load, deterioration over time, tightening force of the cell stack CS, etc.

[0044] The state diagnosis unit 36 ​​diagnoses the internal state of the fuel cell FC based on the equivalent circuit model ECM that reflects the parameters identified by the parameter identification unit 34. The state diagnosis unit 36 ​​of this embodiment diagnoses the internal state of the fuel cell FC based on the anode diffusion resistance R H Based on this, it is determined whether or not there is a shortage of fuel gas.

[0045] The state diagnosis unit 36 ​​uses the following judgment conditions [JC1] to [JC3], for example, and judges that the fuel is insufficient when the judgment conditions are met.

[0046] [JC1]R H ≧ abnormal threshold [JC2]R H is above the abnormal threshold multiple times in succession [JC3]R H exceeds the abnormal threshold multiple times within a specified period

[0047] Here, the determination of whether or not there is a lack of fuel is made by the anode diffusion resistance R H and the moving average value of the anode diffusion resistance R H The abnormality threshold value in the judgment conditions may be changed according to the battery temperature, battery voltage, battery load, internal pressure of the fuel cell FC, stoichiometry on the anode side, etc.

[0048] Next, the operation of the fuel cell system 1 when diagnosing the internal state of the fuel cell FC will be described with reference to Figures 5 to 7. Figure 7 is a flowchart showing the flow of the abnormality countermeasure processing executed by the control unit 20. The control routine shown in Figure 5 is executed periodically or irregularly while the fuel cell FC is generating electricity.

[0049] 5, in step S100, diagnostic device 30 superimposes an AC current of a predetermined frequency on fuel cell FC. Diagnostic device 30 changes the frequency of the AC current in a frequency range from low to high (for example, 0.01 Hz to 10 kHz).

[0050] Next, in step S110, the diagnostic device 30 measures the internal impedance of the fuel cell FC based on the electrochemical impedance method while changing the frequency of the alternating current superimposed on the fuel cell FC.

[0051] Subsequently, the diagnostic device 30 sets the equivalent circuit model ECM in step S120. Specifically, the diagnostic device 30 reads the equivalent circuit model ECM stored in the storage unit M in advance.

[0052] Next, in step S130, the diagnostic device 30 sets constraints for identifying the parameters constituting the equivalent circuit model ECM. These constraints are conditions for distinguishing between the gas diffusion characteristics of the anode and the cathode. In this embodiment, the constraints impose certain constraints on the cutoff frequency of the anode diffusion component and the cutoff frequency of the cathode diffusion component.

[0053] Next, in step S140, the diagnostic device 30 compares the internal impedance with the equivalent circuit model ECM to identify a plurality of parameters constituting the equivalent circuit model ECM. Specifically, the diagnostic device 30 sets predetermined constraints on the cutoff frequency of the anodic diffusion component AD and the cutoff frequency of the cathodic diffusion component CD, and identifies each parameter so that the constraints are satisfied.

[0054] Here, FIG. 6 shows the anode diffusion resistance R identified by the diagnostic device 30. H and the cathode diffusion resistance R O In Fig. 6, the Cole-Cole plot (proposed) when each parameter is identified with constraints is shown in the upper left, and the Cole-Cole plot (comparison example) when each parameter is identified without constraints is shown in the upper right.

[0055] As shown in Figure 6, the Cole-Cole plot of the comparative example behaves similarly to the Cole-Cole plot of the present invention. However, in the comparative example, the diffusion resistance R H , R O There is a large variation in the two, making it difficult to distinguish between them.

[0056] In contrast, in this proposal, the diffusion resistance R H , R O There is almost no variation in the resistance of each diffused resistor R H , R O Since there is a significant difference between the two, it is possible to distinguish between them.

[0057] Next, in step S150, the diagnostic device 30 diagnoses the internal state of the fuel cell FC based on the equivalent circuit model ECM that reflects the parameters identified by the parameter identification unit 34. The diagnostic device 30 of this embodiment diagnoses the internal state of the fuel cell FC based on the anode diffusion resistance R H Based on this, the diagnostic device 30 determines whether the fuel cell FC is in a fuel shortage state. After storing the diagnostic results of the internal state of the fuel cell FC in the memory unit M, the diagnostic device 30 ends the diagnostic process of the fuel cell FC.

[0058] Next, the control process executed by the control unit 20 based on the diagnosis results of the diagnosis device 30 will be described with reference to Fig. 7. The control routine shown in Fig. 7 is executed periodically or irregularly while the fuel cell FC is generating electricity.

[0059] 7, in step S200, the control unit 20 reads the diagnosis result of the internal state of the fuel cell FC made by the diagnosis device 30 from the memory unit M. Then, in step S210, the control unit 20 determines whether the fuel cell FC is in a fuel shortage state.

[0060] If the fuel cell FC is in a fuel shortage state, the control unit 20 proceeds to step S220, and if the fuel cell FC is not in a fuel shortage state, the control unit 20 skips the processing of step S220 and ends this processing.

[0061] If the fuel cell FC is in a fuel-starved state, the control unit 20 executes recovery processing in step S220. Recovery processing is processing for recovering from an abnormal state when the diagnosis result of the internal state of the fuel cell FC by the diagnosis device 30 indicates an abnormal state. If the fuel cell FC is in a fuel-starved state, the control unit 20 of this embodiment executes recovery processing to restore the fuel-starved state to a normal state. If the fuel cell FC is in a fuel-starved state, the control unit 20 executes at least one of the processing steps [RP1] to [RP7] listed below as recovery processing, for example.

[0062] [RP1] Increasing the amount of fuel gas supplied reduces the accumulation of generated water at the anode [RP2] Reduce the humidity of the fuel gas to prevent the accumulation of generated water at the anode [RP3] By reducing the pressure on the anode side and increasing the water vapor partial pressure on the cathode side, the produced water is moved from the anode to the cathode. [RP4] Increasing the temperature of fuel gas and oxidant gas reduces the amount of water produced [RP5] By increasing the load on the fuel cell FC, the temperature of each battery cell C is raised, thereby reducing the amount of water produced. [RP6] By lowering the water vapor partial pressure on the cathode side, the produced water is moved from the anode to the cathode. [RP7] Lowering the upper limit of the sweep current from the fuel cell FC to reduce the amount of water produced

[0063] The abnormal state of the fuel cell FC is restored to a normal state by executing such recovery processing by the control unit 20. The recovery processing described above may be performed temporarily or permanently, but it is desirable to continue it until the diagnosis result of the diagnosis device 30 indicates a normal state.

[0064] The diagnostic device 30 described above identifies parameters constituting an equivalent circuit model based on a first physical quantity correlated with the gas diffusion rate in the anode and a second physical quantity correlated with the gas diffusion rate in the cathode. The diagnostic device 30 then diagnoses the internal state of the fuel cell FC based on the equivalent circuit model in which the parameters have been identified. In this way, if the diagnostic device 30 is configured to identify parameters including the diffusion resistance and the diffusion capacitance based on physical quantities correlated with the gas diffusion rates of the anode and the cathode, respectively, the difference in the gas diffusion rates of the anode and the cathode is reflected in the equivalent circuit model. Using such an equivalent circuit model makes it easier to understand the gas transport characteristics at the anode separately from the gas transport characteristics at the cathode, thereby enabling the gas transport characteristics at the anode to be appropriately evaluated.

[0065] The diagnostic device 30 of this embodiment also has the following features.

[0066] (1) The diagnostic device 30 determines the cutoff frequency of the anode diffusion component, which is determined using the anode diffusion resistance and the anode diffusion capacitance, as a physical quantity correlated with the gas diffusion rate at the anode. The diagnostic device 30 also determines the cutoff frequency of the cathode diffusion component, which is determined using the cathode diffusion resistance and the cathode diffusion capacitance, as a physical quantity correlated with the gas diffusion rate at the cathode. The diagnostic device 30 then identifies the parameters of the equivalent circuit model ECM based on the cutoff frequencies of the anode diffusion component and the cathode diffusion component. This makes it easier to separately understand the gas transport characteristics at the anode and the gas transport characteristics at the cathode.

[0067] (2) The fuel cell system 1 includes a diagnostic device 30 and a control unit 20 that performs recovery processing to recover from an abnormal state when the diagnostic result of the diagnostic device 30 on the internal state of the fuel cell FC indicates an abnormal state. This allows recovery from the abnormal state when the diagnostic result of the diagnostic device 30 indicates an abnormal state.

[0068] (3) Specifically, the diagnostic device 30 determines whether or not the fuel gas is insufficient, based on the anode diffusion resistance. If the fuel gas is insufficient, the control unit 20 performs a recovery process to restore the fuel gas insufficiency state to a normal state. If the accumulation of generated water inside the fuel cell FC inhibits the diffusion of fuel gas on the anode side, resulting in a fuel gas insufficiency state, this can cause a malfunction of the fuel cell FC. For this reason, as in this embodiment, it is desirable that the fuel cell system 1 be configured to be able to restore the fuel gas insufficiency state to a normal state.

[0069] (Modification of the first embodiment) Although the diagnostic device 30 of the first embodiment determines the cutoff frequencies of the anode diffusion component and the anode diffusion component, and identifies the parameters of the equivalent circuit model based on the cutoff frequencies, the present invention is not limited to this. For example, the diagnostic device 30 may estimate the diffusion rates of gas at the anode and the cathode using a map or the like that defines the relationship between the diffusion components and the diffusion rates of gas at the anode and the cathode, and identify the parameters of the equivalent circuit model based on the estimation results.

[0070] The fuel cell system 1 is configured to determine whether or not there is a shortage of fuel gas based on the magnitude of the anode diffusion resistance, but is not limited to this. The fuel cell system 1 may also be configured to determine whether or not there is a shortage of fuel gas based on both the anode diffusion resistance and the anode diffusion capacity.

[0071] Furthermore, the fuel cell system 1 is configured to determine whether or not there is a lack of fuel gas based on the anode diffusion resistance, and if there is a lack of fuel gas, to restore the lack of fuel state to a normal state by performing a recovery process, but is not limited to this. For example, the fuel cell system 1 may be configured to determine whether or not there is a lack of air based on the cathode diffusion resistance, and if there is a lack of gas, to restore the lack of gas state to a normal state by performing a recovery process. Note that the recovery process in the fuel cell system 1 is not essential. For example, the fuel cell system 1 may be configured to execute a process to notify of an abnormality instead of the recovery process. This also applies to the following embodiments.

[0072] (First modified example of the equivalent circuit model) In the first embodiment, the equivalent circuit model ECM is configured by a series circuit in which the anode diffusion component AD and the cathode diffusion component CD are each connected in parallel to a diffusion resistor and a diffusion capacitor, but the equivalent circuit model ECM is not limited to this. For example, as shown in Fig. 8, the equivalent circuit model ECM may be configured by a nested circuit in which the cathode diffusion component CD is nested within the anode diffusion component AD.

[0073] (Second modified example of equivalent circuit model) The equivalent circuit model ECM may include only the anode diffusion component AD, omitting the cathode diffusion component CD from the anode diffusion component AD and the cathode diffusion component CD. In this case, the diagnostic device 30 may be configured to, for example, determine the cutoff frequency of the anode diffusion component as a physical quantity correlated with the gas diffusion rate in the anode, and identify the parameters of the equivalent circuit model ECM based on the cutoff frequency of the anode diffusion component.

[0074] (Third modified example of equivalent circuit model) The equivalent circuit model ECM may be configured to include only the cathodic diffusion component CD, omitting the anode diffusion component AD and the cathode diffusion component CD. In this case, the diagnostic device 30 may be configured to, for example, determine the cutoff frequency of the cathode diffusion component as a physical quantity correlated with the gas diffusion rate in the cathode, and identify the parameters of the equivalent circuit model ECM based on the cutoff frequency of the cathode diffusion component.

[0075] (Second embodiment) Next, a second embodiment will be described with reference to Fig. 11. In this embodiment, differences from the first embodiment will be mainly described.

[0076] As explained in the first embodiment, the gas diffusion resistance of fuel gas is smaller than that of air. If the gas diffusion resistance of fuel gas is too small, it may be difficult to evaluate the gas diffusion characteristics of the fuel gas. In this embodiment, fuel gas corresponds to a "low resistance gas" and air corresponds to a "high resistance gas."

[0077] In contrast, the diagnostic device 30 of this embodiment is configured to perform a process to increase the gas diffusion resistance of fuel gas, which is a low-resistance gas, and a process to decrease the gas diffusion resistance of air, which is a high-resistance gas. The diagnostic process performed by the diagnostic device 30 of this embodiment will be described below with reference to FIG.

[0078] Here, the control process shown in Fig. 11 is based on the control process shown in Fig. 5. The processes of steps S100, S110, S120, S130, S140, and S150 shown in Fig. 11 are the same as those described in the first embodiment, and therefore description thereof will be omitted.

[0079] As shown in FIG. 11, the diagnostic device 30 proceeds to step S105 with an AC current superimposed on the fuel cell FC, and executes a gas diffusion control process for controlling the diffusion of gas supplied to the fuel cell FC.

[0080] The diagnostic device 30 of this embodiment executes a restriction process to restrict the diffusion of the fuel gas, which is a low-resistance gas, inside the fuel cell FC so that the gas diffusion resistance of the fuel gas, which is a low-resistance gas, increases. For example, the diagnostic device 30 restricts the diffusion of the fuel gas, which is a low-resistance gas, inside the fuel cell FC by reducing the amount of fuel gas supplied to the fuel cell FC. In this case, the diagnostic device 30 reduces the amount of fuel gas supplied to a range that does not result in a fuel shortage state.

[0081] Furthermore, the diagnostic device 30 executes a promotion process to promote the diffusion of air, which is a high-resistance gas, so as to reduce the gas diffusion resistance of air, which is a high-resistance gas. For example, the diagnostic device 30 promotes the diffusion of air, which is a high-resistance gas, inside the fuel cell FC by increasing the amount of air supplied to the fuel cell FC.

[0082] In a state where the gas diffusion resistance of the fuel gas, which is a low resistance gas, is controlled to be large and the gas diffusion resistance of the air, which is a high resistance gas, is controlled to be small, the diagnostic device 30 measures the internal impedance of the fuel cell FC in step S110.

[0083] The rest of the configuration is the same as that of the first embodiment. The fuel cell system 1 of this embodiment can obtain the same effects as those of the first embodiment that are achieved by a configuration common to or equivalent to that of the first embodiment.

[0084] The fuel cell system 1 of this embodiment also has the following features.

[0085] (1) The fuel cell system 1 includes a diagnostic device 30, an air supply unit SAP that controls the amount of air supplied to the fuel cell FC, and a fuel supply unit SFP that controls the amount of fuel gas supplied to the fuel cell FC. When identifying each parameter of the equivalent circuit model ECM, the diagnostic device 30 executes a restriction process that restricts the diffusion of low-resistance gas in the fuel cell FC and a promotion process that promotes the diffusion of high-resistance gas in the fuel cell FC. In this way, restricting the diffusion of low-resistance gas to increase the diffusion resistance of low-resistance gas, or promoting the diffusion of high-resistance gas to reduce the diffusion characteristics of high-resistance gas, has the advantage of making it easier to evaluate the gas diffusion characteristics of the fuel gas.

[0086] (Modification of the second embodiment) The diagnostic device 30 of the second embodiment is configured to execute both the restriction process and the acceleration process as the gas diffusion control process, but is not limited to this. The diagnostic device 30 may execute either the restriction process or the acceleration process as the gas diffusion control process. Furthermore, the contents of the restriction process and the acceleration process may be different from those described above.

[0087] (Third embodiment) Next, a second embodiment will be described with reference to Figures 12 and 13. In this embodiment, differences from the first embodiment will be mainly described.

[0088] In this embodiment, as shown in FIG. 12, an example will be described in which a diagnostic device 30A and an electrochemical reaction system according to the present disclosure are applied to a diagnostic device 30A for an electrolysis device EC and a water electrolysis system 1A.

[0089] The water electrolysis system 1A is configured as a system for producing fuel by electrolyzing water. As shown in Fig. 12, the water electrolysis system 1A includes an electrolysis device EC, an air supply unit SAP, a water supply unit SWP, and a control device 10A for the electrolysis device EC.

[0090] The electrolysis device EC receives air as a reducing agent and water vapor as an oxidizing agent as input, electrolyzes the water vapor using electrical energy, and outputs fuel. In this embodiment, the electrolysis device EC corresponds to a "reaction device." In addition, in this embodiment, air corresponds to a "first gas" as a reducing agent, and water vapor corresponds to a "second gas" as an oxidizing agent.

[0091] Specifically, the electrolysis device EC is configured as a cell stack CS in which multiple solid polymer electrolytic cells are stacked. Although not shown, each solid polymer electrolytic cell includes an electrolyte membrane, an anode, a cathode, and separators that form air and steam channels. When power is supplied from a power source (not shown), the electrolytic cell separates and outputs hydrogen and oxygen through the electrolysis of steam as shown in the following reaction formulas F3 to F5.

[0092] (Anode)2O 2- →O2+4e - …(F3)

[0093] (cathode) H2O+2e - →H2+O 2- …(F4)

[0094] (Whole) 2H2O → 2H2 + O2…(F5) The electrolysis device EC is connected to an air supply unit SAP including an air flow path and a water supply unit SWP including a water vapor flow path. Air and hydrogen, which serve as reducing agents, are supplied to the electrolysis device EC through the air supply unit SAP and the water supply unit SWP.

[0095] The air supply unit SAP uses atmospheric air as a supply source and supplies the air from the supply source to the electrolysis device EC using a blower or the like (not shown). The air supply unit SAP constitutes a "first gas supply unit" that controls the supply amount of a first gas, which serves as a reducing agent, to the electrolysis device EC, which is a reaction device.

[0096] The water supply unit SWP supplies water vapor generated in a vaporizer (not shown) to the electrolysis device EC using a blower (not shown) or the like. The water supply unit SWP constitutes a "second gas supply unit" that controls the amount of second gas, which serves as an oxidant, supplied to the electrolysis device EC, which is a reaction device.

[0097] In the electrolyzer EC, oxygen and hydrogen are separated and produced by electrolysis of water vapor and discharged as off-gas. The hydrogen output from the electrolyzer EC is stored as fuel in a hydrogen tank HT or the like.

[0098] The control device 10A of the electrolysis device EC is configured by a computer including a processor and a memory unit M. The control device 10A of this embodiment is equipped with a control unit 20A that controls various devices in the fuel cell system 1 and a diagnostic device 30A that diagnoses the internal state of the fuel cell FC. The control unit 20A and the diagnostic device 30A may be configured by common hardware or may be configured by separate hardware.

[0099] The control unit 20A outputs control signals to various controlled devices such as the air supply unit SAP and the water supply unit SWP to control the operation of the various controlled devices. Furthermore, when the diagnosis result of the internal state of the electrolysis device EC by the diagnosis device 30A indicates an abnormal state, the control unit 20A performs recovery processing to recover from the abnormal state. The control unit 20A includes, as functional units for realizing various functions, an equipment control unit 21A that controls the operation of the various controlled devices and a recovery execution unit 22A that executes recovery processing.

[0100] The diagnostic device 30A measures the internal impedance of the electrolytic equipment EC and diagnoses the internal state of the electrolytic equipment EC using an equivalent circuit model based on the measured internal impedance. The diagnostic device 30A includes an impedance measurement unit 32A, a parameter identification unit 34A, and a state diagnosis unit 36A as functional units for realizing various functions.

[0101] The impedance measurement unit 32A measures the internal impedance of the electrolysis device EC based on the electrochemical impedance method. Specifically, the impedance measurement unit 32A superimposes an AC current of a predetermined frequency on the electrolysis device EC, and measures the internal impedance of the electrolysis device EC based on the AC signal containing multiple frequencies output from the electrolysis device EC. The internal impedance measured by the impedance measurement unit 32A is used to fit the parameters of the equivalent circuit model ECM stored in the memory unit M.

[0102] Here, the equivalent circuit model ECM is a circuit model that simulates the electrolysis device EC, and is stored in advance in the storage unit M. As described in the first embodiment, the equivalent circuit model ECM includes parameters that indicate the gas transport properties of the anode and cathode of the electrolysis device EC. Note that, as in the modified example of the first embodiment, the equivalent circuit model ECM may have a circuit configuration that includes parameters that indicate the gas transport properties of one of the anode and cathode of the electrolysis device EC.

[0103] The parameter identification unit 34A compares the internal impedance measured by the impedance measurement unit 32A with the equivalent circuit model ECM to identify a plurality of parameters that constitute the equivalent circuit model ECM. Upon completion of the parameter identification, the parameter identification unit 34A stores the equivalent circuit model ECM reflecting the parameters in the memory unit M.

[0104] As in the first embodiment, the parameter identification unit 34A identifies the parameters that constitute the equivalent circuit model ECM based on a first physical quantity that is correlated with the gas diffusion rate in the anode and a second physical quantity that is correlated with the gas diffusion rate in the cathode.

[0105] The state diagnosis unit 36A diagnoses the internal state of the electrolysis device EC based on the equivalent circuit model ECM that reflects the parameters identified by the parameter identification unit 34 A. The state diagnosis unit 36A of the present embodiment is configured to determine whether or not there is a gas shortage state where there is a shortage of water vapor, based on the cathode diffusion resistance.

[0106] The state diagnosis unit 36A determines that the vehicle is out of gas when the following conditions [JC4] to [JC6] are met.

[0107] [JC4] Cathode diffusion resistance ≧ abnormal threshold [JC5] Cathode diffusion resistance exceeds the abnormal threshold multiple times in succession [JC6] Cathode diffusion resistance exceeds the abnormal threshold multiple times within a specified period

[0108] Here, the determination of whether or not there is an out-of-gas state may be performed using the moving average value of the cathode diffusion resistance, the slope of an approximation curve indicating the trend of the cathode diffusion resistance, etc. The abnormality threshold value in the determination conditions is preferably changed depending on the temperature, voltage, internal pressure of the electrolysis device EC, stoichiometry on the cathode side, etc.

[0109] Next, the abnormality countermeasure processing executed by the control unit 20A based on the diagnosis results of the diagnosis device 30A will be described with reference to Fig. 13. The control routine shown in Fig. 13 is executed periodically or irregularly during operation of the electrolysis device EC.

[0110] 13, in step S300, the control unit 20A reads the diagnosis result of the internal state of the electrolysis device EC by the diagnostic device 30A from the memory unit M. Then, in step S310, the control unit 20A determines whether the electrolysis device EC is out of gas.

[0111] If the electrolysis device EC is out of gas, the control unit 20A proceeds to step S320, and if the electrolysis device EC is not out of gas, the control unit 20A skips the process of step S320 and ends this process.

[0112] If the electrolysis device EC is out of gas, the control unit 20A executes recovery processing in step S320. The recovery processing is a process for recovering from an abnormal state when the diagnosis result of the internal state of the electrolysis device EC by the diagnostic device 30A indicates an abnormal state. In this embodiment, when the electrolysis device EC is out of gas, the control unit 20A executes recovery processing to restore the out-of-gas state to a normal state. When the electrolysis device EC is out of gas, the control unit 20A executes recovery processing, for example, a process for increasing the supply amount of water vapor to suppress accumulation of produced water at the cathode. This restores the abnormal state of the electrolysis device EC to a normal state. The recovery processing may be executed temporarily or permanently, but is preferably continued until the diagnosis result of the diagnostic device 30A indicates a normal state.

[0113] The rest of the configuration is the same as that of Embodiment 1. The water electrolysis system 1A of this embodiment can obtain the same effects as those of the first embodiment that are achieved by a configuration common to or equivalent to that of the first embodiment.

[0114] The water electrolysis system 1A of this embodiment also has the following features.

[0115] (1) The diagnostic device 30A determines whether or not the vehicle is in a gas shortage state due to a lack of water vapor based on the cathode diffusion resistance. If the vehicle is in a gas shortage state, the control unit 20A performs a recovery process to restore the gas shortage state to a normal state.

[0116] A gas-out state in which the second gas is depleted due to impeded diffusion on the cathode side can cause a malfunction of the electrolysis device EC. Therefore, it is desirable that the water electrolysis system 1A be configured to be able to restore a normal state from a gas-out state.

[0117] (Modification of the third embodiment) In the third embodiment, the electrolysis device EC is described as electrolyzing water vapor to output hydrogen as fuel, but the gases and the like supplied to the electrolysis device EC are not limited to those described above. For example, the electrolysis device EC may be configured to electrolyze a mixed gas of water vapor and carbon dioxide to output methane as fuel. In this case, the mixed gas of water vapor and carbon dioxide corresponds to the "second gas."

[0118] Furthermore, in the third embodiment, air is supplied as a reducing agent to the electrolysis device EC, but the gases and the like supplied to the electrolysis device EC are not limited to those described above. For example, the electrolysis device EC may be configured so that nitrogen is supplied to the anode as a purge gas instead of air. In this case, nitrogen corresponds to the "first gas."

[0119] The diagnostic device 30 of the third embodiment is preferably configured to execute the gas diffusion control process described in the second embodiment when identifying the parameters of the equivalent circuit model ECM.

[0120] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as follows.

[0121] The above-described fuel cell system 1 is preferably configured to perform recovery processing to recover from the abnormal state when the diagnosis result of the internal state of the fuel cell FC by the diagnosis device 30 indicates an abnormal state, but it does not have to be configured in this way. The same applies to the water electrolysis system 1A.

[0122] In the above-described embodiment, an example has been described in which the diagnostic device 30A of the present disclosure is applied to a solid oxide fuel cell FC or an electrolysis device EC, but the application of the diagnostic device 30A is not limited to this. The diagnostic device 30A can also be applied to other reaction devices, such as a polymer electrolyte fuel cell FC or an electrolysis device EC.

[0123] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle.

[0124] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle.

[0125] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., the shapes, positional relationships, etc. are not limited to those unless otherwise specified or when they are fundamentally limited to specific shapes, positional relationships, etc.

[0126] The controller and method of the present disclosure may be implemented on a special-purpose computer by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. The controller and method of the present disclosure may be implemented on a special-purpose computer by configuring a processor with one or more dedicated hardware logic circuits. The controller and method of the present disclosure may be implemented on one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits. The computer program may also be stored on a computer-readable non-transitory tangible storage medium as instructions executed by a computer.

[0127] [Aspects of the present disclosure]

[0128] [First viewpoint] A diagnostic device for diagnosing a reaction device (FC, EC) that outputs electric energy by an electrochemical reaction of a first gas that serves as an oxidant and a second gas that serves as a reductant, or that receives as input a first gas that serves as a reductant and a second gas that serves as an oxidant, and electrolyzes the second gas using electric energy to output fuel, an impedance measuring unit (32, 32A) that measures the internal impedance of the reaction device based on an AC signal including a plurality of frequencies output from the reaction device; a memory unit (M) in which an equivalent circuit model simulating the electrochemical characteristics of the reaction device is stored; a parameter identification unit (34, 34A) that compares the internal impedance measured by the impedance measurement unit with the equivalent circuit model to identify a plurality of parameters that configure the equivalent circuit model; a state diagnosis unit (36, 36A) that diagnoses an internal state of the reaction equipment based on the equivalent circuit model in which the parameters identified by the parameter identification unit are reflected, the equivalent circuit model includes one or more anode diffusion resistances and one or more anode diffusion capacitances as the parameters representing the gas transport characteristics of the anode of the reactor; The parameter identification unit identifies the parameters including the anode diffusion resistance and the anode diffusion capacitance based on a physical quantity that has a correlation with a gas diffusion rate in the anode of the reactor.

[0129] [Second viewpoint] A diagnostic device for diagnosing a reaction device (FC, EC) that outputs electric energy by an electrochemical reaction of a first gas that serves as an oxidant and a second gas that serves as a reductant, or that receives as input a first gas that serves as a reductant and a second gas that serves as an oxidant, and electrolyzes the second gas using electric energy to output fuel, an impedance measuring unit (32, 32A) that measures the internal impedance of the reaction device based on an AC signal including a plurality of frequencies output from the reaction device; a memory unit (M) in which an equivalent circuit model simulating the electrochemical characteristics of the reaction device is stored; a parameter identification unit (34, 34A) that compares the internal impedance measured by the impedance measurement unit with the equivalent circuit model to identify a plurality of parameters that configure the equivalent circuit model; a state diagnosis unit (36, 36A) that diagnoses an internal state of the reaction equipment based on the equivalent circuit model in which the parameters identified by the parameter identification unit are reflected, the equivalent circuit model includes one or more cathode diffusion resistances and one or more cathode diffusion capacitances as the parameters representing the gas transport characteristics of the cathode of the reactor; The parameter identification unit identifies the parameters including the cathode diffusion resistance and the cathode diffusion capacitance based on a physical quantity that has a correlation with a gas diffusion rate in the cathode of the reaction device.

[0130] [Third Perspective] A diagnostic device for diagnosing a reaction device (FC, EC) that outputs electric energy by an electrochemical reaction of a first gas that serves as an oxidant and a second gas that serves as a reductant, or that receives as input a first gas that serves as a reductant and a second gas that serves as an oxidant, and electrolyzes the second gas using electric energy to output fuel, an impedance measuring unit (32, 32A) that measures the internal impedance of the reaction device based on an AC signal including a plurality of frequencies output from the reaction device; a memory unit (M) in which an equivalent circuit model simulating the electrochemical characteristics of the reaction device is stored; a parameter identification unit (34, 34A) that compares the internal impedance measured by the impedance measurement unit with the equivalent circuit model to identify a plurality of parameters that configure the equivalent circuit model; a state diagnosis unit (36, 36A) that diagnoses an internal state of the reaction equipment based on the equivalent circuit model in which the parameters identified by the parameter identification unit are reflected, the equivalent circuit model includes one or more anode diffusion resistances and one or more anode diffusion capacitances as the parameters indicating the gas transport characteristics of the anode of the reactor, and includes one or more cathode diffusion resistances and one or more cathode diffusion capacitances as the parameters indicating the gas transport characteristics of the cathode of the reactor; The parameter identification unit identifies the parameter based on a first physical quantity that is correlated with a gas diffusion rate in an anode of the reaction device and a second physical quantity that is correlated with a gas diffusion rate in a cathode of the reaction device.

[0131] [Fourth viewpoint] In the equivalent circuit model, when a circuit formed by the anode diffusion resistance and the anode diffusion capacitance is an anode diffusion component, The diagnostic device according to the first or third aspect, wherein the parameter identification unit determines a cutoff frequency of the anode diffusion component specified using the anode diffusion resistance and the anode diffusion capacitance as a physical quantity correlated with a gas diffusion rate in the anode, and identifies the parameter based on the cutoff frequency of the anode diffusion component.

[0132] [Fifth viewpoint] In the equivalent circuit model, when a circuit formed by the cathode diffusion resistance and the cathode diffusion capacitance is defined as a cathode diffusion component, The diagnostic device according to the second or third aspect, wherein the parameter identification unit determines a cutoff frequency of the cathode diffusion component specified using the cathode diffusion resistance and the cathode diffusion capacitance as a physical quantity correlated with a gas diffusion rate in the cathode, and identifies the parameter based on the cutoff frequency of the cathode diffusion component.

[0133] [Sixth viewpoint] In the equivalent circuit model, when a circuit formed by the anode diffusion resistance and the anode diffusion capacitance is defined as an anode diffusion component, and a circuit formed by the cathode diffusion resistance and the cathode diffusion capacitance is defined as a cathode diffusion component, the parameter identification unit determines a cutoff frequency of the anode diffusion component specified using the anode diffusion resistance and the anode diffusion capacitance as a physical quantity correlated with a gas diffusion rate at the anode of the reactor, and determines a cutoff frequency of the cathode diffusion component specified using the cathode diffusion resistance and the cathode diffusion capacitance as a physical quantity correlated with a gas diffusion rate at the cathode, and identifies the parameters based on the cutoff frequencies of the anode diffusion component and the cathode diffusion component, respectively.

[0134] [Seventh viewpoint] 1. An electrochemical reaction system comprising: A diagnostic device (30, 30A) according to any one of the first to sixth aspects; The reaction device; a first gas supply unit (SAP) that controls the amount of a first gas supplied to the reaction device; a second gas supply unit (SFP, SWP) that controls the amount of the second gas supplied to the reaction device; When, of the first gas and the second gas, a gas having a small gas diffusion resistance in the reaction device is defined as a low resistance gas, and a gas having a small gas diffusion resistance in the reaction device is defined as a high resistance gas, The diagnostic device performs at least one of a restriction process that restricts the diffusion of the low-resistivity gas in the reaction device and a promotion process that promotes the diffusion of the high-resistivity gas in the reaction device through control of at least one of the first gas supply unit and the second gas supply unit when identifying the parameters using the parameter identification unit, in an electrochemical reaction system.

[0135] [Eighth viewpoint] 1. An electrochemical reaction system comprising: A diagnostic device (30, 30A) according to any one of the first to sixth aspects; The reaction device; and a control unit (20, 20A) that performs recovery processing to recover from the abnormal state when the diagnosis result of the internal state of the reaction device by the diagnosis device indicates an abnormal state.

[0136] [Ninth viewpoint] the reaction device is a fuel cell (FC) that outputs electric energy through the electrochemical reaction, The diagnostic device (30) is configured to determine whether or not the second gas is in a lack of combustion state based on the gas diffusion characteristics of the anode of the reactor, The electrochemical reaction system according to an eighth aspect, wherein the control unit (20) restores the fuel shortage state to a normal state by the restoration process when the fuel shortage state occurs.

[0137] [10th viewpoint] the reactor is an electrolyzer (EC) that outputs fuel through the electrolysis; the diagnostic device (30A) is configured to determine whether or not a gas shortage state occurs due to a shortage of the second gas based on the gas diffusion characteristics of the cathode of the reaction device; The electrochemical reaction system according to an eighth aspect, wherein the control unit (20A) restores the out-of-gas state to a normal state by the restoration process when the out-of-gas state occurs. [Explanation of symbols]

[0138] 1. Fuel cell system (electrochemical reaction system) 1A Water electrolysis system (electrochemical reaction system) FC fuel cell EC electrolyzer

Claims

1. A diagnostic device for diagnosing a reaction device (FC, EC) that outputs electric energy by an electrochemical reaction of a first gas that serves as an oxidant and a second gas that serves as a reducing agent, or that receives as input a first gas that serves as a reducing agent and a second gas that serves as an oxidant, and electrolyzes the second gas using electric energy to output fuel, an impedance measuring unit (32, 32A) that measures the internal impedance of the reaction device based on an AC signal including a plurality of frequencies output from the reaction device; a memory unit (M) in which an equivalent circuit model simulating the electrochemical characteristics of the reaction device is stored; a parameter identification unit (34, 34A) that compares the internal impedance measured by the impedance measurement unit with the equivalent circuit model to identify a plurality of parameters that configure the equivalent circuit model; a state diagnosis unit (36, 36A) that diagnoses an internal state of the reaction device based on the equivalent circuit model in which the parameters identified by the parameter identification unit are reflected, the equivalent circuit model includes one or more anode diffusion resistances and one or more anode diffusion capacitances as the parameters representing the gas transport characteristics of the anode of the reactor; The parameter identification unit identifies the parameters including the anode diffusion resistance and the anode diffusion capacitance based on a physical quantity that has a correlation with a gas diffusion rate in the anode of the reactor.

2. A diagnostic device for diagnosing a reaction device (FC, EC) that outputs electric energy by an electrochemical reaction of a first gas that serves as an oxidant and a second gas that serves as a reducing agent, or that receives as input a first gas that serves as a reducing agent and a second gas that serves as an oxidant, and electrolyzes the second gas using electric energy to output fuel, an impedance measuring unit (32, 32A) that measures the internal impedance of the reaction device based on an AC signal including a plurality of frequencies output from the reaction device; a memory unit (M) in which an equivalent circuit model simulating the electrochemical characteristics of the reaction device is stored; a parameter identification unit (34, 34A) that compares the internal impedance measured by the impedance measurement unit with the equivalent circuit model to identify a plurality of parameters that configure the equivalent circuit model; a state diagnosis unit (36, 36A) that diagnoses an internal state of the reaction device based on the equivalent circuit model in which the parameters identified by the parameter identification unit are reflected, the equivalent circuit model includes one or more cathode diffusion resistances and one or more cathode diffusion capacitances as the parameters representing the gas transport characteristics of the cathode of the reactor; The parameter identification unit identifies the parameters including the cathode diffusion resistance and the cathode diffusion capacitance based on a physical quantity that has a correlation with a gas diffusion rate in the cathode of the reaction device.

3. A diagnostic device for diagnosing a reaction device (FC, EC) that outputs electric energy by an electrochemical reaction of a first gas that serves as an oxidant and a second gas that serves as a reducing agent, or that receives as input a first gas that serves as a reducing agent and a second gas that serves as an oxidant, and electrolyzes the second gas using electric energy to output fuel, an impedance measuring unit (32, 32A) that measures the internal impedance of the reaction device based on an AC signal including a plurality of frequencies output from the reaction device; a memory unit (M) in which an equivalent circuit model simulating the electrochemical characteristics of the reaction device is stored; a parameter identification unit (34, 34A) that compares the internal impedance measured by the impedance measurement unit with the equivalent circuit model to identify a plurality of parameters that configure the equivalent circuit model; a state diagnosis unit (36, 36A) that diagnoses an internal state of the reaction device based on the equivalent circuit model in which the parameters identified by the parameter identification unit are reflected, the equivalent circuit model includes one or more anode diffusion resistances and one or more anode diffusion capacitances as the parameters indicating the gas transport characteristics of the anode of the reactor, and includes one or more cathode diffusion resistances and one or more cathode diffusion capacitances as the parameters indicating the gas transport characteristics of the cathode of the reactor; The parameter identification unit identifies the parameter based on a first physical quantity that is correlated with a gas diffusion rate in an anode of the reaction device and a second physical quantity that is correlated with a gas diffusion rate in a cathode of the reaction device.

4. In the equivalent circuit model, when a circuit formed by the anode diffusion resistance and the anode diffusion capacitance is an anode diffusion component, 4. The diagnostic device according to claim 1, wherein the parameter identification unit determines a cutoff frequency of the anode diffusion component specified using the anode diffusion resistance and the anode diffusion capacitance as a physical quantity correlated with a gas diffusion rate in the anode of the reactor, and identifies the parameter based on the cutoff frequency of the anode diffusion component.

5. In the equivalent circuit model, when a circuit formed by the cathode diffusion resistance and the cathode diffusion capacitance is defined as a cathode diffusion component, 4. The diagnostic device according to claim 2, wherein the parameter identifying unit determines a cutoff frequency of the cathode diffusion component specified using the cathode diffusion resistance and the cathode diffusion capacitance as a physical quantity correlated with a gas diffusion rate in the cathode, and identifies the parameter based on the cutoff frequency of the cathode diffusion component.

6. In the equivalent circuit model, when a circuit formed by the anode diffusion resistance and the anode diffusion capacitance is defined as an anode diffusion component, and a circuit formed by the cathode diffusion resistance and the cathode diffusion capacitance is defined as a cathode diffusion component, 4. The diagnostic device according to claim 3, wherein the parameter identification unit determines a cutoff frequency of the anode diffusion component specified using the anode diffusion resistance and the anode diffusion capacitance as a physical quantity correlated with a gas diffusion rate at the anode of the reactor, and determines a cutoff frequency of the cathode diffusion component specified using the cathode diffusion resistance and the cathode diffusion capacitance as a physical quantity correlated with a gas diffusion rate at the cathode of the reactor, and identifies the parameters based on the cutoff frequencies of the anode diffusion component and the cathode diffusion component, respectively.

7. 1. An electrochemical reaction system comprising: A diagnostic device (30, 30A) according to any one of claims 1 to 3; The reaction device; a first gas supply unit (SAP) that controls the amount of a first gas supplied to the reaction device; a second gas supply unit (SFP, SWP) that controls the supply amount of the second gas to the reaction device; When, of the first gas and the second gas, a gas having a small gas diffusion resistance in the reaction device is defined as a low resistance gas, and a gas having a small gas diffusion resistance in the reaction device is defined as a high resistance gas, The diagnostic device performs at least one of a restriction process that restricts the diffusion of the low-resistivity gas in the reaction device and a promotion process that promotes the diffusion of the high-resistivity gas in the reaction device through control of at least one of the first gas supply unit and the second gas supply unit when identifying the parameters using the parameter identification unit, in an electrochemical reaction system.

8. 1. An electrochemical reaction system comprising: A diagnostic device (30, 30A) according to any one of claims 1 to 3; The reaction device; and a control unit (20, 20A) that performs recovery processing to recover from the abnormal state when the diagnosis result of the internal state of the reaction device by the diagnostic device indicates an abnormal state.

9. the reaction device is a fuel cell (FC) that outputs electric energy through the electrochemical reaction; The diagnostic device (30) is configured to determine whether or not the second gas is in a lack of combustion state based on the gas diffusion characteristics of the anode of the reaction device, 9. The electrochemical reaction system according to claim 8, wherein the control unit (20) restores the fuel shortage state to a normal state by the restoration process when the fuel shortage state occurs.

10. the reaction device is an electrolysis device (EC) that outputs fuel by the electrolysis, the diagnostic device (30A) is configured to determine whether or not a gas shortage state occurs due to a shortage of the second gas based on the gas diffusion resistance of the cathode of the reaction device, 9. The electrochemical reaction system according to claim 8, wherein, when the gas is out of the state, the control unit (20A) restores the gas out of the state to a normal state by the restoration process.

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