Fuel cell performance estimation device

Abstract

To provide a fuel cell performance estimation device capable of estimating a net performance of a temporally deteriorated solid polymer fuel cell.SOLUTION: A fuel cell performance estimation device comprises: (A) first means sequentially acquiring a voltage V[i] and a current I[i] of a solid polymer fuel cell at a time [i], and storing them in a memory and; (B) second means calculating a catalyst potential Vcat[i] of a cathode at the time [i], calculating a surface utilization rate θact[i] of the acquired effective noble metal system catalyst particle at the time [i] by using the calculated catalyst potential Vcat[i], and storing them into a memory; (C) third means calculating an electrode catalyst surface area AECS[i] at the time [i] and an activation SA[i] per surface area of the noble metal system catalyst particle at the time [i] by using the V[i], the Vcat[i], and / or an accumulation time of power generation, and storing them into the memory; and (D) fourth means of calculating an estimated value IVest[i] of an IV characteristic by using a θact[i], an AECS[i], and the SA[i], and storing them into the memory.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a fuel cell performance estimating device, and more particularly to a fuel cell performance estimating device capable of estimating the net performance of a polymer electrolyte fuel cell that has deteriorated over time. [Background technology]

[0002] A polymer electrolyte fuel cell is equipped with a membrane electrode assembly (MEA) in which catalyst-containing catalyst layers are bonded to both sides of an electrolyte membrane. The catalyst layer is the reaction field for the electrode reaction, and generally consists of a composite of carbon carrying catalyst particles such as platinum and a solid polymer electrolyte (catalyst layer ionomer). In a polymer electrolyte fuel cell, a gas diffusion layer is usually arranged on the outside of the catalyst layer. A current collector (separator) equipped with a gas flow path is also arranged on the outside of the gas diffusion layer. A polymer electrolyte fuel cell usually has a structure (fuel cell stack) in which a plurality of unit cells each consisting of such an MEA, gas diffusion layer, and current collector are stacked.

[0003] When a polymer electrolyte fuel cell is used as an on-board power source, the voltage of the polymer electrolyte fuel cell varies greatly depending on the driving conditions of the vehicle. When the polymer electrolyte fuel cell is in a low-load state, the power generation efficiency is high, but the cathode catalyst is exposed to a high potential state, so that the catalytic components are easily eluted from the cathode catalyst. On the other hand, when the polymer electrolyte fuel cell is in a high-load state, the power generation efficiency is low, but the cathode catalyst is exposed to a low potential state, so that the eluted catalytic components are easily redeposited on the surface of the cathode catalyst. Therefore, when the cathode catalyst is repeatedly exposed to high and low potential states, there is a problem that the cathode catalyst gradually deteriorates.

[0004] On the other hand, the performance of a polymer electrolyte fuel cell is affected not only by the steady voltage drop caused by catalyst degradation, but also by temporary voltage fluctuations caused by changes in power generation conditions (i.e., voltage fluctuations caused by the formation and reduction of an oxide film on the catalyst surface). Therefore, it is difficult to accurately estimate the true performance of a polymer electrolyte fuel cell at the current time by simply monitoring the voltage of the polymer electrolyte fuel cell, which changes from moment to moment.

[0005] In order to solve this problem, various proposals have been made in the past. For example, Patent Document 1 states: (a) measuring a fuel cell stack voltage of a fuel cell power generation system; (b) changing the effective electrode area of ​​the fuel cell in the simulation model so that the stack voltage of the simulation model follows the fuel cell stack voltage; (c) If the effective electrode area of ​​the fuel cell in the simulation model falls outside the normal range, it is determined to be abnormal. A fuel cell power generation monitoring system is disclosed. The same document states: (A) This method makes it possible to accurately monitor the deterioration state inside the fuel cell power generation system; and (B) By using such a simulation model, it is possible to obtain a future prediction of the effective electrode area of ​​the fuel cell if operation continues under the current conditions. is stated.

[0006] In Patent Document 2, (a) A time (learning stop time) from the start of power generation until a change in the current-voltage characteristics occurs due to the formation of an oxide film on the catalyst of the oxidizer electrode is set in advance, (b) approximating the relationship between the fuel cell current X and voltage Y with a linear equation: Y = A × X + B, and updating parameters A and B using the current X and voltage Y obtained from the start of power generation until the learning stop time is reached; (c) Substituting the rated current Imax of the fuel cell into a linear equation including the updated parameters A and B, calculates the expected voltage Vmin (=A×Imax+B) for Imax; (e) When Vmin falls below a predetermined value, it is determined that the fuel cell has deteriorated. A controller for a fuel cell system is disclosed.

[0007] The same document states: (A) When an oxide film is formed on the catalyst of the oxidizer electrode, a recoverable change in characteristics occurs. However, if a deterioration diagnosis is performed based on the recoverable change in characteristics, an erroneous deterioration diagnosis will be performed; and (B) In the case where the current-voltage characteristics of a fuel cell are approximated by a linear equation, if the calculation for updating parameters A and B is stopped before an oxide film is formed on the catalyst of the oxidizer electrode (before the learning stop time is reached), the change in characteristics caused by the formation of the oxide film is not taken into consideration when updating parameters A and B, so that deterioration of the fuel cell can be detected with high accuracy. is stated.

[0008] Patent Document 3 states: (a) The initial voltage of the fuel cell is V 1 , the voltage immediately after the Nth start is V 2n , the elapsed time T from the Nth startup n After this time, the voltage is V 3n After the Nth operation is stopped, the voltage when the oxide film on the cathode catalyst surface is reduced by the crossover hydrogen is V 4n In the case where T n Based on this, the recoverable voltage drop (=V 4n -V 3n ) is estimated, (b) Total voltage drop (=V 1 -V 3n ) to calculate the recoverable voltage drop (=V 4n -V 3n ) to determine the irrecoverable voltage drop (=V 1 -V 4n ) is calculated, (c) determining that the fuel cell has deteriorated when the amount of irrecoverable voltage drop reaches or exceeds a predetermined value; A fuel cell system is disclosed. The document describes that this method makes it possible to accurately estimate the amount of irrecoverable voltage drop.

[0009] Furthermore, Patent Document 4 states: (a) using an operating state acquisition means, acquiring a relationship between an oxidation-reduction reaction rate of a Pt catalyst used in the fuel cell and an output voltage or a temperature of the fuel cell; (b) Using a characteristic estimation means, a current-voltage hysteresis H is calculated based on the obtained relationship, and an IV characteristic is estimated based on the calculated current-voltage hysteresis H. A fuel cell system is disclosed.

[0010] The method described in Patent Document 1 is a method for determining an abnormality when the effective electrode area of ​​a fuel cell falls outside the normal range, and does not take into account temporary fluctuations in cell voltage. Therefore, temporary fluctuations in cell voltage may be regarded as changes in the effective electrode area of ​​the fuel cell, and the simulation model may be corrected. As a result, there is a risk of detecting an abnormality even when the fuel cell is normal.

[0011] The method described in Patent Document 2 suppresses erroneous deterioration diagnosis by setting a learning stop time and not using data after the occurrence of voltage fluctuations due to oxides for updating parameters A and B. However, fuel cells generally generate power in many cases with oxides attached to the catalyst surface. Therefore, the method described in Patent Document 2 has the problem that accurate deterioration diagnosis cannot be performed for most of the time during power generation.

[0012] The methods described in Patent Documents 3 and 4 correct the current-voltage characteristics by adjusting the effect of oxides by elapsed time or hysteresis, and judge the presence or absence of degradation using the corrected current-voltage characteristics. However, fuel cells used in vehicles and the like rarely continue to operate at a constant load, and the current and voltage usually change in a complex pattern. Therefore, there is a risk that the accuracy of estimating degradation will decrease in the method of correcting the current-voltage characteristics by using elapsed time or hysteresis.

[0013] Furthermore, the performance of a fuel cell varies not only due to steady voltage drops caused by catalyst degradation and temporary voltage fluctuations caused by the formation and reduction of an oxide film on the catalyst surface, but also due to voltage drops caused by failures (irreversible voltage drops that occur accidentally due to causes other than catalyst degradation). However, there have been no examples of fuel cell performance estimation devices proposed that are capable of accurately determining voltage drops caused by failures without being affected by steady voltage drops or temporary voltage fluctuations. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] JP 2007-305327 A [Patent Document 2] JP 2006-139935 A [Patent Document 3] JP 2006-147404 A [Patent Document 4] International Publication No. 2011 / 036765 Summary of the Invention [Problem to be solved by the invention]

[0015] An object of the present invention is to provide a fuel cell performance estimating device capable of estimating the net performance of a polymer electrolyte fuel cell that has deteriorated over time. Another problem to be solved by the present invention is to provide a fuel cell performance estimating device that can accurately determine the presence or absence of a malfunction. [Means for solving the problem]

[0016] In order to solve the above problems, a fuel cell performance estimation device according to the present invention comprises: (A) a first means for sequentially acquiring at least a voltage V[i] and a current I[i] of a polymer electrolyte fuel cell at a time [i] and storing the V[i] and the I[i] in a memory; (B) calculating a catalytic potential Vcat[i] of the cathode of the polymer electrolyte fuel cell at the time [i] using at least the V[i]; Using the Vcat[i], an effective surface utilization rate θact[i] of the precious metal-based catalyst particles contained in the solid polymer fuel cell at the time [i] is calculated; A second means for storing the Vcat[i] and the θact[i] in the memory; (C) Using the V[i], the Vcat[i], and / or the integrated time of power generation of the solid polymer electrolyte fuel cell, the electrode catalyst surface area A at the time [i] ECS [i] and the activity SA[i] per surface area of ​​the precious metal catalyst at the time [i] are calculated, and the A ECS a third means for storing the SA[i] and the SA[i] in the memory; (D) Said θact[i], said A ECS a fourth means for calculating an estimated value IVest[i] of an IV characteristic that indicates a relationship between I[i] and an estimated voltage Vest[i] of the solid polymer electrolyte fuel cell, using I[i] and SA[i], and storing the IVest[i] in the memory; It is equipped with:

[0017] The fuel cell performance estimation device according to the present invention comprises: (E) A fifth means for determining a failure of the polymer electrolyte fuel cell by using the IVest[i]. It may further comprise: Effect of the Invention

[0018] By sequentially acquiring the voltage V[i] and current I[i] of the polymer electrolyte fuel cell at time [i], it is possible to calculate the cathode catalytic potential Vcat[i] using at least V[i]. In addition, by knowing Vcat[i], it is possible to calculate the effective surface utilization rate θact[i] of the precious metal catalyst. θact[i] is correlated with temporary voltage fluctuations caused by the formation and reduction of an oxide film. In addition, when V[i], Vcat[i], or the cumulative time of power generation is known, the electrode catalyst surface area A at time [i] can be calculated using these. ECS [i] and the activity per surface area SA[i] of the precious metal catalyst at time [i] can be calculated. ECS Both [i] and SA[i] are correlated with steady voltage drops caused by catalyst deterioration.

[0019] Furthermore, the obtained I[i], the calculated θact[i], A ECS Using [i] and SA[i], it is possible to calculate an estimated value IVest[i] of the IV characteristics of the polymer electrolyte fuel cell at time [i]. The IVest[i] obtained in this way represents a current-voltage characteristic that is free of the effects of steady voltage drops caused by catalyst deterioration and temporary voltage fluctuations caused by the formation and reduction of an oxide film on the catalyst surface (i.e., an estimated value of the current-voltage characteristic assuming that no failure has occurred). Therefore, by comparing the actual current-voltage characteristic IV[i] of the polymer electrolyte fuel cell at time [i] with IVest[i], it is possible to accurately determine whether or not a failure has occurred. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is a schematic cross-sectional view of a Pt particle on which an oxide film is formed. [Diagram 2] 13 is a flowchart for calculating an estimated value IVest[i] of the current-voltage characteristics and for determining a fault. [Diagram 3]FIG. 13 is a diagram showing the relationship between the estimated value IVest[i] of the current-voltage characteristics, the sensor value 1 (the actual measured value IV[i] of the current-voltage characteristics under normal conditions), and the sensor value 2 (the actual measured value IV'[i] of the current-voltage characteristics under fault conditions). [Figure 4] Fig. 4(A) is a schematic diagram of the current-voltage characteristics when power is generated under certain power generation conditions. Fig. 4(B) is a schematic diagram of the current fluctuations and voltage fluctuations when a fuel cell (FC) vehicle is in operation. Fig. 4(C) is a schematic diagram of the actual measured values ​​of the current-voltage characteristics obtained by plotting the relationship between the current and voltage shown in Fig. 4(B) as a scatter diagram. [Diagram 5] FIG. 13 is a schematic diagram of fault determination using an estimated value IVest[i] of the current-voltage characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] An embodiment of the present invention will be described in detail below. [1. Fuel cell performance estimation device] The fuel cell performance estimation device according to the present invention comprises: (A) a first means for sequentially acquiring at least a voltage V[i] and a current I[i] of a polymer electrolyte fuel cell at a time [i] and storing the V[i] and the I[i] in a memory; (B) calculating a catalytic potential Vcat[i] of the cathode of the polymer electrolyte fuel cell at the time [i] using at least the V[i]; Using the Vcat[i], an effective surface utilization rate θact[i] of the precious metal-based catalyst particles contained in the solid polymer fuel cell at the time [i] is calculated; A second means for storing the Vcat[i] and the θact[i] in the memory; (C) Using the V[i], the Vcat[i], and / or the integrated time of power generation of the solid polymer electrolyte fuel cell, the electrode catalyst surface area A at the time [i] ECS [i] and the activity SA[i] per surface area of ​​the precious metal catalyst at the time [i] are calculated, and the A ECS a third means for storing the SA[i] and the SA[i] in the memory; (D) Said θact[i], said A ECS a fourth means for calculating an estimated value IVest[i] of an IV characteristic that indicates a relationship between I[i] and an estimated voltage Vest[i] of the solid polymer electrolyte fuel cell, using I[i] and SA[i], and storing the IVest[i] in the memory; It is equipped with:

[0022] The fuel cell performance estimation device according to the present invention comprises: (E) A fifth means for determining a failure of the polymer electrolyte fuel cell by using the IVest[i]. It may further comprise:

[0023] [1.1. First means] The first means is a means for sequentially acquiring at least the voltage V[i] and current I[i] of the polymer electrolyte fuel cell at time [i], and storing V[i] and I[i] in a memory. The first means may further include, in addition to V[i] and I[i], a means for sequentially acquiring the high-frequency impedance R[i] of the solid polymer fuel cell at time [i] and storing R[i] in a memory. Furthermore, the first means further acquires, in addition to V[i] and I[i], a high-frequency impedance R[i] and a temperature T FC The control unit 10 may further include means for sequentially acquiring the cathode air pressure Pca[i], the cathode air stoichiometry STca[i], and the cathode air pressure Pca[i], and storing these in a memory.

[0024] Various physical property values ​​in the first means (i.e., V[i], I[i], R[i], T FC The method of acquiring I[i], Pca[i], and STca[i] is not particularly limited, and the most suitable method can be selected according to the type of physical property. For example, it is preferable to measure R[i] by superimposing a high frequency on I[i] or V[i] using FDC or the like. In the present invention, the temperature T FCStrictly speaking, "[i]" refers to the temperature of the cathode catalyst, but when the temperature of the cathode catalyst cannot be measured directly, it is preferable to measure a temperature that can be regarded as equivalent to the temperature of the cathode catalyst (for example, the temperature of the cooling water discharged from the solid polymer fuel cell). The same applies to other physical properties, and a physical property value X that is difficult to measure directly may be substituted with another physical property value X' that can be regarded as equivalent to the physical property value X and is easy to measure.

[0025] These physical property values ​​acquired in the first means are used to calculate various physical property values ​​required to calculate the estimated value IVest[i] of the IV characteristics. For example, V[i] is used to calculate the catalytic potential Vcat[i] of the cathode catalyst. In addition to V[i], I[i] and R[i] may also be used to calculate the catalytic potential Vcat[i] of the cathode catalyst. The calculated Vcat[i] is further used to calculate other physical property values ​​necessary for calculating the estimated value IVest[i] of the IV characteristic. Also, R[i], T FC [i], Pca[i], and STca[i] may be used to calculate a more accurate estimate of the IV characteristics, IVest[i].

[0026] Here, "voltage V[i]" refers to the potential difference across the fuel cell stack at time [i] (ie, the total voltage of the polymer electrolyte fuel cells). Strictly speaking, the "catalytic potential Vcat[i] of the cathode catalyst" refers to the value obtained by adding the potential drop caused by the internal resistance to the potential of the cathode of each single cell. Strictly speaking, Vcat[i] is calculated based on V[i], I[i], and R[i], but when R[i] cannot be obtained, it may be calculated by an approximation using only V[i]. Details of the calculation method of Vcat[i] will be described later.

[0027] [1.2. Second means] The second method is calculating a catalytic potential Vcat[i] of the cathode of the polymer electrolyte fuel cell at the time [i] using at least the V[i]; Using the Vcat[i], an effective surface utilization rate θact[i] of the precious metal-based catalyst particles contained in the solid polymer fuel cell at the time [i] is calculated; The Vcat[i] and the θact[i] are stored in the memory. It is a means.

[0028] [1.2.1. Calculation of Vcat[i]] First, the catalytic potential Vcat[i] of the cathode of the polymer electrolyte fuel cell at time [i] is calculated using at least V[i]. The calculated Vcat[i] is stored in memory.

[0029] In the present invention, the method of calculating Vcat[i] is not particularly limited. For example, the second means may include a means for calculating Vcat[i] using the following formula (1). Vcat[i] expressed by formula (1) is an approximation of Vcat[i] that ignores the potential drop caused by internal resistance. Formula (1) is less accurate than formula (2) described later. However, by using formula (1), Vcat[i] can be calculated without using I[i] and R[i], so the calculation of Vcat[i] can be simplified.

[0030]

number

[0031] Moreover, the second means may include means for calculating the Vcat[i] using the following equation (2) instead of or in addition to the above-mentioned equation (1). Strictly speaking, Vcat[i] is expressed by the formula (2). In the formula (2), the first term on the right side represents the potential difference (cell voltage) between both ends of the single cell. In the first term on the right side, V[i] is multiplied by N cellThe potential per cell is calculated by dividing by . The second term on the right side represents the potential drop due to internal resistance per unit cell. In the second term on the right side, I[i] and R[i] are converted to values ​​per area or per cell, respectively. Using equation (2) makes it possible to accurately calculate Vcat[i]. In order to accurately calculate IVest[i], it is preferable to use equation (2) to calculate Vcat[i].

[0032]

number

[0033] [1.2.2. Calculation of θact[i]] Next, the effective surface utilization rate θact[i] of the precious metal catalyst particles contained in the solid polymer fuel cell at time [i] is calculated using Vcat[i]. The calculated θact[i] is stored in memory. Here, the "effective surface utilization rate θact[i]" refers to the ratio of the area of ​​the surface utilized for the oxygen reduction reaction (ORR) (i.e., the surface not covered with an oxide film) to the surface area of ​​the precious metal catalyst particle.

[0034] [A. Precious metal catalyst particles] In the present invention, the term "precious metal catalyst particles (hereinafter, simply referred to as "catalyst particles")" refers to particles made of a metal or alloy containing a precious metal element, and which have activity in the oxygen reduction reaction (ORR). In the present invention, the material of the catalyst particles is not particularly limited as long as it exhibits ORR activity. (a) Precious metals (Au, Ag, Pt, Pd, Rh, Ir, Ru, Os), (b) An alloy containing two or more precious metal elements; (c) Alloys containing one or more precious metal elements and one or more base metal elements (e.g., Fe, Co, Ni, Cr, V, Ti, etc.) etc.

[0035] [B. Types of oxides] When the catalyst particles on the cathode side are exposed to a high potential, the catalyst components are more likely to dissolve from the catalyst particles. On the other hand, when the catalyst particles are exposed to a high potential, an oxide film (including hydroxide) is formed on the surface of the catalyst particles, which inhibits the dissolution of the catalyst components from the catalyst particles. However, because the rate at which the oxide film forms is slow, if the potential of the cathode fluctuates suddenly, the formation of the oxide film is delayed, and the catalyst components are more likely to dissolve from the catalyst particles. In other words, if the fuel cell is used continuously in an environment where sudden potential fluctuations are repeated, the catalyst particles will eventually deteriorate. In other words, the durability of the cathode-side precious metal-based catalyst particles depends on the total amount of precious metal oxide and precious metal hydroxide present on the surface of the precious metal-based catalyst particles. On the other hand, the surface of the precious metal catalyst particle covered with an oxide film has a lower ORR activity than the surface that is not covered with an oxide film. Therefore, the IV characteristics of the solid polymer electrolyte fuel cell depend on the θact[i] of the catalyst particle.

[0036] The precious metal oxide present on the surface of the precious metal catalyst particles is (a) precious metal hydroxide adsorbed on the surface of precious metal-based catalyst particles; (b) precious metal oxide adsorbed on the surface of precious metal-based catalyst particles; and (c) Precious metal oxide formed just below the surface of a precious metal catalyst particle due to oxygen diffusion into the particle. They can be broadly divided into:

[0037] A schematic cross-sectional view of a Pt particle on which an oxide film has been formed is shown in Figure 1. When a Pt particle is exposed to a high potential, an oxide (including a hydroxide) is formed on the surface of the Pt particle. In this case, the oxide on the surface of the Pt particles is (a) Pt hydroxide (PtOH) adsorbed on the surface of Pt particles ad ), (b) Pt oxide (PtO ad ), and (c) Oxygen diffuses into the interior of Pt particles, forming Pt oxide (PtO sub ) It consists of:

[0038] Where PtOH ad The coverage of the precious metal hydroxide adsorbed on the surface of the precious metal catalyst particle at time i is defined as θox1[i]. θox1[i] is the surface area (S 0 ) relative to the area of ​​the precious metal hydroxide adsorbed on the surface of the precious metal catalyst particle (S 1 ) ratio (=S 1 / S 0 ) Similarly, PtO ad The coverage of the precious metal oxide adsorbed on the surface of the precious metal catalyst particle at time i is θox2[i]. θox2[i] is the coverage of the precious metal oxide adsorbed on the surface of the precious metal catalyst particle at time i. 0 The area of ​​the precious metal oxide adsorbed on the surface of the precious metal catalyst particle (S 2 ) ratio (=S 2 / S 0 ) Similarly, PtO sub The coverage of the precious metal oxide present inside the precious metal catalyst particle at time i is defined as θox3[i]. θox3[i] is defined as S 0 The area of ​​the precious metal oxide present inside the precious metal catalyst particle (S 3 ) ratio (=S 3 / S 0 )

[0039] As shown in Figure 1, PtOH was applied to the surface of the Pt particles. ad or PtO ad Just below the area where PtO is adsorbed sub Therefore, the coverage of the entire Pt particle does not necessarily coincide with the sum of θox1[i] to θox3[i]. Each of θox1[i] to θox3[i] can be calculated sequentially using a reaction model based on the reaction rate equation. Also, once θox1[i] to θox3[i] are known, they can be used to calculate θact[i].

[0040] [C. Reaction Model] There are various methods for calculating θact[i]. In the present invention, the method for calculating θact[i] is not particularly limited, and an optimal method can be used depending on the purpose. The calculated θact[i] is stored in the memory. In particular, the second means preferably includes a means for calculating θact[i] using the following formula (3) and / or formula (4). Either one of these may be used to calculate θact[i], or they may be used separately depending on the purpose.

[0041]

number

[0042] however, θox1[i] is the coverage of the precious metal hydroxide adsorbed on the surface of the precious metal-based catalyst particle at the time [i]; θox2[i] is the coverage of the precious metal oxide adsorbed on the surface of the precious metal-based catalyst particle at the time [i]; θox3[i] is the coverage of the precious metal oxide present inside the precious metal-based catalyst particle at the time [i]; Γ is the maximum amount of oxygen coverage per unit surface area (constant), Ts is the calculation step size. α 1 ~α 4 , α 11 ~α 17 , α 21 ~α 27 , α 31 ~α 37 are the fitting coefficients, respectively.

[0043] Specifically, Ts represents the time from time [i-1] to time [i]. The value of Ts is not particularly limited, and it is preferable to set an optimal value according to the purpose. Ts is usually set in the range of 0.01 s to 100 s. α 1 ~α 37 are preferably determined so as to fit the actual IV characteristics and test results obtained by cyclic voltammetry (CV), respectively. v 1 ~v 3 is each oxide or hydroxide (MO ad , M.O.H. ad , M.O. sub ) reaction rate. G 1 ~G 3 v 1 ~v 3 represents the free energy of the reaction.

[0044] θox1[i-1], θox2[i-1], and θox3[i-1] are the coverages at time [i-1], and are already stored in the memory. θox1[i-1], θox2[i-1], and θox3[i-1] can be calculated by sequential calculations if the initial values ​​are known. The initial values ​​may be held at the time of the previous stop, and may be used as the initial values. In general, when the fuel cell is stopped, it is often held at a low potential, and at that time, all oxides are reduced. Therefore, the initial values ​​after stopping may be θox1=θox2=θox3=0. Therefore, if Vcat[i] is obtained, θact[i] can be calculated from equation (3) or equation (4).

[0045] Equation (4) is the total surface (α 1 ) and the respective coverage and coefficient (α 2 ~α 4) is multiplied by θox1[i] and then subtracted to calculate θact[i]. θox1[i] represents the coverage of hydroxide by one-electron reaction. θox2[i] and θox3[i] represent the coverage of oxide by two-electron reaction, respectively. Assuming that one platinum surface site is destroyed per one-electron reaction, α 1 = 1, α 2 = 1, α 3 = 2, α 4 In actual use, the platinum surface is not uniform, so α 1 ~α 4 is determined as applicable to the test results.

[0046] However, formula (4) does not take into account that the surface oxidized species (coverage θox1[i], θox2[i]) and the internal oxidized species (coverage θox3[i]) occur at the same platinum site, and in such a case, there is a concern that θact[i] may be underestimated. For example, when Vcat[i] remains high continuously, the above problem becomes more pronounced as θox1[i], θox2[i], and θox3[i] each become large, and there is a concern that the accuracy may decrease. In contrast, formula (3) has the advantage that it can estimate with high accuracy even in the above case by taking the ratio of the surface oxidized species to the internal oxidized species. On the other hand, in other cases, there is a concern that formula (3) may have lower accuracy than formula (4).

[0047] [1.3. Third means] The third means calculates the electrode catalyst surface area A at time [i] using V[i], Vcat[i], and / or the integrated time of power generation of the solid polymer electrolyte fuel cell. ECS The activity SA[i] per surface area of ​​the precious metal catalyst at time [i] and time [i] is calculated, and A ECS SA[i] and SA[i] are stored in memory.

[0048] [1.3.1. Electrocatalyst surface area A ECS Calculation of [i] "Electrocatalyst surface area A ECS"[i]" refers to the electrochemically effective surface area of ​​the precious metal catalyst particle at time [i]. ESC There are various methods for calculating [i]. ECS The method of calculating [i] is not particularly limited, and the most suitable method can be used depending on the purpose. ECS [i] is stored in memory.

[0049] The third means calculates A using the following formula (5), formula (6), and / or formula (7): ECS It is preferable that the method includes a means for calculating [i]. ECS To calculate [i], any one of these may be used, or they may be used in combination depending on the purpose.

[0050]

number

[0051] however, A ECS0 is the initial value (constant) of the electrode catalyst surface area, Ts is the calculation step size. B 1 , D 1 , D 2 , D 3 , D 4 are the fitting coefficients, respectively. In addition, A ECS0 , B 1 , D 1 , D 2 , D 3 , and D 4 It is preferable to perform separate power generation tests in advance and set the values ​​so as to match the test results.

[0052] Equation (5) is expressed as A using the cumulative time (=ΣTs) of power generation in the solid polymer electrolyte fuel cell. ESC This is a formula for calculating [i]. In general, the longer the cumulative time of power generation in a fuel cell, the greater the number of times that catalyst particles are dissolved and reprecipitated. ECS[i] decreases monotonically with the accumulation time. Equation (5) is ECS This is an approximation formula that approximates the change in [i] as a linear function of the integrated time. Equation (5) has low estimation accuracy, but has the advantage of reducing calculation costs.

[0053] Equation (6) is expressed as A using Ts, θact[i], and Vcat[i]. ECS This is the formula for calculating [i]. Compared to formula (5), formula (6) is ECS In equation (5), A is calculated based on the assumption that dissolution and precipitation of the catalyst components occurs regardless of Vcat[i]. ECS [i] is calculated, but A ECS [i] should actually depend on Vcat[i]. In formula (6), we focus on the phenomenon during dissolution and assume that the amount of dissolution is proportional to an exponential function with e as the base and Vcat[i] as the power exponent. We also assume that the dissolution phenomenon of the catalyst component occurs only in areas not covered by oxides, and multiply the above exponential function by θact[i]. On the other hand, formula (6) has the disadvantage of being more expensive to calculate than formula (5).

[0054] Equation (7) is expressed as A using Ts, θact[i], and V[i]. ECS Equation (7) has the advantage that it does not require the measurement of the high frequency impedance R[i] required to calculate Vcat[i] expressed by equation (2), but it has the disadvantage that the accuracy is reduced.

[0055] A using equations (6) to (7) ECS The calculation in [i] may be replaced in whole or in part by a more sophisticated physical model calculation, such as that described in Reference 1. Using the physical model calculation, A ECS The estimation accuracy of [i] can be improved. Here, the "physical model" refers to a model that uses a theoretical formula to estimate the degradation of the electrode catalyst over time and calculates the A ECSThis refers to a model that can estimate A[i] (and SA[i], which will be described later). For example, Reference 2 discloses a method for predicting the deterioration of an electrode catalyst in a fuel cell. Using the method described in the same document, A ECS [i] can be estimated. Such a physical model is also reported in Reference 3 below.

[0056] [Reference 1] Darling, RM and JP Meyers(2003), "Kineti model of platinum dissolution in PEMFCs," Journal of the Electrochemical Society 150(11): A1523-A1527 [Reference 2] JP 2010-236989 A [Reference 3] Sekine, S. (2020), "PtCo Catalyst Dissolution and Oxidation Modeling for Durability Improvement of Automotive Fuel Cell," ECS transaction

[0057] [1.3.2. Calculation of activity SA[i]] "Activity SA[i]" refers to the activity per surface area of ​​a precious metal-based catalyst particle at time [i]. There are various methods for calculating SA[i]. In the present invention, the calculation formula for SA[i] is not particularly limited, and an optimal calculation formula can be used depending on the purpose. The calculated SA[i] is stored in memory.

[0058] The third means preferably includes a means for calculating SA[i] using the following formula (8) and / or formula (9). Either one of these may be used to calculate SA[i], or they may be used separately depending on the purpose.

[0059]

number

[0060] however, SA 0 is the initial value (constant) of the activity per surface area of ​​the noble metal catalyst, A ECS0 is the initial value (constant) of the electrode catalyst surface area, Ts is the calculation step size. B 2 , B 3 are the fitting coefficients, respectively. In addition, SA 0 , B 2 , and B 3 It is preferable to perform separate power generation tests in advance and set the values ​​so as to match the test results.

[0061] Equation (8) is a calculation formula for calculating SA[i] using the accumulated time (=ΣTs) of power generation in a polymer electrolyte fuel cell. In general, the longer the accumulated time of power generation in a fuel cell, the greater the number of repeated dissolution and redeposition of catalyst particles, so SA[i] monotonically decreases with accumulated time. Equation (8) is an approximation formula that approximates such changes in SA[i] as a linear function of accumulated time. Equation (8) has low estimation accuracy, but has the advantage of reducing calculation costs.

[0062] Equation (9) is A ECS Equation (9) is a formula for calculating SA[i] using [i]. Equation (9) expresses the relationship between SA[i] and the platinum surface area maintenance rate (A ECS [i] / A ECS0 ) and calculates SA[i]. Equation (9) has the advantage of being more accurate than equation (8), but has the disadvantage of increased calculation cost.

[0063] A ECS As with the calculation of [i], the calculation of SA[i] using formulas (8) to (9) may be entirely or partially replaced with calculations using a more sophisticated physical model. Using calculations using a physical model can improve the estimation accuracy of SA[i]. Details of the physical model are as described above, and therefore will not be described here.

[0064] [1.4. Fourth means] The fourth means is θact[i], A ECS a fourth means for calculating an estimated value IVest[i] of the IV characteristic representing the relationship between I[i] and the estimated voltage Vest[i] of the solid polymer fuel cell using I[i] and SA[i], and storing IVest[i] in memory. There are various methods for calculating Vest[i]. In the present invention, the method for calculating Vest[i] is not particularly limited, and an optimal method can be selected depending on the purpose. The calculated relationship between Vest[i] and I[i], i.e., IVest[i], is stored in a memory.

[0065] The fourth means may include a means for calculating IVest[i] expressed by the following formula (10). Strictly speaking, Vest[i] is the temperature T of the polymer electrolyte fuel cell at time [i]. FC It also depends on Vest[i], high frequency impedance R[i], cathode air pressure Pca[i], and cathode air stoichiometry STca[i]. Equation (10) is an approximation of Vest[i] that regards these as constants. Although the estimation accuracy of equation (10) is inferior to that of equation (11) described later, equation (10) has the advantage of reducing the calculation cost.

[0066]

number

[0067] however, Vocv is the open circuit voltage of the polymer electrolyte fuel cell, I 0 [i] is the exchange current density, Rgas[i] is the gas diffusion resistance, A ECS0 is the initial value (constant) of the electrode catalyst surface area, SA 0 is the initial value (constant) of the activity per surface area of ​​the noble metal catalyst, C 1 ~C 9are the compatibility coefficients, respectively. In addition, C 1 ~C 9 It is preferable to carry out another power generation test in advance and set the value so as to match the test results.

[0068] In equation (10), the first term on the right side represents the open circuit voltage, the second term on the right side represents the activation overpotential, the third term on the right side represents the concentration overpotential, and the fourth term on the right side represents the resistance overpotential. In addition, in the formula (10), "exchange current density I 0 "[i]" is the current density when the oxidation and reduction phenomena are in equilibrium, and indicates the ease of the power generation reaction. Furthermore, in equation (10), "gas diffusion resistance Rgas[i]" indicates the difficulty of diffusion of fuel / oxidizing gas.

[0069] The fourth means may include a means for calculating the IVest[i] expressed by the following formula (11) instead of or in addition to formula (10). Either formula (10) or formula (11) may be used to calculate IVest[i], or they may be used separately depending on the purpose. Equation (11) is used to calculate Vest[i]. FC [i], R[i], Pca[i], and STca[i] are taken into consideration. Therefore, although the calculation cost of formula (11) is higher than that of formula (10), the estimation accuracy is improved.

[0070]

number

[0071] [1.5. Fifth means] The fuel cell performance estimation device according to the present invention comprises: (E) A fifth means for determining a failure of the polymer electrolyte fuel cell by using the IVest[i]. The device may further include:

[0072] IVest[i] obtained as described above represents the current-voltage characteristic that eliminates the effects of steady voltage drops caused by catalyst deterioration and temporary voltage fluctuations caused by the formation and reduction of an oxide film on the catalyst surface (i.e., the estimated value of the current-voltage characteristic when it is assumed that no fault has occurred). Therefore, the use of IVest[i] makes it possible to accurately determine the presence or absence of a fault. There are various methods for determining a fault using IVest[i]. In the present invention, the method for determining a fault using IVest[i] is not particularly limited, and an optimal method can be selected according to the purpose. Specifically, the fault determination method includes the following methods.

[0073] [1.5.1. Comparison of V[i] and Vest[i]: Method A] The fifth means may include a means A for comparing V[i] at time [i] with Vest[i] obtained by substituting I[i] for IVest[i], and determining whether or not the solid polymer fuel cell has failed. Substituting I[i] for VIest[i] gives Vest[i]. Ideally, Vest[i] will match V[i] if the polymer electrolyte fuel cell is not malfunctioning. Therefore, if Vest[i] deviates significantly from V[i], it can be assumed that a malfunction has occurred.

[0074] The means A for comparing V[i] and Vest[i] is not particularly limited, and the most suitable means can be selected depending on the purpose. (a) The absolute value of the difference between V[i] and Vest[i] is the first threshold ε 1 When it exceeds ε 1 A means A1 for determining a malfunction when the above condition is met; (b) The ratio of V[i] to Vest[i] (=V[i] / Vest[i]) is the second threshold ε 2 or ε 2 A means A2 for determining a malfunction when: (c) The ratio of the difference between Vest[i] and V[i] (=(Vest[i]-V[i]) / V[i]) is the third threshold ε 3 When it exceeds ε 3 Means A3 for determining a malfunction when the above condition is satisfied etc. The fifth means may be any one of these means, or may be two or more of these means. 1 ~ε 3 The value of is not particularly limited, and an optimal value can be selected depending on the purpose.

[0075] [1.5.2. Comparison between Vm[T] and Vm_est[T]: Method B] The fifth means may include a means B for calculating an average voltage Vm[T] and an average estimated voltage Vm_est[T] over a certain time interval ΔT using V[i] and Vest[i], respectively, and for comparing the calculated Vm[T] with Vm_est[T] to determine whether or not the solid polymer fuel cell has failed.

[0076] When the voltage V[i] is known, it can be used to calculate the average voltage Vm[T]. Similarly, when the estimated voltage Vest[i] is known, it can be used to calculate the average estimated voltage Vm_set[T]. If the polymer electrolyte fuel cell is not faulty, Vm_est[T] also ideally coincides with Vm[T]. Therefore, when Vm_set[T] deviates significantly from Vm[T], it can be estimated that a fault has occurred. Means B, which uses the average value, is likely to cancel out transient voltage fluctuations caused by fluctuations in operating conditions. Therefore, means B has a higher estimation accuracy than means A, which uses an estimated value at a certain time [i].

[0077] Here, "average voltage Vm[T]" refers to the average voltage value obtained by extracting V[i] when I[i] is the reference current Is during a certain time interval ΔT and averaging these. The "average estimated voltage Vm_est[T]" refers to the average value of the estimated voltage obtained by extracting Vest[i] when I[i] is Is during ΔT and averaging these. "Time interval ΔT" refers to the time interval for extracting data necessary to calculate Vm[T] and Vm_est[T]. "Reference current Is" refers to the current that serves as the reference when extracting V[i] and Vest[i] (i.e., the current that serves as the reference when calculating the average voltage Vm[T] and the average estimated voltage Vm_est[T]).

[0078] The method of calculating Vm[T] and Vm_est[T] is not particularly limited, and it is preferable to select an optimal method depending on the purpose. Means B is: A means for calculating the Vm[T] using the following formula (12); A means for calculating the Vm_est[T] using the following formula (13); It is preferred that the compound contains

[0079]

number

[0080] ΔT is not particularly limited, and an optimal time interval can be selected depending on the purpose. In general, if ΔT is too short, erroneous judgment may occur due to the influence of noise on the value acquisition unit. Therefore, ΔT is preferably at least twice the calculation step width Ts. ΔT is more preferably at least five times Ts, and even more preferably at least ten times Ts. On the other hand, if ΔT is too long, the time until a fault is determined will be long. Therefore, ΔT is preferably 10,000 times Ts or less. ΔT is more preferably 1,000 times Ts or less, and even more preferably 100 times Ts or less.

[0081] The means B for comparing Vm[T] and Vm_est[T] is not particularly limited, and an optimal means can be selected depending on the purpose. (a) The absolute value of the difference between Vm[T] and Vm_est[T] is the fourth threshold ε 4 When it exceeds ε 4 A means B1 for determining that the device is faulty when the above condition is met; (b) The ratio of Vm[T] to Vm_est[T] (=Vm[T] / Vm_est[T]) is the fifth threshold ε 5 or ε 5 A means B2 for determining a malfunction when: (c) The ratio of the difference between Vm_est[T] and Vm[T] to Vm[T] (=(Vm_est[T]-Vm[T]) / Vm[T]) is the sixth threshold ε 6 When it exceeds ε 6 Means for determining a malfunction when the above is true B3 etc. The fifth means may be any one of these means, or may be two or more of these means. 4 ~ε 6 The value of is not particularly limited, and an optimal value can be selected depending on the purpose.

[0082] [2. Fuel cell performance estimation method] FIG. 2 shows a flowchart for calculating the estimated value IVest[i] of the current-voltage characteristics and for determining a fault. First, in step 1 (hereinafter simply referred to as "S1"), various sensors are used to sequentially obtain at least the voltage V[i] and current I[i] of the polymer electrolyte fuel cell at time [i], and V[i] and I[i] are stored in memory (first means). In this case, in addition to V[i] and I[i], the high-frequency impedance R[i] of the polymer electrolyte fuel cell at time [i] may also be obtained. In addition to these, the temperature T FC [i], the cathode air pressure Pca[i], and the cathode air stoichiometry STca[i] may further be acquired.

[0083] Next, proceed to S2. In S2, at least V[i] is used to calculate the catalytic potential Vcat[i] of the cathode of the polymer electrolyte fuel cell at time [i]. Next, Vcat[i] is used to calculate the effective surface utilization rate θact[i] of the precious metal catalyst particles contained in the polymer electrolyte fuel cell at time [i]. Furthermore, the obtained Vcat[i] and θact[i] are stored in memory (second means). The details of the calculation method of Vcat[i] and θact[i] are as described above, so the explanation will be omitted.

[0084] Next, proceed to S3. In S3, the electrode catalyst surface area A at time [i] is calculated using V[i], Vcat[i], and / or the integrated time of power generation of the solid polymer electrolyte fuel cell. ECS The activity SA[i] per surface area of ​​the precious metal catalyst at time [i] and time [i] is calculated, and A ECS [i] and SA[i] are stored in memory (third means). ECS The details of the method for calculating [i] and SA[i] are as described above, and therefore will not be described here.

[0085] Next, proceed to S4. In S4, θact[i], A ECSUsing [i] and SA[i], an estimated value IVest[i] of the IV characteristics that represents the relationship between I[i] and the estimated voltage Vest[i] of the polymer electrolyte fuel cell is calculated, and IVest[i] is stored in memory (fourth means). The details of the calculation method of IVest[i] are as described above, so a description thereof will be omitted.

[0086] Next, the process proceeds to S5. In S5, a fault determination is performed on the polymer electrolyte fuel cell using IVest[i] (fifth means). Details of the fault determination method are as described above, and therefore will not be described here. Note that, if only the calculation of IVest[i] is performed, S5 can be omitted. Next, the process proceeds to S6. In S6, it is determined whether or not to continue the control. If the control is to be continued (S6: YES), the process returns to S1, and the above-mentioned steps S1 to S6 are repeated. On the other hand, if the control is not to be continued (S6: NO), the control is ended.

[0087] [3. Effect] [3.1. Current-voltage characteristics under normal and fault conditions] FIG. 3 shows the relationship between the estimated value IVest[i] of the current-voltage characteristics, sensor value 1 (the actual measured value IV[i] of the current-voltage characteristics under normal conditions), and sensor value 2 (the actual measured value IV'[i] of the current-voltage characteristics under fault conditions).

[0088] When a fuel cell is completed and generates power under certain power generation conditions, the performance of the fuel cell (performance at the time of initial evaluation) will be at its maximum value. However, if the fuel cell is operated for a long time, the catalyst particles will repeatedly dissolve and re-precipitate, and the performance of the fuel cell will decrease as the cumulative time of power generation increases. In addition, when the fuel cell is actually operated, the power generation conditions change from moment to moment during operation, so the performance of the fuel cell may temporarily fluctuate even if the catalyst particles have not deteriorated. Therefore, sensor value 1 at time [i] (actual measured value IV[i] of the current-voltage characteristics under normal conditions) is the initial performance minus the steady voltage drop and temporary voltage fluctuation.

[0089] On the other hand, if the fuel cell fails, the sensor value 2 at time [i] (the measured value IV'[i] of the current-voltage characteristics at the time of failure) will be the initial performance minus the steady voltage drop, temporary voltage fluctuation, and voltage drop due to the failure. Therefore, by monitoring the change over time of IV[i], ideally, it will be possible to determine whether or not a failure has occurred. However, in reality, even if there is no voltage drop due to a fault or a steady voltage drop, temporary voltage fluctuations may become large. In such cases, if a fault is determined based on the change in IV[i] over time, it may be erroneously determined.

[0090] On the other hand, if it is possible to calculate the estimated value of the steady voltage drop and the estimated value of the temporary voltage fluctuation using various methods, it is possible to calculate the estimated value IVest[i] of the current-voltage characteristics at time [i] by subtracting these from the initial performance. When no fault occurs, ideally, IVest[i] matches IV[i]. On the other hand, when a fault occurs, IVest[i] deviates significantly from IV[i]. Therefore, by comparing IV[i] with IVest[i], it is possible to accurately determine the presence or absence of a fault.

[0091] [3.2. Temporary voltage fluctuations] Figure 4(A) shows a schematic diagram of the current-voltage characteristics when power is generated under certain power generation conditions. Figure 4(B) shows a schematic diagram of the current fluctuations and voltage fluctuations when a fuel cell (FC) vehicle is in operation. Figure 4(C) shows a schematic diagram of the actual measured values ​​of the current-voltage characteristics obtained by plotting the relationship between the current and voltage shown in Figure 4(B) as a scatter diagram.

[0092] "Fuel cell performance" corresponds to the voltage value for an arbitrary current (reference current Is) in the current-voltage characteristic (IV characteristic) shown in Figure 4(A), for example. This IV characteristic fluctuates depending on the history during power generation. For example, consider driving an FC vehicle shown in Figure 4(B). In this case, the amount of power generated by the fuel cell is not constant, so the current and voltage fluctuate over time. If the relationship between current and voltage at this time is plotted as a scatter diagram, it becomes the IV characteristic shown in Figure 4(C). This is different from the IV characteristic in Figure 4(A), which could be drawn with a single line, but is a curve with a distribution. This distribution corresponds to "temporary voltage fluctuation." This temporary fluctuation component makes it difficult to estimate IV with high accuracy, and for example, when determining a failure, it may be difficult to distinguish between a voltage drop due to a failure and a temporary voltage fluctuation.

[0093] The following factors may cause the performance of a fuel cell to fluctuate temporarily: (a) Transient voltage fluctuations due to temporary fluctuations in the effective area or activity of the catalyst. (b) Temporary voltage fluctuations caused by transient changes in power generation conditions, such as changes in gas supply conditions (flow rate, pressure, humidity) and temperature. Of these, (b) can be offset to some extent by using the average value calculated over a certain time interval ΔT when making a judgment. However, for (a), there has traditionally been no effective sensing method, and because the current state changes depending on the usage history up to that point, it has been difficult to estimate temporary voltage fluctuations.

[0094] 3.3. Calculation of IVest[i] The inventors of the present application found that the phenomenon of (a) above can be expressed based on the estimated values ​​θox1, θox2, and θox3 of the oxides on the surface / inside of the catalyst based on the reaction rate equation, and the surface charge rate θact calculated using them. This makes it possible to determine whether the problem is a malfunction or a temporary deterioration in performance, and enables malfunction detection with higher accuracy than before.

[0095] That is, by sequentially acquiring the voltage V[i] and current I[i] of the polymer electrolyte fuel cell at time [i], it is possible to calculate the cathode catalytic potential Vcat[i] using at least V[i]. In addition, if Vcat[i] is known, it is possible to calculate the effective surface utilization rate θact[i] of the precious metal catalyst. θact[i] is correlated with temporary voltage fluctuations caused by the formation and reduction of an oxide film. In addition, when V[i], Vcat[i], or the cumulative time of power generation is known, the electrode catalyst surface area A at time [i] can be calculated using these. ECS [i] and the activity per surface area SA[i] of the precious metal catalyst at time [i] can be calculated. ECS Both [i] and SA[i] are correlated with steady voltage drops caused by catalyst deterioration.

[0096] Furthermore, the obtained I[i], the calculated θact[i], A ECS Using [i] and SA[i], it is possible to calculate an estimated value IVest[i] of the IV characteristics of the polymer electrolyte fuel cell at time [i]. The IVest[i] obtained in this way represents a current-voltage characteristic that is free of the effects of steady voltage drops caused by catalyst deterioration and temporary voltage fluctuations caused by the formation and reduction of an oxide film on the catalyst surface (i.e., an estimated value of the current-voltage characteristic assuming that no failure has occurred). Therefore, by comparing the actual current-voltage characteristic IV[i] of the polymer electrolyte fuel cell at time [i] with IVest[i], it is possible to accurately determine whether or not a failure has occurred.

[0097] [3.4. Failure determination] FIG. 5 shows a schematic diagram of fault determination using the estimated value IVest[i] of the current-voltage characteristic. As shown in FIG. 5, until a fault occurs, Vest[i] or its average value Vm_est[T] calculated by the method according to the present invention almost coincides with V[i] or its average value Vm[T]. On the other hand, even if a fault occurs, the voltage drop due to the fault is not reflected in Vest[i] or its average value Vm_est[T]. Therefore, after the fault occurs, Vest[i] or its average value Vm_est[T] largely deviates from V[i] or its average value Vm[T]. Therefore, for example, when the difference between the two exceeds a certain threshold, it can be determined that a fault has occurred.

[0098] Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the present invention. [Industrial Applicability]

[0099] The fuel cell performance estimating device according to the present invention can be used to estimate the performance of a fuel cell vehicle at the current time and to determine whether or not there is a malfunction in the fuel cell.

Claims

1. (A) a first means for sequentially acquiring at least a voltage V[i] and a current I[i] of a polymer electrolyte fuel cell at a time [i] and storing the V[i] and the I[i] in a memory; (B) calculating a catalytic potential Vcat[i] of the cathode of the polymer electrolyte fuel cell at the time [i] using at least the V[i]; Using the Vcat[i], an effective surface utilization rate θact[i] of the precious metal-based catalyst particles contained in the solid polymer fuel cell at the time [i] is calculated; A second means for storing the Vcat[i] and the θact[i] in the memory; (C) Said V [i], the Vcat[i], and / or the integrated time of power generation of the solid polymer electrolyte fuel cell are used to calculate the electrode catalyst surface area A at the time [i]. ECS [i] and the activity SA[i] per surface area of ​​the precious metal catalyst at the time [i] are calculated, and ECS a third means for storing the SA[i] and the SA[i] in the memory; (D) Preface θact[i], Preface A ECS a fourth means for calculating an estimated value IVest[i] of an IV characteristic that represents a relationship between I[i] and an estimated voltage Vest[i] of the solid polymer electrolyte fuel cell, using I[i] and SA[i], and storing the IVest[i] in the memory; A fuel cell performance estimation device comprising:

2. 2. The fuel cell performance estimating device according to claim 1, wherein the second means includes means for calculating the Vcat[i] using the following equation (1): [0010] However, N cell is the number of cells stacked in the polymer electrolyte fuel cell.

3. the first means further includes means for sequentially acquiring a high-frequency impedance R[i] of the polymer electrolyte fuel cell at the time [i] and storing the R[i] in the memory; 3. The fuel cell performance estimating device according to claim 1, wherein the second means includes means for calculating the Vcat[i] using the following equation (2): [0025] however, N cell is the number of stacked cells of the polymer electrolyte fuel cell, A cell is the area of ​​the cell.

4. 4. The fuel cell performance estimation device according to claim 1, wherein the second means includes means for calculating the θact[i] using the following equation (3) and / or equation (4): [0030] however, θox1[i] is the coverage of the precious metal hydroxide adsorbed on the surface of the precious metal-based catalyst particle at the time [i]; θox2[i] is the coverage of the precious metal oxide adsorbed on the surface of the precious metal-based catalyst particle at the time [i], θox3[i] is the coverage of the precious metal oxide present inside the precious metal-based catalyst particle at the time [i], Γ is the maximum surface coverage of oxygen per unit surface area (constant), Ts is the calculation step size, α 1 ~α 4 , α 11 ~α 17 , α 21 ~α 27 , α 31 ~α 37 are the fitting coefficients, respectively.

5. The third means calculates the A using the following formula (5), formula (6), and / or formula (7). ECS The fuel cell performance estimation device according to any one of claims 1 to 4, further comprising a means for calculating [i]. [0045] however, A ECS0 is the initial value (constant) of the electrode catalyst surface area, Ts is the calculation step size, B 1 , D 1 , D 2 , D 3 , D 4 are the fitting coefficients, respectively.

6. 6. The fuel cell performance estimation device according to claim 1, wherein the third means includes means for calculating the SA[i] using the following equation (8) and / or equation (9): [0050] however, S.A. 0 is the initial value (constant) of the activity per surface area of ​​the noble metal catalyst, A ECS0 is the initial value (constant) of the electrode catalyst surface area, Ts is the calculation step size, B 2 , B 3 are the fitting coefficients, respectively.

7. 7. The fuel cell performance estimating device according to claim 1, wherein the fourth means includes a means for calculating the IVest[i] expressed by the following equation (10). [006] however, Vocv is the open circuit voltage of the polymer electrolyte fuel cell, I 0 [i] is the exchange current density, Rgas[i] is the gas diffusion resistance, A ECS0 is the initial value (constant) of the electrode catalyst surface area, S.A. 0 is the initial value (constant) of the activity per surface area of ​​the noble metal catalyst, C 1 ~C 9 are the fitting coefficients, respectively.

8. The first means further calculates the high-frequency impedance R[i] and the temperature T FC [i], the cathode air pressure Pca[i], and the cathode air stoichiometry STca[i] are sequentially acquired, and the acquired values ​​are stored in the memory.

8. The fuel cell performance estimating device according to claim 1, wherein the fourth means includes a means for calculating the IVest[i] expressed by the following equation (11). [0070] however, Vocv is the open circuit voltage of the polymer electrolyte fuel cell, I 0 [i] is the exchange current density, Rgas[i] is the gas diffusion resistance, A ECS0 is the initial value (constant) of the electrode catalyst surface area, S.A. 0 is the initial value (constant) of the activity per surface area of ​​the noble metal catalyst, C 4 , C 6 , C 7 and C 9 , and C 10 ~C 16 are the fitting coefficients, respectively.

9. (E) a fifth means for determining a failure of the solid polymer electrolyte fuel cell by using the IVest[i]. The fuel cell performance estimating device according to claim 1 , further comprising:

10. The fuel cell performance estimation device of claim 9, wherein the fifth means includes a means A for comparing the V[i] at the time [i] with the Vest[i] obtained by substituting the I[i] into the IVest[i], and determining whether the solid polymer fuel cell has failed.

11. The means A is (a) The absolute value of the difference between V[i] and Vest[i] is equal to a first threshold ε 1 or when the above ε 1 A means A1 for determining a malfunction when the above condition is met; (b) The ratio of V[i] to Vest[i] (=V[i] / Vest[i]) is equal to or smaller than a second threshold ε 2 or when the ε 2 Means A2 for determining a malfunction when: (c) Said V The ratio of the difference between Vest[i] and V[i] (=(Vest[i]-V[i]) / V[i]) to the third threshold ε 3 or when the above ε 3 Means A3 for determining a malfunction when the above condition is met The fuel cell performance estimation device according to claim 10 , comprising:

12. The fuel cell performance estimation device according to any one of claims 9 to 11, wherein the fifth means includes a means B for calculating an average voltage Vm[T] and an average estimated voltage Vm_est[T] over a certain time interval ΔT using V[i] and Vest[i], respectively, and comparing the calculated Vm[T] with Vm_est[T] to determine whether the solid polymer fuel cell has failed.

13. The means B is A means for calculating the Vm[T] using the following formula (12); A means for calculating the Vm_est[T] using the following formula (13); The fuel cell performance estimation device according to claim 12 , comprising: [0080] Here, Is is a reference current used when calculating the average voltage Vm[T] and the average estimated voltage Vm_est[T].

14. The means B is (a) The absolute value of the difference between Vm[T] and Vm_est[T] is equal to or smaller than a fourth threshold ε 4 or when the above ε 4 A means B1 for determining a malfunction when the above condition is met; (b) The ratio of Vm[T] to Vm_est[T] (=Vm[T] / Vm_est[T]) is equal to or smaller than a fifth threshold ε 5 or when the ε 5 and / or means B2 for determining a malfunction when (c) The ratio of the difference between the Vm_est[T] and the Vm[T] to the Vm[T] (=(Vm_est[T]-Vm[T]) / Vm[T]) is equal to a sixth threshold ε 6 or when the above ε 6 Means B3 for determining a malfunction when the above condition is met The fuel cell performance estimation device according to claim 12 or 13, comprising:

Images