A method and apparatus for diagnosing causes of end plate effects in a fuel cell

Abstract

The application discloses a kind of fuel cell end plate effect cause diagnosis method and device, it is related to fuel cell technical field, can solve the problem that existing technology cannot accurately identify end plate effect cause, leading to improvement measure blind and high cost problem.It is specific technical scheme: from the front end of electric pile, rear end plate effect influence area and middle part selects single cell as test object;Collect the single cell voltage and electrochemical impedance spectrum data of each test object, extract activation impedance and mass transfer impedance;With middle part cell voltage as benchmark, by changing coolant temperature and cathode gas flow, temperature and mass transfer sensitivity coefficient are calibrated;Calculate the activation impedance difference parameter and mass transfer impedance difference parameter between front end and middle part, rear end and middle part;The ratio of the activation impedance difference parameter and mass transfer impedance difference parameter of front end and rear end is calculated and compared with preset threshold value, respectively determine the cause type of front end and rear end end plate effect.The application is used for fuel cell end plate effect cause diagnosis.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and specifically to a method and apparatus for diagnosing the causes of endplate effects in fuel cells. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) stack typically consists of dozens to hundreds of individual cells stacked together and secured by end plates and tie rods at both ends. Figure 1 As shown. During operation, the output voltage of individual cells near the two ends of the fuel cell stack is often lower than that in the middle region; this phenomenon is called the "endplate effect." Figure 2 As shown, the endplate effect directly reduces the overall output power and energy conversion efficiency of the fuel cell stack, leading to poor performance consistency among individual cells and increasing the difficulty of stack control. Under long-term operation or harsh environments, severe endplate effects can cause stack damage and lifespan degradation, making it one of the key technological bottlenecks restricting the development of high-power, long-life fuel cell stacks.

[0003] Currently, the industry generally believes that the main causes of the endplate effect include low end temperature and poor mass transfer of reactant gases. However, in practical engineering applications, the specific causes of the endplate effect are very complex. It may be dominated by a single factor or influenced by a combination of factors, and the causes may differ between different fuel cell stacks and even between the front and rear endplates of the same stack. The industry currently lacks analytical methods to identify the specific causes of the endplate effect, and improvements are usually made based on empirical operations, such as increasing end insulation or optimizing end gas distribution. Since these measures may not address the actual causes, the effectiveness of the improvements is uncertain. Summary of the Invention

[0004] To address the problem that existing technologies cannot accurately identify the specific causes of fuel cell endplate effects, leading to blind and costly improvement measures, this invention provides a method and apparatus for diagnosing the causes of fuel cell endplate effects. The technical solution is as follows:

[0005] According to a first aspect of the present invention, a method for diagnosing the causes of endplate effects in fuel cells is provided, the method comprising:

[0006] At least one single cell was selected as the test object from the endplate effect area of ​​the front endplate, the endplate effect area of ​​the rear endplate, and the middle part of the fuel cell stack.

[0007] Under preset operating conditions, the individual voltage of each test object is collected, and the electrochemical impedance spectroscopy data of each test object is obtained, and the activation impedance and mass transfer impedance of each test object are extracted from them.

[0008] Using the single cell voltage in the middle section as a reference, the temperature sensitivity coefficient and mass transfer sensitivity coefficient were calibrated by changing the stack coolant temperature and cathode gas flow rate respectively and monitoring the voltage change of the middle section single cell.

[0009] Based on the activation impedance, the mass transfer impedance, the temperature sensitivity coefficient, and the mass transfer sensitivity coefficient, the activation impedance difference parameter and the mass transfer impedance difference parameter between the front-end battery and the middle battery, and between the rear-end battery and the middle battery are calculated respectively.

[0010] The ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the front-end battery and the rear-end battery is calculated respectively. Based on the comparison result of the ratio with the preset threshold, the cause type of endplate effect near the front-end plate and the rear-end plate is determined respectively.

[0011] This invention provides a method for diagnosing the causes of endplate effects in fuel cells. First, at least one single cell is selected as a test object from the endplate effect influence areas of the front and rear ends of the fuel cell stack, as well as the middle section. Then, under preset operating conditions, the single-cell voltage and electrochemical impedance spectroscopy (EIS) data of each test object are collected, and the activation impedance and mass transfer impedance of each test object are extracted. Next, using the single-cell voltage of the middle cell as a reference, the temperature sensitivity coefficient and mass transfer sensitivity coefficient are calibrated by changing the stack coolant temperature and cathode gas flow rate while monitoring the voltage change of the middle cell. Based on the activation impedance, mass transfer impedance, temperature sensitivity coefficient, and mass transfer sensitivity coefficient, the activation impedance difference parameter and mass transfer impedance difference parameter between the front and middle cells, and between the rear and middle cells, are calculated, respectively. Finally, the ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter for the front and rear cells is calculated, and the cause type of the endplate effect near the front and rear ends is determined based on the comparison result of the ratio with a preset threshold. This invention's method can pinpoint the specific causes of endplate effects at the front and rear ends of a fuel cell stack under specific conditions, thereby achieving more targeted improvements and effectively enhancing the voltage consistency of individual cells within the stack. Furthermore, this method, based on electrochemical impedance spectroscopy analysis, features short cycles and broad applicability, making it suitable for various fuel cell stacks and operating conditions. It reduces the number of repetitive tests and trial-and-error processes, saving material costs and shortening development cycles for enterprises.

[0012] As a further aspect of the present invention: the step of selecting at least one single cell as a test object from the endplate effect influence area of ​​the front endplate, the endplate effect influence area of ​​the rear endplate, and the middle part of the fuel cell stack specifically includes:

[0013] Select the single cell closest to the front panel, the single cell closest to the rear panel, and the single cell located in the center of the stack.

[0014] As a further aspect of the present invention: when multiple single cells are selected as test objects from the front end plate effect influence area, the rear end plate effect influence area, or the middle of the stack, the single cell voltage of the test object is taken as the average value of the voltages of the selected multiple single cells, and the activation impedance and mass transfer impedance are taken as the average value of the impedances of the selected multiple single cells.

[0015] As a further aspect of the present invention: a method for extracting the activation impedance and mass transfer impedance of each test object from the electrochemical impedance spectroscopy data specifically includes:

[0016] The relaxation time distribution of the electrochemical impedance spectroscopy data is analyzed, and the peak value appearing in the first frequency range is taken as the activation impedance, and the peak value appearing in the second frequency range is taken as the mass transfer impedance, wherein the first frequency range is greater than the second frequency range.

[0017] As a further aspect of the present invention: a method for extracting the activation impedance and mass transfer impedance of each test object from the electrochemical impedance spectroscopy data specifically includes:

[0018] The electrochemical impedance spectroscopy data are fitted with an equivalent circuit, and the activation impedance and the mass transfer impedance are extracted from the fitting results.

[0019] As a further aspect of the present invention: the calibration of temperature sensitivity coefficient and mass transfer sensitivity coefficient by using the single cell voltage of the central cell as a reference, and by changing the stack coolant temperature and cathode gas flow rate respectively, while monitoring the voltage change of the central cell, specifically includes:

[0020] Calculate the absolute value of the voltage difference between the front-end battery and the middle battery, and the absolute value of the voltage difference between the rear-end battery and the middle battery, and use the maximum value of the two as the calibration value;

[0021] Using the individual cell voltage of the central battery as a reference, the temperature of the stack coolant is reduced. When the individual cell voltage of the central battery drops by the calibrated amount, the real-time coolant temperature is recorded, and the temperature sensitivity coefficient is calculated based on the initial coolant temperature and the real-time coolant temperature.

[0022] Using the single-cell voltage of the central battery as a reference, the cathode gas flow rate is reduced. When the single-cell voltage of the central battery drops by the calibrated amount, the real-time cathode gas flow rate is recorded, and the mass transfer sensitivity coefficient is calculated based on the initial cathode gas flow rate and the real-time cathode gas flow rate.

[0023] As a further aspect of the present invention, the temperature sensitivity coefficient is calculated using the following formula:

[0024] S T (j=x) = T(i) / [T(i) - T(exp)]

[0025] Among them, S T (j=x) Here, T(i) is the temperature sensitivity coefficient, T(i) is the initial coolant temperature, and T(exp) is the real-time coolant temperature when the mid-cell voltage drops to the calibrated value.

[0026] The mass transfer sensitivity coefficient is calculated using the following formula:

[0027] S mass(j=x) = Q(i) / [Q(i) - Q(exp)]

[0028] Among them, S mass(j=x) Q(i) is the mass transfer sensitivity coefficient, Q(i) is the initial cathode gas flow rate, and Q(exp) is the real-time cathode gas flow rate when the voltage of the middle cell drops to the calibrated value.

[0029] As a further aspect of the present invention: the difference in activation impedance between the front-end battery and the middle battery is calculated using the following formula:

[0030]

[0031] in, This is a parameter representing the difference in activation impedance between the front-end and middle-end cells. The activation impedance of the front-end battery. The activation impedance of the middle battery. Temperature sensitivity coefficient;

[0032] The mass transfer impedance difference parameter between the front-end battery and the middle battery is calculated using the following formula:

[0033]

[0034] in, This represents the mass transfer impedance difference parameter between the front-end and middle-end cells. The mass transfer impedance of the front-end battery is... The mass transfer impedance of the middle battery is... The mass transfer sensitivity coefficient;

[0035] The difference in activation impedance between the rear-end battery and the middle battery is calculated using the following formula:

[0036]

[0037] in, This is a parameter representing the difference in activation impedance between the back-end and middle-end batteries. The activation impedance of the back-end battery. The activation impedance of the middle battery. Temperature sensitivity coefficient;

[0038] The mass transfer impedance difference parameter between the rear battery and the middle battery is calculated using the following formula:

[0039]

[0040] in, This represents the mass transfer impedance difference parameter between the back-end battery and the middle battery. The mass transfer impedance of the back-end battery. The mass transfer impedance of the middle battery is... is the mass transfer sensitivity coefficient.

[0041] As a further aspect of the present invention: the preset threshold includes a first threshold and a second threshold, wherein the first threshold is less than the second threshold; the step of determining the cause type of endplate effect near the front end plate and near the rear end plate based on the comparison result of the ratio and the preset threshold specifically includes:

[0042] When the ratio is less than or equal to the first threshold, it is determined that the endplate effect near the corresponding endplate is dominated by gas mass transfer factors.

[0043] When the ratio is greater than or equal to the second threshold, it is determined that the endplate effect near the corresponding endplate is temperature-dominated.

[0044] When the ratio is greater than the first threshold and less than the second threshold, the endplate effect near the corresponding endplate is determined to be of the temperature and gas mass transfer coupling type.

[0045] According to a second aspect of the present invention, a diagnostic device for the cause of endplate effect in a fuel cell is provided, characterized in that it includes: a selection module, an acquisition module, a calibration module, a calculation module, and a determination module;

[0046] The selection module is used to select at least one single cell as a test object from the front end plate end plate effect influence area, the rear end plate end plate effect influence area and the middle part of the fuel cell stack, respectively.

[0047] The acquisition module is used to collect the individual voltage of each test object under preset working conditions, and to acquire the electrochemical impedance spectroscopy data of each test object, and extract the activation impedance and mass transfer impedance of each test object from them.

[0048] The calibration module is used to calibrate the temperature sensitivity coefficient and mass transfer sensitivity coefficient by changing the stack coolant temperature and cathode gas flow rate respectively, and monitoring the voltage change of the central single cell, with the single cell voltage as a reference.

[0049] The calculation module is used to calculate the difference parameters of activation impedance and mass transfer impedance between the front-end battery and the middle battery, and between the rear-end battery and the middle battery, respectively, based on the activation impedance, the mass transfer impedance, the temperature sensitivity coefficient, and the mass transfer sensitivity coefficient.

[0050] The determination module is used to calculate the ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the front-end battery and the rear-end battery, respectively, and determine the cause type of endplate effect near the front-end plate and the rear-end plate based on the comparison result of the ratio with a preset threshold.

[0051] This invention provides a diagnostic device for the endplate effect of a fuel cell, comprising: a selection module, an acquisition module, a calibration module, a calculation module, and a judgment module; the selection module selects at least one single cell from the endplate effect influence areas of the front endplate, the rear endplate effect influence areas, and the middle section of the fuel cell stack as test objects; the acquisition module collects the single-cell voltage of each test object under preset operating conditions, and acquires the electrochemical impedance spectroscopy data of each test object, and extracts the activation impedance and mass transfer impedance of each test object; the calibration module uses the single-cell voltage of the middle cell as a reference, and adjusts the fuel cell stack by changing the single-cell voltage of the middle cell. The device monitors coolant temperature and cathode gas flow rate, and monitors the voltage changes of the middle single cell, calibrating temperature sensitivity coefficients and mass transfer sensitivity coefficients. The calculation module calculates the activation impedance difference parameters and mass transfer impedance difference parameters between the front-end and middle cells, and between the rear-end and middle cells, based on activation impedance, mass transfer impedance, temperature sensitivity coefficients, and mass transfer sensitivity coefficients. The judgment module calculates the ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter for the front-end and rear-end cells, and determines the cause type of endplate effect near the front-end and rear-end plates based on the comparison result of the ratio with a preset threshold. This invention can identify the specific causes of endplate effects at the front and rear plates for specific fuel cell stacks and operating conditions, thereby achieving more targeted improvement effects and effectively enhancing the voltage consistency of each single cell in the fuel cell stack. Furthermore, this device uses electrochemical impedance spectroscopy for analysis and identification, featuring short cycle time and strong universality, applicable to different fuel cell stacks and operating conditions, reducing the number of repeated experiments and trial-and-error processes, saving material costs and shortening the development cycle for enterprises.

[0052] According to a third aspect of the present invention, a fuel cell endplate effect cause diagnosis device is provided, the fuel cell endplate effect cause diagnosis device comprising a processor and a memory, the memory storing at least one computer instruction, the instruction being loaded and executed by the processor to perform the steps performed in the fuel cell endplate effect cause diagnosis method described above.

[0053] According to a fourth aspect of the present invention, a computer-readable storage medium is provided, the storage medium storing at least one computer instruction, the instruction being loaded and executed by a processor to perform the steps performed in the fuel cell endplate effect cause diagnosis method described in any of the preceding claims.

[0054] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0055] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0056] Figure 1 These are the main components and structural diagrams of fuel cell stacks in existing technologies;

[0057] Figure 2 These are schematic diagrams of individual cells at different locations in a fuel cell stack in existing technology.

[0058] Figure 3 This is a flowchart of the fuel cell endplate effect cause diagnosis method provided in the embodiments of the present invention;

[0059] Figure 4 This is a schematic diagram of the connection between the test object single cell and the AC impedance device in the fuel cell endplate effect cause diagnosis method provided in the embodiment of the present invention;

[0060] Figure 5 This is a structural diagram of the fuel cell endplate effect cause diagnosis device provided in an embodiment of the present invention. Detailed Implementation

[0061] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention.

[0062] This invention provides a method for diagnosing the causes of endplate effects in fuel cells, such as... Figure 3 As shown, the method includes the following steps:

[0063] Step 101: Select at least one single cell from the front end plate end plate effect area, the rear end plate end plate effect area, and the middle part of the fuel cell stack as the test object.

[0064] In practical use, such as Figure 2As shown, single cells 1 to 3 are the end-plate effect influence area of ​​the front-end board, defined as the front-end cells (i.e., the voltage of these three single cells is significantly lower than that of the middle single cell); single cells n-2 to n are the end-plate effect influence area of ​​the rear-end board, defined as the rear-end cells; the other single cells can be regarded as the middle cells.

[0065] In one embodiment, at least one single cell is selected as the test object from the endplate effect influence area of ​​the front endplate, the endplate effect influence area of ​​the rear endplate, and the middle part of the fuel cell stack, respectively, specifically including:

[0066] Select the single cell closest to the front panel, the single cell closest to the rear panel, and the single cell located in the center of the stack.

[0067] In this embodiment, the single cell 1 closest to the front-end board, the single cell n closest to the rear-end board, and the single cell (n+1) / 2 (rounded to the nearest integer) located at the center of the fuel cell stack can be selected as the test and analysis objects. The selected single cells are connected to the AC impedance analyzer via signal acquisition lines, such as... Figure 4 As shown.

[0068] This invention selects the individual cells closest to the front end plate, closest to the rear end plate, and located at the center of the fuel cell stack as test objects. This allows for accurate reflection of the typical state of the end-plate effect zone and the normal zone with a minimal number of test points. This selection method avoids deploying test equipment on all individual cells of the entire fuel cell stack, simplifying the testing operation while ensuring diagnostic accuracy and facilitating engineering implementation.

[0069] Step 102: Under preset operating conditions, collect the individual voltage of each test object and obtain the electrochemical impedance spectroscopy data of each test object, and extract the activation impedance and mass transfer impedance of each test object from them.

[0070] In actual use, the fuel cell stack is loaded to a specific current density x (denoted as j=x) and operated under standard conditions (gas, coolant temperature, pressure, dew point, etc.) at that current density as specified by the manufacturer, and stabilized for 10 minutes. The stack coolant temperature at this time is denoted as T(i), and the cathode gas flow rate is denoted as Q(i).

[0071] In one embodiment, when multiple single cells are selected as test objects from the endplate effect region of the front endplate, the endplate effect region of the rear endplate, or the middle of the stack, the single cell voltage of the test object is taken as the average value of the voltages of the selected multiple single cells, and the activation impedance and mass transfer impedance are taken as the average value of the impedances of the selected multiple single cells.

[0072] In this embodiment, it is only necessary to ensure that at least one piece is selected from the endplate effect influence area of ​​the front-end board, at least one piece is selected from the endplate effect influence area of ​​the rear-end board, and at least one piece is selected from the middle of the stack. In actual use, one or more pieces can be selected from single cells 1 to 3, one or more pieces from single cells n-2 to n, and one or more pieces from other single cells as test objects. The specific selection method can be flexibly adjusted according to the actual engineering needs and the number of signal acquisition lines of the AC impedance analyzer, such as... Figure 4 As shown.

[0073] Specifically, read the individual cell voltages of the selected test cells: V(F) (voltage of cell 1), V(R) (voltage of cell n), and V(M) (voltage of cell (n+1) / 2).

[0074] If the test objects at the front / rear / middle are multiple single cells, then V(F) is the average voltage of the selected front-end cells; V(R) is the average voltage of the selected rear-end cells; and V(M) is the average voltage of the selected middle cells.

[0075] This invention's method selects multiple individual cells from the front-end board, rear-end board, and middle section, and uses the average value of their respective voltages and impedances for subsequent calculations. This effectively suppresses measurement fluctuations caused by manufacturing differences or local anomalies in individual cells. This averaging process enhances the representativeness and stability of the test data, allowing the diagnostic results to more accurately reflect the actual state of each area and reducing the interference of random factors in determining the cause.

[0076] In one embodiment, a method for extracting the activation impedance and mass transfer impedance of each test object from electrochemical impedance spectroscopy data specifically includes:

[0077] Relaxation time distribution analysis was performed on the electrochemical impedance spectroscopy data. The peak value appearing in the first frequency range was taken as the activation impedance, and the peak value appearing in the second frequency range was taken as the mass transfer impedance. The first frequency range is larger than the second frequency range.

[0078] In this embodiment, activation impedance refers to reaction activation impedance, and mass transfer impedance refers to reactant gas mass transfer impedance. Specifically: Start the AC impedance meter, use the frequency sweep mode, and set the frequency range to (10kHz~0.1Hz). Record the complete Nyquist plot of the selected test object. Perform DRT (relaxation time distribution) analysis on the frequency sweep test data, and read the activation impedance R0 for each test object. act (F) (Front-end), R act (R) (backend), R act (M) (Middle); Mass transfer impedance R of each test object mass (F) (Front-end), R mass (R) (backend), Rmass (M) (Central). (R) act That is, the peak appearing in the range of 100~10Hz after DRT transformation; R mass Peaks typically appear in the range of 10 to 0.1 Hz.

[0079] This invention utilizes the relaxation time distribution analysis of electrochemical impedance spectroscopy data and extracts activation impedance and mass transfer impedance according to frequency ranges, effectively separating the physicochemical processes corresponding to different frequencies within the fuel cell stack. Since activation impedance primarily reflects temperature-dependent reaction kinetics and mass transfer impedance primarily reflects gas concentration-dependent diffusion processes, this extraction method provides clear physical significance for subsequent cause determination, avoids mutual interference between different impedance components, and improves the reliability of diagnostic results.

[0080] In one embodiment, a method for extracting the activation impedance and mass transfer impedance of each test object from electrochemical impedance spectroscopy data specifically includes:

[0081] Equivalent circuit fitting was performed on the electrochemical impedance spectroscopy data, and the activation impedance and mass transfer impedance were extracted from the fitting results.

[0082] In practical use, R act and R mass It can also be obtained by equivalent circuit fitting calculation based on the Nyquist plot.

[0083] The method of this invention obtains the impedance values ​​of each polarization process without depending on frequency range division by performing equivalent circuit fitting on electrochemical impedance spectroscopy data and extracting activation impedance and mass transfer impedance. This approach provides another feasible method for data analysis and enhances the adaptability of the method to different fuel cell stacks and test conditions.

[0084] In addition, a fixed-frequency test can be used, where the impedance value measured at a fixed frequency approximates R. act R mass For example, the impedance value at 100Hz is selected as R. act The impedance value at 1Hz is R mass .

[0085] Step 103: Using the single cell voltage of the central cell as a reference, calibrate the temperature sensitivity coefficient and mass transfer sensitivity coefficient by changing the stack coolant temperature and cathode gas flow rate respectively, and monitoring the voltage change of the central cell.

[0086] In one embodiment, using the single-cell voltage of the central cell as a reference, the temperature sensitivity coefficient and mass transfer sensitivity coefficient are calibrated by changing the stack coolant temperature and cathode gas flow rate respectively, and monitoring the voltage change of the central cell. Specifically, this includes:

[0087] Calculate the absolute value of the voltage difference between the front-end battery and the middle battery, and the absolute value of the voltage difference between the rear-end battery and the middle battery, and use the maximum value of the two as the calibration value.

[0088] Using the individual cell voltage of the middle battery as a reference, the stack coolant temperature is reduced. When the individual cell voltage of the middle battery drops to the calibrated value, the real-time coolant temperature is recorded, and the temperature sensitivity coefficient is calculated based on the initial coolant temperature and the real-time coolant temperature.

[0089] Using the single-cell voltage of the middle cell as a reference, the cathode gas flow rate is reduced. When the single-cell voltage of the middle cell drops to a calibrated value, the real-time cathode gas flow rate is recorded, and the mass transfer sensitivity coefficient is calculated based on the initial cathode gas flow rate and the real-time cathode gas flow rate.

[0090] In practical use, calculate the voltage difference between the front battery and the middle battery (take the absolute value): ΔV (FM) = |V(F)- V(M)|; calculate the voltage difference between the rear battery and the middle battery (take the absolute value): ΔV (RM) = |V(R)- V(M)|.

[0091] Sensitivity coefficient calibration value determination: Define the larger of ΔV(FM) and ΔV(RM) as the calibration value at this current density, denoted as Std. (j=x) .

[0092] Sensitivity coefficient calibration: Calibration is performed using the single-cell voltage V(M) in the middle as a reference.

[0093] (1) Temperature sensitivity coefficient calibration: Gradually decrease the stack coolant temperature while keeping other operating conditions unchanged. At the same time, the V(M) value can be observed to gradually decrease. When the voltage of the middle single cell drops from V(M) to V(M)-Std (j=x), read the real-time temperature of the stack coolant and record it as T(exp). Calculate the temperature sensitivity coefficient based on the initial coolant temperature and the real-time coolant temperature.

[0094] (2) Mass transfer sensitivity coefficient calibration: Gradually reduce the cathode gas flow rate of the fuel cell stack while keeping other operating conditions unchanged. At the same time, the value of V(M) can be observed to gradually decrease. When the voltage of the middle single cell drops from V(M) to V(M) - Std (j=x), read the real-time value of the cathode gas flow rate at this time and record it as Q(exp). Calculate the mass transfer sensitivity coefficient based on the initial cathode gas flow rate and the real-time cathode gas flow rate.

[0095] This calibration method avoids calibration deviations caused by using a fixed voltage drop, ensuring that the sensitivity coefficient accurately reflects the impact of temperature and flow rate changes on the voltage under the operating conditions. This provides a reasonable normalized benchmark for subsequent impedance difference parameter calculations. Furthermore, using the central battery as the monitoring object during calibration eliminates the interference of endplate effects on the calibration process, guaranteeing the reliability of the calibration results.

[0096] In one embodiment, the temperature sensitivity coefficient is calculated using the following formula:

[0097] S T (j=x) = T(i) / [T(i) - T(exp)]

[0098] Among them, S T (j=x) T is the temperature sensitivity coefficient, T(i) is the initial coolant temperature, and T(exp) is the real-time coolant temperature when the battery voltage drops to the calibration value in the middle section.

[0099] The mass transfer sensitivity coefficient is calculated using the following formula:

[0100] S mass(j=x) = Q(i) / [Q(i) - Q(exp)]

[0101] Among them, S mass(j=x) Q(i) is the mass transfer sensitivity coefficient, Q(i) is the initial cathode gas flow rate, and Q(exp) is the real-time cathode gas flow rate when the voltage of the middle cell drops to the calibration value.

[0102] The method of this invention calculates the temperature sensitivity coefficient and mass transfer sensitivity coefficient using the above formulas, quantifying the impact of temperature and flow rate changes on voltage into comparable values, and providing a quantitative basis for subsequently converting impedance differences into equivalent temperature or flow rate deviations.

[0103] Step 104: Based on activation impedance, mass transfer impedance, temperature sensitivity coefficient, and mass transfer sensitivity coefficient, calculate the activation impedance difference parameter and mass transfer impedance difference parameter between the front-end battery and the middle battery, and between the rear-end battery and the middle battery, respectively.

[0104] In one embodiment, the activation impedance difference parameter between the front-end battery and the middle battery is calculated using the following formula:

[0105]

[0106] in, This is a parameter representing the difference in activation impedance between the front-end and middle-end cells. The activation impedance of the front-end battery. The activation impedance of the middle battery. Temperature sensitivity coefficient;

[0107] The mass transfer impedance difference between the front-end cell and the middle cell is calculated using the following formula:

[0108]

[0109] in, This represents the mass transfer impedance difference parameter between the front-end and middle-end cells. The mass transfer impedance of the front-end battery is... The mass transfer impedance of the middle battery is... The mass transfer sensitivity coefficient;

[0110] The difference in activation impedance between the rear-end battery and the middle battery is calculated using the following formula:

[0111]

[0112] in, This is a parameter representing the difference in activation impedance between the back-end and middle-end batteries. The activation impedance of the back-end battery. The activation impedance of the middle battery. Temperature sensitivity coefficient;

[0113] The mass transfer impedance difference between the rear-end battery and the middle battery is calculated using the following formula:

[0114]

[0115] in, This represents the mass transfer impedance difference parameter between the back-end battery and the middle battery. The mass transfer impedance of the back-end battery. The mass transfer impedance of the middle battery is... is the mass transfer sensitivity coefficient.

[0116] The method of this invention calculates the activation impedance difference parameter and the mass transfer impedance difference parameter using the above formula. The impedance difference between the end and middle cells is normalized using temperature sensitivity coefficient and mass transfer sensitivity coefficient, respectively. This transforms the activation impedance change and mass transfer impedance change, which originally had different physical meanings and could not be directly compared, to the same scale, laying the calculation foundation for determining the dominant factor of the endplate effect through the ratio.

[0117] Step 105: Calculate the ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the front-end battery and the back-end battery respectively. Based on the comparison results of the ratio with the preset threshold, determine the cause type of endplate effect near the front-end plate and the back-end plate respectively.

[0118] In practical applications, the ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the front-end battery and the back-end battery is calculated using the following formulas.

[0119] The ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the front-end cell:

[0120]

[0121] The ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the downstream battery:

[0122] .

[0123] In one embodiment, the preset threshold includes a first threshold and a second threshold, wherein the first threshold is less than the second threshold; based on the comparison result between the ratio and the preset threshold, the cause type of endplate effect near the front end plate and near the rear end plate is determined, specifically including:

[0124] When the ratio is less than or equal to the first threshold, the endplate effect near the corresponding endplate is determined to be dominated by gas mass transfer factors.

[0125] When the ratio is greater than or equal to the second threshold, the endplate effect near the corresponding endplate is determined to be temperature-dominated.

[0126] When the ratio is greater than the first threshold and less than the second threshold, the endplate effect near the corresponding endplate is determined to be of the temperature and gas mass transfer coupling type.

[0127] In this embodiment, the first threshold can be set to 0.2, and the second threshold can be set to 5. Specifically: identification of the cause of the front-end board endplate effect (based on the value of K(F)):

[0128] If the value is ≤0.2, then it is determined that "the endplate effect near the front plate is dominated by gas mass transfer factors";

[0129] If the value is ≥5, then it is determined that "the endplate effect near the front end plate is dominated by temperature factors";

[0130] If the value is greater than 0.2 and less than 5, then it is determined that "the endplate effect near the front-end plate is a coupled influence of temperature and gas mass transfer".

[0131] Identification of the cause of end-plate effect (based on the value of K(R)):

[0132] If the value is ≤0.2, then it is determined that "the endplate effect near the rear end plate is dominated by gas mass transfer factors";

[0133] If the value is ≥5, then it is determined that "the end plate effect near the rear end plate is dominated by temperature factors";

[0134] If the value is greater than 0.2 and less than 5, then it is determined that "the endplate effect near the endplate is a coupled effect of temperature and gas mass transfer".

[0135] The method of this invention compares the calculated ratio with a preset threshold to clearly classify the causes of the endplate effect into three categories: gas mass transfer factor-dominated, temperature factor-dominated, and coupled influence of both. This classification provides a direct basis for the selection of subsequent optimization measures: for the temperature-dominated type, the focus can be on end heating or insulation; for the mass transfer-dominated type, the focus can be on optimizing the gas distribution structure; and for the coupled type, improvements in both aspects need to be considered comprehensively, thereby improving the pertinence and effectiveness of the improvement measures.

[0136] This invention provides a method for diagnosing the causes of endplate effects in fuel cells. First, at least one single cell is selected as a test object from the endplate effect influence areas of the front and rear ends of the fuel cell stack, as well as the middle section. Then, under preset operating conditions, the single-cell voltage and electrochemical impedance spectroscopy (EIS) data of each test object are collected, and the activation impedance and mass transfer impedance of each test object are extracted. Next, using the single-cell voltage of the middle cell as a reference, the temperature sensitivity coefficient and mass transfer sensitivity coefficient are calibrated by changing the stack coolant temperature and cathode gas flow rate while monitoring the voltage change of the middle cell. Based on the activation impedance, mass transfer impedance, temperature sensitivity coefficient, and mass transfer sensitivity coefficient, the activation impedance difference parameter and mass transfer impedance difference parameter between the front and middle cells, and between the rear and middle cells, are calculated, respectively. Finally, the ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter for the front and rear cells is calculated, and the cause type of the endplate effect near the front and rear ends is determined based on the comparison result of the ratio with a preset threshold. This invention's method can pinpoint the specific causes of endplate effects at the front and rear ends of a fuel cell stack under specific conditions, thereby achieving more targeted improvements and effectively enhancing the voltage consistency of individual cells within the stack. Furthermore, this method, based on electrochemical impedance spectroscopy analysis, features short cycles and broad applicability, making it suitable for various fuel cell stacks and operating conditions. It reduces the number of repetitive tests and trial-and-error processes, saving material costs and shortening development cycles for enterprises.

[0137] Based on the above Figure 3 The corresponding embodiment describes a method for diagnosing the cause of endplate effect in a fuel cell. The following is an embodiment of the device of the present invention, which can be used to execute the method embodiment of the present invention.

[0138] This invention provides a diagnostic device for the cause of endplate effect in fuel cells, such as... Figure 5 As shown, the device includes: a selection module 201, an acquisition module 202, a calibration module 203, a calculation module 204, and a judgment module 205;

[0139] Module 201 is used to select at least one single cell as a test object from the front end plate end plate effect influence area, the rear end plate end plate effect influence area and the middle part of the fuel cell stack, respectively.

[0140] The acquisition module 202 is used to acquire the individual voltage of each test object under preset working conditions, and to acquire the electrochemical impedance spectroscopy data of each test object, and extract the activation impedance and mass transfer impedance of each test object from them.

[0141] The calibration module 203 is used to calibrate the temperature sensitivity coefficient and mass transfer sensitivity coefficient by changing the stack coolant temperature and cathode gas flow rate respectively, and monitoring the voltage change of the central single cell, with the single cell voltage of the central cell as a reference.

[0142] Calculation module 204 is used to calculate the difference parameters of activation impedance and mass transfer impedance between the front-end battery and the middle battery, and between the rear-end battery and the middle battery, based on activation impedance, mass transfer impedance, temperature sensitivity coefficient and mass transfer sensitivity coefficient, respectively.

[0143] The determination module 205 is used to calculate the ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the front-end battery and the rear-end battery respectively, and determine the cause type of endplate effect near the front-end plate and the rear-end plate respectively based on the comparison result of the ratio with the preset threshold.

[0144] This invention provides a diagnostic device for the cause of endplate effect in fuel cells, comprising: a selection module 201, an acquisition module 202, a calibration module 203, a calculation module 204, and a judgment module 205. The selection module 201 selects at least one single cell from the endplate effect influence areas of the front and rear ends of the fuel cell stack as test objects. The acquisition module 202, under preset operating conditions, acquires the single-cell voltage of each test object and the electrochemical impedance spectroscopy data of each test object, and extracts the activation impedance and mass transfer impedance of each test object from the data. The calibration module 203 uses the single-cell voltage of the middle cell as a basis... The device calibrates temperature and mass transfer sensitivity coefficients by changing the coolant temperature and cathode gas flow rate of the fuel cell stack and monitoring the voltage changes of the middle cell. Calculation module 204 calculates the activation impedance difference parameters and mass transfer impedance difference parameters between the front and middle cells, and between the rear and middle cells, based on activation impedance, mass transfer impedance, temperature sensitivity coefficient, and mass transfer sensitivity coefficient. Judgment module 205 calculates the ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter for the front and rear cells, and determines the cause of endplate effects near the front and rear plates based on the comparison of the ratio with preset thresholds. This invention can identify the specific causes of endplate effects at the front and rear plates for specific fuel cell stacks and operating conditions, thereby achieving more targeted improvement and effectively enhancing the voltage consistency of each cell in the fuel cell stack. Furthermore, this device, based on electrochemical impedance spectroscopy, features short cycle time and broad applicability, suitable for different fuel cell stacks and operating conditions, reducing the number of repeated experiments and trial-and-error processes, saving material costs and shortening the development cycle for enterprises.

[0145] Based on the above Figure 3 In addition to the fuel cell endplate effect diagnosis method described in the corresponding embodiments, another embodiment of the present invention provides a fuel cell endplate effect diagnosis device. This device includes a processor and a memory, wherein the memory stores at least one computer instruction, which is loaded and executed by the processor to achieve the above-described results. Figure 3 The corresponding embodiment describes a method for diagnosing the causes of fuel cell endplate effects.

[0146] Based on the above Figure 3 In addition to the fuel cell endplate effect diagnosis method described in the corresponding embodiments, this invention also provides a computer-readable storage medium. For example, a non-transitory computer-readable storage medium may be a read-only memory (ROM), a random access memory (RAM), a CD-ROM, magnetic tape, a floppy disk, or an optical data storage system. This storage medium stores at least one computer instruction for executing the above-described... Figure 3 The diagnostic methods for the causes of fuel cell endplate effects described in the corresponding embodiments will not be repeated here.

[0147] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0148] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for diagnosing the causes of endplate effect in fuel cells, characterized in that, The method includes: At least one single cell was selected as the test object from the endplate effect area of ​​the front endplate, the endplate effect area of ​​the rear endplate, and the middle part of the fuel cell stack. Under preset operating conditions, the individual voltage of each test object is collected, and the electrochemical impedance spectroscopy data of each test object is obtained, and the activation impedance and mass transfer impedance of each test object are extracted from them. Using the single cell voltage in the middle section as a reference, the temperature sensitivity coefficient and mass transfer sensitivity coefficient were calibrated by changing the stack coolant temperature and cathode gas flow rate respectively and monitoring the voltage change of the middle section single cell. Based on the activation impedance, the mass transfer impedance, the temperature sensitivity coefficient, and the mass transfer sensitivity coefficient, the activation impedance difference parameter and the mass transfer impedance difference parameter between the front-end battery and the middle battery, and between the rear-end battery and the middle battery are calculated respectively. The ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the front-end battery and the rear-end battery is calculated respectively. Based on the comparison result of the ratio with the preset threshold, the cause type of endplate effect near the front-end plate and the rear-end plate is determined respectively. The temperature sensitivity coefficient is calculated using the following formula: S T (j=x) = T(i) / [T(i) - T(exp)] Among them, S T (j=x) Here, T(i) is the temperature sensitivity coefficient, T(i) is the initial coolant temperature, and T(exp) is the real-time coolant temperature when the mid-cell voltage drops to the calibrated value. The mass transfer sensitivity coefficient is calculated using the following formula: S mass(j=x) = Q(i) / [Q(i) - Q(exp)] Among them, S mass(j=x) Q(i) is the mass transfer sensitivity coefficient, Q(i) is the initial cathode gas flow rate, and Q(exp) is the real-time cathode gas flow rate when the voltage of the middle cell drops to the calibrated value. The activation impedance difference parameter between the front-end battery and the middle battery is calculated using the following formula: in, This is a parameter representing the difference in activation impedance between the front-end and middle-end cells. The activation impedance of the front-end battery. The activation impedance of the middle battery. Temperature sensitivity coefficient; The mass transfer impedance difference parameter between the front-end battery and the middle battery is calculated using the following formula: in, This represents the mass transfer impedance difference parameter between the front-end and middle-end cells. The mass transfer impedance of the front-end battery is... The mass transfer impedance of the middle battery is... The mass transfer sensitivity coefficient; The difference in activation impedance between the rear-end battery and the middle battery is calculated using the following formula: in, This is a parameter representing the difference in activation impedance between the back-end and middle-end batteries. The activation impedance of the back-end battery. The activation impedance of the middle battery. Temperature sensitivity coefficient; The mass transfer impedance difference parameter between the rear battery and the middle battery is calculated using the following formula: in, This represents the mass transfer impedance difference parameter between the back-end battery and the middle battery. The mass transfer impedance of the back-end battery. The mass transfer impedance of the middle battery is... The mass transfer sensitivity coefficient; The ratios of the activation impedance difference parameter to the mass transfer impedance difference parameter for the front-end and rear-end cells are calculated using the following formulas: The ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the front-end cell: The ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the downstream battery: The preset threshold includes a first threshold and a second threshold, wherein the first threshold is less than the second threshold; the step of determining the cause type of endplate effect near the front end plate and near the rear end plate based on the comparison result of the ratio and the preset threshold specifically includes: When the ratio is less than or equal to the first threshold, it is determined that the endplate effect near the corresponding endplate is dominated by gas mass transfer factors. When the ratio is greater than or equal to the second threshold, it is determined that the endplate effect near the corresponding endplate is temperature-dominated. When the ratio is greater than the first threshold and less than the second threshold, the endplate effect near the corresponding endplate is determined to be of the temperature and gas mass transfer coupling type.

2. The method for diagnosing the cause of endplate effect in fuel cells according to claim 1, characterized in that, The process of selecting at least one single cell from the endplate effect influence areas of the front and rear plates of the fuel cell stack as test subjects specifically includes: Select the single cell closest to the front panel, the single cell closest to the rear panel, and the single cell located in the center of the stack.

3. The method for diagnosing the cause of endplate effect in fuel cells according to claim 1, characterized in that, When multiple single cells are selected as test objects from the front end plate effect area, the rear end plate effect area, or the middle of the stack, the single cell voltage of the test object is taken as the average value of the voltages of the selected multiple single cells, and the activation impedance and mass transfer impedance are taken as the average value of the impedances of the selected multiple single cells.

4. The method for diagnosing the cause of endplate effect in fuel cells according to claim 1, characterized in that, The method for extracting the activation impedance and mass transfer impedance of each test object from the electrochemical impedance spectroscopy data specifically includes: The relaxation time distribution of the electrochemical impedance spectroscopy data is analyzed, and the peak value appearing in the first frequency range is taken as the activation impedance, and the peak value appearing in the second frequency range is taken as the mass transfer impedance, wherein the first frequency range is greater than the second frequency range.

5. The method for diagnosing the cause of endplate effect in fuel cells according to claim 1, characterized in that, The method for extracting the activation impedance and mass transfer impedance of each test object from the electrochemical impedance spectroscopy data specifically includes: The electrochemical impedance spectroscopy data are fitted with an equivalent circuit, and the activation impedance and the mass transfer impedance are extracted from the fitting results.

6. The method for diagnosing the cause of endplate effect in fuel cells according to claim 1, characterized in that, The process of calibrating temperature sensitivity and mass transfer sensitivity coefficients by using the single cell voltage of the central cell as a reference, and by changing the stack coolant temperature and cathode gas flow rate while monitoring the voltage change of the central cell, specifically includes: Calculate the absolute value of the voltage difference between the front-end battery and the middle battery, and the absolute value of the voltage difference between the rear-end battery and the middle battery, and use the maximum value of the two as the calibration value; Using the individual cell voltage of the central battery as a reference, the temperature of the stack coolant is reduced. When the individual cell voltage of the central battery drops by the calibrated amount, the real-time coolant temperature is recorded, and the temperature sensitivity coefficient is calculated based on the initial coolant temperature and the real-time coolant temperature. Using the single-cell voltage of the central battery as a reference, the cathode gas flow rate is reduced. When the single-cell voltage of the central battery drops by the calibrated amount, the real-time cathode gas flow rate is recorded, and the mass transfer sensitivity coefficient is calculated based on the initial cathode gas flow rate and the real-time cathode gas flow rate.

7. A diagnostic device for the cause of endplate effect in fuel cells, characterized in that, include: The module includes a selection module, an acquisition module, a calibration module, a calculation module, and a judgment module. The selection module is used to select at least one single cell as a test object from the front end plate end plate effect influence area, the rear end plate end plate effect influence area and the middle part of the fuel cell stack, respectively. The acquisition module is used to collect the individual voltage of each test object under preset working conditions, and to acquire the electrochemical impedance spectroscopy data of each test object, and extract the activation impedance and mass transfer impedance of each test object from them. The calibration module is used to calibrate the temperature sensitivity coefficient and mass transfer sensitivity coefficient by changing the stack coolant temperature and cathode gas flow rate respectively, and monitoring the voltage change of the central single cell, with the single cell voltage as a reference. The temperature sensitivity coefficient is expressed by formula S. T (j=x) = T(i) / [T(i) - T(exp)] is calculated, where S T (j=x) The temperature sensitivity coefficient is T(i), where T(i) is the initial coolant temperature, and T(exp) is the real-time coolant temperature at the calibrated point when the mid-cell voltage drops; the mass transfer sensitivity coefficient is expressed by formula S. mass(j=x) = Q(i) / [Q(i) - Q(exp)] is calculated, where S mass(j=x) Q(i) is the mass transfer sensitivity coefficient, Q(i) is the initial cathode gas flow rate, and Q(exp) is the real-time cathode gas flow rate when the voltage of the middle cell drops to the calibrated value. The calculation module is used to calculate the activation impedance difference parameter and mass transfer impedance difference parameter between the front-end battery and the middle battery, and between the rear-end battery and the middle battery, respectively, based on the activation impedance, the mass transfer impedance, the temperature sensitivity coefficient, and the mass transfer sensitivity coefficient; the activation impedance difference parameter between the front-end battery and the middle battery is calculated using the formula... Calculate, where, This is a parameter representing the difference in activation impedance between the front-end and middle-end cells. The activation impedance of the front-end battery. The activation impedance of the middle battery. The temperature sensitivity coefficient; the mass transfer impedance difference parameter between the front-end battery and the middle battery is determined by the formula. Calculate, where, This represents the mass transfer impedance difference parameter between the front-end and middle-end cells. The mass transfer impedance of the front-end battery is... The mass transfer impedance of the middle battery is... The mass transfer sensitivity coefficient; the activation impedance difference parameter between the rear battery and the middle battery is determined by the formula. Calculate, where, This is a parameter representing the difference in activation impedance between the back-end and middle-end batteries. The activation impedance of the back-end battery. The activation impedance of the middle battery. The temperature sensitivity coefficient; the mass transfer impedance difference parameter between the rear battery and the middle battery is determined by the formula. Calculate, where, This represents the mass transfer impedance difference parameter between the back-end battery and the middle battery. The mass transfer impedance of the back-end battery. The mass transfer impedance of the middle battery is... The mass transfer sensitivity coefficient; The determination module is used to calculate the ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the front-end battery and the back-end battery, respectively. The ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the front-end battery is calculated using the formula... Calculation; the ratio of the activation impedance difference parameter to the mass transfer impedance difference parameter of the back-end battery is obtained through the formula. Calculate; based on the comparison result of the ratio and the preset threshold, determine the cause type of endplate effect near the front end plate and the rear end plate respectively; the preset threshold includes a first threshold and a second threshold, and the first threshold is less than the second threshold; when the ratio is less than or equal to the first threshold, determine that the endplate effect near the corresponding end plate is dominated by gas mass transfer factors; when the ratio is greater than or equal to the second threshold, determine that the endplate effect near the corresponding end plate is dominated by temperature factors; when the ratio is greater than the first threshold and less than the second threshold, determine that the endplate effect near the corresponding end plate is a temperature and gas mass transfer coupled influence type.

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