Fuel cell water management fault diagnosis method and system

Abstract

The invention provides a fuel cell water management fault diagnosis method and system. The method comprises the following steps: controlling the on-off of the output current of the fuel cell by using DC / DC, periodically recording the voltage change before and after the current interruption, and processing to obtain step data of voltage response and relaxation data of voltage response; calculating ohmic resistance according to the step data of the voltage response; calculating a diffusion resistance coefficient according to relaxation data of the voltage response; judging the dry and wet state in the fuel cell according to the ohmic resistance and the diffusion resistance coefficient; and adjusting operation parameters in real time according to the dry and wet state in the fuel cell, so that the fuel cell is kept in the optimal working state. The system comprises a data acquisition unit, an ohmic resistance calculation unit, a diffusion resistance coefficient calculation unit, a dry and wet state judgment unit and a central control unit. By periodically monitoring the change of the ohmic resistance and the diffusion resistance coefficient in the fuel cell, the real-time feedback of the dry and wet state in the fuel cell is realized.

Description

Technical Field

[0001] The present invention relates to the field of fuel cell technology, and in particular to a fuel cell water management fault diagnosis method and system. Background Art

[0002] The performance and life of proton exchange membrane fuel cells (PEMFCs) largely rely on the balance of their internal dry and wet states. Accurate diagnosis and monitoring of the dry and wet states inside the fuel cell are essential for optimizing battery performance and extending its service life. However, the current diagnostic methods for fuel cell water management failures are very limited, and electrochemical impedance spectroscopy is mainly used to monitor and diagnose fuel cell stacks.

[0003] Patent CN 117457949 A discloses a fuel cell water fault diagnosis method and system based on electrochemical impedance spectroscopy. By measuring the electrochemical impedance spectrum curve of the fuel cell under different water content states, the curve characteristic points and local change characteristics with high correlation with water content are extracted, and the relationship between the curve characteristics and the water fault state of the fuel cell stack is established. CN116381503 A discloses a fuel cell electrochemical impedance spectrum estimation method for water management fault diagnosis. The impedance estimation method of multi-model fusion is used to achieve impedance estimation in the full frequency range. Although the above method has improved the efficiency and accuracy of EIS for fuel cell water management faults to a certain extent, it still cannot solve the problems of maximum current limitation, high instrument cost, complex data processing, and long testing time when EIS is applied to high-power stacks. Summary of the invention

[0004] Based on the above background technology, the present invention provides a fuel cell water management fault diagnosis method and system, which is mainly used to determine the dryness and wetness inside the fuel cell. The present invention mainly uses a data acquisition unit, a DC / DC control unit, an analysis unit and a central control unit, and determines the dryness and wetness inside the fuel cell based on the current interruption method. The existing fuel cell system can be used for monitoring without modification, which reduces the cost and test time, and improves the stability and test efficiency.

[0005] The technical means adopted by the present invention are as follows:

[0006] A fuel cell water management fault diagnosis method, comprising:

[0007] The DC / DC is used to control the on and off of the output current of the fuel cell, and the voltage changes before and after the current is interrupted are periodically recorded to obtain the step data of the voltage response and the relaxation data of the voltage response;

[0008] Calculate the ohmic resistance based on the step data of the voltage response;

[0009] Based on the relaxation data of the voltage response, the diffusion resistance coefficient is calculated;

[0010] The dry and wet state inside the fuel cell can be determined by ohmic resistance and diffusion resistance coefficient;

[0011] According to the dry and wet conditions inside the fuel cell, the operating parameters are adjusted in real time to keep the fuel cell in the best working condition.

[0012] Furthermore, the voltage change before and after the current interruption is expressed as E(t), and the calculation formula is as follows:

[0013]

[0014] Among them, I 0 is the current density before the current is interrupted, R m is the ohmic resistance, k is the diffusion resistance coefficient, and t is the time.

[0015] Furthermore, the ohmic resistance is calculated based on the step data of the voltage response, and the calculation formula is as follows:

[0016] R m =ΔV / I 0

[0017] Among them, I 0 is the current density before the current is interrupted, and ΔV is the step change in voltage before and after the current is interrupted.

[0018] Furthermore, the diffusion resistance coefficient is calculated based on the relaxation data of the voltage response, and the calculation formula is as follows:

[0019] k=k 1 / I 0

[0020] Among them, k 1 The voltage is related to the relaxation phase of the voltage change. The slope of the linear fit.

[0021] Furthermore, the specific process of judging the dry and wet state inside the fuel cell by using the ohmic resistance and the diffusion resistance coefficient is as follows:

[0022] When the calculated ohmic resistance R m becomes larger, it means that the humidity inside the fuel cell decreases;

[0023] When the ohmic resistance R m remains unchanged, and the diffusion resistance coefficient k increases, the humidity inside the fuel cell increases.

[0024] Corresponding to the fuel cell water management fault diagnosis method in the present application, the present application also provides a fuel cell water management fault diagnosis system, including: a data acquisition unit, an ohmic resistance calculation unit, a diffusion resistance coefficient calculation unit, a dry and wet state judgment unit and a central control unit, wherein:

[0025] The data acquisition unit is used to control the on and off of the output current of the fuel cell by using DC / DC, and periodically record the voltage change before and after the current is interrupted, and process to obtain the step data of the voltage response and the relaxation data of the voltage response;

[0026] The ohmic resistance calculation unit is used to calculate the ohmic resistance according to the step data of the voltage response processed by the data acquisition unit;

[0027] The diffusion resistance coefficient calculation unit is used to calculate the diffusion resistance coefficient according to the relaxation data of the voltage response processed by the data acquisition unit;

[0028] The dry-wet state judgment unit is used to judge the dry-wet state inside the fuel cell according to the ohmic resistance calculated by the ohmic resistance calculation unit and the diffusion resistance coefficient calculated by the diffusion resistance coefficient calculation unit;

[0029] The central control unit is used to adjust the operating parameters in real time according to the dry and wet state inside the fuel cell determined by the dry and wet state determination unit, so as to keep the fuel cell in the best working state.

[0030] Furthermore, the data acquisition unit is an oscilloscope, a data acquisition card or a voltage inspection system.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The present invention provides a fuel cell water management fault diagnosis method and system, which uses a current interruption method to comprehensively analyze ohmic resistance and diffusion resistance coefficient to diagnose water management faults such as membrane drying and flooding that occur during the operation of the fuel cell, thereby effectively improving the performance and stability of the fuel cell.

[0033] The present invention can perform dry-wet diagnosis inside the fuel cell through ohmic resistance and diffusion resistance coefficient without modifying the fuel cell stack, thereby avoiding the influence of complete hydration of the membrane electrode on the diagnosis result when diagnosing through ohmic resistance in the prior art (after the membrane electrode is fully hydrated, even if the humidity increases or even flooding occurs, the ohmic resistance of the battery remains almost unchanged). The diagnosis result is more accurate and the cost is greatly reduced. In addition, the present invention can complete the test within a time scale of milliseconds, greatly improving the test efficiency.

[0034] The fuel cell water management fault diagnosis method and system provided by the present invention realizes real-time feedback of the dry and wet state inside the fuel cell by periodically monitoring the changes of the ohmic resistance and diffusion resistance coefficient inside the fuel cell.

[0035] Based on the above reasons, the present invention can be widely promoted in the fields of fuel cells and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0037] Figure 1 This is a flow chart of the fuel cell water management fault diagnosis method in the present invention.

[0038] Figure 2 This is a test principle diagram of the current interruption method in the present invention.

[0039] Figure 3 Graph showing the experimental results in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0041] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0042] like Figure 1As shown, the present invention provides a fuel cell water management fault diagnosis method, comprising:

[0043] The DC / DC is used to control the on and off of the output current of the fuel cell, and the voltage changes before and after the current is interrupted are periodically recorded to obtain the step data of the voltage response and the relaxation data of the voltage response;

[0044] In a specific implementation, as an embodiment of the present invention, the voltage change before and after the current interruption is expressed as E(t), and the calculation formula is as follows:

[0045]

[0046] Among them, I 0 is the current density before the current is interrupted, R m is the ohmic resistance, k is the diffusion resistance coefficient, and t is the time.

[0047] Calculate the ohmic resistance based on the step data of the voltage response;

[0048] In a specific implementation, as an embodiment of the present invention, the ohmic resistance is calculated according to the step data of the voltage response, and the calculation formula is as follows:

[0049] R m =ΔV / I 0

[0050] Among them, I 0 is the current density before the current is interrupted, and ΔV is the step change in voltage before and after the current is interrupted.

[0051] Based on the relaxation data of the voltage response, the diffusion resistance coefficient is calculated;

[0052] In a specific implementation, as an embodiment of the present invention, the diffusion resistance coefficient is calculated based on the relaxation data of the voltage response, and the calculation formula is as follows:

[0053] k=k 1 / I 0

[0054] Among them, k 1 The voltage is related to the relaxation phase of the voltage change. The slope of the linear fit.

[0055] The dry and wet state inside the fuel cell can be determined by ohmic resistance and diffusion resistance coefficient;

[0056] In specific implementation, as an embodiment of the present invention, the specific process of judging the dry and wet state inside the fuel cell by using the ohmic resistance and the diffusion resistance coefficient is:

[0057] When the calculated ohmic resistance Rm becomes larger, it means that the humidity inside the fuel cell decreases;

[0058] When the ohmic resistance R m remains unchanged, and the diffusion resistance coefficient k increases, the humidity inside the fuel cell increases.

[0059] According to the dry and wet conditions inside the fuel cell, the operating parameters are adjusted in real time to keep the fuel cell in the best working condition.

[0060] Corresponding to the fuel cell water management fault diagnosis method in the present application, the present application also provides a fuel cell water management fault diagnosis system, including: a data acquisition unit, an ohmic resistance calculation unit, a diffusion resistance coefficient calculation unit, a dry and wet state judgment unit and a central control unit, wherein:

[0061] The data acquisition unit is used to control the on and off of the output current of the fuel cell by using DC / DC, and periodically record the voltage change before and after the current is interrupted, and process to obtain the step data of the voltage response and the relaxation data of the voltage response;

[0062] The ohmic resistance calculation unit is used to calculate the ohmic resistance according to the step data of the voltage response processed by the data acquisition unit;

[0063] The diffusion resistance coefficient calculation unit is used to calculate the diffusion resistance coefficient according to the relaxation data of the voltage response processed by the data acquisition unit;

[0064] The dry-wet state judgment unit is used to judge the dry-wet state inside the fuel cell according to the ohmic resistance calculated by the ohmic resistance calculation unit and the diffusion resistance coefficient calculated by the diffusion resistance coefficient calculation unit;

[0065] The central control unit is used to adjust the operating parameters in real time according to the dry and wet state inside the fuel cell determined by the dry and wet state determination unit, so as to keep the fuel cell in the best working state.

[0066] In a specific implementation, as an embodiment of the present invention, the data acquisition unit is an oscilloscope, a data acquisition card or a voltage inspection system.

[0067] As for the embodiments of the present invention, since they correspond to the embodiments above, the description is relatively simple. For the relevant similarities, please refer to the description of the above embodiments, which will not be described in detail here.

[0068] Example 1

[0069] like Figure 1 As shown, the present invention provides a fuel cell water management fault diagnosis method and system, Figure 2The schematic diagram of the current interruption method test, where (a) is the current interruption contour curve applied to the battery, and (b) is the response of the battery voltage over time after the current is interrupted.

[0070] When implemented, the experimental object was 25cm 2 For a single-cell proton exchange membrane fuel cell, the test system mainly includes fuel cell test bench, electronic load, electrochemical workstation, digital oscilloscope and other equipment.

[0071] In Example 1, the fuel cell was operated to a current density of 800 mA / cm 2 , battery temperature 70℃, intake air humidity 21%, hydrogen-air stoichiometric ratio 1.5 / 2.5, back pressure 1bar, running for 60min;

[0072] The electronic load is controlled to be interrupted for 1 second, and the digital oscilloscope records the voltage change within 24ms before and after the interruption, and the ohmic resistance and diffusion resistance coefficient are calculated;

[0073] The electrochemical workstation tested the electrochemical impedance spectrum of the battery. The test frequency range was 10kHz-0.1Hz, the AC signal was a current signal, and the current amplitude was 5%. The EIS data were fitted using Zview software, and the equivalent circuit model used for fitting was the simplified Randles model.

[0074] Example 2

[0075] Based on Example 1, the fuel cell was operated to a current density of 800 mA / cm 2 , battery temperature 70℃, intake air humidity 63%, hydrogen-air stoichiometric ratio 1.5 / 2.5, back pressure 1bar, running for 60min;

[0076] The electronic load is controlled to be interrupted for 1 second, and the digital oscilloscope records the voltage change within 24ms before and after the interruption, and the ohmic resistance and diffusion resistance coefficient are calculated;

[0077] The electrochemical workstation tested the electrochemical impedance spectrum of the battery. The test frequency range was 10kHz-0.1Hz, the AC signal was a current signal, and the current amplitude was 5%. The EIS data were fitted using Zview software, and the equivalent circuit model used for fitting was the simplified Randles model.

[0078] Example 3

[0079] Based on Example 1, the fuel cell was operated to a current density of 800 mA / cm 2 , battery temperature 70℃, intake air humidity 100%, hydrogen-air stoichiometric ratio 1.5 / 2.5, back pressure 1bar, run for 60min;

[0080] The electronic load is controlled to be interrupted for 1 second, and the digital oscilloscope records the voltage change within 24ms before and after the interruption, and the ohmic resistance and diffusion resistance coefficient are calculated;

[0081] The electrochemical workstation tested the electrochemical impedance spectrum of the battery. The test frequency range was 10kHz-0.1Hz, the AC signal was a current signal, and the current amplitude was 5%. The EIS data were fitted using Zview software, and the equivalent circuit model used for fitting was the simplified Randles model.

[0082] The experimental results of Examples 1-3 are as follows Figure 3 As shown, (a) is a schematic diagram of voltage change, (b) is an electrochemical impedance spectroscopy data diagram, (cd) are current interruption method data diagrams, (e) is an ohmic resistance data diagram; (f) is a diffusion resistance coefficient and Warburg impedance coefficient data diagram.

[0083] When changing the intake air humidity, Figure 3 It can be seen that the ohmic resistance of Example 1 is much greater than that of Example 2, indicating that the interior of the fuel cell of Example 1 is in a relatively dry state; while the ohmic resistances of Example 2 and Example 3 are almost the same, and it is necessary to make a judgment in combination with the diffusion resistance coefficient. Figure 3 f It can be seen that the diffusion resistance coefficient of Example 3 is larger and consistent with the trend of the Warburg impedance coefficient obtained by electrochemical impedance spectrum fitting. This shows that the method disclosed in the present invention can diagnose the dry and wet state inside the fuel cell by combining the ohmic resistance and diffusion resistance coefficient obtained by the current interruption method.

[0084] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0085] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0086] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0087] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0088] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0089] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fuel cell water management fault diagnosis method, characterized in that: include: The DC / DC is used to control the on and off of the output current of the fuel cell, and the voltage changes before and after the current is interrupted are periodically recorded to obtain the step data of the voltage response and the relaxation data of the voltage response; Calculate the ohmic resistance based on the step data of the voltage response; Based on the relaxation data of the voltage response, the diffusion resistance coefficient is calculated; The dry and wet state inside the fuel cell can be determined by ohmic resistance and diffusion resistance coefficient; According to the dry and wet conditions inside the fuel cell, the operating parameters are adjusted in real time to keep the fuel cell in the best working condition.

2. A fuel cell water management fault diagnosis method according to claim 1, characterized in that: The voltage change before and after the current interruption is expressed as E(t), and the calculation formula is as follows: Where I0 is the current density before the current is interrupted, R m is the ohmic resistance, k is the diffusion resistance coefficient, and t is the time.

3. A fuel cell water management fault diagnosis method according to claim 1, characterized in that: The ohmic resistance is calculated based on the step data of the voltage response, and the calculation formula is as follows: R m =ΔV / I0 Where I0 is the current density before the current is interrupted, and ΔV is the step change in voltage before and after the current is interrupted.

4. A fuel cell water management fault diagnosis method according to claim 1, characterized in that: The diffusion resistance coefficient is calculated based on the relaxation data of the voltage response, and the calculation formula is as follows: k=k1 / I0 Among them, k1 is the relaxation phase of voltage change, voltage and The slope of the linear fit.

5. A fuel cell water management fault diagnosis method according to claim 1, characterized in that: The specific process of judging the dry and wet state inside the fuel cell by using the ohmic resistance and the diffusion resistance coefficient is as follows: When the calculated ohmic resistance R m becomes larger, it means that the humidity inside the fuel cell decreases; When the ohmic resistance R m remains unchanged, and the diffusion resistance coefficient k increases, the humidity inside the fuel cell increases.

6. A fuel cell water management fault diagnosis system implemented based on the fuel cell water management fault diagnosis method according to any one of claims 1 to 5, characterized in that: include: Data acquisition unit, ohmic resistance calculation unit, diffusion resistance coefficient calculation unit, dry and wet state judgment unit and central control unit, wherein: The data acquisition unit is used to control the on and off of the output current of the fuel cell by using DC / DC, and periodically record the voltage change before and after the current is interrupted, and process to obtain the step data of the voltage response and the relaxation data of the voltage response; The ohmic resistance calculation unit is used to calculate the ohmic resistance according to the step data of the voltage response processed by the data acquisition unit; The diffusion resistance coefficient calculation unit is used to calculate the diffusion resistance coefficient according to the relaxation data of the voltage response processed by the data acquisition unit; The dry-wet state judgment unit is used to judge the dry-wet state inside the fuel cell according to the ohmic resistance calculated by the ohmic resistance calculation unit and the diffusion resistance coefficient calculated by the diffusion resistance coefficient calculation unit; The central control unit is used to adjust the operating parameters in real time according to the dry and wet state inside the fuel cell determined by the dry and wet state determination unit, so as to keep the fuel cell in the best working state.

7. A fuel cell water management fault diagnosis system according to claim 6, characterized in that: The data acquisition unit is an oscilloscope, a data acquisition card or a voltage inspection system.

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