A fuel cell water management fault diagnosis method and system

Abstract

The application 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 the step data of the voltage response and the relaxation data of the voltage response; calculating the ohmic resistance according to the step data of the voltage response; calculating the diffusion resistance coefficient according to the relaxation data of the voltage response; judging the dry-wet state inside the fuel cell through the ohmic resistance and the diffusion resistance coefficient; and adjusting the operation parameters in real time according to the dry-wet state inside the fuel cell, so that the fuel cell can keep the best working state. The system comprises a data acquisition unit, an ohmic resistance calculation unit, a diffusion resistance coefficient calculation unit, a dry-wet state judgment unit and a central control unit. The application realizes the real-time feedback of the dry-wet state inside the fuel cell by periodically monitoring the change of the ohmic resistance and the diffusion resistance coefficient inside the fuel cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cells, in particular, and especially relates to a fuel cell water management fault diagnosis method and system. BACKGROUND

[0002] The performance and life of a proton exchange membrane fuel cell (PEMFC) depend largely on the balance of its internal dry and wet states. Accurate diagnosis and monitoring of the internal dry and wet states of a fuel cell are crucial for optimizing cell performance and extending service life. However, there are very limited methods for diagnosing fuel cell water management faults, and the main method is to use electrochemical impedance spectroscopy 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 fuel cell electrochemical impedance spectroscopy curve under different water content states, the curve feature points and local change features with high correlation with water content are extracted, and the relationship between the curve features and the fuel cell stack water fault state is established. CN 116381503 A discloses a fuel cell electrochemical impedance spectroscopy estimation method for water management fault diagnosis. By using a multi-model fusion impedance estimation method, impedance estimation in the full frequency range is achieved. Although the above methods improve the efficiency and accuracy of EIS for fuel cell water management faults to some extent, they 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

[0004] Based on the above background technology, the present application provides a fuel cell water management fault diagnosis method and system, which is mainly used to judge the dry and wet degree inside the fuel cell. The present application mainly uses a data acquisition unit, a DC / DC control unit, an analysis unit and a central control unit to judge the dry and wet degree inside the fuel cell based on the current interruption method. The existing fuel cell system can be monitored without modification, which reduces the cost and testing time, and improves the stability and testing efficiency.

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

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

[0007] The output current of the fuel cell is controlled by the DC / DC control, and the voltage change before and after the current interruption is recorded periodically to obtain the step data of the voltage response and the relaxation data of the voltage response;

[0008] According to the step data of the voltage response, the ohmic resistance is calculated;

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

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

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

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

[0013]

[0014] Where I0 is the current density before the current interruption, R m is the ohmic resistance, k is the diffusion resistance coefficient, and t is the time.

[0015] Further, the ohmic resistance is calculated according to the step data of the voltage response, and the calculation formula is as follows:

[0016] R m = ΔV / I0

[0017] Where I0 is the current density before the current interruption, and ΔV is the step change of the voltage before and after the current interruption.

[0018] Further, the diffusion resistance coefficient is calculated according to the relaxation data of the voltage response, and the calculation formula is as follows:

[0019] k = k1 / I0

[0020] Where k1 is the slope of the linear fitting of the voltage and in the relaxation stage of the voltage change.

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

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

[0023] When the ohmic resistance R m does not change, but the diffusion resistance coefficient k becomes larger, 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, comprising: a data acquisition unit, an ohmic resistance calculation unit, a diffusion resistance coefficient calculation unit, a dry-wet state determination unit and a central control unit, wherein:

[0025] The data acquisition unit is configured to utilize the on-off control of the output current of the fuel cell by the DC / DC to periodically record the voltage change before and after the current interruption, and to process the step data of the voltage response and the relaxation data of the voltage response.

[0026] The ohmic resistance calculation unit is configured 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 configured 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 configured to judge the dry-wet state inside the fuel cell by 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 configured to adjust the operation parameters in real time according to the dry-wet state inside the fuel cell judged by the dry-wet state judgment unit, so as to keep the fuel cell in the best working state.

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

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

[0032] The present application provides a fuel cell water management fault diagnosis method and system, which comprehensively analyzes the ohmic resistance and the diffusion resistance coefficient by the current interruption method, diagnoses the water management faults such as membrane dryness and water flooding during the operation of the fuel cell, and thus effectively improves the performance and stability of the fuel cell.

[0033] The present application can diagnose the dry-wet state inside the fuel cell by the ohmic resistance and the diffusion resistance coefficient without modifying the stack, avoids the influence of the complete hydration of the membrane electrode on the diagnosis result in the prior art (after the complete hydration of the membrane electrode, the ohmic resistance of the battery almost remains unchanged even if the humidity increases or water flooding occurs), the diagnosis result is more accurate, the cost is greatly reduced, and the test can be completed within a millisecond time scale, which greatly improves the test efficiency.

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

[0035] Based on the above reasons, the present application can be widely popularized in the field of fuel cells. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained based on these drawings without creative labor.

[0037] Figure 1 Flow chart of fuel cell water management fault diagnosis method in the present application.

[0038] Figure 2 Test principle diagram of current interruption method in the present application.

[0039] Figure 3 Experimental result diagram in the embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to make the person skilled in the art better understand the present application, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

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

[0042] As shown in Figure 1 The present application provides a fuel cell water management fault diagnosis method, comprising:

[0043] The output current of the fuel cell is controlled by DC / DC, and the voltage change before and after current interruption is recorded periodically, and the step data of voltage response and the relaxation data of voltage response are obtained by processing;

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

[0045]

[0046] where I0 is the current density before the current interruption, R m is the ohmic resistance, k is the diffusion resistance coefficient, and t is the time.

[0047] According to the step data of the voltage response, the ohmic resistance is calculated;

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

[0049] R m = ΔV / I0

[0050] where I0 is the current density before the current interruption, and ΔV is the step change of the voltage before and after the current interruption.

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

[0052] In implementation, as an embodiment of the present application, according to the relaxation data of the voltage response, the diffusion resistance coefficient is calculated, and the calculation formula is as follows:

[0053] k = k1 / I0

[0054] where k1 is the slope of the linear fitting of the voltage and in the relaxation stage of the voltage change.

[0055] The dry and wet states inside the fuel cell are determined by the ohmic resistance and the diffusion resistance coefficient;

[0056] In implementation, as an embodiment of the present application, the specific process of determining the dry and wet states inside the fuel cell by the ohmic resistance and the diffusion resistance coefficient is as follows:

[0057] When the calculated ohmic resistance R m becomes larger, it indicates that the humidity inside the fuel cell decreases.

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

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

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

[0061] The data acquisition unit is used for periodically recording the voltage change before and after the current interruption by using the on-off of the DC / DC control output current of the fuel cell, and processing the step data of the voltage response and the relaxation data of the voltage response;

[0062] The ohmic resistance calculation unit is used for calculating 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 for calculating 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 for judging the dry-wet state inside the fuel cell by 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 for adjusting the operation parameters in real time according to the dry-wet state inside the fuel cell judged by the dry-wet state judgment unit, so as to keep the fuel cell in the best working state.

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

[0067] For the embodiment of the application, since it corresponds to the above embodiment, the description is relatively simple, and the related similar parts can be referred to the above embodiment, and will not be described in detail here.

[0068] Embodiment 1

[0069] As shown in the Figure 1 application, a fuel cell water management fault diagnosis method and system are provided, Figure 2 is a current interruption method test principle diagram, wherein (a) is a current interruption profile curve applied to the battery, and (b) is the response of the battery voltage with time after the current interruption.

[0070] In the implementation, the experimental object is a 25cm 2 single cell proton exchange membrane fuel cell, and the test system mainly comprises a fuel cell test bench, an electronic load, an electrochemical workstation, a digital oscilloscope and the like.

[0071] In embodiment 1, the fuel cell is operated to: a current density of 800 mA / cm2 , cell temperature 70℃, inlet humidity 21%, H2 / air stoichiometry 1.5 / 2.5, back pressure 1 bar, running for 60 min;

[0072] The electronic load was interrupted for 1 s, and the voltage change within 24 ms before and after the interruption was recorded by a digital oscilloscope, and the ohmic resistance and diffusion resistance coefficient were calculated;

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

[0074] Example 2

[0075] On the basis of Example 1, the fuel cell was operated to: current density 800 mA / cm 2 , cell temperature 70℃, inlet humidity 63%, H2 / air stoichiometry 1.5 / 2.5, back pressure 1 bar, running for 60 min;

[0076] The electronic load was interrupted for 1 s, and the voltage change within 24 ms before and after the interruption was recorded by a digital oscilloscope, and the ohmic resistance and diffusion resistance coefficient were calculated;

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

[0078] Example 3

[0079] On the basis of Example 1, the fuel cell was operated to: current density 800 mA / cm 2 , cell temperature 70℃, inlet humidity 100%, H2 / air stoichiometry 1.5 / 2.5, back pressure 1 bar, running for 60 min;

[0080] The electronic load was interrupted for 1 s, and the voltage change within 24 ms before and after the interruption was recorded by a digital oscilloscope, and the ohmic resistance and diffusion resistance coefficient were calculated;

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

[0082] The experimental results of Examples 1-3 are as follows Figure 3As shown, (a) is a voltage change schematic diagram, (b) is an electrochemical impedance spectrum data diagram, (c-d) 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] In the case of changing the humidity of the intake air, Figure 3 It can be seen that the ohmic resistance of Example 1 is much larger than that of Example 2, indicating that the fuel cell in Example 1 is in a relatively dry state; and the ohmic resistance of Example 2 is almost the same as that of Example 3, at this time, the diffusion resistance coefficient needs to be combined for judgment, Figure 3 It can be seen that the diffusion resistance coefficient of Example 3 is larger, and the trend is consistent with the Warburg impedance coefficient obtained by electrochemical impedance spectrum fitting. This shows that the method disclosed in the present application can diagnose the dry and wet state of the fuel cell inside by combining the ohmic resistance and diffusion resistance coefficient obtained by the current interruption method.

[0084] The above-mentioned embodiment numbers of the present application are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0085] In the above-mentioned embodiments of the present application, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0086] In several embodiments provided in the present application, it should be understood that the disclosed technical content can be implemented by other ways. Among them, the above-mentioned device embodiments are only schematic, for example, the division of the units can be a logical function division, and actual implementation can have another division way, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point, the coupling or direct coupling or communication connection between the units or modules shown or discussed can be indirect coupling or communication connection through some interfaces, units or modules, which can be electrical or other forms.

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

[0088] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The above integrated unit can be realized in the form of hardware or in the form of software functional unit.

[0089] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application, essentially or in other words, the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a mobile hard disk, a magnetic disk or an optical disk, and various 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 application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A fuel cell water management failure diagnosis method characterized by comprising: The method comprises the following steps: Controlling the on-off of the output current of the fuel cell by DC / DC, and periodically recording the voltage change before and after the current interruption, and processing the step data of the voltage response and the relaxation data of the voltage response; The voltage change before and after the current interruption is expressed as The calculation formula is as follows: wherein is the current density before current interruption, is the ohmic resistance, is the diffusion resistance coefficient, is the time; According to the step data of the voltage response, calculating the ohmic resistance, and the calculation formula is as follows: wherein J0is the current density before current interruption, and AV is the step change in voltage before and after current interruption. According to the relaxation data of the voltage response, calculating the diffusion resistance coefficient, and the calculation formula is as follows: wherein, for the relaxation phase of the voltage change, the voltage and slope of the linear fit; Judging the dry-wet state inside the fuel cell through the ohmic resistance and the diffusion resistance coefficient; When the calculated ohmic resistance becomes larger, it indicates that the humidity inside the fuel cell is decreasing; When the ohmic resistance remains unchanged, and the diffusion resistance coefficient increases, the humidity inside the fuel cell increases; According to the dry-wet state inside the fuel cell, adjusting the operation parameters in real time to keep the fuel cell in the best working state.

2. A fuel cell water management failure diagnosis system implemented based on the fuel cell water management failure diagnosis method described in claim 1, characterized by The method comprises the following steps: A data acquisition unit, an ohmic resistance calculation unit, a diffusion resistance coefficient calculation unit, a dry-wet state judgment unit and a central control unit, wherein: The data acquisition unit is used for controlling the on-off of the output current of the fuel cell by DC / DC, and periodically recording the voltage change before and after the current interruption, and processing the step data of the voltage response and the relaxation data of the voltage response; The ohmic resistance calculation unit is used for calculating 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 for calculating 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 for judging the dry-wet state inside the fuel cell through 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 for adjusting the operation parameters in real time according to the dry-wet state inside the fuel cell judged by the dry-wet state judgment unit, so as to keep the fuel cell in the best working state.

3. A fuel cell water management fault diagnostic system according to claim 2, wherein The data acquisition unit is an oscilloscope, a data acquisition card or a voltage inspection system.

Images