Fuel cell stack gas starvation fault diagnosis method based on EIS

Abstract

The invention provides an EIS-based gas starvation fault diagnosis method for a fuel cell stack. The method comprises the following steps: S1, collecting an impedance modulus Z1 of the fuel cell stack at a first characteristic frequency f1 in real time; s2, comparing the impedance modulus Z1 with a modulus reference value Zref; and S3, judging whether an absolute value of a difference value between the impedance modulus Z1 and the modulus reference value Zref is greater than a first threshold value epsilon 1, and if so, identifying that the fuel cell stack has a gas starvation fault, and if not, returning to the step S1 so as to continuously collect the impedance modulus Z1 of the fuel cell stack at the characteristic frequency f1. According to the gas starvation fault diagnosis method disclosed by the invention, the diagnosis result can be quickly and reliably obtained, and hydrogen starvation and air starvation can be distinguished through different parameters.

Description

Technical Field

[0001] The present disclosure relates to health status monitoring of a fuel cell stack, and more particularly to a gas starvation fault diagnosis method for a fuel cell stack based on EIS. Background Art

[0002] It is very important to monitor the state of health (SOH) of the proton exchange membrane fuel cell stack to avoid damage or severe degradation. Gas starvation (i.e., insufficient gas) is a common fault during the operation of the proton exchange membrane fuel cell stack. Gas starvation includes hydrogen starvation (also known as anode starvation) and air starvation (also known as cathode starvation). Among them, hydrogen starvation can cause anode carbon corrosion, thereby seriously damaging the anode structure. Air starvation will not cause fatal damage, but it will cause the performance of the fuel cell stack to deteriorate, and the resulting hydrogen evolution reaction will cause safety issues. Therefore, it is necessary to monitor the gas starvation phenomenon online, i.e. in real time, to avoid structural damage or performance degradation.

[0003] In the prior art, online diagnostic methods are mostly limited to water content measurement. For example, US 2019 / 0131638 A1 proposes a method for diagnosing water content in a fuel cell stack based on EIS. However, this method does not involve the diagnosis of gas starvation failures. In addition, hydrogen starvation and air starvation diagnostic methods based on EIS have also been proposed. For example, CN 109726452 B proposes an online proton exchange membrane fuel cell fault diagnosis method based on impedance spectroscopy. However, this method requires real-time measurement of the EIS of the fuel cell stack, which takes a long time. In addition, this method cannot distinguish between hydrogen starvation and air starvation failures. Both of these failures can cause performance degradation or fluctuations, but the countermeasures are completely different.

[0004] The present invention is designed based on the above background. Summary of the invention

[0005] In order to solve one or more problems existing in the prior art, the present disclosure proposes a gas starvation fault diagnosis method for a fuel cell stack based on EIS (electrochemical impedance spectroscopy), the method comprising: step S1: collecting the impedance modulus Z1 of the fuel cell stack at a first characteristic frequency f1 in real time; step S2: comparing the impedance modulus Z1 with a modulus reference value Zref; and step S3: determining whether the absolute value of the difference between the impedance modulus Z1 and the modulus reference value Zref is greater than a first threshold ε1, if so, identifying that the fuel cell stack has a gas starvation fault; if not, returning to step S1 to continuously collect the impedance modulus Z1 of the fuel cell stack at the characteristic frequency f1.

[0006] In one embodiment, when the absolute value of the difference between the impedance modulus Z1 and the modulus reference value Zref is greater than the first threshold value ε1, the method further includes: step S4: collecting the impedance phase PA of the fuel cell stack at the second characteristic frequency f2 in real time, wherein the second characteristic frequency f2 is greater than the first characteristic frequency f1; step S5: comparing the impedance phase PA with the phase reference value PAref; and step S6: determining whether the absolute value of the difference between the impedance phase PA and the phase reference value PAref is greater than the second threshold value ε2, and if so, identifying that the fuel cell stack has a hydrogen starvation fault; if not, identifying that the fuel cell stack has an air starvation fault.

[0007] In one embodiment, the method further includes: before step 1, measuring the EIS of the fuel cell stack under standard operating conditions, hydrogen starvation conditions, and air starvation conditions, respectively; obtaining a Bode diagram of the response of the impedance modulus of the fuel cell stack as the frequency changes based on the measured EIS; and selecting the first characteristic frequency f1 based on the Bode diagram, wherein at the first characteristic frequency f1, the impedance modulus of the fuel cell stack in the hydrogen starvation state and the air starvation state are substantially equal, and are higher than the impedance modulus under the standard operating conditions.

[0008] In one embodiment, the modulus reference value Zref is equal to the impedance modulus of the fuel cell stack at the first characteristic frequency f1 under standard operating conditions.

[0009] In one embodiment, the first characteristic frequency f1 is in the range of 1 to 10 Hz.

[0010] In one embodiment, the method further includes: obtaining a Bode diagram of the response of the impedance phase of the fuel cell stack to frequency changes based on the measured EIS; and selecting the second characteristic frequency f2 based on the Bode diagram, wherein, at the second characteristic frequency f2, the impedance phase of the fuel cell stack under a hydrogen starved state is lower than the impedance phase under standard operating conditions, and the impedance phase of the fuel cell stack under an air starved state is substantially equal to the impedance phase under standard operating conditions.

[0011] In one embodiment, the phase reference value PAref is equal to the impedance phase of the fuel cell stack at the second characteristic frequency f2 under standard operating conditions.

[0012] In one embodiment, the second characteristic frequency f2 is in the range of 600-5000 Hz.

[0013] In one embodiment, the fuel cell stack includes at least one fuel cell, characterized in that the method further includes: collecting in real time the impedance modulus Z1' of one of the fuel cells at a third characteristic frequency f1'; comparing the impedance modulus Z1' with the modulus reference value Zref'; and determining whether the absolute value of the difference between the impedance modulus Z1' and the modulus reference value Zref' is greater than a third threshold value ε3, and if so, identifying that a gas starvation fault has occurred in the fuel cell.

[0014] In one embodiment, the method further includes: collecting the impedance phase PA' of the fuel cell at a fourth characteristic frequency f2' in real time, wherein the fourth characteristic frequency f2' is greater than the third characteristic frequency f1'; comparing the impedance phase PA' with a phase reference value PAref'; and determining whether the absolute value of the difference between the impedance phase PA' and the phase reference value PAref' is greater than a fourth threshold value ε4, and if so, identifying that a hydrogen starvation fault occurs in the fuel cell; if not, identifying that an air starvation fault occurs in the fuel cell.

[0015] The present disclosure also proposes a gas starvation fault diagnosis method for a fuel cell based on EIS, the method comprising: collecting the impedance modulus Z1' of the fuel cell at a third characteristic frequency f1' in real time; comparing the impedance modulus Z1' with a modulus reference value Zref'; judging whether the absolute value of the difference between the impedance modulus Z1' and the modulus reference value Zref' is greater than a third threshold value ε3, and if so, identifying that the fuel cell has a gas starvation fault; then, collecting the impedance phase PA' of the fuel cell at a fourth characteristic frequency f2' in real time, wherein the fourth characteristic frequency f2' is greater than the third characteristic frequency f1'; comparing the impedance phase PA' with a phase reference value PAref'; and judging whether the absolute value of the difference between the impedance phase PA' and the phase reference value PAref' is greater than a fourth threshold value ε4, and if so, identifying that the fuel cell has a hydrogen starvation fault; if not, identifying that the fuel cell has an air starvation fault.

[0016] In one embodiment, the method further includes: measuring the EIS of the fuel cell under standard operating conditions, hydrogen starvation conditions, and air starvation conditions, respectively; obtaining a Bode diagram of the impedance modulus of the fuel cell in response to frequency changes, and a Bode diagram of the impedance phase of the fuel cell in response to frequency changes based on the measured EIS; and selecting the third characteristic frequency f1' and the fourth characteristic frequency f2' based on the obtained Bode diagrams, wherein, at the third characteristic frequency f1', the impedance moduli of the fuel cell in the hydrogen starvation state and the air starvation state are substantially equal, and higher than the impedance modulus under the standard operating conditions, and wherein, at the fourth characteristic frequency f2', the impedance phase of the fuel cell in the hydrogen starvation state is lower than the impedance phase under the standard operating conditions, and the impedance phase of the fuel cell in the air starvation state is substantially equal to the impedance phase under the standard operating conditions.

[0017] In one embodiment, the third characteristic frequency f1' is in the range of 1-10 Hz, and the fourth characteristic frequency f2' is in the range of 600-5000 Hz.

[0018] The gas starvation fault diagnosis method of a fuel cell stack based on EIS according to the present disclosure can quickly and reliably obtain the diagnosis result. In addition, the method can distinguish hydrogen starvation from air starvation through different parameters, so that an appropriate control strategy can be adopted based on the diagnosis result.

[0019] The above summary of the invention briefly summarizes some embodiments of the present disclosure to provide a basic understanding of some aspects discussed herein. This summary of the invention is not intended to provide a broad overview of the present disclosure, nor is it intended to delimit the scope of the present disclosure. The sole purpose of this summary of the invention is to present some concepts in a simplified form as an introduction to the detailed description presented below. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate specific embodiments of the present disclosure and, together with the general description of the present disclosure given above and the detailed description of the embodiments given below, serve to explain the present disclosure.

[0021] Figure 1 The EIS of a typical proton exchange membrane fuel cell stack and its equivalent circuit model are shown;

[0022] Figure 2 Schematically shows a test device for measuring the impedance of a fuel cell stack;

[0023] Figure 3 shows the EIS of the fuel cell stack measured under standard operating conditions, hydrogen starvation conditions, and air starvation conditions;

[0024] Figure 4 Shown based on Figure 3 Bode plot obtained by EIS showing the response of the impedance modulus of the fuel cell stack to the change of frequency, where the abscissa is the frequency, displayed in logarithmic form, and the ordinate is the impedance modulus;

[0025] Figure 5 Shown based on Figure 3 A Bode plot obtained by EIS of the fuel cell stack showing the response of the impedance phase as the frequency changes, wherein the abscissa is the frequency, displayed in logarithmic form, and the ordinate is the impedance phase; and

[0026] Figure 6 The figure is a flow chart of an online process of a method for diagnosing gas starvation faults of a fuel cell stack based on EIS according to an embodiment of the present disclosure.

[0027] It should be understood that the attached drawings only provide a somewhat simplified representation of various features of the basic principles of the present disclosure. The specific design features disclosed herein (including, for example, the specific size, orientation, location and shape of the various illustrated components) may be determined in part by the specific intended application and use environment. DETAILED DESCRIPTION

[0028] The present disclosure is described below by specific embodiments. It should be understood that specific embodiments are provided only for the purpose of facilitating a thorough understanding of the present disclosure, and are not intended to limit the present disclosure. Therefore, the following embodiments are merely exemplary, and the scope of protection of the present disclosure is limited only by the appended claims.

[0029] Electrochemical impedance spectroscopy is a widely used characterization technology in electrochemistry. During the test, a weak AC signal is applied to the test system to stimulate the system under test to obtain a corresponding feedback electrical signal. Through EIS, the kinetic information inside the system under test can be obtained without destroying the system under test. The present disclosure applies EIS technology to fuel cell stacks, aiming to diagnose gas starvation faults in fuel cell stacks with the help of EIS. Figure 1 The EIS of a typical proton exchange membrane fuel cell stack and its equivalent circuit model are shown. The EIS is measured in the frequency range of 1 Hz to 10 kHz, and the measurement frequency (angular velocity) increases gradually from right to left.

[0030] like Figure 1 As shown in Figure 1, the EIS of a typical proton exchange membrane fuel cell stack or its fuel cell presents a shape of a small circle connected to a large circle with an upward tail. Among them, the ohmic loss is caused by the transfer of protons and electrons, which is equivalent to the resistance R Ω ; Anode activation loss is caused by hydrogen reaction, which is equivalent to resistance Rf,A With capacitor C dl,A The cathode activation loss is caused by the oxygen reaction, and the mass transfer loss is caused by the gas transmission. Together, they are equivalent to a resistance R f,C With reactance Z W In series, and then with capacitor C dl,C Therefore, the equivalent circuit model of a typical proton exchange membrane fuel cell stack is as follows: Figure 1 Typically, anode activation loss is difficult to detect because it is much smaller than cathode activation loss.

[0031] On the above theoretical basis, the inventors of the present application found that when a gas starvation fault occurs in a fuel cell stack, its impedance modulus at a lower characteristic frequency (for example, in the range of 1-10 Hz) increases significantly compared to the standard operating condition. The above standard operating condition refers to the normal operating state of the fuel cell stack without a gas starvation fault or any other type of fault. Furthermore, when the gas starvation fault is specifically a hydrogen starvation fault, the impedance phase of the fuel cell stack at a higher characteristic frequency (for example, in the range of 600-5000 Hz) is significantly lower than that of an air starvation fault. Among them, in the air starvation fault state, the impedance phase of the fuel cell stack at the higher characteristic frequency is substantially the same as the impedance phase under the standard operating condition.

[0032] Based on the above findings, the inventor of the present application proposes a gas starvation fault diagnosis method for a fuel cell stack based on EIS. The diagnosis method includes an offline process and an online process.

[0033] The offline process includes measuring the EIS of the fuel cell stack under standard operating conditions, hydrogen starvation conditions, and air starvation conditions. This measurement can be performed with the help of Figure 2 The test equipment shown is carried out. Figure 2 A fuel cell stack 1 is schematically shown, which includes 9 fuel cells 2a-2i sandwiched between end plates. Those skilled in the art will appreciate that the fuel cell stack 1 may include any other number of fuel cells. The EIS of the fuel cell stack 1 may be measured with the aid of Figure 2 The measurements are carried out at points 3 and 3'. Figure 3 1 shows the EIS of the fuel cell stack 1 measured under standard operating conditions, hydrogen starvation conditions, and air starvation conditions. Figure 3 As shown in FIG. 1 , “○”, “□” and “×” are used to represent the discrete points of the EIS of the fuel cell stack 1 measured under the standard working condition, the hydrogen starvation state and the air starvation state, respectively. The approximate shape formed by these discrete points is similar to Figure 1 The EIS of a typical proton exchange membrane fuel cell stack 1 shown is similar. Figure 3It can be seen that in the gas starvation fault state, the upward tail on the right side of the EIS of the fuel cell stack 1 significantly shifts to the right, and the slope increases. This indicates that the resistance of the fuel cell stack 1 in the gas starvation fault state is much greater.

[0034] Next, the above-mentioned off-line process includes obtaining a Bode diagram (such as Figure 4 ) and the Bode plot of the impedance phase response as the frequency changes (as shown in Figure 5 ). Figure 4 It can be seen that in the low frequency region (usually in the range of 1-10 Hz), the impedance modulus of the fuel cell stack 1 in the gas starvation fault state is significantly greater than the impedance modulus in the standard working condition. Figure 5 It can be seen that in the high frequency region (for example, at a frequency of 600-5000 Hz), the impedance phase of the fuel cell stack 1 in the hydrogen starvation fault state is significantly smaller than the impedance phase in the air starvation fault state and the standard operating condition. Next, the above-mentioned offline process includes selecting the characteristic frequency f1 located in the low frequency region and the characteristic frequency f2 located in the high frequency region based on the obtained Bode diagram. Among them, at the characteristic frequency f1, the impedance modulus of the fuel cell stack 1 in the hydrogen starvation and air starvation states is basically equal, and significantly higher than the impedance modulus under the standard operating condition. Therefore, the characteristic frequency f1 helps to diagnose the gas starvation fault. At the characteristic frequency f2, the impedance phase of the fuel cell stack 1 in the hydrogen starvation state is significantly lower than the impedance phase under the standard operating condition, and the impedance phase of the fuel cell stack 1 in the air starvation state is basically equal to the impedance phase under the standard operating condition. Therefore, the characteristic frequency f2 helps to further distinguish whether the diagnosed gas starvation fault is a hydrogen starvation fault or an air starvation fault. The above-mentioned "basically equal" and "basically equal" mean that the difference between the two is maintained within a certain threshold range, or the difference between the two is small enough to be basically negligible.

[0035] The online process of the gas starvation fault diagnosis method according to the present disclosure will be described in detail below. The online process includes Figure 6The steps are shown in the flowchart. Specifically, at step S1, the online process collects the impedance modulus Z1 of the fuel cell stack 1 at the characteristic frequency f1 determined above in real time. At step S2, the online process compares the collected impedance modulus Z1 with the modulus reference value Zref. The modulus reference value Zref can be the impedance modulus of the fuel cell stack 1 at the characteristic frequency f1 under standard operating conditions. At step S3, it is determined whether the absolute value of the difference between Z1 and Zref is greater than the first threshold ε1. If not, it means that the fuel cell stack 1 has not yet suffered a gas starvation failure. At this time, the online process returns to step S1 to continue collecting the impedance modulus Z1 of the fuel cell stack 1 at the characteristic frequency f1. If it is determined that the absolute value of the difference between Z1 and Zref is greater than the first threshold ε1, it indicates that a gas starvation failure has occurred in the fuel cell stack. At this time, the online process proceeds to step S4. At step S4, the online process collects the impedance phase PA of the fuel cell stack 1 at the characteristic frequency f2 in real time. At step S5, the online process compares the collected impedance phase PA with the phase reference value PAref. The phase reference value PAref may be the impedance phase of the fuel cell stack 1 at the characteristic frequency f2 under standard operating conditions. At step S6, it is determined whether the absolute value of the difference between PA and PAref is greater than the second threshold ε2. If so, fault A is identified, i.e., hydrogen starvation fault. If not, fault B is identified, i.e., air starvation fault.

[0036] Steps S1-S3 of the online process of the gas starvation fault diagnosis method described above are used to diagnose whether a gas starvation fault has occurred in the fuel cell stack 1, and steps S4-S6 are used to distinguish whether the diagnosed gas starvation fault is a hydrogen starvation fault or an air starvation fault.

[0037] Next, the technician can take corresponding countermeasures according to the type of gas starvation fault diagnosed. For example, when a hydrogen starvation fault occurs, the intake flow rate of hydrogen can be increased accordingly; when an air starvation fault occurs, the intake flow rate of air can be increased accordingly.

[0038] According to the EIS-based gas starvation fault diagnosis method for the fuel cell stack 1 disclosed in the present invention, the relatively time-consuming process of measuring EIS is performed offline. Therefore, when performing online fault diagnosis, it is only necessary to apply electrical signals at two characteristic frequencies to the fuel cell stack 1 and obtain the impedance modulus and phase at the characteristic frequencies accordingly, so that the diagnostic results can be obtained quickly and reliably.

[0039] The gas starvation fault diagnosis method of the fuel cell stack 1 based on EIS described above regards the entire stack 1 as an electrochemical test system, and its purpose is to diagnose whether a gas starvation fault occurs in the entire stack 1. Those skilled in the art will understand that a gas starvation fault in the stack 1 can be a gas starvation fault occurring in any position or in any number of fuel cells therein. The gas starvation faults occurring in these fuel cells will be concentratedly reflected in the changes in the EIS of the fuel cell stack 1. Therefore, through the above-mentioned gas starvation fault diagnosis method, the gas starvation fault occurring in the stack 1 can be identified with the aid of only a set of devices for measuring the stack 1 as a whole. This can simplify the measuring device and save costs.

[0040] In some cases, it may be desirable not only to diagnose whether a gas starvation fault occurs in the entire stack 1, but also to further identify which fuel cell or fuel cells in the stack 1 have a gas starvation fault. In this case, the above-mentioned EIS-based gas starvation fault diagnosis method for the fuel cell stack 1 may also include a diagnostic step performed on some of the fuel cells therein.

[0041] In a preferred embodiment according to the present disclosure, it is also possible to Figure 2 The measurement points 4 and 4' in the figure measure the EIS of the bottom fuel cell 2i under standard conditions, hydrogen starvation conditions, and air starvation conditions. This fuel cell 2i is prone to flooding and is therefore prone to gas starvation failures. In addition, the EIS of the top fuel cell 2a can also be measured because this fuel cell 2a is the farthest from the air inlet and is therefore also prone to gas starvation failures. Those skilled in the art will understand that the EIS of any other fuel cell can also be measured as needed. The measured EIS will be consistent with the Figure 3 The EIS of the entire stack 1 shown is similar. Next, a Bode plot of the impedance modulus of the fuel cell 2i as it changes with frequency can be obtained based on the measured EIS (similar to Figure 4 similar) and the Bode plot of the impedance phase response as it changes with frequency (similar to Figure 5Similarly). Similarly, in the low-frequency region (usually in the range of 1-10 Hz), the impedance modulus of the fuel cell 2i in the gas starvation fault state is significantly greater than the impedance modulus under the standard operating condition; and in the high-frequency region (for example, at a frequency of 600-5000 Hz), the impedance phase of the fuel cell 2i in the hydrogen starvation fault state is significantly smaller than the impedance phase under the air starvation fault state and the standard operating condition. Next, the characteristic frequency f1' located in the low-frequency region and the characteristic frequency f2' located in the high-frequency region can be selected based on the obtained Bode diagram. Among them, at the characteristic frequency f1', the impedance modulus of the fuel cell 2i in the hydrogen starvation and air starvation states is basically equal, and significantly higher than the impedance modulus under the standard operating condition. Therefore, the characteristic frequency f1' is helpful in diagnosing the gas starvation fault of the fuel cell 2i. At the characteristic frequency f2', the impedance phase of the fuel cell 2i in the hydrogen starvation state is significantly lower than the impedance phase under the standard operating condition, and the impedance phase of the fuel cell 2i in the air starvation state is basically equal to the impedance phase under the standard operating condition. Therefore, the characteristic frequency f2' helps to further distinguish whether the diagnosed gas starvation fault is a hydrogen starvation fault or an air starvation fault. The characteristic frequency f1' of the fuel cell 2i can be close to the characteristic frequency f1 of the entire stack 1, or even equal to f1. Similarly, the characteristic frequency f2' of the fuel cell 2i can be close to the characteristic frequency f2 of the entire stack 1, or even equal to f2.

[0042] The above describes the off-line process of the gas starvation fault diagnosis method performed on the fuel cell 2i. The following describes the on-line process of the diagnosis method. The on-line process is the same as that described above with reference to FIG. Figure 6The process described is similar. First, the impedance modulus Z1' of the fuel cell 2i at the characteristic frequency f1' is collected in real time, and the collected impedance modulus Z1' is compared with the modulus reference value Zref'. The modulus reference value Zref' can be the impedance modulus of the fuel cell 2i at the characteristic frequency f1' under standard conditions. Next, it is determined whether the absolute value of the difference between Z1' and Zref' is greater than the third threshold ε3. If not, the process returns to continuously collect the impedance modulus Z1' of the fuel cell 2i at the characteristic frequency f1'. If it is determined that the absolute value of the difference between Z1' and Zref' is greater than the third threshold ε3, then the impedance phase PA' of the fuel cell 2i at the characteristic frequency f2' is collected, and the collected impedance phase PA' is compared with the phase reference value PAref'. The phase reference value PAref' can be the impedance phase of the fuel cell 2i at the characteristic frequency f2' under standard conditions. Next, it is determined whether the absolute value of the difference between PA' and PAref' is greater than the fourth threshold ε4. If so, fault A, i.e., hydrogen starvation fault, is identified. If not, a B fault, ie, an air starvation fault, is identified. The third threshold ε3 may be close to the first threshold ε1, or even equal to the first threshold ε1. Similarly, the fourth threshold ε4 may be close to the second threshold ε2, or even equal to the second threshold ε2.

[0043] The above fault diagnosis steps performed on the fuel cell 2i help to further diagnose whether the gas starvation fault in the stack 1 occurs in the fuel cell 2i. It will be understood that the above fault diagnosis steps can be performed on multiple fuel cells in the stack 1 to identify which fuel cell or fuel cells the gas starvation fault in the stack 1 specifically occurs in.

[0044] In one embodiment according to the present disclosure, the gas starvation fault diagnosis method of a fuel cell stack based on EIS may only include performing fault diagnosis steps on certain fuel cells in the stack, without performing fault diagnosis steps on the entire stack. In this case, these fuel cells are preferably fuel cells in the stack that are prone to gas starvation faults. In this case, the gas starvation fault diagnosis method of a fuel cell stack based on EIS can directly identify which specific fuel cell has a gas starvation fault, so as to take more accurate countermeasures.

[0045] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the embodiments of the present disclosure. As used herein, the singular forms of "a", "an" and "said" are intended to include singular and plural forms, and the terms "and" and "or" are each intended to include substitutions and combinations, unless the context indicates otherwise. It can be further understood that the terms "include" or "comprise" when used in this specification specify the presence of the features, integers, actions, steps, operations, elements or components, but do not exclude the presence or addition of one or more other features, integers, actions, steps, operations, elements, components or groups thereof. Unless otherwise expressly stated, the steps described in the claims do not necessarily have to be performed in the order described. On the contrary, some of the steps may be performed in the opposite order or simultaneously, as long as the corresponding functions can be achieved.

[0046] Although all disclosures have been illustrated by the description of various embodiments, and although these embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications will be readily apparent to those skilled in the art. Therefore, the present disclosure in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Therefore, departures may be made from these details without departing from the spirit or scope of the applicant's general inventive concept.

Claims

1. A gas starvation fault diagnosis method for a fuel cell stack based on EIS, characterized in that: The method comprises: Step S1: collecting the impedance modulus Z1 of the fuel cell stack at the first characteristic frequency f1 in real time; Step S2: comparing the impedance modulus Z1 with a modulus reference value Zref; and Step S3: Determine whether the absolute value of the difference between the impedance modulus Z1 and the modulus reference value Zref is greater than a first threshold value ε1. If so, identify that a gas starvation fault has occurred in the fuel cell stack; if not, return to step S1 to continue collecting the impedance modulus Z1 of the fuel cell stack at the characteristic frequency f1.

2. The gas starvation fault diagnosis method according to claim 1, characterized in that: In a case where the absolute value of the difference between the impedance modulus Z1 and the modulus reference value Zref is greater than the first threshold ε1, the method further includes: Step S4: collecting the impedance phase PA of the fuel cell stack at the second characteristic frequency f2 in real time, wherein the second characteristic frequency f2 is greater than the first characteristic frequency f1; Step S5: Compare the impedance phase PA with a phase reference value PAref; and Step S6: Determine whether the absolute value of the difference between the impedance phase PA and the phase reference value PAref is greater than a second threshold ε2. If so, it is identified that a hydrogen starvation fault occurs in the fuel cell stack; if not, it is identified that an air starvation fault occurs in the fuel cell stack.

3. The gas starvation fault diagnosis method according to claim 1 or 2, characterized in that: The method further comprises: before step 1, Measuring the EIS of the fuel cell stack under standard working conditions, hydrogen starvation conditions, and air starvation conditions respectively; Obtaining a Bode plot of the impedance modulus of the fuel cell stack in response to frequency changes based on the measured EIS; and The first characteristic frequency f1 is selected based on the Bode diagram, Wherein, at the first characteristic frequency f1, the impedance modulus of the fuel cell stack in a hydrogen starved state and an air starved state is substantially equal, and is higher than the impedance modulus under standard operating conditions.

4. The gas starvation fault diagnosis method according to claim 3, characterized in that: The modulus reference value Zref is equal to the impedance modulus of the fuel cell stack under standard operating conditions at the first characteristic frequency f1.

5. The gas starvation fault diagnosis method according to claim 1, characterized in that: The first characteristic frequency f1 is in the range of 1 to 10 Hz.

6. The gas starvation fault diagnosis method according to claim 3, characterized in that: The method further comprises: Obtaining a Bode diagram of the impedance phase of the fuel cell stack in response to frequency changes based on the measured EIS; and Select the second characteristic frequency f2 based on the Bode diagram, Among them, at the second characteristic frequency f2, the impedance phase of the fuel cell stack in the hydrogen starvation state is lower than the impedance phase under the standard operating condition, and the impedance phase of the fuel cell stack in the air starvation state is basically equal to the impedance phase under the standard operating condition.

7. The gas starvation fault diagnosis method according to claim 6, characterized in that: The phase reference value PAref is equal to the impedance phase of the fuel cell stack at the second characteristic frequency f2 under standard operating conditions.

8. The gas starvation fault diagnosis method according to claim 2, characterized in that: The second characteristic frequency f2 is in the range of 600-5000 Hz.

9. The gas starvation fault diagnosis method according to claim 2, wherein: The fuel cell stack comprises at least one fuel cell, wherein the method further comprises: collecting in real time the impedance modulus Z1' of one of the fuel cells at the third characteristic frequency f1'; comparing the impedance modulus Z1' with a modulus reference value Zref'; and It is determined whether the absolute value of the difference between the impedance modulus Z1' and the modulus reference value Zref' is greater than a third threshold ε3. If so, it is identified that a gas starvation fault occurs in the fuel cell.

10. The gas starvation fault diagnosis method according to claim 9, characterized in that: The method further comprises: collecting in real time the impedance phase PA' of the fuel cell at a fourth characteristic frequency f2', wherein the fourth characteristic frequency f2' is greater than the third characteristic frequency f1'; comparing the impedance phase PA' with a phase reference value PAref'; and It is determined whether the absolute value of the difference between the impedance phase PA' and the phase reference value PAref' is greater than a fourth threshold ε4. If so, it is identified that a hydrogen starvation fault occurs in the fuel cell; if not, it is identified that an air starvation fault occurs in the fuel cell.

11. A method for diagnosing gas starvation faults of a fuel cell based on EIS, characterized in that: The method comprises: collecting in real time the impedance modulus Z1' of the fuel cell at the third characteristic frequency f1'; Comparing the impedance modulus Z1' with a modulus reference value Zref'; Determine whether the absolute value of the difference between the impedance modulus Z1' and the modulus reference value Zref' is greater than a third threshold ε3, and if so, identify that a gas starvation fault occurs in the fuel cell; Next, the impedance phase PA' of the fuel cell at the fourth characteristic frequency f2' is collected in real time, wherein the fourth characteristic frequency f2' is greater than the third characteristic frequency f1'; comparing the impedance phase PA' with a phase reference value PAref'; and It is determined whether the absolute value of the difference between the impedance phase PA' and the phase reference value PAref' is greater than a fourth threshold ε4. If so, it is identified that a hydrogen starvation fault occurs in the fuel cell; if not, it is identified that an air starvation fault occurs in the fuel cell.

12. The gas starvation fault diagnosis method according to claim 11, characterized in that: The method further comprises: Measuring the EIS of the fuel cell under standard working conditions, hydrogen starvation conditions, and air starvation conditions respectively; Obtaining a Bode plot of the impedance modulus of the fuel cell in response to a change in frequency, and a Bode plot of the impedance phase of the fuel cell in response to a change in frequency based on the measured EIS; and The third characteristic frequency f1' and the fourth characteristic frequency f2' are selected based on the obtained Bode diagram, Wherein, at the third characteristic frequency f1', the impedance modulus of the fuel cell in the hydrogen starvation state and the air starvation state is substantially equal, and is higher than the impedance modulus under the standard operating condition, and wherein, at the fourth characteristic frequency f2', the impedance phase of the fuel cell in the hydrogen starvation state is lower than the impedance phase under the standard operating condition, and the impedance phase of the fuel cell in the air starvation state is substantially equal to the impedance phase under the standard operating condition.

13. The gas starvation fault diagnosis method according to claim 11, characterized in that: The third characteristic frequency f1' is in the range of 1-10 Hz, and the fourth characteristic frequency f2' is in the range of 600-5000 Hz.

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