A method and system for diagnosing a single cell fault of a fuel cell stack

Abstract

The application discloses a kind of single cell piece fault diagnosis method and system of fuel cell stack, it is related to the technical field of battery test, the method includes the following steps: hydrogen cavity of electric pile is supplied with hydrogen, air cavity is supplied with air, and the first type of single cell piece to be measured that output voltage is lower than average voltage threshold is selected;Hydrogen cavity is stopped to supply hydrogen, air cavity is stopped to supply air, and the second type of single cell piece to be measured that output voltage drop rate is higher than average drop rate is selected;Hydrogen cavity is supplied with hydrogen again, and air cavity nitrogen is supplied, whether the hydrogen permeation current density of any single cell piece to be measured in the first type of single cell piece to be measured and the second type of single cell piece to be measured under preset linear scanning voltage is higher than preset hydrogen permeation current density threshold is judged;If yes, diagnose the single cell piece to be measured as air-tightness unqualified.The application selects single cell piece that possibly exists air-tightness fault in electric pile, diagnoses whether the proton exchange membrane of selected single cell piece exists membrane perforation, improves diagnostic efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery testing, and in particular to a single cell fault diagnosis method and system for a fuel cell stack. BACKGROUND

[0002] A proton exchange membrane fuel cell is a classification of fuel cells, and a stack is formed by stacking multiple single cells in a series manner, alternately stacking bipolar plates and membrane electrodes, embedding a sealing element between each single cell, and fastening the stack by a screw after being compressed by front and rear end plates, thereby forming a proton exchange membrane fuel cell stack. A single cell is mainly composed of a cathode, an anode, and a membrane electrode. The cathode and the anode provide hydrogen and air for the membrane electrode, respectively. Hydrogen and air undergo an electrochemical reaction at the membrane electrode to generate electric energy, heat energy, and water. Multiple single cells in series form a proton exchange membrane fuel cell stack.

[0003] After the stack is stored at a low temperature, water inside the stack is frozen, which may cause the membrane electrode to be pierced by ice, resulting in membrane perforation. Long-term operation of the stack may also cause the membrane to be thinned or perforated. Membrane perforation may cause hydrogen and air to mix, and if hydrogen and air simultaneously appear on the catalyst of the same side electrode, the chemical energy released by the reaction is only released in the form of heat, thereby forming a large amount of heat release, causing the temperature of the fuel cell stack to rise sharply. When the local temperature of the proton exchange membrane exceeds its tolerance limit, a local hole is burned through, further causing more hydrogen and oxygen to mix, thereby causing the risk of thermal runaway of the fuel cell stack. In the prior art, each single cell is diagnosed by a membrane electrode airtightness tool before stacking to determine whether the proton exchange membrane has membrane perforation, and the diagnosis efficiency is low. SUMMARY

[0004] Embodiments of the present application provide a single cell fault diagnosis method and system for a fuel cell stack to solve the technical problem that related technologies cannot quickly diagnose single cells with air tightness faults.

[0005] In a first aspect, a single cell fault diagnosis method for a fuel cell stack is provided. Hydrogen is supplied to a hydrogen cavity of the stack, and air is supplied to an air cavity of the stack. First type single cells to be tested with an output voltage lower than an average voltage threshold are selected.

[0006] Supplying of hydrogen to the hydrogen cavity of the stack and supplying of air to the air cavity of the stack are stopped. Second type single cells to be tested with a higher output voltage drop rate than an average drop rate are selected.

[0007] Hydrogen is again supplied to the hydrogen cavity of the stack, and nitrogen is supplied to the air cavity of the stack. It is determined whether a hydrogen permeation current density of any single cell to be tested in the first type single cells to be tested and the second type single cells to be tested at a preset linear scanning voltage is higher than a preset hydrogen permeation current density threshold.

[0008] If yes, the single battery piece is diagnosed as unqualified in air tightness; if no, the single battery piece is diagnosed as qualified in air tightness.

[0009] In some embodiments, before the step of judging whether the hydrogen permeation current density of any single battery piece in the first type and the second type under a preset linear scanning voltage is higher than a preset hydrogen permeation current density threshold, the hydrogen cavity of the electric pile is supplied with hydrogen and the air cavity is supplied with nitrogen.

[0010] The hydrogen cavity and the air cavity of the electric pile are supplied with nitrogen, and the voltage of the first type and the second type of single battery pieces in the electric pile is swept to below a preset voltage threshold.

[0011] In some embodiments, the preset voltage threshold is 0.1V.

[0012] In some embodiments, the step of supplying the hydrogen cavity of the electric pile with hydrogen and the air cavity with air comprises:

[0013] The flow of hydrogen and air is controlled within a preset flow value.

[0014] In some embodiments, before the step of judging whether the hydrogen permeation current density of any single battery piece in the first type and the second type under a preset linear scanning voltage is higher than a preset hydrogen permeation current density threshold, the hydrogen cavity of the electric pile is supplied with hydrogen and the air cavity is supplied with nitrogen.

[0015] The hydrogen cavity of the electric pile is supplied with hydrogen and the air cavity is supplied with nitrogen.

[0016] The hydrogen permeation current densities of a plurality of single battery pieces qualified in air tightness are collected.

[0017] The preset hydrogen permeation current density threshold is determined according to each hydrogen permeation current density.

[0018] In some embodiments, the preset linear scanning voltage is 400mV.

[0019] In a second aspect, a single battery piece fault diagnosis system of a fuel cell electric pile is provided, which comprises an information collection device and a control terminal.

[0020] The hydrogen cavity of the electric pile is supplied with hydrogen and the air cavity is supplied with air, and the control terminal selects a first type of single battery piece with an output voltage lower than an average voltage threshold based on the output voltage of each single battery piece obtained by the information collection device.

[0021] stop supplying hydrogen to the hydrogen cavity of the fuel cell stack and supplying air to the air cavity of the fuel cell stack, the control terminal calculates an average output voltage drop rate of each of the single battery pieces to be tested based on the output voltage drop rate of each of the single battery pieces to be tested obtained by the information acquisition device, and selects a second type of single battery piece to be tested with a higher output voltage drop rate than the average output voltage drop rate;

[0022] supply hydrogen to the hydrogen cavity of the fuel cell stack and supply nitrogen to the air cavity of the fuel cell stack, the control terminal judges whether the hydrogen permeation current density of any of the first type of single battery piece to be tested and the second type of single battery piece to be tested at the preset linear scanning voltage is higher than the preset hydrogen permeation current density threshold value based on the hydrogen permeation current density of any of the first type of single battery piece to be tested and the second type of single battery piece to be tested at the preset linear scanning voltage;

[0023] If yes, the control terminal diagnoses that the single battery piece to be tested is not qualified in air tightness; if no, the control terminal diagnoses that the single battery piece to be tested is qualified in air tightness.

[0024] In some embodiments, the information acquisition device comprises a voltage acquisition component.

[0025] In some embodiments, the information acquisition device further comprises a current acquisition component.

[0026] In some embodiments, the control terminal is a computer or an industrial computer.

[0027] The technical scheme provided by the present application has the beneficial effects that:

[0028] The single battery piece fault diagnosis method and system of the fuel cell stack provided by the embodiments of the present application supply hydrogen to the hydrogen cavity of the fuel cell stack and supply air to the air cavity of the fuel cell stack, and select a first type of single battery piece to be tested with an output voltage lower than an average voltage threshold value; stop supplying hydrogen to the hydrogen cavity of the fuel cell stack and supplying air to the air cavity of the fuel cell stack, and select a second type of single battery piece to be tested with a higher output voltage drop rate than an average drop rate; supply hydrogen to the hydrogen cavity of the fuel cell stack and supply nitrogen to the air cavity of the fuel cell stack, and judge whether the hydrogen permeation current density of any of the first type of single battery piece to be tested and the second type of single battery piece to be tested at a preset linear scanning voltage is higher than a preset hydrogen permeation current density threshold value; if yes, diagnose that the single battery piece to be tested is not qualified in air tightness; if no, diagnose that the single battery piece to be tested is qualified in air tightness. The present application selects the single battery piece to be tested in the fuel cell stack that may exist air tightness fault, diagnoses whether the proton exchange membrane of the selected single battery piece to be tested exists membrane perforation, and improves the diagnosis efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to make the technical solutions in the embodiments of the present application clearer, the accompanying drawings needed in the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description only need to be some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0030] Figure 1 A flow chart of a single cell fault diagnosis method of a fuel cell stack provided by the embodiments of the present application;

[0031] Figure 2 Another flow chart of a single cell fault diagnosis method of a fuel cell stack provided by the embodiments of the present application;

[0032] Figure 3 A schematic diagram of a single cell fault diagnosis system of a fuel cell stack provided by the embodiments of the present application. DETAILED DESCRIPTION

[0033] In order to make the technical solutions in the embodiments of the present application clearer, the accompanying drawings needed in the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description only need to be some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0034] The embodiments of the present application provide a single cell fault diagnosis method and system of a fuel cell stack, which can solve the technical problem that it is difficult to quickly diagnose the single cell with air tightness fault in the prior art.

[0035] Referring to Figure 1 The single cell fault diagnosis method of a fuel cell stack provided by the embodiments of the present application includes the following steps:

[0036] In step S10, hydrogen is supplied to the hydrogen cavity of the stack, air is supplied to the air cavity, and the first type of single cell to be tested with an output voltage lower than the average voltage threshold is selected.

[0037] In the technical solution provided by the step S10 of the application, the hydrogen cavity, the air cavity, the cooling liquid cavity manifold and the load output line of the stack are connected with the stack test bench, each single cell in the stack is connected with a voltage inspection line, and each voltage inspection line is connected with the test bench to ensure that the gas circuit and the electric circuit are normally transmitted before starting the test; the hydrogen cavity of the stack is supplied with hydrogen, the air cavity is supplied with air, and the cooling liquid cavity is supplied with cooling liquid, and the supply flow is determined according to the number of single cells in the stack, the open circuit voltage of the stack is quickly established, the average single cell voltage is calculated through the control terminal, the average voltage threshold is determined, and all single cells with output voltages lower than the average voltage threshold are selected as the first type of single cells to be tested.

[0038] In the technical solution provided by the step S20 of the application, after all single cells with output voltages lower than the average voltage threshold are selected as the first type of single cells to be tested, the supply of hydrogen to the hydrogen cavity of the stack and the supply of air to the air cavity are stopped, the output voltage drop of each single cell is obtained through the control terminal, the average voltage drop speed and the voltage drop rate of each single cell are calculated, and the single cells with output voltage drop rates higher than the average voltage drop rate are selected as the second type of single cells to be tested.

[0039] In the technical solution provided by the step S20 of the application, after all single cells with output voltages lower than the average voltage threshold are selected as the first type of single cells to be tested, the supply of hydrogen to the hydrogen cavity of the stack and the supply of air to the air cavity are stopped, the output voltage drop of each single cell is obtained through the control terminal, the average voltage drop speed and the voltage drop rate of each single cell are calculated, and the single cells with output voltage drop rates higher than the average voltage drop rate are selected as the second type of single cells to be tested.

[0040] In the technical solution provided by the step S30 of the application, after the first type of single cells to be tested and the second type of single cells to be tested are selected, the hydrogen cavity of the stack is supplied with hydrogen again, and the air cavity is supplied with nitrogen, and it is judged whether the hydrogen permeation current density of any single cell to be tested in the first type of single cells to be tested and the second type of single cells to be tested under a preset linear scanning voltage is higher than a preset hydrogen permeation current density threshold.

[0041] In the technical solution provided by the step S30 of the application, after the first type of single cells to be tested and the second type of single cells to be tested are selected, the hydrogen permeation current density of the first type of single cells to be tested and the second type of single cells to be tested is tested, the positive and negative electrodes of the stack and the inspection lines of the two types of single cells to be tested are connected with the hydrogen permeation current density testing device, the hydrogen cavity of the stack is supplied with hydrogen and the air cavity is supplied with nitrogen through the control terminal, and it is judged whether the hydrogen permeation current density of any single cell to be tested in the first type of single cells to be tested and the second type of single cells to be tested under a preset linear scanning voltage is higher than a preset hydrogen permeation current density threshold.

[0042] In the technical solution provided by the step S40 of the application, if yes, it is diagnosed that the single cell to be tested is unqualified in air tightness; and if no, it is diagnosed that the single cell to be tested is qualified in air tightness.

[0043] In the technical solution provided in the step S40 of the present application, any one of the first type of to-be-tested single cell and the second type of to-be-tested single cell with the hydrogen permeation current density higher than the preset hydrogen permeation current density threshold under the preset linear scanning voltage is a single cell with unqualified air tightness, and the rest of the to-be-tested single cells are single cells with qualified air tightness. The present application accurately and quickly locates the single cell with unqualified air tightness of the membrane electrode in the fuel cell stack, facilitates the replacement of the single cell with air tightness problem, reduces the difficulty of stack repair, and improves the diagnosis efficiency.

[0044] The embodiment of the present application provides a single cell fault diagnosis method of a fuel cell stack. The steps S10 to S40 of the fault diagnosis method supply hydrogen to a hydrogen cavity of the stack and supply air to an air cavity. If the output voltage of any one of the single cells is lower than an average voltage threshold, the single cell is a first type of to-be-tested single cell. The supply of hydrogen to the hydrogen cavity of the stack and the supply of air to the air cavity are stopped. If the output voltage drop rate of a second type of to-be-tested single cell is higher than an average drop rate, the second type of to-be-tested single cell is a second type of to-be-tested single cell. Hydrogen is further supplied to the hydrogen cavity of the stack and nitrogen is further supplied to the air cavity. It is judged whether the hydrogen permeation current density of any one of the first type of to-be-tested single cell and the second type of to-be-tested single cell under a preset linear scanning voltage is higher than a preset hydrogen permeation current density threshold. If yes, the to-be-tested single cell is diagnosed as a single cell with unqualified air tightness. If no, the to-be-tested single cell is diagnosed as a single cell with qualified air tightness. The steps S10 to S40 preliminarily screen the first type of to-be-tested single cell and the second type of to-be-tested single cell with possible unqualified air tightness, and accurately diagnose the air tightness of the first type of to-be-tested single cell and the second type of to-be-tested single cell through the hydrogen permeation current density, thereby solving the technical problem that it is difficult to quickly diagnose the single cell with air tightness fault in the prior art, and achieving the purpose of quickly and accurately locating the single cell with unqualified air tightness of the membrane electrode in the fuel cell stack.

[0045] As an optional implementation, in one of the embodiments, before the step S30 of supplying hydrogen to the hydrogen cavity and nitrogen to the air cavity of the stack, and selecting the test single cells with the hydrogen permeation current density higher than the preset hydrogen permeation current density threshold value from the first type of test single cells and the second type of test single cells, the method further comprises: supplying nitrogen to the hydrogen cavity and the air cavity of the stack, and blowing the voltage of the first type of test single cells and the second type of test single cells in the stack to below the preset voltage threshold value. The stack is a device for generating electricity by hydrogen-oxygen reaction. When the steps S10 and S20 are performed, the stack is in an open circuit voltage state, and the stack establishes a high potential. When the step S30 of testing the hydrogen permeation current density is performed, the stack is connected to a constant potential instrument, so as to apply an external voltage to the stack. The anode serves as a counter electrode and a reference electrode, and the cathode serves as a working electrode. A certain amount of hydrogen is supplied to the anode side of the stack, and a certain amount of nitrogen is supplied to the cathode side. The temperature, humidity and back pressure of the hydrogen and nitrogen are controlled. After a period of stabilization, the starting voltage, the termination voltage, the scanning speed, the number of cycles and the sampling points are set. The hydrogen permeation current density test is performed, and the hydrogen permeation current-time curve I-t is recorded. Finally, the hydrogen permeation current test curve V-I diagram is obtained. When the constant potential instrument is connected, if the stack is still in a high potential state, the high potential of the stack itself will affect the hydrogen permeation current density test. The voltage of the first type of test single cells and the second type of test single cells in the stack is blown to below the preset voltage threshold value, so as to ensure that the potential of the stack itself has no effect on the hydrogen permeation current density test.

[0046] As an optional implementation, in one of the embodiments, the preset voltage threshold value is 0.1 V. By setting the preset voltage threshold value to 0.1 V, it is ensured that the potential of the stack itself does not affect the hydrogen permeation current density test, and at the same time, the risk of electric shock of the personnel during the test is reduced, and the safety of the test is improved.

[0047] As an optional implementation, in one of the embodiments, the step of supplying hydrogen to the hydrogen cavity and air to the air cavity of the stack comprises controlling the flow rate of hydrogen and air within a preset flow rate value. The preset flow rate value is determined according to the number of single cells in the stack, that is, the flow rate of hydrogen and air corresponds to the idling operating condition of the stack. When the number of single cells in the stack is 10, and the membrane electrode active area is 300 cm 2 , the flow rate of hydrogen is controlled to be 6 L / min, and the flow rate of air is controlled to be 20 L / min, so that the stack can quickly establish an open circuit voltage, and the efficiency of the test process is improved.

[0048] As an optional implementation, in one of the embodiments, in step S30, the hydrogen cavity of the stack is supplied with hydrogen and the air cavity is supplied with nitrogen, and before the step of selecting the test single cell with the hydrogen permeation current density higher than the preset hydrogen permeation current density threshold value from the first type of test single cells and the second type of test single cells, a control group is set, and the single cells that perform normally in steps S10 and S20 are selected, and the hydrogen permeation current density test device is accessed through the inspection line, as shown in Figure 2 S501, the hydrogen cavity of the stack is supplied with hydrogen and the air cavity is supplied with nitrogen, S502, the hydrogen permeation current densities of a plurality of single cells with qualified air tightness, i.e., the aforementioned single cells that perform normally, are collected, and S503, the average value of each hydrogen permeation current density is determined to determine the preset hydrogen permeation current density threshold value.

[0049] As an optional implementation, in one of the embodiments, in step S30, the preset linear scanning voltage is 400 mV, when the linear scanning voltage is lower than 400 mV, the oxidation reaction is incomplete, the measured value is small, when the linear scanning voltage is higher than 400 mV, the V-I curve obtained by the hydrogen permeation current density test is basically flat, and the value changes little, the hydrogen permeation current density at 400 mV is taken to represent the hydrogen permeation amount, at this time, the oxidation reaction is complete, the measured value is accurate and changes obviously, and the accuracy of the test result is improved.

[0050] In the single cell fault diagnosis method of the fuel cell stack, steps S10 to S20 are to preliminarily screen the first type of test single cells and the second type of test single cells with possible air tightness problems: the hydrogen cavity of the stack is supplied with hydrogen and the air cavity is supplied with air, if the output voltage of any single cell is lower than the average voltage threshold value, the single cell is the first type of test single cell, and the supply of hydrogen to the hydrogen cavity of the stack and the supply of air to the air cavity are stopped, if the output voltage of the second type of test single cell with a higher output voltage drop rate than the average drop rate is the second type of test single cell. Steps S30 to S40 are to test the hydrogen permeation current density of the preliminarily screened first type of test single cells and the second type of test single cells: the hydrogen cavity of the stack is supplied with hydrogen and the air cavity is supplied with nitrogen, it is judged whether the hydrogen permeation current density of any test single cell under the preset linear scanning voltage is higher than the preset hydrogen permeation current density threshold value, if yes, the test single cell is diagnosed as unqualified in air tightness, and if no, the test single cell is diagnosed as qualified in air tightness, thereby solving the technical problem that it is difficult to quickly diagnose the single cell with air tightness failure in the prior art, and achieving the purpose of quickly and accurately locating the single cell with unqualified membrane electrode air tightness in the fuel cell stack.

[0051] The embodiment also provides a single cell fault diagnosis system of a fuel cell stack, as shown in Figure ThreeAs shown, the information acquisition device and the control terminal are provided with hydrogen and air, the control terminal selects first type of single battery piece with output voltage lower than average voltage threshold based on output voltage of each single battery piece obtained by the information acquisition device, stops supplying hydrogen and air to the hydrogen cavity and the air cavity of the stack, calculates average output voltage drop rate of each single battery piece based on output voltage drop rate of each single battery piece obtained by the information acquisition device, and selects second type of single battery piece with output voltage drop rate higher than average drop rate.

[0052] As an optional implementation, in one embodiment, the information acquisition device comprises a voltage acquisition component, which is configured to obtain voltage of the single battery piece.

[0053] The hydrogen cavity and the air cavity of the stack are supplied with hydrogen and air, the control terminal selects first type of single battery piece with output voltage lower than average voltage threshold based on output voltage of each single battery piece obtained by the voltage acquisition component, stops supplying hydrogen and air to the hydrogen cavity and the air cavity of the stack, calculates average output voltage drop rate of each single battery piece based on output voltage drop rate of each single battery piece obtained by the voltage acquisition component, and selects second type of single battery piece with output voltage drop rate higher than average drop rate.

[0054] As an optional implementation, in one embodiment, the information acquisition device further comprises a current acquisition component, which is configured to obtain current of the single battery piece. In step S30, the hydrogen cavity and the air cavity of the stack are supplied with hydrogen and nitrogen, the control terminal judges whether the hydrogen permeation current density of any single battery piece of the first type and the second type at the preset linear scanning voltage is higher than the preset hydrogen permeation current density threshold based on the hydrogen permeation current density of any single battery piece of the first type and the second type at the preset linear scanning voltage obtained by the current acquisition component, if yes, the control terminal diagnoses that the single battery piece is unqualified in air tightness, and if no, the control terminal diagnoses that the single battery piece is qualified in air tightness.

[0055] As an optional implementation, in one embodiment of the application, the control terminal is a computer or an industrial computer, and the computer or the industrial computer is used to calculate various values, so as to improve the efficiency and accuracy of the test.

[0056] In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise explicitly specified and limited, the terms "mounting", "connection", and "connection" should be understood broadly, for example, it can be a fixed connection, or a detachable connection, or an integral connection; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or a connection between two elements inside. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0057] It should be noted that in the present application, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the sentence "including a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0058] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features of the present application.

Claims

1. A method of diagnosing a single cell failure of a fuel cell stack, characterized by, The method comprises the following steps: Step S10: supplying hydrogen to the hydrogen cavity of the stack and supplying air to the air cavity, and selecting first type single battery pieces with output voltage lower than average voltage; Step S20: stopping supplying hydrogen to the hydrogen cavity of the stack and supplying air to the air cavity, and selecting second type single battery pieces with output voltage drop rate higher than average drop rate; Step S30: supplying hydrogen to the hydrogen cavity of the stack and supplying nitrogen to the air cavity, and judging whether the hydrogen permeation current density of any one of the first type single battery pieces and the second type single battery pieces at a preset linear scanning voltage is higher than a preset hydrogen permeation current density threshold value; Step S40: if yes, diagnosing that the single battery piece is of unqualified air tightness; and if no, diagnosing that the single battery piece is of qualified air tightness; The preset hydrogen permeation current density threshold value is determined by collecting hydrogen permeation current densities of a plurality of single battery pieces which are normal in steps S10 and S20, and determining the preset hydrogen permeation current density threshold value by averaging the plurality of hydrogen permeation current densities.

2. The method of claim 1, wherein Before the step of supplying hydrogen to the hydrogen cavity of the stack and supplying nitrogen to the air cavity, and judging whether the hydrogen permeation current density of any one of the first type single battery pieces and the second type single battery pieces at a preset linear scanning voltage is higher than a preset hydrogen permeation current density threshold value, the method further comprises the following steps: Supplying nitrogen to the hydrogen cavity and the air cavity of the stack, and sweeping the voltage of the first type single battery pieces and the second type single battery pieces in the stack to below a preset voltage threshold value.

3. A method of diagnosing a malfunction of a single cell of a fuel cell stack according to claim 2, characterized by: The preset voltage threshold value is 0.1 V.

4. The method of claim 1, wherein The step of supplying hydrogen to the hydrogen cavity of the stack and supplying air to the air cavity comprises the following steps: Controlling the flow of hydrogen and air to be within a corresponding preset flow value respectively.

5. The method of claim 1, wherein: The preset linear scanning voltage is 400 mV.

6. A fuel cell stack single cell failure diagnosis system for executing the fuel cell stack single cell failure diagnosis method according to claim 1, characterized by The method comprises the following steps: An information collection device and a control terminal; Supplying hydrogen to the hydrogen cavity of the stack and supplying air to the air cavity, and selecting first type single battery pieces with output voltage lower than average voltage based on the output voltage of each single battery piece obtained by the information collection device; Stopping supplying hydrogen to the hydrogen cavity of the stack and supplying air to the air cavity, and calculating the average output voltage drop rate of each single battery piece based on the output voltage drop rate of each single battery piece obtained by the information collection device, and selecting second type single battery pieces with output voltage drop rate higher than average drop rate; Supplying hydrogen to the hydrogen cavity of the stack and supplying nitrogen to the air cavity, and judging whether the hydrogen permeation current density of any one of the first type single battery pieces and the second type single battery pieces at a preset linear scanning voltage is higher than a preset hydrogen permeation current density threshold value based on the hydrogen permeation current density of any one of the first type single battery pieces and the second type single battery pieces at a preset linear scanning voltage obtained by the information collection device; If yes, diagnosing that the single battery piece is of unqualified air tightness; and if no, diagnosing that the single battery piece is of qualified air tightness; The preset hydrogen permeation current density threshold is determined by collecting hydrogen permeation current densities of a plurality of single cells that are normal in steps S10 and S20, and determining the preset hydrogen permeation current density threshold by averaging the plurality of hydrogen permeation current densities.

7. A fuel cell stack single cell sheet failure diagnosis system according to claim 6, characterized by: The information acquisition device comprises a voltage acquisition component.

8. A fuel cell stack single cell sheet failure diagnosis system according to claim 6, characterized by: The information acquisition device further comprises a current acquisition component.

9. A fuel cell stack single cell sheet failure diagnosis system according to claim 6, characterized by: The control terminal is a computer or an industrial computer.

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