A method for diagnosing a failure of a hydrogen exhaust valve for a fuel cell power generation system

Abstract

This invention proposes a diagnostic method for hydrogen exhaust valves used in fuel cells, specifically for diagnosing faults in the fuel cell power system's power generation process where the hydrogen exhaust valve cannot be opened. During power generation, it was observed that when the hydrogen exhaust valve fails to open, the pressure at the fuel cell hydrogen inlet deviates very little from the actual set pressure, remaining essentially consistent with the set pressure. It was also found that after the hydrogen exhaust valve fails to open, and the fuel cell power generation system continues to operate, impurities such as water and nitrogen accumulate at the anode, leading to performance degradation. Based on this phenomenon, this invention uses a comprehensive diagnostic approach, considering the deviation between the set hydrogen pressure and the target pressure, as well as whether the fuel cell power system experiences a voltage undervoltage fault, to comprehensively diagnose the hydrogen exhaust valve's inability to open. This method is independent of changes in fuel cell performance, is simple, convenient, and provides a more accurate diagnosis of whether the hydrogen exhaust valve is unable to open.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a fault diagnosis method for a hydrogen exhaust valve used in a fuel cell power generation system. Background Technology

[0002] A fuel cell is a device that generates electricity. It primarily works by introducing hydrogen and oxygen into the anode and cathode of the fuel cell stack, respectively, to initiate an electrochemical reaction. This electricity generation process also generates heat. A coolant is introduced into the fuel cell to dissipate this heat and maintain stable operation at an optimal temperature. Generally, a fuel cell, along with a hydrogen supply system, an oxygen supply system, and a cooling system, forms a fuel cell power generation system. This system can be used as a power source in vehicles, as a stationary power generation unit, or in other scenarios requiring electricity.

[0003] Currently, the mainstream fuel cells both domestically and internationally are proton exchange membrane (PEM) type. During operation, the hydrogen supplied to the anode in these fuel cells requires extremely high purity, generally 99.99% or higher. To meet this requirement, high-purity compressed hydrogen is directly supplied to the fuel cell anode. Furthermore, to improve hydrogen utilization, the hydrogen at the anode outlet is not directly discharged but recycled. During fuel cell operation, compressed air is typically supplied directly to the cathode, and the main components of air are nitrogen and oxygen. Although the PEM only allows protons to pass through during the reaction, due to concentration differences, impurities such as nitrogen and moisture at the cathode can slowly permeate to the anode. As the reaction continues, these impurities accumulate, eventually leading to a decrease in hydrogen concentration at the anode and ultimately reducing the fuel cell's output performance.

[0004] To address the aforementioned issues, a hydrogen venting valve and a vapor-water separator are employed in the anode circulation system of a fuel cell. The vapor-water separator primarily separates liquid water from the circulating gas at the anode, preventing it from re-entering the anode side of the fuel cell. The separated liquid water is stored in a water distributor. By controlling the opening and closing of the hydrogen venting valve, the water and impurity gases accumulated in the anode are discharged to the outside, thereby controlling the stable power generation of the fuel cell.

[0005] In a fuel cell power system, the hydrogen vent valve is a control device without feedback. If the hydrogen vent valve cannot be opened, the power system cannot obtain its status. As the electrical reaction continues, the nitrogen concentration on the anode side will continue to accumulate, and water will also accumulate, eventually causing the fuel cell power system to shut down. Therefore, fault diagnosis of the hydrogen vent valve is a very important task.

[0006] Currently, Chinese invention patents CN112054230A, CN116706157A, and CN118367179A describe diagnostic methods for hydrogen discharge valves.

[0007] Patent CN112054230A focuses on determining the water content of the fuel cell, not on diagnosing malfunctions of the hydrogen discharge valve itself. When the hydrogen discharge valve cannot open, the flow rates of both should be roughly the same; when the hydrogen discharge valve cannot close, the standard outlet flow rate should be much higher than the theoretical flow rate. Furthermore, fuel cell systems are complex to operate and influenced by many factors. On the one hand, constructing a MAP (Magnetic Mapping) through calibration is labor-intensive; on the other hand, this method often leads to misjudgments during real-time analysis, easily causing frequent system shutdowns and hindering stable operation. Patent CN116706157A requires that the hydrogen pressure change and the duty cycle change of the pressure control device must meet the patent's requirements during the opening and closing of the hydrogen discharge / drain valve. However, in actual systems, these patent requirements are not always perfectly met; it depends on the pressure control device and pressure control requirements. Therefore, judging malfunctions based solely on the patent's content can lead to misdiagnosis of hydrogen discharge / drain valve malfunctions.

[0008] In the invention patent CN118367179A, the fluctuation of hydrogen pressure and the change of fuel cell stack voltage are used to diagnose the failure of the hydrogen discharge valve to open when the actual hydrogen pressure deviates from the target pressure within a specified range and the fuel cell voltage gradually decreases during this process. The magnitude of the voltage drop is used to diagnose the failure of the hydrogen discharge valve to open. However, this method has a problem: during the fuel cell unloading process, the voltage drop may already exist, so this method may lead to misdiagnosis during the unloading process. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of the prior art as described in the background section by proposing a fault diagnosis method for hydrogen exhaust valves in fuel cell power generation systems.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A fault diagnosis method for a hydrogen discharge valve used in a fuel cell power generation system includes:

[0012] S1. Key switch on;

[0013] S2. Determine whether the fuel cell power system is in operation, wherein the operation status is the state in which the fuel cell power system outputs power to the outside.

[0014] S3. If S2 determines that it is true, then the hydrogen discharge valve fault diagnosis command is activated.

[0015] S4. Check whether the absolute value of the deviation between the set hydrogen pressure P_HInSet and the actual hydrogen pressure P_HIn is less than the preset threshold P_abs.

[0016] S5. If S4 is correct, further determine whether the duration of the pressure deviation being less than P_abs is greater than N times the opening interval of the hydrogen discharge valve, where N is an integer not less than 2.

[0017] S6. If S5 is determined to be yes, check whether there is a single cell undervoltage fault in the fuel cell power system.

[0018] S7. If S6 is not determined, then if no single cell undervoltage fault is triggered after the maintenance time t1, the hydrogen discharge valve is determined to be functioning normally.

[0019] S8. If S6 determines that the fault is that the hydrogen discharge valve cannot be opened, the fault is identified and the information is uploaded to the system for maintenance.

[0020] As a further step in the method of the present invention, the preset threshold P_abs ranges from 0.5 kPa to 1 kPa.

[0021] As a further step in the method of the present invention, the opening interval of the hydrogen discharge valve is 7 seconds, and the value of N is 2, corresponding to a maintenance time of 14 seconds.

[0022] As a further step in the method of the present invention, the condition for determining the undervoltage fault of the single cell is that the voltage of the single cell is lower than a preset voltage threshold V_min, where V_min is 0.4V.

[0023] As a further step in the method of the present invention, the time t1 is the shortest time required for the fuel cell to trigger an undervoltage fault when the hydrogen discharge valve cannot be opened at the minimum operating power, and the value of t1 is 400 seconds.

[0024] As a further step in the method of the present invention, in step S4, the set pressure of hydrogen P_HInSet is dynamically adjusted according to the operating conditions of the fuel cell stack, and the actual hydrogen pressure P_HIn is monitored in real time by a hydrogen inlet pressure sensor.

[0025] As a further step in the method of the present invention, the fault diagnosis method is executed continuously during the hydrogen discharge valve opening interval, and the diagnosis results are fed back in real time through the control unit of the fuel cell power system.

[0026] As a further step in the method of the present invention, it also includes means for performing the fault diagnosis method, the means comprising:

[0027] Hydrogen inlet pressure sensor is used to detect the actual hydrogen pressure P_HIn;

[0028] Hydrogen venting valve, configured to open periodically to release impurity gases;

[0029] The individual cell inspection module is used to monitor the voltage of individual cells in the fuel cell stack;

[0030] The control unit is used to comprehensively determine the hydrogen discharge valve malfunction based on pressure deviation and individual cell voltage status.

[0031] As a further step in the method of the present invention, the hydrogen discharge valve is connected to a gas-water separator, which is used to separate liquid water in the anode circulating gas and discharge it to the tailpipe through the hydrogen discharge valve.

[0032] As a further step in the method of the present invention, the control unit is configured to automatically trigger system shutdown or power reduction operation to protect the fuel cell stack after determining that the hydrogen discharge valve cannot be opened.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] In existing methods for diagnosing hydrogen vent valve malfunctions, the failure to open relies on changes in hydrogen pressure during the valve's opening process. This single approach is prone to misdiagnosis. This patent uses a comprehensive diagnostic approach, considering the deviation between the actual and set hydrogen pressure when the vent valve fails to open, as well as whether individual cells in the fuel cell stack are under-voltage. This method is more accurate, simpler, and easier to implement. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the troubleshooting process for the hydrogen discharge valve failing to open, as shown in the example.

[0036] Figure 2 This is a diagram of the hydrogen gas path structure of the fuel cell power generation system in the embodiment;

[0037] Figure 3 This is a diagram showing the hydrogen set pressure under different operating conditions in the embodiments;

[0038] Figure 4 This is a diagram showing the undervoltage of a single cell in the fuel cell stack when the hydrogen venting valve cannot be opened in the embodiment.

[0039] Figure 5 This is a corresponding case diagram for the diagnosis when the hydrogen discharge valve cannot be opened in the embodiment. Detailed Implementation

[0040] The invention will be more readily understood by referring to the following detailed description of preferred embodiments and included examples. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail.

[0041] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0042] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this invention do not impose any limitation on the quantity requirement (i.e., the number of times) of the elements or components. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0044] This embodiment provides a fault diagnosis method for hydrogen discharge valves in fuel cell power generation systems, such as... Figure 2 As shown, the fuel cell power generation system consists of a hydrogen pressure and flow regulating proportional valve 10, a hydrogen inlet pressure sensor 20, a hydrogen pressure relief valve 30, a hydrogen circulation pump 40, a gas-water separator 50, a hydrogen discharge valve 60, a tailpipe 70, a CVM single-cell inspection system 80, and a fuel cell stack 90. ​​The cooling system, air supply system, and power system are not described in detail here. The hydrogen pressure and flow rate regulating proportional valve 10 regulates the flow rate and pressure required for the operation of the fuel cell stack 90. ​​The hydrogen inlet pressure sensor 20 is used to detect the pressure at the inlet of the fuel cell stack 90 to prevent the inlet pressure from being within an unreasonable range. After the hydrogen reacts in the fuel cell stack 90, the remaining hydrogen passes through the gas-water separator 50 to separate the liquid water from the hydrogen. The hydrogen then enters the fuel cell stack 90 through the hydrogen circulation pump 240, and the separated liquid water is discharged into the tailpipe 70 through the drain and exhaust valve 60. The hydrogen pressure relief valve 30 mainly prevents the incoming hydrogen pressure from exceeding the working pressure. When the pressure is detected to be higher than the working pressure, the hydrogen pressure relief valve 30 will automatically open to release pressure to maintain the inlet pressure of the stack below the working pressure.

[0045] like Figure 1 The present embodiment provides a fault diagnosis method for a hydrogen discharge valve in a fuel cell power generation system, including the following steps:

[0046] S1, Key switch on

[0047] S2. Determine whether the fuel cell power system is in operation, wherein the operating state is the state in which the fuel cell power system outputs power to the outside.

[0048] S3. If the determination in step S2 is yes, then issue a fault diagnosis command for the hydrogen discharge valve to open it.

[0049] S4. Determine whether the absolute value of the deviation between the set hydrogen pressure P_HInSet and the actual hydrogen pressure P_HIn is less than P_abs; the set hydrogen pressure P_HInSet is correlated with the operating conditions of the fuel cell stack, as follows: Figure 3 As shown; the preferred value for P_abs is generally 1 kPa, as in this implementation example. Figure 5 In this case, when the hydrogen venting valve is normally open, the P_abs value is generally within 6 kPa. When the hydrogen venting valve malfunctions, the P_abs value is less than 0.5 kPa. The P_abs value used in this implementation case is 0.5 kPa. The optimal P_abs value can be matched according to the actual operating system status.

[0050] S5. If the determination in step S4 is yes, further determine whether the duration of the pressure deviation being less than P_abs is greater than N times the interval between opening the hydrogen discharge valve. The interval between opening the hydrogen discharge valve is the set time interval for opening the hydrogen discharge valve. The minimum value of N for the interval between opening the hydrogen discharge valve is 2, but it can also be a larger value such as 3, 4, or 5. In this embodiment, when the duration of the pressure deviation being less than P_abs by 0.5 kPa is greater than 14 seconds, the 14 seconds is twice the interval between opening the hydrogen discharge valve, and the interval between opening the hydrogen discharge valve is 7 seconds.

[0051] S6. If the determination in step S5 is yes, further determine whether the fuel cell power system has a fuel cell individual undervoltage. A fuel cell individual undervoltage occurs because a fuel cell pair consists of multiple individual cells. The low voltage of each individual cell in the fuel cell pair is detected through individual cell inspection. When a cell voltage triggers a predetermined protection voltage, it is considered a single cell undervoltage. Specific single cell undervoltage conditions are as follows: Figure 4 As shown, if the voltage of a single cell falls below Vmin, the system will continuously transmit a single cell undervoltage fault. Vmin can generally be selected as 0.4V, or other values ​​can be selected, depending on the protection of the single cell voltage limit of the fuel cell stack. In this implementation case, Vmin is set to 0.4V.

[0052] S7. If the determination in step S6 is negative, a maintenance time t1 is performed. If no undervoltage is triggered in the fuel cell unit within the specified time t1, it indicates that the hydrogen discharge valve is functioning normally. The time t1 represents the maintenance time for the fuel cell unit to be undervoltage triggered when the hydrogen discharge valve cannot open, under the minimum allowable operating power. In this implementation case, t1 is 400s. (See the diagnostic implementation case.) Figure 5 In the process, after the hydrogen discharge valve fails to open and a unit voltage undervoltage fault occurs, the system uploads the unit undervoltage status, with 1 indicating that a unit undervoltage has occurred.

[0053] S8. If the determination in step S6 is yes, then it can be further determined that the unvented hydrogen valve has a fault that prevents it from opening, and the information is uploaded to the system for maintenance. The examples described herein are merely illustrative, used to explain some features of the method described in this invention. The appended claims are intended to claim the broadest possible scope, and the embodiments presented herein are merely illustrative of selected implementations based on combinations of all possible embodiments. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A failure diagnosis method for a hydrogen discharge valve for a fuel cell power generation system, characterized by, Includes the following steps: S1. Key switch on; S2. Determine whether the fuel cell power system is in operation, wherein the operation status is the state in which the fuel cell power system outputs power to the outside. S3. If S2 determines that it is true, then the hydrogen discharge valve fault diagnosis command is activated. S4. Check whether the absolute value of the deviation between the set hydrogen pressure P_HInSet and the actual hydrogen pressure P_HIn is less than the preset threshold P_abs. S5. If S4 is correct, further determine whether the duration of the pressure deviation being less than P_abs is greater than N times the opening interval of the hydrogen discharge valve, where N is an integer not less than 2. S6. If S5 is determined to be yes, check whether there is a single cell undervoltage fault in the fuel cell power system. S7. If S6 is not determined, then if no single cell undervoltage fault is triggered after the maintenance time t1, the hydrogen discharge valve is determined to be functioning normally. S8. If S6 determines that the fault is that the hydrogen discharge valve cannot be opened, the fault is identified and the information is uploaded to the system for maintenance.

2. The fault diagnosis method for a hydrogen discharge valve in a fuel cell power generation system according to claim 1, characterized in that, The preset threshold P_abs ranges from 0.5 kPa to 1 kPa.

3. The fault diagnosis method for a hydrogen discharge valve in a fuel cell power generation system according to claim 1, characterized in that, The hydrogen discharge valve opens at 7-second intervals, and the value of N is 2, corresponding to a duration of 14 seconds.

4. The fault diagnosis method for a hydrogen discharge valve in a fuel cell power generation system according to claim 1, characterized in that, The condition for determining the undervoltage fault of a single cell is that the voltage of the single cell is lower than a preset voltage threshold V_min, where V_min is 0.4V.

5. A fault diagnosis method for a hydrogen discharge valve in a fuel cell power generation system according to claim 1, characterized in that, The time t1 is the shortest time required for the fuel cell to trigger an undervoltage fault when the hydrogen discharge valve cannot be opened at the minimum operating power, and the value of t1 is 400 seconds.

6. A fault diagnosis method for a hydrogen discharge valve in a fuel cell power generation system according to claim 1, characterized in that, In step S4, the set hydrogen pressure P_HInSet is dynamically adjusted according to the operating conditions of the fuel cell stack, and the actual hydrogen pressure P_HIn is monitored in real time by a hydrogen inlet pressure sensor.

7. A fault diagnosis method for a hydrogen discharge valve in a fuel cell power generation system according to claim 1, characterized in that, The fault diagnosis method is executed continuously during the hydrogen discharge valve opening interval, and the diagnosis results are fed back in real time through the control unit of the fuel cell power system.

8. A fault diagnosis device for a hydrogen discharge valve in a fuel cell power generation system according to claim 1, characterized in that, The fault diagnosis apparatus is used to perform the fault diagnosis method according to any one of claims 1-7, the apparatus comprising: Hydrogen inlet pressure sensor is used to detect the actual hydrogen pressure P_HIn; Hydrogen venting valve, configured to open periodically to release impurity gases; The individual cell inspection module is used to monitor the voltage of individual cells in the fuel cell stack; The control unit is used to comprehensively determine the hydrogen discharge valve malfunction based on pressure deviation and individual cell voltage status.

9. A fault diagnosis device for a hydrogen discharge valve in a fuel cell power generation system according to claim 8, characterized in that, The hydrogen discharge valve is connected to the gas-water separator, which is used to separate liquid water from the anode circulating gas and discharge it to the tailpipe through the hydrogen discharge valve.

10. A fault diagnosis device for a hydrogen discharge valve in a fuel cell power generation system according to claim 8, characterized in that, The control unit is configured to automatically trigger system shutdown or power reduction operation to protect the fuel cell stack after determining that the hydrogen discharge valve cannot be opened.

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