Fault diagnosis method for hydrogen discharge valve for fuel cell power generation system

Abstract

The invention provides a method for diagnosing a hydrogen discharge valve for a fuel cell, which is used for diagnosing a fault that the hydrogen discharge valve cannot be opened in a power generation process of a fuel cell power system. In the power generation process of a fuel cell power system, when the current hydrogen discharge valve cannot be opened, the pressure of a hydrogen inlet of a fuel cell has a small deviation from the actually set pressure, the pressure is basically kept consistent with the set pressure, and the state is maintained all the time; after a hydrogen discharge valve cannot be opened and a fuel cell power generation system continuously operates, foreign gases such as water and nitrogen are continuously accumulated on an anode, so that the performance is reduced; in combination with the phenomenon, after the hydrogen discharge valve cannot be opened, the fault that the hydrogen discharge valve cannot be opened is comprehensively diagnosed according to the deviation between the hydrogen set pressure and the target pressure and whether the fuel cell power system has the undervoltage fault, the method does not depend on the performance change of the fuel cell, and the method is simple and easy to implement. And whether the hydrogen discharge valve cannot be opened or not can be diagnosed conveniently and more accurately.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a fault diagnosis method for a hydrogen exhaust valve used in a fuel cell power generation system. Background Art

[0002] A fuel cell is a device that generates electricity. It mainly generates electricity by introducing a certain amount of hydrogen and oxygen into the anode and cathode of the fuel cell stack to produce an electrochemical reaction. The process of generating electricity is also accompanied by the generation of heat. A certain amount of coolant is introduced into the fuel cell to remove the generated heat and maintain the fuel cell to work stably at the optimal temperature. Generally, a fuel cell is combined with a hydrogen supply device, an oxygen supply device, and a cooling device to form a fuel cell power generation system, which can be equipped in a vehicle as a power device, as a fixed power generation device, or in other scenarios where electricity is needed.

[0003] At present, the mainstream fuel cells at home and abroad are of the proton exchange membrane type. The hydrogen provided by the anode during the operation of this type of fuel cell has extremely high requirements for its purity, generally requiring the purity of hydrogen to reach 99.99% or above; in order to meet the above requirements, the hydrogen supply uses high-purity compressed hydrogen to be directly supplied to the anode of the fuel cell. At the same time, in order to improve the utilization rate of hydrogen, the hydrogen at the anode outlet is not directly discharged, but recycled; for the fuel cell during operation, the cathode side generally uses air for compression and then directly sent to the cathode of the fuel cell. The main components of the air are nitrogen and oxygen; although the proton exchange membrane only allows protons in the reaction process to pass through, due to concentration differences and other reasons, impurities such as nitrogen and water in the cathode will slowly penetrate into the anode. As the reaction continues, they will accumulate, eventually leading to a decrease in the hydrogen concentration on the anode side, and ultimately resulting in a decrease in the output performance of the fuel cell.

[0004] In order to solve the above problems, a hydrogen discharge valve and a water-gas separator are used in the anode circulation system of the fuel cell. The water-gas separator is mainly used to separate the liquid water in the circulating gas at the anode to prevent it from entering the anode side of the fuel cell again. The separated liquid water is stored in the water separator. By controlling the switch of the hydrogen discharge valve, the water and impurity gases accumulated in the anode are discharged to the outside to control the stable power generation of the fuel cell.

[0005] The hydrogen drain valve is a control device without feedback in the fuel cell power system. Once the hydrogen drain valve cannot be opened, the power system cannot obtain its status. As the power 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 drain valve is a very important task.

[0006] Currently, the diagnostic methods for the hydrogen discharge valve are introduced respectively in Chinese invention patents CN112054230A, CN116706157A and CN118367179A: In the patent CN112054230A, it focuses on judging the water content in the fuel cell rather than the fault of the hydrogen discharge valve itself. When the hydrogen discharge valve cannot be opened, the two flow rates should be basically the same. When the hydrogen discharge valve cannot be closed, the standard outlet flow rate should be much higher than the theoretical flow rate. Moreover, the operation of the fuel cell system is relatively complex and there are many influencing factors. On the one hand, it is laborious to construct a MAP through the calibration method. On the other hand, there are many misjudgments caused by real-time analysis of this method, which easily leads to frequent shutdowns of the system due to faults and is not conducive to the stable operation of the system. In CN116706157A, according to the requirements of this patent, it must be satisfied that during the opening and closing process of the hydrogen discharge valve / drain valve in the system control, the change in hydrogen pressure and the change in the duty cycle of the pressure control device meet the requirements in the patent. In the actual system, the above requirements in the patent are not always well met, which depends on the pressure control device and the pressure control requirements. Therefore, misjudgments of the faults of the hydrogen discharge valve / drain valve will occur when judging according to the invention content of the patent.

[0007] In the invention patent CN118367179A, the fluctuation of hydrogen pressure and the change of stack voltage are adopted. When the hydrogen discharge valve cannot be opened, the deviation between the actual hydrogen pressure and the target pressure is within the specified range and the fuel cell voltage will gradually decrease during this process. The size of the voltage drop is used to diagnose the fault that the hydrogen discharge valve cannot be opened through the two. There is a problem with this method. During the load reduction process of the fuel cell, the voltage drop may exist itself. Therefore, this method may have misdiagnosis phenomena during the load reduction process. Summary of the Invention

[0008] The purpose of the present invention is to solve the disadvantages existing in the prior art proposed in the background technology, and to propose a fault diagnosis method for the hydrogen discharge valve used in a fuel cell power generation system.

[0009] In order to achieve the above purpose, the present invention adopts the following technical solutions: A fault diagnosis method for the hydrogen discharge valve used in a fuel cell power generation system, including: S1. The key switch is turned on; S2. Judge whether the fuel cell power system is in an operating state, and the operating state is the state where the fuel cell power system outputs power to the outside; S3. If the judgment in S2 is yes, start the hydrogen discharge valve fault diagnosis instruction; S4. Detect 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 the judgment in S4 is yes, further determine whether the duration for which the pressure deviation is less than P_abs is greater than N times the hydrogen discharge valve opening interval, where N is an integer not less than 2; S6. If the judgment in S5 is yes, detect whether there is a single cell under-voltage fault in the fuel cell power system; S7. If the judgment in S6 is no, when no single cell under-voltage fault is triggered after the duration t1, determine that the hydrogen discharge valve functions normally; S8. If the judgment in S6 is yes, determine that the hydrogen discharge valve cannot open and upload the system for maintenance.

[0010] As a further step in the method of the present invention, the value range of the preset threshold P_abs is 0.5 kPa to 1 kPa.

[0011] As a further step in the method of the present invention, the hydrogen discharge valve opening interval is 7 seconds, and the value of N is 2, corresponding to a maintenance time of 14 seconds.

[0012] As a further step in the method of the present invention, the determination condition for the single cell under-voltage fault is that the voltage of the single cell is lower than the preset voltage threshold V_min, where V_min is 0.4 V.

[0013] As a further step in the method of the present invention, the time t1 is the shortest time required to trigger a single cell under-voltage fault when the hydrogen discharge valve cannot open at the minimum operable power of the fuel cell, and the value of t1 is 400 seconds.

[0014] As a further step in the method of the present invention, in step S4, the set pressure P_HInSet of hydrogen 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 through a hydrogen inlet pressure sensor.

[0015] As a further step in the method of the present invention, the fault diagnosis method is continuously executed within the hydrogen discharge valve opening interval, and the diagnosis result is real-time fed back through the control unit of the fuel cell power system.

[0016] As a further step in the method of the present invention, it further includes a device for executing the fault diagnosis method according to any one of claims 1-7, and the device includes: A hydrogen inlet pressure sensor for detecting the actual hydrogen pressure P_HIn; A hydrogen discharge valve configured to be periodically opened to discharge impurity gases; A single cell inspection module for monitoring the voltage of single cells in the fuel cell stack; A control unit for comprehensively determining the hydrogen discharge valve fault according to the pressure deviation and the single cell voltage state.

[0017] As a further aspect of the method of the present invention, the hydrogen discharge valve is connected to the steam-water separator, and the steam-water separator is configured to separate the liquid water in the anode recycle gas and discharge it to the tail discharge pipe through the hydrogen discharge valve.

[0018] As a further aspect of 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 a failure in opening the hydrogen discharge valve.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: In the existing failure diagnosis method for the inability to open the hydrogen discharge valve, it relies on the change process of the hydrogen pressure during the opening process of the hydrogen discharge valve to directly diagnose the failure of the hydrogen discharge valve to open. Such a single method is likely to result in misjudgment. This patent comprehensively diagnoses through the deviation between the actual hydrogen pressure and the set hydrogen pressure when the hydrogen discharge valve cannot be opened, as well as whether the single cells of the fuel cell stack are under-voltage. This failure diagnosis method for the inability to open the hydrogen discharge valve is more accurate, simple in method, and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the flowchart for diagnosing the failure of the hydrogen discharge valve to open in the embodiment; Figure 2 is the structural diagram of the hydrogen path of the fuel cell power generation system in the embodiment; Figure 3 is the diagram of the set hydrogen pressure under different working conditions in the embodiment; Figure 4 is the diagram of under-voltage of the single cells of the fuel cell stack when the hydrogen discharge valve cannot be opened in the embodiment; Figure 5 is the corresponding case diagram for diagnosis when the hydrogen discharge valve cannot be opened in the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The content of the present invention can be more easily understood by referring to the following detailed description of the preferred embodiments of the present invention and the included examples. Unless otherwise defined, 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 belongs. In case of conflict, the definitions in this specification shall prevail.

[0022] As used herein, the term "prepared from" is synonymous with "comprising". As used herein, the terms "comprising", "including", "having", "containing" or any other variation thereof are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus containing the recited 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.

[0023] In addition, the indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirements (i.e., the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the singular form of the element or component also includes the plural form, unless the quantity clearly refers to the singular form.

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0025] This embodiment provides a fault diagnosis method for the hydrogen discharge valve of a fuel cell power generation system, as Figure 2 shown. The fuel cell power generation system is composed 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 steam-water separator 50, a hydrogen discharge valve 60, a tail discharge pipe 70, a CVM single-cell inspection 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 regulating proportional valve 10 is used to regulate 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 steam-water separator 50 to separate the liquid water in the hydrogen, and the hydrogen enters the fuel cell stack 90 through the hydrogen circulation pump 240. The separated liquid water is discharged into the tail discharge pipe 70 through the drain and exhaust valve 60. The hydrogen pressure relief valve 30 is mainly used to prevent the inlet hydrogen pressure from being higher than the working pressure. When the detected pressure is higher than the working pressure, the hydrogen pressure relief valve 30 will automatically open for pressure relief to maintain the inlet pressure of the stack not exceeding the working pressure.

[0026] As Figure 1 shown, this embodiment provides a fault diagnosis method for the hydrogen discharge valve of a fuel cell power generation system, including the following steps: S1. Turn on the key switch S2. Determine whether the fuel cell power system is in an operating state, where the operating state is a state where the fuel cell power system has power output to the outside. S3. If it is determined to be yes in step S2, issue a hydrogen discharge valve fault diagnosis command to turn it on. 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 corresponds to the operating conditions of the fuel cell stack, and the specific correspondence is as follows Figure 3 shown. Generally, the value of P_abs can be preferably 1 kPa. In this implementation case, asFigure 5 Among them, when the hydrogen discharge valve is normally open, the value of P_abs is generally within 6 kPa. After the hydrogen discharge valve fails, the value of P_abs is less than 0.5 kPa. In this implementation case, the P_abs adopted is 0.5 kPa, and the best P_abs can be matched according to the actual operating system state.

[0027] S5. When the judgment in step S4 is yes, further judge whether the maintenance time when the pressure deviation is less than P_abs is greater than N times the opening interval of the hydrogen discharge valve. The interval time of the hydrogen discharge valve is the set opening time interval of the hydrogen discharge valve; for the N times the opening interval of the hydrogen discharge valve, the minimum value of N is 2, and it can also be larger values such as 3, 4, 5, etc.; in this implementation, when it is judged that the maintenance time after the pressure deviation is less than P_abs of 0.5 kPa is greater than 14 s, the 14 s is 2 times the opening interval of the hydrogen discharge valve, and the opening interval of the hydrogen discharge valve is 7 s; S6. When the judgment in step S5 is yes, further judge whether there is under-voltage of a single fuel cell in the fuel cell power system; under-voltage of a single fuel cell means that the fuel cell is composed of multiple single cells, and the voltage of each single cell of the fuel cell pair will be detected by single cell inspection to detect the corresponding battery voltage. When the single cell voltage triggers the specified set protection voltage, it is under-voltage of a single cell. Specifically, under-voltage of a single cell is as follows Figure 4 As shown, when the voltage of a single cell is lower than Vmin, the system will upload the under-voltage fault of a single cell. Generally, Vmin can be selected as 0.4 V, or other values can also be selected according to the protection of the single cell voltage limit of the fuel cell stack. In this implementation case, Vmin is 0.4 V; S7. When the judgment in step S6 is no, maintain the time t1. If the under-voltage of a single fuel cell is not triggered within the specified time t1, it means that the function of the hydrogen discharge valve is normal; the time t1 represents the maintenance time when the fuel cell is at the minimum allowable operating power and the hydrogen discharge valve cannot be opened, triggering the under-voltage of a single fuel cell; t1 in this implementation case is 400 s, such as in the diagnostic implementation case Figure 5 Among them, after the hydrogen discharge valve cannot be opened and the under-voltage fault of the single cell voltage occurs, the system uploads the under-voltage state of a single cell, and 1 indicates the occurrence of under-voltage of a single cell; S8. When the judgment in step S6 is yes, it can be directly judged that the hydrogen discharge valve cannot be opened, and the system is uploaded for maintenance.

[0028] The examples involved in this text are merely illustrative, used to explain some features of the method described in the present invention. The appended claims are intended to claim the broadest scope conceivable, and the embodiments presented herein are merely illustrative of selected implementation manners from all possible combinations of embodiments. Therefore, the applicant's intention is that the appended claims should not be limited by the selection of examples that illustrate the features of the present 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 whenever possible.

Claims

1. A fault diagnosis method for a hydrogen discharge valve used in a fuel cell power generation system, characterized in that, It includes the following steps: S1. Turn on the key switch; S2. Determine whether the fuel cell power system is in an operating state, where the operating state is the state in which the fuel cell power system outputs power externally; S3. If the determination in S2 is yes, start the hydrogen discharge valve fault diagnosis instruction; S4. Detect 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 the determination in S4 is yes, further determine whether the maintenance time of the pressure deviation less than P_abs is greater than N times the hydrogen discharge valve opening interval time, where N is an integer not less than 2; S6. If the determination in S5 is yes, detect whether there is a single cell under-voltage fault in the fuel cell power system; S7. If the determination in S6 is no, when no single cell under-voltage fault is triggered after the maintenance time t1, determine that the hydrogen discharge valve functions normally; S8. If the determination in S6 is yes, determine that the hydrogen discharge valve cannot be opened and upload it to the system for maintenance.

2. The fault diagnosis method for a hydrogen discharge valve used in a fuel cell power generation system according to claim 1, wherein, The value range of the preset threshold P_abs is from 0.5 kPa to 1 kPa.

3. A fault diagnosis method for a hydrogen discharge valve used in a fuel cell power generation system according to claim 1, characterized in that, The hydrogen discharge valve opening interval time is 7 seconds, and the value of N is 2, and the corresponding maintenance time is 14 seconds.

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

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

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

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

8. A fault diagnosis device for a hydrogen discharge valve used in a fuel cell power generation system according to claim 1, characterized in that, The fault diagnosis device is used to execute any one of claims 1-7, and the device includes: A hydrogen inlet pressure sensor for detecting the actual hydrogen pressure P_HIn; A hydrogen discharge valve configured to be periodically opened to discharge impurity gases; A single cell inspection module for monitoring the voltage of the single cells in the fuel cell stack; A control unit for comprehensively determining the hydrogen discharge valve fault according to the pressure deviation and the single cell voltage state.

9. The fault diagnosis device for a hydrogen discharge valve used in a fuel cell power generation system according to claim 8, characterized in that, The hydrogen discharge valve is connected to a steam-water separator, and the steam-water separator is used to separate the liquid water in the anode recycle gas and discharge it to the tail exhaust pipe through the hydrogen discharge valve.

10. A fault diagnosis method for a hydrogen discharge valve used 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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