Freezing diagnosis method and system for drain valve of fuel cell

Abstract

The invention provides a freezing diagnosis method and system for a drain valve of a fuel cell, and the method employs the change amplitude of a proportional valve control duty ratio in different states of the drain valve as a judgment basis, i.e., when the drain valve operates normally, the duty ratio of the proportional valve is obviously improved, and when the drain valve is frozen, the duty ratio of the proportional valve is not obviously reduced. And the control duty ratio of the proportional valve is basically unchanged. According to the method, the freezing state of the drain valve can be pre-judged before cold start, cold start failure caused by forced start of the fuel cell is prevented, damage to an electric pile is reduced, reference can be provided for heating unfreezing time, invalid cold start time is prevented from being increased due to too long heating, and energy waste is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell control, and further to a freezing diagnosis method and system for a fuel cell drain valve. Background Art

[0002] In the prior art fuel cell system, if the moisture in the hydrogen path is not fully blown dry when the system is shut down, the residual moisture in the drain valve can easily cause the valve core to freeze in a low temperature environment (-30°C ~ 4°C). The drain valve cannot be opened when the system is started next time, and the water in the gas-water separator cannot be discharged in time, which can easily cause cold start failure.

[0003] Currently, there are drain valves on the market with integrated heating functions that melt the ice by heating, but there are still certain defects: the heating time required to melt the ice is usually determined by experiments, and each cold start requires a fixed heating time. On the one hand, the heating time cannot accurately determine whether the ice has melted. If the drain valve is still frozen, forced starting will cause start failure. On the other hand, if freezing does not occur, it is still necessary to wait for the heating process, which in disguise prolongs the cold start time.

[0004] Therefore, there is an urgent need for a method for determining the freezing state of the drain valve before cold start to avoid cold start failure or long invalid time of cold start. Summary of the invention

[0005] In view of the problems in the prior art that freezing of the drain valve causes cold start failure of the fuel cell and too long heating and thawing time leads to increased invalid cold start time, the purpose of the present invention is to provide a freezing diagnosis method and system for the drain valve of the fuel cell, which uses the variation amplitude of the proportional valve control duty cycle under different states of the drain valve as a basis for judgment, and pre-judges the freezing state of the drain valve before cold start, preventing the cold start failure caused by forced start of the fuel cell and reducing damage to the fuel cell stack. It can also provide a reference for the heating and thawing time to avoid increasing invalid cold start time due to too long heating and reduce energy waste.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for diagnosing freezing of a drain valve of a fuel cell system, wherein the fuel cell system comprises a fuel cell stack, a proportional valve arranged upstream of a hydrogen inlet port, and a drain valve arranged downstream of a hydrogen outlet port, comprising the following steps:

[0008] S1. Close the drain valve and control the opening of the proportional valve to make the hydrogen inlet pressure reach a preset pressure;

[0009] S2, open the drain valve and wait for the first preset time T 1 , calculate the proportional valve in the first preset time T 1The maximum control duty cycle D 1 ;

[0010] S3, close the drain valve and wait for a second preset time T 2 , calculate the proportional valve at the second preset time T 2 The average control duty cycle D 2 ;

[0011] S4, according to the maximum control duty cycle D 1 and the average control duty cycle D 2 The difference △D is used to determine whether the drain valve is frozen.

[0012] In some implementations, the specific step of determining whether the drain valve is frozen in step S4 is: determining whether the drain valve is frozen based on a comparison result of the ΔD and a preset fault threshold.

[0013] In some embodiments, the specific steps of judging whether the drain valve is frozen based on the comparison result of the △D and the preset fault threshold in step S4 are: when the △D is less than the preset fault threshold, the number of faults is increased by 1; repeating steps S2-S3, recording the number of faults, and judging whether the drain valve is frozen based on the number of faults.

[0014] In some embodiments, the step S4 also includes: after calculating the △D, the number of diagnosis times is increased by 1; the specific steps of judging whether the drain valve is frozen according to the number of faults in the step S4 are: S41, when the number of faults reaches the preset number of faults, judging whether the drain valve is frozen; S42, when the number of faults is less than the preset number of faults, judging whether the drain valve is frozen according to the number of diagnosis times.

[0015] In some embodiments, the specific steps of determining whether the drain valve is frozen based on the number of diagnosis times described in step S42 are: S421. When the number of diagnosis times reaches the preset number of diagnosis times, determining that the drain valve is not frozen; S422. When the number of diagnosis times is less than the preset number of faults, repeating steps S2-S3; the preset number of diagnosis times is greater than the preset number of faults.

[0016] In some embodiments, after the hydrogen inlet pressure reaches the preset pressure in step S1, wait for a third preset time T 3 Then execute step S2.

[0017] In some embodiments, the step S0 is also included: receiving a start instruction for drain valve freeze diagnosis and starting a drain valve freeze diagnosis process; during the drain valve freeze diagnosis process, prompting that the drain valve freeze diagnosis is being executed, and outputting a diagnosis result after the drain valve freeze diagnosis process is completed.

[0018] In some implementations, the drain valve opening diagnosis process described in step S0 also includes: S01, obtaining the ambient temperature, and determining whether the ambient temperature is less than a preset temperature. If so, executing step S1.

[0019] The present invention also provides a freezing diagnosis system for a fuel cell drain valve, which is applied to the above-mentioned fuel cell system drain valve freezing diagnosis method, comprising: a hydrogen inlet pressure sensor for measuring the hydrogen inlet pressure; a proportional valve duty ratio sensor for respectively measuring the maximum control duty ratio D of the proportional valve when the drain valve is closed and opened. 1 and the average control duty cycle D 2 ; an instruction receiving module for receiving a start instruction for the drain valve freezing diagnosis; a control module for controlling the opening and closing of the drain valve and the proportional valve; a calculation module for calculating the maximum control duty cycle D 1 With the average control duty cycle D 2 The difference △D, the number of faults and the number of diagnoses; a status output module, which is used to prompt that the drain valve freezing diagnosis is being performed during the process of the drain valve freezing diagnosis, and output the diagnosis result according to the calculation result of the calculation module.

[0020] The present invention also provides a data processing system to implement the above-mentioned fuel cell system drain valve freezing diagnosis method, including a memory and a processor, the memory is used to store a computer program, and the processor is used to execute the computer program.

[0021] Compared with the prior art, the freezing diagnosis method and system of the fuel cell drain valve provided by the present invention have the following beneficial effects:

[0022] 1. The freezing diagnosis method for the fuel cell drain valve provided by the present invention uses the variation range of the proportional valve control duty cycle under different states of the drain valve as the judgment basis. The method is simple and easy to implement. On the one hand, the freezing state of the drain valve can be pre-judged before cold start to prevent the failure of the fuel cell cold start and reduce damage to the battery stack. On the other hand, it can provide a reference for the heating and thawing time of the drain valve to avoid the heating time being too short, the ice layer not completely melted affecting the cold start, or the heating time being too long, which increases the invalid cold start time and reduces energy loss.

[0023] 2. The freezing diagnosis system of the fuel cell drain valve provided by the present invention does not require additional hardware equipment, but utilizes the components of the original fuel cell device and only adds software active control. It has low cost, simple implementation process, and is easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The preferred implementation modes will be described below in a clear and understandable manner with reference to the accompanying drawings to further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of the present invention.

[0025] Figure 1 It is a structural schematic diagram of an existing fuel cell hydrogen supply system;

[0026] Figure 2 This is a schematic flow chart of the freezing diagnosis method provided by the present invention.

[0027] Description of Figure Numbers:

[0028] 1—proportional valve; 2—hydrogen inlet pressure sensor; 3—fuel cell stack; 4—gas-water separator; 5—hydrogen circulation pump; 6—hydrogen discharge valve; 7—water discharge valve. DETAILED DESCRIPTION

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0030] In order to simplify the drawings, only the parts related to the invention are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically drawn or marked. In this article, "one" not only means "only one", but also means "more than one".

[0031] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0032] In this document, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In addition, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0034] Example 1

[0035] like Figure 1 As shown, the fuel cell system in the prior art includes a fuel cell stack 3, the fuel cell stack 3 is provided with a hydrogen inlet pipeline and a hydrogen outlet pipeline, the hydrogen inlet pipeline is provided with a proportional valve 1 and a hydrogen inlet pressure sensor 2 in sequence, and the hydrogen outlet pipeline is provided with a gas-water separator 4, the gas outlet and the liquid outlet of the gas-water separator 4 are connected to the hydrogen discharge valve 6 and the water discharge valve 7 respectively through pipelines, during the operation of the system, the hydrogen separated in the gas-water separator 4 re-enters the hydrogen inlet pipeline along with the hydrogen circulation pump 5, and the water discharge valve 7 will be opened periodically to discharge the liquid water separated in the gas-water separator 4, to prevent the liquid water from entering the stack along with the hydrogen circulation pump 5, causing anode flooding, and affecting the normal operation of the fuel cell system and the life of the stack.

[0036] Since liquid water will flow through the drain valve 7, if the water is not fully blown out when shutting down, in a low temperature environment (-30℃~4℃), the residual water will easily cause the valve core to freeze. The next time the fuel cell is started, the drain valve 7 cannot be opened, and the water in the gas-water separator 4 cannot be discharged in time, which can easily cause a cold start failure.

[0037] Therefore, the present invention provides a fuel cell system drain valve freezing diagnosis method, which determines the freezing state of the drain valve 7 before cold start, and executes the startup procedure after confirming that the drain valve 7 can be opened normally.

[0038] like Figure 2 As shown, the drain valve freezing diagnosis method includes the following steps:

[0039] S0, receiving a drain valve freezing diagnosis start instruction, and starting the drain valve freezing diagnosis process;

[0040] During the drain valve freeze diagnosis process, a prompt is given that the drain valve freeze diagnosis is being executed, and the diagnosis result is output after the drain valve freeze diagnosis process is completed.

[0041] Before the drain valve is opened, the diagnostic process also includes step S01, obtaining the ambient temperature, determining whether the ambient temperature is less than a preset temperature, and if so, executing step S1;

[0042] S1. Close the drain valve 7, control the opening of the proportional valve 6, make the hydrogen inlet pressure reach the preset pressure, and wait for the third preset time T. 3 ;

[0043] S2, open the drain valve 7 and wait for the first preset time T 1 , calculate the proportional valve 1 at the first preset time T 1 The maximum control duty cycle D 1 ;

[0044] S3, close the drain valve 7 and wait for the second preset time T 2 , calculate the proportional valve 1 at the second preset time T 2 The average control duty cycle D 2 ;

[0045] S4, according to the maximum control duty cycle D 1 and the average control duty cycle D 2 The difference △D is used to determine whether the drain valve 7 is frozen.

[0046] In the above process, T 1 、T 2 and T 3 The time can be adjusted according to the test. Preferably, T 1 The time is 0.5s, T 2 The time is 1s, T 3 The time is 1s.

[0047] The preset pressure is preferably 130 kPa, and the preset temperature is preferably 4°C.

[0048] It should be noted that step S1 is a preparatory step before the diagnosis begins, which adjusts the hydrogen inlet pressure to a preset pressure and maintains it for a period of time to ensure the normal operation of the subsequent freezing diagnosis process, thereby improving the stability of the diagnosis process and the accuracy of the diagnosis results.

[0049] Furthermore, in step S4, the specific step of determining whether the drain valve 7 is frozen is as follows: determining whether the drain valve 7 is frozen according to the comparison result of ΔD and a preset fault threshold.

[0050] The above-mentioned preset fault thresholds are different under different hydrogen pressures, and the specific values ​​need to be determined based on experiments.

[0051] Furthermore, the specific steps of judging whether the drain valve 7 is frozen according to the comparison result of ΔD and the preset fault threshold are as follows:

[0052] When △D is less than the preset fault threshold, the number of faults increases by 1;

[0053] Repeat steps S2-S3 and record the number of faults, and determine whether the drain valve 7 is frozen based on the number of faults.

[0054] Furthermore, step S4 also includes: after calculating ΔD, the number of diagnosis times is increased by 1.

[0055] In step S4, the specific steps of judging whether the drain valve 7 is frozen according to the number of faults are as follows:

[0056] S41, when the number of faults reaches the preset number of faults, it is determined that the drain valve 7 is frozen;

[0057] S42: When the number of faults is less than the preset number of faults, determine whether the drain valve 7 is frozen according to the number of diagnosis.

[0058] In the above steps, the preset number of faults can be determined according to experimental results. In the present invention, the preset number of faults is preferably 3 times.

[0059] Further, in step S42, the specific steps of determining whether the drain valve 7 is frozen according to the number of diagnosis times are as follows:

[0060] S421, when the number of diagnosis times reaches the preset number of diagnosis times, it is determined that the drain valve 7 is not frozen;

[0061] S422. When the number of diagnosis times is less than the preset number of fault times, steps S2-S3 are repeated to perform the freezing judgment process of the drain valve 7 again.

[0062] The above-mentioned preset diagnosis times are greater than the preset fault times. The preset diagnosis times can be determined according to experimental results. In the present invention, the preset diagnosis times are preferably 6 times.

[0063] The freezing diagnosis method provided by the present invention involves the control of hydrogen inlet pressure: according to the deviation between the target hydrogen inlet pressure and the actual inlet pressure feedback, the control duty ratio of the proportional valve 1 is adjusted to achieve the purpose of stabilizing the hydrogen inlet pressure, that is, when the hydrogen discharge valve 6 or the water discharge valve 7 is opened, the actual hydrogen inlet pressure will decrease. At this time, the adjustment mechanism of the control duty ratio of the proportional valve 1 is opened to increase the opening of the proportional valve 1 to maintain the target hydrogen inlet pressure.

[0064] The drain valve freezing diagnosis method uses the change range of the control duty ratio of the proportional valve 1 when the drain valve 7 is in different states as the judgment basis. Specifically, when the system is running, if the drain valve 7 is opened normally, that is, the drain valve 7 is not frozen, part of the hydrogen will be released to the hydrogen out-of-stack pipeline along with the drain valve 7. In order to maintain the hydrogen in-stack pressure, the hydrogen in-stack pressure is adjusted by controlling the opening of the proportional valve 1. Therefore, the control duty ratio of the proportional valve 1 will be significantly improved. When the drain valve 7 is frozen, the hydrogen will not be released to the hydrogen out-of-stack pipeline. At this time, the hydrogen in-stack pressure does not change, and the control duty ratio of the proportional valve 1 does not change significantly.

[0065] It should be noted that, in order to eliminate interference, the hydrogen exhaust valve 6 needs to be kept closed during the freezing diagnosis process.

[0066] Example 2

[0067] On the basis of Example 1, the present invention further provides a freezing diagnosis system for a fuel cell drain valve, which is applied to the freezing diagnosis method for a fuel cell system drain valve described in Example 1, and comprises:

[0068] The hydrogen inlet pressure sensor 2 is used to measure the hydrogen inlet pressure.

[0069] Proportional valve duty cycle sensor, used to measure the maximum control duty cycle D of proportional valve 1 when drain valve 7 is closed and opened 1 and the average control duty cycle D 2 .

[0070] The command receiving module is used to receive the start command of the drain valve freezing diagnosis.

[0071] The control module is used to control the opening and closing of the drain valve 7 and the proportional valve 1 during the freezing diagnosis process.

[0072] Calculation module, used to calculate the maximum control duty cycle D 1 and the average control duty cycle D 2 The difference △D, the number of faults and the number of diagnoses;

[0073] The status output module is used to prompt that the drain valve freeze diagnosis is being executed during the drain valve freeze diagnosis process, and output the diagnosis result according to the calculation result of the calculation module.

[0074] The status output module can be any type of display device in the prior art that can provide status information. The display device can include LED lights, display screens and other equipment to facilitate operators to intuitively obtain the freeze diagnosis results and freeze diagnosis operation process.

[0075] In some embodiments, the system further includes a temperature sensor for detecting the ambient temperature, and the temperature sensor transmits the collected temperature signal to the control module.

[0076] After receiving the start instruction of the drain valve freezing diagnosis, the control module sends a control instruction to the control module, firstly determines whether the ambient temperature is lower than the preset temperature through the temperature sensor, and formally starts the drain valve freezing diagnosis process when the ambient temperature is lower than the preset temperature. The control module first outputs the control instruction of adjusting the hydrogen inlet pressure to the proportional valve 1 and the drain valve 7. When the hydrogen inlet pressure reaches the preset pressure, the control module outputs the control instruction of adjusting the hydrogen inlet pressure to the drain valve 1 within the first preset time T. 1 The control command to open within the second preset time T 2 At the same time, the proportional valve duty ratio sensor will measure the maximum control duty ratio D of proportional valve 1. 1 and the average control duty cycle D 2 The numerical value is transmitted to the calculation module, and the calculation module outputs the diagnosis result to the status output module after calculation. The operator can obtain the diagnosis result through the status output module.

[0077] Example 3

[0078] Based on Example 1, the present invention provides a data processing system, including a memory and a processor, wherein the memory is used to store a computer program, and the processor is used to execute the computer program to implement the above-mentioned fuel cell system drain valve freezing diagnosis method.

[0079] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for diagnosing freezing of a drain valve of a fuel cell system, wherein the fuel cell system comprises a fuel cell stack, a proportional valve arranged upstream of a hydrogen inlet, and a drain valve arranged downstream of a hydrogen outlet, wherein: The steps include: S1. Close the drain valve and control the opening of the proportional valve to make the hydrogen inlet pressure reach a preset pressure; S2, opening the drain valve, waiting for a first preset time T1, and calculating a maximum control duty ratio D1 of the proportional valve within the first preset time T1; S3, closing the drain valve, waiting for a second preset time T2, and calculating an average control duty cycle D2 of the proportional valve within the second preset time T2; S4. Determine whether the drain valve is frozen according to the difference ΔD between the maximum control duty cycle D1 and the average control duty cycle D2.

2. The fuel cell system drain valve freezing diagnosis method according to claim 1, characterized in that: The specific step of determining whether the drain valve is frozen in step S4 is: determining whether the drain valve is frozen according to the comparison result of ΔD and a preset fault threshold.

3. The fuel cell system drain valve freezing diagnosis method according to claim 2, characterized in that: The specific steps of judging whether the drain valve is frozen according to the comparison result of ΔD and the preset fault threshold in step S4 are: When the ΔD is less than the preset fault threshold, the number of faults is increased by 1; Repeat steps S2-S3, record the number of failures, and determine whether the drain valve is frozen based on the number of failures.

4. The fuel cell system drain valve freezing diagnosis method according to claim 3, characterized in that: The step S4 further includes: after calculating the ΔD, the number of diagnosis times is increased by 1; The specific steps of judging whether the drain valve is frozen according to the number of faults in step S4 are as follows: S41, when the number of failures reaches a preset number of failures, determining that the drain valve is frozen; S42: When the fault number is less than the preset fault number, determine whether the drain valve is frozen according to the diagnosis number.

5. The fuel cell system drain valve freezing diagnosis method according to claim 4, characterized in that: The specific steps of determining whether the drain valve is frozen according to the diagnosis times in step S42 are as follows: S421, when the number of diagnosis times reaches a preset number of diagnosis times, determining that the drain valve is not frozen; S422, when the number of diagnosis times is less than the preset number of diagnosis times, repeating steps S2-S3; The preset diagnosis number is greater than the preset fault number.

6. The fuel cell system drain valve freezing diagnosis method according to claim 1, characterized in that: After the hydrogen inlet pressure reaches the preset pressure in step S1, step S2 is performed after waiting for a third preset time T3.

7. The fuel cell system drain valve freezing diagnosis method according to claim 1, characterized in that: The method further includes step S0: receiving a drain valve freezing diagnosis start instruction and starting a drain valve freezing diagnosis process; During the drain valve freezing diagnosis process, it is prompted that the drain valve freezing diagnosis is being executed, and the diagnosis result is output after the drain valve freezing diagnosis process is completed.

8. The fuel cell system drain valve freezing diagnosis method according to claim 7, characterized in that: The drainage valve opening diagnosis process described in step S0 also includes: S01. Obtain the ambient temperature and determine whether the ambient temperature is less than a preset temperature. If so, execute step S1.

9. A fuel cell drain valve freezing diagnosis system, applied to the fuel cell system drain valve freezing diagnosis method according to any one of claims 1 to 8, characterized in that: include: Hydrogen inlet pressure sensor, used to measure the hydrogen inlet pressure; A proportional valve duty cycle sensor, used to measure a maximum control duty cycle D1 and an average control duty cycle D2 of the proportional valve when the drain valve is closed and opened, respectively; An instruction receiving module, used for receiving a start instruction of the drain valve freezing diagnosis; A control module, used for controlling the opening and closing of the drain valve and the proportional valve; A calculation module, used for calculating the difference ΔD between the maximum control duty cycle D1 and the average control duty cycle D2, the number of faults and the number of diagnoses; The status output module is used to indicate that the drain valve freezing diagnosis is being performed during the process of the drain valve freezing diagnosis, and output the diagnosis result according to the calculation result of the calculation module.

10. A data processing system, characterized in that: It comprises a memory and a processor, wherein the memory is used to store a computer program, and the processor is used to execute the computer program to implement the fuel cell system drain valve freezing diagnosis method as described in any one of claims 1-8.

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