Control method for fuel cell low temperature shutdown purging and start-up

Abstract

The application provides a control method for fuel cell low-temperature shutdown purging and starting, comprising the following steps: obtaining the ambient temperature of the fuel cell in real time; obtaining the high-frequency impedance threshold value required to be reached by the next normal starting after the shutdown purging according to the ambient temperature based on a calibration file; controlling the purging state based on the obtained high-frequency impedance threshold value or the purging duration; obtaining the purging mode of the last shutdown process and the high-frequency impedance value of the stack at the end of the purging before the fuel cell is started again at low temperature; controlling the activation duration based on the purging mode of the last shutdown process, the high-frequency impedance value of the stack at the end of the purging and the high-frequency impedance threshold value, and completing the starting of the fuel cell. The purpose of reducing the performance attenuation caused by the low-temperature purging of the fuel cell is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fuel cells, and particularly relates to a control method for low-temperature shutdown purging and starting of a fuel cell. BACKGROUND

[0002] A proton exchange membrane fuel cell releases electric energy through chemical reaction of hydrogen and oxygen, and is currently the most efficient hydrogen energy utilization mode because it is not limited by the Carnot limit. The proton exchange membrane fuel cell has many outstanding advantages, such as high energy conversion rate, high energy density, low noise, and zero emission. However, in a low-temperature state, the operating performance of the fuel cell is greatly affected by temperature. Shutdown at low temperature needs to be purged to a high impedance value to ensure normal starting. The membrane electrode is prone to dryness during the purging process, and the catalyst activity is low after rapid purging, which causes poor proton exchange membrane conduction and performance degradation of the fuel cell after the next start.

[0003] Currently, shutdown of the fuel cell under low-temperature conditions mostly adopts a load purging mode, and the high-frequency impedance value of the stack is used as the end-of-purging determination condition. The shutdown purging time is also limited, and less attention is paid to the influence of the purging process on the performance after the next start.

[0004] The present application has found that the prior art has the following defects in the implementation of the technical solution:

[0005] 1. The low-temperature purging process has an influence on the performance after the next start, and it is difficult to recover after a long time;

[0006] 2. The end-of-purging determination condition at normal temperature and low temperature is relatively single, and the fuel cell cannot be accurately purged to the most suitable state for the next normal start;

[0007] 3. The start under low-temperature conditions does not identify the state at the end of the last shutdown, and accordingly, the performance recovery operation is not taken. SUMMARY

[0008] In view of the problems in the prior art, the present application provides a control method for low-temperature shutdown purging and starting of a fuel cell, which at least partially solves the performance degradation problem caused by low-temperature purging of the fuel cell in the prior art.

[0009] In a first aspect, the present application provides a control method for low-temperature shutdown purging and starting of a fuel cell, comprising:

[0010] real-time acquisition of an ambient temperature of the fuel cell;

[0011] obtaining, based on a calibration file, a high-frequency impedance threshold value to be reached by the fuel cell after normal start after shutdown purging corresponding to the ambient temperature;

[0012] control the purging state based on the obtained high-frequency impedance threshold value or purging duration;

[0013] obtain the purging mode and the high-frequency impedance value of the stack at the end of purging in the last shutdown process before the fuel cell is started up again at low temperature;

[0014] control the activation duration based on the purging mode, the high-frequency impedance value of the stack at the end of purging in the last shutdown process and the high-frequency impedance threshold value, and complete the start-up of the fuel cell.

[0015] Optionally, the control of the purging state based on the obtained high-frequency impedance threshold value or purging duration comprises:

[0016] monitoring the high-frequency impedance value of the stack in real time during the purging process, and exiting the purging state when the high-frequency impedance value of the stack reaches the high-frequency impedance threshold value;

[0017] Optionally, the control of the purging state based on the obtained high-frequency impedance threshold value or purging duration comprises:

[0018] Optionally, the control of the activation duration based on the purging mode, the high-frequency impedance value of the stack at the end of purging in the last shutdown process and the high-frequency impedance threshold value, and the completion of the start-up of the fuel cell comprises:

[0019] if the purging mode in the last shutdown process is low-temperature purging and the high-frequency impedance value of the stack at the end of purging is greater than the high-frequency impedance threshold value, performing the activation operation synchronously in the process of starting up with the low-cathode stoichiometric ratio strategy.

[0020] Optionally, the activation duration in the activation operation is calibrated according to the high-frequency impedance value of the stack at the end of purging.

[0021] Optionally, the method further comprises the following step after the step of controlling the purging state based on the obtained high-frequency impedance threshold value or purging duration:

[0022] stopping the gas supply after the purging stage is exited, and performing the discharging operation until the voltage of the stack is lower than 36V.

[0023] Optionally, the obtaining of the high-frequency impedance threshold value corresponding to the next normal start-up after shutdown purging according to the ambient temperature based on the calibration file comprises:

[0024] obtaining the corresponding set purging target temperature based on the ambient temperature.

[0025] Optionally, when the ambient temperature is -5C° to 0C°, the set purging target temperature is 60C°.

[0026] when the ambient temperature is -10C° to -5C°, the set purging target temperature is 65C°.

[0027] When the ambient temperature is -15°C to -10°C, the target purging temperature is set to 70°C.

[0028] Secondly, embodiments of this disclosure also provide a fuel cell using any of the control methods described in the first aspect.

[0029] Thirdly, embodiments of this disclosure also provide a vehicle that uses any of the control methods described in the first aspect.

[0030] This invention provides a control method for low-temperature shutdown purging and startup of a fuel cell. This method enables the fuel cell to be purged to a suitable state for the next startup after shutdown at low temperatures, while simultaneously activating the startup process to perform performance recovery. The control method identifies the target state at the end of purging by recognizing the ambient temperature and simultaneously performs activation operations during startup to recover the impact of the purging process on fuel cell performance, thereby reducing the performance degradation caused by low-temperature purging. Attached Figure Description

[0031] The above and other objects, features and advantages of this disclosure will become more apparent from the accompanying drawings, in which like reference numerals generally denote like parts.

[0032] Figure 1 A flowchart illustrating the high-frequency impedance threshold obtained in the control method for low-temperature shutdown purging and startup of a fuel cell provided in this embodiment of the disclosure;

[0033] Figure 2 for Figure 1 Processing flowchart of the processing module;

[0034] Figure 3 This is a flowchart illustrating the control method for controlling the start-up of a fuel cell in the low-temperature shutdown purging and start-up control method provided in this embodiment of the present disclosure. Detailed Implementation

[0035] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0036] It should be apparent that the following description is merely illustrative of the embodiments of the disclosure and that other advantages and benefits can be realized from the disclosure. It should be apparent that the described embodiments are not the only way to implement the present disclosure and that the scope of the disclosure should be determined with reference to the appended claims. The embodiments described below are merely specific examples of the disclosure and should not be construed as limiting the scope of the disclosure. The disclosure can be implemented or applied in other different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the disclosure, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the disclosure.

[0037] It should be noted that the following describes various aspects of the embodiments within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms and that any particular structure and / or function described herein is merely illustrative. Based on the disclosure, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, an apparatus and / or a method can be implemented using any number of the aspects set forth herein. In addition, this apparatus and / or method can be implemented using other structures and / or functionality in addition to or instead of one or more of the aspects set forth herein.

[0038] It should also be noted that the drawings provided in the following embodiments are only schematic and are intended to provide a basic understanding of the basic concepts of the present disclosure. The drawings only show the components related to the present disclosure and are not drawn according to the number, shape and size of the components when actually implemented, and the shape, number and proportion of each component can be arbitrarily changed when actually implemented, and the layout of the components can be more complex.

[0039] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the aspects described can be practiced without these specific details.

[0040] As shown in the following Figure 1 The embodiments disclosed a control method for low-temperature shutdown and start-up of a fuel cell, comprising:

[0041] obtaining the ambient temperature of the fuel cell in real time;

[0042] obtaining the high-frequency impedance threshold required to be reached by the next normal start-up after shutdown and purging according to the ambient temperature based on the calibration file;

[0043] controlling the purging state based on the obtained high-frequency impedance threshold or purging duration

[0044] obtaining the purging mode of the last shutdown process and the high-frequency impedance value of the stack at the end of purging before the fuel cell is started again at low temperature;

[0045] controlling the activation duration based on the purging mode of the last shutdown process, the high-frequency impedance value of the stack at the end of purging and the high-frequency impedance threshold value, and completing the start of the fuel cell.

[0046] Optionally, the purging state is controlled based on the obtained high-frequency impedance threshold value or purging duration, comprising:

[0047] monitoring the high-frequency impedance value of the stack in real time during the purging process, and exiting the purging state when the high-frequency impedance value of the stack reaches the high-frequency impedance threshold value;

[0048] if the purging duration reaches the set purging duration and the high-frequency impedance value of the stack does not reach the high-frequency impedance threshold value, then exiting the purging state.

[0049] Optionally, the purging state is controlled based on the purging mode of the last shutdown process, the high-frequency impedance value of the stack at the end of purging and the high-frequency impedance threshold value, and completing the start of the fuel cell, comprising:

[0050] if the purging mode of the last shutdown process is low-temperature purging and the high-frequency impedance value of the stack at the end of purging is greater than the high-frequency impedance threshold value, then performing the activation operation simultaneously with the start process of the cathode low stoichiometric ratio strategy.

[0051] Optionally, the activation duration in the activation operation is calibrated according to the high-frequency impedance value of the stack at the end of purging.

[0052] Optionally, after the step of controlling the purging state based on the obtained high-frequency impedance threshold value or purging duration, further comprising:

[0053] stopping the gas supply after exiting the purging stage, and performing the discharging operation until the voltage of the stack is lower than 36V.

[0054] Optionally, the high-frequency impedance threshold value reached by the next normal start after shutdown purging corresponding to the ambient temperature is obtained based on the calibration file, comprising:

[0055] obtaining the corresponding set purging target temperature based on the ambient temperature.

[0056] Optionally, when the ambient temperature is -5C° to 0C°, the set purging target temperature is 60C°.

[0057] when the ambient temperature is -10C° to -5C°, the set purging target temperature is 65C°.

[0058] when the ambient temperature is -15C° to -10C°, the set purging target temperature is 70C°.

[0059] The fuel cell system needs to be equipped with a temperature sensor to monitor the ambient temperature in real time. When the fuel cell system needs to perform shutdown operation at the end of the running process, the ambient temperature is identified and low-temperature purging is performed. The impedance threshold value required to be reached for normal start-up next time after shutdown purging under different ambient temperatures is obtained through calibration. The change of high-frequency impedance value of the stack is monitored in real time during the purging process, and it is identified whether the impedance threshold value under the corresponding ambient temperature is reached. If it is reached, the purging state is exited; otherwise, the purging is performed until the highest time length is reached and then the purging state is exited. Then the gas supply is stopped, and the shutdown is completed after the discharge process is completed.

[0060] Before the fuel cell system needs to be started at low temperature, the purging mode and the high-frequency impedance value of the stack at the end of the last shutdown process need to be identified. If it is low-temperature purging and the impedance value at the end of purging is greater than the impedance threshold value causing performance degradation of the stack, the activation operation is performed synchronously during the startup process of the low-dosage ratio strategy of the cathode. The activation time is calibrated according to the high-frequency impedance value of the stack at the end of the last shutdown purging. Different high-frequency impedance values correspond to activation operations under different time lengths to ensure performance recovery effect. After the low-dosage ratio rapid warm-up and activation are completed, the fuel cell jumps to the normal running state, the startup is completed, and then different power load operations can be freely performed.

[0061] In one specific application scenario,

[0062] As shown in Figure 1 , Figure 2 and Figure 3 , a control method for low-temperature shutdown purging and startup of a fuel cell in the embodiment specifically includes the following steps:

[0063] S1: When the fuel cell needs to be shut down in a low-temperature state (ambient temperature below 0℃), the fuel cell controller issues a shutdown instruction, and the program automatically identifies the current ambient temperature for low-temperature purging;

[0064] S2: During the low-temperature purging process, the program automatically identifies the high-frequency impedance threshold value of the stack (which needs to be calibrated, and the target purging temperature is also calibrated) that can meet the normal start-up next time under the ambient temperature (range) it is in. The load purging is performed until the target impedance threshold value is reached or the maximum purging time length is reached, and then the purging stage is exited. For example, if the ambient temperature is -10℃ to -5℃, the purging is performed at 65℃ until the high-frequency impedance value of the stack is 200mΩ or the maximum purging time length is reached, and then the purging stage is exited.

[0065] S3: After the purging stage is exited, the gas supply is stopped, the discharge operation is performed until the voltage of the stack is lower than 36V, and the shutdown is completed;

[0066] S4: When the fuel cell needs to be started in a low-temperature state (ambient temperature is lower than 0 DEG C), the fuel cell controller issues a start instruction, the program automatically identifies the last low-temperature shutdown state (high-frequency impedance value of the stack at the end of purging), and determines whether performance recovery operation is needed according to the state; if not, normal mode starting is performed;

[0067] S5: If performance recovery operation is needed, the required activation (cathode low-dosage ratio operation) duration is determined again according to the high-frequency impedance value of the stack at the end of purging in the last shutdown, and the cathode low-dosage ratio activation state is maintained until the duration is reached; if the high-frequency impedance value of the stack at the end of purging in the last shutdown is in the range of 200-250 m omega, the low-dosage ratio operation is maintained for 60 s and then the state is exited; during the operation, the fuel cell system DC target current is controlled to be lower than 200 A, the fuel cell average single cell voltage is controlled to be about 200 mV by controlling the cathode flow, the cooling liquid inlet target temperature is maintained at 60 DEG C, and the inlet and outlet target temperature difference is 10 DEG C;

[0068] S6: After the low-dosage ratio fast warm-up and activation are completed, the fuel cell returns to the normal operation state, and starting is completed, so that different power load operations can be freely performed.

[0069] The activation method of the embodiment can also be executed in the normal operation state of the fuel cell, and has the performance recovery effect, but the process produces high heat and has low output power, which increases the heat dissipation load and cannot meet the high-power demand.

[0070] The low-temperature shutdown of the fuel cell adopts a step-by-step load purging mode, the state after shutdown is ensured to be reasonable by identifying the ambient temperature range, normal starting next time can be met, performance decay caused by purging is reduced, and the shutdown efficiency is improved;

[0071] The state after the last shutdown is identified before starting the fuel cell, the cathode low-dosage ratio activation mode is adopted, the low-temperature purging process is synchronized, and the performance decay caused by the low-temperature purging process is recovered.

[0072] The embodiment also discloses a fuel cell using the control method disclosed in the embodiment.

[0073] The embodiment also discloses a vehicle using the control method disclosed in the embodiment.

[0074] The embodiment has the following advantages:

[0075] 1. The low-temperature shutdown adopts a step-by-step load purging mode, reduces the influence of purging on the performance after next starting, improves the purging efficiency, and shortens the shutdown duration.

[0076] 2. Identify the last shutdown state before starting, determine whether to perform the corresponding activation operation, recover the performance degradation caused by the inevitable purging process, and use the activation method to match the low-temperature starting process to improve the activation efficiency.

[0077] 3. Make the low-temperature shutdown purging and starting process performance recovery operation automatically respond through the control method.

[0078] The above describes the basic principles of the present disclosure in combination with specific embodiments, but it should be noted that the advantages, advantages, effects, etc. mentioned in the present disclosure are only examples and not limitations, and these advantages, advantages, effects, etc. cannot be considered as the necessary possession of each embodiment of the present disclosure. In addition, the above specific details of the disclosure are only for the purpose of example and for the purpose of understanding, and not for the purpose of limitation, and the above details do not limit the present disclosure to the above specific details.

[0079] In the present disclosure, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. The words such as "include", "contain", "have" and the like are open words, which mean "including but not limited to", and can be used interchangeably. The words "or" and "and" used herein mean the word "and / or", and can be used interchangeably unless the context clearly indicates otherwise. The word "such as" used herein means the phrase "such as but not limited to", and can be used interchangeably.

[0080] In addition, as used herein, "or" used in the list of items starting with "at least one" indicates separate listing, so that for example, the list of "at least one of A, B or C" means A or B or C, or AB or AC or BC, or ABC (i.e. A and B and C). In addition, the phrase "exemplary" does not mean that the described example is preferred or better than other examples.

[0081] It should also be noted that in the system and method of the present disclosure, each component or each step can be decomposed and / or recombined. These decompositions and / or recombination should be considered as equivalent solutions of the present disclosure.

[0082] Various changes, modifications, and alterations to the techniques described herein can be made without departing from the teachings of the attached claims. Moreover, the scope of the claims of this disclosure is not limited to the particular aspects described above. In addition, where a process, machine, manufacture, composition of matter, means, method, or result containing procedural, business, and other steps is described, it is understood that the description is meant to encompass the specific implementation of the steps described, as well as the substitution of equivalent steps, or equivalent steps in the performance order. Accordingly, the attached claims are to be interpreted as embracing the specific aspects and embodiments described herein, as well as future modifications, changes, and alterations of the aspects and embodiments.

[0083] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other aspects without departing from the scope of the disclosure. Thus, the present disclosure is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0084] The above description has been presented for the purpose of illustration and description. Furthermore, this description is not intended to limit the embodiments of the disclosure to the forms disclosed herein. Although several example aspects and embodiments have been discussed, those skilled in the art will recognize certain modifications, alterations, additions, and sub-combinations.

Claims

1. A control method for low-temperature shutdown purging and start-up of a fuel cell, characterized in that, include: Real-time acquisition of the ambient temperature of the fuel cell; Based on the calibration file, the high-frequency impedance threshold required for the next normal startup after shutdown and purge at the corresponding ambient temperature is obtained. During the purging process, the high-frequency impedance value of the fuel cell stack is monitored in real time. When the high-frequency impedance value of the fuel cell stack reaches the high-frequency impedance threshold, the purging state is exited. Specifically, the ambient temperature of -5℃ to 0℃ corresponds to the purging target temperature of 60℃ and the high-frequency impedance value of 150mΩ when the purging state is exited after purging. The ambient temperature of -10℃ to -5℃ corresponds to the purging target temperature of 65℃ and the high-frequency impedance value of 200mΩ when the purging state is exited after purging. The ambient temperature of -15℃ to -10℃ corresponds to the purging target temperature of 70℃ and the high-frequency impedance value of 250mΩ when the purging state is exited after purging. If the high-frequency impedance value of the fuel cell stack does not reach the high-frequency impedance threshold after the purge time has reached the set purge time, the purge state will be exited. Before the fuel cell restarts at low temperature, obtain the purging mode of the previous shutdown process and the high-frequency impedance value of the stack at the end of the purging process. If the purge mode of the previous shutdown process was low temperature purge and the high frequency impedance value of the stack at the end of the purge was greater than the high frequency impedance threshold, then the required activation time is determined again based on the high frequency impedance value of the stack at the end of the previous shutdown purge. The activation time is used to indicate the duration of low metering ratio operation of the cathode. During the low-temperature start-up process, the cathode low-meter ratio activation operation is performed simultaneously on the fuel cell, and the cathode low-meter ratio activation state is maintained until the activation time is reached. During operation, the target current of the fuel cell DC converter is controlled to be lower than 200A, the cathode flow rate is controlled to maintain the average cell voltage of the fuel cell within 200mV and within the allowable error range, the target temperature of the coolant inlet is maintained at 60°C, and the target temperature difference between the inlet and outlet is maintained at 10°C. After activation, the fuel cell returns to normal operation, and startup is complete.

2. The control method for low-temperature shutdown, purging, and start-up of a fuel cell according to claim 1, characterized in that, The activation time during the activation operation is calibrated based on the high-frequency impedance value of the stack at the end of the purging process.

3. The control method for low-temperature shutdown, purging, and start-up of a fuel cell according to claim 1, characterized in that, The method further includes: After the purging phase ends, gas supply is stopped, and a discharge operation is performed until the stack voltage drops below 36V.

4. The control method for low-temperature shutdown, purging, and start-up of a fuel cell according to claim 1, characterized in that, The high-frequency impedance threshold required for the next normal startup after shutdown purging at the ambient temperature, obtained based on the calibration file, includes: The target purging temperature is determined based on the ambient temperature.

5. The control method for low-temperature shutdown, purging, and start-up of a fuel cell according to claim 4, characterized in that, When the ambient temperature is -5°C to 0°C, the target purging temperature is set to 60°C. When the ambient temperature is -10°C to -5°C, the target purging temperature is set to 65°C. When the ambient temperature is -15°C to -10°C, the target purging temperature is set to 70°C.

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