Cathode closed air-cooled fuel cell system and humidity adjustment method thereof

Abstract

The application provides a cathode closed air-cooled fuel cell system and a humidity adjusting method thereof, and belongs to the technical field of fuel cells. The system comprises a stack, an air compressor, an air filter, a hot air recovery tank, a first electromagnetic valve, a second electromagnetic valve and a third electromagnetic valve. The cathode inlet of the stack is connected with the air compressor through a pipeline, the air compressor is connected with the air filter through a pipeline, the air filter is connected with the first electromagnetic valve through a pipeline, and a first three-way valve is arranged on the pipeline. The hot air recovery tank is provided with a discharge outlet and a recovery port arranged in a heat dissipation area facing the stack. The discharge outlet is connected with the second electromagnetic valve through a pipeline, the second electromagnetic valve is connected with the first three-way valve through a pipeline, and a second three-way valve is arranged on the pipeline. The cathode outlet of the stack is connected with the third electromagnetic valve through a pipeline, and the third electromagnetic valve is connected with the second three-way valve through a pipeline. The application can realize the control of the humidity of the stack by using the hot air recovery branch formed by the hot air recovery tank and the three electromagnetic valves.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell, in particular to a cathode closed air-cooled fuel cell system and a humidity adjusting method thereof. BACKGROUND

[0002] The stack humidity is one of the important factors affecting the performance of the fuel cell, and the current mainstream control strategy is to add a membrane humidifier in the fuel cell system for external humidification. However, the membrane humidifier needs to rely on a complex flow channel design when in use, resulting in large flow loss, and the membrane material is easily affected by pressure and temperature, so that the membrane humidifier has poor humidity adjusting effect on the stack. SUMMARY

[0003] The main purpose of the present application is to provide a cathode closed air-cooled fuel cell system and a humidity adjusting method thereof to solve one or more technical problems in the prior art and at least provide a beneficial choice or create conditions.

[0004] To achieve the above-mentioned purpose, one aspect of the present application provides a cathode closed air-cooled fuel cell system, which comprises a stack, an air compressor, an air filter, a hot air recovery tank, a first electromagnetic valve, a second electromagnetic valve and a third electromagnetic valve.

[0005] The cathode inlet of the stack is connected with the air compressor through a pipeline, the air compressor is connected with the air filter through a pipeline, the air filter is connected with the first electromagnetic valve through a pipeline, and a first three-way valve is arranged on the pipeline connecting the air filter with the first electromagnetic valve.

[0006] The hot air recovery tank is provided with a recovery port and a discharge port, the recovery port is arranged towards the heat dissipation area of the stack, the discharge port is connected with the second electromagnetic valve through a pipeline, the second electromagnetic valve is connected with the first three-way valve through a pipeline, and a second three-way valve is arranged on the pipeline connecting the second electromagnetic valve with the first three-way valve.

[0007] The cathode outlet of the stack is connected with the third electromagnetic valve through a pipeline, and the third electromagnetic valve is connected with the second three-way valve through a pipeline.

[0008] Further, the system further comprises an exhaust electromagnetic valve, the exhaust electromagnetic valve is in an intermittent opening state, and the anode outlet of the stack is connected with the exhaust electromagnetic valve through a pipeline.

[0009] Further, the system further comprises a high-pressure hydrogen storage tank and a pressure reducing valve, the anode inlet of the stack is connected with the pressure reducing valve through a pipeline, and the pressure reducing valve is connected with the high-pressure hydrogen storage tank through a pipeline.

[0010] Further, the system further comprises a back pressure valve, a third three-way valve is arranged on a pipeline connecting the cathode outlet of the stack with the third electromagnetic valve, and the back pressure valve is connected with the third three-way valve through a pipeline.

[0011] Further, the system further comprises a heat dissipation device, which is used for dissipating heat of the stack in the working state.

[0012] To achieve the above-mentioned purpose, another aspect of the present application provides a humidity adjusting method, which is applied to the above-mentioned cathode closed air-cooled fuel cell system, and the method comprises:

[0013] obtaining an anode pressure drop of the stack;

[0014] in the case that the anode pressure drop of the stack is less than or equal to a preset pressure drop threshold value, obtaining an ambient temperature of the stack, and adjusting states of the first electromagnetic valve and the second electromagnetic valve according to the ambient temperature of the stack;

[0015] obtaining a cathode inlet humidity of the stack;

[0016] judging whether the cathode inlet humidity of the stack is equal to a preset humidity threshold value; if yes, keeping the state of the third electromagnetic valve unchanged; if no, adjusting an opening degree of the third electromagnetic valve, and returning to the step of obtaining the cathode inlet humidity of the stack.

[0017] Further, the adjusting of the opening degree of the third electromagnetic valve comprises:

[0018] in the case that the cathode inlet humidity of the stack is less than the preset humidity threshold value, increasing the opening degree of the third electromagnetic valve;

[0019] in the case that the cathode inlet humidity of the stack is greater than the preset humidity threshold value, decreasing the opening degree of the third electromagnetic valve.

[0020] Further, the adjusting of the states of the first electromagnetic valve and the second electromagnetic valve according to the ambient temperature of the stack comprises:

[0021] in the case that the ambient temperature of the stack is less than a first preset temperature threshold value, controlling the first electromagnetic valve to be in a full-closed state and controlling the second electromagnetic valve to be in a full-open state;

[0022] in the case that the ambient temperature of the stack is greater than or equal to the first preset temperature threshold value, controlling the first electromagnetic valve to be in a full-open state and controlling the second electromagnetic valve to be in a full-closed state.

[0023] Further, the method further comprises:

[0024] prolong the length of each opening of the exhaust electromagnetic valve when the anode pressure drop of the stack is greater than the preset pressure drop threshold value;

[0025] acquire the temperature of the stack, and adjust the states of the first electromagnetic valve, the second electromagnetic valve and the third electromagnetic valve according to the temperature of the stack.

[0026] Further, the adjusting the states of the first electromagnetic valve, the second electromagnetic valve and the third electromagnetic valve according to the temperature of the stack comprises:

[0027] when the temperature of the stack is less than a second preset temperature threshold value, controlling the first electromagnetic valve to be in a full-closed state, controlling the second electromagnetic valve to be in a full-open state, and keeping the state of the third electromagnetic valve unchanged;

[0028] when the temperature of the stack is greater than or equal to the second preset temperature threshold value, controlling the first electromagnetic valve to be in a full-open state, controlling the second electromagnetic valve to be in a full-closed state, and controlling the third electromagnetic valve to be in a full-closed state.

[0029] The present application has at least the following beneficial effects: by arranging the first electromagnetic valve at the cathode inlet side of the stack to control the external air entering the stack, arranging the hot air recovery tank and the second electromagnetic valve around the stack to control the recovery of the exhaust gas discharged by the whole stack during operation, and arranging the third electromagnetic valve at the cathode outlet side of the stack to control the recovery of the wet air recirculated by the cathode of the stack during operation, the heat air recovery branch formed by the hot air recovery tank and the three electromagnetic valves can assist in realizing the control of the stack humidity, and the overall structure is simple and compact, without the need for complex flow channel design. When it is determined that the water flooding does not occur in the stack according to the anode pressure drop of the stack, by adjusting the states of the first electromagnetic valve and the second electromagnetic valve according to the ambient temperature of the stack, and appropriately adjusting the opening degree of the third electromagnetic valve according to the cathode inlet humidity of the stack, the stack humidity can be effectively controlled. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a structural schematic diagram of a cathode closed air-cooled fuel cell system provided by an embodiment of the present application;

[0031] Figure 2 is a flow schematic diagram of a humidity adjusting method provided by an embodiment of the present application. DETAILED DESCRIPTION

[0032] For the purpose of making the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application. When the following description refers to the accompanying drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with embodiments of the present application. They are only examples of systems and methods consistent with some aspects of the embodiments of the present application as detailed in the appended claims.

[0033] It can be understood that the terms "first", "second" and the like used in the present application can be used herein to describe various concepts, but unless specifically stated, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another concept. For example, without departing from the scope of the embodiments of the present application, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information.

[0034] 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 the present application belongs. The terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0035] Stack humidity is one of the important factors affecting the performance of fuel cells. If the stack humidity is insufficient, the proton conduction resistance will be increased, resulting in stack membrane cracking and degradation. If the stack humidity is too high, the electrodes of the stack will be flooded, affecting the electrochemical reaction inside the stack. The current mainstream control strategy is to add a membrane humidifier in the fuel cell system for external humidification. The membrane humidifier recovers water and heat from the exhaust gas of the fuel cell and exchanges these humid heat to the reaction gas entering the fuel cell, i.e. using the water vapor generated during the operation of the fuel cell, through the heat and mass transfer process of the membrane, the water vapor is converted into liquid water, and then transferred to the reaction gas through the membrane, so as to achieve the purpose of humidification. However, the membrane humidifier needs to rely on a complex flow channel design when in use, resulting in large flow loss, and the membrane material is easily affected by pressure and temperature, so that the membrane humidifier has poor humidity adjustment effect on the stack. And in the whole process of stack humidity control, no measures are taken when the stack is flooded.

[0036] Therefore, the application provides a cathode closed air-cooled fuel cell system and a humidity adjusting method thereof. The system comprises a first electromagnetic valve arranged at the cathode inlet side of the stack to control the external air entering the stack, a heat air recovery tank and a second electromagnetic valve arranged around the stack to control the recovery of the exhaust gas discharged from the whole stack during the operation of the stack, and a third electromagnetic valve arranged at the cathode outlet side of the stack to control the recovery of the humid air recirculated from the cathode of the stack during the operation of the stack. The heat air recovery branch formed by the heat air recovery tank and the three electromagnetic valves can assist in controlling the humidity of the stack, and the overall structure is simple and compact, and does not need to be designed with a complex flow channel. When it is determined that the water flooding does not occur in the stack according to the anode pressure drop of the stack, the state of the first electromagnetic valve and the second electromagnetic valve is adjusted according to the ambient temperature of the stack, and the opening degree of the third electromagnetic valve is adjusted according to the cathode inlet humidity of the stack, so that the humidity of the stack can be effectively controlled.

[0037] Figure 1 Fig. 1 is a structural schematic diagram of a cathode closed air-cooled fuel cell system provided by the application. The system comprises a stack 101, an air compressor 102, an air filter 103, a heat air recovery tank 104, a high-pressure hydrogen storage tank 105, a heat dissipation device 106, a back pressure valve 107, a pressure reducing valve 108, an exhaust electromagnetic valve 109, a first electromagnetic valve 110, a second electromagnetic valve 111 and a third electromagnetic valve 112.

[0038] The cathode inlet of the stack 101 is connected with the air compressor 102 through a pipeline, the air compressor 102 is connected with the air filter 103 through a pipeline, the air filter 103 is connected with the first electromagnetic valve 110 through a pipeline, and the first electromagnetic valve 110 is connected with the atmosphere. The air in the atmosphere enters the air filter 103 through the first electromagnetic valve 110, the solid particles and other impurities in the air are filtered by the air filter 103, and then the filtered air is compressed by the air compressor 102 and then delivered to the stack 101 for electrochemical reaction.

[0039] The heat air recovery tank 104 is provided with a recovery port and a discharge port. The recovery port is mainly arranged towards the heat dissipation area of the stack 101, and the discharge port is connected with the second electromagnetic valve 111 through a pipeline. A first three-way valve 113 is arranged on the pipeline connecting the air filter 103 with the first electromagnetic valve 110, and the second electromagnetic valve 111 is connected with the first three-way valve 113 through a pipeline. The exhaust gas discharged from the stack 101 during the operation of the stack 101 is recovered by the heat air recovery tank 104, and then the exhaust gas is delivered to the gas ready to enter the air filter 103 through the second electromagnetic valve 111 for sufficient mixing, so that energy recovery can be achieved.

[0040] The cathode outlet of the stack 101 is connected with the third electromagnetic valve 112 through a pipeline, the second three-way valve 114 is arranged on the pipeline in which the second electromagnetic valve 111 is connected with the first three-way valve 113, the third electromagnetic valve 112 is connected with the second three-way valve 114 through a pipeline, the third three-way valve 115 is arranged on the pipeline in which the cathode outlet of the stack 101 is connected with the third electromagnetic valve 112, the back pressure valve 107 is connected with the third three-way valve 115 through a pipeline, and the back pressure valve 107 is connected with the atmospheric environment; for the wet air recirculated by the cathode of the stack 101 during the working process, the wet air can be transported to the gas ready to enter the air filter 103 through the third electromagnetic valve 112 for sufficient mixing, so that energy recovery can be realized, or the wet air can be directly discharged to the atmospheric environment through the back pressure valve 107, the back pressure valve 107 can be arranged to control the pressure in the stack 101, so as to protect the stack 101 in the working state.

[0041] The anode inlet of the stack 101 is connected with the pressure reducing valve 108 through a pipeline, the pressure reducing valve 108 is connected with the high-pressure hydrogen storage tank 105 through a pipeline, the anode outlet of the stack 101 is connected with the tail gas electromagnetic valve 109 through a pipeline, and the tail gas electromagnetic valve 109 is connected with the atmospheric environment; the hydrogen provided by the high-pressure hydrogen storage tank 105 is transported to the stack 101 for electrochemical reaction through the pressure reducing valve 108, and the moisture and nitrogen discharged from the anode outlet of the stack 101 during the working process are discharged to the atmospheric environment through the tail gas electromagnetic valve 109, and the tail gas electromagnetic valve 109 can also be arranged to effectively prevent the hydrogen in the stack 101 from escaping to the atmospheric environment, thereby improving the utilization rate of hydrogen.

[0042] The heat dissipation device 106 can be at least one of a heat dissipation fan, a radiator, a heat exchanger, etc., to dissipate heat of the stack 101 in the working state, thereby assisting in realizing temperature control of the stack 101 and being beneficial to prolonging the service life of the stack 101; in the present application, the heat dissipation fan is preferably adopted, which can be arranged above or on the side of the stack 101 to ensure that air can smoothly flow over the surface of the stack 101, and the heat dissipation fan and the hot air recovery tank 104 are preferably arranged on the upper and lower sides of the stack 101, so that the heat dissipation fan does not affect the recovery of the exhaust gas generated by the stack 101 by the hot air recovery tank 104 during the working process.

[0043] It should be noted that before the humidity of the above-mentioned cathode closed air-cooled fuel cell system is adjusted, the exhaust electromagnetic valve 109 is set to be intermittently opened, which can be understood as limiting the exhaust electromagnetic valve 109 to operate alternately between opening and closing according to a certain time period, and the time period is artificially set. The first electromagnetic valve 110 is set to be always open, the second electromagnetic valve 111 is set to be always closed, and the third electromagnetic valve 112 is set to be always closed. In addition, a plurality of sensors need to be set to collect data, which specifically shows that: a humidity sensor is set at the cathode inlet of the stack 101 to collect the humidity of the cathode inlet of the stack 101; a first pressure sensor is set at the anode inlet of the stack 101 to collect the anode inlet pressure of the stack 101; a second pressure sensor is set at the anode outlet of the stack 101 to collect the anode outlet pressure of the stack 101; a first temperature sensor is embedded on the bipolar plate of the stack 101 to collect the temperature of the stack 101; and a second temperature sensor is set in the indoor space environment where the stack 101 is located, which should be as close to the stack 101 as possible to collect the ambient temperature of the stack 101.

[0044] The cathode closed air-cooled fuel cell system provided by the embodiment of the present application can control the humidity of the stack by setting the first electromagnetic valve at the cathode inlet side of the stack to control the external air entering the stack, setting the hot air recovery tank and the second electromagnetic valve around the stack to control the recovery of the exhaust gas discharged by the whole stack during operation, and setting the third electromagnetic valve at the cathode outlet side of the stack to control the recovery of the wet air recirculated by the cathode of the stack during operation. The hot air recovery branch formed by the hot air recovery tank and the three electromagnetic valves can assist in realizing the control of the humidity of the stack, and the overall structure is simple and compact, without the need for complex flow channel design.

[0045] Figure 2 is an optional flowchart of a humidity adjustment method provided by the embodiment of the present application, mainly applied to the method in the above-mentioned cathode closed air-cooled fuel cell system, Figure 2 which can but is not limited to include steps S201 to S209:

[0046] Step S201, obtaining the anode pressure drop of the stack;

[0047] Step S202, judging whether the anode pressure drop of the stack is greater than a preset pressure drop threshold; if yes, it means that the water flooding phenomenon occurs in the stack, and step S208 is executed; if no, it means that the water flooding phenomenon does not occur in the stack, and step S203 is executed;

[0048] Step S203, obtaining the ambient temperature of the stack, and adjusting the states of the first electromagnetic valve and the second electromagnetic valve according to the ambient temperature of the stack;

[0049] Step S204, obtaining the cathode inlet humidity of the stack;

[0050] Step S205, judging whether the cathode inlet humidity of the stack is equal to the preset humidity threshold value; if yes, it indicates that the stack humidity is qualified, and step S207 is executed; if no, it indicates that the stack humidity is too high or too low, and step S206 is executed;

[0051] Step S206, adjusting the opening degree of the third electromagnetic valve, and returning to execute step S204;

[0052] Step S207, keeping the state of the third electromagnetic valve unchanged;

[0053] Step S208, prolonging the opening duration of the exhaust electromagnetic valve each time;

[0054] Step S209, obtaining the temperature of the stack, and adjusting the states of the first electromagnetic valve, the second electromagnetic valve and the third electromagnetic valve according to the temperature of the stack.

[0055] In the present application, a controller can be configured for the above-mentioned cathode closed air-cooled fuel cell system. When the controller is in a start-up running state, the above-mentioned humidity adjustment method can be executed cyclically, that is, after step S207 or step S209 is executed, step S201 will be executed again. When the controller is switched from the start-up running state to the shutdown state, the above-mentioned humidity adjustment method will no longer be used to control the above-mentioned cathode closed air-cooled fuel cell system, that is, no matter which step is executed, the whole control process will be directly ended.

[0056] In some embodiments, the implementation of step S201 includes obtaining the anode inlet pressure and the anode outlet pressure of the stack, and subtracting the anode inlet pressure from the anode outlet pressure to obtain the anode pressure drop of the stack.

[0057] In step S202 of some embodiments, the determination of the preset pressure drop threshold value includes obtaining the working current of the stack, and obtaining the corresponding preset pressure drop threshold value under the working current of the stack by table lookup. The table records a plurality of continuous different working current ranges of the stack and the corresponding preset pressure drop threshold values of each working current range. These data are determined by pre-experiment.

[0058] In step S203 of some embodiments, the states of the first electromagnetic valve and the second electromagnetic valve are adjusted according to the ambient temperature of the stack, and the corresponding implementation includes:

[0059] determining whether the ambient temperature of the stack is less than a first preset temperature threshold, the first preset temperature threshold can be selected in the range of [5℃, 15℃], and preferably set to 10℃; if yes, controlling the first electromagnetic valve to be in a fully closed state, and controlling the second electromagnetic valve to be in a fully open state, so that the hot air recovery tank can transmit the air heated by the stack in the recovery part to the air supply branch through the second electromagnetic valve, the air supply branch being formed by the cathode inlet of the stack, the air compressor and the air filter, so as to improve the air temperature at the cathode inlet of the stack; if no, controlling the first electromagnetic valve to be in a fully open state, and controlling the second electromagnetic valve to be in a fully closed state, so that the air in the atmospheric environment can be transmitted to the air supply branch through the first electromagnetic valve, ensuring that the electrochemical reaction in the stack is carried out normally.

[0060] In the above step S205 of some embodiments, the following is explained for the case that the cathode inlet humidity of the stack is equal to the preset humidity threshold: if the absolute deviation between the cathode inlet humidity of the stack and the preset humidity threshold is detected to be in the range of [0%RH, 0.5%RH], it is determined that the cathode inlet humidity of the stack is equal to the preset humidity threshold.

[0061] In the above step S206 of some embodiments, the opening of the third electromagnetic valve can be adjusted according to the relationship between the cathode inlet humidity of the stack and the preset humidity threshold, the preset humidity threshold can be selected in the range of [20%RH, 40%RH], and preferably set to 30%RH, and the corresponding embodiments include:

[0062] In the case that the cathode inlet humidity of the stack is less than the preset humidity threshold, the opening of the third electromagnetic valve is increased, and the opening of the third electromagnetic valve is limited to increase to a preset opening threshold at most, the preset opening threshold is preferably set to 20%, so as to increase the humid air generated by the cathode recirculation of the stack and transmitted to the air supply branch, and improve the air moisture content at the cathode inlet of the stack; and in the case that the cathode inlet humidity of the stack is greater than the preset humidity threshold, the opening of the third electromagnetic valve is reduced, so as to reduce the humid air generated by the cathode recirculation of the stack and transmitted to the air supply branch, and reduce the air moisture content at the cathode inlet of the stack.

[0063] In the above step S209 of some embodiments, the states of the first electromagnetic valve, the second electromagnetic valve and the third electromagnetic valve are adjusted according to the temperature of the stack, and the corresponding embodiments include:

[0064] determining whether the temperature of the stack is less than a second preset temperature threshold, the second preset temperature threshold can be selected in the range of [50℃, 70℃], and preferably set to 60℃; if yes, controlling the first electromagnetic valve to be in a full closed state, controlling the second electromagnetic valve to be in a full open state, and controlling the state of the third electromagnetic valve to remain unchanged, so that the air heated by the stack and recovered by the hot air recovery tank can be transmitted to the air supply branch through the second electromagnetic valve, to improve the air temperature at the cathode inlet of the stack, and thereby reduce the air humidity at the cathode inlet of the stack; if no, controlling the first electromagnetic valve to be in a full open state, controlling the second electromagnetic valve to be in a full closed state, and controlling the third electromagnetic valve to be in a full closed state, so that the air in the atmospheric environment can be transmitted to the air supply branch through the first electromagnetic valve, to ensure that the electrochemical reaction in the stack is carried out normally.

[0065] The humidity adjusting method applied to the cathode closed air-cooled fuel cell system provided by the embodiments of the present application can effectively control the stack humidity, which is conducive to alleviating the membrane dry phenomenon of the stack, by adjusting the states of the first electromagnetic valve and the second electromagnetic valve according to the ambient temperature of the stack, and appropriately adjusting the opening degree of the third electromagnetic valve according to the cathode inlet humidity of the stack. The water flooding phenomenon of the stack can be accelerated to alleviate, the service life of the stack can be improved, the stack can be restored to the normal state as soon as possible, the exhaust loss of the tail gas electromagnetic valve can be reduced, and the hydrogen utilization rate of the stack can be improved, by controlling the first electromagnetic valve to be in a full closed state and the second electromagnetic valve to be in a full open state after prolonging the length of each opening of the tail gas electromagnetic valve.

[0066] Although the description of the present application has been quite detailed and particularly described with respect to several embodiments, it is not intended to be limited to any of these details or embodiments or any special embodiment, but should be considered to effectively cover the intended scope of the present application by referring to the appended claims, taking into account the prior art to provide a broad interpretation of these claims. In addition, the present application is described above in embodiments that the inventor can foresee, the purpose of which is to provide a useful description, and non-essential modifications to the present application that have not yet been foreseen can still represent equivalent modifications of the present application.

Claims

1. A humidity control method for a cathode-closed air-cooled fuel cell system, characterized in that, The cathode-closed air-cooled fuel cell system includes a fuel cell stack, an air compressor, an air filter, a hot air recovery box, a first solenoid valve, a second solenoid valve, and a third solenoid valve. The cathode inlet of the fuel cell stack is connected to the air compressor via a pipeline. The air compressor is connected to the air filter via a pipeline. The air filter is connected to the first solenoid valve via a pipeline. A first three-way valve is installed on the pipeline connecting the air filter and the first solenoid valve. The hot air recovery box has a recovery port and an outlet. The recovery port is positioned facing the heat dissipation area of ​​the fuel cell stack. The outlet is connected to the second solenoid valve via a pipeline. The second solenoid valve is connected to the first three-way valve via a pipeline. A second three-way valve is installed on the pipeline connecting the second solenoid valve and the first three-way valve. The cathode outlet of the fuel cell stack is connected to the third solenoid valve via a pipeline. The third solenoid valve is connected to the second three-way valve via a pipeline. The method includes: Obtain the anode voltage drop of the fuel cell stack; When the anode voltage drop of the fuel cell stack is less than or equal to a preset voltage drop threshold, the ambient temperature of the fuel cell stack is obtained, and the states of the first solenoid valve and the second solenoid valve are adjusted according to the ambient temperature of the fuel cell stack. Obtain the cathode inlet humidity of the fuel cell stack; Determine whether the cathode inlet humidity of the fuel cell stack is equal to a preset humidity threshold; if yes, control the state of the third solenoid valve to remain unchanged; if no, adjust the opening of the third solenoid valve and return to the step of obtaining the cathode inlet humidity of the fuel cell stack.

2. The humidity control method according to claim 1, characterized in that, The cathode closed-loop air-cooled fuel cell system also includes an exhaust gas solenoid valve, which is intermittently open, and the anode outlet of the fuel cell stack is connected to the exhaust gas solenoid valve via a pipeline.

3. The humidity control method according to claim 1, characterized in that, The cathode closed-loop air-cooled fuel cell system also includes a high-pressure hydrogen storage tank and a pressure reducing valve. The anode inlet of the fuel cell stack is connected to the pressure reducing valve via a pipeline, and the pressure reducing valve is connected to the high-pressure hydrogen storage tank via a pipeline.

4. The humidity control method according to claim 1, characterized in that, The cathode closed-loop air-cooled fuel cell system also includes a back pressure valve. A third three-way valve is provided on the pipeline connecting the cathode outlet of the fuel cell stack to the third solenoid valve. The back pressure valve is connected to the third three-way valve through the pipeline.

5. The humidity control method according to claim 1, characterized in that, The cathode closed-loop air-cooled fuel cell system also includes a heat dissipation device for dissipating heat from the fuel cell stack during operation.

6. The humidity control method according to claim 1, characterized in that, Adjusting the opening degree of the third solenoid valve includes: If the humidity at the cathode inlet of the fuel cell stack is less than the preset humidity threshold, increase the opening of the third solenoid valve; If the humidity at the cathode inlet of the fuel cell stack is greater than the preset humidity threshold, the opening of the third solenoid valve is reduced.

7. The humidity control method according to claim 1, characterized in that, The adjustment of the states of the first and second solenoid valves based on the ambient temperature of the fuel cell stack includes: When the ambient temperature of the fuel cell stack is lower than a first preset temperature threshold, the first solenoid valve is controlled to be fully closed and the second solenoid valve is controlled to be fully open. When the ambient temperature of the fuel cell stack is greater than or equal to the first preset temperature threshold, the first solenoid valve is controlled to be fully open and the second solenoid valve is controlled to be fully closed.

8. The humidity control method according to claim 2, characterized in that, The method further includes: If the anode voltage drop of the fuel cell stack is greater than the preset voltage drop threshold, the opening duration of the exhaust gas solenoid valve is extended each time. The temperature of the fuel cell stack is obtained, and the states of the first solenoid valve, the second solenoid valve, and the third solenoid valve are adjusted according to the temperature of the fuel cell stack.

9. The humidity control method according to claim 8, characterized in that, The adjustment of the states of the first solenoid valve, the second solenoid valve, and the third solenoid valve according to the temperature of the fuel cell stack includes: When the temperature of the fuel cell stack is lower than the second preset temperature threshold, the first solenoid valve is controlled to be fully closed, the second solenoid valve is controlled to be fully open, and the state of the third solenoid valve is controlled to remain unchanged. When the temperature of the fuel cell stack is greater than or equal to the second preset temperature threshold, the first solenoid valve is controlled to be fully open, the second solenoid valve is controlled to be fully closed, and the third solenoid valve is controlled to be fully closed.

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