A fuel cell system shutdown purging method, device, apparatus and storage medium

Abstract

The application discloses a fuel cell system shutdown purging method, device, equipment and storage medium, wherein the purging method comprises: a first stage purging: when the fuel cell system is shutdown, a current is loaded to a first preset current for operation, the temperature of the electric pile is controlled to be greater than a preset temperature, and the electric pile is subjected to load operation purging; when the average voltage or the minimum voltage is less than the first preset voltage, the operation current is reduced; a second stage purging: when the actual current is reduced to a second preset current, the electric pile is continuously discharged, the air supply of the cathode side is quickly stopped and is static for a period of time; when the minimum voltage is less than the second preset voltage, the air supply of the cathode side is quickly recovered and the air volume is increased, and the temperature is reduced to continue purging; and when the average voltage or the minimum voltage is less than a third preset voltage, the shutdown is ended. The application can solve the problem that the anode side porous electrode is difficult to dry, and the low-temperature storage performance and the low-temperature lossless starting performance of the fuel cell system below zero degrees are improved.

Description

Technical Field

[0001] This invention relates to the field of fuel cell system technology, and in particular to a method, apparatus, equipment and storage medium for shutting down and purging a fuel cell system. Background Technology

[0002] During operation, proton exchange membrane fuel cells contain both gaseous and liquid water in the reaction zone. During low-temperature cold starts (below 0°C), because the cell temperature is below the freezing point of water, residual water from the previous shutdown and water generated by the electrochemical reaction may freeze. Once the water in the fuel cell stack freezes, it hinders the transport of reactant gases. The resulting ice deposits generate stress within the stack, damaging not only the catalyst interface and the matrix material of the porous electrodes but also the flow channels, pipes, and sealing structures.

[0003] Therefore, under cold conditions, to ensure the smooth and damage-free startup of the battery stack and fuel cell system in low-temperature environments, the water content within the porous electrodes must be controlled within a reasonable range. During normal shutdown operation, the current and hydrogen flow rate are relatively low, making it difficult to dry the water content in the anode-side porous electrodes. A larger airflow can be used on the cathode side, making it easier to dry the cathode-side porous electrodes. Therefore, controlling the water content in the anode-side porous electrodes is a key aspect of low-temperature shutdown purging.

[0004] Currently, most cryogenic shutdown purging methods operate with low current and high airflow (metering ratio of 3-10 times or more), while monitoring the stack's internal resistance or minimum voltage to determine if the stack is dry. However, this method results in the membrane electrode being at a high potential for an extended period, significantly impacting its lifespan. Furthermore, this method struggles to dry the anode; after shutdown, condensation re-occurs on the anode side as the stack temperature drops, making it difficult to meet cryogenic storage requirements and hindering cryogenic startup.

[0005] To address this challenge, some patents employ multi-stage purging with relatively small airflow and low temperatures, while simultaneously monitoring parameters such as the internal resistance of the battery stack. This reduces the water content of the stack to meet the target value for low-temperature storage. However, due to the low purging temperature and small airflow, this method requires a long purging time to completely remove water vapor / water from the battery stack, resulting in prolonged downtime and impacting the customer's user experience. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a method, apparatus, equipment, and storage medium for shutting down and purging a fuel cell system. This method solves the problem of difficulty in drying the porous electrodes on the anode side, while avoiding the high potential issues caused by high-volume purging. It also improves the performance of the fuel cell system for sub-zero temperature storage and low-temperature non-destructive start-up. Furthermore, it resolves the problem of excessively long shutdown purging times caused by multi-stage purging with lower airflow and temperature, shortening downtime, improving the user experience, and reducing hydrogen consumption during system shutdown purging.

[0007] The technical solution adopted in this invention is as follows:

[0008] A method for shutting down and purging a fuel cell system includes:

[0009] First stage purging: When the fuel cell system is shut down, the current is applied to the first preset current I1 to operate, and the stack temperature is controlled to be higher than the preset temperature T. The stack is purged under load. When the average or minimum segment voltage is less than the first preset voltage V1, the operating current is reduced to the second preset current I2.

[0010] Second stage purging: When the actual current drops to the second preset current I2, the stack continues to discharge, the air supply to the cathode side is quickly stopped and the stack remains still for a period of time, so that the remaining water or water vapor on the anode side can quickly migrate to the cathode side through electrochemical dragging; when the minimum section voltage is less than the second preset voltage V2, the air supply to the cathode side is quickly restored and the air volume is increased, while the temperature is reduced and purging continues; when the average section voltage or the minimum section voltage is less than the third preset voltage V3, the shutdown ends.

[0011] Furthermore, the first stage of purging includes the following steps:

[0012] S1. Set the preset temperature T for the first stage of purging, control the thermostat to maintain the temperature of the cooling medium at the fuel cell inlet or outlet above the preset temperature T, apply the first preset current density J1, set the purging air metering ratio α1 on the cathode side, and α1 should be greater than the air metering ratio used for normal operation under the current density J1; perform load purging on the stack until the average or minimum segment voltage drops to the first preset voltage V1.

[0013] S2. When the average or minimum segment voltage drops to the first preset voltage V1, the operating current density is reduced, and the operating air volume on the cathode side is reduced, while the speed of the hydrogen circulation pump on the anode side remains unchanged; when the actual current density reaches the second preset current density J2, the first stage of purging ends.

[0014] Furthermore, the second stage of purging includes the following steps:

[0015] S3. When the actual current density in step S2 reaches the second preset current density J2, shut down the air compressor and simultaneously close the air intake throttle valve and air outlet throttle valve of the humidifier to maintain the continuous discharge of the fuel cell stack under the second preset current density J2, maintain the speed of the hydrogen circulation pump, and keep the system stationary for a period of time.

[0016] S4. When the minimum section voltage is less than the second preset voltage V2, quickly restore the supply of air volume on the cathode side, open the intake throttle valve and the exhaust throttle valve of the humidifier, start the air compressor, and continue purging; at the same time, the thermostat is switched to the large circulation mode, and the radiator is increased to quickly cool and purge the fuel cell stack; when the average section voltage or the minimum section voltage is less than the third preset voltage V3, the second stage of purging ends, and the entire shutdown process ends.

[0017] Furthermore, the second stage of purging includes the following steps:

[0018] S3'. When the actual current density in step S2 reaches the second preset current density J2, open the bypass throttle valve to keep the air compressor running, and at the same time close the intake throttle valve and the exhaust throttle valve of the humidifier to keep the fuel cell stack continuously discharging under the second preset current density J2, maintain the speed of the hydrogen circulation pump, and keep the system stationary for a period of time.

[0019] S4'. When the minimum stage voltage is less than the second preset voltage V2, quickly restore the supply of air volume on the cathode side, open the intake throttle valve and the exhaust throttle valve of the humidifier, close the bypass throttle valve, and continue purging; at the same time, the thermostat switches to the large circulation mode, and the radiator is increased to quickly cool and purge the fuel cell stack; when the average stage voltage or the minimum stage voltage is less than the third preset voltage V3, the second stage of purging ends, and the entire shutdown process ends.

[0020] A fuel cell system shutdown purging device includes: an air filter, a flow meter, an air compressor, an intercooler, an intake throttle valve, a humidifier, an outlet throttle valve, a bypass throttle valve, a hydrogen supply module, a hydrogen circulation pump, a gas-liquid separator, an exhaust valve, a drain valve, a cooling pump, a thermostat, and a radiator. The air filter, flow meter, air compressor, intercooler, intake throttle valve, humidifier, and outlet throttle valve are connected sequentially. One end of the bypass throttle valve is connected to the intercooler, and the other end is connected to the exhaust valve. The hydrogen supply module, hydrogen circulation pump, and gas-liquid separator are connected sequentially, and the gas-liquid separator is connected to the exhaust valve and drain valve respectively. The cooling pump, thermostat, and radiator are interconnected. The humidifier, hydrogen supply module, gas-liquid separator, cooling pump, and thermostat are all connected to the fuel cell stack.

[0021] Furthermore, during the operation of the purging device, air enters the air filter through a pipeline, is filtered, and then enters the flow meter to monitor the air flow rate. It then enters the air compressor for pressurization, is cooled by the intercooler, and enters the humidifier for humidification. It then enters the fuel cell stack for a chemical reaction. After the reaction, the humidified air exits the fuel cell stack and re-enters the humidifier to humidify the dry air at the humidifier inlet. The humidified air exits the humidifier and is discharged through the outlet throttle valve. Hydrogen enters the fuel cell stack for a chemical reaction after being depressurized by the hydrogen supply module. After the reaction, excess hydrogen undergoes gas-liquid separation through a gas-liquid separator. The separated liquid water is drained through a drain valve, and the separated hydrogen is mixed again with fresh hydrogen from the hydrogen supply module by a hydrogen circulation pump and then enters the fuel cell stack for further reaction.

[0022] A computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the above-described fuel cell system shutdown and purging method.

[0023] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the shutdown and purging method for the fuel cell system.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) During the first stage of purging, a higher temperature and appropriate air volume are used for purging under load, which can quickly remove most of the water vapor / water in the fuel cell stack and avoid the generation of high potential.

[0026] (2) During the first stage of purging, a smaller current is used for purging under load, which can reduce the amount of water generated by the stack and facilitate the rapid removal of water vapor / water from the stack.

[0027] (3) During the second stage of purging, the cathode air supply is quickly shut off while the stack is continuously discharged. Through electrochemical dragging (electrochemical dragging is the most important water transport mode in proton membrane), the water on the anode side is quickly migrated to the cathode side, solving the problem of water vapor / water on the anode side being difficult to drain completely, and also facilitating subsequent purging and drainage of the cathode side.

[0028] (4) During the second stage of purging, after the water on the anode side migrates to the cathode side due to electrochemical drag, the cathode side is purged by increasing the air volume and cooling the temperature. This can accelerate the rapid discharge of the remaining small amount of water vapor / water in the fuel cell stack and shorten the purging time.

[0029] (5) Through the above two stages of purging, the water vapor / water in the fuel cell stack can be quickly purged and discharged during the shutdown stage, so that the system can meet the sub-zero temperature storage conditions. Attached Figure Description

[0030] Figure 1This is a flowchart of the fuel cell system shutdown and purging method according to Embodiment 1 of the present invention.

[0031] Figure 2 This is a schematic diagram of the fuel cell system shutdown purging device according to Embodiment 3 of the present invention.

[0032] Attached reference numerals: 1-Air filter, 2-Flow meter, 3-Air compressor, 4-Intercooler, 5-Intake throttle valve, 6-Humidifier, 7-Fuel stack, 8-Outlet throttle valve, 9-Bypass throttle valve, 10-Hydrogen supply module, 11-Hydrogen circulation pump, 12-Gas-water separator, 13-Exhaust valve, 14-Drain valve, 15-Cooling pump, 16-Thermostat, 17-Radiator. Detailed Implementation

[0033] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments are now described. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] like Figure 1 As shown, this embodiment provides a method for shutting down and purging a fuel cell system, including:

[0036] First stage purging: When the fuel cell system is shut down, the current is applied to the first preset current I1 to operate, and the stack temperature is controlled to be higher than the preset temperature T. The stack is purged under load. When the average or minimum segment voltage is less than the first preset voltage V1, the operating current is reduced to the second preset current I2.

[0037] Second stage purging: When the actual current drops to the second preset current I2, the stack continues to discharge, the air supply to the cathode side is quickly stopped and the stack remains still for a period of time, so that the remaining water or water vapor on the anode side can quickly migrate to the cathode side through electrochemical dragging; when the minimum section voltage is less than the second preset voltage V2, the air supply to the cathode side is quickly restored and the air volume is increased, while the temperature is reduced and purging continues; when the average section voltage or the minimum section voltage is less than the third preset voltage V3, the shutdown ends.

[0038] Preferably, the first stage of purging includes the following steps:

[0039] S1. Set the preset temperature T for the first stage of purging, control the thermostat to maintain the temperature of the cooling medium at the fuel cell inlet or outlet above the preset temperature T, apply the first preset current density J1, set the purging air metering ratio α1 on the cathode side, and α1 should be greater than the air metering ratio used for normal operation under the current density J1; perform load purging on the fuel cell stack until the average or minimum purging voltage drops to the first preset voltage V1.

[0040] S2. When the average or minimum segment voltage drops to the first preset voltage V1, the operating current density is reduced, and the operating airflow on the cathode side is reduced, while the speed of the hydrogen circulation pump on the anode side remains unchanged; when the actual current density reaches the second preset current density J2, the first stage of purging ends. The first stage of purging can purge most of the water vapor / water in the fuel cell stack.

[0041] Preferably, the second stage of purging includes the following steps:

[0042] S3. When the actual current density in step S2 reaches the second preset current density J2, turn off the air compressor and simultaneously close the intake and exhaust throttle valves of the humidifier. Maintain the continuous discharge of the fuel cell stack at the second preset current density J2, and keep the hydrogen circulation pump running at its speed, allowing the system to stand still for a period of time. During this period, hydrogen will be continuously supplied to the anode side. As the fuel cell stack continues to discharge, the protons produced by the catalytic reaction on the anode side will carry water molecules through the proton exchange membrane from the anode to the cathode, thereby migrating the remaining small portion of water molecules that are difficult to purge from the anode side to the cathode side. During the standstill period, the air supply to the cathode side stops, so the fuel cell stack voltage will continue to decrease, and after a period of time, the voltage will drop to a very low level.

[0043] S4. When the minimum segment voltage is less than the second preset voltage V2, quickly restore the air supply to the cathode side, open the humidifier's inlet and outlet throttle valves, start the air compressor, and continue purging; simultaneously, switch the thermostat to large circulation, and increase the radiator to quickly cool and purge the fuel cell stack. After migrating water vapor / water from the anode side to the cathode side through step S3, increasing the purging airflow and lowering the temperature can quickly remove the remaining water vapor / water from the porous electrodes of the cathode and anode, shortening the shutdown purging time. When the average segment voltage or the minimum segment voltage is less than the third preset voltage V3, the second stage of purging ends, and the entire shutdown process is complete.

[0044] Specifically, the shutdown purging method in this example can be implemented through the following steps:

[0045] S1. The preset first-stage temperature is 50℃. The thermostat is controlled to maintain the temperature of the cooling medium at the fuel cell inlet or outlet at ≥50℃. The applied current density is 0.1~0.3A / cm². 2Between these conditions, a suitable amount of purging air is supplied to the cathode side (greater than the air metering ratio used for normal operation under this electrical density) to maintain the average section voltage not exceeding 0.85V. The system is then purged under load until the average section voltage drops to the preset voltage of 0.75V.

[0046] S2. When the average voltage drops to the preset voltage of 0.75V, reduce the operating voltage density to between 0.05 and 0.2A / cm², and simultaneously reduce the operating airflow on the cathode side while keeping the speed of the hydrogen circulation pump on the anode side unchanged. When the actual voltage density reaches the set voltage density, the first stage of purging ends. The first stage of purging can purge most of the water vapor / water in the fuel cell stack.

[0047] S3. When the actual electrical density reaches the set electrical density in step S2, shut down the air compressor, and simultaneously close the intake and exhaust throttle valves to maintain continuous discharge of the fuel cell stack at the target electrical density. Maintain the speed of the hydrogen circulation pump and allow the system to stand still for a period of time. During this period, hydrogen will be continuously supplied to the anode side. As the fuel cell stack continues to discharge, protons generated by the catalytic reaction on the anode side will carry water molecules through the proton exchange membrane from the anode to the cathode, thereby migrating the remaining small portion of water molecules that are difficult to purge from the anode side to the cathode side. During the standstill period, the air supply to the cathode side is stopped, so the fuel cell stack voltage will continue to drop. After a period of time, the voltage will drop to a very low level. When the minimum voltage is ≤ the preset value of 0.2V, the air supply to the cathode side will be quickly restored.

[0048] S4. When the minimum plenum voltage is ≤ 0.2V (preset value), quickly open the intake and exhaust throttle valves, start the air compressor, and provide a larger air metering ratio for purging. Simultaneously, switch the thermostat to large circulation mode and increase the radiator's capacity for rapid cooling and purging of the fuel cell stack. After step S3, which migrates water vapor / water from the anode side to the cathode side, increasing the purging airflow and lowering the temperature can quickly remove remaining water vapor / water from the porous electrodes of the anode and cathode, shortening the shutdown purging time. When the average plenum voltage is below the preset voltage of 0.75V, the second stage of purging ends, and the entire shutdown process is complete.

[0049] Example 2

[0050] This embodiment is based on embodiment 1:

[0051] This embodiment provides a method for shutting down and purging a fuel cell system. The difference between this embodiment and Embodiment 1 lies in the second stage of purging. The second stage of purging in this embodiment includes the following steps:

[0052] S3'. When the actual current density in step S2 reaches the second preset current density J2, open the bypass throttle valve to keep the air compressor running, and simultaneously close the humidifier's intake and exhaust throttle valves to maintain continuous discharge of the fuel cell stack at the second preset current density J2, maintaining the speed of the hydrogen circulation pump and allowing the system to stand still for a period of time. During this period, hydrogen will be continuously supplied to the anode side. As the fuel cell stack continues to discharge, the protons produced by the catalytic reaction on the anode side will carry water molecules through the proton exchange membrane from the anode to the cathode, thereby migrating the remaining small portion of water molecules that are difficult to purge from the anode side to the cathode side. During the standstill period, the air supply to the cathode side stops, so the fuel cell stack voltage will continue to decrease, and after a period of time, the voltage will drop to a very low level.

[0053] S4'. When the minimum segment voltage is less than the second preset voltage V2, quickly restore the air supply to the cathode side, open the humidifier's inlet and outlet throttle valves, close the bypass throttle valve, and continue purging; simultaneously, the thermostat switches to the large circulation mode, increasing the radiator to rapidly cool and purge the fuel cell stack. After migrating water vapor / water from the anode side to the cathode side through step S3', increasing the purging airflow and lowering the temperature can quickly remove the remaining water vapor / water from the porous cathode and anode electrodes, shortening the shutdown purging time. When the average segment voltage or the minimum segment voltage is less than the third preset voltage V3, the second stage of purging ends, and the entire shutdown process is complete.

[0054] Specifically, the shutdown purging method in this example can be implemented through the following steps:

[0055] S1. The preset first-stage temperature is 50℃. The thermostat is controlled to maintain the temperature of the cooling medium at the fuel cell inlet or outlet at ≥50℃. The applied current density is 0.1~0.3A / cm². 2 Between these conditions, a suitable amount of purging air is supplied to the cathode side (greater than the air metering ratio used for normal operation under this electrical density) to maintain the average section voltage not exceeding 0.85V. The system is then purged under load until the average section voltage drops to the preset voltage of 0.75V.

[0056] S2. When the average voltage drops to the preset voltage of 0.75V, reduce the operating voltage density to between 0.05 and 0.2A / cm², and simultaneously reduce the operating airflow on the cathode side while keeping the speed of the hydrogen circulation pump on the anode side unchanged. When the actual voltage density reaches the set voltage density, the first stage of purging ends. The first stage of purging can purge most of the water vapor / water in the fuel cell stack.

[0057] S3'. When the actual electrical density reaches the set electrical density in step S2, open the bypass throttle valve to keep the air compressor running, while simultaneously closing the intake and exhaust throttle valves to maintain continuous discharge of the fuel cell stack at the target electrical density and maintain the speed of the hydrogen circulation pump, allowing the system to stand still for a period of time. During this period, hydrogen will be continuously supplied to the anode side. As the fuel cell stack continues to discharge, the protons produced by the catalytic reaction on the anode side will carry water molecules through the proton exchange membrane from the anode to the cathode, thereby migrating the remaining small portion of water molecules that are difficult to purge from the anode side to the cathode side. During the standstill period, the air supply to the cathode side stops, so the fuel cell stack voltage will continue to drop. After a period of time, the voltage will drop to a very low level. When the minimum voltage is ≤ the preset value of 0.2V, the air supply to the cathode side is quickly restored.

[0058] S4'. When the minimum plenum voltage is ≤ 0.2V (preset value), quickly open the intake and exhaust throttle valves and close the bypass throttle valve to provide a larger air metering ratio for purging. Simultaneously, the thermostat switches to the large circulation mode, and the radiator is increased to rapidly cool and purge the fuel cell stack. After step S3', which migrates water vapor / water from the anode side to the cathode side, increasing the purging airflow and lowering the temperature can quickly remove residual water vapor / water from the porous electrodes of the anode and cathode, shortening the shutdown purging time. When the average plenum voltage is below the preset voltage of 0.75V, the second stage of purging ends, and the entire shutdown process is complete.

[0059] Example 3

[0060] This embodiment is based on embodiment 1:

[0061] like Figure 2 As shown, this embodiment provides a fuel cell system shutdown purging device, including: an air filter, a flow meter, an air compressor, an intercooler, an intake throttle valve, a humidifier, an outlet throttle valve, a bypass throttle valve, a hydrogen supply module, a hydrogen circulation pump, a gas-liquid separator, an exhaust valve, a drain valve, a cooling pump, a thermostat, and a radiator; the air filter, flow meter, air compressor, intercooler, intake throttle valve, humidifier, and outlet throttle valve are connected in sequence; one end of the bypass throttle valve is connected to the intercooler, and the other end is connected to the exhaust valve; the hydrogen supply module, hydrogen circulation pump, and gas-liquid separator are connected in sequence, and the gas-liquid separator is connected to the exhaust valve and drain valve respectively; the cooling pump, thermostat, and radiator are interconnected; the humidifier, hydrogen supply module, gas-liquid separator, cooling pump, and thermostat are all connected to the fuel cell stack.

[0062] Specifically, during the operation of the purging device, air enters the air filter through a pipeline, is filtered, and then enters the flow meter to monitor the air flow rate. It then enters the air compressor for pressurization, is cooled by the intercooler, and enters the humidifier for humidification. It then enters the fuel cell stack for chemical reaction. After the reaction, the humid air exits the fuel cell stack and enters the humidifier again to humidify the dry air at the humidifier inlet. The humid air at the humidifier outlet is discharged through the exhaust throttle valve. Hydrogen enters the fuel cell stack for chemical reaction after being depressurized by the hydrogen supply module. After the reaction, the excess hydrogen passes through the gas-liquid separator for gas-liquid separation. The separated liquid water is discharged through the drain valve, and the separated hydrogen is mixed again with fresh hydrogen from the hydrogen supply module by the hydrogen circulation pump and enters the fuel cell stack for reaction.

[0063] Example 4

[0064] This embodiment is based on embodiment 1:

[0065] This embodiment provides a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the fuel cell system shutdown and purging method of Embodiment 1. The computer program can be in the form of source code, object code, executable file, or some intermediate form.

[0066] Example 5

[0067] This embodiment is based on embodiment 1:

[0068] This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the fuel cell system shutdown and purging method of Embodiment 1. The computer program can be in the form of source code, object code, executable file, or some intermediate form. The storage medium includes any entity or device capable of carrying computer program code, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc. It should be noted that the content contained in the storage medium can be appropriately added to or subtracted according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the storage medium does not include electrical carrier signals and telecommunication signals.

[0069] It should be noted that, for the sake of simplicity, the foregoing method embodiments are described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

Claims

1. A method for shutting down and purging a fuel cell system, characterized in that, include: First stage purging: When the fuel cell system is shut down, the current is applied to the first preset current I1 to operate, and the stack temperature is controlled to be higher than the preset temperature T. The stack is purged under load. When the average or minimum segment voltage is less than the first preset voltage V1, the operating current is reduced to the second preset current I2. Second stage purging: When the actual current drops to the second preset current I2, the stack continues to discharge, the air supply to the cathode side is quickly stopped and the stack remains still for a period of time, so that the remaining water or water vapor on the anode side can quickly migrate to the cathode side through electrochemical dragging; when the minimum section voltage is less than the second preset voltage V2, the air supply to the cathode side is quickly restored and the air volume is increased, while the temperature is reduced and purging continues; when the average section voltage or the minimum section voltage is less than the third preset voltage V3, the shutdown ends.

2. The fuel cell system shutdown and purging method according to claim 1, characterized in that, The first stage of purging includes the following steps: S1. Set the preset temperature T for the first stage of purging, control the thermostat to maintain the temperature of the cooling medium at the fuel cell inlet or outlet above the preset temperature T, apply the first preset current density J1, set the purging air metering ratio α1 on the cathode side, and α1 should be greater than the air metering ratio used for normal operation under the current density J1; perform load purging on the stack until the average or minimum segment voltage drops to the first preset voltage V1. S2. When the average or minimum segment voltage drops to the first preset voltage V1, the operating current density is reduced, and the operating air volume on the cathode side is reduced, while the speed of the hydrogen circulation pump on the anode side remains unchanged; when the actual current density reaches the second preset current density J2, the first stage of purging ends.

3. The fuel cell system shutdown and purging method according to claim 2, characterized in that, The second stage of purging includes the following steps: S3. When the actual current density in step S2 reaches the second preset current density J2, shut down the air compressor and simultaneously close the air intake throttle valve and air outlet throttle valve of the humidifier to maintain the continuous discharge of the fuel cell stack under the second preset current density J2, maintain the speed of the hydrogen circulation pump, and keep the system stationary for a period of time. S4. When the minimum section voltage is less than the second preset voltage V2, quickly restore the supply of air volume on the cathode side, open the intake throttle valve and the exhaust throttle valve of the humidifier, start the air compressor, and continue purging; at the same time, the thermostat is switched to the large circulation mode, and the radiator is increased to quickly cool and purge the fuel cell stack; when the average section voltage or the minimum section voltage is less than the third preset voltage V3, the second stage of purging ends, and the entire shutdown process ends.

4. The fuel cell system shutdown and purging method according to claim 2, characterized in that, The second stage of purging includes the following steps: S3'. When the actual current density in step S2 reaches the second preset current density J2, open the bypass throttle valve to keep the air compressor running, and at the same time close the intake throttle valve and the exhaust throttle valve of the humidifier to keep the fuel cell stack continuously discharging under the second preset current density J2, maintain the speed of the hydrogen circulation pump, and keep the system stationary for a period of time. S4'. When the minimum stage voltage is less than the second preset voltage V2, quickly restore the supply of air volume on the cathode side, open the intake throttle valve and the exhaust throttle valve of the humidifier, close the bypass throttle valve, and continue purging; at the same time, the thermostat switches to the large circulation mode, and the radiator is increased to quickly cool and purge the fuel cell stack; when the average stage voltage or the minimum stage voltage is less than the third preset voltage V3, the second stage of purging ends, and the entire shutdown process ends.

5. A fuel cell system shutdown purging device, applied to the fuel cell system shutdown purging method according to any one of claims 1-4, characterized in that, The fuel cell system shutdown purging device includes: an air filter, a flow meter, an air compressor, an intercooler, an intake throttle valve, a humidifier, an outlet throttle valve, a bypass throttle valve, a hydrogen supply module, a hydrogen circulation pump, a gas-liquid separator, an exhaust valve, a drain valve, a cooling pump, a thermostat, and a radiator. The air filter, flow meter, air compressor, intercooler, intake throttle valve, humidifier, and outlet throttle valve are connected in sequence. One end of the bypass throttle valve is connected to the intercooler, and the other end is connected to the exhaust valve. The hydrogen supply module, hydrogen circulation pump, and gas-liquid separator are connected in sequence, and the gas-liquid separator is connected to the exhaust valve and drain valve, respectively. The cooling pump, thermostat, and radiator are interconnected. The humidifier, hydrogen supply module, gas-liquid separator, cooling pump, and thermostat are all connected to the fuel cell stack.

6. The fuel cell system shutdown purging device according to claim 5, characterized in that, When the purging device is running, air enters the air filter through a pipeline, and after filtration, it enters the flow meter to monitor the air flow rate. Then, it enters the air compressor for pressurization, passes through the intercooler for cooling, and then enters the humidifier for humidification. Finally, it enters the fuel cell stack for chemical reaction. After the reaction, the humid air exits the fuel cell stack and enters the humidifier again to humidify the dry air at the humidifier inlet. The humid air at the humidifier outlet is discharged through the exhaust throttle valve. Hydrogen enters the fuel cell stack for chemical reaction after being depressurized by the hydrogen supply module. After the reaction, the excess hydrogen passes through the gas-liquid separator for gas-liquid separation. The separated liquid water is discharged through the drain valve, and the separated hydrogen is mixed again with fresh hydrogen from the hydrogen supply module by the hydrogen circulation pump and then enters the fuel cell stack for reaction.

7. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the fuel cell system shutdown and purging method according to any one of claims 1-4.

8. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the fuel cell system shutdown and purging method according to any one of claims 1-4.

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