Hydrogen-oxygen fuel cell control method in low-temperature environment and hydrogen-oxygen fuel cell system

Abstract

The invention provides an oxyhydrogen fuel cell control method in a low-temperature environment and an oxyhydrogen fuel cell system, which can realize stable and efficient operation of an oxyhydrogen fuel cell in the low-temperature environment, and comprises the following steps: a low-temperature preheating stage: detecting the temperature of an electric pile and the temperature of each valve body; if the temperature is smaller than or equal to T1, an auxiliary heating module is started to heat the electric pile and / or the valve body; if not, entering a pile starting stage: judging whether the pile temperature is lower than T2; if yes, starting a galvanic pile heater to cooperate with a galvanic pile fan to heat the galvanic pile, and stopping heating until the galvanic pile temperature is higher than T5; when the temperature of the electric pile is not lower than T2, a hydrogen inlet valve, an exhaust valve and a drainage valve are opened, and an air blower and an air pump are started; after time N1, the system enters closed-loop regulation control operation; the temperature of the valve body is continuously detected, and if the temperature of the valve body is lower than T6, an auxiliary heating module is started for heating; and when it is detected that the voltage of the lithium battery of the system is higher than a second preset voltage threshold V2, the system is shut down for sweeping.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen-oxygen fuel cell control technology, and specifically relates to a hydrogen-oxygen fuel cell control method and a hydrogen-oxygen fuel cell system under low-temperature conditions. Background Technology

[0002] Hydrogen-oxygen fuel cells convert the chemical energy of hydrogen and oxygen into electrical energy through an electrochemical reaction. They are characterized by high efficiency and low emissions, and are suitable for various application scenarios such as vehicle-mounted and distributed power sources.

[0003] However, in low-temperature environments, especially below 0°C, hydrogen-oxygen fuel cells face significant challenges in terms of start-up performance, operating efficiency, and reliability. This is mainly due to the complex coupling of water / ice management, decreased proton conductivity, and slowed reaction kinetics. Specifically, water produced inside the stack and in the gas path is prone to freezing at low temperatures, causing channel blockage, increased pressure drop, and even localized oxygen deficiency and overheating, affecting stack performance and lifespan. In addition, the proton conductivity of the proton exchange membrane decreases with decreasing temperature, leading to increased internal resistance and slower electrochemical reaction rates, thus reducing the fuel cell's output capacity. Furthermore, the slower reaction kinetics at low temperatures require appropriate thermal management and control strategies to compensate for this.

[0004] In existing technologies, specific measures have been taken to address the low-temperature operating conditions of fuel cells, such as preheating the stack by adding in-stack or out-of-stack heating devices and implementing a certain degree of temperature control during operation. These measures have improved the operation of fuel cells in low-temperature environments to some extent, but the following shortcomings still exist: Cold start difficulties: In extremely cold environments, it is difficult to achieve rapid and uniform heating through external heating or by utilizing the heat generated within the reactor itself. This can easily lead to localized overheating or the formation of destructive ice crystals, resulting in a low success rate and reliability of the start-up. Unstable operation: When operating in extremely cold environments, existing control strategies are unable to accurately maintain the stack temperature at the optimal operating point, which can easily lead to temperature fluctuations, affecting the stability and energy efficiency of the system.

[0005] Post-shutdown antifreeze: If the system is not optimized for low-temperature conditions after shutdown, residual water may freeze in the low-temperature environment, affecting the next cold start and even damaging the membrane electrode and valve body. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a hydrogen-oxygen fuel cell control method and a hydrogen-oxygen fuel cell system for low-temperature environments. This method enables stable and efficient operation of hydrogen-oxygen fuel cells in low-temperature environments, overcoming the problems of difficult start-up, unstable operation, and easy icing damage after shutdown in existing hydrogen-oxygen fuel cells at low temperatures.

[0007] The technical solution is as follows: a method for controlling a hydrogen-oxygen fuel cell under low-temperature conditions, characterized by comprising: Low-temperature preheating stage: The stack temperature and the temperatures of various valves in the hydrogen-oxygen fuel cell system are monitored. The valve temperatures are the temperatures collected from at least one of the following valves: hydrogen exhaust valve, oxygen exhaust valve, drain valve, and oxygen shut-off valve. If the stack temperature or the valve temperature is less than or equal to a first preset temperature threshold T1, the auxiliary heating module is activated to heat the stack and / or the valves. When both the stack temperature and the valve temperature are higher than the first temperature threshold T1, the stack start-up stage begins. During the fuel cell stack startup phase: Determine whether the fuel cell stack temperature is lower than the second preset temperature threshold T2; if so, start the fuel cell stack heater and fuel cell stack fan to heat the fuel cell stack until the fuel cell stack temperature is higher than the fifth preset temperature threshold T5 and then stop; when the fuel cell stack temperature is not lower than the second preset temperature threshold T2, open the hydrogen inlet valve, exhaust valve and drain valve, and start the blower and air pump. After the first preset time N1, the fuel cell current sampling begins, and the system enters closed-loop regulation and control operation. During the closed-loop regulation and control process, the valve body temperature is continuously monitored. If the valve body temperature is lower than the sixth preset temperature threshold T6, the auxiliary heating module is turned on for heating; otherwise, the auxiliary heating module is turned off. When the lithium battery voltage of the hydrogen-oxygen fuel cell system is detected to be higher than the second preset voltage threshold V2, the hydrogen-oxygen fuel cell system shuts down.

[0008] Furthermore, during the shutdown phase, the hydrogen-oxygen fuel cell system performs the following steps: After the hydrogen-oxygen fuel cell system is shut down, open the hydrogen inlet valve, exhaust valve, and drain valve; Turn on the cooling fan, air pump and blower, and run the cooling fan, air pump and blower at the first preset opening M1, the second preset opening M2 and the third preset opening M3 respectively; turn off the auxiliary heating module and fuel cell fan, and stop the air pump and blower after running for a second preset time N2. After running for the third preset time T3, the cooling fan is stopped, and then all valves and auxiliary power are turned off.

[0009] Furthermore, during the stack startup phase, before opening the hydrogen inlet valve, vent valve, and drain valve, an ambient temperature determination step is also included: Detect whether the ambient temperature is greater than the third preset temperature threshold T3; if so, start the cooling fan until the ambient temperature is lower than the fourth preset temperature threshold T4, then stop the cooling fan.

[0010] Furthermore, during the shutdown phase, before turning on the cooling fan, air pump, and blower, a valve body insulation step is also included: Check if the valve body temperature is less than the seventh preset temperature threshold T7; if so, start the auxiliary heating module until the valve body temperature is higher than the eighth preset temperature threshold T8, then stop the auxiliary heating module.

[0011] Furthermore, the first preset temperature threshold T1 is -20℃ to 0℃; the second preset temperature threshold T2 is -10℃ to -5℃; the fifth preset temperature threshold T5 is -5℃ to 0℃; and the sixth preset temperature threshold T6 is -5℃ to 0℃.

[0012] Furthermore, the third preset temperature threshold T3 is 0°C to 10°C; the fourth preset temperature threshold T4 is 0°C to 5°C.

[0013] Furthermore, the seventh preset temperature threshold T7 is 0°C to 5°C; the eighth preset temperature threshold T8 is 2°C to 10°C.

[0014] Furthermore, the first preset time N1 is 30 to 60 seconds; the second preset time N2 is 30 to 60 seconds; and the third preset time N3 is 30 to 60 seconds.

[0015] Furthermore, the first preset opening M1 is 25% to 80%; the second preset opening M2 is 50% to 90%; and the third preset opening M3 is 25% to 90%.

[0016] A hydrogen-oxygen fuel cell system, comprising: The battery pack, DC-DC module, and lithium battery are provided. The input terminal of the DC-DC module is connected to the battery pack, and the output terminal of the DC-DC module is connected to the lithium battery and the load. An auxiliary heating module is used to heat the valve body and fuel cell stack in low-temperature environments; The BOP module includes a hydrogen inlet valve, an oxygen vent valve, a drain valve, an oxygen shut-off valve, a blower, an air pump, a cooling fan, a fuel cell stack fan, and temperature sensors; at least five temperature sensors are provided, which are used to detect the temperature of the hydrogen vent valve, the oxygen vent valve, the drain valve, the oxygen shut-off valve, and the fuel cell stack, respectively. The FCU main control module is connected to the DC-DC module, the auxiliary heating module, and the BOP module, and the FCU main control module executes the above-described method.

[0017] Furthermore, the BOP module also includes a pressure sensor for pressure detection.

[0018] Compared with the prior art, the present invention has the following advantages: This invention employs a tiered control strategy with multiple temperature thresholds at various stages of the hydrogen-oxygen fuel cell system. This enables precise preheating control before startup, ensuring the stack rapidly warms to startup conditions while preventing damage from localized overheating. This significantly improves startup success rate and speed in low-temperature environments. Furthermore, the invention utilizes real-time temperature monitoring and adaptive heating control during operation. It dynamically adjusts auxiliary heating based on valve body temperature changes, ensuring stable system operation in low-temperature environments and preventing icing issues, thus improving system reliability and efficiency. During shutdown, auxiliary heating of the valve body, combined with multi-stage opening control of fans, air pumps, and blowers, thoroughly removes residual water from the stack, effectively preventing icing after shutdown and ensuring smooth startup, thereby extending battery life. This invention establishes a complete low-temperature environment control process for a hydrogen-oxygen fuel cell system by setting various temperature thresholds and preset time delays, combined with the opening parameters of the fan, air pump, and blower. This process covers the entire cycle before startup, during startup, during operation, and after shutdown, and can solve the problems of difficult startup, unstable operation, and easy icing damage of fuel cells in low-temperature environments. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the steps of a hydrogen-oxygen fuel cell system control method under low-temperature conditions according to the present invention. Figure 2 A flowchart of the cryogenic preheating stage and the fuel cell stack startup stage in one embodiment of the method; Figure 3 This is a flowchart of the shutdown phase in one embodiment of the method; Figure 4 This is a block diagram of a hydrogen-oxygen fuel cell system for low-temperature environments according to the present invention. Detailed Implementation

[0020] See Figure 1 , 2 3. A control method for a hydrogen-oxygen fuel cell system under low-temperature conditions according to the present invention includes: S1: Low temperature preheating stage: Detect the stack temperature of the hydrogen-oxygen fuel cell system and the temperature of each valve body of the hydrogen-oxygen fuel cell system. The valve body temperature is the temperature of at least one of the hydrogen discharge valve, oxygen discharge valve, drain valve and oxygen shut-off valve. If the stack temperature or valve body temperature is less than or equal to the first preset temperature threshold T1, start the auxiliary heating module to heat the stack and / or valve body. In this embodiment, the first temperature threshold T1 is set to -10℃. The selection of T1 in this embodiment takes into account the following factors: below -10℃, there may be ice crystals or condensation inside the valve body. Directly opening the valve may cause the valve core to jam or the seal to fail. At the same time, the proton conductivity of the proton exchange membrane inside the fuel cell stack decreases significantly at this temperature, and preheating is required to improve performance. When the temperature of the fuel cell stack and all valve bodies are higher than the first temperature threshold T1, it indicates that the system is not in an extremely low temperature environment and can directly enter the next stage, ending the low temperature preheating stage and shortening the start-up time.

[0021] S2: Fuel cell stack start-up stage: Determine whether the fuel cell stack temperature is lower than the second preset temperature threshold T2; when the fuel cell stack temperature is lower than the second preset temperature threshold T2, it means that the fuel cell stack temperature is too low and needs to be further heated. Start the fuel cell stack heater and fuel cell stack fan to heat the fuel cell stack until the fuel cell stack temperature is higher than the fifth preset temperature threshold T5 and then stop to prevent the fuel cell stack temperature from becoming too high. In this embodiment, the second temperature threshold T2 is set to -8℃, and the fifth temperature threshold T5 is set to -2℃. Below -8℃, there may be a lot of ice crystals inside the fuel cell stack, which need to be continuously heated to melt. When the temperature rises to -2℃, it is close to the freezing point, a large amount of ice crystals inside the fuel cell stack melt, and the proton conductivity of the proton exchange membrane is also restored to a certain extent. Heating can be stopped, and the temperature can be increased by the heat generated by the fuel cell stack itself during the subsequent startup process.

[0022] When the stack temperature is not lower than the second preset temperature threshold T2, the temperature preparation before startup is completed, the system enters the formal startup stage, the hydrogen inlet valve, exhaust valve and drain valve are opened to allow hydrogen and oxygen to enter the stack, the air pump is started to allow the reaction products to be discharged, and the blower is started to provide sufficient air. After the blower and air pump are turned on, a first preset time N1 is required to wait for the system to establish stable pressure and flow. In this embodiment, the first preset time N1 is set to 45 seconds. The determination of the first preset time N1 takes into account that it usually takes 30-60 seconds for gas to enter the fuel cell stack from the pipeline and fill each flow channel; at the same time, the fuel cell stack also needs a certain stabilization time from the open circuit voltage state to be able to carry current. After the first preset time N1, the current sampling of the battery stack begins. The output voltage and current of the battery stack are obtained through the DC-DC module, and the system enters closed-loop regulation and control operation. The working mode of the DC-DC module is dynamically adjusted according to the load demand and the state of the lithium battery. The specific method of closed-loop regulation and control can be PID control, fuzzy control or other control algorithms. This invention does not specifically limit this method. During the closed-loop regulation and control process, the data from the temperature sensors installed on the hydrogen exhaust solenoid valve, oxygen exhaust solenoid valve, drain solenoid valve, and oxygen shut-off valve are read in real time to continuously monitor the valve body temperature. If the temperature of any valve body is detected to be lower than the sixth preset temperature threshold T6, it indicates that the corresponding valve body may be affected by the low temperature environment and there is a risk of icing or malfunction. In this case, the auxiliary heating module is activated to heat the valve body. When the temperature of all valve bodies is higher than the sixth temperature threshold T6, it indicates that the valve body temperature is normal, and the auxiliary heating module is shut down to save energy.

[0023] In this embodiment, the sixth temperature threshold T6 is set to -2℃. The selection of the sixth temperature threshold T6 is based on the following considerations: -2℃ is close to the freezing point. Below this temperature, ice crystals may begin to form or condensation may accumulate inside the valve body. Timely heating can prevent freezing. At the same time, -2℃ also leaves a certain safety margin, so that heating will not be frequently started and stopped due to temperature fluctuations. In this embodiment, the adaptive control strategy ensures that even if the external ambient temperature continues to decrease or the valve body temperature drops due to system heat dissipation, the valve body can still be kept within a safe temperature range in a low-temperature environment, avoiding system shutdown due to valve body failure.

[0024] When the lithium battery voltage of the hydrogen-oxygen fuel cell system is detected to be higher than the second preset voltage threshold V2, it indicates that the lithium battery is fully charged or the load demand has decreased, and the hydrogen-oxygen fuel cell system shuts down.

[0025] In one embodiment, during the fuel cell stack startup phase, when the stack temperature is higher than the second temperature threshold T2, the stack temperature is relatively high, but further checks of the ambient temperature are required. An ambient temperature determination step is also included before opening the hydrogen inlet valve, exhaust valve, and drain valve. If the ambient temperature is higher than the third preset temperature threshold T3, it indicates that the ambient temperature is too high and may be detrimental to the heat dissipation of the fuel cell stack. If so, the cooling fan is started until the ambient temperature is lower than the fourth preset temperature threshold T4, at which point the cooling fan is stopped. This can prevent the fuel cell stack temperature from running out of control due to excessively high ambient temperature during startup.

[0026] In this embodiment, the third temperature threshold T3 is set to 5°C and the fourth temperature threshold T4 is set to 2°C. This invention is mainly aimed at low temperature environments, but in some cases the ambient temperature may be temporarily high, requiring appropriate pre-cooling to ensure the stability of subsequent control. In this embodiment, ambient temperature judgment is introduced before startup, which can optimize the thermal management state when the system starts up.

[0027] In this embodiment, by preheating and heating the valve body and the fuel cell stack in stages, startup failures caused by component freezing or excessively low temperatures can be avoided, enabling rapid and reliable low-temperature cold starts. During startup and operation, by monitoring and assisting in heating the fuel cell stack, valve body, and ambient temperature, the continuous and stable operation of the hydrogen-oxygen fuel cell system in a low-temperature environment is ensured, avoiding performance fluctuations.

[0028] In one embodiment of the present invention, the hydrogen-oxygen fuel cell system further includes S3: a shutdown phase, in which the following steps are performed: After the hydrogen-oxygen fuel cell system is shut down, open the hydrogen inlet valve, exhaust valve and drain valve to ensure that the purging gas can enter the stack and carry away the moisture. Check if the valve body temperature is less than the seventh preset temperature threshold T7; if so, start the auxiliary heating module to prevent the valve body from failing to open normally due to low temperature during the purging process or from freezing due to water vapor brought by the purging airflow at the valve body; continuously monitor the valve body temperature, and when all valve body temperatures are higher than the eighth temperature threshold T8, turn off the auxiliary heating module. In this embodiment, the seventh temperature threshold T7 is set to 2°C and the eighth temperature threshold T8 is set to 5°C. When the temperature is below 2°C, there is a risk of icing in the valve body, which requires heating. When the temperature rises to 5°C, there is sufficient safety margin, and heating can be stopped. At the same time, 5°C is not too high and will not cause unnecessary energy waste.

[0029] The cooling fan, air pump, and blower are activated for purging. They operate at preset opening degrees M1, M2, and M3, respectively. In this embodiment, the cooling fan opening degree M1 is set to 50%, the air pump opening degree M2 to 70%, and the blower opening degree M3 to 60%. The lower opening degree of the cooling fan provides sufficient airflow to promote the diffusion of moisture outside the fuel cell stack without excessive cooling. The higher opening degree of the air pump provides sufficient pressure to blow water out of the gas channels inside the fuel cell stack. The moderate opening degree of the blower provides continuous airflow without causing excessive pressure or temperature inside the fuel cell stack. Through multi-level opening degree control, a highly efficient purging effect can be achieved, thoroughly removing moisture without adversely affecting the fuel cell stack.

[0030] In this embodiment, after the purging begins, the low-temperature auxiliary heating and the fuel cell stack fan are turned off to avoid unnecessary energy consumption. After running for a second preset time N2, the air pump and blower are stopped. In this embodiment, the second preset time N2 is set to 45 seconds, which can ensure that the high-pressure airflow generated by the air pump and blower blows out most of the liquid water in the internal flow channels of the fuel cell stack.

[0031] After running for a third preset time T3, the cooling fan is stopped. In this embodiment, the third preset time T3 is set to 45 seconds to use the continuous airflow of the cooling fan to further dry the residual moisture on the outside of the fuel cell stack and in the pipeline. Then, all valves are closed and the system enters standby mode, waiting for the next startup.

[0032] The purging process during the shutdown phase in the embodiment can remove moisture from the fuel cell stack to the maximum extent, effectively preventing freezing in low-temperature environments after shutdown, ensuring the safety of the fuel cell stack and valve body, and ensuring a smooth start-up next time.

[0033] In this embodiment, by shutting down and purging, the cooling fan, air pump and blower work together at a specific opening to quickly and thoroughly remove moisture from the inside of the fuel cell stack. This effectively prevents ice formation after shutdown from damaging the core components and can improve the system's lifespan and the success rate of the next startup.

[0034] Example 2 The difference between Example 2 and Example 1 is that the specific values ​​of each temperature threshold and time parameter are different, while the other parts are the same.

[0035] The parameter settings in this embodiment are as follows: The first temperature threshold T1 is set to -15℃; The second temperature threshold T2 is set to -9℃; The fifth temperature threshold T5 is set to -3℃; The third temperature threshold T3 is set to 8℃; The fourth temperature threshold T4 is set to 4℃; The sixth temperature threshold T6 is set to -4℃; The seventh temperature threshold T7 is set to 3℃; The eighth temperature threshold, T8, is set to 6°C. The first preset time N1 is set to 50 seconds; The preset voltage threshold V2 is set to 13V; The opening M1 of cooling fan 13 is set to 60%; The opening degree M2 of air pump 12 is set to 80%; The opening degree M3 of blower 11 is set to 70%; The second preset time N2 is set to 50 seconds; The third preset time N3 is set to 50 seconds.

[0036] This embodiment is suitable for applications with lower ambient temperatures, larger fuel cell capacity, or higher requirements for start-up speed. By adjusting these parameters, optimal control effects can be obtained under different practical application conditions.

[0037] Example 3 The difference between Example 3 and Example 1 is that the specific values ​​of each temperature threshold and time parameter are different, while the other parts are the same.

[0038] In this embodiment: The first temperature threshold T1 is set to -5℃; The second temperature threshold T2 is set to -6℃; The fifth temperature threshold T5 is set to -1℃; The third temperature threshold T3 is set to 3℃; The fourth temperature threshold T4 is set to 1℃; The sixth temperature threshold T6 is set to -1℃; The seventh temperature threshold T7 is set to 1℃; The eighth temperature threshold, T8, is set to 4°C. The first preset time N1 is set to 35 seconds; The preset voltage threshold V2 is set to 12.8V; The opening M1 of cooling fan 13 is set to 40%; The opening degree M2 of air pump 12 is set to 65%; The opening degree M3 of blower 11 is set to 50%; The second preset time N2 is set to 40 seconds; The third preset time N3 is set to 40 seconds.

[0039] This embodiment is suitable for applications with relatively high ambient temperatures (such as -5℃ to 5℃), small fuel cell capacity, or strict energy consumption requirements.

[0040] As can be seen from the above three embodiments, the control method of the present invention has good adaptability and flexibility, and can adjust each control parameter according to actual application needs, so as to achieve optimal economy while ensuring control effect.

[0041] Example 4: See Figure 4 In an embodiment of the present invention, a hydrogen-oxygen fuel cell system is also provided, comprising: The battery stack 1, DC-DC module 2, and lithium battery 3 are connected. The input terminal of DC-DC module 2 is connected to battery stack 1, and the output terminal of DC-DC module 2 is connected to lithium battery 3 and load 4. The auxiliary heating module is used to heat the valve body and fuel cell stack in low-temperature environments. The auxiliary heating module can be a separately installed heater or a fuel cell stack heater in conjunction with the fuel cell stack fan. The BOP module includes a hydrogen inlet valve 5, a hydrogen exhaust solenoid valve 15, an oxygen exhaust solenoid valve 6, a drain solenoid valve 7, an oxygen shut-off valve 8, a blower 9, an air pump 10, a cooling fan 11, a fuel cell stack fan 12, and temperature sensors; at least five temperature sensors are provided, which are used to detect the temperature of the hydrogen exhaust valve, the oxygen exhaust valve, the drain valve, the oxygen shut-off valve, and the fuel cell stack. The FCU main control module 13 is connected to the DC-DC module 2, the auxiliary heating module and the BOP module respectively, and the FCU main control module 13 executes the methods of embodiments 1 to 3 above.

[0042] In addition, in this embodiment, the BOP module also includes a pressure sensor 14, which includes a hydrogen inlet pressure sensor and an oxygen inlet pressure sensor for pressure detection.

[0043] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0044] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for controlling a hydrogen-oxygen fuel cell under low-temperature conditions, characterized in that, include: Low-temperature preheating stage: The stack temperature and the temperatures of various valves in the hydrogen-oxygen fuel cell system are monitored. The valve temperatures are the temperatures collected from at least one of the following valves: hydrogen exhaust valve, oxygen exhaust valve, drain valve, and oxygen shut-off valve. If the stack temperature or the valve temperature is less than or equal to a first preset temperature threshold T1, the auxiliary heating module is activated to heat the stack and / or the valves. When both the stack temperature and the valve temperature are higher than the first temperature threshold T1, the stack start-up stage begins. During the fuel cell stack startup phase: it is determined whether the fuel cell stack temperature is lower than the second preset temperature threshold T2; if so, the fuel cell stack heater and fuel cell stack fan are started to heat the fuel cell stack until the fuel cell stack temperature is higher than the fifth preset temperature threshold T5 and then stopped; when the fuel cell stack temperature is not lower than the second preset temperature threshold T2, the hydrogen inlet valve, exhaust valve and drain valve are opened, and the blower and air pump are started; after the first preset time N1, fuel cell stack current sampling begins, and the system enters closed-loop regulation and control operation; during the closed-loop regulation and control process, the valve body temperature is continuously monitored; if the valve body temperature is lower than the sixth preset temperature threshold T6, the auxiliary heating module is turned on for heating; otherwise, the auxiliary heating module is turned off. When the lithium battery voltage of the hydrogen-oxygen fuel cell system is detected to be higher than the second preset voltage threshold V2, the hydrogen-oxygen fuel cell system shuts down.

2. The hydrogen-oxygen fuel cell control method under low-temperature conditions according to claim 1, characterized in that, During the shutdown phase, the hydrogen-oxygen fuel cell system performs the following steps: After the hydrogen-oxygen fuel cell system is shut down, open the hydrogen inlet valve, exhaust valve, and drain valve; Turn on the cooling fan, air pump and blower, and run the cooling fan, air pump and blower at the first preset opening M1, the second preset opening M2 and the third preset opening M3 respectively; turn off the auxiliary heating module and fuel cell fan, and stop the air pump and blower after running for a second preset time N2. After running for the third preset time N3, the cooling fan stops, and then all valves are closed, and the system enters standby mode, waiting for the next startup.

3. The hydrogen-oxygen fuel cell control method under low-temperature conditions according to claim 2, characterized in that, During the fuel cell stack startup phase, before opening the hydrogen inlet valve, vent valve, and drain valve, an ambient temperature determination step is also included: Detect whether the ambient temperature is greater than the third preset temperature threshold T3; if so, start the cooling fan until the ambient temperature is lower than the fourth preset temperature threshold T4, then stop the cooling fan.

4. The hydrogen-oxygen fuel cell control method under low-temperature conditions according to claim 3, characterized in that, During the shutdown phase, before turning on the cooling fan, air pump, and blower, a valve body insulation step is also included: Check if the valve body temperature is less than the seventh preset temperature threshold T7; if so, start the auxiliary heating module until the valve body temperature is higher than the eighth preset temperature threshold T8, then stop the auxiliary heating module.

5. The hydrogen-oxygen fuel cell control method under low-temperature conditions according to claim 1, characterized in that: The first preset temperature threshold T1 is -20℃ to 0℃; The second preset temperature threshold T2 is -10℃ to -5℃; The fifth preset temperature threshold T5 is -5℃ to 0℃; The sixth preset temperature threshold T6 is -5℃ to 0℃.

6. The hydrogen-oxygen fuel cell control method under low-temperature conditions according to claim 4, characterized in that: The third preset temperature threshold T3 is 0°C to 10°C; The fourth preset temperature threshold T4 is 0°C to 5°C; The seventh preset temperature threshold T7 is 0°C to 5°C; The eighth preset temperature threshold T8 is 2℃ to 10℃.

7. The hydrogen-oxygen fuel cell control method under low-temperature conditions according to claim 2, characterized in that: The first preset time N1 is 30 seconds to 60 seconds; The second preset time N2 is 30 seconds to 60 seconds; The third preset time N3 is 30 to 60 seconds.

8. The hydrogen-oxygen fuel cell control method under low-temperature conditions according to claim 2, characterized in that: The first preset opening M1 is 25% to 80%; The second preset opening M2 is 50% to 90%; The third preset opening M3 is 25% to 90%.

9. A hydrogen-oxygen fuel cell system, characterized in that: include: The battery pack, DC-DC module, and lithium battery are provided. The input terminal of the DC-DC module is connected to the battery pack, and the output terminal of the DC-DC module is connected to the lithium battery and the load. An auxiliary heating module is used to heat the valve body and fuel cell stack in low-temperature environments; The BOP module includes a hydrogen inlet valve, a hydrogen outlet valve, an oxygen outlet valve, a drain valve, an oxygen shut-off valve, a blower, an air pump, a cooling fan, a fuel cell stack fan, and temperature sensors; at least five temperature sensors are provided, which are used to detect the temperature of the hydrogen outlet valve, the oxygen outlet valve, the drain valve, the oxygen shut-off valve, and the fuel cell stack, respectively. The FCU main control module is connected to the DC-DC module, the auxiliary heating module and the BOP module respectively, and the FCU main control module executes the hydrogen-oxygen fuel cell control method under low temperature environment as described in any one of claims 1 to 8.

10. A hydrogen-oxygen fuel cell system according to claim 9, characterized in that: The BOP module also includes a pressure sensor for pressure detection.

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