A fuel cell system and a control method

Abstract

The present invention discloses a fuel cell system and a control method. A fuel cell system includes: a fuel cell stack, an air pump, a humidifier, a back pressure valve, a water pump, a radiator, a hydrogen inlet valve group, a check valve, and a hydrogen water separator. The provided system includes multiple humidification branches, which can adopt different humidification methods under different conditions. On the one hand, it can recycle the water generated by itself to achieve the purpose of self-humidification of the fuel cell, improve the operating temperature of the fuel cell, enhance the performance of the fuel cell, and extend the system life. On the other hand, by only adjusting the opening degree of the three-way valve, the backflow of the exhaust gas can be controlled to change the performance of the fuel cell and make it reach the optimal performance state. On the further hand, different humidification branches can be selected according to different working conditions to adapt to the operation under multiple working conditions.

Description

Technical Field

[0001] The present invention belongs to the field of fuel cells, and particularly relates to a fuel cell system and a control method. Background Art

[0002] A hydrogen fuel cell is an electrochemical power generation device that uses hydrogen and oxygen as raw materials to carry out an electrochemical reaction to generate water while converting chemical energy into electrical energy, and has the advantages of high energy conversion efficiency, environmental friendliness, simple structure, convenient operation, etc.

[0003] PEMFC generally uses a perfluorosulfonic acid resin membrane as a proton exchange membrane. Experiments show that it can only exhibit good proton exchange properties under a certain humidity condition. At present, it is very difficult to achieve stable fuel cell performance through the method of internal self-humidification in the battery. Usually, a humidifier is added at the air inlet to increase the humidity of the incoming air to ensure the output performance of the fuel cell. At present, a membrane tube humidifier or a plate humidifier is generally used in the fuel cell system. Water in the air with a large water content during the reaction process is transferred to the fresh air side through the form of concentration difference to increase the humidity of the fresh air and ensure the fuel cell performance output. However, on the one hand, due to the usually large volume of the humidifier, the system structure will be complicated, and the membrane humidifier will increase the gas resistance on the cathode side, increasing the power consumption of the air supply air pump or blower on the cathode side and reducing the system efficiency. On the other hand, it cannot respond in a timely manner to changes in the operating conditions and environmental conditions during the operation of the fuel cell stack. Summary of the Invention

[0004] Aiming at the defects of the existing invention technology, the purpose of the present invention is to provide an operating process of a fuel cell system with multiple humidification branches. On the one hand, the liquid water generated by anode water separation flows back to the cathode humidifier, and at the high-temperature outlet of the air pump, the liquid water vaporizes to achieve humidification on the cathode side of the fuel cell, increasing the operating temperature of the fuel cell, thereby improving the fuel cell performance; on the other hand, it is more adaptable to changes in working conditions. To achieve the above purpose, the process scheme adopted by the present invention is: providing a fuel cell system, including a fuel cell stack, an air pump, a humidifier, a water pump, a radiator, and a hydrogen water separator; the air pump, the humidifier, the fuel cell stack, and the hydrogen water separator are connected by pipelines to form a first humidification branch or a second humidification branch; the first humidification branch is: the outlet of the air pump is connected to the gas inlet of the humidifier, the gas outlet of the humidifier is connected to the cathode inlet of the fuel cell, the anode outlet of the fuel cell stack is connected to the air inlet of the hydrogen water separator, and the water outlet of the hydrogen water separator is connected to the liquid inlet of the humidifier; the second humidification branch is: the outlet of the air pump is connected to the gas inlet of the humidifier, the gas outlet of the humidifier is connected to the cathode inlet of the fuel cell, the anode outlet of the fuel cell stack is connected to the air inlet of the hydrogen water separator, the water outlet of the hydrogen water separator is connected to the liquid inlet of the humidifier, and the cathode outlet of the fuel cell stack is connected to the inlet of the air pump through a back pressure valve and a three-way valve.

[0005] The air pump, fuel cell stack, back pressure valve, and three-way valve are connected by pipelines to form a third humidification branch. The outlet of the air pump is connected to the cathode inlet of the fuel cell stack, the cathode outlet of the fuel cell stack is connected to the inlet of the back pressure valve, the outlet of the back pressure valve is connected to the three-way valve, and the three-way valve is connected to the inlet of the air pump. The exhaust gas at the cathode outlet of the fuel cell stack is divided into two paths by the three-way valve. One path is directly discharged into the atmosphere and is marked as the first path, and the other path is connected to the inlet of the air pump and is marked as the second path.

[0006] The radiator, water pump, and fuel cell stack form a coolant loop. The inlet of the water pump is connected to the outlet end of the radiator, the outlet of the water pump is connected to the coolant inlet of the fuel cell stack, and the coolant outlet of the fuel cell stack is connected to the inlet of the radiator.

[0007] Based on the above technical solutions, preferably, the gas outlet of the hydrogen water separator is connected to the anode inlet of the fuel cell stack through a check valve and a hydrogen inlet valve group to form a hydrogen circulation loop.

[0008] Based on the above technical solutions, preferably, the hydrogen water separator is provided with a filter element for gas-liquid separation and a liquid level sensor. A drain valve is provided at the water outlet of the hydrogen water separator. The liquid level is monitored by the liquid level sensor, and the drain valve at the water outlet is controlled to discharge the anode water, so that the separated liquid water is discharged from the water outlet to the inlet end of the humidifier through the control of the tail drain valve.

[0009] Based on the above technical solutions, preferably, the humidifier includes a humidifier housing and a water-absorbing material located inside the housing. A water distribution tray is provided at the top end inside the humidifier housing, and a drainage chamber and a liquid discharge port are provided at the bottom. The water distribution tray is evenly distributed with a plurality of micropores; the liquid water entering the humidifier flows into the micropores of the water distribution tray at the top of the humidifier and flows out into the water-absorbing material. When the water-absorbing material is saturated, the liquid water enters the drainage chamber and is discharged through the liquid discharge port.

[0010] Based on the above technical solutions, preferably, the diameter of the liquid discharge port of the humidifier is about 0.5 - 1 mm, and the water-absorbing material is absorbent cotton or a hydrophilic coating; the diameter of the micropores evenly distributed on the water distribution tray of the humidifier is 2 - 5 mm.

[0011] On the other hand, a humidification method for a fuel cell system is provided. Using the above fuel cell system, humidification is performed through the first humidification branch, the second humidification branch, or the third humidification branch.

[0012] Based on the above technical solutions, preferably, the specific steps of the first humidification branch are as follows: The liquid water separated by the hydrogen water separator is refluxed into the humidifier; during the operation of the fuel cell system, the rotational speed of the air pump is increased to increase the air supply, so that the temperature at the outlet of the air pump gradually rises and is introduced into the humidifier; the liquid water in the humidifier vaporizes to form a mixed air with low-temperature humidification and enters the fuel cell stack.

[0013] The specific steps of the third humidification branch are: by controlling the opening degree of the three-way valve, controlling the air flow rates of the first path and the second path, and thus controlling the flow rate of the tail gas reflux. After mixing with the fresh air at the cathode inlet, a mixed air with low-temperature humidification is formed and enters the fuel cell stack; the specific steps of the second humidification branch include the specific steps of the first humidification branch and the third humidification branch.

[0014] Based on the above technical solutions, preferably, when the first humidification branch is adopted, the working sheet pressure of the fuel cell stack is controlled to be 30 - 50 kPa, the air humidity at the cathode inlet of the fuel cell stack is 80% - 100%, by controlling the heat dissipation of the radiator, the inlet temperature of the fuel cell coolant is 60 - 70 °C, the outlet temperature of the coolant is 65 - 75 °C, the humidification area in the humidifier is 50% - 80%, and the air pressure on the anode side of the fuel cell stack is 10 - 30 kPa higher than that on the cathode side.

[0015] When the third humidification branch is adopted, the working sheet pressure of the fuel cell stack is controlled to be 10 - 30 kPa, the air humidity at the cathode inlet of the fuel cell stack is 30% - 50%, by controlling the heat dissipation of the radiator, the inlet temperature of the fuel cell coolant is 55 - 60 °C, the outlet temperature of the coolant is 60 - 65 °C; the air pressure on the anode side of the fuel cell stack is 10 - 30 kPa higher than that on the cathode side, and the ratio of the tail gas reflux air flow rate to the fresh air flow rate in the second path is 1:1 ~ 1:3.

[0016] When the second humidification branch is adopted, the working sheet pressure of the fuel cell stack is increased to 60 - 100 kPa, the air humidity at the cathode inlet of the fuel cell stack is 60% - 80%, by controlling the heat dissipation of the radiator, the inlet temperature of the fuel cell coolant is 75 - 80 °C, the outlet temperature of the coolant is 80 - 85 °C, the humidification area in the humidifier is 50% - 80%, the air pressure on the anode side of the fuel cell stack is 10 - 30 kPa higher than that on the cathode side, and the ratio of the tail gas reflux air flow rate to the fresh air flow rate in the second path is 1:1 ~ 1:3.

[0017] Based on the above technical solutions, preferably, when the operating power of the fuel cell stack is less than 10 kW and the ambient temperature is lower than 55 °C, the third humidification branch is adopted; when the operating power of the fuel cell stack is greater than 10 kW and the ambient temperature is lower than 40 °C, the first humidification branch is adopted; when the operating power of the fuel cell stack is greater than 10 kW and the ambient temperature is 40 - 55 °C, the second humidification branch is adopted.

[0018] The system provided by this application includes multiple humidification branches, which can adopt different humidification methods under different conditions. On the one hand, it can recycle the water generated by itself to achieve the purpose of self-humidification of the fuel cell, improve the operating temperature of the fuel cell, improve the performance of the fuel cell, and extend the system life. On the other hand, by only adjusting the opening degree of the three-way valve, the tail gas return flow can be controlled, the performance of the fuel cell can be changed, and it can reach the optimal performance state. On the third hand, different humidification branches can be selected according to different working conditions, and it can adapt to the operation under multiple working conditions.

[0019] The humidification system provided by this application can use the first humidification method under the conditions of low temperature and high power (when the operating power of the fuel cell stack is greater than 10 kW and the ambient temperature is lower than 40 °C), and use the water generated at the anode to flow back to control the performance of the fuel cell stack to reach the optimal state. The process is simple, easy to implement, and the system efficiency is high; when the operating power of the fuel cell stack is greater than 10 kW and the ambient temperature is 40 - 55 °C, the second humidification method is used. In a high-temperature environment, by controlling the back pressure valve, the working pressure of the fuel cell stack is increased to increase the amount of water generated at the anode. As the power of the fuel cell stack increases, by adjusting the rotational speed of the air pump, the air supply amount is increased, and the temperature at the outlet of the air pump gradually rises. The high-temperature air is introduced into the humidifier, and the liquid water in the humidifier is vaporized to form a low-temperature humidified mixed air and enter the fuel cell. When the amount of water generated at the anode is not enough to reach the required air humidity, by controlling the opening degree of the three-way valve on the cathode side, the cathode gas tail gas is refluxed to increase the cathode air humidity entering the fuel cell stack, thereby controlling the performance of the fuel cell stack to reach the optimal state. The process is simple, easy to implement, and the system efficiency is high; under low-power conditions, less water is generated at the anode, and the third humidification method is used. By controlling the opening degree of the three-way valve, the return flow of the cathode gas is increased, and the cathode air humidity entering the fuel cell stack is increased, thereby controlling the performance of the fuel cell stack to reach the optimal state. The process is simple, easy to implement, and the system efficiency is high.

[0020] For the humidifier used in the system of the present invention, through the design of the water separation tray and the water-absorbing material, the liquid water can be evenly distributed in the humidifier. The liquid water is vaporized and cooled in the humidifier, reducing the temperature of the cathode gas and increasing the gas humidity. By optimizing the humidifier, the gas resistance of the humidifier can be reduced, the energy consumption of the air pump can be reduced, and the humidifier can be prevented from being flooded by liquid water. Description of the Drawings

[0021] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0022] Figure 1 It is the operation process of cathode side humidification of the fuel cell system.

[0023] Figure 2 It is the structure diagram of the cathode humidifier of the fuel cell system. Specific embodiments

[0024] To make the technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention:

[0025] As Figure 1 shown, a fuel cell system includes a fuel cell stack, an air pump, a humidifier, a back pressure valve, a water pump, a radiator, a hydrogen inlet valve group, a check valve, and a hydrogen water separator. The air pump inlet is connected to the atmospheric environment, the air pump outlet is connected to the inlet of the humidifier, the humidifier outlet is connected to the cathode inlet of the fuel cell stack, the cathode outlet end of the fuel cell stack is connected to the inlet of the back pressure valve, the back pressure valve outlet is connected to the inlet of the three-way valve, and the three-way valve outlets are respectively connected to the air pump inlet and the atmospheric environment; the water pump inlet is connected to the radiator outlet, the water pump outlet is connected to the coolant inlet of the fuel cell stack, and the coolant outlet of the fuel cell stack is connected to the radiator inlet; the anode of the fuel cell includes an anode inlet, which is connected to the outlet of the hydrogen inlet valve group, the inlet of the inlet valve group is connected to the hydrogen source, the anode outlet of the fuel cell stack is connected to the inlet of the anode hydrogen water separator, the anode hydrogen water separator has an inlet, an outlet, and a water outlet, the water outlet is located below the inlet and the outlet, a filter element for gas-water separation and a liquid level sensor are provided inside the anode hydrogen water separator, the filter element is used to separate the water in the gas entering the anode hydrogen water separator to the water outlet, a drain valve is provided at the water outlet, the liquid level sensor is used to determine the liquid level height inside the anode hydrogen water separator, control the drain valve at the water outlet to discharge the anode water, the water outlet is connected to the liquid inlet of the humidifier, and by controlling the drain valve, the water at the water outlet is discharged to the liquid inlet of the cathode humidifier. The outlet of the anode hydrogen water separator is connected to the return port of the hydrogen inlet valve group of the fuel cell stack, thus forming a complete fuel cell system.

[0026] In a fuel cell system, an air pump is used to pump fresh air into the fuel cell stack at a certain flow rate. The outlet of the air pump is connected to a humidifier. The humidifier includes air inlets and outlets and liquid water inlets and outlets. Among them, the liquid water inlet is connected to the drain port of the anode hydrogen water separator. The liquid water discharged from the anode water separator enters the humidifier. During the operation of the fuel cell system, as the power of the fuel cell stack increases, the air pump adjusts the rotational speed to increase the air supply. At the same time, the temperature at the outlet of the air pump gradually rises. The anode liquid water enters the humidifier, mixes with the high-temperature air at the outlet of the air pump and vaporizes, and then forms low-temperature humidified mixed air and enters the fuel cell, which can increase the operating temperature of the fuel cell, so that the performance of the fuel cell stack reaches the best state.

[0027] Aiming at the defects of the existing invention technology, the purpose of the present invention is to provide an optimized fuel cell humidifier, which returns the liquid water generated by anode water separation to the cathode humidifier, and makes the liquid water evenly distributed through the humidifier. At the high-temperature outlet of the air pump, the liquid water vaporizes, realizing the cooling and humidification of the cathode gas of the fuel cell, thereby improving the performance of the fuel cell. To achieve the above purpose, the humidifier adopted in the present invention is: the humidifier includes a humidifier housing, a cathode gas inlet and outlet, a liquid water return port, a liquid water drain port and a water-absorbing material. The water-absorbing material used is absorbent cotton and is distributed in a ring on the inner surface of the humidifier housing. Among them, the liquid inlet return port is above the absorbent cotton. The humidifier mainly returns the liquid water separated by the anode water separator to the humidifier on the cathode side under the pressure difference between the anode and the cathode.

[0028] The liquid water flows into the water distribution tray at the top of the humidifier through the liquid inlet. The water distribution tray is provided with a plurality of micropores. The liquid water flows out of the micropores of the water distribution tray into the water-absorbing material and is evenly distributed in the water-absorbing material. A liquid water drain chamber is arranged at the bottom of the humidifier and is connected to the liquid water outlet. When the water-absorbing material is saturated, the excess liquid water flows to the bottom drain chamber. During the operation of the fuel cell system, the air pump pumps a certain flow rate of fresh air into the fuel cell stack. As the power of the fuel cell stack increases, the air pump adjusts the rotational speed to increase the air supply. The temperature at the outlet of the air pump gradually rises. The high-temperature air is introduced into the humidifier, causing the liquid water in the humidifier to vaporize, forming low-temperature humidified mixed air and entering the fuel cell, so that the performance of the fuel cell stack reaches the best state. At the same time, the excess liquid water is discharged from the drain port under the action of air pressure.

[0029] As Figure 2As shown, the diameter of the water outlet of the humidifier is about 0.5 - 1 mm; the water-absorbing material in the humidifier can be absorbent cotton or a hydrophilic coating. At the liquid inlet of the humidifier, the air pressure on the anode side of the fuel cell system is 10 - 30 kPa higher than that on the cathode side. The stoichiometric ratio of the cathode gas flow rate in the humidifier is 1.5 - 3 times. The diameter of the micropores evenly distributed on the water distribution plate of the humidifier is 2 - 5 mm.

[0030] Example 1

[0031] 260 fuel cell stacks are adopted. By means of air pump air supply, air is provided for the cathode inlet of the fuel cell. The absolute air pressure is about 1.3 bar. When the liquid water on the anode does not flow back to the cathode side, the power of the fuel cell is 35 kW, the outlet temperature of the air pump is 70 degrees Celsius, the temperature of the gas entering the cathode side of the fuel cell stack is 70 °C, the humidity is about 2%, the air flow stoichiometric ratio is about 2.5 times, the outlet temperature of the coolant of the fuel cell stack is 60 °C, the working current is 220 A, and the voltage is 159 V. When the liquid water on the anode flows back to the cathode humidifier, the power of the fuel cell is 40 kW, the outlet temperature of the air pump is 80 degrees Celsius, the humidification area of the humidifier is about 60%. After passing through the humidifier, the temperature of the gas entering the cathode side of the fuel cell stack is 50 °C, the humidity is 70%, the air flow stoichiometric ratio is about 2 times, the outlet temperature of the coolant of the fuel cell stack is 70 °C, the working current is 250 A, and the voltage is 160 V. Thus, it can be seen that by adopting the method of anode liquid water reflux, the performance of the fuel cell stack can be significantly improved.

[0032] Example 2

[0033] 110 fuel cell stacks are adopted. By means of air pump air supply, air is provided for the cathode inlet of the fuel cell. The air flow stoichiometric ratio is about 4 times, and the absolute air pressure is about 1.15 bar. The outlet temperature of the coolant of the fuel cell stack is about 50 °C. By adjusting the three-way valve at the cathode outlet of the fuel cell, the flow rates of the first passage and the second passage can be controlled. When the flow rate of the second passage is 0, that is, the cathode outlet exhaust gas does not flow back, at this time, the operating power of the fuel cell is 3 kW, and the voltage is about 78 V. When the ratio of the flow rate of the first passage to the flow rate of the second passage is controlled to be 1:2, at this time, the voltage of the fuel cell is about 83 V, and the power is about 3.3 kW. Thus, it can be seen that by adopting cathode exhaust gas reflux, the performance of the fuel cell stack can be significantly improved.

[0034] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A control method for a fuel cell system, characterized in that include: The fuel cell system comprises: a fuel cell stack, an air pump, a humidifier, a water pump, a radiator, a hydrogen intake valve group, and a hydrogen water separator; The air pump, humidifier, fuel cell stack, and hydrogen water separator are connected to form a first humidification branch or a second humidification branch through pipelines; the first humidification branch is as follows: the air pump outlet is connected to the humidifier gas inlet, the humidifier gas outlet is connected to the cathode inlet of the fuel cell stack, the fuel cell stack anode outlet is connected to the air inlet of the hydrogen water separator, and the water outlet of the hydrogen water separator is connected to the liquid inlet of the humidifier; the second humidification branch is as follows: the air pump outlet is connected to the humidifier gas inlet, the humidifier gas outlet is connected to the cathode inlet of the fuel cell stack, the fuel cell stack anode outlet is connected to the air inlet of the hydrogen water separator, the water outlet of the hydrogen water separator is connected to the liquid inlet of the humidifier, and the fuel cell stack cathode outlet is connected to the air pump inlet through a back pressure valve and a three-way valve; The air pump, the fuel cell stack, the back pressure valve, and the three-way valve are connected to form a third humidification branch through a pipeline, the air pump outlet is connected to the cathode inlet of the fuel cell stack, the cathode outlet of the fuel cell stack is connected to the back pressure valve inlet, the back pressure valve outlet is connected to the three-way valve, the three-way valve is connected to the air pump inlet, and the exhaust gas at the cathode outlet of the fuel cell stack is divided into two passages by the three-way valve, one of which is directly discharged into the atmosphere and marked as the first passage, and the other passage is connected to the air pump inlet and marked as the second passage; The radiator, water pump and fuel cell stack form a coolant loop, the water pump inlet is connected to the outlet end of the radiator, the water pump outlet is connected to the coolant inlet of the fuel cell stack, and the fuel cell stack coolant outlet is connected to the radiator inlet; the humidifier includes a humidifier shell and a water absorbing material located in the shell; Humidification is performed through the first humidification branch, the second humidification branch or the third humidification branch; When the operating power of the fuel cell stack is less than 10kW and the ambient temperature is lower than 55°C, the third humidification branch is used; When the operating power of the fuel cell stack is greater than 10kW and the ambient temperature is lower than 40°C, the first humidification branch is used; When the operating power of the fuel cell stack is greater than 10kW and the ambient temperature is 40-55°C, the second humidification branch is used.

2. The control method of the fuel cell system according to claim 1, characterized in that: The gas outlet of the hydrogen water separator is connected to the anode inlet of the fuel cell stack through a check valve and a hydrogen inlet valve group to form a hydrogen circulation loop.

3. The control method of the fuel cell system according to claim 1, characterized in that: The hydrogen water separator is provided with a gas-water separation filter element and a liquid level sensor. The water outlet of the hydrogen water separator is provided with a drain valve. The liquid level is monitored by the liquid level sensor, and the outlet drain valve is controlled to discharge the anode water, so that the separated liquid water is discharged from the water outlet to the liquid inlet end of the humidifier through the control of the tail drain valve.

4. The control method of the fuel cell system according to any one of claims 1 to 3, characterized in that: A water distribution tray is arranged at the top of the humidifier shell, and a drainage chamber and a liquid discharge port are arranged at the bottom.

5. The control method of the fuel cell system according to claim 4, characterized in that: The water separation plate has multiple micropores evenly distributed thereon; the liquid water entering the humidifier flows into the micropores of the water separation plate at the top of the humidifier and flows out to the water absorbing material; when the water absorbing material is saturated with liquid water, it enters the drainage chamber and is discharged through the drainage port.

6. The control method of the fuel cell system according to claim 4, characterized in that: The diameter of the liquid discharge port of the humidifier is 0.5-1mm, and the water-absorbing material is water-absorbing cotton or a hydrophilic coating; the diameter of the evenly distributed micropores of the water distribution plate of the humidifier is 2-5mm.

7. The control method according to claim 1, characterized in that: The humidification step of the first humidification branch includes the following: (1) Return the liquid water separated by the hydrogen water separator to the humidifier; (2) During the operation of the fuel cell system, the speed of the air pump is increased, the air supply is increased, and the outlet temperature of the air pump is gradually increased and passed into the humidifier; (3) The liquid water in the humidifier vaporizes to form low-temperature humidified mixed air that enters the fuel cell stack; The humidification step of the third humidification branch is: by controlling the opening of the three-way valve, the air flow of the first passage and the second passage is controlled, and then the flow of the exhaust gas reflux is controlled, and after being mixed with the fresh air at the cathode inlet, the low-temperature humidified mixed air is formed and enters the fuel cell stack; The specific steps of the second humidification branch include the specific steps of the first humidification branch and the third humidification branch.

8. The control method according to claim 1, characterized in that: When the first humidification branch is used, the working gauge pressure of the fuel cell stack is controlled to be 30-50 kPa, the air humidity entering the cathode inlet of the fuel cell stack is 80%-100%, the fuel cell coolant inlet temperature is 60-70°C, the coolant outlet temperature is 65-75°C, the humidification area in the humidifier is 50%-80%, and the anode side pressure of the fuel cell stack is 10-30 kPa higher than the cathode side pressure; When the third humidification branch is used, the working gauge pressure of the fuel cell stack is controlled to be 10-30 kPa, the air humidity entering the cathode inlet of the fuel cell stack is 30%-50%, the fuel cell coolant inlet temperature is 55-60°C, and the coolant outlet temperature is 60-65°C. The anode side pressure of the fuel cell stack is 10-30 kPa higher than the cathode side pressure. The ratio of the exhaust gas return air flow rate to the fresh air flow rate of the second passage is 1:1~1:3; When the second humidification branch is used, the working gauge pressure of the fuel cell stack is increased to 60-100kPa, the air humidity entering the cathode inlet of the fuel cell stack is 60%-80%, the fuel cell coolant inlet temperature is 75-80℃, the coolant outlet temperature is 80-85℃, the humidification area in the humidifier is 50%-80%, the anode side pressure of the fuel cell stack is 10-30kPa higher than the cathode side pressure, and the exhaust gas return air flow rate of the second passage is 1:1~1:3 to the fresh air flow rate.

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