Fuel cell system and low-temperature cold start method thereof

Abstract

The invention discloses a fuel cell system which comprises a hydrogen supply system, an air supply system, a proton exchange membrane fuel cell stack and a cooling system, and the cooling system, the hydrogen supply system and the air supply system are connected with the proton exchange membrane fuel cell stack. The hydrogen supply system and the air supply system are arranged to realize oxygen starvation of the proton exchange membrane fuel cell stack by respectively adjusting hydrogen flow and air flow during cold start; the cooling system comprises a radiator assembly and a water pump connected with the proton exchange membrane fuel cell stack, and the water pump does not work during cold start. According to the fuel cell system, heat dissipated in the self-starting process is increased in an oxygen starvation mode, the situation that too much water is generated in the galvanic pile and is condensed into ice to block a flow channel is avoided by changing the current density of the galvanic pile in the cold starting process, and the failure of low-temperature cold starting of the fuel cell system can be avoided. The invention also discloses a low-temperature cold start method of the fuel cell system.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell engines, and in particular, relates to a fuel cell system and a low-temperature cold start method thereof. Background Art

[0002] As air pollution and greenhouse effect have become increasingly serious in recent years, in response to the call of the "dual carbon policy", finding a sustainable alternative fuel that can also reduce greenhouse gas emissions such as CO2 has become a very promising and valuable research direction. Fuel cells, as an efficient power generation device that is not limited by the Carnot cycle and can convert hydrogen into electricity, have attracted more and more attention.

[0003] Proton exchange membrane fuel cells are power generation devices that convert chemical energy into electrical energy. The core component, the membrane electrode, can effectively conduct ions at -20°C, laying the foundation for low-temperature power generation in fuel cells. However, the main product of fuel cells is water. During and after each operation, water will be present at the cathode and anode. If the shutdown temperature is below 0°C, the membrane electrode catalyst and proton exchange membrane will be covered with ice, thus affecting their startup reaction performance. Severe freezing will prevent the reaction from occurring, and even cause irreversible damage to the membrane electrode.

[0004] There are two main types of heating methods for cold start of fuel cell stacks, namely external heating and internal heating. The external heating method can meet the needs of low-temperature cold start to a certain extent, but it requires the addition of additional external heating equipment, which will take up additional space and weight and consume a lot of energy, and also increase the overall cost, so the internal heating method will be the main trend of future development. The internal heating methods can be roughly divided into the following types: self-heating by controlling the output characteristics of the stack; self-heating through gas deficiency; self-heating by introducing a reaction gas mixture into the stack. In general, the method of controlling the output characteristics of the stack to achieve self-heating has better energy-saving effects and is more effective than other heating schemes.

[0005] Since the fuel cell system needs to adapt to startup, operation, and shutdown in various environments, the current fuel cell system has a long low-temperature cold start time. The coolant in the stack will cause the stack temperature to drop rapidly. When the temperature is below zero during the startup phase, it is easy to cause the membrane electrode to freeze and the gas flow path to be blocked by ice, resulting in cold start failure and irreversible attenuation of the fuel cell stack. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a fuel cell system, the purpose of which is to avoid low temperature cold start failure of the fuel cell system.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a fuel cell system, including a hydrogen supply system for providing hydrogen during a cold start process, an air supply system for providing air during a cold start process, a proton exchange membrane fuel cell stack and a cooling system for providing cooling circulating water during a cold start process, the cooling system, the hydrogen supply system and the air supply system are connected to the proton exchange membrane fuel cell stack, and the hydrogen supply system and the air supply system are configured to achieve oxygen starvation of the proton exchange membrane fuel cell stack by respectively adjusting the hydrogen flow rate and the air flow rate during a cold start; the cooling system includes a radiator assembly and a water pump connected to the proton exchange membrane fuel cell stack, and the water pump is configured to temporarily stop working during the gas shortage start stage.

[0008] The cooling system can form a small cooling water circulation loop that does not flow through the radiator assembly and a large cooling water circulation loop that flows through the radiator assembly.

[0009] The cooling system also includes a PTC, a thermostat, a deionizer and an intercooler. The PTC is connected to the water pump and the thermostat, the PTC is located between the water pump and the thermostat, the deionizer is connected to the thermostat and the intercooler, the intercooler is connected to the water pump, and the thermostat is connected to the proton exchange membrane fuel cell stack.

[0010] A stop valve is arranged between the thermostat and the deionizer, and the stop valve is connected to the thermostat and the deionizer.

[0011] The radiator assembly is connected to a particle filter, and the particle filter is connected to the thermostat.

[0012] Temperature sensors and pressure sensors are provided in pipelines connecting the hydrogen supply system and the air supply system with the proton exchange membrane fuel cell stack.

[0013] A temperature and pressure integrated sensor is arranged in the pipeline connecting the water pump and the proton exchange membrane fuel cell stack.

[0014] The present invention also provides a low-temperature cold start method for a fuel cell system, comprising:

[0015] Breaking the ice;

[0016] Entering the first gas shortage start-up phase, stopping the water pump to allow the proton exchange membrane fuel cell stack to reach a first set current density;

[0017] Entering the second gas-deficient startup phase, starting the water pump to allow the proton exchange membrane fuel cell stack to reach a second set current density;

[0018] The water temperature entering the reactor is ≥T4°, and the low-temperature cold start is completed.

[0019] The first gas-deficient startup phase is to adjust the air supply system, start the air compressor of the air supply system, set the target speed of the air compressor, adjust the hydrogen supply system, and continuously supply hydrogen to the proton exchange membrane fuel cell stack so that the proton exchange membrane fuel cell stack reaches a first set current density.

[0020] The second stage of the gas shortage startup is to adjust the air supply system, set the target speed of the air compressor of the air supply system, adjust the hydrogen supply system, continuously introduce hydrogen into the proton exchange membrane fuel cell stack, so that the proton exchange membrane fuel cell stack reaches a second set current density, start the water pump, turn on the PTC, and keep the shut-off valve and bypass valve normally closed.

[0021] The fuel cell system of the present invention adopts an oxygen starvation method to increase the heat dissipated during the self-starting process, and avoids excessive water in the stack by changing the current density of the stack during the cold start process, which condenses into ice to block the flow channel. The water pump is not turned on when starting from a low temperature to prevent the cooling water from taking away the heat in the stack. In the second stage, in order to prevent local overheating of the stack, the water pump is turned on, and the deionizer stop valve and the PTC bypass valve in the cooling small cycle are closed to reduce the volume of the cooling path, so that the water temperature of the cooling path in the small cycle increases faster, and the rapid cold start process is completed, which can avoid the failure of low-temperature cold start of the fuel cell system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of a fuel cell system of the present invention;

[0023] Figure 2 is a flow chart of a low temperature cold start method for a fuel cell system of the present invention;

[0028] The marks in the above figures are: 1. Hydrogen supply system; 2. Temperature sensor; 3. Proton exchange membrane fuel cell stack; 4. Intercooler; 5. Temperature and pressure integrated sensor; 6. Water pump; 7. Bypass valve; 8. PTC (positive temperature coefficient heater); 9. Expansion kettle; 10. Radiator assembly; 11. Particulate filter; 12. Cooling system; 13. Thermostat; 14. Shut-off valve; 15. Deionizer; 16. Tail exhaust assembly; 17. Air supply system; 18. Pressure sensor. DETAILED DESCRIPTION

[0029] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0030] It should be noted that when an element is referred to as being "fixed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower" and similar expressions used in this article are for illustrative purposes only.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly connected by technicians in the technical field to which the present invention belongs. The terminology used in the specification of the present invention is for the purpose of describing specific embodiments and is not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0032] like Figure 1 As shown, the present invention provides a fuel cell system, including a hydrogen supply system 1 for providing hydrogen during a cold start, an air supply system 17 for providing air during a cold start, a proton exchange membrane fuel cell stack 3 and a cooling system 12 for providing cooling circulating water during a cold start, the cooling system 12, the hydrogen supply system 1 and the air supply system 17 are connected to the proton exchange membrane fuel cell stack 3, the hydrogen supply system 1 and the air supply system 17 are configured to achieve oxygen starvation of the proton exchange membrane fuel cell stack 3 by respectively adjusting the hydrogen flow rate and the air flow rate during a cold start; the cooling system 12 includes a radiator assembly 10 and a water pump 6 connected to the proton exchange membrane fuel cell stack 3, and the water pump 6 is configured to temporarily not work during the gas shortage start stage.

[0033] Specifically, the present invention is to improve the low-temperature cold start speed of the fuel cell engine system, avoid the cold start failure of the fuel cell system, reduce the additional load of the system, and reduce the system volume. In the present invention, by optimizing the cold start strategy of the ordinary fuel cell engine system, during the cold start, oxygen starvation is first achieved according to the different flow rates of the anode and cathode reactants to increase the calorific value in the chemical reaction process. During the process, the water pump 6 is not turned on to reduce the heat loss in the stack; secondly, when the temperature rises to the set target value, in order to prevent local hot spots inside the stack, the water pump 6 is turned on, cooling water is introduced, and the heater is turned on at the same time, the deionizer 15 shut-off valve and the bypass valve 7 are closed to reduce the cooling water volume and shorten the heating time; then the stack output power is changed to accelerate the heating of the stack and complete the self-starting process.

[0034] like Figure 1 As shown, the cooling system 12 can form a small cooling water circulation loop that does not flow through the radiator assembly 10 and a large cooling water circulation loop that flows through the radiator assembly 10. The cooling system 12 also includes a PTC 8, a thermostat 13, a deionizer 15 and an intercooler 4, the PTC 8 is connected to the water pump 6 and the thermostat 13, the PTC 8 is located between the water pump 6 and the thermostat 13, the deionizer 15 is connected to the thermostat 13 and the intercooler 4, the intercooler 4 is connected to the water pump 6, and the thermostat 13 is connected to the proton exchange membrane fuel cell stack 3.

[0035] The present invention adopts a self-starting mode to improve the self-heating of the fuel cell stack during the cold start process, shorten the start-up time of the fuel cell engine system in a low temperature environment, avoid low-temperature cold start failure of the fuel cell, increase the life of the fuel cell stack, reduce the additional heating space of the fuel cell, and reduce the additional consumption of the fuel cell.

[0036] The oxygen starvation method is used to increase the heat dissipated during the self-starting process. By changing the current density of the battery stack during the cold start process, excessive water is prevented from being generated in the battery stack and condensed into ice to block the flow channel. The water pump 6 is not turned on when starting from a low temperature to prevent the cooling water from taking away the heat in the battery stack. In the second stage, to prevent local overheating of the battery stack, the water pump 6 is turned on, and the stop valve 14 and the bypass valve 7 in the cooling small cycle are closed to reduce the volume of the cooling path, so that the water temperature of the cooling path in the small cycle increases faster, completing the rapid cold start process.

[0037] like Figure 1 As shown, one end of the water pump 6 is connected to the water outlet of the proton exchange membrane fuel cell stack 3, the other end of the water pump 6 is connected to one end of the radiator assembly 10, the other end of the radiator assembly 10 is connected to one end of the particle filter 11, and the other end of the particle filter 11 is connected to the thermostat 13. One end of the PTC 8 is connected to the pipeline connecting the water pump 6 and the radiator assembly 10, and the other end of the PTC 8 is connected to the thermostat 13. The cooling system 12 also includes a bypass valve 7, one end of the bypass valve 7 is connected to the pipeline connecting the water pump 6 and the PTC 8, and the other end of the bypass valve 7 is connected to the pipeline connecting the thermostat 13 and the PTC 8. After the bypass valve 7 is opened, the cooling water from the water pump 6 flows to the thermostat 13 through the bypass valve 7; after the bypass valve 7 is closed, the cooling water from the water pump 6 flows to the thermostat 13 through the PTC 8.

[0038] like Figure 1As shown, a stop valve 14 is provided between the thermostat 13 and the deionizer 15, and the stop valve 14 is connected to the thermostat 13 and the deionizer 15. The stop valve 14 is connected to one end of the deionizer 15, and the other end of the deionizer 15 is connected to one end of the intercooler 4, and the other end of the intercooler 4 is connected to the pipeline connecting the water pump 6 and the water outlet of the proton exchange membrane fuel cell stack 3. The intercooler 4 is also connected to the expansion kettle 9, the radiator assembly 10 is connected to the expansion kettle 9, and the expansion kettle 9 is connected to the pipeline connecting the water pump 6 and the water outlet of the proton exchange membrane fuel cell stack 3.

[0039] like Figure 1 As shown, a temperature sensor 2 and a pressure sensor 18 are provided in the pipeline connecting the hydrogen supply system 1 and the proton exchange membrane fuel cell stack 3. The temperature sensor 2 is used to detect the gas temperature in the pipeline, and the pressure sensor 18 is used to detect the gas pressure in the pipeline. A temperature sensor 2 and a pressure sensor 18 are provided in the pipeline connecting the air supply system 17 and the proton exchange membrane fuel cell stack 3. The temperature sensor 2 is used to detect the gas temperature in the pipeline, and the pressure sensor 18 is used to detect the gas pressure in the pipeline.

[0040] like Figure 1 As shown, a temperature-pressure integrated sensor 5 is provided in the pipeline connecting the water pump 6 and the proton exchange membrane fuel cell stack 3, and the temperature-pressure integrated sensor 5 is used to detect the temperature and pressure of the coolant in the pipeline connecting the water pump 6 and the proton exchange membrane fuel cell stack 3. A temperature-pressure integrated sensor 5 is also provided in the pipeline connecting the thermostat 13 and the proton exchange membrane fuel cell stack 3, and the temperature-pressure integrated sensor 5 is used to detect the temperature and pressure of the coolant in the pipeline connecting the thermostat 13 and the proton exchange membrane fuel cell stack 3.

[0041] like Figure 1 As shown, a temperature sensor 2 is provided in the pipeline connecting the radiator assembly 10 and the particulate filter 11 , and the temperature sensor 2 is used to detect the temperature of the coolant in the pipeline.

[0042] like Figure 1 As shown, the hydrogen supply system 1 is directly connected to the proton exchange membrane fuel cell stack 3, the air supply system 17 is directly connected to the proton exchange membrane fuel cell stack 3, and the tail exhaust assembly 16 is directly connected to the proton exchange membrane fuel cell stack 3. The cooling water small circulation loop is composed of a water pump 6, a PTC 8, a bypass valve 7, a deionizer 15, a thermostat 13 and an intercooler 4. The cooling water outlet of the proton exchange membrane fuel cell stack 3 is connected to the inlet of the water pump 6, the outlet of the water pump 6 is connected to the inlet of the PTC 8, the outlet of the PTC 8 is connected to the inlet of the thermostat 13, the outlet of the water pump 6 is also connected to the inlet of the thermostat 13 through the bypass valve 7, and the outlet of the thermostat 13 is connected to the inlet of the proton exchange membrane fuel cell stack 3, completing the cooling water small circulation.

[0043] The cooling water large circulation loop is composed of a water pump 6, a radiator assembly 10, a particle filter 11 and a thermostat 13. The cooling water outlet of the proton exchange membrane fuel cell stack 3 is connected to the inlet of the water pump 6, the outlet of the water pump 6 is connected to the radiator assembly 10, the outlet of the radiator assembly 10 is connected to the particle filter 11, the outlet of the particle filter 11 is connected to the thermostat 13, and the thermostat 13 is connected to the proton exchange membrane fuel cell stack 3. After the shut-off valve 14 is closed, the cooling water flowing out of the outlet of the proton exchange membrane fuel cell stack 3 flows through the water pump 6, the radiator assembly 10, the particle filter 11 and the thermostat 13 in sequence, and finally flows into the proton exchange membrane fuel cell stack 3, completing the cooling water large circulation.

[0044] The fuel cell system of the above structure can reduce the small circulation volume of the cooling path in the gas shortage startup stage 2 by adding a stop valve between the thermostat and the deionizer. The same heat generation of the stack can increase the coolant temperature to a higher level. In the gas shortage startup stage 1, the water pump is not turned on, so that the heat generated by the stack is used to increase the temperature inside the stack, thereby preventing the proton exchange membrane in the stack from freezing.

[0045] like Figure 2 As shown, the present invention also provides a low temperature cold start method for a fuel cell system, comprising the following steps:

[0046] S1. Ice breaking;

[0047] S2, entering the first gas shortage start-up phase, stopping the water pump 6, so that the proton exchange membrane fuel cell stack 3 reaches a first set current density;

[0048] S3, entering the second gas shortage start-up phase, starting the water pump 6, so that the proton exchange membrane fuel cell stack 3 reaches the second set current density;

[0049] S4. When the temperature of the cooling water inlet of the proton exchange membrane fuel cell stack reaches a fourth set value, the low-temperature cold start is terminated.

[0050] The air supply system 17 is used to provide air during the cold start process, and the air flow rate and air pressure can be adjusted. The hydrogen supply system 1 is used to provide hydrogen during the cold start process, and the hydrogen flow rate and hydrogen pressure can be adjusted. The cooling system 12 of the fuel cell system provides cooling circulating water during the cold start process.

[0051] like Figure 2 As shown, before the above step S1, when the fuel cell system is ready to start, the system state is first reset, and then the hydrogen inlet pressure closed-loop control component is self-checked. The ambient temperature state is judged according to the feedback signal of the temperature sensor 2. When the ambient temperature is greater than zero, the fuel cell system is started at room temperature. When the ambient temperature is less than zero, the hydrogen circulation pump and the heating solenoid valve of the hydrogen supply system 1 are started to break the ice.

[0052] In the above step S2, after the ice breaking is completed, the temperature state of the cooling water in the cooling system 12 is determined according to the feedback signal of the temperature sensor 2. When the temperature of the cooling water is greater than the set temperature, the fuel cell system starts at normal temperature; when the temperature of the cooling water does not reach the set temperature, it enters the insufficient gas start-up phase 1. Entering the insufficient gas start-up phase 1, the air supply system 17 is adjusted, the air compressor of the air supply system 17 is started, and the speed of the air compressor is set to the first target speed S1. The air supply system 17 continuously introduces under-pressure quantitative oxygen O1 to the proton exchange membrane fuel cell stack 3, and the hydrogen supply system 1 is adjusted. The hydrogen supply system 1 continuously introduces hydrogen H1 to the proton exchange membrane fuel cell stack 3, so that the proton exchange membrane fuel cell stack 3 reaches the first set current density A1.

[0053] In the above step S2, the air outlet temperature T2 of the air supply system 17 and the hydrogen outlet temperature T3 of the hydrogen supply system 1 are continuously detected. When the air outlet temperature is greater than the second set value T2 and the hydrogen outlet temperature is greater than the third set value T3, the gas shortage start-up stage 2 is entered.

[0054] In the above step S3, enter the second gas-deficient startup stage, adjust the air supply system 17, set the speed of the air compressor of the air supply system 17 to the second target speed S2, the air supply system 17 continuously introduces under-pressure quantitative oxygen O2 to the proton exchange membrane fuel cell stack 3, adjust the hydrogen supply system 1, and the hydrogen supply system 1 continuously introduces hydrogen H2 to the proton exchange membrane fuel cell stack 3, so that the proton exchange membrane fuel cell stack 3 reaches the second set current density A2, start the water pump 6, set the speed of the water pump 6 to S3, turn on the PTC8, the shut-off valve 14 and the bypass valve 7 are normally closed, and the cooling water flowing out of the outlet of the proton exchange membrane fuel cell stack 3 flows through the water pump 6, PTC8 and the thermostat 13 in turn, and finally flows into the proton exchange membrane fuel cell stack 3 to perform a small cooling water circulation.

[0055] In the above step S3 , the temperature of the cooling water inlet of the proton exchange membrane fuel cell stack 3 is continuously detected.

[0056] In the above step S4, when the temperature of the cooling water inlet of the proton exchange membrane fuel cell stack 3 reaches the fourth set value T4, the fourth set value T4>0, the low-temperature cold start of the fuel cell system is completed, and then the air supply system 17 and the air supply system 17 are adjusted, the fuel cell system enters the normal operation stage, and the low-temperature cold start is completed.

[0057] In the above-mentioned low-temperature cold start method, the first set current density A1 is different from the second set current density A2, and the second set current density A2 is greater than the first set current density A1. The underpressure quantitative oxygen amount O1 introduced by the air supply system 17 to the proton exchange membrane fuel cell stack 3 in the short-gas start stage is different from the underpressure quantitative oxygen amount O2 introduced to the proton exchange membrane fuel cell stack 3 in the short-gas start stage, and the underpressure quantitative oxygen amount O1 is less than the underpressure quantitative oxygen amount O2. The amount of hydrogen H1 introduced by the hydrogen supply system 1 to the proton exchange membrane fuel cell stack 3 in the short-gas start stage is different from the amount of hydrogen H2 introduced to the proton exchange membrane fuel cell stack 3 in the short-gas start stage, and the amount of hydrogen H1 is less than the amount of hydrogen H2. Therefore, the hydrogen supply system 1 and the air supply system 17 achieve oxygen starvation of the proton exchange membrane fuel cell stack 3 by adjusting the hydrogen flow rate and the air flow rate respectively during cold start. During cold start, oxygen starvation is first achieved according to the different flow rates of the anode and cathode reactants to increase the calorific value in the chemical reaction process. The current density of the battery stack is changed during the cold start process to avoid excessive water in the battery stack from condensing into ice to block the flow channel. At the same time, the water pump 6 is not turned on during low-temperature start to prevent the cooling water from taking away the heat in the battery stack. In the second stage, to prevent local overheating of the battery stack, the water pump 6 is turned on, and the stop valve 14 and the bypass valve 7 in the cooling small cycle are closed to reduce the volume of the cooling path, so that the water temperature of the cooling path in the small cycle increases faster, completing the rapid cold start process.

[0058] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A fuel cell system, comprising a hydrogen supply system for providing hydrogen during a cold start, an air supply system for providing air during a cold start, a proton exchange membrane fuel cell stack, and a cooling system for providing cooling circulating water during a cold start, wherein the cooling system, the hydrogen supply system, and the air supply system are connected to the proton exchange membrane fuel cell stack, and characterized in that: The hydrogen supply system and the air supply system are configured to achieve oxygen starvation of the proton exchange membrane fuel cell stack by adjusting the hydrogen flow rate and the air flow rate respectively during cold start; the cooling system includes a radiator assembly and a water pump connected to the proton exchange membrane fuel cell stack, and the water pump is configured to temporarily stop working during the gas shortage start-up stage.

2. The fuel cell system according to claim 1, characterized in that: The cooling system can form a small cooling water circulation loop that does not flow through the radiator assembly and a large cooling water circulation loop that flows through the radiator assembly.

3. The fuel cell system according to claim 2, characterized in that: The cooling system also includes a PTC, a thermostat, a deionizer and an intercooler. The PTC is connected to the water pump and the thermostat, the PTC is located between the water pump and the thermostat, the deionizer is connected to the thermostat and the intercooler, the intercooler is connected to the water pump, and the thermostat is connected to the proton exchange membrane fuel cell stack.

4. The fuel cell system according to claim 3, characterized in that: A stop valve is arranged between the thermostat and the deionizer, and the stop valve is connected to the thermostat and the deionizer.

5. The fuel cell system according to claim 3, characterized in that: The radiator assembly is connected to a particle filter, and the particle filter is connected to the thermostat.

6. The fuel cell system according to any one of claims 1 to 5, characterized in that: Temperature sensors and pressure sensors are arranged in the pipelines connecting the hydrogen supply system and the air supply system with the proton exchange membrane fuel cell stack.

7. The fuel cell system according to any one of claims 1 to 5, characterized in that: A temperature and pressure integrated sensor is arranged in the pipeline connecting the water pump and the proton exchange membrane fuel cell stack.

8. The low temperature cold start method of a fuel cell system according to any one of claims 1 to 7, characterized in that: include: Breaking the ice; Entering the first gas shortage start-up phase, stopping the water pump to allow the proton exchange membrane fuel cell stack to reach a first set current density; Entering the second gas-deficient startup phase, starting the water pump to allow the proton exchange membrane fuel cell stack to reach a second set current density; When the temperature of the cooling water inlet of the proton exchange membrane fuel cell stack reaches the fourth set value, the low-temperature cold start ends.

9. The low temperature cold start method of the fuel cell system according to claim 8, characterized in that: The first gas-deficient startup phase is to adjust the air supply system, start the air compressor of the air supply system, set the target speed of the air compressor, adjust the hydrogen supply system, and continuously supply hydrogen to the proton exchange membrane fuel cell stack so that the proton exchange membrane fuel cell stack reaches a first set current density.

10. The low temperature cold start method of a fuel cell system according to claim 8, characterized in that: The second stage of the gas shortage startup is to adjust the air supply system, set the target speed of the air compressor of the air supply system, adjust the hydrogen supply system, continuously introduce hydrogen into the proton exchange membrane fuel cell stack, so that the proton exchange membrane fuel cell stack reaches a second set current density, start the water pump, turn on the PTC, and keep the shut-off valve and bypass valve normally closed.

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