A method for low temperature test, pre-check and cold start of a fuel cell system

Abstract

The application provides a fuel cell system low-temperature test, pre-check and cold start method, comprising: box purging, stack purging, measuring high-frequency impedance value, judging whether the high-frequency impedance value is greater than or equal to a set value; lowering the fuel cell system to room temperature, setting a cold start environment bin temperature, waiting for the environment bin temperature to drop to a set temperature, and placing the fuel cell stack for at least 12 hours; judging whether the fuel cell system cooling liquid temperature drops to a set temperature; performing fuel cell system cold start; judging whether the engine is successfully started; and troubleshooting after engine start failure. The application can combine the low-temperature operation characteristics of the fuel cell system, realize coordinated pre-check of each component, and realize low-temperature cold start of the fuel cell system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell vehicle thermal management, in particular to a fuel cell system low-temperature test, pre-check and cold start method. BACKGROUND

[0002] Proton exchange membrane fuel cell (PEMFC) has become one of the most promising vehicle power sources due to its high energy efficiency, no influence of Carnot cycle and low noise and zero pollution during operation. However, when the fuel cell operates in a low-temperature environment, especially during startup, the reactants generate water and freeze, which leads to a decline in the operating performance of the fuel cell and even failure to start, thereby limiting the wide application of the fuel cell.

[0003] Unlike the cold start of the fuel cell stack, when the fuel cell system is used as a vehicle power source to drive the vehicle, more attention should be paid to the coordination and startup cooperation of the fuel cell system. On the one hand, the cold start of the fuel cell system level should be realized; on the other hand, the cooperation of each component and subsystem should be considered, especially the pre-check of the components prone to failure or freezing in low temperature before the cold start, so as to promptly troubleshoot the fault and realize efficient cold start. Therefore, a suitable fuel cell system pre-check and cold start method should be designed according to the operating characteristics of the fuel cell in a low-temperature environment to ensure the efficient operation of the fuel cell system in a low-temperature environment.

[0004] In summary, there is currently a lack of a fuel cell system low-temperature test, pre-check and cold start method that can combine the low-temperature operating characteristics of the fuel cell system and realize the coordinated pre-check of each component. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provides a fuel cell system low-temperature test, pre-check and cold start method. The method includes two sub-methods: (1) a fuel cell system cold start test method; and (2) a fuel cell system pre-check and cold start method. The fuel cell system cold start test method includes the following steps: S1. purging; S2. freezing; and S3. starting the machine. The fuel cell system pre-check and cold start method includes the following steps: S3.2.1. performing a cold start pre-check of the fuel cell system; S3.2.2. performing a cold start preheating of the fuel cell system; and S3.2.3. performing a self-start of the fuel cell system. Real-time data collection and monitoring and early warning are performed during the cold start test and pre-check of the fuel cell. Finally, a fuel cell system cold start test and pre-check method suitable for the low-temperature operating characteristics of the fuel cell system is formed.

[0006] The present application aims to overcome the shortcomings of the prior art and provides a fuel cell system low-temperature test, pre-check and cold start method. The method includes two sub-methods: (1) a fuel cell system cold start test method; and (2) a fuel cell system pre-check and cold start method. The fuel cell system cold start test method includes the following steps: S1. purging; S2. freezing; and S3. starting the machine. The fuel cell system pre-check and cold start method includes the following steps: S3.2.1. performing a cold start pre-check of the fuel cell system; S3.2.2. performing a cold start preheating of the fuel cell system; and S3.2.3. performing a self-start of the fuel cell system. Real-time data collection and monitoring and early warning are performed during the cold start test and pre-check of the fuel cell. Finally, a fuel cell system cold start test and pre-check method suitable for the low-temperature operating characteristics of the fuel cell system is formed.

[0007] S1. Purge;

[0008] Comprising:

[0009] Box purge; Purging the leaked hydrogen in the fuel cell stack box to avoid hydrogen concentration exceeding the standard;

[0010] Stack purge; Purging the water generated by the reaction in the fuel cell stack to prevent damage to the stack due to water freezing in low temperature environment, and to reduce the heat required for ice melting during cold start process;

[0011] Measuring high frequency impedance value; Measuring the high frequency impedance value of the fuel cell stack to determine the water content of the fuel cell stack;

[0012] Determine whether the high frequency impedance value is greater than or equal to the set value; Feedback on the result of the fuel cell stack purge, observe whether the water content of the fuel cell stack is reduced to a certain extent through the stack purge process, if it is reduced to a certain water content, continue to purge to ensure the initial water content during the cold start process.

[0013] S2. Freeze;

[0014] The step S2 comprises the following sub-steps:

[0015] S2.1. Lower the fuel cell system to room temperature; After purging the fuel cell stack, lower the fuel cell system to room temperature for freezing operation to avoid the impact of rapid temperature change on system life;

[0016] S2.2. Set the cold start environment chamber temperature; Set the environment chamber temperature condition according to different fuel cell system cold start requirements;

[0017] S2.3. Wait for the environment chamber temperature to drop to the set temperature; Observe the temperature change of the cold start environment chamber;

[0018] S2.4. Let the fuel cell stack stand for at least 12 hours; In order to ensure that the fuel cell system is completely frozen.

[0019] S3. Start the machine;

[0020] The S3 start process comprises the following sub-steps:

[0021] S3.1. Determine whether the fuel cell system cooling liquid temperature is reduced to the set temperature; Whether this cold start experiment meets the experimental conditions by observing the inlet and outlet temperature of the fuel cell stack, whether the cooling liquid is reduced to the set temperature;

[0022] S3.2. Perform fuel cell system cold start;

[0023] S3.3. judging whether the engine is successfully started; judging whether the fuel cell system is successfully started in this cold start experiment through the signal information transmitted in step S3.2;

[0024] S3.4. troubleshooting after the engine fails to start; when the judging whether the engine is successfully started in step S3.3. is no, troubleshooting the fuel cell system in this cold start experiment.

[0025] S3.2. includes the following steps:

[0026] S3.2.1. performing a cold start pre-check of the fuel cell system;

[0027] including a cold start pre-check of the hydrogen circulation pump, the hydrogen pressure control module and the gas-water separator in the fuel cell system;

[0028] Further, the hydrogen circulation pump is pre-checked by the following formula:

[0029] |R H1 -R H2 |≤R set

[0030] wherein R H1 is the set value of the rotation speed of the hydrogen circulation pump, R H2 is the actual value of the rotation speed of the hydrogen circulation pump, and R set is the allowable deviation of the actual rotation speed and the set rotation speed of the hydrogen circulation pump, and the pre-check of the hydrogen circulation pump is realized by observing the actual rotation speed and the set rotation speed; if the observation condition satisfies the above judgment, it is judged that the component works normally, and the pre-check is passed, otherwise it is considered that the component does not work normally, and troubleshooting is performed.

[0031] Further, the hydrogen pressure control module is pre-checked, and the pre-check components of the hydrogen pressure control module are the hydrogen medium pressure sensor, the hydrogen low pressure sensor, the hydrogen supply on-off valve and the hydrogen supply pressure regulating valve.

[0032] Further, in the pre-check process of the hydrogen medium pressure sensor, the change of the medium pressure sensor reading is observed:

[0033] |P1-P2|≥P set1

[0034] wherein P1 is the medium pressure sensor observation pressure at t1, P2 is the medium pressure sensor observation pressure at t2, and P set1 is the set value of the allowable deviation of the medium pressure, and if the observation condition satisfies the above judgment, it is judged that the component works normally, and the pre-check is passed, otherwise it is considered that the component does not work normally, and troubleshooting is performed.

[0035] Further, the pre-checking process of the hydrogen supply switch valve is to open the hydrogen supply switch valve and observe the change of the hydrogen medium pressure sensor reading:

[0036] |P3-P4|≤P set2

[0037] Wherein, P3 is the hydrogen supply source pressure of the fuel cell system, P4 is the medium pressure sensor observed pressure after the hydrogen supply switch valve is opened, P set1 is the allowed set value of the hydrogen supply source pressure of the fuel cell system and the medium pressure sensor observed pressure when the hydrogen supply switch valve is opened. If the observation condition meets the above judgment, it is judged that the part works normally and passes the pre-checking. Otherwise, it is considered that the part does not work normally and troubleshooting is performed.

[0038] Further, in the pre-checking process of the hydrogen low pressure sensor, the change of the hydrogen low pressure sensor reading is observed:

[0039] |P5-P6|≥P set3

[0040] Wherein, P5 is the low pressure sensor observed pressure at t3, P6 is the low pressure sensor observed pressure at t4, P set3 is the low pressure deviation allowed set value. If the observation condition meets the above judgment, it is judged that the part works normally and passes the pre-checking. Otherwise, it is considered that the part does not work normally and troubleshooting is performed.

[0041] Further, the pre-checking process of the hydrogen supply proportional valve is to open the hydrogen supply pressure regulating valve and observe the change of the hydrogen medium pressure sensor reading:

[0042] |P7-P8|≤P set4

[0043] Wherein, P7 is the medium pressure sensor observed pressure of the fuel cell system, P8 is the low pressure sensor observed pressure of the fuel cell system, P set4 is the allowed set value of the medium pressure sensor observed pressure of the fuel cell system and the medium pressure sensor observed pressure when the hydrogen supply pressure regulating valve is opened. If the observation condition meets the above judgment, it is judged that the part works normally and passes the pre-checking. Otherwise, it is considered that the part does not work normally and troubleshooting is performed.

[0044] Further, the drainage valve of the gas-water separator is started and pre-checked;

[0045] Further, the drainage valve is closed at t5, maintained for Δt, opened at t6, maintained for Δt, and at t7, if:

[0046] |P9-P 10|≤P set5

[0047] and |P 10 -P 11 |≥P ett6

[0048] and |P 10 -P 11 |-|P9-P 10 |≥P set7

[0049] If the observation condition meets the above judgment, it is judged that the part is working normally, and the pre-check is passed, otherwise it is considered that the work is not normal, and the fault is checked. Among them, P9 is the pressure observed by the hydrogen out-of-pile pressure sensor at t5, P 10 is the pressure observed by the hydrogen out-of-pile pressure sensor at t6, P 11 is the pressure observed by the hydrogen out-of-pile pressure sensor at t7,

[0050] P set5 , P set6 , P set7 are the pressure allowable set values when the drain valve pre-checks.

[0051] S3.2.2. Perform cold start preheating of the fuel cell system;

[0052] By using a positive temperature coefficient heater (PTC), the cooling liquid in the fuel cell system is preheated;

[0053] Further, in the fuel cell system cold start preheating condition judgment:

[0054] T i1 ORT out <5℃

[0055] Among them, T in is the cooling liquid inlet temperature, and T out is the cooling liquid outlet temperature; when the cooling liquid inlet or outlet temperature is less than 5℃, the cooling liquid is preheated;

[0056] Further, when the preheating working condition is met, set the PTC working mode, and the PTC can work in target power or target temperature mode;

[0057] Further, after completing the setting of the working mode, wait for the PTC high voltage relay to close;

[0058] Further, after the PTC high voltage relay is closed, the PTC starts to work at the set power;

[0059] Further, after the PTC starts to work at the set power, the heat generated by the PTC exchanges with the coolant to preheat the coolant of the fuel cell system until the temperature of the coolant in and out of the stack is greater than or equal to 5 DEG C.

[0060] S3.2.3. performing self-start of the fuel cell system;

[0061] The fuel cell stack is heated by the heat generated by the chemical reaction of the fuel cell itself in the constant current start mode, so that the fuel cell stack can realize fast cold start:

[0062] When the system completes the pre-check, it enters S3.2.3. to perform self-start of the fuel cell system, the oxygen supply system, the hydrogen supply system and the cooling system start to work, and the fuel cell starts to generate electricity and heat;

[0063] Further, the system variables are monitored in the constant current self-start mode, the operation data are recorded, and real-time monitoring and early warning are performed;

[0064] Further, it is judged whether the fuel cell system can be stably operated for more than five minutes;

[0065] Further, if the fuel cell system can be stably operated for more than five minutes, it is determined that the cold start of the fuel cell system is successful, otherwise, it is determined that the cold start of the fuel cell system fails.

[0066] The present application has the advantages that the present application can provide a fuel cell system low-temperature test, pre-check and cold start method, which establishes (1) a fuel cell system cold start test method; (2) a fuel cell system pre-check and cold start method, two sub-methods. In the fuel cell system cold start test method, the cold start of the fuel cell system is tested by purging, freezing and starting. In the fuel cell system pre-check and cold start method, the pre-check and cold start of the fuel cell system are realized by pre-check, pre-heating and self-start. The proposed application can combine the low-temperature operation characteristics of the fuel cell system to realize coordinated pre-check of each component and realize low-temperature cold start of the fuel cell system. BRIEF DESCRIPTION OF DRAWINGS

[0067] Figure 1 The fuel cell system cold start test method flow chart of the present application;

[0068] Figure 2 The fuel cell system pre-check and cold start method flow chart of the present application;

[0069] Figure 3 The fuel cell system pre-check result chart in the embodiment; DETAILED DESCRIPTION

[0070] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0071] The objective of this invention is achieved through the following technical solution: a method for low-temperature testing, pre-inspection and cold start of a fuel cell system includes two sub-methods: (1) a test method for cold start of a fuel cell system; (2) a method for pre-inspection and cold start of a fuel cell system.

[0072] like Figure 1 As shown, the cold start test method for a fuel cell system includes the following steps:

[0073] S1. Purging;

[0074] Step S1 includes the following sub-steps:

[0075] S1.1. Chamber purging;

[0076] The chamber purging described in step S1.1 is to purge the leaked hydrogen inside the fuel cell stack chamber to prevent the hydrogen concentration from exceeding the standard.

[0077] S1.2. Purge of fuel cell stack;

[0078] Step S1.2. The stack purging is to purge the water generated by the reaction inside the fuel cell stack to prevent damage to the stack due to water freezing in a low-temperature environment, and to reduce the heat required for ice melting during the cold start process.

[0079] S1.3. Measure the high-frequency impedance value;

[0080] The measurement of high-frequency impedance value in step S1.3 is to measure the high-frequency impedance value of the fuel cell stack to determine the water content of the fuel cell stack;

[0081] S1.4. Determine whether the high-frequency impedance value is greater than or equal to the set value;

[0082] The step S1.4, which determines whether the high-frequency impedance value is greater than or equal to the set value, is to provide feedback on the result of the fuel cell stack purging and observe whether the water content of the fuel cell stack has been reduced to a certain level through the stack purging process. If the water content has not been reduced to a certain level, purging continues to ensure the initial water content during the cold start process.

[0083] S2. Freezing;

[0084] Step S2 includes the following sub-steps:

[0085] S2.1. Cool the fuel cell system to room temperature;

[0086] Step S2.1, the fuel cell system is reduced to room temperature, is to reduce the fuel cell system to room temperature after purging the fuel cell stack to avoid the influence of temperature change on the system life by performing a freezing operation;

[0087] S2.2. Set the cold start environment chamber temperature;

[0088] Step S2.2, setting the cold start environment chamber temperature, is to set the environment chamber temperature condition according to the cold start requirements of different fuel cell systems;

[0089] S2.3. Wait for the environment chamber temperature to drop to the set temperature;

[0090] Step S2.3, waiting for the environment chamber temperature to drop to the set temperature, is to observe the temperature change of the cold start environment chamber;

[0091] S2.4. Let the fuel cell stack stand for at least 12 hours;

[0092] Step S2.4, letting the fuel cell stack stand for at least 12 hours, is to ensure that the fuel cell system is completely frozen.

[0093] S3. Start the machine;

[0094] The S3. Start the machine process includes the following sub-steps:

[0095] S3.1. Determine whether the fuel cell system cooling liquid temperature has dropped to the set temperature;

[0096] Step S3.1, determining whether the fuel cell system cooling liquid temperature has dropped to the set temperature, is to observe whether the cooling liquid has dropped to the set temperature by the inlet and outlet temperature of the fuel cell stack to determine whether the cold start experiment has reached the experimental conditions;

[0097] S3.2. Perform a cold start of the fuel cell system;

[0098] Step S3.2, performing a cold start of the fuel cell system, is to perform sub-method (2) fuel cell system pre-check and cold start method;

[0099] S3.3. Determine whether the machine is started successfully;

[0100] Determine whether the fuel cell system is successfully started in this cold start experiment by the signal information transmitted by step S3.2;

[0101] S3.4. Perform fault diagnosis after the machine fails to start;

[0102] When S3.3. determines that the machine is not successfully started, perform fault diagnosis on the fuel cell system in this cold start experiment;

[0103] The above is the implementation step of the sub-method (1) fuel cell system cold start test method.

[0104] As shown in Figure 2 S3.2, the fuel cell system pre-check and cold start method includes the following steps:

[0105] S3.2.1. Perform a cold start pre-check of the fuel cell system;

[0106] Including the cold start pre-check of the hydrogen circulation pump, the hydrogen pressure control module and the gas-water separator in the fuel cell system;

[0107] Further, the pre-check of the hydrogen circulation pump is performed by the following formula:

[0108] |R H1 -R H2 |≤R set

[0109] Wherein, R H1 is the set value of the hydrogen circulation pump speed, R H2 is the actual value of the hydrogen circulation pump speed, and R set is the allowable deviation of the actual speed and the set speed of the hydrogen circulation pump. The pre-check of the hydrogen circulation pump is realized by observing the actual speed and the set speed. If the observation condition meets the above judgment, it is judged that the component is working normally, and the pre-check is passed. Otherwise, it is considered that the component is not working normally, and troubleshooting is performed.

[0110] Further, the pre-check of the hydrogen pressure control module is performed. When the pre-check of the hydrogen pressure control module is performed, the pre-check components are the hydrogen medium pressure sensor, the hydrogen low pressure sensor, the hydrogen supply switch valve and the hydrogen supply pressure regulating valve.

[0111] Further, in the pre-check process of the hydrogen medium pressure sensor, the change of the medium pressure sensor reading is observed:

[0112] |P1-P2|≥P set1

[0113] Wherein, P1 is the medium pressure sensor observation pressure at t1, P2 is the medium pressure sensor observation pressure at t2, and P set1 is the set value of the allowable deviation of the medium pressure. If the observation condition meets the above judgment, it is judged that the component is working normally, and the pre-check is passed. Otherwise, it is considered that the component is not working normally, and troubleshooting is performed.

[0114] Further, the pre-check process of the hydrogen supply switch valve is to open the hydrogen supply switch valve and observe the change of the hydrogen medium pressure sensor reading:

[0115] |P3-P4|≤Pset2

[0116] P3 is the pressure of the hydrogen supply source of the fuel cell system, P4 is the pressure observed by the medium pressure sensor after the hydrogen supply switch valve is opened, P set1 P3 is the pressure of the hydrogen supply source of the fuel cell system, P4 is the pressure observed by the medium pressure sensor after the hydrogen supply switch valve is opened, P

[0117] Further, in the pre-checking process of the hydrogen low pressure sensor, the change of the reading of the hydrogen low pressure sensor is observed:

[0118] |P5-P6|≥P set3

[0119] P5 is the pressure observed by the low pressure sensor at t3, P6 is the pressure observed by the low pressure sensor at t4, P set3 P5 is the pressure observed by the low pressure sensor at t3, P6 is the pressure observed by the low pressure sensor at t4, P

[0120] Further, the pre-checking process of the hydrogen supply proportional valve is to open the hydrogen supply pressure regulating valve and observe the change of the reading of the hydrogen medium pressure sensor:

[0121] |P7-P8|≤P set4

[0122] P7 is the pressure observed by the medium pressure sensor of the fuel cell system, P B P7 is the pressure observed by the medium pressure sensor of the fuel cell system, P set4 P7 is the pressure observed by the medium pressure sensor of the fuel cell system, P

[0123] Further, the drain valve of the gas-water separator is started and pre-checked;

[0124] Further, the drain valve is closed at t5, maintained for Δt, the drain valve is opened at t6, maintained for Δt, and at t7, if:

[0125] |P9-P 10 |≤P set5

[0126] and |P 10 -P 11| ≥ P set6

[0127] and | P 10 -P 11 | - | P9-P 10 | ≥ P set7

[0128] If the observation condition meets the above judgment, it is judged that the part is working normally, and the pre-check is passed, otherwise it is considered that the work is not normal, and the fault is checked. Among them, P9 is the pressure observed by the hydrogen out-of-pile pressure sensor at t5, P 10 is the pressure observed by the hydrogen out-of-pile pressure sensor at t6, P 11 is the pressure observed by the hydrogen out-of-pile pressure sensor at t7, P set5 , P set6 , P set7 are the pressure allowable set values when the drain valve is pre-checked, respectively.

[0129] S3.2.2. Perform cold start preheating of the fuel cell system;

[0130] By using a positive temperature coefficient heater (PTC), the cooling liquid in the fuel cell system is preheated;

[0131] Further, in the cold start preheating condition judgment of the fuel cell system:

[0132] T in ORT out < 5℃

[0133] Among them, T in is the cooling liquid inlet temperature, and T out is the cooling liquid outlet temperature; when the cooling liquid inlet or outlet temperature is less than 5℃, the cooling liquid is preheated;

[0134] Further, when the preheating working condition is met, set the PTC working mode, and the PTC can work in target power or target temperature mode;

[0135] Further, after completing the setting mode, wait for the PTC high voltage relay to close;

[0136] Further, after the PTC high voltage relay is closed, the PTC starts to work at the set power;

[0137] Further, after the PTC starts to work at the set power, the heat generated by the PTC exchanges with the cooling liquid to preheat the cooling liquid of the fuel cell system until the cooling liquid inlet and outlet temperature ≥ 5℃;

[0138] S3.2.3. performing fuel cell system self-starting;

[0139] In the constant current starting mode, the fuel cell stack is heated by the heat generated by the chemical reaction of the fuel cell itself, so that the fuel cell stack can be quickly cold started:

[0140] When the system completes the pre-check, it enters the S3.2.3. fuel cell system self-starting state, and the oxygen supply system, hydrogen supply system and cooling system start to work, and the fuel cell starts to generate electricity and heat;

[0141] Further, in the constant current self-starting mode, the system variables are monitored, the operation data are recorded, and the real-time monitoring and early warning are performed;

[0142] Further, it is judged whether the fuel cell system can be stably operated for more than five minutes;

[0143] Further, if the fuel cell system can be stably operated for more than five minutes, it is determined that the fuel cell system cold starting is successful, otherwise, it is determined that the fuel cell system cold starting fails.

[0144] In this embodiment, according to the experimental results of the fuel cell system low temperature test, pre-check and cold starting method, as shown in Figure 3 , the hydrogen circulation pump pre-checking according to the fuel cell system low temperature test, pre-checking and cold starting method is shown, at this time the required speed of the hydrogen circulation pump has been determined according to the state of the fuel cell system. After sending the start command to the hydrogen circulation pump, as shown in Figure 3 , the actual speed of the hydrogen circulation pump is much smaller than the required speed of the hydrogen circulation pump, and the difference between the actual speed of the hydrogen circulation pump and the required speed of the hydrogen circulation pump is much larger than the allowable deviation of the speed, which does not meet the judgment requirement in the following formula:

[0145] |R H1 -R H2 |≤R set

[0146] Therefore, at this time, the fuel cell system low temperature test, pre-checking and cold starting method is proposed, which determines that the failure occurs in the S3.2.1. fuel cell system cold starting pre-checking step in S3, and determines that the fuel cell hydrogen circulation pump enters the failure state at this time, and considers that the fuel cell system cold starting fails at this time. After recording and analyzing the data, it is considered that the failure occurred at this time is due to the circulation of water in the hydrogen circulation system, which causes the hydrogen circulation pump to stall, so the troubleshooting result is that the hydrogen circulation pump stalls.

[0147] In summary, the low-temperature test, pre-check and cold start method of the fuel cell system is based on the proposed (1) fuel cell system cold start test method; (2) fuel cell system pre-check and cold start method, two sub-methods, through purging, freezing and starting, the test of cold start of the fuel cell system is realized; in the fuel cell system pre-check and cold start method, through pre-check, pre-heating and self-starting, the pre-check and cold start of the fuel cell system are realized. The proposed method can combine the low-temperature operation characteristics of the fuel cell system, realize the cold start test and fault judgment of the fuel cell system completely, carry out fault troubleshooting, and provide a basis for the development of the fuel cell system.

[0148] The above is the preferred embodiment of the present application, it should be understood that the present application is not limited to the form disclosed herein, should not be seen as excluding other embodiments, but can be used in other combinations, modifications and environments, and can be modified within the scope of the concept described herein, by the above teaching or related art or knowledge, the modification and change made by the person skilled in the art without departing from the spirit and scope of the present application, should be within the protection scope of the claims of the present application.

Claims

1. A method for low temperature testing, pre-checking and cold starting of a fuel cell system, characterized in that, The method comprises the following steps: S1. Purging; comprising: Box purging; purging the leaked hydrogen in the fuel cell stack box to avoid excessive hydrogen concentration; Stack purging; purging the water generated in the fuel cell stack to avoid damage to the stack due to water freezing in low temperature environment, and to reduce the heat required for ice melting during cold start process; Measuring high-frequency impedance value; measuring the high-frequency impedance value of the fuel cell stack to determine the water content of the fuel cell stack; Determining whether the high-frequency impedance value is greater than or equal to a set value; feeding back the result of purging the fuel cell stack, observing whether the water content of the fuel cell stack is reduced to a certain extent through the stack purging process, if not, continue purging to ensure the initial water content during the cold start process; S2. Freezing; the step S2 comprises the following sub-steps: S2.

1. Reducing the fuel cell system to room temperature; after purging the fuel cell stack, reducing the fuel cell system to room temperature before freezing operation to avoid the impact of rapid temperature change on system life; S2.

2. Setting the temperature of the cold start environment chamber; setting the temperature condition of the environment chamber according to the cold start demand of different fuel cell systems; S2.

3. Waiting for the temperature of the environment chamber to drop to a set temperature; observing the temperature change of the cold start environment chamber; S2.

4. Letting the fuel cell stack stand for at least 12 hours; to ensure that the fuel cell system is completely frozen; S3. Starting; the S3 starting process comprises the following sub-steps: S3.

1. Determining whether the fuel cell system cooling liquid temperature is reduced to a set temperature; observing whether the cold start experiment reaches the experimental condition by the inlet and outlet temperature of the fuel cell stack, whether the cooling liquid is reduced to a set temperature; S3.

2. Cold starting the fuel cell system; S3.

3. Determining whether the starting is successful; determining whether the fuel cell system successfully starts in this cold start experiment through the signal information transmitted by step S3.2; S3.

4. Fault checking after starting failure; when S3.

3. determines that the starting is not successful, checking the fault of the fuel cell system in this cold start experiment.

2. The method of claim 1, wherein the fuel cell system low temperature test, pre-check and cold start method further comprises: The step S3.2 comprises the following steps: S3.2.

1. Cold start pre-checking of the fuel cell system; Including cold start pre-checking of the hydrogen circulation pump, hydrogen pressure control module and gas-water separator in the fuel cell system; S3.2.

2. Cold start preheating of the fuel cell system; preheating the cooling liquid in the fuel cell system by using a positive temperature coefficient thermistor heater PTC; S3.2.

3. Self-starting of the fuel cell system; using constant current starting mode, heating the fuel cell stack by the heat generated by the chemical reaction of the fuel cell itself, so that the fuel cell stack can realize rapid cold start: After the system completes the pre-checking, it enters the S3.2.

3. self-starting state of the fuel cell system, the oxygen supply system, the hydrogen supply system and the cooling system start working, the fuel cell starts generating electricity and producing heat; Monitoring system variables in constant current self-starting mode, recording operation data and real-time monitoring and early warning; determining whether the fuel cell system can be stably operated for more than five minutes; if the fuel cell system can be stably operated for more than five minutes, determining that the cold start of the fuel cell system is successful, otherwise, determining that the cold start of the fuel cell system is unsuccessful.

3. The method of claim 2, wherein the fuel cell system low temperature test, pre-check and cold start method further comprises: The step S3.2.1 specifically includes; The hydrogen circulation pump is pre-tested, and whether the hydrogen circulation pump can be stably operated for more than five minutes is determined by the following formula: ， wherein, is a hydrogen circulation pump rotation speed set value, is a hydrogen circulation pump rotation speed actual value, is a hydrogen circulation pump actual rotation speed and set rotation speed allowable deviation, through observation of the actual rotation speed and the set rotation speed, pre-checking of the hydrogen circulation pump is realized; if the observation condition satisfies the above judgment, it is judged that the part works normally, through pre-checking, otherwise it is considered that it does not work normally, and troubleshooting is carried out; The hydrogen pressure control module is pre-tested, and the pre-tested components are the hydrogen medium-pressure pressure sensor, the hydrogen low-pressure pressure sensor, the hydrogen supply switch valve and the hydrogen supply pressure regulating valve; During the pre-test of the hydrogen medium-pressure pressure sensor, the change of the hydrogen medium-pressure pressure sensor is observed; ， wherein, is the pressure observed by the medium pressure sensor at the instant, is the pressure observed by the medium pressure sensor at the instant, is a medium pressure deviation allowable set value, if the observation condition satisfies the above judgment, it is judged that the component works normally, and the pre-check is passed, otherwise it is considered that the component does not work normally, and troubleshooting is performed. The pre-test of the hydrogen supply switch valve is to open the hydrogen supply switch valve and observe the change of the hydrogen medium-pressure pressure sensor; ， wherein, Pfuelcell is the pressure of the hydrogen supply source of the fuel cell system, Pfuelcell is the pressure of the hydrogen supply source of the fuel cell system, Pfuelcell is the pressure of the hydrogen supply source of the fuel cell system, During the pre-test of the hydrogen low-pressure pressure sensor, the change of the hydrogen low-pressure pressure sensor is observed; ， wherein, is the pressure observed by the low-pressure pressure sensor at the moment, is the pressure observed by the low-pressure pressure sensor at the moment, is a low-pressure pressure deviation allowable set value, if the observation condition satisfies the above judgment, it is judged that the component is working normally, and the pre-checking is passed, otherwise it is considered that the component is not working normally, and troubleshooting is performed. The pre-test of the hydrogen supply proportional valve is to open the hydrogen supply pressure regulating valve and observe the change of the hydrogen medium-pressure pressure sensor; ， wherein, Pmid is the pressure observed by the mid-pressure sensor in the fuel cell system, Plow is the pressure observed by the low-pressure sensor in the fuel cell system, Pmax is the allowable set value of the pressure observed by the mid-pressure sensor in the fuel cell system when the hydrogen supply pressure regulating valve is open, and the pressure observed by the low-pressure sensor in the fuel cell system, if the observation conditions satisfy the above judgment, it is judged that the component is working normally, and the pre-check is passed, otherwise it is considered that the component is not working normally, and troubleshooting is performed. The drainage valve of the gas-water separator is pre-tested; At the drain valve is closed, maintaining the drain valve is opened, maintaining the drain valve is opened, maintaining the drain valve is opened, maintaining the drain valve is opened, maintaining ， and , and , If the observation condition satisfies the above judgment, it is judged that the part is working normally, and the pre-check is passed, otherwise it is considered that the work is not normal, and the fault is checked; wherein For The pressure observed by the hydrogen out-of-stack pressure sensor at the moment, For The pressure observed by the hydrogen out-of-stack pressure sensor at the moment, For The pressure observed by the hydrogen out-of-stack pressure sensor at the moment, , , Respectively, the pressure allowable set value when the drain valve pre-checks.

4. The method of claim 2, wherein the fuel cell system low temperature test, pre-check and cold start method further comprises: The step S3.2.2 specifically includes; Before the cold start of the fuel cell system, the pre-heating condition of the fuel cell system is determined; <5℃， wherein, Tin is the inlet coolant temperature, Tout is the outlet coolant temperature; when the inlet or outlet coolant temperature is less than 5°C, preheating of the coolant is performed; After the pre-heating working condition is met, the PTC working mode is set, and the PTC works in the target power or target temperature mode; After the working mode is set, the PTC high-voltage relay is closed; After the PTC high-voltage relay is closed, the PTC starts to work in the set power; After the PTC starts to work at the set power, the heat generated by the PTC exchanges with the coolant, preheats the coolant of the fuel cell system, and the coolant in and out of the stack 5°C.

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