Fuel cell system starting method and fuel cell system

Abstract

The invention provides a fuel cell system starting method and a fuel cell system. The fuel cell system starting method comprises the following steps: a pressure maintaining judgment step; a time judgment step and an execution step; when the air-to-air starting mode is adopted, performing hydrogen purging on the anode of the fuel cell system, controlling the pressure in the anode of the fuel cell system to be greater than the pressure in the cathode at the moment, and controlling the pressure difference to be a first set pressure difference; when the normal starting mode is adopted, performing hydrogen purging on the anode of the fuel cell system, controlling the pressure in the anode to be greater than the pressure in the cathode at the moment, and controlling the pressure difference to be a second set pressure difference; wherein the first set pressure difference is larger than the second set pressure difference. The method provided by the invention can effectively balance the selection among the starting time, the hydrogen consumption and the service life of the electric pile, and ensures that the fuel cell system is started in a corresponding suitable mode in different states.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a fuel cell system starting method and a fuel cell system. Background Art

[0002] After an existing fuel cell system is shut down, the residual oxygen in the fuel cell stack will continue to react with hydrogen. If there is a large amount of residual oxygen, it will diffuse to the anode and a chemical reaction of hydrogen and oxygen will occur at the anode, generating a high potential and corroding the catalyst carbon carrier, thereby causing irreversible damage to the stack. Therefore, after the fuel cell system is shut down, hydrogen will continue to be supplied to the anode to completely consume the oxygen.

[0003] After being shut down, the fuel cell system will continue to supply hydrogen to the anode. Therefore, under ideal conditions, both the anode and cathode are filled with hydrogen (i.e., a hydrogen-hydrogen environment) before the next startup of the fuel cell system. However, due to the sealing problem of the fuel cell, after the fuel cell has been parked for a long time, the air in the external environment will enter the stack and consume the hydrogen, resulting in both the anode and cathode being filled with air (i.e., an empty environment) before the next startup of the fuel cell. In theory, starting in a "hydrogen-hydrogen" environment is the ideal startup state for the fuel cell, while starting in an "empty-air" environment will cause a hydrogen-air interface to be formed at the moment when hydrogen is introduced during startup, thereby damaging the life of the fuel cell stack.

[0004] In the prior art of fuel cell system starting methods, after hydrogen is introduced into the anode of the fuel cell, it is usually determined whether it is an empty start (i.e., whether the gas composition of the cathode and anode before starting is air) based on the increase in the average cell voltage; if the average cell voltage rises to a certain threshold, it is determined to be an empty start.

[0005] In the existing method for handling the empty-start of a fuel cell, hydrogen is purged to the anode when the fuel cell is started. This purging method is a timed and constant-pressure purging method, that is, the anode is purged at a certain pressure for a certain time; however, this method has the following disadvantages: when there is oxygen at the anode, the average cell voltage is rapidly established at the moment of hydrogen introduction, and this process is very short. However, the method of judging by the rising threshold of the average cell voltage in the prior art has a certain delay. Therefore, the empty-start method after the voltage rises has already generated a high potential, which has already caused damage to the life of the fuel cell stack. The existing fuel cell system startup method does not take into account the gas composition in the anode before purging; if it is a normal startup, no hydrogen-air interface will be generated when hydrogen is introduced into the anode for purging. At this time, a conventional startup strategy can be adopted without purging, which delays the startup time; if it is an air-to-air startup, a hydrogen-air interface will be generated when hydrogen is introduced into the anode for purging. In this case, the air needs to be blown out of the fuel cell as soon as possible to shorten the time of the hydrogen-air interface and avoid damaging the life of the fuel cell stack; the timed and constant-pressure purging method does not take into account the gas composition inside the anode before startup, so it is impossible to effectively balance factors such as startup time, hydrogen consumption, and fuel cell stack life. Especially for the case of an air-to-air startup, the use of low-pressure and long-term purging may further reduce the service life of the fuel cell stack. Summary of the invention

[0006] The present invention provides a fuel cell system startup method and a fuel cell system to solve the problem in the prior art that the anode timing and constant pressure purge method cannot effectively balance the startup time, hydrogen consumption and fuel cell stack life.

[0007] In order to solve the above-mentioned problem, according to one aspect of the present invention, there is provided a method for starting a fuel cell system, comprising: a pressure maintaining determination step: determining whether the fuel cell system performs anode pressure maintaining, and selecting an air-to-air starting mode or a normal starting mode according to the determination result; a time determination step: obtaining the downtime of the fuel cell system; when the downtime is greater than the set time, an air-to-air starting mode is adopted; when the downtime is not greater than the set time, a normal starting mode is adopted; the time determination step can be selectively executed or not executed; an execution step: when the air-to-air starting mode is adopted, the anode of the fuel cell system is purged with hydrogen, at which time the pressure in the anode of the fuel cell system is controlled to be greater than the pressure in the cathode, and the pressure difference is a first set pressure difference; when the normal starting mode is adopted, the anode of the fuel cell system is purged with hydrogen, at which time the pressure in the anode is controlled to be greater than the pressure in the cathode, and the pressure difference is a second set pressure difference; wherein the first set pressure difference is greater than the second set pressure difference.

[0008] Furthermore, when the fuel cell system is not performing anode pressure maintenance, the time determination step is skipped and the empty-to-air start method in the execution step is performed; when the fuel cell system is already performing anode pressure maintenance, the time determination step is executed.

[0009] Furthermore, the fuel cell system startup method also includes a learning correction step, which includes: judging whether to correct the set time based on the average cell voltage of the fuel cell system in the execution step; when the average cell voltage is less than the correction voltage threshold, maintaining the set time unchanged; when the average cell voltage is greater than or equal to the correction voltage threshold, obtaining a correction value based on the maximum value of the average cell voltage, subtracting the correction value from the set time, and obtaining a new set time.

[0010] Furthermore, the fuel cell system starting method also includes a voltage determination step, which includes: determining whether the average cell voltage of the fuel cell system is greater than a safety voltage threshold, and selecting an empty-to-air starting mode or a normal starting mode according to the determination result; when the average cell voltage is greater than the safety voltage threshold, an empty-to-air starting mode is adopted; when the average cell voltage is less than or equal to the safety voltage threshold, a normal starting mode is adopted.

[0011] Optionally, the fuel cell system starting method also includes a voltage determination step, which includes: selecting an empty-to-air starting mode or a normal starting mode based on whether the average cell voltage of the fuel cell system is greater than a safety voltage threshold; wherein a pressure maintenance determination step, a time determination step and a voltage determination step are performed in sequence to select an empty-to-air starting mode or a normal starting mode.

[0012] Optionally, the pressure maintenance determination step is first executed. When the fuel cell system is not performing anode pressure maintenance, it is determined that the empty-to-air start mode is adopted, and the time determination step and the voltage determination step are skipped to perform the empty-to-air start mode in the execution step; when the fuel cell system is already performing anode pressure maintenance, the time determination step is executed; when the downtime is greater than the set time, it is determined that the empty-to-air start mode is adopted, and the voltage determination step is directly skipped to perform the empty-to-air start mode in the execution step; when the downtime is not greater than the set time, the voltage determination step is executed; in the voltage determination step, when the average cell voltage is greater than the safety voltage threshold, it is determined that the empty-to-air start mode is adopted, and the empty-to-air start mode in the execution step is performed; when the average cell voltage is less than or equal to the safety voltage threshold, it is determined that the normal start mode is adopted, and the normal start mode in the execution step is performed.

[0013] Furthermore, when the fuel cell system is started in an empty-to-air mode, the first set pressure difference is set in a range of 40-60 kPa; when the fuel cell system is started in a normal mode, the second set pressure difference is set in a range of 20-30 kPa.

[0014] According to another aspect of the present invention, a fuel cell system is provided, and the fuel cell system applies the above-mentioned fuel cell system startup method; the fuel cell system includes a real-time clock, and the real-time clock is used to record the downtime of the fuel cell system.

[0015] Furthermore, the fuel cell system also includes: a fuel cell stack, a hydrogen pressure regulating valve, a gas-water separator, a nitrogen and water discharge valve, an air compressor, an intercooler, a humidifier, a bypass valve, a shut-off valve and a back pressure valve; the hydrogen pressure regulating valve is connected to the anode inlet of the fuel cell stack and is used to adjust the pressure of hydrogen entering the anode; the gas-water separator is connected to the anode outlet of the fuel cell stack and is used to separate the gas and liquid water discharged from the anode outlet; one end of the nitrogen and water discharge valve is connected to the gas-water separator and the other end is connected to the outside; the nitrogen and water discharge valve is used to discharge the liquid water discharged from the gas-water separator and the nitrogen in the anode to the outside; the outlet of the air compressor is connected to the intercooler The inlet of the intercooler is connected to provide a set volume of air for the cathode of the fuel cell stack; the outlet of the intercooler is connected to the inlets of the bypass valve and the humidifier respectively, and is used to adjust the temperature of the air after being pressurized by the air compressor; the outlet of the humidifier is connected to one end of the stop valve, and is used to humidify the air; the bypass valve is connected to the outside, and when the bypass valve is in the open state, the air blown out by the intercooler is directly discharged to the outside and does not enter the cathode of the fuel cell stack; the other end of the stop valve is connected to the cathode, and is used to control the amount of air entering the cathode; the inlet of the back-pressure valve is connected to the cathode, and the outlet of the back-pressure valve is connected to the outside, and the back-pressure valve is used to control the pressure of the cathode.

[0016] Furthermore, when the fuel cell system is started normally, the range of the second set pressure difference is set to 20-30 kPa; the nitrogen exhaust and water drain valve is controlled to be opened and closed periodically, the bypass valve is controlled to be in an open state, and the air compressor is controlled to run at a first speed; when the fuel cell system is started in an air-to-air mode, the range of the first set pressure difference is set to 40-60 kPa; the nitrogen exhaust and water drain valve is controlled to be in an open state, the bypass valve is controlled to be in an open state, and the air compressor is controlled to run at a second speed; wherein the second speed is greater than the first speed.

[0017] Applying the technical solution of the present invention, the present invention provides a method for starting a fuel cell system, comprising: a pressure maintenance determination step: determining whether the fuel cell system performs anode pressure maintenance, and selecting an air-to-air start mode or a normal start mode according to the determination result; a time determination step: obtaining the downtime of the fuel cell system; when the downtime is greater than the set time, an air-to-air start mode is adopted; when the downtime is not greater than the set time, a normal start mode is adopted; the time determination step can be selectively executed or not executed; an execution step: when the air-to-air start mode is adopted, the anode of the fuel cell system is purged with hydrogen, at which time the pressure in the anode of the fuel cell system is controlled to be greater than the pressure in the cathode, and the pressure difference is a first set pressure difference; when the normal start mode is adopted, the anode of the fuel cell system is purged with hydrogen, at which time the pressure in the anode is controlled to be greater than the pressure in the cathode, and the pressure difference is a second set pressure difference; wherein the first set pressure difference is greater than the second set pressure difference. The present invention proposes a pressure holding determination step and a time determination step, and flexibly selects different starting modes according to the downtime and pressure holding conditions. Compared with the existing timed and constant pressure purging method for the anode, the method of the present invention can effectively balance the selection between the starting time, hydrogen consumption and the life of the stack, and ensures that the fuel cell system adopts a corresponding appropriate method to start under different conditions. Under the premise of ensuring a short starting time, the damage to the service life of the stack is also reduced as much as possible; the method of the present invention does not completely rely on monitoring the average cell voltage to determine whether it is an empty-to-air start, but mainly determines whether it is an empty-to-air start based on the parking time. Therefore, the judgment of the empty-to-air start can be completed before starting, rather than during the starting process, effectively avoiding the execution delay of the empty-to-air start caused by the average cell voltage being established too quickly; at the same time, the method of the present invention effectively distinguishes between normal start and empty-to-air start, adopts different starting strategies, and realizes the rapid purging of the anode by the empty-to-air start mode by setting the first set pressure difference to be greater than the second set pressure difference, thereby reducing the duration of the hydrogen-air interface; by setting the time determination step to be selectively executed or not executed, the fuel cell system starting method can complete the start more quickly in some cases. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 A flowchart showing some steps of a method for starting a fuel cell system provided by an embodiment of the present invention is shown;

[0020] Figure 2 A logic judgment flow chart of a fuel cell system startup method provided by another embodiment of the present invention is shown;

[0021] Figure 3 A partial structural schematic diagram of a fuel cell system provided by an embodiment of the present invention is shown.

[0022] The above drawings include the following reference numerals:

[0023] 10. Battery stack;

[0024] 20. Hydrogen pressure regulating valve;

[0025] 30. Gas-water separator;

[0026] 40. Nitrogen drain valve;

[0027] 50. Air compressor;

[0028] 60. Intercooler;

[0029] 70. Humidifier;

[0030] 80. Bypass valve;

[0031] 90. Stop valve;

[0032] 100. Back pressure valve. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] like Figures 1 to 3 As shown, an embodiment of the present invention provides a fuel cell system startup method, comprising:

[0035] Pressure maintenance determination step: determine whether the fuel cell system is performing anode pressure maintenance, and select an empty-air start mode or a normal start mode according to the determination result;

[0036] Time determination step: obtaining the downtime of the fuel cell system; when the downtime is greater than the set time, an empty start mode is adopted; when the downtime is not greater than the set time, a normal start mode is adopted; the time determination step can be selectively executed or not executed;

[0037] Execution steps: When an air-to-air start-up method is adopted, the anode of the fuel cell system is purged with hydrogen, and the pressure in the anode of the fuel cell system is controlled to be greater than the pressure in the cathode, and the pressure difference is a first set pressure difference; when a normal start-up method is adopted, the anode of the fuel cell system is purged with hydrogen, and the pressure in the anode is controlled to be greater than the pressure in the cathode, and the pressure difference is a second set pressure difference; wherein the first set pressure difference is greater than the second set pressure difference.

[0038] The present invention proposes a pressure holding determination step and a time determination step, and flexibly selects different starting modes according to the downtime and pressure holding conditions. Compared with the existing timed and constant pressure purging method for the anode, the method of the present invention can effectively balance the selection between the starting time, hydrogen consumption and the life of the stack, and ensures that the fuel cell system adopts a corresponding appropriate method to start under different conditions. Under the premise of ensuring a short starting time, the damage to the service life of the stack is also reduced as much as possible; the method of the present invention does not completely rely on monitoring the average cell voltage to determine whether it is an empty-to-air start, but mainly determines whether it is an empty-to-air start based on the parking time. Therefore, the judgment of the empty-to-air start can be completed before starting, rather than during the starting process, effectively avoiding the execution delay of the empty-to-air start caused by the average cell voltage being established too quickly; at the same time, the method of the present invention effectively distinguishes between normal start and empty-to-air start, adopts different starting strategies, and realizes the rapid purging of the anode by the empty-to-air start mode by setting the first set pressure difference to be greater than the second set pressure difference, thereby reducing the duration of the hydrogen-air interface; by setting the time determination step to be selectively executed or not executed, the fuel cell system starting method can complete the start more quickly in some cases.

[0039] It should be noted that due to the sealing problem of the fuel cell system, after a long period of shutdown, air in the external environment will enter the fuel cell stack 10 and consume all the hydrogen, causing the anode and cathode of the fuel cell system to be filled with air before the next start-up (i.e., empty start state). The above process is strongly related to the shutdown duration of the fuel cell system. Based on the above reasons, the present invention proposes a time determination step for judgment.

[0040] Specifically, when the fuel cell system is not performing anode pressure maintenance, the time determination step is skipped and the empty-to-air start method in the execution step is performed; when the fuel cell system is already performing anode pressure maintenance, the time determination step is performed. Usually, when the fuel cell system is abnormally shut down or the anode pressure is not maintained after shutdown, the remaining oxygen in the fuel cell system cannot be completely consumed. Based on this situation, the next time the fuel cell system is started, it can be directly determined as an empty-to-air start condition, and the empty-to-air start method in the execution step is performed, ensuring the rapid startup of the fuel cell system.

[0041] It is worth noting that: in a specific embodiment of the present invention, it is possible to determine whether the anode pressure is maintained based on the sealing condition of the anode after hydrogen purging when the fuel cell system is shut down (i.e., whether the anode is effectively sealed after hydrogen purging), and a comprehensive judgment can be made based on the gas composition and pressure conditions in the anode after shutdown; it is also possible to preliminarily determine whether the anode pressure is maintained by detecting whether the fuel cell system has performed the conventional shutdown purge action normally.

[0042] The fuel cell system startup method also includes a learning correction step, which includes: judging whether to correct the set time according to the average cell voltage of the fuel cell system in the execution step. By setting the learning correction step, the effective correction of the set time is guaranteed, thereby ensuring the accuracy and reliability of the time determination step.

[0043] Specifically, the correction of the set time includes: when the average cell voltage is less than the correction voltage threshold, the set time is maintained unchanged; when the average cell voltage is greater than or equal to the correction voltage threshold, a correction value is obtained according to the maximum value of the average cell voltage, and the correction value is subtracted from the set time to obtain a new set time. Considering that the sealing performance of the fuel cell system may gradually deteriorate with the running time, the set time should be corrected in time to ensure that the set time is representative.

[0044] It should be noted that: in a specific embodiment of the present invention, the correction value can be obtained by looking up a table (for example, an empirical correction table) according to the maximum voltage of the anode during hydrogen purging. The higher the voltage, the larger the correction value; the empirical correction table can be obtained by summarizing the experimental data obtained by bench testing the fuel cell system. For example: during the bench test, the staff first establishes a coordinate system with the X-axis as the maximum average cell voltage and the Y-axis as the downtime value. Multiple sets of data are obtained based on multiple bench tests and filled into the above coordinate system accordingly. Then, based on the numerical fitting calculation, an empirical formula (for example, a linear formula) for the mathematical relationship between the data is obtained, and a complete empirical correction table is calculated. When the subsequent staff needs to obtain the correction value, the corresponding maximum voltage of the anode (that is, the maximum average cell voltage) can be quickly queried, which is convenient and quick.

[0045] The fuel cell system startup method also includes a voltage determination step, which includes: determining whether the average cell voltage of the fuel cell system is greater than a safety voltage threshold, and selecting an empty startup mode or a normal startup mode according to the determination result. By setting the voltage determination step, the startup safety of the fuel cell system is ensured.

[0046] Specifically, when the average cell voltage is greater than the safety voltage threshold, the empty-to-air start mode is adopted; when the average cell voltage is less than or equal to the safety voltage threshold, the normal start mode is adopted. This configuration further makes the start of the fuel cell system safer, the duration of the hydrogen-air interface is as short as possible, and the service life of the fuel cell system is protected.

[0047] In a specific embodiment of the present invention, the fuel cell system startup method further includes a voltage determination step, which includes: selecting an empty-to-air startup mode or a normal startup mode according to whether the average cell voltage of the fuel cell system is greater than a safety voltage threshold; wherein the pressure maintenance determination step, the time determination step, and the voltage determination step are sequentially performed to select an empty-to-air startup mode or a normal startup mode. By setting the pressure maintenance determination step, the time determination step, and the voltage determination step to be performed sequentially, a comprehensive judgment of the state of the fuel cell system at startup is ensured, making the selection of the startup mode more accurate (for example, selecting a normal startup mode or an empty-to-air startup mode).

[0048] like Figure 2 As shown, in a specific embodiment of the present invention, the pressure maintenance determination step is first executed. When the fuel cell system does not perform anode pressure maintenance, it is determined that the empty-to-empty start mode is adopted, and the time determination step and the voltage determination step are skipped to perform the empty-to-empty start mode in the execution step; when the fuel cell system has performed anode pressure maintenance, the time determination step is executed; when the downtime is greater than the set time, the empty-to-empty start mode is determined, and the voltage determination step is directly skipped to perform the empty-to-empty start mode in the execution step; when the downtime is not greater than the set time, the voltage determination step is executed; in the voltage determination step, when the average cell voltage is greater than the safety voltage threshold, the empty-to-empty start mode is determined to be adopted, and the empty-to-empty start mode in the execution step is performed; when the average cell voltage is less than or equal to the safety voltage threshold, the normal start mode is determined to be adopted, and the normal start mode in the execution step is performed. By adopting the above steps, a complete set of fuel cell system startup logic is formed, which can effectively distinguish the startup state of the fuel cell system, and adopt different startup strategies accordingly. The empty-to-empty start mode can quickly purge the anode, reducing the duration of the hydrogen-air interface; at the same time, the above method also enables the fuel cell system to complete startup more quickly in some cases.

[0049] Specifically, when the fuel cell system performs an air-to-air start mode, the first set pressure difference is set in the range of 40-60kPa; when the fuel cell system performs a normal start mode, the second set pressure difference is set in the range of 20-30kPa. This setting ensures that the air-to-air start mode can quickly purge the anode and reduce the duration of the hydrogen-air interface; on the other hand, it reduces the hydrogen consumption in the normal start mode.

[0050] The present invention also proposes a fuel cell system, which uses the above-mentioned fuel cell system startup method; the fuel cell system includes a real-time clock (for example, a common RTC clock), and the real-time clock is used to record the downtime of the fuel cell system. By setting the real-time clock, a reliable record of the downtime of the fuel cell system is achieved, providing structural support for subsequent staff to read data and combine with intelligent terminals for intelligent startup control.

[0051] like Figure 3 As shown, the fuel cell system further includes: a fuel cell stack 10, a hydrogen pressure regulating valve 20, a gas-water separator 30, a nitrogen and water discharge valve 40, an air compressor 50, an intercooler 60, a humidifier 70, a bypass valve 80, a stop valve 90 and a back pressure valve 100;

[0052] The hydrogen pressure regulating valve 20 is connected to the anode inlet of the fuel cell stack 10 and is used to regulate the pressure of hydrogen entering the anode;

[0053] The gas-water separator 30 is connected to the anode outlet of the fuel cell stack 10 and is used to separate the gas and liquid water discharged from the anode outlet;

[0054] One end of the nitrogen-discharging and water-draining valve 40 is connected to the gas-water separator 30, and the other end is connected to the outside; the nitrogen-discharging and water-draining valve 40 is used to discharge the liquid water discharged from the gas-water separator 30 and the nitrogen in the anode to the outside;

[0055] The outlet of the air compressor 50 is connected to the inlet of the intercooler 60 to provide a set volume of air for the cathode of the fuel cell stack 10;

[0056] The outlet of the intercooler 60 is communicated with the inlet of the bypass valve 80 and the humidifier 70 respectively, and is used to adjust the temperature of the air pressurized by the air compressor 50;

[0057] The outlet of the humidifier 70 is connected to one end of the stop valve 90 for humidifying the air;

[0058] The bypass valve 80 is in communication with the outside. When the bypass valve 80 is in an open state, the air blown out of the intercooler 60 is directly discharged to the outside and does not enter the cathode of the fuel cell stack 10.

[0059] The other end of the stop valve 90 is connected to the cathode and is used to control the amount of air entering the cathode;

[0060] The inlet of the back pressure valve 100 is communicated with the cathode, and the outlet of the back pressure valve 100 is communicated with the outside. The back pressure valve 100 is used to control the pressure of the cathode.

[0061] Such an arrangement not only ensures the simplification of the overall structure of the fuel cell system, but also enables the fuel cell system to start quickly and work reliably afterwards.

[0062] Optionally, when the fuel cell system is in a normal startup mode, the second set pressure difference is set to a range of 20-30 kPa; the nitrogen and water discharge valve 40 is controlled to open and close periodically, the bypass valve 80 is controlled to be in an open state, and the air compressor 50 is controlled to operate at the first speed. This arrangement reduces the hydrogen consumption in the normal startup mode, effectively saves hydrogen, and reduces costs.

[0063] Optionally, when the fuel cell system is started in an empty-air mode, the range of the first set pressure difference is set to 40-60kPa; the nitrogen and water discharge valve 40 is controlled to be in an open state, the bypass valve 80 is controlled to be in an open state, and the air compressor 50 is controlled to run at a second speed; wherein the second speed is greater than the first speed. By setting the range of the first set pressure difference and the nitrogen and water discharge valve 40 in an open state, it is ensured that hydrogen can quickly purge the air in the anode, shortening the duration of the hydrogen-air interface and avoiding the reduction of the service life of the stack 10; and since a large amount of hydrogen introduced will be discharged into the tail gas, the bypass valve 80 is set to be in an open state, and the air compressor 50 is set to run at the second speed, which effectively avoids the problem of excessive hydrogen concentration in the tail gas.

[0064] It is worth noting that in a specific embodiment of the present invention, the electronic control unit of the fuel cell system controls the hydrogen pressure regulating valve 20 through a built-in PID controller to adjust the pressure of hydrogen entering the fuel cell stack 10, thereby ensuring the stability of the hydrogen pressure entering the stack.

[0065] In summary, the present invention provides a fuel cell system startup method and a fuel cell system. The present invention proposes a pressure maintenance determination step and a time determination step, and flexibly selects different startup methods according to the downtime and pressure maintenance conditions. Compared with the existing timed and constant pressure purge method for the anode, the method of the present invention can effectively balance the selection between startup time, hydrogen consumption and stack life, and ensure that the fuel cell system is started in a corresponding appropriate manner under different conditions. Under the premise of ensuring a short startup time, the damage to the service life of the stack is minimized as much as possible; the method of the present invention does not completely rely on monitoring the average cell voltage to determine whether it is empty. Empty start mainly determines whether it is an empty-air start based on the parking time. Therefore, the judgment of empty-air start can be completed before starting, rather than making a judgment during the starting process, which effectively avoids the execution delay of empty-air start caused by the average cell voltage being established too quickly; at the same time, the method of the present invention effectively distinguishes between normal start and empty-air start, and adopts different starting strategies. By setting the first set pressure difference to be greater than the second set pressure difference, the empty-air start method realizes the rapid purge of the anode and reduces the duration of the hydrogen-air interface; by setting the time judgment step to be selectively executed or not, the fuel cell system starting method can complete the startup more quickly in some cases.

[0066] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0067] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0068] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0069] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0070] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fuel cell system startup method, characterized in that: include: Pressure maintenance determination step: determine whether the fuel cell system is performing anode pressure maintenance, and select an empty-air start mode or a normal start mode according to the determination result; Time determination step: obtaining the downtime of the fuel cell system; when the downtime is greater than the set time, adopting the empty start mode; when the downtime is not greater than the set time, adopting the normal start mode; the time determination step can be selectively performed or not performed; Execution steps: When the air-to-air starting method is adopted, the anode of the fuel cell system is purged with hydrogen, and the pressure in the anode of the fuel cell system is controlled to be greater than the pressure in the cathode, and the pressure difference is a first set pressure difference; when the normal starting method is adopted, the anode of the fuel cell system is purged with hydrogen, and the pressure in the anode is controlled to be greater than the pressure in the cathode, and the pressure difference is a second set pressure difference; wherein the first set pressure difference is greater than the second set pressure difference.

2. The fuel cell system startup method according to claim 1, characterized in that: When the fuel cell system is not performing anode pressure maintenance, the time determination step is skipped and the empty-to-air start method in the execution step is performed; when the fuel cell system is already performing anode pressure maintenance, the time determination step is performed.

3. The fuel cell system startup method according to claim 1, characterized in that: The fuel cell system startup method further includes a learning and correction step, wherein the learning and correction step includes: judging whether to correct the set time according to the average cell voltage of the fuel cell system in the execution step; When the average cell voltage is less than the correction voltage threshold, the set time is maintained unchanged; when the average cell voltage is greater than or equal to the correction voltage threshold, a correction value is obtained according to the maximum value of the average cell voltage, and the correction value is subtracted from the set time to obtain a new set time.

4. The fuel cell system startup method according to claim 1, characterized in that: The fuel cell system startup method further includes a voltage determination step, wherein the voltage determination step includes: determining whether the average cell voltage of the fuel cell system is greater than a safety voltage threshold, and selecting the empty startup mode or the normal startup mode according to the determination result; When the average cell voltage is greater than the safety voltage threshold, the empty-to-empty start mode is adopted; when the average cell voltage is less than or equal to the safety voltage threshold, the normal start mode is adopted.

5. The fuel cell system startup method according to claim 1, characterized in that: The fuel cell system starting method also includes a voltage determination step, which includes: selecting the empty-to-air starting method or the normal starting method based on whether the average cell voltage of the fuel cell system is greater than a safety voltage threshold; wherein the pressure maintenance determination step, the time determination step and the voltage determination step are performed in sequence to select the empty-to-air starting method or the normal starting method.

6. The fuel cell system startup method according to claim 5, characterized in that: First, the pressure maintenance determination step is executed. When the fuel cell system is not performing anode pressure maintenance, it is determined that the empty-to-air start mode is adopted, and the time determination step and the voltage determination step are skipped to perform the empty-to-air start mode in the execution step; when the fuel cell system has been performing anode pressure maintenance, the time determination step is executed; when the downtime is greater than the set time, it is determined that the empty-to-air start mode is adopted, and the voltage determination step is directly skipped to perform the empty-to-air start mode in the execution step; when the downtime is not greater than the set time, the voltage determination step is executed; in the voltage determination step, when the average cell voltage is greater than the safety voltage threshold, it is determined that the empty-to-air start mode is adopted, and the empty-to-air start mode in the execution step is performed; when the average cell voltage is less than or equal to the safety voltage threshold, it is determined that the normal start mode is adopted, and the normal start mode in the execution step is performed.

7. The fuel cell system startup method according to claim 1, characterized in that: When the fuel cell system performs the empty-to-air start-up mode, the first set pressure difference is set in the range of 40-60 kPa; when the fuel cell system performs the normal start-up mode, the second set pressure difference is set in the range of 20-30 kPa.

8. A fuel cell system, characterized in that: The fuel cell system applies the fuel cell system startup method according to any one of claims 1 to 7; the fuel cell system includes a real-time clock, and the real-time clock is used to record the downtime of the fuel cell system.

9. The fuel cell system according to claim 8, characterized in that: The fuel cell system further comprises: a fuel cell stack (10), a hydrogen pressure regulating valve (20), a gas-water separator (30), a nitrogen and water discharge valve (40), an air compressor (50), an intercooler (60), a humidifier (70), a bypass valve (80), a stop valve (90) and a back pressure valve (100); the hydrogen pressure regulating valve (20) is communicated with the anode inlet of the fuel cell stack (10) and is used to regulate the pressure of hydrogen entering the anode; the gas-water separator (30) is communicated with the anode outlet of the fuel cell stack (10) and is used to separate the gas and liquid water discharged from the anode outlet; one end of the nitrogen and water discharge valve (40) is communicated with the gas-water separator (30) and the other end is communicated with the outside; the nitrogen and water discharge valve (40) is used to discharge the liquid water discharged from the gas-water separator (30) and the nitrogen in the anode to the outside; the outlet of the air compressor (50) is communicated with the intercooler (60) ) is connected to the inlet of the intercooler (60) for providing a set volume of air to the cathode of the battery stack (10); the outlet of the intercooler (60) is respectively connected to the inlet of the bypass valve (80) and the humidifier (70) for adjusting the temperature of the air after the air compressor (50) is pressurized; the outlet of the humidifier (70) is connected to one end of the stop valve (90) for humidifying the air; the bypass valve (80) is connected to the outside, and when the bypass valve (80) is in an open state, the air blown out by the intercooler (60) is directly discharged to the outside and does not enter the cathode of the battery stack (10); the other end of the stop valve (90) is connected to the cathode for controlling the amount of air entering the cathode; the inlet of the back pressure valve (100) is connected to the cathode, and the outlet of the back pressure valve (100) is connected to the outside, and the back pressure valve (100) is used to control the pressure of the cathode.

10. The fuel cell system according to claim 9, characterized in that: When the fuel cell system is in the normal startup mode, the second set pressure difference is set to a range of 20-30 kPa; the nitrogen and water discharge valve (40) is controlled to open and close periodically, the bypass valve (80) is controlled to be in an open state, and the air compressor (50) is controlled to operate at a first speed; When the fuel cell system performs the air-to-air start mode, the first set pressure difference is set in the range of 40-60 kPa; the nitrogen and water discharge valve (40) is controlled to be in an open state, the bypass valve (80) is controlled to be in an open state, and the air compressor (50) is controlled to operate at a second speed; wherein the second speed is greater than the first speed.

Images