Internal and external pressure difference balancing method of fuel cell system and fuel cell system

Abstract

The embodiment of the invention provides an internal and external pressure difference balancing method of a fuel cell system and the fuel cell system. The method comprises the following steps: when the fuel cell system is shut down, controlling a cathode cavity and an anode cavity of the fuel cell system to be communicated; then acquiring the system temperature when the fuel cell system is shut down, the relative humidity of the cathode cavity and the anode cavity, the environment pressure and the environment temperature to determine a target pressure value; and then hydrogen in an anode hydrogen inlet pipeline is controlled to be conveyed to the anode cavity till the cavity pressure of the cathode cavity and the cavity pressure of the anode cavity are both matched with the target pressure value. And the anode hydrogen inlet pipeline is communicated with the anode cavity. The method can effectively prevent the formation of a hydrogen-air interface and prolong the life of a galvanic pile.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell, and particularly relates to a method for balancing internal and external pressure difference of a fuel cell system and the fuel cell system. BACKGROUND

[0002] When air (containing oxygen) exists in the cathode cavity and the anode cavity of the fuel cell stack, a hydrogen-air interface is generated when the fuel cell stack is started, which causes the anode potential and the cathode potential to rise and causes start-up corrosion. Therefore, what needs to be done to prevent the hydrogen-air interface is to avoid oxygen residue in the cavity after shutdown and to avoid air from the outside escaping into the cavity after shutdown.

[0003] At present, the prior art mainly adopts an oxygen-consuming shutdown strategy, that is, before the system is shut down, excess hydrogen is introduced into the anode cavity to accelerate the consumption of residual oxygen in the anode cavity, so as to avoid oxygen residue after shutdown.

[0004] However, this way of the prior art is prone to cause imbalance between the cathode cavity and the anode cavity and the external environment pressure, form internal and external pressure difference, and cause the sealing performance to decrease. SUMMARY

[0005] The method for balancing internal and external pressure difference of the fuel cell system and the fuel cell system provided by the present application are used to balance the pressure in the cathode cavity and the anode cavity and the external environment pressure, prevent the sealing performance of the cathode cavity and the anode cavity from decreasing, and achieve the effect of preventing the hydrogen-air interface.

[0006] In a first aspect, the present application provides a method for balancing internal and external pressure difference of a fuel cell system, comprising:

[0007] When the fuel cell system is shut down, the cathode cavity and the anode cavity of the fuel cell system are controlled to be communicated;

[0008] The system temperature when the fuel cell system is shut down, the relative humidity of the cathode cavity and the anode cavity, the environment pressure and the environment temperature of the fuel cell system are acquired;

[0009] Based on the system temperature, the relative humidity, the environment pressure and the environment temperature, a target pressure value is determined;

[0010] The hydrogen in the anode hydrogen gas inlet pipeline is controlled to be delivered to the anode cavity until the cavity pressure of the cathode cavity and the anode cavity is matched with the target pressure value; wherein the anode hydrogen gas inlet pipeline is communicated with the anode cavity.

[0011] In a possible implementation, the anode cavity is connected with an anode hydrogen gas outlet pipeline, the anode hydrogen gas outlet pipeline is connected with a water outlet pipeline through a drain valve, and the water outlet pipeline is communicated with the stack cathode pipeline of the cathode cavity.

[0012] In one possible implementation, controlling the cathode cavity and anode cavity of the fuel cell system to be in communication includes:

[0013] When the fuel cell system is shut down, the drain valve is opened to allow the anode cavity to communicate with the cathode cavity through the anode hydrogen outlet pipeline, the drain valve, the water outlet pipeline, and the stack cathode pipeline.

[0014] In one possible implementation, the hydrogen in the controlled anode hydrogen inlet pipeline is delivered to the anode cavity until the cavity pressures of both the cathode cavity and the anode cavity match the target pressure value, including:

[0015] The target duration is determined based on the volume of the cathode cavity, the volume of the anode cavity, and the valve diameter of the drain valve.

[0016] When the continuous opening duration of the drain valve is greater than or equal to the target duration, the first pressure value collected by the first pressure sensor installed in the anode cavity and the second pressure value collected by the second sensor installed in the cathode cavity are obtained.

[0017] If the difference between the first pressure value and the second pressure value is less than or equal to a preset threshold and matches the target pressure value, then the drain valve is controlled to close; wherein, when the drain valve is closed, the cathode cavity and the anode cavity are mutually disconnected.

[0018] In one possible implementation, a vapor-water separator is connected between the anode hydrogen outlet pipeline and the drain valve, the vapor-water separator including a water storage box and a liquid level sensor; the method further includes:

[0019] When the fuel cell system is working normally, the liquid level value obtained by the liquid level sensor in detecting the liquid level of the water storage box is acquired.

[0020] The drain valve is controlled to remain open for a specified duration to discharge liquid water from the water storage box to the cathode pipeline of the fuel cell stack.

[0021] In one possible implementation, determining the target pressure value based on the system temperature, the relative humidity, the ambient pressure, and the ambient temperature includes:

[0022] Based on the system temperature, the relative humidity, and the first correspondence, the initial water vapor partial pressure is determined;

[0023] Based on the aforementioned ambient temperature and the second correspondence table, the final water vapor partial pressure is determined;

[0024] The target pressure value is determined based on the ambient pressure, the initial water vapor partial pressure, and the final water vapor partial pressure.

[0025] In one possible implementation, before the hydrogen in the controlled anode hydrogen inlet line is delivered to the anode cavity, the method further includes:

[0026] Obtain the cathode chamber pressure and / or anode chamber pressure;

[0027] If the target pressure value is less than the cathode cavity pressure and / or the anode cavity pressure, then the supply of hydrogen to the anode cavity through the anode hydrogen inlet pipeline shall be stopped.

[0028] In one possible implementation, the anode cavity and / or the cathode cavity are equipped with a hydrogen concentration sensor; the method further includes:

[0029] When the fuel cell system is shut down, the hydrogen concentration changes in the anode cavity and / or the cathode cavity are monitored by the hydrogen concentration sensor.

[0030] Based on the hydrogen concentration change, determine the time required for the hydrogen concentration in the anode cavity and / or the cathode cavity to decrease to zero;

[0031] Based on the required duration, the protection duration of the hydrogen-air interface of the fuel cell system is determined.

[0032] Secondly, embodiments of this application provide a fuel cell system, including:

[0033] The hydrogen supply system is used to deliver hydrogen to the anode chamber through the anode hydrogen inlet line when the fuel cell system is operating normally.

[0034] The anode hydrogen outlet pipeline is connected to the anode cavity and is used to discharge the liquid water inside the anode cavity;

[0035] A control pipeline, connecting the anode cavity and the cathode cavity, is used to control the connection or disconnection between the anode cavity and the cathode cavity;

[0036] The hydrogen supply system is also used to deliver hydrogen to the anode cavity and the cathode cavity when the fuel cell system is shut down and the anode cavity and the cathode cavity are connected, until the cavity pressure of the cathode cavity and the anode cavity are both matched with the target pressure value.

[0037] The fuel cell system and the internal and external pressure difference balancing method provided in this application embodiment, after the fuel cell system is shut down, connect the anode and cathode cavities and continue to supply hydrogen to the anode cavity by controlling the hydrogen supply system until it matches the target pressure value. This can balance the pressure of the anode and cathode cavities with atmospheric pressure, significantly reduce the risk of sealing failure caused by pressure difference, thereby preventing outside air from entering the anode and cathode cavities, effectively suppressing the formation of hydrogen-air interface, and extending the stack life. Attached Figure Description

[0038] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0039] Figure 1 This is a schematic diagram of the structure of a fuel cell system provided in an embodiment of this application;

[0040] Figure 2 A schematic diagram of the internal and external pressure difference balancing method for the fuel cell system provided in this application;

[0041] Figure 3 A flowchart of the anode and cathode cavity conduction and cutoff control method provided in the embodiments of this application;

[0042] Figure 4 This is a schematic diagram of the hydrogen-air interface protection duration detection process provided in an embodiment of this application;

[0043] Figure 5 This is a schematic diagram of the controller structure provided in this application.

[0044] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0045] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0046] Fuel cell systems are widely used in new energy vehicles (such as hydrogen fuel cell buses and logistics vehicles), distributed power generation equipment, and aerospace propulsion systems. In actual operation, fuel cell stacks frequently undergo start-up and shutdown processes (e.g., frequent start-ups and shutdowns during rush hour on city buses). During shutdown, uneven distribution of hydrogen and air (including oxygen) within the stack, coupled with insufficient system sealing, easily leads to the formation of a hydrogen-air interface. This hydrogen-air interface not only causes abnormal increases in anode and cathode potentials but also accelerates the corrosion of the membrane electrode catalyst, significantly shortening stack life and reducing overall system efficiency. Furthermore, in low-temperature or high-humidity environments, the condensation and partial pressure changes of water vapor further exacerbate the risk of hydrogen-air interface formation, placing higher demands on the reliability and durability of fuel cell systems.

[0047] The specific reasons for the formation of the hydrogen-air interface are as follows: When the fuel cell stack is shut down for a period of time, air (containing oxygen) diffuses back into the anode cavity and anode flow channel of the stack through the seals or air ducts. During the startup process of the fuel cell stack, hydrogen enters the stack, causing hydrogen to meet with oxygen in the air at the anode. This inevitably creates a hydrogen-air interface, leading to an increase in anode potential and corrosion of the membrane electrode catalyst.

[0048] For fuel cell systems with a hydrogen-air interface, relevant technologies provide methods for preventing and monitoring the hydrogen-air interface, as detailed below:

[0049] (1) The main method for monitoring the hydrogen-air interface is to install an oxygen concentration sensor in the anode or cathode cavity. The presence of the hydrogen-air interface is monitored by the oxygen concentration sensor each time the machine is started. However, the oxygen concentration sensor has problems such as easy drift, inaccurate measurement, difficult installation, and difficult operation.

[0050] (2) Regarding the prevention methods for the hydrogen-air interface, considering that in practical applications, due to the permeability of the proton exchange membrane, as long as oxygen is present in both the hydrogen and air cavities, it will eventually diffuse evenly into the anode and cathode cavities, the main measures to prevent the hydrogen-air interface are to avoid the presence of residual oxygen in the cavities after shutdown and to prevent outside air from escaping into the cavities after shutdown. The specific measures are as follows:

[0051] ① Regarding how to avoid oxygen residue after shutdown: Since excessive hydrogen is usually introduced into the anode chamber after shutdown in order to continue to consume the residual oxygen in the anode chamber, there will be no oxygen residue in the anode chamber in the early stage of shutdown. Even if there is a trace amount of oxygen, it will not reach the catalyst layer to form a hydrogen-air interface.

[0052] ② Regarding the prevention of outside air ingress, oxygen mainly enters the anode and cathode chambers through leaks in the sealing system. Under normal system sealing design and process quality, the pressure difference between the chambers and the external atmospheric pressure becomes the driving force for gas diffusion after shutdown. When the internal and external pressure difference is zero, the valve control achieves the highest sealing performance, and the diffusion rate of outside air into the chambers is the lowest. Therefore, after shutdown and when the system temperature drops to ambient temperature, balancing the pressure in the anode and cathode chambers with the external ambient pressure is one of the main methods to reduce outside air ingress. However, due to factors such as the pressure difference between the anode and cathode upon shutdown (the gas in the anode and cathode does not have enough time to diffuse evenly), the large volume difference between the anode and cathode chambers, and temperature changes altering the partial pressure of water vapor, the pressure balance between the anode and cathode chambers and atmospheric pressure is poor after the fuel cell system cools down and the gas diffuses evenly.

[0053] Based on the problem that traditional methods for preventing hydrogen-air interfaces cannot effectively balance the pressure inside the anode and cathode cavities with atmospheric pressure, this application provides a method for balancing the internal and external pressure differences of a fuel cell system and a fuel cell system. When the fuel cell system is shut down, by controlling the connection between the cathode cavity and the anode cavity of the fuel cell system and by controlling the amount of hydrogen delivered to the anode cavity, the cavity pressures of both the cathode and anode cavities are kept to match the target pressure value. In this way, the pressure inside the anode and cathode cavities can be balanced with atmospheric pressure to prevent hydrogen-air interfaces.

[0054] The target pressure value is determined based on system temperature, relative humidity, ambient pressure, and ambient temperature.

[0055] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0056] Figure 1 This is a schematic diagram of the structure of the fuel cell system provided in the embodiments of this application, such as... Figure 1 As shown, on the anode side, the hydrogen supply system is connected to the anode cavity via an anode hydrogen inlet pipe, which is equipped with an ejector and related valves. At the other end of the anode cavity is an anode hydrogen outlet pipe, which is connected to the anode cavity and used to drain the liquid water from the anode cavity.

[0057] The ejector is used to automatically recover and recycle the residual hydrogen that has not been reacted at the anode by utilizing the energy of high-pressure hydrogen.

[0058] The cathode side of the fuel cell system is equipped with components such as an air filter, flow meter, air compressor, intercooler, bypass valve, on / off valve, humidifier, back pressure valve, and silencer.

[0059] Among them, the air filter, flow meter and intercooler belong to the cathode air subsystem and are used to filter, meter and cool the air (containing oxygen) entering the cathode of the fuel cell stack.

[0060] Additionally, a humidifier is used to humidify the cathode air. A back pressure valve is used to control the cathode exhaust back pressure, optimizing stack performance.

[0061] To achieve pressure balance between the anode and cathode chambers in the fuel cell system and the external environment, and to prevent outside air from entering the anode and cathode chambers due to pressure differences after the fuel cell system shuts down, the anode and cathode chambers can be connected via control lines after shutdown. Simultaneously, hydrogen supply systems continue to deliver hydrogen to both chambers until the pressure in both chambers matches the target pressure value.

[0062] The target pressure value can be the external atmospheric pressure or it can be calculated based on various environmental factors in the actual working environment.

[0063] Furthermore, in some embodiments, reference continues to be made to the above. Figure 1 The control piping mentioned above may include a steam-water separator, a drain valve, and a water outlet pipe. The anode chamber is connected to the steam-water separator through the anode chamber gas outlet pipe, the steam-water separator is connected to the water outlet pipe through the drain valve, and the water outlet pipe is connected to the cathode stack cathode piping of the cathode chamber.

[0064] The gas-water separator is used to separate the residual hydrogen and liquid water in the anode chamber. The separated liquid water is discharged through the cathode pipeline of the fuel cell stack after passing through the drain valve and the outlet pipe. This not only enables the connection between the cathode chamber and the anode chamber, but also enables the discharge of liquid water. Moreover, it only requires minimal modification to the original fuel cell system piping structure (i.e., just connect the outlet pipe connected to the drain valve to the cathode pipeline of the fuel cell stack), making the modification cost very low and the modification convenient.

[0065] When the drain valve is activated, the liquid water in the steam-water separator will first be slowly discharged through the water outlet pipe and the cathode pipe of the fuel cell stack. As the liquid level in the steam-water separator continues to drop, the anode cavity will eventually be connected to the cathode cavity through the anode hydrogen outlet pipe, the steam-water separator, the drain valve, the water outlet pipe and the cathode pipe of the fuel cell stack.

[0066] Figure 2 This is a schematic diagram of the internal and external pressure difference balancing method for a fuel cell system provided in this application. This method can be applied to fuel cell systems. Taking the fuel cell system as the implementing entity as an example, such as... Figure 2 As shown, the method includes:

[0067] Step 210: When the fuel cell system is shut down, control the connection between the cathode cavity and the anode cavity of the fuel cell system.

[0068] Step 220: Obtain the system temperature, relative humidity of the cathode cavity and anode cavity, ambient pressure and ambient temperature when the fuel cell system is shut down.

[0069] Step 230: Determine the target pressure value based on system temperature, relative humidity, ambient pressure, and ambient temperature.

[0070] Step 240: Control the delivery of hydrogen from the anode hydrogen inlet pipeline to the anode cavity until the pressure in both the cathode and anode cavities matches the target pressure value. The anode hydrogen inlet pipeline is connected to the anode cavity.

[0071] In actual operation of a fuel cell system, the fuel cell stack needs to undergo frequent start-up and shutdown processes. When the fuel cell stack starts up and the fuel cell system is working normally, it consumes hydrogen in the anode chamber and oxygen in the cathode chamber. When the fuel cell stack shuts down, in order to prevent hydrogen-air interface, all the oxygen in the anode and cathode chambers needs to be consumed, and it is necessary to prevent outside air (containing oxygen) from escaping into the anode and cathode chambers.

[0072] Regarding step 210 above, the anode cavity and the cathode cavity can be connected via a control pipeline, and the control pipeline can be equipped with the aforementioned... Figure 1 The drain valve in the middle enables communication between the anode chamber and the cathode chamber when the drain valve is opened.

[0073] In particular, after the anode cavity and the cathode cavity are connected for a period of time, the cavity pressure of the anode cavity and the cavity pressure of the cathode cavity gradually approach the same level.

[0074] In addition, when the fuel cell stack is shut down, in order to prevent the presence of oxygen in the anode and cathode chambers from causing a hydrogen-air interface after the fuel cell stack is restarted, the hydrogen supply system needs to continue supplying hydrogen to the anode chamber for a period of time to consume the residual oxygen in the anode and cathode chambers.

[0075] Regarding step 220 above, the system temperature refers to the current fuel cell stack temperature, which can be obtained through a temperature sensor. The relative humidity refers to the relative humidity in the anode and cathode chambers after oxygen consumption. This relative humidity can be obtained by installing humidity sensors in both chambers.

[0076] The relative humidity value is related to the shutdown purging strategy. It can be determined by comparing the difference between the actual humidity and the target humidity in the two chambers after the fuel cell system is cooled to ambient temperature, and then adjusting the difference to obtain the adjusted value as the relative humidity.

[0077] Among them, the shutdown purging strategy refers to a series of programmed operations performed when the fuel cell system is shut down (i.e., turned off). Its main purpose is to manage the state inside the stack after shutdown: (1) remove liquid water and supersaturated water vapor from the stack membrane electrode and gas flow channels; (2) remove residual gas from the two chambers.

[0078] Additionally, ambient pressure can refer to the atmospheric pressure of the environment in which the fuel cell system operates, which can be collected by a pressure sensor installed in the environment where the fuel cell system is located. Ambient temperature can refer to the temperature of the environment in which the fuel cell system operates, which can be collected by a temperature sensor installed in the environment where the fuel cell system is located.

[0079] The purpose of calculating the target pressure value in steps 230 and 240 above is to ensure that the pressure in both the anode and cathode chambers equals atmospheric pressure when the fuel cell system is shut down and the stack temperature drops to atmospheric temperature.

[0080] The pressure in both the cathode and anode chambers is matched with the target pressure value. This can mean that the pressure in both chambers is equal to the target pressure value, or that the difference between the pressure and the target pressure value is within a threshold range.

[0081] In this embodiment, after the fuel cell system is shut down and the oxygen consumption operation of the anode and cathode chambers is completed, the oxygen consumption will cause the chamber pressure in the anode and cathode chambers to be less than or equal to the atmospheric pressure of the external environment. This may result in the possibility of outside air diffusing into the anode and cathode chambers.

[0082] By balancing the pressure in the two chambers and controlling the pressure of the anode and cathode chambers connected during hydrogen supply to match the target pressure value, the pressure in the anode and cathode chambers is increased, making the pressure in the anode and cathode chambers close to or equal to atmospheric pressure. This prevents outside air from diffusing into the anode and cathode chambers due to the pressure difference after shutdown, thus avoiding the occurrence of a hydrogen-air interface during subsequent startup.

[0083] The internal and external pressure difference balancing method for a fuel cell system provided in this application embodiment can achieve precise pressure balance between the anode and cathode chambers and atmospheric pressure by connecting the two chambers after the fuel cell system is shut down and continuing to control the hydrogen supply system to supply hydrogen to the anode chamber. This significantly reduces the risk of sealing failure caused by pressure difference, prevents outside air from diffusing into the anode and cathode chambers, effectively suppresses the formation of hydrogen-air interface, and extends the life of the fuel cell stack.

[0084] Furthermore, in some embodiments, the target pressure value can be calculated through the following steps:

[0085] Step 11: Determine the initial water vapor partial pressure based on system temperature, relative humidity, and the first correspondence;

[0086] Step 12: Determine the final water vapor partial pressure based on the ambient temperature and the second correspondence table;

[0087] Step 13: Determine the target pressure value based on the ambient pressure, initial water vapor partial pressure, and final water vapor partial pressure.

[0088] In this embodiment, the ambient temperature sensor value can be collected when the fuel cell system stops consuming oxygen and the load is disconnected, and this value can be used as the ambient temperature T1. Simultaneously, the average value of the inlet and outlet water temperatures at the same time can be collected and used as the system temperature T2.

[0089] Regarding step 11 above, the first correspondence can be in tabular form, i.e., a data correspondence table. For example, the first correspondence could be a table of temperature and saturated water vapor pressure, which can be generated based on water vapor property data.

[0090] Based on the system temperature T2, the saturated vapor pressure P_sat(T2) can be found in the table corresponding to temperature and saturated vapor pressure. Then, the initial partial pressure of water vapor P_H2O1 is calculated using the following formula:

[0091] P_H2O1=P_sat(T2)*H

[0092] In the above formula, H represents relative humidity.

[0093] Regarding step 12 above, the second correspondence can also be the temperature-saturated water vapor pressure correspondence table mentioned above. By using the ambient temperature T1, the water vapor pressure P_H2O2 corresponding to the ambient temperature can be found in the temperature-saturated water vapor pressure correspondence table, which is used as the final water vapor partial pressure.

[0094] Regarding step 13 above, the formula for calculating the target pressure is as follows:

[0095] - +

[0096] In the above formula, Indicates the target pressure value; The pressure represents the expected pressure when the fuel cell system cools down to ambient temperature. It is considered as the current ambient atmospheric pressure and can be obtained by a sensor that collects the ambient atmospheric pressure of the system. P_H2O1 represents the initial water vapor partial pressure, and P_H2O2 represents the final water vapor partial pressure.

[0097] In this embodiment, the effects of system temperature, relative humidity, and ambient temperature on water vapor partial pressure are dynamically calculated using a formula algorithm. Based on ambient pressure, initial water vapor partial pressure, and final water vapor partial pressure, the effect of temperature change on the water vapor partial pressure in the cavity can be accurately calculated, ensuring that the calculated target pressure value is more consistent with atmospheric pressure, thereby achieving effective balance between internal and external pressures. Furthermore, the calculation process is simple and convenient.

[0098] Furthermore, in some embodiments, after calculating the target pressure value, the target pressure value can be compared with the pressure in both chambers to determine if any abnormalities have occurred. The specific processing steps are as follows:

[0099] Step 21: Obtain the cathode chamber pressure and / or anode chamber pressure;

[0100] Step 22: If the target pressure value is less than the cathode cavity pressure and / or the anode cavity pressure, stop supplying hydrogen to the anode cavity through the anode hydrogen inlet pipeline.

[0101] In this embodiment, since oxygen consumption is performed on both the cathode and anode chambers after the fuel cell system is shut down to prevent the presence of oxygen in the chambers and the hydrogen-air interface from occurring during subsequent startup, the pressure in the cathode chamber and the anode chamber is generally lower than the target pressure value.

[0102] If the pressure in the cathode cavity and / or the anode cavity exceeds the target pressure value, the supply of hydrogen to the anode cavity through the anode hydrogen inlet pipeline must be stopped.

[0103] When the cathode cavity pressure and / or anode cavity pressure is found to be greater than the target pressure value, corresponding operations can be performed depending on the situation:

[0104] In scenario (1), if the fuel cell system continues to shut down until ambient temperature, and the chamber pressure is lower than atmospheric pressure, it indicates that the oxygen consumption during shutdown was insufficient. After the oxygen consumption ends and the load is disconnected, there is still a large amount of oxygen in the chamber, which continues to react with hydrogen to produce water after the load is disconnected. In this case, the oxygen consumption shutdown strategy needs to be checked.

[0105] In case (2), if the cavity pressure is still higher than atmospheric pressure after the system continues to shut down to ambient temperature, it means that the cavity pressure P0 was already very high after the oxygen consumption during shutdown. In this case, the cavity needs to obtain a higher initial pressure (equal to P0 + oxygen partial pressure consumed during shutdown) after the air inlet and outlet valves are closed. The premise of this case is that the cavity pressure is relatively high during shutdown purging, but high cavity pressure is not conducive to rapid purging. In practice, this situation generally does not occur.

[0106] This application embodiment uses pressure comparison to stop supplying hydrogen to the anode cavity when the calculated target pressure value is less than the cathode cavity pressure and / or anode cavity pressure. This can avoid excessively high pressure in both the anode and cathode cavities and ineffective hydrogen supply.

[0107] The following section describes the internal and external pressure difference balancing process of the entire fuel cell system, taking into account its piping structure.

[0108] In some embodiments, in order to achieve communication between the anode cavity and the cathode cavity, the anode hydrogen gas outlet pipe can be connected to a drain valve, and then the water outlet pipe can be connected through the drain valve. At the same time, the water outlet pipe is directly connected to the cathode pipeline of the cathode cavity.

[0109] In traditional fuel cell systems, the outlet pipe in the anode circulation pipeline is usually directly connected to the tailpipe, which makes it impossible to achieve communication between the anode cavity and the cathode cavity.

[0110] In this embodiment, the water outlet pipe that was originally connected to the tail drain is connected to the fuel cell stack air outlet pipe (i.e., the fuel cell stack cathode pipe). This allows for the connection between the anode chamber and the cathode chamber with minimal modification cost.

[0111] In this embodiment, the connection between the anode cavity and the cathode cavity is achieved by using a water outlet pipe, so that hydrogen can be injected into the cathode cavity at the same time as the anode cavity, without the need to add additional valves and pipelines. Moreover, it can achieve the connection between the anode and cathode cavities while ensuring the original drainage function, significantly reducing the modification cost.

[0112] Furthermore, in some embodiments, the connection between the anode cavity and the cathode cavity can be controlled by the following steps: when the fuel cell system is shut down, the drain valve is opened so that the anode cavity is connected to the cathode cavity through the anode hydrogen outlet pipeline, the drain valve, the water outlet pipeline and the stack cathode pipeline.

[0113] In this embodiment, when the drain valve is opened, the liquid water in the anode cavity can flow through the drain valve and the outlet pipe, and then be discharged from the cathode pipe of the fuel cell stack. After the liquid water in the anode cavity is discharged, the hydrogen gas outlet pipe from the anode to the drain valve, the outlet pipe, and the cathode pipe of the fuel cell stack are all open, thereby realizing the connection between the anode cavity and the cathode cavity.

[0114] In this embodiment, by directly using a drain valve to control the connection or disconnection between the anode and cathode chambers, the modification cost can be reduced, and the pressure balance between the anode and cathode chambers and the external pressure can be achieved with minimal modification cost.

[0115] Furthermore, in some embodiments, Figure 3A flowchart of the anode and cathode cavity conduction and cutoff control method provided in the embodiments of this application is shown below. Figure 3 As shown, it includes the following steps:

[0116] Step 310: When the fuel cell system is shut down, control the drain valve to open so that the anode cavity is connected to the cathode cavity through the anode hydrogen outlet pipeline, drain valve, water outlet pipeline and stack cathode pipeline.

[0117] Step 320: Determine the target duration based on the volume of the cathode cavity, the volume of the anode cavity, and the valve diameter of the drain valve;

[0118] Step 330: When the continuous opening duration of the drain valve is greater than or equal to the target duration, acquire the first pressure value collected by the first pressure sensor installed in the anode cavity and the second pressure value collected by the second sensor installed in the cathode cavity.

[0119] Step 340: If the difference between the first pressure value and the second pressure value is less than or equal to the preset threshold and matches the target pressure value, then control the drain valve to close.

[0120] When the drain valve is closed, the cathode cavity and the anode cavity are disconnected from each other.

[0121] Regarding step 310 above, when the fuel cell system is shut down and oxygen consumption is complete (for example, when the voltage is detected to have dropped to a very small lower threshold), the drain valve is opened to connect the anode and cathode chambers.

[0122] Regarding step 320 above, the target duration is related to the volume of the cathode cavity, the volume of the anode cavity, and the diameter of the drain valve. For example, the larger the volume of the cathode cavity and the anode cavity, and the smaller the diameter of the drain valve, the longer the target duration will be.

[0123] In addition, the target duration can be determined by observing the changes in the readings of the pressure sensors in the two chambers after the drain valve is opened. That is, the time is taken as the target duration when the drain valve is opened and the time until the pressure in the two chambers is completely balanced.

[0124] Regarding steps 330 and 340 above, during the opening of the drain valve, the hydrogen in the anode hydrogen inlet pipe can be controlled to continue to be delivered to the anode cavity. At this time, due to the injection of hydrogen, the cavity pressure of the anode cavity and cathode cavity will slowly increase. When the pressure of the anode and cathode cavities is balanced and the target pressure value is reached, the drain valve is controlled to close. At this time, the cathode cavity and anode cavity are cut off from each other, and the hydrogen in the anode cavity is no longer injected into the cathode cavity.

[0125] In this embodiment, the opening of the drain valve enables communication between the cathode and anode chambers, allowing hydrogen gas from the anode chamber to enter the cathode chamber. This achieves equal pressure in both chambers and balances the pressure with the external environment. Furthermore, the drain valve retains its original drainage function, ensuring pressure balance is achieved with minimal modification costs.

[0126] Further, please refer to the above. Figure 1 In some embodiments, as described above Figure 1 Taking the drain valve as an example, a vapor-water separator is connected between the anode hydrogen outlet pipeline and the drain valve. The vapor-water separator includes a water storage box and a liquid level sensor.

[0127] The water storage box is used to store the liquid water discharged from the anode cavity, while the liquid level sensor is used to measure the liquid level of the liquid water stored in the water storage box.

[0128] In this embodiment, when the fuel cell stack is started and the fuel cell system is working normally, the liquid level value obtained by the liquid level sensor from the liquid level detection of the water storage box can be obtained. When the liquid level value reaches the preset upper limit liquid level, the drain valve is controlled to be continuously opened for a calibration time to discharge the liquid water in the water storage box to the stack cathode pipeline.

[0129] In this embodiment, since the outlet pipe of the anode cavity is connected to the cathode pipeline of the fuel cell stack, in order to prevent hydrogen gas in the anode cavity from rushing into the cathode cavity during the drainage process, it is necessary to control the opening time of the drain valve.

[0130] During the drainage process, the liquid water in the gas-water separator is discharged first, while the residual hydrogen gas is at risk of being discharged only after the liquid water has been drained. Therefore, a calibration time needs to be set to prevent residual hydrogen gas from being discharged into the cathode piping of the fuel cell stack.

[0131] The calibration duration must ensure that, during normal operation of the fuel cell system, only water is drained into the cathode line of the fuel cell stack, and no hydrogen is discharged. For example, this calibration duration can be determined based on the drain valve diameter and liquid level.

[0132] In this embodiment of the application, by setting the calibration time, the drain valve can achieve communication between the anode cavity and the cathode cavity, while also retaining the drain valve's draining function. This ensures that the drain valve can complete the draining normally when the fuel cell system is working normally, and prevents hydrogen from entering the cathode cavity through the stack cathode pipeline.

[0133] Furthermore, in some embodiments, after the internal and external pressure differential of the fuel cell system is balanced, hydrogen concentration sensors can be installed in the anode cavity and / or cathode cavity. By sensing the hydrogen consumption time through these sensors, the preventive effect of this solution on the hydrogen-air interface can be quantified. Specifically, Figure 4 This is a schematic diagram of the hydrogen-air interface protection duration detection process provided in the embodiments of this application, as shown below. Figure 4 As shown, it includes the following steps:

[0134] Step 410: After the fuel cell system is shut down, monitor the changes in hydrogen concentration in the anode cavity and / or cathode cavity using a hydrogen concentration sensor;

[0135] Step 420: Based on the change in hydrogen concentration, determine the time required for the hydrogen concentration in the anode cavity and / or cathode cavity to decrease to zero;

[0136] Step 430: Determine the protection duration of the hydrogen-air interface of the fuel cell system based on the required duration.

[0137] In this embodiment, the readings of the hydrogen concentration sensor are not considered during normal operation of the fuel cell system. The changes in hydrogen concentration in the chambers (cathode chamber and anode chamber) are only considered after the fuel cell system is shut down. The purpose is to detect the hydrogen concentration in the mixed gas after the gas components in the two chambers have fully diffused through the proton exchange membrane after a long shutdown.

[0138] Specifically, after the fuel cell system shuts down and an oxygen-consuming shutdown strategy is adopted, nitrogen, hydrogen, and water vapor will generally be present in the anode and cathode cavities (since oxygen-consuming shutdown cannot be 100% achieved and there is an error, trace amounts of oxygen will still remain in the cavity. These oxygens will continue to react with hydrogen after shutdown, so their amount can be ignored), and they are evenly distributed in the anode and cathode cavities through the proton exchange membrane.

[0139] As outside air continuously seeps into the cavity, the oxygen inside reacts with the hydrogen in the cavity to form water under the action of a catalyst. Only when the hydrogen in the cavity is exhausted does oxygen begin to accumulate. The moment when the hydrogen concentration in the cavity drops to 0 is the moment when oxygen begins to accumulate. At this point, the hydrogen-air interface will occur when the machine is turned on.

[0140] The severity of the hydrogen-air interface's impact depends on the cumulative oxygen concentration (an oxygen concentration sensor can be added to the system to assess its severity). During the period from shutdown until the hydrogen concentration drops to zero, due to active hydrogen protection, even if air seeps into the cavity, a hydrogen-air interface will not occur upon startup. This period can be considered the effective protection duration, and changes in hydrogen concentration during this time can reflect the entry of external oxygen.

[0141] In this embodiment, the effective protection duration of the hydrogen-air interface comprehensively reflects indicators such as the airtightness of the fuel cell system. The longer the effective protection duration, the more difficult it is for outside air to enter the anode and cathode cavities, and the better the airtightness.

[0142] In this embodiment, by installing a hydrogen concentration sensor in the cathode cavity or anode cavity pipeline, the protection time from the shutdown of the fuel cell system to the hydrogen concentration in the cavity dropping to 0 can be detected. This can be used to determine when the fuel cell system will generate a hydrogen-air interface upon startup, and to evaluate the effective duration of preventing the hydrogen-air interface. This method has the characteristics of high accuracy, good economy, and easy operation, and can realize feedback adjustment to optimize the strategy for preventing the hydrogen-air interface.

[0143] The present solution will be described in detail below through a complete embodiment.

[0144] Refer to the above Figure 1 In order to balance the internal and external pressure difference after the fuel cell system is shut down with minimal modification cost, and to evaluate the effect of preventing hydrogen-air interface, the drain valve outlet pipe originally connected to the tailpipe can be directly changed to be connected to the cathode pipeline of the fuel cell stack, and hydrogen concentration sensors can be connected to the anode and cathode chambers.

[0145] First, when the fuel cell system is working normally: the anode hydrogen circulation pipeline is equipped with a gas-water separator, which includes a water storage box and a liquid level sensor. When the liquid level sensor detects the liquid level, it opens the drain valve to discharge the water in the water storage box after a calibrated time.

[0146] The calibration time must be such that during normal operation, only water is discharged into the cathode pipeline of the fuel cell stack, and no hydrogen gas is discharged into the cathode pipeline of the fuel cell stack.

[0147] Secondly, after the fuel cell system shuts down and finishes consuming oxygen (for example, when the voltage drops to a very small lower threshold), the drain valve is opened to connect the anode and cathode chambers. The pressure in the two chambers is controlled to reach the target pressure value by controlling the hydrogen supply valve and the pressure sensors in both chambers.

[0148] The target pressure value is calculated using the following formula:

[0149] - +

[0150] In the above formula, Indicates the target pressure value; This represents the desired pressure when the fuel cell system cools down to ambient temperature. It is equal to the current ambient atmospheric pressure and can be obtained by a sensor that collects the ambient atmospheric pressure of the system. P_H2O1 represents the initial water vapor partial pressure, and P_H2O2 represents the final water vapor partial pressure.

[0151] Then, after the internal and external pressure difference is balanced after the fuel cell system is shut down, the sensor data of the hydrogen concentration sensor is read to monitor the change of hydrogen concentration after shutdown. The time from the start of shutdown to the hydrogen concentration dropping to 0 is regarded as the effective protection time of the hydrogen-air interface, that is, the longest effective time that this scheme can prevent the generation of hydrogen-air interface.

[0152] The solution provided in this application for balancing the internal and external pressure difference of a fuel cell system after shutdown injects hydrogen into the cathode cavity through a drain valve without adding additional valves and pipelines; the target pressure value calculated by the formula algorithm is closer to atmospheric pressure, and the entire process control calibration is simple; and the use of a mature and reliable hydrogen concentration sensor to evaluate the effective duration of preventing hydrogen-air interface is highly accurate, economical, and easy to operate.

[0153] Figure 5 This is a schematic diagram of the controller structure provided in this application. Figure 5 As shown, the controller 50 provided in this embodiment includes at least one processor 501 and a memory 502. Optionally, the controller 50 further includes a communication component 503. The processor 501, memory 502, and communication component 503 are connected via a bus.

[0154] In a specific implementation, at least one processor 501 executes computer execution instructions stored in memory 502, causing at least one processor 501 to perform the above-described method.

[0155] The specific implementation process of processor 501 can be found in the above method embodiments, and its implementation principle and technical effect are similar. It will not be repeated here.

[0156] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0157] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0158] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0159] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0160] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for balancing the internal and external pressure differences of a fuel cell system, characterized in that, include: When the fuel cell system shuts down, the cathode chamber and anode chamber of the fuel cell system are connected. The system temperature, relative humidity of the cathode cavity and the anode cavity, and ambient pressure and temperature of the fuel cell system at the time of shutdown are obtained. The target pressure value is determined based on the system temperature, the relative humidity, the ambient pressure, and the ambient temperature. The hydrogen inlet pipeline is controlled to deliver hydrogen to the anode cavity until the cavity pressure of both the cathode cavity and the anode cavity matches the target pressure value; wherein the anode hydrogen inlet pipeline is connected to the anode cavity.

2. The method according to claim 1, characterized in that, The anode cavity is connected to an anode hydrogen gas outlet pipeline, which is connected to a water outlet pipe via a drain valve. The water outlet pipe is connected to the cathode stack cathode pipeline of the cathode cavity.

3. The method according to claim 2, characterized in that, The control of the cathode cavity and anode cavity of the fuel cell system is connected, including: When the fuel cell system is shut down, the drain valve is opened to allow the anode cavity to communicate with the cathode cavity through the anode hydrogen outlet pipeline, the drain valve, the water outlet pipeline, and the stack cathode pipeline.

4. The method according to claim 3, characterized in that, The process of controlling the delivery of hydrogen from the anode hydrogen inlet pipeline to the anode cavity until the cavity pressures of both the cathode cavity and the anode cavity match the target pressure value includes: The target duration is determined based on the volume of the cathode cavity, the volume of the anode cavity, and the valve diameter of the drain valve. When the continuous opening duration of the drain valve is greater than or equal to the target duration, the first pressure value collected by the first pressure sensor installed in the anode cavity and the second pressure value collected by the second sensor installed in the cathode cavity are obtained. If the difference between the first pressure value and the second pressure value is less than or equal to a preset threshold and matches the target pressure value, then the drain valve is controlled to close. When the drain valve is closed, the cathode cavity and the anode cavity are disconnected from each other.

5. The method according to claim 2, characterized in that, A vapor-water separator is connected between the anode hydrogen outlet pipeline and the drain valve. The vapor-water separator includes a water storage box and a liquid level sensor. The method further includes: When the fuel cell system is working normally, the liquid level value obtained by the liquid level sensor in detecting the liquid level of the water storage box is acquired. The drain valve is controlled to remain open for a specified duration to discharge liquid water from the water storage box to the cathode pipeline of the fuel cell stack.

6. The method according to claim 1, characterized in that, Determining the target pressure value based on the system temperature, relative humidity, ambient pressure, and ambient temperature includes: Based on the system temperature, the relative humidity, and the first correspondence, the initial water vapor partial pressure is determined; Based on the aforementioned ambient temperature and the second correspondence table, the final water vapor partial pressure is determined; The target pressure value is determined based on the ambient pressure, the initial water vapor partial pressure, and the final water vapor partial pressure.

7. The method according to claim 6, characterized in that, Before the hydrogen in the controlled anode hydrogen inlet pipeline is delivered to the anode cavity, the method further includes: Obtain the cathode chamber pressure and / or anode chamber pressure; If the target pressure value is less than the cathode cavity pressure and / or the anode cavity pressure, then the supply of hydrogen to the anode cavity through the anode hydrogen inlet pipeline shall be stopped.

8. The method according to claim 1, characterized in that, The anode cavity and / or the cathode cavity are equipped with hydrogen concentration sensors; the method further includes: When the fuel cell system is shut down, the hydrogen concentration changes in the anode cavity and / or the cathode cavity are monitored by the hydrogen concentration sensor. Based on the hydrogen concentration change, determine the time required for the hydrogen concentration in the anode cavity and / or the cathode cavity to decrease to zero; Based on the required duration, the protection duration of the hydrogen-air interface of the fuel cell system is determined.

9. A fuel cell system, characterized in that, include: The hydrogen supply system is used to deliver hydrogen to the anode chamber through the anode hydrogen inlet line when the fuel cell system is operating normally. The anode hydrogen outlet pipeline is connected to the anode cavity and is used to discharge the liquid water inside the anode cavity; A control pipeline, connecting the anode cavity and the cathode cavity, is used to control the connection or disconnection between the anode cavity and the cathode cavity; The hydrogen supply system is also used to deliver hydrogen to the anode cavity and the cathode cavity when the fuel cell system is shut down and the anode cavity and the cathode cavity are connected, until the cavity pressure of the cathode cavity and the anode cavity are both matched with the target pressure value.

10. The system according to claim 9, characterized in that, The control pipeline includes a steam-water separator, a drain valve, and a water outlet pipe; the anode chamber is connected to the steam-water separator, the steam-water separator is connected to the water outlet pipe via the drain valve, and the water outlet pipe is connected to the cathode stack cathode pipeline of the cathode chamber. When the drain valve is activated, the anode cavity is connected to the cathode cavity through the anode hydrogen outlet pipeline, the steam-water separator, the drain valve, the water outlet pipe, and the stack cathode pipeline.

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