Fuel cell cathode humidity control device and method

Abstract

The invention discloses a fuel cell cathode humidity control device and method, belongs to the technical field of fuel cells, and aims to solve the technical problem that the current fuel cell cathode humidity control method has certain defects in the aspects of power consumption, response speed, regulation and control comprehensiveness and the like and is still difficult to meet the requirement of efficient and stable operation of a fuel cell system. The method comprises the following steps: respectively measuring the cathode humidity and load current of the fuel cell stack through a humidity sensor and a current sensor; determining a current working mode of the fuel cell stack according to the cathode humidity and the load current; wherein the current working mode is one of a safety mode, a transient mode and a steady state mode; calling a corresponding air flow determination strategy based on the current working mode, and obtaining a current air flow demand value; and a control signal is generated according to the current working mode and the current air flow demand value, and the air compressor, the adjusting valve and the back pressure valve are controlled to execute control operation.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a device and method for controlling humidity of a cathode of a fuel cell. Background Art

[0002] As one of the core carriers of new energy technology, the durability of proton exchange membrane fuel cells has become a key bottleneck restricting industrialization. The life decay of proton exchange membrane fuel cells is mainly due to chemical degradation and mechanical damage of the membrane electrode assembly. Among them, the humidity increases sharply when the load is increased, and the reverse water migration under low-speed conditions leads to membrane dehydration. The local dry-wet cycle caused by the imbalance of water management on the cathode side is the main reason for the catalytic layer peeling and membrane perforation.

[0003] There are five main methods for controlling the humidity of the cathode of fuel cells: 1. An external vaporizing nozzle humidifier with controllable humidification can directly control the humidity of the fuel cell, but it will generate additional parasitic power consumption and affect the overall power output performance of the fuel cell system. 2. Air shutdown purge and load purge are the disposal methods after the fuel cell system is shut down. They can solve specific life attenuation problems, but they cannot respond to humidity changes during operation. 3. Regulating the evaporation, condensation and discharge of cathode water through the cooling system is an effective water management strategy, but both thermal management control and water management control have obvious response time lag problems. The superposition of the two may lead to slower response, resulting in larger overshoot or erroneous control operations. 4. The collection and recycling of wet air or liquid water includes two schemes: one is to collect condensed water and use it in the air supply circuit, and the other is to directly connect the wet air (exhaust gas) to the air intake end for circulation. The scheme for collecting condensed water relies on the vaporization of the controllable humidifier, while the direct exhaust gas circulation is relatively poor in controllability. 5. Controlling the air flow during operation can indirectly affect the exhaust efficiency of the moist air from the cathode, but on the one hand, the control effect is limited, and on the other hand, the air flow cannot be controlled based solely on humidity. If the load factor is not considered at the same time, the output power of the fuel cell system cannot be guaranteed.

[0004] In summary, although there are various methods for controlling the cathode humidity of fuel cells at present, each has its limitations, especially in terms of power consumption, response speed, and comprehensiveness of regulation. It is still difficult to meet the needs of efficient and stable operation of fuel cell systems. Summary of the invention

[0005] The embodiments of the present invention provide a fuel cell cathode humidity control device and method for solving the following technical problems: the current fuel cell cathode humidity control method has certain defects in power consumption, response speed, and comprehensive regulation, and it is still difficult to meet the requirements of efficient and stable operation of the fuel cell system.

[0006] The embodiment of the present invention adopts the following technical solution: In one aspect, an embodiment of the present invention provides a fuel cell cathode humidity control device, the device comprising: the device at least comprises: an air compressor, a membrane humidifier, a back pressure valve and a regulating valve; The air compressor is connected to the inlet of the dry chamber of the membrane humidifier, and the outlet of the dry chamber is connected to the cathode inlet of the fuel cell stack; The cathode outlet of the fuel cell stack is connected to the inlet of the wet chamber of the membrane humidifier, and the outlet of the wet chamber is connected to the back pressure valve; The two ends of the regulating valve are respectively connected to the dry chamber outlet and the wet chamber inlet of the membrane humidifier to form a circulation passage between the dry chamber and the wet chamber of the membrane humidifier.

[0007] In a feasible implementation, when the cathode of the fuel cell stack is in a high humidity state, the regulating valve performs an opening operation based on a control signal, and the gas in the membrane humidifier flows from the dry chamber outlet to the wet chamber inlet through the regulating valve under the action of the pressure difference, thereby reducing the humidity of the wet chamber, thereby reducing the humidification efficiency of the membrane humidifier on the dry chamber air; When the cathode of the fuel cell stack is in a low humidity state, the regulating valve performs an opening operation based on the control signal, and the back pressure valve reduces its opening degree based on the control signal, and the gas in the membrane humidifier flows from the wet chamber inlet to the dry chamber outlet through the regulating valve under the action of the pressure difference, thereby humidifying the air entering the fuel cell stack; When the fuel cell stack is in a normal humidity state, the regulating valve performs a closing operation based on a control signal.

[0008] In a feasible implementation manner, the device further comprises: a humidity sensor, a DCDC converter and a current sensor; The humidity sensor is connected to the cathode of the fuel cell stack and is used to monitor the humidity of the cathode; The DCDC converter is connected to the current output terminal of the fuel cell stack to regulate the voltage outputted by the fuel cell and obtain the load current; The current sensor is installed in the connection path between the DCDC converter and the current output end of the fuel cell stack, and is used to obtain the load current and send it to the DCDC converter.

[0009] On the other hand, an embodiment of the present invention further provides a method for controlling humidity of a cathode of a fuel cell, the method comprising: The humidity sensor and the current sensor are used to measure the cathode humidity and the load current of the fuel cell stack respectively; Determining a current operating mode of the fuel cell stack according to the cathode humidity and the load current; wherein the current operating mode is one of a safety mode, a transient mode, and a steady-state mode; Based on the current working mode, a corresponding air flow determination strategy is called, and a current air flow demand value is obtained; A control signal is generated according to the current working mode and the current air flow demand value to control the air compressor, the regulating valve and the back pressure valve to perform a control operation.

[0010] In a feasible implementation manner, determining the current operating mode of the fuel cell stack according to the cathode humidity and the load current specifically includes: Determining a corresponding reference humidity according to the load current; When the absolute value of the difference between the cathode humidity and the reference humidity exceeds a first preset threshold, the current operating mode of the fuel cell stack is a safety mode; When the absolute value of the difference between the cathode humidity and the reference humidity does not exceed the first preset threshold, the current change rate of the load current exceeds the second preset threshold, and the duration exceeds the preset duration, the fuel cell stack enters the transient mode; When the absolute value of the difference between the cathode humidity and the reference humidity does not exceed the first preset threshold, and the current change rate of the load current does not exceed the second preset threshold, the current operating mode of the fuel cell stack is the steady-state mode.

[0011] In a feasible implementation manner, calling a corresponding air flow determination strategy based on the current working mode and obtaining a current air flow demand value specifically includes: When the current working mode is the safety mode, calling the first air flow demand calculation formula in the first air flow determination strategy, obtaining the required parameters in the formula, and calculating the corresponding first air flow demand value; When the current working mode is the transient mode, calling the second air flow determination strategy, querying a preset mapping table according to the load current, and obtaining a corresponding second air flow demand value; When the current working mode is the steady-state mode, the third air flow determination strategy is called, the weight coefficient is determined according to the current operating state, and the current first air flow demand value and the second air flow demand value are weighted calculated according to the weight coefficient to obtain the third air flow demand value.

[0012] In a feasible implementation, when the current working mode is the safety mode, the air flow demand calculation formula in the first air flow determination strategy is called, and the required parameters in the formula are obtained to calculate the corresponding first air flow demand value, specifically including: When the current working mode is the safety mode, the cathode inlet air pressure of the fuel cell stack is obtained through the cathode inlet pressure sensor. ; According to the first air flow demand calculation formula , calculate a first air flow demand value; in, It is a calibration parameter, which is related to the selection of fuel cell system; It is a calibration parameter, which is related to the length and shape of the cathode flow channel of the fuel cell stack; I is the load current; is the relative humidity constant of air, calibrated according to the operating environment; is the reference humidity; , is the relative humidity of saturated water vapor at the current temperature T; , is the absolute concentration of saturated water vapor at the current temperature T; where R is the universal gas constant, is the molar mass of water.

[0013] In a feasible implementation manner, after calling the corresponding air flow determination strategy based on the current working mode and calculating the current air flow demand value, the method further includes: When the current working mode is the safe mode, if the difference between the cathode humidity and the reference humidity is greater than , the regulating valve is controlled to open, and the gas flow through the regulating valve is calculated according to the cathode inlet pressure and cathode outlet pressure of the fuel cell stack; wherein, is the first preset threshold; If the difference between the cathode humidity and the reference humidity is less than , the back pressure valve is controlled to decrease its opening to increase the gas pressure in the exhaust passage, and the regulating valve is controlled to open at the same time, and the gas flow through the regulating valve is calculated according to the cathode inlet pressure and cathode outlet pressure of the fuel cell stack; The gas flow passing through the regulating valve is compensated to the first air flow demand value to obtain an actual air flow demand value in the safety mode.

[0014] In a feasible implementation, the gas flow through the regulating valve is calculated according to the cathode inlet pressure and the cathode outlet pressure of the fuel cell stack, specifically including: Based on the linear nozzle equation q=k(p in -p out ), calculate the gas flow q through the regulating valve; where k>0, represents the linear nozzle equation coefficient of the regulating valve, p in is the cathode inlet pressure of the fuel cell stack, p out is the cathode outlet pressure of the fuel cell stack; When only the regulating valve is opened, dry air flows from the dry chamber outlet of the membrane humidifier into the wet chamber inlet, and the air passes through the fuel cell stack to generate pressure loss, p in >p out , at this time q is positive; When the regulating valve is opened and the back pressure valve opening is reduced, the gas pressure in the exhaust passage is raised. in <p out , then q is a negative value.

[0015] In a feasible implementation manner, a control signal is generated according to the current working mode and the current air flow demand value to control the air compressor, the regulating valve and the back pressure valve to perform a control operation, specifically including: Generate a regulating valve control signal and a back pressure valve control signal according to the current working mode; and control the opening and closing of the regulating valve based on the regulating valve control signal, and control the opening degree of the back pressure valve based on the back pressure valve control signal; An air compressor control signal is generated according to the current air flow demand value; and based on the air compressor control signal, the air compressor is controlled to input the required air flow to the fuel cell stack.

[0016] Compared with the prior art, the fuel cell cathode humidity control method and device provided by the embodiment of the present invention have the following beneficial effects: 1. The humidity of the fuel cell cathode is controlled by adjusting the air flow output by the air compressor, avoiding the additional power consumption generated by an external controllable humidifier.

[0017] 2. It can control the humidity of the fuel cell cathode in real time during operation. Compared with the shutdown purge solution, on the one hand, it can proactively avoid the fuel cell cathode from being too dry or too wet. On the other hand, it can make immediate adjustments to the over-dryness or over-wetness without shutting down the system.

[0018] 3. The air flow requirements of the fuel cell cathode humidity and load current are taken into consideration at the same time, and different operating modes and corresponding air flow demand algorithms are provided. Compared with a single solution, it can take into account the water management balance and normal power output of the fuel cell.

[0019] 4. The influence of the pressure difference between the inlet and outlet of the battery cathode on the gas flow direction of the circulation path was carefully considered, and a valve control scheme was proposed. Only one additional regulating valve was used to achieve two-way air flow in the circulation path, meeting the regulation needs in both over-humidity and over-dryness conditions.

[0020] 5. The layout of the circulation path can, on the one hand, meet the requirement of purging the wet chamber of the membrane humidifier in the case of over-humidity, and on the other hand, directly introduce the wet air into the fuel cell stack in the case of over-dryness to avoid the wet air entering the intercooler to produce condensation, or entering the dry chamber of the membrane humidifier to reduce the water concentration difference between the dry and wet chambers.

[0021] In summary, the fuel cell cathode humidity control method provided by the present invention does not require shutdown for purging, can take into account both water management balance and normal power output, and has a fast control response speed, which can meet the requirements of efficient and stable operation of the fuel cell system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings: Figure 1 A schematic structural diagram of a fuel cell cathode humidity control device provided by an embodiment of the present invention; Figure 2 A flow chart of a method for controlling humidity in a cathode of a fuel cell provided by an embodiment of the present invention; Figure 3 A control method flow chart corresponding to the first embodiment provided by the present invention; Figure 4 This is a flow chart of the control method corresponding to the second embodiment provided in the embodiment of the present invention.

[0023] Reference numerals: 1. Air compressor; 2. Intercooler; 3. Membrane humidifier; 31. Membrane humidifier dry chamber; 32. Membrane humidifier wet chamber; 4. Fuel cell stack; 51. Back pressure valve; 52. Control valve; 6. DCDC converter; 7. Controller unit; 8. Mass flow meter; 91. Cathode inlet pressure sensor; 92. Cathode outlet pressure sensor; 10. Humidity sensor; 11. Temperature sensor; 12. Current sensor. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] First, an embodiment of the present invention provides a fuel cell cathode humidity control device, such as Figure 1 As shown, the device at least includes: an air compressor 1, a membrane humidifier 3, a back pressure valve 51, a regulating valve 52, and a fuel cell stack 4; The air compressor 1 is connected to the inlet of the membrane humidifier dry chamber 31, and the outlet of the membrane humidifier dry chamber 31 is connected to the cathode inlet of the fuel cell stack 4. The cathode outlet of the fuel cell stack 4 is connected to the inlet of the membrane humidifier wet chamber 32, and the outlet of the membrane humidifier wet chamber 32 is connected to the back pressure valve 52.

[0026] Furthermore, if Figure 1 As shown, two ends of the regulating valve 52 are respectively connected to the outlet of the membrane humidifier dry chamber 31 and the inlet of the membrane humidifier wet chamber 31 to form a circulation passage between the membrane humidifier dry chamber and the wet chamber.

[0027] As a feasible implementation, when the cathode of the fuel cell stack 4 is in a high humidity state, the regulating valve 52 performs an opening operation based on a control signal, and the gas in the membrane humidifier 3 flows from the dry chamber outlet to the wet chamber inlet through the regulating valve 52 under the action of the pressure difference, reducing the humidity of the wet chamber, thereby reducing the humidification efficiency of the membrane humidifier on the dry chamber air, and reducing the humidity of the air entering the cathode inlet of the fuel cell stack. When the cathode of the fuel cell stack 4 is in a low humidity state, the regulating valve 52 performs an opening operation based on the control signal, and at the same time, the back pressure valve 51 reduces the opening based on the control signal, and the pressure in the exhaust passage is increased. The gas in the membrane humidifier 3 flows from the wet chamber inlet to the dry chamber outlet through the regulating valve 52 under the action of the pressure difference, and humidifies the air entering the fuel cell stack 4. When the fuel cell stack 4 is in a normal humidity state, the regulating valve 52 performs a closing operation based on the control signal, and the entire battery system operates normally.

[0028] It should be noted that the inlet and outlet of the dry chamber and the wet chamber of the membrane humidifier 3 are not one-way channels. The gas can flow in or out from the inlet, and similarly, the gas can flow out or in from the outlet. The inlet and outlet in the present invention are only used to assist in describing the positional relationship between the components and are not used to limit the flow direction of the gas.

[0029] Furthermore, if Figure 1 As shown, the device further includes: a humidity sensor 10 , a DCDC converter 6 and a current sensor 12 .

[0030] The humidity sensor 10 is connected to the cathode of the fuel cell stack 4 to monitor the humidity of the cathode. The DCDC converter 6 is connected to the current output terminal of the fuel cell stack to regulate the voltage outputted by the fuel cell and obtain the load current. The current sensor 12 is installed in the connection path between the DCDC converter 6 and the current output terminal of the fuel cell stack 4 to obtain the load current and send it to the DCDC converter 6.

[0031] Furthermore, if Figure 1 As shown, the fuel cell cathode humidity control device further includes: an intercooler 2 , a controller unit 7 , a mass flow meter 8 , a cathode inlet pressure sensor 91 , a cathode outlet pressure sensor 92 and a temperature sensor 11 .

[0032] The intercooler 2 is installed between the air compressor 1 and the membrane humidifier 3 to cool the high-temperature gas at the tail end of the air compressor 1. A mass flow meter 8 is installed between the air compressor 1 and the intercooler 2 to monitor the mass flow of air output by the air compressor 1. The cathode inlet pressure sensor 91 is installed in the passage between the membrane humidifier dry chamber 31 and the cathode of the fuel cell stack 4, and the cathode outlet pressure sensor 92 is installed in the passage between the membrane humidifier wet chamber 32 and the cathode of the fuel cell stack 4 to monitor the pressure difference on both sides of the regulating valve 52 and to calculate the air flow through the regulating valve 52. The temperature sensor 11 is installed on the cathode of the fuel cell stack 4 to monitor the cathode temperature and calculate the phase state of the cathode water, thereby proposing the flow demand. The controller unit 7 is connected in communication with the entire fuel cell cathode humidity control device to receive all sensor signals in the fuel cell cathode humidity control device, perform calculations, and send control signals to the valve and the air compressor.

[0033] In order to improve the life of fuel cells, humidity control is crucial. During the operation of the fuel cell stack 4, hydrogen ions pass through the proton exchange membrane and combine with oxygen at the cathode to generate water. Therefore, humidity control from the cathode side, that is, the air supply subsystem, is the most efficient way. Based on the principle of air purging water vapor and liquid water in the cathode chamber, the present invention proposes a control method that controls the air mass flow rate to affect the water discharge rate. Under high humidity, the air flow rate is appropriately increased to enhance the shear force of air purge; under low humidity, the air flow rate is appropriately reduced to avoid proton exchange membrane dehydration.

[0034] On the basis of the above basic principles: let the load current also participate in the decision of air flow demand. This is because different load currents will have different required flow rates, and humidity cannot be considered alone when adjusting air flow. Based on humidity and current signals, the air flow demand is decided in three modes: safe mode, transient mode, and steady-state mode. Among them, when the humidity signal deviates seriously from the normal value, it enters the safe mode, and humidity control is given priority in the safe mode; when the humidity signal does not deviate seriously and the load is in the process of loading or unloading, it enters the transient mode, and the flow demand in the transient mode gives priority to meeting the change demand of the load current; when the humidity signal does not deviate seriously and the load does not change significantly, it enters the steady-state mode, and the current load and humidity are considered at the same time to control the air flow.

[0035] On the basis of the above basic principles, in the safety mode: introduce a circulation passage and a regulating valve 52 connecting the dry chamber 31 and the wet chamber 32 of the membrane humidifier. Under high humidity, open the regulating valve 52, and the gas flows from the outlet of the dry chamber 31 to the inlet of the wet chamber 32 through the regulating valve 52 under the action of the pressure difference, and quickly purges and reduces the humidity of the wet chamber 32 to avoid excessive humidification of the membrane humidifier 3; under low humidity, open the regulating valve 52, and simultaneously reduce the opening of the back pressure valve 51, and hold up the pressure of the exhaust passage, so that the gas flows from the inlet of the wet chamber 32 to the outlet of the dry chamber 31 through the regulating valve 52 under the action of the pressure difference, and humidifies the air entering the fuel cell stack 4. After the humidity is normal, close the regulating valve 52 and enter the transient mode or steady-state mode.

[0036] Based on the above device, the embodiment of the present invention also provides a method for controlling the humidity of the cathode of a fuel cell, such as Figure 2 As shown, the fuel cell cathode humidity control method specifically includes steps S101-S104: S101. Measure the cathode humidity and load current of the fuel cell stack respectively through a humidity sensor and a current sensor. Specifically, during the operation of the fuel cell, Figure 1 The humidity sensor 10 in the device shown measures the cathode humidity of the fuel cell stack 4 in real time. At the same time, the current sensor 12 measures the load current of the fuel cell stack in real time.

[0037] Furthermore, the reference humidity is preset according to the load current. .

[0038] As a feasible implementation, the reference humidity represents the recommended humidity for the fuel cell to meet a healthy water management state under a certain current load. A mapping table of load currents of different sizes and reference humidity can be prepared in advance, and the corresponding reference humidity can be found in the mapping table after the load current is obtained.

[0039] S102. Determine the current operating mode of the fuel cell stack according to the cathode humidity and the load current; wherein the current operating mode is one of a safety mode, a transient mode and a steady-state mode.

[0040] Specifically, when the absolute value of the difference between the cathode humidity and the reference humidity exceeds a first preset threshold, the current operating mode of the fuel cell stack is a safety mode.

[0041] When the absolute value of the difference between the cathode humidity and the reference humidity does not exceed the first preset threshold, the current change rate of the load current exceeds the second preset threshold, and the duration exceeds the preset time, the fuel cell stack enters the transient mode.

[0042] When the absolute value of the difference between the cathode humidity and the reference humidity does not exceed the first preset threshold, and the current change rate of the load current does not exceed the second preset threshold, the current operating mode of the fuel cell stack is the steady-state mode.

[0043] In one embodiment, the humidity sensor monitors the cathode humidity of the fuel cell stack. After that, the reference humidity corresponding to the load current Compare and calculate the difference , when the absolute value of the difference , enter safe mode.

[0044] when Continue to judge the change of current load. When the current change rate , and the duration exceeds 300ms, it enters transient mode.

[0045] when and , it is determined to be a steady-state mode.

[0046] It should be noted that the specific thresholds need to be calibrated according to actual conditions. The above embodiments are only examples and are not numerical limitations on the thresholds in this application.

[0047] S103: Call the corresponding air flow determination strategy based on the current working mode, and obtain the current air flow demand value.

[0048] Specifically, when the current working mode is the safety mode, the first air flow demand calculation formula in the first air flow determination strategy is called, and the required parameters in the formula are obtained to calculate the corresponding first air flow demand value.

[0049] When the current working mode is the transient mode, the second air flow determination strategy is called, and a preset mapping table is queried according to the load current to obtain a corresponding second air flow demand value.

[0050] When the current working mode is the steady-state mode, the third air flow determination strategy is called, the weight coefficient is determined according to the current operating state, and the current first air flow demand value and the second air flow demand value are weighted calculated according to the weight coefficient to obtain the third air flow demand value.

[0051] As a feasible implementation method, when the current working mode is the safety mode, the cathode inlet air pressure of the fuel cell stack is obtained by the cathode inlet pressure sensor. ; According to the first air flow demand calculation formula , calculate the first air flow demand value.

[0052] in, It is a calibration parameter, which is related to the selection of fuel cell system; It is a calibration parameter, which is related to the length and shape of the cathode flow channel of the fuel cell stack; I is the load current; is the relative humidity constant of air, calibrated according to the operating environment; For reference humidity.

[0053] , is the relative humidity of saturated water vapor at the current temperature T; , is the absolute concentration of saturated water vapor at the current temperature T; where R is the universal gas constant, is the molar mass of water.

[0054] Q1 is the air flow requirement in the safety mode when the humidity sensor measurement value is too high or too low. It is based on the flow-humidity equation and aims to quickly control the relative humidity to near the recommended humidity. Specifically, when the actual humidity is too high, the air flow is increased, and when the actual humidity is too low, the air flow is reduced.

[0055] As a feasible implementation method, when the current working mode is the transient mode, the reference air flow rate is preset with reference to the load current I. (can be obtained through the mapping table), the reference air flow here It is only based on the current and is set to satisfy the fuel cell system's sufficient reactants under a certain current load. When the current load suddenly changes, in order to avoid hydrogen and oxygen starvation caused by insufficient reactants, there are: .

[0056] As a feasible implementation method, when the current working mode is the steady-state mode, the fuel cell system operates smoothly. The air flow demand should meet the reactant demand of the fuel cell stack on the one hand, and on the other hand, it should also make forward-looking compensation for possible water management imbalance. Therefore, the weighted average of Q1 and Q2 is defined as the third air flow demand Q3, which is: .

[0057] In the formula, is a weight coefficient used to allocate the weights of Q1 and Q2. In an example, the recommended value of the weight coefficient during stable operation is 0.1~0.2, and the recommended value of the weight coefficient during cold start is 0.5~0.6.

[0058] Furthermore, when the current working mode is the safety mode, since the judgment condition is that the absolute value of the difference between the current humidity and the reference humidity is greater than the preset threshold, it can be further divided into two situations: over-humidity and over-dryness, that is: If the difference between cathode humidity and reference humidity is greater than At this time, it is an over-humidification situation. The control valve is opened to connect the outlets of the membrane humidifier dry chamber 31 and the membrane humidifier wet chamber 32. Under the action of the pressure difference, dry air flows into the membrane humidifier wet chamber 32, reducing the water concentration in the wet chamber, thereby reducing the humidification efficiency of the membrane humidifier 3. After opening the regulating valve, the gas flow through the regulating valve is calculated according to the cathode inlet pressure and cathode outlet pressure of the fuel cell stack; wherein, is the first preset threshold.

[0059] If the difference between the cathode humidity and the reference humidity is less than At this time, it is too dry. The back pressure valve is controlled to reduce the opening to increase the gas pressure in the exhaust passage. At the same time, the regulating valve is controlled to open. Under the action of the pressure difference, humid air flows into the inlet of the fuel cell stack 4 to increase the cathode humidity. After opening the regulating valve, the gas flow through the regulating valve is calculated according to the cathode inlet pressure and cathode outlet pressure of the fuel cell stack.

[0060] Furthermore, the gas flow passing through the regulating valve is compensated to the first air flow demand value to obtain an actual air flow demand value in the safety mode.

[0061] As a feasible implementation method, the gas flow rate of the regulating valve is calculated as follows: Based on the linear nozzle equation q=k(p in -p out ), calculate the gas flow q through the regulating valve; where k>0, represents the linear nozzle equation coefficient of the regulating valve, p in is the cathode inlet pressure of the fuel cell stack, p out is the cathode outlet pressure of the fuel cell stack.

[0062] When only the regulating valve is opened, dry air flows from the dry chamber outlet of the membrane humidifier into the wet chamber inlet, and the air passes through the fuel cell stack to generate pressure loss, p in >p out , at this time q is a positive value. When the regulating valve is opened and the back pressure valve opening is reduced, the gas pressure in the exhaust passage is raised, p in <p out , at this time q is a negative value. The gas flow q passing through the regulating valve is compensated to the first air flow demand value Q1, that is, the two are added to obtain the actual air flow demand value in the safety mode.

[0063] S104, generating a control signal according to the current working mode and the current air flow demand value, and controlling the air compressor, the regulating valve and the back pressure valve to perform control operations.

[0064] Specifically, according to the current working mode, a regulating valve control signal and a back pressure valve control signal are generated; and based on the regulating valve control signal, the opening and closing of the regulating valve are controlled, and based on the back pressure valve control signal, the opening degree of the back pressure valve is controlled.

[0065] Furthermore, an air compressor control signal is generated according to the current air flow demand value; and based on the air compressor control signal, the air compressor is controlled to input the required air flow into the fuel cell stack.

[0066] As a feasible implementation method, in order to achieve the required air flow demand, the controller performs calculations and sends a speed control signal to the air compressor. In the safety mode, the air compressor speed control signal is calculated according to the sum of the first air flow demand value and the compensation air flow Q1+q; in the transient mode, the air compressor speed control signal is calculated according to the second air flow demand Q2; in the steady-state mode, the air compressor speed control signal is calculated according to the third air flow demand Q3.

[0067] Based on the above fuel cell cathode humidity control device and method, the present invention can derive a variety of different execution processes, which are illustrated by two embodiments below.

[0068] Embodiment 1: Figure 3 A control method flow chart corresponding to the first embodiment provided in the present invention is shown in FIG. Figure 3 As shown, the humidity sensor and the DCDC converter simultaneously collect the cathode humidity and current load information of the fuel cell stack, and then immediately calculate the first air flow demand Q1 and the second air flow demand Q2 by the method provided above.

[0069] Furthermore, whether the current fuel cell has entered the safety mode is determined based on whether the absolute value of the difference between the cathode humidity and the reference humidity is greater than 15%. If so, the first air flow demand Q1 is used forcibly. At this time, two control strategies are used based on whether the humidity is too dry or too wet: if the humidity is too high, that is, the difference between the cathode humidity and the reference humidity is greater than 15%, the regulating valve 52 is opened to open the circulation passage, and the air flow q passing through the regulating valve is calculated to compensate for the first air flow demand Q1. If the humidity is too low, that is, the difference between the cathode humidity and the reference humidity is less than -15%, the opening of the back pressure valve 51 is reduced to increase the air pressure of the exhaust passage of the battery, and the regulating valve 52 is opened at the same time to allow the gas in the membrane humidifier to flow from the wet chamber into the dry chamber to humidify the air flowing into the battery, and the air flow q passing through the regulating valve is calculated to compensate for the first air flow demand Q1, and the air compressor is controlled.

[0070] If the absolute value of the difference between the cathode humidity and the reference humidity is not greater than 15%, then continue to determine whether the rate of change of the load current is greater than 5A / s. If so, when this situation lasts for more than 300ms, it is determined that the current fuel cell has entered the transient mode, and the second air flow demand Q2 is forced to control the air compressor. If not, it is determined that the current fuel cell has entered the steady-state mode, and the weighted average of Q1 and Q2 is used to obtain Q3 to control the air compressor. Embodiment 2: Figure 4 The control method flow chart corresponding to the second embodiment provided in the embodiment of the present invention, the present invention can also adopt a decision sequence of first determining whether the battery enters the transient mode, and then determining whether to enter the safe mode, such as Figure 4 As shown, after calculating Q1 and Q2, first determine whether the current battery enters the transient mode based on whether the load current change rate is greater than 5A / s and the duration is greater than 300ms. If not, then continue to determine whether the current battery enters the safe mode based on whether the absolute value of the difference between the cathode humidity and the reference humidity is greater than 15%. The rest of the process is the same as the embodiment.

[0071] It should be noted that there is no strict order between calculating Q1 and Q2 and determining the current working mode in the present invention. Q1 and Q2 can be calculated first and then the mode can be determined, or the mode can be determined first and then Q1 and Q2 can be calculated. The present invention does not limit this order. As long as it does not affect the execution of the entire process, any sequence changes, equivalent replacements, etc. made within the principles provided by the present invention should be included in the protection scope of the present invention.

[0072] Each embodiment of the present invention is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device, equipment, and non-volatile computer storage medium embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments.

[0073] The above describes specific embodiments of the present invention. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0074] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present invention should be included in the protection scope of the present invention.

Claims

1. A fuel cell cathode humidity control device, characterized in that: The device at least comprises: an air compressor, a membrane humidifier, a back pressure valve and a regulating valve; The air compressor is connected to the inlet of the dry chamber of the membrane humidifier, and the outlet of the dry chamber is connected to the cathode inlet of the fuel cell stack; The cathode outlet of the fuel cell stack is connected to the inlet of the wet chamber of the membrane humidifier, and the outlet of the wet chamber is connected to the back pressure valve; The two ends of the regulating valve are respectively connected to the dry chamber outlet and the wet chamber inlet of the membrane humidifier to form a circulation passage between the dry chamber and the wet chamber of the membrane humidifier.

2. A fuel cell cathode humidity control device according to claim 1, characterized in that: When the cathode of the fuel cell stack is in a high humidity state, the regulating valve performs an opening operation based on the control signal, and the gas in the membrane humidifier flows from the dry chamber outlet to the wet chamber inlet through the regulating valve under the action of the pressure difference, thereby reducing the humidity of the wet chamber, thereby reducing the humidification efficiency of the membrane humidifier on the dry chamber air; When the cathode of the fuel cell stack is in a low humidity state, the regulating valve performs an opening operation based on the control signal, and the back pressure valve reduces its opening degree based on the control signal, and the gas in the membrane humidifier flows from the wet chamber inlet to the dry chamber outlet through the regulating valve under the action of the pressure difference, thereby humidifying the air entering the fuel cell stack; When the fuel cell stack is in a normal humidity state, the regulating valve performs a closing operation based on a control signal.

3. A fuel cell cathode humidity control device according to claim 1, characterized in that: The device also includes: a humidity sensor, a DCDC converter and a current sensor; The humidity sensor is connected to the cathode of the fuel cell stack and is used to monitor the humidity of the cathode; The DCDC converter is connected to the current output terminal of the fuel cell stack to regulate the voltage outputted by the fuel cell and obtain the load current; The current sensor is installed in the connection path between the DCDC converter and the current output end of the fuel cell stack, and is used to obtain the load current and send it to the DCDC converter.

4. A fuel cell cathode humidity control method, applied to a fuel cell cathode humidity control device as claimed in any one of claims 1 to 3, characterized in that: The method comprises: The humidity sensor and the current sensor are used to measure the cathode humidity and the load current of the fuel cell stack respectively; Determining a current operating mode of the fuel cell stack according to the cathode humidity and the load current; wherein the current operating mode is one of a safety mode, a transient mode, and a steady-state mode; Based on the current working mode, a corresponding air flow determination strategy is called, and a current air flow demand value is obtained; A control signal is generated according to the current working mode and the current air flow demand value to control the air compressor, the regulating valve and the back pressure valve to perform a control operation.

5. A fuel cell cathode humidity control method according to claim 4, characterized in that: Determining the current operating mode of the fuel cell stack according to the cathode humidity and the load current specifically includes: Determining a corresponding reference humidity according to the load current; When the absolute value of the difference between the cathode humidity and the reference humidity exceeds a first preset threshold, the current operating mode of the fuel cell stack is a safety mode; When the absolute value of the difference between the cathode humidity and the reference humidity does not exceed the first preset threshold, the current change rate of the load current exceeds the second preset threshold, and the duration exceeds the preset duration, the fuel cell stack enters the transient mode; When the absolute value of the difference between the cathode humidity and the reference humidity does not exceed the first preset threshold, and the current change rate of the load current does not exceed the second preset threshold, the current operating mode of the fuel cell stack is the steady-state mode.

6. A fuel cell cathode humidity control method according to claim 4, characterized in that: Based on the current working mode, the corresponding air flow determination strategy is called, and the current air flow demand value is obtained, specifically including: When the current working mode is the safety mode, calling the first air flow demand calculation formula in the first air flow determination strategy, obtaining the required parameters in the formula, and calculating the corresponding first air flow demand value; When the current working mode is the transient mode, calling the second air flow determination strategy, querying a preset mapping table according to the load current, and obtaining a corresponding second air flow demand value; When the current working mode is the steady-state mode, the third air flow determination strategy is called, the weight coefficient is determined according to the current operating state, and the current first air flow demand value and the second air flow demand value are weighted calculated according to the weight coefficient to obtain the third air flow demand value.

7. A fuel cell cathode humidity control method according to claim 6, characterized in that: When the current working mode is the safety mode, the air flow demand calculation formula in the first air flow determination strategy is called, and the required parameters in the formula are obtained to calculate the corresponding first air flow demand value, specifically including: When the current working mode is the safety mode, the cathode inlet air pressure of the fuel cell stack is obtained through the cathode inlet pressure sensor. ; According to the first air flow demand calculation formula , calculate a first air flow demand value; in, It is a calibration parameter, which is related to the selection of fuel cell system; It is a calibration parameter, which is related to the length and shape of the cathode flow channel of the fuel cell stack; I is the load current; is the relative humidity constant of air, calibrated according to the operating environment; is the reference humidity; , is the relative humidity of saturated water vapor at the current temperature T; , is the absolute concentration of saturated water vapor at the current temperature T; where R is the universal gas constant, is the molar mass of water.

8. A fuel cell cathode humidity control method according to claim 5, characterized in that: After calling the corresponding air flow determination strategy based on the current working mode and calculating the current air flow demand value, the method further includes: When the current working mode is the safe mode, if the difference between the cathode humidity and the reference humidity is greater than , the regulating valve is controlled to open, and the gas flow through the regulating valve is calculated according to the cathode inlet pressure and cathode outlet pressure of the fuel cell stack; wherein, is the first preset threshold; If the difference between the cathode humidity and the reference humidity is less than , the back pressure valve is controlled to decrease its opening to increase the gas pressure in the exhaust passage, and the regulating valve is controlled to open at the same time, and the gas flow through the regulating valve is calculated according to the cathode inlet pressure and cathode outlet pressure of the fuel cell stack; The gas flow passing through the regulating valve is compensated to the first air flow demand value to obtain an actual air flow demand value in the safety mode.

9. A fuel cell cathode humidity control method according to claim 8, characterized in that: According to the cathode inlet pressure and cathode outlet pressure of the fuel cell stack, the gas flow through the regulating valve is calculated, including: Based on the linear nozzle equation q=k(p in -p out ), calculate the gas flow q through the regulating valve; where k>0, represents the linear nozzle equation coefficient of the regulating valve, p in is the cathode inlet pressure of the fuel cell stack, p out is the cathode outlet pressure of the fuel cell stack; When only the regulating valve is opened, dry air flows from the dry chamber outlet of the membrane humidifier into the wet chamber inlet, and the air passes through the fuel cell stack to generate pressure loss, p in >p out , at this time q is positive; When the regulating valve is opened and the back pressure valve opening is reduced, the gas pressure in the exhaust passage is raised. in <p out , then q is a negative value.

10. A fuel cell cathode humidity control method according to claim 4, characterized in that: Generate a control signal according to the current working mode and the current air flow demand value to control the air compressor, the regulating valve and the back pressure valve to perform a control operation, specifically including: Generate a regulating valve control signal and a back pressure valve control signal according to the current working mode; and control the opening and closing of the regulating valve based on the regulating valve control signal, and control the opening degree of the back pressure valve based on the back pressure valve control signal; An air compressor control signal is generated according to the current air flow demand value; and based on the air compressor control signal, the air compressor is controlled to input the required air flow to the fuel cell stack.

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