A fuel cell cathode humidity control device and method

Abstract

The present invention discloses a fuel cell cathode humidity control device and method, which belongs to the field of fuel cell technology and is used to solve 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. The method includes: measuring the cathode humidity and load current of the fuel cell stack respectively through a humidity sensor and a current sensor; determining the 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 the corresponding air flow determination strategy based on the current working mode, and obtaining the current air flow demand value; 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 the control operation.

Description

Technical Field

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

[0002] As one of the core carriers of new energy technologies, the durability of proton exchange membrane fuel cells has become a key bottleneck restricting industrialization. The life attenuation of proton exchange membrane fuel cells mainly stems from the chemical degradation and mechanical damage of the membrane electrode assembly. Among them, the sudden increase in humidity when the load is increased, and the reverse water migration under low-speed conditions lead 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 peeling of the catalyst layer and membrane perforation.

[0003] The existing fuel cell cathode humidity control methods mainly fall into the following five categories: 1. An externally added humidifying nozzle humidifier with controllable humidification amount can directly regulate the humidity of the fuel cell, but it will generate additional parasitic power consumption, affecting the overall power output performance of the fuel cell system. 2. Air shutdown purge and on-load purge are disposal methods after the fuel cell system shuts down, which can solve specific life attenuation problems, but cannot respond to humidity changes during operation. 3. Adjusting the evaporation, condensation, and discharge of cathode water through the cooling system is an effective water management strategy, but both the thermal management control and water management control have obvious response time lags. The superposition of the two may lead to a slower response, resulting in a larger overshoot or incorrect control operation. 4. Collection and recycling of wet air or liquid water include two schemes. One is to collect condensed water and use it for the air supply circuit, and the other is to directly connect the wet air (tail gas) to the intake end for circulation. The scheme of collecting condensed water depends on the vaporization of a controllable humidifier, and the direct tail gas circulation has relatively poor controllability. 5. Controlling the air flow during operation can indirectly affect the discharge efficiency of the cathode humid air. On the one hand, the regulation effect is limited, and on the other hand, the air flow cannot be controlled only based on humidity. Without considering the load factor at the same time, the output power of the fuel cell system cannot be guaranteed.

[0004] In summary, although the current fuel cell cathode humidity control methods are diverse, each has its limitations, especially in terms of power consumption, response speed, and regulation comprehensiveness, and still cannot meet the requirements of efficient and stable operation of the fuel cell system. Summary of the Invention

[0005] Embodiments of the present invention provide a fuel cell cathode humidity control device and method to solve the following technical problems: The current fuel cell cathode humidity control methods have certain defects in terms of power consumption, response speed, regulation comprehensiveness, etc., and still cannot meet the requirements of efficient and stable operation of the fuel cell system.

[0006] Embodiments of the present invention adopt the following technical solutions:

[0007] On the one hand, an embodiment of the present invention provides a fuel cell cathode humidity control device, which includes: The device at least includes: an air compressor, a membrane humidifier, a back pressure valve, and a regulating valve;

[0008] 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;

[0009] 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;

[0010] Both ends of the regulating valve are respectively connected to the dry chamber outlet and the wet chamber inlet of the membrane humidifier, forming a circulation path between the dry chamber and the wet chamber of the membrane humidifier.

[0011] In a feasible embodiment, 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 a pressure difference, reducing the humidity of the wet chamber, and further reducing the humidification efficiency of the membrane humidifier for the dry chamber air;

[0012] When the cathode of the fuel cell stack is in a low humidity state, the regulating valve performs an opening operation based on a control signal, and at the same time the back pressure valve reduces the opening based on a control signal. 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 a pressure difference, humidifying the air entering the fuel cell stack;

[0013] When the fuel cell stack is in a normal humidity state, the regulating valve performs a closing operation based on a control signal.

[0014] In a feasible embodiment, the device further includes: a humidity sensor, a DCDC converter, and a current sensor;

[0015] The humidity sensor is connected to the cathode of the fuel cell stack for monitoring the cathode humidity;

[0016] The DCDC converter is connected to the current output terminal of the fuel cell stack for regulating the voltage output by the fuel cell to the outside and obtaining the load current;

[0017] The current sensor is installed in the connection path between the DCDC converter and the current output terminal of the fuel cell stack for obtaining the load current and sending it to the DCDC converter.

[0018] On the other hand, an embodiment of the present invention also provides a fuel cell cathode humidity control method, which includes:

[0019] Measure the cathode humidity and load current of the fuel cell stack through a humidity sensor and a current sensor respectively;

[0020] Determine the 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;

[0021] Call the corresponding air flow determination strategy based on the current working mode, and obtain the current air flow demand value;

[0022] Generate a control signal according to the current working mode and the current air flow demand value, and control the air compressor, the regulating valve and the back pressure valve to perform control operations.

[0023] In a feasible implementation manner, determining the current working mode of the fuel cell stack according to the cathode humidity and the load current specifically includes:

[0024] Determine the corresponding reference humidity according to the load current;

[0025] When the absolute value of the difference between the cathode humidity and the reference humidity exceeds a first preset threshold, the current working mode of the fuel cell stack is the safety mode;

[0026] 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 a second preset threshold, and the duration exceeds a preset duration, the fuel cell stack enters the transient mode;

[0027] 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 working mode of the fuel cell stack is the steady state mode.

[0028] In a feasible implementation manner, calling the corresponding air flow determination strategy based on the current working mode, and obtaining the current air flow demand value specifically includes:

[0029] In the case where the current working mode is the safety mode, call the first air flow demand calculation formula in the first air flow determination strategy, obtain the required parameters in the formula, and calculate the corresponding first air flow demand value;

[0030] In the case where the current working mode is the transient mode, call the second air flow determination strategy, query a preset mapping table according to the load current, and obtain the corresponding second air flow demand value;

[0031] When the current working mode is the steady state mode, the third air flow rate determination strategy is called, the weight coefficient is determined according to the current operating state, and the current first air flow rate demand value and the second air flow rate demand value are weighted and calculated according to the weight coefficient to obtain the third air flow rate demand value.

[0032] In a feasible implementation manner, when the current working mode is the safety mode, the air flow rate demand calculation formula in the first air flow rate determination strategy is called, the required parameters in the formula are obtained, and the corresponding first air flow rate demand value is calculated, specifically including:

[0033] 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 ;

[0034] According to the first air flow rate demand calculation formula , calculate the first air flow rate demand value;

[0035] Among them, is a calibration parameter related to the fuel cell system selection; is a calibration parameter related to the cathode flow channel length and shape of the fuel cell stack; I is the load current; is the air relative humidity constant, calibrated according to the operating environment; is the reference humidity;

[0036] , is the relative humidity of saturated water vapor at the current temperature T;

[0037] , is the absolute concentration of saturated water vapor at the current temperature T; among them, R is the universal gas constant, is the molar mass of water.

[0038] In a feasible implementation manner, after calling the corresponding air flow rate determination strategy based on the current working mode and calculating the current air flow rate demand value, the method further includes:

[0039] When the current working mode is the safety mode, if the difference between the cathode humidity and the reference humidity is greater than , then control the regulating valve to open, and calculate the gas flow rate through the regulating valve according to the cathode inlet pressure and the cathode outlet pressure of the fuel cell stack; among them, is the first preset threshold;

[0040] If the difference between the cathode humidity and the reference humidity is less than , the opening of the back pressure valve is controlled to decrease so as to increase the gas pressure in the exhaust passage. Meanwhile, the regulating valve is controlled to open, and the gas flow rate through the regulating valve is calculated according to the cathode inlet pressure and the cathode outlet pressure of the fuel cell stack;

[0041] The gas flow rate through the regulating valve is compensated to the first air flow rate demand value to obtain the actual air flow rate demand value in the safety mode.

[0042] In a feasible implementation manner, calculating the gas flow rate through the regulating valve according to the cathode inlet pressure and the cathode outlet pressure of the fuel cell stack specifically includes:

[0043] Based on the linear nozzle equation q = k(p in - p out ), the gas flow rate q through the regulating valve is calculated; 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, and p out is the cathode outlet pressure of the fuel cell stack;

[0044] When only the regulating valve is opened, the 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 a pressure loss, p in > p out , and at this time q is a positive value;

[0045] When the regulating valve is opened and the opening of the back pressure valve is decreased, the gas pressure in the exhaust passage is increased, p in < p out , and at this time q is a negative value.

[0046] In a feasible implementation manner, generating a control signal according to the current working mode and the current air flow rate demand value, and controlling the air compressor, the regulating valve, and the back pressure valve to perform control operations specifically includes:

[0047] Generating a regulating valve control signal and a back pressure valve control signal according to the current working mode; and controlling the opening and closing of the regulating valve based on the regulating valve control signal, and controlling the opening of the back pressure valve based on the back pressure valve control signal;

[0048] Generating an air compressor control signal according to the current air flow rate demand value; and controlling the air compressor to input the required air flow rate to the fuel cell stack based on the air compressor control signal.

[0049] Compared with the prior art, a fuel cell cathode humidity control method and device provided by an embodiment of the present invention have the following beneficial effects:

[0050] 1. The humidity control of the fuel cell cathode is achieved by adjusting the air flow output by the air compressor, avoiding the additional power consumption generated by an externally added controllable humidifier.

[0051] 2. It can control the humidity of the fuel cell cathode in real time during operation. Compared with the shutdown purge scheme, on the one hand, it can proactively avoid the fuel cell cathode from being too dry or too wet, and on the other hand, it can immediately adjust the over-dry and over-wet conditions without shutting down the machine.

[0052] 3. Considering both the humidity of the fuel cell cathode and the air flow requirements of the load current, different operating modes and corresponding air flow requirement algorithms are provided. Compared with a single scheme, it can take into account the water management balance of the fuel cell and normal power output.

[0053] 4. Seriously considering the influence of the pressure difference between the inlet and outlet of the battery cathode on the gas flow direction of the circulation path, a valve control scheme is proposed. Only one additional regulating valve is used to achieve the two-way air flow of the circulation path, meeting the adjustment requirements in both over-wet and over-dry situations.

[0054] 5. The layout position of the circulation path on the one hand satisfies the purging of the wet cavity of the membrane humidifier in the over-wet situation, and on the other hand directly introduces the wet air into the stack in the over-dry situation, avoiding the condensation of the wet air entering the intercooler or reducing the water concentration difference between the wet and dry cavities by entering the dry cavity of the membrane humidifier.

[0055] In summary, the fuel cell cathode humidity control method provided by the present invention does not require shutdown purging, can take into account the water management balance and normal power output, and has a fast control response speed, meeting the requirements of efficient and stable operation of the fuel cell system. Description of the Drawings

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. In the drawings:

[0057] Figure 1 It is a schematic structural diagram of a fuel cell cathode humidity control device provided by an embodiment of the present invention;

[0058] Figure 2 It is a flowchart of a fuel cell cathode humidity control method provided by an embodiment of the present invention;

[0059] Figure 3 It is a flowchart of the control method corresponding to Embodiment 1 provided by an embodiment of the present invention;

[0060] Figure 4 This is the flowchart of the control method corresponding to the second embodiment provided by the embodiments of the present invention.

[0061] Reference numerals:

[0062] 1. Air compressor; 2. Intercooler; 3. Membrane humidifier; 31. Dry chamber of the membrane humidifier; 32. Wet chamber of the membrane humidifier; 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 implementation manners

[0063] In order to enable those skilled in the art of the present technology to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of this specification, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0064] First, the embodiments of the present invention provide a fuel cell cathode humidity control device, as Figure 1 shown, the device at least includes: an air compressor 1, a membrane humidifier 3, a back pressure valve 51, a control valve 52, and a fuel cell stack 4;

[0065] The air compressor 1 is connected to the inlet of the dry chamber 31 of the membrane humidifier, and the outlet of the dry chamber 31 of the membrane humidifier 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 wet chamber 32 of the membrane humidifier, and the outlet of the wet chamber 32 of the membrane humidifier is connected to the back pressure valve 52.

[0066] Further, as Figure 1 shown, both ends of the control valve 52 are respectively connected to the outlet of the dry chamber 31 of the membrane humidifier and the inlet of the wet chamber 31 of the membrane humidifier, forming a circulation path between the dry chamber and the wet chamber of the membrane humidifier.

[0067] 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 the control signal. Under the action of the pressure difference, the gas in the membrane humidifier 3 flows from the dry chamber outlet to the wet chamber inlet through the regulating valve 52, reducing the humidity of the wet chamber, thereby reducing the humidification efficiency of the membrane humidifier for the air in the dry chamber and decreasing 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. At the same time, the back pressure valve 51 reduces the opening degree based on the control signal, increasing the pressure in the exhaust passage. Under the action of the pressure difference, the gas in the membrane humidifier 3 flows from the wet chamber inlet to the dry chamber outlet through the regulating valve 52 to humidify 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.

[0068] It should be noted that the inlets and outlets of the dry chamber and the wet chamber of the membrane humidifier 3 are not one-way channels. Gas can flow in or out from the inlet, and similarly, gas can flow out or in from the outlet. The inlets and outlets in the present invention are only used to assist in describing the positional relationship between various components and do not limit the gas flow direction.

[0069] Further, as Figure 1 shown, the device further includes: a humidity sensor 10, a DCDC converter 6, and a current sensor 12.

[0070] The humidity sensor 10 is connected to the cathode of the fuel cell stack 4 and is used to monitor the cathode humidity. The DCDC converter 6 is connected to the current output terminal of the fuel cell stack and is used to regulate the voltage output 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 and is used to obtain the load current and send it to the DCDC converter 6.

[0071] Further, as Figure 1 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.

[0072] The intercooler 2 is installed between the air compressor 1 and the membrane humidifier 3, and is used 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, and is used to monitor the air mass flow output by the air compressor 1. The cathode inlet pressure sensor 91 is installed in the passage between the dry chamber 31 of the membrane humidifier and the cathode of the fuel cell stack 4, and the cathode outlet pressure sensor 92 is installed in the passage between the wet chamber 32 of the membrane humidifier and the cathode of the fuel cell stack 4, and is used to monitor the pressure difference on both sides of the regulating valve 52, and is used to calculate the air flow rate through the regulating valve 52. The temperature sensor 11 is installed on the cathode of the fuel cell stack 4, and is used to monitor the cathode temperature, and is used for the phase state calculation of the cathode water, and further proposes the flow rate requirement. The controller unit 7 is communicatively connected to the entire fuel cell cathode humidity control device, and is used to receive all the sensor signals in the fuel cell cathode humidity control device, perform operations, and send control signals to the valves and the air compressor.

[0073] To improve the fuel cell life, 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, starting from the cathode side, that is, the air supply subsystem, to carry out humidity control is the most efficient way. Based on the principle of the purging effect of air on water vapor and liquid water in the cathode cavity, the present invention proposes a control method for affecting the water discharge rate by controlling the air mass flow rate. At high humidity, appropriately increase the air flow rate to enhance the shearing force of air purging; at low humidity, appropriately reduce the air flow rate to avoid dehydration of the proton exchange membrane.

[0074] Based on the above basic principle: Let the load current also participate in the decision-making of the air flow rate requirement. This is because different load currents will have different required flow rates, and when adjusting the air flow rate, humidity cannot be the only factor considered. Based on the humidity and current signals, three modes, namely the safety mode, the transient mode, and the steady state mode, are divided to make decisions on the air flow rate requirement. Among them, when the humidity signal seriously deviates from the normal value, enter the safety mode, and humidity control is prioritized in the safety mode; when the humidity signal has no serious deviation and the load is in the process of loading or unloading, enter the transient mode, and the flow rate requirement in the transient mode gives priority to meeting the change requirement of the load current; when the humidity signal has no serious deviation and the load has no obvious change, enter the steady state mode, and control the air flow rate considering the current load and humidity simultaneously.

[0075] Based on the above basic principle, in the safe mode: a circulation path connecting the dry chamber 31 and the wet chamber 32 of the membrane humidifier and a regulating valve 52 are introduced. At high humidity, the regulating valve 52 is opened, and under the action of the pressure difference, the gas flows from the outlet of the dry chamber 31 through the regulating valve 52 to the inlet of the wet chamber 32, quickly purging to reduce the humidity of the wet chamber 32 and avoiding excessive humidification of the membrane humidifier 3; at low humidity, the regulating valve 52 is opened, and at the same time, the opening of the back pressure valve 51 is reduced to build up the pressure in the exhaust passage, so that the gas flows from the inlet of the wet chamber 32 through the regulating valve 52 to the outlet of the dry chamber 31 under the action of the pressure difference to humidify the air entering the fuel cell stack 4. After the humidity returns to normal, the regulating valve 52 is closed, and the transient mode or the steady state mode is entered.

[0076] Based on the above device, an embodiment of the present invention further provides a fuel cell cathode humidity control method, as Figure 2 shown, the fuel cell cathode humidity control method specifically includes steps S101 - S104:

[0077] S101. Measure the cathode humidity and the load current of the fuel cell stack through a humidity sensor and a current sensor respectively.

[0078] Specifically, during the operation of the fuel cell, through the Figure 1 humidity sensor 10 in the device shown, the cathode humidity of the fuel cell stack 4 is measured in real time. At the same time, the load current of the fuel cell stack is measured in real time through the current sensor 12.

[0079] Furthermore, a reference humidity is preset according to the magnitude of the load current .

[0080] As a feasible implementation manner, the reference humidity is expressed as the recommended humidity when the fuel cell meets the healthy water management state and under a certain current load. A mapping table of different load current magnitudes and reference humidity can be formulated in advance, and the corresponding reference humidity can be found in the mapping table after obtaining the load current.

[0081] S102. Determine the 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 the safe mode, the transient mode and the steady state mode.

[0082] Specifically, when the absolute value of the difference between the cathode humidity and the reference humidity exceeds the first preset threshold, the current working mode of the fuel cell stack is the safe mode.

[0083] 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.

[0084] 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.

[0085] In one embodiment, after the humidity sensor monitors the cathode humidity of the fuel cell stack and compares it with the reference humidity corresponding to the load current and calculates the difference , when the absolute value of the difference , it enters the safety mode.

[0086] When , it continues to judge the change of the current load. When the current change rate and the duration exceeds 300 ms, it enters the transient mode.

[0087] When and , it is determined as the steady-state mode.

[0088] It should be noted that the specific thresholds need to be calibrated according to the actual situation. The above embodiments are only examples and do not limit the numerical values of each threshold in this application.

[0089] S103. Call the corresponding air flow determination strategy based on the current operating mode and obtain the current air flow demand value.

[0090] Specifically, in the case where the current operating mode is the safety mode, call the first air flow demand calculation formula in the first air flow determination strategy, obtain the required parameters in the formula, and calculate the corresponding first air flow demand value.

[0091] In the case where the current operating mode is the transient mode, call the second air flow determination strategy, query the preset mapping table according to the load current, and obtain the corresponding second air flow demand value.

[0092] In the case where the current operating mode is the steady-state mode, call the third air flow determination strategy, determine the weight coefficient according to the current operating state, and perform weighted calculation on the current first air flow demand value and the second air flow demand value according to the weight coefficient to obtain the third air flow demand value.

[0093] As a feasible implementation manner, in the case where the current operating mode is the safety mode, obtain the cathode inlet air pressure of the fuel cell stack through the cathode inlet pressure sensor ;

[0094] According to the first air flow demand calculation formula , calculate the first air flow demand value.

[0095] Among them, is a calibration parameter, related to the selection of the fuel cell system; is a calibration parameter, 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.

[0096] , is the relative humidity of saturated water vapor at the current temperature T;

[0097] , is the absolute concentration of saturated water vapor at the current temperature T; among them, R is the universal gas constant, is the molar mass of water.

[0098] Q1 is the air flow demand under the condition that the measurement value of the humidity sensor is too high or too low, that is, in the safety mode. It is established based on the flow-humidity equation, and the purpose is 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 decreased.

[0099] As a feasible implementation method, when the current working mode is the transient mode, the reference air flow (which can be obtained by looking up the mapping table) is preset with reference to the magnitude of the load current I. The reference air flow given only depends on the current, and is set to ensure sufficient reactants for the fuel cell system under a certain current load. When the current load changes suddenly, to avoid the hydrogen and oxygen starvation phenomena caused by insufficient reactants, there is: .

[0100] 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, on the one hand, meet the reactant demand of the fuel cell stack, and on the other hand, also make a forward-looking compensation for the possible water management imbalance. Therefore, it is set that the weighted average of Q1 and Q2 is defined as the third air flow demand Q3, and there is: .

[0101] In the formula, is the weight coefficient, used to allocate the proportion of Q1 and Q2. In an example, the recommended value of the weight coefficient during the smooth operation process is 0.1 - 0.2, and the recommended value of the weight coefficient during the cold start process is 0.5 - 0.6.

[0102] Further, 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 cases: over-wet and over-dry, that is:

[0103] If the difference between the cathode humidity and the reference humidity is greater than , in this case of over-wet, control the regulating valve to open, connect the outlet of the dry chamber 31 of the membrane humidifier and the wet chamber 32 of the membrane humidifier. Under the action of the pressure difference, dry air flows into the wet chamber 32 of the membrane humidifier, reducing the water concentration in the wet chamber, and thus reducing the humidification efficiency of the membrane humidifier 3. After opening the regulating valve, calculate the gas flow rate through the regulating valve according to the cathode inlet pressure and the cathode outlet pressure of the fuel cell stack; where is the first preset threshold.

[0104] If the difference between the cathode humidity and the reference humidity is less than , in this case of over-dry, control the back pressure valve to reduce its opening degree to increase the gas pressure in the exhaust passage. At the same time, control the regulating valve 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, calculate the gas flow rate through the regulating valve according to the cathode inlet pressure and the cathode outlet pressure of the fuel cell stack.

[0105] Further, compensate the gas flow rate through the regulating valve to the first air flow rate demand value to obtain the actual air flow rate demand value in the safety mode.

[0106] As a feasible implementation method, the gas flow rate calculation method of the regulating valve is as follows:

[0107] Based on the linear nozzle equation q = k(p in - p out ), calculate the gas flow rate 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, and p out is the cathode outlet pressure of the fuel cell stack.

[0108] When only the regulating valve is opened, dry air flows from the outlet of the dry chamber of the membrane humidifier into the inlet of the wet chamber, and the air generates a pressure loss after passing through the fuel cell stack, p in > p out , and at this time q is positive. When the regulating valve is opened and the opening degree of the back pressure valve is reduced, the gas pressure in the exhaust passage is increased, p in < p out , and at this time q is negative. Compensate the gas flow rate q through the regulating valve to the first air flow rate demand value Q1, that is, add the two to obtain the actual air flow rate demand value in the safety mode.

[0109] S104. Generate a control signal according to the current working mode and the current air flow demand value, and control the air compressor, the regulating valve, and the back pressure valve to perform control operations.

[0110] Specifically, generate a regulating valve control signal and a back pressure valve control signal according to the current working mode; and based on the regulating valve control signal, control the opening and closing of the regulating valve, and based on the back pressure valve control signal, control the opening degree of the back pressure valve.

[0111] Furthermore, generate an air compressor control signal according to the current air flow demand value; and based on the air compressor control signal, control the air compressor to input the required air flow to the fuel cell stack.

[0112] As a feasible implementation manner, 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, calculate the air compressor speed control signal according to the sum Q1 + q of the first air flow demand value and the compensation air flow; in the transient mode, calculate the air compressor speed control signal according to the second air flow demand Q2; in the steady state mode, calculate according to the third air flow demand Q3.

[0113] 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 the following two embodiments.

[0114] Embodiment 1:

[0115] Figure 3 For the control method flowchart corresponding to Embodiment 1 provided by the embodiment of the present invention, as Figure 3 shown, the humidity sensor and the DCDC converter simultaneously collect the cathode humidity and the 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 through the method provided above.

[0116] Further, according to whether the absolute value of the difference between the cathode humidity and the reference humidity is greater than 15%, it is determined whether the current fuel cell has entered the safety mode. If so, the first air flow demand Q1 is forced to be used. At this time, according to whether the humidity is too dry or too wet, there are two control strategies: 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 path, and the air flow q passing through the regulating valve is calculated and compensated in 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 in the exhaust path of the battery. At the same time, the regulating valve 52 is opened to allow the gas in the membrane humidifier to flow from the wet chamber to the dry chamber to humidify the air flowing into the battery, and the air flow q passing through the regulating valve is calculated and compensated in the first air flow demand Q1 to control the air compressor.

[0117] If the absolute value of the difference between the cathode humidity and the reference humidity is not greater than 15%, then continue to judge whether the change rate of the load current is greater than 5 A / s. If so, when this situation lasts for more than 300 ms, it is judged that the current fuel cell has entered the transient mode, and the second air flow demand Q2 is forced to be used to control the air compressor. If not, it is judged that the current fuel cell has entered the steady state mode, and then the weighted average value of Q1 and Q2 is used to obtain Q3 to control the air compressor.

[0118] Embodiment 2:

[0119] Figure 4 The flowchart of the control method corresponding to Embodiment 2 provided by the present invention. The present invention can also adopt the decision sequence of first judging whether the battery enters the transient mode and then judging whether it enters the safety mode. As Figure 4 shown, after calculating Q1 and Q2, first judge whether the current battery enters the transient mode according to whether the change rate of the load current is greater than 5 A / s and lasts for more than 300 ms. If not, then continue to judge whether the current battery enters the safety mode according to whether the absolute value of the difference between the cathode humidity and the reference humidity is greater than 15%. The remaining processes are the same as those in Embodiment 1.

[0120] It should be noted that in the present invention, calculating Q1 and Q2 and judging the current working mode do not have a strict sequence. It is possible to calculate Q1 and Q2 first and then perform the mode judgment, or to perform the mode judgment first and then calculate Q1 and Q2. The present invention does not limit this sequence, as long as it does not affect the execution of the whole process. Any sequence change, equivalent replacement and other schemes made within the principle provided by the present invention should be included in the protection scope of the present invention.

[0121] Each embodiment in the present invention is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the embodiments of the device, equipment, and non-volatile computer storage medium, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiments.

[0122] The specific embodiments of the present invention have been described above. Additionally, the processes depicted in the drawings do not necessarily require the specific order or consecutive order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0123] The above description is only for the embodiments of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and changes can be made to the embodiments of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the embodiments of the present invention shall be included within 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, so that the device performs: 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, 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, 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, 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 the first air flow demand value; wherein, 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; 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, a weight coefficient is determined according to the current operating state, and a weighted calculation is performed on the current first air flow demand value and the second air flow demand value according to the weight coefficient to obtain a third air flow demand value; 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.

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, 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, 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, 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 the first air flow demand value; wherein, 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; 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, a weight coefficient is determined according to the current operating state, and a weighted calculation is performed on the current first air flow demand value and the second air flow demand value according to the weight coefficient to obtain a third air flow demand value; 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 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.

7. A fuel cell cathode humidity control method according to claim 6, 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.

8. 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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