Fuel cell purging control system and control method

Abstract

The invention discloses a fuel cell purging control system and control method. The system comprises an electric pile; the electric pile is provided with an air conveying module, a hydrogen conveying module and a temperature control module; the air conveying module and the hydrogen conveying module are used for blowing the inner side of the electric pile, and the power of the air conveying module, the power of the hydrogen conveying module and the power of the temperature control module are controlled according to the water temperature at the outlet of the electric pile, so that the net output power of the control system is zero; the temperature of the electric pile is adjusted through the temperature control module, when the temperature is lower than the preset target value and the net output power is zero, the temperature of the electric pile and the rotating speed of the air compressor are increased, then purging is conducted, the water removal effect is improved, and the purging speed is increased.

Description

Technical Field

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

[0002] The environmental suitability of fuel cells is a key factor in determining their large-scale application in real-world scenarios. In low-temperature environments below 0°C, liquid water in the diffusion layer and membrane electrode freezes, causing volume expansion changes. Frequent freezing and thawing can cause irreversible mechanical damage. Freezing of the diffusion layer and catalyst layer can hinder fuel cell gas diffusion and reduce catalytic reaction efficiency, leading to cold start failure of the fuel cell system. Therefore, purging the fuel cell before low-temperature storage aims to reduce the amount of liquid water inside the cell, thereby minimizing irreversible damage to the cell caused by freezing and thawing, and ensuring a successful cold start of the fuel cell system.

[0003] However, when existing fuel cells are purged, when the system water temperature is low, liquid water is not easy to evaporate, which can easily lead to the inability to completely remove the liquid water. In addition, the purging time is too long. During no-load purging, the voltage of a single cell is higher than 0.9V. It is in a high potential and membrane dry state for a long time, which can easily cause carbon corrosion and lead to a significant decrease in the catalytic performance of the membrane electrode.

[0004] For a control system that is parked after being shut down, the system can only be purged by running it for a period of time. This is inefficient and consumes a lot of energy, and it is easy to cause the power battery to overcharge. Summary of the Invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a fuel cell purge control system and control method.

[0006] In order to achieve the above-mentioned object, the present invention adopts the following technical solution: a fuel cell purge control system, comprising:

[0007] Battery stack;

[0008] The fuel cell stack is provided with an air delivery module, a hydrogen delivery module and a temperature control module;

[0009] The inside of the fuel cell stack is purged through the air delivery module and the hydrogen delivery module, and the power of the air delivery module, the hydrogen delivery module and the temperature control module are controlled according to the water temperature at the outlet of the fuel cell stack, so that the net output power of the control system is zero.

[0010] As a further description of the above technical solution: the air delivery module includes an air filter, the output end of the air filter is connected to the input end of the air compressor, the output end of the air compressor is connected to the input end of the intercooler, and the output end of the intercooler is connected to a three-way valve; the output end of the three-way valve is connected to a humidifier or a tail exhaust pipe.

[0011] As a further description of the above technical solution: the hydrogen delivery module includes a proportional valve, and the output end of the proportional valve is connected to the fuel cell stack.

[0012] As a further description of the above technical solution: the fuel cell stack is connected to a water distribution component and a hydrogen circulation pump in sequence, and the output end of the hydrogen circulation pump is connected to the output end of the proportional valve.

[0013] As a further description of the above technical solution: the output end of the water distribution component is connected to the tail discharge pipeline.

[0014] As a further description of the above technical solution: the temperature control module includes a water pump, and the input end of the water pump receives the circulating medium delivered by the fuel cell stack.

[0015] As a further description of the above technical solution: the output end of the water pump is connected to the input end of the thermostat, the output end of the thermostat is respectively connected to a radiator and a heater connected in parallel, the output ends of the radiator and the heater are connected to the fuel cell stack, so that the circulating medium circulates between the fuel cell stack and the temperature control module.

[0016] Also included is a fuel cell purge control method, comprising:

[0017] S1: Get the water temperature at the stack outlet;

[0018] S2: determining whether the water temperature reaches a preset purge target value based on the water temperature; if so, executing the purge;

[0019] S3: If not, enter the heating state and return to step S1, wherein when entering the heating state, the net output power of the control system is set to zero according to a preset control strategy.

[0020] As a further description of the above technical solution: the preset control strategy includes:

[0021] Controlling the current density in the temperature-raising state, controlling the pressure and flow of hydrogen delivery according to the current density, and calculating the corresponding pressure and flow of air delivery to control the speed of the air compressor;

[0022] If the air compressor has reached the maximum power and the net output power of the control system is not zero, the heater is turned on to increase the power of the temperature control module until the net output power is zero.

[0023] As a further description of the above technical solution: the ambient temperature outside the control system is obtained. If the ambient temperature is less than 0°C and no purge is performed before the control system is shut down, the control system directly enters a heating state after being turned on.

[0024] The above technical solution has the following advantages or beneficial effects:

[0025] The temperature of the fuel cell stack is adjusted through the temperature control module. When the temperature is lower than the preset target value, the temperature of the fuel cell stack and the speed of the air compressor are increased when the net output power is zero, and then purging is performed, which improves the water removal effect and speeds up the purging speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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 description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a schematic diagram of the structure of the control system proposed by the present invention;

[0028] Figure 2 This is a flow chart of the control method proposed in the present invention.

[0029] Legend:

[0030] 1. Fuel cell stack; 2. Air filter; 3. Air compressor; 4. Intercooler; 5. Three-way valve; 6. Humidifier; 7. Tail exhaust pipe; 8. Proportional valve; 9. Water distribution component; 10. Hydrogen circulation pump; 11. Water pump; 12. Thermostat; 13. Radiator; 14. Heater. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Reference Figure 1The present invention provides an embodiment of a fuel cell purge control system, comprising: a fuel cell stack 1; the fuel cell stack 1 is provided with an air delivery module, a hydrogen delivery module and a temperature control module; the inside of the fuel cell stack 1 is purged through the air delivery module and the hydrogen delivery module, and the power of the air delivery module, the hydrogen delivery module and the temperature control module is controlled according to the water temperature at the outlet of the fuel cell stack 1, so that the net output power of the control system is zero.

[0033] In this embodiment, the air delivery module provides the air required for the reaction to the cathode of the fuel cell stack 1, and the hydrogen delivery module provides the hydrogen required for the reaction to the anode of the fuel cell stack 1. The temperature control module controls the reaction temperature of the fuel cell stack 1, and delivers the circulating medium to the fuel cell stack 1 to absorb the heat generated by the fuel cell stack 1. The circulating medium can be optionally water. The air delivery module and the hydrogen delivery module provide the necessary reactants for the fuel cell stack 1, and the temperature control module creates a suitable working environment for the fuel cell stack 1. When the power demand of the fuel cell stack 1 increases, the air delivery module will increase the air supply through the air compressor 3, and the hydrogen delivery module will increase the hydrogen supply through the proportional valve 8. At the same time, the temperature control module will adjust the flow rate and heat dissipation method of the circulating medium according to the heat generated by the fuel cell stack 1 to maintain the temperature stability of the fuel cell stack 1.

[0034] When the system is shut down and needs to be purged, the air delivery module and the hydrogen delivery module are used to purge the inside of the fuel cell stack 1 to remove impurities, moisture, residual gas, etc. inside the fuel cell stack 1. In a low-temperature environment, purging can also prevent moisture from freezing and causing damage to the fuel cell stack 1, ensuring the cleanliness and stability of the interior of the fuel cell stack 1. The water temperature at the outlet of the fuel cell stack 1 reflects the working status and internal temperature of the fuel cell stack 1, making the net output power of the control system zero, which means that the control system does not output electrical energy to the outside, and is in the preparation stage before the control system is started, the purge stage after shutdown, or when an abnormal situation requires adjustment, the net output power is controlled to zero. It can ensure that the control system performs internal adjustments in a safe and stable state, avoiding the impact on external equipment due to unstable or abnormal output power.

[0035] The air delivery module includes an air filter 2, the output end of the air filter 2 is connected to the input end of the air compressor 3, the output end of the air compressor 3 is connected to the input end of the intercooler 4, the output end of the intercooler 4 is connected to the three-way valve 5; the output end of the three-way valve 5 is connected to the humidifier 6 or the tail exhaust pipe 7.

[0036] In this embodiment, the air filter 2 filters out dust, particles, impurities, etc. in the air to prevent impurities from entering subsequent equipment, wearing out the components of the air compressor 3, or adhering to the surface of the electrodes of the fuel cell stack 1 and affecting the electrochemical reaction. The air compressor 3 compresses the clean air that passes through the air filter 2 to increase the oxygen delivery rate and pressure to meet the oxygen demand of the fuel cell stack 1 under different working conditions. The process of air compression by the air compressor 3 will increase the air temperature. The high-temperature air entering the fuel cell stack 1 will affect its performance. The compressed high-temperature air is cooled by the intercooler 4 to ensure that the fuel cell stack 1 performs electrochemical reactions in a suitable temperature environment. The three-way valve 5 plays a diversion control role, directing the air passing through the intercooler 4 to different paths. When the fuel cell stack 1 needs to humidify the air, the three-way valve 5 directs the air to the humidifier 6, so that the air reaches the appropriate humidity before entering the fuel cell stack 1, avoiding the air humidity being too low and the proton exchange membrane conductivity being deteriorated; when the control system needs to perform operations such as purging, the three-way valve 5 can direct the air to the tail pipe 7, discharging it out of the control system to maintain a stable air environment inside the control system.

[0037] The hydrogen delivery module includes a proportional valve 8, the output end of the proportional valve 8 is connected to the fuel cell stack 1, and the fuel cell stack 1 is connected to the water distribution component 9 and the hydrogen circulation pump 10 in sequence. The output end of the hydrogen circulation pump 10 is connected to the output end of the proportional valve 8, and the output end of the water distribution component 9 is connected to the tail exhaust pipeline 7.

[0038] In this embodiment, the proportional valve 8 adjusts the flow rate and pressure of hydrogen entering the fuel cell stack 1 according to the instructions of the fuel cell control system (FCU), ensuring that hydrogen and air participate in the electrochemical reaction in the fuel cell stack 1 in appropriate proportions, thereby improving the power generation efficiency and stability of the fuel cell stack 1 and avoiding performance degradation or failure due to improper hydrogen supply.

[0039] During the electrochemical reaction of hydrogen, water will be produced and flow along with the hydrogen. The water in the hydrogen is separated by the water separator 9, and the separated water is discharged to the tail discharge pipe 7 through the output end to maintain the dryness and stability of the hydrogen delivery module. The hydrogen circulation pump 10 transports the hydrogen in the fuel cell 1 that has not participated in the reaction back to the fuel cell 1, thereby improving the utilization rate of the hydrogen. The tail discharge pipe 7 receives the water separated by the water separator 9 and the water in the fuel cell 1 during purging, maintains the internal pressure and material balance of the hydrogen delivery module, and ensures the normal operation of the control system.

[0040] The temperature control module includes a water pump 11, whose input receives circulating medium from the fuel cell stack 1. The output of the water pump 11 is connected to the input of a thermostat 12. The output of the thermostat 12 is connected to a radiator 13 and a heater 14 connected in parallel. The outputs of the radiator 13 and heater 14 are connected to the fuel cell stack 1, allowing the circulating medium to circulate between the fuel cell stack 1 and the temperature control module.

[0041] In this embodiment, the input end of the water pump 11 receives the circulating medium from the battery stack 1, and then pressurizes it through mechanical power so that it can circulate between the entire temperature control module and the battery stack 1. The thermostat 12 performs temperature regulation and diversion functions, controlling the flow direction of the medium according to the temperature of the circulating medium. When the temperature of the circulating medium is low, the thermostat 12 directs the circulating medium to the heater 14 to quickly increase the temperature of the circulating medium so that the battery stack 1 can reach the appropriate operating temperature as soon as possible. When the temperature of the circulating medium is high, the thermostat 12 directs most of the circulating medium to the radiator 13, which dissipates heat through the radiator 13, lowering the temperature of the circulating medium and ensuring that the battery stack 1 operates within an appropriate temperature range. The radiator 13 is used to cool the circulating medium, quickly cooling the high-temperature circulating medium, and then returning the cooled circulating medium to the battery stack 1 to continue absorbing the heat generated by the battery stack 1. The heater 14 can optionally be a PTC heater 14. When the battery stack 1 is started or in a low-temperature operating condition, the circulating medium temperature is low, which is not conducive to the normal operation of the battery stack 1. At this time, the heater 14 heats the circulating medium. During the purge, the heater 14 heats up to maintain the net output power of the control system at zero, and discharges the water evaporated by heating in the fuel cell stack 1 to improve the dehydration effect.

[0042] Reference Figure 2 , further comprising an embodiment of a fuel cell purge control method, comprising:

[0043] S1: Get the water temperature at the stack outlet;

[0044] S2: Determine whether the preset purge target value is reached based on the water temperature. If so, execute the purge;

[0045] S3: If not, enter the heating state and return to step S1, wherein when entering the heating state, the net output power of the control system is set to zero according to a preset control strategy.

[0046] In this embodiment, the water temperature at the outlet of the battery stack is obtained, which can intuitively reflect the heat situation inside the battery stack, and the obtained water temperature is compared with the preset purge target value. If the water temperature reaches or exceeds this target value, it means that a lot of heat may have accumulated inside the battery stack. At this time, performing a purge operation can effectively remove impurities and water vapor inside the battery stack. When the water temperature does not reach the preset purge target value, the control system enters a heating state through the temperature control module. Under low temperature conditions, the performance of the battery stack may be affected. If power is continued to be output to the outside at this time, it will not only be inefficient, but may also cause damage to the battery stack. By setting the net output power to zero, the control system can concentrate energy on increasing the temperature of the battery stack, preventing the generation of high potential, and thereby improving the durability of the battery stack.

[0047] When the water temperature at the stack outlet is greater than or equal to the target value, the control system performs on-load purge, and the on-load current density is controlled at 0.1-0.3A / cm 2 At this time, the air delivery module and the hydrogen delivery module have begun to supply a certain amount of oxygen and hydrogen, and the fuel cell stack generates a certain current, which is generally 1%-10% of the rated power. The electricity generated by the fuel cell stack is used for the electrical load components in the air delivery module, hydrogen delivery module and temperature control module, including air compressors, hydrogen circulation pumps, water pumps, etc.

[0048] The preset control strategies include:

[0049] Control the current density under the temperature rising state, control the pressure and flow of hydrogen delivery according to the current density, calculate the corresponding pressure and flow of air delivery, and use them to control the speed of the air compressor;

[0050] If the air compressor has reached the maximum power and the net output power of the control system is not zero, the heater is turned on to increase the power of the temperature control module until the net output power is zero.

[0051] In this embodiment, when the water temperature at the stack outlet is lower than the target value, the control system enters the heating state and keeps the net output power at zero. The control system pulls the current through the DCDC and controls the current density in the heating state to 0.5-0.8A / cm 2 , the current density is closed-loop controlled according to the average single-chip voltage, optionally, the average single-chip voltage is 0.3V,

[0052] The hydrogen delivery module controls the proportional valve and hydrogen circulation pump so that the pressure and flow of hydrogen at the inlet of the fuel cell stack correspond to the current density during normal operation, that is, the anode hydrogen pressure and flow are controlled according to the load current of the DCDC.

[0053] During the heating process, the air delivery module, hydrogen delivery module, and temperature control module consume power equal to the total output power of the control system, maintaining a net output power of zero. Except for the air compressor, the response and power consumption of all other components are consistent with normal operation at the current density. The power consumption of the air compressor is calculated based on the theoretical power consumption formula, which controls the compressor speed. The three-way valve opening and air flow are controlled based on the average single-chip voltage and compressor speed. When the air compressor reaches maximum power consumption and cannot meet the net output power of zero, the heater is turned on to increase power consumption. After the temperature is raised to the target value, the control system performs a purge.

[0054] Get the ambient temperature outside the control system. If the ambient temperature is less than 0°C and the control system is not purged before shutdown, the control system will directly enter the heating state after startup.

[0055] In this embodiment, when the fuel cell vehicle is parked for a long time, the ambient temperature is monitored to be lower than 0°C and the purge is not performed before the control system is shut down. At this time, the FCU sends a purge instruction to the control system, the control system starts up and directly enters the heating state. After the water temperature at the outlet of the fuel cell stack reaches the target value, the control system performs load purge to prevent carbon corrosion caused by high potential during the no-load purge process.

[0056] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fuel cell purge control system, characterized in that: include: Battery stack; The fuel cell stack is provided with an air delivery module, a hydrogen delivery module and a temperature control module; The inside of the fuel cell stack is purged through the air delivery module and the hydrogen delivery module, and the power of the air delivery module, the hydrogen delivery module and the temperature control module are controlled according to the water temperature at the outlet of the fuel cell stack, so that the net output power of the control system is zero.

2. The control system according to claim 1, characterized in that: The air delivery module includes an air filter, the output end of the air filter is connected to the input end of the air compressor, the output end of the air compressor is connected to the input end of the intercooler, the output end of the intercooler is connected to a three-way valve; the output end of the three-way valve is connected to a humidifier or a tail exhaust pipe.

3. The control system according to claim 2, characterized in that: The hydrogen delivery module includes a proportional valve, and an output end of the proportional valve is connected to the fuel cell stack.

4. The control system according to claim 3, characterized in that: The fuel cell stack is connected to a water distribution component and a hydrogen circulation pump in sequence, and an output end of the hydrogen circulation pump is connected to an output end of the proportional valve.

5. The control system according to claim 4, characterized in that: The output end of the water distribution component is connected to the tail discharge pipeline.

6. The control system according to claim 1, characterized in that: The temperature control module includes a water pump, and an input end of the water pump receives the circulating medium delivered by the fuel cell stack.

7. The control system according to claim 6, characterized in that: The output end of the water pump is connected to the input end of the thermostat, the output end of the thermostat is respectively connected to a radiator and a heater connected in parallel, the output ends of the radiator and the heater are connected to the fuel cell stack, so that the circulating medium circulates between the fuel cell stack and the temperature control module.

8. A fuel cell purge control method, characterized in that: include: S1: Get the water temperature at the outlet of the stack; S2: determining whether the water temperature reaches a preset purge target value based on the water temperature; if so, executing the purge; S3: If not, enter the heating state and return to step S1, wherein when entering the heating state, the net output power of the control system is set to zero according to a preset control strategy.

9. The control method according to claim 8, characterized in that: The preset control strategy includes: Controlling the current density in the temperature-raising state, controlling the pressure and flow of hydrogen delivery according to the current density, and calculating the corresponding pressure and flow of air delivery to control the speed of the air compressor; If the air compressor has reached the maximum power and the net output power of the control system is not zero, the heater is turned on to increase the power of the temperature control module until the net output power is zero.

10. The control method according to claim 8, characterized in that: The ambient temperature outside the control system is obtained. If the ambient temperature is less than 0° C. and the control system is not purged before being shut down, the control system directly enters a heating state after being turned on.

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