Fuel cell control strategy and proton exchange membrane fuel cell system
By employing a phased control strategy of first consuming oxygen and then consuming hydrogen during the start-up and shutdown of the fuel cell, a low-oxygen and nitrogen-rich environment is constructed, solving the problems of hydrogen leakage and high-potential corrosion of the cathode catalyst, and achieving long life and safety of the fuel cell stack.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-03-31
AI Technical Summary
During the start-up and shutdown process of existing fuel cells, problems such as hydrogen leakage and high-potential corrosion of the cathode catalyst have not been effectively resolved, leading to safety hazards and reduced stack durability.
A staged control strategy of first consuming oxygen and then consuming hydrogen is adopted. By adjusting the gas pressure and concentration, a low-oxygen and nitrogen-rich environment is created to slow down the hydrogen-oxygen reaction rate, ensuring that the voltage drop of a single cell is gradual and consistent, and avoiding the need for additional equipment configuration.
It significantly extends the lifespan of the fuel cell stack, reduces system hardware costs, avoids the safety hazard of hydrogen leakage, and ensures the operational safety and stability of the stack.
Smart Images
Figure CN121769147A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fuel cell technology, and in particular to a fuel cell control strategy and a proton exchange membrane fuel cell system. Background Technology
[0002] Optimizing the start-up and shutdown process of fuel cells is a core aspect of improving overall system performance, extending lifespan, and ensuring safety. The purpose of optimizing the start-up and shutdown control strategy of proton exchange membrane fuel cells (PEMFC) is mainly to reduce the formation time of the hydrogen-oxygen interface and suppress high-potential corrosion of the catalyst.
[0003] The existing method involves purging the anode channel with gas (hydrogen or nitrogen) after start-up and shutdown. However, insufficient sealing of the hydrogen purging path or delayed valve closure may lead to hydrogen leakage and safety hazards. Nitrogen purging requires additional nitrogen cylinders, increasing costs. Therefore, currently, a loading method is usually used during start-up and shutdown to consume the remaining reaction gas (hydrogen-consuming discharge or oxygen-consuming discharge). Using a load to consume hydrogen can avoid the high potential caused by hydrogen back diffusion on the cathode side, reducing carbon support corrosion and catalyst oxidation. Using a load to consume oxygen directly removes oxygen from the cathode. The oxygen concentration gradually decreases, the single cell voltage drops more smoothly and the voltage drop is more consistent, which can reduce cross-diffusion with hydrogen at the anode.
[0004] Using a load to consume hydrogen, the voltage of the lower-performing cells drops rapidly during hydrogen discharge. While the voltage of other cells remains high, the voltage of the lower-performing cells has already dropped to a very low level, necessitating premature disconnection of the load. However, the other cells remain at a high potential and have a significant amount of residual hydrogen, thus failing to achieve the purpose of consuming hydrogen. Using a load to consume oxygen, it is difficult to achieve a complete seal in the cathode gas path. Oxygen from the environment can slowly permeate to the cathode side of the stack through the pipeline, and hydrogen can slowly leak to the cathode side through the membrane electrode assembly. This hydrogen can react directly with oxygen on the catalyst surface on the cathode side, affecting the stack's operational durability. Summary of the Invention
[0005] To address the problems existing in the background art, the present invention provides a fuel cell control strategy and a proton exchange membrane fuel cell system, which reduces the time the hydrogen / air interface exists inside the cell and lowers the high potential on the cathode catalyst surface.
[0006] The technical solution of this invention is as follows: This invention provides a fuel cell control strategy, including a shutdown strategy and a startup strategy. The shutdown strategy is as follows: Step 1: Upon receiving the shutdown command, the fuel cell enters idle mode; Step 2: Enter the oxygen-consuming discharge stage. Adjust the hydrogen inlet pressure on the anode side to 10-30 kPa, keep the tail valve on the anode side open, and close the air inlet valve and air outlet valve on the cathode side. Step 3: Connect the fuel cell to the DC / DC converter, set the first discharge current, and when the minimum voltage of the stack cell is less than the first voltage threshold, disconnect the DC / DC converter and close the proportional valve on the anode side. Step 4: Enter the hydrogen-consuming discharge stage. Adjust the inlet pressure on the cathode side to 10-30 kPa to make the oxygen concentration between the first and second concentration thresholds. Close the proportional valve and tail valve on the anode side. Step 5: Connect the fuel cell to the DC / DC converter, set the second discharge current, and when the minimum voltage of the stack cell is less than the second voltage threshold, disconnect the DC / DC converter and close the air compressor and air inlet valve; Step 6: Open the tailpipe valve on the anode side to allow air to enter.
[0007] By performing a phased operation of first oxygen-consuming discharge and then hydrogen-consuming discharge, the oxygen concentration in the air chamber is rapidly reduced during the oxygen-consuming discharge stage, creating a low-oxygen, nitrogen-rich environment for the cathode. The subsequent hydrogen-consuming discharge stage introduces air with a low concentration of oxygen, effectively slowing down the hydrogen-oxygen reaction rate. This results in a smoother and more consistent voltage drop in the single cell, significantly shortening the time the hydrogen / air interface remains inside the cell. Simultaneously, it effectively mitigates the corrosive effect of the high potential on the cathode catalyst surface on the carbon support, significantly extending the lifespan of the fuel cell stack. Furthermore, the entire process eliminates the need for additional nitrogen cylinders and other equipment, reducing system hardware costs. It also avoids the potential safety hazards of leakage caused by hydrogen purging, ensuring the safety and stability of the fuel cell stack operation.
[0008] Preferably, when the fuel cell enters the idling state, the load current drops to 30-100A, which can realize the smooth transition of the stack from normal operation to shutdown discharge operation, avoid the impact of sudden current changes on core components such as the stack membrane electrode, ensure the stability of the stack structure, and lay a good working condition foundation for the construction of low oxygen environment and the control of hydrogen-oxygen reaction rate in subsequent staged discharge operation.
[0009] Preferably, both the first and second discharge currents are 2-10A, with the first discharge current being greater than the second discharge current. This avoids irreversible damage to the fuel cell stack caused by high-current discharge. Furthermore, by setting a parameter ratio where the first discharge current is greater than the second discharge current, the different stages of the reaction—rapid oxygen depletion during oxygen-consuming discharge and gradual control during hydrogen-consuming discharge—are adapted to the characteristics of these reactions. During the oxygen-consuming stage, a relatively large current is used to rapidly consume cathode oxygen, efficiently creating a low-oxygen, nitrogen-rich environment. During the hydrogen-consuming stage, a relatively small current is used to precisely match the low-concentration oxygen atmosphere, further slowing down the hydrogen-oxygen reaction rate. This ensures the smoothness and consistency of the single-cell voltage drop, improving the efficiency and targeting of different discharge stages.
[0010] Preferably, the first voltage threshold is 0.3-0.5V, the second voltage threshold is 0.1-0.3V, and the first voltage threshold is greater than the second voltage threshold. By setting a stepped voltage threshold, using the first voltage threshold as the termination criterion for oxygen-consuming discharge, it can be ensured that the oxygen at the cathode is fully consumed, thus creating a stable low-oxygen and nitrogen-rich environment for the subsequent hydrogen-consuming discharge stage. Using a lower second voltage threshold as the termination criterion for hydrogen-consuming discharge can maximize the consumption of residual hydrogen at the anode, while avoiding the degradation of the stack performance due to excessively low voltage. Combined with the gentle hydrogen-oxygen reaction process, it further alleviates the corrosion of the carbon support by the high potential on the cathode catalyst surface and extends the service life of the stack.
[0011] Preferably, the first concentration threshold is 3-5%, and the second concentration threshold is 10-15%. Controlling the cathode oxygen concentration in the hydrogen-consuming discharge stage within the range of 3-15% can provide sufficient but not excessive reaction medium for the hydrogen oxidation reaction at the anode. This precisely matches the need to slow down the hydrogen-oxygen reaction rate, ensuring that the hydrogen consumption reaction continues stably while avoiding excessive cross-diffusion of hydrogen and oxygen due to excessively high oxygen concentration, or ineffective discharge reaction due to excessively low oxygen concentration. This ensures the smoothness and consistency of voltage drop during hydrogen-consuming discharge and shortens the existence time of the hydrogen / air interface inside the battery.
[0012] Preferably, when the anode and cathode are supplied with gas simultaneously, maintaining the hydrogen infeed pressure 5-10 kPa higher than the air infeed pressure can optimize the pressure balance on both sides of the membrane electrode, reduce gas cross-diffusion, avoid uneven distribution of reaction gas due to pressure imbalance, ensure the uniformity of the reaction inside the stack, ensure that the reaction state of each cell is consistent during the oxygen consumption and hydrogen consumption stages, further improve the consistency of voltage drop, and alleviate the carbon carrier corrosion problem caused by local high potential.
[0013] Preferably, the startup strategy is to purge the anode cavity with hydrogen before current loading to drive out residual oxygen in the anode cavity.
[0014] Preferably, the hydrogen purging time of the anode cavity is 5-10 seconds, which can quickly remove residual air or other impurity gases in the anode flow channel, avoid abnormal reactions caused by the mixing of hydrogen and residual gases during the start-up phase, and at the same time, a stable anode hydrogen atmosphere can be established in advance, eliminating the need for additional nitrogen cylinders and other equipment, effectively controlling system hardware costs, providing good reaction conditions for subsequent current loading, ensuring the stability of the stack reaction during the start-up phase, reducing local high-potential corrosion caused by uneven gas mixing, and extending the overall service life of the stack.
[0015] A proton exchange membrane fuel cell system includes a fuel cell stack, a DC / DC converter, and a control unit. The DC / DC converter is connected to the fuel cell stack. The control unit includes a processor and a memory. The processor is used to implement fuel cell control strategies. By configuring the DC / DC converter, current regulation between the fuel cell stack and the load is achieved to meet the different current parameter requirements of the oxygen-consuming and hydrogen-consuming discharge stages. The processor and memory of the control unit work together to accurately execute various shutdown and startup strategy steps, realize real-time monitoring and intelligent control of the fuel cell stack operating conditions, ensure the stable construction of a low-oxygen, nitrogen-rich environment during the oxygen-consuming stage, and accurately control the oxygen concentration and reaction rate during the hydrogen-consuming stage. This ensures that parameters such as pressure, current, and voltage at each stage operate strictly according to preset thresholds, ensures the smoothness and consistency of single-cell voltage drop, effectively shortens the hydrogen / air interface existence time, alleviates the corrosion of the carbon support by the high potential on the cathode catalyst surface, ensures the efficient implementation of control strategies, improves the safety and reliability of the entire fuel cell system, and extends the service life of the fuel cell stack.
[0016] Preferably, the anode inlet end of the fuel cell stack is equipped with a proportional valve and an ejector, the anode exhaust end is equipped with a tail valve, the anode exhaust end is connected to the tail valve through a moisture absorber, the moisture absorber is connected to the ejector, and a one-way valve is provided between the moisture absorber and the ejector; the cathode inlet end of the fuel cell stack is equipped with an air compressor and an air inlet valve, and the cathode exhaust end is equipped with an oxygen concentration sensor and an air outlet valve. The anode-side proportional valve and ejector precisely regulate the hydrogen intake flow and pressure. Combined with a moisture absorber and check valve, they enable anode drainage and hydrogen recycling, improving hydrogen utilization while maintaining humidity balance within the anode. The tail valve at the anode exhaust end promptly discharges water and excess impurities generated during the reaction, ensuring unobstructed flow in the anode channel and providing a stable anode hydrogen environment for both oxygen and hydrogen consumption stages. The cathode-side air compressor and air inlet valve provide a stable oxygen supply for the hydrogen-consuming discharge stage, precisely matching the oxygen concentration threshold control requirements. The oxygen concentration sensor at the cathode exhaust end monitors oxygen concentration changes in real time, providing data support for the control unit to precisely adjust the cathode intake pressure, ensuring the oxygen concentration remains within the preset threshold range. This ensures stable control of the hydrogen-oxygen reaction rate during the hydrogen-consuming discharge stage, maintaining consistent single-cell voltage drops and further mitigating high-potential corrosion on the cathode catalyst surface. The coordinated operation of these components further enhances the system's stability and durability, extending the stack's lifespan.
[0017] As can be seen from the above technical solutions, the advantages of the present invention are: By performing a phased operation of first oxygen-consuming discharge and then hydrogen-consuming discharge, the oxygen concentration in the air chamber is rapidly reduced during the oxygen-consuming discharge stage, creating a low-oxygen, nitrogen-rich environment for the cathode. The subsequent hydrogen-consuming discharge stage introduces air with a low concentration of oxygen, effectively slowing down the hydrogen-oxygen reaction rate. This results in a smoother and more consistent voltage drop in the single cell, significantly shortening the time the hydrogen / air interface remains inside the cell. Simultaneously, it effectively mitigates the corrosive effect of the high potential on the cathode catalyst surface on the carbon support, significantly extending the lifespan of the fuel cell stack. Furthermore, the entire process eliminates the need for additional nitrogen cylinders and other equipment, reducing system hardware costs. It also avoids the potential safety hazards of leakage caused by hydrogen purging, ensuring the safety and stability of the fuel cell stack operation. Attached Figure Description
[0018] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a flowchart illustrating the shutdown strategy in the fuel cell control strategy according to one or more embodiments of the present invention. Figure 2 This is a schematic diagram of the structure of a proton exchange membrane fuel cell system according to one or more embodiments of the present invention.
[0020] The components represented by the various reference numerals in the diagram are: 1. Fuel cell stack; 2. DC / DC converter; 3. Proportional valve; 4. Ejector; 5. Check valve; 6. Moisture separator; 7. Tail exhaust valve; 8. Air compressor; 9. Air inlet valve; 10. Oxygen concentration sensor; 11. Air outlet valve. Detailed Implementation
[0021] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this patent, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this patent.
[0022] This invention proposes a fuel cell control strategy, including a shutdown strategy and a startup strategy, such as... Figure 1 As shown, the shutdown strategy includes: Step 1: Upon receiving the shutdown command, the fuel cell enters the idling state, and the load current drops to 30-100A. This enables a smooth transition of stack 1 from normal operating conditions to shutdown discharge conditions, avoiding the impact of sudden current changes on core components such as the stack membrane electrode assembly, ensuring the stability of the stack structure, and laying a good working condition foundation for the construction of a low-oxygen environment and the regulation of the hydrogen-oxygen reaction rate in subsequent staged discharge operations. Step 2: Enter the oxygen-consuming discharge stage. Adjust the proportional valve 3 on the anode side to make the hydrogen inlet pressure on the anode side 10-30 kPa, and keep the tail exhaust valve 7 on the anode side open. Close the air compressor 8, air inlet valve 9 and air outlet valve 11. Step 3: Disconnect the DC / DC converter 2 from the power battery. Connect the positive and negative terminals of the fuel cell to a discharge resistor inside the DC / DC converter 2. Set the first discharge current of the discharge resistor to I1. When the lowest voltage of the fuel cell stack 1 is less than the first voltage threshold U1, disconnect the DC / DC converter 2 and close the proportional valve 3 on the anode side. During shutdown, the output of DC / DC converter 2 is disconnected from the power battery and connected to a discharge resistor inside DC / DC converter 2, allowing a small current to be applied for discharge.
[0023] Step 4: Enter the hydrogen-consuming discharge stage. Turn on the air compressor 8 and the air inlet valve 9, adjust the inlet pressure on the cathode side to 10-30 kPa, so that the oxygen concentration Q is between the first concentration threshold Q1 and the second concentration threshold Q2, and close the proportional valve 3 and the tail valve 7 on the anode side. Step 5: Connect the positive and negative terminals of the fuel cell to a discharge resistor inside the DC / DC converter 2. Set the second discharge current of the discharge resistor to I2. When the lowest voltage of the fuel cell stack 1 is less than the second voltage threshold U2, disconnect the DC / DC converter 2 and close the air compressor 8 and the air inlet valve 9. Step 6: Open the tailpipe valve 7 on the anode side to allow air to pass through and balance the air pressure on both sides of the membrane.
[0024] The first discharge current I1 and the second discharge current I2 are both 2-10A, with I1 being greater than I2. This avoids irreversible damage to the stack 1 caused by high-current discharge. At the same time, by setting the parameter ratio that the first discharge current I1 is greater than the second discharge current I2, it is adapted to the different stage characteristics of the oxygen-consuming discharge's rapid oxygen reduction and the hydrogen-consuming discharge's slow-controlled reaction. In the oxygen-consuming stage, a relatively large current is used to quickly consume the cathode oxygen, efficiently creating a low-oxygen, nitrogen-rich environment. In the hydrogen-consuming stage, a relatively small current is used to precisely match the low-concentration oxygen atmosphere, further slowing down the hydrogen-oxygen reaction rate, ensuring the smoothness and consistency of the single cell voltage drop, and improving the efficiency and targeting of different discharge stages.
[0025] The first voltage threshold U1 is 0.3-0.5V, and the second voltage threshold U2 is 0.1-0.3V, with U1 being greater than U2. By setting a stepped voltage threshold, using the first voltage threshold U1 as the termination criterion for oxygen-consuming discharge, it is possible to ensure that the oxygen at the cathode is fully consumed, thus creating a stable low-oxygen and nitrogen-rich environment for the subsequent hydrogen-consuming discharge stage. Using the lower second voltage threshold U2 as the termination criterion for hydrogen-consuming discharge can maximize the consumption of residual hydrogen at the anode, while avoiding the degradation of the stack performance due to excessively low voltage. Combined with the gentle hydrogen-oxygen reaction process, it further alleviates the corrosion of the carbon support by the high potential on the cathode catalyst surface, extending the stack's service life.
[0026] The first oxygen concentration threshold Q1 is 3-5%, and the second concentration threshold Q2 is 10-15%. This provides a sufficient but not excessive reaction medium for the oxidation reaction of hydrogen at the anode, precisely matching the need to slow down the hydrogen-oxygen reaction rate. This ensures that the hydrogen consumption reaction continues stably while avoiding excessive cross-diffusion of hydrogen and oxygen due to excessively high oxygen concentration, or ineffective discharge reaction due to excessively low oxygen concentration. This ensures the smoothness and consistency of voltage drop during hydrogen-consuming discharge and shortens the existence time of the hydrogen / air interface inside the battery.
[0027] In this invention, when gas is supplied to both the cathode and anode simultaneously, the air compressor 8 on the cathode side and the proportional valve 3 on the anode side are controlled to maintain the hydrogen inlet pressure 5-10 kPa higher than the air inlet pressure. This optimizes the pressure balance on both sides of the membrane electrode, reduces gas cross-diffusion, avoids uneven distribution of reaction gases due to pressure imbalance, ensures the uniformity of the reaction inside the stack, ensures the consistency of the reaction state of each cell in the oxygen and hydrogen consumption stages, further improves the consistency of voltage drop, and alleviates the carbon carrier corrosion problem caused by local high potential.
[0028] The startup strategy is to purge the anode chamber with a large flow of hydrogen for 5-10 seconds before current loading to drive out any residual oxygen in the anode chamber.
[0029] Typically, the above control strategy first uses oxygen-consuming discharge to reduce the oxygen concentration in the air chamber, creating a low-oxygen, nitrogen-rich environment for the cathode. Then, air with a low concentration of oxygen is introduced to slow down the hydrogen-oxygen reaction rate during hydrogen-consuming discharge. As a result, the voltage drop of a single cell is more gradual and the voltage drop is more consistent. This reduces the time that the hydrogen / air interface exists inside the cell and alleviates the corrosion of the carbon support by the high potential on the cathode catalyst surface, thereby improving the lifespan of the fuel cell stack.
[0030] Example 1 Fuel cell shutdown strategies include: Step 1: Upon receiving the shutdown command, the fuel cell enters idle mode, and the load current drops to 30A; Step 2: Enter the oxygen-consuming discharge stage. Adjust the proportional valve 3 on the anode side to make the hydrogen inlet pressure 10 kPa, and keep the tail exhaust valve 7 on the anode side open. Close the air compressor 8, air inlet valve 9 and air outlet valve 11. Step 3: Disconnect the DC / DC converter 2 from the power battery. Connect the positive and negative terminals of the fuel cell to a discharge resistor inside the DC / DC converter 2. Set the first discharge current of the discharge resistor to 4A. When the lowest voltage of the fuel cell stack 1 is less than 0.3V, disconnect the DC / DC converter 2 and close the proportional valve 3 on the anode side. Step 4: Enter the hydrogen-consuming discharge stage. Turn on the air compressor 8 and the air inlet valve 9, adjust the inlet pressure on the cathode side to 10 kPa, so that the oxygen concentration is between 3% and 10%, and close the proportional valve 3 and the tail valve 7 on the anode side. Step 5: Connect the positive and negative terminals of the fuel cell to a discharge resistor inside the DC / DC converter 2. Set the second discharge current of the discharge resistor to 2A. When the lowest voltage of the fuel cell stack 1 is less than 0.1V, disconnect the DC / DC converter 2 and close the air compressor 8 and the air inlet valve 9. Step 6: Open the tailpipe valve 7 on the anode side to allow air to pass through and balance the air pressure on both sides of the membrane.
[0031] When starting up a proton exchange membrane fuel cell system, the anode chamber is purged with a high flow rate of hydrogen for 5 seconds before current loading.
[0032] Example 2 Fuel cell shutdown strategies include: Step 1: Upon receiving the shutdown command, the fuel cell enters idle mode, and the load current drops to 100A; Step 2: Enter the oxygen-consuming discharge stage. Adjust the proportional valve 3 on the anode side to make the hydrogen inlet pressure 30 kPa, and keep the tail exhaust valve 7 on the anode side open. Close the air compressor 8, air inlet valve 9 and air outlet valve 11. Step 3: Disconnect the DC / DC converter 2 from the power battery. Connect the positive and negative terminals of the fuel cell to a discharge resistor inside the DC / DC converter 2. Set the first discharge current of the discharge resistor to 10A. When the lowest voltage of the fuel cell stack 1 is less than 0.5V, disconnect the DC / DC converter 2 and close the proportional valve 3 on the anode side. Step 4: Enter the hydrogen-consuming discharge stage. Turn on the air compressor 8 and the air inlet valve 9, adjust the inlet pressure on the cathode side to 30 kPa, so that the oxygen concentration is between 5% and 15%, and close the proportional valve 3 and the tail valve 7 on the anode side. Step 5: Connect the positive and negative terminals of the fuel cell to a discharge resistor inside the DC / DC converter 2. Set the second discharge current of the discharge resistor to 6A. When the lowest voltage of a single cell in the fuel cell stack 1 is less than 0.3V, disconnect the DC / DC converter 2 and close the air compressor 8 and the air inlet valve 9. Step 6: Open the tailpipe valve 7 on the anode side to allow air to pass through and balance the air pressure on both sides of the membrane.
[0033] When starting up a proton exchange membrane fuel cell system, the anode chamber is purged with a high flow rate of hydrogen for 10 seconds before current loading.
[0034] Example 3 Fuel cell shutdown strategies include: Step 1: Upon receiving the shutdown command, the fuel cell enters idle mode, and the load current drops to 60A; Step 2: Enter the oxygen-consuming discharge stage. Adjust the proportional valve 3 on the anode side to make the hydrogen inlet pressure 20 kPa, and keep the tail exhaust valve 7 on the anode side open. Close the air compressor 8, air inlet valve 9 and air outlet valve 11. Step 3: Disconnect the DC / DC converter 2 from the power battery. Connect the positive and negative terminals of the fuel cell to a discharge resistor inside the DC / DC converter 2. Set the first discharge current of the discharge resistor to 8A. When the lowest voltage of the fuel cell stack 1 is less than 0.4V, disconnect the DC / DC converter 2 and close the proportional valve 3 on the anode side. Step 4: Enter the hydrogen-consuming discharge stage. Turn on the air compressor 8 and the air inlet valve 9, adjust the inlet pressure on the cathode side to 20 kPa, so that the oxygen concentration is between 4% and 12%, and close the proportional valve 3 and the tail valve 7 on the anode side. Step 5: Connect the positive and negative terminals of the fuel cell to a discharge resistor inside the DC / DC converter 2. Set the second discharge current of the discharge resistor to 6A. When the lowest voltage of the fuel cell stack 1 is less than 0.2V, disconnect the DC / DC converter 2 and close the air compressor 8 and the air inlet valve 9. Step 6: Open the tailpipe valve 7 on the anode side to allow air to pass through and balance the air pressure on both sides of the membrane.
[0035] When starting up a proton exchange membrane fuel cell system, the anode chamber is purged with a high flow rate of hydrogen for 8 seconds before current loading.
[0036] Example 4 In a typical embodiment of the present invention, a proton exchange membrane fuel cell system is proposed, such as... Figure 2 As shown, it includes: 500 active cells with an area of 350 cm². 2The system comprises a fuel cell stack 1, a DC / DC converter 2, and a control unit. The fuel cell stack 1 has a proportional valve 3 and an ejector 4 at its anode inlet and a tailpipe valve 7 at its anode exhaust. The fuel cell stack 1 has an air compressor 8 and an air inlet valve 9 at its cathode inlet and an oxygen concentration sensor 10 and an air outlet valve 11 at its cathode exhaust. The DC / DC converter 2 is connected to the fuel cell stack 1 and has an internal discharge resistor, allowing a small current to be applied for discharge during shutdown. The control unit includes a processor and a memory. The memory stores computer instructions, which, when executed by the processor, cause the processor to perform the aforementioned actions. The fuel cell control strategy can precisely execute various shutdown and startup strategies, realize real-time monitoring and intelligent control of the stack's operating conditions, ensure the stable construction of a low-oxygen, nitrogen-rich environment during the oxygen consumption stage, and accurately control the oxygen concentration and reaction rate during the hydrogen consumption stage. It ensures that parameters such as pressure, current, and voltage at each stage operate strictly according to preset thresholds, ensures the smoothness and consistency of single-cell voltage drop, effectively shortens the hydrogen / air interface existence time, alleviates the corrosion of the carbon support by the high potential on the cathode catalyst surface, ensures the efficient implementation of the control strategy, improves the safety and reliability of the entire fuel cell system, and extends the stack's service life.
[0037] In this embodiment, the anode exhaust end of the fuel cell stack 1 is connected to the tail exhaust valve 7 via a moisture absorber 6, and the moisture absorber 6 is also connected to the ejector 4. A one-way valve 5 is provided between the moisture absorber 6 and the ejector 4. The proportional valve 3 and ejector 4 on the anode side can precisely regulate the hydrogen intake flow rate and pressure. Together with the moisture absorber 6 and one-way valve 5, they can realize the recycling of anode drainage and hydrogen, improving hydrogen utilization while maintaining the humidity balance inside the anode. The tail valve 7 at the anode exhaust end can promptly discharge the water and excess impurities generated in the reaction, ensuring the smooth flow of the anode channel and providing a stable anode hydrogen environment for the oxygen and hydrogen consumption stages. The configuration of the air compressor 8 and air inlet valve 9 on the cathode side can provide a stable oxygen supply for the hydrogen consumption discharge stage, accurately matching the control requirements of the oxygen concentration threshold. The oxygen concentration sensor 10 at the cathode exhaust end can monitor the changes in oxygen concentration in real time, providing data support for the control unit to accurately adjust the cathode intake pressure, ensuring that the oxygen concentration is always within the preset threshold range, ensuring the stable control of the hydrogen-oxygen reaction rate during the hydrogen consumption discharge stage, keeping the voltage drop of the single cell consistent, and further mitigating the high-potential corrosion on the cathode catalyst surface. The coordinated work of all components further improves the stability and durability of the system operation and extends the service life of the fuel cell stack.
[0038] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A fuel cell control strategy, comprising: The shutdown policy and startup policy are characterized in that the shutdown policy is: Step 1: Upon receiving the shutdown command, the fuel cell enters idle mode; Step 2: Enter the oxygen-consuming discharge stage, adjust the hydrogen inlet pressure on the anode side to 10-30 kPa, open the tail valve (7) on the anode side, and close the air inlet valve (9) and air outlet valve (11) on the cathode side. Step 3: Connect the fuel cell to the DC / DC converter (2), set the first discharge current, and when the lowest voltage of the stack (1) cell is less than the first voltage threshold, disconnect the DC / DC converter (2) and close the proportional valve (3) on the anode side. Step 4: Enter the hydrogen-consuming discharge stage, adjust the inlet pressure on the cathode side to 10-30 kPa, so that the oxygen concentration is between the first concentration threshold and the second concentration threshold, and close the proportional valve (3) and tail valve (7) on the anode side. Step 5: Connect the fuel cell to the DC / DC converter (2), set the second discharge current, and when the lowest voltage of the stack (1) cell is less than the second voltage threshold, disconnect the DC / DC converter (2) and shut down the air compressor (8) and the air inlet valve (9). Step 6: Open the tailpipe valve (7) on the anode side to allow air to enter.
2. The fuel cell control strategy according to claim 1, characterized in that, When the fuel cell enters the idling state, the load current drops to 30-100A.
3. The fuel cell control strategy according to claim 1, characterized in that, Both the first discharge current and the second discharge current are 2-10A, and the first discharge current is greater than the second discharge current.
4. The fuel cell control strategy according to claim 1, characterized in that, The first voltage threshold is 0.3-0.5V, the second voltage threshold is 0.1-0.3V, and the first voltage threshold is greater than the second voltage threshold.
5. The fuel cell control strategy according to claim 1, characterized in that, The first concentration threshold is 3-5%, and the second concentration threshold is 10-15%.
6. The fuel cell control strategy according to claim 1, characterized in that, When both the anode and cathode are supplied with gas, the hydrogen infeed pressure should be 5-10 kPa higher than the air infeed pressure.
7. The fuel cell control strategy according to claim 1, characterized in that, The startup strategy is to purge the anode cavity with hydrogen before applying current.
8. The fuel cell control strategy according to claim 7, characterized in that, The hydrogen purging time for the anode chamber is 5-10 seconds.
9. A proton exchange membrane fuel cell system, characterized in that, include: The fuel cell stack (1), DC / DC converter (2), and control unit are connected to the fuel cell stack (1). The control unit includes a processor and a memory, and the processor is used to implement the fuel cell control strategy as described in any one of claims 1-8.
10. The proton exchange membrane fuel cell system according to claim 9, characterized in that, The anode inlet of the fuel cell stack (1) is equipped with a proportional valve (3) and an ejector (4), and the anode exhaust is equipped with a tail valve (7). The anode exhaust is connected to the tail valve (7) through a moisture absorber (6). The moisture absorber (6) is connected to the ejector (4). A one-way valve (5) is provided between the moisture absorber (6) and the ejector (4). The cathode inlet of the fuel cell stack (1) is equipped with an air compressor (8) and an air inlet valve (9). The cathode exhaust is equipped with an oxygen concentration sensor (10) and an air outlet valve (11).