Fan selection and simplified fault-tolerant control method based on dynamic self-regulation mechanism of air-cooled fuel cell

Abstract

The application relates to a fan type selection and simplified fault-tolerant control method based on a dynamic self-adjusting mechanism of an air-cooled fuel cell, and belongs to the technical field of battery management, and comprises the following steps: S1, selecting a reference fan to test air supply under different powers; S2, performing a plurality of single-variable experiments to obtain an optimal air supply; S3, calculating characteristic curves of different fans under different powers according to three laws of the fan, obtaining a wind resistance characteristic curve of a fuel cell system, and obtaining intersection points of the wind resistance characteristic curve and the characteristic curves of different fans; S4, screening fan types according to a type selection rule and using the intersection point positions; S5, comparing powers corresponding to the characteristic curves of the fans whose intersection points are greater than and closest to the optimal air supply in the fans meeting basic conditions, and finally matching the fan with the minimum power consumption to the fuel cell system; and S6, constructing a simplified and fault-tolerant control strategy to control the fan.

Description

Technical Field

[0001] This invention belongs to the field of battery management technology and relates to a fan selection and simplified fault-tolerant control method based on the dynamic self-adjustment mechanism of air-cooled fuel cells. Background Technology

[0002] Fuel cells directly convert the chemical energy of hydrogen and oxygen into electrical energy through electrochemical reactions, making them an environmentally friendly and efficient power generation system. Among them, air-cooled proton exchange membrane fuel cells (PEMFCs) are widely favored in the light vehicle and drone markets due to their portability, simple structure, and low power generation costs. Air-cooled fuel cell systems are simple, requiring only a fan to blow ambient air directly into the cathode as reactants and coolant. Therefore, the internal parameters of the stack are strongly coupled, making fan control strategies complex and significantly impacting performance. However, air-cooled fuel cells possess dynamic self-adjustment capabilities, meaning that even with unchanged external control strategies, the stack can adjust its state according to different operating conditions to achieve better performance. This invention considers the dynamic self-adjustment mechanism as a crucial factor in the design of air-cooled fuel cell systems, proposing two fan selection rules to obtain fan models with high compatibility with air-cooled fuel cell systems. Through multiple sets of experiments, the optimal PWM duty cycle and current threshold are obtained to simplify the fan control strategy and enhance its fault tolerance, mitigating further damage to the stack caused by control failure in fault conditions. Summary of the Invention

[0003] In view of this, the purpose of this invention is to design a fan selection and simplified fault-tolerant control method based on the dynamic self-adjustment mechanism of air-cooled fuel.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A fan selection and simplified fault-tolerant control method based on the dynamic self-adjustment mechanism of air-cooled fuel cells includes the following steps:

[0006] S1: Select a reference fan to test the airflow at different power levels;

[0007] S2: Conduct multiple sets of single-variable experiments. In each set of experiments, the fuel cell stack is operated under dynamic step conditions within the rated current range. Under the premise of meeting the basic heat dissipation and oxygen supply requirements of the fuel cell stack, different air supply volumes are used, the fuel cell stack output voltage is recorded, and the optimal air supply volume is obtained by comparing the experimental results.

[0008] S3: Calculate the characteristic curves of different fans at different power levels according to the three laws of fans, obtain the wind resistance characteristic curve of the fuel cell system, and obtain the intersection point of the system wind resistance characteristic curve and the characteristic curves of different fans.

[0009] S4: According to the selection rules, the intersection of the fan characteristic curve and the system characteristic curve when the fuel cell load is at rated current is used as the operating point of the fan to screen the fan models;

[0010] S5: Among the fans that meet the basic conditions, compare the power corresponding to the characteristic curves whose intersection point is greater than and closest to the optimal air supply volume, and finally match the fan with the lowest power consumption to the fuel cell system.

[0011] S6: Construct simplified and fault-tolerant control strategies to control the fan.

[0012] Furthermore, step S2 specifically includes:

[0013] S21: Enables the fuel cell stack to operate under dynamic step conditions within the rated current range;

[0014] S22: Change the reference fan power;

[0015] S23: Determine whether the basic heat dissipation and oxygen supply requirements are met. If not, return to step S21. If they are met, determine the optimal air supply based on the fuel cell stack output.

[0016] Furthermore, the three laws of fans include:

[0017]

[0018]

[0019]

[0020] Where Q1 and Q2 are the airflow generated by the fan, U1 and U2 are the fan speeds, P1 and P2 are the voltage drops across the fan, and W1 and W2 are the fan power.

[0021] Furthermore, the selection rule is as follows: the intersection points on different power characteristic curves are all located to the left of the fan stall zone and there is a corresponding horizontal axis flow rate value that is not lower than the optimal air supply.

[0022] Furthermore, the simplification and fault-tolerant control strategy described in step S6 includes:

[0023] S61: The PWM duty cycle at which this fan can achieve the optimal airflow is obtained through testing and defined as the optimal duty cycle u1;

[0024] S62: Run the fuel cell stack under the same dynamic step condition as in the previous experiment, and adjust it based on the optimal PWM duty cycle to obtain multiple sets of experimental results;

[0025] S63: Calculate the dispersion σ of the stack output voltage under different current densities from small to large, and find the value of σ that is closest to the dispersion threshold σ. *The current I1 is defined as the critical value.

[0026] Furthermore, in step S63, Where N is the number of experimental groups, V i For each group of experiments, output voltage. This represents the average output voltage of all experimental groups.

[0027] The beneficial effects of this invention are as follows: the two fan selection rules proposed in this invention effectively improve the fan selection efficiency and enhance the compatibility between the fan and the fuel cell system, ensuring that the fan and the fuel cell stack operate within their optimal operating range. This simplified fault-tolerant control strategy allows air-cooled fuel cells to avoid complex and inefficient fan control strategies when operating under lower current conditions, and effectively mitigates further damage to the fuel cell stack when a fuel cell failure occurs during operation.

[0028] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0030] Figure 1 Flowchart for fan selection and parameter determination;

[0031] Figure 2 A flowchart for simplifying and fault-tolerant control strategies. Detailed Implementation

[0032] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0033] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0034] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0035] This invention proposes two selection rules for fans based on the dynamic self-regulation mechanism of air-cooled fuel cells and the three laws of fans. The fan's characteristics primarily depend on its structural design; fans operating at different power levels exhibit characteristic curves of the same shape. The characteristic curve value is directly proportional to the fan speed; doubling the fan speed doubles the characteristic curve value. Using the three laws of fans, the characteristic curves for different power levels can be obtained: the ratio of flow rates equals the power ratio to the power of one-third, and the ratio of voltage drops equals the power ratio to the power of the square of three-thirds. The intersection of the fan characteristic curve and the system characteristic curve when the stack load is at rated current is determined as the fan's operating point. Although the intersection when the load current is at rated current is closer to the Y-axis than the intersection when the load current is zero, resulting in lower mechanical efficiency of the fan under load, the high voltage drop is beneficial for removing impurities from the cathode channel under high load. When the load current decreases during the operation of the fuel cell stack, the oxygen consumed by the electrochemical reaction decreases, and the airflow through the fuel cell stack increases. As a result, the system characteristic curve will gradually move away from the Y-axis as the load current decreases, and the intersection point will move towards the direction of large airflow, thus avoiding the problem of insufficient airflow.

[0036] The fan selection and parameter determination process in this invention is as follows: Figure 1As shown. First, the fan must meet two basic selection rules: the intersection points of different power characteristic curves and the system characteristic curve when the stack load current is the rated current I0 must all be located to the left of the fan stall zone, and there must be a corresponding horizontal axis flow rate value not lower than the optimal air supply. Using these rules, the basic conditions of the fan are screened. Under the premise of meeting the rules, the fan with the horizontal axis flow rate closest to the optimal air supply and the lowest power consumption at the intersection point is selected. The fan speed is controlled by adjusting the PWM duty cycle, and the duty cycle value when the optimal air supply is reached is recorded, i.e., the optimal PWM duty cycle u1. The selected fan is matched to the fuel cell system, so that the stack operates under the same dynamic conditions as in previous experiments. In each experiment, only the PWM duty cycle is appropriately adjusted, while other conditions remain consistent. The fan controller adjusts the PWM signal duty cycle according to demand. When the controller receives the PWM signal, it adjusts the output voltage according to the signal duty cycle, thereby controlling the fan motor speed. During this process, the stack can operate stably through its own dynamic self-adjustment capability. The dispersion of the stack output voltage data under different currents is calculated according to the standard variance formula, and the calculation results are approximated to the dispersion threshold σ. * The current I1 is defined as the critical value. The specific steps are as follows:

[0037] 1) Select a reference fan to test the airflow at different power levels;

[0038] 2) Conduct multiple sets of single-variable experiments. In each set of experiments, the fuel cell stack is operated under dynamic step conditions within the rated current range. Under the premise of meeting the basic heat dissipation and oxygen supply requirements of the fuel cell stack, different air supply volumes are used, the output voltage of the fuel cell stack is recorded, and the optimal air supply volume is obtained by comparing the experimental results.

[0039] 3) According to the three laws of fans Calculate the characteristic curves of different fans at different power levels, obtain the wind resistance characteristic curve of the fuel cell system, and find the intersection point between the system wind resistance characteristic curve and the characteristic curves of different fans.

[0040] 4) Based on the two proposed selection rules, the fan models are filtered using the intersection point;

[0041] 5) Among the fans that meet the basic conditions, compare the power corresponding to the characteristic curves whose intersection point is greater than and closest to the optimal air supply volume, and finally match the fan with the lowest power consumption to the fuel cell system.

[0042] 6) The PWM duty cycle at which the fan can achieve the optimal airflow is obtained through testing and defined as the optimal duty cycle u1;

[0043] 7) Run the fuel cell stack under the same dynamic conditions as in the previous experiments, and make appropriate adjustments based on the optimal PWM duty cycle to obtain multiple sets of experimental results;

[0044] 8) According to Calculate the dispersion of the stack output voltage under different current densities from small to large, and find the value of σ that is closest to the dispersion threshold σ. * The current I1 is defined as the critical value.

[0045] The simplified fault-tolerant control method in this invention utilizes two important parameters obtained experimentally: the optimal PWM duty cycle u1 and the stack current critical value I1. When the air-cooled fuel cell operates normally under loads below the current critical value, the fan control signal is set to the optimal PWM duty cycle. When the load exceeds the current critical value, factors such as current density and environmental conditions are considered. In the event of a non-emergency shutdown fault in the air-cooled fuel cell, the fan is immediately switched to the optimal PWM value to prevent further damage caused by improper temperature control. The simplified and fault-tolerant control strategy formulation process is as follows: Figure 2 As shown.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A fan selection and simplified fault-tolerant control method based on the dynamic self-adjustment mechanism of air-cooled fuel cells, characterized in that: Includes the following steps: S1: Select a reference fan to test the airflow at different power levels; S2: Conduct multiple sets of single-variable experiments. In each set of experiments, the fuel cell stack is operated under dynamic step conditions within the rated current range. Under the premise of meeting the basic heat dissipation and oxygen supply requirements of the fuel cell stack, different air supply volumes are used, the fuel cell stack output voltage is recorded, and the optimal air supply volume is obtained by comparing the experimental results. S3: Calculate the characteristic curves of different fans at different power levels according to the three laws of fans, obtain the wind resistance characteristic curve of the fuel cell system, and obtain the intersection point of the system wind resistance characteristic curve and the characteristic curves of different fans. S4: According to the selection rules, the intersection of the fan characteristic curve and the system characteristic curve when the fuel cell load is at rated current is used as the operating point of the fan to screen the fan models; S5: Among the fans that meet the basic conditions, compare the power corresponding to the characteristic curves whose intersection point is greater than and closest to the optimal air supply volume, and finally match the fan with the lowest power consumption to the fuel cell system. S6: Construct a simplified and fault-tolerant control strategy to control the fan; The selection rule is as follows: the intersection points on different power characteristic curves are all located to the left of the fan stall zone and there is a corresponding horizontal axis flow rate value that is not lower than the optimal air supply volume; The simplification and fault-tolerant control strategy described in step S6 includes: S61: The PWM duty cycle at which this fan achieves optimal airflow was determined through testing and defined as the optimal duty cycle. ; S62: Run the fuel cell stack under the same dynamic step condition as in the previous experiment, and adjust it based on the optimal PWM duty cycle to obtain multiple sets of experimental results; S63: Calculate the dispersion of the stack output voltage under different current densities from small to large. ,Will Closest to discrete threshold current It is set as the critical value.

2. The fan selection and simplified fault-tolerant control method based on the dynamic self-adjustment mechanism of air-cooled fuel cells according to claim 1, characterized in that: Step S2 specifically includes: S21: Enables the fuel cell stack to operate under dynamic step conditions within the rated current range; S22: Change the reference fan power; S23: Determine whether the basic heat dissipation and oxygen supply requirements are met. If not, return to step S21. If they are met, determine the optimal air supply based on the fuel cell stack output.

3. The fan selection and simplified fault-tolerant control method based on the dynamic self-adjustment mechanism of air-cooled fuel cells according to claim 1, characterized in that: The three laws of fans include: in and The airflow generated by the fan, and This refers to the fan speed. and For the voltage drop of the fan, and This is the fan's power.

4. The fan selection and simplified fault-tolerant control method based on the dynamic self-adjustment mechanism of air-cooled fuel cells according to claim 1, characterized in that: In step S63, ,in Number of experimental groups For each group of experiments, output voltage. This represents the average output voltage of all experimental groups.

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