Fuel cell shutdown voltage reduction method and system based on voltage state

Abstract

The invention discloses a fuel cell shutdown voltage reduction method and system based on a voltage state, and belongs to the technical field of fuel cell systems. The method comprises the following steps: aiming at a fuel cell, in a discharging process after a shutdown purging process is finished, detecting a stack voltage and a minimum single cell voltage; and identifying the current voltage state based on the stack voltage and the lowest single battery voltage, and dynamically adjusting the discharge current based on the voltage state until the discharge process is finished. According to the method, various different voltage states can be intelligently identified, the discharge current is dynamically adjusted, the voltage of an individual single battery is effectively prevented from being too low or reversed while rapid voltage reduction is ensured, the technical problem that a traditional fixed current discharge method cannot give consideration to both the shutdown efficiency and the pile durability is solved, and the method is suitable for large-scale popularization and application. And the shutdown safety and the service life of the fuel cell system are obviously improved.

Description

Technical Field

[0001] This invention relates to the field of fuel cell system technology, and more specifically, to a method and system for reducing voltage during fuel cell shutdown based on voltage state. Background Technology

[0002] A fuel cell is a chemical device that directly converts the chemical energy of fuel into electrical energy. It can be applied in industries such as automotive, power generation, shipbuilding, aerospace, and home power. Fuel cell shutdown and discharge is a crucial operation during the shutdown process. Its purpose is to close the anode and cathode inlet and outlet valves after purging under load, reduce the high voltage of the fuel cell by applying a constant small current load, and simultaneously consume residual oxygen within the fuel cell to create a nitrogen-rich environment. This prevents hydrogen from permeating into the cathode and forming a hydrogen-oxygen interface, which would cause corrosion and performance degradation of the carbon materials.

[0003] Because fuel cell operation is affected by environmental factors, operating conditions, performance degradation, etc., the internal state is not consistent after each shutdown and purging. Different individual cells may have different internal temperatures, humidity, gas distribution and leakage, resulting in different voltage states of different individual cells during discharge.

[0004] Given the varying voltage states of individual cells, determining how to rationally set a small current load for discharge, rapidly reduce the overall stack voltage, shorten the discharge time, and effectively create a nitrogen-rich environment to prevent individual cells from experiencing low voltage or reverse polarity is crucial for the rapid shutdown and durability of fuel cells.

[0005] Therefore, existing technologies need to be improved to provide safer, more adaptive shutdown discharge solutions. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and system for reducing voltage during fuel cell shutdown based on voltage state.

[0007] According to a first aspect of the present invention, a method for voltage reduction during fuel cell shutdown based on voltage state is provided. The method includes the following steps: For fuel cells, during the discharge process after the shutdown purging process, the stack voltage and the lowest single cell voltage are detected; Based on the stack voltage and the lowest single cell voltage, the current voltage state is identified, and the discharge current is dynamically adjusted based on the voltage state until the discharge process ends. Specifically, when the single-cell voltage is greater than the threshold V1, the corresponding discharge current is set to I1, and the discharge current is dynamically adjusted according to the following process: If the stack voltage is greater than the threshold U2 and the lowest single cell voltage is less than the threshold V2, it is determined to be in the first state, and the discharge current is adjusted to I2, and I1>I2. If the stack voltage is less than or equal to the threshold U2 and the lowest single cell voltage is greater than or equal to the threshold V2, it is determined to be in the second state and the discharge circuit I1 is maintained. If the stack voltage is less than or equal to the threshold U2 and the lowest single cell voltage is less than V3, it is determined to be in the third state, and the discharge current is set to 0A. Among them, V1 > V2, I1 > I2.

[0008] According to a second aspect of the present invention, a fuel cell shutdown voltage reduction system based on voltage state is provided. The system includes: a fuel cell, a voltage monitoring module, a load control module, and a controller, wherein: The voltage monitoring module is used to detect the stack voltage and the lowest single cell voltage during the discharge process after the shutdown purging process for the fuel electric field. The controller is used to identify the current voltage state based on the stack voltage and the lowest single cell voltage, and to dynamically adjust the discharge current based on the voltage state; The load control module responds to the controller's instructions and performs adjustments to the discharge current of the fuel cell; Specifically, when the single-cell voltage is greater than the threshold V1, the corresponding discharge current is set to I1, and the discharge current is dynamically adjusted according to the following process: If the stack voltage is greater than the threshold U2 and the lowest single cell voltage is less than the threshold V2, it is determined to be in the first state, and the discharge current is adjusted to I2, and I1>I2. If the stack voltage is less than or equal to the threshold U2 and the lowest single cell voltage is greater than or equal to the threshold V2, it is determined to be in the second state and the discharge circuit I1 is maintained. If the stack voltage is less than or equal to the threshold U2 and the lowest single cell voltage is less than V3, it is determined to be in the third state, and the discharge current is set to 0A. Among them, V1 > V2, I1 > I2.

[0009] According to a third aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0010] According to a fourth aspect of the present invention, a computer device is provided, including a memory and a processor, wherein a computer program capable of running on the processor is stored in the memory, and the processor executes the computer program to implement the steps of the above-described method.

[0011] Compared with existing technologies, the advantages of this invention lie in the fact that the provided fuel cell shutdown voltage reduction method and system based on voltage state achieves rapid, safe, and adaptive shutdown discharge by real-time monitoring of the total stack voltage and the lowest single cell voltage, and dynamically and stepwise adjusting the discharge current according to their combined state. This invention can adapt to the inconsistent characteristics within the fuel cell stack, effectively preventing individual single cell voltages from becoming too low or reversing polarity while ensuring rapid voltage reduction. It solves the technical problem that traditional fixed-current discharge methods cannot simultaneously achieve shutdown efficiency and stack durability, significantly improving the shutdown safety and lifespan of the fuel cell system.

[0012] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0013] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0014] Figure 1 This is a flowchart of a fuel cell shutdown voltage reduction method based on voltage state according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the voltage and current operation of a fuel cell stack according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the voltage of a single cell in a fuel cell according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the voltage and current operation of a state two fuel cell stack according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the voltage of a single cell in a state two fuel cell according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the voltage and current operation of a state-three fuel cell stack according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the voltage of a single cell in a state-three fuel cell according to an embodiment of the present invention; Figure 8 This is a schematic diagram of a voltage-state-based fuel cell shutdown voltage reduction system according to an embodiment of the present invention. Detailed Implementation

[0015] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0016] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0017] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0018] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0019] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0020] In general, the fuel cell shutdown voltage reduction method based on voltage state provided by the present invention includes: detecting the stack voltage and the lowest single cell voltage during the discharge process after the shutdown purging process is completed; determining the current voltage state based on the stack voltage and the lowest single cell voltage; and dynamically adjusting the discharge current based on the voltage state until the discharge process ends.

[0021] Specifically, see Figure 1 As shown, the provided voltage-state-based fuel cell shutdown voltage reduction method includes the following steps: S1, the shutdown purging process is over, and the discharge process is started.

[0022] S2 monitors whether the voltage of a single cell is greater than or equal to V1.

[0023] S3, if the monitored single-cell voltage is greater than or equal to V1, then set the discharge current I1.

[0024] After the purging process is completed, if the lowest single cell voltage is ≥ V1, an initial discharge current I1 is set to start discharging, and the discharge current is dynamically adjusted through the following steps during the discharge process.

[0025] S4: Check if the stack voltage is greater than U2 and the minimum single cell voltage is less than V2. If so, proceed to state one.

[0026] S5 sets the discharge current I2.

[0027] Where I1>I2, that is, in state one, the discharge continues in a relatively mild manner.

[0028] S6 checks whether the stack voltage is less than U3 or whether the lowest single cell voltage is less than V3.

[0029] S11, if the stack voltage is less than U3 or the lowest single cell voltage is less than V3, set the discharge current to 0A and stop discharging.

[0030] S7, check if the stack voltage is less than or equal to U2 and the lowest single cell voltage is greater than or equal to V2. If so, enter state two.

[0031] S8 maintains the discharge current I1.

[0032] Where I1>I2, that is, in state two, the discharge process is completed at the fastest speed.

[0033] S9 checks if the stack voltage is less than or equal to U2 or if the lowest single cell voltage is less than V3. If so, it enters state three.

[0034] S11, if the stack voltage is less than U3 or the lowest single cell voltage is less than V3, set the discharge current to 0A and stop discharging.

[0035] S10 checks whether the stack voltage is less than or equal to U2 and the lowest single cell voltage is less than V3.

[0036] S11, if the stack voltage is less than or equal to U2 and the lowest single cell voltage is less than V3, set the discharge current to 0A and stop discharging.

[0037] S12, the discharge process ends.

[0038] It should be noted that during the discharge process, three different adjustment branches are entered based on the voltage state: State 1, State 2, and State 3. State 1 indicates that the voltage drop of individual cells within the stack has shown some inconsistency, but is not yet severe. At this time, to protect the lower-voltage cells, the discharge current is reduced from I1 to a smaller I2, continuing discharge in a gentler manner. State 2 indicates that the overall stack voltage has dropped significantly, and the voltage drop of individual cells is relatively uniform, with no abnormally low-voltage cells. At this time, the current larger discharge current I1 is maintained to complete the discharge process as quickly as possible. State 3 indicates severe inconsistency, with the voltage of some individual cells dropping to near the critical protection value. At this time, immediate protective measures are taken, reducing the discharge current to 0A and terminating the discharge to prevent the individual cell from being damaged due to reverse polarity.

[0039] Figure 2 This is a schematic diagram of the fuel cell stack voltage and current operation in state one. Figure 3 This is a schematic diagram of the voltage of a single cell in a fuel cell under state one.

[0040] At time t1, the discharge process begins. At this time, the voltage of a single cell is greater than or equal to V1, and the total voltage (pile voltage) is U1. At time t2, the lowest single cell voltage is less than V2, and the pile voltage is greater than U2. The discharge current is then adjusted to I2.

[0041] At time t3, if the single cell voltage is less than V3 or the stack voltage is less than U3, the discharge current is set to 0A, and the discharge stops.

[0042] Reference Figure 4 and Figure 5 The diagrams showing the voltage and current operation of the fuel cell stack in state two and the voltage of a single fuel cell are presented respectively.

[0043] At time t1, the discharge process begins, with the single-cell voltage greater than or equal to V1 and the total voltage U1. At time t2, the lowest single-cell voltage is greater than V2, and the stack voltage is between U2 and U3, maintaining the discharge current at I1.

[0044] At time t3, if the single cell voltage is less than V3 or the stack voltage is less than U3, the discharge current is set to 0A, and the discharge stops.

[0045] Reference Figure 6 and Figure 7 The diagrams showing the voltage and current operation of the fuel cell stack in state three and the voltage of a single fuel cell are presented respectively.

[0046] Similarly, at time t1, the discharge process begins, at which point the voltage of a single cell is greater than or equal to V1, and the total voltage is U1. At time t2, the lowest single cell voltage is less than V3. Although the stack voltage is between U2 and U3, the discharge current needs to be set to 0A immediately to stop the discharge.

[0047] Accordingly, the present invention also provides a voltage-state-based fuel cell shutdown voltage reduction system for implementing one or more aspects of the above-described method. For example, see [link to relevant documentation]. Figure 8As shown, the system includes a fuel cell, a voltage monitoring module, a load control module, and a controller (FCU). The voltage monitoring module monitors or acquires the stack voltage and individual cell voltage. The controller identifies the current voltage state based on the stack voltage and individual cell voltage, and dynamically adjusts the discharge current accordingly. The controller (FCU) is responsible for executing the aforementioned discharge control strategy for the fuel cell and can adjust multiple voltage thresholds (such as V2, V3, U1, U2, U3). The load control module adjusts the discharge current for the fuel cell according to the controller's instructions. Thresholds U2, U3, V1, V2, and V3 can be dynamically calibrated and adjusted according to different fuel cell system models, operating states, or life stages. For example, the stack voltage threshold is related to the number of cells, the individual cell voltage threshold is related to the protection strategy, and the discharge current setting is related to the protection threshold and the effective reaction area of ​​the stack.

[0048] In summary, after shutdown and purging, this invention intelligently identifies different voltage states (such as state one, state two, state three, etc.) by real-time monitoring of the stack voltage and the lowest single-cell voltage and comparing them with preset thresholds, and then dynamically adjusts the discharge current (switching between I1, I2, and 0A). This design adapts to the inconsistent characteristics within the stack, ensuring rapid voltage reduction while effectively preventing individual cells from becoming too low or reversing polarity. It solves the technical challenge of traditional fixed-current discharge methods failing to balance shutdown efficiency and stack durability, significantly improving the shutdown safety and lifespan of the fuel cell system.

[0049] In summary, compared with the prior art, the present invention has the following main advantages: 1) This invention abandons the traditional method of fixed current discharge and dynamically adjusts the current through real-time voltage feedback. It has strong adaptability and can adapt to the shutdown requirements of the fuel cell stack under different conditions (such as different humidity and aging degree).

[0050] 2) When the voltage is good (such as in state two), the present invention uses a large current discharge to shorten the downtime; when inconsistency is detected (such as in state one), the current is reduced in time; when serious inconsistency occurs (such as in state three), the discharge is stopped immediately. This effectively avoids the reverse polarity phenomenon caused by the low voltage of individual cells, greatly improves the durability and reliability of the system, and balances efficiency and safety.

[0051] 3) This invention sets up multiple voltage thresholds (such as V2, V3, U1, U2, U3), which constitute a complete set of judgment and protection logic, ensuring that the discharge process always takes place within a safe voltage window, and realizing intelligent protection.

[0052] 4) The present invention has a clear logic and is easy to implement in software within existing fuel cell controllers (FCUs) without increasing hardware costs, thus possessing high practicality and promotional value.

[0053] This invention can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of the invention.

[0054] Various aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0055] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processor of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner; thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0056] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0057] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions. It will be known to those skilled in the art that implementation in hardware, implementation in software, and implementation using a combination of software and hardware are equivalent.

[0058] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein. The scope of the invention is defined by the appended claims.

Claims

1. A method for reducing voltage during fuel cell shutdown based on voltage state, characterized in that, Includes the following steps: For fuel cells, during the discharge process after the shutdown purging process, the stack voltage and the lowest single cell voltage are detected; Based on the stack voltage and the lowest single cell voltage, the current voltage state is identified, and the discharge current is dynamically adjusted based on the voltage state until the discharge process ends. Specifically, when the single-cell voltage is greater than the threshold V1, the corresponding discharge current is set to I1, and the discharge current is dynamically adjusted according to the following process: If the stack voltage is greater than the threshold U2 and the lowest single cell voltage is less than the threshold V2, it is determined to be in the first state, and the discharge current is adjusted to I2, and I1>I2. If the stack voltage is less than or equal to the threshold U2 and the lowest single cell voltage is greater than or equal to the threshold V2, it is determined to be in the second state and the discharge circuit I1 is maintained. If the stack voltage is less than or equal to the threshold U2 and the lowest single cell voltage is less than V3, it is determined to be in the third state, and the discharge current is set to 0A. Among them, V1 > V2, I1 > I2.

2. The method according to claim 1, characterized in that, In the first state, if the stack voltage is detected to be less than U3 or the single cell voltage is less than V3, the discharge current is set to 0A and the discharge process ends, where U2 > U3 and V1 > V2 > V3.

3. The method according to claim 1, characterized in that, In the second state, if the stack voltage is detected to be less than U3 or the single cell voltage is less than V3, the discharge current is set to 0A and the discharge process ends, where U2 > U3 and V1 > V2 > V3.

4. The method according to claim 3, characterized in that, U2, U3, V1, V2, and V3 are dynamically adjusted according to the actual operating status of the fuel cell system.

5. A voltage reduction system for fuel cell shutdown based on voltage state, characterized in that, It includes a fuel cell, a voltage monitoring module, a load control module, and a controller, among which: The voltage monitoring module is used to detect the stack voltage and the lowest single cell voltage during the discharge process after the shutdown purging process for the fuel electric field. The controller is used to identify the current voltage state based on the stack voltage and the lowest single cell voltage, and to dynamically adjust the discharge current based on the voltage state; The load control module responds to the controller's instructions and performs adjustments to the discharge current of the fuel cell; Specifically, when the single-cell voltage is greater than the threshold V1, the corresponding discharge current is set to I1, and the discharge current is dynamically adjusted according to the following process: If the stack voltage is greater than the threshold U2 and the lowest single cell voltage is less than the threshold V2, it is determined to be in the first state, and the discharge current is adjusted to I2, and I1>I2. If the stack voltage is less than or equal to the threshold U2 and the lowest single cell voltage is greater than or equal to the threshold V2, it is determined to be in the second state and the discharge circuit I1 is maintained. If the stack voltage is less than or equal to the threshold U2 and the lowest single cell voltage is less than V3, it is determined to be in the third state, and the discharge current is set to 0A. Among them, V1 > V2, I1 > I2.

6. The system according to claim 5, characterized in that, The controller is also used to dynamically adjust voltage thresholds V1, U2, V2, and V3.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 4.

8. A computer device comprising a memory and a processor, wherein a computer program capable of running on the processor is stored in the memory, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 4.

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