Fuel cell over-temperature power limiting control method and device

Abstract

The application relates to a fuel cell over-temperature limited power control method and device, and belongs to the technical field of fuel cell control. The application adopts an over-temperature limited power quick load reduction control strategy, avoids triggering a secondary over-temperature fault to cause load reduction shutdown, can improve working current according to a temperature difference value, guarantees that a fuel cell engine outputs according to maximum capacity, avoids triggering an over-temperature limited power fault again, frequently reduces and loads, influences engine life, avoids the situation that over-temperature limited power caused by occasional reasons makes allowable load current small and large current cannot be loaded.

Description

Technical Field

[0001] This invention relates to a method and apparatus for controlling the over-temperature power limit of a fuel cell, belonging to the field of fuel cell control technology. Background Technology

[0002] During operation, the temperature of a fuel cell needs to be controlled within a certain range to ensure proper hydrothermal management and improve its durability. However, due to limited space in commercial fuel cell vehicles, such as trucks, there is limited space to install radiators. During prolonged high-power operation, currently installed radiators often cannot meet the heat dissipation requirements of the fuel cell system. Therefore, appropriate over-temperature control strategies are needed to ensure that the fuel cell does not overheat due to insufficient heat dissipation, thus affecting its safe operation.

[0003] Currently, the common approach is to reduce load when the temperature exceeds the limit. Based on the over-temperature situation, the fuel cell's power is limited. If the temperature remains high after power limitation, the fuel cell shuts down directly. While this method addresses insufficient heat dissipation, a single unsuccessful load reduction triggers a secondary over-temperature fault, leading to a shutdown and severely impacting the fuel cell's normal operation and consequently, vehicle efficiency. Furthermore, existing control strategies re-enable the vehicle's target power after the temperature recovers, causing frequent load changes for the fuel cell engine and significantly affecting its lifespan. Summary of the Invention

[0004] The purpose of this invention is to provide a fuel cell over-temperature power limiting control method and device to solve the problem that current fuel cell over-temperature control methods easily cause the fuel cell to shut down, thus affecting the normal use of the fuel cell.

[0005] To solve the above-mentioned technical problems, the present invention provides a fuel cell over-temperature power limit control method, which includes the following steps:

[0006] 1) Determine whether the over-temperature power limit alarm is triggered based on the over-temperature power limit threshold determined by the current operating current;

[0007] 2) When triggered, record the number of over-temperature occurrences and reduce the operating current according to the first set step size;

[0008] 3) Based on the over-temperature power limit threshold determined by the new operating current, the over-temperature power limit alarm trigger judgment is performed again. If it is not triggered, the power limit operation state is entered.

[0009] 4) If triggered again, the operating current will continue to decrease according to the first set step size, and the over-temperature power limit alarm will be triggered again until the over-temperature power limit alarm is no longer triggered.

[0010] When the over-temperature power limit alarm is triggered, the present invention reduces the operating current according to a first set step size, and continues to determine whether the over-temperature power limit alarm is triggered again under the new operating current. If it is triggered again, the operating current is reduced again until the over-temperature power limit alarm is no longer triggered, thereby realizing multiple rapid load reduction control. The present invention adopts a rapid load reduction control strategy for over-temperature power limit to avoid triggering a secondary over-temperature fault that would lead to load reduction shutdown, thus ensuring the operating time of the fuel cell.

[0011] Furthermore, when entering the power-limited operation state, the difference between the reaction temperature and the current over-temperature power-limited threshold is calculated. When the difference is less than the first threshold, if the target power is greater than the output power, the power-limited operation continues; if the target power is not greater than the output power, the operation is based on the target power. When the difference is not less than the first threshold, the operating current is increased by a second set step size until the temperature difference is less than the first threshold or the operating current reaches the maximum loadable current. The second set step size is less than 1 / 3 of the first set step size.

[0012] This invention can also increase the operating current based on the temperature difference, ensuring that the fuel cell engine outputs at its maximum capacity, while avoiding the re-triggering of over-temperature power limit faults, frequent load reduction and loading, and thus affecting engine life.

[0013] Furthermore, when the operating current reaches the maximum loadable current, if the difference between the reaction temperature and the over-temperature power threshold is greater than the second threshold, the number of over-temperature cycles is reduced by one, the maximum loadable current is increased, and the operating current is increased again according to the second set step size.

[0014] In this invention, after the operating current reaches the maximum loadable current, if the difference between the reaction temperature and the over-temperature power threshold is greater than the second threshold, it indicates that the current heat dissipation capacity is sufficient. Therefore, the over-temperature count is reduced by 1 to increase the maximum loadable current, allowing the operating current to continue to be loaded once, further ensuring that the fuel cell engine can output at its maximum capacity.

[0015] Furthermore, the maximum loadable current is equal to the rated current minus the allowable current change value multiplied by the number of over-temperature cycles.

[0016] The present invention uses the rated current minus the allowable current change by a multiple of the number of over-temperature cycles as the maximum loadable current, so that the maximum loadable current can increase as the number of over-temperature cycles decreases, thereby maximizing the operating current.

[0017] Furthermore, the allowable current change value refers to the current value corresponding to the maximum allowable power change.

[0018] The present invention uses the current value corresponding to the maximum allowable power change as the allowable current change value, which can ensure that the determined maximum loadable current is within the requirement of the maximum allowable power change.

[0019] Furthermore, if the difference between the reaction temperature and the over-temperature power limit threshold is not greater than the second threshold, if the target power is greater than the output power, the power limit operation continues; if the target power is not greater than the output power, the operation is based on the target power.

[0020] When the difference between the reaction temperature and the over-temperature power limit threshold is not greater than a second threshold, the present invention performs power limiting control according to the change of the target power. When the target power decreases, the control is performed according to the target power to ensure that the output power of the fuel cell meets the target requirements. When the target power increases, the power limiting operation continues to ensure that the temperature does not continue to rise.

[0021] Furthermore, the first set step size is determined by the engine's rated current and the maximum output current at the maximum ambient temperature.

[0022] The present invention determines the first set step size based on the engine rated current and the maximum output current at the maximum ambient temperature, which can meet the needs of rapid load reduction while avoiding excessive load reduction that would result in insufficient fuel cell output power.

[0023] Furthermore, in step 2), when the over-temperature power alarm is triggered, the thermostat opening is set to the maximum and the fan speed is set to the maximum.

[0024] When the over-temperature power limit alarm is triggered, the present invention controls the thermostat opening to the maximum and the fan speed to the maximum to dissipate heat.

[0025] The present invention also provides a fuel cell over-temperature power limit control device, including a processor, characterized in that the processor is used to execute instructions to implement the above-described fuel cell over-temperature power limit control method. Attached Figure Description

[0026] Figure 1 This is a flowchart of the fuel cell over-temperature power control method in an embodiment of the present invention. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0028] Example of Fuel Cell Over-Temperature Power Limit Control Method

[0029] This invention first determines whether an over-temperature power limit alarm has been triggered based on the over-temperature power limit threshold determined by the current operating current. If triggered, the number of over-temperature events is recorded, and the operating current is reduced by a first set step size. Then, based on the new operating current and the over-temperature power limit threshold determined, the over-temperature power limit alarm trigger determination is performed again. If not triggered, the system enters a power-limited operation state. If triggered again, the operating current is further reduced by the first set step size, and the over-temperature power limit alarm trigger determination is performed again, until no further over-temperature power limit alarms are triggered. Through the above process, this invention can achieve rapid load reduction for over-temperature power limits, avoiding the problem of load reduction shutdown caused by triggering a secondary over-temperature fault. The implementation flow of this method is as follows: Figure 1 As shown below, a detailed explanation will follow.

[0030] 1. Determine if the over-temperature power limit alarm has been triggered.

[0031] The current operating current and reaction temperature of the fuel cell are obtained. Since different operating currents correspond to different over-temperature power thresholds, this invention needs to determine the corresponding over-temperature power threshold (temperature value) based on the current operating current of the fuel cell. The obtained reaction temperature is compared with the determined over-temperature power threshold. If the current reaction temperature is greater than the determined over-temperature power threshold, it indicates that the current temperature is too high, and the over-temperature power alarm will be triggered. Different operating currents of the fuel cell have optimal reaction temperatures, which are generally determined through experimental calibration in the early stages. The over-temperature power threshold is generally 3°C higher than the optimal reaction temperature. For some fuel cell systems that are not as temperature sensitive, this value can be set larger, generally determined by the inherent characteristics of the fuel cell itself.

[0032] 2. When the over-temperature power limit alarm is triggered, the operating current of the fuel cell and the heat sink are controlled.

[0033] Assuming the radiator in this embodiment includes a thermostat and a cooling fan, if an over-temperature power limit alarm is triggered, it indicates that the current temperature is too high. The thermostat needs to be controlled to operate at its maximum opening, and the fan needs to be controlled to operate at its maximum speed. If the current state is already in this state, it remains unchanged, and the over-temperature count is recorded as 1. Simultaneously, the fuel current operating current is controlled to decrease according to a first set step size A, and stabilized for a set time. In this embodiment, the set time is 30 seconds. In other implementations, this time can be increased or decreased. The first set step size A can be set according to the difference between the engine's rated current and the maximum output current at the maximum ambient temperature, plus a certain margin. The temperature response speed is much slower than the current change. If the current decrease is too small, a secondary over-temperature fault may be triggered before a secondary load reduction occurs. This method of setting the first set step size A ensures that when an over-temperature power limit occurs, the load can be quickly reduced to the current point under maximum heat dissipation capacity, preventing the temperature from continuing to rise and triggering a secondary over-temperature fault, and directly shutting down the engine.

[0034] 3. Perform the over-temperature power limit alarm trigger judgment again.

[0035] After running for 30 seconds with the operating current reduced by the first set step size A, the over-temperature power limit alarm trigger judgment is performed again. Since the operating current has been reduced by A at this time, it is necessary to redetermine the corresponding over-temperature power limit threshold and perform the over-temperature power limit alarm trigger judgment according to the redetermined over-temperature power limit threshold. That is, the reaction temperature is compared with the redetermined over-temperature power limit threshold. If the reaction temperature is greater than the redetermined over-temperature power limit threshold, it indicates that the over-temperature power limit alarm has been triggered.

[0036] When triggered again, the fuel current and operating current continue to decrease according to the first set step size A, the number of over-temperature events is recorded +1, and the system runs stably for 30 seconds. The system then performs judgment and control again until the over-temperature power limit alarm is no longer triggered.

[0037] 4. Implement power-limited operation control.

[0038] When the over-temperature power limit alarm no longer triggers, the fuel cell is controlled to enter the power limit operation state. The difference between the reaction temperature and the over-temperature power limit threshold is judged, and control is performed according to the magnitude of the difference.

[0039] 5. When the difference is small, operate at the target power or the limited power.

[0040] If the difference between the reaction temperature and the over-temperature power limit threshold is less than the first threshold, it indicates that the difference between the two is relatively small. In this embodiment, the first threshold is 2°C. When the temperature difference between the two is small, it is determined whether the target power should be adjusted. If it is not adjusted, the power limit operation continues. If it is adjusted, it is determined whether the adjusted target power is greater than the output power. If it is greater than the output power, the power limit operation continues. If it is less than the output power, the response is based on the latest adjusted target power.

[0041] 6. When the difference is large, slow loading control should be implemented.

[0042] If the difference between the reaction temperature and the over-temperature power limit threshold is greater than the first threshold, it indicates a significant difference between the two. After the temperature difference remains large for a certain period (3-5 seconds), the operating current is increased by the second set step size B, and the system is stabilized for 30 seconds. B should be at least less than 1 / 3 of A, employing a fast descent and slow loading strategy to ensure that over-temperature does not recur during loading. After 30 seconds of stable operation, the difference between the reaction temperature and the over-temperature power limit threshold is again checked to see if it is still greater than the first threshold. If so, the operating current is increased by the second set step size B until the difference between the reaction temperature and the over-temperature power limit threshold is less than the first threshold or the operating current reaches the maximum loadable current. The maximum loadable current is calculated as Irated - C * n, where n is the number of over-temperature occurrences, and C is the allowable current change, referring to the current value corresponding to the maximum allowable power change. This ensures that the determined maximum loadable current is within the requirements of the maximum allowable power change. In this embodiment, C is the current corresponding to a power change of 2-3 kW, and the current loading does not exceed the maximum loadable current.

[0043] If the difference between the reaction temperature and the over-temperature power limit threshold is less than the first threshold, control is performed according to step 5. If the operating current reaches the maximum loadable current, the difference between the reaction temperature and the current over-temperature power limit threshold is determined. If the difference is greater than the second set threshold, it indicates that the heat dissipation capacity is sufficient. Therefore, the number of over-temperature cycles n is reduced by 1, and the maximum loadable current (the maximum loadable current increases as n decreases) is redefined, allowing for one more load cycle. The second set threshold is greater than the first set threshold; in this embodiment, the second set threshold is 3°C. When the difference is ≤3°C, it is determined whether the target power has been adjusted. If not, power-limited operation continues. If adjusted, it is determined whether the adjusted target power is greater than the output power. If it is greater than the output power, power-limited operation continues. If it is less than the output power, the response is based on the latest adjusted target power.

[0044] This invention employs a rapid load reduction control strategy based on over-temperature power limitation to avoid triggering a secondary over-temperature fault that would lead to load reduction and shutdown. Simultaneously, it can increase the operating current based on the temperature difference to ensure that the fuel cell engine outputs at its maximum capacity, while avoiding triggering the over-temperature power limitation fault again, frequent load reduction and loading, which would affect engine life. It also avoids situations where over-temperature power limitation caused by occasional reasons results in a small allowable loading current, making it impossible to load a large current.

[0045] Example of a fuel cell over-temperature power control device:

[0046] This embodiment of a fuel cell over-temperature power limit control device includes a memory, a processor, and an internal bus. The processor and memory communicate and interact with each other via the internal bus. The memory includes at least one storage device capable of storing data. The processor executes various functional applications and data processing by running software programs and modules stored in the memory, thereby implementing the fuel cell over-temperature power limit control method described in this embodiment of the invention.

[0047] In other words, the methods in the above method embodiments should be understood as a flow of a fuel cell over-temperature power control method that can be implemented by computer program instructions. These computer program instructions can be provided to a processor, causing the processor to execute these instructions to produce the functions specified in the above method flow.

[0048] The processor can be a microprocessor (MCU), a programmable logic device (FPGA), or other processing devices.

[0049] Memory can be any type of memory that uses electrical energy to store information, such as RAM and ROM; it can also be any type of memory that uses magnetic energy to store information, such as hard disks, floppy disks, magnetic tapes, magnetic core memory, magnetic bubble memory, and USB flash drives; it can also be any type of memory that uses optical energy to store information, such as CDs and DVDs; and of course, it can also be other types of memory, such as quantum memory and graphene memory.

[0050] Specific implementation methods have been given above, but the present invention is not limited to the described implementation methods. The basic idea of ​​the present invention lies in the above basic scheme. For those skilled in the art, designing various modified models, formulas, and parameters based on the teachings of the present invention does not require creative effort. Changes, modifications, substitutions, and variations made to the implementation methods without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for controlling the over-temperature power limitation of a fuel cell, characterized in that, The control method includes the following steps: 1) Determine whether an over-temperature power limit alarm is triggered based on the over-temperature power limit threshold determined by the current operating current; 2) When triggered, record the number of over-temperature occurrences and reduce the operating current according to the first set step size; 3) Based on the over-temperature power limit threshold determined by the new operating current, the over-temperature power limit alarm trigger judgment is performed again. If it is not triggered, the power limit operation state is entered. The difference between the reaction temperature and the current over-temperature power limit threshold is calculated. When the difference is less than the first threshold, if the target power is greater than the output power, the power limit operation continues. If the target power is not greater than the output power, the operation is performed according to the target power. When the difference is not less than the first threshold, the operating current is increased according to the second set step size until the difference is less than the first threshold or the operating current reaches the maximum loadable current. When the operating current reaches the maximum loadable current, if the difference between the reaction temperature and the over-temperature power limit threshold is greater than the second threshold, the over-temperature count is reduced by one, the maximum loadable current is increased, and the operating current is increased again according to the second set step size. 4) If triggered again, the operating current will continue to decrease according to the first set step size, and the over-temperature power limit alarm will be triggered again until the over-temperature power limit alarm is no longer triggered.

2. The fuel cell over-temperature power limiting control method according to claim 1, characterized in that, The second set step size is less than 1 / 3 of the first set step size.

3. The fuel cell over-temperature power limiting control method according to claim 1, characterized in that, The maximum loadable current is equal to the rated current minus the allowable current change value multiplied by the number of over-temperature cycles.

4. The fuel cell over-temperature power limiting control method according to claim 3, characterized in that, The allowable current change value refers to the current value corresponding to the maximum allowable power change.

5. The fuel cell over-temperature power limiting control method according to claim 1, characterized in that, If the difference between the reaction temperature and the over-temperature power limit threshold is not greater than the second threshold, the power limit operation will continue if the target power is greater than the output power, and the operation will proceed according to the target power if the target power is not greater than the output power.

6. The fuel cell over-temperature power limiting control method according to claim 1, characterized in that, The first set step size is determined by the engine's rated current and the maximum output current at the maximum ambient temperature.

7. The fuel cell over-temperature power limiting control method according to claim 1, characterized in that, In step 2), when the over-temperature power alarm is triggered, the thermostat opening is set to the maximum and the fan speed is set to the maximum.

8. A fuel cell over-temperature power limiting control device, characterized in that, Includes a processor, the processor being configured to execute instructions to implement the fuel cell over-temperature power control method as described in any one of claims 1-7.

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