Low-voltage protection method and device based on fan pwm, equipment and medium

Abstract

The application provides a fan PWM-based low-voltage protection method, device, equipment and medium, the method comprising: collecting the duty cycle value of the fan PWM at a preset time interval, and calculating the average value of all duty cycle values in each collection period at a preset collection period; calculating the duty cycle reference value of each collection period based on the average value of the current collection period and the duty cycle reference value of the previous collection period according to a preset comparison algorithm; collecting the real-time duty cycle value of the current fan PWM, and judging whether the current is in a low-voltage state based on the real-time duty cycle value and the duty cycle reference value corresponding to the current collection period according to a preset low-voltage judgment algorithm; if the current is in a low-voltage state, entering a low-voltage protection mode. The application calculates the duty cycle reference value based on the change of the duty cycle of the fan PWM and the dynamic adjustment mechanism to judge the low-voltage state, so that the system can more accurately identify the low-voltage and implement intelligent protection measures, effectively avoiding the damage of the compressor and the AC contactor and other components.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and in particular to a low-voltage protection method, device, equipment and medium based on wind turbine PWM. Background Technology

[0002] In regions with harsh power grid operating environments, such as the Middle East, South Asia, and parts of Africa, power grid voltage fluctuates frequently and with large amplitudes. In particular, during peak electricity load periods, persistent low voltage or sudden voltage drops often occur, leading to frequent malfunctions in high-power inductive loads such as air conditioners and refrigerators, including compressor burnout, AC contactor contact welding, or coil breakdown. These malfunctions severely affect equipment lifespan and electrical safety.

[0003] Existing low-voltage protection schemes are mainly divided into two categories: fixed threshold voltage detection method and current-based substitution judgment method. The former requires an additional voltage sampling circuit, resulting in high hardware costs, weak anti-interference ability, and the fixed threshold cannot adapt to the complex and ever-changing characteristics of power grid fluctuations, which easily leads to false tripping or failure to tripping. The latter, although eliminating the voltage sampling step, is affected by multiple factors such as load conditions, ambient temperature, and equipment aging, resulting in problems such as inaccurate judgment, delayed response, and high false judgment rate.

[0004] Therefore, existing technologies generally suffer from problems such as single criteria, poor adaptability, high hardware costs, and high risk of false tripping / failure to trip. Especially in complex power grid environments with severe voltage fluctuations and no stable reference, it is difficult to achieve reliable, intelligent, and low-cost protection and recovery control. Summary of the Invention

[0005] This invention provides a low-voltage protection method, device, equipment, and medium based on fan PWM, aiming to accurately identify low voltage and intelligently implement low-voltage protection measures to effectively solve the technical problem that inductive loads are easily damaged in low-voltage environments.

[0006] In a first aspect, embodiments of the present invention provide a low-voltage protection method based on wind turbine PWM, comprising: acquiring the duty cycle value of wind turbine PWM at preset time intervals, and calculating the average value of all duty cycle values ​​in each acquisition cycle according to a preset acquisition period; calculating a duty cycle reference value for each acquisition cycle based on the average value of the current acquisition cycle and the duty cycle reference value of the previous acquisition cycle according to a preset comparison algorithm; acquiring the real-time duty cycle value of the current wind turbine PWM, and determining whether the current state is low-voltage based on the real-time duty cycle value and the duty cycle reference value corresponding to the current acquisition cycle according to a preset low-voltage judgment algorithm; if the current state is low-voltage, then entering a low-voltage protection mode.

[0007] Secondly, embodiments of the present invention also provide a low-voltage protection device based on wind turbine PWM, which includes a unit for performing the above-described method.

[0008] Thirdly, embodiments of the present invention also provide a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the above-described method.

[0009] Fourthly, embodiments of the present invention also provide a computer-readable storage medium storing a computer program, the computer program including program instructions that, when executed by a processor, can implement the above-described method.

[0010] This application provides a low-voltage protection method, device, computer equipment, and storage medium based on fan PWM. It indirectly reflects voltage fluctuations by using the duty cycle variation of fan PWM, and adjusts the duty cycle reference value for each acquisition cycle through a dynamic adjustment mechanism to determine the low-voltage state. This makes the method applicable to voltage reference value deviations in different regions and the characteristics of different fan models, improving the adaptability and accuracy of the method. Furthermore, this method replaces the traditional current threshold method, avoiding the problem of the traditional current threshold method being affected by load changes. This allows the system to more accurately identify the low-voltage state when the voltage is abnormal, and implement intelligent protection measures and intelligent recovery control accordingly. This effectively avoids damage to critical components such as compressors and AC contactors, achieving the technical effects of improving system stability and extending equipment life. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 A schematic flowchart illustrating a low-voltage protection method based on wind turbine PWM provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a sub-process of the low-voltage protection method based on wind turbine PWM provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a sub-process of the low-voltage protection method based on wind turbine PWM provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a sub-process of the low-voltage protection method based on wind turbine PWM provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of a sub-process of the low-voltage protection method based on wind turbine PWM provided in an embodiment of the present invention; Figure 6This is a schematic diagram of a sub-process of the low-voltage protection method based on wind turbine PWM provided in an embodiment of the present invention; Figure 7 A schematic block diagram of a low-voltage protection device based on wind turbine PWM provided in an embodiment of the present invention; Figure 8 A schematic block diagram of a computer device provided for an embodiment of the present invention. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0015] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0016] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0017] Please see Figure 1This is a schematic flowchart of a low-voltage protection method based on fan PWM provided in this invention. In this application, the low-voltage protection method based on fan PWM is applied to air conditioning equipment in regions with frequent power grid voltage fluctuations (such as the Middle East and South Asia), and is particularly suitable for refrigeration systems containing both a fan and a compressor. The method involves the fan running stably at a preset target speed after the air conditioner starts. The system collects the fan PWM duty cycle value periodically and iteratively updates the duty cycle reference value. Combining the real-time duty cycle with the reference value, a low-voltage state is determined. When protection is triggered, the low-voltage duty cycle value is recorded and the compressor operation is stopped. In protection mode, the duty cycle is continuously monitored, and the compressor operation is automatically restored after the recovery conditions are met. This method utilizes the fan as an indirect voltage sensing element, eliminating the need for additional voltage sampling circuits. It solves the problems of single criteria, poor adaptability, and high hardware costs in existing technologies, achieving low-cost, high-reliability low-voltage protection and automatic recovery control.

[0018] This application provides a low-voltage protection method, device, equipment, and medium based on wind turbine PWM. The low-voltage protection method based on wind turbine PWM includes: acquiring the duty cycle value of the wind turbine PWM at preset time intervals, and calculating the average value of all duty cycle values ​​in each acquisition cycle according to a preset acquisition period; calculating the duty cycle reference value of each acquisition cycle based on the average value of the current acquisition cycle and the duty cycle reference value of the previous acquisition cycle based on a preset comparison algorithm; acquiring the real-time duty cycle value of the current wind turbine PWM, and determining whether the current state is low-voltage based on the real-time duty cycle value and the duty cycle reference value corresponding to the current acquisition cycle based on a preset low-voltage judgment algorithm; if the current state is low-voltage, then entering the low-voltage protection mode.

[0019] This application indirectly reflects voltage fluctuations by using the duty cycle change based on the PWM of the wind turbine, and adjusts the duty cycle reference value for each acquisition cycle through a dynamic adjustment mechanism to determine the low voltage state. This makes the judgment method applicable to voltage reference value deviations in different regions and the characteristics of different wind turbines, improving the adaptability and accuracy of the judgment method. At the same time, this judgment method replaces the traditional current threshold judgment method, avoiding the problem of the traditional current threshold method being affected by load changes. This allows the system to more accurately identify the low voltage state when the voltage is abnormal, and implement intelligent protection measures and intelligent recovery control accordingly. This can effectively avoid damage to key components such as compressors and AC contactors, achieving the technical effects of improving system stability and extending equipment life.

[0020] Figure 1 This is a flowchart illustrating the low-voltage protection method based on wind turbine PWM provided in an embodiment of the present invention. Figure 1 As shown, the method includes the following steps S10-S40.

[0021] It should be noted that this method is applicable to electrical systems with fans and compressors, such as air conditioners, dehumidifiers, and dryers. It enables low-voltage detection and protection based on the fan's PWM, effectively protecting the compressor and AC contactor. In this embodiment, the method is primarily used in air conditioning systems to protect the air conditioner from low-voltage conditions in areas with large voltage fluctuations, thereby extending the air conditioner's lifespan.

[0022] S10. Collect the duty cycle value of the fan PWM at preset time intervals, and calculate the average value of all duty cycle values ​​in each preset collection period.

[0023] Specifically, the preset time interval refers to the fixed time length between two adjacent duty cycle value acquisition actions preset by the system, such as acquiring a duty cycle value every 10 seconds; the preset acquisition cycle refers to the fixed time length preset by the system to complete one round of complete duty cycle value acquisition and average calculation. A single acquisition cycle includes multiple acquisition actions executed at preset time intervals, such as every 10 minutes as one acquisition cycle. The fan PWM refers to the pulse width modulation signal used to drive the fan, and its duty cycle value is defined as the ratio of the high-level duration to the entire PWM cycle, usually expressed as a percentage, directly reflecting the driving strength of the controller on the fan.

[0024] To ensure that the collected duty cycle data accurately reflects the impact of grid voltage fluctuations on the fan load, the system first ensures that the fan operates stably at a preset target fan speed value after the electrical equipment is started. In this embodiment, the electrical equipment refers to an air conditioner, but in other usage scenarios, the electrical equipment can also refer to a refrigerator, dehumidifier, water heater, dryer, etc., and is not limited here. The preset target fan speed value is determined based on the fixed fan speed value corresponding to the user-set fan speed mode (or the user-set heating, cooling, dehumidification, etc. function modes). This fixed value is calibrated by multi-condition testing before leaving the factory to ensure that the fan can maintain a stable output state under different environments.

[0025] During stable operation of the wind turbine, the controller initiates a periodic data acquisition process: sampling the current PWM duty cycle value of the wind turbine at preset time intervals (e.g., every 10 seconds) to obtain an instantaneous duty cycle value. Simultaneously, the system sets a preset acquisition period (e.g., every 10 minutes), continuously acquiring multiple duty cycle sampling points within each period to form a duty cycle sequence. For example, when the time interval is 10 seconds and the acquisition period is 10 minutes, a total of 60 duty cycle data points are acquired within each acquisition period. When the acquisition period ends, the controller performs an arithmetic mean calculation on the duty cycle values ​​of all sampling points within that period, i.e., summing the duty cycle values ​​of all sampling points and dividing by the total number of sampling points to obtain the average duty cycle value for that acquisition period. This average duty cycle value essentially represents the average drive level of the wind turbine load within the time period of that acquisition period. Its physical significance lies in eliminating instantaneous fluctuations caused by switching actions, mechanical fluctuations, or transient electromagnetic interference, providing a stable and representative characteristic quantity.

[0026] The process of collecting data at the preset time interval and calculating the average value according to the preset collection cycle is continuously repeated during system operation. Each collection cycle independently generates a new duty cycle average value. This average value sequence will be used as an input parameter by the subsequent low voltage protection logic module to compare with a preset threshold or trend, thereby accurately determining whether the grid voltage is in a low state and providing a reliable data basis for low voltage protection based on wind turbine PWM.

[0027] S20. Based on a preset comparison algorithm, calculate the duty cycle reference value for each acquisition cycle according to the mean value of the current acquisition cycle and the duty cycle reference value of the previous acquisition cycle.

[0028] Specifically, the duty cycle reference value refers to the standard drive level used to characterize the wind turbine's normal operation under stable grid conditions, serving as a dynamically updated reference value. To accurately track the slow changes in wind turbine load during long-term system operation, while avoiding frequent reference jumps due to instantaneous grid fluctuations or sampling noise, this embodiment introduces a recursive update mechanism based on a preset comparison algorithm, and pre-sets a reliable initial state for this mechanism.

[0029] The preset comparison algorithm is a fixed calculation rule preset before the system leaves the factory, used to iteratively calculate the duty cycle reference value for each acquisition cycle. The mean value of the current acquisition cycle refers to the arithmetic mean of the PWM duty cycle values ​​of all wind turbines within the current acquisition cycle; the duty cycle reference value of the previous acquisition cycle refers to the reference value determined by calculation in the previous acquisition cycle and used for iterative calculation.

[0030] In practical implementation, the system first needs to establish an initial reference value: In the first acquisition cycle after initial power-on or reset, since there is no historical reference data, the system will directly use the preset initial reference value as the duty cycle reference value for that cycle. This initial reference value is not arbitrarily set, but is obtained experimentally during the calibration phase before the equipment leaves the factory: the device under test is placed under rated voltage conditions, and its fan is made to run stably at a preset target fan speed. Then, sampling is performed using the same acquisition parameters as the actual operation (e.g., acquiring data every 10 seconds, continuously acquiring 60 data points, forming a sequence P0 to P60). The arithmetic mean of these 60 duty cycle values ​​is calculated, and the calculated mean is stored as the initial reference value in the controller's non-volatile memory. This initial reference value represents the fan drive characteristic value of the equipment under standard power grid conditions.

[0031] When the electrical equipment is powered on and running for the first time on-site, during the first data acquisition cycle, the controller directly reads the preset initial reference value from the memory and uses it as the duty cycle reference value for the first cycle. From the second data acquisition cycle onwards, the system begins a recursive update process: at the end of each data acquisition cycle, the controller obtains the average duty cycle value for the current cycle and inputs it along with the duty cycle reference value from the previous cycle into a preset comparison algorithm module. This algorithm module contains comparison logic and update rules. For example, a dead zone range that allows fluctuations can be set. If the change in the current average value relative to the previous reference average value does not exceed this range, the previous reference average value is maintained as the reference average value for the current data acquisition cycle; if the change exceeds the range, a new value is calculated according to the preset rules and used as the duty cycle reference value for the current data acquisition cycle.

[0032] In this way, an independent duty cycle reference value corresponding to that cycle is generated at the end of each acquisition cycle. This value is based on the initial reference value calibrated at the factory, which ensures the accuracy of the reference. It can also slowly change with the long-term trend of the wind turbine load in subsequent operation and resist interference from short-term grid fluctuations or sampling noise.

[0033] Unlike existing technologies that use fixed thresholds as the judgment criteria, the judgment benchmark in this embodiment can be applied to different rated voltage values ​​in different regions. The duty cycle benchmark value of each acquisition cycle is dynamically adjusted according to the characteristics of different wind turbines, thereby providing a stable and adaptive comparison benchmark for low voltage protection judgment, avoiding misjudgment, and improving the adaptability and accuracy of low voltage protection.

[0034] In one embodiment, such as Figure 2 As shown, step S20 includes steps S21-S24.

[0035] S21. Calculate the first absolute difference between the mean value of the current acquisition cycle and the duty cycle reference value of the previous acquisition cycle. S22. Compare the first absolute difference with the duty cycle reference value of the previous acquisition cycle with the preset first ratio. S23. If the first absolute difference is less than or equal to the duty cycle reference value of the previous acquisition cycle of the preset first ratio, then the average value of the current acquisition cycle shall be used as the duty cycle reference value of the next acquisition cycle. S24. If the first absolute difference is greater than the duty cycle reference value of the previous acquisition cycle of the preset first ratio, then the duty cycle reference value of the previous acquisition cycle shall be used as the duty cycle reference value of the next cycle.

[0036] Specifically, in this embodiment, the preset comparison algorithm is defined as a set of logical rules that calculate the absolute difference between the current period average and the historical benchmark value, and determine whether to update the benchmark value based on the relationship between the difference and a preset ratio threshold.

[0037] In the first data acquisition cycle after the system is powered on for the first time, since there is no historical reference data, the preset initial reference value is directly used as the duty cycle reference value for this cycle. This initial reference value is a fixed constant, which is obtained by collecting multiple duty cycle data and calculating the average value under rated voltage conditions before the equipment leaves the factory, and is stored in the controller.

[0038] Starting from the second acquisition cycle, at the end of each acquisition cycle, the controller executes the following update process: First, it calculates the first absolute difference between the average duty cycle obtained in the current acquisition cycle and the duty cycle reference value used in the previous acquisition cycle. The first absolute difference refers to the absolute value of the difference between the average value of the current acquisition cycle and the duty cycle reference value of the previous acquisition cycle. Then, it compares the first absolute difference with the result obtained by multiplying the duty cycle reference value of the previous acquisition cycle by a preset first ratio. The preset first ratio refers to a fixed ratio threshold preset before the system leaves the factory, which is a positive number less than 1, such as 2%, and can be pre-calibrated according to different models or application scenarios.

[0039] If the first absolute difference is less than or equal to the product of the preset first ratio and the duty cycle reference value of the previous acquisition cycle, then the average value of the current acquisition cycle is determined to be within the allowable fluctuation range, and the controller uses the average value of the current acquisition cycle as the duty cycle reference value for the next acquisition cycle and stores it.

[0040] If the first absolute difference is greater than the product of the preset first ratio and the duty cycle reference value of the previous acquisition cycle, it is determined that the average value fluctuation of the current acquisition cycle is too large, which may be due to power grid transients or abnormal interference. At this time, the controller maintains the duty cycle reference value of the previous acquisition cycle unchanged and uses it as the reference value for the next acquisition cycle.

[0041] More specifically, the average value of the current collection period is The duty cycle baseline value for the previous acquisition cycle is The duty cycle reference value for the next acquisition cycle is The preset first ratio is The preset comparison algorithm includes: like ,but ; like ,but .

[0042] In this way, an independent duty cycle reference value is generated after each acquisition cycle. This value is based on the factory calibration value as a reliable starting point, can be gradually updated when the wind turbine characteristics drift slowly, and maintains reference stability when the power grid fluctuates significantly, thus providing an accurate and robust comparison reference for undervoltage protection.

[0043] S30. Collect the real-time duty cycle value of the current fan PWM, and determine whether the current state is low voltage based on the real-time duty cycle value and the duty cycle reference value corresponding to the current collection period according to the preset low voltage judgment algorithm.

[0044] Specifically, the real-time duty cycle value refers to the instantaneous duty cycle value that the controller directly collects from the wind turbine PWM drive signal at the current moment. It is usually expressed as a percentage and reflects the real-time drive intensity output by the controller to maintain the target speed of the wind turbine under the current grid voltage and load conditions.

[0045] The preset low voltage judgment algorithm is a fixed comparison calculation and state judgment rule that is preset before the system leaves the factory and is used to determine the low voltage state of the power grid based on duty cycle data.

[0046] The duty cycle benchmark value corresponding to the current acquisition cycle refers to the standard value determined by the aforementioned periodic average calculation and recursive update process, which is used to characterize the expected drive level of the wind turbine under normal grid conditions in the current time period. This value is stored in the controller's register or memory and is updated at the end of each acquisition cycle.

[0047] The low voltage state refers to an abnormal power grid condition in which the grid voltage amplitude is lower than the rated value, which may cause inductive load failure.

[0048] In order to monitor the power grid status in real time and detect voltage drops in a timely manner, this embodiment continuously executes the low voltage status judgment process during the stable operation of the wind turbine: In each preset judgment cycle (e.g., per second or per power frequency cycle), the controller first reads the real-time duty cycle value at the current moment, and at the same time retrieves the duty cycle reference value corresponding to the current acquisition cycle from the memory.

[0049] Subsequently, the controller invokes a preset low-voltage judgment algorithm to process these two values. This algorithm is a set of pre-installed logic rules within the control program used to assess the deviation of the real-time drive level from a reference value. Specifically, the algorithm calculates the difference or relative rate of change between the real-time duty cycle value and the reference average, and compares the result with a preset threshold. This threshold can be a fixed constant or a proportional value related to the reference average, such as setting an allowable upper limit offset. If the positive deviation of the real-time duty cycle value from the reference average exceeds the preset threshold, the algorithm determines that the current grid voltage is low, because the wind turbine requires an abnormally increased drive intensity to maintain the target speed, indirectly reflecting a decrease in input voltage. Conversely, if the deviation is within the threshold range, the voltage is determined to be normal.

[0050] Once a low voltage condition is detected, the controller immediately outputs a control signal to trigger corresponding protection actions, such as stopping the compressor, recording fault codes, or issuing an alarm.

[0051] Through the above method, this embodiment achieves rapid and accurate low-voltage state identification based on real-time drive parameters and dynamic reference of the wind turbine, providing a reliable triggering basis for subsequent protection measures.

[0052] In one embodiment, such as Figure 3 As shown, step S30 may include steps S31-S33.

[0053] S31. Calculate the second absolute difference between the real-time duty cycle value and the duty cycle reference value corresponding to the current acquisition cycle; S32. Compare the second absolute difference with the duty cycle reference value corresponding to the current acquisition cycle of the preset second ratio; S33. If the second absolute difference is greater than or equal to the duty cycle reference value corresponding to the current acquisition cycle of the preset second ratio, then it is determined that the current state is low voltage.

[0054] This embodiment describes the specific process for continuously performing low-voltage judgment during stable wind turbine operation: At each preset judgment time, the controller first reads the current real-time duty cycle value and simultaneously retrieves the duty cycle reference value corresponding to the current acquisition cycle from the memory. Subsequently, the controller calculates the second absolute difference between the real-time duty cycle value and the reference value. The second absolute difference refers to the absolute value of the difference between the real-time duty cycle value and the duty cycle reference value, and this difference quantifies the degree of deviation of the current drive intensity from the normal reference.

[0055] Next, the controller obtains a preset second ratio value, which is a positive number less than 1 (e.g., 4%, 10%). The specific value can be pre-calibrated according to different models or application scenarios. The preset second ratio is multiplied by the duty cycle reference value corresponding to the current acquisition cycle to obtain an allowable fluctuation limit value.

[0056] The controller compares the calculated second absolute difference with this allowable fluctuation limit. If the second absolute difference is greater than or equal to the allowable fluctuation limit, it is determined that the positive deviation of the current real-time duty cycle value from the reference value has exceeded the normal fluctuation range. This means that the wind turbine needs an abnormally increased drive strength to maintain the preset target wind turbine speed, which indirectly indicates that the grid voltage has dropped to a low state. The controller then outputs a low voltage state determination signal.

[0057] If the second absolute difference is less than the upper limit of the allowable fluctuation, the current voltage is determined to be normal, and the system continues to operate normally.

[0058] More specifically, the real-time duty cycle value is The duty cycle reference value corresponding to the current acquisition cycle is The preset second ratio is The preset low voltage detection algorithm includes: like If so, it will enter the low voltage protection mode; like Then it will continue to operate normally.

[0059] Through the above method, this embodiment realizes a quantitative comparison based on real-time drive parameters and dynamic benchmark, providing an accurate and reliable trigger judgment basis for low voltage protection.

[0060] In one embodiment, such as Figure 4 As shown, step S30 also includes steps S34-S35.

[0061] S34. Collect the real-time duty cycle value of the current fan PWM and the current fan speed value corresponding to the real-time duty cycle value; S35. Based on the preset low voltage judgment algorithm, determine whether the current state is low voltage by comprehensively considering the real-time duty cycle value, the duty cycle reference value corresponding to the current acquisition cycle, the current fan speed value, and the preset target fan speed value.

[0062] Specifically, the real-time fan speed value refers to the actual rotational speed of the fan impeller, which is collected in real time by a speed detection unit (such as a Hall sensor or a back EMF detection circuit), usually in revolutions per minute (RPM). The preset target fan speed value refers to a fixed speed value corresponding to the user-set windshield mode, or a default preset speed value under other special modes. This speed value is calibrated by multi-condition testing before leaving the factory and stored in the controller to ensure that the fan can maintain the expected stable output state under different environments.

[0063] To further improve the reliability of low voltage detection when there are large changes in wind turbine load or control errors, this embodiment introduces speed feedback as a comprehensive judgment basis in addition to the judgment based solely on duty cycle.

[0064] During stable operation of the wind turbine, the controller simultaneously performs two data acquisitions within each preset judgment cycle: reading the current real-time duty cycle value and obtaining the current wind turbine speed value corresponding to that duty cycle value through the speed detection unit. Subsequently, the controller retrieves the duty cycle reference value corresponding to the current acquisition cycle and the preset target wind turbine speed value for this operating mode from the memory.

[0065] The controller compares the real-time duty cycle value with the baseline average duty cycle value to assess the degree of deviation in drive intensity; at the same time, it compares the current fan speed value with the preset target speed value to calculate the speed deviation.

[0066] Based on a preset low-voltage judgment algorithm, the controller makes a logical judgment by combining the above two comparison results: if the real-time duty cycle value is significantly higher than the reference value but the speed has not yet reached the target value, or if the speed deviation exceeds the allowable range and the duty cycle is close to or has reached the adjustment limit, then it is determined that the current state is low-voltage. The above judgment logic is only for illustrative purposes, and the specific judgment logic can be formulated according to different usage scenarios and requirements. For example, when the real-time duty cycle value has been adjusted to the maximum limit but the actual fan speed still cannot be increased to the target fan speed, it indicates that the input voltage is too low, causing the fan drive capability to reach its limit. At this time, even if the deviation of the real-time duty cycle value does not trigger a single criterion, the system can still decisively enter the low-voltage protection based on the speed deviation.

[0067] For example, if the target fan speed is set to 1400 RPM, and the stable operation can reach 1400 RPM, then only steps S31-S33 above are needed to determine whether it is in a low voltage state; assuming the duty cycle is positively adjusted to the output voltage, the duty cycle is adjusted to be close to the maximum limit (i.e. At this point, the current fan speed can only reach 1200 rpm (which is less than the target fan speed). Therefore, it is not possible to determine whether the low voltage state is under the above steps S31-S33. Instead, laboratory measurements can be used. For example, if the voltage is below 165V, the low voltage protection mode needs to be entered. In this case, even if the fan speed is set to 1400 rpm, it can only reach a maximum of 1200 rpm. The actual speed value can be used as a condition to determine whether the low voltage state is under the above conditions.

[0068] This embodiment effectively avoids misjudgment of a single parameter due to sudden changes in the mechanical load of the fan or control errors by using the joint judgment mechanism of the duty cycle and the fan speed. It further realizes accurate identification of low voltage and provides a more comprehensive and reliable triggering basis for low voltage protection.

[0069] S40. If the current voltage is low, enter the low voltage protection mode.

[0070] Specifically, the low voltage state refers to an abnormal power grid condition in which the grid voltage amplitude is lower than the rated value and there is a risk of damage to inductive loads, as determined by the system through a preset low voltage judgment algorithm based on the real-time duty cycle value of the fan PWM and the duty cycle reference value, or by combining the actual speed of the fan with the preset target speed. The low voltage protection mode refers to a protection control operation mode that is preset by the system before leaving the factory and is specifically set for abnormal low voltage conditions, in order to avoid the risk of overcurrent and overheating damage to core components such as compressors and AC contactors under low voltage conditions.

[0071] In practice, while the wind turbine is running stably at the preset target wind turbine speed, the system continuously and cyclically executes the real-time acquisition and judgment process for low voltage status, synchronously acquiring the low voltage status judgment result output by each judgment process. When the judgment result clearly indicates that the current low voltage status is being reached, the system immediately triggers the preset protection trigger logic, terminates the currently executing normal operation control mode, and directly switches to the preset low voltage protection mode. After entering the low voltage protection mode, the system executes the preset protection control actions, while continuously monitoring the power grid conditions during the operation of the protection mode, cyclically verifying the low voltage status, until the low voltage status is determined to be completely resolved. Then, the system executes the preset recovery process to exit the low voltage protection mode and return to the normal operation control process.

[0072] This embodiment provides timely, reliable, and intelligent protection for electrical equipment, effectively solving the technical problem of inductive loads being easily damaged in low-voltage environments, and providing the necessary data foundation for subsequent recovery of operation.

[0073] In one embodiment, step S40 may include step S41.

[0074] S41. If the current voltage is low, the low voltage duty cycle value of the current fan PWM is collected and recorded, and the low voltage protection mode is entered to control the compressor to stop running.

[0075] Specifically, the low-voltage duty cycle value refers to the duty cycle value of the fan PWM drive signal collected in real time at the moment when the system determines that it has entered a low-voltage state.

[0076] In practice, the system pre-stores low-voltage state judgment rules and low-voltage protection mode control logic. During the stable operation of the fan at the preset target speed, the system continuously and cyclically executes the real-time acquisition and judgment process of low-voltage state. When the system determines that it is currently in a low-voltage state, it immediately acquires and latches the low-voltage duty cycle value corresponding to the fan PWM at the current moment and stores the value in the system's designated storage area for the subsequent automatic judgment process of voltage recovery. After completing the recording of the low-voltage duty cycle value, the system immediately terminates the normal operation control process, switches to the preset low-voltage protection mode, outputs control commands to control the compressor to stop running, cuts off the compressor power supply circuit, and avoids the risk of equipment damage caused by compressor overcurrent and overheating under low-voltage conditions.

[0077] This embodiment achieves reliable, intelligent, and low-cost protection while retaining the necessary field data for subsequent intelligent recovery control.

[0078] In one embodiment, such as Figure 5 As shown, steps S411-S413 may be included after step S41.

[0079] S411. Real-time acquisition of the current duty cycle value of the fan PWM in low voltage protection mode; S412. Based on a preset recovery algorithm, determine whether the current voltage has returned to normal based on the duty cycle reference value under the corresponding period of the current duty cycle value and the low voltage duty cycle value; S413. If the normal state is restored, control the compressor to operate normally.

[0080] Specifically, the current duty cycle value refers to the instantaneous duty cycle value of the wind turbine PWM collected in real time by the controller in each monitoring cycle after the system enters the low voltage protection mode. The duty cycle reference value corresponding to the low voltage duty cycle value refers to the duty cycle reference value of the acquisition cycle corresponding to the moment the low voltage protection is triggered. This value is stored together with the low voltage duty cycle value in non-volatile memory. The preset recovery algorithm refers to the comparison calculation and status determination rules preset by the system before leaving the factory for determining whether the grid voltage has returned to normal; the normal state refers to the normal operating condition where the grid voltage returns to the rated range and there is no risk of load damage.

[0081] In order to exit the protection state in a timely manner and automatically restart the compressor after the voltage is restored, this embodiment continues to execute the voltage recovery judgment process in protection mode.

[0082] In practice, after the system enters the low voltage protection mode and completes the latching and recording of the low voltage duty cycle value and the corresponding cycle duty cycle reference value, it continuously executes the real-time acquisition process. It acquires the current duty cycle value of the fan PWM in the low voltage protection mode in real time, and synchronously retrieves the two latched reference values ​​and inputs them into the preset recovery algorithm to complete the difference calculation and threshold comparison or other algorithm specifications, which are not specifically limited here. If the calculation result meets the preset recovery conditions and the state continues to reach the preset stable time, the system determines that the current voltage has returned to the normal state, and then exits the low voltage protection mode, outputs control commands to control the compressor to resume normal operation, and returns to the normal operation control process of the system.

[0083] Through the above specific implementation process, this embodiment realizes automatic recovery judgment based on the monitoring of the fan duty cycle, ensuring that the equipment can return to normal working state in a timely, accurate and reliable manner after the voltage is restored.

[0084] In one embodiment, such as Figure 6 As shown, step S412 may include steps S4121-S4123.

[0085] S4121. Calculate the third absolute difference between the current duty cycle value and the duty cycle reference value under the corresponding period of the low voltage duty cycle value; S4122. Compare the magnitude of the third absolute difference with the duty cycle reference value corresponding to the low-voltage duty cycle value of the preset third ratio under the same period. S4123. If the third absolute difference is greater than or equal to the duty cycle reference value under the corresponding period of the low voltage duty cycle value of the preset third ratio, and is maintained for a preset stable time, then it is determined that the current voltage has returned to normal.

[0086] Specifically, the third absolute difference refers to the absolute value of the difference between the current duty cycle value and the baseline value under the corresponding cycle of the low voltage duty cycle value; the preset third ratio and the preset stabilization time are both fixed threshold parameters preset before the system leaves the factory.

[0087] To ensure timely exit from protection mode and automatic compressor restart after voltage recovery, this embodiment continuously executes the voltage recovery judgment process in low-voltage protection mode. The controller collects the current duty cycle value in real time at preset monitoring intervals, and simultaneously retrieves the duty cycle reference value and low-voltage duty cycle value recorded at the protection time from memory. Subsequently, the controller calls a preset recovery algorithm for judgment: first, it calculates the third absolute difference between the current duty cycle value and the reference value recorded at the protection time; this difference quantifies the degree of recovery of the current drive intensity relative to the original reference. The reference value at the protection time, rather than the reference value of the current cycle, is used for judgment because it represents a stable reference level before the voltage drop, making recovery judgment more accurate and reliable.

[0088] Subsequently, the controller acquires a preset third ratio value, which is a positive number less than 1 (e.g., 4%), and the specific value is obtained through experimental calibration; multiplying the preset third ratio by the baseline value recorded at the protection time, a recovery judgment threshold is obtained.

[0089] The controller compares the calculated third absolute difference with this recovery judgment threshold. If the third absolute difference is greater than or equal to the recovery judgment threshold, it indicates that the current wind turbine duty cycle has recovered to a sufficient level relative to the original reference, indirectly reflecting that the grid voltage has recovered. At the same time, to ensure voltage stability rather than instantaneous fluctuations, the controller further monitors whether this state continues to maintain a preset stable time (e.g., 30 seconds).

[0090] If this condition is met consistently within the preset stable time, it is ultimately determined that the grid voltage has returned to normal. At this point, the controller outputs a control signal to restart the compressor, restoring the system to normal operation.

[0091] More specifically, the current duty cycle value is Low-voltage duty cycle The duty cycle reference value under the corresponding period is The preset third ratio is The preset recovery algorithm includes: like Then the compressor will operate normally; like If so, it will remain in low voltage protection mode.

[0092] Through the above specific implementation process, this embodiment achieves accurate recovery judgment based on the protection time reference value, effectively avoiding frequent start-stop due to voltage fluctuations.

[0093] This application indirectly reflects voltage fluctuations by using the duty cycle change based on the PWM of the wind turbine, and adjusts the duty cycle reference value for each acquisition cycle through a dynamic adjustment mechanism to determine the low voltage state. This makes the judgment method applicable to voltage reference value deviations in different regions and the characteristics of different wind turbines, improving the adaptability and accuracy of the judgment method. At the same time, this judgment method replaces the traditional current threshold judgment method, avoiding the problem of the traditional current threshold method being affected by load changes. This allows the system to more accurately identify the low voltage state when the voltage is abnormal, and implement intelligent protection measures and intelligent recovery control accordingly. This can effectively avoid damage to key components such as compressors and AC contactors, achieving the technical effects of improving system stability and extending equipment life.

[0094] Figure 7 This is a schematic block diagram of a low-voltage protection device 300 based on wind turbine PWM provided in an embodiment of the present invention. Figure 7 As shown, corresponding to the above-described low-voltage protection method based on wind turbine PWM, the present invention also provides a low-voltage protection device 300 based on wind turbine PWM. This low-voltage protection device 300 includes a unit for executing the above-described low-voltage protection method based on wind turbine PWM, and the device can be configured in a computer device. Specifically, please refer to... Figure 7 The low voltage protection device 300 based on wind turbine PWM includes a data acquisition unit 301, a calculation unit 302, a judgment unit 303, and a protection unit 304.

[0095] The acquisition unit 301 is used to acquire the duty cycle value of the fan PWM at preset time intervals and calculate the average value of all duty cycle values ​​in each acquisition cycle according to the preset acquisition period. The calculation unit 302 is used to calculate the duty cycle reference value for each acquisition cycle based on the average value of the current acquisition cycle and the duty cycle reference value of the previous acquisition cycle according to a preset comparison algorithm. The judgment unit 303 is used to collect the real-time duty cycle value of the current wind turbine PWM, and determine whether the current state is low voltage based on the real-time duty cycle value and the duty cycle reference value corresponding to the current collection period according to the preset low voltage judgment algorithm. Protection unit 304 is used to enter low voltage protection mode if the current voltage state is low.

[0096] In one embodiment, the calculation unit 302 includes a first calculation unit, a first comparison unit, and a determination unit.

[0097] The first calculation unit is used to calculate the first absolute difference between the mean value of the current acquisition cycle and the duty cycle reference value of the previous acquisition cycle. The first comparison unit is used to compare the first absolute difference with the duty cycle reference value of the previous acquisition cycle with a preset first ratio. The determining unit is configured to, if the first absolute difference is less than or equal to the duty cycle reference value of the previous acquisition cycle at the preset first ratio, use the average value of the current acquisition cycle as the duty cycle reference value of the next acquisition cycle; and if the first absolute difference is greater than the duty cycle reference value of the previous acquisition cycle at the preset first ratio, use the duty cycle reference value of the previous acquisition cycle as the duty cycle reference value of the next cycle.

[0098] In one embodiment, the judgment unit 303 includes a second calculation unit, a second comparison unit, a first judgment unit, a first acquisition unit, and a second judgment unit.

[0099] The second calculation unit is used to calculate the second absolute difference between the real-time duty cycle value and the duty cycle reference value corresponding to the current acquisition cycle; The second comparison unit is used to compare the second absolute difference with the duty cycle reference value corresponding to the current acquisition cycle of the preset second ratio; The first judgment unit is used to determine that the current state is low voltage if the second absolute difference is greater than or equal to the duty cycle reference value corresponding to the current acquisition cycle of the preset second ratio. The first acquisition unit is used to acquire the real-time duty cycle value of the current fan PWM and the current fan speed value corresponding to the real-time duty cycle value; The second judgment unit is used to comprehensively judge whether the current state is low voltage based on the preset low voltage judgment algorithm, the real-time duty cycle value, the duty cycle reference value corresponding to the current acquisition cycle, the current fan speed value, and the preset target fan speed value.

[0100] In one embodiment, the protection unit 304 includes a recording and control unit.

[0101] The recording and control unit is used to collect and record the low-voltage duty cycle value of the current fan PWM if the current voltage state is low, and then enter the low-voltage protection mode to control the compressor to stop running.

[0102] In one embodiment, the low voltage protection device 300 based on wind turbine PWM further includes a recovery unit 305.

[0103] The recovery unit 305 is used to collect the current duty cycle value of the fan PWM in the low voltage protection mode in real time; based on the preset recovery algorithm, it determines whether the current voltage has returned to normal state according to the current duty cycle value and the duty cycle reference value of the corresponding period of the low voltage duty cycle value; if it has returned to normal state, it controls the compressor to run normally.

[0104] In one embodiment, the recovery unit 305 includes a third calculation unit, a third comparison unit, and a third judgment unit.

[0105] The third calculation unit is used to calculate the third absolute difference between the current duty cycle value and the duty cycle reference value under the corresponding period of the low voltage duty cycle value; The third comparison unit is used to compare the third absolute difference with the duty cycle reference value under the corresponding period of the low voltage duty cycle value at the preset third ratio. The third judgment unit is used to determine that the current voltage has returned to normal if the third absolute difference is greater than or equal to the duty cycle reference value under the corresponding period of the low voltage duty cycle value of the preset third ratio, and is maintained for a preset stable time.

[0106] It should be noted that those skilled in the art can clearly understand that the specific implementation process of the above-mentioned low voltage protection device based on wind turbine PWM and each unit can be referred to the corresponding description in the foregoing method embodiments. For the sake of convenience and brevity, it will not be repeated here.

[0107] The aforementioned low-voltage protection device 300 based on wind turbine PWM can be implemented as a computer program, which can be used in, for example... Figure 8 It runs on the computer device shown.

[0108] Please see Figure 8 , Figure 8 This is a schematic block diagram of a computer device provided in an embodiment of this application. The computer device 500 can be a terminal or a server. The terminal can be an electronic device with communication functions, such as a smartphone, tablet, laptop, desktop computer, personal digital assistant, or wearable device. The server can be a standalone server or a server cluster composed of multiple servers.

[0109] See Figure 8 The computer device 500 includes a processor 502, a memory, and a network interface 505 connected via a system bus 501. The memory may include a non-volatile storage medium 503 and internal memory 504.

[0110] The non-volatile storage medium 503 may store an operating system 5031 and a computer program 5032. The computer program 5032 includes program instructions that, when executed, cause the processor 502 to perform a low-voltage protection method based on a wind turbine PWM.

[0111] The processor 502 provides computing and control capabilities to support the operation of the entire computer device 500.

[0112] The internal memory 504 provides an environment for the operation of the computer program 5032 in the non-volatile storage medium 503. When the computer program 5032 is executed by the processor 502, the processor 502 can execute a low-voltage protection method based on the fan PWM.

[0113] This network interface 505 is used for network communication with other devices. Those skilled in the art will understand that... Figure 8 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device 500 to which the present application is applied. The specific computer device 500 may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0114] The processor 502 is used to run a computer program 5032 stored in the memory to implement the steps of the above-mentioned low voltage protection method based on wind turbine PWM.

[0115] It should be understood that in the embodiments of this application, the processor 502 may be a central processing unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0116] It will be understood by those skilled in the art that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program includes program instructions and can be stored in a storage medium, which is a computer-readable storage medium. The program instructions are executed by at least one processor in the computer system to implement the process steps of the embodiments of the above methods.

[0117] Therefore, the present invention also provides a storage medium. This storage medium can be a computer-readable storage medium. The storage medium stores a computer program, wherein the computer program includes program instructions. When executed by a processor, the program instructions cause the processor to perform the steps of the aforementioned low-voltage protection method based on wind turbine PWM.

[0118] The storage medium can be any computer-readable storage medium capable of storing program code, such as a USB flash drive, portable hard drive, read-only memory (ROM), magnetic disk, or optical disk.

[0119] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0120] In the several embodiments provided by this invention, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For example, the division of each unit is merely a logical functional division, and there may be other division methods in actual implementation. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0121] The steps in the method of this invention can be adjusted, merged, or reduced in order according to actual needs. The units in the device of this invention can be merged, divided, or reduced according to actual needs. Furthermore, the functional units in the various embodiments of this invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0122] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, a terminal, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention.

[0123] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A low-voltage protection method based on fan PWM, characterized in that, The method includes: The duty cycle value of the fan PWM is collected at preset time intervals, and the average value of all duty cycle values ​​in each collection cycle is calculated according to the preset collection period. The duty cycle reference value for each acquisition cycle is calculated based on the average value of the current acquisition cycle and the duty cycle reference value of the previous acquisition cycle, according to a preset comparison algorithm. The real-time duty cycle value of the current wind turbine PWM is collected, and based on the preset low voltage judgment algorithm, it is determined whether the current state is low voltage according to the real-time duty cycle value and the duty cycle reference value corresponding to the current collection period. If the current voltage is low, it will enter the low voltage protection mode.

2. The method according to claim 1, characterized in that, The step of calculating the duty cycle reference value for each acquisition cycle based on the average value of the current acquisition cycle and the duty cycle reference value of the previous acquisition cycle using a preset comparison algorithm includes: Calculate the first absolute difference between the mean value of the current acquisition period and the duty cycle reference value of the previous acquisition period; Compare the first absolute difference with the duty cycle reference value of the previous acquisition cycle at a preset first ratio; If the first absolute difference is less than or equal to the duty cycle reference value of the previous acquisition cycle of the preset first ratio, then the average value of the current acquisition cycle is used as the duty cycle reference value of the next acquisition cycle. If the first absolute difference is greater than the duty cycle reference value of the previous acquisition cycle of the preset first ratio, then the duty cycle reference value of the previous acquisition cycle will be used as the duty cycle reference value of the next cycle.

3. The method according to claim 1, characterized in that, The step of acquiring the real-time duty cycle value of the current wind turbine PWM and determining whether the current state is in a low voltage state based on the real-time duty cycle value and the duty cycle reference value corresponding to the current acquisition cycle according to the preset low voltage judgment algorithm includes: Calculate the second absolute difference between the real-time duty cycle value and the duty cycle reference value corresponding to the current acquisition cycle; Compare the second absolute difference with the duty cycle reference value corresponding to the current acquisition cycle of the preset second ratio; If the second absolute difference is greater than or equal to the duty cycle reference value corresponding to the current acquisition cycle of the preset second ratio, then it is determined that the current state is low voltage.

4. The method according to claim 1, characterized in that, The step of acquiring the real-time duty cycle value of the current wind turbine PWM and determining whether the current state is in a low voltage state based on the real-time duty cycle value and the duty cycle reference value corresponding to the current acquisition cycle according to the preset low voltage judgment algorithm further includes: Collect the real-time duty cycle value of the current fan PWM and the current fan speed value corresponding to the real-time duty cycle value; Based on the preset low voltage judgment algorithm, the algorithm comprehensively judges whether the current state is low voltage by considering the real-time duty cycle value, the duty cycle reference value corresponding to the current acquisition cycle, the current fan speed value, and the preset target fan speed value.

5. The method according to claim 1, characterized in that, The step of entering the low-voltage protection mode if the current voltage state is low includes: If the current voltage is low, the low voltage duty cycle value of the current fan PWM is collected and recorded, and the low voltage protection mode is entered to control the compressor to stop running.

6. The method according to claim 5, characterized in that, The steps following the initial statement regarding acquiring and recording the low-voltage duty cycle value of the current fan PWM if the current voltage condition is low, entering low-voltage protection mode, and controlling the compressor to stop running include: Real-time acquisition of the current duty cycle value of the fan PWM when it is in low voltage protection mode; Based on a preset recovery algorithm, it is determined whether the current voltage has returned to normal state according to the duty cycle reference value under the corresponding period of the current duty cycle value and the low voltage duty cycle value; If the system returns to normal, the compressor will operate normally.

7. The method according to claim 6, characterized in that, The step of determining whether the current voltage has returned to normal based on the preset recovery algorithm according to the current duty cycle value and the duty cycle reference value of the corresponding period of the low voltage duty cycle value includes: Calculate the third absolute difference between the current duty cycle value and the duty cycle reference value under the corresponding period of the low-voltage duty cycle value; Compare the magnitude of the third absolute difference with the duty cycle reference value corresponding to the low-voltage duty cycle value under the preset third ratio; If the third absolute difference is greater than or equal to the duty cycle reference value under the corresponding period of the low voltage duty cycle value of the preset third ratio, and remains stable for a preset period of time, then it is determined that the current voltage has returned to normal.

8. A low-voltage protection device based on fan PWM, characterized in that, Includes a unit for performing the method as described in any one of claims 1-7.

9. A computer device, characterized in that, The computer device includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method as described in any one of claims 1-7.

10. A storage medium, characterized in that, The storage medium stores a computer program, which includes program instructions that, when executed by a processor, can implement the method as described in any one of claims 1-7.

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