Automatic control method and system of wet cooling tower variable frequency fan and storage medium

Abstract

The application relates to the technical field of wet cooling towers, and discloses an automatic control method and system for a variable-frequency fan of a wet cooling tower and a storage medium. A current rotating speed value of the fan is obtained through a rotating speed sensor, a target rotating speed value in a fan rotating speed control instruction is extracted, and a rotating speed difference value of the two is calculated. A first difference value range corresponding to rotating speed adjustment and a second difference value range corresponding to air leakage adjustment are preset. When the rotating speed difference value is in the first difference value range, a rotating speed adjustment algorithm is used to calculate a fan adjustment increment to adjust the rotating speed of the fan. When the rotating speed difference value is in the second difference value range, the opening blades of an air leakage opening are controlled to move, and the opening amplitude is adjusted according to the adjustment ratio of the rotating speed difference value and the maximum value of the second difference value range. The application can quickly adapt to real-time fluctuations of circulating water heat dissipation conditions, effectively reduces the operating energy consumption of the fan under the premise of ensuring the heat exchange effect of the wet cooling tower, and improves the adjustment response efficiency and energy-saving performance of the variable-frequency fan of the cooling tower.

Description

Technical Field

[0001] This application relates to the technical field of wet cooling towers, and in particular to an automatic control method, system and storage medium for a variable frequency fan of a wet cooling tower. Background Technology

[0002] In industrial settings such as industrial production, power supply, and chemical smelting, where water resource recycling is essential, wet cooling towers are crucial auxiliary equipment for ensuring the stable operation of production systems. Their core function is to dissipate the large amount of heat absorbed by industrial circulating water during use to the external environment through gas-liquid contact heat exchange, thereby reducing the circulating water temperature to within the range required by the production process. This achieves water resource recycling and reduces water consumption.

[0003] The heat exchange efficiency of a wet cooling tower directly depends on the degree of gas-liquid contact, and the operating state of the fan, as the power source for airflow circulation within the cooling tower, plays a decisive role in the heat exchange effect. With the development of energy-saving technologies, variable frequency fans are gradually replacing traditional fixed-speed fans in wet cooling towers. These fans can adjust their speed to change the airflow, thus adapting to cooling demands under different operating conditions. When the heat dissipation demand of the circulating water is large, the fan speed is increased to increase the airflow and improve heat exchange efficiency; when the heat dissipation demand is small, the fan speed is decreased to reduce the airflow. This achieves preliminary optimization of fan operating energy consumption while ensuring cooling effect, combining the advantages of energy saving and adjustment flexibility.

[0004] Currently, in industrial production processes, the heat demand of circulating water fluctuates in real time with factors such as production load, ambient temperature, and inlet water temperature. Although the fans of existing wet cooling towers can be speed-adjusted, the speed adjustment is a gradual process with a certain lag. This lag increases the energy consumption of the fans when production factors fluctuate, and the energy consumption of the fans needs to be further reduced. Summary of the Invention

[0005] In order to reduce the energy consumption caused by frequent and large-scale adjustments of the fan when production factors fluctuate, this application provides an automatic control method, system and storage medium for a variable frequency fan of a wet cooling tower.

[0006] In a first aspect, this application provides an automatic control method for a variable frequency fan in a wet cooling tower, employing the following technical solution: An automatic control method for a variable frequency fan in a wet cooling tower includes the following steps: The current speed of the fan is obtained based on a preset speed sensor. The fan outlet is equipped with an air outlet channel, and an air vent is provided in the air outlet channel. The air vent is equipped with an opening blade for adjusting the opening area. The opening area of ​​the air vent is positively correlated with the opening amplitude of the opening blade. Obtain the fan speed control command, extract the required fan speed from the fan speed control command as the target speed value, and calculate the difference between the target speed value and the current speed value as the speed difference value. If the speed difference is within the preset first difference range, the fan adjustment increment is calculated based on the speed difference according to the preset speed adjustment algorithm, and the fan speed is adjusted according to the fan adjustment increment to achieve the target speed value; the first difference range is the set of values ​​that are greater than the preset opening adjustment value; If the speed difference is within the preset second difference range, the rotating blades are controlled to open the vent. The ratio between the absolute value of the speed difference and the absolute value of the maximum value within the second difference range is calculated as the adjustment ratio. The opening amplitude of the opening blades is adjusted according to the adjustment ratio. The larger the adjustment ratio, the larger the opening amplitude; the smaller the adjustment ratio, the smaller the opening amplitude. The values ​​within the second difference range are less than the values ​​within the first difference range, and all are negative.

[0007] By adopting the above technical solution, when the speed difference is within the first difference range, the air volume is quickly increased by speed adjustment to ensure heat exchange efficiency; when the speed difference is within the second difference range, the air volume is quickly adjusted by adjusting the opening degree of the vent blades, reducing the lag of the gradual change in fan speed. While ensuring the cooling effect of circulating water, adapting to the real-time fluctuations of production load, ambient temperature and other operating conditions, it effectively reduces the energy consumption of the fan operation and improves the energy efficiency and control response efficiency of the cooling tower operation.

[0008] Optionally, the method further includes the following steps: When the speed difference is within the first difference range, the control state is marked as the first state; when the speed difference is within the second difference range, the control state is marked as the second state. The frequency at which the control state switches between the first and second states is called the control frequency. If the control frequency is greater than the preset reference frequency, the ratio of the control frequency to the reference frequency is calculated as the control adjustment value, and the opening adjustment value is adjusted according to the control adjustment value. If the opening adjustment value is greater than 0, then the larger the control adjustment value, the smaller the opening adjustment value; the smaller the control adjustment value, the larger the opening adjustment value. Otherwise, the larger the control adjustment value, the larger the opening adjustment value; the smaller the control adjustment value, the smaller the opening adjustment value.

[0009] By adopting the above technical solution, when the opening adjustment value is positive, the applicable range of speed adjustment is expanded to favor fan speed adjustment; when the opening adjustment value is negative, the applicable range of vent blade adjustment is expanded to favor blade opening adjustment.

[0010] Optionally, the method further includes the following steps: The duration during which the current control state remains in the second state is defined as the first duration. If the first duration is longer than the preset first reference duration, the first difference range is temporarily set to the preset full value range, and the second difference range is temporarily set to the preset minimum value range, so that the speed difference is always within the first difference range. The duration for which the current control state remains in the first state is defined as the second duration. If the second duration is longer than the preset second reference duration, then the first difference range and the second difference range are restored.

[0011] By adopting the above technical solution, the duration of the second state is accumulated in real time. When the duration exceeds the preset reference duration, the speed difference range is temporarily adjusted, and the system is forced to switch to the full-capacity fan speed regulation mode, reducing the equipment operation risks and losses caused by long-term reliance on blade regulation. At the same time, by monitoring the duration of the first state, the original range is restored after the speed regulation is stable, thus restoring the rapid response advantage of blade regulation.

[0012] Optionally, the method further includes the following steps: If the control frequency is less than the preset setting frequency, the ratio of the control frequency to the setting frequency is calculated as a temporary adjustment value; where the setting frequency is less than the reference frequency. The first reference duration is adjusted based on the temporary adjustment value. The larger the temporary adjustment value, the longer the first reference duration; the smaller the temporary adjustment value, the shorter the first reference duration.

[0013] By adopting the above technical solution, the larger the temporary adjustment value, the longer the first reference time is, giving full play to the advantages of rapid response and low energy consumption of blade adjustment; the smaller the temporary adjustment value, the shorter the first reference time is, and the forced switch to wind turbine speed adjustment is made in time.

[0014] Optionally, the method further includes the following steps: The fan is provided with at least one air inlet channel, the air inlet channel has an air inlet, and the air inlet is provided with wind-blocking blades for adjusting the wind-blocking area. The outdoor wind speed value is obtained by a wind speed sensor installed outside the fan. If the outdoor wind speed value is greater than the preset outdoor reference value, the ratio between the outdoor wind speed value and the outdoor reference value is calculated as the outdoor adjustment value. The wind-blocking area of ​​the wind deflector blades is adjusted according to the outdoor adjustment value. The larger the outdoor adjustment value, the larger the wind-blocking area, and the smaller the outdoor adjustment value, the smaller the wind-blocking area.

[0015] By adopting the above technical solution, when the outdoor wind speed exceeds the preset reference value, the larger the wind-blocking area is, and vice versa. This can effectively limit the air flow velocity inside the tower under high wind speed conditions, reduce insufficient heat exchange between circulating water and air caused by excessive flow velocity, and make full use of the auxiliary suction / air intake of natural wind to reduce the operating load of the fan and reduce energy consumption.

[0016] Optionally, the method further includes the following steps: If the outdoor wind speed value is greater than the preset outdoor reference value, then calculate the dispersion value of the outdoor wind speed value. If the dispersion value is greater than the preset reference dispersion value, the outdoor reference value is adjusted according to the dispersion value. The larger the dispersion value, the smaller the outdoor reference value; the smaller the dispersion value, the larger the outdoor reference value.

[0017] By adopting the above technical solution, the greater the dispersion, the smaller the outdoor reference value, and the easier it is to trigger the windshield blade adjustment; the smaller the dispersion, the larger the outdoor reference value, reducing unnecessary adjustment actions.

[0018] Optionally, the opening blade is rotatably connected to the vent, and the rotation angle of the opening blade is positively correlated with the opening area of ​​the vent; the opening blade adopts any one of the following two structures: Structure 1: The opening blades are provided in multiple ways, and the multiple opening blades are arranged in sequence along the flow cross section of the air vent. The two ends of each opening blade are rotatably connected to the side wall mounting base of the air vent through a rotating shaft. Each opening blade can rotate independently or synchronously around the corresponding rotating shaft to adjust the flow opening area of ​​the air vent. Structure 2: The opening blades are fan-shaped plate structures, with multiple fan-shaped opening blades distributed in an umbrella shape at the air vent. The roots of each fan-shaped opening blade are hinged to the central fixed shaft of the air vent. By rotating synchronously around the central fixed shaft, the opening area of ​​the air vent can be continuously adjusted.

[0019] By adopting the above technical solution and using a dual-structure design with rotating connection, the multi-piece arrangement hinged or umbrella-shaped fan-shaped central hinged structure can be flexibly selected according to the spatial layout and control requirements of the cooling tower vent. This can achieve both graded and precise adjustment of the vent opening area and continuous and smooth control, while ensuring stable operation of the rotating connection method.

[0020] Optionally, the opening blade is slidably connected to the vent, and the sliding distance of the opening blade is positively correlated with the opening area of ​​the vent. The opening blade is a fan-shaped plate structure or a non-fan-shaped plate structure, and the number of opening blades is one or more. The side wall of the vent is provided with a sliding guide rail extending along the flow cross section. The opening blade slides along the sliding guide rail through a slider to adjust the flow opening area of ​​the vent. When multiple opening blades are provided, the multiple opening blades are arranged symmetrically or staggered along the flow cross section of the vent, and the opening amplitude is adjusted by synchronous or asynchronous sliding.

[0021] By adopting the above technical solution and using a sliding connection structure that combines a slider and a guide rail, the shape and number of blades can be flexibly adapted to different specifications of air vents. The overall structure is simple, easy to install and maintain, and the opening area can be stably adjusted by the reciprocating sliding of the blades.

[0022] Secondly, this application provides an automatic control system for a wet cooling tower variable frequency fan, which adopts the following technical solution: An automatic control system for a variable frequency fan of a wet cooling tower includes a processor, wherein the processor executes the steps of the automatic control method for the variable frequency fan of the wet cooling tower as described in any of the preceding claims.

[0023] Thirdly, this application provides a storage medium, which adopts the following technical solution: A storage medium storing a program, which, when executed by a processor, implements the steps of the automatic control method for a wet cooling tower variable frequency fan as described in any one of the preceding claims.

[0024] In summary, this application includes at least one of the following beneficial technical effects: This application effectively solves the problem of variable frequency fan speed regulation lag by combining fan speed regulation and vent blade regulation with a dual-mode collaborative control strategy. At the same time, it combines adaptive adjustment of the control frequency to adjust the adjustment threshold, monitoring the duration of the adjustment state to reduce long-term unbalanced operation of the equipment, adaptive optimization of the duration parameters according to the stability of the operating conditions, and introduces adaptive windbreak adjustment of outdoor wind speed and its dispersion. Combined with various reliable open blades of rotating and sliding types, it achieves precise air volume control. It can fully adapt to the real-time dynamic fluctuations of production load, ambient temperature, and outdoor wind conditions. While ensuring the heat exchange and cooling effect of the wet cooling tower, it reduces the energy consumption of the fan operation, reduces equipment damage caused by frequent switching of adjustment states, and improves the system control response efficiency, operating condition adaptability, and long-term operational stability. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the steps of an automatic control method for a variable frequency fan in a wet cooling tower.

[0026] Figure 2 This is a flowchart illustrating the steps of dual-mode adaptive control to prevent frequent switching.

[0027] Figure 3 This is a flowchart illustrating the steps for monitoring the duration of the adjustment mode and forcibly switching back to normal. Detailed Implementation

[0028] The embodiments of this application are described in detail below, and examples of the embodiments are shown in the accompanying drawings.

[0029] In the description of this specification, the references to "certain embodiments," "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples" refer to specific features, structures, materials, or characteristics described in connection with the described embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0030] This application discloses an automatic control method for a variable frequency fan in a wet cooling tower, referring to... Figure 1 It includes the following steps: The current speed of the fan is obtained based on a preset Hall effect speed sensor. The speed sensor is installed at the output shaft of the fan motor to collect the speed signal in real time and convert it into an electrical signal. The air outlet of the fan is located at the air outlet at the top of the cooling tower and extends vertically. A ring-shaped air vent is opened in the middle section of the air outlet, or an air vent is opened in the non-circumferential direction. The air vent is equipped with an opening blade for adjusting the flow opening area. The opening blade is made of high-strength aluminum alloy, which has corrosion resistance and lightweight characteristics. The opening area of ​​the air vent is linearly positively correlated with the opening amplitude of the opening blade, that is, the larger the movement amplitude of the opening blade, the larger the flow cross-sectional area of ​​the air vent.

[0031] The system receives the fan speed control command through the PLC of the industrial control system. This command is generated by the system based on real-time operating parameters such as circulating water inlet temperature, outlet temperature, production load and ambient temperature. The preset target operating speed of the fan is extracted from the fan speed control command as the target speed value. The difference between the target speed value and the current speed value is calculated by the difference calculation module and recorded as the speed difference value. Speed ​​difference value = target speed value - current speed value. The system presets a first difference range and a second difference range. The first difference range is the set of values ​​greater than the preset opening adjustment value. The preset opening adjustment value can be preset according to the cooling tower model and operating conditions, for example, -50rpm, specifically (-50rpm, +200rpm], covering some negative values ​​and all positive values. If the speed difference falls within the first difference range, the system calls the preset PID speed adjustment algorithm to calculate the fan adjustment increment based on the absolute value and positive / negative attribute of the speed difference. Positive values ​​correspond to speed increase increments, and negative values ​​correspond to speed decrease increments. The system outputs an adjustment signal to the fan motor through the frequency converter to drive the fan speed to gradually adjust to the target speed value, ensuring the stability and accuracy of speed adjustment.

[0032] The second difference range is a set of negative values ​​with large absolute values, such as [-300rpm, -50rpm]. All values ​​within this range are less than the minimum value of the first difference range and are all negative. If the speed difference is within this second difference range, the system sends an action command to the electric actuator of the vent to control the opening blades to open the vent. At the same time, the proportional calculation module calculates the ratio of the speed difference to the maximum value within the second difference range, which is -50rpm. This is recorded as the adjustment ratio. For example, when the speed difference is -200rpm, the adjustment ratio = |-200rpm| / |-50rpm| = 4. The opening amplitude of the opening blades is linearly adjusted according to this adjustment ratio. The larger the adjustment ratio, the greater the rotation or sliding amplitude of the opening blades and the larger the vent opening area. Conversely, the smaller the opening amplitude, the smaller the opening amplitude, thus achieving rapid and precise control of airflow.

[0033] By adopting the above technical solution, when the speed difference is within the first difference range, which contains a large positive value, it corresponds to scenarios requiring a significant speed increase, such as a sudden increase in the heat dissipation of circulating water. The PID speed regulation algorithm achieves a smooth increase in fan speed, rapidly increasing airflow to ensure gas-liquid contact heat exchange efficiency. When the speed difference is within the second difference range, which contains a large negative value, it corresponds to scenarios requiring a significant speed decrease, such as a sudden drop in production load. The flow area is directly adjusted by regulating the opening degree of the vent blades, rapidly changing the airflow inside the tower. This reduces the 3-5 second adjustment lag caused by the gradual change in speed of traditional variable frequency fans, shortening the adjustment response time. While adapting to real-time fluctuations in operating conditions such as production load, ambient temperature, and circulating water temperature, it reduces the long-term operation of the fan in the inefficient speed regulation range, effectively reducing the fan's operating energy consumption. This ensures that the circulating water cooling effect always meets the production process requirements and improves the energy efficiency and control response efficiency of the cooling tower.

[0034] Reference Figure 2 In this embodiment, the method further includes the following steps: When the speed difference falls into the first difference range (speed adjustment range), the control system marks the current control state as the first state through the built-in state marking module and stores the marking information in the real-time database; when the speed difference falls into the second difference range (air leakage adjustment range), it is simultaneously marked as the second state, and a timestamp is triggered when the state changes. A preset configurable statistical period T, such as 30 seconds to 5 minutes, is used to adapt to the operating condition fluctuation characteristics of different industrial scenarios. The frequency statistics module accumulates the number of times N between the first state and the second state within the statistical period. The control frequency is calculated according to the formula: control frequency f=N / T, with the unit being times / minute, and is fed back to the control core in real time.

[0035] A preset reference frequency f0, for example, 3~8 times / minute, is used for experimental calibration based on the mechanical fatigue life of the fan actuator and the optimal range of system energy consumption. If the calculated control frequency f is greater than the reference frequency f0, it indicates that the drastic fluctuation of the operating condition leads to frequent switching between the two adjustment modes. At this time, the proportional calculation module calculates the control adjustment value k = f / f0, k > 1, and the larger the value of k, the more drastic the switching. Based on this control adjustment value, the opening adjustment value is adaptively adjusted, which is the critical boundary threshold between the first and second difference ranges, in rpm.

[0036] The adjustment logic is as follows: If the current opening adjustment value S > 0, for example, the initial S = -40 rpm: the larger the control adjustment value k, the larger the reduction of the opening adjustment value S, i.e., S1 = S × (1 - k × α); the smaller the control adjustment value k, the larger the increase of the opening adjustment value S, i.e., S1 = S × (1 - k × α). For example: when k = 1.5, S1 = -40 × (1 - 1.5 × 0.2) = -32 rpm; when k = 2.0, S1 = -40 × (1 - 2.0 × 0.2) = -24 rpm. After adjustment, the first difference range (S1, +∞) expands significantly, and the second difference range (-∞, S1) contracts. The operating conditions that originally belonged to the air leakage adjustment are included in the speed adjustment. Among them, +∞ is the maximum value of the numerical type defined in the first difference range, or a logical judgment method that is greater than S1; -∞ is the minimum value of the numerical type defined in the second difference range, or a logical judgment method that is less than or equal to S1.

[0037] If the current opening adjustment value S≤0, for example, the initial S=-60rpm: the larger the control adjustment value k, the larger the reduction of the opening adjustment value S, that is, the more negative the value, i.e., S1=S×(1+k×α); the smaller the control adjustment value k, the smaller the increase of the opening adjustment value S, i.e., S1=S×(1+k×α). For example: when k=1.6, S1=-60×(1+1.6×0.2)=-79.2rpm; when k=2.2, S1=-60×(1+2.2×0.2)=-86.4rpm. After adjustment, the first difference range (S1, +∞) expands synchronously, and the second difference range (-∞, S1) contracts. The low difference conditions that originally required air leakage adjustment are switched to speed adjustment.

[0038] By adopting the above technical solution, and with the help of status marking, timestamp recording, and frequency calculation, accurate monitoring and quantitative evaluation of the switching status of the two adjustment modes can be achieved. This allows for the rapid identification of system oscillation problems caused by frequent fluctuations in operating conditions. When the switching frequency exceeds the reference threshold, the opening adjustment value is dynamically optimized by controlling the linkage calculation of the adjustment value and the quantification coefficient, and the applicable range of speed adjustment and air leakage adjustment is flexibly adjusted. This effectively reduces the frequent start-stop and mechanical shock of actuators (open blade shaft, fan motor), thereby reducing equipment wear rate, and also reduces the additional energy consumption caused by sudden changes in airflow during mode switching. At the same time, it keeps the fluctuation range of air volume in the tower within a reasonable range, improves the stability and smoothness of airflow organization, ensures the consistency of circulating water heat exchange effect, and further enhances the system's adaptability to complex and variable operating conditions. Under the premise of ensuring the cooling needs of the production process, it also takes into account the reliability of equipment operation and long-term energy-saving efficiency.

[0039] Reference Figure 3 In this embodiment, to address the equipment operating condition imbalance problem that may be caused by long-term reliance on blade adjustment, a continuous monitoring and dynamic range switching mechanism is designed. The method also includes the following steps: The timing module built into the control system accumulates the duration of the current control state in the second state (air vent blade adjustment mode) in real time, which is recorded as the first duration. The timing is automatically started when the system enters the second state and is immediately reset to zero when the state switches to the first state. A first reference duration T is preset, for example, 15~30 minutes. Based on the mechanical fatigue life of the open blades and the adaptability test calibration of the fan operating conditions, it can be flexibly configured according to the cooling tower model and industrial scenario requirements. If the first duration counted by the timing module exceeds T1, it indicates that the system has been relying on blade adjustment to maintain the operating conditions for a long time. At this time, the control system sends a parameter update command to temporarily switch the first difference range to the preset full value range, that is, to cover all possible speed difference ranges, such as (-∞, +∞). At the same time, the second difference range is temporarily set to the preset minimum value range, that is, to only include a very small negative value range, such as (-∞, -500rpm]. This range is almost impossible to trigger in actual operating conditions. By adjusting this parameter, all speed differences are forced to fall into the first difference range, and the system automatically switches to the full fan speed adjustment mode, with speed adjustment replacing blade adjustment to maintain the air volume demand.

[0040] Simultaneously, through another independent timing module, the duration of the current control state continuously in the first state (fan speed adjustment mode) is accumulated in real time and recorded as the second duration. The timing is triggered when the system enters the first state and is reset to zero when the state switches to the second state.

[0041] A second reference duration T2 is preset, for example, 5 to 10 minutes. Based on the stability verification cycle calibration of the fan speed adjustment, if the second duration exceeds T2, it indicates that the fan speed adjustment has been stably adapted to the current operating conditions. The control system sends a parameter restoration command to restore the first difference range and the second difference range to the initial preset values. The system then re-enables the dual-mode adaptation logic of speed adjustment + blade adjustment.

[0042] By adopting the above technical solutions, on the one hand, the potential operational hazards such as mechanical fatigue, seal aging, and shaft jamming caused by the open blades being in a fixed opening position for a long time are reduced. At the same time, problems such as airflow turbulence and inefficient motor operation caused by the fan maintaining a low speed for a long time are also reduced, thus extending the overall service life of the blades and the fan motor. On the other hand, by dynamically switching between forced speed regulation and stabilization and restoration, the fan speed is brought back to a reasonable operating range while ensuring the stability of the fan operation. This increases the participation of speed regulation and reduces the limitations of a single regulation mode. It retains the rapid response advantage of blade regulation and quick adaptation to fluctuations in operating conditions. At the same time, by periodically regulating the speed to calibrate the fan operating status, the stability of airflow organization in the tower is improved, the uniformity of circulating water heat exchange is improved, and the additional energy consumption caused by long-term inefficient operation is further reduced, achieving a dynamic balance between blade regulation and speed regulation.

[0043] In this embodiment, the dynamic adaptability of the first reference duration is optimized for stable operating conditions to achieve precise matching between the adjustment strategy and the degree of stability. The specific method also includes the following steps: The preset setting frequency f1, for example, 1~2 times / minute, is less than the reference frequency f0. Based on the threshold test calibration of stable industrial operating conditions, this logic is triggered only when the switching between the two adjustment states is at a low frequency and the operating conditions are stable.

[0044] The number of switching times N within the statistical period T is calculated as f = N / T. If the real-time calculated control frequency f is less than the set frequency f1, it indicates that the system is currently in a stable operating phase with no frequent fluctuations. At this time, the temporary adjustment value m = f / f1 is calculated through the proportional calculation module. Since f < f1, m ∈ (0, 1]. The closer the value of m is to 1, the more stable the operating condition is, but there are still slight fluctuations. The closer the value of m is to 0, the more stable the operating condition is.

[0045] A preset first reference duration base value T1_base, for example, 20 minutes, is set as the basic duration for which blade adjustment can continue. A calibration coefficient γ is configured, for example, 0.8~1.5, which is calibrated according to equipment characteristics and energy-saving requirements. The first reference duration is dynamically adjusted based on the temporary adjustment value m. The adjustment formula is: adjusted first reference duration T1_adjust=T1_base×m×γ. Upper and lower limit thresholds for T1_adjust are set, for example, the lower limit is 5 minutes and the upper limit is 35 minutes, to reduce adjustment imbalance caused by excessively short or long durations.

[0046] Specific adaptation example: If T1_base=20 minutes and γ=1.2, when m=0.9, the control frequency is close to the set frequency, the operating condition is relatively stable but with slight fluctuations, T1_adjust=20×0.9×1.2=21.6 minutes, extending the first reference duration to allow the blade adjustment to continue to play its role; when m=0.3, the control frequency is much lower than the set frequency, the operating condition is extremely stable, T1_adjust=20×0.3×1.2=7.2 minutes, shortening the first reference duration to trigger the forced speed adjustment earlier.

[0047] Meanwhile, the temporary adjustment value m is dynamically updated in real time following the control frequency and refreshed once every statistical cycle. The first reference duration after adjustment is also updated in real time to ensure dynamic adaptation to the stability of the operating conditions and reduce the adaptation lag caused by fixed duration.

[0048] By adopting the above technical solutions, when the operating conditions are relatively stable (m is large), the allowable duration of blade adjustment is extended to maximize the advantages of fast blade adjustment response and low energy consumption, and reduce the energy consumption increase caused by unnecessary forced speed adjustment; when the operating conditions are extremely stable (m is small), the first reference time is shortened and the speed adjustment is forcibly switched in time, thereby reducing the problems of low-speed and inefficient operation of the fan, decreased airflow organization stability, and accelerated aging of blade seals caused by long-term reliance on blade adjustment from the source.

[0049] In this embodiment, to address the interference of outdoor natural wind fluctuations on the airflow inside the tower, an adaptive windbreak adjustment mechanism on the air inlet side is designed. The method further includes the following steps: At least one air inlet channel is evenly arranged along the circumference or bottom of the cooling tower at the air inlet of the fan. The channel cross-section is rectangular or circular and is designed to fit the overall structure of the cooling tower. At the air inlet of the air inlet channel, there are baffle blades for adjusting the wind-blocking area. The blades are made of corrosion-resistant fiberglass or aluminum alloy and are arc-shaped or flat. They are rotatably connected to the air inlet frame through a rotating shaft. An electric actuator drives the blades to rotate. The rotation angle of the baffle blades is linearly related to the wind-blocking area. The wind-blocking area is the smallest when the rotation angle is 0° and the wind-blocking area is the largest when the rotation angle is 90°.

[0050] An ultrasonic wind speed sensor is fixedly installed on the top or side of the cooling tower in an unobstructed area to collect outdoor natural wind speed data in real time and convert it into an electrical signal to be transmitted to the control system. The system filters the wind speed data to obtain the effective outdoor wind speed value; the filtering process removes instantaneous pulse interference.

[0051] The preset outdoor reference value v0, for example, 3 m / s, is based on the rated wind speed of the cooling tower and the experimental calibration of the heat exchange efficiency threshold. It can be adjusted according to the regional wind conditions. If the processed outdoor wind speed value v is greater than v0, it indicates that the natural wind has had a significant impact on the airflow inside the tower. At this time, the outdoor adjustment value n is calculated by the division operation module: n = v / v0, n > 1, and the larger the value of n, the more the outdoor wind speed exceeds the reference value.

[0052] The current windbreak area is fed back in real time by a blade angle sensor, and the target windbreak area is calculated in combination with the outdoor adjustment value. The larger the outdoor adjustment value n is, the larger the target windbreak area, the larger the blade flip angle, and the smaller the air inlet flow area. The smaller the outdoor adjustment value n is, the smaller the target windbreak area, the smaller the blade flip angle, and the larger the air inlet flow area. For example, when v0 = 3m / s, when v = 4.5m / s, n = 1.5, and the blades are controlled to flip to the corresponding angle, so that the windbreak area increases by 50% compared to the initial state. When v = 3.6m / s, n = 1.2, and the windbreak area increases by 20%, ensuring the adjustment accuracy and wind speed adaptability. At the same time, upper and lower limits for windbreak area adjustment are set, such as 10%~80% of the flow area, to reduce airflow turbulence caused by complete closure or excessive opening.

[0053] By adopting the above technical solutions, on the one hand, under high wind speed conditions (v>v0), by increasing the windbreak area and reducing the flow cross section of the air inlet, the air velocity inside the tower is precisely limited, reducing insufficient contact time between circulating water and air and inadequate heat exchange caused by excessive flow velocity. At the same time, it suppresses airflow turbulence and backflow, preventing abnormal operating conditions such as "surge" and "overload" of the fan. On the other hand, by adjusting the windbreak area and wind speed in a coordinated manner, the auxiliary suction of natural wind (exhaust cooling tower) or the air intake assistance (blowing cooling tower) can be fully utilized to reduce the fan drive load, reduce the long-term low-load and inefficient operation of the fan under high wind interference, and significantly reduce additional energy consumption.

[0054] In this embodiment, the windbreak adjustment trigger logic is optimized for unstable wind conditions such as gusts and turbulence to improve the accuracy of wind condition adaptation. The method also includes the following steps: When the outdoor wind speed value v obtained by the wind speed sensor is greater than the preset outdoor reference value v0, the wind speed dispersion analysis process is initiated: a statistical window is set, for example, 5 seconds, to adapt to the time characteristics of wind speed fluctuations. Within this window, N sets of continuous wind speed data are collected, N≥30, to ensure statistical validity. The standard deviation σ of the wind speed data within the window is calculated using the standard deviation algorithm. Then, the percentage of wind speed fluctuation is calculated using the formula: dispersion value δ=(σ / v_avg)×100%, where v_avg is the average wind speed within the window. The larger the δ value, the more severe the wind speed fluctuation and the more unstable the wind conditions.

[0055] A preset reference dispersion value δ0, for example, 15%~25%, is calibrated based on experiments on the stability of airflow inside the tower under different wind conditions. It can be flexibly configured according to the regional wind characteristics. If the calculated dispersion value δ is greater than δ0, it indicates that there are drastic fluctuations in the current wind conditions, such as gusts or turbulence. The windbreak adjustment trigger threshold needs to be optimized to adapt. At this point, the discrete adjustment coefficient k_δ = δ / δ0 is calculated through the proportional calculation module, where k_δ > 1, and the larger δ is, the larger k_δ is. An adjustment coefficient β is configured, for example, 0.7~0.9, to reduce excessive threshold adjustment. The outdoor reference value is dynamically lowered according to the formula: adjusted outdoor reference value v0' = v0 × (1 - (k_δ - 1) × β). If δ is less than or equal to δ0, it indicates that the wind condition is relatively stable. The outdoor reference value is moderately raised according to the formula: v0' = v0 × (1 + (δ0 - δ) / δ0 × β). Upper and lower limits of v0' are set, for example, the lower limit is 1.5 m / s and the upper limit is 4 m / s, to reduce the threshold from exceeding the reasonable adaptation range.

[0056] Specific example: Initially, v0 = 3 m / s, δ0 = 20%, β = 0.8; when δ = 30% (k_δ = 1.5), v0' = 3 × (1 - (1.5 - 1) × 0.8) = 3 × 0.6 = 1.8 m / s, the trigger threshold is significantly reduced; when δ = 10% (stable wind conditions), v0' = 3 × (1 + (20% - 10%) / 20% × 0.8) = 3 × 1.4 = 4.2 m / s, and finally 4 m / s is taken because the upper limit is reached.

[0057] Meanwhile, the dispersion value is adjusted in real time and synchronized with the outdoor reference value, and refreshed once per statistical window to ensure that the trigger threshold is always dynamically adapted to the current wind condition fluctuation characteristics. By adopting the above technical solutions, when the wind conditions fluctuate drastically (δ>δ0), lowering the outdoor reference value makes it easier to trigger the wind deflector adjustment, allowing the blades to respond to gust impacts in advance, reducing the amplitude of airflow oscillations inside the tower, reducing heat exchange efficiency fluctuations caused by sudden increases and decreases in wind speed, and reducing mechanical wear on the fan impeller and blade shaft caused by airflow impacts; when the wind conditions are stable (δ≤δ0), raising the outdoor reference value reduces unnecessary adjustment actions of the wind deflector blades, reduces the increase in energy consumption and mechanical wear caused by frequent start-stop, maximizes the use of the auxiliary draft of stable natural wind, and further reduces the operating load of the fan.

[0058] In this embodiment, one type of open blade structure involves the open blade being rotatably connected to the vent, and the rotation angle of the open blade is positively correlated with the opening area of ​​the vent; the open blade adopts any one of the following two structures: Structure 1: The open blades are made of corrosion-resistant high-strength aluminum alloy or fiberglass, suitable for the high temperature and humidity conditions of cooling towers. Multiple open blades are provided, with the number adapted to the cross-sectional size of the vent, typically 4 to 8 blades. These open blades are evenly arranged circumferentially along the annular cross-section of the vent. Adjacent blade edges are designed with overlapping sealing edges, with a gap ≤2mm to reduce airflow leakage. Both ends of each open blade are rotatably connected to an integrated mounting base on the inner wall of the vent via precision bearing shafts. One end of the shaft extends to the outside of the mounting base and is equipped with a linkage gear or synchronous pulley, driven by an electric actuator. The control system can be configured to allow each open blade to rotate independently around its corresponding shaft (suitable for asymmetrical airflow adjustment) or rotate synchronously (suitable for uniform airflow adjustment). The rotation angle range is 0° to 90°. At 0°, the blades are closed with the smallest opening area, and at 90°, the blades are fully extended with the largest opening area. An angle sensor provides real-time feedback on the blade position, enabling precise, graded adjustment of the vent's airflow opening area.

[0059] Structure 2: The opening blades are fan-shaped plate structures, with the central angle evenly distributed according to the number of blades. For example, 6 blades correspond to a 60° central angle. The blade edges adopt an arc transition design to reduce airflow resistance. The material is the same as that of Structure 1. Multiple fan-shaped opening blades are distributed radially in an umbrella shape in the central area of ​​the vent. The roots of each fan-shaped opening blade are hinged together to the fixed shaft at the center of the vent via a high-strength flange. The fixed shaft is connected to the output end of the electric actuator via a coupling. A thrust bearing is installed between the blade roots and the fixed shaft to withstand airflow pressure and reduce rotational wear. The electric actuator drives the central fixed shaft to rotate, causing all the fan-shaped opening blades to rotate synchronously around the fixed shaft. The rotation angle is 0°~90°, corresponding to a continuous change in the opening area from 0 to 100%. With the help of an absolute encoder, closed-loop control of the blade angle is realized to ensure the smoothness and consistency of the opening area adjustment.

[0060] By adopting the above technical solutions, the dual-structure design with rotating connections can be flexibly selected according to the spatial layout of the cooling tower vents (such as circular / square vents, whether there is an internal support structure) and the required airflow control precision: the multi-piece arranged hinged structure is suitable for large-size annular vents, with excellent sealing performance, and the independent rotation mode can specifically adjust the local airflow, adapting to scenarios with uneven airflow inside the tower; the umbrella-shaped fan-shaped central hinged structure is compact, occupies little space, and has a fast synchronous rotation response speed, adapting to small and medium-sized vents and the need for rapid airflow adjustment; both structures adopt bearing-type rotating connections, with low operating resistance and low mechanical wear, which can achieve graded precise adjustment and continuous smooth control of the vent opening area, while ensuring the stability and sealing of the adjustment process, effectively improving the control precision of vent adjustment and airflow utilization efficiency, and adapting to the cooling tower operation requirements in different industrial scenarios.

[0061] In other embodiments, another type of open blade structure involves the open blade slidingly connected to the vent, with the sliding distance of the open blade being positively correlated with the opening area of ​​the vent. The open blade is a fan-shaped plate structure (suitable for annular vents) or a non-fan-shaped plate structure such as a rectangle or polygon (suitable for square or rectangular vents). There are one or more open blades; a single blade is suitable for small-sized vents, and multiple blades are suitable for large-sized vents. The inner wall of the vent is provided with a high-precision sliding guide rail extending radially or axially along the flow cross-section. The guide rail is made of wear-resistant stainless steel, with a lubricating coating on the surface, a friction coefficient ≤0.1, and a T-shaped or dovetail-shaped cross-section to prevent the slider from falling off. The two sides of the open blade are fixedly connected to the slider by bolts. Rolling bearings are used to reduce sliding resistance. The slider and sliding guide rail form a clearance fit with a clearance of ≤0.5mm. The slider is driven to slide back and forth along the guide rail by an electric push rod or lead screw motor, which in turn drives the opening blades to move synchronously. The sliding stroke range is 0 to the maximum coverage length of the blade. When the stroke is 0, the blade is contracted and the opening area is the smallest. When the stroke is at its maximum, the blade is fully extended and the opening area is the largest. When multiple opening blades are set, the multiple blades are arranged symmetrically or staggered along the flow cross section of the air outlet. Symmetrical arrangement is suitable for uniform air volume adjustment, and staggered arrangement improves sealing performance. The blades slide synchronously (overall air volume adjustment) or asynchronously (local air volume fine adjustment) through the branch controller. During the adjustment process, the blades always keep in contact with the guide rail to ensure the regularity of the airflow channel.

[0062] By adopting the above technical solution, the sliding connection structure of the slider and guide rail has strong versatility: the blade shape can be customized as needed, and the number can be flexibly increased or decreased, adapting to different specifications of air vents such as round, square, and rectangular; the overall structure consists of blades, sliders, guide rails, and drive mechanisms, with fewer parts and lower assembly difficulty, and the detachable design of the guide rails and sliders facilitates later maintenance; the blades adjust the opening area through linear sliding, with no rotational impact during the adjustment process, resulting in high operational stability, and the sliding sealing surface is fitted with an elastic sealing strip, resulting in low airflow leakage rate; compared with the rotating structure, the sliding structure has a simpler manufacturing process, which can significantly reduce the processing, installation, and use costs of the air vent adjustment mechanism while ensuring stable adjustment of the opening area, making it suitable for cost-sensitive industrial scenarios with relatively simple operating conditions, further expanding the adaptability range of the cooling tower variable frequency fan control system.

[0063] This application also discloses an automatic control system for a wet cooling tower variable frequency fan, including a processor, wherein the processor executes the steps of the automatic control method for the wet cooling tower variable frequency fan as described in any of the above embodiments.

[0064] This application also discloses a storage medium storing a program, which, when executed by a processor, implements the steps of the automatic control method for the variable frequency fan of the wet cooling tower described in any of the above embodiments.

[0065] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An automatic control method for a variable frequency fan in a wet cooling tower, characterized in that, Includes the following steps: The current speed of the fan is obtained based on a preset speed sensor. The fan outlet is equipped with an air outlet channel, and an air vent is provided in the air outlet channel. The air vent is equipped with an opening blade for adjusting the opening area. The opening area of ​​the air vent is positively correlated with the opening amplitude of the opening blade. Obtain the fan speed control command, extract the required fan speed from the fan speed control command as the target speed value, and calculate the difference between the target speed value and the current speed value as the speed difference value. If the speed difference is within the preset first difference range, the fan adjustment increment is calculated based on the speed difference according to the preset speed adjustment algorithm, and the fan speed is adjusted according to the fan adjustment increment to achieve the target speed value; the first difference range is the set of values ​​that are greater than the preset opening adjustment value; If the speed difference is within the preset second difference range, the rotating blades are controlled to open the vent. The ratio between the absolute value of the speed difference and the absolute value of the maximum value within the second difference range is calculated as the adjustment ratio. The opening amplitude of the opening blades is adjusted according to the adjustment ratio. The larger the adjustment ratio, the larger the opening amplitude; the smaller the adjustment ratio, the smaller the opening amplitude. The values ​​within the second difference range are less than the values ​​within the first difference range, and all are negative.

2. The automatic control method for the variable frequency fan of a wet cooling tower according to claim 1, characterized in that, The method also includes the following steps: When the speed difference is within the first difference range, the control state is marked as the first state; when the speed difference is within the second difference range, the control state is marked as the second state. The frequency at which the control state switches between the first and second states is called the control frequency. If the control frequency is greater than the preset reference frequency, the ratio of the control frequency to the reference frequency is calculated as the control adjustment value, and the opening adjustment value is adjusted according to the control adjustment value. If the opening adjustment value is greater than 0, the larger the control adjustment value, the smaller the opening adjustment value; the smaller the control adjustment value, the larger the opening adjustment value. Otherwise, the larger the control adjustment value, the larger the opening adjustment value; the smaller the control adjustment value, the smaller the opening adjustment value.

3. The automatic control method for the variable frequency fan of a wet cooling tower according to claim 1, characterized in that, The method also includes the following steps: The duration during which the current control state remains in the second state is defined as the first duration. If the first duration is longer than the preset first reference duration, the first difference range is temporarily set to the preset full value range, and the second difference range is temporarily set to the preset minimum value range, so that the speed difference is always within the first difference range. The duration for which the current control state remains in the first state is defined as the second duration. If the second duration is longer than the preset second reference duration, then the first difference range and the second difference range are restored.

4. The automatic control method for the variable frequency fan of a wet cooling tower according to claim 3, characterized in that, The method also includes the following steps: If the control frequency is less than the preset setting frequency, the ratio of the control frequency to the setting frequency is calculated as a temporary adjustment value; where the setting frequency is less than the reference frequency. The first reference duration is adjusted based on the temporary adjustment value. The larger the temporary adjustment value, the longer the first reference duration; the smaller the temporary adjustment value, the shorter the first reference duration.

5. The automatic control method for the variable frequency fan of a wet cooling tower according to claim 1, characterized in that, The method also includes the following steps: The fan is provided with at least one air inlet channel, the air inlet channel has an air inlet, and the air inlet is provided with wind-blocking blades for adjusting the wind-blocking area. The outdoor wind speed value is obtained by a wind speed sensor installed outside the wind turbine. If the outdoor wind speed value is greater than the preset outdoor reference value, the outdoor adjustment value is calculated based on the ratio between the outdoor wind speed value and the outdoor reference value. Adjust the windshield blade area according to the outdoor adjustment value. The larger the outdoor adjustment value, the larger the windshield area, and the smaller the outdoor adjustment value, the smaller the windshield area.

6. The automatic control method for the variable frequency fan of a wet cooling tower according to claim 5, characterized in that, The method also includes the following steps: If the outdoor wind speed value is greater than the preset outdoor reference value, then calculate the dispersion value of the outdoor wind speed value. If the dispersion value is greater than the preset reference dispersion value, the outdoor reference value will be adjusted according to the dispersion value. The larger the dispersion value, the smaller the outdoor reference value. The smaller the dispersion value, the larger the outdoor reference value.

7. The automatic control method for the variable frequency fan of a wet cooling tower according to claim 1, characterized in that, The open blade is rotatably connected to the vent, and the rotation angle of the open blade is positively correlated with the opening area of ​​the vent; the open blade adopts any one of the following two structures: Structure 1: The opening blades are provided in multiple ways, and the multiple opening blades are arranged in sequence along the flow cross section of the air vent. The two ends of each opening blade are rotatably connected to the side wall mounting base of the air vent through a rotating shaft. Each opening blade can rotate independently or synchronously around the corresponding rotating shaft to adjust the flow opening area of ​​the air vent. Structure 2: The opening blades are fan-shaped plate structures, with multiple fan-shaped opening blades distributed in an umbrella shape at the air vent. The roots of each fan-shaped opening blade are hinged to the central fixed shaft of the air vent. By rotating synchronously around the central fixed shaft, the opening area of ​​the air vent can be continuously adjusted.

8. The automatic control method for the variable frequency fan of a wet cooling tower according to claim 1, characterized in that, The opening blade is slidably connected to the vent, and the sliding distance of the opening blade is positively correlated with the opening area of ​​the vent. The opening blade is a fan-shaped plate structure or a non-fan-shaped plate structure, and the number of opening blades is one or more. The side wall of the vent is provided with a sliding guide rail extending along the flow cross section. The opening blade slides along the sliding guide rail through a slider to adjust the flow opening area of ​​the vent. When multiple open blades are provided, the multiple open blades are arranged symmetrically or staggered along the flow cross section of the air vent, and the opening amplitude is adjusted by synchronous or asynchronous sliding.

9. An automatic control system for a variable frequency fan in a wet cooling tower, characterized in that, Includes a processor, wherein the processor performs the steps of the automatic control method for a wet cooling tower variable frequency fan as described in any one of claims 1-8.

10. A storage medium, characterized in that, The storage medium stores a program that, when executed by a processor, implements the steps of the automatic control method for the variable frequency fan of a wet cooling tower according to any one of claims 1-8.

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