Frequency conversion soft start control method for fan of water cooling system of dry-type transformer

Abstract

The invention discloses a frequency conversion soft start control method for a fan of a water cooling system of a dry-type transformer. The method comprises the steps of S1, system initialization and parameter presetting, S2, multi-dimensional operation data real-time collection, S3, composite thermal load calculation based on temperature difference and flow, S4, intelligent decision making of fan starting and stopping and the rotating speed, and S5, frequency conversion soft starting and soft stopping execution. By introducing variable-frequency soft start and intelligent control strategies, current and mechanical impact during fan start are thoroughly eliminated, and the reliability and the service life of equipment are remarkably improved. The temperature of the transformer winding is monitored in real time and linked with the parameters of the water cooling system, so that the rotating speed of the fan is accurately and smoothly adjusted, the transformer is ensured to run in the optimal temperature interval all the time, and the dual purposes of efficiently saving energy and reducing running noise are achieved. The method is high in modularization degree, can be easily transformed and upgraded on an existing system, and has good economical efficiency and popularization value.

Description

Technical Field

[0001] This application relates to the field of transformer technology, specifically to a variable frequency soft start control method for a fan in a dry-type transformer water-cooling system. Background Technology

[0002] Dry-type transformers are widely used in modern power systems, and the heat generated during their operation needs to be dissipated promptly to ensure safety and extend their lifespan. Common water-cooling systems typically use forced-air cooling fans for final heat dissipation. Traditional fans often employ direct starting at power frequency or simple star-delta starting methods, generating inrush currents of 5-7 times the rated current at startup. This not only impacts the power grid and affects the stable operation of other equipment but also generates significant mechanical stress, shortening the lifespan of the fan motor and transmission components. Furthermore, traditional control methods cannot precisely adjust based on the actual temperature rise of the transformer, resulting in fans running at full speed under light loads or low temperatures, leading to energy waste and noise pollution. Therefore, there is an urgent need for a fan control method that can achieve smooth startup, energy saving, noise reduction, and enhanced system intelligence. Summary of the Invention

[0003] Therefore, this application provides a variable frequency soft start control method for the fan of a dry-type transformer water cooling system to solve the problems of existing technologies that cannot accurately adjust the fan according to the actual temperature rise of the transformer, and that the fan still runs at full speed under light load or low temperature conditions, resulting in energy waste and noise pollution.

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

[0005] A variable frequency soft-start control method for a fan in a dry-type transformer water-cooled system, characterized by comprising the following steps;

[0006] Step S1: System Initialization and Parameter Presetting: The core control module is powered on and initialized, and key operating parameters are preset. These key operating parameters include the soft start trigger threshold T-start for transformer winding temperature, the soft stop trigger threshold T-stop, the target safe temperature range [T-low, T-high], the rated frequency f-rated of the fan motor, the maximum soft start acceleration time t-acc-max, the maximum soft stop deceleration time t-dec-max, and the minimum fan operating frequency f-min; wherein, T-start > T-stop, and T-start is within the target safe temperature range [T-low, T-high].

[0007] Step S2: Real-time acquisition of multi-dimensional operation data: The temperature monitoring module continuously collects the real-time winding temperature T-winding of multiple points of the dry transformer and calculates its average or maximum value as the representative temperature T-current; at the same time, the water cooling parameter monitoring module collects the inlet pipe temperature T-water-in, outlet pipe temperature T-water-out, and water flow rate F-water of the water cooling system in real time and transmits these data to the core control module.

[0008] Step S3: Calculation of composite heat load based on temperature difference and flow rate: The core control module calculates the real-time heat dissipation Q of the water cooling system based on the collected water cooling parameters. The calculation formula is Q=c×ρ×F-water×(T-water-out-T-water-in), where c is the specific heat capacity of water and ρ is the density of water. Subsequently, the core control module combines the representative temperature T-current with the calculated real-time heat dissipation Q and calculates the demand frequency f-demand corresponding to the theoretical required speed of the fan system through a preset heat dissipation model.

[0009] Step S4: Intelligent decision-making for fan start / stop and speed: The core control module compares the temperature T-current with a preset threshold: When T-current continuously exceeds the soft start trigger threshold T-start for a preset delay time Δt1, the core control module sends a start command and a target frequency command to the variable frequency drive module. The initial value of the target frequency command is the smaller of the demand frequency f-demand and the rated frequency f-rated; when T-current drops below the soft stop trigger threshold T-stop and continues for a preset delay time Δt2, the core control module sends a soft stop command to the variable frequency drive module.

[0010] Step S5: Variable Frequency Soft Start and Soft Stop Execution: Upon receiving the start command, the variable frequency drive module controls the fan motor to accelerate smoothly to the target frequency from 0Hz with an acceleration time t-acc dynamically calculated by the core control module. The dynamic acceleration time t-acc is adjusted linearly or non-linearly within the preset maximum soft start acceleration time t-acc-max range according to the target frequency, ensuring that the starting current is always less than 1.5 times the rated current of the motor. Upon receiving the soft stop command, the variable frequency drive module controls the fan motor to decelerate smoothly to 0Hz from the current operating frequency with a deceleration time t-dec dynamically calculated by the core control module. The dynamic deceleration time t-dec is adjusted within the preset maximum soft stop deceleration time t-dec-max range according to the current operating frequency.

[0011] Preferably, in step S1, the preset minimum operating frequency f-min of the fan is set to no less than 20Hz to ensure that the fan motor can maintain stable torque output and effective ventilation and heat dissipation under any operating conditions.

[0012] Preferably, in step S3, the heat dissipation model is a neural network model or fuzzy control model trained based on historical operating data. Its input variables include at least the temperature T-current, the real-time heat dissipation Q, and the ambient temperature T-ambient, and the output variable is the demand frequency f-demand.

[0013] Preferably, in step S4, the delay times Δt1 and Δt2 are configurable, and Δt1 < Δt2, to prevent frequent fan start-stop due to slight temperature fluctuations near the threshold, thereby improving system stability.

[0014] Preferably, in step S5, the specific calculation method for the dynamically calculated acceleration time t-acc is: t-acc = (f-target ÷ f-rated) × k × t-acc-max, where f-target is the target frequency at startup, and k is an adjustment coefficient between 0.8 and 1.2, used for fine-tuning according to the motor characteristics; similarly, the calculation method for the dynamically calculated deceleration time t-dec is: t-dec = (f-current ÷ f-rated) × t-dec-max, where f-current is the current operating frequency of the fan when the soft stop command is issued.

[0015] Preferably, in step S5, during the soft start acceleration process, the frequency converter drive module monitors the output current of the motor in real time. If the current exceeds the set safety limit I-limit, the frequency rise process is automatically paused and the constant current acceleration mode is switched to. After the current drops below the safety limit I-limit, the acceleration process is continued. The safety limit I-limit is set to 1.3 times the rated current of the motor.

[0016] Preferably, the system further includes step S6: adaptive frequency adjustment during operation: During normal fan operation, the core control module continuously executes steps S2 and S3 and updates the demand frequency f-demand in real time; when the absolute value of the difference between the updated f-demand and the current fan operating frequency f-current exceeds the preset frequency adjustment dead zone Δf, the core control module instructs the frequency converter drive module to adjust the current fan operating frequency f-current to the new demand frequency f-demand with a smooth transition time, wherein the transition time is proportional to the frequency change, thereby achieving stepless smooth adjustment of the fan speed.

[0017] This invention offers the following advantages: By introducing variable frequency soft start and intelligent control strategies, it completely eliminates the current and mechanical shock during fan startup, significantly improving equipment reliability and lifespan. Through real-time monitoring of transformer winding temperature and linkage with water cooling system parameters, it achieves precise and smooth adjustment of fan speed, ensuring the transformer always operates within its optimal temperature range, thus achieving the dual goals of high efficiency, energy saving, and reduced operating noise. This method is highly modular, easily adaptable to existing systems, and possesses significant economic and promotional value.

[0018] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0019] To more intuitively illustrate the prior art and this application, exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).

[0020] Figure 1 This is a step diagram of a variable frequency soft start control method for a fan in a dry-type transformer water-cooled system according to this application. Detailed Implementation

[0021] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. It should be understood that these embodiments are merely for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Technical engineers in the field can make some non-essential improvements and adjustments to the present invention based on the above-described content. 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.

[0022] like Figure 1As shown, this application discloses a variable frequency soft start control method for a fan in a dry-type transformer water-cooling system. Step S1: System initialization and parameter preset: The core control module is powered on and initialized, and key operating parameters are preset. The key operating parameters include the soft start trigger threshold T-start of the transformer winding temperature, the soft stop trigger threshold T-stop, the target safe temperature range [T-low, T-high], the rated frequency f-rated of the fan motor, the maximum soft start acceleration time t-acc-max, the maximum soft stop deceleration time t-dec-max, and the minimum operating frequency f-min of the fan; wherein, T-start > T-stop, and T-start is within the target safe temperature range [T-low, T-high].

[0023] Step S2: Real-time acquisition of multi-dimensional operation data: The temperature monitoring module continuously collects the real-time winding temperature T-winding of multiple key points of the dry-type transformer and calculates its average or maximum value as the representative temperature T-current; at the same time, the water cooling parameter monitoring module collects the inlet pipe temperature T-water-in, outlet pipe temperature T-water-out, and water flow rate F-water of the water cooling system in real time and transmits these data to the core control module.

[0024] Step S3: Calculation of composite heat load based on temperature difference and flow rate: The core control module calculates the real-time heat dissipation Q of the water cooling system based on the collected water cooling parameters. The calculation formula is Q=c×ρ×F-water×(T-water-out-T-water-in), where c is the specific heat capacity of water and ρ is the density of water. Subsequently, the core control module combines the representative temperature T-current with the calculated real-time heat dissipation Q and calculates the demand frequency f-demand corresponding to the theoretical required speed of the fan system through a preset heat dissipation model.

[0025] Step S4: Intelligent decision-making for fan start / stop and speed: The core control module compares the temperature T-current with a preset threshold: When T-current continuously exceeds the soft start trigger threshold T-start for a preset delay time Δt1, the core control module sends a start command and a target frequency command to the variable frequency drive module. The initial value of the target frequency command is the smaller of the demand frequency f-demand and the rated frequency f-rated; when T-current drops below the soft stop trigger threshold T-stop and continues for a preset delay time Δt2, the core control module sends a soft stop command to the variable frequency drive module.

[0026] Step S5: Variable Frequency Soft Start and Soft Stop Execution: Upon receiving the start command, the variable frequency drive module controls the fan motor to accelerate smoothly to the target frequency from 0Hz with an acceleration time t-acc dynamically calculated by the core control module. The dynamic acceleration time t-acc is adjusted linearly or non-linearly within the preset maximum soft start acceleration time t-acc-max range according to the target frequency, ensuring that the starting current is always less than 1.5 times the rated current of the motor. Upon receiving the soft stop command, the variable frequency drive module controls the fan motor to decelerate smoothly to 0Hz from the current operating frequency with a deceleration time t-dec dynamically calculated by the core control module. The dynamic deceleration time t-dec is adjusted within the preset maximum soft stop deceleration time t-dec-max range according to the current operating frequency.

[0027] Step S6: Adaptive Frequency Adjustment During Operation: During normal fan operation, the core control module continuously executes steps S2 and S3 and updates the demand frequency f-demand in real time. When the absolute value of the difference between the updated f-demand and the fan's current operating frequency f-current exceeds the preset frequency adjustment dead zone Δf, the core control module instructs the frequency converter drive module to adjust the fan's current operating frequency f-current to the new demand frequency f-demand with a smooth transition time. The transition time is proportional to the frequency change, thereby achieving stepless smooth adjustment of the fan speed.

[0028] In implementing this invention, firstly, key temperature and frequency thresholds are preset. Then, the system enters a continuous monitoring cycle. The temperature monitoring module collects the transformer winding temperature, and the water cooling parameter monitoring module simultaneously collects water temperature and flow rate data. The core control module does not simply control the switching based on a single temperature threshold, but rather comprehensively considers the winding temperature and water cooling capacity, dynamically calculating the precise required fan frequency using a built-in heat dissipation model. This forms the basis of intelligent decision-making. When the temperature triggers the start-up condition, the system does not start at full speed directly, but the frequency converter drive module executes a smooth frequency rise curve (soft start), strictly limiting the starting current to less than 1.5 times the rated current, completely eliminating electrical and mechanical shocks. During normal operation, the system continuously performs the above monitoring and calculations. Once the calculated required frequency changes, it instructs the frequency converter to steplessly adjust the fan speed, achieving "on-demand cooling," maximizing energy saving and noise reduction while ensuring cooling effect. When the temperature drops to the stop threshold, the system executes a symmetrical soft stop process, further ensuring equipment lifespan.

[0029] In step S1, the preset minimum operating frequency f-min of the fan is set to no less than 20Hz to ensure that the fan motor can maintain stable torque output and effective ventilation and heat dissipation under any operating condition. This ensures that the fan motor can obtain a sufficient voltage-frequency ratio (V / F ratio) under any speed regulation condition, thereby outputting stable torque and preventing stalling or vibration due to insufficient torque at low frequencies. On the other hand, it ensures that even at the lowest speed, the fan can provide a basic but certain amount of ventilation, avoid the formation of local hot spots, and provide the most basic protective cooling for the transformer.

[0030] In step S3, the heat dissipation model is a neural network model or fuzzy control model trained based on historical operating data. Its input variables include at least the temperature T-current, the real-time heat dissipation Q, and the ambient temperature T-ambient. The output variable is the demand frequency f-demand. The heat dissipation model can handle multiple nonlinearly related input variables (such as temperature, flow rate, and ambient temperature). Through learning and inference, it more accurately maps the current real heat load state of the system, thereby calculating the optimal demand frequency. This improves the system's control accuracy and adaptability.

[0031] In step S4, the delay times Δt1 and Δt2 are configurable, and Δt1 < Δt2, to prevent frequent fan start-stop cycles caused by slight temperature fluctuations near the threshold, thereby improving system stability. Temperature rise is usually caused by load changes and requires a rapid response to prevent overheating; while temperature drop is a slow process. Setting a longer stop delay can effectively avoid unnecessary fan start-stop cycles caused by brief temperature drops (such as instantaneous load reduction). This "fast start, slow stop" logic greatly enhances the system's anti-interference capability and operational stability.

[0032] In step S5, the specific calculation method for the dynamically calculated acceleration time t-acc is: t-acc = (f-target ÷ f-rated) × k × t-acc-max, where f-target is the target frequency at startup, and k is an adjustment coefficient between 0.8 and 1.2, used for fine-tuning according to the motor characteristics; similarly, the calculation method for the dynamically calculated deceleration time t-dec is: t-dec = (f-current ÷ f-rated) × t-dec-max, where f-current is the current operating frequency of the fan when the soft stop command is issued.

[0033] This scheme sets the speed adjustment time to be proportional to the target frequency, rather than a fixed value. This makes the time required to accelerate from 0Hz to 25Hz only about half the time required to accelerate to full speed of 50Hz. This achieves the matching of the acceleration process with the target task, ensuring smoothness and avoiding unnecessary delays, thus optimizing the control response speed. The adjustment coefficient k provides the flexibility to fine-tune according to the specific parameters of the motor.

[0034] In step S5, during the soft-start acceleration process, the frequency converter drive module monitors the motor's output current in real time. If the current exceeds the set safety limit I-limit, the frequency increase process is automatically paused, and the system switches to constant current acceleration mode. Once the current drops below the safety limit I-limit, the acceleration process continues. The safety limit I-limit is set to 1.3 times the motor's rated current. During acceleration, if the motor current abnormally rises and exceeds the safety limit I-limit due to sudden changes in fan load or other reasons, the frequency converter will pause frequency increase and maintain the current frequency operation until the current drops. This effectively prevents the frequency converter from tripping or the motor from being damaged due to overcurrent, ensuring that the soft-start process can be completed safely and reliably under various load conditions.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A variable frequency soft-start control method for a fan in a dry-type transformer water-cooled system, characterized in that, Includes the following steps; Step S1: System initialization and parameter preset: The core control module is powered on and initialized, and key operating parameters are preset. The key operating parameters include the soft start trigger threshold T-start of the transformer winding temperature, the soft stop trigger threshold T-stop, the target safe temperature range [T-low, T-high], the rated frequency f-rated of the fan motor, the maximum acceleration time t-acc-max of the soft start, the maximum deceleration time t-dec-max of the soft stop, and the minimum operating frequency f-min of the fan. Step S2: Real-time acquisition of multi-dimensional operation data: The temperature monitoring module continuously collects the real-time winding temperature T-winding of multiple points of the dry transformer and calculates its average or maximum value as the representative temperature T-current; at the same time, the water cooling parameter monitoring module collects the inlet pipe temperature T-water-in, outlet pipe temperature T-water-out, and water flow rate F-water of the water cooling system in real time and transmits these data to the core control module. Step S3: Calculation of composite heat load based on temperature difference and flow rate: The core control module calculates the real-time heat dissipation Q of the water cooling system based on the collected water cooling parameters. The calculation formula is Q=c×ρ×F-water×(T-water-out-T-water-in), where c is the specific heat capacity of water and ρ is the density of water. Subsequently, the core control module combines the representative temperature T-current with the calculated real-time heat dissipation Q and calculates the demand frequency f-demand corresponding to the theoretical required speed of the fan system through a preset heat dissipation model. Step S4: Intelligent decision-making for fan start / stop and speed: The core control module compares the temperature T-current with a preset threshold: When T-current continuously exceeds the soft start trigger threshold T-start for a preset delay time Δt1, the core control module sends a start command and a target frequency command to the variable frequency drive module. The initial value of the target frequency command is the smaller of the demand frequency f-demand and the rated frequency f-rated; when T-current drops below the soft stop trigger threshold T-stop and continues for a preset delay time Δt2, the core control module sends a soft stop command to the variable frequency drive module. Step S5: Variable frequency soft start and soft stop execution: After receiving the start command, the variable frequency drive module controls the fan motor to start from 0Hz and smoothly accelerate to the target frequency with an acceleration time t-acc dynamically calculated by the core control module. The dynamic acceleration time t-acc is adjusted linearly or non-linearly within the preset maximum soft start acceleration time t-acc-max range according to the target frequency to ensure that the starting current is always less than 1.5 times the rated current of the motor. Upon receiving a soft stop command, the variable frequency drive module controls the fan motor to smoothly decelerate to 0Hz from the current operating frequency with a deceleration time t-dec dynamically calculated by the core control module. The dynamic deceleration time t-dec is adjusted within the preset maximum soft stop deceleration time t-dec-max range according to the magnitude of the current operating frequency.

2. The variable frequency soft-start control method for a fan in a dry-type transformer water-cooled system according to claim 1, characterized in that, In step S1, T-start > T-stop, and T-start is within the target safe temperature range [T-low, T-high], and the preset minimum operating frequency of the fan, f-min, is not lower than 20Hz.

3. The variable frequency soft-start control method for a fan in a dry-type transformer water-cooled system according to claim 1, characterized in that, In step S3, the heat dissipation model is a neural network model or fuzzy control model trained based on historical operating data. Its input variables include at least the temperature T-current, the real-time heat dissipation Q, and the ambient temperature T-ambient. The output variable is the demand frequency f-demand.

4. The variable frequency soft-start control method for a fan in a dry-type transformer water-cooled system according to claim 1, characterized in that, In step S4, the delay times Δt1 and Δt2 are configurable, and Δt1 < Δt2.

5. The variable frequency soft-start control method for a fan in a dry-type transformer water-cooled system according to claim 1, characterized in that, In step S5, the specific calculation method for the dynamically calculated acceleration time t-acc is: t-acc = (f-target ÷ f-rated) × k × t-acc-max, where f-target is the target frequency at startup, and k is an adjustment coefficient between 0.8 and 1.2, used for fine-tuning according to the motor characteristics; similarly, the calculation method for the dynamically calculated deceleration time t-dec is: t-dec = (f-current ÷ f-rated) × t-dec-max, where f-current is the current operating frequency of the fan when the soft stop command is issued.

6. The variable frequency soft-start control method for a fan in a dry-type transformer water-cooled system according to claim 1, characterized in that, In step S5, during the soft start acceleration process, the frequency converter drive module monitors the output current of the motor in real time. If the current exceeds the set safety limit I-limit, the frequency rise process is automatically paused and the constant current acceleration mode is switched to. After the current drops below the safety limit I-limit, the acceleration process continues. The safety limit I-limit is set to 1.3 times the rated current of the motor.

7. The variable frequency soft-start control method for a fan in a dry-type transformer water-cooled system according to claim 1, characterized in that, It also includes step S6: adaptive frequency adjustment during operation: During normal fan operation, the core control module continuously executes steps S2 and S3 and updates the demand frequency f-demand in real time; when the absolute value of the difference between the updated f-demand and the fan's current operating frequency f-current exceeds the preset frequency adjustment dead zone Δf, the core control module instructs the frequency converter drive module to adjust the fan's current operating frequency f-current to the new demand frequency f-demand with a smooth transition time. The transition time is proportional to the frequency change, thereby realizing stepless smooth adjustment of the fan speed.

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