A speed sensorless control device and method for reverse wind start of an EC fan

Abstract

The present application relates to the technical field of fan, and particularly relates to a control device and method for reverse wind starting of a speed sensorless EC fan, which comprises: an observer module for collecting fan data; a rotating speed detection module for comparing the rotating speed of the fan with a preset rotating speed threshold value, and sending a braking signal when the threshold value is exceeded; a wind direction judgment module for judging the initial rotating direction of the fan wheel, and sending a braking signal when it is determined that the current rotating direction of the fan is reverse rotation; a braking module fixed on an external shell, which brakes the rotating shaft of the fan when receiving the braking signals from the rotating speed detection module and the wind direction judgment module; and a control module for receiving the signals from the rotating speed detection module and the wind direction judgment module, and correcting the observer module by dynamically adjusting the driving frequency. The present application can realize reliable reverse rotation protection without increasing hardware cost, avoids the failure risk of physical sensors in dense building environment, and eliminates the risk of structural damage to the equipment caused by passive reverse rotation overspeed due to strong adverse wind.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fan, in particular to a control device and method for reverse wind starting of EC fan without speed sensor. BACKGROUND

[0002] In the environment of urban high-density building groups, the complex wind field structure poses a severe challenge to the operation of the fan. The wind gap effect formed between buildings can significantly accelerate the local wind speed, while the building corners and gap areas are prone to strong vortex and variable direction gusts. When the fan is hit by a strong instantaneous reverse airflow, passive reverse rotation may occur, and its speed can exceed the safety threshold of the mechanical structure or electrical system in a very short time, directly threatening the system reliability.

[0003] In this scenario, passive reverse rotation overspeed of the fan has become a core safety hazard. The traditional monitoring methods have significant limitations: the mechanical wind speed meter or photoelectric encoder is easily disturbed by physical shielding and mechanical vibration in the densely distributed rooftop space equipment, especially in adverse weather conditions such as rain, snow and dust, making it difficult to accurately detect the reverse state in real time. The physical encoder has a double risk: it may be damaged by mechanical impact when the speed is reversed, or the braking instruction may be delayed due to signal transmission delay, further increasing the failure probability.

[0004] To ensure the long-term stable operation of the new air system in urban high-density building groups and improve the maintenance efficiency, it is urgent to develop a fan safety protection system based on speed sensorless technology, which integrates real-time monitoring of reverse wind state and intelligent braking control function, to eliminate the structural damage risk caused by passive reverse rotation overspeed in strong reverse wind. SUMMARY

[0005] The purpose of the present application is to provide a control device and method for reverse wind starting of EC fan without speed sensor, to solve the problems existing in the prior art.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] A control device for reverse wind starting of EC fan without speed sensor, comprising:

[0008] An observer module for collecting fan data; wherein the fan data includes fan speed, angle and back electromotive force;

[0009] A speed detection module for comparing the fan speed with a preset speed threshold, and sending a braking signal when the preset speed threshold is exceeded;

[0010] A wind direction judgment module for determining the initial direction of the wind wheel, and sending a braking signal when it is determined that the current direction of the fan is reverse rotation;

[0011] A brake module is fixed on the outer shell for receiving brake signals from the rotating speed detection module and the wind direction judgment module, and brakes the fan rotating shaft when receiving brake signals from both modules.

[0012] A control module is used for receiving signals from the rotating speed detection module and the wind direction judgment module, and correcting the observer module by dynamically adjusting the driving frequency.

[0013] Optionally, the observer module adopts an adaptive sliding mode observer, constructs a sliding mode surface dynamic equation based on motor stator current and voltage signals, ensures system stability by designing a Lyapunov function with a stator current error as a sliding mode surface, and dynamically adjusts the observer switching gain online by using an adaptive algorithm; at the same time, a saturation function is introduced to replace the sign function to smooth the filter processing of the observer output, and the real-time high-precision estimation of the rotor speed and position information is performed in combination with the PWM driving frequency parameter transmitted by the control module, and the optimized estimation result is transmitted to the rotating speed detection module.

[0014] Optionally, the observer module includes:

[0015] A back electromotive force observation unit is used for collecting the back electromotive force according to a current error equation;

[0016] A sliding mode surface unit generates a sliding mode surface state through real-time integral operation of the current error, and the output is used for controlling the gain of the observer module and solving the back electromotive force;

[0017] A parameter adaptive unit dynamically adjusts the gain of the observer module by setting stability conditions and parameter update law based on the sliding mode surface state and using a Lyapunov function.

[0018] Optionally, the wind direction judgment module injects a high-frequency square wave pulse with a preset amplitude into the stator winding, collects three-phase current response signals and decouples them into dq-axis components through coordinate transformation, discriminates the initial rotating direction of the fan based on the phase characteristic difference of the d-axis current ripple amplitude, and sends a brake signal to the brake module when detecting a reverse rotation feature.

[0019] Optionally, the brake module includes an electromagnet, a spring set and a brake pad; the brake pad is located on both sides of the fan rotating shaft, the electromagnet is fixed on the side of the brake pad away from the fan rotating shaft, one end of the spring set is connected to the side of the brake pad away from the fan rotating shaft, and the other end is fixed on the outer shell.

[0020] When not braking, the spring set separates the brake pad and the rotating shaft;

[0021] When braking, the electromagnet is powered to generate an electromagnetic attraction force to overcome the elastic force of the spring set and press the brake pad against the rotating shaft.

[0022] The brake piece surface has heat dissipation grooves, and the brake piece is internally provided with a temperature alarm.

[0023] Optionally, the control module dynamically adjusts the PWM duty cycle and frequency output by the inverter according to the wind direction state, the phase deviation angle and the torque compensation instruction, and feeds back the real-time driving frequency to the observer module to correct the rotor position observation model; wherein the wind direction state includes: downwind state and upwind state.

[0024] In the upwind starting phase, the control module first applies a low-frequency small-amplitude voltage vector to lock the initial position of the rotor through the observer module; then dynamically corrects the q-axis current given value based on the phase deviation angle to ensure that the electromagnetic torque and the aerodynamic torque are in the same direction, and gradually increases the speed by using a gradual torque compensation strategy to suppress the influence of the reverse electromotive force on the system stability, until the upwind critical region is left.

[0025] A speed sensorless EC fan upwind starting control method for implementing the speed sensorless EC fan upwind starting control device described above, the method comprises:

[0026] The wind direction judgment module injects a pulse signal to judge the wind direction after power-on initialization;

[0027] The observer module observes whether the fan speed exceeds a threshold value;

[0028] When it is detected that the fan is reversed and the speed exceeds the threshold value, the brake module is started;

[0029] The observer module estimates the fan speed in real time;

[0030] When it is detected that the speed is lower than a safety threshold value, the fan is started in the forward direction.

[0031] The beneficial effects of the present application are:

[0032] The application provides a speed sensorless EC fan reverse wind starting control device, which comprises the following steps: collecting fan data by using an observer module; detecting fan rotating speed by using a rotating speed detection module, and sending a brake signal when the rotating speed exceeds a preset rotating speed threshold; determining the initial rotating direction of the fan wheel by using a wind direction judgment module, and sending a brake signal when the current rotating direction of the fan is determined to be reverse rotation; receiving brake signals from the rotating speed detection module and the wind direction judgment module by using a brake module, and braking the fan when brake signals from the two modules are received simultaneously; and receiving brake signals from the rotating speed detection module and the wind direction judgment module by using a control module, and correcting the observer module by using a PWM driving frequency parameter. The embodiment can realize reliable reverse rotation protection without increasing hardware cost, avoids the failure risk of physical sensors in dense building environments, and eliminates the risk of structural damage to equipment caused by passive reverse rotation overspeed under strong adverse wind. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0034] Figure 1 The application provides a speed sensorless EC fan reverse wind starting control device composition diagram;

[0035] Figure 2 The application provides a reverse wind starting brake module composition diagram;

[0036] Figure 3 The application provides a signal transmission connection diagram between the reverse wind starting device modules;

[0037] Figure 4 The application provides a reverse wind starting control method flow chart;

[0038] Figure 5 The application provides a reverse wind starting device observer module system structure diagram;

[0039] 1, observer module; 2, rotating speed detection module; 3, wind direction judgment module; 4, control module; 5, brake module; 5-1, electromagnet; 5-2, spring set; 5-3, brake pad; 5-4, heat dissipation groove; 6, fan blade; 7, fan rotating shaft; 8, motor; 9, controller. DETAILED DESCRIPTION

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0041] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] This embodiment proposes a control device for starting an EC fan without a speed sensor against the wind, including:

[0043] Observer module 1 is used to collect wind turbine data, including wind turbine speed, angle, and back electromotive force.

[0044] The speed detection module 2 is used to detect the fan speed and send a braking signal when the speed exceeds the preset speed threshold.

[0045] Wind direction determination module 3 is used to determine the initial rotation of the wind turbine. When it is determined that the wind turbine is currently rotating in the opposite direction, a braking signal is sent.

[0046] Braking module 5 is used to receive braking signals from speed detection module 2 and wind direction judgment module 3. When braking signals are received from both modules at the same time, the fan is braked.

[0047] The control module 4 is used to receive signals from the speed detection module 2 and the wind direction judgment module 3, and to correct the observer module by dynamically adjusting the drive frequency.

[0048] like Figure 3 As shown in this embodiment, a control device for starting a wind turbine without a speed sensor against the wind includes: an observer module 1, a wind direction judgment module 2, a speed detection module 3, a braking module 5, and a control module 4.

[0049] The observer module 1 is connected to the speed detection module 2 and the control module 4. The observer module 1 predicts the wind turbine speed through the adaptive sliding mode observer model and transmits the predicted speed, angle and back electromotive force to the speed detection module 2.

[0050] The speed detection module 2 is connected to the observer module 1, the control module 4 and the braking module 5. It compares the estimated speed of the fan with the set speed threshold. When the speed exceeds the threshold, it sends a braking trigger signal to the braking module 5. It processes the signal transmitted by the observer module 1 and transmits the final speed value, speed error estimate and speed change rate to the control module 4.

[0051] The wind direction judgment module 3 is connected to the control module 4 and the brake module 5, and the wind direction judgment module 3 determines the initial rotation direction of the wind wheel by injecting a high-frequency square wave pulse into the stator winding. When it is determined that the current rotation direction of the wind turbine is reverse rotation, a brake signal is sent to the brake module 5.

[0052] As shown in Figure 2 The brake module 5 is fixed on the outer shell and brakes when the wind turbine reaches the braking condition. The brake module 5 is fixed on the outer shell and receives signals from the rotation speed detection module 2 and the wind direction judgment module 3. When the wind turbine reverse rotation signal from the wind direction judgment module 3 and the rotation speed threshold signal from the rotation speed detection module 2 are received at the same time, the controller 9 of the brake module 5 is powered on to generate a magnetic force of the electromagnet 5-1, so as to quickly press the brake pad 5-3 against the wind turbine shaft 7 to brake, and the wind turbine shaft 7 is connected to the wind turbine blade 6, as shown in Figure 1 .

[0053] The control module 4 is connected to the wind direction judgment module 3, the rotation speed detection module 2 and the observer module 1, and dynamically adjusts the control signal according to the feedback result to improve the dynamic response of the motor 8. The control module 4 receives signals from the rotation speed detection module 2 and the wind direction judgment module 3, dynamically adjusts the PWM duty cycle and frequency of the inverter output, and feeds back the real-time driving frequency to the observer module 1 to correct the rotor position observation model.

[0054] The embodiment can realize reliable reverse protection without increasing hardware cost, and eliminate the risk of structural damage to the equipment caused by passive reverse overspeed.

[0055] Further, the observer module 1 adopts an adaptive sliding mode observer, constructs a sliding mode surface dynamic equation based on motor stator current and voltage signals, ensures system stability by designing a Lyapunov function with a stator current error as a sliding mode surface, and dynamically adjusts the observer switching gain online by using an adaptive algorithm; At the same time, a saturation function is introduced to replace the sign function to smooth the filter processing of the observer output, and the PWM driving frequency parameter transmitted by the control module is combined to realize real-time high-precision estimation of the rotor speed and position information, and the optimized estimation result is transmitted to the rotation speed detection module 2.

[0056] Further, the observer module 1 includes:

[0057] The back electromotive force observation unit is used to collect the back electromotive force according to the current error equation;

[0058] The sliding mode surface unit is used to generate a sliding mode surface state through real-time integral operation of the current error, and the output is used to control the gain of the observer module and the back electromotive force solution;

[0059] The parameter adaptive unit is used to automatically adjust the parameters of the observer module by setting stability conditions and parameter update law through Lyapunov function.

[0060] In particular, in the present embodiment, the observer module 1 comprises: a back electromotive force observation unit, a sliding mode surface unit, a parameter adaptation unit.

[0061] The back electromotive force observation unit constructs a current error equation: where is the actual current, observed current;

[0062] The sliding mode surface unit comprises:

[0063] The sliding mode surface design: , ;

[0064] The sliding mode control law: the saturation function is used instead of the sign function, is the boundary layer thickness;

[0065] The control input: where K is the adaptive adjustment coefficient;

[0066] The equivalent control term: ;

[0067] The parameter adaptation unit: the Lyapunov function is designed as , , is the adaptive rate coefficient;

[0068] The derivative is ;

[0069] The stability condition: by designing can ensure , is the convergence rate parameter and ;

[0070] The parameter update law: , is the correction factor and .

[0071] The sliding mode surface defines the control objective of the system; the dynamic equation describes the process of the system moving towards the control objective; the sliding mode control law generates the control input based on the dynamic equation to actively and robustly achieve the control objective; the control input is the signal that realizes the control action, including the part for driving and information extraction; the equivalent control term is the solution of the sliding mode surface dynamic equation under the ideal sliding mode condition, and the information of the back electromotive force can be obtained after filtering.

[0072] By adopting the above-mentioned observer module 1, the traditional mechanical sensor is replaced, and the influence of external environmental problems on the normal start of the fan is avoided. The system structure of the observer module 1 of the reverse wind starting device is as shown in Figure 5 .

[0073] Further, the rotating speed detection module 2 compares the rotating speed estimation value output by the observer module 1 with a preset reverse wind starting safety threshold value, detects whether there is an overspeed risk, and sends a torque compensation instruction to the control module 4 and a brake triggering signal to the brake module 5 when it is detected that the rotating speed of the fan exceeds the threshold value.

[0074] Further, the wind direction judgment module 3 injects a high-frequency square wave pulse with an amplitude less than 5% of the rated current into the stator winding, collects three-phase current response signals and decouples them into dq-axis components through coordinate transformation, and distinguishes the initial rotating direction of the fan based on the phase characteristic difference of the d-axis current ripple amplitude. When the reverse rotating feature is detected, the brake triggering signal is sent to the brake module 5. The wind direction judgment module 3 determines that the fan is reverse rotating when it is detected that the high-frequency response ripple amplitude of the d-axis current is significantly higher than the reference value in the positive rotating direction, and takes brake measures.

[0075] Further, the brake module 5 includes an electromagnet 5-1, a spring set 5-2 and a brake pad 5-3; wherein the brake pad 5-3 is located on both sides of the fan rotating shaft 7, the electromagnet 5-1 is fixed on the side of the brake pad 5-3 away from the fan rotating shaft 7, and one end of the spring set 5-2 is connected to the side of the brake pad 5-3 away from the fan rotating shaft 7 and the other end is fixed to the external shell;

[0076] When not braking, the spring set 5-2 separates the brake pad 5-3 and the rotating shaft 7;

[0077] When braking, the electromagnet 5-1 is energized to generate an electromagnetic attraction force to overcome the elastic force of the spring set 5-2 and press the brake pad 5-3 tightly against the rotating shaft 7;

[0078] The surface of the brake pad 5-3 has a heat dissipation groove 5-4, and the brake pad 5-3 also has a temperature alarm inside, which automatically cuts off the power supply when the temperature exceeds the preset temperature due to continuous braking.

[0079] After the electromagnet 5-1 is energized, an electromagnetic attraction force is generated , under the drive of the electromagnetic attraction force, the brake pads 5-3 on both sides overcome the elastic force of the spring set 5-2 and move synchronously towards the center of the rotating shaft 7, and the brake pad 5-3 is in close contact with the surface of the rotating shaft 7, generating a large sliding friction force and static friction force in the instant of contact and during continuous contact.

[0080] The electromagnetic attraction force generated by the electromagnet 5-1 during braking ensures that the brake pad 5-3 exerts a constant normal pressing force on the rotating shaft 7 , the compression force continuously generates braking torque between the brake pad 5-3 and the rotating shaft 7 . The braking torque acts on the fan rotating shaft 7 in the opposite direction of the rotating direction, rapidly consumes the kinetic energy of the rotating shaft 7, and slows it down until it is less than the preset safety threshold.

[0081] The braking torque generated between the brake pad 5-3 and the rotating shaft 7 during braking is determined by the friction force. Among them is the braking friction coefficient, is the effective friction radius, is the number of brake pads 5-3 participating in the friction action. It must be greater than the driving torque that the fan rotating shaft 7 can generate under the maximum adverse wind load, and a certain safety factor is left.

[0082] During braking, the electromagnet 5-1 needs to generate enough suction force to provide compression force and overcome the spring set 5-2 tension. The generated electromagnetic suction force , wherein is derived by the target braking torque , is the force of the spring set 5-2 when the brake pad 5-3 is tightly held, is the clamping force transmission efficiency coefficient.

[0083] Further, the control module 4 dynamically adjusts the PWM duty cycle and frequency output by the inverter according to the wind direction state, phase deviation angle and torque compensation instruction, and feeds back the real-time driving frequency to the observer module 1 to correct the rotor position observation model; wherein, the wind direction state includes: downwind state and adverse wind state; the rotor position observation model refers to the model of the adaptive sliding mode observer adopted by the observer module; the main correction is the stator inductance Ls of the back-EMF observation unit, the integral gain k of the sliding mode surface unit, and the adaptive coefficient of the parameter adaptive unit.

[0084] During the adverse wind starting stage, the control module 4 first applies a low-frequency small-amplitude voltage vector to lock the initial position of the rotor through the observer module 1; then dynamically corrects the q-axis current given value based on the phase deviation angle, ensures that the electromagnetic torque and the aerodynamic torque are in the same direction, and gradually increases the speed using the progressive torque compensation strategy, suppresses the influence of the back-EMF on the system stability, and until it leaves the adverse wind critical area.

[0085] Specifically, the control module 4 adopts a vector control strategy based on rotor field orientation to form a compound closed-loop control architecture, and the core modules are the torque current component calculation unit and the observer module 1.

[0086] The outer ring of the compound closed-loop control architecture is the speed tracking control loop, and the input is the speed error , ωref is the motor speed reference value, ω is the motor speed actual value, controller 9 is a PI regulator with anti-windup compensation wherein Kp is the proportional gain, Ki is the integral time constant, Ksw is the anti-windup gain , ωref is the motor speed reference value, Ilim is the axis current limit value, output q-axis current command .

[0087] The inner loop of the compound closed-loop control architecture takes controller 9 as the core, and realizes sensorless high-precision control by real-time estimation of the motor state and feedback to the outer loop control.

[0088] Further, as shown in Figure 4 , the embodiment also proposes a speed sensorless EC fan reverse wind starting control method, comprising:

[0089] Step one: after the wind direction judgment module is powered on and initialized, inject a pulse signal to judge the wind direction;

[0090] Step two: the observer module observes whether the fan speed exceeds the threshold value;

[0091] Step three: when the fan is detected to be reversed and the speed exceeds the threshold value, start the brake module;

[0092] Step four: the observer module estimates the fan speed in real time;

[0093] Step five: when the speed is detected to be lower than the safety threshold value, the fan is started in the forward direction.

[0094] The above-described embodiments are only descriptions of the preferred modes of the present application and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art shall fall within the protection scope determined by the claims of the present application.​​​

Claims

1. A control apparatus for speed sensorless EC fan reverse wind startup, characterized by, include: The observer module is used to collect wind turbine data; wherein, the wind turbine data includes: wind turbine speed, angle, and back electromotive force; The observer module includes: The back electromotive force observation unit is used to acquire the back electromotive force according to the current error equation; The sliding surface unit generates the sliding surface state through real-time integration of the current error, and its output is used to control the gain of the observer module and the calculation of the back electromotive force. The parameter adaptive unit, based on the sliding surface state, adopts the Lyapunov function and dynamically adjusts the gain of the observer module by setting stability conditions and parameter update laws; The speed detection module is used to compare the fan speed with a preset speed threshold, and send a braking signal when the preset speed threshold is exceeded. The wind direction determination module is used to determine the initial rotation of the wind turbine. When it is determined that the wind turbine is currently rotating in the opposite direction, a braking signal is sent. The braking module, fixed on the outer housing, is used to receive braking signals from the speed detection module and the wind direction judgment module. When braking signals are received from both modules at the same time, the fan shaft is braked. The control module is used to receive signals from the speed detection module and the wind direction judgment module, and to correct the observer module by dynamically adjusting the drive frequency; The control module dynamically adjusts the PWM duty cycle and frequency output by the inverter based on wind direction, phase deviation angle, and torque compensation commands, and feeds back the real-time drive frequency to the observer module to correct the rotor position observation model. The wind direction includes both tailwind and headwind conditions. The rotor position observation model refers to the adaptive sliding mode observer model used by the observer module. The corrections include the stator inductance Ls of the back EMF observation unit, the integral gain k of the sliding mode unit, and the adaptive coefficients of the parameter adaptive unit. During the headwind start-up phase, the control module first applies a low-frequency, small-amplitude voltage vector and locks the rotor's initial position through the observer module. Then, based on the phase deviation angle, the q-axis current setpoint is dynamically corrected to ensure that the electromagnetic torque and aerodynamic torque are in the same direction. A progressive torque compensation strategy is then adopted to gradually increase the speed and suppress the influence of the back electromotive force on the system stability until the system leaves the headwind critical zone.

2. The control apparatus of speed sensorless EC fan reverse air start of claim 1, wherein, The observer module employs an adaptive sliding mode observer, constructing a dynamic equation for the sliding surface based on the motor stator current and voltage signals. It ensures system stability by designing a Lyapunov function with the stator current error as the sliding surface and uses an adaptive algorithm to dynamically adjust the observer switching gain online. Simultaneously, a saturation function is introduced to replace the sign function for smoothing and filtering the observer output. Combined with the PWM drive frequency parameters transmitted from the control module, it performs real-time, high-precision estimation of rotor speed and position information, and transmits the optimized estimation results to the speed detection module.

3. The speed sensorless EC wind turbine start-of-wind control of claim 1, wherein, The wind direction determination module injects a high-frequency square wave pulse of preset amplitude into the stator winding, collects the three-phase current response signal, and decouples it into dq-axis components through coordinate transformation. Based on the phase characteristic difference of the d-axis current ripple amplitude, it determines the initial direction of the wind turbine. When a reverse rotation feature is detected, it sends a braking signal to the braking module.

4. The speed sensorless EC windmii!i reverse wind start control of claim 1, wherein, The brake module comprises an electromagnet, a spring group and a brake shoe; wherein the brake shoe is located on both sides of the fan rotating shaft, the electromagnet is fixed on the side of the brake shoe away from the fan rotating shaft, and one end of the spring group is connected to the side of the brake shoe away from the fan rotating shaft and the other end is fixed to the external shell; When not braking, the spring group separates the brake shoe and the rotating shaft; When braking, the electromagnet is powered to generate an electromagnetic attraction force to overcome the elastic force of the spring group and press the brake shoe against the rotating shaft; The brake shoe surface has a heat dissipation groove, and the brake shoe further has a temperature alarm inside, which automatically cuts off power when the temperature exceeds the preset temperature due to continuous braking.

5. A control method of speed sensorless EC fan reverse wind startup, characterized by, The control device for implementing the windmill reverse start without speed sensor according to any one of claims 1-4, the method comprising: Injecting a pulse signal to determine the wind direction after the wind direction determination module is powered on and initialized; The observer module observes whether the fan rotating speed exceeds the threshold value; Starting the brake module when the fan is detected to be reversed and the rotating speed exceeds the threshold value; The observer module estimates the fan rotating speed in real time; Starting the fan in the forward direction when the rotating speed is detected to be lower than the safety threshold value.

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