A quick start control method and system for industrial fan in headwind and tailwind scenarios

Abstract

The application discloses a quick start control method and system of industrial fans in headwind and tailwind scenes. The application adjusts the short-circuit time until the sampling value of the sampled phase current falls within the current threshold range, and then the initial rotating speed and rotor position of the motor are obtained. Moreover, all possible initial states can be actively identified and adapted, whether it is static, headwind or tailwind. The system can find and execute the corresponding safe start strategy, thereby greatly improving the start success rate and operation reliability in complex natural wind field environment. For the headwind state, the system allows the motor to directly enter closed-loop operation, fully utilizes the kinetic energy of wind energy, realizes smooth and rapid start with the trend, shortens the start time, reduces unnecessary braking energy loss, and improves the overall energy efficiency.

Description

Technical Field

[0001] This invention relates to the technical field of industrial fan drives, specifically to a rapid start-up control method and system for industrial fans in both headwind and tailwind scenarios. Background Technology

[0002] Traditional industrial fans can only accelerate and start safely from zero speed when the fan is stationary. If the fan has an initial speed due to the external airflow before startup, and the motor speed at startup is unknown, the drive will still start accelerating the fan motor from zero speed. In this case, the output speed of the drive and the actual speed of the motor will not match, leading to problems such as increased current and abnormal motor speed. In severe cases, this may damage the drive or the motor. To solve this problem, the three phases of the motor are usually short-circuited. By sampling the phase current, the rotor position is estimated based on the current feedback, and then the rotor speed is estimated based on the sampling time interval, thus obtaining the initial motor speed. Drive and speed are then adjusted based on this initial speed. However, this process presents the following two problems: 1. When shorting the three-phase windings of a motor, the choice of shorting time is crucial. The size of the rotor flux linkage and the current speed of the motor both affect the size of the shorting current. Only by using the appropriate shorting time can the appropriate current be obtained, and only then can the speed estimation result be obtained. Otherwise, if the current is too small, the estimation result will be inaccurate, while if the current is too large, it will cause overcurrent or even burn out the drive or motor. 2. When industrial fans lack a dedicated backwind start-up strategy, they will expose a series of serious defects in scenarios where the rotor's pre-rotation direction is opposite to the target direction (i.e., backwind state). These problems not only increase the risk of start-up failure but also have a chain reaction of negative impacts on equipment lifespan, operational stability, and user experience. Frequent start-up failures and mechanical damage can shorten the fan's mean time between failures (MTBF) to less than 50% of the design value. The back electromotive force generated by the reverse rotation of the motor is opposite to the inverter's output voltage, triggering IGBT module overvoltage or overcurrent protection, leading to start-up failure. To reduce costs, most wind turbine applications now use sensorless solutions. However, since the position of the motor rotor cannot be directly obtained from the hardware level during startup, this greatly increases the difficulty and success rate of starting the motor. It can be said that whether the startup problem can be optimized and improved to a great extent is the key factor in evaluating the quality of a sensorless control solution.

[0003] The lack of a robust reverse-start strategy essentially leads to "energy runaway" on circuit boards. The conflict between reverse rotation and forward startup causes current and voltage to exceed design thresholds, resulting in a complete collapse of reliability across the entire supply chain, from instantaneous damage to power devices to chronic aging of energy storage components, from logic errors in control chips to physical damage to wiring. This not only significantly shortens the mean time between failures (MTBF) of the circuit board but also triggers secondary failures due to device failures (such as power supply burnout caused by short circuits), significantly increasing maintenance costs and downtime risks. Therefore, without a reliable reverse-start strategy, the circuit board faces a fundamental threat from "controllable operation" to "potential failure."

[0004] For IGBTs, the torque counteraction during headwind startup can cause the stator current to surge instantaneously to 5-8 times its rated value (far exceeding the device's safety threshold of 1.5 times its rated current). The conduction loss of an IGBT increases with the square of the current, potentially leading to melting of the internal metallization layer or breakdown of the gate oxide layer within a short period. Electrolytic capacitors, on the other hand, experience accelerated aging: the headwind startup surge current generates significant ripple voltage in the electrolytic capacitor. This ripple current induces Joule heating through the electrolyte, accelerating electrolyte evaporation and significantly increasing the annual capacitance decay rate. When the capacitance drops below 70% of its initial value, it causes DC bus voltage fluctuations, amplifying the current surge. For film capacitors, this can easily lead to localized breakdown. Film capacitors used to absorb high-frequency switching noise may experience localized dielectric field strength exceeding the breakdown threshold under voltage spikes, causing leakage current to rise from the μA level to the mA level, ultimately resulting in the loss of filtering functionality and allowing high-frequency noise to intrude into the control circuitry. Summary of the Invention

[0005] This application provides a rapid start-up control method and system for industrial fans in both headwind and tailwind scenarios, to solve the problem of how to achieve safe and reliable start-up of sensorless industrial fans in any initial state (stationary, rotating with the wind, rotating against the wind), and to fundamentally avoid the electrical shock and hardware damage caused by starting against the wind.

[0006] To address the aforementioned technical problems, firstly, this application provides a rapid start-up control method for industrial fans in both headwind and tailwind scenarios, comprising: Before the motor starts, the initial speed, current direction of rotation and rotor position of the motor rotor are estimated by the zero-vector short-circuit time dynamic optimization method. The current motion state of the motor is determined by the initial speed of the motor rotor, the current direction of rotation, and the rotor position. The current motion state of the motor includes a tailwind state, a headwind state, or a stationary state. The target strategy is selected from multiple preset motor starting strategies based on the current motion state and initial speed of the motor; the preset motor starting strategies include a direct start strategy and a start strategy after braking.

[0007] In one embodiment, the method for estimating the initial speed, rotation direction, and rotor position of the motor rotor using the zero-vector short-circuit time dynamic optimization method is as follows: The three-phase windings of the motor are short-circuited according to the preset initial short-circuit time, so that the three-phase windings of the motor are in a short-circuit state. The phase current generated under the short-circuit state is sampled, and the sampled value of the phase current is compared with a preset current threshold range. The short-circuit time is adjusted until the sampled value of the phase current falls within the current threshold range. Based on the sampled values ​​of the phase current falling within the current threshold range, the initial speed and rotor position of the motor are estimated, and the current rotation direction is determined based on the continuously estimated changes in rotor position.

[0008] In one embodiment, the method for adjusting the short-circuit time is as follows: If the sampled value of the phase current is less than the lower limit of the current threshold range, the sampled value of the phase current is increased by extending the next short-circuit time. If the sampled value of the phase current is greater than the upper limit of the current threshold range, the sampled value of the phase current is reduced by shortening the next short-circuit time.

[0009] In one embodiment, the method for estimating the initial speed and rotor position of the motor based on sampled values ​​of the phase current falling within the current threshold range is as follows: The sampled values ​​of the phase currents falling within the current threshold range are integrated, and the rotor flux linkage vector is estimated by combining the motor's resistance parameters. The initial position and rotational speed of the rotor are calculated based on the magnetic flux vector of the rotor.

[0010] In one embodiment, the method for determining the current motion state of the motor by the initial rotational speed, current rotation direction, and rotor position of the motor rotor is as follows: Based on the rotor position information estimated by the state observer, the current rotation direction of the rotor is determined. The current rotation direction is compared with a preset target direction to determine the current motion state; If the current rotation direction is consistent with the target direction and the initial rotation speed is greater than zero, it is determined to be a tailwind state; If the current rotation direction is opposite to the target direction and the initial rotation speed is greater than zero, it is determined to be a headwind state; If the initial rotational speed is zero, it is determined to be in a stationary state.

[0011] In one embodiment, the method for determining the target strategy from multiple preset motor starting strategies based on the current motor motion state and initial speed is as follows: If the current motion state is a tailwind state and the initial speed is higher than the first speed threshold, then the direct start strategy is selected, and the motor is controlled to directly enter closed-loop operation; If the current motion state is a tailwind state and the initial speed is lower than or equal to the first speed threshold, then the braking and starting strategy is selected, the motor is controlled to brake to a stop, and then start from a standstill. If the current motion state is a headwind state, then the braking and restart strategy is selected, and the motor is controlled to brake to a stop before starting from a standstill.

[0012] In one embodiment, the braking method for selecting the braking-after-start strategy is as follows: When the initial speed is lower than the preset braking threshold, the first level of braking intensity is adopted. The first level of braking intensity maintains a relatively flat braking current curve by adjusting the PID parameters of the braking current. When the initial speed is higher than or equal to the preset braking threshold, a second-level braking intensity is adopted. The second-level braking intensity generates a steeper braking current curve by increasing the given value of the braking current, so as to achieve rapid braking.

[0013] In one embodiment, during the process of controlling the motor startup and operation according to the target strategy, a real-time safety protection strategy based on wind speed disturbance is also executed, the safety protection strategy including: Downwind overvoltage protection monitors the DC bus voltage in real time. When the DC bus voltage rises to the first voltage threshold due to downwind energy feedback, the discharge unit is activated to consume excess power. When the DC bus voltage rises further to a higher second voltage threshold, the discharge unit is controlled to stop working and actively reduce the motor output current until the bus voltage drops or an overvoltage alarm is triggered. Backflow overcurrent protection, real-time monitoring of motor output current and actual speed; When the output current reaches the maximum allowable value of the system and continues for a first preset time, and the deviation between the actual speed and the target speed exceeds the tolerance value, a first-level protection is triggered, and the output torque limit value is reduced from the torque corresponding to the maximum allowable value to the torque corresponding to a preset percentage of the maximum allowable value. If the speed deviation does not decrease within the specified time, the secondary protection is triggered, dynamically extending the preset acceleration and deceleration time to reduce the acceleration and torque required by the system. When the actual rotational speed is detected to start tracking the target rotational speed, the first and second level protections are automatically released, restoring normal torque output and acceleration / deceleration time.

[0014] Secondly, this application also provides a rapid start-up control system for industrial fans in both forward and reverse wind scenarios, applied to the aforementioned rapid start-up control method for industrial fans in both forward and reverse wind scenarios, the system comprising: The acquisition module is used to acquire the phase current of the motor at the start-up moment; The status observation module is communicatively connected to the acquisition module and is used to estimate the initial speed, current rotation direction and rotor position of the motor using the phase current as input. The main control module determines whether the motor is in a tailwind, headwind, or stationary state based on the initial speed, current rotation direction, and rotor position of the motor; and executes the corresponding start-up strategy according to the determination result.

[0015] In one embodiment, the control system further includes a discharge module connected to the DC bus for dissipating energy fed back during motor braking or power generation.

[0016] The beneficial effects of the above-mentioned rapid start-up control method and system for industrial fans in both headwind and tailwind scenarios are as follows: This application achieves accurate initial motor speed and rotor position by adjusting the short-circuit time until the sampled phase current falls within the current threshold range. Furthermore, it proactively identifies and adapts to all possible initial states—stationary, with the wind, or against the wind—and executes the corresponding safe start-up strategy, significantly improving start-up success rate and operational reliability in complex natural wind environments. In the case of a with the wind, the system allows the motor to directly enter closed-loop operation, fully utilizing wind kinetic energy for a smooth and rapid start-up, shortening start-up time and reducing unnecessary braking energy loss, thus improving overall energy efficiency. Moreover, by accurately identifying the headwind state before startup and forcibly selecting a braking-based start-up strategy, it proactively avoids direct conflict between the driver output and the actual rotor direction, thereby eliminating overcurrent and overvoltage impacts at the source and protecting core power devices such as IGBTs and capacitors. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a rapid start-up control method for an industrial fan in both headwind and tailwind scenarios, as shown in an embodiment of this application. Figure 2 This is a schematic diagram illustrating the structure of a rapid start-up control system for an industrial fan in both forward and reverse wind scenarios, as shown in an embodiment of this application. Figure 3 for Figure 2 This application embodiment shows a schematic diagram of the data acquisition module of a rapid start-up control system for an industrial fan in both headwind and tailwind scenarios; Figure 4 for Figure 2This application embodiment shows a schematic diagram of the discharge module of a rapid start-up control system for an industrial fan in both forward and reverse wind scenarios. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intermediary component present. Conversely, when a component is said to be "directly" connected to another component, there is no intermediary component.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] like Figure 1 As shown, in a first aspect, this application provides a rapid start-up control method for industrial fans in both headwind and tailwind scenarios, including: S1. Before the motor starts, the initial speed, current direction of rotation and rotor position of the motor rotor are estimated by the zero-vector short-circuit time dynamic optimization method. The method for estimating the initial speed, rotation direction, and rotor position of the motor rotor using the zero-vector short-circuit time dynamic optimization method is as follows: S11. Short-circuit the three-phase windings of the motor according to the preset initial short-circuit time, so that the three-phase windings of the motor are in a short-circuit state. In motor vector control, zero vector control refers to a specific combination of switching transistors (typically all three-phase upper bridge arms are off, all three-phase lower bridge arms are on, or vice versa), which is equivalent to directly short-circuiting the three-phase windings of the motor together with a wire. Short-circuiting is equivalent to directly connecting the three terminals (U, V, W) of the motor with a switch, forming a closed conductive circuit.

[0022] Zero-vector short circuit: This is equivalent to suddenly short-circuiting both ends of these three sets of coils with a single wire. At this point, the rotating magnet (rotor) will induce a current in the short-circuited coils. The faster the magnet rotates, the larger the induced current. Preset initial short circuit time: This is a very short time value preset in the program by the engineer, for example, 5 milliseconds (ms). The principle for choosing the preset initial short circuit time is safety first, ensuring that even at high speeds, a dangerously large current will not be generated due to an excessively long short circuit time.

[0023] S12. Sample the phase current generated under the short-circuit state, and compare the sampled value of the phase current with a preset current threshold range. Adjust the short-circuit time until the sampled value of the phase current falls within the current threshold range. The method for adjusting the short-circuit time is as follows: S121. If the sampled value of the phase current is less than the lower limit of the current threshold range, the sampled value of the phase current is increased by extending the next short-circuit time. S122. If the sampled value of the phase current is greater than the upper limit of the current threshold range, the sampled value of the phase current is reduced by shortening the next short-circuit time.

[0024] A single fixed short-circuit time (e.g., 5ms) cannot accommodate all speeds. Too low a speed results in a weak current signal, leading to a poor signal-to-noise ratio; too high a speed results in a strong current signal, posing an overcurrent risk. Therefore, the sampled phase current value needs to be within an ideal preset current threshold range. This preset current threshold range is a range of current values ​​pre-set by engineers based on the capabilities of the motor and driver. For example, the preset initial short-circuit time is 5ms, and the current threshold range is 5A-15A. The first short-circuit time is 5ms. At the end of the 5ms short-circuit time, the phase current is sampled. Due to the high speed and large back electromotive force, the current rises sharply, and the sampled phase current value reaches 25A. 25A > 15A, the phase current is too large, so the next short-circuit time needs to be shortened. The short-circuit time is shortened to 2ms, and the short-circuit is executed again. At the end of the 2ms short-circuit time, the sampled phase current value is 12A. 12A is between 5A and 15A. The current falls within the current threshold range. Once the adjustment process is complete, the system will use the phase current data collected during this 2ms short circuit to estimate the initial speed and rotor position.

[0025] S13. Based on the sampled values ​​of the phase current falling within the current threshold range, the initial speed and rotor position of the motor are estimated, and the current rotation direction is determined according to the continuously estimated rotor position changes.

[0026] The method for estimating the initial speed and rotor position of the motor based on the sampled values ​​of the phase current falling within the current threshold range is as follows: S131. Integrate the sampled values ​​of the phase currents that fall within the current threshold range, and estimate the rotor flux linkage vector by combining the motor resistance parameters. S132. Calculate the initial position and rotational speed of the rotor based on the flux linkage vector of the rotor.

[0027] The magnetic flux linkage generated by the permanent magnets of the motor rotor is imprinted in the current generated in the short-circuit circuit, both in strength and direction. Therefore, we first need to estimate the rotor's magnetic flux linkage vector. During the three-phase short circuit of the motor, the winding terminal voltage U = 0 = R*i + dΨ / dt, where: U = 0 (because the three phases are short-circuited, the terminal voltage is zero); R: stator winding resistance, a known quantity; i: sampled value of phase current; Ψ: total magnetic flux linkage; dΨ / dt: rate of change of magnetic flux linkage; transforming the formula, we get: dΨ = -R*i*dt; this formula shows that a small change in magnetic flux linkage (dΨ) is equal to the negative resistance multiplied by the current multiplied by the small change in time (dt). To know the change in total magnetic flux linkage over the entire short circuit time (e.g., 2ms), we need to sum up -R*i*dt at every instant. During the 2ms short-circuit process, the controller samples the current i(t) multiple times at an extremely high frequency (e.g., 1 million times per second). For each sample, it calculates: ΔΨ = -R*i*Δt, where Δt is the time interval between two samples. Then, all these ΔΨ values ​​are summed up to obtain the total change Ψ of the flux linkage vector within the 2ms. For example, assuming the resistance R = 10hm, the sampling period Δt = 1 microsecond, and the sampled value of the phase current i = 10A at a certain moment, then the flux linkage increment at that moment is: ΔΨ = -1*10*0.000001 = -0.00001Weber. The controller accumulates thousands upon thousands of such ΔΨ values ​​throughout the 2ms, ultimately obtaining a total flux linkage vector (Ψ_α, Ψ_β). The direction of this vector represents the direction pointed to by the current rotor poles (NS poles).

[0028] We have already obtained the flux linkage vector Ψ, which can be mathematically represented by two perpendicular components (Ψ_α, Ψ_β). The rotor position angle θ is the angle of this vector. This angle can be calculated using the inverse trigonometric function θ = arctan2(Ψ_β, Ψ_α) to obtain the initial position of the rotor. For example, if Ψ_α = 0.02 Weber and Ψ_β = 0.05 Weber, then θ = arctan2(0.05, 0.02) ≈ 68.2°. Therefore, at the current moment, the N-pole centerline of the motor rotor points to an electrical angle of 68.2 degrees, thus obtaining the initial position of the rotor.

[0029] Rotational speed is the rate of change of position. A single short circuit only yields one position, not the velocity. Therefore, the system repeats the entire short circuit, sampling, integration, and position calculation process within a very short time interval (e.g., 1 ms). This gives us two position values: θ1 calculated from the first short circuit and θ2 calculated from the second short circuit. The time interval between the two short circuits is ΔT (e.g., 1 ms). The initial rotational speed ω can then be calculated using the formula ω = (θ2 - θ1) / ΔT. For example, if the first position θ1 = 68.2°, and the second position θ2 = 78.2° after 1 ms, with a time interval ΔT = 0.001 seconds, then the initial rotational speed ω = (78.2 - 68.2) / 0.001 = 10,000 degrees / second.

[0030] S2. The current motion state of the motor is determined by the initial speed of the motor rotor, the current direction of rotation, and the rotor position. The current motion state of the motor includes a tailwind state, a headwind state, or a stationary state. The method for determining the current motion state of the motor by the initial speed, current direction of rotation, and rotor position of the motor rotor is as follows: S21. Based on the rotor position information estimated by the state observer, determine the current rotation direction of the rotor; S22. Compare the current rotation direction with the preset target direction to determine the current motion state; S23. If the current rotation direction is consistent with the target direction and the initial rotation speed is greater than zero, it is determined to be a downwind state. S24. If the current rotation direction is opposite to the target direction and the initial rotation speed is greater than zero, it is determined to be a headwind state. S25. If the initial rotational speed is zero, it is determined to be in a stationary state.

[0031] For example, at time t1, the rotor position is estimated to be θ1 = 30°, and at time t2, the rotor position is estimated to be θ2 = 40°. The angle difference between the two consecutive positions is calculated as: Δθ = θ2 - θ1 = 10°. Since Δθ > θ and θ is a positive number, the rotor is rotating in the direction of increasing angle, which we define as positive rotation. If this direction is consistent with the target direction of normal fan operation, it is a tailwind state.

[0032] If θ1=30°, θ2=20°, then Δθ=20°-30°=-10°, Δθ<θ, θ is a negative number, As the rotor position angle decreases, the rotor is rotating in the direction of decreasing angle, which we define as reverse rotation. If this direction is opposite to the target direction for normal fan operation, it is considered a headwind.

[0033] Δθ≈0, the rotor position angle does not change significantly, and the rotor is at rest.

[0034] S3. Based on the current motion state and initial speed of the motor, determine the target strategy from multiple preset motor starting strategies; the preset motor starting strategies include direct starting strategy and braking-after-start strategy.

[0035] The method for selecting a target strategy from multiple preset motor starting strategies based on the current motion state and initial speed of the motor is as follows: S31. If the current motion state is a tailwind state and the initial speed is higher than the first speed threshold, then the direct start strategy is selected to control the motor to directly enter closed-loop operation. If the fan is being blown by a strong tailwind and is rotating in the normal operating direction at a speed exceeding the first speed threshold (e.g., >100 RPM), the controller does not apply any braking. Instead, it immediately calculates the voltage and frequency that are perfectly synchronized with the motor's current speed and position, and outputs them directly, allowing the motor to seamlessly enter closed-loop vector control operation. Afterward, it smoothly adjusts to the target speed.

[0036] S32. If the current motion state is a tailwind state and the initial speed is lower than or equal to the first speed threshold, then select the braking and starting strategy, control the motor to brake to a stop, and then start from a stationary state. If the fan's initial speed is below or equal to the first speed threshold, the fan blades will rotate very slowly in the forward direction. The controller will first apply braking to bring the fan to a complete stop before initiating the normal startup process from a standstill. This is because at extremely low speeds, rotor position estimation may not be accurate enough, and directly switching to the closed loop could easily cause the controller's magnetic field to become out of sync with the rotor's actual magnetic field, leading to jitter and inrush current. Therefore, directly synchronizing from this low-speed state offers limited performance improvement but carries a high risk. It is more reliable and consistent to brake first and then start from an absolutely known zero state.

[0037] S33. If the current motion state is a headwind state, then select the braking and starting strategy, control the motor to brake to a stop, and then start from a stationary state.

[0038] When the fan is blown in the opposite direction by the wind (i.e., in a headwind situation), regardless of the speed, the controller will immediately activate the brakes to resolutely stop the motor. It will wait until the fan comes to a complete stop before restarting. This is because starting against the wind causes the driver's positive rotating magnetic field to directly oppose the rotor's reverse mechanical rotation. This is equivalent to an electrical short circuit, generating a huge surge current and voltage that can easily burn out the IGBT power transistors and DC bus capacitors.

[0039] In one embodiment, the braking method for selecting the braking-after-start strategy is as follows: When the initial speed is lower than the preset braking threshold, the first level of braking intensity is adopted. The first level of braking intensity maintains a relatively flat braking current curve by adjusting the PID parameters of the braking current. When the initial speed is higher than or equal to the preset braking threshold, a second-level braking intensity is adopted. The second-level braking intensity generates a steeper braking current curve by increasing the given value of the braking current, so as to achieve rapid braking.

[0040] For example, the preset braking threshold is set to 100 RPM. The system determines that it is in a tailwind condition and the engine speed (50 RPM) is below the braking threshold (100 RPM), therefore, it selects a braking-after-start strategy and activates the first level of braking intensity. The braking current's PID parameters are adjusted. Methods for adjusting the braking current's PID parameters include reducing the proportional gain (P): making the system less sensitive to errors and avoiding over-adjustment; reducing the integral gain (I): slowing down the elimination of steady-state errors and further increasing smoothness; and adjusting the derivative gain (D): suppressing the system's rate of change. This makes the fan stop very smoothly, without any jerking, and minimizes the impact on the mechanical structure and circuitry.

[0041] When the system determines that there is a headwind and the engine speed (500 RPM) is significantly higher than the braking threshold (100 RPM), it selects a braking-after-start strategy and activates the second-level braking intensity. Instead of aiming for a smooth braking, the system directly issues a higher current target command, for example, increasing the braking current setpoint from 10A at low speed to 18A. The PID controller will output its power as quickly as possible to ensure the actual current tracks this high target value, thereby generating strong braking torque. Because the high-speed rotor contains a large amount of kinetic energy, if braking is too slow, this kinetic energy will continuously be converted into electrical energy and fed back to the DC bus, easily leading to excessively high bus voltage.

[0042] In one embodiment, during the process of controlling the motor startup and operation according to the target strategy, a real-time safety protection strategy based on wind speed disturbance is also executed, the safety protection strategy including: Downwind overvoltage protection monitors the DC bus voltage in real time. When the DC bus voltage rises to the first voltage threshold due to downwind energy feedback, the discharge unit is activated to consume excess power. When the DC bus voltage rises further to a higher second voltage threshold, the discharge unit is controlled to stop working and actively reduce the motor output current until the bus voltage drops or an overvoltage alarm is triggered. Backflow overcurrent protection, real-time monitoring of motor output current and actual speed; When the output current reaches the maximum allowable value of the system and continues for a first preset time, and the deviation between the actual speed and the target speed exceeds the tolerance value, a first-level protection is triggered, and the output torque limit value is reduced from the torque corresponding to the maximum allowable value to the torque corresponding to a preset percentage of the maximum allowable value. If the speed deviation does not decrease within the specified time, the secondary protection is triggered, dynamically extending the preset acceleration and deceleration time to reduce the acceleration and torque required by the system. When the actual rotational speed is detected to start tracking the target rotational speed, the first and second level protections are automatically released, restoring normal torque output and acceleration / deceleration time.

[0043] After the motor has been successfully started and is in operation, sudden strong tailwinds or headwinds during operation may damage the motor.

[0044] If a strong tailwind accelerates the fan beyond the motor's control speed, the motor becomes a generator, converting mechanical energy into electrical energy and feeding it back to the driver's DC bus, causing the bus voltage to spike. For example, the first voltage threshold is 780V, and the second is 820V. When the fan speed continues to increase due to the strong wind, the DC bus voltage is pushed up to 785V. The system detects this voltage exceeding 780V and immediately activates the bleeder module. The bleeder module uses a braking resistor to dissipate excess electrical energy and suppress the voltage rise. If the wind is too strong, the bleeder module may be operating at full load, but the voltage continues to rise uncontrollably, reaching 822V. To prevent the bleeder resistor from overheating and burning out due to prolonged overload, the system will control the bleeder module to stop working, actively reducing the motor output current and decreasing energy feedback, thereby lowering the bus voltage.

[0045] If the strong headwind resistance is enormous, even if the motor outputs maximum torque, it will be unable to increase or maintain its speed, causing the current to remain at its maximum value for an extended period. This poses a risk of overheating and burning out the IGBT and motor windings. For example, the system allows a maximum current Imax of 50A, a first preset time T1 of 3 seconds, a preset percentage of 80%, and a second preset time T2 of 5 seconds.

[0046] If the fan encounters a strong headwind, its actual speed will decrease from 500 RPM, while the target speed remains at 500 RPM. The motor outputs its maximum current of 50A for 3 seconds, but the speed is still below 450 RPM (deviation > 50 RPM). The system triggers Level 1 protection, reducing the output torque limit from the torque corresponding to 50A to the torque corresponding to 40A (50A * 80%), immediately releasing the overcurrent condition and protecting the IGBT. If, after triggering Level 1 protection, another 5 seconds pass and the fan speed continues to slowly decrease due to excessive resistance and cannot recover, the system triggers Level 2 protection, dynamically extending the preset acceleration / deceleration time, for example, extending the acceleration time from 60 seconds to 120 seconds. Extending the acceleration / deceleration time means the required acceleration is reduced. Therefore, the required torque naturally decreases, alleviating current pressure and perfectly complementing Level 1 protection. If the system continuously monitors and detects that the actual speed begins to rise and can re-track the target speed, the system automatically releases both Level 1 and Level 2 protection, restoring normal torque output and acceleration / deceleration time.

[0047] like Figure 2 As shown, in a second aspect, this application also provides a rapid start-up control system for industrial fans in both forward and reverse wind scenarios, applied to the aforementioned rapid start-up control method for industrial fans in both forward and reverse wind scenarios, the system comprising: like Figure 3 As shown, acquisition module 1 is used to acquire the phase current of the motor at the start-up moment; The status observation module 2 is communicatively connected to the acquisition module and is used to estimate the initial speed, current rotation direction and rotor position of the motor using the phase current as input. The main control module 3 determines whether the motor is in a tailwind state, a headwind state, or a stationary state based on the initial speed, current rotation direction, and rotor position of the motor; and executes the corresponding start-up strategy according to the determination result.

[0048] In the sensorless control scenario, acquisition module 1 is used to collect the phase current at the moment of motor startup. The speed of the permanent magnet synchronous motor is estimated based on the state observation module 2, which takes the phase current value of the three-phase winding as input. Therefore, the phase current values ​​iu, iv, and iw are sampled by controlling the IPM switches in an orderly manner through PWM1-6, ensuring the normal operation of the state observation module 2. In the control algorithm of the main control module 3, iq controls the electromagnetic torque and id controls the rotor flux. To minimize the interference of the given iq and id values ​​on the motor's upwind speed, the given iq and id values ​​are 0. This minimizes the impact on the current state of the motor and allows the state observation module 2 to operate normally, obtaining the initial speed ω and rotor position of the motor, laying the foundation for the motor's upwind braking.

[0049] like Figure 4As shown, in one embodiment, the control system further comprises a discharge module 4, wherein the discharge module 4 is connected to a DC bus and configured to consume energy fed back during motor braking or power generation.

[0050] When the motor generates power due to downwind or braking, the fed-back energy causes the DC bus voltage to rise continuously. The sampled voltage V_sample also rises accordingly. When the voltage rises to a certain level such that V_sample(IN+)>V_ref(IN-), the state of the comparator 41 flips, and the output thereof changes from a low level to a high level. After being amplified by a driving circuit, this high-level signal drives the power switching tube 42 to conduct completely, and the braking resistor Pump is directly connected to the DC bus through the conducted switching tube 42, forming a powerful discharge loop. A large amount of electrical energy flows into the braking resistor instantaneously and is consumed in the form of heat. As the energy is consumed rapidly, the DC bus voltage starts to drop, and the sampled voltage V_sample also drops accordingly. When the voltage drops to make V_sample(IN+)<V_ref(IN-), the comparator 41 flips again, the output changes back to a low level, the power switching tube 41 is turned off, the loop of the braking resistor is cut off, and the discharge stops.

[0051] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction between the combinations of these technical features, they should be considered as falling within the scope recorded in this specification.

[0052] The above-described embodiments merely represent several embodiments of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the scope of the patent for the present invention. It should be noted that, for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A rapid start-up control method for an industrial fan in both headwind and headwind scenarios, characterized in that: include: Before the motor starts, the initial speed, current direction of rotation and rotor position of the motor rotor are estimated by the zero-vector short-circuit time dynamic optimization method. The current motion state of the motor is determined by the initial speed of the motor rotor, the current direction of rotation, and the rotor position. The current motion state of the motor includes a tailwind state, a headwind state, or a stationary state. The target strategy is selected from multiple preset motor starting strategies based on the current motion state and initial speed of the motor. The preset motor starting strategy includes a direct starting strategy and a braking-after-starting strategy; The method for estimating the initial speed, rotation direction, and rotor position of the motor rotor using the zero-vector short-circuit time dynamic optimization method is as follows: The three-phase windings of the motor are short-circuited according to the preset initial short-circuit time, so that the three-phase windings of the motor are in a short-circuit state. The phase current generated under the short-circuit state is sampled, and the sampled value of the phase current is compared with a preset current threshold range. The short-circuit time is adjusted until the sampled value of the phase current falls within the current threshold range. Based on the sampled values ​​of the phase current falling within the current threshold range, the initial speed and rotor position of the motor are estimated, and the current rotation direction is determined based on the continuously estimated changes in rotor position. The method for adjusting the short-circuit time is as follows: If the sampled value of the phase current is less than the lower limit of the current threshold range, the sampled value of the phase current is increased by extending the next short-circuit time. If the sampled value of the phase current is greater than the upper limit of the current threshold range, the sampled value of the phase current is reduced by shortening the next short-circuit time; The braking method for selecting the braking-after-start strategy is as follows: When the initial speed is lower than the preset braking threshold, the first level of braking intensity is adopted. The first level of braking intensity maintains a relatively flat braking current curve by adjusting the PID parameters of the braking current. When the initial speed is higher than or equal to the preset braking threshold, a second-level braking intensity is adopted. The second-level braking intensity generates a steeper braking current curve by increasing the given value of the braking current, so as to achieve rapid braking. During the process of controlling the motor startup and operation according to the target strategy, a real-time safety protection strategy based on wind speed disturbance is also executed, which includes: Downwind overvoltage protection monitors the DC bus voltage in real time. When the DC bus voltage rises to the first voltage threshold due to downwind energy feedback, the discharge unit is activated to consume excess power. When the DC bus voltage rises further to a higher second voltage threshold, the discharge unit is controlled to stop working and actively reduce the motor output current until the bus voltage drops or an overvoltage alarm is triggered. Backflow overcurrent protection, real-time monitoring of motor output current and actual speed; When the output current reaches the maximum allowable value of the system and continues for a first preset time, and the deviation between the actual speed and the target speed exceeds the tolerance value, a first-level protection is triggered, and the output torque limit value is reduced from the torque corresponding to the maximum allowable value to the torque corresponding to a preset percentage of the maximum allowable value. If the speed deviation does not decrease within the specified time, the secondary protection is triggered, dynamically extending the preset acceleration and deceleration time to reduce the acceleration and torque required by the system. When the actual rotational speed is detected to start tracking the target rotational speed, the first and second level protections are automatically released, restoring normal torque output and acceleration / deceleration time.

2. The rapid start-up control method for industrial fans in both headwind and tailwind scenarios according to claim 1, characterized in that: The method for estimating the initial speed and rotor position of the motor based on the sampled values ​​of the phase current falling within the current threshold range is as follows: The sampled values ​​of the phase currents falling within the current threshold range are integrated, and the rotor flux linkage vector is estimated by combining the motor's resistance parameters. The initial position and rotational speed of the rotor are calculated based on the magnetic flux vector of the rotor.

3. The rapid start-up control method for industrial fans in both headwind and tailwind scenarios according to claim 2, characterized in that: The method for determining the current motion state of the motor by the initial speed, current direction of rotation, and rotor position of the motor rotor is as follows: Based on the rotor position information estimated by the state observer, the current rotation direction of the rotor is determined. The current rotation direction is compared with a preset target direction to determine the current motion state; If the current rotation direction is consistent with the target direction and the initial rotation speed is greater than zero, it is determined to be a tailwind state; If the current rotation direction is opposite to the target direction and the initial rotation speed is greater than zero, it is determined to be a headwind state; If the initial rotational speed is zero, it is determined to be in a stationary state.

4. The rapid start-up control method for industrial fans in both headwind and tailwind scenarios according to claim 3, characterized in that: The method for selecting a target strategy from multiple preset motor starting strategies based on the current motion state and initial speed of the motor is as follows: If the current motion state is a tailwind state and the initial speed is higher than the first speed threshold, then the direct start strategy is selected, and the motor is controlled to directly enter closed-loop operation; If the current motion state is a tailwind state and the initial speed is lower than or equal to the first speed threshold, then the braking and starting strategy is selected, the motor is controlled to brake to a stop, and then start from a standstill. If the current motion state is a headwind state, then the braking and restart strategy is selected, and the motor is controlled to brake to a stop before starting from a standstill.

5. A rapid start-up control system for an industrial fan in both headwind and headwind scenarios, characterized in that, A system for a rapid start-up control method for an industrial fan in a headwind or tailwind scenario as described in any one of claims 1 to 4, the system comprising: The acquisition module is used to acquire the phase current of the motor at the start-up moment; The status observation module is communicatively connected to the acquisition module and is used to estimate the initial speed, current rotation direction and rotor position of the motor using the phase current as input. The main control module determines whether the motor is in a tailwind, headwind, or stationary state based on the initial speed, current rotation direction, and rotor position of the motor; and executes the corresponding start-up strategy according to the determination result.

6. The rapid start-up control system for industrial fans in both headwind and tailwind scenarios according to claim 5, characterized in that, The control system also includes a discharge module connected to the DC bus, which is used to dissipate the energy fed back during motor braking or power generation.

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