Control method for forward and reverse wind starting of outdoor fan

Abstract

The invention relates to the technical field of motor control, in particular to a control method for forward and reverse wind starting of an outdoor fan, which comprises the following steps: S1, zero current control; s2, obtaining a back electromotive force; s3, angle acquisition and speed determination; s4, performing assignment; and S5, convergence. According to the method, the counter electromotive force is obtained through zero-current control and a filtering algorithm, meanwhile, the angle and the speed are obtained and determined, assignment is carried out, the whole process is carried out in a software calculation mode, starting of the motor can be effectively ensured, the initial angle and the initial speed of the fan under the action of external wind can be rapidly judged before starting, and the starting accuracy is improved. Therefore, reliable starting of the fan is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a control method for starting an outdoor fan in both forward and reverse winds. Background Art

[0002] As the global energy crisis intensifies, improving energy efficiency has become a top priority. During the operation of outdoor fans, changes in wind direction will have a significant impact on their energy consumption. Starting the fan in the downwind condition can use natural wind power to reduce the energy input required when the fan is started, thereby reducing energy consumption. On the contrary, when starting against the wind, the fan needs to overcome greater resistance and consume more energy. Therefore, by controlling the start-up of outdoor fans in the upwind and downwind conditions, efficient energy utilization can be achieved and operating costs can be reduced.

[0003] The existing technology mainly uses a hardware system to collect the back electromotive force of the motor to calculate the initial speed of the motor to complete the start of the motor. When the fan is not started normally, the motor blades rotate at high speed due to the influence of external wind, and the back electromotive force cannot be directly obtained. The hardware circuit is mainly used to obtain the back electromotive force, which makes the system complicated, and the initial angle and speed of the fan under the action of external wind cannot be obtained, and the reliable start of the fan cannot be guaranteed. Summary of the invention

[0004] The present invention aims at the deficiencies in the prior art and provides the following technical solutions:

[0005] A control method for starting an outdoor fan in both forward and reverse winds comprises the following steps:

[0006] S1: Zero current control: Make the motor relatively static and current-free before starting, and obtain the rotation speed of the motor in the external environment at this time;

[0007] S2: Obtaining back electromotive force: Make the current stable and close to zero, use the filtering algorithm to obtain the back electromotive force at this time, and complete the acquisition of the back electromotive force;

[0008] S3: Angle acquisition and speed determination: In the first cycle, the first angle is acquired by using the inverse tangent, and in the second cycle, the second angle is acquired by using the inverse tangent. Then, the speed is acquired by differentiating the two acquired angles to determine the rotation speed of the motor at this time.

[0009] S4: Assignment: Assign the angle and speed obtained in S3 to the loop;

[0010] S5: Convergence: The loop converges successfully and the motor starts smoothly.

[0011] As an improvement of the above technical solution, the calculation formula of the filtering algorithm in step S2 is:

[0012] Vfiltered (n) = α × V measured (n)+(1-α)×V filtered (n-1)

[0013] Among them, V filtered (n) is the back EMF value after filtering at the current moment, V measured (n) is the back electromotive force value measured at the current moment, V filtered (n-1) is the back electromotive force value after filtering at the previous moment, and α is the filtering coefficient.

[0014] As an improvement of the above technical solution, the calculation formula of the first angle θ1 in step S3 is:

[0015]

[0016] Among them, tan -1 represents the inverse tangent function, U α represents the voltage of the α axis, U β Indicates the voltage of the β axis.

[0017] As an improvement of the above technical solution, the calculation formula of the second angle θ2 in step S3 is:

[0018]

[0019] Among them, tan -1 represents the inverse tangent function, U α represents the voltage of the α axis, U β Indicates the voltage of the β axis.

[0020] As an improvement of the above technical solution, the calculation formula for obtaining the speed after differentiation in step S3 is:

[0021]

[0022] Among them, w e Indicates the acquisition speed, T1 indicates the time in the first cycle, and T2 indicates the time in the second cycle.

[0023] As an improvement of the above technical solution, the loop in step S4 refers to a Foc loop.

[0024] Beneficial effects of the present invention:

[0025] Through zero current control and filtering algorithm to obtain back electromotive force, the angle and speed are determined and assigned. The whole process is carried out by software calculation, which can effectively ensure the starting of the motor and quickly determine the initial angle and speed of the fan under the action of external wind before starting, so as to ensure the reliable starting of the fan. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the two-phase static α, β coordinate system of the present invention;

[0027] Figure 2 The two-phase d and q rotating coordinate system of the present invention;

[0028] Figure 3 This is the motor loop Foc vector control block diagram of the present invention;

[0029] Figure 4 The rotor position angle identified when the fan blades of the present invention are blown by wind;

[0030] Figure 5 It is the rotor speed identified when the fan blades of the present invention are blown by wind. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] Please refer to Figure 1-Figure 5 As shown, the present invention provides a control method for starting an outdoor fan in both forward and reverse winds, comprising the following steps:

[0033] S1: Zero current control: Make the motor relatively static and current-free before starting, and obtain the rotation speed of the motor in the external environment at this time;

[0034] S2: Obtaining back electromotive force: Make the current stable and close to zero, use the filtering algorithm to obtain the back electromotive force at this time, and complete the acquisition of the back electromotive force;

[0035] S3: Angle acquisition and speed determination: In the first cycle, the first angle is acquired by using the inverse tangent, and in the second cycle, the second angle is acquired by using the inverse tangent. Then, the speed is acquired by differentiating the two acquired angles to determine the rotation speed of the motor at this time.

[0036] S4: Assignment: Assign the angle and speed obtained in S3 to the loop;

[0037] S5: Convergence: The loop converges successfully and the motor starts smoothly.

[0038] In this case, zero current control is first performed and back electromotive force is obtained. The acquisition of back electromotive force lays the foundation for the subsequent determination of angle and speed. In the first cycle, the first angle is obtained by inverse tangent operation, and this angle is obtained after the back electromotive force is obtained.

[0039] Back EMF reflects the operating status of the motor, which can help determine the initial position and movement trend of the motor. After obtaining the back EMF, the system has important information about the motor status, which provides a relatively clear starting point and reference basis for angle acquisition in the first cycle.

[0040] Without accurate acquisition of back EMF, the angle calculation in the first cycle may lack accuracy and reliability. Because back EMF is closely related to the rotation state of the motor, it provides key information input for angle calculation, affecting the accuracy and effectiveness of angle acquisition.

[0041] In short, the acquisition of back electromotive force provides an important premise and basis for the acquisition of the first cycle angle. The two are closely linked in the process of motor starting control, and together play a role in achieving precise control and smooth starting of the motor.

[0042] Among them, Figure 1 and Figure 2 As shown, Figure 1 is a two-phase stationary α and β coordinate system, Figure 2 is the two-phase d, q rotating coordinate system, where φ is the current loop angle, and is the angle between the d, q axis and the α, β axis,

[0043] α, β axis voltage equation

[0044]

[0045] When the α-axis current i α =0 and β-axis current i β =0

[0046] U α =-w e φ r sinθ

[0047] U β =w e φ r cosθ

[0048] Among them, R s is the resistance of the motor, is the differential of the α-axis current, is the differential of the β-axis current, L α is the α-axis inductance of the motor, L β is the β-axis inductance of the motor, w e is the motor rotor angular velocity, φ r is the motor flux, i α is the motor α-axis current, i β is the motor β-axis current.

[0049] In the state of zero current control, the d-axis reference current i d_ref and q-axis reference current i q_ref The current loop angle φ is forced to zero. The d-axis and q-axis currents of the current loop are controlled by two PI controllers respectively. After the current loop converges and stabilizes, due to the given reference current i d_ref ,i q_ref is equal to zero, so the d-axis feedback current i d_bak and q-axis feedback current i q_bak It will also stabilize to zero;

[0050] Among them, i d_ref and i q_ref is the reference current set, i d_bak and i q_bak It is the current fed back from the loop and is the current when the motor is actually running.

[0051] i d_bak and i q_bak The feedback current is the corresponding formula i d and i q , represents the actual current of the motor. According to the park coordinate transformation, we can know that:

[0052] i d =i α cosφ+i β sinφ

[0053] i q =-i α sinφ+i β cosφ

[0054] According to the inverse transformation of clack coordinates:

[0055] U α =U d cosφ-U q sinφ

[0056] U β =U d sinφ+U q cosφ

[0057] From the park coordinate transformation, we can know that when the current loop angle φ is forced to 0:

[0058] i d =i α ,i q =i β

[0059] From the inverse transformation of park coordinates, we know that when the current loop angle φ is forced to 0:

[0060] U α =U d

[0061] U β =U q

[0062] Among them, Park coordinate transformation (also known as Park transformation) is a mathematical transformation that transforms variables (usually current and voltage) in a three-phase AC system from a stationary three-phase coordinate system (abc coordinate system) to a rotating two-phase coordinate system (dq coordinate system).

[0063] The significance generated:

[0064] (1) Simplified motor model: In the analysis and control of three-phase AC motors, the Park coordinate transformation can be used to simplify the originally complex three-phase motor model into a DC motor model that is easier to analyze and control. In the dq coordinate system, the motor's inductance, resistance and other parameters become constants, and the motor's torque and flux can be controlled independently, which greatly simplifies the design of the control algorithm.

[0065] (2) Easy to implement vector control: Park coordinate transformation is the basis of AC motor vector control. By transforming the three-phase current into the dq coordinate system, the motor's excitation current (d-axis current) and torque current (q-axis current) can be controlled separately, achieving precise control of the motor speed and torque.

[0066] Clark coordinate transformation (also known as Clark transformation) transforms the variables in the three-phase AC system from the stationary three-phase coordinate system (abc coordinate system) to the stationary two-phase coordinate system (α-β coordinate system). Clark coordinate inverse transformation transforms from the α-β coordinate system back to the abc coordinate system.

[0067] The significance generated:

[0068] (1) Simplified analysis and control: Clark coordinate transformation and inverse transformation can simplify the analysis and control problems of three-phase systems into those of two-phase systems, thus reducing computational complexity.

[0069] (2) Facilitate the implementation of specific control: In some control algorithms, it is necessary to first perform Clark coordinate transformation to process the variables in the coordinate system, and then perform inverse transformation back to the three-phase coordinate system to achieve control of the three-phase motor.

[0070] Among them, when the current loop converges and stabilizes, the d-axis feedback current i d and q-axis feedback current i q Stabilize to zero, and the φ angle of the current loop is forced to 0. From the park coordinate transformation, we know that i d=i α ,i q =i β , so i α ,i β It is also equal to zero. According to the voltage equation of the αβ axis stationary coordinate system (the voltage equation of the α and β axes described above) and the inverse transformation of the park coordinate system, it can be known that the output of the two current loops is equal to U d =U α =-w e φ r sinθ and U q =U β =w e φ r cosθ, and then replaced the back EMF sampling circuit, and still obtained the α-axis back EMF -w e φ r sinθ, β-axis back electromotive force w e φ r cosθ, thereby ensuring that the current is stable and close to zero during the process of obtaining the back electromotive force, so as to ensure that the back electromotive force is obtained by using the filtering algorithm, providing a strong condition for obtaining the back electromotive force.

[0071] Among them, the initial angle and speed of the motor can be effectively calculated by obtaining the back electromotive force, and the initial angle and speed of the fan under the action of external wind can be quickly determined before starting to ensure the reliable starting of the fan.

[0072] The calculation formula of the filtering algorithm in step S2 is:

[0073] V filtered (n) = α × V measured (n)+(1-α)×V filtered (n-1)

[0074] Among them, V filtered (n) is the back EMF value after filtering at the current moment, V measured (n) is the back electromotive force value measured at the current moment, V filtered (n-1) is the back EMF value after filtering at the previous moment, and α is the filtering coefficient, which ranges from 0 to 1. The filtering coefficient determines the strength of the filtering. The larger α is, the greater the influence of the current measurement value on the filtering result, and the less obvious the filtering effect is; the smaller α is, the greater the influence of historical data on the filtering result, and the more obvious the filtering effect is.

[0075] Among them, the benefits of using filtering algorithms to obtain back EMF include:

[0076] (1) Improve accuracy:

[0077] The filtering algorithm can remove noise and interference in the measurement signal, so as to extract the back EMF signal more accurately. In practical applications, there may be various electromagnetic interferences and noises in the motor operating environment, which will affect the measurement accuracy of the back EMF. Through filtering, the influence of noise can be reduced and the measurement accuracy of the back EMF can be improved.

[0078] For example, when the motor is running at high speed, the measured back EMF signal may fluctuate and be distorted due to the influence of electromagnetic interference and switching noise. Using a low-pass filtering algorithm can effectively remove high-frequency noise, making the back EMF signal smoother and more stable, thereby improving the accuracy of the measurement.

[0079] (2) Enhanced stability:

[0080] The filtering algorithm can make the back-EMF signal more stable and reduce the fluctuation and mutation of the signal. This is very important for the stability of the motor control system, because unstable back-EMF signal may cause unstable motor control or even failure.

[0081] For example, during the motor startup and acceleration process, the back EMF signal may change and fluctuate greatly. Using a filtering algorithm can gradually stabilize the back EMF signal to avoid shock and interference to the motor control system, thereby improving the stability of the motor control system.

[0082] (3) Facilitate subsequent processing:

[0083] The back-EMF signal after filtering is smoother and more stable, which is convenient for subsequent signal processing and analysis. For example, the back-EMF signal after filtering can be used to estimate the motor speed, detect the position, etc., so as to achieve more accurate motor control.

[0084] In addition, the filtered back-EMF signal can also be used as a feedback signal for closed-loop control of the motor control system to improve the performance and stability of the motor control system.

[0085] (4) Improve system reliability:

[0086] In the motor control system, accurate acquisition of back EMF is crucial for the normal operation and control of the motor. Using filtering algorithms can improve the measurement accuracy and stability of back EMF, thereby improving the reliability of the motor control system.

[0087] For example, if the back EMF measurement is inaccurate, it may cause unstable motor control or even failure. Using filtering algorithms can reduce this risk and improve the reliability of motor control systems.

[0088] (5) Simplify system design:

[0089] Filtering algorithms can simplify the design of motor control systems to a certain extent. Since filtering algorithms can remove noise and interference, they can reduce the need for hardware filters and reduce system cost and complexity.

[0090] In addition, the filtering algorithm can also make the back-EMF signal smoother and more stable, which is convenient for subsequent signal processing and analysis, thereby simplifying the software design of the system.

[0091] (6) Improve system adaptability:

[0092] Different motor operating environments and working conditions may have different effects on the measurement of back EMF. Using filtering algorithms can make the measurement of back EMF more adaptable to different environments and conditions and improve the adaptability of the system.

[0093] For example, when the motor is running at high speed, the back EMF signal may change and fluctuate greatly due to the influence of electromagnetic interference and switching noise. Using a filtering algorithm can make the back EMF signal more stable, thereby improving the adaptability of the system at high speed.

[0094] The calculation formula of the first angle θ1 in step S3 is:

[0095]

[0096] Among them, tan -1 represents the inverse tangent function, U α represents the voltage of the α axis, U β Indicates the voltage of the β axis.

[0097] The calculation formula of the second angle θ2 in step S3 is:

[0098]

[0099] Among them, tan -1 represents the inverse tangent function, U α represents the voltage of the α axis, U β Indicates the voltage of the β axis.

[0100] The calculation formula for obtaining the speed after differentiation in step S3 is:

[0101]

[0102] Among them, w e Indicates the acquisition speed, T1 indicates the time in the first cycle, and T2 indicates the time in the second cycle.

[0103] The loop in step S4 is a Foc loop.

[0104] Among them, the Foc loop can provide conditions for the convergence of the Foc loop in order to facilitate successful convergence, and the meaning of convergence is: generally, the motor is started in a stationary state, and the initial speed value and the initial angle value are 0, which are all known. When the motor starts, the motor speed and angle can be quickly identified, thereby controlling the motor rotation; but because the outdoor fan is affected by the strong wind and is in a rotating state, the motor has a speed before starting, but the initialization value defaults to the motor initial speed, which is 0. By adopting this method, the speed of the motor can be identified before the motor starts, and the running angle and angular velocity of the motor can be quickly tracked when starting.

[0105] Among them, the current and voltage in the loop are obtained through coordinate transformation. Coordinate transformation requires angles, and the angle is integrated by the speed. Therefore, the speed and angle of the motor must be obtained during the initial startup to ensure that the current after coordinate transformation during the startup process is correct and is the current actually required by the motor. The motor can then successfully complete the startup with the initial speed.

[0106] in, Figure 3 What is shown in the figure is the connection relationship between the circuit structures, which can represent the coordinate transformation of the current during the control process.

[0107] For convergence, when the motor starts, an initial angle and speed of the motor need to be provided to the entire loop. The motor can start smoothly, the loop can converge, and then the angle and speed can be obtained in real time during operation.

[0108] Among them, Figure 4 and Figure 5 Represents the angle and speed respectively.

[0109] Among them, the specific steps of controlling the forward and reverse wind start-up of the outdoor fan are as follows:

[0110] 1. Conditions for zero current control

[0111] The achievement of zero current condition makes the motor in a relatively static state without current interference before starting. This creates an ideal environment for the subsequent accurate acquisition of back EMF and avoids the influence of unnecessary current noise on back EMF measurement. At the same time, the zero current state also helps to reduce the impact current at the moment of motor starting, protect the motor and related electronic components, and improve the reliability and stability of the system.

[0112] 2. Conditions for obtaining back electromotive force

[0113] When the conditions for acquiring back EMF are met, the system can accurately determine the initial state and operating trend of the motor. Back EMF reflects the rotation state and speed change of the motor. By acquiring back EMF, the system can infer the approximate position and direction of movement of the motor, providing an important reference for subsequent precise control of the motor. This helps to achieve smooth startup and efficient operation of the motor and reduce vibration and errors during startup.

[0114] 3. Conditions for angle acquisition

[0115] Accurately acquiring the angle information of the motor is the key to achieving precise control. By performing angle calculations within a specific period, the system can determine the current position and rotation angle of the motor. This provides the basis for the vector control of the motor, enabling the system to adjust the output of current and voltage according to the angle information to achieve precise control of the motor speed and torque. The accuracy of angle acquisition directly affects the control accuracy and dynamic performance of the motor.

[0116] 4. Conditions for determining speed

[0117] Determining the speed of the motor is crucial to achieving motor speed regulation and dynamic response control. By determining the speed polarity based on the angle increment and obtaining the speed by differentiating the angle, the system can monitor the motor's operating speed in real time and adjust it according to actual needs. This enables the motor to achieve fast response and stable operation in different working scenarios, improving production efficiency and equipment performance.

[0118] 5. Conditions for assignment

[0119] When the conditions for assignment are met, the system assigns key values ​​such as the motor angle and speed to the loop, which provides the necessary conditions for the convergence of the loop and enables the system to self-adjust and optimize according to these assigned parameters. Assignment enables the system to more accurately grasp the operating status of the motor, thereby achieving more precise control. At the same time, this also lays the foundation for the start-up and stable operation of the motor.

[0120] 6. Convergence Conditions

[0121] The satisfaction of the motor starting conditions means that the system has completed all preparations and the loop has converged to a stable state. At this point, the motor can start smoothly and run according to the predetermined control strategy. The successful start-up of the motor indicates the effectiveness and reliability of the entire control system, providing strong power support for subsequent production and application. At the same time, a stable start-up process also helps to reduce equipment wear and energy consumption, and improve the service life and economy of the system.

[0122] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them.

Claims

1. A control method for starting an outdoor fan in both forward and reverse winds, characterized in that: The following steps are involved: S1: Zero current control: Make the motor relatively static and current-free before starting, and obtain the rotation speed of the motor in the external environment at this time; S2: Obtaining back electromotive force: Make the current stable and close to zero, use the filtering algorithm to obtain the back electromotive force at this time, and complete the acquisition of the back electromotive force; S3: Angle acquisition and speed determination: In the first cycle, the first angle is acquired by using the arc tangent, and in the second cycle, the second angle is acquired by using the arc tangent. Then, the speed is acquired by differentiating the two acquired angles to determine the rotation speed of the motor at this time. S4: Assignment: Assign the angle and speed obtained in S3 to the loop; S5: Convergence: The loop converges successfully and the motor starts smoothly.

2. The control method for starting an outdoor fan in both forward and reverse winds according to claim 1, characterized in that: The calculation formula of the filtering algorithm in step S2 is: V filtered (n)=α×V measured (n)+(1-α)×V filtered (n-1) Among them, V filtered (n) is the back EMF value after filtering at the current moment, V measured (n) is the back electromotive force value measured at the current moment, V filtered (n-1) is the back electromotive force value after filtering at the previous moment, and α is the filtering coefficient.

3. The control method for starting an outdoor fan in both forward and reverse winds according to claim 1, characterized in that: The calculation formula of the first angle θ1 in step S3 is: Among them, tan -1 represents the inverse tangent function, U α represents the voltage of the α axis, U β Indicates the voltage of the β axis.

4. The control method for starting an outdoor fan in both forward and reverse winds according to claim 1, characterized in that: The calculation formula of the second angle θ2 in step S3 is: Among them, tan -1 represents the inverse tangent function, U α represents the voltage of the α axis, U β Indicates the voltage of the β axis.

5. The control method for starting an outdoor fan in both forward and reverse winds according to claim 1, characterized in that: The calculation formula for obtaining the speed after differentiation in step S3 is: Among them, w e Indicates the acquisition speed, T1 indicates the time in the first cycle, and T2 indicates the time in the second cycle.

6. The control method for starting an outdoor fan in both forward and reverse winds according to claim 1, characterized in that: The loop in step S4 is a Foc loop.

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