A method for controlling the starting of a permanent magnet synchronous motor fan against the wind

Abstract

This invention discloses a method for controlling the reverse wind start of a permanent magnet synchronous motor fan, based on i p_break Determine the peak value i of the motor winding phase current in open-loop operation mode. p0 On the one hand, this invention avoids the problem of excessive amplitude of the three-phase sinusoidal current forming the active rotating magnetic field, which could cause rotor vibration and lead to motor starting failure. On the other hand, it avoids the problem of insufficient torque generated by too small phase current in the motor windings during open-loop operation, preventing the motor from operating normally in open-loop mode. Furthermore, this invention can also be based on i p_break Peak phase current i in closed-loop mode for determining rotor position p_close Then according to i p_close The setpoints for the d-axis current loop and q-axis current loop are calculated. Compared with the traditional d-axis current control scheme, the optimization of the d-axis current loop can improve the starting torque of the motor during mode switching and improve the ability to start against the wind.

Description

Technical Field

[0001] This invention relates to the technical field of motor control, and in particular to a method for controlling the reverse wind start of a permanent magnet synchronous motor fan. Background Technology

[0002] Due to their simple structure, high efficiency, and wide speed range, permanent magnet synchronous motor fans are widely used in indoor air purification, mine tunnel ventilation, and other fields. Fans often encounter headwinds during operation, and headwind start-up failure is the most common fault. In recent years, headwind start-up control methods for permanent magnet synchronous motor fans have become a very important research direction in the field of fan control.

[0003] Huo Junya et al. studied a sensorless control method for starting a permanent magnet synchronous motor fan against the wind in the journal "Daily Electrical Appliances" (2014, NO.7). However, this method only studied the problems of identifying the headwind state and estimating the headwind speed, and did not study the difference between the headwind starting control method and the starting control method under no headwind conditions.

[0004] The patent (ZL201910660918.1) proposes a method to improve the starting performance of permanent magnet synchronous motors without position sensor control. However, this method is only proposed for the condition without headwind and does not consider the optimization of the d and q axis current loops under headwind conditions, as well as the optimization of starting parameter values ​​for different headwind intensities.

[0005] In Computer Simulation (2012, VOL.29, NO.10), Meng Zhaojun et al. proposed a control method to improve the maximum starting torque and efficiency of permanent magnet synchronous motors. The method uses the maximum torque-current ratio control technology to improve the starting torque. However, this method is based on the permanent magnet synchronous motor having a position sensor for control. It only optimizes the d-axis and q-axis current loops for the case of rotor position angle closed-loop mode and constant current amplitude. When the permanent magnet synchronous motor of the wind turbine does not have a position sensor for control, this strategy to improve the starting torque is not suitable for switching between several modes of reverse wind starting. Summary of the Invention

[0006] The purpose of this invention is to provide a method for controlling the reverse wind start of a permanent magnet synchronous motor fan, in order to overcome the problems of excessive amplitude of the three-phase sinusoidal current that generates the active rotating magnetic field during the open-loop operation stage, the start-up failure caused by rotor vibration, and the start-up failure caused by insufficient phase current of the motor windings and insufficient electromagnetic torque.

[0007] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0008] A method for controlling the reverse-wind start-up of a permanent magnet synchronous motor fan involves first braking the fan when it rotates in the opposite direction under reverse wind drive, and then using a variable frequency vector control scheme to drive the fan from rest to rotation in the forward direction. This method includes four stages: braking mode, open-loop rotor position mode, open-loop to closed-loop rotor position switching mode, and closed-loop rotor position mode. The specific steps are as follows:

[0009] Apply brakes to the fan to stop it from rotating in the opposite direction, and measure the stator current amplitude i during the braking process. p_break ;

[0010] Based on the braking stator current amplitude i p_break Determine the peak value i of the motor winding phase current in open-loop operation mode. p_open Open-loop operating frequency f open Peak phase current i in rotor position closed-loop mode p_close ;

[0011] Based on the peak value of the phase current i in the motor winding p_open Open-loop operating frequency f open A three-phase sinusoidal current is generated in the motor windings to form an active rotating magnetic field, enabling the permanent magnet synchronous motor to operate in an open-loop mode with the rotor in the positive direction. The d-axis current i in the open-loop operation mode is calculated using the Clark and Park transformation formulas. d and q-axis current i q ;

[0012] The motor operates at the open-loop frequency f open After running for a period of time, it enters the rotor position open-loop to closed-loop switching mode. During the switching process, the vector control calculation angle gradually transitions from the angle generated by the open-loop operating frequency to the rotor position estimation angle. The peak value of the motor winding phase current changes from i p_open The phase current peak value i gradually decreases to the closed loop at the rotor position. p_close ;

[0013] After the rotor position open-loop to closed-loop switching mode is completed, it enters the rotor position closed-loop operation mode, based on the phase current peak value i. p_close Calculate the setpoints for the d-axis current regulator and the q-axis current regulator, and after entering the rotor position closed-loop operation mode, use the speed regulator to make the motor reach the given speed.

[0014] Furthermore, braking the wind turbine includes:

[0015] The three upper bridge arm power transistors of the three-phase power amplifier circuit are simultaneously disconnected, while the three lower bridge arm power transistors of the three-phase power amplifier circuit are simultaneously turned on. Any one phase winding of the three-phase winding of the permanent magnet synchronous motor will form a closed current loop with the other two phase windings through the power transistor connected to it. The motor rotor rotating under the headwind will operate as a generator. The current in the closed loop will generate a reversing torque on the motor rotor, which will brake the motor and stop it.

[0016] Furthermore, the stator current amplitude i during braking is detected. p_break include:

[0017] Detect the maximum and minimum values ​​of the first N current cycles in the phase current waveform, take the absolute values ​​of the maximum and minimum values, and then calculate the average of these values:

[0018]

[0019] Among them, i max_i i min_i These represent the maximum and minimum current values ​​in the i-th current cycle of the phase current during braking, respectively, and N represents the number of phase current cycles during braking.

[0020] Furthermore, based on the braking stator current amplitude i p_break Determine the peak value i of the motor winding phase current in open-loop operation mode. p_open Open-loop operating frequency f open Peak phase current i in rotor position closed-loop mode p_close Calculate using the following formula:

[0021] i p_open =ξ*i p_break

[0022] i p_close =ζ*i p_break

[0023]

[0024] In the above formula, according to i p_open i p_close with i p_break Calculated according to the principle of proportionality, ξ and ζ are respectively used to calculate i p_open i p_close Proportional coefficient; Open-loop operating frequency f open Changes and i p_break The trend of change is opposite, when i p_break An increase in f indicates an increase in headwind intensity, necessitating a reduction in the open-loop operating frequency. open Decrease, and conversely, when i p_break When f decreases openIncrease, i in the above formula p_break_max f open_min These represent the braking stator current amplitude and open-loop operating frequency of the system under the strongest headwind, respectively. open_max This indicates the open-loop operating frequency of the system when it starts without headwind.

[0025] Furthermore, based on the peak value i of the motor winding phase current... p_open Open-loop operating frequency f open The expression for generating a three-phase sinusoidal current in the motor windings is:

[0026]

[0027] Among them, i u i v i w These are the three-phase sinusoidal currents of the motor windings, and t is the time parameter.

[0028] Furthermore, in the open-loop operation mode at the rotor position, the d-axis current i in the open-loop operation mode is calculated using the CLARK transformation formula and the PARK transformation formula. d and q-axis current i q Combining the Clark transform and the Park transform, we have the following calculation formula:

[0029]

[0030] Among them, i d i q These are the d-axis current and the q-axis current, respectively, θ open θ is the angle generated by the open-loop operating frequency in the rotor position open-loop mode. open =2πf open t, f open t represents the open-loop operating frequency, and t represents the time parameter.

[0031] Furthermore, during the rotor position open-loop to closed-loop switching mode transition, the vector control calculation angle θ is generated by the open-loop operating frequency. open Gradually transition to rotor position estimation angle θ est The calculation formula is as follows:

[0032] θ(n)=θ open (n-1)+η(n)[θ est (n)-θ open (n-1)]

[0033]

[0034] Where θ(n-1) and θ(n) are the vector control angles for the (n-1)th and nth iterations, respectively.est (n) represents the rotor position estimation angle in the nth iteration; η represents the weighting coefficient for gradual transition, with a value range of η = 0 to 1, while η(n-1) and η(n) are the weighting coefficients for the (n-1)th and nth iterations, respectively, and Δη is the change in the weighting coefficient for each iteration.

[0035] Furthermore, during the switching process from open-loop to closed-loop rotor position switching mode, the peak value of the motor winding phase current changes from i p_open The peak phase current i gradually approaches the closed loop of the rotor position p_close This is achieved by controlling the setpoints of the d-axis current regulator and the q-axis current regulator, calculated using the following formula:

[0036]

[0037]

[0038] in, These are the given values ​​for the d-axis current regulator in the (n-1)th and nth iterations, respectively. The given values ​​for the q-axis current regulator in the (n-1)th and nth iterations are Δi, respectively. d , Δi q These represent the changes in d-axis and q-axis currents during each iteration. It is the d-axis current setpoint after the open-loop to closed-loop mode switch is completed. ρ is a proportionality coefficient, used to increase the starting torque during mode switching. It is the d-axis current setpoint after the open-loop to closed-loop mode switch is completed. The system is based on the given value and the actual current value i d i q The d-axis and q-axis currents are controlled by PI control respectively.

[0039] Furthermore, after the rotor position open-loop to closed-loop switching mode is completed, it enters the rotor position closed-loop operation mode, based on the phase current peak value i. p_close The inputs to the d-axis and q-axis current regulators are calculated using the maximum torque-to-current ratio algorithm, according to the following formula:

[0040]

[0041]

[0042] in, ψ represents the setpoint values ​​for the d-axis current regulator and the q-axis current regulator, respectively. f For permanent magnet flux linkage, L d L qThese are the d-axis and q-axis inductances, respectively.

[0043] Compared with existing technologies, the principles and advantages of this technical solution are as follows:

[0044] Due to the braking stator current amplitude i p_break It can not only measure the intensity of headwinds, but also the magnetic flux linkage ψ of the permanent magnet in a permanent magnet synchronous motor. f Proportional, therefore this technical solution is based on i p_break Determine the peak value i of the motor winding phase current in open-loop operation mode. p0 On the one hand, it can avoid the problem that the rotor may vibrate due to the excessive amplitude of the three-phase sinusoidal current that forms the active rotating magnetic field, which may lead to motor starting failure; on the other hand, it can avoid the problem that the torque generated by the insufficient phase current of the motor winding in the open-loop operation mode is not enough, which may prevent the motor from operating normally in the open loop.

[0045] Furthermore, this invention is based on i p_break Peak phase current i in closed-loop mode for determining rotor position p_close Then according to i p_close Calculate the given values ​​for the d-axis current loop and q-axis current loop, compared with the traditional d-axis current... Compared to other control schemes, d-axis current loop optimization can improve the starting torque of the motor during mode switching and enhance the ability to start against wind. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the services required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 Block diagram of a sensorless vector control system for a permanent magnet synchronous motor;

[0048] Figure 2 Circuit connection diagram of three-phase power amplifier circuit and permanent magnet synchronous motor (PMSM);

[0049] Figure 3 Waveform diagram of motor phase current when the fan is successfully started against the wind according to an embodiment of the present invention;

[0050] Figure 4 A partially enlarged view of the phase current during braking mode;

[0051] Figure 5 A partially enlarged view of the phase current when the rotor successfully starts against the wind and switches from open-loop to closed-loop position.

[0052] Figure 6 Waveform diagram of motor phase current when the fan fails to start against the wind according to an embodiment of the present invention;

[0053] Figure 7 A partially enlarged view of the phase current when the rotor fails to start against the wind and the position switches from open-loop to closed-loop mode. Detailed Implementation

[0054] The present invention will be further described below with reference to specific embodiments:

[0055] like Figure 1 The block diagram of the permanent magnet synchronous motor fan counter-wind start control system (existing) of this invention includes units such as dual-resistor sampling circuit, Clarke and PARK transformation, maximum torque-current ratio control (MTPA), speed loop, dq-axis current loop, PARK inverse transformation, position and speed estimation, SVPWM calculation, three-phase power amplifier circuit and permanent magnet synchronous motor (PMSM).

[0056] The method for controlling the reverse wind start of a permanent magnet synchronous motor fan described in this embodiment includes the following steps:

[0057] Apply brakes to the fan:

[0058] The three upper bridge arm power transistors of the three-phase power amplifier circuit are simultaneously disconnected, while the three lower bridge arm power transistors of the three-phase power amplifier circuit are simultaneously turned on. Any one phase winding of the three-phase winding of the permanent magnet synchronous motor will form a closed current loop with the other two phase windings through the power transistor connected to it. The motor rotor rotating under the headwind will operate as a generator. The current in the closed loop will generate a reversing torque on the motor rotor, which will brake the motor and stop it.

[0059] After the fan stops rotating in the opposite direction, the stator current amplitude i is detected during the braking process. p_ b rea k, specifically:

[0060] Detect the maximum and minimum values ​​of the first N current cycles in the phase current waveform, take the absolute values ​​of the maximum and minimum values, and then calculate the average of these values:

[0061]

[0062] Among them, i max_i i min_i These represent the maximum and minimum current values ​​in the i-th current cycle of the phase current during braking, respectively, and N represents the number of phase current cycles during braking.

[0063] Based on the braking stator current amplitude i p_break Determine the peak value i of the motor winding phase current in open-loop operation mode.p_open Open-loop operating frequency f open Peak phase current i in rotor position closed-loop mode p_close The calculation formula is as follows:

[0064] i p_open =ξ*i p_break

[0065] i p_close =ζ*i p_break

[0066]

[0067] In the above formula, according to i p_open i p_close with i p_break Calculated according to the principle of proportionality, ξ and ζ are respectively used to calculate i p_open i p_ c l ose Proportional coefficient; Open-loop operating frequency f open Changes and i p_break The trend of change is opposite, when i p_break An increase in f indicates an increase in headwind intensity, necessitating a reduction in the open-loop operating frequency. open Decrease, and conversely, when i p_break When f decreases open Increase, i in the above formula p_break_max f open_min These represent the braking stator current amplitude and open-loop operating frequency of the system under the strongest headwind, respectively. open_max This indicates the open-loop operating frequency of the system when it starts without headwind.

[0068] Based on the peak value of the phase current i in the motor winding p_open Open-loop operating frequency f open The expression for generating a three-phase sinusoidal current in the motor windings is:

[0069]

[0070] Among them, i u i v i w These represent the three-phase sinusoidal currents of the motor windings, and t is the time parameter.

[0071] This creates an active rotating magnetic field, enabling the permanent magnet synchronous motor to operate in an open-loop mode with the rotor in the positive direction. The d-axis current i in the open-loop mode is then calculated using the Clark and Park transformation formulas. d and q-axis current i q The calculation formula is as follows:

[0072]

[0073] Among them, i d i q These are the d-axis current and the q-axis current, respectively, θ open θ is the angle generated by the open-loop operating frequency in the rotor position open-loop mode. open =2πf open t, f open The open-loop operating frequency is t, and the time parameter is t.

[0074] The motor operates at the open-loop frequency f open After running for a set time, the rotor position switches from open-loop to closed-loop mode. During the switching process, the vector control calculation angle gradually transitions from the angle generated by the open-loop operating frequency to the rotor position estimation angle. The calculation formula is as follows:

[0075] θ(n)=θ open (n-1)+Θ(n)[θ est (n)-θ open (n-1)]

[0076]

[0077] Where θ(n-1) and θ(n) are the vector control angles for the (n-1)th and nth iterations, respectively. est (n) is the rotor position estimation angle of the nth iteration; η represents the weighting coefficient of the gradual transition, with a value range of η = 0 to 1, while η(n-1) and η(n) are the weighting coefficients of the (n-1)th and nth iterations, respectively, and Δη is the change value of the weighting coefficient in each iteration.

[0078] The peak phase current of the motor winding is determined by i p_open The phase current peak value i gradually decreases to the closed loop at the rotor position. p_close This is achieved by controlling the setpoints of the d-axis current regulator and the q-axis current regulator, calculated using the following formula:

[0079]

[0080]

[0081] in, These are the given values ​​for the d-axis current regulator in the (n-1)th and nth iterations, respectively. The given values ​​for the q-axis current regulator in the (n-1)th and nth iterations are Δi, respectively. d , Δi q These represent the changes in d-axis and q-axis currents during each iteration. It is the d-axis current setpoint after the open-loop to closed-loop mode switch is completed. ρ is a proportionality coefficient, used to increase the starting torque during mode switching. It is the d-axis current setpoint after the open-loop to closed-loop mode switch is completed. The system is based on the given value and the actual current value i d i q The d-axis and q-axis currents are controlled by PI control respectively.

[0082] After the rotor position open-loop to closed-loop switching mode is completed, it enters the rotor position closed-loop operation mode, based on the phase current peak value i. p_close The inputs to the d-axis and q-axis current regulators are calculated using the maximum torque-to-current ratio algorithm, according to the following formula:

[0083]

[0084]

[0085] in, ψ represents the setpoint values ​​for the d-axis current regulator and the q-axis current regulator, respectively. f For permanent magnet flux linkage, L d L q These are the d-axis and q-axis inductances, respectively.

[0086] After entering the rotor position closed-loop operation mode, the speed regulator enables the motor to reach the given speed.

[0087] In this embodiment, due to the braking stator current amplitude i p_break It can not only measure the intensity of headwinds, but also the magnetic flux linkage ψ of the permanent magnet in a permanent magnet synchronous motor. f Proportional, therefore this embodiment is based on i p_break Determine the peak value i of the motor winding phase current in open-loop operation mode. p0 On the one hand, this avoids the problem of excessive amplitude of the three-phase sinusoidal current forming the active rotating magnetic field, which could cause rotor vibration and lead to motor starting failure; on the other hand, it avoids the problem of insufficient torque generated by too small phase current in the motor windings during open-loop operation, preventing the motor from operating normally in open-loop mode. Furthermore, this embodiment is based on i p_break Peak phase current i in closed-loop mode for determining rotor position p_close Then according to i p_close Calculate the given values ​​for the d-axis current loop and q-axis current loop, compared with the traditional d-axis current... Compared to other control schemes, d-axis current loop optimization can improve the starting torque of the motor during mode switching and enhance the ability to start against wind.

[0088] To demonstrate the effectiveness of the solution described in this embodiment, the following experiment was conducted:

[0089] When the wind turbine motor is powered off, the oncoming natural wind drives the impeller to rotate in the opposite direction of normal operation. If the motor is powered on in this situation, it needs to be stopped first using some method, i.e., achieving reverse wind braking, before it can start normally. When the reverse wind is weak, the existing drive circuit of the permanent magnet synchronous motor can achieve reverse wind braking of the wind turbine without the need for additional hardware. For example... Figure 2 The following is an embodiment of the present invention. Figure 1 The system block diagram shows the circuit connections of the three-phase power amplifier circuit and the permanent magnet synchronous motor (PMSM), including the U-phase power transistors (Q1 / Q2), V-phase power transistors (Q3 / Q4), and W-phase power transistors (Q5 / Q6). When Figure 2 When the intermediate power transistors Q1, Q3, and Q5 are cut off while the power transistors Q2, Q4, and Q6 are turned on, any one of the three phase windings U, V, and W of the permanent magnet synchronous motor will form a closed current loop with the other two phase windings through the power transistor connected to it. In this way, the motor rotor rotating under the headwind will operate as a generator. The current in the closed loop generates a reversing torque on the motor rotor, which will brake the motor and stop it, thus realizing the headwind braking of the fan.

[0090] The following analysis uses the steady-state voltage equation and electromagnetic torque equation of the permanent magnet synchronous motor to examine the relationship between the amplitude of the braking stator current, the intensity of the headwind, and the performance of the permanent magnet synchronous motor in this invention.

[0091] The steady-state voltage equation of the permanent magnet synchronous motor in the rotor magnetic field-oriented synchronous rotating coordinate system is:

[0092]

[0093] The electromagnetic torque equation of a permanent magnet synchronous motor is:

[0094]

[0095] In equations (1) and (2), u d The output voltage of the d-axis current regulator, u q i is the output voltage of the q-axis current regulator. d i is the actual feedback value of the d-axis current. q The actual feedback value of the q-axis current; R is the stator resistance; L d L q ψ represents the inductance along the d and q axes, respectively; ω is the electric angular velocity of the motor, and ψ... f For permanent magnet flux linkage; p n This represents the number of pole pairs of the motor.

[0096] In braking mode, the steady-state voltage equation (1) can be written as follows:

[0097]

[0098] In equation (3) i d_break , iq_break The d-axis current and q-axis current are calculated separately under braking mode, and can be obtained from equation (3).

[0099]

[0100] From equation (4), the stator current i under braking mode can be obtained. break for:

[0101]

[0102] As can be seen from equation (5), when the motor speed ω against the wind is constant, the stator current i in braking mode is... break With the permanent magnet flux linkage ψ of the motor f Proportional to the corresponding stator current amplitude i p_break Also related to the magnetic flux linkage ψ of the permanent magnet in the motor f Proportional.

[0103] To investigate the relationship between the motor's speed ω in the face wind and the stator current amplitude i under braking mode. p_break Based on this relationship, the electromagnetic torque equation (2) is further transformed to obtain the motor braking torque equation under the headwind braking mode:

[0104]

[0105] For the same permanent magnet flux linkage ψ f When the speed ω of the motor against the wind is constant, the higher the speed ω of the motor against the wind, the greater the resistance torque of the motor against the wind, and the greater the braking torque required by the motor. It can be seen from equation (6) that the required stator current i break The larger the value, the greater the corresponding stator current amplitude i. p_break Also bigger.

[0106] like Figure 3 This is a waveform diagram of the motor phase current of a fan successfully starting against the wind according to an embodiment of the present invention. The rated speed of the fan is 2000 rpm, and the speed of the fan against the wind before power-on is 600 rpm. Figure 3 The motor phase current waveform includes four stages: braking mode, rotor position open-loop mode, rotor position open-loop to closed-loop switching mode, and rotor position closed-loop mode. The braking mode takes about 1.2 seconds, the rotor position open-loop mode takes about 5.5 seconds, and the rotor position open-loop to closed-loop switching mode takes about 0.65 seconds. After successful start-up, the system remains in rotor position closed-loop mode for the rest of the running time.

[0107] like Figure 4 yes Figure 3 A partially enlarged view of the phase current in the braking mode is shown in the figure. In this example, the maximum and minimum values ​​of the phase current in the first three cycles of the braking mode were measured.

[0108] i max_1 =6.3A,i max_2 =6.5A,i max_3 =6.4A

[0109] i min_1 =-8.5A,i min_2 =-6.5A,i min_3 =-6.3A

[0110] Take the absolute values ​​of the above maximum and minimum values, and then calculate the average of these values ​​to get i. p_break =6.75A. As shown in the figure, taking ξ = 0.85, we get i p_open ≈5.8A, taking ζ = 0.3, we get i p_close ≈2.1A.

[0111] like Figure 5 yes Figure 3 A partially enlarged view of the phase current during the open-loop to closed-loop switching mode of the rotor position. During this process, the peak value of the motor winding phase current changes from i... p_open =5.8A gradually decreases to the peak value i p_close =2.1A, Figure 5 It can be seen that the sinusoidal wave of the phase current is smooth and continuous, and the frequency of the phase current gradually increases during the switching process, proving that... Figure 3 The headwind start-up process was successful.

[0112] exist Figure 3 After the system enters the rotor position closed-loop mode, the phase current i of the motor... p_close ≈2.1A, using the Maximum Torque-to-Current Ratio (MPTA) algorithm, the corresponding given values ​​for the d-axis current loop and q-axis current loop are as follows:

[0113] like Figure 6 This is a waveform diagram of the motor phase current when the fan fails to start against the wind, according to an embodiment of the present invention. The fan speed against the wind is also 600 rpm. The obtained braking stator current amplitude i p_break Similarly, the peak phase current i selected by the control system in the open-loop mode of rotor position is... p_open Open-loop stable operating frequency f open and Figure 3 The scheme parameters are the same, but the d-axis current loop optimization scheme of this invention is not used in the rotor position open-loop to closed-loop switching mode and the rotor position closed-loop mode. Instead, the traditional d-axis current loop optimization scheme is used. The control scheme resulted in insufficient starting torque of the motor, leading to starting failure.

[0114] like Figure 7 yes Figure 6 A partially enlarged view of the phase current during the braking mode. Figure 7 The phase current sine wave exhibited fluctuations in amplitude and abrupt changes in frequency, indicating that the motor rotor was actually in a stalled state. Figure 6 The corresponding headwind start was unsuccessful.

[0115] contrast Figure 3 and Figure 6 It can be seen that the present invention is based on i p_break Determining the peak value of the motor winding phase current in open-loop operation mode can prevent the rotor from vibrating due to excessively large amplitude of the three-phase sinusoidal current that forms the active rotating magnetic field, leading to motor start-up failure. It also avoids the problem of insufficient torque due to insufficient phase current in the motor windings in open-loop operation mode, preventing normal open-loop operation. Simultaneously, based on i... p_close The method for optimizing the calculation of the given values ​​of the d-axis current loop and q-axis current loop is compared with the traditional method. Compared to other control schemes, this method can improve the starting torque of the motor during mode switching and enhance the ability to start against the wind.

[0116] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, any changes made in accordance with the shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for controlling the reverse-wind starting of a permanent magnet synchronous motor fan, characterized in that, When the fan rotates in the opposite direction under the drive of the wind, the fan is first braked, and then a variable frequency vector control scheme is used to drive the fan from a standstill to rotate in the forward direction. This includes four stages: braking mode, open-loop rotor position mode, open-loop to closed-loop rotor position switching mode, and closed-loop rotor position mode. The specific steps are as follows: Apply brakes to the fan to stop it from rotating in the opposite direction, and measure the stator current amplitude during the braking process. ; Based on the amplitude of the stator current during braking Determine the peak value of the motor winding phase current under open-loop operation mode Open-loop operating frequency Peak phase current in rotor position closed-loop mode ; Based on the peak value of the phase current of the motor winding Open-loop operating frequency Three-phase sinusoidal currents are generated in the motor windings, thereby forming an active rotating magnetic field. This enables the permanent magnet synchronous motor to operate in an open-loop mode with the rotor in the positive direction. The d-axis current in the open-loop mode is calculated using the Clark and Park transformation formulas. and q-axis current ; Motor at open-loop operating frequency After running for a set time, the rotor position enters the open-loop to closed-loop switching mode. During the switching process, the vector control calculation angle gradually transitions from the angle generated by the open-loop operating frequency to the rotor position estimation angle. The peak value of the motor winding phase current changes from... The phase current peak value gradually decreases to the closed-loop phase current at the rotor position. ; After the rotor position open-loop to closed-loop switching mode is completed, it enters the rotor position closed-loop operation mode, based on the phase current peak value. Calculate the setpoints of the d-axis current regulator and the q-axis current regulator, and after entering the rotor position closed-loop operation mode, use the speed regulator to make the motor reach the given speed; Detecting the stator current amplitude during braking. include: Detect the maximum and minimum values ​​of the first N current cycles in the phase current waveform, take the absolute values ​​of the maximum and minimum values, and then calculate the average of these values: ； in, , These represent the maximum and minimum current values ​​in the i-th current cycle of the phase current during braking, respectively, and N represents the number of cycles of the phase current during braking. Based on the amplitude of the stator current during braking Determine the peak value of the motor winding phase current under open-loop operation mode Open-loop operating frequency Peak phase current in rotor position closed-loop mode Calculate using the following formula: ； ； ； According to the above formula , and Calculated according to the principle of direct proportion , Calculate respectively , Proportional coefficient; Open-loop operating frequency Changes and The trend of change is opposite, when An increase indicates an increase in headwind intensity, necessitating a reduction in the open-loop operating frequency. Decrease, and vice versa When decreasing Increase, in the above formula , These represent the braking stator current amplitude and open-loop operating frequency of the system when subjected to the strongest headwind, respectively. This indicates the open-loop operating frequency of the system when it starts up without headwind. Vector control calculation angle during rotor position open-loop to closed-loop switching mode switching Angle generated by open-loop operating frequency Gradually transition to rotor position estimation angle The calculation formula is as follows: ； ； in, , These are the vector control angles for the (n-1)th and nth iterations, respectively. Estimate the angle for the rotor position in the nth iteration; The weighting coefficients represent the gradual transition, and their range of values ​​is... ,and , These are the weighting coefficients for the (n-1)th and nth iterations, respectively. This represents the change in the weighting coefficients during each iteration. During the switching process from open-loop to closed-loop rotor position switching mode, the peak value of the motor winding phase current changes from... The peak phase current as the rotor position closes This is achieved by controlling the setpoints of the d-axis current regulator and the q-axis current regulator, calculated using the following formula: ； ； in, , These are the given values ​​for the d-axis current regulator in the (n-1)th and nth iterations, respectively. , These are the given values ​​for the q-axis current regulator in the (n-1)th and nth iterations, respectively. , These represent the changes in d-axis and q-axis currents during each iteration. It is the d-axis current setpoint after the open-loop to closed-loop mode switch is completed. , This is a proportional coefficient, used to improve the starting torque during mode switching. It is the d-axis current setpoint after the open-loop to closed-loop mode switch is completed. The system is based on the given value , and actual current value , The d-axis and q-axis currents are controlled by PI control respectively.

2. The method for controlling the reverse wind start of a permanent magnet synchronous motor fan according to claim 1, characterized in that, Braking the wind turbine includes: The three upper bridge arm power transistors of the three-phase power amplifier circuit are simultaneously disconnected, while the three lower bridge arm power transistors of the three-phase power amplifier circuit are simultaneously turned on. Any one phase winding of the three-phase winding of the permanent magnet synchronous motor will form a closed current loop with the other two phase windings through the power transistor connected to it. The motor rotor rotating under the headwind will operate as a generator. The current in the closed loop will generate a reversing torque on the motor rotor, which will brake the motor and stop it.

3. The method for controlling the reverse wind start of a permanent magnet synchronous motor fan according to claim 1, characterized in that, Based on the peak value of the phase current of the motor winding Open-loop operating frequency The expression for generating a three-phase sinusoidal current in the motor windings is: ； in, These are the three-phase sinusoidal currents of the motor windings, and t is the time parameter.

4. The method for controlling the reverse wind start of a permanent magnet synchronous motor fan according to claim 1, characterized in that, The d-axis current in the open-loop operation mode at the rotor position is calculated using the CLARK transform formula and the PARK transform formula. and q-axis current Combining the Clark transform and the Park transform, we have the following calculation formula: ； in, , These are the d-axis current and the q-axis current, respectively. The angle generated by the open-loop operating frequency in the rotor position open-loop mode. , t represents the open-loop operating frequency, and t represents the time parameter.

5. The method for controlling the reverse wind start of a permanent magnet synchronous motor fan according to claim 1, characterized in that, After the rotor position open-loop to closed-loop switching mode is completed, it enters the rotor position closed-loop operation mode, based on the phase current peak value. The inputs to the d-axis and q-axis current regulators are calculated using the maximum torque-to-current ratio algorithm, according to the following formula: ； ； in, , These represent the setpoints for the d-axis current regulator and the q-axis current regulator, respectively. It is a permanent magnet flux linkage. , These are the d-axis and q-axis inductances, respectively.

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