WO2017214972A1

WO2017214972A1 - Device and method for stably stopping motor

Info

Publication number: WO2017214972A1
Application number: PCT/CN2016/086157
Authority: WO
Inventors: 刘军锋; 张东花; 徐铁柱
Original assignee: 深圳市英威腾电气股份有限公司
Priority date: 2016-06-17
Filing date: 2016-06-17
Publication date: 2017-12-21
Also published as: CN107005191A; CN107005191B

Abstract

Disclosed are a device and a method for stably stopping a motor. In this method, a first d-axis current reference value (id_ref1), a first q-axis current reference value (iq_ref1), and a first synchronous angle (Theta_fed) before a motor are stopped are set to be the initial values of a second d-axis current reference value (id_ref2), a second q-axis current reference value (iq_ref2) and a second synchronous angle (Theta_ref) for stopping the motor when stopping the motor. Moreover, when a normal control mode is changed to a stop braking mode, the d and q axes respectively use the same proportional integral controllers (4, 5), so that a severe current change and voltage change during the motor stopping are prevented, thereby smoothly stopping the motor without the occurrence of a pulsation or a reverse rotation of the motor before stopping.

Description

Apparatus and method for stably stopping a motor

Technical field

The present application belongs to the technical field of motor control, and more particularly to an apparatus and method for continuously rotating or swinging a motor shaft when the motor is stably stopped without stopping.

Background technique

Current methods for stopping the motor include an inverter down-conversion method, an inverter output direct current method, and a flux braking method.

The inverter down-conversion method means that when the inverter is used to drive the motor, the inverter reduces the output frequency by a certain slope, so that the frequency of the alternating current applied to the motor is gradually decreased. In this process, the generated torque is opposite to the direction of rotation of the motor. From the input end of the motor, the motor performs negative work, and the mechanical energy consumed during the stop process is fed back externally, thereby achieving motor shutdown. With this method, for a large inertia load or a fast stop, due to the strong inertia of the load, even if the output frequency is close to 0 Hz, the motor will rotate without stopping immediately.

The inverter output DC method means that when the motor is driven by the inverter, the inverter outputs a direct current to the motor in order to stop the motor quickly. When the motor is still rotating, a certain magnitude of direct current is injected into the stator winding of the motor to form a DC static magnetic field, and the rotating rotor cuts the static magnetic field to generate braking torque, thereby causing the motor to stop rapidly. With this method, the stop of the motor can be accelerated, but the magnitude of the braking torque is determined by the angle between the DC magnetic field strength and the stator/rotor magnetic field. Subject to the overcurrent capability of the inverter and the withstand capability of the motor, the DC current applied to the motor is limited, which determines that the DC field strength of the stator is limited. Therefore, for a very inertial motion load, a sufficient stator/rotor field angle is required to generate a sufficiently large braking torque. This means that during the stop process, there is a phenomenon that the rotor overshoots and then is pulled back, which is represented by the back and forth oscillation of the motor shaft.

The flux braking method refers to reducing the frequency while increasing the stator flux density of the motor. As the magnetic flux increases, a larger braking torque is generated, and the stopping process of the induction motor is accelerated. However, a larger stator excitation loss is also generated, which is converted into thermal energy, which causes the motor temperature to rise. Therefore, for frequent braking, the use of flux braking is limited.

Summary of the invention

According to an aspect of the present application, there is provided a device for stably stopping a motor (hereinafter referred to as a motor stabilizing stop device), comprising: a frequency command unit for generating a response to a rotational speed command to cause the motor to reach a desired rotational speed Operating frequency; a normally controlled axial and angular controller for generating a first q-axis current reference value and a first d-axis current reference value when the motor is in a normal control mode, and estimating the rotor of the motor a real-time position of the flux linkage to obtain a first synchronization angle; an axial and angular controller of the braking state for generating a second q-axis current reference value, the second d when the motor is in the brake stop mode a shaft current reference value and a second synchronization angle; a current reference value selection unit configured to respectively use the first q-axis current reference value and the first d-axis current reference value when the motor is in a normal control mode The final q-axis current reference value and the final d-axis current reference value output are also used to respectively use the second q-axis current reference value and the second d-axis current reference value when the motor is in the brake stop mode a final q-axis current reference value and the final d-axis current reference value output; a synchronization angle selection unit for outputting the first synchronization angle as a final synchronization angle when the motor is in a normal control mode, and also for The second synchronization angle is output as the final synchronization angle when the motor is in the brake stop mode; wherein the normal control mode corresponds to a normal operation period of the motor, and the operation is performed after receiving the motor stop command The frequency is gradually decreased by the set ramp and is greater than the stop frequency; the brake stop mode corresponds to the operating frequency being equal to the stop frequency and less than During off frequency.

According to another aspect of the present application, there is provided a method of achieving a stable stop of a motor using the aforementioned means.

According to the apparatus and method of the present invention for stably stopping the motor, when the motor is stopped, the first d-axis current reference value, the first q-axis current reference value, and the first synchronization angle are set to be used before the motor is stopped. The second d-axis current reference value, the second q-axis current reference value, and the initial value of the second synchronization angle that are stopped by the motor, and the normal ratio is changed to the stop brake mode d and the q-axis respectively use the same ratio The integral controller, thereby preventing a sharp current change and a voltage change during the stop of the motor, causes the motor to be smoothly stopped without occurrence of pulsation or reverse rotation of the motor and then stopping.

DRAWINGS

1 is a schematic structural view of a motor stabilizing stop device according to an embodiment of the present application;

2 is a schematic structural view of an inverter in the embodiment shown in FIG. 1;

3 is another schematic structural view of the inverter in the embodiment shown in FIG. 1;

4 is a schematic structural view of still another embodiment of the inverter in the embodiment shown in FIG. 1;

FIG. 5 is a schematic structural diagram of still another embodiment of the inverter in the embodiment shown in FIG. 1; FIG.

6 is another schematic structural view of the inverter in the embodiment shown in FIG. 1;

7 is another schematic structural view of the inverter in the embodiment shown in FIG. 1;

8 is a functional block diagram of a motor stabilization stop device according to an embodiment of the present application;

FIG. 9 is a schematic diagram showing changes in operating frequency, d-axis current reference, and q-axis current reference during normal control and stop of the motor according to an embodiment of the present invention.

detailed description

The present application will be further described in detail below with reference to the accompanying drawings.

Fig. 1 schematically shows the structure of a motor stabilizing stop device 100 according to an embodiment of the present application. In the motor stabilizing stop device 100 of an embodiment of the present application, the operation of the motor And two modes: normal control mode and brake stop mode. The normal control mode corresponds to a period during normal operation of the motor and a period in which the operating frequency is gradually decreased by a set ramp but greater than the stop frequency after receiving the motor stop command; the brake stop mode corresponds to the operating frequency reaching the stop frequency and less than the stop. Frequency during this period. That is to say, after receiving the motor stop command, when the operating frequency f_ref gradually decreases by the set ramp and is greater than the stop frequency, the motor operates in the normal control mode; when the operating frequency f_ref reaches the stop frequency and is less than the stop frequency, The motor operates in brake stop mode.

1, the motor stabilizing stop device 100 includes a three-phase AC power source 18, a rectifying unit 19, an inverter bridge unit 20, an inverter 22, and an electric motor 21, wherein the three-phase AC power source 18 passes through a rectifying unit 19 to convert an AC power source. For DC, and then through the inverter bridge unit 20, the output frequency and the amplitude adjustable voltage signal are driven to drive the motor 21. The method for stably stopping the motor proposed in the embodiment of the present application is almost realized and completed in the inverter 22, which generates a specific by a space vector PWM (pulse width modulation) unit 6 (see FIG. 7). The pulse train controls the inverter bridge unit 20, thereby enabling the motor to be stably stopped.

The three-phase AC power source 18 provides three-phase AC power to drive the motor 21.

The rectifying unit 19 receives the three-phase AC power supplied from the three-phase AC power source 18 and converts the received three-phase AC power into DC power.

The inverter bridge unit 20 receives the DC power supplied from the rectifying unit 19, and then generates a PWM voltage, which is a frequency and amplitude adjustable voltage, by using the power switching device in response to the PWM signal generated by the inverter 22.

The motor 21 generates a rotation power by a PWM voltage supplied from the inverter bridge unit 20. In one embodiment, the motor 21 can be an induction motor; in another embodiment, the motor 21 can also be a permanent magnet synchronous motor. This application does not limit the type of motor.

The inverter 22 is for generating a PWM signal for driving the motor 21. Since the inverter 22 is an important factor for controlling the steady stop of the motor 21, it will be described in more detail below.

Example 1:

As shown in FIG. 2, the inverter 22 in the motor stabilizing stop device of the present embodiment may include: a frequency command unit 1, a normally controlled axial and angular controller A, and an axial and angular controller B of a brake state. The current reference value selection unit 15 and the synchronization angle selection unit 17.

The frequency command unit 1 is operative to generate an operating frequency f_ref corresponding to the desired rotational speed in response to the rotational speed command.

The normally controlled axial and angular controller A is for generating a first q-axis current reference value iq_ref1 and a first d-axis current reference value id_ref1 when the motor is in the normal control mode, and estimating the rotor flux linkage of the motor 21 in real time. Position to get the first synchronization angle Theta_fed. Specifically, the normally controlled axial and angular controller A may include a speed PI controller and a normal control d-axis current generator, wherein the speed PI controller is configured to generate a first match with the load when the motor is in the normal control mode The q-axis current reference value iq_ref1; the normal control d-axis current generator is used to generate a first d-axis current reference value id_ref1 of the flux control current when the motor is in the normal control mode. Here, the d and q axes are coordinate axes. In order to obtain the control characteristics similar to DC motors, a coordinate system is established on the rotor of the motor. This coordinate system rotates synchronously with the rotor, taking the direction of the rotor magnetic field as the d-axis and perpendicular to the rotor magnetic field. The direction is the q-axis, and the mathematical model of the electrode is converted to this coordinate system, and the decoupling of the d-axis and the q-axis can be realized, thereby obtaining good control characteristics.

The axial and angular controller B of the braking state is for generating a second q-axis current reference value iq_ref2, a second d-axis current reference value id_ref2, and a second synchronization angle Theta_ref when the motor is in the brake stop mode. Specifically, the axial and angular controller of the braking state may include a brake q-axis current generator, a brake d-axis current generator, and a brake angle integrator. Wherein the brake q-axis current generator is configured to generate a second q-axis current reference value iq_ref2 when the motor is in the brake stop mode; the brake d-axis current generator is configured to generate the second d when the motor is in the brake stop mode The shaft current reference value id_ref2; the brake angle integrator is used to integrate the operating frequency when the motor is in the brake stop mode to generate a second synchronization angle Theta_ref.

The current reference value selection unit 15 is configured to output the first q-axis current reference value and the first d-axis current reference value as the final q-axis current reference value iq_ref and the final d-axis current reference value id_ref, respectively, when the motor is in the normal control mode. And when the motor is in the brake stop mode, the second q-axis current reference value and the second d-axis current reference value are respectively output as the final q-axis current reference value and the final d-axis current reference value.

The synchronization angle selection unit 17 is for outputting the first synchronization angle as the final synchronization angle Theta_e when the motor is in the normal control mode, and also for outputting the second synchronization angle as the final synchronization angle when the motor is in the brake stop mode.

According to the embodiment, when the motor is stopped, the first d-axis current reference value, the first q-axis current reference value, and the first synchronization angle before the motor is stopped are set as the second d-axis for the motor to stop. The current reference value, the second q-axis current reference value, and the initial value of the second synchronization angle, and the normal proportional control mode is changed to the stop braking mode. The d and q axes respectively use the same proportional integral controller, thereby preventing The sharp current change and the voltage change during the stop of the motor cause the motor to stop smoothly without pulsation or reverse rotation of the motor and then stop.

Example 2:

As shown in FIG. 3, the inverter 22 in the motor stabilizing stop device of the present embodiment includes the frequency command unit 1 of the first embodiment, the axial and angular controller A of the normal control, and the axial and angular angles of the brake state. Controller B, current reference value selection unit 15 and synchronization angle selection list In addition to the element 17, a q-axis current PI controller 4, a d-axis current PI controller 5, and a space vector pulse width modulation unit 6 are also included. Wherein, the q-axis current PI controller 4 is configured to generate a q-axis voltage reference value Uq_ref according to the final q-axis current reference value; the d-axis current PI controller 5 is configured to generate a d-axis voltage reference value according to the final d-axis current reference value. Ud_ref; space vector pulse width modulation unit 6 is for generating a drive pulse sequence supplied to the inverter unit 20 for driving the motor, and for magnetic based on the q-axis voltage reference value, the d-axis voltage reference value, and the final synchronization angle The two-phase stationary coordinate system of the chain observations has reference voltages U_alfa and U_beta.

Example 3:

As shown in FIG. 4, the inverter 22 in the motor stabilizing stop device of the present embodiment includes, in addition to the corresponding components of Embodiment 2, a rotor flux angle observation and velocity estimating unit 8 for stationary according to two phases. The reference voltage of the coordinate system and the currents i_alfa, i_beta in the two-phase stationary coordinate system estimate the real-time position of the rotor flux linkage of the motor and the real-time frequency f_fed of the mechanical axis of the motor, wherein the real-time position of the rotor flux linkage of the motor includes the first synchronization angle The real-time frequency of the mechanical shaft is fed back to form a closed loop control with the operating frequency.

Example 4:

As shown in FIG. 5, the inverter 22 in the motor stabilizing stop device of the present embodiment includes, in addition to the corresponding components of Embodiment 3, a three-phase-two-phase converting unit 7 for sampling the motor. The current ias, ibs of 21 is converted into currents i_alfa, i_beta in a two-phase stationary coordinate system, which is then supplied to the rotor flux angle observation and velocity estimating unit 8.

Example 5:

As shown in FIG. 6, the inverter 22 in the motor stabilizing stop device of the present embodiment includes, in addition to the corresponding components of the foregoing embodiments, a brake q-axis initial value setting unit 10 and a brake d-axis initial value. The setting unit 11 and the angle integrator initial value setting unit 16. The brake q-axis initial value setting unit 10 is configured to set the first q-axis current reference value to an initial value of the brake q-axis current generator when the motor is in the brake stop mode; the brake d-axis initial The value setting unit 11 is configured to set the first d-axis current reference value as an initial value of the brake d-axis current generator when the motor is in the brake stop mode; the angle integrator initial value setting unit 16 is configured to When the motor is in the brake stop mode, the first synchronization angle is set to the initial value of the brake angle integrator.

Example 6

As shown in FIG. 7, the inverter 22 in the motor stabilizing stop device of the present embodiment includes, in addition to the corresponding components of the foregoing embodiments, a rotary coordinate transformation unit 9 for combining two phases according to the final synchronization angle. The current in the stationary coordinate system is converted into currents id_fed and iq_fed in the rotating coordinate system, and further forms a current closed-loop control with the final d-axis current reference value and the final q-axis current reference value.

Based on the above embodiments, the present application further provides a motor stable stop method, the method comprising:

Providing a frequency command unit in response to the response speed command, generating an operating frequency f_ref corresponding to the motor to a desired speed;

When the motor is in the normal control mode, the first q-axis current reference value iq_ref1 and the first d-axis current reference value id_ref1 are generated, and the real-time position of the rotor flux linkage of the motor is estimated to obtain the first synchronization angle Theta_fed, and the first The q-axis current reference value and the first d-axis current reference value are respectively output as the final q-axis current reference value iq_ref and the final d-axis current reference value id_ref, and the first synchronization angle is output as the final synchronization angle Theta_e;

When the motor is in the brake stop mode, generating a second q-axis current reference value iq_ref2, a second d-axis current reference value id_ref2, and a second synchronization angle Theta_ref, and the second q-axis current reference value and the second d-axis current The reference value is output as the final q-axis current reference value and the final d-axis current reference value, respectively, and the second synchronization angle is output as the final synchronization angle.

In another embodiment, the method may further include:

According to the final q-axis current reference value, generating a q-axis voltage reference value Uq_ref;

According to the final d-axis current reference value, generating a d-axis voltage reference value Ud_ref;

A drive pulse sequence supplied to the inverter unit 20 for driving the motor and a two-phase stationary coordinate system reference voltage U_alfa for flux linkage observation are generated based on the q-axis voltage reference value, the d-axis voltage reference value, and the final synchronization angle , U_beta.

In still another embodiment, the method may further include: estimating the real-time position of the rotor flux linkage of the motor and the mechanical axis of the motor in real time according to the two-phase stationary coordinate system reference voltage and the currents i_alfa, i_beta in the two-phase stationary coordinate system. The frequency f_fed, the real-time position includes a first synchronization angle, and the mechanical shaft real-time frequency is fed back to form a rotational speed closed-loop control with the operating frequency.

In still another embodiment, the method may further include converting the current ias, ibs of the sampled motor into a current in a two-phase stationary coordinate system.

In still another embodiment, the method may further include: setting the first q-axis current reference value to an initial value of the brake q-axis current generator when the motor is in the brake stop mode, the first d The shaft current reference value is set to the initial value of the brake d-axis current generator, and the first synchronization angle is set as the initial value of the brake angle integrator.

In still another embodiment, the method may further include: converting the current in the two-phase stationary coordinate system to the currents id_fed, iq_fed in the rotating coordinate system according to the final synchronization angle, and further, with the final d-axis current reference value and The final q-axis current reference forms a current closed-loop control.

The motor stabilizing stop device having the above configuration will be described in detail below by way of an example. In this example, the inverter 22 may include a frequency command unit 1, a speed PI controller 2, a normal control d-axis current generator 3, a q-axis current PI controller 4, a d-axis current PI controller 5, and a space vector PWM unit. 6. Three-phase-two-phase transformation unit 7, rotor flux linkage angle observation and velocity estimation unit 8, rotational coordinate transformation unit 9, brake q-axis initial value setting unit 10, brake d-axis initial value setting unit 11, Braking q-axis current generator 12, brake d-axis current generator 13, braking angle integrator 14, current reference value selection unit 15, angle integrator initial value setting The unit 16 and the synchronization angle selection unit 17 are provided.

The function of the frequency command unit 1 is to generate an operating frequency f_ref corresponding to the required rotational speed in response to the rotational speed command.

The speed PI controller 2 is used to generate a first q-axis current reference value iq_ref1 that matches the load in the normal control mode (ie, before the operating frequency reaches the stop frequency).

The normal control d-axis current generator 3 is used to generate a first d-axis current reference value id_ref1 of the flux control current in the normal control mode (ie, before the operating frequency reaches the stop frequency).

The q-axis current PI controller 4 is used to generate a q-axis voltage reference value Uq_ref.

The d-axis current PI controller 5 is used to generate a d-axis voltage reference value Ud_ref.

The space vector PWM unit 6 is for generating a drive pulse sequence supplied to the driver unit 20 and two-phase stationary coordinate system reference voltages U_alfa and U_beta for flux linkage observation based on Ud_ref, Uq_ref and final synchronization angle Theta_e.

The three-phase-two-phase conversion unit 7 is for converting the currents ias and ibs of the sampled motor 21 into currents i_alfa and i_beta in a two-phase stationary coordinate system.

The rotation coordinate transformation unit 9 is configured to convert the currents i_alfa and i_beta in the two-phase stationary coordinate system into currents id_fed and iq_fed in the rotating coordinate system according to the final synchronization angle Theta_e, and further with the final d-axis current reference value id_ref, and finally q The shaft current reference value iq_ref forms a current closed loop control.

The rotor flux linkage angle observation and velocity estimating unit 8 is configured to estimate the real-time position of the motor rotor flux linkage according to the two-phase stationary coordinate system reference voltages U_alfa, U_beta and the two-phase stationary coordinate system currents i_alfa, i_beta, that is, the first synchronization Angle Theta_fed and the real-time frequency f_fed of the motor mechanical axis. The real-time frequency f_fed of the motor shaft and the operating frequency f_ref form a closed loop control of the speed.

The brake q-axis initial value setting unit 10 is configured to set the first q-axis current reference value iq_ref1 to an initial value of the brake q-axis current generator 12 when the motor is switched from the normal control mode to the brake stop mode. , for example, its initial value of integration;

The brake d-axis initial value setting unit 11 is configured to set the first d-axis current reference value id_ref1 to an initial value of the brake d-axis current generator 13 when the motor is switched from the normal control mode to the brake stop mode. For example, its integral initial value.

The brake q-axis current generator 12 is for generating a second q-axis current reference value iq_ref2 when the motor is in the brake stop mode.

The brake d-axis current generator 13 is for generating a second d-axis current reference value id_ref2 when the motor is in the brake stop mode.

The brake angle integrator 14 is configured to integrate the operating frequency f_ref when the motor is in the brake stop mode to generate a second synchronization angle Theta_ref;

The current reference value selection unit 15 is configured to select the first d-axis current reference value id_ref1 when the motor is in the normal control mode, and select the first d-axis current reference value id_ref1. Selecting the first q-axis current reference value iq_ref1, and when the motor is in the brake stop mode, the final d-axis current reference value selects the second d-axis current reference value id_ref2, and finally the q-axis current reference value selects the second q-axis current reference value Iq_ref2.

The angle integrator initial value setting unit 16 is configured to set the first synchronization angle Theta_fed to the initial value of the brake angle integrator 14 when the motor is switched from the normal control mode to the brake stop mode.

The synchronization angle selection unit 17 is for selecting the first synchronization angle Theta_fed when the motor is in the normal control mode, and selecting the second synchronization angle Theta_ref when the motor is in the brake stop mode.

According to an embodiment of the present application, the first d-axis current reference value id_ref1 outputted before the motor is stopped (corresponding to the normal control mode), the first q-axis current reference value iq_ref1, and the first synchronization angle Theta_fed, when the motor is stopped (corresponding to The brake stop mode) is set to the second d-axis current reference value id_ref2 for the motor stop, the second q-axis current reference value iq_ref2, and the initial value of the second synchronization angle Theta_ref. Also, when the normal control mode is switched to the stop brake mode, the same PI controller (proportional integral controller) is used for the d and q axes. Therefore, according to the embodiment of the present invention, the sharp current change and the voltage change during the stop of the motor are prevented, so that the motor is smoothly stopped without occurrence of pulsation or reverse rotation of the motor and then stopping.

Fig. 9 is a view showing the operation frequency, the d-axis current reference, and the q-axis current reference change in the normal control and stop of the motor in the method of stably stopping the motor by using the motor stabilizing stop device of an embodiment of the present application.

With respect to the apparatus for stably stopping the motor of the embodiment shown in Fig. 8, it can be seen from Fig. 9 that the motor is in the normal control mode before time t2, and the motor is in the brake stop mode at time t2 and thereafter. Wherein, at time t1 (corresponding to receiving the motor stop command) to t2 (corresponding to the operating frequency equal to the stop frequency), the inverter 22 is still operating in the normal control mode, but the operating frequency is gradually decreased according to the set slope, therefore, t1 The -t2 phase actually uses the frequency reduction method.

Specifically, at time 0-t1, the motor 21 operates normally, and the frequency command unit 1 outputs an operating frequency f_ref corresponding to the desired speed of the motor, at this time f_ref=f_run, the speed PI controller 2 and the normal control d-axis current generator 3 respectively generating a first q-axis current reference value iq_ref1 and a first d-axis current reference value id_ref1, and the current reference value selecting unit 15 selects and outputs the first q-axis current reference value iq_ref1 and the first d-axis current reference value id_ref1, which are synchronized. The angle selection unit 17 selects the output as the first synchronization angle Theta_fed;

At time t1 and time t1-t2, as described above, the inverter 22 is still operating in the normal control mode, and the final d, q-axis current reference value and final synchronization angle are the first d-axis and q-axis current reference values, respectively. The first sync angle.

At time t2, when the operating frequency reaches the stop frequency, ie f_ref=f_stop, brake q-axis The initial value setting unit 10 sets the first q-axis current reference value iq_ref1 as an initial value of the brake q-axis current generator 12, and the brake d-axis initial value setting unit 11 sets the first d-axis current reference value id_ref1 The initial value of the brake d-axis current generator 13 is set, and the angle integrator initial value setting unit 16 sets the first synchronization angle as the initial value of the brake angle integrator 14; after the time t2, the brake q-axis The current generator 12 generates a second q-axis current reference value iq_ref2, the brake d-axis current generator 13 generates a second d-axis current reference value id_ref2, and the brake angle integrator 14 generates a second synchronization angle Theta_ref; the current reference value selection unit 15 selects the output of the second q-axis current reference value iq_ref2 and the second d-axis current reference value id_ref2, and the synchronization angle selection unit 17 selects the output of the second synchronization angle Theta_ref, so when the operating frequency is less than the stop frequency, the inverter 22 forms a current closed-loop, frequency open-loop I/F control system, and the operating frequency is not directly zeroed, but gradually decreases with a smaller slope to ensure good follow-up of current control, so it can be controlled from normal Smooth switching from system mode to brake stop mode, no sharp jitter of voltage and current.

Next, in conjunction with Figs. 8 and 9, a method of causing the motor to be stably stopped by the foregoing apparatus in the embodiment of the present application is described, in which the motor is switched from the normal control mode to the process of stopping to the stop mode in the brake stop mode.

Before the stop frequency (ie, the stage before the time t1 in FIG. 9), the current reference value selection unit 15 selects the first d-axis current reference value id_ref1 and the first q-axis current reference value iq_ref1, that is, the final d-axis current reference value selection A d-axis current reference value id_ref1, the final q-axis current reference value selects the first q-axis current reference value iq_ref1; the synchronization angle selection unit 17 selects the first synchronization angle Theta_fed, that is, the final synchronization angle Theta_e selects the first synchronization angle Theta_fed. Therefore, a double closed loop control system in which the current closed loop control is an inner loop and the frequency closed loop control is an outer loop is formed. The drive motor 21 operates stably at the operating frequency and automatically adapts to changes in the load. At this stage, the operating frequency is f_run, the d-axis current is id_a, and the q-axis current is iq_a. Where f_run is the set operating frequency and id_a is the no-load excitation current of the motor. For permanent magnet synchronous motors, id_a can be 0, and iq_a is the torque current that is automatically adapted to the load during steady-state operation of the motor.

Referring to the time t1 in FIG. 9, the inverter 22 obtains a stop command, the operating frequency is gradually decreased with a set ramp, the control motor frequency and the rotational speed are gradually decreased, and is reduced to the stop frequency f_stop at time t2, preferably F_stop can be set to 3Hz.

At this time (corresponding to time t2), the brake d-axis initial value setting unit 11 sets the value id_a of the first d-axis current reference value id_ref1 to the initial value of the brake d-axis current generator 13, and sets the first q-axis. The value iq_a of the current reference value id_ref1 is set as the initial value of the brake q-axis current generator 12; the brake q-axis initial value setting unit 10 sets the first q-axis current reference value iq_ref1 to the brake q-axis current generation The initial value of the device 12; the angle integrator initial value setting unit 16 sets the value of the first synchronization angle Theta_fed as the initial value of the brake angle integrator 14. The brake d-axis current generator 13 generates a second d-axis current reference value id_ref2; the brake q-axis current occurs The controller 12 generates a second q-axis current reference value iq_ref2; the brake angle integrator 14 integrates the operating frequency f_ref to generate a second synchronization angle Theta_ref. Therefore, the current and the angle are not abruptly changed, and the sudden change of the output current and the output voltage is avoided, and the smooth switching from the normal control to the brake stop can be realized, and the current and the voltage are not sharply shaken.

When the motor is in the brake stop mode, the current reference value selection unit 15 selects the second d-axis current reference value id_ref2 and the second q-axis current reference value iq_ref2, that is, the final d-axis current reference value selects the second d-axis current reference value id_ref2 The final q-axis current reference value selects the second q-axis current reference value iq_ref2; the synchronization angle selection unit 17 selects the second synchronization angle Theta_ref, that is, the final synchronization angle Theta_e selects the second synchronization angle Theta_ref. Therefore, when the operating frequency is less than the stop frequency (i.e., after time t2), the inverter 22 forms a current closed loop, frequency open loop I/F (current/frequency) control system.

After time t2, the inverter 22 shifts to the stop braking mode, and the operating frequency is gradually decreased with a smaller slope to ensure good followability of the current control. The brake d-axis current generator 13 starts from its initial value id_a and remains unchanged to maintain the stabilization of the excitation current; the brake q-axis current generator 12 gradually increases from its initial value iq_a by a fixed slope. Reach iq_b at time t3, preferably

Wherein, I _motor is the rated current of the motor, I _{inverter_max} is the maximum current allowed by the inverter; the second synchronization angle Theta_ref starts from the initial value, and integrates the operation frequency f_ref for the space vector PWM unit 6 to generate the inverter bridge The drive pulse sequence of the unit 20, and the rotary coordinate transformation unit 9 obtain feedback currents id_fed and iq_fed for current closed-loop control.

At time t2 to t3, the inverter 22 controls the motor to gradually reduce the rotational speed with a sufficiently large output current, and since the output current can reach 2 times the rated current of the motor or the maximum current allowed by the inverter, even for a load with a large inertia. Or, in the case of rapid stop, it is also possible to output sufficient torque to stably reduce the motor speed to the operating frequency and greatly consume the rotational kinetic energy of the motor.

Since the kinetic energy of the motor has been greatly consumed at times t2 to t3. The brake q-axis current generator 12 starts from iq_b, gradually decreases by a fixed slope, and reaches iq_c at time t4, preferably

Where I _dc = (0.5 ~ 1.0) × min {I _motor , I _inverter }, I _inverter is the rated current of the inverter. Thereby, overheating of the inverter caused by long-time output of a large current is avoided. At the same time, the operating frequency f_ref is reduced to 0, and the second synchronization angle Theta_ref is obtained by performing the f_ref integral operation, and therefore, Theta_ref remains unchanged.

Therefore, starting from time t4, the inverter 22 outputs a direct current to the motor, the magnitude of which is I _dc .

From the time t4, until the time t5, the inverter 22 is switched to the DC braking mode to consume the remaining small kinetic energy of the motor so that the motor can be stably stopped without continuing to rotate or swing back and forth after the motor stops. Preferably, the time from t4 to t5 may be between several hundred milliseconds and several seconds, depending on the load inertia, the larger the inertia, the longer the time, the smaller the inertia and the shorter the time.

At time t5, the inverter 22 turns off the drive pulse sequence to the inverter bridge unit 20, and stops the braking process from being completed.

It can be seen that the motor stable stopping device and the method thereof according to the embodiments of the present application can realize smooth switching from normal control to braking stop, and can stably stop even for a fast stop or a load with a large inertia. It will not continue to rotate or swing back and forth after the motor stops, and the current and voltage changes smoothly during the whole stop process without violent jitter. Moreover, with the motor stopping method provided by the embodiment of the present application, it is only necessary to add a plurality of software modules capable of realizing the foregoing functions on the basis of the normal control system, so that the motor can be stably stopped, which is convenient for engineering implementation without increasing hardware cost. .

The invention has been described above with reference to specific examples, and is intended to be illustrative of the invention. Variations to the above-described embodiments may be made in accordance with the teachings of the present invention.

Claims

A device for stably stopping an electric motor (21), comprising:

a frequency command unit (1) for responding to the rotational speed command to generate an operating frequency (f_ref) corresponding to the motor to a desired rotational speed;

a normally controlled axial and angular controller for generating a first q-axis current reference value (iq_ref1) and a first d-axis current reference value (id_ref1) when the motor is in a normal control mode, and estimating the motor Real-time position of the rotor flux linkage to obtain a first synchronization angle (Theta_fed);

An axial and angular controller of the brake state for generating a second q-axis current reference value (iq_ref2), a second d-axis current reference value (id_ref2), and a second synchronization when the motor is in the brake stop mode Angle (Theta_ref);

a current reference value selection unit (15) for using the first q-axis current reference value and the first d-axis current reference value as final Q-axis current reference values (iq_ref) when the motor is in the normal control mode And a final d-axis current reference value (id_ref) output, further for using the second q-axis current reference value and the second d-axis current reference value as the final when the motor is in the brake stop mode a q-axis current reference value and the final d-axis current reference value output;

a synchronization angle selection unit (17) for outputting the first synchronization angle as a final synchronization angle (Theta_e) when the motor is in a normal control mode, and for using the motor when the motor is in the brake stop mode a second synchronization angle is output as the final synchronization angle;

Wherein the normal control mode corresponds to a normal operation period of the motor, and the operating frequency gradually decreases by a set ramp and is greater than a stop frequency after receiving the motor stop command; the brake stop mode corresponds to the operating frequency equal to The stop frequency and the period less than the stop frequency.
The apparatus of claim 1 wherein said normally controlled axial and angular controller comprises:

a speed PI controller (2) for generating the first q-axis current reference value that matches the load when the motor is in a normal control mode;

The d-axis current generator (3) is normally controlled for generating a first d-axis current reference value of the flux control current when the motor is in the normal control mode.
The apparatus of claim 1 wherein said axial and angular control of said braking condition comprises:

a brake q-axis current generator (12) for generating the second q-axis current reference value when the motor is in the brake stop mode;

a brake d-axis current generator (13) for generating the second d-axis current reference value when the motor is in the brake stop mode;

Brake angle integrator (14) for use when the motor is in the brake stop mode The operating frequency is integrated to generate the second synchronization angle.
The device of claim 1 further comprising:

a q-axis current PI controller (4) for generating a q-axis voltage reference value (Uq_ref) according to the final q-axis current reference value;

a d-axis current PI controller (5) for generating a d-axis voltage reference value (Ud_ref) according to the final d-axis current reference value;

a space vector pulse width modulation unit (6) for generating an inverter unit for driving the motor based on the q-axis voltage reference value, the d-axis voltage reference value, and the final synchronization angle The drive pulse sequence of (20) and the two-phase stationary coordinate system reference voltage (U_alfa, U_beta) for flux linkage observation.
The device of claim 4, further comprising:

a rotor flux linkage angle observation and velocity estimating unit (8) for estimating a rotor flux linkage of the motor based on the two-phase stationary coordinate system reference voltage and the current (i_alfa, i_beta) in the two-phase stationary coordinate system A real-time position and a mechanical shaft real-time frequency (f_fed) of the motor, the real-time position including the first synchronization angle, the mechanical shaft real-time frequency being fed back to form a rotational speed closed-loop control with the operating frequency.
The device of claim 5, further comprising:

A three-phase-two-phase conversion unit (7) for converting the current (ias, ibs) of the sampled motor into a current in the two-phase stationary coordinate system.
The device of claim 1 further comprising:

a brake q-axis initial value setting unit (10) for setting the first q-axis current reference value to an initial value of the brake q-axis current generator when the motor is in the brake stop mode ;

a brake d-axis initial value setting unit (11) for setting the first d-axis current reference value to an initial value of the brake d-axis current generator when the motor is in the brake stop mode ;

An angle integrator initial value setting unit (16) for setting the first synchronization angle to an initial value of the brake angle integrator when the motor is in the brake stop mode.
The device of claim 1 further comprising:

a rotating coordinate transformation unit (9) for converting a current in the two-phase stationary coordinate system into a current (id_fed, iq_fed) in a rotating coordinate system according to the final synchronization angle, and further to the final d-axis The current reference value and the final q-axis current reference form a current closed loop control.
A method for stably stopping a motor, comprising:

Providing a frequency command unit (1) in response to the response speed command to generate an operating frequency (f_ref) corresponding to the motor to a desired speed;

The first q-axis current reference value (iq_ref1) is generated when the motor is in the normal control mode. And a first d-axis current reference value (id_ref1), and estimating a real-time position of a rotor flux linkage of the motor to obtain a first synchronization angle (Theta_fed), and the first q-axis current reference value and the first a d-axis current reference value is output as a final q-axis current reference value (iq_ref) and a final d-axis current reference value (id_ref), respectively, and the first synchronization angle is output as a final synchronization angle (Theta_e);

When the motor is in the brake stop mode, generating a second q-axis current reference value (iq_ref2), a second d-axis current reference value (id_ref2), and a second synchronization angle (Theta_ref), and the second q-axis current a reference value and the second d-axis current reference value are respectively output as the final q-axis current reference value and the final d-axis current reference value, and the second synchronization angle is output as the final synchronization angle;

Wherein the normal control mode corresponds to a normal operation period of the motor, and the operating frequency gradually decreases by a set ramp and is greater than a stop frequency after receiving the motor stop command; the brake stop mode corresponds to the operating frequency equal to The stop frequency and the period less than the stop frequency.
The method of claim 9 further comprising:

Generating a q-axis voltage reference value (Uq_ref) according to the final q-axis current reference value;

Generating a d-axis voltage reference value (Ud_ref) according to the final d-axis current reference value;

Generating a drive pulse sequence for the inverter unit (20) for driving the motor, and for flux linkage, based on the q-axis voltage reference value, the d-axis voltage reference value, and the final synchronization angle Observed two-phase stationary coordinate system reference voltage (U_alfa, U_beta).
The method of claim 10, further comprising:

Determining the real-time position of the rotor flux linkage of the motor and the real-time frequency of the mechanical axis of the motor (f_fed) according to the two-phase stationary coordinate system reference voltage and the current (i_alfa, i_beta) in the two-phase stationary coordinate system. The real-time position includes the first synchronization angle, and the mechanical shaft real-time frequency is fed back to form a speed closed loop control with the operating frequency.
The method of claim 11 further comprising:

The sampled current (ias, ibs) of the motor is converted to a current in the two-phase stationary coordinate system.
The method of claim 9 further comprising:

Setting the first q-axis current reference value to an initial value of the brake q-axis current generator when the motor is in a brake stop mode, and setting the first d-axis current reference value to the An initial value of the brake d-axis current generator is set to an initial value of the brake angle integrator.
The method of claim 9 further comprising:

Converting the current in the two-phase stationary coordinate system to a current (id_fed, iq_fed) in a rotating coordinate system according to the final synchronization angle, and further, the final d-axis current reference value and the final q-axis current reference The value forms a current closed loop control.