Permanent magnet synchronous motor operation method and permanent magnet synchronous motor

Abstract

The invention discloses a permanent magnet synchronous motor operation method and a permanent magnet synchronous motor. The method comprises the following steps: injecting high-frequency pulsating voltage to obtain a high-frequency injection observation angle for motor control by extracting high-frequency current response; before the rotating speed of the motor reaches a first threshold value, starting a sliding-mode observer to obtain an observation angle under sliding-mode observation; when it is judged that the rotating speed of the motor reaches the first threshold value, the injection amplitude of the high-frequency voltage is linearly reduced, and the observation angle under sliding mode observation is used for motor control. The present disclosure mitigates jitter of a switching point by linearly reducing a high-frequency voltage injection amplitude during switching from a low speed to a high speed. Furthermore, speed regulation in a full speed range of the motor is planned, and signal injection and signal processing processes of switching from low speed to high speed and switching from high speed to low speed of the motor are designed, so that the motor can realize on-load smooth transition at a high-low speed switching point.

Description

Technical Field

[0001] The present disclosure relates to the field of motors, and in particular to a permanent magnet synchronous motor operation method and a corresponding permanent magnet synchronous motor. Background Art

[0002] In the process of controlling a permanent magnet synchronous motor (PMSM), in order to obtain the maximum torque output throughout the entire control cycle, FOC (Field-Oriented Control) is often used to control the motor. Both Park transformation and inverse Park transformation in FOC control require the knowledge of the rotor position θ. The closer the detected rotor position θ is to the actual position, the closer the torque output in the control process is to the maximum torque output.

[0003] In some applications, it is necessary to realize position detection and motor control without sensors. Since low-speed and medium-high-speed position detection use different detection methods, the process of motor speed change involves the switching of position detection methods. In the prior art, only the conversion from low speed to high speed is involved, and there is motor jitter at the switching point.

[0004] Therefore, an improved permanent magnet synchronous motor position detection scheme is needed. Summary of the invention

[0005] A technical problem to be solved by the present disclosure is to provide a permanent magnet synchronous motor operation method and a permanent magnet synchronous motor. Specifically, the present disclosure proposes a method of using high-frequency injection position observation at low speed and a sliding mode observer position observation at high speed, and linearly reducing the high-frequency voltage injection amplitude in the switch from low speed to high speed to reduce the jitter of the switching point. Furthermore, the present disclosure also plans the full speed range speed regulation of the motor, designs the signal injection and signal processing process for the motor to switch from low speed to high speed and from high speed to low speed, so that the motor can achieve a smooth transition with load at the high and low speed switching point.

[0006] According to a first aspect of the present disclosure, a permanent magnet synchronous motor operation method is provided, comprising: injecting a high-frequency pulsating voltage to obtain a high-frequency injection observation angle for motor control by extracting a high-frequency current response; before the motor speed reaches a first threshold, turning on a sliding mode observer to obtain an observation angle under sliding mode observation; when it is determined that the motor speed reaches the first threshold, linearly reducing the injection amplitude of the high-frequency voltage, and using the observation angle under sliding mode observation for motor control.

[0007] Optionally, the method further comprises: in the process of the injection amplitude of the high-frequency voltage linearly decreasing to zero, obtaining a low-frequency response current of the injected high-frequency voltage for current loop operation.

[0008] Optionally, in the process of linearly decreasing the injection amplitude of the high-frequency voltage to zero, obtaining the low-frequency response current of the injected high-frequency voltage for current loop operation includes: in the process of linearly decreasing the injection amplitude of the high-frequency voltage to zero, recording the response current when the d-axis injection voltage passes through the zero point; and calculating the average value of the response currents of adjacent zero-crossing points as the low-frequency response current for current loop operation.

[0009] Optionally, the method also includes: when the motor speed is not less than a first threshold, using the observation angle under the sliding mode observation for motor control; when it is determined that the motor speed drops to a second threshold, linearly increasing the injection amplitude of the high-frequency voltage, wherein the second threshold is less than the first threshold; and after the injection amplitude of the high-frequency voltage increases to a predetermined amplitude, using the high-frequency injection observation angle for motor control.

[0010] Optionally, the method further comprises: after the injection amplitude of the high-frequency voltage increases to reach the predetermined amplitude, closing the sliding mode observer.

[0011] Optionally, the method further comprises: in the process of the injection amplitude of the high-frequency voltage linearly increasing from zero to the predetermined amplitude, obtaining a low-frequency response current of the injected high-frequency voltage for current loop operation.

[0012] Optionally, the method further includes: when the injection amplitude of the high-frequency voltage increases to reach the predetermined amplitude, using the observation angle under sliding mode observation at the current high-speed to low-speed switching moment as the initial high-frequency injection observation angle at the high-speed to low-speed switching moment.

[0013] Optionally, the method further comprises: when the injection amplitude of the high-frequency voltage increases to reach the predetermined amplitude, using the sliding mode observer PI integral value as the initial speed at the moment of switching from high speed to low speed of the high-frequency voltage injection.

[0014] Optionally, when the injection amplitude of the high-frequency voltage increases to reach the predetermined amplitude, using the sliding mode observer PI integral value as the initial speed at the moment of switching from high speed to low speed of the high-frequency voltage injection includes: collecting n sliding mode observer PI integral values ​​before the injection amplitude of the high-frequency voltage increases to reach the predetermined amplitude; and calculating the average value of the n sliding mode observer PI integral values ​​as the initial speed at the moment of switching from high speed to low speed of the high-frequency voltage injection.

[0015] Optionally, before the step of injecting a high-frequency pulse voltage to extract a high-frequency current response to obtain a high-frequency injection observation angle for motor control, it also includes: starting the motor, identifying the initial position of the motor and determining the rotor polarity of the motor.

[0016] According to a second aspect of the present disclosure, a permanent magnet synchronous motor operation method is provided, including: injecting a high-frequency pulsating voltage to obtain a high-frequency injection observation angle for motor control by extracting a high-frequency current response; when the motor speed reaches a first threshold, switching from high-frequency voltage injection observation to sliding mode observation; when the motor speed is not less than the first threshold, using the observation angle under the sliding mode observation for motor control; when it is determined that the motor speed drops to a second threshold, switching from the sliding mode observation to the high-frequency voltage injection; and when the motor speed is less than the second threshold, using the high-frequency injection observation angle for motor control, wherein the second threshold is less than the first threshold.

[0017] Optionally, during the process of the motor speed decreasing from above the first threshold to the second threshold, the observation angle under the sliding mode observation is used for motor control; and during the process of the motor speed increasing from below the second threshold to the first threshold, the high-frequency injection observation angle is used for motor control.

[0018] Optionally, in the switching from the high-frequency voltage injection to the sliding mode observation, the injection amplitude of the high-frequency voltage injection is linearly reduced from a predetermined amplitude to zero; and in the switching from the sliding mode observation to the high-frequency voltage injection, the injection amplitude of the high-frequency voltage injection is linearly increased from zero to the predetermined amplitude.

[0019] According to a third aspect of the present disclosure, a permanent magnet synchronous motor is provided, comprising: a motor; a magnetic oriented vector control module for controlling the motor, and comprising: a high-frequency injection observer for injecting a high-frequency pulse voltage to obtain a high-frequency injection observation angle by extracting a high-frequency current response; a sliding mode observer for performing a sliding mode observation to obtain an observation angle under the sliding mode observation; and a switching module for executing the method as described in the first aspect or the second aspect to use the high-frequency injection observation angle or the observation angle under the sliding mode observation for motor control.

[0020] Therefore, the operating scheme of the present disclosure can especially reduce the jitter of the switching point by linearly reducing the high-frequency voltage injection amplitude when switching from low speed to high speed. Furthermore, the low-frequency current can be conveniently obtained by recording the peak voltage when the voltage passes through zero point to avoid the use of filters and reduce the amount of calculation. The present disclosure also designs the switching from high speed to low speed, and avoids motor loss of control caused by continuous switching by setting a switching point with a lower speed than the switching point from low speed to high speed. Furthermore, when switching from high speed to low speed, the present disclosure also assigns an initial value to the high-frequency voltage injection PI integral value at the time of switching from high speed to low speed by using the sliding mode observation angle and / or the sliding mode observer PI integral value to achieve instantaneous convergence of the high-frequency injection and a smooth speed reduction conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components in the exemplary embodiments of the present disclosure.

[0022] Figure 1 The schematic diagram of FOC control for PMSM is shown.

[0023] Figure 2 shows the real d-axis vs. injected voltage Graph of the angles between the axes.

[0024] Figure 3 An example of position detection based on high frequency injection is shown.

[0025] Figure 4 An example of position detection based on sliding mode observation is shown.

[0026] Figure 5 A schematic diagram of the sliding mode observer observation angle and the high-frequency injection observation angle when the motor rotates at a low speed is shown.

[0027] Figure 6 A schematic flow chart of a method for operating a permanent magnet synchronous motor according to an embodiment of the present disclosure is shown.

[0028] Figure 7 An example of changes in the observation angle and the dq-axis voltage when switching is performed according to the operating method of the present invention is shown.

[0029] Figure 8 The schematic diagram of the two-point average current filtering method is shown.

[0030] Fig. 9 A comparison chart before and after the two-point average current filtering method is shown.

[0031] Fig.10 A specific operation flow when switching from low speed to high speed is shown.

[0032] Fig.11 A schematic diagram showing a dual switching point setting from low speed to high speed and from high speed to low speed according to an embodiment of the present disclosure is shown.

[0033] Fig.12 An example of changes in the observation angle and the dq-axis voltage when switching is performed according to the operating method of the present invention is shown.

[0034] Fig.13 A simulation example of the observation angle and dq-axis voltage changes when high-frequency voltage injection is used directly for observation at the end of switching is shown.

[0035] Fig.14 An enlarged view of the sliding mode observation angle and time near the end switching moment is shown.

[0036] Fig.15 The specific switching process between the high-frequency injection observer and the sliding mode observer is shown.

[0037] Fig.16 A schematic flow chart of a method for operating a permanent magnet synchronous motor according to an embodiment of the present invention is shown.

[0038] Fig.17 A schematic diagram of the composition of a FOC module of a permanent magnet synchronous motor according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0040] In the control process of permanent magnet synchronous motor (PMSM), in order to obtain the maximum torque output in the entire control cycle, FOC (magnetic oriented vector control) is often used to control the motor. Figure 1 The schematic diagram of FOC control for PMSM is shown.

[0041] As shown in the figure, a position sensor such as a magnetic encoder obtains the rotor speed n and the rotor position θ of the motor M. In practical applications, for example, a speed reference n obtained based on user input ref The difference is made with the rotor speed n obtained and is input into the PID 1 (i.e., speed loop PID). The output of the speed loop PID is the q-axis reference current i qref For simplicity, when weak magnetic control is not performed, the d-axis reference current i dref = 0. At this time, the reference current i of the q-axis and d-axis can be qref and i dref The q-axis and d-axis current i of the motor are actually fed back q and i d Make a difference and pass through PID 2 (i.e., q-axis current loop) and PID 3 (i.e., the d-axis current loop) outputs the q-axis and d-axis voltages V after adjustment. d and V q , and then converted into α-axis and β-axis voltage V through Park inverse transformation α and Vβ , and then through SVPWM (space voltage vector modulation) to obtain the three-phase voltage V a 、V b 、V c , and then drives the motor M to rotate through the three-phase inverter bridge. In FOC control, the three-phase current i is obtained through the sampling resistor a 、i b 、i c , after Clark transformation, we get the α-axis and β-axis current i α and i β , and then the feedback d-axis and q-axis currents i are obtained through Park transformation d and i q , enter PID 2 and PID 3 Participate in current loop control.

[0042] In addition, in many cases, the motor needs to be weakly controlled, that is, the d-axis reference current i dref ≠0. At this time, the MTPA control strategy can be used to optimally control the permanent magnet synchronous motor, especially the salient pole PMSM in the constant torque region. Specifically, the MTPA (Maximum Torque Per Ampere, maximum torque current ratio control) control strategy is an optimal control strategy for the constant torque region of FOC control. Using this strategy, the maximum electromagnetic torque can be output while using the same current; similarly, the current required can be minimized while outputting the same torque. When using the MTPA control strategy, you can 1 (ie, speed loop PID) obtains the q-axis reference current i qref , sent to the MTPA control module to output the optimized d-axis reference current i dref .

[0043] Regardless of whether the MTPA control strategy is implemented, in FOC control, Park transform and Park inverse transform, such as Figure 1 As shown, all of them need to be carried out under the condition of rotor position θ (that is, the electrical angle θ of the motor rotor. The motor rotor rotates one electrical cycle of 360°, so the value range of the vertical axis position (θ) in the following position-time figure is 0°~360°), and the closer the detected rotor position θ is to the actual position, the closer the torque output in the control process is to the maximum torque output.

[0044] Position detection is generally divided into sensor position detection and sensorless position detection. Sensor position detection generally includes Hall sensor position detection and encoder position detection. This detection method is achieved by installing a Hall sensor or a magnetic encoder on the motor. Figure 1The rotor position and speed detection module in the controller can be realized by a magnetic encoder.

[0045] However, in some applications, for example, due to cost or integration considerations, it is necessary to achieve position detection and motor control without sensors. Sensorless detection generally includes position detection methods such as sliding mode observer position detection, Lumberg observer position detection, and high-frequency injection position detection. Among them, the sliding mode observer and Lumberg observer observe the rotor position information based on the motor back electromotive force model. The back electromotive force of the motor is small during static and low-speed operation, and it is not easy to observe the rotor position. Therefore, the sliding mode observer and Lumberg observer are suitable for medium and high-speed position observation. Pulse high-frequency injection injects a pulse voltage signal into the d-axis and detects the high-frequency current response of the q-axis to detect the rotor position. This method does not depend on the motor back electromotive force and is only related to the high-frequency response current. It is suitable for static and low-speed position observation.

[0046] In order to facilitate the understanding of the principles of the present disclosure, the theoretical basis of the operation of the present disclosure will be explained as follows. Figure 2 shows the real d-axis vs. injected voltage The angle relationship diagram between the axes. Here, the α axis and the β axis are the rectangular coordinate axes established on the motor stator. The d axis and the q axis are the coordinate axes of the rotor. Let the angle between the real d axis and the α axis be θ r , the injected voltage The angle between the axis and the α axis is The difference between the two is Δθ r .

[0047] First, based on Figure 3 Equations (1) to (5) describe the principle of high frequency injection position detection. Specifically, Figure 3 An example of position detection based on high frequency injection is shown.

[0048] The following will be combined Figure 3 Taking pulsed high-frequency injection as an example, the specific implementation process of high-frequency injection is described. Figure 3 As shown, a voltage U can be injected into the d-axis m cos(ω i t), where U m is the injected signal amplitude, ω i is the angular frequency of the injected signal. The q-axis high-frequency current response iq obtained in this way will contain the component of the rotor position information θ. By bandpass filtering (BPF) the q-axis current, modulation (with sin(ω it) and then pass through a low-pass filter (LPF) and a PI regulator to obtain the rotor speed n, and then the rotor speed n can be integrated (I) to obtain the rotor position θ. Here, the rotor position θ obtained by high-frequency injection observation can also be called the high-frequency injection observation position, or the high-frequency injection observation angle, or the observed d-axis direction (that is, In addition, it should be understood that in addition to the pulse high-frequency injection shown in the figure, square wave high-frequency injection can also be performed.

[0049] When high-frequency injection is used to observe the rotor position angle, due to various reasons, the observed angle may be equal to the real angle, or it may be opposite to the real angle (180° difference). For this reason, when using high-frequency injection to observe the rotor position, especially when the motor is started, it is necessary to determine the polarity of the rotor, that is, to determine whether the real d-axis direction (or the real rotor angle) is the observed angle or the direction that differs from the observed angle by 180°. For example, the existing square wave high-frequency injection polarity judgment can be adopted in the observed d-axis direction (that is, The positive and negative voltages are injected into the rotor shaft. Based on the saturated salient pole effect, the magnitude of the current response obtained by injecting the positive and negative voltages is determined, and the polarity of the rotor is determined. Figure 3 The example shown also includes an initial position polarity judgment module.

[0050] The voltage model of IPMSM (Interior PMSM, i.e. built-in PMSM) on the dq coordinate axis is:

[0051]

[0052] Where U d , U q is the voltage on the dq axis, i d 、i q is the current on the dq axis, ω r is the rotor electrical angular velocity, ψ f is the rotor permanent magnet flux, L d and L q is the inductance on the dq axis, R s is the stator resistance.

[0053] Since the real dq position cannot be obtained, in fact, the observed A high-frequency pulse voltage signal is injected into the coordinate system, and the injected high-frequency signal is:

[0054]

[0055] In the formula, |U i | is the amplitude of the high-frequency signal, ω i is the high frequency signal frequency.

[0056] Furthermore, the observed The high frequency response current in the coordinate system is:

[0057]

[0058] In the formula θ r is the true rotor position, To observe the rotor position. is the difference between the true rotor position and the observed rotor position.

[0059] Due to the actual control process of the motor, the observation The coordinate system contains not only high-frequency response current but also low-frequency current. The high-frequency response current is used to observe the rotor position, and the low-frequency response current is used to drive the motor to rotate. Therefore, a filtering method is required to extract the high-frequency response current.

[0060]

[0061] High frequency response current After modulation and low-pass filtering, we get:

[0062]

[0063] Among them, ε θ is the angular error, ε θ Get the rotor speed through the PI link Rotor speed After the integration link, the rotor observation position is obtained like Figure 3 shown.

[0064] As above combined Figure 3 Equations (1) to (5) describe the principle of high frequency injection position detection. Figure 4 Equations (6) to (8) describe the working principle of the sliding mode observer. Figure 4 An example of position detection based on sliding mode observation is shown. Sliding mode observation reconstructs the back electromotive force of the motor through the voltage and current of the motor stator coordinate system. The back electromotive force of the motor contains the electrical angle and electrical angular velocity information of the motor rotor. The observer can work based on real and accurate voltage and current.

[0065] Therefore, the voltage equation of IPMSM on the αβ coordinate axis can be transformed into:

[0066]

[0067] Where: i α 、i β is the current on the αβ axis, u α、u β is the voltage on the αβ axis, E α and E β is the back electromotive force on the αβ axis, where

[0068] The sliding mode observer observes E α and E β , so the classic sliding mode observer can be constructed according to formula (6):

[0069]

[0070] in is the estimated value, u smoα 、u smoβ is the sliding mode control law and is the control input of the sliding mode observer.

[0071] Using equation (7) and equation (6) as a difference, we get:

[0072]

[0073] In the formula, Control Law Among them, K α , K β is the sliding mode gain,

[0074] By putting E α and E β The introduction of the phase-locked loop structure enables the system to stabilize after it reaches the sliding surface. Then you can use u smoα 、u smoβ Complete the observation of the rotor position.

[0075] Although the sliding mode observation is highly robust and has little disturbance to the system, it cannot be used at low speeds because the back EMF is induced by the moving rotor on the motor stator. In other words, in order to perform position observation at all speeds, it is necessary to use the high-frequency injection observation as described above at low speeds, combined with the sliding mode observation used at medium and high speeds, which involves switching between high-frequency injection observation and sliding mode observation.

[0076] When the motor rotates under high-frequency injection observation, the sliding mode observer can also be in operation. Since the sliding mode observer observes the rotor position through the voltage signal and current signal on the αβ coordinate axis (stationary coordinate system), the sliding mode observer can still observe the rotor position normally when the motor is in the high-frequency injection closed-loop control process. Figure 5The diagram shows the observation angle of the sliding mode observer and the high-frequency injection observation angle when the motor rotates at a low speed. In the figure, the HFI angle refers to the high-frequency injection observation angle, and the SMO angle refers to the sliding mode observation angle. In the example shown in the figure, the motor is at a low speed of 200r / min, and the position is observed by high-frequency voltage injection. As shown in the figure, due to the injection of high-frequency voltage signals, the current of the αβ coordinate axis has a high-frequency component, which causes a large jitter in the angle observed by the sliding mode observer.

[0077] Since the sliding mode observer is used to observe the speed and position, the injected high-frequency voltage signal is an interference signal for the control process. Therefore, when the motor reaches the threshold speed and needs to switch from high-frequency injection observation to sliding mode observation, if the high-frequency voltage signal is directly removed, the motor will vibrate greatly due to the sudden change of the operating conditions, which is not conducive to actual control. Therefore, the present disclosure proposes a motor control method that linearly reduces the amplitude of the injected signal.

[0078] Figure 6 A schematic flow chart of a method for operating a permanent magnet synchronous motor according to an embodiment of the present disclosure is shown. Figure 7 An example of changes in the observation angle and the dq-axis voltage when switching is performed according to the operating method of the present invention is shown.

[0079] In step S610, a high-frequency pulse voltage is injected to obtain a high-frequency injection observation angle for motor control by extracting a high-frequency current response. At this time, the motor is rotating at a low speed and the back electromotive force is small, so the high-frequency voltage injection method can be used to observe the angle more accurately. Specifically, it can be as follows Figure 3 As shown, the high-frequency injection observation angle is obtained by injecting voltage into the d-axis and from the high-frequency current response of the q-axis for motor control.

[0080] Furthermore, due to the above combination Figure 4As shown, the observation of the sliding mode observer takes some time to stabilize to the sliding mode surface. At the same time, since the high-frequency injection observer is a closed-loop observer (the high-frequency injection observer is only effective when the angle and speed of the high-frequency injection observer participate in the closed-loop control), it cannot be in the open-loop mode (the angle and speed of other observers participate in the closed-loop control, and the high-frequency injection observer cannot observe the angle and speed). Therefore, when the high-frequency injection is used for position observation, the sliding mode observer can observe but does not participate in the closed-loop control. To this end, in step S620, before the motor speed reaches the first threshold (for example, 900r / min in the following example), the sliding mode observer can be turned on to obtain the observation angle under the sliding mode observation. Specifically, the sliding mode observation of the sliding mode observer can be turned on when, for example, the motor speed reaches a certain speed lower than the first threshold, or after the motor completes the initial startup. The present disclosure does not limit the observation start time of the sliding mode observer, as long as the initial convergence of the sliding mode surface is completed at the "start switching time" (although it is still jittering due to the high-frequency injection interference).

[0081] Then, in step S630, when it is determined that the motor speed reaches the first threshold, the injection amplitude of the high-frequency voltage is linearly reduced, and the observation angle under the sliding mode observation is used for motor control. When the motor speed reaches the set first threshold speed, for example, when the motor gradually accelerates from startup to the first threshold of 900r / min, the high-frequency injection observer is switched to the sliding mode observer.

[0082] Before the step of injecting a high-frequency pulse voltage to extract a high-frequency current response to obtain a high-frequency injection observation angle for motor control, the method further includes: starting the motor, identifying the initial position of the motor and determining the rotor polarity of the motor. In other words, Figure 6 The switching method shown is an operation after the motor startup process, corresponding to, for example, the following combination Fig.15 Describes the operations of Phase 3 and beyond.

[0083] Since the injection amplitude of the high-frequency voltage decreases linearly, the high-frequency signal decreases from the predetermined amplitude |U i | (i.e., the amplitude during conventional high-frequency injection) is reduced to zero. Here, the moment when the motor reaches the first threshold speed, such as 900r / min, can be regarded as Figure 7 The "start switching moment" shown in the figure is regarded as the "end switching moment", and the moment when the amplitude of the high-frequency injection signal decreases to zero is regarded as the "end switching moment". Since the observation angle cannot be accurately estimated once the amplitude of the high-frequency injection signal changes, and as mentioned above, the sliding mode observer has been working for a period of time, the angle and speed can be switched directly at the "start switching moment". That is, the angle observed by the sliding mode observer and the speed obtained by the PI loop are used instead to perform related operations of FOC.

[0084] Although the angle (and the angle error obtained from it, and the speed obtained by integrating the angle error) has been observed under the sliding mode observation for motor control at the "start switching moment", at this time, since the sliding mode observer is used to observe the speed and position, the injected high-frequency voltage signal is an interference signal for the control process (such as Figure 7 As shown in the upper part, the SMO angle has a large jitter at the beginning). If the high-frequency voltage signal is directly removed at this time, the motor will have a large jitter due to the sudden change of the operating conditions, which is not conducive to actual control. For this reason, the present disclosure adopts a method of linearly reducing the amplitude of the injected signal. In the time between the start switching moment and the end switching moment, the proportional reduction in the observed The amplitude of the voltage signal injected into the coordinate axis. For example, at the injected voltage signal frequency f i =500Hz, preset amplitude |U i |=2000mV, the amplitude can be reduced by 1% cycle by cycle, so the amplitude of the injected signal can be reduced to zero by 20mv each time within 0.2ms (i.e., 0.2ms between the start switching moment and the end switching moment). As the injected signal gradually decreases, the angle observed by the sliding mode observer ( Figure 7 The SMO angle shown in the upper part) also gradually becomes smoother, and Figure 7 The d-axis voltage shown in the lower portion also tends to be stable.

[0085] When there is a high-frequency voltage injection signal, the response current contains two parts, high-frequency current and low-frequency current, and the low-frequency current needs to participate in the current loop operation. To this end, the permanent magnet synchronous motor operation method of the present invention also includes obtaining the low-frequency response current of the injected high-frequency voltage for the current loop operation when the injection amplitude of the high-frequency voltage is linearly reduced to zero.

[0086] Traditional methods for extracting low-frequency current mostly use low-pass filters, but the use of filters will greatly increase the amount of system calculations. To this end, combined with the relationship between the actual response current and the injection voltage, the present disclosure proposes a current filtering method that averages two points. Figure 8 The schematic diagram of the two-point average current filtering method is shown in FIG. The upper part of the figure shows the dq axis voltage, and the lower part shows the corresponding dq axis current.

[0087] like Figure 8As shown, when the injected voltage signal is at time 1, the injected voltage signal changes from positive to negative, and the response current reaches the maximum positive value. When the injected voltage signal is at time 2, the injected voltage signal changes from negative to positive, and the response current reaches the maximum negative value. Similarly, time 3 is the same as time 1, and time 4 is the same as time 2. Therefore, it is possible to choose to average the response currents at time 1 and time 2, and iterate the time 2 and time 3, time 3 and time 4, and subsequent times to obtain a real-time low-frequency response current. Since the d-axis injection voltage is usually controlled by the PWM wave sent by the MCU control timer module, that is, the zero-crossing point is known, in actual operation, the response current (that is, the positive maximum and negative maximum response current) corresponding to the injection voltage zero-crossing moment can be recorded, and the average is taken as the low-frequency current to participate in the current loop operation.

[0088] To this end, in the process of linearly decreasing the injection amplitude of the high-frequency voltage to zero, obtaining the low-frequency response current of the injected high-frequency voltage for current loop operation may include: in the process of linearly decreasing the injection amplitude of the high-frequency voltage to zero, recording the response current when the d-axis injection voltage passes through the zero point; and calculating the average value of the response currents at adjacent zero-crossing points as the low-frequency response current for current loop operation. Fig. 9 The figure shows the comparison of the two-point average current filtering method before and after use. As shown in the figure, by simply sampling the current extreme value at the voltage zero crossing point and averaging it, a relatively accurate calculation of the low-frequency current can be achieved with a very small amount of calculation.

[0089] After the switching is finished, the amplitude of the injected high-frequency voltage signal is already 0. Therefore, the response current no longer contains high-frequency current components, so the response current can be directly used in the current loop control without the need for current filtering.

[0090] Fig.10 A specific operation flow when switching from low speed to high speed is shown. As shown in the figure, at the start of the switching, the angle and speed can be switched to the angle and speed of the sliding mode observation at the same time. Subsequently, the amplitude of the high-frequency voltage signal is gradually reduced (for example, linearly proportionally reduced), and the current is filtered at the same time, and the obtained low-frequency current is used for the calculation of the current loop. When the amplitude of the high-frequency voltage signal is reduced to 0, the current does not need to be filtered and reaches the end of the switching time, thereby completing the switching.

[0091] In the permanent magnet synchronous motor operation scheme disclosed in the present invention, not only the switching method of position observation when the motor is switched from low speed to high speed is included, but also the switching method when the motor is switched from high speed to low speed is included. In the present disclosure, when switching from low speed to high speed, the motor speed reaches the first threshold as the switching point; and when switching from high speed to low speed, the motor speed drops to the second threshold as the switching point. Here, the first threshold and the second threshold have different values, and the second threshold is less than the first threshold.

[0092] This is because if the first threshold is also used as the switching point when switching from high speed to low speed, then when the motor speed is set to be near the first threshold, it will cause frequent jumps between high-frequency injection observation and sliding mode observation, so that continuous switching will cause control process disorder. If the second threshold used when switching from high speed to low speed is greater than the first threshold, it will cause the motor speed to switch from high-frequency injection to sliding mode observation when it switches from a speed between the first and second thresholds to above the second threshold again (because the switching point is at the first threshold which is smaller than the second threshold).

[0093] To this end, according to Figure 6 The motor operation method further includes: when the motor speed is not less than a first threshold value (for example, 900 r / min in the previous example), using the sliding mode observation angle for motor control; when it is determined that the motor speed drops to a second threshold value, linearly increasing the injection amplitude of the high-frequency voltage (for example, increasing proportionally from 0 to |U i |), wherein the second threshold is less than the first threshold; and after the injection amplitude of the high-frequency voltage increases to reach a predetermined amplitude, a high-frequency injection observation angle is used for motor control.

[0094] Specifically, when the motor is controlled by the sliding mode observer, it is detected in real time whether the speed threshold is less than the speed threshold 2. If it is less than the speed threshold 2, the high-frequency injection observer is switched. The two speed threshold solutions designed in the present disclosure can avoid continuous switching of the motor, that is, threshold speed 1 (i.e., the first threshold) and threshold speed 2 (i.e., the second threshold) are designed respectively. In the motor used in the experiment, threshold speed 1 is 900r / min and threshold speed 2 is 600r / min.

[0095] Fig.11 A schematic diagram showing a dual switching point setting from low speed to high speed and from high speed to low speed according to an embodiment of the present disclosure is shown.

[0096] When the motor speed direction switches from low speed to high speed, high-frequency injection control is used below threshold speed 1, and when the speed is greater than threshold speed 1, it starts to switch to sliding mode observer, and threshold speed 2 does not participate in control; when the motor speed direction switches from high speed to low speed, sliding mode observer control is used above threshold speed 2, and when the speed is less than threshold speed 2, it starts to switch to high-frequency injection observer, and threshold speed 1 does not participate in control. If only one speed threshold is used, at the speed switching threshold point, the speed will jitter near the switching point, and the motor will continuously switch from high speed (sliding mode observer) to low speed (high-frequency injection observer) or from low speed (high-frequency injection observer) to high speed (sliding mode observer), resulting in disordered control process and motor out of control. The two speed threshold methods are equivalent to designing two different switching points in the switching process from high speed to low speed and from low speed to high speed, thereby avoiding the switching out of control caused by continuous switching.

[0097] In the switching from low speed to high speed, since the sliding mode observer can observe in advance and the high-frequency voltage injection cannot realize position observation during the amplitude reduction process, it can be Figure 7 As shown in the upper part, the switch from the high-frequency injection observation angle (and its obtaining speed) to the sliding mode observation angle (and its obtaining speed) is completed at the beginning of the switching moment, and then the linear reduction of the amplitude of the high-frequency injection voltage is completed.

[0098] In the switching from high speed to low speed, the linear increase of amplitude still needs a period of time, that is, it also includes the start switching time and the end switching time. However, since the high-frequency injection is a closed-loop observer, although the voltage signal is injected between the start switching time and the end switching time, since the sliding mode observer is still used to observe the angle, the high-frequency injection cannot correctly observe the rotor position at this time. Therefore, it is necessary to increase the injection amplitude of the high-frequency voltage to a predetermined amplitude (that is, after the following Fig.12 Specifically, at the moment of ending the switching, the angle and speed can be instantly switched, that is, the angle and speed observed by the sliding mode observer are switched to the angle and speed observed by the high-frequency injection.

[0099] Fig.12 An example of the change of the observation angle and the dq axis voltage when switching according to the operation method of the present invention is shown. Specifically, Fig.12 The observation angle and dq axis voltage change of the position observation method when the motor speed changes from high speed to low speed are shown. As shown in the figure, in the process of the injection amplitude of the high-frequency voltage increasing linearly from zero to the predetermined amplitude, that is, in the time period from the start switching moment to the end switching moment, although the interference from the high-frequency injection is getting bigger and bigger, the sliding mode observer still observes and completes the switching at the end switching moment.

[0100] In addition, when the injection amplitude of the high-frequency voltage increases linearly from zero to a predetermined amplitude, it is still necessary to obtain the low-frequency response current of the injected high-frequency voltage for current loop calculation. For example, the extreme current averaging method as described above is used to calculate the low-frequency current.

[0101] However, since it takes some time for the high-frequency injection angle to converge to the real angle, if the high-frequency injection observation angle is directly used to participate in FOC closed-loop control when the motor ends switching, the FOC control will be out of control during the motor re-convergence process. Fig.13 The simulation example of the observation angle and dq axis voltage change when high-frequency voltage injection is used directly for observation at the end of switching is shown. As shown in the figure, the high-frequency voltage injection observer cannot correctly observe the rotor position after being connected, and when the high-frequency injection angle completes convergence, the motor reverses, which is not allowed in practical applications.

[0102] To this end, some parameters of the high-frequency injection link need to be operated. The present disclosure accelerates the convergence process of high-frequency injection by assigning values ​​to the parameters in the high-frequency injection control process, so that the sliding mode observer can be stably switched to the high-frequency injection observer in the motor control.

[0103] In one embodiment, an initial angle assignment can be performed. At this time, the motor operation method of the present invention further includes: when the injection amplitude of the high-frequency voltage increases to a predetermined amplitude, the observation angle under the sliding mode observation at the current high-speed to low-speed switching moment is used as the initial high-frequency injection observation angle at the high-speed to low-speed switching moment. Further, an initial speed assignment can also be performed. At this time, the motor operation method of the present invention further includes: when the injection amplitude of the high-frequency voltage increases to a predetermined amplitude, the sliding mode observer PI integral value is used as the initial speed at the high-speed to low-speed switching moment of the high-frequency voltage injection.

[0104] The following describes the specific operations and effects of the assignment. Fig.12 , point A in the figure refers to the observation angle of the sliding mode observer at the end of switching.

[0105] Specifically, at point A, the sliding mode observer switches to high-frequency injection. Fig.12 In the out-of-control situation shown, it is necessary to inject an initial correct angle into the high frequency, and the angle in the subsequent control process is also obtained by integrating the angle as the initial value of integration. At point A, the angle observed by the SMO observer can be considered as the real angle, so the sliding mode angle of this point is assigned to the high frequency injection as the angle for high frequency injection to participate in control, ensuring the correctness of the FOC control at point A.

[0106] By assigning the sliding mode angle of point A to the high frequency injection, the correctness of the angle of point A is guaranteed. On this basis, the correctness of the subsequent angles must be guaranteed to ensure that the high frequency injection can observe the angle normally and the FOC control process is normal. Figure 3 ) It can be seen that the angle error is converted into the rotor speed through the PI (proportional integral) link, and the rotor position is obtained by integrating the speed; similarly, the sliding mode observer also obtains the rotor speed by converting the angle error into the PI (proportional integral) link (see Figure 4 ), and the rotor position is obtained by integrating the speed.

[0107] In order to ensure that the angle obtained by the subsequent PI after high-frequency injection is correct, it is necessary to assign the initial value (speed) of the PI integral, that is, to assign the integral value (speed) in the sliding mode phase-locked loop PI to the high-frequency injection PI integral value.

[0108] However, at point A, the sliding mode observation angle is in oscillation due to high-frequency voltage injection, so directly reading the observation angle at point A may not be able to deduce the correct angle error, resulting in distortion of the integrated velocity. Fig.14 . Fig.14 An enlarged view of the sliding mode observation angle and time near the end switching moment is shown. Fig.14 Can be seen as Fig.11 The enlarged diagram of the relationship between the sliding mode observation angle and time in the box shown. 1 ~A 3 Points can be considered as possible candidates for A.

[0109] If you choose A 1 The integral value (speed) is assigned, and the high-frequency injection angle will be along A 1 The arrow moves, the deviation from the true angle gradually increases, and the motor control process is out of control; if you select A 2 The integral value (speed) is assigned, and the high-frequency injection angle will be along A 2 The arrow points to the direction of movement, and the motor movement direction is basically consistent with the real direction, and the motor can be controlled normally; if you select A 3 The integral value (speed) is assigned, and the high-frequency injection angle will be along A 3 The arrow point moves, the deviation from the true angle gradually increases, and the motor control process is out of control.

[0110] Depend on Fig.14 It can be seen that there is correct angle error information in the sliding mode observation angle, but it cannot be achieved by directly calculating the angle error during switching. Therefore, the sliding mode observer PI integral value, which is the initial speed at the time of switching from high speed to low speed of the high-frequency voltage injection, can be obtained by sliding average.

[0111] It can be known through actual derivation that after the high-frequency voltage signal is injected, the oscillation period of the angle observed by the sliding mode observer is the same as the frequency of the injected voltage signal. Therefore, after the sliding mode observer PI integral value is subjected to sliding average filtering, the influence of the speed fluctuation caused by the high-frequency voltage injection can be removed, and a more accurate real speed value of the motor can be obtained. To this end, when the injection amplitude of the high-frequency voltage increases to a predetermined amplitude, the sliding mode observer PI integral value is used as the initial speed at the high-speed to low-speed switching moment of the high-frequency voltage injection, including: collecting n sliding mode observer PI integral values ​​before the injection amplitude of the high-frequency voltage increases to a predetermined amplitude; and obtaining the average value of the n sliding mode observer PI integral values ​​as the initial speed at the high-speed to low-speed switching moment of the high-frequency voltage injection.

[0112] In one example, the length of the filter array Among them, f s is the FOC control frequency, f i is the frequency of the injected voltage signal. In a practical example, f s =16KHz, f i =500Hz, K is a positive integer greater than 0, for example, K=4, that is, 128-point sliding average filtering. The sliding average is used to remove the influence of speed fluctuation caused by high-frequency voltage injection.

[0113] In one embodiment, the sliding average process can be implemented as follows:

[0114] Suppose the sliding mode PI integral value of the data being moved is input_data; buffer is an array of length n, used to store n input data; index is the coordinate index, used to indicate the location of the latest data, input_data k The following table shows the data stored in the array at the current moment.

[0115]

[0116] Specifically, the data stored in buffer[0] is input_data k-index , buffer[index] stores the latest data input_data k , buffer[index+1] stores the earliest data input_data k-n+1 . Thus, the sum of all data in the buffer is:

[0117]

[0118] The average output value is:

[0119]

[0120] When new data input_data k+1 When it arrives, at this time sum k First, subtract the earliest data input_data stored in buffer[index+1] k-n+1 , input the latest data into data k+1 Store it in buffer[index+1], and add 1 to index, that is, index re-indexes the latest data. As shown in the following table.

[0121]

[0122] thereby:

[0123]

[0124] With this algorithm, each time new data is added, only a small amount of calculation is required to achieve the sliding average.

[0125] In one embodiment, n integral values ​​before point A may be collected for average calculation. In another embodiment, integral values ​​during this period of time may be collected to ensure that the average value can be provided as the initial angle when point A arrives.

[0126] After the initial angle assignment and the high-frequency injection PI integral value assignment are completed at the end of the switching, the high-frequency injection control process can be as follows: Fig.12 As shown, a smooth switch from sliding mode observer to high frequency injection is achieved.

[0127] In one embodiment, the present disclosure may also be implemented as a position observation solution within a full speed range. Fig.15 The specific switching process between the high-frequency injection observer and the sliding mode observer is shown.

[0128] The specific control process is divided into 6 stages, namely stage 1 (initial position identification), stage 2 (polarity judgment), stage 3 (high-frequency injection rotation and speed magnitude judgment), stage 4 (smooth switching when the motor speed is greater than threshold speed 1), stage 5 (sliding mode observer rotation and speed magnitude judgment), stage 6 (smooth switching when the motor speed is less than threshold speed 2). The focus of this disclosure is to design the specific implementation steps of the switching process to ensure the stability and smoothness of the switching.

[0129] Phase 1 and Phase 2 are conventional processing methods in the process of high frequency injection control of the motor, such as initial position recognition based on high frequency injection and polarity judgment based on diagonal position injection. The switching method described in the present disclosure is performed after the startup process covered by Phase 1 and Phase 2.

[0130] In stage 3, the motor is in the process of high-frequency injection rotation. At this time, the sliding mode observer can also be in operation. Since the sliding mode observer observes the rotor position through the voltage signal and current signal on the αβ coordinate axis (stationary coordinate system), when the motor is in the process of high-frequency injection closed-loop control, the sliding mode observer can still observe the rotor position normally. Figure 4 The diagram shows the observation angle of the sliding mode observer and the high-frequency injection observation angle when the motor is at 200r / min and the high-frequency injection is used to control the motor rotation. It can be seen that due to the injection of high-frequency voltage signals and the presence of high-frequency current in the current of the αβ coordinate axis, the angle observed by the sliding mode observer has a large jitter.

[0131] When the speed reaches the speed threshold 1, for example, 900r / min, the high-frequency injection observer starts to switch to the sliding mode observer, that is, entering stage 4. Since the high-frequency injection observer is a closed-loop observer (it is only effective when the angle and speed of the high-frequency injection observer participate in the closed-loop control), it cannot be in the open-loop mode (the angle and speed of other observers participate in the closed-loop control, and the high-frequency injection observer cannot observe the angle and speed), so Figure 7 As shown in FIG. 1 , when the switching starts, the angle and speed are switched first. At this time, the high-frequency voltage signal is gradually removed by linearly reducing the amplitude of the injected signal to prevent the motor from vibrating greatly. Figure 7 As shown. In the time between the start switching moment and the end switching moment, the proportional reduction in the observed The amplitude of the voltage signal injected into the coordinate axis, and as the injected signal gradually decreases, the angle observed by the sliding mode observer gradually becomes smoother.

[0132] When the motor is running in stage 5, the motor rotation is controlled by the sliding mode observer, and it can detect in real time whether the speed threshold is less than the speed threshold 2. If it is less than the speed threshold 2, it starts to switch to the high-frequency injection observer. In the present disclosure, two speed threshold solutions are designed to avoid continuous switching of the motor, such as Fig.11 shown.

[0133] When the motor is running in stage 6, that is, the motor switches from high speed (sliding mode observer) to low speed (high-frequency injection observer), since high-frequency injection observes the motor position through high-frequency response current, the high-frequency voltage signal should be injected first at the beginning of the switch. In order to avoid the instantaneous injection of large voltage causing changes in system working conditions and causing motor jitter, the linear increase injection method is also adopted. Fig.12As shown in the figure, the injected voltage signal gradually increases from 0 to a given value. As the injected voltage signal increases, the angle jitter amplitude observed by the sliding mode observer gradually increases. Since high-frequency injection is a closed-loop observer, it is impossible to correctly observe the rotor position when the sliding mode observer is used to observe the angle. Therefore, at the moment of ending the switching, the angle and speed must be switched instantaneously, that is, the angle and speed observed by the sliding mode observer are switched to the angle and speed observed by the high-frequency injection. At the same time, in order to avoid Fig.13 In the out-of-control condition shown in the figure, you can choose to assign the angle of the sliding mode observer to the high-frequency injection angle, and at the same time, perform a fixed-period smoothing filter on the sliding mode observer PI integral value and assign it to the high-frequency injection PI integral initial value to complete the instantaneous convergence of the high-frequency injection and achieve smooth switching.

[0134] The present invention may also be implemented as a solution for avoiding continuous switching of the motor by setting two speed thresholds. Fig.16 A schematic flow chart of a method for operating a permanent magnet synchronous motor according to an embodiment of the present invention is shown.

[0135] In step S1610, a high-frequency pulse voltage is injected to obtain a high-frequency injection observation angle for motor control by extracting a high-frequency current response. In step S1620, when the motor speed reaches a first threshold, a switch is made from high-frequency voltage injection observation to sliding mode observation. In step S1630, when the motor speed is not less than the first threshold, the observation angle under sliding mode observation is used for motor control. In step S1640, when it is determined that the motor speed drops to a second threshold, a switch is made from sliding mode observation to high-frequency voltage injection. In step S1650, when the motor speed is less than the second threshold, a high-frequency injection observation angle is used for motor control. At this time, the second threshold is less than the first threshold.

[0136] like Fig.11 As shown, in the process of the motor speed decreasing from above the first threshold to the second threshold, the observation angle under sliding mode observation is used for motor control; and in the process of the motor speed increasing from below the second threshold to the first threshold, the high-frequency injection observation angle is used for motor control.

[0137] The method can also utilize the method of linearly adjusting the injection voltage amplitude of the present invention as described above. In this case, the injection amplitude of the high-frequency voltage can be linearly reduced from a predetermined amplitude to zero in the switching from high-frequency voltage injection observation to sliding mode observation; and in the switching from sliding mode observation to high-frequency voltage injection, the injection amplitude of the high-frequency voltage can be linearly increased from zero to the predetermined amplitude.

[0138] In addition, the present invention can also be implemented as a permanent magnet synchronous motor. Fig.17 FIG. 1 shows a schematic diagram of the composition of a FOC module of a permanent magnet synchronous motor according to an embodiment of the present invention. Figure 3 and Figure 4 , Fig.17 The FOC module shown additionally includes functions that can be executed Figure 6 and / or Fig.16 The modules of the permanent magnet synchronous motor operation method are shown, in particular the modules for switching.

[0139] Specifically, Fig.17 The permanent magnet synchronous motor shown may include: a motor M; a magnetic oriented vector control (FOC) module 1700 for controlling the motor. All components except the motor M in the figure may be considered as part of the magnetic oriented vector control (FOC) module 1700. The FOC module 1700 may include: a high frequency injection observer 1710 for injecting a high frequency pulse voltage U into the d-axis. i cos(ω i t) and from the q-axis high-frequency current response i q A high-frequency injection observation angle is obtained for high-frequency injection observation; a sliding mode observer 1720 is used to perform sliding mode observation to obtain the observation angle under sliding mode observation; and a switching module 1730 is used to execute the method of operation as described above to complete the switching of the observation mode between high and low speeds, so as to use the high-frequency injection observation angle or the observation angle under sliding mode observation for motor control.

[0140] The operating method of the permanent magnet synchronous motor and the corresponding permanent magnet synchronous motor according to the present invention have been described in detail above with reference to the accompanying drawings. The operating scheme disclosed in the present invention can especially reduce the jitter of the switching point by linearly reducing the high-frequency voltage injection amplitude in the switching from low speed to high speed. Furthermore, the present invention designs a method combining high-frequency injection and sliding mode observer, realizes the speed regulation of the motor in the full speed range under sensorless control, and designs and processes the details of the switching process, so that the motor can still ensure smooth rotation during the switching process.

[0141] Specifically, the present disclosure proposes the following:

[0142] Design of 6 switching stages in full speed range for high frequency injection and sliding mode observer;

[0143] A method of switching high frequency injection to a sliding mode observer to linearly reduce the injected voltage signal to reduce motor jitter;

[0144] The method of taking the average as the low-frequency current during the high-frequency injection operation avoids the method of reducing the amount of calculation used by the filter;

[0145] The speed threshold is designed to avoid the motor losing control due to continuous switching between low speed (high-frequency injection observer) to high speed (sliding mode observer) or high speed (sliding mode observer) to low speed (high-frequency injection observer); and

[0146] During the switching process from high speed (sliding mode observer) to low speed (high-frequency injection observer), the angle of the sliding mode observer is assigned to the high-frequency injection angle. At the same time, the sliding mode observer PI integral value is smoothed and filtered at a fixed period and assigned to the high-frequency injection PI integral initial value to complete the instantaneous convergence of the high-frequency injection and achieve smooth switching.

[0147] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein are selected to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for operating a permanent magnet synchronous motor, comprising: Injecting a high-frequency pulse voltage to obtain a high-frequency injection observation angle for motor control by extracting a high-frequency current response; Before the motor speed reaches a first threshold, the sliding mode observer is turned on to obtain an observation angle under sliding mode observation; When it is determined that the motor speed reaches a first threshold, the injection amplitude of the high-frequency voltage is linearly reduced, and the observation angle under the sliding mode observation is used for the motor control.

2. The method of claim 1, further comprising: In the process that the injection amplitude of the high-frequency voltage is linearly reduced to zero, a low-frequency response current of the injected high-frequency voltage is obtained for current loop calculation.

3. The method of claim 2, wherein: In the process that the injection amplitude of the high-frequency voltage is linearly reduced to zero, obtaining the low-frequency response current of the injected high-frequency voltage for current loop calculation includes: In the process of linearly decreasing the injection amplitude of the high-frequency voltage to zero, recording the response current when the d-axis injection voltage passes through the zero point; and The average value of adjacent zero-crossing point response currents is calculated as the low-frequency response current for current loop operation.

4. The method of claim 1, further comprising: When the motor speed is not less than a first threshold, using the observation angle under the sliding mode observation for motor control; When it is determined that the motor speed drops to a second threshold, linearly increasing the injection amplitude of the high-frequency voltage, wherein the second threshold is less than the first threshold; as well as After the injection amplitude of the high frequency voltage increases to reach a predetermined amplitude, the high frequency injection observation angle is used for motor control.

5. The method of claim 4, further comprising: After the injection amplitude of the high-frequency voltage increases to reach the predetermined amplitude, the sliding mode observer is turned off.

6. The method of claim 4, further comprising: In the process that the injection amplitude of the high-frequency voltage increases linearly from zero to the predetermined amplitude, a low-frequency response current of the injected high-frequency voltage is obtained for current loop operation.

7. The method of claim 4, further comprising: When the injection amplitude of the high-frequency voltage increases to reach the predetermined amplitude, the observation angle under the sliding mode observation at the current high-speed to low-speed switching moment is used as the initial high-frequency injection observation angle at the high-speed to low-speed switching moment.

8. The method of claim 4, further comprising: When the injection amplitude of the high-frequency voltage increases to reach the predetermined amplitude, the sliding mode observer PI integral value is used as the initial speed at the moment of switching from high speed to low speed of the high-frequency voltage injection.

9. The method of claim 8, wherein: When the injection amplitude of the high-frequency voltage increases to reach the predetermined amplitude, using the sliding mode observer PI integral value as the initial speed at the high-speed to low-speed switching moment of the high-frequency voltage injection includes: collecting n sliding mode observer PI integral values ​​before the injection amplitude of the high frequency voltage increases to reach the predetermined amplitude; and An average value of the n sliding mode observer PI integral values ​​is obtained as the initial speed at the time of switching from the high speed to the low speed when the high-frequency voltage is injected.

10. The method of claim 1, wherein: Before the step of injecting a high-frequency pulse voltage to obtain a high-frequency injection observation angle for motor control by extracting a high-frequency current response, the method further includes: The motor is started, and an initial position of the motor is identified and a rotor polarity of the motor is determined.

11. A method for operating a permanent magnet synchronous motor, comprising: Injecting a high-frequency pulse voltage to obtain a high-frequency injection observation angle for motor control by extracting a high-frequency current response; When the motor speed reaches a first threshold, switching from high-frequency voltage injection observation to sliding mode observation is performed; When the motor speed is not less than the first threshold, using the observation angle under the sliding mode observation for motor control; When it is determined that the motor speed drops to a second threshold, switching from the sliding mode observation to the high-frequency voltage injection is performed; as well as When the motor speed is less than the second threshold, a high frequency injection observation angle is used for motor control. The second threshold is smaller than the first threshold.

12. The method of claim 11, wherein When the motor speed decreases from above the first threshold to the second threshold, using the sliding mode observation angle for motor control; and During the process of the motor speed increasing from below the second threshold to the first threshold, the high frequency injection observation angle is used for motor control.

13. The method of claim 11, wherein In switching from the high-frequency voltage injection to the sliding mode observation, linearly reducing the injection amplitude of the high-frequency voltage injection from a predetermined amplitude to zero; and And in the switching process from the sliding mode observation to the high-frequency voltage injection, the injection amplitude of the high-frequency voltage injection is linearly increased from zero to the predetermined amplitude.

14. A permanent magnet synchronous motor, comprising: Motor; A magnetic oriented vector control module is used to control the motor and comprises: A high-frequency injection observer, used for injecting a high-frequency pulse voltage to obtain a high-frequency injection observation angle by extracting a high-frequency current response; A sliding mode observer, used for performing sliding mode observation to obtain an observation angle under sliding mode observation; and A switching module, used to execute the method as described in any one of claims 1-13, so as to use the high-frequency injection observation angle or the sliding mode observation angle for motor control.

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