Permanent magnet synchronous motor operating method and permanent magnet synchronous motor

Abstract

Disclosed are a permanent magnet synchronous motor operation method and a permanent magnet synchronous motor. The method comprises: injecting a high-frequency voltage to obtain an initial observation angle by extracting a high-frequency current response; selecting a reference injection angle closest to the initial observation angle from a plurality of reference injection angles as a first injection angle, the reference injection angle being away from a sector switching position in a voltage vector circle; injecting an equal-amplitude voltage vector at the first injection angle and a second injection angle 180 degrees away from the first injection angle to obtain first and second current vectors respectively; and taking the initial observation angle or an opposite angle as a rotor angle based on a comparison result of the two current vectors. The application is based on the saturation saliency effect, injects voltage at a reference angle away from the sector switching position in the voltage vector circle and an opposite angle thereof, compares the amplitudes of the response current vectors to determine whether the rotor position is the same as or opposite to the initial observation angle, and is particularly suitable for solving the problem that electrode polarity determination is prone to error in a single-resistance mode.

Description

Technical Field

[0001] This disclosure relates to the field of electric motors, and more particularly to an operating method for a permanent magnet synchronous motor and a corresponding permanent magnet synchronous motor. Background Technology

[0002] In the control process of 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.

[0003] Both the Park transform and inverse Park transform in FOC control require knowledge of the rotor position θ. The closer the detected rotor position θ is to the true position, the closer the torque output during control will be to the maximum torque output. Although position sensors such as magnetic encoders can be used to measure the rotor position θ in existing technologies, some applications require sensorless position detection and motor control.

[0004] One implementation of sensorless detection is high-frequency injection position detection. High-frequency injection position detection is suitable for low speeds and is widely used during motor startup. However, when observing rotor position angles, high-frequency injection can lead to various issues where the observed angle may be equal to or opposite to the true angle (a difference of 180°), resulting in poor FOC control performance.

[0005] Therefore, an improved high-frequency injection position detection scheme is needed. Summary of the Invention

[0006] One technical problem this disclosure aims to solve is to provide an improved high-frequency injection rotor polarity determination scheme. This scheme is based on the reference angle of the switching position of the sector away from the voltage vector circle and its reverse angle of the saturated salient pole effect, and determines whether the rotor position is the same as or opposite to the initial observation angle by comparing the magnitude of the response current vector.

[0007] According to a first aspect of this disclosure, a method for operating a permanent magnet synchronous motor is provided, comprising: injecting a high-frequency voltage to obtain an initial observation angle by extracting a high-frequency current response; selecting a reference injection angle closest to the initial observation angle from a plurality of reference injection angles as a first injection angle, wherein the reference injection angle is an angle away from a sector switching position in a voltage vector circle; injecting a short-time constant-amplitude voltage vector at the first injection angle and a second injection angle differing from the first injection angle by 180° to obtain a first current vector obtained by injecting voltage at the first injection angle and a second current vector obtained by injecting voltage at the second injection angle; and, based on a comparison result of the first current vector and the second current vector, taking the initial observation angle or an angle differing from the initial observation angle by 180° as a rotor angle.

[0008] Optionally, based on the comparison result of the first current vector and the second current vector, taking the initial observation angle or an angle that differs from the initial observation angle by 180° as the rotor angle includes: taking the initial observation angle as the rotor angle when it is determined that the amplitude of the first current vector is greater than the amplitude of the second current vector; and taking an angle that differs from the initial observation angle by 180° as the rotor angle when it is determined that the amplitude of the first current vector is less than the amplitude of the second current vector.

[0009] Optionally, selecting the reference injection angle closest to the initial observation angle from multiple reference injection angles as the first injection angle includes: selecting the two closest reference injection angles that are ahead and behind the initial observation angle from multiple reference injection angles as two first injection angles, and injecting a short-time constant amplitude voltage vector at the first injection angle and at a second injection angle that differs from the first injection angle by 180° to obtain a first current vector obtained by injecting voltage at the first injection angle and a second current vector obtained by injecting voltage at the second injection angle. This includes: injecting a short-time constant amplitude voltage vector at the two first injection angles and at the two second injection angles that differ from the two first injection angles by 180° to obtain two first current vectors obtained by injecting voltage at the two first injection angles and two second current vectors obtained by injecting voltage at the two second injection angles.

[0010] Optionally, based on the comparison result of the first current vector and the second current vector, taking the initial observation angle or an angle that differs from the initial observation angle by 180° as the rotor angle includes: taking the initial observation angle as the rotor angle when it is determined that the sum of the amplitudes of the two first current vectors is greater than the sum of the amplitudes of the two second current vectors; and taking an angle that differs from the initial observation angle by 180° as the rotor angle when it is determined that the sum of the amplitudes of the two first current vectors is less than the sum of the amplitudes of the two second current vectors.

[0011] Optionally, injecting a voltage vector of equal amplitude at the first injection angle and a second injection angle that differs from the first injection angle by 180° includes: under open-loop control, the q-axis voltage is given as 0; injecting the voltage vector of equal amplitude into the d-axis voltage at the first injection angle and the second injection angle, wherein the angle difference between one of the first injection angle and the second injection angle and the rotor angle is less than 90°.

[0012] Optionally, the sector switching positions in the voltage vector circle include 0°, 60°, 120°, 180°, 240°, and 300°, and the reference injection angle is the sector center angle away from the sector switching position, including 30°, 90°, 150°, 210°, 270°, and 330°.

[0013] Optionally, obtaining the initial observation angle by injecting high-frequency voltage and extracting the high-frequency current response includes: under open-loop control, obtaining the initial observation angle of high-frequency injection observation by injecting the high-frequency voltage onto the d-axis and extracting the high-frequency current response from the q-axis current.

[0014] Optionally, the first current vector and the second current vector obtained include obtaining the first d-axis current response and the second d-axis current response.

[0015] Optionally, the currents of phase a, phase b, and phase c are obtained using single-resistor sampling; the q-axis current response, the first d-axis current response, and the second d-axis current response are calculated based on the obtained currents of phase a, phase b, and phase c.

[0016] According to a second aspect of this disclosure, a permanent magnet synchronous motor is provided, comprising: a motor; a magnetic orientation vector control module for controlling the motor, and comprising: a high-frequency injection observation module for obtaining an initial observation angle of the high-frequency injection observation from the voltage injected into the d-axis and the high-frequency current response of the q-axis; and a polarity determination module for performing the method according to the first aspect of the present invention, determining the initial observation angle or an angle differing from the initial observation angle by 180° as the rotor angle.

[0017] Therefore, the operation scheme of the present invention can, in particular, perform equal-amplitude voltage vector injection at the first injection angle of the initial observation angle obtained by the nearest high-frequency injection and the second injection angle in the opposite direction. It utilizes the influence of the saturated salient pole effect on the d-axis inductance to affect the magnitude of the d-axis current to determine the rotor polarity, thereby improving the accuracy of rotor polarity determination. It is also particularly suitable for solving the problem that the sampling effect of three-phase current near the sector switching position of the voltage vector circle in single-resistance mode is poor, which leads to easy errors in polarity determination. Attached Figure Description

[0018] The above and other objects, features and advantages of this disclosure will become more apparent from the more detailed description of exemplary embodiments thereof taken in conjunction with the accompanying drawings, in which the same reference numerals generally represent the same components.

[0019] Figure 1 The FOC control principle diagram for PMSM is shown.

[0020] Figure 2 An example of position detection based on high-frequency injection is shown.

[0021] Figure 3 The main structure diagram of a three-phase PWM inverter PMSM load using single-resistor sampling is shown.

[0022] Figure 4A -C shows the sector diagrams of the rotor in different d-axis directions and the corresponding modulation sector waveforms.

[0023] Figure 5 A method for operating a permanent magnet synchronous motor according to an embodiment of the present invention is shown.

[0024] Figure 6 A graph showing the angular relationship between the actual d-axis and the d-axis of the injected voltage is presented.

[0025] Figure 7 The theoretical current values ​​obtained with and without considering the saturated salient pole effect are shown.

[0026] Figure 8 An example of determining the true position of the rotor based on the present invention is shown.

[0027] Figure 9 A schematic diagram of the composition of the FOC module of a permanent magnet synchronous motor according to an embodiment of the present invention is shown. Detailed Implementation

[0028] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0029] In the control process of permanent magnet synchronous motor (PMSM), in order to obtain the maximum torque output throughout the entire control cycle, FOC (magnetic orientation vector control) is often used to control the motor. Figure 1 The FOC control principle diagram for PMSM is shown.

[0030] As shown in the figure, a position sensor, such as a magnetic encoder, acquires the rotor speed n and rotor position θ of motor M. In practical applications, for example, a speed reference n obtained from user input... ref The difference between the measured rotor speed n and the actual rotor speed is calculated and input to PID1 (i.e., the speed loop PID). The output of the speed loop PID is the q-axis reference current i. qref For simplicity, when field weakening control is not performed, the d-axis reference current i can be set. dref =0. At this point, the reference currents i on the q-axis and d-axis can be set to 0. qref and i dref The actual q-axis and d-axis currents i fed back by the motor q and i d The difference is calculated, and after being regulated by PID2 (i.e., the q-axis current loop) and PID3 (i.e., the d-axis current loop) respectively, the output q-axis and d-axis voltages V are obtained. d and V q Then, through the inverse Park transform, it is converted into α-axis and β-axis voltages V. α and V β Then, the three-phase voltage V is obtained through SVPWM (Space Vector Modulation). a V b V c The current is then transmitted to the motor M via a three-phase inverter bridge. In FOC control, the three-phase current i is obtained through a sampling resistor. a i b i c After Clark transformation, the α-axis and β-axis currents i are obtained. α and i β Then, after Park transformation, the feedback d-axis and q-axis currents i are obtained. d and i q Input PID2 and PID3 respectively to participate in the current loop control.

[0031] In addition, although Figure 1Not shown in the diagram, but in many cases, field weakening control of the motor is required, that is, the d-axis reference current i is used in this case. dref ≠0. At this point, the MTPA control strategy can be used for optimal control of permanent magnet synchronous motors, especially salient-pole PMSMs, in the constant torque region. Specifically, MTPA (Maximum Torque Per Ampere) control is an optimal control strategy for FOC control within the constant torque region. Using this strategy, the maximum electromagnetic torque can be output with the same current; similarly, the minimum current is required to output the same torque. When using the MTPA control strategy, the q-axis reference current i can be obtained from PID1 (i.e., the speed loop PID). qref The current is fed into the MTPA control module to output the optimized d-axis reference current i. dref .

[0032] Regardless of whether the MTPA control strategy is implemented, in FOC control, the Park transform and inverse Park transform, for example... Figure 1 All of the above can only be performed under the condition of rotor position θ (i.e. the electrical angle θ of the motor rotor. The motor rotor rotates 360° in one revolution, so the value range of the vertical axis position (θ) in the following position-time diagram is 0° to 360°). The closer the detected rotor position θ is to the actual position, the closer the torque output in the control process will be to the maximum torque output.

[0033] Position detection is generally divided into sensor-based position detection and sensorless position detection. Sensor-based position detection typically includes Hall sensor position detection and encoder position detection, which is achieved by installing Hall sensors or magnetic encoders on the motor. For example... Figure 1 The rotor position and speed detection module can be implemented by a magnetic encoder.

[0034] However, in some applications, such as for cost or integration considerations, it is necessary to achieve position detection and motor control without sensors. Sensorless detection methods include sliding mode position detection, Luneburg position detection, and high-frequency injection position detection. Among these, sliding mode position detection and Luneburg position detection are suitable for high speeds, while high-frequency injection position detection is suitable for low speeds. It mainly relies on the single salient polarity of the motor and is widely used during motor startup.

[0035] Figure 2 An example of position detection based on high-frequency injection is shown.

[0036] The following will combine Figure 2 Taking pulsed high-frequency injection as an example, the specific implementation process of high-frequency injection is described. Figure 2 As shown, a voltage U can be injected into the d-axis. m cos(i t), where U m ω is the amplitude of the injected signal. i The angular frequency of the injected signal is given. The resulting q-axis high-frequency current response iq will contain a component of the rotor position information θ. This is achieved through bandpass filtering (BPF) of the q-axis current, modulated (with sin( i Multiplying the values ​​of t and y, and passing them through a low-pass filter (LPF) and a PI controller, the rotor speed n can be obtained. Then, integrating (I) the rotor speed n yields the rotor position θ. Here, the rotor position θ obtained from high-frequency injection observation can also be called the high-frequency injection observation position, the high-frequency injection observation angle, or the d-axis direction of the observation. Furthermore, it should be understood that in addition to the pulsed high-frequency injection shown in the figure, square wave high-frequency injection can also be performed.

[0037] When using high-frequency injection to observe rotor position and angle, various factors can cause the observed angle to be either equal to or opposite to the true angle (a difference of 180°). Therefore, when using high-frequency injection to observe rotor position, especially during motor startup, it is necessary to determine the rotor polarity, i.e., whether the true d-axis direction (or true rotor angle) is the observed angle or a direction 180° different from it. For example, existing square-wave high-frequency injection polarity determination can be achieved by injecting voltages in both directions along the observed d-axis direction (i.e., the initial observation angle of the high-frequency injection). Based on the saturated salient pole effect, the magnitude of the current response obtained from injecting voltages in both directions is determined to identify the rotor polarity. In industrial applications using single resistors for current sampling, when the rotor d-axis direction is far from the sector switching position in the voltage vector circle, the sampling effect of three-phase current is good, and the existing polarity determination method can accurately determine the rotor polarity. However, when the rotor d-axis direction is close to the sector switching position, the sampling effect of three-phase current is poor, and it is difficult to accurately determine the rotor polarity using existing polarity determination methods. If the polarity is determined incorrectly, it will cause the motor to start in reverse.

[0038] In practical engineering applications, FOC often uses single-resistor sampling in order to control costs. Figure 3 The main structure diagram of a three-phase PWM inverter PMSM load using single-resistor sampling is shown. In a FOC-based PMSM speed control system, an inverter is needed to convert DC power into AC power in order to apply PWM. Figure 3 In the three-phase PWM inverter PMSM load shown, power transistors VT1 and VT4 are the upper and lower arm switches of phase A, respectively, and D1 and D4 are used to provide i during the dead time. a The freewheeling diode; power transistors VT2 and VT5 are the upper and lower arm switching transistors of phase B, respectively; D2 and D5 are used to provide i during the dead time. bThe freewheeling diode; power transistors VT3 and VT6 are the upper and lower arm switching transistors of phase C, respectively; D3 and D6 are used to provide i during the dead time. c A freewheeling diode. For example, when a voltage of U4 (100) is applied to the three phases A, B, and C in the modulation sector waveform diagram, it means that the upper arm switch VT1 of phase A is turned on, and the lower arm switches VT5 and VT6 of phases B and C are turned on. At this time, the current flowing through the single resistor is the positive current i of phase A. a (It is equal to the negative current i in phase BC) b and i c (The sum of the two), therefore, single-resistor sampling can only obtain the positive current i of phase A. a When a voltage of U6(110) is applied to the three phases ABC, it means that the upper arm switches VT1 and VT2 of phase AB are open, and the lower arm switch VT6 of phase C is open. At this time, the current flowing through the single resistor is the negative current of phase C. c (It is equal to the positive current i of phase AB) a and i b (sum of the two phases), therefore single-resistor sampling can only obtain the negative current of phase C. c In summary, unlike three-resistor sampling, Figure 3 The single resistor shown can only collect the current flowing in the opposite direction to the other two phases. This makes it easy to be affected by the conduction time of the drive circuit at the sector switching position in the voltage vector circle, resulting in poor sampling effect of the three-phase current.

[0039] Figure 4A -C shows the sector diagrams of the rotor in different d-axis directions and the corresponding modulation sector waveforms.

[0040] Figure 4A The sector diagram of the voltage vector circle shown illustrates two voltage vectors U, with the first sector as an example. x U y Where the voltage vector U x The angle between the voltage vector U and the axis of phase A winding (α axis) is 0°, and the voltage vector U is... y The angle between the phase A winding axis (α axis) and the axis of the phase A winding is 30°.

[0041] According to the basic principle of PWM speed regulation, since positive and negative voltages can only be applied to the three phases A, B, and C, the vector angle positions, except for 0°, 60°, 120°, 180°, 240°, and 300° where the sector switching positions are located, are obtained by synthesizing the voltage vectors of two adjacent phases of U4(100), U6(110), U2(010), U3(011), U1(001), and U5(101). Figure 4A From the sector vector circle, we can see that U4(100, where "100" represents Figure 3(Phase A upper tube is conducting, phase BC lower tube is conducting) represents the 0° direction, U6(110, where similarly, "110" represents Figure 3 (In the diagram, the upper transistor of phase AB is conducting, and the lower transistor of phase C is conducting, representing a 60° direction.) To synthesize a 30° voltage vector, U4 (0°) and U6 (60°) are combined and act for the same duration to obtain the synthesized 30° voltage vector. This means selecting the two voltage vectors (0° and 60°) closest to the desired 30° voltage vector for synthesis. Therefore, U... x The voltage vector is obtained solely from U4(0°) without synthesis, resulting in poor sampling of the three-phase current. In contrast, U y Located at the d-axis in the middle of the two sector switching positions, and with U4(0°) and U6(60°) having the same duration, the sampling effect of the three-phase current is the best.

[0042] Specifically, Figure 4B The voltage vector U is shown. x The modulated sector waveform. At the sector switching position, only one voltage vector is active. As shown in the figure, U x The only vector during the conduction process is the U4(100) voltage vector, therefore, if... Figure 3 Single-resistor sampling can only sample the phase current i of phase a. a If you want to reconstruct the three-phase current i a i b i c This needs to be achieved by inserting other voltage vectors and phase shifting operations, but this operation will result in the output voltage vector not being the true U. x This will introduce some deviation. Furthermore, even with this operation, the inserted voltage vectors are generally short, resulting in a short sampling window, which will lead to large fluctuations in the sampled three-phase current, affecting the final measurement accuracy.

[0043] Figure 4C The voltage vector U is shown. y The modulated sector waveform. Voltage vector U y It is located far from the sector switching position, that is, its voltage vector position is located in the middle of the two sector switching positions. As shown in the figure, U y The voltage vector during the conduction process is the result of the combined action of the U4(100) voltage vector and the U6(100) voltage vector, and the two voltage vectors act for the same duration. The negative current of phase c is obtained by sampling at sampling point 1. c The positive current i of phase a is obtained at sampling point 2. a The voltage vector conduction time at sampling points 1 and 2 is relatively long, resulting in a longer sampling window and smaller current fluctuations. The current i can be obtained using Kirchhoff's laws. b This allows for a more accurate determination of the three-phase current.

[0044] In other words, the further the voltage vector is from the sector switching position, the more uniform the synthesis of two adjacent vectors in U1 to U6 can be obtained, and the better the effect of single resistor sampling of three-phase current. To this end, an improved high-frequency injection rotor polarity determination scheme is proposed. This scheme is based on the saturated salient pole effect, injecting voltage at a reference angle far from the sector switching position and its reverse angle, and determining whether the actual rotor position (i.e., the actual "rotor angle" or "d-axis direction") is the same as or opposite to the observed position by comparing the magnitude of the response current vector.

[0045] Figure 5 A method for operating a permanent magnet synchronous motor according to an embodiment of the present invention is illustrated. This method determines the rotor polarity by combining a reference injection angle with a re-injection, i.e., whether the rotor angle should be the initial observed angle or a reverse angle differing by 180°.

[0046] In step S510, a high-frequency voltage is injected to obtain the initial observation angle. The initial observation angle can be obtained as follows: Figure 2 As shown, the initial observation angle is obtained by injecting a high-frequency voltage onto the d-axis and extracting the high-frequency current response from the q-axis current, wherein the high-frequency voltage injected onto the d-axis can be a high-frequency pulsating voltage signal (e.g., Figure 2 The U shown m cos(ω i t)) or high-frequency square wave voltage signal.

[0047] It is worth noting that high-frequency injection position detection is performed during motor startup before the FOC controls the motor to rotate, and includes two stages: stationary position detection (obtaining the initial observation angle) and polarity determination. Figure 2 During the initial observation angle acquisition phase, the motor operates under open-loop control. At this time, the V outputs of PID2 and PID3 are... d and V q It is 0, only in V d A high-frequency voltage signal (high-frequency pulsed voltage signal or high-frequency square wave signal) is injected; during the polarity determination phase, it is still open-loop control, only V d A short-duration, constant-amplitude voltage vector is injected for polarity determination. After position detection is complete, the FOC controls the motor to rotate in a closed loop. At this point, all three PID controllers participate in the control. Figure 2 Under the closed-loop control shown, the speed loop PID1 and the dq-axis current loops PID2 and PID3 all participate in the control.

[0048] Subsequently, in step S520, the reference injection angle closest to the initial observation angle from a plurality of reference injection angles can be selected as the first injection angle. Here, the reference injection angle is the angle in the voltage vector circle away from the sector switching position, and preferably is the angle located in the middle of each sector in the voltage vector circle. As previously stated... Figure 4A Analysis of -C shows that during single-resistor sampling, the injected voltage vector direction is U. x When the angle between the injected voltage vector and the axis of winding A, B, or C is 0° (i.e., the direction of the injected voltage vector is U), x When the sector switching position in the voltage vector circle is considered, the sampling effect of three-phase current is the worst. The sector switching positions in the voltage vector circle include 0°, 60°, 120°, 180°, 240°, and 300°; while the injected voltage vector direction U... y When the angle between the current and the axis of winding A, B, or C is 30°, it is easier to obtain accurate three-phase current. Therefore, during the polarity determination process, the preferred directions of the injected voltage vector are 30°, 90°, 150°, 210°, 270°, and 330°. That is, multiple reference injection angles can be 30°, 90°, 150°, 210°, 270°, and 330°.

[0049] In step S530, a voltage vector of equal amplitude can be injected at both the first injection angle and a second injection angle that differs from the first injection angle by 180° to obtain a first current vector obtained by injecting voltage at the first injection angle and a second current vector obtained by injecting voltage at the second injection angle. Here, the voltage injection at the first and second injection angles is a short-duration, equal-amplitude voltage injection. "Short-duration" refers to a very short absolute injection time, typically only a few PWM switching cycles, to avoid overcurrent reactions due to excessively long injection times. Furthermore, it should be understood that "first" and "second" are merely used to distinguish between different objects of the same kind, and do not imply the order or importance of the two.

[0050] Therefore, in step S540, the initial observation angle or the angle that differs from the initial observation angle by 180° can be taken as the rotor angle based on the comparison result of the first current vector and the second current vector.

[0051] Due to the presence of the saturated salient pole effect, the d-axis inductance L d It will vary with the d-axis current i d Change, specifically, when i d When the current is greater than 0, as the d-axis current increases, the d-axis inductance L... d Gradually decrease, while when i dWhen the value is less than 0, the d-axis inductance remains unchanged. Therefore, the rotor polarity can be determined based on the relative magnitudes of the first and second current vectors. Thus, the obtained first and second current vectors include obtaining the first and second d-axis current responses.

[0052] Furthermore, based on the comparison result of the first current vector and the second current vector, taking the initial observation angle or an angle that differs from the initial observation angle by 180° as the rotor angle may include: taking the initial observation angle as the rotor angle when it is determined that the amplitude of the first current vector is greater than the amplitude of the second current vector; and taking an angle that differs from the initial observation angle by 180° as the rotor angle when it is determined that the amplitude of the first current vector is less than the amplitude of the second current vector.

[0053] In one embodiment, rotor polarity can be determined based on the magnitude of the current amplitude after injecting a short-term equal-amplitude voltage vector from a closest reference injection angle and its opposite angle. For example, when the initial observation angle is 20°, the closest 30° and its opposite 210° can be selected from 30°, 90°, 150°, 210°, 270°, and 330° for voltage injection (with the same amplitude). Based on the magnitude of the current vector obtained for each angle, the actual rotor angle can be determined to be 20° or its opposite 200°.

[0054] In another embodiment, rotor polarity can be determined based on the magnitude of the current amplitude after injection at the two closest reference injection angles and their opposite angles. This doubles the number of current sampling points, making the determination method more reliable.

[0055] Therefore, selecting the reference injection angle closest to the initial observation angle from multiple reference injection angles as the first injection angle includes: selecting the two closest reference injection angles that are ahead and behind the initial observation angle from multiple reference injection angles as two first injection angles, and injecting a short-time constant amplitude voltage vector at the first injection angle and at a second injection angle that differs from the first injection angle by 180°, to obtain a first current vector obtained by injecting voltage at the first injection angle and a second current vector obtained by injecting voltage at the second injection angle includes: injecting a short-time constant amplitude voltage vector at the two first injection angles and at two second injection angles that differ from the two first injection angles by 180°, to obtain two first current vectors obtained by injecting voltage at the two first injection angles and two second current vectors obtained by injecting voltage at the two second injection angles.

[0056] Based on the comparison results of the first current vector and the second current vector, taking the initial observation angle or an angle that differs from the initial observation angle by 180° as the rotor angle includes: taking the initial observation angle as the rotor angle when it is determined that the sum of the amplitudes of the two first current vectors is greater than the sum of the amplitudes of the two second current vectors; and taking an angle that differs from the initial observation angle by 180° as the rotor angle when it is determined that the sum of the amplitudes of the two first current vectors is less than the sum of the amplitudes of the two second current vectors.

[0057] Injections in the same direction and in opposite directions can be performed sequentially. Specifically, short-duration, equal-amplitude voltage vectors can be injected into the two first injection angles to obtain the sum of two first current vectors obtained from the voltage injection at the two first injection angles; and after obtaining the sum of the two first current vectors, short-duration, equal-amplitude voltage vectors can be injected into the two second injection angles to obtain the sum of two second current vectors obtained from the voltage injection at the two second injection angles.

[0058] Similarly, for example, with an initial observation angle of 20°, two closest reference injection angles can be selected from 30°, 90°, 150°, 210°, 270°, and 330°: 30° and 330°, and 210° and 150° respectively, which are opposite to 30° and 330°. First, voltage vector injections can be performed at 30° and 330°, thereby obtaining the sum of the d-axis current amplitudes. Subsequently, voltage vector injections can be performed at 210° and 150°, thereby obtaining the sum of the d-axis current amplitudes. It should be understood that the voltage injection amplitudes at these angles should be the same, or at least the sum of the voltage vector amplitudes at 0° and 330° should be the same as the sum of the voltage vector amplitudes at 210° and 150°. Then, based on the magnitude of the sum of the d-axis current amplitudes, it can be determined whether the actual rotor angle is 20° or its opposite 200°.

[0059] The polarity determination method of the present invention is particularly applicable to Figure 5 The diagram shows the use of a single resistor to sample and obtain the currents of phases a, b, and c, and then the calculation of the q-axis current response i based on the obtained phases a, b, and c currents. q and the first d-axis current response i d and the second d-axis current response i d The sampling scenario. As before. Figure 1 As shown, the three-phase current i is obtained through the sampling resistor. a i b i c After Clark transformation, the α-axis and β-axis currents i are obtained. α and i β Then, after Park transformation, the feedback d-axis and q-axis currents i are obtained. d and iq .

[0060] The theoretical basis for the above-described operation of this invention will be explained below. Figure 6 The actual d-axis and the injected voltage are shown. A diagram showing the angular relationship between the axes. Here, let θ be the angle between the true d-axis and the α-axis. r Injected voltage The angle between the axis and the α-axis is The difference between the two is Δθ r .

[0061] The voltage model of IPMSM (Interior PMSM) on the dq coordinate axis is as follows:

[0062]

[0063] Here, R s L is the stator resistance. d For the d-axis inductance, L q For q-axis inductance, ω e Let ψ be the electric angular velocity (which can be obtained from the rotational speed n). f It is a magnetic flux.

[0064] When voltage injection is performed, the injection time is generally short (usually a few PWM switching cycles) to avoid overcurrent reactions caused by excessively long injection times. Because the injection time is short, the current response is mainly influenced by the inductance; therefore, by removing the minimum term, (1-1) can be simplified to:

[0065]

[0066]

[0067] Since the injected voltage vector is four of six voltage vectors: 30°, 90°, 150°, 210°, 270°, and 330°, and the angle between the true d-axis and the α-axis is θ. r Injected voltage The angle between the axis and the α-axis is Then the injected voltage can be Transforming the coordinate system to the true dg coordinate system, we get:

[0068]

[0069] Expanded to:

[0070]

[0071] At this point, we can define Equation 1-5 can be simplified to:

[0072]

[0073] According to Equation 1-3, the rate of change of current on the actual dq coordinate axis is:

[0074]

[0075] Because the injection voltage is only Since the d-axis inductance has saturated salient polarity, while the q-axis inductance does not, equation 1-7 can be simplified to:

[0076]

[0077] Transform the rate of change of current in the true dq coordinate system to the observed value. With a coordinate system, we can now obtain:

[0078]

[0079] As mentioned earlier, during the entire process of detecting the rotor angle θ, the high-frequency injected voltage has a high frequency and a mean of 0 during the initial observation angle acquisition stage in the first stage, and the voltage injection time is very short during the polarity determination stage, only a few PWM cycles. Therefore, the current response generated by the two voltage injections will not cause the motor to move, that is, the motor is in a stationary state. Therefore, Δθ is a constant value.

[0080]

[0081] Expanded to:

[0082]

[0083] In the formula Simplifying, we get:

[0084]

[0085] thereby:

[0086]

[0087] As can be seen from the above, without considering the saturated salient pole effect, when Δθ is smaller, in Inject the same amount of time t on square wave voltage hour, shaft current rate of change The larger the value, the longer the time t will be. on The current obtained The larger it is. But t onIt generally shouldn't be too long. On the one hand, if it's too long, it will cause the motor to rotate; on the other hand, if t... on Too long The current will tend to stabilize, but the polarity determination is based on the current change process. At this time, the polarity determination is prone to error.

[0088] When considering the saturated salient pole effect, i.e., the d-axis inductance L d (Δθ) with the d-axis current i d Changes with change, when i d When Δθ > 0, as Δθ decreases, the d-axis inductance L d (Δθ) will gradually decrease, and the d-axis current will gradually increase (when Δθ=0, the d-axis current i) d (maximum); while when i d When <0, the d-axis inductance remains unchanged. Equation 1-12 can be rewritten as:

[0089]

[0090] Equation 1-13 can be rewritten as:

[0091]

[0092] In one embodiment, Figure 5 Step S530 (i.e., the second short-time constant amplitude voltage vector) is under open-loop control (i.e. Figure 2 Speed ​​loop PID1, current loop PID2 and PID3 are all disconnected, and the q-axis voltage U q Given 0); then at the first injection angle and the reverse second injection angle, the d-axis voltage U d A short-duration, constant-amplitude voltage vector is injected. This is due to one of the first and second injection angles... Compared to the actual rotor angle θ r When the angle difference Δθ is less than 90°, saturated convexity will occur. Therefore, the obtained first current vector and second current vector (i d Differences: For example, the true d-axis θ r It's 20°, assuming the first and second injection voltage angles are... If the angles are 30° and 210° respectively, then Δθ is 10° and 190°, and 2Δθ is 20° and 380°. Therefore, their cos(2Δθ) must be equal. However, due to the saturated convexity, their L values ​​are different. d (Δθ) is different (specifically, when Δθ is less than 90°, L) d Get smaller, i d When i increases and Δθ = 0 d (Maximum), for example here When the angle is 30°, a saturated convex polarity will occur when Δθ is 10°, therefore L d(θ=30°) <L d (θ=210°), resulting in an injection direction that is closer to the true angle. The obtained ID is relatively large, and the actual rotor angle is determined based on this.

[0093] Figure 7 The theoretical currents obtained with and without considering the saturation salient pole effect are shown for different Δθ values. The value can be obtained based on Equation 1-13. Figure 7 The theoretical current without considering the saturation salient pole effect Value; and based on Equation 1-15, we obtain Figure 7 Theoretical current considering saturated salient pole effect Value. As shown in the figure, if the saturated salient pole effect is not considered, then at the current angle to U d The current value obtained by injecting voltage is the same as that at the reverse angle (difference of 180°) towards U. d The injected voltage produces the same current value. However, when considering the saturation salient effect, the current value is equal to the current value at the reference injection angle at the actual location. d The d-axis current amplitude obtained by injecting voltage will be larger.

[0094] Figure 8 An example of determining the true rotor position based on this invention is shown. For example, the true rotor position is located at the d-axis position in the figure, with an angle θ between it and the rotor A-phase winding axis (α-axis). r The angle is 20°, while the rotor position observed through high-frequency injection is located at the d1 axis position in the figure (in this example, the position observed by high-frequency injection differs from the actual position by 180°; in reality, there are two cases where the position observed by high-frequency injection is the same as the actual position or differs from the actual position by 180°), and the angle θ between it and the rotor A-phase winding axis (α axis) is... r The value is 200°. Therefore, among the six reference injection angles, the two closest to the d1 axis position (200°) are selected to inject short-duration equal-amplitude voltage vectors, specifically at 150° and 210°. Simultaneously, short-duration equal-amplitude voltage vectors are injected at 330° and 30°, which differ from these two reference injection angles by 180°. Based on the saturated salient pole effect, L... d (θ=150°)>L d (θ=330°), L d (θ=210°)>L d (θ=30°). Therefore, combining with (1-14), we can know that... Since the injected voltage vector is always at time t on square wave voltage Therefore, we can conclude that: Thus, by judging and The magnitude of the difference determines the polarity of the rotor. In this example, Therefore, the true rotor position is between 330° and 30°, which is the angle observed by the high-frequency injection: 200° - 180° = 20°. This allows for accurate rotor position determination even with single-resistor sampling.

[0095] In addition, the present invention can also be implemented as a permanent magnet synchronous motor. Figure 9 A schematic diagram of the composition of the FOC module of a permanent magnet synchronous motor according to an embodiment of the present invention is shown. Compared to Figure 2 , Figure 7 The FOC module shown additionally includes executable functions. Figure 5 The diagram illustrates the operation method of a permanent magnet synchronous motor, particularly the polarity determination module.

[0096] Specifically, Figure 9 The permanent magnet synchronous motor shown may include: a motor M; and a magnetic orientation vector control (FOC) module 900 for controlling the motor. All components in the figure except for the motor M can be considered part of the FOC module 900. This FOC module 900 may include: a high-frequency injection observation module 910 for monitoring the high-frequency pulse voltage U injected along the d-axis. m cos(ω i t) and from the q-axis high-frequency current response i q The initial observation angle (i.e., initial rotor position θ) for high-frequency injection observation is obtained; and the polarity determination module 920 is used to perform actions such as... Figure 5 The method corresponding to steps S520 to S540 determines the rotor angle as either the initial observation angle or an angle differing from the initial observation angle by 180°. It is worth noting that, in one embodiment, when the polarity determination module 920 executes the method described above, Figure 9 The FOC module 900 shown is under open-loop control (i.e. Figure 2 (The speed loop PID1, current loop PID2, and PID3 are all disconnected and do not participate in the control), and the q-axis voltage U q The given value is 0; then the high-frequency injection observation module 910 injects voltage U onto the d-axis at the first injection angle and the reverse second injection angle. d Injecting a constant-amplitude voltage vector (e.g., injecting a short-duration constant-amplitude voltage vector). Figure 9 (Not shown). Due to one of the first and second injection angles. Compared to the actual rotor angle θ r The angle difference Δθ is less than 90°, thus generating saturated convex polarity. Therefore, the first current vector and the second current vector (i) obtained by the polarity determination module 920 dThe difference leads to an injection direction that is closer to the true angle, resulting in an i. d The value is relatively large, which is used to determine the actual rotor angle.

[0097] Specifically, the polarity determination module 920 can select the two closest angles (preferably 30°, 90°, 150°, 210°, 270°, and 330°) from multiple reference injection angles based on the obtained initial rotor position θ, and perform short-term equal-amplitude voltage vector injections at their opposite angles, and obtain the sum of the amplitudes of the d-axis current responses. If the sum of the amplitudes of the d-axis current responses at the two closest angles is greater than the sum of the amplitudes of the d-axis current responses injected at the opposite angles, then the rotor position is determined to be θ; otherwise, it is θ+180°.

[0098] The operation 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.

[0099] This invention is particularly applicable to injecting at four of the six reference injection angles (30°, 90°, 150°, 210°, 270°, and 330°, i.e., the six angles in the voltage vector circle far from the sector switching position) in a single-resistor sampling mode. This ensures a sufficiently long sampling window, reduces fluctuations in the sampling current, and solves the problem of short sampling windows and easy errors in rotor polarity determination when polarity determination is near sector switching in conventional high-frequency injection single-resistor mode.

[0100] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for operating a permanent magnet synchronous motor, comprising: Under open-loop control, the initial observation angle for high-frequency injection observation is obtained by injecting high-frequency voltage into the d-axis and extracting high-frequency current response from the q-axis current. The reference injection angle closest to the initial observation angle is selected from multiple reference injection angles as the first injection angle, wherein the reference injection angle is the sector center angle in the voltage vector circle away from the sector switching position, including 30°, 90°, 150°, 210°, 270° and 330°; Injecting equal-amplitude voltage vectors at a first injection angle and a second injection angle 180° different from the first injection angle, to obtain a first d-axis current response obtained by injecting voltage at the first injection angle and a second d-axis current response obtained by injecting voltage at the second injection angle; and Based on the comparison results of the first d-axis current response and the second d-axis current response, the initial observation angle or the angle differing from the initial observation angle by 180° is taken as the rotor angle. Specifically, single-resistor sampling is used to obtain the currents of phase a, phase b, and phase c, and the q-axis current response, the first d-axis current response, and the second d-axis current response are calculated based on the obtained currents of phase a, phase b, and phase c.

2. The method as described in claim 1, wherein, Based on the comparison results of the first d-axis current response and the second d-axis current response, the initial observation angle or the angle differing from the initial observation angle by 180° is taken as the rotor angle, including: When it is determined that the amplitude of the first d-axis current response is greater than the amplitude of the second d-axis current response, the initial observation angle is taken as the rotor angle; and When it is determined that the amplitude of the first d-axis current response is less than the amplitude of the second d-axis current response, the angle that differs from the initial observation angle by 180° is taken as the rotor angle.

3. The method as described in claim 1, wherein, Selecting the reference injection angle closest to the initial observation angle from multiple reference injection angles as the first injection angle includes: From multiple reference injection angles, the two closest reference injection angles that are ahead and behind the initial observation angle are selected as the two first injection angles, and Injecting equal-amplitude voltage vectors at a first injection angle and a second injection angle 180° different from the first injection angle to obtain a first d-axis current response obtained by injecting voltage at the first injection angle and a second d-axis current response obtained by injecting voltage at the second injection angle includes: A voltage vector of equal amplitude is injected at the two first injection angles and at two second injection angles that are 180° apart from the two first injection angles, in order to obtain two first d-axis current responses obtained by injecting voltage at the two first injection angles and two second d-axis current responses obtained by injecting voltage at the two second injection angles.

4. The method of claim 3, wherein, Based on the comparison results of the first d-axis current response and the second d-axis current response, the initial observation angle or the angle differing from the initial observation angle by 180° is taken as the rotor angle, including: When it is determined that the sum of the amplitudes of the two first d-axis current responses is greater than the sum of the amplitudes of the two second d-axis current responses, the initial observation angle is taken as the rotor angle; and When it is determined that the sum of the amplitudes of the two first d-axis current responses is less than the sum of the amplitudes of the two second d-axis current responses, the angle that differs from the initial observation angle by 180° is taken as the rotor angle.

5. The method of claim 1, wherein, Injecting a constant-amplitude voltage vector at the first injection angle and at a second injection angle that differs from the first injection angle by 180° includes: Under open-loop control, the q-axis voltage is given as 0. The equal-amplitude voltage vector is injected into the d-axis voltage at the first injection angle and the second injection angle. Wherein, the angle difference between one of the first injection angle and the second injection angle and the rotor angle is less than 90°.

6. A permanent magnet synchronous motor, comprising: Electric motor; A magnetic orientation vector control module, used to control the motor, includes: The high-frequency injection observation module is used to obtain the initial observation angle for high-frequency injection observation from the voltage injected along the d-axis and the high-frequency current response along the q-axis. as well as The polarity determination module is used to execute the method as described in any one of claims 1-5 to determine the initial observation angle or an angle that differs from the initial observation angle by 180° as the rotor angle.

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