Method for determining initial rotor angle of permanent magnet synchronous motor and permanent magnet synchronous motor

Abstract

The invention discloses a permanent magnet synchronous motor initial rotor angle determination method and a permanent magnet synchronous motor. The method comprises the following steps: injecting square wave pulses in different predetermined directions in sequence according to a two-two conduction mode and a three-three conduction mode so as to obtain a current value corresponding to each predetermined direction; selecting a first maximum current value in the three-three conduction so as to determine a first angle, and selecting a second maximum current value in the two-two conduction so as to determine a second angle; and determining an initial rotor angle of the motor according to the first and second angles. According to the invention, the initial position of the rotor is determined according to the square wave injection direction corresponding to the maximum response current respectively determined by the two-two conduction and the three-three conduction. Furthermore, the difference degree between the response currents can be quantized, and the initial positions determined by the two-two conduction and the three-three conduction respectively are adjusted according to the quantized value, so that a more accurate initial position point is obtained.

Description

Technical Field

[0001] The present disclosure relates to the field of motors, and in particular to a method for determining an initial rotor angle of a permanent magnet synchronous motor and a permanent magnet synchronous motor. Background Art

[0002] In the control process of permanent magnet synchronous motor (PMSM), in order to obtain the maximum torque output in the entire control cycle, FOC (Field-Oriented Control) is often used to control the motor.

[0003] Park transformation and inverse Park transformation in FOC control both require 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. Common PMSM 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; sensorless detection generally includes sliding mode position detection, Lumberg position detection and other position detections. Among them, the incremental encoder detection in encoder position detection and sensorless position detection usually use VF (constant voltage-frequency ratio) or IF (constant current-frequency ratio) starting methods at startup. When performing VF / IF startup, the initial position of the rotor needs to be known to avoid motor reversal caused by open-loop forced drag. However, the existing initial position detection scheme (for example, injection position detection) is susceptible to noise interference and is likely to be opposite to the actual position, so it is difficult to avoid the occurrence of motor reversal.

[0004] Therefore, an improved rotor initial position identification scheme is needed. Summary of the invention

[0005] A technical problem to be solved by the present disclosure is to provide a method for determining the initial rotor angle of a permanent magnet synchronous motor and a permanent magnet synchronous motor. The method determines the initial position of the rotor according to the square wave injection direction corresponding to the maximum response current determined by the two-two conduction and the three-three conduction. Furthermore, the degree of difference between the response currents can be quantified, and the initial positions determined by the two-two conduction and the three-three conduction can be adjusted according to the quantified value, thereby obtaining a more accurate initial position point.

[0006] According to a first aspect of the present disclosure, a method for determining an initial rotor position of a permanent magnet synchronous motor is provided, comprising: injecting square wave pulses in different predetermined directions in sequence according to a 2-2 conduction and a 3-3 conduction manner to obtain a current value corresponding to each predetermined direction; selecting a first maximum current value from a plurality of first current values ​​of the predetermined direction corresponding to the 3-3 conduction, determining a first angle according to the first maximum current value, and selecting a second maximum current value from a plurality of second current values ​​of the predetermined direction corresponding to the 2-2 conduction, determining a second angle according to the second maximum current value; and obtaining an average of the first angle and the second angle as the initial rotor angle of the motor.

[0007] Optionally, the three-three conduction square wave pulse injection is performed in multiple first predetermined injection directions, and the two-two conduction square wave pulse injection is performed in multiple second predetermined injection directions, one of the second predetermined injection directions is spaced between every two adjacent first predetermined injection directions, and the spacing angles on both sides are equal.

[0008] Optionally, a first maximum current value is selected from multiple first current values ​​in a predetermined direction corresponding to the three-three conduction, a first angle is determined based on the first maximum current value, and a second maximum current value is selected from multiple second current values ​​in the predetermined direction corresponding to the two-two conduction, and a second angle is determined based on the second maximum current value, including: measuring a first degree of difference between the first maximum current value and current values ​​corresponding to adjacent injection directions on both sides, and determining the first angle based on the first degree of difference; and measuring a second degree of difference between the second maximum current value and current values ​​corresponding to adjacent injection directions on both sides, and determining the second angle based on the second degree of difference.

[0009] Optionally, measuring the first degree of difference between the first maximum current value and the current values ​​corresponding to the adjacent injection directions on both sides, and determining the first angle according to the first degree of difference includes: obtaining the first standard deviation of the multiple first current values; calculating the ratio of the difference between the first maximum current value and the current values ​​corresponding to the adjacent injection directions on both sides to the first standard deviation, so as to obtain a first reduction angle error and a first increase angle error; and determining whether the first angle is greater than, equal to or less than the injection angle corresponding to the first maximum current value according to the first reduction angle error and the first increase angle error, wherein measuring the second degree of difference between the second maximum current value and the current values ​​corresponding to the adjacent injection directions on both sides, and determining the second angle according to the second degree of difference includes: obtaining the second standard deviation of the multiple second current values; calculating the ratio of the difference between the second maximum current value and the current values ​​corresponding to the adjacent injection directions on both sides to the second standard deviation, so as to obtain a second reduction angle error and a second increase angle error; and determining whether the second angle is greater than, equal to or less than the injection angle corresponding to the second maximum current value according to the second reduction angle error and the second increase angle error.

[0010] Optionally, determining whether the first angle is greater than, equal to or less than the injection angle corresponding to the first maximum current value based on the first increasing angle error and the first decreasing angle error includes: selecting a smaller value from the first decreasing angle error and the first increasing angle error as the first error; when the first error is greater than the first threshold, determining that the first angle is equal to the injection angle corresponding to the first maximum current value; when the first error is the first decreasing angle error and is less than the first threshold, determining that the first angle is between the injection angle corresponding to the first maximum current value and an adjacent smaller injection angle; and when the first error is the first increasing angle error and is less than the first threshold, determining that the first angle is between the injection angle corresponding to the first maximum current value and an adjacent larger injection angle , wherein, according to the second increasing angle error and the second decreasing angle error, determining whether the second angle is greater than, equal to or less than the injection angle corresponding to the second maximum current value includes: selecting a smaller value from the second decreasing angle error and the second increasing angle error as the second error; when the second error is greater than the second threshold, determining that the second angle is equal to the injection angle corresponding to the second maximum current value; when the second error is the second decreasing angle error and is less than the second threshold, determining that the second angle is between the injection angle corresponding to the second maximum current value and an adjacent smaller injection angle; and when the second error is the second increasing angle error and is less than the second threshold, determining that the second angle is between the injection angle corresponding to the second maximum current value and an adjacent larger injection angle.

[0011] Optionally, a three-by-three conduction square wave pulse injection is performed in six first predetermined injection directions, and a two-by-two conduction square wave pulse injection is performed in six second predetermined injection directions, and when the first error is less than the first threshold, the first angle is equal to the injection angle corresponding to the first maximum current value increased or decreased by 30°; when the second error is less than the second threshold, the second angle is equal to the injection angle corresponding to the second maximum current value increased or decreased by 30°.

[0012] Optionally, conduction control is performed in a 2-2 conduction mode and a 3-3 conduction mode to inject square wave pulses in different predetermined directions, including: after completing the square wave pulse injection in the current predetermined direction, waiting for a predetermined time and then starting the square wave pulse injection in the next predetermined direction, wherein the predetermined time is an integer multiple of the square wave voltage time.

[0013] Optionally, the stator winding of the motor is controlled to be turned on in a 2-2 conduction manner and a 3-3 conduction manner, square wave pulses are injected in different predetermined directions, and the current value corresponding to each predetermined direction is obtained, including: during the square wave injection in each predetermined direction, the response current of the d-axis is sampled and observed multiple times, and the accumulated value or average value of the response current of the d-axis sampled multiple times is used as the current value corresponding to the corresponding predetermined direction, wherein the response current of the d-axis is obtained by sampling the three-phase winding current and then subjecting it to coordinate transformation.

[0014] Optionally, during the injection of square waves in each predetermined direction, the response current of the d-axis is sampled multiple times, and the accumulated value or average value of the response current of the d-axis sampled multiple times is used as the current value in the corresponding predetermined direction, including: during the injection of square waves in each predetermined direction, the response current of the d-axis is sampled multiple times continuously using an analog-to-digital converter ADC; the sampled values ​​are transferred to an array corresponding to the corresponding value in real time through direct memory access DMA; and the accumulated value or average value is calculated based on the sampled values ​​stored in the corresponding array.

[0015] According to a second aspect of the present disclosure, a permanent magnet synchronous motor is provided, comprising: a motor; a magnetic oriented vector control module, used to control the motor and execute the method described in the first aspect to determine the initial rotor angle, and comprising: an injection module, used to perform conduction control in a two-two conduction and a three-three conduction manner to inject square wave pulses in different predetermined directions; an acquisition module, used to obtain the current value corresponding to each of the predetermined directions; and a calculation module, used to select a first maximum current value from a plurality of first current values ​​of the predetermined direction corresponding to the three-three conduction, and determine a first angle according to the first maximum current value; select a second maximum current value from a plurality of second current values ​​of the predetermined direction corresponding to the two-two conduction, and determine a second angle according to the second maximum current value; and obtain the average of the first angle and the second angle as the initial rotor angle of the motor.

[0016] Optionally, the acquisition module includes: a sampling submodule, used to sample the response current of the observed d-axis during square wave injection; and a storage submodule, used to store the sampled response current of the observed d-axis, and thereby obtain the current value corresponding to each of the predetermined directions.

[0017] Therefore, the initial rotor angle determination method disclosed in the present invention determines the initial position by combining the maximum response current determined by the two-two conduction and the three-three conduction. Further, the optimal initial position can be found by the standard deviation discrimination method to improve the resolution of the rotor initial position identification. Further, the response current sampling values ​​can be accumulated, and the rotor initial position can be determined according to the size of the accumulated value or its mean, thereby eliminating high-frequency interference and improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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.

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

[0020] Figure 2 An example of the relative relationship between the real d-axis and q-axis and the observed d-axis and q-axis under the αβ coordinate axis is shown.

[0021] Figure 3 The theoretical current obtained with different Δθ without considering the saturation salient effect is shown. value.

[0022] Figure 4 The theoretical current obtained by considering the saturation salient effect with different Δθ is shown. value.

[0023] Figure 5 A schematic diagram showing the voltage vectors in six directions during the three-to-three conduction process.

[0024] Figure 6 An example of current flow when three-three conduction occurs is shown.

[0025] Figure 7 Shows Figure 6 Schematic diagram of the resultant voltage under the conditions of winding flow shown.

[0026] Figure 8 An example of current flow when two-two conduction occurs is shown.

[0027] Fig. 9 Shows Figure 8 Schematic diagram of the resultant voltage under the conditions of winding flow shown.

[0028] Fig. 10A -C is a schematic diagram showing the direction of the synthetic voltage vector for two-two conduction and three-three conduction.

[0029] Fig.11 A schematic flow chart of a method for determining an initial rotor angle of a permanent magnet synchronous motor according to an embodiment of the present disclosure is shown.

[0030] Fig.12 The injected voltage and the response current at various predetermined angles are shown.

[0031] Fig.13 The response currents sampled when square wave pulses are injected at multiple predetermined angles and the corresponding accumulated values ​​are shown.

[0032] Fig.14 A schematic diagram of a permanent magnet synchronous motor according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0033] 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.

[0034] 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.

[0035] 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 subtraction is made from the acquired rotor speed n and is input to PID1 (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 The q-axis and d-axis voltages V are output after being adjusted by PID2 (i.e., q-axis current loop) and PID3 (i.e., d-axis current loop) respectively. d and V q , and then converted into α-axis and β-axis voltage V through Park inverse transformation α and V β , 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 , respectively input PID2 and PID3 to participate in current loop control.

[0036] exist Figure 1 Among the components shown, except for the motor M and the three-phase inverter bridge, the other parts can be regarded as part of the MCU (microcontroller) of the motor, which is used to perform FOC control on the motor.

[0037] In FOC control, Park transform and Park inverse transform are as follows: Figure 1 All of the above require knowledge of the rotor position θ (i.e., the electrical angle θ of the motor rotor. The motor rotor rotates 360° in one electrical cycle. Therefore, the value range of the vertical axis position (θ) in the following position-time figure 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 is to the maximum torque output.

[0038] 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 1 The rotor position and speed detection module in the controller can be realized by a magnetic encoder.

[0039] However, in some applications, for example, due to cost or integration considerations, it is necessary to realize position detection and motor control without sensors. Sensorless detection includes sliding mode position detection, Lumberg position detection, injection position detection, etc. Among them, the incremental encoder detection in the encoder position detection and the sensorless position detection usually adopt VF (constant voltage-frequency ratio) or IF (constant current-frequency ratio) starting method at startup. When performing VF / IF startup, it is necessary to know the initial position of the rotor to avoid motor reversal caused by open-loop forced drag, and the existing initial position detection scheme (for example, injection position detection) is susceptible to noise interference and may be opposite to the actual position, so it is difficult to avoid the occurrence of motor reversal. In some applications, such as some pump loads, motor reversal can easily damage the equipment.

[0040] At present, the most common initial position recognition method is the signal processing method of square wave pulse injection, which is mostly carried out in six directions of 0°, 60°, 120°, 180°, 240°, and 300°. After a period of injection (depending on the characteristics of the motor, the time is different, generally tens or hundreds of microseconds), the response current at this time is sampled by ADC (the current value is sampled once in each of the six directions), and according to the magnitude of the response current in the six directions, the injection direction with the largest response current is selected as the initial position of the rotor. This signal processing method works better for response currents with less noise, but in some application scenarios where the current is mixed with larger noise, this signal processing method is very likely to cause errors in the initial position judgment of the rotor.

[0041] At the same time, the above method uses a method of injecting a pulse every 60°, and the resolution of the initial position of the rotor is low. For example, after the pulse is injected in six directions, the current amplitude response in the 0° direction is the largest, and the method considers 0° to be the true position of the rotor. However, in reality, the response current amplitude obtained when the rotor is in the range of -330° to 30° is the largest at 0°, and the theoretical resolution is ±30°. Furthermore, this method is susceptible to interference from environmental noise during actual operation. When the rotor position is slightly greater than 30° or slightly greater than -330°, the current amplitude response in the 0° direction may be the largest. At this time, the rotor resolution even exceeds ±30°, resulting in a lower resolution.

[0042] For this reason, in the present disclosure, square wave pulse injection is selected in twelve directions of 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°. Further, in order to ensure that the drive output does not change when the corresponding angle is injected, that is, the voltage vector is not synthesized by more than one voltage vector, but is driven by a single vector, thereby ensuring the continuity of the response current. Specifically, a three-three conduction mode is adopted at 0°, 60°, 120°, 180°, 240°, and 300°, and a two-two conduction mode is adopted at 30°, 90°, 150°, 210°, 270°, and 330°. The first angle at which the response current is the largest determined by the three-three conduction and the second angle at which the response current is the largest determined by the two-two conduction can be comprehensively considered, and the initial position of the rotor is determined accordingly.

[0043] Furthermore, since the response currents obtained by the three-three conduction and the two-two conduction are not equal, the two-two conduction and three-three conduction standard deviation discrimination methods are used to find the optimal initial position point to improve the rotor position measurement resolution.

[0044] In addition, when the obtained response current is mixed with large noise that affects the measurement accuracy, the ADC on the MCU can be used to continuously sample the response current signal after the pulse is injected, and the average is calculated. This multiple averaging method can be combined with the above standard deviation discrimination method to determine the initial position of the rotor. In this way, the influence of the burr phenomenon on the measurement accuracy is avoided, and the rotor position measurement accuracy is improved.

[0045] In order to facilitate the understanding of the principles of the present disclosure, the following will first describe the injection determination of the initial position of the rotor, as well as the principles of three-three conduction and two-two conduction. When performing principle analysis, the current fluctuation caused by the turning on and off of the MOS tube is not considered, and only the analysis is performed from the perspective of principle. At this time, the observed d-axis can be at any position between 0° and 360°. The introduction of this principle part is mainly to prove that when the observed d-axis position is closer to the actual d-axis position of the rotor, the response current is the largest. Therefore, when performing initial position identification, for example, a square wave pulse voltage vector can be injected at 0°, 60°, 120°, 180°, 240°, and 300° using a three-three conduction method, and a square wave pulse voltage vector can be injected at 30°, 90°, 150°, 210°, 270°, and 330° using a two-two conduction method, and these 12 vector directions are respectively used as the observed d-axis directions (at this time, the observed d-axis directions are no longer any position between 0° and 360°, but these 12 fixed angles), and the initial position of the rotor is determined by finding the observed d-axis response currents in the 12 voltage vector directions of the three-three conduction method and the two-two conduction method. The relevant principles will be introduced as follows.

[0046] The voltage model of IPMSM (Interior PMSM, i.e. built-in PMSM) on the dq coordinate axis is:

[0047]

[0048] Among them, 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.

[0049] When a square wave pulse voltage is injected, the injection time is generally short to avoid an overcurrent reaction caused by a long injection time. Therefore, when a square wave voltage is injected into the observation d axis, the motor is in a stationary state, so the back electromotive force can be ignored. Since the stator resistance is very small, it can also be ignored. Therefore, equation (1) can be simplified to:

[0050]

[0051]

[0052] In the actual control process, since it is impossible to know the actual position of the rotor, θ r , so it is observed A square wave pulse voltage is injected into the coordinate system. Figure 2 The figure shows the relative relationship between the real d-axis and q-axis and the observed d-axis and q-axis under the αβ coordinate axis. As shown in the figure, the real position of the rotor can be set as θ r , the rotor observation position is When injecting, the actual position of the rotor is unknown, so the injection is performed while observing the d-axis.

[0053] The injected voltage The coordinate system is transformed into the real dq coordinate system, and we get:

[0054]

[0055] Expand to:

[0056]

[0057] definition, Then formula (5) can be simplified as:

[0058]

[0059] According to formula (3), the real current change rate on the dq coordinate axis is:

[0060]

[0061] Since the injected voltage is only Axis injection, so formula (7) can be simplified as:

[0062]

[0063] Transform the current change rate under the real dq coordinate axis to the observed Coordinate system, we can get:

[0064]

[0065] Since the motor is at rest, Δθ is a constant, so:

[0066]

[0067] Expand to:

[0068]

[0069] In the formula

[0070] Simplified:

[0071]

[0072] thereby:

[0073]

[0074] Without considering the saturation salient effect (i.e., at this time, the d-axis inductance L d Not with d-axis current i d When Δθ is smaller, Inject for the same time t on Square wave voltage hour, Shaft current Rate of change The larger the square wave voltage time t on The current obtained The bigger, Figure 3 The theoretical current obtained with different Δθ without considering the saturation salient effect is shown. value.

[0075] During the actual injection, t on Too long will cause the motor to saturate, making it impossible to distinguish the current when different square wave pulse injection angles are used. In addition, too long an injection time will cause the motor to rotate. Therefore, in practical applications, depending on the characteristics of the motor, a few tens or hundreds of microseconds are generally selected for injection.

[0076] When considering the saturation salient pole effect, that is, the d-axis inductance L d () With the d-axis current i d Change and change, when i d >0, as the d-axis current increases, the d-axis inductance L d () will gradually decrease, and when i d <0, the d-axis inductance remains unchanged. Formula (12) can be expressed as:

[0077]

[0078] Formula (13) can be expressed as:

[0079]

[0080] At this time, the theoretical current obtained when Δθ (that is, as mentioned above, Δθ represents the angle between the observed d-axis and the real d-axis) is different Value Figure 4 shown. Figure 4 The theoretical current obtained with different Δθ when the saturation salient effect is not considered is shown. value.

[0081] Based on formula (15) and Figure 4 It can be seen that the smaller Δθ is, the closer the position of the injected square wave pulse signal is. The closer to the true rotor position θ r , the larger the response current is.

[0082] From the above derivation, it can be seen that regardless of whether the saturation saliency is considered, The larger the direction, the smaller Δθ is. This provides a theoretical basis for taking the injection direction with the largest response current as the initial position of the rotor when a square wave is injected in different directions.

[0083] In the prior art, square wave injection can be performed by three-to-three conduction or two-to-two conduction. Three-to-three conduction is a control method used in FOC. Of the six MOS tubes in the three-phase winding, three are always in the on state and the other three are in the off state. The following will be analyzed in combination with the voltage and current model of FOC.

[0084] Figure 5 The schematic diagram of the voltage vectors in six directions during the three-three conduction process is shown. As shown in the figure, in the case of three-three conduction, the voltage vectors in six directions of 0°, 60°, 120°, 180°, 240°, and 300° are output during the FOC control process.

[0085] Taking U4 (100) as an example, at this time, phase A is positively conducting, phase B is negatively conducting, and phase C is negatively conducting. The current flowing into the motor is positive, and the current flowing out is negative. At this time, the current flow direction is as follows: Figure 6 shown. Figure 6 An example of current flow when three-three conduction occurs is shown.

[0086] The equivalent circuit is that the B-phase winding and the C-phase winding are connected in parallel and then in series with the A-phase winding. Therefore, the A-phase winding current is i a , the B phase current winding current is i b , the C phase current winding current is i c ,i a = -2×i b = -2×i c .

[0087] At this time, the synthetic voltage vector is

[0088]

[0089] Thus, the magnitude of the resultant voltage is:

[0090]

[0091] Figure 7 Shows Figure 6 Schematic diagram of the resultant voltage under the condition of winding flow direction shown. Figure 7 As shown, at this time, the direction of the synthetic vector points to the axis of the A-phase winding (0° direction).

[0092] As above combined Figure 6 and Figure 7 An example is given where the composite voltage vector of A+BC- points to the axis of the A-phase winding (in the 0° direction) when three-three is turned on. Similarly, the composite voltage vector of A+B+C- points between the axes of the A-phase winding and the B-phase winding (in the 60° direction); the composite voltage vector of A-B+C- points to the axis of the B-phase winding (in the 120° direction); the composite voltage vector of A-B+C+ points between the axes of the B-phase winding and the C-phase winding (in the 180° direction); the composite voltage vector of AB-C+ points to the axis of the C-phase winding (in the 240° direction); and the composite voltage vector of A+B-C+ points between the axes of the C-phase winding and the A-phase winding (in the 300° direction).

[0093] 2-2 conduction is a control method used in BLDC (brushless DC motor) applications, but it can be used in FOC to identify the initial position of the motor. In the 2-2 conduction state, only 2 of the 6 MOS tubes of the three-phase winding are in the on state, and the other 4 are in the off state.

[0094] Figure 8An example of the current flow when two are turned on is shown in FIG. Figure 8 In the example, AC is turned on. At this time, the A-phase winding is forward-conducting and the C-phase winding is negative-conducting. The current flowing into the motor is positive and the current flowing out is negative. At this time, the current flow direction is as shown in the figure.

[0095] The equivalent circuit is the A-phase winding and the C-phase winding in series. Therefore, the A-phase winding current is i a , the C phase winding current is i c ,i a =-i c ,

[0096] At this time, the synthetic voltage vector is

[0097]

[0098] Thus, the magnitude of the resultant voltage is:

[0099]

[0100] Fig. 9 Shows Figure 8 Schematic diagram of the resultant voltage under the condition of winding flow direction shown. Fig. 9 As shown, the direction of the AC composite voltage vector is 30°. Similarly, the direction of the BC composite voltage vector is 90°, the direction of the BA composite voltage vector is 150°, the direction of the CA composite voltage vector is 210°, the direction of the CB composite voltage vector is 270°, and the direction of the AB composite voltage vector is 330°. At the same time, the amplitude of the composite voltage vector when two-two is turned on is the amplitude of the composite voltage vector when three-three is turned on. times.

[0101] Fig. 10A -C is a schematic diagram showing the direction of the synthetic voltage vector for two-two conduction and three-three conduction. Fig. 10A The conventional 2-2 conduction mode is shown, and the voltage vector is injected in six directions: 30°, 90°, 150°, 210°, 270°, and 330°. For example, if the voltage vector is injected in the 30° direction (A phase is forward-conducted, C phase is negatively-conducted), the response current is the largest. At this time, the rotor position can be determined to be in the range of 0° to 60°, and the angle measurement error is ±30°. Due to the interference of environmental noise during the application process in actual operation, the rotor resolution may exceed ±30°.

[0102] Fig. 10BThe conventional three-three conduction mode is shown, and the voltage vector is injected in six directions: 0°, 60°, 120°, 180°, 240°, and 300°. For example, if the voltage vector is injected in the 60° direction (A phase is forward-conducted, B phase is forward-conducted, and C phase is negatively-conducted), the response current obtained at this time is the largest, and the rotor position can be determined to be within the range of 30° to 90°, and the angle measurement error is ±30° (and affected by environmental noise during the application process, the rotor resolution may exceed ±30°).

[0103] That is, no matter whether 2-2 conduction or 3-3 conduction is selected, the measurement error is ±30° (due to the interference of environmental noise during the application process, the rotor resolution may exceed ±30°). In addition, since the voltage amplitudes actually injected by 2-2 conduction and 3-3 conduction are not equal, the current responses obtained under the same conditions are also different, and they cannot be compared with each other. Only the current vectors obtained by 2-2 conduction can be compared with each other, and the current vectors obtained by 3-3 conduction can be compared with each other. In other words, it is impossible to directly increase the measurement error to ±15° by injecting six voltage vectors of 2-2 conduction and six voltage vectors of 3-3 conduction and comparing their amplitudes to find the maximum value of the current response.

[0104] Fig. 10C It shows that the square wave voltage signal is injected by selecting the two-two conduction and the three-three conduction, and the current vector obtained by the two-two conduction and the 12 current vectors obtained by the three-three conduction are obtained respectively.

[0105] To this end, in the present disclosure, the current vectors i(30°), i(90°), i(150°), i(210°), i(270°), i(330°) obtained by 2-2 conduction are selected for comparison to find the maximum value, and the current vectors i(0°), i(60°), i(120°), i(180°), i(240°), i(300°) obtained by 3-3 conduction are selected for comparison to find the maximum value. Subsequently, the initial position of the speed is determined according to the angle corresponding to the maximum value in 2-2 conduction and the angle corresponding to the maximum value in 3-3 conduction.

[0106] Assume that the maximum current vector obtained by 2-2 conduction is i(30°), and the maximum current vector obtained by 3-3 conduction is i(60°). At this time, the rotor position is taken as the average of the angles corresponding to the maximum current vectors of 2-2 conduction and 3-3 conduction, and the rotor position is: (30°+60°) / 2=45°, while the actual rotor position is within the range of 30°~60°, which can reduce the measurement error to ±15°.

[0107] Fig.11 A schematic flow chart of a method for determining an initial rotor angle of a permanent magnet synchronous motor according to an embodiment of the present disclosure is shown.

[0108] In step S1110, square wave pulses are injected in different predetermined directions in a 2:2 conduction and 3:3 conduction manner to obtain the current value corresponding to each predetermined direction. Here, the stator winding of the motor can be controlled to be turned on in a 2:2 conduction manner to achieve injection in six directions of 30°, 90°, 150°, 210°, 270°, and 330°, and then injected in six directions of 0°, 60°, 120°, 180°, 240°, and 300° in a 3:3 conduction manner; twelve directions can be injected sequentially in increasing angles of 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 300°, and 330°; even random injection is performed, as long as the square wave injection is completed in the directions corresponding to the 3:3 conduction and the 2:2 conduction, and the corresponding current value in each predetermined method is obtained. In one embodiment of the present disclosure, since the response current requires a certain return time to zero (usually the square wave voltage time t on In other embodiments, multiple square wave pulses may be input in each predetermined direction, and in order to eliminate the influence of the previous pulse response current, the time interval between the previous and next pulses needs to be several times the square wave voltage time t on time.

[0109] In step S1120, a first maximum current value is selected from a plurality of first current values ​​in a predetermined direction corresponding to the three-three conduction, a first angle is determined according to the first maximum current value, and a second maximum current value is selected from a plurality of second current values ​​in a predetermined direction corresponding to the two-two conduction, and a second angle is determined according to the second maximum current value. Here, the plurality of current values ​​obtained by the three-three conduction and the plurality of current values ​​obtained by the two-two conduction are processed respectively. To this end, it is necessary that in the plurality of predetermined directions of the three-three conduction, the square wave pulses have the same square wave voltage time t on1 and the same pulse amplitude U m1 In multiple predetermined directions of two-two conduction, the square wave pulse has the same square wave voltage time t on2 and the same pulse amplitude U m2 In one embodiment, t on1 Can be used with t on2 Equal, U m1 Can be used with U m2 At this time, in the 12 injections for the two-two conduction and the three-three conduction, the square wave voltage time t can be injected each time. on and the same pulse amplitude U m square wave pulse.

[0110] In combination Fig.11In the initial rotor angle determination method of the present disclosure, it is necessary to consider both the first angle and the second angle to calculate the initial rotor angle of the motor. To this end, the initial rotor angle of the motor can be determined based on the first angle obtained by processing the three-three conduction current value and the second angle obtained by processing the two-two conduction current value. Therefore, in step S1130, the average of the first angle and the second angle can be obtained as the initial rotor angle of the motor.

[0111] Here, "first" and "second" are used to refer to objects of the same category but different from each other, rather than to imply a precedence or order of importance between the two. Here, the "first angle" corresponds to the initial rotor angle determined based on the current value obtained by the three-three conduction. The "second angle" corresponds to the initial rotor angle determined based on the current value obtained by the two-two conduction. By comprehensively considering these two angles, such as taking an average or a weighted value, the final initial rotor angle of the motor is determined.

[0112] The initial rotor angle determination method disclosed in the present invention performs the three-three conduction square wave pulse injection in multiple first predetermined injection directions, and performs the two-two conduction square wave pulse injection in multiple second predetermined injection directions. The first and second predetermined injection directions are spaced apart from each other. Specifically, one of the second predetermined injection directions is spaced apart between every two adjacent first predetermined injection directions, and the spacing angles on both sides are equal.

[0113] According to the previous theoretical derivation, whether or not the saturation saliency is considered, The larger the direction, the smaller Δθ. In other words, when injecting square waves in different directions, the injection direction with the largest response current can be used as the initial position of the rotor. To this end, in one embodiment, the angle corresponding to the first maximum current value among the multiple first current values ​​corresponding to the multiple first predetermined injection directions of the three-three conduction can be directly determined as the first angle. At the same time, the angle corresponding to the second maximum current value among the multiple second current values ​​corresponding to the multiple second predetermined injection directions of the two-two conduction can be directly determined as the second angle.

[0114] Specifically, when the rotor position is near the injected voltage vector (12 directions of 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°), such as when the motor is at the 90° position, for the 22 conduction, the voltage vector is injected in the 90° direction among the six voltage vectors (30°, 90°, 150°, 210°, 270°, and 330°) in the 22 conduction, that is, the B phase is forwardly conducted and the C phase is negatively conducted, and the response current obtained is the largest. Because the motor position is at 90°, the closer the direction of the injected voltage vector in the 22 conduction is to the actual position, the larger the response current obtained. At this time, the 22 conduction considers the rotor's actual position, that is, the second angle is 90° (the actual rotor position is theoretically between 60° and 120°).

[0115] For the three-three conduction, the injected voltage vector is 0°, 60°, 120°, 180°, 240°, 300°. When the motor rotor position is at 90°, the response current amplitude obtained by injecting the voltage vector in the 60° direction (A phase positive conduction, B phase positive conduction, C phase negative conduction) and injecting the voltage vector in the 120° direction (A phase negative conduction, B phase positive conduction, C phase negative conduction) is the largest, and the two response current amplitudes are approximately equal, because the absolute difference from the real position is 30°. If the response current obtained at 60° is slightly greater than the response current obtained at 120°, the three-three conduction considers the real rotor position, that is, the first angle is 60° (the real rotor position is theoretically between 30° and 90°).

[0116] Since the actual rotor position is considered to be at 90° when the 2+2 conduction is on, the actual rotor positions considered by the 2+2 conduction and the 3+3 conduction are averaged, and the rotor position is considered to be: (90°+60°) / 2=75°. In fact, affected by the current interference in the actual control process, when the motor rotor position is slightly greater than 90°, the response current obtained at 60° will be slightly greater than the response current obtained at 120°. For example, this phenomenon will occur when the motor is in the range of (90°~95°), resulting in the actual detection position error being between 15° and 20°, greater than 15°.

[0117] If the response current obtained at 60° is slightly less than the response current obtained at 120°, then the response current at 120° is considered to be the maximum response current. At this time, the three-three conduction considers that the true rotor position is 120°. The two-two conduction considers that the true rotor position is at 90°, so the true rotor positions considered by the two-two conduction and the three-three conduction are averaged, and the rotor position is considered to be: (90°+120°) / 2=115°. In fact, affected by the current interference in the actual control process, when the motor rotor position is slightly less than 90°, the response current of 120° will be slightly greater than the response current obtained at 60°. For example, when the motor is in the range of (85°~90°), this phenomenon will occur, resulting in the actual detection position error being between 15°~20°, which is greater than 15°.

[0118] Fig.12 The injected voltage and response current at multiple predetermined angles are shown. As shown in the figure, there is high-frequency interference in the response current in 12 directions. The square wave pulses injected in the six predetermined directions (0°, 60°, 120°, 180°, 240°, 300°) in the three-three conduction have the same amplitude, and the six predetermined directions (30°, 90°, 150°, 210°, 270°, 330°) in the two-two conduction have the same amplitude. Since there is no need to compare the response current obtained by the two-two conduction with the response current obtained by the three-three conduction, there is no restriction on the amplitude relationship between the square waves injected by the two-two conduction and the three-three conduction.

[0119] Assumptions Fig.12 The current response shown corresponds to the situation where the current rotor real position is near 90°. At this time, both the 22 conduction and the 33 conduction perform voltage vector injection. Among the 30°, 90°, 150°, 210°, 270°, and 330° voltage vectors injected by the 22 conduction, the current response vector (point C) obtained when the 90° voltage vector is injected is the largest, and is clearly distinguished from the response current (point A) obtained by injecting the adjacent 30° voltage vector and the response current (point E) obtained by injecting the 150° voltage vector. For the 33 conduction, among the injected 0°, 60°, 120°, 180°, 240°, and 300° voltage vectors, the response current (point B) obtained by injecting the 60° voltage vector and the response current (point D) obtained by injecting the 120° voltage vector are very close. When the rotor real position is near 90°, there is a misjudgment phenomenon. This leads to an increase in the measurement error.

[0120] In order to further reduce the measurement error and avoid the misjudgment phenomenon when two maximum response currents are close to each other when two-two conduction or three-three conduction occurs, this proposal proposes a method for judging whether two adjacent current vectors are close by the degree of difference (such as standard deviation).

[0121] At this time, selecting a first maximum current value from multiple first current values ​​in the predetermined direction corresponding to the three-three conduction, determining a first angle based on the first maximum current value, and selecting a second maximum current value from multiple second current values ​​in the predetermined direction corresponding to the two-two conduction, and determining the second angle based on the second maximum current value can include: measuring a first degree of difference between the first maximum current value and adjacent injection angle current values ​​on both sides, and determining the first angle based on the first degree of difference; and measuring a second degree of difference between the second maximum current value and adjacent injection angle current values ​​on both sides, and determining the second angle based on the second degree of difference.

[0122] Combination Fig.11 In the example shown, in a 2-2 conduction, the second angle can be determined based on the difference between point C and points A and E in the adjacent injection directions. In a 3-3 conduction, no matter whether point B or point D has a larger value, the first angle can be determined based on the difference between the current response value and the adjacent injection direction.

[0123] Since the simple difference cannot well determine the degree of difference, in a preferred embodiment, the present disclosure introduces a standard deviation to determine whether two adjacent current vectors are close. At this time, measuring the first degree of difference between the first maximum current value and the current values ​​corresponding to the adjacent injection directions on both sides, and determining the first angle according to the first degree of difference may include: obtaining the first standard deviation of the multiple first current values; calculating the ratio of the difference between the first maximum current value and the current values ​​corresponding to the adjacent injection directions on both sides to the first standard deviation to obtain a first reduced angle error (here, "reduced angle error" refers to the error measure of the corresponding current value in the direction with the smaller angle of the two predetermined directions adjacent to the direction corresponding to the maximum current value) and a first increased angle error (here, "increased angle error" refers to the error measure of the corresponding current value in the direction with the larger angle of the two predetermined directions adjacent to the direction corresponding to the maximum current value); and according to The first decreasing angle error and the first increasing angle error determine whether the first angle is greater than, equal to or less than the injection angle corresponding to the first maximum current value, wherein the second degree of difference between the second maximum current value and the current values ​​of the adjacent injection angles on both sides is measured, and the second angle is determined according to the second degree of difference, including: obtaining the second standard deviation of the multiple second current values; calculating the ratio of the difference between the second maximum current value and the current values ​​of the adjacent injection angles on both sides to the second standard deviation to obtain the second decreasing angle error and the second increasing angle error; and determining whether the second angle is greater than, equal to or less than the injection angle corresponding to the second maximum current value according to the second decreasing angle error and the second increasing angle error.

[0124] Specifically, a smaller value can be selected from the first reduction angle error and the first increase angle error as the first error; when the first error is greater than the first threshold, the first angle is determined to be equal to the injection angle corresponding to the first maximum current value; when the first error is the first reduction angle error and is less than the first threshold, the first angle is determined to be between the injection angle corresponding to the first maximum current value and the adjacent smaller injection angle; and when the first error is the first increase angle error and is less than the first threshold, the first angle is determined to be between the injection angle corresponding to the first maximum current value and the adjacent larger injection angle. And according to the second increase angle error and the second reduction angle error, determining whether the second angle is greater than, equal to or less than the injection angle corresponding to the second maximum current value includes: selecting a smaller value from the second reduction angle error and the second increase angle error as the second error; when the second error is greater than the second threshold, determining that the second angle is equal to the injection angle corresponding to the second maximum current value; when the second error is the second reduction angle error and is less than the second threshold, determining that the second angle is between the injection angle corresponding to the second maximum current value and the adjacent smaller injection angle; and when the second error is the second increase angle error and is less than the second threshold, determining that the second angle is between the injection angle corresponding to the second maximum current value and the adjacent larger injection angle.

[0125] As mentioned above, the square wave pulse injection of three-three conduction can be performed in six first predetermined injection directions (0°, 60°, 120°, 180°, 240°, 300°), and the square wave pulse injection of two-two conduction can also be performed in six second predetermined injection directions (30°, 90°, 150°, 210°, 270°, 330°). Therefore, when the first error is less than the first threshold, the first angle is equal to the injection angle corresponding to the first maximum current value increased or decreased by 30°; when the second error is less than the second threshold, the second angle is equal to the injection angle corresponding to the second maximum current value increased or decreased by 30°.

[0126] In one embodiment, the specific implementation steps of the above method for determining the initial angle based on standard deviation are:

[0127] 1. Inject the voltage vector corresponding to the three-three conduction, and obtain the corresponding response currents i(0°), i(60°), i(120°), i(180°), i(240°), and i(300°). Calculate the standard deviation MSE1 (i.e., the first standard deviation), find the maximum response current i(α), and calculate the difference between i(α) and its adjacent response currents i(α-60°) and i(α+60°), and divide it by the standard deviation to obtain error1 (i.e., the first reduction angle error) and error2 (i.e., the first increase angle error), mmin error1 =min(error1, error2) (i.e., the first error), when min error1 >error threshold (Here, error threshold Corresponding to the first threshold, in practical applications, error is generally threshold Set to 1), consider i(α) as the maximum response current obtained by three-three conduction, the true position of the rotor, that is, the first angle α real =α, when min error1 <error threshold When error1 is min errer1 , then i(α-30°) is considered to be the maximum response current obtained by three-three conduction, and the actual rotor position α real =α-30°; if error2 is min error1 , then i(α+30°) is considered to be the maximum response current obtained by three-three conduction, and the actual rotor position α real =α+30°

[0128] 2. Inject the voltage vector corresponding to the two-two conduction to obtain the corresponding response currents i(30°), i(90°), i(150°), i(210°), i(270°), and i(330°). Calculate the standard deviation MSE2 (i.e., the second standard deviation), find the maximum response current i(β), and calculate the difference between i(β) and its adjacent response currents i(β-60°) and i(β+60°), and divide it by the standard deviation to obtain error3 (i.e., the second angle reduction error) and error4 (i.e., the second angle increase error), min error2 =min(error3, error4) (i.e., the second error), when min error2 >error threshold (error here threshold Corresponding to the second threshold, which is usually the same as the first threshold, in practical applications, error threshold Set to 1), consider i(β) as the maximum response current obtained by three-three conduction, the true position of the rotor, that is, the second angle β real =β; when minerror2 <error threshold When error3 is min error2 , then i(β-30°) is considered to be the maximum response current obtained by two-two conduction, and the actual rotor position β real =β-30°; if error4 is min error2 , then i(β+30°) is considered to be the maximum response current obtained by three-three conduction, and the true rotor position β real =β+30°.

[0129] 3. The true rotor position determined by combining the 2-2 conduction and the 3-3 conduction is

[0130] Combination Fig.12 For example, first record the current responses obtained from the 0°, 60°, 120°, 180°, 240°, and 300° voltage vectors injected by the three-three conduction, and their values ​​are i(0°) = 2.39A, i(60°) = 2.71A, i(120°) = 2.72A, i(180°) = 2.32A, i(240°) = 2.39A, and i(300°) = 2.39A. The standard deviation of the current in these six directions is:

[0131]

[0132] The maximum response current is i(120°)=2.72A, and the two adjacent response currents are i(60°)=2.71A and i(180°)=2.32A.

[0133]

[0134]

[0135] Take the minimum value of error1 and error2, because the closer to the maximum response current i(120°), the smaller the difference between the two. If error1 is smaller, it can be roughly considered that 60° is closer to the true position of the rotor. At the same time, the value of error1 is 0.055, which is much smaller than the standard deviation. It can be considered that the distance between i(120°) and i(60°) and the true position of the rotor is close, and i(90°) can be considered as the maximum response current that can be obtained. The rotor position judged by the three-three conduction is 90°.

[0136] The current responses obtained from the 30°, 90°, 150°, 210°, 270°, and 330° voltage vectors injected by the two-two conduction are recorded, and their values ​​are i(30°) = 1.80A, i(90°) = 1.98A, i(150°) = 1.76A, i(210°) = 1.71A, i(270°) = 1.82A, and i(330°) = 1.74A. The standard deviation of the current in these six directions is:

[0137]

[0138] The maximum response current is i(90°)=1.98A, and the two adjacent response currents are i(30°)=1.80A and i(150°)=1.76A.

[0139]

[0140]

[0141] Take the minimum value of error3 and error4, because the closer it is to the maximum response current i(90°), the smaller the difference between the two. If error3 is smaller, it can be roughly considered that 30° is closer to the true position of the rotor. At the same time, the value of error3 is 1.875, which exceeds the average standard deviation (that is, the first threshold, which is usually 1). It can be considered that i(90°) exceeds i(30°) and i(150°), that is, the rotor position judged by the 2-2 conduction is 90°.

[0142] The actual rotor position is averaged by the three-three conduction and the two-two conduction, and the rotor position is considered to be: (90°+90°) / 2=90°

[0143] In actual use, since the current will be at a higher value after the last pulse injection, if you directly change the injection direction, the response current will change based on the last current, resulting in inaccurate judgment. Therefore, a square wave pulse injection is completed at one angle for a period of time (for example, the voltage injection time t on After the square wave pulse voltage injection in one direction is completed, the injection will be stopped for a period of time to wait for the response current to return to zero. Therefore, it is usually necessary to wait for a predetermined time after completing the square wave pulse injection in the current predetermined direction before starting the square wave pulse injection in the next predetermined direction, wherein the predetermined time is an integer multiple of the square wave voltage time. Here, the integer multiple can be 2 times, or more than 2 times. That is, after completing the square wave pulse voltage injection in one direction, the injection will be stopped for a period of time to wait for the response current to return to zero, and the injection stop time is generally several times the square wave voltage injection time. Fig.12In order to more intuitively display the current response process when injecting a square wave voltage pulse, the display of the injection stop time is shortened, and the current response diagram obtained by continuous sampling is shown. However, in some embodiments, only one or several response currents may be sampled each time a square wave pulse is injected.

[0144] In actual operation, we may encounter situations where the current noise is large. Fig.12 As shown in the figure, there is a lot of noise in the response current, and the noise amplitude is large. If only one current value is sampled, it is very easy to be interfered by the noise, resulting in failure to judge the initial position of the rotor. In addition, the injection of a square wave signal for a short time (such as within 100us) will cause a large change in the current impact, and the response current will show Fig.12 The shape of the triangular wave shown. To this end, in one embodiment, the anti-interference ability can be significantly improved by continuously sampling the response current and processing its signal. At this time, the stator winding of the motor is controlled to be turned on in a 2-2 conduction and a 3-3 conduction manner, and square wave pulses are injected in different predetermined directions. The current value corresponding to each predetermined direction is obtained, which may include: during the square wave injection in each predetermined direction, the d-axis response current is sampled and observed multiple times, and the accumulated value or average value of the multiple sampled response currents is used as the current value in the corresponding predetermined direction.

[0145] Furthermore, during the injection of the square wave in each predetermined direction, the d-axis direction response current is sampled and observed multiple times, and the use of the accumulated value or average value of the multiple sampled response currents as the current value in the corresponding predetermined direction may include: during the injection of the square wave in each predetermined direction, the d-axis response current is continuously sampled and observed multiple times using an analog-to-digital converter (ADC); the sampled values ​​are transferred in real time to an array corresponding to the corresponding value through direct memory access (DMA); and the accumulated value or average value is calculated based on the sampled values ​​stored in the corresponding array.

[0146] Unlike the general high-frequency injection algorithm (whose observation d-axis position may be at any position between 0° and 360°), square wave pulse injection usually selects twelve fixed directions of 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330° as the observation d-axis for square wave pulse voltage injection in order to avoid current fluctuations caused by the turning on and off of the MOS tube.

[0147] Specifically, when configuring the MCU, configure the ADC to continuous mode. For example, in an ADC, the clock frequency is configured to be up to 40MHz, and the sampling time is configured to be 7.5 ADC clocks. Since the ADC takes 12.5 ADC clocks to convert one piece of data, the time required for the ADC to sample and convert one piece of data is ((7.5+12.5) / 40MHz=0.5us). At the same time, configure the DMA mode, and start the ADC when the square wave pulse voltage injection starts in each direction (0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°). The data sampled by the ADC is transferred to the corresponding array in real time through DMA. Since the square wave voltage lasts for 100us, it takes 0.5us for the ADC to sample and convert one piece of data, so that at t on Two hundred samples can be sampled within a certain time, so the length of the array corresponding to each direction can be configured to 200.

[0148] Specifically, the ADC hardware can be configured in continuous sampling mode: the ADC sampling time and sampling channel are fixed, and multiple sampling and conversions are completed in one trigger. After each conversion is completed and the result is stored in the ADC_RDATA register, an EOC (end of convert) signal is generated to notify the DMA to read the ADC conversion result from the ADC_RDATA register to the array.

[0149] Based on Fig.12 In different embodiments, square wave pulses can be injected sequentially in 6 or 12 predetermined directions. After completing the pulse voltage injection in twelve or six directions, the data in the arrays corresponding to the twelve directions can be accumulated. Here, 12 arrays can be configured for the 12 injection directions. In one embodiment, the number of configured arrays can also be less than 12, as long as the accumulated value or average calculation based on part of the arrays is completed during the injection process.

[0150] Fig.13 The sampled response currents and the corresponding accumulated values ​​(ie, the sum of the response currents) when the square wave pulses are injected at a plurality of predetermined angles are shown.

[0151] As shown in the figure above, the cumulative current value of 0° sampling is 248.9A, the cumulative current value of 30° sampling is 188.6A, the cumulative current value of 60° sampling is 283.4A, the cumulative current value of 90° sampling is 208.3A, the cumulative current value of 120° sampling is 278.0A, the cumulative current value of 150° sampling is 180.7A, the cumulative current value of 180° sampling is 242.4A, the cumulative current value of 210° sampling is 174.6A, the cumulative current value of 240° sampling is 255.1A, the cumulative current value of 270° sampling is 186.9A, the cumulative current value of 300° sampling is 256.5A, and the cumulative current value of 330° sampling is 177.3A. The cumulative value method is adopted, and the signal processing method of standard deviation discrimination is adopted at the same time.

[0152] Record the standard deviation MSE1=18.58 of each response current i(0°), i(60°), i(120°), i(180°), i(240°), and i(300°) under three-three conduction, record the difference between the maximum response current i(60°)=283.4 and the adjacent response currents i(0°)=248.9 and i(120°)=278.0, and divide it by the standard deviation MSE1 to obtain error1=1.86 and error2=0.29, min error1 =min(error1,error2)=0.29, when min error1 <1, i(90°) is considered to be the maximum response current obtained by three-three conduction, α real =90°.

[0153] Record the standard deviation MSE2=12.15 of each response current i(30°), i(90°), i(150°), i(210°), i(270°), and i(330°) under two-two conduction, the maximum response current i(90°)=208.3, the difference between adjacent response currents i(30°)=188.6 and i(150°)=180.7, and divide them by the standard deviation MSE2 to get error3=1.62 and error4=2.27, min error2 =min(error3,error4)=1.62, when min error2 >1, i(90°) is considered to be the maximum response current obtained by three-three conduction, β real =90°.

[0154] The true rotor position determined by the combination of three-three conduction and two-two conduction is

[0155] The use of the cumulative value method can greatly reduce the interference caused by noise and improve the success rate of rotor initial position identification. After continuous current sampling, it is still necessary to stop injection for a period of time to wait for the response current to return to zero. When it returns to zero, the processed array can be directly assigned zero and the current is no longer collected, because the current is invalid at this time, which also facilitates the filter to converge and stabilize to the 0 state. Therefore, it is convenient to start collecting from zero point later.

[0156] The present disclosure may also be implemented as a permanent magnet synchronous motor. Fig.14 FIG. 1 is a schematic diagram of a permanent magnet synchronous motor according to an embodiment of the present invention. Figure 1 , Fig.14 The display of some common components in the motor and the magnetic oriented vector control module is omitted, and the components more relevant to the initial rotor angle determination method of the present disclosure are emphasized.

[0157] Therefore, the permanent magnet synchronous motor of the present disclosure may include: a motor; and a magnetic orientation vector control module for controlling the motor. The magnetic orientation vector control module 1400 includes an injection module 1410 , an acquisition module 1420 and a calculation module 1430 .

[0158] The injection module 1410 is used to perform conduction control in a 2-2 conduction and a 3-3 conduction mode to inject square wave pulses in different predetermined directions. As shown in the figure, the injection module 1410 will inject square wave pulses in the 12 predetermined directions shown in the figure. These 12 predetermined synthetic voltage vector directions can be achieved by applying corresponding voltages to the three-phase windings under the control of the timer (TIMER) of the MCU shown in the figure. Furthermore, when the 3-3 conduction is on, a voltage with an amplitude of || can be applied to the observed d-axis direction (0°, 60°, 120°, 180°, 240°, 300°). const | square wave pulse, and when the two are turned on, a pulse with an amplitude of square wave pulse.

[0159] Subsequently, the acquisition module 1420 can be used to obtain the current value corresponding to each direction. In one embodiment, the acquisition module 1420 may include a sampling submodule for sampling and observing the response current in the d-axis direction during the square wave injection. The sampling submodule may be the ADC in the illustrated MCU, and may be set to a continuous sampling mode for continuous sampling during the application of the square wave voltage. The acquisition module 1420 may also include a storage submodule for storing the sampled response current in the d-axis direction, and thereby obtaining the current value corresponding to each direction. In the case of continuous ADC sampling, the storage submodule may include 12 arrays for recording multiple response current values ​​collected during the pulse application in 12 predetermined directions.

[0160] Subsequently, the calculation module 1430 can be used to: select a first maximum current value from a plurality of first current values ​​of a predetermined direction corresponding to the three-three conduction, and determine a first angle according to the first maximum current value; select a second maximum current value from a plurality of second current values ​​of a predetermined direction corresponding to the two-two conduction, and determine a second angle according to the second maximum current value; and determine the initial rotor angle of the motor according to the first angle and the second angle. Specifically, the calculation module 1430 may include an accumulation submodule for accumulating the respective response current values ​​in the 12 arrays. Subsequently, the standard deviation judgment submodule included in the calculation module 1430 can execute a standard deviation judgment method, and finally determine the optimal initial rotor position by performing the standard deviation-based judgment operation on the 12 accumulated values ​​as described above.

[0161] The above has described in detail the method for determining the initial rotor angle of a permanent magnet synchronous motor and the corresponding permanent magnet synchronous motor according to the present disclosure with reference to the accompanying drawings. The method for determining the initial rotor angle of the present invention performs initial position determination by combining two-two conduction and three-three conduction. Furthermore, the optimal initial position point can be found by the standard deviation discrimination method to improve the resolution of the rotor initial position identification. The response current sampling values ​​can also be accumulated, and the initial position of the rotor can be determined based on the size of the accumulated value or its mean, thereby eliminating high-frequency interference and improving measurement accuracy.

[0162] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended 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 determining an initial rotor angle of a permanent magnet synchronous motor, comprising: Injecting square wave pulses in different predetermined directions in sequence according to a 2-2 conduction and a 3-3 conduction mode to obtain a current value corresponding to each predetermined direction; Select a first maximum current value from a plurality of first current values ​​in a predetermined direction corresponding to three-three conduction, determine a first angle according to the first maximum current value, and select a second maximum current value from a plurality of second current values ​​in a predetermined direction corresponding to two-two conduction, and determine a second angle according to the second maximum current value; as well as An average of the first angle and the second angle is calculated as an initial rotor angle of the motor.

2. The method of claim 1, wherein: The three-three conduction square wave pulse injection is performed in multiple first predetermined injection directions, and the two-two conduction square wave pulse injection is performed in multiple second predetermined injection directions, one of the second predetermined injection directions is spaced between every two adjacent first predetermined injection directions, and the spacing angles on both sides are equal.

3. The method of claim 1, wherein: Selecting a first maximum current value from a plurality of first current values ​​in a predetermined direction corresponding to three-three conduction, determining a first angle according to the first maximum current value, and selecting a second maximum current value from a plurality of second current values ​​in a predetermined direction corresponding to two-two conduction, and determining a second angle according to the second maximum current value comprises: measuring a first difference between the first maximum current value and current values ​​corresponding to adjacent injection directions on both sides, and determining the first angle according to the first difference; and A second difference between the second maximum current value and current values ​​corresponding to adjacent injection directions on both sides is measured, and the second angle is determined according to the second difference.

4. The method of claim 3, wherein: Measuring a first difference between the first maximum current value and current values ​​corresponding to adjacent injection directions on both sides, and determining the first angle according to the first difference comprises: Obtaining a first standard deviation of the plurality of first current values; Calculating a ratio of a difference between the first maximum current value and current values ​​corresponding to adjacent injection directions on both sides to the first standard deviation to obtain a first reduction angle error and a first increase angle error; and determining, according to the first decreasing angle error and the first increasing angle error, whether the first angle is greater than, equal to, or less than an injection angle corresponding to the first maximum current value, The step of measuring a second difference between the second maximum current value and current values ​​corresponding to adjacent injection directions on both sides, and determining the second angle according to the second difference includes: Obtaining a second standard deviation of the plurality of second current values; Calculating a ratio of a difference between the second maximum current value and current values ​​corresponding to adjacent injection directions on both sides to the second standard deviation to obtain a second reduced angle error and a second increased angle error; and According to the second decreasing angle error and the second increasing angle error, it is determined whether the second angle is greater than, equal to, or less than an injection angle corresponding to the second maximum current value.

5. The method of claim 4, wherein: Determining, according to the first increasing angle error and the first decreasing angle error, whether the first angle is greater than, equal to, or less than an injection angle corresponding to the first maximum current value includes: Selecting a smaller value from the first decreasing angle error and the first increasing angle error as a first error; When the first error is greater than the first threshold, determining that the first angle is equal to an injection angle corresponding to the first maximum current value; When the first error is the first reduced angle error and is smaller than the first threshold, determining that the first angle is between an injection angle corresponding to the first maximum current value and an adjacent smaller injection angle; and When the first error is the first increased angle error and is less than the first threshold, it is determined that the first angle is between the injection angle corresponding to the first maximum current value and an adjacent larger injection angle, Wherein, determining whether the second angle is greater than, equal to, or less than an injection angle corresponding to the second maximum current value according to the second increase angle error and the second decrease angle error includes: Selecting a smaller value from the second decreasing angle error and the second increasing angle error as a second error; When the second error is greater than the second threshold, determining that the second angle is equal to the injection angle corresponding to the second maximum current value; When the second error is the second reduced angle error and is less than the second threshold, determining that the second angle is between the injection angle corresponding to the second maximum current value and an adjacent smaller injection angle; and When the second error is the second increased angle error and is smaller than the second threshold, it is determined that the second angle is between the injection angle corresponding to the second maximum current value and an adjacent larger injection angle.

6. The method of claim 5, wherein: A three-to-three conduction square wave pulse injection is performed in six first predetermined injection directions, and a two-to-two conduction square wave pulse injection is performed in six second predetermined injection directions, and When the first error is less than the first threshold, the first angle is equal to the injection angle corresponding to the first maximum current value increased or decreased by 30°; When the second error is less than the second threshold, the second angle is equal to the injection angle corresponding to the second maximum current value increased or decreased by 30°.

7. The method of claim 1, wherein: Conducting control in a 2-2 conduction and a 3-3 conduction manner to inject square wave pulses in different predetermined directions includes: After completing the square wave pulse injection in the current predetermined direction, wait for a predetermined time before starting the square wave pulse injection in the next predetermined direction, wherein the predetermined time is an integer multiple of the square wave voltage time.

8. The method of claim 1, wherein: The stator winding of the motor is controlled to be turned on in a 2-2 conduction mode and a 3-3 conduction mode, square wave pulses are injected in different predetermined directions, and the current value corresponding to each predetermined direction is obtained, including: During the square wave injection in each predetermined direction, the response current of the d-axis is sampled and observed multiple times, and the accumulated value or average value of the response current of the d-axis sampled multiple times is used as the current value corresponding to the corresponding predetermined direction, wherein the response current of the d-axis is obtained by sampling the three-phase winding current and then transforming the coordinates.

9. The method of claim 8, wherein: During the square wave injection in each predetermined direction, the response current of the d-axis is sampled and observed multiple times, and the accumulated value or average value of the response current of the d-axis sampled multiple times is used as the current value in the corresponding predetermined direction, which includes: During the square wave injection in each predetermined direction, the response current of the observation d-axis is continuously sampled multiple times using an analog-to-digital converter ADC; The sampled values ​​are transferred to an array corresponding to the response in real time through direct memory access (DMA); and The accumulated value or the average value is calculated according to the sampling values ​​stored in the corresponding array.

10. A permanent magnet synchronous motor, comprising: Motor; A magnetic oriented vector control module, used to control the motor and execute the method according to any one of claims 1 to 9 to determine the initial angle of the rotor, and comprising: An injection module, used for performing conduction control in a 2-2 conduction mode and a 3-3 conduction mode to inject square wave pulses in different predetermined directions; an acquisition module, used to acquire a current value corresponding to each of the predetermined directions; and Computing module for Selecting a first maximum current value from a plurality of first current values ​​of a predetermined direction corresponding to the three-three conduction, and determining a first angle according to the first maximum current value; Selecting a second maximum current value from a plurality of second current values ​​of a predetermined direction corresponding to the 2-2 conduction, and determining a second angle according to the second maximum current value; and An average of the first angle and the second angle is calculated as an initial rotor angle of the motor.

11. The permanent magnet synchronous motor according to claim 10, wherein: The acquisition module comprises: A sampling submodule, used for sampling and observing the response current of the d-axis during the square wave injection; The storage submodule is used to store the sampled response current of the observed d-axis, and thereby obtain the current value corresponding to each of the predetermined directions.

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