Method for identifying locked-rotor condition of motor, frequency converter and storage medium

Abstract

The invention discloses a method for identifying a locked-rotor condition of a motor, a frequency converter and a storage medium. The method for recognizing the locked-rotor condition of the motor in the compressor comprises the steps that first preset detection voltage is applied to a stator of the motor, and first stator current flowing through the stator of the motor is detected; obtaining a first position angle of the rotor based on the first predetermined detection voltage and the first stator current; applying a predetermined DC voltage to a stator of the motor based on the first position angle; applying a second predetermined detection voltage to the stator of the motor, and detecting a second stator current flowing through the stator of the motor; obtaining a second position angle of the rotor based on the second predetermined detection voltage and the second stator current; and identifying a locked-rotor condition of the motor based on the first position angle and the second position angle.

Description

Technical Field

[0001] The present disclosure relates to the electrical field, and in particular to a method for identifying a stall condition of a motor, a frequency converter, and a storage medium. Background Art

[0002] When the rotor of the compressor motor is blocked due to unexpected reasons (for example, mechanical failure), if the inverter directly starts the compressor motor, a large starting current will flow through the inverter because the motor rotor is blocked, which may cause damage to the inverter. Therefore, it is necessary to detect whether the motor rotor is blocked before starting the motor. Summary of the invention

[0003] A brief overview of the disclosure is given below in order to provide a basic understanding of certain aspects of the disclosure. However, it should be understood that this overview is not an exhaustive overview of the disclosure. It is not intended to identify the key or important parts of the disclosure, nor is it intended to limit the scope of the disclosure. Its purpose is simply to give certain concepts of the disclosure in a simplified form as a prelude to a more detailed description given later.

[0004] In view of the above problems, an object of the present disclosure is to provide a method for identifying a stall condition of a motor, a frequency converter and a storage medium.

[0005] According to a first aspect of the present disclosure, a method for identifying a stall condition of a motor is provided, the method comprising: applying a first predetermined detection voltage to the stator of the motor to detect a first stator current flowing through the stator of the motor; obtaining a first position angle of the rotor based on the first predetermined detection voltage and the first stator current; applying a predetermined DC voltage to the stator of the motor based on the first position angle; applying a second predetermined detection voltage to the stator of the motor to detect a second stator current flowing through the stator of the motor; obtaining a second position angle of the rotor based on the second predetermined detection voltage and the second stator current; and identifying the stall condition of the motor based on the first position angle and the second position angle.

[0006] Optionally, identifying the stall condition of the motor includes: calculating a difference between the first position angle and the second position angle; and determining that the motor is in a stall condition when the calculated difference is less than or equal to a predetermined angle difference threshold.

[0007] Optionally, the predetermined angle difference threshold is within an electrical angle range of 10° to 80°.

[0008] Optionally, the motor is an embedded three-phase permanent magnet synchronous motor.

[0009] Optionally, obtaining the first position angle of the rotor includes: processing a first predetermined detection voltage and a first stator current through Clarke transformation, Park transformation, filtering, and proportional integration to obtain the magnetic pole position of the rotor; performing polarity detection; and processing the magnetic pole position based on the polarity detection result to obtain the first position angle.

[0010] Optionally, obtaining the second position angle of the rotor includes: processing a second predetermined detection voltage and a second stator current through Clarke transformation, Park transformation, filtering, and proportional integration to obtain the magnetic pole position of the rotor; performing polarity detection; and processing the magnetic pole position based on the polarity detection result to obtain the second position angle.

[0011] Optionally, the first predetermined detection voltage and the second predetermined detection voltage are both high-frequency low-voltage alternating current voltages.

[0012] Optionally, the first predetermined detection voltage and the second predetermined detection voltage are the same.

[0013] Optionally, applying a predetermined DC voltage to the stator of the motor includes: selecting a stator winding in the stator of the motor whose phase angle is not equal to the first position angle; and applying the predetermined DC voltage to the selected stator winding.

[0014] Optionally, when a predetermined DC voltage is applied to the selected stator winding, the amplitude of the detected DC current flowing through the stator is within a range of 20% to 100% of the amplitude of the rated current of the motor.

[0015] According to a second aspect of the present disclosure, a frequency converter is provided, comprising a processing unit, wherein the processing unit is configured to execute the method according to the first aspect of the present disclosure.

[0016] According to a third aspect of the present disclosure, a machine-readable storage medium storing program instructions is provided. When the program instructions are executed by a machine, the machine executes the method according to the first aspect of the present disclosure.

[0017] Other aspects of the embodiments of the present disclosure are given in the following description, wherein the detailed description is used to fully disclose the preferred embodiments of the embodiments of the present disclosure without imposing limitations thereon. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present disclosure may be better understood by referring to the detailed description given below in conjunction with the accompanying drawings, wherein the same or similar reference numerals are used throughout the drawings to represent the same or similar components. The accompanying drawings, together with the following detailed description, are included in and form a part of the present specification to further illustrate the preferred embodiments of the present disclosure and to explain the principles and advantages of the present disclosure. Among them:

[0019] Figure 1is a circuit diagram showing a specific implementation of a frequency converter according to an embodiment of the present disclosure;

[0020] Figure 2 is a schematic diagram showing a specific example of a motor driven by a frequency converter according to an embodiment of the present disclosure;

[0021] Figure 3A is a schematic diagram showing an example of a detection voltage applied to an embedded permanent magnet synchronous motor;

[0022] Figure 3B The figure shows that the embedded permanent magnet synchronous motor Figure 3A A schematic diagram of an example of the three-phase stator current detected in the case of the detection voltage shown;

[0023] Figure 3C It is shown that by Figure 3B Schematic diagram of current traces obtained by converting the three-phase stator current into the αβ coordinate system;

[0024] Figure 4 is a flowchart showing an example of a process of motor stall identification processing according to an embodiment of the present disclosure; and

[0025] Figure 5 It is a schematic diagram showing a process of obtaining the magnetic pole position of a motor rotor according to the present disclosure. DETAILED DESCRIPTION

[0026] Exemplary embodiments of the present disclosure will be described below in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of the actual implementation are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the process of developing any such actual implementation in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and these constraints may vary from implementation to implementation. In addition, it should be understood that although the development work may be very complex and time-consuming, it is only a routine task for those skilled in the art who benefit from the content of this disclosure.

[0027] It is also necessary to explain here that in order to avoid obscuring the present disclosure due to unnecessary details, only the device structure and / or processing steps closely related to the scheme according to the present disclosure are shown in the accompanying drawings, while other details that are not closely related to the present disclosure are omitted.

[0028] The embodiments according to the present disclosure are described in detail below with reference to the accompanying drawings.

[0029] First, refer to Figure 1The implementation example of the frequency converter 100 according to the embodiment of the present disclosure is described. The frequency converter 100 may include a rectifier bridge 102, a filter capacitor 104, a three-phase inverter bridge 106 and a processing unit 110, but the specific configuration of the frequency converter 100 is not limited thereto, and those skilled in the art may select a suitable configuration of the frequency converter according to actual needs. Figure 1 As shown, the inverter 100 may be connected to an alternating current (AC) power source 120 and used to drive a motor 130 .

[0030] like Figure 1 As shown, the processing unit 110 can be used to control the three-phase inverter bridge 106 . However, as those skilled in the art will appreciate, when the inverter 100 has other configurations, the processing unit 110 can be used to control other components of the inverter 100 .

[0031] In addition, considering that the configurations and functions of the rectifier bridge 102 , the filter capacitor 104 and the three-phase inverter bridge 106 are well known in the art, they will not be described in detail herein.

[0032] Note that Figure 1 100 also shows an AC power source and a motor connected to the frequency converter 100, but the AC power source and the motor may not be components of the frequency converter 100. Figure 1 In order to conveniently identify each functional block, each functional block is marked with a dotted line frame, but the dotted line frame does not constitute a limitation on the specific configuration of the inverter.

[0033] The three-phase motor may include a three-phase induction motor, a permanent magnet synchronous motor such as an embedded permanent magnet synchronous motor and a surface mounted permanent magnet synchronous motor, etc. For example, in the case where the motor is an embedded permanent magnet synchronous motor, since the magnet (e.g., a permanent magnet including an N pole and an S pole) 202 is embedded in the rotor 204 of the embedded permanent magnet synchronous motor, as shown in FIG. Figure 2 As shown in FIG. 1 , the inductance at the stator coil (three-phase coil) 206 varies with the position of the magnet 202 in the rotor 204. Figure 2 As shown, the embedded permanent magnet synchronous motor may further include a shaft 208 and a stator core 210. The inverter 100 according to the embodiment of the present disclosure applies a predetermined detection voltage to the motor in the compressor before starting the motor to identify whether the motor is in a stalled state, and the identification result according to the embodiment of the present disclosure is not affected by the initial position of the rotor in the embedded permanent magnet synchronous motor.

[0034] The following will refer to Figure 3A , Figure 3B , Figure 3C , Figure 4 as well as Figure 5 , the motor stall identification process according to the present invention is further explained.

[0035] When the motor is an embedded permanent magnet synchronous motor, the inductance at the stator coil of the motor changes with the change of the position of the magnet in the rotor of the motor. This phenomenon is called the "salient polarity" of the embedded permanent magnet synchronous motor. Due to the "salient polarity" of the embedded permanent magnet synchronous motor, even if an external force such as Figure 3A The symmetrical three-phase detection voltage shown in FIG. 1 and the amplitude of the three-phase stator current are also asymmetrical, as shown in FIG. Figure 3B As shown, it should be recognized that Figure 3B The three-phase stator currents shown in are for example only and are not limiting.

[0036] Figure 3C Shown by Figure 3B The schematic diagram of the current traces obtained by performing Clarke transformation on the three-phase stator current shown in FIG. Figure 3C As shown, in the αβ coordinate system, the current trajectory is an ellipse, where the major axis direction of the ellipse is related to the initial position of the rotor. It should be recognized that Figure 3C The current traces shown in are for example only and are not limiting.

[0037] Note that although Figure 3C It is shown that the current trajectory in the αβ coordinate system obtained by performing Clarke transformation on the three-phase stator current is elliptical, but when the motor is some motors other than the embedded permanent magnet synchronous motor (for example, a surface mounted permanent magnet synchronous motor), the amplitude of the three-phase stator current can be symmetrical, and the current trajectory in the αβ coordinate system obtained by performing Clarke transformation on the three-phase stator current can be circular. In this case, the radius of the circular current trajectory is equal to the amplitude of the three-phase stator current.

[0038] Figure 4 Detailed description is a flowchart showing an example of a flow of a motor stall identification process according to an embodiment of the present disclosure.

[0039] The motor stall identification process starts at step S401 .

[0040] In step S402, a first predetermined detection voltage is applied to the stator of the motor in the compressor and a three-phase stator current flowing through the stator of the motor is detected, which is referred to as the first stator current below. According to an embodiment of the present invention, the first predetermined detection voltage may be a high-frequency low-voltage AC voltage. For example, the frequency of the first predetermined detection voltage may be approximately twice the rated frequency of the motor, and the amplitude of the first predetermined detection voltage may be in the range of 5%-10% of the amplitude of the rated voltage of the motor. It should be recognized that the above is only an example and not a limitation. The first predetermined detection voltage may also be a high-frequency low-voltage AC voltage with a frequency and amplitude different from the above example. In addition, according to an embodiment of the present invention, the duration of applying the first predetermined detection voltage to the stator of the motor may be about 0.2 seconds (s), 0.5 seconds, 1 second, 2 seconds, or 3 seconds. Of course, this is only for example and not for limitation. In other embodiments of the present invention, the duration of applying the first predetermined detection voltage to the stator of the motor may also be any other duration. The motor stall identification process enters step S403.

[0041] In step S403, the first predetermined detection voltage and the first stator current are processed by Clarke transformation, Park transformation, filtering and proportional integration to obtain the magnetic pole position of the rotor. Figure 5 The schematic diagram is a diagram showing the processing process of obtaining the magnetic pole position of the motor rotor according to the present disclosure, wherein HPF represents high pass filtering, and PI represents proportional integration.

[0042] The three-phase stator current detected flowing through the stator of the motor is converted into the αβ coordinate system by Clarke transformation. For example, Clarke transformation can be expressed by the following equation (1).

[0043]

[0044] In the above formula (1), i A 、i B and i C They represent the A-phase current, B-phase current and C-phase current of the stator respectively, i α and i β They respectively represent the current along the α-axis and the current along the β-axis in the αβ coordinate system.

[0045] Park transform, filtering, and proportional-integral techniques can be used to calculate the current i in the αβ coordinate system. α and i β To get the magnetic pole position θ of the motor rotor r .

[0046]

[0047]

[0048] In the above formula (2), i d and i q They represent the current i passing through the α axis in the αβ coordinate system. α and the β-axis current i β Current parameters obtained after Park transformation. θ v is the electrical angle of the high-frequency low-voltage AC voltage applied to the stator of the motor. In addition, in the above formula (3), i dh and i qh They represent the effects of high-pass filtering on i d and i q The current parameters obtained after filtering. αh and i βh Respectively represent the dh and i qh The current parameters are obtained after inverse Park transformation. Using the proportional integral controller based on i αh 、i βh and θ v To get the magnetic pole position θ of the motor rotor r The motor stall identification process proceeds to step S404.

[0049] Polarity detection is performed in step S404 because the magnetic pole position θ of the motor rotor obtained in step S403 is r It may be the N pole position or the S pole position. r and θ r Pulse voltages are applied at two angles of +π, and the amplitude of the resulting pulse current is detected. It should be appreciated that polarity detection can be performed using polarity detection techniques known in the art, which will not be described in detail herein. The motor stall identification process proceeds to step S405.

[0050] In step S405, the magnetic pole position of the motor rotor is processed based on the polarity detection result to obtain the first position angle. r and θ r The amplitudes of the two pulse currents obtained by applying a pulse voltage at an angle of +π are compared. If r When the pulse voltage is applied at the angle, the current amplitude obtained is larger, then the first position angle Sitar1 is determined to be θ r , if in θ r When the pulse voltage is applied at an angle of +π, the current amplitude is larger, so the first position angle Sitar1 is determined to be θ r +π. The motor stall identification process proceeds to step S406.

[0051] In step S406, a stator winding in the three-phase motor whose phase angle is different from the first position angle is selected, and a predetermined DC voltage is applied to the selected stator winding, so as to adjust the rotor position of the three-phase motor. According to an embodiment of the present invention, the DC voltage applied is a three-phase DC voltage. According to one embodiment of the present invention, the duration of applying the predetermined DC voltage to the selected stator winding may be a time in the range of 0.5s to 2s. Of course, this is only for example and not for limitation. In other embodiments of the present invention, the duration of applying the predetermined DC voltage to the selected stator winding may also be any other duration. Table 1 below shows some combinations of the correspondence between the first position angle and the selected stator winding of the three-phase motor to which the predetermined DC voltage is applied.

[0052] First position angle Stator winding to which DC voltage is applied 120°～180° W(-120°) 60°～120° U(0°) 0°～60° V(120°) -60°～0° W(-120°) -120°～-60° U(0°) -180°～-120° V(120°)

[0053] Table 1

[0054] As shown in Table 1 above, for example, for a three-phase motor in which the W phase lags the U phase by 120° electrical angle and the V phase leads the U phase by 120° electrical angle, when the first position angle is in the range of 120° to 180° electrical angle, a DC voltage is applied to the W phase stator winding of the three-phase motor, when the first position angle is in the range of 60° to 120° electrical angle, a DC voltage is applied to the U phase stator winding of the three-phase motor, when the first position angle is in the range of 0° to 60° electrical angle, a DC voltage is applied to the V phase stator winding of the three-phase motor, when the first position angle is in the range of -60° to 0° electrical angle, a DC voltage is applied to the W phase stator winding of the three-phase motor, when the first position angle is in the range of -120° to -60° electrical angle, a DC voltage is applied to the U phase stator winding of the three-phase motor, and when the first position angle is in the range of -180° to -120° electrical angle, a DC voltage is applied to the V phase stator winding of the three-phase motor. It should be appreciated that the embodiments of the present invention are not limited thereto, that is, in addition to the combinations shown in Table 1, there are other combinations.

[0055] According to one embodiment of the present invention, when a predetermined DC voltage is applied to a selected phase stator winding (U / V / W phase) of a three-phase motor, the amplitude of the detected DC current is within a range of 20% to 100% of the amplitude of the rated current. Of course, this is only for example and not for limitation. In other embodiments of the present invention, when a predetermined DC voltage is applied to a selected phase stator winding (U / V / W phase) of a three-phase motor, the amplitude of the detected DC current may be within an amplitude range different from the above example range. The motor stall identification process enters step S407.

[0056] In step S407, a second predetermined detection voltage is applied to the stator of the motor and a second stator current is detected. The motor stall identification process enters step S408. According to one embodiment of the present invention, the duration of applying the second predetermined detection voltage to the stator of the motor may be about 0.2 seconds, 0.5 seconds, 1 second, 2 seconds, or 3 seconds. Of course, this is only for example and not for limitation. In other embodiments of the present invention, the duration of applying the second predetermined detection voltage to the stator of the motor may also be any other duration.

[0057] In step S408, the second predetermined detection voltage and the second stator current are processed by Clarke transformation, Park transformation, filtering and proportional integration to obtain the magnetic pole position of the rotor. The motor stall identification process enters step S409.

[0058] In step S409, polarity detection is performed. The motor stall identification process proceeds to step S410.

[0059] In step S410, the magnetic pole position of the motor rotor is processed based on the polarity detection result to obtain a second position angle Sitar2. The motor stall identification process proceeds to step S411.

[0060] It should be appreciated that the processing in steps S407-S410 is similar to the operations performed in steps S402-S405, and detailed descriptions of steps with similar processing are omitted herein.

[0061] In step S411, the difference D1 between the first position angle Sitar1 and the second position angle Sitar2 is calculated, wherein the difference D1 can be obtained by the absolute difference between the first position angle Sitar1 and the second position angle Sitar2, that is, D1 = |Sitar1 - Sitar2|. The motor stall identification process enters step S412.

[0062] In step S412, the difference D1 is compared with a predetermined angle difference threshold, wherein when a DC voltage is applied based on the corresponding relationship in Table 1, the predetermined angle difference threshold may be in the range of 10° to 50° electrical angle. In addition, in addition to the corresponding relationship in Table 2, when the electrical angle of the applied DC voltage is selected as Sitar1+90° electrical angle or Sitar1-90° electrical angle, the predetermined angle difference threshold may be in the range of 10° to 80° electrical angle.

[0063] In step S412, when the comparison result is that the difference D1 is greater than the angle difference threshold, the motor stall identification process enters step S413 to determine that the motor passes the test, indicating that the detected motor is not stalled. Then the motor stall identification process enters step S415, and the motor stall identification process ends.

[0064] In step S412, when the comparison result is that the difference D1 is less than or equal to the angle difference threshold, the motor stall identification process proceeds to step S414 to determine that the motor is stalled. Then the process proceeds to step S415, and the motor stall identification process ends.

[0065] It should be appreciated that according to the embodiments of the present disclosure, the processing unit of the frequency converter can perform the above motor stall identification process. The present invention is not limited thereto, and other processing devices independent of the frequency converter can also perform the above motor stall identification process.

[0066] The above motor stall identification process will be further described below with reference to a test example.

[0067] In the first test example, before the embedded permanent magnet synchronous motor is officially put into operation, a fixture is used to lock the rotor of the motor in different positions (i.e., the rotor of the motor is blocked) to test the motor blocking identification process. According to the motor blocking identification process disclosed in the present invention, the first position angle Sitar1 of the rotor and the second position angle Sitar2 of the rotor can be obtained, and the difference D1 between Sitar1 and Sitar2 can be calculated based on Sitar1 and Sitar2. If the difference D1 is less than or equal to the angle difference threshold (e.g., 10° electrical angle), it is determined that the motor is blocked. The test results of the first test example are shown in Table 2 below.

[0068] <![CDATA[Sitar1 (electrical angle)]]> <![CDATA[Sitar2 (electrical angle)]]> <![CDATA[D1]]> -3.9° -7.1° 3.2 226.9° 226.8° 0.1 125.7° 129.0° 3.3 235.7° 232.5° 3.2 118.8° 117.9° 0.9 -5.8° -9.2° 3.4 226.9° 224.9° 2.0 100.2° 98.1° 2.1

[0069] Table 2

[0070] It can be seen that in the first test example, by using the motor stall identification process disclosed in the present invention, it is possible to accurately identify that the motor rotor is stalled when the motor's rotor is in different initial positions. In other words, the motor stall identification process according to the present invention is not affected by the initial position of the motor rotor.

[0071] In the second test example, the rotor of the embedded permanent magnet synchronous motor is in a free state, that is, the rotor of the motor is not blocked, and the above-mentioned motor blocking identification process is performed before the motor is started for testing. The first position angle Sitar1 and the second position angle Sitar2 are obtained respectively by the above-mentioned process disclosed in the present invention. Then, based on Sitar1 and Sitar2, the difference D1 between Sitar1 and Sitar2 is calculated. If the difference D1 is less than or equal to the angle difference threshold (for example, 10° electrical angle), it is determined that the rotor of the motor is blocked.

[0072] The test results of the second test example are shown in Table 3 below.

[0073] <![CDATA[Sitar1 (electrical angle)]]> <![CDATA[Sitar2 (electrical angle)]]> <![CDATA[D1]]> 253.5° 1.4° 252.1 1.1° 112.9° 111.8 113.47° 9.79° 103.7 311.0° 220.6° 90.4 220.0° 100.2° 119.8 99.3° 339.0° 239.6 344.2° 222.1° 122.1 221.9° 103.7° 103.7

[0074] Table 3

[0075] It can be seen that in the second test example, using the motor stall identification process disclosed in the present invention, when the motor's rotor is in different initial positions, it can be accurately identified that the motor rotor is not stalled. In other words, the motor stall identification process according to the present invention is not affected by the initial position of the motor rotor.

[0076] It should be pointed out that although the operation of the method for motor stall identification and processing according to the embodiment of the present disclosure is described above, this is only an example and not a limitation, and those skilled in the art may modify the above embodiments according to the principles of the present disclosure, for example, the functional modules and operations in each embodiment may be added, deleted or combined, and such modifications shall fall within the scope of the present disclosure.

[0077] In addition, the present disclosure also provides a storage medium and a program product. It should be understood that the machine executable instructions in the storage medium and the program product according to the embodiments of the present disclosure can also be configured to perform the above-mentioned motor stall identification process, so the contents not described in detail here can refer to the description of the previous corresponding parts, and will not be repeated here.

[0078] Accordingly, the storage medium for carrying the program product including the machine executable instructions is also included in the disclosure of the present invention, including but not limited to a floppy disk, an optical disk, a magneto-optical disk, a memory card, a memory stick, etc.

[0079] In addition, it should be noted that the above series of processes and devices can also be implemented by software and / or firmware. In the case of implementation by software and / or firmware, the program constituting the software is installed from a storage medium or a network to a computer with a dedicated hardware structure, and the computer can perform various functions when various programs are installed.

[0080] In the above embodiments, a plurality of functions included in one unit can be implemented by separate devices. Alternatively, a plurality of functions implemented by a plurality of units in the above embodiments can be implemented by separate devices respectively. In addition, one of the above functions can be implemented by a plurality of units. Needless to say, such a configuration is included in the technical scope of the present disclosure.

[0081] The scope of the present invention is not limited to the embodiments and technical effects described in detail above in conjunction with the accompanying drawings. It should be understood by those skilled in the art that, depending on design requirements and other factors, various modifications or variations may be made to the implementations provided herein without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for identifying a stall condition of a motor, comprising: Applying a first predetermined detection voltage to the stator of the motor to detect a first stator current flowing through the stator of the motor; Obtaining a first position angle of the rotor based on the first predetermined detection voltage and the first stator current; Based on the first position angle, applying a predetermined DC voltage to the stator of the motor; Applying a second predetermined detection voltage to the stator of the motor to detect a second stator current flowing through the stator of the motor; Obtaining a second position angle of the rotor based on the second predetermined detection voltage and the second stator current; as well as The stall condition of the electric machine is identified based on the first position angle and the second position angle.

2. The method according to claim 1, wherein: Identifying the stall condition of the motor includes: calculating a difference between the first position angle and the second position angle; and When the calculated difference is less than or equal to a predetermined angle difference threshold, it is determined that the motor has the stall condition.

3. The method according to claim 2, wherein: The predetermined angle difference threshold is within the electrical angle range of 10° to 80°.

4. The method according to claim 1, wherein: The motor is an embedded three-phase permanent magnet synchronous motor.

5. The method according to claim 4, wherein: Obtaining the first position angle of the rotor comprises: Processing the first predetermined detection voltage and the first stator current by Clarke transformation, Park transformation, filtering, and proportional integration to obtain the magnetic pole position of the rotor; Perform polarity detection; The magnetic pole position is processed based on the polarity detection result to obtain the first position angle.

6. The method according to claim 4, wherein: Obtaining the second position angle of the rotor comprises: Processing the second predetermined detection voltage and the second stator current by Clarke transformation, Park transformation, filtering, and proportional integration to obtain the magnetic pole position of the rotor; Perform polarity detection; The magnetic pole position is processed based on the polarity detection result to obtain the second position angle.

7. The method according to any one of claims 1 to 6, wherein: The first predetermined detection voltage and the second predetermined detection voltage are both high-frequency low-voltage AC voltages.

8. The method according to any one of claims 1 to 6, wherein: The first predetermined detection voltage and the second predetermined detection voltage are the same.

9. The method according to any one of claims 1 to 6, wherein the first predetermined detection voltage is applied to the stator of the motor before the motor is started.

10. The method according to any one of claims 1 to 6, wherein applying a predetermined DC voltage to the stator of the motor comprises: Selecting a stator winding in the stator of the motor whose phase angle is not equal to the first position angle; A predetermined DC voltage is applied to the selected stator winding.

11. The method according to claim 10, wherein: When the predetermined DC voltage is applied to the selected stator winding, the amplitude of the detected DC current flowing through the stator is within a range of 20% to 100% of the amplitude of the rated current of the motor.

12. A frequency converter, comprising a processing unit, wherein the processing unit is configured to execute the method according to any one of claims 1-11.

13. A machine-readable storage medium storing program instructions, which, when executed by a machine, enables the machine to perform the method according to any one of claims 1 to 11.

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