Back electromotive force sampling circuit and sampling method for permanent magnet synchronous motor

Abstract

The present invention provides a back electromotive force sampling circuit and sampling method for a permanent magnet synchronous motor, and also provides a back electromotive force sampling device and a computer-readable storage medium for a permanent magnet synchronous motor. The method includes: forcibly turning off the IGBT of an inverter that supplies power to the permanent magnet synchronous motor; when the stator current of the permanent magnet synchronous motor decreases to zero, sampling the back electromotive force of the permanent magnet synchronous motor; after the back electromotive force sampling is successful, canceling the forced turn-off of the IGBT of the inverter. By directly sampling the back electromotive force in the present invention, the accuracy of the sampled back electromotive force during the low-speed operation of the permanent magnet synchronous motor is improved; the rotor position and speed during the low-speed operation of the permanent magnet synchronous motor can be accurately estimated based on the back electromotive force, thereby improving the control accuracy of the permanent magnet synchronous motor and solving the problem of poor low-speed operation performance of the permanent magnet synchronous motor in the related art.

Description

Technical Field

[0001] The present invention relates to the field of permanent magnet synchronous motor control, and in particular, to a back electromotive force sampling circuit, a sampling method, a device, and a medium for a permanent magnet synchronous motor. Background Art

[0002] The drive system of a permanent magnet synchronous motor usually requires a position sensor to detect the rotor position and speed. However, adding a sensor will increase the cost, volume, and reduce the reliability. Therefore, in the prior art, the variable frequency air conditioner drive system generally uses a sensorless algorithm to detect the rotor position and speed, which can achieve the effect of a position sensor when the motor runs at medium and high speeds.

[0003] When the permanent magnet synchronous motor runs at medium and high speeds, the rotor speed and position of the motor can be estimated by calculating the back electromotive force. However, when the motor runs at low speed, the back electromotive force is small and the noise in the system is large, so it is difficult to calculate the back electromotive force using the back electromotive force-based estimation method at low speed, and thus the rotor speed and position of the motor cannot be accurately estimated. However, although the estimation scheme using the high-frequency signal injection method can effectively control the motor at low speed, it requires the motor to have obvious salient pole characteristics. In addition, when using this method to design a printed circuit board (Printed Circuit Board, abbreviated as PCB), it is required that the high-frequency signal can be sampled smoothly, and the requirement for the digital signal processing (Digital Signal Processing, abbreviated as DSP) computing ability is also relatively high.

[0004] In summary, there is a need for a sensorless permanent magnet synchronous motor voltage detection circuit and its low-speed operation control method to calculate the accurate rotor position and speed when the permanent magnet synchronous motor runs at low speed, so as to improve the low-speed operation performance of the permanent magnet synchronous motor. Summary of the Invention

[0005] The present invention provides a back electromotive force sampling circuit, a sampling method, a device, and a medium for a permanent magnet synchronous motor, so as to at least solve the problem of poor low-speed operation performance of the permanent magnet synchronous motor in the related art.

[0006] In a first aspect, an embodiment of the present invention provides a back electromotive force sampling circuit for a permanent magnet synchronous motor, including: a controller and a voltage detection circuit, where the voltage detection circuit includes: a first differential amplifier and a second differential amplifier, wherein,

[0007] The first input terminal of the first differential amplifier is electrically connected to the first detection terminal, the second input terminal of the first differential amplifier is electrically connected to the second detection terminal, the first input terminal of the second differential amplifier is also electrically connected to the second detection terminal, and the second input terminal of the second differential amplifier is electrically connected to the third detection terminal;

[0008] The first detection terminal, the second detection terminal, and the third detection terminal are used to be electrically connected to the first phase line, the second phase line, and the third phase line of the permanent magnet synchronous motor one by one;

[0009] The output terminal of the first differential amplifier is electrically connected to the first input terminal of the controller, the output terminal of the second differential amplifier is electrically connected to the second input terminal of the controller, the controller further includes an output terminal, and the output terminal of the controller is used to be electrically connected to the IGBT of the inverter that supplies power to the permanent magnet synchronous motor.

[0010] In a second aspect, an embodiment of the present invention provides a method for sampling the back electromotive force of a permanent magnet synchronous motor, including:

[0011] Forcibly turn off the IGBT of the inverter that supplies power to the permanent magnet synchronous motor;

[0012] When the stator current of the permanent magnet synchronous motor decreases to zero, sample the back electromotive force of the permanent magnet synchronous motor;

[0013] After the back electromotive force sampling is successful, cancel the forced turn-off of the IGBT of the inverter.

[0014] In a third aspect, an embodiment of the present invention provides a back electromotive force sampling device for a permanent magnet synchronous motor, including: at least one processor, at least one memory, and computer program instructions stored in the memory, and when the computer program instructions are executed by the processor, the method described in the second aspect is implemented.

[0015] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, on which computer program instructions are stored, and when the computer program instructions are executed by a processor, the method described in the second aspect is implemented.

[0016] Through the back electromotive force sampling circuit, sampling method, device and medium of the permanent magnet synchronous motor provided by the embodiments of the present invention, the IGBT of the inverter that supplies power to the permanent magnet synchronous motor is forced to turn off; when the stator current of the permanent magnet synchronous motor decreases to zero, the back electromotive force of the permanent magnet synchronous motor is sampled; after the back electromotive force sampling is successful, the forced turn-off of the IGBT of the inverter is cancelled. By directly sampling the back electromotive force in the present invention, the accuracy of the sampled back electromotive force during the low-speed operation of the permanent magnet synchronous motor is improved; based on this back electromotive force, the rotor position and speed during the low-speed operation of the permanent magnet synchronous motor can be accurately estimated, thereby improving the control accuracy of the permanent magnet synchronous motor and solving the problem of poor low-speed operation performance of the permanent magnet synchronous motor in the related art. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0018] Figure 1a is a schematic diagram of the topological structure of the back electromotive force sampling circuit of the permanent magnet synchronous motor according to the embodiments of the present invention;

[0019] Figure 1b is a schematic diagram of the topological structure of the connection between the back electromotive force sampling circuit of the permanent magnet synchronous motor and the permanent magnet synchronous motor system according to the embodiments of the present invention;

[0020] Figure 2 is a flowchart of the back electromotive force sampling method of the permanent magnet synchronous motor according to the embodiments of the present invention;

[0021] Figure 3 is a schematic diagram of the hardware structure of the back electromotive force sampling device of the permanent magnet synchronous motor according to the embodiments of the present invention;

[0022] Figure 4 is a flowchart of the operation control method of the permanent magnet synchronous motor according to the preferred embodiments of the present invention;

[0023] Figure 5 is a schematic diagram of the current decay sampling algorithm according to the preferred embodiments of the present invention;

[0024] Figure 6 is a schematic diagram of the topological structure of the back electromotive force sampling circuit of the permanent magnet synchronous motor according to the preferred embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can be implemented without some of these specific details. The following description of the embodiments is only provided to provide a better understanding of the present invention by showing examples of the present invention.

[0026] It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or device. Without further limitation, an element defined by the statement "comprising..." does not exclude the existence of additional identical elements in the process, method, article, or device comprising the element.

[0027] In this embodiment, a back electromotive force sampling circuit for a permanent magnet synchronous motor is provided. Figure 1a is a schematic diagram of the topological structure of the back electromotive force sampling circuit for a permanent magnet synchronous motor according to an embodiment of the present invention. Figure 1b is a schematic diagram of the topological structure of the connection between the back electromotive force sampling circuit for a permanent magnet synchronous motor and the permanent magnet synchronous motor system according to an embodiment of the present invention. As Figure 1a and Figure 1b shown, the back electromotive force sampling circuit includes a controller 5 and a voltage detection circuit 4. The voltage detection circuit 4 includes: a first differential amplifier 41 and a second differential amplifier 42. Among them,

[0028] The first input terminal of the first differential amplifier 41 is electrically connected to the first detection terminal, the second input terminal of the first differential amplifier 41 is electrically connected to the second detection terminal, the first input terminal of the second differential amplifier 42 is also electrically connected to the second detection terminal, and the second input terminal of the second differential amplifier 42 is electrically connected to the third detection terminal.

[0029] As Figure 1b shown, the first detection terminal, the second detection terminal, and the third detection terminal are used to be electrically connected to the first phase line, the second phase line, and the third phase line of the permanent magnet synchronous motor one by one.

[0030] The output terminal of the first differential amplifier 41 is electrically connected to the first input terminal of the controller 5, and the output terminal of the second differential amplifier 42 is electrically connected to the second input terminal of the controller 5. The controller 5 further includes an output terminal 51, and the output terminal 51 of the controller 5 is used to be electrically connected to the IGBT of the inverter 2 that supplies power to the permanent magnet synchronous motor 3.

[0031] In Figure 1b the permanent magnet synchronous motor system also includes a rectifier 1 connected in series between the mains power and the inverter.

[0032] Through the back electromotive force sampling circuit of the permanent magnet synchronous motor described above, the controller 5 can forcibly turn off the IGBT of the inverter that supplies power to the permanent magnet synchronous motor; when the stator current of the permanent magnet synchronous motor decreases to zero, sample the back electromotive force of the permanent magnet synchronous motor; after the back electromotive force sampling is successful, cancel the forced turn-off of the IGBT of the inverter. By directly sampling the back electromotive force through the above circuit, the accuracy of the sampled back electromotive force during the low-speed operation of the permanent magnet synchronous motor is improved; based on this back electromotive force, the rotor position and speed during the low-speed operation of the permanent magnet synchronous motor can be accurately estimated, thereby improving the control accuracy of the permanent magnet synchronous motor and solving the problem of poor low-speed operation performance of the permanent magnet synchronous motor in the related art.

[0033] Optionally, the voltage detection circuit further includes: a first bidirectional voltage regulator 43 composed of two voltage regulators connected in reverse series, a second bidirectional voltage regulator 44 composed of two voltage regulators connected in reverse series, a first resistor 45, a second resistor 46, a third resistor 47, and a fourth resistor 48, where

[0034] the first resistor 45 is connected in series between the first input terminal of the first differential amplifier 41 and the first detection terminal; the second resistor 46 is connected in series between the second input terminal of the first differential amplifier 41 and the second detection terminal; the third resistor 47 is connected in series between the first input terminal of the second differential amplifier 42 and the second detection terminal; the fourth resistor 48 is connected in series between the second input terminal of the second differential amplifier 42 and the third detection terminal;

[0035] the first bidirectional voltage regulator 43 is connected in series between the first input terminal and the second input terminal of the first differential amplifier 41; the second bidirectional voltage regulator 44 is connected in series between the first input terminal and the second input terminal of the second differential amplifier 42.

[0036] The function of the above bidirectional voltage regulator is to limit the input voltage of the differential amplifier, while the function of the first resistor to the fourth resistor is to act as current-limiting resistors to protect the bidirectional voltage regulator and prevent the bidirectional voltage regulator from being broken down due to excessive detection current.

[0037] Optionally, the voltage detection circuit further includes: a resistor group 49 formed by connecting three resistors in a Y shape, wherein three terminals of the resistor group 49 are respectively and electrically connected to the first detection terminal, the second detection terminal, and the third detection terminal. Since there may be parasitic capacitors and leakage inductances that cause resonance on the three phase lines of the permanent magnet synchronous motor, damping resistors connected in a Y shape are connected to the three detection terminals connected to the phase lines, which can suppress resonance and improve the sampling quality.

[0038] Optionally, the controller 5 further includes: a timing module, which is configured to start timing for a predetermined duration when the IGBT of the inverter that supplies power to the permanent magnet synchronous motor is forced to turn off, and cancel the forced turn-off of the IGBT after the timer times out.

[0039] The advantages of the back electromotive force sampling circuit of the permanent magnet synchronous motor described above are simple structure and high sampling accuracy of the back electromotive force. The parameter selection of each component in the back electromotive force sampling circuit can be specifically selected according to actual needs and requirements. The advantages of the back electromotive force sampling circuit of the permanent magnet synchronous motor described above will be described and illustrated in combination with other embodiments of the present invention.

[0040] In this embodiment, a method for sampling the back electromotive force of a permanent magnet synchronous motor is also provided. Figure 2 is a flowchart of a method for sampling the back electromotive force of a permanent magnet synchronous motor according to an embodiment of the present invention. As shown in Figure 2, the process includes the following steps:

[0041] Step S201, forcibly turn off the IGBT of the inverter that supplies power to the permanent magnet synchronous motor;

[0042] Step S202, when the stator current of the permanent magnet synchronous motor decreases to zero, sample the back electromotive force of the permanent magnet synchronous motor;

[0043] Step S203, after the back electromotive force sampling is successful, cancel the forced turn-off of the IGBT of the inverter.

[0044] Optionally, after canceling the forced turn-off of the IGBT of the inverter, the rotor position and speed of the permanent magnet synchronous motor can be estimated according to the collected back electromotive force.

[0045] Optionally, before step S201, the method may further include: determining whether the rotational speed of the permanent magnet synchronous motor exceeds a preset value; in this case, in step S201, when the determination result is that the rotational speed of the permanent magnet synchronous motor does not exceed the preset value, forcibly turning off the IGBT of the inverter that supplies power to the permanent magnet synchronous motor. Otherwise, when the determination result is that the rotational speed of the permanent magnet synchronous motor exceeds the preset value, sampling the terminal voltage of the phase line of the permanent magnet synchronous motor; estimating the back electromotive force of the permanent magnet synchronous motor according to the sampled terminal voltage of the phase line; estimating the rotor position and the magnitude of the rotational speed of the permanent magnet synchronous motor according to the estimated back electromotive force.

[0046] Through the above method, a method for estimating or calculating the rotor position and the magnitude of the rotational speed of the motor according to the rotational speed of the permanent magnet synchronous motor is realized, so that the back electromotive force sampling method of the permanent magnet synchronous motor provided by the embodiments of the present invention can sample more accurate back electromotive force under both low rotational speed and high rotational speed conditions.

[0047] Optionally, a large number of experiments and analyses show that in this embodiment, the above preset value is preferably 190 rpm to 210 rpm, and more preferably 200 rpm.

[0048] The back electromotive force sampling method of the permanent magnet synchronous motor provided in this embodiment will be described and illustrated in combination with preferred embodiments.

[0049] In addition, combined with Figure 2 the back electromotive force sampling method of the permanent magnet synchronous motor described in the embodiments of the present invention can be implemented by a back electromotive force sampling device of the permanent magnet synchronous motor. Figure 3 FIG. shows a schematic hardware structure diagram of a back electromotive force sampling device of a permanent magnet synchronous motor provided by an embodiment of the present invention.

[0050] The back electromotive force sampling device of the permanent magnet synchronous motor may include a processor 31 and a memory 32 storing computer program instructions.

[0051] Specifically, the above processor 31 may include a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention.

[0052] The memory 32 may include a mass storage for data or instructions. By way of example and not limitation, the memory 32 may include a hard disk drive (HDD), a floppy disk drive, a flash memory, an optical disk, a magneto-optical disk, a magnetic tape, or a universal serial bus (USB) drive, or a combination of two or more of these. Where appropriate, the memory 32 may include removable or non-removable (or fixed) media. Where appropriate, the memory 32 may be internal or external to the data processing device. In a particular embodiment, the memory 32 is a non-volatile solid-state memory. In a particular embodiment, the memory 32 includes a read-only memory (ROM). Where appropriate, the ROM may be a mask-programmed ROM, a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), an electrically rewritable ROM (EAROM), or a flash memory, or a combination of two or more of these.

[0053] The processor 31 reads and executes the computer program instructions stored in the memory 32 to implement any one of the back electromotive force sampling methods of the permanent magnet synchronous motor in the above embodiments.

[0054] In one example, the back electromotive force sampling device of the permanent magnet synchronous motor may further include a communication interface 33 and a bus 30. Among them, as Figure 3 shown, the processor 31, the memory 32, and the communication interface 33 are connected through the bus 30 and complete communication with each other.

[0055] The communication interface 33 is mainly used to implement communication between the modules, devices, units, and / or devices in the embodiments of the present invention.

[0056] The bus 30 includes hardware, software, or both, and couples the components of the back electromotive force sampling device of the permanent magnet synchronous motor to each other. By way of example and not limitation, the bus may include an accelerated graphics port (AGP) or other graphics bus, an enhanced industry standard architecture (EISA) bus, a front-side bus (FSB), a hyperTransport (HT) interconnect, an industry standard architecture (ISA) bus, an InfiniBand interconnect, a low pin count (LPC) bus, a memory bus, a microChannel architecture (MCA) bus, a peripheral component interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a serial advanced technology attachment (SATA) bus, a video electronics standards association local (VLB) bus, or other suitable buses, or a combination of two or more of these. Where appropriate, the bus 30 may include one or more buses. Although the embodiments of the present invention describe and illustrate specific buses, the present invention contemplates any suitable bus or interconnect.

[0057] When the back electromotive force sampling device of the permanent magnet synchronous motor is working, the processor 31 reads and executes the computer program instructions stored in the memory 32, so as to implement the combination of Figure 2 The back electromotive force sampling method of the permanent magnet synchronous motor described.

[0058] In addition, in combination with the back electromotive force sampling method of the permanent magnet synchronous motor in the above embodiments, the embodiments of the present invention can provide a computer-readable storage medium to implement. Computer program instructions are stored on the computer-readable storage medium; when the computer program instructions are executed by a processor, any one of the back electromotive force sampling methods in the above embodiments is implemented.

[0059] In order to make the description of the embodiments of the present invention clearer, the following is described and illustrated in conjunction with preferred embodiments.

[0060] This preferred embodiment provides a back electromotive force sampling circuit and method for a sensorless permanent magnet synchronous motor, and provides a permanent magnet synchronous motor operation control method based on the back electromotive force sampling method.

[0061] For the flowchart of the sensorless permanent magnet synchronous motor operation control method of this preferred embodiment, please refer to Figure 4 It is found that when the permanent magnet synchronous motor runs at a low speed, the back electromotive force obtained by sampling is more accurate, and when the permanent magnet synchronous motor runs at a high speed, the estimated back electromotive force is more accurate. Therefore, in this preferred embodiment, when the speed of the permanent magnet synchronous motor is less than 200 rpm (other values can be selected according to the actual situation), the terminal voltage of the permanent magnet synchronous motor is sampled by a differential sampling circuit to obtain the back electromotive force, and then the rotor position and speed of the permanent magnet synchronous motor are calculated; when the speed of the permanent magnet synchronous motor is greater than 200 rpm, the back electromotive force is directly estimated, and then the rotor position and speed of the permanent magnet synchronous motor are estimated.

[0062] Since the terminal voltage of the stator of the permanent magnet synchronous motor is composed of the back electromotive force and the voltage drop caused by the stator resistance and inductance, it is necessary to make the stator current 0 (turn off all the arms of the inverter) when measuring the back electromotive force, so that no current will pass through the stator resistance and inductance of the permanent magnet synchronous motor, and thus no voltage drop will be generated on the stator resistance and inductance. At this time, the back electromotive force is equal to the terminal voltage of the motor stator.

[0063] The permanent magnet synchronous motor operation control method provided by this preferred embodiment includes the following steps:

[0064] Step 1. When the speed of the permanent magnet synchronous motor is less than 200 rpm, the back electromotive force is obtained by adding a current decay sampling algorithm to the current control, specifically as Figure 5As shown. At the initial stage of this algorithm, the inverter forced shutdown flag is set to 1, causing all the inverter bridge arms to shut down simultaneously. After the stator current gradually decays to 0, the stator terminal voltage is sampled.

[0065] In Figure 5 , T est is the time for sampling and calculating the rotational speed, and T dip is the current decay time. According to the characteristics of the switching device, the decay time of the current after the switching device shuts down is less than 0.2 ms. Therefore, the start time of sampling the stator terminal voltage can be set to any time after 0.2 ms from the shutdown of the switching device, preferably sampling the stator terminal voltage at 0.25 ms after the shutdown of the switching device. As Figure 5 shown, T est is affected by the stator terminal voltage sampling time on the one hand and the processor's estimated rotational speed time on the other hand. In some embodiments, the value of T est can be from 1 ms to 5 ms, preferably set to 2 ms.

[0066] Step 2: The back electromotive force sampling circuit of the permanent magnet synchronous motor is as Figure 6 shown. The terminal voltage of the permanent magnet synchronous motor is sampled through a differential sampling circuit, and after being output by the differential amplifier, the terminal line voltage of the permanent magnet synchronous motor and can be obtained. The voltage sampled at this time is the back electromotive force. Then the inverter forced shutdown flag is set to 0 to cancel the forced shutdown. The maximum measurable back electromotive force is clamped at 5 V by R 2 and two zener diodes connected in reverse series, thereby being able to limit the maximum operating speed of the permanent magnet synchronous motor within 200 rpm. Since there may be parasitic capacitance and leakage inductance that cause resonance at the terminals of the permanent magnet synchronous motor, a damping resistor R 1 connected in a Y shape is connected at the motor terminals to suppress resonance.

[0067] Step 3: After sampling the terminal line voltage and of the permanent magnet synchronous motor, the phase voltage of the motor terminals of the permanent magnet synchronous motor can be calculated. Then, its d and q axis components in the rotating coordinate system can be calculated. According to the relationship between the back electromotive force and the rotation angle , the position of the rotor can be calculated, and at the same time, the rotational speed of the rotor can be calculated as where K Eis the back electromotive force constant. Thus, the position and speed of the permanent magnet synchronous motor rotor at low speed are accurately obtained. Then, according to the conventional field-oriented control algorithm, the permanent magnet synchronous motor is controlled, which can improve the performance of the permanent magnet synchronous motor during low-speed operation.

[0068] Step 4: When the speed continues to rise and is greater than 200 rpm, the inverter forced shutdown flag bit is always in the 0 state. Therefore, all the bridge arms of the inverter will not be turned off simultaneously. At this time, after obtaining the terminal voltage of each phase of the permanent magnet synchronous motor, the back electromotive force is estimated by a software algorithm to obtain the back electromotive force, and then the d-axis and q-axis components in the rotating coordinate system are calculated, and further the position and speed magnitude of the rotor are accurately calculated. Finally, the permanent magnet synchronous motor is controlled according to the conventional field-oriented control algorithm.

[0069] The calculation method for calculating the position and speed magnitude of the rotor based on the d-axis and q-axis components can adopt any known calculation method in the field. For example: using the back electromotive force A α and B β , through the formula estimate the position angle of the motor rotor Based on the obtained position angle , calculate the estimated value of the motor rotor position angle through an angle compensation function related to the speed Using the obtained to perform differentiation to obtain the motor rotor speed v.

[0070] In summary, through the above embodiments of the present invention, which are preferred implementation manners, not only a brand-new back electromotive force sampling circuit for a permanent magnet synchronous motor is provided, but also a method for accurately controlling the low-speed and high-speed operation of a permanent magnet synchronous motor based on this back electromotive force sampling circuit is provided. Controlling the permanent magnet synchronous motor based on the technical solutions introduced in the embodiments of the present invention can make the starting of the permanent magnet synchronous motor simple and reliable, the starting more gentle under heavy load conditions of the permanent magnet synchronous motor, and the low-speed operation of the permanent magnet synchronous motor more stable.

[0071] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An electromotive force sampling circuit for a permanent magnet synchronous motor, characterized in that, it includes: a controller and a voltage detection circuit, wherein the voltage detection circuit includes: a first differential amplifier and a second differential amplifier, where the first input terminal of the first differential amplifier is electrically connected to the first detection terminal, the second input terminal of the first differential amplifier is electrically connected to the second detection terminal, the first input terminal of the second differential amplifier is also electrically connected to the second detection terminal, and the second input terminal of the second differential amplifier is electrically connected to the third detection terminal; the first detection terminal, the second detection terminal, and the third detection terminal are used to be electrically connected to the first phase line, the second phase line, and the third phase line of the permanent magnet synchronous motor one by one; the output terminal of the first differential amplifier is electrically connected to the first input terminal of the controller, the output terminal of the second differential amplifier is electrically connected to the second input terminal of the controller, the controller further includes an output terminal, and the output terminal of the controller is used to be electrically connected to the IGBT of the inverter that supplies power to the permanent magnet synchronous motor; the voltage detection circuit further includes: a first bidirectional voltage regulator diode, a second bidirectional voltage regulator diode, a first resistor, a second resistor, a third resistor, and a fourth resistor, where the first resistor is connected in series between the first input terminal of the first differential amplifier and the first detection terminal; the second resistor is connected in series between the second input terminal of the first differential amplifier and the second detection terminal; the third resistor is connected in series between the first input terminal of the second differential amplifier and the second detection terminal; the fourth resistor is connected in series between the second input terminal of the second differential amplifier and the third detection terminal; the first bidirectional voltage regulator diode is connected in series between the first input terminal and the second input terminal of the first differential amplifier; the second bidirectional voltage regulator diode is connected in series between the first input terminal and the second input terminal of the second differential amplifier.

2. The electromotive force sampling circuit for a permanent magnet synchronous motor according to claim 1, characterized in that, the voltage detection circuit further includes: a resistor group formed by connecting three resistors in a Y shape, where the three terminals of the resistor group are electrically connected to the first detection terminal, the second detection terminal, and the third detection terminal one by one.

3. The electromotive force sampling circuit for a permanent magnet synchronous motor according to claim 1, characterized in that, the controller further includes: a timing module.

4. An electromotive force sampling method for a permanent magnet synchronous motor, applied to the electromotive force sampling circuit for a permanent magnet synchronous motor according to any one of claims 1 to 3, characterized in that, it includes: forcing the IGBT of the inverter that supplies power to the permanent magnet synchronous motor to turn off; when the stator current of the permanent magnet synchronous motor decreases to zero, sampling the electromotive force of the permanent magnet synchronous motor; after the electromotive force sampling is successful, canceling the forced turn-off of the IGBT of the inverter.

5. The electromotive force sampling method for a permanent magnet synchronous motor according to claim 4, characterized in that, after canceling the forced turn-off of the IGBT of the inverter, the method further includes: Estimate the rotor position and rotational speed of the permanent magnet synchronous motor according to the detected back electromotive force.

6. The back electromotive force sampling method of the permanent magnet synchronous motor according to claim 4, wherein, before forcibly turning off the IGBT of the inverter that supplies power to the permanent magnet synchronous motor, the method further includes: judging whether the rotational speed of the permanent magnet synchronous motor exceeds a preset value; wherein, forcibly turning off the IGBT of the inverter that supplies power to the permanent magnet synchronous motor includes: forcibly turning off the IGBT of the inverter that supplies power to the permanent magnet synchronous motor when the rotational speed of the permanent magnet synchronous motor does not exceed the preset value.

7. The back electromotive force sampling method of the permanent magnet synchronous motor according to claim 6, wherein, the method further includes: when the rotational speed of the permanent magnet synchronous motor exceeds the preset value, sampling the line voltage of the phase lines of the permanent magnet synchronous motor; estimating the back electromotive force of the permanent magnet synchronous motor according to the sampled line voltage of the phase lines; estimating the rotor position and rotational speed of the permanent magnet synchronous motor according to the estimated back electromotive force.

8. The back electromotive force sampling method of the permanent magnet synchronous motor according to claim 6, wherein, the preset value is 190 rpm to 210 rpm.

9. A back electromotive force sampling device for a permanent magnet synchronous motor, wherein, it includes: at least one processor, at least one memory, and computer program instructions stored in the memory, and when the computer program instructions are executed by the processor, the method according to any one of claims 4 to 8 is implemented.

10. A computer-readable storage medium, on which computer program instructions are stored, wherein, when the computer program instructions are executed by a processor, the method according to any one of claims 4 to 8 is implemented.

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