CN110365259A - Counter electromotive force sampling circuit and sampling method of permanent magnet synchronous motor - Google Patents

Abstract

The invention provides a counter electromotive force sampling circuit and a sampling method of a permanent magnet synchronous motor, and also provides a counter electromotive force sampling device and a computer-readable storage medium of a permanent magnet synchronous motor. The method includes: forcibly turning off the IGBT of the inverter that provides power for 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; the back electromotive force sampling is successful After that, cancel the forced shutdown of the IGBT of the inverter. By directly sampling the back electromotive force of the present invention, the accuracy of the back electromotive force sampled when the permanent magnet synchronous motor is running at low speed is improved; according to the back electromotive force, the rotor position and speed of the permanent magnet synchronous motor when running at low speed can be accurately estimated, and then the permanent magnet synchronous motor can be improved. The control accuracy of the synchronous motor solves the problem of poor low-speed operation performance of the permanent magnet synchronous motor in the related art.

Description

The counter electromotive force sampling circuit and sampling method of permanent magnet synchronous motor

technical field

The present invention relates to the field of permanent magnet synchronous motor control, in particular, to a counter electromotive force sampling circuit, sampling method, equipment and medium of a permanent magnet synchronous motor.

Background technique

The drive system of the permanent magnet synchronous motor usually needs a position sensor to detect the rotor position and rotational speed, but adding the sensor will increase the cost, increase the volume and reduce the reliability. Therefore, the inverter air conditioner drive system in the prior art generally uses a position sensorless algorithm to detect the rotor position and speed, which can achieve the effect of the position sensor when the motor is running at medium and high speeds.

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

In summary, there is a need for a position sensorless permanent magnet synchronous motor voltage detection circuit and its low-speed operation control method, which can calculate the precise rotor position and speed when the permanent magnet synchronous motor is running at low speed, thereby improving the low-speed operation of the permanent magnet synchronous motor. run performance.

Contents of the invention

The invention provides a back electromotive force sampling circuit, sampling method, equipment and medium of a permanent magnet synchronous motor, to at least solve the problem of poor low-speed operation performance of the permanent magnet synchronous motor in the related art.

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

The first input end of the first differential amplifier is electrically connected to the first detection end, the second input end of the first differential amplifier is electrically connected to the second detection end, and the first input end of the second differential amplifier terminal 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 electrically connect the first phase line, the second phase line and the third phase line of the permanent magnet synchronous motor one by one;

The output end of the first differential amplifier is electrically connected to the first input end of the controller, the output end of the second differential amplifier is electrically connected to the second input end of the controller, and the controller It also includes an output terminal, the output terminal of the controller is used for electrical connection with the IGBT of the inverter that provides power for the permanent magnet synchronous motor.

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

Forced to turn off the IGBT of the inverter that provides power to the permanent magnet synchronous motor;

When the stator current of the permanent magnet synchronous motor is reduced to zero, the counter electromotive force of the permanent magnet synchronous motor is sampled;

After the counter electromotive force is successfully sampled, the forced shutdown of the IGBT of the inverter is cancelled.

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, when the computer program instructions When executed by the processor, the method described in the second aspect is realized.

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.

Through the back electromotive force sampling circuit, sampling method, equipment and medium of the permanent magnet synchronous motor provided by the embodiment of the present invention, the IGBT of the inverter that provides power for the permanent magnet synchronous motor is forcibly turned off; when the stator current of the permanent magnet synchronous motor decreases When the value is zero, the counter electromotive force of the permanent magnet synchronous motor is sampled; after the counter electromotive force is successfully sampled, the forced shutdown of the IGBT of the inverter is cancelled. By directly sampling the back electromotive force of the present invention, the accuracy of the back electromotive force sampled when the permanent magnet synchronous motor is running at low speed is improved; according to the back electromotive force, the rotor position and speed of the permanent magnet synchronous motor when running at low speed can be accurately estimated, and then the permanent magnet synchronous motor can be improved. The control accuracy of the synchronous motor solves the problem of poor low-speed operation performance of the permanent magnet synchronous motor in the related art.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention, and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute improper limitations to the present invention. In the attached picture:

Fig. 1 a is the topological structure schematic diagram of the counter electromotive force sampling circuit of the permanent magnet synchronous motor according to the embodiment of the present invention;

Fig. 1 b is the schematic diagram of the topological structure that the counter electromotive force sampling circuit of the permanent magnet synchronous motor according to the embodiment of the present invention is connected with the permanent magnet synchronous motor system;

Fig. 2 is the flowchart of the counter electromotive force sampling method of the permanent magnet synchronous motor according to the embodiment of the present invention;

Fig. 3 is the hardware structural representation of the counter electromotive force sampling equipment of the permanent magnet synchronous motor according to the embodiment of the present invention;

Fig. 4 is the flow chart of the permanent magnet synchronous motor operation control method according to the preferred embodiment of the present invention;

5 is a schematic diagram of a current decay sampling algorithm according to a preferred embodiment of the present invention;

Fig. 6 is a schematic diagram of the topology of the counter electromotive force sampling circuit of the permanent magnet synchronous motor according to the preferred embodiment of the present invention.

Detailed ways

The characteristics and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by showing examples of the present invention.

It should be noted that in this article, 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 that there is a relationship between these entities or operations. There is no such actual relationship or order between them. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the statement "comprising..." does not exclude the presence of additional identical elements in the process, method, article or device that includes the element.

In this embodiment, a back electromotive force sampling circuit of a permanent magnet synchronous motor is provided. Fig. 1a is a schematic diagram of the topology of a back electromotive force sampling circuit of a permanent magnet synchronous motor according to an embodiment of the present invention, and Fig. 1b is a schematic diagram of a counter electromotive force sampling circuit according to an embodiment of the present invention The schematic diagram of the topological structure of the back electromotive force sampling circuit of the permanent magnet synchronous motor connected with the permanent magnet synchronous motor system, as shown in Figure 1a and Figure 1b, the back electromotive force sampling circuit includes a controller 5 and a voltage detection circuit 4, the voltage detection circuit 4 Including: a first differential amplifier 41, a second differential amplifier 42, wherein,

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

As shown in Figure 1b, the first detection terminal, the second detection terminal and the third detection terminal are used to electrically connect the first phase line, the second phase line and the third phase line of the permanent magnet synchronous motor one by one;

The output end of the first differential amplifier 41 is electrically connected to the first input end of the controller 5, the output end of the second differential amplifier 42 is electrically connected to the second input end of the controller 5, and the controller 5 also includes an output end 51 , the output terminal 51 of the controller 5 is used to electrically connect with the IGBT of the inverter 2 that provides power for the permanent magnet synchronous motor 3 .

The permanent magnet synchronous motor system in Fig. 1b also includes a rectifier 1 connected in series between the mains and the inverter.

Through the above-mentioned counter electromotive force sampling circuit of the permanent magnet synchronous motor, the controller 5 can forcibly turn off the IGBT of the inverter that provides power for the permanent magnet synchronous motor; when the stator current of the permanent magnet synchronous motor is reduced to zero, the The counter electromotive force of the magnetic synchronous motor is sampled; after the counter electromotive force is successfully sampled, the forced shutdown of the IGBT of the inverter is cancelled. By directly sampling the back electromotive force through the above circuit, the accuracy of the back electromotive force sampled when the permanent magnet synchronous motor is running at low speed is improved; according to the back electromotive force, the rotor position and speed of the permanent magnet synchronous motor when running at low speed can be accurately estimated, and then the permanent magnet synchronous motor can be improved. The control accuracy of the synchronous motor solves the problem of poor low-speed operation performance of the permanent magnet synchronous motor in the related art.

Optionally, the voltage detection circuit further includes: a first bidirectional voltage regulator tube 43 composed of two voltage regulator tubes reversely connected in series, a second bidirectional voltage regulator tube 44 composed of two reverse voltage regulator tubes connected in reverse series, a first Resistor 45, second resistor 46, third resistor 47 and fourth resistor 48, wherein,

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 The 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;

The first bidirectional regulator tube 43 is connected in series between the first input terminal and the second input terminal of the first differential amplifier 41; the second bidirectional regulator tube 44 is connected in series between the first input terminal and the second input terminal of the second differential amplifier 42 between the ends.

The function of the above-mentioned bidirectional voltage regulator is to limit the input voltage of the differential amplifier, and the functions of the first resistor to the fourth resistor are to play the role of current limiting resistors to protect the bidirectional voltage regulator and prevent the bidirectional voltage regulator from being damaged due to excessive detection current. And was broken down.

Optionally, the voltage detection circuit further includes: a resistance group 49 composed of three resistors connected in Y-type, wherein the three terminals of the resistance group 49 are respectively connected to the first detection terminal, the second detection terminal and the third detection terminal one by one. ground electrical connection. Since there may be parasitic capacitance and leakage inductance that cause resonance on the three phase lines of the permanent magnet synchronous motor, a Y-connected damping resistor is connected to the three detection terminals connected to the phase lines to suppress resonance and improve sampling quality.

Optionally, the controller 5 also includes: a timing module, which is used to start the timing of a predetermined duration when the IGBT of the inverter providing power for the permanent magnet synchronous motor is forcibly turned off, and cancel the timing after the timer expires. Forced shutdown of the IGBT.

The above-mentioned counter electromotive force sampling circuit of the permanent magnet synchronous motor has the advantages of simple structure and high sampling accuracy of the counter electromotive force. The parameter selection of each component in the above counter electromotive force sampling circuit can be specifically selected according to actual needs and requirements. The advantages of the above-mentioned counter electromotive force sampling circuit of the permanent magnet synchronous motor will be described and illustrated in conjunction with other embodiments of the present invention.

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

Step S201, forcibly turning off the IGBT of the inverter that provides power for the permanent magnet synchronous motor;

Step S202, when the stator current of the permanent magnet synchronous motor decreases to zero, sampling the counter electromotive force of the permanent magnet synchronous motor;

In step S203, after the counter electromotive force is successfully sampled, the forced shutdown of the IGBT of the inverter is cancelled.

Optionally, after canceling the forced shutdown of the IGBT of the inverter, the rotor position and speed of the permanent magnet synchronous motor can be estimated according to the collected counter electromotive force.

Optionally, before step S201, the method may also include: judging whether the rotational speed of the permanent magnet synchronous motor exceeds a preset value; When the value is set, the IGBT of the inverter that provides power to the permanent magnet synchronous motor is forcibly turned off. Otherwise, when the speed of the permanent magnet synchronous motor exceeds the preset value, the terminal voltage of the phase line of the permanent magnet synchronous motor is sampled; according to the collected terminal voltage of the phase line, the permanent magnet synchronous motor is estimated. Back electromotive force: According to the estimated back electromotive force, estimate the rotor position and speed of the permanent magnet synchronous motor.

Through the above method, the method of estimating or calculating the rotor position and the speed of the motor according to the speed switching 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 embodiment of the present invention can be used at low In the case of rotating speed and high rotating speed, more accurate back electromotive force can be obtained by sampling.

Optionally, a large number of experiments and analyzes have shown that in this embodiment the preset value is preferably 190rpm to 210rpm, more preferably 200rpm.

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

In addition, the back electromotive force sampling method of the permanent magnet synchronous motor of the embodiment of the present invention described in conjunction with Fig. 2 can be realized by the back electromotive force sampling device of the permanent magnet synchronous motor. Fig. 3 shows a schematic diagram of the hardware structure of the back electromotive force sampling device of the permanent magnet synchronous motor provided by the embodiment of the present invention.

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.

Specifically, the above-mentioned processor 31 may include a central processing unit (CPU), or an Application Specific Integrated Circuit (ASIC), or may be configured as one or more integrated circuits implementing the embodiments of the present invention.

Memory 32 may include mass storage for data or instructions. By way of example and not limitation, memory 32 may include a hard disk drive (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 (Universal Serial Bus, USB) drive or two or more Combinations of multiple of the above. Storage 32 may include removable or non-removable (or fixed) media, where appropriate. Memory 32 may be internal or external to the data processing arrangement, where appropriate. In particular embodiments, memory 32 is non-volatile solid-state memory. In particular embodiments, memory 32 includes read-only memory (ROM). Where appropriate, the ROM may be mask programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically rewritable ROM (EAROM), or flash memory or A combination of two or more of the above.

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

In an example, the back electromotive force sampling device of the permanent magnet synchronous motor may also include a communication interface 33 and a bus 30. Wherein, as shown in FIG. 3 , the processor 31 , the memory 32 , and the communication interface 33 are connected through the bus 30 and complete mutual communication.

The communication interface 33 is mainly used to realize the communication between various modules, devices, units and/or devices in the embodiment of the present invention.

The bus 30 includes hardware, software, or both, and couples the components of the back EMF sampling device of the permanent magnet synchronous motor to each other. By way of example and not limitation, the bus may include Accelerated Graphics Port (AGP) or other graphics bus, Enhanced Industry Standard Architecture (EISA) bus, Front Side Bus (FSB), HyperTransport (HT) interconnect, Industry Standard Architecture (ISA) Bus, Infiniband Interconnect, Low Pin Count (LPC) Bus, Memory Bus, Micro Channel Architecture (MCA) Bus, Peripheral Component Interconnect (PCI) Bus, PCI-Express (PCI-X) Bus, Serial Advanced Technology Attachment (SATA) bus, Video Electronics Standards Association Local (VLB) bus or other suitable bus or a combination of two or more of these. Bus 30 may comprise one or more buses, where appropriate. Although embodiments of the invention describe and illustrate a particular bus, the invention contemplates any suitable bus or interconnect.

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, thereby realizing the back electromotive force sampling method of the permanent magnet synchronous motor described in conjunction with Fig. 2 .

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 for implementation. 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 of the permanent magnet synchronous motor in the above-mentioned embodiments is realized.

In order to make the description of the embodiments of the present invention clearer, the following describes and illustrates in conjunction with preferred embodiments.

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

Please refer to FIG. 4 for the flow chart of the operation control method of the position sensorless permanent magnet synchronous motor in this preferred embodiment. The study found that when the permanent magnet synchronous motor is running at low speed, the back electromotive force obtained by sampling is more accurate, and when the permanent magnet synchronous motor is running at high speed, the estimated back electromotive force is more accurate. Therefore, in this preferred embodiment, when the rotational speed of the permanent magnet synchronous motor is less than 200rpm (other values can be selected according to the actual situation), the terminal voltage of the permanent magnet synchronous motor is sampled through the differential sampling circuit to obtain the counter electromotive force, and then calculate The rotor position and speed of the permanent magnet synchronous motor; when the speed of the permanent magnet synchronous motor is greater than 200rpm, the counter electromotive force is directly estimated, and then the rotor position and speed of the permanent magnet synchronous motor are estimated.

Since the stator terminal voltage 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 bridge arms of the inverter) when measuring the back electromotive force, then it will not There is current passing through the stator resistance and inductance of the permanent magnet synchronous motor, so that there will be no voltage drop on the stator resistance and inductance. At this time, the back electromotive force is equal to the stator terminal voltage of the motor.

The permanent magnet synchronous motor operation control method provided in this preferred embodiment includes the following steps:

Step 1. When the speed of the permanent magnet synchronous motor is less than 200rpm, the counter electromotive force is obtained by adding the current attenuation sampling algorithm to the current control, as shown in Figure 5. In the initial stage of the algorithm, the flag position of the inverter is forced to be turned off to 1, so that all bridge arms of the inverter are turned off at the same time, and the stator terminal voltage is sampled after the stator current gradually decays to 0.

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 is turned off is less than 0.2ms. Therefore, the time to start sampling the voltage at the stator terminal can be set to any time after 0.2ms after the switching device is turned off. The stator terminal voltage is sampled 0.25ms after the device is turned off. As shown in FIG. 5 , T _est is affected by the sampling time of the stator terminal voltage on the one hand, and is also affected by the estimated rotational speed time of the processor on the other hand. In some embodiments, the value of T _est can be 1ms to 5ms, Preferably, it can be set to 2ms.

Step 2. The back electromotive force sampling circuit of the permanent magnet synchronous motor is shown in Figure 6. The terminal voltage of the permanent magnet synchronous motor is sampled through the differential sampling circuit, and the terminal line voltage of the permanent magnet synchronous motor can be obtained after being output by the differential amplifier and The voltage sampled at this time is the counter electromotive force. Then set the forced shutdown flag of the inverter to 0 to cancel the forced shutdown. The maximum measurable back electromotive force is clamped at 5V by R ₂ and the two regulator tubes in reverse series, which can limit the maximum operating speed of the permanent magnet synchronous motor within 200rpm. Since there may be parasitic capacitance and leakage inductance that may cause resonance on the terminals of the permanent magnet synchronous motor, _a Y-connected damping resistor R1 is connected to the motor terminals to suppress resonance.

Step 3. Obtain the terminal line voltage of the permanent magnet synchronous motor through sampling and Afterwards, the phase voltages at the motor terminals of the PMSM can be calculated Then calculate its d, q axis components in the rotating coordinate system According to the relationship between the back electromotive force and the rotation angle The position of the rotor is calculated, and the speed of the rotor can also be calculated as where K _E is the back electromotive force constant. So far, the position and speed of the permanent magnet synchronous motor rotor at low speeds have been accurately obtained, and then the permanent magnet synchronous motor is controlled according to the conventional field oriented control algorithm, which can improve the performance of the permanent magnet synchronous motor at low speed.

Step 4. When the rotation speed continues to rise to more than 200rpm, make the flag bit of the inverter forced to shut down be at 0 all the time, so all the bridge arms of the inverter will not be shut down at the same time. At this time, after obtaining the terminal voltage of each phase of the permanent magnet synchronous motor, use a software algorithm to estimate the back electromotive force to obtain the back electromotive force, and then calculate its d, q axis components in the rotating coordinate system, and then accurately calculate the rotor Finally, the permanent magnet synchronous motor is controlled according to the conventional field oriented control algorithm.

The calculation method for calculating the position and rotational speed of the rotor according to the d and q axis components can adopt any calculation method known in the art, for example: using the counter electromotive force A _α and B _β , through the formula Estimate the position angle of the motor rotor The position angle obtained in the estimate On the basis of , the estimated value of the rotor position angle of the motor is calculated by a speed-related angle compensation function obtained by using right Differentiate to get the motor rotor speed v.

In summary, the above-mentioned embodiment of the present invention is a preferred implementation mode, which not only provides a brand-new back electromotive force sampling circuit of a permanent magnet synchronous motor, but also provides a permanent magnet synchronous motor based on the back electromotive force sampling circuit. A method for precise control of motors running at low and high speeds. The control of the permanent magnet synchronous motor based on the technical solution introduced in the embodiment of the present invention can make the permanent magnet synchronous motor start simple and reliable, and the permanent magnet synchronous motor can be started more gently under the heavy load condition, and the permanent magnet synchronous motor Low speed operation is more stable.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (11)

1. A counter electromotive force sampling circuit of a permanent magnet synchronous motor, characterized in that it comprises: a controller and a voltage detection circuit, wherein the voltage detection circuit comprises: a first differential amplifier, a second differential amplifier, wherein, The first input end of the first differential amplifier is electrically connected to the first detection end, the second input end of the first differential amplifier is electrically connected to the second detection end, and the first input end of the second differential amplifier terminal 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 electrically connect with the first phase line, the second phase line and the third phase line of the permanent magnet synchronous motor; The output end of the first differential amplifier is electrically connected to the first input end of the controller, the output end of the second differential amplifier is electrically connected to the second input end of the controller, and the controller It also includes an output terminal, the output terminal of the controller is used for electrical connection with the IGBT of the inverter that provides power for the permanent magnet synchronous motor. 2. The back electromotive force sampling circuit of permanent magnet synchronous motor according to claim 1, is characterized in that, described voltage detection circuit also comprises: the first bidirectional voltage regulator tube, the second bidirectional voltage regulator tube, the first resistance, the first The second resistor, the third resistor and the fourth resistor, wherein, 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 first detection terminal. Between the two detection terminals; 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 with the second of the second differential amplifier between the input terminal and the third detection terminal; The first bidirectional voltage regulator tube is connected in series between the first input terminal and the second input terminal of the first differential amplifier; the second bidirectional voltage regulator tube is connected in series with the first input terminal of the second differential amplifier and the second input terminal. 3. The back electromotive force sampling circuit of permanent magnet synchronous motor according to claim 1, is characterized in that, described voltage detection circuit also comprises: the resistance group that is made up of three resistance Y-type connections, wherein, the resistance group of described resistance group The three terminals are electrically connected to the first detection terminal, the second detection terminal and the third detection terminal one by one. 4. The counter electromotive force sampling circuit of the permanent magnet synchronous motor according to claim 1, wherein the controller further comprises: a timing module. 5. A back electromotive force sampling method of a permanent magnet synchronous motor, characterized in that, comprising: Forced to turn off the IGBT of the inverter that provides power to the permanent magnet synchronous motor; When the stator current of the permanent magnet synchronous motor decreases to zero, sampling the counter electromotive force of the permanent magnet synchronous motor; After the counter electromotive force is successfully sampled, the forced shutdown of the IGBT of the inverter is cancelled. 6. The back electromotive force sampling method of the permanent magnet synchronous motor according to claim 5, is characterized in that, after canceling the forced shutdown of the IGBT of the inverter, the method also includes: Estimating the rotor position and rotational speed of the permanent magnet synchronous motor according to the collected counter electromotive force. 7. The back electromotive force sampling method of permanent magnet synchronous motor according to claim 5, is characterized in that, before the IGBT of the inverter that provides power supply for permanent magnet synchronous motor, described method also comprises: 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 provides power for the permanent magnet synchronous motor includes: when the speed of the permanent magnet synchronous motor does not exceed the preset value, forcibly turning off the permanent magnet synchronous motor IGBTs that provide power to the inverter. 8. The back electromotive force sampling method of permanent magnet synchronous motor according to claim 7, is characterized in that, described method also comprises: When the rotational speed of the permanent magnet synchronous motor exceeds the preset value, sampling the line voltage of the phase line of the permanent magnet synchronous motor; Estimate the counter electromotive force of the permanent magnet synchronous motor according to the collected line-to-line voltage of the phase line; Estimate the rotor position and rotational speed of the permanent magnet synchronous motor according to the estimated counter electromotive force. 9. The back electromotive force sampling method of a permanent magnet synchronous motor according to claim 7, wherein the preset value is 190rpm to 210rpm. 10. A counter electromotive force sampling device for a permanent magnet synchronous motor, characterized in that it includes: at least one processor, at least one memory, and computer program instructions stored in the memory, when the computer program instructions are processed The method according to any one of claims 5 to 9 is realized when the device is executed. 11. A computer-readable storage medium, on which computer program instructions are stored, wherein the method according to any one of claims 5 to 9 is implemented when the computer program instructions are executed by a processor.