A low-noise position sensorless control method for dual three-phase permanent magnet motors

Abstract

The present invention discloses a low-noise position sensorless control method for a dual three-phase permanent magnet motor. The method uses a half-cycle random frequency square wave signal to replace the traditional fixed frequency square wave signal to eliminate the power spectrum peak at the injection signal frequency; then the half-cycle random frequency square wave signal is intermittently injected into two sets of windings by random winding selection. While ensuring that the injection signal amplitude remains unchanged, the content of the high-frequency response current is further reduced. The high-frequency response of the two sets of windings is mapped to the same coordinate system through a transformation matrix to complete the demodulation of the position information. The method can not only realize the position estimation of the dual three-phase permanent magnet motor at low speed, but also weaken the noise problem caused by the injection of high-frequency signals, and solve the problem that the application of the high-frequency signal injection method of the dual three-phase permanent magnet motor without position sensor control is limited in low-noise occasions.

Description

Technical Field

[0001] The present invention belongs to the field of permanent magnet synchronous motor drive control application, and in particular relates to a low-noise position sensorless control method for a dual three-phase permanent magnet motor. Background Art

[0002] Multiphase permanent magnet motors have the advantages of high power density, high torque density, and high reliability. They have broad application prospects in aerospace, ship propulsion, electric vehicles, and other fields. Dual three-phase permanent magnet synchronous motors inherit the advantages of multiphase permanent magnet motors, and at the same time have more advantages in torque output and other aspects. Dual three-phase permanent magnet synchronous motors have two sets of three-phase windings with a 30° difference, which is more flexible in control structure. Permanent magnet synchronous motors usually require mechanical position sensors to obtain position information to achieve their high-performance control. However, the use and installation of mechanical position sensors will increase the weight of the system and the difficulty of structural design. In some extreme applications, there will also be reliability issues. High-frequency signal injection is an effective low-speed position sensorless control solution. Common high-frequency signal injections mainly include sinusoidal signal injection, square wave signal injection, and arbitrary signal injection. However, high-frequency signal injection will bring noise problems, which seriously affect the comfort of users. Therefore, it is of great practical significance to study low-noise position sensorless control strategies.

[0003] In order to weaken the noise impact caused by the injection of high-frequency signals, domestic and foreign scholars have proposed some methods, such as reducing the injection signal amplitude, adjusting the injection signal frequency, random frequency signals, etc. The Chinese invention patent "A PMSM driver noise suppression method based on pseudo-random technology" (patent number: CN112865617A) discloses a PMSM driver noise suppression method based on pseudo-random technology. The method ensures that the simplest integer ratio in the injection frequency must have an even number by designing a random injection method, thereby eliminating the generation of discrete spectrum; at the same time, the fundamental current and high-frequency current are obtained by the differential method, and the envelope method is used for position information demodulation. The Chinese invention patent "A permanent magnet synchronous motor rotor position observer with random frequency high-frequency square wave voltage injection" (patent number: CN106849804A) discloses a permanent magnet synchronous motor rotor position observer with random frequency high-frequency square wave voltage injection in order to solve the problem of noise generation in the existing sensorless control of built-in permanent magnet synchronous motors based on high-frequency signal injection method. The observer includes three parts: a random frequency signal generator, an envelope extraction device and an orthogonal phase-locked loop. This method can be applied to the control system of built-in permanent magnet synchronous motor, does not require additional hardware, and has a significant effect in reducing noise. However, the above method reduces noise by injecting a continuous random frequency signal to expand the power spectrum peak of the current at a fixed frequency. How to reduce the induced high-frequency current component by injecting a discontinuous high-frequency voltage signal while ensuring that the injected amplitude remains unchanged, thereby reducing the noise caused by the injected signal and realizing noise-reduced position sensorless control is the main factor considered by the present invention. Summary of the invention

[0004] Purpose of the invention: In order to solve the noise problem caused by high-frequency signal injection into position sensorless control, a noise reduction method suitable for position sensorless control of dual three-phase permanent magnet motors is proposed. By injecting discontinuous high-frequency signals, the noise caused by the high-frequency injection signal is weakened while ensuring the position sensorless control performance of the motor.

[0005] Technical solution: To achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a low-noise position sensorless control method for a dual three-phase permanent magnet motor, the implementation steps of which include:

[0007] Step 1, synthesizing a half-cycle random frequency square wave signal: select two square wave signals with different amplitudes and frequencies, use a random number to select in each half cycle and form a half-cycle random square wave signal;

[0008] Step 2, construct a discontinuous signal and inject it into the winding: utilizing the characteristics of the two independent windings of the dual three-phase permanent magnet motor, a continuous half-cycle random square wave signal is randomly selected and injected into the two windings respectively;

[0009] Step 3: Estimate the motor position angle and speed to achieve sensorless control. Use the mathematical model of the motor to derive the pure inductance model under high-frequency signal injection, and establish a position estimation coordinate system. Map the response currents in the two sets of windings to the same coordinate system through a transformation matrix. Establish a demodulation coordinate system to demodulate the high-frequency response current containing position information, and then use an observer to estimate the position angle and speed, and feedback the position angle and speed information to the dual three-phase permanent magnet motor dual dq control system to complete sensorless control.

[0010] Furthermore, the specific process of Step 1 is as follows:

[0011] Synthesize a complete random frequency square wave signal using two square wave signals with different frequencies. Define the signal with a higher frequency as Square Wave 1, and its amplitude is V h1 ; Define the signal with a lower frequency as Square Wave 2, and its amplitude is V h2 . Generate two random numbers P between 0 and 1 through the linear congruence method to select the square wave signal at the end of each half cycle. When P is less than k1, select Square Wave 1; otherwise, select Square Wave 2.

[0012] Furthermore, the specific process of Step 2 is as follows:

[0013] Select the winding for injection within each half cycle. Use the digital system to generate a second random number Q. When Q < k2, inject the signal of the half cycle into both Winding 1 and Winding 2 simultaneously; when k2 < Q < k3, inject only the square wave signal of the half cycle into Winding 1; when k3 < Q < 1, inject only the square wave signal of the half cycle into Winding 2. After half a cycle ends, the system will regenerate the random number and execute in a loop.

[0014] Furthermore, the specific process of Step 3 is as follows:

[0015] The dual three-phase permanent magnet motor has two independent three-phase windings, namely Winding ABC and Winding DEF. Its voltage equation in the rotating coordinate system can be expressed as

[0016]

[0017] In the formula, u d , u q , u z1 and u z2 are the voltages of the dq axis and the z1z2 axis, i d , i q , i z1 and i z2 are the currents of the dq axis and the z1z2 axis, L d , L q and L aalis the dq axis inductance and leakage inductance, ω is the electrical angular velocity, ψ f is the permanent magnet flux, R s is the winding resistance.

[0018] Taking winding ABC as an example, when the motor is running at low speed and a high-frequency signal is injected, the effects of resistance, back electromotive force and cross-coupling terms in the motor can be ignored. At this time, the voltage equation is equivalent to a pure inductance equation, which is expressed as

[0019]

[0020] In the formula, s is the differential operator, u d1h and u q1h is the high frequency voltage of dq axis, i d1h and i q1h is the high-frequency current of the dq axis, L dh and L qh is the high frequency incremental inductance of the dq axis.

[0021] Define the rotation transformation matrix as

[0022]

[0023] Define the square wave function as

[0024]

[0025] Where T represents the period of the square wave signal, t m (t,T) represents the remainder of t divided by T. A high-frequency square wave voltage signal is injected into the d-axis, expressed as

[0026]

[0027] In the formula, u inj represents the high-frequency square wave voltage injected into the d-axis, V h represents the amplitude of the injected voltage. The high-frequency current in the rotating coordinate system is obtained, which is expressed as

[0028]

[0029] In the formula, The high-frequency current response of the two-phase stationary coordinate system is further obtained as

[0030]

[0031] Under the dual dq control structure, the high-frequency current responses of the two sets of windings are synthesized to demodulate the position information. The currents in the two sets of windings can be mapped to the same coordinate system using the transformation matrix, which can be expressed as

[0032]

[0033] Where, the first and second rows represent the synthesized αβ axis components respectively. The direction of the synthesized coordinate system is the same as that of the coordinate system of winding ABC, and its components are obtained by adding the mapping of winding ABC and winding DEF. e represents the rotor position, and θ e =θ e1 =θ e2 +π / 6, Δθ e represents the position estimation error. At the same time, dq2 * Coordinate system and αβ2 * The coordinate systems are mapped from the dq2 coordinate system and αβ2 coordinate system of the winding DEF. According to the principle of random frequency square wave signal generation, the synthesized injection signal can be expressed as

[0034]

[0035] and

[0036]

[0037] In the formula, represents the random factor, T1 and T2 are the periods of two square wave voltage signals. Therefore, the mapped high-frequency current can be expressed as

[0038]

[0039] Further rewritten as

[0040]

[0041] Therefore, the high-frequency current response of the αβ axis of the synthetic coordinate system can be expressed as

[0042]

[0043] After comprehensive analysis, we can get

[0044]

[0045] Where A = (cosΔθ e1 +cosΔθ e2 ), B=(sinΔθ e1 +sinΔθ e2 ).

[0046] In order to obtain the position information in the high-frequency current response, a demodulation coordinate system is established. This coordinate system is defined as dq v coordinate system, which lags behind the estimated coordinate system by π / 4. Therefore, we can get dq v The high-frequency current in the coordinate system is

[0047]

[0048] Where, L dif =(L dh –L qh ) / 2. When Δθ e ≈0, the above formula can be rewritten as

[0049]

[0050] Due to L qh >L dif , L in the above formula qh ±L dif sin(2Δθ e ) is always greater than zero. Therefore, the absolute value form of the above formula can be written as

[0051]

[0052] Using the inverse transformation matrix, we can obtain αβ v The high-frequency current of the shaft is expressed as

[0053]

[0054] In the formula,

[0055]

[0056] When Δθ e ≈0, X1=X2≈0. At this time, the above formula can be simplified to

[0057]

[0058] When the motor runs at low speed, the motor's electrical frequency is much smaller than the frequency of the injected signal. In order to make the integral value of the injected signal positive, a low-pass filter is used to process the above equation. At the same time, in order to eliminate the influence of parameter changes, the output is normalized. Therefore, the final output current can be obtained as

[0059]

[0060] The position error can be obtained by passing the output high-frequency current through an orthogonal phase-locked loop observer, which is expressed as

[0061]

[0062] The position error is tracked by a proportional-integral controller (PI). When the position error is zero, it means that the estimated position angle is equal to the true position angle. At this time, the estimated position angle and speed of the motor are obtained.

[0063] The estimated speed is subtracted from the given speed and then passes through a PI controller to form a speed closed loop; the estimated position angle is then fed back to the Parker transformation matrix to form a current closed loop.

[0064] Beneficial effects of the present invention:

[0065] 1) The discontinuous signal injection method proposed in the present invention can weaken the high-frequency response component caused by the injection, thereby suppressing the noise caused by the injected signal;

[0066] 2) The present invention uses a randomly generated square wave signal, which is simpler to generate than a sine wave or other signal, and can effectively increase the frequency of the injected signal to the switching frequency level;

[0067] 3) The present invention can obtain better position estimation performance and realize position sensorless control of dual three-phase permanent magnet motor at low speed;

[0068] 4) The present invention eliminates a set of position demodulation procedures by mapping the high-frequency response currents in the two sets of windings to the same coordinate system;

[0069] 5) The present invention does not require the participation of position demodulation signals and is therefore not affected by system delays;

[0070] 6) The present invention is applicable to both surface mounted and embedded dual three-phase permanent magnet synchronous motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 A block diagram of a dual three-phase permanent magnet motor position sensorless noise reduction control according to an embodiment of the present invention;

[0072] Figure 2 A flowchart of discontinuous signal generation according to an embodiment of the present invention;

[0073] Figure 3 A waveform diagram of the injection into the winding according to an embodiment of the present invention;

[0074] Figure 4 A high frequency signal demodulation block diagram of an embodiment of the present invention;

[0075] Figure 5 A power spectrum density comparison diagram of an embodiment of the present invention;

[0076] Figure 6 A rotation speed comparison diagram of an embodiment of the present invention;

[0077] Figure 7 This is a position angle comparison diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0078] In order 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.

[0079] As Figure 1 shown, the present invention proposes a method for controlling a dual three-phase permanent magnet motor without a position sensor with low noise.

[0080] The specific implementation steps of the proposed method for controlling a dual three-phase permanent magnet motor without a position sensor with low noise include:

[0081] Step 1, synthesize a half-cycle random frequency square wave signal.

[0082] As Figure 2 shown is the flowchart for constructing discontinuous injection. A complete random frequency square wave signal is synthesized using two square wave signals with different frequencies. The signal with a higher frequency is defined as square wave 1, and its amplitude is V h1 ; the signal with a lower frequency is defined as square wave 2, and its amplitude is V h2 . Two random numbers P between 0 and 1 are generated by the linear congruence method to select the square wave signal at the end of each half-cycle. When P is less than k1, square wave 1 is selected; otherwise, square wave 2 is selected.

[0083] Step 2, construct a discontinuous signal and inject it into the winding.

[0084] Inject into the winding is selected within each half-cycle. A second random number Q is generated using a digital system. When Q < k2, the signal of the half-cycle is injected into both winding 1 and winding 2 simultaneously; when k2 < Q < k3, only the square wave signal of the half-cycle is injected into winding 1; when k3 < Q < 1, only the square wave signal of the half-cycle is injected into winding 2. After half a cycle ends, the system will generate random numbers again and execute in a loop. The finally generated injection voltage is as Figure 3 shown.

[0085] Step 3, process the high-frequency response current, demodulate the position angle and speed, and participate in the control without a position sensor.

[0086] The dual three-phase permanent magnet motor has two independent three-phase windings, namely winding ABC and winding DEF. Its voltage equation in the rotating coordinate system can be expressed as

[0087]

[0088] In the formula, u d , u q , u z1 and u z2 are the voltages of the dq axis and the z1z2 axis, i d , iq ,i z1 and i z2 is the current of dq axis and z1z2 axis, L d , L q and L aal is the dq axis inductance and leakage inductance, ω is the electrical angular velocity, ψ f is the permanent magnet flux, R s is the winding resistance.

[0089] Taking winding ABC as an example, when the motor is running at low speed and a high-frequency signal is injected, the effects of resistance, back electromotive force and cross-coupling terms in the motor can be ignored. At this time, the voltage equation is equivalent to a pure inductance equation, which is expressed as

[0090]

[0091] In the formula, s is the differential operator, u d1h and u q1h is the high frequency voltage of dq axis, i d1h and i q1h is the high-frequency current of the dq axis, L dh and L qh is the high frequency incremental inductance of the dq axis.

[0092] Define the rotation transformation matrix as

[0093]

[0094] Define the square wave function as

[0095]

[0096] Where T represents the period of the square wave signal, t m (t,T) represents the remainder of t divided by T. A high-frequency square wave voltage signal is injected into the d-axis, expressed as

[0097]

[0098] In the formula, u inj represents the high-frequency square wave voltage injected into the d-axis, V h represents the amplitude of the injected voltage. The high-frequency current in the rotating coordinate system is obtained, which is expressed as

[0099]

[0100] In the formula, The high-frequency current response of the two-phase stationary coordinate system is further obtained as

[0101]

[0102] Under the dual dq control structure, the high-frequency current responses of the two sets of windings are synthesized to demodulate the position information. The currents in the two sets of windings can be mapped to the same coordinate system using the transformation matrix, which can be expressed as

[0103]

[0104] Where, the first and second rows represent the synthesized αβ axis components respectively. The direction of the synthesized coordinate system is the same as that of the coordinate system of winding ABC, and its components are obtained by adding the mapping of winding ABC and winding DEF. e represents the rotor position, and θ e =θ e1 =θ e2 +π / 6, Δθ e represents the position estimation error. At the same time, dq2 * Coordinate system and αβ2 * The coordinate systems are mapped from the dq2 coordinate system and αβ2 coordinate system of the winding DEF. According to the principle of random frequency square wave signal generation, the synthesized injection signal can be expressed as

[0105]

[0106] and

[0107]

[0108] In the formula, represents the random factor, T1 and T2 are the periods of two square wave voltage signals. Therefore, the mapped high-frequency current can be expressed as

[0109]

[0110] Further rewritten as

[0111]

[0112] Therefore, the high-frequency current response of the αβ axis of the synthetic coordinate system can be expressed as

[0113]

[0114] After comprehensive analysis, we can get

[0115]

[0116] Where A = (cosΔθ e1 +cosΔθ e2 ), B=(sinΔθ e1 +sinΔθ e2 ).

[0117] In order to obtain the position information in the high-frequency current response, a demodulation coordinate system is established. This coordinate system is defined as dq v coordinate system, which lags behind the estimated coordinate system by π / 4. Therefore, we can get dq v The high-frequency current in the coordinate system is

[0118]

[0119] Where, L dif =(L dh –L qh ) / 2. When Δθ e ≈0, the above formula can be rewritten as

[0120]

[0121] Due to L qh >L dif , L in the above formula qh ±L dif sin(2Δθ e ) is always greater than zero. Therefore, the absolute value form of the above formula can be written as

[0122]

[0123] Using the inverse transformation matrix, we can obtain αβ v The high-frequency current of the shaft is expressed as

[0124]

[0125] In the formula,

[0126]

[0127] When Δθ e ≈0, X1=X2≈0. At this time, the above formula can be simplified to

[0128]

[0129] When the motor runs at low speed, the motor's electrical frequency is much smaller than the frequency of the injected signal. In order to make the integral value of the injected signal positive, a low-pass filter is used to process the above equation. At the same time, in order to eliminate the influence of parameter changes, the output is normalized. Therefore, the final output current can be obtained as

[0130]

[0131] The position error can be obtained by passing the output high-frequency current through an orthogonal phase-locked loop observer, which is expressed as

[0132]

[0133] The position error is tracked by the proportional integral controller (PI). When the position error is zero, it means that the estimated position angle is equal to the true position angle. At this time, the estimated position angle and speed of the motor are obtained. Figure 4 The figure shows the high-frequency signal demodulation block diagram. The estimated speed is subtracted from the given speed and then passes through the PI controller to form a speed closed loop; the estimated position angle is then fed back to the Parker transformation matrix to form a current closed loop.

[0134] Figure 5 They are power spectrum density comparison diagrams. At this time, the motor runs at 50r / min, and the power spectrum density analysis is performed using the motor C phase current as an example. Figure 5 (a) shows the current power spectrum density result when there is no injection signal. At this time, there is no power spectrum peak in the current power spectrum density. Figure 5 (b) and Figure 5 (c) shows the current power spectrum density results after fixed frequency 35V 0.5kHz and 70V 1kHz square wave voltage injection. It can be seen that when fixed frequency square wave voltage is injected, there are large power spectrum peaks at the injection frequency and its odd multiple frequencies. The maximum power spectrum peaks are -6.2dB and -4.6dB respectively. The current power spectrum density results of traditional full cycle random frequency square wave injection are shown in Figure 5 (c) shows. At this time, two square wave signals (35V 0.5kHz and 70V 1kHz) are randomly selected in each full cycle and injected into the two windings at the same time. It can be seen that random frequency injection can effectively expand the current power spectrum distribution, and the maximum power spectrum peak is reduced to -13.9dB. Figure 5 (e) shows the current power spectrum density result of the traditional half-cycle random frequency square wave injection, and its maximum power spectrum peak is -19.3dB. It can be seen that the half-cycle random frequency further reduces the maximum power spectrum peak compared to the full-cycle random frequency, thereby having a better noise reduction effect. When the same amplitude voltage signal is injected, the current power spectrum density result of the method disclosed in this patent is as follows Figure 5 As shown in (f), it can be seen that compared with the traditional half-cycle random injection, the current power spectrum is further diffused, with the maximum peak at -22.3dB, which has a better noise suppression effect.

[0135] Figure 6 and Figure 7 The following are the comparison diagrams of motor speed and position angle. At this time, the motor is running under rated load and the given speed is 50r / min. Figure 6 It can be seen that the estimated speed basically follows the actual speed, and the speed error is within 5r / min. Figure 7 As shown in the figure, the estimated position angle is consistent with the true position angle, the position error fluctuates slightly, and the position error is kept between ±0.2rad, which has a good position estimation effect.

[0136] The above embodiments are only used to illustrate the design ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. A low-noise position sensorless control method for a dual three-phase permanent magnet motor, characterized in that: The steps include the following: Step 1, synthesize a half-cycle random frequency square wave signal: Select two square wave signals with different amplitudes and frequencies, and use a random number to make a selection every half cycle to form a half-cycle random square wave signal; Step 2, form a discontinuous signal and inject it into the windings: Utilize the characteristics of two independent windings of a dual three-phase permanent magnet motor, and randomly select and inject a continuous half-cycle random square wave signal into the two windings respectively. Specifically, select the windings for injection every half cycle, generate a random number Q using a digital system, define two probability values k2 and k3 to control the selection of the injected windings, and 0 < k2 < k3 < 1. When Q < k2, inject the half-cycle signal into both the ABC winding and the DEF winding simultaneously; when k2 < Q < k3, inject only the half-cycle square wave signal into winding 1; when k3 < Q < 1, inject only the half-cycle square wave signal into winding 2. After half a cycle ends, the system will regenerate a random number and execute in a loop; Step 3, estimate the motor position angle and speed to achieve sensorless control: Utilize the mathematical model of the motor to derive a pure inductance model under high-frequency signal injection, and establish a position estimation coordinate system; map the response currents in the two windings to the same coordinate system through a transformation matrix; establish a demodulation coordinate system, demodulate the high-frequency response current containing position information, and then use an observer to estimate the position angle and speed, and feedback the position angle and speed information to the dual dq control system of the dual three-phase permanent magnet motor to complete sensorless control.

2. The low-noise position sensorless control method for dual three-phase permanent magnet motor according to claim 1, characterized in that: The specific steps of Step 1 include: Use two square wave signals of different frequencies to synthesize a complete random frequency square wave signal. Define the higher frequency signal as square wave 1, whose amplitude is V h1 ; The lower frequency signal is defined as square wave 2, whose amplitude is V h2 , a random number P from 0 to 1 is generated by the linear congruential method to select the square wave signal at the end of each half cycle. When P is less than k1, square wave 1 is selected; otherwise, square wave 2 is selected.

3. The low-noise position sensorless control method for dual three-phase permanent magnet motor according to claim 1, characterized in that: The specific steps of using the mathematical model of the motor to derive a pure inductance model under high-frequency signal injection in Step 3 include: When injecting a high-frequency signal during low-speed operation of the motor, the effects of resistance, back electromotive force, and cross-coupling terms in the motor can be ignored, and the voltage equation can be equivalent to a pure inductance equation, expressed as In the formula, s is the differential operator, u d1h and u q1h is the high frequency voltage of dq axis, i d1h and i q1h is the high-frequency current of the dq axis, L dh and L qh is the high frequency incremental inductance of the dq axis.

4. The low-noise position sensorless control method for dual three-phase permanent magnet motors according to claim 3 is characterized in that: The specific steps of establishing a position estimation coordinate system in Step 3 include: Define the rotation transformation matrix as T(θ), where θ is the angle between the rotation transformation coordinate systems, Define the square wave function as φ sqr (t,T), and Where T represents the period of the square wave signal, t m (t,T) represents the remainder of t divided by T; a high-frequency square wave voltage signal is injected into the d-axis, expressed as In the formula, u inj represents the high-frequency square wave voltage injected into the d-axis, V h represents the amplitude of the injected voltage, obtain the high-frequency current in the rotating coordinate system, expressed as In the formula, θ e1 and is the true position angle and estimated position angle of ABC winding, Δθ e1 is the position error, and the high-frequency current response of the two-phase stationary coordinate system is further obtained as 5. The low-noise position sensorless control method for dual three-phase permanent magnet motors according to claim 1, characterized in that: The specific steps of mapping the response currents in the two windings to the same coordinate system through a transformation matrix in Step 3 include: Under the dual dq control structure, synthesize the high-frequency current responses of the two windings to demodulate the position information, and use the transformation matrix T to map the currents in the two windings to the same coordinate system. The mapped high-frequency current can be expressed as In the formula, i α2h 、i β2h is the high-frequency current of the αβ axis in the DEF winding, and the high-frequency current response of the αβ axis in the synthetic coordinate system can be expressed as i α1h and i β1h is the high frequency current of the αβ axis in the ABC winding, After synthesis, it can be obtained that Where A = (cosΔθ e1 +cosΔθ e2 ), B=(sinΔθ e1 +sinΔθ e2 ), Δθ e Represents the position estimation error, and the subscripts 1 and 2 represent the windings ABC, DEF, and L of the dual three-phase motor respectively. dh , L qh is the high frequency incremental inductance of the dq axis, θ e represents the rotor position angle, is the synthetic injection signal, and In the formula represents the random factor, T s1 and T s2 are the periods of two square wave voltage signals, φ sqr is a square wave function, u inj represents the high-frequency square wave voltage injected into the d-axis, V h It represents the amplitude of the injected voltage. The subscripts 1 and 2 represent winding ABC and winding DEF of the dual three-phase motor respectively.

6. The low-noise position sensorless control method for dual three-phase permanent magnet motors according to claim 5, characterized in that: The specific steps of establishing a demodulation coordinate system in Step 3 include: In order to obtain the position information in the high-frequency current response, a demodulation coordinate system is established; this coordinate system is defined as dq v coordinate system, which lags behind the estimated coordinate system by π / 4; therefore, we get dq v The high-frequency current in the coordinate system is Where, T -1 is the inverse matrix of the rotation transformation matrix, L dif =(L dh –L qh ) / 2, represents the estimated position angle, Δθ e Represents the position estimation error, when Δθ e ≈0, the above formula can be rewritten as Due to L qh >L dif , L in the above formula qh ±L dif sin(2Δθ e ) is always greater than zero, so the absolute value form of the above formula can be written as 7. The low-noise position sensorless control method for dual three-phase permanent magnet motors according to claim 6, characterized in that: The specific steps of demodulating the high-frequency response current containing position information in Step 3 include: Using the inverse transformation matrix, we can obtain αβ v The high-frequency current of the shaft is expressed as In the formula, When Δθ e ≈0,X1=X2≈0, at this time, the above formula can be simplified to When the motor is running at low speed, the electrical frequency of the motor is much lower than the frequency of the injected signal; in order to make the integral value of the injected signal positive, use a low-pass filter to process the above formula; at the same time, in order to eliminate the influence of parameter changes, normalize the output. Therefore, the final output current can be obtained as 8. The low-noise position sensorless control method for dual three-phase permanent magnet motors according to claim 7, characterized in that: The specific steps of using an observer to estimate the position angle and speed in Step 3 include: The position error can be obtained by passing the output high-frequency current through a quadrature phase-locked loop observer, expressed as The position error is tracked by a proportional-integral controller (PI). When the position error is zero, it means that the estimated position angle is equal to the true position angle. At this time, the estimated position angle and speed of the motor are obtained.

9. The low-noise position sensorless control method for dual three-phase permanent magnet motors according to claim 8, characterized in that: The specific steps of feeding back the position angle and speed information to the dual three-phase permanent magnet motor dual dq control system in step 3 include: The estimated speed is subtracted from the given speed and then passes through a PI controller to form a speed closed loop; the estimated position angle is then fed back to the Parker transformation matrix to form a current closed loop.

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