Permanent magnet synchronous motor current harmonic suppression method and system based on voltage injection

Abstract

The invention discloses a permanent magnet synchronous motor current harmonic suppression method and system based on voltage injection. Firstly, according to an electrical dynamic equation of the permanent magnet synchronous motor on a two-phase synchronous rotation orthogonal coordinate system, a mathematical model of main current harmonics is established; then, according to the negative sequence Park transformation matrix and the positive sequence Park transformation matrix, an analytical expression of harmonic waves is obtained; and finally, a low-pass filter is introduced to extract a direct-current component of harmonic waves, suppression of the current harmonic waves is realized based on a PI controller, and the obtained voltage is injected into the design of a current loop regulator. The harmonic voltage injection method provided by the invention can obviously reduce the harmonic component, the phase current distortion and the total harmonic distortion degree, effectively improves the control performance of a driving system, is easy to understand and implement, and is suitable for the design of a high-performance servo control system of the permanent magnet synchronous motor.

Description

Technical Field

[0001] The present invention belongs to the technical field of permanent magnet synchronous motor control, and in particular relates to a method and system for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection. Background Art

[0002] In recent years, with the advancement of power electronics, automatic control, and computer technologies, AC drive control systems have gradually replaced DC speed control systems in the field of high-performance speed regulation. Permanent magnet synchronous motors (PMSMs), with their high power density, large torque-to-inertia ratio, and fast dynamic response, have become a dominant force in AC speed regulation systems. However, due to factors such as mechanical manufacturing processes, motor design, cogging, magnetic saturation in the magnetic circuit, and the dead-zone and nonlinearity of the inverter drive circuit, higher harmonics are unavoidable in the winding current of PMSMs. Harmonic amplitude decreases with increasing harmonic order, so the fifth and seventh harmonics are primarily considered, while higher harmonics can be ignored.

[0003] With the continuous development and improvement of control theory, many scholars have devoted themselves to the research of current harmonic suppression of permanent magnet synchronous motors. Xu Jiaqun, Wang Tianqi, Jia Pufan. Quasi-resonant active disturbance rejection control (ADRC) for permanent magnet synchronous motors [J]. Proceedings of the CSEE, 2023, 43(6): 2450-2459. A new quasi-resonant active disturbance rejection control method (ADRC) is proposed to suppress the current harmonics of permanent magnet synchronous motors and improve the robustness of the system. In addition, based on the traditional extended state observer (ESO), the introduction of low-pass filter and repetitive control technology can significantly improve the estimation and compensation capabilities of periodic disturbances. The adaptive resonant controller-based active disturbance rejection technology can effectively handle uncertain disturbances, thereby improving the current harmonic suppression effect of permanent magnet synchronous motors. A method for suppressing the sixth harmonic in torque ripple is proposed by combining a new reduced-order vector resonant controller with a generalized active disturbance rejection technology. To address the delay problem caused by adaptive notch filters when suppressing current harmonics, harmonic prediction methods are used to replace traditional steepest gradient techniques. Based on a Chebyshev filter and a PI controller, a method for suppressing the fifth and seventh harmonics was proposed, significantly reducing the total harmonic distortion (THD) of the current. To improve the voltage utilization of the DC side of the inverter, a harmonic injection method was proposed to reduce torque ripple. In summary, the research on current harmonic suppression in permanent magnet synchronous motor drive systems has important theoretical value and engineering significance. However, existing technologies mostly focus on constructing observers and performing compensation methods. Such technologies involve complex control strategies and numerous adjustment parameters, and their harmonic suppression capabilities are limited. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for suppressing current harmonics in a permanent magnet synchronous motor based on voltage injection, which significantly reduces harmonic components, phase current distortion and total harmonic distortion, effectively improves the control performance of the drive system, and is easier to understand and implement.

[0005] To achieve the purpose of the present invention, on the one hand, the present invention provides a method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection, comprising the following steps:

[0006] Step 1: Through vector transformation, according to the phase current equation of the permanent magnet synchronous motor, a mathematical model of the main current harmonics is established in a two-phase synchronous rotating orthogonal coordinate system;

[0007] Step 1-1: Obtain a mathematical model of the surface-mounted permanent magnet synchronous motor in a two-phase synchronous rotating orthogonal coordinate system through coordinate transformation, including electrical dynamics and motion equations;

[0008] Step 1-2: Introduce Park transformation in vector control to achieve the transformation from a two-phase stationary orthogonal coordinate system to a two-phase synchronous rotating orthogonal coordinate system;

[0009] Steps 1-3: In an actual permanent magnet synchronous motor servo system, the phase current of the stator winding contains the 5th and 7th harmonics to obtain the three-phase current:

[0010] Step 1-4: According to Clarke transformation and Park transformation in the vector control, the three-phase current is converted into stator winding current on two-phase synchronous rotating orthogonal coordinate axes, completing the establishment of a mathematical model of the main current harmonics.

[0011] Step 2: Extracting the DC component of the harmonics based on the mathematical model of the main current harmonics using Park transformation and low-pass filter;

[0012] Step 2-1: define a negative-sequence 6th Park transform for the 5th current harmonic, and obtain a 5th harmonic DC mathematical expression based on the mathematical model of the main current harmonics;

[0013] Step 2-2: define a negative-sequence 6th Park transform for the 7th current harmonic, and obtain a 7th harmonic DC mathematical expression based on the mathematical model of the main current harmonics;

[0014] Step 2-3: Introduce a low-pass filter based on the inertial link to perform low-pass filtering on the converted signal;

[0015] Step 2-4: Extract the DC components of the fifth and seventh current harmonics from the converted signal after low-pass filtering.

[0016] Step 3: Based on the harmonic DC component, apply the inverse Park transform to design a current loop controller based on voltage injection;

[0017] Step 3-1: Use the PI controller to output the voltage signal and perform a negative-sequence and positive-sequence sixth-order Park inverse transform on it;

[0018] Step 3-2, converting the voltage signal after the negative sequence and positive sequence sixth-order Park inverse transformation into the two-phase synchronous rotating orthogonal coordinate system;

[0019] Step 3-3: inject the voltage signal converted and processed in step 3-2 into the DC component, compensate it into the current loop controller, and obtain a current loop controller based on voltage injection.

[0020] Step 4: According to the current loop controller, a synthesized control voltage and a suppression effect evaluation mechanism are obtained.

[0021] Step 4-1: Obtaining a synthesized control voltage according to the current loop controller;

[0022] Step 4-2: Define the inhibition ratio and obtain the inhibition effect evaluation mechanism.

[0023] On the other hand, the present invention also provides a system for a method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection, comprising the following modules:

[0024] A current regulator module is used to obtain a d-axis control voltage and a q-axis control voltage according to the feedback d-axis current signal and the q-axis current signal;

[0025] The d-axis PI current regulator module is used to obtain the current error by calculating the difference between the d-axis current signal and the given signal, and use the current error as input to obtain the d-axis fundamental wave control voltage signal;

[0026] The q-axis PI current regulator module is used to obtain the current error by calculating the difference between the q-axis current signal and the given signal, and use the current error as input to obtain the q-axis fundamental control voltage signal;

[0027] The negative-sequence sixth-order Parker transformation matrix module is used to obtain the transformed d-axis and q-axis fifth-order harmonic signals according to the input d-axis current signal and q-axis current signal, and send them to the low-pass filter module;

[0028] The positive sequence 6th Parker transformation matrix module is used to obtain the transformed d-axis and q-axis 7th harmonic signals according to the input d-axis current signal and q-axis current signal, and send them to the low-pass filter module;

[0029] The low-pass filter module filters out the AC component based on the input of the negative-sequence 6th Park transformation matrix module and the positive-sequence 6th Park transformation matrix module, obtains the 5th and 7th DC components of the d-axis and q-axis current harmonics, and sends them to the harmonic voltage injection module;

[0030] The harmonic PI control module is used to obtain the harmonic current error by subtracting the 5th and 7th DC components of the d-axis and q-axis current harmonics from the input d-axis given signal, and use it as input to obtain the injection voltage signals of the 5th and 7th DC components of the d-axis and q-axis harmonics;

[0031] A negative-sequence 6th-order Parker inverse transformation matrix module is used to obtain transformed d-axis and q-axis 5th-order harmonic voltage signals according to the input d-axis and q-axis 5th-order harmonic DC component injection voltage signals;

[0032] A positive sequence 6th order Parker inverse transformation matrix module is used to obtain transformed d-axis and q-axis 7th order harmonic voltage signals according to the input d-axis and q-axis 7th order harmonic DC component injection voltage signals;

[0033] The d-axis actual voltage synthesis module is used to obtain the actual d-axis synthetic voltage by summing the input d-axis control voltage and the d-axis harmonic voltage;

[0034] The q-axis actual voltage synthesis module is used to obtain the actual q-axis synthetic voltage by summing the input q-axis control voltage and the q-axis harmonic voltage.

[0035] Compared with the prior art, the significant progress of the present invention lies in: (1) the present invention takes the surface-mounted permanent magnet synchronous motor as the research object, and based on the two-phase synchronous rotating orthogonal coordinate system, by introducing Clarke and Park transformations, the 5th and 7th harmonics in the phase current are converted into the 6th harmonic in the dq coordinate system, and the mathematical model of the main harmonics is established;

[0036] (2) The present invention can extract the DC components of the 5th and 7th harmonics by introducing the 6th Park transformation matrix and a low-pass filter based on the inertial link (the cut-off frequency should be as low as possible). The fundamental signal and the remaining harmonics in the analytical expression have high-order AC characteristics (i.e., the 6th and 12th).

[0037] (3) In order to effectively suppress the extracted harmonic DC components, the present invention applies a classic PI controller, whose output voltage undergoes a negative-sequence and positive-sequence sixth-order Park inverse transformation, and injects the converted harmonic voltage control signal into the fundamental voltage to achieve suppression of current harmonics;

[0038] (4) The comparison results and the defined suppression ratio of the present invention show that the harmonic voltage injection method proposed in the present invention can significantly reduce the harmonic components, phase current distortion and total harmonic distortion, and effectively improve the control performance of the drive system.

[0039] In order to more clearly illustrate the functional characteristics and structural parameters of the present invention, further description is given below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0041] Figure 1 This is the overall control block diagram of the current harmonic suppression of the present invention;

[0042] Figure 2 is the phase current iA response curve of the speed control system of the present invention (without adding the suppression algorithm);

[0043] Figure 3 This is the Fourier analysis of the phase current of the speed control system of the present invention (without adding the suppression algorithm);

[0044] Figure 4 is the phase current iA response curve of the speed control system of the present invention (with the suppression algorithm added);

[0045] Figure 5 It is the phase current Fourier analysis of the speed control system of the present invention (with the suppression algorithm added). DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0047] The present invention provides a method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection, combined with Figure 1 , including the following steps:

[0048] Step 1: Through vector transformation, according to the phase current equation of the permanent magnet synchronous motor, a mathematical model of the main current harmonics is established in a two-phase synchronous rotating orthogonal coordinate system;

[0049] Step 2: extracting the DC component of the harmonics based on the mathematical model of the main current harmonics using a sixth-order Park transform and a low-pass filter;

[0050] Step 3: According to the harmonic DC component, apply the sixth-order Park inverse transform to design a current loop controller based on voltage injection;

[0051] Step 4: According to the current loop controller, a synthesized control voltage and a suppression effect evaluation mechanism are obtained.

[0052] The step 1 specifically includes the following steps:

[0053] Step 1-1: Obtain a mathematical model of the surface-mounted permanent magnet synchronous motor in a two-phase synchronous rotating orthogonal coordinate system through coordinate transformation, including electrical dynamics and motion equations;

[0054] Step 1-2: Introduce Park transformation in vector control to achieve the transformation from a two-phase stationary orthogonal coordinate system to a two-phase synchronous rotating orthogonal coordinate system;

[0055] Steps 1-3: In an actual permanent magnet synchronous motor servo system, the phase current of the stator winding contains the 5th and 7th harmonics to obtain the three-phase current:

[0056] Step 1-4: According to Clarke transformation and Park transformation in the vector control, the three-phase current is converted into stator winding current on two-phase synchronous rotating orthogonal coordinate axes, completing the establishment of a mathematical model of the main current harmonics.

[0057] The specific formula of step 1 is as follows:

[0058] The electrical dynamics and motion equations of step 1-1 are as follows:

[0059]

[0060] Where, Ls is the inductance of the stator winding; d / dt is the differential operator; i d and i q are the currents of the d-axis and q-axis stator windings respectively; u d and u q are the voltages of the d-axis and q-axis stator windings respectively; R s is the resistance of the stator winding; f is the permanent magnet flux, ω e is the electrical angular velocity;

[0061] Correspondingly, the mechanical dynamic equation is:

[0062]

[0063] Where J is the moment of inertia; K T =3p n ψ f / 2 is the electromagnetic torque coefficient, p n is the pole pair number; F is the viscous friction coefficient; T m is the load torque disturbance; ω m is the mechanical angular velocity, and satisfies ω e =p n ω m ;

[0064] The steps 1-2 are shown below:

[0065]

[0066] Among them, α and β are the α-axis and β-axis of the two-phase stationary orthogonal coordinate system respectively, and the electrical angle θ e =ω e t, t is time; i α and i β are the currents of the α-axis and β-axis stator windings respectively; T 2s / 2r is the transformation matrix;

[0067] The three-phase currents of steps 1-3 are shown as follows:

[0068]

[0069] Among them, i A 、i B 、i C are the phase currents of the stator winding respectively; I 1st , I 5th , I 7th Represents the current amplitude of the fundamental wave, 5th and 7th harmonic respectively; θ 1st ,θ 5th ,θ 7th They represent the corresponding initial phase angles respectively;

[0070] The mathematical model of the main current harmonics in steps 1-4 is shown below:

[0071]

[0072] The fifth and seventh harmonics in the three-phase current are finally transformed into the sixth harmonic in a two-phase synchronously rotating orthogonal coordinate system.

[0073] The step 2 specifically includes the following steps:

[0074] Step 2-1: define a negative-sequence 6th Park transform for the 5th current harmonic, and obtain a 5th harmonic DC mathematical expression based on the mathematical model of the main current harmonics;

[0075] Step 2-2: define a negative-sequence 6th Park transform for the 7th current harmonic, and obtain a 7th harmonic DC mathematical expression based on the mathematical model of the main current harmonics;

[0076] Step 2-3: Introduce a low-pass filter based on the inertial link to perform low-pass filtering on the converted signal;

[0077] Step 2-4: Extract the DC components of the fifth and seventh current harmonics from the converted signal after low-pass filtering.

[0078] The step 2 is specifically shown in the following formula:

[0079] In step 2-1, the negative sequence 6th Park transformation is defined for the 5th current harmonic, as shown in the following formula:

[0080]

[0081] in, is the negative order 6th order Parker transformation matrix;

[0082] At the same time, based on the mathematical model of the main current harmonics, the mathematical expression of the 5th harmonic DC is obtained:

[0083]

[0084] in, and are the transformed d-axis and q-axis 5th harmonic signals respectively;

[0085] In step 2-2, the negative sequence 6th Park transformation is defined for the 7th current harmonic, as shown in the following formula:

[0086]

[0087] in, is the positive order 6th order Parker transformation matrix;

[0088] At the same time, based on the mathematical model of the main current harmonics, the mathematical expression of the 7th harmonic DC is obtained:

[0089]

[0090] The steps 2-3 are shown below:

[0091]

[0092] Among them, G LPF (s) is the transfer function of the low-pass filter, s is the Laplace operator; the time constant T LPF =1 / K LPF , K LPF is the gain of the inertia link;

[0093] The steps 2-4 are shown below:

[0094]

[0095] in, They are the 5th and 7th DC components of the d-axis and q-axis current harmonics, respectively.

[0096] The step 3 specifically includes the following steps:

[0097] Step 3-1: Use the PI controller to output the voltage signal and perform a negative-sequence and positive-sequence sixth-order Park inverse transform on it;

[0098] Step 3-2, converting the voltage signal after the negative sequence and positive sequence sixth-order Park inverse transformation into the two-phase synchronous rotating orthogonal coordinate system;

[0099] Step 3-3: inject the voltage signal converted and processed in step 3-2 into the DC component, compensate it into the current loop controller, and obtain a current loop controller based on voltage injection.

[0100] The step 3 is specifically shown in the following formula:

[0101] The step 3-1 is shown in the following formula:

[0102]

[0103] in, and are negative-sequence and positive-sequence 6th-order Parker inverse transform matrices respectively; the superscript symbol -1 indicates the inverse operation;

[0104] The step 3-2 is shown as follows:

[0105]

[0106] in, are the transformed d-axis and q-axis 5th and 7th harmonic voltage signals respectively; are the injected voltage signals of the 5th and 7th harmonic DC components of the d-axis and q-axis respectively;

[0107] The step 3-3 is shown in the following formula:

[0108]

[0109] Among them, u d 、u q are the final d-axis and q-axis control voltage signals respectively; They are the d-axis and q-axis fundamental voltage control signals respectively.

[0110] 8. The method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection according to claim 7, wherein step 4 specifically comprises the following steps:

[0111] Step 4-1: Obtaining a synthesized control voltage according to the current loop controller;

[0112] Step 4-2: Define the inhibition ratio and obtain the inhibition effect evaluation mechanism.

[0113] The step 4 is specifically shown in the following formula:

[0114] The step 4-1 is shown in the following formula:

[0115]

[0116] Among them, u dc and u qc are the actual d-axis and q-axis composite voltages respectively; u d and u q Equivalent to the fundamental voltage in electrical dynamics and motion equations; d th =u 5th cos(-6ω e t+θ5th )+u 7th cos(6ω e t+θ 7th ) and q th =u 5th sin(-6ω e t+θ 5th )+u 7th sin(6ω e t+θ 7th ) are the harmonic voltages of the d-axis and q-axis respectively, which are modeled as interference, and u 5th and u 7th Represent the voltage amplitudes of the 5th and 7th harmonics respectively;

[0117] The step 4-2 is shown in the following formula:

[0118]

[0119] Among them, Δv represents the amount of change in the value; V NO and V YES Respectively represent the values ​​before and after adding the suppression algorithm.

[0120] The present invention also includes a system for a method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection, comprising the following modules:

[0121] A current regulator module is used to obtain a d-axis control voltage and a q-axis control voltage according to the feedback d-axis current signal and the q-axis current signal;

[0122] The d-axis PI current regulator module is used to obtain the current error by calculating the difference between the d-axis current signal and the given signal, and use the current error as input to obtain the d-axis fundamental wave control voltage signal;

[0123] The q-axis PI current regulator module is used to obtain the current error by calculating the difference between the q-axis current signal and the given signal, and use the current error as input to obtain the q-axis fundamental control voltage signal;

[0124] The negative-sequence sixth-order Parker transformation matrix module is used to obtain the transformed d-axis and q-axis fifth-order harmonic signals according to the input d-axis current signal and q-axis current signal, and send them to the low-pass filter module;

[0125] The positive sequence 6th Parker transformation matrix module is used to obtain the transformed d-axis and q-axis 7th harmonic signals according to the input d-axis current signal and q-axis current signal, and send them to the low-pass filter module;

[0126] The low-pass filter module filters out the AC component based on the input of the negative-sequence 6th Park transformation matrix module and the positive-sequence 6th Park transformation matrix module, obtains the 5th and 7th DC components of the d-axis and q-axis current harmonics, and sends them to the harmonic voltage injection module;

[0127] The harmonic PI control module is used to obtain the harmonic current error by subtracting the 5th and 7th DC components of the d-axis and q-axis current harmonics from the input d-axis given signal, and use it as input to obtain the injection voltage signals of the 5th and 7th DC components of the d-axis and q-axis harmonics;

[0128] A negative-sequence 6th-order Parker inverse transformation matrix module is used to obtain transformed d-axis and q-axis 5th-order harmonic voltage signals according to the input d-axis and q-axis 5th-order harmonic DC component injection voltage signals;

[0129] A positive sequence 6th order Parker inverse transformation matrix module is used to obtain transformed d-axis and q-axis 7th order harmonic voltage signals according to the input d-axis and q-axis 7th order harmonic DC component injection voltage signals;

[0130] The d-axis actual voltage synthesis module is used to obtain the actual d-axis synthetic voltage by summing the input d-axis control voltage and the d-axis harmonic voltage;

[0131] The q-axis actual voltage synthesis module is used to obtain the actual q-axis synthetic voltage by summing the input q-axis control voltage and the q-axis harmonic voltage.

[0132] The above method was used to verify the inhibitory effect, and the parameters were adjusted according to the comparison results.

[0133] In this embodiment, in order to verify the effectiveness and advantages of the proposed current harmonic suppression strategy, a system model was built and simulation experiments were performed using the Matlab / Simulink platform. The key parameters of the permanent magnet synchronous motor are shown in Table 1 (the rated line voltage and rated line current of the motor are U n =220V and I n =2A), the algorithm verification adopts a discrete model with a fixed step size, and the discrete step size is set to T s =5×10 -7 s, the bus voltage is set to The PWM (Pulse Width Modulation) wave frequency is 10kHz, and the simulation time is set to 0.3s. The permanent magnet synchronous motor adopts a dual closed-loop vector servo control structure, with a speed outer loop (with amplitude limiter) and a current inner loop (with amplitude limiter, i.e. Figure 1 The ACR in the PI controller is used, and its main parameters are shown in Table 2. Figure 1 The parameters of the PI controller for the 5th and 7th harmonic DC components are set to K p_5th=300,K i_5th =7×10 3 , K p_7th =200 and K i_7th =5×10 3 , and the output limit is ±0.95×U n .

[0134] Table 1 Key parameters of permanent magnet synchronous motor

[0135]

[0136] Table 2 Controller parameter settings

[0137]

[0138] In order to highlight the advantages of the voltage injection harmonic suppression method, the present invention sets the dead time to 5μs. In addition, the harmonic amplitude is set to u 5th =20 and u 7th =10, the corresponding initial phase angles are all set to zero, i.e. θ 5th =θ 7th =0.

[0139] When the speed reference value is set to 50πrad / s, T m = 0.5N·m load disturbance, and without adding harmonic suppression algorithm, the response performance of the permanent magnet synchronous motor speed control system is as follows: Figure 2 and Figure 3 As shown. When the permanent magnet synchronous motor enters the steady state, the current frequency is f e =50Hz (i.e. the fundamental frequency of Fourier analysis), the phase current curve of 5 cycles after 0.15s is as follows Figure 2 As shown. Figure 2 It can be seen that the phase current is obviously distorted, and its spectrum distribution is as follows: Figure 3 As shown. Figure 3 It can be seen that the fundamental amplitude of the phase current is 0.3795A, the total harmonic distortion is as high as 21.15%, and the 5th and 7th harmonics account for 19.61% and 7.297% respectively.

[0140] When the current harmonic suppression algorithm based on voltage injection is added, the response performance of the permanent magnet synchronous motor speed control system is as follows: Figure 4 and Figure 5 As shown. Figure 2 and Figure 4 It can be seen that the phase current distortion phenomenon is significantly improved. Figure 3 and Figure 5 It can be seen that the fundamental amplitude of the phase current is 0.3796A, the total harmonic distortion is reduced to 3.17%, and the proportions of the 5th and 7th harmonics are 0.6847% and 0.6571% respectively, both less than 1%.

[0141] according to Figure 3 and Figure 5 , and the calculation results of the formula in step 4-2 show that the total harmonic distortion, 5th harmonic suppression, and 7th harmonic suppression ratios are 85%, 96.5%, and 91%, respectively. This shows that the current suppression algorithm proposed in this invention significantly improves the control performance of the permanent magnet synchronous motor drive system when affected by high-order harmonics, significantly reducing phase current distortion and total harmonic distortion.

[0142] It should be noted that, in this document, relational terms such as first and second, etc., are used only 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 "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0143] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection, characterized in that: The following steps are involved: Step 1: Through vector transformation, according to the phase current equation of the permanent magnet synchronous motor, a mathematical model of the main current harmonics is established in a two-phase synchronous rotating orthogonal coordinate system; Step 2: Extracting the DC component of the harmonics based on the mathematical model of the main current harmonics using Park transformation and low-pass filter; Step 3: Based on the harmonic DC component, apply the inverse Park transform to design a current loop controller based on voltage injection; Step 4: According to the current loop controller, a synthesized control voltage and a suppression effect evaluation mechanism are obtained.

2. The method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection according to claim 1, characterized in that: The step 1 specifically includes the following steps: Step 1-1: Obtain a mathematical model of the surface-mounted permanent magnet synchronous motor in a two-phase synchronous rotating orthogonal coordinate system through coordinate transformation, including electrical dynamics and motion equations; Step 1-2: Introduce Park transformation in vector control to achieve the transformation from a two-phase stationary orthogonal coordinate system to a two-phase synchronous rotating orthogonal coordinate system; Steps 1-3: In an actual permanent magnet synchronous motor servo system, the phase current of the stator winding contains the 5th and 7th harmonics to obtain the three-phase current: Step 1-4: According to Clarke transformation and Park transformation in the vector control, the three-phase current is converted into stator winding current on two-phase synchronous rotating orthogonal coordinate axes, completing the establishment of a mathematical model of the main current harmonics.

3. The method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection according to claim 2, characterized in that: The specific formula of step 1 is as follows: The electrical dynamics and motion equations of step 1-1 are as follows: Among them, L s is the inductance of the stator winding; d / dt is the differential operator; i d and i q are the currents of the d-axis and q-axis stator windings respectively; u d and u q are the voltages of the d-axis and q-axis stator windings respectively; R s is the resistance of the stator winding; f is the permanent magnet flux, ω e is the electrical angular velocity; Correspondingly, the mechanical dynamic equation is: Where J is the moment of inertia; K T =3p n ψ f / 2 is the electromagnetic torque coefficient, p n is the pole pair number; F is the viscous friction coefficient; T m is the load torque disturbance; ω m is the mechanical angular velocity, and satisfies ω e =p n ω m ; The steps 1-2 are shown below: Among them, α and β are the α-axis and β-axis of the two-phase stationary orthogonal coordinate system respectively, and the electrical angle θ e =ω e t, t is time; i α and i β are the currents of the α-axis and β-axis stator windings respectively; T 2s / 2r is the transformation matrix; The three-phase currents of steps 1-3 are shown as follows: Among them, i A 、i B 、i C are the phase currents of the stator winding respectively; I 1st , I 5th , I 7th Represents the current amplitude of the fundamental wave, 5th and 7th harmonic respectively; θ 1st ,θ 5th ,θ 7th They represent the corresponding initial phase angles respectively; The mathematical model of the main current harmonics in steps 1-4 is shown below: The fifth and seventh harmonics in the three-phase current are finally transformed into the sixth harmonic in a two-phase synchronously rotating orthogonal coordinate system.

4. The method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection according to claim 3, characterized in that: The step 2 specifically includes the following steps: Step 2-1: define a negative-sequence 6th Park transform for the 5th current harmonic, and obtain a 5th harmonic DC mathematical expression based on the mathematical model of the main current harmonics; Step 2-2: define a negative-sequence 6th Park transform for the 7th current harmonic, and obtain a 7th harmonic DC mathematical expression based on the mathematical model of the main current harmonics; Step 2-3: Introduce a low-pass filter based on the inertial link to perform low-pass filtering on the converted signal; Step 2-4: Extract the DC components of the fifth and seventh current harmonics from the converted signal after low-pass filtering.

5. The method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection according to claim 4, characterized in that: The step 2 is specifically shown in the following formula: In step 2-1, the negative sequence 6th Park transformation is defined for the 5th current harmonic, as shown in the following formula: in, is the negative order 6th order Parker transformation matrix; At the same time, based on the mathematical model of the main current harmonics, the mathematical expression of the 5th harmonic DC is obtained: in, and are the transformed d-axis and q-axis 5th harmonic signals respectively; In step 2-2, the negative sequence 6th Park transformation is defined for the 7th current harmonic, as shown in the following formula: in, is the positive order 6th order Parker transformation matrix; At the same time, based on the mathematical model of the main current harmonics, the mathematical expression of the 7th harmonic DC is obtained: The steps 2-3 are shown below: Among them, G LPF (s) is the transfer function of the low-pass filter, s is the Laplace operator; the time constant T LPF =1 / K LPF , K LPF is the gain of the inertia link; The steps 2-4 are shown below: in, They are the 5th and 7th DC components of the d-axis and q-axis current harmonics, respectively.

6. The method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection according to claim 5, characterized in that: The step 3 specifically includes the following steps: Step 3-1: Use the PI controller to output the voltage signal and perform a negative-sequence and positive-sequence sixth-order Park inverse transform on it; Step 3-2, converting the voltage signal after the negative sequence and positive sequence sixth-order Park inverse transformation into the two-phase synchronous rotating orthogonal coordinate system; Step 3-3: inject the voltage signal converted and processed in step 3-2 into the DC component, compensate it into the current loop controller, and obtain a current loop controller based on voltage injection.

7. The method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection according to claim 6, characterized in that: The step 3 is specifically shown in the following formula: The step 3-1 is shown in the following formula: in, and are negative-sequence and positive-sequence 6th-order Parker inverse transform matrices respectively; the superscript symbol -1 indicates the inverse operation; The step 3-2 is shown in the following formula: in, are the transformed d-axis and q-axis 5th and 7th harmonic voltage signals respectively; are the injected voltage signals of the 5th and 7th harmonic DC components of the d-axis and q-axis respectively; The step 3-3 is shown in the following formula: Among them, u d 、u q are the final d-axis and q-axis control voltage signals respectively; They are the d-axis and q-axis fundamental voltage control signals respectively.

8. The method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection according to claim 7, characterized in that: The step 4 specifically includes the following steps: Step 4-1: Obtaining a synthesized control voltage according to the current loop controller; Step 4-2: Define the inhibition ratio and obtain the inhibition effect evaluation mechanism.

9. The method for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection according to claim 8, characterized in that: The step 4 is specifically shown in the following formula: The step 4-1 is shown in the following formula: Among them, u dc and u qc are the actual d-axis and q-axis composite voltages respectively; u d and u q Equivalent to the fundamental voltage in electrical dynamics and motion equations; d th =u 5th cos(-6ω e t+θ 5th )+u 7th cos(6ω e t+θ 7th ) and q th =u 5th sin(-6ω e t+θ 5th )+u 7th sin(6ω e t+θ 7th ) are the harmonic voltages of the d-axis and q-axis respectively, which are modeled as interference, and u 5th and u 7th Represent the voltage amplitudes of the 5th and 7th harmonics respectively; The step 4-2 is shown in the following formula: Among them, Δv represents the amount of change in the value; V NO and V YES Respectively represent the values ​​before and after adding the suppression algorithm.

10. A system for suppressing current harmonics of a permanent magnet synchronous motor based on voltage injection according to any one of claims 1 to 9, characterized in that: Includes the following modules: A current regulator module is used to obtain a d-axis control voltage and a q-axis control voltage according to the feedback d-axis current signal and the q-axis current signal; The d-axis PI current regulator module is used to obtain the current error by calculating the difference between the d-axis current signal and the given signal, and use the current error as input to obtain the d-axis fundamental wave control voltage signal; The q-axis PI current regulator module is used to obtain the current error by calculating the difference between the q-axis current signal and the given signal, and use the current error as input to obtain the q-axis fundamental control voltage signal; The negative-sequence sixth-order Parker transformation matrix module is used to obtain the transformed d-axis and q-axis fifth-order harmonic signals according to the input d-axis current signal and q-axis current signal, and send them to the low-pass filter module; The positive sequence 6th Parker transformation matrix module is used to obtain the transformed d-axis and q-axis 7th harmonic signals according to the input d-axis current signal and q-axis current signal, and send them to the low-pass filter module; The low-pass filter module filters out the AC component based on the input of the negative-sequence 6th Park transformation matrix module and the positive-sequence 6th Park transformation matrix module, obtains the 5th and 7th DC components of the d-axis and q-axis current harmonics, and sends them to the harmonic voltage injection module; The harmonic PI control module is used to obtain the harmonic current error by subtracting the 5th and 7th DC components of the d-axis and q-axis current harmonics from the input d-axis given signal, and use it as input to obtain the injection voltage signals of the 5th and 7th DC components of the d-axis and q-axis harmonics; A negative-sequence 6th-order Parker inverse transformation matrix module is used to obtain transformed d-axis and q-axis 5th-order harmonic voltage signals according to the input d-axis and q-axis 5th-order harmonic DC component injection voltage signals; A positive sequence 6th order Parker inverse transformation matrix module is used to obtain transformed d-axis and q-axis 7th order harmonic voltage signals according to the input d-axis and q-axis 7th order harmonic DC component injection voltage signals; The d-axis actual voltage synthesis module is used to obtain the actual d-axis synthetic voltage by summing the input d-axis control voltage and the d-axis harmonic voltage; The q-axis actual voltage synthesis module is used to obtain the actual q-axis synthetic voltage by summing the input q-axis control voltage and the q-axis harmonic voltage.

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