A permanent magnet synchronous motor current harmonic suppression method and device and electronic equipment

Abstract

The application discloses a permanent magnet synchronous motor current harmonic suppression method and device and electronic equipment, and belongs to the technical field of motor control. The harmonic suppression method comprises the following steps: S11, constructing a dq-axis linear extended state observer (LESO) by a permanent magnet synchronous motor model, and building a control model based on the linear extended state observer; S12, performing a load experiment under different rotating speeds to determine the frequency omega n of high-frequency harmonics; and S13, connecting a corresponding wave trap in series in a disturbance compensation loop of the existing LESO according to the frequency omega n obtained in the previous step. According to the current harmonic suppression method, high-frequency harmonics outside the bandwidth of the observer can be suppressed in addition to the harmonics inside the bandwidth of the observer.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, and more specifically, relates to a method and device for suppressing current harmonics in a permanent magnet synchronous motor, as well as electronic equipment. Background Technology

[0002] Disturbances in servo systems constrain the improvement of motor drive system control performance. In particular, the contradiction between the current demands for high precision and high performance in servo systems and the complex applications they face has led to an increasing need to improve the disturbance immunity of servo systems. Currently, there are two main approaches to suppressing disturbances and uncertainties in servo systems: one is to address the disturbance source by improving motor design, optimizing driver circuits and topology, and enhancing the stability of the overall mechanical structure; the other is to focus on control strategies, employing advanced control strategies or specific control strategies for certain situations to suppress disturbances.

[0003] Due to the dead-zone effect and the influence of non-sinusoidal back EMF, periodic disturbances at specific frequencies account for a significant proportion of current loop disturbances, and these disturbances generally change with the motor's fundamental frequency: as the motor speed increases, the disturbance frequency also increases. If traditional LESO is used to suppress these disturbances, the observer bandwidth needs to be increased; however, increasing the bandwidth will worsen the system noise response, ultimately leading to a decrease in overall control performance. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a method, device and electronic equipment for suppressing current harmonics of permanent magnet synchronous motor, the purpose of which is to optimize the noise response of the traditional LESO system during the current suppression process.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for suppressing current harmonics in a permanent magnet synchronous motor is provided, for suppressing high-frequency components of the stator current of the permanent magnet synchronous motor, specifically including the following steps:

[0006] Step S11: Construct the dq-axis LESO from the permanent magnet synchronous motor model, tune the gain of the observer, add the linear expansion state observer to the current loop to observe the current loop disturbance, and add the disturbance observation value to the current loop to construct a disturbance compensation loop.

[0007] Step S12: Conduct load experiments at different speeds, and analyze the harmonic content of the dq-axis current using Fast Fourier Transform (FFT) to obtain the frequency ω of the high-frequency harmonics. n ;

[0008] Step S13: From the ω nA notch filter is constructed and connected in series in the disturbance compensation loop to suppress the high frequency harmonics.

[0009] In one embodiment, the constructed dq-axis LESO in step S11 is:

[0010]

[0011] wherein, are the voltage commands of the dq-axis respectively; i df , i qf are the feedback currents of the dq-axis respectively, are the estimated values of i df , i qf ; e d , e q are the errors between the corresponding estimated values and feedback values respectively; f d , f q are the disturbance voltages of the dq-axis respectively, are the estimated values of f d , f q ; are the derivative values of the corresponding variables respectively; β pd , β id , β pq , β iq are the observer gains of the corresponding variables respectively; L s is the stator inductance. The constructed observer, with the disturbance observation compensated into the control loop, can suppress the harmonic disturbance within the observer bandwidth in the current loop.

[0012] The gains of the observer are set by the bandwidth method, i.e.:

[0013] β pd = 2L s ω od ,

[0014]

[0015] wherein ω od , ω oq are the dq-axis LESO bandwidths respectively, and ω od = ω oq .

[0016] In one embodiment, the method further comprises step S12: conducting load experiments at different speeds, analyzing the harmonic content of the dq-axis currents by fast Fourier transform, and thus obtaining the frequency ω n of the high frequency harmonics.

[0017] In one of the embodiments, the method further comprises: adjusting, by the processor, the notch filter according to the disturbance compensation value of the dq axis before the notch filtering. n The notch filter is constructed, and a transfer function G notch (s) is:

[0018]

[0019] wherein ζ1 and ζ2 are damping coefficients of the notch filter, and according to the above formula, the notch filter characteristics need to be adjusted not only by adjusting the notch frequency, but also by adjusting the damping coefficient. However, the physical meaning of the damping coefficient variable is not clear. In order to make the parameters correspond to the physical meaning and simplify the parameter adjustment process, the following variables are introduced:

[0020]

[0021] wherein B w is the notch width of the notch filter, Q is the quality factor of the notch filter, and D p is the notch depth of the notch filter. According to the above variables, the related expression of the damping coefficient of the notch filter is:

[0022]

[0023] According to the above formula, only the notch center frequency ω n , the quality factor Q and the notch depth D p of the notch filter need to be set to complete the parameter configuration of the notch filter.

[0024] In one of the embodiments, the method further comprises: after completing the configuration of the notch filter, the constructed notch filter is further connected in series to the disturbance compensation loop, and the dq axis disturbance compensation value after the notch filtering is:

[0025]

[0026] wherein ω and ω are the dq axis disturbance compensation values before the notch filtering, respectively.

[0027] According to another aspect of the present application, an electronic device is provided, comprising a memory and a processor, the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0028] According to another aspect of the present application, a computer readable storage medium is provided, which stores a computer program, and the computer program is executed by a processor to implement the steps of the above method.

[0029] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0030] The application provides a permanent magnet synchronous motor current harmonic suppression method, LESO is constructed in a dq axis current loop, when the rotating speed is improved, the current loop harmonic disturbance frequency is also rising, at this time, to ensure the disturbance suppression effect, the observer bandwidth needs to be improved. However, improving the observer bandwidth will make the system noise response worse, thereby causing the overall harmonic content of the system to be improved, and a notch filter is added in the disturbance compensation loop of LESO to improve the suppression ability of the system to high frequency noise. Through the current harmonic suppression method provided by the application, the observer bandwidth can be improved while suppressing the high frequency harmonic of a specific frequency, thereby improving the overall disturbance suppression ability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a current harmonic suppression step flow chart in an embodiment of the application;

[0032] Figure 2 is a current control structure diagram after LESO is added in an embodiment of the application;

[0033] Figure 3 is a notch filter characteristic curve diagram in an embodiment of the application;

[0034] Figure 4 is a current control block diagram after the notch filter is added in LESO in an embodiment of the application;

[0035] Figure 5 is a system noise response characteristic curve when different notch frequencies are used in an embodiment of the application;

[0036] Figure 6 is a noise response characteristic curve when different notch frequencies of the notch filter are simultaneously connected to the disturbance feedback in an embodiment of the application;

[0037] Figure 7 is a current curve under PI control at (a) 600 rpm and (b) 900 rpm in an embodiment of the application;

[0038] Figure 8 is a comparison diagram of (a) dq axis and (b) A phase current FFT at 600 rpm and 900 rpm in an embodiment of the application;

[0039] Figure 9 is a current curve before and after the notch filter is added in LESO at 900 rpm in an embodiment of the application;

[0040] Figure 10 is a comparison diagram of (a) dq axis and (b) A phase current FFT before and after the notch filter is added in LESO at 900 rpm in an embodiment of the application. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0042] like Figure 1 The diagram shows the steps of a method for suppressing current harmonics in a permanent magnet synchronous motor, which includes the following steps:

[0043] Step S11: Construct the dq-axis LESO from the permanent magnet synchronous motor model and add the disturbance compensation value observed by the LESO to the existing PI control loop.

[0044] The permanent magnet synchronous motor model is as follows:

[0045]

[0046] In the formula, u d u q These are the d-axis and q-axis components of the stator voltage, respectively; L d L q These are the d-axis and q-axis inductances of the stator flux linkage windings, respectively; i d i q These are the d-axis and q-axis components of the stator current, respectively; ψ f For rotor permanent magnet flux linkage; R s ω is the stator resistance; e ω is the rotor's electric angular velocity.

[0047] The structure of the current loop PI controller is as follows:

[0048]

[0049] In the formula, u d u q The instruction value; i d i q The instruction value; i df i qf i after considering noise d i q The feedback value, i df =i d +δ d i qf =i q +δ q ;K pd K idK pq K iq These represent the corresponding PI controller gains.

[0050] For ease of analysis, the PI controller of the current loop is adjusted using the bandwidth method and the integral constant method based on the control model, and the bandwidth of the dq-axis current loop is made the same:

[0051]

[0052] In the formula, ω i For the bandwidth of the current loop controller, These are the integral constants of the dq-axis current loop PI controller, respectively;

[0053] Based on the permanent magnet synchronous motor model, i df and i qf As a state variable, and for surface-mounted permanent magnet synchronous motors, the stator inductance L is defined. s =L d =L q Construct the following state equations:

[0054]

[0055] In the formula, f d For including -(R) s i df -ω e L s i qf The d-axis perturbation voltage of the term; f q For including -[R s i qf +ω e (L s i qf +ψ f The q-axis perturbation voltage.

[0056] Based on the above state equations, the LESO of the dq axis can be established as follows:

[0057]

[0058] in, For i df i qf The estimated value; e d e q These represent the errors between the corresponding estimated values ​​and the feedback values; f d f q The estimated value; These are the derivative values ​​of the corresponding variables; β pd β id βpq , β iq are the corresponding observer gains, respectively.

[0059] After the disturbance estimation is completed, feedforward compensation is performed in the controller, which can be obtained from equation (2):

[0060]

[0061] Based on the above analysis, taking the q-axis current loop as an example, the corresponding control block diagram is shown in FIG. 2, and the observation performance of LESO is analyzed, and there is: Figure 2

[0062]

[0063] Define Δ q = L s s 2 + β pq s + β iq as the characteristic polynomial of the observer, and the observer parameters are set by using the bandwidth method, and there is:

[0064]

[0065] In the formula, ω oq is the observer bandwidth.

[0066] The above completes the construction of the dq-axis LESO, however, the observer only has good suppression effect on low-frequency disturbance, if you want to improve the disturbance suppression ability, you need to further increase the observer bandwidth. This will cause the system to respond to higher frequency noise, and worsen the system performance. Therefore, on the basis of LESO, a notch filter is connected in series at the disturbance compensation term to optimize the noise response of the system, thereby realizing the improvement of the observer bandwidth.

[0067] Step S12: Perform load experiments at different speeds, analyze the harmonic content of the dq-axis current by fast Fourier transform, and obtain the frequency ω n of the high-frequency harmonic.

[0068] Step S13: On the basis of the existing LESO, construct a notch filter from the known ω n , and connect it in series in the disturbance compensation loop to realize the suppression of the high-frequency harmonic.

[0069] The notch filter is constructed from ω n , and the transfer function G notch (s) of the notch filter is:

[0070]

[0071] ​Wherein, ζ1, ζ2 are the damping coefficient of the notch filter, from the above formula, adjusting the notch filter characteristics, not only need to adjust the notch frequency, but also need to adjust the damping coefficient. But the physical meaning of the damping coefficient variable is not clear, in order to make the parameters corresponding to the physical meaning, and simplify the process of adjusting parameters, the following variables are introduced:

[0072]

[0073] Wherein, B w is the notch width of the notch filter, Q is the quality factor of the notch filter, D p is the notch depth of the notch filter. According to the above variables, the related expression of the damping coefficient of the notch filter is obtained as follows:

[0074]

[0075] From the above formula, only need to set the notch center frequency ω n , the quality factor Q and the notch depth D p of the notch filter can complete the parameter configuration of the notch filter. For example Figure 3 is the amplitude frequency characteristic curve when the parameters of the notch filter are changed.

[0076] After completing the configuration of the notch filter, the constructed notch filter is further connected in series to the disturbance compensation loop, and the dq axis disturbance compensation value after the notch is as follows:

[0077]

[0078] Wherein, are the dq axis disturbance compensation values before the notch respectively. The improved controller structure is shown in Figure 4 , from the superposition principle, considering the influence of each input of the system on the disturbance observation, the following formula can be obtained:

[0079]

[0080] The above formula is rewritten as follows:

[0081]

[0082] Wherein G 3n (s) = -R s β iq G notch (s)s / Δ q ;

[0083] G 4n (s) = β iq G notch (s)s / Δ q ;

[0084] G5n (s)=L s β iq G notch (s) / Δ q ;

[0085] By compensating the system for the disturbance after notch filtering, we can obtain:

[0086]

[0087] By combining equations (15) and (16), we can obtain

[0088]

[0089] in Therefore, the system response transfer function with the added feedback notch filter can be obtained as follows:

[0090]

[0091] Among them, G rqn (s) is the instruction response transfer function, G dqn (s) is the disturbance response transfer function, G δqn (s) is the noise response transfer function.

[0092] To verify the effectiveness of adding the notch filter, the quality factor of the notch filter was fixed at Q = 50, and the notch depth D was... p =40, the notch filter frequency can be changed by G δqn (s) Draw the Bode plot of the system's noise response as follows: Figure 5 As shown, from Figure 5 As can be seen from the data, the gain of the system at the corresponding notch frequency is attenuated, which verifies the effectiveness of the proposed notch filter.

[0093] In addition, if the actual system has disturbances at multiple frequency points, multiple notch filters can be connected in series. Figure 6 This demonstrates a fixed notch filter quality factor Q = 50 and a notch depth D. p =60, Bode plot of the system noise response when three notch filters with frequencies of 1000Hz, 2000Hz and 3000Hz are connected in series at the disturbance feedback. Figure 6 As can be seen, after adding the notch filter, the gain of the system noise response at the notch frequency decreased, which effectively verifies the algorithm's suppression effect on noise at multiple frequencies.

[0094] Example 2

[0095] The present invention also relates to an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0096] The electronic device can be a desktop computer, laptop, handheld computer, or cloud server, etc. The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The memory can be used to store computer programs and / or modules. The processor performs various functions of the electronic device by running or executing the computer programs and / or modules stored in the memory, and by accessing data stored in the memory.

[0097] Example 3

[0098] The present invention also relates to a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described above.

[0099] Specifically, the memory may include high-speed random access memory, as well as non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital cards (SD), flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0100] Example 4

[0101] To verify the effectiveness and superiority of the control method proposed in this invention, the following experiments were conducted:

[0102] First, a harmonic frequency experiment was conducted: the motor under test used a PI control algorithm, and the dq-axis current loop PI controller parameters were set to ω. i =2000πrad / s, integration time constant Command speeds of 600 rpm and 900 rpm were given respectively, and the system was operated in steady state under a fixed load. Feedback current was acquired via a host computer and analyzed using FFT. Furthermore, since verifying the current loop disturbance suppression capability requires a focus on the current harmonic distortion rate, if... Under control, the THD calculation of the d-axis current has a reference value of 0, and the result cannot be intuitively represented. Therefore, this experiment will give... A closed-loop experiment was conducted. From this, we can obtain the following...Figure 7 The current waveforms of i d , i q and i a from top to bottom, respectively, and the FFT analysis results are shown in Figure 8 .

[0103] As can be seen from Figure 7 , under the same control algorithm, the stator current THD of 600 rpm and 900 rpm is basically the same. After FFT analysis of the current waveform, it can be found that in addition to the fundamental frequency harmonic caused by the dead zone effect, there is a relatively obvious harmonic with a frequency of 2260 Hz in the dq-axis current, and this part of the harmonic does not change with the change of the motor fundamental frequency. It should be noted that the fixed frequency harmonic in the d-q coordinate system is reflected in the three-phase coordinate system, which corresponds to the frequency of ± fundamental frequency. For 600 rpm, the fundamental frequency is 50 Hz, so 2260 Hz in the three-phase reference coordinate system is 2210 Hz and 2310 Hz; for 900 rpm, the fundamental frequency is 75 Hz, so 2260 Hz in the three-phase reference coordinate system is 2185 Hz and 2335 Hz. The high-frequency part reflected in (b) of Figure 8 is exactly the same as the above analysis, so the following conclusion can be drawn: there is a fixed frequency high-frequency harmonic in the dq-axis feedback current.

[0104] Further, the verification experiment of the feedback notch filter is carried out: in order to more obviously verify the theory, the algorithm switching is carried out under the steady state of the observer bandwidth of 3000π rad / s, and the current waveforms before and after adding the notch filter are recorded. As can be known from the previous experiment, the dq-axis current of the driver has a high-frequency harmonic at a fixed frequency of 2260 Hz, so the specific parameter design of the notch filter is as follows: the notch center frequency ω n = 4520π rad / s, the notch quality factor Q = 50, and the notch depth D p = 40. The specific experimental results are shown in Figure 9 , and the proportion of the main frequency harmonic is shown in Figure 10 .

[0105] As can be known from Figure 9 and Figure 10 , the addition of the feedback notch filter slightly reduces the stator current THD, while significantly reducing the THD of i q , and also reducing i qFurther analysis of the main harmonic FFT results shows that the addition of the feedback notch filter significantly reduces the THD ratio of the specific frequency noise of the dq-axis current, from 3.89% and 2.48% to 1.26% and 1.24%, respectively. At the same time, the THD ratio of the stator current is reduced from 1.24% and 1.31% to 0.62% and 0.63%, respectively.

[0106] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for suppressing current harmonics in a permanent magnet synchronous motor, characterized in that, The permanent magnet synchronous motor control circuit includes a current loop and includes the following steps: Step S11: Construction of a permanent magnet synchronous motor model dq An axially extended state observer is used. The gain of the observer is tuned, and the linearly extended state observer is applied to the current loop to observe the current loop disturbance. The observed disturbance values ​​are then added to the current loop to construct a disturbance compensation loop. dq The axial expansion state observer is: in, , They are respectively dq Voltage command for the shaft; , Each after taking noise into account dq Shaft feedback current, , They are respectively dq Shaft feedback current, , for , The estimated value; , These represent the errors between the corresponding estimated values ​​and the feedback values; , They are respectively dq Shaft disturbance voltage. , for , The estimated value; , , , These are the derivative values ​​of the corresponding variables; , , , These are the corresponding observer gains; The stator inductance is used; the gain of the observer is tuned using the bandwidth method, i.e.: in, , For respectively dq Bandwidth of the axial expansion state observer. ; Step S12: Conduct load experiments at different speeds and analyze the results. dq Harmonic content of shaft current, and obtain the frequency of high-frequency harmonics. ; Step S13: From the aforementioned A notch filter is constructed and connected in series in a disturbance compensation circuit to suppress this high-frequency harmonic.

2. The method for suppressing current harmonics in a permanent magnet synchronous motor as described in claim 1, characterized in that, In step S12, load experiments are conducted at different rotational speeds, and the results are analyzed using Fast Fourier Transform. dq The harmonic content of the shaft current is used to obtain the frequency of the high-frequency harmonics. .

3. The method for suppressing current harmonics in a permanent magnet synchronous motor as described in claim 1, characterized in that, The transfer function of the notch filter built in step S13 for: in, , is the damping coefficient of the notch filter.

4. The method for suppressing current harmonics in a permanent magnet synchronous motor as described in claim 3, characterized in that, The expression for the damping coefficient of the notch filter is: in, The quality factor of the notch filter. The notch depth is the depth of the notch filter.

5. The method for suppressing current harmonics in a permanent magnet synchronous motor as described in claim 3, characterized in that, In step S13, the notch filter is connected in series in the disturbance compensation circuit to reduce the frequency of the disturbance compensation value. High-frequency harmonics, after notch filtering dq Shaft disturbance compensation value , for: in, , Before the notch wave dq Shaft disturbance compensation value.

6. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 5.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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