A control method for suppressing high-frequency howling of permanent magnet synchronous motor

Abstract

A control method for suppressing high-frequency howling of a permanent magnet synchronous motor relates to the field of motor control and noise suppression, and includes the following steps: Step 1: Considering the influence of rotor position on pulse width modulation, design a segmented hybrid switching frequency modulation strategy: Step 2: Simulate and determine the frequency, spread spectrum width and proportional coefficient of the triangular wave periodic function in the segmented hybrid switching frequency modulation strategy, Step 3: According to Step 1 and Step 2, obtain the change value of the switching frequency with the rotor position, and output six-way drive signals after space vector pulse width modulation, which are used to control the on and off of the switch tube of the permanent magnet synchronous motor driver inverter, so as to achieve the purpose of suppressing the high-frequency howling of the permanent magnet synchronous motor. The present invention suppresses high-frequency sideband harmonics, thereby suppressing the high-frequency howling of the permanent magnet synchronous motor. The method is low-cost, easy to implement, and does not need to add additional hardware equipment; a segmented hybrid switching frequency spread spectrum modulation strategy is set to better disperse and suppress high-frequency current harmonics and high-frequency howling noise.

Description

Technical Field

[0001] The present invention relates to the field of motor control and noise suppression, and in particular to a control method for suppressing high-frequency howling of a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors have the advantages of compact structure, high efficiency, stable and reliable operation, and high torque density, and are widely used in various industries. During operation, permanent magnet synchronous motors will inevitably generate electromagnetic noise, mechanical noise, and aerodynamic noise, which cannot meet the requirements of auditory quietness and comfort for people in some occasions. Among them, electromagnetic noise is the main source of noise for permanent magnet synchronous motors. Inverter pulse width modulation will introduce high-frequency current harmonics into the three-phase current of permanent magnet synchronous motors. Their frequencies are concentrated near the switching frequency and its integer multiples. Higher switching frequencies will cause permanent magnet synchronous motors to generate high-frequency electromagnetic harmonics, which in turn excite high-frequency howling noise. High-frequency howling noise is sharp and harsh, which is more likely to cause subjective irritation in the audience and greatly affect comfort. At present, the main method to suppress electromagnetic noise is the motor body parameter optimization method, but this method mainly weakens the low-frequency electromagnetic force, and has limited effect on suppressing the high-frequency electromagnetic force and high-frequency howling noise introduced by the inverter. In addition, the motor body parameter optimization method will increase the design, manufacturing and time costs of the motor, and it may not be able to optimize the output performance and noise at the same time. Starting from the control strategy, the high-frequency current harmonics introduced by pulse width modulation can be weakened, and the high-frequency howling of the permanent magnet synchronous motor can be suppressed without increasing the hardware cost.

[0003] The existing patent search involving methods for suppressing electromagnetic noise of permanent magnet synchronous motors is as follows:

[0004] (1) Use the motor body parameter optimization method to suppress electromagnetic noise. The patent search is as follows: ① Huang Xiaoqiang of Nidec Kaiyu Automotive Electrical (Jiangsu) Co., Ltd. applied for a magnetic tile for reducing electromagnetic noise, application number: CN202023289480.8, authorization announcement number: CN213959832U; ② Wang Liming of Jiamusi Electric Co., Ltd. applied for a winding for reducing the electromagnetic noise of AC motor, application number: CN202020191919.4, authorization announcement number: CN211377731U; ③ Kong Qingbo of Guangzhou Xiaopeng Automobile Technology Co., Ltd. applied for a motor and automobile for suppressing motor electromagnetic noise and improving NVH, application number: CN201910095608.X, authorization announcement number: CN109921571A; ④ He Junming of Zhejiang Panhu Power Technology Co., Ltd. applied for a magnetic steel for reducing motor electromagnetic noise, application number: CN202023288362.5, authorization announcement number: CN214412418U.

[0005] (2) Spread spectrum modulation is used to suppress the high-frequency electromagnetic noise introduced by the permanent magnet synchronous motor inverter. The patent search is as follows: ① Liu Shichang of Shanghai Institute of Electric Power applied for a method and device for vibration reduction and noise reduction of permanent magnet synchronous motor based on spread spectrum modulation technology, application number: CN202111512660.4, authorization announcement number: CN114362636A; ② Xi'an University of Technology applied for a random switching frequency modulation method of NPC converter based on ripple current peak, application number: CN201711432404.8, authorization announcement number: CN108054948A; ③ Wang Gang of China First Automobile Co., Ltd. applied for a method for reducing the switching frequency noise of permanent magnet synchronous motor, application number: CN202011099873.4, authorization announcement number: CN112332720A; ④ Jiang Dong of Huazhong University of Science and Technology applied for a current source inverter switching frequency modulation method and system, application number: CN202010696679.8, authorization announcement number: CN111934577B.

[0006] After comprehensive investigation of existing technologies, the current technology for suppressing electromagnetic noise of permanent magnet synchronous motors still has the following problems that need to be solved:

[0007] (1) The motor body parameter optimization method can weaken the low-order electromagnetic force and low-order electromagnetic noise to a certain extent. However, the optimization of the motor body parameters will increase the manufacturing cost and cannot suppress the high-frequency howling noise caused by high-frequency current harmonics.

[0008] (2) The spread spectrum modulation method can effectively suppress high-frequency electromagnetic noise. However, the existing technology does not take into account the impact of the operating state of the permanent magnet synchronous motor on the spread spectrum modulation, and cannot produce a good harmonic suppression effect. In addition, the existing random switching frequency spread spectrum modulation technology is limited by hardware, and the random numbers generated are "pseudo-random", which greatly reduces the harmonic suppression effect. Therefore, it is urgent to consider the impact of the change in rotor position during the operation of the permanent magnet synchronous motor on the pulse width modulation, and propose a technology that can increase the randomness of the switching frequency and improve the high-frequency harmonic suppression effect. Summary of the invention

[0009] In view of the shortcomings of the prior art in suppressing the high-frequency whistling noise of permanent magnet synchronous motors, the present invention proposes a control method for suppressing the high-frequency whistling noise of permanent magnet synchronous motors, which suppresses the high-frequency whistling noise of permanent magnet synchronous motors by weakening the high-frequency sideband current harmonics. The main advantages of this technology are: (1) Starting from the motor control strategy, the high-frequency sideband harmonics are suppressed, thereby suppressing the high-frequency whistling of the permanent magnet synchronous motor. The method is low-cost, easy to implement, and does not require the addition of additional hardware equipment; (2) Considering the impact of the rotor position change on the pulse width modulation during the operation of the permanent magnet synchronous motor, a segmented hybrid switching frequency spread spectrum modulation strategy is set to better disperse and suppress the high-frequency current harmonics and high-frequency whistling noise.

[0010] A control method for suppressing high-frequency howling of a permanent magnet synchronous motor mainly comprises the following steps:

[0011] Step 1: Considering the influence of rotor position on pulse width modulation, a segmented hybrid switching frequency modulation strategy is designed;

[0012] Step 2: Determine the frequency, spread spectrum width and proportional coefficient of the triangular wave periodic function in the segmented hybrid switching frequency modulation strategy by simulation;

[0013] Step 3: According to step 1 and step 2, the change value of the switching frequency with the rotor position is obtained, and six drive signals are output after space vector pulse width modulation to control the on and off of the inverter switch tube. The suppression effect of high-frequency current harmonics is verified through simulation.

[0014] The specific operations of step 1 are as follows:

[0015] Considering the influence of rotor position on pulse width modulation, a segmented hybrid switching frequency pulse width modulation strategy is designed:

[0016] When the permanent magnet synchronous motor rotor is in different positions, the switching frequency of the inverter of the permanent magnet synchronous motor driver is expressed by formula (1).

[0017]

[0018] In the formula, f s (t) is the actual switching frequency (Hz), and T s =1 / f s ; f0 is the center frequency (Hz), which is the same as the carrier frequency under the fixed switching frequency; a is the proportional coefficient of random frequency modulation (-); R is a random number that varies within the range of ±1 (-); b is the proportional coefficient of periodic frequency modulation (-); f(t) is the frequency of the triangle wave periodic function with an amplitude of ±1 (Hz); Δf H is the spread spectrum width of the hybrid switching frequency modulation (Hz); θ is the rotor position (°).

[0019] Formula (1) is the segmented hybrid switching frequency modulation strategy of permanent magnet synchronous motor.

[0020] The specific operation of step 2 is as follows:

[0021] Step 2.1: Substitute the switching frequency value f obtained in step 1 s (t), replace the fixed center frequency value f0 of the space vector pulse width modulation link in the permanent magnet synchronous motor vector control model (the permanent magnet synchronous motor vector control model is based on i d =0 is the overall control strategy), and a permanent magnet synchronous motor control model based on a hybrid switching frequency pulse width modulation strategy is established in Matlab&Simulink software.

[0022] Step 2.2: Determine the frequency f(t) of the triangular wave periodic function. Select different periodic function frequencies and substitute them into the permanent magnet synchronous motor control model based on the segmented hybrid switching frequency pulse width modulation strategy established in step 2.1 for simulation. Compare the high-frequency sideband current harmonic content and select the frequency with good harmonic suppression effect as the periodic function frequency.

[0023] Step 2.3: Determine the spread width Δf of the hybrid switching frequency modulation H Select different spread spectrum widths, substitute them into the permanent magnet synchronous motor control model based on the segmented hybrid switching frequency pulse width modulation strategy established in step 2.1 for simulation, compare the high-frequency sideband current harmonic content, and select the value with good harmonic suppression effect as the spread spectrum width.

[0024] Step 2.4: Determine the proportional coefficients a and b of random frequency modulation and periodic frequency modulation. The proportional coefficient relationship is: a+b=1. Select different proportional coefficients and substitute them into the permanent magnet synchronous motor control model based on the segmented hybrid switching frequency pulse width modulation strategy established in step 2.1 for simulation. Compare the high-frequency sideband current harmonic content and select the case with good harmonic suppression effect as the value of a and b.

[0025] The specific operations of step 3 are as follows:

[0026] Step 3.1: For the permanent magnet synchronous motor control model based on the segmented hybrid switching frequency pulse width modulation strategy established in step 2.1, substitute the selected periodic function frequency, spread spectrum width, proportional coefficients a and b for simulation, and set the center switching frequency to f0 to obtain the change value of the switching frequency with the rotor position (f s (t)), used to drive the inverter switch on and off.

[0027] Step 3.2: Set the operating conditions of the permanent magnet synchronous motor in the simulation software, and obtain the three-phase current of the permanent magnet synchronous motor by simulating the permanent magnet synchronous motor control model based on the segmented hybrid switching frequency pulse width modulation strategy. Take one of the phase currents for fast Fourier transform to obtain the high-frequency sideband current harmonic content near the integer multiple switching frequency, and verify the suppression effect of high-frequency current harmonics.

[0028] The control method for suppressing high-frequency whistling of a permanent magnet synchronous motor of the present invention can take into account the influence of the rotor position on pulse width modulation when the motor is running, and increase the diffusion and suppression effect of high-frequency sideband current harmonics by reasonably designing the segmented hybrid switching frequency pulse width modulation method, and reduce the high-frequency whistling of the motor caused by inverter pulse width modulation, thereby improving the NVH performance of the permanent magnet synchronous motor. At the same time, the method is implemented through strategy changes and software, without adding additional hardware equipment, saving costs and being easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0030] Figure 1 is a flow chart of the control method of the present invention;

[0031] Figure 2 It is the law of variation of the zero vector action time T0 in the sector with the rotor position;

[0032] Figure 3 It is a schematic diagram of a motor control model of a hybrid switching frequency pulse width modulation algorithm considering rotor position proposed by the present invention;

[0033] Figure 4 It is the variation of the actual switching frequency with the rotor position under the modulation strategy proposed by the present invention;

[0034] Figure 5 is the harmonic content of phase A current before and after the control strategy of the present invention is added at rated speed;

[0035] Figure 6 It is a comparison of the A phase current waterfall diagram before and after the control strategy of the present invention is added in the acceleration condition;

[0036] Figure 7 It is the comparison of the noise sound pressure level spectrum before and after adding the control strategy of the present invention at rated speed;

[0037] Figure 8 It is the comparison of the noise sharpness before and after adding the control strategy of the present invention at the rated speed;

[0038] Fig. 9 It is a comparison of the noise waterfall diagram before and after the control strategy of the present invention is added to the acceleration condition;

[0039] Fig.10 It is a comparison of sharpness before and after adding the control strategy of the present invention under acceleration conditions. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0041] Taking a surface-mounted permanent magnet synchronous motor as an example, the process of suppressing the high-frequency howling of the motor by using the control strategy of the present invention is described in detail. Figure 1 The flowchart of the control method of the present invention is shown in FIG. 1 , and the specific implementation steps are as follows:

[0042] Step 1: Considering the influence of rotor position on pulse width modulation, a segmented hybrid switching frequency modulation strategy is designed.

[0043] The q-axis current fluctuation generated by the space vector pulse width modulation link in the motor control system is shown in formula (A1):

[0044]

[0045] In the formula, Δi q is the q-axis current fluctuation (A), is the average voltage of q axis (V), T0 is the zero vector action time in the sector (s); L q is the q-axis inductance (H).

[0046] The q-axis current fluctuation will cause the high-frequency electromagnetic force to increase, generating high-frequency howling noise. The q-axis current fluctuation is positively correlated with the zero vector action time T0 in the sector. In the space vector pulse width modulation strategy, the change rule of the zero vector action time T0 in the sector with the rotor position is: in each sector, as the rotor position increases, T0 decreases first and then increases, such as Figure 2 shown.

[0047] Taking sector I (0~π / 3) as an example, in the range of 0~π / 6, as the rotor position increases, T0 gradually decreases; in the range of π / 6~π / 3, as the rotor position increases, T0 gradually increases, and the same rule applies to other sectors.

[0048] Considering the influence of rotor position on pulse width modulation, a hybrid switching frequency pulse width modulation strategy is designed: At positions (k is 1, 5, 9, 13, 17, 21), T0 is small and is affected by T s The impact is relatively small. The randomness of the switching frequency can be increased by combining the periodic switching frequency spread spectrum modulation with the random switching frequency spread spectrum modulation strategy; T s The reduction of can promote the reduction of T0, so Position, T can be appropriately reduced s , that is, increase f s On this basis, adding a random process can realize spread spectrum modulation while reducing the zero vector action time T0. The switching frequency at different rotor positions can be expressed by formula (A2).

[0049]

[0050] In the formula, f s (t) is the actual switching frequency (Hz), and T s =1 / f s; f0 is the center frequency (Hz), which is the same as the carrier frequency under the fixed switching frequency; a is the proportional coefficient of random frequency modulation (-); R is a random number that varies within the range of ±1 (-); b is the proportional coefficient of periodic frequency modulation (-); f(t) is the frequency of the triangle wave periodic function with an amplitude of ±1 (Hz); Δf H is the spread spectrum width of the hybrid switching frequency modulation (Hz); θ is the rotor position (°).

[0051] Step 2: Determine the frequency, spread spectrum width and proportional coefficient of the triangular wave periodic function in the segmented hybrid switching frequency modulation strategy by simulation;

[0052] The specific operation of step 2 is as follows:

[0053] Step 2.1: Substitute the switching frequency value f obtained in step 1 s (t), replace the fixed center frequency value f0 of the space vector pulse width modulation link in the permanent magnet synchronous motor vector control model (the permanent magnet synchronous motor vector control model is based on i d = 0 is the overall control strategy), and a permanent magnet synchronous motor control model based on a hybrid switching frequency pulse width modulation strategy is established in Matlab & Simulink software. Figure 3 shown.

[0054] Step 2.2: Determine the frequency f(t) of the triangular wave periodic function. Select four periodic function frequencies: 50Hz, 100Hz, 150Hz, and 200Hz, and fix the spread spectrum width to Δf H =1000Hz, the proportional coefficients a and b are both 0.5. Substitute the permanent magnet synchronous motor control model based on the hybrid switching frequency pulse width modulation strategy established in step 2.1 for simulation and compare the peak harmonic content of the high-frequency sideband current. The peak harmonic content of the current under the four periodic function frequencies is 2.36%, 1.71%, 1.25%, and 1.87%, respectively. 150Hz is selected as the periodic function frequency.

[0055] Step 3.4: Determine the spread width Δf of the hybrid switching frequency modulation H . Select different spread spectrum widths: 500Hz, 1000Hz, 1500Hz, 2000Hz, select the frequency of the periodic function f(t) = 150Hz, and the proportional coefficients a and b are both 0.5. Substitute the permanent magnet synchronous motor control model based on the hybrid switching frequency pulse width modulation strategy established in step 2.1 for simulation and compare the peak harmonic content of the high-frequency sideband current. The peak harmonic content of the current under the four spread spectrum widths is 1.86%, 1.51%, 1.27%, and 1.25%, respectively. As the spread spectrum width continues to increase, the harmonic suppression effect will be better, but frequency aliasing will also occur, increasing the risk of resonance. Therefore, 1500Hz is selected as the periodic function frequency.

[0056] Step 3.5: Determine the proportional coefficients a and b of random frequency modulation and periodic frequency modulation. The proportional coefficient relationship is: a+b=1. Select different values ​​of a and b, substitute them into the permanent magnet synchronous motor control model based on the hybrid switching frequency pulse width modulation strategy established in step 2.1 for simulation, and compare the high-frequency sideband current harmonic content, see Table A1. According to the harmonic suppression effect, select a=0.8 and b=0.2.

[0057] Table A1

[0058]

[0059] Step 3: According to step 1 and step 2, the change value of the switching frequency with the rotor position is obtained, and six drive signals are output after space vector pulse width modulation to control the on and off of the inverter switch tube. The suppression effect of high-frequency current harmonics is verified through simulation.

[0060] The specific operations of step 3 are as follows:

[0061] Step 3.1: For the permanent magnet synchronous motor control model based on the hybrid switching frequency pulse width modulation strategy established in step 2.1, substitute the selected periodic function frequency of 150Hz, spread spectrum width of 1500Hz, proportional coefficients a=0.8, b=0.2 for simulation, and set the central switching frequency to f s =10kHz, and the switching frequency changes with the rotor position, which is used to drive the inverter switch on and off. Taking the first sector (0~π / 3) as an example, the switching frequency changes with the rotor position as shown in Figure 4 shown.

[0062] Step 3.2: In Matlab & Simulink software, the target speed of the permanent magnet synchronous motor of this embodiment is set to the rated speed of 2000r / min, the load torque is 3N·m, the three-phase current of the steady-state working condition is simulated, the A-phase current is taken for fast Fourier transform, and the high-frequency current harmonic peak value before and after the control strategy of the present invention is added is simulated and compared, as shown in FIG. Figure 5 As shown in Figure 1, the peak value of high-frequency current harmonics is reduced by 74.86%. Acceleration condition simulation is performed, and the speed is accelerated to the rated speed within 5s. The three-phase current waterfall diagram is shown in Figure 1. Figure 6 , the order lines near 10kHz and 20kHz become shallower and the content decreases. The suppression effect of current harmonics is verified by simulation of steady-state constant speed condition and non-steady-state acceleration condition.

[0063] The control strategy of the present invention has been experimentally verified to suppress the high-frequency howling of the permanent magnet synchronous motor. The sound pressure level and sharpness changes under steady-state conditions are shown in Figure 2. Figure 7 and Figure 8As shown in the figure, the total sound pressure level under this condition is reduced from 51.77dB to 46.33dB, a decrease of 5.44dB, and the high-frequency howling noise peak is reduced from 49.06dB to 19.31dB, a decrease of 29.72dB; the average sharpness is reduced from 4.61acum to 4.10acum, a decrease of 11.06%. The frequency domain waterfall diagram of the sound pressure level and the change of sharpness under the acceleration condition are shown in the figure. Fig. 9 and Fig.10 As shown in the figure, the amplitude and sharpness of the high-frequency noise sound pressure level near the switching frequency are reduced.

Claims

1. A control method for suppressing high-frequency howling of a permanent magnet synchronous motor, mainly comprising the following steps: Step 1: Consider the influence of rotor position on pulse width modulation and design a segmented hybrid switching frequency modulation strategy: When the permanent magnet synchronous motor rotor is in different positions, the switching frequency of the inverter of the permanent magnet synchronous motor driver is expressed by formula (1): In the formula, f s (t) is the actual switching frequency (Hz), f0 is the center frequency (Hz), a is the proportional coefficient of random frequency modulation; R is a random number that varies within the range of ±1; b is the proportional coefficient of periodic frequency modulation; f(t) is the frequency of the triangle wave periodic function with an amplitude of ±1 (Hz); Δf H is the spread spectrum width of the hybrid switching frequency modulation (Hz); θ is the rotor position (°); Step 2: Simulate and determine the frequency, spread width and proportional coefficient of the triangle wave periodic function in the segmented hybrid switching frequency modulation strategy. The specific operations are as follows: Step 2.1: Substitute the switching frequency value f obtained in step 1 s (t), replace the fixed center frequency value f0 of the space vector pulse width modulation link in the permanent magnet synchronous motor vector control model, and establish a permanent magnet synchronous motor control model based on the segmented hybrid switching frequency pulse width modulation strategy in the simulation software; Step 2.2: Determine the frequency f(t) of the triangle wave periodic function Select different periodic function frequencies, substitute them into the permanent magnet synchronous motor control model based on the segmented hybrid switching frequency pulse width modulation strategy established in step 2.1 for simulation, compare the high-frequency sideband current harmonic content, and select the frequency with good harmonic suppression effect as the periodic function frequency; Step 2.3: Determine the spread width Δf of the segmented hybrid switching frequency modulation H Select different spread spectrum widths, substitute them into the permanent magnet synchronous motor control model based on the segmented hybrid switching frequency pulse width modulation strategy established in step 2.1 for simulation, compare the high-frequency sideband current harmonic content, and select the value with the best harmonic suppression effect as the spread spectrum width; Step 2.4: Determine the proportional coefficients a and b of random frequency modulation and periodic frequency modulation The proportional coefficient relationship is: a+b=1. Select different proportional coefficients and substitute them into the permanent magnet synchronous motor control model based on the segmented hybrid switching frequency pulse width modulation strategy established in step 2.1 for simulation. Compare the high-frequency sideband current harmonic content and select the case with good harmonic suppression effect as the value of a and b. Step 3: According to step 1 and step 2, the change value of the switching frequency with the rotor position is obtained, and six drive signals are output after space vector pulse width modulation to control the on and off of the switching tube of the permanent magnet synchronous motor driver inverter to achieve the purpose of suppressing the high-frequency howling of the permanent magnet synchronous motor.

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