A method and device for analyzing a common-mode excitation source of electromagnetic interference conducted by a motor system, and a readable medium

Abstract

This invention relates to the field of electromagnetic interference (EMI) technology for motor systems, and discloses a method, apparatus, and readable medium for analyzing common-mode excitation sources of conducted EMI in motor systems. The analysis method includes the following steps: based on the vector control equations of the motor system, determining the correspondence between the amplitude and frequency of the driver output voltage and the motor speed; establishing a differential common-mode equivalent circuit of the motor system to obtain a steady-state time-frequency domain model of the common-mode excitation source; based on the steady-state time-frequency domain model of the conducted EMI common-mode excitation source, obtaining a transient equivalent circuit of the single-phase switch action of the motor system considering speed conditions; combining the transient equivalent circuit, establishing a transient time-frequency domain model of the common-mode excitation source; obtaining the spectral expression of the common-mode excitation source; and establishing the spectral expression of the common-mode excitation source. This invention can quantitatively reveal the mapping relationship between the amplitude of high-frequency conducted EMI and speed, significantly reducing the workload and cost of electromagnetic compatibility testing.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic interference technology for motor systems, and in particular to a method, apparatus, and readable medium for analyzing common-mode excitation sources of conducted electromagnetic interference in motor systems. Background Technology

[0002] The motor system is one of the main sources of conducted electromagnetic interference (EMI) in new energy vehicles, severely affecting their electromagnetic compatibility (EMC) performance and greatly hindering conducted emission tests (such as voltage and current methods). As a high-voltage, high-current electrical system with diverse coupling paths in new energy vehicles, the motor system generates significant electromagnetic interference energy, a wide frequency band, and diverse propagation coupling paths during normal operation due to its high voltage, high current, and complex structure. In intelligent connected systems, the motor system exchanges information at high speed with the engine control unit (ECU), and the high-speed operation of high-power switching devices (such as SiC or IGBT power devices) in the system contributes to this interference. u / d t and d i / d t Changes in characteristics and operating conditions will generate high-amplitude, wide-bandwidth electromagnetic interference (EMI) problems. Studying the impact of changes in operating conditions on the conducted electromagnetic problems of motor systems has good engineering value and practical significance. Currently, most motor systems employ pulse width modulation (PWM) technology. Their output voltage contains a large amount of common-mode components, making it one of the main sources of common-mode electromagnetic interference (EMI), primarily operating in the low-frequency range (below 150kHz). The switching devices in the motor system generate significant d... u / d t and d i / d t This results in a large number of high-frequency common-mode components in the output voltage and current, making it another major source of conducted electromagnetic interference (EMI) common-mode excitation, primarily affecting the high-frequency range (1MHz-30MHz). Therefore, analyzing the influencing factors of the common-mode EMI model of the motor system and its effects across different frequency bands is crucial for effectively addressing EMI issues.

[0003] The analysis of the influencing factors of common-mode electromagnetic interference is mainly divided into two parts: common-mode impedance model and common-mode interference source model. The common-mode impedance model mainly focuses on high-frequency impedance modeling.

[0004] One existing high-frequency three-phase motor model, applicable to both star-connected and delta-connected windings, forms a complete drive system with inverters, cables, etc., and is of reference value for the study of bearing current, electromagnetic interference, and winding overvoltage issues. The accuracy of these high-frequency impedance models can provide a reference for establishing the conduction path of electromagnetic interference excitation sources.

[0005] Currently, Fast Fourier Transform (FFT) analysis is mainly used to obtain the spectral characteristic distribution of electromagnetic interference (EMI) excitation sources. Since the output waveform of a three-phase inverter is influenced by both the carrier wave and the modulation wave, existing techniques based on double Fourier transforms provide accurate theoretical derivations of the spectral characteristics and harmonic distribution of conducted EMI common-mode excitation sources, but these derivations have small errors compared to experimental results. However, they do not further consider the impact of operating conditions on spectral characteristics. Analyzing the influence of operating conditions on common-mode EMI is crucial. However, current variations caused by load torque will significantly affect the switching characteristics of critical components; therefore, studying the influence of rotational speed on the characteristics of conducted EMI common-mode excitation sources is of great significance. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention aims to provide a method, device and readable medium for analyzing common-mode excitation sources of conducted electromagnetic interference in motor systems. This method can provide a theoretical basis for the low-frequency electromagnetic compatibility design of motor systems, quantitatively reveal the mapping relationship between the amplitude of conducted electromagnetic interference and the rotational speed in the high-frequency band, make up for the lack of rotational speed parameters in the high-frequency band analysis of existing methods, and significantly reduce the workload and cost of electromagnetic compatibility testing.

[0007] This invention is achieved using the following technical solution: a method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system, comprising the following steps: S1: Based on the vector control equations of the motor system, determine the correspondence between the amplitude and frequency of the driver output voltage and the motor speed; S2: Establish the differential and common-mode equivalent circuit of the motor system, and combine the switching pulse sequence under the pulse width modulation strategy to obtain the common-mode excitation source of conducted electromagnetic interference within a switching cycle. Perform Fourier transform on the common-mode excitation source to obtain the steady-state time-frequency domain model of the common-mode excitation source. S3: Based on the steady-state time-frequency domain model of the common-mode excitation source of conducted electromagnetic interference, the high-frequency ringing effect caused by the transient characteristics of power switch operation is considered. Combined with the stator winding voltage equation of the motor, the transient equivalent circuit of single-phase switch operation of the motor system considering the speed condition is obtained. S4: Combine the transient equivalent circuit to establish a transient time-frequency domain model of the common-mode excitation source; S5: Perform a Fourier transform on the transient time-frequency domain model of the common-mode excitation source to obtain the spectrum expression of the common-mode excitation source; S6: Based on the common-mode excitation source spectrum expression, establish the mapping relationship between the transient jump amplitude of the common-mode excitation source spectrum expression and the amplitude of high-frequency conducted electromagnetic interference, and determine the influence law of speed condition on high-frequency conducted electromagnetic interference.

[0008] Furthermore, the motor system is a permanent magnet synchronous motor system, and the vector control equation adopts... i d =0 vector control strategy; In step S1, i d Under the condition that = 0, the relationship between the driver output voltage and the motor speed is: In the formula, u d , u q These are the stator voltages. d - q Axial components, i d , i q These are the stator currents. d - q Axial components, R s For stator resistance, L d , L q They are respectively d - q Shaft inductance component, ω e This refers to the rotor's electrical angular velocity; for surface-mounted three-phase permanent magnet synchronous motors L d ≈ L q , ψ m It is a permanent magnet flux linkage; Transform the above equation to a static state. α - β In a coordinate system, the mathematical equations for the voltage and rotational speed output by the driver are as follows: According to the above equation in the natural coordinate system, the mathematical equation for the output phase voltage of the driver is: In the formula, R For stator resistance, L For stator equivalent inductance, ω e The rotor's electric angular velocity, θ e The rotor electrical angle; Based on the above formula, the phase voltages of the three-phase windings can be written in a unified form as follows: .

[0009] Furthermore, the pulse width modulation strategy is SVPWM (Space Vector Pulse Width Modulation). In step S2, according to the modulation principle of space vector pulse width modulation, the duration of action of the two effective vectors and the two zero vectors in one switching cycle is: In the formula, d m , d n These are the duty cycles of the two effective vectors. d 0、 d 7 is the zero vector duty cycle. U out For the output voltage vector, U dc This is the DC bus voltage. k out It is the sector number where the reference vector is located. The angle between the output voltage vector and the principal vector. is the modulation coefficient.

[0010] Furthermore, in step S2, the differential and common-mode equivalent circuit of the motor system includes the following circuit elements: Stator winding three-phase output voltage u A , u B , u C DC bus voltage U dc DC side neutral point O Midpoint of three-phase load of motor N , The switching action in the common-mode equivalent circuit is the same as that in the differential-mode equivalent circuit; based on the definition of the common-mode excitation source of conducted electromagnetic interference, the three-phase grounding of the inverter is obtained. O The output voltage equation of the point: In the formula, u cm It serves as a common-mode excitation source for conducting electromagnetic interference in motor systems. Adding the three equations above and applying the three-phase balance of the motor, we obtain the common-mode excitation source of conducted electromagnetic interference.u cm for: The common-mode excitation source of conducted electromagnetic interference in one switching cycle is: In the formula, [ t 1, t 2, t 3, t 4, t 5, t 6,]=[T d 0, T( d 0+ d m ), T( d 0+ d m + d n T(0.5+) d 7), T(0.5+ d 7+ d n ), T(1- d 0)], T is one switching cycle, A double Fourier transform is used to model the common-mode excitation source of conducted electromagnetic interference (EMI) in the frequency domain, resulting in a steady-state time-frequency domain model. The EMI common-mode excitation source is a periodic function of the high-frequency carrier and the low-frequency fundamental wave, and is piecewise smooth within one switching cycle. This means the EMI common-mode excitation source satisfies the Fourier expansion condition. A Fourier expansion using trigonometric functions yields the mathematical expression for the steady-state time-frequency domain model: in, .

[0011] Furthermore, in step S3, the transient equivalent circuit includes the following circuit elements: DC bus voltage U dc Parasitic resistance of switching device on / off circuit R Loop Stray inductance L Loo and parasitic capacitance C Loop Equivalent resistance of motor windings R and equivalent inductance L 1. Motor winding end capacitance to ground C g1 Neutral point to ground capacitance C g2 and the back electromotive force of the motor stator windingE ; Among them, the back electromotive force of the motor stator winding E The expression is , ω e The rotor's electric angular velocity, ψ m It is a permanent magnet flux linkage. θ e Rotor electrical angle; back electromotive force E The amplitude is proportional to the motor speed, which causes the total excitation source amplitude in the differential-common-mode equivalent circuit to increase with increasing speed.

[0012] Furthermore, in step S4, During the switching process, the complex frequency domain expression of the common-mode excitation source of conducted electromagnetic interference is: As can be seen from the above equation, the instant of switching action can be regarded as a second-order damped oscillation process, and its resonant frequency is... f for: The transient time-frequency domain model of the common-mode excitation source is as follows: In the formula, ω n , ω d , β、ζ The parasitic parameters of the differential common-mode circuit are the resonant angular frequency, sinusoidal decaying oscillation frequency, oscillation phase, and damping ratio. e ( t - t i The value is the equivalent electromotive force under operating conditions, and the motor speed at that time is given by the value. n Decision, that is ;at this time ω n , ω d , β、ζ The following conditions must be met: .

[0013] Furthermore, in step S5, The common-mode excitation source spectrum expression is: In the formula, f 0 represents the switching frequency, i.e. , a n For the common-mode excitation source Fourier coefficients, Fourier coefficients an The expression is: In the formula, T One switching cycle Td 0 represents the duration of the zero vector within the switching cycle. E The operating condition is the equivalent potential. α 1. α The expression for 2 is: .

[0014] Furthermore, in step S6, The spectrum of the electromagnetic excitation source is divided into frequency bands, namely low-frequency band and high-frequency band. In the low-frequency band, [the following is selected / selected]... f c 3 f c and 5 f c We will conduct pattern analysis at this point. f c The switching frequency is used; the ringing frequency in the high-frequency band is selected for pattern analysis.

[0015] An electronic device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system.

[0016] A computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention provides a method, apparatus, and readable medium for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system. It establishes an analytical correspondence between the driver output voltage and the motor speed through vector control equations, and introduces this relationship into the construction process of the switching pulse sequence under a pulse width modulation strategy. This makes the duty cycle distribution in the steady-state time-frequency domain expression of the common-mode excitation source a function of the rotational speed. After Fourier transform, the law of variation of the amplitude of conducted electromagnetic interference in the low-frequency band with the rotational speed can be quantitatively revealed, providing a theoretical basis for low-frequency electromagnetic compatibility design.

[0018] 2. The present invention provides a method, apparatus, and readable medium for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system. By establishing a transient equivalent circuit that includes parasitic parameters of switching devices and speed-related back EMF, the ringing effect and back EMF influence, which are neglected in traditional excitation source models, are incorporated into the analysis framework. The transient time-frequency domain model of the common-mode excitation source can quantitatively reveal the mapping relationship between the amplitude of conducted electromagnetic interference in the high-frequency band and the rotational speed, thus making up for the deficiency of existing methods in the lack of rotational speed parameters in high-frequency band analysis.

[0019] 3. The present invention provides a method, apparatus, and readable medium for analyzing common-mode excitation sources of conducted electromagnetic interference (EMI) in a motor system. It combines steady-state and transient analysis, establishing mapping relationships between the characteristics of EMI in the low-frequency and high-frequency bands and speed operating conditions, forming a parameterized analysis framework for common-mode excitation sources covering the entire frequency band. This framework allows engineers to predict the EMI spectrum distribution at different speeds through analytical calculations without conducting experiments at every speed point, significantly reducing the workload and cost of electromagnetic compatibility (EMC) testing. It provides an efficient theoretical tool for optimizing filter parameters and designing EMC for motor drive systems. Attached Figure Description

[0020] Figure 1 This is the inverter topology diagram for a three-phase two-level voltage source permanent magnet synchronous motor system; Figure 2 This represents the relationship between the magnitude of the driver's output voltage vector and its rotational speed at different rotational speeds in a stationary coordinate system. Figure 3 For the three-phase ground of the motor system within one switching cycle O Output voltage waveform of the point; Figure 4 This is a schematic diagram of the differential and common-mode equivalent circuit of a motor system provided in an embodiment of the present invention; Figure 5 The embodiment of the present invention provides a working condition considering rotational speed (back electromotive force). E A schematic diagram of the transient equivalent circuit of a single-phase switch action in a motor system. Figure 6 This is a diagram illustrating the influence of operating potential on transient step amplitude provided in an embodiment of the present invention. Figure 7 This is a transient time-domain waveform diagram of a common-mode excitation source for conducted electromagnetic interference under switching action provided in an embodiment of the present invention. Figure 8 A comparison of the steady-state and transient frequency domain waveforms of the conducted electromagnetic interference common-mode excitation source provided in the embodiments of the present invention; Figure 9 Frequency domain waveforms of the common-mode excitation source of conducted electromagnetic interference under different rotational speed states provided in embodiments of the present invention; Figure 10The waveforms of the common-mode excitation source of conducted electromagnetic interference under different rotational speeds in the experiment are shown in the frequency domain. Detailed Implementation

[0021] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0022] The purpose of this invention is to address the shortcomings of existing technologies by providing a method, apparatus, and readable medium for analyzing common-mode excitation sources of conducted electromagnetic interference in motor systems.

[0023] Example 1 A method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system includes the following steps: S1: Based on the vector control equations of the motor system, determine the correspondence between the amplitude and frequency of the driver output voltage and the motor speed; S2: Establish the differential and common-mode equivalent circuit of the motor system, and combine the switching pulse sequence under the pulse width modulation strategy to obtain the common-mode excitation source of conducted electromagnetic interference within a switching cycle. Perform Fourier transform on the common-mode excitation source to obtain the steady-state time-frequency domain model of the common-mode excitation source. S3: Based on the steady-state time-frequency domain model of the common-mode excitation source of conducted electromagnetic interference, the high-frequency ringing effect caused by the transient characteristics of power switch operation is considered. Combined with the stator winding voltage equation of the motor, the transient equivalent circuit of single-phase switch operation of the motor system considering the speed condition is obtained. S4: Combine the transient equivalent circuit to establish a transient time-frequency domain model of the common-mode excitation source; S5: Perform a Fourier transform on the transient time-frequency domain model of the common-mode excitation source to obtain the spectrum expression of the common-mode excitation source; S6: Based on the common-mode excitation source spectrum expression, establish the mapping relationship between the transient jump amplitude of the common-mode excitation source spectrum expression and the amplitude of high-frequency conducted electromagnetic interference, and determine the influence law of speed condition on high-frequency conducted electromagnetic interference.

[0024] In this embodiment, the motor system in step S1 is a three-phase two-level voltage source permanent magnet synchronous motor system. The inverter topology of a three-phase two-level voltage source permanent magnet synchronous motor system in the prior art is as follows: Figure 1 As shown.

[0025] The mathematical model for the stator voltage and electromagnetic torque of a permanent magnet synchronous motor system in a synchronous rotating coordinate system is as follows: (1) (2) In the formula, u d , u q These are the stator voltages. d - q Axial components, i d , i q These are the stator currents. d - q Axial components, R s For stator resistance, L d , L q They are respectively d - q Shaft inductance component. For surface-mounted three-phase permanent magnet synchronous motors. L d ≈ L q , T e For electromagnetic torque, ψ m It is a permanent magnet flux linkage. ω e The rotor's electric angular velocity, P This represents the number of pole pairs in a permanent magnet synchronous motor.

[0026] In this embodiment, the vector control equation in step S1 adopts i d =0 vector control strategy. i d =0 vector control strategy not only has the advantage of simple control algorithm, but also can simultaneously achieve maximum torque-to-current ratio control and obtain maximum linear control torque. Permanent magnet synchronous motor systems typically employ this strategy. i d =0 vector control strategy.

[0027] exist i d Under the condition that = 0, the relationship between the driver output voltage and the motor speed is: , (3) Transform equation (3) to a static state α - β In a coordinate system, the mathematical equations for the voltage and rotational speed output by the driver are as follows: (4) According to equation (4) in the natural coordinate system, the mathematical equation for the output phase voltage of the driver is: (5) In the formula, R For stator resistance, L For stator equivalent inductance, ω e The rotor's electric angular velocity, θ e The rotor electrical angle is given.

[0028] According to equation (5), the phase voltage of the three-phase winding can be written in a unified form as follows: (6) Based on the motor voltage equations (4) and (6), it can be seen that to control the rotational speed of the system, the amplitude and frequency of the driver's output voltage must be controlled. To fully utilize the driver's power-to-volume ratio, the output voltage at rated speed is the driver's maximum output voltage. For example... Figure 2 As shown, this illustrates the relationship between the driver output voltage vector and rotational speed in the complex plane coordinate system.

[0029] Figure 2 Analysis shows that rotational speed has a significant impact on the output voltage amplitude. Therefore, this invention studies the effect of rotational speed on the common-mode excitation source of conducted electromagnetic interference, based on the influence of rotational speed on the output voltage amplitude.

[0030] In this embodiment, the pulse width modulation strategy in step S2 is SVPWM (Space Vector Pulse Width Modulation); according to the modulation principle of SVPWM, the duration of action of the two effective vectors and two zero vectors in one switching cycle can be calculated as follows: (7) In the formula, d m , d n These are the duty cycles of the two effective vectors. d 0、 d 7 is the zero vector duty cycle. U out For the output voltage vector, U dc This is the DC bus voltage. k out It is the sector number where the reference vector is located. The angle between the output voltage vector and the principal vector. is the modulation coefficient.

[0031] like Figure 3As shown, based on SVPWM space vector pulse width modulation and considering the ringing effect caused by inverter parasitic parameters at the switching moment, taking sector I as an example, the three-phase grounding at this time is obtained. O Output voltage waveform at the point.

[0032] In this embodiment, the motor system is modeled as an inductive load, taking into account inverter parasitic parameters and cable insulation parameters. In step S2, the differential and common-mode equivalent circuit of the motor system is as follows: Figure 4 As shown, it includes the following circuit elements: stator winding, three-phase output voltage. u A , u B , u C DC bus voltage U dc DC side neutral point O Midpoint of three-phase load of motor N .

[0033] The switching action in the common-mode equivalent circuit is the same as that in the differential-mode equivalent circuit. Based on the definition of the common-mode excitation source of conducted electromagnetic interference, the three-phase grounding parameters of the inverter are obtained. O The output voltage equation of the point: (8) In the formula, u cm It serves as a common-mode excitation source for conducting electromagnetic interference in motor systems.

[0034] Adding the three equations above and applying the three-phase balance of the motor, we obtain the common-mode excitation source of conducted electromagnetic interference. u cm for: (9) According to equation (9) and Figure 3 It can be seen that the frequency and amplitude of the common-mode excitation source of conducted electromagnetic interference are related to the switch arrangement sequence (steady state) and the dumbbell oscillation (transient state) of the switch action. According to equation (9) and Figure 3 The SVPWM switching sequence and the common-mode excitation source of conducted electromagnetic interference in one switching cycle are: (10) In the formula, [ t 1, t 2, t 3, t 4, t 5, t 6,]=[T d 0, T( d 0+ d m), T( d 0+ d m + d n T(0.5+) d 7), T(0.5+ d 7+ d n ), T(1- d 0)], T is one switching cycle.

[0035] The common-mode excitation source of conducted electromagnetic interference (EMI) is related to the carrier frequency and the output frequency. A double Fourier transform is used to model the EMI common-mode excitation source in the frequency domain, yielding a steady-state time-frequency domain model. The EMI common-mode excitation source is a periodic function of the high-frequency carrier and the low-frequency fundamental wave, and it is piecewise smooth within one switching cycle. That is, the EMI common-mode excitation source satisfies the Fourier expansion condition. Performing a Fourier expansion using trigonometric functions, the mathematical expression of the steady-state time-frequency domain model is obtained as follows: (11) in, (12) In step S3, based on the steady-state time-frequency domain model of the common-mode excitation source of conducted electromagnetic interference, the high-frequency ringing effect caused by the transient characteristics of the power switch operation is considered. Simultaneously, combined with the stator winding voltage equation of the motor, the result considering the speed operating condition (back electromotive force) is obtained. E The transient equivalent circuit of single-phase switch operation of the motor system is as follows: Figure 5 As shown, the back electromotive force affected by the rotational speed condition also exists in the resonant circuit at this time.

[0036] like Figure 5 As shown, the transient equivalent circuit includes the following circuit elements: DC bus voltage U dc Parasitic resistance of switching device on / off circuit R Loop Stray inductance L Loo and parasitic capacitance C Loop Equivalent resistance of motor windings R and equivalent inductance L 1. Motor winding end capacitance to ground C g1 Neutral point to ground capacitance C g2 and the back electromotive force of the motor stator winding E ; Among them, the back electromotive force of the motor stator winding E The expression is , ω e The rotor's electric angular velocity, θ e Rotor electrical angle; back electromotive force E The amplitude is related to the operating speed.

[0037] In step S4, during the switching operation, stray inductance and junction capacitance existing in the differential and common-mode circuits are generated. LC Series resonance results in a high-frequency ringing effect. The complex frequency domain expression for the common-mode excitation source of conducted electromagnetic interference is as follows: (13) As can be seen from equation (13), the instant of the switching action can be regarded as a second-order damped oscillation process, and its resonant frequency is f for: (14) The high-frequency resonant frequency is determined by the parasitic parameters of the switching devices in the main circuit of the driver, the stray inductance, and the insulation parameters in the motor system. Since the resonant frequency reaches MHz, it will induce high-frequency resonance of the common-mode excitation source of conducted electromagnetic interference, which will greatly increase the amplitude of its high-frequency range (1MHz-30MHz).

[0038] Therefore, the transient characteristics of the common-mode electromagnetic interference excitation source need to be considered at the moment of switching action. Combining equation (10), the transient time-frequency domain model of the common-mode excitation source is obtained as follows: (15) In the formula, ω n , ω d , β、ζ The parasitic parameters of the differential common-mode circuit (including power devices and motor common-mode circuits) include the ringing angular frequency, sinusoidal decay oscillation frequency, oscillation phase, and damping ratio, with the resonant frequency mainly near the resonant frequency formed by the junction capacitance and stray inductance of the switching devices. e ( t - t i The value is the equivalent electromotive force under operating conditions, and the motor speed at that time is given by the value. n Decision, that is .at this time ω n , ω d , β、ζ The following conditions must be met: (16) In this embodiment, offline impedance testing was performed to obtain... R Loop =0.15Ω, L Loop =4.59μH, C Loop =3.55nF, R =47Ω, L =2.64H, C g1 =49.8nF, C g2 =122nF, the transient time-frequency domain model parameters of the common-mode excitation source of conducted electromagnetic interference are obtained according to equations (15) and (16), as shown in Table 1.

[0039] Table 1 Transient time-frequency domain model parameters of common-mode excitation source of conducted electromagnetic interference Unlike traditional second-order damped systems, the resonant circuit in this case contains a back electromotive force. E With single-phase circuit input voltage U dc Taking / 2=50V as an example, its effect on the transient step amplitude is as follows: Figure 6 As shown.

[0040] back electromotive force E This causes the step amplitude to exceed twice the input voltage, making Figure 5 The amplitude of the excitation source in the circuit increases due to the circuit's resonant frequency. f In the MHz band, rotational speed will therefore affect the high-frequency resonance amplitude of conducted electromagnetic interference.

[0041] like Figure 7 As shown, based on the steady-state time-domain waveform of the common-mode excitation source of conducted electromagnetic interference, the transient time-domain waveform of the motor system under vector control during switching action is presented.

[0042] from Figure 7 The transient time-domain waveform diagram shows that the waveform of the common-mode excitation source of conducted electromagnetic interference consists of a steady-state stepped waveform and a transient sinusoidal decaying oscillation function, that is, the transient model is established based on the steady-state model. In order to perform spectral analysis on the low-frequency band (below 150kHz) and high-frequency band (1MHz-30MHz) of the common-mode excitation source of conducted electromagnetic interference, Fourier transform is used to obtain the Fourier coefficients of equation (15). a n The expression is: (17) In the formula, T One switching cycle Td 0 represents the duration of the zero vector within the switching cycle. E The operating condition is the equivalent potential. α 1. α The expression for 2 is: (18) Based on the above analysis, the spectrum expression for the common-mode excitation source of conducted electromagnetic interference can be obtained as follows: (19) In the formula, f 0 represents the switching frequency, i.e. 。

[0043] Based on mathematical analysis of steady-state and transient models of electromagnetic interference excitation sources, the influence of conducted electromagnetic interference is extended from the low-frequency band of hundreds of kHz to the high-frequency band of MHz. Combining equations (13), (14), and (19), as... Figure 8 As shown in the figure, this embodiment provides a comparison of the steady-state frequency domain waveform and the transient frequency domain waveform of the common-mode excitation source of conducted electromagnetic interference. It can be found that the ringing effect caused by the parasitic parameters in the switching device increases the amplitude of the electromagnetic interference excitation source spectrum in the high-frequency range (1MHz-30MHz), thereby forming an amplitude spike.

[0044] like Figure 8 As shown, to more clearly demonstrate the influence of rotational speed on different frequency bands of the conducted electromagnetic excitation source, the spectrum is divided into frequency bands. These are divided into a low-frequency band (below 150kHz) and a high-frequency band (1MHz-30MHz). The intensity of conducted electromagnetic interference in the low-frequency band is related to the modulation strategy and the steady-state transition time interval of the electromagnetic interference excitation source, while the intensity of conducted electromagnetic interference in the high-frequency band is related to the rotational speed and the transient transition amplitude of the electromagnetic interference excitation source. Based on the Fourier transform, to reflect the effectiveness of the amplitude change, a frequency band (below 150kHz) is selected... f c 3 f c and 5 f c We will conduct pattern analysis at this point. f c The switching frequency is used; the ringing frequency in the high-frequency range (1MHz-30MHz) is selected for pattern analysis.

[0045] The influence of rotational speed on different frequency bands of electromagnetic interference excitation sources is as follows: Figure 9 As shown, at the switching frequency f cThe amplitude of the electromagnetic interference excitation source at that location is negatively correlated with the rotational speed, meaning it decreases as the rotational speed increases; 3 f c The amplitude of the electromagnetic interference excitation source first decreases and then increases with increasing rotational speed; 5 f c As the rotational speed increases, the amplitude of the electromagnetic interference excitation source first decreases, then increases, and then decreases again. With the increase of rotational speed, the amplitude of the high-frequency conducted electromagnetic interference common-mode excitation source increases, that is, the spectral amplitude of the conducted electromagnetic interference common-mode excitation source in the range of 1MHz-30MHz increases with the increase of rotational speed.

[0046] In this embodiment, the power device of the electric drive controller is a Mitsubishi PSS75SA2F6. The parasitic parameters of the power device are obtained through the datasheet and measurement methods. The device parameters are shown in Table 2.

[0047] Table 2 Device Parameter Table rotational speed n Equivalent back electromotive force under operating conditions E The effective value correspondence is shown in Table 3, that is, as the rotational speed increases, the equivalent potential... E The effective value increases.

[0048] Table 3. Effective values ​​of equivalent electromotive force E under different speed conditions The three-phase voltage signal output from the inverter was acquired using a high-frequency differential voltage probe (YOKOGAWA-701938, 100MHz bandwidth), and the waveform was observed and recorded using a high-speed digital oscilloscope (YOKOGAWA-DL850E). The frequency domain waveforms of the conducted electromagnetic interference common-mode excitation source at different speeds are shown below. Figure 10 As shown, it can be observed that as the rotational speed increases, the low-frequency range (below 150kHz, especially...) that is of interest in this embodiment... f c 3 f c 5 f c And the amplitude variation law of common-mode excitation sources of conducted electromagnetic interference in the high-frequency band (1MHz-30MHz) and Figure 9 Maintain consistency.

[0049] An electronic device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system.

[0050] A computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system.

[0051] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system, characterized in that, Includes the following steps, S1: Based on the vector control equations of the motor system, determine the correspondence between the amplitude and frequency of the driver output voltage and the motor speed; S2: Establish the differential and common-mode equivalent circuit of the motor system, and combine the switching pulse sequence under the pulse width modulation strategy to obtain the common-mode excitation source of conducted electromagnetic interference within a switching cycle. Perform Fourier transform on the common-mode excitation source to obtain the steady-state time-frequency domain model of the common-mode excitation source. S3: Based on the steady-state time-frequency domain model of the common-mode excitation source of conducted electromagnetic interference, considering the high-frequency ringing effect caused by the transient characteristics of power switch operation, and combined with the stator winding voltage equation of the motor, the transient equivalent circuit of single-phase switch operation of the motor system considering the speed condition is obtained. S4: Combine the transient equivalent circuit to establish a transient time-frequency domain model of the common-mode excitation source; S5: Perform a Fourier transform on the transient time-frequency domain model of the common-mode excitation source to obtain the spectrum expression of the common-mode excitation source; S6: Based on the common-mode excitation source spectrum expression, establish the mapping relationship between the transient jump amplitude of the common-mode excitation source spectrum expression and the amplitude of high-frequency conducted electromagnetic interference, and determine the influence law of speed condition on high-frequency conducted electromagnetic interference.

2. The method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system according to claim 1, characterized in that, The motor system is a permanent magnet synchronous motor system, and the vector control equation adopts... i d =0 vector control strategy; In step S1, i d Under the condition that = 0, the relationship between the driver output voltage and the motor speed is: ； In the formula, u d , u q These are the stator voltages. d - q Axial components, i d , i q These are the stator currents. d - q Axial components, R s For stator resistance, L d , L q They are respectively d - q Shaft inductance component, ω e This refers to the rotor's electrical angular velocity; for surface-mounted three-phase permanent magnet synchronous motors L d ≈ L q , ψ m It is a permanent magnet flux linkage; Transform the above equation to a static state. α-β In a coordinate system, the mathematical equations for the voltage and rotational speed output by the driver are as follows: ； According to the above equation in the natural coordinate system, the mathematical equation for the output phase voltage of the driver is: ； In the formula, R For stator resistance, L For stator equivalent inductance, ω e The rotor's electric angular velocity, θ e The rotor electrical angle; Based on the above formula, the phase voltages of the three-phase windings can be written in a unified form as follows: 。 3. The method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system according to claim 2, characterized in that, The pulse width modulation strategy is SVPWM (Space Vector Pulse Width Modulation). In step S2, according to the modulation principle of space vector pulse width modulation, the duration of action of the two effective vectors and the two zero vectors in one switching cycle is: ； In the formula, d m , d n These are the duty cycles of the two effective vectors. d 0、 d 7 is the zero vector duty cycle. U out For the output voltage vector, U dc This is the DC bus voltage. k out It is the sector number where the reference vector is located. The angle between the output voltage vector and the principal vector. is the modulation coefficient.

4. The method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system according to claim 3, characterized in that, In step S2, the differential and common-mode equivalent circuit of the motor system includes the following circuit elements: Stator winding three-phase output voltage u A , u B , u C DC bus voltage U dc DC side neutral point O Midpoint of three-phase load of motor N , The switching action in the common-mode equivalent circuit is the same as that in the differential-mode equivalent circuit; based on the definition of the common-mode excitation source of conducted electromagnetic interference, the three-phase grounding of the inverter is obtained. O The output voltage equation of the point: ； In the formula, u cm It serves as a common-mode excitation source for conducting electromagnetic interference in motor systems. Adding the three equations above and applying the three-phase balance of the motor, we obtain the common-mode excitation source of conducted electromagnetic interference. u cm for: ； The common-mode excitation source of conducted electromagnetic interference in one switching cycle is: ； In the formula, [ t 1, t 2, t 3, t 4, t 5, t 6,]=[T d 0, T( d 0+ d m ), T( d 0+ d m + d n T(0.5+) d 7), T(0.5+ d 7+ d n ), T(1- d 0)], T is one switching cycle, A double Fourier transform is used to model the common-mode excitation source of conducted electromagnetic interference in the frequency domain, resulting in a steady-state time-frequency domain model. The common-mode excitation source of conducted electromagnetic interference is a periodic function of the high-frequency carrier and the low-frequency fundamental wave, and it is piecewise smooth within one switching cycle. That is, the common-mode excitation source of conducted electromagnetic interference satisfies the Fourier expansion condition. A Fourier expansion using trigonometric functions yields the mathematical expression of the steady-state time-frequency domain model: ； in, 。 5. The method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system according to claim 4, characterized in that, In step S3, the transient equivalent circuit includes the following circuit elements: DC bus voltage U dc Parasitic resistance of switching device on / off circuit R Loop Stray inductance L Loo and parasitic capacitance C Loop Equivalent resistance of motor windings R and equivalent inductance L 1. Motor winding end capacitance to ground C g1 Neutral point to ground capacitance C g2 and the back electromotive force of the motor stator winding E ; Among them, the back electromotive force of the motor stator winding E The expression is , ω e The rotor's electric angular velocity, ψ m It is a permanent magnet flux linkage. θ e The rotor electrical angle is denoted by E; the amplitude of the back electromotive force E is proportional to the motor speed, causing the amplitude of the total excitation source in the differential-common-mode equivalent circuit to increase with increasing speed.

6. The method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system according to claim 5, characterized in that, In step S4, During the switching process, the complex frequency domain expression of the common-mode excitation source of conducted electromagnetic interference is: ； As can be seen from the above equation, the instant of switching action can be regarded as a second-order damped oscillation process, and its resonant frequency is... f for: ； The transient time-frequency domain model of the common-mode excitation source is as follows: ； In the formula, ω n , ω d , β、ζ The parasitic parameters of the differential common-mode circuit are the resonant angular frequency, sinusoidal decaying oscillation frequency, oscillation phase, and damping ratio. e ( t - t i The value is the equivalent electromotive force under operating conditions, and the motor speed at that time is given by the value. n Decision, that is ;at this time ω n , ω d , β、ζ The following conditions must be met: 。 7. The method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system according to claim 6, characterized in that, In step S5, The common-mode excitation source spectrum expression is: ； In the formula, f 0 represents the switching frequency, i.e. , a n For the common-mode excitation source Fourier coefficients, Fourier coefficients a n The expression is: ； In the formula, T One switching cycle Td 0 represents the duration of the zero vector within the switching cycle. E The operating condition is the equivalent potential. α 1. α The expression for 2 is: 。 8. The method for analyzing common-mode excitation sources of conducted electromagnetic interference in a motor system according to claim 7, characterized in that, In step S6, The spectrum of the electromagnetic excitation source is divided into frequency bands, namely low-frequency band and high-frequency band. In the low-frequency band, [the following is selected / selected]... f c 3 f c and 5 f c We will conduct pattern analysis at this point. f c The switching frequency is used; the ringing frequency in the high-frequency band is selected for pattern analysis.

9. An electronic device, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method according to any one of claims 1-8.

10. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the steps of the method according to any one of claims 1-8.

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