Behavior-level modeling and EMI analysis method for all-in-one motor driving system

Abstract

The invention relates to the technical field of motor driving, and particularly discloses an all-in-one motor driving system behavior-level modeling and EMI analysis method which is different from a modeling mode depending on physical structure parameters, the system is regarded as a black box, a vector fitting algorithm is introduced to carry out high-precision approximation on complex impedance frequency characteristics of a passive side, and an EMI analysis result is obtained. The impedance of the all-in-one motor is fitted into a rational function composed of poles and residuals, equivalence is performed on the system based on the rational function, and a system equivalent circuit is established, so that the applicability and simulation efficiency of the model in circuit simulation are remarkably improved. The invention aims to realize accurate prediction of conducted electromagnetic interference by constructing a system-level simulation model containing an accurate interference source and broadband impedance characteristics, and finally verifies the effectiveness of the modeling method through experimental tests, thereby providing an efficient and practical method for solving the complex EMC problem of the electric vehicle.

Description

Technical Field

[0001] This invention relates to the field of motor drive technology, and in particular to a method for behavioral-level modeling and EMI analysis of all-in-one motor drive systems. Background Technology

[0002] With the rapid development of power electronics technology, all-in-one motor drive systems have been widely used in industrial manufacturing, medical, public transportation, aerospace, solar power generation, wind power generation, electric vehicles, and other fields, playing an important role in automated production and even economic restructuring. However, electromagnetic interference (EMI) issues within all-in-one motor drive systems have hindered their promotion and application. Therefore, constructing an accurate EMI model for all-in-one motor drive systems is crucial for optimizing electromagnetic compatibility (EMC) design.

[0003] While time-domain modeling methods can accurately simulate switching states, their simulation times are extremely long and they often face convergence problems, making them unsuitable for the rapid prediction needs of complex systems. In contrast, frequency-domain modeling techniques have attracted much attention due to their efficiency, but they still face many challenges in handling nonlinear characteristics, high-frequency oscillations, and mixed-mode noise.

[0004] To address the aforementioned challenges, while existing high-frequency equivalent circuit modeling and traditional black-box modeling methods have solved the EMI prediction problem to some extent, simple resistor, inductor, and capacitor networks struggle to maintain high accuracy over a wide frequency band due to the complex impedance characteristics resulting from the high integration of all-in-one motor drive systems. Summary of the Invention

[0005] This invention provides a behavioral-level modeling and EMI analysis method for all-in-one motor drive systems, which solves the technical problem that it is difficult to predict conducted electromagnetic interference in all-in-one motor drive systems and it is difficult to maintain high accuracy over a wide frequency band.

[0006] To address the above technical problems, this invention provides a behavioral-level modeling method for an all-in-one motor drive system, comprising:

[0007] The conducted EMI test platform for the all-in-one motor drive system is considered as a linear time-invariant black box system. Based on Thevenin's theorem, a corresponding three-terminal Thevenin equivalent circuit is constructed. The all-in-one motor drive system conducted EMI test platform includes a high-voltage DC input power supply, a shielded box, the all-in-one motor drive system, and an EMI receiver. The all-in-one motor drive system includes an inverter and an all-in-one motor. The three terminals refer to the overall impedance of the all-in-one motor drive system. The impedance of the high-voltage DC input power supply and the impedance of the all-in-one motor ;

[0008] Impedance is obtained through testing. ;

[0009] Using a vector fitting algorithm to measure impedance It is fitted to a rational function consisting of poles and residues;

[0010] The all-in-one motor drive system is equivalently represented based on the rational function to obtain the system equivalent circuit.

[0011] Furthermore, the rational function is expressed as: ,in For the residue of order n, Let be the nth order pole, d be a constant term, h be a first-order term, and s be a complex frequency.

[0012] Furthermore, impedance is obtained through testing. include:

[0013] When the all-in-one motor drive system is in standby mode, the overall impedance of the all-in-one motor drive system is measured using a high-voltage isolation plate and a vector network analyzer. ;

[0014] Subsequently, the connection between the all-in-one motor drive system and the shielded box was disconnected and the power was turned off. The input power impedance was then measured again at the positive and negative terminals of the shielded box using a vector network analyzer. ;

[0015] Based on the overall impedance of the all-in-one motor drive system and input power supply impedance Calculate impedance .

[0016] Furthermore, based on the overall impedance of the all-in-one motor drive system and input power supply impedance Calculate impedance Specifically, it includes:

[0017] Calculate the admittance matrix of the all-in-one motor drive system. ;

[0018] Admittance matrix Convert to impedance form to obtain impedance .

[0019] Furthermore, the all-in-one motor drive system is equivalently represented based on the rational function, including:

[0020] The constant term and linear term in the rational function are equivalent to a constant term equivalent circuit consisting of a resistor and an inductor connected in series.

[0021] The real poles and residues in the rational function are equivalent to real terms of a parallel resistor and inductor in an equivalent sub-circuit.

[0022] The poles and residues of the rational function that are conjugate complex pairs are equivalent to a second-order sub-circuit containing resistors, inductors, and capacitors.

[0023] By connecting the three types of equivalent sub-circuits in series, the system equivalent circuit of the all-in-one motor drive system is obtained.

[0024] Furthermore, the equivalent sub-circuit of the constant term includes a series resistor. and inductor The equivalent relationship is ;

[0025] The equivalent sub-circuit for the real terms includes capacitors connected in parallel. ,resistance The equivalent relationship is .

[0026] Furthermore, the second-order sub-circuit includes resistors connected in parallel. ,capacitance and a resistor-inductor series branch, wherein the resistor-inductor series branch includes resistors connected in series. and inductor The equivalent relationship is:

[0027] ,

[0028] Among them, the parameters P, M, and K, which are defined to simplify the formula form, are:

[0029] .

[0030] Furthermore, the impedance Fit to rational function At that time, its parameters , , d, and h are calculated using the following steps:

[0031] Introduce a helper function ,Will and Multiply to get ;

[0032] Assumption and Since the poles are the same, the approximate determinant is:

[0033] ;

[0034] Linearizing the approximate determinant, we obtain the equation:

[0035] ,

[0036] in, , Represent the initial poles and auxiliary functions The residue;

[0037] By setting a set of initial poles Solving the above equation yields The coefficient; The zero point becomes the new pole in the next iteration; after iteration, the poles converge, thus determining the final pole that meets the required accuracy. , , and .

[0038] The present invention also provides an EMI analysis method for an all-in-one motor drive system, the key of which is to perform EMI simulation analysis based on the system equivalent circuit obtained by the behavioral-level modeling method of the all-in-one motor drive system.

[0039] This invention provides a behavioral-level modeling and EMI analysis method for all-in-one motor drive systems, proposing a behavioral-level modeling technique. Unlike modeling methods that rely on physical structural parameters, this invention treats the system as a black box and introduces a vector fitting algorithm to accurately approximate the complex impedance-frequency characteristics of the passive side, thus accurately representing the impedance of the all-in-one motor. A rational function consisting of poles and residues is fitted to the system, and an equivalent circuit is established based on this rational function, significantly improving the applicability and efficiency of the model in circuit simulation. This invention aims to accurately predict conducted electromagnetic interference in the 150kHz to 30MHz frequency band by constructing a system-level simulation model that includes precise interference sources and wide-bandwidth impedance characteristics. Finally, experimental testing verifies the effectiveness of this modeling method, providing an efficient and practical approach to solving complex EMC problems in electric vehicles. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the conducted EMI test platform for the all-in-one motor drive system provided in this embodiment of the invention;

[0041] Figure 2 This is a common-mode and differential-mode EMI path diagram of the all-in-one motor drive system provided in this embodiment of the invention;

[0042] Figure 3 This is an electromagnetic compatibility model diagram of the all-in-one motor drive system provided in the embodiments of the present invention;

[0043] Figure 4 This is a circuit diagram of the equivalent sub-circuit of the constant term provided in an embodiment of the present invention;

[0044] Figure 5 This is a circuit diagram of the equivalent sub-circuit provided in the embodiments of the present invention when the poles and residues are real numbers;

[0045] Figure 6 This is a circuit diagram of the equivalent sub-circuit when the poles and residues are conjugate complex pairs, as provided in the embodiments of the present invention;

[0046] Figure 7 This is the overall equivalent circuit of the all-in-one motor drive system provided in the embodiments of the present invention;

[0047] Figure 8 This is a schematic diagram of the parameter extraction experimental platform provided in an embodiment of the present invention;

[0048] Figure 9 This is the embodiment of the present invention that provides the following: The result of the impedance amplitude after performing the vector fitting algorithm. Figure 9 In the diagram, (a), (b), (c), and (d) represent the impedances, respectively. , , , The amplitude;

[0049] Figure 10 This is the embodiment of the present invention that provides the following: The impedance phase result after performing a vector fitting algorithm Figure 10 In the diagram, (a), (b), (c), and (d) represent the impedances, respectively. , , , The phase;

[0050] Figure 11 This refers to noise current data measured by the radio frequency current probe provided in this embodiment of the invention.

[0051] Figure 12 This is an LTspice simulation schematic diagram of the all-in-one motor drive system provided in this embodiment of the invention;

[0052] Figure 13 This is a comparison chart of the simulated EMI spectrum and the actual measurement results provided in the embodiments of the present invention. Detailed Implementation

[0053] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0054] The all-in-one motor drive system is a crucial component of modern new energy vehicles. According to GB / T18655-2018 "Limits and Measurement Methods for Radio Interference Characteristics of Vehicles, Ships and Internal Combustion Engines for the Protection of Onboard Receivers" and GB / T18387-2017 "Limits and Measurement Methods for Electromagnetic Field Emission Intensity of Electric Vehicles," the system-level conducted EMI test platform consists of a high-voltage DC power supply, a shielded box (using a linear impedance stabilization network LISN, where -N represents the negative terminal and -P represents the positive terminal), high and low voltage DC cables, a load, the all-in-one motor drive system, and an EMI receiver. The all-in-one motor drive system includes an inverter and an all-in-one motor. Figure 1 A schematic diagram of a conducted EMI test platform for an all-in-one motor drive system is presented.

[0055] In an all-in-one motor drive system, the main interference originates from the inverter. The IGBTs in the inverter generate high-frequency interference during high-speed switching, and this interference propagates through the common-mode and differential-mode coupling paths in the all-in-one motor drive system. The common-mode and differential-mode EMI paths in the all-in-one motor drive system are as follows: Figure 2 As shown in the red and blue paths, the common-mode EMI coupling path of the multi-function motor drive system includes the capacitance of the motor stator winding to the housing, the cable shielding layer, LISN, and grounding circuit. The differential-mode EMI coupling path includes the differential-mode impedance of components such as LISN, inverter bridge, and motor.

[0056] This embodiment proposes using a vector fitting algorithm to fit the measured impedance of the multi-function motor drive system (data varying with frequency) into a rational function consisting of poles and residues. According to circuit network theory, a single-input, single-output linear Nth-order circuit can be represented by a network function:

[0057] (1)

[0058] in, , Let be the coefficients of each order term of the transfer function, and s be the complex frequency.

[0059] To transform the network function into an RLC equivalent circuit, equation (1) is rewritten in pole and residue form, i.e.:

[0060] (2)

[0061] in For the residue of order n, Let be the nth order pole, d be a constant term, h be a first-order term, and s be a complex frequency.

[0062] Because of directly solving the poles It is a nonlinear problem, and the vector fitting algorithm introduces an auxiliary function. ,Will and Multiply to get Assuming and Since the poles are the same, the approximate determinant can be obtained as:

[0063] (3)

[0064] The linearized equation (3) is equal to its approximate expression:

[0065] (4)

[0066] in, , Represent the initial poles and auxiliary functions The residue;

[0067] By setting a set of initial poles Solving the above equation yields The coefficient. The zero point becomes the new pole in the next iteration. After several iterations, the poles converge, thus determining the final pole that meets the required accuracy. , , and .

[0068] This embodiment also proposes a behavioral-level modeling method based on Thevenin's Theorem for constructing an electromagnetic compatibility model of an all-in-one motor drive system. Its equivalent model is as follows: Figure 3 As shown, it includes an integrated motor and an equivalent impedance circuit on the LISN side, as well as a positive and negative equivalent interference source model. This method divides the acquisition of model parameters into two stages: physical testing and data post-processing.

[0069] This modeling method treats the all-in-one motor drive system as a linear time-invariant (LTI) black box system, with its topology based on a three-terminal Thevenin equivalent circuit. To obtain the unknown parameters required for the model, testing is conducted in two independent states: static and dynamic.

[0070] 1) State A (Static):

[0071] To extract time-independent impedance parameters, the test was conducted under static, no-switching conditions with the all-in-one motor driver. First, with the system in standby mode, the overall impedance of the all-in-one motor drive system was measured using a high-voltage isolation board and a vector network analyzer. Subsequently, the connection between the multi-function motor and the LISN was disconnected and the power was turned off. The input power impedance was then measured again at the positive and negative terminals of the LISN using a vector network analyzer. .

[0072] 2) State B (Dynamic):

[0073] To extract the equivalent noise source, the test was conducted under normal operating conditions of the all-in-one motor. An RF current probe was clipped to the positive and negative input terminals of the all-in-one motor, and the motor controller maintained the motor at 1000 rpm. The noise current was then obtained by measuring the current signal sensed by the RF current probe using an oscilloscope. .

[0074] After the test is completed, the impedance measured in state A is... and input power supply impedance By converting each value to admittance and subtracting them to eliminate the influence of the power network, the admittance matrix of the multi-functional motor can be obtained. The calculation is as follows:

[0075] (5)

[0076] Then Converting to impedance form, we obtain the impedance of the multi-in-one resistor:

[0077] (6)

[0078] exist After obtaining the data, it is converted into a format suitable for circuit simulation using the vector fitting algorithm described above.

[0079] The time-domain positive and negative currents measured in state B. and It is converted into a frequency domain current vector through a fast Fourier transform. Based on Kirchhoff's voltage law, the frequency domain voltage source vector can be further derived. :

[0080] ,

[0081] When the known equation (2) , , and When the parameters are equal, the equivalent circuit corresponding to the network function can be solved using these parameters.

[0082] because and Since it is a constant term, it can be represented by a resistor. and inductor Perform series equivalent circuitry, with constant term equivalent sub-circuit as follows: Figure 4 As shown, the equivalent relationship is: .

[0083] When the poles and residues are real numbers, a capacitor can be used. ,resistance Equivalent circuits in parallel configurations, with corresponding real-valued equivalent sub-circuits as follows: Figure 5 As shown.

[0084] Substituting the circuit impedance into equation (2) yields:

[0085] (8)

[0086] According to equation (8), we can solve for:

[0087] (9)

[0088] When the poles and residues are conjugate complex pairs, a set of conjugate complex pairs, when combined, corresponds to a second-order sub-circuit containing resistors, inductors, and capacitors; specifically, it includes parallel resistors. ,capacitance and a resistor-inductor series branch, wherein the resistor-inductor series branch includes resistors connected in series. and inductor , Figure 6 The corresponding second-order sub-circuit is given.

[0089] The circuit impedance expression is:

[0090] (10)

[0091] The equivalent circuit impedance expression is:

[0092] (11)

[0093] For equation (11) to be equal to equation (10), the following must be satisfied:

[0094] (12)

[0095] Solving equation (12) yields:

[0096] (13)

[0097] Among them, the parameters P, M, and K, which are defined to simplify the formula form, are:

[0098] (14)

[0099] In summary, the transfer function of equation (2) It can be divided into three fractions, each representing a type of equivalent circuit. Connecting all the sub-circuits in series yields the overall equivalent circuit, such as... Figure 7 As shown.

[0100] To accurately obtain the high-frequency impedance characteristics of an all-in-one motor drive system, this invention constructs as follows: Figure 8 The parameter extraction experimental platform shown can be used to obtain a 2×2 impedance matrix by connecting a vector network analyzer to the two SMA ports on the high-voltage isolation board. .

[0101] (15)

[0102] Figure 9 The result derived from equation (6) is given. The result of the impedance amplitude after performing the vector fitting algorithm. Figure 9 In the diagram, (a), (b), (c), and (d) represent the impedances, respectively. , , , The amplitude. Figure 10 The result derived from equation (6) is given. The impedance phase result after performing a vector fitting algorithm Figure 10 In the diagram, (a), (b), (c), and (d) represent the impedances, respectively. , , , The phase. By comparison Figure 9 , Figure 10 The original and fitted data show that the vector fitting algorithm is basically consistent in the 2~30MHz frequency band.

[0103] Figure 11 The noise current data obtained by the radio frequency current probe are presented, in which the positive interference current is significantly greater than that of the negative current.

[0104] To verify the accuracy of the equivalent model of the all-in-one motor drive system proposed in this invention, a conducted EMI test platform for the all-in-one motor drive system was built. The test scenario was conducted in a 3-meter anechoic chamber according to standard GB / T 18387-2017. The reference grounding plane of the test bench was made of 0.6mm galvanized steel plate, 900mm above the ground, with a distance of 250mm between grounding copper strips. The maximum output voltage of the high-voltage power supply in the anechoic chamber was 600V; in this test, a 550V output voltage was selected. The rated voltage of the tested motor was 630V, and the rated power was 220kW. Since this test focused on high-voltage characteristics, a low-voltage LISN was not connected; copper foil was used to wrap the low-voltage cable to reduce interference from the low-voltage cable during the test.

[0105] In terms of simulation, based on the complete system equivalent model extracted above, conducted EMI simulation analysis was performed using the circuit simulation software LTspice. Figure 12 The LTspice simulation schematic of the all-in-one motor drive system is presented. The time-domain current waveforms at both ends of the LISN are extracted, and the conducted EMI voltage is obtained through 50Ω standard resistors on both sides. The EMI voltage spectrum is then calculated. Finally, the simulated EMI spectrum is compared with actual measurement results to verify the model's accuracy. The comparison results are as follows: Figure 13 As shown.

[0106] By comparing experimental and simulation results, within the frequency band of 150kHz to 30MHz, the average conducted EMI of the equivalent model of the all-in-one motor drive system does not exceed 6dBµV, and the error is around 5dBµV in the 3 to 30MHz range. However, the error can reach as high as 15dBµV at some frequency points in the 150kHz to 3MHz range. In summary, within the frequency band range of standard GB / T 18387-2017, the measured and simulation results of the behavioral model of conducted EMI of the all-in-one motor are basically in agreement, indicating that the modeling method is correct and effective.

[0107] In summary, this invention proposes a behavioral-level modeling method based on a vector fitting algorithm to address the conducted electromagnetic interference (EMI) problem of multi-functional motor drive systems in new energy vehicles. By establishing a Thevenin equivalent circuit model and combining frequency domain impedance measurement with dynamic noise source extraction, efficient and accurate modeling of the system's conducted EMI characteristics is achieved. The vector fitting algorithm is used to fit the measured impedance data into a rational function form and further convert it into an equivalent circuit, significantly improving the model's applicability and simulation efficiency in circuit simulation. Experimental results show that the established model agrees well with the measured data in the 150kHz~30MHz frequency band, with errors controlled within 6dBµV at most frequency points, verifying the effectiveness and practicality of the modeling method.

[0108] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A behavioral-level modeling method for an all-in-one motor drive system, characterized in that, include: The conducted EMI test platform for the all-in-one motor drive system is considered as a linear time-invariant black box system. Based on Thevenin's theorem, a corresponding three-terminal Thevenin equivalent circuit is constructed. The all-in-one motor drive system conducted EMI test platform includes a high-voltage DC input power supply, a shielded box, the all-in-one motor drive system, and an EMI receiver. The all-in-one motor drive system includes an inverter and an all-in-one motor. The three terminals refer to the overall impedance of the all-in-one motor drive system. The impedance of the high-voltage DC input power supply and the impedance of the all-in-one motor ; Impedance is obtained through testing. ; Using a vector fitting algorithm to measure impedance It is fitted to a rational function consisting of poles and residues; The all-in-one motor drive system is equivalently represented based on the rational function to obtain the system equivalent circuit.

2. The behavioral-level modeling method for an all-in-one motor drive system according to claim 1, characterized in that: The rational function is expressed as: Where s is the complex frequency, For the residue of order n, Let be the nth order pole, d be a constant term, and h be a first-order term.

3. The behavioral-level modeling method for an all-in-one motor drive system according to claim 2, characterized in that, Impedance is obtained through testing. include: When the all-in-one motor drive system is in standby mode, the overall impedance of the all-in-one motor drive system is measured using a high-voltage isolation plate and a vector network analyzer. ; Subsequently, the connection between the all-in-one motor drive system and the shielded box was disconnected and the power was turned off. The input power impedance was then measured again at the positive and negative terminals of the shielded box using a vector network analyzer. ; Based on the overall impedance of the all-in-one motor drive system and input power supply impedance Calculate impedance .

4. The behavioral-level modeling method for an all-in-one motor drive system according to claim 3, characterized in that, Based on the overall impedance of the all-in-one motor drive system and input power supply impedance Calculate impedance Specifically, it includes: Calculate the admittance matrix of the all-in-one motor drive system. ; Admittance matrix Convert to impedance form to obtain impedance .

5. The behavioral-level modeling and analysis method for an all-in-one motor drive system according to claim 4, characterized in that, Equivalents of the all-in-one motor drive system based on the rational function include: The constant term and linear term in the rational function are equivalent to a constant term equivalent circuit consisting of a resistor and an inductor connected in series. The real poles and residues in the rational function are equivalent to real terms of a parallel resistor and inductor in an equivalent sub-circuit. The poles and residues of the rational function that are conjugate complex pairs are equivalent to a second-order sub-circuit containing resistors, inductors, and capacitors. By connecting the three types of equivalent sub-circuits in series, the system equivalent circuit of the all-in-one motor drive system is obtained.

6. The behavioral-level modeling method for an all-in-one motor drive system according to claim 5, characterized in that: The equivalent sub-circuit of the constant term includes resistors in series. and inductor The equivalent relationship is ; The equivalent sub-circuit for the real terms includes capacitors connected in parallel. ,resistance The equivalent relationship is .

7. The behavioral-level modeling method for an all-in-one motor drive system according to claim 6, characterized in that, The second-order sub-circuit includes resistors connected in parallel. ,capacitance and a resistor-inductor series branch, wherein the resistor-inductor series branch includes resistors connected in series. and inductor The equivalent relationship is: ， Among them, the parameters P, M, and K, which are defined to simplify the formula form, are: 。 8. The behavioral-level modeling method for an all-in-one motor drive system according to any one of claims 2 to 7, characterized in that, impedance Fit to rational function At that time, its parameters , , d, and h are calculated using the following steps: Introduce a helper function ,Will and Multiply to get ; Assumption and Since the poles are the same, the approximate determinant is: ； Linearizing the approximate determinant, we obtain the equation: ， in, , Represent the initial poles and auxiliary functions The residue; By setting a set of initial poles Solving the above equation yields The coefficient; The zero point becomes the new pole in the next iteration; after iteration, the poles converge, thus determining the final pole that meets the required accuracy. , , and .

9. An EMI analysis method for an all-in-one motor drive system, characterized in that, EMI simulation analysis is performed on the system equivalent circuit obtained by the behavioral-level modeling method of the all-in-one motor drive system according to any one of claims 1 to 8.

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