A method for constructing a general motor grounding current calculation model suitable for both time domain and wide frequency domain

Abstract

This invention relates to a method for constructing a universal grounding current calculation model for motors that is applicable to both the time domain and a wide frequency domain, belonging to the field of motor drive systems. The universal grounding circuit model of this invention has a simple structure, comprising five parts: bearings, stator windings, stator core, rotor, and internal parasitic coupling capacitance of the motor. The model establishes equivalent circuit models for each part based on the distribution of the actual physical components of the motor, and calculates the specific parameter values ​​of each circuit element using frequency response test results of the motor's common-mode impedance, differential-mode impedance, rotor-casing impedance, and impedance between the three-phase winding short-circuit point and the rotor. Compared to existing models, this invention features simple calculation, accurate prediction, consideration of common-mode and differential-mode effects, applicability to a wider frequency range, and is not limited to specific motor types, enabling more accurate calculation of high-frequency grounding current for motors in the context of high-speed, high-voltage, and high-frequency development.

Description

Technical Field

[0001] This invention belongs to the field of motor drive systems and relates to a method for constructing a universal grounding current calculation model for motors that is applicable to both the time domain and the wide frequency domain. Background Technology

[0002] With the development of power electronics technology, motor drive systems are increasingly adopting high-performance wide-bandgap semiconductor devices, such as silicon carbide (SiC) and gallium nitride (GaN). These devices offer higher switching speeds, lower losses, and better thermal performance, driving motor drive systems towards higher speeds, higher voltages, and higher frequencies. However, this trend has also brought new challenges, particularly the enhanced common-mode and differential-mode effects at high frequencies, leading to increasingly serious high-frequency electromagnetic interference (EMI) and radio frequency interference (RFI) problems.

[0003] To address these issues, accurate prediction of the motor grounding current is necessary. Predicting the motor grounding current is crucial for assessing common-mode and differential-mode effects in motors and is fundamental for resolving high-frequency EMI and RFI problems. Existing motor grounding current prediction models mainly include distributed parameter models and lumped parameter models. Distributed parameter models consist of numerous circuit elements arranged spatially along the motor windings, making calculations complex and requiring extensive test data. Therefore, lumped parameter models are widely used for the analysis and calculation of high-frequency grounding currents in motors.

[0004] However, most existing lumped parameter prediction models for motor grounding current employ simple winding models, neglecting the influence of the stator core on the grounding circuit. Furthermore, they largely ignore the differential-mode effect of the motor, only predicting the common-mode grounding current generated by the common-mode effect. In addition, the transmission impedance under the common-mode / differential-mode effect of the motor exhibits strong frequency-dependent characteristics, resulting in significant differences in grounding current at different frequencies. Therefore, existing motor grounding current prediction models are no longer able to accurately calculate the actual grounding current of motors in the context of high-speed, high-voltage, and high-frequency development. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for constructing a universal grounding current calculation model for motors that is applicable to both the time domain and the wide frequency domain.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for constructing a universal grounding current calculation model for motors that is applicable to both the time domain and a wide frequency domain, the method comprising the following steps:

[0008] Based on the distribution of the actual physical components of the motor, equivalent circuit models of five parts are established: bearings, stator windings, stator core, rotor, and internal parasitic coupling capacitors of the motor.

[0009] The specific parameter values ​​of each circuit component are calculated based on the frequency response test results of the motor's common-mode impedance, differential-mode impedance, rotor-casing impedance, and impedance between the three-phase winding short-circuit point and the rotor.

[0010] Furthermore, the model takes three-phase voltage / current as input and high-frequency grounding current as output.

[0011] Furthermore, the specific parameter values ​​of the model components are determined by parameter calculation based on the impedance frequency response test results of different parts of the motor.

[0012] Furthermore, the grounding circuit of the model is composed of different parts in different frequency ranges, specifically in the low frequency range of 0–10 Hz. 5 Hz, the grounding circuit consists of three types of parasitic coupling capacitors.

[0013] Furthermore, the model operates in the low-to-mid frequency range, i.e., 10 5 Hz~10 6 At Hz, the grounding current is affected by the stray inductance of the winding and the eddy current loss resistance of the winding. Therefore, the grounding circuit in the low-to-medium frequency range consists of the common-mode / differential-mode stray inductance of the winding, the common-mode / differential-mode eddy current loss resistance, the capacitance between the winding and the casing / rotor, and the grounding impedance composed of the rotor and stator core.

[0014] Furthermore, the model operates in the mid-to-high frequency range, i.e., 10 6 Hz~10 7 At Hz, common-mode inter-turn stray elements and differential-mode inter-turn stray elements become dominant, and the grounding circuit in this frequency range consists of common-mode inter-turn stray elements or differential-mode inter-turn stray elements and the grounding impedance composed of winding and housing / rotor capacitance, rotor and stator core.

[0015] Furthermore, the model operates in the high-frequency range, i.e., 10. 7 Hz~+∞, the high-frequency component of the grounding current only flows through the leakage flux, additional loss resistance and grounding impedance of the winding suspension part. The high-frequency grounding circuit consists of winding leakage flux, additional loss resistance and grounding impedance.

[0016] Furthermore, the modeling method includes establishing equivalent circuit models of five parts—bearings, stator windings, stator core, rotor, and internal parasitic coupling capacitance—based on the distribution of the actual physical components of the motor. The specific parameter values ​​of each circuit element are calculated using the frequency response test results of the motor's common-mode impedance, differential-mode impedance, rotor-casing impedance, and impedance between the three-phase winding short-circuit point and the rotor.

[0017] Furthermore, the common-mode winding stray inductance and eddy current loss resistance in the modeling method are calculated using the first local minimum frequency and impedance results from the common-mode impedance test.

[0018] Furthermore, the stray inductance of the differential mode winding and the eddy current loss resistance in the modeling method are calculated using the frequency and impedance results of the first anti-resonance point of the differential mode impedance test.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The motor grounding current calculation model proposed in this invention considers a wider frequency range (10) 3 Hz-10 8 The common-mode and differential-mode effects in the Hz range can more accurately predict the high-frequency grounding current of motors, especially in the context of the development of high speed, high voltage and high frequency.

[0021] (2) Compared with the existing complex models, the present invention adopts a lumped parameter model, which has a simple structure, is easy to understand and apply, and the parameter values ​​of the circuit components can be obtained through simple calculations.

[0022] (3) This invention is not limited to a specific type of motor and can be applied to various types of motors such as permanent magnet synchronous motors and three-phase asynchronous induction motors, thus improving the versatility of the model.

[0023] (4) The model parameters of the present invention are calculated based on the impedance frequency domain test results of various parts of the motor, which reduces the dependence on external test data and reduces test costs and time.

[0024] (5) By accurately predicting the motor grounding current, the present invention helps to optimize motor design, reduce high-frequency electromagnetic interference and radio frequency interference, and improve the performance and reliability of motor drive system.

[0025] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0027] Figure 1 This is a framework diagram of the ground current prediction model proposed in this invention;

[0028] Figure 2 For Z ls Partial impedance equivalent circuit model;

[0029] Figure 3 For Z phase Partial impedance equivalent circuit model;

[0030] Figure 4 For Z stator and Z rotor Partial impedance equivalent circuit model. Detailed Implementation

[0031] 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 be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0033] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0034] like Figures 1-4 As shown, C wrt C represents the capacitance between the input winding and the rotor. wrn C represents the capacitance between the neutral point winding and the rotor. wra This represents the capacitance between the stator winding and the rotor at the midpoint; similarly, C wft C wfa C wfnThese represent the parasitic coupling capacitances between the three-phase windings on the input side, intermediate position, and neutral point side, and the chassis, respectively; C rf This represents the parasitic coupling capacitance between the casing and the rotor. Z phase L represents the equivalent impedance of the winding section, where L s and L ss These represent the common-mode winding stray inductance and the differential-mode winding stray inductance, respectively; R e and R ee These represent the common-mode eddy current loss resistance and the differential-mode eddy current loss resistance, respectively; C tt R tt L tt Common-mode stray elements representing inter-turn effects in windings; C ww R ww L ww Differential-mode stray element representing the inter-turn effect of windings. Z ls L represents the equivalent impedance of the suspension portion of the winding, where L ls R represents the leakage flux of the suspended portion of the winding. ls This represents the additional loss resistance. The bearing impedance section can be equivalently represented as bearing resistance or bearing capacitance based on the time-varying RC characteristics of the bearing. Stator core impedance Z stator and rotor impedance Z rotor Then, based on the frequency response characteristics of the impedance, it can be obtained through... Figure 4 The four-step trapezoidal vortex model shown is used for modeling.

[0035] The specific modeling method of this invention is as follows:

[0036] Based on the distribution of the actual physical components of the motor, equivalent circuit models of five parts are established: bearings, stator windings, stator core, rotor, and internal parasitic coupling capacitors. The specific parameter values ​​of each circuit element are calculated using the frequency response test results of the motor's common-mode impedance, differential-mode impedance, rotor-casing impedance, and impedance between the three-phase winding short-circuit point and the rotor.

[0037] The calculation method for the specific parameter values ​​of each circuit element:

[0038] 1. Stator to chassis capacitor C wf (including C) wft C wfa C wfn ) calculation

[0039] The total capacitance C between the winding and the housing wf_total It can be accessed through 10 3 -10 5 any frequency f within the Hz range cm_LF Common-mode impedance test results Z cm_LF The calculation yielded:

[0040]

[0041] The capacitance C between the stator winding and the housing at the input terminal and neutral point wft and C wfn It can be used at any frequency f around 2MHz cm_HF Common-mode impedance test results Z cm_HF The calculation yielded:

[0042]

[0043] Capacitor C at the middle position of the winding wfa The calculation expression is:

[0044] C wfa =C wf_total -(C wft +C wfn (3)

[0045] 2. Capacitance C between the casing and the rotor rf The capacitance C between the winding and the rotor wr Calculation

[0046] The capacitance C between the casing and the rotor rf The capacitance C between the winding and the rotor wr It can be accessed through 10 3 -10 6 Impedance test between rotor and casing at any frequency f within the Hz range (Z) rf ) and impedance test between the three-phase winding short-circuit point and the rotor (Z wr ) was calculated.

[0047] The capacitance C between the casing and the rotor rf The impedance test results between the rotor and the housing (Z) rf The impedance test results between the three-phase winding short-circuit point and the rotor (Z) wr The calculation expression for ) is:

[0048]

[0049] Among them, C test_Zwr For Z wr The capacitance value, C, from the impedance test results. test_Zrf For Z rf The capacitance value obtained from the impedance test.

[0050] The total capacitance C between the winding and the rotor wr_total The impedance test results between the rotor and the housing (Z) rf The impedance test results between the three-phase winding short-circuit point and the rotor (Z) wr The calculation expression for ) is:

[0051]

[0052] Among them, C wr_total =3C wrt +3C wra +3C wrn C in different positions wr (C wra C wrt and C wrn The capacitor C can be connected from the stator to the housing. wf Arranged in the same proportion.

[0053] 3. Common-mode winding stray inductance L s and eddy current loss resistance R e Calculation

[0054] Common mode winding stray inductance L s and eddy current loss resistance R e It can be calculated from the frequency and impedance value of the first local minimum point in the common-mode impedance test results.

[0055] Common mode winding stray inductance L s and eddy current loss resistance R e The impedance value Z of the first local minimum in the common-mode impedance test results cm-1 The relational expression is:

[0056]

[0057] In the formula, Z g The equivalent circuit representing the parallel connection of the stator core and rotor, i.e., Z... g =Z stator ∥Z rotor Z Cg,p C at frequency f1 at this point g,p The impedance value, C gp (p = t, a, n) represents the position of C at different locations. wf and C wr Parallel equivalent circuit, i.e., C gp =C wfp +C wrp ; ω1=2·π·f1 (the same applies below); Z Re-Ls For R e and L s The equivalent impedance of a parallel circuit

[0058]

[0059] 4. Differential mode winding stray inductance L ss and eddy current loss resistance R ee Calculation

[0060] Four frequency ranges are set, with low frequency (0-10) 5 Hz), in the mid-low frequency range (10 5 ~106Hz), in the mid-to-high frequency range (10 6 Hz~10 7 Hz), in the high-frequency range (10 7 (Hz~+∞), because the equivalent circuit is more complex in the mid-frequency range, the mid-frequency range is divided into two parts, "mid-low" and "mid-high", for description.

[0061] Differential mode winding stray inductance L ss and eddy current loss resistance R ee It can be used at low and mid-low frequencies (~10) 6 The frequency and impedance value of the first anti-resonance point in the differential mode impedance test results (Hz) are calculated.

[0062] Differential mode winding stray inductance L ss and eddy current loss resistance R ee The impedance value Z at the first anti-resonance point of the differential mode impedance dm-a The relational expression is:

[0063]

[0064] In the formula, K i (i = 1, 2, 3, 4) are intermediate variables, K1 = Z Cgt ·Z Cga ·Z Cgn K2 = Z Cga ·Z Cgn K3 = Z Cgt ·Z Cga K4 = Z Cgt ·Z Cgn Z Cg =Z Cgt +Z Cga +Z Cgn Z RL For R e -L s and R ee -L ss The equivalent impedance of a series circuit, Z RL =Z Re-Ls +Z Ree-Lss Z Ree-Lss For R ee and L ss The equivalent impedance of a parallel circuit

[0065] 5. Common-mode stray element C due to winding inter-turn effect tt Rtt L tt Sum and difference mode stray element C ww R ww L ww Calculation

[0066] Inter-turn effect capacitance (including common-mode inter-turn capacitance C) tt Sum and difference mode inter-turn capacitance C ww Typically, the winding to stator capacitor C wf Ten times lower, C tt and C ww It can be calculated as:

[0067]

[0068] Common-mode stray element R tt L tt It can be calculated from the frequency and impedance value of the first anti-resonance point in the common-mode impedance test results. The differential-mode stray element R... ww L ww It can be calculated from the frequency and impedance value of the first resonant point in the differential mode impedance test results.

[0069] Common-mode stray element R tt L tt The impedance value Z at the first anti-resonance point of the common-mode impedance cm-2 The relational expression is:

[0070]

[0071] In the formula,

[0072] Differential mode stray element R ww L ww The impedance value Z at the first resonant point of the differential mode impedance dm-b The relational expression is:

[0073]

[0074] In the formula,

[0075] 6. Leakage flux L of the suspended portion of the winding ls and additional loss resistance R ls Calculation

[0076] Leakage flux L of the suspension section of the winding ls and additional loss resistance R ls The results of common-mode impedance or differential-mode impedance tests can be obtained in the high-frequency range (10) 7 The pure inductive impedance value at any frequency (Hz~) is calculated.

[0077] Leakage flux L of the suspension section of the winding ls and additional loss resistance R ls The pure inductive impedance value Z at high frequencies compared to common-mode impedance testing cm-3 The relational expression is:

[0078]

[0079] Leakage flux L of the suspension section of the winding ls and additional loss resistance R ls The differential-mode impedance test shows the purely inductive impedance value Z at high frequencies. dm-c The relational expression is:

[0080]

[0081] In the formula, Z ls The leakage flux L at any frequency within the high-frequency range ls and additional loss resistance R ls The equivalent impedance Z of a series circuit ls =R ls +j·ω k ·L ls (k = 3, c).

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for constructing a universal grounding current calculation model for motors that is applicable to both the time domain and a wide frequency domain, characterized in that: The method includes the following steps: Based on the distribution of the actual physical components of the motor, equivalent circuit models of five parts are established: bearings, stator windings, stator core, rotor, and internal parasitic coupling capacitors of the motor. The specific parameter values ​​of each circuit element are calculated based on the frequency response test results of the motor's common-mode impedance, differential-mode impedance, rotor-casing impedance, and three-phase winding short-circuit point-rotor impedance. The modeling method includes establishing equivalent circuit models of five parts—bearings, stator windings, stator core, rotor, and internal parasitic coupling capacitors—based on the distribution of the actual physical components of the motor. The specific parameter values ​​of each circuit element are calculated using the frequency response test results of the motor's common-mode impedance, differential-mode impedance, rotor-casing impedance, and impedance between the short-circuit point of the three-phase winding and the rotor. The common-mode winding stray inductance and eddy current loss resistance in the modeling method are calculated using the first local minimum frequency and impedance results of the common-mode impedance test. Common mode winding stray inductance L s and common-mode eddy current loss resistor R e The impedance value Z of the first local minimum in the common-mode impedance test results cm-1 The relational expression is: In the formula, Z Cgp For C at frequency f1 gp The impedance value, p = t or a or n; C gp Indicates C at different positions wf and C wr Parallel equivalent circuit; C wf Including the parasitic coupling capacitance C between the three-phase winding input side winding and the housing. wft The parasitic coupling capacitance C between the winding at the middle position of the three-phase winding and the casing. wfa The parasitic coupling capacitance C between the three-phase winding neutral point side winding and the housing wfn C wr This represents the capacitance between the winding and the rotor; C gp =C wfp +C wrp ; ω1=2·π·f1;Z Re-Ls For R e and L s The equivalent impedance of a parallel circuit The stray inductance and eddy current loss resistance of the differential mode winding in the modeling method are calculated by the frequency and impedance results of the first anti-resonance point of the differential mode impedance test. Differential mode winding stray inductance L ss Sum and difference mode eddy current loss resistance R ee The impedance value Z at the first anti-resonance point of the differential mode impedance dm-a The relational expression is: In the formula, K i As intermediate variables, i = 1, 2, 3, 4, K1 = Z Cgt ·Z Cga ·Z Cgn K2 = Z Cga ·Z Cgn K3 = Z Cgt ·Z Cga K4 = Z Cgt ·Z Cgn Z Cg =Z Cgt +Z Cga +Z Cgn Z RL For R e -L s and R ee -L ss The equivalent impedance of a series circuit, Z RL =Z Re-Ls +Z Ree-Lss Z Ree-Lss For R ee and L ss The equivalent impedance of a parallel circuit 2. The method for constructing a universal grounding current calculation model for motors that is applicable to both the time domain and wide frequency domain, as described in claim 1, is characterized in that: The model takes three-phase voltage or three-phase current as input and high-frequency grounding current as output.

3. The method for constructing a universal grounding current calculation model for motors that is applicable to both the time domain and wide frequency domain, as described in claim 1, is characterized in that: The specific parameter values ​​of the components in the model are determined by parameter calculation based on the impedance frequency response test results of different parts of the motor.

4. The method for constructing a universal grounding current calculation model for motors that is applicable to both the time domain and wide frequency domain, as described in claim 1, is characterized in that: The grounding circuit of the model is composed of different parts in different frequency ranges. In the low frequency range, i.e., 0 to 10 Hz, the grounding circuit is composed of different parts. 5 Hz, the grounding circuit consists of three types of parasitic coupling capacitors.

5. The method for constructing a universal grounding current calculation model for motors that is applicable to both the time domain and wide frequency domain, as described in claim 1, is characterized in that: The model operates in the high-frequency range, 10 7 Hz~+∞, the high-frequency component of the grounding current only flows through the leakage flux, additional loss resistance and grounding impedance of the winding suspension part. The high-frequency grounding circuit consists of winding leakage flux, additional loss resistance and grounding impedance.

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