Method for calculating parasitic capacitance of common-mode EMI filter inductor of NiZn material

Abstract

The invention discloses a method for calculating stray capacitance of a NiZn material common-mode EMI filter inductor. The method comprises the steps that S1, a distributed stray capacitance network model is established based on the actual high-frequency electric field behavior of the NiZn material common-mode EMI filter inductor; s2, acquiring stray capacitance parameters in the distributed stray capacitance network model based on a two-dimensional finite element simulation method; and S3, establishing a lumped capacitance calculation formula, and calculating the lumped parasitic capacitance of the NiZn material common mode EMI filter inductor based on the lumped capacitance calculation formula and the parasitic capacitance parameters. According to the method, a distributed stray capacitance network model is established based on the actual high-frequency electric field behavior of the NiZn material common-mode EMI filter inductor; the influence of a magnetic core material is fully considered, and high errors generated when a traditional distributed stray capacitance network is subjected to NiZn material common-mode EMI filter inductance are avoided. In addition, the process of obtaining the parasitic capacitance parameters in the distributed parasitic capacitance network model is simplified, resources consumed for obtaining the parameters through finite element simulation are reduced, and the efficiency of obtaining the parasitic capacitance parameters through finite element simulation is improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-pressure valve cold sensor systems, and in particular to a method for calculating parasitic capacitance of a common-mode EMI filter inductor of a NiZn material. Background Art

[0002] The rapid development of economy and emerging industries has led to a continuous increase in electricity demand. UHV DC transmission is in line with my country's industrial layout and meets the requirements of high efficiency, low loss and long-distance transmission. Under long-term operation of high current, the converter valve, as a key component, will generate a lot of heat, resulting in failure to work properly. In severe cases, the transmission system may even be locked and the main grid may collapse. Therefore, the valve cooling system has become an important auxiliary equipment for the converter valve. Its sensor is responsible for collecting important data of the circulating water and transmitting it to the control system. The stability is directly related to the normal operation of the system. In the converter station, the high-frequency electromagnetic radiation generated by the densely arranged power electronic equipment is easy to induce common-mode interference signals on the signal line. At the same time, the miniaturization design of the sensor also makes the internal circuit susceptible to interference. Common-mode inductors in common-mode filters are usually used to suppress these interferences, but the presence of parasitic capacitance causes high-frequency signals to deviate their impedance from the ideal value. Therefore, accurate modeling of common-mode inductors is crucial to optimize common-mode filters, meet electromagnetic interference standards, and not increase the weight and size of the device.

[0003] At present, the modeling of parasitic capacitance of common-mode EMI filter inductors is mainly divided into the following three steps: (1) Establishing a distributed parasitic capacitance network of the filter inductor; (2) Using analytical methods or finite element simulation methods to obtain the capacitance parameter values ​​in the distributed parasitic capacitance network; (3) Using the energy conservation method or the star-delta transformation method to obtain a lumped value of the distributed parasitic capacitance network, that is, the lumped parasitic capacitance. For the first step, the winding on the filter inductor is specifically subdivided into N turns according to the number of turns, and then each turn is assumed to be a two-dimensional unit, which is represented as a node in the circuit. The capacitive coupling effect between adjacent nodes needs to be considered, but the capacitive coupling effect between non-adjacent nodes is very weak, so it can be ignored. In addition, the magnetic core is modeled as a node separately. Since the distributed capacitance network has reliable accuracy and is convenient for designers to optimize the high-frequency characteristics of the filter inductor, it has been widely used. For the second step, the analytical method used to obtain the parameters in the parasitic capacitance network can save a lot of computing resources compared to finite element simulation, but related studies have pointed out that the calculation boundary of the analytical method is difficult to determine, which is easy to cause large errors. For different situations, it is necessary to develop corresponding analytical formulas separately, which will also cause certain difficulties in parameter calculation. Therefore, the current mainstream still uses the finite element method to calculate parameters. In the third step, the energy conservation method or the star-delta transformation method can be used to calculate the lumped parasitic capacitance. However, relevant studies have pointed out that compared with the energy conservation method, the star-delta transformation method lacks the actual consideration of the winding potential, which will cause huge errors. Therefore, the energy conservation method is usually used to calculate the lumped parasitic capacitance. However, there are certain limitations in the three steps of modeling the parasitic capacitance of the common-mode EMI filter inductor. The first and second steps are often only suitable for the magnetic core that can be assumed to be a perfect conductor. If the magnetic core is not suitable for this assumption, it will cause a large error in modeling. Whether the magnetic core is suitable for the perfect conductor assumption can often be considered from the material properties of the magnetic core itself. For materials with high dielectric constant or high conductivity, they can often be regarded as perfect conductors. If the dielectric constant and conductivity of the material are very low, the magnetic core cannot be used for the perfect conductor assumption and can only be regarded as a medium. Traditional common-mode EMI filter inductors can usually be divided into nanocrystalline materials, MnZn materials and NiZn materials. Among them, common-mode EMI filter inductors made of nanocrystalline materials and MnZn materials have particularly high initial magnetic permeability and are suitable for high frequencies of several MHz. Common-mode EMI filter inductors made of NiZn materials are widely used in higher frequencies due to the low core loss and stable magnetic permeability of the material itself.In common-mode EMI filter inductors, nanocrystalline materials are often assumed to be perfect conductors (PEC) due to their high conductivity and the high dielectric constant of the MnZn core. This is reflected in the modeling, that is, the core is assumed to be a node in the first step and its parameters are extracted in the second step. However, in NiZn cores, due to their own material properties, the PEC assumption is no longer applicable. Therefore, the traditional parasitic capacitance modeling method is no longer applicable to NiZn cores. Summary of the invention

[0004] The present invention provides a method for calculating the parasitic capacitance of a common-mode EMI filter inductor made of NiZn material, so as to overcome the technical problem that the prior art cannot accurately obtain the parasitic capacitance of the common-mode EMI filter inductor made of NiZn material.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] A method for calculating the parasitic capacitance of a common-mode EMI filter inductor of a NiZn material, the specific steps comprising:

[0007] S1: Establish a distributed parasitic capacitance network model based on the actual high-frequency electric field behavior of NiZn material common-mode EMI filter inductors;

[0008] S2: Obtaining parasitic capacitance parameters in the distributed parasitic capacitance network model based on a two-dimensional finite element simulation method;

[0009] S3: Establish a lumped capacitance calculation formula, and calculate the lumped parasitic capacitance of the NiZn material common-mode EMI filter inductor based on the lumped capacitance calculation formula and the parasitic capacitance parameters.

[0010] Furthermore, in S1, the process of establishing a distributed parasitic capacitance network model based on the actual high-frequency electric field behavior of the NiZn material common-mode EMI filter inductor is:

[0011] Use NiZn core as dielectric;

[0012] Based on the distributed parasitic capacitance network of the traditional common-mode EMI filter inductor, the electric field inside the magnetic core is characterized as the static capacitance Ccs of the magnetic core. At the same time, it is assumed that the voltage of each turn in the winding is linearly distributed.

[0013] Based on the above conditions, each turn of the winding is regarded as a node, the inter-turn capacitance Ctt is connected between adjacent nodes, one end of the capacitance between the turn and the core Ctc is connected to the node, and the other end is connected in series with one end of the static capacitance Ccs of the core corresponding to each turn of the winding, and the other end of the static capacitance Ccs of the core is connected to the capacitance Ctc between the turn and the core of the last turn of the winding, thereby establishing a distributed parasitic capacitance network model.

[0014] Further, in S2, the process of obtaining the parasitic capacitance parameters in the distributed parasitic capacitance network model is:

[0015] S21: Simulate the axial section and the radial section along the tangential expansion of the NiZn material common mode EMI filter inductor to obtain the simulated axial section model and the radial section model along the tangential expansion;

[0016] S22: Calculating and obtaining two-dimensional axial cross-section parasitic capacitance parameters based on the axial cross-section model;

[0017] S23: Calculating and obtaining two-dimensional radial cross-section parasitic capacitance parameters based on the radial cross-section model developed along the tangential direction;

[0018] S24: Calculate the total series capacitance and the total turn-to-turn capacitance within one turn based on the two-dimensional axial cross-section parasitic capacitance parameters and the two-dimensional radial cross-section parasitic capacitance parameters.

[0019] Further, in S22, the two-dimensional axial section parasitic capacitance parameters calculated based on the axial section model include:

[0020] Based on the axial cross-section model, numerical simulation is performed to obtain the series capacitance dc of the static capacitance Ccs per unit core and the capacitance between the turn and the core Ctc. c,i,o , dc c,i,o Multiply by the height h corresponding to the common mode EMI filter inductor of NiZn material w , the total axial cross-sectional series capacitance is obtained as follows:

[0021] C c,i,o =dc c,i,o ·h w (1)

[0023] Based on the axial cross-section model, the numerical simulation is performed to obtain the capacitance value dc per unit turn. tt,i,o , dc tt,i,o Multiply by the height h corresponding to the common mode EMI filter inductor of NiZn material w , the total axial cross-sectional turn-to-turn capacitance is obtained as follows:

[0024] C tt,i,o =dc tt,i,o ·h w (2).

[0025] Further, in S23, the two-dimensional radial cross-section parasitic capacitance parameters calculated based on the radial cross-section model developed along the tangential direction include:

[0026] Based on the numerical simulation of the radial cross-section model unfolded along the tangential direction, the static capacitance per unit core and the series capacitance value dc between the turn and the core are obtained. c,l,l , dc c,l,l Multiply by the difference between the inner and outer radii of the NiZn material common mode EMI filter inductor to obtain the total radial cross-sectional series capacitance, the formula is as follows:

[0027] C c,l,l =dc c,l,l ·(R co -R cin ) (3)

[0028] In the formula, R co is the outer diameter of the NiZn common mode EMI filter inductor; R cin It is the inner diameter of the common mode EMI filter inductor of NiZn material;

[0029] Based on the numerical simulation of the radial cross-section model developed along the tangential direction, the capacitance value dc per unit turn is obtained. tt,l,l , dc tt,l,l Multiply by the difference between the inner and outer radii of the NiZn material common mode EMI filter inductor to obtain the total radial cross-section turn-to-turn capacitance, the formula is as follows:

[0030] C tt,l,l =dc tt,l,l ·(R co -R cin ) (4).

[0031] Further, in S24, the total series capacitance within one turn is calculated based on the two-dimensional axial cross-section parasitic capacitance parameter and the two-dimensional radial cross-section parasitic capacitance parameter, and is expressed as:

[0032] C c =C c,i,o +C c,l,l (5).

[0033] Further, in S24, the total turn-to-turn capacitance within one turn is calculated based on the two-dimensional axial cross-section parasitic capacitance parameter and the two-dimensional radial cross-section parasitic capacitance parameter, and is expressed as:

[0034] C tt =C tt,i,o +C tt,l,l (6).

[0035] Furthermore, in S3, the lumped capacitance calculation formula established is:

[0036]

[0037] Among them, C ck is the total series capacitance of the kth turn, and N is the total number of turns.

[0038] Beneficial effects: The present invention establishes a distributed parasitic capacitance network model based on the actual high-frequency electric field behavior of the common-mode EMI filter inductor of NiZn material; the influence of the magnetic core material is fully considered, and the high error generated by the traditional distributed parasitic capacitance network when it is used for the common-mode EMI filter inductor of NiZn material is avoided. In addition, the present invention simplifies the process of obtaining the parasitic capacitance parameters in the distributed parasitic capacitance network model, reduces the resources consumed by the finite element simulation to obtain the parameters, and improves the efficiency of the finite element simulation to obtain the parasitic capacitance parameters. In summary, the method proposed in the present invention can help designers better optimize the NiZn common-mode EMI filter inductor, improve its high-frequency performance and the EMI noise reduction level of the filter, and improve the design efficiency, eliminate the shortcomings of the traditional common-mode EMI filter inductor high-frequency parasitic capacitance modeling, and make the model suitable for calculating the common-mode EMI filter inductor of NiZn material. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 A flow chart of a method for calculating parasitic capacitance of a common-mode EMI filter inductor of NiZn material in the present invention;

[0041] Figure 2 This is the geometric structure diagram of the common mode EMI filter inductor made of NiZn material;

[0042] Figure 3 This is the lumped circuit diagram of the common mode EMI filter inductor made of NiZn material;

[0043] Figure 4 This is a distributed parasitic capacitance network diagram of the NiZn material common mode EMI filter inductor proposed by the present invention;

[0044] Figure 5 This is a basic schematic diagram of the common mode EMI filter inductor made of NiZn material;

[0045] Figure 6 It is a schematic diagram of the axial cross-section model of the common-mode EMI filter inductor made of NiZn material;

[0046] Figure 7 This is a schematic diagram of the radial cross-section model of the NiZn material common-mode EMI filter inductor unfolded along the tangential direction.

[0047] In the figure: 1, axial section; 2, radial section. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] In view of the problem that the existing common-mode EMI filter inductor high-frequency parasitic capacitance modeling method is only suitable for magnetic cores made of nanocrystalline materials and MnZn materials and the finite element simulation is inefficient in extracting parasitic capacitance parameters, this embodiment provides a method for calculating the parasitic capacitance of the common-mode EMI filter inductor of NiZn material, such as Figure 1 As shown, the specific steps include:

[0050] S1: Establish a distributed parasitic capacitance network model based on the actual high-frequency electric field behavior of NiZn material common-mode EMI filter inductors;

[0051] S2: Obtaining parasitic capacitance parameters in the distributed parasitic capacitance network model based on a two-dimensional finite element simulation method;

[0052] S3: Establish a lumped capacitance calculation formula, and calculate the lumped parasitic capacitance of the NiZn material common-mode EMI filter inductor based on the lumped capacitance calculation formula and the parasitic capacitance parameters, so as to achieve an overall evaluation of the inductor.

[0053] In a specific embodiment, in S1, the process of establishing a distributed parasitic capacitance network model based on the actual high-frequency electric field behavior of the common-mode EMI filter inductor of NiZn material is:

[0054] According to the actual high-frequency electric field behavior of the NiZn common-mode EMI filter inductor, it can be determined that the NiZn core is a dielectric, not a conductor. Therefore, this embodiment uses the NiZn core as a dielectric and, based on the distributed parasitic capacitance network of the traditional common-mode EMI filter inductor, characterizes the electric field inside the core as the core static capacitance Ccs, and assumes that the voltage of each turn in the winding is linearly distributed. Based on the above conditions, each turn of the winding is regarded as a node, the inter-turn capacitance Ctt is connected between adjacent nodes, one end of the turn-to-core capacitance Ctc is connected to the node, and the other end is connected in series with one end of the core static capacitance Ccs corresponding to each turn of the winding, and the other end of the core static capacitance Ccs is connected to the turn-to-core capacitance Ctc of the last turn of the winding, thereby establishing the following: Figure 4The distributed parasitic capacitance network model shown shows the interconnection relationship between the various capacitors.

[0055] Specifically, Figure 4 As shown, C 12 ,…,C N-2,N-1 ,…,C N-1,N They represent the turn-to-turn capacitance Ctt, C 1c ,…,C N-2,c ,…,C N-1,c ,…,C Nk Respectively represent the turn and core capacitance Ctc, C cs1 ,C cs2 ,C cs3 Respectively represent the static capacitance of the magnetic core. Each node is connected to the inter-turn capacitance Ctt and the turn-to-core capacitance Ctc, which correspond to the electric field energy between the windings and between the windings and the magnetic core, respectively. Ctt is connected between adjacent nodes, while Ctc is connected to the node at one end and the static capacitance Ccs of the magnetic core at the other end. At the same time, Ccs is connected to the Ctc of the last turn of the winding. This is because the electric field lines usually flow to the area with the lowest electric potential, and it is difficult to determine which turn the electric field lines end at. In order to characterize this phenomenon, without affecting the accuracy, this embodiment assumes that all electric field lines flowing through the magnetic core end at the last turn, that is, all Ccs are connected to the last node.

[0056] Specifically, the distributed parasitic capacitance network of the NiZn material common mode EMI filter inductor in this embodiment fully considers the influence of the magnetic core material, avoiding the high error generated by the traditional distributed parasitic capacitance network when applying the NiZn material common mode EMI filter inductor. At the same time, through precise modeling and optimized design, the parasitic capacitance characteristics of the inductor are more accurately estimated, thereby improving the performance and stability of the inductor in practical applications and reducing errors in the design and manufacturing process.

[0057] In a specific embodiment, in S2, the process of obtaining the parasitic capacitance parameters in the distributed parasitic capacitance network model is:

[0058] S21: Simulate the axial section and the radial section along the tangential expansion of the NiZn material common mode EMI filter inductor to obtain the simulated axial section model and the radial section model along the tangential expansion;

[0059] S22: Calculating and obtaining two-dimensional axial cross-section parasitic capacitance parameters based on the axial cross-section model;

[0060] S23: Calculate and obtain the two-dimensional radial section parasitic capacitance parameters based on the radial section model developed along the tangential direction;

[0061] S24: Calculate the total series capacitance and the total turn-to-turn capacitance within one turn based on the two-dimensional axial cross-section parasitic capacitance parameters and the two-dimensional radial cross-section parasitic capacitance parameters.

[0062] Specifically, in this embodiment, the geometric structure diagram of the application object of the high-frequency parasitic capacitance calculation method of the NiZn material common-mode EMI filter inductor proposed in this embodiment is as follows: Figure 2 As shown in the figure, the NiZn material common mode EMI filter inductor consists of a magnetic core and two symmetrically wound windings. Figure 3 The lumped equivalent circuit diagram of the common-mode EMI filter inductor made of NiZn material is shown. lumped is the lumped parasitic capacitance corresponding to a single winding. By simplifying the NiZn material common mode EMI filter inductor into two basic surfaces and taking full account of the geometric factors on the two basic surfaces, the simplification from three-dimensional simulation to two-dimensional simulation is achieved, which greatly improves the simulation efficiency. Figure 5 As shown, the basic surfaces are axial section 1 and radial section 2, as Figure 6 As shown in the figure, for the axial section, the section can be directly used as a 2D simulation model; however, for the radial section, as shown in the figure, Figure 7 As shown, the cross section cannot be directly modeled as a two-dimensional model, so this embodiment establishes a radial cross-section model developed along the tangential direction, and after obtaining the parasitic capacitance parameters on two basic planes, the actual three-dimensional parasitic capacitance value can be obtained.

[0063] Specifically, the simplified finite element simulation method provided in this embodiment can obtain the parasitic capacitance parameter value of the common-mode EMI filter inductor of NiZn material by simulating only two basic surfaces of the inductor. This method significantly improves the efficiency of finite element simulation and avoids the high resource consumption problem of detailed simulation of the entire inductor in traditional simulation. Through this method, the simulation process is not only more efficient, but also reduces the resource requirements for computing hardware, allowing designers to complete the parasitic capacitance analysis of complex inductors with limited hardware resources, greatly improving the design cycle and cost-effectiveness.

[0064] In a specific embodiment, in S22, the two-dimensional axial section parasitic capacitance parameters calculated based on the axial section model include:

[0065] Based on the axial cross-section model, numerical simulation is performed to obtain the series capacitance dc of the static capacitance Ccs per unit core and the capacitance between the turn and the core Ctc. c,i,o , dc c,i,o Multiply by the height h corresponding to the common mode EMI filter inductor of NiZn material w , the total axial cross-sectional series capacitance is obtained as follows:

[0066] C c,i,o =dc c,i,o·h w (1)

[0068] Based on the axial cross-section model, the numerical simulation is performed to obtain the capacitance value dc per unit turn. tt,i,o , dc tt,i,o Multiply by the height h corresponding to the common mode EMI filter inductor of NiZn material w , the total axial cross-sectional turn-to-turn capacitance is obtained as follows:

[0069] C tt,i,o =dc tt,i,o ·h w (2).

[0070] In a specific embodiment, in S23, the two-dimensional radial cross-section parasitic capacitance parameters are calculated based on the radial cross-section model developed along the tangential direction, including:

[0071] Based on the numerical simulation of the radial cross-section model unfolded along the tangential direction, the static capacitance per unit core and the series capacitance value dc between the turn and the core are obtained. c,l,l , dc c,l,l Multiply by the difference between the inner and outer radii of the NiZn material common mode EMI filter inductor to obtain the total radial cross-sectional series capacitance, the formula is as follows:

[0072] C c,l,l =dc c,l,l ·(R co -R cin ) (3)

[0073] In the formula, R co is the outer diameter of the NiZn common mode EMI filter inductor; R cin It is the inner diameter of the common mode EMI filter inductor of NiZn material;

[0074] Based on the numerical simulation of the radial cross-section model developed along the tangential direction, the capacitance value dc per unit turn is obtained. tt,l,l , dc tt,l,l Multiplying the difference between the inner and outer radii of the NiZn material common mode EMI filter inductor to obtain the total radial cross-section turn-to-turn capacitance, the formula is as follows:

[0075] C tt,l,l =dc tt,l,l ·(R co -R cin ) (4).

[0076] In a specific embodiment, in S24, the total series capacitance within one turn is calculated based on the two-dimensional axial cross-section parasitic capacitance parameter and the two-dimensional radial cross-section parasitic capacitance parameter, and is expressed as:

[0077] Cc =C c,i,o +C c,l,l (5).

[0078] In a specific embodiment, in S24, the total turn-to-turn capacitance within one turn is calculated based on the two-dimensional axial cross-section parasitic capacitance parameter and the two-dimensional radial cross-section parasitic capacitance parameter, and is expressed as:

[0079] C tt =C tt,i,o +C tt,l,l (6).

[0080] In a specific embodiment, the potential in the winding is considered to be an equipotential distribution, and the energy conservation principle is used to obtain the equivalent capacitance C of the NiZn material common mode EMI filter inductor. lumped , in order to make a general assessment of the parasitic capacitance of the core, in S3, the lumped capacitance calculation formula established is:

[0081]

[0082] Among them, C ck is the total series capacitance of the kth turn, and N is the total number of turns.

[0083] Specifically, the calculation formula for the lumped capacitance of the common-mode EMI filter inductor of NiZn material in this embodiment provides designers with a simple and accurate calculation tool that can help them quickly calculate the lumped capacitance of the inductor. The introduction of this formula avoids the need to obtain the capacitance value through complex impedance testing in the traditional method, thereby improving design efficiency and reducing time and testing costs.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the parasitic capacitance of a common-mode EMI filter inductor of NiZn material, characterized in that: The specific steps include: S1: Establish a distributed parasitic capacitance network model based on the actual high-frequency electric field behavior of NiZn material common-mode EMI filter inductors; S2: Obtaining parasitic capacitance parameters in the distributed parasitic capacitance network model based on a two-dimensional finite element simulation method; S3: Establish a lumped capacitance calculation formula, and calculate the lumped parasitic capacitance of the NiZn material common-mode EMI filter inductor based on the lumped capacitance calculation formula and the parasitic capacitance parameters.

2. The method for calculating the parasitic capacitance of the common-mode EMI filter inductor of NiZn material according to claim 1, characterized in that: In S1, the process of establishing a distributed parasitic capacitance network model based on the actual high-frequency electric field behavior of the NiZn material common-mode EMI filter inductor is as follows: Use NiZn core as dielectric; Based on the distributed parasitic capacitance network of the traditional common-mode EMI filter inductor, the electric field inside the magnetic core is characterized as the static capacitance Ccs of the magnetic core. At the same time, it is assumed that the voltage of each turn in the winding is linearly distributed. Based on the above conditions, each turn of the winding is regarded as a node, the inter-turn capacitance Ctt is connected between adjacent nodes, one end of the capacitance between the turn and the core Ctc is connected to the node, and the other end is connected in series with one end of the static capacitance Ccs of the core corresponding to each turn of the winding, and the other end of the static capacitance Ccs of the core is connected to the capacitance Ctc between the turn and the core of the last turn of the winding, thereby establishing a distributed parasitic capacitance network model.

3. The method for calculating the parasitic capacitance of the common-mode EMI filter inductor of NiZn material according to claim 2, characterized in that: In S2, the process of obtaining the parasitic capacitance parameters in the distributed parasitic capacitance network model is as follows: S21: Simulate the axial section and the radial section along the tangential expansion of the NiZn material common mode EMI filter inductor to obtain the simulated axial section model and the radial section model along the tangential expansion; S22: Calculating and obtaining two-dimensional axial cross-section parasitic capacitance parameters based on the axial cross-section model; S23: Calculating and obtaining two-dimensional radial cross-section parasitic capacitance parameters based on the radial cross-section model developed along the tangential direction; S24: Calculate the total series capacitance and the total turn-to-turn capacitance within one turn based on the two-dimensional axial cross-section parasitic capacitance parameters and the two-dimensional radial cross-section parasitic capacitance parameters.

4. The method for calculating the parasitic capacitance of the common-mode EMI filter inductor of NiZn material according to claim 3, characterized in that: In S22, the two-dimensional axial section parasitic capacitance parameters calculated based on the axial section model include: Based on the axial cross-section model, numerical simulation is performed to obtain the series capacitance dc of the static capacitance Ccs per unit core and the capacitance between the turn and the core Ctc. c,i,o , dc c,i,o Multiply by the height h corresponding to the common mode EMI filter inductor of NiZn material w , the total axial cross-sectional series capacitance is obtained as follows: C c，i，o =dc c,i,o ·h w (1) Based on the axial cross-section model, the numerical simulation is performed to obtain the capacitance value dc per unit turn. tt,i,o , dc tt,i，o Multiply by the height h corresponding to the common mode EMI filter inductor of NiZn material w , the total axial cross-sectional turn-to-turn capacitance is obtained as follows: C tt,i，o =dc tt,i，o ·h w (2)。 5. The method for calculating the parasitic capacitance of the common-mode EMI filter inductor of NiZn material according to claim 4, characterized in that: In S23, the two-dimensional radial section parasitic capacitance parameters calculated based on the radial section model developed along the tangential direction include: Based on the numerical simulation of the radial cross-section model unfolded along the tangential direction, the static capacitance per unit core and the series capacitance value dc between the turn and the core are obtained. c，l，l , dc c，l，l Multiply by the difference between the inner and outer radii of the NiZn material common mode EMI filter inductor to obtain the total radial cross-sectional series capacitance, the formula is as follows: C c，l，l =dc c，l，l ·(R co -R cin ) (3) In the formula, R co is the outer diameter of the NiZn common mode EMI filter inductor; R cin It is the inner diameter of the common mode EMI filter inductor of NiZn material; Based on the numerical simulation of the radial cross-section model developed along the tangential direction, the capacitance value dc per unit turn is obtained. tt,l,l , dc tt,l，l Multiply by the difference between the inner and outer radii of the NiZn material common mode EMI filter inductor to obtain the total radial cross-section turn-to-turn capacitance, the formula is as follows: C tt,l,l =dc tt,l,l ·(R co -R cin ) (4)。 6. The method for calculating the parasitic capacitance of the common-mode EMI filter inductor of NiZn material according to claim 5, characterized in that: In S24, the total series capacitance within one turn is calculated based on the two-dimensional axial cross-section parasitic capacitance parameter and the two-dimensional radial cross-section parasitic capacitance parameter, and is expressed as: C c =C c，i，o +C c，l，l (5)。 7. The method for calculating the parasitic capacitance of the common-mode EMI filter inductor of NiZn material according to claim 6, characterized in that: In S24, the total turn-to-turn capacitance within one turn is calculated based on the two-dimensional axial cross-section parasitic capacitance parameter and the two-dimensional radial cross-section parasitic capacitance parameter, and is expressed as: C tt =C tt，i，o +C tt，l，l (6)。 8. The method for calculating the parasitic capacitance of the common-mode EMI filter inductor of NiZn material according to claim 7, characterized in that: In S3, the lumped capacitance calculation formula is established as: Among them, C ck is the total series capacitance of the kth turn, and N is the total number of turns.

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