High-frequency transformer parasitic parameter regulation and control method considering high-frequency eddy current effect

Abstract

A high-frequency transformer parasitic parameter regulation and control method considering a high-frequency eddy current effect comprises the following steps: determining a high-frequency transformer winding structure and geometrical shape parameters, and calculating static capacitance between adjacent layers of a winding according to a capacitor model; determining a winding method of the winding, and calculating to obtain equivalent stray capacitance between adjacent layers of the winding according to an energy equivalence principle between the layers of the winding; determining a winding arrangement mode, a primary winding layer number NP and a secondary winding layer number NS, calculating stray capacitance among terminals of the windings according to an energy equivalence principle, and if the magnitude of the stray capacitance meets the parameter design requirement of the high-frequency transformer, performing the next step; a leakage inductance calculation model of the high-frequency transformer is established according to the winding structure, the geometrical shape, the winding winding method and the winding arrangement mode, and leakage inductance parameters are extracted; if the leakage inductance cannot meet the parameter design requirement of the high-frequency transformer; and if the leakage inductance can meet the parameter design requirement of the high-frequency transformer, ending the calculation. The method can be applied to accurate evaluation of parasitic parameters of the high-frequency transformer, leakage inductance and parasitic capacitance parameters are controlled within a reasonable range, the calculation amount and calculation time required by optimization design are reduced, and the method is convenient and rapid.

Description

Technical Field

[0001] The present invention relates to the field of high-frequency transformer design, and in particular to a method for controlling parasitic parameters of a high-frequency transformer taking high-frequency eddy current effects into consideration. Background Art

[0002] The use of cross-transposition technology (overlapping of primary and secondary layers or turns) can weaken the proximity effect, reduce the leakage magnetic field strength and AC resistance value in the magnetic components, and thus reduce the leakage inductance and winding loss, but at the same time it will change the relative position and facing area between the windings, affecting the distribution and size of the parasitic capacitance parameters in the transformer. The parasitic capacitance parameters and leakage inductance parameters work together to produce high-frequency oscillations, which have a significant impact on the impedance characteristics of the high-frequency transformer and seriously threaten the normal operation of the power electronic circuit. Therefore, accurately controlling the parasitic parameters in the high-frequency transformer is crucial to the overall design of the transformer.

[0003] In the existing technology, the parasitic parameter control method of high-frequency transformer usually only considers one of the parasitic parameters, leakage inductance and parasitic capacitance, while the winding structure, geometry, winding method and arrangement have a temporal and spatial synchronization on the two. When the leakage inductance value decreases, the parasitic capacitance value increases, and vice versa. At present, domestic and foreign scholars have carried out a lot of research on the methods of extracting and controlling the parasitic parameters of high-frequency transformers, such as:

[0004] (1) Reference [1]: Cogitore B, Keradec JP, Barbaroux J. The two-winding transformer: an experimental method to obtain a wide frequency range equivalent circuit [J]. IEEE Transactions on Instrumentation and Measurement, 1994, 43(2): 364-371. The parasitic parameters such as leakage inductance and capacitance in the broadband equivalent circuit are extracted through the open-circuit impedance characteristic curve of the high-frequency transformer port, thus avoiding the complex electromagnetic field calculation. However, it cannot reflect the relationship between the parasitic parameters and the internal structure of the transformer.

[0005] (2) Reference [2]: Yang Huina, Bai Shuqing. Influence of different winding structures of high-frequency transformer on distributed capacitance [J]. Journal of North China Electric Power University (Natural Science Edition), 2014, 41(04): 48-55. The influence of the winding structure of the high-frequency transformer used in the flyback converter on the parasitic capacitance is analyzed in detail, but the leakage inductance parameter is ignored.

[0006] (3) Reference [3]: Ouyang Z, Zhang J, Hurley W G. Calculation of leakage inductance for high frequency transformers [J]. IEEE Transactions on Power Electronics, 2015, 30(10): 5769-5775. Analytical calculation formulas are given for the leakage inductance and AC resistance of high-frequency transformers under different winding arrangements, and the influence of cross-commutation and high-frequency eddy current effect on leakage inductance and winding loss is analyzed in detail, but the parasitic capacitance parameters are ignored.

[0007] (4) Reference [4]: ​​Chen Bin, Li Lin, Zhao Zhibin. An analytical calculation method for leakage inductance of large-capacity high-frequency transformer considering frequency-varying characteristics [J]. Proceedings of the CSEE, 2017, 37(13): 3928-3937. An analytical calculation formula considering the frequency-varying characteristics of leakage inductance was derived, and the influence of the winding arc area at the core corner on the leakage magnetic energy was considered. However, the calculation process is relatively complicated for the leakage inductance parameter control in the transformer design stage.

[0008] (5) Reference [5]: Kane MM, Kulkarni S V. MTL-based analysis to distinguish high-frequency behavior of interleaved windings in power transformers [J]. IEEE Transactions on Power Delivery, 2013, 28(4): 2291-2299. A method for calculating the parasitic parameters per unit length of high-frequency transformer windings is proposed using the multi-conductor transmission line method. This method can accurately analyze the high-frequency behavior of the windings. However, the excessive number of circuit elements makes it unsuitable for the regulation of the parasitic parameters of high-frequency transformers. Summary of the invention

[0009] Aiming at the regulation of parasitic parameters of high-frequency transformers, the present invention provides a method for regulating leakage inductance parameters and parasitic capacitance parameters of high-frequency transformers that comprehensively considers high-frequency eddy current effects. The method considers the influence of winding structure, geometric shape, winding method and arrangement mode on the size of parasitic capacitance parameters, and provides a calculation method for parasitic capacitance between terminals of the winding; then, a corresponding transformer model is established in ANSYS / Maxwell electromagnetic field simulation software to extract leakage inductance parameters, thereby improving calculation accuracy.

[0010] The technical solution adopted by the present invention is:

[0011] A method for controlling parasitic parameters of a high-frequency transformer considering high-frequency eddy current effects comprises the following steps:

[0012] Step 1: Determine the parameters of the high-frequency transformer winding structure and geometry (such as circular conductor, rectangular conductor, Litz wire, etc.), and calculate the static capacitance between adjacent layers of the winding according to the parallel plate capacitor model;

[0013] Step 2: Determine the winding method (standard winding, flyback winding, etc.), and calculate the equivalent parasitic capacitance between adjacent layers of the winding according to the energy equivalence principle between winding layers;

[0014] Step 3: Determine the winding arrangement and the number of initial winding layers N P 、N number of secondary winding layers S , according to the energy equivalent principle, the parasitic capacitance between the terminals of the winding is calculated. If the parasitic capacitance meets the requirements of the high-frequency transformer parameter design, proceed to the next step, otherwise repeat steps 1 to 3;

[0015] Step 4: According to the winding structure, geometry, winding method and winding arrangement, a leakage inductance calculation model of the high-frequency transformer is established to extract the leakage inductance parameters;

[0016] Step 5: If the leakage inductance cannot meet the high-frequency transformer parameter design requirements, repeat steps 1 to 4; if the leakage inductance can meet the high-frequency transformer parameter design requirements, the calculation ends;

[0017] Through the above steps, the parasitic parameters of the high-frequency transformer are regulated.

[0018] In step 1, the high-frequency transformer parameters include: conductor radius r0, interlayer insulation distance h, conductor insulation layer thickness δ, conductor turn distance d tt , average turn length of two-layer winding L c , Winding height L d , Equivalent insulation distance between layers d eff .

[0019] In step 1, the calculation expression of the static capacitance between adjacent layers of the winding is as follows:

[0020]

[0021] Where: ε0 and ε1 are the vacuum dielectric constant and the equivalent relative dielectric constant of the interlayer medium respectively; L c is the average turn length of the two-layer winding; L d is the winding height; d eff is the equivalent insulation distance between layers.

[0022] In step 2, the calculation expression of the equivalent parasitic capacitance between adjacent layers of the winding is as follows:

[0023] C L1 =C0 / 3

[0024] C L1 is the equivalent parasitic capacitance between adjacent layers of winding under standard winding method;

[0025] C L2 =C0 / 4

[0026] C L2 It is the equivalent parasitic capacitance between adjacent layers of the winding under the flyback winding method.

[0027] In step 3, the winding arrangement includes: no cross-transposition, partial cross-transposition and complete cross-transposition winding arrangement;

[0028] The calculation expression of the parasitic capacitance between the winding terminals is as follows:

[0029]

[0030] Where: N1 and N2 are the number of adjacent layers of the primary and secondary windings respectively; N3 is the number of adjacent layers of different windings; C 1k ~C 6k The 6 capacitances between the kth adjacent layers of different windings are converted into the capacitance at the terminal connection; k represents the number of the adjacent layers of the kth different windings; C t1 Represents the capacitance between the two terminals A and B; C t2 Represents the capacitance between the two terminals C and D; C t3 Represents the capacitance between the two terminals B and D; C t4 Represents the capacitance between the two terminals A and C; C t5 Represents the capacitance between the two terminals B and C; C t6 Represents the capacitance between terminals A and D. The terminal numbers are as follows: Figure 6 As shown; C p ' pi and C s ' si The i-th interlayer equivalent capacitance of the primary and secondary windings is converted into the capacitance at the terminal connection.

[0031] In step 3, according to the role of the capacitor in the operation of the high-frequency transformer, if resonance with the inductor is required to obtain high efficiency, the size of the parasitic capacitor needs to be determined according to the resonance calculation formula, and the size of the parasitic capacitor needs to meet the design requirements of the high-frequency transformer.

[0032]

[0033] Where: C r1 is the resonant capacitance required on the primary side; L σ1 is the resonant leakage inductance required on the primary side; Cr2 is the resonant capacitance required on the secondary side; L σ2 is the resonant leakage inductance required on the secondary side.

[0034] In step 4, based on the magnetic field energy method, a calculation model of the high-frequency transformer is established according to the winding structure, geometry, winding method and arrangement. Based on the energy method and the linear leakage magnetic field strength of the conductor area, the leakage inductance calculation model is obtained as follows:

[0035]

[0036] Where: MLT 12 , MLT1 and MLT2 are the average turn lengths between the primary and secondary windings, and between the primary winding and the secondary winding respectively; △ 12 is the isolation distance between the primary and secondary windings; d1 and d2 are the thicknesses of the primary and secondary windings respectively; μ is the magnetic permeability; m1 is the number of primary winding layers; and h is the winding height.

[0037] In step 5, if the leakage inductance cannot meet the high-frequency transformer parameter design requirements, steps 1 to 4 are repeated; if the leakage inductance can meet the high-frequency transformer parameter design requirements, the calculation ends.

[0038] The present invention provides a method for controlling parasitic parameters of a high-frequency transformer taking into account high-frequency eddy current effects, and the technical effects are as follows:

[0039] This method can be applied to the accurate evaluation of parasitic parameters of high-frequency transformers, and the leakage inductance and parasitic capacitance parameters can be controlled within a reasonable range, which reduces the amount of calculation and time required for the optimization design. It is convenient and fast, and provides a basis for the connection of series inductance and resonant capacitance to the working circuit of high-frequency transformers, further improving the stability of the equipment and facilitating engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0041] Figure 1 A flow chart established for the control method of the present invention.

[0042] Figure 2 It is the parasitic capacitance network of the high frequency transformer.

[0043] Figure 3 It is the equivalent parallel plate capacitor model between winding layers.

[0044] Figure 4 (a) is the standard winding method and the interlayer voltage distribution diagram;

[0045] Figure 4 (b) is the flyback winding method and interlayer voltage distribution diagram.

[0046] Figure 5 Schematic diagram of four typical winding arrangements for high-frequency transformers.

[0047] Figure 6 It is a lumped parameter six-capacitor characterization model.

[0048] Figure 7 (a) is a schematic diagram of the distributed equivalent capacitance characterization model under the winding non-cross-transposition arrangement;

[0049] Figure 7 (b) is a schematic diagram of the distributed equivalent capacitance characterization model under the winding partial cross-transposition arrangement;

[0050] Figure 7 (c) is a schematic diagram of the distributed equivalent capacitance characterization model under the winding complete cross-transposition arrangement;

[0051] Figure 7 (d) is a schematic diagram of the distributed equivalent capacitance characterization model under the winding complete two-cross transposition arrangement.

[0052] Figure 8(a) is a diagram showing the distribution of electric field strength and electric field energy density in a winding arrangement without cross-transposition;

[0053] FIG8( b ) is a diagram showing the distribution of electric field strength and electric field energy density in a partially cross-transposed arrangement of windings;

[0054] FIG8(c) is a diagram showing the distribution of electric field strength and electric field energy density in a completely cross-transposed arrangement of windings;

[0055] Figure 8(d) is the distribution diagram of the electric field strength and electric field energy density under the winding complete two-cross transposition arrangement.

[0056] FIG9( a ) is a diagram showing the distribution of leakage magnetic field intensity and leakage magnetic field energy density in a winding arrangement without cross-transposition;

[0057] FIG9( b ) is a diagram showing the distribution of leakage magnetic field intensity and leakage magnetic field energy density in a winding partial cross-transposition arrangement;

[0058] FIG9( c ) is a diagram showing the distribution of leakage magnetic field intensity and leakage magnetic field energy density in a completely cross-transposed arrangement of windings;

[0059] Figure 9(d) is a diagram showing the distribution of leakage magnetic field intensity and leakage magnetic field energy density in a winding complete two-cross transposition arrangement.

[0060] Fig.10 Schematic diagram of the high-frequency transformer model and impedance measurement platform.

[0061] Fig.11 These are the leakage inductance extraction results for four winding arrangements without cross-transposition. DETAILED DESCRIPTION

[0062] A method for controlling parasitic parameters of a high-frequency transformer comprises the following steps:

[0063] Step 1: Determine the high-frequency transformer winding structure and geometry (such as round conductor, rectangular conductor, Litz wire, etc.) and other parameters: conductor radius r0, interlayer insulation distance h, conductor insulation layer thickness δ, conductor turn distance d tt , average turn length of two-layer winding L c , Winding height L d , Equivalent insulation distance between layers d eff Considering the different geometric shapes of windings, the calculation method of the equivalent insulation distance between layers is also different. The equivalent insulation distance between layers is calculated according to the conductor radius, the insulation distance between layers, the thickness of the conductor insulation layer, and the distance between the conductor turns. The static capacitance between adjacent layers of the winding is calculated according to the parallel plate capacitor model.

[0064] The calculation expression of static capacitance between adjacent layers of winding is as follows:

[0065]

[0066] Where: ε0 and ε1 are the vacuum dielectric constant and the equivalent relative dielectric constant of the interlayer medium respectively; L c is the average turn length of the two-layer winding; L d is the winding height; d eff is the equivalent insulation distance between layers.

[0067] Equivalent insulation distance d between circular conductor layers eff The calculation formula is as follows:

[0068] d eff =2r0+h-2.3(r0+δ)+0.26d tt

[0069] Where: r0 is the radius of the circular conductor; h is the interlayer insulation distance; δ is the thickness of the conductor insulation layer; d tt is the distance between conductor turns. Step 2: Determine the winding method (standard winding, flyback winding, etc.), considering that the winding method will change the electrostatic field energy stored in the interlayer insulation material, thereby changing the interlayer equivalent capacitance. According to the interlayer voltage distribution function of the winding, the equivalent parasitic capacitance between adjacent layers of the winding is calculated based on the interlayer energy equivalence principle of the winding;

[0070] The calculation expression of equivalent parasitic capacitance between adjacent layers of winding is as follows:

[0071] C L1 =C0 / 3

[0072] C L1is the equivalent parasitic capacitance between adjacent layers of winding under standard winding method;

[0073] C L2 =C0 / 4

[0074] C L2 is the equivalent parasitic capacitance between adjacent layers of the winding under the flyback winding method;

[0075] Step 3: Determine the winding arrangement (no cross-commutation, partial cross-commutation, and complete cross-commutation), the initial number of winding layers N P 、N number of secondary winding layers S The winding arrangement will change the relative position and facing area between the windings, affecting the distribution and size of the parasitic capacitance parameters in the transformer. The parasitic capacitance between the terminals of the winding is calculated according to the energy equivalence principle. If the parasitic capacitance meets the transformer parameter design requirements, proceed to the next step, otherwise repeat steps 1 to 3.

[0076] The calculation expression for converting the interlayer equivalent capacitance into the capacitance at the terminal connection is as follows

[0077]

[0078] Where: C p ' p and C s ' s N is the equivalent capacitance between the primary and secondary winding layers converted into the capacitance at the terminal connection; Layer is the number of winding layers; N L,k is the number of turns of the kth layer of winding; N L,i With N L,i+1 are the number of turns of the i-th layer and the i+1th layer of the winding respectively; C i,i+1 is the capacitance between the i-th and i+1-th layers of the winding.

[0079] Taking the fourth layer of the four layers of the primary and secondary windings in the case of partial cross-transposition of the high-frequency transformer as an example, the electrostatic field energy stored between adjacent layers of different windings is converted into six capacitors in the lumped six-capacitor model at the terminal connection, which is expressed as

[0080]

[0081] Where: a~f are voltage coefficients.

[0082] The calculation expression of the parasitic capacitance between the winding terminals is as follows:

[0083]

[0084] Where: N1 and N2 are the number of adjacent layers of the primary and secondary windings respectively; N3 is the number of adjacent layers of different windings; C 1k ~C6k The 6 capacitances between the kth adjacent layers of different windings are converted into the capacitance at the terminal connection; C p ' pi and C s ' si The i-th interlayer equivalent capacitance of the primary and secondary windings is converted into the capacitance at the terminal connection.

[0085] Step 4: Based on the magnetic field energy method, establish a calculation model of the high-frequency transformer according to the winding structure, geometry, winding method and arrangement. Based on the energy method and the linear leakage magnetic field strength of the conductor area, the leakage inductance calculation model is obtained as follows:

[0086]

[0087] Where: MLT 12 , MLT1 and MLT2 are the average turn lengths between the primary and secondary windings, and between the primary winding and the secondary winding respectively; △ 12 is the isolation distance between the primary and secondary windings; d1 and d2 are the thicknesses of the primary and secondary windings respectively; μ is the magnetic permeability; m1 is the number of primary winding layers; and h is the winding height.

[0088] Extract leakage inductance parameters. If the leakage inductance cannot meet the transformer parameter design requirements, repeat steps 1 to 4. Embodiment:

[0089] The present invention provides a method for controlling parasitic parameters of a high-frequency transformer, and its application scope is not limited to the type of transformer, the structure of the core window, other electrical equipment connected to the outside of the transformer, etc. The process of the method for controlling parasitic parameters of a high-frequency transformer proposed by the present invention is as follows: Figure 1 shown.

[0090] Under the following assumptions, parasitic parameters are controlled:

[0091] ①. The capacitance effect between winding turns can be ignored.

[0092] ② There is no capacitance effect between the winding, the core and the shell;

[0093] ③. The spatial field strength between windings is evenly distributed.

[0094] Step S1: Determine the parameters such as the structure and geometry of the high-frequency transformer winding (such as round conductor, rectangular conductor, Litz wire, etc.): conductor radius r0, interlayer insulation distance h, conductor insulation layer thickness δ, conductor turn-to-turn distance d tt , average turn length L of two-layer winding c , Winding height L d , Equivalent insulation distance between layers d effConsidering the different winding geometric shapes, the calculation method of the equivalent insulation distance between layers is also different. The equivalent insulation distance between layers is calculated based on the conductor radius, interlayer insulation distance, conductor insulation layer thickness, and conductor turn-to-turn distance. The parasitic capacitance of the high-frequency transformer mainly exists between the turns of the winding and between the winding layers. Figure 2 As shown in the figure, the static capacitance between adjacent layers of the winding is calculated based on the parallel plate capacitor model. Figure 3 shown.

[0095] The calculation expression of static capacitance between adjacent layers of winding is as follows:

[0096]

[0097] Where: ε0 and ε1 are the vacuum dielectric constant and the equivalent relative dielectric constant of the interlayer medium respectively; L c is the average turn length of the two-layer winding; L d is the winding height; d eff is the equivalent insulation distance between layers.

[0098] Equivalent insulation distance d between circular conductor layers eff The calculation formula is as follows:

[0099] d eff =2r0+h-2.3(r0+δ)+0.26d tt

[0100] Where: r0 is the radius of the circular conductor; h is the interlayer insulation distance; δ is the thickness of the conductor insulation layer; d tt is the distance between conductor turns.

[0101] Step S2: Determine the winding method (standard winding method, flyback winding method, etc.), considering that the winding winding method will change the electrostatic field energy stored in the interlayer insulation material, thereby changing the interlayer equivalent capacitance. According to the winding interlayer voltage distribution function, Figure 4 As shown, the equivalent parasitic capacitance between adjacent layers of the winding is calculated based on the energy equivalence principle between winding layers;

[0102] The calculation expression of equivalent parasitic capacitance between adjacent layers of winding is as follows:

[0103] C L1 =C0 / 3

[0104] C L1 is the equivalent parasitic capacitance between adjacent layers of winding under standard winding method;

[0105] C L2 =C0 / 4

[0106] C L2 is the equivalent parasitic capacitance between adjacent layers of the winding under the flyback winding method;

[0107] Step S3: Determine the winding arrangement (winding arrangement such as no cross-transposition, partial cross-transposition and complete cross-transposition), the initial number of winding layers N P 、N number of secondary winding layers S , the winding arrangement will change the relative position and facing area between windings, such as Figure 5 As shown in the figure, the distribution and size of the parasitic capacitance parameters in the transformer are affected. The parasitic capacitance between the winding terminals is calculated based on the energy equivalent principle, as shown in the figure. Figure 6 If the parasitic capacitance meets the transformer parameter design requirements, proceed to the next step, otherwise repeat steps S1 to S3;

[0108] The calculation expression for converting the interlayer equivalent capacitance into the capacitance at the terminal connection is as follows

[0109]

[0110] Where: C p ' p and C s ' s N is the equivalent capacitance between the primary and secondary winding layers converted into the capacitance at the terminal connection; Layer is the number of winding layers; N L,k is the number of turns of the kth layer of winding; N L,i With N L,i+1 are the number of turns of the i-th layer and the i+1th layer of the winding respectively; C i,i+1 is the capacitance between the i-th and i+1-th layers of the winding.

[0111] Taking the fourth layer of the four layers of the primary and secondary windings in the case of partial cross-transposition of the high-frequency transformer as an example, the electrostatic field energy stored between adjacent layers of different windings is converted into six capacitors in the lumped six-capacitor model at the terminal connection, which is expressed as

[0112]

[0113] Where: a~f are voltage coefficients.

[0114] The parasitic capacitance calculation expression between the winding terminals is as follows:

[0115]

[0116] Where: N1 and N2 are the number of adjacent layers of the primary and secondary windings respectively; N3 is the number of adjacent layers of different windings; C 1k ~C 6k The 6 capacitances between the kth adjacent layers of different windings are converted into the capacitance at the terminal connection; C p ' pi and C s ' siThe i-th interlayer equivalent capacitance of the primary and secondary windings is converted into the capacitance at the terminal connection.

[0117] Further converted into three lumped capacitors:

[0118]

[0119] Where: C A is the primary winding equivalent capacitance; C B is the primary winding equivalent capacitance; C C is the equivalent capacitance between the primary and secondary windings; n is the turns ratio between the primary and secondary windings.

[0120] Step S4: using ANSYS / Maxwell electromagnetic field simulation software to establish a finite element simulation model of the high-frequency transformer according to the winding structure, geometric shape, winding method and arrangement, selecting current source excitation in the eddy current field solver, sweeping the frequency to extract the leakage inductance at each frequency point, and extracting the leakage inductance parameters. If the leakage inductance cannot meet the transformer parameter design requirements, repeating steps S1 to S4;

[0121] Taking four transformers with no cross-commutation, partial cross-commutation and full cross-commutation winding arrangements as examples, their structural parameters are shown in Table 1.

[0122] Table 1 Main design parameters of high frequency transformer model

[0123]

[0124]

[0125] Figure 7 (a)~ Figure 7 (d) is the distribution of parasitic capacitance between winding layers. Figure 7 (a)~ Figure 7 (d) It can be seen that the greater the degree of winding cross-transposition, the tighter the electrostatic coupling between the primary and secondary windings, which leads to a decrease in the parasitic capacitance between the layers in the same primary and secondary windings, while the parasitic capacitance between adjacent layers of the primary and secondary windings increases.

[0126] The parasitic capacitance between the winding terminals is calculated through steps S1 to S3, and the parasitic capacitance parameters are extracted and verified by modeling in finite element software, such as Figure 8(a) to Figure 8(d) As shown, from Figure 8(a) to Figure 8(d) It can be seen that the electric field energy density is mainly distributed between layers, and the inter-turn electric field energy density is very small, so the influence of the inter-turn capacitance can be ignored. In addition, the electric field strength and electric field energy density are unevenly distributed in the section where each turn of the circular conductor is located. The comparison results are shown in Table 2. The analytical calculation results are basically consistent with the finite element simulation results, and the average deviation between the two is 5.31%.

[0127] Table 2 Analytical calculation and simulation results of six capacitor parameters of high-frequency transformer

[0128]

[0129] The main reason for the above deviation is that the analytical calculation method equates the adjacent layers of the winding to a parallel plate capacitor model, and the effect of the circular solid conductor on the uneven distribution of the spatial field strength cannot be fully considered in the equivalent process. It is further converted into an equivalent three-capacitor between the winding terminals, as shown in Table 3.

[0130] Table 3 Parameters of three capacitors between high-frequency transformer terminals

[0131]

[0132] Table 3 shows that the equivalent capacitance C of the primary side is A The equivalent capacitance C on the secondary side B equal, while the equivalent capacitances of the primary and secondary sides of a complete cross-commutation are not equal.

[0133] The finite element simulation model of the high-frequency transformer is established by using ANSYS / Maxwell electromagnetic field simulation software according to the winding structure, geometry, winding method and arrangement. The current source excitation is selected in the eddy current field solver, and the leakage inductance at each frequency point is extracted by sweeping the frequency. The leakage inductance parameters are extracted, such as Figure 9(a) to Figure 9(d) As shown in the figure, the magnetic field intensity and magnetic field energy density distribution diagram are given when the frequency is 100kHz and the effective value of the conductor current is 1A. Compared with the maximum magnetic field intensity of 8kA / m in the case of no cross-transposition, the maximum magnetic field intensity in the case of partial cross-transposition is 4kA / m, which is reduced by half; the magnetic field intensity of the two complete cross-transposition cases is 2kA / m, which is reduced to 1 / 4 of the original. The leakage inductance parameters of the high-frequency transformer test model are measured using the Agilent 4294A high-precision impedance analyzer. The measurement frequency range is 40Hz~20MHz, and open-short circuit calibration is performed before measurement to improve the accuracy of the measurement results.

[0134] During the measurement, a low level current is applied to ensure that the transformer operates in the linear region. Fig.10 As shown. Since the secondary winding of the test model is short-circuited, the leakage inductance measured under the four arrangements is attributed to the primary winding, and compared with the leakage inductance results extracted by finite element method, as shown Fig.11 As shown, from Fig.11 It can be seen that the leakage inductance is the same under the two complete cross-commutation modes, and the greater the degree of cross-commutation, the smaller the leakage inductance.

[0135] Table 4 shows the leakage inductance at low and high frequencies. The leakage inductance obtained by the finite element simulation method is based on the leakage magnetic field energy in the winding area. In the intermediate frequency band, the leakage inductance obtained by the two methods is basically consistent. When the applied frequency is less than the resonant frequency, the inductance plays a major role, but when the frequency is close to the resonance point, the influence of the parasitic capacitance cannot be ignored. The above reasons make it impossible for the experimental method to extract the leakage inductance parameters close to the resonance point and higher frequencies.

[0136] Table 4 Winding low-frequency and high-frequency leakage inductance parameters

[0137]

[0138] Combining Table 3 and Table 4, it can be analyzed that if the electromagnetic interference requirements are strict, the common-mode port effective capacitance C can be controlled when the leakage inductance parameter size is increased. C If the leakage inductance is strict, the parasitic capacitance can be increased and the winding arrangement can be completely crossed. In addition, the winding structure, geometry, and winding method can be adjusted. In summary, it is necessary to balance the leakage inductance and parasitic capacitance according to the requirements of the specific application scenarios of the high-frequency transformer and control them within a reasonable range.

[0139] The present invention discloses a method for controlling the parasitic parameters of a high-frequency transformer, wherein the magnitude of the leakage inductance and the parasitic capacitance is selected by changing the winding structure, geometric shape, winding method and arrangement mode. The present invention can be applied to the accurate evaluation of the parasitic parameters of the high-frequency transformer, and the magnitude of the leakage inductance and the parasitic capacitance parameters are controlled within a reasonable range, thereby reducing the amount of calculation and the calculation time required for the optimization design, being convenient and fast, providing a basis for connecting the series inductance and the resonant capacitance to the working circuit of the high-frequency transformer, further improving the stability of the equipment, and being beneficial to engineering applications.

Claims

1. A method for controlling parasitic parameters of a high-frequency transformer considering high-frequency eddy current effects, characterized in that The following steps are involved: Step 1: Determine the structure and geometric parameters of the high-frequency transformer winding, and calculate the static capacitance between adjacent layers of the winding according to the capacitor model; Step 2: Determine the winding method, and calculate the equivalent parasitic capacitance between adjacent layers of the winding according to the energy equivalence principle between winding layers; Step 3: Determine the winding arrangement and the number of initial winding layers N P 、N number of secondary winding layers S , according to the energy equivalent principle, the parasitic capacitance between the terminals of the winding is calculated. If the parasitic capacitance meets the requirements of the high-frequency transformer parameter design, proceed to the next step, otherwise repeat steps 1 to 3; Step 4: According to the winding structure, geometry, winding method and winding arrangement, a leakage inductance calculation model of the high-frequency transformer is established to extract the leakage inductance parameters; Step 5: If the leakage inductance cannot meet the high-frequency transformer parameter design requirements, repeat steps 1 to 4; if the leakage inductance can meet the high-frequency transformer parameter design requirements, the calculation ends; Through the above steps, the parasitic parameters of the high-frequency transformer are regulated.

2. A method for controlling parasitic parameters of a high-frequency transformer considering high-frequency eddy current effect according to claim 1, characterized in that: In step 1, the high-frequency transformer parameters include: conductor radius r0, interlayer insulation distance h, conductor insulation layer thickness δ, conductor turn distance d tt , average turn length of two-layer winding L c , Winding height L d , Equivalent insulation distance between layers d eff .

3. A method for controlling parasitic parameters of a high-frequency transformer considering high-frequency eddy current effect according to claim 2, characterized in that: In step 1, the calculation expression of the static capacitance between adjacent layers of the winding is as follows: Where: ε0 and ε1 are the vacuum dielectric constant and the equivalent relative dielectric constant of the interlayer medium respectively; L c is the average turn length of the two-layer winding; L d is the winding height; d eff is the equivalent insulation distance between layers.

4. The method for controlling parasitic parameters of a high-frequency transformer considering high-frequency eddy current effect according to claim 1, characterized in that: In step 2, the calculation expression of the equivalent parasitic capacitance between adjacent layers of the winding is as follows: C L1 =C0 / 3 C L1 is the equivalent parasitic capacitance between adjacent layers of winding under standard winding method; C L2 =C0 / 4 C L2 It is the equivalent parasitic capacitance between adjacent layers of the winding under the flyback winding method.

5. The method for controlling parasitic parameters of a high-frequency transformer considering high-frequency eddy current effect according to claim 1, characterized in that: In step 3, the winding arrangement includes: no cross-transposition, partial cross-transposition and complete cross-transposition winding arrangement; the parasitic capacitance calculation expression between each terminal of the winding is as follows: Where: N1 and N2 are the number of adjacent layers of the primary and secondary windings respectively; N3 is the number of adjacent layers of different windings; C 1k ~C 6k The 6 capacitances between the kth adjacent layers of different windings are converted into the capacitance at the terminal connection; k represents the number of the adjacent layers of the kth different windings; C t1 Represents the capacitance between the two terminals A and B; C t2 Represents the capacitance between the two terminals C and D; C t3 Represents the capacitance between the two terminals B and D; C t4 Represents the capacitance between the two terminals A and C; C t5 Represents the capacitance between the two terminals B and C; C t6 Represents the capacitance between the two terminals A and D; C p ' pi and C s ' si The i-th interlayer equivalent capacitance of the primary and secondary windings is converted into the capacitance at the terminal connection.

6. The method for controlling parasitic parameters of a high-frequency transformer considering high-frequency eddy current effect according to claim 1, characterized in that: In step 3, the parasitic capacitance is determined according to the resonance calculation formula, and the parasitic capacitance needs to meet the design requirements of the high-frequency transformer; Where: C r1 is the resonant capacitance required on the primary side; L σ1 is the resonant leakage inductance required on the primary side; C r2 is the resonant capacitance required on the secondary side; L σ2 is the resonant leakage inductance required on the secondary side.

7. The method for controlling parasitic parameters of a high-frequency transformer considering high-frequency eddy current effect according to claim 1, characterized in that: In step 4, based on the magnetic field energy method, a calculation model of the high-frequency transformer is established according to the winding structure, geometric shape, winding method and arrangement mode; based on the energy method and the linear leakage magnetic field strength of the conductor area, the leakage inductance calculation model is obtained as follows: Where: MLT 12 , MLT1 and MLT2 are the average turn lengths between the primary and secondary windings, and between the primary winding and the secondary winding respectively; △ 12 is the isolation distance between the primary and secondary windings; d1 and d2 are the thicknesses of the primary and secondary windings respectively; μ is the magnetic permeability; m1 is the number of primary winding layers; and h is the winding height.

8. The method for controlling parasitic parameters of a high-frequency transformer considering high-frequency eddy current effect according to claim 1, characterized in that: In step 5, if the leakage inductance cannot meet the high-frequency transformer parameter design requirements, steps 1 to 4 are repeated; if the leakage inductance can meet the high-frequency transformer parameter design requirements, the calculation ends.

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