Design and comprehensive evaluation method for mixed winding of high-frequency transformer

Abstract

The invention belongs to the technical field of transformers, and particularly relates to a high-frequency transformer mixed winding design and comprehensive evaluation method which mainly comprises the following steps: designing primary and secondary windings by considering three winding types of copper foil, flat copper wire and litz wire according to electrical indexes and design requirements of a high-frequency transformer, and giving a design scheme; establishing a fine calculation model for loss of different types of windings, and deducing loss expressions of primary and secondary windings in different design schemes; providing evaluation indexes reflecting winding efficiency, cost effectiveness and heat dissipation performance; establishing a comprehensive evaluation model based on an AHP-entropy weight combination method and a TOPSIS method which are combined subjectively and objectively; according to a comprehensive evaluation result, selecting an optimal high-frequency transformer winding design scheme; the method provides a new thought for the optimization design of the high-frequency transformer, can realize the balance between the winding performance and the cost of the transformer, and is beneficial to engineering application.

Description

Technical Field

[0001] The invention belongs to the technical field of transformers, and in particular relates to a high-frequency transformer hybrid winding design and comprehensive evaluation method. Background Art

[0002] As the core component of power conversion and transmission, high-frequency transformers are widely used in rail transit, electric vehicle charging stations, aerospace, and new energy DC grid connection. High-frequency transformers not only undertake the task of voltage conversion, but also need to maintain efficient, stable, and reliable working conditions in a high-frequency environment, which puts more stringent requirements on the design of transformers. Among them, the winding is an important component of the high-frequency transformer, and its design directly affects the performance parameters of the transformer such as efficiency, temperature rise, cost, and reliability.

[0003] At present, the commonly used types of high-frequency transformer windings mainly include copper foil, flat copper wire and Litz wire. Copper foil exhibits low AC resistance and skin effect in high-frequency applications due to its good conductivity and heat dissipation performance, but the winding process is relatively complicated; flat copper wire has a higher current carrying capacity and is easy to wind, but it is susceptible to skin effect at high frequencies; Litz wire is made of multiple strands of fine wires, which effectively reduces the skin effect and proximity effect at high frequencies, but the cost is relatively high. Although high-frequency transformers have made significant technological progress, they still face many challenges in the design and application process.

[0004] First, the skin effect and proximity effect of the winding are aggravated at high frequencies, resulting in a significant increase in winding loss, which affects the efficiency of the transformer. The accurate calculation of winding loss is a complex issue, which is affected by many factors, including the geometry of the winding, material properties, and operating frequency. Secondly, how to reduce material and labor costs and improve production efficiency while meeting performance requirements is a key issue that designers need to solve. In addition, as the application scope of high-frequency transformers expands, heat dissipation problems are gradually emerging. How to effectively manage heat to ensure the stability and safety of the equipment has become an important issue in the design process. Summary of the invention

[0005] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a high-frequency transformer hybrid winding design and comprehensive evaluation method, which can help designers select the best among many schemes, improve design efficiency, reduce development costs, achieve a balance between performance and cost, and facilitate the engineering application of high-frequency transformers.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] The high-frequency transformer hybrid winding design and comprehensive evaluation method comprises the following steps:

[0008] S1: Select the corresponding winding type according to the electrical specifications and design requirements of the high-frequency transformer;

[0009] When changing the winding type, the bare area of ​​each turn of the winding conductor on the primary and secondary sides is kept equal;

[0010] S2: For different types of windings, the calculation models of winding losses are established respectively, and the loss expressions of primary and secondary windings of different design schemes are derived;

[0011] S3: Establish a comprehensive evaluation index system to evaluate the feasibility of different winding design schemes. The evaluation indicators include winding loss, space utilization, material cost, winding difficulty and temperature rise;

[0012] S4: Based on the evaluation index proposed in step S3, a comprehensive evaluation model is established, and the weight of each evaluation index is determined by using the subjective and objective AHP-entropy weight combination method, and then the hybrid winding design scheme is evaluated by the TOPSIS method to calculate the comprehensive evaluation score of each scheme;

[0013] S5: Sort and compare the solutions according to the scores in step S4, and select the winding design solution with the highest score as the final solution.

[0014] Furthermore, in step S1, the calculation formula for keeping the bare area of ​​each turn of the winding wire on the primary and secondary sides equal is:

[0015]

[0016] In the above formula, A xp and A xs are the bare area of ​​the wire per turn of the primary and secondary windings, I p and I s are the primary and secondary currents, J cp and J cs are the current densities of the primary and secondary windings respectively.

[0017] Further, in step S2, the AC resistance coefficient F of the primary and secondary windings is rp and F rs The calculation formula is:

[0018] S2.1: For copper foil and flat copper wire windings, use Dowell's formula for calculation:

[0019]

[0020] in,

[0021]

[0022] In the above formula, mp and m s are the number of layers of primary and secondary windings respectively; Δ 1 and Δ 2 are the normalized thickness of the primary and secondary windings to the skin depth, respectively;

[0023] S2.2: For Litz wire windings, use Tourkhani’s formula for calculation:

[0024]

[0025] in,

[0026]

[0027] In the above formula, the parameter ζ p / s =d Lp / s / δ,d Lp / s is the diameter of the primary and secondary single-strand Litz wire, δ is the skin depth of the strand, n L1 and n L2 are the total number of Litz wires on the primary and secondary sides, β L1 and β L2 are the filling factors of the primary and secondary Litz wires respectively;

[0028] According to the type of primary and secondary windings, select the corresponding formula for calculation, and the primary and secondary winding losses are P wp and P ws , high frequency transformer winding loss P w for:

[0029]

[0030] In the above formula, R dc_p and R dc_s are the DC resistances of the primary and secondary windings respectively.

[0031] Furthermore, in step S3, the calculation process of the evaluation index is:

[0032] S3.1: Evaluation index of winding design efficiency;

[0033] a. Winding loss P w

[0034] Winding loss P of each solution w Solve it according to the calculation formula in step S2;

[0035] b. Space utilization η w

[0036]

[0037] In the above formula, Np and N s are the turns of the primary and secondary windings respectively, h p and h s are the primary and secondary winding heights, d p and d s They are the thickness of the primary and secondary windings along the winding direction respectively;

[0038] S3.2: Evaluation indicators of cost-effectiveness of winding design solutions;

[0039] a. Material cost C w

[0040] C w =ρ wp V wp u wp +ρ ws V ws u ws ;

[0041] in,

[0042] In the above formula, ρ wp and ρ ws are the unit volume densities of the primary and secondary windings respectively; V wp and V ws are the total volumes of the primary and secondary windings, u wp and u ws are the unit weight prices of the primary and secondary windings, respectively. m_p and l m_s are the approximate average turn lengths of the primary and secondary windings respectively;

[0043] b. Winding difficulty DOW

[0044] The difficulty of winding DOW is evaluated by the transformer manufacturer into four levels;

[0045] DOW∈{A,B,C,D};

[0046] In the above formula, A represents easy, B represents average, C represents difficult, and D represents difficult;

[0047] S3.3: Evaluation index of heat dissipation performance of winding design scheme;

[0048] a. Temperature rise T w

[0049] Winding temperature rise T under natural air cooling conditions w for:

[0050]

[0051] In the above formula, A tp and A ts are the surface areas of the primary and secondary windings respectively; k p and k s They are the area correction factors of the primary and secondary windings, respectively, and depend on the heat dissipation performance of copper foil, flat copper wire and Litz wire.

[0052] Further, in step S4, the process of using the AHP-entropy weight combination method and the TOPSIS method for comprehensive evaluation is as follows:

[0053] S4.1: APH method

[0054] Assume that the previous level A contains A 1 , A 2 , ..., A m There are m factors in total, and their hierarchical total ranking weights are a 1 、a 2 , ..., a m , suppose the next level B contains n factors B 1 , B 2 , ..., B n , they are about A j The hierarchical single sorting weights are b 1j , ..., b nj , the total hierarchical ranking weight w of each factor in layer B i AHP The calculation formula is:

[0055]

[0056] Assume that layer B is j The pairwise comparison judgment matrix of the relevant factors is subjected to consistency test in single sorting, and the single sorting consistency index is obtained as CI(j), (j=1,...,m), and the corresponding average random consistency index is RI(j). Then the calculation formula of the random consistency ratio of the total sorting of layer B is:

[0057]

[0058] When CR<0.10, the hierarchical total ranking result is considered to have satisfactory consistency and the analysis result is accepted;

[0059] S4.2: Entropy Weight Method

[0060] Assume that the original data matrix of m evaluation indicators and n evaluation objects is A=(a ij ) m×n , after normalization, we get R = (r ij ) m×n , for the index with the largest value being the best, the normalized formula is:

[0061]

[0062] For indicators with small values ​​as the best, the normalization formula is:

[0063]

[0064] The entropy h of the i-th evaluation index i for:

[0065]

[0066] When f ii = 0, let ln f ii =0.1;

[0067] After defining the entropy of the i-th evaluation index, the entropy weight w of the i-th evaluation index is obtained i EWM for:

[0068]

[0069] Weight coefficient w i It reflects the amount of information of the indicator. The larger the entropy weight is, the greater the role of the indicator in comprehensive decision-making, reflecting the degree of difference between indicators.

[0070] S4.3: TOPSIS method

[0071] The comprehensive weight w is calculated based on the AHP-entropy weight combination method i T for:

[0072]

[0073] In the above formula, α is the subjective preference coefficient, 1-α is the objective preference coefficient, and α=0.7;

[0074] The evaluation matrix is ​​processed under standard conditions to obtain the standardized evaluation result v ij T , the weighted judgment matrix r is obtained by multiplying the comprehensive weight and the standardized evaluation matrix ij T for:

[0075]

[0076] The Euclidean distance between each solution and the positive and negative ideal solutions is calculated based on the elements of the weighted judgment matrix:

[0077]

[0078] The closeness reflects the closeness of the selected solution to the positive ideal solution, and the calculation formula is:

[0079]

[0080] Furthermore, in step S5, the solutions are sorted and compared from large to small according to the closeness results, and the winding design solution with the highest score is selected as the final solution.

[0081] Compared with the prior art, the present invention has the following beneficial effects:

[0082] (1) The present invention proposes to use different combinations of copper foil, flat copper wire, copper wire and Litz wire to design the primary and secondary windings of a high-frequency transformer, providing a variety of combination options, which can be flexibly adjusted according to specific application requirements, adapting to different working conditions and performance requirements, and providing a new idea for the optimization design of high-frequency transformers;

[0083] (2) The present invention proposes a method for accurately calculating the loss of mixed windings, which realizes the accurate calculation of the loss of different types of windings on the primary and secondary sides, which is beneficial to optimize the design of high-frequency transformers and improve the energy efficiency of the system;

[0084] (3) The present invention establishes a comprehensive evaluation model for the hybrid winding design of a high-frequency transformer, and systematically evaluates different winding design schemes through multiple dimensions, which can achieve a balance between the performance and cost of the high-frequency transformer winding, and is beneficial to engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 is a flow chart of the method of the present invention;

[0086] Figure 2 It is a structural schematic diagram of hybrid winding design scheme 1;

[0087] Figure 3 It is a structural schematic diagram of hybrid winding design scheme 2;

[0088] Figure 4 It is a structural schematic diagram of hybrid winding design scheme 3;

[0089] Figure 5 This is a comprehensive evaluation index system diagram for the design of high-frequency transformer hybrid windings;

[0090] Figure 6 This is the implementation flow chart of the comprehensive evaluation method. DETAILED DESCRIPTION

[0091] The present invention is further described below in conjunction with specific embodiments.

[0092] like Figure 1As shown, the high-frequency transformer hybrid winding design and comprehensive evaluation method of the present invention comprises the following steps:

[0093] S1: Taking a high-frequency transformer with a core-type nanocrystalline core structure as an example, its electrical indicators are shown in the following table:

[0094] index Numeric Rated capacity / kVA 20 High voltage side voltage / V 700 Low voltage side voltage / A 400 Operating frequency / kHz 10

[0095] Design requirements: The primary and secondary windings are coaxially wound on the core columns on both sides, and the primary windings on the core columns on both sides are connected in series. The total number of turns is 56, the current is 28.5A, and the current density is 1A / nm 2 The secondary windings of the two core columns are connected in series, with a total number of turns of 32, a current of 50A, and a current density of 1A / mm 2 .

[0096] Considering three types of windings, copper foil, flat copper wire and Litz wire, the primary and secondary windings are designed, and three design schemes are given as shown in the following table.

[0097] Solution 1 Solution 2 Solution 3 Original Edge Copper Foil Flat copper wire Litz Wire Secondary side Litz Wire Litz Wire Litz Wire

[0098] When changing different winding types, in order to ensure that the current density of the primary and secondary windings remains unchanged, the bare area of ​​each turn of the winding wire on the primary and secondary sides should be equal. The calculation formula is:

[0099]

[0100] In the above formula, A xp and A xs are the bare area of ​​the wire per turn of the primary and secondary windings, I p and I s are the primary and secondary currents, J cp and J cs are the current densities of the primary and secondary windings respectively.

[0101] The calculation shows that the bare area of ​​the wire per turn of the primary and secondary windings is 28.5mm 2 and 50mm 2 .

[0102] Figure 2-Figure 4 The following are the structural schematic diagrams of the three schemes. The winding structure design parameters of each scheme are shown in the following table (unit: mm):

[0103]

[0104] Note: h l1 and d l1 are the width and thickness of each turn of copper foil on the primary side; h f1 and d f1 are the width and thickness of each turn of the original flat copper wire, dL1 d L2 D is the diameter of the single strand Litz wire selected for the primary and secondary sides respectively; L1 and D L2 They are the diameters of each bundle of primary and secondary Litz wires respectively (the filling factor is 0.44).

[0105] S2: For different types of windings, the calculation models of winding losses are established respectively, and the loss expressions of the primary and secondary windings of different design schemes are derived.

[0106] AC resistance coefficient F of primary and secondary windings rp and F rs The calculation formula is:

[0107] S2.1: For copper foil and flat copper wire windings, use Dowell's formula for calculation:

[0108]

[0109] in,

[0110]

[0111] In the above formula, m p and m s are the number of layers of primary and secondary windings respectively; Δ 1 and Δ 2 are the normalized thicknesses of the primary and secondary windings relative to the skin depth, respectively.

[0112] S2.2: For Litz wire windings, use Tourkhani’s formula for calculation:

[0113]

[0114]

[0115] in,

[0116]

[0117] In the above formula, the parameter ζ p / s =d Lp / s / δ,d Lp / s is the diameter of the primary and secondary single-strand Litz wire, δ is the skin depth of the strand, n L1 and n L2 are the total number of Litz wires on the primary and secondary sides, β L1 and β L2 are the filling factors of the primary and secondary Litz wires respectively;

[0118] According to the type of primary and secondary windings, select the corresponding formula for calculation, and the primary and secondary winding losses are Pwp and P ws , high frequency transformer winding loss P w for:

[0119]

[0120] In the above formula, R dc_p and R dc_s are the DC resistances of the primary and secondary windings respectively.

[0121] S3: Figure 5 As shown, Figure 5 It is a comprehensive evaluation index system for the hybrid winding design of high-frequency transformers. In order to comprehensively evaluate the advantages and disadvantages of the hybrid winding design, this scheme proposes five evaluation indicators: winding loss, space utilization, material cost, winding difficulty, and temperature rise. The specific calculation is as follows:

[0122] S3.1: Evaluation index of winding design efficiency;

[0123] a. Winding loss P w

[0124] Winding loss P of each solution w Obtained by solving the calculation formula in step S2;

[0125] b. Space utilization η w

[0126]

[0127] In the above formula, N p and N s are the turns of the primary and secondary windings respectively, h p and h s are the primary and secondary winding heights, d p and d s They are the thickness of the primary and secondary windings along the winding direction respectively.

[0128] S3.2: Evaluation indicators of cost-effectiveness of winding design solutions;

[0129] a. Material cost C w

[0130] C w =ρ wp V wp u wp +ρ ws V ws u ws ;

[0131] in,

[0132] In the above formula, ρ wp and ρ ws are the unit volume densities of the primary and secondary windings respectively; V wp and V ws are the total volumes of the primary and secondary windings, u wp and u ws are the unit weight prices of the primary and secondary windings, respectively. m_p and l m_s are the approximate average turn lengths of the primary and secondary windings respectively;

[0133] b. Winding difficulty DOW

[0134] The difficulty of winding directly affects production efficiency and cost. The processing and winding process complexity of different types of windings are different, which needs to be fully considered in the design stage. The difficulty of winding is qualitatively evaluated based on the structural complexity of the winding, the type of wire, the insulation requirements and other factors. The difficulty of winding DOW is evaluated by the transformer manufacturer into four levels;

[0135] DOW∈{A,B,C,D};

[0136] In the above formula, A stands for easy, B stands for average, C stands for difficult, and D stands for difficult.

[0137] S3.3: Evaluation index of heat dissipation performance of winding design scheme;

[0138] a. Temperature rise T w

[0139] Winding temperature rise T under natural air cooling conditions w for:

[0140]

[0141] In the above formula, A tp and A ts are the surface areas of the primary and secondary windings respectively; k p and k s They are the area correction factors of the primary and secondary windings, respectively, and depend on the heat dissipation performance of copper foil, flat copper wire and Litz wire.

[0142] According to the above formula, the evaluation values ​​of the five secondary indicators of different hybrid winding design schemes can be calculated, as shown in the following table:

[0143]

[0144] S4: Figure 6 The figure shows the main implementation process of comprehensive evaluation using the AHP-entropy weight method combined method and the TOPSIS method. The specific process is:

[0145] S4.1: APH method

[0146] Assume that the previous level A contains A 1 , A 2 , ..., A m There are m factors in total, and their hierarchical total ranking weights are a 1 、a 2 , ..., a m , suppose the next level B contains n factors B 1 , B 2 , ..., B n , they are about A j The hierarchical single sorting weights are b 1j , ..., b nj , when B j With A j When there is no correlation, b ij = 0. The total ranking weight of each factor in layer B is w i AHP The calculation formula is:

[0147]

[0148] Assume that layer B is j The pairwise comparison judgment matrix of the relevant factors is subjected to consistency test in single sorting, and the single sorting consistency index is obtained as CI(j), (j=1,...,m), and the corresponding average random consistency index is RI(j). Then the calculation formula of the random consistency ratio of the total sorting of layer B is:

[0149]

[0150] When CR<0.10, the hierarchical total ranking result is considered to have satisfactory consistency and the analysis result is accepted.

[0151] S4.2: Entropy Weight Method

[0152] Assume that the original data matrix of m evaluation indicators and n evaluation objects is A=(a ij ) m×n , after normalization, we get R = (r ij ) m×n , for the index with the largest value being the best, the normalized formula is:

[0153]

[0154] For indicators with small values ​​as the best, the normalization formula is:

[0155]

[0156] The entropy h of the i-th evaluation indexi for:

[0157]

[0158] When f ii = 0, let ln f ii =0.1;

[0159] After defining the entropy of the i-th evaluation index, the entropy weight w of the i-th evaluation index is obtained i EWM for:

[0160]

[0161] Weight coefficient w i It reflects the amount of information of the indicator. The larger the entropy weight is, the greater the role of the indicator in comprehensive decision-making is. It intuitively and effectively reflects the degree of difference between indicators.

[0162] S4.3: TOPSIS method

[0163] The comprehensive weight w is calculated based on the AHP-entropy weight combination method i T for:

[0164]

[0165] In the above formula, α is the subjective preference coefficient, 1-α is the objective preference coefficient, and α is usually taken as 0.7;

[0166] The evaluation matrix is ​​processed under standard conditions to obtain the standardized evaluation result v ij T , the weighted judgment matrix r is obtained by multiplying the comprehensive weight and the standardized evaluation matrix ij T for:

[0167]

[0168] The Euclidean distance between each solution and the positive and negative ideal solutions is calculated based on the elements of the weighted judgment matrix:

[0169]

[0170]

[0171] The closeness reflects the closeness of the selected solution to the positive ideal solution, and the calculation formula is:

[0172]

[0173] According to the above steps, the weights of the three primary indicators of efficiency, cost-effectiveness and heat dissipation performance are calculated by AHP method as 0.43, 0.43 and 0.14 respectively. Then the weights of the secondary indicators under each primary indicator are calculated in turn as shown in the following table:

[0174]

[0175] The distance between each hybrid winding design and the ideal solution (after normalization) is calculated using the TOPSIS method, as shown in the elements of Z:

[0176]

[0177] Each row of the matrix Z represents the score of each solution on the five secondary indicators.

[0178] Step S5: Sort the schemes from large to small according to the closeness results. The comprehensive evaluation scores of all evaluation schemes are shown in the following table:

[0179] plan Comprehensive score Sorting Solution 1 0.37 1 Solution 2 0.30 3 Solution 3 0.32 2

[0180] From the results, we can see that after comprehensive efficiency, cost-effectiveness and heat dissipation performance indicators, Scheme 1 has the highest total score, and Scheme 2 has the lowest total score. Therefore, Scheme 1 should be selected first, followed by Scheme 3.

[0181] By optimizing the above schemes, it is ultimately possible to meet the requirements of high-frequency transformers for winding design and achieve comprehensive optimization in terms of efficiency, cost-effectiveness and heat dissipation performance, thereby maximizing the comprehensive benefits and facilitating the application of high-frequency transformers in practical engineering.

Claims

1. A high-frequency transformer hybrid winding design and comprehensive evaluation method, characterized in that: The method comprises the following steps: S1: Select the corresponding winding type according to the electrical specifications and design requirements of the high-frequency transformer; When changing the winding type, the bare area of ​​each turn of the winding conductor on the primary and secondary sides is kept equal; S2: For different types of windings, the calculation models of winding losses are established respectively, and the loss expressions of primary and secondary windings of different design schemes are derived; S3: Establish a comprehensive evaluation index system to evaluate the feasibility of different winding design schemes. The evaluation indicators include winding loss, space utilization, material cost, winding difficulty and temperature rise; S4: Based on the evaluation index proposed in step S3, a comprehensive evaluation model is established, and the weight of each evaluation index is determined by using the subjective and objective AHP-entropy weight combination method, and then the hybrid winding design scheme is evaluated by the TOPSIS method to calculate the comprehensive evaluation score of each scheme; S5: Sort and compare the solutions according to the scores in step S4, and select the winding design solution with the highest score as the final solution.

2. The high-frequency transformer hybrid winding design and comprehensive evaluation method according to claim 1 is characterized in that: In step S1, the calculation formula for keeping the bare area of ​​each turn of winding wire on the primary and secondary sides equal is: In the above formula, A xp and A xs are the bare area of ​​the wire per turn of the primary and secondary windings, I p and I s are the primary and secondary currents respectively, J cp and J cs are the current densities of the primary and secondary windings respectively.

3. The high-frequency transformer hybrid winding design and comprehensive evaluation method according to claim 2 is characterized in that: In step S2, the AC resistance coefficient F of the primary and secondary windings is rp and F rs The calculation formula is: S2.1: For copper foil and flat copper wire windings, use Dowell's formula for calculation: in, In the above formula, m p and m s are the number of layers of the primary and secondary windings, respectively; Δ1 and Δ2 are the normalized thicknesses of the primary and secondary windings to the skin depth, respectively; S2.2: For Litz wire windings, use Tourkhani’s formula for calculation: in, In the above formula, the parameter ζ p / s =d Lp / s / δ,d Lp / s is the diameter of the primary and secondary single-strand Litz wire, δ is the skin depth of the strand, n L1 and n L2 are the total number of Litz wires on the primary and secondary sides, β L1 and β L2 are the filling factors of the primary and secondary Litz wires respectively; According to the type of primary and secondary windings, select the corresponding formula for calculation, and the primary and secondary winding losses are P wp and P ws , high frequency transformer winding loss P w for: In the above formula, R dc_p and R dc_s are the DC resistances of the primary and secondary windings respectively.

4. The high-frequency transformer hybrid winding design and comprehensive evaluation method according to claim 3 is characterized in that: In step S3, the calculation process of the evaluation index is: S3.1: Evaluation index of winding design efficiency; a. Winding loss P w Winding loss P of each solution w Obtained by solving the calculation formula in step S2; b. Space utilization η w In the above formula, N p and N s are the turns of the primary and secondary windings respectively, h p and h s are the primary and secondary winding heights, d p and d s They are the thickness of the primary and secondary windings along the winding direction respectively; S3.2: Evaluation indicators of cost-effectiveness of winding design solutions; a. Material cost C w C w =ρ wp V wp you wp +r ws V ws you ws ; in, In the above formula, ρ wp and ρ ws are the unit volume densities of the primary and secondary windings respectively; V wp and V ws are the total volumes of the primary and secondary windings, u wp and u ws are the unit weight prices of the primary and secondary windings, respectively. m_p and l m_s are the approximate average turn lengths of the primary and secondary windings respectively; b. Winding difficulty DOW The difficulty of winding DOW is evaluated by the transformer manufacturer into four levels; DOW∈{A,B,C,D}; In the above formula, A represents easy, B represents average, C represents difficult, and D represents difficult; S3.3: Evaluation index of heat dissipation performance of winding design scheme; a. Temperature rise T w Winding temperature rise T under natural air cooling conditions w for: In the above formula, A tp and A ts are the surface areas of the primary and secondary windings respectively; k p and k s They are the area correction factors of the primary and secondary windings, respectively, and depend on the heat dissipation performance of copper foil, flat copper wire and Litz wire.

5. The high-frequency transformer hybrid winding design and comprehensive evaluation method according to claim 4 is characterized in that: In step S4, the process of comprehensive evaluation using the AHP-entropy weight combination method and the TOPSIS method is as follows: S4.1: APH method Assume that the previous level A contains A1, A2, ..., A m There are m factors in total, and their hierarchical total ranking weights are a1, a2, ..., a m , suppose the next level B contains n factors B1, B2, ..., B n , they are about A j The hierarchical single sorting weights are b 1j , ..., b nj , the total hierarchical ranking weight w of each factor in layer B i AHP The calculation formula is: Assume that layer B is j The pairwise comparison judgment matrix of the relevant factors is subjected to consistency test in single sorting, and the single sorting consistency index is obtained as CI(j), (j=1,...,m), and the corresponding average random consistency index is RI(j). Then the calculation formula of the random consistency ratio of the total sorting of layer B is: When CR<0.10, the hierarchical total ranking result is considered to have satisfactory consistency and the analysis result is accepted; S4.2: Entropy Weight Method Assume that the original data matrix of m evaluation indicators and n evaluation objects is A=(a ij ) m×n , after normalization, we get R = (r ij ) m×n , for the index with the largest value being the best, the normalized formula is: For indicators with small values ​​as the best, the normalization formula is: The entropy h of the i-th evaluation index i for: When f ii = 0, let ln f ii =0.1; After defining the entropy of the i-th evaluation index, the entropy weight w of the i-th evaluation index is obtained i EWM for: Weight coefficient w i It reflects the amount of information of the indicator. The larger the entropy weight is, the greater the role of the indicator in comprehensive decision-making, reflecting the degree of difference between indicators. S4.3: TOPSIS method The comprehensive weight w is calculated based on the AHP-entropy weight combination method i T for: In the above formula, α is the subjective preference coefficient, 1-α is the objective preference coefficient, and α=0.7; The evaluation matrix is ​​processed under standard conditions to obtain the standardized evaluation result v ij T , the weighted judgment matrix r is obtained by multiplying the comprehensive weight and the standardized evaluation matrix ij T for: The Euclidean distance between each solution and the positive and negative ideal solutions is calculated based on the elements of the weighted judgment matrix: The closeness reflects the closeness of the selected solution to the positive ideal solution, and the calculation formula is:

6. The high-frequency transformer hybrid winding design and comprehensive evaluation method according to claim 5 is characterized in that: In step S5, the schemes are sorted and compared from large to small according to the closeness results, and the winding design scheme with the highest score is selected as the final scheme.

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