CN111985136A - Parameter design method for fillet square coupler of IPT system - Google Patents

Abstract

The invention provides a parameter design method of a fillet square coupler of an IPT system, which comprises the following steps: determining the air gap height, the maximum transverse offset distance, the coil area and the wire diameter of the rounded square coupler; establishing an equivalent model of the rounded square coupler based on a Newman formula, and normalizing the structural parameters of the first turn of coil; and establishing a mutual inductance model of the round corner square coupler by taking the normalized structural parameters of the first turn coil as variables, and respectively establishing a lifting percentage expression of the just-opposite coupling mutual inductance of the round corner square coupler compared with the square coupler and a lifting percentage expression of the coupling mutual inductance of the round corner square coupler at the maximum offset point compared with the circular coupler on the basis of the mutual inductance model, so that the first turn coil normalized structural parameters which are optimal in the two mutual inductance lifting percentages are the optimal structural parameters of the coupler. The invention can shorten the design period of the coupler and improve the system performance by improving the coupling performance of the coupler to the maximum extent.

Description

Parameter design method for fillet square coupler of IPT system

Technical Field

The invention relates to a wireless power transmission technology, in particular to a parameter design method of a rounded square coupler of an IPT system.

Background

Wireless Power Transfer (WPT) was first introduced in the united states of the nineteenth century. The novel power access mode is a novel power access mode which realizes that electric energy is transmitted from source equipment to powered equipment by means of space intangible soft media (such as magnetic fields, electric fields, lasers, microwaves and the like). The technology realizes the electrical isolation between power supply equipment and power receiving equipment, thereby fundamentally avoiding the problems of device abrasion, poor contact, contact spark and the like caused by the traditional wired power supply mode, being a clean, safe and flexible novel power supply mode and being selected as one of ten future scientific research directions by American 'technical review' magazines.

Inductive Power Transfer (IPT) technology has attracted attention and research widely due to its characteristics of large Power Transfer capacity, high efficiency, and the like. Compared with a wired electric energy transmission mode of traditional electric equipment, characteristics such as power transmission capacity, efficiency and cost are main indexes which are mainly considered in the research of a wireless electric energy transmission system, and are also important points in the research of the current wireless electric energy transmission field. The magnetic circuit coupling mechanism is used as an important link for transmitting electric energy from a primary side to a secondary side in an IPT system, and the design quality directly determines the power transmission capacity and efficiency of the system, so that the research design of the magnetic circuit mechanism in the wireless electric energy transmission system becomes more important, and one of the key indexes for measuring the performance of the magnetic circuit coupling mechanism for wireless electric energy transmission is the mutual inductance M between the primary side coil and the secondary side coil.

Through the existing research and application, the circular coupler and the square coupler are two kinds of couplers which are the widest in application range and the most researched in the IPT technical field at present. The rounded square coupler is a coupler with the same simple structure, low cost and easy engineering application as the round and square couplers. The different structural parameters of the round-corner square coupler can enable the round-corner square coupler and the square coupler to combine in different degrees, and the optimal structural parameters enable the round-corner square coupler and the square coupler to combine in the maximum degree, so that the coupling performance of the coupler is improved to the maximum degree, and the electric energy transmission efficiency of the system is improved. However, few methods exist for parametric design of rounded square couplers, and no methods exist for optimal design parameters. If the optimal structural parameter design method for the rounded square coupler is adopted, the optimal structural parameter can be quickly obtained, the processing efficiency of the coil and the efficiency in practical engineering application can be improved, and the improvement of the electric energy transmission efficiency of an IPT system is facilitated.

Disclosure of Invention

The purpose of the invention is as follows: in order to make up for the blank of the prior art, the invention provides a parameter design method of a rounded square coupler of an IPT system, which can calculate the optimal structural parameters of the rounded square couplers with different sizes according to the application background, and can improve the coupling performance of the rounded square coupler through the design of the optimal structural parameters, thereby improving the electric energy transmission efficiency of the IPT system. On the other hand, the parameter design method can improve the processing efficiency of the coil and shorten the system design period in practical engineering application.

The technical scheme is as follows: in order to achieve the technical effects, the technical scheme provided by the invention is as follows:

a parameter design method of an IPT system fillet square coupler comprises a primary coil and a secondary coil, wherein the structure and parameters of the primary coil and the secondary coil are the same; the method comprises the following steps:

(1) according to the application background, the basic parameters of the rounded square coupler are determined, and comprise the following steps: air gap height h between primary coil and secondary coil, maximum lateral offset_maxCoil area S and litz wire diameter d;

(2) based on a Newman formula and a model of the round corner square coupler, establishing an equivalent model of the round corner square coupler: neglecting the wire diameter of the litz wire, enabling the primary side coil and the secondary side coil to be equivalent to round-corner square coils which are coaxial and have different sizes, wherein each turn of coil is composed of four straight line sections with the same length and four quarter circular arcs with the same round-corner radius;

after equivalence, the structural parameters of each turn of coil are as follows: l_eqi＝l，

l_eqiIs the length of each straight line segment of the ith turn of coil, r_eqiIs the arc radius length of the ith turn of coil, r^*The length of the outer diameter of the arc part of the outermost coil before equivalence is represented by l, and the length of the straight line section of each layer of coil before equivalence is represented by l;

(3) carrying out normalization processing on the structural parameters of each turn of coil to obtain normalized structural parameters:

wherein the content of the first and second substances,

is the arc radius length of the 1 st turn coil, i.e.

The normalized structural parameters satisfy the following conditions:

condition 1:

condition 2:

wherein N represents the total number of turns;

(4) establishing a mutual inductance model of the rounded square coupler:

wherein λ is_peqiIs a normalized structural parameter, lambda, of the ith turn coil of the primary side_seqjNormalized structural parameters, M, for the j-th turn of the secondary winding_{rou_squ}Is the mutual inductance sum between all turns of the primary side coil and all turns of the secondary side coil, f (lambda)_peqi，λ_seqjAnd h) is a mutual inductance expression between any two turns of coils on the original secondary side, and is transverse offset;

(5) when positive coupling is established, with λ_eq ^*Expression Per for percentage improvement of mutual inductance of rounded square coupler as variable compared to mutual inductance of square coupler_alig(λ_eq ^*) (ii) a Set at the maximum offset point by lambda_eq ^*Expression Per for percentage improvement of mutual inductance of rounded square coupler as variable compared to circular coupler_off(λ_eq ^*)：

Wherein M is_squAnd M_cirRepresenting the mutual inductance of the square and circular couplers, respectively;

step 6: solving for λ of the rounded square coupler_eq ^*Taking the maximum value λ_{eq_max} ^*Times Per_off(λ_{eq_max} ^*) And Per_alig(λ_{eq_max} ^*) And establishing a solution model of the optimal structure parameters by the following judgment conditions:

a: if Per_off(λ_{eq_max} ^*)＞Per_alig(λ_{eq_max} ^*) Then with | Per_alig(λ_eq ^*)-Per_off(λ_eq ^*) The minimum value of | is taken as the target, and lambda is taken_eq ^*Establishing an optimization model for optimizing variables:

min：|Per_alig(λ_eq ^*)-Per_off(λ_eq ^*)|

so that | Per_alig(λ_eq ^*)-Per_off(λ_eq ^*) Lambda with the smallest | value_eq ^*Namely the optimal structural parameters of the rounded square coupler.

B: if Per_off(λ_{eq_max} ^*)≤Per_alig(λ_{eq_max} ^*) Then traverse λ_eq ^*By judging Per_off(λ_eq ^*)-Per_alig(λ_eq ^*) Whether all the values are less than 0 to establish a solution model of the optimal structural parameters:

and B.a: traverse lambda_eq ^*If all values of (1) satisfy Per_off(λ_eq ^*)-Per_alig(λ_eq ^*) If the result is less than 0, establishing an optimization model:

max：Per_off(λ_eq ^*)

so that Per_off(λ_eq ^*) Maximum value of λ_eq ^*Namely the optimal structural parameters of the rounded square coupler.

B.b: traverse lambda_eq ^*If there is a value satisfying Per_off(λ_eq ^*)-Per_alig(λ_eq ^*) Lambda of condition > 0_eq ^*Then the optimization model is min: | Per_alig(λ_eq ^*)-Per_off(λ_eq ^*)|；

If the number of solutions for the optimization model is two, then a smaller λ is selected_eq ^*As the optimal solution.

Further, f (λ)_peqi，λ_seqjThe expression of h) is:

f(λ_peqi，λ_seqj，，h)＝M_line+M_arc+M_line-arc

wherein M is_line-arcThe total mutual inductance between the arc segment and the straight line segment between the primary coil and the secondary coil is expressed as follows:

wherein A is_p～D_pEach representing 4 straight line segments, A, of the primary coil_s～D_s4 straight line segments, l, each representing a secondary winding_pk(k is equal to 1 to 4) represents 4 arc segments of the primary coil, l_sk(k belongs to 1-4) represents 4 arc line segments of the secondary side coil; m_lineAnd M_arcThe total mutual inductance of the straight line segment and the arc segment is respectively expressed as:

further, the formula f (λ)_peqi，λ_seqj，，h)＝M_line+M_arc+M_line-arcMiddle and primary sideThe mutual inductance between any section of the coil and any section of the secondary coil is solved through a Newman formula:

wherein dl 'and dl "are the lengths of the two element lines l' and l", D is the distance between the two length elements, and θ is the angle between the length elements.

Has the advantages that: compared with the prior art, the invention has the following advantages:

the optimal structural parameter determining method of the round-corner square coupler can quickly obtain the optimal structural parameter, so that the optimal round-corner square coupler has the advantages of the coupling characteristics of the round coupler and the square coupler to the maximum extent, the mutual inductance coupling characteristic of the optimal round-corner square coupler is stronger than that of the round coupler and the square coupler to the maximum extent, the coupling characteristic is improved to the great extent, and the electric energy transmission efficiency is improved. In addition, the method is suitable for couplers with various parameters and has universality.

Drawings

FIG. 1 is a flow chart of optimal configuration parameter determination for a rounded square coupler according to an embodiment;

FIG. 2 is a schematic diagram of a rounded square coupler according to an embodiment;

FIG. 3 is a simulation model of a rounded square coupler based on Maxwell finite element simulation software according to an embodiment;

FIG. 4 shows the mutual inductance between primary and secondary coils at different air gap heights under the positive coupling condition with λ and the h being 25mm in the example_eq ^*The relationship curve of (1);

FIG. 5 shows the mutual inductance between primary and secondary coils at different air gap heights at the maximum offset distance according to λ when h is 25mm in the embodiment_eq ^*The relationship curve of (1);

FIG. 6 shows the mutual inductance between primary and secondary coils at different air gap heights under the positive coupling condition with λ when h is 10mm in the example_eq ^*The relationship curve of (1);

FIG. 7 shows an embodimentIn the case of h being 10mm, the mutual inductance between primary and secondary side coils at different air gap heights under the maximum offset distance is dependent on lambda_eq ^*The relationship curve of (1);

FIG. 8 shows Per for example, h 25mm_aligAnd Per_offAnd λ_eq ^*The relationship curve of (1);

FIG. 9 shows Per for 10mm in example h_aligAnd Per_offAnd λ_eq ^*The relationship of (1).

Detailed Description

The terminology used in the following embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

It should be noted that the terms "upper", "lower", "left", "right", and the like used in the embodiments of the present application are described in terms of the angles shown in the drawings, and should not be construed as limiting the embodiments of the present application. In addition, in this context, it will also be understood that when an element is referred to as being "on" or "under" another element, it can be directly on "or" under "the other element or be indirectly on" or "under" the other element via an intermediate element.

The invention aims to provide a parameter design scheme of a fillet square coupler of an IPT system, which can calculate the optimal structural parameters of the fillet square couplers with different sizes according to application backgrounds so as to improve the coupling performance of the fillet square coupler and further improve the electric energy transmission efficiency of the IPT system.

In view of the above, the present invention provides a method for designing parameters of a rounded square coupler of an IPT system, which will be described in detail with reference to the following embodiments and accompanying drawings.

Example (b):

fig. 2 is a schematic structural diagram of a rounded square coupler in an embodiment of the present invention, where the rounded square coupler includes two parts, namely a primary power transmitting coil and a secondary power pickup coil. The primary side electric energy transmitting coil and the secondary side electric energy picking coil are opposite and parallel in spatial position and are both planar coils formed by winding litz wires with the wire diameter d from outside to inside;

the primary side electric energy transmitting coil and the secondary side electric energy pickup coil are completely the same in structure, and each turn of coil is a rounded square formed by four straight-line segments with the same length and four quarter circular arcs with the same rounded corner radius; the length of the straight line segment of each turn of coil is equal and is marked as l. The fillet sizes of the inner turn coil and the outer turn coil are different, and the arc radius of the inner turn coil is smaller than that of the outer turn coil. Let us note here that the radius of the fillet of the first turn (outermost turn) is r^*。

Fig. 3 is a simulation model of the rounded square coupler in the finite element simulation software Maxwell according to the embodiment. The structure and parameter configuration method of the two coils on the primary side and the secondary side are shown in figure 2.

In this embodiment, a parameter design flow of the rounded square coupler is shown in fig. 1:

step 1: in a practical system, the coil size, the air gap height h and the maximum offset distance_maxAs is generally known, the coil dimensions are determined primarily by the coil area S, the litz wire diameter d, and the number of coil turns. In this embodiment, the coil area S is 22500mm²And the wire diameter d is 2.5mm, and the number of turns is 10. Taking into account the actual coil area, set_max50 mm. To verify the optimum parameter determination method in the present invention, h 25mm and h 10mm were respectively given so that the rounded square coupler λ was rounded_eq ^*Per at maximum value_offAre respectively less than Per_aligAnd greater than Per_aligTo verify the solution model of the optimal structural parameters in the present invention, respectively.

Step 2: an equivalent mutual inductance model of the rounded square coupler is established based on the principle of the Newman formula: neglecting the diameter of litz wire, all being equivalent to the round angle square coil of coaxial and not unidimensional with former secondary side coil, and the equivalent structure parameter of each circle coil satisfies:

l_p＝l_s＝l＝l_peq＝l_seq＝l_eq，r_peq ^*＝r_seq ^*＝r_eq ^*＝r^*-(d/2)，r_peqi＝r_seqi＝r_eqi＝r_eq ^*-d*(i-1)＝r^*-d*(i-1/2)。

wherein l_peq、r_peq ^*And r_peqiRespectively representing the length of an equivalent straight-line section of a primary side coil, the equivalent fillet radius of a primary side first turn coil and the equivalent fillet radius of primary side different turn coils; l_seq、r_seq ^*And r_seqiRespectively showing the equivalent straight-line segment length of the secondary side coil, the equivalent fillet radius of the first turn coil of the secondary side and the equivalent fillet radius of different turns of the secondary side.

And step 3: normalization processing of first turn equivalent coil structure parameter l based on equivalent mutual inductance analytic model of rounded square coupler_eqAnd r_eq ^*Let λ be_eq ^*＝l_eq/r_eq ^*And then the ith turn is equivalent to the coil structure parameter lambda_eqiComprises the following steps:

λ_eqi＝l_eq/r_eqi ^*＝λ_eq ^**r_eq ^*/(r_eq ^*-d*(i-1)) (1)

the size of the primary side coil and the secondary side coil is limited by the practical application background, so that the coil area is constant and satisfies the formula (2):

from the formula 2, it can be seen that for any λ_eq ^*，l_eqAnd r_eq ^*Is unique. With reference to equation 1, the mutual inductance coupling characteristic of the rounded square coupler can be determined by the normalized parameter structure parameter λ of the first turn coil_eq ^*And (6) determining.

Meanwhile, the structural parameters of the first turn coil are selected to satisfy the formula (3):

since the wire diameter d is 2.5mm and the number of turns is 10, r is_eq ^*The minimum value should be greater than 25mm, i.e. the maximum lambda_eq ^*4.07, and

λ_eq ^*not equal to 0 to ensure that each turn of coil is a rounded square coil.

And 4, step 4: based on step 2, establish λ_eq ^*Mutual inductance model M of round corner square coupler as variable_{rou_squ}(λ_eq ^*)：

Wherein λ is_peqiIs a normalized structural parameter, lambda, of the ith turn coil of the primary side_seqjNormalized structural parameters, M, for the j-th turn of the secondary winding_{rou_squ}Is the mutual inductance sum between all turns of the primary side coil and all turns of the secondary side coil, f (lambda)_peqi，λ_seqjAnd h) is a mutual inductance expression between any two turns of coils on the primary side and the secondary side, and specifically comprises the following steps:

f(λ_peqi，λ_seqj，，h)＝M_line+M_arc+M_line-arc (5)

M_line-arcthe total mutual inductance between the arc segment and the straight line segment between the primary coil and the secondary coil can be expressed as follows:

and M_lineAnd M_areThe total mutual inductance of the straight line segment and the arc segment is respectively expressed as:

equations (6) to (8) can be solved by the Newman equation (9):

wherein dl 'and dl "are the lengths of the two element lines l' and l", D is the distance between the two length elements, and θ is the angle between the length elements.

Fig. 3 to 6 can be obtained based on the expressions (1) to (9), and the coupling characteristics of the rounded square coupler will be described based on fig. 3 to 6.

FIGS. 4-5 show the mutual inductance and different λ of the rounded square coupler for the right-side coupling and 50mm_eq ^*The relationship (2) of (c). Both figures were obtained under conditions of h 25 mm. Taking into account λ_eq ^*The corresponding shapes for ∞ and 0 are not rounded squares, so the symbols in fig. 4 and 5 are hollow, again because λ_eq ^*> 4.07, thus lambda_eq ^*The curve between ∞ and 4.07 is a broken line. But made of_eq ^*In the sense of (a)_eq ^*But also as the only structural parameter of a circular or square coupler.

As can be seen from FIG. 4, λ_eq ^*The smaller, the closer the positive coupling characteristic is to a circular coupler; lambda [ alpha ]_eq ^*The larger, the positive coupling characteristic and the circular couplingThe more the phase difference, but the closer to the square coupler. Thus, λ_eq ^*The smaller the rounded square coupler, the more strong positive coupling characteristic of the circular coupler is obtained because of lambda_eq ^*The smaller the positive mutual inductance coupling characteristic is. As can be seen from FIG. 5, λ_eq ^*The smaller the offset coupling characteristic, the closer to a circular coupler, λ_eq ^*The larger the offset coupling characteristic and the smaller the difference in the square coupler. Can see lambda_eq ^*The change in (2) allows the rounded square coupler to achieve the strong offset rejection of the square coupler to varying degrees because of the greater offset coupling mutual inductance than the circular coupler.

FIGS. 6-7 show the mutual inductance and different λ of the rounded square coupler for the right-side coupling and 50mm_eq ^*The relationship (2) of (c). Fig. 6 to 7 were all obtained under the condition that h is 10mm, and fig. 4 to 5 were obtained from fig. 7 and fig. 6 in the same manner.

In summary, at λ_eq ^*Within the desirable range, the round corner square coupler has the mutual inductance coupling characteristics of the round coupler and the square coupler in different degrees, so that the optimal lambda exists_eq ^*The round corner square coupler has the mutual inductance coupling characteristic of the round coupler and the square coupler to the maximum extent.

And 5: establishing a percentage expression Per for improving mutual inductance of a rounded square coupler in positive coupling compared with mutual inductance of a square coupler_alig(0, h) and establishing a percentage of mutual inductance improvement expression Per of the rounded square coupler at the maximum offset point compared to the circular coupler_off(＝50mm，h)：

Wherein M is_squThe mutual inductance expression of the square coupler is shown by the following formula (7)(9) And (6) solving to obtain. M_cirThe mutual inductance expression of the circular coupler is obtained by solving the following equations (7) and (9).

Step 6: and solving the optimal structure parameters according to the following optimal structure parameter solving model establishing method.

Solving for the rounded square coupler λ_eq ^*Has the maximum value of lambda_{eq_max} ^*Per of time_off(λ_{eq_max} ^*) And Per_alig(λ_{eq_max} ^*) Establishing a solving model of the optimal structure parameters by the following judgment conditions:

a: if Per_off(λ_{eq_max} ^*)＞Per_alig(λ_{eq_max} ^*) Then with | Per_alig(λ_eq ^*)-Per_off(λ_eq ^*) The minimum value of | is taken as the target, and lambda is taken_eq ^*Establishing an optimization model for optimizing variables:

min：|Per_alig(λ_eq ^*)-Per_off(λ_eq ^*)| (12)

so that | Per_alig(λ_eq ^*)-Per_off(λ_eq ^*) Lambda with the smallest | value_eq ^*Namely the optimal structural parameters of the rounded square coupler.

B: if Per_off(λ_{eq_max} ^*)≤Per_alig(λ_{eq_max} ^*) Then traverse λ_eq ^OfTaking value by judging Per_off(λ_eq ^*)-Per_alig(λ_eq ^*) Whether the value of (a) is less than 0 to establish a solution model of the optimal structural parameters:

and B.a: traverse lambda_eq ^*If all values of (1) satisfy Per_off(λ_eq ^*)-Per_alig(λ_eq ^*) < 0, i.e. there is no lambda satisfying the condition_eq ^*Then, establishing an optimization model:

max：Per_off(λ_eq ^*) (13)

so that Per_off(λ_eq ^*) Maximum value of λ_eq ^*Namely the optimal structural parameters of the rounded square coupler.

B.b: traverse lambda_eq ^*If all values of (1) satisfy Per_off(λ_eq ^*)-Per_alig(λ_eq ^*) Is not less than 0, i.e. there is lambda satisfying the condition_eq ^*Then the optimization model is the same as equation (12).

Wherein the number of solutions satisfying the formula (12) is 1 to 2. If the number of solutions is two, then the smaller λ is selected_eq ^*As the optimal solution.

According to the parameters of the actual coupler, based on step 4, when h is 25 mm:

λ_eq ^*maximum value of 4.07, Per_off1.6%, and Per_alig2.42%. Therefore, the determination condition B is satisfied. By traversing λ_eq ^*Value, absence may be such that Per_offGreater than Per_aligλ of_eq ^*Thus, the determination condition a in the determination condition B is satisfied, i.e. Per is required_ofrMaximum value is the target, in λ_eq ^*Establishing an optimization model for optimizing variables:

max：Per_off(λ_eq ^*) (14)

so that Per_offMaximum value of λ_eq ^*Namely the optimal structural parameters of the rounded square coupler.

In FIG. 8, when h is 25mm, Per_aligAnd Per_offAnd λ_eq ^*The relationship of (1). From the figure, it can be seen that r is_eq ^*＝55mm，λ_eq ^*When equal to 0.88, Per_offMaximum, about 1.4%, so λ_{eq_opt} ^*0.88. At this time, the optimum rounded square coupler has better coupling characteristics than the square coupler, regardless of whether it is offset or not. Compared with a circular coupler, the anti-offset performance of the optimal round-corner square coupler is improved by 1.4% compared with that of the circular coupler, and the positive coupling characteristic is only weakened by 0.3%.

According to the parameters of the actual coupler, based on step 4, when h is 10 mm:

λ_eq ^*maximum value of 4.07, Per_off2%, and Per_alig1.84%. Therefore, | Per is required to satisfy the determination condition A_alig(λ_eq ^*)-Per_off(λ_eq ^*) The minimum value of | is taken as the target, and lambda is taken_eq ^*Establishing an optimization model for optimizing variables:

min：|Per_alig(λ_eq ^*)-Per_off(λ_eq ^*)| (15)

so that | Per_alig(λ_eq ^*)-Per_off(λ_eq ^*) Lambda with the smallest | value_eq ^*Namely the optimal structural parameters of the rounded square coupler.

FIG. 9 shows that when h is 10mm, Per_aligAnd Per_offAnd λ_eq ^*When r is known as a relation curve of_eq ^*＝62mm，λ_eq ^*When equal to 0.59, Per_alig＝Per_off4% so_{eq_opt} ^*0.59. At this time, the optimum rounded square coupler has better coupling characteristics than the square coupler, regardless of whether it is offset or not. Compared with a circular coupler, the anti-offset performance of the optimal round-corner square coupler is improved by 4% compared with that of the circular coupler, and the positive coupling performance is improved by 0.7%.

Since the optimal configuration parameter determination model of the B-condition in the determination condition B is the same as the determination condition a, the determination method is the same.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims (3)

1. A parameter design method of an IPT system fillet square coupler comprises a primary coil and a secondary coil, wherein the structure and parameters of the primary coil and the secondary coil are the same; the method is characterized by comprising the following steps:

(1) according to the application background, the basic parameters of the rounded square coupler are determined, and comprise the following steps: air gap height h between primary coil and secondary coil, maximum lateral offset_maxCoil area S and litz wire diameter d;

(2) based on a Newman formula and a model of the round corner square coupler, establishing an equivalent model of the round corner square coupler: neglecting the wire diameter of the litz wire, enabling the primary side coil and the secondary side coil to be equivalent to round-corner square coils which are coaxial and have different sizes, wherein each turn of coil is composed of four straight line sections with the same length and four quarter circular arcs with the same round-corner radius;

after equivalence, the structural parameters of each turn of coil are as follows: l_eqi＝l，

l_eqiIs the length of each straight line segment of the ith turn of coil, r_eqiIs the arc radius length of the ith turn of coil, r^*The length of the outer diameter of the arc part of the outermost coil before equivalence is represented by l, and the length of the straight line section of each layer of coil before equivalence is represented by l;

(3) carrying out normalization processing on the structural parameters of each turn of coil to obtain normalized structural parameters:

wherein λ is_eq ^*＝l_eq/r_eq ^*，r_eq ^*Is the arc radius length of the 1 st turn coil, i.e.

The normalized structural parameters satisfy the following conditions:

condition 1:

condition 2:

wherein N represents the total number of turns;

(4) establishing a mutual inductance model of the rounded square coupler:

wherein λ is_peqiIs a normalized structural parameter, lambda, of the ith turn coil of the primary side_seqjNormalized structural parameters, M, for the j-th turn of the secondary winding_{rou_squ}Is the mutual inductance sum between all turns of the primary side coil and all turns of the secondary side coil, f (lambda)_peqi，λ_seqjAnd h) is a mutual inductance expression between any two turns of coils on the original secondary side, and is transverse offset;

(5) when positive coupling is established, with λ_eq ^*Expression Per for percentage improvement of mutual inductance of rounded square coupler as variable compared to mutual inductance of square coupler_alig(λ_eq ^*) (ii) a Set at the maximum offset point by lambda_eq ^*Expression Per for percentage improvement of mutual inductance of rounded square coupler as variable compared to circular coupler_off(λ_eq ^*)：

Wherein M is_squAnd M_cirRepresenting the mutual inductance of the square and circular couplers, respectively;

step 6: solving for the rounded corner squareLambda of the coupler_eq ^*Taking the maximum value λ_{eq_max} ^*Times Per_off(λ_{eq_max} ^*) And Per_alig(λ_{eq_max} ^*) And establishing a solution model of the optimal structure parameters by the following judgment conditions:

a: if Per_off(λ_{eq_max} ^*)＞Per_alig(λ_{eq_max} ^*) Then with | Per_alig(λ_eq ^*)-Per_off(λ_eq ^*) The minimum value of | is taken as the target, and lambda is taken_eq ^*Establishing an optimization model for optimizing variables:

min：|Per_alig(λ_eq ^*)-Per_off(λ_eq ^*)|

so that | Per_alig(λ_eq ^*)-Per_off(λ_eq ^*) Lambda with the smallest | value_eq ^*Namely the optimal structural parameters of the rounded square coupler.

B: if Per_off(λ_{eq_max} ^*)≤Per_alig(λ_{eq_max} ^*) Then traverse λ_eq ^*By judging Per_off(λ_eq ^*)-Per_alig(λ_eq ^*) Whether all the values are less than 0 to establish a solution model of the optimal structural parameters:

and B.a: traverse lambda_eq ^*If all values of (1) satisfy Per_off(λ_eq ^*)-Per_alig(λ_eq ^*) If the result is less than 0, establishing an optimization model:

max：Per_off(λ_eq ^*)

so that Per_off(λ_eq ^*) Maximum value of λ_eq ^*Namely the optimal structural parameters of the rounded square coupler.

B.b: traverse lambda_eq ^*If there is a value satisfying Per_off(λ_eq ^*)-Per_alig(λ_eq ^*) Lambda of condition > 0_eq ^*Then the optimization model is min: | Per_alig(λ_eq ^*)-Per_off(λ_eq ^*)|；

If the number of solutions for the optimization model is two, then a smaller λ is selected_eq ^*As the optimal solution.

2. The method of claim 1, wherein f (λ) is the parameter of an IPT system rounded square coupler_peqi，λ_seqjThe expression of h) is:

f(λ_peqi，λ_seqj，，h)＝M_line+M_arc+M_line-arc

wherein M is_line-arcThe total mutual inductance between the arc segment and the straight line segment between the primary coil and the secondary coil is expressed as follows:

wherein A is_p～D_pEach representing 4 straight line segments, A, of the primary coil_s～D_s4 straight line segments, l, each representing a secondary winding_pk(k is equal to 1 to 4) represents 4 arc segments of the primary coil, l_sk(k belongs to 1-4) represents 4 arc line segments of the secondary side coil; m_lineAnd M_arcThe total mutual inductance of the straight line segment and the arc segment is respectively expressed as:

3. the method of claim 2, wherein the parameter design method is applied to a rounded square coupler of an IPT systemCharacterized in that said formula f (λ)_peqi，λ_seqj，，h)＝M_line+M_arc+M_line-arcIn the method, the mutual inductance between any section of the primary coil and any section of the secondary coil is solved through a Newman formula:

wherein dl 'and dl "are the lengths of the two element lines l' and l", D is the distance between the two length elements, and θ is the angle between the length elements.

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