Calculation method for self-inductance of magnetic coupling mechanism of flat plate type wireless power transmission system

Abstract

The invention relates to the technical field of wireless power transmission, in particular to a method for calculating the self-inductance of a magnetic coupling mechanism of a flat plate type wireless power transmission system. Comprising the following steps that S1, when inductance of a magnetic coupling mechanism with a coil being a plane spiral coil is calculated, size parameters of the plane spiral coil are determined, and the size parameters comprise the coil inner radius # imgabs0 #, the wire spacing # imgabs1 #, the coil turn number # imgabs2 # and the wire diameter # imgabs3 #; and S2, enabling the multi-turn planar spiral coil to be equivalent to a plurality of concentric circles with equal turn intervals for modeling, and calculating the self-inductance of the multi-turn coil through a formula.

Description

Technical Field

[0001] The invention relates to the technical field of wireless power transmission, and in particular to a method for calculating the self-inductance of a magnetic coupling mechanism of a flat-plate wireless power transmission system. Background Art

[0002] As an innovative contactless power supply method, magnetic coupling resonance wireless power transmission technology successfully solves the problems faced by traditional limited charging, such as complex line layout, vulnerable connection components (such as aging and leakage problems), and sparks caused by plugging and unplugging operations. This significantly improves the safety, reliability and convenience of the device charging process.

[0003] In the magnetic coupling resonant wireless power transmission system, the design of the magnetic coupling mechanism (i.e., the transmission coil) is closely related to the transmission efficiency, constant voltage gain, constant current gain, transmission power, etc. of the entire system. Therefore, it is very necessary to conduct in-depth research on the self-inductance and mutual inductance in the wireless power transmission system.

[0004] In the prior art, the inductance parameters of the magnetic coupling mechanism of the wireless power transmission system can be designed and optimized through finite element simulation software, but the finite element method is only used for smaller models. When faced with large-scale models, the calculation time often reaches tens of minutes to hours, and it is easy to cause errors.

[0005] In the past, many scholars have conducted extensive research on the analytical calculation methods of the self-inductance and mutual inductance of magnetic coupling mechanisms from the perspective of magnetic energy or magnetic vector potential, and proposed many formulas. At present, the calculation method of mutual inductance has matured, and both finite element simulation and experiments have shown that the error is small. However, the existing calculation formula is only applicable when the number of turns is very small and the turn spacing is much larger than the wire diameter. Therefore, it is urgent to propose a method that is not restricted by applicable conditions and can quickly and accurately calculate the self-inductance of the coil of the magnetic coupling mechanism, so as to shorten the design time of the magnetic coupling mechanism. Summary of the invention

[0006] The technical problem solved by the present invention is to provide a method for calculating the self-inductance of the magnetic coupling mechanism of a flat-plate wireless power transmission system. The basic solution provided by the present invention: a method for calculating the self-inductance of a magnetic coupling mechanism of a flat-plate wireless power transmission system, comprising the following steps: S1. When calculating the inductance of a magnetic coupling mechanism in which the coil is a planar spiral coil, determine the size parameters of the planar spiral coil, the size parameters including the inner radius of the coil , conductor spacing , coil turns , conductor diameter ; S2. Model the multi-turn planar spiral coil equivalent to multiple turns of concentric circles with equal turn spacing, and calculate the self-inductance of the multi-turn coil using the formula:

[0007] Where L is the self-inductance of the multi-turn coil, is the self-inductance of the i-th coil turn, is the mutual inductance between the ith coil turn and the jth coil turn.

[0008] Further, the method further comprises the following steps: S3. Calculate the self-inductance of the i-th turn of a multi-turn concentric circle with equal spacing Inner sense and external self-sensing ; Among them, the calculation of internal self-inductance The following steps are involved: S31, calculate the thickness The magnetic field energy per unit length of a thin cylinder is:

[0009] in is the outer diameter of the cylinder, V is the volume of the cylinder; S32. Integrate the magnetic field energy to obtain the magnetic field energy per unit length in a uniform current-carrying cylindrical conductor:

[0010] S33. The internal self-inductance of a cylindrical conductor with uniform current per unit length is obtained as:

[0011] S34, the internal self-inductance of the i-th coil is obtained as:

[0012] in, is the vacuum permeability, is the geometric axis radius of the i-th coil, .

[0013] Further, the external self-inductance is calculated in S3 The following steps are involved: S35, inner edge of the conductor As the boundary of the loop, the center line of the external action of the current flowing through it is regarded as concentrated on the geometric axis. , equating the external self-inductance of the thin wire to and The mutual inductance between the circuits formed; S36, calculate the current in loop 1 exist The magnetic vector potential generated at:

[0014] S37. The magnetic flux generated by loop 1 and interlinked with loop 2 is:

[0015] S38. Calculate the mutual inductance of loop 1 and loop 2 as:

[0016] Where R is and The distance between S39, the external self-inductance of the i-th coil is obtained as:

[0017] S310, calculating the self-inductance of the i-th coil turn according to the internal self-inductance and external self-inductance of the i-th coil turn: .

[0018] Further, the method further comprises the following steps: S41. Calculate the mutual inductance between the i-th coil and the j-th coil according to the magnetic vector potential:

[0019] in, is the radius of the geometric axis of the j-th coil, .

[0020] The principle and advantages of the present invention are as follows: In the present invention, for the first time, the planar spiral coil is equivalent to equally spaced concentric circles with the same number of turns. Then, starting from the definition of magnetic energy and magnetic vector potential, the analytical expression of the self-inductance of the planar spiral coil is derived and established, realizing the analytical calculation of the self-inductance of the coil of the wireless power transmission system, and having the characteristic of not imposing applicable conditions restrictions on "ratio of coil turn spacing to wire diameter, number of coil turns". The proposed analytical calculation method for the self-inductance parameters of the planar spiral coil has a high calculation accuracy, while taking into account both densely wound (turn spacing is 0) and loosely wound (turn spacing is not 0) coils, without applicable conditions restrictions. This is the advantage and positive effect of the present invention compared with the prior art, and it is an inevitable technical effect brought about by or produced by the technical features. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of geometric parameters of a planar spiral coil in an embodiment of a method for calculating the self-inductance of a magnetic coupling mechanism of a planar wireless power transmission system of the present invention; Figure 2The calculation method of the self-inductance of the magnetic coupling mechanism of the flat-plate wireless power transmission system of the present invention is Figure 1 Schematic diagram of multi-turn concentric circles with equal turn spacing equivalent to a planar spiral coil; Figure 3 A single-turn coil self-inductance calculation model in an embodiment of a method for calculating the self-inductance of a magnetic coupling mechanism of a flat-plate wireless power transmission system of the present invention; Figure 4 A uniform current-carrying cylindrical conductor in the embodiment of the method for calculating the self-inductance of the magnetic coupling mechanism of the flat-plate wireless power transmission system of the present invention; Figure 5 A multi-turn coil self-inductance calculation model in an embodiment of a method for calculating the self-inductance of a magnetic coupling mechanism of a flat-plate wireless power transmission system of the present invention; Figure 6 A data table for verifying the accuracy of the self-inductance analytical solution in the embodiment of the method for calculating the self-inductance of the magnetic coupling mechanism of the flat-plate wireless power transmission system of the present invention; Figure 7 are the main parameters of the simulation model in the embodiment of the method for calculating the self-inductance of the magnetic coupling mechanism of the flat-plate wireless power transmission system of the present invention; Figure 8 The figure shows a comparison between the analytical solution and the simulation result in an embodiment of a method for calculating the self-inductance of a magnetic coupling mechanism of a planar wireless power transmission system of the present invention. DETAILED DESCRIPTION

[0022] The following is further described in detail through specific implementation methods: The embodiment is basically as shown in the attached Figure 1 As shown: A method for calculating the self-inductance of a magnetic coupling mechanism of a flat-plate wireless power transmission system comprises the following steps: like Figure 1 As shown, Figure 1 A schematic diagram of geometric parameters of a planar spiral coil of a magnetic coupling mechanism used in the present invention; S1. When calculating the inductance of a magnetic coupling mechanism in which the coil is a planar spiral coil, determine the size parameters of the planar spiral coil, the size parameters including the inner radius of the coil , conductor spacing , coil turns , conductor diameter ; S2. Model the multi-turn planar spiral coil as a multi-turn concentric circle with equal turn spacing, and calculate the self-inductance of the multi-turn coil by formula. Specifically, Figure 1 The multi-turn planar spiral coil shown is equivalent to Figure 2 The multi-turn concentric circles with equal turn spacing are shown:

[0023] Where L is the self-inductance of the multi-turn coil, is the self-inductance of the i-th coil turn, is the mutual inductance between the ith coil turn and the jth coil turn.

[0024] Further, the method further comprises the following steps: S3, calculation Figure 3 As shown, the self-inductance of the i-th turn of a multi-turn concentric circle with equal spacing is Inner sense and external self-sensing ; Among them, the calculation of internal self-inductance The following steps are involved: S31, such as Figure 4 As shown, the calculated thickness is The magnetic field energy per unit length of a thin cylinder is:

[0025] in is the outer diameter of the cylinder, V is the volume of the cylinder; S32. Integrate the magnetic field energy to obtain the magnetic field energy per unit length in a uniform current-carrying cylindrical conductor:

[0026] S33. The internal self-inductance of a cylindrical conductor with uniform current per unit length is obtained as:

[0027] S34, the internal self-inductance of the i-th coil is obtained as:

[0028] in, is the vacuum permeability, is the geometric axis radius of the i-th coil, .

[0029] Further, the external self-inductance is calculated in S3 The following steps are involved: S35, inner edge of the conductor As the boundary of the loop, the center line of the external action of the current flowing through it is regarded as concentrated on the geometric axis. , equating the external self-inductance of the thin wire to and The mutual inductance between the circuits formed; S36, calculate the current in loop 1 exist The magnetic vector potential generated at:

[0030] S37. The magnetic flux generated by loop 1 and interlinked with loop 2 is:

[0031] S38. Calculate the mutual inductance of loop 1 and loop 2 as:

[0032] Where R is and The distance between S39, the external self-inductance of the i-th coil is obtained as:

[0033] φ 1 for With origin 0 Connection and x The angle of the axes; φ 3 With origin 0 Connection and x The angle of the axis.

[0034] S310, calculating the self-inductance of the i-th coil turn according to the internal self-inductance and external self-inductance of the i-th coil turn: .

[0035] φ 1 for With origin 0 Connection and x The angle of the axes; φ 3 With origin 0 Connection and x The angle of the axis.

[0036] Further, the method further comprises the following steps: S41, such as Figure 5 As shown, the mutual inductance between the i-th coil and the j-th coil is calculated based on the magnetic vector potential:

[0037] in, is the radius of the geometric axis of the j-th coil, .

[0038] In the present invention, for the first time, the planar spiral coil is equivalent to equally spaced concentric circles with the same number of turns. Then, starting from the definition of magnetic energy and magnetic vector potential, the analytical expression of the self-inductance of the planar spiral coil is derived and established, realizing the analytical calculation of the self-inductance of the coil of the wireless power transmission system, which has the characteristics of not imposing applicable conditions on the "ratio of coil turn spacing to wire diameter, number of coil turns". The proposed analytical calculation method for the self-inductance parameters of the planar spiral coil has high calculation accuracy, while taking into account both densely wound (turn spacing is 0) and loosely wound (turn spacing is not 0) coils, without applicable conditions. This is the advantage and positive effect of the present invention compared with the prior art, and it is an inevitable technical effect brought about by or produced by the technical features.

[0039] Figure 6 The data table is used to verify the accuracy of the analytical solution of the self-inductance. The experiment shows that the maximum error between the analytical solution and the experimental value of the self-inductance of the planar spiral coil with 6 different wire gauges (wire diameter × number of strands) is 4.12%.

[0040] Figure 7 These are the main dimensional parameters of the planar spiral coil established using Comsol Multiphysics finite element simulation software. Figure 8 Comparison between analytical solution and finite element simulation results. The simulation results show that the error between the analytical solution and the finite element solution of the coil self-inductance is within 3.00%.

[0041] The above are only embodiments of the present invention. Common knowledge such as the known specific structures and characteristics in the scheme is not described in detail here. Ordinary technicians in the relevant field know all the common technical knowledge in the technical field to which the invention belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for calculating the self-inductance of a magnetic coupling mechanism of a flat-plate wireless power transmission system, characterized in that: The following steps are involved: S1. When calculating the inductance of a magnetic coupling mechanism in which the coil is a planar spiral coil, determine the size parameters of the planar spiral coil, the size parameters including the inner radius of the coil , conductor spacing , coil turns , wire diameter ; S2. Model the multi-turn planar spiral coil equivalent to multiple turns of concentric circles with equal turn spacing, and calculate the self-inductance of the multi-turn coil using the formula: Where L is the self-inductance of the multi-turn coil, is the self-inductance of the i-th coil turn, is the mutual inductance between the i-th coil and the j-th coil; The following steps are also included: S3. Calculate the self-inductance of the i-th turn of a multi-turn concentric circle with equal spacing Inner sense and external self-sensing ; Among them, the calculation of internal self-inductance The following steps are involved: S31, calculate the thickness The magnetic field energy per unit length of a thin cylinder is: in is the outer diameter of the cylinder, V is the volume of the cylinder; S32. Integrate the magnetic field energy to obtain the magnetic field energy per unit length in a uniform current-carrying cylindrical conductor: S33. The internal self-inductance of a cylindrical conductor with uniform current per unit length is obtained as: S34, the internal self-inductance of the i-th coil is obtained as: in, is the vacuum permeability, is the geometric axis radius of the i-th coil, , I is the current; The external self-inductance is calculated in S3 The following steps are involved: S35, inner edge of the conductor As the boundary of the loop, the center line of the external action of the current flowing through it is regarded as concentrated on the geometric axis. , equating the external self-inductance of the thin wire to and The mutual inductance between the circuits formed; S36, calculate the current in loop 1 exist The magnetic vector potential generated at: S37. The magnetic flux generated by loop 1 and interlinked with loop 2 is: S38. Calculate the mutual inductance of loop 1 and loop 2 as: Where R is and The distance between S39, the external self-inductance of the i-th coil is obtained as: φ 1 for With origin 0 Connection and x The angle of the axis; φ 2 for With origin 0 Connection and x The angle of the axis; S310, calculating the self-inductance of the i-th coil turn according to the internal self-inductance and external self-inductance of the i-th coil turn: ； φ 1 for With origin 0 Connection and x The angle of the axis; φ 3 With origin 0 Connection and x The angle of the axis.

2. The method for calculating the self-inductance of the magnetic coupling mechanism of the planar wireless power transmission system according to claim 1, characterized in that: The following steps are also included: S41. Calculate the mutual inductance between the i-th coil and the j-th coil according to the magnetic vector potential: in, is the radius of the geometric axis of the j-th coil, .

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