Hybrid magnetic shielding structure for wireless charging and optimization method thereof

Abstract

The invention discloses a hybrid magnetic shielding structure for wireless charging and an optimization method thereof, and relates to the technical field of power electronic energy conversion. The invention aims to solve the problem that a mixed shielding method adopted in wireless power transmission lacks a coil, an active shielding topological structure and a ferrite structure. The hybrid magnetic shielding structure comprises an inner layer shielding coil and an outer layer shielding coil which are opposite in current direction, and the current direction of the inner layer shielding coil is the same as that of an inner DD type coil. Constructing a finite element model of the hybrid magnetic shielding structure; evaluating the sensitivity of various to-be-optimized variables in the finite element model by using an SQP algorithm, and sorting the to-be-optimized variables; and optimizing the to-be-optimized variables according to the sensitivity sequence by using electromagnetic simulation software to obtain an optimization result.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronic energy conversion. Background Art

[0002] As an efficient and convenient way of power transmission, magnetically coupled resonant wireless power transmission technology (MCR-WPT) has attracted more and more attention. In recent years, with the development of power electronics technology, wireless power transmission technology has also been continuously improved and innovated. With the popularization and rapid development of smart devices such as new energy vehicles, smart phones, and drones, traditional wired charging methods are gradually unable to meet people's growing charging needs. Compared with wired charging, the transmitter and receiver of the wireless charging system do not require a physical connection between the circuits, and energy is transferred through a coupled magnetic field. However, for high-power wireless power transmission systems, if the coupler and shielding are not designed properly, a strong magnetic field may be generated, which will not only reduce the transmission efficiency of the system, but also pose a potential threat to electronic equipment in the vehicle and human safety. Therefore, in-depth research on MCR-WPT system shielding technology is crucial to improving power transmission efficiency, enhancing power transmission safety, and promoting the intelligent development of power transmission.

[0003] Passive and active shielding are considered to be two common methods to solve the problem of magnetic flux leakage. Among them, the shielding coil in passive shielding generates a counteracting magnetic field in the opposite direction of the main coil magnetic field through electromagnetic induction, without the need to add external excitation. The most typical one is ferrite shielding. However, the poor magnetic properties (magnetic saturation, magnetic permeability, Curie temperature) and mechanical properties (ductility, firmness) of ferrite lead to its insufficient ability to shield MFL. Although active shielding can alleviate magnetic flux leakage in specific areas, it will cause a corresponding reduction in mutual inductance and affect the coupling of magnetic fields.

[0004] In order to ensure the shielding effect while minimizing the impact on transmission efficiency, many researchers use a mixture of active suppression coils and ferrites to achieve better transmission efficiency and leakage magnetic shielding performance. However, in the hybrid shielding method, the optimal design strategy for the coil and active shielding topology and ferrite has not yet been clarified. The structural optimization of the two is a key factor in improving the performance of the hybrid system, but it is also a major challenge. Summary of the invention

[0005] The present invention aims to solve the problem that the hybrid shielding method used in wireless power transmission lacks the coil and the active shielding topology structure and the ferrite structure are poor. A hybrid magnetic shielding structure for wireless charging and an optimization method thereof are now provided.

[0006] The hybrid magnetic shielding structure for wireless charging includes: two layers of inner and outer shielding coils with opposite current directions, wherein the current direction of the inner shielding coil is the same as the current direction of the internal DD-type coil, and both layers of shielding coils are located below the ferrite core 4.

[0007] Furthermore, there is a distance between the two layers of shielding coils.

[0008] Furthermore, the two layers of shielding coils are both located 2 cm to 5 cm below the ferrite core 4 .

[0009] The above-mentioned optimization method of the hybrid magnetic shielding structure for wireless charging includes:

[0010] Constructing a finite element model of the hybrid magnetic shielding structure for wireless charging;

[0011] Use the SQP algorithm to evaluate and rank the sensitivity of various variables to be optimized in the finite element model;

[0012] Electromagnetic simulation software (Ansys Electronics Desktop) is used to optimize various variables to be optimized in order of sensitivity to obtain the optimization results.

[0013] Furthermore, the variables to be optimized include: the number of turns and radius of the two-layer shielding coils, and the thickness of the ferrite core 4 .

[0014] Furthermore, the electromagnetic simulation software (Ansys Electronics Desktop) is used to optimize various variables to be optimized in order of sensitivity, including:

[0015] Each type of optimization method for variables to be optimized includes:

[0016] Two observation lines are set on the hybrid magnetic shielding structure, and variable parameters are sampled in a preset variable interval. All sampled parameters are input into the electromagnetic simulation software to determine whether parameters that minimize the magnetic induction intensity and maximize the magnetic flux density reduction rate can be found at the two observation lines. If so, the found parameters are taken as the optimal parameters. Otherwise, the sampling step size of the preset variable interval is reduced, sampling is performed again in the preset variable interval, and then the electromagnetic simulation software is used to search for the optimal parameter until the optimal parameter is obtained.

[0017] Furthermore, the above two observation lines are:

[0018] An observation line is parallel to the surface of the hybrid magnetic shielding structure and is located 5 cm to 10 cm above the hybrid magnetic shielding structure;

[0019] Another observation line is perpendicular to the surface of the hybrid magnetic shielding structure and is located 8 cm to 16 cm outside the outer shielding coil.

[0020] The present invention combines the sensitivity evaluation model to analyze the influencing parameters of the active shielding coil and the ferrite core, providing a concise and intuitive way to understand the impact of parameter variables on the target. This method can clearly see which factors are affecting system performance and how these impacts are propagated.

[0021] The present invention adopts the technical means of sensitivity assessment, which can quickly identify the input variables that have a significant impact on the output results.

[0022] The present invention does not require complicated coding and structure, and the hybrid shielding structure can effectively weaken the leakage magnetic field of the WPT system in the target area to achieve a good shielding effect.

[0023] By evaluating the performance of the model under different input parameter changes, it can be determined whether the model is overly dependent on certain assumptions or parameter values. This helps to identify potential weaknesses in the model and take appropriate measures to improve it. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the hybrid magnetic shielding structure of the present invention.

[0025] Figure 2 Schematic diagram of coil and shielding structure, where (a) is a traditional circular coil, (b) is a rectangular coil, (c) is a DD type coil, (d) is a traditional circular coil magnetic shielding structure; (e) is a traditional rectangular coil magnetic shielding structure; (f) is a hybrid magnetic shielding structure.

[0026] Figure 3 Schematic diagram of the yz cross section of the magnetic field enhancement and weakening of the wireless power transmission system.

[0027] Figure 4 Flowchart of an optimization method for a hybrid magnetic shielding structure for wireless charging.

[0028] In the figure: 1 primary coil, 2 inner shielding coil, 3 outer shielding coil, 4 ferrite core. DETAILED DESCRIPTION

[0029] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0030] At present, the traditional magnetic shielding design in the field of power electronic energy conversion technology is aimed at circular and rectangular coils, while there are few studies on multipolar coils such as DD coils, DDQ coils, QDQP coils, etc. Compared with traditional unipolar coils, multipolar coils show significant advantages, mainly reflected in their superior magnetic field coupling ability and excellent anti-offset performance. Therefore, the present invention focuses on exploring the magnetic field leakage characteristics of bipolar DD type coils, aiming to improve energy transmission efficiency and reduce magnetic flux leakage during power transmission.

[0031] Specific implementation method 1. Reference Figure 1 and Figure 2 Specifically describing this embodiment, the hybrid magnetic shielding structure for wireless charging described in this embodiment includes: a passive ferrite core 4 and an active magnetic shielding coil, and the active magnetic shielding coil includes an inner shielding coil 2 and an outer shielding coil 3 with opposite current directions. The current direction of the inner shielding coil 2 is the same as the current direction of the internal DD-type coil, and both shielding coils are located 2cm to 5cm below the ferrite core 4. There is a distance between the two shielding coils.

[0032] The working principle of the proposed coil structure is explained by comparing it with the existing coil structure:

[0033] Figure 2 a and 2b are traditional coil structures. Since they do not have any shielding structure, a large leakage magnetic field will be generated between the transmitting coil and the receiving coil. In addition, the unipolar coil used has poor magnetic field coupling capability and anti-offset performance, which affects the efficiency of the system to a certain extent. Figure 2 d and 2e are active coil structures connected in reverse series to the primary coil 1, in which the current direction is opposite to that of the primary coil 1, which has a shielding effect, but also weakens the magnetic field between the transmitting coil and the receiving coil, which has a significant negative impact on the efficiency of the WPT system.

[0034] Figure 2 c is the DD type coil used in this embodiment, Figure 2 f is an active magnetic shielding coil provided in this embodiment, which has two layers of coils, namely, an inner shielding coil 2 and an outer shielding coil 3. The current direction of the inner shielding coil 2 is the same as the current in the primary coil 1, thereby generating a magnetic field in the same direction as the primary coil 1, enhancing the mutual inductance of the wireless power transmission system, and having the function of compensating the transmission efficiency of the WPT system. The outer shielding coil 3 has an opposite current direction to that in the primary coil 1, and is used to weaken the magnetic field strength outside the coil, thereby playing a shielding role.

[0035] The inner shielding coil 2 of the active active magnetic shielding coil has the same current direction as the primary coil 1, and is coupled with the coil, thereby generating a higher coupling magnetic field, improving the coupling performance between coils, and improving the efficiency of power transmission. The outer shielding coil 3 of the active active magnetic shielding coil has an opposite current to the primary coil 1, and is used to shield the magnetic field outside the main coupling coil, wherein the outer shielding coil 3 maintains a certain distance from the inner shielding coil 2 to achieve better shielding performance, minimize the leakage magnetic field of the main coil, and thus protect the surrounding electronic equipment and personal safety.

[0036] The thickness of the ferrite core 4 is set to be adjustable to shield the magnetic field above the vehicle. The ferrite core 4 can play the role of enriching the magnetic lines of force. In this way, not only can the leakage magnetic field strength be limited, but also the self-inductance of the coupling coil and the mutual inductance between the coupling coils can be effectively increased, so that the quality factor Q and coupling coefficient k of the coupling coil are higher, thereby improving the power transmission efficiency of the MCR-WPT system.

[0037] Specific implementation method II. Reference Figure 3 and Figure 4 Specifically describing this embodiment, the optimization method of the hybrid magnetic shielding structure for wireless charging described in this embodiment includes: based on the hybrid magnetic shielding structure, constructing a finite element simulation model including a bipolar DD-type coil, an active magnetic shielding coil, a ferrite core 4 and a wireless power transmission (WPT) system.

[0038] Set the type and range of variables to be optimized. The variables to be optimized include: ferrite core thickness t, number of turns of outer shielding coil N2, radius of outer shielding coil L out , the spacing between shielding coils on the same side L sh And the number of turns of the inner shielding coil is N1.

[0039] The SQP algorithm is used to evaluate the sensitivity of various variables to be optimized and sort them, and the various variables to be optimized are output in order from large to small. Electromagnetic simulation software (Ansys Electronics Desktop) is used to optimize various variables to be optimized and obtain the optimization results, ensuring that the leakage magnetic field of the optimized WPT system at the observation line is minimized, and the transmission efficiency is least affected, so as to achieve efficient power transmission.

[0040] Specifically, the optimization method for each type of variable to be optimized is:

[0041] The geometric center of the hybrid magnetic shielding structure is used as the coordinate origin to construct a three-dimensional coordinate system xyz, where the z-axis is parallel to the plane of the hybrid magnetic shielding structure. Two observation lines are set, observation line 1 is parallel to the surface of the hybrid magnetic shielding structure and is located 5 to 10 cm above the hybrid magnetic shielding structure; observation line 2 is parallel to the z-axis and is located 8 to 16 cm outside the outer shielding coil.

[0042] The variables to be optimized in the preset variable interval are input into the electromagnetic simulation software to determine whether parameters that minimize the magnetic induction intensity B and maximize the magnetic flux density reduction rate MFDRR can be found at observation lines 1 and 2. If so, the found parameters are taken as the optimal parameters. Otherwise, the sampling step in the variable interval is reduced, the parameters are resampled in the variable interval, and then the electromagnetic simulation software is used to search for the optimal value until the optimal parameters are obtained.

[0043] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A hybrid magnetic shielding structure for wireless charging, characterized in that: include: The inner and outer layers of the shielding coil have opposite current directions, wherein the current direction of the inner shielding coil is the same as the current direction of the internal DD-type coil, and both layers of the shielding coil are located below the ferrite core (4).

2. The hybrid magnetic shielding structure for wireless charging according to claim 1, characterized in that: A distance is left between the two layers of shielding coils.

3. The hybrid magnetic shielding structure for wireless charging according to claim 1 or 2, characterized in that: The two layers of shielding coils are both located 2 cm to 5 cm below the ferrite core (4).

4. The optimization method of the hybrid magnetic shielding structure for wireless charging according to claim 1, 2 or 3, characterized in that: include: Constructing a finite element model of the hybrid magnetic shielding structure for wireless charging; Use the SQP algorithm to evaluate and rank the sensitivity of various variables to be optimized in the finite element model; Electromagnetic simulation software is used to optimize various variables to be optimized in order of sensitivity to obtain the optimization results.

5. The optimization method of the hybrid magnetic shielding structure for wireless charging according to claim 4, characterized in that: The variables to be optimized include: the number of turns and radius of the two-layer shielding coil, and the thickness of the ferrite core (4).

6. The optimization method of the hybrid magnetic shielding structure for wireless charging according to claim 4 or 5, characterized in that: The electromagnetic simulation software is used to optimize various variables to be optimized in order of sensitivity, including: Each type of optimization method for variables to be optimized includes: Two observation lines are set on the hybrid magnetic shielding structure, and variable parameters are sampled in a preset variable interval. All sampled parameters are input into the electromagnetic simulation software to determine whether parameters that minimize the magnetic induction intensity and maximize the magnetic flux density reduction rate can be found at the two observation lines. If so, the found parameters are taken as the optimal parameters. Otherwise, the sampling step size of the preset variable interval is reduced, sampling is performed again in the preset variable interval, and then the electromagnetic simulation software is used to search for the optimal parameter until the optimal parameter is obtained.

7. The optimization method of the hybrid magnetic shielding structure for wireless charging according to claim 6, characterized in that: The two observation lines are: An observation line is parallel to the surface of the hybrid magnetic shielding structure and is located 5 cm to 10 cm above the hybrid magnetic shielding structure; Another observation line is perpendicular to the surface of the hybrid magnetic shielding structure and is located 8 cm to 16 cm outside the outer shielding coil.

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