Parallel shielded coil structure and optimization method thereof

Abstract

This invention relates to the field of power electronics technology and discloses a parallel shielded coil structure and its optimization method. The optimization method is based on a parallel shielded coil structure, which includes a transmitting coil, a receiving coil, a first compensation coil, a second compensation coil, and a resonant compensation circuit. The transmitting and receiving coils are coaxial, tightly wound circular coils, while the first and second compensation coils are parallel, concentric, tightly wound circular coils. The method determines the number of turns of the transmitting and receiving coils, their axial distance, the axial distance between the first and second compensation coils, and the coil placement relationship. It optimizes the number of turns of the first and second compensation coils and the distance between the transmitting and compensation coils. Based on the optimization results, the parameters of the compensation capacitor in the resonant compensation circuit are obtained. This effectively suppresses leakage magnetic fields without adding an additional shielding coil, and also improves energy transmission efficiency and space compactness.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and specifically relates to a parallel shielded coil structure and its optimization method. Background Technology

[0002] Existing wireless power transmission technologies offer numerous advantages over traditional wired transmission technologies. However, the increased magnetic field strength caused by leakage flux in their power transmission structures poses a significant threat to electronic equipment and personal safety. Traditional shielding methods are categorized into passive and active shielding. Passive shielding methods include magnetic shielding, conductive shielding, and resonant reactive shielding. Magnetic shielding involves placing ferrite around the wireless charging system, aligning the system's main magnetic circuit with the ferrite, effectively reducing the magnetic field strength of the surrounding space. Conductive shielding effectively shields against magnetic flux leakage by placing horizontally or vertically grounded metal shielding plates around the wireless charging system. Resonant reactive shielding utilizes a resonant reactive shielding coil to induce a current in the shielding coil using leakage flux, thereby canceling the original magnetic field. Active magnetic shielding, through active adjustment of the magnetic field generated by the shielding coil, completely cancels the original magnetic field. However, passive shielding, which uses high-permeability materials to absorb or reflect electromagnetic radiation, often leads to an increase in the size and weight of the device. The resulting eddy current losses also affect energy transmission efficiency, and the economic issues associated with shielding materials cannot be ignored. Traditional active shielding reduces leakage magnetic field by adding an external excitation power supply or generating a reverse magnetic field using anti-series shielding coils. However, external power supplies increase the size of the wireless charging device, increase energy loss and affect transmission efficiency, and the control algorithms are often complex, making it difficult to guarantee the shielding effect. Summary of the Invention

[0003] To address the above problems, this invention provides a parallel shielded coil structure and its optimization method, which effectively suppresses leakage magnetic field.

[0004] The purpose of this invention is to provide a method for optimizing a parallel shielded coil structure. The method is based on a parallel shielded coil structure, which includes a transmitting coil, a receiving coil, a first compensation coil, a second compensation coil, and a resonant compensation circuit. The resonant compensation circuit is connected to the transmitting coil and the receiving coil, respectively. Both the transmitting coil and the receiving coil are coaxial tightly wound circular coils, and the first compensation coil and the second compensation coil are concentric tightly wound circular coils placed in parallel. The method for optimizing the parallel shielded coil structure includes the following steps: Determine the number of turns of the transmitting coil and the receiving coil, the axial distance between the transmitting coil and the receiving coil, the axial distance between the first compensation coil and the second compensation coil, and the arrangement of the transmitting coil, the receiving coil, the first compensation coil, and the second compensation coil; Optimize the number of turns of the first compensation coil and the second compensation coil, as well as the distance between the transmitting coil and the first compensation coil, and between the receiving coil and the second compensation coil; Based on the optimized number of turns of the first and second compensation coils, as well as the distances between the transmitting coil and the first compensation coil, and between the receiving coil and the second compensation coil, the compensation capacitor parameters in the resonant compensation circuit are obtained.

[0005] Furthermore, determining the number of turns of the transmitting coil and the receiving coil, the axial distance between the transmitting coil and the receiving coil, the axial distance between the first compensation coil and the second compensation coil, and the arrangement of the transmitting coil, the receiving coil, the first compensation coil, and the second compensation coil includes... The number of turns in the transmitting and receiving coils is preset; The axial distance between the transmitting coil and the receiving coil is equal to the axial distance between the first compensation coil and the second compensation coil, and a preset axial distance is used; The arrangement of the transmitting coil, receiving coil, first compensation coil, and second compensation coil satisfies the following conditions: The first compensation coil is arranged parallel above the receiving coil, and the second compensation coil is arranged parallel above the transmitting coil.

[0006] Furthermore, optimizing the number of turns of the first and second compensation coils, as well as the distances between the transmitting coil and the first compensation coil, and between the receiving coil and the second compensation coil, includes: Determine design variables, including turns control parameters. x 1 and distance control parameters x 2; Define the objective function: In the formula, For integer decision vectors, The magnetic field strength; Define the following constraints: Variable boundary constraints: control parameters x 1 and distance control parameters x 2. Each within the preset range; Integer constraint: Both design variables must be integers; Turns constraint: Number of turns of the first compensation coil and the second compensation coil n Within the preset number of turns; Distance constraint: The distance d between the center point of the transmitting coil and the center point of the first compensation coil, and between the center point of the receiving coil and the center point of the second compensation coil. c Within the preset distance range; Calculate the inductance values ​​of the transmitting and receiving coils; Based on the calculated inductance values ​​of the transmitting and receiving coils, as well as the determined objective function and constraints, the number of turns of the compensation coil and the distance between the center point of the compensation coil and the center point of the transmission coil are obtained through optimization iteration using a genetic algorithm.

[0007] Furthermore, the inductance values ​​of the transmitting and receiving coils are calculated to satisfy:

[0008] In the formula, n is the preset number of turns of the transmitting coil and the receiving coil. L i For the first i Self-inductance of coil; M ij For the first i Turns of coil and the first j Mutual inductance between coils; Among them, the i self-inductance of coil L i for:

[0009] In the formula, α i For the first i The radius of the cylindrical wire in the coil from the central axis. r It refers to the diameter of the cylindrical conductor. The permeability of free space, For the first A current line element on a coil and The included angle of the axis, For the first A current line element on a coil and The included angle of the axis; Among them, the i Turns of coil and the first j Mutual inductance between coils:

[0010] In the formula, a i For the first i The radius of the cylindrical wire in the coil from the central axis. b j For the first j The radius of the cylindrical wire in the coil from the central axis. μ 0 is the permeability of free space. φ 1 is the first i A current line element on a coil and The included angle of the axis, For the first j A current line element on a coil and The included angle of the axis.

[0011] Furthermore, based on the calculated inductance values ​​of the transmitting and receiving coils, as well as the determined objective function and constraints, the number of turns of the compensation coil and the distance between the center point of the compensation coil and the center point of the transmission coil are obtained through optimization iteration using a genetic algorithm, including joint simulation using COMSOL and MATLAB.

[0012] Furthermore, based on the optimized number of turns of the first and second compensation coils, and the distances between the transmitting coil and the first compensation coil, and between the receiving coil and the second compensation coil, the compensation capacitor parameters in the resonant compensation circuit are obtained, including:

[0013] In the formula, C 1. C 2. C 3. C 4 represents the resonant capacitor in the resonant compensation circuit. L 1. L 2. L 3. L 4 are the transmitting coils L 2. Receiving coil L 3. First and second compensation coils L 1. L 4 inductance, Let be the system angular frequency.

[0014] Another object of the present invention is to provide a parallel shielded coil structure, including a transmitting coil, a receiving coil, a first compensation coil, a second compensation coil, and a resonant compensation circuit, wherein the resonant compensation circuit is connected to the transmitting coil and the receiving coil respectively, wherein... Both the transmitting and receiving coils are coaxial, tightly wound circular coils, and the number of turns is preset. The first compensation coil and the second compensation coil are concentric closely wound circular coils placed in parallel. The axial distance between the transmitting coil and the receiving coil is equal to the axial distance between the first compensation coil and the second compensation coil, and both are preset axial distances; The first compensation coil is arranged parallel above the receiving coil, and the second compensation coil is arranged parallel above the transmitting coil. The number of turns of the first and second compensation coils, the distance between the transmitting coil and the first compensation coil, the distance between the receiving coil and the second compensation coil, and the parameters of the compensation capacitor in the resonant compensation circuit are all optimized using the parallel shielded coil structure optimization method described above.

[0015] Furthermore, the axial and radial distance offsets of the first and second compensation coils, as well as the transmitting and receiving coils, satisfy the following: Axial distance offset range: 50mm < Δ d <150mm, radial offset distance Δ r ≤40mm.

[0016] Furthermore, the first compensation coil and the second compensation coil are the primary side compensation coil and the secondary side compensation coil, respectively, and both the primary side compensation coil and the secondary side compensation coil are concentric closely wound circular coils of the same size.

[0017] Furthermore, in a concentric closely wound circular coil, the coil in the same layer has a multi-turn structure, and the winding method of each wire in the same layer is the same.

[0018] Furthermore, the conductors used for the transmitting coil and the receiving coil have the same wire diameter; the resonant compensation circuit includes a resonant capacitor and a compensation inductor connected in series.

[0019] The parallel shielded coil structure of the present invention effectively suppresses leakage magnetic field without adding an additional shielded coil. By adjusting the arrangement of the first compensation coil and the second compensation coil, the magnetic field distribution produces a controllable cancellation effect, while achieving high energy transmission efficiency and space compactness.

[0020] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of a parallel shielded coil structure is shown in an embodiment of the present invention; Figure 2 This diagram illustrates the arrangement of a parallel shielded coil structure in an embodiment of the present invention. Figure 3 A schematic diagram of a parallel shielded coil structure circuit is shown in an embodiment of the present invention; Figure 4The figure shows an iterative result diagram of a genetic algorithm in an embodiment of the present invention; Figure 5 A comparison diagram of the magnetic fields of a shielded coil and an unshielded coil in an embodiment of the present invention is shown; Figure 6a Another magnetic field comparison diagram of shielded and unshielded coils in an embodiment of the present invention is shown; Figure 6b A shielding effect diagram of an embodiment of the present invention is shown; Figure 7a The diagram shows the waveforms of system voltage and current in an embodiment of the present invention; Figure 7b An experimental voltage and current waveform and power diagram are shown in an embodiment of the present invention; Figure 7c An experimental voltage and current waveform and power diagram are shown in an embodiment of the present invention; Figure 8a The following is a spectral noise floor diagram of an unshielded coil according to an embodiment of the present invention; Figure 8b The following is a spectral noise floor diagram of a shielded coil installed according to an embodiment of the present invention; Figure 8c This invention illustrates a magnetic field spectrum diagram before the installation of a shielding coil, according to an embodiment of the invention. Figure 8d This invention illustrates a magnetic field spectrum diagram after installing a shielding coil in one embodiment. Figure 9 A schematic diagram of a fixing point and a shielding coil in an embodiment of the present invention is shown; Figure 10 An equivalent circuit diagram from an embodiment of the present invention is shown. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1As shown in the figure, an optimization method for a parallel shielded coil structure is introduced in this embodiment of the invention. The optimization method is based on a parallel shielded coil structure, which includes a transmitting coil, a receiving coil, a first compensation coil, a second compensation coil, and a resonant compensation circuit. The resonant compensation circuit is connected to the transmitting coil and the receiving coil, respectively. Both the transmitting coil and the receiving coil are coaxial tightly wound circular coils, and the first compensation coil and the second compensation coil are parallel concentric tightly wound circular coils. The optimization method for the parallel shielded coil structure includes the following steps: First, determine the number of turns of the transmitting coil and the receiving coil, the axial distance between the transmitting coil and the receiving coil, the axial distance between the first compensation coil and the second compensation coil, and the arrangement of the transmitting coil, the receiving coil, the first compensation coil, and the second compensation coil; then, optimize the number of turns of the first compensation coil and the second compensation coil, and the distance between the transmitting coil and the first compensation coil, and between the receiving coil and the second compensation coil; finally, based on the optimized number of turns of the first compensation coil and the second compensation coil, and the distance between the transmitting coil and the first compensation coil, and between the receiving coil and the second compensation coil, obtain the compensation capacitor parameters in the resonant compensation circuit. Without adding an extra shielding coil, leakage magnetic field is effectively suppressed. By adjusting the arrangement of the first and second compensation coils, the magnetic field distribution produces a controllable cancellation effect, while achieving high energy transmission efficiency and compact space.

[0025] Specifically, Figure 1 In the middle, the first compensation coil and the second compensation coil are respectively the primary side compensation coils. L 1 and secondary compensation coil L 4, such as Figure 2 As shown, the primary side compensation coil L 1 and secondary compensation coil L 4 are all concentric closely wound circular coils of the same size. A concentric closely wound circular coil can be a solenoid. In the same plane, the wires are wound into a multi-turn coil in a circle. The same layer of coils in a concentric closely wound circular coil has a multi-turn structure, and the winding method of each wire in the same layer is the same.

[0026] In this embodiment of the invention, the primary-side compensation coil used L 1 and secondary compensation coil L 4 can be copper wire, iron coil, enameled wire, or Litz wire, but is not limited to these. Any material with strong conductivity and low energy loss is suitable for this invention.

[0027] In this embodiment of the invention, the transmitting coil L 2 and receiving coil L The number of turns and wire diameter of the 3 coils are the same, and the wire diameter is also a known parameter. Preferably, the wire diameters of the first and second compensation coils are also known parameters, such as... Figure 3The primary and secondary compensation coils shown L 1. L 4. Placed parallel to the transmitting and receiving coils and fixed on the base plate. For ease of winding, the transmitting and receiving coils are made of metal coils or Litz wire. Figure 1 The equivalent circuit diagram of the structure is shown, with the transmitting and receiving coils on the plane shaded. Further, the primary-side compensation coil... L 1 and secondary compensation coil L 4 preset axial distance d 1 is a fixed parameter, transmission coil and Preset axial distance These are also fixed parameters. Since the coils are placed in parallel, therefore... ( Figure 3 H d After the system parameters are tuned, the primary and secondary compensation coils... L 1. L 4. The offsets in axial and radial distances are tolerable within small ranges, when the axial distance offset range is: 50mm < Δ d With a radius of less than 150mm and a radial offset distance Δr ≤ 40mm (unit: millimeters), the system can still operate stably, although the transmission efficiency and shielding effect decrease slightly. High-frequency harmonics are filtered out using system coupling resonance, achieving a large low-energy transmission impedance at the resonant frequency, thus realizing efficient energy transmission.

[0028] In this invention example, the primary and secondary compensation coils L 1. L 4. Select a concentric, tightly wound circular coil with small size and high transmission efficiency, and use primary and secondary compensation coils. L 1. L The physical parameters of 4 are the same. Among them, the primary and secondary compensation coils... L 1. L The number of turns of 4 and the distance between the center point of the compensation coil (first compensation coil and second compensation coil) and the center point of the transmission coil (transmitting coil and receiving coil) ( Figure 3 H s The result is obtained through iterative genetic algorithm. Specifically, it includes the following steps: First, the preset number of turns and placement spacing (preset axial distance) of the transmission coils (i.e., transmitting and receiving coils) are designed, where the transmission coil is a coaxial, tightly wound circular coil. Under the preset number of turns and preset axial distance, the inductance values ​​of the transmitting and receiving coils are obtained using the following formula, and the self-inductance and mutual inductance of the coils are verified through simulation. For example... Figure 9 The self-inductance of the multi-turn coil shown can be considered as the sum of the self-inductance of each internal circular coil and the mutual inductance between any two internal coils, that is:

[0029] In the formula, L i For the first i Self-inductance of coil; M ij For the first i Turns of coil and the first j Mutual inductance between coils.

[0030] Among them, the i self-inductance of coil L i for:

[0031] In the formula, α i For the first i The radius from the cylindrical conductor in the coil (i.e., the conductor in the coil is cylindrical) to the central axis. r It is the diameter of a cylindrical conductor (i.e., the radius of the conductor). The permeability of free space, For the first A current line element on a coil and The included angle of the axis, For the first A current line element on a coil and The included angle of the axis.

[0032] Among them, the i Turns of coil and the first j Mutual inductance between coils:

[0033] In the formula, a i For the first i The radius of the cylindrical wire in the coil from the central axis. b j For the first j The radius of the cylindrical wire in the coil from the central axis. μ 0 is the permeability of free space. φ 1 is the first i A current line element on a coil and The included angle of the axis, For the first i A current line element on a coil and The included angle of the axis.

[0034] The inductance parameters of the designed coaxial tightly wound circular transmission coil, obtained from the above simulation, are as follows: 25 turns, 2.45mm wire diameter, 70mm inner diameter, and 240mm outer diameter. L 2= L 3 = 91.6 μ H (Micro-Hen), L 2 and L The preset axial distance for 3 is 100mm, that is d 1= d 2 = 100mm. Each number of turns and placement distance corresponds to a specific current parameter. Because the mutual inductance between the coils differs with each number of turns and placement distance, the current in the circuit varies, resulting in a different magnetic field. Therefore, the number of turns and placement spacing of the transmission coil are not limited to these values ​​and can be adaptively adjusted to accommodate changes in the circuit or environment.

[0035] Secondly, based on the magnetic field distribution analysis of the compensation coils (first compensation coil and second compensation coil, also known as primary side compensation coil) L 1 and secondary compensation coil L 4) Analyze the surrounding spatial magnetic flux patterns to determine the optimal placement of the compensation coils for achieving magnetic field shielding. Specifically, the relationship between the compensation coils and the surrounding spatial magnetic flux patterns satisfies the following: the first compensation coil is arranged parallel to the receiving coil above it, and the second compensation coil is arranged parallel to the transmitting coil above it. That is, the magnetic flux patterns satisfy the following: if the magnetic field generated by the transmitting coil at the shielding point is defined as positive, this placement ensures that the magnetic field generated by the compensation coils near the shielding point is negative, thus achieving magnetic field cancellation at the shielding point and achieving a shielding effect.

[0036] Then, a genetic algorithm is used to iterate the number of turns of the compensation coil and the distance between the center point of the compensation coil and the center point of the transmission coil. Under the objective function of minimizing the shielding electromagnetic intensity and the constraints of the number of coil turns and the distance between the transmission and shielding coils, the optimal number of turns of the compensation coil and the distance between the center point of the compensation coil and the center point of the transmission coil are obtained. The specific steps include: The following design variables were determined in the WPT (Wireless Power Transfer) shielded coil optimization model based on a genetic algorithm: number of turns control parameters. x 1: Integer variable, value range [1, 10], corresponding to the actual number of turns of the shielding coil. ; Distance control parameters x 2: Integer variable, value range [1, 15], corresponding to the actual installation distance. The range of values ​​for the turns control parameter and the distance control parameter is not limited to this; they can be adjusted adaptively according to changes in the application circuit, etc.

[0037] Determine the objective function and constraints: Objective function: Minimize the magnetic field strength value (unit: Gauss) of the point probe obtained by the joint simulation of COMSOL (multiphysics simulation software) and MATLAB, and the distance of the point probe from the shielding coil is 500mm.

[0038] Constraints: 1) Variable boundary constraints: , ,in (Half the number of turns, to avoid odd numbers of turns changing the center of the magnetic field). (Constrained at the point of optimal shielding efficiency).

[0039] 2) Integer constraint: Both design variables must be integers; 3) Turns constraint: The number of turns n of the first compensation coil and the second compensation coil is within a preset range, subject to boundary constraints. To ensure the actual number of turns n The value range of is [2, 20]; 4) Distance constraints: determined by the upper bound of the variable. Ensure actual distance ; That is, the objective function and constraints satisfy:

[0040] in: For integer decision vectors, B probe This represents the magnetic field strength and the actual number of turns. n The constrained range of values ​​is [2, 20], and the actual distance is... d c The value range is [300, 440] mm. However, it is not limited to this. The value ranges of the above boundary constraints, integer constraints, number of turns, and actual distance are also considered. d c The range of values ​​can be adjusted adaptively according to the application scenario, etc.

[0041] Finally, based on the calculated inductance values ​​of the transmitting and receiving coils, and the determined objective function and constraints, a genetic algorithm is used for iterative optimization to obtain the number of turns of the compensation coil and the distance between the center point of the compensation coil and the center point of the transmitting coil. Each iteration proceeds as follows: the self-inductance and mutual inductance of the coils are calculated based on the variable parameters (using the methods described above), and then the current value is solved using a circuit model. Subsequently, this current value is used as the excitation condition in the COMSOL simulation model to simulate the corresponding spatial magnetic field distribution. Figure 10 In this context, the formula for calculating circuit current is as follows:

[0042] In the formula, , , , These are the currents flowing through the first compensation coil, the transmitting coil, the receiving coil, and the second compensation coil, respectively. The circuit input voltage. R L For load resistance, ω The resonant angular frequency, M For the mutual inductance between the transmitting coil and the receiving coil, L 1 and L 4 represents the self-inductance of the first compensation coil and the second compensation coil, respectively. C 4 is a parallel compensation inductor on the receiving side. Among them, L 1 and L 4 represents the self-inductance of the first compensation coil and the second compensation coil, which can also be calculated using the above self-inductance formula.

[0043] The genetic algorithm described above should have at least 50 iterations, a population size of 30-50, a crossover probability of 0.6-0.8, and a mutation probability of 0.01-0.05. However, these parameters are not limited to and can be adjusted according to different circuit environments.

[0044] The genetic algorithm described above shows that, in the 28th generation, the compensation coil has 8 turns, and the distance between the transmission coil and the compensation coil is... The shielded magnetic field is approximately In addition, it can achieve excellent shielding effect, and in The shielding effect is optimal at this location, with a peak shielding efficiency reaching [value missing]. The average shielding efficiency can reach In the experiment, the sample was taken as shown in Figure 6(a).

[0045] Finally, based on the known parameters of the transmission coil L 2. L 3. And the shielding coil obtained by the genetic algorithm. L 1. L 4. Perform resonance calculations for each loop of the bilateral LCC to finally obtain the compensation capacitor under resonance conditions. C 1. C 2. C 3. C 4 parameters. Among them, the distance between the compensation coil and the transmission coil. d cWithin a suitable range, its physical layout affects the system's transmission power and efficiency, as well as the shielding effect at shielding points, by influencing the system's coupling coefficient. By adjusting the system's circuit parameters, series and parallel resonance of the primary and secondary circuits can be achieved, such as... Figure 1 As shown, the resonant capacitor C 1. C 2. C 3. C 4 with resonant inductor L 1. L 2. L 3. L 4 (transmitting coil) L 2. Receiving coil L 3. First and second compensation coils L 1. L The relationship between the inductance of 4 and the inductance can be obtained from the following formula.

[0046]

[0047] In the above steps, the compensation coil L 1. L 4. The inductance function is transformed from being solely performed by a traditional bilateral LCC to having coupled mutual inductance characteristics. This inductor enhances the magnetic field of the transmission coil near the source and acts as a shielding coil to reduce electromagnetic intensity at a distance. Furthermore, the inductance in the formula can be obtained using the aforementioned formula when the number of turns and the known radius of the coil are known. Leakage magnetic fields are effectively suppressed without adding an additional shielding coil. By adjusting the spatial relative position, winding direction, and number of turns of the first and second compensation coils, a controllable cancellation effect in the magnetic field distribution is achieved, simultaneously realizing high energy transfer efficiency and spatial compactness.

[0048] For example, Figure 4 The optimization results are plotted, with the horizontal axis representing the number of iterations (Generation) and the vertical axis BM representing the magnetic flux density at a distance of 500 mm from the center of the coil. The Optimal Point in the graph represents the optimal point. The evaluation objective was normalized by minimization standardization to facilitate understanding the meaning of each point in the graph. In fact, Figure 5 Each point in the diagram represents a separate iteration, illustrating the impact of different turns and positions of the shielding coil on the WPT system. To obtain optimal coil parameters and facilitate engineering applications, a resolution of 1 turn and 1 mm was chosen for the number of turns and position, respectively. Optimal coil parameters were obtained by comparing the transmission efficiency and leakage magnetic shielding performance of the WPT system.

[0049] Figure 5A bilateral LCC-compensated wireless power transfer system was simulated in MATLAB software with predefined parameters. Maxwell simulation using the set parameters showed that the magnetic field was significantly reduced at the target plane (500 mm from the coil center): the peak shielding efficiency along the coil's central axis was 77.84%, and the average shielding efficiency across the entire plane exceeded 49.14%. Contour lines visually confirmed the significant reduction in field strength compared to the unshielded baseline.

[0050] Figure 6a This chart shows a comparison of the magnetic fields of shielded and unshielded coils (B0 unshielded coil, B...). shield (with shielded coil), the horizontal axis represents distance. Figure 6b This is a diagram showing the shielding effect (the deviation after shielding is removed). Where B... shield The magnetic field strength of the shielded coil was enhanced up to 50 mm, but decreased sharply after 50 mm. This demonstrates that active shielding not only enhances the original transmitted magnetic field but also significantly reduces the shielded magnetic field outside the transmission point. Therefore, compared to an unshielded coil, the shielded coil exhibits increased magnetic leakage at certain locations, but all remain within the target safe zone. Magnetic leakage is significantly improved at a distance of 400 to 450 mm from the coil center.

[0051] Furthermore, through experimental verification, Figure 7a This is a waveform diagram of the voltage and input power of the shielded coil used in the system, with a resistive load of... (Ohms), indicating that the system is in a resonant state. For a wireless power transfer system, the DC power input voltage... U p 4.99V, input current I p 0.156A (Amperes); RMS AC output voltage U o The voltage is 4.23V, and the load is... Transmission efficiency η for (Percentage), which is basically consistent with the theoretical simulation results. Figure 7b This is a waveform diagram of the voltage and input power of the system without using the shielded coil, under a resistive load. This indicates that the system is in a resonant state. For wireless power transmission systems, the DC power input voltage... for Input current for AC output voltage RMS value for The load is The transmission efficiency η is As mentioned above, the magnetic enhancement effect of the shielding coil near the transmission coil has a slight effect on efficiency. In reality, small errors introduced by the experimental equipment lead to slight differences between the transmission performance test results and the theoretical simulation results. Figure 8a and Figure 8c The spectral noise floor diagrams are shown for the unshielded coil and the shielded coil. Figure 8b and Figure 8d The middle section shows the experimental results of the magnetic field spectrum before and after installing the shielded coil. The noise floor amplitude values ​​for the unshielded and shielded coils are respectively... (decibel microvolts) and The electromagnetic field strength of the unshielded coil system is The electromagnetic field strength of the shielded coil is The shielding coil reduces the leakage magnetic field electromotive force. The shielding efficiency at the same point as the simulation reached The similarity is still strong enough to prove the correctness of the theoretical analysis within the allowable error range.

[0052] By optimizing the coil design of the compensating inductor, electromagnetic shielding is achieved without changing the circuit structure or introducing additional shielding coils. Magnetic integration technology is used to reduce the coil size while maintaining power transmission efficiency. Experiments show that the proposed design achieves a transmission efficiency of 89.79% at 85 kHz, with a leakage magnetic field strength reduced by more than 50% at 600 mm from the coil center. The shielding efficiency in critical areas reaches 60.95%, and the magnetic field strength meets international safety standards (<27 μT). This provides an efficient and economical solution for electromagnetic compatibility optimization of WPT systems.

[0053] like Figure 1As shown in the figure, this embodiment of the invention also introduces a parallel shielded coil structure, which includes a transmitting coil, a receiving coil, a first compensation coil, a second compensation coil, and a resonant compensation circuit. The resonant compensation circuit is connected to the transmitting coil and the receiving coil, respectively. Both the transmitting coil and the receiving coil are coaxial, tightly wound circular coils with a preset number of turns. The first compensation coil and the second compensation coil are parallel, concentrically wound circular coils. The axial distance between the transmitting coil and the receiving coil is equal to the axial distance between the first compensation coil and the second compensation coil, and both are preset axial distances. The first compensation coil is arranged parallel above the receiving coil, and the second compensation coil is arranged parallel above the transmitting coil. The number of turns of the first and second compensation coils, the distances between the transmitting coil and the first compensation coil, the receiving coil and the second compensation coil, and the compensation capacitor parameters in the resonant compensation circuit are all optimized using the parallel shielded coil structure optimization method described above. This effectively suppresses leakage magnetic fields without adding an extra shielding coil. By adjusting the arrangement of the first and second compensation coils, a controllable cancellation effect is achieved in their magnetic field distribution, while simultaneously achieving high energy transmission efficiency and spatial compactness.

[0054] In this embodiment of the invention, the axial and radial distance offsets of the first compensation coil, the second compensation coil, the transmitting coil, and the receiving coil satisfy the following: Axial distance offset range: 50mm < Δ d <150mm, radial offset distance Δ r ≤40mm.

[0055] In this embodiment of the invention, the first compensation coil and the second compensation coil are the primary side compensation coil and the secondary side compensation coil, respectively, and both the primary side compensation coil and the secondary side compensation coil are concentric closely wound circular coils of the same size.

[0056] In this embodiment of the invention, the same layer of coils in the concentric closely wound circular coil has a multi-turn structure, and the winding method of each wire in the same layer is the same.

[0057] In this embodiment of the invention, the wire diameters of the transmitting coil and the receiving coil are the same; the resonant compensation circuit includes a resonant capacitor and a compensation inductor connected in series.

[0058] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for optimizing the structure of a parallel shielded coil, characterized in that, The method is based on a parallel shielded coil structure, which includes a transmitting coil, a receiving coil, a first compensation coil, a second compensation coil, and a resonant compensation circuit. The resonant compensation circuit is connected to the transmitting coil and the receiving coil, respectively. Both the transmitting coil and the receiving coil are coaxial tightly wound circular coils, and the first compensation coil and the second compensation coil are concentric tightly wound circular coils placed in parallel. The method for optimizing the parallel shielded coil structure includes the following steps: Determine the number of turns of the transmitting coil and the receiving coil, the axial distance between the transmitting coil and the receiving coil, the axial distance between the first compensation coil and the second compensation coil, and the arrangement of the transmitting coil, the receiving coil, the first compensation coil, and the second compensation coil; Optimize the number of turns of the first compensation coil and the second compensation coil, as well as the distance between the transmitting coil and the first compensation coil, and between the receiving coil and the second compensation coil; Based on the optimized number of turns of the first and second compensation coils, as well as the distances between the transmitting coil and the first compensation coil, and between the receiving coil and the second compensation coil, the compensation capacitor parameters in the resonant compensation circuit are obtained.

2. The method for optimizing a parallel shielded coil structure according to claim 1, characterized in that, Determining the number of turns of the transmitting coil and the receiving coil, the axial distance between the transmitting coil and the receiving coil, the axial distance between the first compensation coil and the second compensation coil, and the arrangement of the transmitting coil, the receiving coil, the first compensation coil, and the second compensation coil includes... The number of turns in the transmitting and receiving coils is preset; The axial distance between the transmitting coil and the receiving coil is equal to the axial distance between the first compensation coil and the second compensation coil, and a preset axial distance is used; The arrangement of the transmitting coil, receiving coil, first compensation coil, and second compensation coil satisfies the following conditions: The first compensation coil is arranged parallel above the receiving coil, and the second compensation coil is arranged parallel above the transmitting coil.

3. The method for optimizing the parallel shielded coil structure according to claim 2, characterized in that, This includes optimizing the number of turns of the first and second compensation coils, as well as the distances between the transmitting coil and the first compensation coil, and between the receiving coil and the second compensation coil. Determine design variables, including turns control parameters. x 1 and distance control parameters x 2; Define the objective function: In the formula, For integer decision vectors, The magnetic field strength; Define the following constraints: Variable boundary constraints: control parameters x 1 and distance control parameters x 2. Each within the preset range; Integer constraint: Both design variables must be integers; Turns constraint: Number of turns of the first compensation coil and the second compensation coil n Within the preset number of turns; Distance constraint: The distance d between the center point of the transmitting coil and the center point of the first compensation coil, and between the center point of the receiving coil and the center point of the second compensation coil. c Within the preset distance range; Calculate the inductance values ​​of the transmitting and receiving coils; Based on the calculated inductance values ​​of the transmitting and receiving coils, as well as the determined objective function and constraints, the number of turns of the compensation coil and the distance between the center point of the compensation coil and the center point of the transmission coil are obtained through optimization iteration using a genetic algorithm.

4. The method for optimizing the parallel shielded coil structure according to claim 3, characterized in that, The inductance values ​​of the transmitting and receiving coils are calculated to satisfy: In the formula, n is the preset number of turns of the transmitting coil and the receiving coil. L i For the first i Self-inductance of coil; M ij For the first i Turns of coil and the first j Mutual inductance between coils; Among them, the i self-inductance of coil L i for: In the formula, α i For the first i The radius of the cylindrical wire in the coil from the central axis. r It refers to the diameter of the cylindrical conductor. The permeability of free space, For the first A current line element on a coil and The included angle of the axis, For the first A current line element on a coil and The included angle of the axis; Among them, the i Turns of coil and the first j Mutual inductance between coils: In the formula, a i For the first i The radius of the cylindrical wire in the coil from the central axis. b j For the first j The radius of the cylindrical wire in the coil from the central axis. μ 0 is the permeability of free space. φ 1 is the first i A current line element on a coil and The included angle of the axis, For the first j A current line element on a coil and The included angle of the axis.

5. The method for optimizing the parallel shielded coil structure according to claim 4, characterized in that, Based on the calculated self-inductance and mutual inductance of the transmitting and receiving coils, as well as the determined objective function and constraints, the number of turns of the compensation coil and the distance between the center point of the compensation coil and the center point of the transmitting coil are obtained through optimization iteration using a genetic algorithm. This includes joint simulation using COMSOL and MATLAB.

6. The method for optimizing the parallel shielded coil structure according to claim 5, characterized in that, Based on the optimized number of turns of the first and second compensation coils, and the distances between the transmitting coil and the first compensation coil, and between the receiving coil and the second compensation coil, the compensation capacitor parameters in the resonant compensation circuit are obtained, including: In the formula, C 1. C 2. C 3. C 4 represents the resonant capacitor in the resonant compensation circuit. L 1. L 2. L 3. L 4 are the transmitting coils L 2. Receiving coil L 3. First and second compensation coils L 1. L 4 inductance, Let be the system angular frequency.

7. A parallel shielded coil structure, characterized in that, It includes a transmitting coil, a receiving coil, a first compensation coil, a second compensation coil, and a resonant compensation circuit. The resonant compensation circuit is connected to both the transmitting coil and the receiving coil. Both the transmitting and receiving coils are coaxial, tightly wound circular coils, and the number of turns is preset. The first compensation coil and the second compensation coil are concentric closely wound circular coils placed in parallel. The axial distance between the transmitting coil and the receiving coil is equal to the axial distance between the first compensation coil and the second compensation coil, and both are preset axial distances; The first compensation coil is arranged parallel above the receiving coil, and the second compensation coil is arranged parallel above the transmitting coil. The number of turns of the first compensation coil and the second compensation coil, the distance between the transmitting coil and the first compensation coil, the distance between the receiving coil and the second compensation coil, and the parameters of the compensation capacitor in the resonant compensation circuit are all optimized using the parallel shielded coil structure optimization method described in any one of claims 1-6.

8. The parallel shielded coil structure according to claim 7, characterized in that, The axial and radial distance offsets of the first and second compensation coils, as well as the transmitting and receiving coils, satisfy the following: Axial distance Δ d Offset range: 50mm < Δ d <150mm, radial offset distance Δ r ≤40mm.

9. The parallel shielded coil structure according to claim 8, characterized in that, The first compensation coil and the second compensation coil are the primary side compensation coil and the secondary side compensation coil, respectively. Both the primary side compensation coil and the secondary side compensation coil are concentric closely wound circular coils of the same size.

10. The parallel shielded coil structure according to claim 9, characterized in that, In a concentric closely wound circular coil, the coil in the same layer has a multi-turn structure, and the winding method of each wire in the same layer is the same.

11. The parallel shielded coil structure according to claim 10, characterized in that, The conductors used for the transmitting and receiving coils have the same wire diameter; the resonant compensation circuit includes a resonant capacitor and a compensation inductor connected in series.

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