An IPT system with a highly integrated magnetic coupler and an IPT system integration method

Abstract

The present invention relates to wireless power transfer technology, and particularly to an IPT system with a highly integrated magnetic coupler and an IPT system integration method; in this method, three integrated coils and the design process of the integrated coils are proposed; among them, the integrated reverse transmitting coil is to achieve better anti-offset characteristics and high efficiency; the secondary-side integrated inductance coil aims to achieve zero-voltage switching condition configuration so that the output power and anti-offset characteristics are not affected; the primary-side integrated inductance coil aims to decouple from other coils and further improve the compactness without affecting the characteristics.

Description

Technical Field

[0001] The present invention relates to wireless power transfer technology, and particularly to an IPT system with a highly integrated magnetic coupler and an IPT system integration method. Background Art

[0002] With the rapid growth of population and economy, the problems of traditional energy shortage and environmental pollution have become increasingly prominent. The magnetic coupling wireless power transfer (IPT) system has been proven to be an excellent solution, with characteristics such as avoiding bulky cables, the availability of current isolation, more flexible operation, weather resistance, low maintenance, and higher safety. It has been widely used in biomedical implants, consumer electronics, and electric vehicles.

[0003] The IPT system gets rid of the bondage of physical media, giving the primary coil and the secondary coil considerable flexibility. However, mechanical independence makes it difficult to achieve perfect alignment. The offset will cause a change in the mutual inductance between the coupled coils, resulting in a decrease in the transmitted power, instability, and more power loss. Therefore, the anti-offset performance is an important performance index of the IPT system.

[0004] Based on previous studies, the improvement of the anti-offset performance of the IPT system is mainly studied from the following three aspects. The first is to reduce the change in the mutual inductance between the transmitting coil and the receiving coil by changing the shape of the magnetic coupling mechanism. The focus of these methods is to achieve stable single-coupling power transfer through the design of coil shape, magnetic core structure, coil polarity, and winding method. The second is to adopt a control scheme to match the mutual inductance under offset. The additional control module increases the complexity of the IPT system, and the customization requirements of different systems weaken the universality. The third is to design the compensation topology and parameters to achieve stable transmitted power under the change of mutual inductance. In the parameter configuration of these methods, the constant output current characteristic is changed. Since the coupling channel essentially remains unchanged, its anti-offset effect is limited.

[0005] The LCC compensation topology has been widely adopted because it provides power proportional to the coupling coefficient and realizes a constant output current working mode for battery charging applications. However, it requires more inductive components, which increases the complexity of the system. At the same time, the external compensation inductor has the following problems:

[0006] 1) It requires additional space, making the system bulky;

[0007] 2) When a large current passes through the compensation inductor, the heat generation problem is difficult to solve;

[0008] 3) Using more magnetic cores increases the cost;

[0009] 4) It is not conducive to the modularization of wireless power transfer devices. Summary of the Invention

[0010] To solve the above problems, the present invention proposes an IPT system with a highly integrated magnetic coupler and an IPT system integration method, in which three integrated coils are proposed. Among them, the integrated reverse transmitting coil is for achieving better anti-offset characteristics and high efficiency; the secondary-side integrated inductance coil aims to achieve zero voltage switching (ZVS) condition configuration so that the output power and anti-offset characteristics are not affected; the primary-side integrated inductance coil aims to achieve decoupling from other coils and further improve the compactness without affecting the characteristics.

[0011] In a first aspect, the present invention provides an IPT system with a highly integrated magnetic coupler. The IPT system includes an inverter, a highly integrated magnetic coupler, a rectifier, and a load; the highly integrated magnetic coupler includes a transmitting end and a receiving end; the transmitting end includes a transmitting coil L p1 , an integrated reverse coil L p2 , a primary-side integrated inductance coil L pf , a first magnetic core plate, and a first shielding plate; the first magnetic core plate is placed on the first shielding plate, the transmitting coil L p1 is arranged on the first magnetic core plate, the integrated reverse coil L p2 is arranged inside the transmitting coil L p1 , and the integrated reverse coil L p2 and the transmitting coil L p1 are centrosymmetric structures;

[0012] The receiving end includes a receiving coil L s , a secondary-side integrated inductance coil L sf , a second magnetic core plate, and a second shielding plate; the second magnetic core plate is placed on the second shielding plate, the receiving coil L s is arranged on the second magnetic core plate, and the secondary-side integrated inductance coil L sf is arranged inside the receiving coil L s .

[0013] Further, the primary-side integrated inductance coil L pf is a double-stage coil, and 4 double-stage coils are arranged between the transmitting coil L p1 and the integrated reverse coil L p2 ; 1 double-stage coil has 2 current loops, and 4 double-stage coils have a total of 8 current loops, and the polarities between every two current loops are opposite.

[0014] In a second aspect, based on the highly integrated magnetic coupler structure proposed in the first aspect, the present invention proposes an IPT system integration method with a highly integrated magnetic coupler, including the following steps:

[0015] S1. Construct an initial magnetic coupler according to the operating frequency, input voltage, and output power of the IPT system; the initial magnetic coupler includes a transmitting end and a receiving end; the transmitting end is provided with a transmitting coil L p1 , and the receiving end is provided with a receiving coil L s ; the number of turns and dimensions of the transmitting coil L p1 and the receiving coil L s are preset, and the mutual inductance between the transmitting coil L p1 and the receiving coil L s is defined as M p1s ;

[0016] S2. Set an integrated reverse coil L p2 at the transmitting end of the initial magnetic coupler, and determine the number of turns of the integrated reverse coil L p2 according to the output power of the IPT system; define the mutual inductance difference between the transmitting coil L p1 , the integrated reverse coil L p2 and the receiving coil L s as the first mutual inductance M ps ;

[0017] S3. Perform finite element analysis through MAXWELL, traverse the dimensions of the integrated reverse coil L p2 , and determine whether the first mutual inductance M ps is stable within a 40% alignment deviation. If so, proceed to step S4; otherwise, continue traversing;

[0018] S4. Set a secondary-side integrated inductance coil L sf at the receiving end of the initial magnetic coupler, and define the mutual inductance difference between the transmitting coil L p1 , the integrated reverse coil L p2 and the secondary-side integrated inductance coil L sf as the second mutual inductance M psf ;

[0019] S5. Define the ratio of the second mutual inductance M psf to the first mutual inductance M ps as ε; traverse the number of turns and dimensions of the secondary-side integrated inductance coil L sf , and determine whether it satisfies ε ≤ ξ, where ξ is the desired inductive index; if so, proceed to step S5; otherwise, continue traversing;

[0020] S6. Set a primary-side integrated inductance coil L pf at the transmitting end of the initial magnetic coupler, and traverse the number of turns and dimensions of the primary-side integrated inductance coil L pf according to the output power at the transmitting end of the initial magnetic coupler to obtain the finally optimized highly integrated magnetic coupler.

[0021] Further, the circuit topology of the IPT system with a highly integrated magnetic coupler includes a primary-side LCC topology compensation network and a secondary-side LCC topology compensation network; the primary-side LCC topology compensation network includes a transmitting coil L p1 , an integrated reverse coil L p2 , a primary-side integrated inductance coil L pf , a capacitor C p and a capacitor C pf ; the secondary-side LCC topology compensation network includes a receiving coil L s , a secondary-side integrated inductance coil L sf , a capacitor C s and a capacitor C sf ;

[0022] The primary-side integrated inductance coil L pf , the capacitor C p , the transmitting coil L p1 and the integrated reverse coil L p2 are connected in series in sequence, and the circuit composed of the capacitor C p , the transmitting coil L p1 and the integrated reverse coil L p2 is connected in parallel with the capacitor C pf ; among them, the transmitting coil L p1 and the integrated reverse coil L p2 are connected in reverse series; the secondary-side integrated inductance coil L sf , the capacitor C s and the receiving coil L s are connected in series in sequence, and the circuit composed of the capacitor C s and the receiving coil L s is connected in parallel with the capacitor C sf ;

[0023] The mutual inductance difference between the transmitting coil L p1 , the integrated reverse coil L p2 and the receiving coil L s is the first mutual inductance M ps ; the mutual inductance difference between the transmitting coil L p1 , the integrated reverse coil L p2 and the secondary-side integrated inductance coil L sf is the second mutual inductance M psf ; the mutual inductance between the transmitting coil L p1 and the integrated reverse coil L p2 is the first in-phase internal mutual inductance M p12 ; the mutual inductance between the secondary-side integrated inductance coil L sf and the receiving coil L s is the second in-phase internal mutual inductance M ssf .

[0024] Further, the second same-side internal mutual inductance M ssf is equivalent to a T-network and integrated with the secondary-side LCC topology compensation network, and is decoupled through the following formula:

[0025]

[0026] L sfe = L sf + M ssf

[0027]

[0028] The decoupling formula of the first same-side internal mutual inductance M p12 is expressed as:

[0029]

[0030] where L se represents the equivalent value of the receiving coil L s and the series compensation capacitor C s ; ω represents the system resonance angular frequency; L sfe represents the superimposed equivalent of the secondary-side integrated inductor coil L sf and the second same-side internal mutual inductance M ssf ; C sfe represents the superimposed equivalent of the secondary-side parallel compensation capacitor C sf and the second same-side internal mutual inductance M ssf ; L p represents the superimposed equivalent of the transmitting coil L p1 , the integrated reverse coil L p2 and the primary-side series compensation capacitor C p .

[0031] Further, the equivalent circuit of the circuit topology package of the IPT system is obtained by using the fundamental harmonic approximation method, and through Kirchhoff's law, we get:

[0032]

[0033] The resonance relationship is expressed as:

[0034] ω 2 L pf C pf = ω 2 L p C pf = ω 2 L se C sfe = ω 2 L sfe C sfe = 1

[0035] Among them, represents the inverter output current, represents the current passing through the transmitting coil, represents the current passing through the receiving coil, represents the output current, represents the inverter output voltage, R e represents the equivalent load of the rectifier and the load together.

[0036] Furthermore, by simplifying the Kirchhoff's law formula through the resonance relation, we get:

[0037]

[0038] Derived from the simplified formula:

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045] Among them, represents the inverter output voltage, represents the modulus of the inverter output voltage, represents the modulus of the transmitting coil current, represents the modulus of the output current, P out represents the output power, K1 represents the coefficient defined by the system parameters, Z in represents the total equivalent impedance of the system from the input end.

[0046] Advantages of the present invention:

[0047] In the highly integrated magnetic coupler proposed by the present invention, the three integrated coils (integrated reverse coil, primary side integrated inductance coil, secondary side integrated inductance coil) share the magnetic core and the in-layer space with the main coils (transmitting coil, receiving coil), greatly improving the compactness of the coupler.

[0048] In the IPT system integration method with a highly integrated magnetic coupler proposed by the present invention, first, the coupling change characteristics are changed by setting an integrated reverse coil at the transmitting end to obtain an equivalent mutual inductance difference to replace the original single coupling. Secondly, an integrated inductor coil is set on the secondary side at the receiving end, and a design variable is introduced into the integrated inductor coil on the secondary side to obtain the required inverter output phase angle to ensure the ZVS condition. Finally, an integrated inductor coil is set on the primary side at the transmitting end, so that the integrated inductor coil on the primary side can be decoupled from other coils in the offset state and the alignment state, making the full magnetic integration more feasible. Description of the Drawings

[0049] Figure 1 Schematic three-dimensional structure diagram of the highly integrated magnetic coupler of the present invention;

[0050] Figure 2 Circuit topology diagram of the IPT system based on the highly integrated magnetic coupler of the present invention;

[0051] Figure 3 Equivalent circuit diagram of the same-side internal mutual inductance decoupling of the secondary-side LCC topology compensation network of the present invention;

[0052] Figure 4 Equivalent circuit diagram of the IPT system based on the highly integrated magnetic coupler of the present invention;

[0053] Figure 5 Design flow chart of the highly integrated magnetic coupler of the present invention;

[0054] Figure 6 Schematic plan structure diagram of the highly integrated magnetic coupler of the present invention;

[0055] Figure 7 Mutual inductance M of the present invention p1s Change curve from full alignment to 180 mm (40%) offset;

[0056] Figure 8 Coil structure definition diagram of the highly integrated magnetic coupler of the present invention;

[0057] Figure 9 Schematic diagram of magnetic flux density analysis of the present invention;

[0058] Figure 10 Schematic diagram of angle definition of the present invention;

[0059] Figure 11 Equivalent mutual inductance difference M under offset of the present invention ps Change curve;

[0060] Figure 12 Subject to the number of turns n of the present invention w5The parameters of the secondary - side inductance coil affected by the distance and length l5;

[0061] Figure 13 For the M during the offset of the present invention psf , M ps and the variation diagrams of ε;

[0062] Figure 14 The design diagram of the primary - side integrated inductance coil of the present invention;

[0063] Figure 15 The system output power and efficiency under the offset condition of the present invention;

[0064] Wherein, 1 - receiving coil, 2 - transmitting coil, 3 - second shielding plate, 4 - primary - side integrated inductance coil, 5 - integrated reverse coil, 6 - secondary - side integrated inductance coil, 7 - second magnetic core plate, 8 - first magnetic core plate, 9 - first shielding plate. Specific embodiments

[0065] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0066] The present invention proposes an IPT system with a highly integrated magnetic coupler and an IPT system integration method. The IPT system with a highly integrated magnetic coupler includes an inverter, a highly integrated magnetic coupler, a rectifier, and a load.

[0067] In one embodiment, the structure of the highly integrated magnetic coupler proposed by the present invention is as Figure 1 shown, including a transmitting end and a receiving end; the transmitting end includes a transmitting coil 2, an integrated reverse coil 5, a primary - side integrated inductance coil 4, a first magnetic core plate 8, and a first shielding plate 9; the first magnetic core plate 8 is placed on the first shielding plate 9, the transmitting coil 2 is arranged on the first magnetic core plate 8, the integrated reverse coil 5 is arranged inside the transmitting coil 2, and the integrated reverse coil 5 and the transmitting coil 2 are centrosymmetric structures;

[0068] The receiving end includes a receiving coil 1, a secondary - side integrated inductance coil 6, a second magnetic core plate 7, and a second shielding plate 3; the second magnetic core plate 7 is placed on the second shielding plate 3, the receiving coil 1 is arranged on the second magnetic core plate 7, and the secondary - side integrated inductance coil 6 is arranged inside the receiving coil 1.

[0069] Among them, the first magnetic core plate and the second magnetic core plate are both used to enhance coupling, and the first shielding plate and the second shielding plate are both for reducing electromagnetic leakage. The highly integrated magnetic coupler proposed by the present invention aims to improve the anti-offset performance in the x-direction and y-direction and achieve the complete integration of the LCC-compensated IPT system.

[0070] In one embodiment, the circuit topology of the IPT system based on the highly integrated magnetic coupler is as Figure 2 shown, where U dc is the voltage of the DC power supply. The voltage-fed inverter is composed of MOSFETs S1 - S4, C o is the filter capacitor, R L is the equivalent load, the rectifier is composed of diodes D1 - D4, I in is the inverter current vector, I p is the transmitting coil current vector, I s is the receiving coil current vector, I out is the output current vector; the operating frequency of the system is f, and the angular frequency is ω = 2πf.

[0071] As shown by Figure 2 , the circuit topology of the highly integrated magnetic coupler includes a primary-side LCC topology compensation network and a secondary-side LCC topology compensation network; the primary-side LCC topology compensation network includes a transmitting coil L p1 , an integrated reverse coil L p2 , a primary-side integrated inductor coil L pf , a capacitor C p and a capacitor C pf ; the secondary-side LCC topology compensation network includes a receiving coil L s , a secondary-side integrated inductor coil L sf , a capacitor C s and a capacitor C sf ;

[0072] The primary-side integrated inductor coil L pf , the capacitor C p , the transmitting coil L p1 and the integrated reverse coil L p2 are connected in series in sequence, and the circuit composed of the capacitor C p , the transmitting coil L p1 and the integrated reverse coil L p2 is connected in parallel with the capacitor C pf ; among them, the transmitting coil L p1 and the integrated reverse coil L p2 are connected in reverse series; the secondary-side integrated inductor coil L sf , the capacitor C s and the receiving coil L s are connected in series in sequence, and the capacitor C s and the receiving coil Ls The composed circuit is in parallel with capacitor C sf ;

[0073] The mutual inductance difference between the transmitting coil L p1 , the integrated reverse coil L p2 and the receiving coil L s is the first mutual inductance M ps ; The mutual inductance difference between the transmitting coil L p1 , the integrated reverse coil L p2 and the secondary side integrated inductance coil L sf is the second mutual inductance M psf ; The mutual inductance between the transmitting coil L p1 and the integrated reverse coil L p2 is the first same-side internal mutual inductance M p12 ; The mutual inductance between the secondary side integrated inductance coil L sf and the receiving coil L s is the second same-side internal mutual inductance M ssf .

[0074] In this embodiment, for the sake of more simplicity and to simplify the calculation process, the first mutual inductance and the second mutual inductance are defined as:

[0075] M ps = M p1s - M p2s (1)

[0076] M psf = M p1sf - M p2sf (2)

[0077] Wherein, M p1s is the mutual inductance between the transmitting coil L p1 and the receiving coil L s , M p2s is the mutual inductance between the integrated reverse coil L p2 and the receiving coil L s , M p1sf is the mutual inductance between the transmitting coil L p1 and the secondary side integrated inductance coil L sf , M p2sf is the mutual inductance between the integrated reverse coil L p2 and the secondary side integrated inductance coil L sf .

[0078] Specifically, the second same-side internal mutual inductance M ssf can be equivalent to a T-shaped network, as Figure 3 shown, M ssf is integrated together as part of the secondary side LCC topology compensation network and decoupled by the following equations (3)-(5):

[0079]

[0080] L sfe = L sf + M ssf (4)

[0081]

[0082] Among them, L se represents the equivalent value of the receiving coil L s and the series compensation capacitor C s ; L sfe represents the superposition equivalent of the secondary-side integrated inductor L sf and the mutual inductance M ssf ; C sfe represents the superposition equivalent of the secondary-side parallel compensation capacitor C sf and the mutual inductance M ssf .

[0083] In addition, the M p12 with the same-side internal mutual inductance can be decoupled by the following formula (6):

[0084]

[0085] Among them, L p represents the superposition equivalent of the primary-side transmitting coil L p1 , the primary-side reverse coil L p2 and the primary-side series compensation capacitor C p .

[0086] In one embodiment, based on the fundamental harmonic approximation (FHA) method, the equivalent circuit of the IPT system's circuit topology is obtained. As Figure 4 shown, the square-wave voltage is approximated as a sinusoidal source U1, and the rectifier and the resistive load together are equivalent to R e = 8R L / π2. The coupling in the circuit is represented by the relevant source. In this embodiment, the theoretical feasibility of the proposed method is mainly analyzed, and the power loss of the components is ignored.

[0087] Based on the equivalent circuit, according to Kirchhoff's law, it is obtained that:

[0088]

[0089] At the same time, the resonance relationship is expressed as:

[0090] ω 2 L pf C pf = ω 2 L p C pf = ω2 L se C sfe = ω 2 L sfe C sfe = 1 (8)

[0091] Among them, represents the inverter output current, represents the current passing through the transmitting coil, represents the current passing through the receiving coil, represents the output current, represents the inverter output voltage, R e represents the equivalent load of the rectifier and the load together.

[0092] Simplify the Kirchhoff's law formula through the resonance relation formula to obtain:

[0093]

[0094] Derive from the simplified formula to obtain:

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101] Among them, represents the inverter output voltage, represents the modulus of the inverter output voltage, represents the modulus of the transmitting coil current, represents the modulus of the output current, P out represents the output power, K1 represents the coefficient defined by the system parameters, Z in represents the total equivalent impedance of the system from the input end.

[0102] According to the derived current-related formulas (10), (11), it can be known that I p and I out are independent of the load, so the system has a constant current output characteristic. From formulas (12), (13), it can be known that K1 is determined by the designed system parameters and will not change under offset conditions. Therefore, the anti-offset performance of the system depends on M ps 2. The mathematical derivation result of Equation (12) is compatible with the single-coupling energy transfer mode, and the essence of power transmission remains unchanged. For a general single-coupling IPT system, improving the anti-offset ability through the design of the coupling mechanism is limited. In contrast, the mutual inductance difference M ps is expected to achieve stable output power under offset conditions. In this paper, a detailed design of the integrated reverse coil is carried out to optimize the stability of M ps .

[0103] Specifically, based on the inverter current calculated according to (14) and the input impedance of the IPT system calculated according to (15), it can be seen that M psf does not affect the output power, but affects the imaginary part of the total input impedance of the system. In this embodiment, the phase angle between the inverter voltage and the inverter current is defined as α, and its positive and negative values represent inductive and capacitive respectively, and the absolute value represents the degree of deviation of the system from the resonance point; the ratio of M psf to M ps is defined as ε, then the tangent value of α is expressed as:

[0104]

[0105] According to (16), the resonance state of the IPT system can be quantified through M psf . Under normal parameter configurations, the resonance state can be restricted through the design of the magnetic coupler. ε can be designed to be a small value to ensure normal output power and ZVS operating state.

[0106] In one embodiment, based on the above theory, an anti-offset parameter optimization method for an IPT system based on a highly integrated magnetic coupler is proposed. First, an initial magnetic coupling mechanism is constructed as the design background, and then an integrated reverse coil is set to determine the variable M ps to improve the offset tolerance; then an integrated inductance coil on the secondary side is set to determine ε for configuring the ZVS condition; finally, an integrated inductance coil on the primary side is set to achieve decoupling. In this embodiment, the structure of the highly integrated magnetic coupler modeled by MAXWELL is as shown in Figure 6 : The parameter definitions describing the size of the highly integrated magnetic coupler are shown in Table 1:

[0107] Table 1 Parameters of the highly integrated magnetic coupler

[0108]

[0109] In one embodiment, a typical example of an IPT system applicable to the 3kW power level is used to illustrate the parameter optimization design method. The specific process is as shown in Figure 5 : including:

[0110] S1. Construct an initial magnetic coupler according to the operating frequency, input voltage, and output power of the IPT system; the initial magnetic coupler includes a transmitting end and a receiving end; the transmitting end is provided with a transmitting coil L p1 , and the receiving end is provided with a receiving coil L s ; the number of turns and dimensions of the transmitting coil L p1 and the receiving coil L s are preset, and the mutual inductance between the transmitting coil L p1 and the receiving coil L s is defined as M p1s ;

[0111] Specifically, the size of the transmitting coil L p1 is 450mm×450mm×5mm, and its number of turns n w1 is 10; the size of the receiving coil L s is 300mm×300mm×5mm, and its number of turns n w4 is 12. The magnetic core plate is a ferrite plate for enhancing the magnetic field, and the shielding plate is an aluminum shielding plate for electromagnetic shielding. The transmission distance d between the transmitting end and the receiving end is 150mm.

[0112] Figure 7 shows the change curve of the mutual inductance M p1s from alignment to 180mm (40%) offset. From the well-aligned situation to the 40% offset situation, the mutual inductance drops by nearly 40%. For an IPT system with a single mutual inductance for power transmission, it is difficult to essentially improve the anti-offset performance through the parameter design of the magnetic coupling mechanism. Therefore, the present invention adds an integrated reverse coil on the primary side to change the coupling of power transmission, thereby improving the anti-offset performance.

[0113] S2. Set an integrated reverse coil L p2 at the transmitting end of the initial magnetic coupler, and determine the number of turns of the integrated reverse coil L p2 according to the output power of the IPT system; define the difference in mutual inductance between the transmitting coil L p1 , the integrated reverse coil L p2 and the receiving coil L s as the first mutual inductance M ps ;

[0114] S3. Perform finite element analysis through MAXWELL, traverse the dimensions of the integrated reverse coil L p2 , and determine whether the first mutual inductance M ps is stable within a 40% alignment deviation. If so, enter step S4; otherwise, continue to traverse;

[0115] The integrated reverse coil is designed to improve the coupling performance between the transmitting coil and the receiving coil. Therefore, it is expected that the coupling characteristics between the integrated reverse coil and the receiving coil are roughly the same as those between the transmitting coil and the receiving coil. In this way, the equivalent mutual inductance obtained by superimposing the two coupling mechanisms can remain sufficiently stable under offset conditions. The transmitting coil L p1 , the integrated reverse coil L p2 and the receiving coil L s The change in the mutual inductance difference M ps determines the anti-offset performance of the IPT system. When the primary coil is fixed, the position, size, and number of turns of the integrated reverse coil play a crucial role. Therefore, to obtain a more stable M ps , the integrated reverse coil needs to be carefully designed.

[0116] Specifically, as Figure 8 shown, the integrated reverse coil is designed inside the transmitting coil, and they are centrosymmetric, as Figure 8 (a) shown. Each side of the coil with multiple turns is equivalent to its central position for analysis. The corresponding parameters are marked in Figure 8 (b), and the four sides of the transmitting coil are l ai (i = 1, 2, 3, 4); the four sides of the integrated reverse coil are l bj (j = 1, 2, 3, 4); the four sides of the receiving coil are l cv (v = 1, 2, 3, 4). The endpoints of the coil are marked for definition. Among them, A1, B1, C1, and D1 are the four endpoints of the transmitting coil; A2, B2, C2, and D2 are the four endpoints of the integrated reverse coil; F, G, H, and J are the four endpoints of the receiving coil. Considering that l c1 and l a1 are parallel, the perpendicular distance from any point on l c1 to l a1 is equal, which is defined as r.

[0117] The magnetic flux density analysis is as Figure 9 shown, and the magnetic field intensity generated by l a1 at point F is:

[0118]

[0119] Among them, I represents the current values of the transmitting coil and the integrated reverse coil, represents the direction vector, l1 represents the length of the side of the transmitting coil, and θ1 is the Figure 9 (a) marked angle.

[0120] Q1 is the distance from F to A (referring to A1, A2). Q2 is the superposition of the lengths of lc2 and Q1. In Figure 9 (a), l c1The average value of the magnetic flux density on is calculated by integration as:

[0121]

[0122] where θ2 is Figure 9 the angle marked in (a).

[0123] l a1 The magnetic flux generated at the receiving coil Ls is:

[0124]

[0125] l a1 and L s The mutual inductance between them is:

[0126]

[0127] Similarly, in order to obtain the mutual inductance between the other side and the receiving coil, the relevant angles are defined in Figure 10 and by the same token, we can get:

[0128]

[0129]

[0130]

[0131]

[0132]

[0133] where μ0 represents the magnetic permeability of vacuum, and the angle information of θ5, θ6, θ9, θ 10 , θ 15 , θ 16 , θ 11 , θ 12 , θ 13 and θ 14 is as shown in Figure 10 .

[0134] Therefore, for qualitative analysis, the mutual inductance M1 between the receiving coil and the transmitting coil, and the mutual inductance M2 between it and the integrated reverse coil can be expressed as

[0135]

[0136] To more intuitively express the characteristics of the equivalent mutual inductance, the corresponding mutual inductances are combined:

[0137]

[0138] Each item includes the mutual inductance generated by the transmitting coil and the integrated reverse coil, and their directions are opposite. In addition, according to (20), (21) and Figure 8 , the following relational expressions can be obtained:

[0139]

[0140] θ2 - θ1 < θ4 - θ3, θ8 - θ7 < θ6 - θ5,

[0141] θ 16 -θ 15 <θ 14 -θ 13 ,θ 10 -θ9 < θ 12 -θ 11

[0142] According to (23) and (24), the integrated reverse coil effectively converts the original single mutual inductance into an equivalent mutual inductance difference, thereby improving the anti-offset performance. In addition, based on the qualitative analysis of the mutual inductance expression under offset comprehensively considered in (20) and (21), two characteristics are revealed, which can further guide the design of the integrated reverse coil. First, the number of turns of the integrated reverse coil has a negative gain effect on the equivalent mutual inductance under offset, and the influence is relatively large. Second, due to the changes in the side length ratio and angle difference in (24), the equivalent side length of the integrated reverse coil has a slight positive gain effect on the equivalent mutual inductance during misalignment. Therefore, the number of turns and size can be used as thickness parameters. Specifically, for the number of turns parameter, the larger the number of turns of the integrated reverse coil, the more stable the equivalent mutual inductance difference, but the more mutual inductance cancellation occurs. For the size parameter, the larger the size of the integrated reverse coil, the more stable the equivalent mutual inductance value, but the more mutual inductance is eliminated. For different numbers of turns, there is an optimal size value corresponding to the best anti-offset performance. The finally optimized equivalent mutual inductance value varies with the selection of the number of turns. In the existing research on reverse coils, after designing the number of turns, a corresponding unique optimal size value is obtained. This requires a compromise between the best performance and power transfer ability. However, if the number of layers of the integrated reverse coil is increased, the equivalent size can be increased at a fixed number of turns, improving the power transfer ability while achieving performance improvement.

[0143] In the 3kW power level prototype of this embodiment, the number of turns of the integrated reverse coil is designed to be 12. In order to achieve a stable M ps during misalignment, the side length l2 is optimized. In Figure 11(a), as l2 increases, compared with the fully aligned case, the difference in mutual inductance in the offset case increases more significantly. When l2 = 200 mm and l2 = 220 mm, the difference in mutual inductance in the offset case even exceeds that in the fully aligned case. When l2 = 180 mm, the difference in mutual inductance remains stable from good alignment to 40% misalignment. The IPT system using this difference in mutual inductance for power transmission has excellent anti-offset performance. Figure 11 (b) further shows the coupling characteristics of M p1s and M p2s when l2 = 180 mm. Therefore, the size of the integrated reverse coil is designed to be 180 mm × 180 mm × 5 mm.

[0144] S4. Set the secondary-side integrated inductance coil L sf at the receiving end of the initial magnetic coupler, and define the difference in mutual inductance between the transmitting coil L p1 , the integrated reverse coil L p2 and the secondary-side integrated inductance coil L sf as the second mutual inductance M psf ;

[0145] S5. Define the ratio of the second mutual inductance M psf to the first mutual inductance M ps as ε; traverse the number of turns and size of the secondary-side integrated inductance coil L sf , and determine whether ε ≤ ξ is satisfied, where ξ is the desired inductive index; if so, go to step S5, otherwise continue to traverse;

[0146] After designing the integrated reverse coil, due to the stable difference in mutual inductance, the anti-offset performance is improved. The secondary-side integrated inductance coil can be further designed to optimize the ZVS operating conditions. Under the commonly used 50% duty cycle control strategy, the ZVS operating state is closely related to the phase angle α of the inverter output voltage and current. According to Figure 3 , the equivalent inductance in the secondary-side LCC topology compensation network of the IPT system is L sfe , which is the superposition of L sf and M ssf . Therefore, the key design of the secondary-side integrated inductance coil lies in the requirements of L sf and M ssf . Taking n w5 and l5 as variables, the temperature contour maps of L sf and M ssf are obtained by the traversal method, as shown in Figure 12 . The results show that under the same parameters, the internal mutual inductance M ssf is close to the self-inductance L sf configuration. While achieving a smaller self-inductance L sf , the required equivalent self-inductance L sfe can be obtained.. According to (16), the size of the secondary - side integrated inductor coil is expected to be small enough. In the 3 - kW power - stage prototype, the size of the secondary - side integrated inductor coil is designed to be 140 mm×140 mm×5 mm. The number of turns n w4 is designed to be 4.

[0147] Under the designed secondary - side integrated inductor coil, M psf 、M ps and their ratio ε during the offset change as Figure 13 shown. The results show that ε remains at a minimum value above 0 and a maximum value within 0.1. It can not only ensure the ZVS operating state but also make the turn - off current not too large.

[0148] S6. Set the primary - side integrated inductor coil L pf at the transmitting end of the initial magnetic coupler. According to the output power of the transmitting end of the initial magnetic coupler, traverse the number of turns and size of the primary - side integrated inductor coil L pf to obtain the finally optimized highly integrated magnetic coupler.

[0149] Specifically, according to the total power level (including voltage and current) output at the transmitting end, determine the required primary - side (primary) circuit impedance, so as to determine the required integrated coil inductance value. Through the simulation software, traverse the number of turns and size of the primary - side integrated inductor coil L pf to make the self - inductance value close to the required value.

[0150] Focusing on improving the compactness of the coupler, the inductor in the primary - side LCC topology compensation network is realized through a coupling coil without affecting the system characteristics. Considering the adaptability to the x - direction and y - direction offsets, the primary - side integrated inductor coil is designed as a special bipolar coil, as Figure 14 (a) shown. Different from the usual bipolar structure, the bipolar coil proposed in this paper has eight current loops. Among them, two adjacent current loops have opposite polarities. The transmitting coil and the integrated reverse coil are unipolar. Due to central symmetry, the primary - side integrated inductor coil is naturally decoupled from them.

[0151] The design of the primary - side integrated inductor is determined by l3, l4 and n w3 . For different n w3 and l3l - corresponding primary - side integrated inductors, with l4 = 60 mm selected, they are obtained by the traversal method, as Figure 14 shown. The size of the primary - side integrated inductor can be designed according to the required inductance value in the 3 - kW power - stage IPT system. n w3 is designed to be 3, and l3 is designed to be 200 mm.

[0152] In one embodiment, experiments were conducted using the highly integrated magnetic coupler obtained by the above IPT system applicable to the 3kW power level. At the input end, a DC power supply and a high-power inverter were used to provide 300V AC excitation for the resonant circuit. The inverter used a CREE silicon carbide MOSFET (C2M0025120D) with an internal resistance of 20mΩ to reduce power loss and improve output stability. The PWM control signal of the MOSFET was generated by the control chip DSP28335. The output was a fixed frequency of 85kHz. At the output end, a CREE C3D20060D diode was used for the rectifier to provide DC current for the EA-CPS-8080 electronic load. The output resistance was set to 30Ω. The coil was made of 1000 strands of AWG 38 litz wire. The magnetic material PC95 was used to construct the ferrite plate. The measured parameters of the coupling mechanism and the calculated resonant parameters are shown in Table 2:

[0153] Table 2 Measured Parameters of the Highly Integrated Magnetic Coupler

[0154]

[0155]

[0156] The experimental results revealed two points. First, the system worked effectively under good alignment and different offset distances. Second, the inverter operated in an ideal slightly inductive load state, and the integrated coil on the secondary side effectively optimized the ZVS condition.

[0157] Figure 15 The output power and the overall DC-DC system efficiency of the IPT system for offset were given when RL = 30Ω. In the offset range of 18cm, the output power range was from 2.9kW to 3.1kW. The average output power was 3kW. At the working condition with an offset of 18cm, the output power decreased to 2.9kW, which was 97% of the value in the well-aligned position (3.1kW). Under the same conditions, the overall efficiency of the IPT system could still be maintained above 93%. The results verified that the proposed method had good anti-offset performance.

[0158] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An integrated method for an IPT system with a highly integrated magnetic coupler, characterized in that, The IPT system includes an inverter, a highly integrated magnetic coupler, a rectifier, and a load; the highly integrated magnetic coupler includes a transmitting end and a receiving end; the transmitting end includes a transmitting coil L p1 , an integrated reverse coil L p2 , a primary-side integrated inductance coil L pf , a first magnetic core plate, and a first shielding plate; the first magnetic core plate is placed on the first shielding plate, and the transmitting coil L p1 is arranged on the first magnetic core plate, and the integrated reverse coil L p2 is arranged inside the transmitting coil L p1 , and the integrated reverse coil L p2 and the transmitting coil L p1 are centrosymmetric structures; The receiving end includes a receiving coil L s , a secondary-side integrated inductance coil L sf , a second magnetic core plate and a second shielding plate; the second magnetic core plate is placed on the second shielding plate, and the receiving coil L s is arranged on the second magnetic core plate, and the secondary-side integrated inductance coil L sf is arranged inside the receiving coil L s ; Primary-side integrated inductance coil L pf is a dual-stage coil, and the transmitting coil L p1 and the integrated reverse coil L p2 are provided with 4 dual-stage coils therebetween; one dual-stage coil has 2 current loops, and the 4 dual-stage coils have a total of 8 current loops, and the polarities between every two current loops are opposite; The IPT system integration method includes the following steps: S1. Construct an initial magnetic coupler according to the operating frequency, input voltage, and output power of the IPT system; the initial magnetic coupler includes a transmitting end and a receiving end; the transmitting end is provided with a transmitting coil L p1 , and the receiving end is provided with a receiving coil L s ; the number of turns and dimensions of the transmitting coil L p1 and the receiving coil L s are preset, and the mutual inductance between the transmitting coil L p1 and the receiving coil L s is defined as M p1s ; S2. Set an integrated reverse coil L at the transmitting end of the initial magnetic coupler p2 and determine the number of turns of the integrated reverse coil L according to the output power of the IPT system p2 ; Define the mutual inductance difference between the transmitting coil L p1 , the integrated reverse coil L p2 and the receiving coil L s as the first mutual inductance M ps ; S3. Perform finite element analysis through MAXWELL to traverse the size of the integrated reverse coil L p2 to determine whether the first mutual inductance M ps is stable within an alignment deviation of 40%. If so, proceed to step S4; otherwise, continue traversing. S4. Set the secondary-side integrated inductance coil L at the receiving end of the initial magnetic coupler sf , define the transmitting coil L p1 , the integrated reverse coil L p2 and the mutual inductance difference between the secondary-side collective inductance coil L sf is the second mutual inductance M psf ; S5. Define the ratio of the second mutual inductance M psf to the first mutual inductance M ps as ε; traverse the number of turns and dimensions of the secondary-side integrated inductor coil L sf to determine whether ε ≤ ξ is satisfied, where ξ is the desired inductive index; if so, proceed to step S5, otherwise continue the traversal; S6. Set the primary side integrated inductor coil L at the transmitting end of the initial magnetic coupler pf , traverse the number of turns and dimensions of the primary side integrated inductor coil L according to the output power at the transmitting end of the initial magnetic coupler pf to obtain the finally optimized highly integrated magnetic coupler.

2. The integrated method of an IPT system with a highly integrated magnetic coupler according to claim 1, wherein The inverter is a voltage-fed inverter, which is composed of MOSFET S1, MOSFET S2, MOSFET S3 and MOSFET S4; the rectifier includes diodes D1, D2, D3 and D4.

3. A method for integrating an IPT system with a highly integrated magnetic coupler according to claim 1, characterized in that, The circuit topology of the IPT system includes a primary-side LCC topology compensation network and a secondary-side LCC topology compensation network; the primary-side LCC topology compensation network includes a transmitting coil L p1 , an integrated reverse coil L p2 , a primary-side integrated inductance coil L pf , a capacitor C p and a capacitor C pf ; the secondary-side LCC topology compensation network includes a receiving coil L s , a secondary-side integrated inductance coil L sf , a capacitor C s and a capacitor C sf ; The primary-side integrated inductance coil L pf , capacitor C p , transmitting coil L p1 and integrated reverse coil L p2 are connected in series in sequence. The circuit composed of capacitor C p , transmitting coil L p1 and integrated reverse coil L p2 is in parallel with capacitor C pf ; among them, transmitting coil L p1 and integrated reverse coil L p2 are connected in reverse series; the secondary-side collective inductance coil L sf , capacitor C s and receiving coil L s are connected in series in sequence. The circuit composed of capacitor C s and receiving coil L s is in parallel with capacitor C sf . Transmitting coil L p1 , integrated reverse coil L p2 and receiving coil L s have a mutual inductance difference of the first mutual inductance M ps ; the transmitting coil L p1 , integrated reverse coil L p2 and the secondary side integrated inductance coil L sf have a mutual inductance difference of the second mutual inductance M psf ; the transmitting coil L p1 and the integrated reverse coil L p2 have a mutual inductance of the first same-side internal mutual inductance M p12 ; the secondary side integrated inductance coil L sf and the receiving coil L s have a mutual inductance of the second same-side internal mutual inductance M ssf .

4. A method for integrating an IPT system with a highly integrated magnetic coupler according to claim 1, characterized in that Decouple the second same-side internal mutual inductance M ssf equivalent to a T-network and integrated with the secondary-side LCC topology compensation network, and decoupled by the following formula: L sfe = L sf + M ssf The first same-side internal mutual inductance M p12 The decoupling formula is expressed as: Among them, L se represents the equivalent value of the receiving coil L s and the series compensation capacitor C s ; ω represents the system resonance angular frequency, L sfe represents the equivalent superposition of the secondary-side integrated inductor coil L sf and the second same-side internal mutual inductance M ssf ; C sfe represents the equivalent superposition of the secondary-side parallel compensation capacitor C sf and the second same-side internal mutual inductance M ssf ; L p represents the equivalent superposition of the transmitting coil L p1 , the integrated reverse coil L p2 and the primary-side series compensation capacitor C p .

5. An IPT system integration method with a highly integrated magnetic coupler according to claim 4, characterized in that The equivalent circuit of the circuit topology package of the IPT system is obtained by using the basic harmonic approximation method, and through Kirchhoff's law, it is obtained that: The resonance relationship is expressed as: ω 2 L pf C pf = ω 2 L p C pf = ω 2 L se C sfe = ω 2 L sfe C sfe = 1 Among them, represents the inverter output current, represents the current passing through the transmitting coil, represents the current passing through the receiving coil, represents the output current, represents the inverter output voltage, R e represents the load equivalently formed by the rectifier bridge and the load together.

6. The integrated method of an IPT system with a highly integrated magnetic coupler according to claim 5, wherein By simplifying the Kirchhoff's law formula through the resonance relationship formula, it is obtained that: Derived from the simplified formula: Among them, represents the inverter output voltage, represents the magnitude of the inverter output voltage, represents the magnitude of the transmitting coil current, represents the magnitude of the output current, P out represents the output power, K1 represents the coefficient defined by the system parameters, Z in represents the total equivalent impedance of the system from the input end.

7. An IPT system integration method with a highly integrated magnetic coupler according to claim 6, characterized in that The derivation result according to the simplified formula shows that M psf does not affect the output power, but affects the imaginary part of the total input impedance of the IPT system; define the phase angle between the inverter voltage and the inverter current as α, the positive and negative values of which respectively represent inductive and capacitive, and the absolute value represents the degree of deviation of the IPT system from the resonance point; through M psf quantifies the resonance state of the IPT system, expressed as:

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