Equivalent circuit model of wireless electric energy transmission system and modeling method

Abstract

The invention provides a wireless power transmission system equivalent circuit model and a modeling method. The wireless power transmission system equivalent circuit model comprises a magnetic coupling structure and a stray capacitance equivalent module, and the stray capacitance equivalent module is connected with the magnetic coupling structure; the magnetic coupling structure comprises a transmitting side coil and a receiving side coil, and the stray capacitance equivalent module is used for equivalently representing the turn-to-turn capacitance of the transmitting side coil of the magnetic coupling structure, the turn-to-turn capacitance of the receiving side coil and the turn-to-turn capacitance between the ith turn of transmitting side coil and the mth turn of receiving coil; wherein i and m are positive integers greater than 0. Therefore, by establishing the accurate circuit model considering the stray capacitance of the wireless electric energy transmission system and identifying the stray capacitance, the stability of the wireless electric energy transmission system is improved, and the electric energy transmission capability is improved.

Description

Technical Field

[0001] This invention relates to the field of wireless power transmission and communication technology, and in particular to an equivalent circuit model and modeling method for a wireless power transmission system. Background Technology

[0002] Wireless power transfer technology is an effective solution to many problems of plug-and-play wired charging, such as low safety, complex wiring, and incompatible and insufficient interfaces. It has broad application prospects in fields such as implantable medical devices, consumer electronics, AGVs (Automated Guided Vehicles), and electric vehicles.

[0003] Lightweight design and portability are ongoing goals for wireless power transfer devices, especially wireless power receiving systems. Both academic and engineering studies have proven that increasing the operating frequency is an effective way to improve the power density of power electronic converters and inductors in the system. Furthermore, higher frequencies can fully utilize the advantages of SiC and GaN semiconductor power devices, such as high switching speed, low on-resistance, and good temperature resistance.

[0004] Existing studies have neglected the impact of parasitic parameters on system performance. For example, in a 6.78MHz wireless power transmission system, based on LC series resonance, the compensation capacitance is only a few pF. However, under this condition, the parasitic capacitance of the wireless power transmitting and receiving coils can also reach the pF level. This affects the system's resonant state, leading to a sharp decrease in system output power and transmission efficiency, and an increased risk of thermal runaway.

[0005] Therefore, how to establish a precise circuit that takes into account the parasitic capacitance of wireless power transmission systems and accurately identify it has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an equivalent circuit model and modeling method for a wireless power transmission system, used to establish an accurate circuit that takes into account the parasitic capacitance of the wireless power transmission system and to accurately identify it.

[0007] In a first aspect, the present invention provides an equivalent circuit model of a wireless power transmission system, comprising: a magnetic coupling structure and a stray capacitance equivalent module, wherein the stray capacitance equivalent module is connected to the magnetic coupling structure; the magnetic coupling structure includes a transmitting coil and a receiving coil, and the stray capacitance equivalent module is used to equivalently characterize the inter-turn capacitance of the transmitting coil, the inter-turn capacitance of the receiving coil, and the inter-turn capacitance between the i-th transmitting coil and the m-th receiving coil of the magnetic coupling structure; Where i and m are both positive integers greater than 0.

[0008] Optionally, the wireless power transmission system further includes a transmitter-side compensation network, a receiver-side compensation network, an inverter, and a rectifier. The inverter is connected to the transmitter-side coil of the magnetic coupling coil through the transmitter-side compensation network; the rectifier is connected to the receiver-side coil of the magnetic coupling coil through the receiver-side compensation network.

[0009] Optionally, the output power of the equivalent circuit model is:

[0010] in, The inverter output voltage, The input voltage of the rectifier. The internal resistance of the transmitting coil is... The internal resistance of the receiving coil is... Let be the determinant of the admittance matrix. The admittance matrix is ​​the equivalent inductance of the coil. Let be the admittance matrix of the stray capacitance. For load.

[0011] Optionally, the efficiency of the equivalent circuit model is:

[0012] in, The internal resistance of the transmitting coil is... The internal resistance of the receiving coil is... For load, Let be the determinant of the admittance matrix. The admittance matrix is ​​the equivalent inductance of the coil. Let be the admittance matrix of the stray capacitance.

[0013] Secondly, based on the same inventive concept, this invention provides a modeling method based on an equivalent circuit model of a wireless power transmission system, comprising: Obtain the geometric parameters of the magnetic coupling structure, determine the electric field distribution density between each conductive component in the magnetic coupling structure, and establish a preliminary parameter matrix of stray capacitance; By mapping stray capacitances to the capacitor network topology in the equivalent circuit, an equivalent circuit model of the wireless power transmission system as described above is constructed. The equivalent circuit model is subjected to open-circuit and / or short-circuit tests, and the stray capacitance of the magnetic coupling structure is identified in conjunction with the preliminary parameter matrix.

[0014] Optionally, the step of performing open-circuit and / or short-circuit tests on the equivalent circuit model to identify the stray capacitance of the magnetic coupling structure includes: An open-circuit test was performed on the receiving side of the equivalent circuit model. , The receiving-side inductor current; the port voltage of the receiving-side coil under open-circuit test on the receiving side. for:

[0015] in, The internal resistance of the transmitting coil, The first admittance in the admittance matrix. The second admittance in the admittance matrix, that is... and The sum of, This is the voltage across the transmitting side when the receiving side is open. This refers to the current across the transmitting side when the receiving side is open.

[0016] Optionally, the step of performing open-circuit and / or short-circuit tests on the equivalent circuit model to identify the stray capacitance of the magnetic coupling structure includes: A short-circuit test was performed on the receiving side of the equivalent circuit model. , The voltage at the receiving coil port; the inductor current on the transmitting side under a short-circuit test in the receiving network. for:

[0017] The inductor current under short-circuit test on the receiving side. for:

[0018] in, This is the third admittance in the admittance matrix. This is the fourth admittance in the admittance matrix. This represents the voltage across the transmitting side when the receiving side is short-circuited.

[0019] Optionally, the step of performing open-circuit and / or short-circuit tests on the equivalent circuit model to identify the stray capacitance of the magnetic coupling structure includes: An open-circuit test was performed on the transmitter side of the equivalent circuit model. , The transmitting side inductor current; the port voltage of the transmitting side under open-circuit test. for:

[0020] The output current of the transmitting side under the open-circuit test. for:

[0021] in, This represents the voltage across the receiver when the transmitting side is open.

[0022] Optionally, the step of performing open-circuit and / or short-circuit tests on the equivalent circuit model to identify the stray capacitance of the magnetic coupling structure includes: A short-circuit test was performed on the transmitter side of the equivalent circuit model. , The voltage at the transmitting coil port; the input current of the transmitting side under short-circuit test at the transmitting side. for:

[0023] The output current of the transmitting side under short-circuit test. for:

[0024] in, This represents the voltage across the receiver when the transmitter is short-circuited.

[0025] Optionally, the geometric parameters of the magnetic coupling structure include the number of coil turns, coil size, and coil spacing.

[0026] The technical solution provided by this invention has the following advantages compared with the prior art: This invention provides an equivalent circuit model and modeling method for a wireless power transmission system, including: a magnetic coupling structure and a stray capacitance equivalent module, wherein the stray capacitance equivalent module is connected to the magnetic coupling structure; the magnetic coupling structure includes a transmitting coil and a receiving coil, and the stray capacitance equivalent module is used to equivalently characterize the inter-turn capacitance of the transmitting coil, the inter-turn capacitance of the receiving coil, and the inter-turn capacitance between the i-th transmitting coil and the m-th receiving coil of the magnetic coupling structure; wherein i and m are both positive integers greater than 0. By establishing an accurate circuit considering the stray capacitance of the wireless power transmission system, the influence of stray capacitance on mathematical models such as system output power, transmission efficiency, and voltage gain is analyzed. Based on two-port short-circuit and open-circuit tests, a stray capacitance identification method is proposed. The simulation and experimental platform verified the effectiveness of the proposed circuit, mathematical model, and parameter identification method. This is beneficial to improving the stability of the wireless power transmission system and enhancing the wireless power transmission capability. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0028] 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, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The diagram shown is a schematic diagram of a wireless power transmission system provided in an embodiment of the present invention; Figure 2 The diagram shown is a schematic representation of the stray capacitance distribution of a magnetic coupling structure in a wireless power transmission system according to an embodiment of the present invention. Figure 3 for Figure 2 Equivalent circuit diagram of a six-capacitor circuit; Figure 4 for Figure 3 A simplified circuit diagram; Figure 5 The figure shown is an equivalent circuit diagram of a wireless power transmission system based on an SS compensation network provided by an embodiment of the present invention; Figure 6 A modeling method for an equivalent circuit model of a wireless power transmission system provided in an embodiment of the present invention; Figure 7 The diagram shown is a schematic of a wireless power transfer system based on a Class EF2 resonant inverter according to an embodiment of the present invention. Figure 8 The figure shown is an experimental platform for a 6.78MHz wireless power transmission system based on an SS compensation network provided by an embodiment of the present invention; Figure 9 The diagram shown is a comparison of inverter drive signals under the conditions of ignoring and taking into account stray capacitance of magnetic coupling structure according to an embodiment of the present invention. Figure 10 The figure shown is a waveform diagram of the inverter output voltage and current when stray capacitance is ignored, according to an embodiment of the present invention. Figure 11 The figure shown is a waveform diagram of the inverter output voltage and current considering stray capacitance according to an embodiment of the present invention; Figure 12 The figure shown is a schematic diagram of the receiving-side coil voltage and load current waveforms provided by the present invention; Figure 13 The figure shown is a DC-DC peak efficiency diagram measured by a HIOKI PW6001 power analyzer provided by the present invention. Detailed Implementation

[0030] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Many specific details are set forth in the following description to provide a thorough understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the present invention, and not all embodiments.

[0031] Figure 1 The diagram shown is a schematic representation of a wireless power transmission system according to an embodiment of the present invention. Please refer to it. Figure 1 The wireless power transmission system 100 includes a transmitter-side compensation network 30, a receiver-side compensation network 50, an inverter 20, and a rectifier 40. The inverter 20 is connected to the transmitter-side coil 11 of the magnetic coupling structure 10 through the transmitter-side compensation network 30; the rectifier 40 is connected to the receiver-side coil 12 of the magnetic coupling structure 10 through the receiver-side compensation network 50.

[0032] Specifically, the wireless power transfer system 100 comprises a magnetic coupling structure 10 (or loosely coupled transformer), a transmitting-side compensation network 30, a receiving-side compensation network 50, an inverter 20, and a rectifier 40. The magnetic coupling structure 10 includes a transmitting-side coil 11 and a receiving-side coil 12. In the wireless power transfer system 100, the transmitting-side coil 11 is connected to the inverter 20 via the transmitting-side compensation network 30. Furthermore, the inverter 20 is connected to an external power source. The inverter 20, as a key component for energy conversion and transfer, converts the DC power supplied by the external power source into high-frequency AC power, providing the necessary excitation power to the transmitting-side coil 11 and converting the input electrical energy into magnetic field energy. For example, in a wireless charging system, the transmitter converts the input DC power into high-frequency AC power, generating an alternating magnetic field through the transmitting-side coil 11. In wireless communication, the transmitting-side coil 11 is used to convert electrical signals into electromagnetic wave signals for transmission. The receiving coil 12 is connected to the rectifier 40 via the receiving compensation network 50. The receiving coil 12 is situated within the magnetic field generated by the transmitting coil 11. According to the principle of electromagnetic induction, when the magnetic field around the receiving coil 12 changes, an induced electromotive force and induced current are generated in the coil, thereby converting magnetic field energy into electrical energy and achieving energy reception. In wireless communication, the receiving coil 12 is used to receive electromagnetic wave signals and convert them into electrical signals for subsequent processing. The rectifier 40, connected to the receiving coil 12, is used to realize energy reception and utilization, converting the high-frequency AC power induced by the receiving coil 12 into DC power to supply power to loads (such as batteries, electrical equipment, etc.). In related technologies, the inter-turn capacitance of the magnetic coupling structure 10 is usually ignored, and the magnetic coupling structure 10 is only equivalent to a T-type or mutual inductance model. However, for a MHz wireless power transmission system 100, the inter-turn capacitance of the magnetic coupling structure 10 can reach the pF level, comparable to the compensation capacitance level, and therefore cannot be ignored. To address the aforementioned problems, this invention provides an equivalent circuit model of a wireless power transmission system, used to establish an accurate circuit considering the stray capacitance of the wireless power transmission system 100.

[0033] Figure 2 The diagram shown is a schematic representation of the stray capacitance distribution of a magnetic coupling structure in a wireless power transmission system according to an embodiment of the present invention. Figure 3 for Figure 2 The equivalent circuit diagram of a six-capacitor circuit. Figure 4 for Figure 3 For a simplified circuit diagram, please refer to... Figures 1 to 4The present invention provides an equivalent circuit model of a wireless power transmission system, including: a magnetic coupling structure 10 and a stray capacitance equivalent module 60, wherein the stray capacitance equivalent module 60 is connected to the magnetic coupling structure 10; the magnetic coupling structure 10 includes a transmitting coil 11 and a receiving coil 12, and the stray capacitance equivalent module 60 is used to equivalently characterize the inter-turn capacitance of the transmitting coil 11, the inter-turn capacitance of the receiving coil 12, and the inter-turn capacitance between the i-th transmitting coil 11 and the m-th receiving coil 12 of the magnetic coupling structure 10; wherein i and m are both positive integers greater than 0.

[0034] For details, please refer to Figure 2 The inter-turn capacitance of the transmitting coil 11 turns is defined as The inter-turn capacitance of the receiving coil is defined as... The inter-turn capacitance between the i-th turn transmitting coil 11 and the m-th turn receiving coil 12 is defined as... The subscripts i, j, m, and n represent the number of turns of the transmitting coil 11 and the receiving coil 12, respectively. In this way, the stray capacitances in the magnetic coupling structure 10 can be classified into the inter-turn capacitance of the transmitting coil 11, the inter-turn capacitance of the receiving coil 12, and the inter-turn capacitance between a certain coil on the receiving side and a certain coil on the transmitting side. This facilitates the classification and identification of various inter-turn capacitances in the equivalent circuit, providing a basis for establishing an accurate equivalent circuit for the wireless power transmission system 100 that takes into account stray capacitances.

[0035] Please refer to Figure 3 , This indicates the self-inductance of the transmitting coil 11. This represents the self-inductance of the receiving coil 12, and M represents the mutual inductance between the transmitting coil 11 and the receiving coil 12. , where k is the coupling coefficient. This indicates the internal resistance of the transmitting coil 11. This indicates the internal resistance of the receiving coil 12. , , , , , These represent the two-port equivalent capacitances of the transmitting coil 11 and the receiving coil 12, respectively. Thus, the stray capacitance in the wireless power transfer system 100 can be equivalently represented as... Figure 3 The six-capacitor equivalent circuit in the middle will Figure 2 Classifying the various stray capacitances in the data simplifies calculations.

[0036] Furthermore, Figure 3 It can be simplified to Figure 4 , Figure 4 for Figure 3 The equivalent circuit diagram of the three capacitors is shown below. Please refer to it. Figure 4 , This indicates the inter-turn capacitance of the emitter-side inductor. This indicates the inter-turn capacitance of the receiving-side inductor. This represents the inter-turn capacitance between the transmitting coil 11 and the receiving coil 12. That is, Figure 3 The six-capacitor equivalent circuit in the diagram is further simplified to... Figure 4 The three-capacitor equivalent circuit in the diagram can further classify various stray capacitors in the wireless power transmission system 100, which is beneficial for simplifying calculations.

[0037] Figure 5 The diagram shown is an equivalent circuit diagram of a wireless power transfer system based on an SS compensation network according to an embodiment of the present invention. Please refer to... Figure 5 According to Kirchhoff's voltage law, Figure 5 It can be represented as: (1) In the formula, Represented as the emitter-side inductor current, This is expressed as the receiving-side inductor current. This is represented as the voltage at port 11 of the transmitting coil. This is represented as the voltage at port 12 of the receiving coil. This is represented as the output voltage of inverter 20. This is expressed as the input voltage of rectifier 40, and (2) (3) (4) (5) (6) (7) Let be the determinant of the admittance matrix. The admittance matrix is ​​the equivalent inductance of the coil. Let be the admittance matrix of the stray capacitance. For load.

[0038] definition, (8) In the formula, (9) Furthermore, equation (1) can be simplified to, (10) To improve power transmission capability and minimize the inverter's 20 volt-ampere capacity, the transmitter-side compensation network 30 and receiver-side compensation network 50 are designed as follows: (11) (12) Therefore, the output power of the wireless power transmission system 100 is expressed as: (13) For load, Let be the determinant of the admittance matrix. The admittance matrix is ​​the equivalent inductance of the coil. Let be the admittance matrix of the stray capacitance.

[0039] The transmission efficiency of a wireless power transmission system 100 is expressed as: (14) Thus, by establishing an equivalent circuit for the wireless power transmission system 100 that takes into account stray capacitance, the formulas for the output power and transmission efficiency of the wireless power transmission system 100 that takes into account stray capacitance can be derived, providing a basis for subsequent identification of the capacitance parameters of stray capacitance.

[0040] Figure 6 A modeling method for an equivalent circuit model of a wireless power transmission system provided in this embodiment of the invention is available for reference. Figure 6 This invention provides a modeling method based on an equivalent circuit model of a wireless power transmission system, comprising: Step S1: Obtain the geometric parameters of the magnetic coupling structure 10, determine the electric field distribution density between each conductive component in the magnetic coupling structure 10, and establish the preliminary parameter matrix of the stray capacitance. Step S2: Map stray capacitances to the capacitor network topology in the equivalent circuit to construct the equivalent circuit model of the wireless power transmission system as described above; Step S3: Perform open-circuit and / or short-circuit tests on the equivalent circuit model, and identify the stray capacitance of the magnetic coupling structure 10 in conjunction with the preliminary parameter matrix.

[0041] Specifically, in step S1, the geometric parameters of the magnetic coupling structure 10 are obtained, such as the number of coil turns, coil radius and length, the relationship between coupling coefficient and spacing, etc., which are not listed here. The specific type of geometric parameters can be obtained according to actual needs. The electric field distribution density between each conductive component in the magnetic coupling structure 10 is determined, and a preliminary parameter matrix of stray capacitance is established. Furthermore, the preliminary parameter matrix can be derived and simplified to facilitate subsequent parameter identification.

[0042] In step S2, the structure of the wireless power transfer system 100 is first analyzed to determine the locations where stray capacitors may exist. For example, in an optional embodiment provided by the present invention, for the inter-turn capacitance of the transmitting coil 11, the inter-turn capacitance of the receiving coil 12, and the inter-turn capacitance of the transmitting coil 11 and the receiving coil 12, an equivalent circuit model for wireless power transfer is established based on the actual structure of the wireless power transfer system 100 and the distribution of stray capacitors. Generally, stray capacitors can be equivalently represented as capacitors connected in parallel or series with other components. For example, inter-turn stray capacitors can be equivalently represented as capacitors connected in parallel with the coil inductance, and so on. Based on the equivalent location of the stray capacitors, they are incorporated into the capacitor network topology of the entire equivalent circuit. For example, if there are multiple stray capacitors, they may form series, parallel, or more complex hybrid connection methods. When constructing the capacitor network topology, the mutual influence between stray capacitors and between stray capacitors and other circuit components must be considered. For example, multiple parallel stray capacitors can be combined into an equivalent capacitor, the value of which is the sum of the values ​​of the parallel capacitors; series stray capacitors can also be combined into an equivalent capacitor, and so on, thereby mapping the stray capacitors to the capacitor network topology in the equivalent circuit of the wireless power transmission system 100.

[0043] In step S3, open-circuit and / or short-circuit tests are performed on the equivalent circuit model, and the stray capacitance of the magnetic coupling structure 10 is identified using the preliminary parameter matrix. The stray capacitance parameters are identified through theoretical calculations of the preliminary parameter matrix combined with electromagnetic field simulation software. Thus, through the above steps, a modeling method based on the equivalent circuit model of a wireless power transmission system can be provided. Based on establishing an accurate equivalent circuit of the wireless power transmission system 100 according to the stray capacitance, the parameters of the stray capacitance are further identified, clarifying that the inter-turn capacitance of the inductor coil is comparable to that of the compensation capacitor, both being several pF and not negligible.

[0044] Please refer to Figures 1 to 6 In step S3, open-circuit and / or short-circuit tests are performed on the equivalent circuit model to identify stray capacitances of the magnetic coupling structure 10, including: An open-circuit test was performed on the receiving side of the equivalent circuit model. , The current in the receiving-side inductor; the port voltage of the receiving-side coil 12 under open-circuit testing on the receiving side. for:

[0045] in, The internal resistance of the transmitting coil 11 is... The first admittance in the admittance matrix. The second admittance in the admittance matrix, that is... and The sum of, This is the voltage across the transmitting side when the receiving side is open. This refers to the current across the transmitting side when the receiving side is open.

[0046] Please refer to Figure 3 Combining this with the aforementioned formulas (1) to (10), we can obtain: (15) (16) In the formula, the subscript "oc / Rx" indicates that the receiver side performs an open-circuit test, and "oc / Tx", "sc / Tx" and "sc / Rx" below represent the transmitter side open-circuit, transmitter side short-circuit and receiver side short-circuit tests, respectively.

[0047] According to equations (15) and (16), we can solve for the following: (17) (18) Please continue to refer to this. Figures 1 to 6 In step S3, open-circuit and / or short-circuit tests are performed on the equivalent circuit model to identify stray capacitances of the magnetic coupling structure 10, including: A short-circuit test was performed on the receiving side of the equivalent circuit model. , The voltage at port 12 of the receiving coil; the inductor current on the transmitting side under short-circuit testing of the receiving network. for:

[0048] Inductor current under short-circuit test on the receiving side for:

[0049] in, This is the third admittance in the admittance matrix. This is the fourth admittance in the admittance matrix. This represents the voltage across the transmitting side when the receiving side is short-circuited.

[0050] Please continue to refer to this. Figures 1 to 6 In step S3, open-circuit and / or short-circuit tests are performed on the equivalent circuit model to identify stray capacitances of the magnetic coupling structure 10, including: An open-circuit test was performed on the emitter side of the equivalent circuit model. , The transmitter-side inductor current; the port voltage of the transmitter under open-circuit testing conditions. for:

[0051] Output current of the transmitter under open-circuit test for:

[0052] in, This represents the voltage across the receiver when the transmitting side is open.

[0053] Please continue to refer to this. Figures 1 to 6 In step S3, open-circuit and / or short-circuit tests are performed on the equivalent circuit model to identify stray capacitances of the magnetic coupling structure 10, including: A short-circuit test was performed on the emitter side of the equivalent circuit model. , The voltage at port 11 of the transmitting coil; the input current of the transmitting side under short-circuit test. for:

[0054] Output current of the transmitter under short-circuit test for:

[0055] in, This represents the voltage across the receiver when the transmitter is short-circuited.

[0056] Please refer to Figures 1 to 6 The geometric parameters of the magnetic coupling structure 10 include the number of coil turns, coil size, coil spacing, core shape, and dielectric constant of the dielectric material.

[0057] The geometric parameters of the magnetic coupling structure 10 are crucial to the performance of the wireless power transfer system 100. For example, the number of turns and winding method of the coil, the core structure, and the shape of the coil affect the magnetic field distribution and coupling uniformity, while the coil spacing and the dielectric constant of the dielectric material determine the mutual inductance coefficient and coupling coefficient, etc. These will not be listed here. By obtaining the geometric parameters of the magnetic coupling structure 10, combined with theoretical formulas and the experimental platform of the wireless power transfer system, it is beneficial to accurately identify the capacitance parameters of stray capacitors.

[0058] Effect verification Figure 7 The diagram shown is a schematic of a wireless power transfer system based on a Class EF2 resonant inverter according to an embodiment of the present invention. Figure 8 The image shows an experimental platform for a 6.78MHz wireless power transfer system based on an SS compensation network, provided by an embodiment of the present invention. Please refer to [the documentation / reference]. Figures 7 to 8 The parameters of the wireless power transmission system 100 and the parasitic capacitances calculated based on equations (17) to (24) are shown in Table 1 below.

[0059] Table 1 System Parameters

[0060] Figure 9 The diagram shown is a comparison of inverter drive signals under the conditions of ignoring and considering stray capacitance of the magnetic coupling structure according to an embodiment of the present invention. Figure 10 The figure shown is a waveform diagram of the inverter output voltage and current when stray capacitance is ignored, according to an embodiment of the present invention. Figure 11 The figure shown is a waveform diagram of the inverter output voltage and current considering stray capacitance according to an embodiment of the present invention. Please refer to it. Figures 1 to 11 Please refer to this. Figure 9 The drive signals vgs.QA(t) and vgs.QB(t) for QA and QB respectively are complementary and alternately turned on. Additionally, please refer to... Figure 10 When stray capacitance is ignored, there is a significant phase difference between the output voltage and current of inverter 20, meaning the system is in a detuned state. Please refer to [reference needed]. Figure 11 After taking stray capacitance into account, the output voltage and current of inverter 20 are in phase. This proves the effectiveness of the equivalent circuit of the wireless power transfer system 100 of the present invention, which takes stray capacitance into account.

[0061] Figure 12 The diagram shown illustrates the waveforms of the receiving-side coil voltage and load current provided by this invention. Please refer to it. Figure 12 The voltage and load current of the receiving coil 12 are 90° out of phase, which is consistent with the theory. Figure 13 The figure shows a DC-DC peak efficiency diagram measured by the HIOKI PW6001 power analyzer provided by the present invention. As can be seen from the figure, the peak efficiency of the improved wireless power transmission system provided by the present invention is as high as 91.6%.

[0062] In summary, this invention provides an equivalent circuit model and modeling method for a wireless power transfer system, comprising: a magnetic coupling structure and a stray capacitance equivalent module, wherein the stray capacitance equivalent module is connected to the magnetic coupling structure; the magnetic coupling structure includes a transmitting coil and a receiving coil, and the stray capacitance equivalent module is used to equivalently characterize the inter-turn capacitance of the transmitting coil, the inter-turn capacitance of the receiving coil, and the inter-turn capacitance between the i-th transmitting coil and the m-th receiving coil of the magnetic coupling structure; wherein i and m are both positive integers greater than 0. This invention addresses MHz wireless power transfer systems, proposing an accurate circuit and mathematical model, studying the impact of stray capacitance of the magnetic coupling structure on system transmission efficiency, voltage gain, and other performance characteristics, and analyzing the stray capacitance identification method based on two-port short-circuit and open-circuit tests. An experimental prototype of a 6.78MHz wireless power transfer system based on an SS compensation network verifies the accuracy and effectiveness of the theoretical analysis. Experimental results show that in a 6.78MHz wireless power transfer system, the inter-turn capacitance of the inductor coil is comparable to that of the compensation capacitor, both being several pF, and therefore should not be ignored. The Class EF2 inverter operates in a soft-switching state, which reduces switching losses and achieves a peak system efficiency of up to 91.6%.

[0063] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. An equivalent circuit model of a wireless power transmission system, characterized in that, include: A magnetic coupling structure and a stray capacitance equivalent module are provided, wherein the stray capacitance equivalent module is connected to the magnetic coupling structure; the magnetic coupling structure includes a transmitting coil and a receiving coil, and the stray capacitance equivalent module is used to equivalently characterize the inter-turn capacitance of the transmitting coil, the inter-turn capacitance of the receiving coil, and the inter-turn capacitance between the i-th transmitting coil and the m-th receiving coil of the magnetic coupling structure. Where i and m are both positive integers greater than 0.

2. The equivalent circuit model of the wireless power transmission system as described in claim 1, characterized in that, The wireless power transmission system further includes a transmitter-side compensation network, a receiver-side compensation network, an inverter, and a rectifier. The inverter is connected to the transmitter-side coil of the magnetic coupling coil through the transmitter-side compensation network; the rectifier is connected to the receiver-side coil of the magnetic coupling coil through the receiver-side compensation network.

3. The equivalent circuit model of the wireless power transmission system as described in claim 2, characterized in that, The output power of the equivalent circuit model is: in, The inverter output voltage, The input voltage of the rectifier. The internal resistance of the transmitting coil is... The internal resistance of the receiving coil is... Let be the determinant of the admittance matrix. The admittance matrix is ​​the equivalent inductance of the coil. Let be the admittance matrix of the stray capacitance. For load.

4. The equivalent circuit model of the wireless power transmission system as described in claim 2, characterized in that, The efficiency of the equivalent circuit model is: in, The internal resistance of the transmitting coil is... The internal resistance of the receiving coil is... For load, Let be the determinant of the admittance matrix. The admittance matrix is ​​the equivalent inductance of the coil. Let be the admittance matrix of the stray capacitance.

5. A modeling method based on an equivalent circuit model of a wireless power transmission system, characterized in that, include: Obtain the geometric parameters of the magnetic coupling structure, determine the electric field distribution density between each conductive component in the magnetic coupling structure, and establish a preliminary parameter matrix of stray capacitance; By mapping stray capacitances to the capacitor network topology in the equivalent circuit, an equivalent circuit model of the wireless power transmission system as described in any one of claims 1-4 is constructed. The equivalent circuit model is subjected to open-circuit and / or short-circuit tests, and the stray capacitance of the magnetic coupling structure is identified in conjunction with the preliminary parameter matrix.

6. The modeling method based on the equivalent circuit model of a wireless power transmission system as described in claim 5, characterized in that, The step of performing open-circuit and / or short-circuit tests on the equivalent circuit model to identify stray capacitances in the magnetic coupling structure includes: An open-circuit test was performed on the receiving side of the equivalent circuit model. , The receiving-side inductor current; the port voltage of the receiving-side coil under open-circuit testing on the receiving side. for: in, The internal resistance of the transmitting coil, The first admittance in the admittance matrix. The second admittance in the admittance matrix, that is... and The sum of, This is the voltage across the transmitting side when the receiving side is open. This refers to the current across the transmitting side when the receiving side is open.

7. The modeling method based on the equivalent circuit model of a wireless power transmission system as described in claim 5, characterized in that, The step of performing open-circuit and / or short-circuit tests on the equivalent circuit model to identify the stray capacitance of the magnetic coupling structure includes: A short-circuit test was performed on the receiving side of the equivalent circuit model. , The voltage at the receiving coil port; the inductor current on the transmitting side under a short-circuit test in the receiving network. for: The inductor current under short-circuit test on the receiving side. for: in, This is the third admittance in the admittance matrix. This is the fourth admittance in the admittance matrix. This represents the voltage across the transmitting side when the receiving side is short-circuited.

8. The modeling method based on the equivalent circuit model of a wireless power transmission system as described in claim 5, characterized in that, The step of performing open-circuit and / or short-circuit tests on the equivalent circuit model to identify stray capacitances in the magnetic coupling structure includes: An open-circuit test was performed on the transmitter side of the equivalent circuit model. , The transmitting side inductor current; the port voltage of the transmitting side under open-circuit test. for: The output current of the transmitting side under the open-circuit test of the transmitting side for: in, This represents the voltage across the receiver when the transmitting side is open.

9. The modeling method based on the equivalent circuit model of a wireless power transmission system as described in claim 5, characterized in that, The step of performing open-circuit and / or short-circuit tests on the equivalent circuit model to identify the stray capacitance of the magnetic coupling structure includes: A short-circuit test was performed on the transmitter side of the equivalent circuit model. , The voltage at the transmitting coil port; the input current of the transmitting side under short-circuit test at the transmitting side. for: The output current of the transmitting side under short-circuit test. for: in, This represents the voltage across the receiver when the transmitter is short-circuited.

10. The modeling method based on the equivalent circuit model of a wireless power transmission system as described in claim 5, characterized in that, The geometric parameters of the magnetic coupling structure include the number of coil turns, coil size, and coil spacing.

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