A three-coil wireless power transfer system design method and system

Abstract

The present application relates to a kind of three-coil wireless power transmission system design method and system, belong to wireless power transmission technical field, solve the problem of large output voltage variation amplitude in prior art, low system stability.The method comprises: constructing three-coil wireless power transmission system, primary side transmitting end includes transmitting coil, secondary side receiving end includes receiving coil, relay end includes relay coil, the transmitting coil and relay coil are non-coplanar symmetric arrangement relative to receiving coil;Self-induction of transmitting coil, receiving coil and relay coil is set, so that the mutual inductance value between transmitting coil and receiving coil and the mutual inductance value between relay coil and receiving coil are same, and first mutual inductance value, first mutual inductance value is variable value;The mutual inductance value between transmitting coil and relay coil is second mutual inductance value, and the second mutual inductance value is constant value;Determine first mutual inductance value range based on preset output voltage range and output voltage and first mutual inductance value relationship.

Description

Technical Field

[0001] This invention relates to the field of wireless power transmission technology, and in particular to a design method and system for a three-coil wireless power transmission system. Background Technology

[0002] Wireless power transfer technology utilizes the principle of electromagnetic induction to transfer energy. The input voltage is first inverted into a high-frequency voltage by the inverter in the front-end, and then transmitted to the secondary side through a compensation network and magnetic coupling mechanism. On the secondary side, after passing through a compensation network and rectifier circuit, the output DC power supplies the subsequent load. Compared to traditional plug-and-play charging, wireless power transfer technology effectively reduces the use of cables and has advantages such as greater freedom of transmission, lower maintenance costs, and higher safety performance. It is widely used in charging applications for electric vehicles, consumer electronics, medical devices, and other devices.

[0003] However, in actual use, deviations often occur in the primary and secondary magnetic coupling mechanisms. These deviations reduce the coupling coefficient between the primary and secondary sides, decrease the system's transmission efficiency, and cause significant fluctuations in the output voltage, which is detrimental to system stability. When the primary and secondary sides shift laterally or longitudinally, the output voltage may drop or rise sharply, exceeding the adjustment range of the subsequent DC / DC regulator circuit, severely affecting system stability and the reliability of the load power supply.

[0004] Existing technologies mainly improve upon this by optimizing the compensation network and designing the magnetic coupling mechanism. Regarding the compensation network, higher-order topologies (such as S / LCC and LCC / S) achieve constant current / constant voltage output through topology switching or parameter optimization. Furthermore, the combination of bilateral LCC and SS compensation utilizes the complementary coupling coefficient to partially offset the effects of offset. As for the magnetic coupling mechanism, improved flat solenoids, quadrature coils, and "H"-shaped structures reduce leakage flux and improve the coupling coefficient through shape optimization. However, these methods still have limitations: the design of higher-order compensation topologies is complex, resulting in insufficient dynamic response; while shape optimization of the magnetic coupling mechanism can improve local anti-offset capability, it is difficult to adapt to multi-directional offset scenarios and has high manufacturing costs. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a design method and system for a three-coil wireless power transmission system, in order to solve the problems of large output voltage fluctuations and low system stability when the positions of the primary and secondary sides of the existing wireless power transmission system are changed.

[0006] On one hand, embodiments of the present invention provide a design method for a three-coil wireless power transfer system, comprising the following steps:

[0007] A three-coil wireless power transmission system is constructed, comprising a primary-side transmitter, a secondary-side receiver, and a repeater. The primary-side transmitter includes a transmitting coil, the secondary-side receiver includes a receiving coil, and the repeater includes a repeater coil. The transmitting coil and the repeater coil are arranged in a non-coplanar symmetrical manner relative to the receiving coil.

[0008] The self-inductance of the transmitting coil, receiving coil, and relay coil is set such that the mutual inductance values ​​between the transmitting coil and the receiving coil, and between the relay coil and the receiving coil, are the same, both being the first mutual inductance value, which is a variable value; the mutual inductance value between the transmitting coil and the relay coil is the second mutual inductance value, which is a constant value.

[0009] The range of the first mutual inductance value is determined based on the preset output voltage range and the relationship between the output voltage and the first mutual inductance value.

[0010] As a further improvement to this application, the transmitting coil and the relay coil are arranged in a non-coplanar symmetrical manner with the receiving coil, including:

[0011] The transmitting coil and the relay coil are symmetrically distributed on both sides of the spatial position of the receiving coil, and the relative positions of the transmitting coil and the relay coil remain unchanged.

[0012] As a further improvement to this application, the method further includes:

[0013] When any coil deviates, the positional relationship between the transmitting coil, the relay coil, and the receiving coil is adjusted synchronously, thereby synchronously adjusting the mutual inductance between the transmitting coil and the receiving coil, as well as the mutual inductance between the relay coil and the receiving coil, so that the first mutual inductance value is kept within the range of the first mutual inductance value.

[0014] As a further improvement of this application, the primary-side transmitting end further includes a transmitting compensation capacitor connected in series with the transmitting coil, the secondary-side receiving end further includes a receiving compensation capacitor connected in series with the receiving coil, and the relay end further includes a relay compensation capacitor connected in series with the relay coil; the method further includes:

[0015] Based on the resonant angular frequency of the three-coil wireless power transmission system, the values ​​of the transmitting compensation capacitor, the relay compensation capacitor, and the receiving compensation capacitor are determined so that the transmitting compensation capacitor, the relay compensation capacitor, and the receiving compensation capacitor satisfy the resonance condition with the corresponding coil.

[0016] As a further improvement of this application, the relationship between the output voltage and the first mutual inductance value is shown in the calculation formula (1);

[0017]

[0018] Among them, U out U is the output voltage of the three-coil wireless power transfer system. inR is the input voltage of the three-coil wireless power transmission system, A is the first mutual inductance value, B is the second mutual inductance value, and ω is the system resonant angular frequency.

[0019] As a further improvement to this application, the range of the first mutual inductance value is:

[0020]

[0021] Where A is the first mutual inductance value, A max Let B be the first maximum mutual inductance, R be the load resistance, B be the second mutual inductance, and ω be the system resonant angular frequency.

[0022] When A=A max At that time, the output voltage reaches its maximum value.

[0023] As a further improvement to this application, the resonance condition is as shown in calculation formula (3);

[0024]

[0025] Where L1 is the transmitting coil, L2 is the relay coil, L3 is the receiving coil, C1 is the transmitting compensation capacitor, C2 is the relay compensation capacitor, C3 is the receiving compensation capacitor, and ω is the system resonant angular frequency.

[0026] On the other hand, embodiments of the present invention provide a three-coil wireless power transmission system, characterized in that the system comprises:

[0027] The device comprises a primary transmitter, a secondary receiver, and a relay. The primary transmitter includes a transmitting coil and a transmitting compensation capacitor connected in series with it. The secondary receiver includes a receiving coil and a receiving compensation capacitor connected in series with it. The relay includes a relay coil and a relay compensation capacitor connected in series with it. The transmitting coil and the relay coil are symmetrically distributed on both sides of the spatial position of the receiving coil, and the relative positions of the transmitting coil and the relay coil remain unchanged.

[0028] As a further improvement to this application, the primary-side transmitter also includes a front-end inverter, a voltage regulator capacitor, and an input voltage source;

[0029] The front-end inverter consists of four MOSFETs Q1, Q2, Q3, and Q4, where,

[0030] The source of Q1 is connected to the drain of Q3 to form the first bridge arm; the source of Q2 is connected to the drain of Q4 to form the second bridge arm; the connection point of Q1 and Q3 is connected to one end of the transmitting coil, and the connection point of Q2 and Q4 is connected to the other end of the transmitting coil.

[0031] The positive terminal of the input voltage source is connected to the drain of Q1 and Q2 respectively, and the negative terminal is connected to the source of Q3 and Q4 respectively;

[0032] The voltage regulator capacitor is connected in parallel between the positive and negative terminals of the input voltage source.

[0033] As a further improvement of this application, the secondary receiving end also includes a rectifier circuit, a filter capacitor, and a resistive load;

[0034] The full-bridge rectifier circuit consists of four rectifier diodes D1, D2, D3, and D4, among which...

[0035] The anode of D1 is connected to the cathode of D3, and the connection point of D1 and D3 serves as the first input terminal of the secondary receiving end; the anode of D2 is connected to the cathode of D4, and the connection point of D2 and D4 serves as the second input terminal of the secondary receiving end; the first input terminal is connected to one end of the receiving coil, and the second input terminal is connected to the other end of the receiving coil.

[0036] The cathodes of D1 and D2 are both connected to one end of the filter capacitor and one end of the resistive load; the anodes of D3 and D4 are both connected to the other end of the filter capacitor and the other end of the resistive load.

[0037] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0038] 1. This invention uses a non-coplanar symmetrical three-coil arrangement, in which the transmitting coil and the relay coil are symmetrically distributed on both sides of the receiving coil and their relative positions are fixed. When the system is offset, the mutual inductance values ​​of the transmitting coil and the receiving coil, and the mutual inductance values ​​of the relay coil and the receiving coil change synchronously. Combined with the resonance condition and the output voltage relationship, this effectively improves the range of variation of the coupling coefficient and greatly enhances the system's anti-offset performance.

[0039] 2. By setting the constraint relationship between the first mutual inductance value and the second mutual inductance value, and optimizing the maximum value of the first mutual inductance value, the output voltage exhibits the characteristic of first rising and then falling during the offset process. The output voltage fluctuation amplitude and large offset distance of the present invention are greatly reduced, and the design complexity of the subsequent DC / DC voltage regulator circuit is reduced.

[0040] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0041] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0042] Figure 1 This is a schematic flowchart illustrating a design method for a three-coil wireless power transmission system according to an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of a three-coil arrangement provided in an embodiment of the present invention;

[0044] Figure 3 This is a graph showing the relationship between the output voltage and the first mutual inductance value according to an embodiment of the present invention.

[0045] Figure 4 This is a schematic diagram of a three-coil wireless power transmission system according to an embodiment of the present invention. Detailed Implementation

[0046] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0047] Example 1

[0048] A specific embodiment of the present invention discloses a design method for a three-coil wireless power transfer system, such as... Figure 1 As shown. A design method for a three-coil wireless power transfer system includes the following steps:

[0049] Step S1: Construct a three-coil wireless power transmission system, which includes a primary-side transmitter, a secondary-side receiver, and a repeater. The primary-side transmitter includes a transmitting coil, the secondary-side receiver includes a receiving coil, and the repeater includes a repeater coil. The transmitting coil and the repeater coil are arranged in a non-coplanar symmetrical manner relative to the receiving coil.

[0050] The transmitting coil is connected to the power supply via a pre-amplifier, converting direct current (DC) into high-frequency alternating current (AC). This generates an alternating magnetic field in the transmitting coil, providing the energy source for wireless power transmission. The receiving coil captures the energy from the alternating magnetic field generated by the transmitting coil and converts the received high-frequency AC into DC through rectification and filtering circuits, providing power to the downstream load. The repeater coil assists in power transmission. Through mutual inductive coupling with the transmitting and receiving coils, it enhances the system's anti-offset performance, ensuring stable power transmission even when the primary and secondary winding positions change.

[0051] Specifically, such as Figure 2As shown, the non-coplanar symmetrical arrangement of the transmitting coil and the relay coil relative to the receiving coil includes: the transmitting coil and the relay coil are symmetrically distributed on both sides of the spatial position of the receiving coil, and the relative positions of the transmitting coil and the relay coil remain unchanged.

[0052] The transmitting coil and the repeater coil are located on opposite sides of the receiving coil and are symmetrically distributed with the receiving coil at the center. This arrangement helps optimize the mutual inductance between the coils, ensuring that the system's performance changes consistently when the position shifts, thereby improving the overall anti-shift capability.

[0053] Furthermore, the primary-side transmitting end also includes a transmitting compensation capacitor connected in series with the transmitting coil, the secondary-side receiving end also includes a receiving compensation capacitor connected in series with the receiving coil, and the relay end also includes a relay compensation capacitor connected in series with the relay coil; the method further includes:

[0054] Based on the resonant angular frequency of the three-coil wireless power transmission system, the values ​​of the transmitting compensation capacitor, the relay compensation capacitor, and the receiving compensation capacitor are determined so that the transmitting compensation capacitor, the relay compensation capacitor, and the receiving compensation capacitor satisfy the resonance condition with the corresponding coil.

[0055] A compensation capacitor is a capacitor element connected in series with a coil to form a resonant circuit. The function of the compensation capacitor is to adjust the impedance matching of the system by resonating with the self-inductance of the coil, thereby improving the efficiency and stability of power transmission. In this invention, the transmitting compensation capacitor, the relay compensation capacitor, and the receiving compensation capacitor are connected in series with their respective transmitting coil, relay coil, and receiving coil to ensure that each part of the circuit operates normally at the system's resonant angular frequency.

[0056] The resonance condition is shown in calculation formula (1);

[0057]

[0058] Where L1 is the transmitting coil, L2 is the relay coil, L3 is the receiving coil, C1 is the transmitting compensation capacitor, C2 is the relay compensation capacitor, C3 is the receiving compensation capacitor, and ω is the system resonant angular frequency.

[0059] Step S2: Set the self-inductance of the transmitting coil, receiving coil, and relay coil so that the mutual inductance values ​​between the transmitting coil and the receiving coil, and between the relay coil and the receiving coil, are the same, both being the first mutual inductance value, which is a variable value; the mutual inductance value between the transmitting coil and the relay coil is the second mutual inductance value, which is a constant value.

[0060] After the system is built, the next step is to set the self-inductance of the transmitting coil, receiving coil, and repeater coil, ensuring that the mutual inductance values ​​between the transmitting and receiving coils, as well as between the repeater and receiving coils, are the same, denoted as the first mutual inductance value. The magnitude of the mutual inductance value depends on factors such as the geometry of the coils, their relative positions, the number of turns, and the surrounding medium.

[0061] Step S3: Determine the range of the first mutual inductance value based on the preset output voltage range and the relationship between the output voltage and the first mutual inductance value.

[0062] like Figure 3 As shown, Figure 3 The graph shows the relationship between the output voltage and the first mutual inductance value. As the positional relationship and offset distance of the primary and secondary sides change, when the mutual inductance between the transmitting coil and the receiving coil, and between the relay coil and the receiving coil, changes, the output voltage first increases and then decreases. When the mutual inductance between the transmitting coil and the receiving coil, and between the relay coil and the receiving coil, fluctuates between points A1 and A2, the fluctuation of the output voltage is relatively small.

[0063] The relationship between the output voltage and the first mutual inductance value is shown in calculation formula (2);

[0064]

[0065] Among them, U out U is the output voltage of the three-coil wireless power transfer system. in R is the input voltage of the three-coil wireless power transmission system, A is the first mutual inductance value, B is the second mutual inductance value, and ω is the system resonant angular frequency.

[0066] The range of the first mutual inductance value is:

[0067]

[0068] Where A is the first mutual inductance value, A max Let B be the first maximum mutual inductance, R be the load resistance, B be the second mutual inductance, and ω be the system resonant angular frequency.

[0069] When A=A max At that time, the output voltage reaches its maximum value.

[0070] Furthermore, the range of the first mutual inductance value when the output voltage fluctuation is small can be determined by observing the curve of the relationship between the output voltage and the first mutual inductance value, thereby further limiting the range of the first mutual inductance value.

[0071] Step S4: When any coil deviates, the positional relationship between the transmitting coil, the relay coil, and the receiving coil is adjusted synchronously, thereby synchronously adjusting the mutual inductance between the transmitting coil and the receiving coil, as well as the mutual inductance between the relay coil and the receiving coil, so that the first mutual inductance value is kept within the range of the first mutual inductance value.

[0072] During the operation of a three-coil wireless power transmission system, the position information of the coils can be monitored in real time by position sensors installed on each coil. The position sensors can be optical sensors, magnetic sensors, or mechanical sensors, etc.

[0073] Based on the monitored offset, the positional relationship between the transmitting coil, the relay coil, and the receiving coil is adjusted synchronously to keep the mutual inductance values ​​between the transmitting coil and the receiving coil, as well as between the relay coil and the receiving coil, within the range of the first mutual inductance value.

[0074] The above embodiments of the present invention have the following beneficial effects: The present invention uses a non-coplanar symmetrical three-coil arrangement, that is, the transmitting coil and the relay coil are symmetrically distributed on the receiving coil side and their relative positions are fixed. When the system is offset, the mutual inductance values ​​of the transmitting coil and the receiving coil, and the mutual inductance values ​​of the relay coil and the receiving coil change synchronously. Combined with the resonance condition and the output voltage relationship, the range of variation of the coupling coefficient is effectively improved, and the anti-offset performance of the system is greatly improved. By setting the constraint relationship between the first mutual inductance value and the second mutual inductance value, and optimizing the maximum value of the first mutual inductance value, the output voltage exhibits the characteristic of rising first and then falling during the offset process. The output voltage fluctuation amplitude and large offset distance of the present invention are greatly reduced, and the design complexity of the subsequent DC / DC voltage regulator circuit is reduced.

[0075] Example 2

[0076] Another specific embodiment of the present invention discloses a three-coil wireless power transmission system, such as... Figure 4 As shown. A three-coil wireless power transfer system, the system comprising:

[0077] The device comprises a primary transmitter, a secondary receiver, and a relay. The primary transmitter includes a transmitting coil and a transmitting compensation capacitor connected in series with it. The secondary receiver includes a receiving coil and a receiving compensation capacitor connected in series with it. The relay includes a relay coil and a relay compensation capacitor connected in series with it. The transmitting coil and the relay coil are symmetrically distributed on both sides of the spatial position of the receiving coil, and the relative positions of the transmitting coil and the relay coil remain unchanged.

[0078] Furthermore, the primary-side transmitter also includes a front-end inverter, a voltage regulator capacitor, and an input voltage source;

[0079] The front-end inverter consists of four MOSFETs Q1, Q2, Q3, and Q4, where,

[0080] The source of Q1 is connected to the drain of Q3 to form the first bridge arm; the source of Q2 is connected to the drain of Q4 to form the second bridge arm; the connection point of Q1 and Q3 is connected to one end of the transmitting coil, and the connection point of Q2 and Q4 is connected to the other end of the transmitting coil.

[0081] The positive terminal of the input voltage source is connected to the drain of Q1 and Q2 respectively, and the negative terminal is connected to the source of Q3 and Q4 respectively;

[0082] The voltage regulator capacitor is connected in parallel between the positive and negative terminals of the input voltage source.

[0083] The voltage regulator capacitor stabilizes the input voltage, reducing the impact of voltage fluctuations on inverter operation and ensuring reliable system operation. The input voltage source provides DC power to the upstream inverter. The inverter converts the DC power into high-frequency AC power through the sequential switching of Q1, Q2, Q3, and Q4, which in turn drives the transmitting coil to generate an alternating magnetic field. The current changes in the transmitting and relay coils induce an electromotive force in the receiving coil, enabling wireless power transmission.

[0084] The receiving coil receives high-frequency AC power, which is then rectified and filtered by a resonant circuit composed of receiving compensation capacitors, and converted into stable DC power to provide power support for downstream load equipment.

[0085] The output voltage of the front-end inverter is shown in calculation formula (4);

[0086]

[0087] Among them, U in U is the input voltage. AB This is the output voltage of the front-end inverter.

[0088] Furthermore, the secondary receiving end also includes a rectifier circuit, a filter capacitor, and a resistive load;

[0089] The full-bridge rectifier circuit consists of four rectifier diodes D1, D2, D3, and D4, among which...

[0090] The anode of D1 is connected to the cathode of D3, and the connection point of D1 and D3 serves as the first input terminal of the secondary receiving end; the anode of D2 is connected to the cathode of D4, and the connection point of D2 and D4 serves as the second input terminal of the secondary receiving end; the first input terminal is connected to one end of the receiving coil, and the second input terminal is connected to the other end of the receiving coil; the cathodes of D1 and D2 are simultaneously connected to one end of the filter capacitor and one end of the resistive load; the anodes of D3 and D4 are simultaneously connected to the other end of the filter capacitor and the other end of the resistive load.

[0091] The anode of D1 is connected to the cathode of D3, and their connection point serves as the first input terminal of the secondary receiving end, used to input the alternating current induced at one end of the receiving coil. The anode of D2 is connected to the cathode of D4, and their connection point serves as the second input terminal of the secondary receiving end, used to input the alternating current induced at the other end of the receiving coil. The cathodes of D1 and D2 are connected together to one end of the filter capacitor and one end of the resistive load, forming the positive output path of electrical energy. The anodes of D3 and D4 are connected together to the other end of the filter capacitor and the other end of the resistive load, forming the negative output path of electrical energy.

[0092] The filter capacitor filters the DC current, reducing ripple components in the voltage and making the output voltage smoother and more stable. Finally, the rectified and filtered DC current passes through a resistive load.

[0093] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0094] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A design method for a three-coil wireless power transfer system, characterized in that, Includes the following steps: A three-coil wireless power transmission system is constructed, comprising a primary-side transmitter, a secondary-side receiver, and a repeater. The primary-side transmitter includes a transmitting coil, the secondary-side receiver includes a receiving coil, and the repeater includes a repeater coil. The transmitting coil and the repeater coil are arranged in a non-coplanar symmetrical manner relative to the receiving coil. Set the self-inductance of the transmitting coil, receiving coil, and relay coil so that the mutual inductance values ​​between the transmitting coil and the receiving coil and between the relay coil and the receiving coil are the same, which is the first mutual inductance value. The first mutual inductance value is a variable value. The mutual inductance between the transmitting coil and the repeater coil is a second mutual inductance value, which is a constant value. The range of the first mutual inductance value is determined based on the preset output voltage range and the relationship between the output voltage and the first mutual inductance value.

2. The method according to claim 1, characterized in that, The transmitting coil and relay coil are arranged in a non-coplanar symmetrical manner with the receiving coil, including: The transmitting coil and the relay coil are symmetrically distributed on both sides of the spatial position of the receiving coil, and the relative positions of the transmitting coil and the relay coil remain unchanged.

3. The method according to claim 1, characterized in that, The method further includes: When any coil deviates, the positional relationship between the transmitting coil, the relay coil, and the receiving coil is adjusted synchronously, thereby synchronously adjusting the mutual inductance between the transmitting coil and the receiving coil, as well as the mutual inductance between the relay coil and the receiving coil, so that the first mutual inductance value is kept within the range of the first mutual inductance value.

4. The method according to claim 1, characterized in that, The primary transmitting end also includes a transmitting compensation capacitor connected in series with the transmitting coil; the secondary receiving end also includes a receiving compensation capacitor connected in series with the receiving coil; and the relay end also includes a relay compensation capacitor connected in series with the relay coil; the method further includes: Based on the resonant angular frequency of the three-coil wireless power transmission system, the values ​​of the transmitting compensation capacitor, the relay compensation capacitor, and the receiving compensation capacitor are determined so that the transmitting compensation capacitor, the relay compensation capacitor, and the receiving compensation capacitor satisfy the resonance condition with the corresponding coil.

5. The method according to claim 1, characterized in that, The relationship between the output voltage and the first mutual inductance value is shown in calculation formula (1); Among them, U out U is the output voltage of the three-coil wireless power transfer system. in R is the input voltage of the three-coil wireless power transmission system, A is the first mutual inductance value, B is the second mutual inductance value, and ω is the system resonant angular frequency.

6. The method according to claim 5, characterized in that, The range of the first mutual inductance value is: Where A is the first mutual inductance value, A max Let B be the first maximum mutual inductance, R be the load resistance, B be the second mutual inductance, and ω be the system resonant angular frequency. When A=A max At that time, the output voltage reaches its maximum value.

7. The method according to claim 4, characterized in that, The resonance condition is shown in calculation formula (3); Where L1 is the transmitting coil, L2 is the relay coil, L3 is the receiving coil, C1 is the transmitting compensation capacitor, C2 is the relay compensation capacitor, C3 is the receiving compensation capacitor, and ω is the system resonant angular frequency.

8. A three-coil wireless power transmission system, characterized in that, The system includes: The device comprises a primary transmitter, a secondary receiver, and a relay. The primary transmitter includes a transmitting coil and a transmitting compensation capacitor connected in series with it. The secondary receiver includes a receiving coil and a receiving compensation capacitor connected in series with it. The relay includes a relay coil and a relay compensation capacitor connected in series with it. The transmitting coil and the relay coil are symmetrically distributed on both sides of the spatial position of the receiving coil, and the relative positions of the transmitting coil and the relay coil remain unchanged.

9. The system according to claim 8, characterized in that, The primary-side transmitter also includes a front-end inverter, a voltage regulator capacitor, and an input voltage source; The front-end inverter consists of four MOSFETs Q1, Q2, Q3, and Q4, where, The source of Q1 is connected to the drain of Q3 to form the first bridge arm; the source of Q2 is connected to the drain of Q4 to form the second bridge arm; the connection point of Q1 and Q3 is connected to one end of the transmitting coil, and the connection point of Q2 and Q4 is connected to the other end of the transmitting coil. The positive terminal of the input voltage source is connected to the drain of Q1 and Q2 respectively, and the negative terminal is connected to the source of Q3 and Q4 respectively; The voltage regulator capacitor is connected in parallel between the positive and negative terminals of the input voltage source.

10. The system according to claim 9, characterized in that, The secondary receiving end also includes a rectifier circuit, a filter capacitor, and a resistive load; The full-bridge rectifier circuit consists of four rectifier diodes D1, D2, D3, and D4, among which... The anode of D1 is connected to the cathode of D3, and the connection point of D1 and D3 serves as the first input terminal of the secondary receiving end; the anode of D2 is connected to the cathode of D4, and the connection point of D2 and D4 serves as the second input terminal of the secondary receiving end; the first input terminal is connected to one end of the receiving coil, and the second input terminal is connected to the other end of the receiving coil. The cathodes of D1 and D2 are both connected to one end of the filter capacitor and one end of the resistive load; the anodes of D3 and D4 are both connected to the other end of the filter capacitor and the other end of the resistive load.

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