Low-voltage, high-current, three-stage scalable wireless power transmission circuit and control method

Abstract

The present invention discloses a low-voltage, high-current, three-stage, scalable wireless power transmission circuit and control method. The power transmission circuit includes an input stage, a coil stage, and an output stage, wherein the input stage includes multiple inverter modules and corresponding input transformer modules; the coil stage includes a coil module and a corresponding coil compensation network; and the output stage includes multiple rectifier modules and corresponding output transformer modules. The above technical solution can achieve high-power transmission in high-aspect-ratio, low-voltage, and high-current environments, effectively reducing the current stress of switching devices and improving circuit reliability, scalability, and versatility. The coupling of coil modules on the same side does not affect system power transmission, and there is no need to consider the cross-coupling problem of parallel coil modules. The input transformer module and the output transformer module can not only achieve electrical isolation and voltage gain adjustment, but also achieve natural current sharing between the input-stage inverter module and the output-stage rectifier module.

Description

Technical Field

[0001] The present invention relates to wireless power transmission technology, and in particular to a low-voltage, high-current, three-stage expandable wireless power transmission circuit and a control method. Background Art

[0002] The rapid development of power devices and electronic technology is driving the rapid adoption of new energy sources. In recent years, the development of new energy vehicles, multi-electric aircraft, and all-electric aircraft has also led to the emergence of numerous novel architectures and theories in the field of power applications. Wireless power transmission, as an emerging power transmission method, has become a research hotspot due to its safety and convenience. Replacing traditional wired power transmission with wireless methods will significantly improve the flexibility and reliability of power supply systems.

[0003] In low-voltage, high-current wireless power delivery applications, high current stress on both input and output devices poses challenges to device selection and system reliability. To reduce coil size and increase transmission distance, the coil's pitch-to-diameter ratio (the ratio of transmission distance to the coil's maximum side length or diameter) should be maximized. However, when the pitch-to-diameter ratio is high, the inter-coil coupling coefficient and coil-level voltage gain are low. This leads to high voltage and current stress on the coil and its compensation components, as well as high conduction losses in the coil branches, during high-power transmission. This reduces efficiency and reliability, making parameter optimization difficult. Summary of the Invention

[0004] Purpose of the invention: The present invention provides a low-voltage, high-current, three-stage expandable wireless power transmission circuit and control method. The multi-module parallel wireless power transmission circuit architecture can realize high-power transmission in high-aspect ratio, low-voltage, high-current situations. The input and output stages use multiple modules in parallel to effectively reduce the current stress of the switching device. The modular design effectively improves the circuit reliability, scalability and versatility; the coil-level multi-module parallel connection can effectively reduce the voltage and current stress of the coil and its compensation element, facilitates the coil parameter design, and improves efficiency. The parallel structure of the coil level makes the coupling of the coil modules on the same side not affect the system power transmission, so there is no need to consider the cross-coupling problem of the parallel coil modules; the input-stage transformer module and the output-stage transformer module can not only realize electrical isolation and voltage gain adjustment, but also realize natural current sharing of the input-stage inverter module and the output-stage rectifier module.

[0005] Technical solution: The present invention provides a low-voltage, high-current, three-stage scalable wireless power transmission circuit, including: an input stage, a coil stage, and an output stage, wherein: the input stage includes multiple inverter modules and corresponding multiple input transformer modules; each inverter module is respectively connected to the voltage input terminal and the input side of the corresponding input transformer module, and the input transformer module is connected in series on the output side; the coil stage includes a transmitting coil module and a corresponding transmitting coil compensation network on the transmitting side of the coil stage, and a receiving coil module and a corresponding receiving coil compensation network on the receiving side of the coil stage, the transmitting coil module includes multiple layers of transmitting coils, the transmitting coil compensation network includes a resonant cavity and a transmitting compensation capacitor corresponding to each layer of transmitting coils, the receiving coil module includes multiple layers of receiving coils, and the receiving coil compensation network includes a receiving coil corresponding to each layer of receiving coils. receiving compensation capacitors; one end of each layer of transmitting coils is connected in series with the corresponding transmitting compensation capacitors and then connected in parallel to the first transmitting connection point, the other end of each layer of transmitting coils is connected to the second transmitting connection point, the first transmitting connection point and the second transmitting connection point are connected to the resonant cavity, and the resonant cavity is connected to the two ends of the output side of the series-connected input transformer module; one end of each layer of receiving coils is connected in series with the corresponding receiving compensation capacitors and then connected in parallel to the first receiving connection point, the other end of each layer of transmitting coils is connected to the second receiving connection point, the first receiving connection point and the second receiving connection point are respectively connected to the two ends of the input side of the series-connected output transformer module; the output stage includes multiple rectifier modules and corresponding multiple output transformer modules; each rectifier module is respectively connected to the voltage output end and the output side of the corresponding output transformer module, and the output transformer modules are connected in series on the input side.

[0006] Specifically, the common LC resonant cavity includes a resonant inductor and a resonant capacitor, the two ends of the resonant capacitor are connected to the first emission connection point and the second emission connection point respectively, one end of the resonant inductor is connected to one end of the output side of the series-connected input transformer module, and the other end of the resonant inductor is connected to the first emission connection point.

[0007] Specifically, the transmitting coil and the receiving coil are square planar coils.

[0008] Specifically, the transmitting coil and the receiving coil use Litz wire, and are wound from the outermost turn to the innermost turn.

[0009] Specifically, magnetic cores are laid on the outermost layers of the transmitting coil and the receiving coil.

[0010] Specifically, the pitch-to-diameter ratio is 0.8 to 1.2.

[0011] Specifically, the inverter module adopts a full-bridge inverter circuit topology, and the rectifier module adopts an active bridge rectifier circuit topology.

[0012] The present invention also provides a control method for a three-stage expandable wireless power transmission circuit, which adopts the low-voltage, high-current three-stage expandable wireless power transmission circuit described in any one of the above items of the present invention, including: when the output voltage of the voltage output end is higher than the rated voltage, adjusting the internal phase shift angle of the input-stage inverter bridge to perform voltage regulation; the inverter bridge refers to a structure composed of all inverter modules; when the output voltage of the voltage output end is lower than the rated voltage, adjusting the internal phase shift angle of the output-stage rectifier bridge to perform voltage regulation; the rectifier bridge refers to a structure composed of all rectifier modules.

[0013] Specifically, by adjusting the transmitting compensation capacitor and the receiving compensation capacitor respectively, the impedance of different coil branches on the same side is adjusted to reduce the circulating current between the coils.

[0014] Specifically, the resonance conditions of the transmitting coil compensation network are as follows:

[0015] ω s L f =1 / ω s C f =ω s L eq-total ,

[0016] Among them, ω s Represents the resonant angular frequency, L f Represents the resonant inductance, C f Represents the resonant capacitance, L eq-total Indicates the equivalent inductance of the transmitting coil module and the transmitting compensation capacitor;

[0017] The resonance conditions of the receiving coil compensation network are as follows:

[0018] ω s L eq-sm =1 / ω s C sm , L eq-sm =L sm +∑ M i＝1，i≠m M mi ,

[0019] Among them, L eq-sm Represents the equivalent inductance of the receiving coil module, C sm Indicates the receiving coil L of the mth layer sm The corresponding receiving compensation capacitor, M mi represents the mutual inductance between the m-th layer receiving coil and the i-th layer receiving coil, m = 1, 2, ..., M.

[0020] Beneficial effects: Compared with the existing technology, the present invention has the following significant advantages: it realizes high-power transmission in high-aspect ratio, low-voltage and high-current situations, effectively reduces the current stress of switching devices, improves circuit reliability, scalability and versatility, the coupling of coil modules on the same side does not affect the power transmission of the system, and there is no need to consider the cross-coupling problem of parallel coil modules. The input transformer module and the output transformer module can not only realize electrical isolation and voltage gain adjustment, but also realize natural current sharing of the input-stage inverter module and the output-stage rectifier module. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the system architecture of a three-stage scalable wireless power transmission circuit provided by the present invention;

[0022] Figure 2 A schematic diagram of the stacked structure of the transmission coil provided by the present invention;

[0023] Figure 3 This is a control schematic diagram of the dual-module parallel architecture provided by the present invention;

[0024] Figure 4 A topological diagram of a dual-module parallel circuit provided by the present invention;

[0025] FIG5(a) and FIG5(b) are respectively system control waveform diagrams provided by the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0027] See Figure 1 , which is a schematic diagram of the system architecture of the three-stage scalable wireless power transmission circuit provided by the present invention.

[0028] The present invention provides a low-voltage, high-current, three-stage scalable wireless power transmission circuit, comprising: an input stage, a coil stage, and an output stage, wherein: the input stage comprises a plurality of inverter modules and a corresponding plurality of input transformer modules; each inverter module is respectively connected to a voltage input terminal and an input side of a corresponding input transformer module, and the input transformer modules are connected in series on the output side; the coil stage comprises a transmitting coil module and a corresponding transmitting coil compensation network on the transmitting side of the coil stage, and a receiving coil module and a corresponding receiving coil compensation network on the receiving side of the coil stage, wherein the transmitting coil module comprises multiple layers of transmitting coils, the transmitting coil compensation network comprises a resonant cavity and a transmitting compensation capacitor corresponding to each layer of transmitting coils, the receiving coil module comprises multiple layers of receiving coils, and the receiving coil compensation network comprises a receiving compensation capacitor corresponding to each layer of receiving coils; One end of each layer of transmitting coil is connected to the corresponding transmitting compensation capacitor and then connected in parallel to the first transmitting connection point, the other end of each layer of transmitting coil is connected to the second transmitting connection point, the first transmitting connection point and the second transmitting connection point are connected to the common LC resonant cavity, and the common LC resonant cavity is connected to the two ends of the output side of the input transformer module connected in series; one end of each layer of receiving coil is connected to the corresponding receiving compensation capacitor and then connected in parallel to the first receiving connection point, the other end of each layer of transmitting coil is connected to the second receiving connection point, the first receiving connection point and the second receiving connection point are respectively connected to the two ends of the input side of the output transformer module connected in series; the output stage includes multiple rectifier modules and corresponding multiple output transformer modules; each rectifier module is respectively connected to the voltage output end and the output side of the corresponding output transformer module, and the output transformer modules are connected in series on the input side.

[0029] In an embodiment of the present invention, the common LC resonant cavity includes a resonant inductor and a resonant capacitor, where the two ends of the resonant capacitor are respectively connected to the first emission connection point and the second emission connection point, one end of the resonant inductor is connected to one end of the output side of the series-connected input transformer module, and the other end of the resonant inductor is connected to the first emission connection point.

[0030] In the embodiment of the present invention, the inverter module adopts a full-bridge inverter circuit topology, and the rectifier module adopts an active bridge rectifier circuit topology.

[0031] In a specific implementation, the input stage consists of N inverter modules and N input transformer modules. The coil stage consists of a transmitting coil module including M layers of transmitting coils and their compensation network, and a receiving coil module including M layers of receiving coils and their compensation network. The transmitting side uses an LCCL compensation network, and the receiving side uses an LC compensation network. These networks have the characteristics of constant current in the transmitting coil and constant voltage output on the receiving side, meaning that both the transmitting coil current and the receiving side output voltage are independent of the load. The output stage consists of N rectifier modules and N output transformer modules. The input stage is connected to the coil stage, and the coil stage is connected to the output stage via transformers. The input transformer module T inThe input side is connected to the inverter module in parallel, and then connected in series on the output side to the coil-level LCCL compensation network. The input-level inverter module naturally shares the current, where n = 1, 2, ..., N, and the output transformer module T on After being connected in series on the input side, it is connected to the coil-level LC compensation network, and after being connected to the rectifier module on the output side, it is connected in parallel. The output-level rectifier module naturally shares the current.

[0032] In a specific implementation, the coil-level input-side LCCL compensation network includes a resonant inductor L f , resonant capacitor C f , transmitting coil L pm and its series compensation capacitor C pm , where m=1,2,…,M, the coil-level transmitting side shares a common L f and C f The common LC resonant cavity composed of the transmitting coil L pm The corresponding compensation capacitor C pm After the series connection, the parallel connection is connected to the common LC resonant cavity. The LC compensation network includes the receiving coil L sm and its series compensation capacitor C sm , and the receiving coil L sm The corresponding compensation capacitor C sm After being connected in series and then in parallel, the low-voltage DC power supply is boosted by the input-stage inverter module and the input-stage transformer as the coil-stage AC input voltage u p , the alternating current generates an induced voltage on the receiving side, which is then converted into the coil-level output voltage u after passing through the LC compensation network. s , and then the output stage transformer steps down the voltage and the output stage rectifier module to supply power to the load, which includes but is not limited to drones, electric vehicles, industrial robots, etc.

[0033] See Figure 2 , which is a schematic diagram of the stacked structure of the transmission coil provided by the present invention.

[0034] In an embodiment of the present invention, the transmitting coil and the receiving coil are square planar coils, and the transmitting coil and the receiving coil are made of Litz wire. The winding method is from the outermost turn to the inside. A magnetic core is laid on the outermost layer of the transmitting coil and the receiving coil, and the pitch-to-diameter ratio is 0.8 to 1.2.

[0035] In a specific implementation, both the transmitting coil module and the receiving coil module use square planar coils with strong anti-offset characteristics. In order to reduce the influence of the skin effect at high frequencies, Litz wire is selected and wound tightly from the outermost turn to the inside. In a specific embodiment of the present invention, the side length of the coil module is 30 cm, the distance between the first layer of transmitting coils and the first layer of receiving coils is 30 cm, the distance to diameter ratio is 1, and the coupling coefficient is 0.037. The coil modules on the same side are stacked from the inside to the outside, and a magnetic core can be laid on the outermost layer to constrain the magnetic field and increase the self-inductance of the coil, thereby indirectly increasing the mutual inductance. Taking into account the coil wire diameter and layer thickness, as the number of stacked coil modules increases, the coupling coefficient between the outer coils gradually decreases, and the system weight and cost increase accordingly. Therefore, it is necessary to compromise the design of the number of coil modules based on the actual application scenario.

[0036] The present invention also provides a control method for the low-voltage, high-current, three-stage expandable wireless power transmission circuit provided by the present invention, including: when the output voltage of the voltage output end is higher than the rated voltage, adjusting the internal phase shift angle of the input-stage inverter bridge to perform voltage regulation; the inverter bridge refers to a structure composed of all inverter modules; when the output voltage of the voltage output end is lower than the rated voltage, adjusting the internal phase shift angle of the output-stage rectifier bridge to perform voltage regulation; the rectifier bridge refers to a structure composed of all rectifier modules.

[0037] In the embodiment of the present invention, the impedances on different coils on the same side are adjusted by adjusting the transmitting compensation capacitor and the receiving compensation capacitor respectively, thereby reducing the circulating current between the coils.

[0038] In the embodiment of the present invention, the resonance conditions of the transmitting coil compensation network are as follows:

[0039] ω s L f =1 / ω s C f =ω s L eq-total ,

[0040] Among them, ω s Represents the resonant angular frequency, L f Represents the resonant inductance, C f Represents the resonant capacitance, L eq-total Indicates the equivalent inductance of the transmitting coil module and the corresponding transmitting compensation capacitor connected in series and then in parallel;

[0041] The resonance conditions of the receiving coil compensation network are as follows:

[0042] ω s L eq-sm =1 / ω s C sm , L eq-sm =L sm +∑ Mi＝1，i≠m M mi ,

[0043] Among them, L eq-sm Represents the equivalent inductance of the receiving coil module, C sm Indicates the receiving coil L of the mth layer sm The corresponding receiving compensation capacitor, M mi represents the mutual inductance between the m-th layer receiving coil and the i-th layer receiving coil, m = 1, 2, ..., M.

[0044] In the specific implementation, by adjusting the coil series compensation capacitor C pm and C sm To balance the impedance of different coil branches on the same side, thereby reducing or even eliminating the circulating current between different coil modules on the same side, so there is no need to consider the cross-coupling problem between the coils of the modules on the same side.

[0045] See Figure 3 , which is a control schematic diagram of the dual-module parallel architecture provided by the present invention.

[0046] In the specific implementation, the input-stage inverter module uses a full-bridge inverter circuit topology, the coil stage employs an LCCL-LC compensation network, and the output-stage rectifier module uses an active bridge rectifier circuit topology. The number of input-stage inverter modules, the number of parallel coil modules at the coil stage, the number of output-stage rectifier modules, and the number of input-stage and output-stage transformers are all two.

[0047] In the specific implementation, the closed-loop control strategy adopted by the circuit is phase-shift control, in which the two inverter modules of the input stage are exactly the same, and their control timing is exactly the same; the two rectifier modules of the output stage are exactly the same, so their control timing is also exactly the same. Due to the characteristics of the coil-level LCCL-LC compensation network, the coil-level input voltage u p The fundamental component U p and coil level output voltage u s The fundamental component U s In phase, it is necessary to fix the external phase shift angle of the input stage inverter bridge and the output stage rectifier bridge, and adjust the output voltage by adjusting their internal phase shift angles. The specific description is:

[0048] (1) When the output voltage of the circuit output terminal is higher than the rated voltage (U o ≥U rated ), the output stage rectifier bridge phase shift angle is zero, adjust the input stage inverter bridge internal phase shift angle θ i To adjust the output voltage;

[0049] (2) When the output voltage at the circuit output terminal is lower than the rated voltage (U o rated ​), the phase-shifting angle of the input-stage inverter bridge is zero, and the internal phase-shifting angle θ of the output-stage rectifier bridge is adjusted o to adjust the output voltage.

[0050] In specific implementation, compared with the traditional single-sided internal phase-shifting control method, the above control method can not only broaden the voltage regulation range, but also increase the soft-switching range of the system and reduce the switching loss.

[0051] Refer to Figure 4 , which is the topology diagram of the dual-module parallel circuit provided by the present invention.

[0052] In specific implementation, U in and U o are the input power supply voltage and the output load voltage respectively, and Q i1 ~Q i4 and Q i5 ~Q i8 respectively constitute two full-bridge inverter modules of the input stage, and T i1 and T i2 are the input-stage transformer modules. u p is the coil-level input voltage, and its fundamental component is U p ; u s is the coil-level output voltage, and its fundamental component is U s . The coil level adopts an LCCL-LC compensation network, and L f and C f are the resonant inductor and the resonant capacitor respectively. The self-inductances of the transmitting coil and the receiving coil are L pi , L si (i = 1, 2) respectively, and their respective series compensation capacitors are C pi , C si (i = 1, 2) respectively. M jk (j = 1, 2, 3; k = 2, 3, 4; j < k) are the mutual inductances between the four coils respectively. The C pi on the transmitting side is connected in series with L pi and then in parallel. The C si on the receiving side is connected in series with L si and then in parallel. By adjusting C pi and C si to adjust the coil branch impedance to equalize the coil current and reduce or even eliminate the circulating current between the coils. Therefore, the coupling between the same-side coils does not affect the system power transmission. R pi and R si are the parasitic resistances in the corresponding coil branches respectively, including the coil parasitic resistance and the compensation capacitor parasitic resistance. T o1 and T o2 are the output transformer modules, and Q o1 ~Q o4 and Q o5 ~Qo8 The two active bridge rectifier modules constitute the output stage respectively. The coil-level output voltage passes through the rectifier module and capacitor C o After filtering, the load is supplied with power.

[0053] Refer to FIG5(a) and FIG5(b), which are waveform diagrams of system control provided by the present invention.

[0054] In the specific implementation, since the control of the same modules is exactly the same, only the waveform of a single module is given here. Figure 5(a) is U o ≥U rated The waveform of the phase shift angle in the input stage inverter module is adjusted when U o rated The waveform of the phase shift angle in the output stage rectifier module is adjusted when the output stage rectifier module is turned on. Here, Figure 5(a) is used as an example for a brief description. Figure 5(a) shows U o ≥U rated The inverter module and rectifier module drive voltage timing diagram and the coil level input voltage and output voltage waveform diagram, when the circuit is in a fully resonant state, according to the characteristics of the LCCL-LC compensation network, U p and U s The phase is consistent. At this time, the phase shift angle of the output stage rectifier module is zero, that is, u s The output stage inverter module adopts internal phase shift control, that is, adjusting the leading bridge arm (by Q i1 and Q i3 ) and the lagging bridge arm (composed of Q i2 and Q i4 The phase difference of the composition) is controlled while ensuring that U p and U s The phase is consistent, and the same is true for Figure 5(b).​

Claims

1. A low-voltage, high-current, three-stage scalable wireless power transmission circuit, characterized in that: include: Input stage, coil stage, and output stage, where: The input stage includes multiple inverter modules and corresponding multiple input transformer modules; each inverter module is respectively connected to the voltage input terminal and the input side of the corresponding input transformer module, and the input transformer modules are connected in series on the output side; The coil level includes a transmitting coil module and a corresponding transmitting coil compensation network on the transmitting side of the coil level, and a receiving coil module and a corresponding receiving coil compensation network on the receiving side of the coil level. The transmitting coil module includes multiple layers of transmitting coils, and the transmitting coil compensation network includes a common LC resonant cavity and a transmitting compensation capacitor corresponding to each layer of transmitting coils. The receiving coil module includes multiple layers of receiving coils, and the receiving coil compensation network includes a receiving compensation capacitor corresponding to each layer of receiving coils. One end of each layer of transmitting coil is connected in series with the corresponding transmitting compensation capacitor and then connected in parallel to the first transmitting connection point. The other end of each layer of transmitting coil is connected to the second transmitting connection point. The first transmitting connection point and the second transmitting connection point are connected to the A common LC resonant cavity is connected, and the common LC resonant cavity is connected to the two ends of the output side of the series-connected input transformer module; one end of each layer of receiving coil is connected in series with the corresponding receiving compensation capacitor and then connected in parallel to the first receiving connection point, and the other end of each layer of transmitting coil is connected to the second receiving connection point, and the first receiving connection point and the second receiving connection point are respectively connected to the two ends of the input side of the series-connected output transformer module; the common LC resonant cavity includes a resonant inductor and a resonant capacitor, and the two ends of the resonant capacitor are respectively connected to the first transmitting connection point and the second transmitting connection point, one end of the resonant inductor is connected to one end of the output side of the series-connected input transformer module, and the other end of the resonant inductor is connected to the first transmitting connection point; The output stage includes multiple rectifier modules and corresponding multiple output transformer modules; each rectifier module is respectively connected to the voltage output end and the output side of the corresponding output transformer module, and the output transformer modules are connected in series on the input side.

2. The low-voltage, high-current, three-stage scalable wireless power transmission circuit according to claim 1, characterized in that: The transmitting coil and the receiving coil are square planar coils.

3. The low-voltage, high-current, three-stage scalable wireless power transmission circuit according to claim 2, characterized in that: The transmitting coil and receiving coil use Litz wire, and the winding method is from the outermost turn to the inner part.

4. The low-voltage, high-current, three-stage scalable wireless power transmission circuit according to claim 3, characterized in that: A magnetic core is laid on the outermost layer of the transmitting coil and the receiving coil.

5. The low-voltage, high-current, three-stage scalable wireless power transmission circuit according to claim 4, characterized in that: The pitch-to-diameter ratio is 0.8 to 1.

2.

6. The low-voltage, high-current, three-stage scalable wireless power transmission circuit according to claim 1, characterized in that: The inverter module adopts a full-bridge inverter circuit topology, and the rectifier module adopts an active bridge rectifier circuit topology.

7. A control method for a three-stage scalable wireless power transmission circuit, characterized in that: The low-voltage, high-current, three-stage scalable wireless power transmission circuit according to any one of claims 1 to 6 comprises: When the output voltage at the output end of the circuit is higher than the rated voltage, the internal phase shift angle of the input stage inverter bridge is adjusted to adjust the voltage; the inverter bridge refers to the structure composed of all inverter modules; When the output voltage at the output end of the circuit is lower than the rated voltage, the internal phase shift angle of the output stage rectifier bridge is adjusted to adjust the voltage; the rectifier bridge refers to the structure composed of all rectifier modules.

8. The control method of the three-stage scalable wireless power transmission circuit according to claim 7, wherein: By adjusting the transmitting compensation capacitor and the receiving compensation capacitor respectively, the impedance of different coil branches on the same side is adjusted to reduce the circulating current between the coils.

9. The control method of the three-stage scalable wireless power transmission circuit according to claim 8, wherein: The resonance conditions of the transmitting coil compensation network are as follows: oh s L f =1 / h s C f =ω s L eq-total , Among them, ω s Represents the resonant angular frequency, L f Represents the resonant inductance, C f Represents the resonant capacitance, L eq-total Indicates the equivalent inductance of the transmitting coil module and the corresponding transmitting compensation capacitor connected in series and then in parallel; The resonance conditions of the receiving coil compensation network are as follows: oh s L eq-sm =1 / h s C sm ,L eq-sm =L sm +∑ M i=1，i≠m M mi , Among them, L eq-sm Represents the equivalent inductance of the receiving coil module, C sm Indicates the receiving coil L of the mth layer sm The corresponding receiving compensation capacitor, M mi represents the mutual inductance between the m-th layer receiving coil and the i-th layer receiving coil, m=1,2,…,M.

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