Electric field coupling type wireless electric energy transmission system without compensation inductor on receiving side

Abstract

The invention discloses an electric field coupling type wireless electric energy transmission system without a compensation inductor on a receiving side. The system adopts a high-order matching network design and has a unilateral compensation characteristic, a compensation inductance element is not needed at a receiving side, the size of the receiving side is remarkably reduced, and the structural light weight of the receiving side is realized. The high-order matching network adopts multi-stage T-type resonance network cascading, so that input impedance is ensured to be pure resistive, and constant current or constant voltage output irrelevant to a load is realized according to stage parity. The overall gain distribution of the system is optimized by taking the transmission efficiency as an optimization target and taking the voltage stress of the coupling pole plate and the current stress of the resonance compensation element as constraint conditions, so that the transmission efficiency of the system is maximized under the fixed transmission gain.

Description

Technical Field

[0001] The present invention belongs to the field of wireless power transmission technology, and in particular relates to an electric field coupling wireless power transmission system without compensation inductance at the receiving side. Background Art

[0002] As a new type of power transmission method, wireless power transmission technology has the advantages of safety, reliability and convenience, and has gradually become a method to replace traditional wired charging. The capacitive wireless power transfer (CPT) system has been widely used in low-power applications such as implanted biomedical devices and consumer electronics due to its advantages such as light, thin and low-cost coupling mechanism, and the coupling electric field is not easy to generate eddy current loss in the adjacent metal. The design of the compensation circuit is crucial to improving the performance of CPT and achieving specific output characteristics. Most electronic devices are powered by lithium batteries. During the actual charging process of lithium batteries, the equivalent resistance of lithium batteries changes. In order to ensure the safety, durability and performance of the battery, the system needs to have constant current (CC) and constant voltage (CV) output characteristics that are independent of the load. The operating frequency of the CPT system is relatively high, generally at the MHz level. The inductor components in the traditional bilateral compensation network need to use high-frequency magnetic cores or air-core inductors. The high-frequency magnetic core has large losses and heavy weight. The relative permeability of the air-core inductor is low, which will cause the volume of the compensation inductor to increase, and increase the volume and cost of the receiving end. In addition, due to the low order of the compensation network and the low degree of design freedom, it is difficult to achieve high transmission efficiency while achieving constant output. Therefore, it is of great research significance to design an electric field coupled wireless power transmission system without compensation inductor on the receiving side. Summary of the invention

[0003] The purpose of the present invention is to design an electric field coupling wireless power transmission system without compensation inductance on the receiving side. To achieve the above purpose, the technical solution adopted by the present invention is:

[0004] The electric field coupling type wireless power transmission system without compensation inductor at the receiving side comprises: a high-frequency full-bridge inverter circuit composed of four metal oxide semiconductor field effect transistors; a high-order matching network composed of N-level LC series-parallel resonant circuits as a primary side high-order compensation circuit, wherein X Sm (m=1,2,...,n) and X Pm (m=1,2,...,n) represents the reactance of the resonant elements in the series and parallel branches respectively; the capacitive coupler of two emitter plates and two receiver plates; the rectifier circuit composed of four diodes and the load resistor R LThe left side of the primary high-order compensation circuit is connected to the high-frequency full-bridge inverter circuit, and the right side of the primary high-order compensation circuit is connected to the two emitter plates of the capacitor coupler. The two receiving plates of the capacitor coupler are connected to the load resistor R after passing through the rectifier circuit. L The series resonant element in the matching network is further modeled as two compensation elements X mT1 (m=1,2,...,n) and X (m+1)T3 (m=1,2,...,n) are connected in series, so the high-order matching network is regarded as a cascade of N-stage T-type resonant networks. The input voltage of the high-frequency full-bridge inverter circuit is V dc The effective value of the fundamental component of the output voltage of the high-frequency full-bridge inverter circuit is U s1 The equivalent excitation voltage source model of the capacitive coupler includes the equivalent self-capacitance C on the emitter plate side. α , the equivalent self-capacitance C on the receiving plate side β , the excitation voltage source V on the emitter plate side α , the excitation voltage source V on the receiving plate side β , where V α =I β / jωC M ,V β =I α / jωC M ,ω is the resonant angular frequency of the system, C M is the mutual capacitance of the capacitive coupler, I α and I β are the voltage on the emitter plate side and the current on the receiving plate side of the capacitive coupler, I 1 , I 2 …I n are the currents in each branch, I o and U o is the system’s AC output current and output voltage, I L and U L are the DC output current and output voltage of the system.

[0005] The schematic diagram of the design of an electric field coupling type wireless power transmission system without compensation inductance on the receiving side includes two parts: a high-order matching network and a coupling mechanism equivalent voltage source model. The basic principle of system parameter design is: the high-order matching network is regarded as a cascade of N-stage T-type resonant circuits, wherein the first-stage T-type resonant circuit, the coupling mechanism equivalent voltage source model, and the load are analyzed for resonance conditions as a whole, and the second to N-stage T-type resonant circuits are analyzed for resonance conditions as a whole; wherein, X mT1 ,X mT2 ,X mT3 (m=1,2,3…,n) respectively represent the reactance of the three resonant elements of the m-th level T-type resonant circuit; input voltage Us1 After the Nth stage T-type resonant circuit, a constant current output I is obtained. n-1 , and then through the N-1th level T-type resonant circuit to obtain a constant voltage output U n-2 , and so on, finally after passing through the first stage T-type resonant circuit, the constant current output I is obtained. o Or constant voltage output U o The specific output characteristics are determined by the number of stages N. When N is an odd number, the system has a constant current output, and when N is an even number, the system has a constant voltage output. After each resonant circuit meets the resonance condition, the equivalent input impedance is resistive, so the overall equivalent input impedance of the system is resistive.

[0006] When the number of resonant network stages N is an odd number, the resonance condition is met:

[0007]

[0008] At this time, the system has a constant current output, and the equivalent input impedance of the system is Z inn Purely resistive:

[0009]

[0010] The overall transmission gain of the system is G i-u for:

[0011]

[0012] When the number of resonant network stages N is an even number, the resonance condition is met:

[0013]

[0014] At this time, the system has a constant voltage output, and the equivalent input impedance of the system is Z inn Purely resistive:

[0015]

[0016] The overall transmission gain of the system is G u-u for:

[0017]

[0018] At this time I α ,I m (m=1,2,...,n) is:

[0019]

[0020]

[0021] The efficiency η of the system is:

[0022]

[0023] When the resonance conditions are met, since the input impedance of each stage of the T-type resonant network is purely resistive and has the characteristic of converting a constant voltage source / constant current source into a constant current source / constant voltage source, the overall resonant network can have a purely resistive input impedance, reducing the flow of reactive power in the system and improving system efficiency. Therefore, a high-order compensation network with multiple-stage T-type resonant networks in cascade can be used as the compensation topology of the primary side of the system.

[0024] In order to maximize the system transmission efficiency under fixed gain, it is necessary to determine the parameters of each stage of T-type matching network compensation components. At this time, the overall gain of the system G set As the equality constraint, the efficiency function of the system is used as the objective function to establish the Lagrangian function. At the same time, the voltage stress U on the plate is α and the current stress I flowing through the component m As a constraint, the specific value of each compensation component parameter is further determined. When the number of system resonant network stages is an odd number, the parameters of each stage of the T-type compensation network must meet the following requirements:

[0025]

[0026] In order to meet the voltage stress U α and the current I on the compensation element m Not exceeding the design range, the following conditions must be met:

[0027]

[0028] |I m |<I Tmax (12)

[0029] Similarly, when the number of system resonant network levels is an even number, it must satisfy:

[0030]

[0031] |I m |<I Tmax (15)

[0032] When the size of the capacitive coupler and the input-output gain power of the system are determined, the parameters of each component in the compensation network can be determined through the above-mentioned resonance conditions and constraints.

[0033] Through the above parameter design, since there is no compensating inductance element on the receiving side of the system, the volume of the receiving side of the system is reduced, and the lightweight design of the system is achieved. Through reasonable parameter design and gain distribution, the technical effect of maximizing the system transmission efficiency under the condition of constant output characteristics of the system is achieved.

[0034] Compared with the prior art, the present invention has the following significant advantages: the receiving side of the electric field coupling wireless power transmission system of the present invention does not require compensation inductance, which reduces the volume of the receiving side of the system, and maximizes the system transmission efficiency through reasonable compensation network parameter design.

[0035] The following is a detailed description with reference to the accompanying drawings in conjunction with embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The topology structure of an electric field coupling wireless power transmission system without compensation inductance on the receiving side using a high-order matching network;

[0037] Figure 2 An excitation voltage source model for an electric field coupled wireless power transmission system without compensation inductance on the receiving side using a high-order matching network;

[0038] Figure 3 The circuit topologies designed by the present design method each have constant output current characteristics;

[0039] Figure 4 The circuit topologies designed by the present design method each have constant output voltage characteristics;

[0040] Figure 5 The relationship between the load output current and voltage of the electric field coupling wireless power transmission system without compensation inductance on the receiving side and the change of the load resistance; DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0042] like Figure 1 As shown, the electric field coupling type wireless power transmission system without compensation inductor on the receiving side includes: a high-frequency full-bridge inverter circuit composed of four metal oxide semiconductor field effect transistors; a high-order matching network composed of N-level LC series-parallel resonant circuits as a primary side high-order compensation circuit, wherein X Sm (m=1,2,...,n) and X Pm (m=1,2,...,n) represents the reactance of the resonant elements in the series and parallel branches respectively; the capacitive coupler of two emitter plates and two receiver plates; the rectifier circuit composed of four diodes and the load resistor R L The left side of the primary high-order compensation circuit is connected to the high-frequency full-bridge inverter circuit, and the right side of the primary high-order compensation circuit is connected to the two emitter plates of the capacitor coupler. The two receiving plates of the capacitor coupler are connected to the load resistor R after passing through the rectifier circuit. L The series resonant element in the matching network is further modeled as two compensation elements X mT1(m=1,2,...,n) and X (m+1)T3 (m=1,2,...,n) are connected in series, so the high-order matching network is regarded as a cascade of N-stage T-type resonant networks. The input voltage of the high-frequency full-bridge inverter circuit is V dc The effective value of the fundamental component of the output voltage of the high-frequency full-bridge inverter circuit is U s1 , the equivalent excitation voltage source model of the capacitive coupler includes the equivalent self-capacitance C on the emitter plate side α , the equivalent self-capacitance C on the receiving plate side β , the excitation voltage source V on the emitter plate side α , the excitation voltage source V on the receiving plate side β , where V α =I β / jωC M ,V β =I α / jωC M ,ω is the resonant angular frequency of the system, C M is the mutual capacitance of the capacitive coupler, I α and I β are the voltage on the emitter plate side and the current on the receiving plate side of the capacitive coupler, I 1 , I 2 …I n are the currents in each branch, I o and U o is the system’s AC output current and output voltage, I L and U L are the DC output current and output voltage of the system.

[0043] like Figure 2 As shown, the schematic diagram of the design of the electric field coupling type wireless power transmission system without compensation inductance on the receiving side includes two parts: a high-order matching network and a coupling mechanism equivalent voltage source model. The basic principle of system parameter design is: the high-order matching network is regarded as a cascade of N-stage T-type resonant circuits, wherein the first-stage T-type resonant circuit, the coupling mechanism equivalent voltage source model, and the load are analyzed for resonance conditions as a whole, and the second to N-stage T-type resonant circuits are analyzed for resonance conditions as a whole; wherein, X mT1 ,X mT2 ,X mT3 (m=1,2,3…,n) respectively represent the reactance of the three resonant elements of the m-th level T-type resonant circuit; input voltage U s1 After the Nth stage T-type resonant circuit, a constant current output I is obtained. n-1 , and then through the N-1th level T-type resonant circuit to obtain a constant voltage output U n-2 , and so on, finally after passing through the first stage T-type resonant circuit, the constant current output I is obtained.o Or constant voltage output U o The specific output characteristics are determined by the number of stages N. When N is an odd number, the system has a constant current output, and when N is an even number, the system has a constant voltage output. After each resonant circuit meets the resonance condition, the equivalent input impedance is resistive, so the overall equivalent input impedance of the system is resistive.

[0044] When the number of resonant network stages N is an odd number, the resonance condition is met:

[0045]

[0046] At this time, the system has a constant current output, and the equivalent input impedance of the system is Z inn Purely resistive:

[0047]

[0048] The overall transmission gain of the system is G i-u for:

[0049]

[0050] When the number of resonant network stages N is an even number, the resonance condition is met:

[0051]

[0052] At this time, the system has a constant voltage output, and the equivalent input impedance of the system is Z inn Purely resistive:

[0053]

[0054] The overall transmission gain of the system is G u-u for:

[0055]

[0056] At this time I α ,I m (m=1,2,...,n) is:

[0057]

[0058]

[0059] The efficiency η of the system is:

[0060]

[0061] When the resonance conditions are met, since the input impedance of each stage of the T-type resonant network is purely resistive and has the characteristic of converting a constant voltage source / constant current source into a constant current source / constant voltage source, the overall resonant network can have a purely resistive input impedance, reducing the flow of reactive power in the system and improving system efficiency. Therefore, a high-order compensation network with multiple-stage T-type resonant networks in cascade can be used as the compensation topology of the primary side of the system.

[0062] In order to maximize the system transmission efficiency under fixed gain, it is necessary to determine the parameters of each stage of T-type matching network compensation components. At this time, the overall gain of the system G set As the equality constraint, the efficiency function of the system is used as the objective function to establish the Lagrangian function. At the same time, the voltage stress on the plate and the current stress flowing through the component are used as constraints to further determine the specific value of each compensation component parameter. When the number of resonant network stages of the system is an odd number, the parameters of each T-type compensation network must meet the following requirements:

[0063]

[0064] In order to meet the voltage stress U α and the current I on the compensation element m Not exceeding the design range, the following conditions must be met:

[0065]

[0066] |I m |<I Tmax (12)

[0067] Similarly, when the number of system resonant network levels is an even number, it must satisfy:

[0068]

[0069] |I m |<I Tmax (15)

[0070] When the size of the capacitive coupler and the input-output gain power of the system are determined, the parameters of each component in the compensation network can be determined through the above-mentioned resonance conditions and constraints.

[0071] Through the above parameter design, since there is no compensating inductance element on the receiving side of the system, the volume of the receiving side of the system is reduced, and the lightweight design of the system is achieved. Through reasonable parameter design and gain distribution, the technical effect of maximizing the system transmission efficiency under the condition of constant output characteristics of the system is achieved.

[0072] Compared with the prior art, the present invention has the following significant advantages: the receiving side of the electric field coupling wireless power transmission system of the present invention does not require compensation inductance, which reduces the volume of the receiving side of the system, and maximizes the system transmission efficiency through reasonable compensation network parameter design.

[0073] Example: Simulation and experimental results analysis.

[0074] When the mutual capacitance C of the capacitive coupler M =1.254nF, equivalent self-capacitance C on the emitter and receiver plates of the capacitive coupler α =C β =11.15pF, the effective value of the inverter output voltage U s =50V, the switching frequency is 800kHz, and the system power is designed to be 50W. The compensation circuits with 3 and 2 compensation network levels can be obtained respectively, such as Figure 4 and Figure 5 . Figure 4 The parameters of the constant current output system are: L 1T2 =19.78uH, L 1T3 =11.78uH, L 2T2 =24.87uH, L 3T1 =14.43uH, L 3T3 =12.54uH, C 1T1 =2.01nF, C 2T1 =1.59nF, C 2T3 =1.59nF, C 3T2 =3.18nF; Figure 5 The parameters of the constant current output system are: L 1T2 =31.56uH,L 2T1 =34.84uH,L 2T3 =30.84uH C 1T1 =1.292nF,C 2T1 =1.28nF. Figure 5 This is the relationship between the output current and voltage as the load resistance changes from 10Ω to 100Ω. This process includes the constant current and constant voltage stages of battery charging. The load current I o Approximately 1.08A, load voltage U o It is approximately 52.5V, which means constant current output and constant voltage output are achieved.

[0075] It can be seen from the above embodiments that the electric field coupling wireless power transmission system without compensation inductor on the receiving side proposed by the present invention can achieve constant voltage output and constant current output of the system, and the receiving side can achieve a lightweight design without compensation inductor.

[0076] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. An electric field coupling wireless power transmission system without compensation inductor on the receiving side, characterized in that: It includes a high-frequency full-bridge inverter circuit composed of four metal oxide semiconductor field effect transistors; a high-order matching network composed of N-level LC series-parallel resonant circuits as a primary side high-order compensation circuit, wherein X Sm (m=1,2,...,n) and X Pm (m=1,2,...,n) represents the reactance of the resonant elements in the series and parallel branches respectively; the capacitive coupler of two emitter plates and two receiver plates; the rectifier circuit composed of four diodes and the load resistor R L The left side of the primary high-order compensation circuit is connected to the high-frequency full-bridge inverter circuit, and the right side of the primary high-order compensation circuit is connected to the two emitter plates of the capacitor coupler. The two receiving plates of the capacitor coupler are connected to the load resistor R after passing through the rectifier circuit. L The series resonant element in the matching network is further modeled as two compensation elements X mT1 (m=1,2,...,n) and X (m+1)T3 (m=1,2,...,n) are connected in series, so that the high-order matching network is regarded as a cascade of N-stage T-type resonant networks; the input voltage of the high-frequency full-bridge inverter circuit is V dc The effective value of the fundamental component of the output voltage of the high-frequency full-bridge inverter circuit is U s1 The equivalent excitation voltage source model of the capacitive coupler includes the equivalent self-capacitance C on the emitter plate side. α , the equivalent self-capacitance C on the receiving plate side β , the excitation voltage source V on the emitter plate side α , the excitation voltage source V on the receiving plate side β , where V α =I β / jωC M ,V β =I α / jωC M ,ω is the resonant angular frequency of the system, C M is the mutual capacitance of the capacitive coupler, I α and I β are the voltage on the emitter plate side and the current on the receiving plate side of the capacitive coupler, I1, I2…I n are the currents in each branch, I o and U o is the system’s AC output current and output voltage, I L and U L are the DC output current and output voltage of the system.

2. The electric field coupling wireless power transmission system without compensation inductor on the receiving side according to claim 1, characterized in that: The design schematic diagram includes two parts: the high-order matching network and the coupling mechanism equivalent voltage source model. The basic principle of system parameter design is: the high-order matching network is regarded as a cascade of N-stage T-type resonant circuits, in which the first-stage T-type resonant circuit, the coupling mechanism equivalent voltage source model, and the load are analyzed as a whole for resonance conditions, and the second to N-stage T-type resonant circuits are analyzed as a whole for resonance conditions; where X mT1 ,X mT2 ,X mT3 (m=1,2,3…,n) respectively represent the reactance of the three resonant elements of the m-th level T-type resonant circuit; input voltage U s1 After the Nth stage T-type resonant circuit, a constant current output I is obtained. n-1 , and then through the N-1th level T-type resonant circuit to obtain a constant voltage output U n-2 , and so on, finally after passing through the first stage T-type resonant circuit, the constant current output I is obtained. o Or constant voltage output U o , the specific output characteristics are determined by the number of stages N. When N is an odd number, the system has a constant current output, and when N is an even number, the system has a constant voltage output; each resonant circuit has the characteristic of resistive equivalent input impedance after meeting the resonance condition, so the overall equivalent input impedance of the system is resistive: When the number of resonant network stages N is an odd number, the resonance condition is met: At this time, the system has a constant current output, and the equivalent input impedance of the system is Z inn Purely resistive: The overall transmission gain of the system is G i-u for: When the number of resonant network stages N is an even number, the resonance condition is met: At this time, the system has a constant voltage output, and the equivalent input impedance of the system is Z inn Purely resistive: The overall transmission gain of the system is G u-u for: At this time I α ,I m (m=1,2,...,n) is: The efficiency η of the system is: When the resonance conditions are met, since each level of the T-type resonant network has a purely resistive input impedance and the characteristic of converting the constant voltage source / constant current source into a constant current source / constant voltage source, the overall resonant network can have a purely resistive input impedance, reducing the system reactive power flow and improving the system efficiency. Therefore, a high-order compensation network with multiple-stage T-type resonant networks in cascade can be used as the compensation topology of the primary side of the system.

3. The electric field coupling wireless power transmission system without compensation inductor on the receiving side according to claim 2, characterized in that: In order to maximize the system transmission efficiency under fixed gain, it is necessary to determine the parameters of each stage of T-type matching network compensation components. At this time, the overall gain G of the system set As the equality constraint, the efficiency function of the system is used as the objective function to establish the Lagrangian function. At the same time, the voltage stress U on the plate is α and the current stress I flowing through the component m As a constraint condition, the specific value of each compensation component parameter is further determined; when the number of system resonant network stages is an odd number, the parameters of each stage of the T-type compensation network must meet the following requirements: In order to meet the voltage stress U α and the current I on the compensation element m Not exceeding the design range, the following conditions must be met: |I m |<I Tmax (12) Similarly, when the number of system resonant network stages is an even number, the parameters of each stage of the T-type compensation network must meet the following requirements: |I m |<I Tmax (15) When the size of the capacitive coupler and the input-output gain power of the system are determined, the parameters of each component in the compensation network can be determined through the above-mentioned resonance conditions and constraints; through the above-mentioned parameter design, since there is no compensating inductor component on the receiving side of the system, the volume of the receiving side of the system is reduced, and the lightweight design of the system is achieved, and through reasonable parameter design and gain distribution, the technical effect of maximizing the system transmission efficiency under the condition of constant output characteristics of the system is achieved.

Images