Bilateral LC Compensated ECPT System Based on Parity-Time Symmetry and Its Design Method

Abstract

The present invention proposes a bilateral LC compensation ECPT system based on parity-time symmetry and a design method thereof, the system includes a primary transmitting circuit and a secondary receiving circuit, the parameters of the system are configured to make the system work in a floating frequency real eigenstate; the primary transmitting circuit also includes a negative resistance gain circuit, and the negative resistance gain circuit is equivalent to a negative resistance whose absolute value is equal to the load value. The present invention introduces the parity-time symmetry principle into the system, configures the system parameters to make the system work in a floating frequency real eigenstate, and configures the resistance gain circuit to make the system gain and loss balance in the floating frequency real eigenstate. At this time, the system can self-oscillate, and the oscillation frequency is adaptively adjusted as the system parameters change. That is, when the plate is offset or the distance between the plates changes, even if the self-capacitance and mutual capacitance change, the system operating frequency is still at the resonant frequency, and the energy efficiency will not be reduced at this time, and the output power will maintain a stable value.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transmission, and in particular to a bilateral LC compensation ECPT system based on parity-time symmetry and a design method thereof. Background Art

[0002] Electric field coupling wireless power transmission uses the interactive electric field generated by the capacitance between metal plates to transmit wireless power. Under the action of high-frequency alternating current, an interactive electric field is formed between the transmitting plate and the receiving plate of the coupling structure, which then generates displacement current, thereby realizing wireless energy transmission.

[0003] In the electric field coupled wireless power transmission system, when the offset and relative distance of the primary and secondary plates of the coupling mechanism change and are no longer within the original parameters, the self-capacitance and mutual capacitance of the capacitor plates will change, causing the system resonant frequency to shift and detune, resulting in a significant decrease in the power transmission capacity, far away from the designed maximum output power. In order to solve this problem, the most commonly used method is to add a controller and adjust the inverter input frequency to be consistent with the system resonant frequency in real time through closed-loop negative feedback control. However, the controller is on the primary side, and in order to receive the feedback signal, it is usually necessary to set up a communication module on the primary and secondary sides, which not only increases the cost, but also the communication accuracy and speed between the primary and secondary sides are not enough, which may cause a decrease in control effect and reliability. Summary of the invention

[0004] Purpose of the invention: In order to solve the technical problems of system detuning and output power reduction caused by the offset and spacing change of coupling plates during electric field coupled wireless power transmission, the present invention provides a bilateral LC compensation ECPT system based on parity-time symmetry and a design method thereof, which can enable the ECPT system itself to have inherent output anti-offset characteristics to solve the above-mentioned problems.

[0005] Technical solution: The present invention introduces the principle of parity-time symmetry into the system and finds that when the gain and loss are balanced, the system can self-oscillate, and the oscillation frequency is adaptively adjusted as the system parameters change. That is, when the plate is offset or the plate spacing changes, even if the self-capacitance and mutual capacitance change, the system operating frequency is still at the resonant frequency, and the energy efficiency will not be reduced, and the output power will maintain a stable value, which expands the effective energy transfer range of the ECPT system.

[0006] Based on the above principle, the present invention proposes a bilateral LC compensation ECPT system based on parity-time symmetry, comprising a primary-side transmitting circuit and a secondary-side receiving circuit, wherein the parameters of the system are configured to enable the system to operate in a floating frequency real eigenstate;

[0007] The primary transmitting circuit also includes a negative resistance gain circuit, and the negative resistance gain circuit is equivalent to a negative resistor whose absolute value is equal to the load value.

[0008] On the other hand, the present invention also proposes a design method for the bilateral LC compensation ECPT system based on parity-time symmetry, comprising the following steps:

[0009] (1) constructing an equivalent circuit model of the system, and determining the equivalent self-inductance of the primary and secondary coupling plates and the mutual inductance between the primary and secondary coupling plates according to the transmission distance between the primary and secondary coupling plates;

[0010] (2) determining the operating angular frequency of the system and calculating the inductance and capacitance values ​​in the primary and secondary LC compensation circuits;

[0011] (3) Determine the load resistance R L , determine the equivalent resistance of the negative resistance gain circuit based on the parity-time symmetry principle;

[0012] (4) Determine the parameters of each component in the actual circuit based on the parameters in the equivalent circuit model

[0013] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0014] 1. The present invention designs a bilateral LC compensation ECPT system based on the parity-time symmetry principle. The real part of the input impedance of the system is always RL at the zero-phase corner point (floating frequency real eigenstate). At this time, the system is in a self-excited oscillation state, and the operating frequency tracks the zero-phase corner point. At this time, the system can still maintain stable output power under the change of the pole plate, and the energy transmission space range is wide. Compared with the traditional electric field coupled wireless power transmission system that can only achieve efficient energy transmission within a specific spatial range, the ECPT system proposed by the present invention can achieve stable output power when the pole plate is offset and the spacing changes;

[0015] 2. The ECPT system proposed in the present invention can realize automatic tuning, does not require a complex negative feedback system and does not require an additional communication module, simplifies the design, and saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the circuit structure of the bilateral LC compensation ECPT system involved in Embodiment 1 of the present invention;

[0017] Figure 2 is an equivalent circuit model diagram of the bilateral LC compensation ECPT system involved in Example 1 of the present invention;

[0018] Figure 3 A schematic diagram of modeling the primary and secondary coupling plates of the circuit involved in Example 1;

[0019] Figure 4 (a) is a comparison diagram of the changes in the system output power when the bilateral LC compensation ECPT system circuit involved in Example 1 operates at ω1, ω2 and ω0 and there is an X-axis offset between the primary and secondary coupling plates; Figure 4 (b) is a comparison diagram of the changes in system output power when the bilateral LC compensation ECPT system circuit involved in Example 1 operates at ω1, ω2 and ω0, and there is a Z-axis offset between the primary and secondary coupling plates. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. However, it should be understood that the present invention can be implemented in various forms, and some exemplary and non-limiting embodiments shown in the accompanying drawings and described below are not intended to limit the present invention to the specific embodiments described.

[0021] Embodiment 1:

[0022] This embodiment exemplarily provides a bilateral LC compensation ECPT system designed based on the parity-time symmetry principle. The circuit structure is as follows: Figure 1 As shown, it includes a primary transmitting circuit and a secondary receiving circuit, the primary transmitting circuit includes a primary coupling plate and a primary LC compensation circuit, and the secondary receiving circuit includes a secondary coupling plate and a secondary LC compensation circuit. The parameters of the system are configured to make the system work in a floating frequency real eigenstate; the primary transmitting circuit also includes a negative resistance gain circuit, and the negative resistance gain circuit is equivalent to a negative resistance whose resistance value is equal to the load value.

[0023] Figure 1 The equivalent circuit of the circuit shown is Figure 2 shown.

[0024] According to KCL, we can get Figure 2 The mathematical model of the equivalent circuit shown is:

[0025]

[0026] Among them, Y L1 , Y L2 Y is the admittance of the compensation inductance in the primary transmitting circuit and the secondary receiving circuit; C1 , Y C2 Y is the admittance of the parallel capacitor and the equivalent self-capacitance of the plate in the primary transmitting circuit and the secondary receiving circuit; M is the admittance of the equivalent mutual capacitance between the coupling plates; Y RL is the load admittance; V1 is the power supply voltage; V2 is the load terminal voltage; V C1 、V C2 It is the voltage across the parallel capacitor of the primary circuit and the secondary circuit and the equivalent self-capacitance of the plate.

[0027] According to the above formula, the input impedance Z can be obtained in for:

[0028]

[0029] The voltage on the load is:

[0030]

[0031] Substituting into the specific RLC, the real part of the input impedance is:

[0032]

[0033]

[0034] Among them, L1 and L2 are the compensation inductors in the primary transmitting circuit and the secondary receiving circuit; C in1 , C in2 is the self-capacitance of the plates in the primary transmitting circuit and the secondary receiving circuit; C ex1 , C ex2 is the parallel capacitor in the primary transmitting circuit and the secondary receiving circuit; C M is the equivalent mutual capacitance of the coupling plates; R L is the load resistance.

[0035] The imaginary part of the input impedance is:

[0036]

[0037] Setting the imaginary part to 0 gives the zero phase corner point:

[0038]

[0039] ω 1,2 Substitute the real part of the input impedance and find that the real part of the input impedance at the zero-phase corner is always R L .

[0040] The output power of the system is:

[0041]

[0042] Bring in ω 1,2 And the specific RLC value can get the value of output power P.

[0043] Since the input impedance is constant R L ,so

[0044]

[0045] From the above analysis, we can see that according to the PT symmetry principle, the gain and loss are equal, that is, |-R|=|R L |. At this time, the system is in a self-excited oscillation state, and the operating frequency tracks the zero-phase corner point. According to the law of energy conservation, the equation is listed as

[0046] |I L1 | 2 ·(-R)+|I L2 | 2 ·R L =0

[0047] The secondary current of the system is constant and equal to the primary current, and the load power remains stable and does not decrease. At this time, the wireless power transmission system operates in a floating frequency real intrinsic state. When the plate offsets or the spacing changes, the system frequency automatically tracks the zero phase angle point and ensures constant output power.

[0048] Embodiment 2:

[0049] With respect to the system proposed in Example 1, this embodiment proposes a design method for the system:

[0050] (1) Select the appropriate plate according to the actual application requirements (power level, transmission range).

[0051] (2) Calculate the equivalent self-inductance C of the coupling plate based on the plate and the transmission distance d in1 , C in2 and mutual inductance C M .

[0052] (3) According to the actual working frequency range ω, according to C1 = C ex1 +C in1 、C2=C ex2 +C in2 , L1=L2 Select appropriate compensation inductors L1, L2 and parallel capacitors C ex1 , C ex2 .

[0053] (4) Determine the load resistance R L , according to the PT symmetry principle, |-R|=|R L |Get the primary negative resistance -R.

[0054] (5) Figure 1 As shown, the negative resistance gain circuit used in this embodiment is composed of resistors R1 to R4, diodes D1, D2 and an operational amplifier. Determine the values ​​of R1-R4 in the negative resistance circuit built with the op amp.

[0055] According to the circuit parameters determined in the above steps, an electric field coupled wireless power transmission system is built. The wireless power transmission system operates in a floating frequency state. At this time, when the plate offsets or the spacing changes, the system frequency automatically tracks the zero-phase corner point and ensures that the output power is constant.

[0056] Technical effect verification:

[0057] In order to verify the effectiveness of the bilateral LC compensation ECPT system and its design method proposed in the above embodiment, we use MATLAB software to build a model of the system. The parameters are set as V1 = 1V, L1 = L2 = 90uH, R L =5Ω, C ex1 =C ex2 =120pF, R1=R2=3kΩ, R3=3Ω, R4=4Ω. A diode is connected in parallel at both ends of R3 to stimulate self-oscillation and stabilize the amplitude. After connecting R4 in series, it is equivalent to 5Ω. Through COMSOL simulation of a set of actual plates, Figure 3 As shown (unit: mm), in the case of X-axis offset C in1 , C in2 The value range is 3.17pF-5.12pF, C M The range is 1.10pF-3.58pF; when the Z-axis plate spacing changes, C in1 , C in2 The value range is 2.70pF-18.30pF, C M The range is 0.72pF-16.90pF.

[0058] Figure 4 (a) is a comparison diagram of the changes in the system output power when the bilateral LC compensation ECPT system circuit involved in Example 1 operates at ω1, ω2 and ω0 and there is an X-axis offset between the primary and secondary coupling plates; Figure 4 (b) is a comparison diagram of the changes in the system output power when the bilateral LC compensation ECPT system circuit involved in Example 1 operates at ω1, ω2 and ω0, and when the primary and secondary coupling plates are offset in the Z axis. Figure 4 As shown in (a) and (b), the circuit constructed using the PT symmetry principle maintains a stable output power of 200mW when the plate is offset on the X-axis regardless of whether it is at ω1 or ω2. When ω0 is used without tuning, the output power varies with the plate offset and spacing, and is lower than the PT symmetric structure circuit.

[0059] In fact, when the capacitor plates are offset and the spacing changes, in addition to the change in the resonant frequency point, the system also has the same frequency splitting phenomenon as the magnetic coupling wireless power transmission system, which causes the system output power to be at a lower point. The present invention can automatically track the split power point. Compared with the closed-loop control system, the system structure is greatly reduced while achieving the same function.

[0060] It should be understood that, where technically feasible, the technical features listed above for different embodiments can be combined with each other to form other embodiments within the scope of the present invention. In addition, the specific examples and embodiments described in the present invention are non-limiting, and the structures, steps, and sequences described above can be modified accordingly without departing from the scope of protection of the present invention.

Claims

1. A bilateral LC compensation ECPT system based on parity-time symmetry, comprising a primary transmitting circuit and a secondary receiving circuit, characterized in that: The parameters of the system are configured to make the system operate in a floating frequency real eigenstate; The primary transmitting circuit also includes a negative resistance gain circuit, and the negative resistance gain circuit is equivalent to a negative resistor whose absolute value is equal to the load value; The mathematical model of the equivalent circuit of the bilateral LC compensation ECPT system circuit based on parity-time symmetry is: Among them, Y L1 , Y L2 Y is the admittance of the compensation inductance in the primary transmitting circuit and the secondary receiving circuit; C1 , Y C2 Y is the admittance of the parallel capacitor and the equivalent self-capacitance of the plate in the primary transmitting circuit and the secondary receiving circuit; M is the admittance of the equivalent mutual capacitance between the coupling plates; Y RL is the load admittance; V1 is the power supply voltage; V2 is the load terminal voltage; V C1 、V C2 The voltage across the primary circuit and the secondary circuit parallel capacitor and the equivalent self-capacitance of the plate; Input impedance Z in for: The voltage on the load is: The real part of the input impedance is: Among them, L1 and L2 are the compensation inductors in the primary transmitting circuit and the secondary receiving circuit; C in1 , C in2 is the self-capacitance of the plates in the primary transmitting circuit and the secondary receiving circuit; C ex1 , C ex2 is the parallel capacitor in the primary transmitting circuit and the secondary receiving circuit; C M is the equivalent mutual capacitance of the coupling plates; R L is the load resistance; The imaginary part of the input impedance is: Setting the imaginary part to 0 gives the zero phase corner: ω 1,2 Substitute the real part of the input impedance and find that the real part of the input impedance at the zero-phase corner is always R L ; The output power of the system is: Bring in ω 1,2 And the specific RLC value can get the value of output power P; Since the input impedance is constant R L ,so According to the PT symmetry principle, the gain and loss are equal, that is, |-R|=|R L |; At this time, the system is in a self-excited oscillation state, and the operating frequency tracks the zero-phase corner point. According to the law of energy conservation, the equation is listed: |I L1 | 2 ·(-R)+|I L2 | 2 ·R L =0; The secondary current of the system is constant and equal to the primary current, and the load power remains stable and does not decrease; at this time, the wireless power transmission system operates in a floating frequency real intrinsic state. When the plates are offset or the spacing changes, the system frequency automatically tracks the zero phase angle point and ensures constant output power.

2. The design method of the bilateral LC compensation ECPT system based on parity-time symmetry as claimed in claim 1, characterized in that: The following steps are involved: (1) constructing an equivalent circuit model of the system, and determining the equivalent self-inductance of the primary and secondary coupling plates and the mutual inductance between the primary and secondary coupling plates according to the transmission distance between the primary and secondary coupling plates; (2) determining the operating angular frequency of the system and calculating the inductance and capacitance values ​​in the primary and secondary LC compensation circuits; (3) Determine the load resistance R L , determine the equivalent resistance of the negative resistance gain circuit based on the parity-time symmetry principle; (4) Determine the parameters of each component in the actual circuit based on the parameters in the equivalent circuit model.

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