Hybrid coupling wireless power transmission system with controllable output based on PT symmetry

Abstract

The invention provides a PT symmetry-based hybrid coupling wireless power transmission system with controllable output power. The output power can be adjusted while the high anti-offset characteristic is maintained. In the system, the stable output of the system when a coupling mechanism deviates is realized by enabling the system to be in a PT symmetrical state, and meanwhile, the power and efficiency of the stable output of the system are changed by changing the ratio of the reciprocal of series inductors in an LL type compensation network of a receiving end to the sum of the reciprocals of the two inductors. Compared with a common hybrid coupling wireless power transmission system, the hybrid coupling wireless power transmission system has the advantage that the output power and efficiency can be adjusted under the conditions that the system keeps high offset resistance and the load resistance and the input voltage of the system are not changed.

Description

Technical Field

[0001] The present invention belongs to wireless power transmission technology, and in particular relates to a wireless power transmission system with controllable output based on PT symmetry. Background Art

[0002] Wireless power transmission (WPT) technology can transfer power from an input source to a load without the need for physical wires or conductors, thus eliminating the problem of wire losses. Currently, wireless power transmission relies on three main methods: magnetic field coupling (IPT), electric field coupling (CPT), and hybrid coupling (HWPT). IPT uses medium- and high-frequency magnetic fields as the energy transmission medium, while CPT uses high-frequency electric fields, enabling power transmission without direct electrical connection. IPT has a longer transmission distance, but the coupling mechanism is bulky and generates eddy current losses; CPT has no eddy current losses and is lightweight. Hybrid coupling combines the advantages of both methods, allowing inductors and capacitors to compensate for each other. It has become a research hotspot in recent years. In hybrid-coupled WPT systems, when the primary and secondary inductors and capacitor plates of the coupling mechanism shift and their relative distances change, the mutual inductance of the inductors and the mutual capacitance of the capacitor plates change, causing the system's resonant frequency to shift. This in turn leads to instability in the system's output power and efficiency, preventing it from achieving expected values.

[0003] PT symmetry (Parity Time symmetry, PT) is an important concept in quantum mechanics and classical physics. PT symmetry is the combination of space inversion and time inversion. Traditional wireless power transmission systems will produce frequency splitting under strong coupling conditions, greatly reducing the system transmission efficiency and output power. However, systems based on PT symmetry theory can adapt the system frequency under strong coupling conditions, improving the robustness and stability of the system output. Studies have shown that in PT symmetric wireless power transmission systems, the system coupling coefficient has a critical value K cr In the hybrid coupled wireless power transmission system, the system coupling coefficient K is composed of the inductive coupling coefficient K L and capacitance coupling coefficient K C Add together and we get, when K is lower than K cr When K is higher than K, the system is in the weak coupling region, that is, the PT breaking region; cr When the system is in the strong coupling region, known as the PT symmetric region, the output power and efficiency are stable only when the system is in the PT symmetric region. When the load of a PT symmetric wireless power transmission system changes, the system output power also changes accordingly. Therefore, it is necessary to propose a hybrid coupling wireless power transmission system that maintains a constant output power when the coupling coefficient changes and can adjust the output power to a constant value when the load changes. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides a hybrid coupled wireless power transmission system with controllable output based on PT symmetry, which can reduce the distance sensitivity of the coupling mechanism of the HWPT system and adjust the stable value of the output power while the coupling mechanism is offset.

[0005] The technical solution of the present invention is: the output-controllable hybrid coupling wireless power transmission system based on PT symmetry proposed by the present invention.

[0006] The system includes a transmitting circuit and a receiving circuit;

[0007] The transmitting circuit includes a negative resistance circuit containing a drive control circuit and a hybrid resonant circuit at the transmitting end; the negative resistance circuit is composed of an inverter DC power supply, an inverter circuit, a current detection circuit, a zero-crossing comparison circuit and a drive circuit; the hybrid resonant circuit at the transmitting end includes a coupling coil L1, a primary emitter plate P1, a primary emitter plate P4, a parallel capacitor C ex1 , and compensation inductor L f1 .

[0008] The receiving circuit includes a receiving end hybrid resonant circuit, a rectifier circuit and a load R L The receiving end hybrid resonant circuit includes a coupling coil L2, a secondary side receiving plate P2, a secondary side receiving plate P3, and a parallel capacitor C ex2 , parallel compensation inductor L f2P and series compensation inductor L f2S ; Parallel compensation inductor L f2P It is connected in parallel between the coupling coil L2 and the secondary receiving plate P3. f2P and series compensation inductor L f2S With load R L Equivalent to the compensation inductor L f2 With equivalent load R Leq Series structure.

[0009] The mutual inductance between the coupling coil L1 and the coupling coil L2 is defined as M, and the mutual capacitance between the capacitor plates P1, P2, P3, and P4 is defined as C. M . Series compensation inductor L f2S The reciprocal of the compensation inductance L f2 The ratio of the reciprocal of is defined as λ.

[0010] The present invention also proposes a design method for the output-controllable hybrid coupled wireless power transmission system based on PT symmetry, comprising the following steps:

[0011] Step 1: Build an equivalent circuit model of the system, and determine the self-inductance, mutual inductance, equivalent self-capacitance, and equivalent mutual capacitance of the primary and secondary sides in the equivalent circuit based on the simulation results of the inductor coil and capacitor plate of the coupling mechanism;

[0012] Step 2: Determine the system's inherent operating frequency, and determine the compensation inductance L of the primary and secondary sides based on the inherent operating frequency and the equivalent inductance and equivalent capacitance obtained in step 1. f1,2 ;

[0013] Step 3: Determine the negative resistance circuit and select the appropriate inverter DC power supply and field effect transistor.

[0014] Step 4: Determine the load resistance according to the output power requirement.

[0015] Step 5: Determine the value of λ based on the system output power and load resistance, and further solve the parallel compensation inductance L f2P and series compensation inductor L f2S The value of .

[0016] Beneficial effects

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The PT symmetrical hybrid coupled wireless power transmission system of the present invention can maintain the output power and efficiency basically unchanged when the coupling mechanism is offset or the distance changes. Compared with the traditional HWPT system, the system proposed by the present invention can improve the energy transmission distance and the system's anti-offset capability, and achieve stable output power and efficiency.

[0019] (2) The LL-type compensation network proposed in the present invention can change the equivalent load resistance of the system. Compared with the traditional PT system, the PT system containing the LL-type compensation network described in the present invention can adjust the output power stability value of the PT symmetrical system without changing the load resistance and input voltage of the system, providing a convenient method for adjusting the output power of the hybrid coupled wireless power transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A circuit diagram of a hybrid coupled wireless power transmission system with controllable output based on PT symmetry;

[0021] Figure 2 An equivalent circuit of a hybrid coupled wireless power transfer system with controllable output based on PT symmetry;

[0022] Figure 3 A coupling mechanism for a PT-symmetrical output-controllable hybrid-coupled wireless power transmission system;

[0023] Figure 4 Operating frequency f varies with capacitance coupling coefficient K C and inductive coupling coefficient K L ;

[0024] Figure 5(a) Output power P OUT Variation diagram with offset distance d;

[0025] Figure 5 (b) Variation of efficiency η with offset distance d;

[0026] Figure 6 (a) Output power P OUT With series compensation inductor L f2S Reciprocal and compensation inductance L f2 Variation of the reciprocal ratio λ;

[0027] Figure 6 (b) Efficiency η changes with series compensation inductance L f2S Reciprocal and compensation inductance L f2 Variation of the reciprocal ratio λ; DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0029] The hybrid coupled wireless power transmission system proposed in this invention, based on PT symmetry and controllable output, dynamically adjusts the system's operating frequency based on the coupling coefficient of the coupling mechanism when the coupling mechanism shifts. The specific principle of this system is to utilize the mutual coupling of electric and magnetic fields to simultaneously transfer energy, achieving stable and adjustable output. The system's negative resistance circuit is considered gain, while the remaining components (such as inductance, capacitance, and resistance) are considered losses.

[0030] Conditions for PT symmetry: From the system's perspective, the gain and loss of the entire system are equal; from the perspective of the primary and secondary sides, the total energy contained in the primary side is the gain minus the loss of the primary side, the total energy consumed by the secondary side is the total loss of the secondary side, and the total energy of the primary side is equal to the total energy consumed by the secondary side.

[0031] according to Figure 1 As shown, the hybrid coupled wireless power transmission system with output controllable based on PT symmetry includes a transmitting side circuit and a receiving side circuit. The transmitting side circuit includes a DC inverter power supply, an inverter circuit, a current detection circuit, a zero-crossing comparison circuit, a PWM wave generation circuit, a drive control circuit, a primary coupling coil L1, primary emitter plates P1 and P2, and a primary compensation inductor L f1 The receiving side circuit includes the secondary side coupling coil L2, the secondary side receiving plates P3 and P4, and the secondary side parallel compensation inductor L f2P , secondary side series compensation inductor L f2S , rectifier circuit and load resistor R L .

[0032] like Figure 2 As shown, V DC is the DC inverter power supply voltage value, Uin To provide an equivalent input voltage source, connect the secondary side in parallel with the compensation inductor L. f2P Compensation inductor L in series with the secondary side f2S The circuit composed of the two is called LL type compensation network, then the LL type compensation network and the load resistance can be equivalent to the compensation inductor L f2 With equivalent load R Leq In series.

[0033]

[0034] Let 1 / L f2S =λ / L f2 , then formula (2) can be simplified as:

[0035]

[0036] According to the application requirements, the self-inductance L1, L2 and mutual inductance M of the coupling coil and the self-capacitance C1, C2 and mutual capacitance C of the coupling plate can be obtained. M and load R L At this time, the compensation inductor L f1 With L f2 The value of can be expressed as:

[0037]

[0038] Among them, ω0 is the initial working angular frequency, that is, the natural working angular frequency, and its value is 2πe 6 .

[0039] The circuit state equation of the system is:

[0040]

[0041] in

[0042]

[0043] According to the energy equivalence principle, the circuit parameters are linked to the energy to obtain the energy a n for:

[0044]

[0045] Among them, ω n is the primary and secondary side resonant frequency, A n is the amplitude of the energy mode, i.e. a n The amplitude, θ n is the phase of the energy mode, and the Euler expansion of equation (7) yields:

[0046]

[0047] The derivative of formula (7) with respect to t can be obtained as follows:

[0048]

[0049] Substituting Equations (8) and (9) into Equation (5), we can obtain the coupled mode equation of the system:

[0050]

[0051] Among them, G0 is the quantity related to the DC inverter power supply, Γ 10 is the loss on the transmitting side, Γ2 is the loss on the receiving side, which is composed of the loss of the circuit and the loss of the load, K L With K C is the coupling coefficient between the transmitting side and the receiving side, which can be expressed as:

[0052]

[0053] The characteristic equation of formula (10) can be solved to obtain the operating frequency ω and critical coupling coefficient K of the system in the PT symmetric state: cr :

[0054]

[0055] like Figure 4 As shown, when K L +K C >K cr When the system has two operating frequencies, the system will automatically select the appropriate operating frequency to meet the PT symmetry state and achieve constant power and constant efficiency output of the system.

[0056] From equations (2) and (3), we can see that the load and the LL compensation network are equivalent to the inductor L f2 With load R Leq series connection, so the system output power and efficiency are:

[0057]

[0058] It can be seen from formula (14) that the output power and efficiency are independent of mutual inductance and mutual capacitance, but only related to λ. Therefore, the system output power and efficiency can be changed by adjusting λ. The hybrid coupled wireless power transmission system achieves adjustable output power under the condition of constant output.

[0059] Technical effect verification:

[0060] In order to verify the effectiveness of the hybrid coupled wireless power transmission system with output controllable based on PT symmetry proposed in the above embodiment, a model of the proposed system was built using MATLAB software. The parameters were set to V DC=100V, L1=L2=7.68e-6H, C1=C2=2.72e-11F, C ex1 =C ex2 =5e-12F, R1=R2=1.5Ω, R L =20Ω, L f1 =9.21e-5H, equivalent L f2 =9.21e-5H. In the case of X-axis offset (0-100mm), the range of M is 1.61e-6 to 1.13e-7H, C M The range of variation is 2.02e-11F to 8.96e-12F. Figure 5 This graph shows the changes in system output power and efficiency when the primary-secondary coupling mechanism is offset along the X-axis during operation of the HWPT system circuit in the embodiment. The coupling mechanism maintains stable system output power and efficiency despite X-axis offset, maintaining output power at approximately 354 W and efficiency at approximately 0.84, demonstrating system robustness. Figure 6 The figure shows the changes in system output power and efficiency when the value of λ in the LL compensation network changes during operation of the HWPT system circuit in the embodiment. Therefore, the system output power and efficiency can be adjusted by changing λ in the LL compensation network, and the system achieves constant output power and adjustable efficiency.

Claims

1. A hybrid coupled wireless power transmission system with controllable output based on PT symmetry, characterized in that: The circuit consists of a transmitting circuit and a receiving circuit. The transmitting circuit includes a negative resistance circuit containing a driving control circuit and a hybrid resonant circuit at the transmitting end; the receiving circuit includes a hybrid resonant circuit at the receiving end, a rectifier circuit and a load R L .

2. The hybrid coupled wireless power transmission system with controllable output based on PT symmetry according to claim 1, characterized in that: The transmitting circuit is composed of a negative resistance circuit and a transmitting end hybrid resonant circuit, wherein the negative resistance circuit is composed of an inverter DC power supply, an inverter circuit, a current detection circuit, a zero-crossing comparison circuit and a drive circuit; the transmitting end hybrid resonant circuit includes a coupling coil L1, a coupling capacitor C1 and a compensation inductor L f1 .

3. The hybrid coupled wireless power transmission system with controllable output based on PT symmetry according to claim 1, characterized in that: The receiving circuit is composed of a coupling coil L2, a coupling capacitor C2, a parallel compensation inductor L f2P and series compensation inductor L f2S ; Parallel compensation inductor L f2P Connected in parallel across the coupling coil L2 and the coupling capacitor C2.

4. The hybrid coupled wireless power transmission system with controllable output based on PT symmetry according to claim 1, characterized in that: The LL type compensation network is composed of a parallel compensation inductor L f2P and series compensation inductor L f2S The LL type compensation network and the load resistance can be equivalent to the equivalent compensation inductor L f2 With equivalent load R Leq Series, equivalent compensation inductor L f2 With equivalent load R Leq The expression is: Let 1 / L f2S =λ / L f2 , then formula (2) can be simplified to From formula (3), we can see that the equivalent load is related to λ. By changing the value of λ, the value of the load resistance can be dynamically adjusted to adjust the stable value of the output power.

5. The hybrid coupled wireless power transmission system with controllable output based on PT symmetry according to claim 1, characterized in that: When the system works in the PT symmetric region, the operating frequency is not fixed, and the operating frequency ω is related to the critical coupling coefficient K cr for: The system will automatically adjust the frequency to meet constant power and constant efficiency output.

6. The hybrid coupled wireless power transmission system with controllable output based on PT symmetry according to claim 1, characterized in that: The system output power and efficiency are constant and adjustable. By connecting the LL type compensation network in series on the receiving side, the output power and efficiency can be obtained as follows: From formula (5), it can be seen that adjusting the value of λ can adjust the output power and efficiency. Moreover, the output power and efficiency are independent of the mutual inductance and mutual capacitance, but only related to λ. The system achieves adjustable output under the condition of constant output.

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