A design method of wireless power transmission system with anti-deviation

Abstract

The application provides a wireless power transmission system design method with anti-deviation, and the design target is that when the relative position between transmission coils of the WPT system changes, the system can keep the transmission efficiency constant by adjusting the working frequency of the system. First, based on the nonlinear parity time symmetry theory, the wireless power transmission system is modeled and analyzed, and the WPT system model based on the E-class inverter circuit is analyzed by combining the formula deduced by the E-class inverter circuit model. Second, according to the system circuit modeling theory, a self-oscillation feedback control loop is designed. Finally, different coupling coefficients are set to simulate different relative positions, and the overall circuit of the WPT system is simulated and analyzed by using a simulation software. The application solves the problem that the transmission efficiency of the traditional WPT system lacks stability under the influence of the change of the relative position in a certain transmission range, and makes the WPT system have a certain anti-deviation.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission technology, specifically relating to a design method for a wireless power transmission system with offset resistance. Background Technology

[0002] Wireless Power Transfer (WPT) technology refers to a technology that transfers electrical energy from the power source to the load in a non-contact manner. In recent years, it has been widely used in consumer electronics products such as mobile phones. Because this technology can transfer electrical energy without directly using power cords, it avoids problems such as excessive wear and tear on plugs, exposed wires, and electrical sparks associated with traditional charging methods. It offers high convenience and safety, potentially improving people's lifestyles. Although wireless power transfer technology has made significant progress, currently, the relative positions of the transmitting and receiving coils in most wireless power transfer systems remain fixed. When these relative positions change, the transmission efficiency of the WPT system fluctuates considerably. This fluctuation can even affect the electrical equipment, making the system unstable and unable to meet practical application requirements, thus limiting the development of wireless power transfer technology to some extent.

[0003] To address this issue, wireless power transfer technology with offset resistance has been proposed. This refers to a wireless power transfer system whose transmission performance remains stable within a certain range, largely unaffected by changes in relative position. Current research in this area mainly focuses on two technical approaches: transmission coil structure design and circuit topology design. Regarding the first approach, some literature has designed a wireless power transfer system consisting of a four-sided cubic transmitting coil and a square receiving coil. When the receiving coil moves in a circular offset around the transmitting coil at a distance of 30cm, the system's transmission efficiency reaches approximately 60%, thus demonstrating offset resistance, but lacking offset degrees of freedom. Other literature has designed a wireless power transfer system with a four-curved surface transmitting coil and a circular coil. This system maintains a stable output power of 13W and a stable transmission efficiency of approximately 60% when there is no misalignment in multiple angular directions, demonstrating good offset resistance, but lacking offset resistance at certain multi-angular offset locations. Because the transmission coils of tetrahedral and quadruple curved surface transmitting coil systems occupy a large volume and are expensive to manufacture, they are not suitable for small consumer electronics products. Regarding the second technical approach, some literature addresses the high switching losses and noise of wireless power transfer systems by designing an LCCL-LC topology circuit to achieve ZVS control. This system can achieve 5W output power under different coupling coefficients, with a transmission efficiency of approximately 80% and a fluctuation rate not exceeding 3.7%. Other literature, combining parity-time symmetry theory, controls the front-end inverter circuit as an equivalent negative resistance, making the output power of the wireless power transfer system unaffected by changes in the coupling coefficient. When the WPT system changes the coupling coefficient, it has an output power of 400W with an error not exceeding 3.4% and a transmission efficiency of approximately 92%, exhibiting good anti-offset performance. However, this system is only suitable for frequencies of kHz and below.

[0004] In summary, current offset-resistant wireless power transfer technologies have the following shortcomings: 1. The transmission coil occupies a large space and has a high manufacturing cost; 2. The transmission coil lacks offset freedom; 3. The system is used at a relatively low frequency. Therefore, designing a high-frequency, miniaturized offset-resistant wireless power transfer system with high transmission freedom has significant practical value. Summary of the Invention

[0005] The technical problem to be solved by this invention is: how to make the WPT system maintain stable transmission efficiency when the relative positions of the transmission coils of the wireless power transmission system change.

[0006] This invention relates to a design method for a wireless power transfer system with offset resistance. When the relative positions of the transmission coils in a WPT system change, the system can maintain a constant transmission efficiency by adjusting its operating frequency. First, based on nonlinear parity-time symmetric theory, the wireless power transfer system is modeled and analyzed. Combined with the derivation formula of the Class E inverter circuit model, the WPT system model based on the Class E inverter circuit is analyzed. Second, based on the system circuit modeling theory, a self-oscillating feedback control loop is designed. Finally, different coupling coefficients are set to simulate different relative positions, and simulation software is used to simulate and analyze the overall circuit of the WPT system. This invention solves the problem of the lack of stability in the transmission efficiency of traditional WPT systems due to changes in relative position within a certain transmission range, thus giving the WPT system a certain degree of offset resistance.

[0007] The specific technical solution adopted by this invention to solve its technical problem is as follows:

[0008] A design method for a wireless power transfer system with anti-offset capability is characterized by the following: the design objective is to maintain a constant transmission efficiency by adjusting the system's operating frequency when the relative positions of the transmission coils in the WPT system change. First, based on nonlinear parity-time symmetric theory, the wireless power transfer system is modeled and analyzed, and the WPT system model based on the E-type inverter circuit is analyzed using the derived formulas. Second, based on the WPT system circuit modeling theory, a self-oscillating feedback control loop is designed and obtained.

[0009] Furthermore, different coupling coefficients were set to simulate different relative positions, and simulation software was used to simulate and analyze the overall circuit of the WPT system obtained from the design.

[0010] Furthermore, the wireless power transmission system includes a transmitter, a receiver, and a drive control circuit. The transmitter is powered by a DC power supply, which is converted into high-frequency AC power by a Class E inverter circuit and transmitted to the receiver through the transmitting and receiving coils to supply the load.

[0011] The transmitting end includes a DC power supply, a Class E inverter circuit, a series compensation capacitor, and a transmitting coil; the receiving end includes a receiving coil, a parallel compensation capacitor, and a load.

[0012] The drive control circuit includes a current acquisition coil between the output terminal and the drive terminal of the Class E inverter circuit, a phase delay module, a phase compensation module, a zero-crossing comparison module, and a drive unit module.

[0013] Furthermore, let L t L r C represents the self-inductance of the transmitting and receiving coils in the wireless power transmission system, respectively. t Cr These are the series compensation capacitors for the transmitting coil and the parallel compensation capacitors for the receiving coil, respectively, where ω0 is the natural angular frequency of the system, and ω is the operating angular frequency of the system, R L Let K be the load resistance; according to the nonlinear parity-time symmetric theory, when the coupling coefficient K of the WPT system satisfies K≥Γ r At that time, the system's operating angular frequency expression satisfies: Among them, Γ r This is the critical coupling coefficient.

[0014] Furthermore, based on the nonlinear parity-time symmetric theory, a modeling and analysis of the WPT system based on class-E inverters is performed, using the system transmission efficiency expression η = Γ. L / (Γ 10 +Γ L +Γ 20 We know that the coupling coefficient K satisfies K≥Γ r At the same time, adjusting the operating frequency of the WPT system to cope with changes in the coupling coefficient does not change the transmission efficiency of the wireless power transmission system, according to C0, C t The circuit parameters of the WPT system are designed based on the expression of the critical coupling coefficient, and a self-oscillating feedback loop is designed based on the working principle of the E-type inverter circuit.

[0015] Wherein, the load resistance R L The resulting loss constant is Γ L =1 / Q L =ω0L r / R L Parasitic resistance R of the transmitting coil t The resulting loss constant is Γ 10 =1 / Q Rt =R t / ω0L t Parasitic resistance R of the receiving coil r The resulting loss constant is Γ 20 =1 / Q Rr =R r / ω0L r The system's natural angular frequency is:

[0016] Furthermore, a wireless power transfer system with anti-offset capability is designed according to the above-described wireless power transfer system design method with anti-offset capability: the output current signal of the Class E inverter circuit is acquired and converted into a corresponding voltage drive signal to drive the Class E inverter circuit, and the phase of the voltage drive signal lags the output current signal of the Class E inverter circuit by 147.5°.

[0017] Furthermore, a wireless power transmission system with offset resistance is designed and obtained according to the above-described wireless power transmission system design method with offset resistance:

[0018] When the parasitic resistance of the coil is neglected, the critical coupling coefficient is... The output efficiency of the WPT system circuit is optimal when the switching transistor is controlled by a square wave voltage drive signal with a duty cycle of 50% and the circuit operates under ZVS and ZVDS conditions.

[0019] At this time, when the operating frequency of the WPT system changes, the phase of the voltage drive signal lags the output current signal of the Class E inverter circuit by 147.5°, thereby maintaining a stable transmission efficiency for the WPT system. The expression for the parallel capacitor C0 in the WPT system circuit is:

[0020]

[0021] In the WPT system circuit, the compensation capacitor C t The expression is:

[0022]

[0023] As a preferred embodiment, this invention proposes a wireless power transfer system (WPT) based on a Class E inverter. This WPT system is offset-resistant and includes a transmitter, a receiver, and a drive control circuit. The transmitter includes a DC power supply, a Class E inverter circuit, a series compensation capacitor, and a transmitting coil connected in sequence. The receiver includes a receiving coil, a parallel compensation capacitor, and a load. The drive control circuit includes a current acquisition coil between the output of the Class E inverter circuit and the drive unit, a phase delay module, a phase compensation module, a zero-crossing comparison module, and a drive unit module. The transmitter is powered by a DC power supply, which outputs high-frequency AC power through the Class E inverter circuit. This AC power is transmitted to the receiver via the transmitting and receiving coils to supply the load. The drive control circuit acquires the output current signal of the Class E inverter circuit and converts it into a corresponding voltage drive signal to drive the Class E inverter circuit, with the phase of the voltage drive signal lagging the output current signal of the Class E inverter circuit by 147.5°.

[0024] L t L r These are the self-inductances of the transmitting and receiving coils in the wireless power transmission system, respectively, C. r These are the series compensation capacitors for the transmitting coil and the parallel compensation capacitors for the receiving coil, respectively, where ω0 is the natural angular frequency of the system, and ω is the operating angular frequency of the system, R L Let be the load resistance. According to the nonlinear parity-time symmetric theory, when the coupling coefficient K of the WPT system satisfies K≥Γ... r At that time, the system's operating angular frequency expression satisfies: At this point, the constant transmission efficiency of the invented WPT system is: η = Γ L / (Γ 10 +Γ L +Γ 20 The output power is: P L =ω0Γ L |a t | 2 , where Γ r Γ is the critical coupling coefficient. r =Γ L +Γ 20 .

[0025] Considering the high quality factor of the transmission coil in the invented WPT system, and neglecting the parasitic resistance of the coil, the critical coupling coefficient is... When the switching transistors of the invented WPT system circuit are controlled by a square wave voltage drive signal with a duty cycle of 50%, and the circuit operates under ZVS and ZVDS conditions, the output efficiency of the invented system circuit is optimal. At this time, the phase lag of the voltage drive signal of the circuit behind the output current signal of the Class E inverter circuit by 147.5°, and the expression for the parallel capacitor C0 in the invented WPT system circuit is:

[0026]

[0027] The compensation capacitor C in the invented WPT system circuit t The expression is:

[0028]

[0029] Compared to existing technologies, this invention and its preferred embodiment model and analyze a WPT system based on a nonlinear parity-time symmetric theory. From the expression for the system transmission efficiency η, it can be seen that the coupling coefficient K satisfies K≥Γ. r At the same time, adjusting the operating frequency of the WPT system to cope with changes in the coupling coefficient does not change the transmission efficiency of the wireless power transmission system, according to C0, C t The circuit parameters of the WPT system can be designed using the critical coupling coefficient expression. Based on the working principle of the Class E inverter circuit, a self-oscillating feedback loop is designed so that when the operating frequency of the designed WPT system changes, the phase of the voltage drive signal lags behind the output current signal of the Class E inverter circuit by about 147.5°, thereby enabling the WPT system to maintain stable transmission efficiency. Attached Figure Description

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0031] Figure 1This is a general framework diagram of an embodiment of the present invention.

[0032] Figure 2 This is a circuit diagram of a WPT system based on an E-inverter circuit.

[0033] Figure 3 The equivalent circuit diagram for decoupling a WPT system.

[0034] Figure 4 This is the circuit diagram for the drive control of the WPT system.

[0035] Figure 5 The graphs show the output power versus coupling coefficient of the WPT system based on the E inverter circuit, and the transmission efficiency versus coupling coefficient of the WPT system based on the E inverter circuit.

[0036] Figure 6 This is a schematic diagram of the overall principle of an embodiment of the present invention. Detailed Implementation

[0037] To make the features and advantages of this patent more apparent and understandable, specific embodiments are provided below for detailed explanation:

[0038] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0039] In this embodiment, firstly, nonlinear parity-time symmetric theory is used to theoretically analyze the WPT system to obtain expressions for the system's operating angular frequency, output power, and transmission efficiency. For example... Figure 1 , Figure 6 This is a schematic diagram of a WPT system based on nonlinear parity-time symmetry, ω t g1, g 10 and γ 10 These are the natural resonant angular frequency, total gain, and gain ratio of the source resonator, as well as the internal resistance R of the transmitting coil. t The inherent loss rate generated; ω r γ r γ L γ 20 These are the natural resonant angular frequency of the receiving resonator, the total loss rate, the load loss rate, and the internal resistance R of the receiving coil, respectively. r The inherent loss rate generated, and γ r =γ L +γ 20 κ is the coupling ratio between the two resonators, a t a r 2-norm |a t | 2 、|ar | 2 These represent the energy stored in the source resonator and the receiving resonator, respectively.

[0040] The loss rate and gain rate relationships of the nonlinear parity-time symmetric WPT system are expressed as follows: γ 10 =R t / (2L t ), γ 20 =R r / (2L r ), γ L =1 / (2R) L C r ) and g1 = g 10 -γ 10 The dynamic equations of its WPT system are:

[0041]

[0042] Where g1 depends on |a t The characteristic equation of the WPT system in steady state is:

[0043]

[0044] For the expression to have real solutions, it must satisfy the following:

[0045] [i(ω-ω t )-g1][i(ω-ω r )+γ r ]+κ 2 =0 (3)

[0046] Under resonant matching conditions, the WPT system satisfies ω t =ω r =ω0, that is, the system's natural angular frequency ω0 satisfies: Separating the real and imaginary parts of the characteristic equation, we obtain:

[0047]

[0048] Simplifying the equation, we obtain that the WPT system satisfies κ≥γ. r At that time, the relationship between the system's operating angular frequency ω and coupling rate κ is:

[0049]

[0050] The relationship between the system's gain and coupling rate is:

[0051] g1=γ r (6)

[0052] The energy modulus ratio of the system in steady state is as follows:

[0053]

[0054] From equations and , it can be seen that the over-coupling region (κ≥γ) r The WPT system will have two frequencies. The system has the same total gain in both frequency modes, and the total gain and total loss satisfy g1 = γ. r This indicates that the energy of the WPT system is balanced, and the energy mode amplitude distributions of the two frequency modes are equal, thus this mode satisfies the nonlinear parity-time symmetric theory.

[0055] Based on nonlinear parity-time symmetric theory, the output power expression of the WPT system is:

[0056] P L =2γ L |a r | 2 (8)

[0057] Furthermore, the simplified expression for the transmission efficiency of the WPT system is:

[0058]

[0059] To concretize the abstract nonlinear parity WPT system model theory, its theoretical formulas will be transformed. The relationship between the loss rate and the loss coefficient is: Γ 10 =2γ 10 / ω0、Γ 20 =2γ 20 / ω0、Γ L =2γ L / ω0. The relationship between the coupling ratio κ and the coupling coefficient K is:

[0060] κ=Kω0 / 2 (10)

[0061] Substituting the relationship between the loss rate and the loss coefficient into the expression, we obtain the relationship between the system's operating angular frequency ω and the coupling coefficient K as follows:

[0062]

[0063] Substituting the relationship between the loss rate and the loss coefficient into the expression, we obtain the expression for the system's output power as follows:

[0064] P L =ω0Γ L |a t | 2 (12)

[0065] in, Im This represents the peak current flowing through the coil, indicating that when the coupling coefficient is greater than the critical loss coefficient (K≥Γ), the current is at its peak. r When the coupling coefficient is 0, the output power of the system depends only on the current flowing through the transmitting coil and is independent of the coupling coefficient.

[0066] Substituting the relationship between the loss rate and the loss coefficient into the expression, we obtain the expression for the system's transmission efficiency as follows:

[0067]

[0068] Secondly, in order to obtain the basis for designing the main circuit parameters of a wireless power transfer system with offset resistance, a modeling and analysis of the wireless power transfer system circuit based on an E-inverter circuit is performed based on the theory of nonlinear parity-time symmetric WPT systems. For example... Figure 2 As shown, the WPT system circuit includes a choke inductor L. f The switching transistor T and the parallel capacitors C0 and C t The capacitor for compensating the transmitting coil is connected in series, C r The receiving coil compensation capacitors are connected in parallel, L t L r Let R represent the self-inductance of the transmitting and receiving coils, respectively. Assuming a high coil quality factor, the parasitic resistance of the coils can be ignored. L Indicates load.

[0069] According to L r and C r From the expression for the parallel resonant angular frequency, the natural angular frequency of the system can be obtained as: Based on the theory of nonlinear parity-time symmetric WPT systems, the quality factor formed by the load resistance is: Q L =R L / (ω0L r The critical coupling coefficient is and Substituting the expression for the natural angular frequency into Γ L =ω0L r / R L In the above, the expression for the loss coefficient of the load resistance is obtained as follows:

[0070]

[0071] When the transmission coil has a high quality factor, the critical coupling coefficient Γ of the WPT system is negligible in terms of coil resistance. r ≈Γ L ,in accordance with Figure 2 Reflection impedance Z ref The expression is:

[0072]

[0073] Will Substituting into the expression, it simplifies to:

[0074]

[0075] According to the expression, the reflection impedance Z ref The expression for the real part of the reflection resistance is:

[0076]

[0077] Substituting the equation into the simplified expression, the expression for the reflection resistance is:

[0078]

[0079] According to the expression, the reflection impedance Z ref The expression for the imaginary part, i.e., the reflected reactance, is:

[0080]

[0081] Because, Γ r ≈Γ L <<1,Γ L 2 << 1, and substituting the expression into the formula, it can be simplified to:

[0082]

[0083] Will Figure 2 The wireless power transfer system circuit decoupling based on E-inverter is obtained Figure 3 The equivalent circuit shown is obviously... Figure 3 The equivalent circuit shown is a Class E inverter circuit. In this case, the total equivalent impedance Z of the equivalent circuit is... eq for:

[0084] Z eq =Z ref +jX t =R ref +j(X t +X ref ) (twenty one)

[0085] From the equation, the total equivalent resistance can be obtained as:

[0086] R eq =R ref =Γ L L t ω0 (22)

[0087] From the formula, the total equivalent reactance can be obtained as:

[0088]

[0089] Due to Γ r ≈Γ L <<1,Γ L 2 << 1, and substituting the expression into the formula, it can be simplified to:

[0090]

[0091] Among them, X t =ω0L t -1 / (ω0C t ), where ω0 represents the system's natural angular frequency.

[0092] When using a square wave voltage drive signal with a duty cycle of 50% for control Figure 3 The switch T of the E-type inverter circuit shown is used when the circuit operates under ZVS and ZVDS conditions. Figure 3 The Class E inverter circuit shown exhibits optimal output efficiency. At this point, the phase lag of the voltage drive signal of this circuit behind the output current signal of the Class E inverter circuit by 147.5°. Figure 3 The expression for the parallel capacitor C0 in the Class E inverter circuit shown is:

[0093]

[0094] Figure 3 The relationship between the total equivalent reactance and the total equivalent resistance of the E-type inverter circuit shown is as follows:

[0095]

[0096] Substitute the formula into X. t =ω0L t -1 / (ω0C t In ) then Figure 3 The compensation capacitor C in the Class E inverter circuit shown t The expression is:

[0097]

[0098] The above derivation shows that when the system is in the overcoupled region, i.e. When the coupling coefficient between the coils changes, the operating angular frequency of the WPT system changes. Figure 3The equivalent impedance of the Class E inverter circuit shown does not change with the coupling coefficient K and the operating angular frequency ω. The equivalent resistance is only related to the self-inductance of the transmitting coil, the natural angular frequency ω0, the load resistance, the self-inductance of the receiving coil, and the compensation capacitor of the WPT system. The equivalent reactance is only related to the self-inductance of the transmitting coil and the compensation capacitor. These influencing factors remain basically unchanged after the WPT system is designed. Therefore, adjusting the operating frequency of the WPT system to cope with the change of the coupling coefficient does not change the total equivalent impedance and transmission efficiency of the wireless power transmission system.

[0099] Finally, to ensure the designed wireless power transfer system exhibits anti-migration capability, a circuit theory analysis of the wireless power transfer system based on the E-inverter circuit is conducted, and a drive control loop is designed for the WPT system. For example... Figure 4 As shown, the working principle of the drive control loop to achieve self-oscillation feedback regulation is as follows: the current sampling section uses a small coil weakly coupled to the transmitting coil to collect the current i flowing through the transmission coil of the WPT system. t A resistor R is connected in series with the acquisition coil. s A loop is formed that converts the acquired current signal into a specific current i. t Phase-lag voltage signal u s-in After passing through the phase compensation circuit, the voltage signal u is obtained. s-out The voltage signal, after passing through a zero comparator and a drive unit, generates a square wave signal with a 50% duty cycle that can drive the switching transistor T. This signal controls the switching transistor T's on and off states. During the above adjustment process, the operating angular frequency ω of the WPT system is automatically adjusted; therefore, the switching transistor drive signal lags behind i. t phase for:

[0100]

[0101] By properly setting the resistance and capacitance values ​​of the compensation circuit, the phase lag angle can be reduced within a certain frequency range. Adjusting to 147.5° enables self-oscillation feedback control, giving the designed wireless power transmission system anti-offset capability.

[0102] Based on the above analysis, and according to the system simulation parameters, the designed wireless power transmission system was simulated and verified in the simulation software. The specific simulation design parameters of the WPT system are shown in Table 1.

[0103] Table 1. Simulation Parameters of WPT System

[0104] <![CDATA[Direct current voltage V dc / V]]> 12 <![CDATA[Self-inductance L of the receiving coil r / μH]]> 3.2 <![CDATA[Choke inductor L f / μH]]> 39 <![CDATA[Load resistance R L / Ω]]> 4200 <![CDATA[Switching tube parallel capacitor C0 / pF]]> 600 <![CDATA[Self-inductance L of the acquisition coil s / μH]]> 0.3 <![CDATA[Transmitting coil compensation capacitor C t / pF]]> 182 <![CDATA[Phase delay adjustment resistor R s / Ω]]> 25 <![CDATA[Receiving coil compensation capacitance C r / pF]]> 175 <![CDATA[Internal resistance R of transmitting coil t / Ω]]> 0.21 <![CDATA[Self-inductance L of the transmitting coil t / μH]]> 3.2 <![CDATA[Internal resistance R of receiving coil r / Ω]]> 0.21

[0105] The coupling coefficient K between the coils was set to different values ​​to simulate the change in their relative positions, and the output power and transmission efficiency of the WPT system were plotted against the coupling coefficient using simulation data. Figure 5 The graphs showing the relationship between output power and coupling coefficient and the relationship between transmission efficiency and coupling coefficient clearly show that when in the overcoupled region, the system's output power decreases slowly as the coupling coefficient decreases, while the system's transmission efficiency remains basically unchanged and stays at around 88%. This indicates that the WPT system in the overcoupled region can maintain stable transmission efficiency when the relative position changes, thus the designed WPT system has a certain degree of anti-offset capability.

[0106] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

[0107] This patent is not limited to the above-described preferred embodiment. Anyone can derive other forms of wireless power transmission system design method with offset resistance based on the teachings of this patent. All equivalent changes and modifications made within the scope of the claims of this invention shall be covered by this patent.

Claims

1. A wireless power transmission system with anti-displacement capability, characterized in that, The design is obtained based on the following offset-resistant wireless power transfer system design method: The design goal is to maintain a constant transmission efficiency by adjusting the system's operating frequency when the relative positions of the transmission coils in the WPT system change. First, based on nonlinear parity-time symmetric theory, the wireless power transmission system is modeled and analyzed. Then, combined with the derivation formula of the E-type inverter circuit model, the WPT system model based on the E-type inverter circuit is analyzed. Second, based on the WPT system circuit modeling theory, a self-oscillating feedback control loop is designed and obtained. Different coupling coefficients are set to simulate different relative positions, and simulation software is used to simulate and analyze the overall circuit of the WPT system obtained from the design. The wireless power transmission system includes a transmitter, a receiver, and a drive control circuit. The transmitter is powered by a DC power supply, which is converted into high-frequency AC power by a Class E inverter circuit and transmitted to the receiver through the transmitting and receiving coils to supply the load. The transmitting end includes a DC power supply, a Class E inverter circuit, a series compensation capacitor, and a transmitting coil; the receiving end includes a receiving coil, a parallel compensation capacitor, and a load. The drive control circuit includes a current acquisition coil between the output terminal and the drive terminal of the Class E inverter circuit, a phase delay module, a phase compensation module, a zero-crossing comparison module, and a drive unit module. set up , These are the self-inductances of the transmitting and receiving coils in the wireless power transmission system, respectively. , These are the series compensation capacitors for the transmitting coil and the parallel compensation capacitors for the receiving coil, respectively. Let be the natural angular frequency of the system, and , The operating angular frequency of the system. For the load resistance; according to the nonlinear parity-time symmetric theory, when the coupling coefficient of the WPT system... satisfy At that time, the system's operating angular frequency expression satisfies: ,in, The critical coupling coefficient; Based on the nonlinear parity-time symmetric theory, a WPT system based on a class-E inverter circuit is modeled and analyzed, and the system's transmission efficiency is expressed by the formula... It was learned that in the coupling coefficient satisfy At the same time, adjusting the operating frequency of the WPT system to cope with changes in the coupling coefficient does not change the transmission efficiency of the wireless power transmission system, according to C0, C t The circuit parameters of the WPT system are designed based on the expression of the critical coupling coefficient, and a self-oscillating feedback loop is designed based on the working principle of the E-type inverter circuit. Among them, Q L The quality factor formed by the load resistance, the load resistance The resulting loss constant is parasitic resistance of transmitting coil The resulting loss constant is Parasitic resistance of the receiving coil The resulting loss constant is The system's natural angular frequency is: ; When the parasitic resistance of the coil is neglected, the critical coupling coefficient is... When a square wave voltage drive signal with a duty cycle of 50% is used to control the switching transistors of the WPT system circuit, and the circuit operates under ZVS and ZVDS conditions, the output efficiency of the system circuit is optimal. At this time, when the operating frequency of the WPT system changes, the phase of the voltage drive signal lags behind the output current signal of the Class E inverter circuit by 147.

5. ° This ensures that the WPT system maintains stable transmission efficiency, and the parallel capacitors in the WPT system circuit... The expression is: WPT system circuit The expression is: 。

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