Constant voltage and constant current output design method for cwpt system for lithium battery charging

Abstract

The application discloses a constant-voltage and constant-current output design method of a CWPT system for charging a lithium battery, and constant-voltage and constant-current output is realized by compensating network configuration of the CWPT system, and then parameter optimization design is carried out on the compensating network configuration of the CWPT system, wherein the compensating network configuration comprises the following steps: if both the primary side order and the secondary side order of the CWPT system are odd numbers, the primary side order of the CWPT system is recorded as m, and the secondary side order is recorded as n; if at least one of the primary side order and the secondary side order of the CWPT system is an even number, the CWPT system is transformed into a CWPT system with both the primary side order and the secondary side order being odd numbers, the primary side order of the transformed CWPT system is recorded as m, and the secondary side order is recorded as n; and the compensating network configuration is carried out according to different situations of m and n. The compensating network configuration and the parameter optimization design have strong universality and are suitable for CWPT systems with different orders.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of wireless charging, and more particularly relates to a constant-voltage constant-current output design method for a CWPT system for lithium battery charging. BACKGROUND

[0002] Wireless power transfer (WPT) technology can transfer energy through electric fields, magnetic fields, microwaves, etc., realize cable-free and intelligent device power supply, and has been widely applied in electric vehicles, unmanned aerial vehicles, consumer electronics and other fields. In particular, capacitive wireless power transfer (CWPT) technology has attracted more and more attention due to its simple transmission mechanism structure, no eddy current loss, low cost, light weight and other advantages.

[0003] At present, CWPT technology is mostly still in the research and experimental stage, and has few practical applications, especially for devices that use lithium batteries as power sources. Since lithium battery charging usually includes constant-voltage charging and constant-current charging stages, the CWPT system is required to have constant-voltage and constant-current output capabilities.

[0004] In summary, there is an urgent need to develop a CWPT system suitable for lithium battery charging with constant-voltage and constant-current output switching capabilities. SUMMARY

[0005] In view of the above defects or improvement needs of the prior art, the application provides a constant-voltage and constant-current output design method for a CWPT system for lithium battery charging, which has strong universality in compensation network configuration and parameter optimization design and is suitable for CWPT systems of different orders.

[0006] To achieve the above-mentioned purpose, the application provides a constant-voltage and constant-current output design method for a CWPT system for lithium battery charging, which includes compensation network configuration of the CWPT system, and parameter optimization design of the compensation network configuration of the CWPT system.

[0007] If the primary side order and the secondary side order of the CWPT system are both odd numbers, the primary side order of the CWPT system is denoted as m, and the secondary side order is denoted as n. If at least one of the primary side order and the secondary side order of the CWPT system is an even number, the CWPT system is transformed into a CWPT system with odd primary side order and odd secondary side order, and the primary side order of the transformed CWPT system is denoted as m, and the secondary side order is denoted as n.

[0008] If m≥3 and n≥3, the compensation network of the constant voltage output mode of the CWPT system is configured as: (m-1) / 2 third-order T-type compensation units, one second-order inverse Γ-type compensation unit, two first-order series compensation units, (n-3) / 2 third-order π-type compensation units, and one second-order Γ-type compensation unit are connected in sequence; the compensation network of the constant current output mode of the CWPT system is configured as: one second-order inverse Γ-type compensation unit, (m-3) / 2 third-order π-type compensation units, two first-order series compensation units, one second-order Γ-type compensation unit, (n-3) / 2 third-order T-type compensation units, one second-order inverse Γ-type compensation unit, and one first-order series compensation unit are connected in sequence.

[0009] Further, the compensation network configuration further includes:

[0010] If m≥3 and n=1, the compensation network of the constant voltage output mode of the CWPT system is configured as: one second-order inverse Γ-type compensation unit, (m-3) / 2 third-order π-type compensation units, two first-order series compensation units, and one second-order Γ-type compensation unit are connected in sequence; the compensation network of the constant current output mode of the CWPT system is configured as: (m-1) / 2 third-order T-type compensation units, one second-order inverse Γ-type compensation unit, and two first-order series compensation units are connected in sequence.

[0011] Further, the compensation network configuration further includes:

[0012] If m=1 and n≥3, the compensation network of the constant voltage output mode of the CWPT system is configured as: one second-order inverse Γ-type compensation unit, two first-order series compensation units, one second-order Γ-type compensation unit, and (n-1) / 2 third-order T-type compensation units are connected in sequence; the compensation network of the constant current output mode of the CWPT system is configured as: one third-order T-type compensation unit, one second-order inverse Γ-type compensation unit, (n-3) / 2 third-order π-type compensation units, and one first-order series compensation unit are connected in sequence.

[0013] Further, if at least one of the primary side order and the secondary side order of the CWPT system is even, the CWPT system is transformed into a CWPT system with both the primary side order and the secondary side order being odd by transforming the equivalent π-type circuit of the coupling mechanism and the primary side self-capacitance and the secondary side self-capacitance of the CWPT system into an equivalent T-type circuit.

[0014] Further, the calculation formula for transforming the equivalent π-type circuit of the coupling mechanism and the primary side self-capacitance and the secondary side self-capacitance of the CWPT system into an equivalent T-type circuit is:

[0015]

[0016]

[0017]

[0018] in, Indicates the primary-side self-capacitance. Indicates the secondary side self-capacitance. Indicates the transmission capacitance of the coupling mechanism. , , These represent the first, second, and third capacitors of the transformed equivalent T-type circuit, respectively.

[0019] Furthermore, the parameter optimization design for the compensation network configuration of the CWPT system includes the following steps:

[0020] set up , As independent variables, This indicates the constant current operating frequency of the CWPT system. This indicates the constant voltage operating frequency of the CWPT system;

[0021] The system's average transmission efficiency is established based on the compensation network configuration. , The function is solved with the objective of maximizing the average transmission efficiency of the system. , The optimal solution, based on , The optimal solution is calculated to determine the optimal parameters of the electrical compensation elements in the compensation network configuration of the CWPT system.

[0022] Furthermore, the CWPT system meets the following requirements.

[0023]

[0024]

[0025] in, Indicates the first The impedance of the primary-side compensation element Indicates the first The impedance of the secondary side compensation element , , Both represent the equivalent impedance of the coupling mechanism. Equivalent to and ,Will Equivalent to and , , ,1≤ ≤ ,1≤ ≤ .

[0026] Overall, the above technical solutions conceived by the present application have strong versatility in compensating network configuration and parameter optimization design, and are applicable to CWPT systems of different orders. For CWPT systems of different orders, constant voltage and constant current output can be achieved according to the design method of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a compensation network configuration schematic diagram of the constant voltage output mode of the embodiment of the present application;

[0028] Figure 2 is a compensation network configuration schematic diagram of the constant current output mode of the embodiment of the present application;

[0029] Figure 3 is an equivalent circuit diagram of a primary 4-order and secondary 2-order CWPT system of the embodiment of the present application;

[0030] Figure 4 is an equivalent circuit diagram of a primary 3-order and secondary 1-order CWPT system of the embodiment of the present application;

[0031] Figure 5 is a constant current output configuration diagram of a primary 3-order and secondary 1-order CWPT system of the embodiment of the present application;

[0032] Figure 6 is a constant voltage output configuration diagram of a primary 3-order and secondary 1-order CWPT system of the embodiment of the present application;

[0033] Figure 7 is a parameter optimization design flowchart of the embodiment of the present application;

[0034] Figure 8 is an inverter output voltage and current waveform of the constant voltage mode of the embodiment of the present application;

[0035] Figure 9 is a load voltage and current waveform of the constant voltage mode of the embodiment of the present application;

[0036] Figure 10 is an inverter output voltage and current waveform of the constant current mode of the embodiment of the present application;

[0037] Figure 11 is a load voltage and current waveform of the constant current mode of the embodiment of the present application. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0039] In the description of the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. "Multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0040] In this embodiment of the invention, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, apparatus, product or device that includes a series of steps or modules is not necessarily limited to those steps or modules that are explicitly listed, but may include other steps or modules that are not explicitly listed or that are inherent to such process, method, product or device.

[0041] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0042] This invention provides a constant voltage and constant current output design method for a CWPT system used for lithium battery charging, comprising: configuring a compensation network for the CWPT system, and then optimizing the parameters of the compensation network configuration. Constant voltage or constant current output of the same circuit can be achieved simply by switching the operating frequency, without changing the circuit's structural composition.

[0043] like Figure 1 and Figure 2 As shown, Figure 1 Constant voltage output was achieved. Figure 2 Constant current output is achieved primarily by configuring basic compensation units. These basic compensation units include first-order series type (constant current to constant current), first-order parallel type (constant voltage to constant voltage), second-order Γ type (constant current to constant voltage), second-order inverse Γ type (constant voltage to constant current), third-order π type (constant current to constant current), and third-order T type (constant voltage to constant voltage). Under constant voltage input, these six basic compensation units exhibit constant current or constant voltage output characteristics.

[0044] By properly configuring the basic compensation units, the same CWPT system can achieve constant voltage or constant current output by switching the operating frequency. Specifically, for a CWPT system with a primary-side compensation network of order m and a secondary-side compensation network of order n, it is assumed that the system input is a constant voltage source.

[0045] Figure 1 In the context of a CWPT system, if both the primary and secondary orders are odd, let m be the primary order and n be the secondary order. If both m and n are greater than or equal to 3, the constant voltage output mode of the system can be configured as follows: (m-1) / 2 third-order T-type, 1 second-order inverse Γ-type, 2 first-order series-type, (n-3) / 2 third-order π-type, and 1 second-order Γ-type basic compensation units cascaded together. The output from the power supply side to the load side is closed. The system operates on a constant voltage-constant voltage-constant current-constant current-constant current-constant voltage configuration. Similarly, the constant current output mode can be configured as follows: a cascaded basic compensation unit consisting of one second-order inverse Γ-type, (m-3) / 2 third-order π-type, two first-order series-type, one second-order Γ-type, (n-3) / 2 third-order T-type, one second-order inverse Γ-type, and one first-order series-type. The output relationship from the power supply side to the load side is constant voltage-constant current-constant current-constant current-constant voltage-constant voltage-constant current. The resonant condition of the components constituting the system is...

[0046] (1)

[0047] (2)

[0048] Equation (1) represents the constant voltage output resonance condition of the system, and equation (2) represents the constant current output resonance condition of the system. Wherein, Indicates the first The impedance of the primary-side compensation element Indicates the first The impedance of the secondary side compensation element , , Both represent the equivalent impedance of the coupling mechanism. Equivalent to and ,Will Equivalent to and , , ,1≤ ≤ ,1≤ ≤ .

[0049] If at least one of the primary and secondary orders of the CWPT system is even, then the CWPT system is transformed into a CWPT system in which both the primary and secondary orders are odd. The primary order of the transformed CWPT system is denoted as m, and the secondary order is denoted as n.

[0050] Specifically, if at least one of the primary and secondary orders of the CWPT system is even, the coupling mechanism can usually be equivalent to a π-type circuit. For ease of analysis, the equivalent π-type circuit of the coupling mechanism and the parallel capacitor of the primary and secondary self-capacitors can be transformed into an equivalent T-type circuit through star-delta transformation. Then, the CWPT system can be transformed into the case where the orders of the primary and secondary compensation networks are both odd.

[0051] If m≥3 and n=1, the compensation network configuration for the constant voltage output mode of the CWPT system is as follows: one second-order inverse Γ-type compensation unit, (m-3) / 2 third-order π-type compensation units, two first-order series compensation units, and one second-order Γ-type compensation unit are cascaded in sequence. The compensation network configuration for the constant current output mode of the CWPT system is as follows: (m-1) / 2 third-order T-type compensation units, one second-order inverse Γ-type compensation unit, and two first-order series compensation units are cascaded in sequence.

[0052] If m=1 and n≥3, the compensation network configuration for the constant voltage output mode of the CWPT system is as follows: one second-order inverse Γ-type compensation unit, two first-order series compensation units, one second-order Γ-type compensation unit, and (n-1) / 2 third-order T-type compensation units are cascaded in sequence. The compensation network configuration for the constant current output mode of the CWPT system is as follows: one third-order T-type compensation unit, one second-order inverse Γ-type compensation unit, (n-3) / 2 third-order π-type compensation units, and one first-order series compensation unit are cascaded in sequence.

[0053] If both m and n are less than or equal to 2, the system cannot simultaneously achieve constant voltage and constant current output under ZPA conditions.

[0054] like Figure 3 As shown, a CWPT system with primary edge order of 4 and secondary edge order of 2 is described. This indicates a parallel compensation capacitor on the primary side. and This indicates a primary-side series compensation inductor. This indicates a secondary-side series compensation inductor. This indicates a parallel compensation capacitor on the primary side. This indicates a parallel compensation capacitor on the secondary side; the coupling mechanism is equivalent to a π-type circuit. Indicates the primary-side self-capacitance. Indicates the secondary side self-capacitance. The transmission capacitance is represented by the π-type to T-type relationship table in the star-delta transformation, which is then converted to the following: Figure 4The CWPT system shown is transformed with the primary order denoted as m and the secondary order denoted as n, where m=3 and n=1. The coupling mechanism is equivalent to a T-type circuit. , , The first, second, and third capacitors represent the equivalent T-type circuit after the transformation. The transformation formulas are shown in Table 1. Both the π-type and T-type equivalent circuits of the coupling mechanism are used in the circuit analysis of CPT systems. The π-type equivalent circuit is suitable for analyzing situations such as changes in the capacitance of the coupling mechanism, while the T-type equivalent circuit is suitable for analyzing the transmission characteristics of the system and higher-order cases of the compensation network.

[0055] Table 1. Relationship between Star Triangle Variations

[0056]

[0057] Figure 5 This is a constant current output configuration diagram of the transformed primary-side 3rd order and secondary-side 1st order CWPT system according to an embodiment of the present invention. and Indicates the primary-side series compensation inductor The compensation network configuration for the constant current output mode of the CWPT system is as follows: one third-order T-type compensation unit, one second-order inverse-Γ-type compensation unit, and two first-order series-connected compensation units are cascaded in sequence.

[0058] Figure 6 This is a constant voltage output configuration diagram of a transformed primary-side 3rd order and secondary-side 1st order CWPT system according to an embodiment of the present invention. The compensation network configuration for the constant voltage output mode of the CWPT system is as follows: one second-order inverse Γ-type compensation unit, two first-order series compensation units, and one second-order Γ-type compensation unit are cascaded in sequence.

[0059] By optimizing the parameters of the compensation network configuration of the CWPT system, the system transmission efficiency can be maximized under constant voltage or constant current output conditions.

[0060] The parameter optimization design is explained in detail below. The parameter optimization design process is as follows: Figure 7 As shown.

[0061] To optimize system transmission efficiency, first set... and Let be independent variables, representing the system's constant current operating frequency and constant voltage operating frequency, respectively. Based on this, an optimization equation is established. That is, system transmission efficiency and and Relevant. Based on Kirchhoff's laws, the system voltage equation is established as follows:

[0062] (3)

[0063] in, The first row of the matrix represents the impedance through which the mesh current related to the mesh voltage flows when calculating the first mesh voltage equation. This represents the impedance of the first mesh when calculating the voltage equation for the first mesh. This represents the impedance of the second mesh when calculating the voltage equation for the first mesh. This represents the impedance of the second mesh when calculating the voltage equation for the second mesh, and so on. Indicates the calculation of the first When the first mesh voltage equation is... The impedance of each mesh aperture, This represents the current in the first mesh. This represents the current in the second mesh, and so on. Indicates the first Current per mesh opening, Given the system input voltage, the system efficiency is... It can be solved as

[0064] (4)

[0065] in, express A mesh current matrix, Indicates the equivalent resistance. This represents the conjugate of the first mesh current vector. It refers to the department that seeks truth.

[0066] Furthermore, the optimization equation can be expressed as:

[0067] (5)

[0068] in, This indicates the constant current operating frequency of the CWPT system. This indicates the constant voltage operating frequency of the CWPT system. Indicates the duration of the constant current output segment of the system. Indicates the duration of the constant voltage output segment of the system. This indicates the total output duration of the system. This represents the equivalent load during the constant current output phase of the system. This represents the equivalent load during the constant voltage output phase of the system, and the range of variation of the equivalent load during the constant current output phase of the system. Divided into The segment represents the range of equivalent load variation during the constant voltage output phase of the system. Divided into part, This indicates the system efficiency during the constant current phase. The system efficiency during the constant voltage phase is represented by the average transmission efficiency of the entire system during its operation. Based on the system's charging requirements. , , , , , , , , , , Parameters, among which Indicates the voltage gain of the system. Indicates the transconductance of the system. Indicates the system input voltage. This indicates the internal resistance of the compensating inductor. Because... For nonlinear multivariate equations, the "Globalsearch" optimization algorithm in MATLAB can be used to find the optimal solution, which can solve for the global optimum and thus calculate the optimal operating frequency. and .

[0069] by Figures 3-5 The circuit is used as an example to illustrate the working principle involved in parameter optimization.

[0070] Will , , , , Substituting into formulas (1) and (2) above, we obtain the following formula:

[0071] (6)

[0072] Transconductance in constant current output mode of computing system and input impedance for

[0073] (7)

[0074] in, Represents the imaginary unit. express impedance, express impedance, express impedance, express impedance, express impedance, express impedance, express The impedance. Calculate the voltage gain in constant voltage output mode of the system. and input impedance for

[0075] (8)

[0076] in, express impedance, express The impedance.

[0077] The system voltage equation is

[0078] (9)

[0079] in

[0080] (10)

[0081] in, Inductance internal resistance, Inductance internal resistance, Inductance internal resistance, Inductance impedance, Indicates capacitance impedance, Inductance impedance, Indicates capacitance impedance, Indicates capacitance impedance, Indicates capacitance impedance, Inductance The impedance.

[0082] The computing system transmission efficiency is

[0083] (11)

[0084] The parameter optimization equation is as follows

[0085] (12)

[0086] The parameters of all compensation components in the calculation system are as follows:

[0087] (13)

[0088] Substituting the basic parameters shown in Table 2, the optimal compensation parameter solution can be calculated, as shown in Table 3.

[0089] Table 2 System Basic Parameters

[0090]

[0091] Table 3 Optimal System Parameters

[0092]

[0093] To verify the effectiveness of the method proposed in this invention, a system was built in Simulink as follows: Figure 3 The circuit model shown is designed with three load switching modes: 40Ω, 60Ω, and 80Ω, using power electronic switches. The switching times are 0.2s and 0.4s, respectively. The system simulation duration is 0.6s, and the frequencies are set to 476kHz and 525kHz, respectively.

[0094] The output voltage and current waveforms of the constant voltage mode inverter and the load voltage and current waveforms are as follows: Figure 8 and Figure 9 As shown, the output voltage and current waveforms of the constant current mode inverter and the load voltage and current waveforms are as follows: Figure 10 and Figure 11 As shown.

[0095] Simulation results show that the system satisfies the ZPA condition in both constant voltage and constant current modes. With the switching of load resistance, the system output voltage remains stable and almost unchanged in constant voltage mode, and the voltage gain reaches the design value. In constant current mode, the system output current remains almost unchanged, and the transconductance reaches 0.045, which is consistent with the numerical calculation results.

[0096] It must be noted that the constant voltage and constant current output design method for CWPT systems used for lithium battery charging proposed in this invention is mainly applicable to high-order compensated systems. For low-order compensated CWPT systems, due to the limited number of compensation components and low design freedom, it is not possible to achieve both constant voltage and constant current output modes when a constant voltage source is used as input. Furthermore, constant voltage and constant current output can also be achieved through control circuit design. The simulation example above uses a primary-side 4th-order and secondary-side 2nd-order compensated CWPT system. Those skilled in the art will readily understand that other high-order compensated CWPT systems can also utilize the design method proposed in this invention, and all should be included within the scope of protection of this invention.

[0097] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A constant voltage and constant current output design method for a CWPT system used for lithium battery charging, characterized in that, The compensation network configuration of the CWPT system is performed, followed by parameter optimization design of the compensation network configuration. The compensation network configuration includes: If both the primary and secondary orders of the CWPT system are odd, the primary order of the CWPT system is denoted as m and the secondary order as n. If at least one of the primary and secondary orders of the CWPT system is even, the CWPT system is transformed into a CWPT system in which both the primary and secondary orders are odd. If m≥3 and n≥3, the compensation network configuration for the constant voltage output mode of the CWPT system is as follows: (m-1) / 2 third-order T-type compensation units, 1 second-order inverse Γ-type compensation unit, 2 first-order series compensation units, (n-3) / 2 third-order π-type compensation units and 1 second-order Γ-type compensation unit are cascaded in sequence. The compensation network configuration for the constant current output mode of the CWPT system is as follows: 1 second-order inverse Γ-type compensation unit, (m-3) / 2 third-order π-type compensation units, 2 first-order series compensation units, 1 second-order Γ-type compensation unit, (n-3) / 2 third-order T-type compensation units, 1 second-order inverse Γ-type compensation unit and 1 first-order series compensation unit are cascaded in sequence.

2. The constant voltage and constant current output design method for a CWPT system for lithium battery charging as described in claim 1, characterized in that, The compensation network configuration also includes: If m≥3 and n=1, the compensation network configuration for the constant voltage output mode of the CWPT system is as follows: one second-order inverse Γ-type compensation unit, (m-3) / 2 third-order π-type compensation units, two first-order series compensation units, and one second-order Γ-type compensation unit are cascaded in sequence. The compensation network configuration for the constant current output mode of the CWPT system is as follows: (m-1) / 2 third-order T-type compensation units, one second-order inverse Γ-type compensation unit, and two first-order series compensation units are cascaded in sequence.

3. The constant voltage and constant current output design method for a CWPT system for lithium battery charging as described in claim 1, characterized in that, The compensation network configuration also includes: If m=1 and n≥3, the compensation network configuration for the constant voltage output mode of the CWPT system is as follows: one second-order inverse Γ-type compensation unit, two first-order series compensation units, one second-order Γ-type compensation unit, and (n-1) / 2 third-order T-type compensation units are cascaded in sequence. The compensation network configuration for the constant current output mode of the CWPT system is as follows: one third-order T-type compensation unit, one second-order inverse Γ-type compensation unit, (n-3) / 2 third-order π-type compensation units, and one first-order series compensation unit are cascaded in sequence.

4. The constant voltage and constant current output design method for a CWPT system for lithium battery charging as described in claim 1, characterized in that, If at least one of the primary and secondary orders of the CWPT system is even, the CWPT system can be transformed into a CWPT system with both the primary and secondary orders being odd by transforming the equivalent π-type circuit of the coupling mechanism of the CWPT system and the primary and secondary self-capacits into an equivalent T-type circuit.

5. The constant voltage and constant current output design method for a CWPT system for lithium battery charging as described in claim 4, characterized in that, The formulas for transforming the equivalent π-type circuit and primary-side self-capacitance and secondary-side self-capacitance of the coupling mechanism of the CWPT system into an equivalent T-type circuit are as follows: in, Indicates the primary-side self-capacitance. Indicates the secondary side self-capacitance. Indicates the transmission capacitance of the coupling mechanism. , , These represent the first, second, and third capacitors of the transformed equivalent T-type circuit, respectively.

6. The constant voltage and constant current output design method for a CWPT system for lithium battery charging as described in claim 1, characterized in that, The parameter optimization design for the compensation network configuration of the CWPT system includes the following steps: set up , As independent variables, This indicates the constant current operating frequency of the CWPT system. This indicates the constant voltage operating frequency of the CWPT system; The system's average transmission efficiency is established based on the compensation network configuration. , The function is solved with the objective of maximizing the average transmission efficiency of the system. , The optimal solution, based on , The optimal solution is calculated to determine the optimal parameters of the compensation elements in the compensation network configuration of the CWPT system.

7. The constant voltage and constant current output design method for a CWPT system for lithium battery charging as described in claim 1, characterized in that, CWPT system meets in, Indicates the first The impedance of the primary-side compensation element Indicates the first The impedance of the secondary side compensation element , , Both represent the equivalent impedance of the coupling mechanism. Equivalent to and ,Will Equivalent to and , , ,1≤ ≤ ,1≤ ≤ .

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