MC-WPT system parameter design method adaptive to multi-power-level transmission

Abstract

The invention provides an MC-WPT system parameter design method adaptive to multi-power-level transmission, which is used for solving the technical problem that an existing MC-WPT system has no interoperability due to the fact that one transmitting end corresponds to one receiving end. The method comprises the specific steps that S1, the coupling coefficient of a primary side coil and a secondary side coil specified by the national standard is determined; s2, determining the inductance value lower limit of the primary side compensation inductor under each power level according to the system transmission efficiency; s3, the inductance value lower limit of the primary side compensation inductor under each power level is determined according to the system current stress, and the inductance value upper limit of the primary side compensation inductor under each power level is determined according to the system output power requirement; s4, obtaining an intersection of the inductance value interval of the primary side compensation inductor of each power level, and selecting a proper inductance value of the primary side compensation inductor; s5, after the inductance value of the primary side compensation inductor is determined, primary side system parameters are determined according to the resonance relation. According to the method and the device, the primary side parameters under multiple power levels are set, so that the charging requirements of multiple power levels are met.

Description

Technical Field

[0001] The present invention relates to the field of wireless power transmission, and in particular to a method for designing parameters of a MC-WPT system adapted for multi-power level transmission. Background Art

[0002] The rapid development of wireless power transmission technology has brought new solutions for charging electric vehicles. It has the advantages of being easy to use, fast, safe and reliable, with high energy storage rate and the ability to realize automated charging. It can well solve the inherent shortcomings of wired charging of electric vehicles. Nowadays, electric vehicles have been studied in detail in terms of electromagnetic shielding, bio-electromagnetic safety, energy and signal transmission, dynamic wireless charging, and foreign object detection. However, there has been relatively little research progress on the interoperability of wireless charging of electric vehicles. The formulation of international standards for wireless charging of electric vehicles has basically met the development needs of the industry, but the compatibility between different power levels is currently poor. The interoperability of wireless charging of electric vehicles has become one of the key issues that need to be urgently addressed in the development of the industry.

[0003] At present, the commonly used power levels are 3.7kW, 7.7kW, and 11kW, which correspond to the wireless charging systems WPT1, WPT2, and WPT3 respectively. With the development of high-power demand for wireless charging of electric vehicles, the receiving end power level of 22kW is defined as WPT4; for the ground clearance range of the receiving end, it is mainly divided into three categories: 100-150mm, 140-210mm, and 170-250mm. At present, there are few studies on the interoperability of high-power receiving ends. In the existing literature, the interoperability between the same transmitter coil and different receiver coils under 3.3kW and 6.6kW power conditions is studied. It is found that the ground transmitter coil adopts a bipolar coil topology, while the receiver coil adopts a monopolar circular coil, a solenoid coil, and a DD coil. The coil combination effect is best when the ground transmitter adopts a bipolar coil and the vehicle-mounted receiver adopts a DD coil. However, the bipolar line has a large mass and the coil has overlapping parts, which increases the thickness of the transmitter. Summary of the invention

[0004] The purpose of the present invention is to provide a MC-WPT system parameter design method adapted for multi-power level transmission, which is used to solve the technical problem that the existing MC-WPT system has one transmitter corresponding to one receiver and lacks interoperability.

[0005] A method for designing parameters of an MC-WPT system adapted for multi-power level transmission, wherein the MC-WPT comprises a primary circuit and a secondary circuit, wherein the primary circuit comprises a primary compensation circuit and a primary coil, wherein the secondary circuit comprises a secondary compensation circuit and a secondary coil, wherein the primary compensation circuit and the secondary compensation circuit are symmetrically arranged LCC topology structures, wherein the primary compensation circuit comprises a primary compensation inductor and two primary compensation capacitors, and the specific steps of the parameter design method are as follows:

[0006] S1: Determine the coupling coefficient between the primary coil and the secondary coil specified in the national standard;

[0007] S2: Determine the lower limit of the inductance value of the primary compensation inductor at each power level according to the system transmission efficiency;

[0008] S3: Determine the lower limit of the inductance value of the primary compensation inductor at each power level according to the system current stress, and determine the upper limit of the inductance value of the primary compensation inductor at each power level according to the system output power requirement;

[0009] S4: taking the intersection of the inductance value ranges of the primary compensation inductor of each power level, and selecting a suitable inductance value of the primary compensation inductor;

[0010] S5: After determining the inductance value of the primary compensation inductor, determine the primary system parameters according to the resonance relationship.

[0011] Optionally, the specific steps of determining the coupling coefficient between the primary coil and the secondary coil specified in the national standard in step S1 are:

[0012] S1.1 According to the national standard, determine the multiple power levels that the MC-WPT system needs to meet;

[0013] S1.2 Select the primary coil and the secondary coil structure, wherein the coil structure includes but is not limited to a circular coil, a rectangular coil and a DD coil;

[0014] S1.3 Select the power transfer value that the primary circuit needs to meet according to the requirements, set the basic parameters of the primary coil according to the power transfer value, and obtain the self-inductance value of the primary coil through simulation;

[0015] S1.4 performs comsol simulation based on the basic parameters of the primary coil set in step S1.3 and the secondary coils of different sizes specified in the national standard, simulates the coupling coefficient of the primary coil and the secondary coil under different gaps, and selects the coupling coefficient according to the upper and lower limits of the coupling coefficient.

[0016] Optionally, the power levels in step S1.1 include: MF-WPT1, MF-WPT2, ..., MF-WPTn; where: n is a positive integer ≥ 2.

[0017] Optionally, the basic parameters of the primary coil include the number of turns of the primary coil, the outer length and width of the coil, the inner length and width of the coil, the length and width of the primary coil core, and the length and width of the aluminum plate;

[0018] When the primary circuit is installed, the primary coil core is installed on the aluminum plate, the primary coil is installed on the primary coil core, and the primary coil is electrically connected to one end of the primary compensation circuit.

[0019] Optionally, in step S2, the specific steps of determining the lower limit of the inductance value of the primary compensation inductor at each power level according to the system transmission efficiency are:

[0020] S2.1 Construct the fundamental wave approximate model of the MC-WPT system, calculate the active power and reactive power expressions of the fundamental wave approximate model, and construct the total power loss expression of the system, and calculate the system transmission efficiency expression through the active power and the total power loss of the system;

[0021] The system transmission efficiency is equal to the quotient of the absolute value of the active power and the total system power, and the total system power is equal to the sum of the absolute value of the active power and the total system power loss;

[0022] S2.2 constructs an efficiency curve of the system transmission efficiency changing with the primary compensation inductance through simulation, sets the efficiency limit value, intersects the primary compensation inductance range at each power level, obtains the lower limit of the inductance value of the primary compensation inductance that meets multiple power levels, and obtains the first interval of the inductance value of the primary compensation inductance.

[0023] Optionally, in step S3, the specific method for determining the lower limit of the inductance value of the primary compensation inductor at each power level according to the system current stress is:

[0024] An upper limit value of the current stress of the primary compensation inductor is set, and an electric stress curve diagram showing the change of the current stress value of the primary compensation inductor with the inductance value of the primary compensation inductor is simulated, and a lower limit value of the inductance value of the primary compensation inductor that meets the upper limit value constraint condition of the current stress is selected to obtain a second interval of the inductance value of the primary compensation inductor.

[0025] Optionally, in step S3, the specific method for determining the upper limit of the inductance value of the primary compensation inductor at each power level according to the system output power requirement is:

[0026] Construct the system output power expression, and draw the curve of the inductance value of the primary compensation inductor changing with the primary coil when the inductance ratio is different through simulation;

[0027] A power limit curve is set in the curve graph, and an upper limit value of the inductance value of the primary compensation inductor under each power level is selected according to the power limit curve to obtain a third interval of the inductance value of the primary compensation inductor.

[0028] Optionally, in step S4, the specific method of taking the intersection of the inductance value intervals of the primary compensation inductor of each power level and selecting the appropriate inductance value of the primary compensation inductor is:

[0029] The inductance value interval of the primary compensation inductor is obtained by taking the intersection of the first interval, the first interval and the third interval of the inductance value of the primary compensation inductor obtained in step S2 and step S3, and the inductance value of the primary compensation inductor is selected according to the principle of maximizing the system transmission efficiency.

[0030] Due to the adoption of the above technical solution, the present invention has the following advantages:

[0031] This application selects multiple power levels according to the national standard, calculates the inductance range of the primary compensation inductor under multiple power levels, and then determines the inductance value of the primary compensation inductor, and sets the primary parameters according to the resonant relationship to meet the charging needs of multiple power levels.

[0032] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings of the present invention are as follows.

[0034] Figure 1 The figure is a flow chart of the parameter design method of the present invention.

[0035] Figure 2 It is a circuit structure diagram of the bilateral LCC compensation BIPT system of the present invention.

[0036] Figure 3 This is a diagram of the fundamental wave approximate model of the bilateral LCC compensation BIPT system of the present invention.

[0037] Figure 4 It is a curve diagram of system transmission efficiency at three power levels of the present invention.

[0038] Figure 5 It is a curve diagram showing the relationship between the current stress and the primary compensation inductance of the present invention.

[0039] Figure 6 It is the system power curve diagram under three power levels of the present invention.

[0040] Figure 7 This is the DC side input and output voltage and current diagram when the primary and secondary sides are aligned.

[0041] Figure 8This is a diagram of the DC input and output voltage and current when the primary and secondary sides are offset. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0043] Embodiment 1:

[0044] like Figure 2 The BIPT system of bilateral LCC compensation shown in FIG. 1 includes a primary circuit and a secondary circuit. The primary circuit includes a primary DC power supply V dp , primary full-bridge inverter, primary compensation circuit and primary coil L p The secondary circuit includes a primary coil L connected in sequence s , secondary side compensation circuit, secondary side full bridge inverter and secondary side DC power supply V ds .

[0045] In this embodiment, the primary compensation circuit and the secondary compensation circuit are symmetrically arranged LCC topology structures. rp , primary compensation capacitor C fp And the primary compensation capacitor C p The secondary side compensation circuit includes a secondary side compensation circuit L rs , primary compensation capacitor C fs And the primary compensation capacitor C s The primary full-bridge inverter includes four switch tubes S1-S4, and the secondary full-bridge inverter includes four switch tubes T1-T4.

[0046] In this embodiment, the primary DC voltage V dp is the grid power supply, the secondary DC power supply V ds It is the battery power source of the electric vehicle. When the electric vehicle is charging, the primary side supplies power to the secondary side. When the grid load is large, power can also be supplied to the primary side through the secondary side.

[0047] In this embodiment, ignoring the system harmonic components, the fundamental wave equivalent circuit of the system is as follows: Figure 3 shown. Figure 3 Middle,U p_1 and U s_1 They are respectively the fundamental components of the original and secondary full-bridge output voltages.

[0048]

[0049] Where δ is the phase angle of the secondary full-bridge output fundamental voltage lagging the primary full-bridge fundamental voltage.

[0050] Write down the KVL equation of the original secondary side:

[0051]

[0052] Where j is an imaginary number, ω is the system angular frequency, is the current of the primary coil, is the current of the primary compensation inductor, L rs is the current of the secondary coil, The current of the secondary side compensation inductor, M is the mutual inductance of the primary coil and the secondary coil.

[0053]

[0054] For system efficiency analysis, the absolute values ​​of active power and reactive power transmitted by the system can be obtained according to the above formula:

[0055]

[0056] The inductance ratio of the coil self-inductance to the compensation inductance is:

[0057]

[0058] In the formula, α p is the inductance ratio of the primary coil and the primary compensation inductor, α s It is the inductance ratio of the secondary coil and the secondary compensation inductor.

[0059] The total loss of the system can be expressed as:

[0060]

[0061] In the formula, Q p is the quality factor of the primary and secondary coils, Q r To compensate the quality factor of the inductor branch, they are defined as:

[0062]

[0063] The transmission efficiency of the system can be approximately calculated as:

[0064]

[0065] Where T is the ratio of the primary and secondary excitation voltages, and β is the primary and secondary compensation inductance ratio:

[0066]

[0067] Embodiment 2:

[0068] like Figure 1 A method for designing MC-WPT system parameters adapted to multi-power level transmission is shown, and the specific steps are as follows:

[0069] S1: Determine the coupling coefficient between the primary coil and the secondary coil specified by the national standard; the specific steps are:

[0070] S1.1 According to the national standard, determine the multiple power levels that the MC-WPT system needs to meet, the power levels include: MF-WPT1, MF-WPT2, ..., MF-WPTn; where: n ≥ 2 positive integer;

[0071] In this embodiment, n=3, and the power levels of the MC-WPT system are determined in the national standard GB / T38775.7 as MF-WPT1, MF-WPT2, and MF-WPT3, respectively. MF-WPT1, MF-WPT2, and MF-WPT3 correspond to three power levels of 3.7kW, 7.7kW, and 11kW, respectively.

[0072] S1.2 Select the primary coil and the secondary coil structure, wherein the coil structure includes but is not limited to a circular coil, a rectangular coil and a DD coil;

[0073] In this embodiment, since the parameters of the transmitter reference magnetic coupling mechanism of different power levels are different, there are various shape structures such as circular coils, rectangular coils and DD-type coils. When the DD-type coil is offset from the transmitter coil, the coupling coefficient decreases rapidly. Therefore, this application selects the primary coil and the secondary coil as rectangular coils.

[0074] S1.3 Select the power transfer value that the primary circuit needs to meet according to the demand, set the basic parameters of the primary coil according to the power transfer value, and obtain the self-inductance value of the primary coil through simulation; the basic parameters of the primary coil include the number of turns of the primary coil, the outer length and width of the coil, the inner length and width of the coil, the length and width of the primary coil core, and the length and width of the aluminum plate;

[0075] When the primary circuit is installed, the primary coil core is installed on the aluminum plate, the primary coil is installed on the primary coil core, and the primary coil is electrically connected to one end of the primary compensation circuit.

[0076] In this embodiment, the basic parameters of the primary coil are shown in Table 1. According to the COMSOL simulation results, the self-inductance of the transmitting coil is 84uH. Since this article is aimed at the LCC-LCC circuit topology and needs to be compatible with secondary coils of three power levels of 3.7kW, 7.7kW and 11kW, it is necessary to perform interoperability design on system parameters such as the primary resonant capacitor and resonant inductor.

[0077] Table 1 Primary coil structure parameters

[0078]

[0079] S1.4 performs comsol simulation based on the basic parameters of the primary coil set in step S1.3 and the secondary coils of different sizes specified in the national standard, simulates the coupling coefficient of the primary coil and the secondary coil under different gaps, and selects the coupling coefficient according to the upper and lower limits of the coupling coefficient.

[0080] In this embodiment, Comsol simulation is performed on the designed primary coil and coils of different sizes specified in the national standard, and the coupling coefficient between the coils is shown in Table 2.

[0081] Table 2 Coupling coefficient of primary and secondary coils

[0082]

[0083]

[0084] Through simulation, it can be seen that the minimum coupling coefficient of the designed primary coil and the three power levels MF-WPT1, MF-WPT2 and MF-WPT3 coils in the GB / T38775.6 national standard is 0.119, and the maximum coupling coefficient is 0.124. Therefore, the coupling coefficient of the subsequent parameter design of this application is selected as 0.12.

[0085] S2: Determine the lower limit of the inductance value of the primary compensation inductor at each power level according to the system transmission efficiency; the specific steps are:

[0086] S2.1 Construct the fundamental wave approximate model of the MC-WPT system, calculate the active power and reactive power expressions of the fundamental wave approximate model, and construct the total power loss expression of the system, and calculate the system transmission efficiency expression through the active power and the total power loss of the system;

[0087] The system transmission efficiency is equal to the quotient of the absolute value of the active power and the total system power, and the total system power is equal to the sum of the absolute value of the active power and the total system power loss;

[0088] S2.2 constructs an efficiency curve of the system transmission efficiency changing with the primary compensation inductance through simulation, sets the efficiency limit value, intersects the primary compensation inductance range at each power level, obtains the lower limit of the inductance value of the primary compensation inductance that meets multiple power levels, and obtains the first interval of the inductance value of the primary compensation inductance.

[0089] In this embodiment, the system efficiency is analyzed. From the analysis of the transmission efficiency formula in Embodiment 1, it can be seen that when T=1 and δ=π / 2, the system efficiency formula is:

[0090]

[0091] The system efficiency is expressed as α through the above formula p The efficiency curve related to β is as follows Figure 4shown. Figure 4 (a) is the transmission efficiency curve of the system at 3.7kW. Figure 4 (b) is the transmission efficiency curve of the system at 7.7kW. Figure 4 (c) is the transmission efficiency curve of the system at 11kW. Where k is 0.12, and a is s =a p , Q r With Q p Take 600. As can be seen from the figure, in order to make the DC-DC transmission efficiency of the three power levels of 3.7kW, 7.7kW and 11kW greater than or equal to 95% at the same time, Lrp needs to be greater than 12uH. At the same time, when Lrp is equal to 22uH, the efficiency of the MF-WPT3 power level reaches the maximum.

[0092] S3: Determine the lower limit of the inductance value of the primary compensation inductor at each power level according to the system current stress, and determine the upper limit of the inductance value of the primary compensation inductor at each power level according to the system output power requirement; the specific steps are:

[0093] S3.1 sets the upper limit value of the current stress of the primary compensation inductor, simulates the electric stress curve of the current stress value of the primary compensation inductor changing with the inductance value of the primary compensation inductor, and selects the lower limit value of the inductance value of the primary compensation inductor that meets the upper limit value restriction condition of the current stress, and obtains the second inductance value interval of the primary compensation inductor;

[0094] In this embodiment, if Figure 5 As shown, in practice, the current stress of the components needs to be considered, and the coil current I Lp It needs to be less than 63.64A. There is a current expression to make the current stress about L rp It can be seen that L rp The value needs to be greater than 16uH to meet the requirements.

[0095] S3.2 constructs the system output power expression, and draws a curve chart of the inductance value of the primary compensation inductor changing with the primary coil when the inductance ratio is different through simulation;

[0096] A power limit curve is set in the curve graph, and an upper limit value of the inductance value of the primary compensation inductor under each power level is selected according to the power limit curve to obtain a third interval of the inductance value of the primary compensation inductor.

[0097] In this embodiment, according to the above analysis, the system output power expression is:

[0098]

[0099] Take a s =a p , β takes the ratio of the outer diameter of the original and secondary coils as 5 / 6, and further simplifies to It is further shown that L p With L rp Selected curve graph. Figure 6 As shown, Figure 6 (a) is the system power curve when the system power level is 3.7kW. Figure 6 (b) is the system power curve when the system power level is 7.7kW. Figure 6 (c) is the system power curve when the system power level is 11kW. p With L rp The selected values ​​all meet the requirements, and it can be concluded that the output power requirement of MF-WPT1 is met, then L rp It must be less than or equal to 27uH; if it meets the output power requirements of MF-WPT2, then L rp It must be less than or equal to 26uH. To meet the MF-WPT3 output power requirements, Lrp must be less than or equal to 22uH.

[0100] S4: taking the intersection of the inductance value ranges of the primary compensation inductor of each power level, and selecting a suitable inductance value of the primary compensation inductor;

[0101] S5: After determining the inductance value of the primary compensation inductor, determine the primary system parameters according to the resonance relationship.

[0102] In this embodiment, if the system efficiency, current stress limit and system output power limit under the MF-WPT1, MF-WPT2 and MF-WPT3 power levels are to be met, L rp The value of must be greater than 16uH and less than or equal to 22uH. At the same time, in order to maximize the system efficiency, L is selected rp It is 22uH, and the primary system parameters can be further determined based on the resonance relationship.

[0103] Table 3 Primary system parameters

[0104]

[0105] S6 simulation verification:

[0106] In order to verify whether the designed primary coil can meet the output power and output efficiency requirements under different power levels and different ground clearances, simulations are carried out under the straight-on and offset conditions, taking the power level MF-WPT1 and the ground clearance Z1 as an example.

[0107] like Figure 7 and Figure 8As shown, when the power level is MF-WPT1 and the ground clearance is Z1, the output power of the system can reach 3.7kW when facing and offset by adjusting the phase shift angle in the primary and secondary sides, and the efficiency is 95.27% and 92.98% respectively, meeting the interoperability indicators required by the national standard. Among them: Figure 7 (a) is the primary DC input voltage and DC input current when the primary and secondary coils are facing each other when the power level is MF-WPT1 and the ground clearance is Z1; Figure 7 (b) shows the DC output voltage and DC output current of the secondary side when the power level is MF-WPT1 and the ground clearance is Z1, and the primary and secondary coils are facing each other. Figure 8 (a) shows the primary DC input voltage and DC input current when the primary and secondary coils are offset when the power level is MF-WPT1 and the ground clearance is Z1; Figure 8 (b) shows the secondary DC output voltage and DC output current when the primary-secondary coil is offset when the power level is MF-WPT1 and the ground clearance is Z1.

[0108] Following similar steps, the groups of different power levels and ground clearances under the straight-on and offset conditions are simulated in Simulink. The actual simulation data obtained are shown in Table 4. It can be seen that the output power can meet the requirements and the efficiency is greater than 80%, meeting the interoperability requirements.

[0109] Table 4 Output power and efficiency under different power levels and ground clearances in the straight and offset conditions

[0110]

[0111] In summary, this paper proposes a system parameter design method for the power and efficiency limitations of the electric vehicle bidirectional wireless charging system. First, an energy efficiency model of the bilateral LCC compensation BIPT system is established, and the current stress and system efficiency are analyzed. Then, the output power and efficiency are used as indicators for the design of the magnetic coupling mechanism, and the magnetic coupling mechanism is designed. Finally, simulation is used to verify that the designed coupling mechanism and system parameters meet the indicator requirements of the electric vehicle BIPT system.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for designing system parameters of an MC-WPT system adapted for multi-power level transmission, wherein the MC-WPT comprises a primary circuit and a secondary circuit, wherein the primary circuit comprises a primary compensation circuit and a primary coil, wherein the secondary circuit comprises a secondary compensation circuit and a secondary coil, wherein the primary compensation circuit and the secondary compensation circuit are symmetrically arranged LCC topology structures, wherein the primary compensation circuit comprises a primary compensation inductor and two primary compensation capacitors, wherein: The specific steps of the parameter design method are: S1: Determine the coupling coefficient between the primary coil and the secondary coil specified in the national standard; S2: Determine the lower limit of the inductance value of the primary compensation inductor at each power level according to the system transmission efficiency; S3: Determine the lower limit of the inductance value of the primary compensation inductor at each power level according to the system current stress, and determine the upper limit of the inductance value of the primary compensation inductor at each power level according to the system output power requirement; S4: taking the intersection of the inductance value ranges of the primary compensation inductor of each power level, and selecting a suitable inductance value of the primary compensation inductor; S5: After determining the inductance value of the primary compensation inductor, determine the primary system parameters according to the resonance relationship.

2. According to claim 1, a MC-WPT system parameter design method adapted for multi-power level transmission is characterized in that: The specific steps for determining the coupling coefficient between the primary coil and the secondary coil specified by the national standard in step S1 are: S1.1 According to the national standard, determine the multiple power levels that the MC-WPT system needs to meet; S1.2 Select the primary coil and the secondary coil structure, wherein the coil structure includes but is not limited to a circular coil, a rectangular coil and a DD coil; S1.3 Select the power transfer value that the primary circuit needs to meet according to the requirements, set the basic parameters of the primary coil according to the power transfer value, and obtain the self-inductance value of the primary coil through simulation; S1.4 performs comsol simulation based on the basic parameters of the primary coil set in step S1.3 and the secondary coils of different sizes specified in the national standard, simulates the coupling coefficient of the primary coil and the secondary coil under different gaps, and selects the coupling coefficient according to the upper and lower limits of the coupling coefficient.

3. The method for designing MC-WPT system parameters for multi-power level transmission according to claim 2, characterized in that: The power levels in step S1.1 include: MF-WPT1, MF-WPT2, ..., MF-WPTn; wherein: n is a positive integer ≥ 2.

4. The method for designing MC-WPT system parameters for multi-power level transmission according to claim 2, characterized in that: The basic parameters of the primary coil include the number of turns of the primary coil, the outer length and width of the coil, the inner length and width of the coil, the length and width of the primary coil core, and the length and width of the aluminum plate; When the primary circuit is installed, the primary coil core is installed on the aluminum plate, the primary coil is installed on the primary coil core, and the primary coil is electrically connected to one end of the primary compensation circuit.

5. The method for designing MC-WPT system parameters for multi-power level transmission according to claim 1, characterized in that: The specific steps of determining the lower limit of the inductance value of the primary compensation inductor at each power level according to the system transmission efficiency in step S2 are: S2.1 Construct the fundamental wave approximate model of the MC-WPT system, calculate the active power and reactive power expressions of the fundamental wave approximate model, and construct the total power loss expression of the system, and calculate the system transmission efficiency expression through the active power and the total power loss of the system; The system transmission efficiency is equal to the quotient of the absolute value of the active power and the total system power, and the total system power is equal to the sum of the absolute value of the active power and the total system power loss; S2.2 constructs an efficiency curve of the system transmission efficiency changing with the primary compensation inductance through simulation, sets the efficiency limit value, intersects the primary compensation inductance range at each power level, obtains the lower limit of the inductance value of the primary compensation inductance that meets multiple power levels, and obtains the first interval of the inductance value of the primary compensation inductance.

6. The method for designing MC-WPT system parameters for multi-power level transmission according to claim 5, characterized in that: The specific method for determining the lower limit of the inductance value of the primary compensation inductor at each power level according to the system current stress in step S3 is: An upper limit value of the current stress of the primary compensation inductor is set, and an electric stress curve diagram showing the change of the current stress value of the primary compensation inductor with the inductance value of the primary compensation inductor is simulated, and a lower limit value of the inductance value of the primary compensation inductor that meets the upper limit value constraint condition of the current stress is selected to obtain a second interval of the inductance value of the primary compensation inductor.

7. The method for designing MC-WPT system parameters for multi-power level transmission according to claim 6, characterized in that: The specific method for determining the upper limit of the inductance value of the primary compensation inductor at each power level according to the system output power requirement in step S3 is: Construct the system output power expression, and draw the curve of the inductance value of the primary compensation inductor changing with the primary coil when the inductance ratio is different through simulation; A power limit curve is set in the curve graph, and an upper limit value of the inductance value of the primary compensation inductor under each power level is selected according to the power limit curve to obtain a third interval of the inductance value of the primary compensation inductor.

8. The method for designing MC-WPT system parameters for adapting to multi-power level transmission according to claim 7, characterized in that: In step S4, the intersection of the inductance value intervals of the primary compensation inductor of each power level is taken, and the specific method of selecting the appropriate inductance value of the primary compensation inductor is: The inductance value interval of the primary compensation inductor is obtained by taking the intersection of the first interval, the first interval and the third interval of the inductance value of the primary compensation inductor obtained in step S2 and step S3, and the inductance value of the primary compensation inductor is selected according to the principle of maximizing the system transmission efficiency.

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