Capacitive coupling-based single-transmitting multi-receiving wireless power supply system for electric vehicles

Abstract

The present application belongs to the technical field of wireless power transmission, and aims at the problems of insufficient flexible power supply capability, poor anti-interference capability, low energy efficiency and lack of universal design method of the existing capacitive coupling multi-load electric vehicle wireless power supply system, and provides an electric vehicle single-transmitting multi-receiving wireless power supply system based on capacitive coupling, which uses the mudguard of the electric vehicle as a third plate to enhance the stray capacitance and provide a current loop; an optimized model of the coupler considering cross coupling and a circuit design model ignoring cross coupling are established; a transmitting side CLL-M compensation circuit with isolation is adopted to realize constant voltage output of the transmitting plate and constant current output of the load; and a universal design method suitable for multiple electric vehicles is provided. The system can effectively improve the energy efficiency characteristics, has flexible power supply capability and strong anti-interference capability, and can determine the minimum load spacing ignoring cross coupling, and each load outside the spacing maintains independent output.

Description

Technical Field

[0001] This invention relates to the field of wireless power transfer (WPT) technology, and more particularly to a single-transmitter, multiple-receiver wireless power supply system for electric vehicles based on capacitive coupling. Background Technology

[0002] Single-capacitor coupled wireless power transfer (SCC-WPT) technology has been researched and applied in transportation, drones, medical equipment, and service robots due to its advantages such as lightweight coupler, low eddy current loss, easily customizable shape, ability to transfer energy across metals, and good anti-offset performance. The power transfer mechanism of SCC-WPT technology is as follows: in the absence of a clear current return path, a complete electrical loop is formed through the system's stray capacitance, the self-capacitance of the metal plates, and the ground. Compared to traditional electric field coupled systems, this reduces the number of coupling plates, lowers cross-coupling, and improves the flexibility of powering multiple loads.

[0003] Existing SCC-WPT system coupling structures are mainly classified into four types: both the transmitter and receiver sides are grounded, neither side is grounded, both sides are ungrounded (including a repeater board), and the transmitter side is grounded while the receiver side is ungrounded. Among these, the type with the transmitter side grounded and the receiver side ungrounded balances system energy efficiency and flexible power supply capabilities. To improve energy efficiency and robustness by increasing the stray capacitance to ground on the receiver side, existing methods include adding an additional electrode (three-electrode coupling mechanism) or a suspended conductor on the receiver side, or embedding the grounding side into the ground via metal to optimize ground conductivity.

[0004] In the field of multi-load wireless power supply, traditional capacitor-based wireless power transfer systems are mainly divided into three structures: many-to-many, one-to-many, and domino-style structures. Many-to-many structures typically require multiple inverters in parallel, leading to complex control issues, high coupler losses, poor offset resistance, and complex coupler construction with an excessive number of plates. One-to-many structures generally suffer from complex power distribution problems, resulting in lower output power. Furthermore, most studies have not considered the impact of cross-coupling between loads on the system and have failed to adequately address power decoupling issues. Domino-style structures are suitable for long-distance transmission, but their offset resistance is poor, and the additional relay inductors increase system size and losses. Overall, existing CPT multi-load power supply systems perform poorly under rotational and angular offset conditions, exhibiting limited flexible power supply capabilities; most studies have not considered the effects of cross-coupling between loads, and a simple and reliable universal design scheme for multi-load systems is lacking.

[0005] Therefore, the current multi-load CPT systems mainly have the following technical problems: First, they lack flexible power supply capability, making it difficult to maintain constant output when horizontal, rotating, or angularly offset; second, they have poor anti-interference capability, making it difficult to achieve multi-channel power decoupling and active distribution under load changes, shifting in and out, cross-coupling, or environmental influences; third, the system energy efficiency characteristics, especially the energy efficiency of the SCC-WPT system, are low; and fourth, there is a lack of simple and easy-to-implement general design schemes for multi-load systems. Summary of the Invention

[0006] This invention provides a single-transmitter, multi-receiver wireless power supply system for electric vehicles based on capacitive coupling. The technical problem it solves is that the existing SCC-WPT multi-load wireless power supply system lacks a general optimization and design method when considering cross-coupling between loads, making it difficult to balance high energy efficiency, flexible power supply, and anti-interference capabilities.

[0007] To address the above technical problems, this invention provides a single-transmitter, multi-receiver wireless power supply system for electric vehicles based on capacitive coupling, comprising a transmitter and at least one electric vehicle load. The transmitter includes a transmitting electrode plate; each electric vehicle load includes a receiving electrode plate, a mudguard, and a secondary-side compensation network. The mudguard serves as a third electrode plate that enhances the stray capacitance on the receiving side and provides a current loop. The receiving electrode plate and the mudguard are respectively connected to the secondary-side compensation network.

[0008] Furthermore, the system is designed using the following parameter design process:

[0009] The first step is to determine the basic input parameters of the system and the actual physical constraints;

[0010] The second step is to optimize the coupler geometry while taking into account all cross-coupling capacitances.

[0011] The third step is to design a compensation network based on an equivalent model that ignores cross-coupling;

[0012] The fourth step is to calculate the values ​​of all compensation components based on the output power requirements.

[0013] Furthermore, the first step specifically includes:

[0014] Determine the DC input voltage based on the actual voltage range of the power supply.

[0015] The system operating frequency is selected based on the internationally permitted frequency bands for wireless power transmission and the capabilities of the power devices.

[0016] The dimensional constraints of the coupler parameters are determined based on the chassis space of the electric vehicle and the installation position of the mudguard. The coupler parameters include the distance of the transmitting plate from the ground, the transmission distance, the shortest distance from the mudguard to the receiving plate, the spacing between each load, the length and width of the transmitting plate, the side length of the receiving plate, and the outer radius of the mudguard.

[0017] Furthermore, the second step specifically includes:

[0018] The ground is set as the reference node, and the transmitting electrode, each receiving electrode, and the mudguard are set as different nodes. A multi-port capacitor network model is established, and the coupling coefficient between any two ports and the coupling gain from the transmitting port to each receiving port are defined accordingly.

[0019] With the mudguard parameters and load spacing fixed, the side length of the receiving electrode and the distance from the ground of the transmitting electrode are changed simultaneously within the determined size constraints. The corresponding coupling gain and coupling coefficient are calculated respectively. Based on the calculation results, the side length of the receiving electrode and the distance from the ground of the transmitting electrode that make both larger are selected.

[0020] With the selected receiving electrode side length and transmitting electrode distance from the ground fixed, within the size constraints, change the mudguard radius and the distance from the mudguard to the receiving electrode, recalculate the coupling gain and coupling coefficient, and select the mudguard radius and distance where both are at their maximum allowable values.

[0021] Change the horizontal spacing between each load and repeat the above optimization process. Determine the minimum spacing that can be ignored for cross-coupling based on the change in output power, and ensure that the actual load spacing is not less than this minimum spacing.

[0022] Furthermore, the third step specifically includes:

[0023] The impedance parameters obtained from electromagnetic simulation are converted into admittance parameters. A simplified equivalent circuit of admittance parameters is constructed under the assumption of ignoring cross coupling, where the transmitting side is equivalent to a capacitor, each receiving side is equivalent to a capacitor, and there is a controlled current source between the transmitting side and each receiving side.

[0024] A CLL compensation network is set on the transmitting side so that the CLL compensation network and the equivalent capacitance of the transmitting port together form a CLLC resonant structure; an M-type secondary side compensation network is set on each receiving side.

[0025] Furthermore, the third step also includes: connecting an LC filter to the inverter output; and connecting a 1:1 isolation transformer after the LC filter.

[0026] Furthermore, the fourth step specifically includes:

[0027] Determine the single load and total output power targets based on the battery capacity and expected charging time of each electric vehicle.

[0028] The effective value of the inverter output fundamental voltage is calculated from the DC input voltage. The emitter voltage is expressed as a function of the input fundamental voltage and the inductance ratio. The output current is expressed as a function of the emitter voltage and the M-type compensation parameters. The above relationships are combined and the required inductance ratio is derived from the target output power. The inductance ratio is defined as the ratio of the series inductance to the parallel inductance in the CLL compensation network.

[0029] Based on the series resonance condition, the series inductance value is calculated from the operating angular frequency and the equivalent capacitance of the transmitting port. Then, the parallel inductance value is calculated according to the definition of the inductance ratio. Finally, the compensation capacitor value is calculated from the operating angular frequency and the parallel inductance value according to the parallel resonance condition.

[0030] For each receiving side, the equivalent capacitance of the receiving port is obtained by electromagnetic simulation. After selecting additional parallel capacitors, they are added together to obtain the total equivalent capacitance. The series inductance value is calculated from the operating angular frequency and the total equivalent capacitance according to the resonance condition. Then, the secondary inductance value is calculated from the expected coupling coefficient of M-type compensation and the calculated series inductance value.

[0031] Furthermore, the fourth step also includes:

[0032] The equivalent load resistance of the system under rated output current is calculated and compared with the load resistance value that optimizes efficiency. If the actual battery equivalent resistance deviates from the optimal value, a DC / DC converter is added after the rectified and filtered output for impedance matching.

[0033] Furthermore, after completing all parameter calculations, verification is performed, including:

[0034] By combining circuit simulation and electromagnetic field simulation, we check whether the inverter output voltage and current waveforms meet the soft-switching conditions.

[0035] Simulate the dynamic switching in and out process of the load to verify whether the output current remains constant and whether the power distribution is stable.

[0036] Change the position offset, rotation offset, or angular offset of the receiving end, and observe whether the degree of change in the coupling capacitance is within the preset allowable range;

[0037] If the simulation results deviate from expectations, then revert to the coupler size in step two or the inductance ratio in step four, and repeat the above steps until the design requirements are met.

[0038] Furthermore, the transmitter also includes a full-bridge inverter, the LC filter is connected to the two output terminals of the full-bridge inverter, the primary inductance of the 1:1 isolation transformer is connected to the output terminal of the LC filter, one end of the secondary inductor is connected to the CLL compensation network, and the center tap of the secondary inductor is grounded.

[0039] This invention addresses the technical problems of existing capacitively coupled wireless power supply systems for electric vehicles in multi-load scenarios, including insufficient flexible power supply capability, poor anti-interference capability, low system energy efficiency, and lack of universal design methods. It provides a capacitively coupled single-transmitter, multi-receiver wireless power supply system for electric vehicles. Based on a three-plate coupler, and considering the electric vehicle's structure, the system uses the mudguard as a third plate to enhance stray capacitance on the receiving side and provide a current loop. A universal optimization model for the coupler considering cross-coupling between loads and a universal circuit design model ignoring cross-coupling are derived. Energy efficiency is improved by optimizing coupler size and circuit topology. A CLL-M compensation circuit with isolation on the transmitting side is designed to achieve constant voltage output from the transmitting plate and constant current output from the loads, with the transmitting side grounded through the secondary side of an ideal transformer. A simple and universal multi-load design scheme is provided, applicable to wireless charging systems for any number of electric bicycles. Using the above technical solution, the system effectively improves energy efficiency, possesses flexible power supply capability and strong anti-interference capability, and can determine the minimum spacing range where cross-coupling between loads can be ignored. Outside this range, each load can maintain independent output. Attached Figure Description

[0040] Figure 1 This is a circuit structure diagram of a single-transmitter, multiple-receiver wireless power supply system for electric vehicles based on capacitive coupling, provided in an embodiment of the present invention.

[0041] Figure 2 This is the directed connectivity graph of the multi-load SCC-WPT system coupler provided in the embodiments of the present invention, considering all capacitors;

[0042] Figure 3 This is a simplified circuit model diagram of the coupler in the multi-load SCC-WPT system provided in this embodiment of the invention, ignoring cross-coupling between loads;

[0043] Figure 4 This is a circuit model diagram of the Y-parameter of the coupler provided in an embodiment of the present invention;

[0044] Figure 5 This is a front view of the coupler provided in an embodiment of the present invention;

[0045] Figure 6 This is a 3D diagram of the coupler provided in an embodiment of the present invention;

[0046] Figure 7 These are three-dimensional and contour plots showing the changes in coupling gain and coupling coefficient with the distance between the transmitting electrode and the ground and the side length of the receiving electrode, as provided in the embodiments of the present invention; wherein (a) is a three-dimensional plot of coupling gain, (b) is a three-dimensional plot of coupling coefficient, (c) is a two-dimensional contour plot of coupling gain, and (d) is a two-dimensional contour plot of coupling coefficient;

[0047] Figure 8This is a line graph showing the changes in coupling gain and coupling coefficient with the distance from the mudguard to the receiving electrode and the radius of the mudguard, provided in the embodiments of the present invention; where (a) is a graph showing the change in coupling gain and (b) is a graph showing the change in coupling coefficient.

[0048] Figure 9 This is a circuit topology diagram of a three-load system provided in an embodiment of the present invention;

[0049] Figure 10 This is a simplified equivalent circuit diagram provided by an embodiment of the present invention, ignoring cross-coupling between loads;

[0050] Figure 11 This is a graph showing the variation of various parameters when the three-load SCC-WPT system provided in this embodiment of the invention achieves maximum efficiency; where (a) is a graph showing the relationship between efficiency and load and frequency, (b) is a graph showing the relationship between optimal load and operating frequency, (c) is a graph showing the relationship between efficiency and M-type compensation coupling coefficient, and (d) is a graph showing the relationship between efficiency and compensation topology inductance ratio.

[0051] Figure 12 This is a flowchart of the system parameter design provided in an embodiment of the present invention;

[0052] Figure 13 The following are simulation results of the system input and output voltage provided in the embodiments of the present invention; wherein (a) is the inverter output voltage and current waveform diagram, and (b) is the inverter output voltage and current, equivalent load voltage and output power waveform diagram during the load switching in and out process;

[0053] Figure 14 This is a simulation result diagram showing the impact of reduced load spacing on load output power provided in an embodiment of the present invention;

[0054] Figure 15 This is a simulation result diagram of the coupling capacitance of a single load in a free position as a function of position offset, provided by an embodiment of the present invention.

[0055] Figure 16 This is a simulation result diagram of the coupling capacitance of a single load in a free position as a function of rotational offset, provided by an embodiment of the present invention.

[0056] Figure 17 This is a simulation result diagram of the coupling capacitance of a single load in a free position as a function of angular offset, provided by an embodiment of the present invention. Detailed Implementation

[0057] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0058] The single-transmitter, multi-receiver wireless power supply system (multi-load SCC-WPT system) for electric vehicles based on capacitive coupling provided in this embodiment of the invention, taking an electric motorcycle / bicycle as an example, has the following circuit structure: Figure 1 As shown, it includes a transmitter and multiple electric vehicle load terminals. The transmitter includes a transmitter side and a transmitter electrode. Each electric vehicle load terminal includes a receiver electrode, a mudguard, and a receiver side. The transmitter side is powered by a DC power supply (…). The receiving side consists of a full-bridge inverter (DC / AC, direct current to alternating current), a primary-side compensation network, and a secondary-side compensation network, a full-bridge rectifier, and a load. The system is composed of three plates. Based on the design concept of a three-plate coupler, and combined with the structure of the electric vehicle, the mudguard is used as the third plate to enhance the stray capacitance on the receiving side and provide a current loop. It is connected to the secondary compensation network with the receiving plate.

[0059] Figure 2 This diagram illustrates the directed connectivity of the coupler in a multi-load SCC-WPT system, considering all capacitances (self-capacitance, mutual capacitance, and cross-coupling capacitance). The system has a total of... There are several nodes, with node 0 representing the ground and also serving as the reference node; node 1 represents the emitting electrode, and nodes 2 to... Node number represents the receiving electrode plate and the mudguard. The nodes together form Ports and One directional branch road, of which This represents the total coupling capacitance between nodes. Define a node. and The positive direction of the capacitance branch between them is... point to This also serves as a reference direction for the branch current. The branch number is defined as follows:

[0060] (1)

[0061] in, .

[0062] According to the superposition theorem, the relationship between port voltage and port current can be expressed as:

[0063] (2)

[0064] in, to for Voltage at each port, to for Current at each port, It is an impedance symmetric matrix. Each element in is defined as:

[0065] (3)

[0066] in, Indicates the system's operating angular frequency; ,when hour Indicates port or self-capacitance, hour Indicates port and The mutual capacitance between them can be calculated by the following formula:

[0067] (4)

[0068] in, It is an incidence matrix that describes the relationship between nodes and branches. It is the branch admittance matrix. It is the identification matrix for extracting port branches. This is the branch capacitance matrix. It's worth noting that the port mutual capacitance can be positive or negative, depending on the coupling relationship between the plates; the strength of the coupling between ports is negatively correlated with the absolute value of the port mutual capacitance.

[0069] Based on equations (2) to (4), a Z-parameter controlled voltage source model of the coupler can be established, that is, each port is equivalent to its own capacitance and P-1 current-controlled voltage sources (CCVS) connected in series. The coupling coefficient between the coupler ports can then be defined as:

[0070] (5)

[0071] It reflects the system's power transmission capability.

[0072] The combined equation (2) Parametric equations and multiport networks Parametric equations:

[0073] (6)

[0074] The method of obtaining the short-circuit is used. Parameter representation parameter:

[0075] (7)

[0076] The matrix, when its first row and first column are removed, is a symmetric matrix; where Elements of the matrix Represented as:

[0077] (8)

[0078] use , … This represents the coupling gain between the transmit and receive ports, used to describe the strength of the coupling between them, and is defined as the ratio of the receive-side port voltage to the transmit-side port voltage. Its relationship with the coupling coefficient is as follows:

[0079] (9)

[0080] This embodiment will incorporate a coupler. Coupling coefficient under parameters and The coupling gain under certain parameters is optimized to improve the coupling coefficient and coupling gain, thereby enhancing the system's energy efficiency.

[0081] Figure 3 A simplified coupler circuit model of a multi-load SCC-WPT system is presented, ignoring cross-coupling between loads. Based on... Figure 3 The voltage-current relationship at the P port of the system is as follows:

[0082] (10)

[0083] The symmetric matrix can be obtained using the short-circuit method. The main diagonal element is:

[0084] (11)

[0085] in, Refers to the total equivalent self-capacitance of port 1. Indicates port The equivalent self-capacitance, .

[0086] The other elements in the first column are:

[0087] (12)

[0088] in, This is to simplify the expression of custom parameters, specifically as follows:

[0089] (13)

[0090] When the cross-coupling effect between loads is ignored, the matrix All elements except those in the first row, first column, and main diagonal are 0.

[0091] At this time, let:

[0092] (14)

[0093] in, In The coupling coefficient between the transmit and receive ports under the parametric model. This refers to the mutual capacitance between the transmitting and receiving ports. The mutual capacitance between the receiving port and the transmitting port is equal to the mutual capacitance between them. .

[0094] Depend on It can be seen that, The elements of the first row and first column of the matrix are:

[0095] (15)

[0096] From equation (7), we can see that The elements of the first row and first column of the matrix are:

[0097] (16)

[0098] and Other elements of the matrix can be used by the open-short-circuit method. The parameters indicate that... The matrix is ​​a symmetric matrix excluding the first row and first column, and the elements on the main diagonal are 0. The reciprocal of the parameter; all other elements are 0. That is... The matrix can be represented as:

[0099] (17)

[0100] According to equation (17), the coupler can be obtained. Parametric equivalent circuit model such as Figure 4 As shown, this model is also called the inverse hybrid parameter equivalent model, where the transmitter equivalent capacitance is... and total current for:

[0101] (18)

[0102] This embodiment will utilize the method of ignoring cross-coupling. Optimize the circuit using a parametric equivalent model.

[0103] This embodiment considers the transmission capacity of the system's energy transmission channel, namely the power transmission capacity and port coupling strength between the transmitting and receiving ports. Combining the coupling coefficient and coupling gain, and taking a three-load scenario as an example, it aims to maximize these two indicators and optimize the system's coupler while considering all cross-couplings between loads. The front view and 3D diagram of the coupler proposed in this embodiment are shown below. Figure 5 and Figure 6 As shown. In the Ansys Maxwell simulation, the ground P0 is replaced by a 3000×3000×1mm aluminum plate, and the voltage excitation is set to 0V; the system powers three identical electric bicycles, and the receiving plate P... 2 / 4 / 6 Both length and width are l1; mudguard P 3 / 5 / 7 The coupler is a quarter-sphere with radius R, which increases the stray capacitance to ground on the receiving side. The mudguard and receiving electrode are highly symmetrical along the central axis, and the distance d3 from the center of the sphere to the receiving electrode is the length of the hypotenuse of an isosceles right triangle. Furthermore, all loads are equally spaced. Both the transmitting and receiving electrodes are made of 1mm thick aluminum plates, while the mudguard, due to considerations of processing difficulty, hardness, and cost, uses 3mm thick copper. Based on the limitations of practical applications, the dimensions of the coupler are constrained as shown in Table 1.

[0104] Table 1. Dimensional parameters of the coupling mechanism

[0105]

[0106] Simulations were performed on four sets of data with load spacing of 100 mm, 200 mm, 300 mm, and 400 mm. The simulation results show that the load spacing does not affect the coupling gain and coupling coefficient between the transmit and receive ports, and the coupling gain and coupling coefficient of the three loads with respect to the transmit port are approximately equal. This is because, from a physical perspective, changing the load spacing does not affect the coupling between the transmit and receive ports, but only the coupling between the load ports; furthermore, since three identical loads are used, their coupling to the transmit port is the same, so we can assume:

[0107] (19)

[0108] In summary, this embodiment only shows the optimization results when d4=300mm. The optimization results of d1 and l1 when d3 and R are fixed are discussed separately; and the optimization results of d3 and R when d1 and l1 are fixed are discussed separately.

[0109] Figure 7 The optimization results for d1 and l1 are shown when d3=400mm and R=100mm. Figure 7 In the middle (a) and (b), respectively, are three-dimensional plots showing the coupling gain and coupling coefficient as a function of d1 and l1. Figure 7 In the diagram, (c) and (d) are two-dimensional contour plots showing the coupling gain and coupling coefficient as a function of d1 and l1, respectively. Figure 7 It can be seen that increasing the side length l1 of the receiving electrode significantly increases the coupling gain and coupling coefficient; increasing the distance d1 of the transmitting electrode from the ground significantly increases the coupling coefficient, but slightly decreases the coupling gain. Therefore, d1=50mm and l1=300mm are chosen. At this time, the coupling gain is 0.721 and the coupling coefficient is 0.12.

[0110] Figure 8 The optimization results for d3 and R are shown when d1=50mm and l1=300mm. Figure 8 In the diagram, (a) and (b) are line graphs showing the coupling gain and coupling coefficient as a function of d3 and R, respectively. Figure 8 It can be seen that increasing d3 and R will increase the coupling gain and coupling coefficient. Therefore, d3 is selected as 400 mm and R as 100 mm.

[0111] This embodiment uses three loads for verification. Figure 9 The designed circuit topology is shown. The transmitter consists of a DC power supply, a full-bridge inverter, and an LC filter (including two sets of LC series networks connected in series at the two outputs of the inverter, namely inductors). ,capacitance ,inductance ,capacitance ), 1:1 isolation transformer (primary inductance) Secondary inductor CLL boost compensation (including capacitor) Parallel inductors and series inductors The inverter consists of a receiving plate (P1) and a transmitting plate (P1); each receiving end consists of a receiving plate, a baffle plate, an M-type constant current compensation, a full-bridge rectifier, a filter capacitor, and a load. The LC filter removes high-order harmonics from the inverter output voltage and distributes them evenly across the bridge arms to balance the common-mode impedance; the 1:1 isolation transformer isolates the power supply and provides a grounding point. (The last part, "capacitor," appears to be a repetition and can be omitted.) to Used to increase the equivalent capacitance of the receiving port and reduce the value of the compensation inductor. It is the output voltage of the inverter; It is the output current of the inverter. and for The effective value of the fundamental voltage after LC filtering is:

[0112] (20)

[0113] Figure 10A simplified equivalent circuit is shown, neglecting cross-coupling between loads. The equivalent capacitance C at the emitter port is... a Controlled source current The following relationship must be satisfied:

[0114] ,(twenty one)

[0115] The equivalent capacitance of the receiving port is:

[0116] .(twenty two)

[0117] The full-bridge rectifier and the load are equivalent to resistors, i.e. The primary-side CLL compensation topology and the equivalent capacitance C of the transmitter port. a This system constitutes a CLLC constant voltage compensation, providing both voltage gain and reactive power compensation. Due to the large size of the transmitting plate, no additional capacitor is needed on the transmitting side; furthermore, CLLC compensation effectively reduces the resonant inductance compared to LCLC compensation. The constant voltage across the transmitting plate contributes to a uniform electric field distribution near the plate; the M-type compensation on the receiving side achieves constant current output and provides isolation to reduce the influence of the oscilloscope probe on the system. The resonant condition of the CLL-M compensation topology is:

[0118] ,(twenty three)

[0119] in At this time, the voltage of the emitter plate is:

[0120] ,(twenty four)

[0121] in, This is the inductance ratio of the CLL compensated topology. At this time, the output current at each load port is:

[0122] (25)

[0123] in, , , These represent the mutual inductance values ​​of the M-type compensation networks in the three receivers.

[0124] As can be seen from the above formula, as long as the input voltage... If this remains constant, the output current can remain constant. Simultaneously, in the resonant state, the response impedance of the secondary side of the M-type compensation to the primary side is:

[0125] (26)

[0126] Therefore, the currents on the primary side are as follows:

[0127] (27)

[0128] According to equations (23) and (24), the voltage and current gains of the system can be obtained as follows:

[0129] (28)

[0130] According to equation (24), the output power of the system can be obtained as:

[0131] (29)

[0132] When the parasitic resistance of each component in the system is ignored, we can obtain:

[0133] (30)

[0134] This represents the inductance L flowing through the secondary side of the isolation transformer. s The current.

[0135] At this point, the inductance can be obtained. and The currents on are respectively:

[0136] (31)

[0137] At this point, Maple is used to initially optimize parameters such as voltage gain, M-type compensation topology coupling coefficient, system operating frequency, and load size, with the goal of maximizing system efficiency. Combining the above formula and neglecting the losses in the system's capacitors, inverters, rectifiers, couplers, etc., only the losses in the inductor coil are considered. Substituting the simulated capacitance value from Ansys Maxwell for d4=300mm into the calculation, a set of system parameters is given in Table 2, where C... ex1 -C ex3 The value of the compensation inductor is determined to balance system efficiency and compensation. The law that the three-load SCC-WPT system must satisfy to achieve maximum efficiency is as follows: Figure 11 As shown, (a) is the relationship between efficiency and load and frequency, (b) is the relationship between optimal load and operating frequency, (c) is the relationship between efficiency and M-type compensation coupling coefficient, and (d) is the relationship between efficiency and compensation topology inductance ratio.

[0138] Table 2 Circuit Optimization Parameters

[0139]

[0140] Depend on Figure 11 It can be known that:

[0141] 1) At maximum efficiency, there is an approximately linear one-to-one correspondence between the optimal load and the optimal operating frequency. Based on experience, considering the difficulty of tuning and minimizing the system inductance, a system operating frequency of 1.5MHz is selected, at which point the optimal load is 150Ω. In practical applications, the equivalent resistance of an electric bicycle battery is not this large, requiring the addition of a DC / DC converter in the subsequent stage.

[0142] 2) The system efficiency reaches its maximum when the M-type compensation topology coupling coefficient is around 0.2.

[0143] 3) Compensation topology inductance ratio The change has little impact on system efficiency. Its value is adjusted based on the target output power.

[0144] Based on the above analysis, the system parameter design process is as follows: Figure 12 As shown, the steps include:

[0145] Step 1: Determine the basic input parameters of the system and the actual physical constraints;

[0146] Step 2: Optimize the coupler geometry while taking into account all cross-coupling capacitors;

[0147] Step 3: Design a compensation network based on an equivalent model that ignores cross-coupling;

[0148] Step 4: Calculate the values ​​of all compensation components based on the output power requirements.

[0149] (1) First step: Determine the basic input parameters of the system and the actual physical constraints

[0150] Before proceeding with electrical design, the basic requirements must first be defined based on the actual application scenario (e.g., outdoor wireless charging for electric bicycles). This step specifically includes:

[0151] 1. Determine the DC input voltage (E) based on the actual voltage range of the power supply. dc ).

[0152] The DC input voltage is selected based on the actual voltage range of the power supply type (such as battery bank, photovoltaic panel, or mains rectifier output). This value will be used to calculate the effective value of the fundamental voltage output by the inverter according to equation (20). In this embodiment, E dc =300 V.

[0153] 2. Select the system operating frequency (f) based on the internationally permitted frequency bands for wireless power transmission and the capabilities of the power devices.

[0154] Taking into account the permitted frequency bands for international wireless power transmission, the switching losses and drive capabilities of power switching devices, and the size and quality factor of resonant inductors and capacitors, a specific operating frequency is selected. If system efficiency is also a consideration, refer to... Figure 11 The optimal load and operating frequency correspondence shown in Figure (a) is used to select the frequency point that maximizes efficiency based on the expected load range within the same graph. In this example, 1.5 MHz is selected.

[0155] 3. Determine the dimensional constraints of the coupler parameters based on the space of the electric vehicle chassis and the installation position of the mudguards.

[0156] Based on mechanical constraints such as the chassis space of the electric vehicle, the actual shape and installation position of the mudguards, and the area that the transmitting electrode can cover, the value ranges of the parameters listed in Table 1 are determined. These parameters include: the distance of the transmitting electrode from the ground, the transmission distance, the shortest distance from the mudguard to the receiving electrode, the spacing between each load, the length and width of the transmitting electrode, the side length of the receiving electrode, and the outer radius of the mudguard. All subsequent optimizations must be performed within these constraints. The specific limiting parameters and their constraint ranges of the coupler in this embodiment are listed in Table 1, and optimization is performed within these ranges during the design process.

[0157] (2) Second step: Coupler size optimization considering all cross-coupled capacitors

[0158] This step aims to maximize the coupling gain and coupling coefficient between the transmit and receive ports, and uses electromagnetic field simulation software (such as Ansys Maxwell) for parametric scanning. Specifically, it includes:

[0159] 1. Set the ground as the reference node, and set the transmitting plate, each receiving plate, and the mudguard as different nodes to establish a multi-port capacitor network model, and define the coupling coefficient between any two ports and the coupling gain from the transmitting port to each receiving port accordingly.

[0160] In this embodiment, the ground is set as the reference node (node ​​0), the transmitting electrode is set as node 1, and the receiving electrode and mudguard of each electric vehicle are set as consecutively numbered nodes. The port Z-parameter matrix is ​​calculated using equations (2) to (4), which includes all self-capacitance, mutual capacitance, and cross-coupling capacitance between loads. Then, the coupling coefficient between any two ports is defined according to equation (5), and the coupling gain from the transmitting port to each receiving port is defined according to equation (9).

[0161] 2. With the mudguard parameters and load spacing fixed, within the determined size constraints, simultaneously change the side length of the receiving electrode and the distance from the ground of the transmitting electrode, calculate the corresponding coupling gain and coupling coefficient respectively, and select the side length of the receiving electrode and the distance from the ground of the transmitting electrode that make both larger based on the calculation results.

[0162] Temporarily fix the mudguard parameters (e.g., take the shortest distance from the mudguard to the receiving electrode as 400 mm, and the mudguard radius as 100 mm) and the load spacing (e.g., take 300 mm). Within the allowable range in Table 1, simultaneously change the side length of the receiving electrode and the distance of the transmitting electrode from the ground, and calculate the coupling gain and coupling coefficient defined above for each set of values. Plot as shown. Figure 7 The three-dimensional surface plots and contour plots (a) to (d) are shown. It can be observed that the larger the side length of the receiving electrode, the more significant the improvement in both indicators; increasing the distance of the transmitting electrode from the ground significantly improves the coupling coefficient, but slightly reduces the coupling gain. A compromise value is selected based on the actual focus (for example, in this embodiment, the distance of the transmitting electrode from the ground is 50 mm, and the side length of the receiving electrode is 300 mm).

[0163] 3. Fix the selected receiving electrode side length and the distance of the transmitting electrode from the ground. Within the size constraints, change the mudguard radius and the distance from the mudguard to the receiving electrode, recalculate the coupling gain and coupling coefficient, and select the mudguard radius and distance that are both at the maximum allowable values.

[0164] With the previously selected receiving electrode side length and transmitting electrode distance from the ground fixed, the mudguard radius and the distance from the mudguard to the receiving electrode are changed. The coupling gain and coupling coefficient are then recalculated to obtain the following results: Figure 8 The line graph shown illustrates this. Simulations demonstrate that the larger these two dimensions are, the better the coupling performance. Therefore, within the limits allowed by the mechanical structure, the maximum value within each constraint range is taken (e.g., radius 100 mm, distance 400 mm).

[0165] 4. Change the horizontal spacing between each load, repeat the above optimization process, determine the minimum spacing that can ignore cross coupling based on the change in output power, and ensure that the actual load spacing is not less than this minimum spacing.

[0166] Change the horizontal spacing between each load (e.g., 100 mm, 200 mm, 300 mm, 400 mm), repeat the above optimization process, and observe whether the transmit-receive coupling changes with the spacing. Results (e.g.) Figure 14 As shown in the diagram, when the spacing is reduced to 100mm, the load output power changes by approximately 15%, while the mutual influence is minimal when the spacing is greater than this value. Therefore, a minimum spacing where cross-coupling is negligible can be determined. In actual layout, the actual distance between any two loads should not be less than this value.

[0167] (3) Third step: Design compensation network based on equivalent model that ignores cross coupling

[0168] Once the actual spacing between all loads is greater than the minimum spacing determined in the previous step, cross-coupling between loads can be ignored, and a simplified equivalent circuit (such as...) can be used. Figure 4(As shown) to design the compensation topology for the transmitting and receiving sides. Specifically, this step includes:

[0169] 1. Convert the Z parameters obtained from electromagnetic simulation into Y parameters. Under the assumption of ignoring cross-coupling, construct a simplified equivalent circuit of Y parameters, where the transmitting side is equivalent to a capacitor, each receiving side is equivalent to a capacitor, and there is a controlled current source between the transmitting side and each receiving side.

[0170] The Z parameters obtained from electromagnetic simulation are converted into Y parameters using equation (7). Under the assumption of neglecting cross-coupling, the Y matrix has the concise form shown in equation (17): only the elements in the first row, first column, and diagonal are non-zero. Based on this matrix, a... Figure 4 The equivalent circuit model shown is such that the transmitting side is equivalent to a capacitor, each receiving side is also equivalent to a capacitor, and there is a controlled current source between the transmitting side and each receiving side.

[0171] 2. Set up a CLL compensation network on the transmitting side so that the CLL compensation network and the equivalent capacitance of the transmitting port together form a CLLC resonant structure, so that the series inductor and the equivalent capacitance of the transmitting port resonate in series, and the parallel inductor and the compensation capacitor resonate in parallel, thereby keeping the voltage of the transmitting plate constant.

[0172] Transmitter-side circuit structure as follows Figure 9 As shown, the structure includes an LC filter, a 1:1 isolation transformer, and a CLL compensation network. This CLL network, together with the equivalent capacitance of the transmitter port, forms a CLLC resonant structure. The design is based on the two resonant conditions given in equation (23): Let the series inductance L... p2 The equivalent capacitance of the transmitting port resonates in series at the operating frequency, while the parallel inductance L... p1 With capacitor C p Parallel resonance occurs. At this time, the voltage on the emitting plate will remain constant, and its magnitude will be related to the input fundamental voltage and the inductance ratio (L). p2 With L p1 The relationship between the ratios is given by equation (24).

[0173] 3. Set up an M-type secondary compensation network on each receiving side, and make the output current independent of the load resistance according to the resonance condition to achieve constant current output.

[0174] Each receiver (e.g.) Figure 9 All of them (shown) adopt M-type compensation network. The design is based on the resonance condition similar to equation (23), so that the output current is independent of the load resistance, thereby realizing constant current output. Its expression is shown in equation (25). The value of the additional parallel capacitor needs to be weighed against the system efficiency and the inductor volume. The 165 pF given in Table 2 can be used as the starting value.

[0175] 4. Connect an LC filter at the inverter output to filter out high-order harmonics and balance the common-mode impedance. Connect a 1:1 isolation transformer after the filter and ground its secondary center tap to achieve electrical isolation and provide a grounding point for the emitter plate.

[0176] An LC filter must be connected to the inverter output. Its function is to filter out high-order harmonics in the square wave voltage output by the inverter, and at the same time balance the common-mode impedance of the two branches. After the filter, a 1:1 isolation transformer should be connected, with its secondary center tap grounded, which achieves both electrical isolation and provides a clear grounding point for the emitter plate.

[0177] (4) Fourth step: Calculate the values ​​of all compensation components based on the output power requirements.

[0178] This step specifically includes:

[0179] 1. Determine the single load and total output power targets based on the battery capacity and expected charging time of each electric vehicle.

[0180] Based on the battery capacity and expected charging time of each electric vehicle, determine the power required for each load. The total power is the number of loads multiplied by the power of a single load. The relationship between the system output power and various electrical parameters is given in equation (29).

[0181] 2. Calculate the effective value of the inverter output fundamental voltage from the DC input voltage. Express the emitter voltage as a function of the input fundamental voltage and the inductance ratio. Express the output current as a function of the emitter voltage and the M-type compensation parameters. Combine the above relationships and deduce the required inductance ratio from the target output power.

[0182] The effective value of the inverter output fundamental voltage is calculated from the DC input voltage using equation (20). Then, the emitter voltage is expressed as the ratio of the input fundamental voltage to the inductance (L) using equation (24). p2 / L p1 The output current is a function of the emitter voltage, M-type compensation parameters, etc., using equation (25). These relationships are combined, and the required inductance ratio is derived from the target output power. Reference should be made during this period. Figure 11 The efficiency optimization rules are shown.

[0183] 3. Based on the series resonance condition, calculate the series inductance value from the operating angular frequency and the equivalent capacitance of the transmitting port. Then, calculate the parallel inductance value according to the definition of the inductance ratio. Finally, calculate the compensation capacitor value from the operating angular frequency and the parallel inductance value according to the parallel resonance condition. For each receiving side, obtain the equivalent capacitance of the receiving port from electromagnetic simulation. Select additional parallel capacitors and add them together to obtain the total equivalent capacitance. Calculate the series inductance value from the operating angular frequency and the total equivalent capacitance according to the resonance condition. Then, calculate the secondary inductance value based on the expected coupling coefficient of the M-type compensation and the calculated series inductance value.

[0184] First, based on the series resonance condition in equation (23), the series inductance L is calculated from the operating angular frequency and the known equivalent capacitance of the transmitting port. p2 The value of λ. Then, using the definition of inductance ratio (λ=L) p2 / L p1 Calculate the parallel inductance L p1 Then, according to the parallel resonance condition of equation (23), from the operating angular frequency and L... p1 Calculate the capacitance C p .

[0185] For each receiving side, the equivalent capacitance of the receiving port is first obtained through electromagnetic simulation. Then, an additional parallel capacitor (refer to 165 pF in Table 2) is selected, and the two are added together to obtain the total equivalent capacitance of the receiving port. Then, based on the resonance condition similar to equation (23), the series inductance L is calculated from the operating angular frequency and the total equivalent capacitance. 1j Finally, based on the expected coupling coefficient of the M-type compensation (recommended to be 0.2) and the calculated L... 1j The secondary inductance L is calculated using the coupling coefficient relationship required for constant current compensation. 2j .

[0186] All inductors should have a quality factor as high as possible (e.g., 300 in Table 2) to reduce coil losses.

[0187] 4. Calculate the equivalent load resistance of the system under rated output current and compare it with the load resistance value that optimizes efficiency. If the actual battery equivalent resistance deviates from the optimal value, add a DC / DC converter after the rectified and filtered output for impedance matching.

[0188] After calculating the equivalent load resistance of the system under rated output current, and with Figure 11 In section (a), the optimal load resistance value is compared. If the actual battery equivalent resistance deviates significantly from the optimal value, a DC / DC converter (such as a Buck or Boost circuit) should be added after the rectified and filtered output to transform the battery-side impedance to the optimal load point, thereby maintaining the system at its highest efficiency.

[0189] After completing all parameter calculations, it is recommended to use circuit simulation software (such as Simplier) in conjunction with electromagnetic field simulation software for system-level verification, including:

[0190] By combining circuit simulation and electromagnetic field simulation, we check whether the inverter output voltage and current waveforms meet the soft-switching conditions.

[0191] Simulate the dynamic switching in and out process of the load to verify whether the output current remains constant and whether the power distribution is stable.

[0192] Change the position offset, rotation offset, or angle offset of the receiving end, and observe whether the degree of change in the coupling capacitance is within the preset allowable range to determine the flexible power supply capability and anti-interference performance.

[0193] If the simulation results deviate from expectations, then revert to the coupler size in step two or the inductance ratio in step four, and repeat the above steps until the design requirements are met.

[0194] The following simulation verification of the three-load SCC-WPT system is performed.

[0195] The simulation results of the system input and output voltages are as follows: Figure 13 As shown, Figure 13 In the middle (a), the inverter output voltage and current (U) are shown. in I in Waveform, Figure 13 (b) represents the inverter output voltage and current (U) during the load shedding process. in I in ), equivalent load voltage (V) out1 ) and the output power (P) of load 1, load 2 and load 3. out1 P out2 and P out3 The waveform diagram. From Figure 13 It can be seen that the system has implemented soft switching and can maintain a stable constant voltage output when the load is switched in or out.

[0196] The general-purpose Simulator co-simulation model simulated the effect of reducing the load spacing (d4) on the load output power, and the results are as follows: Figure 14 As shown. From Figure 14 It can be seen that the output power changes by 15% when the load spacing is reduced to 100mm. Due to simulation errors, the three loads are not evenly distributed in terms of power.

[0197] The power supply characteristics of a single load in a free position were simulated, and the simulation results for position offset, rotational offset, and angular offset are as follows: Figure 15 , Figure 16 and Figure 17 As shown. From Figures 15 to 17 It can be seen that the coupling capacitor C M Since the changes in position offset, rotation offset, and angle offset are not significant, this system can achieve good flexible power supply and anti-interference performance even when the cross-coupling between loads 100mm away is not strong.

[0198] In summary, the single-transmitter, multi-receiver wireless power supply system for electric vehicles based on capacitive coupling provided by this invention solves the problems of insufficient flexible power supply capability, poor anti-interference capability, and lack of universal design method in the prior art through the following technical means:

[0199] First, by using the electric vehicle's own mudguard as the third electrode plate, the stray capacitance on the receiving side is enhanced and a current return path is formed without adding an additional coupling plate. Combined with the three-electrode coupling structure, the coupler is made lightweight and its structure is simplified.

[0200] Second, a multi-port Z-parameter network model (Equations (2)-(4)) that simultaneously considers all cross-coupled capacitors was established, and the coupling coefficient (Equation (5)) and coupling gain (Equation (9)) were defined accordingly. The coupler size was optimized by parameterized scanning with the goal of maximizing these two indicators, so as to maintain constant power output under horizontal, rotational and angular offset conditions.

[0201] Third, under the assumption of neglecting cross-coupling between loads, the equivalent circuit of the Y-parameter is derived (Equation (17) and Figure 4 The CLL-M compensation topology was designed: the transmitter side forms a CLLC resonant structure with the equivalent capacitance of the transmitter port through the CLL network (Equation (23)) to keep the voltage of the transmitter plate constant; the receiver side adopts an M-type compensation network to make the output current independent of the load (Equation (25)) and realizes multi-channel power decoupling and active allocation.

[0202] Fourth, simulation is performed by changing the load spacing. Figure 14 The minimum spacing for negligible cross-coupling (100 mm in the example) was determined, providing a quantitative basis for the physical layout of multi-load systems.

[0203] Fifth, a general parameter design process is proposed. Figure 12 This design can be extended to wireless charging systems for any number of electric vehicles.

[0204] Simulation results ( Figures 13-15 The effectiveness of the above-mentioned technical means has been verified: the system maintains constant voltage and constant current output when the load is switched in and out, each load is independent when the load spacing is greater than the minimum threshold, and the output power fluctuates little under position offset, rotation offset and angle offset, and has flexible power supply capability and strong anti-interference performance.

[0205] Therefore, this invention not only overcomes the shortcomings of existing SCC-WPT multi-load systems in that they are difficult to balance high energy efficiency, flexible power supply and anti-interference capability under the influence of cross coupling, but also provides a simple and universal design method with significant industrial applicability.

[0206] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A single-transmitter, multiple-receiver wireless power supply system for electric vehicles based on capacitive coupling, characterized in that, The device includes a transmitter and at least one electric vehicle load. The transmitter includes a transmitting electrode. Each electric vehicle load includes a receiving electrode, a mudguard, and a secondary compensation network. The mudguard serves as a third electrode to enhance the stray capacitance on the receiving side and provide a current loop. The receiving electrode and the mudguard are respectively connected to the secondary compensation network.

2. The electric vehicle single-transmitter multi-receiver wireless power supply system based on capacitive coupling according to claim 1, characterized in that, The system is designed using the following parameter design process: The first step is to determine the basic input parameters of the system and the actual physical constraints; The second step is to optimize the coupler geometry while taking into account all cross-coupling capacitances. The third step is to design a compensation network based on an equivalent model that ignores cross-coupling; The fourth step is to calculate the values ​​of all compensation components based on the output power requirements.

3. The electric vehicle single-transmitter multiple-receiver wireless power supply system based on capacitive coupling according to claim 2, characterized in that, The first step specifically includes: Determine the DC input voltage based on the actual voltage range of the power supply. The system operating frequency is selected based on the internationally permitted frequency bands for wireless power transmission and the capabilities of the power devices. The dimensional constraints of the coupler parameters are determined based on the chassis space of the electric vehicle and the installation position of the mudguard. The coupler parameters include the distance of the transmitting plate from the ground, the transmission distance, the shortest distance from the mudguard to the receiving plate, the spacing between each load, the length and width of the transmitting plate, the side length of the receiving plate, and the outer radius of the mudguard.

4. The electric vehicle single-transmitter multiple-receiver wireless power supply system based on capacitive coupling according to claim 3, characterized in that, The second step specifically includes: The ground is set as the reference node, and the transmitting electrode, each receiving electrode, and the mudguard are set as different nodes. A multi-port capacitor network model is established, and the coupling coefficient between any two ports and the coupling gain from the transmitting port to each receiving port are defined accordingly. With the mudguard parameters and load spacing fixed, the side length of the receiving electrode and the distance from the ground of the transmitting electrode are changed simultaneously within the determined size constraints. The corresponding coupling gain and coupling coefficient are calculated respectively. Based on the calculation results, the side length of the receiving electrode and the distance from the ground of the transmitting electrode that make both larger are selected. With the selected receiving electrode side length and transmitting electrode distance from the ground fixed, within the size constraints, change the mudguard radius and the distance from the mudguard to the receiving electrode, recalculate the coupling gain and coupling coefficient, and select the mudguard radius and distance where both are at their maximum allowable values. Change the horizontal spacing between each load and repeat the above optimization process. Determine the minimum spacing that can be ignored for cross-coupling based on the change in output power, and ensure that the actual load spacing is not less than this minimum spacing.

5. The electric vehicle single-transmitter multiple-receiver wireless power supply system based on capacitive coupling according to claim 4, characterized in that, The third step specifically includes: The impedance parameters obtained from electromagnetic simulation are converted into admittance parameters. A simplified equivalent circuit of admittance parameters is constructed under the assumption of ignoring cross coupling, where the transmitting side is equivalent to a capacitor, each receiving side is equivalent to a capacitor, and there is a controlled current source between the transmitting side and each receiving side. A CLL compensation network is set on the transmitting side so that the CLL compensation network and the equivalent capacitance of the transmitting port together form a CLLC resonant structure; an M-type secondary side compensation network is set on each receiving side.

6. The electric vehicle single-transmitter multiple-receiver wireless power supply system based on capacitive coupling according to claim 5, characterized in that, The third step also includes: connecting an LC filter to the inverter output; and connecting a 1:1 isolation transformer after the LC filter.

7. The electric vehicle single-transmitter multiple-receiver wireless power supply system based on capacitive coupling according to claim 6, characterized in that, The fourth step specifically includes: Determine the single load and total output power targets based on the battery capacity and expected charging time of each electric vehicle. The effective value of the inverter output fundamental voltage is calculated from the DC input voltage. The emitter voltage is expressed as a function of the input fundamental voltage and the inductance ratio. The output current is expressed as a function of the emitter voltage and the M-type compensation parameters. The above relationships are combined and the required inductance ratio is derived from the target output power. The inductance ratio is defined as the ratio of the series inductance to the parallel inductance in the CLL compensation network. Based on the series resonance condition, the series inductance value is calculated from the operating angular frequency and the equivalent capacitance of the transmitting port. Then, the parallel inductance value is calculated according to the definition of the inductance ratio. Finally, the compensation capacitor value is calculated from the operating angular frequency and the parallel inductance value according to the parallel resonance condition. For each receiving side, the equivalent capacitance of the receiving port is obtained by electromagnetic simulation. After selecting additional parallel capacitors, they are added together to obtain the total equivalent capacitance. The series inductance value is calculated from the operating angular frequency and the total equivalent capacitance according to the resonance condition. Then, the secondary inductance value is calculated from the expected coupling coefficient of M-type compensation and the calculated series inductance value.

8. The electric vehicle single-transmitter multiple-receiver wireless power supply system based on capacitive coupling according to claim 7, characterized in that, The fourth step also includes: The equivalent load resistance of the system under rated output current is calculated and compared with the load resistance value that optimizes efficiency. If the actual battery equivalent resistance deviates from the optimal value, a DC / DC converter is added after the rectified and filtered output for impedance matching.

9. The electric vehicle single-transmitter multiple-receiver wireless power supply system based on capacitive coupling according to any one of claims 2 to 8, characterized in that, After all parameter calculations are completed, verification is performed, including: By combining circuit simulation and electromagnetic field simulation, we check whether the inverter output voltage and current waveforms meet the soft-switching conditions. Simulate the dynamic switching in and out process of the load to verify whether the output current remains constant and whether the power distribution is stable. Change the position offset, rotation offset, or angular offset of the receiving end, and observe whether the degree of change in the coupling capacitance is within the preset allowable range; If the simulation results deviate from expectations, then revert to the coupler size in step two or the inductance ratio in step four, and repeat the above steps until the design requirements are met.

10. The electric vehicle single-transmitter multiple-receiver wireless power supply system based on capacitive coupling according to claim 9, characterized in that: The transmitter also includes a full-bridge inverter. The LC filter is connected to the two output terminals of the full-bridge inverter. The primary inductance of the 1:1 isolation transformer is connected to the output terminal of the LC filter. One end of the secondary inductor is connected to the CLL compensation network. The center tap of the secondary inductor is grounded.

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