Three-plate electric field-coupled wireless power transfer system and parameter design method

Abstract

This invention provides a three-plate electric field coupling wireless power transmission system and its parameter design method. The system includes a power transmitter and a power receiver. The power transmitter includes a DC power supply, an inverter, a transmitter compensation topology circuit, and energy transmitting plates. The power receiver includes a first energy receiving plate, a second energy receiving plate, a receiver compensation topology circuit, a rectifier, and a load device. The area of ​​the energy transmitting plate is greater than the sum of the areas of the first and second energy receiving plates. The first and second energy receiving plates are positioned relative to the energy transmitting plate and can move synchronously on their respective bearing surfaces. The advantages are: wireless power transmission is achieved using the self-capacitance and mutual capacitance of the three plates; the structure is simple, the cost is low, and the space occupation is small. It is particularly suitable for mobile power supply of desktop devices, offering high flexibility. The system parameters are not easily affected by the length of the wiring, and parameter design is convenient.

Description

Technical Field

[0001] This invention relates to wireless power transfer technology, specifically to a three-plate electric field coupling wireless power transfer system and its parameter design method. Background Technology

[0002] Wireless power transfer (WPT) technology enables the non-electrical contact transmission of electrical energy through carriers such as magnetic fields, electric fields, lasers, and microwaves. This technology effectively solves the problems of limited device flexibility and safety hazards caused by traditional wired power supply methods. Currently, experts and scholars both domestically and internationally have conducted research on this technology and achieved considerable theoretical results in applications such as electric vehicles, consumer electronics, and home appliances. Electric-field Coupled Wireless Power Transfer (EC-WPT) technology has attracted widespread attention from researchers both domestically and internationally due to its advantages, including simple and lightweight coupling mechanisms, flexible shapes, low cost, minimal electromagnetic interference to the surrounding environment, ability to transmit energy through metal obstacles, and minimal eddy current losses in the metal conductors around and between the coupling mechanism. It is gradually being applied in mobile devices, electric vehicles, biomedical equipment, and underwater equipment. However, traditional EC-WPT systems require two pairs of electrodes to form the coupling mechanism. These two pairs of electrodes severely limit the application of this technology in wireless power supply for two-dimensional planar mobile devices, especially its convenience in dynamic wireless power supply.

[0003] Single-capacitive coupled wireless power transfer (SCC-WPT) technology couples to the ground through stray capacitance, self-capacitance, or grounding to form an electrical circuit, thus enabling wireless power transfer with only a pair of electrodes. Due to its unique characteristics, this technology is more suitable for static and dynamic wireless power supply of one or more devices in a two-dimensional plane. Compared to the coupling mechanism of magnetically coupled wireless power transfer systems, this technology requires only very thin metal electrodes, reducing both cost and weight.

[0004] Existing electric field-coupled wireless power transfer systems, from the perspective of coupling structure, are as follows: Figure 1As shown, there are generally two scenarios. One is to use two metal plates as passive electrodes to form a complete electrical connection loop, with the coupling mechanism consisting of four metal plates, such as the wireless power transmission system based on electric field coupling disclosed in Chinese Patent 201210358473.X. This method has certain limitations in application scenarios, requiring that the two pairs of metal plates be aligned, resulting in poor equipment mobility. The other method uses ground to replace the two passive electrodes to form an electrical loop, with the coupling mechanism consisting of two metal plates, such as the single-capacitor coupled wireless power transmission device disclosed in Chinese Patent 202011542454.3. With this structure, a loop is usually formed through stray capacitance at the receiving end. The size of this stray capacitance is related to the length of the receiving end connection and will change according to the actual application requirements, making system parameter design relatively difficult. Summary of the Invention

[0005] Based on the above problems, the primary objective of this invention is to propose a three-plate electric field-coupled wireless power transfer system. By adding an extra plate at the energy receiving end to generate stray capacitance at infinity, the impact of the receiver wiring length on parameter design and system performance is reduced. This makes it suitable for mobile power supply in a two-dimensional plane.

[0006] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0007] A three-plate electric field-coupled wireless power transmission system includes a power transmitter and a power receiver. The key feature is that the power transmitter includes a DC power supply, an inverter, a transmitter compensation topology circuit, and an energy transmitting plate; the power receiver includes a first energy receiving plate, a second energy receiving plate, a receiver compensation topology circuit, a rectifier, and a load device. The area of ​​the energy transmitting plate is greater than the sum of the areas of the first and second energy receiving plates. The first and second energy receiving plates are positioned relative to the energy transmitting plate and can move synchronously on their respective bearing surfaces.

[0008] Optionally, the first energy receiving electrode and the second energy receiving electrode are fixedly arranged side by side on the same plane.

[0009] Optionally, one output terminal of the transmitting end compensation topology circuit is connected to the ground, using the ground as the passive electrode of the power transmitting end, and the other output terminal is connected to the energy transmitting plate, serving as the active electrode of the power transmitting end; the first energy receiving plate serves as the active electrode of the power receiving end, and the passive electrode of the power receiving end is replaced by the second energy receiving plate.

[0010] Optionally, an insulating dielectric layer is provided between the energy emitting electrode and the first energy receiving electrode, and between the energy emitting electrode and the second energy receiving electrode.

[0011] Optionally, the insulating dielectric layer is disposed on the outer surface of the energy emitting electrode.

[0012] Optionally, the insulating dielectric layer is disposed on the outer surface of the first energy receiving electrode and the second energy receiving electrode.

[0013] Optionally, the energy emitting plate is disposed on a desktop, and the power receiving end is disposed on a monitor, laptop, mouse, or keyboard.

[0014] Optionally, both the transmitting end compensation topology circuit and the receiving end compensation topology circuit adopt an LC series compensation structure.

[0015] Based on the above system, this invention also proposes a parameter design method for a three-plate electric field-coupled wireless power transfer system, comprising the following steps:

[0016] S1: Determine the load resistance, system angular frequency, transmission distance, and the shape and size of the first and second energy receiving plates according to the application scenario requirements;

[0017] S2: Determine the shape and size of the energy emitting plate based on the movement range of the power receiving end;

[0018] S3: Set an insulating dielectric layer by increasing the proportion of the insulating dielectric between the energy emitting plate and the first energy receiving plate, and decreasing the proportion of the insulating dielectric between the energy emitting plate and the second energy receiving plate, thus increasing the coupling capacitance C. M To obtain the maximum value;

[0019] S4: Based on the shape, size and parameters of the insulating dielectric layer determined in steps S1 to S3, the mutual capacitance and self capacitance of each electrode plate are obtained.

[0020] S5: Construct the system admittance transfer function based on the mutual compatibility coefficient, and determine the initial constraint range of the mutual compatibility coefficient based on the Bode plot of the admittance function;

[0021] S6: Determine the mutual compatibility coefficient k based on the relationship curve between system transmission efficiency and mutual compatibility coefficient. c The value of ;

[0022] S7: Determine the component parameters in the transmitter compensation topology circuit and the receiver compensation topology circuit according to the following equation;

[0023]

[0024]

[0025] L1 = L2;

[0026]

[0027] Where ω is the system angular frequency, C M For coupling capacitor, C 12 C is the capacitance between the energy emitting plate and the first energy receiving plate. 13 C is the capacitance between the energy emitting plate and the second energy receiving plate. 23 C is the capacitance between the first energy receiving plate and the second energy receiving plate. 11 C is the self-capacitance value of the energy emitting electrode. 22 C is the self-capacitance value of the first energy receiving plate. 33 L1 is the self-capacitance value of the second energy receiving plate; C is the compensation inductance value in the transmitter compensation topology circuit. ex1 L1 is the compensation capacitor value in the transmitter compensation topology circuit; L2 is the compensation inductor value in the receiver compensation topology circuit. ex2 The compensation capacitor value is used in the compensation topology circuit of the receiving end.

[0028] Optionally, in step S4, the mutual capacitance and self-capacitance of each plate are obtained using the finite element simulation software Ansoft Maxwell.

[0029] The effects of this invention are:

[0030] This invention proposes a three-plate electric field coupling wireless power transmission system and parameter design method. It utilizes the self-capacitance and mutual capacitance of the three plates to achieve wireless power transmission. The system has a simple structure, low cost, and small space occupation. It is particularly suitable for mobile power supply of two-dimensional planar devices, has high flexibility, and the system parameters are not easily affected by the length of the wiring, making parameter design more convenient. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0032] Figure 1 This is a schematic diagram of the principle structure of an electric field-coupled wireless power transfer coupling mechanism in the prior art;

[0033] Figure 2 A schematic diagram of a three-plate electric field-coupled wireless power transfer system is provided for this invention.

[0034] Figure 3 This is a schematic diagram of the structure of the three-plate electric field coupling mechanism in a specific embodiment of the present invention;

[0035] Figure 4 The curve showing the relationship between mutual capacitance and the proportion of insulating medium;

[0036] Figure 5 The curve showing the relationship between mutual capacitance and plate thickness;

[0037] Figure 6 The curve showing the relationship between mutual capacitance and the width of the energy-emitting electrode;

[0038] Figure 7 The circuit model diagram is for an equivalent six capacitors;

[0039] Figure 8 System circuit topology diagram for bilateral LC compensation;

[0040] Figure 9 for Figure 8 The system equivalent circuit;

[0041] Figure 10 The equivalent model diagram of the controlled voltage source in the system circuit is shown.

[0042] Figure 11 For coupling capacitor C M Surface plots of dielectric constants ε2 and ε3;

[0043] Figure 12 For coupling capacitor C M Surface plots relating dielectric constant ε2 and plate width w3;

[0044] Figure 13 Bode plot of the system transfer admittance function;

[0045] Figure 14 The system efficiency η varies with the mutual compatibility coefficient k c Line graph;

[0046] Figure 15 Design a flowchart for system parameters;

[0047] Figure 16 To experimentally verify the obtained voltage u in and current i in Waveform. Detailed Implementation

[0048] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0049] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by those skilled in the art to which this invention pertains.

[0050] This embodiment provides a three-plate electric field-coupled wireless power transfer system, such as Figure 2 , Figure 3 As shown, it includes a power transmitting end and a power receiving end. The power transmitting end includes a DC power supply, an inverter, a transmitting end compensation topology circuit, and an energy transmitting plate. The power receiving end includes a first energy receiving plate, a second energy receiving plate, a receiving end compensation topology circuit, a rectifier, and a load device. The area of ​​the energy transmitting plate is greater than the sum of the areas of the first energy receiving plate and the second energy receiving plate. The first energy receiving plate and the second energy receiving plate are disposed opposite to the energy transmitting plate and can move synchronously on the bearing surface opposite to the energy transmitting plate.

[0051] In this system, the ground is used as one of the passive electrodes at the energy transmitting end, and a metal plate is used as the other passive electrode at the energy receiving end. The energy transmitting electrode P1, the first energy receiving electrode P2, and the second energy receiving electrode P3 together form a three-plate coupling mechanism. In specific implementation, the plates are all made of thin metal, and the area of ​​plate P1 is larger than the sum of the areas of plates P2 and P3. P2 and P3 are fixedly arranged side by side on the same plane with relatively fixed positions.

[0052] Combination Figure 2 It can be seen that one output terminal of the transmitter compensation topology circuit is connected to the ground, using the ground as the passive electrode of the power transmitter, and the other output terminal is connected to the energy transmitting plate, serving as the active electrode of the power transmitter; the first energy receiving plate serves as the active electrode of the power receiver, and the passive electrode of the power receiver is replaced by the second energy receiving plate.

[0053] With the above structure, the device can stably obtain power even when it moves freely within the range of the energy emitting plate. This allows the device to receive stable power while moving freely in a two-dimensional plane. Therefore, the energy emitting plate can be placed on a desktop, and the power receiving end can be placed on a monitor, laptop, mouse, or keyboard, thereby further advancing the realization of a "tailless desktop". Of course, it can also be used in other two-dimensional dynamic wireless power supply applications such as mobile robots and electric vehicles.

[0054] In consumer electronics and related applications, the requirements for transmission distance are generally not high, and for safety reasons, the electrode plates are usually insulated and wrapped during the design process to prevent users from directly touching them. Similarly, the emitting electrode plate also needs to be insulated. Therefore, in practical applications, the medium between the electrodes is not only air, but also various insulating media exist between the emitting and receiving electrodes. Therefore, in specific implementations, insulating media layers are usually provided between the energy emitting electrode plate and the first energy receiving electrode plate, as well as between the energy emitting electrode plate and the second energy receiving electrode plate. The insulating media layers can be provided on the outer surface of the energy emitting electrode plate, or simultaneously on the outer surfaces of both the first and second energy receiving electrodes plate.

[0055] Since the thickness and material selection of the insulating medium affect the capacitance between the plates, thus influencing the system design, the material, size, and structure of the insulating medium are crucial to the design of the coupling mechanism. A schematic diagram of the coupling mechanism is shown below. Figure 3 As shown, three mutual capacitances C can be formed between each pair of the three plates. 12 C 13 and C 23 .

[0056] Without considering the edge effect of the plates, the capacitance between the parallel plates can be calculated using equation (1):

[0057] C s =ε0·ε r ·S / d (1)

[0058] In the formula, ε0 = 8.85 × 10 -12 F / m is the absolute permittivity, ε r Let S be the relative permittivity of the insulating medium between the plates, S be the area of ​​the plates, and d be the distance between the plates.

[0059] As shown in formula (1), the size of a parallel plate capacitor is determined by the size of the plates, the area of ​​the plates facing each other, and the dielectric constant of the dielectric. Let the capacitance C... 12 For example, there are two layers of insulating medium and air medium between plates P1 and P2, such as Figure 3 As shown on the left, the total capacitance C of the insulating medium is... i The capacitance C between the two plates 12 We can obtain it through equation (2):

[0060]

[0061] In the formula C r This is the capacitance value based on the proportion of air dielectric between the plates; other mutual capacitances can be obtained in the same way.

[0062] Simultaneously, three self-capacitance Cs can be formed between the three plates and infinity (which can also be considered as the ground). 11 C 22 and C 33 The magnitude of the self-capacitance is determined by its geometric dimensions and shape. For a rectangular plate, its self-capacitance can be calculated using equation (3):

[0063]

[0064] In the formula, c is the perimeter of the plate and S is the area of ​​the plate.

[0065] Since the dielectric constant of insulating media is greater than that of air, given a fixed electrode size and distance, using as many high-dielectric-constant insulating media as possible will result in a larger mutual capacitance value. For ease of analysis, Table 1 provides the relevant parameter definitions and values ​​for the coupling mechanism. The mutual capacitance between the coupling mechanisms can be simulated and calculated using the finite element software Ansoft Maxwell.

[0066] Table 1 Parameters of the coupling mechanism

[0067]

[0068] Figure 4 The relationship between the proportions and mutual capacitance of air and insulating medium between the plates is presented. In the simulation, to simplify the analysis, epoxy resin is used as the insulating medium with a relative permittivity of 4.2, w2 and w3 are set to 145 mm, and the plate thickness is 2 mm. Figure 4 As can be seen, the higher the proportion of insulating medium between the transmitting and receiving plates, the greater the capacitance C. 12 and C 13 The larger the value of C and the larger its proportion, the faster the capacitance increases; 23 The value of mutual capacitance first increases and then decreases as the proportion of insulating medium increases. Therefore, during the design process, different proportions of insulating medium can be selected according to the system parameter design requirements to obtain the required mutual capacitance value.

[0069] Figure 5 Curves showing mutual capacitance versus electrode thickness are presented. Similar to the simulation above, w2 and w3 are also set to 145 mm, and no insulating medium is added between the electrodes. The graph shows that the three mutual capacitance values ​​do not change significantly with increasing thickness. Therefore, electrode thickness does not affect the mutual capacitance. In practical designs, the electrodes can be designed as extremely thin metal electrodes, such as using thin-film electrodes as transmitting and receiving electrodes, which can further reduce cost and weight.

[0070] When the size of the charging area at the receiving end is fixed, the different proportions of the receiving plates P2 and P3 in the charging area will also affect the size of the mutual capacitance of the coupling mechanism. Figure 6 The curves of mutual capacitance and the ratio of emitter plate width are presented. No insulating medium was added during the simulation, and the plate thickness was 2 mm. The graph shows that as the width ratio increases, the mutual capacitance C... 12 The mutual compatibility C increases accordingly, and the growth rate decreases as the ratio increases. 13 Then with C 12 The trend is the opposite. Mutual capacitive C 23 As the ratio increases, it first increases and then decreases, reaching its maximum value when the ratio is approximately 1, meaning the two plates are the same size.

[0071] As can be seen from the above analysis, the three-plate coupling mechanism proposed in this embodiment can form six capacitors, including three mutual capacitors and three self capacitors. These six capacitors can form a complete electrical circuit. By constructing a model of six capacitors, system modeling and parameter design can be easily realized.

[0072] The mutual capacitance and self-capacitance of the three metal plates together form six capacitors, which are then... Figure 7 Its equivalent circuit model and equivalent Π-type circuit can be seen.

[0073] According to the analysis of two-port networks:

[0074]

[0075] In the formula, Y is the Y-parameter matrix of the two-port system. ij Let Y be the Y parameter of the two-port network, and Y 12 =Y 21 .

[0076] The Y-parameters of a two-port network can be obtained by short-circuiting ports 11 and 22 respectively. The calculation method is as follows:

[0077]

[0078] in,

[0079]

[0080] Similar to a coupling coil, capacitor C can be... M Let the mutual capacitance of the coupling mechanism be defined as the mutual capacitance, and let capacitors C1 and C2 be defined as the self-capacitance of the coupling mechanism. Then, the mutual capacitance coefficient of the coupling mechanism can be defined as follows:

[0081] In practical applications, since the system also involves transmitter and receiver compensation topologies, the compensation capacitors will affect the system's mutual capacitance coefficient. During the design phase, because LC compensation has advantages such as filtering out high-order harmonics, providing voltage boosting, and requiring fewer components, this embodiment uses an LC series compensation structure for both the transmitter and receiver compensation topologies. The circuit topology of the tri-plate ECPT system based on bilateral LC compensation is as follows: Figure 8 As shown. The high-frequency inverter circuit at the transmitting end consists of four MOSFETs S1-S4, and the rectifier circuit at the receiving end consists of four diodes D1-D4 connected to a filter capacitor C. o Convert AC power to DC power for load R L The function of the compensation network consists of two inductors L1 and L2 and two compensation capacitors C. ex1 C ex2 Composition, C ex1 and C ex2 Used to increase the resonant capacitance, the mutual capacitance coefficient of the coupling mechanism is:

[0082]

[0083] By analyzing the circuit using the fundamental frequency approximation method, the equivalent circuit diagram of the system can be obtained, such as... Figure 9 As shown. The rectifier filter and load resistor can be equivalent to resistor R. eq R eq =8R L / π 2 Capacitor C f1 Additional compensation capacitor C ex1 And equivalent π capacitance C1-C M Composed of parallel connections, capacitor C f2 The same applies.

[0084] Because the open-circuit impedance matrix Z and the short-circuit admittance matrix Y are inverses of each other, that is:

[0085] Z = Y -1 (8)

[0086] Right now

[0087] In the formula Δ Y =Y 11 Y 22 -Y 12 Y 21 .

[0088] Therefore, the relationship between port voltage and current can also be expressed by the following formula:

[0089]

[0090] In the formula

[0091] According to formula (10), we can... Figure 9 The system equivalent circuit in the model is converted into a voltage source model, such as Figure 10 As shown.

[0092] Therefore, the resonance condition of the system can be obtained by the series resonance of the inductor and the equivalent capacitance, and the relationship of the system's resonant angular frequency can be further derived, namely:

[0093]

[0094] Based on impedance analysis and formula (12), the input impedance Z of the system can be derived. in ,Right now:

[0095]

[0096] Simultaneously, the system's input and output currents can be obtained using the loop current method, namely:

[0097]

[0098] From formula (14), it can be seen that when the system is in resonance, the phase difference between the input current and the output current is 90°, and the output current is independent of the load, so the system can achieve constant current output. Ignoring the internal resistance of the components, the output power of the system is:

[0099]

[0100] When the input voltage and resistance are constant, the output current is related to the coupling capacitor C. M Positively correlated with the mutual compatibility coefficient k c It exhibits an exponential negative correlation. Therefore, to increase system power, the coupling capacitor should be increased as much as possible, and k should be appropriately limited. c The size of . According to formulas (14) and (15), although by continuously decreasing k c A value of k can achieve high-gain output current and output power, but c The smaller the value of k, the greater the impact of even slight fluctuations in system parameters on the system's output characteristics, increasing the system's sensitivity and making tuning more difficult in practical applications. Therefore, it is necessary to adjust k. c The size is constrained.

[0101] Based on the above analysis, the system's working mechanism is relatively clear. Due to the influence of the insulating medium, plate thickness, and the proportion of the transmitting plate on mutual capacitance, the three-plate coupling mechanism can be designed according to the corresponding requirements. To simplify the analysis, the compensation topology of the transmitting and receiving ends is set as a symmetrical structure. Once the coupling capacitor C... M and mutual compatibility coefficient kc Once confirmed, C f1 and C f2 It can be obtained according to formula (7), and the inductance can be obtained by formula (12). The load resistance is determined by the requirements of the electrical equipment.

[0102] Therefore, this embodiment also provides a parameter design method for a three-plate electric field-coupled wireless power transfer system, including the following steps:

[0103] S1: Determine the load resistance, system angular frequency, transmission distance, and the shape and size of the first and second energy receiving plates according to the application scenario requirements;

[0104] S2: Determine the shape and size of the energy emitting plate based on the movement range of the power receiving end;

[0105] S3: Set an insulating dielectric layer by increasing the proportion of the insulating dielectric between the energy emitting plate and the first energy receiving plate, and decreasing the proportion of the insulating dielectric between the energy emitting plate and the second energy receiving plate, thus increasing the coupling capacitance C. M To obtain the maximum value;

[0106] S4: Based on the shape, size and parameters of the insulating dielectric layer determined in steps S1 to S3, the mutual capacitance and self capacitance of each electrode plate are obtained using the finite element simulation software Ansoft Maxwell.

[0107] S5: Construct the system admittance transfer function based on the mutual compatibility coefficient, and determine the initial constraint range of the mutual compatibility coefficient based on the Bode plot of the admittance function;

[0108] S6: Determine the mutual compatibility coefficient k based on the relationship curve between system transmission efficiency and mutual compatibility coefficient. c The possible values ​​of ;

[0109] S7: Determine the component parameters in the transmitter compensation topology circuit and the receiver compensation topology circuit according to the following equation;

[0110]

[0111]

[0112] L1 = L2;

[0113]

[0114] Where ω is the system angular frequency, C M For coupling capacitor, C 12 C is the capacitance between the energy emitting plate and the first energy receiving plate. 13 C is the capacitance between the energy emitting plate and the second energy receiving plate.23 C is the capacitance between the first energy receiving plate and the second energy receiving plate. 11 C is the self-capacitance value of the energy emitting electrode. 22 C is the self-capacitance value of the first energy receiving plate. 33 L1 is the self-capacitance value of the second energy receiving plate; C is the compensation inductance value in the transmitter compensation topology circuit. ex1 L1 is the compensation capacitor value in the transmitter compensation topology circuit; L2 is the compensation inductor value in the receiver compensation topology circuit. ex2 The compensation capacitor value is used in the compensation topology circuit of the receiving end.

[0115] In the specific design, once the input voltage, load resistance, and system frequency are determined, the system's transmission power is determined by the coupling capacitor C. M and mutual compatibility coefficient k c Decision. From formula (7), we know that k c Size and C M Therefore, the size and shape of the coupling mechanism must first be determined based on the application requirements, thereby determining the coupling capacitor C. M The value of C. According to formulas (7), (12) and (15), C M The larger the value of C, the greater the system transmission power, and at the same time, as C... M Increasing the capacitance C can further reduce the values ​​of resonant inductors L1 and L2, thereby reducing system losses and size. Therefore, when designing the coupling mechanism, the coupling capacitance C should be increased as much as possible. M The value of .

[0116] From formula (6), we can know that the coupling capacitance C M The size and capacitance C 12 C 13 C 33 C 22 Directly related, taking the plate parameters of the coupling mechanism in Table 1 as an example, and from both formula (1) and formula (2), the capacitance C can be determined. 12 C 13 C 33 C 22 Both are related to the size of the electrodes. If the widths w2 and w3 of the emitting electrodes are both set to 145mm and 10mm apart, and assuming that the electrodes are entirely insulated, then the coupling capacitance C... M The relationship with dielectric constants ε2 and ε3 is as follows: Figure 11 As shown. To obtain a higher C M The dielectric constant ε3 should be minimized while the dielectric constant ε2 should be increased. Since air has the lowest relative dielectric constant, the proportion of the insulating medium between emitter plates P1 and P2 can be increased, while the proportion between plates P1 and P3 can be minimized. This increases the mutual capacitance C. 12Reduce mutual capacitance C 13 To increase the coupling capacitance C M The purpose.

[0117] Based on the above analysis, in order to increase the coupling capacitance C M The dielectric constant ε2 should be increased as much as possible while the dielectric constant ε3 should be decreased. Therefore, a larger proportion of insulating medium can be used between plates P1 and P2, and a smaller proportion between P1 and P3. To simplify the analysis, in the simulation, insulating medium is used to isolate P1 and P2, but no insulating medium is added between P1 and P3. Since the distance between P2 and P3 is 10mm, the width of the receiving plates P2 and P3 satisfies: w3 = 0.29 - w2. Therefore, the coupling capacitance C M The relationship between the electrode width and the dielectric constant ε2 is as follows: Figure 12 As shown. The coupling capacitance C can be increased by increasing the dielectric constant ε2 of the insulating medium and changing the electrode width. M The size of the coupling capacitance is shown in the figure. The dashed lines in the figure represent the mapping of the maximum value of the coupling capacitance under different dielectric constants in the xy plane, which can provide a reference for the design of coupling mechanisms.

[0118] Regarding the mutual compatibility coefficient k c As can be seen from formula (15), the system power is inversely proportional to the mutual compatibility coefficient, k c The smaller the value, the greater the power. But k c Reducing the frequency response also increases system sensitivity, increases system input current, and increases system losses. Therefore, it is necessary to analyze the system's frequency characteristics and give k. c The scope of constraints.

[0119] Based on formulas (10) and (11), the transfer admittance function of the system can be derived:

[0120]

[0121] Where A = sL2 + R eq B = sC f2 A+1.

[0122] When the system frequency f and the coupling capacitance C M and load resistance R L When fixed, the compensation inductance and capacitance can be obtained using formulas (7) and (12). According to formula (16), the Bode plots of the transfer admittance function under different mutual capacitance coefficients are shown below. Figure 13 As shown in the figure, the increase in system transfer admittance is given for different mutual compatibility coefficients. It can be seen that as k... cThe smaller the coefficient of capacitance, the greater the output current gain, which means a greater output power. However, as shown in the figure, the smaller the system mutual capacitance coefficient, the higher the system sensitivity, leading to a series of problems such as increased control difficulty and poor system robustness. Therefore, considering both system gain and robustness, at a frequency f of 2MHz, C... M When the voltage is 5pF and the load resistance is 30Ω, k c It should be selected between 0.025 and 0.075.

[0123] At the same time, system efficiency is also related to k. c The values ​​are related. Let R1 and R2 be the ESR (Equivalent Series Resistance) of the transmitter and receiver, respectively. Then the efficiency of the system is:

[0124]

[0125] In the formula I in I R These are the effective values ​​of the input current at the transmitting end and the output current at the receiving end, respectively.

[0126] Since the series resistance is mostly provided by the parasitic resistance of the inductor, it is defined here as:

[0127]

[0128] Q1 and Q2 are the quality factors of inductors L1 and L2, respectively. In high-frequency system experiments, air-core inductors wound with 0.03×1800 high-frequency Litz wire are usually used, and the Q value is approximately 450 based on experience.

[0129] Considering both system gain and robustness, at a frequency f of 2MHz, C M When the current is 5pF and the load resistance is 30Ω, according to Figure 13 It is known that k c The optimal range is 0.025–0.075. Meanwhile, according to… Figure 14 It can be seen that the system efficiency increases with k c It increases with the increase of , when 0.04 <k c When k is less than 0.1, the system efficiency tends to stabilize and is greater than 85%. Therefore, considering all factors, a more optimal value for k is selected. c =0.05.

[0130] In summary, the parameter design process for the three-plate electric field-coupled wireless power transfer system proposed in this invention can be as follows: Figure 15 As shown.

[0131] To verify the effectiveness of the tri-plate electric field coupling wireless power transfer system proposed in this invention, a specific experimental setup was constructed. This setup mainly consists of a DC power supply, a full-bridge inverter, a transmitting-end LC resonant network, a grounding wire, a tri-plate coupling mechanism, a receiving-end LC resonant network, a full-bridge rectifier, a filter capacitor, and a 40W LED load. The full-bridge inverter uses an IMZ120R045M1 MOSFET as its switching transistor, and the rectifier consists of four SiC diodes GHXS030A120S. The resonant inductor is wound with 0.03×1800 high-frequency Litz wire, and the resonant capacitor is composed of C0G surface-mount capacitors. One end of the transmitting-end compensation topology is directly grounded via a single wire. Based on the application requirements of desktop equipment, the receiving-end resonant network, rectifier, filter capacitor, and load are integrated onto the receiving-end plate in the experiment.

[0132] In the experiment, when fabricating the coupling mechanism, the emitting plate P1 was constructed from a 600×600mm aluminum plate, with a 10mm distance between the emitting and receiving plates. The receiving plates P2 and P3 were both constructed from a single layer of copper foil and attached to a 300×300mm thin acrylic plate, with a 10mm gap between plates P2 and P3. Based on the previous analysis, to obtain a larger coupling capacitance C... M Mutual compatibility C needs to be increased. 12 Reduce mutual capacitance C 13 Therefore, in the experiment, acrylic insulation was used between plates P1 and P2 to increase the dielectric constant ε2, while no acrylic plate was added between receiving plates P1 and P3 to reduce the dielectric constant ε. 3。 Since the relative permittivity of acrylic is approximately 3.5, to further increase the coupling capacitance, the receiving plates P2 and P3 need to be set to different sizes. According to... Figure 12 Based on the analysis, if w3 is set to 100mm, then the size of receiving plate P2 is 300×190mm, and the size of receiving plate P3 is 300×100mm. The experimental parameters are shown in Table 2. The coupling capacitance value is 3pF, which is due to the relatively small dielectric constant of the acrylic plate.

[0133] Table 2 System Parameters

[0134]

[0135] In the experiment, the system's DC input voltage was 80V, the inverter's operating frequency was 2MHz, and the load was a 40W LED light. The inverter's output voltage and current waveforms are as follows: Figure 16 As shown, the inverter voltage waveform slightly leads the current waveform, which is beneficial for the system to achieve ZVS operation. The figure shows that the effective value of the voltage square wave is approximately 82V, and the effective value of the current is 0.96A.

[0136] The experiment revealed that using the oscilloscope's voltage and current probes to measure the load resistance significantly impacted the system output. This is because the voltage and current probes are coupled to ground through the oscilloscope, affecting the system's input impedance and thus causing changes in the system output. Therefore, to demonstrate the system's performance, a 40W LED was used as the load in this experiment. Figure 16 As can be seen, the LED light is lit on a "desktop" 10mm away, and based on the brightness, the output power can be judged to be approximately 30W. At this time, the DC power supply displays an input voltage of 79.99V and an input current of 1.13A, so the calculated input power of the system is 90.1W, and the system efficiency is approximately 30%.

[0137] To visually illustrate the flexibility of the proposed single-field coupling system in an arbitrary two-dimensional plane, the receiver was placed at each of the four corners of the transmitting plate, while other experimental conditions remained unchanged. The experiment showed that the LED could be successfully lit with essentially the same brightness regardless of the receiver's position on the transmitting plate. These experimental results demonstrate that the invention, employing a three-plate coupling mechanism and the proposed parameter design method, can successfully achieve wireless power transmission, and verify the effectiveness and feasibility of the system.

[0138] In summary, this invention proposes a three-plate electric field-coupled wireless power transmission system and parameter design method. It utilizes the self-capacitance and mutual capacitance of the three plates to achieve wireless power transmission. This invention analyzes the characteristics of mutual capacitance and self-capacitance in the three-plate coupling mechanism, as well as the influence of the insulating medium and plate thickness on the mutual capacitance. Using the two-port network principle, a six-capacitor model and equivalent circuit of the coupling mechanism are given. For the SCC-WPT system with a bilateral LC resonant network, a controlled voltage source model and resonance conditions are presented. Then, combined with the coupling coefficient k... c The system efficiency analysis provides a design method for system parameters. Finally, experiments verify the feasibility and effectiveness of the theoretical analysis. The system can receive effective electrical energy at any location on the "desktop," enabling dynamic power supply for two-dimensional planar mobile devices. The three-plate coupling mechanism proposed in this invention is lower in cost, lighter in weight, and occupies less space. Compared to the previous bipolar SCC-WPT system where the receiver was not grounded, the addition of a third plate increases the ground coupling capacitor without the need for additional wires or metal balls, thus improving the system's flexibility in two-dimensional planar mobile power supply. This invention further reveals the working mechanism of the SCC-WPT system, contributing to improved system performance. It provides a new technology for wireless power supply of mobile devices on a two-dimensional plane and has promising application prospects in desktop mobile devices, mobile robots, and other fields.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and such transformations should be covered within the scope of the claims and specification of the present invention.

Claims

1. A three-plate electric field-coupled wireless power transfer system, comprising a power transmitter and a power receiver, characterized in that, The power transmitting end includes a DC power supply, an inverter, a transmitting end compensation topology circuit, and an energy transmitting plate. The power receiving end includes a first energy receiving plate, a second energy receiving plate, a receiving end compensation topology circuit, a rectifier, and a load device. The area of ​​the energy transmitting plate is greater than the sum of the areas of the first energy receiving plate and the second energy receiving plate. The first energy receiving plate and the second energy receiving plate are disposed opposite to the energy transmitting plate and can move synchronously on the bearing surface opposite to the energy transmitting plate. Both the transmitting end compensation topology circuit and the receiving end compensation topology circuit adopt an LC series compensation structure, and the component parameters in the transmitting end compensation topology circuit and the receiving end compensation topology circuit are determined according to the following equation; ； ； ； ； in, The mutual compatibility factor is... Let C be the system angular frequency. M For coupling capacitor, C 12 C is the capacitance between the energy emitting plate and the first energy receiving plate. 13 C is the capacitance between the energy emitting plate and the second energy receiving plate. 23 C is the capacitance between the first energy receiving plate and the second energy receiving plate. 11 C is the self-capacitance value of the energy emitting electrode. 22 C is the self-capacitance value of the first energy receiving plate. 33 This is the self-capacitance value of the second energy receiving electrode. The compensation inductance value is used to compensate for the topology of the transmitter. The compensation capacitor value in the transmitter compensation topology circuit; The compensation inductance value is used in the compensation topology circuit of the receiving end. The compensation capacitor values ​​in the receiving end compensation topology circuit are C1 and C2, which are intermediate variables.

2. The three-plate electric field-coupled wireless power transfer system according to claim 1, characterized in that, The first energy receiving electrode and the second energy receiving electrode are fixedly arranged side by side on the same plane.

3. The three-plate electric field-coupled wireless power transfer system according to claim 1, characterized in that, One output of the transmitting end compensation topology circuit is connected to the ground, using the ground as the passive electrode of the power transmitting end, and the other output is connected to the energy transmitting plate, serving as the active electrode of the power transmitting end; the first energy receiving plate serves as the active electrode of the power receiving end, and the passive electrode of the power receiving end is replaced by the second energy receiving plate.

4. The three-plate electric field-coupled wireless power transfer system according to claim 3, characterized in that, An insulating dielectric layer is provided between the energy emitting electrode and the first energy receiving electrode, and between the energy emitting electrode and the second energy receiving electrode.

5. The three-plate electric field-coupled wireless power transfer system according to claim 4, characterized in that, The insulating dielectric layer is disposed on the outer surface of the energy emitting electrode.

6. The three-plate electric field-coupled wireless power transfer system according to claim 4 or 5, characterized in that, The insulating dielectric layer is disposed on the outer surface of the first energy receiving electrode and the second energy receiving electrode.

7. The three-plate electric field-coupled wireless power transfer system according to claim 1, characterized in that, The energy emitting plate is mounted on a desktop, and the power receiving end is mounted on a monitor, laptop, mouse, or keyboard.

8. The parameter design method for the three-plate electric field-coupled wireless power transfer system as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: Determine the load resistance, system angular frequency, transmission distance, and the shape and size of the first and second energy receiving plates according to the application scenario requirements; S2: Determine the shape and size of the energy emitting plate based on the movement range of the power receiving end; S3: Set an insulating dielectric layer by increasing the proportion of the insulating dielectric between the energy emitting plate and the first energy receiving plate, and decreasing the proportion of the insulating dielectric between the energy emitting plate and the second energy receiving plate, thus increasing the coupling capacitance C. M To obtain the maximum value; S4: Based on the shape, size and parameters of the insulating dielectric layer determined in steps S1 to S3, the mutual capacitance and self capacitance of each electrode plate are obtained. S5: Construct the system admittance transfer function based on the mutual compatibility coefficient, and determine the initial constraint range of the mutual compatibility coefficient based on the Bode plot of the admittance function; S6: Determine the mutual compatibility coefficient based on the relationship curve between system transmission efficiency and mutual compatibility coefficient. The value of ; S7: Determine the component parameters in the transmitter compensation topology circuit and the receiver compensation topology circuit according to the following equation; ； ； ； 。 9. The parameter design method according to claim 8, characterized in that, In step S4, the mutual capacitance and self-capacitance of each plate are obtained using the finite element simulation software Ansoft Maxwell.

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