Adjustable critical coupling CLL type PT-WPT transmission system and method based on negative magnetic metamaterials

Abstract

This invention discloses an adjustable critically coupled CLL-type PT-WPT transmission system and method based on negative magnetic metamaterials, mainly addressing the problems of poor transmission performance in the weakly coupled region, difficulty in independently controlling the critical coupling coefficient, and difficulty in adapting metamaterials in existing systems. The solution includes: 1) designing a broadband, low-loss negative magnetic metamaterial unit based on the system's operating frequency; 2) designing transmit and receive coils matched to the target operating frequency, and arranging the negative magnetic metamaterial between the transmit and receive coils to redirect and compress the magnetic flux distribution; 3) adding an additional inductor to the transmit circuit to form a CLL-type PT circuit, achieving control of the critical coupling coefficient; 4) performing parameter simulation optimization by combining the coil, metamaterial, and circuit models. This invention can extend the stable and efficient operating distance of the system without changing the coil geometry, improving transmission power and efficiency, and can be used in drones, mobile robots, industrial AGVs, and implantable medical devices.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transfer technology, and further relates to parity-time symmetric wireless power transfer (PT-WPT), magnetic field modulation of negative magnetic metamaterials, and capacitor-inductor-inductor (CLL) resonant compensation topology technology. Specifically, it is a tunable critically coupled CLL-type PT-WPT transmission system and method based on negative magnetic metamaterials, which can be used for stable and efficient wireless power supply in scenarios such as drones, mobile robots, industrial AGVs, and implantable medical devices. Background Technology

[0002] With the widespread adoption of wireless charging for consumer electronics such as smartphones, smartwatches, and wireless headphones, and the increasing demand for continuous power supply over medium and long distances from drone swarms, new energy vehicles, IoT terminals, and industrial mobile platforms, wireless power transfer (WPT) technology has become an important technological approach to improve device endurance and deployment flexibility. It transmits energy through electromagnetic fields without direct wire connections, avoiding problems such as mechanical contact wear, inconvenient plugging and unplugging, and difficulties in power supply in sealed environments. As the continuous power supply demands of drones, mobile robots, automated guided vehicles, IoT terminals, and implantable medical devices increase, the transmission distance, output stability, and transmission efficiency of magnetically coupled resonant wireless power transfer systems have become key indicators in engineering applications. Traditional magnetically coupled resonant systems rely on near-field magnetic coupling between the transmitting and receiving coils for energy exchange. When the coil spacing increases or the relative position shifts, leading to a decrease in the coupling coefficient, the output power and transmission efficiency typically decrease significantly.

[0003] The PT-WPT system introduces parity-time symmetry theory into wireless power transmission. By constructing equivalent gain at the transmitter and equivalent loss at the receiver, the system can maintain stable output within a certain coupling range while satisfying the PT symmetry condition. Compared with ordinary uncompensated inductively coupled systems, the PT-WPT system has stronger resonant energy exchange capability and distance adaptability, making it suitable for wireless power supply scenarios with high requirements for stable output power and high transmission efficiency.

[0004] In recent years, existing related technologies mainly include the following categories: The first category is to introduce high-order compensation networks or relay coils into PT-WPT systems, such as the high-order compensated wireless power transmission system based on parity-time symmetry principle and relay coils disclosed in Y. Qu et al., Wireless Power Transfer System With High-Order Compensation Network Based on Parity-Time-Symmetric Principle and RelayCoil, IEEE Transactions on Power Electronics, 2023, 38(1): 1314-1323. It extends the working distance through S / S / PS compensation network and relay coils. Although it can improve the transmission performance in the weakly coupled region to a certain extent, its critical coupling condition is still mainly limited by the inherent parameters of the coil and the compensation parameters. The capacitance distribution is more complex than the design, and the requirements for parameter accuracy and debugging conditions are high when implementing it in engineering. The second type of scheme adds a variable inductor, variable capacitor, and DC-DC converter at the transmitting end, relying on dynamic adjustment of resonant parameters and input voltage to maintain a parity-time (PT) symmetrical operating point. A typical example is the constant power, constant efficiency three-coil wireless power transfer (WPT) system proposed by Wang Zhaoyan et al. This scheme adds a third coil and a matching compensation network to optimize output performance, and can stabilize the output power within a limited range. However, when the operating frequency and transmission distance fluctuate, the coil and compensation network parameters must be rematched, and the critical coupling coefficient cannot be independently controlled by a single parameter on the transmitting side. Although this type of scheme can improve the system's adaptability to distance changes, it requires real-time coordination control of multiple variables, has complex control algorithms, many hardware adjustment structures, and the switching adjustment process may introduce additional losses, reducing system efficiency and reliability. The third category involves introducing metamaterials with negative or near-zero permeability into traditional wireless power transfer systems. For example, Y. Cho et al., "Hybrid metamaterial with zero and negative permeability to enhance efficiency in wireless power transfer system," IEEE WPTC, 2016: 1-3, combines metamaterials with negative and near-zero permeability in a traditional wireless power transfer system, improving coil coupling and transmission efficiency by altering the near-field magnetic flux distribution. This approach demonstrates the magnetic field focusing effect of metamaterials, but it is geared towards traditional WPT systems and does not consider the gain-loss balance and critical coupling conditions of PT-WPT systems. Furthermore, the metamaterial's loss and operating bandwidth affect its enhancement effect under frequency variations.

[0005] In summary, existing PT-WPT control schemes each have their shortcomings: fixed-parameter schemes have limited coupling and adjustment capabilities; multi-variable dynamic control schemes have high hardware and control complexity and are prone to introducing additional losses; traditional metamaterials are only suitable for ordinary wireless power transmission systems, and their narrowband and loss characteristics can disrupt the symmetric equilibrium of the PT. Currently, there is still a lack of an integrated scheme that can achieve independent single-end control of critical coupling, while also possessing low loss and wideband magnetic field enhancement. Existing technologies have high hardware costs and are difficult to debug, making it difficult to adapt to the miniaturized and highly stable wireless power supply requirements of various scenarios such as mobile devices and industrial robots. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing an adjustable critical coupling CLL-type PT-WPT transmission system and method based on negative magnetic metamaterials. This aims to solve the problems of existing solutions lacking broadband, low-loss magnetic field enhancement methods, difficulty in matching PT-WPT gain and loss balance with metamaterials, and the inability to independently adjust the critical coupling coefficient, thus limiting the efficient and stable transmission distance.

[0007] The basic idea of ​​this invention is as follows: First, a broadband, low-loss negative magnetic metamaterial unit adapted to the PT-WPT operating frequency is designed and placed between the transmitting and receiving coils. The effective magnetic flux density at the receiving coil is increased through the redirection and compression of near-field magnetic flux by the negative magnetic metamaterial. Then, an additional inductor is introduced on the transmitting side to form a transmitting CLL-type PT-WPT circuit structure. The additional inductor alters the equivalent impedance and equivalent loss of the transmitting circuit, reducing the critical coupling coefficient of the system without changing the coil geometry. Finally, the negative magnetic metamaterial, the coupling coil, and the improved PT-WPT circuit are jointly designed and simulated for optimization, thereby improving the system's transmission power, transmission efficiency, and stable operating distance in the weakly coupled region. This invention can enhance the effective magnetic flux between coils using a broadband, low-loss negative magnetic metamaterial, and, combined with the independent control of the critical coupling coefficient using the transmitting-side CLL topology, significantly widens the system's efficient and stable weakly coupled operating range, improving the output power and transmission efficiency of wireless power transmission.

[0008] To achieve the above objectives, the technical solution of the present invention includes the following:

[0009] A tunable critically coupled emission CLL-type PT-WPT system enhanced by a negative magnetic metamaterial includes a transmitter, a receiver, and a negative magnetic metamaterial located between them;

[0010] The transmitting end includes a negative resistance gain module, a transmitting circuit compensation capacitor Ct, a transmitting coil Lt, an additional inductor module Ls, and an equivalent resistance of the transmitting circuit; wherein Ct, Lt, and Ls are connected between the same pair of nodes in the transmitting circuit, forming a capacitor-inductor-inductor CLL resonant network; and this network is electrically connected to the negative resistance gain module and provides equivalent gain to the transmitting circuit;

[0011] The receiving end includes a receiving coil Lr, a receiving circuit compensation capacitor Cr, a receiving circuit parasitic resistance, and a load resistance RL; wherein Lr and Cr form a receiving resonant circuit, RL is connected to the output end of the receiving resonant circuit, and the transmitting end Lt is magnetically coupled to the receiving end Lr.

[0012] The negative magnetic metamaterial has its plate surface arranged parallel to the coil planes of Lt and Lr, so that the near-field magnetic flux generated by the transmitting coil Lt is coupled to the receiving coil Lr after being redirected and compressed by the negative magnetic metamaterial.

[0013] The inductance value of the additional inductor module Ls and the capacitance value of the transmitting circuit compensation capacitor Ct are configured according to the target operating frequency and the preset critical coupling coefficient. They are used to change the equivalent inductance and equivalent loss parameters of the transmitting circuit and adjust the critical coupling coefficient of the PT-WPT system while keeping the geometry of the transmitting coil Lt and the receiving coil Lr unchanged.

[0014] Furthermore, this invention also proposes a method for wireless power transmission using the above-mentioned system, comprising the following steps:

[0015] (1) Input system preset parameters: Input the target operating frequency, target transmission distance, target critical coupling coefficient matching the distance, load resistance value, and fixed geometric parameters of transmitting coil Lt and receiving coil Lr;

[0016] (2) Parameter matching solution: Calculate the receiving circuit compensation capacitor Cr based on the target operating frequency; combine the equivalent loss of the transmitting circuit, the total loss of the receiving circuit, and the preset target critical coupling coefficient to solve the inductance value of the additional inductor module Ls and the capacitance value of the transmitting circuit compensation capacitor Ct; make the transmitting CLL resonant circuit and the receiving resonant circuit resonate at the target operating frequency at the same time, and the system critical coupling coefficient is adapted to the target transmission distance.

[0017] (3) System hardware assembly and layout: The additional inductor module Ls, the transmitting circuit compensation capacitor Ct, and the negative resistance gain module are connected to the transmitting end to form a CLL resonant network; a negative magnetic metamaterial with a working bandwidth covering the target working frequency is selected and its plate is arranged parallel between the transmitting coil Lt and the receiving coil Lr; the receiving coil Lr, the receiving compensation capacitor Cr, and the load resistor RL form a receiving resonant circuit.

[0018] (4) Wireless power transmission excitation: An AC excitation signal is supplied to the negative resistance gain module of the transmitting end, and the transmitting coil Lt generates an alternating near-field magnetic flux; the alternating magnetic flux is coupled to the receiving coil Lr after being constrained, redirected and compressed by the negative magnetic metamaterial, and the energy is processed by the receiving resonant circuit and then stably output to the load resistor RL.

[0019] (5) Frequency conversion adaptive adjustment: When the target operating frequency changes, the geometric structure of the transmitting coil Lt and the receiving coil Lr remains unchanged. Only the parameters of the adjustable components of the transmitting and receiving circuits are reconfigured to complete the resetting of the critical coupling coefficient and realize wireless power transmission.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] First, this invention adds an additional inductor to the transmitting circuit to construct a CLL-type resonant network. The additional inductor can work with the transmitting coil to change the two types of control degrees of freedom: equivalent inductance and equivalent loss on the transmitting side. Without changing the geometric structure such as coil size and number of turns, the critical coupling coefficient of the system can be flexibly adjusted and configured, effectively widening the coupling range that satisfies parity-time symmetric stable operation, greatly extending the efficient and stable wireless transmission distance of the system, and improving the power supply stability under long-distance weak coupling conditions.

[0022] Secondly, this invention can switch and tune additional inductor parameters according to different target operating frequencies, and quickly reconstruct the resonant state and critical coupling operating point by matching with compensation capacitors. There is no need to redesign and process the transmitting and receiving coils for each frequency point, which greatly reduces the coil development, sample processing and whole machine debugging cycle in multi-frequency and frequency conversion wireless power supply scenarios, and significantly reduces the R&D and mass production costs of multi-frequency band equipment.

[0023] Third, the present invention deploys negative magnetic metamaterial units between the transmitting and receiving coils, and uses their negative permeability characteristics to constrain, redirect and compress the near-field magnetic flux in space, thereby increasing the coupling magnetic flux density of the receiving coil; at the same time, the magnetic field enhancement structure of the negative magnetic metamaterial and the adjustable critical coupling CLL topology form a synergistic gain, doubly optimizing the energy coupling capability of the weak coupling range, effectively improving the output power and overall energy transmission efficiency under long-distance operating conditions.

[0024] Fourth, compared with the traditional control scheme of adding relay coils and multi-level adjustable compensation networks, the present invention only relies on the additional inductor on the transmitting side and the matching compensation capacitor to complete all parameter adjustment. The overall topology has fewer components, fewer control variables, a simple system hardware architecture, and low control algorithm complexity, which facilitates batch production, online debugging and subsequent equipment maintenance, and has stronger practicality. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the tunable critical coupling emission CLL-type PT-WPT system loaded with negative magnetic metamaterials in this invention.

[0026] Figure 2 This is a flowchart of the joint design simulation process for the system of this invention;

[0027] Figure 3 This is a schematic diagram of the negative magnetic metamaterial unit model in this invention;

[0028] Figure 4 The graph shows the equivalent permeability of the negative magnetic metamaterial of this invention at an operating frequency of 6.78 MHz.

[0029] Figure 5 This is a schematic diagram of the coupling coil model in this invention;

[0030] Figure 6 This is a schematic diagram of the coil model loaded with negative magnetic metamaterial in this invention;

[0031] Figure 7 Figure 1 shows the system simulation results provided in the embodiments of the present invention. Figure 2(a) shows the distribution of the coil coupling magnetic field without metamaterial loading, and Figure 3(b) shows the distribution of the coil coupling magnetic field after metamaterial loading.

[0032] Figure 8 This is the circuit topology diagram of the adjustable critical coupling emitter CLL type PT-WPT system of the present invention;

[0033] Figure 9 This is a co-simulation circuit diagram of the adjustable critical coupling emission CLL type PT-WPT system of the present invention. Detailed Implementation

[0034] The present invention will now be further described with reference to the accompanying drawings.

[0035] Example 1: Refer to Figure 1 This invention proposes a tunable critically coupled transmit CLL-type PT-WPT system enhanced by a negative magnetic metamaterial, specifically comprising a transmitter, a receiver, and a negative magnetic metamaterial located between them; the transmitter includes a negative resistance gain module, a transmitter circuit compensation capacitor Ct, a transmitter coil Lt, an additional inductor module Ls, and an equivalent resistance of the transmitter circuit; wherein Ct, Lt, and Ls are connected between the same pair of nodes in the transmitter circuit, forming a capacitor-inductor-inductor CLL resonant network; and this network is electrically connected to the negative resistance gain module and provides equivalent gain to the transmitter circuit; the receiver includes a receiver coil Lr, a receiver circuit compensation capacitor Cr, a receiver circuit parasitic resistance, and a load resistance RL; wherein Lr and Cr form a... A receiving resonant circuit is formed, with RL connected to the output terminal of the receiving resonant circuit. The transmitting coil Lt and the receiving coil Lr are magnetically coupled. The negative magnetic metamaterial has its plate surface parallel to the coil plane of Lt and Lr, so that the near-field magnetic flux generated by the transmitting coil Lt is redirected and compressed by the negative magnetic metamaterial and coupled to the receiving coil Lr. The inductance value of the additional inductor module Ls and the capacitance value of the transmitting circuit compensation capacitor Ct are configured according to the target operating frequency and the preset critical coupling coefficient. They are used to change the equivalent inductance and equivalent loss parameters of the transmitting circuit and adjust the critical coupling coefficient of the PT-WPT system while keeping the geometry of the transmitting coil Lt and the receiving coil Lr unchanged.

[0036] In this embodiment, the parallel equivalent inductance Leq of the transmitting coil Lt and the additional inductor module Ls satisfies Leq=LtLs / (Lt+Ls), the inherent resonant angular frequency of the transmitting circuit satisfies ωt=1 / √(LeqCt), and the inherent resonant angular frequency of the receiving circuit satisfies ωr=1 / √(LrCr). The additional inductor module Ls, the transmitting circuit compensation capacitor Ct, and the receiving circuit compensation capacitor Cr are configured such that ωt=ωr=2πf0, where f0 is the target operating frequency.

[0037] The inductance value of the aforementioned additional inductor module Ls is determined based on the equivalent loss of the transmitting circuit, the total loss of the receiving circuit, the load resistance RL, and the coil coupling coefficient corresponding to the target transmission distance. This ensures that the critical coupling coefficient of the configured system is not greater than the coil coupling coefficient corresponding to the target transmission distance, thereby maintaining the system in a PT-symmetrical operating state. In this embodiment, the additional inductor module Ls is constructed using replaceable fixed inductors, a segmented switchable inductor group consisting of at least two inductor branches and switching devices, or continuously adjustable inductors. When the target operating frequency changes, the resonant frequency and critical coupling coefficient are reset without redesigning the transmitting and receiving coils by replacing, switching, or adjusting the additional inductor module Ls and correspondingly configuring the transmitting circuit compensation capacitor Ct and the receiving circuit compensation capacitor Cr.

[0038] In this embodiment, the aforementioned negative magnetic metamaterial includes a PCB-type dielectric substrate and a circular helical metal conductor disposed on the surface of the dielectric substrate. Preferably, the dielectric substrate is FR4, and the conductivity of the copper conductor is preferably 5.8 × 10^7 S / m. The negative magnetic metamaterial has a negative real part of equivalent permeability within the operating frequency band including the target operating frequency. Preferably, the unit side length Sub-L of the negative magnetic metamaterial is 324–325 mm, the inner diameter iner_d of the circular helical copper conductor is 96–98 mm, the turn spacing ds_1 is 1.3–1.5 mm, the linewidth w_1 is 4.2–4.5 mm, the metal thickness t_1 is 0.1 mm, and the dielectric substrate thickness h_1 is 3.2–3.4 mm.

[0039] In this embodiment, both the transmitting coil Lt and the receiving coil Lr are planar square spiral copper coils. Preferably, the outer side length Lout of the coil is 297-298 mm, the gap_2 between the coil and the edge of the substrate is 7.4-7.7 mm, the turn spacing ds_2 is 10.5-10.6 mm, the line width w_2 is 17.1-17.5 mm, the copper conductor thickness t_2 is 0.035 mm, the coil substrate thickness h_2 is 1.0-1.2 mm, and the via diameter Via-d is 3 mm.

[0040] Example 2: Refer to Figure 1-2 This embodiment proposes a method for wireless power transmission using the system described in Embodiment 1, specifically including the following steps:

[0041] Step 1) Input system preset parameters: Input the target operating frequency, target transmission distance, target critical coupling coefficient matching the distance, load resistance value, and fixed geometric parameters of the transmitting coil Lt and receiving coil Lr;

[0042] Step 2) Parameter Matching Solution: Calculate the receiving circuit compensation capacitor Cr based on the target operating frequency; combine the equivalent loss of the transmitting circuit, the total loss of the receiving circuit, and the preset target critical coupling coefficient to solve for the inductance value of the additional inductor module Ls and the capacitance value of the transmitting circuit compensation capacitor Ct; ensure that the transmitting CLL resonant circuit and the receiving resonant circuit resonate simultaneously at the target operating frequency, and that the system critical coupling coefficient is adapted to the target transmission distance. In this embodiment, the inductance value of the additional inductor module Ls and the capacitance value of the transmitting circuit compensation capacitor Ct are solved in the following way in this step: Define the parallel equivalent inductance of the transmitting circuit Leq=LtLs / (Lt+Ls), solve for the inherent resonant angular frequency of the transmitting circuit according to ωt=1 / √(LeqCt), and solve for the inherent resonant angular frequency of the receiving circuit according to ωr=1 / √(LrCr); by setting ωt and ωr to be equal, the combined parameters of the additional inductor module Ls, the transmitting circuit compensation capacitor Ct, and the receiving circuit compensation capacitor Cr are matched and determined.

[0043] Step 3) System hardware assembly and layout: Connect the additional inductor module Ls, the transmitting circuit compensation capacitor Ct, and the negative resistance gain module to the transmitting end to form a CLL resonant network; select a negative magnetic metamaterial whose working bandwidth covers the target working frequency, and arrange its plate surface parallel between the transmitting coil Lt and the receiving coil Lr; the receiving coil Lr, the receiving compensation capacitor Cr, and the load resistor RL form a receiving resonant circuit.

[0044] Step 4) Wireless power transfer excitation: An AC excitation signal is supplied to the negative resistance gain module of the transmitting end, and the transmitting coil Lt generates an alternating near-field magnetic flux; the alternating magnetic flux is coupled to the receiving coil Lr after being constrained, redirected and compressed by the negative magnetic metamaterial, and the energy is processed by the receiving resonant circuit and then stably output to the load resistor RL.

[0045] Step 5) Frequency Adaptive Adjustment: When the target operating frequency changes, the geometry of the transmitting coil Lt and the receiving coil Lr remains unchanged. Only the parameters of the adjustable components of the transceiver circuit are reconfigured to complete the retuning of the critical coupling coefficient and realize wireless power transmission.

[0046] In this embodiment, the geometric structure of the transmitting coil Lt and the receiving coil Lr includes the number of turns, the outer diameter of the coil, and the coil spacing; the adjustable components of the transmitting and receiving circuits include the additional inductor module Ls on the transmitting side, the transmitting circuit compensation capacitor Ct, and the receiving circuit compensation capacitor Cr on the receiving side. The critical coupling coefficient is tuned only by reconfiguring the combined parameters of the three components.

[0047] Example 3: The overall implementation steps of the wireless power transmission method proposed in this example are the same as in Example 2. Specific parameter settings are now provided for reference. Figure 1-9 The implementation process of the method of the present invention will be described in further detail.

[0048] In this embodiment, a negative magnetic metamaterial unit with a center operating frequency of 6.78MHz and a coil unit model with a center operating frequency of 6.78MHz were designed. A PT-WPT circuit model based on a PP-type transmitter-side additional inductor was established. Combining the metamaterial and the coupled coil with the improved PT-WPT circuit, a new WPT system model was formed. The overall structure is as follows: Figure 1 As shown, the design flowchart is as follows: Figure 2 As shown, the designed negative magnetic metamaterial unit is as follows: Figure 3 As shown; the simulation yielded the equivalent permeability curve of the negative magnetic material as shown in the figure. Figure 4 As shown; the designed coupling coil structure is as follows Figure 5 As shown. The specific implementation process includes the following:

[0049] Step 1: Design a negative magnetic metamaterial unit with a specific frequency.

[0050] Reference Figure 3 In this embodiment, the dielectric substrate of the negative magnetic metamaterial unit is made of FR4 material, with a dielectric constant of approximately 4.4 and a loss tangent of approximately 0.02. The top metal layer adopts a circular spiral copper structure with a copper conductivity of approximately 5.8 × 10^7 S / m. By scanning parameters such as unit side length, spiral linewidth, turn spacing, metal thickness, and dielectric thickness, the negative magnetic metamaterial exhibits negative permeability characteristics around 6.78 MHz.

[0051] Table 1. Dimensional parameters of negative magnetic metamaterial units (unit: mm)

[0052] Sub-L 324～325 iner_d 96～98 ds_1 1.3～1.5 w_1 4.2～4.5 t_1 0.1 h_1 3.2～3.4

[0053] Reference Figure 4 Equivalent parameters were extracted from the aforementioned negative magnetic metamaterial. Near the operating frequency of 6.78 MHz, the real part of the equivalent permeability is approximately -1.01, the loss term is approximately -0.12, and the resonant frequency is approximately 6.2 MHz. These results demonstrate that the designed metamaterial can provide a negative magnetic response near the target operating frequency, thus providing conditions for magnetic field focusing between coils.

[0054] Step 2: Design a coupling coil with a specific frequency.

[0055] Reference Figure 5 Both the transmitting and receiving coils employ a planar square helical coil structure, with copper conductors of 0.035mm thickness. By adjusting the outer side length, wire width, turn spacing, and number of turns, the inductance of both the transmitting and receiving coils is made approximately 3μH, which, together with the subsequent compensation capacitor, satisfies the resonance requirement around 6.78MHz.

[0056] Table 2. Dimensions of the coupling coil (unit: mm)

[0057] Lout 297～298 gap_2 7.4～7.7 ds_2 10.5～10.6 w_2 17.1～17.5 t_2 0.035 h_2 1.0～1.2 Via-d 3

[0058] Step 3: Load the negative magnetic metamaterial between the transmitting coil and the receiving coil.

[0059] To utilize the electromagnetic focusing effect of negative magnetic metamaterials, they are loaded between coils, specifically as follows: Figure 6 As shown, loading a negative magnetic metamaterial between the receiving and transmitting coils can converge the originally diverging near-field waves to the vicinity of the receiving coil. When the near-field waves pass through the metamaterial unit, they become a denser beam, increasing the magnetic density near the receiving coil and thus enhancing the magnetic field energy, thereby improving the system's transmission performance. Simulations of the coil coupling model without and with the metamaterial are shown in the following figures: Figure 7 As shown, negative magnetic metamaterials alter the magnetic flux distribution path between the transmitting and receiving coils, causing the originally radially diffusing magnetic flux to be redirected and compressed within the metamaterial region, thereby increasing the effective magnetic flux coupling of the receiving coil.

[0060] Reference Figure 6 A negative magnetic metamaterial is placed parallel to the two coils, causing the near-field magnetic flux generated by the transmitting coil to be redirected and compressed after passing through the metamaterial region. (See reference...) Figure 7 Compared with the coil coupling without metamaterial, the magnetic field distribution near the receiving coil is more concentrated after the metamaterial is loaded, indicating that the negative magnetic metamaterial can increase the effective magnetic flux coupling of the receiving coil, thereby improving the wireless power transmission performance.

[0061] Step 4: Establish the CLL-type PT-WPT transmitting circuit.

[0062] Reference Figure 8The transmitting end consists of a negative resistance gain module, a compensation capacitor C1, a transmitting coil inductance Lt, an additional inductance Ls, and the equivalent resistance of the transmitting circuit; the receiving end consists of a receiving coil inductance Lr, a compensation capacitor Cr, the parasitic resistance of the receiving circuit, and a load resistance RL. The additional inductance Ls, together with the transmitting coil, changes the equivalent inductance and equivalent loss parameters of the transmitting circuit, thereby making the critical coupling coefficient of the system adjustable. When the natural resonant angular frequencies of the two circuits are equal, the natural resonant angular frequency of the transmitting circuit can be expressed as ωt = 1 / sqrt((LtLs / (Lt+Ls))Ct), and the natural resonant angular frequency of the receiving circuit can be expressed as ωr = 1 / sqrt(LrCr). The system coupling rate κ is related to the mutual inductance of the coils and the equivalent inductance. When the system is in a PT symmetric state, the operating angular frequency splits into ω = ωt ± sqrt(κ^2 - γr^2); when the coupling rate is below the critical condition, the system enters a PT broken state. Implementation includes establishing the coupling mode equations:

[0063] ;

[0064] In the formula The natural resonant angular frequency of the transmitting circuit is , and the natural resonant angular frequency of the receiving circuit is . , The coupling coefficient between the transmitting and receiving coils. This refers to the mutual inductance between coils. The excitation coefficient is negative resistance. for The effective value, that is, the effective value of AC voltage. Let be the overall gain coefficient of the transmit circuit. The inherent loss of the transmit circuit is... The inherent loss of the receiving circuit is The system load loss is The total loss of the receiving circuit is When the natural resonant angular frequencies of the two circuits are equal , The coupling ratio of the system, , It is mutual intuition Related variables.

[0065] When the system reaches stability, the stability equation obtained from the coupled-mode equations is as follows:

[0066] ,

[0067] Find the operating angular frequency at the current moment:

[0068] ;

[0069] when The operating angular frequency is At this point, the PT-WPT system is in a PT broken state.

[0070] when and The operating angular frequency is At this point, the PT-WPT system is in a PT-symmetric state.

[0071] Therefore, the critical coupling rate of the system is The critical coupling coefficient can be obtained from the following formula:

[0072] ;

[0073] Therefore, it can be concluded that the critical coupling coefficient of the system is related to the equivalent loss parameter of the transmit circuit. Directly related.

[0074] This invention introduces an additional inductor into the transmitting circuit, so that the equivalent inductance and parasitic resistance on the transmitting side work together to increase the degree of freedom of equivalent loss control of the transmitting circuit without changing the geometry of the transmitting coil, thereby reducing the critical coupling coefficient.

[0075] In this embodiment, by introducing an additional inductor Ls into the transmitting circuit, the equivalent inductance of the transmitting side and the parasitic loss of the additional inductance jointly affect the equivalent loss parameter of the transmitting circuit. Without changing the geometry of the transmitting coil, the critical coupling coefficient required for the system to satisfy the PT symmetry condition is changed, thereby extending the stable and efficient working distance in the weak coupling region.

[0076] The additional inductor alters the equivalent impedance characteristics of the transmitting circuit, causing a change in the negative resistance excitation amplitude required by the system under PT symmetry conditions, thereby achieving a lower critical coupling requirement under the same excitation conditions.

[0077] Step 5: Co-simulation and parameter optimization.

[0078] Reference Figure 9 We performed a joint transient simulation using the coil model and negative magnetic metamaterial model from Maxwell and the PT-WPT circuit model from Simplier. By scanning the distance between the two coils, we obtained the coupling coefficient at different distances and compared the system output power and transmission efficiency before and after loading the metamaterial.

[0079] The effects of the present invention will be further explained below with reference to simulation experiments.

[0080] 1. Simulation Conditions: The simulation experiment in this embodiment was conducted in the Ansys Electronics Desktop environment. The electromagnetic models of the coil and metamaterial were built using Maxwell, and the circuit model was built using Simplorer. The two were used for joint transient simulation. The system design operating frequency was 6.78MHz, the excitation power supply was ±10V, the load resistance was 2.775kΩ, and the operational amplifier used in the negative resistance gain module was an LM7171.

[0081] Table 3 Circuit Simulation Parameter Table

[0082] C1 0.1837 nF C2 2 nF C3 0.1837 nF L1 3 μH L2 0.3 μH R1 2000 Ω R2 220 Ω R3 2775 Ω R4 30 Ω

[0083] 2. Simulation content: First, the equivalent permeability of the negative magnetic metamaterial unit is extracted to verify that it has a negative magnetic response near 6.78MHz; then, coil coupling models with and without metamaterial are established respectively, and the magnetic field distribution and coil coupling coefficient are compared in the two cases; finally, the coil model, metamaterial model and transmitting CLL type PT-WPT circuit model are simulated together to read the load output power and calculate the transmission efficiency.

[0084] 3. Simulation Results: Based on the circuit parameters shown in Table 3, the critical coupling coefficient of the system in this embodiment can be calculated to be 0.143. By scanning the coil spacing parameters, a weak coupling transmission spacing was selected for comparative simulation before and after loading the metamaterial. The results are shown in Table 4.

[0085] Table 4 Comparison of system transmission power and efficiency before and after loading electromagnetic metamaterials

[0086] Unloaded electromagnetic metamaterials 0.0142 70 0.57 Loading electromagnetic metamaterials 0.0146 90 0.68

[0087] As shown in Table 4, under similar weak coupling conditions, the system coupling coefficient increased from 0.0142 to 0.0146 after loading the electromagnetic metamaterial, the load output power increased from 70mW to 90mW, and the transmission efficiency increased from 0.57 to 0.68. The increased output power indicates an increase in the effective energy received at the receiving end, while the improved efficiency indicates a reduction in ineffective losses during transmission. Combined with... Figure 7 The magnetic field distribution results show that the negative magnetic metamaterial can enhance the magnetic field energy density near the receiving coil by redirecting and compressing the magnetic flux. The above simulation analysis proves the correctness and effectiveness of the method proposed in this invention.

[0088] The parts of this invention not described in detail are common knowledge to those skilled in the art.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, those skilled in the art, after understanding the content and principle of the present invention, may make various modifications and changes in form and detail without departing from the principle and structure of the present invention. However, these modifications and changes based on the concept of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A tunable critically coupled emission CLL-type PT-WPT system enhanced by a negative magnetic metamaterial, characterized in that, include: The transmitter, the receiver, and the negative magnetic metamaterial located between them; The transmitting end includes a negative resistance gain module, a transmitting circuit compensation capacitor Ct, a transmitting coil Lt, an additional inductor module Ls, and an equivalent resistance of the transmitting circuit; wherein Ct, Lt, and Ls are connected between the same pair of nodes in the transmitting circuit, forming a capacitor-inductor-inductor CLL resonant network; and this network is electrically connected to the negative resistance gain module and provides equivalent gain to the transmitting circuit; The receiving end includes a receiving coil Lr, a receiving circuit compensation capacitor Cr, a receiving circuit parasitic resistance, and a load resistance RL; wherein Lr and Cr form a receiving resonant circuit, RL is connected to the output end of the receiving resonant circuit, and the transmitting end Lt is magnetically coupled to the receiving end Lr. The negative magnetic metamaterial has its plate surface arranged parallel to the coil planes of Lt and Lr, so that the near-field magnetic flux generated by the transmitting coil Lt is coupled to the receiving coil Lr after being redirected and compressed by the negative magnetic metamaterial. The inductance value of the additional inductor module Ls and the capacitance value of the transmitting circuit compensation capacitor Ct are configured according to the target operating frequency and the preset critical coupling coefficient. They are used to change the equivalent inductance and equivalent loss parameters of the transmitting circuit and adjust the critical coupling coefficient of the PT-WPT system while keeping the geometry of the transmitting coil Lt and the receiving coil Lr unchanged.

2. The system according to claim 1, characterized in that, The parallel equivalent inductance Leq of the transmitting coil Lt and the additional inductor module Ls satisfies Leq=LtLs / (Lt+Ls), the inherent resonant angular frequency of the transmitting circuit satisfies ωt=1 / √(LeqCt), and the inherent resonant angular frequency of the receiving circuit satisfies ωr=1 / √(LrCr). The additional inductor module Ls, the transmitting circuit compensation capacitor Ct, and the receiving circuit compensation capacitor Cr are configured such that ωt=ωr=2πf0, where f0 is the target operating frequency.

3. The system according to claim 1 or 2, characterized in that, The inductance value of the additional inductor module Ls is determined based on the equivalent loss of the transmitting circuit, the total loss of the receiving circuit, the load resistance RL, and the coil coupling coefficient corresponding to the target transmission distance, so that the critical coupling coefficient of the configured system is not greater than the coil coupling coefficient corresponding to the target transmission distance, thereby maintaining the system in a PT symmetrical working state.

4. The system according to claim 1, characterized in that, The additional inductor module Ls can be a replaceable fixed inductor, a segmented switchable inductor group consisting of at least two inductor branches and switching devices, or a continuously adjustable inductor. When the target operating frequency changes, the resonant frequency and critical coupling coefficient can be reset without redesigning the transmitting and receiving coils by replacing, switching, or adjusting the additional inductor module Ls and configuring the transmitting circuit compensation capacitor Ct and the receiving circuit compensation capacitor Cr accordingly.

5. The system according to claim 1, characterized in that, The negative magnetic metamaterial includes a PCB-type dielectric substrate and a circular spiral metal conductor disposed on the surface of the dielectric substrate; the negative magnetic metamaterial has a negative real part of equivalent permeability within the operating frequency band including the target operating frequency.

6. The system according to claim 5, characterized in that, The negative magnetic metamaterial has a unit side length Sub-L of 324–325 mm, an inner diameter iner_d of 96–98 mm, a turn spacing ds_1 of 1.3–1.5 mm, and a line width w_1 of 4.2–4.5 mm.

7. The system according to claim 1, characterized in that, Both the transmitting coil Lt and the receiving coil Lr are planar square spiral copper coils. The outer side length Lout of the coil is 297-298 mm, the gap_2 between the coil and the edge of the substrate is 7.4-7.7 mm, the turn spacing ds_2 is 10.5-10.6 mm, the line width w_2 is 17.1-17.5 mm, the copper conductor thickness t_2 is 0.035 mm, the coil substrate thickness h_2 is 1.0-1.2 mm, and the via diameter Via-d is 3 mm.

8. A method for wireless power transmission using the system described in any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Input system preset parameters: Input the target operating frequency, target transmission distance, target critical coupling coefficient matching the distance, load resistance value, and fixed geometric parameters of transmitting coil Lt and receiving coil Lr; (2) Parameter matching solution: Calculate the receiving circuit compensation capacitor Cr based on the target operating frequency; combine the equivalent loss of the transmitting circuit, the total loss of the receiving circuit, and the preset target critical coupling coefficient to solve the inductance value of the additional inductor module Ls and the capacitance value of the transmitting circuit compensation capacitor Ct; make the transmitting CLL resonant circuit and the receiving resonant circuit resonate at the target operating frequency at the same time, and the system critical coupling coefficient is adapted to the target transmission distance. (3) System hardware assembly and layout: The additional inductor module Ls, the transmitting circuit compensation capacitor Ct, and the negative resistance gain module are connected to the transmitting end to form a CLL resonant network; a negative magnetic metamaterial with a working bandwidth covering the target working frequency is selected and its plate is arranged parallel between the transmitting coil Lt and the receiving coil Lr; the receiving coil Lr, the receiving compensation capacitor Cr, and the load resistor RL form a receiving resonant circuit. (4) Wireless power transmission excitation: An AC excitation signal is supplied to the negative resistance gain module of the transmitting end, and the transmitting coil Lt generates an alternating near-field magnetic flux; the alternating magnetic flux is coupled to the receiving coil Lr after being constrained, redirected and compressed by the negative magnetic metamaterial, and the energy is processed by the receiving resonant circuit and then stably output to the load resistor RL. (5) Frequency conversion adaptive adjustment: When the target operating frequency changes, the geometric structure of the transmitting coil Lt and the receiving coil Lr remains unchanged. Only the parameters of the adjustable components of the transmitting and receiving circuits are reconfigured to complete the resetting of the critical coupling coefficient and realize wireless power transmission.

9. The wireless power transmission method according to claim 8, characterized in that: The inductance value of the additional inductor module and the capacitance value of the transmitting circuit compensation capacitor in step (2) are solved as follows: Define the equivalent inductance in parallel for the transmitting circuit: Leq = LtLs / (Lt+Ls), The natural resonant angular frequency of the transmitting circuit is calculated using ωt = 1 / √(LeqCt), and the natural resonant angular frequency of the receiving circuit is calculated using ωr = 1 / √(LrCr). By setting ωt and ωr to be equal, the combined parameters of the additional inductor module Ls, the compensation capacitor Ct of the transmitting circuit, and the compensation capacitor Cr of the receiving circuit are determined.

10. The method according to claim 9, characterized in that: The geometric structure of the transmitting coil Lt and the receiving coil Lr in step (5) includes the number of turns, the outer diameter of the coil, and the coil spacing; the adjustable components of the transmitting and receiving circuit include the additional inductor module Ls on the transmitting side, the transmitting circuit compensation capacitor Ct, and the receiving circuit compensation capacitor Cr on the receiving side. The critical coupling coefficient can be tuned by reconfiguring the combined parameters of the three components.

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