Anti-offset flat solenoid coil wireless power transmission system and parameter optimization method thereof

Abstract

The invention discloses an anti-offset flat solenoid coil wireless power transmission system, which comprises a transmitting end solenoid and a receiving end solenoid, and is characterized in that the transmitting end solenoid comprises a first magnetic core which is integrally in a flat plate shape, and two ends of the first magnetic core are provided with auxiliary magnetic cores which extend along the edge; the auxiliary magnetic core protrudes upwards relative to the first magnetic core. The first magnetic core is provided with first coils wound in the length direction of the auxiliary magnetic cores, the first coils are distributed between the two auxiliary magnetic cores at intervals, and the protruding height of the first coils relative to the first magnetic core is smaller than that of the auxiliary magnetic cores. The anti-offset flat solenoid coil wireless power transmission system and the parameter optimization method thereof have the advantages of being reasonable in structural design, high in adaptive capacity, low in implementation cost, capable of improving transmission efficiency and anti-offset capacity and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of radio transmission, and in particular to an anti-deviation flat solenoid coil wireless power transmission system and a parameter optimization method thereof. Background Art

[0002] Inductive power transfer (IPT) technology is a cutting-edge power supply technology that uses the principle of near-field electromagnetic coupling to achieve non-physical contact transmission of electric energy. Compared with traditional plug-in charging, this technology effectively reduces the use of cables and has the advantages of large degrees of freedom, low maintenance cost, and high safety. It has long been commercialized and widely used in battery charging occasions such as electric vehicles, portable consumer electronic devices, intelligent unmanned systems, and medical electronic devices. However, the above advantages are all based on the premise that the primary and secondary coupling mechanisms are facing each other. In actual situations, the magnetic coupling mechanism inevitably has an offset. After the offset, the system mutual inductance and coupling coefficient change greatly, resulting in unstable transmission power, reduced efficiency, and significant deterioration of system performance.

[0003] In order to improve the anti-offset capability of the IPT system, the existing technology mainly studies by adjusting the control strategy, resonant topology or coupling mechanism. In terms of control strategy, the anti-offset capability of the IPT coupling mechanism is enhanced by phase shift control, but the feedback signal at the receiving end needs to be transmitted to the transmitting end in real time, which has high requirements for wireless communication. The use of variable frequency control will make the input impedance angle of the IPT system too large during the control process, resulting in excessive current stress at the transmitting end, affecting the stability of the system. At the same time, such a control method also has high requirements for communication. In terms of compensation topology, topologies such as T / S, SP / S, S / SP and LCC / S have been proposed in recent years. The LCC / S topology inherits the advantages of the LCC / LCC topology while using fewer components, and has the characteristics of constant input and output voltage and easy soft switching. Although the anti-offset performance can be improved through the compensation topology, the addition of too many resonant components increases the system order and increases the difficulty of analysis. In the design of coupling mechanisms, a large number of studies have attempted to improve the anti-offset performance by optimizing the structure of the coupling coil. In order to construct a uniform magnetic field to improve the system's anti-offset capability, researchers have proposed coupling mechanisms such as bipolar (BP) coils, tripolar (TP) coils, solenoid (FSP) coils, double D-type (DD) coils, and double D-type orthogonal (DDQ) coils. Among them, the flat solenoid coil magnetic coupling mechanism has excellent anti-offset performance compared to the planar circular and planar square magnetic coupling mechanisms. From this, magnetic coupling mechanisms such as grid solenoids and Japanese solenoids have been derived, all of which have good anti-offset performance, but their transmitters and receivers use square cores of the same size. However, this consistent requirement for the size of the magnetic core cannot adapt to different application scenarios, and its implementation will greatly increase the system cost. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is: how to provide an anti-deviation flat solenoid coil wireless power transmission system and its parameter optimization method which has a reasonable structural design, strong adaptability, low implementation cost, and can improve transmission efficiency and anti-deviation capability.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A flat solenoid coil wireless power transmission system with anti-offset, including a transmitting end solenoid, the transmitting end solenoid including a first magnetic core that is overall flat, the two ends of the first magnetic core have auxiliary magnetic cores extending along the edges, the auxiliary magnetic cores protrude upward relative to the first magnetic core; the first magnetic core has a first coil wound along the length direction of the auxiliary magnetic core, the first coils are distributed and spaced apart between the two auxiliary magnetic cores, and the protruding height of the first coil relative to the first magnetic core is less than the protruding height of the auxiliary magnetic core.

[0007] In the above structure, since auxiliary magnetic cores are provided at both ends of the first magnetic core and the thickness of the first coil is smaller than the height of the auxiliary magnetic core, the solenoid at the transmitting end can better converge the magnetic lines of force, and the receiving end is in the upper area of ​​the first magnetic core. Both have high transmission efficiency, good anti-offset capability, and strong adaptability. It is not necessary to require the transmitting end and the receiving end to use square magnetic cores of the same size, and it is easy to implement.

[0008] Furthermore, the first coils are symmetrically distributed from the middle of the first magnetic core to both sides, and the distance between two adjacent first coils gradually decreases from the middle to both sides.

[0009] Furthermore, the distance between two adjacent first coils gradually decreases from the middle to both sides in an arithmetic progression.

[0010] Furthermore, it also includes a receiving end solenoid, which includes a second magnetic core that is overall in the shape of a flat plate, and the second magnetic core has a second coil that is wound in the same direction as the first coil, and the second coils are distributed and arranged on the second magnetic core at intervals.

[0011] Furthermore, the second coils are arranged on the second magnetic core at equal intervals.

[0012] Furthermore, the first coil and the second coil are wound with Litz wire.

[0013] Furthermore, it includes an energy transmission module located at the transmitting end and a voltage receiving module located at the receiving end, wherein the energy transmission module includes a DC power supply, an inverter circuit, a primary side compensation network and the transmitting end solenoid which are connected in sequence; the inverter circuit includes a full-bridge inverter circuit composed of four GaN Mosfet tubes with consistent parameters; the voltage receiving module includes a secondary side compensation network, a rectifier structure and a DC-DC converter which are connected in sequence.

[0014] Furthermore, the input voltage range of the DC-DC converter is 22-50V, and the constant voltage output is 20V.

[0015] A method for optimizing parameters of a wireless power transmission system comprises the following steps:

[0016] S1. First, obtain the wireless power transmission system as described above, and determine the size, operating frequency and air gap distance of the first magnetic core and the second magnetic core;

[0017] S2. Determine the number of turns N1 of the first coil and the number of turns N2 of the second coil according to the size of the first magnetic core and the second magnetic core, and set the offset and simulation step of the receiving end solenoid relative to the transmitting end solenoid in the X direction and the Y direction; arrange the first coil and the second coil on the corresponding first magnetic core and the second magnetic core in an equidistant manner, respectively, as an initial state;

[0018] S3, simulate in Maxwell according to the simulation step size within the offset in the X direction and the Y direction, and record the self-inductance L1 of the transmitting coil, the self-inductance L2 of the receiving coil, and the mutual inductance M 12 After calculating the coupling coefficient, the difference between the maximum and minimum values ​​is taken as the range R i ;

[0019] S4, according to tolerance d i Arrange the spacing of the first coil from the middle to both sides in an arithmetic progression, let d i =d i-1 -α,d i-1 is the previous tolerance, α is the tolerance step; repeat step S3 to calculate the range R i And compared with the last extreme R i-1 Compare, if R i ≤R i-1 , execute step S5; otherwise, let d i =d i-1 +α, repeat step S3 and calculate the range R i And compared with the last extreme R i-1 Compare, if R i ≤R i-1 , execute step S5; otherwise, i =d i-1+α, determine the next tolerance, and repeat step S4;

[0020] S5, within tolerance d i The coupling coefficient is calculated under the following conditions. If the coupling coefficient satisfies the preset value, the tolerance of the equidistant distribution of the first coil on the first magnetic core is determined as d i ; Otherwise, repeat step S4.

[0021] In summary, the anti-deviation flat solenoid coil wireless power transmission system and parameter optimization method thereof of the present invention have the advantages of reasonable structural design, strong adaptability, low implementation cost, and the ability to improve transmission efficiency and anti-deviation capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the circuit topology diagram of the IPT system.

[0023] Figure 2 This is the LCC / S compensation topology diagram.

[0024] Figure 3 It is the LCC / S AC equivalent model.

[0025] Figure 4 It is a magnetic coupling mechanism for a traditional flat solenoid coil.

[0026] Figure 5 Magnetic flux distribution of the traditional flat solenoid coil magnetic coupling mechanism.

[0027] Figure 6 It is the equivalent magnetic circuit model of the traditional flat solenoid magnetic coupling mechanism.

[0028] Figure 7 It is an improved flat solenoid coil magnetic coupling mechanism.

[0029] Figure 8 To design a flow chart.

[0030] Fig. 9 XY plane magnetic flux density distribution diagram of different launching mechanisms.

[0031] Fig.10 This is the YZ plane magnetic induction intensity distribution diagram of the improved flat solenoid coupling mechanism.

[0032] Fig.11 Schematic diagram of CCRR variation law of different coupling mechanisms.

[0033] Fig.12 The graph shows the variation of the offset coupling coefficient of different coupling mechanisms in the XY plane.

[0034] Fig.13 It is a test platform for experimental prototypes.

[0035] Fig.14 This is a comparison chart of system efficiency curves.

[0036] Fig.15 This is the waveform diagram of the experimental prototype of the improved coupling mechanism IPT system.

[0037] Fig.16 This is the waveform diagram of the inverter voltage and transmitting coil current of the improved coupling mechanism IPT system.

[0038] Fig.17 This is the DC-DC converter input voltage, output voltage, and current waveform.

[0039] Fig.18 Thermal imaging of the system.

[0040] Fig.19 This is the system output loss distribution diagram. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with embodiments.

[0042] The wireless power transmission system of this embodiment enhances the anti-offset performance of the system by changing the structure of the flat solenoid transmitting core and the winding layout. By establishing an equivalent model of the LCC-S compensation circuit, its output characteristics are analyzed, and the parameter configuration method of its resonant element is derived. Then, a magnetomotive force model is established to analyze the magnetic field distribution characteristics of the coil, and the magnetic field distribution law and coupling coefficient change law of different spatial positions of the mechanism are revealed through finite element simulation. A 100W prototype was built to verify the effectiveness and feasibility of the proposed magnetic coupling mechanism.

[0043] System introduction and LCC / S compensation topology analysis: Figure 1 This is the circuit topology diagram of the IPT system, which consists of five parts: full-bridge inverter, LCC / S compensation topology, loosely coupled transformer, rectifier bridge, and DC-DC converter. dc is the system input DC voltage; S1~S4 are GaN switch tubes; U AB is the equivalent input AC voltage after full-bridge inversion; L1 is the self-inductance of the transmitting coil; L2 is the self-inductance of the receiving coil; R1 is the internal resistance of the transmitting coil; R2 is the internal resistance of the receiving coil; L f Compensation inductance for the transmitter; C f is the parallel compensation capacitor at the transmitting end; C1 is the series compensation capacitor at the transmitting end; C2 is the series compensation capacitor at the receiving end; R ab is the equivalent resistive load; D is the rectifier bridge; U ab is the voltage before rectification; C d is the output filter capacitor; R L is the load resistance; U Lis the input voltage of the DC-DC converter. The DC-DC converter can achieve a 20V constant voltage output and an output power of up to 100W.

[0044] The LCC / S type compensation topology used in this embodiment is as follows Figure 2 As shown in Figure 1. This topology is composed of LCC compensation at the transmitter and S compensation at the receiver. When the system is operating at the operating frequency f, L2 and C2 resonate in series. Since the LCC / S compensation network has good high-order filtering characteristics, the harmonic approximation method can be used for analysis. The LCC / S AC equivalent model is shown in Figure 1. Figure 3 shown.

[0045] When the system is in resonance, it can be seen from the LCC working characteristics that the input impedance Z in For pure resistance, there is the following relationship:

[0046]

[0047] According to Kirchhoff's law, Figure 3 The KCL and KVL equations of the LCC / S circuit model are shown in formula (2):

[0048]

[0049] Can be obtained:

[0050]

[0051] It can be seen from formula (3) that the transmitting coil excitation current is only related to the compensation inductance and the AC input voltage, and has nothing to do with the mutual inductance, self-inductance and load. The transmitting coil excitation current has a constant current characteristic.

[0052] Rectified input voltage It can be expressed as:

[0053]

[0054] We can get:

[0055]

[0056] Therefore, the system voltage gain G is:

[0057]

[0058] From formula (6), we can see that the voltage gain G and the equivalent load R ab , receiving coil internal resistance R2, transmitting end compensation inductance L f It is related to the mutual inductance M, and the output voltage at the receiving end has a constant voltage characteristic.

[0059] Magnetic field analysis of coupling mechanism: Considering the application scenarios of wireless charging, the position of the transmitter is generally fixed, such as electric vehicles, mobile phone wireless charging, robots, drones, etc. The transmitter is less restricted by space and size, while the receiving end is affected by factors such as user needs and product size, and its volume is generally limited. Therefore, the volume of the receiving end is often smaller than that of the transmitting end. This not only reduces the amount of magnetic core used at the receiving end, but also reduces manufacturing costs and improves the flexibility of the receiving end equipment. Based on this, most traditional flat solenoid coil coupling mechanisms are like Figure 4 As shown, it includes a transmitting end and a receiving end. Both ends use ferrite cores of the same thickness. The length and width of the transmitting end are twice that of the receiving end. The size of the transmitting end core is 100mm×50mm×2.5mm, the size of the receiving end core is 50mm×25mm×2.5mm, the transmission air gap of the coupling mechanism is 10mm, and the Litz wire Loose Wrapped around the ferrite core and evenly spaced along the X-axis, it has a single flux direction structure with only one flux loop in the cross section of its core.

[0060] Figure 5 The magnetic flux distribution of the coupling mechanism formed by the traditional flat solenoid coil is shown. Unlike the square and circular coil cores with double magnetic flux loops in their cross-section, when the flat solenoid coupling mechanism is offset at the receiving end, there will be no magnetic lines of force in opposite directions in the main magnetic flux, thus avoiding the phenomenon of mutual cancellation, causing its coupling coefficient to decrease slowly. The dotted line in the figure represents the distribution of magnetic lines of force in the coupling mechanism. The magnetic flux of the flat solenoid coupling mechanism is mainly composed of the self-coupling part and the mutual coupling part, among which the magnetic flux of the mutual coupling part is the main factor affecting the mutual inductance and coupling coefficient.

[0061] Depend on Figure 5 The magnetic flux distribution characteristics are used to represent the distribution of magnetic flux and construct Figure 6 The equivalent magnetic circuit model shown in Figure 1. The product of the excitation current of the transmitting coil and the receiving coil and the number of turns determines the magnetic motive force of the circuit. Figure 6 In, R m11 and R m12 Represents the self-coupled magnetoresistance at the transmitter, R m21 and R m22 represents the self-coupled magnetic resistance at the receiving end, and R 12 Represents the mutual coupling magnetoresistance. Φ m1 is the self-coupled magnetic flux at the transmitting end, Φ m2 is the self-coupling magnetic flux at the receiving end, Φ 12 It is the mutually coupled magnetic flux, n1i1 is the magnetomotive force at the transmitting end, and n2i2 is the magnetomotive force at the receiving end.

[0062] according to Figure 6 The equivalent magnetic circuit model of the traditional flat solenoid coupling mechanism is composed of the self-coupling magnetic resistance Rm11 , R m12 , and the self-coupled magnetoresistance R at the receiving end m21 , R m22 Do the following:

[0063]

[0064] Based on the equivalent magnetic circuit model of the coupling mechanism, the formulas for leakage inductance and coupling inductance are derived:

[0065]

[0066] In summary, the value of the coupling coefficient k of the coupling mechanism is:

[0067]

[0068] From equation (12), we can see that the coupling coefficient k is only related to the self-coupling magnetic resistance R m1 , R m2 and the mutual coupling magnetoresistance R 12 Correlation, reduce R 12 Or increase R m1 , R m2 All of these can improve the coupling coefficient. The size, shape, winding distribution, and flux path of the core all affect the magnetic resistance. Therefore, by optimizing the winding method of the coil, the magnetic flux and magnetic resistance can be changed, thereby improving the coupling coefficient. In summary, when the surface area of ​​the coil covering the core increases, the area of ​​the coupled part increases, which helps to reduce the magnetic resistance of the leakage magnetic circuit, thereby improving the coupling coefficient. At the same time, increasing the spacing between the coil windings will increase the magnetic resistance of the leakage magnetic circuit, which will also improve the coupling coefficient.

[0069] Improved flat solenoid coil structure: In order to converge the magnetic lines of force and make them more concentrated so as to improve the coupling coefficient of the coupling mechanism, a large amount of Litz wire is often required, which not only increases the weight of the system but also greatly increases the cost of the system. To this end, this embodiment improves the traditional flat solenoid coil, designs a U-shaped ferrite core structure to converge the magnetic lines of force, and reconstructs the coil winding distribution method, and proposes an improved flat solenoid coil, such as Figure 7As shown in the figure, the receiving end solenoid is located at the top, and the transmitting end solenoid is located at the bottom, including a first magnetic core that is flat as a whole, and the two ends of the first magnetic core have auxiliary magnetic cores extending along the edge, and the auxiliary magnetic cores are protruding upward relative to the first magnetic core; the first magnetic core has a first coil wound along the length direction of the auxiliary magnetic core, and the first coils are distributed and arranged between the two auxiliary magnetic cores at intervals, and the protruding height of the first coil relative to the first magnetic core is less than the protruding height of the auxiliary magnetic core. The first coils are symmetrically distributed from the middle of the first magnetic core to both sides, and the distance between two adjacent first coils gradually decreases from the middle to both sides.

[0070] In order to better compare the effects of different coupling mechanism parameters and anti-drift capability, the coupling coefficient retaining ratio (CCRR) is defined as:

[0071]

[0072] Where: k0 and k mis are the coupling coefficients of the coupling mechanism after alignment and offset, respectively.

[0073] With the help of finite element simulation analysis software Ansys Maxwell, the simulation design was carried out, and the core size of the transmitter was determined to be 100mm×50mm×2.5mm, the core size of the receiver was 50mm×25mm×2.5mm, and the transmission air gap of the magnetic coupling mechanism was 10mm. At the same time, according to the size of the core, the number of turns of the primary winding N1 was determined to be 15, the number of turns of the receiving winding N2 was determined to be 11, and the offset of the receiving end relative to the primary was [-30mm, 30mm] in the X direction, with a step length of 5mm, and [-15mm, 15mm] in the Y direction, with a step length of 3mm. The receiving end winding adopts equal spacing with a spacing of 0.1mm. The primary winding adopts a non-uniform arrangement. The winding spacing increases arithmetic progression from both sides to the middle in turn, with a tolerance of d, showing a dense form on both sides and sparse in the middle.

[0074] Record the transmitting coil self-inductance L1, receiving coil self-inductance L2 and mutual inductance M corresponding to each simulation point when the transmitting coil spacing changes 12 After calculating the coupling coefficient, record it as a set of data, where the difference between the maximum and minimum values ​​is recorded as the range and expressed as R. i The smaller the range, the smaller the change in the coupling coefficient within the offset range, that is, the stronger the anti-offset ability. By continuously optimizing the spacing, R i , improve the anti-deviation ability of the coupling mechanism. The design flow chart is as follows Figure 8 As shown, the specific steps are:

[0075] S1. Figure 7 Based on the structure shown, the size, operating frequency and air gap distance of the first magnetic core and the second magnetic core are first determined;

[0076] S2. Determine the number of turns N1 of the first coil and the number of turns N2 of the second coil according to the size of the first magnetic core and the second magnetic core, and set the offset and simulation step of the receiving end solenoid relative to the transmitting end solenoid in the X direction and the Y direction; arrange the first coil and the second coil on the corresponding first magnetic core and the second magnetic core in an equidistant manner, respectively, as an initial state;

[0077] S3, simulate in Maxwell according to the simulation step size within the offset in the X direction and the Y direction, and record the self-inductance L1 of the transmitting coil, the self-inductance L2 of the receiving coil, and the mutual inductance M 12 After calculating the coupling coefficient, the difference between the maximum and minimum values ​​is taken as the range R i ;

[0078] S4, according to tolerance d i Arrange the spacing of the first coil from the middle to both sides in an arithmetic progression, let d i =d i-1 -α,d i-1 is the previous tolerance, α is the tolerance step, and in this embodiment α is 0.04 mm; repeat step S3 to calculate the range R i And compared with the last extreme R i-1 Compare, if R i ≤R i-1 , execute step S5; otherwise, let d i =d i-1 +α, repeat step S3 and calculate the range R i And compared with the last extreme R i-1 Compare, if R i ≤R i-1 , execute step S5; otherwise, i =d i-1 +α, and then the next tolerance is determined, and step S4 is repeated; when implemented, i =d i-1 -α and d i =d i-1 +α, there must be one that satisfies R i ≤R i-1 .

[0079] S5, within tolerance d i The coupling coefficient is calculated under the following conditions. If the coupling coefficient satisfies the preset value, the tolerance of the equidistant distribution of the first coil on the first magnetic core is determined as d i ; Otherwise, repeat step S4.

[0080] The coupling coefficient with the smallest change in the offset range is selected as the optimal parameter, and d=0.64 is finally selected to determine the specific coupling mechanism parameters.

[0081] Comparison with the traditional flat solenoid coil structure: In order to further illustrate the anti-deviation characteristics of the proposed coupling mechanism, the finite element simulation software ANSYS MAXWELL was used to establish simulation models of multiple sets of magnetic coupling mechanisms with winding methods and core shapes as variables. To ensure the effectiveness of the comparison, the ferrite core materials, winding turns, air gap distance and Litz wire specifications of different mechanisms are the same, and the receiving end uses the same flat solenoid coil with equidistant windings.

[0082] In the absence of a receiving end, only the transmitting mechanism is stimulated for simulation. Fig. 9 The XY plane magnetic flux density distribution of different launching mechanisms is shown, where: Fig. 9 (a) is the traditional type, Fig. 9 (b) Only the winding method is changed, Fig. 9 (c) Only the core shape is changed, Fig. 9 (d) is the improved arithmetic progression, Fig. 9 (d) is the improved geometric progression, Fig. 9 (e) is the improved cumulative difference series. Fig. 9 (a) and Fig. 9 (b) The magnetic flux density of the traditional type is mainly concentrated in the middle of the core. Although its maximum magnetic flux density is slightly higher than that of the type that only changes the winding method, the magnetic flux density of the type that only changes the winding method is evenly distributed on the entire plane. Fig. 9 (a) and Fig. 9 (c) After changing the shape of the magnetic core, its overall magnetic flux density has been greatly improved. The U-shaped structure formed by the magnetic core plays the role of converging the magnetic lines of force, but the magnetic flux density of both sides still has a significant attenuation. This uneven distribution of magnetic flux is the main reason for the rapid decrease in the coupling coefficient when the receiving end of the coupling mechanism is offset; Fig. 9 (a) and Fig. 9 (d) The improved transmitting core has greatly improved the magnetic flux density and the uniformity of magnetic flux density distribution, which means that when the improved coupling mechanism is dynamically offset, the coupling coefficient will remain stable in a wider range and decrease more slowly.

[0083] Fig. 9 (e) Fig. 9 (f) The magnetic flux density distribution at the transmitting end corresponding to the winding spacing arranged in geometric progression and cumulative difference progression, respectively. The core structure of both has changed. Because the windings on both sides are too dense, the magnetic field generated by the two in space is double-humped. It can be clearly seen from the figure that the magnetic flux density is concentrated on the left and right sides. Fig. 9(d), it can be clearly seen that the magnetic core with winding spacing arranged in an arithmetic sequence is significantly better than the magnetic core arranged in a geometric sequence or a cumulative sequence in terms of uniformity of magnetic density distribution. Therefore, these two mechanisms are no longer analyzed in subsequent simulations.

[0084] Fig.10 The YZ plane magnetic induction intensity distribution diagram of the improved flat solenoid coupling mechanism. Fig.10 (a) shows that the magnetic induction intensity near the magnetic core is evenly distributed on the left and right sides. Fig.10 (b) is the magnetic induction intensity distribution when the receiving end is offset by 15 mm in the positive direction of Y. At this time, the magnetic induction intensity distribution in the magnetic core of the receiving end is dense on the left and sparse on the right, indicating that the magnetic flux is gathering in the negative direction of Y during the offset process. Different from the planar square and planar circular coupling mechanisms, this will slow down the increase of magnetic resistance, so that the coupling coefficient decreases more slowly. The traditional flat solenoid coupling mechanism also has this feature, and this property is well continued in the improved coupling mechanism.

[0085] The CCRR variation rules of different coupling mechanisms are as follows: Fig.11 As shown, Fig.11 (a) The CCRR variation rules of the four coupling mechanisms when the receiving end is offset in the X-axis direction are given. When the offset reaches 30 mm, the CCRR of the traditional coupling mechanism decreases the fastest, dropping to 0.656; the CCRR of the coupling mechanism that only changes the winding method drops to 0.789; the CCRR of the coupling mechanism that only changes the core shape drops to 0.791; and the CCRR of the improved coupling mechanism only drops to 0.93, with a slow decline rate, always remaining above 90%. Fig.11 (b) shows the CCRR changes of the four coupling mechanisms when the receiving end is offset in the Y-axis direction. The traditional flat solenoid coil already has a very outstanding Y-direction anti-offset performance. Although the CCRR changes of the four coupling mechanisms when they are offset in the Y-axis direction are not much different and can all be maintained at a high level, the improved coupling mechanism still performs better.

[0086] Fig.12 The variation law of coupling coefficients of different coupling mechanisms with XY plane offset is given. With the increase of X-axis offset distance, the coupling coefficient of the improved coupling mechanism decays at a rate of 0.003 / cm, which is less than 0.016 / cm of the traditional type, less than 0.008 / cm of the type that only changes the winding method, and less than 0.01 / cm of the type that only changes the core shape. When the coupling mechanism is offset in the Y-axis direction, the change rates of coupling coefficients of different coupling mechanisms are 0.006 / cm of the traditional type, 0.004 / cm of the type that only changes the winding method, 0.005 / cm of the type that only changes the core shape, and 0.003 / cm of the improved type, respectively. The improved type still has an advantage. Based on the above comparison, it can be seen that the improved flat solenoid coupling mechanism has the best anti-offset performance.

[0087] Experimental verification: To verify the anti-drift performance of the IPT system, the following Fig.13 (a) shows the experimental prototype test platform. The parameters of the IPT system prototype are shown in Table 1. The debugging equipment shown in the figure mainly includes a DC power supply, an auxiliary power supply, a voltage probe, a current probe, an oscilloscope and an electronic load. The IPT system is mainly composed of a full-bridge inverter circuit, a compensation mechanism, a rectifier bridge, and a DC-DC circuit. In addition, two coupling mechanisms, a traditional type and an improved type, are wound based on a flat solenoid coil. The specific design is as follows Fig.13 (c) and Fig.13 As shown in (d), the air gap distance between the transmitting end and the receiving end of the coupling mechanism is 10 mm.

[0088] Table 1 Basic parameters of the system

[0089]

[0090] Table 2 Parameters of traditional coupling mechanism

[0091]

[0092] Table 3 Parameters of improved coupling mechanism

[0093]

[0094] Fig.14 The efficiency curves of the system using the traditional coupling mechanism and the improved coupling mechanism are compared. The results show that the system efficiency of the traditional coupling mechanism is 91.4% when the receiving end is aligned; when it is offset by 30mm in the X direction, the efficiency drops to 60.5%; when it is offset by 15mm in the Y direction, the efficiency drops to 80.6%. This significant drop in efficiency is caused by the rapid drop in the coupling coefficient of the traditional flat solenoid coil coupling mechanism when it is offset in the horizontal position.

[0095] In contrast, the system efficiency of the improved coupling mechanism is 89.3% when the receiving end is aligned; when it is offset by 30mm in the X direction, the efficiency is 83.1%; when it is offset by 15mm in the Y direction, the efficiency is 85.6%; when the system built based on the improved coupling mechanism is offset in the X and Y directions, the system efficiency remains above 83%. The experimental results are basically consistent with the simulation results of the relationship between the CCRR of the two coupling mechanisms and the offset, which verifies the superiority of the proposed improved coupling mechanism in anti-offset ability.

[0096] exist Fig.15 This is the waveform diagram of the experimental prototype of the improved coupling mechanism IPT system, including the main working waveforms of the system under the receiving end in positive alignment, X-direction offset, Y-direction offset, and X- and Y-direction offset, including the output voltage UAB and inverter output current I AB The input voltage U before receiving end rectification ab and the input current I2 before rectification. The DC input voltage is always kept at 100V at different positions, and the load R L =4. The experimental results show that under different offset conditions, there is a small phase difference between the inverter output voltage and current, the system impedance is inductive, the switching device can always be in the ZVS state, soft switching is achieved, and the system can achieve efficient energy transmission. Fig.15 (g) and Fig.15 (h) shows the voltage and current before rectification when the system is offset in both X and Y directions. Fig.15 (b) When the waveform is aligned, the voltage and current change rate after the offset does not exceed 5%, which can be approximately considered as a constant output of the system, verifying the system's anti-offset performance in the XY plane.

[0097] Fig.16 The waveforms of the inverter voltage and the transmitting coil excitation current of the improved coupling mechanism IPT system are shown in three different positions: positive alignment, 30mm offset in the positive direction of X, and 15mm offset in the positive direction of Y. The experimental results show that the transmitting coil excitation current I1 is always consistent with the inverter output voltage U1 at the three different positions. AB The phase difference of 90° is always maintained, and the amplitudes of the transmitting coil excitation current I1 at three different positions are approximately equal, which is consistent with the theoretical derivation of formula (3), reflecting the transmission characteristics of the LCC / S compensation topology.

[0098] The improved coupling mechanism proposed in this embodiment has very good anti-offset performance. At the same time, in order to ensure the constant output voltage, a DC-DC converter that can achieve a wide input range of 22 to 55V and a constant voltage output of 20V is added to the front end of the load side, and its maximum efficiency is 96%. Fig.17 They are respectively the input voltage U of the DC-DC converter during startup and surge L , output current I out And the output voltage U out Waveform, Fig.17 In the left figure, U L From 0V to 25V, Fig.17 In the right figure, U L It suddenly increases from 25V to 50V. As can be seen from the figure, in the two processes, the output voltage and current of the converter can be well tracked and have a fast response speed, which reflects the good static and dynamic performance of the DC-DC converter.

[0099] The IPT system worked continuously for 20 minutes under rated conditions. The thermal imaging of the system is shown below: Fig.18As shown. The largest loss of the system comes from the rectifier bridge, which still reaches 42.6℃ even with the heat sink mounted. The second is the coupling mechanism, such as Fig.18 As shown in (b)-(e), regardless of whether it is facing or offset in the X or Y direction, the core temperature is relatively stable and is mainly concentrated in the center of the transmitting core. The maximum temperature is 56.2°C, which is the temperature rise caused by hysteresis loss and eddy current loss. The receiving core temperature is much lower than the transmitting end, not exceeding 30°C. When the system is in a long-term working state, the primary side needs to select a reasonable heat dissipation method. The receiving core does not require additional heat dissipation devices due to its small size and low heat loss. It is more suitable for implantation in mobile portable devices such as mobile phones and drones. At the same time, the excellent anti-offset performance of the coupling mechanism makes its application prospects broader. The losses of the compensation mechanism, inverter, and DC-DC converter are relatively small, and there are other losses caused by line losses and circuit modeling deviations. The specific system output loss distribution is shown in the figure. Fig.19 ,Subsequent research will continue to improve and achieve efficiency optimization.

[0100] The improved flat solenoid coil wireless power transmission system of this embodiment adopts an improved flat solenoid magnetic coupling mechanism and LCC-S compensation network topology, which effectively improves the system's anti-offset characteristics. The magnetic coupling mechanism parameter optimization method and the parameter configuration conditions of the LCC-S compensation network are given. When the receiving end of the built prototype is offset within the range of ±50 in the X and Y directions, the system output voltage fluctuation rate is maintained within 5%, and the transmission efficiency reaches more than 89%, which verifies the effectiveness and feasibility of the proposed system.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A flat solenoid coil wireless power transmission system with anti-deviated properties, comprising a transmitting end solenoid, characterized in that: The transmitting end solenoid includes a first magnetic core which is generally flat, and two ends of the first magnetic core have auxiliary magnetic cores extending along the edges, and the auxiliary magnetic cores protrude upward relative to the first magnetic core; the first magnetic core has a first coil wound along the length direction of the auxiliary magnetic core, and the first coils are distributed and spaced between the two auxiliary magnetic cores, and the protruding height of the first coil relative to the first magnetic core is less than the protruding height of the auxiliary magnetic core.

2. The anti-deviated flat solenoid coil wireless power transmission system as claimed in claim 1, characterized in that: The first coils are symmetrically distributed from the middle of the first magnetic core to both sides, and the distance between two adjacent first coils gradually decreases from the middle to both sides.

3. The anti-deviated flat solenoid coil wireless power transmission system as claimed in claim 2, characterized in that: The distance between two adjacent first coils gradually decreases from the middle to both sides in an arithmetic progression.

4. The anti-deviation flat solenoid coil wireless power transmission system according to any one of claims 1 to 3, characterized in that: It also includes a receiving end solenoid, which includes a second magnetic core that is in the shape of a flat plate as a whole. The second magnetic core has a second coil that is wound in the same direction as the first coil. The second coils are distributed and arranged on the second magnetic core at intervals.

5. The anti-deviated flat solenoid coil wireless power transmission system as claimed in claim 4, characterized in that: The second coils are arranged on the second magnetic core at equal intervals.

6. The anti-deviation flat solenoid coil wireless power transmission system according to claim 4 or 5, characterized in that: The first coil and the second coil are formed by winding Litz wire.

7. The anti-deviation flat solenoid coil wireless power transmission system according to claim 4 or 5, characterized in that: It includes an energy transmission module located at the transmitting end and a voltage receiving module located at the receiving end. The energy transmission module includes a DC power supply, an inverter circuit, a primary compensation network and the transmitting end solenoid which are connected in sequence; the inverter circuit includes a full-bridge inverter circuit composed of four GaN Mosfet tubes with consistent parameters; the voltage receiving module includes a secondary compensation network, a rectifier structure and a DC-DC converter which are connected in sequence.

8. The anti-deviated flat solenoid coil wireless power transmission system as claimed in claim 7, characterized in that: The input voltage range of the DC-DC converter is 22-50V, and the constant voltage output is 20V.

9. A method for optimizing parameters of a wireless power transmission system, characterized in that: The steps include: S1. First, obtain the anti-deviation flat solenoid coil wireless power transmission system as claimed in any one of claims 1 to 8, including a receiving end solenoid matched with a transmitting end solenoid, and determine the size, operating frequency and air gap distance of the first magnetic core; S2, setting the offset and simulation step of the receiving end solenoid relative to the transmitting end solenoid in the X direction and the Y direction; arranging the first coil on the first magnetic core in an equidistant manner as an initial state; S3, simulate in Maxwell according to the simulation step within the offset in the X direction and the Y direction, and record the self-inductance L1 of the transmitting coil of the transmitting end solenoid, the self-inductance L2 of the receiving coil of the receiving end solenoid, and the mutual inductance M 12 After calculating the coupling coefficient, the difference between the maximum and minimum values ​​is taken as the range R i ; S4, according to tolerance d i Arrange the spacing of the first coil from the middle to both sides in an arithmetic progression, let d i =d i-1 -α,d i-1 is the previous tolerance, α is the tolerance step; repeat step S3 to calculate the range R i And compared with the last extreme R i-1 Compare, if R i ≤R i-1 , execute step S5; Otherwise, let d i =d i-1 +α, repeat step S3, calculate the range R i And compared with the last extreme R i-1 Compare, if R i ≤R i-1 , execute step S5; Otherwise, in d i =d i-1 +α, determine the next tolerance, and repeat step S4; S5, within tolerance d i The coupling coefficient is calculated under the following conditions. If the coupling coefficient satisfies the preset value, the tolerance of the equidistant distribution of the first coil on the first magnetic core is determined as d i ; Otherwise, repeat step S4.

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