CN203537076U - Variable-coupling coefficient magnetic resonance wireless power transmission system - Google Patents

Abstract

The utility model discloses a variable coupling coefficient magnetic resonance wireless power transmission system in the technical field of magnetic coupling resonance wireless power transmission, which mainly solves the problem that the transmission efficiency of the magnetic resonance wireless power transmission system drops sharply with the increase of the transmission distance. The system adjusts the distance between the source coil and the transmitting coil, the receiving coil and the load coil at the same time, so that the magnetic resonance wireless power transfer system satisfies the critical coupling condition equation and works in the critical coupling state. The utility model accurately obtains the conditions required for the system to be in the critical coupling state, so that the magnetic resonance wireless power transmission system always works in a high-efficiency mode.

Description

Magnetic resonance wireless power transfer system with variable coupling coefficient

technical field

The utility model belongs to the technical field of magnetic coupling resonance wireless power transmission, and relates to a magnetic resonance wireless power transmission system with variable coupling coefficient, in particular to a method for improving transmission by changing the coupling coefficient of a transmitter and a receiver of the magnetic coupling resonance wireless power transmission system. A system of efficiency and distance.

Background technique

Since Nikola Tesla proposed the theory of wireless power transfer a century ago, wireless power transfer has been a hot research topic. Experts at home and abroad have been conducting research on wireless power transmission for many years, but the progress of scientific research has been slow until June 2007. Marin Soljacic, a professor of physics at the Massachusetts Institute of Technology (MIT), and his team members proposed a magnetic coupling based on strong magnetic coupling. A new scheme of resonance. In the experiment, two coils with a diameter of 60cm and copper wires were used, and the natural resonance frequency of the coils was at 9.9MHz. Using the principle of magnetic coupling resonance, a 60W light bulb about 2m away from the power supply was successfully lit. , Later this technology was called WiTricity, so far, opened up the research grand occasion of wireless power transmission technology. In order to make the wireless power transmission technology be applied as soon as possible, on September 1, 2010, the Wireless Power Consortium (WPC), the world's first standardization organization to promote wireless charging technology, announced in Beijing that it would introduce the Qi wireless charging international standard first. In China, the Communication Electromagnetic Compatibility Quality Supervision Center of the Ministry of Information Industry also joined the organization. Shenzhen Sangfei Consumer Communication Co., Ltd. is a supporter of the Qi standard and the only Chinese company among the executive director members of the alliance.

At present, there are three ways to realize wireless power transmission at home and abroad:

1. Electromagnetic induction type - similar to a loosely coupled transformer, the electromagnetic induction of the primary and secondary coils generates a current, thereby transferring energy from the transmitting end to the receiving end, suitable for short-distance transmission with high efficiency.

2. Electromagnetic radiation type - its basic principle is similar to the ore radio used in the early days. At present, there are relatively mature theories, with a wide range of action and high transmission power, but it has a great impact on the biological environment and low efficiency.

3. Magnetic coupling resonance - a new scheme proposed by Marin Soljacic of MIT and his team members. The principle is to use the non-radiative near-field coupling of the magnetic field to transfer energy, which greatly reduces the damage to the human body , which prolongs the distance of wireless power transmission. This method has high transmission efficiency, long distance and high power. It is the mainstream direction of future wireless power transmission development.

The magnetic coupling resonance wireless power transmission system transmits energy through the magnetic coupling resonance between two symmetrical coils, and the coupling coefficient has an important influence on the transmission efficiency of the system. According to the size of the coupling coefficient, the magnetically coupled resonant wireless power transfer system can be divided into three working areas: strong coupling, critical coupling, and weak coupling.

The study found that when the wireless power transmission system is in the strong coupling region, the transmission efficiency of the system reaches the maximum value on both sides of the resonance frequency, that is, frequency splitting occurs. As the transmission distance increases, the coupling coefficient decreases and the frequency splitting phenomenon gradually disappears. When the coupling coefficient satisfies the critical coupling condition, the transmission efficiency of the system reaches the maximum value at the resonant frequency. As the coupling coefficient further decreases and reaches the weak coupling region, the transmission efficiency of the system decreases sharply with the decrease of the coupling coefficient, but the system The best transmission state is always at the resonant frequency.

Therefore, the transmission efficiency of the wireless power transmission system is not always at the maximum at the resonant frequency, but has the maximum transmission efficiency and the optimal transmission distance at the critical coupling state.

To sum up, the best working state of the magnetic coupling resonant wireless power transfer system is that the system is always in the critical coupling state, so that the system can obtain the maximum transmission efficiency and the optimal transmission distance at the resonant frequency. However, the transmission distance corresponding to the critical coupling state is determined, which makes it impossible for the system to be in the critical coupling state all the time, and the transmission distance has an obvious adjustment effect on the coupling coefficient. As the transmission distance increases, the coupling coefficient decreases. small, the system transmission efficiency will drop sharply, which seriously hinders the popularization and application of wireless power transmission system. Therefore, we must find a technical method to realize the above-mentioned scheme—keep the system in the critical coupling state all the time, in order to obtain the maximum The transmission efficiency and the optimal transmission distance.

Utility model content

Technical problem: The purpose of this utility model is to solve the problem that the transmission efficiency of the system drops sharply due to the increase of the transmission distance and the decrease of the coupling coefficient of the magnetic coupling resonance wireless power transmission system, and consider that the system obtains the maximum at the critical coupling point. Transmission efficiency and optimal transmission distance, a variable coupling coefficient magnetic resonance wireless power transfer system is proposed. The system adjusts the coupling coefficient of the system transmitter and receiver at the same time, so that the system is always in a critical coupling state, with maximum transmission efficiency and optimal transmission distance. At the same time, the utility model can significantly improve the distance and efficiency of wireless energy transmission , which can well meet the requirements of the equipment for the efficiency and distance of the wireless power transmission system.

For realizing above-mentioned object, the technical scheme of the realization of the present utility model is as follows:

A variable coupling coefficient magnetic resonance wireless power transmission system described in the utility model includes a transmitter and a receiver.

The transmitter includes a high-frequency signal generator, an impedance matching network, a source coil and a transmitting coil, and the high-frequency signal generator outputs a high-frequency signal of rated power.

One side of the source coil is connected to the high-frequency signal generator through an impedance matching network, and the other side forms a step-up transformer network with the transmitting coil by electromagnetic induction.

The impedance matching network is a passive matching network composed of capacitors and inductors; or an active matching network composed of source followers, emitter followers and buffers composed of active and passive devices.

The receiver includes a receiving coil and a load coil, and the receiving coil and the load coil form a step-down transformer network by electromagnetic induction.

The load coil is connected in series with a matching capacitor equal in size to the impedance matching network, and is directly connected to the AC load device, or supplied to the DC load device or circuit through a rectifier circuit; the rectifier circuit includes half-wave rectification, full-wave rectification and bridge rectification.

The transmitting coil and the receiving coil use their own equivalent resistance at high frequency, parasitic capacitance and their own inductance to form a resonant circuit, and the transmitting coil and the receiving coil have the same resonant frequency.

The distance between the source coil and the transmitting coil and the distance between the receiving coil and the load coil are always kept equal, the electrical parameters of the source coil and the load coil are the same, and the transmitting coil and the receiving coil also have the same electrical parameters, that is, the inductance of the coil, The high frequency parasitic capacitance, equivalent resistance and no-load figure of merit are all the same.

The transmitting coil obtains the high-frequency oscillating signal from the high-frequency signal generator from the source coil through electromagnetic induction, and sends it out in the form of non-radiating near-field electromagnetic waves, and the receiving coil receives the high-frequency oscillation signal through the magnetic coupling resonance between the coils. The high-frequency oscillating signal transmitted by the transmitting coil supplies energy to the load coil through electromagnetic induction.

All coils are wound by copper wire, aligned in the coaxial direction, the distance between the source coil and the transmitting coil, the distance between the transmitting coil and the receiving coil, the distance between the receiving coil and the load coil is adjustable, with the distance between the transmitting coil and the receiving coil , that is, the change of the transmission distance, when the system deviates from the critical coupling state, adjust the coupling coefficient of the transmitter and receiver at the same time, that is, adjust the distance between the source coil and the transmit coil, the distance between the receive coil and the load coil at the same time, and maintain The two distances are equal, thereby changing their coupling coefficients, the system satisfies the critical coupling condition, and works in the critical coupling state.

In the variable coupling coefficient magnetic resonance wireless power transmission system of the present invention, there is no magnetic coupling between non-adjacent coils, the source coil and the load coil in the system are both single-turn coils, and the transmitting coil and the receiving coil have the same turns number of multi-turn coils.

The variable coupling coefficient magnetic resonance wireless power transmission system includes an external excitation source high-frequency signal generator, an impedance matching network, a source coil, a transmitting coil, a receiving coil, a load coil and load equipment.

The beneficial effects of the utility model are:

1. The utility model can make the magnetic coupling resonance wireless power transmission system always work in the critical coupling state, and ensure that the transmission efficiency of the system always reaches the maximum value and the transmission distance reaches the optimum.

2. Compared with the existing technology, the system always works in the critical coupling state, which significantly improves the transmission efficiency and transmission distance, further solves the problem that the transmission efficiency of the system is restricted by the transmission distance, and improves the utilization efficiency of electric energy .

Description of drawings

Fig. 1 is a schematic diagram of the system of variable coupling coefficient magnetic resonance wireless power transmission of the present invention;

Fig. 2 is the equivalent circuit model diagram of the variable coupling coefficient magnetic resonance wireless power transmission system of the present invention;

Fig. 3 is an example physical diagram of the variable coupling coefficient magnetic resonance wireless power transmission system of the present invention;

Fig. 4 is a comparison diagram of transmission efficiency between the variable coupling coefficient magnetic resonance wireless power transmission system of the present invention and the prior art;

Detailed ways

In order to make the content and advantages of the technical solution of the utility model clearer, the variable coupling coefficient magnetic resonance wireless power transmission system of the utility model will be further described in detail below in conjunction with the accompanying drawings. It should be emphasized that the following descriptions are only illustrative, not intended to limit the scope of the present utility model and its application.

The implementation process of the variable coupling coefficient magnetic resonance wireless power transmission system of the present invention will be described in detail below in conjunction with the accompanying drawings.

Fig. 1 is a schematic diagram of the system of variable coupling coefficient magnetic resonance wireless power transmission of the present invention.

As shown in FIG. 1 , the variable coupling coefficient magnetic resonance wireless power transmission system of the present invention includes a high-frequency signal generator, an impedance matching network, a source coil, a transmitting coil, a receiving coil, a load coil and a load device.

The high-frequency signal generator sends out high-frequency signal pulses, and transmits the energy signal to the source coil through the impedance matching network. The energy transmitting coil of the system uses electromagnetic induction to obtain the high-frequency oscillation signal sent by the high-frequency signal generator from the source coil. , and then transmitted in the form of non-radiative near-field electromagnetic waves. The energy receiving coil of the system receives the high-frequency oscillation signal transmitted by the transmitting coil through the magnetic coupling resonance between the coils, and then supplies energy to the load coil and the load equipment through electromagnetic induction. The source coil and the load coil are both single-turn coils. The coil and the receiving coil are multi-turn coils with the same number of turns, and the distance between the transmitting coil and the receiving coil is the transmission distance of the system.

All coils are wound by copper wires and aligned in the coaxial direction. As the transmission distance gradually increases from small to large, the maximum points of system transmission power gradually merge from 2 to 1, that is, the system working state changes from strong coupling From critical coupling to weak coupling.

Fig. 2 is an equivalent circuit model diagram of the variable coupling coefficient magnetic resonance wireless power transmission system of the present invention.

As shown in Figure 2, the equivalent circuit model of the magnetic coupling resonance wireless power transfer system of the present invention has four coil loops: source coil loop, transmitting coil loop, receiving coil loop, load coil loop, L ₁ , L ₂ , L ₃ , L ₄ are the inductances of the source coil, transmitting coil, receiving coil and load coil respectively, R _e1 , R _e2 , R _e3 , R _e4 are the inductances of the source coil, transmitting coil, receiving coil and load coil at high frequency Equivalent resistance, C _p1 is the sum of the parasitic capacitance of the source coil at high frequency and the matching capacitance in the impedance matching network, C _p2 and C _p3 are the parasitic capacitance of the transmitting coil and receiving coil at high frequency respectively, and C _p4 is The sum of the parasitic capacitance of the load coil at high frequency and the matching capacitance in series with it, V _S is the output voltage of the high frequency signal generator, V _L is the load voltage, _RS and _RL are the internal voltage of the high frequency signal generator resistance and load resistance; k ₁₂ is the coupling coefficient between the source coil and the transmitting coil, k ₂₃ is the coupling coefficient between the transmitting coil and the receiving coil, and k ₃₄ is the coupling coefficient between the receiving coil and the load coil.

The equivalent circuit model analysis steps of the magnetic coupling resonance wireless power transmission of the present utility model are as follows:

1. The equivalent circuit of the system is analyzed to obtain the following equation:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="V\; S"\; filenames="DEST\_PATH\_HSB0000120321180000022.png"\; state="\{\{state\}\}">V</figure-callout></span><figure-callout\; id="0"\; label="V\; S"\; filenames="DEST\_PATH\_HSB0000120321180000022.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{cccc}{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 13</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 14</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; four</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 31</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 32</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 33</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 34</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 41</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 42</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 43</span>}}& {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 44</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\\ {\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}\end{array}\right]$

V _S is the output voltage of the high-frequency signal generator, Z _ii is the loop impedance, Z _ij is the coupling impedance between adjacent loops, I _i is the loop current, i, j=1, 2, 3, 4, respectively corresponding to the source coil loop, transmitting coil loop, receiving coil loop, load coil loop.

如下所述：2. Solving I ₁ and I ₄ for the determinant in step 1, the input-output voltage ratio of the system can be obtained

As described below:

$\left|\frac{V_L}{V_S}\right|=\left|\frac{I_4{R}_L}{I_1{R}_S}\right|=\frac{k_{12}{k}_{34}{k}_{\mathrm{twenty\; three}}{Q}_1{Q}_2{Q}_3}{1+k_{12}{k}_{34}{Q}_1{Q}_2+k_{\mathrm{twenty\; three}}^2{Q}_2{Q}_3}\sqrt{\frac{R_L}{R_S}},$ Among them, V _L is the load voltage, R _L and R _S are the internal resistance of the voltage source and the load resistance respectively, k ₁₂ is the coupling coefficient between the source coil and the transmitting coil, k ₃₄ is the coupling coefficient between the receiving coil and the load coil, k ₂₃ is the coupling coefficient between the transmitting coil and the receiving coil, Q ₁ , Q ₂ , and Q ₃ are the quality factors of the source coil, the transmitting coil, and the receiving coil respectively, and it can be known from the symmetry of the system structure that k ₁₂ =k ₃₄ , Q ₂ =Q ₃ .

3. Impedance matching, that is, when the input impedance Z _in = _RS , the signal source has the maximum output power, and the expression of the transmission efficiency η of the system is as follows: $\mathrm{\&eta;}=\frac{V_L^2}{R_L}/\frac{V_S^2}{4R_S}={\left[\frac{2k_{12}^2{k}_{\mathrm{twenty\; three}}{Q}_1{Q}_2^2}{1+k_{12}^2{Q}_1{Q}_2+k_{\mathrm{twenty\; three}}^2{Q}_2^2}\right]}^2.$

因系统取得最大传输效率的点是在临界耦合处，故上式即为系统工作在临界耦合状态时，耦合系数k₂₃和k₁₂所需满足的临界耦合条件等式。4. The quality factor of each coil in the system is a known quantity that can be measured indirectly: $Q_1=\frac{w_0{L}_1}{R_{e1}+R_S},$ $Q_2=\frac{w_0{L}_2}{R_{e2}},Q_3=\frac{w_0{L}_3}{R_{e3}},{\mathrm{<figure-callout\; id="4"\; label="Q"\; filenames="DEST\_PATH\_HSB0000120321180000012.png"\; state="\{\{state\}\}">Q</figure-callout>}}_4=\frac{w_0{L}_4}{{\mathrm{<figure-callout\; id="4"\; label="R\; e"\; filenames="DEST\_PATH\_HSB0000120321180000012.png"\; state="\{\{state\}\}">R</figure-callout>}}_e+R_L},$ Wherein w ₀ is the angular frequency of the signal produced by the high-frequency signal generator of the external excitation source, and Q ₄ is the quality factor of the load coil, so in the step 3, when the derivative of η to k ₂₃ can obtain the maximum transmission efficiency of the system, k The critical coupling condition equation satisfied by ₂₃ and k ₁₂ :

Because the point where the system obtains the maximum transmission efficiency is at the critical coupling, the above formula is the critical coupling condition equation that the coupling coefficients k ₂₃ and k ₁₂ need to satisfy when the system works in the critical coupling state.

Fig. 3 is an example physical diagram of the variable coupling coefficient magnetic resonance wireless power transmission system of the present invention.

As shown in Figure 3, this embodiment is a critical coupling implementation scheme for a magnetic coupling resonance wireless power transfer system with an operating frequency of f ₀ =7.65 MHz. The internal resistance and load resistance of the high-frequency signal generator are both 50 ohms, and all coils are It is wound by a copper wire with a section radius of 1mm and aligned in the coaxial direction. The diameter of the source coil is 28cm, which is connected with an impedance matching network and a high-frequency signal generator with an output power of 5W. The diameters of the transmitting coil and the receiving coil are both 60cm. In order to obtain a high quality factor Q, the self-capacitance and inductance of the coil are used for resonance , the diameter of the load coil is 28cm, connected with a load resistance of 50 ohms, followed by an oscilloscope (for measuring the energy of the signal), the specific coil parameters are shown in Table 1.

Table 1

Fig. 4 is a comparison diagram of transmission efficiency between the variable coupling coefficient magnetic resonance wireless power transmission system of the present invention and the prior art.

In the existing wireless power transmission system (fixed coupling), the distance d ₁₂ between the source coil and the transmitting coil, and the distance d ₃₄ between the receiving coil and the load coil are all fixed, which are all set to 1cm in this embodiment, and the transmission distance d ₂₃ is from 10cm Change to 100cm with a step size of 5cm.

Keeping the above system structure unchanged, as the transmission distance increases, the coupling coefficient drops sharply, and the whole system is in a weakly coupled state. The change of the transmission efficiency of the system with the transmission distance is shown in the dotted curve in Figure 4.

A variable coupling coefficient magnetic resonance wireless power transmission system proposed by the utility model:

Step A: Determine the wireless energy transmission distance d ₂₃ of the variable coupling coefficient magnetic resonance wireless power transmission system, that is, the distance between the transmitting coil and the receiving coil;

和

计算所述系统发射线圈和接收线圈的耦合系数k₂₃；其中，M₂₃是发射线圈和接收线圈的互感系数，L₂、L₃为发射线圈和接收线圈的电感，是可通过仪器直接测量的已知量，u₀为真空磁导率，u₀=4π×10^-7亨利／米，N₂、N₃为发射线圈和接收线圈的匝数，O₂、O₃是发射线圈和接收线圈的导线回路，O₂、O₃与N₂、N₃均为已知量，dl₂、dl₃分别是发射线圈和接收线圈上的一个微元，d₂₃是发射线圈和接收线圈的间距；Step B: According to the wireless energy transmission distance d ₂₃ described in step A, use the formula

and

Calculate the coupling coefficient k ₂₃ of the transmitting coil and the receiving coil of the system; wherein, M ₂₃ is the mutual inductance coefficient of the transmitting coil and the receiving coil, and L ₂ and L ₃ are the inductances of the transmitting coil and the receiving coil, which can be directly measured by the instrument Known quantity, u ₀ is vacuum magnetic permeability, u ₀ =4π×10 ^-7 Henry/m, N ₂ , N ₃ are the turns of transmitting coil and receiving coil, O ₂ , O ₃ are transmitting coil and receiving coil The wire loop of , O ₂ , O ₃ and N ₂ , N ₃ are all known quantities, dl ₂ , dl ₃ are a microelement on the transmitting coil and receiving coil respectively, and d ₂₃ is the distance between the transmitting coil and the receiving coil;

其中，w₀是外加激励源高频信号发生器所产生信号的角频率，L₁是源线圈的电感值，R_e1是源线圈在高频下的等效电阻，R_S是外加激励源高频信号发生器的内阻；

其中，w₀是高频信号发生器所产生信号的角频率，L₂是发射线圈的电感值，R_e2是发射线圈在高频下的等效电阻；Step C: Use the formula When calculating the critical coupling state, the coupling coefficient k ₁₂ of the system source coil and the transmitting coil; wherein, k ₁₂ is the coupling coefficient between the source coil and the transmitting coil, and k ₂₃ is the coupling coefficient between the transmitting coil and the receiving coil , Q ₁ and Q ₂ are the quality factors of the source coil and the transmitting coil respectively, which are known quantities that can be indirectly measured by instruments;

Among them, w ₀ is the angular frequency of the signal generated by the external excitation source high-frequency signal generator, L ₁ is the inductance value of the source coil, R _e1 is the equivalent resistance of the source coil at high frequency, R _S is the height of the external excitation source The internal resistance of the frequency signal generator;

Among them, w ₀ is the angular frequency of the signal generated by the high frequency signal generator, L ₂ is the inductance value of the transmitting coil, R _e2 is the equivalent resistance of the transmitting coil at high frequency;

Step D: adjusting the coupling coefficient of the system source coil and transmitting coil to k ₁₂ .

According to the steps described above, step D specifically includes the following steps:

和

计算源线圈和发射线圈的间距d₁₂；其中，M₁₂是源线圈和发射线圈的互感系数，L₁、L₂为源线圈和发射线圈的电感，是可通过仪器直接测量的已知量，u₀为真空磁导率，u₀=4π×10^-7亨利／米，N₁、N₂为源线圈和发射线圈的匝数，O₁、O₂是源线圈和发射线圈的导线回路，O₁、O₂与N₁、N₂均为已知量，dl₁、dl₂分别是源线圈和发射线圈上的一个微元，d₁₂是源线圈和发射线圈的间距；Step 1: According to the calculated coupling coefficient k ₁₂ , use the formula

and

Calculate the distance d ₁₂ between the source coil and the transmitting coil; where, M ₁₂ is the mutual inductance coefficient of the source coil and the transmitting coil, L ₁ and L ₂ are the inductances of the source coil and the transmitting coil, which are known quantities that can be directly measured by instruments, u ₀ is the vacuum magnetic permeability, u ₀ =4π×10 ^-7 Henry/m, N ₁ and N ₂ are the turns of the source coil and the transmitting coil, O ₁ and O ₂ are the wire loops of the source coil and the transmitting coil, O ₁ , O ₂ and N ₁ , N ₂ are all known quantities, dl ₁ , dl ₂ are a microelement on the source coil and the transmitting coil respectively, and d ₁₂ is the distance between the source coil and the transmitting coil;

Step 2: Adjust the distance between the source coil and the transmitting coil to d ₁₂ , so far the coupling coefficient between the source coil and the transmitting coil has been adjusted to k ₁₂ ;

Step 3: Adjust the spacing d ₃₄ between the receiving coil and the load coil to be equal to d _12. The system works in a critical coupling state and has the maximum transmission efficiency and optimal transmission distance. The experimental results are shown in the solid line curve in Figure 4 .

As shown in Figure 4, under the same conditions, the variable coupling coefficient magnetic resonance wireless power transmission system proposed by the utility model significantly improves the transmission efficiency of the system. When the transmission distance is 80cm and 100cm, the transmission efficiency is effectively increased by about 30cm respectively. % and 20%.

The above is only a preferred embodiment of the utility model, but the scope of protection of the utility model is not limited thereto, any equivalent modification or Transformation should be covered within the protection scope of the present utility model.

Claims (11)

1. A variable coupling coefficient magnetic resonance wireless power transmission system, characterized in that it comprises a transmitter and a receiver; The transmitter includes a high-frequency signal generator, an impedance matching network, a source coil and a transmitting coil, and the high-frequency signal generator outputs a high-frequency signal of rated power; One side of the source coil is connected to the high-frequency signal generator through an impedance matching network, and the other side and the transmitting coil form a step-up transformer network by electromagnetic induction; The receiver includes a receiving coil and a load coil, and the receiving coil and the load coil form a step-down transformer network by electromagnetic induction. 2 . A variable coupling coefficient magnetic resonance wireless power transmission system according to claim 1 , wherein the impedance matching network is a passive matching network consisting of capacitors and inductors. 3. A kind of variable coupling coefficient magnetic resonance wireless power transmission system according to claim 1, characterized in that, the impedance matching network is an active matching network, a source follower composed of active and passive devices, an emitter pole follower and buffer. 4. A variable coupling coefficient magnetic resonance wireless power transmission system according to claim 1, wherein the load coil is connected in series with a matching capacitor equal in size to the impedance matching network, and is directly connected to an AC load device. 5. A kind of variable coupling coefficient magnetic resonance wireless power transmission system according to claim 1, the load coil supplies DC load equipment or circuits through a rectifier circuit; the rectifier circuit includes half-wave rectification, full-wave rectification and bridge rectification rectification. 6. A variable coupling coefficient magnetic resonance wireless power transmission system according to claim 1, wherein the transmitting coil and the receiving coil utilize their own equivalent resistance at high frequencies, parasitic capacitance and their own inductance to form a resonance The circuit, the transmitting coil and the receiving coil have the same resonant frequency; The distance between the source coil and the transmitting coil and the distance between the receiving coil and the load coil are always kept equal, the electrical parameters of the source coil and the load coil are the same, and the transmitting coil and the receiving coil also have the same electrical parameters. 7 . The variable coupling coefficient magnetic resonance wireless power transmission system according to claim 6 , wherein the electrical parameters include coil inductance, high-frequency parasitic capacitance, equivalent resistance, and no-load quality factor. 8. A kind of variable coupling coefficient magnetic resonance wireless power transfer system according to claim 6, characterized in that, all coils are wound by copper wires, aligned in the coaxial direction, the distance between the source coil and the transmitting coil, the transmitting coil and The distance between the receiving coil and the distance between the receiving coil and the load coil is adjustable; The transmitting coil obtains the high-frequency oscillating signal from the high-frequency signal generator from the source coil through electromagnetic induction, and sends it out in the form of non-radiating near-field electromagnetic waves, and the receiving coil receives the high-frequency oscillation signal through the magnetic coupling resonance between the coils. The high-frequency oscillating signal transmitted by the transmitting coil supplies energy to the load coil through electromagnetic induction. 9. A variable coupling coefficient magnetic resonance wireless power transfer system according to claim 8, characterized in that, as the distance between the transmitting coil and the receiving coil, that is, the transmission distance changes, when the system deviates from the critical coupling state, simultaneously Adjust the coupling coefficients of the transmitter and receiver to change their coupling coefficients. The system meets the critical coupling conditions and works in the critical coupling state. 10. A variable coupling coefficient magnetic resonance wireless power transfer system according to claim 9, characterized in that the adjustment of the coupling coefficient is by simultaneously adjusting the distance d ₁₂ between the source coil and the transmitting coil, the receiving coil and the load coil d ₃₄ and keep the two distances equal, ie d ₁₂ =d ₃₄ . 11. A variable coupling coefficient magnetic resonance wireless power transfer system according to claim 9, wherein there is no magnetic coupling between non-adjacent coils in the system, and the source coil and the load coil in the system are both single Turn Coil, Transmitting Coil and Receiving Coil are multi-turn coils with the same number of turns.

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