A fixed-parameter frequency split external optimization method and circuit

Abstract

The present application relates to wireless power transmission technical field, especially to a kind of fixed parameter frequency split external optimization method and circuit, including the resonant circuit of the construction transmitting module, receiving module and optimization coil circuit;By setting the different parameters of optimization coil circuit, the mutual inductance coupling between transmitting coil, receiving coil and optimization coil is calculated using magnetic coupling formula, the forward transfer function is obtained by combining Kirchhoff's law, and the maximum transmission efficiency value is obtained at the working frequency point of the resonant circuit by the forward transfer function and the coupling strength.The present application solves the existing method needs to change the working frequency or coil radius, number of turns, relative distance, internal parameters such as circuit compensation capacitor size and compensation mode;System needs to suspend work and carry out multi-element joint debugging matching or need turn ratio, relative distance and other reference values before system is formed, but in many engineering fields, such operation is often not allowed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless power transmission, and in particular to a fixed-parameter frequency splitting external optimization method and circuit. BACKGROUND

[0002] With the development of power electronics technology, the transmission mode of electric energy becomes more and more diversified, among which the development of wireless power transmission is the most rapid. Wireless power transmission can avoid the direct connection of electrical equipment and power grid, has the advantages of flexibility, safety, reliability, etc., and overcomes the instability of electrical contact and the limitations of electrical equipment movement, thereby providing a new way for energy transmission. There are three typical transmission modes of wireless power transmission, which are short-distance transmission technology based on electromagnetic induction, medium-distance transmission technology based on magnetic resonance coupling, and long-distance transmission technology based on microwaves.

[0003] In the field of wireless power transmission, magnetic resonance coupling is a strong coupling mode of near magnetic field. The electric energy transmission efficiency under magnetic resonance is very high, and is not affected by the transmission channel crossing certain materials and metal obstacles, so that high-efficiency non-directional transmission can be realized within the transmission range. However, in actual application, due to the strong coupling between the double coils, the system will appear frequency splitting phenomenon when working, which makes the transmission efficiency of the system rapidly decrease at the resonance point.

[0004] As known, the best working frequency of the resonance circuit is the inherent resonance frequency of the circuit. The method for improving the maximum transmission efficiency of the wireless power transmission system is mainly to improve the inherent resonance frequency, so that the system works at a higher transmission efficiency.

[0005] However, under the condition that the coil distance is unchanged, the increase of the working frequency makes the coil work in the over-coupling state, which makes the transmission capacity at the coil resonance frequency (i.e. the working frequency) decrease rapidly, thereby reducing the energy transmission capacity of the system.

[0006] For this phenomenon, the existing technology research proposes several suppression methods: first, impedance matching. From the coil level, the mutual inductance between the coils can be affected by changing the material, the number of turns, etc. From the circuit level, a variety of impedance matching circuits with topological structure can be added for optimization. However, it is difficult to modify the existing coil parameters, and the compensation circuit needs to be modified after the system stops working, which is a complicated process; second, frequency tracking control. When the system element parameters cannot be changed in the over-coupling area, the working frequency can be changed to keep the working frequency always in the best working state. However, this method requires a complex feedback control or single-chip microcomputer control circuit, and in the case that the coil distance is unchanged, it can only exit the over-coupling area by reducing the working frequency, which limits the upper limit of the system transmission capacity. SUMMARY

[0007] The technical problem solved by the application is that the existing method needs to change the working frequency or the internal parameters of the system, such as the radius of the coil, the number of turns, the relative distance, the size and compensation mode of the circuit compensation capacitor; the system needs to be temporarily suspended for multi-element joint debugging and matching, or the reference values such as the number of turns and the relative distance are needed before the system is formed, but such operation is often not allowed in many engineering fields.

[0008] In the magnetic coupling resonance type wireless power transmission, in the over-coupling state, the system works at the resonance frequency, the peak value of the system transmission power becomes the valley value, and the consistency of the peak value of the system transmission power and the transmission efficiency is destroyed.

[0009] The technical scheme adopted by the application is a fixed parameter frequency splitting external optimization method, which comprises the following steps:

[0010] The resonance circuit of the transmitting module, the receiving module and the optimization coil circuit is constructed;

[0011] By setting different parameters of the optimization coil circuit, the mutual inductance coupling between the transmitting coil, the receiving coil and the optimization coil is calculated by using the magnetic coupling formula, the forward transmission function is obtained by combining the Kirchhoff law, and the maximum transmission efficiency value is obtained at the working frequency point of the resonance circuit by using the forward transmission function and the coupling strength.

[0012] The different parameters of the optimization coil include the coil radius c of the optimization coil circuit, the position d1 of the optimization coil relative to the transmitting coil, and the compensation capacitor C of the optimization coil T .

[0013] For a simple double-coil magnetic coupling resonance type wireless power transmission system, by using the Kirchhoff law and the two-port network analysis method, under the condition that the number of turns, the coil radius, the relative position, the circuit compensation parameter and the system working frequency of the transmitting coil and the receiving coil are unchanged, the optimization coil circuit is added near the transmitting coil to weaken the over-coupling state between the original transmitting and receiving coil combination, improve the system power transmission capacity, and combine the magnetic coupling algorithm to effectively suppress the frequency splitting phenomenon and ensure the transmission performance of the system.

[0014] Further, the mutual inductance coupling between the transmitting coil, the receiving coil and the optimization coil includes the mutual inductance coupling M SR between the transmitting coil and the receiving coil, the mutual inductance coupling M ST between the transmitting coil and the optimization coil, and the mutual inductance coupling M TR between the receiving coil and the optimization coil, and the specific formula is as follows:

[0015]

[0016]

[0017]

[0018] wherein a, N s are radius, number of turns of the transmitting coil, b, N R are radius, number of turns of the receiving coil, μ0 is vacuum permeability, K(), E() are first, second kind of elliptic integral respectively, D is the distance between the transmitting coil and the receiving coil, c, N T are radius, number of turns of the optimized coil, the distance between the optimized coil and the transmitting coil is d1, the distance between the optimized coil and the receiving coil is d2, the distance between the transmitting coil and the receiving coil is D = d1 + d2,

[0019] Further, according to Kirchhoff's law, the equation group is constructed:

[0020]

[0021] wherein, is the optimized circuit current, M TR is the mutual inductance between the optimized coil and the receiving coil, M ST is the mutual inductance between the transmitting coil and the optimized coil, ω is the system operating angular frequency;

[0022] Further, the forward transfer function formula is:

[0023]

[0024] wherein, V = 2ω 3 M ST M SR M TR , transmitting circuit impedance Z s = R V + R S + jωX S , receiving circuit impedance Z R = R R + R L + jωX R , optimized circuit impedance Z T = R R + jωX T ;

[0025] Further, the coupling strength formula is:

[0026]

[0027] wherein L s is the inductance of the transmitting coil, L R is the inductance of the receiving coil, U LR is the voltage across the receiving coil;

[0028] A circuit of a frequency splitting external optimization method with fixed parameters, comprising: an alternating current source, a transmitting coil circuit, a receiving coil circuit and an optimization coil circuit, the alternating current source inputs include resistance R v and alternating current source AC; the transmitting coil circuit includes inductance L s , resistance R s and compensation capacitor C s ; the receiving coil circuit includes inductance L R , resistance R R and compensation capacitor C R , and the load is R L ; the optimization coil circuit includes inductance L T , resistance R T and compensation capacitor C T ; the forward transmission value and the coupling strength value of the transmitting coil and the receiving coil at the resonance frequency point are changed through the optimization coil circuit, and the transmission efficiency is improved.

[0029] The beneficial effects of the present application are:

[0030] The present application provides an external optimization method based on a double-coil wireless power transmission system, when the system works in an over-coupling area, or the system parameters change, and the frequency splitting phenomenon occurs, a coil is added near the source for optimization to maintain high-efficiency operation of the system; and has the characteristics of simple structure and flexible control. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a three-coil fixed parameter frequency splitting external optimization circuit block diagram of the present application;

[0032] Figure 2 is a three-coil fixed parameter frequency splitting external optimization circuit diagram of the present application;

[0033] Figure 3 is a double-coil wireless transmission circuit diagram of the present application;

[0034] Figure 4 is a two-port network model of the double-coil wireless transmission of the present application;

[0035] Figure 5 is a double-coil wireless transmission resonance simulation result of the present application;

[0036] Figure 6 is a forward transmission function diagram when the radius c of the optimization coil of the present application is 0.1m;

[0037] Figure 7 is a forward transmission function diagram when the radius c of the optimization coil of the present application is 0.13m;

[0038] Figure 8 is a forward transmission function diagram when the radius c of the optimized coil of the present application is 0.16m;

[0039] Figure 9 is a forward transmission function diagram when the relative distance d1 between the optimized coil and the transmitting coil of the present application is 0.05m;

[0040] Figure 10 is a forward transmission function diagram when the relative distance d1 between the optimized coil and the transmitting coil of the present application is 0.1m;

[0041] Figure 11 is a forward transmission function diagram when the relative distance d1 between the optimized coil and the transmitting coil of the present application is 0.15m;

[0042] Figure 12 is a forward transmission function diagram when the compensation capacitor C of the optimized coil of the present application is 1.22x10 T F; -11

[0043] Figure 13 is a forward transmission function diagram when the compensation capacitor C of the optimized coil of the present application is 1.52x10 T F; -11

[0044] Figure 14 is a forward transmission function diagram when the compensation capacitor C of the optimized coil of the present application is 2.5x10 T F; -11

[0045] Figure 15 is a forward transmission function simulation diagram when the radius, position and compensation capacitor of the optimized coil are optimally combined in the present application;

[0046] Figure 16 is a resonance simulation comparison result of the wireless transmission parameters of the optimized coil and the double coil in the present application;

[0047] Figure 17 is a flux linkage simulation diagram of the optimized coil and the double coil in the present application. DETAILED DESCRIPTION

[0048] The present application will be further described below in conjunction with the accompanying drawings and embodiments, which are simplified schematic diagrams and only schematically show the basic structure of the present application, and thus only show the components related to the present application.

[0049] As shown in Figure 1 , a fixed parameter frequency splitting external optimization method includes the following steps:

[0050] Constructing a resonance circuit of a transmitting module, a receiving module and an optimized coil circuit; ​​​

[0051] By setting different parameters of the optimization coil, mutual inductance coupling between the transmitting coil, the receiving coil and the optimization coil is calculated by using the magnetic coupling formula, the forward transfer function is obtained by combining the Kirchhoff law, and the maximum transmission efficiency value is obtained at the working frequency point of the resonant circuit by the forward transfer function and the coupling strength formula.

[0052] As Figure 2 For the circuit of the frequency splitting external optimization method of fixed parameters, the transmitting module includes: an alternating current source input and a transmitting coil circuit, the alternating current source input includes a resistance R v And an alternating current source AC; the transmitting coil circuit includes: inductance L s , resistance R s And compensation capacitor C s of the transmitting coil; the receiving module includes a receiving coil circuit and a load, the receiving coil circuit includes: inductance L R , resistance R R And compensation capacitor C R of the receiving coil, and the load is R L ; the optimization coil circuit includes: inductance L T , resistance R T And compensation capacitor C T of the optimization coil;

[0053] The element parameters and relative positions of the transmitting coil circuit and the receiving coil circuit remain unchanged, and the working frequency remains unchanged at the resonant frequency;

[0054] As Figure 3 shown is a double-coil wireless power transmission system, the mutual inductance M SR between the transmitting coil and the receiving coil is obtained according to the magnetic coupling theory:

[0055]

[0056] Wherein, a, N s is the radius and the number of turns of the transmitting coil, b, N R is the radius and the number of turns of the receiving coil, μ0 is the vacuum permeability, K(), E() are the first and second type elliptic integrals respectively, D is the distance between the transmitting coil and the receiving coil,

[0057] According to the Kirchhoff law, a system of equations can be constructed:

[0058]

[0059] Wherein, X S is the reactance of the transmitting coil, is the current of the transmitting coil circuit, is the current of the receiving coil circuit, M SRFor the mutual inductance between the transmitting coil and the receiving coil, U s is the AC power supply voltage.

[0060] Since the double-coil wireless power transmission system works in the radio frequency field, the power transmission mode of the analog radio frequency antenna is adopted, and the two-port network model of the system is established, as shown in Figure 4 The evaluation criteria for the energy transmission capability of the system are return loss S 11 , forward transmission coefficient S 21 , reverse transmission coefficient S 12 , and output return loss S 22 .

[0061] The forward power transmission capability of the resonant circuit is determined by S 21 , and the greater the value of S 21 , the higher the energy transmission efficiency of the system; according to the resonant circuit parameter modeling, wherein U L is the voltage across the load R L , the forward transmission function of the system can be obtained as:

[0062]

[0063] The coupling strength of the double-coil resonant circuit is determined by k1, and k1 close to 1 indicates that the coupling effect is better, k1 greater than 1 causes frequency splitting, and k1 less than 1 causes under coupling; the closer k1 is to 1, the higher the transmission efficiency of the system, and according to the resonant circuit parameter modeling, the coupling strength k1 formula is obtained as:

[0064] As shown in the simulation results in Figure 5 , the frequency splitting phenomenon of the double-coil is obvious, the resonant frequencies of the transmitting coil circuit and the receiving coil circuit of the system are both 3MHz, D=0.3m, a=b=0.17m, C S =C R =1.28e -11 F, and the load R L =20Ω; when the system works at the resonant frequency, the forward transmission value S 21 =0.45 of the system, k1=2.78, and the system works at the valley point of energy transmission.

[0065] The occurrence of the frequency splitting phenomenon is due to the over coupling between the transmission coils, and in order to weaken the coupling between the coils, two methods can be used: reducing the resonant frequency or increasing the transmission distance, but the above two methods will weaken the maximum energy transmission capability of the system and weaken the working level of the system, therefore, the magnetic coupling between the coils is directly adjusted by optimizing the coil circuit to coordinate the transmitting and receiving sides, so that the transmission efficiency of the system is improved when the system works at a fixed working frequency and fixed parameters.

[0066] The resonance circuit of the optimized coil circuit is increased in the double coil, and the radius c of the optimized coil, the relative distance d1 between the optimized coil and the transmitting coil, and the compensation capacitance C of the optimized coil are analyzed T The influence on transmission efficiency;

[0067] Further, according to the magnetic coupling theory, when the resonance circuit of the optimized coil circuit is included, the mutual inductance M between the transmitting coil and the optimized coil ST , the mutual inductance M between the receiving coil and the optimized coil TR :

[0068]

[0069]

[0070] Wherein, c, N T is the radius and the number of turns of the optimized coil, the distance between the optimized coil and the transmitting coil is d1, and the distance between the optimized coil and the receiving coil is d2,

[0071] According to Kirchhoff's law, the equation set is constructed:

[0072]

[0073] Wherein, is the optimized circuit current, M TR is the mutual inductance between the optimized coil and the receiving coil, M ST is the mutual inductance between the transmitting coil and the optimized coil, ω is the working angular frequency of the system, X T is the reactance of the optimized coil;

[0074] As Figures 6-8 the radius c of the optimized coil is 0.1m, 0.13m and 0.16m respectively, d1 and C T are constant, by changing the size of the optimized coil radius c, it can be seen from the figure that the coil radius c does not change the position of the main peak, the larger the value of c, the two side peaks gradually move away from the main peak;

[0075] As Figures 9-11 the relative distance d1 between the optimized coil and the transmitting coil is 0.05m, 0.1m and 0.15m respectively, c and C T are constant, by changing the relative position of the optimized coil and the transmitting coil, it can be seen that the choice of the relative position d1 makes the forward transmission function S change, the relative two side peaks gradually approach the main peak with the increase of d1, in the process of d1 change, the size of S parameter changes, which shows that under the condition of this parameter setting, there is an optimal combination of b, d1 and C T which makes the system transmission capacity strongest.

[0076] As Figures 12-14To optimize the compensation capacitor C of the coil T 1.22×10 -11 F, 1.52×10 -11 F and 2.5×10 -11 F, c and d1 are constant, the compensation capacitor C of the coil T not only greatly affect the relative position of the two peaks, and the position of the two peaks relative to the main peak, but also affect the size and position of the main peak, by reasonable adjustment of the compensation capacitor C2, the optimal forward transmission function S of the system can appear at the system operating frequency point.

[0077] Further, the forward transmission function formula of the resonant circuit containing the optimization coil circuit is:

[0078]

[0079] wherein, V = 2ω 3 M ST M SR M TR , The transmit circuit impedance Z s = R V + R S +jωX S , the receive circuit impedance Z R = R R + R L +jωX R , the optimization circuit impedance Z T = R R +jωX T ;

[0080] As Figure 15 , 16 shown, the resonant circuit containing the optimization coil circuit works at the same resonant frequency, according to different load R L , there is an optimal combination of optimization coil circuit parameters, that is, the optimal optimization coil radius c, the optimal distance d1 between the optimization coil and the transmit coil and the optimal compensation capacitor C T of the optimization coil circuit;

[0081] The coupling strength K2 of the three-coil resonant circuit is modeled according to the resonant circuit parameters, and the coupling strength formula is obtained:

[0082] When the resonant frequency f0 = 3MHz, the distance d1 between the optimization coil and the transmit coil = 0.125m, the optimization coil radius c = 0.1694, and the compensation capacitor C T of the optimization coil = 3.848e -11 F, S 31= 0.949, K2 = 0.91;

[0083] Figure 17 The optimization of the coil pair influences the magnetic flux linkage between the transmitting coil and the receiving coil. After optimization, the magnetic flux linkage between the transmitting coil and the receiving coil near the resonance frequency f0 = 3 MHz is significantly reduced.

[0084] Based on the above ideal embodiments according to the present application, through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the content of the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A fixed parameter frequency splitting external optimization method, characterized by, The method comprises the following steps: constructing a resonance circuit of a transmitting module, a receiving module and an optimization coil circuit; By setting different parameters of the optimization coil circuit, the mutual inductance coupling between the transmitting coil, the receiving coil and the optimization coil is calculated by using a magnetic coupling formula, a forward transfer function is obtained by combining Kirchhoff's law, and the maximum transmission efficiency value is obtained at the working frequency point of the resonance circuit by the forward transfer function and the coupling strength; The mutual inductance coupling between the transmitting coil, the receiving coil and the optimization coil comprises: Mutual inductive magnetic coupling between the transmitting coil and the receiving coil Mutual inductive magnetic coupling between the transmitting coil and the optimization coil Mutual inductive magnetic coupling between the receiving coil and the optimization coil The specific formula is as follows: Where a, N s b, N are the radius and number of turns of the transmitting coil. R The radius and number of turns of the receiving coil; Permeability of free space; K (), E () represent the first and second elliptic integrals, respectively; D is the distance between the transmitting and receiving coils; c and N are the distances between the transmitting and receiving coils, respectively. T To optimize the coil radius and number of turns; to optimize the distance between the coil and the transmitting coil. The optimized distance between the coil and the receiving coil is: The distance between the transmitting coil and the receiving coil is D= ; ; .

2. The fixed-parameter frequency split external optimization method of claim 1, wherein, The different parameters of the optimization coil include: a coil radius c of the optimization coil circuit, a position d1 of the optimization coil relative to the transmitting coil, a compensation capacitor of the optimization coil C T .

3. The fixed-parameter frequency split external optimization method of claim 1, wherein, The equation set of the Kirchhoff's law is: wherein, is the optimized circuit current, is the optimized coil and receiver coil mutual inductance, is the transmitter coil and optimized coil mutual inductance, is the system operating angular frequency; is the transmitter coil reactance, is the optimized coil reactance, is the AC current source input resistance, is the transmitter coil resistance, R L is the load resistance, R R is the receiver coil resistance.

4. The fixed-parameter frequency split external optimization method of claim 3, wherein, The formula of the forward transfer function is: (7) wherein , , , transmit circuit impedance , receive circuit impedance , .

5. The fixed-parameter frequency split external optimization method of claim 4, wherein, The formula of the coupling strength is: K2 （8） wherein, L s Ls is the inductance of the transmit coil, L R Lr is the inductance of the receive coil, Vr is the voltage across the receive coil.

6. A circuit employing the fixed-parameter frequency-splitting external optimization method of claim 1, wherein, comprises: AC current source, transmitting coil circuit, receiving coil circuit and optimizing coil circuit, AC current source input includes resistance R v and AC source AC; transmitting coil circuit includes inductance of transmitting coil L s , resistance R s and compensation capacitor C s ; receiving coil circuit includes inductance of receiving coil L R , resistance R R and compensation capacitor C R , load is R L ; optimizing coil circuit includes inductance of optimizing coil L T , resistance R T and compensation capacitor C T ; by optimizing coil circuit, the forward transmission value and the coupling strength value of transmitting coil and receiving coil at the resonance frequency point are changed, and the transmission efficiency is improved.

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