Cavity resonance wireless power transmission system for three-dimensional omnidirectional wireless power transmission

Abstract

The present invention discloses a cavity resonance type wireless power transmission system for three-dimensional omnidirectional wireless power transmission, including two transmitting coils, a receiving coil, and a resonant cavity, wherein the two transmitting coils and the receiving coil are both arranged in the resonant cavity; the wall joints of the resonant cavity are connected by capacitors, and two mutually decoupled series LC resonant circuits are formed in the X and Y directions of the resonant cavity respectively; the two transmitting coils are used to excite the magnetic field in the two directions of the resonant cavity respectively, and the magnetic field amplitude and phase in the two directions of the cavity of the resonant cavity are controlled by adjusting the voltage phase between the two transmitting coils, and finally the desired type of magnetic field is obtained. The present invention can not only improve the uniformity of the magnetic field in the cavity, but also realize 360° wireless power transmission without dead angles.

Description

Technical Field

[0001] The present invention relates to the field of wireless power transmission, and in particular to a cavity resonance type wireless power transmission system for realizing three-dimensional omnidirectional wireless power transmission. Background Art

[0002] The traditional wireless power transmission method is to directly transmit power wirelessly through two coupled coils or electrode plates, which can achieve high-power wireless power transmission. However, the disadvantages of this type of system are also very obvious, that is, the transmission distance is limited. When the transmission distance is close to the diameter of the coil itself, the system transmission efficiency will drop sharply. In addition, the wireless charging system using electrode plates has low biosafety because it transmits energy through coupled electric fields.

[0003] Early cavity resonant wireless power transmission technology stimulated the eigenmode magnetic field in the resonant cavity through the transmitter. This method can form a stable magnetic field distribution in the cavity, and can obtain a high transmission efficiency (>50%) at most positions in the cavity through the receiving coil. The disadvantage is that the operating frequency of the system is high (>100MHz), and there is a strong electric field in the cavity, and the biosafety of the system is low. In 2017, Disney researchers MJChabalko and others added capacitors to the resonant cavity to construct a quasi-static resonant cavity wireless power transmission system, which reduced the operating frequency of the system and limited the electric field in the system, greatly improving the biosafety of the system, but the magnetic field uniformity in the system was poor, so they later adopted the superposition of two magnetic field modes to improve the magnetic field uniformity in the resonant cavity. The defect of this method is that in order to avoid mutual interference between the two modes, the frequencies of the two modes need to be set to be different, which undoubtedly directly affects the transmission efficiency of the entire system. At the same time, the magnetic field in all the above cavity resonant wireless power transmission systems is a pulsating magnetic field, that is, the magnetic field direction is single, which will cause the receiver to only obtain relatively stable electrical energy in a specific direction. Once the direction of the receiver changes, the overall transmission characteristics of the system will be reduced. Summary of the invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a cavity resonance type wireless power transmission system for three-dimensional omnidirectional wireless power transmission, aiming to solve the problem that the transmission characteristics of the system, especially the received power, change dramatically when the position or angle of the receiver in the wireless charging system changes. The present invention uses two transmitting coils to respectively excite the magnetic field in two directions of the resonant cavity, and controls the magnetic field amplitude and phase in two directions in the cavity by adjusting the voltage phase between the two transmitting coils, and finally obtains the desired type of magnetic field.

[0005] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A cavity resonance wireless power transmission system for three-dimensional omnidirectional wireless power transmission includes two transmitting coils, a receiving coil, and a resonant cavity, wherein the two transmitting coils and the receiving coil are both arranged in the resonant cavity. The wall joints of the resonant cavity are connected by capacitors, and two mutually decoupled series LC resonant circuits are formed in the X and Y directions of the resonant cavity, respectively. The two transmitting coils are used to excite the magnetic field in the two directions of the resonant cavity, respectively, and the magnetic field amplitude and phase in the two directions of the cavity of the resonant cavity are controlled by adjusting the voltage phase between the two transmitting coils, and finally the desired type of magnetic field is obtained.

[0007] Preferably, alternating currents of the same frequency with a phase difference of 90 degrees are introduced into the two transmitting coils to respectively excite magnetic fields in the X and Y directions of the resonant cavity, and synthesize them to obtain a rotating magnetic field.

[0008] Preferably, the excitation voltage amplitudes at both ends of the two transmitting coils are adjusted by observing the receiving voltage value or the input impedance value so that the magnetic field intensity moduli in two directions in the cavity are the same.

[0009] Preferably, the transmitting coil and the receiving coil are both wound with a single metal wire or Litz wire, and the resonant frequency is configured to be the resonant frequency f0 of the resonant cavity through a series capacitor.

[0010] Preferably: for the X or Y direction, the resonant cavity and the capacitor on the cavity wall are constructed as a series LC equivalent circuit model according to the flow direction of the current in the resonant cavity in a specific working mode. At this time, considering the resistance value of the cavity wall, the transmitting coil and the resonant cavity are equivalent to a double-coil mutual inductance model, and the input impedance of the transmitting coil end is:

[0011] ;

[0012] in, represents the input impedance, represents the resistance of the transmitting coil, represents the resistance of the resonant cavity, represents the system operating angular frequency, represents the mutual inductance between the transmitting coil and the resonant cavity, represents the equivalent inductance of the resonant cavity, represents the resonant capacitance of the resonant cavity, represents the imaginary part, represents the inductance of the transmitting coil, Represents the resonant capacitance of the transmitting coil.

[0013] Preferably, the real part of the input impedance at the transmitting coil end is:

[0014] ;

[0015] in, Indicates input impedance.

[0016] Preferably, when the system frequency is equal to the characteristic frequency of the resonant cavity, the frequency corresponding to the peak value of the real part of the input impedance is regarded as the resonant frequency f0 of the resonant cavity.

[0017] Preferably, the two transmitting coils are placed close to the cavity wall and perpendicular to the cavity wall.

[0018] Preferably, the transmitting coil is located in 70% of the space close to the center of the resonant cavity.

[0019] Preferably, the receiving coil is placed at the center of the resonant cavity.

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

[0021] 1. The cavity resonance wireless power transmission system for three-dimensional omnidirectional wireless power transmission proposed in the present invention can effectively solve the problem of magnetic field inhomogeneity in traditional PI or PD resonant cavity modes without destroying the original space in the cavity.

[0022] 2. In the present invention, since the frequencies of the alternating magnetic fields in two different directions in the resonant cavity are consistent, the receiving coil only needs to meet this one resonant frequency, and there is no need to design multiple resonant circuits with different frequencies, which greatly simplifies the receiver design and streamlines the receiving circuit.

[0023] 3. The present invention proposes a three-dimensional omnidirectional wireless power transmission cavity resonance wireless power transmission system. In most of the space of the system, there exists a rotating magnetic field with small amplitude fluctuation. Compared with the pulsating magnetic field in the existing systems of this type, the rotating magnetic field in the present invention has a strong angular anti-offset characteristic, which can overcome the fluctuation of the electric energy receiving power caused by the angle change of the receiving coil to a great extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of a cavity resonance type wireless power transmission system for realizing three-dimensional omnidirectional wireless power transmission provided by the present invention;

[0025] Figure 2 It is a curve diagram showing the change of the real part and the imaginary part of the input impedance with the voltage frequency when the transmitting coil is placed in the resonant cavity in the present invention;

[0026] Figure 3 It is a relationship diagram between the magnetic induction intensity B and the spatial position change in the cavity at the Z=0.5h plane in the resonant cavity of the present invention;

[0027] Figure 4It is a schematic diagram of the change of the magnetic induction intensity amplitude and the magnetic field direction in one cycle at the Z=0.5h plane in the resonant cavity of the present invention;

[0028] Figure 5 It is a schematic diagram of the transmission efficiency in the present invention with respect to the position and angle of the receiving coil, wherein the light-colored portion is the efficiency change of the traditional PI mode, and the dark-colored portion is the efficiency change of the present invention.

[0029] In the figure, 1 is a capacitor, 2 is a transmitting coil, 3 is a receiving coil, H is the height of the cavity, W is the width of the surrounding metal cavity walls, and L is the maximum width of the cavity. DETAILED DESCRIPTION

[0030] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0031] like Figure 1 This embodiment is a cavity resonance type wireless power transmission system for three-dimensional omnidirectional wireless power transmission, including two transmitting coils, a receiving coil, and a resonant cavity, wherein the two transmitting coils and the receiving coil are arranged in the resonant cavity. The wall joints of the resonant cavity are connected by capacitors, forming two mutually decoupled series LC resonant circuits in the X and Y directions of the resonant cavity respectively. In another embodiment, the main body of the resonant cavity wall is made of metal aluminum, and a capacitor is embedded between the upper and lower cavity walls. The X and Y directions of the resonant cavity can be regarded as two independent current loops, and the capacitor added to the cavity wall and the equivalent circuits in these two directions constitute a series LC resonant circuit. In another embodiment, the resonant cavity is an octagonal prism, and the ratio of the side opening width to the side cavity wall width is 1:1. In another embodiment, the two transmitting coils are placed close to the cavity wall and perpendicular to the cavity wall, so that the normal directions of the two transmitting coils are perpendicular to each other, so as to obtain a larger mutual inductance coefficient between the resonant cavity. In another embodiment, the transmitting coil is a spiral square planar coil, and the receiving coil is a spiral square planar coil. The receiving coil can be located at any position in the resonant cavity, Figure 1 The receiving coil is placed at the center of the cavity, where the best angular anti-deviation characteristics can be obtained. In another embodiment, when the transmitting coil is located in the area of ​​about 70% of the center of the cavity, the transmission characteristics of the system are very excellent. By arbitrarily changing the position and horizontal angle of the receiving coil in the 70% space near the center of the resonant cavity, relatively stable electrical energy can be received.

[0032] In this embodiment, H=400 mm, W=325 mm, and L=630 mm.

[0033] In another embodiment, the resonant cavity is composed of an aluminum metal shell and a capacitor, and a capacitor with a specific capacitance is embedded between the aluminum metal shell to achieve adjustment of the operating frequency.

[0034] ;

[0035] Among them, L2 is the equivalent inductance of the resonant cavity, C2 is the capacitance of the capacitor embedded between the shells, and f0 is the operating frequency of the system.

[0036] The two transmitting coils are used to excite the magnetic field in two directions of the resonant cavity, and the magnetic field amplitude and phase in two directions in the resonant cavity are controlled by adjusting the voltage phase between the two transmitting coils. The amplitude and phase of the magnetic field in two directions in the cavity completely follow the amplitude and phase of the excitation voltage applied to both ends of the transmitting coils in their respective directions. First, the phase difference of the excitation voltage of the two transmitting coils is fixed to 90 degrees. Next, the magnetic field amplitudes in two directions in the cavity are measured to see if they are consistent. If they are different, the magnetic field amplitudes in two directions are made the same by adjusting the excitation voltage amplitude of the transmitting coil.

[0037] The same frequency alternating current with a phase difference of 90 degrees is passed through the two transmitting coils to stimulate the magnetic fields in the X and Y directions of the resonant cavity respectively, and the rotating magnetic field is synthesized.

[0038] The excitation voltage amplitudes of the two transmitting coils are adjusted by observing the receiving voltage value or the transmitting impedance value so that the moduli of the magnetic field strength in two directions in the cavity are the same.

[0039] The transmitting coil and the receiving coil are both wound with a single metal wire or Litz wire, and the resonant frequency is configured to be the resonant frequency f0 of the resonant cavity through a series capacitor.

[0040] The resonant frequency of the receiving coil is adjusted to the resonant frequency f0 of the resonant cavity.

[0041] For the X or Y direction, the resonant cavity and the capacitor on the cavity wall are constructed as a series LC equivalent circuit model according to the flow direction of the current in the resonant cavity in a specific working mode. At this time, considering the resistance value of the cavity wall, the transmitting coil and the resonant cavity can be equivalent to a double-coil mutual inductance model, and the input impedance of the transmitting coil end is:

[0042] ;

[0043] in, represents the input impedance, represents the resistance of the transmitting coil, represents the resistance of the resonant cavity, represents the system operating angular frequency, represents the mutual inductance between the transmitting coil and the resonant cavity, represents the equivalent inductance of the resonant cavity, represents the resonant capacitance of the resonant cavity, represents the imaginary part, represents the inductance of the transmitting coil, Represents the resonant capacitance of the transmitting coil.

[0044] The real part of the input impedance at the transmitting coil end is:

[0045] ;

[0046] in, Represents the real part of the input impedance.

[0047] It can be seen that since the resistance R2 of the resonant cavity of the present invention is extremely small (about 0.001Ω), when the system frequency is equal to the characteristic frequency of the resonant cavity, that is, When , the real part of the input impedance will increase sharply. Therefore, the frequency corresponding to the peak value of the real part of the input impedance is regarded as the resonant frequency f0 of the resonant cavity.

[0048] By adjusting the capacitors in the X and Y directions of the resonant cavity, the resonant frequencies of the equivalent LC circuits in these two directions can be adjusted to be consistent.

[0049] The operating frequency of the system can reach above MHz, making the transmission efficiency higher.

[0050] The system efficiency is related to the quality factor Q of the transceiver coil and the cavity. A higher transmission efficiency can be obtained by using a multi-strand Litz coil and a high-conductivity metal cavity. The transmission efficiency of the system can also be improved by increasing the number of turns of the transceiver coil or increasing the ratio of the transceiver coil to the cavity size.

[0051] The present invention can realize three-dimensional omnidirectional wireless power transmission by controlling the angular positions of two transmitting coils and the phases of the excitation voltages on the two coils.

[0052] Figure 2 It is a curve diagram of the real and imaginary parts of the input impedance changing with the voltage frequency when the transmitting coil is placed in the resonant cavity in the present invention. The resonant cavity is equivalent to a series LC loop. According to the double-coil equivalent circuit model, when the resistance of the resonant cavity equivalent to the series LC loop is about 2 orders of magnitude lower than the reactance value generated by its own inductance at the operating frequency, the frequency corresponding to the highest point of the real part of the reflected impedance at both ends of the transmitting coil is the resonant frequency of the resonant cavity, that is, Figure 2 The frequency corresponding to the peak value of the reflected impedance in is the resonant frequency f0 of the resonant cavity in this working mode.

[0053] When the two tuned transmitting coils are fed with alternating current of 90° phase difference and frequency f0, the system can excite the following Figure 3The magnetic field distribution shown in the figure is the magnetic induction intensity B at the Z=0.5h plane in the resonant cavity. Figure 3 In the resonance cavity, the magnetic induction intensity fluctuates greatly at the opening of the resonance cavity, while the magnetic field distribution inside the resonance cavity is very uniform, especially in the center far away from the cavity wall, where there is a relatively strong magnetic induction intensity.

[0054] like Figure 4 It is a schematic diagram of the change of the magnetic induction intensity amplitude and the magnetic field direction in one cycle in the resonant cavity of the present invention. When the voltages in the two transmitting coils match the input impedances in their respective directions, a true circular rotating magnetic field will appear at the center of the resonant cavity, that is, the voltage level received by the receiving coil at this location in any horizontal direction (XY direction) remains basically consistent, and the transmission efficiency and output power of the system remain relatively stable.

[0055] Figure 5 It is a schematic diagram of the transmission efficiency change with respect to the angle of the receiving coil in the present invention. This figure is a radar diagram of the system transmission efficiency change when the receiving coils are located at A, B, C, and D in the cavity and undergo a horizontal 360° angle offset (A, B, C, and D are located in the Z=0.5h plane). At point A, the system transmission efficiency fluctuation caused by the change of the receiving coil is less than 10%, and the fluctuation mainly comes from experimental errors.

[0056] The dual excitation method proposed in the present invention can greatly improve the uniformity of the magnetic field in the cavity while achieving 360° wireless power transmission without dead angles. Compared with the existing cavity resonance wireless power transmission system, it has great advantages in terms of the anti-drift characteristics of the receiving coil position and angle, and has great application prospects in scenarios such as smart homes.

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A cavity resonance wireless power transmission system for three-dimensional omnidirectional wireless power transmission, characterized in that: The invention comprises two transmitting coils, a receiving coil and a resonant cavity, wherein the two transmitting coils and the receiving coil are both arranged in the resonant cavity; the wall joints of the resonant cavity are connected by capacitors, and two mutually decoupled series LC resonant circuits are formed in the X and Y directions of the resonant cavity respectively; the two transmitting coils are used to excite the magnetic field in the two directions of the resonant cavity respectively, and the magnetic field amplitude and phase in the two directions in the cavity of the resonant cavity are controlled by adjusting the voltage phase between the two transmitting coils, so as to finally obtain the required type of magnetic field; The same frequency alternating current with a phase difference of 90 degrees is passed into the two transmitting coils to stimulate the magnetic field in the X and Y directions of the resonant cavity respectively, and the rotating magnetic field is synthesized. By observing the receiving voltage value or the input impedance value, the excitation voltage amplitude at both ends of the two transmitting coils is adjusted so that the modulus of the magnetic field intensity in two directions in the cavity is the same; The transmitting coil and the receiving coil are both wound with a single metal wire or Litz wire, and the resonant frequency is configured to be the resonant frequency f0 of the resonant cavity through a series capacitor; For the X or Y direction, the resonant cavity and the capacitor on the cavity wall are constructed as a series LC equivalent circuit model according to the flow direction of the resonant cavity current. At this time, considering the resistance value of the cavity wall, the transmitting coil and the resonant cavity are equivalent to a double-coil mutual inductance model, and the input impedance of the transmitting coil end is: ； in, represents the input impedance, represents the resistance of the transmitting coil, represents the resistance of the resonant cavity, represents the system operating angular frequency, represents the mutual inductance between the transmitting coil and the resonant cavity, represents the equivalent inductance of the resonant cavity, represents the resonant capacitance of the resonant cavity, represents the imaginary part, represents the inductance of the transmitting coil, represents the resonant capacitance of the transmitting coil; The real part of the input impedance at the transmitting coil end is: in, Represents the real part of the input impedance.

2. The cavity resonance type wireless power transmission system for three-dimensional omnidirectional wireless power transmission according to claim 1, characterized in that: When the system frequency is equal to the characteristic frequency of the resonant cavity, the frequency corresponding to the peak value of the real part of the input impedance is regarded as the resonant frequency f0 of the resonant cavity.

3. The cavity resonance type wireless power transmission system for three-dimensional omnidirectional wireless power transmission according to claim 2, characterized in that: Two transmitting coils are placed close to and perpendicular to the cavity wall.

4. The cavity resonance type wireless power transmission system for three-dimensional omnidirectional wireless power transmission according to claim 3, characterized in that: The transmitting coil is located in the 70% space near the center of the resonant cavity.

5. The cavity resonance type wireless power transmission system for three-dimensional omnidirectional wireless power transmission according to claim 4, characterized in that: The receiving coil is placed at the center of the cavity of the resonant cavity.

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