Single capacitance coupling wireless power transmission system for mobile receiving equipment

Abstract

The invention relates to the technical field of electric field coupling wireless power transmission (CPT), and particularly discloses a single-capacitor coupling wireless power transmission system for mobile receiving equipment. The system uses the ground as a power transmission path, and the primary side of a coupling mechanism only needs one emission pole plate P1; a receiving pole plate P2 and a receiving pole plate P3 are installed on the bottom layer and the top layer of the mobile receiving device respectively, the receiving pole plate P3 can be replaced by a metal shell of the mobile receiving device, and therefore parasitic capacitance of the metal shell and self-capacitance of the receiving pole plate P3 serve as a part of an energy transmission channel. In addition, the receiving pole plate P3 is designed to be a circular plate, so that the same power transmission capability at any angle can be ensured in a rotating application environment. Experimental results show that the system can output stable power at any position in the emission pole plate P1, and the free positioning characteristic is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric field coupled wireless power transmission (CPT), and in particular to a single capacitor coupled wireless power transmission system for a mobile receiving device. Background Art

[0002] Wireless power transmission has attracted widespread attention due to its safety and flexibility, and has been widely used in multiple industrial fields, such as electric vehicles, drones, consumer electronics, and mobile robots.

[0003] With the requirement for convenient power supply for mobile receiving devices, traditional static wireless power transmission can no longer meet the needs of most application scenarios. For example, realizing free position power supply of mobile receiving devices in a large planar area can not only reduce the burden of carrying batteries, but also improve work efficiency. Therefore, some researchers focus their research on wireless power transmission systems with free position power supply function in large planar areas. At present, magnetic field coupled wireless power transmission (IPT) and electric field coupled wireless power transmission (CPT) are two commonly used technologies. IPT usually requires multiple coils and control methods to maintain a stable magnetic flux in a large planar area, resulting in problems such as high cost and low efficiency. In contrast, CPT uses a metal plate as a coupling mechanism, which has the advantages of lightness and low cost in a large planar area.

[0004] At present, some research works have realized the free position wireless power supply characteristics of the receiving end by adopting active control methods and combining CPT technology, such as using array emitter plates and adjusting variable capacitance or inductance through multiple relays, or using crossed finger electrodes as emitter plates, and controlling the switch array to activate the corresponding plate position, so as to realize the free position power supply characteristics on the plane. However, additional control will increase the complexity of the system. Using a passive method is an effective way to simplify the system. Some studies have proposed an array emitter plate with a compact coupling mechanism to achieve free displacement of the receiving load in the x and y directions, but this structure cannot overcome the twisting problem of the coil outlet during the rotation of the IPT system. Summary of the invention

[0005] The present invention provides a single capacitor coupling wireless power transmission system for a mobile receiving device, and solves the technical problem that the current electric field coupling wireless power transmission system that realizes the free position of the receiving end cannot overcome the problem of twisting of the coil outlet end of the IPT system during rotation.

[0006] In order to solve the above technical problems, the present invention provides a single capacitor-coupled wireless power transmission system for a mobile receiving device, which is provided with a transmitting structure and a mobile receiving device, wherein the transmitting structure includes the earth and a transmitting plate P1 located above the earth, and the bottom layer and the top layer of the mobile receiving device are respectively installed with a receiving plate P2 and a receiving plate P3; the earth, the transmitting plate P1, the receiving plate P2, and the receiving plate P3 are arranged in layers from bottom to top to form a single capacitor coupling mechanism; the mobile receiving device moves within the range of the transmitting plate P1.

[0007] Preferably, the distance between the receiving plate P3 and the ground and the size of the receiving plate P3 are set so that the self-capacitance of the receiving plate P3 is constant.

[0008] Preferably, the receiving plate P3 is a circular plate, and the self-capacitance C of the receiving plate P3 is self Constant at C self =8ε0r3, ε0 is the permittivity of free space, and r3 is the radius of the receiving plate P3.

[0009] Preferably, when the mobile receiving device adopts a metal shell, the receiving electrode plate P2 is the metal shell of the mobile receiving device.

[0010] Preferably, the single capacitor coupling mechanism is equivalent to a capacitor C1-C M 、C2-C M and mutual capacitance C M Connected, capacitor C1-C M Connect the transmitter AC output, capacitor C2-C M Connect the receiving end AC input, mutual capacitance C M Connect capacitor C1-C M With capacitor C2-C M The coupling coefficient k of the single capacitor coupling mechanism is c Defined as

[0011] Preferably, C 12 represents the equivalent capacitance between the emitter plate P1 and the receiver plate P2, C 1G represents the equivalent capacitance between the emitter plate P1 and the earth, C 13 represents the equivalent capacitance between the emitter plate P1 and the receiver plate P3, C 2G represents the equivalent capacitance between the receiving plate P2 and the earth, C 3G represents the equivalent capacitance between the receiving plate P3 and the earth, C 23Represents the equivalent capacitance between the receiving electrode plate P2 and the receiving electrode plate P3.

[0012] Preferably, the system further comprises a primary compensation circuit, wherein the primary compensation circuit comprises a capacitor C f1 、Inductance L f1 and an inductor L1, the two ends of which are connected to the ground and the emitter plate P1, respectively. f1 and capacitor C f1 Connected in series between the two ends of the inverter output; inductor L f1 Together with the inductor L1, they serve as the primary coil and the secondary coil to form a primary transformer.

[0013] Preferably, the capacitor C f1 、Inductance L f1 and inductor L1 satisfies ω 2 L1C1(1-k c 2 )=1,ω 2 L f1 C f1 =1, ω is the operating angular frequency of the system.

[0014] Preferably, the system further comprises a secondary side compensation circuit, wherein the secondary side compensation circuit comprises a capacitor C f2 , capacitor C ex , inductor L2 and inductor L f2 , capacitor C ex The two ends of the inductor L2 are connected to the receiving plate P2 and the receiving plate P3 respectively, and the two ends of the inductor L2 are connected to the capacitor C ex The two ends of the inductor L f2 and capacitor C f2 Connected in series between the two ends of the rectifier input, the inductor L2 and the inductor L f2 They serve as the primary coil and the secondary coil respectively to form a secondary transformer.

[0015] Preferably, the capacitor C ex , inductor L2, inductor L f2 and capacitor C f2 Satisfy 2 L2(C2+C ex )(1-k c 2 )=1,ω 2 L f2 C f2 =1.

[0016] The present invention provides a single capacitor-coupled wireless power transmission system for a mobile receiving device. The system uses the earth as a power transmission path. The primary side of its coupling mechanism only needs one transmitting plate P1. The bottom layer and top layer of the mobile receiving device are respectively installed with receiving plates P2 and P3. The receiving plate P3 can be replaced by a metal shell of the mobile receiving device, thereby utilizing the parasitic capacitance of the metal shell and the self-capacitance of the receiving plate P3 as part of the energy transmission channel. In addition, the receiving plate P3 is designed as a circular plate, which can ensure the same power transmission capability at any angle in a rotating application environment. Experimental results show that the system can output stable power at any position within the transmitting plate P1, realizing the free positioning characteristic. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the spatial layout of a single capacitor-coupled wireless power transmission system for a mobile receiving device provided by an embodiment of the present invention;

[0018] Figure 2 is a side view of a system coupling mechanism provided by an embodiment of the present invention;

[0019] Figure 3 is an equivalent circuit diagram of a system coupling mechanism provided by an embodiment of the present invention;

[0020] Figure 4 C provided by the embodiment of the present invention 3G Relationship diagram with d3 (r3=200mm);

[0021] Figure 5 is the coupling capacitor C provided in the embodiment of the present invention M Relationship diagram between r2 and d1 (d3 = 500 mm);

[0022] Figure 6 is a simulation result diagram of the free positioning characteristic provided by an embodiment of the present invention (d3=500mm);

[0023] Figure 7 is a circuit topology diagram of a system provided by an embodiment of the present invention;

[0024] Figure 8 The embodiment of the present invention provides Figure 7 Equivalent circuit diagram of

[0025] Fig. 9 The following are key waveforms and data diagrams of the system provided by the embodiments of the present invention: (a) input and output waveform diagrams, (b) system output power and efficiency diagrams;

[0026] Fig.10 is a graph showing the relationship between output power and efficiency at different points provided by an embodiment of the present invention;

[0027] Fig.11 It is a diagram of the power and efficiency of receiving devices at different positions in a large-area plane provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following specifically illustrates the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided for illustrative purposes only and cannot be understood as limiting the present invention. The accompanying drawings are provided for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0029] Figure 1 The structure of a single capacitor-coupled wireless power transmission system with a large free area for mobile receiving devices is shown, in which the earth is used as a power transmission path. On the primary side, a DC power supply is combined with an inverter to provide AC excitation, and then through a primary compensation circuit, the earth and the emitter plate P1 work as a transmitting structure. The area of ​​the emitter plate P1 is larger than the receiving plate P2 set at the bottom of the mobile receiving device, and the mobile receiving device can move freely within the range of the emitter plate P1.

[0030] Specifically, the bottom layer and the top layer of the mobile receiving device are respectively installed with receiving plates P2 and P3, and the receiving end is also provided with a compensation circuit, a converter and a load resistor R L . The receiving plate P2 is placed at the bottom of the mobile receiving device, and can be replaced by a metal shell in practical applications. The receiving plate P3 should be placed on the top of the mobile receiving device, because during the movement, the constant self-capacitance of the receiving plate P3 requires it to remain in an isolated charged state. When the distance between the receiving plate P3 and the ground is much greater than the radius of the receiving plate P3, the self-capacitance of the receiving plate P3 can be considered constant. When a circular plate is used, the self-capacitance of the receiving plate P3 can be expressed by the following formula:

[0031] C self =8ε0r3 (1)

[0032] Among them, ε0 is the permittivity of free space, which is approximately equal to the permittivity of air, and r3 is the radius of the receiving plate P3.

[0033] In addition, when the mobile receiving device moves within the range of the transmitting plate P1, other capacitance parameters can also remain unchanged. Therefore, the proposed system has good free-position wireless power supply characteristics.

[0034] Figure 2The figure shows a side view of a coupling mechanism, wherein the earth, the emitter plate P1, and the receiving plates P2 and P3 serve as a coupling mechanism, the earth and the emitter plate P1 serve as an emitting structure, and the receiving plates P2 and P3 serve as receiving structures. d1, d2, and d3 represent the distance between the earth and the emitter plate P1, the distance between the emitter plate P1 and the receiving plate P2, and the distance between the emitter plate P1 and the receiving plate P3, respectively. The side lengths of the receiving plates P2 and P3 are represented by r2 and r3, respectively. Six capacitors, C, are formed between the earth, the emitter plate P1, and the receiving plates P2 and P3. 12 represents the equivalent capacitance between the emitter plate P1 and the receiver plate P2, C 1G represents the equivalent capacitance between the emitter plate P1 and the ground, C 13 represents the equivalent capacitance between the emitter plate P1 and the receiver plate P3, C 2G Represents the equivalent capacitance between the receiving plate P2 and the ground, C 3G Represents the equivalent capacitance between the receiving plate P3 and the ground, C 23 Represents the equivalent capacitance between the receiving plate P2 and the receiving plate P3.

[0035] Figure 3 Shown Figure 2 Equivalent circuit of the coupling mechanism shown. Figure 3 (a) shows the six-capacitor equivalent circuit diagram of the coupling mechanism. The six-capacitor model can be simplified to a π-type circuit. The single-capacitor coupling mechanism is equivalent to the capacitor C1-C M 、C2-C M and mutual capacitance C M Connected, capacitor C1-C M Connect the transmitter AC output, capacitor C2-C M Connect the receiving end AC input, mutual capacitance C M Connect capacitor C1-C M With capacitor C2-C M Between, such as Figure 3 As shown in (b), the equivalent capacitances C1, C2 and the mutual capacitance C M The expression of coupling coefficient k is as follows. c Defined as

[0036]

[0037] In the coupling mechanism, the transmission distance d2 and the size of the receiving plate P2 are determined by actual needs. Taking the mobile receiving device as a service robot as an example, the distance d1 between the earth and the emitter plate P1 is about 50mm, and the radius of the emitter plate P1 is about 200mm. The size of the emitter plate P1 is set to a square metal plate of 1000mm×1000mm×1mm. All coupling mechanisms are simulated in ANSYS Maxwell software, and a square metal plate of 1000mm×1000mm×1mm is set with a voltage of 0V to replace the earth as the earth in ANSYS Maxwell.

[0038] Figure 4 The capacitance C is shown with different d3 and different side length l1. 3G The radius of the receiving plate P3 is set to 200 mm, the distance d2 between the emitting plate P1 and the receiving plate P2 is 20 mm, and the ground, the emitting plate P1, the receiving plate P2 and the receiving plate P3 are located on concentric axes. Figure 4 The results show that the capacitor C 3G As d3 increases, it continues to increase and gradually approaches the self-capacitance value. The simulation results are consistent with formula (1). As the side length l1 of the emitter plate P1 increases, at the same distance d3 (the distance between the emitter plate P1 and the receiving plate P3), the capacitance C 3G This is because as the emitter plate P1 increases, the coupling between the emitter plate P1 and the receiving plate P3 is enhanced, thereby weakening the coupling between the receiving plate P3 and the ground.

[0039] Coupling capacitor C M It is the key factor that determines the power transmission capacity of the system. Therefore, the coupling mechanism should be optimized to obtain a larger mutual capacitance C M . Figure 5 The mutual capacitance C is shown under different parameters (radius r2 and distance d1 of the receiving plate P2). M It can be observed that as the distance d1 (the distance between the earth and the emitter plate P1) increases, the mutual capacitance C M The radius r2 of the receiving plate P2 is proportional to the mutual capacitance C M The value is closely related to the mutual capacitance C M It will continue to increase with the increase of radius r2.

[0040] In order to realize the free position wireless power supply characteristics of the proposed system, the lower left corner of the transmitter plate P1 is used as the origin of the xoy plane, and the rotation angle of the mobile receiving device is set to θ, as shown in Figure 1 As shown in FIG. 1 , since both receiving plates P2 and P3 are circular plates, the rotational misalignment of the receiving plates P2 and P3 will not affect the system. Figure 6 The simulation results of the free position wireless power supply characteristics are shown. When the mobile receiving device receives power at different locations, the mutual capacitance C M The difference between the highest point and the lowest point is 0.46pF, and the change rate is only 5.4%. M It is higher at the four corners. When the emitter plate P1 is large enough, the proposed system will have a larger free power supply area.

[0041] Circuit topology of single capacitor coupled wireless power transmission system for mobile receiving device Figure 7 As shown, the full-bridge inverter on the primary side and the converter on the secondary side are composed of four MOSFETs and four diodes respectively. The primary compensation circuit includes a capacitor C f1 、Inductance L f1 and inductor L1. The secondary compensation circuit includes capacitor C f2 、Inductance L f2 , inductor L2 and capacitor C ex , where the capacitor C ex It is used to compensate the capacitance of the receiving end and reduce the value of the inductor L2. The two ends of the inductor L1 are connected to the ground and the emitter plate P1 respectively. f1 and capacitor C f1 Connected in series between the two ends of the inverter output; inductor L f1 The capacitor C and the inductor L1 are used as the primary coil and the secondary coil to form a primary transformer. ex The two ends of the inductor L2 are connected to the receiving plate P2 and the receiving plate P3 respectively, and the two ends of the inductor L2 are connected to the capacitor C ex The two ends of the inductor L f2 and capacitor C f2 Connected in series between the two ends of the rectifier input, the inductor L2 and the inductor L f2 They serve as the primary coil and the secondary coil respectively to form a secondary transformer.

[0042] The fundamental harmonic approximation (FHA) method and Figure 3 The coupler model shown in (b) has an equivalent resistance expressed as R eq =R L ×8 / π2, so Figure 7 can be simplified to Figure 8 shown.

[0043] In order to achieve system resonance, the relationship between system parameters can be obtained by the following formula:

[0044]

[0045] The coupling coefficient k here is c is defined as

[0046] According to formula (3), when the parasitic capacitance on the components is ignored, the output current of the system can be derived by the following formula:

[0047]

[0048] ω is the operating angular frequency and resonant angular frequency of the system, and ω=2πf, where f is the resonant frequency corresponding to ω.

[0049] In order to verify the proposed system and method, a 500W large-area free-position wireless power transmission system prototype with single capacitor coupling is constructed in this embodiment. The system consists of a copper foil transmitting plate (transmitter plate P1) with a size of 1000mm×1000mm×0.2mm and two aluminum receiving plates (receiving plate P2 and receiving plate P3) with a radius of 200mm and a thickness of 1mm. The geometric distances are as follows: d1=50mm, d2=20mm, d3=500mm.

[0050] In the compensation network, the air-core inductor L f1 , L1, L f2 and L2 are wound with Litz wire (specification 0.04×1500) and have corresponding equivalent resistances, respectively expressed as R f1 , R1, R f2 and R2. Compensation capacitor C f1 and C f2 It consists of multiple NP0 type capacitors connected in series and in parallel, each with a rated voltage of 1kV and a capacitance of 1nF, to achieve higher voltage and current tolerance. The key parameters of the prototype system are listed in Table 1.

[0051] Table 1 System parameters

[0052]

[0053] The resonant frequency of the system is 1MHz. Under the best matching with 44Ω load, the DC input voltage is about 110V. The key waveforms and data of the oscilloscope and power analyzer are as follows: Fig. 9 shown. Fig. 9 (a) shows the output waveform of the inverter and the input current waveform of the rectifier. The system implements zero phase angle (ZPA) mode, and the phase difference between the two current waveforms is about 90°, ensuring optimal power transmission. Fig. 9 (b) shows that the system output power P out The power consumption is 538W, and the efficiency η is about 84.7%. These experimental results show that 2In a large-area plane, the mobile receiving device is suitable for the size of a service robot and can also achieve efficient and high-power energy transmission using a single capacitor-coupled wireless power transfer system.

[0054] Fig.10 Shows the system output power P at different positions out The relationship between the output power P and the efficiency η. The lower left corner of the emitter plate P1 is taken as the origin of the xoy plane. Points 1, 2 and 3 represent the mobile receiving device placed at the lower left corner (x = 0.2m, y = 0.2m), the middle (x = 0.5m, y = 0.5m) and the upper right corner (x = 0.8m, y = 0.8m) of the emitter plate P1, respectively. out With the increase of , the efficiency η continues to increase and reaches a maximum efficiency of nearly 85%. In addition, under different positions, P out This is consistent with efficiency, which verifies the correctness of the theory.

[0055] In order to verify the wireless power transmission performance of a small mobile receiving device at different positions in a large plane, several typical positions were selected for experiments. The power reception and efficiency of the mobile receiving device were measured at different x-coordinates and when the y-coordinate was fixed at 0.2m, 0.4m, 0.6m and 0.8m. The experimental results are shown in Figure 2. Fig.11 As shown. It can be observed that as the mobile receiving device moves throughout the plane, the system is able to maintain at least 500W of power and the efficiency remains above 83%. This proves that the large-area single capacitor-coupled wireless power transfer system is capable of achieving high-power and high-efficiency energy transfer over a wide range of planar spaces.

[0056] In summary, the embodiment of the present invention provides a new type of large-area free-position wireless power supply single capacitor coupling wireless power transmission system, which can provide wireless power supply for various mobile receiving devices such as mobile receiving robots. The system adopts a transmitting plate P1 and uses the earth as a path for power transmission. The metal shell of the mobile receiving device can also be used as one of the receiving plates, which significantly simplifies the system structure and reduces the overall system cost, while realizing wireless power supply in a large area and free position.

[0057] Finally, this embodiment constructed a prototype of a single capacitor-coupled wireless power transmission system with a 1m2 wireless power supply area. The system achieved an output power of 538W and an efficiency of 84.7%. In addition, the experimental results show that even over a large area, the system can maintain an efficiency of more than 83% and provide more than 500W of stable power transmission. This proves that the single capacitor-coupled wireless power transmission system can provide efficient, high-power and stable wireless energy transmission for mobile receiving devices in a large area, providing a new solution for large-area free-position WPT technology.

[0058] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A single capacitor coupled wireless power transmission system for a mobile receiving device, characterized in that: A transmitting structure and a mobile receiving device are provided, wherein the transmitting structure includes the earth and a transmitting plate P1 located above the earth, and the bottom layer and the top layer of the mobile receiving device are respectively installed with a receiving plate P2 and a receiving plate P3; the earth, the transmitting plate P1, the receiving plate P2, and the receiving plate P3 are arranged in layers from bottom to top to form a single capacitor coupling mechanism; the mobile receiving device moves within the range of the transmitting plate P1.

2. The single capacitor coupling wireless power transmission system for mobile receiving device according to claim 1, characterized in that: The distance between the receiving plate P3 and the ground and the size of the receiving plate P3 are set so that the self-capacitance of the receiving plate P3 is constant.

3. The single capacitor coupling wireless power transmission system for mobile receiving equipment according to claim 2, characterized in that: The receiving plate P3 is a circular plate, and the self-capacitance C of the receiving plate P3 is self Constant at C self =8ε0r3, ε0 is the permittivity of free space, and r3 is the radius of the receiving plate P3.

4. The single capacitor coupled wireless power transmission system for mobile receiving device according to claim 3, characterized in that: When the mobile receiving device adopts a metal shell, the receiving electrode plate P2 is the metal shell of the mobile receiving device.

5. The single capacitor coupled wireless power transmission system for mobile receiving devices according to any one of claims 1 to 4, characterized in that: The single capacitor coupling mechanism is equivalent to the capacitor C1-C M 、C2-C M and mutual capacitance C M Connected, capacitor C1-C M Connect the transmitter AC output, capacitor C2-C M Connect the receiving end AC input, mutual capacitance C M Connect capacitor C1-C M With capacitor C2-C M The coupling coefficient k of the single capacitor coupling mechanism is c Defined as 6. The single capacitor coupling wireless power transmission system for mobile receiving equipment according to claim 5, characterized in that: C 12 represents the equivalent capacitance between the emitter plate P1 and the receiver plate P2, C 1G represents the equivalent capacitance between the emitter plate P1 and the earth, C 13 represents the equivalent capacitance between the emitter plate P1 and the receiver plate P3, C 2G represents the equivalent capacitance between the receiving plate P2 and the earth, C 3G represents the equivalent capacitance between the receiving plate P3 and the earth, C 23 Represents the equivalent capacitance between the receiving electrode plate P2 and the receiving electrode plate P3.

7. The single capacitor coupling wireless power transmission system for mobile receiving equipment according to claim 6, characterized in that: The system also includes a primary compensation circuit, the primary compensation circuit includes a capacitor C f1 、Inductance L f1 and an inductor L1, the two ends of which are connected to the ground and the emitter plate P1, respectively. f1 and capacitor C f1 Connected in series between the two ends of the inverter output; inductor L f1 Together with the inductor L1, they serve as the primary coil and the secondary coil to form a primary transformer.

8. The single capacitor coupling wireless power transmission system for mobile receiving equipment according to claim 7, characterized in that: Capacitor C f1 、Inductance L f1 and inductor L1 satisfies ω 2 L f1 C f1 =1, ω is the operating angular frequency of the system.

9. The single capacitor coupling wireless power transmission system for mobile receiving equipment according to claim 8, characterized in that: The system also includes a secondary side compensation circuit, the secondary side compensation circuit includes a capacitor C f2 , capacitor C ex , inductor L2 and inductor L f2 , capacitor C ex The two ends of the inductor L2 are connected to the receiving plate P2 and the receiving plate P3 respectively, and the two ends of the inductor L2 are connected to the capacitor C ex The two ends of the inductor L f2 and capacitor C f2 Connected in series between the two ends of the rectifier input, the inductor L2 and the inductor L f2 They serve as the primary coil and the secondary coil respectively to form a secondary transformer.

10. The single capacitor coupling wireless power transmission system for mobile receiving equipment according to claim 9, characterized in that: Capacitor C ex , inductor L2, inductor L f2 and capacitor C f2 Satisfy 2 L2(C2+C ex )(1-k c 2 )=1,ω 2 L f2 C f2 =1.

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