A method for uniformizing electromagnetic field in cavity for wireless power transmission

Abstract

The application discloses a cavity electromagnetic field homogenization method for wireless energy transmission. The application uses an internal multi-port method to calculate electromagnetic field distribution in a metasurface resonant cavity under certain port configuration, and then finds a suitable port connection mode through a genetic algorithm, so that the electromagnetic field in the cavity is approximately uniformly distributed. The application realizes uniform distribution of electromagnetic field in the resonant cavity, and can realize efficient transmission everywhere in the cavity.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission, and specifically relates to a method for homogenizing the electromagnetic field within a cavity for wireless power transmission. Background Technology

[0002] Wireless power transfer has developed rapidly in recent years, with significant applications in major fields such as smart electronics, electric vehicles, and power transmission. In some special situations, traditional power transmission methods pose safety risks, and it is difficult to use traditional power distribution methods involving overhead power lines for base stations on isolated islands or mountaintops. Therefore, wireless power transfer has become increasingly important and urgent. There are various methods of wireless power transfer, among which intracavity wireless power transfer is a highly efficient method. It can completely concentrate energy within the cavity, with no energy outflow. Its development has made it possible to achieve highly secure power transmission in three-dimensional space.

[0003] However, because the resonant modes in the resonant cavity are non-uniform—that is, the electromagnetic field is stronger in some areas and weaker in others—and the transmission power and efficiency of wireless energy are related to the magnitude of the field, the existence of these resonant nulls limits the transmission power and efficiency at the null locations. Summary of the Invention

[0004] This invention provides a method for homogenizing the electromagnetic field within a cavity for wireless power transmission. The aim is to explore an internal multi-port method to adjust the modes within the resonant cavity, attempting to construct composite modes within the resonant cavity to achieve a nearly uniform cavity field distribution and eliminate the existence of resonant zeros. This enables efficient energy transmission throughout the resonant cavity.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0006] A method for homogenizing the electromagnetic field within a cavity for wireless power transmission includes the following steps:

[0007] S1. Establish a metasurface resonant cavity and set several ports on the metasurface;

[0008] S2. Set the port type to S-Parameter type in discrete ports, and simulate all ports at the frequency points that need optimization. parameter;

[0009] S3. Set the port current of each port to a unit current, simulate the field distribution of each port at the frequency point to be optimized, and use... Indicates port The electric field distribution;

[0010] S4. Calculate the actual current at each port of the frequency point to be optimized using the internal multi-port method. Indicates port The actual current is used to calculate the actual total field. , Maximum number of ports;

[0011] S5. Set the field value difference and function , Indicates the first The electric field amplitude at the point that needs optimization This represents the average field value of all points that need optimization. The number of optimized field points selected;

[0012] S6. Obtained using a genetic algorithm The minimum value.

[0013] Furthermore, the metasurface resonator described in step S1 is a metal mesh resonator.

[0014] Furthermore, the metal mesh resonant cavity has a length of 916 mm, a width of 916 mm, and a height of 1204 mm.

[0015] Furthermore, the aperture of the metal mesh resonant cavity is set to 80mm, the edge width between two adjacent meshes is 16mm, and the edge width of each face is 34mm.

[0016] Furthermore, a 1mm wide slit is cut out at the center of the mesh edge.

[0017] Furthermore, the gaps are set as internal ports, and the reconfigurability of the metasurface is achieved by changing the connection and disconnection of the ports.

[0018] Furthermore, internal ports are provided on the bottom and top surfaces of the metal mesh resonant cavity, totaling 288 ports, with 144 ports on each surface.

[0019] Furthermore, in step S2, the simulation of all ports at the frequency points requiring optimization is performed. The parameter condition is set to a single frequency point of 278MHz.

[0020] Furthermore, in step S4 The value ranges from 1 to 288. It is 288.

[0021] Furthermore, in step S5 , It is 58.

[0022] The present invention has the following technical effects:

[0023] (1) The present invention uses an internal multi-port method to adjust the mode in the resonant cavity, constructs a composite mode in the resonant cavity, realizes an approximately uniform cavity field distribution, and eliminates the existence of the resonant zero point.

[0024] (2) The electromagnetic field value was basically homogenized in the cavity, and the energy was transferred efficiently everywhere. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the metal mesh resonant cavity in the embodiment;

[0026] Figure 2 This is a partial schematic diagram of the metal mesh in the embodiment;

[0027] Figure 3 This is a schematic diagram of the gaps on the edge of the metal mesh in the embodiment;

[0028] Figure 4 This is a schematic diagram showing the top surface of the bottom surface of the resonant cavity after adding a port in the embodiment;

[0029] Figure 5 This is a schematic diagram of the bottom port as viewed along the negative Z-axis in the embodiment;

[0030] Figure 6 This is a schematic diagram of the top port as viewed along the negative Z-axis in the embodiment;

[0031] Figure 7 A diagram showing the relationship between port current and voltage in the internal multi-port method.

[0032] Figure 8 A diagram showing the formula for calculating the actual port current using the internal multi-port method;

[0033] Figure 9 The example diagram shows the "electric field value - Y-axis" before and after optimization for the linear section x=466mm.

[0034] Figure 10 The example diagram shows the "electric field value - Y-axis" before and after optimization for the linear section x=626mm.

[0035] Figure 11 The example diagram shows the "electric field value - Y-axis" before and after optimization for the linear x=274mm. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments. These embodiments are merely one specific example of the present invention and not the entirety of the invention. Furthermore, the invention is not limited to the metal mesh metasurface resonator shown in this example; it is equally applicable to other metasurface resonators. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort should fall within the scope of protection of the present invention.

[0037] Since a changing electric field can generate a magnetic field, and a changing magnetic field can generate an electric field, this embodiment only presents the entire process by optimizing the electric field value.

[0038] Create a system in CST such as Figure 1 The metal mesh resonant cavity shown is 916mm long, 916mm wide, and 1204mm high. The preset frequency is 278MHz. To confine the energy within the cavity, the aperture of the metal mesh is set to 80mm, the width of the edge between two adjacent mesh openings is 16mm, and the edge width of each face is 34mm. Figure 2 As shown.

[0039] Make a 1mm wide slit in the center of the mesh edge, such as... Figure 3 As shown, the resonant cavity is made into a metasurface. The slots are designated as internal ports, and the reconfigurability of the metasurface is achieved by changing the connection and disconnection of these ports. To shorten simulation time, internal ports are only placed on the bottom and top surfaces of the resonant cavity, totaling 288 ports (144 on each surface). The resonant cavity after adding the ports is shown below. Figure 4 As shown, viewed along the negative Z-axis, the internal ports of the bottom and top surfaces are respectively as follows: Figure 5 , Figure 6 As shown.

[0040] First, set the port type to S-Parameter type in discrete ports, select the frequency domain solver, and set the condition to a single frequency point of 278MHz. Simulate the results for all ports at the frequency point to be optimized. Parameters. Then change the port type to a unit current source port in discrete ports, and simulate to obtain the electric field values. Extract the plane. The electric field distribution results are extracted within the range of , ,unit .use Indicates port The electric field distribution.

[0041] With port 1 set as the external power supply port, according to the internal multi-port method, the port current and voltage satisfy the following... Figure 7 The relationship shown, For port voltage, For port The current, when hour, The preset frequency is 278MHz (lower port). , mutual impedance, when hour, Preset frequency port Self-impedance, For port The impedance of connection or disconnection. Based on the relation The S-parameters are obtained from the simulation. When the port is in a connected state, it can be replaced with 0 and a larger value, respectively. In this embodiment... The value ranges from 1 to 288.

[0042] Figure 7 The relation can be transformed to obtain the following: Figure 8 The relationship shown is due to Unit current, i.e. Therefore, the actual current at the port can be directly passed through Figure 8 The relationship shown is obtained. Finally, it is obtained through the formula. Calculate the actual total field , This is the maximum number of ports, in this example. It is 288.

[0043] In genetic algorithms, the objective function is set as follows: , Indicates the first The electric field amplitude at the point that needs optimization This represents the average field value of all points that need optimization. In this embodiment, the optimal number of field points is selected. , The value is 58. Optimization can yield a more uniform electric field distribution within the resonant cavity. Figure 9 , Figure 10 , Figure 11 They were shown respectively , , Optimization results on the three lines.

[0044] The two sides of the cavity are difficult to adjust due to boundary conditions. During the optimization process, the objective function can be... This is set to the middle segment. The optimization algebra number in this embodiment is relatively small, only 60. If the optimization algebra number is set to a larger number, even better results can be obtained. Furthermore, this invention is not limited to the metal mesh metasurface resonator shown in this embodiment; it is also applicable to other metasurface resonators.

Claims

1. A method for homogenizing the electromagnetic field within a cavity for wireless power transmission, characterized in that, Includes the following steps: S1. Establish a metasurface resonant cavity and set several ports on the metasurface; S2. Set the port type to S-Parameter type in discrete ports, and simulate the S-parameters of all ports at the frequency points to be optimized; S3. Set the port current of each port to a unit current, simulate the field distribution of each port at the frequency point to be optimized, and use E q This represents the electric field distribution at port q; S4. Calculate the actual current at each port of the frequency point to be optimized using the internal multi-port method, and use i q The actual current i at port q q Calculate the actual total field Q represents the maximum number of ports; S5. Set the field value difference and function E total (m) represents the electric field amplitude at the m-th field point that needs optimization. This represents the average field value of all field points that need to be optimized, where p is the number of field points selected for optimization. S6. Use a genetic algorithm to find the minimum value of Diff.

2. The method for homogenizing the electromagnetic field within a cavity for wireless power transmission according to claim 1, characterized in that, The metasurface resonator mentioned in step S1 is a metal mesh resonator.

3. The method for homogenizing the electromagnetic field within a cavity for wireless power transmission according to claim 2, characterized in that, The metal mesh resonant cavity has a length of 916 mm, a width of 916 mm, and a height of 1204 mm.

4. The method for homogenizing the electromagnetic field within a cavity for wireless power transmission according to claim 3, characterized in that, The aperture of the metal mesh resonant cavity is set to 80mm, the edge width between two adjacent meshes is 16mm, and the edge width of each face is 34mm.

5. The method for homogenizing the electromagnetic field within a cavity for wireless power transmission according to claim 4, characterized in that, Make a 1mm wide slit in the center of the mesh edge.

6. The method for homogenizing the electromagnetic field within a cavity for wireless power transmission according to claim 1, characterized in that, The gaps are set as internal ports, and the reconfigurability of the metasurface is achieved by changing the connection and disconnection of the ports.

7. The method for homogenizing the electromagnetic field within a cavity for wireless power transmission according to claim 2, characterized in that, Internal ports are provided on the bottom and top surfaces of the metal mesh resonant cavity, totaling 288 ports, with 144 ports on each surface.

8. The method for homogenizing the electromagnetic field within a cavity for wireless power transmission according to claim 1, characterized in that, The condition for simulating the S-parameters of all ports at the frequency point to be optimized in step S2 is to set it to a single frequency point of 278MHz.

9. The method for homogenizing the electromagnetic field within a cavity for wireless power transmission according to claim 1, characterized in that, In step S4, the value of q ranges from 1 to 288, and Q is 288.

10. The method for homogenizing the electromagnetic field within a cavity for wireless power transmission according to claim 1, characterized in that, In step S5, m∈[1,58] and p is 58.

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