CN106981933B - Wireless power transmission system and distance-adaptive driving coil configuration method - Google Patents

Abstract

The invention provides a wireless power transmission system and a driving coil configuration method based on distance self-adaption, and relates to the technical field of wireless power transmission. The system comprises a high-frequency driving power supply, a driving coil group, a transmitting coil, a receiving coil and a load coil group, wherein the driving coil group comprises n parallel driving coils which are of non-coaxial structures and are on the same plane, the load coil group and the driving coil group are completely symmetrical, and the transmitting coil and the receiving coil are completely symmetrical. Based on the system, the conditions met by the maximum efficiency transmission of the system under different transmission distances are determined, and the conditions are converted into implicit functions of the radius of the driving coil, so that the optimal radius, inductance and series compensation capacitance are obtained. The wireless power transmission system adopts the non-coaxial driving coil group, realizes the portability of the wireless power transmission device, effectively reduces the system loss, and ensures that the system still carries out wireless power transmission with maximum efficiency when the transmission distance changes based on the distance self-adaptive driving coil configuration method.

Description

Wireless power transmission system and distance-adaptive driving coil configuration method

Technical field

The present invention relates to the technical field of wireless power transmission, and in particular, to a wireless power transmission system and a distance-adaptive driving coil configuration method.

Background technique

In recent years, as the contact lines of traditional wired power transmission systems are prone to sparks and conductors are prone to wear and tear, the research on wireless power transmission technology has attracted more and more attention. The application scope of this technology has also ranged from small mobile devices to industrial fields. Keep widening. In 2007, MIT scientists achieved a new breakthrough in wireless power transmission technology. They discovered that magnetic coupling resonant technology can effectively improve the wireless power transmission distance and transmission power, and successfully lit up a lamp 2 meters away in the experiment. A 60-watt light bulb. Since then, magnetic coupling resonant technology has become a key technology studied by domestic and foreign scholars in medium and long-distance wireless power transmission.

Since the transmission efficiency of the two-coil magnetically coupled resonant wireless power transmission system is relatively sensitive to distance, domestic and foreign researchers usually use the method of adding relay coils to further expand the transmission range and improve the transmission efficiency. The most common ones are three-coil and four-coil structure. However, no matter which structure is used, when the transmission distance changes, the coupling between coils will also change, causing frequency splitting in the system. The occurrence of frequency splitting will cause the transmission efficiency of the system to drop sharply.

Contents of the invention

In view of the shortcomings of the existing technology, the present invention provides a wireless power transmission system and a distance-adaptive driving coil configuration method. It adopts a symmetrical four-coil wireless power transmission system and the driving coil group adopts a non-coaxial structure to realize wireless transmission. The portability of the transmission device can effectively reduce system losses. The drive coil configuration method based on distance adaptation can ensure that the system still transmits wireless power at maximum efficiency when the transmission distance changes, greatly improving system efficiency.

On the one hand, the present invention provides a wireless power transmission system, which is a non-coaxial four-coil magnetic coupling resonance system, including a high-frequency drive power supply, a drive coil group, a transmitting coil, a receiving coil and a load coil group; the high-frequency drive The power supply and the driving coil group are connected in series to form a driving circuit loop; the two ends of the load coil group are connected to the load that requires electricity to form a load circuit loop; the transmitting coil and the receiving coil are independently and coaxially arranged between the driving coil group and the load. Between the coil groups, the transmitting coil and the receiving coil are completely symmetrical; the driving coil group includes n parallel-connected driving coils, the load coil group includes n parallel-connected load coils, and the load coil group and the driving coil group are completely symmetrical; the driving coil, The transmitting coil, the receiving coil and the load coil all include an inductor coil and a series compensation capacitor. One end of the inductor coil in the drive coil group and the load coil group is connected to one point, and the other end is connected in series with a corresponding series compensation capacitor; the high-frequency drive power supply is connected with The drive coil groups and the load coil group and the load requiring electricity are all connected through selector switches to ensure that the drive coils in the drive coil group are selectively connected according to the transmission distance and the load coils are connected symmetrically; n drive coils It is a non-coaxial structure and is in the same plane; n load coils are a non-coaxial structure and is in the same plane. The specific value of n is configured and determined according to the maximum transmission distance.

On the other hand, the present invention also provides a driving coil configuration method for a wireless power transmission system based on distance adaptive. This method is based on the above-mentioned non-coaxial four-coil magnetically coupled resonant wireless power transmission system and calculates the system's Transmission efficiency expression, and obtain the conditions that the coupling coefficient and coil quality factor should meet when the system has maximum efficiency transmission. By converting this condition into an implicit function related to the radius of the driving coil, the optimal radius of the driving coil can be obtained, and then Determine the inductance and series compensation capacitance of the driving coil to complete the configuration of a driving coil. The parameters of the load coil and the driving coil are completely consistent; then change the transmission distance between the transmitting coil and the receiving coil, and configure a new driving coil using the above method; Then change the transmission distance between the transmitting coil and the receiving coil, and then configure a new driving coil using the above method; this cycle continues until n driving coils are configured and the entire configuration of the driving coil group is completed; when the system performs wireless power transmission At this time, according to the actual transmission distance, the driving coil whose radius, inductance and series compensation capacitance meet the conditions of maximum transmission efficiency is selected from n drive coils to be turned on, so that the system always transmits wireless power in a state of maximum efficiency transmission.

Further, the transmission distance between the transmitting coil and the receiving coil changes in equal increments, that is, the distance difference between two adjacent transmission distances is Among them, D is the maximum transmission distance, that is, the maximum distance between the transmitting coil and the receiving coil defined according to actual conditions. Each transmission distance in the configuration is _di =i·Δd, i=1, 2,...,n.

Furthermore, the specific steps to obtain the optimal radius, inductance and series compensation capacitance of the drive coil in the distance-adaptive drive coil configuration method are as follows:

Step 1: Set the basic parameters of the wireless power transmission system, and initialize the loop variable i = 1; set the angular frequency of the high-frequency driving source to ω ₀ , and the driving coil, transmitting coil, receiving coil and load coil of the system all meet the requirements of Resonance occurs at this angular frequency; the inductance, resistance, quality factor and series compensation capacitance of the system transmitting coil and receiving coil are the same, that is, L _t =L _r , R _t =R _r , Q _t =Q _r , C _t =C _r ; The inductance parameters of the transmitting coil and the receiving coil are artificially set, and the inductance parameters of the driving coil and the load coil are calculated. The inductance, series compensation capacitance, resistance and quality factor of the driving coil and the load coil are the same respectively, that is, L _di = L _li , R _di =R _li , C _di =C _li , Q _di =Q _li , i=1, 2,...,n; all coils in the system use the same winding radius, denoted as a;

Step 2: When the transmission distance between the transmitting coil and the receiving coil is _di , determine the transmission efficiency expression of the wireless power transmission system as shown in Equation (1);

Among them, k _dit and k _tr respectively represent the coupling coefficient between the driving coil and the transmitting coil, and the coupling coefficient between the transmitting coil and the receiving coil;

Step 3: Find the partial derivative of the transmission efficiency expression (1) Determine the conditions that the wireless power transmission system should satisfy when maximizing transmission efficiency: Equation (2);

Step 4: Calculate the mutual inductance M _tr between the transmitting coil and the receiving coil through the mutual inductance calculation formula. The mutual inductance calculation formula is shown in Equation (3);

Among them, μ ₀ is the vacuum magnetic permeability, the value is 4π×10 ^-7 ; r _t is the radius of the transmitting coil, r _r is the radius of the receiving coil; d is the lateral offset of the transmitting coil and the receiving coil (between the central axis) distance; k ² =4αV((1+αV) ² +β ² ) ^-1 , where α=r _r r _t ^-1 , β=d _i r _t ^-1 , d _i is the distance between the plane of the transmitting coil and the receiving coil, that is, the transmission distance between the transmitting coil and the receiving coil; Ψ(k)=(1-k ² /2)K(k)-E(k) , K(k) and E(k) are elliptic integrals of the first kind and elliptic integrals of the second kind respectively,/>

Step 5: Determine the coupling coefficient k _tr between the transmitting coil and the receiving coil based on the transmitting coil inductance L _t , the receiving coil inductance L _r and the mutual inductance M _tr between the transmitting coil and the receiving coil. The calculation formula is as shown in Equation (4) Show;

Step 6: Set the radius of the driving coil to r _di . When the distance remains unchanged and the transmitting coil is determined, determine the distance between the driving coil and the transmitting coil according to the calculation formula (5) of the mutual inductance and the calculation formula (6) of the coupling coefficient. The implicit function relationship between the coupling coefficient k _dit and the drive coil radius r _di ;

Among them, r _t is the radius of the transmitting coil; d′ is the distance between the lateral offset (between the central axis) of the driving coil and the transmitting coil; k′ ² =4α′V′((1+α′V′) ² +β ′ ² ) ^-1 , where α′=r _t r _di ^-1 , β′=cr _di ^-1 , V′=(1+d′ ² r _t ^-2 -2d′r _t ^{- 1} cosφ) ^1/2 , c is the distance between the plane of the driving coil and the transmitting coil;

Step 7: The inductance L _di of the drive coil has the following relationship with the radius r _di ,

L _di =μ ₀ r _di [ln(8r _di /a)-1.75] (7)

Then the quality factor of the driving coil is Q _di =ω ₀ L _di /R _di , which is a function of the radius r _di of the driving coil;

According to the conditional expression (2) satisfied by the wireless power transmission system when the transmission efficiency is maximum, determine the unique driving coil radius r _di ;

Step 8: Determine the inductance L _di of the drive coil according to the drive coil radius r _di determined in step 7 and equation (7); according to the resonant frequency formula Determine the series compensation capacitance C _di of the driving coil. At this time, the system performs wireless power transmission with maximum efficiency;

Step 9: Determine whether the loop variable i is equal to n. If so, the step ends and the configuration of the drive coil is completed; if not, then i=i+1, increment the transmission distance by an equal amount, and return to step 2 to determine the new drive coil. radius, inductance and series compensation capacitance.

It can be seen from the above technical solution that the beneficial effects of the present invention are: a wireless power transmission system and a driving coil configuration method based on distance adaptive provided by the present invention. The driving coil group of the wireless power transmission system adopts a non-coaxial structure, and n The drive coils are all on the same plane, which can greatly reduce the size of the transmitter of the wireless power transmission system, making the wireless power transmission device more portable, and can effectively avoid excessively long connecting lines between the drive power supply and the drive coil, effectively reducing system losses. ; Based on the non-coaxial four-coil magnetically coupled resonant wireless power transmission system, with the system achieving distance adaptive maximum efficiency wireless power transmission as the goal, the n drive coils of the drive coil group are configured through the drive coil configuration method to achieve Maximum efficiency transmission of wireless energy. When the transmission distance changes, the wireless power transmission system can still ensure that the wireless energy transmission system transmits wireless energy with maximum efficiency, greatly improving the system efficiency and well solving the problem of wireless energy transmission system when the transmission distance changes. The problem of sharp decline in transmission efficiency provides clear guidance for mid-distance wireless power transmission systems to achieve distance-adaptive maximum efficiency transmission.

Description of drawings

Figure 1 is a structural topology diagram of a wireless power transmission system provided by an embodiment of the present invention;

Figure 2 is the equivalent circuit diagram of Figure 1;

Figure 3 is a flow chart of a driving coil configuration method based on distance adaptation provided by an embodiment of the present invention;

FIG. 4 is a graph showing the relationship between transmission efficiency and transmission distance of the wireless power transmission system provided by the embodiment of the present invention.

In the picture: 1. High-frequency driving power supply; 2. Driving coil group; 3. Transmitting coil; 4. Receiving coil; 5. Load coil group; 6. Load; 7. Driving circuit; 8. Transmitting circuit; 9. Receiver circuit ;10. Load circuit; 11. Selector switch.

Detailed ways

Specific implementations of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the invention but are not intended to limit the scope of the invention.

A wireless power transmission system is a non-coaxial four-coil magnetic coupling resonance system, including a high-frequency driving power supply 1, a driving coil group 2, a transmitting coil 3, a receiving coil 4 and a load coil group 5. The high-frequency driving power supply 1 and the driving coil group 2 are connected in series to form a driving circuit loop. Both ends of the load coil group 5 are connected to the load 6 that requires electricity to form a load circuit loop; the transmitting coil 3 and the receiving coil 4 are independently and coaxially arranged in sequence. Between the driving coil group 2 and the load coil group 5, the transmitting coil 3 and the receiving coil 4 are completely symmetrical. The drive coil group 2 includes n parallel drive coils, and the load coil group 5 includes n parallel load coils. The load coil group 5 is completely symmetrical with the drive coil group 2; the drive coil, the transmitting coil, the receiving coil and the load coil all include inductors. Coils and corresponding series compensation capacitors, one end of the inductance coil in the drive coil group 2 and the load coil group 5 is connected to one point, and the other end is connected in series with the corresponding series compensation capacitor. Between the high-frequency drive power supply 1 and the drive coil group 2, the load The coil group 5 and the load 6 requiring electricity are connected through a selector switch 11 to ensure that the drive coils in the drive coil group 2 are selectively connected according to the transmission distance, and the load coils are connected symmetrically; the n drive coils are non-identical. axial structure and in the same plane; n load coils have a non-coaxial structure and are in the same plane. The specific value of n is configured and determined according to the maximum transmission distance. In this embodiment, the maximum transmission distance (that is, due to the emission limit limited by actual conditions The maximum distance between the coil and the plane where the receiving coil is located) is 0.5m, and the number of driving coils is n=4. The structural topology of the system is shown in Figure 1.

Figure 2 shows the equivalent circuit diagram of the above wireless power transmission system (n=4), including a driving circuit 7, a transmitting circuit 8, a receiving circuit 9 and a load circuit 10. The drive circuit 7 includes a high-frequency drive power supply V _S and its internal resistance R _S and four groups of parallel CRL circuits, where L _di (i=1, 2, 3, 4) is the inductance of the drive coil, R _di (i=1 , 2, 3, 4) is the parasitic resistance of the driving coil, C _di (i=1, 2, 3, 4) is the series compensation capacitance of the driving coil. The transmitting circuit 8 includes a set of series-connected CRL circuits, where L _t is the inductance of the transmitting coil, R _t is the parasitic resistance of the transmitting coil, and C _t is the series compensation capacitance of the transmitting coil. The receiving circuit 9 includes a set of series-connected CRL circuits, where L _r is the inductance of the receiving coil, R _r is the parasitic resistance of the receiving coil, and C _r is the series compensation capacitance of the receiving coil. The load circuit 10 includes a load resistor R _L and four groups of parallel CRL circuits, where L _li (i=1, 2, 3, 4) is the inductance of the load coil, and R _li (i=1, 2, 3, 4) is The parasitic resistance of the load coil, _Cli (i=1, 2, 3, 4) is the series compensation capacitance of the load coil.

Based on the above non-coaxial four-coil magnetically coupled resonant wireless power transmission system, in order to achieve system distance adaptive maximum efficiency wireless power transmission and solve the problem that the transmission efficiency of the wireless power transmission system drops sharply when the transmission distance changes, this implementation This example provides a distance-adaptive driving coil configuration method. First, calculate the wireless energy transmission efficiency expression of the system, and obtain the conditions that the coupling coefficient should meet when the system transmits with maximum efficiency. By converting this condition into the driving coil The implicit function related to the radius is used to obtain the optimal radius of the driving coil, and then the inductance and series compensation capacitance of the driving coil are determined to complete the configuration of a driving coil; then the transmission distance between the transmitting coil and the receiving coil is changed in equal increments, Still configure a new drive coil using the above method; then change the transmission distance between the transmitting coil and the receiving coil, and then configure a new drive coil using the above method; this cycle continues until n drive coils are configured and the drive coil is completed All configurations for Group 2. Among them, the incremental amount when the transmission distance between the transmitting coil and the receiving coil changes in equal increments, that is, the distance difference between two adjacent transmission distances is Among them, D is the maximum transmission distance, and the transmission distances changed in the configuration are _di =i·Δd, i=1, 2,...,n. In this embodiment, according to the maximum transmission distance of 0.5m, the transmission distance increment is 0.1m, and the transmission distance is changed four times, thereby configuring four drive coils. In the specific implementation, the change in the transmission distance between the transmitting coil and the receiving coil can also be an equal amount of decreasing change, and the configuration result is the same as an equal amount of increasing change. It can also be based on the actual maximum transmission distance and actual conditions. , artificially set the rules for changing the transmission distance in the configuration. The parameters of the load coil and the drive coil are completely consistent, and the load coil changes with the drive coil. As shown in Figure 3, the specific method of driving coil configuration is as follows.

Step 1: Set the basic parameters of the wireless power transmission system, and initialize the loop variable i = 1; set the angular frequency of the high-frequency driving source to ω ₀ , and the system driving coil, transmitting coil, receiving coil and load coil all meet this requirement Resonance occurs at the frequency; all coils in the system use the same winding, and the winding radius is a; the system transmitting coil and the receiving coil are completely symmetrical, and the driving coil group and the load system coil group are completely symmetrical, so the inductance, resistance, quality of the transmitting coil The factor and series compensation capacitance are the same as the inductance, resistance, quality factor and series compensation capacitance of the receiving coil, that is, L _t =L _r , R _t =R _r , Q _t =Q _r ,C _t =C _r , and the driving coil's The inductance, series compensation capacitor, resistance, and quality factor are the same as those of the load system coil, that is, L _di = L _li , R _di = R _li , C _di = C _li , Q _di = Q _li , i=1, 2, 3, 4. The inductance parameters of the transmitting coil and the receiving coil are artificially set during design, and the inductance parameters of the driving coil and load coil are calculated during the design process. In this embodiment, the angular frequency ω ₀ =2π*13.56MHz, and the winding radius a= 2.5mm, the inductance of the transmitting coil and the receiving coil is L _t =L _r =15.56uH.

According to the resonant frequency formula Determine the series compensation capacitance of the transmitting coil as/> The series compensation capacitance of the receiving coil is/> According to the parasitic resistance calculation formula/> Among them, σ and l represent the conductivity of the copper wire and the total length of the coil (the length after straightening) respectively. The parasitic resistance of the transmitting coil is determined as The parasitic resistance of the receiving coil is/> According to the formula for calculating the quality factor/> Determine the quality factor of the transmitting coil as/> The quality factor of the receiving coil is

Step 2: When the transmission distance is _di (the distance between the transmitting coil 3 and the receiving coil 4), determine the transmission efficiency η of the wireless power transmission system, and the expression is as shown in equation (1);

Among them, k _dit and k _tr respectively represent the coupling coefficient between the driving coil and the transmitting coil and the coupling coefficient between the transmitting coil and the receiving coil. In this embodiment, the transmission distance is first set to d ₁ =0.1m.

Step 3: Find the partial derivative of the transmission efficiency expression (1) Determine the conditions that the wireless power transmission system should satisfy when maximizing transmission efficiency: Equation (2);

Only when the coupling coefficients k _dit and k _tr and the quality factors Q _di and Q _t satisfy the above relationship, the efficiency of the system's wireless power transmission is maximum.

Step 4: Calculate the mutual inductance M _tr between the transmitting coil and the receiving coil through the mutual inductance calculation formula. The mutual inductance calculation formula is shown in Equation (3).

Among them, μ ₀ is the vacuum magnetic permeability, the value is 4π×10 ^-7 ; r _t is the radius of the transmitting coil, r _r is the radius of the receiving coil; d is the lateral offset of the transmitting coil and the receiving coil (between the central axis) distance; k ² =4αV((1+αV) ² +β ² ) ^-1 , where α=r _r r _t ^-1 , β=d _i r _t ^-1 , d _i is the distance between the plane of the transmitting coil and the receiving coil, that is, the transmission distance between the transmitting coil and the receiving coil; Ψ(k)=(1-k ² /2)K(k)-E(k) , K(k) and E(k) are elliptic integrals of the first kind and elliptic integrals of the second kind respectively,/> φ and θ are integral symbols and will not appear in the calculation results. In this embodiment, the calculated mutual inductance between the transmitting coil and the receiving coil is M _tr =1.2450 μH.

Step 5: Determine the coupling coefficient k _tr between the transmitting coil and the receiving coil based on the transmitting coil inductance L _t , the receiving coil inductance L _r and the mutual inductance M _tr between the transmitting coil and the receiving coil calculated in step 4 , the calculation formula is shown in Equation (4).

In this embodiment, the calculated coupling coefficient between the transmitting coil and the receiving coil is k _tr =0.1281.

Step 6: Set the radius of the driving coil to r _di . When the distance remains unchanged and the transmitting coil is determined, determine the distance between the driving coil and the transmitting coil according to the calculation formula (5) of the mutual inductance and the calculation formula (6) of the coupling coefficient. The implicit function relationship between the coupling coefficient k _dit and the drive coil radius r _di .

Among them, r _t is the radius of the transmitting coil; d′ is the distance between the lateral offset (between the central axis) of the driving coil and the transmitting coil; k′ ² =4α′V′((1+α′V′) ² +β ′ ² ) ^-1 , where α′=r _t r _di ^-1 , β′=cr _di ^-1 , V′=(1+d′ ² r _t ^-2 -2d′r _t ^{- 1} cosφ) ^1/2 , c is the distance between the plane where the driving coil and the transmitting coil are located. In order to reduce the volume of the transmitting end, c takes a smaller value. In this embodiment, c=0.025m.

Step 7: The inductance L _di of the drive coil and r _di have the following relationship,

L _di =μ ₀ r _di [ln(8r _di /a)-1.75] (7)

Then the quality factor of the driving coil Q _di =ω ₀ L _di /R _di is also a function of the radius r _di of the driving coil; according to the conditional expression (2) that the wireless power transmission system satisfies when the transmission efficiency is maximum, the radius of the unique driving coil is determined. In this embodiment, when the transmission distance is d ₁ =0.1m, the determined driving coil radius is r _d1 =0.095m.

Conditions that should be met to transmit the maximum efficiency of the system It is converted into an implicit function related to the radius r _di of the driving coil, and the inductance of the driving coil is reversely deduced by solving the optimal radius r _di , and then the series compensation capacitance of the driving coil is obtained.

Step 8: Determine the drive coil inductance L _di according to the drive coil radius r _di determined in step 7 and equation (7); according to the resonant frequency formula Determine the drive coil series compensation capacitance C _di . In this embodiment, when the transmission distance is d ₁ =0.1m, the determined driving coil inductance is L _d1 =2.245 μH, and the driving coil series compensation capacitance is C _d1 =61.363pF. The system load coil and drive coil parameters are completely consistent. At this time, the system performs wireless power transmission with maximum efficiency.

Step 9: Determine whether the loop variable i is equal to n. If so, the configuration of the drive coil is completed; if not, then i=i+1, increase the transmission distance by an equal amount, and return to step 2 to determine the new drive coil radius and inductance. and series compensation capacitor.

In this embodiment, when the transmission distance changes from d ₁ =0.1m to d ₂ =0.2m according to the principle of equal increment, repeat the above steps 2 to 9 to determine the new driving coil radius r _d2 =0.075m, and the driving coil The inductor L _d2 =1.683μH and the drive coil are connected in series with the compensation capacitor C _d2 =81.853pF. The load coil follows the change of the drive coil, so that the system still meets the maximum efficiency transmission conditions. When the transmission distance becomes d ₃ =0.3m again, repeat the above steps 2 to 9, and you can determine the new driving coil radius r _d3 =0.06m, the driving coil inductance L _d3 =1.279μH and the driving coil series compensation capacitor C _d3 = 107.71pF, the load coil follows the change of the drive coil, so that the system still meets the maximum efficiency transmission condition. When the transmission distance becomes d ₄ =0.4m again, repeat the above steps 2 to 8 to determine the new driving coil radius r _d4 =0.055m, the driving coil inductance L _d4 =1.084μH and the driving coil series compensation capacitor C _d4 =127.08pF, the load coil follows the change of the drive coil, so that the system still meets the maximum efficiency transmission condition.

In the specific implementation, the order of the solution process (step 2 to step 8) corresponding to each transmission distance is not limited. As long as the corresponding sizes and inductance and capacitance parameters of the n drive coils are determined, the configuration is completed.

Based on the transmission efficiency of different coil radii under all transmission distances, a fitting curve diagram of transmission distance and efficiency under different coil radii is drawn, as shown in Figure 4, which is the transmission distance and transmission under different coil radii obtained in this embodiment. Fitted curve plot of efficiency. When the system performs wireless power transmission, according to the actual transmission distance, the driving coil whose radius, inductance and series compensation capacitance meet the conditions of maximum transmission efficiency is selected from n drive coils to be turned on, so that the system always operates in a state of maximum efficiency transmission. Wireless power transmission. In this embodiment, when the transmission distance changes within 0.5m, according to the corresponding relationship between the transmission distance and the four transmission efficiency values in the graph, the coil radius corresponding to the largest transmission efficiency is selected, and then the four configured Among the drive coils, the drive coil with the radius selected by the selector switch is turned on. At this time, the system energy transmission efficiency reaches the maximum. Therefore, when the transmission distance continues to change, by comparing the relationship between transmission distance and efficiency under different coil radii, it can be determined that at any transmission distance, the transmission method with the highest efficiency can be achieved by switching coils.

The wireless power transmission system and its distance-adaptive driving coil configuration method proposed in this embodiment can well solve the problem of a sharp decline in the transmission efficiency of the wireless power transmission system when the transmission distance changes, laying a solid foundation for the application of wireless power transmission technology in COSCO. Provides clear guidance for achieving range-adaptive maximum efficiency transmission within a range.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it can still be used Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent substitutions are made to some or all of the technical features; however, these modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the scope of the claims of the present invention.

Claims (1)

1. A distance-adaptive driving coil configuration method for a wireless power transmission system, used to configure a driving coil in a wireless power transmission system, which is characterized by: The wireless power transmission system is a non-coaxial four-coil magnetic coupling resonant system, including a high-frequency driving power supply (1), a driving coil group (2), a transmitting coil (3), a receiving coil (4) and a load coil group ( 5); The high-frequency driving power supply (1) and the driving coil group (2) are connected in series to form a driving circuit loop; the two ends of the load coil group (5) are connected to the load that requires electricity to form a load circuit loop; The transmitting coil (3) and the receiving coil (4) are independently and coaxially arranged between the driving coil group (2) and the load coil group (5). The transmitting coil (3) and the receiving coil (4) are completely symmetrical; the driving coil The group (2) includes n parallel-connected drive coils, and the load coil group (5) includes n parallel-connected load coils. The load coil group (5) is completely symmetrical with the drive coil group (2); the drive coil, the transmitting coil, Both the receiving coil and the load coil include an inductor coil and a series compensation capacitor. One end of the inductor coil in the drive coil group (2) and the load coil group (5) is connected to one point, and the other end is connected in series with a corresponding series compensation capacitor; high frequency The driving power supply (1) and the driving coil group (2), and the load coil group (5) and the load requiring electricity (6) are all connected through the selector switch (11) to ensure that the driving coil group (2) The drive coil is selectively turned on according to the transmission distance, and the load coil is turned on relatively symmetrically; n drive coils have a non-coaxial structure and are in the same plane; n load coils have a non-coaxial structure and are in the same plane, the specific value of n Configuration is determined based on the maximum transmission distance; Calculate the transmission efficiency expression of the wireless power transmission system, and obtain the conditions that the coupling coefficient and coil quality factor should meet when the system reaches maximum efficiency transmission. By converting this condition into an implicit function related to the drive coil radius, we can obtain The optimal radius of the driving coil is then determined, and the inductance and series compensation capacitance of the driving coil are determined to complete the configuration of a driving coil. The parameters of the load coil and the driving coil are completely consistent; then the transmission distance between the transmitting coil and the receiving coil is changed, and the above is still used. Method to configure a new drive coil; then change the transmission distance between the transmitting coil and the receiving coil, and then configure a new drive coil using the above method; this cycle continues until n drive coils are configured and the entire drive coil group is completed Configuration; when the system performs wireless power transmission, according to the actual transmission distance, the driving coil whose radius, inductance and series compensation capacitance meet the maximum transmission efficiency conditions is selected from n drive coils to be turned on, so that the system always transmits at maximum efficiency. status for wireless power transmission; The transmission distance between the transmitting coil and the receiving coil changes in equal increments, that is, the distance difference between two adjacent transmission distances is Among them, D is the maximum transmission distance, that is, the maximum distance between the transmitting coil and the receiving coil defined according to actual conditions. The transmission distances in the configuration are _di =i·Δd, i=1,2,...,n; The specific steps to obtain the optimal radius of the drive coil and then determine the inductance and series compensation capacitance of the drive coil are as follows: Step 1: Set the basic parameters of the wireless power transmission system, and initialize the loop variable i = 1; set the angular frequency of the high-frequency driving source to ω ₀ , and the driving coil, transmitting coil, receiving coil and load coil of the system all meet the requirements of Resonance occurs at this angular frequency; the inductance, resistance, quality factor and series compensation capacitance of the system transmitting coil and receiving coil are the same, that is, L _t =L _r , R _t =R _r , Q _t =Q _r , C _t =C _r ; The inductance parameters of the transmitting coil and the receiving coil are artificially set, and the inductance parameters of the driving coil and the load coil are calculated. The inductance, series compensation capacitance, resistance and quality factor of the driving coil and the load coil are the same respectively, that is, L _di = L _li , R _di =R _li , C _di =C _li , Q _di =Q _li , i=1,2,…,n; all coils in the system use the same winding radius, denoted as a; Step 2: When the transmission distance between the transmitting coil and the receiving coil is _di , determine the transmission efficiency expression of the wireless power transmission system as shown in Equation (1); Among them, k _dit and k _tr respectively represent the coupling coefficient between the driving coil and the transmitting coil, and the coupling coefficient between the transmitting coil and the receiving coil; Step 3: Find the partial derivative of the transmission efficiency expression (1) Determine the conditions that the wireless power transmission system should satisfy when maximizing transmission efficiency: Equation (2); Step 4: Calculate the mutual inductance M _tr between the transmitting coil and the receiving coil through the mutual inductance calculation formula. The mutual inductance calculation formula is shown in Equation (3); Among them, μ ₀ is the vacuum magnetic permeability, the value is 4π×10 ^-7 ; r _t is the radius of the transmitting coil, r _r is the radius of the receiving coil; d is the lateral offset distance between the transmitting coil and the receiving coil; k ² = 4αV((1+αV) ² +β ² ) ^-1 , where α=r _r r _t ^-1 , β=d _i r _t ^-1 , d _i is the distance between the plane of the transmitting coil and the receiving coil, that is, the transmission distance between the transmitting coil and the receiving coil; Ψ(k)=(1-k ² /2)K(k)-E(k) , K(k) and E(k) are elliptic integrals of the first kind and elliptic integrals of the second kind respectively,/> Step 5: Determine the coupling coefficient k _tr between the transmitting coil and the receiving coil based on the transmitting coil inductance L _t , the receiving coil inductance L _r and the mutual inductance M _tr between the transmitting coil and the receiving coil. The calculation formula is as shown in Equation (4) Show; Step 6: Set the radius of the driving coil to r _di . When the distance remains unchanged and the transmitting coil is determined, determine the distance between the driving coil and the transmitting coil according to the calculation formula (5) of the mutual inductance and the calculation formula (6) of the coupling coefficient. The implicit function relationship between the coupling coefficient k _dit and the drive coil radius r _di ; Among them, r _t is the radius of the transmitting coil; d′ is the lateral offset distance between the driving coil and the transmitting coil; k′ ² =4α′V′((1+α′V′) ² +β ^′2 ) ^-1 , Among them, α′=r _t r _di ^-1 , β′=cr _di ^-1 , V′=(1+d′ ² r _t ^-2 -2d′r _t ^-1 cosφ) ^1/2 , c is the driving coil and The distance between the planes where the transmitting coil is located; Step 7: The inductance L _di of the drive coil has the following relationship with the radius r _di , L _di =μ ₀ r _di [ln(8r _di /a)-1.75] (7) Then the quality factor of the driving coil is Q _di =ω ₀ L _di /R _di , which is a function of the radius r _di of the driving coil; According to the conditional expression (2) satisfied by the wireless power transmission system when the transmission efficiency is maximum, determine the unique driving coil radius r _di ; Step 8: Determine the inductance L _di of the drive coil according to the drive coil radius r _di determined in step 7 and equation (7); according to the resonant frequency formula Determine the series compensation capacitance C _di of the driving coil. At this time, the system performs wireless power transmission with maximum efficiency; Step 9: Determine whether the loop variable i is equal to n. If so, the step ends and the configuration of the drive coil is completed; if not, then i=i+1, increment the transmission distance by an equal amount, and return to step 2 to determine the new drive coil. radius, inductance and series compensation capacitance.