JP6758630B2 - Wireless power transfer system - Google Patents

Description

The present invention relates to a wireless power transmission system.

Mobile terminals such as smartphones and tablet PCs (personal computers) and electric vehicles are in the stage of widespread use, but it is hard to say that the storage batteries essential for these have the necessary and sufficient capacity at present. By arranging charging infrastructure everywhere, it is possible to create a situation where the storage battery is always fully charged. As one of the measures, wireless power transmission is suddenly attracting attention. Various methods such as an electromagnetic induction method, an electric field resonance method (also referred to as an electric field resonance method), a magnetic field resonance method (also referred to as a magnetic field resonance method), and a radio wave emission method have been proposed for wireless power transmission. In particular, the electromagnetic induction method and the electric / magnetic field resonance method have a problem that the power transmission efficiency is significantly lowered depending on the relative positional relationship between the power transmitting device and the power receiving device.

In a general wireless power transmission system, the transmission efficiency is designed to be maximized when the power transmission device and the power reception device are in a facing (directly in front) positional relationship. If the power transmitting device and the power receiving device deviate from each other in the opposite direction, the power transmission efficiency is significantly reduced (FIG. 4A). FIG. 4A is a side view schematically showing the positional relationship between the power transmission device 501 and the power receiving devices 502 to 504. The power transmission device 501 shown in FIG. 4A is horizontally installed in the space 513 between the floor surface 511 and the ceiling surface 512. The power receiving devices 502 to 504 are horizontally placed on the floor surface 514 in the indoor space 515 between the ceiling surface 512 and the floor surface 514. Of the power receiving devices 502 to 504, the power receiving device 503 faces the power transmitting device 501, and the power receiving devices 502 and 504 do not face each other. In this case, the power transmission efficiency from the power transmission device 501 to the power receiving device 503 is high, and the power transmission efficiency from the power transmission device 501 to the power receiving devices 502 and 504 is low. For example, it has been reported that the power transmission efficiency is reduced to less than half when the power transmission / reception device deviates from the facing direction by several cm. In order to prevent a decrease in transmission efficiency, a method of physically rotating the power transmission device can be considered, but there are problems that it is difficult to install the power transmission device and that the installation space is expensive (Fig. 4 (b)). .. FIG. 4B is a side view schematically showing the positional relationship between the power transmitting device 505 and the power receiving device 506. In FIG. 4B, the same components as those shown in FIG. 4A are designated by the same reference numerals. The power transmission device 505 is installed in a state of being rotated obliquely with respect to the ceiling surface 512 so as to partially protrude from the space 513 between the floor surface 511 and the ceiling surface 512. The power receiving device 506 is horizontally placed on the floor surface 514 at a position deviated from directly below the power transmission device 505 in the rotation direction of the power transmission device 505. In this case, the power transmission efficiency from the power transmitting device 505 to the power receiving device 506 is higher than that when the power receiving device 506 is located directly below the power transmitting device 505.

As a conventional technique for reducing the influence of deviation, there is a system such as the magnetic field resonance type power feeding system described in Patent Document 1, which reduces the influence of deviation from the positional relationship that maximizes transmission efficiency. However, even in this system, the power transmission efficiency decreases when the deviation from the facing position becomes large.

Japanese Unexamined Patent Publication No. 2013-200812

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a wireless power transmission system capable of realizing highly efficient power transmission in an arbitrary positional relationship between a power transmission device and a power receiving device. To do.

In order to solve the above problems, one aspect of the present invention is a transmission device having a plurality of transmission side resonant circuits including a coil and an inductance circuit and having an AC power supply for supplying power to each transmitting side resonant circuit, and a coil and an inductance circuit. It is provided with a power receiving device having one or a plurality of power receiving side resonant circuits and having a load circuit of each of the power receiving side resonant circuits, and the plurality of transmitting side resonant circuits and the one or the plurality of receiving side resonant circuits are resonantly coupled. This is a system for wirelessly transmitting power from the AC power supply to the load circuit, and each inductance of the respective inductance circuits can be obtained when the transmitting device and the power receiving device are arranged in a predetermined positional relationship. The power transmission efficiency calculated by using the circuit equation representing the power transmitting device and the power receiving device with each self-inductance of each coil and each mutual inductance between the coils as a constant and each resonance as a variable. It is a wireless power transmission system having each value determined based on.

Further, one aspect of the present invention is a power transmission device having a plurality of transmission side resonance circuits including a coil and a reactance circuit, and having an AC power supply for supplying power to each of the transmission side resonance circuits via a first reactance circuit, and a coil. A power receiving device having a plurality of power receiving side resonance circuits including a reactance circuit and a load circuit connected to each power receiving side resonance circuit via a second reactance circuit is provided, and the plurality of power transmitting side resonance circuits and the plurality of power receiving side resonance circuits are provided. It is a system that wirelessly transmits power from the AC power supply to the load circuit by resonantly coupling with the power receiving side resonance circuit of the above, and each reactance of the reactance circuit, the first reactance circuit, and the second reactance circuit is The power transmission obtained when the power transmission device and the power receiving device are arranged in a predetermined positional relationship, with each self-inductance of each coil and each mutual inductance between the coils as a constant and each reactance as a variable. It is a wireless power transmission system having each value determined based on the transmission efficiency of the power calculated by using the circuit equation representing the device and the power receiving device.

According to the present invention, highly efficient power transmission can be realized in an arbitrary positional relationship between the power transmitting device and the power receiving device.

It is a schematic diagram for demonstrating the structural example of the Embodiment of this invention. It is a circuit diagram for demonstrating the structural example of the Embodiment of this invention. It is a schematic diagram for demonstrating the application example of the wireless power transmission system 10 shown in FIG. It is a schematic diagram for demonstrating the background technique of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram schematically showing a configuration example of an embodiment of a wireless power transmission system according to the present invention. The wireless power transmission system 10 shown in FIG. 1 is a magnetic field resonance type wireless power transmission system, and includes a power transmission device 1 and a power receiving device 2.

The power transmission device 1 has a plurality of resonance circuits (transmission side resonance circuits) 11, 12, 13 and 14 including a coil (inductor) and a reactance circuit, and is an alternating current that supplies power to the resonance circuits 11, 12, 13 and 14. It has a power source 15. Further, the power transmission device 1 has a reactance circuit (first reactance circuit) 16. In the present application, the reactance circuit is a circuit composed of a capacitor having a capacitive reactance and a coil having an inductive reactance. For example, each reactance circuit can be composed of one capacitor each. Further, the resonance frequency of the resonance circuit including the coil and the reactance circuit is a frequency at which the inductive reactance and the capacitive reactance of the resonance circuit become equal.

The resonant circuit 11 has a coil 111 and a reactance circuit 112 connected in series. The resonant circuit 12 has a coil 121 and a reactance circuit 122 connected in series. The resonance circuit 13 has a coil 131 and a reactance circuit 132 connected in series. The resonant circuit 14 has a coil 141 and a reactance circuit 142 connected in series. The coils 111, 121, 131, and 141 are arranged so that the axial direction is the vertical direction with respect to the floor surface 514. Further, the power transmission device 1 has a reactance circuit 16 and supplies electric power from the AC power supply 15 to the resonance circuits 11, 12, 13 and 14 via the reactance circuit 16. The output frequency of the AC power supply 15 and the resonance frequencies of the resonance circuits 11, 12, 13 and 14 are the same.

Each end of the coils 111, 121, 131 and 141 is commonly connected to one of the outputs of the AC power source 15. The other end of the coil 111 is connected to one end of the reactance circuit 112. The other end of the coil 121 is connected to one end of the reactance circuit 122. The other end of the coil 131 is connected to one end of the reactance circuit 132. The other end of the coil 141 is connected to one end of the reactance circuit 142. The other ends of the reactance circuits 112, 122, 132 and 142 are commonly connected to one end of the reactance circuit 16. The other end of the reactance circuit 16 is connected to the other end of the output of the AC power supply 15.

On the other hand, the power receiving device 2 has a resonance circuit (power receiving side resonance circuit) 21 including a coil and a reactance circuit, and also has a load circuit 22 of the resonance circuit 21. The resonance circuit 21 has a coil 211 and a reactance circuit 212 connected in series. The resonance frequency of the resonance circuit 21 is the same as the resonance frequency of the resonance circuits 11, 12, 13 and 14. One end of the coil 211 is connected to one end of the load circuit 22. The other end of the coil 211 is connected to one end of the reactance circuit 212. The other end of the reactance circuit 212 is connected to the other end of the load circuit 22. The load circuit 22 may be, for example, a single light bulb as shown in the figure, or may include a rectifier circuit, a voltage conversion circuit, a storage battery, other electric / electronic circuits, and the like.

The wireless power transmission system 10 of the present embodiment wirelessly transmits power from the AC power supply 15 to the load circuit 22 by resonantly coupling the plurality of resonance circuits 11 to 14 on the power transmission side and the resonance circuits 21 on the power reception side. Further, in the wireless power transmission system 10, the power transmission device 1 and the power receiving device 2 are arranged so as to have a predetermined positional relationship. In the present embodiment, the positional relationship between the power transmitting device 1 and the power receiving device 2 is, for example, the coordinates of the three-dimensional (or two-dimensional) power transmitting device 1 and the coordinates of the power receiving device 2, and the resonance circuits 11, 12, 13 and 14. It can also be defined by the axial direction of each coil of the resonant circuit 21. For example, even if the positions of the power receiving devices 2 are the same, if the directions of the coils 211 are different, the positional relationship will be different.

Further, in the present embodiment, each self-inductance of the coils 111, 121, 131 and 141 and the coil 211 and each mutual inductance between the coils are actually measured in a predetermined positional relationship between the power transmission device 1 and the power receiving device 2. It is acquired in advance by obtaining it by calculation processing or by combining measurement and calculation processing. Acquiring in advance means acquiring each reactance of the reactance circuits 112, 122, 132 and 142 and the reactance circuit 212 (or the reactance circuit 16) before setting. Then, the reactances of the reactance circuits 112, 122, 132 and 142 and the reactance circuit 212 (or the reactance circuit 16) are set to optimized values so that the power transmission efficiency becomes high. That is, in the wireless power transmission system 10 of the present embodiment, the self and mutual inductance of each coil are acquired according to the positional relationship between the power transmission device 1 and the power receiving device 2, and then each reactance of each reactance circuit is set to, for example, constant. The combination of each reactance that maximizes the power transmission efficiency (or high efficiency above a certain level) is selected by changing the range, and the reactance circuit having the selected value is mounted on the power transmission device 1 and the power receiving device 2. By setting each reactance of each reactance circuit in this way, in the present embodiment, when power is supplied in a specific direction (that is, even when arranged in an arbitrary positional relationship) in the magnetic field resonance type wireless power transmission system, the power transmission device High power transmission efficiency can be realized without physical rotation of.

The embodiment of the present invention is not limited to the configuration shown in FIG. For example, the number of resonance circuits 11 to 14 included in the power transmission device 1 is not limited to four, and may be two or more. However, when adjusting the feeding direction three-dimensionally, it is desirable that the number is three or more. Further, the number of resonance circuits 21 included in the power receiving device 2 is not limited to one, and may be two or more. Further, when the number of resonance circuits is two or more, a reactance circuit (second reactance circuit) may be provided between each resonance circuit and the load circuit 22.

Next, the procedure for determining each reactance of each reactance circuit in the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a circuit diagram showing a configuration example of an embodiment of the wireless power transmission system according to the present invention. The wireless power transmission system 10a shown in FIG. 2 includes a power transmission device 1a and a power reception device 2a. The power transmission device 1a includes a resonance circuit 31, a resonance circuit 32, an AC voltage source 301, a resistor (register) 302, and a reactance circuit (first reactance circuit) 303. Here, the AC voltage source 301 is an ideal voltage source having an internal resistance of zero, and the resistance 302 corresponds to the internal resistance of an actual voltage source. The resonance circuit 31 has a reactance circuit 304 and a coil 305 connected in series. The resonance circuit 32 has a reactance circuit 306 and a coil 307 connected in series. The power receiving device 2a has a resonance circuit 41, a resonance circuit 42, a reactance circuit (second reactance circuit) 405, and a resistor 406. The resonance circuit 41 has a reactance circuit 401 and a coil 402 connected in series. The resonant circuit 42 has a reactance circuit 403 and a coil 404 connected in series.

In the power transmission device 1a, one of the outputs of the AC voltage source 301 is grounded and the other is connected to one end of the resistor 302. The other end of the resistor 302 is connected to one end of the reactance circuit 303. The other end of the reactance circuit 303 is connected to each end of the reactance circuit 304 and the reactance circuit 306. The other end of the reactance circuit 304 is connected to one end of the coil 305. The other end of the reactance circuit 306 is connected to one end of the coil 307. The other ends of the coil 305 and the coil 307 are grounded.

In the power receiving device 2a, one end of the coil 402 is connected to one end of the reactance circuit 401, and the other end is grounded. One end of the coil 404 is connected to one end of the reactance circuit 403, and the other end is grounded. The other ends of the reactance circuit 401 and the reactance circuit 403 are connected to one end of the reactance circuit 405. The other end of the reactance circuit 405 is connected to one end of the resistor 406. The other end of the resistor 406 is grounded.

In the wireless power transmission system 10 shown in FIG. 1, the power transmission device 1 has four resonance circuits 11 to 14, and the power receiving device 2 has one resonance circuit 21. On the other hand, in the wireless power transmission system 10a shown in FIG. 2, the power transmission device 1a has two resonance circuits 31 and 32, and the power receiving device 2a has two resonance circuits 41 and 42. In the wireless power transmission system 10a shown in FIG. 2, the resonant circuits 31 and 32 correspond to, for example, the resonant circuits 11 and 12 shown in FIG. The reactance circuit 303 of FIG. 2 corresponds to the reactance circuit 16 of FIG. The AC voltage source 301 and resistor 302 of FIG. 2 correspond to the AC power source 15 of FIG. For example, the resonant circuit 41 of FIG. 2 corresponds to the resonant circuit 21 of FIG. The resistor 406 of FIG. 2 corresponds to the load circuit 22 of FIG. Further, the power receiving device 2a of FIG. 2 is newly provided with a resonance circuit 42 and a reactance circuit 405.

In addition, the output voltage of the AC voltage source 301 is a voltage _{V in.} The self-inductances of the coils 305, 307, 402 and 404 are inductances L ₁₁ , L ₂₂ , L ₃₃ and L ₄₄ , respectively. The mutual inductance between coil 305 and coil 307 is inductance L ₁₂ or L ₂₁ . The mutual inductance between the coil 305 and the coil 402 is an inductance L ₁₃ or L ₃₁ . The mutual inductance between coil 305 and coil 404 is inductance L ₁₄ or L ₄₁ . The mutual inductance between the coil 307 and the coil 402 is an inductance L ₂₃ or L ₃₂ . The mutual inductance between coil 307 and coil 404 is inductance L ₂₄ or L ₄₂ . The mutual inductance between the coil 402 and the coil 404 is an inductance L ₃₄ or L ₄₃ . The resistance value (resistance) of the resistor 302 (the internal resistance of the actual AC voltage source) is the resistance value R ₀ . The resistance value of the resistor 406 is the resistance value _RL .

Further, it is assumed that the reactances of the reactance circuits 303, 304, 306, 401, 403 and 405 are reactances X ₀ , X ₁ , X ₂ , X ₃ , X ₄ and X ₅ , respectively. It is assumed that the currents flowing through the resistance 302, the reactance circuit 304, the reactance circuit 306, the reactance circuit 401, the reactance circuit 403 and the resistance 406 are the currents i ₀ , i ₁ , i ₂ , i ₃ , i ₄ and i ₅ , respectively. The terminal voltage of the series circuit of the AC voltage source 301 and the resistor 302 (that is, the output circuit of the actual AC voltage source), the coil 305, the coil 307, the coil 402, the coil 404, and the resistor 406 are the voltages V ₀ , V ₁ , respectively. Suppose they are V ₂ , V ₃ , V ₄ and V ₅ . The voltage V ₅ is the output voltage V _out of the wireless power transmission system 10a.

The circuit showing the wireless power transmission system 10a shown in FIG. 2 can be represented by the following circuit equation. The following circuit equation represents a steady-state sinusoidal AC circuit with currents i ₀ , i ₁ , i ₂ , i ₃ , i ₄ and i _5, and voltages V ₀ , V ₁ , V ₂ , V ₃ , V ₄ and V ₅ are represented by facers, and circuit elements are represented by complex impedance.

Here, ω is the angular frequency of the output of the AC voltage source 301, and j is an imaginary unit.

In the present embodiment, when determining each reactance of each reactance circuit using the above circuit equation, the self-inductances L ₁₁ and L are determined in a predetermined positional relationship between the power transmitting device 1a and the power receiving device 2a prior to the determination. Measured or calculated the mutual reactances L ₁₂ or L ₂₁ , L ₁₃ or L ₃₁ , L ₁₄ or L ₄₁ , L ₂₃ or L ₃₂ , L ₂₄ or L ₄₂ , L ₃₄ or L ₄₃ with ₂₂ , L ₃₃ and L _44. Get by. In addition, the resistance value R ₀ (the internal resistance of the actual AC voltage source) and the resistance value _RL are also acquired by actual measurement or calculation. Further, the voltage V _in is is set to a predetermined value. In this case, the voltage _{V in,} the inductance _{L 11, L 22, L 33} and _{L 44, L 12} or _{L 21, L 13} or _{L 31, L 14} or _{L 41, L 23} or _{L 32, L 24} or _{L 42,} L ₃₄ or L ₄₃ , resistance values R ₀ and _RL are known values (ie, constants). On the other hand, the reactances X ₀ , X ₁ , X ₂ , X ₃ , X ₄ and X ₅ of the reactance circuits 303, 304, 306, 401, 403 and 405 are undetermined values (that is, variables).

Then, each reactance of each reactance circuit is determined so that the power transmission efficiency η shown below is maximized.

Here, a power supplied to the P _L resistor 406, P _in is the power output from the AC voltage source 301, is expressed as follows.

Here, the function Re is a function that returns the real part, and the function conj is a function that returns the conjugate complex number.

The value of each reactance of each reactance circuit that maximizes the power transmission efficiency η (or high efficiency above a certain level) is calculated by, for example, changing each reactance within a certain range to calculate the power transmission efficiency η multiple times. It can be determined by selecting the combination of each reactance at which the power transmission efficiency η is the maximum (or high efficiency above a certain level) among the plurality of power transmission efficiency ηs. When the maximum (or high efficiency above a certain level) power transmission efficiency η is calculated by combining a plurality of combinations, for example, the Q value (Quality factor) of the resonant circuit, the coupling coefficient k, and the like are taken into consideration. The combination can be selected.

As described above, according to the present embodiment, highly efficient wireless power supply can be realized regardless of the positional relationship of power transmission / reception. In addition, since there is no need for physical rotation of the power transmission device, the installation space and installation method are the same as those of a normal power transmission device.

FIG. 3 shows an application image when the wireless power transmission system 10 shown in FIG. 1 (or the wireless power transmission system 10a shown in FIG. 2) is used for the electric serving car 3 in a hospital. FIG. 3 is a side view schematically showing the positional relationship between the power transmission device 1 and the power receiving device 2 installed in the electric serving car 3. In FIG. 3, the same components as those shown in each figure are designated by the same reference numerals, and the description thereof will be omitted as appropriate. The wireless power transmission system 10 shown in FIG. 3 is a system that charges a storage battery (not shown) of the electric serving car 3 in front of a kitchen or the like by wireless power transmission. If there is a duct 516, lighting equipment, or the like behind the ceiling of the standby place of the electric serving car 3, it is difficult to install the power transmission device 1 directly above the standby place. In this case, the power transmission efficiency is lowered in the conventional system, but in this system, even if the power transmission device 1 is installed in an oblique direction other than the vertical direction of the power receiving device 2, the power transmission device 1 is installed horizontally in the normal installation. Highly efficient power transmission is possible in any way.

As described above, according to each embodiment of the present invention, highly efficient power transmission can be realized in an arbitrary positional relationship between the power transmitting device and the power receiving device. At that time, the power transmission device does not have to be physically rotated.

It should be noted that the embodiments of the present invention are not limited to those described above, and include those within a range not departing from the gist of the invention. For example, each reactance circuit and each coil may have a configuration in which a plurality of reactance circuits and a plurality of coils are connected in parallel or in series.

1, 1a Transmission device 2, 2a Power receiving device 10, 10a Wireless power transmission system 11, 12, 13, 14, 21, 31, 32, 41, 42 Resonant circuit 15 AC power supply 16, 112, 122, 132, 142, 212 , 303, 304, 306, 401, 403, 405 Reactance circuit 22 Load circuit 111, 121, 131, 141, 211, 305, 307, 402, 404 Coil 301 AC voltage source 302, 406 Resistor

Claims (2)

A power transmission device having a plurality of power transmission side resonance circuits composed of a coil and a reactance circuit and having an AC power supply for supplying power to each power transmission side resonance circuit.
It is provided with a power receiving device having one or more power receiving side resonance circuits including a coil and a reactance circuit, and having a load circuit of each power receiving side resonance circuit.
A system for wirelessly transmitting electric power from the AC power supply to the load circuit by resonantly coupling the plurality of power transmitting side resonance circuits and the one or more power receiving side resonance circuits.
Each reactance of each reactance circuit has a constant of each self-inductance of each coil and each mutual inductance between each coil obtained when the power transmission device and the power receiving device are arranged in a predetermined positional relationship. A wireless power transmission system having each value determined based on the power transmission efficiency calculated by using a circuit equation representing the power transmission device and the power reception device with each reactance as a variable. A power transmission device having a plurality of power transmission side resonance circuits composed of a coil and a reactance circuit, and having an AC power source for supplying power to each power transmission side resonance circuit via a first reactance circuit.
It is provided with a power receiving device having a plurality of power receiving side resonance circuits composed of a coil and a reactance circuit, and having a load circuit connected to each power receiving side resonance circuit via a second reactance circuit.
A system for wirelessly transmitting electric power from the AC power supply to the load circuit by resonantly coupling the plurality of power transmitting side resonance circuits and the plurality of power receiving side resonance circuits.
Each reactance of the reactance circuit, the first reactance circuit, and the second reactance circuit obtains each self-inductance of the coil and the self-inductance obtained when the power transmission device and the power receiving device are arranged in a predetermined positional relationship. A radio having each value determined based on the power transmission efficiency calculated by using a circuit equation representing the power transmitting device and the power receiving device in which each mutual inductance between each coil is a constant and each reactance is a variable. Power transmission system.

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