JP7177567B1 - Power transmission device for wireless power transmission system - Google Patents

Abstract

Disclosed is a power transmission device for a wireless power transmission system capable of improving power transmission efficiency more than conventionally when a plurality of power transmission coils are used. A power transmitting device 2 in a wireless power transmitting system 1 that performs wireless power transmission between power transmitting coils 11, 12, 13 and a power receiving coil 20, and is connected to a plurality of power transmitting coils 11, 12, 13 and a predetermined power source 30. and an inverter circuit 40 that supplies power to the power transmission coils 11, 12, and 13. The inverter circuit 40 includes a plurality of legs 41, 42, and 43 that are provided for each of the power transmission coils 11, 12, and 13 and connected in parallel. have

Description

The present invention relates to a power transmission device of a wireless power transmission system that performs wireless power transmission between a power transmission coil and a power reception coil.

A wireless power transmission system is known in which a plurality of power transmission coils are arranged side by side on the same plane and wireless power transmission is performed without finely controlling the position of the power reception coils (see, for example, Patent Document 1). The wireless power transmission device described in Patent Document 1 includes a transmission antenna including a series resonant capacitor and a plurality of switchable transmission coils, an inverter whose output side is connected to the transmission antenna, and a controller that controls the inverter. determines one power transmission coil to be used for power transmission based on a predetermined condition.

JP 2018-78754 A

However, in the wireless power transmission system described in Patent Literature 1, one power transmission coil is used for power transmission, so the power transmission efficiency decreases depending on the position of the power reception coil. For example, when the power transmission coils are arranged in an array, if the power reception coils are positioned above the joints of the power transmission coils, the power transmission efficiency is greatly reduced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power transmission device for a wireless power transmission system that can improve power transmission efficiency compared to the conventional one when a plurality of power transmission coils are used. to provide.

In order to achieve the above object, in the present invention,
A power transmission device in a wireless power transmission system that performs wireless power transmission between a power transmission coil and a power reception coil,
a plurality of the power transmission coils;
a power transmission device of a wireless power transmission system, comprising: an inverter circuit connected to a predetermined power supply, having a plurality of legs provided for each of the power transmission coils and connected in parallel to each other, and supplying power to each of the power transmission coils; provided.

The power transmission device of the wireless power transmission system preferably includes a power factor compensation circuit forming a resonance circuit together with each of the power transmission coils.

In the power transmission device of the wireless power transmission system,
one end sides of the power transmission coils are connected to each other;
A connection portion on one end side of each power transmission coil is connected to a predetermined voltage portion in the inverter circuit,
The power factor compensation circuit is interposed between a connection portion on one end side of each of the power transmission coils and the predetermined voltage portion of the inverter circuit, and the inductance or capacitance is set based on the mutual inductance between the power transmission coils. preferably includes an inductor or capacitor.

In the power transmission device of the wireless power transmission system, the power factor compensation circuit is provided for each of the power transmission coils, and is a capacitor whose capacitance is set based on the self-inductance of each power transmission coil and the mutual inductance between the power transmission coils. is preferably included.

The power transmission device of the wireless power transmission system preferably includes a mutual inductance compensation circuit that adjusts the mutual inductance based on the mutual inductance difference between the power transmission coils.

In the power transmission device of the wireless power transmission system,
one end sides of the power transmission coils are connected to each other;
A connection portion on one end side of each power transmission coil is connected to a predetermined voltage portion in the inverter circuit,
The power factor compensation circuit is interposed between a connection portion on one end side of each of the power transmission coils and the portion of the inverter circuit where the predetermined voltage is applied, and the mutual power between the power transmission coils adjusted by the mutual inductance compensation circuit is adjusted. Preferably, the inductance or capacitance is set based on the inductance.

In the power transmission device of the wireless power transmission system,
The power factor compensation circuit is configured to provide capacitance based on the self-inductance of each power transmission coil, the self-inductance of the mutual inductance compensation circuit, and the mutual inductance between the power transmission coils adjusted by the mutual inductance compensation circuit. is set and a capacitor is provided for each of said transmitting coils.

The power transmission device of the wireless power transmission system includes a control unit that controls the switching element of the leg of the inverter circuit,
It is preferable that the control unit controls the currents of the power transmission coils such that the current ratio of the power transmission coils becomes the mutual inductance ratio between the power transmission coils and the power reception coils.

Moreover, in the present invention,
A power transmission device in a wireless power transmission system that performs wireless power transmission between a power transmission coil and a power reception coil,
a plurality of the power transmission coils assigned to one of a plurality of power transmission groups;
an inverter circuit connected to a predetermined power supply, having a plurality of legs provided for each power transmission group and connected in parallel with each other, and supplying power to each power transmission group;
a switching circuit for switching a power supply destination such that the power from the inverter circuit is supplied to one of the power transmission coils selected from each of the power transmission groups; and a power transmission device for a wireless power transmission system. be.

According to the power transmission device of the wireless power transmission system of the present invention, when a plurality of power transmission coils are used, power transmission efficiency can be improved more than conventionally.

1 is a circuit diagram of a power transmitting device and a power receiving device of a wireless power transmission system showing a first embodiment of the present invention; FIG. It is plane explanatory drawing of a power transmission coil and a receiving coil. FIG. 4 is an explanatory diagram showing switching timing of each leg; It is plane explanatory drawing of the power transmission coil and power receiving coil which show the 2nd Embodiment of this invention. 1 is a circuit diagram of a power transmitting device and a power receiving device of a wireless power transmission system; FIG. It is a plane explanatory view of the power transmission coil which shows the 3rd Embodiment of this invention. 1 is a circuit diagram of a power transmitting device and a power receiving device of a wireless power transmission system; FIG. It is a plane explanatory view of the power transmission coil which shows the 4th Embodiment of this invention. 1 is a circuit diagram of a power transmitting device and a power receiving device of a wireless power transmission system; FIG. It is plane explanatory drawing of the power transmission coil and power receiving coil which show the 5th Embodiment of this invention. 1 is a circuit diagram of a power transmission device of a wireless power transmission system; FIG. It is a plane explanatory view of the power transmission coil which shows the 6th Embodiment of this invention. 1 is a circuit diagram of a power transmission device of a wireless power transmission system; FIG. It is plane explanatory drawing of the power transmission coil which shows the 7th Embodiment of this invention. 1 is a circuit diagram of a power transmission device of a wireless power transmission system; FIG. It is a circuit diagram of a power transmission device showing a modification. It is a circuit diagram of a power transmission device showing a modification. It is a circuit diagram of a power transmission device showing a modification. It is a circuit diagram of a power transmission device showing a modification. It is a circuit diagram of a power transmission device showing a modification. It is a circuit diagram of a power receiving device showing a modification. It is a circuit diagram of a power receiving device showing a modification. It is a circuit diagram of a power transmission device showing a comparative example. It is a simulation result which shows the power transmission efficiency of an Example and a comparative example.

1 to 3 show a first embodiment of the present invention, FIG. 1 is a circuit diagram of a wireless power transmission system, FIG. 2 is a plan view of power transmission coils and power reception coils, and FIG. 3 is switching of each leg. It is an explanatory view showing .

As shown in FIG. 1, this wireless power transmission system 1 includes a power transmission device 2 having a plurality of power transmission coils 11, 12, and 13, and a power reception device having a power reception coil 20 that performs wireless power transmission with the power transmission coils 11, 12, and 13. 3 and . In this embodiment, as shown in FIG. 2, three power transmission coils 11, 12, and 13 having a predetermined thickness and having a circular shape in plan view are arranged adjacently on the same plane so as not to overlap each other. In this embodiment, the three power transmission coils 11, 12, and 13 are the same. The power transmitting device 2 and the power receiving device 3 are relatively movable, and wireless power transmission is possible in a state where the power receiving coil 20 is in close proximity to each of the power transmitting coils 11 , 12 , and 13 .

As shown in FIG. 1 , the power transmission device 2 includes an inverter circuit 40 connected to a DC power supply 30 and supplying power to each power transmission coil 11 , 12 , 13 . The inverter circuit 40 has a plurality of legs 41, 42, 43 provided for each of the power transmission coils 11, 12, 13 and connected in parallel between positive and negative busbars. In this embodiment, since there are three power transmission coils 11, 12 and 13, there are also three legs 41, 42 and 43 correspondingly. Each leg 41, 42, 43 has positive side switching elements 41a, 42a, 43a connected to the positive side of the DC power supply 30 and negative side switching elements 41b, 42b, 43b connected to the negative side in series. It is connected. As the switching elements 41a, 41b, 42a, 42b, 43a, 43b, for example, transistors such as IGBTs, MOSFETs, and HEMTs can be used. Positive nodes 41c, 42c, 43c connected to the other ends of the power transmission coils 11, 12, 13 are set between the positive switching elements 41a, 42a, 43a and the negative switching elements 41b, 42b, 43b. .

The inverter circuit 40 also has a positive side capacitor 51 and a negative side capacitor 52 connected in series between the positive and negative bus lines. The positive side capacitor 51 and the negative side capacitor 52 equally divide the input voltage from the DC power supply 30 . That is, when the input voltage of the DC power supply 30 is E, the voltage between the positive side capacitor 51 and the negative side capacitor 52 is designed to be E/2. A negative node 53 connected to one end of each power transmission coil 11 , 12 , 13 is set between the positive capacitor 51 and the negative capacitor 52 .

As shown in FIG. 1, one end of each power transmission coil 11, 12, 13 is connected to each other. In this embodiment, so-called Y-connection is used, and a connection node 14 is set at one end of each of the power transmission coils 11 , 12 , and 13 . In this manner, one end of each of the power transmission coils 11 , 12 , 13 is connected to the intermediate voltage of the input voltage of the DC power supply 30 via the inductor 60 . The other end of each power transmission coil 11, 12, 13 is connected to each leg 41, 42, 43 via resonance capacitors 61, 62, 63, respectively. In this embodiment, the inductor 60 and the resonance capacitors 61, 62, 63 together with the power transmission coils 11, 12, 13 form a power factor compensation circuit 70 forming a resonance circuit.

The inductor 60 has an inductance set based on the mutual inductance between the power transmission coils 11 , 12 , and 13 . Also, the capacitance of each resonance capacitor 61 , 62 , 63 is set in consideration of the self-inductance of each power transmission coil 11 , 12 , 13 and the mutual inductance between each power transmission coil 11 , 12 , 13 .

Specifically, in the present embodiment, the self-inductances of the power transmission coils 11, 12, 13 are equal to each other, and the mutual inductances of the power transmission coils 11, 12, 13 are also equal to each other. However, since the power transmission coils 11, 12, and 13 weaken each other's magnetic fields when currents flow in the same direction, the value of mutual inductance is negative. When the operating angular frequency of the device is ω, the self-inductance of each power transmission coil 11, 12, 13 is L _t , and the mutual inductance between each power transmission coil 11, 12, 13 is −M _t (M _t > 0), each The capacitance _Ct of the resonant capacitors 61, 62, 63 and the inductance _L0 of the inductor 60 are
C _t =1/(ω ² (L _t +M _t ))
_{L0 = Mt}
is set.

Further, as shown in FIG. 1 , the power receiving device 3 has a resonance capacitor 21 and a load resistor 22 that are connected in series with the power receiving coil 20 . The power transmitted from the power transmission device 2 is supplied to the load resistor 22 . In the power receiving device 3, the resonance capacitor 21 forms a power factor compensation circuit on the power receiving side. When the self- _inductance of the receiving coil 20 is _Lr , the capacitance Cr of the resonance capacitor 21 is
C _r =1/(ω ² L _r )
is set.

The power transmission device 2 also has a control section 80 that controls switching operations of the switching elements 41a, 41b, 42a, 42b, 43a, and 43b. M _t1r , M _t2r , and M _t3r are mutual inductances between the first to third power transmission coils 11, 12, and 13 and the power reception coil 20, and I _t1 is the current of the first to third power transmission coils 11, 12, and 13. , _{It2 and It3 ,} the control unit 80
M _t1r :M _t2r :M _t3r =I _t1 :I _t2 :I _t3
Each switching element 41a, 41b, 42a, 42b, 43a, 43b is controlled so that Here, when the winding resistance of each power transmission coil 11, 12, 13 can be ignored, the ratio of the phase voltages output by the inverter circuit 40 is the mutual inductance M between each power transmission coil 11, 12, 13 and the power reception coil 20 Matches the ratio of _t1r , _Mt2r and _Mt3r . In this case, the control unit 80 may control the current ratio of each power transmission coil 11 , 12 , 13 according to the output voltage ratio of the inverter circuit 40 . As shown in FIG. 3, when the mutual inductances M _t1r , M _t2r and M _t3r are negative, the control unit 80 controls the phase of the current to be shifted by 180° (π) with respect to the positive mutual inductances. .

According to the power transmission device 2 of the wireless power transmission system 1 configured as described above, current is applied to each of the power transmission coils 11, 12, and 13 during wireless power transmission. It is possible to improve power transmission efficiency compared to the conventional one that flows. In particular, when the power receiving coil 20 is positioned between the power transmitting coils 11, 12, and 13, the power transmission efficiency is significantly improved.

Further, the control unit 80 controls each of the power transmission coils 11, 12, and 13 so that the current ratio of each of the power transmission coils 11, 12, and 13 becomes the mutual inductance ratio between each of the power transmission coils 11, 12, and 13 and the power reception coil 20. Since the currents of 12 and 13 are controlled, the power transmission efficiency is extremely high. Furthermore, since one inverter circuit 40 supplies electric power to the plurality of power transmission coils 11, 12, and 13, there is no need to provide a plurality of inverter circuits corresponding to the plurality of power transmission coils, thereby miniaturizing the apparatus. can be planned.

In addition, since one end sides of the power transmission coils 11, 12, and 13 are connected to each other and then connected to the predetermined voltage portion of the power supply voltage 30 via the inductor 60, the power transmission coils 11, 12, and 13 A resonance circuit can be configured corresponding to the mutual inductance of Further, since the resonance capacitors 61, 62, 63 are provided for the power transmission coils 11, 12, 13, respectively, resonance circuits can be configured corresponding to the self-inductances of the power transmission coils 11, 12, 13, respectively. In particular, in the present embodiment, by setting C _t =1/(ω ² (L _t +M _t )) and L ₀ =M _t (M _t >0), The reactance component can be canceled.

4 and 5 show a second embodiment of the present invention. FIG. 4 is a plan view of a power transmitting coil and a power receiving coil, and FIG. 5 is a circuit diagram of a power transmitting device and a power receiving device of a wireless power transmission system. .

In the wireless power transmission system 101 of the present embodiment, as shown in FIG. 4, two power transmission coils 111 and 112 having a predetermined thickness and having a rectangular shape in plan view are arranged adjacently on the same plane so as not to overlap each other. . In this embodiment, the two power transmission coils 111 and 112 are the same. The power receiving device 103 also includes a power receiving coil 120 and a resonance capacitor 121 and a load resistor 122 that are connected in series with the power receiving coil 120 .

As shown in FIG. 5 , the power transmission device 102 includes an inverter circuit 140 connected to a DC power supply 130 and supplying power to the power transmission coils 111 and 112 . The inverter circuit 140 has two legs 141 and 142 provided for each of the power transmission coils 111 and 112 and connected in parallel between the positive and negative busbars. Positive nodes 141c and 142c connected to the other ends of the power transmission coils 111 and 112 are set between the positive switching elements 141a and 142a and the negative switching elements 141b and 142b connected in series.

The inverter circuit 140 also has a positive side capacitor 151 and a negative side capacitor 152 between the positive and negative bus lines. The positive side capacitor 151 and the negative side capacitor 152 equally divide the input voltage from the DC power supply 130 . A negative node 153 connected to one end of each of the power transmission coils 111 and 112 is set between the positive capacitor 151 and the negative capacitor 152 .

As shown in FIG. 5 , one ends of the power transmission coils 111 and 112 are connected to each other, and a connection node 114 is set. One end of each power transmission coil 111 , 112 is connected to an intermediate voltage of the input voltage of DC power supply 130 via inductor 160 . Also, the other ends of the power transmission coils 111 and 112 are connected to the legs 141 and 142 via resonance capacitors 161 and 162, respectively. In this embodiment, the inductor 160 and the resonance capacitors 161 and 162 together with the power transmission coils 111 and 112 form a power factor compensation circuit 170 that forms a resonance circuit.

The inductor 160 has an inductance set based on the mutual inductance between the power transmission coils 111 and 112 . Also, the capacitances of the resonance capacitors 161 and 162 are set based on the self-inductance of the power transmission coils 111 and 112 and the mutual inductance between the power transmission coils 111 and 112 .

Also in the present embodiment, the self-inductances of the power transmission coils 111 and 112 are equal to each other, and the magnetic fields weaken each other when currents flow in the same direction. becomes. When the operating angular frequency of the device is ω, the self-inductance of each of the power transmission coils 111 and 112 is L _t , and the mutual inductance between the power transmission coils 111 and 112 is −M _t , the capacitance of each of the resonance capacitors 161 and 162 is C _t and The inductance _L0 of inductor 160 is
C _t =1/(ω ² (L _t +M _t ))
L ₀ =M _t (M _t >0)
is set.

Further, as shown in FIG. 5, the power receiving device 103 has a resonance capacitor 121 and a load resistor 122 that are connected in series with the power receiving coil 120 . When the self- _inductance of the receiving coil 120 is _Lr , the capacitance Cr of the resonance capacitor 121 is
C _r =1/(ω ² L _r )
is set.

The power transmission device 102 also has a control unit 180 that controls switching operations of the switching elements 141a, 141b, 142a, and 142b. When the mutual inductance between the first and second power transmitting coils 111, 112 and the power receiving coil 120 is _Mt1r , _Mt2r , and the currents of the first and second power transmitting coils 111, 112 are _It1 , _It2 , The control unit 180
M _t1r :M _t2r =I _t1 :I _t2
Each switching element 141a, 141b, 142a, 142b is controlled so that Here, when the winding resistance of each of the power transmission coils 111 and 112 can be ignored, the ratio of the phase voltages output by the inverter circuit 140 is the mutual inductance M _t1r and M _t2r between each of the power transmission coils 111 and 112 and the power reception coil 120. corresponds to the ratio of In this case, the control unit 180 may control the current ratio of the power transmission coils 111 and 112 according to the output voltage ratio of the inverter circuit 140 .

According to the power transmission device 102 of the wireless power transmission system 101 configured as described above, current is applied to each of the power transmission coils 111 and 112 during wireless power transmission. can improve the power transmission efficiency compared to that of In particular, when the power receiving coil 120 is positioned between the power transmitting coils 111 and 112, power transmission efficiency is greatly improved.

Further, the control unit 180 adjusts the currents of the power transmission coils 111 and 112 so that the ratio of the currents of the power transmission coils 111 and 112 becomes the ratio of the mutual inductance between the power transmission coils 111 and 112 and the power reception coil 120. Since it is controlled, the power transmission efficiency is extremely high. Furthermore, since one inverter circuit 140 supplies electric power to the plurality of power transmission coils 111 and 112, there is no need to provide a plurality of inverter circuits corresponding to the plurality of power transmission coils, thereby miniaturizing the device. can be done.

In addition, since one end side of each of the power transmission coils 111 and 112 is connected to each other and then connected to the predetermined voltage portion of the power supply voltage 130 via the inductor 160, the mutual inductance between the power transmission coils 111 and 112 can be accommodated. A resonant circuit can be configured by Also, since the resonance capacitors 161 and 162 are provided in the power transmission coils 111 and 112, respectively, the resonance circuits can be configured corresponding to the self-inductances of the power transmission coils 111 and 112, respectively. In this embodiment, by setting C _t =1/(ω ² (L _t +M _t )) and L ₀ =M _t (M _t >0), the reactance component due to self-inductance and mutual inductance can be canceled.

6 and 7 show a third embodiment of the present invention, wherein FIG. 6 is a plan view of a power transmission coil, and FIG. 7 is a circuit diagram of a power transmission device and a power reception device of a wireless power transmission system.

As shown in FIG. 6, in the wireless power transmission system 201 of the present embodiment, the power transmission coils 111 and 112 of the second embodiment are partially overlapped and arranged so that the magnetic fields are strengthened when currents flow in the same direction. It is That is, the value of mutual inductance between the power transmission coils 111 and 112 is positive. Also, in the wireless power transmission system 201 of this embodiment, as shown in FIG. 7, a capacitor 260 is arranged instead of the inductor 160 of the second embodiment. Otherwise, the configuration is the same as that of the second embodiment.

Capacitance of capacitor 260 is set based on mutual inductance between power transmission coils 111 and 112 . When the self-inductance of each power transmission coil 111, 112 is _Lt , and the mutual inductance between each power transmission coil 111, 112 is Mt, the capacitance _Ct of each resonance capacitor 161, 162 and the capacitance _C0 of the capacitor 260 are _:
C _t = 1/(ω ² (L _t −M _t ))
C ₀ =1/(ω ² M _t )
is set.
With the wireless power transmission system 201 configured as described above, it is possible to obtain the same effects as those of the second embodiment.

8 and 9 show a fourth embodiment of the present invention. FIG. 8 is a plan view of a power transmission coil, and FIG. 9 is a circuit diagram of a power transmission device and a power reception device of a wireless power transmission system.

In the wireless power transmission system 301 of the present embodiment, as shown in FIG. 8, another power transmission coil 113 is arranged adjacent to the adjacent power transmission coils 111 and 112 of the second embodiment. . Also in this embodiment, the three power transmission coils 111, 112, and 113 are the same. That is, the number of power transmission coils 111, 112, and 113 of power transmission device 302 is three. In the present embodiment, the mutual inductance between the power transmission coil 111 on the one end side and the power transmission coil 112 on the center side and between the power transmission coil 112 on the center side and the power transmission coil 113 on the other end side are equal, but the power transmission coil 111 on the one end side and the mutual inductance between the power transmission coil 113 on the other end side.

As shown in FIG. 9, the inverter circuit 340 of the power transmission device 302 has three legs 141, 142, 143 provided for each of the power transmission coils 111, 112, 113 between the positive and negative busbars. Positive nodes 141c, 142c, 141c, 142c connected to the other ends of the power transmission coils 111, 112, 113 are placed between the positive switching elements 141a, 142a, 143a and the negative switching elements 141b, 142b, 143b connected in series. 143c is set. One end of each power transmission coil 111, 112, 113 is connected to each other, and a connection node 314 is set. One end of each power transmission coil 111 , 112 , 113 is connected to an intermediate voltage of the input voltage of DC power supply 130 via inductor 360 . The other end of each power transmission coil 111, 112, 113 is connected to each leg 141, 142, 143 via resonance capacitors 361, 362, 363, respectively. In this embodiment, the inductor 360 and the resonance capacitors 361, 362, 363 together with the power transmission coils 111, 112, 113 form a power factor compensation circuit 370 forming a resonance circuit.

Furthermore, transformers 391, 392 are interposed between each resonance capacitor 361, 362, 363 and each leg 141, 142, 143 in this embodiment. In this embodiment, there are two transformers, a transformer 391 corresponding to each of the power transmission coils 111 and 112 on the one end side and the center side, and a transformer 392 corresponding to each of the power transmission coils 112 and 113 on the center side and the other end side. Devices 391, 392 are provided. Each transformer 391, 392 makes the sum of its mutual inductance and the mutual inductance between each transmitting coil 111, 112, 113 equal to each other. That is, each transformer 391 and 392 constitutes a mutual inductance compensation circuit 390 that adjusts mutual inductance based on the mutual inductance difference between each of the power transmission coils 111 , 112 and 113 . The mutual inductance compensation circuit 390 can also be configured by one transformer corresponding to each of the power transmission coils 111 and 113 on the one end side and the other end side.

In this embodiment, the inductance of inductor 360 is set based on the adjusted mutual inductance. Also, since the mutual inductance compensation circuit 390 has self-inductance, the capacitances _Ct1 , _Ct2 and _Ct3 of the resonance capacitors 361, 362 and 363 are set in consideration of the self-inductance of the transformers 391 and 392. be. Specifically, L' _t1 , L' _t2 , and L' _t3 are the sums of the self-inductances of the power transmission coils 111, 112, and 113 and the self-inductances of the transformers 391 and 392, and the power transmission coils 111 after adjustment. , 112 and 113 is -M _t (M _t >0), the capacitances C _t1 , C _t2 and C _t3 of the resonance capacitors 361, 362 and 363 and the inductance L ₀ of the inductor 360 are given by
_Ct1 =1/(ω2 ⁽ L' _t1 +Mt)), _Ct2 =1/(ω2 ⁽ L' _t2 + _Mt )), _{Ct3 =} 1/(ω2 ⁽ L' _t3 + _Mt ))
_{L0 = Mt}
is set.

In addition, the control unit 380 controls each of the power transmission coils 111, 112, and 113 so that the current ratio of each of the power transmission coils 111, 112, and 113 becomes the mutual inductance ratio between each of the power transmission coils 111, 112, and 113 and the power reception coil 120. 112, 113 current is controlled.
According to the wireless power transmission system 301 configured as described above, in addition to the effects of the third embodiment, mutual inductance compensation between the power transmission coils 111, 112, and 113 is achieved by providing the mutual inductance compensation circuit 390. are equal to each other.

10 and 11 show a fifth embodiment of the present invention. FIG. 10 is a plan view of a power transmission coil and a power reception coil, and FIG. 11 is a circuit diagram of a power transmission device of a wireless power transmission system. Note that the circuit diagram of the power receiving device is omitted in FIG. Although the power receiving device, the power receiving coil, and the like are not shown in FIG. 11, the power receiving device, the power receiving coil, and the like are the same as those in the second embodiment.

As shown in FIG. 10, the wireless power transmission system of this embodiment further includes two power transmission coils 113 and 114 adjacent to each other in a direction perpendicular to the alignment direction of the two power transmission coils 111 and 112 of the second embodiment. are provided. That is, the power transmission coils 111, 112, 113, and 114 of the power transmission device 402 are four. In this embodiment, the four power transmission coils 111, 112, 113, and 114 are the same. In the present embodiment, the power transmission coils 111, 112, 113, and 114 adjacent in the alignment direction or the direction orthogonal thereto have the same mutual inductance, but the power transmission coils 111, 112, 113, 113, 113, 113 114 is different.

As shown in FIG. 11, the inverter circuit 440 of the power transmission device 402 has four legs 141, 142, 143, 144 provided for each of the power transmission coils 111, 112, 113, 114 between the positive and negative busbars. Positive switching elements 141a, 142a, 143a, 144a and negative switching elements 141b, 142b, 143b, 144b connected in series with the other ends of the power transmission coils 111, 112, 113, 114 Side nodes 141c, 142c, 143c, and 144c are set. One ends of the power transmission coils 111, 112, 113, and 114 are connected to each other, and a connection node 414 is set. One end of each power transmission coil 111 , 112 , 113 , 114 is connected to an intermediate voltage of the input voltage of DC power supply 130 via inductor 460 . The other end of each power transmission coil 111, 112, 113, 114 is connected to each leg 141, 142, 143, 144 via resonance capacitors 461, 462, 463, 464, respectively. In this embodiment, the inductor 460 and the resonance capacitors 461, 462, 463, 464 together with the power transmission coils 111, 112, 113, 114 form a power factor compensation circuit 470 forming a resonance circuit.

Further, in this embodiment, transformers 491 and 492 are interposed between the resonance capacitors 461, 462, 463 and 464 and the legs 141, 142, 143 and 144, respectively. Each transformer 491, 492 makes the sum of its mutual inductance and mutual inductance between each transmitting coil 111, 112, 113, 114 equal to each other. That is, each transformer 491, 492 constitutes a mutual inductance compensation circuit 490 that adjusts mutual inductance based on the mutual inductance difference between each of the power transmission coils 111, 112, 113, 114. FIG. As in the fourth embodiment, the inductance of the inductor 460 is set based on the adjusted mutual inductance, and the capacitances of the resonance capacitors 461, 462, 463, and 464 are set in consideration of the adjusted self-inductance. be done.

In addition, the control unit 480 controls each power transmission coil 111 , 112 , 113 , 114 so that the current ratio of each power transmission coil 111 , 112 , 113 , 114 becomes the mutual inductance ratio between each power transmission coil 111 , 112 , 113 , 114 and the power reception coil 120 . The currents of the power transmission coils 111, 112, 113, and 114 are controlled.
With the wireless power transmission system configured as described above, it is possible to obtain the same effects as those of the fourth embodiment.

12 and 13 show a sixth embodiment of the present invention, wherein FIG. 12 is a plan view of the power transmission coil and FIG. 13 is a circuit diagram of the power transmission device of the wireless power transmission system. 12 and 13 do not show the power receiving device, the power receiving coil, etc., but the power receiving device, the power receiving coil, etc. are the same as in the first embodiment.

As shown in FIG. 12, in this wireless power transmitting device 502, a plurality of power transmitting coils 511 to 519 are aligned horizontally and diagonally on a predetermined plane. In this embodiment, the same power transmitting coils 511 to 519 are used. In this embodiment, the angle between the horizontal direction and the oblique vertical direction is 60°. As shown in FIG. 13, the power transmission device 502 includes an inverter circuit 40 having three legs 41, 42, 43 as in the first embodiment. Each power transmission coil 511-519 is assigned to one of three power transmission groups corresponding to the number of legs 41,42,43.

In the present embodiment, as shown in FIG. 12, the power transmission coils 511 to 519 belong to the first power transmission group and the power transmission coils belong to the second power transmission group toward one side (right side in FIG. 12). The power transmission coils belonging to the power transmission group and the third power transmission group are repeatedly arranged in this order. In addition, each of the power transmission coils 511 to 519 is arranged in an oblique vertical direction toward one side (upper right direction in FIG. 12), the power transmission coil belonging to the first power transmission group, the power transmission coil belonging to the third power transmission group, and the power transmission coil belonging to the second power transmission group. They are repeatedly arranged in the order of the power transmission coils belonging to the power transmission coils.

As shown in FIG. 13 , each leg 41 , 42 , 43 of the inverter circuit 40 of the wireless power transmission device 502 is connected to the other end of each power transmission coil 511 to 519 via changeover switches 581 , 582 , 583 . Each switch 581, 582, 583 is provided for each power transmission group, and selectively supplies power to one power transmission coil 511 to 519 belonging to each power transmission group. In this embodiment, the changeover switches 581, 582, 583 form a changeover circuit. The control unit 580 switches each switch 581, 582, 583 based on the information about the power receiving coil. In addition, the control unit 580 controls the currents of the power transmission coils 511 to 519 so that the ratio of the currents of the power transmission coils 511 to 519 becomes the ratio of mutual inductance between the power transmission coils 511 to 519 and the power reception coils. .

One end of each of the power transmission coils 511 to 519 is connected to an intermediate voltage of the input voltage of the DC power supply 30 via an inductor 560 while being connected to each other. Changeover switches 581, 582, 583 selectively connected to the other ends of the power transmission coils 511 to 519 are connected to the legs 41, 42, 43 via resonance capacitors 561, 562, 563, respectively. In this embodiment, the inductor 560 and the resonance capacitors 561, 562, 563 together with the power transmission coils 511 to 519 form a power factor compensation circuit 570 forming a resonance circuit.

According to the wireless power transmission device 502 of this embodiment, even when the number of the power transmission coils 511 to 519 is large, all the power transmission coils 511 to 519 can be handled without increasing the number of legs of the inverter circuit 40. can be done.

14 and 15 show a seventh embodiment of the present invention, wherein FIG. 14 is a plan view of the power transmission coil and FIG. 15 is a circuit diagram of the power transmission device of the wireless power transmission system. 14 and 15 do not show the power receiving device, the power receiving coil, etc., but the power receiving device, the power receiving coil, etc. are the same as in the first embodiment.

As shown in FIG. 14, in this wireless power transmitting device 602, a plurality of power transmitting coils 611 to 619 are aligned horizontally and vertically on a predetermined plane. In this embodiment, the same power transmitting coils 611 to 619 are used. As shown in FIG. 14, the power transmission device 602 includes an inverter circuit 640 having four legs 41, 42, 43, 44. In FIG. Each transmitting coil 611-619 is assigned to one of the four transmitting groups corresponding to the number of legs 41,42,43,44.

In the present embodiment, as shown in FIG. 14, the power transmission coils 611 to 619 belonging to the second power transmission group are arranged laterally adjacent to the power transmission coils belonging to the first power transmission group, A power transmission coil belonging to the third power transmission group is arranged vertically adjacent to the power transmission coil belonging to the first power transmission group, and a fourth power transmission group is arranged laterally adjacent to the power transmission coil belonging to the third power transmission group. are arranged. That is, in the horizontal direction, the power transmission coils belonging to the first and second power transmission groups are alternately arranged, or the power transmission coils belonging to the third and fourth power transmission groups are alternately arranged. there is In the vertical direction, the power transmission coils belonging to the first and third power transmission groups are alternately arranged, or the power transmission coils belonging to the second and fourth power transmission groups are alternately arranged. there is

As shown in FIG. 15, each leg 41, 42, 43, 44 of the inverter circuit 640 of the wireless power transmission device 602 is connected to the other end of each of the power transmission coils 611 to 619 via changeover switches 681, 682, 683, 684. be done. Each switch 681, 682, 683, 684 is provided for each power transmission group and selectively supplies power to one power transmission coil 611 to 619 belonging to each power transmission group. In this embodiment, the changeover switches 681, 682, 683, 684 form a changeover circuit. Control unit 680 switches each switch 681, 682, 683, 684 based on the information on the power receiving coil. Furthermore, in the present embodiment, mutual A mutual inductance compensation circuit 690 is interposed to adjust the inductance. Further, the control unit 680 controls the currents of the power transmitting coils 611 to 619 so that the ratio of the currents of the power transmitting coils 611 to 619 becomes the ratio of the mutual inductance between the power transmitting coils 611 to 619 and the power receiving coils. do.

One end of each of the power transmission coils 611 to 619 is connected to an intermediate voltage of the input voltage of the DC power supply 30 via an inductor 660 while being connected to each other. Switches 681, 682, 683, 684 selectively connected to the other ends of power transmission coils 611 to 619 connect legs 41, 42, 43, 44 via resonance capacitors 661, 662, 663, 664, respectively. connected to In this embodiment, the inductor 660 and the resonant capacitors 661, 662, 663, 664 together with the power transmitting coils 611 to 619 form a power factor compensation circuit 670 forming a resonant circuit.

Even if the number of power transmission coils 611 to 619 is large, the wireless power transmission device 602 of the present embodiment can support all the power transmission coils 611 to 619 without increasing the number of legs of the inverter circuit 640. can.

In the sixth and seventh embodiments, the number of legs of the inverter circuit is 3 or 4, but the number of legs may be 2 or 5 or more. , the number of legs can be changed arbitrarily. Also, although the resonance capacitors 661, 662, 663, and 664 are provided on the other end side of each of the power transmission coils 611 to 619, as shown in FIG. It may be provided on one end side of each of the power transmission coils 611 to 619 . Here, if the power transmission coils 611 to 619 have different self-inductances, a resonance capacitor may be provided in series for each of the power transmission coils 611 to 619 .

In each of the above-described embodiments, a plurality of identical power transmission coils are provided. may be provided in plurality. In addition, although each power transmission coil is shown to be positioned on the same plane with each other, it is not necessary to be positioned on the same plane, and it is not necessary to be regularly arranged. There may be no regularity or the like. FIG. 17 shows an example of a circuit diagram of the power transmission device in these cases. The circuit diagram of FIG. 17 is the same as that of FIG.

The three power transmission coils 1111, 1112, and 1113 in the circuit diagram of FIG. 17 have different specifications, are not arranged on the same plane, and have different distances from each other. In the circuit diagram of FIG. 17, a mutual inductance compensation circuit 1390 is provided that includes three transformers 1391, 1392 and 1393 corresponding to each combination of power transmitting coils 1111, 1112 and 1113 respectively. Also, in the circuit diagram of FIG. 17, a power factor compensation circuit 1370 including inductors 1360 and resonance capacitors 1361, 1362, 1363 corresponding to the power transmission coils 1111, 1112, 1113 is provided.

ここで、任意の実数Ｍ´_ｔに対して、

が成立するようにＭ_ｃ１２，Ｍ_ｃ２３，Ｍ_ｃ３１を設定するとともに、Ｌ´_ｔ１，Ｌ´_ｔ2，Ｌ´_ｔ3を

とすると、（１）－（３）式は、

となる。これを整理すると、

となる。そして、Ｃ_ｔ１，Ｃ_ｔ２，Ｃ_ｔ３を、

とし、Ｍ´_ｔが負の場合に、

とすることで、インバータ回路３４０の出力相電圧Ｖ_ｔ1，Ｖ_ｔ２，Ｖ_ｔ３は、

となる。すなわち、各送電コイルの自己インダクタンス及び相互インダクタンスに起因するリアクタンス成分が打ち消されている。尚、Ｍ´_ｔが正の場合は、インダクタ１３６０に代えてキャパシタンスＣ_０が、

となるキャパシタとすることにより、（２０）－（２２）式を得ることができる。
また、図１７の回路図においても、制御部３８０は、
Ｍ_ｔ１ｒ：Ｍ_ｔ２ｒ：Ｍ_ｔ３ｒ＝Ｉ_ｔ１：Ｉ_ｔ２：Ｉ_ｔ３
となるよう各スイッチング素子１４１ａ，１４１ｂ，１４２ａ，１４２ｂ，１４３ａ，１４３ｂを制御する。式（２０）－（２２）から理解されるように、インバータ回路３４０の出力相電圧Ｖ_ｔ1，Ｖ_ｔ２，Ｖ_ｔ３の比は、各送電コイルと受電コイルの相互インダクタンスＭ_ｔ１ｒ，Ｍ_ｔ２ｒ，Ｍ_ｔ３ｒの比に一致する。従って、制御部３８０は、インバータ回路３４０の出力相電圧の比に応じて、各送電コイルの電流の比を制御すればよい。
尚、巻線抵抗が無視できない場合、各送電コイルの抵抗値をｒ_ｔ1，ｒ_ｔ２，ｒ_ｔ３とすると、インバータ回路３４０の出力相電圧Ｖ_ｔ1，Ｖ_ｔ２，Ｖ_ｔ３は、

で表される。従って、各送電コイルの抵抗値ｒ_ｔ1，ｒ_ｔ２，ｒ_ｔ３に関する情報を予め測定等により取得しておき、インバータ回路３４０の出力相電圧及び電流の値から相互インダクタンスの比を求めればよい。Here, the currents and self-inductances of the first to third power transmitting coils 1111, 1112, 1113 are _It1 , _It2 , _It3 , _Lt1 , _Lt2 , _Lt3 , and the capacitances of the resonance capacitors 1361, 1362, 1363 are C _t1 , C _t2 , C _t3 , L _c121 , L _c122 , _Mc12 the self-inductance and mutual inductance of the first and second transmission coil sides of the transformer 1391 corresponding to the first and second transmission coils, L _c232 , L _c233 , M _c23 of the self-inductance and mutual inductance on the side of the second and third power transmission coils of the transformer 1392 corresponding to the second and third power transmission coils, corresponding to the third and first power transmission coils L _c313 , L _c311 , M _c31 are the self-inductance and mutual inductance on the side of the third and first power transmission coils of the transformer 1393 , M _t12 is the mutual inductance between the first power transmission coil and the second power transmission coil, Mutual inductance between the second power transmission coil and the third power transmission coil is M _t23 , mutual inductance between the third power transmission coil and the first power transmission coil is M _t31 , inductance of the inductor 1360 is L ₀ , and the first M _t1r , M _t2r , and M _t3r are the mutual inductances of the third power transmitting coil and the power receiving coil, _Ir is the current of the power receiving coil, and the winding resistances of the first to third power transmitting coils 1111, 1112, and 1113 are ignored. Then, the output phase voltages V _t1 , V _t2 and V _t3 of the inverter circuit 340 are expressed as follows.

Now, for any real number M' _t ,

is established, and L _{' t1 ,} L _{' t2 and} L' _t3 are _set as

Then, formulas (1)-(3) are

becomes. Arranging this gives

becomes. Then, C _t1 , C _t2 and C _t3 are

and when _M't is negative,

As a result, the output phase voltages V _t1 , V _t2 , and V _t3 of the inverter circuit 340 are

becomes. That is, the reactance components resulting from the self-inductance and mutual inductance of each power transmission coil are cancelled. Note that if _M't is positive, instead of the inductor 1360, the capacitance _C0 is

Equations (20)-(22) can be obtained by setting the capacitor as follows.
Also in the circuit diagram of FIG. 17, the control unit 380
M _t1r :M _t2r :M _t3r =I _t1 :I _t2 :I _t3
Each switching element 141a, 141b, 142a, 142b, 143a, 143b is controlled so that As understood from equations (20)-(22), the ratio of the output phase voltages V _t1 , V _t2 , V _t3 of the inverter circuit 340 is the mutual inductance M _t1r , M _t2r , M Matches the ratio of _t3r . Therefore, the control section 380 may control the current ratio of each power transmission coil according to the output phase voltage ratio of the inverter circuit 340 .
When the winding resistance cannot be ignored, and the resistance values of the power transmission coils are _rt1 , _rt2 , and _rt3 , the output phase voltages _Vt1 , _Vt2 , and _Vt3 of the inverter circuit 340 are given by

is represented by Therefore, information about the resistance values r _t1 , r _t2 , and r _t3 of the power transmission coils is acquired in advance by measurement or the like, and the ratio of mutual inductance is obtained from the values of the output phase voltage and current of the inverter circuit 340 .

Further, in each of the above embodiments, the inverter circuit is connected to the DC power supply, but the inverter circuit 1040 may be connected to the AC power supply 1030 as shown in FIG. The circuit configuration can be changed arbitrarily. The circuit diagram of FIG. 18 differs from the circuit diagram of FIG. The difference is that the The first circuit 1051 is, for example, a diode rectifier circuit, an AC-DC converter, or the like, and outputs a DC voltage upon input from the AC power supply 1030 . The second circuit 1054 is, for example, a diode rectifier circuit, an AC-DC converter, a DC-DC converter, a series capacitor with a balancer, or the like. is connected to one end of each of the power transmission coils 11, 12 and 13, and is designed so that each of the power transmission coils 11, 12 and 13 has a predetermined voltage. This predetermined voltage can be arbitrarily set. When the input voltage of the AC power supply 1030 is E, the predetermined voltage can be set to E/2, or the predetermined voltage can be set to 0 or E. can.

In each of the above-described embodiments, each resonant capacitor of the power factor compensation circuit of the power transmission device is connected in series with each power transmission coil to form a series resonant circuit. may be connected to form a parallel resonance circuit, or may form an LCL resonance circuit as shown in FIG. 19, and the configuration of the power factor compensation circuit may be arbitrarily changed. In the power factor compensation circuit 770 of the power transmission device 702 of FIG. 19, the other ends of the power transmission coils 11, 12 and 13 are connected to the legs 41, 42 and 43 via resonance inductors 761, 762 and 763, respectively. , are connected to the intermediate voltage of the input voltage through resonant capacitors 764 , 765 , 766 .

In each of the above-described embodiments, the capacitance of each resonance capacitor is set so that the reactance component of the power transmission device becomes zero, and power can be transmitted at a relatively low input voltage. As shown, capacitors 41d, 41e, 42d, 42e, 43d, and 43e are connected in parallel with switching elements 41a, 41b, 42a, 42b, 43a, and 43b so that the output impedance of inverter 40 has a lagging power factor. By setting the capacitances of the resonance capacitors 61, 62, and 63, the operation of the inverter 40 can be soft switching to improve power transmission efficiency. Further, by using the parasitic capacitances of the switching elements 41a, 41b, 42a, 42b, 43a, and 43b instead of the capacitors 41d, 41e, 42d, 42e, 43d, and 43e, the output impedance of the inverter 40 is set to a lagging power factor. The capacitance of each resonant capacitor 61, 62, 63 can also be set.

In each of the above-described embodiments, the resonant capacitor of the power factor compensation circuit of the power receiving device is connected in series with the power receiving coil to form a series resonant circuit. The transmission coils may be connected in parallel to form a parallel resonance circuit, or may form an LCL resonance circuit as shown in FIG. 22, and the configuration of the power factor compensation circuit may be arbitrarily changed. . In the power receiving device 803 of FIG. 21, the power receiving coil 20 and the resonant capacitor 821 are connected in parallel to the output circuit 822 . 22, the power receiving coil 20 and the resonance capacitor 921 are connected in parallel to the output circuit 923, and the resonance inductor 922 is provided between one end of the power receiving coil 20 and the output circuit 923. there is The output circuits 822 and 923 can be, for example, AC loads, DC loads via rectifiers or AD converters, or the like.

Here, using the power transmission device 2 of the first embodiment as an example and a power transmission device having a conventional configuration as a comparative example, the power transmission efficiency was compared by simulation. FIG. 23 is a circuit diagram of a power transmission device showing a comparative example, and FIG. 24 is a simulation result showing the power transmission efficiency of the example and the comparative example.

As shown in FIG. 23, in the power transmission device of the comparative example, power is supplied from one inverter circuit to any of the power transmission coils 11, 12, and 13 arranged in the same manner as in the first embodiment. .
As shown in FIG. 24 , in the power transmission device of the example, the area of the power receiving coil 20 capable of power transmission was expanded and the power transmission efficiency was improved as compared with the power transmission device of the comparative example. In particular, when the power receiving coil 20 was positioned at the joints of the power transmitting coils 11, 12, and 13, the power transmission efficiency was dramatically improved.

Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the scope of claims. Also, it should be noted that not all combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

1 wireless power transmission system 2 power transmission device 3 power reception device 11 power transmission coil 12 power transmission coil 13 power transmission coil 20 power reception coil 30 DC power supply 40 inverter circuit 41 leg 42 leg 43 leg 44 leg 60 inductor 61 resonance capacitor 62 resonance capacitor 63 resonance capacitor 70 power factor Compensation circuit 80 control unit 101 wireless power transmission system 102 power transmission device 103 power reception device 111 power transmission coil 112 power transmission coil 113 power transmission coil 114 power transmission coil 120 power reception coil 130 DC power supply 140 inverter circuit 141 leg 142 leg 143 leg 144 leg 160 inductor 161 resonance capacitor 162 Resonant Capacitor 170 Power Factor Compensation Circuit 180 Control Unit 201 Wireless Power Transmission System 202 Power Transmission Device 260 Capacitor 270 Power Factor Compensation Circuit 301 Wireless Power Transmission System 302 Power Transmission Device 340 Inverter Circuit 360 Inductor 361 Resonance Capacitor 362 Resonance Capacitor 363 Resonance Capacitor 370 Power Factor Compensation Circuit 380 control unit 390 mutual inductance compensation circuit 391 transformer 392 transformer 402 power transmission device 440 inverter circuit 460 inductor 461 resonance capacitor 462 resonance capacitor 463 resonance capacitor 464 resonance capacitor 470 power factor compensation circuit 480 control unit 490 mutual inductance compensation circuit 491 transformer 492 transformer 502 power transmission device 511 power transmission coil 512 power transmission coil 513 power transmission coil 514 power transmission coil 515 power transmission coil 516 power transmission coil 517 power transmission coil 518 power transmission coil 519 power transmission coil 560 inductor 561 resonance capacitor 562 resonance capacitor 563 resonance capacitor 570 power factor compensation circuit 580 Control unit 581 changeover switch 582 changeover switch 583 changeover switch 602 power transmission device 611 power transmission coil 612 power transmission coil 613 power transmission coil 614 power transmission coil 615 power transmission coil 616 power transmission coil 617 power transmission coil 618 power transmission coil 619 power transmission coil 640 inverter circuit 660 inductor 661 resonance capacitor 662 Resonance capacitor 663 Resonance capacitor 664 Resonance capacitor 670 Power factor compensation circuit 680 Control unit 681 Changeover switch 682 Changeover switch 683 Changeover switch 684 Changeover switch 690 Mutual inductance compensation circuit 702 Power transmission device 761 Resonance inductor 762 Resonance inductor 763 Resonance inductor 764 Resonance capacitor 765 Resonance Capacitor 766 resonant capacitor 770 power factor compensation circuit 803 power receiving device 821 resonant capacitor 822 output circuit 903 power receiving device 921 resonant capacitor 922 resonant inductor 923 output circuit 1111 power transmitting coil 1112 power transmitting coil 1113 power transmitting coil 1360 inductor 1361 resonant capacitor 1362 resonant capacitor 1363 resonant capacitor 1370 power factor compensation circuit 1390 mutual inductance compensation circuit 1391 transformer 1392 transformer 1393 transformer

Claims (1)

A power transmission device in a wireless power transmission system that performs wireless power transmission between a power transmission coil and a power reception coil,
provided for one of the receiving coils a plurality of the power transmission coils;
an inverter circuit connected to a predetermined power supply, having a plurality of legs provided for each of the power transmission coils and connected in parallel with each other, and supplying power to each of the power transmission coils;
a power factor compensation circuit forming a resonance circuit together with each of the power transmission coils;
A control unit that controls the switching element of the leg of the inverter circuit,
The control unit applies a current to each of the power transmitting coils during wireless power transmission to one of the power receiving coils,
one end sides of the power transmission coils are connected to each other;
A connection portion on one end side of each power transmission coil is connected to a predetermined voltage portion in the inverter circuit,
The power factor compensation circuit includes a series resonance circuit including a capacitor provided for each power transmission coil and connected in series with each power transmission coil, and a series resonance circuit provided for each power transmission coil and connected in parallel with each power transmission coil. A parallel resonant circuit including a capacitor, or an inductor provided for each power transmission coil and connected in series with each power transmission coil, and a capacitor provided for each power transmission coil and connected in parallel with each power transmission coil. Having an LCL resonance circuit and having an inductor or a capacitor interposed between a connection portion on one end side of each of the power transmission coils and the predetermined voltage portion of the inverter circuit,
The control unit controls the currents of the power transmission coils so that the ratio of the currents of the power transmission coils becomes the ratio of mutual inductance between the power transmission coils and the power reception coils. .

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