WO2018221532A1 - Power transmission device, wireless power transmission system, and control device - Google Patents

Abstract

[Problem] To control power transmission according to the state of a power reception device without performing communication from the power reception device to a power transmission device. [Solution] A power transmission device comprises: an inverter circuit; a power transmission resonator; a measurement device; and a control circuit. The measurement device measures an input voltage or an output voltage of the inverter circuit, and measures an input current or an output current of the inverter circuit. During power transmission, the control circuit: changes the voltage value of an alternating current power output from the inverter circuit from a first voltage value to a second voltage value; acquires first measured values and second measured values of the voltage and the current measured by the measurement device before and after the change; determines a third voltage value by a process which includes calculation using the first and second measured values; and outputs an alternating current power having the third voltage value from the inverter circuit so as to continue the power transmission.

Description

Power transmission device, wireless power transmission system, and control device

The present application relates to a wireless power transmission system, and a power transmission device and a control device used in the wireless power transmission system.

Development of a wireless power transmission system (also referred to as a non-contact power feeding system) that wirelessly transmits power from a power transmitting device to a power receiving device is underway. Patent Documents 1 and 2 disclose examples of contactless power feeding systems. In the systems of Patent Documents 1 and 2, information such as a received voltage is fed back from a power receiving apparatus to a power transmitting apparatus using wireless communication, and the power transmitting apparatus controls transmission power based on the information.

International Publication No. WO2012 / 073349 International Publication No. WO2014 / 148144

The technologies disclosed in Patent Documents 1 and 2 require communication for feeding back information from the power receiving apparatus to the power transmitting apparatus. The embodiment of the present disclosure provides a technique for appropriately controlling transmission power according to the state of a power receiving apparatus without performing such communication.

A power transmission device in an exemplary embodiment of the present disclosure wirelessly transmits power to a power reception device including a power reception resonator. The power transmission device includes an inverter circuit, a power transmission resonator connected to the inverter circuit, one of a voltage input to the inverter circuit and a voltage output from the inverter circuit, and a current input to the inverter circuit. And a measuring instrument for measuring one of the currents output from the inverter circuit, and a control circuit for controlling the inverter circuit. The control circuit outputs AC power having a first voltage value from the inverter circuit and transmits power from the power transmission resonator to the power reception resonator. The first measurement value is obtained and measured by the measuring instrument in a state where the voltage value of the AC power output from the inverter circuit is changed to a second voltage value different from the first voltage value. A second measured value of voltage and current is obtained, a third voltage value is determined by a process including an operation using the first and second measured values, and the third voltage value is determined from the inverter circuit. AC power is output and power transmission is continued.
In addition, a wireless power transmission system in an exemplary embodiment of the present disclosure includes the above-described power transmission device and a power reception device. The control device in the exemplary embodiment of the present disclosure includes the control circuit in the above-described power transmission device. A program in an exemplary embodiment of the present disclosure is used in a power transmission device that wirelessly transmits power to a power reception device including a power reception resonator.

The comprehensive or specific aspect described above can be realized by an apparatus, a system, a method, an integrated circuit, a computer program, or a recording medium. Or you may implement | achieve with arbitrary combinations of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

According to the embodiment of the present disclosure, it is possible to appropriately control transmission power according to the state of the power receiving device without performing communication from the power receiving device to the power transmitting device.

FIG. 1 is a diagram for describing an overview of a mobile system in an exemplary embodiment of the present disclosure. FIG. 2 is a perspective view schematically illustrating an example of the moving body 200 according to an exemplary embodiment of the present disclosure. FIG. 3 is a perspective view illustrating an example of an arrangement relationship between the power transmission coil unit 105 and the power reception coil unit 205 during charging. FIG. 4 is a block diagram illustrating a configuration of a mobile system in an exemplary embodiment of the present disclosure. FIG. 5 is a diagram illustrating a configuration example of the inverter circuit 120 and the control circuit 140. FIG. 6 is a diagram illustrating an example of a waveform of a pulse signal supplied from the control circuit 140 to the switching elements G1 to G4 and a voltage output from the inverter circuit 120. In FIG. FIG. 7 is a diagram illustrating an equivalent circuit of the power transmission resonator 110 and the power reception resonator 210. FIG. 8A is a perspective view for explaining an example of the shapes and arrangement relationships of power transmission coil 112 and power reception coil 212. FIG. 8B is a diagram schematically illustrating an example of a shape when the power transmission coil 112 is viewed from the Y direction. FIG. 8C is a diagram schematically illustrating an example of the shape when the power receiving coil 212 is viewed from the Y direction. FIG. 9 is a diagram illustrating a configuration example of the rectifier 220, the capacitor 230, and the power storage element 245. FIG. 10 is a flowchart illustrating an example of an operation when the power transmission device 100 starts power transmission. FIG. 11A is a diagram illustrating an equivalent circuit of a wireless power transmission system in an exemplary embodiment of the present disclosure. FIG. 11B is a diagram illustrating another equivalent circuit of the wireless power transmission system in the exemplary embodiment of the present disclosure. FIG. 12 is a flowchart illustrating an operation during power transmission in the exemplary embodiment of the present disclosure. FIG. 13A is a diagram illustrating an example of a time change of the output voltage V1 of the inverter circuit 120. FIG. FIG. 13B is a diagram showing another example of the time change of the output voltage V1 of the inverter circuit 120. FIG. 14A is a diagram illustrating an example of timing between estimation based on two measurements and real-time estimation. 14B is a diagram showing an example of time change of the voltage V1 in the case of controlling the voltage V1 by performing real-time estimated by the period T _2. FIG. 15 is a flowchart illustrating an example of an operation in which estimation by two measurements performed for each period T ₁ and real-time estimation performed for each period T ₂ are combined. FIG. 16A is a schematic diagram illustrating an example in which the voltage measuring device 130 a is connected between the DC power supply 50 and the inverter circuit 120. FIG. 16B is a schematic diagram illustrating a configuration example in which the current measuring device 130 b is connected between the DC power supply 50 and the inverter circuit 120. FIG. 16C is a schematic diagram illustrating an example in which both the voltage measuring device 130 a and the current measuring device 130 b are connected between the DC power supply 50 and the inverter circuit 120. FIG. 17A is a schematic diagram illustrating an example in which the DC-DC converter 250 is connected between the capacitor 230 and the power storage element 245. FIG. 17B is a schematic diagram illustrating an example in which a load resistor 240 such as a motor is arranged instead of the power storage element 245 in the configuration of FIG. 17A.

Before explaining the embodiments of the present disclosure, the knowledge that is the basis of the present disclosure will be described.

In the conventional non-contact power feeding technology, information such as voltage, current, power, or impedance in the power receiving device is fed back to the power transmitting device by wireless communication for power feeding control. In order to realize such wireless communication, for example, a device that performs wireless communication such as Wi-Fi (registered trademark) or Bluetooth (registered trademark) is used for both the power transmission device and the power reception device.

However, when the power receiving device is a device such as a moving body used in a factory or a road, for example, there is a situation where wireless communication cannot be normally performed between the power transmitting device and the power receiving device due to the influence of communication interference or noise. May occur frequently. When wireless communication is disconnected, the power transmission device cannot obtain information on the power reception device, and thus cannot properly control the transmission power. Furthermore, the wireless device requires time for connection and authentication before communication. Until connection and authentication are established, transmission power cannot be controlled. In particular, when power is supplied to a moving power receiving device, even if a slight loss of time occurs, the ratio of the total power supply time occupies a high rate, and power supply efficiency is greatly reduced. Furthermore, the installation of wireless devices causes an increase in cost.

The present inventor has found the above problems and examined a configuration for solving these problems. The present inventor changes the voltage of the AC power to be transmitted at short time intervals during power transmission, and from the information on the voltage and current on the power transmission side measured before and after the change, the mutual inductance between the coils, the power receiving voltage, etc. I found that I can estimate the information. This discovery makes it possible to estimate the state of the power receiving device without performing communication from the power receiving device to the power transmitting device, and to appropriately control the transmission power according to the state.

Hereinafter, an overview of the embodiment of the present disclosure will be described.

The power transmission device according to one embodiment of the present disclosure wirelessly transmits power to a power reception device including a power reception resonator. The power transmission device includes an inverter circuit, a power transmission resonator connected to the inverter circuit, a measuring instrument, and a control circuit that controls the inverter circuit. The measuring instrument measures one of a voltage input to the inverter circuit and a voltage output from the inverter circuit, and one of a current input to the inverter circuit and a current output from the inverter circuit. The control circuit performs the following operations. (1) A first voltage and current measured by the measuring instrument in a state where AC power having a first voltage value is output from the inverter circuit and transmitted from the power transmitting resonator to the power receiving resonator. Get the measured value of. (2) A second voltage and current measured by the measuring instrument in a state where the voltage value of the AC power output from the inverter circuit is changed to a second voltage value different from the first voltage value. Get the measured value of. (3) By processing including calculation using the first and second measurement values, a third voltage value is determined, and AC power having the third voltage value is output from the inverter circuit to transmit power. continue.

With the above configuration, transmission power can be appropriately controlled according to a change in the state of the power receiving device without performing communication from the power receiving device to the power transmitting device.

The power transmission resonator includes a power transmission coil, and the power reception resonator includes a power reception coil. The control circuit estimates the value of one or more parameters indicating the state of the power receiving apparatus, for example, by calculation using the first and second measurement values. The third voltage value can be determined from the estimated parameter value with reference to data defining the correspondence between the value of the one or more parameters and the value of the voltage to be output from the inverter circuit. . Data defining such a correspondence relationship is stored in a recording medium such as a memory in the power transmission apparatus in the form of a table, a mathematical expression or a function, for example. The data can be, for example, a table that defines the correspondence between the mutual inductance between coils or the voltage output from the power receiving resonator and the output voltage of the inverter circuit.

The control circuit performs the determination of the acquisition and the third voltage values of the first and second measurement values, for example, every period T _1. When the value of one or more parameters indicating the state of the power receiving device estimated from the first and second measured values changes from the value of the parameter estimated last time, the control circuit outputs a third voltage value Is set to a value different from the first voltage value. On the other hand, the control circuit sets the third voltage value to the same value as the first voltage value when the value of the parameter is the same as the value of the parameter when estimated last time. Whether or not the value of each parameter has changed from the previously estimated value can be determined by determining whether the difference or rate of change from the previous value of the parameter exceeds a threshold value.

The one or more parameters include a mutual inductance between a power transmission coil included in the power transmission resonator and a power reception coil included in the power reception resonator, a voltage output from the power reception resonator, a current output from the power reception resonator, And at least one of electric power output from the power receiving resonator. Specific processing for estimating these parameters will be described later.

The power receiving device is, for example, a moving body. “Moving object” means a movable object that is driven or charged by electric power. The moving body may be, for example, an automated guided vehicle (AGV), an electric vehicle (EV), a movable robot, or an unmanned aerial vehicle (UAV, so-called drone). The power receiving device may be a device that does not move by itself, such as a portable device.

The power transmission device may include a sensor that detects whether or not the power reception device is moving with respect to the power transmission device. Such a sensor may be, for example, a sensor using visible light or infrared light, or may be a sensor that detects movement of the power receiving device based on a change in voltage or current in a circuit of the power transmitting device.

∙ The measuring instrument performs two measurements continuously within a relatively short time. For example, the measurement is performed twice at a time interval that allows the mutual inductance between the power transmission coil and the power reception coil to be considered constant. This time interval is set shorter as the speed at which the power receiving apparatus moves during power transmission is higher. The measuring instrument may be configured to measure in response to an instruction from the control circuit, or may be configured to constantly monitor the voltage and current at a constant short time interval.

The control circuit can adjust the output voltage of the inverter circuit (hereinafter sometimes referred to as “transmission voltage”) in various ways. For example, the transmission voltage can be adjusted by changing the duty ratio, phase, or frequency of the control signal supplied to each of the plurality of switching elements included in the inverter circuit, or changing the DC voltage input to the inverter circuit. it can. Control of the DC voltage input to the inverter circuit is possible in a form in which the power transmission device includes a DC-DC converter connected between the inverter circuit and the DC power supply. In such a form, the control circuit can change the DC voltage input to the inverter circuit by controlling on / off of the switching element included in the DC-DC converter.

The present disclosure also includes a control device including the above-described control circuit, and a computer program (hereinafter simply referred to as a program) that defines an operation performed by the control circuit. Such a program is stored in a recording medium such as a memory in the power transmission device, for example, and causes the control circuit to execute the above-described operation.

Hereinafter, exemplary embodiments of the present disclosure will be described. However, more detailed explanation than necessary may be omitted. For example, detailed descriptions of already well-known matters and overlapping descriptions for substantially the same configuration may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. The inventor provides the accompanying drawings and the following description in order for those skilled in the art to fully understand the present disclosure, and is not intended to limit the subject matter described in the claims. Absent. In the following description, the same or similar components are denoted by the same reference numerals.

(Embodiment)
<Configuration>
FIG. 1 is a diagram for explaining an outline of a mobile system according to the present embodiment. The mobile system is an example of a wireless power transmission system in the present disclosure. The mobile system can be used as a system for conveying articles in a factory, for example. The mobile body system includes at least one wireless power transmission device (hereinafter simply referred to as “power transmission device”) 100 and at least one mobile body 200. The moving body 200 is an example of a power receiving device. The mobile body 200 can be, for example, an automatic guided vehicle (AGV) that autonomously moves in a factory and transports articles to a necessary place. FIG. 1 illustrates four power transmission devices 100 and four moving bodies 200. The number of each of the power transmission device 100 and the moving body 200 is not limited to four and is arbitrary.

The power transmission device 100 transmits power to the mobile body 200 wirelessly. The power transmission device 100 includes a power transmission coil unit 105 including a power transmission coil that sends AC power to space. The moving body 200 includes a power receiving coil unit 205 including a power receiving coil. When the power transmission coil and the power reception coil are coupled by magnetic field resonance, power is wirelessly transmitted from the power transmission coil to the power reception coil. Thus, in the present embodiment, wireless power transmission by magnetic field resonance coupling (sometimes referred to as “magnetic field resonance coupling” or “resonance magnetic field coupling”) is used. According to the magnetic resonance coupling type wireless power transmission, power transmission over a longer distance is possible as compared with the electromagnetic induction method. Note that the technology of the present disclosure is not limited to the magnetic field resonance coupling method, and can also be applied to wireless power transmission using an electromagnetic induction method. Therefore, this indication includes the composition by an electromagnetic induction system.

The moving body 200 includes a capacitor and a motor. The electric power received by the power receiving coil in the power receiving coil unit 205 is rectified and stored in the capacitor. As the capacitor, a large-capacity and low-resistance capacitor such as an electric double layer capacitor or a lithium ion capacitor can be used. The moving body 200 can move by driving a motor with electric power stored in the capacitor.

When the moving body 200 moves, the amount of electricity stored in the capacitor (that is, the amount of charge) decreases. For this reason, recharging is required to continue the movement. Therefore, when the charge amount falls below a predetermined threshold during movement, the moving body 200 moves to the vicinity of the power transmission device 100 and performs charging. As shown in FIG. 1, if the power transmission device 100 is installed at a plurality of locations, the moving body 200 only needs to move to the vicinity of the nearest power transmission device 100, so that the travel distance can be shortened.

As described above, such a system can be used as a system for conveying articles in a factory, for example. The mobile body 200 typically has a loading platform on which an article is loaded, and functions as a carriage that autonomously moves in the factory and conveys the article to a necessary place. The mobile system is not limited to a factory, and can be used, for example, in a store, a hospital, a home, or any other location. Further, the moving body 200 is not limited to the AGV, and may be another industrial machine or a service robot. The moving body 200 may be any device having a movable mechanism, such as a manned vehicle, an unmanned aircraft (UAV, so-called drone), or a cleaning robot. The power receiving device in the present disclosure is not limited to a moving object. The technology of the present disclosure can be applied to any wireless power transmission system in which the relative position between the power transmission coil and the power reception coil can change during power transmission.

FIG. 2 is a perspective view schematically showing an example of the moving body 200 in the present embodiment. The moving body 200 includes a power receiving coil unit 205 installed on a side surface, a plurality of wheels including drive wheels 207 driven by a motor, and a loading platform 206 on which articles are placed. The power receiving coil unit 205 houses a power receiving resonator including a power receiving coil.

FIG. 3 is a perspective view showing an example of an arrangement relationship between the power transmission coil unit 105 and the power reception coil unit 205 at the time of charging. FIG. 3 shows XYZ coordinates indicating X, Y, and Z directions orthogonal to each other. In the following description, the coordinate system shown in the figure is used. The XY plane is parallel to the horizontal plane or the floor, and the direction in which the moving body 200 advances is the positive direction of the X axis, and the vertical upward direction is the positive direction of the Z axis.

The orientation of the structure shown in the drawings of the present application is set in consideration of the ease of explanation, and does not limit the orientation when the embodiment of the present disclosure is actually implemented. Further, the shape and size of the whole or a part of the structure shown in the drawings do not limit the actual shape and size.

3, the power transmission coil 112 in the power transmission coil unit 105 has a conductor wire (winding) wound so as to be relatively long in the X direction and relatively short in the Z direction. Similarly, the power receiving coil 212 in the power receiving coil unit 205 has a conductor wire (winding) wound so as to be long in the X direction and short in the Z direction. As illustrated, the shapes and sizes of the power transmission coil 112 and the power reception coil 212 in this embodiment are asymmetric. In the present embodiment, the size of the region defined by the winding of the power receiving coil 212 is smaller than the size of the region defined by the winding of the power transmission coil 112.

The power transmission is performed in a state where the power transmission coil 112 and the power reception coil 212 are opposed to each other. More specifically, the surface defined by the winding of the power transmission coil 112 and the surface defined by the winding of the power receiving coil 212 (both parallel to the XZ plane in the illustrated example) face each other. Is charged. Charging is possible not only when these planes are completely parallel, but also when they are inclined to each other.

In this embodiment, since the power transmission coil 112 has a shape that is long in the X direction, even if the moving body 200 is slightly displaced in the X direction, the facing state between the coils is maintained, and power transmission with high efficiency is achieved. Can be maintained.

The moving body 200 can grasp the position and orientation of the mobile device 200 and the position and orientation of the power transmission coil 112 using various sensors. As a result, the power transmission device 100 closest to the own device is identified and moved to the vicinity of the power transmission device 100 so that highly efficient power transmission can be performed, that is, the power reception coil 212 faces the power transmission coil 112 in close proximity. Can take posture. The mobile body 200 may move to the next closest power transmission apparatus 100 when the closest power transmission apparatus 100 is feeding power to another mobile body 200.

Hereinafter, the configuration of the mobile system of this embodiment will be described in more detail.

FIG. 4 is a block diagram showing the configuration of the mobile system of this embodiment.

The power transmission device 100 includes an inverter circuit 120 connected to an external direct current (DC) power supply 50, a power transmission resonator 110 connected to the inverter circuit 120, and a voltage measuring instrument 130a that measures a voltage output from the inverter circuit 120. And a current measuring device 130b that measures the current output from the inverter circuit 120, a control circuit 140 that controls the inverter circuit 120, and a sensor 150 that detects the position and / or movement of the moving body 200. The power transmission resonator 110 includes the power transmission coil 112 described above. In the following description, the voltage measuring instrument 130a and the current measuring instrument 130b may be collectively referred to as “measuring instrument 130”. The measuring instrument 130 in this embodiment measures the voltage and current output from the inverter circuit 120. As will be described later, the voltage measuring instrument 130a may measure the voltage input to the inverter circuit 120. Similarly, the current measuring device 130b may measure a current input to the inverter circuit 120.

The moving body (power receiving device) 200 includes a power receiving resonator 210, a rectifier (rectifier circuit) 220 connected to the power receiving resonator 210, a capacitor 230 connected to the rectifier 220, and a storage element 245 connected to the capacitor 230. And have. The power receiving resonator 210 includes the power receiving coil 212 described above. Power storage element 245 includes an electric double layer capacitor or a battery. In addition, the power transmission apparatus 100 and the moving body 200 may include other components that are not illustrated. Further, the mobile system need not necessarily include all the components shown in FIG. 4 and can be omitted as appropriate.

Hereinafter, each component will be described in more detail.

<DC power supply>
The DC power source 50 is a power source that outputs a DC voltage having a predetermined magnitude. The DC power supply 50 can include, for example, a converter that converts commercial AC power into DC power having the operating voltage of the power transmission device 100 and outputs the DC power.

<Inverter circuit and control circuit>
The inverter circuit 120 converts the DC power supplied from the DC power supply 50 into AC power. The inverter circuit 120 can be, for example, a full bridge inverter circuit. The full bridge inverter circuit can output AC power having a desired frequency and voltage value by adjusting the switching timing of the four switching elements. Each switching element switches between a conductive state and a non-conductive state in accordance with a pulse signal supplied from the control circuit 140.

FIG. 5 is a diagram illustrating a configuration example of the inverter circuit 120 and the control circuit 140. The inverter circuit 120 shown in FIG. 5 has a configuration of a full bridge inverter circuit having four switching elements G1 to G4. Each switching element may be a transistor such as an IGBT (Insulated-gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field-Effect Transistor).

The control circuit 140 includes a control IC 142, a gate driver 144, and a memory 143. The control IC 142 executes the control program stored in the memory 143 to determine the AC power voltage (meaning an effective value; the same applies hereinafter) and frequency to be output to the inverter circuit 120. In the present embodiment, in particular, the voltage or frequency at which the efficiency is maximized is determined based on the values of the voltage V1 and the current I1 measured by the measuring instrument 130. Details of this operation will be described later. The gate driver 144 supplies a pulse signal having a frequency and a duty ratio determined by the control IC 142 to the gates of the switching elements G1 to G4. Thus, the conduction (on) / non-conduction (off) states of the switching elements G1 to G4 are controlled. Note that a part or the whole of the control circuit 140 can be realized by an integrated circuit such as a microcomputer.

Among the four switching elements G1 to G4, at the timing when the switching elements G1 and G4 are turned on (conductive state), a voltage having the same polarity as the DC voltage supplied from the DC power supply 50 is output from the inverter circuit 120. On the other hand, at the timing when switching elements G2 and G3 are on (conducting state), a voltage having a polarity opposite to the DC voltage supplied from DC power supply 50 is output from inverter circuit 120. The control circuit 140 causes the inverter circuit 120 to output AC power having a desired frequency and voltage by adjusting the timing of the pulse signal supplied to each of the switching elements G1 to G4.

FIG. 6 is a diagram illustrating an example of a waveform of a pulse signal supplied from the control circuit 140 to the switching elements G1 to G4 and a voltage output from the inverter circuit 120. In FIG. In FIG. 6, the symbol E represents the magnitude of the voltage output from the DC power supply 50, and the symbol T represents the period. The period during which the output voltage V1 of the inverter circuit 120 is the same as the magnitude E of the output voltage of the DC power supply 50 is controlled by the duty ratio d _inv . In other words, the control circuit 140 can adjust the amplitude and effective value of the AC voltage obtained by approximating the output voltage V ₁ with a sine wave by adjusting the duty ratio d _inv .

Note that the inverter circuit 120 is not limited to the configuration shown in FIG. For example, a half-bridge configuration may be used. Even in such a case, a desired AC voltage can be output by adjusting the timing of the gate drive pulse applied to the two switching elements. The inverter circuit 120 can be realized by, for example, a commercially available high frequency power supply device.

<Power transmission resonator and power reception resonator>
FIG. 7 is a diagram illustrating an equivalent circuit of the power transmission resonator 110 and the power reception resonator 210. The power transmission resonator 110 is a series resonance circuit having an inductance component (L ₁ ), a capacitance component (C ₁ ), and a resistance component (R ₁ ) due to the power transmission coil 112. The power receiving resonator 210 is a series resonant circuit having an inductance component (L ₂ ), a capacitance component (C ₂ ), and a resistance component (R ₂ ) due to the power receiving coil 212. The capacitance components (C1 and C2) may be parasitic capacitance components of the power transmission coil 112 and the power reception coil 212, respectively, or may be due to capacitors provided separately.

The resonance frequency of the power transmission resonator 110 and the resonance frequency of the power reception resonator 210 are set to substantially the same value. The resonance frequency is not particularly limited, but can be set to, for example, 5 kilohertz (kHz) or more and 50 megahertz (MHz) or less. The resonance frequency is more preferably 10 kHz or more and 1 MHz. Each resonator is not limited to a series resonance circuit, but may be a parallel resonance circuit. For example, as disclosed in Patent Document 1, a primary coil coupled to the power transmission resonator 110 by electromagnetic induction and a secondary coil coupled to the power reception resonator 210 by electromagnetic induction are not limited to the illustrated configuration. It may be provided.

FIG. 8A is a perspective view for explaining in more detail the shape and arrangement relationship of the power transmission coil 112 and the power reception coil 212. 8A shows an example in which the width of the power transmission coil 112 in the Y direction is smaller than that in the example of FIG. A two-dot chain line shown in FIG. 8A represents a normal line of the surface defined by the coils 112 and 212. FIG. 8B schematically shows a shape when the power transmission coil 112 is viewed from the Y direction. FIG. 8C schematically shows the shape of the power receiving coil 212 when viewed from the Y direction.

The power transmission coil 112 is a winding wound around a first conductor wire, and includes a first upper portion 112a and a first lower portion 112b that extend in the lateral direction, and two arc-shaped portions that connect these portions. Including. The power receiving coil 212 is a winding wound around a second conductor wire, and includes a second upper portion 212a and a second lower portion 212b that extend in the lateral direction, and two arc-shaped portions that connect these portions. Including.

By the first rectangular surface 112c (FIG. 8B) defined by the upper portion 112a and the lower portion 112b of the power transmission coil 112, and by the second upper portion 212a and the second lower portion 212b of the power receiving coil 212 The defined second rectangular surface 212c (FIG. 8C) is perpendicular or inclined with respect to the horizontal plane. The power receiving coil 112 is disposed on the side surface of the moving body 200, and the second rectangular surface 212c faces the first rectangular surface 112c of the power transmitting coil 112 during power transmission.

The power transmission coil 112 and the power reception coil 212 are not limited to the illustrated shapes. For example, the shape of each coil may be rectangular (including a square) or elliptical (including a circle). The structure of each of the coils 112 and 212 may be appropriately modified depending on the configuration of the applied system. For example, in the present embodiment, each of the coils 112 and 212 has a structure extending in the X direction, but it is not always necessary to have such a structure. In addition, the power transmission coil 112 does not necessarily have to be larger than the power reception coil 212. The power transmission coil 112 and the power reception coil may have the same structure. The structure of each coil 112 is arbitrary as long as power transmission is possible.

<Rectifier, capacitor, storage element>
FIG. 9 is a diagram illustrating a configuration example of the rectifier 220, the capacitor 230, and the power storage element 245.

The rectifier 220 may be a full wave rectifier circuit including a diode bridge and a smoothing capacitor, as shown. The rectifier 220 may be another type of full-wave rectifier circuit or a half-wave rectifier circuit. The rectifier 220 converts AC power from the power receiving resonator 210 into DC power and outputs the DC power.

The capacitor 230 is connected to the rectifier 220 in parallel. Capacitor 230 is provided to reduce and stabilize fluctuations in DC voltage supplied from rectifier 220 to power storage element 245. The capacitor 230 may be omitted if unnecessary.

The power storage element 245 is connected to the capacitor 230 in parallel. The power storage element 245 is, for example, a capacitor or a battery. The power storage element 245 may include both a capacitor and a battery. As the capacitor, for example, an electric double layer capacitor or a lithium ion capacitor can be used. Since an electric double layer capacitor or a lithium ion capacitor has a small internal resistance (for example, several tens of mΩ), charging and discharging with a large current can be performed with low loss. For this reason, rapid charge is possible. In addition, since the capacitance is larger than that of other types of capacitors, a relatively long continuous discharge is possible. As the battery, a secondary battery having high energy density and high charge / discharge efficiency, such as a lithium ion battery, can be used.

<Sensor>
The sensor 150 detects the position or movement of the moving body 200. The sensor 150 can be, for example, a sensor that uses light (visible light or near infrared light). The sensor 150 may be configured to detect the movement of the moving body 200 based on the output of the measuring instrument 130. Based on the time change of at least one of the voltage and current measured by the measuring instrument 130, it can be determined whether or not the moving body 200 is moving.

<Operation>
Next, the operation of the power transmission device 100 will be described.

FIG. 10 is a flowchart illustrating an example of an operation when the power transmission apparatus 100 starts power transmission. When the power is turned on, the control circuit 140 of the power transmission device 100 in this example performs weak power transmission and executes an operation of detecting the moving body 200 that is a power reception device. When the moving body 200 is detected in the vicinity, the control circuit 140 starts power feeding to the moving body 200.

In the example of FIG. 10, the control circuit 140 sets the voltages _{V 1} to minute value starts weak power transmission (step S11). In this state, measuring instrument 130 measures voltage V ₁ and current I ₁ output from inverter circuit 120 (step S12). Based on the values of V ₁ and I ₁ , the control circuit 140 determines whether the moving body 200 exists at a position where it can receive power (step S13). When the mobile body 200 does not exist at a position where power can be received (No in step S14), the control circuit 140 stops weak power transmission (step S15). After the time T ₀ has elapsed (Yes in step S16), the control circuit 140 executes the operation of step S11 again. If the mobile 200 is present capable receiving position (Yes in step S14), and the control circuit 140 starts the power supply to the mobile 200 to increase the output voltage _{V 1.}

The detection of the power receiving device in step S13 can be determined based on, for example, whether the difference between a predetermined reference value that depends on the value of V1 and the value of I1 exceeds a threshold value. As the moving body 200 approaches, the mutual inductance between the power transmission coil and the power reception coil increases. Due to the influence, the current flowing in the circuit of the power transmission device 100 changes. Based on the change in the current, the approach of the moving body 200 can be detected.

In the example of FIG. 10, the approach of the moving body 200 (power receiving device) is detected based on the current and voltage in the circuit of the power transmission device 100. In addition to such a detection method, for example, the approach of the moving body 200 may be detected using the sensor 150 (see FIG. 4).

<Estimation of power receiving device status>
The power transmission apparatus 100 according to the present embodiment estimates the state of the moving body 200 without using information transmitted from the moving body 200 during power feeding to the moving body 200, and appropriately sets the transmission power according to the state. Can be controlled. The method will be specifically described below.

In the following description, information or parameters indicating the state of the moving body 200 may be referred to as “power reception parameters”. The power reception parameter may include, for example, at least one of mutual inductance between coils, current in the circuit of the power reception device, voltage, power, and impedance.

FIG. 11A is a diagram illustrating an equivalent circuit of the wireless power transmission system according to the present embodiment. The equivalent circuit shown in FIG. 11A can also be expressed as shown in FIG. 11B. In FIG. 11A and FIG. 11B, components (see FIG. 4) such as the inverter circuit 120 connected to the power transmission resonator 110 are collectively represented as one AC power source. In addition, components such as the rectifier 220 connected to the power receiving resonator 210 are collectively represented as one load. Let _{RL be} the resistance value of the load. A component such as a rectifier circuit connected to the power receiving resonator 210 actually has a reactance component in addition to a resistance component. However, in FIG. 11A and FIG. 11B, for simplicity, the reactance component is ignored and the load is represented as a resistance. The angular frequency of the AC power to be transmitted is ω, and the mutual inductance is L _m . The angular frequency ω is the same as the driving angular frequency of the inverter circuit 120.

In the following description, AC voltage and AC current are represented by phasor display. That is, voltage and current are treated as complex numbers. In the phasor display, the absolute values of voltage and current represent their effective values.

Let phasor display of the voltage and current of the AC power supply be v ₁ and i ₁ , respectively. When the effective values of the voltage and current of the AC power supply are V ₁ and I ₁ , respectively, V ₁ = | v ₁ | and I ₁ = | i ₁ |. Similarly, V ₂ = | v ₂ | and I ₂ = | i ₂ | where the voltage and current phasor representations of the load are v ₂ and i ₂ , respectively.

Voltage _{v 1} and the current _{i 1} is shown in FIGS. 11A and 11B, represents the voltage _{v 1} and the current _{i 1} of the AC power output from the inverter circuit 120, respectively. A voltage v ₂ and a current i ₂ input to the load represent a voltage and a current output from the power receiving resonator 210, respectively.

From the circuit equations of the equivalent circuit shown in FIGS. 11A and 11B, v ₁ , i _1, v ₂ , and i ₂ satisfy the following expressions (1) and (2).

Here, j is an imaginary unit.

In the following description, it is assumed that ω is equal to the resonance angular frequency ω ₀ = 1 / (L ₁ C ₁ ) ^1/2 = 1 / (L ₂ C ₂ ) ^1/2 . However, even if the resonance condition ω = ω ₀ is not satisfied, the following discussion is valid if the difference between ω and ω ₀ is small. For example, if the value of | ω−ω ₀ | / ω ₀ is 0.05 or less, the following discussion is sufficiently effective.

Substituting v ₂ = R _L i ₂ into equation (2) yields i ₂ = j {ωL _m / (R ₂ + R _L )} i ₁ from the resonance condition ωL ₂ = 1 / ωC ₂ . This equation shows that the phase of i ₂ advances 90 ° from the phase of i ₁ . If i ₂ is eliminated from the equation (1) using this equation, v ₁ = {R ₁ / ω ² Lm ² / (R ₂ + R _L )} i ₁ is obtained. This equation shows that v ₁ and i ₁ have the same phase. Also, from v ₂ = R _L i ₂ , v ₂ and i ₂ have the same phase. From these phase relationships, under resonance conditions, they can be expressed as v ₁ = V ₁ e ^jθ , i ₁ = I ₁ e ^jθ , v ₂ = jV ₂ e ^jθ , and i ₂ = jI ₂ e ^jθ . Here, θ represents a phase. Substituting these v ₁ , i ₁ , v ₂ , and i ₂ into the formulas (1) and (2), V ₁ , I ₁ , V ₂ , and I ₂ are expressed by the following formula (3 ) And (4) are satisfied.

When equations (3) and (4) are solved, the following equations (5) and (6) are obtained.

The effective value V _{1 of the} voltage is obtained by, for example, integrating the real-time waveform of the voltage measured by the voltage measuring instrument 130a in the power transmission device 100. Similarly, the effective value I ₁ of the current is obtained by integrating real-time waveform of the current measured by the current measuring device 130b in the power transmitting apparatus 100.

In equations (5) and (6), there are three unknown parameters V ₂ , I ₂ and L _m . Since the number of equations is less than the number of unknown parameters, V ₂ , I ₂ and L _m cannot be calculated as they are.

Therefore, the power transmission device 100 according to the present embodiment changes the value of the transmission voltage during power transmission, and measures the voltage and current before and after the change. At least one of L _m , V ₂ , and I ₂ can be estimated from the voltage and current values obtained by the two measurements. Hereinafter, this estimation method will be described more specifically.

The control circuit 140 drives the inverter circuit 120 to transmit power from the power transmission coil 112 to the power reception coil 122 during power transmission. This state is referred to as a first state. In the first state, the control circuit 140 acquires measured values of voltage and current measured by the measuring instruments 130a and 130b, respectively. This measurement value is referred to as a first measurement value. Next, the control circuit 140 changes the voltage value output from the inverter circuit 120 to a second value different from the voltage value in the first state. This state is referred to as a second state. In the second state, the control circuit 140 acquires measured values of voltage and current measured by the measuring instruments 130a and 130b, respectively. This measurement value is referred to as a second measurement value.

If the time from acquisition of the first measurement to the acquisition of the second measured value is sufficiently short, the change of the voltage V ₂ of the storage element 245 is small. For example, if the time from the acquisition of the first measurement to the acquisition of the second measured value is less than 0.1 seconds, it is possible to suppress the variation in the voltage V ₂ to 0.1V or less. In this case, the two measurements of the above, V ₂ can be assumed to be constant.

Obtained from the first measurement value, the effective value of the alternating-current power voltage and current output from the inverter circuit 120, and V ₁₀ and I _10, respectively. Obtained from the second measurement value, the effective value of the effective value and the current of the AC power voltage output from the inverter circuit 120, and V ₁₁ and I _11, respectively. Assuming that V ₂ is constant, the following equations (7) and (8) are obtained from equation (5).

Further, the following equation (9) is obtained from the equation (6).

By using equations (7) to (9), three unknown parameters V ₂ , I ₂ and L _m can be calculated.

If V ₂ is eliminated from the equations (7) and (8), the following L _m estimation equation (10) is obtained.

On the other hand, the following V ₂ estimation formula (11) is obtained from the formula (7).

Further, from the equations (9) and (11), the following I ₂ estimation equation (12)
Is obtained.

The control circuit 140 can estimate the mutual inductance L _m , the received voltage V ₂ , and the received current I ₂ by the calculations of equations (10) to (12). As a result, the parameters of the power receiving device can be estimated from the voltage and current information in the power transmitting device 100 without communicating between the power transmitting device 100 and the moving body 200.

Based on the estimated parameters of the power receiving device, the control circuit 140 sets the voltage value of the AC power output from the inverter circuit 120 (the third value, for example, so that one or both of V ₂ and I ₂ have a desired value). (Voltage value) is determined, and power transmission is continued at the determined voltage value. Thereby, even when the mobile body 200 moves during power transmission, power feeding can be optimized. For example, it is possible to suppress a decrease in transmission efficiency or to stabilize power feeding.

In the memory 143 shown in FIG. 5, data such as a table or a mathematical expression that prescribes a correspondence relationship between at least one parameter of L _m , V ₂ , and I ₂ and the voltage V ₁ to be output from the inverter circuit 120 is stored in advance. Stored. The control circuit 140 can determine the value after the change of the voltage V ₁ from the estimated parameter by referring to the data. The data includes the correspondence between the voltage V ₁₀ and current I ₁₀ obtained from the first measurement value, the combination of the voltage V ₁₁ and current I ₁₁ obtained from the second measurement value, and the voltage V ₁ to be transmitted. A relationship may be defined. In that case, the control circuit 140 should transmit power from the combination of V ₁₀ , I ₁₀ , V ₁₁ , and I ₁₁ by referring to the data without performing the calculations of equations (10) to (12). it can be determined voltage V _1.

The control circuit 140 refers to the data, the effective value I ₁₀ RMS V ₁₀ and the current of the voltage obtained from the first measurement value, voltage effective value V ₁₁ and obtained from the second measurement value a combination of the effective value I ₁₁ of the current, estimating the power receiving parameters, such as the mutual inductance L _m.

The memory 143 may store data defining the relationship between the voltage V ₂ in the moving body 200 and the charge amount of the power storage element 245. The control circuit 140 refers to the data, it is possible to estimate the charge amount of the power storage device 245 from the voltage V _2. The control circuit 140 can perform control such that power supply from the power transmission device 100 to the moving body 200 is stopped if the charge amount is equal to or greater than a reference value.

The control circuit 140 estimates the power receiving parameters, for example, every period _{T 1.} The period T ₁ can be set to a value in the range of, for example, several milliseconds (ms) to several seconds. In one example, the period T ₁ can be set to a time on the order of 100 ms. The control circuit 140 changes the voltage V ₁ output from the inverter circuit 120 when the estimated value of the parameter changes from the value estimated at the previous time, and maintains the voltage V ₁ otherwise. To do. Whether or not the estimated value of the parameter has changed can be determined by whether or not the difference or rate of change between the current estimated value and the previous estimated value exceeds a predetermined threshold value. For example, the control circuit 140 changes the voltage V ₁ only when the difference or change rate between the estimated parameter value such as the mutual inductance Lm and the value of the same parameter estimated last time exceeds the threshold value.

Hereinafter, parameter estimation processing during power transmission in the present embodiment will be described with reference to FIG. FIG. 12 is a flowchart showing an operation during power transmission in the present embodiment. When estimating the state of the power receiving device, the control circuit 140 first causes the inverter circuit 120 to output AC power having a first voltage value (step S101). In the present embodiment, the first voltage value is an effective value of the AC voltage that is already being transmitted. The control circuit 140 acquires the first measurement value measured by the measuring instrument 130 in that state (step S102). The first measurement value corresponds to the aforementioned V ₁₀ and I ₁₀ . Since V ₁₀ and I ₁₀ are effective values, when the measurement value output from the measuring instrument 130 is an instantaneous value, the control circuit 140 performs necessary calculations to perform the voltage effective value V ₁₀ and the current effective value. I get ₁₀ .

Next, the control circuit 140 causes the inverter circuit 120 to output AC power having a second voltage value different from the first voltage value (step S103). That is, the transmission voltages V ₁ to change to a different second voltage value to the first voltage value so far. The second voltage value is set to a value that makes the difference from the first voltage value larger than the magnitude of the noise component. For example, the second voltage value can be set to about half the first voltage value. The second voltage value may be set to a value larger than the first voltage value.

In that state, the control circuit 140 acquires the second measured values of voltage and current (step S104). The second measurement value corresponds to the aforementioned V ₁₁ and I ₁₁ . Since V ₁₁ and I ₁₁ are effective values, when the measured value output from the measuring instrument 130 is an instantaneous value, the control circuit 140 performs necessary calculations to perform the effective value V _{11 of the} voltage and the effective value of the current. I ₁₁ is obtained.

Next, the control circuit 140 calculates parameters L _m and V indicating the state of the power receiving device by calculation using the first measurement values (V ₁₀ , I ₁₀ ) and the second measurement values (V ₁₁ , I ₁₁ ). _2, to calculate the _{I 2} (step S105). This calculation is performed using the aforementioned equations (10) to (12). Subsequently, the control circuit 140 refers to data such as a table stored in the memory 143, and from the values of the estimated parameters L _m , V ₂ , and I ₂ , the third voltage of the AC power that is output to the inverter circuit 120 A value is determined (step S106). The control circuit 140 causes the inverter circuit 120 to output AC power having the third voltage value and continues power transmission (step S107). Thereafter, the control circuit 140 determines whether the time _{T 1} from the previous measurement has elapsed (step S108). If the time _{T 1} is passed, is performed the operation of steps S102 S107 again. At this time, the previous third voltage value is treated as a new first voltage value. The first to third voltage values in each process may be different from the previous value.

The third voltage value is set to the same value as the first voltage value when the estimated parameters L _m , V ₂ , and I ₂ have not changed from the previous values. On the other hand, when the values of the estimated parameters L _m , V ₂ , and I ₂ have changed from the previous values, the third voltage value is set to a value different from the first voltage value.

FIG. 13A is a diagram illustrating an example of a time change of the output voltage V ₁ of the inverter circuit 120. In the example of FIG. 13A, the voltage V ₁ was after the first estimate has not changed, i.e., the third voltage value is set to the same value as the first voltage value. On the other hand, after the second and third estimates are voltages V ₁ is changed, i.e., the third voltage value is set to a value different from the first voltage value.

As shown in FIG. 13A, the time required for the acquisition of the first measurement value in step S102 _{(V 10, I} 10) and _{t a.} Second measurement value in step S104 the time required for acquisition of the _{(V 11, I} 11) and _{t b.} Let t _c be the time required for parameter estimation and determination of the third voltage value in steps S105 and S106. In the example of FIG. 13A, the control circuit 140 sets the voltage V ₁ to the second voltage value at time t _b + t _c until the third voltage value is determined after obtaining the first measurement value. ing. Without being limited to this example, after acquiring the second measurement value, the control circuit 140 may return the voltage V1 to the first measurement value and then perform the operations of steps S105 and S106. FIG. 13B shows an example of such an operation. In the example illustrated in FIG. 13B, the time for which the voltage V1 is set to the second measured value is tb, and the parameter of the power receiving apparatus is estimated and the third voltage value is determined at the subsequent time tc.

The above estimation method can be applied both when power supply to the moving body 200 is started and during power supply.

<Real-time estimation of power reception parameters>
In the above example, for example, as shown in FIG. 13A, the voltage value of the AC power output from the inverter circuit 120 is kept constant from the estimation of the power reception parameter by the two measurements until the second measurement starts again. It is. Estimating the power receiving parameters in a shorter period T _1, by changing the voltage value of the AC power output from the inverter circuit 120, the operation of the moving object 200 can be more finely controlled. However, it takes time of t _a + t _b + t _c to perform the measurement twice and the estimation of the power reception parameter. Further, if the second state is frequently set, the operation of the moving body 200 may be affected.

Therefore, estimation of the power reception parameters by two measurements is carried out at a relatively long period T _1, further short period T _2, may be performed to estimate the power reception parameters by one measurement. Period _{T 2} are shorter than the period _{T 1,} for example, _T 2 / _{T 1} may be set to 1/10 or less 1/1000 or more. T ₁ can be, for example, an integer multiple of T ₂ . In one example, the period _{T 1} is about 100 ms, the period _{T 2} are set to about 1 ms. In the following description, the estimation of the power receiving parameters performed in a sufficiently short time interval such as the period T _2, referred to as real-time estimation.

FIG. 14A is a diagram illustrating an example of timing between estimation based on two measurements and real-time estimation. In FIG. 14A, estimation based on two measurements is referred to as estimation 1, and estimation based on one measurement (real-time estimation) is referred to as estimation 2. As shown, estimate 2 is performed more frequently than estimate 1.

In real-time estimation, different methods are applied depending on whether the moving body 200 is moving or stationary during power transmission. If the mobile 200 is moving, the relative position between the transmitting coil and the receiving coil changes, the mutual inductance L _m may vary. On the other hand, the receiving voltage V ₂ for the time T ₂ are largely unchanged. Therefore, using equation (5) Equation (13) below obtained by modifying, as V ₂ is constant, it is possible to estimate only the mutual inductance L _m in real time.

In Equation (13), V ₁ and I ₁ are obtained from real-time measurement by the measuring instruments 130a and 130b. V _2, before performing the real-time estimation is a value obtained by calculation of equation (11). The control circuit 140 can estimate L _m in real time for each period T ₂ using Equation (13). In this case, V ₂ having a small change is estimated for each period T ₁ , and L _m having a large change is estimated for each shorter period T ₂ .

In this example, when the power receiving apparatus is moving with respect to the power transmitting apparatus 100, the control circuit 140 performs a mutual inductance L _m and a calculation using the first and second measured values for each cycle T _1. performing a first process of estimating the voltage V ₂ output from the receiving coil. Then, for each period T ₂ shorter than the period T ₁ , the mutual inductance L _m is estimated by the calculation of Expression (13) using the value of the voltage V ₂ estimated in the previous first process. The sensor 150 can detect that the power receiving device is moving with respect to the power transmitting device 100.

If the moving object 200 is stopped in the power transmission, the mutual inductance L _m does not change, receiving voltage V ₂ may vary. In particular, when the amount of charge in the power storage element 245 is substantially zero at the start of power transmission, V ₂ can vary greatly. Therefore, when the moving body 200 is stopped, it is assumed that L _m is constant, and only V ₂ can be estimated in real time using the following equation (14) that is the same as equation (11). .

In Equation (14), V ₁ and I ₁ are obtained from real-time measurement by the measuring instruments 130a and 130b. L _m is a value obtained by the calculation of Expression (10) before performing real-time estimation. The control circuit 140 can estimate V ₂ in real time for each period T ₂ using Equation (14). In this case, L _m having a small change is estimated for each period T ₁ , and V ₂ having a large change is estimated for each shorter period T ₂ .

In this example, when the power receiving apparatus is stationary with respect to the power transmitting apparatus 100, the control circuit 140 performs the mutual inductance L _m and the calculation using the first and second measured values for each period T _1. performing a first process of estimating the voltage V ₂ output from the receiving coil. Then, the control circuit 140 uses the value of the mutual inductance L _m estimated in the previous first process for each cycle T ₂ shorter than the cycle T ₁ to calculate the voltage V ₂ by the calculation of Expression (14). Is estimated. The sensor 150 can detect that the power receiving device is stationary with respect to the power transmitting device 100.

As described above, in the real-time estimation, it is assumed that parameters with small changes among the power receiving parameters such as L _m , V _2, and I ₂ are constant, and other parameters with large changes are estimated in real time. As the parameter with a small change, an estimation parameter by two measurements performed before the start of real-time estimation is used.

14B is a diagram showing an example of a time variation of the voltage V ₁ of the case of controlling the voltages V ₁ performs real-time estimated by the period T _2. As shown, the control circuit 140 in this example, based on the power receiving parameters estimated by real-time estimation for each period T _2, to determine the voltage value of the AC power output from the inverter circuit 120. Control circuit 140, when the parameters previously estimated, the difference or the rate of change of the newly estimated parameter exceeds a predetermined value, changes the voltage V _1. Thereby, operation | movement of the mobile body 200 can be controlled more finely.

FIG. 15 is a flowchart illustrating an example of an operation in which estimation by two measurements performed for each period T ₁ and real-time estimation performed for each period T ₂ are combined. Steps S202 to S205 in FIG. 15 show an estimation process based on two measurements. Steps S211 to S214 indicate real-time estimation processing.

The control circuit in this example 140, in every cycle _{T 2} shorter than the period _{T 1,} to perform a real-time estimation process in S214 from step S211. Control circuit 140, in step S211, it is determined whether elapsed time T ₂ from the start of the previous real-time estimation process. When this determination is Yes, the control circuit 140 acquires the measured values V ₁ and I ₁ of the voltage and current measured by the measuring instrument in step S212. In step S213, the control circuit 140 estimates a power reception parameter. As described above, if the mobile 200 is moving is assumed to be constant receiving voltage V _2, to estimate the mutual inductance L _m by the calculation formula (13). Conversely, if the mobile 200 is stationary, it is assumed that the mutual inductance L _m is constant, estimates the receiving voltage V ₂ by the operation of Equation (14). Control circuit 140, in step S214, the based on the power receiving parameters estimated by referring to a table to determine the next value of the transmission voltages V ₁ to be set.

Control circuit 140, from the previous step S202 until the time _{T 1} is elapsed, repeats S214 from step S211. When the time _{T 1} is elapsed, perform the S205 from step S202, to determine the updated value of the transmission voltage V1. The processing from step S202 to S205 is the same as the processing described with reference to FIG.

With the above operation, power reception parameters can be estimated with high frequency without performing communication with the power receiving apparatus during power transmission.

<Conversion of current and voltage>
The effective voltage value V ₁ and the effective current value I ₁ used in the above estimation method are effective values of a sine wave signal having an angular frequency ω. However, the voltage output from the inverter circuit 120 is not limited to a sine wave but may be a rectangular wave. In such a case, the control circuit 140 performs the above-described calculation after appropriately converting the value measured by the measuring instrument 130.

The waveform of the voltage output from the inverter circuit 120 may be a rectangular wave. On the other hand, the waveform of the current output from the inverter circuit 120 can be considered to be approximately a sine wave. It is assumed that the voltage is a rectangular wave with a period of 2π / ω having a maximum value V _1m and a minimum value −V _1m . The effective value of the voltage obtained from the measuring instrument 130a is V _1m, and the effective value of the current obtained from the measuring instrument 130b is I _1m .

The effective value V _{1 m} of the voltage of the rectangular wave, can not be used as it is as an effective value V ₁ of the voltage sine wave. It is necessary to derive a coefficient V ₁ of the term 2 ^1/2 V ₁ × sin (ωt + θ) having a sine wave component of the angular frequency ω by expanding the Fourier wave into a Fourier series. Thus, it can be seen that V ₁ = ((2 × 2 ^1/2 ) / π) V _1m . On the other hand, since the current output from the inverter circuit 120 can be handled as a sine wave, I ₁ = I _{1 m} can be obtained.

_Conversion of the DC voltage value V _2dc and DC current value I _2dc of the storage element 145 with the effective value V ₂ of the output voltage from the power receiving resonator and the effective value I ₂ of the output current in the power receiving device will be described.

As shown in FIGS. 4 and 9, the AC power output from power receiving resonator 210 is stored in power storage element 245 as DC power via rectifier 220 and capacitor 230. In the power storage element 245, the DC voltage value is estimated as V _2dc = (π / (2 × 2 ^1/2 )) V _2, and the DC current value is I _2dc = ((2 × 2 ^1/2 ) / π ) I ₂ is estimated. Therefore, when performing power transmission control by estimating V _2dc and I _2dc instead of V ₂ and I ₂ , the control circuit 140 _converts V ₂ and I ₂ to V _2dc and I _2dc based on the above formula. Convert it.

The arrangement of the measuring instruments 130a and 130b or the partial configuration of the storage element 245 may be different from the configuration in the present embodiment. Even in such a case, the processing in the present embodiment can be applied by converting the measured effective value of the voltage and effective value of the current using an appropriate expression.

16A to 16C show other examples of the arrangement of the voltage measuring instrument 130a and the current measuring instrument 130b. FIG. 16A is a schematic diagram illustrating an example in which the voltage measuring device 130 a is connected between the DC power supply 50 and the inverter circuit 120. FIG. 16B is a schematic diagram illustrating an example in which the current measuring device 130 b is connected between the DC power supply 50 and the inverter circuit 120. FIG. 16C is a schematic diagram illustrating an example in which both the voltage measuring device 130 a and the current measuring device 130 b are connected between the DC power supply 50 and the inverter circuit 120.

In the example of FIG. 16A, the voltage measuring instrument 130a measures the voltage input to the inverter circuit 120. Using the effective value V _{1m of the} voltage obtained from the voltage measuring instrument 130a, the effective value of the AC voltage output from the inverter circuit 120 is calculated as V ₁ = ((2 × 2 ^1/2 ) / π) V _1m . Can be obtained by:

In the example of FIG. 16B, the current measuring instrument 130b measures the current input to the inverter circuit 120. Using the effective value I _{1m of the} current obtained from the current measuring device 130b, the effective value of the alternating current output from the inverter circuit 120 is calculated as I ₁ = (π / (2 × 2 ^1/2 )) I _1m Can be obtained by:

In the example of FIG. 16C, the voltage measuring instrument 130a and the current measuring instrument 130b measure the voltage and current input to the inverter circuit 120, respectively. In this example, the effective value of the alternating voltage output from the inverter circuit 120 is obtained by the calculation of V ₁ = ((2 × 2 ^1/2 ) / π) V _1m , and the effective value of the alternating current is I ₁ = ( It can be obtained by calculating π / (2 × 2 ^1/2 ) I _1m .

FIG. 17A is a schematic diagram illustrating an example in which the DC-DC converter 250 is connected between the capacitor 230 and the power storage element 245. FIG. 17B is a schematic diagram illustrating an example in which a load resistor 240 such as a motor is arranged instead of the power storage element 245 in the configuration of FIG. 17A. In these examples, power transmission control may be performed based on the voltage and current of the DC power output from the DC-DC converter 250. In that case, the control circuit 140 calculates the voltage and current output from the DC-DC converter 250 from the values of V2 and I2 calculated by the above-described processing. When the duty ratio D of the DC-DC converter 250 is constant, the DC voltage value is estimated as V _2dc = (π / (2 × 2 ^1/2 )) V ₂ D at the power storage element 245 or the load resistor 240. The The direct current value is estimated as I _2dc = ((2 × 2 ^1/2 ) / π) I ₂ / D.

<Effect>
According to the present embodiment, the transmission power can be appropriately controlled according to the position of the power receiving device, the state of impedance, and the like without performing communication from the power receiving device to the power transmitting device 100. For this reason, for example, it is possible to eliminate an influence such as communication interference that occurs in a use environment such as a factory or a road. In addition, there is no time loss due to connection and approval before communication. Furthermore, since it is not necessary to mount wireless devices in both the electric device 100 and the moving body 200, the system maintainability can be improved, and the size and cost can be reduced.

The power transmitting device and the power receiving device may be equipped with a communication device for a purpose different from the feedback control during power transmission. For example, a form in which communication is performed in order to perform alignment between a power transmission device and a power reception device before starting power transmission is also included in the present disclosure.

The processing based on the expressions (10) to (12), (13), and (14) in the above description is an exemplification, and can be appropriately modified and used. For example, the equation may be corrected and used as necessary so that the error is reduced.

The technology of the present disclosure can be applied to a wireless power transmission system to a moving body such as an automatic guided vehicle (AGV). The technology of the present disclosure can also be applied to other industrial machines, multicopters, service robots, and the like.

50: direct current (DC) power supply 100 ... wireless power transmission device 105 ... power transmission coil unit 110 ... power transmission resonator 112 ... power transmission coil 112a ... first upper part 112b ... number 1. Lower part 1 112c ... first rectangular surface 120 ... inverter circuit 130 ... current measuring device 140 ... control circuit 142 ... control IC 143 ... memory 144 ... gate driver 150 ... sensor 200 ... moving body 205 ... power receiving coil unit 207 ... drive wheel 210 ... power receiving resonator 212 ... power receiving coil 212a ... second upper part 212b ... 2nd lower part 212c ... 2nd rectangular surface 220 ... Rectifier 230 ... Capacitor 240 ... Load such as motor Anti-245 ... electric storage element 250 ··· DC-DC converter

Claims (14)

1. A power transmitting device that wirelessly transmits power to a power receiving device including a power receiving resonator,
   An inverter circuit;
   A power transmission resonator connected to the inverter circuit;
   A measuring instrument for measuring one of a voltage input to the inverter circuit and a voltage output from the inverter circuit, and a current input to the inverter circuit and a current output from the inverter circuit;
   A control circuit for controlling the inverter circuit,
   The control circuit includes:
   First measured values of voltage and current measured by the measuring instrument in a state where AC power having a first voltage value is output from the inverter circuit and transmitted from the power transmitting resonator to the power receiving resonator. Get
   The second measured value of voltage and current measured by the measuring instrument in a state where the voltage value of the AC power output from the inverter circuit is changed to a second voltage value different from the first voltage value. Get
   A third voltage value is determined by a process including an operation using the first and second measurement values;
   A power transmission device that outputs AC power having the third voltage value from the inverter circuit and continues power transmission.
2. The control circuit includes:
   By the calculation using the first and second measured values, the value of one or more parameters indicating the state of the power receiving device is estimated,
   The third voltage value is determined from the estimated value of the parameter with reference to data defining a correspondence relationship between the value of the one or more parameters and the value of the voltage to be output from the inverter circuit. The power transmission device according to claim 1.
3. The control circuit includes:
   Determination of the acquisition and the third voltage value of the first and second measurement values, run in every cycle T _1,
   When the value of the one or more parameters indicating the state of the power receiving device estimated from the first and second measured values changes from the value of the parameter when estimated last time, the third voltage value Is set to a value different from the first voltage value,
   The power transmission device according to claim 2, wherein when the value of the parameter is the same as the value of the parameter estimated last time, the third voltage value is set to the same value as the first voltage value. .
4. The one or more parameters include a mutual inductance between a power transmission coil included in the power transmission resonator and a power reception coil included in the power reception resonator, a voltage output from the power reception resonator, and an output from the power reception resonator. The power transmission device according to claim 2, comprising at least one of a current to be output and electric power output from the power receiving resonator.
5. The one or more parameters include the mutual inductance;
   The effective values of the voltage and current output from the inverter circuit obtained from the first measurement value are V ₁₀ and I ₁₀ , respectively.
   The effective values of the voltage and current output from the inverter circuit obtained from the second measured value are V ₁₁ and I ₁₁ , respectively.
   Let the mutual inductance be L _m ,
   The resistance value of the power transmission resonator and R _1,
   The resistance value of the power receiving resonator is R ₂ ,
   When the drive angular frequency of the inverter circuit is ω,
   The control circuit includes:
   

   

   The power transmission device according to claim 4, wherein the mutual inductance L _m is estimated by the calculation of:
6. The one or more parameters include at least one of a voltage output from the power receiving resonator and a current output from the power receiving resonator,
   The voltage output from the power receiving resonator is V ₂ ,
   When the current output from the power reception resonator and I _2,
   The control circuit includes:
   

   

   Or
   

   

   The power transmission device according to claim 5, wherein the at least _one of the voltage V ₂ and the current I ₁ is estimated by the calculation of:
7. The control circuit, when the power receiving device is moving relative to the power transmission device,
   For each period T ₁ , a first process for estimating the mutual inductance L _m and the voltage V ₂ output from the power receiving resonator is performed by the calculation using the first and second measured values. ,
   For each period T ₂ shorter than the period T ₁ , using the value of the voltage V ₂ estimated in the previous first process,
   

   

   The power transmission device according to claim 6, wherein the mutual inductance L _m is estimated by the calculation of:
8. The control circuit, when the power receiving device is stationary with respect to the power transmission device,
   For each period T ₁ , a first process for estimating the mutual inductance L _m and the voltage V ₂ output from the power receiving resonator is performed by the calculation using the first and second measured values. ,
   For each period T ₂ shorter than the period T ₁ , using the value of the mutual inductance L _m estimated in the previous first process,
   

   

   Estimating the voltage V ₂ by the operation of the power transmission device according to claim 6 or 7.
9. The power transmission device according to any one of claims 1 to 8, further comprising a sensor that detects whether or not the power reception device is moving with respect to the power transmission device.
10. The power transmission device according to any one of claims 1 to 9, wherein the power reception device is a moving body.
11. The inverter circuit has a plurality of switching elements,
    The control circuit supplies a pulse signal for determining a conduction / non-conduction state to each of the plurality of switching elements, and adjusts a duty ratio of the pulse signal to thereby output the alternating current output from the inverter circuit. The power transmission device according to claim 1, which controls a voltage value of electric power.
12. A power transmission device according to any one of claims 1 to 11,
    A wireless power transmission system comprising the power receiving device.
13. A control device comprising the control circuit in the power transmission device according to any one of claims 1 to 11.
14. A program used in a power transmission device that wirelessly transmits power to a power reception device including a power reception resonator,
    The power transmission device is:
    An inverter circuit;
    A power transmission resonator connected to the inverter circuit;
    A measuring instrument for measuring one of a voltage input to the inverter circuit and a voltage output from the inverter circuit, and a current input to the inverter circuit and a current output from the inverter circuit;
    A control circuit for controlling the inverter circuit,
    The program is stored in the control circuit.
    First measured values of voltage and current measured by the measuring instrument in a state where AC power having a first voltage value is output from the inverter circuit and transmitted from the power transmitting resonator to the power receiving resonator. Get
    The second measured value of voltage and current measured by the measuring instrument in a state where the voltage value of the AC power output from the inverter circuit is changed to a second voltage value different from the first voltage value. Get
    A third voltage value is determined by a process including an operation using the first and second measurement values;
    A program that causes the inverter circuit to output AC power having the third voltage value and to continue power transmission.

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