CN110692176A

CN110692176A - Power transmission device, wireless power transmission system, and control device

Info

Publication number: CN110692176A
Application number: CN201880035387.0A
Authority: CN
Inventors: 齐亮
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2017-06-02
Filing date: 2018-05-29
Publication date: 2020-01-14
Also published as: JPWO2018221532A1; WO2018221532A1

Abstract

When communication from the power receiving device to the power transmitting device is not performed, the transmission power is controlled according to the state of the power receiving device. The power transmission device includes an inverter circuit, a power transmission resonator, a measuring device, and a control circuit. The measurer measures an input voltage or an output voltage of the inverter circuit and an input current or an output current of the inverter circuit. The control circuit changes the voltage value of the alternating current power output from the inverter circuit from a 1 st voltage value to a 2 nd voltage value during power transmission, obtains a 1 st measured value and a 2 nd measured value of the voltage and the current measured by the measuring device before and after the change, respectively, determines a 3 rd voltage value through processing including calculation using the 1 st and the 2 nd measured values, and causes the inverter circuit to output the alternating current power having the 3 rd voltage value and continue power transmission.

Description

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

Technical Field

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

Background

Development of a wireless power transmission system (also referred to as a contactless power supply system) that wirelessly transmits power from a power transmitting apparatus to a power receiving apparatus is advancing. Patent documents 1 and 2 disclose examples of a contactless power supply system. In the systems of patent documents 1 and 2, information such as a reception voltage is fed back from a power receiving device to a power transmitting device by wireless communication, and the power transmitting device controls the transmission power based on the information.

Documents of the prior art

Patent document

Patent document 1: international publication No. WO2012/073349

Patent document 2: international publication No. WO2014/148144

Disclosure of Invention

Problems to be solved by the invention

In the techniques disclosed in patent documents 1 and 2, communication for feeding back information from the power receiving apparatus to the power transmitting apparatus is required. Embodiments of the present disclosure provide a technique of appropriately controlling transmission power according to a state of a power-receiving device without performing such communication.

Means for solving the problems

The power transmitting device in an exemplary embodiment of the present disclosure wirelessly transmits power to a power receiving device having a power receiving resonator. The power transmission device includes: an inverter circuit; a power transmission resonator connected to the inverter circuit; a measuring device that 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; and a control circuit that controls the inverter circuit. The control circuit obtains a 1 st measured value of the voltage and the current measured by the measuring device in a state where the inverter circuit is caused to output the alternating current power having a 1 st voltage value and the power is transmitted from the power transmitting resonator to the power receiving resonator, obtains a 2 nd measured value of the voltage and the current measured by the measuring device in a state where the voltage value of the alternating current power output from the inverter circuit is changed to a 2 nd voltage value different from the 1 st voltage value, specifies a 3 rd voltage value by a process including an operation using the 1 st and 2 nd measured values, causes the inverter circuit to output the alternating current power having the 3 rd voltage value and continues the power transmission.

In addition, the wireless power transmission system according to the exemplary embodiment of the present disclosure includes the power transmitting device and the power receiving device described above. The control device in the exemplary embodiment of the present disclosure has the control circuit in the power transmission device described above. The program in the exemplary embodiment of the present disclosure is used in a power transmitting device that wirelessly transmits power to a power receiving device having a power receiving resonator.

The general or specific aspects described above can be implemented by an apparatus, a system, a method, an integrated circuit, a computer program, or a recording medium. Alternatively, it may be realized by any combination of systems, apparatuses, methods, integrated circuits, computer programs, and recording media.

Effects of the invention

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

Drawings

Fig. 1 is a diagram for explaining an outline of a mobile body system in an exemplary embodiment of the present disclosure.

Fig. 2 is a perspective view schematically showing an example of a moving body 200 in an exemplary embodiment of the present disclosure.

Fig. 3 is a perspective view showing an example of the arrangement relationship between the power transmission coil unit 105 and the power reception coil unit 205 during charging.

Fig. 4 is a block diagram showing the structure of a mobile body system in an exemplary embodiment of the present disclosure.

Fig. 5 is a diagram showing a configuration example of the inverter circuit 120 and the control circuit 140.

Fig. 6 is a diagram showing an example of waveforms of the pulse signals supplied from the control circuit 140 to the switching elements G1 to G4 and the voltage output from the inverter circuit 120.

Fig. 7 is a diagram showing an equivalent circuit of power transmitting resonator 110 and power receiving resonator 210.

Fig. 8A is a perspective view for explaining an example of the shape and arrangement relationship of the power transmission coil 112 and the power reception coil 212.

Fig. 8B is a diagram schematically showing an example of the shape of the power transmission coil 112 when viewed from the Y direction.

Fig. 8C is a diagram schematically illustrating an example of the shape of the power receiving coil 212 when viewed from the Y direction.

Fig. 9 is a diagram showing a configuration example of rectifier 220, capacitor 230, and 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 a wireless power transmission system in an exemplary embodiment of the present disclosure.

Fig. 12 is a flowchart showing an operation during power transmission in the exemplary embodiment of the present disclosure.

Fig. 13A is a diagram showing an example of a temporal change in the output voltage V1 of the inverter circuit 120.

Fig. 13B is a diagram showing another example of the temporal change in the output voltage V1 of the inverter circuit 120.

Fig. 14A is a diagram showing an example of the time of estimation from two measurements and real-time estimation.

FIG. 14B is a diagram showing a period T₂An example of the temporal change of the voltage V1 when the voltage V1 is controlled by real-time estimation is shown.

FIG. 15 is a graph showing that each period T will be counted₁Estimation from two measurements made and according to each period T₂An example of the operation of combining the real-time estimation is shown in the flowchart.

Fig. 16A is a schematic diagram showing an example in which voltage measuring device 130a is connected between DC power supply 50 and inverter circuit 120.

Fig. 16B is a schematic diagram showing an example of the configuration in which current measuring device 130B is connected between DC power supply 50 and inverter circuit 120.

Fig. 16C is a schematic diagram showing an example in which both the voltage measuring device 130a and the current measuring device 130b are connected between the DC power supply 50 and the inverter circuit 120.

Fig. 17A is a schematic diagram showing an example in which a DC-DC converter 250 is connected between the capacitor 230 and the power storage element 245.

Fig. 17B is a schematic diagram showing an example in which a load resistor 240 such as a motor is disposed in place of the power storage element 245 in the configuration of fig. 17A.

Detailed Description

Prior to the description of the embodiments of the present disclosure, the knowledge that forms the basis of the present disclosure will be described.

In the conventional non-contact power feeding technique, information such as voltage, current, power, and impedance in the power receiving device is fed back to the power transmitting device by wireless communication in order to control power feeding. In order to realize such wireless communication, devices that perform wireless communication such as Wi-Fi (registered trademark) or Bluetooth (registered trademark) are used for both the power transmitting apparatus and the power receiving apparatus.

However, when the power receiving device is a device such as a mobile body used in a factory, a road, or the like, for example, a situation in which the power transmitting device and the power receiving device cannot normally perform wireless communication due to communication interference or noise may frequently occur. If the wireless communication is interrupted, the power transmitting apparatus cannot obtain information of the power receiving apparatus, and therefore cannot appropriately control the transmission power. Further, the wireless device takes time to connect and authenticate 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, the power supply efficiency is greatly reduced because the power supply time is a high percentage of the total power supply time even with a small time loss. Moreover, the installation of the wireless device leads to an increase in cost.

The present inventors have found the above problems and have studied a structure for solving the problems. The inventor finds that: in power transmission, the voltage of transmitted ac power is changed at short time intervals, and information such as mutual inductance between coils and received voltage can be estimated from information of voltage and current on the power transmission side measured before and after the change. By this discovery, it is possible to estimate the state of the power receiving apparatus without performing communication from the power receiving apparatus to the power transmitting apparatus, and to appropriately control the transmission power according to the state.

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

A power transmitting device according to an aspect of the present disclosure wirelessly transmits power to a power receiving device having a power receiving resonator. The power transmission device includes an inverter circuit, a power transmission resonator connected to the inverter circuit, a measuring device, and a control circuit for controlling the inverter circuit. The measuring device 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) The method includes obtaining a 1 st measured value of the voltage and the current measured by the measuring instrument in a state where the inverter circuit is caused to output the alternating-current power having the 1 st voltage value and the power is transmitted from the power transmitting resonator to the power receiving resonator. (2) The 2 nd measurement value of the voltage and the current measured by the measuring instrument is obtained in a state where the voltage value of the alternating-current power output from the inverter circuit is changed to the 2 nd voltage value different from the 1 st voltage value. (3) The 3 rd voltage value is determined by a process including an operation using the 1 st and 2 nd measured values, and the inverter circuit is caused to output the alternating-current power having the 3 rd voltage value to continue power transmission.

With the above configuration, it is possible to appropriately control the transmission power according to a change in the state of the power receiving apparatus without performing communication from the power receiving apparatus to the power transmitting apparatus.

The power transmitting resonator includes a power transmitting coil and the power receiving resonator includes a power receiving coil. The control circuit estimates the value of one or more parameters indicating the state of the power receiving device by, for example, calculation using the 1 st and 2 nd measured values. The 3 rd voltage value can be determined based on the estimated value of the parameter by referring 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. The data defining such a correspondence relationship is stored in a recording medium such as a memory in the power transmission device, for example, in the form of a table, an equation, or a function. The data may be, for example, a table defining the mutual inductance between the coils or the correspondence relationship between the voltage output from the power receiving resonator and the output voltage of the inverter circuit.

The control circuit for example being arranged for each period T₁The 1 st and 2 nd measurement values are obtained and the 3 rd voltage value is determined. When the value of one or more parameters indicating the state of the power receiving device estimated from the 1 st and 2 nd measured values changes from the value of the parameter estimated last time, the control circuit sets the 3 rd voltage value to a value different from the 1 st voltage value. On the other hand, when the value of the parameter is the same as the value of the parameter at the last estimation, the control circuit sets the 3 rd voltage value to the same value as the 1 st voltage value. Whether or not the value of each parameter has changed from the value at the time of the last estimation can be determined by determining whether or not the difference or the change rate between the value of the parameter and the value at the last time exceeds a threshold value.

The one or more parameters may include at least one of 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 power output from the power reception resonator. The specific process of estimating these parameters will be described later.

The power receiving device is, for example, a mobile body. The "movable body" refers to a movable object that is driven or charged by electric power. The moving body can be, for example, an Automated Guided Vehicle (AGV), an Electric Vehicle (EV), a mobile robot, an Unmanned Aerial Vehicle (UAV), a so-called drone). The power receiving device may be a device that does not move automatically, such as a portable device.

The power transmitting apparatus may also have a sensor that detects whether the power receiving apparatus moves relative to the power transmitting apparatus. Such a sensor may be, for example, a sensor using visible light or infrared light, or a sensor that detects movement of the power receiving device from a change in voltage or current in the circuit of the power transmission device.

The measurer performs two measurements consecutively in a relatively short time. For example, two measurements are taken at a time interval that is considered as the degree to which the mutual inductance between the power transmission coil and the power reception coil is constant. The time interval is set to be shorter as the speed of movement of the power receiving device is higher during power transmission. The measuring device may be configured to perform measurement in response to an instruction from the control circuit, or may be configured to constantly monitor the voltage and the current at fixed short time intervals.

The control circuit can adjust the output voltage of the inverter circuit (hereinafter, sometimes referred to as "transmission voltage") by various methods. For example, the transmission voltage can be adjusted by changing the duty ratio, phase, or frequency of a control signal supplied to each of a plurality of switching elements included in the inverter circuit or by changing the dc voltage input to the inverter circuit. In a system in which the power transmission device includes a DC-DC converter connected between the inverter circuit and the DC power supply, the DC voltage input to the inverter circuit can be controlled. In such an aspect, the control circuit can change the direct-current 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 computer program (hereinafter, simply referred to as a program) that defines operations executed by the control device having the control circuit and the control circuit. Such a program is stored in a recording medium such as a memory in the power transmission device, and causes the control circuit to execute the above-described operation.

Hereinafter, exemplary embodiments of the present disclosure will be described. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid unnecessary redundancy in the following description, which will be readily understood by those skilled in the art. The present inventors have provided drawings and the following description in order to fully understand the present disclosure by those skilled in the art, and do not intend to limit the subject matter described in the claims. In the following description, the same or similar components are denoted by the same reference numerals.

(embodiment mode)

< Structure >

Fig. 1 is a diagram for explaining an outline of a mobile body system in the present embodiment. A mobile body system is an example of a wireless power transmission system in the present disclosure. The mobile body system can be used as a system for transporting articles in a factory, for example. The mobile body system has at least one wireless power transmission device (hereinafter, simply referred to as "power transmission device") 100 and at least one mobile body 200. The mobile body 200 is an example of a power receiving device. The moving body 200 may be, for example, an Automated Guided Vehicle (AGV) that autonomously moves in a factory and transports an article to a required place. Fig. 1 illustrates four power transmission devices 100 and four mobile units 200. The number of power transmission devices 100 and mobile object 200 is not limited to four, and is arbitrary.

The power transmission device 100 wirelessly transmits power to the mobile unit 200. The power transmission device 100 includes a power transmission coil unit 105 including a power transmission coil that transmits ac power to a space. The moving body 200 includes a power receiving coil unit 205 including a power receiving coil. Power is wirelessly transmitted from the power transmission coil to the power receiving coil by coupling the power transmission coil and the power receiving coil using magnetic field resonance. As described above, in the present embodiment, wireless power transmission by magnetic field resonance coupling (also sometimes referred to as "magnetic field resonance coupling" or "resonant magnetic field coupling") is used. According to wireless power transmission of the magnetic field resonance coupling method, power transmission over a longer distance is possible than in the method using electromagnetic induction. The technique of the present disclosure is not limited to the magnetic field resonance coupling method, and can be applied to wireless power transmission by an electromagnetic induction method. Thus, the present disclosure also includes structures by electromagnetic induction.

The movable body 200 includes a capacitor and a motor. The power received by the power receiving coil in the power receiving coil unit 205 is rectified and stored in a 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 movable body 200 can move by driving the motor with the electric power stored in the capacitor.

When the mobile unit 200 moves, the amount of stored electricity (i.e., the amount of charged electricity) in the capacitor decreases. Therefore, in order to continue the movement, recharging is required. Therefore, when the amount of charge is lower than the predetermined threshold value during movement, the mobile unit 200 moves to the vicinity of the power transmission device 100 and is charged. As shown in fig. 1, when the power transmission devices 100 are provided at a plurality of locations, the moving body 200 only needs to move to the vicinity of the nearest power transmission device 100, and thus the moving distance can be shortened.

As described above, such a system can be used as a system for transporting articles in a factory, for example. The mobile unit 200 typically has a stage on which an article is mounted, and functions as a carriage that autonomously moves in a factory and transports the article to a necessary place. The mobile system is not limited to use in a factory, and can be used in, for example, a store, a hospital, a home, and any other places. The moving object 200 is not limited to the AGV, and may be another industrial machine or a service robot. The mobile body 200 can be any device having a movable mechanism, such as a manned Vehicle, an Unmanned Aerial Vehicle (UAV), or a sweeping robot. The power receiving device in the present disclosure is not limited to a mobile body. The technique of the present disclosure can be applied to any wireless power transmission system in which the relative positions of a power transmission coil and a power receiving coil can be changed 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 provided on the side surface; a plurality of wheels including a driving wheel 207 driven by a motor; and a stage 206 on which the article is 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 the arrangement relationship between the power transmission coil unit 105 and the power reception coil unit 205 during charging. XYZ coordinates representing directions X, Y, Z perpendicular to each other are shown in fig. 3. In the following description, the illustrated coordinate system is used. The XY plane is parallel to the horizontal plane or the ground, and the direction in which the mobile unit 200 moves forward is defined as the positive direction of the X axis, and the vertically upward direction is defined as the positive direction of the Z axis.

The orientation of the structure shown in the drawings of the present application is set for convenience of explanation, and is not intended to limit the orientation in which the embodiments of the present disclosure are actually implemented. The shape and size of the whole or a part of the structure shown in the drawings are not limited to actual shapes and sizes.

As shown in fig. 3, the power transmission coil 112 in the power transmission coil unit 105 has a conductor wire (winding) wound 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 the present embodiment are asymmetrical. 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 coil 112 and the power receiving coil 212 face each other and perform power transmission. More specifically, charging is performed in a state where a surface defined by the winding of the transmission coil 112 and a surface defined by the winding of the reception coil 212 (in the illustrated example, both surfaces are parallel to the XZ surface) face each other. Charging can be performed not only when these surfaces are perfectly parallel but also when they are inclined to each other.

In the present embodiment, since the power transmission coil 112 has a shape elongated in the X direction, even if the moving body 200 is slightly displaced in the X direction, the relative state between the coils can be maintained, and efficient power transmission can be maintained.

The mobile unit 200 can grasp the position and direction of the mobile unit and the position and direction of the power transmission coil 112 using various sensors. This makes it possible to specify the power transmission device 100 closest to the own device, move the power transmission device 100 to the vicinity thereof, and assume an attitude in which efficient power transmission is possible, that is, an attitude in which the power receiving coil 212 is opposed to the power transmission coil 112 in close proximity thereto. When the nearest power transmission apparatus 100 is supplying power to another mobile unit 200, the mobile unit 200 may move to the next nearest power transmission apparatus 100.

The structure of the moving body system according to the present embodiment will be described in more detail below.

Fig. 4 is a block diagram showing the structure of the mobile body system of the present 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; a voltage measuring device 130a that measures the voltage output from the inverter circuit 120; a current measuring device 130b that measures a current output from the inverter circuit 120; a control circuit 140 for controlling 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 aforementioned power transmission coil 112. 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 device 130 in the present embodiment measures the voltage and the current output from the inverter circuit 120. As described later, the voltage measuring device 130a may measure the voltage input to the inverter circuit 120. Similarly, the current measuring device 130b may measure the current input to the inverter circuit 120.

The mobile body (power receiving device) 200 includes a power receiving resonator 210, a rectifier (rectifying circuit) 220 connected to the power receiving resonator 210, a capacitor 230 connected to the rectifier 220, and a power storage element 245 connected to the capacitor 230. The power receiving resonator 210 includes the aforementioned power receiving coil 212. Power storage element 245 includes an electric double layer capacitor, a battery, and the like. Further, the power transmission device 100 and the mobile object 200 may have other components not shown. The moving body system does not necessarily have to include all the components shown in fig. 4, and can be omitted as appropriate.

Hereinafter, each constituent element will be described in more detail.

< DC Power supply >

The DC power supply 50 is a power supply that outputs a DC voltage of a predetermined magnitude. DC power supply 50 may include, for example, a converter that converts commercial ac power into DC power having an operating voltage of power transmission device 100 and outputs the DC power.

< inverter circuit and control circuit >

The inverter circuit 120 converts direct-current power supplied from the DC power supply 50 into alternating-current power. The inverter circuit 120 can be, for example, a full-bridge inverter circuit. The full-bridge inverter circuit can output ac power of a desired frequency and voltage value by adjusting the timing of switching of the four switching elements. Each switching element is switched 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 showing a configuration example of the inverter circuit 120 and the control circuit 140. The inverter circuit 120 shown in fig. 5 has a full-bridge inverter circuit including 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 has a control IC142, a gate driver 144, and a memory 143. The control IC142 determines the voltage (effective value, hereinafter the same) and the frequency of the ac power to be output from the inverter circuit 120 by executing the control program stored in the memory 143. In the present embodiment, the voltage or frequency with the highest efficiency is determined based on the values of the voltage V1 and the current I1 measured by the measuring device 130. This operation will be described in detail later. The gate driver 144 supplies a pulse signal having a frequency and a duty ratio determined by the control IC142 to the gates of the switching elements G1 to G4. This controls the on/off states of the switching elements G1 to G4. A part or the whole of the control circuit 140 can be realized by an integrated circuit such as a microcomputer (microcomputer).

At the timing when the switching elements G1 and G4 of the four switching elements G1 to 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 the switching elements G2 and G3 are turned on (on state), a voltage having a polarity opposite to the DC voltage supplied from the DC power supply 50 is output from the inverter circuit 120. The control circuit 140 adjusts the timing of the pulse signal supplied to each of the switching elements G1 to G4, thereby causing the inverter circuit 120 to output ac power of a desired frequency and voltage.

Fig. 6 is a diagram showing an example of waveforms of the pulse signals supplied from the control circuit 140 to the switching elements G1 to G4 and the voltage output from the inverter circuit 120. In fig. 6, symbol E indicates the magnitude of the voltage output from the DC power supply 50, and symbol T indicates the period. By duty cycle d_invThe period during which the output voltage V1 of the inverter circuit 120 is equal to the magnitude E of the output voltage of the DC power supply 50 is controlled. That is, the control circuit 140 adjusts the duty ratio d_invCapable of adjusting the output voltage V by sine wave₁The amplitude and effective value of the ac voltage obtained by the approximation.

The inverter circuit 120 is not limited to the configuration shown in fig. 5. For example, a half-bridge structure is also possible. In this case, the desired ac voltage can be output by adjusting the timing of the gate drive pulse supplied to the two switching elements. The inverter circuit 120 can be realized by a commercially available high-frequency power supply device, for example.

< Power transmitting resonator and Power receiving resonator >

Fig. 7 is a diagram showing an equivalent circuit of power transmitting resonator 110 and power receiving resonator 210. The power transmission resonator 110 is a resonator having a power transmission coil 112 generated inductance component (L)₁) A capacitance component (C)₁) And a resistance component (R)₁) The series resonant circuit of (1). The power receiving resonator 210 has an inductance component (L) generated by the power receiving coil 212₂) A capacitance component (C)₂) And a resistance component (R)₂) The series resonant circuit of (1). Capacitance component (C)₁And C₂) The parasitic capacitance components of the power transmission coil 112 and the power receiving coil 212 may be generated by capacitors provided separately.

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

Fig. 8A is a perspective view for explaining the shapes and arrangement relationships of the power transmission coil 112 and the power reception coil 212 in more detail. Fig. 8A shows an example in which the width of the transmission coil 112 in the Y direction is smaller than that in the example of fig. 3. The two-dot chain line shown in fig. 8A indicates a normal line of a surface defined by the

coils

112 and 212. Fig. 8B schematically shows the shape of the power transmission coil 112 when 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 formed by winding a 1 st conductor wire, and includes a 1 st upper portion 112a and a 1 st lower portion 112b extending in the transverse direction, and two arc-shaped portions connecting the 1 st upper portion 112a and the 1 st lower portion 112 b. The power receiving coil 212 is a winding formed by winding a 2 nd conductor wire, and includes a 2 nd upper portion 212a and a 2 nd lower portion 212b extending in the lateral direction, and two arc-shaped portions connecting the 2 nd upper portion 212a and the 2 nd lower portion 212 b.

The 1 st rectangular surface 112C (fig. 8B) defined by the upper portion 112a and the lower portion 112B of the power transmission coil 112 and the 2 nd rectangular surface 212C (fig. 8C) defined by the 2 nd upper portion 212a and the 2 nd lower portion 212B of the power reception coil 212 are perpendicular or inclined with respect to the horizontal plane. The power receiving coil 112 is disposed on a side surface of the mobile body 200, and the 2 nd rectangular surface 212c faces the 1 st rectangular surface 112c of the power transmission coil 112 during power transmission.

The power transmission coil 112 and the power receiving coil 212 are not limited to the illustrated shapes. For example, the shape of each coil may be rectangular (including square) or elliptical (including circular). The structure of each

coil

112, 212 may be appropriately modified according to the structure of the system to which it is applied. 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 necessarily required to have such a structure. Also, the power transmission coil 112 does not necessarily have to have a larger size than the power receiving coil 212. The power transmission coil 112 and the power receiving coil may have the same structure. The configuration of each coil 112 is arbitrary as long as power transmission is possible.

< rectifier, capacitor, and storage element >

As illustrated, the rectifier 220 may be a full-wave rectifier circuit including a diode bridge and a smoothing capacitor. The rectifier 220 may be a full-wave rectifier circuit of another kind, or may be a half-wave rectifier circuit. The rectifier 220 converts the ac power from the power receiving resonator 210 into dc power and outputs the dc power.

The capacitor 230 is connected in parallel with the rectifier 220. Capacitor 230 is provided to relax and stabilize the variation of the dc voltage supplied from rectifier 220 to power storage device 245. The capacitor 230 may be omitted if it is not required.

The storage element 245 is connected in parallel with the capacitor 230. The power storage device 245 is, for example, a capacitor or a battery. The power storage device 245 may have 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 the electric double layer capacitor or the lithium ion capacitor has a small internal resistance (for example, several tens of m Ω), it can be charged and discharged with a large current with low loss. Therefore, rapid charging can be performed. Further, since the capacitance is larger than that of other types of capacitors, continuous discharge can be performed for a relatively long time. As the storage battery, for example, a secondary battery such as a lithium ion storage battery having high energy density and high charge/discharge efficiency can be used.

< sensor >

The sensor 150 detects the position or movement of the mobile body 200. The sensor 150 can be, for example, a sensor using light (visible light or near infrared light). Sensor 150 may be configured to detect the movement of movable body 200 based on the output of measuring device 130. Whether or not the mobile body 200 is moving can be determined from the temporal change in at least one of the voltage and the current measured by the measuring device 130.

< action >

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 device 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 performs an operation of detecting the moving object 200 as a power reception device. When detecting that the mobile body 200 is located in the vicinity, the control circuit 140 starts power supply to the mobile body 200.

In the example of fig. 10, control circuit 140 applies voltage V₁The value is set to a very small value, and weak power transmission is started (step S11). In this state, the measurer 130 measures the voltage V output from the inverter circuit 120₁And current I₁(step S12). Control circuit 140 according to V₁And I₁Determines whether or not the mobile object 200 is present at a position where power can be received (step S13). When the mobile object 200 is not present at the position where power can be received (no in step S14), the control circuit 140 stops weak power transmission (step S15). Control circuit 140 at elapsed time T₀After that (yes in step S16), the action of step S11 is executed again. In the case where the moving body 200 is present at a position where power can be received (yes in step S14), the control circuit 140 increases the output voltage V₁To start the supply to the moving body 200And (4) electricity.

The detection of the power receiving device in step S13 can be determined, for example, by whether or not the difference between a predetermined reference value depending on the value of V1 and the value of I1 exceeds a threshold value. As the moving body 200 approaches, the mutual inductance of the power transmission coil and the power reception coil increases. This influence changes the circuit flowing through the circuit of power transmission device 100. The approach of the moving body 200 can be detected from the change in the current.

In the example of fig. 10, the approach of the mobile object 200 (power receiving apparatus) is detected from the current and voltage in the circuit of the power transmission apparatus 100. In addition to such a detection method, for example, the approach of the moving object 200 may be detected by the sensor 150 (see fig. 4).

< estimation of State of powered device >

The power transmission device 100 in the present embodiment can estimate the state of the mobile 200 without using information transmitted from the mobile 200 when supplying power to the mobile 200, and can appropriately control the transmission power according to the state. This method will be specifically described below.

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

Fig. 11A is a diagram showing an equivalent circuit of the wireless power transmission system in the present embodiment. The equivalent circuit shown in fig. 11A can also be represented as shown in fig. 11B. In fig. 11A and 11B, components (see fig. 4) such as the inverter circuit 120 connected to the power transmission resonator 110 are collectively shown as one ac power supply. The components such as the rectifier 220 connected to the power receiving resonator 210 are collectively represented as one load. Let the resistance value of the load be R_L. The components such as the rectifier circuit connected to the power receiving resonator 210 actually have a reactance component in addition to a resistance component. However, in fig. 11A and 11B, the reactance component is ignored for simplicity, and the load is represented as a resistance. Let the angular frequency of the transmitted AC power be omega and the mutual inductance be L_m. Angular frequency omegaThe same as the driving angular frequency of the inverter circuit 120.

In the following description, an ac voltage and an ac current are expressed in terms of phasors (phasers). That is, the voltage and current are treated as a complex number. In the phasor display, the absolute values of the voltage and the current represent the respective effective values.

If the phasors of the voltage and current of the AC power supply are respectively shown as v₁And i₁. The effective values of the voltage and current of the AC power supply are respectively set as V₁And I₁Then is V₁＝|v₁I and I₁＝|i₁L. Similarly, if the phasors of the voltage and current of the load are shown as v₂And i₂Then is V₂＝|v₂I and I₂＝|i₂|。

Voltage v shown in fig. 11A and 11B₁And a current i₁Voltages v respectively representing the ac power outputted from the inverter circuit 120₁And a current i₁. Voltage v input to a load₂And a current i₂Each represents a voltage and a current output from power receiving resonator 210.

V is a circuit equation of the equivalent circuit shown in FIG. 11A and FIG. 11B₁、i₁、v₂And i₂Satisfies the following equations (1) and (2).

[ equation 1]

[ equation 2]

Here, j is an imaginary unit.

In the following description, ω is related to the resonance angular frequency ω₀＝1/(L₁C₁)^1/2＝1/(L₂C₂)^1/2Are equal. However, even if the resonance condition ω is not satisfied, ω is set to ω₀As long as ω and ω₀The following argument is based on the small deviation of (a). For example, if | ω - ω₀|/ω₀When the value of (A) is 0.05 or less, the following is sufficiently assumed.

If v is to be₂＝R_Li₂When the formula (2) is substituted, the resonance condition ω L is determined₂＝1/ωC₂To obtain i₂＝j{ωL_m/(R₂+R_L)}i₁. The formula represents i₂Phase ratio i of₁Is advanced by 90 deg.. If i is removed from equation (1) by using the equation₂Then obtain v₁＝{R₁/ω²Lm²/(R₂+R_L)}i₁. The formula represents v₁And i₁With the same phase. And, according to v₂＝R_Li₂，v₂And i₂With the same phase. Can be expressed as v under resonance conditions according to the phase relationship between them₁＝V₁e^jθ、i1＝I₁e^jθ、v₂＝jV₂e^jθAnd i₂＝jI₂e^jθ. Here, θ represents a phase. If these v are to be combined₁、i₁、v₂And i₂Substituting into equations (1) and (2) to obtain V₁、I₁、V₂And I₂The following equations (3) and (4) containing only real numbers are satisfied.

[ equation 3]

R₁I₁+ωL_mI₂＝V₁(3)

[ equation 4]

-ωL_mI₁+R₂I₂＝-V₂(4)

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

[ equation 5]

[ equation 6]

Effective value V of voltage₁For example, by integrating the real-time waveform of the voltage measured by the voltage measuring device 130a in the power transmission device 100. Likewise, the effective value of the current I₁The current measurement device 130b in the power transmission device 100 integrates the real-time waveform of the current measured by the current measurement device.

In equations (5) and (6), V is present₂、I₂And L_mThese three unknown parameters. Since the number of equations is smaller than the number of unknown parameters, it is not possible to directly calculate V₂、I₂And L_m。

Therefore, power transmission apparatus 100 according to the present embodiment changes the value of the power transmission voltage during power transmission, and measures the voltage and current before and after the change. L can be estimated from the values of the voltage and current obtained by two measurements_m、V₂、I₂At least one of (a). This estimation method will be described in more detail below.

The control circuit 140 drives the inverter circuit 120 during power transmission to transmit power from the power transmission coil 112 to the power reception coil 122. This state is referred to as the 1 st state. The control circuit 140 obtains the measured values of the voltage and the current measured by the measuring

devices

130a and 130b, respectively, in the 1 st state. This measurement is referred to as the 1 st measurement. Next, the control circuit 140 changes the value of the voltage output from the inverter circuit 120 to the 2 nd value different from the voltage value in the 1 st state. This state is referred to as the 2 nd state. The control circuit 140 obtains the measured values of the voltage and the current measured by the measuring

devices

130a and 130b, respectively, in the 2 nd state. This measurement is referred to as the 2 nd measurement.

When the time from the acquisition of the 1 st measured value to the acquisition of the 2 nd measured value is sufficiently short, the voltage V of the power storage device 245₂The variation of (c) is small. For example, when the time from the acquisition of the 1 st measured value to the acquisition of the 2 nd measured value is 0.1 seconds or less, the voltage V can be adjusted₂The variation of (A) is suppressed to 0.1V or less. In such a case, it can be assumed that V is in the above-described two measurements₂Is constant.

Let V be the effective values of the voltage and current of the AC power output from the inverter circuit 120 obtained from the 1 st measured value₁₀And I₁₀. Let V be the effective value of the voltage and the effective value of the current of the AC power output from the inverter circuit 120 obtained from the 2 nd measured value₁₁And I₁₁. If it is assumed that V₂If the values are constant, the following equations (7) and (8) are obtained from equation (5).

[ equation 7]

[ equation 8]

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

[ equation 9]

V can be calculated by using equations (7) to (9)₂、I₂And L_mThese three unknown parameters.

If V is removed from equations (7) and (8)₂Then the following L is obtained_mThe estimation formula (10).

[ equation 10]

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

[ equation 11]

Then, the following I is obtained from equations (9) and (11)₂The estimated expression (12).

[ equation 12]

The control circuit 140 can estimate the mutual inductance L by the operation of equations (10) to (12)_mReceiving voltage V₂And receiving a current I₂. Thus, the parameters of the power receiving device can be estimated from the information of the voltage and the current in the power transmitting device 100 without performing communication between the power transmitting device 100 and the mobile object 200.

The control circuit 140 estimates a parameter of the power receiving device, for example, V₂And I₂One or both of them are set to a desired value, the voltage value (3 rd voltage value) of the ac power output from the inverter circuit 120 is determined, and power transmission is continued using the determined voltage value. This enables optimization of power supply even when the mobile unit 200 moves during power transmission. For example, it is possible to suppress a decrease in transmission efficiency or stabilize power supply.

The memory 143 shown in fig. 5 stores pairs L in advance_m、V₂、I₂With the voltage V to be output from the inverter circuit 120₁The correspondence between the data and the data is defined by a table, an equation, or the like. The control circuit 140 can determine the voltage V by referring to the data and according to the estimated parameter₁The changed value of (a). The data may also be for voltage V obtained from the 1 st measurement₁₀And current I₁₀And voltage V obtained from the 2 nd measured value₁₁And current I₁₁In response to the voltage V transmitted₁The correspondence between them is specified. In this case, the control circuit 140 can refer to the data and can calculate from V without performing the calculations of expressions (10) to (12)₁₀、I₁₀、V₁₁、I₁₁In combination withDetermining the voltage V to be transmitted₁。

The control circuit 140 refers to the data and estimates the mutual inductance L from a combination of the following two effective values_mAnd (3) waiting for the power receiving parameters, wherein the two effective values are respectively: effective value V of voltage obtained from the 1 st measured value₁₀And the effective value of the current I₁₀(ii) a And the effective value V of the voltage obtained according to the 2 nd measured value₁₁And the effective value of the current I₁₁。

The voltage V for the mobile body 200 may be stored in the memory 143₂And the amount of charge of the power storage device 245. The control circuit 140 can refer to the data and depend on the voltage V₂The charge amount of the power storage element 245 is estimated. The control circuit 140 can perform control such as stopping power supply from the power transmission device 100 to the mobile body 200 when the charge amount is equal to or greater than a reference value.

The control circuit 140 performs, for example, every period T₁The power receiving parameters are estimated. Period T₁For example, the value can be set to a range of several milliseconds (ms) to several seconds or so. In a certain example, the period T₁Can be set to a time of about 100 ms. When the estimated value of the parameter changes from the value at the last estimation, the control circuit 140 changes the voltage V output from the inverter circuit 120₁Otherwise, the voltage V is maintained₁. Whether or not the estimated value of the fixed parameter has changed can be determined based on whether or not the difference between the current estimated value and the previous estimated value or the change rate exceeds a predetermined threshold. For example, the control circuit 140 is only at the estimated mutual inductance L_mWhen the difference or change rate between the value of the parameter and the value of the same parameter at the last estimation exceeds the threshold value, the voltage V is changed₁。

Hereinafter, a parameter estimation process at the time of power transmission in the present embodiment will be described with reference to fig. 12. 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 the 1 st voltage value (step S101). In the present embodiment, the 1 st voltage value is during power transmission already performedThe effective value of the alternating voltage. The control circuit 140 obtains the 1 st measurement value measured by the measurer 130 in this state (step S102). The 1 st measurement value corresponds to the aforementioned V₁₀And I₁₀. Due to V₁₀And I₁₀Since it is an effective value, when the measurement value output from the measurement device 130 is an instantaneous value, the control circuit 140 performs necessary calculation to obtain an effective value V of voltage₁₀And the effective value of the current I₁₀。

Next, the control circuit 140 causes the inverter circuit 120 to output ac power having a 2 nd voltage value different from the 1 st voltage value (step S103). I.e. the transmission voltage V₁The voltage is changed to the 2 nd voltage value different from the 1 st voltage value up to now. The 2 nd voltage value is set to a value whose difference from the 1 st voltage value is smaller than the magnitude of the noise component. For example, the 2 nd voltage value can be set to a value of about half the 1 st voltage value. The 2 nd voltage value may be set to a value larger than the 1 st voltage value.

The control circuit 140 obtains the 2 nd measurement value of the voltage and the current in this state (step S104). The 2 nd measurement value corresponds to the aforementioned V₁₁And I₁₁. Due to V₁₁And I₁₁Since it is an effective value, when the measurement value output from the measurement device 130 is an instantaneous value, the control circuit 140 performs necessary calculation to obtain an effective value V of voltage₁₁And the effective value of the current I₁₁。

Next, the control circuit 140 utilizes the 1 st measurement (V)₁₀、I₁₀) And 2 nd measured value (V)₁₁、I₁₁) Calculates a parameter L indicating the state of the power receiving device_m、V₂、I₂(step S105). This calculation is performed by the above equations (10) to (12). Next, the control circuit 140 refers to data such as a table stored in the memory 143 and based on the estimated parameter L_m、V₂、I₂Determines the 3 rd voltage value of the ac power to be outputted from the inverter circuit 120 (step S106). The control circuit 140 causes the inverter circuit 120 to output the ac power having the 3 rd voltage value and continues power transmission (step S107). Thereafter, the control circuit 140 determines whether to operate from the topTime T elapsed from one measurement₁(step S108). At the lapse of time T₁In the case of (3), the actions of steps S102 to S107 are executed again. At this time, the previous 3 rd voltage value is treated as a new 1 st voltage value. The 1 st to 3 rd voltage values in each process can be different values from the last one.

At the estimated parameter L_m、V₂、I₂When the value of (3) is not changed from the previous value, the value of the 3 rd voltage is set to the same value as the value of the 1 st voltage. On the other hand, at the estimated parameter L_m、V₂、I₂When the value of (3) is changed from the previous value, the value of the 3 rd voltage is set to a value different from the value of the 1 st voltage.

FIG. 13A shows the output voltage V of the inverter circuit 120₁An example of the temporal change of (1). In the example of FIG. 13A, after the first estimation, the voltage V is₁No change occurs, i.e., the 3 rd voltage value is set to the same value as the 1 st voltage value. On the other hand, after the second and third estimations, the voltage V₁A change occurs, i.e., the 3 rd voltage value is set to a value different from the 1 st voltage value.

As shown in FIG. 13A, let 1 st measurement value (V) in step S102₁₀、I₁₀) The time required for obtaining is t_a. Let the 2 nd measurement value (V) in step S104₁₁、I₁₁) The time required for obtaining is t_b. Let t be the time required for the parameter estimation and the determination of the 3 rd voltage value in steps S105 and S106_c. In the example of FIG. 13A, the time t after the 1 st measurement value is obtained until the 3 rd voltage value is determined_b+t_cIn the internal, the control circuit 140 applies the voltage V₁Set to the 2 nd voltage value. Without being limited to this example, the control circuit 140 may obtain the 2 nd measurement value and then make the voltage V₁After the measurement value is once restored to the 1 st measurement value, the operations of steps S105 and S106 are performed. Fig. 13B shows an example of such an action. In the example shown in fig. 13B, the time tb when the voltage V1 is set to the 2 nd measurement value is followed by the estimation of the parameter of the power receiving device and the determination of the 3 rd voltage value at the subsequent time tc.

The estimation method described above can also be applied to either the time of starting power supply to the mobile unit 200 or the time of power supply.

< real-time estimation of Power receiving parameter >

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 to the restart of the two measurements. According to a shorter period T₁By estimating the power reception parameter and changing the power reception parameter to the voltage value of the ac power output from the inverter circuit 120, the operation of the mobile unit 200 can be controlled more precisely. However, t is required for two measurements and estimation of power reception parameters_a+t_b+t_cTime of (d). Further, if the 2 nd state is frequently set, the operation of the mobile object 200 may be affected.

Therefore, the period T can be made relatively long₁Estimation of the electrical parameters from two measurements is carried out with a short period T₂Estimation of the power receiving parameter from one measurement is performed. Period T₂Specific period T₁Short, e.g. T₂/T₁The range of the pressure can be set to 1/1000 or more and 1/10 or less. T is₁Can be, for example, T₂Integer multiples of. In a certain example, the period T₁Is about 100ms, period T₂Is set to about 1 ms. In the following description, the period T will be described₂Such estimation of the power receiving parameter at sufficiently short time intervals is referred to as real-time estimation.

Fig. 14A is a diagram showing an example of the time of estimation from two measurements and real-time estimation. In fig. 14A, the estimation from two measurements is referred to as estimation 1, and the estimation from one measurement (real-time estimation) is referred to as estimation 2. As illustrated, estimate 2 is performed more frequently than estimate 1.

In the real-time estimation, different methods are applied to the case where the mobile unit 200 is moving during power transmission and the case where the mobile unit is stationary. When the moving body 200 moves, the mutual inductance L varies due to the relative position of the power transmission coil and the power reception coil_mVariations are possible. The other partySurface at time T₂During the period of receiving the voltage V₂And not changed significantly. Therefore, it is possible to use the following equation (13) obtained by modifying equation (5) and assume V₂Constant to mutual inductance L only_mReal-time estimation is performed.

[ equation 13]

In equation (13), V₁And I₁Based on real-time measurements by the

gauges

130a, 130 b. V₂Is a value obtained by the operation of equation (11) before real-time estimation. The control circuit 140 can be controlled for each period T₂Real-time estimation of L using equation (13)_m. In this case, each period T₁For V with small variation₂Making an estimate for each shorter period T₂For L with large variation_mAnd (6) estimating.

In this example, when the power receiving apparatus moves relative to the power transmitting apparatus 100, the control circuit 140 executes the 1 st process in which the 1 st process is performed every cycle T₁The mutual inductance L is calculated by using the 1 st and 2 nd measured values_mAnd a voltage V output from the power receiving coil₂And (6) estimating. Then, the period T is determined for each ratio₁Short period T₂Using the voltage V estimated in the previous 1 st process₂And the mutual inductance L is estimated by the operation of equation (13)_m. The movement of the power receiving device with respect to the power transmission device 100 can be detected by the sensor 150.

When the mobile unit 200 stops during power transmission, the mutual inductance L is present_mDoes not change, but receives a voltage V₂Variations are possible. In particular, when the amount of charge in power storage element 245 is substantially zero at the start of power transmission, V₂Possibly with large variations. Therefore, L can be assumed when the mobile unit 200 is stopped_mConstant, using the same expression (14) as expression (11) for V only₂Real-time estimation is performed.

[ equation 14]

In equation (14), V₁And I₁Based on real-time measurements by the

gauges

130a, 130 b. L is_mIs a value obtained by the operation of equation (10) before real-time estimation. The control circuit 140 can be controlled for each period T₂Using equation (14) to perform the estimation V₂. In this case, each period T₁For L with small change_mMaking an estimate for each shorter period T₂For V with large variation₂And (6) estimating.

In this example, when the power receiving apparatus is stationary with respect to the power transmitting apparatus 100, the control circuit 140 executes the following process 1: according to each period T₁The mutual inductance L is calculated by using the 1 st and 2 nd measured values_mAnd a voltage V output from the power receiving coil₂And (6) estimating. Then, the control circuit 140 controls the duty ratio of the clock signal to be set for each bit period T₁Short period T₂Using the mutual inductance L estimated in the previous 1 st processing_mAnd estimating the voltage V by the operation of equation (14)₂. The sensor 150 can detect that the power receiving apparatus is stationary with respect to the power transmission apparatus 100.

Thus, in real-time estimation, L is assumed_m、V₂And I₂Among the power reception parameters, the parameter with a small change is constant, and the other parameters with a large change are estimated in real time. The less-varying parameters use estimated parameters derived from two measurements taken before starting the real-time estimation.

FIG. 14B is a diagram showing the period T₂Real-time estimation to control voltage V₁Voltage V of time₁An example of the temporal change of (1). As shown in the drawing, the control circuit 140 in this example performs the cycle T-by-cycle estimation based on the power reception parameter estimated in real time₂The voltage value of the ac power output from the inverter circuit 120 is determined. When last estimated parameterWhen the difference or the change rate from the newly estimated parameter exceeds a predetermined value, the control circuit 140 changes the voltage V₁. This enables the operation of the mobile unit 200 to be controlled more precisely.

FIG. 15 is a graph showing that each period T will be counted₁Estimation from two measurements made and according to each period T₂An example of the operation of combining the real-time estimation is shown in the flowchart. Steps S202 to S205 in fig. 15 represent the estimation process according to the two measurements. Steps S211 to S214 represent a real-time estimation process.

The control circuit 140 in this example is arranged to cycle T by each ratio₁Short period T₂The real-time estimation processing of steps S211 to S214 is performed. The control circuit 140 determines in step S211 whether or not the time T has elapsed since the start of the last real-time estimation process₂. If the determination is yes, the control circuit 140 obtains the measured values V of the voltage and the current measured by the measuring device in step S212₁、I₁. In step S213, the control circuit 140 estimates the power receiving parameter. As described above, when the mobile body 200 moves, the reception voltage V is assumed₂Constant and estimating mutual inductance L by the operation of equation (13)_m. In contrast, in the case where the mobile body 200 is stationary, the mutual inductance L is assumed_mConstant, and the reception voltage V is estimated by the operation of equation (14)₂. In step S214, the control circuit 140 determines the power transmission voltage V to be set next time by referring to a table or the like based on the estimated power reception parameter₁The value of (c).

The control circuit 140 has elapsed time T from the last step S202₁Until then, steps S211 to S214 are repeated. If the time T elapses₁Then, steps S202 to S205 are executed to determine the updated value of the power transmission voltage V1. Since the processing of steps S202 to S205 is the same as that described with reference to fig. 12, the description is omitted.

With the above operation, the power reception parameter can be estimated with high frequency without performing communication with the power reception device during power transmission.

< conversion of Current and Voltage >

Effective value V of voltage used in the above estimation method₁And the effective value of the current I₁Is the effective value of a sine wave signal having an angular frequency omega. However, the voltage output from the inverter circuit 120 is not limited to a sine wave, and may be a rectangular wave. In such a case, the control circuit 140 performs the aforementioned operation after appropriately converting the value measured by the measuring device 130.

The waveform of the voltage output from the inverter circuit 120 can be a rectangular wave. On the other hand, the waveform of the current output from the inverter circuit 120 may be considered to be substantially sinusoidal. The above-mentioned voltage has a maximum value V_1mAnd minimum value-V_1mA period of 2 pi/omega. Let V be the effective value of the voltage obtained from the measuring instrument 130a_1mLet the effective value of the current obtained from the measuring device 130b be I_1m。

The effective value V of the voltage of the rectangular wave cannot be obtained_1mEffective value V of voltage directly used as sine wave₁. The rectangular wave needs to be expanded in a Fourier series to derive the term 2 of the component of the sine wave with angular frequency ω^1/2V₁Coefficient V of x sin (ω t + θ)₁. Thus, it can be seen that the value V is set₁＝((2×2^1/2)/π)V_1mAnd (4) finishing. On the other hand, since the current output from the inverter circuit 120 is treated as a sine wave, it can be set to I₁＝I_1m。

DC voltage value V to power storage device 145 in power receiving device_2dcAnd a direct current value I_2dcAnd the effective value V of the output voltage from the power receiving resonator₂And the effective value I of the output current₂The conversion of (b) is explained.

As shown in fig. 4 and 9, the ac power output from power receiving resonator 210 is stored as dc power in power storage element 245 via rectifier 220 and capacitor 230. In the electric storage device 245, the dc voltage value is estimated to be V_2dc＝(π/(2×2^1/2))V₂The value of the direct current is estimated as I_2dc＝((2×2^1/2)/π)I₂. Thus, in estimating V_2dc、I_2dcWithout the need forIs to estimate V₂、I₂When power transmission control is performed, the control circuit 140 may simply convert V according to the above equation₂、I₂Conversion to V_2dc、I_2dcAnd (4) finishing.

The arrangement of measuring

instruments

130a and 130b and the partial configuration of power storage element 245 may be different from those in the present embodiment. Even in this case, the processing in the present embodiment can be applied by converting the measured effective value of the voltage and the measured effective value of the current by an appropriate equation.

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

In the example of fig. 16A, voltage measuring device 130a measures the voltage input to inverter circuit 120. The effective value V of the voltage obtained from the voltage measuring instrument 130a can be used_1mAnd through V₁＝((2×2^1/2)/π)V_1mThe effective value of the ac voltage output from the inverter circuit 120 is obtained by the operation of (a).

In the example of fig. 16B, the current measuring device 130B measures the current input to the inverter circuit 120. The effective value I of the current obtained from the current measuring instrument 130b can be used_1mAnd through I₁＝(π/(2×2^1/2))I_1mThe operation of (3) obtains an effective value of the ac current output from the inverter circuit 120.

In the example of fig. 16C, a voltage measuring device 130a and a current measuring device 130b measure the voltage and the current input to the inverter circuit 120, respectively. In this example, V can pass₁＝((2×2^1/2)/π)V_1mThe effective value of the ac voltage output from the inverter circuit 120 can be obtained by the operation of (I)₁＝(π/(2×2^1/2))I_1mOperation ofTo obtain an effective value of the alternating current.

Fig. 17A is a schematic diagram showing an example in which the DC-DC converter 250 is connected between the capacitor 230 and the storage element 245. Fig. 17B is a schematic diagram showing an example in which a load resistor 240 such as a motor is disposed in place of the power storage device 245 in the configuration of fig. 17A. In these examples, the transmission control may be performed based on the voltage and current of the DC power output from the DC-DC converter 250. In this 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 aforementioned processing. When the duty ratio D of the DC-DC converter 250 is constant, the DC voltage value is estimated to be V in the storage device 245 or the load resistor 240_2dc＝(π/(2×2^1/2))V₂D. The value of the direct current is estimated as I_2dc＝((2×2^1/2)/π)I₂/D。

< Effect >

According to the present embodiment, it is possible to appropriately control transmission power according to the state of the power receiving apparatus such as the position and impedance without performing communication from the power receiving apparatus to the power transmission apparatus 100. Therefore, it is possible to eliminate the influence of communication interference or the like generated in a use environment such as a factory or a road. Further, time loss due to connection and authentication before communication does not occur. Further, since it is not necessary to mount a wireless device on both the wireless power transmission device 100 and the mobile unit 200, it is possible to improve the maintainability of the system, to reduce the size, and to reduce the cost.

The power transmitting apparatus and the power receiving apparatus may be equipped with a communication device for a purpose different from feedback control during power transmission. For example, a method of performing communication for aligning a power transmitting apparatus and a power receiving apparatus before starting power transmission is also included in the present disclosure.

The processing according to expressions (10) to (12), (13), and (14) in the above description is exemplary and can be used in a suitably modified manner. For example, the correction formula may be used as needed to reduce the error.

Industrial applicability

The technology of the present disclosure can be applied to, for example, a wireless power transmission system for a moving object such as an Automated Guided Vehicle (AGV). The techniques of this disclosure can also be applied to other industrial machines, multi-axis aircraft, service robots, and the like.

Description of the symbols

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 … … 1 st upper side portion 112b … … 1 st lower side portion 112c … … 1 st rectangular surface 120 … … inverter circuit 130 … … current measurer 140 … … control circuit 142 … … control IC143 … … memory 144 … … gate driver 150 … … sensor 200 … … power receiving coil unit 207 … … power receiving resonator 212a … … power receiving coil 212b … … 2 nd lower side portion 212c … … 2 rectangular surface 220 … … rectifier 230 … … capacitor … … motor or other load resistance 245 … … power storage element 250 … … DC-DC converter.

Claims

1. A power transmitting device wirelessly transmits power to a power receiving device having a power receiving resonator,

the power transmission device includes:

an inverter circuit;

a power transmission resonator connected to the inverter circuit;

a measuring device that 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; and

a control circuit that controls the inverter circuit,

the control circuit performs the following processing:

obtaining a 1 st measured value of the voltage and the current measured by the measuring instrument in a state where the inverter circuit is caused to output the alternating-current power having the 1 st voltage value and the power is transmitted from the power transmitting resonator to the power receiving resonator,

obtaining a 2 nd measurement value of the voltage and the current measured by the measuring instrument in a state where the voltage value of the alternating-current power output from the inverter circuit is changed to a 2 nd voltage value different from the 1 st voltage value,

determining a 3 rd voltage value by a process including an operation using the 1 st measurement value and the 2 nd measurement value,

the inverter circuit is caused to output the alternating-current power having the 3 rd voltage value and to continue power transmission.

2. The power transmission device according to claim 1,

the control circuit estimates values of one or more parameters indicating a state of the power-supplied device by the operation using the 1 st measurement value and the 2 nd measurement value,

the 3 rd voltage value is determined based on the estimated value of the parameter with reference to data defining a correspondence between the value of the one or more parameters and the value of the voltage to be output from the inverter circuit.

3. The power transmission device according to claim 2,

the control circuit performs the following processing:

according to each period T₁Performing the obtaining of the 1 st and 2 nd measurement values and the determining of the 3 rd voltage value,

setting the 3 rd voltage value to a value different from the 1 st voltage value when the value of the one or more parameters indicating the state of the power-supplied device estimated from the 1 st and 2 nd measured values has changed from the value of the parameter estimated last time,

setting the 3 rd voltage value to the same value as the 1 st voltage value when the value of the parameter is the same as the value of the parameter at the last estimation.

4. The power transmission device according to claim 2 or 3,

the one or more parameters include at least one of 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 power output from the power reception resonator.

5. The power transmission device according to claim 4,

the one or more parameters include the mutual inductance,

the effective values of the voltage and the current outputted from the inverter circuit obtained from the 1 st measured value are respectively set as V₁₀And I₁₀、

Setting effective values of the voltage and the current outputted from the inverter circuit obtained from the 2 nd measured value as V₁₁And I₁₁、

Let the mutual inductance be L_m、

Setting the resistance value of the power transmission resonator to R₁、

Setting the resistance value of the power receiving resonator to R₂、

When the driving angular frequency of the inverter circuit is set to ω,

the control circuit estimates the mutual inductance L by an operation of equation 1 below_m，

[ equation 1]

6. The power transmission device according to claim 5,

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,

setting a voltage output from the power receiving resonator to V₂、

Setting a current output from the power receiving resonator to I₂When the temperature of the water is higher than the set temperature,

the control circuit estimates the voltage V by the operation of equation 2 or equation 3 below₂And the current I₁At least one of the above-mentioned (b),

[ equation 2]

[ equation 3]

7. The power transmission device according to claim 6,

when the power receiving device moves relative to the power transmitting device,

the control circuit performs the following 1 st processing: according to each period T₁The mutual inductance L is measured by the operation using the 1 st and 2 nd measurement values_mAnd a voltage V output from the power receiving resonator₂The estimation is carried out in such a way that,

the control circuit controls the period T according to each ratio₁Short period T₂Using the voltage V estimated in the 1 st process of the previous time₂And estimating the mutual inductance L by the operation of the following equation 4_m，

[ equation 4]

8. The power transmission device according to claim 6 or 7,

when the power receiving device is stationary with respect to the power transmitting device,

the control circuit controls the period T according to each ratio₁Short period T₂Using the mutual inductance L estimated in the 1 st process of the previous time_mAnd the voltage V is estimated by the operation of equation 5 below₂，

[ equation 5]

9. The power transmission device according to any one of claims 1 to 8,

the power transmitting device also has a sensor that detects whether the power receiving device is moving relative to the power transmitting device.

10. The power transmission device according to any one of claims 1 to 9,

the power receiving device is a mobile body.

11. The power transmission device according to any one of claims 1 to 10,

the inverter circuit has a plurality of switching elements,

the control circuit supplies a pulse signal that determines a conduction/non-conduction state to each of the plurality of switching elements, and controls a voltage value of the alternating-current power output from the inverter circuit by adjusting a duty ratio of the pulse signal.

12. A wireless power transmission system, having:

the power transmission device of any one of claims 1 to 11; and

the power receiving device.

13. A control device having the control circuit in the power transmitting device according to any one of claims 1 to 11.

14. A program for use in a power transmitting device that wirelessly transmits power to a power receiving device having a power receiving resonator,

the power transmission device includes:

an inverter circuit;

a power transmission resonator connected to the inverter circuit;

a control circuit that controls the inverter circuit,

the program causes the control circuit to perform the following actions: