Non-contact power transmission system

Abstract

To provide a non-contact power transmission system capable of performing appropriate power transmission to mobiles during moving and stopping.SOLUTION: A non-contact power transmission system 1 comprises a power transmission unit 8, a power transmission power conversion unit 7, and a power transmission side control device 9. The power transmission unit 8 comprises a primary side coil for sending alternating-current power to be transmitted to a power reception device 4. The power transmission power conversion unit 7 comprises a plurality of transistors connected to the primary side coil. The power transmission power conversion unit 7 converts direct-current power supplied from a power supply unit 6 to alternating-current power. When a coupling coefficient is smaller than a predetermined value or a power transmission duration time is equal to or longer than a predetermined first time at the time of power transmission by the power transmission unit 8, the power transmission side control device 9 changes transmission power in decreasing tendency toward zero depending on a lapse of time until power transmission stop.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a contactless power transfer system. [Background technology]

[0002] In recent years, research and development has been conducted into charging vehicles equipped with secondary batteries that contribute to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy. Conventionally, in a contactless power transmission system that supplies power from a power transmitting side to a power receiving side by contactless power transmission, a system is known in which, based on information transmitted from the power receiving side to the power transmitting side, a supply power corresponding to the power required by the power receiving side is transmitted from the power transmitting side to the power receiving side (see, for example, Patent Document 1 and Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-136274 [Patent Document 2] International Publication No. 2020 / 049853 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology for charging and supplying power to vehicles equipped with secondary batteries, it is desirable to transmit power appropriately according to the power demand of the vehicle when transmitting or receiving power to a moving or stopped vehicle. For example, if a sudden increase in supplied power occurs when a coil on the power receiving side approaches or moves away from a coil on the power transmitting side, problems such as an increase in load due to a drop in frequency in the power transmitting system power supply and a power supply interruption due to overcurrent detection caused by current hunting may occur.

[0005] An object of the present invention is to provide a contactless power transfer system that can transfer power appropriately to a moving object while it is moving or stopped, thereby contributing to energy efficiency. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the above object, the present invention employs the following aspects. (1): A contactless power transfer system according to one aspect of the present invention (e.g., contactless power transfer system 1 in the embodiments) includes a power transmitting coil (e.g., primary coil 8a in the embodiments) that contactlessly transfers power to a power receiving coil (e.g., secondary coil 15a in the embodiments), a power transmitting power conversion unit (e.g., power transmitting power conversion unit 7 in the embodiments) that is connected to the power transmitting coil and converts power supplied from a power source (e.g., power supply unit 6 in the embodiments), and a power transmitting control device (e.g., power transmitting side control device 9 in the embodiments) that controls the operation of the power transmitting side power conversion unit, and when power is being transferred by the power transmitting side coil, the power transmitting control device changes the transmitted power to a decreasing trend depending on the time that has elapsed until power transfer is stopped.

[0007] (2): In the contactless power transmission system described in (1) above, the power transmitting side control device may change the transmission power to a decreasing trend when the degree of coupling between the power transmitting side coil and the power receiving side coil is less than a predetermined degree or the duration of power transmission by the power transmitting side coil is equal to or longer than a predetermined time during power transmission by the power transmitting side coil.

[0008] (3): The contactless power transmission system described in (2) above may include a current sensor (e.g., current sensor 9a in the embodiment) that detects the current flowing through the power transmission side coil, and the power transmission side control device may obtain the degree of coupling based on the detected value of the current output from the current sensor.

[0009] (4): In the contactless power transmission system described in (2) above, after stopping the power transmission when the power transmission duration reaches or exceeds the predetermined time, the power transmitting side control device may transition the power transmitting side power conversion unit to a reception standby state in which information regarding the power transmission is received from the power receiving side coil.

[0010] (5): In the contactless power transmission system described in any one of (1) to (4) above, the power transmitting side power conversion unit may include a plurality of switching elements (e.g., transistors 7a and 7b in the embodiment) connected to the power transmitting side coil, and the power transmitting side control device may control the transmission power by the duty ratio or phase shift amount of a signal that instructs the operation of the plurality of switching elements.

[0011] (6): The contactless power transmission system described in (4) above includes the receiving coil, a receiving power conversion unit (e.g., receiving power conversion unit 16 in the embodiment) connected to the receiving coil, and a receiving control device (e.g., receiving control device 17 in the embodiment) that controls the operation of the receiving power conversion unit, and when the power reception duration during power reception by the receiving coil reaches a predetermined time or more, the receiving control device may transition the receiving power conversion unit to a transmission state in which information regarding the power transmission is transmitted from the receiving coil to the transmitting coil, and after transmitting the information regarding the power transmission, transition the receiving power conversion unit from the transmission state to a power reception standby state. [Effects of the Invention]

[0012] According to the above (1), the power transmission-side control device changes the transmission power to a decreasing trend depending on the time elapsed until the power transmission is stopped, thereby suppressing an increase in the load on the power source and the occurrence of an overcurrent. For example, it is possible to suppress the occurrence of problems such as an increase in the load due to a frequency drop in the power transmission-side system power source and a power supply stop due to an overcurrent detection caused by current hunting.

[0013] In the case of (2) above, when the coupling degree is less than a predetermined degree or the duration of power transmission is equal to or longer than a predetermined time, the power transmitting control device reduces the transmitted power, thereby suppressing an increase in power loss or the occurrence of overcharging on the power receiving side. Appropriate power transmission according to the request can be performed to a moving or stopped mobile object.

[0014] In the case of (3) above, the power transmission side control device controls the power transmission based on the degree of coupling obtained based on the current detected on the power transmission side, so that appropriate power transmission can be performed for each of multiple moving bodies, such as multiple vehicles, each with different required power.

[0015] In the case of (4) above, the transmitting side control device can acquire new information regarding power transmission at predetermined intervals, and can transmit power appropriately in accordance with the requirements of the receiving side while suppressing the occurrence of problems such as overcharging on the receiving side.

[0016] In the case of (5) above, the power transmitting side control device controls the transmission power by the duty ratio or the amount of phase shift, so that the transmission power can be controlled quickly even when the power receiving device moves relative to the power transmitting device.

[0017] In the case of (6) above, the receiving-side control device can transmit new information regarding power transmission at predetermined intervals, and can receive appropriate power according to the requirements of the receiving side while suppressing the occurrence of problems such as overcharging on the receiving side. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram showing an example of the configuration of a contactless power transmission system according to an embodiment of the present invention; [Figure 2] 1 is a diagram showing an example of the configuration of a contactless power transmission system according to an embodiment of the present invention; [Figure 3] FIG. 2 is a diagram showing details of the configuration of a contactless power transmission system according to an embodiment of the present invention. [Figure 4]1 is a diagram showing the configuration of a power transmitting unit and a power receiving unit of a contactless power transfer system according to an embodiment of the present invention. [Figure 5] FIG. 2 is a diagram showing a T-type equivalent circuit in the contactless power transfer system according to the embodiment of the present invention. [Figure 6] 4 is a flowchart showing a power receiving side process of the contactless power transmission system according to the embodiment of the present invention. [Figure 7] 4 is a flowchart showing a power transmission side process of the contactless power transmission system according to the embodiment of the present invention. [Figure 8] 8 is a flowchart showing the power transmission control shown in FIG. 7. [Figure 9] 5A and 5B are diagrams showing an example of changes in power transmission-side voltage and power transmission-side current during ramp-up control in the contactless power transmission system according to the embodiment of the present invention. [Figure 10] 4A and 4B are diagrams showing an example of changes in power transmission-side voltage and power transmission-side current during ramp-down control in the contactless power transfer system according to the embodiment of the present invention. [Figure 11] FIG. 3 is a diagram showing an example of a correspondence relationship between a power transmission side output and a coupling coefficient in the contactless power transfer system according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a contactless power transfer system according to an embodiment of the present invention will be described with reference to the accompanying drawings. 1 and 2 are diagrams illustrating an example of the configuration of a contactless power transfer system 1 according to an embodiment. A contactless power transfer system 1 according to the embodiment supplies power to a mobile body from outside the mobile body (such as a travel path) by contactless power transfer. The mobile body is, for example, a vehicle V. The vehicle V is, for example, an electrically powered vehicle such as an electric vehicle, a hybrid vehicle, or a fuel cell vehicle. The outside of the mobile body (such as a travel path) is, for example, a travel path R of the vehicle V.

[0020] (contactless power transmission system) As shown in Figures 1 and 2, the contactless power transfer system 1 of the embodiment includes, for example, a power transmission device 2 installed on a driving path R of a vehicle V, a drive control device 3, a power receiving device 4, and an on-board communication device 5 mounted on the vehicle V. The contactless power transfer system 1 of the embodiment may include only components external to the vehicle V (for example, the power transmission device 2), or may perform contactless power transfer by combining components mounted on the vehicle V (for example, the drive control device 3, the power receiving device 4, and the on-board communication device 5) with the contactless power transfer system 1 external to the vehicle V. The contactless power transfer system 1 of the embodiment may include only components mounted on the vehicle V (for example, the drive control device 3, the power receiving device 4, and the on-board communication device 5), or may perform contactless power transfer by combining components external to the vehicle V (for example, the power transmission device 2) with the contactless power transfer system 1 mounted on the vehicle V.

[0021] The power transmitting device 2 includes, for example, a communication system M constituting a power transmitting side communication device, a power supply unit 6, at least one set (for example, multiple sets) of a power transmitting power conversion unit 7 and a power transmitting unit 8, and a power transmitting side control device 9. The communication system M communicates wirelessly with an in-vehicle communication device 5 that constitutes a power receiving side communication device mounted on a vehicle V. The communication system M constitutes at least a part of a system for electronically collecting tolls, such as an ETC (Electronic Toll Collection System) on toll roads, and a system for exchanging road traffic information and various types of information for driving assistance. The communication system M includes at least one roadside communication device Ma that wirelessly communicates with an in-vehicle communication device 5 of a vehicle V by road-to-vehicle communication, and a communication control device Mb. Each of the at least one roadside communication device Ma and the communication control device Mb are connected via, for example, a wired or wireless communication network. The communication network includes, for example, the Internet, a mobile communication network, a LAN (Local Area Network), a WAN (Wide Area Network), etc.

[0022] The roadside communication device Ma is arranged, for example, a predetermined distance upstream of a coupling section (communication section and power transmission section) described later on the roadway R of the vehicle V. The roadside communication device Ma is equipped with various communication devices such as an antenna for wireless communication. The communication control device Mb controls the operation of all roadside communication devices Ma that are associated with it in advance. The communication control device Mb is a software function unit that functions when a processor such as a CPU (Central Processing Unit) executes a predetermined program. The software function unit is an ECU that includes a processor such as a CPU, a ROM (Read Only Memory) that stores programs, a RAM (Random Access Memory) that temporarily stores data, and electronic circuits such as a timer. At least a part of the communication control device Mb may be an integrated circuit such as an LSI (Large Scale Integration).

[0023] The communication system M and the in-vehicle communication device 5 correspond to, for example, a primary authentication device and a secondary authentication device, and exchange authentication information that is exclusively assigned to at least each vehicle V. The communication system M and the in-vehicle communication device 5 attempt to exchange first information, for example, by wireless communication between the roadside communication device Ma and the in-vehicle communication device 5 of a nearby vehicle V at a predetermined period or the like.

[0024] For example, the first information transmitted from the in-vehicle communication device 5 to the communication system M includes at least information related to power transmission. The information related to power transmission includes, for example, information on a power transmission request such as the required power and required frequency for power transmission from the power transmitting device 2 to the vehicle V, and information necessary for billing and settlement for the power transmission. The information necessary for billing and settlement is information specific to the vehicle V, such as the presence and identifier of an IC card or an in-vehicle transponder for toll collection.

[0025] For example, the first information transmitted from the communication system M to the in-vehicle communication device 5 includes at least key information and information related to the installation of the power transmission device 2. The key information is, for example, information that is generated while being updated at a predetermined period so as to be different for each authorized vehicle V (i.e., vehicle V permitted to perform power transmission) passing through a predetermined power transmission section described below. The key information is information required for the power transmission device 2 to authenticate the power receiving device 4 of the vehicle V and to start power transmission. The information related to the installation of the power transmission device 2 is, for example, information such as the installation intervals of multiple power transmission units 8 described below and the distance from the roadside communication device Ma.

[0026] For example, when the communication system M acquires information necessary for charging and settling for power transmission from the in-vehicle communication device 5, it checks whether electronic payment is possible. If the communication system M checks that electronic payment is possible, it transmits permission information indicating permission for power transmission and key information necessary to start power transmission to the in-vehicle communication device 5. When the communication system M transmits the key information to the in-vehicle communication device 5, it transmits information combining the same key information and information related to power transmission received from the in-vehicle communication device 5 to the power transmitting side control device 9 described below.

[0027] The power supply unit 6 is connected to, for example, a plurality of transmission power conversion units 7. The power supply unit 6 includes, for example, an AC power supply such as a commercial power supply, an AC-DC converter that converts the AC power into DC power, and a power smoothing capacitor. The power supply unit 6 converts the AC power supplied from the AC power supply into DC power using the AC-DC converter.

[0028] Fig. 3 is a diagram showing the detailed configuration of the contactless power transfer system 1 according to the embodiment. Fig. 4 is a diagram showing the configurations of the power transmitting unit 8 and the power receiving unit 15 of the contactless power transfer system 1 according to the embodiment. As shown in FIG. 3, the transmission power conversion unit 7 includes, for example, an inverter that converts DC power into AC power. The inverter of the transmission power conversion unit 7 includes, for example, a first bridge circuit formed by a plurality of switching elements and rectifying elements bridge-connected in two phases, and a capacitor. Each switching element is, for example, a transistor such as a SiC (Silicon Carbide) MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The plurality of switching elements are high-side arm and low-side arm transistors 7a, 7b that form a pair in each phase. The rectifying element is, for example, a freewheeling diode connected in parallel to each of the transistors 7a, 7b. The capacitor 7c is connected in parallel to the first bridge circuit. The transmission power conversion unit 7 includes, for example, a sensor such as a current sensor that detects the current of the DC power.

[0029] The power transmitting unit 8 is connected to the AC terminals of the first bridge circuit of the power transmitting power converter 7. The power transmitting unit 8 transmits power by changing a high-frequency magnetic field, for example, through magnetic field coupling such as magnetic resonance or electromagnetic induction. As shown in FIGS. 3 and 4, the power transmitting unit 8 includes a resonant circuit formed by, for example, a primary coil 8a, a primary resistor 8b, and a primary capacitor 8c connected in series. The power transmitting unit 8 includes sensors such as a current sensor 9a that detects a current (power transmitting side current) It flowing through the resonant circuit and a voltage sensor 9b that detects a voltage (power transmitting side voltage) Vt of the resonant circuit.

[0030] The power transmitting side control device 9 comprehensively controls the power transmitting devices 2. The power transmitting side control device 9 is a software function unit that functions when a processor such as a CPU (Central Processing Unit) executes a predetermined program. The software function unit is an ECU that includes a processor such as a CPU, a ROM (Read Only Memory) that stores programs, a RAM (Random Access Memory) that temporarily stores data, and electronic circuits such as a timer. At least a part of the power transmitting side control device 9 may be an integrated circuit such as an LSI (Large Scale Integration).

[0031] For example, in power transmission control during power transmission between the power transmitting device 2 and the power receiving device 4, the power transmitting side control device 9 independently controls the current switching operation of each of the multiple power transmitting power conversion units 7. As shown in Fig. 2, for example, the power transmitting side control device 9 independently controls each of the multiple power transmitting power conversion units 7 so that multiple pairs of power transmitting power conversion units 7 and power transmitting units 8 individually transmit power to the power receiving devices 4 of different vehicles V (e.g., two different vehicles Va, Vb, etc.) at appropriate timing including simultaneously.

[0032] The transmission side control device 9 generates, for example, a control signal for each of the multiple transmission power conversion units 7 indicating the timing for driving each switching element on (conducting) and off (cutting), and also generates a gate signal for actually driving each switching element on and off based on the control signal. For example, the power transmission side control device 9 transmits power to the power receiving device 4 of the vehicle V corresponding to each power transmission power conversion unit 7 and each power transmission unit 8 by controlling the on (conduction) and off (cutoff) switching of each switching element for each of the multiple power transmission power conversion units 7 in accordance with information on a predetermined drive frequency or a required frequency received from the power receiving device 4.

[0033] For example, prior to the start of power transmission between the power transmitting device 2 and the power receiving device 4, the power transmitting side control device 9 controls communication between the power transmitting device 2 and the power receiving device 4 via the primary side coil 8a and the secondary side coil 15a. For example, when the power transmitting side control device 9 receives information that is a combination of key information and information related to power transmission from the communication system M, it recognizes that the same key information has been transmitted to the in-vehicle communication device 5 of the vehicle V, and transitions the power transmitting device 2 from a stopped state to a reception standby state. The stopped state of the power transmitting device 2 is a state in which the switching operation of each of the multiple power transmitting power conversion units 7 is stopped, for example, by maintaining each switching element of each of the multiple power transmitting power conversion units 7 in an off (blocked) state. The reception standby state of the power transmitting device 2 is a state in which the transmission of information from the power receiving device 4 of the vehicle V is detected. The reception standby state of the power transmitting device 2 is, for example, a short-circuit state of each of the power transmitting power conversion units 7.

[0034] 3, when each transmitting power converter 7 is short-circuited, the transmitting-side control device 9 short-circuits the primary coil 8a by turning on the low-side arm transistor 7b of each phase. As a result, when the primary power transmitting device 2 is viewed from the secondary power receiving device 4, the impedance of the primary side becomes very large. However, when a magnetic field is generated by the secondary coil 15a of the power receiving device 4 during PING transmission (described later), communication from the power receiving device 4 is detected by the voltage induced in the primary coil 8a of the power transmitting device 2. The transmitting-side control device 9 acquires information superimposed on the PING signal by demodulating the voltage detected during PING transmission.

[0035] For example, when the power transmitting side control device 9 receives key information via a PING signal transmitted from the secondary coil 15a of the power receiving device 4 to an appropriate primary coil 8a of the power transmitting device 2, the power transmitting side control device 9 verifies the key information based on a combination of the key information previously received from the communication system M and information related to power transmission. If the key information received from the communication system M and the power receiving device 4 matches, the power transmitting side control device 9 transitions the transmitting power conversion unit 7 corresponding to the primary coil 8a that received the key information from a reception standby state to a search state (search mode). In the search state of the transmitting power conversion unit 7, the power transmitting side control device 9 estimates a coupling coefficient k between the primary coil 8a and the secondary coil 15a based on current detection in the power transmitting unit 8, while outputting a voltage pulse to the primary coil 8a by a current switching operation in the transmitting power conversion unit 7, for example.

[0036] In the search state of each transmission power conversion unit 7, the power transmission side control device 9 acquires the mutual inductance Lm, the coupling coefficient k, and the efficiency between the primary coil 8a and the secondary coil 15a based on the detection values ​​output from the current sensor 9a and the voltage sensor 9b of the power transmission unit 8. The efficiency is, for example, the AC power transmission efficiency η when the load of the vehicle V of the contactless power transfer system 1 is a constant voltage. AC is. FIG. 5 is a diagram showing a T-type equivalent circuit in the contactless power transfer system 1 of the embodiment. As shown in FIG. 5, the T-type equivalent circuit of the contactless power transfer system 1 is described by, for example, the voltage Vt of the AC voltage source 21, the capacitance Ct, internal resistance Rt, self-inductance Lt, and current It of the power transmitting unit 8, the mutual inductance Lm, the capacitance Cr, internal resistance Rr, self-inductance Lr, and current Ir of the power receiving unit 15, and the voltage Vr of the load resistor 22. The load resistance 22 corresponds to, for example, a receiving power conversion unit 16 described below and a load resistance A connected between the DC terminals (positive and negative poles) of the receiving power conversion unit 16. The load resistance A is, for example, the drive control device 3.

[0037] Kirchhoff's law for the closed circuit shown in FIG. 5 is expressed as shown in the following equation (1) using the angular frequency ω and the imaginary unit j.

[0038]

number

[0039] In each of the power transmitting device 2 and the power receiving device 4, when the capacitances Ct and Cr are set so as to resonate at the angular frequency ω0, the relationship with the self-inductances Lt and Lr is expressed as shown in the following equation (2).

[0040]

number

[0041] Based on the above formulas (1) and (2), the currents It and Ir are expressed as shown in the following formula (3).

[0042]

number

[0043] In relation to the phase relationship between the voltage Vt and the voltage Vr, the power receiving device 4 has a power receiving power conversion unit 16 (described later) that operates as a rectifier, so the voltage Vr and the current Ir basically have the same sign and no phase difference. Therefore, the ratio between the voltage Vr and the current Ir, as expressed in the following equation (4), is a real number. Voltages Vt and Vr are written as shown in the following equation (5) based on the real amplitude ratio α, and it is recognized that, for example, voltage Vr has a phase lead of 90° relative to voltage Vt.

[0044]

number

[0045]

number

[0046] The mutual inductance Lm and the coupling coefficient k are expressed as shown in the following equation (6). The AC output Pt on the transmitting side and the AC output Pr on the receiving side are expressed as shown in the following equation (7) based on the average currents It(ave) and Ir(ave) based on the above equation (3), the above equation (5), and the following equation (6).

[0047]

number

[0048]

number

[0049] AC transmission efficiency η AC As shown in the following equation (8), AC transmission efficiency η is expressed by the ratio of the averages of the real parts Re(Pt) and Re(Pr) of the AC outputs Pt and Pr in the above equation (7). AC is described by the resistance values ​​Rt, Rr, self-inductances Lt, Lr, and angular frequency ω0, which are circuit constants specific to the system, the voltage ratio α obtained from the PING signal described later, and the coupling coefficient k, which changes while the vehicle V is running.

[0050]

number

[0051] Based on the current It in the above equation (3) and the above equations (5) and (6), the coupling coefficient k is expressed as shown in the following equation (9).

[0052]

number

[0053] The power transmission side control device 9 obtains the AC to AC conversion efficiency from the detected values ​​of the voltage Vt and current It on the power transmission side based on the above formulas (8) and (9). The power transmission side control device 9 further obtains the DC to DC conversion efficiency (total power transmission efficiency) by adding the loss in conversion between AC and DC.

[0054] For example, when the coupling coefficient k estimated in the searching state of each transmitting power converter 7 reaches a predetermined value ka or more within a predetermined time, the transmitting side control device 9 transitions each transmitting power converter 7 from the searching state to the power transmission control state. The predetermined value ka is, for example, a value corresponding to a predetermined value (e.g., 80%) of the efficiency of power transmission (e.g., overall efficiency). The power transmission control state of each transmitting power converter 7 is, for example, a state in which power transmission is controlled at the power and frequency requested by the power receiving device 4. On the other hand, for example, if the coupling coefficient k estimated in the search state of each transmission power conversion unit 7 does not reach a predetermined value ka or more within a predetermined time, the transmission side control device 9 returns each transmission power conversion unit 7 from the search state to a reception standby state.

[0055] The power transmission-side control device 9 executes control to stop power transmission, for example, when the coupling coefficient k estimated in the power transmission control state of each power transmission power converter 7 becomes less than a predetermined value ka, or when the duration from the start of the power transmission control state reaches or exceeds a predetermined first time. The predetermined first time is, for example, a threshold time for determining whether to temporarily stop the power transmission control state in order to confirm or change information related to power transmission in the power transmission control state. For example, when the coupling coefficient k estimated in the power transmission control state of each power transmission power converter 7 becomes less than a predetermined value ka, the power transmission-side control device 9 stops power transmission by each power transmission power converter 7. For example, when the duration from the start of the power transmission control state of each power transmission power converter 7 reaches or exceeds the predetermined first time, the power transmission-side control device 9 temporarily stops the power transmission control state of each power transmission power converter 7 and attempts to reacquire information related to power transmission and resume the power transmission control state. The control operation of the power transmitting side control device 9 will be described in detail later.

[0056] 1, 2, and 3, the drive control device 3 of the vehicle V includes, for example, a power storage device 11, a power conversion unit 13, and a rotating electric machine 14. The power receiving device 4 of the vehicle V includes, for example, a power receiving unit 15 and a received power conversion unit 16. The drive control device 3 and the power receiving device 4 include, for example, a common power receiving-side control device 17.

[0057] The power storage device 11 is connected to a power conversion unit 13 and a received power conversion unit 16, which will be described later. The power storage device 11 is charged by power transmitted contactlessly from a power transmission device 2 outside the vehicle V. The power storage device 11 exchanges power with a rotating electric machine 14 via the power conversion unit 13. The power storage device 11 includes, for example, a battery, a current sensor for detecting the battery current, and a voltage sensor for detecting the battery voltage. The battery is, for example, a secondary battery such as a lead acid battery, a lithium ion battery, a sodium ion battery, a nickel-metal hydride battery, or an all-solid-state battery, a capacitor such as an electric double layer capacitor, or a combined battery that combines a secondary battery and a capacitor.

[0058] The power conversion unit 13 is connected to a rotating electric machine 14. The power conversion unit 13 includes, for example, a second element module that converts between DC power and AC power, and a capacitor for smoothing voltage. The second element module includes, for example, a second bridge circuit formed by a plurality of switching elements and rectifying elements bridge-connected in three phases. Each switching element is, for example, a transistor such as an IGBT (Insulated Gate Bipolar Transistor) or a SiC MOSFET. The plurality of switching elements are high-side arm and low-side arm transistors 13a and 13b that form a pair in each phase. The rectifying elements are, for example, freewheeling diodes connected in parallel to each of the transistors 13a and 13b. A voltage smoothing capacitor 13c is connected in parallel to the second bridge circuit.

[0059] The second element module controls the operation of the rotating electric machine 14 by receiving and sending electric power. For example, when the rotating electric machine 14 is powered, the second element module converts DC power input from the positive and negative DC terminals 13p, 13n into three-phase AC power and supplies the three-phase AC power from the three-phase AC terminals 13d to the rotating electric machine 14. The second element module generates a rotational driving force by sequentially commutating the current to the three-phase stator windings of the rotating electric machine 14. For example, during regeneration of the rotating electric machine 14, the second element module converts three-phase AC power input from the three-phase stator windings into DC power by driving the switching elements of each phase to turn on (conduct) and off (cut) in synchronization with the rotation of the rotating electric machine 14. The second element module can supply the DC power converted from the three-phase AC power to the power storage device 11.

[0060] The rotating electric machine 14 is, for example, a three-phase AC brushless DC motor provided for driving the vehicle V. The rotating electric machine 14 includes a rotor having a permanent magnet for a field, and a stator having three-phase stator windings that generate a rotating magnetic field that rotates the rotor. The three-phase stator windings are connected to three-phase AC terminals 13d of the power conversion unit 13. The rotating electric machine 14 generates rotational driving force by power running using electric power supplied from the power conversion unit 13. When the rotating electric machine 14 is connected to the wheels of the vehicle V, for example, it generates driving force by power running using electric power supplied from the power conversion unit 13. The rotating electric machine 14 may generate electric power by performing regenerative operation using rotational power input from the wheel side of the vehicle V. When the rotating electric machine 14 is connected to the internal combustion engine of the vehicle V, it may generate electric power using the power of the internal combustion engine.

[0061] The power receiving unit 15 is connected to AC terminals of a third bridge circuit of the receiving power conversion unit 16, which will be described later. The power receiving unit 15 receives power by changes in a high-frequency magnetic field transmitted from the power transmitting unit 8, for example, by magnetic field coupling such as magnetic resonance or electromagnetic induction. As shown in FIG. 4, the power receiving unit 15 includes a resonant circuit formed by, for example, a secondary coil 15a, a secondary resistor 15b, and a secondary capacitor 15c connected in series. The power receiving unit 15 includes sensors such as a current sensor that detects a current (power receiving side current) Ir flowing through the resonant circuit and a voltage sensor that detects a voltage (power receiving side voltage) Vr of the resonant circuit.

[0062] 1, 2, and 3 is connected to the power conversion unit 13. The receiving power conversion unit 16 includes a so-called full-bridgeless (or bridgeless and totem-pole) power factor correction (PFC) circuit that converts AC power into DC power. The so-called bridgeless PFC is a PFC that does not include a bridge rectifier made up of multiple bridge-connected diodes, and the so-called totem-pole PFC is a PFC that includes a pair of switching elements of the same conductivity type that are connected in series in the same direction (totem-pole connection).

[0063] The receiving power conversion unit 16 includes, for example, a third bridge circuit formed by a plurality of switching elements and rectifying elements bridge-connected in two phases, and a capacitor. Each switching element is, for example, a transistor such as a SiC MOSFET. The plurality of switching elements are high-side arm and low-side arm transistors 16a, 16b that form a pair in each phase. The rectifying element is, for example, a freewheeling diode connected in parallel to each of the transistors 16a, 16b. The capacitor 16c is connected in parallel to the third bridge circuit. The receiving power conversion unit 16 includes, for example, a sensor such as a current sensor that detects the current of the DC power.

[0064] For example, a power receiving device 4 equipped with a power receiving unit 15 and a power receiving power conversion unit 16 receives power transmitted from the power transmitting device 2 by controlling the on (conduction) and off (cutoff) switching of each switching element of the power receiving power conversion unit 16 in accordance with information on the frequency of power transmission by the power transmitting device 2.

[0065] The power receiving side control device 17 comprehensively controls, for example, the drive control device 3, the power receiving device 4, and the in-vehicle communication device 5 of the vehicle V. The power receiving side control device 17 is a software function unit that functions when a predetermined program is executed by a processor such as a CPU (Central Processing Unit). The software function unit is an ECU that includes a processor such as a CPU, a ROM (Read Only Memory) that stores programs, a RAM (Random Access Memory) that temporarily stores data, and electronic circuits such as a timer. At least a part of the power receiving side control device 17 may be an integrated circuit such as an LSI (Large Scale Integration).

[0066] For example, in power reception control during power transmission between the power transmission device 2 and the power receiving device 4, the power receiving side control device 17 controls the current switching operation of each of the drive control device 3 and the power receiving device 4. For example, the power receiving side control device 17 generates control signals indicating the timing to drive each switching element of the drive control device 3 and the power receiving device 4 on (conducting) and off (cutting), and generates gate signals for actually driving each switching element on and off based on the control signals. For example, the power receiving side control device 17 controls the switching of each switching element of the power receiving device 4 to rectify the AC power received from the power transmitting device 2 into DC power and improve the power factor of the input voltage and input current.

[0067] For example, the power receiving side control device 17 controls the output according to the target output by a synchronous rectification operation that synchronously drives multiple switching elements of the power receiving device 4 on and off, and a short-circuit operation that short-circuits the secondary side coil 15a. For example, the power receiving side control device 17 controls the synchronous rectification operation in accordance with the magnitude and phase of the current generated in the power receiving unit 15 by the power transmitted from the power transmitting device 2, i.e., the current Ir flowing through the secondary side coil 15a. The power receiving side control device 17 controls the multiple switching elements of the power receiving power conversion unit 16 by soft switching of so-called zero voltage switching (ZVS). In zero voltage switching (ZVS), each switching element is turned on (switched from an off state to an on state) after the voltage across both ends of the switching element is made zero by discharging the output capacitance (parasitic capacitance) in the off state during the dead time period of each phase.

[0068] For example, the power receiving side control device 17 controls the short-circuit operation by turning on only the low-side arm of each phase while continuing the zero voltage switching (ZVS) synchronous rectification operation in the high-side arm of each phase of the power receiving power conversion unit 16. By short-circuiting the secondary coil 15a, the power receiving side control device 17 increases the secondary-side impedance when the secondary-side power receiving device 4 is viewed from the primary-side power transmitting device 2, thereby reducing the primary-side current (power transmitting side current: current It flowing through the primary-side coil 8a). The power receiving side control device 17 controls the current It of the primary-side power transmitting device 2 by the secondary-side power receiving device 4, thereby performing independent power control such as stopping power transmission on the power receiving device 4 side.

[0069] For example, prior to the start of power transmission between the power transmission device 2 and the power receiving device 4, the power receiving side control device 17 controls communication between the power transmission device 2 and the power receiving device 4 via the primary side coil 8a and the secondary side coil 15a. The power receiving-side control device 17 defines, for example, a section near the power transmitting device 2 where the degree of coupling between the primary coil 8a of the power transmitting device 2 and the secondary coil 15a of the power receiving device 4 is equal to or greater than a predetermined degree as a coupling section. In the coupling section, the power receiving-side control device 17 sets a communication section for communication between the primary coil 8a and the secondary coil 15a and a power transmission section for power transmission. The communication sections are, for example, a first communication section and a second communication section set before and after the power transmission section along the direction of movement of the vehicle V.

[0070] For example, the power receiving side control device 17 defines a coupling section in which the degree of coupling between the primary side coil 8a and the secondary side coil 15a is equal to or greater than a predetermined degree as a section in which the efficiency of power transmission is equal to or greater than a predetermined value (e.g., zero).The power receiving side control device 17 defines a section in the coupling section in which the efficiency of power transmission is equal to or greater than a first predetermined value (e.g., 80%) and the relative horizontal distance between the primary side coil 8a and the secondary side coil 15a is equal to or less than the first predetermined distance as a power transmission section in which the degree of coupling between the primary side coil 8a and the secondary side coil 15a is relatively high.The power receiving side control device 17 defines a section in the coupling section in which the efficiency of power transmission is less than the first predetermined value and equal to or greater than a second predetermined value (e.g., 0%) and the relative horizontal distance between the primary side coil 8a and the secondary side coil 15a is greater than the first predetermined distance and equal to or less than the second predetermined distance as a communication section in which the degree of coupling between the primary side coil 8a and the secondary side coil 15a is relatively low. The communication section is, for example, a first communication section and a second communication section that are set before and after the power transmission section along the direction of movement of the vehicle V. Note that a state in which the horizontal distance is zero is, for example, a state in which the central axes of the primary coil 8a and the secondary coil 15a are aligned. The power transmitted in the power transmission section is regulated, for example, to be equal to or less than an appropriate required power.

[0071] For example, when the power receiving-side control device 17 receives key information and information about the installation of the power transmitting device 2 through communication between the roadside communication device Ma of the communication system M and the in-vehicle communication device 5 before the vehicle V arrives at the coupling section, the power receiving-side control device 17 sets the communication timing for the initial communication section, i.e., the first communication section, for each of the multiple power transmitting units 8, depending on, for example, information such as the installation intervals of the multiple power transmitting units 8 and the distance from the roadside communication device Ma, and the traveling state of the vehicle V (i.e., the moving state of the power receiving device 4).

[0072] For example, when the power receiving unit 15 reaches the first communication section of the appropriate power transmitting unit 8, the power receiving side control device 17 transitions the power receiving device 4 from the short-circuit state to the transmission state. The short-circuit state of the power receiving device 4 is a state in which the secondary coil 15a is short-circuited by turning on the low-side arm transistor 16b of each phase of the power receiving power conversion unit 16. The transmission state of the power receiving device 4 is a state in which the secondary coil 15a transmits second information to the power transmitting power conversion unit 7 and primary coil 8a in a reception standby state by a so-called ping signal. The power receiving side control device 17 communicates, for example, by a voltage induced in the primary coil 8a of the power transmitting device 2 by a magnetic field generated in the secondary coil 15a by a current switching operation by switching in the power receiving power conversion unit 16. The power receiving side control device 17 executes the PING transmission by, for example, generating a two-level digital signal, so-called dominant and recessive, by switching a carrier wave for contactlessly transmitting power from the secondary side coil 15a to the primary side coil 8a at a predetermined duty ratio. The predetermined duty ratio is, for example, a predetermined minimum to about 50%. Note that the power receiving side control device 17 may transmit the second information by, for example, amplitude modulating the carrier wave by changing the switching duty ratio.

[0073] The power receiving side control device 17 transmits a PING signal at a predetermined cycle, for example, from several tens of microseconds to several milliseconds, and transmits information about power transmission in the power transmission section as second information from the secondary side coil 15a to the primary side coil 8a. The information about power transmission includes, for example, key information acquired by the in-vehicle communication device 5 from the roadside communication device Ma, the required frequency for power transmission, the voltage Vr of the power receiving unit 15, the target output (required power, power consumption) for fail-safe purposes, and information about various abnormalities. The required frequency of power transmission is a frequency required for power transmission from the power transmitting device 2 and is set according to the required power. The required frequency is set so as to suppress a decrease in the efficiency of power transmission and output (power) based on, for example, the minimum ground clearance of the vehicle V, which is related to the distance between the primary coil 8a and the secondary coil 15a, and the mounting layout of the power receiving device 4 on the vehicle V. The required frequency may be set according to, for example, the state of power transmission between the power transmitting device 2 and the power receiving device 4. The target output of power transmission is a target value of the power that the power receiving device 4 receives from the power transmitting device 2, and is set, for example, according to the target driving force of the vehicle V or the rotating electric machine 14, the power consumption of various auxiliary machines connected to the power storage device 11, and the remaining capacity (SOC: State Of Charge) of the power storage device 11, etc.

[0074] For example, when the power receiving side control device 17 completes at least a predetermined number of (e.g., one) PING transmissions, the power receiving device 4 transitions from the transmission state to the power receiving standby state. The power receiving standby state of the power receiving device 4 is a state in which the power receiving device 4 receives power transmitted from the power transmitting power converter 7 and the primary coil 8a in the searching state. For example, when the received power detected in the power receiving standby state reaches or exceeds a predetermined power within a predetermined time, that is, when the power receiving unit 15 reaches the power transmission section, the power receiving side control device 17 transitions the power receiving device 4 from the power receiving standby state to the power receiving control state. The predetermined power is, for example, a predetermined value (e.g., 80%) of the efficiency of power transmission (e.g., overall efficiency), that is, a value corresponding to a predetermined value ka of the coupling coefficient k estimated by the power transmitting side control device 9. On the other hand, the receiving side control device 17 returns the power receiving device 4 from the power receiving standby state to the transmission state, for example, if the received power detected in the power receiving standby state does not reach a predetermined power level or more within a predetermined time, that is, if the power receiving unit 15 has not reached the power transmission section TS.

[0075] For example, when the duration from the start of the power receiving control state of the power receiving power conversion unit 16 reaches a predetermined first time or more, the power receiving side control device 17 executes control to stop the power receiving control state. Note that the predetermined first time is, for example, a threshold time for determining whether to execute PING transmission to update information related to power transmission in the power receiving control state. The control operation of the power receiving side control device 17 will be described in detail later.

[0076] Hereinafter, as the operation of the contactless power transfer system 1, the processes executed by the power transmitting side controller 9 and the power receiving side controller 17 will be described. FIG. 6 is a flowchart showing the power receiving side process executed by the power receiving side control device 17 of the contactless power transfer system 1 in the embodiment. First, in step S01 shown in FIG. 6, the power receiving side control device 17 sets the power receiving device 4 in a short-circuit state. Next, in step S02, the power receiving-side control device 17 determines whether electronic payment for the power transmission from the power transmitting device 2 to the vehicle V is possible through wireless communication (billing communication) between the roadside communication device Ma of the communication system M and the in-vehicle communication device 5. If the determination result is "NO", the power receiving-side control device 17 repeats the processing of step S02. On the other hand, if the determination result is "YES", the power receiving-side control device 17 proceeds to step S03.

[0077] Then, in step S03, the power receiving side control device 17 acquires key information required to start power transmission from the roadside communication device Ma via the in-vehicle communication device 5. Next, in step S04, the power receiving-side control device 17 transitions the power receiving device 4 from the short-circuit state to the transmission state, for example, when the power receiving unit 15 reaches the first communication section CS1 of the appropriate power transmitting unit 8. The power receiving-side control device 17 generates a signal for PING transmission from the secondary side coil 15a of the power receiving device 4 to the primary side coil 8a of the appropriate power transmitting unit 8 of the power transmitting device 2. Next, in step S05, the power receiving side control device 17 executes PING transmission to the primary coil 8a of the appropriate power transmission unit 8 of the power transmission device 2 at a predetermined cycle in the first communication section CS1.

[0078] Next, in step S06, when the power receiving side control device 17 has completed transmitting PING signals at least a predetermined number of times (for example, once), the power receiving device 4 transitions from the transmission state to the power receiving standby state. Next, in step S07, the power receiving-side control device 17 determines whether or not a response signal to the PING transmission has been received from the power transmitting unit 8. If the result of this determination is "NO", the power receiving-side control device 17 repeats the process of step S07. On the other hand, if the result of this determination is "YES", the power receiving-side control device 17 proceeds to step S08.

[0079] Next, in step S08, the power receiving-side control device 17 executes power receiving control for the power transmission from the power transmission device 2 in the power transmission section TS. Next, in step S09, the power receiving-side control device 17 determines whether the duration from the start of the power receiving control state has reached a predetermined first time period or more. If the result of this determination is "NO," the power receiving-side control device 17 returns the process to step S08. On the other hand, if the result of this determination is "YES," the power receiving-side control device 17 proceeds to step S10.

[0080] Next, in step S10, the power receiving side control device 17 stops the power receiving control. Next, in step S11, the power receiving side control device 17 determines whether or not power reception has ended. If the result of this determination is "NO", the power receiving side control device 17 returns the process to step S04. On the other hand, if the result of this determination is "YES", the power receiving side control device 17 advances the process to the end.

[0081] FIG. 7 is a flowchart showing a power transmission side process executed by the power transmission side control device 9 of the contactless power transmission system 1 in the embodiment. First, in step S21 shown in FIG. 7, the power transmitting side control device 9 sets the power transmitting device 2 to a stopped state. Next, in step S22, the power transmitting side control device 9 determines whether or not key information has been transmitted from the roadside communication device Ma to the power receiving device 4. If the determination result is "NO", the power transmitting side control device 9 proceeds to step S23. On the other hand, if the determination result is "YES", the power transmitting side control device 9 proceeds to step S24. Then, in step S23, the power transmitting side control device 9 maintains the stopped state of the power transmitting device 2, and returns the process to step S22. Then, in step S24, the power transmitting side control device 9 causes the power transmitting device 2 to transition from the stopped state to the reception standby state.

[0082] Next, in step S25, the power transmitting side control device 9 determines whether or not a PING signal transmitted from the secondary side coil 15a to the primary side coil 8a has been received in the first communication section of any of the power transmitting units 8. If the determination result is "NO", the power transmitting side control device 9 repeats the process of step S25. On the other hand, if the determination result is "YES", the power transmitting side control device 9 proceeds to step S26. Next, in step S26, the power transmitting side control device 9 compares the key information received in advance from the communication control device Mb with the key information received by the primary side coil 8a from the secondary side coil 15a of the power receiving device 4.

[0083] Next, in step S27, the power transmitting side control device 9 determines whether the key information received from the communication system M (i.e., the same key information as the key information sent from the communication system M to the in-vehicle communication device 5) matches the key information received by the primary side coil 8a from the secondary side coil 15a of the power receiving device 4. If the result of this determination is "YES", that is, if pairing is established between the secondary side coil 15a of the power receiving device 4 and the primary side coil 8a of the power transmitting unit 8 that received the PING signal transmitted from the power receiving device 4, the power transmitting side control device 9 proceeds to step S28. On the other hand, if the result of this determination is "NO", the power transmitting side control device 9 proceeds to end the process. Next, in step S28, the power transmitting side control device 9 transmits a response signal to the PING transmission from the power receiving device 4 to the power receiving device 4 via the paired primary side coil 8a and secondary side coil 15a.

[0084] Next, in step S29, the power transmitting side control device 9 transitions the power transmitting power conversion unit 7 corresponding to the paired primary side coil 8a from a reception standby state to a search state (search mode). In the search state of each power transmitting power conversion unit 7, the power transmitting side control device 9 acquires the mutual inductance Lm, coupling coefficient k, and power transmission efficiency between the paired primary side coil 8a and secondary side coil 15a based on the above formulas (8) and (9) and the respective detection values ​​output from the current sensor 9a and voltage sensor 9b of the power transmitting unit 8.

[0085] Next, in step S30, the power transmitting side control device 9 determines whether the coupling coefficient k estimated in the searching state of the power transmitting power conversion unit 7 reaches a predetermined value (predetermined threshold) ka or more within a predetermined time. If the result of this determination is "NO", the power transmitting side control device 9 returns the process to step S24. On the other hand, if the result of this determination is "YES", the power transmitting side control device 9 proceeds to step S31. Then, in step S31, the power transmitting side control device 9 executes power transmission control for power transmission in the power transmission section by the power transmitting power converter 7 and the power transmitting device 8. Then, the power transmitting side control device 9 advances the process to END.

[0086] FIG. 8 is a flowchart showing the power transmission control shown in FIG. First, in step S41 shown in FIG. 8 , the power transmission-side control device 9 executes ramp-up control for a period spanning a predetermined second time from the start of power transmission (power transmission). The predetermined second time is set, for example, based on at least one of the supply capacity of the power supply unit 6, the number of power transmission units 8 connected to the power supply unit 6, and the moving speed of the power receiving device 4 relative to the power transmission units 8 (such as the speed of a moving object). The predetermined second time is, for example, a time ranging from several tens of microseconds to several milliseconds. In the ramp-up control, the power transmission-side control device 9 sets the transmission power (supply power) from the power transmission units 8 to less than a predetermined power, and changes the transmission power so that it tends to increase toward the predetermined power as time passes from the start of power transmission. The predetermined power is, for example, the power required by the power receiving device 4.

[0087] FIG. 9 is a diagram showing an example of changes in the power transmission side voltage and power transmission side current during the ramp-up control of the contactless power transfer system 1 according to the embodiment. 9, it is observed that the power transmission side voltage (e.g., the effective AC voltage value at the coil end of the power transmission unit 8) gradually increases with the passage of time during the period from time ta to time tb when the ramp-up control is executed. As the power transmission side voltage increases, it is observed that the power transmission side current (e.g., the DC current of the power transmission device 2) gradually increases without becoming an overcurrent.

[0088] In ramp-up control, the power transmission side control device 9 controls the transmission power, for example, by the duty ratio or phase shift amount of a gate signal (pulse signal) that instructs the switching operation of the power transmission power converter 7. The duty ratio is, for example, the ratio of the on time of one of the paired transistors 7a, 7b in each phase of the power transmission power converter 7 (for example, the high-side arm transistor 7a) in one cycle of switching control. The phase shift amount is, for example, the phase difference between the gate signal of the first phase of the two phases of the power transmission power converter 7 and the gate signal of the second phase. The power transmitting side control device 9 changes the duty ratio or the phase shift amount, for example, stepwise or continuously, so as to increase the power transmitting side voltage.

[0089] Next, in step S42 shown in Figure 8, the power transmission side control device 9 continues power transmission by the power transmission unit 8 while repeatedly acquiring the mutual inductance Lm, coupling coefficient k, and power transmission efficiency between the paired primary side coil 8a and secondary side coil 15a. Next, in step S43, the power transmitting side control device 9 determines whether the transmitted power (supplied power) from the power transmitting unit 8 is greater than a predetermined power (for example, the power required by the power receiving device 4) based on, for example, current detection values ​​from various current sensors of the power transmitting device 2. If the result of this determination is "NO", the power transmitting side control device 9 proceeds to step S45. On the other hand, if the result of this determination is "YES", the power transmitting side control device 9 proceeds to step S44. Next, in step S44, the power transmitting side control device 9 executes output reduction control. In the output reduction control, the power transmitting side control device 9 reduces the transmission power from the power transmitting unit 8 toward a predetermined power by, for example, feedback control based on the detected current value.

[0090] Next, in step S45, the power transmitting side control device 9 determines whether the coupling coefficient k is less than a predetermined value (predetermined threshold) ka. If the result of this determination is "NO", the power transmitting side control device 9 proceeds to step S46. On the other hand, if the result of this determination is "YES", the power transmitting side control device 9 proceeds to step S49. Next, in step S46, the power transmitting side control device 9 determines whether the duration from the start of the power transmission control state has reached a predetermined first time period or more. If the result of this determination is "NO", the power transmitting side control device 9 returns the process to step S42. On the other hand, if the result of this determination is "YES", the power transmitting side control device 9 proceeds to step S47.

[0091] Next, in step S47, the power transmitting side control device 9 executes ramp-down control for a period spanning a predetermined third time. The predetermined third time is set, for example, based on at least one of the supply capacity of the power supply unit 6, the number of power transmitting units 8 connected to the power supply unit 6, and the moving speed of the power receiving device 4 relative to the power transmitting units 8 (such as the speed of the moving object). The predetermined third time is, for example, a time period ranging from several tens of microseconds to several milliseconds. In the ramp-down control, the power transmitting side control device 9 decreases the transmitted power (supplied power) from the power transmitting units 8 toward zero, for example, depending on the time elapsed until power transmission is stopped. Next, in step S47, the power transmitting side control device 9 stops power transmission by the power transmitting unit 8, and returns the process to step S24.

[0092] FIG. 10 is a diagram illustrating an example of changes in the power transmission side voltage and the power transmission side current during the ramp-down control of the contactless power transfer system 1 according to the embodiment. 10, it is observed that the power transmission side voltage (e.g., the effective AC voltage value at the coil end of the power transmission unit 8) gradually decreases with the passage of time during the period from time ta to time tb when the ramp-down control is executed. As the power transmission side voltage decreases, it is observed that the power transmission side current (e.g., the DC current of the power transmission device 2) gradually decreases without becoming an overcurrent.

[0093] In ramp-down control, the power transmission side control device 9 controls the transmission power, for example, by changing the duty ratio or phase shift amount of a gate signal (pulse signal) that instructs the switching operation of the power transmission power conversion unit 7. The power transmission side control device 9 changes the duty ratio or phase shift amount, for example, stepwise or continuously, to decrease the power transmission side voltage.

[0094] Furthermore, in step S49 shown in FIG. 8, the power transmitting side controller 9 executes ramp-down control for a predetermined third hour period. Next, in step S50, the power transmitting side control device 9 stops power transmission by the power transmitting unit 8, and the process returns.

[0095] FIG. 11 is a diagram showing an example of the correspondence relationship between the power transmission side output and the coupling coefficient in the contactless power transfer system 1 of the embodiment. As shown in FIG. 11, for example, before time t1, the power transmitting side controller 9 puts the power transmitting device 2 into a stopped state, and the power receiving side controller 17 puts the power receiving device 4 into a short-circuit state.

[0096] For example, at time t1, when the power transmitting side control device 9 receives information on a combination of key information and information on power transmission from the communication system M, it transitions the power transmitting device 2 from a stopped state to a reception standby state. When the power receiving unit 15 reaches the first communication section of the appropriate power transmitting unit 8, the power receiving side control device 17 transitions the power receiving device 4 from a short-circuit state to a transmission state. The power receiving side control device 17 executes PING transmission at least a predetermined number of times (such as once) during the period of the transmission state. When the power transmitting side control device 9 receives the key information by the PING signal, it verifies the key information based on the key information previously received from the communication system M.

[0097] For example, as shown after time t2, the power receiving side control device 17 transitions the power receiving device 4 from the transmission state to the power receiving standby state after completing the PING transmission. If the key information received from the communication system M and the power receiving device 4 matches, the power transmitting side control device 9 transitions the power transmitting power conversion unit 7 corresponding to the primary side coil 8a that received the key information from the reception standby state to a search state (search mode).

[0098] The power transmitting side control device 9 outputs voltage pulses to the primary side coil 8a by switching the current flow in the power transmitting power conversion unit 7 in a search mode, for example, from time t2 to time t3, while estimating the coupling coefficient k between the primary side coil 8a and the secondary side coil 15a based on current detection in the power transmitting unit 8. For example, at time t3 when the coupling coefficient k increases from an appropriate initial value k0 and reaches a predetermined value ka or more within a predetermined time, the power transmitting side control device 9 transitions the power transmitting power conversion unit 7 from the search mode to the power transmitting control state. As the coupling coefficient k reaches the predetermined value ka or more, the power receiving side control device 17 transitions the power receiving device 4 from the power receiving standby state to the power receiving control state at time t3 when the received power detected in the power receiving standby state reaches a predetermined power or more within the predetermined time.

[0099] For example, from time t3 to time t4, the power transmission side control device 9 executes ramp-up control in a region with a relatively low degree of coupling (low efficiency) within a power transmission section where the efficiency of power transmission is equal to or greater than a predetermined efficiency (e.g., 80%). The power transmission side output gradually increases from an initial output P0 toward a predetermined output Pt through the ramp-up control. After the ramp-up control ends, for example, after time t4, the power transmitting side control device 9 continues the power transmission control such that the transmission power (supply power) of the power transmitting unit 8 is limited to a predetermined power (for example, the power required by the power receiving device 4) or less. The power transmitting side control device 9 repeatedly continues to acquire the mutual inductance Lm and coupling coefficient k between the paired primary side coil 8a and secondary side coil 15a, and the efficiency of power transmission, for example, over the period from time t4 to time t5.

[0100] When the coupling coefficient k reaches a value less than a predetermined value (predetermined threshold) ka, for example, after time t5, the power transmitting side control device 9 executes ramp-down control. The power transmitting side output gradually decreases toward zero, for example, through the ramp-down control. After the ramp-down control ends, for example, after time t7, the power transmitting side control device 9 transitions the power transmitting power conversion unit 7 from the power transmission control state to the stopped state. The power receiving side control device 17 transitions the power receiving device 4 from the power receiving control state to the short-circuit state.

[0101] As described above, according to the contactless power transfer system 1 of the embodiment, the transmitted power is gradually increased or decreased over time by ramp-up control and ramp-down control, thereby suppressing an increase in the load on the power supply and the occurrence of an overcurrent. For example, when the secondary coil 15a approaches or moves away from the primary coil 8a, it is possible to suppress the occurrence of problems such as an increase in the load due to a frequency drop or the like in the power transmission system power supply and a power supply interruption due to an overcurrent detection caused by current hunting.

[0102] The power transmission side control device 9 can suppress an increase in power loss by performing ramp-down control and stopping power transmission when the coupling coefficient k is less than a predetermined value (predetermined threshold) ka. The power transmission side control device 9 can suppress the occurrence of malfunctions such as overcharging on the power receiving side by performing ramp-down control and temporarily stopping power transmission when the duration from the start of the power transmission control state is equal to or longer than a predetermined first time. Appropriate power transmission according to request can be performed to a vehicle V that is running or stopped.

[0103] The power transmission side control device 9 controls power transmission using a coupling coefficient k obtained based on the current detected by the power transmission device 2, and therefore can perform appropriate power transmission to each of multiple vehicles V with different required power, for example. The power transmission side control device 9 can newly acquire information related to power transmission every predetermined first time period, and can perform appropriate power transmission according to the power required by each vehicle V.

[0104] Since the power transmitting side control device 9 controls the transmission power by the duty ratio or the amount of phase shift, even when the power receiving device 4 moves relative to the power transmitting device 2, the transmission power can be controlled quickly.

[0105] (Variation) In the above-described embodiment, the communication system M constitutes an electronic toll collection system, but is not limited to this. For example, the communication system M may simply be a system that communicates with the in-vehicle communication device 5 prior to power transmission by the power transmission device 2 in the power transmission section. In the above-described embodiment, key information and information such as required power and required frequency for power transmission are transmitted and received by power transmission between the power transmitting device 2 and the power receiving device 4. However, this is not limiting. For example, the power transmitting device 2 and the power receiving device 4 may each include a communication device for wirelessly communicating with each other, and information may be transmitted and received via the communication device.

[0106] In the above-described embodiment, the contactless power transfer system 1 may include a storage voltage converter that converts input and output power of the power storage device 11, for example, in the case of a hybrid vehicle or the like that is driven by the power storage device 11 and an internal combustion engine as a power source.

[0107] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0108] 1...contactless power transfer system, 2...power transmission device, 3...drive control device, 4...power receiving device, 5...vehicle-mounted communication device, 6...power supply unit (power source), 7...transmission power conversion unit (transmission side power conversion unit), 7a, 7b...transistor (switching element), 8...power transmission unit, 8a...primary side coil (transmission side coil), 9...power transmission side control device, 9a...current sensor, 11...energy storage device, 13...power conversion unit, 14...rotating electric machine, 15...power receiving unit, 15a...secondary side coil (receiving side coil), 16...receiving power conversion unit (receiving side power conversion unit), 17...power receiving side control device, M...communication system, Ma...roadside communication device, Mb...communication control device, V...vehicle

Claims

1. a power transmitting coil that transmits power to a power receiving coil in a wireless manner; a power transmitting side power conversion unit connected to the power transmitting side coil and converting power supplied from a power source; a power transmission side control device that controls the operation of the power transmission side power conversion unit; Equipped with The power transmitting side control device During power transmission by the power transmission side coil, the transmission power is changed to a decreasing trend according to the elapsed time until the power transmission is stopped. Contactless power transmission system.

2. The power transmitting side control device When the degree of coupling between the power transmitting side coil and the power receiving side coil is less than a predetermined degree or when the duration of power transmission by the power transmitting side coil is equal to or longer than a predetermined time, the transmission power is changed to a decreasing tendency. The contactless power transfer system according to claim 1 .

3. a current sensor for detecting a current flowing through the power transmitting coil; The power transmitting side control device The degree of coupling is obtained based on the detected value of the current output from the current sensor. The contactless power transfer system according to claim 2 .

4. The power transmitting side control device After the power transmission is stopped when the power transmission duration reaches or exceeds the predetermined time, the power transmitting side power conversion unit is shifted to a reception standby state in which information about the power transmission is received from the power receiving side coil. The contactless power transfer system according to claim 2 .

5. the power transmitting side power conversion unit includes a plurality of switching elements connected to the power transmitting side coil, The power transmission side control device controls the transmission power according to a duty ratio or a phase shift amount of a signal that instructs the operation of the plurality of switching elements. The contactless power transfer system according to any one of claims 1 to 4.

6. The power receiving coil; a power receiving side power conversion unit connected to the power receiving side coil; a power receiving side control device that controls the operation of the power receiving side power conversion unit; Equipped with The power receiving side control device when a power reception duration time reaches or exceeds a predetermined time during power reception by the power receiving side coil, transitioning the power receiving side power conversion unit to a transmission state in which information regarding the power transmission is transmitted from the power receiving side coil to the power transmitting side coil; After transmitting the information about the power transmission, the power receiving side power conversion unit is shifted from the transmission state to a power reception standby state. The contactless power transfer system according to claim 4 .

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