Non-contact power transmission system

Abstract

The present invention provides a non-contact power transmission system capable of suppressing the occurrence of a failure at the initial stage of the start of power transmission and maintaining appropriate power transmission. This non-contact power transmission system is provided with a power transmission unit, a transmitted power conversion unit, and a power transmission-side control device. The power transmission unit includes a primary coil that transmits AC power transmitted in a non-contact manner to the power reception device. The transmitted power conversion unit includes a plurality of transistors connected to the primary coil. The transmitted power conversion unit converts DC power supplied from the power supply unit to AC power. The power transmission-side control device sets the transmission power at the initial stage of the start of power transmission by the power transmission unit to be less than a predetermined power. The power transmission-side control device changes the transmission power toward the predetermined power with an increase tendency in accordance with the elapsed time from the start of power transmission by the power transmission unit.

Description

Technical Field

[0001] The present invention relates to a contactless power transmission system. Background Art

[0002] In recent years, in order to ensure that more people can obtain reliable, sustainable and advanced energy that is suitable for them, research and development related to charging stations in vehicles equipped with secondary batteries that contribute to energy efficiency has been conducted.

[0003] Conventionally, in a contactless power transmission system for supplying power from a power transmitting side to a power receiving side by non-contact power transmission, there is known a system for transmitting power corresponding to the power required at the power receiving side from the power transmitting side to the power receiving side based on information sent from the power receiving side to the power transmitting side (for example, refer to the following patent documents 1 and patent document 2).

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-136274

[0005] Patent Document 2: International Publication No. 2020 / 049853 Summary of the invention

[0006] In the technology related to charging and supplying power in a vehicle equipped with a secondary battery, it is desired to suppress the adverse conditions that occur with the start of power transmission when the coil on the power receiving side of the vehicle reaches the coil on the power transmitting side in the non-contact power transmission to the moving vehicle. For example, due to the increase in current that occurs with the start of rapid power supply, there may be an increase in load due to a decrease in the frequency of the system power supply on the power transmitting side, and there may be adverse conditions such as power supply stopping due to overcurrent detection due to current fluctuations.

[0007] The present invention has been made in consideration of such a situation, and its object is to provide a non-contact power transmission system that can suppress the occurrence of malfunctions at the beginning of power transmission and maintain appropriate power transmission, thereby contributing to energy efficiency.

[0008] In order to solve the above-mentioned problems and achieve the object, the present invention adopts the following means.

[0009] (1): One aspect of the present invention relates to a contactless power transmission system, wherein the contactless power transmission system comprises: a power transmission unit having a coil for transmitting AC power transmitted in a contactless manner to a power receiving device; a power conversion unit having a plurality of switching elements connected to the coil and converting DC power supplied from a power source into the AC power; and a control device for controlling switching operations of the plurality of switching elements, wherein the control device sets the transmission power at the beginning of power transmission by the power transmission unit to be less than a prescribed power, and changes the transmission power to increase toward the prescribed power according to the elapsed time from the start of power transmission by the power transmission unit.

[0010] (2): Based on the above scheme (1), the control device may also set the initial stage of the power transmission to a period of a specified time from the start of the power transmission, and the control device sets the specified time based on at least any one of the supply capacity of the power source, the number of the power transmission units connected to the power source, and the moving speed of the power receiving device relative to the power transmission unit.

[0011] (3) In the above configuration (1) or (2), the control device may control the transmission power by a duty ratio or a phase shift amount of a signal instructing the switching operation.

[0012] (4): Based on the above scheme (3), the contactless power transmission system may also include a current sensor for detecting the current of the DC power, the control device sets the specified power as the required power of the power receiving device, and when the transmitted power is greater than the specified power, the control device makes the transmitted power move toward the specified power to reduce the tendency change based on the detection value of the current output from the current sensor.

[0013] According to the above scheme (1), a control device is provided for setting the transmission power at the beginning of power transmission to be less than the prescribed power, thereby suppressing the increase of current caused by the start of rapid power supply. The control device changes the transmission power toward the prescribed power in an increasing trend according to the elapsed time from the start of power transmission, thereby suppressing the increase of the load of the power supply and the occurrence of overcurrent. For example, it is possible to suppress the increase of the load caused by the frequency reduction of the system power supply on the power transmission side, and the occurrence of unfavorable situations such as the stop of power supply caused by the detection of overcurrent due to current fluctuation.

[0014] In the case of the above solution (2), the control device sets the initial period of power transmission based on at least one of the supply capacity of the power source, the number of power transmission units connected to the power source, and the moving speed of the power receiving device relative to the power transmission unit, so that the transmission power can be appropriately reduced.

[0015] In the case of the above means (3), the control device controls the transmitted power by the duty ratio or the phase shift amount. Therefore, even when the power receiving device moves relative to the power transmitting unit, the transmitted power can be quickly controlled.

[0016] In the case of the above-mentioned solution (4), the control device controls the transmission power based on the detected value of the current even after the initial stage of power transmission. Therefore, even when power is transmitted sequentially to a plurality of moving objects such as vehicles having different power requirements, an appropriate transmission power can be set. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a diagram showing a configuration of a contactless power transmission system according to an embodiment of the present invention.

[0018] Figure 2 It is a diagram showing the details of the configuration of the contactless power transmission system according to the embodiment of the present invention.

[0019] Figure 3 It is a diagram showing the configuration of a power transmission unit and a power reception unit of a contactless power transmission system according to an embodiment of the present invention.

[0020] Figure 4 1 is a flowchart showing a process on the power receiving side of the contactless power transmission system according to the embodiment of the present invention.

[0021] Figure 5 1 is a flowchart showing a process on the power transmission side of the contactless power transmission system according to the embodiment of the present invention.

[0022] Figure 6 yes Figure 5 The flowchart of power transmission control is shown.

[0023] Figure 7 1 is a diagram showing an example of time changes in the power transmitting side and the power receiving side by ramp-up control in the contactless power transmission system according to the embodiment of the present invention.

[0024] Figure 8 This is a diagram showing an example of the correspondence relationship between the power transmission side voltage, the power transmission side current, the power reception side voltage, and the power reception side current under the duty ratio control of the ramp-up control in the contactless power transmission system according to the embodiment of the present invention.

[0025] Fig. 9 This is a diagram showing an example of the correspondence relationship between the power transmission side voltage, the power transmission side current, the power reception side voltage, and the power reception side current under the phase shift amount control of the ramp-up control in the contactless power transmission system according to the embodiment of the present invention.

[0026] Fig.10This is a diagram showing an example of the relationship between power and efficiency according to horizontal distance (relative movement amount between the primary coil and the secondary coil in a direction parallel to the road surface) in the contactless power transmission system according to the embodiment of the present invention. DETAILED DESCRIPTION

[0027] Hereinafter, a non-contact power transmission system according to an embodiment of the present invention will be described with reference to the drawings.

[0028] Figure 1 and Figure 2 1 is a diagram showing a configuration of a contactless power transmission system 1 according to an embodiment. Figure 3 1 is a diagram showing the configuration of the power transmission unit 8 and the power reception unit 15 of the contactless power transmission system 1 according to the embodiment.

[0029] The contactless power transmission system 1 of the embodiment supplies power to a moving object such as a vehicle from outside the moving object by contactless power transmission. The vehicle is, for example, an electric vehicle such as an electric vehicle, a hybrid vehicle, or a fuel cell vehicle.

[0030] (Contactless power transmission system)

[0031] like Figure 1 and Figure 2 As shown, the contactless power transmission system 1 of the embodiment includes, for example, a power transmission device 2 installed on a travel path of a vehicle, a drive control device 3 and a power receiving device 4 mounted on a mobile body such as a vehicle, and a communication system M. It should be noted that the contactless power transmission system 1 of the embodiment may include at least only components external to the mobile body (for example, the power transmission device 2 and the communication system M), or may perform contactless power transmission by a combination of components mounted on the mobile body (for example, the drive control device 3 and the power receiving device 4) and the contactless power transmission system 1 external to the mobile body.

[0032] The communication system M includes, for example, at least one roadside communication device Ma and a communication control device Mb. The communication system M constitutes at least a part of a system for electronic toll collection such as an ETC (Electronic Toll Collection System) in a toll road.

[0033] The roadside communication device Ma is arranged, for example, at a predetermined distance from the upstream side of the coupling section (communication section and power transmission section) described later in the travel path of the vehicle. The roadside communication device Ma is equipped with an antenna for wireless communication, etc., and communicates with the vehicle-mounted communication device 18 described later mounted on a mobile body such as a vehicle by wireless. When the roadside communication device Ma obtains information required for payment and settlement for power transmission from the power transmission device 2 to the mobile body such as the vehicle from the vehicle-mounted communication device 18, for example, it transmits key information required for starting power transmission and information related to the installation of the power transmission device 2 to the vehicle-mounted communication device 18. The information required for payment and settlement is, for example, information inherent to a mobile body such as a vehicle, such as the presence or absence of an IC card or a vehicle-mounted transponder for charging and an identifier. The key information is, for example, information generated while being updated at a predetermined period in a different manner for each mobile body (i.e., a vehicle, etc., for which execution of power transmission is permitted) that has passed through a predetermined power transmission section. The key information is information required for the power transmission device 2 to authenticate the power receiving device 4 described later of the mobile body such as the vehicle. The information on the installation of the power transmission device 2 is, for example, information on the installation intervals of the plurality of power transmission units 8 described later.

[0034] The communication control device Mb controls the actions of all roadside communication devices Ma with which corresponding relationships have been established in advance. The communication control device Mb is a software function unit that performs its functions by executing a specified program by a processor such as a CPU (Central Processing Unit). The software function unit is an ECU, which has a processor such as a CPU, a ROM (Read Only Memory) for storing programs, a RAM (Random Access Memory) for temporarily storing data, and an electronic circuit such as a timer. It should be noted that at least a part of the communication control device Mb can also be an integrated circuit such as an LSI (Large Scale Integration).

[0035] For example, the communication control device Mb attempts to obtain the information required for payment and settlement through communication between the roadside communication device Ma and the on-board communication device 18 of a mobile body such as a surrounding vehicle at a predetermined period. When the communication control device Mb obtains the information required for payment and settlement from the on-board communication device 18 and confirms that electronic settlement can be performed, it sends permission information indicating that electronic settlement can be performed and key information required to start power transmission to the on-board communication device 18. When the key information is sent from the roadside communication device Ma to the on-board communication device 18, the communication control device Mb sends the same key information to the power transmission side control device 9 described later.

[0036] The power transmission device 2 includes, for example, a power supply unit 6, a power transmission power conversion unit 7, a power transmission unit 8, and a power transmission-side control device 9. The power transmission device 2 may include at least a plurality of power transmission units 8 in a predetermined coupling section in a vehicle travel path.

[0037] 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 capacitor for power smoothing. The power supply unit 6 converts the AC power supplied from the AC power supply into DC power through the AC-DC converter. The power supply unit 6 includes, for example, a current sensor 6a that detects the current of the DC power.

[0038] The power transmission power conversion unit 7, for example, includes an inverter that converts DC power into AC power. The inverter of the power transmission power conversion unit 7 includes, for example, a first bridge circuit formed by a plurality of switching elements and rectifying elements connected in a two-phase bridge, and a capacitor for voltage smoothing. Each switching element is, for example, a transistor such as a MOSFET (Metal Oxide Semi-conductor Field Effect Transistor) of SiC (Silicon Carbide). The plurality of switching elements are transistors 7a, 7b of the high-side arm and the low-side arm of each phase. The rectifying element is, for example, a freewheeling diode connected in parallel with each transistor 7a, 7b. The capacitor 7c for voltage smoothing is connected in parallel with the first bridge circuit.

[0039] The power transmission unit 8 transmits power by means of a change in a high-frequency magnetic field through magnetic field coupling such as magnetic field resonance or electromagnetic induction. Figure 3 As shown, the power transmission unit 8 includes, for example, a resonance circuit formed by a primary coil 8a, a primary resistor 8b, and a primary capacitor 8c connected in series. The power transmission unit 8 includes, for example, a sensor such as a current sensor for detecting a current (power transmission side current) It flowing in the resonance circuit.

[0040] The power transmission side control device 9 comprehensively controls the power transmission device 2. The power transmission side control device 9 is a software function unit that performs its functions by executing a predetermined program by a processor such as a CPU (Central Processing Unit). The software function unit is an ECU, which has a processor such as a CPU, a ROM (Read Only Memory) for storing programs, a RAM (Random Access Memory) for temporarily storing data, and an electronic circuit such as a timer. It should be noted that at least a part of the power transmission side control device 9 may also be an integrated circuit such as an LSI (Large Scale Integration).

[0041] The power transmission-side control device 9 generates, for example, a control signal indicating the timing of driving each switching element to be turned on (conducting) and turned off (cutting off), and generates a gate signal for actually driving each switching element to be turned on and off based on the control signal.

[0042] For example, the power transmission side control device 9 controls the switching operation of the switching elements of the power transmission power conversion unit 7 to be turned on (conducted) and off (cut off) according to a preset driving frequency or information on a required frequency obtained from the power receiving device 4, thereby transmitting power to the power receiving device 4 of a mobile body such as a vehicle.

[0043] For example, when the power transmission side control device 9 obtains the key information from the communication control device Mb, it grasps that the same key information is transmitted from the roadside communication device Ma to the vehicle-mounted communication device 18 of the mobile body, and shifts the power transmission device 2 from the stop state to the reception standby state. The stop state of the power transmission device 2 is, for example, a state in which the switching operation in the power transmission power conversion unit 7 is stopped, such as maintaining each switching element of the power transmission power conversion unit 7 to be disconnected (cut off). The reception standby state of the power transmission device 2 is a state in which the transmission of information from the power receiving device 4 of the mobile body such as a vehicle is detected. The reception standby state of the power transmission device 2 is, for example, a short-circuited state of the power transmission power conversion unit 7.

[0044] The transmission-side control device 9 short-circuits the primary-side coil 8a by setting the transistor 7b of the low-side arm of each phase to be turned on in the short-circuited state of the transmission power conversion unit 7. As a result, when the primary-side transmission device 2 is viewed from the secondary-side reception device 4, the impedance of the primary side becomes a very large value, but when the magnetic field is generated by the secondary-side coil 15a of the reception device 4 at the time of PING transmission described later, the communication from the reception device 4 is detected by the voltage induced in the primary-side coil 8a of the transmission device 2.

[0045] For example, when the power transmission side control device 9 obtains information such as the key information and the required frequency of power transmission from the power receiving device 4, it compares the key information obtained from the communication control device Mb with the key information obtained from the power receiving device 4. When the key information is consistent, the power transmission side control device 9 causes the power transmission device 2 to shift from the reception standby state to the power transmission state. The power transmission state of the power transmission device 2 is, for example, a state in which power transmission of the required frequency of the power receiving device 4 is performed.

[0046] The details of the power transmission control performed by the power transmission-side control device 9 will be described later.

[0047] like Figure 1 and Figure 2As shown, the drive control device 3 of a mobile body such as a vehicle includes, for example, a power storage device 11, a power conversion unit 13, and a rotary electric machine 14. The power receiving device 4 of the mobile body includes, for example, a power receiving unit 15 and a power receiving 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. The power receiving side control device 17 includes, for example, a vehicle-mounted communication device 18.

[0048] The power storage device 11 is connected to a power conversion unit 13 and a power receiving power conversion unit 16 described later. The power storage device 11 is charged by power transmitted in a non-contact manner from a power transmission device 2 outside a mobile body such as a vehicle. The power storage device 11 exchanges power with the rotating electric machine 14 via the power conversion unit 13.

[0049] The power storage device 11 includes, for example, a storage battery such as a lithium ion storage battery, a current sensor for detecting the current of the storage battery, and a voltage sensor for detecting the voltage of the storage battery.

[0050] The power conversion unit 13 is connected to the rotating electric machine 14. The power conversion unit 13 includes, for example, a power converter that converts DC power into AC power. The power converter includes, for example, a second element module and a capacitor for voltage smoothing.

[0051] The second element module, for example, includes a second bridge circuit formed by a plurality of switching elements and a rectifier element connected in a three-phase bridge. Each switching element is, for example, a transistor such as a SiC MOSFET. The plurality of switching elements are transistors 13a and 13b of a high-side arm and a low-side arm of each phase pair. The rectifier element is, for example, a freewheeling diode connected in parallel with each transistor 13a and 13b. A capacitor 13c for voltage smoothing is connected in parallel with the second bridge circuit.

[0052] The second element module controls the operation of the rotating electric machine 14 by transferring power. For example, when the rotating electric machine 14 is powered, the second element module converts the DC power input from the positive and negative DC terminals 13p and 13n into three-phase AC power and supplies the three-phase AC power from the three-phase AC terminal 13d to the rotating electric machine 14. The second element module generates a rotational driving force by sequentially commutating the power supplied to the three-phase stator winding of the rotating electric machine 14.

[0053] The second element module converts the three-phase AC power input from the three-phase stator winding into DC power by driving the switching elements of each phase to be turned on (conducted) and off (cut off) in synchronization with the rotation of the rotating electric machine 14, for example, during the regeneration of the rotating electric machine 14. The second element module can supply the DC power obtained by converting the three-phase AC power to the power storage device 11.

[0054] The rotating electric machine 14 is, for example, a three-phase AC brushless DC motor provided for driving a moving object such as a vehicle. The rotating electric machine 14 includes a rotor having a permanent magnet for excitation and a stator having a three-phase stator winding for generating a rotating magnetic field for rotating the rotor. The three-phase stator winding is connected to the three-phase AC terminals 13d of the power conversion unit 13.

[0055] The rotating electric machine 14 generates a rotational driving force by performing a power traction operation under the action of the electric power supplied from the electric power conversion unit 13. For example, when the rotating electric machine 14 can be connected to the wheels of the vehicle, it generates a driving force by performing a power traction operation under the action of the electric power supplied from the electric power conversion unit 13. The rotating electric machine 14 can also generate power by performing a regenerative operation under the action of the rotational power input from the wheel side of the vehicle. When the rotating electric machine 14 can be connected to the internal combustion engine of the vehicle, it can also generate power by the power of the internal combustion engine.

[0056] The power receiving unit 15 is connected to the power receiving power conversion unit 16. The power receiving unit 15 obtains power by using the change of the high-frequency magnetic field transmitted from the power transmitting unit 8 through magnetic field coupling such as magnetic field resonance or electromagnetic induction. Figure 3 As shown, the power receiving unit 15 includes, for example, a resonant circuit formed by a secondary coil 15a, a secondary resistor 15b, and a secondary capacitor 15c connected in series. The power receiving unit 15 includes, for example, a sensor such as a current sensor for detecting a current (power receiving side current) Ir flowing in the resonant circuit.

[0057] Figure 1 and Figure 2 The receiving power conversion unit 16 shown is connected to the power conversion unit 13. The receiving power conversion unit 16 includes a so-called non-full-bridge type (or non-bridge type and totem pole type) power factor correction (PFC: Power Factor Correction) circuit that converts AC power into DC power. The so-called non-bridge type PFC is a PFC that does not include a bridge rectifier implemented by a plurality of diodes connected by a bridge, and the so-called totem pole PFC is a PFC that includes a pair of switching elements of the same conductivity type connected in series in the same direction (totem pole connection).

[0058] The receiving power conversion unit 16 includes, for example, a third bridge circuit formed by a plurality of switching elements and a rectifying element connected in a two-phase bridge, and a capacitor for voltage smoothing. Each switching element is, for example, a transistor such as a SiC MOSFET. The plurality of switching elements are transistors 16a and 16b of the high-side arm and the low-side arm of each phase pair. The rectifying element is, for example, a freewheeling diode connected in parallel with each transistor 16a and 16b. The capacitor 16c for voltage smoothing is connected in parallel with the third bridge circuit.

[0059] For example, the power receiving device 4 including the power receiving unit 15 and the power receiving power conversion unit 16 controls the switching operation of turning on (conducting) and turning off (cutting off) each switching element of the power receiving power conversion unit 16 based on the information of the frequency of power transmission performed by the power transmitting device 2, thereby obtaining the power transmitted from the power transmitting device 2.

[0060] The power receiving side control device 17 comprehensively controls the drive control device 3 of a mobile body such as a vehicle, the power receiving device 4, and the vehicle-mounted communication device 18. The power receiving side control device 17 is a software function unit that performs functions by executing a predetermined program by a processor such as a CPU (Central Processing Unit). The software function unit is an ECU, which has a processor such as a CPU, a ROM (Read Only Memory) for storing programs, a RAM (Random Access Memory) for temporarily storing data, and an electronic circuit such as a timer. It should be noted that at least a part of the power receiving side control device 17 may also be an integrated circuit such as an LSI (Large Scale Integration).

[0061] The power receiving-side control device 17 generates, for example, a control signal indicating a timing to drive each switching element to be turned on (conducting) or turned off (cutting off), and generates a gate signal for actually driving each switching element to be turned on or off based on the control signal.

[0062] For example, the power receiving-side control device 17 controls the switching operation 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 perform power factor correction of the input voltage and input current.

[0063] For example, the power receiving-side control device 17 controls the output according to the target output by performing a synchronous rectification operation of synchronously driving a plurality of switching elements of the power receiving device 4 to turn on and off, and a short-circuiting operation of short-circuiting the secondary coil 15 a .

[0064] For example, the power receiving side control device 17 controls the synchronous rectification operation according to the magnitude and phase of the current Ir flowing in the secondary coil 15a, which is generated in the power receiving unit 15 due to the power transmitted from the power transmission device 2. The power receiving side control device 17 controls the plurality of switching elements of the power receiving power conversion unit 16 by a soft switching operation called zero voltage switching operation (ZVS). In the zero voltage switching operation (ZVS), each switching element performs an operation of turning on (switching from an off state to an on state) after the voltage across both ends of the switching element is set to zero by discharging the output capacitance (parasitic capacitance) in the off state during the dead time of each phase.

[0065] 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 synchronous rectification operation of the zero voltage switching operation (ZVS) in the high-side arm of each phase of the power receiving power conversion unit 16. The power receiving side control device 17 short-circuits the secondary side coil 15a, thereby increasing the impedance of the secondary side when the secondary side power receiving device 4 is viewed from the primary side power transmitting device 2 and reducing the current on the primary side (power transmission current: current It flowing in the primary side coil 8a). The power receiving side control device 17 controls the current of the primary side power transmitting device 2 by using the secondary side power receiving device 4, thereby performing independent power control such as power transmission stop on the power receiving device 4 side.

[0066] For example, the power receiving-side control device 17 sets a communication section for communication and a power transmission section for power transmission in a coupling section 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 greater than or equal to a predetermined value in the vicinity of the power transmitting device 2. For example, when the power receiving-side control device 17 acquires key information through communication between the roadside communication device Ma and the vehicle-mounted communication device 18 at a time before reaching the coupling section, the information related to power transmission in the power transmission section is transmitted from the power receiving device 4 to the power transmitting device 2 in the communication section before the start of power transmission by the power transmitting device 2 in the power transmission section.

[0067] For example, when the power receiving side control device 17 sets a first communication interval and a second communication interval before and after the power transmission interval along the moving direction of a mobile body (such as a vehicle V), information related to power transmission is sent from the power receiving device 4 to the power transmitting device 2 in the first communication interval which is the initial communication interval.

[0068] The information related to power transmission includes, for example, key information acquired from the roadside communication device Ma, required power and required frequency for power transmission, target output (power consumption) for fail safe, and information related to various abnormalities.

[0069] The required power for power transmission is a target value of power that the power receiving device 4 obtains from the power transmitting device 2 and is set based on, for example, the target driving force of the moving object 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 .

[0070] The required frequency of power transmission is the frequency required for power transmission of the power transmission device 2, and is set according to the required power. The required frequency is set to suppress the reduction of power transmission efficiency and output (power) based on, for example, the minimum ground height of the moving body associated with the distance between the primary coil 8a and the secondary coil 15a and the mounting layout of the power receiving device 4 in the moving body. The required frequency can also be set according to the state of power transmission between the power transmission device 2 and the power receiving device 4, for example.

[0071] It should be noted that, for example, the power receiving side control device 17 can also send information indicating the stop of power transmission in the power transmission interval and communication in the communication interval from the power receiving device 4 to the power transmitting device 2 through communication between the power transmitting device 2 and the power receiving device 4 when the primary side coil 8a is present in the last communication interval (for example, the second communication interval, etc.) of the coupling interval.

[0072] For example, when the power receiving side control device 17 acquires the key information through the communication between the roadside communication device Ma and the vehicle-mounted communication device 18, the information is transmitted by transmitting power from the power receiving device 4 to the power transmitting device 2 in the reception standby state as a so-called Internet packet search (PING) signal in the communication section of the coupling section. The power receiving device 4 communicates by using the voltage induced in the primary side coil 8a of the power transmitting device 2 by the magnetic field generated by the secondary side coil 15a through the energization switching operation based on the switching operation in the power receiving power conversion unit 16. The power receiving side control device 17 performs PING transmission by, for example, switching the carrier used for non-contact power transmission from the power receiving device 4 to the power transmitting device 2 at a predetermined duty ratio to generate two levels of digital signals, namely, dominant (superior) and recessive (inferior). The predetermined duty ratio is, for example, a predetermined minimum to 50%. It should be noted that the power receiving side control device 17 may also transmit information by, for example, amplitude modulation of the carrier based on the duty ratio of the switching operation.

[0073] The power receiving-side control device 17 performs PING transmission at a predetermined period of, for example, several tens of μs to several ms, and upon receiving a response signal to the PING transmission from the power transmitting device 2 , starts power reception control for power transmission from the power transmitting device 2 in the power transmission section.

[0074] The power receiving-side control device 17 sets the timing of PING transmission, for example, based on information related to the installation of the power transmitting device 2 acquired from the roadside communication device Ma and the movement state of the moving body (for example, the vehicle V) (that is, the movement state of the power receiving device 4), so that the communication (that is, the transmission and reception between each other) between the power transmitting device 2 and the power receiving device 4 in the communication section is appropriately completed. For example, the power receiving-side control device 17 sets the transmission cycle based on information such as the installation interval of the plurality of power transmitting units 8 and the speed of the moving body (for example, the vehicle speed of the vehicle V), so that the PING transmission is completed at least a predetermined number of times (one time, etc.) in the communication section.

[0075] It should be noted that, for example, even when the execution of PING transmission in the communication interval is permitted, the power receiving side control device 17 transitions to a standby state for stopping the execution of PING transmission outside the communication interval. For example, the power receiving side control device 17 may start the execution of PING transmission from before the initial communication interval immediately before reaching the next coupling interval in the standby state for PING transmission as the moving body moves.

[0076] Hereinafter, as the operation of the contactless power transmission system 1 , processing executed by the power transmission-side control device 9 and the power reception-side control device 17 will be described.

[0077] Figure 4 1 is a flowchart showing a power receiving-side process executed by the power receiving-side control device 17 of the contactless power transmission system 1 according to the embodiment.

[0078] First, in Figure 4 In step S01 shown, the power receiving side control device 17 determines whether electronic settlement for power transmission from the power transmission device 2 to the mobile body can be performed by sending and receiving information (payment communication) based on wireless communication between the roadside communication device Ma and the vehicle-mounted communication device 18. If the result of its determination is "No", the power receiving side control device 17 repeatedly performs the processing of step S01. On the other hand, if the result of its determination is "Yes", the power receiving side control device 17 advances the processing to step S02.

[0079] Then, in step S02, the power receiving-side control device 17 obtains key information necessary for starting power transmission from the roadside communication device Ma.

[0080] Next, in step S03 , the power receiving-side control device 17 generates a signal for PING transmission to be performed by transmitting electric power from the power receiving device 4 to the power transmitting device 2 .

[0081] Next, in step S04 , the power receiving-side control device 17 executes PING transmission at a predetermined cycle in the first communication section of the coupling section.

[0082] Next, in step S05, the power receiving side control device 17 determines whether a response signal to the PING transmission is received from the power transmitting device 2. If the result of the determination is "No", the power receiving side control device 17 repeats the process of step S05. On the other hand, if the result of the determination is "Yes", the power receiving side control device 17 advances the process to step S06.

[0083] Then, in step S06, the power receiving-side control device 17 executes power receiving control for power transmission from the power transmitting device 2 in the power transmission section. Then, the power receiving-side control device 17 ends the process.

[0084] Figure 5 1 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 according to the embodiment.

[0085] First, in Figure 5 In step S11 shown, the power transmission side control device 9 determines whether the key information is transmitted from the roadside communication device Ma to the power receiving device 4. If the result of its determination is "No", the power transmission side control device 9 advances the process to step S12. On the other hand, if the result of its determination is "Yes", the power transmission side control device 9 advances the process to step S13.

[0086] Then, in step S12 , the power transmission-side control device 9 maintains the stopped state of the power transmission device 2 and returns the process to step S11 .

[0087] Then, in step S13 , the power transmission-side control device 9 shifts the power transmission device 2 from the stopped state to the reception standby state.

[0088] Next, in step S14, the power transmission side control device 9 determines whether a PING signal based on power transmission from the power receiving device 4 to the power transmission device 2 is received in the first communication section of the coupling section. If the result of its determination is "No", the power transmission side control device 9 repeats the process of step S14. On the other hand, if the result of its determination is "Yes", the power transmission side control device 9 advances the process to step S15.

[0089] Next, in step S15 , the power transmission-side control device 9 compares the key information received from the communication control device Mb with the key information received from the power receiving device 4 .

[0090] Next, in step S16, the power transmission side control device 9 determines whether the key information obtained from the communication control device Mb is consistent with the key information obtained from the power receiving device 4. If the result of its determination is "No", the power transmission side control device 9 ends the process. On the other hand, if the result of its determination is "Yes", the power transmission side control device 9 enters step S17.

[0091] Next, in step S17 , the power transmission-side control device 9 transmits a response signal in response to the PING transmission to the power receiving device 4 through the power transmission from the power transmitting device 2 to the power receiving device 4 in the communication section.

[0092] Next, in step S18, the power transmission-side control device 9 starts power transmission control described later for power transmission to the power receiving device 4 at the requested frequency received from the power receiving device 4 in the power transmission section. Then, the power receiving-side control device 17 ends the process.

[0093] Figure 6 yes Figure 5 The flowchart of power transmission control is shown.

[0094] First, in Figure 6 In step S21 shown, the power transmission side control device 9 determines whether it is the initial stage of power transmission. The initial stage of power transmission is, for example, a period of time after a predetermined time has passed since the start of power transmission (electric power transmission). The predetermined time is set based on, for example, 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 unit 8 (the speed of the moving body, etc.). The predetermined time is, for example, a time between tens of μs and several ms.

[0095] If the determination result is "No", the power transmission side control device 9 advances the process to step S24. On the other hand, if the determination result is "Yes", the power transmission side control device 9 advances the process to step S22.

[0096] Next, in step S22, the power transmission side control device 9 performs ramp-up control. In the ramp-up control, the power transmission side control device 9 sets the transmission power (supplied power) from the power transmission unit 8 to be less than the prescribed power, and changes the transmission power to increase toward the prescribed power according to the elapsed time from the start of power transmission. The prescribed power is, for example, the required power of the power receiving device 4.

[0097] Next, in step S23, the power transmission side control device 9 determines whether a predetermined time has passed since the start of power transmission. If the determination result is "No", the power transmission side control device 9 repeatedly performs the determination process of step S23. On the other hand, if the determination result is "Yes", that is, when the transmission power is set to the predetermined power with the end of the initial power transmission start, the power transmission side control device 9 returns the process.

[0098] Furthermore, in step S24 , the power transmission-side control device 9 obtains a detection value of the current (the current of the DC power of the power supply unit 6 ) detected by the current sensor 6 a .

[0099] Next, in step S25, the power transmission side control device 9 determines whether the transmission power (supplied power) from the power transmission unit 8 is greater than the specified power (for example, the required power of the power receiving device 4) based on the detection value of the current output from the current sensor 6a, for example. If the determination result is "No", the power transmission side control device 9 causes the process to enter a return. On the other hand, if the determination result is "Yes", the power transmission side control device 9 causes the process to enter step S26.

[0100] Next, in step S26, the power transmission side control device 9 executes output suppression control. Then, the power transmission side control device 9 returns the process to step S24.

[0101] In the output suppression control, the power transmission-side control device 9 controls the power transmitted from the power transmission unit 8 toward a predetermined power to reduce the tendency change, for example, by feedback control based on the detection value of the current output from the current sensor 6 a .

[0102] Figure 7 1 is a diagram showing an example of time changes in the power transmitting-side power P1 and the power receiving-side power P2 in the ramp-up control in the contactless power transmission system 1 according to the embodiment.

[0103] like Figure 7 As shown, for example, by performing ramp-up control from the power transmission start time t0 to the predetermined time TR, the power transmitted from the power transmission device 2 (power transmission side power P1) and the power received by the power receiving device 4 (power receiving side power P2) are gradually increased from zero. Each power P1, P2 changes with an increasing tendency until reaching the end time ta of the ramp-up control, and becomes a stable state after the end time ta (for example, the power transmission side power P1 reaches the required power Pa of the power receiving device 4, etc.). The waveforms of each power P1, P2 near the power transmission start time t0 have changes caused by the fluctuation of the current, but by reducing the output using the ramp-up control, the generation of excessive power is suppressed.

[0104] The transmission-side control device 9 controls the transmission power, for example, by the duty ratio or phase shift amount of the gate signal (pulse signal) that instructs the switching operation of the transmission power conversion unit 7 during the ramp-up control. The duty ratio is, for example, the ratio of the on-time of one of the paired transistors 7a and 7b (for example, the transistor 7a of the high-side arm) in one cycle of the switching control of each phase of the transmission power conversion unit 7. The phase shift amount is, for example, the phase difference of the gate signal of the second phase of the two phases of the transmission power conversion unit 7 with respect to the gate signal of the first phase.

[0105] Figure 8 1 is a diagram showing an example of the correspondence relationship among the power transmission side voltage Vt, the power transmission side current It, the power reception side voltage Vr, and the power reception side current Ir in the duty ratio control of the ramp-up control in the contactless power transmission system 1 according to the embodiment. Fig. 9 1 is a diagram showing an example of the correspondence relationship among the power transmission side voltage Vt, the power transmission side current It, the power reception side voltage Vr, and the power reception side current Ir in the phase shift amount control of the ramp-up control in the contactless power transmission system 1 according to the embodiment.

[0106] like Figure 8 and Fig. 9 As shown, the power transmission side control device 9 changes the power transmission side voltage Vt (effective value, etc.) in an increasing trend by changing the duty ratio or the phase shift amount in an increasing trend, for example, stepwise or continuously. Figure 8 In the example shown, the duty ratio increases from a first duty ratio D1 to a second duty ratio D2 (> D1 ). Fig. 9 In the example shown, the phase shift amount increases from a first phase shift amount θ1 to a second phase shift amount θ2 (>θ1).

[0107] In the switching operation of the power transmission power conversion unit 7, the duty ratio or phase shift amount changes in an increasing trend. In contrast, for example, the duty ratio of the switching operation of the power reception power conversion unit 16 is set to a predetermined constant value (such as 50%), whereby the power reception side current Ir (effective value, etc.) changes in an increasing trend.

[0108] Fig.10 This is a diagram showing an example of the relationship between power transmission (transmission power) P and efficiency E according to horizontal distance (relative movement amount between the primary coil and the secondary coil in a direction parallel to the road surface) in the contactless power transmission system 1 according to the embodiment.

[0109] like Fig.10As shown, for example, by performing ramp-up control in a relatively low coupling degree (low efficiency) region in a power transmission section where the power transmission efficiency E becomes equal to or higher than a predetermined efficiency Ea (e.g., 80%), the transmission power P is limited to be equal to or lower than the required power Pa. The low efficiency region in the power transmission section is, for example, a region where the absolute value of the horizontal distance becomes a value within a predetermined range ΔL including the predetermined distance La.

[0110] As described above, according to the contactless power transmission system 1 of the embodiment, by providing the power transmission side control device 9 that sets the transmission power at the initial stage of power transmission to be less than the prescribed power, it is possible to suppress the increase in current that accompanies the start of rapid power supply. The power transmission side control device 9 changes the transmission power toward the prescribed power in an increasing trend according to the elapsed time from the start of power transmission, thereby suppressing the increase in load of the power supply unit 6 and the occurrence of overcurrent. For example, it is possible to suppress the occurrence of an increase in load due to a decrease in the frequency of the system power supply on the power transmission side, and the occurrence of an inconvenience such as a stop in power supply due to detection of an overcurrent due to current fluctuations.

[0111] The power transmission side control device 9 sets the initial period of power transmission 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 unit 8, so that the transmitted power can be appropriately reduced.

[0112] Since the power transmission-side control device 9 controls the transmission power by the duty ratio or phase shift amount of the gate signal, the transmission power can be quickly controlled even when the power reception device 4 moves relative to the power transmission unit 8 .

[0113] The power transmission-side control device 9 controls the transmission power based on the detection value of the current output from the current sensor 6a even after the initial power transmission start period. Therefore, even when power is transmitted sequentially to a plurality of moving objects such as vehicles having different power requirements, appropriate transmission power can be set.

[0114] (Variation)

[0115] In the above-mentioned embodiment, the power transmission side control device 9 performs output suppression control based on the detection value of the current output from the current sensor 6a, but is not limited to this. The power transmission side control device 9 is not limited to the current sensor 6a, and may perform output suppression control based on the detection value of other sensors such as a current sensor that detects the current (power transmission side current) It flowing through the resonant circuit of the power transmission unit 8.

[0116] In the above-described embodiment, the communication system M constitutes an electronic toll collection system, but the present invention is not limited thereto. For example, the communication system M may simply be a system that communicates with the vehicle-mounted communication device 18 before the power transmission device 2 transmits power in the power transmission section.

[0117] In the above-mentioned embodiment, the key information and the information such as the required power and required frequency of the power transmission are transmitted and received by the power transmission between the power transmission device 2 and the power receiving device 4, but the present invention is not limited to this. For example, the power transmission device 2 and the power receiving device 4 may each have a communication device for wireless communication with each other, and the information may be transmitted and received via the communication devices.

[0118] In the above-described embodiment, the contactless power transmission system 1 may include a power storage voltage conversion unit that converts input and output power of the power storage device 11 in the case of a hybrid vehicle that uses the power storage device 11 and an internal combustion engine as power sources.

[0119] The embodiments of the present invention are provided as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. These embodiments and their variations are included in the invention and its equivalent scope as they are included in the scope and purpose of the invention.

Claims

1. A contactless power transmission system, wherein: The contactless power transmission system comprises: a power transmission unit having a coil for transmitting AC power to a power receiving device in a non-contact manner; a power conversion unit having a plurality of switching elements connected to the coil and converting DC power supplied from a power source into the AC power; as well as a control device for controlling the switching actions of the plurality of switching elements, The control device sets the power to be transmitted at an initial stage of power transmission by the power transmission unit to be lower than a predetermined power, and changes the power to be transmitted to increase toward the predetermined power according to an elapsed time since the power transmission by the power transmission unit started.

2. The contactless power transmission system according to claim 1, wherein: The control device sets the initial period of power transmission start to a period during which a predetermined time has elapsed since the start of power transmission. The control device sets the predetermined time based on at least any one of a supply capacity of the power source, the number of the power transmission units connected to the power source, and a moving speed of the power reception device relative to the power transmission units.

3. The contactless power transmission system according to claim 1 or 2, wherein: The control device controls the transmission power by a duty ratio or a phase shift amount of a signal instructing the switching operation.

4. The contactless power transmission system according to claim 3, wherein: The contactless power transmission system includes a current sensor for detecting a current of the DC power. The control device sets the predetermined power as the required power of the power receiving device, The control device controls the transmitted power to be directed toward the predetermined power so as to reduce the tendency change based on the detection value of the current output from the current sensor when the transmitted power is larger than the predetermined power.

Images