JP2022158066A - Power transmission device - Google Patents

Abstract

To cope with steep fluctuation of a load during power supply.SOLUTION: A power transmission device 5 transmits power to a power reception device 7 in a non-contact manner, and comprises an inverter 513, a power transmission coil 531 and a control unit 519. The inverter 513 coverts DC power into AC power. The power transmission coil 531 transmits the AC power converted by the inverter 513 to the power reception device 7. The control unit 519 controls stop of the inverter 513 on the basis of inverter output current to be output from the inverter 513.SELECTED DRAWING: Figure 2

Description

The present invention relates to a power transmission device.

2. Description of the Related Art Conventionally, an automated guided vehicle (AGV) that automatically travels in factories, warehouses, and the like to transport packages is known. A wireless power supply system has been developed that supplies power to the AGV in a non-contact manner. The AGV, for example, travels along a preset circulation route, stops at preset positions, and loads and unloads cargo. The wireless power supply system charges the AGV while it is not loading or unloading cargo. A wireless power supply system includes a power transmitting device having a power transmitting coil that transmits power in a contactless manner, and a power receiving device having a power receiving coil that receives power from the power transmitting device.

When the AGV starts while power is being supplied, transient voltage/current increases occur at many locations inside the device. Such transient voltage/current increases include, for example, a power transmission/reception coil current increase, a power transmission/reception resonant capacitor voltage increase, a charging current increase, a charging voltage increase, and the like. For example, in Patent Literature 1, changes in charging power and transmission voltage are monitored, and control is performed so that the charging power does not fluctuate according to changes in the load.

JP 2016-67122 A

However, for example, the power receiving device described in Patent Literature 1 has a problem that it cannot cope with sudden fluctuations in the load during power supply. For example, in a wireless power supply system for AGVs, it is possible to supply high power and high efficiency with a simple resonant circuit design. Many methods are used. If the AGV starts moving while power is being supplied to the AGV by the SS method, the current in the power transmission/reception coil, the voltage of the power transmission/reception resonance capacitor, the battery voltage, etc. will rise sharply, and there is concern that the rated voltage of the element will be exceeded and the device will break down. be done.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to cope with sudden changes in the load during power supply.

A power transmission device according to the present embodiment is a power transmission device that transmits power in a contactless manner to a power receiving device, and includes an inverter that converts DC power into AC power, and the AC power converted by the inverter to the power receiving device. A power transmission coil for transmission, and a control unit that controls stopping of the inverter based on an inverter output current output from the inverter.

In the present embodiment, when the AGV that is supplying power starts from the stopped position, the inverter output current generated by a sudden change in the load corresponding to the decrease in the mutual inductance between the power transmitting coil and the power receiving coil in the power receiving device is used. to control the shutdown of the inverter.

As a result, it is possible to cope with sudden changes in the load caused by the start of the AGV during power feeding, and to suppress or prevent the occurrence of overvoltage in the circuits of the power transmitting device and the power receiving device. As a result, it is possible to suppress or prevent failures of the power transmitting device and the power receiving device due to overvoltage.

In the power transmission device according to the present embodiment, the controller stops the inverter when the time change of the inverter output current in the specified time exceeds the threshold.

In this embodiment, the shortest time resolution of the microcomputer, for example, milliseconds is defined as the specified time, and the time change (increase width) of the inverter output current is acquired during the specified time, and the increase width is compared with the threshold. do. As a result, the power transmission device of the present embodiment can quickly stop the inverter in millisecond units in response to detection of overcurrent exceeding the threshold.

As a result, it is possible to cope with sudden changes in the load caused by the start of the AGV during power feeding, and to suppress or prevent the occurrence of overvoltage in the circuits of the power transmitting device and the power receiving device. As a result, it is possible to suppress or prevent failures of the power transmitting device and the power receiving device due to overvoltage.

In the power transmission device according to the present embodiment, when the average time change of the inverter output current acquired for the plurality of second specified times included in the first specified time exceeds the threshold, Stop the inverter.

In this embodiment, the average value of the rise width of the inverter output current is calculated in the first specified time. Therefore, even if the inverter output current has a detection error, it is possible to stop the inverter when the inverter output current rises sharply due to a sharp change in the load during power supply while avoiding unnecessary shutdown of the inverter. can.

As a result, it is possible to cope with sudden changes in the load caused by the start of the AGV during power feeding, and to suppress or prevent the occurrence of overvoltage in the circuits of the power transmitting device and the power receiving device. As a result, it is possible to suppress or prevent failures of the power transmitting device and the power receiving device due to overvoltage.

In the power transmission device according to the present embodiment, the inverter is stopped when the time change of the inverter output current in the third specified time exceeds the threshold continuously for a predetermined number of times.

In the present embodiment, the inverter is stopped when the time change of the inverter output current in the third specified time continuously exceeds the threshold for a predetermined number of times. Even if the output current has a detection error, unnecessary stopping of the inverter can be avoided, and the inverter can be stopped when the inverter output current rises sharply.

As a result, it is possible to cope with sudden changes in the load caused by the start of the AGV during power feeding, and to suppress or prevent the occurrence of overvoltage in the circuits of the power transmitting device and the power receiving device. As a result, it is possible to suppress or prevent failures of the power transmitting device and the power receiving device due to overvoltage.

In the power transmission device according to the present embodiment, the control unit does not perform control to stop the inverter until a predetermined time has elapsed from the start time of transmission of AC power.

In this embodiment, the overcurrent protection function is disabled by power transmission stop control from immediately after the start of charging until the OCP disabled period elapses, even if the inverter output current rises to meet the desired charging conditions. be able to.

As a result, the inverter can be stopped when the inverter output current rises sharply while suppressing or preventing unnecessary stopping of the inverter immediately after the start of power supply.

According to the above aspect of the present invention, there is an effect that it is possible to cope with sudden changes in the load during power supply.

FIG. 1 is a diagram illustrating an example of a contactless power supply system according to an embodiment. FIG. 2 is a diagram illustrating an example of the circuit configuration of the contactless power supply system according to the embodiment; FIG. 3 is a flowchart illustrating an example of a procedure for power transmission stop control according to the embodiment.

Hereinafter, embodiments of a non-contact (wireless) power feeding system having a power transmitting device according to the present invention will be described in detail based on the drawings. In addition, this invention is not limited by this embodiment. Also, as a non-contact power feeding system, a case where the present invention is applied to an AGV system relating to an AGV that conveys packages in factories and warehouses will be described as an example. Note that the contactless power supply system may be applied to various industrial AGVs such as drones instead of AGVs. In the following embodiments, it is assumed that parts denoted by the same reference numerals perform the same operations, and overlapping descriptions will be omitted as appropriate.

(embodiment)
FIG. 1 is a diagram showing an example of a contactless power supply system 1. As shown in FIG. FIG. 2 is a diagram showing an example of the circuit configuration of the contactless power supply system 1. As shown in FIG. The contactless power supply system 1 charges the battery 3 mounted on the AGV that is stopped. The contactless power supply system 1 includes a power transmission device 5 and a power reception device 7 . The power transmission device 5 wirelessly transmits power to the power reception device 7 by the magnetic resonance method. The power receiving device 7 receives the transmitted AC power and charges the battery 3 with the AC power.

The power transmission device 5 has a power transmission unit 51 and a power transmission coil unit 53 . The power transmission unit 51 is installed, for example, on the floor near a position (stop position) where the AGV stops for work such as loading and unloading of cargo. The power transmission coil unit 53 is electrically connected to the power transmission unit 51 . The power transmission coil unit 53 is installed at a predetermined position with reference to the stop position. The power receiving device 7 is mounted on the AGV.

The power receiving device 7 has a power receiving coil unit 71 and a power receiving unit 73 . The power receiving coil unit 71 faces the power transmitting coil unit 53 when the AGV stops at the stop position. The power receiving coil unit 71 receives AC power from the power transmitting coil unit 53 . The power receiving unit 73 charges the battery 3 based on the received AC power.

The power transmission unit 51 includes a first direct current generator 511 , an inverter 513 , a first current sensor 515 , a drive circuit 517 , a controller 519 and a display 521 . The first DC generator 511 , for example, converts AC power supplied from a three-phase 200 V commercial power supply (AC power supply) 9 into DC power, and outputs the DC power to the inverter 513 . As shown in FIG. 2 , the first DC generator 511 includes, for example, a rectifier circuit DR1 that rectifies three-phase AC power supplied from the AC power supply 9 and a smoothing capacitor C1 that smoothes the output. Although the first DC generation unit 511 rectifies the AC power of the commercial power supply 9 and converts it into DC power, it is not limited to this, and for example, it may be composed of a battery or the like and output DC power. may

Inverter 513 converts DC power into AC power. The inverter 513 functions as an AC voltage source for the power transmission coil unit 53 . The AC power output from inverter 513 has a frequency higher than that of AC in commercial power supply 9 . The output current (inverter output current) output from the inverter 513 is controlled by phase shift control in the control section 519, for example. A controlled object of the phase shift control is, for example, the amplitude (magnitude of the current) of the inverter output current. Note that the control of the output power in the inverter 513 is not limited to phase shift control, and other control methods such as a pulse width modulation (PWM) method and a pulse amplitude modulation (PAM) method. It may be realized by

As shown in FIG. 2, the inverter 513 includes, for example, a first arm (leading arm circuit) LAC and a second arm (following arm circuit) FAC. The leading arm circuit LAC and the following arm circuit FAC are connected in parallel to the first DC generator 511 . The leading arm circuit LAC is configured by, for example, connecting a switching element TR1 and a switching element TR2 in series. The tracking arm circuit FAC is configured by connecting a switching element TR3 and a switching element TR4 in series. The switching elements TR1 to TR4 are described as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) such as SiC-MOSFETs and Si-MOSFETs, but the switching elements are not limited to these. For example, the switching elements TR1 to TR4 may be implemented by other switching elements such as bipolar transistors and IGBTs (Insulated Gate Bipolar Transistors). Further, the inverter 513 is not limited to the full-bridge inverter circuit as shown in FIG. 2, and may be realized by, for example, a half-bridge inverter circuit. Moreover, although the switching elements TR1 to TR4 shown in FIG. 2 are N-channel, they may be realized by P-channel switching elements.

As shown in FIG. 2, the source terminal of the switching element TR1 and the drain terminal of the switching element TR2 are electrically connected. A drain terminal of the switching element TR1 is electrically connected to the positive electrode side of the first DC generator 511, and a source terminal of the switching element TR2 is electrically connected to the negative electrode side of the first DC generator 511. Similarly, the source terminal of the switching element TR3 and the drain terminal of the switching element TR4 are electrically connected. The drain terminal of the switching element TR3 is electrically connected to the positive electrode side of the first DC generator 511, and the source terminal of the switching element TR4 is electrically connected to the negative electrode side of the first DC generator 511.

As shown in FIG. 2, a connection point CP1 between the switching elements TR1 and TR2 in the leading arm circuit LAC and a connection point CP2 between the switching elements TR3 and TR4 in the following arm circuit FAC are connected to the output of the inverter 513. It becomes a terminal (output node). A power transmission coil unit 53 is connected to the output terminal. A driving signal (gate signal) output from the driving circuit 517 is input to gate terminals of the switching elements TR1 to TR4. Under the control of drive circuit 517, switching element TR1 and switching element TR4 and switching element TR2 and switching element TR3 are alternately turned on/off. That is, switching element TR1 and switching element TR2 are exclusively turned on/off, and similarly switching element TR3 and switching element TR4 are exclusively turned on/off. As a result, the inverter 513 generates a high-frequency inverter output current on the order of kilohertz (kHz), for example.

As shown in FIG. 2, the first current sensor 515 is provided, for example, between the power transmission coil 531 and the output terminal CP2. A first current sensor 515 detects the inverter output current. The first current sensor 515 is, for example, a CT (Current Transformer) type current sensor. Note that the first current sensor 515 is not limited to a CT-type current sensor, and any ammeter may be used. First current sensor 515 outputs the current value of the inverter output current to first comparator 525 in control unit 519 .

The drive circuit 517 amplifies the phase signal adjusted by the phase adjuster 523 in the control section 519 to a voltage capable of driving the gates of the switching elements TR1 to TR4. The phase signal corresponds to a pulse signal (signal indicating ON or OFF of switching) input to the gate of each of the switching elements TR1 to TR4. The drive circuit 517 outputs the amplified phase signal as a drive signal to the gate terminals of the switching elements TR1 to TR4.

Control unit 519 performs an OCP (Over Current Protection) function for controlling stoppage of inverter 513 based on the inverter output current output from inverter 513 . The control unit 519 is configured by, for example, a microcomputer including a ROM, a RAM, a CPU, etc., an FPGA (Field-Programmable Gate Array), or the like. The control unit 519 has a phase adjuster 523 and a first comparator 525 .

Phase adjuster 523 adjusts the phase of the phase signal based on the output from first wireless communication section 533 in power transmission coil unit 53 . Phase adjuster 523 thereby controls the inverter output current. The control unit 519 does not perform control to stop the inverter 513 until a predetermined time has elapsed from the start time of transmission of AC power from the power transmission device 5 to the power reception device 7 . The predetermined time is the amount of inverter output current for satisfying desired charging conditions (for example, specified current (specified current) to be charged to the battery 3, specifications of the contactless power supply system 1) immediately after the start of charging the battery 3. A rising period, for example a few seconds. The predetermined time is a period during which the OCP function is disabled (OCP disabled period). The OCP invalid period is set in advance according to, for example, charging conditions and stored in a ROM or the like. The first comparator 525 does not perform control to stop the inverter 513 until the OCP invalid period elapses from the transmission start time.

The phase adjuster 523 adjusts the phase difference in switching timing between the leading arm circuit LAC and the trailing arm circuit FAC. For example, when the phase difference is 0, the switching timings of the switching elements TR1 and TR3 are in phase, and similarly, the switching timings of the switching elements TR2 and TR4 are also in phase. At this time, the on-time of the switching element TR1 and the on-time of the switching element TR4 do not overlap, and similarly, the on-time of the switching element TR2 and the on-time of the switching element TR3 do not overlap. Therefore, the inverter output current becomes 0A.

When the output from first radio communication section 533 is a signal that increases the phase difference (phase increase signal), phase adjuster 523 adjusts the phase signal so that the phase difference increases. At this time, the overlapping ON times of the switching elements TR1 and TR4 become longer, and the overlapping ON times of the switching elements TR2 and TR3 also become longer, so that the inverter output current increases. On the other hand, when the output from first radio communication section 533 is a signal that reduces the phase difference (phase reduction signal), phase adjuster 523 adjusts the phase signal so that the phase difference is reduced. At this time, the overlapping ON times of the switching elements TR1 and TR4 become shorter, and the overlapping ON times of the switching elements TR2 and TR3 also become shorter, so that the inverter output current becomes smaller.

Also, the phase adjuster 523 stops outputting the phase signal to the drive circuit 517 in response to the output of the first comparator 525 regardless of the input from the first wireless communication section 533 . In other words, the phase adjuster 523 responds to the output of the first comparator 525 by priority over the input from the first wireless communication unit 533, for example, by software interrupt processing, and outputs the phase signal to the drive circuit 517. Stop output. As a result, the output of the driving signal from the driving circuit 517 to the switching elements TR1 to TR4 becomes 0 V, and the gates are not driven. As a result, inverter 513 stops. In addition, the phase adjuster 523 may adjust the phase difference to 0 in response to the output of the first comparator 525 . At this time, the switching timings of the switching elements TR1 and TR3 are in phase, and similarly, the switching timings of the switching elements TR2 and TR4 are also in phase. As a result, the inverter output current becomes 0A.

A first comparator 525 reads the inverter output current at a specified time. The specified time is set in advance according to the charging condition of the electric power to the battery 3 . Specifically, the specified time is the shortest resolution of the microcomputer that configures the control unit 519, and is a sufficiently short time of less than one second, such as on the order of milliseconds. In order to make the description concrete, the specified time is assumed to be 20 msec. Note that the prescribed time may be a multiple of the shortest resolution (for example, 20 msec, 40 msec, 60 msec, etc.).

The first comparator 525 compares a threshold preset according to the charging condition with the time change of the inverter output current in the specified time. Specifically, the first comparator 525 starts monitoring the inverter output current and performs the comparison after the OCP invalid period has passed from the transmission start time. The time change of the inverter output current at the specified time is, for example, the absolute value of the difference between the inverter output current read at the present time and the inverter output current read before the specified time from the present time (hereinafter referred to as the difference value as appropriate) is called). The difference value corresponds to the increase width of the inverter output current per specified time. The first comparator 525 calculates a difference value, and outputs a stop signal to the phase adjuster 523 to stop outputting the phase signal from the phase adjuster 523 to the drive circuit 517 when the calculated difference value exceeds the threshold value. output to As a result, the output from the phase adjuster 523 to the drive circuit 517 is set to 0, thereby stopping the inverter 513 . At this time, the inverter output current becomes 0A. The first comparator 525 also outputs a stop signal corresponding to an OCP error indicating execution of the OCP function to the display 521 .

It should be noted that the time change of the inverter output current during the specified time is not limited to the above difference value, and may be, for example, the transition of the change of the inverter output current during the specified time. At this time, the first comparator 525 calculates transition of change in the inverter output current in the specified time. The transition of the change in the inverter output current corresponds to, for example, the slope of the approximation curve that approximates the distribution of the value of the inverter output current with respect to time. At this time, the first comparator 525 compares the transition of the change with the threshold. The first comparator 525 outputs a stop signal to the phase adjuster 523 when the change transition exceeds the threshold.

A display 521 displays information about OCP errors. Indicator 521 is, for example, a warning light. At this time, the indicator 521 lights the OCP error in response to the input of the stop signal. Note that the indicator 521 is not limited to lighting related to the OCP error, and may display a message related to the OCP error. In addition, the indicator 521 turns off in a preset number of seconds (predetermined number of seconds), for example, about 2 seconds after turning on for the OCP error. At this time, the power transmission device 5 clears the OCP error without restarting the power supply including the inverter 513, and enters a standby state until the AGV stops at the stop position. Specifically, after a lapse of a predetermined number of seconds after the stop signal is input, the phase adjuster 523 enters a standby state to wait for an input from the first wireless communication section 533 .

The power transmission coil unit 53 uses the inverter output current to wirelessly transmit power to the power reception coil 711 mounted on the AGV stopped at the stop position. As shown in FIG. 2 , the power transmission coil unit 53 includes a power transmission coil 531 and a resonance capacitor C2 electrically connected to the inverter 513 , and a first wireless communication section 533 . As shown in FIG. 2, the resonance capacitor C2 is connected in series with the power transmission coil 531. As shown in FIG. As a result, the power transmission coil 531 and the resonance capacitor C2 form a series resonance circuit. Note that the resonance capacitor C2 may be connected in parallel with the power transmission coil 531 . At this time, the power transmission coil 531 and the resonance capacitor C2 form a parallel resonance circuit. The power transmission coil 531 transmits the AC power converted by the inverter 513 to the power receiving device 7 by the magnetic field resonance method. Specifically, the power transmission coil 531 non-contactly transmits the AC power to the power reception coil unit 71 of the AGV stopped at the stop position by the inverter output current.

The first wireless communication unit 533 performs wireless communication using infrared rays, for example, with the second wireless communication unit 713 of the AGV stopped at the stop position. When wireless communication is established with second wireless communication unit 713 , first wireless communication unit 533 sends the signal (phase increase signal or phase decrease signal) transmitted from second wireless communication unit 713 to control unit 519 . Output. Establishment of wireless communication corresponds to detection that the AGV has stopped at a stop position where the battery 3 can be charged.

The power receiving device 7 includes a power receiving coil unit 71 and a power receiving unit 73, and is mounted on the AGV. The power receiving coil unit 71 includes a power receiving coil 711, a resonance capacitor C3, and a second wireless communication section 713, as shown in FIG. When the AGV stops at the stop position, the receiving coil 711 magnetically couples with the transmitting coil 531 and receives the AC power transmitted from the transmitting coil 531 in a contactless manner. As shown in FIG. 2 , resonant capacitor C3 is connected in series with receiving coil 711 . As a result, the receiving coil 711 and the resonance capacitor C3 form a series resonance circuit.

As shown in FIG. 2, the circuit configuration in the power transmitting coil unit 53 and the power receiving coil unit 71 is of the SS (Series-Series) system as an example of the magnetic field resonance system. Note that the resonant capacitor C3 may be connected in parallel to the power receiving coil 711 . At this time, power receiving coil 711 and resonance capacitor C3 form a parallel resonance circuit. Further, the circuit configuration of the power transmitting coil unit 53 and the power receiving coil unit 71 is not limited to the SS system as means for realizing the magnetic field resonance system, and examples include SP (Series-Parallel) system, PS ( Parallel-Series) method, PP (Parallel-Parallel) method, or the like.

The second wireless communication unit 713 performs wireless communication with the first wireless communication unit 533 using infrared rays, for example, when the AGV stops at the stop position. When wireless communication is established with first wireless communication unit 533 , second wireless communication unit 713 transmits the signal (phase increase signal or phase decrease signal) received from second comparator 735 to first wireless communication unit 533 . Send to

The power receiving unit 73 has a second direct current generator 731 , a second current sensor 733 and a second comparator 735 . The second DC generator 731 is electrically connected to one end of the receiving coil 711 and one end of the resonance capacitor C3, as shown in FIG. The second DC generator 731 is a DC conversion circuit that converts AC power supplied from the receiving coil unit 71 into DC power. As shown in FIG. 2, the second DC generator 731 includes, for example, a rectifier circuit DR2 that rectifies the AC power generated by the receiving coil 711 and a smoothing capacitor C4 that smoothes the output. An output terminal of the second DC generator 731 is electrically connected to the battery 3 .

A second current sensor 733 is provided between the second DC generator 731 and the battery 3 . The second current sensor 733 detects the current output from the second direct current generator 731 . The current output from the second direct current generator 731 is the current for charging the battery 3 (hereinafter referred to as charging current). Since the configuration of the second current sensor 733 is the same as that of the first current sensor 515, the description thereof is omitted. Second current sensor 733 outputs the current value of the charging current to second comparator 735 .

A second comparator 735 compares the charging current and the specified current. The specified current is set in advance according to charging conditions. When the charging current exceeds the specified current, second comparator 735 outputs a phase reduction signal to second wireless communication section 713 . When the charging current falls below the specified current, second comparator 735 outputs a phase increase signal to second wireless communication section 713 . Note that the second comparator 735 may be mounted in the power transmission unit 51 (for example, the control section 519). At this time, second wireless communication unit 713 transmits the value of the charging current to first wireless communication unit 533 . Second comparator 735 then performs a comparison between the value of the charging current and the specified current and outputs a phase increase or phase decrease signal to phase adjuster 523 .

The power transmission stop control executed according to the present embodiment will be described below. FIG. 3 is a flowchart illustrating an example of a procedure for power transmission stop control.

(Power transmission stop control)
(Step S301)
When wireless communication is established between first wireless communication unit 533 and second wireless communication unit 713, first wireless communication unit 533 detects that the AGV has stopped at the stop position.

(Step S302)
When AGV is detected in step S301, the charging current is less than the specified current, so second wireless communication section 713 transmits a phase increase signal to first wireless communication section 533. FIG. First radio communication section 533 outputs the phase increase signal to phase adjuster 523 . The phase adjuster 523 outputs to the drive circuit 517 a phase signal whose phase difference is increased by the phase increase signal. The drive circuit 517 amplifies the voltage of the phase signal and outputs the amplified drive signal to the switching elements TR1 to TR4. Next, the inverter 513 supplies the inverter output current to the power transmission coil 531 under phase difference feedback control based on the output from the second comparator 735 . The power transmission coil 531 transmits power to the power reception coil 711 . In this step, if the battery 3 is fully charged, the process of step S305 is executed. Control unit 519 does not perform control to stop inverter 513 until the OCP invalid period elapses from the transmission start time of AC power.

(Step S303)
When the OCP invalid period elapses from the AC power transmission start time, the first comparator 525 compares the time change of the inverter output current with the threshold at regular time intervals (step S303). At this time, if the battery 3 is fully charged, the process of step S305 is executed.

(Step S304)
After the process of step S303, if the time change of the inverter output current does not exceed the threshold (No of step S304), the process of step S303 is performed. On the other hand, if the time change of the inverter output current exceeds the threshold (Yes of step S304), the process of step S305 will be performed.

(Step S305)
Control unit 519 executes the OCP function. Inverter 513 is stopped by the OCP function. At this time, supply of the inverter output current to the power transmission coil 531 is stopped. In addition, the indicator 521 shows the OCP error illumination for a predetermined number of seconds.

As described above, according to the power transmission device 5 of the present embodiment, the inverter 513 is stopped based on the inverter output current detected by the first current sensor 515 . In the power transmission device 5 that employs the magnetic resonance method, when the AGV that is supplying power starts from a stop position, the mutual inductance between the power transmission coil 531 and the power reception coil 711 decreases and the inverter output current rises. Focusing on the increase in the inverter output current, which is highly responsive to a decrease in mutual inductance (rapid change in load), the power transmission device 5 of the present embodiment adjusts the inverter 513 based on the inverter output current corresponding to overcurrent. Control the stop. As a result, since the power transmitting device 5 of the present embodiment can cope with sudden fluctuations in the load during power feeding, it is possible to suppress or prevent the occurrence of overvoltage in the circuits of the power transmitting device 5 and the power receiving device 7. can be done. Therefore, in the present power transmitting device 5, failure of the power transmitting device 5 and the power receiving device 7 due to overvoltage can be suppressed or prevented.

In addition, the power transmission device 5 of the present embodiment acquires the time change (increase width) of the inverter output current with the shortest time resolution of the microcomputer, that is, a sufficiently short specified time such as millisecond units, and calculates the increase width. Compare with threshold. As a result, the power transmission device 5 of the present embodiment can stop the inverter 513 in millisecond units in response to detection of overcurrent exceeding the threshold. Therefore, the power transmission device 5 of the present embodiment can cope with abrupt changes in the load accompanying the start of the AGV during power feeding, and can suppress or prevent device failures that occur during power feeding.

For these reasons, according to the present power transmission device 5, in the magnetic resonance method, by monitoring the inverter output current, a transient change in the inverter output current at the start of the AGV during power supply, that is, the occurrence of overcurrent can be detected. can be captured accurately. As a result, according to the present power transmission device 5, it is possible to cope with sudden changes in the load, and high voltages in the circuits (for example, the resonance capacitors C2 and C3) of the power transmission device 5 and the power reception device 7 accompany the increased inverter output current. It is possible to suppress or prevent the occurrence of (overvoltage), and prevent failures specific to the magnetic resonance method in the power transmitting device 5 and the power receiving device 7 . In addition, since the power transmission stop control in this embodiment is a protection function that is completed on the power transmission side, the inverter 513 can respond to short-time current/voltage rises peculiar to the magnetic resonance method without using communication. can be quickly stopped, and the supply of the inverter output current to the power transmission coil 531 can be stopped.

In addition, according to the power transmission device 5 according to the present embodiment, the control for stopping the inverter is not performed until a predetermined time has elapsed from the start time of transmission of AC power. Therefore, the OCP function can be disabled by power transmission stop control from immediately after the start of charging until the OCP disabled period elapses, even if the inverter output current rises in order to satisfy a desired charging condition. As a result, it is possible to suppress or prevent unnecessary stoppage of inverter 513 immediately after the start of power supply, and to stop inverter 513 when the inverter output current rises sharply.

(First modification)
In this modification, the first comparator 525 compares the average of the time change of the inverter output current obtained for a plurality of second specified times included in the first specified time with the threshold. The first specified time is, for example, a multiple of the second specified time corresponding to the shortest resolution and a sufficiently short time like the specified time. In other words, the second specified time corresponds to a time obtained by equally dividing the first specified time. The first specified time corresponds to a period (moving average period) during which the moving average of the rise width of the inverter output current is calculated. For example, if the first specified time is 80 msec and the second specified time is 20 msec, the first comparator 525 outputs the current rise width of the inverter output current, 20 msec before, 40 msec before, and An average value is calculated by dividing the sum of the three inverter output current rise widths 60 msec before by 4, and the calculated average value is compared with the threshold value. The first comparator 525 calculates an average value each time the inverter output current is read, ie every second specified time.

According to this modification, since the average value of the rise width of the inverter output current is calculated in the moving average period set in advance, even if the detected inverter output current has a detection error, the inverter 513 is unnecessary. It is possible to stop the inverter 513 when the inverter output current rises sharply due to a sharp change in the load during power supply while avoiding a sudden stop. As a result, according to the present power transmission device 5, since it is possible to cope with sudden fluctuations in the load during power supply, it is possible to suppress or prevent the occurrence of overvoltage in the circuits of the power transmission device 5 and the power reception device 7. Therefore, in the present power transmission device 5, it is possible to suppress failure of the device that occurs during power feeding.

(Second modification)
This modification is to stop the inverter 513 when the time change of the inverter output current in the third specified time exceeds the threshold continuously for a predetermined number of times. The third specified time may be, for example, the first specified time in the first modified example or the second specified time. The predetermined number of times is, for example, a natural number of 2 or more, and is set in advance and stored in a ROM or the like. Phase adjuster 523 counts the number of stop signals output from first comparator 525 . When the count number of stop signals reaches a predetermined number, phase adjuster 523 stops outputting to drive circuit 517 .

According to this modification, the inverter 513 is stopped when the number of stop signals reaches a predetermined number in succession. Therefore, even if the detected inverter output current has a detection error, While avoiding unnecessary stop of inverter 513, inverter 513 can be stopped when the inverter output current rises sharply. As a result, according to the present power transmission device 5, since it is possible to cope with sudden fluctuations in the load during power supply, it is possible to suppress or prevent the occurrence of overvoltage in the circuits of the power transmission device 5 and the power reception device 7. Therefore, in the present power transmission device 5, it is possible to suppress failure of the device that occurs during power feeding.

(Third modification)
This modification is to execute power transmission stop control according to the charging conditions when the charging conditions are set according to a plurality of AGVs. The control unit 519 stores, in a ROM or the like, a correspondence table (LUT: Look Up Table). Also, the power receiving device 7 stores its own ID in a memory (not shown). The threshold and prescribed time for each of the plurality of power receiving devices mounted on each of the plurality of AGVs are determined based on the charging conditions set by the user and stored in the LUT in association with the identification information of the power receiving device 7.

When wireless communication with the first wireless communication unit 533 is established, the second wireless communication unit 713 transmits the identification information of the power receiving device 7 to the first wireless communication unit 533 . First wireless communication unit 533 outputs the received identification information to control unit 519 . The control unit 519 identifies the threshold and the prescribed time for the power receiving device 7 by matching the identification information with the LUT. The control unit 519 executes the power transmission stop control described in FIG. 3 using the specified threshold value and specified time.

According to the power transmission device 5 according to the present modification, power transmission stop control can be executed according to the power reception conditions of each of the plurality of power reception devices. As a result, according to the present power transmission device 5, it is possible to set and adjust the threshold value and the specified time according to the charging conditions for a plurality of power receiving devices, and to adjust the inverter output current according to the charging conditions desired by the user. Inverter 513 can be stopped during a steep rise.

As described above, according to the power transmission device 5 according to the present embodiment and the modified example, it is possible to cope with sudden changes in the load during power feeding, and to suppress or prevent device failures that occur during power feeding. be able to.

It should be noted that the above-described embodiments and modifications can be combined as appropriate, and are merely examples and do not limit the scope of the invention. In addition, the above-described embodiments and modifications are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1... Contactless power supply system 3... Battery 5... Power transmission device 7... Power reception device 9... AC power supply 51... Power transmission unit 53... Power transmission coil unit 71... Power reception coil unit 73... Power reception unit 511... First direct current generation unit 513 Inverter 515 First current sensor 517 Drive circuit 519 Control unit 521 Indicator 523 Phase adjuster 525 First comparator 531 Power transmission coil 533... First wireless communication unit, 711... Receiving coil, 713... Second wireless communication unit, 731... Second direct current generation unit, 733... Second current sensor, 735... Second comparator

Claims (5)

A power transmitting device that wirelessly transmits power to a power receiving device,
an inverter that converts DC power to AC power;
a power transmission coil that transmits the AC power converted by the inverter to the power receiving device;
a control unit that controls stopping of the inverter based on the inverter output current output from the inverter;
A power transmission device comprising: The control unit stops the inverter when a time change of the inverter output current in a specified time exceeds a threshold.
The power transmission device according to claim 1 . The control unit stops the inverter when an average of temporal changes in the inverter output current obtained for a plurality of second specified times included in the first specified time exceeds a threshold.
The power transmission device according to claim 1 . The control unit stops the inverter when the time change of the inverter output current in a third specified time continuously exceeds a threshold for a predetermined number of times.
The power transmission device according to claim 1 . The control unit does not perform control to stop the inverter until a predetermined time has elapsed from the start time of transmission of the AC power,
The power transmission device according to any one of claims 1 to 4.

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