JP2017085784A - Power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply system in which power can be supplied to a load efficiently.SOLUTION: A controller 24 acquires a transmission power to be supplied to a high-frequency power source 21 from a voltmeter 22 and an ampere meter 23, and transmits it to a controller 35. The controller 35 acquires a receiving power to be supplied to a battery 50 from a voltmeter 33 and an ampere meter 34. The controller 35 furthermore detects a system efficiency which is a ratio of the acquired receiving power with respect to the received transmission power. The control unit 35 adjusts a duty of a DC/DC converter 32 on the basis of the detected system efficiency.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power feeding system, and more particularly to a power feeding system that performs non-contact power feeding.

  In recent years, attention has been focused on wireless power feeding without using a power cord or a power transmission cable as a power feeding system for feeding power to a battery mounted on a hybrid vehicle or an electric vehicle. One of the wireless power feeding techniques is known as a magnetic resonance type.

  This magnetic field resonance type power feeding system includes a pair of resonance coils. One of the pair of resonance coils is installed on the ground of the power supply facility, and the other is mounted on the vehicle. When AC power is supplied to the resonance coil installed in the power supply facility, power is supplied in a non-contact manner from the resonance coil to the resonance coil mounted on the vehicle. A resonance coil mounted on a vehicle supplies electric power supplied without contact to a load such as a battery.

  In the power feeding system described above, if the distance between the resonance coils and the impedance of the load change, the AC power supply and the input impedance of the resonance system cannot be matched, and the reflected power to the AC power supply increases, so that the power can be efficiently loaded. Can not be supplied to.

  Therefore, conventionally, the reflected power reflected by the resonance coil mounted on the vehicle and returned to the AC power source is obtained, and the resonance coil mounted on the vehicle and the load are set so that the reflected power is less than the threshold value. It is considered to adjust the duty of a DC / DC converter provided between them (Patent Document 1). Patent Document 1 also describes that the duty of the DC / DC converter is adjusted based on the ratio of the current and voltage input to the DC / DC converter that directly affects the change in reflected power, that is, the change in impedance. ing.

  However, there is a problem that even if the duty of the DC / DC converter is adjusted according to the reflected power and impedance, the power cannot be efficiently supplied to the load.

Japanese Patent No. 5459058

  Then, this invention makes it a subject to provide the electric power feeding system which can supply electric power to load efficiently.

  In order to solve the above-mentioned problems, an invention according to claim 1 is directed to an AC power supply, a primary resonance coil that receives supply of power from the AC power supply, and magnetic resonance of power from the primary resonance coil. A power supply system comprising: a secondary resonance coil that receives power; and a DC / DC converter provided between the secondary resonance coil and a load to which power is supplied from the secondary resonance coil. System efficiency detecting means for detecting system efficiency which is a ratio of received power supplied to the load with respect to transmitted power to be transmitted, and duty of the DC / DC converter based on the system efficiency detected by the system efficiency detecting means And a duty adjusting means for adjusting the power supply system.

  In the invention according to claim 2, the duty adjustment means obtains a duty that maximizes the system efficiency detected by the system efficiency detection means by changing the duty of the DC / DC converter, and the obtained system efficiency. The power supply system according to claim 1, wherein the duty is adjusted to a maximum.

  The invention according to claim 3 further includes inter-coil efficiency detecting means for detecting inter-coil efficiency, which is a ratio of the power output from the secondary resonant coil to the power input to the primary resonant coil, and the duty The adjustment means changes the duty of the DC / DC converter to obtain a duty that maximizes the inter-coil efficiency detected by the inter-coil efficiency detection means, and determines the duty from the obtained duty that maximizes the inter-coil efficiency. 3. The duty according to claim 1, wherein the duty is reduced, a duty that maximizes the system efficiency detected by the system efficiency detection unit is obtained, and the duty that the obtained system efficiency is maximized is adjusted. It exists in the power supply system.

  As described above, according to the first aspect of the present invention, it is possible to efficiently supply power to the load by adjusting the duty of the DC / DC converter based on the system efficiency.

  According to the second aspect of the present invention, it is possible to adjust the duty to maximize the system efficiency, and to more efficiently supply power to the load.

  According to the third aspect of the present invention, the duty search range where the system efficiency is maximized can be reduced.

It is a circuit diagram showing one embodiment of the electric power feeding system of the present invention in the 1st embodiment. It is a circuit diagram which shows the detail of the DC / DC converter shown in FIG. 2 is a graph showing transmitted power, received power, system efficiency, and rectified efficiency when the duty of the DC / DC converter shown in FIG. 1 is changed. 3 is a graph showing transmitted power, received power, and inter-coil efficiency when the duty of the DC / DC converter shown in FIG. 1 is changed. It is a circuit diagram which shows one Embodiment of the electric power feeding system of this invention in 2nd Embodiment.

(First embodiment)
The power supply system of the present invention in the first embodiment will be described below with reference to FIG. The power feeding system 1 includes a power transmission device 20 disposed on the ground and a power reception device 30 disposed on a vehicle. As shown in FIG. 1, the power transmission device 20 is a device that transmits, for example, power from a DC power supply 40 to a power receiving device 30 described later in a contactless manner.

  As shown in FIG. 1, the power transmission device 20 includes a high-frequency power source 21 as an AC power source, a capacitor C1, a primary resonance coil L1, a voltmeter 22, an ammeter 23, and a controller 24. . The high-frequency power source 21 outputs AC power having a frequency equal to a predetermined resonance frequency from the DC power source 40 described above, for example, high-frequency power of about several MHz.

  The capacitor C1 and the primary resonance coil L1 form a resonance circuit that is connected in series and resonates at a predetermined resonance frequency. In the present embodiment, the capacitor C1 and the primary resonance coil L1 are connected in series, but may be connected in parallel.

  The voltmeter 22 is provided between the DC power supply 40 and the high frequency power supply 21, detects a voltage input to the high frequency power supply 21, and transmits the detection result to a controller 24 described later. The ammeter 23 is provided between the DC power supply 40 and the high frequency power supply 21, detects a current input to the high frequency power supply 21, and transmits the detection result to the controller 24.

  The controller 24 includes a microcomputer having a known CPU, ROM, and RAM, and controls the entire power transmission device 20. The controller 24 performs on / off control of the high-frequency power source 21 in accordance with a request for power transmission. Further, the controller 24 obtains transmission power (= voltage × current) supplied to the high-frequency power source 21 from the voltage and current detected by the voltmeter 22 and the ammeter 23. Further, the controller 24 includes a wireless unit (not shown) and is provided so as to be able to wirelessly communicate with a controller 35 of the power receiving device 30 described later. Then, the controller 24 transmits the obtained transmitted power to the controller 35 of the power receiving device 30.

  The power receiving device 30 includes a secondary resonance coil L2, a capacitor C2, a rectifier 31, a DC / DC converter 32, a voltmeter 33, an ammeter 34, and a controller 35. The secondary resonance coil L2 and the capacitor C2 are connected in series with each other to form a resonance circuit that resonates at a predetermined resonance frequency. In the present embodiment, the secondary resonant coil L2 and the capacitor C2 are connected in series, but may be connected in parallel.

  The rectifier 31 converts the high frequency power received by the secondary resonant coil L2 into DC power. The DC / DC converter 32 converts the DC power converted by the rectifier 31 into DC power having a desired voltage and supplies it to the battery 50 mounted on the vehicle. The battery 50 serves as a power source such as a motor mounted on the vehicle.

  As shown in FIG. 2, the DC / DC converter 32 is a general step-up type composed of a switch SW such as a coil L, a diode D, and an FET. The DC / DC converter 32 outputs an output voltage higher than the input voltage by turning on and off the switch SW.

  The voltmeter 33 is provided between the DC / DC converter 32 and the battery 50, detects the input voltage of the battery 50 as the output voltage of the DC / DC converter 32, and transmits the result to the controller 35. Yes. The ammeter 34 is provided between the DC / DC converter 32 and the battery 50, detects the input current of the battery 50 as the output current of the DC / DC converter 32, and transmits the result to the controller 35. doing.

  The controller 35 includes a microcomputer having a known CPU, ROM, and RAM, and controls the entire power receiving device 30. The controller 35 obtains the received power (= voltage × current) supplied to the battery 50 from the voltage and current detected by the voltmeter 33 and the ammeter 34. The controller 35 includes a wireless unit (not shown) and is provided so as to be able to perform wireless communication with a controller 24 of the power transmission device 20 described later. The controller 35 receives transmitted power from the controller 24 of the power transmission device 20.

  Furthermore, the controller 35 calculates | requires the ratio (received power / transmitted power) of the received power with respect to the received transmitted power as system efficiency. As is clear from the above, the voltmeter 22, the ammeter 23, the controller 24, the voltmeter 33, the ammeter 34, and the controller 35 constitute the system efficiency detecting means in the claims.

  In the power supply system 1 described above, when the charging operation of the battery 50 of the parked vehicle is performed in the power supply facility, the controller 35 of the power receiving device 30 transmits a power transmission request to the controller 24 of the power transmission device 20. When receiving the power transmission request, the controller 24 of the power transmission device 20 turns on the high-frequency power source 21 to generate high-frequency power. When this high-frequency power is supplied to the primary resonance coil L1, the primary resonance coil L1 and the secondary resonance coil L2 magnetically resonate, and power is contacted from the primary resonance coil L1 to the secondary resonance coil L2. Is transmitted. The high frequency power received by the secondary resonance coil L2 is converted to DC power by the rectifier 31, converted into voltage by the DC / DC converter 32, and then supplied to the battery 50.

  In the present embodiment, in order to increase the power transmission efficiency, the duty adjustment processing of the DC / DC converter 32 is performed immediately after the power transmission request is made. Specifically, the controller 35 changes the duty of the DC / DC converter 32. The duty of the DC / DC converter 32 is the on-duty of the switch SW. Then, every time the duty is changed, the controller 35 requests the controller 24 of the power transmission device 20 to transmit the transmitted power.

  The controller 24 obtains transmission power from the voltage and current detected by the voltmeter 22 and the ammeter 23 every time a transmission power transmission request is received, and transmits the transmission power to the controller 35 of the power receiving device 30. Further, the controller 35 obtains the system efficiency from the received transmission power and the received power obtained from the voltmeter 33 and the ammeter 34. That is, the controller 35 obtains the system efficiency every time the duty is changed. Then, the duty at which the system efficiency is maximized is obtained, and the DC / DC converter 32 is controlled to the duty at which the obtained system efficiency is maximized. As is clear from the above, the controller 35 constitutes the duty adjustment means in the claims.

  According to the embodiment described above, the duty of the DC / DC converter 32 is adjusted based on the system efficiency. Thereby, electric power can be efficiently supplied to the battery 50.

  The duty adjustment process described above is periodically performed while the battery 50 is being charged. Thereby, even if the charging state of the battery 50 changes, charging efficiency does not fall.

  Next, the inventors of the present invention transmit power, received power, system efficiency, and post-rectification efficiency when the duty of the DC / DC converter 32 is changed (power / power transmission supplied from the rectifier 31 to the DC / DC converter 32). Power) and inter-coil efficiency (coil output power of the secondary resonance coil L2 / coil input power of the primary resonance coil L1) were simulated. The results are shown in FIGS.

  The DC / DC converter 32 is configured not to be output at the timing when the switch SW is turned on. For this reason, if the duty is excessively increased, the output with respect to the input is reduced, and the system efficiency is lowered. In the example shown in FIG. 3, the system efficiency decreases when the duty is 65% or more. On the other hand, as shown in FIGS. 3 and 4, the efficiency after rectification and the inter-coil efficiency are increased even when the duty is 65% or more.

  As is clear from FIGS. 3 and 4, the post-rectification efficiency and inter-coil efficiency do not depend on the system efficiency. For this reason, even if the duty is adjusted by the efficiency after rectification or the inter-coil efficiency, the power cannot be efficiently supplied to the battery 50. However, according to the present embodiment, the duty is adjusted by obtaining the system efficiency itself. Therefore, it was found that power can be efficiently supplied to the battery 50.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. The difference between the first embodiment and the second embodiment is that in the second embodiment, the power transmission device 20 further includes a voltmeter 25 and an ammeter 26, and the power receiving device 30 further includes a voltmeter 36 and an ammeter 37. It is a prepared point.

  The voltmeter 25 is provided between the high frequency power supply 21 and the primary resonance coil L1, detects a voltage output from the high frequency power supply 21 and input to the primary resonance coil L1, and transmits the detection result to the controller 24. doing. The ammeter 26 is provided between the high frequency power supply 21 and the primary resonance coil L1, detects a current output from the high frequency power supply 21 and input to the primary resonance coil L1, and transmits the detection result to the controller 24. doing.

  The voltmeter 36 is provided between the secondary resonance coil L2 and the rectifier 31 and detects the voltage output from the secondary resonance coil L2 and input to the rectifier 31, and transmits the detection result to the controller 35. doing. The ammeter 37 is provided between the secondary resonance coil L2 and the rectifier 31, detects a current output from the secondary resonance coil L2 and input to the rectifier 31, and transmits the detection result to the controller 35. Yes.

  Next, the operation of the power feeding system 1 in the second embodiment having the above-described configuration will be described. In the duty adjustment process described above, the controller 35 changes the duty of the DC / DC converter 32. Then, every time the duty is changed, the controller 35 requests the controller 24 of the power transmission device 20 to transmit coil input power described later.

  Each time the controller 24 receives a coil input power transmission request, the controller 24 obtains the coil input power (= voltage × current) input to the primary resonance coil L1 from the voltage and current detected by the voltmeter 25 and ammeter 26. To the controller 35 of the power receiving device 30. Further, the controller 35 obtains the inter-coil efficiency from the received coil input power and the coil output power output from the secondary resonance coil L2 obtained from the voltmeter 36 and the ammeter 37. That is, in the duty adjustment process, the controller 35 first obtains the inter-coil efficiency each time the duty is changed. Then, a duty that maximizes the inter-coil efficiency is obtained. As apparent from the above, the voltmeter 25, the ammeter 26, the controller 24, the voltmeter 36, the ammeter 37, and the controller 35 constitute the inter-coil efficiency detecting means in the claims.

  Next, the controller 35 adjusts the DC / DC converter 32 so as to maximize the obtained inter-coil efficiency, and changes the duty in a direction that decreases from the adjusted duty. Next, every time the duty is changed, the controller 35 stops the transmission of the coil input power and requests the transmission of the received power.

  The controller 24 obtains transmission power from the voltage and current detected by the voltmeter 22 and the ammeter 23 every time a transmission power transmission request is received, and transmits the transmission power to the controller 35 of the power receiving device 30. Further, the controller 35 obtains the system efficiency from the received transmission power and the received power obtained from the voltmeter 33 and the ammeter 34. That is, the controller 35 obtains the system efficiency every time the duty is changed. Then, the duty at which the system efficiency is maximized is obtained, and the DC / DC converter 32 is controlled to the duty at which the obtained system efficiency is maximized.

  According to the second embodiment described above, the duty search range that maximizes the system efficiency can be reduced.

  In addition, embodiment mentioned above only showed the typical form of this invention, and this invention is not limited to embodiment. That is, various modifications can be made without departing from the scope of the present invention.

1 Power supply system 21 High frequency power supply (AC power supply)
22 Voltmeter (system efficiency detection means)
23 Ammeter (System efficiency detection means)
24 controller (system efficiency detection means, inter-coil efficiency detection means)
25 Voltmeter (Inter-coil efficiency detection means)
26 Ammeter (Inter-coil efficiency detection means)
32 DC / DC converter 33 Voltmeter (system efficiency detection means)
34 Ammeter (system efficiency detection means)
35 controller (system efficiency detection means, inter-coil efficiency detection means duty adjustment means)
36 Voltmeter (Inter-coil efficiency detection means)
37 Ammeter (Inter-coil efficiency detection means)
50 battery (load)
L1 Primary resonance coil L2 Secondary resonance coil

Claims (3)

An AC power source, a primary resonance coil that receives power from the AC power source, a secondary resonance coil that receives power from the primary resonance coil by magnetic field resonance, the secondary resonance coil, and the secondary resonance coil A power supply system including a DC / DC converter provided between loads to which power from a resonance coil is supplied,
System efficiency detecting means for detecting system efficiency which is a ratio of received power supplied to the load with respect to transmitted power supplied to the AC power supply;
Duty adjustment means for adjusting the duty of the DC / DC converter based on the system efficiency detected by the system efficiency detection means;
A power supply system comprising: The duty adjustment means changes the duty of the DC / DC converter to obtain a duty at which the system efficiency detected by the system efficiency detection means is maximized, and adjusts the obtained duty to the duty at which the obtained system efficiency is maximized. The power feeding system according to claim 1. Further comprising inter-coil efficiency detecting means for detecting inter-coil efficiency, which is a ratio of power output from the secondary resonant coil to power input to the primary resonant coil,
The duty adjustment means changes the duty of the DC / DC converter to obtain a duty at which the inter-coil efficiency detected by the inter-coil efficiency detection means is maximized, and the duty at which the obtained inter-coil efficiency is maximized. The duty is made smaller, the duty that maximizes the system efficiency detected by the system efficiency detecting means is obtained, and the duty that makes the obtained system efficiency maximized is adjusted. The power supply system described.

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