JP2016005394A - Non-contact power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a leakage magnetic field emitted in non-contact power transmission, without separately providing a device for cancelling the leakage magnetic field.SOLUTION: A non-contact power supply system comprises operation setting means for performing setting on AC current to be supplied to power transmission coils of n (n is an integer of 2 or more) power supply devices. The setting is performed so that frequencies of the AC current are the substantially same and phases of the AC current are shifted in order by substantially (360/n) degrees when the n power supply devices perform power transmission.

Description

  The present invention relates to a contactless power supply system including a plurality of contactless power supply apparatuses that supply power in a contactless manner.

  2. Description of the Related Art In recent years, contactless power transmission technology that transmits power in a non-contact manner from a power transmission side to a power reception side has attracted attention. For example, a non-contact charging apparatus that uses this non-contact power transmission technology for charging a storage battery mounted on an electric vehicle or the like is being actively developed. In this non-contact charging device, electric power is transmitted from the power transmission side coil to the power reception side coil via the magnetic field generated by the power transmission side coil. In power transmission through such a magnetic field, a part of the magnetic field generated by the coil on the power transmission side becomes a leakage magnetic field, and this leakage magnetic field may adversely affect other electrical devices.

  In addition, with the widespread use of electric vehicles, the expansion of charging stations (charging stations) is also underway. In this charging station, a plurality of charging devices are often installed. Therefore, when a non-contact charging device is used as the charging device, it is more important to reduce the leakage magnetic field. In order to reduce such a leakage magnetic field, Patent Document 1 uses an external antenna (coil) that generates a magnetic field that cancels the leakage magnetic field generated by the feeder line. If this technology is applied, the leakage magnetic field emitted from the coil on the power transmission side can be reduced also in the contactless charging apparatus.

JP 2008-172947 A

  However, when applying the technique of Patent Document 1, a coil (antenna) for generating a magnetic field for canceling the leakage magnetic field must be provided separately. Furthermore, electric power for generating a magnetic field for canceling the leakage magnetic field is required, and power consumption increases. In addition, in a charging station (charging station) in which a plurality of non-contact charging devices are installed, the generated leakage magnetic field increases, so that the electric power for generating the magnetic field for canceling the leakage magnetic field further increases.

  Therefore, the present invention provides a non-contact power feeding system that can reduce a leakage magnetic field emitted during non-contact power transmission without separately providing a coil (antenna) that generates a magnetic field for canceling the leakage magnetic field. For the purpose.

  In order to solve the above-described problem, a contactless power supply system according to the present invention is a contactless power supply system including a plurality of power supply devices that each independently perform contactless power transmission, and includes a plurality of power supply devices. An operation setting unit configured to set an operation, wherein the operation setting unit includes n units (n is an integer of 2 or more) among the plurality of power supply units when the power supply unit performs power transmission. The frequency of the alternating current supplied to the power transmission coil of the power supply apparatus is set to be substantially the same, and the phase of the alternating current supplied to each power transmission coil is set to be shifted by approximately (360 / n) degrees. It is characterized by doing.

  When leakage magnetic fields are generated from the n power supply devices in this way, the phase of the alternating current flowing through the power transmission coils of the n power supply devices is shifted by (360 / n) degrees to thereby reduce the leakage magnetic field as a whole. The strength can be reduced. That is, by setting the phases of the alternating currents in this way, the strength of the combined magnetic field when the leakage magnetic fields generated from the power transmission coils of those power supply devices are combined is weakened. Therefore, the leakage magnetic field emitted during non-contact power transmission can be reduced without separately providing a coil (antenna) that generates a magnetic field for canceling the leakage magnetic field.

  Furthermore, each of the plurality of power supply devices includes a drive circuit that outputs an alternating voltage, and the alternating current supplied to the power transmission coil is an alternating current based on the alternating voltage output from the drive circuit, and the operation The setting means sets the frequency of the AC voltage output from the drive circuit included in the n power supply devices to be substantially the same, and the phase of the AC voltage supplied to each power transmission coil is approximately (360). / N) It is set so as to be shifted by degrees.

  Thus, by shifting the phase of the AC voltage output from the drive circuits of the n power supply devices by (360 / n) degrees, the phase of the AC current flowing through the power transmission coils of the n power supply devices is (360 / n). ) Can be shifted by degrees.

  The phase difference between the AC voltages is adjusted by temporarily providing a difference in the frequency of the AC voltages output from the drive circuits included in the n power supply devices.

  As described above, by temporarily increasing or temporarily decreasing the frequency of the AC voltage output from the drive circuit of some of the n power supply devices, each AC voltage is set. The phase difference between them can be adjusted so as to have a desired relationship.

  According to the non-contact power feeding system according to the present invention, it is possible to reduce the leakage magnetic field emitted during non-contact power transmission without separately providing a coil (antenna) for generating a magnetic field for canceling the leakage magnetic field.

It is the schematic for demonstrating the structure of the non-contact electric power feeding system of this invention. It is the schematic circuit diagram which showed the power transmission coil, the power receiving coil, and these peripheral circuits. It is a wave form diagram for demonstrating the voltage applied to a power transmission coil. It is a wave form diagram which shows the voltage applied to a power transmission coil, and the electric current supplied to a power transmission coil. It is a figure which shows the phase difference of the electric current which flows through a power transmission coil. It is a figure which shows the phase difference of the electric current which flows through a power transmission coil.

  DESCRIPTION OF EMBODIMENTS Embodiments for carrying out the invention will be described with reference to the drawings. Note that the present invention is not limited by the contents described in the following embodiments. In the following description, the same reference numerals are used for the same elements or elements having the same functions, and redundant description is omitted.

  FIG. 1 is a schematic diagram illustrating a configuration of a contactless power feeding system according to the present embodiment. The non-contact power supply system 10 includes a non-contact power supply device 11, 12, 13 and a control device 14 that controls the operation of the non-contact power supply device 11, 12, 13. Each of the non-contact power feeding apparatuses 11, 12, and 13 includes a power transmission coil. Vehicles 21, 22, and 23 that receive power supplied from non-contact power feeding devices 11, 12, and 13 include non-contact power receiving devices 21 a, 22 a, and 23 a, respectively. Each of the non-contact power receiving devices 21a, 22a, and 23a includes a power receiving coil. In this example, power transmission from the non-contact power feeding device 11 to the non-contact power receiving device 21a, power transmission from the non-contact power feeding device 12 to the non-contact power receiving device 22a, and from the non-contact power feeding device 13 to the non-contact power receiving device 23a. Power transmission is performed at the same time. When power transmission is performed, the non-contact power feeding devices 11, 12, and 13 generate a magnetic field by the power transmission coil. This magnetic field generates an electromotive force in the receiving coils of the non-contact power receiving devices 21a, 22a, and 23a. A current based on the electromotive force is supplied to the storage batteries in the vehicles 21, 22 and 23.

  Further, the power transmission coils of the non-contact power feeding devices 11, 12, and 13 are generated in a plane perpendicular to the magnetic field generated in the central portion of the power transmission coil of the non-contact power feeding device 11 and the central portion of the power transmission coil of the non-contact power feeding device 12. The plane perpendicular to the magnetic field to be generated and the plane perpendicular to the magnetic field generated at the center of the power transmission coil of the non-contact power feeding device 12 are installed so as to be substantially parallel. And when the electric current of the same direction is sent through the power transmission coil of non-contact electric power feeder 11, the power transmission coil of non-contact electric power feeder 12, and the power transmission coil of non-contact electric power feeder 13, the magnetic field of the same direction will generate in each power transmission coil It is set to be.

  Next, a drive circuit that supplies an alternating current to the power transmission coil and a power reception circuit that supplies power received by the power reception coil to the storage battery will be described with reference to FIG. Here, the driving circuit is a circuit incorporated in the non-contact power feeding device, and the power receiving circuit is a circuit incorporated in the non-contact power receiving device. The drive circuit is composed of switch elements SW1 to SW4. The switch element SW1 and the switch element SW2 are connected in series, and the input voltage Vin is applied to both ends thereof. Similarly, the switch element SW3 and the switch element SW4 are connected in series, and the input voltage Vin is applied to both ends thereof. One end of the capacitor Ct is connected to one end of the power transmission coil Lt, the other end of the power transmission coil Lt is connected to the connection point of the switch element SW3 and the switch element SW4, and the other end of the capacitor Ct is the switch element SW1 and the switch element SW2. Connected to the connection point. The current Idr flowing through the power transmission coil Lt is controlled by turning on and off the switch elements SW1 to SW4.

  The power receiving circuit includes a bridge diode Dr and a capacitor Co. One end of the receiving coil Lr is connected to one end of the capacitor Cr, the other end of the receiving coil Lr is connected to one input of the bridge diode Dr, and the other end of the capacitor Cr is connected to the other input of the bridge diode Dr. ing. A capacitor Co is connected between the output terminals of the bridge diode Dr. The current flowing through the receiving coil Lr is full-wave rectified by the bridge diode Dr and supplied to the capacitor Co. Note that a load such as a storage battery is connected to the subsequent stage of the capacitor Co via a DCDC converter or the like.

  Next, the switching operation of the switch elements SW1 to SW4 will be described with reference to FIG. In the example shown in FIG. 3, the switch element SW1 and the switch element SW4 are turned on and off in synchronization. Similarly, the switch element SW2 and the switch element SW3 are turned on and off in synchronization. The voltage Vdr between the connection point of the switch element SW1 and the switch element SW2 and the connection point of the switch element SW3 and the switch element SW4 (voltage based on the connection point side of the switch element SW3 and the switch element SW4) is It changes based on on / off of SW1-4. As shown in FIG. 3, when the switch element SW1 and the switch element SW4 are turned on and the switch element SW2 and the switch element SW3 are turned off, the voltage Vdr becomes a positive voltage value whose absolute value is substantially equal to the input voltage Vin. On the other hand, when the switch element SW1 and the switch element SW4 are turned off and the switch element SW2 and the switch element SW3 are turned on, the voltage Vdr becomes a negative voltage value whose absolute value is substantially equal to the input voltage Vin.

  In the example illustrated in FIG. 1, an alternating current having substantially the same frequency is supplied to the power transmission coil included in the contactless power supply device 11, the power transmission coil included in the contactless power supply device 12, and the power transmission coil included in the contactless power supply device 13. Is set to This frequency is set to about 10 kHz to 200 kHz. Moreover, the phase of the alternating current supplied to each power transmission coil included in the non-contact power supply device 11, the non-contact power supply device 12, and the non-contact power supply device 13 is set to be shifted by approximately 120 degrees. That is, the phase of the alternating current Idr2 that flows through the power transmission coil included in the non-contact power feeding device 12 is set to be 120 degrees behind the phase of the alternating current Idr1 that flows through the power transmission coil included in the non-contact power feeding device 11. The phase of the alternating current Idr3 flowing through the power transmission coil included in the non-contact power feeding device 13 is set to be 120 degrees behind the phase of the alternating current Idr2 flowing through the power transmission coil included in the non-contact power feeding device 12. With this setting, the phase of the magnetic field (leakage magnetic field) based on the alternating currents of the alternating current Idr1, the alternating current Idr2, and the alternating current Idr3 is also shifted by approximately 120 degrees. And the intensity | strength of the leakage magnetic field as a whole is weakened by synthesize | combining three leakage magnetic fields with such a phase difference.

  The frequency of the alternating current flowing through the power transmission coils and the phase difference between the alternating currents flowing through the power transmission coils are set based on a signal given from the control device 14. That is, the operation of each non-contact power feeding device is set by the control device 14. However, each non-contact power feeding device is provided with means for setting its own operation without performing operation setting by the control device 14, and each non-contact power feeding device is based on a reference signal or the like given from the outside. You may make it set own operation | movement. For example, the same reference signal is given to each non-contact power feeding device, and the AC current (alternating voltage) supplied to the power transmission coil by each non-contact power feeding device is set based on the reference signal. Good. At this time, each non-contact power supply apparatus performs its own operation setting based on the number of operating non-contact power supply apparatuses and the operation start order.

  Next, an AC voltage and an AC current (AC current supplied to the power transmission coil) output from the drive circuit will be described with reference to FIG. In FIG. 4, an AC voltage Vdr1 is an AC voltage output from the drive circuit of the non-contact power supply device 11, and an AC voltage Vdr2 is an AC voltage output from the drive circuit of the non-contact power supply device 12. Vdr3 is an AC voltage output from the drive circuit of the non-contact power feeding device 13. The alternating current Idr1 is an alternating current flowing through the power transmission coil of the non-contact power feeding device 11, the alternating current Idr2 is an alternating current flowing through the power transmission coil of the non-contact power feeding device 12, and the alternating current Idr3 is non-contact power feeding. It is an alternating current flowing through the power transmission coil of the device 13.

  As shown in FIG. 4, the phases of the AC voltages Vdr1, Vdr2, and Vdr3 output from the drive circuits of the contactless power supply device 11, the contactless power supply device 12, and the contactless power supply device 13 are shifted by 120 degrees. Is set to That is, the phase of AC voltage Vdr2 is set to be 120 degrees behind the phase of AC voltage Vdr1. The phase of AC voltage Vdr3 is set to be 120 degrees behind the phase of AC voltage Vdr2. Since such AC voltages Vdr1, Vdr2, and Vdr3 are applied to the power transmission coils of the non-contact power feeding devices 11, 12, and 13, the AC currents Idr1, Idr2, and Idr3 flowing through the power transmission coils of the non-contact power feeding devices 11, 12, and 13, respectively. Causes a phase difference of 120 degrees. That is, the phase of AC current Idr2 is 120 degrees behind the phase of AC current Idr1, and the phase of AC current Idr3 is 120 degrees behind the phase of AC current Idr2.

FIG. 5 is a vector diagram showing mutual phase differences in the alternating currents Idr1, Idr2, and Idr3. As shown in this figure, the phase difference between the alternating current Idr1 and the alternating current Idr2, the phase difference between the alternating current Idr2 and the alternating current Idr3, and the alternating current Idr3 and the alternating current Idr1 are equal to each other. The phase is set. Here, the leakage magnetic field generated by the power transmission coil supplied with the alternating current Idr1 is H1, the leakage magnetic field generated by the power transmission coil supplied with the alternating current Idr2 is H2, and the leakage generated by the power transmission coil supplied with the alternating current Idr3. When the magnetic field is H3, the leakage magnetic fields H1, H2, and H3 are given by the following equations.
H1 = A · sin (2πft) (1)
H2 = A · sin (2πft + 2π / 3) (2)
H3 = A · sin (2πft + 4π / 3)
= A · sin (2πft-2π / 3) (3)
Here, A is the amplitude, and f is the frequency of the leakage magnetic field (frequency equal to the frequency of the alternating current).

Equations (2) and (3) can be expanded as follows:
H2 = A {sin2πft · cos (2π / 3)
+ Cos2πft · sin (2π / 3)} (4)
H3 = A {sin2πft · cos (2π / 3)
-Cos2πft · sin (2π / 3)} (5)
From these equations, the combined magnetic field by the leakage magnetic field H1, H2, and H3 is given by the following equation.
H1 + H2 + H3 = A · sin (2πft)
+ A {sin2πft · cos (2π / 3)} × 2 (6)
Here, since cos (2π / 3) = − 0.5, H1 + H2 + H3 = 0. As described above, when leakage magnetic fields are generated from the three power transmission coils (when three non-contact power feeding devices are operating simultaneously), the phase of the alternating current flowing through the power transmission coils is set to 120 (360/3). ) The intensity of the leakage magnetic field as a whole can be reduced by shifting each degree.

  As shown in FIG. 6, when a leakage magnetic field is generated from four power transmission coils (when four non-contact power feeding devices are operating simultaneously), the phase of the alternating current flowing through the power transmission coils is set to 90. By shifting by (360/4) degrees, the strength of the leakage magnetic field as a whole can be reduced.

  That is, in the non-contact power feeding system of the present invention, when n (an integer of 2 or more) non-contact power feeding devices are operating simultaneously, the power transmission coils of these non-contact power feeding devices are (360 / n) degrees each. By supplying an alternating current whose phase is shifted, the strength of the leakage magnetic field as a whole is reduced. That is, since the phase of the magnetic field (leakage magnetic field) based on these alternating currents is also shifted by approximately (360 / n) degrees, the strength of the overall leakage magnetic field, which is a combined magnetic field of these leakage magnetic fields, is weakened. Of the non-contact power supply devices included in the non-contact power supply system, at least the non-contact power supply device in which an alternating current is supplied to the power transmission coil only needs to satisfy the condition regarding this phase.

  In addition, a difference arises in the amplitude A and phase of a leakage magnetic field by the difference in distance from each power transmission coil. However, the phase shift caused by the difference in distance can be ignored when the frequency is set to about 10 kHz to 200 kHz. That is, since the wavelength of the leakage magnetic field generated when the frequency is 10 kHz to 200 kHz is about 30 km to 1.5 km, the difference in distance from the power transmission coil is very small compared to the wavelength of the leakage magnetic field.

Next, a phase shift that occurs based on the difference in distance will be described. The wave Hd of the leakage magnetic field at a location away from the power transmission coil by the distance D is given by
Hd = A · sin (2πft−2πD / λ) (7)
Here, A is the amplitude, f is the frequency of the leakage magnetic field, D is the distance from the power transmission coil, and λ is the wavelength of the leakage magnetic field. Here, the amplitude A is a variable that changes based on the distance D, and includes a component that is inversely proportional to the cube of the distance D and a component that is inversely proportional to the square of the distance D. Further, the equation (1) can be expanded as the following equation.
Hd = A {sin 2πft · cos (2πD / λ)
-Cos2πft · sin (2πD / λ)} (8)
Here, when the frequency f of the leakage magnetic field is 200 kHz (the leakage magnetic field wavelength λ is 1500 m) and the distance D from the power transmission coil is 100 m, cos (2πD / λ) ≈1 and sin (2πD / λ) ≈ It can be set to zero. Therefore, if the wavelength λ of the leakage magnetic field is sufficiently larger than the distance D from the power transmission coil in this way, the following approximate expression can be used for the wave Hd of the leakage magnetic field.
Hd≈A · sin2πft (9)
Thus, when the frequency is 10 kHz to 200 kHz, the phase shift caused by the difference in distance can be ignored.

  Next, a method for adjusting the phase of the alternating current supplied to the power transmission coil of the non-contact power feeding device will be described. For example, there will be described a case where there are four non-contact power supply apparatuses, and three of them are in operation and the four are in operation.

  When three non-contact power feeding devices are operating, the alternating current supplied to them has a phase of 120 (360/3) as in the alternating currents Idr1, Idr2, and Idr3 shown in FIG. It is shifted by degrees. When three non-contact power supply devices are operating in this manner and when another non-contact power supply device is further operated, the phase of the power transmission coil of the non-contact power supply device is 270 degrees from the alternating current Idr1. The delayed alternating current Idr4 is supplied. Further, the phase of the alternating current Idr2 is changed from a state delayed by 120 degrees from the alternating current Idr1 to a state delayed by 90 degrees, and the phase of the alternating current Idr3 is a state delayed by 180 degrees from the state delayed by 240 degrees from the alternating current Idr1. Changed to In this change, the frequency of the alternating currents Idr2 and Idr3 is temporarily increased (that is, the period is temporarily shortened), and the phase difference is decreased. When the phase difference between the alternating current Idr2 and the alternating current Idr1 reaches 90 degrees, the frequency of the alternating current Idr2 is maintained at the same frequency as the frequency of the alternating current Idr1. Similarly, when the phase difference between AC current Idr3 and AC current Idr1 reaches 180 degrees, the frequency of AC current Idr3 is maintained at the same frequency as the frequency of AC current Idr1. In this way, the alternating currents Idr1, Idr2, Idr3, Idr4 are set to phases shifted by 90 (360/4) degrees as shown in FIG.

  Next, a case will be described in which a transition is made from a state where four units are operating to a state where three units are operating. When the four contactless power supply devices are operating, the alternating current supplied to them has a phase of 90 (360/360) as in the alternating currents Idr1, Idr2, Idr3, Idr4 shown in FIG. 4) It is shifted by degrees. When the non-contact power feeding device to which the alternating current Idr4 is supplied is stopped among the four non-contact power feeding devices, the phase of the alternating current Idr2 is 120 degrees behind the state 90 degrees behind the alternating current Idr1 The phase of the alternating current Idr3 is changed from a state delayed by 180 degrees from the alternating current Idr1 to a state delayed by 240 degrees. In this change, the frequency of the alternating currents Idr2 and Idr3 is temporarily reduced (that is, the period is temporarily increased), and the phase difference is increased. When the phase difference between the alternating current Idr2 and the alternating current Idr1 reaches 120 degrees, the frequency of the alternating current Idr2 is maintained at the same frequency as the frequency of the alternating current Idr1. Similarly, when the phase difference between AC current Idr3 and AC current Idr1 reaches 240 degrees, the frequency of AC current Idr3 is maintained at the same frequency as the frequency of AC current Idr1. In this way, the alternating currents Idr1, Idr2, and Idr3 are set to phases shifted by 120 (360/3) degrees as shown in FIG.

  In addition, what is necessary is just to change the frequency of the alternating voltage output from a drive circuit, when changing the frequency of the alternating current supplied to the power transmission coil of a non-contact electric power feeder. That is, when adjusting the phase difference of each AC current, the frequency of the AC voltage output from the drive circuit is temporarily changed, and when the desired phase difference is reached, the frequency of the AC voltage is set to a predetermined value. What is necessary is just to return to a frequency (original frequency).

  As mentioned above, although embodiment of the non-contact electric power feeding system concerning this invention was described, this invention is not limited to embodiment described above, In the range which does not deviate from the summary, various changes are added. be able to. Further, regarding the circuit configuration, structure, control method, and the like of the power transmission coil and drive circuit and the control device that constitute the non-contact power feeding device, various circuit configurations, structures, control methods, etc. that can be easily assumed by those skilled in the art may be used. it can. For example, as the power transmission coil, a spiral-shaped or solenoid-shaped coil, a coil that combines these coils, or a coil that combines these with other-shaped coils or capacitors can be used. Also for the drive circuit, a circuit configuration other than the full bridge configuration as shown in FIG. 2, for example, a half bridge configuration may be used. Further, a circuit for improving the power factor and a circuit for adjusting impedance may be added before the drive circuit or between the drive circuit and the power transmission coil.

  As described above, the contactless power supply system according to the present invention is configured so that when the leakage magnetic fields generated from n (an integer greater than or equal to 2) contactless power supply devices are combined, the strength of the combined magnetic field is reduced. Various modifications and applications can be made without departing from the gist that the phase of the alternating current supplied to the non-contact power feeding apparatus is shifted by 360 / n.

  DESCRIPTION OF SYMBOLS 10 ... Non-contact electric power feeding system, 11, 12, 13 ... Non-contact electric power feeder, 14 ... Control apparatus, 21, 22, 23 ... Vehicle, 21a, 22a, 23a ... Non-contact electric power receiving apparatus.

Claims (3)

A non-contact power feeding system including a plurality of power feeding devices each independently performing non-contact power transmission,
Comprising an operation setting means for setting operations of the plurality of power supply devices;
The operation setting means includes an alternating current supplied to power transmission coils of the n power supply devices when n (n is an integer of 2 or more) power supply devices among the plurality of power supply devices perform power transmission. A non-contact power feeding system, wherein the current frequency is set to be substantially the same, and the phase of the alternating current supplied to each power transmission coil is set to be shifted by approximately (360 / n) degrees. Each of the plurality of power supply devices includes a drive circuit that outputs an alternating voltage,
The alternating current supplied to the power transmission coil is an alternating current based on an alternating voltage output from the drive circuit,
The operation setting means sets the frequency of the AC voltage output from the drive circuit included in the n power supply devices to be substantially the same, and the phase of the AC voltage supplied to each power transmission coil is substantially the same. The non-contact power feeding system according to claim 1, wherein the non-contact power feeding system is set to be shifted by (360 / n) degrees.   The phase difference between the AC voltages is adjusted by temporarily providing a difference in the frequency of the AC voltages output from the drive circuits included in the n power supply devices. The non-contact electric power feeding system of 2.

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