JP5454590B2 - Resonance frequency control method, power transmission device, and power reception device in magnetic resonance power transmission system - Google Patents

Description

  The present invention relates to a resonance frequency control method, a power transmission device, and a power reception device in a magnetic field resonance type power transmission system.

In so-called wireless power transmission or wireless power supply (WPS) in which power is transmitted wirelessly, power (energy) is transmitted and received without using a cable between two spatially separated points. There are two types of wireless power transmission: a method using electromagnetic induction and a method using radio waves. In addition, a method using magnetic field resonance (also referred to as magnetic field resonance, magnetic resonance, or magnetic field resonance mode) has been proposed (Patent Document 1).
Republished WO 98/34319

  An object of the present invention is to make it possible to adjust the resonance frequency of a coil at high speed and accurately in real time in a magnetic field resonance type power transmission system.

  A magnetic resonance power transmission system to which the present invention is applied will be described.

  The method using magnetic field resonance (magnetic field resonance type) can transmit higher power than the method using radio waves, and the transmission distance can be longer than that of electromagnetic induction method. There is an advantage that can be reduced.

  In the method using magnetic field resonance, energy transmission can be performed with high efficiency by setting the resonance frequencies of the power transmission coil and the power reception coil to the same value and performing power transmission at frequencies in the vicinity thereof. It becomes possible.

  In order to increase the efficiency of power transmission in a magnetic field resonance type power transmission system, there is one in which a higher frequency than the frequency of the oscillation signal on the primary coil side is used as the resonance frequency on the secondary coil side (Patent Document 1). According to this, the capacitance can be reduced and the coupling coefficient between the primary coil and the secondary coil can be increased apparently.

  By increasing the degree of coupling between the coils, the efficiency of power transmission can be increased to some extent.

  In order to increase the efficiency of power transmission, it is conceivable to make the resonance peak of each coil as sharp as possible. For this purpose, for example, the Q value of each coil may be designed to be high.

  However, when the Q value is increased, the sensitivity to the deviation of the resonance frequency of both coils is increased, that is, the influence on the reduction of the power transmission efficiency due to the deviation of the resonance frequency of both coils is increased. There is a problem of end.

  For example, the resonance frequency of the coil changes due to changes in environmental factors such as temperature, changes in inductance and capacitance due to the approach of a conductor such as a person or metal, or a magnetic body. There is also a shift in the resonance frequency due to variations in manufacturing.

  Therefore, in the magnetic field resonance type power transmission system having a high Q value, a mechanism for adjusting the resonance frequency of the coil in response to an environmental change or the like is required in order to take advantage of the maximum merit.

  In order to adjust the resonance frequency of the coil to the target frequency, it is necessary to adjust L (inductance) of the coil or C (capacitance) of the capacitor.

  According to one aspect of the method described herein, in a resonance frequency control method in a magnetic field resonance type power transmission system that transmits electric power from a power transmission system coil to a power reception system coil by using magnetic field resonance, a voltage supplied to the power transmission system coil. And the phase of the current flowing in the power transmission coil or the power reception coil are detected, and the resonance frequency of the power transmission coil or the power reception coil is varied so that the phase difference thereof becomes a target value.

  When the degree of coupling between the power transmission coil and the power reception coil increases and a bimodal characteristic appears, a current peak appears at the frequency of the AC power supply. It is also possible to vary the resonance frequency.

  Further, in one form of device described herein, in a magnetic field resonance type power transmission system that transmits power from a power transmission system coil to a power reception system coil using magnetic field resonance, the phase of the voltage supplied to the power transmission system coil and A phase detector that detects a phase of a current flowing through the power transmission coil or the power reception coil, and resonance of the power transmission coil or the power reception coil so that a phase difference between the detected phases becomes a target value. A resonance frequency control unit that varies the frequency.

It is a figure which shows the magnetic field resonance type electric power transmission method. It is a figure which shows the outline | summary of a magnetic field resonance type electric power transmission system. It is a figure which shows the example of a structure of the control part of the electric power transmission system of this embodiment. It is a figure which shows the state of the electric current and phase in resonance frequency control. It is a figure which shows the state of the electric current and phase in resonance frequency control. It is a figure which shows the state of an electric current and a phase when a bimodal characteristic appears. It is a figure which shows the state of the electric current and phase in resonance frequency control when a bimodal characteristic appears. It is a figure which shows the example of the change of the transmission power at the time of performing the resonant frequency control corresponding to a bimodal characteristic. It is a figure which shows the frequency dependence of an electric power transmission system. It is a figure explaining the method of sweeping the resonant frequency of a coil. It is a figure which shows the example of the structure which switches resonance frequency control and bimodal resonance control. It is a flowchart which shows the rough process sequence of resonance frequency control. It is a flowchart which shows the rough process sequence of resonance frequency control.

  In the power transmission system (power transmission device) 1 of the embodiment described below, based on the phase difference Δφ between the voltage of the AC power supply (drive voltage) and the current flowing through the coil, L or C of the coil (resonance circuit) Real-time resonance frequency control.

  In addition, when the coupling between the power transmission coil and the power reception coil is increased and a bimodal characteristic (split) appears, a peak (split peak) appears at the frequency of the AC power supply in order to suppress a decrease in power transmission efficiency. As described above, the resonance frequency of the power transmission coil or the power reception coil is shifted. In order to distinguish the resonance frequency control in this case from the resonance frequency control in the case where the bimodal characteristic does not appear, it may be referred to as “bimodal resonance control”.

  Further, the resonance frequency control in the case of not including “bimodal resonance control” may be described as “normal resonance frequency control”. When simply “resonance frequency control” is described, “bimodal resonance control” is included in principle.

  1 and 2, the power transmission system 1 includes a power transmission coil SC, a power reception coil JC, an AC power supply 11, a power transmission side control unit 14, a device 21 serving as a load, and a power reception side control unit 24.

  In FIG. 2, the power transmission coil SC includes a power supply coil 12 and a power transmission resonance coil 13. The power supply coil 12 is formed by winding a metal wire such as a copper wire or an aluminum wire a plurality of times around a circumference, and an AC voltage (high-frequency voltage) from the AC power source 11 is applied to both ends thereof.

  The power transmission resonance coil 13 includes a coil 131 in which a metal wire such as a copper wire or an aluminum wire is wound circumferentially, and a capacitor 132 connected to both ends of the coil 131, thereby forming a resonance circuit. The resonance frequency f0 is expressed by the following equation (1).

なお、Ｌはコイル１３１のインダクタンス、Ｃはコンデンサ１３２の静電容量である。

Note that L is the inductance of the coil 131, and C is the capacitance of the capacitor 132.

  The coil 131 of the power transmission resonance coil 13 is, for example, a one-turn coil. Although various types of capacitors are used as the capacitor 132, those having as little loss as possible and having a sufficient breakdown voltage are preferable. In the present embodiment, a variable capacitor is used as the capacitor 132 in order to vary the resonance frequency. As the variable capacitor, for example, a variable capacitance device manufactured using MEMS technology is used. A variable capacitance device (varactor) using a semiconductor may be used.

  The power supply coil 12 and the power transmission resonance coil 13 are arranged so as to be electromagnetically closely coupled to each other. For example, they are arranged on the same plane and concentrically. That is, for example, the power supply coil 12 is arranged in a state of being fitted on the inner peripheral side of the power transmission resonance coil 13. Or you may arrange | position with an appropriate distance on the same axis | shaft.

  In this state, when an AC voltage is supplied from the AC power supply 11 to the power supply coil 12, a resonance current flows through the power transmission resonance coil 13 by electromagnetic induction caused by an alternating magnetic field generated in the power supply coil 12. That is, electric power is supplied from the power supply coil 12 to the power transmission resonance coil 13 by electromagnetic induction.

  The power receiving system coil JC includes a power receiving resonance coil 22 and a power extraction coil 23. The power receiving resonance coil 22 includes a coil 221 around which a metal wire such as a copper wire or an aluminum wire is wound, and a capacitor 222 connected to both ends of the coil 221. The resonance frequency f0 of the power receiving resonance coil 22 is expressed by the above equation (1) based on the inductance of the coil 221 and the capacitance of the capacitor 222.

  The coil 221 of the power receiving resonance coil 22 is, for example, a one-turn coil. As the capacitor 222, various types of capacitors are used as described above. In the present embodiment, a variable capacitor is used as the capacitor 222 in order to vary the resonance frequency. As the variable capacitor, for example, a variable capacitance device manufactured using MEMS technology is used. A variable capacitance device (varactor) using a semiconductor may be used.

  The power extraction coil 23 is formed by winding a metal wire such as a copper wire or an aluminum wire a plurality of times in a circumferential shape, and a device 21 as a load is connected to both ends thereof.

  The power receiving resonance coil 22 and the power extraction coil 23 are disposed so as to be electromagnetically closely coupled to each other. For example, they are arranged on the same plane and concentrically. That is, for example, the power extraction coil 23 is disposed in the inner peripheral side of the power reception resonance coil 22. Or you may arrange | position with an appropriate distance on the same axis | shaft.

  In this state, when a resonance current flows through the power receiving resonance coil 22, a current flows through the power extraction coil 23 by electromagnetic induction caused by the alternating magnetic field generated thereby. That is, electric power is transmitted from the power receiving resonance coil 22 to the power extraction coil 23 by electromagnetic induction.

  Since the power transmission coil SC and the power reception coil JC transmit power wirelessly by magnetic field resonance, are the coil surfaces parallel to each other and the coil axes coincide with each other as shown in FIG. Alternatively, they are arranged within an appropriate distance from each other so as not to deviate so much. For example, when the diameters of the power transmission resonance coil 13 and the power reception resonance coil 22 are about 100 mm, they are arranged within a distance range of about several hundred mm.

  In the power transmission system 1 shown in FIG. 2, the direction along the coil axis KS is the main radiation direction of the magnetic field KK, and the direction from the power transmission system coil SC to the power reception system coil JC is the power transmission direction SH.

  Here, when the resonance frequency fs of the power transmission resonance coil 13 and the resonance frequency fj of the power reception resonance coil 22 both coincide with the frequency fd of the AC power supply 11, the maximum power is transmitted. However, if the resonance frequencies fs and fj are deviated from each other or they are deviated from the frequency fd of the AC power supply 11, the transmitted power is lowered and the efficiency is lowered.

  That is, in FIG. 9, the horizontal axis represents the frequency fd [MHz] of the AC power supply 11, and the vertical axis represents the magnitude of the transmitted power [dB]. A curve CV1 indicates a case where the resonance frequency fs of the power transmission resonance coil 13 and the resonance frequency fj of the power reception resonance coil 22 match. In this case, according to FIG. 9, the resonance frequencies fs and fj are 13.56 MHz.

  Curves CV2 and CV3 indicate cases where the resonance frequency fj of the power reception resonance coil 22 is higher by 5% and 10% than the resonance frequency fs of the power transmission resonance coil 13, respectively.

  In FIG. 9, when the frequency fd of the AC power supply 11 is 13.56 MHz, the highest power is transmitted in the curve CV1, but sequentially decreases in the curves CV2 and CV3. Further, when the frequency fd of the AC power supply 11 is shifted from 13.56 MHz, the power transmitted in any of the curves CV1 to CV3 is reduced except when it is slightly shifted upward.

  Therefore, it is necessary to make the resonance frequencies fs and fj of the power transmission resonance coil 13 and the power reception resonance coil 22 coincide with the frequency fd of the AC power supply 11 as much as possible.

  In FIG. 10, the horizontal axis represents the frequency [MHz], and the vertical axis represents the magnitude [dB] of the current flowing through the coil. A curve CV4 shows a case where the resonance frequency of the coil matches the frequency fd of the AC power supply 11. In this case, according to FIG. 10, the resonance frequency is 10 MHz.

  Curves CV5 and CV6 indicate the case where the resonance frequency of the coil is higher or lower than the frequency fd of the AC power supply 11.

  In FIG. 10, the maximum current flows in the curve CV4, but the current decreases in both the curves CV5 and CV6. In addition, when the Q value of the coil is high, the influence on the decrease of the current or the transmission power due to the deviation of the resonance frequency is large.

  Therefore, in the power transmission system 1 of the present embodiment, the power transmission side control unit 14 and the power reception side control unit 24 set the phase φvs of the AC power supply 11 and the phases φis and φij of the current flowing through the power transmission resonance coil 13 and the power reception resonance coil 22. To perform resonance frequency control.

  Here, the power transmission side control unit 14 detects the phase φvs of the voltage Vs supplied to the power transmission system coil SC and the phase φis of the current Is flowing through the power transmission system coil SC, and the phase difference Δφs is a predetermined target value φms. Thus, the resonance frequency fs of the power transmission coil SC is varied.

  That is, the power transmission side control unit 14 includes a current detection sensor SE1, phase detection units 141 and 142, a target value setting unit 143, a feedback control unit 144, and a phase transmission unit 145.

  The current detection sensor SE <b> 1 detects the current Is flowing through the power transmission resonance coil 13. As the current detection sensor SE1, a Hall element, a magnetoresistive element, a detection coil, or the like can be used. The current detection sensor SE1 outputs a voltage signal corresponding to the waveform of the current Is, for example.

  The phase detector 141 detects the phase φvs of the voltage Vs supplied to the power supply coil 12. For example, the phase detection unit 141 outputs a voltage signal corresponding to the waveform of the voltage Vs. In this case, the voltage Vs may be output as it is, or may be divided and output by an appropriate resistor. Therefore, the phase detection unit 141 can be configured by a simple electric wire or by one or a plurality of resistors.

  The phase detector 142 detects the phase φis of the current Is flowing through the power transmission resonance coil 13 based on the output from the current detection sensor SE1. For example, the phase detection unit 142 outputs a voltage signal corresponding to the waveform of the current Is. In this case, the phase detection unit 142 may output the output of the current detection sensor SE1 as it is. Therefore, the current detection sensor SE1 can also serve as the phase detection unit 142.

  Target value setting unit 143 sets and stores target value φms of phase difference Δφs. Therefore, the target value setting unit 143 is provided with a memory for storing the target value φms. As the target value φms, as described later, for example, “−π” or “a value obtained by adding an appropriate correction value a to −π” or the like is set.

  The target value φms may be set by selecting from one or a plurality of data stored in advance, or may be performed by a command from a CPU or a keyboard.

  The feedback control unit 144 resonates the power transmission resonance coil 13 so that the phase difference Δφs between the phase φvs of the voltage Vs of the AC power supply 11 and the phase φis of the current Is of the power transmission resonance coil 13 becomes the set target value φms. The frequency fs is varied.

  The phase transmission unit 145 transmits information about the phase φvs of the voltage Vs supplied to the power supply coil 12 to the power receiving side control unit 24, for example, wirelessly. For example, the phase transmission unit 145 transmits a voltage signal corresponding to the waveform of the voltage Vs as an analog signal or a digital signal. In that case, in order to improve the S / N ratio, a voltage signal corresponding to the waveform of the voltage Vs may be multiplied by an integral multiple and transmitted.

  The power receiving side control unit 24 detects the phase φvs of the voltage VS supplied to the power transmission coil SC and the phase φij of the current IJ flowing through the power receiving coil JC so that the phase difference Δφj becomes a predetermined target value φmj. In addition, the resonance frequency fj of the power receiving coil JC is varied.

  That is, the power reception side control unit 24 includes a current detection sensor SE2, a phase reception unit 241, a phase detection unit 242, a target value setting unit 243, and a feedback control unit 244.

  The current detection sensor SE2 detects a current Ij flowing through the power receiving resonance coil 22. As the current detection sensor SE2, a Hall element, a magnetoresistive element, a detection coil, or the like can be used. The current detection sensor SE2 outputs a voltage signal corresponding to the waveform of the current Ij, for example.

  The phase receiver 241 receives information about the phase φvs transmitted from the phase transmitter 145 and outputs the information. When the voltage signal is multiplied by the phase transmission unit 145, the phase reception unit 241 performs frequency division to restore the original. For example, the phase receiving unit 241 outputs a voltage signal corresponding to the voltage Vs.

  The phase detector 242 detects the phase φij of the current Ij flowing through the power receiving resonance coil 22 based on the output from the current detection sensor SE2. For example, the phase detection unit 242 outputs a voltage signal corresponding to the waveform of the current Ij. In this case, the phase detection unit 242 may output the output of the current detection sensor SE2 as it is. Therefore, the current detection sensor SE2 can also serve as the phase detection unit 242.

  The target value setting unit 243 sets and stores a target value φmj for the phase difference Δφj. As described later, for example, a value obtained by adding “−π / 2” to the target value φms in the power transmission side control unit 14 is set as the target value φmj. That is, “−3π / 2” is set as the target value φmj. Alternatively, a value obtained by adding an appropriate correction value b thereto is set. The method for setting the target value φmj is the same as that for the target value φms.

  The feedback control unit 244 resonates the power receiving resonance coil 22 so that the phase difference Δφj between the phase φvs of the voltage Vs of the AC power supply 11 and the phase φij of the current Ij of the power receiving resonance coil 22 becomes the set target value φmj. The frequency fj is varied.

  The target value setting unit 143 and the feedback control unit 144 in the power transmission side control unit 14, and the target value setting unit 243 and the feedback control unit 244 in the power reception side control unit 24 are examples of resonance frequency control units, respectively.

  This will be described in more detail with reference to FIG. In FIG. 3, elements having the same functions as those shown in FIG. 2 may be denoted by the same reference numerals and description thereof may be omitted or simplified.

  In FIG. 3, a power transmission system (power transmission device) 1 </ b> B includes a power transmission device 3 and a power reception device 4.

  The power transmission device 3 includes an AC power supply 11, a power supply coil 12 including a power supply coil 12 and a power transmission resonance coil 13, a resonance frequency control unit CTs, and the like.

  The power receiving device 4 includes a power receiving system coil JC including a power receiving resonance coil 22 and a power extraction coil 23, a resonance frequency control unit CTj, and the like.

  The resonance frequency control unit CTs on the power transmission side includes a target value setting unit 143, a phase comparison unit 151, an addition unit 152, gain adjustment units 153 and 154, a compensation unit 155, a driver 156, and the like.

  The phase comparison unit 151 compares the phase φis of the current Is detected by the current detection sensor SE1 with the phase φvs of the voltage Vs of the AC power supply 11, and outputs a phase difference Δφs that is the difference between them.

  The adder 152 adds the phase difference Δφs output from the phase comparator 151 and the target value φms set in the target value setting unit 143. In the present embodiment, the target value φms is set so that the sign is reversed with respect to the target phase difference Δφs. Therefore, when the absolute value of the phase difference Δφs matches the target value φms, the adding unit The output of 152 is zero.

  The gain adjusting units 153 and 154 adjust the gain (gain) for each input value or data, or perform conversion of data or the like so that the control is correctly performed.

  The compensation unit 155 determines a gain for the low frequency component, for example. It can be considered that the resonance frequency control unit CTs of this embodiment constitutes a servo system that performs feedback control on the MEMS variable capacitance device that is the capacitor 132. Therefore, an appropriate servo filter is used for the compensation unit 155 in order to stabilize, increase the speed and increase the accuracy of the servo system. Further, a filter circuit or a differential integration circuit for performing the PID operation in such a servo system is used as necessary.

  The driver 156 drives the MEMS variable capacitance device, which is the capacitor 132, and outputs drive KSs to the capacitor 132 in order to variably control the capacitance.

  In a MEMS variable capacitance device (MEMS variable capacitor), for example, a lower electrode and an upper electrode are provided on a glass substrate, and an interval between them is changed by bending due to an electrostatic attraction force due to a voltage applied between them. The capacitance of is variable. An electrode for a capacitor and an electrode for driving may be provided separately. Since the relationship between the voltage applied to the electrodes for driving and the amount of change in capacitance is not linear, the driver 156 performs calculations for conversion or table conversion as necessary.

  The power-reception-side resonance frequency control unit CTj includes a target value setting unit 243, a phase comparison unit 251, an addition unit 252, gain adjustment units 253 and 254, a compensation unit 255, a driver 256, and the like. The configuration and operation of each unit of the power receiving side resonance frequency control unit CTj are the same as the configuration and operation of each unit of the power transmission side resonance frequency control unit CTs described above.

  The power transmission side control unit 14, the power reception side control unit 24, the resonance frequency control units CTs, CTj, etc. in the power transmission systems 1 and 1B can be realized by software or hardware, or a combination thereof. is there. For example, a computer including a CPU, a memory such as a ROM and a RAM, and other peripheral elements may be used to cause the CPU to execute an appropriate computer program. In that case, an appropriate hardware circuit may be used in combination.

  Next, the operation of the resonance frequency control in the power transmission system 1B will be described with reference to FIGS.

  4 to 7, in each figure (A), the horizontal axis represents the frequency f [MHz] of the AC power supply 11, and the vertical axis represents the magnitude [dB] of the current I flowing through each coil. In each figure (B), the horizontal axis represents the frequency f [MHz] of the AC power supply 11, and the vertical axis represents the phase φ [radian] of the current I flowing through each coil. In each of FIGS. 4-7, the figure (A) and the figure (B) respond | correspond.

  The phase φ indicates the phase difference Δφ with reference to the phase φvs of the voltage Vs of the AC power supply 11, that is, the phase φvs of the voltage Vs supplied to the power supply coil 12. That is, the phase φ becomes 0 when it coincides with the phase φvs.

  The symbols CAA1-4, CAB1-4, CBA1-4, CBB1-4, CCA1-4, CCB1-4, CDA1-4, CDB1-4 attached to each curve, These correspond to the power supply coil 12, the power transmission resonance coil 13, the power reception resonance coil 22, and the power extraction coil 23, respectively.

  In the resonance frequency control, the power transmission resonance coil 13 or the power transmission resonance coil 13 and the power reception resonance coil 22 are controlled so that the resonance frequencies fs and fj thereof are 10 MHz.

  4 to 7 show the results of a computer simulation under such conditions.

  FIG. 4 shows a case where the resonance frequency control is performed only by either the power transmission side control unit 14 or the power transmission device 3, and FIG. 5 shows the power transmission side control unit 14 or the power transmission device 3 and the power reception side control unit 24 or the power reception device 4. The case where resonance frequency control is performed by both is shown.

  In FIG. 4, the resonance frequency control is performed on the power transmission resonance coil 13 so that the resonance frequency fs is 10 MHz. In this case, the frequency fd of the AC power supply 11 is set to 10 MHz, and the target value setting unit 143 sets “−π” as the target value φms.

  As indicated by the curve CAA2, the current Is of the power transmission resonance coil 13 is maximum at 10 MHz that matches the frequency fd of the AC power supply 11.

  As shown by the curve CAB2, the phase φis of the current Is of the power transmission resonance coil 13 is −π at 10 MHz which is the resonance frequency fs. That is, it matches the target value φms.

  Further, the power transmission resonance coil 13 can be viewed as a series resonance circuit when viewed from the power supply coil 12. Therefore, it becomes capacitive at a frequency fd lower than the resonance frequency fs and approaches -π / 2, and becomes inductive at a high frequency fd and approaches -3π / 2.

  Thus, the phase φis of the current Is flowing through the power transmission resonance coil 13 changes greatly in the vicinity of the resonance frequency fs. By controlling the phase φis, that is, the phase difference Δφs to be −π, the resonance frequency fs of the power transmission resonance coil 13 can be matched with the frequency fd of the voltage Vs with high accuracy.

  As indicated by the curve CAA1, the current I flowing through the power supply coil 12 is also maximum at the resonance frequency fs. As shown by the curve CAB1, the phase φi of the current I flowing through the power supply coil 12 becomes 0 or a leading phase in the vicinity of the resonance frequency fs, and becomes −π / 2 when it deviates from the resonance frequency fs.

  In FIG. 5, the resonance frequency control is performed on the power transmission resonance coil 13 and the power reception resonance coil 22 so that the resonance frequencies fs and fj are 10 MHz. In this case, the target value setting units 143 and 243 set “−π” as the target value φms and “−3π / 2” as the target value φmj.

  That is, the target value φmj is set to a value “φms−π / 2” obtained by adding −π / 2 to the target value φms, that is, a phase delayed by π / 2 from the target value φms.

  The curve CBA2 and the curve CBB2 are substantially the same as the curve CAA2 and the curve CAB2 in FIG.

  As indicated by the curve CBA3, the current Ij of the power receiving resonance coil 22 is maximum at 10 MHz that matches the frequency fd of the AC power supply 11.

  As indicated by the curve CBB3, the phase φij of the current Ij of the power receiving resonance coil 22 is −3π / 2 at 10 MHz which is the resonance frequency fs. That is, it matches the target value φmj. Further, when the frequency fd becomes lower than the resonance frequency fs, the phase difference Δφ decreases to approach −π / 2, and when the frequency fd becomes higher than the resonance frequency fs, the phase difference Δφ increases to −5π. / 2, that is, approaches -π / 2.

  Thus, the phases φis and φij of the currents Is and Ij flowing through the power transmission resonance coil 13 and the power reception resonance coil 22 change greatly in the vicinity of the resonance frequencies fs and fj. By controlling the phases φis and φij, that is, the phase differences Δφs and Δφj to be −π or −3π / 2, the resonance frequencies fs and fj of the power transmission resonance coil 13 and the power reception resonance coil 22 are increased to the frequency fd of the voltage Vs. Can be matched with accuracy.

  Thus, according to the power transmission systems 1 and 1B of the present embodiment, the resonance frequencies of the power transmission coil SC and the power reception coil JC can be controlled at high speed and accurately in real time.

  As a result, the resonance frequency of the power transmission coil SC and the power reception coil JC can be exactly matched to the frequency fd of the AC power supply 11, and the maximum power can always be transmitted from the power transmission device 3 to the power reception device 4. It is.

  Therefore, even if there are changes in environmental factors, the maximum power can always be transmitted, and energy can be transmitted with high efficiency.

  Further, according to the resonance frequency control method of the present embodiment, control is performed based on the phase difference Δφ of the coil current with respect to the voltage Vs of the AC power supply, so that it is affected by fluctuations in current amplitude as in the case of the sweep search method. And accurate control is possible.

  In the sweep search method, for example, L or C in the power transmission coil SC or the power reception coil JC is swept, and the position where the coil current value is maximum (peak) is searched by trial and error.

However, in the case of such a sweep search method, the following problem can be considered. That is,
(1) Since the current value of the coil always varies depending on the use state, a false detection occurs due to the variation (amplitude variation) of the coil current value, and it is not easy to perform accurate adjustment.
(2) A reciprocating sweep operation is required for adjustment, and time is required for adjustment, and high-speed real-time control is difficult. Even if the adjustment is performed once, it is necessary to adjust again if the use environment changes. Therefore, the use must be suspended each time.

  However, according to the resonance frequency control method of the present embodiment, since control is performed in real time, correction is always performed for fluctuations in the frequency fd of the AC power supply 11 and fluctuations in environmental factors, and the case of the sweep search method. There is no need for readjustment or pause.

  Further, in the power transmission systems 1 and 1B of the present embodiment, when the Q values of the power transmission resonance coil 13 and the power reception resonance coil 22 are high, the sensitivity to the resonance frequency shift between the two coils becomes high.

  However, according to the resonance frequency control method of the present embodiment, since the Q ratio increases, the rate of change in the vicinity of the resonance frequency of the phases φis and φij increases, so that the control sensitivity also increases. As a result, the phase differences Δφs and Δφj can be matched with the target values φms and φmj with higher accuracy, and higher efficiency power transmission can be performed by increasing the Q value.

  Next, the resonance frequency control (bimodal resonance control) when the coupling between the power transmission coil SC and the power receiving coil JC is increased and the bimodal characteristics appear will be described.

  FIG. 6 shows the states of the currents Is and Ij and the phases φis and φij when the bimodal characteristics appear and the bimodal resonance control is not performed.

  That is, the state shown in FIG. 6 appears when, for example, the power receiving coil JC approaches the power transmitting coil SC and the coupling becomes large when operating in the state shown in FIG.

  What was unimodal as shown by curves CBA2, CBA3 in FIG. 5 is bimodal as shown by curves CCA2, CCA3 in FIG. As a result, at the resonance frequency of 10 MHz, as indicated by the curve CCA4, the current extracted from the power extraction coil 23 decreases, and the transmission power decreases.

  Therefore, in the bimodal resonance control, the resonance frequencies of the power transmission coil SC and the power reception coil JC are shifted so that one of the two peaks appears at 10 MHz which is the resonance frequency fs.

  Therefore, in the normal resonance frequency control, “−3π / 2” is set as the target value φmj, but in the bimodal resonance control, the phase obtained by adding −π / 2 as the target value φmj, that is, only π / 2. “−2π” which is a delayed phase is set. That is, the target value φmj is switched from “−3π / 2” to “−2π”.

  Thus, in the bimodal resonance control, “−2π” is set as the target value φmj of the target value setting unit 243.

  The target value φms of the target value setting unit 143 remains “−π” and does not change. Therefore, the difference between the target value φms and the target value φmj is switched from −π / 2 to −π by the bimodal resonance control.

  In FIG. 7, the phase φis of the current Is of the power transmission resonance coil 13 is −π at the resonance frequency fs of 10 MHz, as indicated by the curve CDB2. Further, as indicated by the curve CDB3, the phase φij of the current Ij of the power receiving resonance coil 22 is −2π at 10 MHz which is the resonance frequency fs.

  As shown by the curves CDA2, CDA3 and CDA4, all the currents I are increased by the bimodal resonance control. For example, in the curve CDA4, the current that is about −30 dB in the normal resonance frequency control is about −20 dB in the bimodal resonance control, which is increased by about 10 dB.

  FIG. 8 shows a change state of electric power extracted from the electric power extraction coil 23 when the distance between the power transmission resonance coil 13 and the electric power reception resonance coil 22 is changed between 200 mm and 100 mm.

  FIG. 8 shows the result of the simulation in which the coil diameter is 100 mm, the distance between the power supply coil 12 and the power transmission resonance coil 13 is 50 mm, and the distance between the power reception resonance coil 22 and the power extraction coil 23 is 40 mm. . A 10Ω resistor was connected as the device 21 which is a load of the power extraction coil 23.

  In FIG. 8, a curve CU1 indicates a case where normal resonance frequency control and bimodal resonance control are switched, and a curve CU2 indicates a case where bimodal resonance control is not performed.

  When the bimodal resonance control is not performed, the power decreases as the distance between the coils approaches, as indicated by the curve CU2. On the other hand, as shown by the curve CU1, when switching to the bimodal resonance control when the distance between the coils approaches about 140 mm, the power does not decrease but increases instead.

  Various methods are conceivable as a method for automatically switching between normal resonance frequency control and bimodal resonance control.

  For example, as shown in FIG. 11, the target value setting unit 243C stores a target value φmj1 for normal resonance frequency control and a target value φmj2 for bimodal resonance control. And the double peak detection part 245 for detecting that the double peak characteristic appeared is provided.

  The target value setting unit 243C outputs the target value φmj1 as the target value φmj in the normal resonance frequency control, but outputs the target value φmj2 as the target value φmj when the bimodal detection unit 245 outputs the detection signal S1. . As a result, normal resonance frequency control and bimodal resonance control are automatically switched.

  Note that the twin peak detection unit 245 may detect, for example, that the transmission power is lower than a predetermined amount or that the distance of the power receiving coil JC is closer than a predetermined value. Alternatively, the two target values φmj1 and φmj2 may be switched and output at an appropriate timing, and the target value φm with the larger power may be selected.

  Next, resonance frequency control in the power transmission systems 1 and 1B of the present embodiment will be described with reference to a flowchart.

  In FIG. 12, the phase φvs of the AC power supply 11 is detected (# 11), the phases φis and φij of the power transmission resonance coil 13 and the power reception resonance coil 22 are detected (# 12), and the phase differences Δφs and Δφj are obtained (# 13). ).

  Then, feedback control is performed so that the phase differences Δφs and Δφj coincide with the target values φms and φmj (# 14).

  In FIG. 13, in the feedback control, the target values φmj2 and φmj1 are switched (# 22, 23) depending on whether or not a bimodal characteristic appears (# 21).

  As described above, by performing the bimodal resonance control when the bimodal characteristic appears, it is possible to suppress a decrease in transmission power and to improve the efficiency of power transmission.

  Therefore, it is possible to always transmit the maximum power from the power transmission device 3 to the power reception device 4 by switching between the normal resonance frequency control and the bimodal resonance control when the bimodal characteristics appear. Energy can be transmitted with high efficiency.

  In each embodiment described above, −π is set as the target value φms, and −3π / 2 or −2π is set as the target value φmj. “−π” set as the target value φms is an example of the target value “β”. Further, “−3π / 2” and “−2π” set as the target value φmj are examples of the target values “β−π / 2” and “β−π”, respectively.

  These target values φms and φmj can be variously changed according to the configurations of the power transmission side control unit 14, the power reception side control unit 24, the feedback control units 144 and 244, and the resonance frequency control units CTs and CTj.

  In the present embodiment, the phase and the phase difference are expressed in radians. When the phase or phase difference is α [radian], this is equivalent to (α + 2nπ) [radian]. n is an arbitrary integer. Also, the phase and phase difference may be expressed in degrees instead of radians.

  Further, it has been described that correction values a and b may be added to the target values φms and φms when they are set. Such correction values a and b may be determined so that, for example, the maximum power is actually obtained.

  In the embodiment described above, the configurations of the phase detection units 141 and 142 can be variously changed. That is, it may be a voltage waveform or a current waveform, or a value or data indicating a phase. That is, it may be a signal or data including phase information about the voltage Vs or the current Is.

  In the embodiment described above, the adding unit 152 and the gain adjusting unit 153, and the adding unit 252 and the gain adjusting unit 253 are examples of calculating units, respectively. Although the MEMS variable capacitance device which is the capacitors 132 and 222 is driven by the drivers 156 and 256, other types of capacitors may be driven. Further, the driver 156 may be driven so as to vary the inductance of the coil instead of the capacitor.

  In the embodiment described above, the power transmission system coil SC, the power reception system coil JC, the power transmission side control unit 14, the power reception side control unit 24, the feedback control units 144 and 244, the resonance frequency control units CTs and CTj, the power transmission device 3, and the power reception The configuration, structure, circuit, shape, number, arrangement, etc. of each part or the whole of the device 4 and the power transmission systems 1 and 1B can be appropriately changed in accordance with the gist of the present invention.

The power transmission system (power transmission device) 1, 1B of the above-described embodiment is, for example, a rechargeable battery built in a mobile device such as a mobile phone, a mobile computer, and a portable music player, or a car The present invention can be applied to charging secondary batteries of transportation equipment.
<Explanation of symbols>
1, 1B Power transmission system
3 Power transmission equipment
4 Power receiving device
SC power transmission coil
11 AC power supply
12 Power supply coil
13 Transmission resonance coil
131 coils
132 capacitors
JC Power receiving coil
22 Receiving resonance coil
221 coil
222 capacitors
14 Power transmission side controller
SE1 Power detection sensor
141, 142 Phase detector
143 Target value setting section
144 Feedback control unit
145 Phase transmitter
151 Phase comparator
152 Adder
153, 154 Gain adjuster
155 Compensator
156 driver
21 devices
24 Power-receiving-side control unit
SE2 Power detection sensor
241 Phase receiver
242 Phase detector
243 Target value setting section
244 Feedback control unit
245 Sohomi detector
251 Phase comparator
252 Adder
253, 254 Gain adjuster
255 Compensator
256 drivers
CTs (transmission side) resonance frequency control unit
CTj (reception side) resonance frequency control unit

Claims (16)

In a resonance frequency control method in a magnetic field resonance type power transmission system that transmits electric power from a power transmission coil to a power reception coil using magnetic field resonance,
The phase of the voltage supplied to the power transmission system coil, the phase of the current flowing through the power transmission system coil and the power reception system coil are detected, and the phase of the voltage supplied to the power transmission system coil and the current flowing through the power transmission system coil The resonance frequency of the power transmission coil is varied so that the difference from the phase becomes the first target value, and the difference between the phase of the voltage supplied to the power transmission coil and the phase of the current flowing through the power reception coil is Changing the resonance frequency of the power receiving resonance coil so as to be the second target value;
A resonance frequency control method in a magnetic field resonance type power transmission system. The power transmission coil includes a power supply coil to which an AC power supply is connected, and a power transmission resonance coil that is electromagnetically coupled to the power supply coil.
The power receiving coil includes a power receiving resonant coil that receives power transmitted from the power transmitting coil using magnetic field resonance, and a power extraction coil that is electromagnetically coupled to the power receiving resonant coil.
The phase of the voltage supplied to the power transmission coil is the phase of the voltage of the AC power supply.
The resonance frequency control method in the magnetic field resonance type electric power transmission system according to claim 1.   The resonance frequency control method in the magnetic field resonance type power transmission system according to claim 1, wherein the first target value is β and the second target value is (β−π / 2). The first target value is −π.
The resonance frequency control method in the magnetic field resonance type power transmission system according to any one of claims 1 to 3 . The power transmission coil includes a power supply coil to which an AC power supply is connected, and a power transmission resonance coil that is electromagnetically coupled to the power supply coil.
The power receiving coil includes a power receiving resonant coil that receives power transmitted from the power transmitting coil using magnetic field resonance, and a power extraction coil that is electromagnetically coupled to the power receiving resonant coil.
When the degree of coupling between the power transmission resonance coil and the power reception resonance coil is increased and a bimodal characteristic appears,
The resonance frequency of the power transmission resonance coil is varied so that the target value of the phase difference between the voltage of the AC power supply and the current of the power transmission resonance coil is α ,
Varying the resonance frequency of the power receiving resonance coil such that the target value of the phase difference between the voltage of the AC power supply and the current of the power receiving resonance coil is ( α− π);
The resonance frequency control method in the magnetic field resonance type power transmission system according to any one of claims 1 to 4 . A power transmission coil;
A power receiving coil that receives power transmitted from the power transmitting coil using magnetic field resonance; and
A phase detector for detecting a phase of a voltage supplied to the power transmission coil, a phase of a current flowing through the power transmission coil and the power receiving coil, and
The resonance frequency of the power transmission coil is varied so that the difference between the detected phase of the voltage supplied to the power transmission coil and the phase of the current flowing through the power transmission coil becomes a first target value, and the power transmission A resonance frequency control unit configured to vary a resonance frequency of the power reception resonance coil so that a difference between a phase of a voltage supplied to the system coil and a phase of a current flowing in the power reception system coil becomes a second target value;
Magnetic field resonance type power transmission device. A power transmission coil having a power supply coil to which an AC power supply is connected and a power transmission resonance coil electromagnetically tightly coupled to the power supply coil, and using magnetic field resonance from the power transmission coil to the power reception coil A power transmission device for transmitting power,
A power transmission system phase detection unit that detects a phase of a voltage of the AC power supply and a phase of a current flowing through the power transmission resonance coil;
A power transmission resonance frequency control unit that varies the resonance frequency of the power transmission coil so that the detected phase difference between the phases becomes a target value;
A power transmission device in a magnetic field resonance type power transmission device. The power transmission resonance frequency controller is
A target value setting unit for setting and storing the target value;
A feedback control unit that varies the resonance frequency of the power transmission resonance coil so that the phase difference between the voltage of the AC power supply and the current of the power transmission resonance coil becomes the set target value;
The power transmission apparatus in the magnetic field resonance type power transmission apparatus according to claim 7. The feedback control unit includes:
A phase comparison unit that compares the phase of the voltage with the phase of the current and outputs a phase difference that is a difference between them;
A calculation unit that calculates a phase difference output from the phase comparison unit and a target value set in the target value setting unit;
A driver that drives to vary inductance or capacitance in the power transmission resonance coil,
The power transmission apparatus in the magnetic field resonance type power transmission apparatus according to claim 8. The target value setting unit sets -π as the target value;
The power transmission apparatus in the magnetic field resonance type power transmission apparatus according to claim 8 or 9. A phase information transmission unit that wirelessly transmits information on the phase of the voltage supplied to the power transmission coil;
Power transmitting device in the magnetic field resonance type power transmission device according to any one of claims 7 to 10. A power receiving device in a magnetic field resonance type power transmission device that transmits electric power from a power transmission coil to a power receiving coil using magnetic field resonance,
A phase information receiver for receiving information on the phase of the voltage supplied to the power transmission coil;
A power receiving system phase detector for detecting a phase of a current flowing in the power receiving coil;
A power receiving system resonance frequency control unit that varies a resonance frequency of the power receiving system coil so that a phase difference between a phase of the voltage received by the phase information receiving unit and a phase of the detected current becomes a target value;
A power receiving device in a magnetic field resonance type power transmission device. The power receiving system coil includes a power receiving resonance coil, and a power extraction coil electromagnetically tightly coupled to the power receiving resonance coil,
The power receiving system resonance frequency control unit is
A target value setting unit for setting and storing the target value;
A feedback control unit that varies the resonance frequency of the power receiving resonance coil so that the phase difference between the phase of the voltage received by the phase information receiving unit and the phase of the detected current becomes the target value;
A power receiving device in the magnetic field resonance type power transmission device according to claim 12. The feedback control unit includes:
A phase comparison unit that compares the phase of the voltage with the phase of the current and outputs a phase difference that is a difference between them;
A calculation unit that calculates a phase difference output from the phase comparison unit and a target value set in the target value setting unit;
A driver that drives to vary inductance or capacitance in the power receiving resonance coil,
A power receiving device in the magnetic field resonance type power transmission device according to claim 13. The target value setting unit sets −3π / 2 as the target value;
The power receiving device in the magnetic field resonance type power transmission device according to claim 13 or 14. The target value setting unit sets the target value to −2π when a coupling degree between the power transmission coil and the power reception coil is increased and a bimodal characteristic appears.
The power receiving device in the magnetic field resonance type power transmission device according to any one of claims 13 to 15 .

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