A kind of coil resonance frequency measurement method suitable for radio energy transmission system
Technical field
The invention belongs to electrotechnics correlative technology fields, are suitable for wireless power transmission system more particularly, to one kind
The coil resonance frequency measurement method of system.
Background technique
As electric automatization infiltrates into the every aspect of people's production and life, although traditional " wired " electric energy transmits
Mode has been widely applied, but there is such as security risk, destroys beauty drawback, can no longer meet application demand.Therefore,
Nowadays wireless power transmission (WPT) technology has caused the extensive concern of many researchers, become current era one grinds greatly
Study carefully hot spot.WPT technology can be avoided the shortcomings that traditional " wired " transmission, and in portable communication, smart home, field of traffic, doctor
The fields such as instrument, undersea detection and aerospace are treated all to have practical application value and wide application prospect.Wireless power transmission
Therefore the following ten big scientific researches that dramatic change will be brought to human being's production and life style are chosen as by the U.S. " technology review " magazine
One of revolution direction.
However, there is an insoluble problem in actual application at present: lacking one kind and be preferably suitable for
The measurement method of WPT system coil resonance frequency is based on the prior art, and the inductance L of coil is easier measurement and obtains,
But since distribution capacity, stray capacitance with instrument are difficult to obtain, so coil capacity is difficult to measure, the resonance frequency of coil
The deviation for being difficult the resonance frequency for obtaining or obtaining by conventional method measurement is larger.Correspondingly, there is development for this field
A kind of practicability is preferably suitable for the technical need of the coil resonance frequency measurement method of radio energy transmission system.
Summary of the invention
Aiming at the above defects or improvement requirements of the prior art, the present invention provides one kind to be suitable for wireless power transmission system
A kind of energy is studied and devised to the coil resonance frequency measurement method of system based on the acquisition feature of existing coil resonance frequency
Enough measurement methods suitable for radio energy transmission system for effectively measuring coil resonance frequency.The measurement method pass through by
Be placed between two identical coils to test coil, it is theoretical based on circuit theory and microwave radio, using theory analysis and
Numerical value calculates the method combined to obtain effective measuring coil resonance frequency.The measurement method is passed suitable for radio energy
The measurement of the resonance frequency of defeated system coil, simplifies analysis method, overcomes traditional measurement method survey at high frequencies
Coil resonance frequency error is larger, the disadvantages of test is complicated, and also can for different frequency, various sizes of coil
Its effectively measuring resonance frequency is had laid a good foundation for later wireless power transmission practicalization.
To achieve the above object, the present invention provides a kind of coil resonance frequency surveys suitable for radio energy transmission system
Amount method, the measurement method mainly comprise the steps that
(1) measuring system is provided, the measuring system includes two identical unicoils, and will be between two unicoils
Every setting, wherein two unicoils are respectively transmitting coil and receiving coil, and the transmitting coil is connected to alternating current
Source, the receiving coil is connected to load, while will be placed in the hair to test coil in the radio energy transmission system
Between ray circle and the receiving coil, and the spacing between test coil and the transmitting coil be equal to it is described to survey line
Spacing between circle and the receiving coil;
(2) the scattering parameter modulus value of the measuring system is obtained with the change curve of the frequency of the AC power source, wherein
The frequency of the AC power source corresponding to the peak value of the change curve is the resonance frequency to test coil.
Further, the scattering parameter modulus value of the measuring system is obtained using vector network analyzer with the exchange
The change curve of the frequency of power supply.
Further, the voltage circuit equation of the equivalent circuit of the measurement resonance frequency to test coil are as follows:
In formula, the π of ω=2 f, f are the frequency of the AC power source;RS、VSThe internal resistance of the respectively described AC power source and electricity
Pressure;R1、L1The resistance and inductance of the respectively described transmitting coil;R2、L2、C2It is respectively described to the resistance of test coil, inductance and
Capacitor;R3、L3The resistance and inductance of the respectively described receiving coil, M12For the transmitting coil and described between test coil
Mutual inductance;M23For the receiving coil and the mutual inductance between test coil.
Further, it when analyzing the equivalent circuit, enables:
Further, obtain flowing through the electric current I of the load by the voltage circuit equation3Expression formula are as follows:
Further, pass through the electric current I to the load3Expression formula analyzed to obtain the scattering of the measuring system
Parameter S21Expression formula are as follows:
Further, pass through the scattering parameter S21Expression formula carry out analyzing to obtain the scattering parameter modulus value | S21|
Expression formula are as follows:
Further, numerical value calculating is carried out using expression formula of the MATLAB to the scattering parameter modulus value to obtain the change
Change curve.
Further, the receiving coil and the coefficient of coup between test coil are equal to described to test coil and institute
State the coefficient of coup between transmitting coil.
Further, the transmitting coil and the receiving coil are the unicoils that radius is 10cm.
In general, through the invention it is contemplated above technical scheme is compared with the prior art, it is provided by the invention suitable
Coil resonance frequency measurement method for radio energy transmission system mainly has following
The utility model has the advantages that
1. providing two identical unicoils, and two unicoil intervals are arranged, wherein two unicoils
Respectively transmitting coil and receiving coil, and the spacing between test coil and the transmitting coil be equal to it is described to survey line
Spacing between circle and the receiving coil, so simplifies analysis method, improves measurement efficiency, overcome in high frequency situations
The disadvantages of resonance frequency error that lower traditional measurement method measures coil is larger, experiment is complicated.
2. obtaining the change curve using vector network analyzer, measurement efficiency is so improved, simplifies process;
The measurement method can be suitable for different frequency, various sizes of coil resonance frequency measurement, practicability is stronger, for
The functionization of wireless power transmission provides the foundation afterwards.
3. the measurement method is based on circuit theory and microwave radio is theoretical, while theoretical analysis and numerical method mutually being tied
It closes, it is simple and easy, be conducive to promote and apply.
4. it is calculated using expression formula progress numerical value of the MATLAB to the scattering parameter modulus value to obtain the change curve,
The frequency of the AC power source corresponding to the peak value of the change curve is the resonance frequency to test coil, without multiple
Miscellaneous analysis and calculation method, and worst error can be controlled 3.901% or so, it is ensured that error is within the allowable range.
Detailed description of the invention
Fig. 1 is the coil resonance frequency measurement suitable for radio energy transmission system that better embodiment of the present invention provides
The three-winding equivalent circuit diagram that method is related to.
Fig. 2 is the coil resonance frequency suitable for radio energy transmission system provided using first embodiment of the invention
Graph of relation under the different coefficients of coup that measurement method obtains between scattering parameter modulus value and the frequency of AC power source.
Fig. 3 is the coil resonance frequency suitable for radio energy transmission system provided using second embodiment of the invention
Graph of relation under the different coefficients of coup that measurement method obtains between scattering parameter modulus value and the frequency of AC power source.
Fig. 4 is the coil resonance frequency suitable for radio energy transmission system provided using third embodiment of the invention
Graph of relation under the different coefficients of coup that measurement method obtains between scattering parameter modulus value and the frequency of AC power source.
Fig. 5 is obtained using the coil resonance frequency measurement method provided by the invention suitable for radio energy transmission system
Scattering parameter modulus value and AC power source frequency between graph of relation.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and
It is not used in the restriction present invention.As long as in addition, technical characteristic involved in the various embodiments of the present invention described below
Not constituting a conflict with each other can be combined with each other.
Referring to Fig. 1, the coil resonance frequency measurement method provided by the invention suitable for radio energy transmission system, institute
Measurement method is stated to mainly comprise the steps that
Step 1, provides measuring system, and the measuring system includes two identical unicoils, and by two single lines
Circle interval setting, wherein two unicoils are connected to friendship respectively as transmitting coil and receiving coil, the transmitting coil
Galvanic electricity source, the receiving coil is connected to load, while will be placed in institute to test coil in the radio energy transmission system
State between transmitting coil and the receiving coil, and the spacing between test coil and the transmitting coil be equal to it is described to
Spacing between test coil and the receiving coil.
Specifically, the three-winding equivalent circuit of the resonance frequency to test coil in the radio energy transmission system is measured
Figure is as shown in Figure 1, two identical unicoils of coiling, two unicoils are respectively as transmitting coil and receiving coil, institute
State transmitting coil connection AC power source VS, the AC power source VSFor providing electric energy to the transmitting coil;The receiving coil
Connection load RL.It is described to be placed between the transmitting coil and the receiving coil to test coil, and it is described to test coil with
Spacing between the transmitting coil with it is described equal to the spacing between test coil and the receiving coil.Wherein, RSTo hand over
Galvanic electricity source VSInternal resistance, R1、L1The resistance and inductance of the respectively described transmitting coil, R2、L2、C2It is respectively described to test coil
Resistance, inductance and capacitor, R3、L3The resistance and inductance of the respectively described receiving coil, M12For the transmitting coil and it is described to
Mutual inductance between test coil, M23For the receiving coil and the mutual inductance between test coil.
Ignore between the capacitor and the transmitting coil and the receiving coil of the transmitting coil and the receiving coil
Mutual inductance, the voltage circuit equation of the equivalent circuit is obtained according to Kirchhoff's law are as follows:
In formula (1), the π of ω=2 f.Since the transmitting coil is identical with the receiving coil, and it is described to test coil with
Spacing between the transmitting coil with it is described equal to the spacing between test coil and the receiving coil, to the equivalent electricity
When road is analyzed, Ke Yiling:
Formula (2) are substituted into voltage circuit equation (1), can obtain flowing through the load RLElectric current I3Expression formula are as follows:
To formula (3), further analysis obtains the scattering parameter S of the measuring system21Expression formula are as follows:
By being analyzed formula (5) it can be concluded that, the scattering parameter modulus value of the measuring system | S21| with coupled systemes
The number k and AC power source VSFrequency f it is related, wherein the coefficient of coup k is the transmitting coil and described to test coil
Between the coefficient of coup and the coefficient of coup between test coil and the receiving coil.
Step 2, obtains the scattering parameter modulus value of the measuring system with the change curve of the frequency of the AC power source,
Wherein, when the scattering parameter mould is maximized in the curve frequency of the corresponding AC power source be it is described to
The resonance frequency of test coil.
In one embodiment, the scattering parameter modulus value and the alternating current are obtained according to the formula (5) analysis
Source VSFrequency f between relation curve, and then analyze described between the resonance frequency and the relation curve of test coil
Relationship, obtain the resonance frequency to test coil from there through the relation curve.Below with three embodiments to this hair
It is bright to be described in further detail, in three embodiments, all take R=50 Ω, L=0.45 μ H.
In the first embodiment, L is taken2=50 μ H, C2=11pF, R2=1.6 Ω can then be calculated described to test coil
Resonance frequency theoretical valueBy MATLAB to the formula of the scattering parameter modulus value
(5) carrying out numerical value can be calculated the scattering parameter modulus value and the AC power source V under different coefficient of coup kSFrequency f it
Between relation curve, as shown in Figure 2.
In this second embodiment, L is taken2=9.9 μ H, C2=7.2pF, R2=1 Ω can then be calculated described to test coil
Resonance frequency theoretical valueBy MATLAB to the formula of the scattering parameter modulus value
(5) carrying out numerical value can be calculated scattering parameter modulus value under different coefficient of coup k values | S21| the frequency f with the AC power source VS
Between relation curve, as shown in Figure 3.
In the third embodiment, L is taken2=3.4 μ H, C2=2.2pF, R2=1 Ω can then be calculated described to test coil
Resonance frequency theoretical valueBy MATLAB to the formula of the scattering parameter modulus value
(5) carrying out numerical value can be calculated scattering parameter modulus value under different coefficient of coup k values | S21| the frequency f with the AC power source VS
Between relation curve, as shown in Figure 4.
It can be seen that from Fig. 2, Fig. 3 and Fig. 4 and be decreased to 0.01 from 0.2 with coefficient of coup k, the peak value institute of relation curve
The corresponding AC power source VSFrequency f closer to theoretical value f0, when coefficient of coup k value is 0.01, the two is almost equal.
But when coefficient of coup k is larger, with the increase of the resonance frequency to test coil, frequency f corresponding to peak of curve
With theoretical value f0Error it is bigger.Wherein, table 1 lists theoretical value and measurement under the different coefficient of coup k values of three embodiments
The error of value, available worst error is 3.901% from table 1, and error is within allowed band.To sum up, measuring
When the resonance frequency of test coil, as make smaller i.e. the distance between the coil of coefficient of coup k bigger as possible, so that measured value
It can be more accurate.
The error of theoretical value and measured value under the different coefficient of coup k values of table 1
In another embodiment, referring to Fig. 5, it is humorous based on the above-mentioned coil suitable for radio energy transmission system
Vibration frequency measurement method obtains the scattering parameter modulus value of the measuring system using vector network analyzer with the alternating current
The change curve of the frequency in source, wherein the transmitting coil and the receiving coil are the copper wire windings for being 2.5mm with diameter
Radius is the unicoil of 10cm, and described to test coil is spiral winding that radius is 10cm, and circle number is three circles, and is connected to 41.5pF
Capacitor.In addition, can be seen that from Fig. 5, the peak value of the relation curve between scattering parameter modulus value and the frequency of AC power source is corresponding
Ac power frequency be 13.45MHz, frequency 13.45MHz is then the resonance frequency to test coil.Impedance is used again
Analyzer carries out impedance measurement to test coil to described, and then obtains that inductance is 3.4 μ H, resistance is 0.1 Ω, ignores coil itself
Distribution capacity and stray capacitance, then the resonance frequency to test coil is 13.4MHz, and using vector network analyzer
Experimental result is very close, it is seen that the coil resonance frequency measurement method suitable for radio energy transmission system it is accurate
Property is higher.
Coil resonance frequency measurement method provided by the invention suitable for radio energy transmission system, the measurement method will
Two identical unicoil relative spacing settings, and two lists will be placed in test coil in radio energy transmission system
Between coil, and it is described equal to the spacing between test coil and two unicoils, analysis method is so simplified, simply
It is easy, measurement efficiency is improved, adaptability is stronger.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to
The limitation present invention, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should all include
Within protection scope of the present invention.