阅读说明：本技术 一种电动汽车大功率高效率无线充电自适应实现方法 (High-power high-efficiency wireless charging self-adaption realization method for electric automobile ) 是由 杨凌升 刘鸿 徐诗豪 于 2021-04-01 设计创作，主要内容包括：本发明公开了一种电动汽车大功率高效率无线充电自适应实现方法,包括步骤1、检测并计算带整流电路的电动汽车无线充电系统中充电线圈与汽车线圈的耦合系数k；步骤2、判断k是否大于耦合系数阈值k-(th),若是,则进入步骤3,否则返回步骤1,调整充电线圈位置,改变耦合系数k值；步骤3、计算k对应的输出功率最优频率f-1；步骤4、将充电频率调整为f-1。考虑在频带范围中的分频现象问题,实现电动汽车大功率高效率自适应无线充电。(The invention discloses a high-power high-efficiency wireless charging self-adaptive implementation method for an electric automobile, which comprises the following steps of 1, detecting and calculating a coupling coefficient k of a charging coil and an automobile coil in a wireless charging system of the electric automobile with a rectifying circuit; step 2, judging whether k is larger than a coupling coefficient threshold k or not th If yes, entering the step 3, otherwise, returning to the step 1, adjusting the position of the charging coil, and changing the value of the coupling coefficient k; step 3, calculating the optimal frequency f of the output power corresponding to k 1 (ii) a Step 4, adjusting the charging frequency to f 1 . Taking into account divisions in the frequency bandThe problem of frequency phenomenon is solved, and the high-power high-efficiency self-adaptive wireless charging of the electric automobile is realized.)

1. A high-power high-efficiency wireless charging self-adaptive implementation method for an electric vehicle is characterized by comprising the following steps:

step 1, detecting and calculating a coupling coefficient k of a charging coil and an automobile coil in an electric automobile wireless charging system with a rectifying circuit;

step 2, judging whether k is larger than a coupling coefficient threshold k or not_thIf yes, entering the step 3, otherwise, returning to the step 1, adjusting the position of the charging coil, and changing the value of the coupling coefficient k;

step 3, calculating the optimal frequency f of the output power corresponding to k₁；

Step 4, adjusting the charging frequencyIs f₁。

2. The method for realizing the high-power high-efficiency wireless charging self-adaption of the electric automobile according to claim 1, wherein the charging coil and the automobile coil in the step 1 are both square coils, are litz coils with the diameter of 1.5mm, and have 33 turns.

3. The method for realizing the high-power high-efficiency wireless charging self-adaption of the electric automobile according to claim 1 or 2, wherein the wireless charging system with the rectifying circuit of the electric automobile comprises:

an electromagnetic mutual inductance circuit and a rectification circuit;

the electromagnetic mutual inductance circuit comprises:

the main and the secondary charging coils are charging coils and automobile coils, and the self-inductance of the charging coils is L₁、L₂；

Resonant capacitors connected in series with the primary and secondary charging coils, respectively, and having a capacitance of C₁、C₂；

Charging coil and automobile coil, the coil resistance of which is r respectively_l1、r_l2；

And a power supply V_in；

The rectifier circuit includes:

diode D₁～D₄Capacitor C₃And a load resistor having a resistance value of R_out。

4. The method for realizing the high-power high-efficiency wireless charging self-adaption of the electric automobile according to claim 3, wherein the step 1 specifically comprises the following steps:

obtaining corresponding coil self-inductance L according to specifications of a charging coil and an automobile coil₁、L₂Number of turns of coil N₁、N₂Coil equivalent radii r1, r2, and relative position parameters of the charging coil and the car coil;

and obtaining the coupling coefficient k of the charging coil and the automobile coil by combining a Noemann formula.

5. The method for adaptively realizing high-power high-efficiency wireless charging of the electric automobile according to claim 3, wherein the coupling coefficient threshold k in the step 2 is_thComprises the following steps:

α＝L₁C₁＝L₂C₂

6. the method for realizing the self-adaption of the high-power high-efficiency wireless charging of the electric automobile according to claim 3, wherein the optimal frequency f of the output power corresponding to the k in the step 3 is₁Comprises the following steps:

δ＝k²-1。

Technical Field

The invention belongs to the technical field of electric vehicle charging, and particularly relates to a high-power high-efficiency wireless charging self-adaption implementation method for an electric vehicle.

Background

For the wireless charging system of the electric vehicle, how to realize high output power and high energy transmission efficiency is a problem which must be considered in practical application.

In the most basic electromagnetic mutual inductance circuit, there is a Zero Reactance Frequency (ZRF), i.e. the reactance of the whole circuit is zero as seen from the primary side of the circuit, at which time the whole system can achieve high efficiency energy transfer.

Research shows that the problem of frequency division in a frequency band range is not considered in the conventional electric vehicle wireless charging research.

Disclosure of Invention

The invention aims to solve the technical problem of providing a high-power high-efficiency wireless charging self-adaptive implementation method for an electric vehicle aiming at the defects of the prior art.

In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:

a high-power high-efficiency wireless charging self-adaptive implementation method for an electric vehicle is characterized by comprising the following steps:

step 1, detecting and calculating a coupling coefficient k of a charging coil and an automobile coil in an electric automobile wireless charging system with a rectifying circuit;

step 2, judging whether k is larger than a coupling coefficient threshold k or not_thIf yes, entering the step 3, otherwise, returning to the step 1, adjusting the position of the charging coil, and changing the value of the coupling coefficient k;

step 3, calculating the optimal frequency f of the output power corresponding to k₁；

Step 4, adjusting the charging frequency to f₁。

In order to optimize the technical scheme, the specific measures adopted further comprise:

in the step 1, the charging coil and the automobile coil are both square coils, and are litz coils with the diameter of 1.5mm, and the number of turns is 33 up and down.

The wireless charging system of electric automobile who foretell takes rectifier circuit includes:

an electromagnetic mutual inductance circuit and a rectification circuit;

the electromagnetic mutual inductance circuit comprises:

master-slave charging coils, i.e. charging coils and vehicle coils, comprisingSelf-inductance is respectively L₁、L₂；

Resonant capacitors connected in series with the primary and secondary charging coils, respectively, and having a capacitance of C₁、C₂；

Charging coil and automobile coil, the coil resistance of which is r respectively_l1、r_l2；

And a power supply V_in；

The rectifier circuit includes:

diode D₁～D₄Capacitor C₃And a load resistor having a resistance value of R_out。

The step 1 is specifically as follows:

obtaining corresponding coil self-inductance L according to specifications of a charging coil and an automobile coil₁、L₂Number of turns of coil N₁、N₂Coil equivalent radii r1, r2, and relative position parameters of the charging coil and the car coil;

and obtaining the coupling coefficient k of the charging coil and the automobile coil by combining a Noemann formula.

The coupling coefficient threshold k in the above step 2_thComprises the following steps:

α＝L₁C₁＝L₂C₂

the optimal frequency f of the output power corresponding to the k in the step 3₁Comprises the following steps:

the invention has the following beneficial effects:

the invention provides a frequency selection method under the optimal load impedance, so that the transmission efficiency of a wireless energy supply system is ensured to be high, and meanwhile, the larger output power is obtained, and the wireless energy supply system is more suitable for electric automobiles.

Drawings

FIG. 1 is a diagram of a wireless charging system for an electric vehicle;

FIG. 2 is a diagram of an electric vehicle wireless charging system with a rectifying circuit;

fig. 3 is the real part and imaginary part of the input impedance when k is 0.1 in the embodiment;

fig. 4 is the real part and imaginary part of the input impedance when k is 0.15 in the embodiment;

fig. 5 is the real part and imaginary part of the input impedance when k is 0.2 in the embodiment;

fig. 6 shows the transmission efficiency η and the output power P when k is 0.1 in the embodiment_out；

Fig. 7 shows the transmission efficiency η and the output power P when k is 0.15 in the embodiment_out；

Fig. 8 shows the transmission efficiency η and the output power P when k is 0.2 in the embodiment_out；

FIG. 9 shows example f₀、f₁、f₂To the value of k;

FIG. 10 is a flow chart of the method of the present invention;

fig. 11 shows the square coil size and relative position parameters in the example.

Detailed Description

Embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

The invention is equivalent to the circuit diagram shown in fig. 2 of the wireless charging system of the electric automobile in fig. 1.

In the electromagnetic mutual inductance circuit diagram (outer part of dotted line frame in FIG. 2), where L₁、L₂Is self-inductance of the master and slave charging coils, C₁、C₂Is a resonant capacitor, r_l1、r_l2Is the coil resistance, R_outIs a load resistance, V_inIs a power source for the electric power,is the coil mutual inductance i₁、i₂Respectively the magnitude of the current on both sides, k being the coupling of the coilsThe coefficient, ω ═ 2 π f.

A diode D is arranged in the dotted line frame to convert alternating current into direct current₁～D₄Being an ideal diode, the diode may cause the output voltage to become the absolute value of a sine wave, C₃Is with R_outThe parallel capacitor, when the size of capacitor is relatively big for output voltage becomes the rectangular wave, is equivalent to resistance R with whole rectifier circuit, can draw when whole circuit transmission efficiency is the highest, R and R_outThe relationship is as follows:

using kirchhoff's law, the following equation can be derived:

therefore, from (1) the matrix, the formula (2) can be derived:

solving the obtained i according to the formula (2)₁、i₂Values (3) and (4):

substituting the equation with the value of (5):

and each of the other values in the circuit is defined as follows:

in the invention, the coil is selected to be a square coil (compared with a round coil, the transmission efficiency is preferably higher under the same size), for example, the cable specification and the length (the number of turns) of the transmission coil are determined, the area of the coil is determined generally, and the ZRF frequency f of the coil is determined₀Is determined to be a constant value.

For a wireless transmission system, there is one k_thValue, by changing the value of k, only k > k_thIn time, the circuit will generate frequency division. I.e. the system will exhibit three ZRF frequencies. The output efficiency of the whole circuit can reach the maximum value under three frequencies, and the comparison of the three frequencies ZRF can obtain the output efficiency at the center f₀Where the output efficiency can be maximized, but f₁、f₂Is comparable to it, but at f₁、f₂Output power ratio f of₀Much larger.

f₀F on the left and right₁And f₂As the k value (coil coupling coefficient) changes.

The specific calculated value is shown in formula (7).

The invention discusses the frequency division phenomenon research of the frequency band range by taking 81.38 kHz-90.00 kHz as an example, provides the effects of finding out the corresponding k value range in the frequency band range, carrying out frequency selection through the k value and finding out a ZRF in the standard frequency band range, so that the output efficiency of the whole circuit is higher and the output power reaches the maximum.

Specifically, the invention relates to a high-power high-efficiency wireless charging self-adaptive implementation method for an electric vehicle, which comprises the following steps:

step 1, detecting and calculating a coupling coefficient k of a charging coil and an automobile coil in an electric automobile wireless charging system with a rectifying circuit;

step 2, judging whether k is larger than a coupling coefficient threshold k or not_thIf yes, go to step 3, otherwise return toStep 1, adjusting the position of a charging coil and changing the value of a coupling coefficient k;

step 3, calculating the optimal frequency f of the output power corresponding to k₁；

Step 4, adjusting the charging frequency to f₁。

In the embodiment, in the step 1, the charging coil and the automobile coil are both square coils, and are litz coils with the diameter of 1.5mm, and the number of turns is 33 up and down. These are preferences that can vary.

The step 1 specifically comprises the following steps:

obtaining corresponding coil self-inductance L according to specifications of a charging coil and an automobile coil₁、L₂Number of turns of coil N₁、N₂Coil equivalent radii r1, r2, and relative position parameters of the charging coil and the car coil;

and obtaining the coupling coefficient k of the charging coil and the automobile coil by combining a Noemann formula.

Step 2 the coupling coefficient threshold k_thComprises the following steps:

α＝L₁C₁＝L₂C₂

step 3, the optimal frequency f of the output power corresponding to the k₁Comprises the following steps:

example (b): the coil is selected to be a square coil (the better transmission efficiency is achieved under the same size), a litz coil with the diameter of 1.5mm and the number of turns of 33 turns.

Taking the example coil as an example (which can be adjusted according to actual requirements), the following table is taken for each index value in the circuit:

circuit indicator	Value taking
		L1、L2	395μH
C1、C2	1000Pf
		rl1、rl2	0.04Ω
Rout	37Ω
		Vin	220V
C3	10μf

The relationship between the frequency and the value defined by equation (7) is first obtained using the above numerical values, as shown in fig. 3 to 5.

It can be seen from the relationship curve between the input impedance and the frequency that the k value becomes larger gradually, the more obvious the condition of ZRF occurs, and the phenomenon of three ZRF occurs only when the k value is larger than a certain point. And as is apparent from fig. 5, there is a ZRF frequency point in the range of 81.38kHz to 90.00 kHz. The following relationships of the values of output efficiency and power to frequency are still obtained according to the numerical conditions of the tables as shown in fig. 6-8;

as can be seen from FIGS. 6-8, the change in k-value is for three ZRF points (f)₀、f₁、f₂) Has little effect on efficiency, but for f₀F on the left and right₁、f₂The output power at the point can be seen as f₁、f₂Apparent ratio of output power at point f₀Much larger, so when the k value is determined, the frequency is set to f₁、f₂The high efficiency of 99.5 percent and the high output power of 1.8kW can be achieved.

Since the given frequency range is 81.38 kHz-90.00 kHz, a relation graph of frequency and k value is obtained, and Im [ i ] can be known if a ZRF point is obtained₁]I of formula (6) being 0₁Extracting the imaginary part can obtain the following three equations:

according to the formula (7), a relation graph of frequency and k value can be obtained, and the relation graph is shown in figure 9;

as can be seen in FIG. 9, when the value of k is greater than k_thWhen the circuit is in use, the circuit will generate frequency division, i.e. three ZRF points are generated, and f is taken at the time₁、f₂The circuit efficiency and output power of the corresponding frequency generation of (2) are high.

WhereinWhen the electric automobile stops at the charging position, the charging coil and the automobile coil are fixed in specification (or can be called from the database in advance according to the model number and the model number of the charging coil at the charging point), so that the corresponding L can be obtained₁、L₂Number of turns of coil N₁、N₂And coil equivalent radii r1, r2, and parameters for various relative positions of fig. 11.

The mutual inductance between two square coils at any position can be obtained according to the Noemann formula:

wherein

By mutual inductance, and known L₁、L₂The coupling coefficient k can be obtained and substituted into fig. 10 for adaptive optimization.

k is calculated as:

m is the mutual inductance, calculated from the equation below.

And calculating the mutual inductance M of the two coils according to the formula, and calculating the coupling coefficient k between the main coil and the auxiliary coil after calculating the mutual inductance M because the self-inductance of the two coils can be obtained by the number of turns of the front coil. Briefly, L1, L2 are determined by specification and can be considered known. After M is calculated, k can be obtained.

The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.