A wireless charging system for electric vehicles and a transmitting coil design method for the system

Abstract

The present invention proposes a wireless charging system for electric vehicles and a design method for a transmitting coil of the system. The present invention establishes an equivalent circuit model of the wireless charging system, derives a mathematical expression of the magnetic induction intensity generated by the system transmitting coil at any point in the plane of the receiving coil, constructs an optimization target model based on the derived mathematical expression of the magnetic induction intensity, and combines the constraints of the optimization target model to determine the number of turns, turn spacing, and coil width of the transmitting coil that can generate a relatively uniform magnetic field, thereby determining the coil configuration of the combined planar spiral structure transmitting coil, and finally calculates the magnetic field distribution of the transmitting coil on the plane of the receiving coil and the magnetic flux density modulus distribution of a cross section on the plane through finite element simulation software. The combined planar spiral structure transmitting coil proposed by the present invention can still maintain a relatively stable mutual inductance after the system receiving coil is offset.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless charging, and in particular relates to a design method for a transmitting coil of a wireless charging system with high anti-deviation performance. Background Art

[0002] In recent years, the widespread use of traditional fuel vehicles has brought tremendous pressure on the environment and resources. In order to reduce automobile exhaust emissions, ensure energy security, and promote energy conservation and emission reduction, electric vehicles have received more and more attention. Electric vehicles have the advantages of zero emissions and no pollution, but due to the limited capacity of on-board batteries, inconvenient charging and potential safety hazards, the further promotion and popularization of electric vehicles has been restricted. At present, the common charging methods for electric vehicles are mainly wired charging and wireless charging. Although wired charging is a more common charging method, it has many problems such as the connection part is easily damaged, sparks are easily generated when plugging and unplugging, and it occupies a large area. As a new type of power transmission method, wireless charging does not require wires for conduction or other physical contact to enable power to reach the load end. Compared with wired charging, wireless charging has the advantages of small footprint, convenience and flexibility, no need for plugging and unplugging, and low maintenance cost, so it has received more and more attention. The wireless charging technology of electric vehicles can be mainly divided into three types: static wireless charging, quasi-dynamic wireless charging and dynamic wireless charging. Static wireless charging technology charges the car when it is stopped; quasi-dynamic wireless charging charges the car where it stops for a short time, such as at traffic lights; dynamic wireless charging charges the car while it is driving. By laying a certain length of power supply coil under the ground, electric vehicles can be charged without stopping.

[0003] At present, the theoretical research results of electric vehicle wireless charging technology are fruitful, but the engineering application is still in the experimental stage. There are still many difficulties in the engineering application of electric vehicle wireless charging based on inductive power transmission, the most prominent of which is the inaccurate parking position. Inaccurate parking position will make it difficult to align the transmitting coil and the receiving coil, and may cause a large distance offset between the transmitting coil and the receiving coil, which will seriously reduce the coupling level and reduce the system transmission power to far below the rated power, forcing charging to be impossible.

[0004] In view of the above problems, the present invention proposes a design method for a wireless charging system transmitting coil with high anti-deviance. The combined planar spiral structure transmitting coil designed by this method can generate a relatively uniform magnetic field on the plane of the receiving coil, so that the receiving coil can still maintain good mutual inductance after horizontal deviation, thereby improving the coupling degree of the system coupling mechanism and ensuring the maximum stable operation of the system. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a design method for a wireless charging system transmitter coil with high anti-deviance. The method can generate a relatively uniform magnetic field on the plane of the receiving coil, and can still maintain good mutual inductance when the position of the system receiving coil is horizontally offset, thereby improving the coupling degree of the system magnetic coupling mechanism and ensuring the maximum stable operation of the system.

[0006] The technical solution of the present invention is a design method for a wireless charging system transmitting coil with high anti-deviation performance;

[0007] The technical solution adopted by the present invention to solve its technical problem is: first, an equivalent circuit model of a wireless charging system is established; a mathematical expression of the magnetic induction intensity generated by a transmitting coil of the system at any point in the plane of a receiving coil is derived; an optimization target model is constructed according to the derived mathematical expression of the magnetic induction intensity, and the number of turns, turn spacing and coil width of the transmitting coil that can generate a relatively uniform magnetic field are determined in combination with the constraints of the optimization target model; finally, the magnetic field distribution of the transmitting coil on the plane of the receiving coil and the magnetic flux density modulus distribution of a cross-section on the plane are calculated by finite element simulation software, and the feasibility of the method is verified by simulation.

[0008] A wireless charging system for an electric vehicle, comprising:

[0009] The electric vehicle wireless charging system is composed of a wireless charging transmitting module and a wireless charging receiving module connected wirelessly; the wireless charging transmitting module is laid on the road where the electric vehicle is driving; the wireless charging receiving module is installed on the electric vehicle; the wireless charging transmitting module includes a DC input power supply, a high-frequency inverter circuit, a transmitting SS compensation circuit, and a transmitting coil connected in sequence; the wireless charging receiving module includes a receiving coil, a receiving SS compensation circuit, a rectifier circuit, and a load resistor connected in sequence.

[0010] Preferably, the transmitting SS compensation circuit comprises a transmitting series circuit composed of a transmitting resonant compensation capacitor, a transmitting coil self-inductance, and a transmitting coil equivalent resistance connected in sequence.

[0011] Preferably, the receiving SS compensation circuit comprises a receiving series loop consisting of a receiving resonant compensation capacitor, a receiving coil self-inductance, and a receiving coil equivalent resistance connected in sequence;

[0012] Preferably, the transmitting coil is a planar spiral coil consisting of two parts of several square coils with equal spacing. The entire coil is wound by a single Litz wire. The turn spacing in the center part of the coil is equal, and the turn spacing on the outer side is equal and smaller than the center part.

[0013] Preferably, the receiving coil is a planar spiral coil composed of a plurality of square coils with equal spacing, and the entire coil is wound by a single Litz wire.

[0014] A design method for a transmitting coil in an electric vehicle wireless charging system, specifically comprising:

[0015] An equivalent circuit model of the system is established based on the input voltage of the system, the self-inductance, equivalent resistance and compensation capacitance of the transmitting coil, the self-inductance, equivalent resistance and compensation capacitance of the receiving coil, and the load resistance; a mathematical model of the magnetic induction intensity generated by the transmitting coil at any point on the plane of the receiving coil is established;

[0016] According to the mathematical model of the magnetic induction intensity generated by the system transmitting coil at any point on the receiving coil plane, an optimization target model is constructed; the constraints of the optimization target model are established; the minimization of the optimization target model is taken as the optimization goal, and the number of turns, turn spacing and coil width of the transmitting coil are determined in combination with the constraints of the optimization target model;

[0017] Preferably, the mathematical model of the magnetic induction intensity generated by the transmitting coil at any point on the receiving coil plane is defined as:

[0018]

[0019] Among them, the transmitting coil and the receiving coil are placed coaxially and parallel, 2a is the side length of the system transmitting coil, I is the current flowing through the transmitting coil loop, x is the x-axis coordinate of any point on the receiving coil plane, y is the y-axis coordinate of the point on the receiving coil plane, z is the z-axis coordinate of the point on the receiving coil plane, e z is the z-axis component of the unit vector pointing from any line element on the edge of the transmitting coil to the point on the plane of the receiving coil, and μ0 is the magnetic permeability of vacuum.

[0020] Preferably, the optimization target model is defined as:

[0021] min|B K(i) -B K(i+1) |(d1,W1,N1,...d K ,W K ,N K )

[0022] Among them, B K(i) is any point P of the Kth layer transmitting coil in the receiving coil plane i (x i ,y i ,z i ) of the magnetic induction intensity, B K(i+1) is any point P of the Kth layer transmitting coil in the receiving coil plane i+1 (x i+1 ,y i+1 ,z i+1), K ≥ 1 and is an integer, i ≥ 1 and is an integer, d1 is the turn spacing of the first layer transmitting coil, W1 is the width of the first layer transmitting coil, N1 is the number of turns of the first layer transmitting coil, d K is the turn spacing of the Kth layer transmitting coil, W K N is the width of the K-th layer transmitting coil, K is the number of turns of the K-th layer transmitting coil.

[0023] As a preference, the constraints of the target model are optimized and defined as:

[0024]

[0025] Among them, 2b is the side length of the system receiving coil, and R is the distance between the transmitting coil and the receiving coil.

[0026] Determine the number of turns, turn spacing and coil width of the combined planar spiral structure transmitting coil. The specific process is as follows:

[0027] Step 1.1, assuming that the turn spacing of the first-layer transmitting coil is d1, the width of the first-layer transmitting coil is W1, and the number of turns of the first-layer transmitting coil is N1. The side length of the first turn of the first-layer transmitting coil is 2d1, the side length of the second turn is 4d1, ..., the side length of the N1th turn is 2N1d1, the receiving coil is a single-turn test coil, and the first-layer transmitting coil and the receiving coil are in a coaxial and parallel position. Then the first-layer transmitting coil is at any point p in the plane of the receiving coil. i (x i ,y i ,z i )(i≥1 and is an integer) is:

[0028]

[0029] ...

[0031]

[0032] Among them, B 1,1 The first turn of the first-layer transmitting coil is any point p on the plane of the receiving coil. i (x i ,y i ,z i ) of the magnetic induction intensity, B 1,2 The second turn of the first-layer transmitting coil is at the same point p on the plane of the receiving coil. i (x i ,y i ,z i )'s magnetic induction intensity, The N1th turn of the first-layer transmitting coil is at the same point p on the plane of the receiving coil. i (x i ,y i ,z i )'s magnetic induction intensity.

[0033] Step 1.2, assuming that the turn spacing of the second-layer transmitting coil is d2, the width of the second-layer transmitting coil is W2, and the number of turns of the second-layer transmitting coil is N2. The side length of the first turn of the second-layer transmitting coil is 2(d1+W1+d2), the side length of the second turn is 2(d1+W1+2d2), ..., the side length of the N2th turn is 2(d1+W1+N2d2), the receiving coil is a single-turn test coil, and the second-layer transmitting coil and the receiving coil are in a coaxial and parallel position. Then, at any point p on the same receiving coil plane, the second-layer transmitting coil i (x i ,y i ,z i ) is:

[0034]

[0035] ...

[0037]

[0038] Among them, B 2,1 The first turn of the second-layer transmitting coil is any point p on the same receiving coil plane. i (x i ,y i ,z i ) of the magnetic induction intensity, B 2,2 The second turn of the second transmitting coil is at the same point p on the same receiving coil plane. i (x i ,y i ,z i ) of the magnetic induction intensity, B 2,N2 The N2th turn of the second-layer transmitting coil is at the same point p on the same receiving coil plane. i (x i ,y i ,z i )'s magnetic induction intensity.

[0039] Step 1.3, let the turn spacing of the Kth layer transmitting coil be d K , the width of the Kth layer transmitting coil is W K , the number of turns of the Kth layer transmitting coil is N K , then the side length of the first turn of the K-th layer transmitting coil is 2(d1+W1+...+d K,1 +W K,1+d K ), the side length of the second turn is 2(d1+W1+...+d K,1 +W K,1 +2d K ), ..., Nth K The side length of the turn is 2(d1+W1+...+d K,1 +W K,1 +N K d K ), the receiving coil is a single-turn test coil, the K-th layer transmitting coil and the receiving coil are in a coaxial and parallel position, then the K-th layer transmitting coil is on any point p on the same receiving coil plane i (x i ,y i ,z i ) is:

[0040]

[0041] ...

[0043]

[0044] Among them, B K,1 The first turn of the Kth layer transmitting coil is any point p on the same receiving coil plane. i (x i ,y i ,z i ) of the magnetic induction intensity, B K,2 The second turn of the Kth layer transmitting coil is at the same point p on the same receiving coil plane i (x i ,y i ,z i )'s magnetic induction intensity, The Kth layer of the transmitting coil Nth K The turns are on the same receiving coil plane at the same point p i (x i ,y i ,z i )'s magnetic induction intensity.

[0045] Step 1.4, randomly select i (i≥1 and is an integer) points on the receiving coil plane, and calculate the magnetic induction intensity of the first layer transmitting coil, the second layer transmitting coil, ... the Kth layer transmitting coil at each point.

[0046] Step 1.5, find a suitable set of (d1, W1, N1, d2, W2, N2, ..., d K ,W K ,N K) values, satisfying the optimization target model to obtain the minimum value, that is, there is a set of suitable (d1, W1, N1, d2, W2, N2, ..., d K ,W K ,N K ) is selected so that the magnetic induction intensity generated by the first layer of transmitting coils at each point is approximately equal, the magnetic induction intensity generated by the second layer of transmitting coils at each point is approximately equal, ..., the magnetic induction intensity generated by the Kth layer of transmitting coils at each point is approximately equal.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The present invention conducts modeling analysis on the wireless charging system and derives a mathematical expression for the magnetic induction intensity generated by the system's transmitting coil at any point on the plane of the receiving coil.

[0049] The present invention proposes a design method for a combined planar spiral structure transmitting coil. The method is based on a magnetic induction intensity formula, calculates the magnetic induction intensity of K layers of transmitting coils at any point on the plane of the receiving coil, selects a set of appropriate coil turn spacing, number of turns and coil width so that the magnetic induction intensity of any point of each layer of transmitting coil on the same receiving coil plane is approximately equal, and then obtains a combined planar spiral structure transmitting coil. The combined planar spiral structure transmitting coil can generate a relatively uniform magnetic field on the plane of the receiving coil. When the position of the receiving coil is horizontally offset, the system mutual inductance can still maintain a high level. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is an equivalent circuit model of a wireless charging system described in the present invention.

[0051] Figure 2 It is the spatial rectangular coordinate system of the present invention.

[0052] Figure 3 This is the transmitting coil configuration of the present invention.

[0053] Figure 4 This is the receiving coil configuration of the present invention.

[0054] Figure 5 It is a magnetic field distribution diagram of the transmitting coil of the present invention on the receiving coil plane.

[0055] Figure 6 It is the magnetic flux density modulus distribution of a section line of the transmitting coil on the plane of the receiving coil described in the present invention.

[0056] Figure 7 It is a system mutual inductance curve diagram when the receiving coil described in the present invention is horizontally offset.

[0057] Figure 8 It is a diagram of the steps of the method described in the present invention. DETAILED DESCRIPTION

[0058] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0059] A wireless charging system for an electric vehicle, comprising:

[0060] The electric vehicle wireless charging system is composed of a wireless charging transmitting module and a wireless charging receiving module connected wirelessly; the wireless charging transmitting module is laid on the road where the electric vehicle is driving; the wireless charging receiving module is installed on the electric vehicle; the wireless charging transmitting module is composed of a DC input power supply, a high-frequency inverter circuit, a transmitting SS compensation circuit, and a transmitting coil connected in sequence; the wireless charging receiving module is composed of a receiving coil, a receiving SS compensation circuit, a rectifier circuit, and a load resistor connected in sequence.

[0061] The transmitting SS compensation circuit is composed of a transmitting resonant compensation capacitor, a transmitting coil self-inductance, and a transmitting coil equivalent resistance connected in sequence to form a transmitting series loop.

[0062] The receiving SS compensation circuit is composed of a receiving resonant compensation capacitor, a receiving coil self-inductance, and a receiving coil equivalent resistance connected in sequence to form a receiving series loop;

[0063] The transmitting coil is a planar spiral coil composed of two parts of several square coils with equal spacing. The entire coil is wound by a single Litz wire. The turn spacing in the central part of the coil is equal, and the turn spacing on the outer side is equal but slightly smaller than the central part.

[0064] The receiving coil is a planar spiral coil composed of a number of square coils with equal spacing, and the entire coil is wound by a single Litz wire.

[0065] The present invention provides a design method for a transmitting coil of a wireless charging system with high anti-deviation performance.

[0066] The first embodiment of the present invention is a method for designing a transmitting coil of a wireless charging system with high anti-deviation performance;

[0067] Step 1: Establish an equivalent circuit model of the system based on the input voltage of the system, the self-inductance, equivalent resistance and compensation capacitance of the transmitting coil, the self-inductance, equivalent resistance and compensation capacitance of the receiving coil, and the load resistance; establish a mathematical model of the magnetic induction intensity generated by the transmitting coil at any point on the plane of the receiving coil;

[0068] The mathematical model of the magnetic induction intensity generated by the transmitting coil at any point on the receiving coil plane in step 1 is defined as:

[0069]

[0070] Among them, the transmitting coil and the receiving coil are placed coaxially and parallel, 2a is the side length of the system transmitting coil, I is the current flowing through the transmitting coil loop, x is the x-axis coordinate of any point on the receiving coil plane, y is the y-axis coordinate of the point on the receiving coil plane, z is the z-axis coordinate of the point on the receiving coil plane, e z is the z-axis component of the unit vector pointing from any line element on the edge of the transmitting coil to the point on the plane of the receiving coil, and μ0 is the magnetic permeability of vacuum.

[0071] Step 1.1, the equivalent circuit model of the wireless charging system is as follows Figure 1 As shown in the figure, it mainly includes input voltage source, transmitting coil, receiving coil, compensation capacitor, equivalent resistance and load. s is the AC power supply voltage, C t is the transmitting side compensation capacitor, R1 is the transmitting coil equivalent resistance, L1 is the transmitting coil self-inductance, I1 is the transmitting coil loop current, M 1r is the mutual inductance between the transmitting coil and the receiving coil, R r is the equivalent resistance of the receiving coil, L r is the receiving coil self-inductance, I2 is the current of the receiving coil loop, C r is the compensation capacitor on the receiving side, R L is the load resistance. The system adopts SS type resonant compensation network.

[0072] Step 1.2, according to Figure 2 As shown, the mathematical expression of the magnetic induction intensity generated by the transmitting coil of the system at any point on the plane of the receiving coil is derived. It mainly includes the transmitting coil and the receiving coil. Among them, 2a is the side length of the transmitting coil, 2b is the side length of the receiving coil, R is the distance between the transmitting coil and the receiving coil, and p i (x i ,y i ,z i )(i≥1 and is an integer) is any point on the receiving coil plane, x i ,y i The value range is [-b, b], z i =R, dl1 is any line element on the edge of the transmitting coil, t1 is an edge of the transmitting coil, e R is the unit vector pointing from the line element to point P.

[0073] According to the Biot-Savart law, the t1 edge is at p i (x i ,y i ,z i ) point t1 for:

[0074]

[0075] Among them, I1 is the current flowing through the transmitting coil loop, and μ0 is the magnetic permeability of vacuum.

[0076] The coordinate of dl1 on the x-axis is marked as x'. From the geometric relationship, we can know that:

[0077]

[0078] Among them, e x is a unit vector

[0079] Substituting in, we get:

[0080]

[0081] Further calculations yield:

[0082]

[0083] Among them, e z is a unit vector, α is a unit vector e x and e R The angle between the two is θ, which is the magnetic induction intensity B. t1 The unit vector of e z Angle.

[0084] According to the geometric relationship:

[0085]

[0086]

[0087] From this we can get:

[0088]

[0089] Further calculation shows that the transmitting coil is at p i The magnetic induction intensity generated by the point is:

[0090]

[0091] Step 2: Construct an optimization target model based on the mathematical model of the magnetic induction intensity generated by the system transmitting coil at any point on the receiving coil plane; establish the constraints of the optimization target model; minimize the optimization target model as the optimization goal, and determine the number of turns, turn spacing and coil width of the transmitting coil in combination with the constraints of the optimization target model;

[0092] Step 2.1, determine the optimization objectives and constraints.

[0093] Determine the optimization target. The transmitting coil is composed of K layers of coils. The magnetic induction intensity generated by the transmitting coil at any point on the receiving coil plane is the superposition of the magnetic induction intensity generated by the K layers of coils at that point. Therefore, if the magnetic induction intensity generated by each layer of coils at any point on the receiving coil plane is approximately equal, then the magnetic induction intensity generated by the K layers after superposition at any point on the receiving plane is also approximately equal.

[0094] Determine the constraints. Since any point is taken on the plane of the receiving coil, the coordinate values ​​of the point have a range, and the coordinate values ​​of any point need to be constrained.

[0095] The specific definition is:

[0096] min|B K(i) -B K(i+1) |(d1,W1,N1,...d K ,W K ,N K )

[0097]

[0098] Among them, B K(i) is any point P of the Kth layer transmitting coil in the receiving coil plane i (x i ,y i ,z i ) of the magnetic induction intensity, B K(i+1) is any point P of the Kth layer transmitting coil in the receiving coil plane i+1 (x i+1 ,y i+1 ,z i+1 ), K ≥ 1 and is an integer, i ≥ 1 and is an integer, d1 is the turn spacing of the first layer transmitting coil, W1 is the width of the first layer transmitting coil, N1 is the number of turns of the first layer transmitting coil, d K is the turn spacing of the Kth layer transmitting coil, W K N is the width of the K-th layer transmitting coil, K is the number of turns of the Kth layer transmitting coil, 2b is the side length of the system receiving coil, and R is the distance between the transmitting coil and the receiving coil.

[0099] Step 2.1, assuming that the turn spacing of the first-layer transmitting coil is d1, the width of the first-layer transmitting coil is W1, and the number of turns of the first-layer transmitting coil is N1. The side length of the first turn of the first-layer transmitting coil is 2d1, the side length of the second turn is 4d1, ..., the side length of the N1th turn is 2N1d1, the receiving coil is a single-turn test coil, and the first-layer transmitting coil and the receiving coil are in a coaxial and parallel position. Then the first-layer transmitting coil is at any point p in the plane of the receiving coil. i (x i ,y i,z i )(i≥1 and is an integer) is:

[0100]

[0101] ...

[0103]

[0104] Among them, B 1,1 The first turn of the first-layer transmitting coil is any point p on the plane of the receiving coil. i (x i ,y i ,z i ) of the magnetic induction intensity, B 1,2 The second turn of the first-layer transmitting coil is at the same point p on the plane of the receiving coil. i (x i ,y i ,z i )'s magnetic induction intensity, The N1th turn of the first-layer transmitting coil is at the same point p on the plane of the receiving coil. i (x i ,y i ,z i )'s magnetic induction intensity.

[0105] Step 2.2, assuming that the turn spacing of the second-layer transmitting coil is d2, the width of the second-layer transmitting coil is W2, and the number of turns of the second-layer transmitting coil is N2, then the side length of the first turn of the second-layer transmitting coil is 2(d1+W1+d2), the side length of the second turn is 2(d1+W1+2d2), ..., the side length of the N2th turn is 2(d1+W1+N2d2), the receiving coil is a single-turn test coil, and the second-layer transmitting coil and the receiving coil are in a coaxial and parallel position, then the second-layer transmitting coil is on the same receiving coil plane. Any point p i (x i ,y i ,z i ) is:

[0106]

[0107] ...

[0109]

[0110] Among them, B 2,1 The first turn of the second-layer transmitting coil is any point p on the same receiving coil plane. i (xi ,y i ,z i ) of the magnetic induction intensity, B 2,2 The second turn of the second transmitting coil is at the same point p on the same receiving coil plane. i (x i ,y i ,z i ) of the magnetic induction intensity, B 2,N2 The N2th turn of the second-layer transmitting coil is at the same point p on the same receiving coil plane. i (x i ,y i ,z i )'s magnetic induction intensity.

[0111] Step 2.3, let the turn spacing of the Kth layer transmitting coil be d K , the width of the Kth layer transmitting coil is W K , the number of turns of the Kth layer transmitting coil is N K , then the side length of the first turn of the K-th layer transmitting coil is 2(d1+W1+...+d K,1 +W K,1 +d K ), the side length of the second turn is 2(d1+W1+...+d K,1 +W K,1 +2d K ), ..., Nth K The side length of the turn is 2(d1+W1+...+d K,1 +W K,1 +N K d K ), the receiving coil is a single-turn test coil, the K-th layer transmitting coil and the receiving coil are in a coaxial and parallel position, then the K-th layer transmitting coil is on any point p on the same receiving coil plane i (x i ,y i ,z i ) is:

[0112]

[0113] ...

[0115]

[0116] Among them, B K,1 The first turn of the Kth layer transmitting coil is any point p on the same receiving coil plane. i (x i ,y i ,z i ) of the magnetic induction intensity, BK,2 The second turn of the Kth layer transmitting coil is at the same point p on the same receiving coil plane i (x i ,y i ,z i )'s magnetic induction intensity, The Kth layer of the transmitting coil Nth K The turns are on the same receiving coil plane at the same point p i (x i ,y i ,z i )'s magnetic induction intensity.

[0117] Step 2.4, randomly select i (i≥1 and is an integer) points on the receiving coil plane, and calculate the magnetic induction intensity of the first layer transmitting coil, the second layer transmitting coil, ... the Kth layer transmitting coil at each point.

[0118] Step 2.5, find a suitable set of (d1, W1, N1, d2, W2, N2, ..., d K ,W K ,N K ) values, satisfying the optimization target model to obtain the minimum value, that is, there is a set of suitable (d1, W1, N1, d2, W2, N2, ..., d K ,W K ,N K ) is selected so that the magnetic induction intensity generated by the first layer of transmitting coils at each point is approximately equal, the magnetic induction intensity generated by the second layer of transmitting coils at each point is approximately equal, ..., the magnetic induction intensity generated by the Kth layer of transmitting coils at each point is approximately equal.

[0119] Step 3: According to step 2, K=2 is taken, that is, at this time, the combined planar spiral structure transmitting coil is composed of two layers, and the number of turns, turn spacing and coil width of the combined planar spiral structure transmitting coil are determined according to step 2; the magnetic field distribution of the combined planar spiral structure transmitting coil on the plane of the receiving coil and the magnetic flux density modulus distribution on the plane cross section, as well as the mutual inductance curve of the system during the horizontal deviation of the receiving coil are calculated using finite element simulation software, and the simulation results are analyzed;

[0120] Step 3.1, let K = 2, determine the number of turns, turn spacing and coil width of the combined planar spiral structure transmitting coil, the specific steps are as follows:

[0121] Step 3.1.1, assuming that the turn spacing of the first-layer transmitting coil is d1, the width of the first-layer transmitting coil is W1, and the number of turns of the first-layer transmitting coil is N1. The side length of the first turn of the first-layer transmitting coil is 2d1, the side length of the second turn is 4d1, ..., the side length of the N1th turn is 2N1d1, the receiving coil is a single-turn test coil, and the first-layer transmitting coil and the receiving coil are in a coaxial and parallel position. Then the first-layer transmitting coil is at any point p in the plane of the receiving coil. i (x i ,y i ,z i )(i≥1 and is an integer) is:

[0122]

[0123] ...

[0125]

[0126] Among them, B 1,1 The first turn of the first-layer transmitting coil is any point p on the plane of the receiving coil. i (x i ,y i ,z i ) of the magnetic induction intensity, B 1,2 The second turn of the first-layer transmitting coil is at the same point p on the plane of the receiving coil. i (x i ,y i ,z i )'s magnetic induction intensity, The N1th turn of the first-layer transmitting coil is at the same point p on the plane of the receiving coil. i (x i ,y i ,z i )'s magnetic induction intensity.

[0127] Step 3.1.2, assuming that the turn spacing of the second-layer transmitting coil is d2, the width of the second-layer transmitting coil is W2, and the number of turns of the second-layer transmitting coil is N2, then the side length of the first turn of the second-layer transmitting coil is 2(d1+W1+d2), the side length of the second turn is 2(d1+W1+2d2), ..., the side length of the N2th turn is 2(d1+W1+N2d2), the receiving coil is a single-turn test coil, and the second-layer transmitting coil and the receiving coil are in a coaxial and parallel position, then the second-layer transmitting coil is on the same receiving coil plane. Any point p i (x i ,y i ,z i ) is:

[0128]

[0129] ...

[0131]

[0132] Among them, B 2,1 The first turn of the second-layer transmitting coil is any point p on the same receiving coil plane. i (x i ,y i ,z i ) of the magnetic induction intensity, B 2,2 The second turn of the second transmitting coil is at the same point p on the same receiving coil plane. i (x i ,y i ,z i ) of the magnetic induction intensity, B 2,N2 The N2th turn of the second-layer transmitting coil is at the same point p on the same receiving coil plane. i (x i ,y i ,z i )'s magnetic induction intensity.

[0133] Step 3.1.3, randomly select i points on the plane of the transmitting coil, here let i=50, that is, randomly select 50 points on the plane of the transmitting coil, and calculate the magnetic induction intensity of the first layer transmitting coil and the second layer transmitting coil at these 50 points respectively.

[0134] Step 3.1.4, find a set of suitable (d1, W1, N1, d2, W2, N2) values ​​that satisfy the optimization target model and obtain the minimum value, that is, there is a set of suitable (d1, W1, N1, d2, W2, N2) values ​​so that the magnetic induction intensity generated by the first layer of transmitting coils at 50 points is approximately equal, and the magnetic induction intensity generated by the second layer of transmitting coils at 50 points is approximately equal.

[0135] Step 3.1.5, through optimization, it can be found that when d1 = 2, W1 = 8, N1 = 5, d2 = 0.2, W2 = 4.8, N2 = 25, the magnetic induction intensity generated by the first layer of transmitting coils at 50 points is approximately equal, and the magnetic induction intensity generated by the second layer of transmitting coils at 50 points is approximately equal. The configuration of the transmitting coil is as follows Figure 3 shown.

[0136] Step 3.2, using finite element simulation software to calculate the magnetic field distribution of the transmitting coil on the transmitting coil plane, the magnetic flux density modulus distribution of a section line on the plane, and the mutual inductance of the receiving coil.

[0137] Step 3.2.1, Figure 5 The magnetic field distribution when the distance between the transmitting coil and the receiving coil is R = 5cm is simulated. The darker the red, the stronger the magnetic induction intensity. The darker the blue, the weaker the magnetic induction intensity. Green indicates a better magnetic induction field. As shown in the figure, the magnetic field distribution of the transmitting coil on the plane of the receiving coil shows a trend of strong magnetic field in the middle and weak magnetic field in the outer part. The magnetic field distribution is relatively uniform.

[0138] Step 3.2.2, Figure 6 The magnetic flux density modulus distribution on a section line obtained by simulation when the plane distance between the transmitting coil and the receiving coil is R = 5cm. The section line is fixed at X = 0, Z = 5, and Y changes from 0 to 30 (unit: cm). The horizontal axis of the curve is the change in Y, and the vertical axis is the magnitude of the magnetic flux density modulus. It can be seen from the figure that the overall fluctuation of the magnetic flux density modulus is not large. Taking the horizontal axis 5-25 as a reference, the magnetic flux density modulus fluctuates by about 2% within this range.

[0139] Step 3.2.3, Figure 7 The figure is a graph of the system mutual inductance when the receiving coil is horizontally offset. The horizontal axis is the offset distance (cm) and the vertical axis is the mutual inductance (μH). The receiving coil is initially coaxial with the transmitting coil, that is, the receiving coil is horizontally offset with the center of the transmitting coil as the origin. It can be seen from the graph that when the receiving coil is horizontally offset relative to the transmitting coil, the mutual inductance fluctuation between the receiving coil and the transmitting coil is small, and the mutual inductance fluctuation is only 5% when the receiving coil is offset by 5cm.

[0140] According to the simulation results, the combined planar spiral transmitting coil can generate a relatively uniform magnetic field on the plane of the receiving coil, and can still maintain good mutual inductance during the horizontal offset of the receiving coil relative to the transmitting coil of the wireless charging system, thereby improving the coupling degree of the system coupling mechanism and ensuring the maximum stable operation of the system.

[0141] The above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principle of the present invention, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A design method for a transmitting coil in an electric vehicle wireless charging system, wherein the electric vehicle wireless charging system is composed of a wireless charging transmitting module and a wireless charging receiving module connected wirelessly; the wireless charging transmitting module is laid on the road where the electric vehicle is traveling; the wireless charging receiving module is installed in the electric vehicle; the wireless charging transmitting module includes a DC input power supply, a high-frequency inverter circuit, a transmitting SS compensation circuit, transmitting coil; the wireless charging receiving module includes a receiving coil, a receiving SS Compensation circuit, rectification circuit, load resistance; The launch SS The compensation circuit includes a transmitting series loop formed by connecting a transmitting resonant compensation capacitor, a transmitting coil self-inductance, and a transmitting coil equivalent resistance in sequence; The reception SS The compensation circuit includes a receiving series loop composed of a receiving resonance compensation capacitor, a receiving coil self-inductance, and a receiving coil equivalent resistance connected in sequence; It is characterized in that include: An equivalent circuit model of the system is established based on the input voltage of the system, the self-inductance, equivalent resistance and compensation capacitance of the transmitting coil, the self-inductance, equivalent resistance and compensation capacitance of the receiving coil, and the load resistance; a mathematical model of the magnetic induction intensity generated by the transmitting coil at any point on the plane of the receiving coil is established; Construct an optimization target model based on the mathematical model of the magnetic induction intensity generated by the system transmitting coil at any point on the receiving coil plane; establish the constraint conditions of the optimization target model; The minimization of the optimization target model is taken as the optimization goal, and the number of turns, turn spacing and coil width of the transmitting coil are determined in combination with the constraints of the optimization target model.

2. The design method according to claim 1, characterized in that: The mathematical model of the magnetic induction intensity generated by the transmitting coil at any point on the receiving coil plane is defined as: Among them, the transmitting coil and the receiving coil are placed coaxially and parallel. is the side length of the system transmitting coil, is the current flowing through the transmitting coil loop, is the value of any point on the receiving coil plane Axis coordinates, is the point on the receiving coil plane Axis coordinates, is the point on the receiving coil plane Axis coordinates, is the unit vector of any line element on the edge of the transmitting coil pointing to the point on the plane of the receiving coil. Axis component, is the magnetic permeability of vacuum.

3. The design method according to claim 2, characterized in that: The optimization target model is defined as: in, For the The transmitting coil is located at any point in the plane of the receiving coil. The magnetic induction intensity, For the The transmitting coil is located at any point in the plane of the receiving coil. The magnetic induction intensity, and is an integer, and is an integer, is the turn spacing of the first layer transmitting coil, is the width of the first layer transmitting coil, is the number of turns of the first layer transmitting coil, For the The turn spacing of the transmitting coil, For the Layer transmitting coil width, For the The number of turns of the transmitting coil.

4. The design method according to claim 3, characterized in that: The constraints of the optimization target model are defined as: in, is the side length of the system receiving coil, is the distance between the transmitting coil and the receiving coil.

5. The design method according to claim 3, characterized in that: Determine the number of turns, turn spacing and coil width of the combined planar spiral structure transmitting coil. The specific process is as follows: Step 1.1, assume the number of turns of the first layer transmitting coil is , then the side length of the first turn of the first-layer transmitting coil is , the side length of the second turn is ,…,No. The side length is , the receiving coil is a single-turn test coil, the first-layer transmitting coil and the receiving coil are coaxial and parallel, then the first-layer transmitting coil is at any point in the plane of the receiving coil ( and is an integer) is: … in, The first turn of the first layer of transmitting coil is any point on the plane of the receiving coil. The magnetic induction intensity, The second turn of the first layer transmitting coil is at the same point on the plane of the receiving coil. The magnetic induction intensity, For the first layer of transmitting coil The turns are at the same point on the plane of the receiving coil The magnetic induction intensity; Step 1.2, assume that the turn spacing of the second layer transmitting coil is , the width of the second transmitting coil is , the number of turns of the second layer transmitting coil is , then the side length of the first turn of the second-layer transmitting coil is , the side length of the second turn is ,…,No. The side length is , the receiving coil is a single-turn test coil, the second-layer transmitting coil is coaxially parallel to the receiving coil, then the second-layer transmitting coil is on any point on the same receiving coil plane The magnetic induction intensity is: … in, The first turn of the second-layer transmitting coil is any point on the same receiving coil plane. The magnetic induction intensity, The second turn of the second transmitting coil is at the same point on the same receiving coil plane. The magnetic induction intensity, For the second layer of transmitting coil The turns are on the same receiving coil plane at the same point The magnetic induction intensity; Step 1.3, suppose The turn spacing of the transmitting coil is , No. The width of the transmitting coil is , No. The number of turns of the transmitting coil is , then The side length of the first turn of the transmitting coil is , the side length of the second turn is ,…,No. The side length is , the receiving coil is a single-turn test coil, The transmitting coil and receiving coil are coaxial and parallel. Layer transmitting coil at any point on the same receiving coil plane The magnetic induction intensity is: … in, For the The first turn of the transmitting coil is at any point on the same receiving coil plane. The magnetic induction intensity, For the The second turn of the transmitting coil is on the same plane of the receiving coil at the same point The magnetic induction intensity, For the Transmitting coil The turns are on the same receiving coil plane at the same point The magnetic induction intensity; Step 1.4, take any ( and is an integer) points, respectively calculate the first layer of transmitting coils, the second layer of transmitting coils... The magnetic induction intensity of the transmitting coil at each point; Step 1.5, find a suitable set of ( ) value, satisfying the optimization target model to obtain the minimum value, that is, there is a set of suitable ( ) is selected so that the magnetic induction intensity generated by the first layer of transmitting coils at each point is approximately equal, and the magnetic induction intensity generated by the second layer of transmitting coils at each point is approximately equal, ..., The magnetic induction intensity generated by the transmitting coil at each point is approximately equal.

6. The design method according to claim 1, characterized in that: The transmitting coil is a planar spiral coil composed of two parts of several square coils with equal spacing. The entire coil is wound by a single Litz wire. The turn spacing in the central part of the coil is equal, and the turn spacing on the outer side is equal and smaller than the central part.

7. The design method according to claim 6, characterized in that: The receiving coil is a planar spiral coil composed of a number of square coils with equal spacing, and the entire coil is wound by a single Litz wire.

Images