A short-distance transmitting coil structure applied to a three-phase dynamic wireless power supply system

Abstract

The present invention provides a short-distance transmitting coil structure applied to a three-phase dynamic wireless power supply system. The structure is used to solve the problem of large fluctuations in induced voltage in a three-phase dynamic wireless charging system. The structure of the present invention uses a short-distance transmitting coil to eliminate the harmonic traveling wave magnetic field generated by the three-phase transmitting coil, so that the plane where the receiving end is located mainly contains a fundamental wave traveling wave magnetic field, and the amplitude of the induced voltage of the receiving coil is basically unchanged during the movement process, thereby effectively suppressing the voltage fluctuation of the output in the three-phase dynamic wireless power supply system and realizing the constancy of the output voltage.

Description

Technical Field

[0001] The present invention belongs to the technical fields of wireless power transmission and rail transit, and particularly relates to a short-distance transmitting coil structure applied to a three-phase dynamic wireless power supply system. Background Technique

[0002] Compared with the traditional wired power supply method, the non-contact feature of the wireless power supply method has advantages in terms of safety and convenience. With the continuous progress and improvement of the wireless power transmission technology, its applications are increasing, starting from small-power devices such as toothbrushes, mobile phones, and computers and moving towards high-power devices such as cars and ships. The wireless power supply method can be further divided into static wireless power supply and dynamic wireless power supply according to whether the transmitting end and the receiving end are in a relatively moving state. For the dynamic wireless power supply method, the receiving side can achieve uninterrupted energy transmission during the movement process, which provides a new solution to the problem of short battery life of electric vehicles, that is, electric energy can be replenished during the movement process.

[0003] Research institutions at home and abroad have conducted many studies on the dynamic wireless power supply system. The three-phase wireless power supply better solves the problem of generally low wireless power supply power levels. During the charging process, the receiving end will continuously move, resulting in continuous changes in the coupling mutual inductance between the transmitting coil and the receiving coil, and further causing fluctuations in the output power. Large fluctuations in the output power will bring many negative impacts to the system, such as stress problems of devices such as switches at the receiving end, component life problems, and system stability problems.

[0004] The short-distance transmitting coil structure described in the present invention can suppress the harmonic components of the traveling wave magnetic field generated at the receiving end plane of the three-phase dynamic wireless power supply system by reasonably designing the length value of the short-distance transmitting coil, and can achieve the stability of the system output power, fundamentally solving the problems caused by the power fluctuations. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem of large fluctuations in the induced voltage in the three-phase dynamic wireless charging system, and a short-distance transmitting coil structure applied to a three-phase dynamic wireless power supply system is proposed.

[0006] The present invention is realized through the following technical solutions. The present invention proposes a short-distance transmitting coil structure applied to a three-phase dynamic wireless power supply system. In this structure, a single-phase transmitting coil is equivalently regarded as being composed of multiple rectangular coils with a coil length l T arranged in an array along the x-axis direction, and the distance △x between two adjacent transmitting coils T =τ - l T ; the center distance between two adjacent rectangular coils is τ, and two adjacent transmitting coils are connected by wires; by reasonably designing the length l of the short-distance transmitting coil T, it can eliminate the harmonic traveling magnetic field of the transmitting coil in the receiving end plane, achieving the purpose of suppressing the fluctuation of the output power in the three-phase dynamic wireless power supply system.

[0007] Furthermore, the length l of the short-pitch transmitting coil T The design method is specifically as follows: Taking the coil of phase A in the three-phase short-pitch structure as an example, when a direct current i a＝ I0 is passed through it, the fundamental wave and the i-th harmonic magnetic field are generated by the coil of phase A in the receiving end plane;

[0008] For the fundamental wave magnetic field, the magnetic fields generated by the wire numbered 1 and the wire numbered 2 are distributed at a distance of (τ - l T ) along the x-axis direction, and the phase difference is θ1, where θ1 is related to the coil length l T and satisfies:

[0009]

[0010] From the geometric relationship shown in the magnetic field phasor diagram, it can be known that the amplitude of the fundamental wave magnetic field B z-A1 satisfies:

[0011]

[0012] where N T is the number of turns of the equivalent rectangular coil, B z-1 is the amplitude of the fundamental wave traveling magnetic field generated by a single coil at the receiving end, and the expression of k sT-1 satisfies:

[0013]

[0014] It is easy to prove that k sT-1 ≤1. Define k sT-1 as the fundamental wave short-pitch coefficient at the transmitting end, which is used to represent the degree of attenuation of the amplitude of the fundamental wave magnetic field B z-A1 after using the short-pitch coil at the transmitting end; where the subscript sT represents Short-pitch transmitter coil, that is, the short-pitch transmitting coil, and the number represents the harmonic order of the traveling magnetic field;

[0015] Similarly, the phase angle θ i by which the i-th harmonic magnetic fields generated by the wire numbered 1 and the wire numbered 2 differ along the x-axis direction satisfies:

[0016]

[0017] According to the geometric relationship shown in the magnetic field phasor diagram, the amplitude of the i-th harmonic magnetic field B z-Ai in the short-pitch transmitting coil satisfies:

[0018]

[0019] where k sT-i satisfies the expression:

[0020]

[0021] Define k sT-i as the short - pitch coefficient of the i - th harmonic at the transmitting end. After using a short - pitch coil at the transmitting end, the amplitude attenuation of the magnetic field B of the i - th harmonic z-A1 is as follows:

[0022] To eliminate the magnetic field B of the i - th harmonic z-A1 , k sT-i should satisfy: k sT-i = 0, and the solution is:

[0023]

[0024] In summary, by reasonably designing the length l T of the short - pitch transmitting coil, the purpose of eliminating the magnetic field of the i - th harmonic and suppressing the output fluctuation can be achieved.

[0025] Furthermore, the current flow directions of two adjacent rectangular coils of the short - pitch transmitting coil are the same.

[0026] Furthermore, if it is intended to eliminate the fifth - harmonic magnetic field generated by the transmitting coil, the length of the short - pitch transmitting coil in this structure is designed as where m = 1, 2, 3…n, and n is a positive integer greater than or equal to 1.

[0027] Furthermore, if it is intended to eliminate the seventh - harmonic magnetic field generated by the transmitting coil, the length of the short - pitch transmitting coil in this structure is designed as where m = 1, 2, 3…n, and n is a positive integer greater than or equal to 1.

[0028] Furthermore, if it is intended to simultaneously weaken the fifth - harmonic magnetic field and the seventh - harmonic magnetic field generated by the transmitting coil, the length of the short - pitch transmitting coil in this structure is designed as where m = 1, 2, 3…n, and n is a positive integer greater than or equal to 1.

[0029] Furthermore, to maximize the output voltage, the length of the transmitting - end coil should be close to the pole pitch τ, that is, the selection of m should be such that l T is as close as possible to the pole pitch τ. Since the harmonic order i is odd, it should be made that: The length l of the short - pitch transmitting coil T is:

[0030]

[0031] Advantages of the present invention:

[0032] (1) The structure described in the present invention can ensure that the third harmonic of the traveling wave magnetic field generated in space is zero;

[0033] (2) If the length of the rectangular coil in this structure is designed as where m = 1, 2, 3... n, and n is a positive integer greater than or equal to 1; at this time, the amplitude of the fifth harmonic of the traveling wave magnetic field in the plane where the receiving coil is located is 0, then the fifth harmonic magnetic field generated in the receiving end plane can also be eliminated. During the movement of the receiving end along with the charging device, the induced electromotive force no longer contains the fifth harmonic content, and the output voltage of the system is more stable;

[0034] (3) If the length of the rectangular coil in this structure is designed as where m = 1, 2, 3... n, and n is a positive integer greater than or equal to 1; at this time, the amplitude of the seventh harmonic of the traveling wave magnetic field in the plane where the receiving coil is located is 0, then the seventh harmonic magnetic field generated in the receiving end plane can also be eliminated. During the movement of the receiving end along with the charging device, the induced electromotive force no longer contains the seventh harmonic content, and the output voltage of the system is more stable;

[0035] (4) If the length of the rectangular coil in this structure is designed as where m = 1, 2, 3... n, and n is a positive integer greater than or equal to 1; at this time, the amplitude of the seventh harmonic of the traveling wave magnetic field in the plane where the receiving coil is located is 0, then the fifth and seventh harmonic magnetic fields generated in the receiving end plane can be simultaneously suppressed. During the movement of the receiving end along with the charging device, the fifth harmonic content and the seventh harmonic content of the induced electromotive force both decrease, and the output voltage of the system is more stable. Description of the Drawings

[0036] Figure 1 is a schematic diagram of the structure of a traditional meandering type transmitting coil. Among them, (a) is a single-phase structure, and (b) is a three-phase structure.

[0037] Figure 2 is a schematic diagram of the structure of a short-pitch transmitting coil. Among them, (a) is a single-phase structure, and (b) is a three-phase structure.

[0038] Figure 3 is the B z distribution and its phasor diagram generated by the A-phase short-pitch transmitting coil in the receiving end plane.

[0039] Figure 4 is the relationship diagram of the short-pitch coefficient k sT -i of the transmitting end varying with the length l T of the transmitting coil. Detailed Embodiments

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The present invention provides a transmitting coil structure applied to a three-phase dynamic wireless power supply system and capable of making the induced voltage at the receiving end constant, so as to solve the problem of large fluctuation of the induced voltage in the three-phase dynamic wireless charging system. The structure of the present invention uses a short-pitch transmitting coil to eliminate the harmonic traveling magnetic field generated by the three-phase transmitting coil, so that the plane where the receiving end is located mainly contains the fundamental wave traveling magnetic field, and the amplitude of the induced voltage of the receiving coil is basically unchanged during the movement process, thereby effectively suppressing the fluctuation of the output voltage in the three-phase dynamic wireless power supply system and realizing the constancy of the output voltage.

[0042] Single-phase and three-phase meandering coils are as Figure 1 shown, and their winding method is the tail-swinging method along the x-axis (traveling direction), and each phase is staggered from each other, and the staggering distance is one-third of the period, and it can be equivalent to four tightly connected rectangular coils with a length l T =τ. In the three-phase coil structure applicable to dynamic wireless power supply in the present invention, the coil first winds a coil with a length of l T and a width of w T , then leads out a length of τ along the x-axis from the input end side (positive y-axis side), and continues to wind a coil with a length of l T and a width of w T , and then winds in the same way in turn. It can be found that the center distance and pole pitch of the two coils are τ, and the pole pitch is greater than the coil length, and at the same time, the current directions on the outer sides of two adjacent rectangular coils are the same. If multiple turns are laid for each coil, they should be laid tightly. By designing the length l T of each rectangular distance, better performance can be obtained.

[0043] The short-pitch transmitting coil applied to the dynamic three-phase wireless power supply system described in the present invention can be, but is not limited to, installed under the ground; the schematic diagrams of the single-phase short-pitch coil and the three-phase short-pitch coil are as Figure 2 shown.

[0044] Combined with Figures 1 - 4 , the present invention proposes a short-pitch transmitting coil structure applied to a three-phase dynamic wireless power supply system. In the structure, the single-phase transmitting coil is equivalently regarded as being formed by arranging a plurality of rectangular coils with a coil length l T <τ along the x-axis direction, and the spacing △x T between two adjacent transmitting coils T; The center distance between two adjacent rectangular coils is τ, and two adjacent transmitting coils are connected by the blue dashed-line wires in the figure; By reasonably designing the length l of the short-pitch transmitting coil T , the harmonic traveling magnetic field of the transmitting coil in the receiving-end plane can be eliminated, achieving the purpose of suppressing the fluctuation of the output power in the three-phase dynamic wireless power supply system. In any plane parallel to the transmitting coil, the generated traveling magnetic field only has odd harmonics, and the 3rd harmonic magnetic fields of the three-phase wireless power supply system will cancel each other out in space.

[0045] The length l of the short-pitch transmitting coil mentioned above T The specific design method is as follows: Taking the coil of phase A in the three-phase short-pitch structure as an example, when a direct current i a = I0 is applied to this coil, the fundamental wave and the i-th harmonic magnetic fields are generated by the coil of phase A in the receiving-end plane; As Figure 3 shown.

[0046] For the fundamental wave magnetic field, the magnetic fields generated by the wire numbered 1 and the wire numbered 2 are distributed at a distance of (τ - l T ) along the x-axis direction, and the phase difference is θ1, where θ1 is related to the coil length l T , and satisfies:

[0047]

[0048] From the geometric relationship shown in the magnetic field phasor diagram, it can be known that the amplitude of the fundamental wave magnetic field B z-A1 satisfies:

[0049]

[0050] Where N T is the number of turns of the equivalent rectangular coil, B z-1 is the amplitude of the fundamental wave traveling magnetic field generated by a single coil at the receiving end, and the expression of k sT-1 satisfies:

[0051]

[0052] It is easy to prove that k sT-1 ≤1. Define k sT-1 as the fundamental wave short-pitch coefficient at the transmitting end, which is used to represent the attenuation degree of the amplitude of the fundamental wave magnetic field B z-A1 after using the short-pitch coil at the transmitting end; where the subscript sT represents Short-pitch transmitter coil, that is, the short-pitch transmitting coil, and the number represents the harmonic order of the traveling magnetic field;

[0053] Similarly, it can be obtained that the phase angle θ i by which the i-th harmonic magnetic fields generated by the wire numbered 1 and the wire numbered 2 differ along the x-axis direction satisfies:

[0054]

[0055] According to the geometric relationship shown in the magnetic field phasor diagram, the amplitude of the \(i\)-th harmonic magnetic field \(B\) in the short-pitched transmitting coil can be obtained as follows: z-Ai satisfies:

[0056]

[0057] where \(k\) sT-i has an expression that satisfies:

[0058]

[0059] Define \(k\) sT-i as the \(i\)-th harmonic short-pitch coefficient at the transmitting end, which represents the amplitude attenuation of the \(i\)-th harmonic magnetic field \(B\) z-A1 after using a short-pitched coil at the transmitting end;

[0060] To eliminate the \(i\)-th harmonic magnetic field \(B\) z-A1 , \(k\) sT-i should satisfy: \(k\) sT-i = 0, and the solution is:

[0061]

[0062] In summary, by reasonably designing the length \(l\) T of the short-pitched transmitting coil, the purpose of eliminating the \(i\)-th harmonic magnetic field and suppressing the output fluctuation can be achieved.

[0063] In the process of designing the three-phase short-pitched transmitting coil of the wireless power supply system, in order to achieve the optimal output fluctuation suppression effect, the transmitting coil should be designed to eliminate the 5th harmonic magnetic field. The length of the short-pitched transmitting coil affects both the amplitude of the harmonic magnetic field related to the output voltage fluctuation and the amplitude of the fundamental magnetic field. From the above working principle, it can be seen that the influence of the transmitting coil length on the harmonic magnetic field in the plane where the receiving end is located is reflected in the short-pitch coefficient. Figure 4 The variation relationships of the short-pitch coefficients \(k\) sT-1 and \(k\) sT-i at the transmitting end with the coil length \(l\) T are given. It can be known that:

[0064] (1) When the 5th harmonic magnetic field generated in the receiving end plane needs to be eliminated, the length \(l\) T of the short-pitched transmitting coil is designed as: where \(m = 1, 2, 3 \cdots n\), and \(n\) is a positive integer greater than or equal to 1; at this time, the amplitude of the 5th harmonic of the traveling wave magnetic field in the plane where the receiving coil is located is 0, and the 5th harmonic content in the induced electromotive force at the receiving end is zero. The output voltage is mainly affected by the fundamental magnetic field. During the movement of the charging device at the receiving end, there is no longer 5th harmonic content in the induced electromotive force, and the output voltage of the system is more stable;

[0065] (2) When eliminating the 7th harmonic magnetic field generated in the receiving end plane, the length l of the short-pitch transmitting coil T is designed as: where m = 1, 2, 3…n, and n is a positive integer greater than or equal to 1; at this time, the amplitude of the 7th harmonic of the traveling wave magnetic field in the plane where the receiving coil is located is 0, and the 7th harmonic content in the induced electromotive force at the receiving end is zero. During the movement of the receiving end along with the charging device, there is no longer 7th harmonic content in the induced electromotive force, and the output voltage of the system is more stable;

[0066] (3) When suppressing both the 5th harmonic magnetic field and the 7th harmonic magnetic field generated by the single-phase transmitting coil simultaneously, the length l of the short-pitch transmitting coil T is designed as: where m = 1, 2, 3…n, and n is a positive integer greater than or equal to 1. At this time, both the 5th harmonic magnetic field and the 7th harmonic magnetic field generated by the short-pitch transmitting coil in the receiving end plane will be suppressed, and the harmonic induced voltage generated in the receiving coil will also be suppressed, thereby achieving the purpose of suppressing the output voltage fluctuation of the system; similarly, when both the i-th harmonic component and the (i + 2)-th harmonic component in the magnetic field generated by the single-phase transmitting coil need to be suppressed, the length l of the short-pitch transmitting coil T is designed as: where m = 1, 2, 3…n, and n is a positive integer greater than or equal to 1. At this time, the short-pitch transmitting coil can suppress both the i-th harmonic magnetic field and the (i + 2)-th harmonic magnetic field generated in the receiving coil plane, achieving the purpose of suppressing the output voltage fluctuation of the system;

[0067] (4) When the magnetic field generated by the single-phase transmitting coil simultaneously contains harmonic components such as the i-th, (i + 2)-th, (i + 4)-th, (i + 6)-th, etc., since the higher the harmonic order, the smaller the amplitude of the harmonic induced voltage generated by the harmonic magnetic field in the receiving coil, the length l of the short-pitch transmitting coil T should be selected with the main purpose of suppressing low-order harmonics, and the length l of the short-pitch transmitting coil T is designed as: where m = 1, 2, 3…n, and n is a positive integer greater than or equal to 1.

[0068] In practical applications, in order to maximize the output voltage, the length of the transmitting coil at the transmitting end should be close to the pole pitch τ, that is, the selection of m should be such that l T is as close as possible to the pole pitch τ. Since the harmonic order i is odd, it should be made:

[0069] The length l of the short-pitch transmitting coil T is:

[0070]

[0071] In the application, it should be noted that the winding direction needs to ensure that the current flow directions of two adjacent rectangles of the short-pitch coil are the same.

[0072] The above has introduced in detail a short-pitch transmitting coil structure applied to a three-phase dynamic wireless power supply system. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A short - distance transmitting coil structure applied to a three - phase dynamic wireless power supply system, characterized in that: In the said structure, the single-phase transmitting coil is equivalently regarded as being composed of multiple rectangular coils with a coil length l T <τ, which are arranged in an array along the x-axis direction. The distance △x between two adjacent transmitting coils T = τ - l T ; the center distance between two adjacent rectangular coils is τ, and two adjacent transmitting coils are connected by wires; by reasonably designing the length l of the short-pitch transmitting coil T , the harmonic traveling magnetic field of the transmitting coil in the receiving end plane can be eliminated, and the purpose of suppressing the fluctuation of the output power in the three-phase dynamic wireless power supply system can be achieved; The length l of the short - pitch transmitting coil T The design method is specifically as follows: For the phase - A coil in the three - phase short - pitch structure, when a direct current i a = I0 is passed through this coil, the fundamental - wave and i - th harmonic magnetic fields are generated by the phase - A coil on the receiving - end plane; For the fundamental magnetic field, the magnetic fields generated by the wires numbered 1 and numbered 2 are distributed along the x-axis with a difference of (τ - l T ), and the phase difference is θ1, where θ1 is related to the coil length l T and satisfies: From the geometric relationship shown in the magnetic field phasor diagram, the amplitude of the fundamental magnetic field B z-A1 satisfies: where N T is the number of turns of the equivalent rectangular coil, B z-1 is the amplitude of the fundamental traveling wave magnetic field generated by a single coil at the receiving end, and the expression of k sT-1 satisfies: where k sT-1 ≤ 1, k sT-1 is defined as the fundamental short-pitch coefficient of the transmitter, which is used to represent the degree of amplitude attenuation of the fundamental magnetic field B z-A1 after using short-pitch coils at the transmitter end. The subscript sT represents Short-pitch transmitter coil, that is, short-pitch transmitting coil, and the number represents the harmonic order of the traveling magnetic field; Similarly, the phase angle difference θ of the i-th harmonic magnetic field generated by the wires numbered 1 and 2 along the x-axis can be obtained. i Satisfy: According to the geometric relationship shown in the magnetic field phasor diagram, the amplitude of the i-th harmonic magnetic field B in the short-pitch emitting coil satisfies: z-Ai ​ where k sT-i has an expression that satisfies: Define k sT-i as the short - pitch coefficient of the i - th harmonic at the transmitting end, indicating the amplitude attenuation of the i - th harmonic magnetic field B z-A1 after using a short - pitch coil at the transmitting end; In order to eliminate the i-th harmonic magnetic field B z-A1 , k sT-i should satisfy: k sT-i = 0, and the solution is: By reasonably designing the length l of the short-distance transmitting coil T , the purpose of eliminating the i-th harmonic magnetic field and suppressing the output fluctuation can be achieved.

2. The structure according to claim 1, characterized in that, The current flow directions of two adjacent rectangular coils of the short-distance transmitting coil are the same.

3. The structure according to claim 1, characterized in that, If in order to eliminate the fifth harmonic magnetic field generated by the transmitting coil, the length of the short-pitch transmitting coil in this structure is designed as where m = 1, 2, 3... n, and n is a positive integer greater than or equal to 1.

4. The structure according to claim 1, characterized in that, If in order to eliminate the seventh harmonic magnetic field generated by the transmitting coil, the length of the short-pitch transmitting coil in this structure is designed to be where m = 1, 2, 3…n, and n is a positive integer greater than or equal to 1.

5. The structure according to claim 1, characterized in that, If in order to simultaneously weaken the fifth-harmonic magnetic field and the seventh-harmonic magnetic field generated by the transmitting coil, the length of the short-pitch transmitting coil in this structure is designed as where m = 1, 2, 3... n, and n is a positive integer greater than or equal to 1.

6. The structure according to claim 1, characterized in that, To maximize the output voltage, the length of the transmitting coil should be close to the pole pitch τ, that is, the value of m should be selected such that l T is as close as possible to the pole pitch τ. Since the harmonic order i is odd, it should be made that: The length l of the short-pitch transmitting coil T is:

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