Wireless power transfer coupling mechanism for rail transit

Abstract

This invention provides a wireless power transmission coupling mechanism for rail transit, comprising a primary iron core, a power supply cable, a U-shaped secondary iron core, and a secondary coil. The primary iron core is fixedly connected between two tracks and extends longitudinally along the tracks. The power supply cable is laid on the primary iron core along its extension direction and is used to pass alternating current to generate an alternating magnetic field. The U-shaped secondary iron core is fixedly connected to the bottom of the vehicle with its opening facing downwards or upwards. The secondary coil is wound on the secondary iron core and is used for mutual inductive coupling with the power supply cable to obtain electrical energy. The secondary iron core spans across the primary iron core or is placed longitudinally to the side of the primary iron core, and corresponding parts of the secondary iron core and the primary iron core form an approximately circular magnetic path to guide and converge magnetic field lines. The wireless power transmission coupling mechanism for rail transit provided by this invention can solve the coupling attenuation problem, reduce energy waste, and improve wireless power transmission efficiency.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission technology for rail vehicles, and specifically relates to a wireless power transmission coupling mechanism for rail transit. Background Technology

[0002] With the rapid development of the urban rail transit industry, more and more trams are beginning to adopt electromagnetic induction coupling wireless power transfer technology. Specifically, electromagnetic induction coupling wireless power transfer technology is based on the principle of electromagnetic induction. The wireless power transmission system mainly consists of five parts: DC power bus, high-frequency inverter, resonant compensation circuit, electromagnetic coupling mechanism, and on-board converter. Among them, the electromagnetic coupling mechanism is the key mechanism for realizing wireless power transfer between the track and the vehicle.

[0003] Electromagnetic coupling mechanisms used in rail transit consist of a primary side device and a secondary side device. The primary side device is laid on the guide rail, and the secondary side device is laid on the tram. When alternating current is applied to the primary side device, an alternating magnetic field is generated that passes through the secondary side device, resulting in mutual inductive coupling. This allows the secondary side device to obtain alternating current of the same frequency, thus realizing wireless transmission of electrical energy.

[0004] Currently, in the field of urban rail transit, since the air gap under the vehicle inevitably fluctuates frequently within the normal range during vehicle operation, in order to avoid collisions or frictional interference between the primary and secondary devices during the vertical displacement of the vehicle, the primary and secondary devices are usually directly coupled by tightly wound coils. However, this results in a low coupling coefficient between the primary and secondary devices. Especially during the vertical displacement of the vehicle, there will be obvious mutual inductance coupling attenuation between the primary and secondary devices, which will lead to a large waste of electrical energy and affect the efficiency of wireless power transmission. Summary of the Invention

[0005] This invention provides a wireless power transmission coupling mechanism for rail transit, which aims to solve the problem of mutual inductance coupling attenuation caused by frequent floating of the air gap under the vehicle during operation, reduce power waste, and improve wireless power transmission efficiency.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a wireless power transmission coupling mechanism for rail transit, comprising:

[0007] The primary iron core is used to fix the connection between the two rails and extends longitudinally along the rails.

[0008] The power supply cable is laid on the primary iron core along the extension direction of the primary iron core and is used to pass alternating current to generate an alternating magnetic field.

[0009] The U-shaped secondary iron core is used to fix the bottom of the vehicle with the opening facing down or up.

[0010] The secondary coil, wound on the secondary iron core, is used for mutual inductive coupling with the power supply cable to obtain electrical energy.

[0011] The secondary iron core spans across the primary iron core or stands vertically to the side of the primary iron core. The corresponding parts of the secondary iron core and the primary iron core form an approximately circular magnetic path to guide and gather magnetic field lines.

[0012] In one possible implementation, a winding portion protruding horizontally outward is integrally formed on one of the vertical sidewalls of the primary core, and the power supply cable is laid on the winding portion in a DD-type winding manner; the secondary core is placed vertically on the side of the winding portion, and the secondary coil is wound in a DD-type winding manner.

[0013] In some embodiments, the vertical dimension of the secondary core is greater than the maximum design float of the under-vehicle air gap.

[0014] For example, the winding part is square wave sawtooth type, and the power supply cable is wound into a DD type coil unit on each outward convex sawtooth. The secondary coil is wound on the two side legs of the secondary iron core and is orthogonal to the DD type coil unit.

[0015] For example, the power supply cable is laid in two parallel lines above and below the winding section, and both parallel lines are square-wave shaped and pass around each of the protruding saw teeth on the winding section in sequence.

[0016] In one possible implementation, the power supply cable extends linearly against the top wall of the primary iron core, and the secondary iron core crosses over the primary iron core with its opening facing downwards.

[0017] In some embodiments, the secondary coil is wound on the portion between the two limbs of the secondary core.

[0018] For example, the U-shaped opening of the secondary core in the vertical direction is larger than the maximum design fluctuation of the air gap under the vehicle.

[0019] In some embodiments, there is a lateral gap between the secondary core and the primary core.

[0020] In some embodiments, the primary iron core is a segmented structure arranged in sequence, wherein each segment is provided with a power supply cable, or multiple adjacent segments are provided with a power supply cable.

[0021] The beneficial effects of the wireless power transmission coupling mechanism for rail transit provided by this invention are as follows: Compared with the prior art, the wireless power transmission coupling mechanism for rail transit of this invention, with the U-shaped secondary iron core facing upwards or downwards across the primary iron core, or vertically placed on the side of the primary iron core, can form an approximately circular magnetic path with the primary iron core. This allows most of the magnetic flux in the magnetic field generated after the power supply cable is supplied with alternating current to pass through the secondary coil, thereby increasing the mutual inductance coupling coefficient between the primary and secondary sides, reducing leakage flux, and simultaneously ensuring that the secondary iron core... Whether the secondary coil is placed horizontally across the primary core to utilize the vertical U-shaped depth of the secondary core, or vertically placed to the side of the primary core to utilize the overall vertical height of the secondary core, both methods ensure that the secondary coil always forms an approximately circular magnetic path with the primary core when it undergoes vertical displacement due to the floating of the air gap under the vehicle during vehicle operation. This avoids mutual inductive coupling attenuation between the secondary coil and the power supply cable caused by frequent floating of the air gap under the vehicle, thereby reducing energy waste and improving wireless power transmission efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the axonal structure of a wireless power transmission coupling mechanism for rail transit provided in Embodiment 1 of the present invention;

[0023] Figure 2 This is a front view schematic diagram of a wireless power transmission coupling mechanism for rail transit provided in Embodiment 1 of the present invention;

[0024] Figure 3 This is a schematic diagram of the axonal structure of the wireless power transmission coupling mechanism for rail transit provided in Embodiment 2 of the present invention;

[0025] Figure 4 This is a front view schematic diagram of the wireless power transmission coupling mechanism for rail transit provided in Embodiment 2 of the present invention;

[0026] Figure 5 This is a schematic diagram of the magnetic circuit model of a wireless power transmission coupling mechanism for rail transit provided in Embodiment 1 of the present invention.

[0027] Figure 6 The magnetic induction intensity distribution diagram of the primary-side device composed of the primary-side iron core and the power supply cable was obtained by simulation experiment in Embodiment 1 of the present invention.

[0028] Figure 7 The magnetic induction intensity distribution diagram of the secondary device consisting of the secondary core and the secondary coil was obtained by simulation experiment in Embodiment 1 of the present invention.

[0029] Figure 8 This is a graph showing the anti-air gap displacement results obtained through simulation experiments in Embodiment 1 of the present invention.

[0030] Figure 9 The magnetic flux density distribution of a conventional coupling mechanism without an iron core under simulation test;

[0031] Figure 10 The magnetic induction intensity distribution of the wireless power transmission coupling mechanism for rail transit provided in Embodiment 2 of the present invention is shown in the simulation test.

[0032] In the diagram: 10, primary iron core; 11, winding section; 20, power supply cable; 30, secondary iron core; 40, secondary coil. Detailed Implementation

[0033] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0034] It should be noted that when an element is referred to as being "set on" another element, it can be directly on or indirectly on the other element. It should be understood that terms such as "length," "width," "depth," "height," "front," "rear," "top," "bottom," "inner," "outer," and "side," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings. In particular, directional descriptions of "horizontal" and "vertical" are based on the extension direction of the track; for example, "horizontal" means perpendicular to the track extension direction, and "vertical" means parallel to the track extension direction. These are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of the invention, "a plurality of" and "several" mean two or more, unless otherwise explicitly specified.

[0035] Please refer to the following: Figures 1 to 10The present invention will now describe the wireless power transmission coupling mechanism for rail transit. The wireless power transmission coupling mechanism for rail transit includes a primary iron core 10, a power supply cable 20, a U-shaped secondary iron core 30, and a secondary coil 40. The primary iron core 10 is fixedly connected between two tracks and extends longitudinally along the tracks. The power supply cable 20 is laid on the primary iron core 10 along its extension direction and is used to pass alternating current to generate an alternating magnetic field. The U-shaped secondary iron core 30 is fixedly connected to the bottom of the vehicle with its opening facing downwards or upwards. The secondary coil 40 is wound around the secondary iron core 30 and is used to inductively couple with the power supply cable 20 to obtain electrical energy. The secondary iron core 30 spans across the primary iron core 10 or is placed longitudinally to the side of the primary iron core 10, and the corresponding parts of the secondary iron core 30 and the primary iron core 10 form an approximately circular magnetic path to guide and converge magnetic field lines.

[0036] It should be understood that, in this embodiment, regarding the manner in which the secondary core 30 spans across the primary core 10, please refer to [reference needed]. Figure 3 and Figure 4 This is equivalent to the primary iron core 10 passing through the U-shaped opening of the secondary iron core 30. During vehicle operation, when the air gap fluctuates, the primary iron core 10 can float up and down within the U-shaped opening. Considering that the secondary iron core 30 needs to maintain an appropriate side gap with the primary iron core 10 as the vehicle moves, the secondary iron core 30 and the primary iron core 10 together form an approximately closed-loop ring structure as a magnetic path. The secondary coil 40 is wound using a conventional winding method, and the power supply cable 20 can be laid directly in a straight line. Moreover, if the opening of the secondary iron core 30 faces upwards, it is preferable to... The power supply cable 20 is attached to the bottom wall of the primary iron core 10. If the opening of the secondary iron core 30 is facing down, it is preferable to attach the power supply cable 20 to the top wall of the primary iron core 10. Considering the convenience of installation, the latter method can be preferred here. The power supply cable 20 is equivalent to the primary coil. When an alternating current is passed through the power supply cable 20, it will generate a relatively discrete ring magnetic flux around itself. Based on the guiding and gathering effect of the primary iron core 10 and the secondary iron core 30 on the discrete magnetic flux, most of the magnetic flux can pass through the secondary coil 40 to achieve efficient mutual inductance coupling.

[0037] Regarding the method of placing the secondary iron core 30 vertically on the side of the primary iron core 10, see [link to relevant documentation]. Figure 1 and Figure 2 The secondary iron core 30 and the primary iron core 10 do not affect each other in the vertical direction. Therefore, in the case of changes in the air gap during vehicle operation, as long as the secondary iron core 30 and the primary iron core 10 have an overlap in the horizontal direction, the integrity of the magnetic path can be ensured, and the mutual inductance coupling effect between the secondary coil 40 and the power supply cable 20 can be improved.

[0038] The wireless power transmission coupling mechanism for rail transit provided in this embodiment, compared with the prior art, allows the U-shaped secondary iron core 30 to span across the primary iron core 10 with its opening facing upwards or downwards, or to stand vertically to the side of the primary iron core 10. This enables it to form an approximately circular magnetic path with the primary iron core 10, thereby guiding most of the magnetic flux in the magnetic field generated after the power supply cable 20 is supplied with alternating current to pass through the secondary coil 40. This improves the mutual inductance coupling coefficient between the primary and secondary sides and reduces magnetic leakage. Furthermore, regardless of whether the secondary iron core 30 is horizontally spanned across the primary iron core 10... Whether the secondary core 30 is used in the vertical direction by utilizing the U-shaped depth of the secondary core 30, or by using the method of vertically placing it on the side of the primary core 10 to utilize the overall height of the secondary core 30 in the vertical direction, it can be ensured that when the secondary coil 40 undergoes vertical displacement due to the floating of the air gap under the vehicle during vehicle operation, it always forms an approximately circular magnetic path with the primary core 10. This avoids the situation of mutual inductive coupling attenuation between the secondary coil 40 and the power supply cable 20 due to frequent floating of the air gap under the vehicle, thereby reducing power waste and improving wireless power transmission efficiency.

[0039] In some embodiments, see Figure 1 and Figure 2 , Figures 5 to 8 One of the vertical side walls of the primary iron core 10 has an integrally formed winding portion 11 that protrudes horizontally outward. The power supply cable 20 is laid on the winding portion 11 in a DD-type winding manner. The secondary iron core 30 is vertically placed on the side of the winding portion 11, and the secondary coil 40 is wound in a DD-type winding manner.

[0040] Specifically, in this embodiment, please refer to Figure 1 The winding part 11 is square wave sawtooth type, and the power supply cable 20 is wound into a DD type coil unit on each outward convex sawtooth. The secondary coil 40 is wound on the two side legs of the secondary iron core 30 and is orthogonal to the DD type coil unit.

[0041] Among them, the power supply cable 20 is arranged in two parallel lines above and below the winding part 11, and the two parallel lines are arranged in a square wave shape and pass around each of the protruding saw teeth on the winding part 11 in sequence.

[0042] The DD-type winding method can obtain a rectangular coil with two circuits connected in parallel and magnetic circuits connected in series. This winding method has the characteristics of high magnetic flux path, unipolar magnetic field, low loss and low leakage, which can improve the mutual inductance coupling coefficient and anti-offset performance. In this case, both the power supply cable 20 and the secondary coil 40 adopt the DD-type winding method. When the vehicle is moving, the secondary iron core 30 passes through each sawtooth on the winding part 11 in sequence. This is equivalent to the secondary coil 40 being mutually inducted with each DD-type coil unit in sequence. Since the power supply cable 20 is continuous, the magnetic field generated on each DD-type coil unit is consistent. Therefore, it can improve the power transmission efficiency while ensuring the stability of wireless power transmission.

[0043] The circular magnetic field in the center of the DD-type coil unit, formed by guiding the power supply cable with a U-shaped secondary iron core, passes through the DD-type coil of the secondary device, forming a good coupling mechanism. This significantly improves the coupling coefficient, thereby greatly increasing the power transmission power and efficiency of the wireless power transmission system. For the relatively large coupling mechanism size in rail trains, a simple analysis can be performed using the magnetic circuit method, as follows:

[0044] Assuming the secondary coil has N1 turns and a current of I, and the primary coil (i.e., the power supply cable) has N2 turns, since the permeability of the iron core is much greater than the permeability of the air gap, the magnetic reluctance of the iron core itself can be ignored. Furthermore, since the magnetic flux passing through the primary coil traverses a relatively small air gap (i.e., the lateral gap), the magnetic reluctance of this portion of the air gap can be denoted as R1, and the magnetic reluctance of the remaining portion of the air gap as R0. This yields the magnetic circuit model of this invention as follows: Figure 5 As shown. The expressions for the magnetomotive force F of the secondary coil and the reluctances R0 and R1 are shown in equations (1) to (7), where:

[0045] μ0 is the vacuum permeability, l1 is the length of the air gap in the magnetic circuit passing through the primary coil, and S1 is the cross-sectional area of ​​the air gap.

[0046] Φ1 is the magnetic flux passing through the primary coil, l0 is the air gap length of the remaining part (i.e., the air gap spacing of the U-shaped iron core of the secondary side), and S0 is the cross-sectional area of ​​the air gap.

[0047] Φ0 is the magnetic flux in the remaining air gap, U is the electromotive force induced in the primary coil by the secondary coil current I, and M is the mutual inductance between the primary and secondary coils.

[0048] F=N1I (1)

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] Equation (7) shows that the mutual inductance value does not change with the air gap fluctuation. However, since this magnetic circuit model is too idealistic and does not take into account factors such as core reluctance, core leakage reluctance, and diffused magnetic flux at the air gap edge, a simulation is conducted to better reflect the actual situation of the ability to resist vertical air gap displacement. The specific simulation results can be found in [reference needed]. Figure 6 and Figure 7 It can be clearly seen that, compared with conventional power transmission, the magnetic induction intensity generated by the structure in this embodiment is significantly improved, and the mutual inductance coupling effect is significantly enhanced.

[0056] For a more intuitive view, see [link to relevant documentation]. Figure 8 Simulations of air gap offset resistance show that when the primary and secondary sides are offset by 20mm, the fluctuation of magnetic induction intensity is only 25mH, which is equivalent to 2.5% of the maximum magnetic induction intensity. Therefore, it can be proven that the structure of this embodiment has good resistance to vertical offset, that is, it can avoid a large amount of magnetic leakage caused by the floating of the air gap under the vehicle during vehicle operation, thereby reducing energy waste and improving wireless power transmission efficiency.

[0057] It should be noted that in this embodiment, the vertical dimension of the secondary core 30 is larger than the maximum design float of the air gap under the vehicle. This ensures that as long as the vehicle is in normal operation, the secondary core 30 will not be completely misaligned with the primary core 10 in the vertical direction, thereby ensuring that an approximately circular magnetic path can always be formed between the secondary core 30 and the primary core 10. This reduces magnetic leakage during the air gap float process, increases the magnetic flux passing through the secondary coil 40, and thus improves the wireless power transmission efficiency.

[0058] For some possible implementations, please refer to [link / reference]. Figure 3 and Figure 4 , Figure 9 and Figure 10 The power supply cable 20 extends linearly against the top wall of the primary iron core 10, and the secondary iron core 30 spans the primary iron core 10 with its opening facing downward; the secondary coil 40 is wound on the part between the two side legs of the secondary iron core 30.

[0059] In this embodiment, since the power supply cable 20 is laid directly on the top wall of the primary iron core 10 along the track extension direction, the construction is simple and convenient. Simultaneously, it allows the primary iron core 10 and the lower-facing secondary iron core 30 to form an approximately circular magnetic path, within which the power supply cable 20 is located. This maximizes the guiding and converging effect of the magnetic path on the magnetic field lines, increasing the magnetic flux through the secondary coil 40, reducing magnetic leakage, and thus reducing power loss and improving wireless power transmission efficiency. This conclusion is supported by simulation experiments and comparisons. Figure 9 and Figure 10 The test results clearly show that, under the same primary and secondary air gap conditions, the mutual inductance coupling with the primary iron core 10 is significantly stronger than that of the traditional iron coreless coupling mechanism.

[0060] It should be noted that in this embodiment, the U-shaped opening of the secondary core 30 in the vertical direction is larger than the maximum design fluctuation of the air gap under the vehicle. Since the primary core 10 is located within the U-shaped opening of the secondary core 30, setting the depth of the U-shaped opening (i.e., in the vertical direction) to be larger than the maximum fluctuation of the air gap under the vehicle ensures that an approximately circular magnetic path can always be formed between the secondary core 30 and the primary core 10, thereby reducing magnetic leakage during the air gap fluctuation process, increasing the magnetic flux passing through the secondary coil 40, and thus improving the wireless power transmission efficiency.

[0061] It should be understood that in this embodiment, there is a lateral gap between the secondary core 30 and the primary core 10. Since the vehicle runs along the track, the lateral offset of the vehicle is extremely small. Therefore, the lateral gap can be minimized as much as possible. It is only necessary to ensure that the secondary core 30 and the primary core 10 do not come into contact or rub against each other during vehicle operation. This makes the magnetic path formed by the primary core 10 and the secondary core 30 as close as possible to a closed loop, which can reduce magnetic leakage, reduce power loss, and improve wireless power transmission efficiency.

[0062] In some possible implementations, the primary iron core 10 is a segmented structure arranged in sequence, with each segment corresponding to a power supply cable 20, or multiple adjacent segments sharing a single power supply cable 20. This segmented layout facilitates construction, and the power supply cable 20 can also be segmented, thus avoiding construction difficulties caused by long track lines and ensuring consistent wireless transmission performance.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wireless power transfer coupling mechanism for rail transport, characterized in that, include: The primary iron core is used to fix the connection between the two rails and extends longitudinally along the rails; The power supply cable is laid on the primary iron core along the extension direction of the primary iron core and is used to pass alternating current to generate an alternating magnetic field. The U-shaped secondary iron core is used to fix the bottom of the vehicle with the opening facing down or up. The secondary coil is wound on the secondary iron core and is used to inductively couple with the power supply cable to obtain electrical energy. The secondary side iron core spans across the primary side iron core, and the primary side iron core passes through the U-shaped opening of the secondary side iron core. When the air gap floats during vehicle operation, the primary side iron core can float up and down within the U-shaped opening, and the vertical U-shaped opening size of the secondary side iron core is greater than the maximum designed floating amount of the air gap under the vehicle. Alternatively, the secondary side core is placed vertically to the side of the primary side core, and the secondary side core and the primary side core overlap in the horizontal direction, and the vertical dimension of the secondary side core is greater than the maximum design float of the under-vehicle air gap. The corresponding parts of the secondary iron core and the primary iron core form an approximately circular magnetic path to guide and gather magnetic field lines.

2. The wireless power transfer coupling mechanism for rail transportation of claim 1, wherein, One of the vertical sidewalls of the primary iron core has an integrally formed winding portion that protrudes horizontally outward. The power supply cable is laid on the winding portion in a DD-type winding manner. The secondary iron core is placed vertically to the side of the winding portion, and the secondary coil is wound in a DD-type winding manner.

3. The wireless power transfer coupling means for rail transport of claim 2, wherein, The winding section is square wave sawtooth type, and the power supply cable is wound into a DD type coil unit on each outward convex sawtooth. The secondary coil is wound on the two side legs of the secondary iron core and is orthogonal to the DD type coil unit.

4. The wireless power transfer coupling means for rail transport of claim 3, wherein, The power supply cable is arranged in two parallel lines above and below the winding part, and both parallel lines are square wave-shaped and successively pass around each of the protruding saw teeth on the winding part.

5. The wireless power transfer coupling means for rail transport of claim 1, wherein, The power supply cable extends linearly against the top wall of the primary iron core, and the secondary iron core crosses the primary iron core with its opening facing downwards.

6. The wireless power transfer coupling means for rail transport of claim 5, wherein, The secondary coil is wound around the portion between the two side legs of the secondary core.

7. The wireless power transfer coupling means for rail transport of claim 1, wherein, There is a lateral gap between the secondary iron core and the primary iron core.

8. The wireless power transfer coupling means for rail transport of any of claims 1-7, wherein, The primary iron core is a segmented structure arranged in sequence, wherein each segment is provided with a power supply cable, or multiple adjacent segments are provided with a power supply cable.

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