WPT system and position guidance method based on U-shaped coil positioning assistance

Abstract

The present invention provides a WPT system and position guidance method based on U-shaped coil positioning assistance. The system includes a DC power supply, an inverter module, a primary-side compensation topology module, a transmitting coil, a receiving coil, a secondary-side compensation topology module, a rectifier filter circuit, and a load. At least three U-shaped coils are disposed below the transmitting coil, and are arranged end-to-end to form a polygon. The transmitting coil is placed in a recessed area of ​​the at least three U-shaped coils, with each U-shaped coil having two ends protruding upward from the edge of the transmitting coil. A positioning assistance resonant compensation network is also connected to each U-shaped coil. The input port of the primary-side compensation topology module and the input ports of the multiple positioning assistance resonant compensation networks are connected in parallel to the output port of the inverter module, and each is provided with a power switch. The system can adapt to various magnetic coupling mechanisms without modifying the vehicle structure, and can achieve positioning assistance and position guidance for the receiving coil without affecting the operation of the transmitting coil.

Description

Technical Field

[0001] The present invention relates to wireless power transmission technology, and in particular to a WPT system and a position guidance method based on U-shaped coil positioning assistance. Background Art

[0002] Wireless power transfer (WPT) technology enables energy transfer across air gaps without physical contact. Its inherent safety, speed, and flexibility make it considered a promising alternative to cable charging. Consequently, it has been widely adopted for powering consumer electronics, electric vehicles, specialized machinery, and medical electronics.

[0003] In the wireless charging system of electric vehicles, the deviation of the receiving coil from the optimal charging area will greatly limit its charging power and efficiency. At present, relevant researchers have conducted a lot of research to improve the anti-drift capability of the magnetic coupling mechanism from the aspects of improving the coil structure, changing the compensation network, and optimizing the control strategy. However, in practical applications, the improvement of the offset tolerance of the coupling mechanism is limited. To address this problem, the standard J2964 mentions the positioning technology that combines position detection with the parking process to ensure effective charging of the vehicle. Therefore, realizing vehicle position guidance and position detection under offset is one of the key issues of the current wireless charging system of electric vehicles.

[0004] In the prior art, Chinese Patent No. 202110896403.9 proposed by the present applicant discloses a 4U-type positioning auxiliary magnetic coupling mechanism and a positioning system and method based thereon, which to some extent achieves the auxiliary positioning and offset detection functions of the receiving coil. However, it was found to have the following defects during use:

[0005] (1) The four U-shaped positioning auxiliary coils are located directly below the transmitting coil. When the transmitting coil is tightly wound, it will affect the energy transmission;

[0006] (2) In order to make the end point planes of the four U-shaped positioning auxiliary coils parallel to the plane of the transmitting coil, four small holes need to be reserved in the center of the transmitting coil for the ends of the four U-shaped positioning auxiliary coils to extend out. This imposes constraints on the structural design of the transmitting coil, often requiring secondary modifications to the vehicle-mounted system. In addition, it is not very suitable for transmitting coils with a DD structure.

[0007] (3) The overall structure of the transmitter is relatively large, making it difficult to achieve lightweight application scenarios. Summary of the Invention

[0008] In view of this, the primary purpose of the present invention is to propose a WPT system based on U-shaped coil positioning assistance, which does not require secondary modification of the vehicle-mounted system and can meet the positioning height requirements of different vehicle models without affecting the operation of the power coil. At the same time, it can adapt to a variety of typical magnetic coupling mechanisms.

[0009] In order to achieve the above object, the specific technical solutions adopted by the present invention are as follows:

[0010] A WPT system based on U-shaped coil positioning assistance includes a DC power supply, an inverter module, a primary-side compensation topology module, a transmitting coil, a receiving coil, a secondary-side compensation topology module, a rectifier filter circuit, and a load. The key feature of the system is that at least three U-shaped coils are arranged below the transmitting coil, and the at least three U-shaped coils are sequentially brought together end to end to form a polygon. The transmitting coil is placed in the groove area of ​​the at least three U-shaped coils, and the two ends of each U-shaped coil protrude upward from the edge of the transmitting coil. A positioning assistance resonant compensation network is also connected to each U-shaped coil. The input port of the primary-side compensation topology module and the input ports of multiple positioning assistance resonant compensation networks are all connected in parallel to the output end of the inverter module. A power switch is provided at the input port of the primary-side compensation topology module and the input port of each positioning assistance resonant compensation network.

[0011] Optionally, three U-shaped coils are provided below the transmitting coil, and the three U-shaped coils are arranged end to end and close together to form an equilateral triangle.

[0012] Optionally, the switching frequencies of the power switches on the input ports of each positioning auxiliary resonant compensation network are different.

[0013] Optionally, the primary side compensation topology module and the multiple positioning auxiliary resonant compensation networks all adopt LCC compensation networks.

[0014] Optionally, the transmitting coil is a square coil, a circular coil, a DD coil or a BP coil.

[0015] Optionally, the receiving coil is a square coil, a circular coil, a DD-type coil or a BP-type coil.

[0016] Of course, other coils with regular edge shapes (which can be placed within the groove of the U-shaped auxiliary coil) can also be used as transmitting coils. In addition, the offset trajectory is obtained based on the output voltage of each U-shaped coil under operation. From the mathematical relationship, it can be seen that the offset trajectory is related to the change in mutual inductance between the U-shaped coil and the receiving coil. Therefore, different receiving coils will have different offset trajectories. However, curve fitting can be performed by pre-training to establish sample data.

[0017] Optionally, a voltage acquisition module and a position guidance prompt module are also provided on the load, the voltage acquisition module is used to collect the load output voltage when each U-shaped coil is energized, and the position guidance prompt module is used to form an offset trajectory and provide a position guidance prompt based on the information collected by the voltage acquisition module.

[0018] Based on the above system, the present invention also provides a position guidance method for a WPT system based on U-shaped coil positioning assistance, which is used in the WPT system based on U-shaped coil positioning assistance described above. The key point of the method is that it includes the following steps:

[0019] S1: Conduct optimal location testing based on the system application scenario, select typical locations for data measurement, and obtain reference data for each location point through curve fitting to establish a database;

[0020] S2: When the receiving coil enters the preset area, the system switches to positioning mode, controls each U-shaped coil to energize and collects the output voltage of the load when the corresponding U-shaped coil is working;

[0021] S3: Based on the output voltage of the load when each U-shaped coil is energized, the offset trajectory of the current position of the receiving coil for each U-shaped coil is obtained in combination with the database;

[0022] S4: Determine whether the offset trajectory of the current position of the receiving coil for each U-shaped coil has no intersection. If there is no intersection, correct the position of the receiving coil according to the visual feedback and return to step S2. If there is an intersection, proceed to step S5.

[0023] S5: Determine whether the output voltage on the load of each U-shaped coil is 0 when it is working. If it is 0, when the receiving coil is a square coil or a circular coil, select the offset track intersection away from the U-shaped coil corresponding to the output voltage of 0 as the current position for offset guidance; when the receiving coil is a DD type coil or a BP type coil, the offset track intersects at two points (x1, y1) and (x2, y2), that is, the current position of the receiving coil may be (x1, y1) or (x2, y2). At this time, according to the offset track and the parking direction, it is determined that the receiving coil is currently located at a position that has not yet reached the U-shaped coil corresponding to the output voltage of 0; if it is not 0, determine the current position and enter step S6;

[0024] S6: Determine whether the current position is the optimal point. If so, end the process. Otherwise, generate a position guidance trajectory based on the offset between the current position and the optimal point for correction, and return to step S2 for a loop.

[0025] The effects of the present invention are:

[0026] The position guidance method of the WPT system based on U-shaped coil positioning assistance proposed in the present invention can be applied to electric vehicles without modifying the vehicle structure, can adapt to various magnetic coupling mechanisms, can adapt to models with different chassis heights, and can achieve positioning assistance and position guidance of the receiving coil without affecting the operation of the transmitting coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the specific implementation or the description of the prior art.

[0028] Figure 1 This is a structural diagram of a WPT system based on U-shaped coil positioning assistance in a specific embodiment of the present invention;

[0029] Figure 2 for Figure 1 Schematic diagram of the three-dimensional structure of the magnetic coupling mechanism;

[0030] Figure 3 for Figure 1 Side view of the magnetic coupling mechanism;

[0031] Figure 4 for Figure 1 Circuit diagram of the system shown;

[0032] Figure 5 is the system equivalent circuit schematic;

[0033] Figure 6 The diagram below shows the comparison of the mutual inductance between the DD coil and the U coil.

[0034] Figure 7 The diagram below shows the comparison of the mutual inductance between a circular coil and a U-shaped coil.

[0035] Figure 8 The coupling mechanism models are of different spatial distributions;

[0036] Figure 9 is M under different offset conditions R1(RC-RC) Laws of change;

[0037] Figure 10 is M under different offset conditions R1(DD-DD) Laws of change;

[0038] Figure 11 is the magnetic field distribution of the square-DD type magnetic coupling mechanism;

[0039] Figure 12 k (SC-DD) The relationship diagram with the changes of three ΔX and ΔY;

[0040] Figure 13It is a DD-square magnetic field distribution diagram;

[0041] Figure 14 k (DD-SC) The relationship diagram with the changes of three ΔX and ΔY;

[0042] Figure 15 This is a schematic diagram of the equivalent mutual inductance characteristic trajectory of the square receiving coil;

[0043] Figure 16 This is a schematic diagram of the direction correction guidance of the square receiving coil;

[0044] Figure 17 This is a schematic diagram of the equivalent mutual inductance characteristic trajectory of the DD type receiving coil;

[0045] Figure 18 This is a schematic diagram of the direction correction guidance for the DD type receiving coil;

[0046] Figure 19 This is a flow chart of a location guidance method according to a specific embodiment of the present invention;

[0047] Figure 20 The plane M is the square receiving coil X1O1Y1 R1(SC-SC) Measured value;

[0048] Figure 21 U under different air gaps d when the receiving coil is a square coil O1 、U O2 、U O3 measurement error;

[0049] Figure 22 This is a schematic diagram of position guidance when the receiving coil is a square coil;

[0050] Figure 23 This is the position detection result when the receiving coil is a square coil. DETAILED DESCRIPTION

[0051] The following embodiments of the technical solution of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only examples and are not intended to limit the scope of protection of the present invention.

[0052] It should be noted that, unless otherwise specified, the technical or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0053] like Figures 1-4As shown, this embodiment provides a WPT system based on U-shaped coil positioning assistance, including a DC power supply, an inverter module, a primary-side compensation topology module, a transmitting coil, a receiving coil, a secondary-side compensation topology module, a rectifier filter circuit, and a load. Three U-shaped coils are arranged below the transmitting coil. The three U-shaped coils are arranged end to end to form an equilateral triangle. The transmitting coil is placed in the groove area of ​​the three U-shaped coils, and the two ends of each U-shaped coil protrude upward from the edge of the transmitting coil. Each U-shaped coil is also connected to a positioning assistance resonant compensation network. The input port of the primary-side compensation topology module and the input ports of the three positioning assistance resonant compensation networks are connected in parallel to the output end of the inverter module. A power switch is provided at the input port of the primary-side compensation topology module and the input port of each positioning assistance resonant compensation network. The switching frequency of the power switch at the input port of each positioning assistance resonant compensation network is different. During positioning, each U-shaped coil is controlled at a different operating frequency, and the corresponding load voltage is collected in real time as a positioning signal. When the transmitting coil and the receiving coil are offset, the degree of coupling between the three U-shaped coils and the receiving coil varies. Position detection is achieved by identifying the characteristic trajectory of each output voltage value.

[0054] This embodiment is mainly described using the structures of square coils and DD coils. As one implementation method, both the transmitting coil and the receiving coil can be set as DD-type coils. As another implementation method, both the transmitting coil and the receiving coil can be set as square coils. The positioning auxiliary mechanism used in this embodiment is defined as a 3U-type coil positioning auxiliary structure.

[0055] Combine Figure 2 and Figure 3 It can be seen that without changing the power receiving coil, the auxiliary coil is designed to be distributed at the bottom of the transmitting coil in a U-shaped structure in an equilateral triangle, realizing the position detection function without affecting the operation of the transmitting coil.

[0056] In specific implementation, the primary compensation topology module and the plurality of positioning auxiliary resonant compensation networks all adopt LCC compensation networks, combined with Figure 4 It can be seen that, among them, I t , I1, I2, I3 are the inverter input currents, I T , I R , I U1 , I U2 , I U3 are the currents flowing through the transmitting coil, receiving coil and positioning auxiliary coils U1, U2 and U3 respectively. T , L R , L U1 , L U2 , LU3 are the self-inductances of the transmitting coil, receiving coil, and positioning auxiliary coil, respectively. C T 、C t , C1, C U1 , C2, C U2 , C3, C U3 is the resonant capacitor of the transmitter and the positioning auxiliary end, C R is the resonant capacitance at the receiving end, C O is the filter capacitor, M T1 、M T2 、M T3 are the mutual inductance between the auxiliary coil and the transmitting coil, M R1 、M R2 、M R3 They are the mutual inductances between the three auxiliary coils and the receiving coil, M 12 、M 13 、M 23 is the mutual inductance between the three U-shaped auxiliary coils, M TR is the mutual inductance between the transmitting coil and the receiving coil, U T U1, U2, and U3 are the output voltages after inversion at the transmitter and positioning auxiliary end, R is the battery load, and R eq is the equivalent load, U R 、U O are the output voltage at the receiving end and the voltage across the load R, respectively. To avoid cross-coupling and effectively identify the specific working status of multiple auxiliary coils, a frequency control method is adopted to control the auxiliary coils. Since the transmission efficiency of the main coupling mechanism will be affected when the system is in a state of deviation from the resonant frequency, the switching frequencies of the three U-shaped coils are set to 94.5kHz, 95.5kHz, and 96kHz, and the coupling frequency is set to 95kHz.

[0057] The fundamental wave analysis method is used to mathematically model the system circuit, and the corresponding circuit resonance condition is:

[0058]

[0059] In the positioning state, taking the U1 coil as an example, U2, U3, and TC do not work, that is, I2, I3, and I t is 0, such as Figure 5 shown.

[0060] Without considering the compensation inductance L t Under the conditions of cross coupling of L1, L2, and L3, combined with the compensation condition (1), the relevant loop current can be obtained from Kirchhoff's law:

[0061]

[0062] Considering the rectifier circuit and filter capacitor C O The equivalent resistance at the receiving end is:

[0063]

[0064] It can be seen from equations (2) and (3) that when the inherent parameters of the coil and the input voltage are determined, the output current and output voltage at the load end are proportional to the mutual inductance.

[0065] In the energy transmission state, only the power transmitting coil TC is working. According to the above analysis method, the corresponding loop current is:

[0066]

[0067] The transmission efficiency of the coupling mechanism is:

[0068]

[0069] The system loss is:

[0070]

[0071] Among them, P C is the inherent loss of the control circuit.

[0072] The system transmission efficiency is:

[0073]

[0074] In order to prove the effectiveness of the U-shaped coil, Figure 6 The figure shows the difference between using DD type coil and using U type coil for positioning auxiliary coil. Figure 7 The figure shows the difference between using a circular coil and a U-shaped coil as the positioning auxiliary coil.

[0075] Assuming the receiving coil is a square coil, when the total coil length (w3) is the same, the mutual inductance between the DD-type coil and the U-type coil to the square receiving coil changes with the Y-axis offset and the air gap height d as follows: Figure 6 As shown in the figure, the mutual inductance between the DD and U-shaped coils and the receiving coil decreases with increasing air gap d, and increases first and then decreases with Y-axis offset. The DD coil's mutual inductance changes more significantly from d = 120 mm to d = 150 mm than the U-shaped coil, indicating greater offset sensitivity. However, from d = 200 mm to d = 300 mm, the mutual inductance changes are similar. The change in mutual inductance indicates that the U-shaped coil has a higher vertical magnetic field and a wider magnetic field range than the DD coil.

[0076] Figure 7The figure shows the variation of the mutual inductance between the circular coil, the U-shaped coil, and the square receiving coil under horizontal offset. The copper consumption and coupling spacing used in the analysis process are the same. It can be seen that the circular mechanism has the same offset sensitivity in all directions. When aligned, the mutual inductance between the coils reaches a maximum of 10.097uH. When the horizontal offset is within 40% of the coil diameter, the mutual inductance change remains within about 1uH. When the horizontal offset is 100mm (79.36% of the coil diameter), the mutual inductance becomes 5.058uH. The mutual inductance in this offset range changes by about 49.42%. When the horizontal offset is 200mm, The mutual inductance is almost zero. In the U-shaped mechanism, the deviation tolerance in all directions is consistent within the first and fourth quadrants and the second and third quadrants. When aligned correctly, the mutual inductance between the coils reaches a minimum of 0.227uH. When the horizontal offset is 150mm (50% of the U-shaped coil length), the mutual inductance reaches a maximum of 46.477uH. The mutual inductance variation within this offset range is approximately 99.5%. When the horizontal offset is ΔX = 300mm and ΔY = 300mm, the mutual inductance is 4.166uH. This shows that under the same copper consumption, the U-shaped coil has a wider magnetic field range and a larger mutual inductance variation range than the circular coil.

[0077] From the above analysis, it can be seen that the effect of using a U-shaped coil as a positioning auxiliary coil is significantly better than that of a conventional DD-shaped coil or a circular coil as a positioning auxiliary coil.

[0078] As for the number and arrangement of U-shaped coils, Figure 8 Six ways of distributing the U-shaped positioning auxiliary coil are shown, where O represents the geometric center of the receiving coil. Figure 8 (a) Based on the known mutual inductance of the receiving coil and the U-shaped coil, the projection trajectory corresponding to point O is two symmetrical circles, that is, the detection blind spot is in the form of two axisymmetric circles, and positioning cannot be achieved. Figure 8 In (b), the trajectory of U1 corresponding to a certain mutual inductance is two symmetrical circles, and the trajectory of U2 corresponding to a certain mutual inductance is two symmetrical circles with different radii from U1. In this case, the detection blind spot is the two intersection points of the trajectory circles corresponding to U1 and U2, and accurate positioning is impossible. Figure 8 (c) Figure 8 (d) Figure 8 (e) Figure 8 (f) Position detection can be achieved through the corresponding feature trajectory intersection under horizontal offset conditions. Figure 8 (c), and Figure 8 The distributed structure shown in (e) requires modification of the transmitting coil. Figure 8 (f) More U-shaped coils are used to form a polygon. Although positioning detection can be achieved, the copper consumption and core volume are compared with Figure 8 (d) More redundant. Therefore, the best embodiment of the present invention is Figure 8The 3U-type positioning auxiliary coil structure shown in (d) can also play a supporting role without affecting the operation of the transmitting coil.

[0079] In order to verify the applicability of the 3U-type auxiliary coil in this embodiment, the positioning auxiliary coil is introduced into the existing typical magnetic coupling mechanism, and the magnetic field distribution characteristics are summarized to analyze the adaptability of the magnetic coupler and the feasibility of positioning. R1 、M R2 、M R3 The overall change is 120° rotationally symmetrical. The following is only analyzed by M R1 The changing rules are used to illustrate the practicality of its positioning.

[0080] For the coupling mechanism composed of a square transmitting coil and a square receiving coil, when the power coils are both square coils (SC), the M corresponding to different transmission distances d is R1(SC-SC) Changes such as Figure 9 As shown. Among them, the M corresponding to different distances d R1(SC-SC) The overall plane change law is consistent, and M R1(SC-SC) As d increases, it decreases. In addition, in any quadrant of the X1O1Y1 plane, M R1(SC-SC) As the X-axis offset gradually decreases, the mutual inductance of each point on the X-axis can be approximately 0. As the Y-axis offset increases, it first increases and then decreases. When the transmitting coil and the receiving coil are aligned, the center of the receiving coil structure is located at the center of the auxiliary coil, and there is almost no coupling between the receiving coil and the three U-shaped coils, that is, M R1(SC-SC) =M R2(SC-SC) =M R3(SC-SC) ≈0. When the transmitting coil and the receiving coil are offset, the mutual inductance of the receiving coil and the three U-shaped coils are different, that is, M R1(SC-SC) ≠M R2(SC-SC) ≠M R3(SC-SC) .

[0081] For the coupling mechanism composed of DD type transmitting coil and DD type receiving coil, when the power coils are all DD type coils, the mutual inductance between the auxiliary coil and the receiving coil changes as follows: Figure 10 As shown. Visible M R1(DD-DD) The changing trend at different distances d is consistent and decreases as d increases. In any quadrant of the X1O1Y1 plane, M R1(DD-DD) The inductance decreases gradually with the shift of ΔX and decreases first and then increases slightly with the shift of ΔY. The minimum point is the end point of the U-shaped coil structure. When the transmitting coil and the receiving coil are aligned, the corresponding mutual inductance is M R1(DD-DD) ≠M R2(DD-DD) =M R3(DD-DD) When the transmitting coil and the receiving coil are offset, the mutual inductance between the receiving coil and the three U-shaped coils is different, that is, M R1(DD-DD) ≠M R2(DD-DD)≠M R3(DD-DD) .

[0082] The above analysis shows that when a 3U-shaped auxiliary structure is incorporated into the typical magnetic coupling mechanism, the mutual inductance between each U-shaped coil and its corresponding receiving coil varies with their relative position. Even at d = 250mm, the change in mutual inductance is significant. Therefore, this auxiliary structure is fully applicable to various magnetic coupling systems composed of square and DD-shaped coils, and meets the stringent positioning requirements of most vehicle models.

[0083] Although square coils and DD-type coils are widely used in wireless charging systems, they are difficult to be compatible. In order to illustrate the interoperability of the 3U-type coil positioning auxiliary structure, for the square-DD-type magnetic coupling mechanism, the magnetic field distribution corresponding to the magnetic coupling mechanism is as follows: Figure 11 When the square and DD coils are aligned, they are in a zero coupling state and no energy transfer is possible. Therefore, achieving interoperability requires determining the effective coupling region between the two.

[0084] Figure 12 The coupling coefficient k is in the energy transmission state when d = 100mm. (SC-DD) The law of change with the coil position. k (SC-DD) It decreases with the increase of ΔX and first increases and then decreases with ΔY. The optimal charging area of ​​this magnetic coupling structure is ΔX∈[0mm,50mm], ΔY∈[100mm,130mm].

[0085] For the DD-square magnetic coupling mechanism, the magnetic field distribution corresponding to the magnetic coupling mechanism is as follows: Figure 13 shown. Figure 14 In the energy transfer state, the coupling coefficient k (DD-SC) The law of change with the coil position. It can be seen that k (DD-SC) The changing pattern and the optimal charging area are consistent with those of the square-DD type mechanism.

[0086] When the auxiliary coil is applied to the DD-square and square-DD magnetic coupling mechanisms, the mutual inductance variation between the U-shaped coil and each receiving coil remains the same. Figure 9 、 Figure 10 shown.

[0087] Therefore, in a specific implementation, a voltage acquisition module and a position guidance prompt module can be set on the load. The voltage acquisition module is used to collect the pickup voltage on the load when each U-shaped coil is energized, and the position guidance prompt module is used to form an offset trajectory and give a position guidance prompt based on the information collected by the voltage acquisition module.

[0088] In addition, this embodiment also provides a position guidance method for a WPT system based on U-shaped coil positioning assistance, which is used in the WPT system based on U-shaped coil positioning assistance described above, and includes the following steps:

[0089] S1: Conduct optimal location testing based on the system application scenario, select typical locations for data measurement, and obtain reference data for each location point through curve fitting to establish a database;

[0090] S2: When the receiving coil enters the preset area, the system switches to positioning mode, controls each U-shaped coil to energize and collects the output voltage of the load when the corresponding U-shaped coil is working;

[0091] S3: Based on the output voltage of the load when each U-shaped coil is energized, the offset trajectory of the current position of the receiving coil for each U-shaped coil is obtained in combination with the database;

[0092] S4: Determine whether the offset trajectory of the current position of the receiving coil for each U-shaped coil has no intersection. If there is no intersection, correct the position of the receiving coil according to the visual feedback and return to step S2. If there is an intersection, proceed to step S5.

[0093] S5: Determine whether the output voltage on the load of each U-shaped coil is 0 when it is working. If it is 0, when the receiving coil is a square coil or a circular coil, select the offset track intersection away from the U-shaped coil corresponding to the output voltage of 0 as the current position for offset guidance; when the receiving coil is a DD type coil or a BP type coil, the offset track intersects at two points (x1, y1) and (x2, y2), that is, the current position of the receiving coil may be (x1, y1) or (x2, y2). At this time, according to the offset track and the parking direction, it is determined that the receiving coil is currently located at a position that has not yet reached the U-shaped coil corresponding to the output voltage of 0; if it is not 0, determine the current position and enter step S6;

[0094] S6: Determine whether the current position is the optimal point. If so, end the process. Otherwise, generate a position guidance trajectory based on the offset between the current position and the optimal point for correction, and return to step S2 for a loop.

[0095] For the square receiving coil, combined with M R1(SC-SC) The changing law shows that the M measured at a certain moment R1(SC-SC) Projecting the receiving coil structure center O corresponding to various horizontal offset situations and all offset situations onto the plane corresponding to the U-shaped coil will form two equal-value mutual inductance characteristic trajectories with axial symmetry. Taking U1 as an example, when the projection of the RC structure center O is located on the equal-value mutual inductance characteristic trajectory, the M in this case is R1(SC-SC) Consistent, such as Figure 15 shown.

[0096] When the vehicle enters the recognizable range, the equivalent mutual inductance feature trajectories B and C are obtained. If B and C intersect at two points, that is, the vehicle position has two suspicious position points, the guidance trajectory is initially generated based on the suspicious point farther away. The driver adjusts the parking point according to the guidance trajectory until the single chip detects U O1 ≠0, the vehicle enters the precise positioning area, determines the current horizontal offset position (x, y) of the vehicle, and corrects the guidance trajectory again until the vehicle stops at the optimal charging point. The correction guidance under dynamic driving is shown as follows Figure 16 shown.

[0097] For a DD-type receiving coil, when the transmitting coil and the receiving coil are offset, the projection of the receiving coil structure center O corresponding to all possible offsets onto the plane corresponding to the U-shaped coil will form an axisymmetrically distributed equal-value mutual inductance characteristic trajectory. Taking U1 as an example, the mutual inductance characteristic trajectory is as follows: Figure 17 Due to the magnetic field characteristics of the U-shaped coil, there may still be a certain amount of mutual inductance between the transmitting coil and the receiving coil after a large offset. Figure 10 The M shown R1(DD-DD) The changing rule shows that when the detected M R1(DD-DD) >5uH, M at a certain moment R1(DD-DD) Corresponds to only one characteristic trajectory.

[0098] Through the equivalent mutual inductance characteristic trajectory B and C, we get two suspicious position points (x1, y1) and (x2, y2). Combining the parking direction and the mutual inductance trajectory, we can know that the output voltage U is not detected when U1 is working. O1 When the vehicle position can only be (x1, y1), the exact guidance trajectory is obtained until the microcontroller detects U O1 , correct the guidance trajectory until the vehicle stops at the optimal charging point, the direction guidance is as follows Figure 18 shown.

[0099] In summary, it can be seen that in specific implementation, the magnetic field distribution characteristics after the auxiliary coil is introduced into the typical magnetic coupling mechanism, the position detection algorithm based on the equivalent mutual inductance feature trajectory recognition can be Figure 19 The process shown is as follows:

[0100] 1) When the electric vehicle enters the parking area, the charging system switches to positioning mode;

[0101] 2) The single chip microcomputer controls the working state of U1, U2 and U3 respectively by controlling the working frequency and collects the output voltage (U O1 、U O2 、U O3), the voltage is compared with the database to obtain the corresponding equivalent mutual inductance characteristic trajectory (A, B, C). If there is no intersection between A, B, and C, it is considered that RC has not entered the recognizable area. At this time, the driver adjusts the position according to the visual effect and re-positions the judgment; if there is a unique intersection between A, B, and C, it is considered that the vehicle-mounted receiving coil has entered the precise positioning area. At this time, the intersection coordinates (x, y) are the current corresponding horizontal offset position; when the receiving coil is a square coil: if there is an intersection between B and C, it is considered that the vehicle-mounted receiving coil has entered the recognizable area. At this time, if U O2 >U O3 , it is located in the second quadrant; if U O2 <U O3 , it is located in the third quadrant. When the receiving coil is a DD type coil: If there is an intersection between A, B, and C, the vehicle position can be identified. After identifying the receiving coil area or the current position point, the corresponding guidance trajectory is determined.

[0102] 3) Repeat step 2 until the vehicle enters the precise positioning area, i.e., the U O1 ≠0, and the specific offset distance (x, y) of the receiving coil is determined according to the current output.

[0103] 4) The guidance trajectory is further corrected based on the current actual offset distance (x, y) and fed back to the driving operation assistance interface to guide the driver to stop in an effective charging area. At this point, the positioning mode is terminated and the vehicle switches to charging mode.

[0104] In order to further verify the effectiveness of the above system and method, an experimental prototype was built according to the magnetic coupling mechanism parameters given in Table 1 and combined with the parameter configuration method of the LCC-S compensation circuit.

[0105] Table 1 Main parameters and component models of the prototype

[0106]

[0107] When the receiving coil is a square coil and the air gap height d is 120mm or 250mm respectively, M R1(SC-SC) The measured values ​​of Figure 20 As shown. R1 The change pattern is consistent with the simulation. At the same time, U1 does not cross the position of the transmitter core, while U2 and U3 cross the transmitter core symmetrically, that is, M R2 、M R3 The overall distribution law is better than M R1 Slightly larger. Therefore, U1 output voltage U O1 Comparison of U in multiple typical positions O2 、U O3 Slightly smaller, and U O2 、U O3 The changes are almost the same.

[0108] For the feasibility verification of position guidance and positioning, when the air gap height d = 120mm, d = 250mm, and the XOY plane is horizontally offset, U O1 、U O2 、U O3 The measurement value and error of Figure 21 As shown. In the correct alignment position U O1 =U O2 =U O3 = 0, when TC and RC are horizontally offset, U O1 ≠U O2 ≠U O3 When d=120mm, U O1 、U O2 、U O3 The average relative errors between the experimental measurement and simulation are 3.38%, 4.77%, and 4.55%. When d = 250 mm, U O1 、U O2 、U O3 The average relative errors between experimental measurements and simulations were 9.38%, 8.77%, and 9.55%. Furthermore, as the air gap increased, the output voltages decreased, resulting in a gradual decrease in the positioning range. The overall measurement results were consistent with the expected variation, validating the feasibility of the proposed 3U-type positioning assist mechanism for position guidance and detection under horizontal displacement within the XOY plane.

[0109] To verify the accuracy of the position guidance trajectory, taking d = 120 mm as an example, consider the following three typical cases of the initial position of the receiving coil, the guidance trajectory is as follows Figure 22 shown.

[0110] The receiving coil is located in the second quadrant of XOY: If U O1 =0V, U O2 =14.5V, U O3 =11V, at this time, there are suspicious positions (-200mm, 50mm) and (-190mm, 30mm) in the receiving coil. The position guidance trajectory is defined according to (-200mm, 50mm). When U O1 When ≠0V, the position guidance trajectory is corrected and U is measured. O1 =0.2V, U O2 =12.03V, U O3 =13.2V, indicating that the receiving coil has entered the precise positioning area. At this time, there is a real-time interactive relationship between the guidance trajectory and the dynamic position. That is, the guidance trajectory is corrected in real time according to the dynamic position of the receiving coil until the receiving coil is aligned with the transmitter.

[0111] The receiving coil is located in the third quadrant of XOY: U O1=0V, U O2 =12.86, U O3 =13V, get the suspicious position points (-220mm, -80mm) and (-160mm, 20mm), define the position guidance trajectory according to (-220mm, -80mm), when U is measured O1 When the voltage is ≠0V, the trajectory is corrected and the guidance trajectory is corrected in real time according to the dynamic position of the receiving coil until the receiving coil is aligned with the transmitting coil.

[0112] The receiving coil is located on the negative half of the X axis: U O1 =0V, U O2 =13.5V, U O3 =13.5V, get the suspicious position points (-210mm, 0mm) and (-180mm, 0mm), define the position guidance trajectory according to (-210mm, 0mm), when the measured U O1 When the voltage is ≠0V, the trajectory is corrected, and the guidance trajectory is corrected in real time according to the dynamic position of the receiving coil until the receiving coil is aligned with the transmitting coil.

[0113] The positioning results of the second quadrant in the XOY plane under the magnetic coupling mechanism are as follows Figure 23 As shown in the figure, the actual positioning results are basically consistent with the database positioning results. The positioning accuracy is high within the step size of 50 mm. As the offset position changes, especially at the offset position with low mutual inductance between the U-shaped coil and RC, the positioning accuracy decreases, but still remains within 10 mm.

[0114] In addition, similar tests were performed on the DD-type receiving coil. The specific process will not be described here, but the experimental results show that the actual positioning results are similar to the simulation results and can still meet the actual positioning needs.

[0115] In summary, the present invention addresses the issues of existing methods that require vehicle structure modification for vehicle positioning using auxiliary coils and are limited to the height of the vehicle seat chassis and a single magnetic coupling mechanism. The present invention proposes a WPT system and positioning guidance method based on U-shaped coil positioning assistance. Based on the charging height requirements and the diversity of magnetic coupling mechanisms, the auxiliary coil is designed to have a 3U-shaped structure to adapt to actual positioning needs. The magnetic field characteristics of multiple typical magnetic coupling mechanisms under the intervention of this structure are analyzed to obtain the corresponding trajectory guidance method and positioning algorithm. In the experiment, the position of the receiving coils was detected for square and DD types respectively. In typical areas, the accuracy can reach 10mm, which can meet the actual positioning requirements. Compared with the existing method of using auxiliary coils to realize the position detection of the receiving coil, the proposed coil structure and its positioning method have the following advantages: no modification of the vehicle structure, adaptability to a variety of magnetic coupling mechanisms, adaptability to different chassis heights and vehicle models, and no impact on the operation of the transmitting coil.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and such changes should be included in the scope of the claims and description of the present invention.

Claims

1. A WPT system based on U-shaped coil positioning assistance, comprising a DC power supply, an inverter module, a primary side compensation topology module, a transmitting coil, a receiving coil, a secondary side compensation topology module, a rectifier filter circuit, and a load, characterized in that: At least three U-shaped coils are disposed below the transmitting coil. The at least three U-shaped coils are sequentially brought together end to end to form a polygon. The transmitting coil is placed in the groove area of ​​the at least three U-shaped coils. Both ends of each U-shaped coil protrude upward from the edge of the transmitting coil. A positioning auxiliary resonant compensation network is also connected to each U-shaped coil. The input port of the primary compensation topology module and the input ports of the multiple positioning auxiliary resonant compensation networks are connected in parallel to the output end of the inverter module. A power switch is provided at the input port of the primary compensation topology module and the input port of each positioning auxiliary resonant compensation network. The system selects typical positions with different air gap heights for data measurement, and obtains reference data for each position point through curve fitting, thereby establishing a database. According to the output voltage on the load when each U-shaped coil is energized, the offset trajectory of the current position of the receiving coil for each U-shaped coil is obtained in combination with the database.

2. The WPT system based on U-shaped coil positioning assistance according to claim 1 is characterized in that: Three U-shaped coils are arranged below the transmitting coil, and the three U-shaped coils are arranged end to end and close together to form an equilateral triangle.

3. The WPT system based on U-shaped coil positioning assistance according to claim 1 or 2, characterized in that: The switching frequency of the power switch on the input port of each positioning auxiliary resonant compensation network is different.

4. The WPT system based on U-shaped coil positioning assistance according to claim 3 is characterized in that: The primary side compensation topology module and the plurality of positioning auxiliary resonant compensation networks all adopt LCC compensation networks.

5. The WPT system based on U-shaped coil positioning assistance according to claim 1 or 4, characterized in that: The transmitting coil is a square coil, a circular coil, a DD-type coil or a BP-type coil.

6. The WPT system based on U-shaped coil positioning assistance according to claim 1 or 4, characterized in that: The receiving coil is a square coil, a circular coil, a DD-type coil or a BP-type coil.

7. The WPT system based on U-shaped coil positioning assistance according to claim 1 or 4, characterized in that: A voltage acquisition module and a position guidance prompt module are also provided on the load. The voltage acquisition module is used to collect the load output voltage when each U-shaped coil is energized. The position guidance prompt module is used to form an offset trajectory and provide a position guidance prompt based on the information collected by the voltage acquisition module.

8. A method for guiding the position of a WPT system based on U-shaped coil positioning assistance, used in the WPT system based on U-shaped coil positioning assistance according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: Conduct optimal location testing based on the system application scenario, select typical locations for data measurement, and obtain reference data for each location point through curve fitting to establish a database; S2: When the receiving coil enters the preset area, the system switches to positioning mode, controls each U-shaped coil to energize and collects the output voltage of the load when the corresponding U-shaped coil is working; S3: Based on the output voltage of the load when each U-shaped coil is energized, the offset trajectory of the current position of the receiving coil for each U-shaped coil is obtained in combination with the database; S4: Determine whether the offset trajectory of the current position of the receiving coil for each U-shaped coil has no intersection. If there is no intersection, correct the position of the receiving coil according to the visual feedback and return to step S2. If there is an intersection, proceed to step S5. S5: Determine whether the output voltage on the load of each U-shaped coil is 0 when it is working. If it is 0, when the receiving coil is a square coil or a circular coil, select the offset track intersection away from the U-shaped coil corresponding to the output voltage of 0 as the current position for offset guidance; when the receiving coil is a DD type coil or a BP type coil, the offset track intersects at two points ( x 1, y 1) and ( x 2, y 2), that is, the current receiving coil position may be ( x 1, y 1) or ( x 2, y 2) At this time, the receiving coil is determined to be currently located at a position not yet reaching the U-shaped coil corresponding to an output voltage of 0 based on the offset trajectory and the parking direction; if the output voltage is not 0, the current position is determined and the process proceeds to step S6; S6: Determine whether the current position is the optimal point. If so, end the process. Otherwise, generate a position guidance trajectory based on the offset between the current position and the optimal point for correction, and return to step S2 for a loop.

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