Position deviation and metal foreign body detection system for wireless charging of electric vehicles

Abstract

The present invention discloses a position offset and metal foreign object detection system for wireless charging of electric vehicles. A bidirectional wireless power transmission system is configured between the ground terminal and the vehicle terminal. An array of foreign object detection coils is also configured on the ground terminal coil. When performing metal foreign object detection, the detection voltage of each foreign object detection sub-coil is collected separately. The sum of the detection voltages of two foreign object detection sub-coils at positions symmetrical to the origin is used as a set of reference voltages. Metal foreign object detection is achieved by analyzing the changes in the eight sets of reference voltages. Offset detection sub-coils are also superimposed on the foreign object detection sub-coils at the four vertex corners. When performing vehicle-side coil offset detection, the voltage of any offset detection sub-coil is collected to achieve vehicle-side coil offset detection. The system has the advantages of a simple structure and convenient control, and can achieve both efficient and low-cost vehicle-side offset detection and convenient metal foreign object detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless charging, and more specifically, relates to a position offset and metal foreign body detection system for wireless charging of electric vehicles. Background Art

[0002] Compared to traditional wired charging methods, wireless power transfer (WPT) technology offers advantages such as strong environmental adaptability, high safety, and flexibility and convenience, making it widely used in transportation and other fields. In WPT systems, the magnetic coupling mechanism is the core component for energy transmission, and its offset largely determines the system's efficiency, power output, and other output characteristics.

[0003] In bidirectional wireless charging systems for electric vehicles, due to accuracy issues with manual and automated parking, the on-board pickup coil can be offset during forward power transmission from the grid to the vehicle's battery. This offset between the on-board pickup coil and the ground-based transmitting coil reduces coupling compared to when the two are aligned, resulting in reduced system output power and transmission efficiency. During reverse power transmission from the vehicle's battery to the grid, the offset between the on-board transmitting coil and the ground-based receiving coil can also reduce system output power and transmission efficiency. Furthermore, metallic foreign matter between the coupling mechanisms can heat up due to eddy currents in high-frequency magnetic fields, damaging the system.

[0004] Currently, technologies for detecting coupling mechanism offset and metallic foreign matter between coupling mechanisms mostly rely on two separate systems, each performing its own function. This increases the size of the coupling mechanism and reduces power density. The few integrated detection systems that do combine these two functions rely on sophisticated detection coil design, complex software algorithms, high-frequency detection signals applied to the power coil, or precise calculations of system impedance. These require additional hardware and software, and the precise sampling and calculations are also costly. Summary of the Invention

[0005] In view of this, the present invention provides a position offset and metal foreign object detection system for wireless charging of electric vehicles. The system can transmit a magnetic field in the opposite direction from the vehicle-mounted coil to the transmitting coil, and use the induced voltage of the array detection coil equipped on the ground end to determine the offset direction and offset distance. After the driver adjusts the coupling mechanism to align, the array detection coil is used again, and the magnetic field is emitted from the ground end. The induced voltage of the array detection coil is used to detect metal foreign objects. The two functions can be achieved by using a set of simply arranged array detection coils and their corresponding ordinary voltage sampling devices.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] A position offset and metal foreign body detection system for wireless charging of electric vehicles, including a ground terminal and a vehicle terminal, a two-way wireless power transmission system is configured between the ground terminal and the vehicle terminal, and the two-way wireless power transmission system includes a ground terminal control circuit, a ground terminal coil, a vehicle terminal coil and a vehicle terminal control circuit. The key is that: an array foreign body detection coil is also configured on the ground terminal coil, and the array foreign body detection coil is arranged in a 4×4 form and numbered row by row as foreign body detection sub-coils No. 1 to No. 8. The winding direction of the foreign body detection sub-coils No. 1 to No. 8 is the same, and the other positions are arranged in a 4×4 form. The winding direction of the foreign object detection sub-coil is opposite to that of foreign object detection sub-coils No. 1 to 8. When performing metal foreign object detection, the detection voltage of each foreign object detection sub-coil is collected separately, and the sum of the detection voltages of the two foreign object detection sub-coils at the center symmetrical position of the origin is used as a set of reference voltages. Metal foreign object detection is achieved by analyzing the changes in the 8 sets of reference voltages. Offset detection sub-coils are also superimposed on the foreign object detection sub-coils at the four vertex corners. When performing vehicle-end coil offset detection, the voltage of any of the offset detection sub-coils is collected to achieve vehicle-end coil offset detection.

[0008] Optionally, the ground-end coil is a rectangular planar coil with a hollow area reserved in the center, and the array-type foreign object detection coil is arranged in the hollow area reserved in the center of the ground-end coil.

[0009] Optionally, the offset detection sub-coil and the foreign object detection sub-coil at the corresponding position have the same outline shape and size but different numbers of turns, and the two are insulated and overlapped with each other.

[0010] Optionally, the foreign object detection sub-coil is a rectangular planar coil.

[0011] Optionally, a ground controller is configured in the ground-end control circuit, and a vehicle-mounted controller is configured in the vehicle-end control circuit. The ground controller and the vehicle-mounted controller are connected via wireless communication. The ground controller transmits the detection voltage of any offset detection sub-coil to the vehicle-mounted controller. The vehicle-mounted controller determines the offset distance of the vehicle based on the detection voltage of the offset detection sub-coil and guides the vehicle to correct alignment.

[0012] Optionally, if the selected offset detection sub-coil is the offset detection sub-coil above the foreign object detection sub-coil No. 1, then:

[0013] y=-1.17×10 -4 U1 3 +9.28×10 -3 U1 2 -1.17U1+7.62

[0014] Determine the vehicle's offset distance;

[0015] If the selected offset detection sub-coil is the offset detection sub-coil above the foreign body detection sub-coil No. 4, then follow the steps below:

[0016] y=1.11×10 -4 U4 3 +8.57×10 -3 U4 2 +1.16U4-7.06

[0017] Determine the vehicle's offset distance;

[0018] Wherein: U1 represents the detection voltage of the offset detection sub-coil above the foreign object detection sub-coil No. 1, U4 represents the detection voltage of the offset detection sub-coil above the foreign object detection sub-coil No. 4, and y is the vehicle offset distance.

[0019] Optionally, the offset of the target vehicle is first detected by the offset detection sub-coil, and after the vehicle is guided to correct the alignment, the array-type foreign object detection coil is used to realize real-time detection of metal foreign objects.

[0020] Optionally, the bidirectional wireless power transmission system adopts a bilateral LCC compensation topology.

[0021] Optionally, when performing metal foreign object detection and vehicle-mounted end coil offset detection, the vehicle-mounted end coil sends a detection signal.

[0022] The present invention provides a position deviation and metal foreign body detection system for wireless charging of electric vehicles, which has the following beneficial effects:

[0023] 1. The system has a simple structure and is easy to control. It can realize vehicle-mounted end offset detection efficiently and at low cost, and facilitate parking guidance during wireless charging of electric vehicles.

[0024] 2. It can easily realize the detection of metal foreign objects between the ground end coil and the vehicle end coil to prevent metal foreign objects from damaging the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The topology of the WPT system based on the double-sided LCC resonant network provided in this embodiment;

[0026] Figure 2 A schematic diagram of the size of the coupling mechanism provided in this embodiment;

[0027] Figure 3 A schematic diagram of the coupling mechanism installation structure provided in this embodiment;

[0028] Figure 4 A schematic diagram of the numbering sequence of the array-type metal foreign body detection coils provided in this embodiment;

[0029] Figure 5 The induced voltage value of the array metal foreign body detection coil under alignment;

[0030] Figure 6 The simulation results of the induced voltage of the array coil at different offsets in the y direction;

[0031] Figure 7 is the fitting result of the induced voltage of coil 1 and the offset in the y direction;

[0032] Figure 8 is the fitting result of the induced voltage of coil 4 and the offset in the y direction;

[0033] Figure 9 It is the reference voltage value when there is no metal foreign matter;

[0034] Figure 10 is a schematic diagram of the spatial position of metal foreign matter; Figure 10 (a) is the side view. Figure 10 (b) is a top view;

[0035] Figure 11 This is the distribution map of the locations where metal foreign matter appears;

[0036] Figure 12 The reference voltage changes corresponding to the metal foreign matter appearing at positions 1-5;

[0037] Figure 13 The reference voltage changes corresponding to the metal foreign matter appearing at positions 6-10;

[0038] Figure 14 The reference voltage changes corresponding to the metal foreign matter appearing at positions 11-15;

[0039] Figure 15 The reference voltage changes corresponding to the metal foreign matter appearing at positions 16-20;

[0040] Figure 16 The reference voltage changes corresponding to the metal foreign matter appearing at positions 17-25;

[0041] Figure 17 The reference voltage changes corresponding to the metal foreign matter appearing at positions 26-30;

[0042] Figure 18 The reference voltage changes corresponding to the metal foreign matter appearing at positions 31-35;

[0043] Figure 19The reference voltage changes corresponding to the metal foreign matter appearing at positions 36-40;

[0044] Figure 20 The reference voltage changes corresponding to the metal foreign matter appearing at positions 41-45. DETAILED DESCRIPTION

[0045] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0046] This embodiment provides a position offset and metal foreign body detection system for wireless charging of electric vehicles, including a ground terminal and a vehicle terminal, wherein a Figure 1 As shown in the figure, the bidirectional wireless power transmission system includes a ground-side control circuit, a ground-side coil, a vehicle-side coil, and a vehicle-side control circuit. In this example, a bilateral LCC compensation topology is adopted. For the forward transmission of power, the system input is a DC voltage source U dc , Q1-Q4 form a high-frequency inverter, which becomes a high-frequency AC voltage source U after passing through the inverter in . L T1 、C T1 、C P The primary side LCC resonant compensation network is formed at the ground end, L T2 、C T2 、C S A secondary-side LCC resonant compensation network is formed at the vehicle end, Q5-Q8 form a synchronous rectifier, and the vehicle-end battery is equivalent to the load resistor R, C d is the output filter capacitor.

[0047] The following relationship can be obtained through circuit analysis:

[0048]

[0049] The AC power can be expressed as:

[0050]

[0051] Among them U dc is the DC power supply voltage.

[0052] When each circuit of the system operates at the resonant frequency and the primary and secondary operating frequencies are consistent and meet the following conditions:

[0053] When , the system output voltage and part of the input current are:

[0054]

[0055] For reverse power transmission, the system input is the vehicle battery output voltage U out , Q5-Q8 form a high-frequency inverter, which becomes a high-frequency AC voltage source U after passing through the inverter S , C d L is the input filter capacitor. T2 、C T2 、C S Set up the primary side LCC resonant compensation network at the vehicle end. T1 、C T1 、C P A secondary side LCC resonant compensation network is formed at the ground end, Q1-Q4 form a synchronous rectifier, and the system output is connected to the voltage source U dc , the system circuit analysis is similar to the case of forward power transmission.

[0056] In specific implementation, the coupling mechanism of the system consists of an array of foreign body detection coils, a ground-end coil, a vehicle-mounted coil, and their respective magnetic cores and aluminum plates. Figure 2 and Figure 3 As shown, the ground-end coil is wound with 10 turns of 6.32mm Litz wire, with a wire spacing of 7.68mm. The overall shape is a hollow rectangle, and the size is 500mm×500mm. The vehicle-mounted coil is wound with 13 turns of 6.32mm Litz wire, with a wire spacing of 7.68mm. The overall shape is a hollow rectangle, and the size is 500mm×500mm. The array detection coil is laid flat on the transmitting coil and is wound with Litz wire. The Litz wires are closely arranged to form 20 125mm×125mm open-loop rectangular coils in 16 positions with a wire diameter of 2mm. The array detection coils are arranged in a 4×4 form and numbered row by row as foreign body detection sub-coils 1 to 16, as shown in the figure. Figure 4 As shown, the foreign object detection sub-coils 1 through 8 have the same winding direction, while the foreign object detection sub-coils at the remaining positions have the opposite winding direction. An offset detection sub-coil is superimposed on each of the four corner foreign object detection sub-coils. The specific number of turns is shown in Table 1. Table 1 shows that in this embodiment, two open-loop coils parallel to the xoy plane are superimposed at positions 1, 4, 13, and 16. These coils have the same diameter and are insulated from each other. They are numbered 1.1 and 1.2, with the coil ending in .1 serving as the offset detection sub-coil and the coil ending in .2 serving as the foreign object detection sub-coil. The remaining positions have only one coil, which is shared for both offset and foreign object detection. In subsequent induced voltage diagrams, these coils are represented by numbers 1, 4, 13, and 16. If the number of turns is less than one, the calculation is based on the corresponding central angle of the wound coil. For example, 0.5 turns corresponds to a central angle of 180°.

[0057] Table 1 Number of turns of array detection coil

[0058]

[0059] For most existing electric vehicle charging parking spaces, they usually have rear wheel limiters, so only one direction, namely the y-direction offset, can be considered. When an electric vehicle with a bidirectional wireless charging function is parked in the corresponding charging position, the on-board coil actively emits a magnetic field, and an induced voltage is obtained on the array detection coil at the ground end. The induced voltage will change due to the relative offset direction and distance between the on-board coil and the ground coil. Substitute the parameters in Table 1 and simulate the coupling mechanism in Maxwell. The on-board coil current is set to 50A, and the currents of the other coils are 0. When the on-board coil and the ground coil are aligned, the induced voltage of the array detection coil is as follows: Figure 5 shown.

[0060] It can be clearly seen that under the aligned condition, the induced voltage of most coils is close to 10V, and the induced voltage of coils No. 13 and 16 is around 7V.

[0061] When there is an offset in the y direction between the vehicle-mounted coil and the ground-mounted coil, the induced voltage values ​​of the coils with different numbers on the array detection coil are as follows: Figure 6 As shown, it can be clearly seen that the specific offset direction and offset distance of the vehicle-mounted coil in the y direction can be calculated by the induced voltage values ​​of coils No. 1, No. 4, No. 13, and No. 16. Therefore, when performing vehicle-mounted coil offset detection, the voltage of any of the offset detection sub-coils can be collected to realize vehicle-mounted coil offset detection.

[0062] In the specific implementation, Matlab is used to fit the relationship between the offset y in the y direction and the induced voltage values ​​U1 and U4 of coils 1 and 4, and we can get Figure 7 and Figure 8 The fitting results are shown. Therefore, the offset direction and offset distance can be calculated by the induced voltage values ​​of coils 1 and 4. Specifically, if the selected offset detection sub-coil is the offset detection sub-coil above the foreign object detection sub-coil 1, then according to:

[0063] y=-1.17×10 -4 U1 3 +9.28×10 -3 U1 2 -1.17U1+7.62

[0064] Determine the vehicle's offset distance;

[0065] If the selected offset detection sub-coil is the offset detection sub-coil above the foreign body detection sub-coil No. 4, then follow the steps below:

[0066] y=1.11×10 -4 U4 3+8.57×10 -3 U4 2 +1.16U4-7.06

[0067] Determine the offset distance of the vehicle.

[0068] Typically, a ground controller is configured in the ground-side control circuit, and an on-board controller is configured in the on-board control circuit. The ground controller and the on-board controller are connected via wireless communication. In this example, after the ground-side control system samples the induced voltage, the sampling result is transmitted via WiFi to the central control computer inside the car to calculate the offset distance and direction. The human-computer interaction interface in the car then informs the driver to move the parking space until the on-board coil is aligned with the ground-side coil.

[0069] After the vehicle-mounted coil is aligned with the ground-mounted coil, the array coil is used to detect metal foreign objects. When performing metal foreign object detection, the detection voltage of each foreign object detection sub-coil is collected separately, and the sum of the detection voltages of the two foreign object detection sub-coils at the center symmetrical position of the origin is used as a set of reference voltages. By analyzing the changes in the 8 sets of reference voltages, metal foreign object detection is achieved. Figure 4 The coil origin is the center, and the sum of the coils at symmetrical positions is used as the reference voltage to achieve the purpose of decoupling the paired detection coils from the ground end coil and the vehicle end coil, thereby obtaining the 8 sets of reference voltages shown in Table 2. The coupling mechanism is simulated in Maxwell, with the ground end coil current set to 50A and the other coil currents to 0. The induced voltage of the array detection coil in the absence of metal foreign matter is as follows Figure 9 shown.

[0070] Table 2 Reference voltage for metal foreign body detection

[0071]

[0072] like Figure 10 As shown in the figure, a 63mm×63mm×3mm aluminum sheet is introduced as a metal foreign body at a vertical distance of 75mm from the ground end. Figure 11 The reference voltage is simulated at the 45 positions shown in FIG. 1 , so that the reference voltage change at the corresponding position number can be obtained, as shown in FIG. Figure 12-Figure 20 As shown, the ground end samples the voltage value of each detection coil, obtains the reference voltage, and compares it with the reference value when there is no metal foreign matter to determine whether there is a metal foreign matter between the coupling mechanisms.

[0073] In this example, both the ground-side coil and the vehicle-side coil are rectangular planar coils. However, circular planar coils can also be used depending on the application scenario. The individual sub-coils in the arrayed foreign object detection coil can also be circular planar coils. When performing metal foreign object detection and vehicle-side coil offset detection, the detection signal can be generated by the vehicle-side coil, or additional detection coils can be configured to generate a magnetic field to achieve the corresponding detection.

[0074] In summary, it can be seen that according to the characteristics of the two-way wireless power transmission system, the present invention can realize offset detection and metal foreign body detection by using only a set of simply arranged array detection coils and their matching ordinary voltage sampling devices. It has a simple structure, convenient layout, and high efficiency and speed.

[0075] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A position offset and metal foreign object detection system for wireless charging of electric vehicles, comprising a ground terminal and a vehicle terminal, with a bidirectional wireless power transmission system disposed between the ground terminal and the vehicle terminal. The bidirectional wireless power transmission system comprises a ground terminal control circuit, a ground terminal coil, a vehicle terminal coil, and a vehicle terminal control circuit, characterized in that: An array-type foreign object detection coil is also configured on the ground-end coil. The array-type foreign object detection coil is arranged in a 4×4 form and numbered row by row as foreign object detection sub-coils No. 1 to 16. The winding directions of the foreign object detection sub-coils No. 1 to 8 are the same, and the winding directions of the foreign object detection sub-coils at other positions are opposite to the winding directions of the foreign object detection sub-coils No. 1 to 8. When performing metal foreign object detection, the detection voltage of each foreign object detection sub-coil is collected separately, and the sum of the detection voltages of the two foreign object detection sub-coils at the center symmetrical positions of the origin is used as a group of reference voltages. Metal foreign object detection is achieved by analyzing the changes in the 8 groups of reference voltages. Offset detection sub-coils are also superimposed on the foreign object detection sub-coils at the four vertex corners. When performing vehicle-mounted end coil offset detection, the voltage of any of the offset detection sub-coils is collected to achieve vehicle-mounted end coil offset detection.

2. The position deviation and metal foreign body detection system for wireless charging of electric vehicles according to claim 1, characterized in that: The ground-end coil is a rectangular planar coil with a hollow area reserved in the center. The array-type foreign object detection coil is arranged in the hollow area reserved in the center of the ground-end coil.

3. The position deviation and metal foreign body detection system for wireless charging of electric vehicles according to claim 1, characterized in that: The offset detection sub-coil has the same outline shape and size as the foreign matter detection sub-coil at the corresponding position but has a different number of turns, and the two are insulated and stacked with each other.

4. The position offset and metal foreign body detection system for wireless charging of electric vehicles according to any one of claims 1 to 3, characterized in that: The foreign object detection sub-coil is a rectangular planar coil.

5. The position deviation and metal foreign body detection system for wireless charging of electric vehicles according to claim 1, characterized in that: A ground controller is configured in the ground-end control circuit, and a vehicle-mounted controller is configured in the vehicle-end control circuit. The ground controller and the vehicle-mounted controller are connected via wireless communication. The ground controller transmits the detection voltage of any offset detection sub-coil to the vehicle-mounted controller. The vehicle-mounted controller determines the offset distance of the vehicle based on the detection voltage of the offset detection sub-coil and guides the vehicle to correct alignment.

6. The position offset and metal foreign body detection system for wireless charging of electric vehicles according to claim 1 or 5, characterized in that: If the selected offset detection sub-coil is the offset detection sub-coil above the foreign body detection sub-coil No. 1, follow the steps below: y=-1.17×10 -4 U1 3 +9.28×10 -3 U1 2 -1.17U1+7.62 Determine the vehicle's offset distance; If the selected offset detection sub-coil is the offset detection sub-coil above the foreign body detection sub-coil No. 4, then follow the steps below: y=1.11×10 -4 U4 3 +8.57×10 -3 U4 2 +1.16U4-7.06 Determine the vehicle's offset distance; Wherein: U1 represents the detection voltage of the offset detection sub-coil above the foreign object detection sub-coil No. 1, U4 represents the detection voltage of the offset detection sub-coil above the foreign object detection sub-coil No. 4, and y is the vehicle offset distance.

7. The position deviation and metal foreign body detection system for wireless charging of electric vehicles according to claim 6, characterized in that: The offset detection sub-coil first detects the offset of the target vehicle, and after guiding the vehicle to correct the alignment, the array-type foreign object detection coil is used to achieve real-time detection of metal foreign objects.

8. The position deviation and metal foreign body detection system for wireless charging of electric vehicles according to claim 1, characterized in that: The bidirectional wireless power transmission system adopts a bilateral LCC compensation topology.

9. The position deviation and metal foreign body detection system for wireless charging of electric vehicles according to claim 1, characterized in that: When performing metal foreign object detection and vehicle-mounted end coil deviation detection, the vehicle-mounted end coil sends a detection signal.

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