Secondary side position detection system and control method for wireless charging of electric vehicles

Abstract

The present invention discloses a secondary side position detection system and control method for wireless charging of electric vehicles. The system includes a primary side transmitting coil and a secondary side receiving coil, and is characterized in that at least one beacon coil is installed at the magnetic field zero crossing position below the receiving coil, and the beacon coil is connected to a beacon circuit, and a position detection coil array is laid above the transmitting coil, and each position detection coil in the position detection coil array is connected to a position detection circuit. The effect is that the system cost is low, the space occupied is small, the secondary side position detection can be well realized, and the position detection system has little influence on energy transmission.

Description

Technical Field

[0001] The present invention relates to wireless power transmission technology, and in particular to a secondary side position detection system and a control method for wireless charging of an electric vehicle. Background Art

[0002] Wireless charging technology for electric vehicles uses the principle of electromagnetic induction to transfer electrical energy from the transmitting coil to the receiving coil. It is a new charging method. However, if the offset between the transmitting coil and the receiving coil is too large, it will affect the overall transmission efficiency of the system.

[0003] In order to avoid the reduction of transmission efficiency due to excessive offset between the transmitting coil and the receiving coil, the existing scheme based on detecting the offset of the transmitting coil and the receiving coil parameters has problems such as large errors and inability to identify the direction of the offset, and cannot assist the vehicle to keep the wireless charging receiving coil in the energy transmission area. Summary of the invention

[0004] In view of this, the primary purpose of the present invention is to provide a secondary side position detection system for wireless charging of electric vehicles, which uses a vehicle-side beacon coil and a ground-side receiving coil array to detect the secondary side position, thereby facilitating the position alignment of the electric vehicle during wireless charging.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A secondary side position detection system for wireless charging of an electric vehicle comprises a primary side transmitting coil (1) and a secondary side receiving coil (2), the key of which is that at least one beacon coil (3) is installed at a magnetic field zero crossing position below the receiving coil (2), the beacon coil (3) is connected to a beacon circuit, and a position detection coil array (4) is laid above the transmitting coil (1), each position detection coil in the position detection coil array (4) is connected to a position detection circuit.

[0007] When the energy transmission system is transmitting high power, there is a high current on the receiving coil, which will generate a high voltage on the beacon coil, resulting in unnecessary energy loss. The present invention designs the beacon coil to be located in the zero-crossing region of the magnetic field of the receiving coil, so that the beacon coil covers the same area of ​​magnetic field in two directions, thereby reducing the magnitude of the induced voltage on the beacon coil.

[0008] Optionally, the transmitting coil (1) and the receiving coil (2) operate at a first resonant frequency to achieve energy transmission, and the beacon coil (3) and the corresponding position detection coil in the position detection coil array (4) operate at a second resonant frequency to achieve secondary side position detection.

[0009] Optionally, the first resonant frequency is 85 kHz and the second resonant frequency is 5 MHz.

[0010] Optionally, the position detection coil is a rectangular coil and is spread over the entire upper area of ​​the transmitting coil (1) in an 8*10 array.

[0011] Optionally, a plurality of beacon coils (3) are provided and are symmetrically distributed along the center position of the receiving coil (2), and the number of turns of each beacon coil (3) and each position detection coil is 4 turns.

[0012] Optionally, the beacon circuit includes a DC signal source, a half-bridge inverter and an LCC resonant compensation network.

[0013] Since the energy transmission system has a high current on the transmitting coil when performing high-power transmission, the current will generate a high voltage on the position detection coil, affecting the accuracy of the signal received by the position detection coil group. Optionally, the position detection circuit includes an RLC resonant circuit, a high-pass filter circuit and a rectifier filter circuit, the RLC resonant circuit is a low-quality factor circuit that resonates at the second resonant frequency, so as to reduce the magnitude of the induced voltage of the beacon coil on the transmitting coil, and the high-frequency gain of the high-pass filter circuit at the second resonant frequency is more than 10 times the gain of the first resonant frequency.

[0014] Optionally, the rectification and filtering circuit includes a diode and an RC filter, and the voltage amplitude output by the high-pass filtering circuit is more than 5 times the diode voltage drop value.

[0015] Based on the above system, the present invention also proposes a wireless charging control method for electric vehicles. On the basis of adopting the secondary side position detection system described above, the position of the beacon coil (3) is determined by the detection signal of each position detection coil in the position detection coil array (4) to determine whether the secondary side position is aligned. When the secondary side position is aligned, the transmitting coil (1) is started to realize energy transmission.

[0016] Optionally, the system also determines the number of beacon coils (3) through detection signals of each position detection coil in the position detection coil array (4), determines the power level of the receiving coil (2) according to the number of beacon coils (3), and starts the transmitting coil (1) to achieve energy transmission according to the corresponding power level after the secondary side position is aligned.

[0017] The remarkable effects of the present invention are:

[0018] The system has low cost and occupies little space, and can well realize secondary side position detection. Meanwhile, the position detection system has little impact on energy transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the coupling mechanism structure of the system in a specific embodiment of the present invention;

[0021] Figure 2 for Figure 1 Decomposition state diagram of

[0022] Figure 3 is a circuit schematic diagram of a beacon circuit in a specific embodiment of the present invention;

[0023] Figure 4 is a circuit schematic diagram of a position detection circuit in a specific embodiment of the present invention;

[0024] Figure 5 is the sampling voltage U R Relationship diagram with the self-inductance of the position detection coil;

[0025] Figure 6 P is the energy consumption RL Relationship diagram with the self-inductance of the position detection coil;

[0026] Figure 7 is the relationship diagram between the sampling voltage and the compensation capacitance of the position detection coil;

[0027] Figure 8 is a graph showing the relationship between energy consumption and compensation capacitance of the position detection coil;

[0028] Fig. 9 is the sampling voltage U RL With the sampling resistor R L Relationship diagram;

[0029] Fig.10 P is the energy consumption RL With the sampling resistor R L Relationship diagram;

[0030] Fig.11 This is the zero-crossing position diagram of the beacon coil magnetic field.

[0031] Reference numerals: 1 - transmitting coil, 2 - receiving coil, 3 - beacon coil, 4 - position detection coil array. DETAILED DESCRIPTION

[0032] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0033] In the description of the present invention, “plurality” means two or more than two, unless otherwise clearly and specifically defined.

[0034] like Figure 1 , Figure 2 As shown, this embodiment provides a secondary side position detection system for wireless charging of electric vehicles, including a primary side transmitting coil 1 and a secondary side receiving coil 2, at least one beacon coil 3 is installed at the magnetic field zero crossing position below the receiving coil 2, and the beacon coil 3 is connected to a beacon circuit, and a position detection coil array 4 is laid above the transmitting coil 1, and each position detection coil in the position detection coil array 4 is connected to a position detection circuit.

[0035] In specific implementation, the position detection coil is a rectangular coil, and is spread over the entire upper area of ​​the transmitting coil 1 in an 8*10 array. There are multiple beacon coils 3, which are symmetrically distributed along the center of the receiving coil 2. Each beacon coil 3 and each position detection coil has 4 turns. The transmitting coil 1 and the receiving coil 2 work at 85kHz to achieve energy transmission, and the beacon coil 3 and the corresponding position detection coil in the position detection coil array 4 work at 5MHz to achieve secondary side position detection.

[0036] Combination Figure 3 It can be seen that the beacon circuit includes a DC signal source, a half-bridge inverter and an LCC resonant compensation network. The beacon circuit adopts an LCC resonant mode, and its resonant frequency is selected to be 5MHz, which reduces L 0 Size to increase L 1 The current on L 1 The effective value of the upper current reaches about 5A to improve the detection signal strength of the system.

[0037] Combination Figure 4 As shown, the position detection circuit includes an RLC resonant circuit, a high-pass filter circuit and a rectifier filter circuit. The rectifier filter circuit includes a diode and an RC filter. The RLC resonant circuit in the position detection circuit is designed as a low quality factor circuit, that is, a larger R L ; The 5MHz high-frequency gain of the high-pass filter circuit should be more than 10 times the 85kHz frequency gain; the input voltage amplitude of the rectifier filter circuit (the output voltage amplitude of the high-pass filter circuit) should be more than 5 times the diode voltage drop.

[0038] Due to the uneven distribution of magnetic field, the self-inductance of the position detection coil is as low as 2.2uH, as high as 2.6uH, with an average value of 2.32uH and a median value of 2.4uH. In order to reduce the influence of the discrete distribution of the self-inductance of the position detection coil on the resonance matching and sampling voltage, the self-inductance value of the position detection coil is selected as 2.4uH for resonant capacitance compensation. At this time, the capacitance value is 0.42uF. Figure 5 It can be seen that under the same mutual inductance, R L =100Ω, the position detection coil self-inductance is between 2.2uH and 2.6uH, R L The sampling voltage U RL Basically the same; also by Figure 6 It can be seen that under the same mutual inductance, R L =100Ω, the position detection coil self-inductance is between 2.2uH and 2.6uH, R L There is basically no energy consumption.

[0039] Depend on Figure 7 , Figure 8 It can be seen that according to the self-inductance of the position detection coil, a 470pF capacitor and a 100Ω sampling resistor R are selected. L Parameter calculation is performed, and within the deviation range of ±10% of the inherent deviation of the capacitor, the sampling voltage U RL Stable and low energy consumption P RL .

[0040] Depend on Fig. 9 , Fig.10 It can be seen that although a larger sampling resistor R is selected L It can improve the detection effect, but the larger sampling resistance R L This will cause the 85kHz current induced to the transmitting coil to increase, which will affect the safety of the system. Considering that the sampling voltage needs to pass through a high-pass filter circuit to amplify the 5MHz signal and attenuate the 85kHz signal, the sampling resistor R is selected. L =100Ω.

[0041] Depend on Fig.11 It can be seen that there is a zero-crossing position of the 85kHz magnetic field at the receiving coil, that is, the mutual inductance of the receiving coil and the beacon coil at this position is zero. At this time, the voltage induced on the beacon coil to the receiving coil is zero. This position is the Y-direction installation position of the beacon coil, and the X-direction can be selected at the X=0 position.

[0042] Based on the above system, this embodiment also provides a wireless charging control method for electric vehicles, which adopts the secondary side position detection system mentioned above, determines the position of the beacon coil 3 through the detection signal of each position detection coil in the position detection coil array 4 to determine whether the secondary side position is aligned, and starts the transmitting coil 1 to realize energy transmission when the secondary side position is aligned.

[0043] As another embodiment, there are usually multiple zero-crossing positions of the magnetic field of the receiving coil. Different numbers of beacon coils can be set on the receiving coil according to different vehicle power levels. The number of beacon coils 3 can be determined by the detection signals of each position detection coil in the position detection coil array 4, and the power level of the receiving coil 2 can be determined according to the number of beacon coils 3. After the secondary side position is aligned, the transmitting coil 1 is started to realize energy transmission according to the corresponding power level.

[0044] It is not difficult to see that the secondary side position detection system and control method for wireless charging of electric vehicles proposed in the present invention can eliminate various influences generated by the power system and sensitively detect the center position of the receiving coil, and basically do not generate additional losses, thereby ensuring efficient power transmission.

[0045] Finally, it should be noted that what is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A secondary side position detection system for wireless charging of electric vehicles, comprising a primary side transmitting coil (1) and a secondary side receiving coil (2), characterized in that: At least one beacon coil (3) is installed at a magnetic field zero-crossing position below the receiving coil (2), the beacon coil (3) being connected to a beacon circuit, and a position detection coil array (4) is laid above the transmitting coil (1), each position detection coil in the position detection coil array (4) being connected to a position detection circuit, the number of beacon coils (3) is determined by detection signals of each position detection coil in the position detection coil array (4), the power level of the receiving coil (2) is determined according to the number of beacon coils (3), and after the secondary side position is aligned, the transmitting coil (1) is started to realize energy transmission according to the corresponding power level.

2. The secondary side position detection system for wireless charging of electric vehicles according to claim 1, characterized in that: The transmitting coil (1) and the receiving coil (2) operate at a first resonant frequency to achieve energy transmission, and the beacon coil (3) and the corresponding position detection coil in the position detection coil array (4) operate at a second resonant frequency to achieve secondary side position detection.

3. The secondary side position detection system for wireless charging of electric vehicles according to claim 2, characterized in that: The first resonant frequency is 85 kHz, and the second resonant frequency is 5 MHz.

4. The secondary side position detection system for wireless charging of electric vehicles according to any one of claims 1 to 3, characterized in that: The position detection coil is a rectangular coil and is spread over the entire upper area of ​​the transmitting coil (1) in an 8*10 array.

5. The secondary side position detection system for wireless charging of electric vehicles according to claim 4, characterized in that: A plurality of beacon coils (3) are provided and are symmetrically distributed along the center position of the receiving coil (2); the number of turns of each beacon coil (3) and each position detection coil is 4.

6. The secondary side position detection system for wireless charging of electric vehicles according to claim 1 or 5, characterized in that: The beacon circuit includes a DC signal source, a half-bridge inverter and an LCC resonant compensation network.

7. The secondary side position detection system for wireless charging of electric vehicles according to claim 2 or 3, characterized in that: The position detection circuit includes an RLC resonant circuit, a high-pass filter circuit and a rectifier filter circuit. The RLC resonant circuit is a low-quality factor circuit that resonates at a second resonant frequency. The high-frequency gain of the high-pass filter circuit at the second resonant frequency is more than 10 times the gain of the first resonant frequency.

8. The secondary side position detection system for wireless charging of electric vehicles according to claim 7, characterized in that: The rectification and filtering circuit comprises a diode and an RC filter, and the voltage amplitude output by the high-pass filtering circuit is more than 5 times the voltage drop value of the diode.

9. A wireless charging control method for electric vehicles, characterized in that: A secondary side position detection system as described in any one of claims 1 to 8 is used to determine the position of the beacon coil (3) through the detection signals of each position detection coil in the position detection coil array (4) to determine whether the secondary side position is aligned, and when the secondary side position is aligned, the transmitting coil (1) is started to realize energy transmission.

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