Adaptive control method and system for static wireless charging position of electric vehicle

Abstract

The application relates to the technical field of wireless charging of electric vehicles, and particularly discloses a static wireless charging position adaptive control method and system for electric vehicles, wherein the control method comprises the following steps: acquiring the lateral offset distance of the electric vehicle; judging whether the lateral offset distance is smaller than a first preset distance; if yes, controlling the magnetic coupling mechanism to switch to a double-coil coupling mechanism; if not, controlling the magnetic coupling mechanism to switch to a three-coil coupling mechanism comprising a relay coil; the transmitting coil, the relay coil and the receiving coil all adopt annular planar coils, and the transmitting coil is located in the central blank area of the relay coil. The application combines the characteristics that the two-coil structure has high efficiency when the offset distance is short and the three-coil structure has high efficiency when the offset distance is long, adds a switchable relay coil in the coupling mechanism, and optimizes the radius of the relay coil, so that the system efficiency is always kept at a high level within the allowable range of the lateral offset distance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless charging of electric vehicles, and particularly relates to a static wireless charging position adaptive control method and system for electric vehicles. BACKGROUND

[0002] Wireless power transfer (WPT) technology is widely used in electric vehicles, biomedicine, unmanned aerial vehicles and other fields due to its safety, convenience, reliability and other advantages. Among them, it is most widely used in the field of electric vehicles. However, in the process of applying wireless power transfer system in the field of electric vehicles, a major problem is that during parking, due to the limitations of manual driving technology or parking space, the primary and secondary coils are difficult to achieve complete alignment, and the two coils inevitably have lateral deviation, resulting in a decrease in coupling degree, thereby causing a significant decrease in transmission power and efficiency of the magnetic coupling wireless power transfer system.

[0003] In view of the problem of transmission efficiency and power reduction caused by the deviation of the primary and secondary coils, many documents have proposed solutions. At present, scholars at home and abroad mainly improve the anti-deviation characteristics of the WPT system from three aspects of closed-loop control, compensation topology and coupling mechanism. The way of improving the anti-deviation performance of the WPT system through closed-loop control requires the real-time transmission of the secondary feedback signal to the primary side, which requires high wireless communication. Improving the anti-deviation performance of the WPT system through compensation topology usually increases the reactive loss of the system and reduces the efficiency of the system. Although the effect of improving the anti-deviation performance of the WPT system through improving the coupling mechanism is significant, the coil design is usually complex. SUMMARY

[0004] The present application provides a static wireless charging position adaptive control method and system for electric vehicles, which solves the technical problem of how to achieve efficient transmission of the system through simple coupling mechanism design and control.

[0005] To solve the above technical problems, the present application provides a static wireless charging position adaptive control method for electric vehicles, comprising the steps of:

[0006] S1, obtaining the lateral deviation distance of the electric vehicle;

[0007] S2, judging whether the lateral deviation distance is less than a first preset distance, if yes, controlling the magnetic coupling mechanism to switch to a double-coil coupling mechanism including a transmitting coil and a receiving coil, if not, controlling the magnetic coupling mechanism to switch to a three-coil coupling mechanism including a transmitting coil, a relay coil and a receiving coil; the transmitting coil, the relay coil and the receiving coil all adopt a ring-shaped planar coil, the transmitting coil is located in the central blank area of the relay coil; the relay coil is connected with a relay resonance capacitor to form a closed loop.

[0008] Further, in the step S2, the radius of the relay coil is determined by the following steps:

[0009] L1, taking the radius r of the relay coil as different multiples of the radius of the transmitting coil respectively;

[0010] L2, obtaining the charging efficiency of the wireless charging system using the three-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance at different multiples of the radius of the relay coil, and drawing the corresponding three-coil efficiency variation curve;

[0011] L3, obtaining the charging efficiency of the wireless charging system using the double-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and drawing the corresponding double-coil efficiency variation curve;

[0012] L4, finding the three-coil efficiency variation curve with the highest efficiency value at the intersection of the multiple three-coil efficiency variation curves and the double-coil efficiency variation curve, and taking the coil radius corresponding to the three-coil efficiency variation curve as the selected radius of the relay coil.

[0013] Further, in the step S2, the first preset distance is the lateral offset distance corresponding to the intersection with the highest efficiency value of the double-coil efficiency variation curve in the step L4.

[0014] Further, the step S2 is:

[0015] S21, judging whether the lateral offset distance is between 0 and the first preset distance, between the first preset distance and the second preset distance, or between the second preset distance and the maximum allowable offset distance, if it is between 0 and the first preset distance, executing the step S22, if it is between the first preset distance and the second preset distance, executing the step S23, and if it is between the second preset distance and the maximum allowable offset distance, executing the step S24;

[0016] S22, controlling the magnetic coupling mechanism to switch to the double-coil coupling mechanism including the transmitting coil and the receiving coil;

[0017] S23, controlling the magnetic coupling mechanism to switch to the first three-coil coupling mechanism including the transmitting coil, the first relay coil, and the receiving coil;

[0018] S24, controlling the magnetic coupling mechanism to switch to the second three-coil coupling mechanism including the transmitting coil, the second relay coil, and the receiving coil;

[0019] The transmitting coil, the first relay coil, the second relay coil and the receiving coil are all annular planar coils, the transmitting coil is located in the central blank area of the first relay coil or the second relay coil, and the radius of the first relay coil is smaller than the radius of the second relay coil.

[0020] Further, the radius of the first relay coil is determined by the following steps:

[0021] M1, taking the radius of the first relay coil as different multiples of the radius of the transmitting coil;

[0022] M2, obtaining the charging efficiency of the wireless charging system using the first three-coil coupling mechanism under the radius of the first relay coil with different multiples and the lateral offset distance from 0 to the maximum allowable offset distance, and drawing the corresponding three-coil efficiency variation curve;

[0023] M3, obtaining the charging efficiency of the wireless charging system using the double-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and drawing the corresponding double-coil efficiency variation curve;

[0024] M4, finding the three-coil efficiency variation curve with the highest efficiency value at the intersection of the multiple three-coil efficiency variation curves and the double-coil efficiency variation curve, and taking the coil radius corresponding to the three-coil efficiency variation curve as the selected radius of the first relay coil.

[0025] Further, the radius of the second relay coil is determined by the following steps:

[0026] N1, taking the radius of the second relay coil as E, F, G times of the radius of the transmitting coil, E<F<G;

[0027] N2, obtaining the charging efficiency of the wireless charging system using the second three-coil coupling mechanism under the radius of the second relay coil with different multiples and the lateral offset distance from 0 to the maximum allowable offset distance, and drawing the corresponding three-coil efficiency variation curve;

[0028] N3, obtaining the charging efficiency of the wireless charging system using the double-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and drawing the corresponding double-coil efficiency variation curve;

[0029] N4, finding the intersection point A1 with the highest efficiency value of the multiple three-coil efficiency variation curves and the double-coil efficiency variation curve, and determining the first preset distance as the lateral offset distance corresponding to the A1 point.

[0030] N5, find the intersection point B1 of the three-coil efficiency change curve corresponding to A1 point and other three-coil efficiency change curves with the highest efficiency value after the first preset distance, determine the transverse offset distance corresponding to A1 point as the second preset distance, and take the coil radius corresponding to the three-coil efficiency change curve corresponding to A1 point as the radius of the selected second relay coil.

[0031] Further, in the step N1, E, F, G are determined by the following steps:

[0032] O1, increase by 0.1 times each time, take at least 10 different multiples of the radius of the second relay coil with respect to the radius of the transmitting coil;

[0033] O2, obtain the charging efficiency of the wireless charging system using the second three-coil coupling mechanism from 0 to the maximum allowable offset distance under different multiples of the radius of the second relay coil, and draw the corresponding three-coil efficiency change curve;

[0034] O3, determine the multiple of the radius of the three-coil efficiency change curve with the most gentle change as the F value, determine F minus 0.2 or 0.3 as the E value, and determine F plus 0.2 or 0.3 as the G value.

[0035] The application also provides a static wireless charging position adaptive control system for electric vehicles, which is characterized by comprising an offset distance acquisition module and a coupling mechanism switching module.

[0036] The offset distance acquisition module is used to acquire the transverse offset distance of the electric vehicle.

[0037] The coupling mechanism switching module is used to judge whether the transverse offset distance is less than a first preset distance, if yes, control the magnetic coupling mechanism to switch to a double-coil coupling mechanism comprising a transmitting coil and a receiving coil, if not, control the magnetic coupling mechanism to switch to a three-coil coupling mechanism comprising a transmitting coil, a relay coil and a receiving coil; the transmitting coil, the relay coil and the receiving coil all adopt annular planar coils, the transmitting coil is located in the central blank area of the relay coil; the relay coil is connected with a relay resonance capacitor to form a closed loop.

[0038] Preferably, the coupling mechanism switching module or is used to determine whether the lateral offset distance is between 0 and a first preset distance, between the first preset distance and a second preset distance, or between the second preset distance and a maximum allowable offset distance, and if it is between 0 and the first preset distance, control the magnetic coupling mechanism to switch to a two-coil coupling mechanism including a transmitting coil and a receiving coil, if it is between the first preset distance and the second preset distance, control the magnetic coupling mechanism to switch to a first three-coil coupling mechanism including a transmitting coil, a first relay coil and a receiving coil, and if it is between the second preset distance and the maximum allowable offset distance, control the magnetic coupling mechanism to switch to a second three-coil coupling mechanism including a transmitting coil, a second relay coil and a receiving coil.

[0039] Preferably, the radius of the relay coil is determined by the following steps:

[0040] L1, taking the radius of the relay coil as different multiples of the radius of the transmitting coil;

[0041] L2, obtaining the charging efficiency of the wireless charging system using the three-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance at different multiples of the radius of the relay coil, and drawing a corresponding three-coil efficiency variation curve;

[0042] L3, obtaining the charging efficiency of the wireless charging system using the two-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and drawing a corresponding two-coil efficiency variation curve;

[0043] L4, finding the three-coil efficiency variation curve with the highest efficiency value at the intersection of the multiple three-coil efficiency variation curves and the two-coil efficiency variation curve, and taking the coil radius corresponding to the three-coil efficiency variation curve as the selected radius of the relay coil; the first preset distance is the lateral offset distance corresponding to the intersection with the highest efficiency value of the two-coil efficiency variation curve in step L4;

[0044] The radius of the first relay coil is determined by the following steps:

[0045] M1, taking the radius of the first relay coil as different multiples of the radius of the transmitting coil;

[0046] M2, obtaining the charging efficiency of the wireless charging system using the first three-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance at different multiples of the radius of the first relay coil, and drawing a corresponding three-coil efficiency variation curve;

[0047] M3. Obtain the charging efficiency of the wireless charging system using the dual-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding dual-coil efficiency variation curve.

[0048] M4. Find the three-coil efficiency change curve with the highest efficiency value at the intersection of the three-coil efficiency change curve and the two-coil efficiency change curve, and take the coil radius corresponding to the three-coil efficiency change curve as the radius of the selected first relay coil.

[0049] The radius of the second relay coil is determined by the following steps:

[0050] N1. The radii of the second relay coil are E, F, and G times the radius of the transmitting coil, respectively. <F<G;

[0051] N2. Obtain the charging efficiency of the wireless charging system using the second three-coil coupling mechanism under different multiples of the radius of the second relay coil, with the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding three-coil efficiency variation curve.

[0052] N3. Obtain the charging efficiency of the wireless charging system using the dual-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding dual-coil efficiency variation curve.

[0053] N4. Find the intersection point with the highest efficiency value of the three-coil efficiency change curve and the two-coil efficiency change curve, and mark it as point A1. Then, determine the lateral offset distance corresponding to point A1 as the first preset distance.

[0054] N5. Find the intersection point of the efficiency change curve of the three coils corresponding to point A1 and the highest efficiency value of the efficiency change curve of the other three coils after the first preset distance, and mark it as point B1. Determine the lateral offset distance corresponding to point A1 as the second preset distance, and take the coil radius corresponding to the efficiency change curve of the three coils corresponding to point A1 as the radius of the selected second relay coil.

[0055] In step N1, E, F, and G are determined using the following steps:

[0056] O1. Each time, the radius of the second relay coil is increased by 0.1 times, and at least 10 different multiples of the radius of the transmitting coil are taken;

[0057] O2. Obtain the charging efficiency of the wireless charging system using the second three-coil coupling mechanism under different multiples of the radius of the second relay coil, with the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding three-coil efficiency variation curve.

[0058] O3, determine the multiple of the radius of the three-coil efficiency change curve with the most gentle change as the F value, determine F minus 0.2 or 0.3 as the E value, and determine F plus 0.2 or 0.3 as the F value.

[0059] The application provides a static wireless charging position adaptive control method and system for an electric vehicle, which combines the characteristics that the efficiency of a two-coil structure is high when the offset distance is short and the efficiency of a three-coil structure is high when the offset distance is long, adds a switchable relay coil in the coupling mechanism, the relay coil, the transmitting coil and the receiving coil are all annular planar coils, the transmitting coil is located in the central blank area of the relay coil, and the radius of the relay coil is optimized, so that the system efficiency is always kept at a high level within the allowable range of the lateral offset distance. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is a two-coil WPT system circuit diagram provided by an embodiment of the application for an electric vehicle;

[0061] Figure 2 is a three-coil WPT system circuit diagram provided by an embodiment of the application for an electric vehicle;

[0062] Figure 3 is an equivalent circuit diagram of a three-coil WPT system provided by an embodiment of the application;

[0063] Figure 4 is a curve diagram of mutual inductance between coils varying with the lateral offset distance provided by an embodiment of the application;

[0064] Figure 5 is a curve diagram of the efficiency of a two / three-coil structure varying with the lateral offset distance provided by an embodiment of the application;

[0065] Figure 6 is an equivalent circuit diagram of a three-coil WPT system based on relay coil switching provided by an embodiment of the application;

[0066] Figure 7 is a curve diagram of the efficiency of a two / three-coil structure varying with the size of a relay coil provided by an embodiment of the application;

[0067] Figure 8 is an experimental waveform diagram of a two-coil structure WPT system provided by an embodiment of the application, wherein (a) corresponds to no lateral offset, and (b) corresponds to a lateral offset distance of 10 cm;

[0068] Figure 9 is an experimental waveform diagram of a three-coil structure WPT system provided by an embodiment of the application, wherein (a) corresponds to no lateral offset, and (b) corresponds to a lateral offset distance of 10 cm;

[0069] Figure 10This is a graph showing the experimental efficiency of the two / three-coil WPT system provided in this embodiment of the invention as a function of lateral offset distance. Detailed Implementation

[0070] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0071] Figure 1 This is a circuit diagram of a two-coil WPT system for an electric vehicle. L1 and L2 are the self-inductances of the transmitting and receiving coils, respectively; M... 12 The mutual inductance between them; C1 and C2 are the compensation capacitors of the transmitting and receiving coils; R1 and R2 are the equivalent internal resistances of the transmitting and receiving coils; R L This is a resistive load. S1, S2, S3, and S4 represent inverter switching elements; D1, D2, D3, and D4 represent rectifier switching elements; C L This represents the filter capacitor. U is the DC input. These are the current phasors of the transmitting coil and the receiving coil, respectively.

[0072] To simplify the analysis, Figure 1 Perform an equivalent circuit, the equivalent circuit diagram is as follows: Figure 2 As shown. Among them, R is the output voltage of the inverter circuit. Le It is an equivalent resistive load, and R Le =8R L / π 2 .

[0073] The system's operating angular frequency is ω, which satisfies the following expression:

[0074]

[0075] According to Kirchhoff's laws and the theory of mutual inductance coupling, the circuit equations of each coil in the two-coil WPT system can be obtained as follows:

[0076]

[0077] Where Z1 and Z2 are the loop impedances of the transmitting coil and receiving coil, respectively. The specific expressions for Z1 and Z2 are as follows:

[0078]

[0079] The coil current expression can be obtained from equations (1)-(3) as follows:

[0080]

[0081] The expressions of the output power and the transmission efficiency of the two-coil structure WPT system are as follows:

[0082] P2 = I s 2 R Le (5)

[0083]

[0084] Substituting equation (4) into equation (6), the following expression can be obtained:

[0085]

[0086] A relay coil is added to the transmitting coil side of the two-coil structure WPT system, and a three-coil structure WPT system is formed, and its equivalent circuit diagram is shown in Figure 3 r , C r , R r are the self-inductance, compensation capacitance and equivalent resistance of the relay coil, respectively. M 1r , M 2r are the mutual inductance between the transmitting coil and the relay coil, and the mutual inductance between the receiving coil and the relay coil, respectively. are the current phasors of the transmitting coil, the relay coil and the receiving coil, respectively.

[0087] According to the Kirchhoff's law and the mutual inductance coupling theory, the loop equations of each coil of the three-coil WPT system can be obtained as follows:

[0088]

[0089] wherein, Z r is the loop impedance of the relay coil. The specific expression is as follows:

[0090] Z r = jωL r + 1 / jωC r + R r (9)

[0091] According to further derivation of equation (7), the current expression of the three-coil is as follows:

[0092]

[0093]

[0094]

[0095] wherein,

[0096] ​

[0097] The expressions of output power and transmission efficiency of the three-coil structure WPT system are as follows:

[0098] P3 = I2 2 R Le (14)

[0099]

[0100] The coil simulation model is built in ANSYS MAXWELL simulation software. The radius of the transmitting coil and the relay coil is 10 cm, and the number of turns is 20 turns; the radius of the relay coil is 15 cm, and the number of turns is 10 turns, and the distance between the transmitting coil, the relay coil and the receiving coil is 5 cm. When the transmitting coil and the receiving coil are laterally offset, the mutual inductance between the coils changes as shown in Figure 4 .

[0101] As can be seen from Figure 4 , the mutual inductance M 2r between the relay coil and the receiving coil almost maintains 16 uh when the offset distance is less than 5 cm, and the mutual inductance M 2r slowly decreases to 11 uh when the offset distance increases from 5 cm to 10 cm. With the offset distance increasing from 0 cm to 10 cm, the mutual inductance M 12 between the transmitting coil and the receiving coil rapidly decreases from 29 uh to 9 uh. When the transmitting coil and the receiving coil are laterally offset, the relative position of the transmitting coil and the relay coil does not change, so the mutual inductance M 1r between the transmitting coil and the relay coil almost maintains 23 uh.

[0102] As can be seen from the above analysis, when the lateral offset distance of the transmitting coil and the receiving coil increases, the mutual inductance M 2r between the relay coil and the receiving coil and the mutual inductance M 12 between the transmitting coil and the receiving coil will change. As can be seen from the power and efficiency expressions of the two-coil and three-coil structures, the change of the mutual inductance between the coils will affect the output power and transmission efficiency of the system.

[0103] When ω = 2π×85000 rad / s, R1 = R2 = 0.75 Ω, R r = 0.5 Ω, and R L = 20 Ω, the curves of the transmission efficiency of the two-coil and three-coil structures changing with the lateral offset distance can be drawn according to the expressions (6) and (15) as shown in Figure 5 . Figure 5The middle blue curve is a curve of the transmission efficiency of the two-coil structure varying with the lateral offset distance, the red curve is a curve of the transmission efficiency of the three-coil structure WPT system varying with the lateral offset distance, and A is the intersection of the two curves. It can be seen that, as the lateral offset distance increases from 0 cm to 10 cm, the transmission efficiency of the WPT system of the two-coil structure decreases from 91% to 60.5%, and the decreasing speed gradually increases. When the lateral offset distance increases from 0 cm to 7 cm, the transmission efficiency of the WPT system of the three-coil structure increases from 80.7% to 81.2%. When the lateral offset distance increases from 7 cm to 10 cm, the transmission efficiency begins to decrease slowly to 76%. When the offset distance of the transmitting coil and the receiving coil is less than the offset distance corresponding to the point A, the transmission efficiency of the WPT system of the two-coil structure is higher, and when the offset distance is greater than the offset distance corresponding to the point A, the transmission efficiency of the WPT system of the three-coil structure is higher. Therefore, the wireless charging system for the electric vehicle provided in the embodiment of the application adds a switch in the relay coil loop, as shown in Figure 6 The point A is taken as a switching point, when the lateral offset distance is less than the lateral offset distance corresponding to the point A, the switch K is opened, and the system works in the two-coil structure; when the lateral offset distance is greater than the lateral offset distance corresponding to the point A, the switch K is closed, and the system works in the three-coil structure. In this way, the system can have a higher efficiency in any offset distance.

[0104] The size of the relay coil is crucial to the anti-offset performance. Under the condition that the radius of the transmitting coil and the receiving coil is 10 cm, the number of turns is 20, and the number of turns of the relay coil is fixed at 10, when the radius of the relay coil changes, the transmission efficiency curves of the two-coil and three-coil WPT systems are as shown in Figure 7

[0105] Figure 7 In the formula, r1 represents the radius of the transmitting coil, and r represents the radius of the relay coil. When the radius of the relay coil is 1.3 times the radius of the transmitting coil, the switching point A1 is located at the lateral offset distance of 8 cm, and the efficiency is 77.7%. As the lateral offset distance increases to 10 cm, the system efficiency decreases to 69.4%. When the radius of the relay coil is 1.5 times the radius of the transmitting coil, the switching point A2 is located at the lateral offset distance of 7 cm, and the efficiency is 81%. As the lateral offset distance increases to 10 cm, the system efficiency decreases to 76.2%. When the radius of the relay coil is 1.8 times the radius of the transmitting coil, the switching point A3 is located at the lateral offset distance of 7.5 cm, and the efficiency is 79.8%. As the lateral offset distance increases to 10 cm, the system efficiency slightly increases and then slowly decreases to 79.4%. It can be seen that, when the size of the relay coil is designed to be too small, the anti-offset effect cannot be achieved, and when the size of the relay coil is too large, the near-distance anti-offset effect is poor. When the radius of the relay coil is 1.5 times the radius of the transmitting coil, the system has a better anti-offset effect in the offset distance of 0 to r1. ​

[0106] Based on the above analysis, the embodiment of the application provides a static wireless charging position adaptive control method for an electric vehicle, mainly the control and radius setting of a relay coil, comprising the following steps:

[0107] S1, obtaining a lateral offset distance of the electric vehicle;

[0108] S2, judging whether the lateral offset distance is less than a first preset distance, if yes, controlling the magnetic coupling mechanism to switch to a double-coil coupling mechanism comprising a transmitting coil and a receiving coil, if not, controlling the magnetic coupling mechanism to switch to a three-coil coupling mechanism comprising the transmitting coil, the relay coil and the receiving coil; the transmitting coil, the relay coil and the receiving coil all adopt annular planar coils, the transmitting coil is located in a central blank area of the relay coil; the relay coil is connected with a relay resonance capacitor to form a closed loop.

[0109] In step S2, the radius of the relay coil is determined by the following steps:

[0110] L1, taking the radius r of the relay coil as different multiples of the radius of the transmitting coil;

[0111] L2, obtaining the charging efficiency of the wireless charging system adopting the three-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance at different multiples of the radius of the relay coil, and drawing a corresponding three-coil efficiency variation curve;

[0112] L3, obtaining the charging efficiency of the wireless charging system adopting the double-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and drawing a corresponding double-coil efficiency variation curve;

[0113] L4, finding out the three-coil efficiency variation curve with the highest efficiency value at the intersection of the multiple three-coil efficiency variation curves and the double-coil efficiency variation curve, and taking the coil radius corresponding to the three-coil efficiency variation curve as the selected radius of the relay coil.

[0114] In step S2, the first preset distance is the lateral offset distance corresponding to the intersection with the highest efficiency value of the double-coil efficiency variation curve in step L4.

[0115] By taking the double-coil coupling mechanism within the first preset distance and the three-coil coupling mechanism with the relay coil outside the first preset distance, the system can maintain a high transmission efficiency under the allowable lateral offset distance, realizing high anti-offset of the system.

[0116] In order to realize higher efficiency transmission under a large offset distance, step S2 can also be:

[0117] S21, judging whether the lateral offset distance is between 0 and a first preset distance, between the first preset distance and a second preset distance, or between the second preset distance and a maximum allowable offset distance, if between 0 and the first preset distance, performing step S22, if between the first preset distance and the second preset distance, performing step S23, and if between the second preset distance and the maximum allowable offset distance, performing step S24;

[0118] S22, controlling the magnetic coupling mechanism to switch to a two-coil coupling mechanism including the transmitting coil and the receiving coil;

[0119] S23, controlling the magnetic coupling mechanism to switch to a first three-coil coupling mechanism including the transmitting coil, the first relay coil, and the receiving coil;

[0120] S24, controlling the magnetic coupling mechanism to switch to a second three-coil coupling mechanism including the transmitting coil, the second relay coil, and the receiving coil;

[0121] The transmitting coil, the first relay coil, the second relay coil, and the receiving coil are all annular planar coils, the transmitting coil is located in a central blank area of the first relay coil or the second relay coil, and the radius of the first relay coil is smaller than the radius of the second relay coil.

[0122] The radius of the first relay coil is determined by the following steps:

[0123] M1, taking different multiples of the radius of the transmitting coil as the radius of the first relay coil;

[0124] M2, obtaining the charging efficiency of the wireless charging system using the first three-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance at different multiples of the radius of the first relay coil, and drawing a corresponding three-coil efficiency variation curve;

[0125] M3, obtaining the charging efficiency of the wireless charging system using the two-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and drawing a corresponding two-coil efficiency variation curve;

[0126] M4, finding the three-coil efficiency variation curve with the highest efficiency value at the intersection of the multiple three-coil efficiency variation curves and the two-coil efficiency variation curve, and taking the coil radius corresponding to the three-coil efficiency variation curve as the selected radius of the first relay coil.

[0127] The radius of the second relay coil is determined by the following steps:

[0128] N1, taking E, F, and G times of the radius of the transmitting coil as the radius of the second relay coil, E < F < G;

[0129] N2, obtaining the charging efficiency of the wireless charging system using the second three-coil coupling mechanism under different lateral offset distances from 0 to the maximum allowable offset distance at different multiples of the radius of the second relay coil, and drawing the corresponding three-coil efficiency variation curve;

[0130] N3, obtaining the charging efficiency of the wireless charging system using the double-coil coupling mechanism under different lateral offset distances from 0 to the maximum allowable offset distance, and drawing the corresponding double-coil efficiency variation curve;

[0131] N4, finding the intersection point A1 with the highest efficiency value of the multiple three-coil efficiency variation curves and the double-coil efficiency variation curve, and determining the lateral offset distance corresponding to the A1 point as the first preset distance;

[0132] N5, finding the intersection point B1 with the highest efficiency value of the three-coil efficiency variation curve corresponding to the A1 point and other three-coil efficiency variation curves after the first preset distance, determining the lateral offset distance corresponding to the A1 point as the second preset distance, and determining the coil radius corresponding to the three-coil efficiency variation curve corresponding to the A1 point as the radius of the selected second relay coil.

[0133] In step N1, E, F, and G are determined as follows:

[0134] O1, increasing by 0.1 times each time, taking the radius of the second relay coil as at least 10 different multiples of the radius of the transmitting coil;

[0135] O2, obtaining the charging efficiency of the wireless charging system using the second three-coil coupling mechanism under different lateral offset distances from 0 to the maximum allowable offset distance at different multiples of the radius of the second relay coil, and drawing the corresponding three-coil efficiency variation curve;

[0136] O3, determining the multiple of the radius of the three-coil efficiency variation curve with the most gentle variation as the F value, determining F minus 0.2 or 0.3 as the E value, and determining F plus 0.2 or 0.3 as the G value.

[0137] Note that the above-mentioned relay coil, first relay coil, and second relay coil are used to distinguish the relay coil in three cases. In the circuit of Figure 6 , the relay coil L r .

[0138] By the double coil coupling mechanism within the first preset distance, the first three coil coupling mechanism with the first radius within the first preset distance and the second preset distance for the relay coil, and the second three coil coupling mechanism with the second radius within the second preset distance to the maximum allowable lateral offset distance, the system can keep high transmission efficiency within the allowable lateral offset distance, and high anti-offset of the system is realized. Compared with the three coil coupling mechanism with constant radius, the method can keep higher transmission efficiency within larger lateral offset distance.

[0139] Corresponding to the above-mentioned electric vehicle static wireless charging position adaptive control method, the embodiment of the application also provides an electric vehicle static wireless charging position adaptive control system, which comprises an offset distance acquisition module and a coupling mechanism switching module. The offset distance acquisition module is used to acquire the lateral offset distance of the electric vehicle.

[0140] The coupling mechanism switching module is used to judge whether the lateral offset distance is less than the first preset distance. If yes, the magnetic coupling mechanism is switched to the double coil coupling mechanism comprising the transmitting coil and the receiving coil. If not, the magnetic coupling mechanism is switched to the three coil coupling mechanism comprising the transmitting coil, the relay coil and the receiving coil. The transmitting coil, the relay coil and the receiving coil all adopt annular planar coils, and the transmitting coil is located in the central blank area of the relay coil. The relay coil is connected with a relay resonance capacitor to form a closed loop.

[0141] Corresponding to the above-mentioned method, the coupling mechanism switching module is used to judge whether the lateral offset distance is between 0 and the first preset distance, between the first preset distance and the second preset distance, or between the second preset distance and the maximum allowable offset distance. If it is between 0 and the first preset distance, the magnetic coupling mechanism is switched to the double coil coupling mechanism comprising the transmitting coil and the receiving coil. If it is between the first preset distance and the second preset distance, the magnetic coupling mechanism is switched to the first three coil coupling mechanism comprising the transmitting coil, the first relay coil and the receiving coil. If it is between the second preset distance and the maximum allowable offset distance, the magnetic coupling mechanism is switched to the second three coil coupling mechanism comprising the transmitting coil, the second relay coil and the receiving coil.

[0142] The determination steps of the radii of the relay coil, the first relay coil and the second relay coil are the same as those of the above-mentioned method, which will not be described here.

[0143] The control method of the double coil coupling mechanism within the first preset distance and the three coil coupling mechanism with the relay coil outside the first preset distance is verified by experiments.

[0144] According to Figure 1The WPT system circuit diagram and the three-coil WPT system equivalent circuit diagram based on relay coil switching shown in FIG. 6 are used to build an experimental platform. The transmitting coil, the relay coil and the receiving coil all use Litz wire with a diameter of 1.5 mm and are wound according to the Maxwell simulation size. The self-inductance of the transmitting coil and the circuit parameters of the three-coil WPT system are shown in Table 1.

[0145] Table 1 WPT system circuit parameters

[0146]

[0147] When the system works in a two-coil structure, the system experimental waveforms are shown in Figure 8 . The system operating frequency is 82.101 kHz, and the output power is 20 W. Figure 8 (a) of FIG. 7 shows that when the transmitting coil and the receiving coil have no lateral offset, the effective value of the inverter output voltage u s is 19 V, the effective value of the transmitting coil current i1 is 1.27 A, the output DC voltage u o is 20.4 V, and the system efficiency is 91.7%. Figure 8 (b) of FIG. 7 shows that when the lateral offset distance between the transmitting coil and the receiving coil is 10 cm, the effective value of the inverter output voltage u s is 16 V, the effective value of the transmitting coil current i1 is 4.57 A, the output DC voltage u o is 20.8 V, and the system efficiency is 62%.

[0148] When the system works in a three-coil structure, the system experimental waveforms are shown in Figure 9 . The system operating frequency is 82.101 kHz, and the output power is 20 W. Figure 9 (a) of FIG. 8 shows that when the transmitting coil and the receiving coil have no lateral offset, the effective value of the inverter output voltage u s is 41 V, the effective value of the transmitting coil current i1 is 0.62 A, the output DC voltage u o is 20 V, and the system efficiency is 90.3%. Figure 9 (b) of FIG. 8 shows that when the lateral offset distance between the transmitting coil and the receiving coil is 10 cm, the effective value of the inverter output voltage u s is 43 V, the effective value of the transmitting coil current i1 is 0.68 A, the output DC voltage u o is 20.3 V, and the system efficiency is 85.9%.

[0149] When the system output power is 20 W, the experimental efficiency curves of the two-coil and three-coil structures with the lateral offset distance are shown in Figure 10It can be seen that when the lateral offset distance is less than 3 cm, the efficiency of the two-coil structure is higher than that of the three-coil structure. As the offset distance increases from 3 cm to 10 cm, the efficiency of the two-coil structure decreases rapidly to 62%, while the efficiency of the three-coil structure increases slightly and then decreases slowly to 85.9%. Therefore, taking point A as the switching point, when the lateral offset distance is less than 3 cm, the WPT system uses the two-coil structure, and when the lateral offset distance is greater than 3 cm, the WPT system uses the three-coil structure. In this way, the system efficiency can be ensured to be always above 85% when the lateral offset distance changes from 0 cm to 10 cm.

[0150] The verification process in another way is similar, and the embodiment is not listed again.

[0151] In summary, the electric vehicle static wireless charging position adaptive control method and system provided by the embodiment of the application combines the characteristics that the efficiency of the two-coil structure is high when the offset distance is small and the efficiency of the three-coil structure is high when the offset distance is large, adds a switchable relay coil in the coupling mechanism, the relay coil, the transmitting coil and the receiving coil all adopt annular planar coils, the transmitting coil is located in the central blank area of the relay coil, and the radius of the relay coil is optimized and designed, so that within the allowable range of the lateral offset distance (0 cm to 10 cm), the system efficiency is always kept at a high level (above 85%).

[0152] The above embodiment is a preferred embodiment of the application, but the embodiment of the application is not limited by the above embodiment, and any change, modification, substitution, combination, simplification made without departing from the spirit and principle of the application should be an equivalent replacement mode, and all are included in the protection scope of the application.

Claims

1. An adaptive control method for static wireless charging position of electric vehicles, characterized in that, Including the following steps: S1. Obtain the lateral offset distance of the electric vehicle; S2. Determine whether the lateral offset distance is less than a first preset distance. If so, control the magnetic coupling mechanism to switch to a dual-coil coupling mechanism including a transmitting coil and a receiving coil. Otherwise, control the magnetic coupling mechanism to switch to a three-coil coupling mechanism including a transmitting coil, a relay coil, and a receiving coil. The transmitting coil, the relay coil, and the receiving coil are all ring-shaped planar coils. The transmitting coil is located in the central blank area of ​​the relay coil. The relay coil is connected to a relay resonant capacitor to form a closed loop. In step S2, the radius of the relay coil is determined using the following steps: L1, take the radius of the relay coil. r These are different multiples of the radius of the transmitting coil; L2. Obtain the charging efficiency of the wireless charging system using the three-coil coupling mechanism under different multiples of the radius of the relay coil, with the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding three-coil efficiency variation curve. L3. Obtain the charging efficiency of the wireless charging system using the dual-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding dual-coil efficiency variation curve. L4. Find the three-coil efficiency change curve with the highest efficiency value at the intersection of the three-coil efficiency change curve and the two-coil efficiency change curve, and take the coil radius corresponding to the three-coil efficiency change curve as the radius of the selected relay coil.

2. The adaptive control method for static wireless charging position of electric vehicles according to claim 1, characterized in that, In step S2, the first preset distance is the lateral offset distance corresponding to the intersection point with the highest efficiency value of the dual-coil efficiency change curve in step L4.

3. The adaptive control method for static wireless charging position of electric vehicles according to claim 2, characterized in that, Step S2 may be: S21. Determine whether the lateral offset distance is between 0 and the first preset distance, between the first preset distance and the second preset distance, or between the second preset distance and the maximum allowable offset distance. If it is between 0 and the first preset distance, execute step S22. If it is between the first preset distance and the second preset distance, execute step S23. If it is between the second preset distance and the maximum allowable offset distance, execute step S24. S22, Control the magnetic coupling mechanism to switch to a two-coil coupling mechanism including a transmitting coil and a receiving coil; S23, Control the magnetic coupling mechanism to switch to a first three-coil coupling mechanism including a transmitting coil, a first relay coil and a receiving coil; S24. Control the magnetic coupling mechanism to switch to a second three-coil coupling mechanism including a transmitting coil, a second relay coil, and a receiving coil; The transmitting coil, the first relay coil, the second relay coil, and the receiving coil are all ring-shaped planar coils. The transmitting coil is located in the central blank area of ​​the first relay coil or the second relay coil, and the radius of the first relay coil is smaller than the radius of the second relay coil. The radius of the first relay coil is determined through the following steps: M1. The radius of the first relay coil is taken as a different multiple of the radius of the transmitting coil; M2. Obtain the charging efficiency of the wireless charging system using the first three-coil coupling mechanism under different multiples of the radius of the first relay coil, with the lateral offset distance ranging from 0 to the maximum allowable offset distance, and plot the corresponding three-coil efficiency variation curve. M3. Obtain the charging efficiency of the wireless charging system using the dual-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding dual-coil efficiency variation curve. M4. Find the three-coil efficiency change curve with the highest efficiency value at the intersection of the three-coil efficiency change curve and the two-coil efficiency change curve, and take the radius of the coil corresponding to the three-coil efficiency change curve as the radius of the selected first relay coil.

4. The adaptive control method for static wireless charging position of electric vehicles according to claim 3, characterized in that, The radius of the second relay coil is determined by the following steps: N1. The radii of the second relay coil are E, F, and G times the radius of the transmitting coil, respectively. <F<G; N2. Obtain the charging efficiency of the wireless charging system using the second three-coil coupling mechanism under different multiples of the radius of the second relay coil, with the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding three-coil efficiency variation curve. N3. Obtain the charging efficiency of the wireless charging system using the dual-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding dual-coil efficiency variation curve. N4. Find the intersection point with the highest efficiency value of the three-coil efficiency change curve and the two-coil efficiency change curve, and mark it as point A1. Then, determine the lateral offset distance corresponding to point A1 as the first preset distance. N5. Find the intersection point of the efficiency change curve of the three coils corresponding to point A1 and the highest efficiency value of the efficiency change curve of the other three coils after the first preset distance, and mark it as point B1. Determine the lateral offset distance corresponding to point A1 as the second preset distance, and take the coil radius corresponding to the efficiency change curve of the three coils corresponding to point A1 as the radius of the selected second relay coil.

5. The adaptive control method for static wireless charging position of electric vehicles according to claim 3, characterized in that, In step N1, E, F, and G are determined using the following steps: O1. Each time, the radius of the second relay coil is increased by 0.1 times, and at least 10 different multiples of the radius of the transmitting coil are taken; O2. Obtain the charging efficiency of the wireless charging system using the second three-coil coupling mechanism under different multiples of the radius of the second relay coil, with the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding three-coil efficiency variation curve. O3. Determine the multiple of the radius of the three-coil efficiency change curve with the most gradual change as the F value, determine F minus 0.2 or 0.3 as the E value, and determine F plus 0.2 or 0.3 as the G value.

6. An adaptive control system for static wireless charging position of electric vehicles, characterized in that, Includes an offset distance acquisition module and a coupling mechanism switching module; The offset distance acquisition module is used to acquire the lateral offset distance of the electric vehicle; The coupling mechanism switching module is used to determine whether the lateral offset distance is less than a first preset distance. If so, it controls the magnetic coupling mechanism to switch to a dual-coil coupling mechanism including a transmitting coil and a receiving coil; otherwise, it controls the magnetic coupling mechanism to switch to a three-coil coupling mechanism including a transmitting coil, a relay coil, and a receiving coil. The transmitting coil, the relay coil, and the receiving coil are all ring-shaped planar coils, and the transmitting coil is located in the central blank area of ​​the relay coil. The relay coil is connected to a relay resonant capacitor to form a closed loop. The radius of the relay coil is determined using the following steps: L1, take the radius of the relay coil. r These are different multiples of the radius of the transmitting coil; L2. Obtain the charging efficiency of the wireless charging system using the three-coil coupling mechanism under different multiples of the radius of the relay coil, with the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding three-coil efficiency variation curve. L3. Obtain the charging efficiency of the wireless charging system using the dual-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding dual-coil efficiency variation curve. L4. Find the three-coil efficiency change curve with the highest efficiency value at the intersection point of the three-coil efficiency change curve and the two-coil efficiency change curve, and take the coil radius corresponding to the three-coil efficiency change curve as the radius of the selected relay coil; the first preset distance is the lateral offset distance corresponding to the intersection point with the two-coil efficiency change curve with the highest efficiency value in step L4.

7. The electric vehicle static wireless charging position adaptive control system according to claim 6, characterized in that: The coupling mechanism switching module is used to determine whether the lateral offset distance is between 0 and a first preset distance, between the first preset distance and a second preset distance, or between the second preset distance and the maximum allowable offset distance. If it is between 0 and the first preset distance, the magnetic coupling mechanism is controlled to switch to a two-coil coupling mechanism including a transmitting coil and a receiving coil. If it is between the first preset distance and the second preset distance, the magnetic coupling mechanism is controlled to switch to a first three-coil coupling mechanism including a transmitting coil, a first relay coil, and a receiving coil. If it is between the second preset distance and the maximum allowable offset distance, the magnetic coupling mechanism is controlled to switch to a second three-coil coupling mechanism including a transmitting coil, a second relay coil, and a receiving coil.

8. The electric vehicle static wireless charging position adaptive control system according to claim 7, characterized in that, The radius of the first relay coil is determined through the following steps: M1. The radius of the first relay coil is taken as a different multiple of the radius of the transmitting coil; M2. Obtain the charging efficiency of the wireless charging system using the first three-coil coupling mechanism under different multiples of the radius of the first relay coil, with the lateral offset distance ranging from 0 to the maximum allowable offset distance, and plot the corresponding three-coil efficiency variation curve. M3. Obtain the charging efficiency of the wireless charging system using the dual-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding dual-coil efficiency variation curve. M4. Find the three-coil efficiency change curve with the highest efficiency value at the intersection of the three-coil efficiency change curve and the two-coil efficiency change curve, and take the coil radius corresponding to the three-coil efficiency change curve as the radius of the selected first relay coil. The radius of the second relay coil is determined by the following steps: N1. The radii of the second relay coil are E, F, and G times the radius of the transmitting coil, respectively. <F<G; N2. Obtain the charging efficiency of the wireless charging system using the second three-coil coupling mechanism under different multiples of the radius of the second relay coil, with the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding three-coil efficiency variation curve. N3. Obtain the charging efficiency of the wireless charging system using the dual-coil coupling mechanism under the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding dual-coil efficiency variation curve. N4. Find the intersection point with the highest efficiency value of the three-coil efficiency change curve and the two-coil efficiency change curve, and mark it as point A1. Then, determine the lateral offset distance corresponding to point A1 as the first preset distance. N5. Find the intersection point of the efficiency change curve of the three coils corresponding to point A1 and the highest efficiency value of the efficiency change curve of the other three coils after the first preset distance, and mark it as point B1. Determine the lateral offset distance corresponding to point A1 as the second preset distance, and take the coil radius corresponding to the efficiency change curve of the three coils corresponding to point A1 as the radius of the selected second relay coil. In step N1, E, F, and G are determined using the following steps: O1. Each time, the radius of the second relay coil is increased by 0.1 times, and at least 10 different multiples of the radius of the transmitting coil are taken; O2. Obtain the charging efficiency of the wireless charging system using the second three-coil coupling mechanism under different multiples of the radius of the second relay coil, with the lateral offset distance from 0 to the maximum allowable offset distance, and plot the corresponding three-coil efficiency variation curve. O3. Determine the radius of the curve showing the most gradual change in efficiency of the three coils as the F value, determine the E value by subtracting 0.2 or 0.3 from F, and determine the F value by adding 0.2 or 0.3 to F.

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