Lateral offset resisting method for wireless charging of electric vehicle

Abstract

An anti-lateral deviation method for wireless charging of an electric vehicle is characterized in that operation is carried out based on a buck circuit cascaded among a magnetic coupling mechanism, a vehicle end rectifier and a load, in order to further improve the anti-deviation performance of a system, when lateral deviation is large, a voltage regulation link of the vehicle end rectifier is controlled to control the duty ratio of a buck circuit switching tube, and the voltage regulation link of the vehicle end rectifier is controlled to control the duty ratio of the buck circuit switching tube; the charging power is consistent with the load demand power; the method specifically comprises the steps that firstly, initial parameters of a system are stored in a controller; secondly, determining a range of a load charging voltage, a duty ratio adjustment range and a constraint condition of minimum transmission efficiency; calculating a real-time mutual inductance value according to the load charging voltage; and finally, adjusting the real-time duty ratio of the buck circuit according to the load demand power. According to the invention, charging power adjustment can be realized without the help of an additional algorithm, and only one voltage sensor is needed for acquiring the load voltage and controlling at the vehicle end, so that double-end communication is avoided, and the use quantity and cost of hardware are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless power transmission, and in particular relates to an anti-lateral deviation method for wireless charging of electric vehicles. Background Art

[0002] Wireless Power Transfer (WPT) technology uses the principle of electromagnetic induction to transfer electrical energy from the primary side to the secondary side through the air medium. It has the advantages of no contact sparks, small footprint, and strong environmental adaptability. It is widely used in various fields, such as mobile electronic products, medical equipment, electric vehicles, robots, etc.; among them, wireless charging not only reduces the size of the vehicle battery, but also has greater flexibility in the charging process, and has good development prospects.

[0003] Wireless charging of electric vehicles uses the principle of electromagnetic induction to transmit energy from the ground transmitting coil to the vehicle receiving coil. Affected by artificial parking technology, the ground transmitting coil and the vehicle receiving coil will inevitably be offset, resulting in a decrease in the coupling performance between the coupling coils, which in turn leads to a decrease in load charging power, and in severe cases, power zero may occur.

[0004] In order to improve the anti-offset ability of the coupling coil, a Chinese invention patent with application number 202310963916.6 proposes a static wireless charging position adaptive control method and system for electric vehicles. The control method proposed in this invention requires the use of an additional distance detection device to obtain the offset distance and an additional coupling mechanism switching device to switch the coil, which leads to higher control complexity, and the use of additional distance detection devices further increases the cost.

[0005] The Chinese invention patent with application number 202211342375.7 proposes to install a beacon coil at the zero-crossing position of the magnetic field below the receiving coil, 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 the position detection circuit. When an offset occurs, the vehicle-side beacon coil and the ground-side receiving coil array are used to detect the position of the vehicle-mounted receiving terminal, guiding the position alignment of the electric vehicle during wireless charging. The secondary side position detection system and control method for wireless charging of electric vehicles proposed in this invention cannot autonomously adjust the charging power when the ground transmitting terminal and the vehicle-mounted receiving terminal are offset, and an additional detection device needs to be added, resulting in an increase in cost.

[0006] The Chinese invention patent with application number 202310691988.X proposes an anti-deviated coupling mechanism for wireless charging of electric vehicles and its control method; the transmitting coil in the coupling mechanism proposed in the invention includes 16 transmitting sub-coils, which are arranged in a 4×4 array and divided into 8 coil modules, each coil module is provided with a short-circuit branch with a short-circuit switch, and each coil module is provided with a current reversing switch at both ends. In the first coil module to the fourth coil module, multiple transmitting sub-coils are connected in parallel, and a corresponding circuit breaker is provided on each parallel branch. The coupling mechanism and control process of the invention are complex and consume more coil materials.

[0007] In summary, in dealing with the charging power drop caused by the lateral offset between the on-board receiving terminal of the electric vehicle and the ground transmitting terminal, the existing solutions have the problems of complex coupling mechanism design or control and high system cost. Summary of the invention

[0008] In response to the technical problem that the lateral offset of the on-board receiving end during wireless charging of the above-mentioned electric vehicle causes the load charging power to drop, the present technical solution provides an anti-lateral offset method for wireless charging of electric vehicles, and designs a duty cycle control scheme for the buck circuit cascaded between the magnetic coupling mechanism, the vehicle-end rectifier and the load. The duty cycle is adjusted according to the collected load voltage and load demand power to achieve matching of the system charging power and the load demand power in the lateral offset state; the entire control process does not require the aid of additional algorithms, which simplifies the complexity of the control process; at the same time, only the single data of the load voltage at the vehicle end needs to be detected, and there is no need to collect the load current or the inductor current, thus avoiding the use of too much hardware, thereby reducing the cost in actual use; it can effectively solve the above-mentioned problems.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for resisting lateral offset for wireless charging of electric vehicles is based on a buck circuit cascaded between a magnetic coupling mechanism, a vehicle-end rectifier and a load. In order to further improve the anti-offset performance of the system, when the lateral offset is large, the voltage regulation link of the vehicle-end rectifier is controlled to control the duty cycle of the buck circuit switch tube to achieve the consistency of charging power with the load demand power; the specific operation method is:

[0011] Step 1: Operate based on the electric vehicle wireless charging system and store the initial parameters of the system in the controller;

[0012] The electric vehicle wireless charging system comprises: a double-layer cross-rectangular magnetic coupling mechanism, a buck converter cascaded between the vehicle-end rectifier and the load;

[0013] The initial parameters of the system include: DC input voltage, system operating frequency, compensation inductance, coil internal resistance, load demand power, total efficiency of vehicle-side equipment, and duty cycle of buck circuit switch tube;

[0014] Step 2: Determine the relevant constraints, and calculate the maximum and minimum values ​​of the mutual inductance through the relationship between the mutual inductance and the equivalent impedance, the system transmission efficiency, and the load charging voltage, to determine whether the constraints can be met;

[0015] The relevant constraints include: the range of load charging voltage, the adjustment range of duty cycle, and the minimum transmission efficiency;

[0016] The range of the charging voltage is: U L_min ≤U L ≤U L_max ;

[0017] The adjustment range of the duty cycle is: α min ≤α≤α max ;

[0018] The minimum transmission efficiency is: t_min ; The maximum value of mutual inductance is M max , the minimum value is M min ;

[0019] Among them, U L is the charging voltage, U L_min is the starting value of the charging voltage, U L_max is the final value of the charging voltage; α is the duty cycle, α min is the minimum ratio of the duty cycle, α max is the maximum ratio of the duty cycle;

[0020] Step 3: According to the load voltage collected in real time, calculate the mutual inductance value of the vehicle-mounted receiving terminal in the lateral offset state at that moment, and determine whether the mutual inductance value at this moment is between the maximum and minimum values ​​of the mutual inductance in step 2; the basis for the determination is:

[0021] If the mutual inductance in step 2 is between the maximum and minimum values, the transmission efficiency at this time is output and the next step is entered;

[0022] If it is not between the maximum and minimum values ​​of the mutual inductance in step 2, it is determined that the conditions at this time cannot achieve the matching of the output power and the load charging power, and the user is notified to adjust the vehicle position;

[0023] Step 4: The next adjustment value of the duty cycle α is calculated based on the system charging power and the power required by the load, and the adjustment value of the duty cycle is output to the drive circuit of the buck circuit switch tube to adjust the real-time duty cycle of the buck circuit.

[0024] Furthermore, the double-layer cross-rectangular magnetic coupling mechanism described in step one forms an electric energy transmission channel through a ground-end transmitting coil and a vehicle-end receiving coil; the ground-end transmitting coil and the vehicle-end receiving coil are both composed of Litz wire and a ferrite core.

[0025] Furthermore, the ground-end transmitting coil includes a first layer of ferrite plate laid on the bottom layer, and a second layer of rectangular coil and a third layer of rectangular coil are arranged on the upper side of the first layer of ferrite plate, and the two layers of rectangular coils are both wound by a Litz wire and are orthogonal to form a cross shape; the vehicle-end receiving coil has the same structure as the ground-end transmitting coil and is arranged in opposite directions; the vehicle-end receiving coil is located directly above the ground-end transmitting coil, and when the two are opposite, there is a gap between the cross-shaped coils.

[0026] Furthermore, the second layer rectangular coil and the third layer rectangular coil are both wound by Litz wires with a single wire diameter of 0.1 mm, a total of 1750 wires, and an outer diameter of 6.3 mm.

[0027] Furthermore, the number of turns of the second-layer rectangular coil and the third-layer rectangular coil are both N turns, the coil turn spacing is dmm, and the length-to-width ratio inside the rectangular coil is 2:1; the winding method of the second-layer rectangular coil and the third-layer rectangular coil is: firstly wind the second-layer rectangular coil from the outside to the inside, and then wind the third-layer rectangular coil from the inside to the outside, and the second-layer rectangular coil and the third-layer rectangular coil are in a cross-shaped state perpendicular to each other;

[0028] Furthermore, the ferrite plate is a square structure, the width of which is the same as the length of the rectangular coil, and the thickness is 2 mm.

[0029] Furthermore, the buck circuit is used as a dc-dc converter, and combined with the electric vehicle wireless charging system, the DC voltage input to the system is converted into an AC input for resonance compensation at the transmitter end after being inverted by a full-bridge at the ground end, and then the energy is transmitted to the vehicle end through a magnetic coupling coil, and finally the vehicle end AC input is converted into a DC output for charging the load after vehicle end resonance compensation, full-bridge rectification and the voltage regulation link of the dc-dc converter.

[0030] Furthermore, the relationship between the mutual inductance and equivalent impedance, the system transmission efficiency, and the load charging voltage described in step 2 is:

[0031] The mutual inductance M and the equivalent impedance Z R , the system transmission efficiency η is:

[0032]

[0033] In the above formula, r r is the parasitic resistance of the receiving coil; r t is the parasitic resistance of the transmitting coil; Z eqis the total equivalent impedance of the vehicle-end circuit when the system is in the resonant state; ω0 is the system operating frequency;

[0034] The relationship between the mutual inductance M and the load charging voltage U is:

[0035]

[0036] In the above formula, Lp is the inductance of the ground-end resonant compensation network, and Uin is the DC input voltage at the ground end of the system;

[0037] Furthermore, the expression of the transmission efficiency described in step 3 is:

[0038]

[0039] In the above formula, r r is the parasitic resistance of the receiving coil; r t is the parasitic resistance of the transmitting coil; Z R is the equivalent impedance; ω0 is the system operating frequency;

[0040] Furthermore, the solution method for the system charging power PL described in step 4 is:

[0041]

[0042] In the above formula, Lp is the inductance of the ground-end resonant compensation network, and Uin is the DC input voltage at the ground end of the system;

[0043] Furthermore, the calculation formula for the adjustment value of the duty cycle α at the next moment described in step 4 is:

[0044]

[0045] In the above formula, P ref is the load demand power; η loss is the total efficiency of the vehicle-side equipment; α' is the adjustment value at the next moment, and t+1 is the next moment.

[0046] Beneficial Effects

[0047] The present invention proposes a method for resisting lateral deviation for wireless charging of electric vehicles, which has the following beneficial effects compared with the prior art:

[0048] (1) The present invention designs a duty cycle control scheme based on the buck circuit cascaded between the magnetic coupling mechanism, the vehicle-end rectifier and the load. The real-time mutual inductance value is derived through the load voltage data, and the duty cycle of the vehicle-end buck converter is controlled in combination with the collected load voltage and load demand power. The duty cycle is adjusted to achieve matching of the system charging power and the load demand power in the lateral offset state. The entire control process does not require the use of additional algorithms, which simplifies the complexity of the control process and makes the entire control process simple. At the same time, only the single data of the load voltage at the vehicle end needs to be detected, and there is no need to collect the load current or the inductor current, which avoids the use of too much hardware, and there is no need to use additional auxiliary coils or auxiliary devices. Only a single sensor is needed to collect the load voltage for charging power adjustment, thereby reducing the cost in actual use. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the overall process of the present invention.

[0050] Figure 2 It is a structural schematic diagram of the magnetic coupling mechanism in the present invention.

[0051] Figure 3 This is a topological circuit diagram of the wireless charging system for electric vehicles in the present invention.

[0052] Figure 4 It is a schematic diagram of the finite element simulation magnetic field of the magnetic coupling mechanism in the present invention.

[0053] Figure 5 It is a diagram of the power simulation model based on Maxwell-Simplorer in the embodiment.

[0054] Figure 6 Schematic diagram of the mutual inductance and charging power curve when the vehicle-end receiving coil is laterally offset from -150mm to +150mm in the embodiment.

[0055] Figure 7 It is a schematic diagram of charging power comparison before and after the anti-lateral deviation method of the present invention is adopted when the vehicle-end receiving coil in the embodiment is laterally offset by 150 mm. DETAILED DESCRIPTION

[0056] The technical scheme in the embodiment of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiment of the present invention. The described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Without departing from the design concept of the present invention, various modifications and improvements made to the technical scheme of the present invention by ordinary persons in the art should all fall within the protection scope of the present invention.

[0057] Embodiment 1:

[0058] A method for resisting lateral offset for wireless charging of electric vehicles is based on a buck circuit cascaded between a magnetic coupling mechanism, a vehicle-side rectifier and a load. To further improve the system's anti-offset performance, when the lateral offset is large, the voltage regulation link of the vehicle-side rectifier is controlled to control the duty cycle of the buck circuit switch tube to achieve the consistency of charging power with load demand power. Figure 1 As shown, the specific operation mode of the anti-lateral deviation method for wireless charging of electric vehicles is:

[0059] Step 1: Operate based on the electric vehicle wireless charging system and store the initial parameters of the system into the controller. The initial parameters of the system include: DC input voltage, system operating frequency, compensation inductance, coil internal resistance, load demand power, total efficiency of vehicle-side equipment, and duty cycle of the buck circuit switch tube.

[0060] The electric vehicle wireless charging system comprises: a double-layer cross-rectangular magnetic coupling mechanism, a buck converter cascaded between a vehicle-end rectifier and a load.

[0061] The double-layer cross-rectangular magnetic coupling mechanism includes a ground-end transmitting coil and a vehicle-end receiving coil; the vehicle-end receiving coil is located directly above the ground-end transmitting coil, and there is a certain gap between the two. The ground-end transmitting coil and the vehicle-end receiving coil are coupled together through the magnetic field to achieve the purpose of transmitting energy and form an electric energy transmission channel.

[0062] The ground-end transmitting coil and the vehicle-end receiving coil are both composed of Litz wire and ferrite core; the specific structure is as follows Figure 2 As shown: the ground-end transmitting coil includes a first layer of ferrite flat plate laid on the bottom layer, and a second layer of rectangular coil and a third layer of rectangular coil are arranged on the upper side of the first layer of ferrite flat plate. Both layers of rectangular coils are wound by a Litz wire and are orthogonal to form a cross shape. The vehicle-end receiving coil has the same structure as the ground-end transmitting coil and is arranged in opposite directions; that is, the first layer of ferrite flat plate, the second layer of rectangular coil and the third layer of rectangular coil of the vehicle-end receiving coil are arranged in sequence from top to bottom. The vehicle-end receiving coil is located directly above the ground-end transmitting coil. When the two are opposite, there is a gap between the cross-shaped coils.

[0063] The second layer rectangular coil and the third layer rectangular coil are both wound with Litz wires with a single wire diameter of 0.1mm, a total of 1750 wires, and an outer diameter of 6.3mm. The winding is carried out in a plane spiral shape. The specific winding method is:

[0064] First, the second layer of rectangular coil of the transmitting coil is wound from the outside to the inside, and then the third layer of rectangular coil of the transmitting coil is wound from the outside to the inside. The second layer of rectangular coil is perpendicular to the third layer of rectangular coil in a cross shape, and there is a certain gap between the two. The length and width of the second and third layers of rectangular coils of the ground transmitting end are 160mm and 80mm respectively, the number of turns of the coil is 8 turns, and the turn spacing is 0.5mm. A square ferrite plate is laid on the first layer below the transmitting end coil to reduce the leakage of the magnetic field. The width of the plate is the same as the length of the rectangular coil and the thickness is 2mm. Furthermore, the vehicle-mounted receiving end coil adopts the same winding method as the transmitting end coil, and the ferrite plate is laid on the third layer above the coil. The vehicle-mounted receiving end is located directly above the transmitting end and the two are aligned. The gap between the two is the energy transmission channel, and the transmission distance is set to 150mm.

[0065] Figure 3 The topology circuit diagram of the wireless charging system for electric vehicles is shown in the figure. The buck circuit is Figure 3 The part within the red dotted box.

[0066] Figure 3 S1-S4 in the figure are the four switch tubes of the full-bridge inverter circuit; M is the mutual inductance; L1 is the self-inductance of the ground-end transmitting coil; L2 is the self-inductance of the vehicle-end receiving coil; L P is the inductance of the compensation network; C P , C PP , C2 is the capacitor of the compensation network; S is the switch tube of the buck circuit; VD is the diode; L is the filter inductor; C in , C b is the filter capacitor; R L is the load equivalent impedance.

[0067] The ground transmitting end of the electric vehicle wireless charging system includes a DC input power supply, a ground resonant compensation topology and a ground transmitting coil, and the vehicle-mounted receiving end includes a vehicle-end receiving coil, a vehicle-end resonant compensation topology, a full-bridge uncontrolled rectifier link, a DC-DC link and a load (battery).

[0068] like Figure 3 As shown in the purple dotted box, the ground-end transmitting coil and the vehicle-end receiving coil form a magnetic coupling mechanism, which is an energy transmission channel. The working principle of the entire electric vehicle wireless charging system is as follows: the system is DC-inputted by a DC input power supply, which is converted into AC input for resonance compensation at the transmitting end after full-bridge inversion at the ground end, and then the energy is transmitted to the vehicle-mounted end through the magnetic coupling coil, and finally the vehicle-end AC input is converted into DC output for charging the load after vehicle-end resonance compensation, full-bridge rectification and DC-DC voltage regulation.

[0069] Figure 3The red dotted box in the figure is the buck circuit part, which is the dc-dc link part mentioned above, which is used to solve the problem of the drop in charging power at the vehicle receiving end caused by the lateral offset between the vehicle receiving coil and the ground transmitting coil. Due to the wide range of equivalent impedance characteristics of the buck circuit, the buck circuit is selected for dc-dc conversion.

[0070] Step 2: Determine the relevant constraints, and calculate the maximum and minimum values ​​of the mutual inductance through the relationship between the mutual inductance and the equivalent impedance, the system transmission efficiency, and the load charging voltage to determine whether the constraints can be met.

[0071] The relationship between the mutual inductance and equivalent impedance, the system transmission efficiency, and the load charging voltage is:

[0072] The mutual inductance M and the equivalent impedance Z R , the system transmission efficiency η is:

[0073]

[0074] In the above formula, r r is the parasitic resistance of the receiving coil; r t is the parasitic resistance of the transmitting coil; Z eq It is the total equivalent impedance of the vehicle-end circuit when the system is in the resonant state; ω0 is the operating frequency of the system.

[0075] The relationship between the mutual inductance M and the load charging voltage U is:

[0076]

[0077] In the above formula, L p is the ground-end resonant compensation network inductance, U in is the DC input voltage at the ground end of the system.

[0078] The relevant constraints include: the range of load charging voltage, the adjustment range of duty cycle, and the minimum transmission efficiency;

[0079] The range of the charging voltage is: U L_min ≤U L ≤U L_max ;

[0080] The adjustment range of the duty cycle is: α min ≤α≤α max ;

[0081] The minimum transmission efficiency is: t_min ; The maximum value of mutual inductance is M max , the minimum value is M min ;

[0082] Among them, UL is the charging voltage, U L_min is the starting value of the charging voltage, U L_max is the final value of the charging voltage; α is the duty cycle, α min is the minimum ratio of the duty cycle, α max is the maximum ratio of the duty cycle.

[0083] Step 3: According to the load voltage collected in real time, calculate the mutual inductance value of the vehicle-mounted receiving terminal in the lateral offset state at that moment, and determine whether the mutual inductance value at this moment is between the maximum and minimum values ​​of the mutual inductance in step 2; the basis for the determination is:

[0084] If the mutual inductance in step 2 is between the maximum and minimum values, the transmission efficiency at this time is output and the next step is entered;

[0085] The expression of transmission efficiency η is:

[0086]

[0087] In the above formula, r r is the parasitic resistance of the receiving coil; r t is the parasitic resistance of the transmitting coil; Z R is the equivalent impedance; ω0 is the system operating frequency.

[0088] If it is not between the maximum and minimum values ​​of the mutual inductance in step 2, it is determined that the conditions at this time cannot achieve the matching of the output power and the load charging power, and the user is notified to adjust the vehicle position.

[0089] Step 4: The next adjustment value of the duty cycle α is calculated based on the system charging power and the power required by the load, and the adjustment value of the duty cycle is output to the drive circuit of the buck circuit switch tube to adjust the real-time duty cycle of the buck circuit.

[0090] The calculation formula of the adjustment value of duty cycle α at the next moment is:

[0091]

[0092] In the above formula, P ref is the load demand power; η loss is the total efficiency of the vehicle-side equipment; α' is the adjustment value at the next moment, and t+1 is the next moment.

[0093] Experimental verification:

[0094] In order to verify the feasibility and superiority of this solution, the inventor conducted experiments to verify it; the specific experimental scheme and experimental data are shown below.

[0095] Based on the disclosure in the embodiments Figure 2The double-layer cross-rectangular magnetic coupling mechanism shown in FIG. Figure 3 The topological circuit diagram of the electric vehicle wireless charging system shown in FIG. 1 ; DC voltage U in The input is converted into high-frequency alternating current after being inverted by the full bridge S1-S4. When the ground-end transmitting coil is excited by the alternating current, a magnetic field is generated around the coil, and the vehicle-end receiving coil generates an induced electromotive force. In order to verify the magnetic field distribution characteristics of the coupling mechanism, a finite element simulation model is built in Maxwell; Figure 4 The figure shows the finite element simulation magnetic field schematic diagram of the magnetic coupling mechanism used in the electric vehicle wireless charging system in the experiment. The direction of magnetic field intensity weakening from the inside to the outside in the figure. It can be seen that a relatively uniform magnetic field distribution can be generated above the ground-end transmitting coil, and the magnetic field intensity at the center of the coupling coil is enhanced.

[0096] In order to observe the impact of lateral offset between the coupling coils on the system charging power, the charging power drop characteristics are analyzed through simulation. Figure 2 The magnetic coupling mechanism and Figure 3 The topology circuit of the electric vehicle wireless charging system is designed, and a single-transmitter and single-receiver electric vehicle wireless charging system is built. The mutual inductance and charging power characteristics of the vehicle-mounted receiving coil are analyzed through Maxwell-Simporer finite element simulation when the lateral offset of -150mm-+150mm occurs.

[0097] Will Figure 2 The Maxwell finite element model of the magnetic coupling mechanism in the FET module is integrated into the FET module and added to the Figure 3 In the Simplorer simulation circuit of electric vehicle wireless charging shown in the figure, the resonant compensation topology of the transmitter and the receiver adopts LCC-S type; the specific simulation model is as follows Figure 5 As shown; it should be pointed out that this simulation is for analyzing the charging power characteristics when lateral offset occurs between the coupled coils, and therefore the anti-offset method, i.e., control means, proposed in the present invention is not added. The verification of the anti-offset method will be verified in the implementation below.

[0098] According to the power level of electric vehicle wireless charging, the load charging power of the electric vehicle wireless charging system is set to 3.3kw in the simulation; the system operating frequency is ω0, which is set to 85kHz in the experiment; the DC input voltage is set to 260V; the other specific simulation parameters are shown in Table 1:

[0099]

[0100] like Figure 6The figure shows the simulation results of the mutual inductance between the coupled coils and the system charging power when the vehicle-mounted receiving coil is laterally offset from -150mm to +150mm along the Y-axis. It can be seen that when the lateral offset of the vehicle-mounted receiving end is within 10mm, the mutual inductance fluctuation range is small, and the system charging power can be around 3.3kw. When the lateral offset between the receiving end and the transmitting end exceeds 30mm, the mutual inductance between the coupled coils fluctuates greatly, and the system charging power gradually decreases with the increase of the offset distance, and cannot meet the charging power of 3.3kw.

[0101] according to Figure 6 The simulation experiment obtained the result: when the ground end transmitting coil of the electric vehicle is not aligned with the vehicle end receiving coil during the charging process of the electric vehicle and the offset exceeds the fault tolerance of the magnetic coupling mechanism, the coupling coefficient of the magnetic coupling mechanism will decrease, causing the charging power to fail to reach the load demand power. Based on this, the electric vehicle wireless charging anti-lateral offset method proposed by the present invention is used for operation. The following adopts the method of the present invention combined with the embodiment Figure 2 Double-layer cross-rectangular magnetic coupling mechanism and Figure 3 The topology circuit is described in detail.

[0102] According to the topology of the electric vehicle wireless charging system, the total equivalent impedance Z of the vehicle-side full-bridge uncontrolled rectifier circuit and the buck circuit R for: Where α is the duty cycle of the buck circuit, R L is the load equivalent impedance.

[0103] When the system is in a resonant state, the total equivalent impedance Z of the vehicle-side circuit eq The expression is: Where r r is the parasitic resistance of the receiving coil.

[0104] The total equivalent impedance Z eq The reflected impedance Z referred to the ground ref for: Where M is the mutual inductance, r t is the parasitic resistance of the transmitting coil.

[0105] The input impedance Z of the system working in the resonant state can be obtained from the expression of reflected impedance: in for: Where L P The inductance of the transmitter resonance compensation network.

[0106] According to the mutual inductance theory, the current I2 flowing through the vehicle-end receiving coil is calculated as:

[0107] Where U in is the DC input voltage of the system.

[0108] The total equivalent impedance Z of the vehicle-side full-bridge uncontrolled rectifier circuit and the buck circuit R , calculate the output voltage U of the full-bridge uncontrolled rectifier circuit out : If the internal resistance of the coil is ignored, then U out for:

[0109] According to the input-output relationship between the full-bridge uncontrolled rectifier circuit and the buck circuit, the load charging voltage U is calculated. L for: According to this formula, when a lateral offset occurs between the coupled coils, the real-time mutual inductance value can be calculated based on the load charging voltage:

[0110] Finally, the expression of charging power can be obtained according to the load charging voltage: Similarly, the value of the real-time duty cycle α can be calculated based on the charging power expression:

[0111] Based on the above derivation process, the system charging power P is finally obtained. o The relationship between the duty cycle α of the buck circuit and the mutual inductance M and the duty cycle α of the buck circuit. From the expression of mutual inductance M, it can be seen that the compensation inductance L P Input voltage U in It is usually a fixed value, and only the load charging voltage U L The value of the buck circuit duty cycle α can be used to calculate the real-time mutual inductance value when the coupling coils are lateral offset. From the load charging power expression, it can be seen that the system charging power decreases as M decreases and increases as R L The lateral offset between the coupling coils or the change in load resistance will cause the load charging power to decrease. At this time, the duty cycle α of the buck circuit can be adjusted to match the charging power of the electric vehicle wireless charging system with the load demand power.

[0112] Based on the above analysis of the charging power regulation principle, in order to achieve the purpose of maintaining load charging stability even when the coupling coils at the ground and vehicle ends are not aligned, the main control idea is: input the system-related parameters and the detected load voltage into the buck circuit controller, and then the controller adjusts the duty cycle of the switch tube to achieve stable charging power.

[0113] In this experiment, when initializing the system, the system DC input voltage U in , system operating frequency f0, compensation inductance L P , the internal resistance r of the transmitting coil and the receiving coil t With rr 、Load demand power P ref , the total efficiency η of the vehicle-side equipment loss , and the initial value of the buck circuit duty cycle α are stored in the controller.

[0114] In order to verify the effectiveness of the anti-lateral deviation method proposed in the present invention, the same Figure 6 The same simulation conditions are used for testing. Figure 6 The difference between the simulations is that the simulation for verifying the anti-lateral offset method adds the control means of the present invention to the buck circuit; when the vehicle-mounted receiving end is laterally offset by 150mm along the Y axis, the charging power simulation results of the system are as follows: Figure 7 As shown in the figure, compared with the system charging power before the control method is adopted, after the control method is adopted, the system charging power can be restored to the load demand power of 3.3kw when the vehicle-mounted receiving end is laterally offset by 150mm.

[0115] Finally, it should be noted that the above embodiments are only used to further illustrate the technical solutions of the present invention, rather than to limit it; ordinary technicians in this field should understand that they can still modify the technical solutions of the aforementioned embodiments, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for resisting lateral deviation for wireless charging of electric vehicles, characterized in that: Based on the buck circuit cascaded between the magnetic coupling mechanism, the vehicle-end rectifier and the load, when the lateral offset is large, the voltage regulation link of the vehicle-end rectifier is controlled to control the duty cycle of the buck circuit switch tube to achieve the consistency of charging power with the load demand power; the specific operation method is: Step 1: Operate based on the electric vehicle wireless charging system and store the initial parameters of the system in the controller; The electric vehicle wireless charging system comprises: a double-layer cross-rectangular magnetic coupling mechanism, a buck converter cascaded between the vehicle-end rectifier and the load; The initial parameters of the system include: DC input voltage, system operating frequency, compensation inductance, coil internal resistance, load demand power, total efficiency of vehicle-side equipment, and duty cycle of buck circuit switch tube; Step 2: Determine the relevant constraints, and calculate the maximum and minimum values ​​of the mutual inductance through the relationship between the mutual inductance and the equivalent impedance, the system transmission efficiency, and the load charging voltage, to determine whether the constraints can be met; The relevant constraints include: the range of load charging voltage, the adjustment range of duty cycle, and the minimum transmission efficiency; The range of the charging voltage is: U L_min ≤U L ≤U L_max ; The adjustment range of the duty cycle is: α min ≤α≤α max ; The minimum transmission efficiency is: t_min ; The maximum value of mutual inductance is M max , the minimum value is M min ; Among them, U L is the charging voltage, U L_min is the starting value of the charging voltage, U L_max is the final value of the charging voltage; α is the duty cycle, α min is the minimum ratio of the duty cycle, α max is the maximum ratio of the duty cycle; Step 3: According to the load voltage collected in real time, calculate the mutual inductance value of the vehicle-mounted receiving terminal in the lateral offset state at that moment, and determine whether the mutual inductance value at this moment is between the maximum and minimum values ​​of the mutual inductance in step 2; the basis for the determination is: If the mutual inductance in step 2 is between the maximum and minimum values, the transmission efficiency at this time is output and the next step is entered; If it is not between the maximum and minimum values ​​of the mutual inductance in step 2, it is determined that the conditions at this time cannot achieve the matching of the output power and the load charging power, and the user is notified to adjust the vehicle position; Step 4: The next adjustment value of the duty cycle α is calculated based on the system charging power and the power required by the load, and the adjustment value of the duty cycle is output to the drive circuit of the buck circuit switch tube to adjust the real-time duty cycle of the buck circuit.

2. The method for resisting lateral deviation for wireless charging of electric vehicles according to claim 1, characterized in that: The double-layer cross-rectangular magnetic coupling mechanism described in step one forms an electric energy transmission channel through a ground-end transmitting coil and a vehicle-end receiving coil; the ground-end transmitting coil and the vehicle-end receiving coil are both composed of Litz wire and a ferrite core.

3. The method for resisting lateral deviation for wireless charging of electric vehicles according to claim 2, characterized in that: The ground-end transmitting coil comprises a first layer of ferrite plate laid on the bottom layer, a second layer of rectangular coil and a third layer of rectangular coil are arranged on the upper side of the first layer of ferrite plate, the two layers of rectangular coils are both wound by a Litz wire and are orthogonal to form a cross shape; the vehicle-end receiving coil has the same structure as the ground-end transmitting coil and is arranged in opposite directions; the vehicle-end receiving coil is located directly above the ground-end transmitting coil, and when the two are opposite, there is a gap between the cross-shaped coils.

4. The method for resisting lateral deviation for wireless charging of electric vehicles according to claim 3, characterized in that: The number of turns of the second-layer rectangular coil and the third-layer rectangular coil are both N turns, the coil turn spacing is dmm, and the length-to-width ratio inside the rectangular coil is 2:1; the winding method of the second-layer rectangular coil and the third-layer rectangular coil is: first wind the second-layer rectangular coil from the outside to the inside, and then wind the third-layer rectangular coil from the inside to the outside, and the second-layer rectangular coil and the third-layer rectangular coil are in a cross shape and are perpendicular to each other.

5. The method for resisting lateral deviation for wireless charging of electric vehicles according to claim 4, characterized in that: The ferrite plate is a square structure, the width of which is the same as the length of the rectangular coil, and the thickness is 2 mm.

6. The method for resisting lateral deviation for wireless charging of electric vehicles according to claim 1, characterized in that: The buck circuit is used as a dc-dc converter. In combination with the electric vehicle wireless charging system, the DC voltage input to the system is converted into an AC input for resonance compensation at the transmitter end after being inverted by a full-bridge at the ground end. The energy is then transmitted to the vehicle end through a magnetic coupling coil. Finally, the vehicle end AC input is converted into a DC output for charging the load after vehicle end resonance compensation, full-bridge rectification and the voltage regulation link of the dc-dc converter.

7. The method for resisting lateral deviation for wireless charging of electric vehicles according to claim 1, characterized in that: The relationship between the mutual inductance and equivalent impedance, the system transmission efficiency, and the load charging voltage described in step 2 is: The mutual inductance M and the equivalent impedance Z R , the system transmission efficiency η is: In the above formula, r r is the parasitic resistance of the receiving coil; r t is the parasitic resistance of the transmitting coil; Z eq is the total equivalent impedance of the vehicle-end circuit when the system is in the resonant state; ω0 is the system operating frequency; The relationship between the mutual inductance M and the load charging voltage U is: In the above formula, L p is the ground-end resonant compensation network inductance, U in is the DC input voltage at the ground end of the system.

8. A method for resisting lateral deviation for wireless charging of electric vehicles according to claim 1 or 7, characterized in that: The expression of the transmission efficiency η described in step 3 is: In the above formula, r r is the parasitic resistance of the receiving coil; r t is the parasitic resistance of the transmitting coil; Z R is the equivalent impedance; ω0 is the system operating frequency.

9. The method for resisting lateral deviation for wireless charging of electric vehicles according to claim 1, characterized in that: The system charging power P described in step 4 L The solution is: In the above formula, R L is the load impedance, L p is the ground-end resonant compensation network inductance, U in is the DC input voltage at the ground end of the system.

10. The method for resisting lateral deviation for wireless charging of electric vehicles according to claim 9, characterized in that: The calculation formula for the adjustment value of the duty cycle α at the next moment described in step 4 is: α'＝α(t+1)； In the above formula, P ref The power demanded by the load; η loss is the total efficiency of the vehicle-side equipment; α' is the adjustment value at the next moment, and t+1 is the next moment.

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