Cluster-type wireless charging system for electric vehicles with strong anti-offset characteristics

Abstract

The present invention provides a cluster-type wireless charging system for electric vehicles with strong anti-offset characteristics, which includes an inverter and a cluster-type charging pile. The cluster-type charging pile includes a common magnetic core for primary coils and a number of charging coils arranged on both sides of the common magnetic core for primary coils respectively. Each charging coil is configured with a primary compensation circuit and is switchably connected to the output bus of the inverter through a corresponding primary coil switching element. A secondary coil detection sensor is also configured for each charging coil, and a number of secondary coil detection sensors are connected to a coil detection signal processing module. The coil detection signal processing module controls the corresponding charging coil to work according to the positions of the secondary coils detected by the number of secondary coil detection sensors. The effects are as follows: No matter where the electric vehicle stops, an extremely stable voltage can be obtained; it can charge multiple electric vehicles and can also charge electric vehicles with multiple voltage levels.

Description

Technical Field

[0001] The invention relates to wireless energy transmission technology, and in particular to a cluster type electric vehicle wireless charging system with strong anti-drift characteristics. Background Art

[0002] Wireless power transmission achieves non-electrical contact transmission of electric energy through media such as magnetic fields, electric fields, lasers and microwaves. This technology can effectively solve the problems of limited equipment flexibility and safety hazards caused by traditional wired power supply methods. At present, domestic and foreign experts and scholars have conducted research on this technology in application fields such as electric vehicles, consumer electronics, and household appliances, and have obtained many theoretical results.

[0003] An inductively coupled wireless power transmission system is usually equipped with an energy transmitting coil and an energy receiving coil. The energy transmitting end converts electrical energy into a high-frequency AC signal, which is then converted into magnetic field energy through the energy transmitting coil. After being transmitted over a certain distance in the air, the energy is picked up by the energy receiving coil, thereby realizing wireless power transmission.

[0004] Electric vehicle wireless charging system is a research hotspot in inductively coupled wireless power transmission. However, among the existing research results, most of the focus is on the anti-deviation technology of electric vehicle wireless charging or the multi-load technology of wireless charging, while there is little research on the system that combines the anti-deviation technology and multi-load technology of electric vehicle wireless charging. The present invention combines the anti-deviation technology and multi-load technology of electric vehicle wireless charging to propose a cluster electric vehicle wireless charging system with strong anti-deviation characteristics. Summary of the invention

[0005] In view of this, the purpose of the present invention is to propose a cluster electric vehicle wireless charging system with strong anti-drift characteristics, which can charge multiple electric vehicles at the same time and has strong anti-drift capability, so that the electric vehicles can obtain stable voltage input.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A cluster - type wireless charging system for electric vehicles with strong anti - offset characteristics, the key lies in: including an inverter and a cluster - type charging pile. The cluster - type charging pile includes a common magnetic core for primary coils and a number of charging coils arranged respectively on both sides of the common magnetic core for primary coils. Each charging coil is configured with a primary compensation circuit and is switchably connected to the output bus of the inverter through a corresponding primary coil switching element. For each charging coil, a secondary coil detection sensor is also configured. A number of secondary coil detection sensors are connected to a coil detection signal processing module. The coil detection signal processing module controls the corresponding charging coil to be connected in parallel to the output bus of the inverter according to the position of the secondary coil detected by a number of secondary coil detection sensors to achieve wireless charging.

[0008] Optionally, the charging coils on both sides of the common magnetic core for primary coils have exactly the same structure and parameters.

[0009] Optionally, the charging coils on both sides of the common magnetic core for primary coils are both rectangular planar coils, and are respectively arranged closely in sequence. The current directions of the charging coils on the same side are all the same, and the mutual inductance values between two adjacent charging coils on the same side are the same.

[0010] Optionally, the primary compensation circuit includes an LCC compensation circuit and an adjacent charging coil mutual inductance compensation circuit.

[0011] Optionally, the LCC compensation circuit includes a compensation inductor L 0 , a series resonance capacitor C 0 and a parallel compensation capacitor C 1 . The compensation inductor L 0 and the parallel compensation capacitor C 1 are connected in series and then connected to the output bus of the inverter through a corresponding primary coil switching element. The series resonance capacitor C 0 and the corresponding charging coil form a series and are integrally connected in parallel at both ends of the parallel compensation capacitor C 1 , and satisfy:

[0012] L 0 = αL 1 , 0 < α < 1 and

[0013] where, L 1 is the self - inductance value of the charging coil, α is the inductance ratio, and ω is the system operating angular frequency.

[0014] Optionally, the adjacent charging coil mutual inductance compensation circuit includes adjacent coil compensation inductors connected in series and corresponding to the number of adjacent coils. A compensation inductor short - circuit switch in the normally - closed state is connected to both ends of each adjacent coil compensation inductor. When the primary coil switching element corresponding to the charging coil is closed, the corresponding compensation inductor short - circuit switch is opened.

[0015] Optionally, the self - inductance value of each adjacent coil compensation inductor is equal to the mutual inductance value between two adjacent charging coils on the same side.

[0016] Optionally, a pick - up coil, a secondary - side compensation circuit, and a battery equivalent load are provided on the electric vehicle corresponding to the charging coil. The pick - up coil is also a rectangular planar coil. When the electric vehicle stops near the cluster - type charging pile, the coil detection signal processing module processes the signal of the secondary - side coil detection sensor and immediately controls the primary coil switching element to connect the n charging coils corresponding to the pick - up coil to charge the electric vehicle, where: n satisfies (n - 1)a < c < na, where a is the width of the charging coil and c is the width of the pick - up coil.

[0017] Optionally, the pick - up coil and the secondary - side compensation circuit form an S - type series compensation topology.

[0018] Optionally, the common magnetic core of the primary coils is rectangular and long - strip - shaped, and the charging coils on both sides are in a vertical state.

[0019] The effects of the present invention are as follows:

[0020] (1) The magnetic coupling mechanism proposed by the present invention can be compatible with electric vehicles with a variety of different numbers of load coils, and can simultaneously satisfy the charging of multiple electric vehicles.

[0021] (2) In the system proposed by the present invention, the magnetic coupling mechanism has extremely strong anti - offset performance.

[0022] (3) The circuit structure proposed by the present invention can compensate for the mutual inductance interference between adjacent charging coils. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a three - dimensional structure schematic diagram of the magnetic coupling mechanism of the system in the specific embodiment of the present invention;

[0025] Figure 2 Schematic diagram of the system circuit structure in a specific embodiment of the present invention;

[0026] Figure 3 is Figure 2 Schematic circuit diagram of the primary side compensation circuit in [the original];

[0027] Figure 4 Schematic diagram of the coupling coefficient between each charging coil in a specific embodiment of the present invention;

[0028] Figure 5 Schematic diagram for the derivation of the mutual inductance model of the charging coil in a specific embodiment of the present invention;

[0029] Figure 6 Schematic diagram of the working mechanism of the mutual inductance compensation circuit for adjacent charging coils in a specific embodiment of the present invention;

[0030] Figure 7 Schematic diagram for the derivation of the mutual inductance model of the load coil in a specific embodiment of the present invention;

[0031] Figure 8 Magnetic field distribution diagram when a three - charging - coil vehicle is charging in a specific embodiment of the present invention;

[0032] Figure 9 Variation trend diagram of the sum of the coupling coefficients between the charging coil and the load coil during offset in a specific embodiment of the present invention. Specific implementation mode

[0033] Hereinafter, embodiments of the technical solution of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and thus are only examples and cannot be used to limit the protection scope of the present invention.

[0034] It should be noted that unless otherwise specified, the technical terms or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art to which the present invention belongs.

[0035] As Figure 1 shown, this embodiment provides a cluster - type electric vehicle wireless charging system with strong anti - offset characteristics, including an inverter and a cluster - type charging pile. The cluster - type charging pile includes a common magnetic core for the primary coils and a number of charging coils arranged on both sides A and B of the common magnetic core of the primary coils. In this embodiment, the common magnetic core of the primary coils is placed vertically, and the charging coils on side A and side B are closely attached to both sides of the common magnetic core, forming a two - side co - core magnetic coupling mechanism. The charging coils on both sides A and B have exactly the same structure and parameters, are both rectangular planar coils, and are aligned with each other. Figure 1As can be seen, the width of each rectangular charging coil is a, the height is b, and they are closely arranged in sequence. The current directions of the charging coils on the same side are the same, and the mutual inductance values between two adjacent charging coils on the same side are the same. For the corresponding charging coil structure, a pick-up coil, a secondary compensation circuit, and a battery equivalent load are provided on the electric vehicle. The pick-up coil and the secondary compensation circuit form an S-type series compensation topology. Through Figure 1 As can be seen, the pick-up coil is also a rectangular planar coil with a height of b. The width of the pick-up coil can be set differently for different vehicle models. For example, Figure 1 as shown, the widths of the three pick-up coils are c 1 , c 2 , and c 3 . The load coil of the electric vehicle can be located at the rear of the vehicle. When the vehicle stops at a position at a specified distance from the charging coil, charging starts. Since the charging coils on both sides A and B share a magnetic core, this magnetic coupling mechanism saves the amount of magnetic core to a certain extent.

[0036] Combined with Figure 2 it can be seen that each charging coil is configured with a primary compensation circuit and is connected to the output bus of the frequency converter in a switchable manner through a corresponding primary coil switching element. The frequency converter consists of a rectifier circuit and an inverter circuit; for each charging coil, a secondary coil detection sensor is also configured. A number of secondary coil detection sensors are connected to a coil detection signal processing module. The coil detection signal processing module controls the corresponding charging coil to be connected in parallel to the output bus of the frequency converter according to the positions of the secondary coils detected by the number of secondary coil detection sensors to achieve wireless charging.

[0037] Combined with Figure 3 it can be seen that the primary compensation circuit includes an LCC compensation circuit and an adjacent charging coil mutual inductance compensation circuit. Among them, the LCC compensation circuit includes a compensation inductor L 0 , a series resonance capacitor C 0 , and a parallel compensation capacitor C 1 . The compensation inductor L 0 and the parallel compensation capacitor C 1 are connected in series and then connected to the output bus of the frequency converter through a corresponding primary coil switching element. The series resonance capacitor C 0 and the corresponding charging coil form a series connection and are then connected in parallel across both ends of the parallel compensation capacitor C 1 , and satisfy:

[0038] L 0 =αL 1 , 0 < α < 1 and

[0039] Among them, L 1L is the self - inductance value of the charging coil, α is the inductance ratio, and ω is the system operating angular frequency.

[0040] Meanwhile, the secondary - side series compensation inductor should also satisfy:

[0041] C 2 = 1 / (ω 2 L 2 )(2)

[0042] The adjacent - charging - coil mutual - inductance compensation circuit includes adjacent - coil compensation inductors connected in series corresponding to the number of adjacent coils. A normally - closed compensation - inductor short - circuit switch is connected to both ends of each adjacent - coil compensation inductor. When the primary - side coil switching element corresponding to the charging coil is closed, the corresponding compensation - inductor short - circuit switch is opened. In specific implementation, the self - inductance value of each adjacent - coil compensation inductor is equal to the mutual inductance value between two adjacent charging coils on the same side.

[0043] Through the above design, when an electric vehicle stops near the cluster - type charging pile, the coil detection signal processing module processes the signal of the secondary - side coil detection sensor and immediately controls the primary - side coil switching element to connect the n charging coils corresponding to the pickup coil to charge the electric vehicle, where: n satisfies (n - 1)a < c < na, where a is the width of the charging coil and c is the width of the pickup coil.

[0044] It can be seen that since the system has two groups of coils, A and B, and each group has many charging coils, the system can charge multiple electric vehicles simultaneously; and since the system can change the number of charging coils being charged through the switching switch, the system can supply power to electric vehicles with different load - coil widths.

[0045] Meanwhile, thanks to the addition of multiple charging coils, regardless of whether the parking position of the electric vehicle shifts, by detecting the position of the load coil, the system can detect the position of the load coil, enabling the electric vehicle to be charged by the directly - facing charging coil wherever it stops.

[0046] Since the coils of the magnetic coupling mechanism are arranged side - by - side closely, and there is no shielding measure between the charging coils on the same side, the mutual inductance between the charging coils on the same side cannot be ignored. For example Figure 4A model with four charging coils on the same side working is established, and the simulation values of the coupling coefficients between the coils are marked. The coupling coefficient between adjacent charging coils reaches -0.12, which is about 54% of the coupling coefficient of 0.22 between the charging coil and the load coil in this model and cannot be ignored. The mutual inductance between non-adjacent coils is only 0.016 at most, so it can be ignored. The mutual inductance value of the charging coils on the same side is negative because in the same plane, the mutual inductance current generated between coils with the same current direction is opposite to the current direction in the coils, weakening the inductance of the coils. Usually, these mutual inductance interferences can be compensated by a resonant compensation circuit. However, the charging coils of the magnetic coupling mechanism proposed in the present invention are cut into and out of the circuit at any time. Therefore, whether the charging coils adjacent to a certain charging coil are working will change the mutual inductance interference of this coil, which means that the parameters of the resonant compensation circuit need to be changed, making the circuit very complex.

[0047] To study the mutual inductance interference of adjacent charging coils, it is necessary to analyze the mutual inductance interference model, as Figure 5 For the transformation of the mutual inductance model of the charging coil, Figure 5 (a) is a common mutual inductance model. According to the circuit theorem, the node voltages are:

[0048]

[0049] According to the primary constant current characteristic of the LCC-S compensation circuit adopted in this embodiment, the currents in each charging coil are equal, and according to the current law:

[0050]

[0051] Since the mutual inductance M between adjacent charging coils on the same side is negative, an inductor can be used to compensate and cancel it. As Figure 6 The working mechanism of the mutual inductance compensation circuit of adjacent charging coils when three charging coils are working is shown. The mutual inductance of adjacent coils is all M, so the inductors L 41 、L 32 are all equal to M and are positive values. Each compensation inductor is connected in parallel with a normally closed switch, and the circuit of each charging coil is connected in series with the compensation inductors and normally closed switches with the number of adjacent coils. When the charging coils L 12 、L 13 、L 14 start to work, the normally open switches S 12 、S 13 、S 14 close, connecting the branch into the circuit and generating the mutual inductance interference of adjacent coils; at the same time, the corresponding normally closed switches S 12 、S 13 、S 14 open, turning on the compensation inductors L 42, L 33 , L 43 , L 34 In the access circuit, the mutual inductance interference between adjacent coils is compensated, and the normally closed switch that has not operated still shorts the corresponding compensating inductor, making it have no effect on the circuit. At this time, the mutual inductance interference between the charging coils on the same side is completely compensated.

[0052] Through the research and analysis of the mutual inductance interference between the charging coils on both sides of AB, the mutual inductance interference between the charging coils on the same side, and the mutual inductance interference between the load coils, the present invention proposes a method to solve these interferences. By compensating these mutual inductance interferences, the system can fully achieve the purpose of load, multi-coil compatibility, and anti-offset.

[0053] Each electric vehicle in the system is independent. To make the research universal, a circuit model of the charging scenario with m charging coils turned on to charge electric vehicles as shown in Figure 7 is established, and the mutual inductance between adjacent charging coils and the mutual inductance between adjacent load coils have been compensated and ignored.

[0054] m mutual inductances are generated between the m charging coils and the load coils, that is, m power transmission circuits are formed, and the circuit composed of any charging coil and the load coil is a traditional LCC-S compensation topology circuit. Taking the LCC-S compensation circuit formed by the charging coil L 11 and the load coil L 2 as an example. Assuming that the working angular frequency of the system is ω, the impedance on the load side is:

[0055]

[0056] The impedance reflected by the load impedance to the charging side is:

[0057]

[0058] where I 11 is the current of the charging coil of the selected LCC-S circuit formed by the charging coil L 11 and the load coil L 2 , I 21 is the current obtained by the load coil from the charging coil L 11 , the total current flowing through L 2 is the sum of the currents transmitted by the m charging coils to the load coil L 2 , I 2 , I 2 is:

[0059]

[0060] The total impedance of the selected LCC-S circuit is:

[0061] Z i = R01 +jωL 01 +1 / (A + jωC 11 ) (8)

[0062] Where the value of A is:

[0063] A = 1 / [1 / (jωC 01 ) + jωL 11 + R 11 + Z c (9)

[0064] Since the circuit is in the resonant state, then:

[0065]

[0066] According to formula (10), let L 01 = αL 11 , where 0 < α < 1, then the value of the compensation capacitor is:

[0067]

[0068] Substituting into formulas (5), (6), and (8) gives:

[0069]

[0070] Since the system inputs a high - frequency square wave with an amplitude of U, but the system resonant frequency is the fundamental frequency of the square wave. Let the fundamental voltage input to the system be U S , then:

[0071]

[0072] According to the circuit, there is:

[0073]

[0074] I 01 is the input current of the selected LCC - S circuit. Substituting formula (11) into formula (14) gives:

[0075]

[0076] Then the output power of the selected LCC - S circuit is:

[0077]

[0078] The input power is:

[0079]

[0080] When the coil internal resistance is ignored, formula (15) can be simplified to:

[0081]

[0082] The voltage obtained by the load resistor from this LCC-S circuit is:

[0083]

[0084] As can be seen from formula (18), the selected LCC-S circuit satisfies the constant current characteristic of the charging coil, and since the inductance values of the charging coils are the same, the currents in each charging coil are equal.

[0085] As can be seen from formula (29), the output voltage is constant.

[0086] m LCC-S circuits constitute the entire circuit system, so the total output power and efficiency of the entire system are:

[0087]

[0088]

[0089] The total output voltage of the system is:

[0090]

[0091] As can be seen from formula (22), the output voltage of the system is proportional to the sum of the mutual inductances between the m charging coils and the load coil.

[0092] A set of simulation models are established in the finite element software Maxwell to study the anti-offset performance when 3 charging coils charge the load coil. As Figure 8 shown is the magnetic field distribution when 3 charging coils work to charge the vehicle with the load coil. Only the working charging coils are drawn in the figure. It can be seen that regardless of the offset distance d between the charging coil L 11 and the load coil L 21 , the magnetic field distribution at the load coils L 21 and L 22 is uniform. According to formula (19), it can be known that 3 charging coils can transmit a more constant voltage to the load coil.

[0093] Figure 8 Three coupling coefficients are generated between the 3 charging coils and the 2 charging coils in 3 . Denote the sum of the three coupling coefficients as M 3 . When the offset distance d ranges from 0 to the width of one coil, which is 150 mm, draw the relationship curve of M Figure 9 as shown. Figure 9 In 3 , the average value of M 3The maximum value and the minimum value only change by 1.49% and 2.07% respectively relative to their average value. According to formula (19), when the vehicle is offset, charging it with three charging coils will obtain a very stable output voltage.

[0094] Through the analysis of the output characteristics and anti-offset characteristics, the system proposed by the present invention has good multi-load, multi-coil compatibility, and anti-offset performance. Finally, it should be noted that the above-disclosed is only a preferred embodiment of the present invention, and of course, it cannot be used to limit the scope of the rights of the present invention. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A cluster-type wireless charging system for electric vehicles with strong anti-offset characteristics, Characterized in that: It includes an inverter and a cluster-type charging pile. The cluster-type charging pile includes a common magnetic core for the primary coils and a number of charging coils arranged on both sides of the common magnetic core for the primary coils. Each charging coil is configured with a primary compensation circuit and is switchably connected to the output bus of the inverter through a corresponding primary coil switching element. A secondary coil detection sensor is also configured for each charging coil. A number of secondary coil detection sensors are connected to a coil detection signal processing module. The coil detection signal processing module controls the corresponding charging coils to be connected in parallel to the output bus of the inverter according to the positions of the secondary coils detected by the number of secondary coil detection sensors to achieve wireless charging; The charging coil structures and parameters on both sides of the magnetic core shared by the primary coils are exactly the same; the charging coils on both sides of the magnetic core shared by the primary coils are rectangular planar coils and are respectively arranged closely in sequence. The current directions of the charging coils on the same side are the same, and the mutual inductance values between two adjacent charging coils on the same side are the same; the primary compensation circuit includes an LCC compensation circuit and a mutual inductance compensation circuit for adjacent charging coils; the LCC compensation circuit includes a compensation inductor L 0 , a series resonance capacitor C 0 and a parallel compensation capacitor C 1 . The compensation inductor L 0 and the parallel compensation capacitor C 1 are connected in series and then connected to the output bus of the frequency converter through the corresponding primary coil switching element. The series resonance capacitor C 0 and the corresponding charging coil are connected in series and then integrally connected in parallel at both ends of the parallel compensation capacitor C 1 , and satisfy: L 0 = αL 1， 0 < α < 1 and Among them, L 1 is the self-inductance value of the charging coil, α is the inductance ratio, and ω is the system operating angular frequency; The adjacent charging coil mutual inductance compensation circuit includes adjacent coil compensation inductors connected in series corresponding to the number of adjacent coils. A normally closed compensation inductor short-circuit switch is connected to both ends of each adjacent coil compensation inductor. When the primary coil switching element corresponding to the charging coil is closed, the corresponding compensation inductor short-circuit switch is opened; the self-inductance value of each adjacent coil compensation inductor is equal to the mutual inductance value between two adjacent charging coils on the same side; A pickup coil, a secondary compensation circuit and a battery equivalent load are provided on the electric vehicle corresponding to the charging coil. The pickup coil and the secondary compensation circuit form an S-type series compensation topology.

2. The cluster-type wireless charging system for electric vehicles with strong anti-offset characteristics according to claim 1, Characterized in that: The pickup coil is also a rectangular planar coil. When the electric vehicle is parked near the cluster-type charging pile, the coil detection signal processing module processes the signals of the secondary coil detection sensors and immediately controls the primary coil switching element to connect the n charging coils corresponding to the pickup coil to charge the electric vehicle, where: n satisfies (n - 1)a < c < na, where a is the width of the charging coil and c is the width of the pickup coil.

3. The cluster-type wireless charging system for electric vehicles with strong anti-offset characteristics according to claim 1, Characterized in that: The common magnetic core for the primary coils is rectangular and long, and the charging coils on both sides are in a vertical state.

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