CN115296446A

CN115296446A - High-anti-deflection WPT (wi-Fi protected setup) system based on bipolar coupling mechanism and control method thereof

Info

Publication number: CN115296446A
Application number: CN202210529666.0A
Authority: CN
Inventors: 谢诗云; 杨奕; 李恋; 张路; 熊山香; 张小钦
Original assignee: Chongqing University of Technology
Current assignee: Chongqing University of Technology
Priority date: 2022-05-16
Filing date: 2022-05-16
Publication date: 2022-11-04

Abstract

The invention relates to the technical field of Wireless Power Transmission (WPT), and particularly discloses a high-deflection-resistance WPT system based on a bipolar coupling mechanism and a control method thereof. The DQDD coil is composed of two pairs of decoupling DD coils which are arranged in a double-layer orthogonal mode, and the distribution of an excited magnetic field is regulated and controlled through the amplitude and the phase of exciting currents of the two groups of DD coils; the BP coil can be switched to a single polarity coil by means of a relay circuit, thereby changing the polarity of the magnetic field that can be picked up by the receiving means. According to the method, an additional position detection device is not required to be additionally arranged, the relative position of the horizontal plane of the coupling mechanism and the vertical deflection angle can be obtained, the size and the cost of the system can be effectively reduced, and the obtained position information is used for structure transformation of the receiving BP coil and distribution regulation and control of a magnetic field excited by the transmitting DQDD coil. The experimental results show that: within the horizontal plane 270mm deviation range, the output power is maintained to be about 1.8kW, and the system efficiency is not lower than 88%.

Description

High-anti-offset deflection WPT system based on bipolar coupling mechanism and control method thereof

Technical Field

The invention relates to the technical field of Wireless Power Transfer (WPT), in particular to a high-deflection-resistance WPT system based on a bipolar coupling mechanism and a control method of the high-deflection-resistance WPT system based on the bipolar coupling mechanism.

Background

The electric vehicle charging system adopting the Wireless Power Transfer (WPT) mode does not need cables to connect the charging equipment and a vehicle body, does not have the maintenance problems of contact loss, dust accumulation, mechanical wear and the like, is more convenient, safer and more flexible in charging mode, and can adapt to severe environment, so the electric vehicle Wireless charging system is highly concerned by experts and scholars at home and abroad. In the static wireless charging process of the electric automobile, the transmitting mechanism and the receiving mechanism inevitably have the dislocation condition of offset deflection, and the dislocation can cause the coupling coefficient of the transmitting mechanism and the receiving mechanism and the charging energy efficiency to be sharply reduced. Therefore, the key problem to be solved urgently is to improve the anti-offset performance of the coupling mechanism and improve the stability of the pick-up power of the receiving mechanism.

In order to further improve the anti-offset capability of a static WPT system, the existing literature mainly adopts three modes: adjusting the winding form of the coupling coil, adopting a composite compensation topology and detecting the relative position of the mechanism.

In the aspect of winding the coupling coil, the excitation magnetic field of a spiral tube (SP) coil has a monopole distribution characteristic, and compared with a Circular (CP) coil, the excitation magnetic field has higher coupling magnetic flux density and larger coupling coefficient. However, the coupling magnetic field based on the SP coil transceiving mechanism is distributed bilaterally, and there is a large leakage magnetic flux, thereby increasing eddy current loss in the shielding aluminum plate; double-D (DD) coils produce magnetic fields with two opposite polarities compared to single-polarity coils, so that the DD coil maintains a large coupling coefficient over a wide range of air gaps. But the two opposite polarity magnetic fields will result in a power pick-up blind spot with zero coupling coefficient during the excursion; in order to overcome the defect that a pickup blind spot exists in the transverse offset of the DD coil, a DDQ (Double-D Quadrature, DD) coil winds a Quadrature decoupling Q coil on the central position of the DD coil. When the coupling mechanism based on the DDQ coil is laterally deviated, the coupling magnetic flux of the DD coil is gradually reduced, and the coupling magnetic flux of the Q coil is gradually increased, so that the total coupling magnetic flux is basically maintained unchanged; the Bipolar (BP) coil combines the characteristics of the DD coil and the DDQ coil. By adjusting the overlapping area of the two D-shaped coils in the BP coil, the two D-shaped coils can realize mutual decoupling. Similar to the DDQ coil, independent compensation and control can also be performed at offset. In addition, under the same coupling area, the amount of copper used for the BP coil is smaller than that used for the DDQ coil; triple Polar (TP) coils can form polarizing magnetic fields in multiple directions compared to BP coils. On one hand, the decoupling of three sector coils in the TP coil requires adjusting the overlapping area of the three. On the other hand, the polarization magnetic field of the magnetic field needs independent control of the amplitude and the phase of three excitation currents, so that the complexity of a control circuit is increased; in addition, the number of coils of the transmitting mechanism is increased, and a plurality of coils at different positions are used for obtaining a magnetic field which is uniformly distributed, so that the coupling area is increased, the stability of the power picked up by the receiving mechanism at different offset positions is ensured, and the offset resistance of the system is improved. However, the coupling mechanism wound in this way consumes a large amount of copper, resulting in increased loss and reduced system efficiency.

In the aspect of composite compensation topology, documents propose SP-S composite compensation topology, which realizes that excitation current of a transmitting end is approximately constant in the offset process and solves the problem that the transmission characteristics of four basic compensation topologies (SS, SP, PS and PP) are greatly influenced by the offset of a coupling mechanism; documents provide a bilateral LCC compensation topology with high offset resistance, so that the design difficulty of system parameters is reduced, the influence of coil self-inductance on system impedance is reduced, and the current of a transmitting end coil is not influenced by the change of a coupling coefficient; in order to reduce the volume and weight of the receiving end, some documents adopt an LCC-S topology with a relatively simpler structure, and reduce the compensation elements of the double-sided LCC topology under the condition of having the same advantages of the double-sided LCC topology.

In terms of detecting the relative position of the mechanism, there is a document based on an optical positioning technique of a camera, which positions the receiving mechanism by photographing a mark, and adjusts the relative position of the transmitting and receiving mechanisms according to this to maintain a stable coupling coefficient. However, these marks are greatly affected by environmental factors and have high hardware cost, so they are not suitable for electric vehicle applications; there are documents in which the position of the receiver is detected by means of a magnetic sensor or auxiliary coil, whereby the driver makes a real-time adjustment of the position of the vehicle, so that the transmitter is aligned with the receiver. On one hand, the magnetic sensor needs to be designed with a signal conditioning circuit. On the other hand, the introduced auxiliary coil may interfere with the power transfer mechanism, thereby increasing the complexity and cost of the system.

Disclosure of Invention

The invention provides a high-resistance deflection WPT system based on a bipolar coupling mechanism and a control method thereof, and solves the technical problems that: how to realize the high-anti-offset deflection of the system by improving the structure and the control mode of the coupling mechanism under the condition of not needing to add an additional position detection device.

In order to solve the technical problems, the invention provides a high-impedance deflection WPT system based on a bipolar coupling mechanism, which comprises a direct-current power supply, a high-frequency inverter circuit, a primary side compensation circuit, the bipolar coupling mechanism, a secondary side compensation circuit, a rectifier and a load R which are sequentially connected _L (ii) a The bipolar coupling mechanism comprises a transmitting mechanism and a receiving mechanism;

the transmitting mechanism comprises a transmitting end magnetic core and a DQDD coil which are sequentially stacked, wherein the DQDD coil is formed by a first DD coil L on the surface layer _p1 And a second DD coil L of the inner layer _p2 Are orthogonally superposed; the first DD coil L _p1 And the second DD-coil L _p2 Are all provided with two parameters which are the same, the same winding direction and the distance W _WD The D-type coils are connected in series;

the receiving mechanism comprises sequentially stacked bipolar coils L _S And a receiving end magnetic core; the bipolar coil L _S The device is formed by overlapping a first CP coil and a second CP coil which have the same parameters and opposite winding directions, and the width of a window formed by overlapping the first CP coil and the second CP coil is also W _WD ；

The receiving mechanism also comprises a bipolar coil L connected with the receiving mechanism _S The relay circuit for controlling the bipolar coil L _S The operating mode of (a) is a bipolar operating mode in which the first CP coil and the second CP coil operate simultaneously, or a unipolar operating mode in which only the first CP coil operates or only the second CP coil operates;

the high-frequency inverter circuit comprises a first inverter and a second inverter which are connected with the direct-current power supply in parallel; the primary side compensation circuit comprises a first inverter and a first DD coil L connected with the first inverter _p1 A first primary side compensation network connected between the second inverter and the second DD coil L _p2 A second primary side compensation network therebetween;

the first inverter and the second inverter are used for controlling the working mode of the DQDD coil to be that only the first DD coil L is excited _p1 Or exciting the first DD coil L with currents of the same amplitude and phase difference β _p1 And the second DD-coil L _p2 DQDD coil operating mode.

Preferably, the transmitting end magnetic core and the receiving end magnetic core both adopt square magnetic cores, and the parameter design process of the bipolar coupling mechanism includes the steps of:

a1, determining the total length l of the D-shaped coil according to actual requirements _DD And a total width W _DD The total length l of the first CP coil, i.e., the second CP coil _CP And total width W _CP ＝a+W _WD A transmission distance l between the emitting means and the receiving means _AG A wire diameter T of the D-type coil, i.e., the first CP coil, i.e., the second CP coil _W And the number of winding turns N, a is a specific value determined according to actual requirements;

a2, determining the distance W according to actual requirements _WD And the side length l of the square magnetic core _F Thickness T _F The optimization range of (1);

a3, set side length l _F Thickness T _F Obtaining the spacing W for a set of fixed values _WD According to the change curves of the primary and secondary side coupling coefficients, the self-inductance of the transceiver coil and the mutual inductance of the transceiver coil in the optimized range, the optimal W is determined by referring to the set of change curves and combining the requirements on the primary and secondary side coupling coefficients, the self-inductance of the transceiver coil and the mutual inductance between the transceiver coil _WD A value;

a4, setting the distance W _WD Is the optimum W _WD Value, obtain side length l _F The variation curve of the primary and secondary coupling coefficients and the thickness T in the optimized range _F According to the change curve of the primary and secondary coupling coefficients in the optimization range, the optimal l is determined by combining the requirements on the primary and secondary coupling coefficients and the actual requirements _F Value sum T _F The value is obtained.

Preferably, the first primary side compensation network and the second primary side compensation network both use LCC compensation networks, and the first primary side compensation network includes a first primary side series compensation inductance L _pf1 The first primary side is connected in series with a compensation capacitor C _p1 And a first primary side parallel compensation capacitor C _pf1 The second primary side compensation network comprises a second primary side series compensation inductor L _pf2 A second primary side series compensation capacitor C _p2 And a second primary side parallel compensation capacitor C _pf2 ；

The secondary side compensation circuit adopts a secondary side series compensation capacitor C _s 。

Preferably, the parameter values of the first primary side compensation network, the second primary side compensation network and the secondary side compensation circuit are set as follows:

ω is the operating angular frequency of the system.

The invention also provides a control method of the high-anti-deflection WPT system based on the bipolar coupling mechanism, and aiming at the system, the control method specifically comprises the following steps:

s1, controlling the bipolar coil L _S In a bipolar operating mode, sequentially energizing the first DD-coil L _p1 And the second DD coil L _p2 ；

S2, measuring and exciting the first DD coil L _p1 Time receiving end output voltage V _o1 And energizing the second DD-coil L _p2 Time receiving end output voltage V _o2 ；

S3, according to the output voltage U of the first inverter ₁ The working angular frequency omega of the system, the first DD coil L _p1 The first primary side series compensation inductor L _pf1 The bipolar coil L _S The receiving end outputs a voltage V _o1 The load R _L Calculating the position at which the first DD coil L is excited at this time _p1 First primary and secondary coupling coefficient k of time ^* _p1s According to the output voltage U of the second inverter ₂ The working angular frequency omega of the system, the second DD coil L _p2 The second primary side series compensation inductor L _pf2 The bipolar coil L _S The receiving end outputs a voltage V _o2 Calculating the position at which the second DD coil L is excited _p2 Second primary and secondary coupling coefficient k of time ^* _p2s ；

S4, according to the first primary and secondary side coupling coefficient k ^* _p1s Second primary and secondary coupling coefficient k ^* _p2s Determining an offset distance and a deflection angle of the receiving mechanism;

s5, determining the working mode of the DQDD coil and the bipolar coil L according to the offset distance and the deflection angle of the receiving mechanism _S The operating mode of (c).

Further, the method can be used for preparing a novel materialIn step S3, the first primary-secondary side coupling coefficient

The second primary and secondary coupling coefficient

Respectively self-inductance of definition L _p1 、L _p2 、L _pf1 、 L _pf2 、L _S The figure of merit of (1).

Further, the step S4 specifically includes the steps of:

s41, calculating the first primary and secondary side coupling coefficient k ^* _p1s And k is _{p1s(θ＝0°)} Error value ak in between ₁ The second primary and secondary coupling coefficient k ^* _p2s And k _{p2s(θ＝0°)} Error value ak in between ₂ ，k _{p1s(θ＝0°)} 、k _{p2s(θ＝0°)} Exciting the first DD coil L under the same condition of no angular deflection between the transmitting mechanism and the receiving mechanism respectively calibrated in advance _p1 Time primary and secondary side coupling coefficient and exciting said second DD coil L _p2 The coupling coefficient of the original secondary side;

s42, determining delta k ₁ And Δ k ₂ Whether the sum of (a) and (b) is less than or equal to a first error threshold value epsilon ₁ If yes, determining that no angle deflection exists between the transmitting mechanism and the receiving mechanism so as to execute step S45, otherwise, executing steps S43-S44;

s43, calculating the first primary and secondary side coupling coefficient k ^* _p1s And k is _{p1s(θ＝45°)} Error value ak in between ₃ The second primary and secondary coupling coefficient k ^* _p2s And k is _{p2s(θ＝45°)} Error value ak therebetween ₄ ，k _{p1s(θ＝45°)} 、k _{p2s(θ＝45°)} Respectively in advance, when there is an angular deflection of 45 ° between the transmitter and the receiverExciting the first DD coil L _p1 Time primary and secondary side coupling coefficient and exciting said second DD coil L _p2 The coupling coefficient of the primary side and the secondary side;

s44, determining delta k ₃ And Δ k ₄ Whether the sum of the first and second error thresholds is less than or equal to a second error threshold epsilon ₂ ，ε ₂ Greater than epsilon ₁ If yes, considering that the angle deflection of +45 degrees or-45 degrees exists between the transmitting mechanism and the receiving mechanism, and executing step S46, otherwise, returning to the step S2;

s45, finding out the first primary and secondary side coupling coefficient k in the correlation relationship between the offset distance and the primary and secondary side coupling coefficient in advance calibrated non-angle deflection ^* _p1s The second primary and secondary side coupling coefficient k ^* _p2s The offset distance of the receiving mechanism corresponding to the specific size of (a);

s46, finding out the first original secondary side coupling coefficient k in the correlation between the offset distance and the original secondary side coupling coefficient during the 45-degree angle deflection calibrated in advance ^* _p1s The second primary and secondary side coupling coefficient k ^* _p2s The specific size of (a) corresponds to the offset distance of the receiving mechanism.

Further, when the receiving mechanism has no angular deflection, the step S5 specifically includes:

when the receiving mechanism has no angle deflection, judging whether the offset distance of the receiving mechanism is in a first preset range or a second preset range, and if the offset distance of the receiving mechanism is in the first preset range, controlling the DQDD coil to work in a DD coil working mode and controlling the bipolar coil L to work in the DD coil working mode _S Working in a unipolar working mode, if the DQDD coil is in a second preset range, controlling the DQDD coil to work in a DD coil working mode and controlling the bipolar coil L to work in a bipolar coil L _S The operation is in a bipolar operation mode.

Further, when there is an angle deviation of +45 ° or-45 ° between the receiving mechanism and the transmitting mechanism, the step S5 specifically includes the steps of:

s51, controlling the DQDD coil to work in the DQDD coil working mode and exciting the first inverter and the second inverterThe phase difference of the current is 0 DEG, and the output voltage V of the receiving end at the moment is measured ^* _o1 ；

S52, controlling the phase difference change of the excitation currents of the first inverter and the second inverter to be 180 degrees, and measuring the output voltage V of the receiving end at the moment ^* _o2 ；

S53, judging V ^* _o1 Whether or not it is greater than V ^* _o2 If yes, judging that the deflection angle of the receiving mechanism is +45 degrees and executing a step S54, otherwise, judging that the deflection angle of the receiving mechanism is-45 degrees and executing a step S55;

s54, controlling the phase difference of excitation currents of the first inverter and the second inverter to be 0 DEG, further judging whether the offset distance of the receiving mechanism is in a third preset range or a fourth preset range, and controlling the bipolar coil L if the offset distance of the receiving mechanism is in the third preset range _S Working in a unipolar working mode, and controlling the bipolar coil L if the bipolar coil L is in a fourth preset range _S Working in a bipolar working mode;

s55, controlling the phase difference of excitation currents of the first inverter and the second inverter to be 180 degrees, further judging whether the offset distance of the receiving mechanism is in a fifth preset range or a sixth preset range, and controlling the bipolar coil L if the offset distance of the receiving mechanism is in the fifth preset range _S Working in a unipolar working mode, and controlling the bipolar coil L if the bipolar coil L is in a sixth preset range _S The operation is in a bipolar operation mode.

The invention provides a high-deflection-resistance WPT system based on a bipolar coupling mechanism. The DQDD coil is composed of two pairs of decoupling DD coils which are arranged in a double-layer orthogonal mode, and the distribution of an excited magnetic field is regulated and controlled through the amplitude and the phase of exciting currents of the two groups of DD coils; the BP coil can be switched to a single polarity coil by means of a relay circuit, thereby changing the polarity of the magnetic field that can be picked up by the receiving means. The system constructs an LCC-S compensation network topology based on a two-way inverter-one-way rectifier, and provides network parameter configuration conditions that excitation current of a transmitting mechanism is constant and system output voltage is irrelevant to load.

In addition, the system also provides a control method of the high-resistance deflection WPT system based on the bipolar coupling mechanism, the method does not need to additionally arrange a position detection device, the relative position and the vertical deflection angle of the horizontal plane of the coupling mechanism can be obtained, the size and the cost of the system can be effectively reduced, and the obtained position information is used for receiving the structural transformation of a BP coil and the distribution regulation and control of a magnetic field excited by a transmitting DQDD coil. The experimental results show that: within the horizontal plane 270mm deviation range, the output power is maintained to be about 1.8kW, and the system efficiency is not lower than 88%.

Drawings

Fig. 1 is a circuit diagram of a high-immunity deflection WPT system based on a bipolar coupling mechanism according to an embodiment of the present invention;

FIG. 2 is a perspective view of a dual polarity coupling mechanism provided by an embodiment of the present invention;

FIG. 3 is a front view of a dual polarity coupling mechanism provided by an embodiment of the present invention;

FIG. 4 is a schematic diagram of a DQDD coil winding scheme and an excitation magnetic field provided by an embodiment of the invention;

fig. 5 is a resultant magnetic field distribution diagram of the DQDD coil with a phase difference β =90 ° provided by an embodiment of the present invention;

FIG. 6 is a schematic diagram of a BP coil winding scheme provided by an embodiment of the invention;

fig. 7 is an LCC-S compensation topology provided by an embodiment of the present invention;

FIG. 8 is a diagram illustrating the influence of window width on self-inductance, mutual inductance, and primary-secondary coupling coefficient according to an embodiment of the present invention;

FIG. 9 is a graph illustrating the effect of core size on coupling coefficient provided by an embodiment of the present invention;

FIG. 10 is a schematic diagram of a variable structure and magnetic field regulation provided by an embodiment of the present invention;

FIG. 11 is a coupling coefficient display diagram at different position offsets and angular deflections provided by an embodiment of the present invention;

FIG. 12 is a flow chart of a control method of a high-resistance offset deflection WPT system based on a bipolar coupling mechanism according to an embodiment of the present invention;

fig. 13 is a diagram illustrating a CCAR variation law of different magnetic coupling mechanisms according to an embodiment of the present invention;

FIG. 14 is a graph showing the measurement error of coupling coefficients at different position offsets and angular deflections provided by an embodiment of the present invention;

fig. 15 is a waveform diagram of a laboratory prototype at five positions provided by the embodiment of the invention.

Detailed Description

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, which are given solely for the purpose of illustration and are not to be construed as limitations of the invention, including the drawings which are incorporated herein by reference and for illustration only and are not to be construed as limitations of the invention, since many variations thereof are possible without departing from the spirit and scope of the invention.

To overcome the limitation of combining the existing three anti-offset lifting manners, an embodiment of the present invention first provides a high anti-offset deflection WPT system based on a bipolar coupling mechanism, as shown in the circuit topology diagram of fig. 1, where the system includes sequentially connected dc power supplies U _dc A high-frequency inverter circuit I, a primary side compensation circuit II, a bipolar coupling mechanism III, a secondary side compensation circuit IV, a rectifier V and a load R _L 。

Fig. 2 and 3 respectively show a three-dimensional structure and a front view of a bipolar coupling mechanism, the bipolar coupling mechanism comprises a transmitting mechanism and a receiving mechanism, the transmitting mechanism comprises a transmitting end magnetic core and a DQDD coil which are sequentially stacked, and the DQDD coil is formed by a first DD coil L on the surface layer _p1 (also referred to as DD-coil 1) and a second DD-coil L in the inner layer _p2 (also referred to as DD coil 2) are stacked orthogonally. First DD coil L _p1 And a second DD coil L _p2 Are all provided with two parameters which are the same, the same winding direction and the distance W _WD The D-type coils are connected in series. The receiving mechanism comprises sequentially stacked bipolar coils L _S And a receiving end magnetic core; bipolar coil L _S The device comprises a first CP coil (also called CP coil 1) and a second CP coil (also called CP wire) with the same parameters and opposite winding directionsCircle 2) overlapping composition, the window width formed by the overlapping is W _WD . It can be seen that, based on the orthogonal relationship of the DQDD coils, the transmitting-end magnetic core employs a square magnetic core that coincides with the orthogonal superposition area of the DQDD coils, and the receiving-end magnetic core also employs the same square magnetic core.

As shown in fig. 1, to realize the first DD coil L _p1 A second DD coil L _p2 The high-frequency inverter circuit comprises a first inverter and a second inverter which are connected with a direct-current power supply in parallel, and the primary side compensation circuit comprises a first DD coil L connected with the first inverter and the first DD coil L _p1 A first primary side compensation network connected between the second inverter and the second DD coil L _p2 A second primary compensation network therebetween. The first inverter and the second inverter are used for controlling the working mode of the DQDD coil to only excite the first DD coil L _p1 Or the first DD-coil L is excited with currents of the same amplitude and phase difference beta _p1 And a second DD coil L _p2 DQDD coil operating mode. The first primary side compensation network and the second primary side compensation network both adopt LCC compensation networks, and the first primary side compensation network comprises a first primary side series compensation inductor L _pf1 A first original side series compensation capacitor C _p1 And a first primary side parallel compensation capacitor C _pf1 The second primary side compensation network comprises a second primary side series compensation inductor L _pf2 A second primary side series compensation capacitor C _p2 And a second primary side parallel compensation capacitor C _pf2 . The secondary side compensation circuit adopts a secondary side series compensation capacitor C _s 。

In FIG. 1, U ₁ 、U ₂ Output voltages of the first inverter and the second inverter, I ₁ 、I ₂ Output currents of the first inverter and the second inverter, I _p1 、I _p2 、I _s Current, L, on two sets of DD and receive coils respectively _p1 、L _p2 、L _s Self-inductance, L, of two sets of DD-coils and receiving-coils, respectively _pfi 、C _pi 、C _pfi (i =1,2) constitutes an LCC compensation network of two sets of DD coils, C _s Series compensation capacitors for the receiving coil, M _p1s 、M _p2s The mutual inductance between the two groups of DD coils and the receiving coil is respectively.

The dimensional parameters of the coils are indicated in fig. 2 and 3, including the total length l of the D-shaped coil _DD And total width W _DD The total length l of the first CP coil, i.e., the second CP coil _CP And a total width W _CP ＝a+W _WD (a is a specific value determined according to actual requirements), and the side length l of the square magnetic core _F Thickness T _F And a transmission distance l between the transmitter and the receiver _AG . Total length l of one DD coil _p ＝2W _DD +W _WD The total width is the length l of the D-shaped coil _DD . Bipolar coil L _S Total length of (l) _s Total width W _s ＝l _CP 。

Fig. 4 (a) shows a DQDD coil winding scheme, where the spatial orthogonal positions enable the upper and lower layers of DD coils to be decoupled from each other. The reason for this is that the orthogonal arrangement makes the net magnetic flux of the same layer DD coil and the same layer D-type coil close to zero. The mutually decoupled coil structure means that the excitation currents in the coils can be independently controlled without being influenced by each other, and the difficulty of circuit analysis is reduced.

The amplitude of the excitation current of the DD coil 1 is the same as that of the excitation current of the DD coil 2, and the phase difference beta is set as follows:

I _p1 ＝I _p1 ∠0,I _p2 ＝I _p1 ∠β (1)

magnetomotive force f generated by exciting current in formula (1) in combination with orthogonal position relation of two sets of DD coils _DD1 、 f _DD2 Can be expressed as:

in the formula (2), θ _s For reference to the spatial angle, ω is the angular frequency of operation of the system, F _DD1 ＝F _DD2 。

From equation (2), the resultant magnetomotive force f at an arbitrary point in the XOY plane is:

the expression (3) means that the synthetic magnetomotive force f is related to the phase difference β of the excitation current. The resultant magnetomotive force f when β =0 °,180 °, and 90 ° is as shown in formula (4):

equation (4) illustrates when exciting current I _p1 And I _p2 Is 0 DEG or 180 DEG, the magnetic induction is that excited by a single DD coil

And (4) doubling. And when the difference between the two excitation currents is 90 degrees, the magnetic induction intensity is the same. When the angle is beta =0 degrees, the two-pole magnetic field of the DQDD coil is mainly distributed at the opposite angle of positive 45 degrees; for β =180 °, the two-pole magnetic field is concentrated mainly at the negative 45 ° diagonal. As for β =90 °, the two-pole magnetic field is periodically distributed in a rotating manner with equal amplitude.

A finite element simulation model of the DQDD coil was created by ANSYS Maxwell, and the magnetic field distribution in the region above the launching mechanism in the three excitation modes was obtained as shown in fig. 4 (b), (c), and fig. 5, and it was found that the distribution of the resultant magnetic field was consistent with equation (4).

The receiving mechanism further comprises a connecting bipolar coil L _S For controlling the bipolar coil L _S The operation mode of (a) is a bipolar operation mode in which the first CP coil and the second CP coil are operated simultaneously, or a unipolar operation mode in which only the first CP coil is operated or only the second CP coil is operated. In particular, the relay circuit comprises a relay K ₁ Relay K ₂ 。

Fig. 6 shows a winding scheme and a structure transformation method of the BP coil of the receiving mechanism. Wherein the relay K ₁ Relay K ₂ For structural transformation of the receiving means. When the reception mechanism requires a BP coil, K ₁ And K ₂ COM contact of (2)Both are attracted to the NO terminal as shown in fig. 6 (a). At this point, the receiving mechanism may pick up the bipolar magnetic field. In a bipolar magnetic field, the directions of the magnetic fields in the two coupling areas of the BP coil are consistent, and the magnetic fields in the decoupling areas are opposite. The reverse serial winding mode adopted by the BP coil enables the induced electromotive force of the decoupling area to be zero, and the induced electromotive forces of the two coupling areas are connected in series in the forward direction. When the receiving mechanism needs a CP coil, K ₁ And K ₂ One of the COM contacts is attracted to the NC terminal as shown in fig. 6 (b), (c). If K is ₂ Contact and NC ₂ Attracting, namely accessing from the left coil, and picking up a vertically inward magnetic field in the bipolar magnetic field by the receiving mechanism at the moment; and conversely, the magnetic field is accessed from the right coil, and the direction of the magnetic field picked up at the moment is vertically outward.

The coupling coefficient is one of key parameters for judging the deflection resistance of the coupling mechanism of the WPT system, and the equivalent coupling coefficient k can be adopted for a double-energy-channel coupling mechanism consisting of two groups of transmitting coils and one group of receiving coils _eff Determining, as shown in equation (5):

in the formula, S _u Indicating the pick-up capacity of the receiving coil, VA _i Representing the capacity of the transmission of the transmitting coil; v _oc And I _sc Respectively open-circuit voltage and short-circuit current, V, of the receiving coil _pi And I _pi Terminal voltage and exciting current of the transmitting coil in turn, where S _u And VA _i Can be specifically expressed as:

substituting formula (6) for formula (5), k _eff Can be simplified to formula (7):

in the formula, M _eff And L _eff Equivalent mutual inductance and equivalent self-inductance of the system, respectively, when the system only excites the DD coil 1 or the DD coil 2, M is _eff ＝M _pis ，L _eff ＝L _pi (i =1,2). The equivalent coupling coefficient k derived in this example _eff And comparing the parameter configuration of the follow-up bipolar coupling mechanism with the performance of the coupling mechanism.

FIG. 7 is an equivalent mutual inductance model of FIG. 1, from which the column KVL equation can be written:

in the formula of U _p1s 、U _p2s Is two groups of mutual inductance M _p1s 、M _p2s Induced voltage, X, generated _L 、X _C The reactance of the compensation network and the coil is represented, and the specific meaning is shown in a formula (9):

the parameter configuration method of the LCC-S compensation circuit is given by the formula (10):

from equations (8) to (10), the respective loop currents can be obtained:

as can be seen from the equation (11), when the transmitting terminal compensation network adopts the LCC topology and the working frequency is kept constant, the excitation currents I of the two groups of DD coils in the transmitting mechanism _pi Is only dependent on the amplitude of the inverter output voltage and the inductance L _pfi Independent of load and mutual inductance. The characteristic realizes independent control of excitation current of the two groups of DD coils, and when the inverter outputs a voltage U ₁ 、U ₂ Are equal in amplitude, compensating for the inductance L _pf1 、L _pf2 When the inductance values of (1) are equal, the current I is excited _p1 、I _p2 Are equal in magnitude.

Due to coupling coefficient limited by window width W _WD And magnetic core size T _F 、l _F The method gives the partial size of the magnetic coupling mechanism and the window width W according to the position condition of the complete alignment of the transmitting mechanism and the receiving mechanism and the design standard of the WPT system of the electric automobile released by the country and related organizations _WD And magnetic core size l _F 、 T _F Optimization is performed.

According to the standard GB/T38775 and IEC 61980, the distance l between the transmitting mechanism and the receiving mechanism is selected _AG =130mm; d-shaped coil _DD ＝300mm，W _DD ＝150mm，T _W =2.5mm, N =20 turns, W _W =50mm; CP coil l _CP ＝300mm，W _CP ＝a+W _WD ＝200+W _WD . Therefore DQDD coil l _p ＝300+W _WD (ii) a BP coil l _s ＝300+W _WD ，W _s ＝l _CP =300mm. The first and second columns of the table show the size parameters and optimized range of the magnetic coupling mechanism to be optimized. Wherein the window width W _WD And core length l _F Determines the coverage area of the magnetic field with an optimal range of l _p Is a normalized reference; thickness T of magnetic core _F Determines the strength of the magnetic field in an optimum range of l _AG Is a normalized reference.

TABLE 1 size parameters to be optimized, optimization Range and optimization values

FIG. 8 shows the window width W _WD The rule of influence on the self-inductance, mutual inductance and coupling coefficient of the coil is that the length l of the magnetic core is _F The normalized value was chosen to be 76.9% and the core thickness T _F The content was 9.2%. As can be seen from FIG. 8, with W _WD The curve of the mutual inductance and the coupling coefficient rises first and then tends to be flatSlightly decreased. For the purpose of high transmission efficiency and low coil end voltage, W is selected _WD Is 23%, when the coupling coefficient is maximum and the coil self-inductance is small.

FIG. 9 (a) and (b) show the core lengths l, respectively _F Thickness T of magnetic core _F And (4) influence rule on the coupling coefficient. Window width W when optimizing core size _WD The normalized value was set to 23%. As shown in FIG. 9 (a), the following equation l _F The curve of the coupling coefficient is increased sharply and then decreased in small amplitude, when the length l of the magnetic core is increased _F The normalized value was 76.9%, and the coupling coefficient reached a maximum of 0.186, due to [ (l) _F /l _p )*100％]Greater than 76.9% reduces the self-coupling region reluctance of the transmit coil resulting in a reduced coupling coefficient, while less than 76.9% increases the mutual coupling region reluctance of the transmit and receive coils resulting in a reduced coupling coefficient. As shown in FIG. 9 (b), the following T _F The curve of the coupling coefficient is increased rapidly and then becomes gentle, when the thickness T of the magnetic core is increased _F The normalized value is 9.2%, the coupling coefficient reaches maximum 0.189, the weight and volume of the magnetic core and the size of the existing magnetic core are comprehensively considered, and the thickness T of the ferrite is finally selected _F ＝10mm。

The result of the optimization of the combined window width and core size, for the chosen transmission spacing l of the example _AG =130mm, d-type coil width W _DD And =150mm, the overall dimension parameters of the DQDD magnetic coupling mechanism can be obtained, and the parameters in the table are listed as the design basis of an experimental prototype.

TABLE 2 magnetic coupling mechanism dimensional parameters

To summarize, the parametric design process for a bipolar coupling mechanism comprises the steps of:

a1, determining the total length l of the D-type coil according to actual requirements _DD And a total width W _DD The total length l of the first CP coil, i.e., the second CP coil _CP And a total width W _CP Transmission distance l between the transmitting and receiving means _AG The wire diameter T of the D-type coil, i.e. the first CP coil, i.e. the second CP coil _W And the number of winding turns N, a is a specific value determined according to actual requirements;

a2, determining the distance W according to actual requirements _WD And the side length l of the square magnetic core _F Thickness T _F Optimization range of (e.g., table 1);

a3, set side length l _F Thickness T _F Obtaining the spacing W for a set of fixed values _WD According to the variation curves of the primary and secondary side coupling coefficients, the self-inductance of the transmitter-receiver coil, and the mutual inductance between the transmitter-receiver coil (see fig. 8), the optimal W is determined by referring to the set of variation curves and combining the requirements of the primary and secondary side coupling coefficients, the self-inductance of the transmitter-receiver coil, and the mutual inductance between the transmitter-receiver coil _WD A value;

a4, setting the distance W _WD Is the optimum W _WD Value, obtain side length l _F The variation curve of the primary and secondary coupling coefficients (as shown in FIG. 9 (a)) and the thickness T _F According to the variation curve of the primary and secondary coupling coefficients in the optimization range (as shown in FIG. 9 (b)), referring to the set of variation curves, and determining the optimal l by combining the requirements on the primary and secondary coupling coefficients and the actual requirements _F Value sum T _F The value is obtained.

In conjunction with the above analysis, fig. 10 shows a schematic diagram of the relative position relationship between the receive coil variation structure and the transmitter coil excitation method and the transmitter/receiver mechanism. X 'represents a normalized offset distance, i.e., X' = Δ X/l _P X 100%, in the same way, Y' = DeltaY/l _P X 100%, as shown in FIG. 10. The dotted line intersection in the figure represents the position of the center point of the receiving mechanism, and the transverse distance and the longitudinal distance between every two points are both 10%, namely the transverse-longitudinal offset distance between every two points is 39mm.

Fig. 10 (a) - (d) show four combinations of the transmitting end excitation magnetic field and the receiving end pickup structure in fig. 10 (a 1) - (d 1). Fig. 10 (a 1) is a schematic diagram of a variation structure of a receiving mechanism without angular deflection and magnetic field control. The magnetic field of the emitting means is excited by the DD coil 1 in the offset range defined by the center of the emitting means. The receiving mechanism belongs to (-50, -20) in X' ∈The pickup structure in the range of U.Y' epsilon (-50,50) adopts a CP coil, as shown in a grid area in the figure, and a diagonal area in the figure indicates that a receiving mechanism adopts a BP coil. FIG. 10 (a 2) shows k when the receiving mechanism is not angularly deflected _eff The change rule of (2). As can be seen, the area with the equivalent coupling coefficient not lower than 0.1 accounts for 0.36 in the defined offset range, and compared with the traditional DD-DD magnetic coupling mechanism, the pick-up structure of the receiving mechanism is converted from a BP coil to a CP coil at a specific position, so that the pick-up blind spot is eliminated, and k is enabled to be _eff The change rate in the X direction is more gradual, and the anti-offset capability in the X direction is improved; fig. 10 (b 1) is a schematic view of a variation structure and magnetic field control in which the angular deflection θ = ± 15 ° of the receiving mechanism. The magnetic field of the transmitter is likewise excited by the DD coil 1 in the offset range defined by the center of the transmitter. Unlike the case of no angular deflection, the receiving mechanism employs a CP coil in a pickup structure in the range of X '∈ (-50, -20 £ Y' ∈ (-70,70), as shown by a grid region in the figure, and a diagonal region in the figure indicates that the receiving mechanism employs a BP coil. When the angular deflection θ =15 ° and k are given by (b 2) of fig. 10 _eff The change rule of the equivalent coupling coefficient is known, the area proportion of the equivalent coupling coefficient not less than 0.1 is 0.25; fig. 10 (c 1) and (d 1) are schematic diagrams of a variable structure of angular deflection θ =45 ° and θ = -45 ° of the receiving mechanism and a magnetic field regulation, respectively, in which the structures of the pickup coil of the receiving mechanism are marked by shading and vertical stripes, respectively, at different positions, and at this time, the magnetic field of the transmitting mechanism is excited by the DD coil 1 and regulated to be excited by the DQDD coil. Angular deflections θ =45 °, θ = -45 ° given in (c 2), (d 2) of fig. 10, and k _eff The change law is not difficult to see, when the receiving mechanism has large angle deflection, although k is at the original point _eff The value decreases, but k _eff The area of > 0.1 is still large, accounting for the ratio of the defined offset range of 0.28. After analysis is performed by combining with fig. 10, the magnetic coupling mechanism has higher horizontal offset resistance and angular offset resistance after the variable structure and the magnetic field regulation are introduced.

In the present embodiment, the proposed bipolar coupling mechanism has central symmetry, and the variable structure and magnetic field control of the non-angular deflection and the angular deflection θ = ± 15 ° are similar, so the following discussion mainly discusses two cases of the non-angular deflection and the angular deflection θ =45 °.

The excitation mode of the transmitter and the coil structure change of the receiver depend on the relative position of the transmitter and receiver, so that the receiver needs to be positioned. The system calculates the coupling coefficient based on the output voltage of the double-energy-channel receiving end, and two pairs of DD coils in the DQDD coils of the transmitting mechanism are used as detection coils, so that the purpose of detecting the position of the receiving mechanism is achieved. The detection process sequentially excites the DD coil 1 and the DD coil 2, and the influence of cross coupling between the coils on the detection performance is ignored. When only the inverter of the loop where the DD coil 1 is located is turned on, the current I of the loop at the receiving end can be obtained from the formula (11 e) _s ：

Can obtain the output voltage U of the receiving end when the loop inverter where the DD coil 1 is positioned is switched on _o1 ：

The figure of merit defining self-inductance is:

substituting the formulas (7) and (14) into the formula (13) can further simplify U _o1 ：

Thereby obtaining k _p1s ：

Similarly, when the inverter of the loop where the DD coil 2 is located is turned on, k can be obtained _p2s ：

The obtained coupling coefficient reflects the mutual inductance between the transmitting mechanism and the receiving mechanism, namely reflects the relative position of the transmitting mechanism and the receiving mechanism.

Measuring the self-inductance L at each position _p1 、L _p2 And mutual inductance M _p1s 、M _p2s And calculating the coupling coefficient k at each position _p1s 、k _p2s Thereby, a location profile table can be formed. Taking the coupling mechanism constructed by the dimensional parameters listed in Table 2 as an example, k corresponding to different relative positions of the transceiving mechanism _pis As shown in fig. 13. With fig. 11 as a reference, in practical application, the receiving end output voltages V when the loop inverters where the DD coil 1 and the DD coil 2 are respectively turned on are sequentially measured _o1 、V _o1 (ii) a Further, the actual k is calculated from the equations (16) and (17) ^* _p1s And k ^* _p2s A1, k is ^* _p1s 、k ^* _p2s And comparing the coupling coefficient with a reference standard of the coupling coefficient to determine the position of the receiving mechanism.

A bipolar coupling magnetic field regulation and control flow is provided by combining a regulation and control strategy of the coupling magnetic field and the position detection of the transmitting and receiving mechanism, as shown in fig. 12. Firstly, two groups of DD coils in the DQDD of the transmitting mechanism are sequentially excited, the output voltage of a receiving end when the two groups of DD coils are excited is respectively measured, and a coupling coefficient k at the position is calculated through formulas (16) and (17) ^* _p1s 、k ^* _p2s . Then k is put ^* _p1s 、k ^* _p2s And k in the location characteristic parameter table _{p1s(θ＝0°)} 、k _{p2s(θ＝0°)} (k _{p1s(θ＝0°)} 、k _{p2s(θ＝0°)} Exciting a first DD coil L under the same conditions without angular deflection between a transmitting mechanism and a receiving mechanism respectively calibrated in advance _p1 Primary and secondary coupling coefficient of time and excitation of the second DD coil L _p2 Original and secondary coupling coefficients) of the two, and if the sum of the errors of the two is less than epsilon ₁ If yes, then consider the transmission and receptionThe mechanism has no angular deflection, and the position of the receiving mechanism is determined; if the sum of the errors is larger than epsilon ₁ Then k will be ^* _p1s 、k ^* _p2s And k is _{p1s(θ＝45°)} 、 k _{p2s(θ＝45°)} (k _{p1s(θ＝45°)} 、k _{p2s(θ＝45°)} Exciting a first DD coil L under the same conditions when there is an angular deflection of 45 DEG between the transmitter and receiver, respectively, which are calibrated in advance _p1 Primary and secondary coupling coefficient of time and excitation of the second DD coil L _p2 The original secondary coupling coefficient of time) are compared. If less than epsilon after comparison ₂ If so, considering that the transmitting and receiving mechanism has +45 degrees or-45 degrees of angle deflection, and determining the offset of the receiving mechanism; otherwise, if the error is still larger than epsilon ₂ And then measuring the voltage information again and circulating the steps. Error threshold epsilon ₁ 、ε ₂ Is determined by the maximum relative error between the measured value of the equivalent coupling coefficient and the simulated value. After the position of the receiving mechanism is determined, a transmitting and receiving coil excitation mode and a receiving coil structure are selected according to fig. 10, and high anti-offset deflection performance of the bipolar coupling mechanism is achieved.

Based on the above analysis, the present embodiment further provides a control method of a high-immunity deflection WPT system based on a bipolar coupling mechanism, which specifically includes the steps of:

s1, controlling the bipolar coil L _S In a bipolar operating mode, sequentially energizing the first DD-coil L _p1 And a second DD coil L _p2 ；

S2, measuring and exciting the first DD coil L _p1 Time receiving end output voltage V _o1 And exciting the second DD-coil L _p2 Time receiving end output voltage V _o2 ；

S3, based on the formula (14) to the formula (17), according to the output voltage U of the first inverter ₁ The working angular frequency omega of the system and the first DD coil L _p1 First primary side series compensation inductor L _pf1 Bipolar coil L _S And the output voltage V of the receiving end _o1 Load R _L The first DD coil L is calculated for the position at which the excitation is now to take place _p1 First primary and secondary coupling coefficient k of time ^* _p1s According to the firstOutput voltage U of two inverters ₂ And the working angular frequency omega of the system, and a second DD coil L _p2 A second primary side series compensation inductor L _pf2 Bipolar coil L _S And the output voltage V of the receiving end _o2 The second DD-coil L is calculated for this position and is excited at this time _p2 Second primary and secondary coupling coefficient k of time ^* _p2s ；

S4, according to the first primary and secondary side coupling coefficient k ^* _p1s Second primary and secondary coupling coefficient k ^* _p2s Determining the offset distance and the deflection angle of a receiving mechanism;

s5, determining the working mode of the DQDD coil and the bipolar coil L according to the offset distance and the deflection angle of the receiving mechanism _S The operating mode of (1).

Specifically, step S4 specifically includes the steps of:

s41, calculating a first primary and secondary side coupling coefficient k ^* _p1s And k is _{p1s(θ＝0°)} Error value ak therebetween ₁ Second primary and secondary side coupling coefficient k ^* _p2s And k is _{p2s(θ＝0°)} Error value ak in between ₂ ；

S42, determining delta k ₁ And Δ k ₂ Whether the sum of the first and second error thresholds is less than or equal to a first error threshold epsilon ₁ If yes, the transmitting mechanism and the receiving mechanism are considered to have no angular deflection, and step S45 is executed, otherwise, steps S43 to S44 are executed;

s43, calculating a first primary and secondary side coupling coefficient k ^* _p1s And k is _{p1s(θ＝45°)} Error value ak in between ₃ Second primary and secondary coupling coefficient k ^* _p2s And k is _{p2s(θ＝45°)} Error value ak therebetween ₄ ；

S44, determining delta k ₃ And Δ k ₄ Whether the sum of the first and second error thresholds is less than or equal to a second error threshold epsilon ₂ ，ε ₂ Greater than epsilon ₁ If yes, considering that the transmitting mechanism and the receiving mechanism have +45 degrees or-45 degrees of angle deflection so as to execute the step S46, otherwise, returning to the step S2;

s45, in advance calibrated non-angle deflection, the offset distance and the original distanceIn the correlation relationship of the secondary side coupling coefficient (as shown in fig. 11 (a)), the first original secondary side coupling coefficient k is found ^* _p1s Second primary and secondary side coupling coefficient k ^* _p2s The offset distance (X ', Y') of the receiving mechanism corresponding to the specific size of (a); for example by measuring V _o1 、V _o2 Can calculate k ^* _p1s 、k ^* _p2s (assume k) ^* _p1s ＝0.05，k ^* _p2s = 0.05), k shown in fig. 11 (a) _p1s Contour line and k of middle 0.05 _p2s The 0.05 contour line in the table has an intersection point, the relative position corresponding to the intersection point of the two contour lines is obtained by a table look-up method, and finally the offset distance of the receiving mechanism relative to the transmitting mechanism is determined;

s46, similar to the step S45, in the correlation (as shown in (b) of FIG. 11) between the offset distance and the primary and secondary coupling coefficients at the time of the 45 DEG angle deflection calibrated in advance, find out the first primary and secondary coupling coefficient k ^* _p1s Second primary and secondary side coupling coefficient k ^* _p2s The offset distance (X ', Y') of the receiving mechanism corresponding to the specific size of (a).

Specifically, when the receiving mechanism has no angular deflection, step S5 specifically includes:

determining whether the offset distance of the receiving mechanism is within a first preset range or a second preset range, and if the offset distance is within the first preset range (e.g. the ranges of X 'and Y' corresponding to DD1-CP in (a 1) of fig. 10), controlling the DQDD coil to operate in the DD coil operating mode and the bipolar coil L _S Operating in a unipolar operating mode, and if the range is in a second preset range (e.g. the ranges of X 'and Y' corresponding to DD1-BP in (a 1) of fig. 10), controlling the DQDD coil to operate in the DD coil operating mode and the bipolar coil L _S And the system works in a bipolar working mode (DD 1-BP). For example, measure V _o1 、V _o2 Calculate k ^* _p1s 、k ^* _p2s Based on the coupling coefficient variation rule shown in FIG. 11 (a), k is found ^* _p1s 、k ^* _p2s And the corresponding contour lines determine the offset distance of the receiving mechanism relative to the transmitting mechanism through the intersection point of the two contour lines. According to the determinedWith reference to fig. 10 (a 1), if the receiving mechanism is located in the offset distance area of X '∈ (-50, -20 ≡ Y' ∈ (-50,50) or X '∈ (20,50 ≡ Y' ∈ (-50,50), the DQDD coil operates in the DD coil mode and the bipolar coil L is in the DD coil mode _s Operating in a unipolar operating mode.

When there is an angular deflection of ± 45 ° between the receiving means and the emitting means, step S5 specifically includes the steps of:

s51, controlling the DQDD coil to work in the DQDD coil working mode, enabling the phase difference of excitation currents of the first inverter and the second inverter to be 0 degrees, and measuring the output voltage V of the receiving end at the moment ^* _o1 ；

s54, controlling the phase difference between the excitation currents of the first inverter and the second inverter to be 0 °, further determining whether the offset distance of the receiving mechanism is within a third preset range or a fourth preset range, and if the offset distance is within the third preset range (e.g., the ranges of X 'and Y' corresponding to DQDD-CP in (c 1) of fig. 10), controlling the bipolar coil L _S Operating in a unipolar operating mode, and controlling the bipolar coil L if the operating mode is within a fourth preset range (e.g. the ranges of X 'and Y' corresponding to DQDD-BP in (c 1) of fig. 10) _S Working in a bipolar working mode;

s55, controlling the phase difference between the excitation currents of the first inverter and the second inverter to be 180 °, further determining whether the offset distance of the receiving mechanism is within a fifth preset range or a sixth preset range, and if the offset distance is within the fifth preset range (e.g., the ranges of X 'and Y' corresponding to DQDD-CP in (d 1) of fig. 10), controlling the bipolar coil L _S Operating in the unipolar operating mode, if the voltage is within the sixth predetermined range (e.g. X corresponding to DQDD-BP in (d 1) of fig. 10)', Y') of the bipolar coil L _S The operation is in a bipolar operation mode.

An index for measuring the anti-offset capability of the Coupling mechanism is defined as a Coupling Coefficient Attenuation Ratio (CCAR):

in the formula, k _ali And k _mis Representing the equivalent coupling coefficients at alignment and after offset, respectively. Under the same offset deflection condition, the smaller value of the CCAR indicates the higher tolerance of the offset.

In the embodiment, the CP coil and the DD coil are selected as compared magnetic coupling mechanisms, and the number of turns, the sizes of the coil and the magnetic conducting mechanism and the coupling distance adopted by the DQDD mechanism in the analysis process are the same as those of the other two coupling mechanisms. Compared with CP and DD coupling mechanisms commonly used in a WPT system, the variable structure and magnetic field regulation-based bipolar coupling mechanism has stronger horizontal offset resistance and angular offset resistance. FIG. 13 shows the variation of CCAR with or without angular offset for different magnetic coupling mechanisms. Fig. 13 (a) shows the change law of the CCAR of the three coupling mechanisms without angular offset. The areas of the corresponding regions of the proposed magnetic coupling mechanism, which are not higher than 25% and 50% of the CCAR, are 0.9 times and 1.43 times the CP coil, respectively, compared to the CP coil. At an offset distance of 20%, the increase rate of the CCAR in the X 'direction of the magnetic coupling mechanism is slightly faster than that of the CP coil, but the increase rate of the CCAR in the Y' direction is significantly slower than that of the CP coil. Secondly, the CCAR of the magnetic coupling mechanism with 50% offset is increased to 50%, while the CCAR of the CP coil with 40% offset is increased to 50%, which shows that the magnetic coupling mechanism has higher offset resistance than the CP coil and the performance is more outstanding with larger offset; compared with the DD coil, the magnetic coupling mechanism has a CCAR not higher than 25% corresponding area equal to that of the DD coil, a CCAR not higher than 50% corresponding area 1.5 times that of the DD coil, and a CCAR of the DD coil at a shift of 40% in the X' direction of about 100%, which indicates that the magnetic coupling mechanism has an omnidirectional and wider range of anti-shift performance than the DD coil.

Fig. 13 (b) shows the change law of the CCAR of the three coupling mechanisms when the angular deflection θ =45 °. Compared with CP and DD coils, the area of the corresponding region of the magnetic coupling mechanism CCAR which is not higher than 25% is basically equal to the area of the CP and DD coils; the area of the corresponding area of which the CCAR is not higher than 50% is 1.55 times and 1.49 times of that of the CP and DD coils respectively, which shows that the provided magnetic coupling mechanism has stronger anti-offset deflection performance and more excellent performance compared with the CP and DD coils under the condition of larger deflection and the larger offset distance. Since the magnetic coupling mechanism proposed in this example has central symmetry, the angular deflection θ = -45 ° is similar to the CAR variation law of angular deflection θ =45 ℃, and therefore, no further discussion is given.

After the above comparative analysis is combined, it can be seen that the position and angle anti-offset performance of the magnetic coupling mechanism in the horizontal plane is better than that of the CP and DD magnetic coupling mechanisms, and the performance is more prominent when the offset degree is larger.

According to the size parameters of the magnetic coupling mechanism given in the table 2, an experimental prototype is built by combining a parameter configuration method of an LCC-S compensation circuit, and the offset resistance and the transmission characteristic of the magnetic coupling mechanism after the variable structure and the magnetic field regulation are added are verified. Wherein, the coil windings of the transmitting mechanism and the receiving mechanism are respectively formed by winding litz wires with the diameter of 0.2mm multiplied by 300; the magnetic core material is PC44 manganese zinc ferrite; the aluminum plate is made of 6061 aluminum with the thickness of 3mm and is used for shielding a leaked magnetic field; the insulating paper is used for preventing the two layers of coils from being short-circuited. Table 3 lists the main parameter values and component models of the system. It should be noted that the internal resistance of the single DD coil wound in the transmitting mechanism is 0.26 Ω, and the mutual inductance between the two DD coils is 0.3 μ H, which is negligible compared to the self-inductance, i.e. it can be considered that the decoupling between the two DD coils is achieved. In addition, signal communication between the transceiving mechanisms is realized by a Bluetooth module. Load voltage V _o1 、V _o2 After the voltage is divided by a resistor, sampling is carried out by an ADC module arranged in the MCU and then the sampled data is transmitted to a transmitting terminal; and after the transmitting end determines the position of the receiving mechanism according to the load voltage information, the transmitting end regulates and controls the transmitting magnetic field and sends a relay control signal to the receiving end.

TABLE 3 Main parameter values and component models of prototype

In order to verify the anti-offset performance of the position and angle in the plane of the coupling mechanism XOY provided in this example, 10% (39 mm) as the step length and X '= ± 70% and Y' = ± 70% (X = ± 273mm and Y = ± 273 mm) as the boundaries are taken with the position of the air gap height of 130mm as the reference, and the measured values and errors of the coupling coefficients of the two energy channels under different position offsets and angle deflections are given, as shown in fig. 14.

The facing position k in (a 1) in FIG. 14 _eff =0.183, the maximum relative error between the empirical measurement and the simulated equivalent coupling coefficient in the entire offset range is 8.06%, the minimum relative error is 0.54%, and the average relative error is 3.49%; the opposite position k in (a 2) of FIG. 14 _eff =0.179, the maximum relative error of the experimental measurement values and the simulated equivalent coupling coefficient in the whole offset range is 9.52%, the minimum relative error is 0.83%, and the average relative error is 3.7%. In general, the error between the measurement result and the simulation is small, and the equivalent coupling coefficient and the analysis result of the CCAR change rule are basically consistent, so that the anti-offset performance of the position and the angle of the magnetic coupling mechanism in the XOY plane is verified; FIG. 14 (b 1) and (b 2) show the dual-energy coupling coefficients k for different position shifts without angular deflection _p1s 、k _p2s Compared with the simulation value given in fig. 11, the maximum relative errors of the measured values of (1) are 9.47% and 9.13%, respectively, and the minimum relative errors are both 0; in fig. 14, (c 1) and (c 2) show the dual-energy coupling coefficients k at different positional offsets in the case of angular deflection θ =45 ° _p1s 、k _p2s Compared with the simulation value, the maximum relative error of the measured value of (1) is 8.65% and 9.75%, respectively, and the minimum relative error is 0. Setting an error limit epsilon in the regulation flow chart 12 according to the relative error between the measured value and the simulated value ₁ 、ε ₂ Comprises the following steps:

table 4 shows V _dc 1 when =10V ^# Alignment without angular deflection, 2 ^# No angular deflection X' offset 40%, 3 ^# No angular deflection Y' offset 40%, 4 ^# Angular deflection 45 ° X 'offset-40% and Y' offset 40% and 5 ^# Under five positions of 45 degrees of angular deflection, 40% of X 'offset and 40% of Y' offset, the load voltage V _o1 、V _o2 And find k ^* _p1s 、k ^* _p2s And k _p1s 、k _p2s Error of measured value e ₁ 、e ₂ . Wherein e is ₁ 、e ₂ The maximum relative errors were 3.75%, 4.87%, respectively, and were less than 5%, indicating that the positioning method used can detect the position of the mechanism with sufficient accuracy.

TABLE 4 position detection characteristic parameters and errors

In addition, in order to verify the system transmission characteristics of the LCC-S compensation network of the two-way inverter-one-way rectifier, the voltage and current waveforms of the experimental prototype power conversion circuit and the compensation circuit at the above five positions were measured, as shown in fig. 15. Fig. 15 (a 1) - (a 5) show the voltage and current waveforms output by the system in the single-path inversion operation and the two-path inversion operation in five positions. The phase difference between the inversion output voltage and the current is in the range of 5-10 degrees under different positions, which shows that the input impedance of the system is in weak sensitivity, and ensures that the switching devices all work in a ZVS mode; fig. 15 (b 1) - (b 5) show the current waveforms of the coil of the transmitting mechanism at five positions, and the phase difference between the phase of the current waveform and the phase of the inverted voltage is always kept at 90 °, as shown in fig. 15 (b 4), (b 5), when two-way inversion works, the excitation current I of the coil of the transmitting mechanism _p1 And I _p2 The amplitude of the DQDD coil is equal, and the requirement of the magnetic field excitation current of the DQDD coil is met. In addition, I ₁ 、I ₂ The error percentage of the actual measurement effective value and the corresponding simulation value is within the range of 2-8%; I.C. A _p1 、I _p2 Effective value of actual measurement ofThe error percentage of the corresponding simulation value is in a range of 3% -7%, and the accuracy of the deduced LCC compensation topology transmission characteristic is verified. Fig. 15 (c 1) - (c 5) show the voltage and current waveforms before rectification in five positions, and the power and efficiency of the experimental prototype in five positions are calculated accordingly, as shown in table 5, the output power of the experimental prototype in five positions is about 1.8kW, and the system efficiency is not less than 88%.

TABLE 5 Power and efficiency of experimental prototype at five positions

In summary, the embodiment of the invention provides a high-resistance offset deflection WPT system based on a bipolar coupling mechanism and a control method thereof, which analyze the distribution characteristics of an excitation magnetic field of a DQDD transmitting mechanism and the pickup characteristics of a variable structure BP coil, provide a rule for the action between characteristic parameters and coupling coefficients of the magnetic coupling mechanism, provide a control strategy for changing the pickup structure and regulating the transmission magnetic field, and verify the feasibility and effectiveness of the system through experiments. The coil in the DQDD transmitting mechanism is used as an energy transfer coil and a detection coil at the relative position of the transmitting and receiving mechanism, and additional auxiliary positioning equipment is not needed, so that the volume and the cost of the system can be effectively reduced; compared with the existing common magnetic coupling mechanism, the built magnetic coupling mechanism has stronger offset deflection resistance. The anti-deviation performance and the system efficiency of the system are higher than the set values of the existing standard, and the system has good application prospects in static wireless charging occasions of electric automobiles.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. The WPT system with high offset resistance and deflection based on the bipolar coupling mechanism is characterized by comprising a pair of parallel unitsSequentially connected direct-current power supply, high-frequency inverter circuit, primary side compensation circuit, bipolar coupling mechanism, secondary side compensation circuit, rectifier and load R _L (ii) a The bipolar coupling mechanism comprises a transmitting mechanism and a receiving mechanism;

the receiving mechanism comprises sequentially stacked bipolar coils L _S And a receiving end magnetic core; the bipolar coil L _S The device is composed of two overlapping first CP coils and second CP coils with the same parameters and opposite winding directions, and the width of a window formed by the overlapping is W _WD ；

The receiving mechanism also comprises a bipolar coil L connected with the receiving mechanism _S For controlling the bipolar coil L _S The operating mode of (a) is a bipolar operating mode in which the first CP coil and the second CP coil operate simultaneously, or a unipolar operating mode in which only the first CP coil operates or only the second CP coil operates;

the high-frequency inverter circuit comprises a first inverter and a second inverter which are connected with the direct-current power supply in parallel; the primary side compensation circuit comprises a first inverter and a first DD coil L which are connected with each other _p1 A first primary side compensation network connected between the second inverter and the second DD coil L _p2 A second primary side compensation network therebetween;

the first inverter and the second inverter are used for controlling the working mode of the DQDD coil to be that only the first DD coil L is excited _p1 Or exciting the first DD coil L with currents of the same amplitude and phase difference β _p1 And said second DD-coil L _p2 DQDD coil operating mode.

2. The WPT system, based on the bipolar coupling mechanism, with high deflection resistance, as claimed in claim 1, wherein the transmitting end magnetic core and the receiving end magnetic core are both square magnetic cores, and the parameter design process of the bipolar coupling mechanism includes the following steps:

a1, determining the total length l of the D-shaped coil according to actual requirements _DD And a total width W _DD The total length l of the first CP coil, i.e., the second CP coil _CP And a total width W _CP ＝a+W _WD A transmission distance l between the transmitter and the receiver _AG A wire diameter T of the D-type coil, i.e., the first CP coil, i.e., the second CP coil _W And the number of winding turns N, a is a specific value determined according to actual requirements;

a3, set side length l _F Thickness T _F Obtaining the spacing W for a set of constants _WD According to the change curves of the primary and secondary side coupling coefficients, the self-inductance of the transceiver coil and the mutual inductance of the transceiver coil in the optimized range, the optimal W is determined by referring to the group of change curves and combining the requirements on the primary and secondary side coupling coefficients, the self-inductance of the transceiver coil and the mutual inductance between the transceiver coil _WD A value;

a4, setting the distance W _WD Is the optimum W _WD Value, obtain side length l _F The variation curve of the primary and secondary coupling coefficients and the thickness T within the optimized range _F According to the change curve of the primary and secondary coupling coefficients in the optimization range, the optimal l is determined by referring to the group of change curves and combining the requirements on the primary and secondary coupling coefficients and the actual requirements _F Value sum T _F The value is obtained.

3. The dual-polarity coupling mechanism based high-anti-deflection WPT system as claimed in claim 2, wherein:

the first primary side compensation network and the second primary side compensation network both adopt LCC compensation networks, and the first primary side compensation network and the second primary side compensation network are connected in seriesThe primary side compensation network comprises a first primary side series compensation inductor L _pf1 A first primary side series compensation capacitor C _p1 And a first primary side parallel compensation capacitor C _pf1 The second primary side compensation network comprises a second primary side series compensation inductor L _pf2 A second primary side series compensation capacitor C _p2 And a second primary side parallel compensation capacitor C _pf2 ；

4. The WPT system with high anti-offset deflection based on the bipolar coupling mechanism as claimed in claim 3, wherein the first primary compensation network, the second primary compensation network and the secondary compensation circuit have respective parameter values set as:

ω is the operating angular frequency of the system.

5. The control method of the WPT system based on the bipolar coupling mechanism and having high anti-offset deflection is characterized in that the control method specifically comprises the following steps of:

s1, controlling the bipolar coil L _S In a bipolar operating mode, sequentially energizing the first DD-coil L _p1 And said second DD coil L _p2 ；

S3, according to the output voltage U of the first inverter ₁ The operating angular frequency omega of the system, the first DD coil L _p1 The first primary side series compensation inductor L _pf1 The bipolar coil L _S The receiving end outputs a voltage V _o1 The load R _L Calculating the position at which the first DD coil L is excited at this time _p1 First primary and secondary coupling coefficient k of time ^* _p1s According to the output voltage U of the second inverter ₂ The operating angular frequency omega of the system, the second DD coil L _p2 The second primary side series compensation inductor L _pf2 The bipolar coil L _S The receiving end outputs a voltage V _o2 Calculating the position at which the second DD coil L is excited at this time _p2 Second primary and secondary coupling coefficient k of time ^* _p2s ；

S4, according to the first primary and secondary side coupling coefficient k ^* _p1s Second primary and secondary side coupling coefficient k ^* _p2s Determining an offset distance and a deflection angle of the receiving mechanism;

6. The control method of the WPT system based on the bipolar coupling mechanism with high anti-offset deflection is characterized in that:

in the step S3, the first primary-secondary side coupling coefficient

The second primary and secondary coupling coefficient

Are respectively a defined self-inductance L _p1 、L _p2 、L _pf1 、L _pf2 、L _S The quality factor of (2).

7. The method for controlling the WPT system with high anti-offset deflection based on the bipolar coupling mechanism according to claim 6, wherein the step S4 specifically comprises the steps of:

s41, calculating the first primary and secondary side coupling coefficient k ^* _p1s And k is _{p1s(θ＝0°)} Error value ak therebetween ₁ The second primary and secondary coupling coefficient k ^* _p2s And k _{p2s(θ＝0°)} Error value ak therebetween ₂ ，k _{p1s(θ＝0°)} 、k _{p2s(θ＝0°)} Exciting the first DD coil L under the same condition of no angular deflection between the transmitting mechanism and the receiving mechanism respectively calibrated in advance _p1 Primary and secondary side coupling coefficient of time and excitation of the second DD coil L _p2 The coupling coefficient of the primary side and the secondary side;

s42, determining delta k ₁ And Δ k ₂ Whether the sum of the first and second error thresholds is less than or equal to a first error threshold epsilon ₁ If yes, the transmitting mechanism and the receiving mechanism are considered to have no angular deflection, so that step S45 is executed, and if not, steps S43-S44 are executed;

s43, calculating the first primary and secondary side coupling coefficient k ^* _p1s And k is _{p1s(θ＝45°)} Error value ak in between ₃ The second primary and secondary coupling coefficient k ^* _p2s And k _{p2s(θ＝45°)} Error value ak therebetween ₄ ，k _{p1s(θ＝45°)} 、k _{p2s(θ＝45°)} Exciting the first DD coil L under the same conditions when there is an angular deflection of 45 DEG between the transmitting mechanism and the receiving mechanism, respectively calibrated in advance _p1 Primary and secondary side coupling coefficient of time and excitation of the second DD coil L _p2 The coupling coefficient of the primary side and the secondary side;

s44, determining delta k ₃ And Δ k ₄ Whether the sum of the first and second error thresholds is less than or equal to a second error threshold epsilon ₂ ，ε ₂ Greater than epsilon ₁ If yes, considering that the angle between the transmitting mechanism and the receiving mechanism is deflected by +45 degrees or-45 degrees, and executing step S46, otherwise, returning to the step S2;

s46, finding out the first original secondary side coupling coefficient k in the correlation between the offset distance and the original secondary side coupling coefficient during the 45-degree angle deflection calibrated in advance ^* _p1s The second primary and secondary side coupling coefficient k ^* _p2s The specific size of the receiving mechanism.

8. The method for controlling the WPT system with high anti-offset and deflection based on the dual-polarity coupling mechanism as claimed in claim 7, wherein when the receiving mechanism is not deflected angularly, the step S5 is specifically:

judging whether the offset distance of the receiving mechanism is in a first preset range or a second preset range, and if the offset distance of the receiving mechanism is in the first preset range, controlling the DQDD coil to work in a DD coil working mode and controlling the bipolar coil L to work in the DD coil working mode _S Working in a unipolar working mode, and if the DQDD coil is in a second preset range, controlling the DQDD coil to work in a DD coil working mode and controlling the bipolar coil L to work in a bipolar coil L _S The operation is in a bipolar operation mode.

9. The method for controlling the WPT system with high anti-offset deflection based on the bipolar coupling mechanism as claimed in claim 7, wherein the step S5 comprises the following steps when there is an angular deflection of +45 ° or-45 ° between the receiving mechanism and the transmitting mechanism:

s51, controlling the DQDD coil to work in a DQDD coil working mode, wherein the phase difference of excitation currents of the first inverter and the second inverter is 0 DEG, and measuring the output voltage V of a receiving end at the moment ^* _o1 ；

S52, controlling the phase difference change of the exciting currents of the first inverter and the second inverter to be 180 degrees, and measuring the output voltage V of the receiving end at the moment ^* _o2 ；

S53, judging V ^* _o1 Whether or not it is greater than V ^* _o2 If yes, judging that the deflection angle of the receiving mechanism is +45 degrees and executing the step S54, otherwise, judging that the deflection angle of the receiving mechanism is-45 degrees and executing the step S55；

S54, controlling the phase difference of exciting currents of the first inverter and the second inverter to be 0 degrees, further judging whether the offset distance of the receiving mechanism is in a third preset range or a fourth preset range, and controlling the bipolar coil L if the offset distance of the receiving mechanism is in the third preset range _S Working in a unipolar working mode, and controlling the bipolar coil L if the bipolar coil L is in a fourth preset range _S Working in a bipolar working mode;

s55, controlling the phase difference of excitation currents of the first inverter and the second inverter to be 180 degrees, further judging whether the offset distance of the receiving mechanism is in a fifth preset range or a sixth preset range, and controlling the bipolar coil L if the offset distance of the receiving mechanism is in the fifth preset range _S Working in a unipolar working mode, and if the bipolar coil L is in a sixth preset range, controlling the bipolar coil L _S The operation is in a bipolar operation mode.