Highly anti-deviation deflection WPT system based on bipolar coupling mechanism and control method thereof

Abstract

The present invention relates to the technical field of wireless power transmission (WPT), and specifically discloses a highly anti-deviation deflection WPT system based on a bipolar coupling mechanism and a control method thereof, wherein the transmitting mechanism of the system adopts a double-layer orthogonal DQDD coil, and the receiving mechanism adopts a BP coil. The DQDD coil is composed of two pairs of decoupled DD coils arranged in a double layer orthogonal manner, and the magnetic field distribution excited by the DQDD coil is regulated by the amplitude and phase of the excitation current of the two groups of DD coils; the BP coil can be converted into a unipolar coil with the help of a relay circuit, thereby changing the polarity of the magnetic field that can be picked up by the receiving mechanism. The method does not require the addition of an additional position detection device, and can obtain the relative position and vertical deflection angle of the coupling mechanism in the horizontal plane, which can effectively reduce the volume and cost of the system, and the obtained position information is used for the structural transformation of the receiving BP coil and the distribution regulation of the magnetic field excited by the transmitting DQDD coil. The experimental results show that within the 270mm offset range of the horizontal plane, the output power is maintained at about 1.8kW, and the system efficiency is not less than 88%.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transfer (WPT), and in particular to a high-anti-deviation deflection WPT system based on a bipolar coupling mechanism and a control method for the high-anti-deviation deflection WPT system based on a bipolar coupling mechanism. Background Art

[0002] The electric vehicle charging system using wireless power transfer (WPT) does not require cables to connect the charging equipment and the vehicle body, and there are no maintenance issues such as contact loss, dust accumulation and mechanical wear. The charging mode is more convenient, safe and flexible, and can adapt to harsh environments. Therefore, the electric vehicle wireless charging system has received great attention from experts and scholars at home and abroad. During the static wireless charging process of electric vehicles, the transmitter and the receiver will inevitably have offset deflection misalignment, which will lead to a sharp decrease in the coupling coefficient and charging energy efficiency of the transmitter and receiver. Therefore, improving the anti-offset performance of the coupling mechanism and improving the stability of the power picked up by the receiving mechanism are key issues that need to be urgently solved in the static WPT system of electric vehicles.

[0003] In order to further improve the anti-deviation capability of static WPT systems, existing literature mainly adopts three methods: adjusting the winding form of the coupling coil, adopting a composite compensation topology, and detecting the relative position of the mechanism.

[0004] In terms of coupling coil winding, the excitation magnetic field of the solenoid pad (SP) coil has a unipolar distribution characteristic, and has a higher coupling flux density and a larger coupling coefficient than the circular pad (CP) coil. However, the coupling magnetic field based on the SP coil transceiver mechanism is distributed on both sides, and there is a large leakage flux, which increases the eddy current loss in the shielding aluminum plate; compared with the unipolar coil, the magnetic field generated by the double-D (Double-D, DD) coil has two opposite polarities, which allows the DD coil to maintain a large coupling coefficient in a wide range of air gaps. However, during the offset process, the two reverse polarity magnetic fields will lead to a power pickup blind spot with a zero coupling coefficient; in order to overcome the shortcomings of the DD coil's lateral offset and the pickup blind spot, the DDQ (Double-DQuadrature, DD) coil is wound with an orthogonal decoupling Q coil at the center of the DD coil. When the coupling mechanism based on DDQ coil is laterally offset, as the coupling flux of DD coil gradually decreases, the coupling flux of Q coil gradually increases, so that the total coupling flux remains basically unchanged; Bipolar (BP) coil combines the characteristics of DD coil and DDQ coil. By adjusting the overlapping area of ​​two D-type coils in BP coil, the two D-type coils can be decoupled from each other. Similar to DDQ coil, independent compensation and control can also be performed when offset. In addition, under the same coupling area, the copper content of BP coil is less than that of DDQ coil; Compared with BP coil, Triple Polar (TP) coil can form polarized magnetic fields in multiple directions. On the one hand, the decoupling of three sector coils in TP coil requires adjusting the overlapping area of ​​the three. On the other hand, its polarized magnetic field requires independent control of the amplitude and phase of three excitation currents, which increases the complexity of the control circuit; In addition, by increasing the number of coils in the transmitting mechanism, multiple coils at different positions are used to obtain a uniformly distributed magnetic field, thereby increasing the coupling area and ensuring the stability of the pickup power of the receiving mechanism at different offset positions, improving the system's anti-offset performance. However, the coupling mechanism wound in this way consumes a large amount of copper, resulting in increased losses and reduced system efficiency.

[0005] In terms of composite compensation topologies, some literature has proposed an SP-S composite compensation topology, which achieves that the transmitter excitation current is approximately constant during the offset process, overcoming the problem that the transmission characteristics of the four basic compensation topologies (SS, SP, PS, PP) are greatly affected by the offset of the coupling mechanism; some literature has proposed a double-sided LCC compensation topology with high anti-offset characteristics, which reduces the design difficulty of system parameters, reduces the influence of coil self-inductance on system impedance, and achieves that the transmitter coil current is not affected by changes in the coupling coefficient; in order to reduce the volume and weight of the receiving end, some literature has adopted a relatively simpler LCC-S topology, which has the same advantages as the double-sided LCC topology while reducing the compensation elements of the double-sided LCC topology.

[0006] In terms of the relative position of the detection mechanism, some literature uses the optical positioning technology of the camera to locate the receiving mechanism by shooting the mark, and adjusts the relative position of the transmitting and receiving mechanism to maintain a stable coupling coefficient. However, these marking points are greatly affected by environmental factors and have high hardware costs, so they are not suitable for electric vehicle applications; some literature uses magnetic sensors or auxiliary coils to obtain the position of the receiving mechanism, so that the driver can make real-time adjustments to the position of the vehicle to align the transmitting and receiving mechanism. On the one hand, the magnetic sensor used requires the design of a signal conditioning circuit. On the other hand, the introduced auxiliary coil will interfere with the power transmission mechanism, thereby increasing the complexity and cost of the system. Summary of the invention

[0007] The present invention provides a high-anti-deviation deflection WPT system based on a bipolar coupling mechanism and a control method thereof, and the technical problem solved is: how to achieve high-anti-deviation deflection of the system by improving the structure and control method of the coupling mechanism without adding an additional position detection device.

[0008] In order to solve the above technical problems, the present invention provides a high-anti-deviation deflection WPT system based on a bipolar coupling mechanism, comprising a DC power supply, a high-frequency inverter circuit, a primary compensation circuit, a bipolar coupling mechanism, a secondary compensation circuit, a rectifier and a load R connected in sequence. L ; The bipolar coupling mechanism includes a transmitting mechanism and a receiving mechanism;

[0009] The transmitting mechanism comprises a transmitting end magnetic core and a DQDD coil stacked in sequence, wherein the DQDD coil is composed of a first DD coil L on the surface. p1 And the second DD coil L in the inner layer p2 The first DD coil L p1 and the second DD coil L p2 Both have the same parameters, the same winding direction and a spacing of W. WD The D-type coils are connected in series;

[0010] The receiving mechanism includes a bipolar coil L stacked in sequence S and the receiving end magnetic core; the bipolar coil L S It is composed of two overlapping first CP coils and second CP coils with the same parameters and opposite winding directions. The window width formed by the overlap is also W WD ;

[0011] The receiving mechanism also includes a bipolar coil L connected to the S A relay circuit for controlling the bipolar coil L SThe working mode is a bipolar working mode in which the first CP coil and the second CP coil work simultaneously, or a unipolar working mode in which only the first CP coil works or only the second CP coil works;

[0012] The high-frequency inverter circuit includes a first inverter and a second inverter connected in parallel to the DC power supply; the primary compensation circuit includes a first inverter connected to the first DD coil L p1 The first primary compensation network is connected between the second inverter and the second DD coil L p2 The second primary side compensation network between;

[0013] The first inverter and the second inverter are used to control the working mode of the DQDD coil to only excite the first DD coil L p1 The DD coil working mode or the first DD coil L is excited by the current of the same amplitude and phase difference β p1 and the second DD coil L p2 DQDD coil working mode.

[0014] Preferably, 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 steps of:

[0015] A1. Determine the total length l of the D-type coil according to actual needs DD and the total width W DD , the total length of the first CP coil, that is, the second CP coil, is l CP and the total width W CP =a+W WD , the transmission distance l between the transmitting mechanism and the receiving mechanism AG The wire diameter T of the D-type coil, namely the first CP coil, namely the second CP coil W and the number of winding turns N, a is a specific value determined according to actual needs;

[0016] A2. Determine the spacing W according to actual needs WD And the side length l of the square core F , thickness T F Optimization range:

[0017] A3. Set the side length l F , thickness T F For a set of fixed values, get the spacing W WD The change curves of the primary-secondary coupling coefficient, the self-inductance of the transmitting-receiving coil, and the mutual inductance of the transmitting-receiving coil within the optimization range are referred to, and the optimal W is determined in combination with the requirements for the primary-secondary coupling coefficient, the self-inductance of the transmitting-receiving coil, and the mutual inductance between the transmitting-receiving coil.WD value;

[0018] A4. Set the spacing W WD is the optimal W WD Value, get the side length l F Variation curve of primary-secondary coupling coefficient within the optimization range and thickness T F The change curve of the primary-secondary coupling coefficient within the optimization range is used to determine the optimal l by referring to this group of change curves and combining the requirements for the primary-secondary coupling coefficient and actual needs. F Value and T F value.

[0019] Preferably, the first primary compensation network and the second primary compensation network both adopt LCC compensation networks, and the first primary compensation network includes a first primary series compensation inductor L pf1 、The first primary series compensation capacitor C p1 And the first primary parallel compensation capacitor C pf1 The second primary compensation network includes a second primary series compensation inductor L pf2 , the second primary series compensation capacitor C p2 And the second primary parallel compensation capacitor C pf2 ;

[0020] The secondary side compensation circuit adopts a secondary side series compensation capacitor C s .

[0021] Preferably, the parameter values ​​of the first primary compensation network, the second primary compensation network and the secondary compensation circuit are set as follows:

[0022]

[0023] ω is the operating angular frequency of the system.

[0024] The present invention also provides a control method for a high-anti-deviation deflection WPT system based on a bipolar coupling mechanism. For the above system, the control method specifically includes the steps of:

[0025] S1, control the bipolar coil L S In bipolar working mode, the first DD coil L is excited in turn p1 and the second DD coil L p2 ;

[0026] S2, measuring and exciting the first DD coil L p1 The receiving end output voltage V o1 , and excite the second DD coil L p2 The receiving end output voltage V o2 ;

[0027] S3, according to the output voltage U1 of the first inverter, the working angular frequency ω of the system, and the first DD coil L p1 , the first primary series compensation inductor L pf1 , the bipolar coil L S , the receiving end output voltage V o1 , the load R L Calculate the position at which the first DD coil L is excited p1 The first primary-secondary coupling coefficient k * p1s , according to the output voltage U2 of the second inverter, the operating angular frequency ω of the system, and the second DD coil L p2 The second primary series compensation inductor L pf2 , the bipolar coil L S , the receiving end output voltage V o2 Calculate the position at which the second DD coil L is excited p2 The second primary-secondary coupling coefficient k * p2s ;

[0028] S4, according to the first primary-secondary coupling coefficient k * p1s , the second primary-secondary coupling coefficient k * p2s determining an offset distance and a deflection angle of the receiving mechanism;

[0029] S5. Determine the working mode of the DQDD coil and the bipolar coil L according to the offset distance and deflection angle of the receiving mechanism. S working mode.

[0030] Furthermore, in step S3, the first primary-secondary coupling coefficient The second primary-secondary coupling coefficient The self-inductance L is defined as p1 , L p2 , L pf1 , L pf2 , L S The quality factor of .

[0031] Furthermore, the step S4 specifically includes the steps of:

[0032] S41, calculating the first primary-secondary coupling coefficient k * p1s With k p1s(θ＝0°) The error value Δk1 between the second primary and secondary coupling coefficient k * p2sWith k p2s(θ＝0°) The error value between Δk2, k p1s(θ＝0°) , k p2s(θ＝0°) The first DD coil L is excited under the same conditions when there is no angular deflection between the transmitting mechanism and the receiving mechanism calibrated in advance. p1 When the primary-secondary coupling coefficient and the excitation of the second DD coil L p2 The primary-secondary coupling coefficient when ;

[0033] S42, determining whether the sum of Δk1 and Δk2 is less than or equal to a first error threshold ε1, if so, it is considered that there is no angular deflection between the transmitting mechanism and the receiving mechanism and step S45 is executed, if not, steps S43 to S44 are executed;

[0034] S43, calculating the first primary-secondary coupling coefficient k * p1s With k p1s(θ＝45°) The error value Δk3 between the second primary and secondary coupling coefficient k * p2s With k p2s(θ＝45°) The error value between Δk4, k p1s(θ＝45°) , k p2s(θ＝45°) When there is a 45° angle deflection between the transmitting mechanism and the receiving mechanism, the first DD coil L is excited under the same conditions. p1 When the primary-secondary coupling coefficient and the excitation of the second DD coil L p2 The primary-secondary coupling coefficient when ;

[0035] S44, judging whether the sum of Δk3 and Δk4 is less than or equal to a second error threshold ε2, and ε2 is greater than ε1, if so, it is considered that there is an angle deflection of +45° or -45° between the transmitting mechanism and the receiving mechanism, and step S46 is executed, if not, returning to step S2;

[0036] S45, finding the first primary-secondary coupling coefficient k in the correlation between the offset distance and the primary-secondary coupling coefficient when there is no angle deflection calibrated in advance * p1s , the second primary-secondary coupling coefficient k * p2s The offset distance of the receiving mechanism corresponding to the specific size of

[0037] S46, find the first primary-secondary coupling coefficient k in the correlation between the offset distance and the primary-secondary coupling coefficient when the 45° angle deflection is calibrated in advance * p1s , the second primary-secondary coupling coefficient k * p2sThe specific size of the receiving mechanism corresponds to the offset distance of the receiving mechanism.

[0038] Further, when the receiving mechanism has no angular deflection, step S5 is specifically as follows:

[0039] When the receiving mechanism has no angular deflection, it is determined whether the offset distance of the receiving mechanism is within the first preset range or the second preset range. If it is within the first preset range, the DQDD coil is controlled to operate in the DD coil operating mode and the bipolar coil L S Works in the unipolar working mode. If it is in the second preset range, the DQDD coil is controlled to work in the DD coil working mode and the bipolar coil L S Works in bipolar mode.

[0040] Furthermore, when there is an angle deflection of +45° or -45° between the receiving mechanism and the transmitting mechanism, step S5 specifically includes the following steps:

[0041] S51, control the DQDD coil to work in the DQDD coil working mode and the phase difference between the excitation current of the first inverter and the second inverter is 0°, and measure the output voltage V of the receiving end at this time * o1 ;

[0042] S52, controlling the phase difference between the excitation current of the first inverter and the second inverter to change to 180°, and measuring the output voltage V * o2 ;

[0043] S53, judge V * o1 Is it greater than V * o2 If yes, it is determined that the deflection angle of the receiving mechanism is +45° and step S54 is executed; if no, it is determined that the deflection angle of the receiving mechanism is -45° and step S55 is executed;

[0044] S54, control the phase difference between the excitation current of the first inverter and the second inverter to be 0°, and further determine whether the offset distance of the receiving mechanism is within the third preset range or the fourth preset range. If it is within the third preset range, control the bipolar coil L S Working in the unipolar working mode, if it is in the fourth preset range, the bipolar coil L is controlled S Works in bipolar working mode;

[0045] S55, control the phase difference between the excitation current of the first inverter and the second inverter to be 180°, and further determine whether the offset distance of the receiving mechanism is within the fifth preset range or the sixth preset range. If it is within the fifth preset range, control the bipolar coil L S Working in the unipolar working mode, if it is in the sixth preset range, the bipolar coil L is controlled S Works in bipolar mode.

[0046] The present invention provides a highly anti-deviation deflection WPT system based on a bipolar coupling mechanism, wherein the transmitting mechanism adopts a double-layer orthogonal DQDD coil, and the receiving mechanism adopts a BP coil. The DQDD coil is composed of two pairs of decoupled DD coils arranged in a double layer orthogonal manner, and the magnetic field distribution excited by it is regulated by the amplitude and phase of the excitation current of the two groups of DD coils; the BP coil can be converted into a unipolar coil with the help of a relay circuit, thereby changing the polarity of the magnetic field that can be picked up by the receiving mechanism. The system constructs an LCC-S compensation network topology based on a dual-path inverter-single-path rectifier, and provides network parameter configuration conditions in which the excitation current of the transmitting mechanism is constant and the system output voltage is independent of the load.

[0047] In addition, this system also proposes a control method for a highly anti-deviation deflection WPT system based on a bipolar coupling mechanism. This method does not require the addition of an additional position detection device, and can obtain the relative position of the coupling mechanism in the horizontal plane and the vertical deflection angle, which can effectively reduce the volume and cost of the system. The obtained position information is used for the structural transformation of the receiving BP coil and the distribution control of the magnetic field excited by the transmitting DQDD coil. The experimental results show that within the 270mm offset range on the horizontal plane, the output power is maintained at about 1.8kW, and the system efficiency is not less than 88%. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a circuit diagram of a high-anti-skew deflection WPT system based on a bipolar coupling mechanism provided by an embodiment of the present invention;

[0049] Figure 2 is a stereogram of a bipolar coupling mechanism provided by an embodiment of the present invention;

[0050] Figure 3 is a front view of a bipolar coupling mechanism provided by an embodiment of the present invention;

[0051] Figure 4 It is a DQDD coil winding scheme and excitation magnetic field schematic diagram provided by an embodiment of the present invention;

[0052] Figure 5 is a synthetic magnetic field distribution diagram of the DQDD coil when the phase difference β=90° provided by an embodiment of the present invention;

[0053] Figure 6 It is a schematic diagram of a BP coil winding scheme provided in an embodiment of the present invention;

[0054] Figure 7 is a LCC-S compensation topology diagram provided by an embodiment of the present invention;

[0055] Figure 8 is a diagram showing the influence of window width on self-inductance, mutual inductance and primary-secondary coupling coefficient provided by an embodiment of the present invention;

[0056] Fig. 9 is a diagram showing the influence of the magnetic core size on the coupling coefficient provided by an embodiment of the present invention;

[0057] Fig.10 It is a schematic diagram of variable structure and magnetic field control provided by an embodiment of the present invention;

[0058] Fig.11 is a diagram showing the coupling coefficient under different position offsets and angle deflections provided by an embodiment of the present invention;

[0059] Fig.12 It is a flow chart of a control method of a high-anti-deviation deflection WPT system based on a bipolar coupling mechanism provided by an embodiment of the present invention;

[0060] Fig.13 is a diagram showing the CCAR variation rules of different magnetic coupling mechanisms provided by an embodiment of the present invention;

[0061] Fig.14 1 is a diagram showing the measurement error of the coupling coefficient under different position offsets and angle deflections provided by an embodiment of the present invention;

[0062] Fig.15 These are waveform diagrams of experimental prototypes under five positions provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0063] The following specifically illustrates the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided for illustrative purposes only and cannot be understood as limiting the present invention. The accompanying drawings are provided for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0064] In order to overcome the limitations of the three existing anti-deviation enhancement methods, the embodiment of the present invention first provides a high anti-deviation deflection WPT system based on a bipolar coupling mechanism, such as Figure 1 As shown in the circuit topology diagram, the system includes a DC power supply U connected in sequence dc , high frequency inverter circuit Ⅰ, primary compensation circuit Ⅱ, bipolar coupling mechanism Ⅲ, secondary compensation circuit Ⅳ, rectifier Ⅴ and load R L .

[0065] Figure 2 , Figure 3 The three-dimensional structure and the front view of the bipolar coupling mechanism are shown respectively. The bipolar coupling mechanism includes a transmitting mechanism and a receiving mechanism. The transmitting mechanism includes a transmitting end magnetic core and a DQDD coil stacked in sequence. The DQDD coil is composed of a first DD coil L on the surface. p1 (also called DD coil 1) and the second DD coil L in the inner layer p2 (also referred to as DD coil 2) is orthogonally stacked. The first DD coil L p1 and the second DD coil L p2 Both have the same parameters, the same winding direction and a spacing of W. WD The receiving mechanism includes a bipolar coil L stacked in sequence. S and receiving end magnetic core; bipolar coil L S It is composed of two overlapping CP coils (also called CP coil 1) and second CP coils (also called CP coil 2) with the same parameters and opposite winding directions. The window width formed by the overlap is also W. WD It can be seen that based on the orthogonal relationship of the DQDD coil, the transmitting end magnetic core adopts a square magnetic core that coincides with the orthogonal overlapping area of ​​the DQDD coil, and the receiving end magnetic core also adopts the same square magnetic core.

[0066] like Figure 1 As shown, in order to achieve the first DD coil L p1 , the second DD coil L p2 The high frequency inverter circuit includes a first inverter and a second inverter connected in parallel to a DC power supply, and the primary compensation circuit includes a first inverter connected to a first DD coil L p1 The first primary compensation network is connected between the second inverter and the second DD coil L p2 The first inverter and the second inverter are used to control the working mode of the DQDD coil to excite only the first DD coil L p1 The DD coil working mode or the first DD coil L is excited by the current of the same amplitude and phase difference β p1 and the second DD coil L p2 The first primary compensation network and the second primary compensation network both use LCC compensation networks. The first primary compensation network includes a first primary series compensation inductor L pf1 、The first primary series compensation capacitor C p1 And the first primary parallel compensation capacitor C pf1 The second primary compensation network includes a second primary series compensation inductor L pf2 , the second primary series compensation capacitor C p2And the second primary parallel compensation capacitor C pf2 The secondary side compensation circuit uses a secondary side series compensation capacitor C s .

[0067] Figure 1 In the example, U1 and U2 are the output voltages of the first inverter and the second inverter, I1 and I2 are the output currents of the first inverter and the second inverter, respectively. p1 ,I p2 ,I s are the currents on the two groups of DD coils and the receiving coil, L p1 , L p2 , L s are the self-inductance of the two groups of DD coils and the receiving coil, L pfi , C pi , C pfi (i=1,2) constitutes the LCC compensation network of two groups of DD coils, C s is the series compensation capacitor of the receiving coil, M p1s 、M p2s are the mutual inductances between the two groups of DD coils and the receiving coil.

[0068] Figure 2 , Figure 3 The dimensions of each coil are marked, including the total length l of the D-type coil. DD and the total width W DD , the total length of the first CP coil, that is, the second CP coil, is l CP and the total width W CP =a+W WD (a is a specific value determined according to actual needs), and the side length l of the square core F , thickness T F , and the transmission distance l between the transmitting mechanism and the receiving mechanism AG The total length of a DD coil is l p =2W DD +W WD , the total width is the length l of the D-type coil DD . Bipolar coil L S The total length l s , total width W s = l CP .

[0069] Figure 4(a) shows the DQDD coil winding scheme, and its spatial orthogonal placement makes the upper and lower layers of DD coils decoupled from each other. The reason is that the orthogonal placement makes the net magnetic flux of the DD coils on the same layer and the D-type coils on different layers close to zero. The mutually decoupled coil structure means that the excitation currents in the coils can be controlled independently without being affected by each other, reducing the difficulty of circuit analysis.

[0070] Assume that the excitation current amplitudes of DD coil 1 and DD coil 2 are the same and the phase difference is β, and the expression is:

[0071] I p1 =I p1 ∠0,I p2 =I p1 ∠β (1)

[0072] Combined with the orthogonal position relationship of the two groups of DD coils, the magnetomotive force f generated by the excitation current in equation (1) is DD1 、f DD2 It can be expressed as:

[0073]

[0074] In formula (2), θ s is the reference space angle, ω is the system operating angular frequency, F DD1 =F DD2 .

[0075] From formula (2), we can get the synthetic magnetomotive force f at any point in the XOY plane:

[0076]

[0077] Formula (3) means that the synthetic magnetomotive force f is related to the phase difference β of the excitation current. When β = 0°, 180° and 90°, the synthetic magnetomotive force f is shown in formula (4):

[0078]

[0079] Formula (4) shows that when the excitation current I p1 and I p2 When the phase difference is 0° or 180°, the magnetic induction intensity is the magnetic induction intensity excited by a single DD coil. times. When the two excitation currents differ by 90°, the magnetic induction intensity is the same. Among them, when β=0°, the bipolar magnetic field of the DQDD coil is mainly distributed at the positive 45° diagonal; for β=180°, the bipolar magnetic field is mainly concentrated at the negative 45° diagonal. As for β=90°, the bipolar magnetic field is distributed in a periodic rotation with equal amplitude.

[0080] The finite element simulation model of the DQDD coil was established by ANSYS Maxwell, and the magnetic field distribution in the area above the launch mechanism under the three excitation modes was obtained as follows: Figure 4 (b), (c) and Figure 5 As shown, it can be seen that the distribution of its synthetic magnetic field is consistent with equation (4).

[0081] The receiving mechanism also includes a bipolar coil L connected S The relay circuit is used to control the bipolar coil L S The working mode is a bipolar working mode in which the first CP coil and the second CP coil work simultaneously, or a unipolar working mode in which only the first CP coil works or only the second CP coil works. Specifically, the relay circuit includes a relay K1 and a relay K2.

[0082] Figure 6 The winding scheme and structural transformation method of the BP coil of the receiving mechanism are given. Among them, relay K1 and relay K2 are used for structural transformation of the receiving mechanism. When the receiving mechanism needs a BP coil, the COM contacts of K1 and K2 are both attracted to the NO terminal, such as Figure 6 As shown in (a). At this time, the receiving mechanism can pick up a bipolar magnetic field. In a bipolar magnetic field, the magnetic field directions in the two coupling regions of the BP coil are consistent, while the magnetic fields in the decoupling region are opposite. The reverse series winding method used by the BP coil makes the induced electromotive force in the decoupling region zero, while the induced electromotive force in the two coupling regions is connected in series in the forward direction. When the receiving mechanism needs a CP coil, one of the COM contacts of K1 and K2 is attracted to the NC terminal, as shown in FIG. Figure 6 If the K2 contact is attracted to NC2, the left coil is connected, and the receiving mechanism picks up a vertical inward magnetic field in the bipolar magnetic field; otherwise, the right coil is connected, and the magnetic field picked up is vertically outward.

[0083] The coupling coefficient is one of the key parameters for judging the anti-deviation performance of the coupling mechanism of the WPT system. For the dual-channel coupling mechanism consisting of two sets of transmitting coils and one set of receiving coils, the equivalent coupling coefficient k can be used. eff Determine, as shown in formula (5):

[0084]

[0085] In the formula, S u Indicates the capacity picked up by the receiving coil, VA i Indicates the transmission capacity of the transmitting coil; V oc and I sc are the open circuit voltage and short circuit current of the receiving coil, V pi and I pi are the terminal voltage and excitation current of the transmitting coil, respectively, where Su and VA i It can be specifically expressed as:

[0086]

[0087] Substituting equation (6) into equation (5), k eff It can be simplified to formula (7):

[0088]

[0089] Where M eff and L eff are the equivalent mutual inductance and equivalent self-inductance of the system respectively. When the system only excites DD coil 1 or DD coil 2, M eff =M pis , L eff =L pi (i=1,2). The equivalent coupling coefficient k derived in this example is eff It will be used for the subsequent bipolar coupling mechanism parameter configuration and coupling mechanism performance comparison.

[0090] Figure 7 for Figure 1 Based on the equivalent mutual inductance model, the KVL equation can be obtained:

[0091]

[0092] Where U p1s , U p2s For two sets of mutual inductance M p1s 、M p2s The induced voltage, X L , X C It represents the reactance of the compensation network and coil. Its specific meaning is shown in formula (9):

[0093]

[0094] Formula (10) gives the parameter configuration method of the LCC-S compensation circuit:

[0095]

[0096] From equations (8)-(10), the current of each circuit can be obtained:

[0097]

[0098] From formula (11), it can be seen that when the transmitter compensation network adopts the LCC topology and the operating frequency remains unchanged, the excitation current I of the two groups of DD coils in the transmitter mechanism is pi The amplitude of depends only on the amplitude of the inverter output voltage and the inductance L pfi, which is independent of the load and mutual inductance. This feature realizes the independent control of the excitation current of the two sets of DD coils, and when the amplitudes of the inverter output voltages U1 and U2 are equal, the compensation inductance L pf1 , L pf2 When the inductance values ​​are equal, the excitation current I p1 ,I p2 The magnitudes are equal.

[0099] Since the coupling coefficient is affected by the window width W WD And core size T F , l F In view of the position where the transmitting mechanism and the receiving mechanism are fully aligned, the design standards for WPT systems for electric vehicles issued by the state and relevant organizations are referred to, and the dimensions of the magnetic coupling mechanism are given, and the window width W is WD And core size l F , T F Optimized.

[0100] According to the standards GB / T 38775 and IEC 61980, the distance l between the transmitter and the receiver is selected. AG =130mm; D-type coil l DD =300mm, W DD =150mm, T W =2.5mm, number of turns N=20, W W =50mm; CP coil l CP =300mm, W CP =a+W WD =200+W WD Therefore, DQDD coil l p =300+W WD BP coil l s =300+W WD , W s = l CP =300mm. The first and second columns of the table give the size parameters and optimization range of the magnetic coupling mechanism to be optimized. Among them, the window width W WD and the core length l F Determines the coverage area of ​​the magnetic field, and its optimization range is l p is the normalized reference; the core thickness T F Determines the strength of the magnetic field, and its optimization range is l AG is the normalized benchmark.

[0101] Table 1 Size parameters to be optimized, optimization range and optimization value

[0102]

[0103] Figure 8The window width W is given WD The influence of the coil's self-inductance, mutual inductance and coupling coefficient. At this time, the core length l F The normalized value is selected as 76.9%, and the core thickness T F is 9.2%. Figure 8 It can be seen that with W WD The self-inductance curve first decreases and then flattens, while the mutual inductance and coupling coefficient curves first increase and then slightly decrease. In order to achieve high transmission efficiency and low coil terminal voltage, W is selected. WD The optimal value is 23%, at which the coupling coefficient is maximum and the coil self-inductance is small.

[0104] Fig. 9 (a) and (b) are the core length l F , core thickness T F The influence of the coupling coefficient. When optimizing the core size, the window width W WD The normalized value is set to 23%. Fig. 9 (a) shows that as l F The coupling coefficient curve first rises sharply and then decreases slightly. When the core length l F The normalized value is 76.9%, and the coupling coefficient reaches a maximum of 0.186. The reason is that [(l F / l p )*100%] greater than 76.9% will reduce the magnetic resistance of the self-coupling region of the transmitting coil, resulting in a decrease in the coupling coefficient, while less than 76.9% will increase the magnetic resistance of the mutual coupling region between the transmitting coil and the receiving coil, resulting in a decrease in the coupling coefficient. Fig. 9 (b) shows that as T F The coupling coefficient curve first rises rapidly and then becomes flat. F The normalized value is 9.2%, and the coupling coefficient reaches a maximum of 0.189. Taking into account the weight and volume of the core and the existing core size, the ferrite thickness T is finally selected. F =10mm.

[0105] Based on the optimization results of window width and core size, for the transmission spacing l selected in this example AG =130mm, D-type coil width W DD =150mm, the overall size parameters of the DQDD magnetic coupling mechanism can be obtained, as listed in the table. The parameters in the table will be used as the basis for the design of the experimental prototype.

[0106] Table 2 Dimensional parameters of magnetic coupling mechanism

[0107]

[0108] In summary, the parameter design process of the bipolar coupling mechanism includes the following steps:

[0109] A1. Determine the total length l of the D-type coil according to actual needs DD and the total width W DD , the total length of the first CP coil, that is, the second CP coil, is l CP and the total width W CP , the transmission distance l between the transmitting mechanism and the receiving mechanism 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 needs;

[0110] A2. Determine the spacing W according to actual needs WD and the side length l of the square core F , thickness T F The optimization range of (as shown in Table 1);

[0111] A3. Set the side length l F , thickness T F For a set of fixed values, get the spacing W WD The change curves of the primary-secondary coupling coefficient, the self-inductance of the transmitting and receiving coils, and the mutual inductance between the transmitting and receiving coils within the optimization range (such as Figure 8 ), refer to this group of change curves, and determine the optimal W in combination with the requirements for the primary-secondary coupling coefficient, the self-inductance of the transmitting and receiving coils, and the mutual inductance between the transmitting and receiving coils. WD value;

[0112] A4. Set the spacing W WD is the optimal W WD Value, get the side length l F The variation curve of the primary-secondary coupling coefficient within the optimization range (such as Fig. 9 (a)) and thickness T F The variation curve of the primary-secondary coupling coefficient within the optimization range (such as Fig. 9 (b)), refer to this set of change curves, and determine the optimal l in combination with the requirements for the primary-secondary coupling coefficient and actual needs F Value and T F value.

[0113] Combined with the above analysis, Fig.10 A schematic diagram of the relative position relationship between the receiving coil variable structure and the transmitting coil excitation mode and the transmitting and receiving mechanism is given. X' represents the normalized offset distance, that is, X' = ΔX / l P ×100%, similarly Y′=ΔY / l P ×100%, such as Fig.10The dotted line intersection in the figure indicates the center point of the receiving mechanism, and the horizontal and vertical distances between every two points are both 10%, that is, the horizontal and vertical offset distances between each point are 39 mm.

[0114] Fig.10 (a)-(d) gives Fig.10 There are four combinations of the transmitting end excitation magnetic field and the receiving end pickup structure in (a1)-(d1). Fig.10 (a1) is a schematic diagram of the variable structure and magnetic field control of the receiving mechanism without angle deflection. The magnetic field of the transmitting mechanism is excited by DD coil 1 within the offset range defined by the transmitting mechanism as the center. The receiving mechanism uses CP coils for the pickup structure within the range of X′∈(-50,-20)∪Y′∈(-50,50), as shown in the grid area in the figure, and the diagonal area in the figure indicates that the receiving mechanism uses BP coils. Fig.10 (a2) gives the k when the receiving mechanism has no angular deflection eff As can be seen from the figure, the area with an equivalent coupling coefficient not less than 0.1 accounts for 0.36 in the delimited offset range. Compared with the traditional DD-DD magnetic coupling mechanism, the pickup structure of the receiving mechanism is changed from BP coil to CP coil at a specific position to eliminate the pickup blind spot, making k eff The rate of change in the X direction is more gradual, which improves the anti-drift capability in the X direction; Fig.10 (b1) is a schematic diagram of the variable structure and magnetic field control of the receiving mechanism with an angle deflection of θ = ±15°. Similarly, the magnetic field of the transmitting mechanism is excited by DD coil 1 within the offset range defined by the transmitting mechanism as the center. Different from the case of no angle deflection, the receiving mechanism uses a CP coil for the pickup structure within the range of X′∈(-50,-20)∪Y′∈(-70,70), as shown in the grid area in the figure. The diagonal area in the figure indicates that the receiving mechanism uses a BP coil. Fig.10 (b2) gives k when the angle deflection θ = 15° eff From the changing pattern of , it can be seen that the area with equivalent coupling coefficient not less than 0.1 accounts for 0.25%; Fig.10 (c1) and (d1) are schematic diagrams of the variable structure and magnetic field control of the receiving mechanism with angle deflection of θ = 45° and θ = -45°, respectively. In the figure, the structure of the receiving mechanism pickup coil at different positions is marked with shadows and vertical lines. At this time, the magnetic field of the transmitting mechanism is controlled from the excitation of DD coil 1 to the excitation of DQDD coil. Fig.10 When the angles (c2) and (d2) are deflected by θ = 45° and θ = -45°, k eff It is not difficult to see the changing law. When the receiving mechanism has a large angle deflection, although the origin k eff The value has decreased, but k eff The area ≥0.1 is still relatively large, accounting for 0.28 of the delineated offset range. Fig.10 After analysis, it can be found that the proposed magnetic coupling mechanism has higher resistance to horizontal and angular deviation after introducing variable structure and magnetic field control.

[0115] The bipolar coupling mechanism mentioned in this example has central symmetry, and the variable structure and magnetic field control of no angle deflection and angle deflection θ = ±15° are similar, so the following mainly discusses the two cases of no angle deflection and angle deflection θ = 45°.

[0116] The excitation mode of the transmitting mechanism and the coil structure transformation of the receiving mechanism depend on the relative position of the transmitting and receiving mechanisms, so the receiving mechanism needs to be positioned. This system calculates the coupling coefficient based on the output voltage of the dual-channel receiving end, and uses the two pairs of DD coils in the transmitting mechanism DQDD coil as detection coils to achieve the purpose of detecting the position of the receiving mechanism. The detection process excites DD coil 1 and DD coil 2 in turn, and ignores the influence of cross-coupling between coils on the detection performance. When only the inverter of the loop where DD coil 1 is located is turned on, the current I of the receiving end loop can be obtained by formula (11e): s :

[0117]

[0118] It can be obtained that when the inverter of the circuit where DD coil 1 is located is turned on, the output voltage U of the receiving end is o1 :

[0119]

[0120] The quality factor of self-inductance is defined as:

[0121]

[0122] Substituting equations (7) and (14) into equation (13) can further simplify U o1 :

[0123]

[0124] Based on this, we can get k p1s :

[0125]

[0126] Similarly, when the inverter of the circuit where DD coil 2 is located is turned on, k can be obtained p2s :

[0127]

[0128] The coupling coefficient obtained above reflects the mutual inductance between the transmitting mechanism and the receiving mechanism, that is, reflects the relative positions of the two.

[0129] Measure the self-inductance L at each position p1 , L p2 And mutual inductance M p1s 、M p2s , and calculate the coupling coefficient k at each position p1s , k p2s , thus a position characteristic parameter table can be formed. Taking the coupling mechanism constructed with the size parameters listed in Table 2 as an example, the k corresponding to different relative positions of the transmitting and receiving mechanisms pis ,like Fig.13 As shown. Fig.11 As a reference, in actual application, the output voltage V of the receiving end is measured when the inverters of the circuits where DD coil 1 and DD coil 2 are respectively turned on. o1 、V o1 ; Then, the actual k is calculated by equations (16) and (17): * p1s and k * p2s , k * p1s , k * p2s By comparing with the reference of the coupling coefficient, the position of the receiving mechanism can be determined.

[0130] Combining the control strategy of the coupling magnetic field and the position detection of the transmitting and receiving mechanism, the bipolar coupling magnetic field control process is given, such as Fig.12 First, the two groups of DD coils in the transmitting mechanism DQDD are excited in turn, and the output voltage of the receiving end is measured when the two groups of DD coils are excited. The coupling coefficient k at this position is calculated by equations (16) and (17): * p1s , k * p2s Then k * p1s , k * p2s and k in the position characteristic parameter table p1s(θ＝0°) , k p2s(θ＝0°) (k p1s(θ＝0°) , k p2s(θ＝0°) The first DD coil L is excited under the same conditions when there is no angular deflection between the transmitting mechanism and the receiving mechanism calibrated in advance. p1 The primary-secondary coupling coefficient and the excitation second DD coil L p2 If the sum of the errors is less than ε1, it is considered that the transmitting and receiving mechanism has no angular deflection, and the position of the receiving mechanism is determined; if the sum of the errors is greater than ε1, k * p1s , k * p2s With k p1s(θ＝45°) , kp2s(θ＝45°) (k p1s(θ＝45°) , k p2s(θ＝45°) When there is a 45° angle deflection between the transmitting mechanism and the receiving mechanism, the first DD coil L is excited under the same conditions. p1 The primary-secondary coupling coefficient and the excitation second DD coil L p2 If the error is less than ε2, it is considered that the transmitting and receiving mechanism has an angle deflection of +45° or -45°, and the offset of the receiving mechanism is determined; on the contrary, if the error is still greater than ε2 at this time, the voltage information is measured again and the above steps are repeated. The setting of the error thresholds ε1 and ε2 depends on the maximum relative error between the measured value and the simulated value of the equivalent coupling coefficient. After determining the position of the receiving mechanism, according to Fig.10 The transmitting and receiving coil excitation mode and receiving coil structure are selected to achieve high anti-offset deflection performance of the bipolar coupling mechanism.

[0131] Based on the above analysis, this embodiment also provides a control method for a high-anti-deviation deflection WPT system based on a bipolar coupling mechanism, which specifically includes the following steps:

[0132] S1, control bipolar coil L S In bipolar working mode, the first DD coil L is excited in turn p1 And the second DD coil L p2 ;

[0133] S2, measure and excite the first DD coil L p1 The receiving end output voltage V o1 , and excite the second DD coil L p2 The receiving end output voltage V o2 ;

[0134] S3, based on equations (14) to (17), according to the output voltage U1 of the first inverter, the operating angular frequency ω of the system, and the first DD coil L p1 , the first primary series compensation inductor L pf1 , bipolar coil L S , receiving end output voltage V o1 、Load R L Calculate the position at which the first DD coil L is excited p1 The first primary-secondary coupling coefficient k * p1s According to the output voltage U2 of the second inverter, the operating angular frequency ω of the system, and the second DD coil L p2 , the second primary series compensation inductor L pf2 , bipolar coil L S , receiving end output voltage V o2 Calculate the position at which the second DD coil L is excitedp2 The second primary-secondary coupling coefficient k * p2s ;

[0135] S4, according to the first primary-secondary coupling coefficient k * p1s , the second primary-secondary coupling coefficient k * p2s Determine the offset distance and deflection angle of the receiving mechanism;

[0136] S5. Determine the working mode of the DQDD coil and the bipolar coil L according to the offset distance and deflection angle of the receiving mechanism. S working mode.

[0137] Specifically, step S4 specifically includes the steps of:

[0138] S41, calculate the first primary-secondary coupling coefficient k * p1s With k p1s(θ＝0°) The error value Δk1 between the second primary and secondary coupling coefficient k * p2s With k p2s(θ＝0°) The error value between them is Δk2;

[0139] S42, determining whether the sum of Δk1 and Δk2 is less than or equal to a first error threshold ε1, if so, it is considered that there is no angular deflection between the transmitting mechanism and the receiving mechanism and step S45 is executed, if not, steps S43 to S44 are executed;

[0140] S43, calculating the first primary-secondary coupling coefficient k * p1s With k p1s(θ＝45°) The error value Δk3 between the second primary and secondary coupling coefficient k * p2s With k p2s(θ＝45°) The error value between them is Δk4;

[0141] S44, judging whether the sum of Δk3 and Δk4 is less than or equal to the second error threshold ε2, and ε2 is greater than ε1, if so, it is considered that there is an angle deflection of +45° or -45° between the transmitting mechanism and the receiving mechanism, and step S46 is executed, if not, returning to step S2;

[0142] S45. Correlation between the offset distance and the primary-secondary coupling coefficient when there is no angle deflection in advance calibration (e.g. Fig.11 In (a)), find the first primary-secondary coupling coefficient k * p1s , the second primary-secondary coupling coefficient k * p2sThe specific size of the receiving mechanism corresponds to the offset distance (X′, Y′) of the receiving mechanism; for example, by measuring V o1 、V o2 , k can be calculated * p1s , k * p2s (Assuming k * p1s =0.05, k * p2s =0.05), such as Fig.11 (a) shows k p1s The 0.05 contour line and k p2s The 0.05 contour lines in the figure have an intersection point. The relative position of the intersection point of the two contour lines is obtained by looking up the table, and the offset distance of the receiving mechanism relative to the transmitting mechanism is finally determined.

[0143] S46, similar to step S45, the correlation between the offset distance and the primary-secondary coupling coefficient at the pre-calibrated 45° angle deflection (such as Fig.11 In (b)), find the first primary-secondary coupling coefficient k * p1s , the second primary-secondary coupling coefficient k * p2s The specific size of the receiving mechanism corresponds to the offset distance (X′, Y′).

[0144] Specifically, when the receiving mechanism has no angular deflection, step S5 is specifically as follows:

[0145] Determine whether the offset distance of the receiving mechanism is within the first preset range or the second preset range. If it is within the first preset range (such as Fig.10 The range of X', Y' corresponding to DD1-CP in (a1) controls the DQDD coil to work in the DD coil working mode and the bipolar coil L S Working in unipolar working mode, if it is in the second preset range (such as Fig.10 The range of X', Y' corresponding to DD1-BP in (a1) controls the DQDD coil to work in the DD coil working mode and the bipolar coil L S Operate in bipolar mode (DD1-BP). For example, to measure V o1 、V o2 , calculate k * p1s , k * p2s ,according to Fig.11 (a) Given the variation law of the coupling coefficient, find out k * p1s , k * p2sThe corresponding contour lines are used to determine the offset distance of the receiving mechanism relative to the transmitting mechanism through the intersection of the two contour lines. Fig.10 (a1) If the receiving mechanism is in the offset distance region 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 s Works in unipolar mode.

[0146] When there is an angle deflection of ±45° between the receiving mechanism and the transmitting mechanism, step S5 specifically includes the following steps:

[0147] S51, control the DQDD coil to work in the DQDD coil working mode and the phase difference between the excitation current of the first inverter and the second inverter is 0°, and measure the output voltage V of the receiving end at this time * o1 ;

[0148] S52, controlling the phase difference between the excitation current of the first inverter and the second inverter to change to 180°, and measuring the output voltage V of the receiving end at this time * o2 ;

[0149] S53, judge V * o1 Is it greater than V * o2 If yes, it is determined that the deflection angle of the receiving mechanism is +45° and step S54 is executed; if no, it is determined that the deflection angle of the receiving mechanism is -45° and step S55 is executed;

[0150] S54, control the phase difference between the excitation current of the first inverter and the second inverter to be 0°, and further determine whether the offset distance of the receiving mechanism is within the third preset range or the fourth preset range. If it is within the third preset range (such as Fig.10 The range of X', Y' corresponding to DQDD-CP in (c1) controls the bipolar coil L S Working in unipolar working mode, if it is in the fourth preset range (such as Fig.10 The range of X', Y' corresponding to DQDD-BP in (c1) controls the bipolar coil L S Works in bipolar working mode;

[0151] S55, control the phase difference between the excitation current of the first inverter and the second inverter to be 180°, and further determine whether the offset distance of the receiving mechanism is within the fifth preset range or the sixth preset range. If it is within the fifth preset range (such as Fig.10The range of X', Y' corresponding to DQDD-CP in (d1) controls the bipolar coil L S Working in unipolar working mode, if it is in the sixth preset range (such as Fig.10 The range of X', Y' corresponding to DQDD-BP in (d1) controls the bipolar coil L S Works in bipolar mode.

[0152] The indicator for measuring the anti-drift capability of the coupling mechanism is defined as the coupling coefficient attenuation ratio (CCAR):

[0153]

[0154] In the formula, k ali and k mis They represent the equivalent coupling coefficients during alignment and after offset respectively. Under the same offset deflection, the smaller the CCAR value is, the higher the tolerance of the offset is.

[0155] In this example, CP coil and DD coil are selected as magnetic coupling mechanisms for comparison. During the analysis, the number of turns, coil and magnetic conductive mechanism size, and coupling spacing used by the DQDD mechanism are the same as those of the other two coupling mechanisms. Compared with the CP and DD coupling mechanisms commonly used in WPT systems, the bipolar coupling mechanism based on variable structure and magnetic field control has stronger resistance to horizontal and angular offsets. Fig.13 The variation rules of CCAR of different magnetic coupling mechanisms with and without angle offset. Fig.13 (a) shows the CCAR variation of the three coupling mechanisms without angle offset. Compared with the CP coil, the corresponding area where the CCAR of the proposed magnetic coupling mechanism is not higher than 25% and 50% is 0.9 times and 1.43 times that of the CP coil, respectively. When the offset distance is 20%, the CCAR increase rate of the proposed magnetic coupling mechanism in the X′ direction is slightly faster than that of the CP coil, but the CCAR increase rate in the Y′ direction is significantly slower than that of the CP coil. Secondly, the CCAR of the proposed magnetic coupling mechanism increases to 50% only when it is offset by 50%, while the CCAR of the CP coil increases to 50% when it is offset by 40%, which indicates that the proposed magnetic coupling mechanism has higher anti-offset performance than the CP coil and the greater the offset, the more outstanding its performance is; compared with the DD coil, the area corresponding to the area where the CCAR of the proposed magnetic coupling mechanism is not higher than 25% is equal to that of the DD coil, and the area corresponding to the area where the CCAR is not higher than 50% is 1.5 times that of the DD coil, and the CCAR of the DD coil at a 40% offset in the X′ direction is approximately 100%, which indicates that the proposed magnetic coupling mechanism has all-round and wider range anti-offset performance than the DD coil.

[0156] Fig.13(b) shows the CCAR variation law of the three coupling mechanisms under the condition of angle deflection θ = 45°. Compared with CP and DD coils, the corresponding area of ​​the proposed magnetic coupling mechanism with CCAR not higher than 25% is basically equal to the area of ​​CP and DD coils; and the corresponding area of ​​CCAR not higher than 50% is 1.55 times and 1.49 times of CP and DD coils, respectively. This shows that under larger deflection conditions, the proposed magnetic coupling mechanism has stronger anti-offset deflection performance than CP and DD coils, and its performance is better with greater offset distance. Since the magnetic coupling mechanism proposed in this example has central symmetry, the CAR variation law of angle deflection θ = -45° is similar to that of angle deflection θ = 45°, so it will not be discussed further.

[0157] After comprehensively analyzing the above comparison, it can be seen that the magnetic coupling mechanism proposed in this example is better than the CP and DD magnetic coupling mechanisms in terms of position and angle anti-deviation performance in the horizontal plane, and the greater the degree of deviation, the more outstanding its performance.

[0158] According to the size parameters of the magnetic coupling mechanism given in Table 2, an experimental prototype was built in combination with the parameter configuration method of the LCC-S compensation circuit to verify the anti-offset performance and transmission characteristics of the proposed magnetic coupling mechanism after adding variable structure and magnetic field regulation. Among them, the coil windings of the transmitting mechanism and the receiving mechanism are both wound with Litz wire with a diameter of 0.2mm×300 strands; the core material is PC44 manganese-zinc ferrite; the aluminum plate is made of 6061 aluminum with a thickness of 3mm, and its function is to shield the leakage magnetic field; the insulating paper is used to prevent the two layers of coils from short-circuiting. Table 3 lists the main parameter values ​​and component models of the system. It should be pointed out that the internal resistance of the single DD coil wound in the transmitting mechanism is 0.26Ω, and the mutual inductance between the two layers of DD coils is 0.3μH, which can be ignored compared to its self-inductance, and it can be considered that the two layers of DD coils are decoupled. In addition, the signal communication between the transmitting and receiving mechanisms is realized by the Bluetooth module. Load voltage V o1 、V o2 After the voltage is divided by resistors, it is sampled by the built-in ADC module of the MCU and transmitted to the transmitter. After the transmitter determines the position of the receiving mechanism according to the load voltage information, it adjusts the transmitting magnetic field and sends a relay control signal to the receiver.

[0159] Table 3 Main parameter values ​​and component models of the prototype

[0160]

[0161] In order to verify the anti-deviation performance of the XOY plane position and angle of the coupling mechanism proposed in this example, the position of the air gap height of 130mm is taken as the reference datum, 10% (39mm) is used as the step length, X′=±70%, Y′=±70% (X=±273mm, Y=±273mm) is used as the boundary, and the measured values ​​and errors of the coupling coefficient of the dual energy channel under different position offsets and angle deflections are given, as shown in the figure. Fig.14shown.

[0162] Fig.14 (a1) is aligned with the position k eff =0.183, the maximum relative error between the experimental measurement value and the simulation 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%; Fig.14 (a2) is aligned with the position k eff =0.179, the maximum relative error between the experimental measurement value and the simulation equivalent coupling coefficient in the entire 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 analysis results of the equivalent coupling coefficient and its CCAR variation law are basically consistent, thus verifying the anti-offset performance of the magnetic coupling mechanism in the XOY plane position and angle of this example; Fig.14 (b1) and (b2) are the dual-channel coupling coefficients k under different position offsets without angle deflection. p1s , k p2s The measured value, compared to Fig.11 The given simulation values ​​have maximum relative errors of 9.47% and 9.13% respectively, and minimum relative errors of 0; Fig.14 (c1) and (c2) are the dual-channel coupling coefficients k under different position offsets when the angle deflection θ = 45°. p1s , k p2s The maximum relative errors of the measured values ​​compared to the simulated values ​​are 8.65% and 9.75% respectively, and the minimum relative errors are both 0. According to the relative errors between the measured values ​​and the simulated values, the control process is set. Fig.12 The mean error limits ε1 and ε2 are:

[0163]

[0164] Table 4 gives the V dc =10V, 1 # No angular deflection alignment, 2 # No angle deflection X' offset 40%, 3 # No angle deflection Y' offset 40%, 4 # Angular deflection 45° X' offset -40% and Y' offset 40% and 5 # Under the five positions of 45° angle deflection, 40% X′ offset and 40% Y′ offset, the load voltage V o1 、V o2 , and obtained k * p1s , k * p2s and k p1s , k p2sThe measured value errors are e1 and e2. Among them, the maximum relative errors of e1 and e2 are 3.75% and 4.87% respectively, both less than 5%, which shows that the positioning method adopted can detect the position of the mechanism with sufficient accuracy.

[0165] Table 4 Position detection characteristic parameters and errors

[0166]

[0167] In addition, in order to verify the system transmission characteristics of the LCC-S compensation network of dual-inverter-single-rectifier, the voltage and current waveforms of the power conversion circuit and compensation circuit of the experimental prototype under the above five positions were measured, such as Fig.15 shown. Fig.15 (a1)-(a5) show the voltage and current waveforms of the system output in five positions when the system is working with a single inverter and two inverters. The phase difference between the inverter output voltage and current is in the range of 5° to 10° at different positions, indicating that the system input impedance is weakly inductive, ensuring that the switching devices are all working in ZVS mode; Fig.15 (b1)-(b5) of the figure give the current waveforms of the transmitting mechanism coil under five positions, and the phase difference between the current waveform and the inverter voltage is always maintained at 90°. Fig.15 From (b4) and (b5), it can be seen that when the two inverters are working, the excitation current I p1 with I p2 The amplitudes of are equal, which meets the requirements of the magnetic field excitation current of the DQDD coil. In addition, the error percentage between the measured effective values ​​of I1 and I2 and the corresponding simulation values ​​is in the range of 2% to 8%; I p1 ,I p2 The error percentage between the measured effective value and the corresponding simulation value is in the range of 3% to 7%, which verifies the accuracy of the derived LCC compensation topology transmission characteristics. Fig.15 (c1)-(c5) show the voltage and current waveforms before rectification at five positions, based on which the power and efficiency of the experimental prototypes at five positions are calculated. As shown in Table 5, the output power of the experimental prototypes at five positions is about 1.8kW, and the system efficiency is not less than 88%.

[0168] Table 5 Power and efficiency of the experimental prototype at five positions

[0169]

[0170] In summary, the embodiment of the present invention proposes a highly anti-offset deflection WPT system based on a bipolar coupling mechanism and a control method thereof, analyzes the distribution characteristics of the excitation magnetic field of the DQDD transmitting mechanism and the pickup characteristics of the variable structure BP coil, gives the interaction law between the characteristic parameters of the magnetic coupling mechanism and the coupling coefficient, proposes a control strategy for changing the pickup structure and regulating the transmitting magnetic field, and experimentally verifies the feasibility and effectiveness of the system. The coil in the DQDD transmitting mechanism serves as both an energy transmission coil and a detection coil for the relative position of the transmitting and receiving mechanism. No additional auxiliary positioning equipment is required, which can effectively reduce the size and cost of the system; the constructed magnetic coupling mechanism has stronger anti-offset deflection performance than the currently commonly used magnetic coupling mechanism. The anti-offset performance and system efficiency of the system are higher than the set values ​​of the current standards, and it has good application prospects in static wireless charging of electric vehicles.

[0171] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A highly anti-skew deflection WPT system based on a dual-polarity coupling mechanism, characterized in that: The invention comprises a DC power supply, a high-frequency inverter circuit, a primary compensation circuit, a bipolar coupling mechanism, a secondary compensation circuit, a rectifier and a load R connected in sequence. L ; The bipolar coupling mechanism includes a transmitting mechanism and a receiving mechanism; The transmitting mechanism comprises a transmitting end magnetic core and a DQDD coil stacked in sequence, wherein the DQDD coil is composed of a first DD coil L on the surface. p1 And the second DD coil L in the inner layer p2 The first DD coil L p1 and the second DD coil L p2 Both have the same parameters, the same winding direction and a spacing of W. WD The D-type coils are connected in series; The receiving mechanism includes a bipolar coil L stacked in sequence S and the receiving end magnetic core; the bipolar coil L S It is composed of two overlapping first CP coils and second CP coils with the same parameters and opposite winding directions. The window width formed by the overlap is also W WD ; The receiving mechanism also includes a bipolar coil L connected to the S A relay circuit for controlling the bipolar coil L S The working mode is a bipolar working mode in which the first CP coil and the second CP coil work simultaneously, or a unipolar working mode in which only the first CP coil works or only the second CP coil works; The high-frequency inverter circuit includes a first inverter and a second inverter connected in parallel to the DC power supply; the primary compensation circuit includes a first inverter connected to the first DD coil L p1 The first primary compensation network is connected between the second inverter and the second DD coil L p2 The second primary side compensation network between; The first inverter and the second inverter are used to control the working mode of the DQDD coil to only excite the first DD coil L p1 The DD coil working mode or the first DD coil L is excited by the current of the same amplitude and phase difference β p1 and the second DD coil L p2 DQDD coil working mode.

2. The highly anti-skew deflection WPT system based on a dual-polarity coupling mechanism according to claim 1, characterized in that: 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. Determine the total length l of the D-type coil according to actual needs DD and the total width W DD , the total length of the first CP coil, that is, the second CP coil, is l CP and the total width W CP =a+W WD , the transmission distance l between the transmitting mechanism and the receiving mechanism AG The wire diameter T of the D-type coil, namely the first CP coil, namely the second CP coil W and the number of winding turns N, a is a specific value determined according to actual needs; A2. Determine the spacing W according to actual needs WD And the side length l of the square core F , thickness T F Optimization range: A3. Set the side length l F , thickness T F For a set of fixed values, get the spacing W WD The change curves of the primary-secondary coupling coefficient, the self-inductance of the transmitting-receiving coil, and the mutual inductance of the transmitting-receiving coil within the optimization range are referred to, and the optimal W is determined in combination with the requirements for the primary-secondary coupling coefficient, the self-inductance of the transmitting-receiving coil, and the mutual inductance between the transmitting-receiving coil. WD value; A4. Set the spacing W WD is the optimal W WD Value, get the side length l F Variation curve of primary-secondary coupling coefficient within the optimization range and thickness T F The change curve of the primary-secondary coupling coefficient within the optimization range is used to determine the optimal l by referring to this group of change curves and combining the requirements for the primary-secondary coupling coefficient and actual needs. F Value and T F value.

3. The highly anti-skew deflection WPT system based on the dual-polarity coupling mechanism according to claim 2, characterized in that: The first primary compensation network and the second primary compensation network both adopt LCC compensation networks. The first primary compensation network includes a first primary series compensation inductor L pf1 、The first primary series compensation capacitor C p1 And the first primary parallel compensation capacitor C pf1 The second primary compensation network includes a second primary series compensation inductor L pf2 , the second primary series compensation capacitor C p2 And the second primary parallel compensation capacitor C pf2 ; The secondary side compensation circuit adopts a secondary side series compensation capacitor C s .

4. The highly anti-skew deflection WPT system based on a dual-polarity coupling mechanism according to claim 3, characterized in that: The parameter values ​​of the first primary compensation network, the second primary compensation network and the secondary compensation circuit are set as follows: ω is the operating angular frequency of the system.

5. A control method for a highly anti-deviation deflection WPT system based on a bipolar coupling mechanism, characterized in that: For the highly anti-deviation deflection WPT system based on the bipolar coupling mechanism according to claim 3 or 4, the control method specifically comprises the steps of: S1, control the bipolar coil L S In bipolar working mode, the first DD coil L is excited in turn p1 and the second DD coil L p2 ; S2, measuring and exciting the first DD coil L p1 The receiving end output voltage V o1 , and excite the second DD coil L p2 The receiving end output voltage V o2 ; S3, according to the output voltage U1 of the first inverter, the working angular frequency ω of the system, and the first DD coil L p1 , the first primary series compensation inductor L pf1 , the bipolar coil L S , the receiving end output voltage V o1 , the load R L Calculate the position at which the first DD coil L is excited p1 The first primary-secondary coupling coefficient k * p1s According to the output voltage U2 of the second inverter, the operating angular frequency ω of the system, and the second DD coil L p2 The second primary series compensation inductor L pf2 , the bipolar coil L S , the receiving end output voltage V o2 Calculate the position at which the second DD coil L is excited p2 The second primary-secondary coupling coefficient k * p2s ; S4, according to the first primary-secondary coupling coefficient k * p1s , the second primary-secondary coupling coefficient k * p2s determining an offset distance and a deflection angle of the receiving mechanism; S5. Determine the working mode of the DQDD coil and the bipolar coil L according to the offset distance and deflection angle of the receiving mechanism. S working mode.

6. The control method of the high-anti-deviation deflection WPT system based on the bipolar coupling mechanism according to claim 5 is characterized in that: In step S3, the first primary-secondary coupling coefficient The second primary-secondary coupling coefficient The self-inductance L is defined as p1 , L p2 , L pf1 , L pf2 , L S The quality factor of .

7. The control method of the high anti-deviation deflection WPT system based on the bipolar coupling mechanism according to claim 6 is characterized in that: The step S4 specifically comprises the following steps: S41, calculating the first primary-secondary coupling coefficient k * p1s With k p1s(θ＝0°) The error value Δk1 between the second primary and secondary coupling coefficient k * p2s With k p2s(θ＝0°) The error value between Δk2, k p1s(θ＝0°) , k p2s(θ＝0°) The first DD coil L is excited under the same conditions when there is no angular deflection between the transmitting mechanism and the receiving mechanism calibrated in advance. p1 When the primary-secondary coupling coefficient and the excitation of the second DD coil L p2 The primary-secondary coupling coefficient when ; S42, determining whether the sum of Δk1 and Δk2 is less than or equal to a first error threshold ε1, if so, it is considered that there is no angular deflection between the transmitting mechanism and the receiving mechanism and step S45 is executed, if not, steps S43 to S44 are executed; S43, calculating the first primary-secondary coupling coefficient k * p1s With k p1s(θ＝45°) The error value Δk3 between the second primary and secondary coupling coefficient k * p2s With k p2s(θ＝45°) The error value between Δk4, k p1s(θ＝45°) , k p2s(θ＝45°) When there is a 45° angle deflection between the transmitting mechanism and the receiving mechanism, the first DD coil L is excited under the same conditions. p1 When the primary-secondary coupling coefficient and the excitation of the second DD coil L p2 The primary-secondary coupling coefficient when ; S44, judging whether the sum of Δk3 and Δk4 is less than or equal to a second error threshold ε2, and ε2 is greater than ε1, if so, it is considered that there is an angle deflection of +45° or -45° between the transmitting mechanism and the receiving mechanism, and step S46 is executed, if not, returning to step S2; S45, finding the first primary-secondary coupling coefficient k in the correlation between the offset distance and the primary-secondary coupling coefficient when there is no angle deflection calibrated in advance * p1s , the second primary-secondary coupling coefficient k * p2s The offset distance of the receiving mechanism corresponding to the specific size of S46, find the first primary-secondary coupling coefficient k in the correlation between the offset distance and the primary-secondary coupling coefficient when the 45° angle deflection is calibrated in advance * p1s , the second primary-secondary coupling coefficient k * p2s The specific size of the receiving mechanism corresponds to the offset distance of the receiving mechanism.

8. The control method of the high anti-deviation deflection WPT system based on the bipolar coupling mechanism according to claim 7 is characterized in that: When the receiving mechanism has no angular deflection, step S5 is specifically as follows: Determine whether the offset distance of the receiving mechanism is within the first preset range or the second preset range. If it is within the first preset range, control the DQDD coil to operate in the DD coil operating mode and the bipolar coil L S Works in the unipolar working mode. If it is in the second preset range, the DQDD coil is controlled to work in the DD coil working mode and the bipolar coil L S Works in bipolar mode.

9. The control method of the high anti-deviation deflection WPT system based on the bipolar coupling mechanism according to claim 7, characterized in that: When there is an angle deflection of +45° or -45° between the receiving mechanism and the transmitting mechanism, step S5 specifically includes the following steps: S51, control the DQDD coil to work in the DQDD coil working mode and the phase difference between the excitation current of the first inverter and the second inverter is 0°, and measure the output voltage V of the receiving end at this time * o1 ; S52, controlling the phase difference between the excitation current of the first inverter and the second inverter to change to 180°, and measuring the output voltage V * o2 ; S53, judge V * o1 Is it greater than V * o2 If yes, it is determined that the deflection angle of the receiving mechanism is +45° and step S54 is executed; if no, it is determined that the deflection angle of the receiving mechanism is -45° and step S55 is executed; S54, control the phase difference between the excitation current of the first inverter and the second inverter to be 0°, and further determine whether the offset distance of the receiving mechanism is within the third preset range or the fourth preset range. If it is within the third preset range, control the bipolar coil L S Working in the unipolar working mode, if it is in the fourth preset range, the bipolar coil L is controlled S Works in bipolar working mode; S55, control the phase difference between the excitation current of the first inverter and the second inverter to be 180°, and further determine whether the offset distance of the receiving mechanism is within the fifth preset range or the sixth preset range. If it is within the fifth preset range, control the bipolar coil L S Working in the unipolar working mode, if it is in the sixth preset range, the bipolar coil L is controlled S Works in bipolar mode.

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