WPT system for realizing constant current and constant voltage output on basis of variable-structure hybrid topology

Abstract

The present invention relates to the technical field of wireless power transfer (WPT). Specifically disclosed is a WPT system for realizing constant current and constant voltage output on the basis of a variable-structure hybrid topology. A variable-structure hybrid topology is designed, wherein input ends of CLC-S-type and S-CLC-type topologies are connected in series, and output ends of the CLC-S-type and S-CLC-type topologies are connected in parallel to form a front-stage circuit which is mainly used for improving the system misalignment tolerance; on this basis, a variable-structure T-type compensation topology is incorporated at an output end to form a rear-stage T-type circuit, and constant-current / constant-voltage switching is achieved by changing the structure of the rear-stage T-type circuit. Moreover, in order to improve the system misalignment tolerance, a system compensation parameter is designed. Experiments have verified that the WPT system for realizing constant current and constant voltage output on the basis of a variable-structure hybrid topology provided by the present invention can realize constant-current / constant-voltage switching, and has high misalignment tolerance in both a constant voltage mode and a constant current mode.

Description

WPT system for realizing constant current and constant voltage output based on variable structure type hybrid topology TECHNICAL FIELD

[0001] The application relates to the technical field of wireless power transmission, and in particular to a WPT system for realizing constant current and constant voltage output based on variable structure type hybrid topology. BACKGROUND

[0002] With the rapid development of modern science and technology, the application field of wireless power transmission (WPT) technology is becoming more and more extensive.

[0003] The actual load of a wireless charging system of an electric vehicle is a lithium battery, and on the one hand, the use cycle of the lithium battery needs to be prolonged, and on the other hand, the internal resistance of the lithium battery will change continuously during the charging process, so the wireless charging of the electric vehicle usually adopts a constant current / constant voltage charging mode. Therefore, it is necessary to study a WPT system with constant current / constant voltage output characteristics and anti-deviation capability.

[0004] The existing ways for realizing constant current / constant voltage output of a WPT system mainly include the following: (1) increasing a DC / DC converter in the secondary side; (2) closed-loop control; and (3) variable structure, i.e. topology switching. However, increasing the DC / DC converter in the secondary side will reduce the transmission efficiency of the system, the closed-loop control needs to increase additional communication in the system, the control strategy is relatively complex, and the control cost is increased. Although the current topology switching structure (such as LCC-S type and LCC-LCC type) can realize the constant current / constant voltage output characteristics, the anti-deviation capability of the system is poor. SUMMARY

[0005] The application provides a WPT system for realizing constant current and constant voltage output based on variable structure type hybrid topology, and solves the technical problem of how to design a WPT system with good anti-deviation performance and constant current / constant voltage output through topology switching.

[0006] To solve the above technical problems, the application provides a WPT system for realizing constant current and constant voltage output based on variable structure type hybrid topology, which comprises a first transmitting coil L1, a second transmitting coil L3 connected in series and a first receiving coil L2 and a second receiving coil L4 connected in parallel, wherein the first transmitting coil L1 is decoupled from other coils except for the first receiving coil L2, and the second transmitting coil L3 is decoupled from other coils except for the second receiving coil L4.

[0007] The system further comprises a variable structure type hybrid topology, wherein the variable structure type hybrid topology comprises a front-stage circuit composed of a CLC-S type resonant network and an S-CLC type resonant network and a variable structure type T type topology as a rear-stage circuit.

[0008] The CLC-S type resonance network comprises a first CLC type network connected with the first transmitting coil L1 and a first S type network connected with the first receiving coil L3, and the S-CLC type resonance network comprises a second S type network connected with the second transmitting coil L2 and a second CLC type network connected with the second receiving coil L4.

[0009] The variable structure T type topology is connected in parallel with the first S type network and the second CLC type network; and the variable structure T type topology is used for switching to a constant current output topology or a constant voltage output topology.

[0010] Preferably, the constant current output topology is an LCL type T type network composed of two inductors and one capacitor.

[0011] Preferably, the constant voltage output topology is composed of two inductors and one capacitor connected in series.

[0012] Preferably, the variable structure T type topology comprises an inductor L6, an inductor L7 and a capacitor C7 connected in series between an output end of the pre-stage circuit and an equivalent load resistor R e Preferably, the variable structure T type topology comprises an inductor L6, an inductor L7 and a capacitor C7 connected in series between an output end of the pre-stage circuit and an equivalent load resistor R e Preferably, the variable structure T type topology comprises an inductor L6, an inductor L7 and a capacitor C7 connected in series between an output end of the pre-stage circuit and an equivalent load resistor R

[0013] Preferably, the first CLC type network comprises a capacitor C0 and a capacitor C1 connected in series between the first output end of the equivalent AC source and the same name end of the first transmitting coil L1, and an inductor L0 connected between the common end of the capacitor C0 and the capacitor C1 and the different name end of the first transmitting coil L1, and the different name end of the first transmitting coil L1 is connected with the same name end of the second transmitting coil L3; and the second S type network comprises a capacitor C3 connected between the different name end of the second transmitting coil L3 and the second output end of the equivalent AC source.

[0014] Preferably, the second CLC type network comprises a capacitor C4 and a capacitor C5 connected in series between the same name end of the second receiving coil L4 and the inductor L6, and an inductor L5 connected between the common end of the capacitor C4 and the capacitor C5 and the different name end of the second receiving coil L4, and the different name end of the second receiving coil L4 is connected with the other end of the equivalent load resistor R e Preferably, the first S type network comprises a capacitor C2 connected between the different name end of the first receiving coil L2 and the inductor L6.

[0015] Preferably, the parameters of the variable-structure hybrid topology are determined according to the principle of circuit resonance.

[0016] Further, when the system outputs a constant voltage, the parameters of the variable-structure hybrid topology are determined by the following steps:

[0017] The inductances L1, L2, L3, and L4 are determined according to actual requirements.

[0018] The relationship between the mutual inductances M 12 , M 34 is fitted within a preset offset range, where M 12 represents the mutual inductance between the first transmitting coil L1 and the first receiving coil L2, and M 34 represents the mutual inductance between the second transmitting coil L3 and the second receiving coil L4.

[0019] The output voltage gain G V related to the mutual inductances M 12 , the inductance L0, and the inductance L5 is calculated according to the fitted relationship between the mutual inductances M 12 , M 34 .

[0020] The output voltage gain G V is derived at the gain inflection point M 12m according to the relationship between the output voltage gain G V and the mutual inductance M 12 , and the relationship between M 12m and the inductances L0 and L5 is determined.

[0021] The allowable maximum value G max and the allowable minimum value G min of the output voltage gain G V are determined according to the maximum gain value G VM at the gain inflection point M 12m and the gain value G VR when the system has not been offset, and the value range of M 12 is determined according to G max , G min , and the relationship between the output voltage gain G V and the mutual inductance M 12 .

[0022] The value range of the inductance L5 is determined according to the value range of M 12 and the relationship between M 12 and the inductances L0 and L5.

[0023] The value of the inductance L5 is determined as follows: the value of the inductance L5 in the range of values of the inductance L5 at which the current of the transmitting coil and the current of the receiving coil intersect;

[0024] The value of the inductance L5 and the value of the inductance M 12m The value of the inductance L0 is determined in relation to the inductances L0 and L5;

[0025] The value of the inductance L6 and the values of the capacitances C0, C1, C2, C3, C4, C5 and C6 are determined in accordance with the system resonance relationship;

[0026] When the system is in constant current output, the parameters of the variable-structure hybrid topology are determined by the following steps:

[0027] The parameters of the pre-stage circuit in constant current output are set to be the same as the parameters of the pre-stage circuit in constant voltage output;

[0028] The value of the inductance L7 is determined in relation to the inductance L7; out The value of the inductance L7 is determined in relation to the inductance L7;

[0029] The value of the inductance L6 and the values of the capacitances C6, C7 and C8 are determined in accordance with the resonance relationship.

[0030] Further, when the system is in constant voltage output, the value of M 12 is determined by the following formula:

[0031] wherein M 12min and M 12max respectively represent the minimum value of M 12 when the system is offset within a preset offset range and the maximum value of M 12 when the system is not offset, G V (M 12max ) represents the value of G 12max at M V , G V (M 12min ) represents the value of G 12min at M V , and α represents a proportional factor;

[0032] When the system is in constant current output, the output current I out is in relation to the inductance L7 as follows:

[0033] wherein U in represents the AC input voltage of the system.

[0034] The application provides a WPT system based on a variable structure type hybrid topology for realizing constant current and constant voltage output. BRIEF DESCRIPTION OF DRAWINGS

[0035] Fig. 1 is a CLC-S type compensation topology structure diagram;

[0036] Fig. 2 is an S-CLC type compensation topology structure diagram;

[0037] Fig. 3 is a traditional T type compensation topology structure diagram;

[0038] Fig. 4 is a variable structure type T type compensation topology structure diagram;

[0039] Fig. 5 is a topology structure diagram of the WPT system based on the variable structure type hybrid topology for realizing constant current and constant voltage output;

[0040] Fig. 6 is an equivalent hybrid topology circuit diagram of Fig. 5 when the bidirectional switches S1 and S2 are closed;

[0041] Fig. 7 is an equivalent hybrid topology circuit diagram of Fig. 5 when the bidirectional switches S1 and S2 are opened;

[0042] Fig. 8 is a schematic diagram of a DDQ type magnetic coupling mechanism;

[0043] Fig. 9 is a mutual inductance change curve diagram in a Y axis offset process;

[0044] Fig. 10 is a mutual inductance change curve diagram in an X axis offset process;

[0045] Fig. 11 is a mutual inductance change curve diagram in a Z axis offset process;

[0046] Fig. 12 is a relationship diagram between system output voltage gain and mutual inductance M 12 when the Y axis is offset;

[0047] Fig. 13 is a relationship curve diagram between coil current maximum value and self-inductance L5;

[0048] Fig. 14 is an inverter waveform and output waveform diagram of the system when facing and offsetting in a constant current mode;

[0049] Figure 15 is a graph of system output current and transmission efficiency when the load changes and the Y-axis shifts in constant current mode;

[0050] Figure 16 is a graph of system inverter waveform and output waveform when the load changes and the Y-axis shifts in constant voltage mode;

[0051] Figure 17 is a graph of system output voltage and transmission efficiency when the load changes and the Y-axis shifts in constant voltage mode. DETAILED DESCRIPTION

[0052] The CLC-S compensation topology is shown in Figure 1. In Figure 1, U I is the fundamental voltage after full-bridge inversion, the self-inductance of the primary side transmitting coil is L1, the self-inductance of the secondary side receiving coil is L2, the mutual inductance between the primary side and the secondary side is M 12 , the series compensation capacitances of the primary side are C1 and C2, the series compensation capacitance of the secondary side is C3, the parallel compensation inductance of the primary side is L0, the equivalent load resistance is R e , the currents of the capacitances C1, C2 and C3 are I0, I1 and I3 respectively, and the current of the inductance L0 is I2.

[0053] Ignoring the parasitic parameters of the system, according to the resonance principle of the circuit, the following can be obtained:

[0054] ω represents the working angular frequency of the circuit.

[0055] The KVL and KCL equations are listed, and the voltage of the equivalent load is obtained, i.e. U o = -U I ω 2 M 12 C1 (2)

[0056] It can be seen that the output voltage is only related to the working frequency ω of the system, the series compensation capacitance C1 of the primary side, the mutual inductance M 12 and the input voltage U I of the system. When the system parameters remain unchanged, the system can realize constant voltage output independent of the load. When the primary side input of the CLC-S compensation topology is a constant voltage source, the output voltage is proportional to the input voltage, and the output voltage will become ω 2 M 12 C1 of the input voltage.

[0057] The S-CLC compensation topology is shown in Figure 2. In Figure 2, U I is the fundamental voltage after full-bridge inversion, the self-inductance of the primary side transmitting coil is L1, the self-inductance of the secondary side receiving coil is L2, the mutual inductance between the primary side and the secondary side is M 12, the primary side series compensation capacitor is C1, the secondary side series compensation capacitors are C2 and C3, the primary side parallel compensation inductor is L3, and the equivalent load resistance is R e , the currents of the capacitors C1, C2 and C3 are I0, I1 and I3 respectively, and the current of the inductor L3 is I2.

[0058] Similarly, the output characteristics of the S-CLC compensation topology can be obtained as follows:

[0059] As can be seen from the above formula, the output voltage is only related to the system operating frequency ω, the secondary side compensation capacitor C3, the mutual inductance M 12 and the system input voltage U I When the system parameters remain unchanged, the system can achieve constant voltage output independent of the system load. When the primary side input of the S-CLC compensation topology is a constant voltage source, the output voltage is proportional to the input voltage, and the constant voltage output will become 1 / (ω 2 M 12 C3) of the input voltage.

[0060] According to the above analysis, the output characteristics of the S-CLC compensation topology are opposite to those of the CLC-S compensation topology, so a hybrid topology with anti-offset capability can be constructed by using the CLC-S and S-CLC topology structures to improve the anti-offset performance of the MC-WPT system.

[0061] In order to make the MC-WPT system have constant current / constant voltage output characteristics when offset, the present example reorganizes the output end by using a variable structure to form an output end variable structure type T compensation topology, and changes the equivalent topology structure of the system by using the switching of the bidirectional switch to change the output characteristics of the system. When the load needs constant current charging, the output of the system presents constant current characteristics by changing the output end structure of the system through the bidirectional switch; when the load needs constant voltage charging, the output of the system presents constant voltage characteristics by changing the output end structure through the bidirectional switch.

[0062] The traditional T compensation topology structure is shown in FIG. 3. In FIG. 3, Z0, Z1 and Z2 are three parts of impedance, distributed in the three branches of the T circuit. Among them, U I and I0 are the input voltage and input current of the T topology, and U o and I1 are the output voltage and output current.

[0063] When Z1+Z2=0, the output characteristics of the T compensation topology structure are obtained according to Kirchhoff's law as follows: U o =I0Z2 (4)

[0064] As can be seen from the above formula, the output voltage varies linearly with the input current, and the T-type compensation topology can realize constant voltage output when the input is constant current input.

[0065] Similarly, when Z0+Z2=0, the input characteristics of the T-type compensation topology are analyzed, and the Kirchhoff voltage and current law can be obtained:

[0066] When Z0=﹣Z2, the output current varies linearly with the input voltage, and the T-type compensation topology can realize constant current output when the input is constant voltage input. Therefore, as long as Z0=﹣Z2=Z1 is satisfied, the T-type topology structure can realize constant voltage and constant current output conversion.

[0067] According to the characteristics of the T-type topology structure, the variable structure type T-type compensation topology shown in FIG. 4 is designed in this example. When switches S1 and S2 are closed, Z0=﹣Z2=Z1 is satisfied, the T-type topology is equivalent to FIG. 3, and constant voltage and constant current output conversion can be realized. When switches S1 and S2 are turned off, that is, Z2 in the T-type topology is cut off from the circuit, and Z3 is added to the circuit, Z0+Z1=﹣Z3=Z1 at this time, and the system output is the same as that without the T-type compensation topology, that is, the system output characteristics are not changed.

[0068] Based on the above analysis, the embodiment of the application provides a WPT system for realizing constant current and constant voltage output based on a variable structure type hybrid topology, as shown in FIG. 5, which includes a first transmitting coil L1, a second transmitting coil L3 in series, and a first receiving coil L2 and a second receiving coil L4 in parallel. In order to improve the anti-offset performance and system transmission efficiency, the first transmitting coil L1 is decoupled from other coils except for the first receiving coil L2, and the second transmitting coil L3 is decoupled from other coils except for the second receiving coil L4.

[0069] The system also includes a variable structure type hybrid topology, which includes a front-stage circuit composed of a CLC-S type resonant network and an S-CLC type resonant network, and a variable structure type T-type topology as a back-stage circuit.

[0070] The CLC-S type resonant network includes a first CLC type network connected to the first transmitting coil L1 and a first S type network connected to the first receiving coil L3, and the S-CLC type resonant network includes a second S type network connected to the second transmitting coil L2 and a second CLC type network connected to the second receiving coil L4.

[0071] The variable structure type T-type topology is connected in parallel to the first S type network and the second CLC type network; and the variable structure type T-type topology is used for switching to a constant current output topology or a constant voltage output topology.

[0072] As an example, the constant current output topology is an LCL type T-network composed of two inductors and one capacitor. The constant voltage output topology is composed of two inductors and one capacitor connected in series.

[0073] As an example, as shown in Fig. 5, the variable structure T-network topology includes an inductor L6, an inductor L7 and a capacitor C7 connected in series between the one end of the output of the pre-stage circuit and the equivalent load resistor R e , and further includes a capacitor C6 connected between the other end of the inductor L6 and the inductor L7, i.e. the other output of the pre-stage circuit, and further includes a bidirectional switch S1 connected in series on the branch of the capacitor C6 and a bidirectional switch S2 connected in parallel across the capacitor C7. When the bidirectional switches S1 and S2 are closed, the variable structure T-network topology is switched to the constant current output topology, and when the bidirectional switches S1 and S2 are opened, the variable structure T-network topology is switched to the constant voltage output topology. e

[0074] As an example, the first CLC type network includes a capacitor C0 and a capacitor C1 connected in series between the first output of the equivalent AC source and the same name end of the first transmitting coil L1, and an inductor L0 connected between the common end of the capacitor C0 and the capacitor C1 and the different name end of the first transmitting coil L1, and the different name end of the first transmitting coil L1 is connected to the same name end of the second transmitting coil L3; the second S type network includes a capacitor C3 connected between the different name end of the second transmitting coil L3 and the second output of the equivalent AC source.

[0075] As an example, the second CLC type network includes a capacitor C4 and a capacitor C5 connected in series between the same name end of the second receiving coil L4 and an inductor L6, and an inductor L5 connected between the common end of the capacitor C4 and the capacitor C5 and the different name end of the second receiving coil L4, and the different name end of the second receiving coil L4 is connected to the other end of the equivalent load resistor R e ; the first S type network includes a capacitor C2 connected between the different name end of the first receiving coil L2 and the inductor L6.

[0076] In Fig. 5, U in , U out1 , U out2 represent the AC input voltage, the output voltage of the pre-stage circuit and the output voltage of the post-stage circuit respectively, the currents of C0, C1, C2, C4, C5, L6, C6 are I0, I1, I2, I3, I4, I5, I6 respectively, the system output current is I out , and R E is the equivalent resistance of the post-stage circuit and the equivalent load resistor R e . M ij represents the mutual inductance between L i and L j , i, j = 1, 2, 3, 4, i ≠ j.​

[0077] In this example, the input terminals of CLC-S and S-CLC topologies are connected in series, and the output terminals are connected in parallel, which is the front-stage circuit and is mainly used to improve the anti-offset performance of the system. On this basis, a variable structure T-type compensation topology is added to the output terminal to form a rear-stage T-type circuit. This circuit is composed of two compensation inductors, two compensation capacitors and two bidirectional switches to change the output unit structure of the hybrid topology circuit to achieve the purpose of constant current / constant voltage switching. Next, the constant current / constant voltage output characteristics of the system are analyzed according to the state of bidirectional switch S.

[0078] When the bidirectional switches S1 and S2 in Figure 5 are closed, the equivalent hybrid topology circuit is shown in Figure 6, which is in constant current mode. According to the circuit resonance principle, we can get:

[0079] Ignoring the internal resistance of each part of the system, the circuit analysis gives:

[0080] In the above formula,

[0081] When the cross-coupling effect can be ignored, substituting equation (8) into equation (7) gives the output current and input impedance as:

[0082] The output current is independent of the load value, and the proposed variable structure hybrid topology can achieve constant current output under constant input voltage. When the MC-WPT system is offset, the mutual inductance M 12 , M 34 will decrease, while M 12 , C0 and M 34 , C5 change in opposite directions. At this time, the CLC-S topology will increase the output current, and the S-CLC topology will reduce the output current. Therefore, for the hybrid topology, the output current of the system can be kept constant by reasonable design of system parameters.

[0083] When the bidirectional switches S1 and S2 in Figure 5 are open, the equivalent hybrid topology circuit is shown in Figure 7, which is in constant voltage mode. Similarly, we can get the output voltage of the system as:

[0084] According to the above formula, it can be seen that the input impedance of the system in constant voltage mode is purely resistive, indicating that the system can achieve ZPA in normal operation, reduce reactive power and improve system transmission efficiency. When the cross-coupling M 13 , M 14 , M 23 , M 24The influence can be ignored, as can be seen from formula (10), in the absence of offset, the system can achieve constant voltage output independent of load, and the mutual inductance M 12 、M 34 presents an opposite trend. Therefore, when the MC-WPT system is offset, causing the mutual inductance to fluctuate, the system output voltage can remain unchanged by reasonably optimizing the system compensation parameters, thereby improving the anti-offset capability of the MC-WPT system.

[0085] According to the characteristics of the DDQ type coil, M DDQ ≈0 (the mutual inductance between the DD type coil and the Q type coil is about 0, i.e., the mutual decoupling), that is, in the DDQ type coil, the mutual inductance between the DD type coil and the Q type coil in the primary transmitting coil is about 0. Theoretically, the same side cross coupling M 13 and M 24 are about 0 when the coil is offset in any direction, while the opposite side cross coupling M 14 , M 23 is 0 only when the coil is offset in the Y or Z direction, and the change in self-inductance can be ignored when the coil is offset. Therefore, to meet the design requirements of the coupling mechanism, the DDQ type coil structure is adopted in this example. Therefore, a DDQ type magnetic coupling mechanism for electric vehicle wireless charging is designed as shown in FIG. 8, wherein the first transmitting coil L1 and the first receiving coil L2 adopt DD type coils, the second transmitting coil L3 and the second receiving coil L4 adopt Q type coils, the coordinate axes are as follows: the arrangement direction of the DD coil of the first transmitting coil L1 is the X axis, the wireless transmission gap is the Y axis, the perpendicular to the X and Z axes is the X axis, and the center of the transmitting end DDQ type coil is the coordinate origin.

[0086] As an example, the outer size of the DDQ type coil is 40 cm*40 cm, the number of turns of the DD type coil is 7 turns, the number of turns of the Q type coil is 10 turns, the Y axis inner diameter of the DD type coil is selected as 38 cm, the X axis inner diameter is selected as 11 cm, the inner diameter of the Q type coil is selected as 34 cm, and the transmission distance is 15 cm.

[0087] The measured parameters of the DDQ type coil designed in this example during the offset process are shown in FIGS. 9, 10, and 11. During the Y axis and Z axis offset process, the cross coupling is basically 0. FIG. 9 shows the mutual inductance change curve during the Y axis offset process, and the X axis and Z axis are not offset. During the Y axis offset process, as the offset distance increases, the main mutual inductance gradually decreases, and the remaining cross coupling is basically 0.

[0088] FIG. 10 shows the mutual inductance change curve during the X axis offset process, and the Y axis and Z axis are not offset. During the X axis offset process, as the offset distance increases, the mutual inductance M 34 of the Q type coil gradually decreases, and the mutual inductance M 12The cross coupling M between the primary DD type coil and the secondary Q type coil gradually increases 14 The cross coupling M between the primary Q type coil and the secondary DD type coil gradually increases 23 The cross coupling M between the primary DD type coil and the secondary Q type coil gradually increases 13 The cross coupling M between the primary DD type coil and the secondary Q type coil gradually increases 24 The cross coupling M between the primary DD type coil and the secondary Q type coil gradually increases

[0089] Figure 11 shows the mutual inductance variation curve during the Z-axis offset process, and the X-axis and Y-axis are not offset. During the Z-axis offset process, as the offset distance increases, the main mutual inductance M 12 , M 34 gradually decreases, and the remaining cross couplings are basically zero.

[0090] In order to improve the anti-offset effect of the variable structure type hybrid topology structure during the wireless charging of the electric vehicle, the compensation parameters in the circuit need to be optimized and designed. Therefore, in order to simplify the analysis, the parameters of the main circuit in the constant voltage mode are designed first, and then the parameters of the T type topology circuit in the constant current mode are designed.

[0091] In order to simplify the analysis, the main mutual inductance M 12 , M 34 of the DDQ type coil is equivalent within a certain offset range: M 34 =aM 12 +b (11)

[0092] a and b represent the fitting coefficients, which are constants.

[0093] The mutual inductance values during the Y-axis offset are fitted by using MATLAB, and the relationship between the fitted mutual inductances M 34 and M 12 is as follows: M 34 =1.506M 12 -12.009×10 -6 (12)

[0094] The output voltage gain is defined as:

[0095] According to the above formula, the relationship between the system output voltage gain and the mutual inductance M 12 when the Y-axis is offset is shown in Figure 12. As can be seen from Figure 12, the output voltage gain G V first increases and then decreases with the increase of the mutual inductance M 12 .

[0096] According to the analysis in the foregoing, the following relationship formula can be determined:

[0097] ① In the constant voltage mode, the voltage gain of the system when there is no offset is G VRWhen the system is offset in Y-axis, the deviation of system voltage gain must be controlled within a certain range, which is generally defined as G Vmax = (1 + a)G VR , G Vmin = (1 - a)G VR , the proportional factor a = 5%, that is, G Vmax is defined as the maximum voltage gain during the offset process, and G Vmin is the minimum voltage gain during the offset process.

[0098] ② When the coil is not offset in Y-axis, the system mutual inductance has a maximum value M 12max , M 34max , when the system offset reaches 50% of the coil size, the system mutual inductance has a minimum value M 12min , M 34min , and the self-inductance of the primary and secondary sides of the system remains unchanged during the offset process. Therefore, when the system is not offset, the following relationship exists:

[0099] ③ In Figure 12, the system mutual inductance corresponding to the maximum output voltage gain G VM is M 12m , that is, G VM = G V (M 12m ).

[0100] The relationship between mutual inductance and self-inductance can be determined by taking the derivative at the gain inflection point in Figure 12, that is:

[0101] Solving the above equation gives:

[0102] From Figure 12, when the system is offset, the output voltage gain first increases and then decreases within the mutual inductance range, and at this time the system compensation parameters satisfy the following relationship:

[0103] From equations (14), (16) and (17), the value range of the system compensation parameter L5 can be obtained. For each value of the compensation inductance L5 during the system offset process, the maximum value of the coil current with respect to the inductance L5 can be found, and the relationship curve between the maximum coil current and the self-inductance L5 is shown in Figure 13.

[0104] From Figure 13, it can be seen that during the system offset process, when the value of the compensation inductance L5 is 62.95uH (at the intersection of I1 and I2), the primary and secondary coil currents I1, I2, I3 and I4 have minimum values, which can reduce the loss of the coil and the device, and thus improve the transmission efficiency of the MC-WPT system. Therefore, according to equation (16), the value of the inductance L0 is 7.228uH, and according to the resonance relationship equation (6), the values of the remaining compensation parameters can be obtained.

[0105] Based on the above analysis, the variable structure hybrid topology circuit proposed in this example is based on the constant voltage output of the preceding circuit. The constant voltage is converted to constant current through the subsequent T-type topology. Therefore, the parameters of the main circuit in constant current mode are the same as those in constant voltage mode. The inductance and capacitance parameters of the T-type topology circuit are given by equations (6) and (9) (M 12 and M 34 The parameters have already been determined under the previous parameter settings, so the parameters can be determined based on the output current during constant current charging.

[0106] Therefore, the parameters of the variable structure hybrid topology can be determined through the following steps:

[0107] When the system outputs a constant voltage, the parameters of the variable structure hybrid topology are determined through the following steps:

[0108] Determine the inductors L1, L2, L3, and L4 based on actual needs;

[0109] Mutual inductance M within a preset offset range 12 M 34 The relationship is fitted (as shown in equation (11));

[0110] Based on the fitted mutual inductance M 12 M 34 Relationship calculation and mutual inductance M 12 The output voltage gain G related to inductors L0 and L5 V (as in equation (13));

[0111] Based on the output voltage gain G during offset V Mutual inductance M 12 The relationship (as shown in equation (13)) is that at the gain inflection point M 12m For output voltage gain G V Differentiate (as in equation (15)) to determine M 12m The relationship with inductors L0 and L5 (as shown in equation (16));

[0112] According to M at the gain inflection point 12m Maximum gain G VM The gain value G when the system has no offset VR Determine the output voltage gain G V Maximum allowable value G max With the minimum allowable value G min And according to G max G min and output voltage gain G V Mutual inductance M 12 The relationship (as shown in equation (17)) determines M 12The range of values ​​for;

[0113] According to M 12 The range of values ​​for M and 12 The relationship between inductances L0 and L5 determines the range of values ​​for inductance L5;

[0114] The value of inductor L5 is determined as follows: within the range of inductor L5, the value at which the currents of the transmitting coil and the receiving coil intersect;

[0115] Based on the determined inductance L5 and M 12m The value of inductance L0 is determined by the relationship between inductances L0 and L5 (as shown in equation (16));

[0116] The values ​​of inductor L6 and capacitors C0, C1, C2, C3, C4, C5, and C6 are determined based on the system resonance relationship.

[0117] When the system outputs a constant current, the parameters of the variable structure hybrid topology are determined through the following steps:

[0118] The parameters of the preamplifier circuit when setting constant current output are the same as those when setting constant voltage output.

[0119] Based on the system output current I out The relationship with inductor L7 determines the value of inductor L7;

[0120] The values ​​of inductor L6 and capacitors C6, C7, and C8 are determined based on the resonance relationship.

[0121] Based on the analysis and parameter design above, an experimental setup was constructed. The primary-side transmitting coil and secondary-side receiving coil of the DDQ coupling mechanism have the same parameters, as shown in Table 1. The circuit compensation parameters are also shown in Table 1, where f is the system operating frequency.

[0122] Table 1 MC-WPT System Parameters

[0123] Figure 14(a) shows the system inverter and output waveforms in the constant current mode when the system is facing forward, with an equivalent load resistance of 5Ω. Figure 14(b) shows the system inverter and output waveforms in the constant current mode when the Y-axis is offset by 22cm, with an equivalent load resistance of 20Ω. From the system inverter and output waveforms in the constant current mode in Figure 14 (facing forward and offset), it can be seen that when the equivalent load resistance and offset distance change, the system output current can remain at around 7A, indicating that the system has good anti-offset performance in constant current mode.

[0124] As shown in FIG. 15, the system output current (FIG. 15(a)) and the transmission efficiency curve (FIG. 15(b)) when the load changes and the Y-axis shifts in the constant current mode. In the experiment, the equivalent load resistance of the system is selected as 5Ω-20Ω. When the MC-WPT system shifts in the Y-axis, the system output current first increases and then decreases. When the shift range is ±55%, the system output current has a minimum value of 6.66A, and the fluctuation is within 5%, which meets the performance requirements of the MC-WPT system against the shift. As shown in FIG. 15(b), when the system shifts, the system transmission efficiency gradually decreases, but all can have a high efficiency, and the highest efficiency reaches 93.7%.

[0125] As shown in FIG. 16(a), the system inverter waveform and output waveform in the constant voltage mode under the state of facing each other. At this time, the equivalent load resistance of the system is 20Ω. FIG. 16(b) is the system inverter waveform and output waveform when the Y-axis shifts by 22cm in the constant voltage mode. At this time, the equivalent load resistance of the system is 80Ω. As shown in the system inverter waveform and output waveform of the constant voltage mode when the system shifts in the Y-axis, when the system load and the shift distance change, the system output voltage can be maintained at about 150V, which shows that the anti-shift effect of the system in the constant voltage mode is good, and the system input impedance is weak inductive, which is beneficial to realize the soft switching of the inverter and improve the system transmission efficiency.

[0126] As shown in FIG. 17, the system output voltage (FIG. 17(a)) and the transmission efficiency curve (FIG. 17(b)) when the load changes and the Y-axis shifts. In the experiment, the equivalent load resistance is selected as 20Ω-80Ω. Taking 150V as the system output voltage reference value, when the equivalent load resistance is 20Ω and the Y-axis shifts by ±22cm, the shift range is ±55%, the system output voltage has a minimum value of 142.8V, and the output voltage fluctuation is within 5%, which meets the performance requirements of the MC-WPT system against the shift. As shown in FIG. 17(b), when the system shifts, the system transmission efficiency gradually decreases, but all can have a high efficiency, and the highest transmission efficiency can reach 94%.

[0127] In summary, the embodiment of the present application provides a WPT system for realizing constant current and constant voltage output based on a variable structure type hybrid topology, which has the characteristics of constant voltage output independent of the load based on the CLC-S and S-CLC topology circuits, and the output current and mutual inductance are positively and negatively correlated, respectively, and the characteristics of constant current / constant voltage output conversion of the variable structure type T topology, designs a variable structure type hybrid wireless charging topology based on parameter optimization, and analyzes that the topology has the characteristics of anti-offset constant current output when the cross coupling is zero, selects the DDQ type coil as the coupling mechanism, realizes the cross decoupling of the coupling mechanism on the same side and the opposite side, through the design of appropriate compensation parameters, makes the fluctuation range of the output current / voltage of the system within 5% within the range of 55% offset in the Y direction, realizes the constant current / constant voltage output of the system under the condition of large range offset of the coupling mechanism, and the system has almost no reactive input. The experimental results show that the 1kW system prototype built in the example has a certain anti-offset capability and good constant current and constant voltage output characteristics in the Y direction.

[0128] The above embodiment is a preferred embodiment of the present application, but the embodiments of the present application are not limited by the above embodiment, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods, and all shall be included in the protection scope of the present application.

Claims

The WPT system based on a variable structure type hybrid topology to realize constant current and constant voltage output, characterized in that, The system comprises a first transmitting coil L1, a second transmitting coil L3 connected in series, and a first receiving coil L2 and a second receiving coil L4 connected in parallel, wherein the first transmitting coil L1 is decoupled from other coils except for the first receiving coil L2, and the second transmitting coil L3 is decoupled from other coils except for the second receiving coil L4; the system further comprises a variable-structure hybrid topology, which comprises a pre-stage circuit composed of a CLC-S type resonant network and an S-CLC type resonant network, and a variable-structure T type topology as a post-stage circuit; the CLC-S type resonant network comprises a first CLC type network connected to the first transmitting coil L1 and a first S type network connected to the first receiving coil L3, and the S-CLC type resonant network comprises a second S type network connected to the second transmitting coil L2 and a second CLC type network connected to the second receiving coil L4; the variable-structure T type topology is connected in parallel to the first S type network and the second CLC type network; and the variable-structure T type topology is used for switching to a constant-current output topology or a constant-voltage output topology. The WPT system for realizing constant-current and constant-voltage output based on a variable-structure hybrid topology according to claim 1, characterized in that, The constant-current output topology is an LCL type T type network composed of two inductors and one capacitor. The WPT system for realizing constant-current and constant-voltage output based on a variable-structure hybrid topology according to claim 1, characterized in that: The constant-voltage output topology is composed of two inductors and one capacitor connected in series. The WPT system for realizing constant-current and constant-voltage output based on a variable-structure type hybrid topology according to any one of claims 1-3, characterized in that, The variable-structure type T topology comprises an inductor L6, an inductor L7, and a capacitor C7 connected in series between an output end of the pre-stage circuit and an equivalent load resistor R e The variable-structure type T topology comprises an inductor L6, an inductor L7, and a capacitor C7 connected in series between an output end of the pre-stage circuit and an equivalent load resistor R e The variable-structure type T topology comprises an inductor L6, an inductor L7, and a capacitor C7 connected in series between an output end of the pre-stage circuit and an equivalent load resistor R e The variable-structure type T topology comprises an inductor L6, an inductor L7, and a capacitor C7 connected in series between an output end of the pre-stage circuit and an equivalent load resistor R e The variable-structure type T topology comprises an inductor L6, an inductor L7, and a capacitor C7 connected in series between an output end of the pre-stage circuit and an equivalent load resistor R e The variable-structure type T topology comprises an inductor L6, an inductor L7, and a capacitor C7 connected in series between an output end of the pre-stage circuit and an equivalent load resistor R e The WPT system for realizing constant-current and constant-voltage output based on a variable-structure hybrid topology according to claim 4, characterized in that, The first CLC type network comprises a capacitor C0 and a capacitor C1 connected in series between equivalent AC source first output terminals and like-named terminals of the first transmitting coil L1, and an inductor L0 connected between common terminals of the capacitor C0 and the capacitor C1 and unlike-named terminals of the first transmitting coil L1, wherein the unlike-named terminals of the first transmitting coil L1 are connected to like-named terminals of the second transmitting coil L3; and the second S type network comprises a capacitor C3 connected between unlike-named terminals of the second transmitting coil L3 and equivalent AC source second output terminals. The WPT system for realizing constant-current and constant-voltage output based on a variable-structure hybrid topology according to claim 5, characterized in that, said second CLC type network comprising a capacitor C4, a capacitor C5 connected in series order between the homonymic terminals of said second receiving coil L4 and an inductance L6, and an inductance L5 connected between the common terminals of the capacitor C4 and the capacitor C5 and the heteronymic terminals of said second receiving coil L4, the heteronymic terminals of said second receiving coil L4 being connected to the other terminals of said equivalent load resistance R e ; said first S type network comprising a capacitor C2 connected between the heteronymic terminals of said first receiving coil L2 and the inductance L6. The WPT system for realizing constant-current and constant-voltage output based on a variable-structure hybrid topology according to claim 6, characterized in that, The parameters of the variable-structure hybrid topology are determined according to the circuit resonance principle. The WPT system for realizing constant-current and constant-voltage output based on a variable-structure hybrid topology according to claim 7, characterized in that, When the system outputs constant voltage, the parameters of the variable-structure hybrid topology are determined by the following steps: The inductors L1, L2, L3 and L4 are determined according to actual requirements; fitting a relationship of M 12 , M 34 , M 12 represents a mutual inductance between the first transmitting coil L1 and the first receiving coil L2, M 34 represents a mutual inductance between the second transmitting coil L3 and the second receiving coil L4, within a predetermined offset range According to the relationship of the mutual inductance M 12 , M 34 , the output voltage gain G 12 , the inductance L0, the inductance L5 related to the mutual inductance M V is calculated. Based on the output voltage gain G during offset V Mutual inductance M 12 The relationship at the gain inflection point M 12m For output voltage gain G V Differentiate and determine M 12m Relationship with inductors L0 and L5; The allowable maximum value G V and the allowable minimum value G max of the output voltage gain G min are determined according to the gain maximum value G VM at the gain inflection point M 12m and the gain value G VR when the system is not deviated, and the value range of M 12 is determined according to the relationship between G max , G min and the output voltage gain G V and mutual inductance M 12 . According to M 12 the value range of M 12 The relationship between the inductance L0 and L5 determines the value range of the inductance L5. The inductor L5 is determined to be a value at which the currents of the transmitting coil and the receiving coil intersect within a value range of the inductor L5; According to the determined inductance L5 and M 12m The value of inductance L0 is determined in relation to inductances L0, L5; The inductor L6 and the capacitors C0, C1, C2, C3, C4, C5 and C6 are determined according to the system resonance relationship; When the system outputs constant current, the parameters of the variable-structure hybrid topology are determined by the following steps: The parameters of the pre-stage circuit when outputting constant current are set to be consistent with the parameters of the pre-stage circuit when outputting constant voltage; According to the system output current I out The relationship with the inductance L7 determines the value of the inductance L7; The inductor L6 and the capacitors C6, C7 and C8 are determined according to the resonance relationship. The WPT system for realizing constant-current and constant-voltage output based on a variable-structure hybrid topology according to claim 8, characterized in that, When the system is constant voltage output, M is determined by the following formula 12 The value range of M: wherein M 12min and M 12max respectively represent the minimum value of M 12 when the system is offset within a preset offset range and the maximum value of M 12 when the system is not offset, G V (M 12max ) represents the G 12max value at M V , G V (M 12min ) represents the G 12min value at M V , and a represents a proportional factor; When the system is constant current output, the output current I out The relationship with the inductance L7 is: where U in represents the system AC input voltage. The WPT system for realizing constant-current and constant-voltage output based on a variable-structure type hybrid topology according to claim 8, characterized in that: The first transmitting coil L1 and the second transmitting coil L3 adopt DDQ type coils, and the first receiving coil L2 and the second receiving coil L4 adopt DDQ type coils.

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