Wireless charging system with variable topology structure of variable capacitor on the receiving side

Abstract

To provide a wireless charging system having a variable topology structure of a variable capacitor on a reception side.SOLUTION: An inverter is connected to an input end of a LCL-S type resonator compensation network, and an output end of the LCL-S type resonator compensation network is connected in cascade connection with a T-type resonance compensation network, can be placed in a constant current charging mode. The T-type resonance compensation network is connected to a commutator, and a capacitor CS2 branch circuit is added to the T-type resonance compensation network. A capacitor CSt is connected in parallel to a capacitor CS1 branch circuit of the T-type resonance compensation network, which becomes equivalent to one capacitor branch circuit of a F-type resonance compensation network. The capacitor CS2 is connected in series to a switch S1, the capacitor CSt is connected in series to a switch S2. The switches S1 and S2 are switched on simultaneously, so that the T-type resonance compensation network is converted into the F-type resonance compensation network and placed in the contant voltage charging mode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of wireless charging, and more particularly to a wireless charging system with a variable topology structure of a variable capacitor on the receiving side. [Background technology]

[0002] Currently, the mainstream wireless charging technology for electric vehicles is a two-stage charging method that combines constant current and constant voltage (CC-CV). To quickly and smoothly switch from constant current charging mode to constant voltage charging mode, complex control methods such as DC-DC converters, frequency conversion control, and phase shift control are often used. However, most of these methods require communication between the transmitting and receiving ends, which significantly increases the difficulty and cost of system control. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE INVENTION The present invention aims to provide a wireless charging system with a variable topology structure of a variable capacitor on the receiving side, in order to solve the problems of difficulty in system control and high cost. [Means for solving the problem]

[0004] To achieve the above objectives, the present invention provides the following solutions:

[0005] A wireless charging system with a variable topology structure of a variable capacitor on a receiving side, comprising: an inverter, an LCL-S type resonant compensation network, a T type resonant compensation network, an F type resonant compensation network, a rectifier, and a charging load; the inverter is connected to an input end of the LCL-S type resonant compensation network, and the inverter is used to output an AC voltage source as an input excitation of the LCL-S type resonant compensation network; The output end of the LCL-S type resonant compensation network is cascaded with the T type resonant compensation network to form a constant current charging mode, and the T type resonant compensation network is connected to the rectifier; The T-type resonant compensation network is connected to a capacitor C S2 Add a branch circuit and a capacitor C S1 Capacitor C in the branch circuit St are connected in parallel to form a capacitor branch circuit equivalent to one of the F-type resonant compensation networks, and the capacitor C S2 The branch circuit is connected in series with the switch S1 and the capacitor C St is connected in series with switch S2, and at the same time, switches S1 and S2 are turned on to convert the T-type resonant compensation network into the F-type resonant compensation network, and enter a constant voltage charging mode, in which the F-type resonant compensation network is connected to the rectifier, and the rectifier is connected to the charging load.

[0006] Optionally, the LCL-S type resonant compensation network specifically includes a transmitting side compensation network and a receiving side compensation network; The transmitter compensation network includes a compensation inductance L P1 , compensation capacitor C P , the self-inductance of the transmitting coil L P and the compensation inductance L P1 One end of the compensation inductance L is connected to the inverter. P1 The other end of the compensation capacitor C P and the self-inductance L of the transmitting coil P and the compensation capacitor C P The other end of the inverter and the transmission coil inductance L P are connected to the other end of each The receiving side compensation network includes the self-inductance L of the receiving coil. S and compensation capacitor C S and the self-inductance L of the receiving coil. S One end of the compensation capacitor CS and the self-inductance L of the receiving coil is connected to one end of the S The other end of the capacitor C S2 Branch circuit, parallel capacitor C S1 Branch circuit, capacitor C St and the compensation capacitor C S The other end of the resonant compensation network is connected to the switch S1 and the inductance L S1 is connected to one end of the

[0007] Optionally, the T-type resonant compensation network specifically comprises an inductance L S1 , capacitor C S1 and inductance L S2 Including, The inductance L S1 The other end of the capacitor C S1 and one end of the inductance L S2 connected to one end of the inductance L S2 The other end is connected to the rectifier, and the other end is connected to the capacitor C S1 The other end of the receiving coil is connected to the self-inductance L S is connected to the other end of the

[0008] Optionally, the F-type resonant compensation network specifically comprises: Based on the T-type resonant compensation network, the inductance L S1 The other end of the capacitor C S1 and one end of the inductance L S2 One end of the switch S2 is further connected to the switch S2.

[0009] Optionally, a real-time voltage U across said charging load L Detects the real-time voltage U L is the threshold voltage U for constant current / constant voltage charging ref , the switch S1 and the switch S2 are turned on, and the charging mode changes from a constant current charging mode to a constant voltage charging mode, but the real-time voltage across the charging load does not change.

[0010] Optionally, turning off the switch S1 and the switch S2 to enter the constant current charging mode; In the constant current charging mode, the input impedance of the wireless charging system with a variable topology structure of a variable capacitor on the receiving side is

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[0011] Optionally, turning on the switch S1 and the switch S2 to enter the constant voltage charging mode; In the constant voltage charging mode, the input impedance of the wireless charging system with a variable topology structure of a variable capacitor on the receiving side is

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[0012] According to specific embodiments provided by the present invention, the present invention provides the following technical effects: The present invention provides a wireless charging system with a variable topology structure of a variable capacitor on the receiving side, and controls a changeover switch to turn on and off the compensation capacitor on the receiving side, thereby changing the topology structure of the resonant compensation circuit on the receiving side and realizing charging switching from constant current mode to constant voltage mode. The present invention can maintain a zero phase angle (ZPA) state in both the constant current charging phase and the constant voltage charging phase, with little reactive power introduction and no need for communication between the transmitting side and the receiving side, thereby reducing the difficulty and cost of system control. [Brief explanation of the drawings]

[0013] In order to more clearly describe the embodiments of the present invention or the technical solutions of the prior art, the following briefly describes the drawings that need to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those skilled in the art can also obtain other drawings based on these drawings without creative efforts.

[0014] [Figure 1] FIG. 1 is a circuit diagram of a wireless charging system with a variable topology structure of a variable capacitor on the receiving side. [Figure 2] This is a circuit diagram of an LCL-S type resonant compensation network. [Figure 3] 3A and 3B are equivalent circuit diagrams of the LCL-S type resonant compensation network, where Fig. 3A is the equivalent circuit diagram of the first LCL-S, Fig. 3B is the equivalent circuit diagram of the second LCL-S, and Fig. 3C is the mutual inductance equivalent circuit diagram of the receiving side of the LCL-S. [Figure 4] 4A is a circuit diagram of a T-type resonant compensation network excited by a constant voltage source, and FIG. 4B is a circuit diagram of a T-type resonant compensation network excited by a constant current source. [Figure 5] FIG. 1 is an F-type resonant compensation network circuit diagram. [Figure 6] FIG. 1 is a constant current topology circuit diagram. [Figure 7] FIG. 1 is a constant voltage topology circuit diagram. [Figure 8] FIG. 1 is a topology circuit diagram of an LCL-ST type constant current system. [Figure 9] FIG. 1 is an equivalent circuit diagram of an LCL-ST type constant current system. [Figure 10] FIG. 1 is a topology circuit diagram of an LCL-SF type constant voltage system. [Figure 11] FIG. 1 is an equivalent circuit diagram of an LCL-SF type constant voltage system. [Figure 12] FIG. 1 is a switch control logic diagram. [Figure 13] FIG. 1 is a SIMULINK (registered trademark) simulation model diagram of the LCL-S-(T / F) composite compensation system. [Figure 14] Schematic diagram of the experimental platform for the LCL-S-(T / F) type composite compensation system. [Figure 15] These are simulation waveforms in constant current mode. Figure 15(a) is a simulation waveform of the inverter output voltage and current when RL = 12Ω in constant current mode, Figure 15(b) is a simulation waveform of the inverter output voltage and current when RL = 24Ω in constant current mode, Figure 15(c) is a simulation waveform of the load current when RL = 12Ω in constant current mode, and Figure 15(d) is a simulation waveform of the load current when RL = 24Ω in constant current mode. [Figure 16] Figure 16 shows experimental waveforms in constant current mode. Figure 16(a) shows the experimental waveforms of the inverter output voltage and current when RL = 13.6 Ω in constant current mode, and Figure 16(b) shows the experimental waveforms of the inverter output voltage and current when RL = 24 Ω in constant current mode. [Figure 17]These are simulation waveforms in constant voltage mode. Figure 17(a) is a simulation waveform of the inverter output voltage and current when RL = 24 Ω in constant voltage mode, Figure 17(b) is a simulation waveform of the inverter output voltage and current when RL = 120 Ω in constant voltage mode, Figure 17(c) is a simulation waveform of the load voltage when RL = 24 Ω in constant voltage mode, and Figure 17(d) is a simulation waveform of the load voltage when RL = 120 Ω in constant voltage mode. [Figure 18] Figure 18(a) shows the experimental waveforms of the inverter output voltage and current when RL=24Ω in constant voltage mode, and Figure 18(b) shows the experimental waveforms of the inverter output voltage and current when RL=65Ω in constant voltage mode. [Figure 19] 1 is a curve diagram showing how the charging current and charging voltage of the system change depending on the charging load. [Figure 20] 1 is a graph showing the change in charging efficiency and charging power of the system depending on the charging load resistance. [Figure 21] 3A and 3B are waveform diagrams of the inverter output voltage, current, and load voltage output when switching. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention, and obviously, the described embodiments are only a part of the embodiments of the present invention, and are not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts are included in the scope of protection of the present invention.

[0016] The present invention aims to provide a wireless charging system with a variable topology structure of a variable capacitor on the receiving side, which does not require communication between the transmitting side and the receiving side and reduces the difficulty and cost of system control.

[0017] In order to make the above objects, features and advantages of the present invention more apparent and comprehensible, the present invention will be described in more detail below with reference to the drawings and detailed description of the invention.

[0018] As shown in Figure 1, the present invention provides a wireless charging system with a variable topology structure of a variable capacitor on the receiving side. The wireless charging system with a variable topology structure of a variable capacitor on the receiving side is a constant current / constant voltage wireless power transfer (WPT) system based on an LCL-S-(T / F) type circuit composite compensation topology, and includes an inverter, an LCL-S type resonant compensation network, a T type resonant compensation network, an F type resonant compensation network, a rectifier, and a charging load. The inverter is connected to the input end of the LCL-S type resonant compensation network, and is used to output an AC voltage source as input excitation for the LCL-S type resonant compensation network. The output end of the LCL-S type resonant compensation network is cascaded with the T type resonant compensation network to enter a constant current charging mode. The T type resonant compensation network is connected to the rectifier, and a capacitor C is connected to the T type resonant compensation network. S2 Add a branch circuit and a capacitor C S1 Capacitor C in the branch circuit St are connected in parallel to form a capacitor branch circuit equivalent to one of the F-type resonant compensation networks, and the capacitor C S2 The branch circuit is connected in series with the switch S1 and the capacitor C St is connected in series with switch S2, and at the same time, switches S1 and S2 are turned on to convert the T-type resonant compensation network into the F-type resonant compensation network, and enter a constant voltage charging mode, in which the F-type resonant compensation network is connected to the rectifier, and the rectifier is connected to the charging load.

[0019] In practical applications, Figure 2 is the circuit diagram of the LCL-S type resonant compensation network, and Figure 3 is the equivalent circuit diagram of the LCL-S type resonant compensation network. As shown in Figures 2 and 3, U P(vector) is the inverter output voltage with angular frequency ω, and the sender compensation network consists of a compensation inductance L P1 , compensation capacitor C P , the self-inductance of the transmitting coil L P The receiver compensation network is composed of the self-inductance L of the receiver coil. S , compensation capacitor C S It consists of: P (vector) is the current flowing through the transmitting coil, R1 is the load resistance, U R1 (vector) is the voltage across the load resistor, I R1 (vector) represents the current flowing through the load resistance, M represents the mutual inductance between the transmitting coil and the receiving coil, and the parameters of the LCL-S type resonant compensation circuit satisfy the following relationship:

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[0020] From equation (7), the voltage across the load resistor is given by the high frequency voltage source U P (vector), the mutual inductance M between the primary and secondary coils, and the primary compensation inductor L P1 It can be seen that this is only related to the load R1 and is not related to the charging load R1. In other words, the LCL-S type resonant compensation circuit exhibits constant voltage output characteristics equivalent to a constant voltage source and can meet the constant voltage characteristic requirements of the charging load. Furthermore, from equation (9), it can be seen that the input impedance of the system is purely resistive, and the current and voltage satisfy the ZPA characteristics.

[0021] The output characteristics of the T-type resonant compensation circuit are analyzed as follows. As shown in Figure 4(a) and (b), the T-type resonant compensation circuit is connected to a constant voltage source U S (vector) and constant current source iS (vector), of which the compensation inductor L S1 , L S2 and compensation capacitor C S1 form a T-type compensation network excited by a constant voltage source, and the compensation inductor L S1 ', L S2 ' and compensation capacitor C S1 ' forms a T-type compensation network excited by a constant current source, R2 and R2' are load resistors, and i R2 (vector) and i R2 ' (vector) is the current flowing through the load resistor, and U R2 (vector) represents the voltage across the load resistor R2', and the parameters of the T-type resonant compensation circuit excited by a constant voltage source and a constant current source satisfy the following relationship:

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[0022] From equation (13), when a constant voltage source is used as the excitation source for the T-type resonant compensation circuit, the output current at the load end i R2 It can be seen that (vector) is independent of the size of the load R2, has constant current output characteristics, and externally corresponds to a constant current source.

[0023] As shown in Figure 4(b), when a constant current source is used as the excitation source for the T-type resonant compensation circuit, the following equation is obtained from the KVL law:

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[0024] The input impedance of the T-type resonant compensation circuit excited by the constant voltage source can be calculated as follows:

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[0025] The constant voltage output characteristics of the F-type resonant compensation circuit are analyzed as follows. Compensation capacitor C S2 , C S3 and the compensation inductor L S1 , L S2 Figure 5 shows an F-type resonant compensation circuit consisting of S (vector) is the AC voltage source, R3 is the load resistance, and U R3 (vector) represents the voltage across the load resistor, and i R3 (vector) is the current flowing through the load resistor, and according to Kirchhoff's voltage theorem, the system input voltage U S (vector) and output voltage U R3 The (vector) relationship can be estimated as follows:

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[0026] From the above three types of high-order resonant compensation circuits, we can see that when the parameters of the resonant compensation circuit meet certain resonant conditions, the output will exhibit constant current or constant voltage characteristics, and the input impedances of the three high-order resonant compensation circuits are all pure resistance, so we obtain Table 1. Table 1 is a table of the output characteristics and conditions of the three high-order resonant compensation circuits.

[0027] [Table 1]

[0028] When the LCL-S type resonant compensation circuit uses a constant voltage source as the input excitation, the compensation topology circuit parameter L P1 , C P , L P , L S , C S It can be seen that if satisfies equations (1) and (2), the system has a constant voltage output and the system can achieve ZPA.

[0029] When the T-type resonant compensation network uses a constant voltage source as the input excitation, the resonant compensation network parameter L S1 , L S2 , C S1 If satisfies equation (10), the system has a constant current output and the system can achieve ZPA. When the T-type resonant compensation circuit uses a constant current source as the input excitation, the parameter L of the compensation topology circuit S1 ', L S2 ', C S1 If ' satisfies equation (11), the system has a constant voltage output and the system can achieve ZPA.

[0030] When an F-type resonant compensation circuit uses a constant voltage source as the input excitation, the compensation topology circuit parameter L S1 , L S2 , C S2 , C S3 If satisfies equation (23), the system has a constant voltage output and the system can achieve ZPA.

[0031] Based on the constant current and constant voltage output characteristics of the above-mentioned LCL-S, T, and F type resonant compensation circuits, the switching switch is controlled to turn on and off the receiving side compensation capacitor, changing the topology structure of the receiving side resonant compensation circuit, thereby enabling charging to be switched from constant current mode to constant voltage mode.

[0032] The system of the present invention can maintain the ZPA state in both the constant current charging phase and the constant voltage charging phase without introducing much reactive power, and the present invention does not require communication between the transmitting side and the receiving side, thereby reducing the difficulty and cost of system control. Finally, the rationality and effectiveness of this method are verified through simulations and experiments.

[0033] The present invention uses a constant voltage source U P We analyze an LCL-S type constant voltage resonant compensation circuit excited by (vector), a T type constant current resonant compensation circuit excited by a constant voltage source, and an F type constant voltage resonant compensation circuit. Through the analysis, we find that cascading the output end of an LCL-S type resonant compensation circuit with the input end of a T type resonant compensation circuit can meet the constant current output requirement during charging of an electric vehicle, and cascading the output end of an LCL-S type resonant compensation circuit with the input end of an F type resonant compensation circuit can meet the constant voltage output requirement during charging of an electric vehicle.

[0034] The load voltage U of the LCL-S type resonant compensation circuit shown in Figure 2 R1 is used as the excitation source for the T-type resonant compensation circuit shown in Fig. 4(a), and the constant current topology circuit shown in Fig. 6 is formed by cascade combination, and the load voltage U of the LCL-S-type resonant compensation circuit shown in Fig. 2 is R1(vector) is used as the excitation source of the F-type resonant compensation circuit, and the constant voltage topology circuit shown in Figure 7 is formed by cascade combination. R is the load resistance, and U P (Vector) is a high frequency AC voltage source.

[0035] To switch the constant current topology shown in Figure 6 to the constant voltage topology shown in Figure 7, S2 Add a branch circuit and S3 C so that it is equivalent to S1 C on the branch circuit St The method adopted in this paper is to connect switches S1 and C S2 are connected in series and C S2 Add a branch circuit and turn on switches S2 and C St are connected in series and C St By adding a branch circuit and controlling the switch to be on, the compensation topology at the receiving end changes from T-type to F-type, thereby switching the system from constant current mode to constant voltage mode.

[0036] As shown in Figure 1, the transmitter side adopts a single-phase full-bridge high-frequency inverter circuit, which is composed of switching tubes Q1, Q2, Q3, and Q4. P (vector) and U P (vector) represents the inverter output current and inverter output voltage, and the parameters of the transmitting LCL resonant compensation network are L P1 , C P , L P where M is the mutual inductance of the coil and L S , C S are the self-inductance of the receiving coil and the compensation capacitor on the receiving side, respectively, and the parameters of the T-type resonant compensation network on the receiving side are L S1 , L S2 , C S1 The receiver's F-type resonant compensation network parameters are L S1 , L S2 , C S1 , C St , C S2 It consists of i R(vector) and U R (Vector) are the input current and input voltage of the rectifier, respectively. The receiving rectifier adopts a single-phase uncontrollable rectifier circuit, and the bridge arm is composed of diodes D1, D2, D3, and D4, and Z in represents the input impedance of the system. C f is the filter capacitor, I L and U L are the output current and output voltage of the system, and R L is the equivalent resistance of the charging load.

[0037] Fundamental wave effective value U of inverter output voltage P The relationship between the inverter input DC voltage E is

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[0038] If the phase shift angle of the inverter is π, the equivalent resistance R of the rectification-related circuit is rec and the battery's equivalent internal resistance R L The relationship is

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[0039] A controlled voltage source is used to represent the mutual inductance voltage of the transmitting and receiving coils, R eq is the internal resistance of the rectifier-related circuit and the internal resistance of the charging load, R L The equivalent resistance of the mutual inductance is shown in Figure 9.

[0040] According to Figure 9, the KVL equations for the circuit can be listed as follows:

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[0041] Substituting equations (1), (2), and (10) into equation (31), the equivalent resistance of the system in constant current mode, R eq The current flowing through the

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[0042] equivalent resistance R eq The current i R (vector) and inverter input AC voltage U P (vector), the constant current gain Gi of the system can be calculated as follows:

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[0043] When the voltage across the charging load rises to the threshold voltage for constant current / constant voltage switching, switches S1 and S2 are in the on state, and capacitor C S2 , C St is connected to the system, the system is in constant voltage charging mode, and the system topology circuit consists of an LCL-S and an F-type resonant compensation circuit. The system topology circuit is shown in Figure 10.

[0044] Among them, the compensation capacitor C S2 , C S3 , C S1 , C St satisfies the following relationship:

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[0045] According to Figure 11, the KVL equations for the circuit can be listed as follows:

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[0046] Substituting equations (1), (2), and (23) into equation (36), the equivalent resistance of the system in constant voltage mode, R eq The magnitude of the voltage across both ends can be calculated as follows:

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[0047] equivalent resistance R eq Voltage U across both ends R (vector) and inverter output AC voltage U P (vector), the constant current gain Gv of the system can be calculated as follows:

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[0048] Let the load charging current be I L , charging voltage is U L , DC input voltage of the inverter is E, resonant angular frequency of the system is ω, and self-inductance of the transmitting coil is L P , the self-inductance of the receiving coil is L S , and let M be the mutual inductance between the transmitting coil and the receiving coil.

[0049] From equations (1) and (2), L P1 , C P , C S The value of is calculated as follows:

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[0050] The system simulation and experiment platform is designed as follows. According to FIG. 1, a simulation model of the LCL-S-(T / F) type composite compensation topology circuit shown in FIG. 13 is constructed.

[0051] To verify the feasibility of the proposed theoretical solution, a simulation model was constructed using Simulink® simulation software. Experiments were also conducted to verify a WPT system that achieves constant current and constant voltage output using a compensation topology circuit with a combined LCL-S and T / F connection. An experimental platform for a wireless charging system with a charging current of 1A and a charging voltage of 24V was constructed, as shown in Figure 14. The controller's main control chip is a TI TMS320F28335 processor. The inverter is a single-phase full-bridge inverter circuit consisting of an IRG7PH42UD1. The receiving rectifier uses a full-bridge uncontrolled rectifier circuit consisting of SCS240AE2 fast recovery diodes. The transmitting and receiving coils are formed by winding high-frequency litz wire. A polypropylene film capacitor is used for the compensation capacitor, and the compensation inductor is formed by winding litz wire and an EE65 magnetic core. A sliding rheostat is used in the experiment to simulate the change in internal resistance during battery charging. The specific parameters of the wireless charging system experimental platform are shown in Table 2, which is a parameter table of the experimental system.

[0052] [Table 2]

[0053] The simulation and experimental results are analyzed as follows.

[0054] First, we use Simulink simulation software to build a constant current mode simulation model shown in Figure 8, and simulate and verify the constant current charging stage. Figure 15 shows the charging load R L Figure 15 shows the simulated waveforms of the inverter output and load charging current when the load resistance is 12Ω and 24Ω, respectively. From (a) to (d) of Figure 15, it can be seen that the inverter output current and voltage remain in phase, and the system output current is basically maintained at 1A.

[0055] At the same time, an experimental platform was established to experimentally verify the constant current charging mode under the same experimental parameter settings. In the experiment, the resistance of the resistive load was gradually increased to simulate the resistance change process of the battery during charging, and the load resistance change range was 5Ω to 24Ω.

[0056] Figure 16 shows the experimental waveforms of the inverter and charging load output in constant current mode. Figure 16 (a) and (b) show that the inverter's output voltage and output current basically remain in phase, and the system maintains unit power factor input characteristics. In constant current mode, when the charging load resistance is 13.6 Ω, the charging current is 1.01 A. When the charging load resistance is 24 Ω, the charging current is 1.004 A, with a current change rate of 0.59%. The charging current is hardly affected by the charging load, and the charging current is maintained at 1 A. The system simulation and experimental results are basically consistent.

[0057] When the load voltage reaches the rated switching voltage of 24V, the switching operation performs compensation topology switching, converting the constant current charging stage into a constant voltage charging stage, the system outputs a voltage of 24V, charging the charging load at a constant voltage, and when the output current drops to the cut-off current, charging is terminated.

[0058] First, we use Simulink simulation software to build a constant voltage mode simulation model shown in Figure 10, and simulate and verify the constant voltage charging stage. Figure 17 shows the charging load R LFigure 17 shows the simulated waveforms of the inverter output and load charging voltage when the load resistances are 24Ω and 120Ω, respectively. From (a) to (d) of Figure 17, it can be seen that the inverter output current and voltage remain in phase, and the system output voltage is basically maintained at about 24V.

[0059] At the same time, an experimental platform was established to experimentally verify the constant voltage charging mode under the same experimental parameter settings. In the experiment, the resistance of the resistive load was increased to simulate the battery resistance change process during charging, and the load resistance change range was 24Ω to 120Ω.

[0060] Figure 18 shows the experimental waveforms of the inverter and charging load output in constant voltage mode. From (a) to (b) of Figure 18, U P (vector) and i P It can be seen that the (vector) waveform remains essentially in phase, the system maintains unit power factor input characteristics, and the system can maintain the ZPA state. When the charging load is 24 Ω, the charging voltage is 24 V, and when the charging load is 65 Ω, the charging voltage is 26 V, with a voltage change rate of 7.69%. The slight fluctuations in the charging voltage are due to the fact that the internal resistance of the system was not taken into account in the previous analysis, and there was an error in the compensation component parameters and the theoretical calculated values.

[0061] Besides, in constant current mode, as the equivalent resistance of the charging load gradually increases, the input impedance of the system continues to decrease and the output current of the inverter gradually increases, which verifies the correctness of the theoretical analysis of equation (34). In constant voltage mode, as the equivalent resistance of the charging load gradually increases, the input impedance of the system continues to increase and the output current of the inverter gradually decreases, which verifies the correctness of the theoretical analysis of equation (39). Figure 19 shows the system's charging current and charging voltage as a function of the charging load, with the charging load ranging from 5 to 120 Ω. Figure 19 shows that in constant current mode, the charging current drops from an initial 1.01 A to 1 A, remaining essentially stable at 1 A. In constant voltage mode, the charging voltage increases from an initial 24 V to 27 V. This slight increase in charging voltage is due to the fact that the previous theoretical derivation did not take into account the system's internal resistance, such as inductance and capacitors, and the internal resistance of the coil. This results in the system's DC power output being higher than the theoretical value. As a result, the charging voltage and charging current fluctuate somewhat due to the system's internal resistance, but the charging voltage and charging current can still meet the charging load's needs.

[0062] Figure 20 shows the change in the system's charging efficiency and charging power as a function of the charging load resistance. Throughout the constant-current, constant-voltage charging process, the system's charging efficiency increases from 42% to 78%, and then finally drops to 44% when charging is complete. The charging power reaches a maximum of 24W at the constant-current, constant-voltage switching point. (The charging efficiency here refers to the DC-DC charging efficiency, i.e., the ratio of the charging load output power to the inverter input power.)

[0063] Figure 21 shows the inverter output voltage U when switches S1 and S2 are switched from the off state to the on state. P (vector), output current i P (vector), and the voltage across the charging load U L The inverter output waveform shows that the inverter output voltage amplitude barely changes, while the inverter output current amplitude increases slightly. The voltage across the charging load fluctuates slightly before and after switching, but quickly returns to a stable state in a very short time, enabling fast and stable switching from constant current charging mode to constant voltage charging mode.

[0064] This invention derives an LCL-S-(T / F) type constant current / constant voltage composite compensation topology by reconstructing LCL-S, T, and F type resonant compensation circuits in a composite manner. Then, by controlling the switch switching on the receiving side to switch the compensation capacitor, a theoretical analysis of this new type of constant current / constant voltage composite compensation topology is completed. Next, a simulation model of the proposed theoretical solution is built and verified using MATLAB® / SIMULINK simulation software. Finally, a WPT system that achieves constant current / constant voltage output using a composite topology circuit in which LCL-S type and T / F type resonant compensation circuits are cascaded is experimentally verified, and the charging voltage U L and charging current I L A 24V, 1A wireless charging experimental platform was constructed. During the constant-current charging phase, when the charging load resistance increased from 13.6 Ω to 24 Ω, the system charging current decreased from 1.01 A to 1.004 A, with a current change rate of 0.59%, maintaining a constant system charging current of essentially 1 A. During the constant-voltage charging phase, when the charging load resistance increased from 24 Ω to 65 Ω, the system charging voltage increased from 24 V to 26 V, with a voltage change rate of 7.69%. The system charging voltage increased slightly, but still met the charging load's requirement for constant voltage output. The system achieved a maximum charging efficiency of 78% throughout the entire charging process. The experiment simulated the battery's resistance change during the charging process by gradually increasing the resistance of the resistive load. The experimental results demonstrated that the inverter's output voltage and output current remained essentially in phase, achieving ZPA characteristics with nearly zero reactive power input. Furthermore, during the constant current and constant voltage charging stage, the output current and output voltage of the system remain essentially unchanged, meeting the requirements for constant current or constant voltage output when charging electric vehicles and achieving expected results.

[0065] Each embodiment in this specification is described in stages, and what each embodiment mainly describes is the difference from other embodiments. The same or similar parts between the embodiments may be referred to each other.

[0066] In this specification, specific examples are used to explain the principles and embodiments of the present invention, and the above examples are only used to understand the method of the present invention and its core idea, and at the same time, those skilled in the art can change the form and application scope for implementing the invention according to the idea of ​​the present invention. In summary, the contents of this specification should not be understood as limitations on the present invention. [Explanation of symbols]

[0067] Z ref Reflected Impedance Z in Input Impedance R eq Equivalent resistance of rectifier and charging load U P (Vector) Inverter output voltage i P (Vector) Inverter Output Current U R (Vector) Rectifier Input Voltage I R (Vector) Rectifier Input Current U L Charging Load Voltage I L charging load current R rec Rectifier equivalent resistance R L Equivalent resistance of charging load G i Constant Current Gain G v Constant Voltage Gain U ref Threshold voltage for constant current / constant voltage switching f resonant frequency d Air gap distance M mutual inductance ω resonance angular frequency λ power factor K coupling coefficient U CCVS (Vector) Mutual inductance voltage of the receiving coil P charging power η Charging efficiency L PTransmitting coil self-inductance L S Self-inductance of the receiving coil E DC input voltage

Claims

1. A wireless charging system with a variable topology structure on the receiving side, (a) an inverter; (b) an LCL-S type resonant compensation network having an input connected to the output of the inverter; (c) a variable resonant compensation network whose input end is connected to the output end of the LCL-S type resonant compensation network, configured to function as an F type resonant compensation network or a T type resonant compensation network by switching on and off a built-in first switch (S 1 ) and a built-in second switch (S 2 ); (d) a rectifier having an input connected to the output of the variable resonant compensation network; (e) a charging load connected to the output terminal of the rectifier; (f) the inverter supplies an AC voltage as input excitation of the LCL-S type resonant compensation network to the input end of the LCL-S type resonant compensation network; (g) the LCL-S type resonant compensation network has a transmitting side compensation network and a receiving side compensation network; The transmitting side compensation network includes a transmitting side compensation inductor (L P1 ), a transmitting side compensation capacitor (C P ) and a self-inductor (L P ) of the transmitting coil; one end of the transmitting-side compensation inductor (L P1 ) is connected to the inverter, the other end of the transmitting-side compensation inductor (L P1 ) is connected to one end of the transmitting-side compensation capacitor (C P ) and one end of the self-inductor (L P ) of the transmitting coil, and the other end of the transmitting-side compensation capacitor (C P ) is connected to the inverter and the other end of the self-inductor (L P ) of the transmitting coil, The receiving side compensation network includes a self-inductor (L S ) of the receiving coil and a first receiving side compensation capacitor (C S ); One end of the self-inductor (L S ) of the receiving coil is connected to one end of the receiving-side first compensation capacitor (C S ), the other end of the self-inductor (L S ) of the receiving coil is connected to a receiving-side second compensation capacitor (C S1 ) branch circuit, a receiving-side third compensation capacitor (C S2 ) branch circuit connected in parallel to the receiving-side second compensation capacitor (C S1 ) branch circuit, a receiving-side fourth compensation capacitor (C St ) and the rectifier, and the other end of the receiving-side first compensation capacitor (C S ) is connected to one end of the first switch (S 1 ) and one end of the receiving-side first compensation inductor (L S1 ) in the variable resonant compensation network, (h) the variable resonant compensation network includes a receiving-side second compensation capacitor (C S1 ), a receiving-side third compensation capacitor (C S2 ) connected in series with the first switch (S 1 ), a receiving-side fourth compensation capacitor (C St ) connected in parallel to the receiving-side second compensation capacitor (C S1 ) branch circuit and connected in series with the second switch (S 2 ), a receiving-side first compensation inductor (L S1 ), and a receiving-side second compensation inductor (L S2 ) connected in series with the receiving-side first compensation inductor (L S1 ); the other end of the receiving-side first compensation inductor (L S1 ) is connected to one end of the receiving-side second compensation capacitor (C S1 ) and one end of the receiving-side second compensation inductor (L S2 ), respectively, the other end of the receiving-side second compensation inductor (L S2 ) is connected to the rectifier, and the other end of the receiving-side second compensation capacitor (C S1 ) is connected to the other end of the self-inductor (L S ) of the receiving coil of the receiving-side compensation network in the LCL-S type resonant compensation network; (i) when the first switch (S 1 ) and the second switch (S 2 ) are on, the receiving-side third compensation capacitor (C S2 ) and the receiving-side fourth compensation capacitor (C St ) are incorporated into the variable resonant compensation network, and the variable resonant compensation network functions as an F-type resonant compensation network, so that the wireless charging system operates in a constant voltage charging mode; When the first switch (S 1 ) and the second switch (S 2 ) are off, the third receiving-side compensation capacitor (C S2 ) and the fourth receiving-side compensation capacitor (C St ) are removed from the variable resonant compensation network, and the variable resonant compensation network functions as a T-type resonant compensation network, and as a result, the wireless charging system is configured to operate in a constant current charging mode. A wireless charging system characterized by:

2. A wireless charging system as described in claim 1, wherein when a real-time voltage (U L ) across the charging load is detected and the real-time voltage (U L ) rises to a threshold voltage (U ref ) for switching between constant current charging and constant voltage charging, the first switch (S 1 ) and the second switch (S 2 ) are turned on, thereby transitioning the charging mode of the wireless charging system from the constant current charging mode to the constant voltage charging mode without causing a change in the real-time voltage (U L ).

3. The wireless charging system is configured such that, by turning off the first switch (S1) and the second switch (S2), the charging mode of the wireless charging system transitions from the constant voltage charging mode to the constant current charging mode; The input impedance Z in of the wireless charging system in the constant current charging mode is expressed as follows using the output voltage U P (vector) of the inverter, the output current i P (vector) of the inverter, the inductance L P1 of the transmitting-side compensation inductor (L P1 ), the resonant angular frequency ω, the mutual inductance M, the capacitance C S1 of the receiving-side second compensation capacitor (C S1 ), the capacitance C P of the transmitting-side compensation capacitor (C P ), and the equivalent resistance R eq of the rectifier and the charging load: [Number 49] 3. The wireless charging system of claim 2, wherein:

4. The wireless charging system is configured such that, by turning on the first switch (S1) and the second switch (S2), the charging mode of the wireless charging system transitions from the constant current charging mode to the constant voltage charging mode; The input impedance Z in of the wireless charging system in the constant voltage charging mode is expressed as follows using the output voltage U P (vector) of the inverter, the output current i P (vector) of the inverter, the inductance L P1 of the transmitting side compensation inductor (L P1 ), the inductance L S1 of the receiving side first compensation inductor (L S1 ), the resonance angular frequency ω, the mutual inductance M, the capacitance C P of the transmitting side compensation capacitor (C P ), the inductance L S2 of the receiving side second compensation inductor (L S2 ), and the equivalent resistance R eq of the rectifier and the charging load: [Number 50] 3. The wireless charging system of claim 2, wherein:

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