Wireless charging system having variable topology structure of variable capacitor on reception 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 in particular 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). In order to quickly and smoothly switch from the constant current charging mode to the 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 end and the receiving end, which greatly increases the difficulty and cost of system control. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE PRESENT EMBODIMENT 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 enter 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 be equivalent to one capacitor branch circuit of the F-type resonant compensation network, 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, switch S1 and switch S2 are turned on to convert the T-type resonant compensation network into the F-type resonant compensation network, and enter into 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 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 S and compensation capacitor C S and a 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 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 and the inductance L S2 The other end of the capacitor C is connected to the rectifier. 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 the charging load. L Detects the real-time voltage U L is the threshold voltage U for switching between constant current and constant voltage charging ref , turn on the switch S1 and the switch S2, 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 capacitor variable topology structure on the receiving side is

number

[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 having a variable topology structure of a variable capacitor on the receiving side is

number

[0012] According to the specific embodiment provided by the present invention, the present invention discloses 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 changes the topology structure of the resonant compensation circuit on the receiving side by controlling a changeover switch to switch on and off the compensation capacitor on the receiving side, thereby realizing switching of charging from a constant current mode to a constant voltage mode. The present invention can maintain a zero phase angle (ZPA) state in both the constant current charging stage and the constant voltage charging stage, and there is almost no introduction of reactive power and no need for communication between the transmitting side and the receiving side, thereby reducing the difficulty and cost of system control. [Brief description 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 capacitor variable topology structure on the receiving side. [Diagram 2] FIG. 1 is a circuit diagram of an LCL-S type resonant compensation network. [Diagram 3] 3 is an equivalent circuit diagram of an LCL-S type resonant compensation network, in which (a) in FIG. 3 is an equivalent circuit diagram of a first LCL-S, (b) in FIG. 3 is an equivalent circuit diagram of a second LCL-S, and (c) in FIG. 3 is an equivalent circuit diagram of the mutual inductance of the receiving side of the LCL-S. [Figure 4] 4 is a circuit diagram of a T-type resonant compensation network, in which (a) of FIG. 4 is a circuit diagram of a T-type resonant compensation network excited by a constant voltage source, and (b) of FIG. 4 is a circuit diagram of a T-type resonant compensation network excited by a constant current source. [Diagram 5] FIG. 1 is an F-type resonant compensation network circuit diagram. [Figure 6] FIG. 2 is a constant current topology circuit diagram. [Figure 7] FIG. 2 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. [Figure 13] FIG. 1 is a SIMULINK® simulation model diagram of the LCL-S-(T / F) composite compensation system. [Figure 14] FIG. 1 is a schematic diagram of the experimental platform for the LCL-S-(T / F) type composite compensation system. [Figure 15] 15A is a simulation waveform diagram of the inverter output voltage and current when RL=12Ω in constant current mode, FIG. 15B is a simulation waveform diagram of the inverter output voltage and current when RL=24Ω in constant current mode, FIG. 15C is a simulation waveform diagram of the load current when RL=12Ω in constant current mode, and FIG. 15D is a simulation waveform diagram of the load current when RL=24Ω in constant current mode. [Figure 16] Fig. 16 shows experimental waveforms in constant current mode. Fig. 16(a) shows the experimental waveforms of the inverter output voltage and current when RL=13.6Ω in constant current mode, and Fig. 16(b) shows the experimental waveforms of the inverter output voltage and current when RL=24Ω in constant current mode. [Figure 17]These are simulation waveform diagrams in constant voltage mode. Among them, Fig. 17(a) is a simulation waveform diagram of the inverter output voltage and current when RL=24Ω in constant voltage mode, Fig. 17(b) is a simulation waveform diagram of the inverter output voltage and current when RL=120Ω in constant voltage mode, Fig. 17(c) is a simulation waveform diagram of the load voltage when RL=24Ω in constant voltage mode, and Fig. 17(d) is a simulation waveform diagram of the load voltage when RL=120Ω in constant voltage mode. [Figure 18] Fig. 18(a) is an experimental waveform diagram of the inverter output voltage and current when RL=24Ω in the constant voltage mode, and Fig. 18(b) is an experimental waveform diagram of the inverter output voltage and current when RL=65Ω in the constant voltage mode. [Figure 19] 4 is a curve diagram showing how the charging current and charging voltage of the system change depending on the charging load. [Figure 20] 4 is a curve diagram showing the change in charging efficiency and charging power of the system depending on the charging load resistance. [Figure 21] 4A to 4C are waveform diagrams of the inverter output voltage, current, and load voltage output when switching. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] In the following, the technical solutions in the embodiments of the present invention are clearly and completely described with reference to the drawings in the embodiments of the present invention, obviously, the described embodiments are only a part of the embodiments of the present invention, not all 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 the description of the preferred embodiments of the present invention.

[0018] As shown in FIG. 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 the inverter is used to output an AC voltage source as an input excitation of the LCL-S type resonant compensation network, and 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, and 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 be equivalent to one capacitor branch circuit of the F-type resonant compensation network, 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, turn on switches S1 and S2 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 the 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 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:

number

number

number

number

number

number

number

number

number

[0020] From equation (7), the voltage across the load resistor is P (vector), the mutual inductance M between the primary coil and the secondary coil, and the primary compensation inductor L P1 It can be seen that the LCL-S type resonant compensation circuit only relates to the load R1 and has no relation to the charging load R2. 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. In addition, it can be seen from equation (9) 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 (a) and (b) of Fig. 4, the T-type resonant compensation circuit is S (vector) and constant current source iS (vector), of which the compensation inductor L S1 , L S2 and the 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, 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:

number

number

number

number

[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 corresponds to a constant current source externally.

[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:

number

number

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

number

number

number

[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 The F-type resonant compensation circuit, which is composed 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:

number

number

number

number

number

number

number

[0026] From the above three kinds 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 show 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 realize 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 the 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 / constant voltage output characteristics of the above-mentioned LCL-S, T, and F type resonant compensation circuits, the switching switch is controlled to switch the receiving side compensation capacitor on and off, 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 controlling the system, and finally, the rationality and effectiveness of this method are verified by simulation and experiments.

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

[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 a constant current topology circuit shown in Fig. 6 is formed by cascade combination, and the load voltage U 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 synthesis. 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 Connect in series and C S2 Add a branch circuit and turn on switches S2 and C. St Connect in series and C St By adding a branch circuit and controlling the switch to be turned 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 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 respectively represent the self-inductance of the receiving coil and the compensation capacitor on the receiving side, 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, 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, respectively, 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 this and the inverter input DC voltage E is as follows:

number

number

number

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

number

number

[0039] A controlled voltage source is used to represent the mutual inductance voltage of the transmit and receive coils, R eq is the internal resistance of the rectifier-related circuits 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:

number

[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

number

[0042] equivalent resistance R eq 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:

number

number

[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 is composed of LCL-S and 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:

number

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

number

[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:

number

[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:

number

number

[0048] The charging current of the load is 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 transmission 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:

number

number

number

number

number

number

number

[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] In order to verify the feasibility of the proposed theoretical solution, a simulation model is built and verified using Simulink (registered trademark) simulation software, and at the same time, an experimental verification of the WPT system is carried out using a compensation topology circuit with LCL-S type and T / F type combined connection to realize constant current and constant voltage output. A wireless charging system experimental platform with a charging current of 1A and a charging voltage of 24V is built, and the experimental platform is shown in Figure 14. The main control chip of the controller uses the TMS320F28335 processor made by TI company, the inverter is a single-phase full-bridge inverter circuit composed of model IRG7PH42UD1, the rectifier at the receiving end uses a full-bridge uncontrollable rectifier circuit composed of SCS240AE2 fast recovery diodes, and the transmitting coil and receiving coil 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 EE65 magnetic core. In the experiment, a sliding rheostat is used 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, a constant current mode simulation model shown in Fig. 8 is constructed in the Simulink simulation software, and the constant current charging stage is simulated and verified. L 15 shows the simulated waveforms of the inverter output and the load charging current when the load resistance is 12Ω and 24Ω, respectively. From (a) to (d) in Fig. 15, it can be seen that the inverter output current and voltage maintain the same phase, and the system output current is basically maintained at 1A.

[0055] At the same time, under the same experimental parameter settings, an experimental platform is built to carry out experimental verification of the constant current charging mode. In the experiment, the resistance of the resistive load is gradually increased to simulate the resistance change process of the battery during charging, and the change range of the load resistance is 5Ω~24Ω.

[0056] Figure 16 shows the experimental waveforms of the inverter and charging load output in constant current mode. From Figure 16 (a) and (b), we can see that the inverter output voltage and output current basically maintain the same phase, and the system maintains the unit power factor input characteristic. In constant current mode, when the charging load resistance is 13.6Ω, the charging current is 1.01A, and when the charging load resistance is 24Ω, the charging current is 1.004A, and the current change rate is 0.59%. The charging current is almost unaffected by the charging load, and the charging current is maintained at 1A. 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, charges the charging load at a constant voltage, and when the output current drops to the cut-off current, charging is terminated.

[0058] First, the constant voltage mode simulation model shown in Fig. 10 is constructed in the Simulink simulation software, and the constant voltage charging stage is simulated and verified. L17 shows the simulated waveforms of the inverter output and the load charging voltage when the load resistance is 24Ω and 120Ω, respectively. From (a) to (d) of Fig. 17, it can be seen that the inverter output current and voltage maintain the same phase, and the system output voltage is basically maintained at about 24V.

[0059] At the same time, under the same experimental parameter settings, an experimental platform is built to carry out experimental verification of the constant voltage charging mode. In the experiment, the resistance of the resistive load is increased to simulate the resistance change process of the battery during charging, and the change range of the load resistance is 24Ω~120Ω.

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

[0061] Besides, in the 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 the constant voltage mode, in the process of the equivalent resistance of the charging load gradually increasing, 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 is a curve diagram showing the charging current and charging voltage of the system that change according to the charging load, and the charging load value is 5 to 120 Ω. From Figure 19, we can see that in the constant current mode, the charging current drops from the initial 1.01A to 1A, and the charging current is basically stable at 1A; in the constant voltage mode, the charging voltage increases from the initial 24V to 27V, and the charging voltage increases slightly, but this is because the previous theoretical derivation does not take into account the compensation components such as inductance and capacitor in the system and the internal resistance of the coil, which makes the DC power output value of the system larger than the theoretical value, and as a result, the charging voltage and charging current fluctuate to a certain extent due to the influence of the internal resistance of the system, but the charging voltage and charging current can meet the charging needs of the charging load.

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

[0063] Figure 21 shows the output voltage U of the inverter when the 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 waveform of the inverter output shows that the inverter output voltage amplitude hardly changes, and the inverter output current amplitude increases slightly. Although the voltage across the charging load fluctuates slightly before and after switching, it quickly returns to a stable state in a very short time, realizing fast and stable switching from constant current charging mode to constant voltage charging mode.

[0064] This invention reconstructs the LCL-S, T, and F type resonant compensation circuits in a composite manner, and derives the LCL-S-(T / F) type constant current / constant voltage composite compensation topology. Then, the theoretical analysis of this new type of constant current / constant voltage composite compensation topology is completed by controlling the switch switching on the receiving side to switch the compensation capacitor. Next, a simulation model of the proposed theoretical solution is built and verified using MATLAB (registered trademark) / SIMULINK simulation software. Finally, a WPT system that realizes constant current / constant voltage output using a composite topology circuit in which the LCL-S type and T / F type resonant compensation circuits are cascaded is experimentally verified, and the charging voltage U L and the charging current I L build a wireless charging experimental platform with 24V and 1A respectively. In the constant current charging stage, when the charging load resistance increases from 13.6Ω to 24Ω, the system charging current decreases from 1.01A to 1.004A, the current change rate is 0.59%, and the system charging current basically maintains 1A; in the constant voltage charging stage, when the charging load resistance increases from 24Ω to 65Ω, the system charging voltage increases from 24V to 26V, the voltage change rate is 7.69%, and the system charging voltage increases slightly, but still meets the charging load requirement for constant voltage output. The maximum charging efficiency of the system in the entire charging process is 78%, and in the experiment, the resistance of the resistive load is gradually increased to simulate the change process of the battery resistance during the charging process. The experimental results prove that the inverter output voltage and output current basically maintain the same phase, the system can achieve the ZPA characteristic, and the introduction of reactive power is almost zero. Moreover, during the constant current-constant voltage charging stage, the output current and output voltage of the system basically remain unchanged, which meets the requirement of constant current or constant voltage output when charging electric vehicles and achieves expected results.

[0065] Each embodiment in this specification is described in stages, and what is mainly described in each embodiment 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 applied to explain the principle and embodiment of the present invention, and the above description of the examples is 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 of 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 Equivalent resistance of rectifier 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 PSelf-inductance of the transmitting coil L S Self-inductance of the receiving coil E DC input voltage

Claims

1. 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 be in a constant current charging mode, and the T type resonant compensation network is connected to the rectifier; A capacitor C Ｓ２ A branch circuit is added, and the capacitor C of the T-type resonant compensation network is Ｓ１ Capacitor C in the branch circuit Ｓｔ are connected in parallel to be equivalent to one capacitor branch circuit of the F-type resonant compensation network, and the capacitor C Ｓ２ The branch circuit is switch S １ and the capacitor C Ｓｔ is switch S ２ At the same time, the switch S １ and switch S ２ a variable capacitance variable topology structure on a receiving side, wherein the variable capacitance variable topology structure on a receiving side is turned on to convert the T-type resonant compensation network into the F-type resonant compensation network and enter into a constant voltage charging mode, the F-type resonant compensation network is connected to the rectifier, and the rectifier is connected to the charging load.

2. The LCL-S type resonant compensation network specifically includes a transmitting side compensation network and a receiving side compensation network; The transmission compensation network includes a compensation inductance L Ｐ１ , compensation capacitor C Ｐ , the self-inductance L of the transmitting coil Ｐ and the compensation inductance L Ｐ１ One end of the compensation inductance L 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 a self-inductance L Ｓ and compensation capacitor C Ｓ and the self-inductance L of the receiving coil is Ｓ One end of the compensation capacitor C Ｓ and a self-inductance L of the receiving coil is connected to one end of the receiving coil. 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 switch S １ and the inductance L in the T-type resonant compensation network Ｓ１ The wireless charging system with a variable topology structure of a variable capacitor on a receiving side according to claim 1, characterized in that one end of the variable capacitor is connected to the receiving end of the variable topology structure of the receiving side.

3. Specifically, the T-type resonant compensation network has 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 and the inductance L Ｓ２ The other end of the capacitor C is connected to the rectifier. Ｓ１ The other end of the receiving coil is connected to the self-inductance L Ｓ The wireless charging system having a variable topology structure of a variable capacitor on a receiving side according to claim 2, characterized in that the receiving side is connected to the other end of the variable capacitor.

4. Specifically, the F-type resonant compensation network is 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 S ２ The wireless charging system with a variable topology structure of a variable capacitor on the receiving side according to claim 3, characterized in that it is connected to

5. The real-time voltage U across the charging load Ｌ Detect the real-time voltage U Ｌ is the threshold voltage U for switching between constant current and constant voltage charging ｒｅｆ When the voltage rises to １ and the switch S ２ 5. The wireless charging system with a variable topology structure of a variable capacitor at a receiving side as described in claim 4, wherein the receiving side is 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.

6. The switch S １ and the switch S ２ and then turn off the constant current charging mode. In the constant current charging mode, the input impedance of the wireless charging system with a variable capacitor variable topology structure on the receiving side is [0049] where Z ｉｎ is the input impedance, U Ｐ (vector) is the inverter output voltage, i Ｐ (vector) is the inverter output current, L Ｐ１ is the compensation inductance of the transmitter, ω is the resonant angular frequency, M is the mutual inductance, C Ｓ１ is the receiver compensation capacitor, C Ｐ is the transmitter compensation capacitor, R ｅｑ The wireless charging system with a variable topology structure of a variable capacitor on the receiving side as described in claim 5, characterized in that:

7. The switch S １ and the switch S ２ to turn on the constant voltage charging mode, In the constant voltage charging mode, the input impedance of the wireless charging system having a variable topology structure of a variable capacitor on the receiving side is [Number 50] where Z ｉｎ is the input impedance, U Ｐ (vector) is the inverter output voltage, i Ｐ (vector) is the inverter output current, L Ｐ１ is the compensation inductance on the transmitting side, L Ｓ１ is the first compensation inductance on the receiving side, ω is the resonant angular frequency, M is the mutual inductance, C Ｐ is the transmitter compensation capacitor, L Ｓ２ is the second compensation inductance of the receiving side, R ｅｑ The wireless charging system with a variable topology structure of a variable capacitor on the receiving side as described in claim 5, characterized in that:

Images