Bidirectional wireless power transmission system and wide-range soft switching regulation and control method

Abstract

The invention discloses a bidirectional wireless power transmission system and a wide-range soft switching regulation and control method, and belongs to the technical field of bidirectional wireless power transmission. The invention aims to solve the problem of large switching loss of a bidirectional wireless power transmission system. The system comprises a DC input voltage UDC, an inverter circuit, a first auxiliary network, an input electrolyte capacitor CO1, a transmitting terminal compensation network, a coupling mechanism, a receiving terminal compensation network, a rectification circuit, a second auxiliary network, an output electrolyte capacitor CO2 and a charging voltage UBAT. An input electrolyte capacitor CO1 and a first auxiliary network are arranged in parallel between the DC input voltage UDC and the inverter circuit; the inverter circuit is connected with the coupling mechanism through the transmitting terminal compensation network, and the coupling mechanism is connected with the rectifier circuit through the receiving terminal compensation network; a second auxiliary network and an output electrolytic capacitor CO2 are arranged in parallel between the rectifier circuit and the charging voltage UBAT. According to the invention, wide-range soft switching control can be realized.

Description

Technical Field

[0001] The present invention relates to a bidirectional wireless power transmission system and a wide-range soft-switching control method, belonging to the technical field of bidirectional wireless power transmission. Background Art

[0002] In recent years, with the increasing demand for wireless charging in electronic devices, the bidirectional wireless power transmission technology has gradually come into the public's view. In the fields of electric vehicles, industrial robots, smart furniture, and the Internet of Things, etc., the bidirectional wireless power transmission technology can well achieve the charging of devices and the recovery of energy, realizing the bidirectional flow of energy. Compared with the unidirectional wireless power transmission technology, the bidirectional wireless power transmission technology can dynamically adjust the energy transmission direction and magnitude according to the load demand and power supply status. In a multi-load system, when the power demand of some loads suddenly changes, the system can timely obtain energy supplementation from other power sources or energy storage units, avoiding large voltage fluctuations caused by the inability of a single power supply to respond in time, and ensuring the stability of the voltage at the load end. In addition, since the bidirectional wireless power transmission system can control the energy transmission more flexibly, it can better control the current and voltage waveforms during the power regulation process, effectively reducing the harmonic components and improving the power quality.

[0003] The bidirectional wireless power transmission technology is currently widely used in smart microgrids and implantable medical devices. For example, in the application of smart microgrids, it usually includes various distributed energy sources and energy storage devices, as well as different types of loads. The bidirectional wireless power transmission technology can realize flexible energy interaction between distributed energy sources and energy storage devices, energy storage devices and loads, and loads and loads, optimize the energy distribution and utilization efficiency in the microgrid, improve the stability and reliability of the microgrid, and support the smooth switching between the island operation and grid-connected operation modes of the microgrid. In implantable medical devices, such as cardiac pacemakers, etc., the bidirectional wireless power transmission technology can not only achieve wireless charging of the implanted device from the outside, but also transmit information such as physiological data collected by the implanted device back to the external device through the wireless energy transmission link, realizing the bidirectional transmission of energy and data, reducing the need for additional communication lines and interfaces, reducing the infection risk, and improving the safety and reliability of the device.

[0004] For a bidirectional wireless power transmission system, its power loss is mainly concentrated in the coupling coil and the power converter. However, bidirectional wireless power transmission usually operates at a relatively high system operating frequency and is in a resonant mode, which makes the switching loss of high-frequency switching devices account for a relatively large proportion of the total loss of the system. Therefore, reducing the switching loss of the bidirectional wireless power transmission system is one of the important means to improve the system efficiency.

[0005] The existing technical means to improve switching losses mainly include three types: The first is the dual-phase-shift modulation strategy. By adjusting the inner phase-shift angles of the primary and secondary full-bridges, the transmitted power is changed. At the same time, bilateral modulation can reduce the current stress, but the soft-switching range of this method is limited. The second is the triple-phase-shift modulation strategy. Based on the dual-phase-shift, it adds the degree of freedom of the outer phase-shift angle between the primary and secondary voltages, achieving wide-range zero-voltage turn-on of the system. However, when the system transmitted power decreases, the continuously increasing outer phase-shift angle leads to an increase in the conduction loss. The third is the control method based on adjustable components. By adding an adjustable inductor (capacitor) at the input to adjust the inductance (capacitance) value, while changing the output power, the system is made inductive to achieve zero-voltage turn-on. However, this scheme has a complex structure and high cost.

[0006] To well solve the above problems, the article titled "Pulse Density Modulated ZVS Full-Bridge Converters for Wireless Power Transfer Systems" in the 34th volume, No. 1 of 《IEEE Transactions on Power Electronics》 discloses a soft-switching control method for a bidirectional wireless power transfer system based on an LC series resonance circuit, which improves the soft-switching range of the bidirectional wireless power transfer system. However, there are still the following deficiencies: 1) The total loss of the LC series resonance circuit is greater than the improved switching loss, which has a significant impact on the overall efficiency of the system; 2) The resonance current of the auxiliary network is uncontrollable, resulting in a complex commutation process; 3) The soft-switching range of the switching tube is not the full charge range and there is still a turn-off loss in the main switching tube; 4) The implementation method of soft-switching is easily affected by the change of compensation parameter values.

[0007] Therefore, the soft-switching stability of the bidirectional wireless power transfer system urgently needs to be improved. Summary of the Invention

[0008] Aiming at the problem of large switching losses in the bidirectional wireless power transfer system, the present invention provides a bidirectional wireless power transfer system and a wide-range soft-switching control method.

[0009] A bidirectional wireless power transfer system of the present invention includes a DC input voltage U DC , an inverter circuit, a first auxiliary network, an input electrolytic capacitor C O1 , a transmitter compensation network, a coupling mechanism, a receiver compensation network, a rectifier circuit, a second auxiliary network, an output electrolytic capacitor C O2 and a charging voltage U BAT ; An input electrolytic capacitor C DC is arranged in parallel between the DC input voltage U O1and the first auxiliary network; the inverter circuit is connected to the coupling mechanism through the transmitting-end compensation network, and the coupling mechanism is then connected to the rectifier circuit through the receiving-end compensation network; a second auxiliary network and an output electrolyte capacitor C are arranged in parallel between the rectifier circuit and the charging voltage U BAT ; O2 ; The circuit structure of the first auxiliary network from the DC input voltage U DC side to the inverter circuit side is the same as that of the second auxiliary network from the charging voltage U BAT side to the rectifier circuit side; the first auxiliary network includes a switching tube S A1 , a switching tube S A2 , an inductor L A , a capacitor C A1 , a capacitor C A2 , a diode D A1 and a diode D A2 . By using the switching tube S A1 and the switching tube S A2 to control the resonance state of the inductor L A , the capacitor C A1 and the capacitor C A2 , it provides the necessary conditions for realizing the full-range soft switching of the inverter switching tubes. The energy feedback function is realized through the diode D A1 and the diode D A2 ; the second auxiliary network includes a switching tube S B1 , a switching tube S B2 , an inductor L B , a capacitor C B1 , a capacitor C B2 , a diode D B1 and a diode D B2 . By using the switching tube S B1 and the switching tube S B2 to control the resonance state of the inductor L B , the capacitor C B1 and the capacitor C B2 , it provides the necessary conditions for realizing the full-range soft switching of the rectifier switching tubes. The energy feedback function is realized through the diode D B1 and the diode D B2 ; The first auxiliary network further includes a switching tube S A3 ; The positive pole of the DC input voltage U DC is connected to one end of the input electrolyte capacitor C O1 , and the negative pole of the DC input voltage U DC is connected to the other end of the input electrolyte capacitor C O1 ; the negative pole of the DC input voltage U DC is connected to the anode of the diode D A1 and the capacitor CA1 At one end of, diode D A1 The cathode of is connected to diode D A2 The anode of and capacitor C A2 At one end of, diode D A2 The cathode of is connected to inductor L A At one end of, inductor L A The other end of is connected to capacitor C A1 The other end of and capacitor C A2 The other end of; Diode D A2 The cathode of is connected to the source of switch tube S A2 The source of, switch tube S A2 The drain of is connected to the drain of switch tube S A1 The drain of, switch tube S A1 The source of is connected to the source of switch tube S A3 The source of, switch tube S A3 The drain of is connected to inductor L A The other end of.

[0010] For the bidirectional wireless power transmission system according to the present invention, the inverter circuit includes switch tubes MOSFETS1, MOSFETS2, MOSFETS3 and MOSFETS4. The drain of switch tube MOSFETS1 is connected to the source of switch tube S A3 The source of switch tube MOSFETS1 is connected to the drain of switch tube MOSFETS2. The source of switch tube MOSFETS2 is connected to the negative pole of the DC input voltage U DC ; The source of switch tube MOSFETS2 is connected to the source of switch tube MOSFETS4. The drain of switch tube MOSFETS4 is connected to the source of switch tube MOSFETS3. The drain of switch tube MOSFETS3 is connected to the drain of switch tube MOSFETS1.

[0011] For the bidirectional wireless power transmission system according to the present invention, the transmitting - end compensation network includes a transmitting - side compensation inductor L P1 , a transmitting - side compensation capacitor C P1 and a transmitting - side compensation capacitor C P ; The source of switch tube MOSFETS1 is connected to one end of the transmitting - side compensation inductor L P1 One end of the transmitting - side compensation inductor L P1 The other end of is connected to one end of the transmitting - side compensation capacitor C P1 One end of the transmitting - side compensation capacitor C P1 The other end of is connected to the drain of switch tube MOSFETS4; The other end of the transmitting - side compensation inductor L P1 The other end of is connected to one end of the transmitting - side compensation capacitor C P One end of the transmitting - side compensation capacitor CP The other end is used to connect an input connection end of the coupling mechanism, and the transmitting - side compensation capacitor C P1 The other end is used to connect another input connection end of the coupling mechanism.

[0012] According to the bidirectional wireless power transmission system of the present invention, the coupling mechanism includes a transmitting side and a receiving side. The transmitting side includes a transmitting coil L P , and the receiving side includes a receiving coil L S ; The same - name end of the transmitting coil L P is connected to the other end of the transmitting - side compensation capacitor C P , and the opposite - name end of the transmitting coil L P is connected to the drain of the switching transistor MOSFETS4; The same - name end of the receiving coil L S serves as a connection end of the receiving - side compensation network, and the opposite - name end of the receiving coil L S serves as another connection end of the receiving - side compensation network.

[0013] According to the bidirectional wireless power transmission system of the present invention, the receiving - side compensation network of the receiving end includes a receiving - side compensation capacitor C S , a receiving - side compensation inductor L S1 and a receiving - side compensation capacitor C S1 ; The same - name end of the receiving coil L S is connected to one end of the receiving - side compensation capacitor C S , the other end of the receiving - side compensation capacitor C S is connected to one end of the receiving - side compensation capacitor C S1 , the other end of the receiving - side compensation capacitor C S1 is connected to the opposite - name end of the receiving coil L S ; the other end of the receiving - side compensation capacitor C S is connected to one end of the receiving - side compensation inductor L S1 , the other end of the receiving - side compensation inductor L S1 serves as a connection end of the rectifier circuit, and the other end of the receiving - side compensation capacitor C S1 serves as another connection end of the rectifier circuit.

[0014] According to the bidirectional wireless power transmission system of the present invention, the rectifier circuit includes switching transistors MOSFETS5, MOSFETS6, MOSFETS7, and MOSFETS8. The other end of the receiving - side compensation inductor L S1 is connected to the source of the switching transistor MOSFETS5, the drain of the switching transistor MOSFETS5 is connected to the drain of the switching transistor MOSFETS7, and the source of the switching transistor MOSFETS7 is connected to the receiving - side compensation capacitor C S1The other end is connected to the drain of the switching transistor MOSFETS8. The source of the switching transistor MOSFETS8 is connected to the source of the switching transistor MOSFETS6, and the drain of the switching transistor MOSFETS6 is connected to the source of the switching transistor MOSFETS5.

[0015] According to the bidirectional wireless power transmission system of the present invention, the second auxiliary network further includes a switching transistor S B3 ; The source of the switching transistor S B1 is connected to the drain of the switching transistor MOSFETS7 and the source of the switching transistor S B3 ; the drain of the switching transistor S B1 is connected to the drain of the switching transistor S B2 ; the source of the switching transistor S B2 is connected to one end of the inductor L B ; the other end of the inductor L B is connected to the drain of the switching transistor S B3 and one end of the capacitor C B1 ; the other end of the capacitor C B1 is connected to the source of the switching transistor MOSFETS8; The source of the switching transistor S B2 is connected to the cathode of the diode D B2 ; the anode of the diode D B2 is connected to one end of the capacitor C B2 and the cathode of the diode D B1 ; the other end of the capacitor C B2 is connected to the other end of the inductor L B ; the anode of the diode D B1 is connected to the source of the switching transistor MOSFETS8; The drain of the switching transistor S B1 is connected to one end of the output electrolyte capacitor C O2 and the positive pole of the charging voltage U BAT ; the other end of the output electrolyte capacitor C O2 is connected to the source of the switching transistor MOSFETS8 and the negative pole of the charging voltage U BAT ;

[0016] The present invention also provides a wide-range soft-switching control method for a bidirectional wireless power transmission system, which is used to perform switching control on the bidirectional wireless power transmission system, including: The soft-switching commutation principles of the charging mode and the discharging mode of the bidirectional wireless power transmission system are the same; the soft-switching control in the charging mode within one switching period includes nine soft-switching commutation modes: Mode 1 [0~t0]: Turn on the switching transistor S A1 , and the DC input voltage U DC passes through the switching transistor S A1The switching transistor MOSFETS1 powers the first auxiliary network until the voltage u across the capacitor C A1 and the voltage u across the capacitor C CA1 reach the value of U A2 at time t0; at time t0, turn off the switching transistor S CA2 and turn on the switching transistor S DC simultaneously; A1 A3 A1 Mode 2 [t0~t1]: At time t0, the capacitors C and C A2 limit the rising rate of the voltage u across the switching transistor S A1 to achieve zero-voltage turn-off of the switching transistor S SA1 ; at this time, the voltage u across the switching transistor S A1 is zero, and the switching transistor S A3 achieves zero-voltage turn-on; subsequently, the capacitors C SA3 and C A3 begin to discharge, and the voltages u across the capacitors C A1 and C A2 linearly decrease to zero, reaching time t1; A1 CA1 A2 CA2 A2 A A2 SA2 A2 A Mode 3 [t1~t2]: At time t1, the DC bus voltage has dropped to zero, and the switching transistors MOSFETS1, MOSFETS2, and MOSFETS4 perform zero-loss switching. The switching transistor MOSFET S 3 is in the off state until the switching is completed, reaching time t2; the duration of [t1~t2] is not less than the dead time of the system; Mode 4 [t2~t3]: At time t2, turn on the switching transistor S A2 , and the inductor L A limits the current i A2 when the switching transistor S SA2 is turned on, so that the switching transistor S A2 achieves zero-current turn-on; the voltage u across the inductor L A is U LA , and the current i DC flowing through the inductor L A linearly increases until the current i LA rises to equal the current I0 flowing through the emitter-side compensation inductor L LA , reaching time t3; P1 Mode 5 [t3~t4]: At time t3, the inductor L A and the capacitor C A1 ​Resonance, in the charging state, the current i flowing through the inductor L A and the voltage u across the capacitor C LA increase non-linearly until the voltage u across the capacitor C A1 rises to U CA1 , reaching the moment t4; A1 Modal six [t4~t5]: At the moment t4, the resonance of the inductor L CA1 and the capacitor C DC ends; the inductor L and the body diode of the switch tube S A , the switch tube S A1 and the switch tube S A form a circulating current loop, reaching the moment t5; A1 Modal seven [t5~t6]: At the moment t5, the switch tube S A2 is turned off; the capacitor C A3 limits the rate of change of the voltage across the switch tube S at the turn-off moment, enabling the switch tube S A2 to achieve zero-voltage turn-off; the inductor L A2 and the capacitor C A2 resonate, the inductor L A2 releases electrical energy, the capacitor C A is in the charging mode, the current i flowing through the inductor L A2 decreases non-linearly, and the voltage u across the capacitor C A increases non-linearly until the voltage across the switch tube S A2 is equal to U A , reaching the moment t6; LA Modal eight [t6~t7]: At the moment t6, the resonance of the inductor L A2 and the capacitor C CA2 ends, the voltage across the inductor L A2 remains at U DC , the inductor L releases electrical energy, the current i flowing through the inductor L A decreases linearly, the current i flowing through the inductor L A2 at the moment t6 is greater than the current I0 flowing through the compensation inductor L on the transmitting side A , and starts to flow through the body diode of the switch tube S DC ; until the current i flowing through the inductor L A decreases linearly to be equal to the current I0 flowing through the compensation inductor L on the transmitting side A , the switch tube LA A LA P1 A1 A LA P1 A1 A LA P1 LA P1 P1 P1 SA1 The freewheeling of the body diode ends at time t7; Mode nine [t7~t8]: At time t7, the voltage across the inductor L A remains at U DC , and the current i A flowing through the inductor L LA continues to linearly decrease until it reaches zero at time t8, ending one switching cycle.

[0017] Advantages of the present invention: The present invention improves the bidirectional wireless power transmission system with the help of an active auxiliary network, and can improve the soft-switching stability of the system through commutation control.

[0018] The present invention realizes wide-range soft-switching of the bidirectional wireless power transmission system based on an active auxiliary network, can completely eliminate the switching losses of the main switches during the wireless charging and discharging processes, and the soft-switching operating range is the full load range; among them, the auxiliary switch tubes in the active auxiliary network do not have parallel auxiliary resonant capacitors, which can avoid potential adverse effects on the switch safety caused by the sudden discharge of the parallel resonant capacitors with a surge; during the process of the DC bus voltage dropping, only the energy transfer between the resonant capacitors is relied on, rather than the resonant state. Therefore, during the DC bus voltage dropping period, only the current of the compensation inductor flows through the active auxiliary circuit, thus reducing the losses of the auxiliary circuit, especially significantly improving the efficiency of the bidirectional wireless power transmission system under light load conditions.

[0019] The system of the present invention can achieve soft-switching under light load conditions, is not affected by the change of compensation parameters, and can achieve wide-range soft-switching control. Brief Description of the Drawings

[0020] Figure 1 is the circuit structure topology diagram of the bidirectional wireless power transmission system described in the present invention; in the figure, M PS is the mutual inductance between the transmitting coil L P and the receiving coil L S , u CB1 is the voltage across the capacitor C B1 , u CB2 is the voltage across the capacitor C B2 , i LB is the current flowing through the inductor L B ; Point A is the connection point of the switch tube MOSFETS1 and the switch tube MOSFETS2, Point B is the connection point of the switch tube MOSFETS3 and the switch tube MOSFETS4, Point C is the connection point of the switch tube MOSFETS5 and the switch tube MOSFETS6, and Point D is the connection point of the switch tube MOSFETS7 and the switch tube MOSFETS8; Figures 2 to 10Equivalent circuit diagrams of nine modes within one switching period of the soft-switching commutation process in the charging mode of the wide-range soft-switching control method for the bidirectional wireless power transfer system described in the present invention; among them Figure 2 is the equivalent circuit diagram of the first mode of the commutation process; Figure 3 is the equivalent circuit diagram of the second mode of the commutation process; Figure 4 is the equivalent circuit diagram of the third mode of the commutation process; Figure 5 is the equivalent circuit diagram of the fourth mode of the commutation process; Figure 6 is the equivalent circuit diagram of the fifth mode of the commutation process; Figure 7 is the equivalent circuit diagram of the sixth mode of the commutation process; Figure 8 is the equivalent circuit diagram of the seventh mode of the commutation process; Figure 9 is the equivalent circuit diagram of the eighth mode of the commutation process; Figure 10 is the equivalent circuit diagram of the ninth mode of the commutation process; in the figure, U AB is the voltage between points A and B; Figure 11 is the characteristic working waveform diagram of key components in nine working modes within one switching period of the wide-range soft-switching control method for the bidirectional wireless power transfer system described in the present invention; in the figure, u gS1 represents the driving voltage of the switching tube MOSFET S1, u gS2 represents the driving voltage of the switching tube MOSFET S2, u gSA1 represents the driving voltage of the switching tube S A1 the driving voltage of, u gSA2 represents the driving voltage of the switching tube S A2 the driving voltage of, u gSA3 represents the driving voltage of the switching tube S A3 the driving voltage of, u DA1 represents the voltage across the diode D A1 the current flowing through the diode D DA2 represents the current flowing through the diode D A2 the voltage across, u DA2 represents the voltage across the diode D A the voltage across 2, u SA2 represents the voltage across the switching tube S A2 the current flowing through the switching tube S SA1 represents the current flowing through the switching tube S A1 the current flowing through, u SA1 represents the voltage across the switching tube S A1 the current flowing through the switching tube S SA3 represents the current flowing through the switching tube S A3 the current flowing through; Figure 12 is the simulation waveform diagram of u SA1 and i SA1 in the wide-range soft-switching control method for the bidirectional wireless power transfer system described in the present invention; Figure 13In the wide - range soft - switching control method of the bidirectional wireless power transfer system of the present invention, u SA2 and the current i A2 flowing through the switching transistor S SA2 ; the simulation waveform diagram Figure 14 In the wide - range soft - switching control method of the bidirectional wireless power transfer system of the present invention, the voltage u A3 across both ends of the switching transistor S SA3 and i SA3 ; the simulation waveform diagram Figure 15 In the wide - range soft - switching control method of the bidirectional wireless power transfer system of the present invention, the simulation waveform diagrams of u CA1 , u CA2 and i LA in the charging mode Specific embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention

[0022] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other

[0023] Next, the present invention will be further described in conjunction with the accompanying drawings, but it is not a limitation of the present invention

[0024] Specific embodiment 1. As shown in Figure 1 , the present invention provides a bidirectional wireless power transfer system, including a DC input voltage U DC , an inverter circuit, a first auxiliary network, an input electrolytic capacitor C O1 , a transmitting - end compensation network, a coupling mechanism, a receiving - end compensation network, a rectifier circuit, a second auxiliary network, an output electrolytic capacitor C O2 and a charging voltage U BAT ; An input electrolytic capacitor C DC and a first auxiliary network are arranged in parallel between the DC input voltage U O1 and the inverter circuit; the inverter circuit is connected to the coupling mechanism through the transmitting - end compensation network, and the coupling mechanism is then connected to the rectifier circuit through the receiving - end compensation network; a second auxiliary network and an output electrolytic capacitor C BAT are arranged in parallel between the rectifier circuit and the charging voltage U O2 ; The first auxiliary network is composed of a circuit structure from the DC input voltage U DC side to the inverter circuit side, which is the same as the circuit structure of the second auxiliary network from the charging voltage U BAT side to the rectifier circuit side; the first auxiliary network includes switch tube S A1 , switch tube S A2 , inductor L A , capacitor C A1 , capacitor C A2 , diode D A1 and diode D A2 . By using switch tube S A1 and switch tube S A2 to control the resonance state of inductor L A , capacitor C A1 and capacitor C A2 , it provides the necessary conditions for realizing the full-range soft switching of the inverter switch tube. The energy feedback function is realized through diode D A1 and diode D A2 ; the second auxiliary network includes switch tube S B1 , switch tube S B2 , inductor L B , capacitor C B1 , capacitor C B2 , diode D B1 and diode D B2 . By using switch tube S B1 and switch tube S B2 to control the resonance state of inductor L B , capacitor C B1 and capacitor C B2 , it provides the necessary conditions for realizing the full-range soft switching of the rectifier switch tube. The energy feedback function is realized through diode D B1 and diode D B2 .

[0025] Furthermore, the first auxiliary network further includes switch tube S A3 ; The positive pole of the DC input voltage U DC is connected to one end of the input electrolytic capacitor C O1 , and the negative pole of the DC input voltage U DC is connected to the other end of the input electrolytic capacitor C O1 ; the negative pole of the DC input voltage U DC is connected to the anode of diode D A1 and one end of capacitor C A1 . The cathode of diode D A1 is connected to the anode of diode D A2 and one end of capacitor C A2 . The cathode of diode D A2The cathode of which is connected to the inductance L A One end of the inductance L A The other end is connected to the capacitance C A1 The other end of which and the capacitance C A2 The other end; The diode D A2 The cathode of which is connected to the source electrode of the switching tube S A2 One end of the inductance L A2 The drain electrode of which is connected to the drain electrode of the switching tube S A1 One end of the inductance L A1 The source electrode of which is connected to the source electrode of the switching tube S A3 One end of the inductance L A3 The drain electrode of which is connected to the other end of the inductance L A The other end.

[0026] This embodiment is implemented based on an active auxiliary network. The soft switch can operate within the full load range, and particularly significantly improves the efficiency of the bidirectional wireless power transmission system under light load conditions.

[0027] The inverter circuit includes switching tubes MOSFETS1, MOSFETS2, MOSFETS3, and MOSFETS4. Switching tubes MOSFETS1 and MOSFETS2 form the first bridge arm of the inverter circuit, and switching tubes MOSFETS3 and MOSFETS4 form the second bridge arm of the inverter circuit; the drain electrode of switching tube MOSFETS1 is connected to the source electrode of switching tube S A3 One end of the inductance L DC The source electrode of switching tube MOSFETS1 is connected to the drain electrode of switching tube MOSFETS2, and the source electrode of switching tube MOSFETS2 is connected to the negative pole of the DC input voltage U

[0028] No parallel resonant capacitors are connected to the switching tubes in the inverter circuit. This design method can eliminate the potential adverse effects on the safety of the switching tubes caused by the sudden discharge of the parallel resonant capacitors to generate electric surges. That is to say, not setting parallel resonant capacitors for the switching tubes is more conducive to improving the safety of the switching tubes and ensuring the long-term safe operation of the wireless charging system in a complex industrial environment.

[0029] The transmitting end compensation network includes a transmitting side compensation inductance L P1 , a transmitting side compensation capacitance C P1 and a transmitting side compensation capacitance C P ; The source electrode of switching tube MOSFETS1 is connected to the transmitting side compensation inductance L P1At one end, the transmitting - side compensating inductor L P1 The other end is connected to the transmitting - side compensating capacitor C P1 At one end, the transmitting - side compensating capacitor C P1 The other end is connected to the drain of the switching transistor MOSFETS4; the transmitting - side compensating inductor L P1 The other end is connected to the transmitting - side compensating capacitor C P At one end, the transmitting - side compensating capacitor C P The other end is used to connect to one input connection end of the coupling mechanism, and the transmitting - side compensating capacitor C P1 The other end is used to connect to the other input connection end of the coupling mechanism.

[0030] The coupling mechanism includes a transmitting side and a receiving side. The transmitting side includes a transmitting coil L P , and the receiving side includes a receiving coil L S ; The same - named end of the transmitting coil L P is connected to the other end of the transmitting - side compensating capacitor C P The different - named end of the transmitting coil L P is connected to the drain of the switching transistor MOSFETS4; The same - named end of the receiving coil L S is used as one connection end of the receiving - side compensation network, and the different - named end of the receiving coil L S is used as the other connection end of the receiving - side compensation network.

[0031] The receiving - side compensation network includes a receiving - side compensating capacitor C S , a receiving - side compensating inductor L S1 and a receiving - side compensating capacitor C S1 ; The same - named end of the receiving coil L S is connected to one end of the receiving - side compensating capacitor C S The other end of the receiving - side compensating capacitor C S is connected to one end of the receiving - side compensating capacitor C S1 The other end of the receiving - side compensating capacitor C S1 is connected to the different - named end of the receiving coil L S ; The other end of the receiving - side compensating capacitor C S is connected to one end of the receiving - side compensating inductor L S1 The other end of the receiving - side compensating inductor L S1 is used as one connection end of the rectifying circuit, and the other end of the receiving - side compensating capacitor C S1 is used as the other connection end of the rectifying circuit.

[0032] The rectifier circuit includes switching transistors MOSFETS5, MOSFETS6, MOSFETS7, and MOSFETS8. Switching transistors MOSFETS5 and MOSFETS6 form the first arm of the rectifier circuit, and switching transistors MOSFETS7 and MOSFETS8 form the second arm of the rectifier circuit; the other end of the receiving-side compensation inductor L S1 is connected to the source of switching transistor MOSFETS5. The drain of switching transistor MOSFETS5 is connected to the drain of switching transistor MOSFETS7. The source of switching transistor MOSFETS7 is connected to the other end of the receiving-side compensation capacitor C S1 and the drain of switching transistor MOSFETS8. The source of switching transistor MOSFETS8 is connected to the source of switching transistor MOSFETS6. The drain of switching transistor MOSFETS6 is connected to the source of switching transistor MOSFETS5.

[0033] The second auxiliary network further includes a switching transistor S B3 ; The source of switching transistor S B1 is connected to the drain of switching transistor MOSFETS7 and the source of switching transistor S B3 . The drain of switching transistor S B1 is connected to the drain of switching transistor S B2 . The source of switching transistor S B2 is connected to one end of inductor L B . The other end of inductor L B is connected to the drain of switching transistor S B3 and one end of capacitor C B1 . The other end of capacitor C B1 is connected to the source of switching transistor MOSFETS8; The source of switching transistor S B2 is connected to the cathode of diode D B2 . The anode of diode D B2 is connected to one end of capacitor C B2 and the cathode of diode D B1 . The other end of capacitor C B2 is connected to the other end of inductor L B ; The anode of diode D B1 is connected to the source of switching transistor MOSFETS8; The drain of switching transistor S B1 is connected to one end of the output electrolyte capacitor C O2 and the positive pole of the charging voltage U BAT . The other end of the output electrolyte capacitor C O2 is connected to the source of switching transistor MOSFETS8 and the negative pole of the charging voltage U BAT .

[0034] The bidirectional wireless power transmission system described in this embodiment can achieve efficient charging and discharging in the full load range.

[0035] In this embodiment, the branch composed of diode D A1 (D B1 ), capacitor C A1 (C B1 ), capacitor C A2 (C B2 ) and switching tube S A3 (S B3 ) is designed to be connected in parallel with the bridge arm. By discharging capacitors C A1 (C B1 ) and C A2 (C B2 ), the DC bus voltage is reduced to zero.

[0036] The loop composed of DC input voltage U DC (U BAT ), switching tube S A2 (S B2 ), inductor L A (L B ), switching tube S A3 (S B3 ) and the bridge arm is to store enough energy of DC input voltage U DC (U BAT ) into L A (L B ) before the DC bus voltage rises from zero.

[0037] The loop composed of DC input voltage U DC (U BAT ), switching tube S A2 (S B2 ), inductor L A (L B ) and capacitor C A1 (C B1 ) is to make the DC bus voltage rise from zero through the resonance between inductor L A (L B ) and capacitor C A1 (C B1 ).

[0038] The loop composed of inductor L A (L B ), capacitor C A2 (C B2 ) and diode D A2 (D B2 ) is to utilize the resonance between inductor L A and capacitor C A2 (CB2 ), the resonance between the inductance L A (L B ) transfers part of the redundant energy in the inductance L A2 (C B2 ).

[0039] The circuit composed of the DC input voltage U DC (U BAT ), the switching transistor S A1 (S B1 ), the switching transistor S A3 (S B3 ), the inductance L A (L B ), the diode D A2 (D B2 ) and the diode D A1 (D B1 ) is to feedback part of the redundant energy in the inductance L A (L B ) back to the DC input voltage U DC (U BAT ).

[0040] The designed functions of the switching transistor S A1 (S B1 ) and the switching transistor S A2 (S B2 ) are to trigger the reduction and increase of the DC bus voltage respectively.

[0041] The function of the switching transistor S A3 (S B3 ) is to ensure that the capacitor C A1 (C B1 ) will not be directly connected in parallel with the bridge arm. Otherwise, control interference may cause the bridge arm to be in a through state, and in this way, the capacitor C A1 (C B1 ) suddenly discharges to generate a surge current, which will damage the switching transistors in the inverter circuit or the rectifier circuit.

[0042] During the process of the DC bus voltage drop of the described bidirectional wireless power transmission system, it is only based on the energy transfer between the resonant capacitors, rather than the resonant state. Therefore, during the process of the DC bus voltage drop, only the input current of the transmitter or the receiver will flow through the auxiliary network, which is beneficial to reducing the loss of the auxiliary network. Especially in the case of light load, the efficiency can be effectively improved.

[0043] Specific Embodiment 2. As shown in combination Figures 1 to 11 , the present invention also provides a wide-range soft-switching control method for a bidirectional wireless power transmission system, which is used for switching control of the bidirectional wireless power transmission system described in Specific Embodiment 1, including: The soft-switching commutation principle of the charging mode and the discharging mode of the bidirectional wireless power transmission system is the same; the soft-switching control of the charging mode within one switching cycle includes nine soft-switching commutation modes: Mode 1 [0~t0]: Turn on switch S A1 , and the DC input voltage U DC feeds energy to the first auxiliary network through switch S A1 and switch MOSFETS1 until the voltages u A1 across capacitor C CA1 and the voltage u A2 across capacitor C CA2 reach U DC , reaching time t0; at time t0, turn off switch S A1 and turn on switch S A3 simultaneously. Mode 2 [t0~t1]: At time t0, capacitors C A1 and C A2 limit the rising rate of the voltage u A1 across switch S SA1 , enabling switch S A1 to achieve zero-voltage turn-off; at this time, the voltage u A3 across switch S SA3 is zero until switch S A3 is turned on, and switch S A3 achieves zero-voltage turn-on; subsequently, capacitors C A1 and C A2 start to discharge, and the voltages u A1 across capacitor C CA1 and the voltage u A2 across capacitor C CA2 linearly decrease to zero, reaching time t1. Mode 3 [t1~t2]: At time t1, the DC bus voltage has dropped to zero, and switches MOSFETS1, MOSFETS2, and MOSFETS4 perform zero-loss switching. Switch MOSFET S 3 is in the off state until the switching is completed, reaching time t2; the duration of [t1~t2] is not less than the dead-time working duration of the system. Mode 4 [t2~t3]: At time t2, turn on switch S A2 , and inductor L A limits the current i A2 when switch S SA2 is turned on, enabling switch S A2 to achieve zero-current turn-on; the voltage u A across inductor L LA is U DC , and the current flowing through inductor LA The current i LA increases linearly until the current i LA rises to equal the current I0 flowing through the compensation inductor L on the emission side, reaching the moment t3; P1 Mode Five [t3~t4]: At the moment t3, the inductor L A and the capacitor C A1 resonate and are in a charging state. The current i flowing through the inductor L A LA and the capacitor C A1 The voltage u across CA1 increases non-linearly until the voltage u across the capacitor C A1 CA1 rises to U DC , reaching the moment t4; Mode Six [t4~t5]: At the moment t4, the resonance of the inductor L A and the capacitor C A1 ends; The inductor L A , the body diode of the switch tube S A1 , the switch tube S A2 and the switch tube S A3 form a circulating current loop, reaching the moment t5; Mode Seven [t5~t6]: At the moment t5, the switch tube S A2 turns off; The capacitor C A2 limits the rate of change of the voltage across the switch tube S A2 at the turn-off moment, enabling the switch tube S A2 to achieve zero-voltage turn-off; The inductor L A and the capacitor C A2 resonate. The inductor L A releases electrical energy, and the capacitor C A2 is in a charging mode. The current i flowing through the inductor L A LA decreases non-linearly, and the voltage u across the capacitor C A2 CA2 increases non-linearly until the voltage across the switch tube S A2 equals U DC , reaching the moment t6; Mode Eight [t6~t7]: At the moment t6, the resonance of the inductor L A and the capacitor C A2 ends. The voltage across the inductor L A remains at U DC . The inductor L A releases electrical energy. The current i flowing through the inductor L A LA decreases linearly. The current i flowing through the inductor L A LAGreater than the current I0 flowing through the compensation inductor L on the transmitting side P1 The current starts to flow through the body diode of the switching transistor S A1 until the current i A flowing through the inductor L LA linearly decreases to equal the current I0 flowing through the compensation inductor L on the transmitting side P1 At this time, the freewheeling of the body diode of the switching transistor S A1 ends, reaching time t7; Mode nine [t7~t8]: At time t7, the voltage across the inductor L A remains at U DC The current i A flowing through the inductor L LA continues to linearly decrease until it equals zero, reaching time t8, and a switching cycle ends.

[0044] In this embodiment, the duty cycle of the switching transistor in the auxiliary network and the related delay time can be set to constant values. Therefore, there is no need to adjust the related delay time in real time by detecting the instantaneous value of the input current of the transmitter or receiver, thus eliminating the interference that may be caused by the current detection of the transmitter or receiver, which is very beneficial to improving the reliability of the bidirectional wireless power transmission system.

[0045] Simulation verification: The following verifies and analyzes through software to build a simulation model. The main simulation parameters selected for the simulation are shown in Table 1: Table 1 Main simulation parameters parameter value parameter value <![CDATA[DC input voltage U DC > 100V <![CDATA[Receiving-side compensation inductor L S1 > 22.8µH <![CDATA[System operating frequency f S > 100 kHz <![CDATA[Receiving-side compensation capacitor C S1 > 154.0 nF <![CDATA[Transmitting coil L P > 37.0µH <![CDATA[Receiving-side compensation capacitor C S > 210.8 nF <![CDATA[Receiving coil L S > 39.4µH <![CDATA[Inductor L A (Inductor L B )]]> 2µH <![CDATA[Mutual inductance M between the transmitting coil and the receiving coil PS > 12.75µH <![CDATA[Capacitor C A1 (Capacitor C B1 )]]> 15 nF <![CDATA[Emitter-side compensation inductor L P1 > 21.4µH <![CDATA[Capacitor C A2 (Capacitor C B2 )]]> 22 nF From Figure 12 it can be found that the switching transistor S A1 realizes zero-voltage turn-on and zero-voltage turn-off. From Figure 13 it can be found that the switching transistor S A2 realizes zero-current turn-on and zero-voltage turn-off. From Figure 14 it can be seen that the switching transistor S A3 realizes zero switching loss. From Figure 15 it can be seen that the changing trends of u CA1 , u CA2 and i LA are basically consistent with the theoretical analysis. Thus, the effect of the present invention is verified.

[0046] Although the present invention has been described herein with reference to particular embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should thus be understood that numerous modifications may be made to the exemplary embodiments, and other arrangements may be devised, without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in ways different from those described in the original claims. It should also be understood that the features described in connection with separate embodiments may be used in other described embodiments.

Claims

1. A bidirectional wireless power transmission system, characterized in that, including a DC input voltage U DC , an inverter circuit, a first auxiliary network, an input electrolytic capacitor C O1 , a transmitter compensation network, a coupling mechanism, a receiver compensation network, a rectifier circuit, a second auxiliary network, an output electrolytic capacitor C O2 and a charging voltage U BAT ; Between the DC input voltage U DC and the inverter circuit, an input electrolytic capacitor C O1 and a first auxiliary network are arranged in parallel; the inverter circuit is connected to a coupling mechanism through a transmitting-end compensation network, and the coupling mechanism is then connected to a rectifier circuit through a receiving-end compensation network; between the rectifier circuit and the charging voltage U BAT a second auxiliary network and an output electrolytic capacitor C O2 are arranged in parallel; The first auxiliary network is supplied with a DC input voltage U DC The circuit structure of the inverter circuit side and the second auxiliary network are charged by the charging voltage U BAT The circuit structure of the first auxiliary network is the same as that of the rectifier circuit side; the first auxiliary network includes a switch tube S A1 , switch tube S A2 、Inductance L A , capacitor C A1 , capacitor C A2 、Diode D A1 and diode D A2 , using the switch tube S A1 And switch tube S A2 For inductance L A , capacitor C A1 and capacitor C A2 The resonant state is controlled to provide the necessary conditions for realizing the full range soft switching of the inverter switch tube. A1 and diode D A2 Realize the energy feedback function; the second auxiliary network includes a switch tube S B1 , switch tube S B2 、Inductance L B , capacitor C B1 , capacitor C B2 、Diode D B1 and diode D B2 , using the switch tube S B1 And switch tube S B2 For inductance L B , capacitor C B1 and capacitor C B2 The resonant state is controlled to provide the necessary conditions for realizing the full range soft switching of the rectifier switch tube. B1 and diode D B2 Realize energy feedback function; The first auxiliary network further includes a switching transistor S A3 ; DC input voltage U DC The positive pole is connected to one end of the input electrolytic capacitor C O1 The negative pole of the DC input voltage U DC is connected to the other end of the input electrolytic capacitor C O1 The negative pole of the DC input voltage U DC is connected to the anode of the diode D A1 and one end of the capacitor C A1 The cathode of the diode D A1 is connected to the anode of the diode D A2 and one end of the capacitor C A2 The cathode of the diode D A2 is connected to one end of the inductor L A The other end of the inductor L A is connected to the other end of the capacitor C A1 and the other end of the capacitor C A2 and the other end; Diode D A2 whose cathode is connected to the source of switch transistor S A2 ; the drain of switch transistor S A2 is connected to the drain of switch transistor S A1 ; the source of switch transistor S A1 is connected to the source of switch transistor S A3 ; the source of switch transistor S A3 whose drain is connected to the other end of inductor L A .

2. The bidirectional wireless power transmission system according to claim 1, wherein The inverter circuit includes switching transistors MOSFETS1, MOSFETS2, MOSFETS3, and MOSFETS4. The drain of switching transistor MOSFETS1 is connected to the source of switching transistor S A3 The source of switching transistor MOSFETS1 is connected to the drain of switching transistor MOSFETS2. The source of switching transistor MOSFETS2 is connected to the negative terminal of the DC input voltage U DC The source of switching transistor MOSFETS2 is connected to the source of switching transistor MOSFETS4. The drain of switching transistor MOSFETS4 is connected to the source of switching transistor MOSFETS3. The drain of switching transistor MOSFETS3 is connected to the drain of switching transistor MOSFETS1.

3. The bidirectional wireless power transmission system according to claim 2, wherein The transmitting - end compensation network includes a transmitting - side compensation inductor L P1 , a transmitting - side compensation capacitor C P1 and a transmitting - side compensation capacitor C P ; The source electrode of the switching transistor MOSFET S1 is connected to one end of the emitter-side compensation inductor L P1 ; the other end of the emitter-side compensation inductor L P1 is connected to one end of the emitter-side compensation capacitor C P1 ; the other end of the emitter-side compensation capacitor C P1 is connected to the drain electrode of the switching transistor MOSFET S4; The compensation inductor L on the transmitting side P1 The other end of which is connected to one end of the compensation capacitor C on the transmitting side P The compensation capacitor C on the transmitting side P The other end of which is used to connect to an input connection end of the coupling mechanism. The other end of the compensation capacitor C on the transmitting side P1 The other end of which is used to connect to the other input connection end of the coupling mechanism.

4. The bidirectional wireless power transmission system according to claim 3, wherein The coupling mechanism includes a transmitting side and a receiving side. The transmitting side includes a transmitting coil L P , and the receiving side includes a receiving coil L S ; Transmitting coil L P The same-name terminal of which is connected to the other end of the transmitting-side compensation capacitor C P The other end of the transmitting coil L P The different-name terminal of which is connected to the drain of the switching transistor MOSFET S4; Receiving coil L S The like-named terminal of S is used as one connection terminal of the receiving-end compensation network, and the unlike-named terminal of the receiving coil L is used as the other connection terminal of the receiving-end compensation network.

5. The bidirectional wireless power transmission system according to claim 4, characterized in that, The receiving - end compensation network includes the receiving - side compensation capacitor C S , the receiving - side compensation inductor L S1 and the receiving - side compensation capacitor C S1 ; Receiving coil L S The same-name terminal of which is connected to one end of the receiving-side compensation capacitor C S The other end of the receiving-side compensation capacitor C S The other end of which is connected to one end of the receiving-side compensation capacitor C S1 The other end of the receiving-side compensation capacitor C S1 The other end of which is connected to the different-name terminal of the receiving coil L S The other end of the receiving-side compensation capacitor C S The other end of which is connected to one end of the receiving-side compensation inductor L S1 The other end of the receiving-side compensation inductor L S1 Is used as one connection terminal of the rectifying circuit, and the other end of the receiving-side compensation capacitor C S1 Is used as the other connection terminal of the rectifying circuit.

6. The bidirectional wireless power transmission system according to claim 5, wherein The rectifier circuit includes switching transistors MOSFETS5, MOSFETS6, MOSFETS7, and MOSFETS8, and the receiving-side compensation inductor L S1 The other end of which is connected to the source electrode of switching transistor MOSFETS5, the drain electrode of switching transistor MOSFETS5 is connected to the drain electrode of switching transistor MOSFETS7, and the source electrode of switching transistor MOSFETS7 is connected to the other end of the receiving-side compensation capacitor C S1 and the drain electrode of switching transistor MOSFETS8. The source electrode of switching transistor MOSFETS8 is connected to the source electrode of switching transistor MOSFETS6, and the drain electrode of switching transistor MOSFETS6 is connected to the source electrode of switching transistor MOSFETS5.

7. The bidirectional wireless power transmission system according to claim 6, characterized in that, The second auxiliary network further includes a switching transistor S B3 ; Switching transistor S B1 's source electrode is connected to the drain electrode of switching transistor MOSFETS7 and the source electrode of switching transistor S B3 's source electrode. The drain electrode of switching transistor S B1 's drain electrode is connected to the drain electrode of switching transistor S B2 's drain electrode. The source electrode of switching transistor S B2 's source electrode is connected to one end of inductor L B . The other end of inductor L B is connected to the drain electrode of switching transistor S B3 and one end of capacitor C B1 . The other end of capacitor C B1 is connected to the source electrode of switching transistor MOSFETS8; Switching transistor S B2 whose source is connected to the cathode of diode D B2 ; the anode of diode D B2 is connected to one end of capacitor C B2 and the cathode of diode D B1 ; the other end of capacitor C B2 is connected to the other end of inductor L B ; the anode of diode D B1 is connected to the source of switching transistor MOSFETS8; Switching transistor S B1 whose drain is connected to one end of the output electrolytic capacitor C O2 and the positive electrode of the charging voltage U BAT The other end of the output electrolytic capacitor C O2 is connected to the source of the switching transistor MOSFETS8 and the negative electrode of the charging voltage U BAT .

8. A wide-range soft-switching control method for a bidirectional wireless power transmission system, which is used for switching control of the bidirectional wireless power transmission system described in claim 7, characterized in that Including: The soft-switching commutation principles of the charging mode and the discharging mode of the bidirectional wireless power transfer system are the same; the soft-switching control of the charging mode within one switching cycle includes nine soft-switching commutation modes: Mode 1 [0~t0]: Turn on the switch tube S A1 to conduct, and the DC input voltage U DC is supplied to the first auxiliary network through the switch tube S A1 and the switch tube MOSFETS1 until the voltage u A1 across the capacitor C CA1 and the voltage u A2 across the capacitor C CA2 reach the value of U DC , reaching the moment t0; at the moment t0, turn off the switch tube S A1 and turn on the switch tube S A3 simultaneously; Mode 2 [t0~t1]: At time t0, capacitor C A1 and capacitor C A2 limit the rising rate of the voltage u A1 across the switching device S SA1 to achieve zero-voltage turn-off of the switching device S A1 ; at this time, the voltage u A3 across the switching device S SA3 is zero, and zero-voltage turn-on of the switching device S A3 is achieved; subsequently, capacitors C A1 and C A2 start to discharge, and the voltages u A1 across capacitor C CA1 and the voltage u A2 across capacitor C CA2 linearly decrease to zero, reaching time t1; Mode three [t1~t2]: At time t1, the DC bus voltage has dropped to zero, and the switching transistors MOSFETS1, MOSFETS2, and MOSFETS4 perform zero-loss switching. The switching transistor MOSFETS3 is in the off state until the switching is completed, reaching time t2; the duration of [t1~t2] is not less than the dead-time operating time of the system; Mode Four [t2~t3]: At time t2, turn on switch S A2 to conduct, and inductor L A limits the current i A2 when switch S SA2 conducts, enabling switch S A2 to achieve zero-current turn-on; the voltage u A across inductor L LA is U DC , and the current i A flowing through inductor L LA increases linearly until the current i LA rises to equal the current I0 flowing through the emitter-side compensation inductor L P1 , reaching time t3; Mode Five [t3~t4]: At time t3, the inductor L A and the capacitor C A1 resonate and are in a charging state. The current i A flowing through the inductor L LA and the voltage u A1 across the capacitor C CA1 increase non-linearly until the voltage u A1 across the capacitor C CA1 rises to U DC , reaching time t4; Mode six [t4~t5]: At time t4, inductor L A and capacitor C A1 complete resonance; Inductor L A , the body diode of switch S A1 , switch S A2 and switch S A3 form a circulating current loop and reach time t5; Mode Seven [t5~t6]: At time t5, switch S A2 turns off; capacitor C A2 limits the rate of change of the voltage across switch S A2 at the turn-off moment, enabling switch S A2 to achieve zero-voltage turn-off; inductor L A and capacitor C A2 resonate, inductor L A releases electrical energy, capacitor C A2 is in the charging mode, the current i A flowing through inductor L LA decreases non-linearly, and the voltage u A2 across capacitor C CA2 increases non-linearly until the voltage across switch S A2 equals U DC , reaching time t6; Mode 8 [t6~t7]: At time t6, the inductance L A and capacitor C A2 Resonance ends, inductance L A The voltage across the terminals is maintained at U DC , inductance L A Release electrical energy and flow through inductor L A The current i LA Linear decrease, flowing through the inductor L at time t6 A The current i LA Greater than the current flowing through the transmitter side compensation inductor L P1 The current I0 begins to flow through the switch tube S A1 until the current flows through the inductor L A The current i LA Linearly decreases to equal the current flowing through the transmitter side compensation inductor L P1 The current I0, the switch tube S A1 The body diode freewheeling ends, reaching the moment t7; Mode Nine [t7~t8]: At time t7, the voltage across the inductor L A remains at U DC , and the current i A flowing through the inductor L LA continues to linearly decrease until it reaches zero at time t8, marking the end of a switching cycle.

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