A single-stage bidirectional wireless energy transmission system and transmission method for electric vehicles

Abstract

The present invention discloses a single-stage bidirectional wireless energy transmission system and a transmission method for an electric vehicle, wherein the transmission system includes: a primary-side switching network, a resonant network and a secondary-side switching network; the transmitting end of the resonant network is connected to the output end of the primary-side switching network, and the receiving end of the resonant network is connected to the output end of the secondary-side switching network; the primary-side switching network includes: a first full-bridge circuit; a bus capacitor connected in parallel with the first full-bridge structure; a PFC inductor connected to the input end of the full-bridge structure; the input end of the primary-side switching network is connected to an AC power grid; the secondary-side switching network includes: a second full-bridge circuit; a voltage-stabilizing capacitor connected in parallel with the second full-bridge circuit; the input end of the secondary-side switching network is connected to a battery of the electric vehicle; when energy is transmitted in the forward direction, the battery on the secondary-side switching network side is discharged, and the primary-side switching network outputs AC power to the AC power grid; when energy is transmitted in the reverse direction, the primary-side switching network side provides AC power, and the secondary-side switching network charges the battery.

Description

Technical Field

[0001] The present invention relates to the automotive field, and more particularly to a single-stage bidirectional wireless energy transmission system and a transmission method for an electric vehicle. Background Art

[0002] To promote energy conservation and emission reduction and optimize the energy mix, new energy electric vehicles have become a crucial component of future electrified transportation. Electric vehicles are being vigorously promoted worldwide, gradually replacing fuel-powered vehicles as a new form of daily transportation. With the development of artificial intelligence and the digital age, electric vehicles and the Energy Internet are increasingly being integrated, enabling bidirectional power transmission between the two. This greatly facilitates electric vehicles' participation in grid scheduling and their integration with distributed microgrids. With the ongoing development of the Energy Internet, bidirectional power transmission between electric vehicles and the grid offers significant advantages for peak load shaving, off-load standby, peak power regulation, automatic generation control, and energy distribution. Furthermore, electric vehicle charging stations are widely distributed, resulting in uneven charging loads in both time and space. Electric vehicles capable of bidirectional charging and discharging can be viewed as mobile batteries for absorbing or storing intermittent energy sources such as wind power and photovoltaics. This helps improve the economic and environmental efficiency of the overall energy system and is of great significance to the development of digital and smart grids, as well as the transformation of society's energy structure. Currently, the main charging and discharging methods for electric vehicles on the market are wired and wireless. For wired charging and discharging, frequent plugging and unplugging can easily cause socket wear and aging, generating sparks; damaged lines can lead to safety hazards such as leakage; they are also less adaptable to stormy and frosty weather, occupy a large area, and have high manual operation and maintenance costs. In contrast, wireless charging and discharging has the advantages of small footprint, convenience and flexibility, no plugging and unplugging, high safety, immunity to severe weather, low maintenance costs, strong interaction with the power grid, and more intelligent charging and discharging.

[0003] Therefore, the optimization design, control methods, and interaction strategies of electric vehicle bidirectional wireless charging and discharging systems based on G2V and V2G, as well as grid-connected systems, are attracting more and more attention. Summary of the Invention

[0004] The purpose of the present invention is to propose a single-stage bidirectional wireless energy transmission system and method for electric vehicles. This system can construct a new single-stage bidirectional AC-AC converter with simple control and low cost to replace the two-stage bidirectional AC-DC-AC converter in the current electric vehicle wireless charging and discharging system, which has complex grid-side control and high cost.

[0005] In order to achieve the above objectives, the present invention provides a single-stage bidirectional wireless energy transmission system for electric vehicles, comprising:

[0006] Primary side switching network, resonant network and secondary side switching network;

[0007] The resonant network includes a transmitting end and a receiving end, the transmitting end is connected to the output end of the primary side switching network, and the receiving end is connected to the output end of the secondary side switching network; the transmitting end has a transmitting coil, and the receiving end has a receiving coil, and the transmitting coil and the receiving coil are arranged opposite to each other;

[0008] The primary switch network includes: a first full-bridge circuit; a bus capacitor connected in parallel with the first full-bridge structure; a PFC inductor connected to the input end of the full-bridge structure; the input end of the primary switch network is connected to the AC power grid;

[0009] The secondary side switch network includes: a second full-bridge circuit; a voltage stabilizing capacitor connected in parallel with the second full-bridge circuit; an input end of the secondary side switch network is connected to the battery of the electric vehicle;

[0010] During forward energy transmission, the battery on the secondary switch network side discharges, and the primary switch network outputs AC power to the AC power grid; during reverse energy transmission, the primary switch network side provides AC power, and the secondary switch network charges the battery.

[0011] In an optional solution, the transmitting end further includes a transmitting tuning capacitor connected in series with the transmitting coil; the receiving end further includes a receiving tuning capacitor connected in series with the receiving coil, and the resonant network is an SS topology structure.

[0012] In an optional solution, the transmitting end further includes a first capacitor, a second capacitor and a first inductor, the receiving end further includes a third capacitor, a fourth capacitor and a second inductor, and the resonant network is an LCC-LCC topology structure.

[0013] In an optional solution, the first full-bridge circuit and the second full-bridge circuit each include four fully-controlled switching devices and anti-parallel diodes therefor.

[0014] In an optional solution, the transmitting end of the resonant network and the primary-side switch network are located at the bottom of the electric vehicle, and the receiving end of the resonant network and the secondary-side switch network are buried underground.

[0015] The present invention also provides a single-stage bidirectional wireless energy transmission method for electric vehicles, utilizing the above-mentioned transmission system, the method comprising:

[0016] By using the bipolar PWM modulation method, a sine wave modulated PWM wave v is generated at the output end of the primary switching network. ab , v ab It contains a low-frequency component v with the same frequency as the AC power supply ab,L, and the switching frequency f s The high frequency component v ab,H , assuming the AC voltage of the AC grid is

[0017] v g (t) = V g sinω L t (1)

[0018] Among them, V g is the voltage amplitude of the AC grid, ω L is the voltage angular frequency of the AC grid;

[0019] For the low-frequency component, the following equation is satisfied

[0020]

[0021] Adopt double closed-loop control strategy to make the low-frequency component v ab,L Lagging or leading v g At an angle δ, the current i of the primary switch network circuit input by the AC grid is g AC voltage v with AC grid g Maintaining the same phase or reverse direction, while making the primary switch network work in the rectification or inversion state, realizes the bidirectional flow of energy.

[0022] In the optional scheme, the secondary voltage v is generated by the following method cd : In the second full-bridge structure, the upper and lower switches of the same bridge arm maintain a 50% duty cycle and are switched at a switching frequency f s Operation, the phase lag of adjacent bridge arms is in:

[0023] Among the options, v ab As the input quantity of the primary side of the resonant network, through phase shift control, the input quantity v provided by the secondary side switch network circuit is cd The input quantity v of the primary side switch network circuit ab Cooperate to realize the bidirectional flow of energy between the resonant networks; when the resonant network is an SS topology, v ab Lag v cd When the energy is transferred in the forward direction, v ab Advance v cd When the resonant network is an LCC-LCC topology, the energy is transmitted in the reverse direction. ab Advance v cd When the energy is transferred in the forward direction, v ab Lag v cd , energy is transferred in the reverse direction.

[0024] In an optional solution, during phase shift control, the phase shift angle θ is set to ±90°.

[0025] In an optional solution, the resonant frequency of the resonant network satisfies the following relationship:

[0026]

[0027] Where ω0 is the resonant frequency, ω s is the switching frequency of the primary switching network circuit and the secondary switching network circuit, Lp and Ls are the self-inductance of the transmitting coil and the receiving coil, M is the mutual inductance between the transmitting coil and the receiving coil, there is an air gap between the two windings, and the coupling coefficient k is, where

[0028]

[0029] The beneficial effects of the present invention are:

[0030] On the one hand, the present invention utilizes a single-stage AC-AC structure at the transmitter end, which offers advantages such as a reduced number of components and high power density, further improving charging efficiency and reducing the size and weight of the charger. On the other hand, the bidirectional transmission structure addresses the wide geographical distribution of electric vehicle charging stations and the uneven temporal and spatial distribution of charging loads. By treating electric vehicles as mobile batteries to absorb or store intermittent energy sources such as wind power and photovoltaics, this helps improve the economic and environmental benefits of the overall operation of the energy system, and is of great significance to the construction of digital and smart grids, as well as the transformation of society's energy structure.

[0031] The present invention has other features and advantages that will be apparent from or will be described in detail in the accompanying drawings and the following detailed description incorporated herein, which together serve to explain certain principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings.

[0033] Figure 1 A structural diagram of a single-stage bidirectional wireless energy transmission system for an electric vehicle according to an embodiment of the present invention is shown.

[0034] Figure 2 A structural schematic diagram of a single-stage bidirectional wireless energy transmission system for an electric vehicle according to another embodiment of the present invention is shown.

[0035] Figure 3 A vector diagram of the rectification operation mode of the primary side switch network circuit according to an embodiment of the present invention is shown.

[0036] Figure 4 A vector diagram of an inverter operation mode of a primary side switch network circuit according to an embodiment of the present invention is shown.

[0037] Figure 5 The grid voltage v is shown in FIG. 1 when energy is transmitted in the forward direction according to an embodiment of the present invention. g 、Input current i g And the DC side voltage v dc Simulation and experimental waveforms.

[0038] Figure 6 The figure shows the energy transmission in the forward direction according to an embodiment of the present invention, under sinusoidal modulation with different duty cycles d. ab 、i ab and v cd 、i cd Waveform diagram.

[0039] Figure 7 The grid voltage v is shown in FIG. 1 when energy is transmitted in reverse according to an embodiment of the present invention. g 、Input current i g And the DC side voltage v dc Simulation and experimental waveforms.

[0040] Figure 8 The figure shows the energy reverse transmission under sinusoidal modulation with different duty ratios d according to one embodiment of the present invention. ab 、i ab and v cd 、i cd Waveform diagram. DETAILED DESCRIPTION

[0041] The present invention will be described in more detail below. Although the present invention provides preferred embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0042] The typical bidirectional wireless charging and discharging system architecture for electric vehicles includes power electronic converters on both the grid and vehicle sides, a compensation network, energy transfer coils, the grid, and batteries. In EV wireless charging and discharging systems, the grid side currently primarily utilizes a two-stage cascaded AC-DC-AC converter to bidirectionally convert 50 / 60Hz AC power into high-frequency AC power of tens or hundreds of kHz, while also achieving power factor correction. When charging an EV, one converter rectifies the low-frequency AC power into DC, while the other converter inverts the DC power into high-frequency AC. When discharging an EV, one converter rectifies the high-frequency AC power into DC, while the other converter inverts the DC power into low-frequency AC. Each stage of this two-stage converter is a full-bridge converter with eight MOSFETs. This increases system cost and control complexity, reducing efficiency and power density. However, a single-stage converter designed to replace the two-stage converter must meet both input-side power factor correction and the frequency and power requirements of the output waveform. Therefore, the development of a multifunctional single-stage converter presents significant challenges. Currently, a large number of scholars are committed to studying the use of matrix converters to replace two-stage converters. Although the number of converter stages is reduced, the number of switching tubes is not reduced, and the control becomes more complicated.

[0043] Reference Figure 1 An embodiment of the present invention provides a single-stage bidirectional wireless energy transmission system for electric vehicles, comprising:

[0044] Primary side switching network U1, resonant network U2 and secondary side switching network U3;

[0045] The resonant network U2 includes a transmitting end (left side) and a receiving end (right side), wherein the transmitting end is connected to the output end of the primary switching network U1, and the receiving end is connected to the output end of the secondary switching network U3; the transmitting end has a transmitting coil L ab , the receiving end has a receiving coil L cd , the transmitting coil L ab and the receiving coil L cd relative settings;

[0046] The primary switch network U1 includes: a first full-bridge circuit; a bus capacitor C connected in parallel with the first full-bridge structure; dc ; The PFC inductor Lf is connected to the input end of the full-bridge structure; the input end of the primary switching network U1 is connected to the AC grid;

[0047] The secondary side switch network U3 includes: a second full-bridge circuit; a voltage stabilizing capacitor C0 connected in parallel with the second full-bridge circuit; an input end of the secondary side switch network U3 is connected to the battery EV of the electric vehicle;

[0048] When energy is transmitted in the forward direction, the battery EV on the secondary switch network U3 side discharges, and the primary switch network U1 outputs AC power to the AC power grid; when energy is transmitted in the reverse direction, the primary switch network U1 side provides AC power, and the secondary switch network U3 charges the battery EV.

[0049] In this embodiment, the transmitting end of the resonant network U2 also includes a transmitting tuning capacitor C ab , with the transmitting coil L ab connected in series; the receiving end of the resonant network U2 also includes a receiving tuning capacitor C cd , with the receiving coil L cd Connected in series, the resonant network is a SS topology. Figure 2 In another embodiment, the transmitting end of the resonant network U2 further includes a first capacitor C ab1 , the second capacitor C ab1 and the first inductor L ab1 The receiving end of the resonant network U2 also includes a third capacitor C cd1 , the fourth capacitor C cd2 and the second inductor L cd1 , the resonant network is an LCC-LCC topology structure.

[0050] In this embodiment, the first full-bridge circuit and the second full-bridge circuit each include four fully-controlled switch devices and anti-parallel diodes thereof. Figure 1 or Figure 2 The first full-bridge circuit consists of Sa, Sb, Sc, and Sd, while the second full-bridge circuit consists of S1, S2, S3, and S4. The primary-side switching network U1 is functionally redundant, enabling power factor correction on the low-frequency AC side and directly outputting high-frequency AC at the switching frequency through ports ab. The waveform output from ports ab is a mixture of high and low frequencies, so the secondary-side switching network U2 is also functionally redundant. On the one hand, it resonates with the wireless energy transmission coil, improving energy transmission efficiency; on the other hand, it "passes high frequencies and blocks low frequencies," separating the high-frequency and low-frequency AC outputs from ports ab.

[0051] In this embodiment, the transmitting end of the resonant network and the primary side switch network U1 are located at the bottom of the electric vehicle, and the receiving end of the resonant network and the secondary side switch network U3 are buried underground. When the battery of the electric vehicle needs to be charged or discharged, the vehicle is parked at a charging station. Based on this bidirectional transmission structure, the electric vehicle is regarded as a mobile battery for absorbing or storing intermittent energy such as wind power and photovoltaic power, which helps to improve the economic and environmental benefits of the overall operation of the energy system and is of great significance to the construction of digital power grids, smart power grids, and the transformation of social energy structure. The present invention adopts a single-stage AC-AC structure at the transmitting end, which has the advantages of a small number of components and high power density, which is more conducive to improving charging efficiency and reducing the size and weight of the charger.

[0052] Another embodiment of the present invention further provides a single-stage bidirectional wireless energy transmission method for an electric vehicle, utilizing the above-mentioned transmission system, the method comprising:

[0053] Through the bipolar PWM modulation method, the output end of the primary switching network generates a sinusoidal wave modulated PWM wave v ab , v ab It contains a low-frequency component v with the same frequency as the AC power supply ab,L , and the switching frequency f s The high frequency component v ab,H , assuming the AC voltage of the AC grid is

[0054] v g (t) = V g sinω L t (1)

[0055] Among them, V g is the voltage amplitude of the AC grid, ω L is the voltage angular frequency of the AC grid;

[0056] For the low-frequency component, the following equation is satisfied

[0057]

[0058] Adopt double closed-loop control strategy to make the low-frequency component v ab,L Lagging or leading v g At an angle δ, the current i of the primary switch network circuit input by the AC grid is g AC voltage v with AC grid g Keep the same phase or reverse direction, and make the primary switch network work in rectification ( Figure 3 ) or inversion ( Figure 4 ) state, realizing bidirectional flow of energy and achieving unity power factor.

[0059] U2 is a tuned resonant network, and the resonant frequency satisfies the following relationship

[0060]

[0061] Where: ω0 is the resonant frequency, ω s is the switching frequency of the primary switching network circuit and the secondary switching network circuit, Lp and Ls are the self-inductance of the transmitting coil and the receiving coil, M is the mutual inductance between the transmitting coil and the receiving coil, there is an air gap between the two windings, and the coupling coefficient k is usually 0.12 to 0.3, where

[0062]

[0063] Therefore, the v generated above ab , v cd The high-frequency components of the switching frequency contained in the resonant network can realize mutual energy transmission.

[0064] In this embodiment, the secondary voltage v is generated by the following method cd : In the second full-bridge structure, the upper and lower switches of the same bridge arm maintain a 50% duty cycle and are switched at a switching frequency f s Operation, the phase lag of adjacent bridge arms is This generates the secondary voltage v cd , while eliminating the low-frequency second harmonic of the battery current, where:

[0065] v ab As the input quantity of the primary side of the resonant network, through phase shift control, the input quantity v provided by the secondary side switch network circuit is cd The input quantity v of the primary side switch network circuit ab Cooperate with each other to realize the bidirectional flow of energy between the SS type or LCC-LCC type resonant network, and the phase shift angle is θ. Figure 1 In the SS-type single-stage bidirectional wireless energy transmission system shown in the figure, when v ab Lag v cd When the energy is transferred in the forward direction (G2V), when v ab Advance v cd When , energy is transferred in the reverse direction (V2G). Figure 2 In the LCC-LCC type single-stage bidirectional wireless energy transmission system shown in the figure, when v ab Advance v cd When V ab Lag v cd When θ=±90°, energy is transferred in the reverse direction (V2G); in particular, at θ=±90°, the transferred power reaches its maximum value, and both sides have a unity power factor.

[0066] To verify the feasibility of the proposed single-stage bidirectional wireless energy transfer system topology and control method, the inventors established a simulation model of the topology in Psim and built a 100W power prototype. The experimental verification of the SS-type wireless energy transfer system was conducted, and similar experimental verification of the LCC-LCC-type wireless energy transfer system was conducted.

[0067] Figure 5 It shows the grid voltage v in G2V mode, that is, when energy is transferred in the forward direction. g 、Input current i g And the DC side voltage v dc The waveforms show that the voltage and current on the grid side are essentially in phase, achieving a high power factor close to 1. This prevents distortion of the AC grid voltage and introduces no reactive power into the topology. The input current harmonic distortion (THD) is also well suppressed, remaining within 5% during forward energy transmission.

[0068] When energy is transmitted in the forward direction, that is, in G2V mode, Figure 6 The following table shows the voltage v under different duty cycle d under sinusoidal modulation. ab 、i ab and v cd 、i cd The waveform diagram, where the duty cycle d is the switching tube S in the U1 part a and S d Duty cycle. In (a), d < 50%, in (b), d = 50%, and in (c), d > 50%. It can be seen from the figure that when the phase shift angle θ = 90°, no matter how the duty cycle changes, at this time, the resonant frequency f of the resonant network s Point v ab Always lag v cd 90°, energy is transferred from the grid side to the vehicle side.

[0069] Figure 7 It shows the grid voltage v in V2G mode, that is, when energy is transferred in reverse. g 、Input current i g And the DC side voltage v dc The waveforms show that the voltage and current on the grid side are essentially in phase opposition, achieving a high power factor close to -1. The harmonic distortion (THD) of the AC current can still be controlled within 5%, meeting the expected requirements.

[0070] When energy is transmitted in reverse, that is, in V2G mode, Figure 8 The voltage v under different duty cycle d under sinusoidal modulation is given. ab 、i ab and vcd 、i cd The waveform diagram, where the duty cycle d is the switching tube S in the U1 part a and S d Duty cycle. (a) d < 50%, (b) d = 50%, (c) d > 50%. It can be seen from the figure that when the phase shift angle θ = -90°, no matter how the duty cycle changes, at this time the resonant frequency f of the resonant network s Point v ab Always ahead v cd 90°, energy is transferred from the vehicle side to the grid side.

[0071] This paper proposes a novel single-stage structure for a bidirectional wireless energy transmission system based on SS and LCC-LCC resonant networks. This circuit overcomes the issues of traditional multi-stage structures, such as the large number of switches, low efficiency, bulky converters, and expensive DC bus capacitors. It enables bidirectional energy flow between the AC side and the active load, and exhibits a high power factor close to unity and low current harmonic distortion in both forward and reverse transmission conditions, ensuring no distortion of the grid voltage waveform parameters.

[0072] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for single-stage bidirectional wireless energy transmission in an electric vehicle, the method utilizing a single-stage bidirectional wireless energy transmission system for an electric vehicle, the single-stage bidirectional wireless energy transmission system for an electric vehicle comprising: Primary side switching network, resonant network and secondary side switching network; The resonant network includes a transmitting end and a receiving end, the transmitting end is connected to the output end of the primary side switch network, and the receiving end is connected to the output end of the secondary side switch network; The transmitting end has a transmitting coil, the receiving end has a receiving coil, and the transmitting coil and the receiving coil are arranged opposite to each other; The primary switch network includes: a first full-bridge circuit; a bus capacitor connected in parallel with the first full-bridge structure; a PFC inductor connected to the input end of the full-bridge structure; the input end of the primary switch network is connected to the AC power grid; The secondary side switch network includes: a second full-bridge circuit; a voltage stabilizing capacitor connected in parallel with the second full-bridge circuit; an input end of the secondary side switch network is connected to the battery of the electric vehicle; During forward energy transmission, the battery on the secondary switch network side discharges, and the primary switch network outputs AC power to the AC grid; during reverse energy transmission, the primary switch network side provides AC power, and the secondary switch network charges the battery; Characterized in that the method comprises: By using the bipolar PWM modulation method, a sine wave modulated PWM wave v is generated at the output end of the primary switching network. ab , v ab It contains a low-frequency component v with the same frequency as the AC power supply ab,L , and the switching frequency f s The high frequency component v ab,H , assuming the AC voltage of the AC grid is v g (t) = V g sinω L t(1) where V g is the voltage amplitude of the AC grid, ω L is the voltage angular frequency of the AC grid; For the low-frequency component, the following equation is satisfied Adopt double closed-loop control strategy to make the low-frequency component v ab,L Lagging or leading v g At an angle δ, the current i of the primary switch network circuit input by the AC grid is g AC voltage v with AC grid g Maintaining the same phase or reverse direction, while making the primary switch network work in a rectification or inversion state, to achieve a bidirectional flow of energy; Among them, L f is the PFC inductor connected to the input end of the first full-bridge circuit.

2. The electric vehicle single-stage bidirectional wireless energy transmission method according to claim 1, characterized in that: The transmitting end further includes a transmitting tuning capacitor connected in series with the transmitting coil; the receiving end further includes a receiving tuning capacitor connected in series with the receiving coil, and the resonant network is an SS topology structure.

3. The electric vehicle single-stage bidirectional wireless energy transmission method according to claim 1, characterized in that: The transmitting end further includes a first capacitor, a second capacitor and a first inductor, the receiving end further includes a third capacitor, a fourth capacitor and a second inductor, and the resonant network is an LCC-LCC topology structure.

4. The electric vehicle single-stage bidirectional wireless energy transmission method according to claim 1, characterized in that: The first full-bridge circuit and the second full-bridge circuit each include four fully-controlled switching devices and anti-parallel diodes therein.

5. The electric vehicle single-stage bidirectional wireless energy transmission method according to claim 1, characterized in that: The transmitting end of the resonant network and the primary-side switch network are buried underground, and the receiving end of the resonant network and the secondary-side switch network are located at the bottom of the electric vehicle.

6. The electric vehicle single-stage bidirectional wireless energy transmission method according to claim 1, characterized in that: The secondary voltage v is generated by cd : In the second full-bridge structure, the upper and lower switches of the same bridge arm maintain a 50% duty cycle and are switched at a switching frequency f s Operation, the phase lag of adjacent bridge arms is in:

7. The electric vehicle single-stage bidirectional wireless energy transmission method according to claim 6, characterized in that: v ab As the input quantity of the primary side of the resonant network, through phase shift control, the input quantity v provided by the secondary side switch network circuit is cd The input quantity v of the primary side switch network circuit ab Cooperating with each other, a bidirectional flow of energy between the resonant networks is realized; When the resonant network is SS topology, v ab Lag v cd When the energy is transferred in the forward direction, v ab Advance v cd When , energy is transferred in the reverse direction; When the resonant network is an LCC-LCC topology, v ab Advance v cd When the energy is transferred in the forward direction, v ab Lag v cd , energy is transferred in the reverse direction.

8. The electric vehicle single-stage bidirectional wireless energy transmission method according to claim 7, characterized in that: During phase shift control, the phase shift angle θ is set to ±90°.

9. The electric vehicle single-stage bidirectional wireless energy transmission method according to claim 1, characterized in that: The resonant frequency of the resonant network satisfies the following relationship: Where ω0 is the resonant frequency, ω s is the switching frequency of the primary side switching network circuit and the secondary side switching network circuit, L p and L s are the self-inductances of the transmitting coil and the receiving coil, C p and C s are the capacitances of the transmitting coil and the receiving coil respectively, M is the mutual inductance between the transmitting coil and the receiving coil, there is an air gap between the two windings, and the coupling coefficient is k, where

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