Bidirectional wireless charging and discharging system and method for electric vehicle

Abstract

The invention discloses a two-way wireless charging and discharging system and method for an electric automobile, and relates to the field of wireless charging and discharging of the electric automobile, the system comprises an AD-DC conversion unit and a BIPT link unit, during charging, a rectification voltage reduction module in the AD-DC conversion unit converts three-phase power frequency alternating current of a power grid into direct current, and the direct current is converted into direct current; the current is converted into high-frequency alternating current through a high-frequency inversion module in the BIPT link unit; the GA module generates an alternating magnetic field; the VA module induces and generates high-frequency alternating current; the full-bridge converter converts the direct current into direct current and transmits the direct current to a vehicle battery. During discharging, the full-bridge converter converts direct current output by a vehicle battery into high-frequency alternating current; the VA module generates an alternating magnetic field; the GA module induces and generates high-frequency alternating current; and the direct current is converted into three-phase power frequency alternating current through the rectification and voltage reduction module, and then the three-phase power frequency alternating current is injected into a power grid. The system is wide in regulation and control range, high in energy transmission efficiency and high in anti-offset capability.

Description

Technical Field

[0001] The present application relates to the field of wireless charging and discharging of electric vehicles, and in particular to a bidirectional wireless charging and discharging system and method for electric vehicles. Background Art

[0002] The number of electric vehicles has increased dramatically in recent years. However, the influx of electric vehicles and their associated charging stations can impact the load balance of local power grids and pose challenges to the stability of public grids. Therefore, it is crucial to encourage the development of V2G (Vehicle to Grid) technology to achieve efficient interaction between electric vehicles and the grid.

[0003] According to the charging needs of electric vehicles, the bidirectional wireless charging and discharging system consists of an AC-DC conversion unit that interacts with the power grid and a BIPT (Bidirectional Inductive Power Transfer) link for wireless energy transmission. In order to ensure the economic benefits of electric vehicles during use and reduce the size of the equipment, the bidirectional wireless charging and discharging system needs to have a high energy transmission efficiency. At the same time, in order to meet the charging and discharging needs of different types of vehicle batteries at different states of charge, the bidirectional wireless charging and discharging system needs to regulate the output voltage and current over a wide range. Due to the uncertainty of the parking position, the position between the ground transmitter and the vehicle-mounted receiver will shift, so the bidirectional wireless charging and discharging system should have good anti-shift capability.

[0004] In summary, how to provide a bidirectional wireless charging and discharging system with high energy transmission efficiency, wide output voltage and current control range, and strong anti-offset capability has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The purpose of this application is to provide a bidirectional wireless charging and discharging system and method for electric vehicles, which has the characteristics of wide control range, high energy transmission efficiency, and strong anti-deviation ability, and can realize reliable and efficient bidirectional power transmission.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a bidirectional wireless charging and discharging system for an electric vehicle, wherein the bidirectional wireless charging and discharging system for an electric vehicle includes an AD-DC conversion unit and a BIPT link unit.

[0008] The AD-DC conversion unit includes multiple parallel rectifier and buck modules, and the BIPT link unit includes a high-frequency inverter module, a GA module, a VA module and a full-bridge converter. The rectifier and buck module is connected to the power grid, and the high-frequency inverter module is respectively connected to the rectifier and buck module and the GA module. The GA module and the VA module are wirelessly connected, and the full-bridge converter is respectively connected to the VA module and the vehicle battery.

[0009] The rectifier and step-down module is used to rectify and step down the three-phase industrial frequency AC power of the power grid, output stable DC power, and transmit the DC power to the high-frequency inverter module; the high-frequency inverter module is used to convert the DC power into high-frequency AC power and transmit the high-frequency AC power to the GA module; the GA module is used to generate an alternating magnetic field based on the high-frequency AC power; the VA module is used to induce high-frequency AC power under the action of the alternating magnetic field; the full-bridge converter is used to convert the high-frequency AC power into DC power and transmit it to the vehicle battery.

[0010] The full-bridge converter is also used to convert the direct current output by the vehicle battery into high-frequency alternating current, and transmit the high-frequency alternating current to the VA module; the VA module is also used to generate an alternating magnetic field based on the high-frequency alternating current; the GA module is also used to induce high-frequency alternating current under the action of the alternating magnetic field, and transmit the high-frequency alternating current to the high-frequency inverter module; the high-frequency inverter module is also used to convert the high-frequency alternating current into direct current, and transmit the direct current to the rectifier and step-down module; the rectifier and step-down module is also used to convert the direct current into three-phase industrial frequency alternating current, and inject the three-phase industrial frequency alternating current into the power grid.

[0011] Optionally, each of the rectifier and buck modules includes a rectifier circuit and a buck circuit, the rectifier circuit and the buck circuit are connected, the rectifier circuit is connected to the power grid, and the buck circuit is connected to the high-frequency inverter module.

[0012] The rectifier circuit is used to rectify the three-phase industrial frequency alternating current of the power grid to obtain rectified direct current; the step-down circuit is used to step down the rectified direct current, output the stepped-down stable direct current, and transmit it to the high-frequency inverter module.

[0013] The step-down circuit is also used to step down the DC power transmitted by the high-frequency inverter module and output stable DC power after stepping down; the rectifier circuit is also used to rectify the stable DC power after stepping down and output three-phase industrial frequency AC power, and inject the three-phase industrial frequency AC power into the power grid.

[0014] Optionally, the rectifier circuit includes three groups of first bridge arms, each group of the first bridge arms includes an upper first power switch and a lower first power switch with complementary switching states, the upper first power switch and the lower first power switch both include a first IGBT and a first freewheeling diode, the anode of the first freewheeling diode is connected to the emitter of the first IGBT, the cathode of the first freewheeling diode is connected to the collector of the first IGBT, and the gate of each first IGBT is the rectification control end of the rectifier circuit; in the same first bridge arm, the emitter of the first IGBT in the upper first power switch is connected to the collector of the first IGBT in the lower first power switch; the collector of each of the first IGBTs in the upper first power switch is connected to the positive electrode of the first DC filter capacitor, and the emitter of the first IGBT in each of the lower first power switches is connected to the negative electrode of the first DC filter capacitor, and the contacts of the upper first power switch and the lower first power switch in each group of the first bridge arms are respectively connected to a phase in the power grid.

[0015] Optionally, the step-down circuit includes a group of second bridge arms and an output filter inductor, the second bridge arm includes an upper second power switch and a lower second power switch with complementary switching states, the upper second power switch and the lower second power switch each include a second IGBT and a second freewheeling diode, the anode of the second freewheeling diode is connected to the emitter of the second IGBT, the cathode of the second freewheeling diode is connected to the collector of the second IGBT, the emitter of the second IGBT in the upper second power switch is connected to the collector of the second IGBT in the lower first power switch, the junction of the upper second power switch and the lower second power switch is connected to one end of the output filter inductor, the other end of the output filter inductor is connected to the positive electrode of the second DC filter capacitor, the collector of the second IGBT in the upper second power switch is connected to the positive electrode of the first DC filter capacitor, and the emitter of the second IGBT in the lower second power switch is connected to the negative electrodes of the first DC filter capacitor and the second DC filter capacitor, respectively.

[0016] Optionally, the GA module includes a first compensation network circuit and a second compensation network circuit.

[0017] The first compensation network circuit includes a switching switch K1, a compensation inductor L f1 , compensation capacitor C1, main coil L1, switching switch K2 and compensation capacitor C f1 , the switching switch K1, the compensation inductor L f1 , the compensation capacitor C1, the main coil L1 and the switching switch K2 are connected in sequence, the compensation capacitor C f1 One end is connected to the compensation inductor L f1and the compensation capacitor C1, the compensation capacitor C f1 The other end is connected to the circuit between the main coil L1 and the switching switch K2; the two ends of the first compensation network circuit are connected to the high-frequency inverter module through the switching switch K1 and the switching switch K2.

[0018] The second compensation network circuit includes a switching switch K3, a compensation inductor L f1 , compensation capacitor C1, main coil L1, switching switch K4 and compensation capacitor C f1 , the switching switch K3, the compensation inductor L f1 , the compensation capacitor C1, the main coil L1 and the switching switch K4 are connected in sequence, the compensation capacitor C f1 One end is connected to the compensation inductor L f1 and the compensation capacitor C1, the compensation capacitor C f1 The other end is connected to the circuit between the main coil L1 and the switching switch K4; the two ends of the second compensation network circuit are connected to the high-frequency inverter module through the switching switch K3 and the switching switch K4.

[0019] Optionally, the GA module includes a first charge and discharge mode and a second charge and discharge mode.

[0020] In the first charge and discharge mode, the switching switches K1 and K2 are closed, the switching switches K3 and K4 are disconnected, and the GA module switches to the first compensation network circuit with an operating frequency of 85 kHz to operate, so as to charge or discharge a vehicle with a power level of 6 kW or 11 kW.

[0021] In the second charge and discharge mode, the switching switches K3 and K4 are closed, the switching switches K1 and K2 are disconnected, and the GA module switches to the second compensation network circuit with an operating frequency of 20 kHz to operate, so as to charge or discharge a vehicle with a power level of 30 kW.

[0022] Optionally, the GA module and the VA module both include a main coil and a compensation inductor, the main coil and the compensation inductor are orthogonally arranged, and both the main coil and the compensation inductor are DD coils.

[0023] Optionally, the BIPT link unit adopts a topology structure of a dual-coupled LCC-LCC compensation network.

[0024] Optionally, the number of the rectifier and buck modules is 4, and the output power of each rectifier and buck module is 35kW.

[0025] In a second aspect, the present application provides a bidirectional wireless charging and discharging method for an electric vehicle, which includes a charging method and a discharging method.

[0026] The charging method includes the following steps.

[0027] Get charging instructions.

[0028] According to the charging instruction, the vehicle battery is charged using the electric vehicle bidirectional wireless charging and discharging system described in the first aspect.

[0029] The discharging method includes the following steps.

[0030] Get the discharge instruction.

[0031] According to the discharge instruction, the vehicle battery is discharged using the electric vehicle bidirectional wireless charging and discharging system described in the first aspect.

[0032] According to the specific embodiments provided in this application, this application has the following technical effects:

[0033] The present application provides a bidirectional wireless charging and discharging system and method for electric vehicles, the system including an AD-DC conversion unit and a BIPT link unit, wherein the AD-DC conversion unit includes multiple parallel rectifier and buck modules, and the BIPT link unit includes a high-frequency inverter module, a GA module, a VA module, and a full-bridge converter. By adopting a modular AD-DC conversion unit structural design, multiple parallel rectifier and buck modules are set in the AD-DC conversion unit. Through the coordinated cooperation between the rectifier and buck modules, the high-frequency inverter module, the GA module, the VA module, and the full-bridge converter, the system can achieve efficient operation in a wide power and voltage range, and efficient charging and discharging between the power grid and the vehicle battery. The system has the characteristics of a wide control range, high energy transmission efficiency, and strong anti-offset capability, and can achieve reliable and efficient bidirectional power transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a structural block diagram of a traditional electric vehicle bidirectional wireless charging and discharging system.

[0036] Figure 2 This is the topology diagram of the AC-DC conversion unit in Example 1 of the present application.

[0037] Figure 3 This is a circuit diagram of the BIPT link based on the dual-coupled LCC-LCC compensation network in Example 1 of the present application.

[0038] Figure 4 This is a schematic diagram of the coil integration method in Example 1 of the present application, wherein: Figure 4 (a) is a coil integration method in which the main coil is a rectangular coil and the compensation inductor is a DD coil; Figure 4 (b) is a coil integration method in which the main coil is a DD coil and the compensation inductor is a rectangular coil; Figure 4 (c) in the figure is a coil integration method in which the main coil is a DD coil and the compensation inductor is a DD coil.

[0039] Figure 5 This is a diagram showing the internal composition and layout of the magnetic coupler in Example 1 of the present application, wherein: Figure 5 (a) is the main view of the GA ground terminal; Figure 5 (b) is the main view of the VA vehicle terminal; Figure 5 (c) is the overall top view.

[0040] Figure 6 Schematic diagram of the design process of key parameters in Example 1 of this application.

[0041] Figure 7 This is a structural diagram of the finite element simulation model of the GA module and the VA module in Example 1 of the present application.

[0042] Figure 8 This is the overall topology diagram of the bidirectional wireless charging and discharging system for electric vehicles in Example 1 of the present application.

[0043] Figure 9 This is a flow chart of a bidirectional wireless charging method for an electric vehicle in Example 2 of the present application.

[0044] Figure 10 This is a flowchart of a bidirectional wireless discharge method for an electric vehicle in Example 3 of the present application. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0046] Example 1

[0047] The basic structure of the current traditional electric vehicle bidirectional wireless charging and discharging system is mainly composed of an AC-DC conversion unit that interacts with the power grid and a bidirectional inductive wireless energy transmission link for wireless power transmission, such as Figure 1 As shown, the ground-side and vehicle-side systems together constitute the BIPT link. When the system is operating in the forward charging mode (the grid charges the vehicle battery), the AC-DC converter converts the three-phase AC power from the grid into an intermediate-level DC voltage, while simultaneously performing PFC (Power Factor Correction) to achieve a unity power factor on the grid side and reduce input current harmonic distortion. The high-frequency converter on the ground side converts the intermediate-level DC power into high-frequency AC power, which is then injected into the ground-side compensation network and magnetic coupling coil. The magnetic coupling coil on the vehicle side, under the influence of the alternating magnetic field, induces high-frequency AC power, which resonates with the vehicle-side compensation network to generate high-frequency AC power. This power is then converted to DC power by the vehicle-side high-frequency converter and transferred to the vehicle battery for charging. When the system is operating in the reverse discharging mode (the vehicle battery discharges the grid), the vehicle-side high-frequency converter converts the vehicle battery's DC power into high-frequency AC power, which is then injected into the vehicle-side compensation network and magnetic coupling coil. The magnetic coupling coil on the ground side induces high-frequency AC power under the action of the alternating magnetic field, which resonates with the compensation network on the ground side to generate high-frequency AC power. The high-frequency conversion unit on the ground side converts the DC power into DC power and transmits it to the AC-DC conversion unit. At this time, the AC-DC conversion unit works in the inverter mode, converting the DC power into industrial frequency three-phase AC power and then feeding it into the power grid to discharge the power grid. When the system is positively charged, Figure 1 The AC-DC converter converts the three-phase AC power from the power grid into DC power. During reverse discharge, the DC power is converted back into three-phase AC power and fed back to the grid. As the interface between the bidirectional wireless charging and discharging system and the grid, the AC-DC converter needs to have PFC (power factor correction) to improve the power factor and reduce current harmonic distortion on the grid side. Furthermore, to meet the wide voltage operating range of the subsequent BIPT link units, the AC-DC converter needs to have a wide output range.

[0048] This embodiment proposes a bidirectional wireless charging and discharging system for electric vehicles, comprising an AD-DC conversion unit and a BIPT link unit. The AD-DC conversion unit comprises multiple parallel rectifier and buck modules. The BIPT link unit comprises a high-frequency inverter module, a GA module, a VA module, and a full-bridge converter. The rectifier and buck module is connected to the power grid, the high-frequency inverter module is connected to the rectifier and buck module and the GA module respectively, the GA module is wirelessly connected to the VA module, and the full-bridge converter is connected to the VA module and the vehicle battery respectively.

[0049] In this embodiment, the bidirectional wireless charging and discharging system for electric vehicles includes a charging phase in which the grid charges the vehicle battery and a discharging phase in which the vehicle battery discharges the grid.

[0050] For the charging stage, the functions of each component in the charging process are as follows:

[0051] The rectifier and step-down module rectifies and steps down the three-phase power-frequency AC power from the power grid, outputting stable DC power. This DC power is then transmitted to the high-frequency inverter module. The high-frequency inverter module converts the DC power into high-frequency AC power and transmits this power to the GA module. The GA module generates an alternating magnetic field based on the high-frequency AC power. The VA module induces high-frequency AC power under the influence of the alternating magnetic field. The full-bridge converter converts the high-frequency AC power into DC power and transmits it to the vehicle battery.

[0052] For the discharge stage, the functions of each component in the discharge process are as follows:

[0053] The full-bridge converter converts the DC power from the vehicle battery into high-frequency AC power and transmits it to the VA module. The VA module generates an alternating magnetic field based on the high-frequency AC power. The GA module induces high-frequency AC power in the alternating magnetic field and transmits it to the high-frequency inverter module. The high-frequency inverter module converts the high-frequency AC power into DC power and transmits it to the rectifier-step-down module. The rectifier-step-down module converts the DC power into three-phase industrial-frequency AC power and injects it into the power grid.

[0054] In this embodiment, the AD-DC conversion unit may include 4 rectifier and buck modules, and the output power of the 4 rectifier and buck modules is 35kW. The number and output power of the rectifier and buck modules can also be other values, which can be determined according to actual conditions.

[0055] In this embodiment, each rectifier-step-down module includes a rectifier circuit and a step-down circuit. The rectifier circuit and the step-down circuit are connected, the rectifier circuit is connected to the power grid, and the step-down circuit is connected to the high-frequency inverter module. During the charging phase, the rectifier circuit is used to rectify the three-phase power-frequency AC power from the power grid to obtain rectified DC power. The step-down circuit is used to step down the rectified DC power, output a stable DC power after stepping down, and transmit it to the high-frequency inverter module. During the discharging phase, the step-down circuit is used to step down the DC power transmitted by the high-frequency inverter module, output a stable DC power after stepping down. The rectifier circuit is used to rectify the stable DC power after stepping down, output three-phase power-frequency AC power, and inject the three-phase power-frequency AC power into the power grid.

[0056] In this embodiment, Figure 2 As shown, the AC-DC conversion unit mainly includes a rectifier circuit and a step-down circuit, as well as a Ca 、C b 、C c 、L a 、L b 、L c 、C m 、C n and L n During forward charging, the three-phase power frequency input from the power grid passes through C a 、C b 、C c 、L a 、L b and L c The filter network is transmitted to the rectifier circuit. The rectifier circuit is a three-phase six-switch topology, consisting of three bridge arms. Each bridge arm consists of two power switches with complementary switching states (such as T1 and T2 form a bridge arm). The input current follows the input voltage through sinusoidal pulse width modulation technology, keeping the input current sinusoidal, achieving power factor correction, and outputting a stable DC voltage. Since the rectifier circuit has a boost characteristic and the output DC voltage value V0 ≥ 530V, in order to ensure that the system works in a wide voltage range, it is necessary to add a buck circuit after the rectifier circuit to adjust the DC output voltage. The buck circuit consists of power switches T7 and T8 with complementary switching states and an output filter inductor L n The output voltage is adjusted by controlling the duty cycle of the power switch T7.

[0057] In this embodiment, the rectifier circuit includes three groups of first bridge arms, each group of the first bridge arms includes an upper first power switch (such as T1, T3 and T5) and a lower first power switch (such as T2, T4 and T6) with complementary switching states, wherein the upper first power switch and the lower first power switch each include a first IGBT and a first freewheeling diode, the anode of the first freewheeling diode is connected to the emitter of the first IGBT, the cathode of the first freewheeling diode is connected to the collector of the first IGBT, and the gate of each first IGBT is the rectification control terminal of the rectifier circuit; in the same first bridge arm, the emitter of the first IGBT in the upper first power switch is connected to the collector of the first IGBT in the lower first power switch; the collector of the first IGBT in each of the upper first power switches is connected to the first DC filter capacitor C m The positive electrode of the first IGBT in each of the lower first power switches is connected to the first DC filter capacitor C m The negative electrode of the upper first power switch and the lower first power switch in each group of the first bridge arms are connected to a phase of the power grid respectively.

[0058] In this embodiment, the step-down circuit includes a set of second bridge arms and an output filter inductor Ln The second bridge arm includes an upper second power switch (such as T7) and a lower second power switch (such as T8) with complementary switching states. The upper second power switch and the lower second power switch each include a second IGBT and a second freewheeling diode. The anode of the second freewheeling diode is connected to the emitter of the second IGBT, and the cathode of the second freewheeling diode is connected to the collector of the second IGBT. The emitter of the second IGBT in the upper second power switch is connected to the collector of the second IGBT in the lower first power switch. The junction of the upper second power switch and the lower second power switch is connected to the output filter inductor L. n One end of the output filter inductor L is connected to n The other end is connected to the second DC filter capacitor C n The collector of the second IGBT in the second power switch is connected to the first DC filter capacitor C m The positive electrode of the second IGBT in the lower second power switch is connected to the emitter of the first DC filter capacitor C m and the second DC filter capacitor C n of the negative electrode.

[0059] To meet the charging power requirements of the target vehicle model and considering the system loss, the AC-DC conversion unit needs to have an output capacity of 35kW. When only one set of rectifier circuit and step-down circuit is used, the efficiency is low during low power operation. Therefore, the AC-DC conversion unit adopts a multi-module parallel connection method, such as Figure 2 As shown, a set of rectifier circuits and buck circuits is regarded as a rectifier-buck module. Four rectifier-buck modules are connected in parallel to output 35kW. The number of rectifier-buck modules working is switched according to the required output power to achieve efficient operation within the full power range.

[0060] In this embodiment, the VA module refers to the vehicle-mounted assembly, which includes the vehicle-mounted magnetic coupling coil and the vehicle-mounted compensation network; the GA module refers to the ground-mounted assembly, which includes the ground-mounted magnetic coupler and the ground-mounted compensation network. The VA module and GA module are wirelessly connected. When the vehicle to be charged / discharged is parked above the GA module, a wireless connection is established between the vehicle-mounted VA module and the ground-mounted GA module to achieve wireless charging and discharging. The parameters of the three power levels of electric vehicles selected in this embodiment are shown in Table 1. According to the technical requirements for wireless power transmission equipment, the operating frequency of electric vehicle wireless charging equipment with a rated transmission power between 22kW and 120kW is in the 19-21kHz frequency range, while the operating frequency of equipment with a rated transmission power of 22kW or less is in the 79-90kHz range. Therefore, the operating frequency of 6kW and 11kW devices is 85kHz, and the operating frequency of 30kW devices is 20kHz. The power level and operating frequency of each VA module are determined. Accordingly, to be compatible with these three different power levels, the GA module must include two independently activated resonant networks with different operating frequencies to meet the charging and discharging requirements of electric vehicles.

[0061] Table 1 Parameters of three target vehicle models

[0062]

[0063]

[0064] In this embodiment, the BIPT link unit adopts a dual-coupled LCC-LCC (Line Commutated Converter-Line Commutated Converter) compensation network topology. Due to their constant current source output characteristics, the SS (Series-Series) compensation network and the LCC-LCC compensation network are very suitable for bidirectional charging and discharging scenarios of electric vehicles. When selecting the compensation structure of the BIPT link unit, the self-inductance and mutual inductance values required by the compensation network are first estimated based on the known voltage, frequency, and power requirements. For a 30kW system, if an SS compensation network is used, the required mutual inductance is approximately 65μH, and the self-inductance may exceed 300μH, which will cause the VA module size to exceed the limit. Therefore, the SS compensation network is not suitable for this system. Secondly, the compensation network characteristics and application scenarios need to be considered. The SS compensation network is more efficient under conditions of high magnetic coupling and low offset tolerance. However, when applied to the bidirectional wireless charging and discharging system of electric vehicles, due to the existence of air gap and offset issues, the coupling coefficient is reduced, the efficiency is reduced, and there is also an overcurrent problem. In comparison, the LCC-LCC compensation network is insensitive to changes in ground and vehicle-side loads, and when the coupling coefficient decreases, the current in the coil will decrease accordingly, eliminating the need for additional current limiting measures and ensuring system safety.

[0065] Compared with the traditional single-coupled LCC-LCC compensation network, the dual-coupled LCC-LCC compensation network is a better choice. Its feature is that an additional power transmission path is added outside the main coil. In the case of offset, the magnetic coupling of the compensation inductor helps to improve the transmission efficiency and performance. Therefore, the dual-coupled LCC-LCC compensation network is finally selected as the compensation network in this embodiment. The BIPT link unit is as follows: Figure 3 As shown in the figure, V1 and V2 represent the DC bus voltage output by the AC-DC conversion unit and the vehicle battery voltage, respectively, C0 and C 0’ is the DC bus capacitor, S1~S4 and Q1~Q4 are the full-bridge converters on the grid side and vehicle side respectively, C1, C2, C f1 and C f2 is the compensation capacitor, L1 and L2 are the main coils, and L f1 and L f2 is the compensation inductance, M 12 and M f1f2 are the mutual inductance of the main coil and the compensation inductance respectively. AB is the output voltage of the full-bridge converter on the grid side, v ab is the output voltage of the full-bridge converter on the vehicle side.

[0066] In this embodiment, the GA module includes a first compensation network circuit and a second compensation network circuit. The first compensation network circuit includes a switching switch K1, a compensation inductor L f1 , compensation capacitor C1, main coil L1, switching switch K2 and compensation capacitor C f1 , switching switch K1, compensation inductor L f1 , compensation capacitor C1, main coil L1 and switching switch K2 are connected in sequence, compensation capacitor C f1 One end is connected to the compensation inductor L f1 In the circuit between the compensation capacitor C1, the compensation capacitor C f1 The other end of the first compensation network circuit is connected to the circuit between the main coil L1 and the switching switch K2. The two ends of the first compensation network circuit are connected to the high-frequency inverter module through the switching switch K1 and the switching switch K2. The second compensation network circuit includes the switching switch K3, the compensation inductor L f1 , compensation capacitor C1, main coil L1, switching switch K4 and compensation capacitor C f1 , switching switch K3, compensation inductor L f1 , compensation capacitor C1, main coil L1 and switching switch K4 are connected in sequence, compensation capacitor C f1 One end is connected to the compensation inductor L f1 In the circuit between the compensation capacitor C1, the compensation capacitor C f1The other end of the second compensation network circuit is connected to the circuit between the main coil L1 and the switching switch K4. The two ends of the second compensation network circuit are connected to the high-frequency inverter module through the switching switch K3 and the switching switch K4.

[0067] In this embodiment, the GA module includes a first charge-discharge mode and a second charge-discharge mode. In the first charge-discharge mode, switches K1 and K2 are closed, and switches K3 and K4 are open. The GA module switches to a first compensation network circuit operating at 85kHz to charge or discharge vehicles with a power level of 6kW or 11kW. In the second charge-discharge mode, switches K3 and K4 are closed, and switches K1 and K2 are open. The GA module switches to a second compensation network circuit operating at 20kHz to charge or discharge vehicles with a power level of 30kW.

[0068] In this embodiment, both the GA module and the VA module include a main coil and a compensation inductor, which are arranged orthogonally. Both the main coil and the compensation inductor are DD coils. In practical applications, the main coil and the compensation inductor need to be integrated inside the GA module and / or the VA module. The magnetic coupling coil structure in the BIPT link unit is mainly divided into two types: rectangular coils and DD coils. The coil integration schemes in the dual-coupled LCC-LCC compensation network are mainly as follows: Figure 4 The three types shown, from left to right, are (a) the main coil L is a rectangular coil, the compensation inductor L f is the DD coil; (b) the main coil L is the DD coil, the compensation inductance L f is a rectangular coil; (c) the main coil L is a DD coil, and the compensation inductance L f The DD coil is a DD coil, and in the above three integration schemes, the main coil and the compensation inductor are all arranged orthogonally. These three integration schemes can achieve decoupling between the main coil and the compensation inductor, improve the energy transmission efficiency, and under the premise of meeting the self-inductance requirements, the use of DD coils can reduce the external size or number of turns, reduce the use of materials, and meet the compact layout requirements. Therefore, this embodiment adopts the third integration scheme. The internal layout of the magnetic coupler is as follows Figure 5 As shown, Figure 5 (a) is the main view of the GA ground terminal; Figure 5 (b) is the main view of the VA vehicle terminal; Figure 5 (c) shows a top view of the entire module. The coil and the ferrite layer underneath it are placed on an aluminum plate. For the GA module, heat is transferred to the aluminum plate and dissipated through the heat sink. For the VA module, the 11kW and 30kW modules use liquid cooling, while the 6kW module uses natural cooling.

[0069] The magnetic coupler parameter design process used in this embodiment is as follows: Figure 6As shown, firstly, given the parameters of DC bus voltage V1, vehicle battery voltage V2, AC frequency ω and output power P, the compensation inductor L is designed according to the given parameters. f1 , compensation inductor L f2 , main coil L1, main coil L2, main coil mutual inductance M 12 and the mutual inductance M of the compensation inductor f1f2 and other variables, and then select the appropriate capacitor as C f1 and C f2 , and calculate L f1 and L f2 Then, determine the value of M according to the given parameters 12 and M f1f2 The value range of the main coil L1 and the main coil L2 is estimated, and the corresponding compensation capacitor C1 and compensation capacitor C2 values are calculated. Next, it is determined whether both the inductor and the capacitor are available, that is, whether the required inductance can be obtained within the limitations of the magnetic coupler size and the number of coil turns, and whether the rated voltage requirement can be met by the series connection of the capacitors. When both the inductor and the capacitor are available, the current and voltage are calculated, and it is determined whether the current and voltage are less than the limit. If so, the obtained design data is recorded. If not, return to "Select a suitable capacitor as C f1 and C f2 , and calculate L f1 and L f2 value" step, reselect the appropriate capacitor as C f1 and C f2 , and recalculate L f1 and L f2 When both the inductor and capacitor are unavailable or one of them is unavailable, the process returns to “Select a suitable capacitor as C f1 and C f2 , and calculate L f1 and L f2 value" step, reselect the appropriate capacitor as C f1 and C f2 , and recalculate L f1 and L f2 The above steps are executed repeatedly until all conditions are met.

[0070] Table 2 shows the design values and rated values of the resonant network components obtained according to the design process. The nominal values represent the voltage and current stresses calculated for the selected parameter combination, and the rated values represent the rated voltage and current that the selected components can withstand.

[0071] Table 2 Design values and rated values of resonant network components

[0072]

[0073] After obtaining the design parameter values, the obtained design data is recorded in this embodiment. With the help of finite element simulation tools, the size, number of turns and turn spacing of each magnetic coupling coil winding are reasonably designed to ensure that the self-inductance and mutual inductance reach the target values. The finite element simulation models of the GA module and VA module are finally obtained as shown below. Figure 7 As shown, the finite element simulation model includes a GA coil, a GA magnetic core, a GA aluminum plate and a VA aluminum plate, wherein the GA coil and the GA magnetic core are arranged between the GA aluminum plate and the VA aluminum plate.

[0074] The overall topology of the electric vehicle bidirectional wireless charging and discharging system proposed in this embodiment is as follows: Figure 8 As shown, when the system is forward charging, the three-phase industrial frequency AC power from the power grid is converted into DC power by the AC-DC conversion unit working in the rectification mode and transmitted to the high-frequency conversion unit working in the high-frequency inverter mode in the ground end of the BIPT link unit, and then converted into high-frequency AC power and transmitted to the GA module on the ground end to generate an alternating magnetic field. Under the action of the alternating magnetic field, the VA module induces high-frequency AC power and transmits it to the high-frequency conversion unit working in the rectification mode on the vehicle end, and converts it into DC power and transmits it to the vehicle battery; when the system is reversely discharging, the high-voltage DC power from the vehicle battery is converted into high-frequency AC power by the full-bridge converter on the vehicle end and transmitted to the VA module to generate an alternating magnetic field. Under the action of the alternating magnetic field, the GA module induces high-frequency current and transmits it to the high-frequency conversion unit working in the rectification mode on the ground end, and converts it into DC power and transmits it to the AC-DC conversion unit working in the inverter mode, and converts it into three-phase industrial frequency AC power and injects it into the power grid.

[0075] In this embodiment, the GA module integrates two compensation networks to accommodate vehicles with different operating frequencies and power levels. Switches K1 and K2 are used to switch between the compensation networks. When the system is not operating, switches K1, K2, K3, and K4 are all off. When the power levels of the vehicle to be charged / discharged are 6kW and 11kW, switches K1 and K2 are closed, while switches K3 and K4 are open. The GA module switches to a compensation network operating at an 85kHz frequency, effectively activating the first compensation network. When the power level of the vehicle to be charged / discharged is 30kW, switches K3 and K4 are closed, while switches K1 and K2 are open. The GA module switches to a compensation network operating at a 20kHz frequency, effectively activating the second compensation network. Furthermore, the output voltage of the AC-DC converter unit and the number of operating module groups are appropriately configured based on the vehicle's power level and battery voltage range, ensuring high efficiency across a wide voltage range. At this point, a bidirectional wireless charging and discharging system for electric vehicles that can operate efficiently within a wide voltage range, is compatible with vehicles of different power levels, and operates at different resonant frequencies has been designed from the topology to the control modulation strategy.

[0076] In order to ensure that the bidirectional wireless charging and discharging system for electric vehicles meets the voltage and current indicators of battery charging and discharging of various power vehicles, tolerates changes in the coupling coefficient, and stably and reliably transmits power within the allowable offset range, this embodiment designs a wide-range and efficient bidirectional wireless charging and discharging system for electric vehicles that is adaptable to multiple power levels and compatible with multiple models. The AC-DC conversion unit of the system adopts a modular design, and the number and working mode of the rectifier and buck modules are determined according to the output power requirements to achieve efficient operation within a wide power and voltage range. In order to be compatible with models of different power levels, the ground end part of the BIPT link unit integrates two sets of resonant networks operating at different frequencies. In actual work, combined with the operating characteristics of the AC-DC conversion unit and the BIPT link unit, through modulation and collaborative control strategies, the size and direction of the power flow are reasonably controlled to achieve reliable and efficient bidirectional power transmission.

[0077] This application aims to design a wireless power transmission system suitable for charging and discharging electric vehicles. The system has a modular AC-DC conversion unit and operates efficiently within a wide voltage and power range. In addition, a resonant network operating at different frequencies is integrated on the ground side, which is compatible with electric vehicles of various power levels. Modulation and joint control methods are adopted for the AC-DC conversion unit and the BIPT link unit to flexibly control the size and direction of the power flow. Through the topological structure of the AC-DC conversion unit with a wide range of voltage output and its modular structure design, efficient charging and discharging in the full power range can be effectively achieved. Through the integration of the GA module, and the compensation network within the GA module can operate at two different resonant frequencies, it can meet the charging and discharging needs of vehicles of different power levels, improve the universality of the system, and make it more applicable. By selecting the closed switch and the number of rectifier and buck modules, it is possible to switch between different charging and discharging modes, switch between different power level working modes, and operate the system efficiently.

[0078] Compared to common high-power bidirectional wireless charging and discharging systems, the system in this embodiment can still operate efficiently in the low-power range. The system has a wide operating voltage range, covering low to high voltage, meeting the charging needs of vehicles with different voltage levels. A single ground terminal can charge vehicles of different power levels, demonstrating excellent compatibility and interoperability. The compensation network on the ground terminal can operate at two different resonant frequencies, enabling cross-band operation. The system can achieve efficient bidirectional charging and discharging of electric vehicles, and the control strategy is easy to implement, making it suitable for commercial application and promotion.

[0079] Example 2

[0080] This embodiment provides a bidirectional wireless charging method for electric vehicles, which is applied to the bidirectional wireless charging and discharging system for electric vehicles in Example 1. Figure 9 As shown, the charging method specifically includes the following steps.

[0081] Step S101: Obtain charging instructions.

[0082] Step S102: According to the charging instruction, the electric vehicle bidirectional wireless charging and discharging system of Example 1 is used to charge the vehicle battery. Specifically, the three-phase industrial frequency AC power of the power grid is rectified and stepped down by the rectifier and step-down module to output stable DC power, which is then transmitted to the high-frequency inverter module. The high-frequency inverter module is used to convert the DC power into high-frequency AC power, which is then transmitted to the GA module. The GA module is used to generate an alternating magnetic field based on the high-frequency AC power. The VA module is used to induce high-frequency AC power under the action of the alternating magnetic field. The high-frequency AC power is converted into DC power by a full-bridge converter and transmitted to the vehicle battery, thereby completing the charging process from the power grid to the vehicle battery.

[0083] Example 3

[0084] This embodiment provides a bidirectional wireless discharge method for an electric vehicle, which is applied to the bidirectional wireless charging and discharging system for an electric vehicle in Example 1. Figure 10 As shown, the discharge method specifically includes the following steps.

[0085] Step S201: Obtain a discharge instruction.

[0086] Step S202: According to the discharge instruction, the electric vehicle bidirectional wireless charging and discharging system of Example 1 is used to discharge the vehicle battery. Specifically, the full-bridge converter is used to convert the direct current output by the vehicle battery into high-frequency alternating current, and the high-frequency alternating current is transmitted to the VA module. The VA module is used to generate an alternating magnetic field based on the high-frequency alternating current. The GA module is used to induce high-frequency alternating current under the action of the alternating magnetic field, and the high-frequency alternating current is transmitted to the high-frequency inverter module. The high-frequency alternating current is converted into direct current by the high-frequency inverter module, and the direct current is transmitted to the rectifier and step-down module. The direct current is converted into three-phase industrial frequency alternating current by the rectifier and step-down module, and the three-phase industrial frequency alternating current is injected into the power grid, thereby realizing the discharge process of the vehicle battery to the power grid.

[0087] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0088] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A bidirectional wireless charging and discharging system for electric vehicles, characterized in that: The electric vehicle bidirectional wireless charging and discharging system includes an AD-DC conversion unit and a BIPT link unit; The AD-DC conversion unit includes a plurality of parallel rectifier and buck modules, and the BIPT link unit includes a high-frequency inverter module, a GA module, a VA module and a full-bridge converter. The rectifier and buck modules are connected to the power grid, the high-frequency inverter module is respectively connected to the rectifier and buck modules and the GA module, the GA module is wirelessly connected to the VA module, and the full-bridge converter is respectively connected to the VA module and the vehicle battery; The rectifier and buck module is used to rectify and step down the three-phase industrial frequency AC power of the power grid to output stable DC power, and transmit the DC power to the high-frequency inverter module; the high-frequency inverter module is used to convert the DC power into high-frequency AC power and transmit the high-frequency AC power to the GA module; the GA module is used to generate an alternating magnetic field based on the high-frequency AC power; the VA module is used to induce high-frequency AC power under the action of the alternating magnetic field; the full-bridge converter is used to convert the high-frequency AC power into DC power and transmit it to the vehicle battery; The full-bridge converter is also used to convert the direct current output by the vehicle battery into high-frequency alternating current, and transmit the high-frequency alternating current to the VA module; the VA module is also used to generate an alternating magnetic field based on the high-frequency alternating current; the GA module is also used to induce high-frequency alternating current under the action of the alternating magnetic field, and transmit the high-frequency alternating current to the high-frequency inverter module; the high-frequency inverter module is also used to convert the high-frequency alternating current into direct current, and transmit the direct current to the rectifier and step-down module; the rectifier and step-down module is also used to convert the direct current into three-phase industrial frequency alternating current, and inject the three-phase industrial frequency alternating current into the power grid.

2. The electric vehicle bidirectional wireless charging and discharging system according to claim 1, characterized in that: Each of the rectifier and buck modules includes a rectifier circuit and a buck circuit, the rectifier circuit and the buck circuit are connected, the rectifier circuit is connected to the power grid, and the buck circuit is connected to the high-frequency inverter module; The rectifier circuit is used to rectify the three-phase industrial frequency alternating current of the power grid to obtain rectified direct current; the step-down circuit is used to step down the rectified direct current, output the stepped-down stable direct current, and transmit it to the high-frequency inverter module; The step-down circuit is also used to step down the DC power transmitted by the high-frequency inverter module and output stable DC power after stepping down; the rectifier circuit is also used to rectify the stable DC power after stepping down and output three-phase industrial frequency AC power, and inject the three-phase industrial frequency AC power into the power grid.

3. The electric vehicle bidirectional wireless charging and discharging system according to claim 2, characterized in that: The rectifier circuit includes three groups of first bridge arms, each group of the first bridge arms includes an upper first power switch and a lower first power switch with complementary switching states, the upper first power switch and the lower first power switch each include a first IGBT and a first freewheeling diode, the anode of the first freewheeling diode is connected to the emitter of the first IGBT, the cathode of the first freewheeling diode is connected to the collector of the first IGBT, and the gate of each first IGBT is the rectification control end of the rectifier circuit; in the same first bridge arm, the emitter of the first IGBT in the upper first power switch is connected to the collector of the first IGBT in the lower first power switch; the collector of each of the first IGBTs in the upper first power switch is connected to the positive electrode of the first DC filter capacitor, and the emitter of each of the first IGBTs in the lower first power switch is connected to the negative electrode of the first DC filter capacitor, and the contacts of the upper first power switch and the lower first power switch in each group of the first bridge arms are respectively connected to a phase in the power grid.

4. The electric vehicle bidirectional wireless charging and discharging system according to claim 3, characterized in that: The step-down circuit includes a set of second bridge arms and an output filter inductor. The second bridge arm includes an upper second power switch and a lower second power switch with complementary switching states. The upper second power switch and the lower second power switch each include a second IGBT and a second freewheeling diode. The anode of the second freewheeling diode is connected to the emitter of the second IGBT, and the cathode of the second freewheeling diode is connected to the collector of the second IGBT. The emitter of the second IGBT in the upper second power switch is connected to the collector of the second IGBT in the lower first power switch. The junction of the upper second power switch and the lower second power switch is connected to one end of the output filter inductor. The other end of the output filter inductor is connected to the positive electrode of the second DC filter capacitor. The collector of the second IGBT in the upper second power switch is connected to the positive electrode of the first DC filter capacitor, and the emitter of the second IGBT in the lower second power switch is connected to the negative electrodes of the first DC filter capacitor and the second DC filter capacitor, respectively.

5. The electric vehicle bidirectional wireless charging and discharging system according to claim 1, characterized in that: The GA module includes a first compensation network circuit and a second compensation network circuit; The first compensation network circuit includes a switching switch K1, a compensation inductor L f1 , compensation capacitor C1, main coil L1, switching switch K2 and compensation capacitor C f1 , the switching switch K1, the compensation inductor L f1 , the compensation capacitor C1, the main coil L1 and the switching switch K2 are connected in sequence, the compensation capacitor C f1 One end is connected to the compensation inductor L f1 and the compensation capacitor C1, the compensation capacitor C f1 The other end of the first compensation network circuit is connected to the circuit between the main coil L1 and the switching switch K2; the two ends of the first compensation network circuit are connected to the high-frequency inverter module via the switching switch K1 and the switching switch K2; The second compensation network circuit includes a switching switch K3, a compensation inductor L f1 , compensation capacitor C1, main coil L1, switching switch K4 and compensation capacitor C f1 , the switching switch K3, the compensation inductor L f1 , the compensation capacitor C1, the main coil L1 and the switching switch K4 are connected in sequence, the compensation capacitor C f1 One end is connected to the compensation inductor L f1 and the compensation capacitor C1, the compensation capacitor C f1 The other end is connected to the circuit between the main coil L1 and the switching switch K4; the two ends of the second compensation network circuit are connected to the high-frequency inverter module through the switching switch K3 and the switching switch K4.

6. The electric vehicle bidirectional wireless charging and discharging system according to claim 5, characterized in that: The GA module includes a first charge and discharge mode and a second charge and discharge mode; In the first charge and discharge mode, the switching switches K1 and K2 are closed, the switching switches K3 and K4 are opened, and the GA module switches to the first compensation network circuit with an operating frequency of 85kHz to operate, so as to charge or discharge a vehicle with a power level of 6kW or 11kW; In the second charge and discharge mode, the switching switches K3 and K4 are closed, the switching switches K1 and K2 are disconnected, and the GA module switches to the second compensation network circuit with an operating frequency of 20 kHz to operate, so as to charge or discharge a vehicle with a power level of 30 kW.

7. The electric vehicle bidirectional wireless charging and discharging system according to claim 1, characterized in that: The GA module and the VA module both include a main coil and a compensation inductor, the main coil and the compensation inductor are arranged orthogonally, and both the main coil and the compensation inductor are DD coils.

8. The electric vehicle bidirectional wireless charging and discharging system according to claim 1, characterized in that: The BIPT link unit adopts a topology structure of a double-coupled LCC-LCC compensation network.

9. The electric vehicle bidirectional wireless charging and discharging system according to claim 1, characterized in that: The number of the rectifier and buck modules is 4, and the output power of each rectifier and buck module is 35kW.

10. A bidirectional wireless charging and discharging method for an electric vehicle, characterized in that: The electric vehicle bidirectional wireless charging and discharging method includes a charging method and a discharging method; The charging method comprises the following steps: Get charging instructions; According to the charging instruction, the vehicle battery is charged using the electric vehicle bidirectional wireless charging and discharging system according to any one of claims 1 to 9; The discharge method comprises the following steps: Get discharge instructions; According to the discharge instruction, the vehicle battery is discharged using the electric vehicle bidirectional wireless charging and discharging system according to any one of claims 1 to 9.

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