A bidirectional wireless power transmission system for electric vehicles

Abstract

This invention discloses a bidirectional wireless power transfer system for electric vehicles, relating to the field of wireless charging technology for electric vehicles. By configuring the first and second high-frequency conversion units as full-bridge converters, this invention enables bidirectional power flow. Switches are installed on both the connection branch between the first high-frequency conversion unit and the ground-side compensation network, and on the connection branch between the second high-frequency conversion unit and the vehicle-side compensation network. By controlling the opening and closing of these switches, the entire bidirectional wireless power transfer system can transmit power efficiently across a wide operating range, from light to heavy loads.

Description

Technical Field

[0001] This invention relates to the field of wireless charging technology for electric vehicles, and in particular to a two-way wireless power transmission system for electric vehicles. Background Technology

[0002] Wireless power transfer technology, which achieves contactless energy transfer through magnetic field coupling, has attracted much attention due to its convenience and safety, and is particularly widely used in the field of wireless charging for electric vehicles. In recent years, to fully realize the potential of electric vehicles as a massive distributed energy storage resource, vehicle-to-grid (V2G) technology has received widespread attention. Against this backdrop, researching wide-power, high-efficiency bidirectional wireless power transfer systems is of great significance.

[0003] Based on this, the design schemes of existing wireless power transmission systems generally include the following:

[0004] Option 1: Bidirectional wireless charging topology

[0005] Patent CN107404135A proposes a wireless charging topology with bidirectional energy flow, such as... Figure 7 As shown, it features a two-stage buck-boost circuit, thus its gain is the square of the gain of a typical buck-boost topology. This allows for both high-gain boost and high-gain buck voltage conversion, enabling bidirectional charging across a wide voltage range. It provides a channel for bidirectional energy flow, meeting the wireless power transfer requirements of special environments such as underwater.

[0006] While this solution enables bidirectional power flow across a wide range of voltage levels, it uses two buck-boost circuits and introduces a large number of switching transistors, diodes, and inductors, resulting in high system cost and large size.

[0007] Option ②: Constant current and constant voltage device

[0008] Patent CN115489349A discloses a constant current and constant voltage device for use in wireless charging systems for electric vehicles. For example... Figure 8 As shown, by changing the closed or open state of the secondary-side AC switch, this topology operates in constant voltage charging mode and constant current charging mode, respectively. The output power range of this system is 1.5–6 kW.

[0009] Although this solution can switch between constant current and constant voltage modes, its output power range is narrow (1.5kW~6kW), making it unsuitable for high-power bidirectional charging and discharging scenarios for electric vehicles.

[0010] Option 3: Constant Current and Constant Voltage Wireless Charging System

[0011] Patent CN109980757A proposes a constant current and constant voltage wireless charging system based on topology switching, such as... Figure 9As shown, this scheme adds a switch switching part to the transmitting part (or receiving part), and uses a controller (K1) to control the opening or closing of the switching switch (S1). The system then operates in constant current mode or constant voltage mode, which is suitable for charging the battery.

[0012] Although this solution can achieve the switching between constant current and constant voltage modes, it requires three inductors and one capacitor at the transmitter or ground end, which increases the system cost and size.

[0013] Solution 4: Wide-load-range, high-efficiency WPT system and its optimization method

[0014] Patent CN113629895A discloses a wide-load-range high-efficiency WPT system based on hybrid load matching and its optimization method, the structure of which is as follows: Figure 10 As shown, this invention solves the problem that WPT systems in the prior art cannot always operate in the high-efficiency region. By using a hybrid reconfigurable circuit topology (SS, S-LCC) and rectifier operation mode (full bridge, half bridge), the optimal load can be changed to ensure that the system always operates in the high-efficiency region.

[0015] This scheme enables switching between constant current and constant voltage modes and fully utilizes both half-bridge and full-bridge operating modes, ensuring high efficiency under various load conditions. However, the secondary-side converter of this scheme is a rectifier and does not support bidirectional power flow; secondly, this invention cannot achieve high power charging under light loads, medium power charging under medium loads, and low power charging under heavy loads.

[0016] Option 5: Constant Current-Constant Voltage Charging Wireless Power Transfer System

[0017] Patent CN113794287A proposes a constant current-constant voltage charging wireless power transfer system based on a dual-channel T-type circuit, the structure of which is as follows: Figure 11 As shown, by switching the switching mode and the conduction mode of the power transistor, the system operates in constant current or constant voltage mode respectively.

[0018] This solution can switch between constant current and constant voltage modes; however, the converter mainly operates in half-bridge mode, which limits the maximum output power and makes it unsuitable for high-power bidirectional charging and discharging scenarios in electric vehicles. Summary of the Invention

[0019] The purpose of this invention is to provide a bidirectional wireless power transmission system for electric vehicles that can transmit power with high efficiency over a wide operating range from light to heavy loads.

[0020] To achieve the above objectives, the present invention provides the following solution:

[0021] A two-way wireless power transfer system for electric vehicles includes: a PFC module, a first high-frequency conversion unit, a ground-end compensation network, a magnetic coupling coil, an on-board compensation network, and a second high-frequency conversion unit.

[0022] The PFC module is connected to the power grid and the first high-frequency conversion unit respectively; the first high-frequency conversion unit is connected to the ground-side compensation network; the ground-side compensation network resonates with the vehicle-side compensation network through the magnetic coupling coil; the vehicle-side compensation network is connected to the second high-frequency conversion unit; the second high-frequency conversion unit is connected to the electric vehicle battery;

[0023] Both the first high-frequency conversion unit and the second high-frequency conversion unit are full-bridge converters; a switch is provided on the connection branch between the first high-frequency conversion unit and the ground-side compensation network; a switch is also provided on the connection branch between the second high-frequency conversion unit and the vehicle-mounted compensation network.

[0024] Optionally, the first high-frequency conversion unit includes: power switch S1, power switch S2, power switch S3 and power switch S4;

[0025] One end of power switch S1 and one end of power switch S3 are both connected to the positive terminal of the ground DC bus; one end of power switch S2 and one end of power switch S4 are both connected to the negative terminal of the ground DC bus; the other end of power switch S1 is connected to the other end of power switch S2; the other end of power switch S3 is connected to the other end of power switch S4.

[0026] Optionally, the second high-frequency conversion unit includes: power switch Q1, power switch Q2, power switch Q3 and power switch Q4;

[0027] One end of power switch Q1 and one end of power switch Q3 are both connected to the positive terminal of the electric vehicle battery; one end of power switch Q2 and one end of power switch Q4 are both connected to the negative terminal of the electric vehicle battery; the other end of power switch Q1 is connected to the other end of power switch Q2; and the other end of power switch Q3 is connected to the other end of power switch Q4.

[0028] Optionally, the ground-side compensation network includes: a main inductor L1, a compensation capacitor C1, and a compensation capacitor C. f1 and compensation inductor L f1 ;

[0029] One end of the main inductor L1 is connected to the connection branch of the power switch S1 and the power switch S2 via switch K3; another end of the main inductor L1 is also connected to the connection branch of the power switch S3 and the power switch S4 via switch K2.

[0030] The other end of the main inductor L1 is connected to one end of the compensation capacitor C1; the other end of the compensation capacitor C1 is connected to the compensation capacitor C1. f1 One end and the compensation inductor L f1 One end is connected; the compensation inductor L f1 The other end is connected via switch K1 to the connection branch of power switch S1 and power switch S2; the compensation capacitor C f1 The other end is connected to the connection branch between the switch K2 and the first high-frequency conversion unit.

[0031] Optionally, the on-board compensation network includes: a main inductor L2, a compensation capacitor C2, and a compensation capacitor C. f2 and compensation inductor L f2 ;

[0032] One end of the main inductor L2 is connected to the connection branch of the power switch Q3 and the power switch Q4 via switch K5; another end of the main inductor L2 is also connected to the connection branch of the power switch Q2 and the negative terminal of the electric vehicle battery via switch K6.

[0033] The other end of the main inductor L2 is connected to one end of the compensation capacitor C2; the other end of the compensation capacitor C2 is connected to the compensation capacitor C... f2 One end and the compensation inductor L f2 One end is connected; the compensation inductor L f2 The other end is connected via switch K4 to the connection branch of power switch Q1 and power switch Q2; the compensation capacitor C f2 The other end is connected to the connection branch between the switch K5 and the first high-frequency conversion unit.

[0034] Optionally, the ground-side compensation network includes: a main inductor L1, a compensation capacitor C1, and a compensation capacitor C. f1 and compensation inductor L f1 ;

[0035] One end of the main inductor L1 is connected via switch K3 to the connection branch of power switch S1 and power switch S2; one end of the main inductor L1 is also connected via switch K2 to the connection branch of power switch S3 and power switch S4; one end of the main inductor L1 is connected via switch K4 to the connection branch of power switch S4 and the negative terminal of the ground DC bus.

[0036] The other end of the main inductor L1 is connected to one end of the compensation capacitor C1; the other end of the compensation capacitor C1 is connected to the compensation capacitor C1. f1 One end and the compensation inductor L f1 One end is connected; the compensation inductor Lf1 The other end is connected via switch K1 to the connection branch of power switch S1 and power switch S2; the compensation capacitor C f1 The other end is connected to the connection branch between the switch K2 and the first high-frequency conversion unit.

[0037] Optionally, the on-board compensation network includes: a main inductor L2, a compensation capacitor C2, and a compensation capacitor C. f2 and compensation inductor L f2 ;

[0038] One end of the main inductor L2 is connected to the connection branch of the power switch Q3 and the power switch Q4 via switch K5;

[0039] The other end of the main inductor L2 is connected to one end of the compensation capacitor C2; the other end of the compensation capacitor C2 is connected to the compensation capacitor C... f2 One end and the compensation inductor L f2 One end is connected; the compensation inductor L f2 The other end is connected to the connection branch of the power switch Q1 and the power switch Q2; the compensation capacitor C f2 The other end is connected to the connection branch between the switch K5 and the first high-frequency conversion unit.

[0040] Optionally, the magnetic coupling coil includes a unipolar coil and a bipolar coil;

[0041] Both the unipolar coil and the bipolar coil are symmetrically arranged about the center line.

[0042] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0043] The electric vehicle bidirectional wireless power transmission system provided by the present invention enables bidirectional power flow by setting the first high-frequency conversion unit and the second high-frequency conversion unit as full-bridge converters. A switch is set on the connection branch between the first high-frequency conversion unit and the ground-side compensation network, and a switch is also set on the connection branch between the second high-frequency conversion unit and the vehicle-side compensation network. By controlling the opening and closing of the switches, power can be transmitted with high efficiency over a wide operating range from light load to heavy load. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of the structure of a two-way wireless power transmission system for electric vehicles provided in an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the structure of a magnetic coupling coil provided in an embodiment of the present invention; wherein, Figure 2 (a) is a schematic diagram of the rectangular coil structure. Figure 2 (b) is a schematic diagram of the DD coil. Figure 2 (c) is a schematic diagram of the DDQ coil.

[0047] Figure 3 This is a schematic diagram of the magnetic flux distribution of a magnetically coupled coil provided in an embodiment of the present invention; wherein, Figure 3 (a) is a schematic diagram of the magnetic flux in vertical mode. Figure 3 (b) is a schematic diagram of the magnetic flux distribution in parallel mode;

[0048] Figure 4 This is a schematic diagram of the structure of the compensation network provided in an embodiment of the present invention; wherein, Figure 4 (a) is a schematic diagram of different topologies of the ground-end compensation network. Figure 4 (b) is a schematic diagram of different topologies of the vehicle-mounted compensation network;

[0049] Figure 5 This is a schematic diagram of commonly used compensation network types for electric vehicles provided in embodiments of the present invention; wherein, Figure 5 (a) is a schematic diagram of an SS-type compensation network. Figure 5 (b) is a schematic diagram of an S-LCC type compensation network. Figure 5 (c) is a schematic diagram of an LCC-S type compensation network. Figure 5 (d) is a schematic diagram of an LCC-LCC type compensation network;

[0050] Figure 6 Typical power-efficiency curves of a wireless power transmission system provided in embodiments of the present invention;

[0051] Figure 7 A schematic diagram of the wireless charging topology proposed in embodiment ① of the present invention;

[0052] Figure 8 A schematic diagram of the constant current and constant voltage device structure of the wireless charging system proposed in embodiment ② of the present invention;

[0053] Figure 9 A schematic diagram of the constant current and constant voltage wireless charging system structure proposed in embodiment ③ of the present invention;

[0054] Figure 10A schematic diagram of the wide load range high-efficiency WPT system structure proposed in embodiment ④ of the present invention;

[0055] Figure 11 A schematic diagram of the constant current and constant voltage wireless power transmission system proposed in embodiment ⑤ of the present invention;

[0056] Figure 12 This is a schematic diagram illustrating the analysis of the output characteristics of each resonant compensation network provided in the embodiments of the present invention; wherein, Figure 12 (a) is a schematic diagram illustrating the analysis of the output characteristics of the SS-type compensation network. Figure 12 (b) is a schematic diagram illustrating the analysis of the output characteristics of the S-LCC type compensation network. Figure 12 (c) is a schematic diagram illustrating the analysis of the output characteristics of the LCC-S type compensation network. Figure 12 (d) is a schematic diagram illustrating the analysis of the output characteristics of the LCC-LCC type compensation network;

[0057] Figure 13 The diagram illustrates three schemes for orthogonal decoupling coils provided in embodiments of the present invention; wherein, Figure 13 (a) is a schematic diagram of a structure where the main inductor is a DD coil and the auxiliary inductor is a rectangular coil. Figure 13 (b) is a schematic diagram of a structure where the main inductor is a rectangular coil and the auxiliary inductor is a DD coil. Figure 13 (c) is a schematic diagram of the structure of both the main inductor and the auxiliary inductor being DD coils;

[0058] Figure 14 This is a schematic diagram of the topology of a first type of bidirectional wireless power transmission system for electric vehicles provided in an embodiment of the present invention;

[0059] Figure 15 This is a schematic diagram of various operating modes in the first bidirectional wireless power transfer system for electric vehicles provided by an embodiment of the present invention; wherein, Figure 15 (a) is a schematic diagram of the operating mode of the first type of bidirectional wireless power transfer system for electric vehicles when the on-board battery voltage is low. Figure 15 (b) is a schematic diagram of the working mode of the first type of two-way wireless power transfer system for electric vehicles when the on-board battery voltage rises to a certain level. Figure 15 (c) is a schematic diagram of the operating mode of the first type of two-way wireless power transfer system for electric vehicles when the on-board battery voltage rises to a large value. Figure 15 (d) is a schematic diagram of the working mode of the first electric vehicle bidirectional wireless power transfer system when the on-board battery voltage is high;

[0060] Figure 16 This is a schematic diagram of the topology of a second type of bidirectional wireless power transfer system for electric vehicles provided in an embodiment of the present invention;

[0061] Figure 17 This is a schematic diagram of various operating modes in the second type of bidirectional wireless power transfer system for electric vehicles provided in an embodiment of the present invention; wherein, Figure 17 (a) is a schematic diagram of the operating mode of the second type of bidirectional wireless power transfer system for electric vehicles when the on-board battery voltage is low. Figure 17 (b) is a schematic diagram of the working mode of the second type of two-way wireless power transfer system for electric vehicles when the on-board battery voltage rises to a certain level. Figure 17 (c) is a schematic diagram of the second type of bidirectional wireless power transfer system for electric vehicles when the on-board battery voltage rises to a large value. Figure 17 (d) is a schematic diagram of the working mode of the second type of electric vehicle bidirectional wireless power transfer system when the on-board battery voltage is high;

[0062] Figure 18 A charging curve diagram of the constant current and constant voltage stage during forward power transmission provided in an embodiment of the present invention;

[0063] Figure 19 A power variation curve during forward power transmission is provided for an embodiment of the present invention;

[0064] Figure 20 The current variation curve during reverse power transfer is provided in the embodiment of the present invention;

[0065] Figure 21 The diagram shows the power change curve during reverse power transmission, as provided in an embodiment of the present invention.

[0066] Explanation of reference numerals in the attached figures:

[0067] 1-PFC module, 2-First high-frequency conversion unit, 3-Ground-end compensation network, 4-Magnetic coupling coil, 5-Vehicle-end compensation network, 6-Second high-frequency conversion unit. Detailed Implementation

[0068] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] The purpose of this invention is to provide a bidirectional wireless power transmission system for electric vehicles that can transmit power with high efficiency over a wide operating range from light to heavy loads.

[0070] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0071] like Figure 1 As shown, the electric vehicle bidirectional wireless power transmission system provided by the present invention includes: a PFC module 1, a first high-frequency conversion unit 2, a ground-end compensation network 3, a magnetic coupling coil 4, an on-board compensation network 5, and a second high-frequency conversion unit 6.

[0072] PFC module 1 is connected to both the power grid and the first high-frequency conversion unit 2. The first high-frequency conversion unit 2 is connected to the ground-side compensation network 3. The ground-side compensation network 3 resonates with the vehicle-side compensation network 5 via a magnetic coupling coil 4. The vehicle-side compensation network 5 is connected to the second high-frequency conversion unit 6. The second high-frequency conversion unit 6 is connected to the electric vehicle battery.

[0073] Both the first high-frequency conversion unit 2 and the second high-frequency conversion unit 6 are full-bridge converters. A switch is installed on the connection branch between the first high-frequency conversion unit 2 and the ground-side compensation network 3. A switch is also installed on the connection branch between the second high-frequency conversion unit 6 and the vehicle-mounted compensation network 5.

[0074] Based on the above structure, when the power grid charges the electric vehicle battery (defined as forward power transmission), the AC voltage from the power grid is rectified by the PFC module 1 and converted into an intermediate DC voltage. The first high-frequency conversion unit 2, following the PFC module 1, operates in inverter mode, inverting the intermediate DC to generate high-frequency AC, which is then injected into the resonant network composed of the ground-side compensation network 3 and the magnetic coupling coil 4. Under the influence of the alternating magnetic field, the magnetic coupling coil 4 induces a high-frequency AC voltage, resonating with the on-board compensation network 5, and transferring energy to the electric vehicle battery via the second high-frequency conversion unit 6 (operating in rectification mode, converting high-frequency AC to DC).

[0075] When the battery discharges into the grid (defined as reverse power transfer), the second high-frequency conversion unit 6 operates in inverter mode, inverting the DC power from the electric vehicle battery to generate high-frequency AC power, which is then injected into the resonant network composed of the on-board compensation network 5 and the magnetic coupling coil 4. Under the influence of the alternating magnetic field, the magnetic coupling coil 4 induces a high-frequency AC voltage, which resonates with the ground-side compensation network 3. The energy is then transmitted through the first high-frequency conversion unit 2 (operating in inverter mode, converting high-frequency AC to DC), and inverted into power frequency AC power through the PFC module 1, finally being transferred to the power grid.

[0076] The following describes the specific structure of each part in the electric vehicle bidirectional wireless power transmission system provided by the present invention, based on the technical concept and the technical objectives achieved.

[0077] The magnetic coupling coil 4 and the compensation network are important components of the wireless charging system.

[0078] The magnetic coupling coils in existing wireless charging systems are mainly divided into unipolar coils, bipolar coils, and composite coils. Among unipolar coils, rectangular coils are widely used because they make better use of vehicle chassis space. Bipolar coils are primarily represented by DD coils. By orthogonally stacking DD coils and rectangular coils, a DDQ coil can be obtained, such as... Figure 2 As shown.

[0079] like Figure 3 As shown, the magnetic flux distribution of a unipolar coil is mainly in a vertical pattern, while that of a bipolar coil is in a parallel pattern. Therefore, coils of the same polarity are often used for power transmission. Since the DDQ coil consists of both unipolar and bipolar coils, decoupling of the two coils can be achieved if arranged properly. Taking a unipolar coil as an example, when the magnetic flux flowing from the bipolar coil into the unipolar coil is equal to the magnetic flux flowing out of the unipolar coil, the magnetic flux coupling between the two coils is approximately zero, thus achieving decoupling.

[0080] The typical coupling coefficient k of the magnetic coupling coil 4 in an electric vehicle is around 0.2 to 0.4. In order to enable the coupling system to transmit electrical energy efficiently, reactive power compensation is required for the magnetic coupling coil 4 to form a high-frequency resonant network. The compensation network can effectively reduce the apparent power level of the transmitter inverter and the reactive power of the resonant cavity, improve the power transmission capability, and also realize constant current / constant voltage output, improve transmission efficiency, and resist frequency bifurcation.

[0081] like Figure 4 As shown, based on the connection method between the compensation capacitor / inductor and the magnetic coupling coil 4, there are mainly series (S) compensation, parallel (P) compensation, series-parallel (LCL) compensation, and LCC compensation derived from these. Figure 4 In the diagram, L represents the magnetic coupling coil 4, and C and L... f C f All are compensation elements, with subscripts 1 and 2 representing the ground-based and vehicle-mounted ends, respectively. For electric vehicle applications, commonly used compensation networks are SS, S-LCC, LCC-S, and LCC-LCC, such as... Figure 5 As shown. SS and LCC-LCC can both achieve natural constant current charging, while S-LCC and LCC-S can both achieve natural constant voltage charging.

[0082] Furthermore, existing systems struggle to maintain high efficiency over a wide power range. For example... Figure 6 As shown, for a typical wireless power transmission system, the transmission efficiency increases with the increase of transmission power. That is, the system efficiency is usually not high under light load, but the transmission efficiency is higher under medium and heavy load.

[0083] Furthermore, the design method and output characteristics of the compensation network parameters are analyzed.

[0084] Taking various types of compensation networks as research objects, namely SS, S-LCC, LCC-S, and LCC-LCC, the output characteristics of each type of compensation network are as follows: Figure 12 As shown. Where R eq U is the equivalent load resistance. p and U s Let V1 and V2 be the effective values ​​of the converter excitation voltage, respectively. If the ground-side DC bus voltage and battery voltage are V1 and V2, respectively, and both high-frequency converters are full-bridge circuits, then the maximum effective values ​​of the fundamental frequency of the excitation voltage are as follows:

[0085]

[0086] If both high-frequency converters are half-bridge circuits, then the maximum effective values ​​of the fundamental frequency of the excitation voltage are as follows:

[0087]

[0088] It can be seen that the maximum output voltage of the half-bridge converter is half that of the full-bridge converter. Referring to Table 1, the output power is proportional to the voltage across the terminals.

[0089] Therefore, when the DC bus voltage V1 and the battery voltage V2 are constant:

[0090] If both ends of the converter are in full-bridge mode, the maximum output power is P. max .

[0091] If both ends of the converter are in half-bridge mode, the maximum output power is P. max / 4.

[0092] If the two-ended converters are in full-bridge mode and half-bridge mode respectively, then the maximum output power is P. max / 2.

[0093] Therefore, the maximum output power can be limited by controlling the converter's operating mode.

[0094] Figure 12 In the diagram, L1 and L2 are the main inductors, and C... f1 C1, C f2 C2 is a compensation capacitor, L f1 L f2 To compensate for inductance. M 1-2 and M f1-f2 These represent the mutual inductance between the main coils and the mutual inductance between the auxiliary coils, respectively.

[0095] This invention enables each resonant cavity to operate under pure resonance conditions, where ω0 is the nominal angular frequency.

[0096] For S-compensation, the following conditions are met:

[0097] For LCC compensation, it satisfies

[0098] For traditional LCC compensation, conventional LCC compensation only uses the main inductor L as the power transfer coil (see...). Figure 5 (d)), while the auxiliary inductor L f It only serves as a compensation element. In this invention, the auxiliary inductor L... f1 and L f2 It has both compensation and power transmission functions, so both coils at the ground end and vehicle end of this wireless power transmission system can transmit power.

[0099] Furthermore, to reduce cross-coupling between coils on the same side and coils on opposite sides, this invention uses orthogonal decoupling coils as magnetic coupling coils, such as... Figure 13 As shown, the three coil design schemes are as follows: ① The main inductor L is a DD coil, and the auxiliary inductor L... f For rectangular coils, such as Figure 13 As shown in (a). ② The main inductor is a rectangular coil, and the auxiliary inductor is a DD coil, as shown in (a). Figure 13 As shown in (b). ③ Both the main inductor and the auxiliary inductor are DD coils, but their directions differ by 90°, as shown in (b). Figure 13 As shown in (c), the coils on the same side are symmetrically placed about the center line to achieve decoupling.

[0100] The output characteristics and maximum transmission power of each compensation network are summarized in Table 1 below, where M represents the mutual inductance between inductors, and I... out This represents the output current of the resonant cavity. It is easy to see that as the excitation voltage increases, the transmission power also increases.

[0101] Table 1. Output Characteristic Analysis of Each Resonance Compensation Network

[0102]

[0103] Furthermore, based on the above description, Figure 1 Taking the DC-DC link from the DC bus output of PFC module 1 to the power battery as the research object, and taking the first type of orthogonal decoupling coil as an example, two different topologies of bidirectional wireless power transmission systems for electric vehicles are proposed.

[0104] The topology of the first type of electric vehicle bidirectional wireless power transfer system is as follows: Figure 14As shown. V1 and V2 represent the voltage sources of the DC bus and the power battery, respectively. The high-frequency conversion units (i.e., the first high-frequency conversion unit 2 and the second high-frequency conversion unit 6) of the ground-side compensation network 3 and the vehicle-side compensation network 5 are full-bridge converters, composed of MOSFET power switches S1~S4 and Q1~Q4, respectively (for simplicity, the DC support capacitors between the voltage sources and the full-bridge converters are not shown). L1 and L2 are the main inductors of the ground-side compensation network 3 and the vehicle-side compensation network 5, respectively, C f1 C1, C f2 C2 and C3 are the compensation capacitors for the ground-side compensation network 3 and the vehicle-mounted compensation network 5, respectively. f1 L f2 These are the compensation inductors for the ground-side compensation network 3 and the vehicle-side compensation network 5, respectively.

[0105] Switches K1, K2, K3, K4, K5, and K6 are added to the six branches of the ground-side compensation network 3 and the vehicle-mounted compensation network 5, respectively. These switching switches K1 to K6 can be relays or bidirectional power switches. If a switch is closed, the corresponding branch is connected. If a switch is open, the corresponding branch is disconnected.

[0106] Based on the above description, in the first bidirectional wireless power transmission system for electric vehicles, one end of the main inductor L1 is connected to the connection branch of power switches S1 and S2 via switch K3. Another end of the main inductor L1 is also connected to the connection branch of power switches S3 and S4 via switch K2.

[0107] The other end of the main inductor L1 is connected to one end of the compensation capacitor C1. The other end of the compensation capacitor C1 is connected to the compensation capacitor C... f1 One end and the compensation inductor L f1 One end is connected. Compensating inductor L f1 The other end is connected via switch K1 to the connection branch of power switches S1 and S2. Compensation capacitor C f1 The other end is connected to the connection branch between switch K2 and the first high-frequency conversion unit 2.

[0108] One end of the main inductor L2 is connected via switch K5 to the connection branch of power switches Q3 and Q4. Another end of the main inductor L2 is also connected via switch K6 to the connection branch between power switch Q2 and the negative terminal of the electric vehicle battery.

[0109] The other end of the main inductor L2 is connected to one end of the compensation capacitor C2. The other end of the compensation capacitor C2 is connected to the compensation capacitor C... f2 One end and the compensation inductor L f2 One end is connected. Compensating inductor L f2 The other end is connected via switch K4 to the connection branch of power switches Q1 and Q2. Compensation capacitor Cf2 The other end is connected to the connection branch between switch K5 and the first high-frequency conversion unit 2.

[0110] Unlike traditional unidirectional wireless power transfer systems, whose receiver converters often employ uncontrolled rectification (composed of diodes), thus only allowing forward power transfer, the first bidirectional wireless power transfer system for electric vehicles proposed in this invention uses a topology where all bridge converters are composed of fully controlled devices, enabling bidirectional power flow.

[0111] Figure 15 The various operating modes of the first system topology are shown. Among them:

[0112] (1) When the vehicle battery voltage is low, power is transferred in the forward direction to charge the battery, requiring constant current charging. For example... Figure 15 As shown in (a), when switches K1 and K4 are closed and the remaining switches are open, the ground-end compensation network 3 (hereinafter referred to as the ground end) and the vehicle-mounted compensation network 5 (hereinafter referred to as the vehicle end) form the SS compensation network, and the auxiliary coil L... f1 and L f2 Used for energy transfer. The ground-side high-frequency converter (i.e., the first high-frequency converter unit 2) operates in full-bridge inverter mode, and the vehicle-mounted high-frequency converter (i.e., the second high-frequency converter unit 6) operates in full-bridge rectification mode.

[0113] As the bus voltage and battery voltage increase, the transmitted power also increases. In SS mode, constant current charging can be achieved. Furthermore, due to the low self-inductance and mutual inductance of the auxiliary coil, the system transmits a large power, thus achieving high-power transmission under light loads.

[0114] (2) When the vehicle battery voltage rises to a certain level, power is transferred in the forward direction to charge the battery, maintaining a constant current mode but with a decrease in the required current. For example... Figure 15 As shown in (b), when switches K1, K2, K4, and K5 are closed and the remaining switches are open, the ground-side compensation network 3 and the vehicle-side compensation network 5 form a dual-coupled LCC-LCC compensation network. The main coils L1 and L2 and the auxiliary coil L f1 L f2 Both are used for energy transfer. The ground-side high-frequency converter (i.e., the first high-frequency converter unit 2) operates in full-bridge inverter mode, while the vehicle-mounted high-frequency converter (i.e., the second high-frequency converter unit 6) operates in full-bridge rectification mode.

[0115] As the bus voltage and battery voltage increase, the transmitted power also increases. Constant current charging can be achieved in the dual-coupled LCC-LCC mode. Furthermore, the mutual inductance parameters are designed to keep the system's transmitted power within the target range, thus enabling medium-load, medium-power transmission.

[0116] (3) When the vehicle battery voltage rises to a high value, the power transmission shifts to charge the battery, switching to constant voltage charging mode, and the charging current continuously decreases. For example... Figure 15 As shown in (c), closing switches K1, K2, and K6 while opening the other switches creates an LCC-S compensation network between the ground and vehicle terminals, with main coils L1 and L2 used for power transfer. Constant voltage charging is achieved in LCC-S mode. The ground-side high-frequency converter operates in full-bridge inverter mode. Power switches Q1 and Q2 are always off. By controlling the on / off state of power switches Q3 and Q4, the vehicle-side high-frequency converter operates in half-bridge rectification mode. Therefore, the excitation voltage at the converter ports becomes half that in full-bridge mode, limiting the output capability and making it suitable for low-power transmission under heavy loads.

[0117] (4) When the vehicle battery voltage is high, power is transferred in the reverse direction to discharge into the power grid. For example... Figure 15 As shown in (d), closing switches K3, K4, and K5 while opening the others creates an S-LCC compensation network between the ground and vehicle-mounted ends, with main coils L1 and L2 used for power transfer. In S-LCC mode, constant voltage discharge can be achieved. The vehicle-mounted high-frequency converter operates in full-bridge inverter mode, while the ground-mounted high-frequency converter operates in full-bridge rectification mode. Therefore, reverse high-power transmission can be achieved.

[0118] The topology of the second type of electric vehicle two-way wireless power transfer system is as follows: Figure 16 As shown in the diagram. This scheme adds switches K1 to K4 and switch K5 to the four branches on the ground end and one branch on the vehicle end, respectively.

[0119] Specifically, one end of the main inductor L1 is connected via switch K3 to the connection branch of power switches S1 and S2. Another end of the main inductor L1 is also connected via switch K2 to the connection branch of power switches S3 and S4. Finally, one end of the main inductor L1 is connected via switch K4 to the connection branch between power switch S4 and the negative terminal of the ground DC bus.

[0120] The other end of the main inductor L1 is connected to one end of the compensation capacitor C1. The other end of the compensation capacitor C1 is connected to the compensation capacitor C... f1 One end and the compensation inductor L f1 One end is connected. Compensating inductor L f1 The other end is connected via switch K1 to the connection branch of power switches S1 and S2. Compensation capacitor C f1 The other end is connected to the connection branch between switch K2 and the first high-frequency conversion unit 2.

[0121] One end of the main inductor L2 is connected to the connection branch of power switches Q3 and Q4 via switch K5.

[0122] The other end of the main inductor L2 is connected to one end of the compensation capacitor C2. The other end of the compensation capacitor C2 is connected to the compensation capacitor C... f2 One end and the compensation inductor L f2 One end is connected. Compensating inductor L f2 The other end is connected to the connection branch of power switch Q1 and power switch Q2. Compensation capacitor C f2 The other end is connected to the connection branch between switch K5 and the first high-frequency conversion unit 2.

[0123] Figure 17 The operating modes of the second system topology are shown. Among them:

[0124] (1) When the vehicle battery voltage is low, power is transferred in the forward direction to charge the battery, requiring constant current charging. For example... Figure 17 As shown in (a), when switch K1 is closed and the other switches are open, the ground end and the vehicle end form an SS compensation network, and the auxiliary coil L f1 and L f2 Used for energy transfer. The ground-side high-frequency converter operates in full-bridge inverter mode, while the vehicle-mounted high-frequency converter operates in full-bridge rectification mode.

[0125] As the bus voltage and battery voltage increase, the transmitted power also increases. In SS mode, constant current charging can be achieved. Furthermore, due to the low self-inductance and mutual inductance of the auxiliary coil, the system transmits a large power, thus achieving high-power transmission under light loads.

[0126] (2) When the vehicle battery voltage rises to a certain level, power is transferred in the forward direction to charge the battery, maintaining constant current charging mode but with a decrease in the required current. For example... Figure 17 As shown in (b), when switches K1, K2, and K5 are closed and the remaining switches are open, a dual-coupled LCC-LCC compensation network is formed between the ground end and the vehicle end. The main coils L1 and L2 and the auxiliary coil L f1 L f2 Both are used for energy transfer. The ground-side high-frequency converter operates in full-bridge inverter mode, while the vehicle-mounted high-frequency converter operates in full-bridge rectification mode.

[0127] As the bus voltage and battery voltage increase, the transmitted power also increases. Constant current charging can be achieved in the dual-coupled LCC-LCC mode. Furthermore, the mutual inductance parameters are designed to keep the system's transmitted power within the target range, thus enabling medium-load, medium-power transmission.

[0128] (3) When the vehicle battery voltage rises to a higher value, the power is transferred in the forward direction to charge the battery, switching to constant voltage charging mode, and the charging current continuously decreases. For example... Figure 17As shown in (c), closing switches K4 and K5 and opening the other switches creates an S-LCC compensation network between the ground and vehicle terminals, with main coils L1 and L2 used for power transfer. Constant voltage charging is achieved in S-LCC mode. Power switches S1 and S2 are always off. By controlling the on / off state of S3 and S4, the ground-side high-frequency converter operates in half-bridge inverter mode. Power switch Q1 is always off, and Q2 is always on. By controlling the on / off state of Q3 and Q4, the vehicle-side high-frequency converter operates in half-bridge rectification mode. Therefore, the excitation voltage at both ends of the converter is half that in full-bridge mode, limiting the output capability and making it suitable for low-power transmission under heavy loads.

[0129] (4) When the vehicle battery voltage is high, power is transferred in the reverse direction to discharge into the power grid. For example... Figure 17 As shown in (d), closing K3 and K5 and opening the other switches creates an S-LCC compensation network between the ground and vehicle-mounted ends, with main coils L1 and L2 used for power transfer. In S-LCC mode, constant voltage discharge can be achieved. The vehicle-mounted high-frequency converter operates in full-bridge inverter mode, while the ground-mounted high-frequency converter operates in full-bridge rectification mode. Therefore, reverse high-power transmission can be achieved.

[0130] Based on the above operating mode, the charging curve during forward power transfer is as follows: Figure 18 As shown. When the battery is lightly loaded, the SS mode (the first operating mode of the first or second topology) is used, which is the constant current stage (high current charging). When the battery is medium loaded, the LCC-LCC mode (the second operating mode of the first or second topology) is used, which is the constant current stage (low current charging). When the battery is heavily loaded, the LCC-S mode (the third operating mode of the first topology) or the S-LCC mode (the third operating mode of the second topology) is used, which is the constant voltage stage (current continuously decreasing).

[0131] The power change curve during forward power transmission is as follows: Figure 19 As shown. When the battery is lightly loaded, the SS mode is used; as the bus voltage and battery voltage increase, the transmitted power increases accordingly. When the battery is medium loaded, the LCC-LCC mode is used; as the bus voltage and battery voltage increase, the transmitted power increases accordingly. When the battery is heavily loaded, the LCC-S or S-LCC mode is used; as the battery's equivalent resistance increases, the charging current and power continuously decrease.

[0132] Traditional wireless power transmission systems undergo a charging process from light load to heavy load within the same operating mode, inevitably resulting in low efficiency during the light load phase. However, the topology proposed in this invention ensures that the system operates within the corresponding medium-load and heavy-load ranges in each operating mode (for example, the maximum output capacity of SS mode is 30kW, but in this invention's system it operates only between 11kW and 30kW; the maximum output capacity of LCC-LCC mode is 11kW, but in this invention's system it operates only between 5kW and 11kW), thus maintaining consistently high transmission efficiency.

[0133] The current and power change curves during reverse power transfer are as follows: Figure 20 and Figure 21 As shown. The system provided by this invention operates in S-LCC mode (the fourth mode of the two topologies). As the battery voltage decreases, the discharge current gradually decreases, and the discharge power also decreases accordingly. When the battery voltage drops to a medium voltage, reverse discharge terminates.

[0134] Based on the above description, the bidirectional wireless power transfer system for electric vehicles provided by the present invention has the following advantages compared with the prior art:

[0135] 1) This invention proposes three orthogonal decoupled coil schemes, in which both the main inductor and the auxiliary inductor can transfer energy, realizing bidirectional power flow.

[0136] 2) This invention proposes two switchable bidirectional wireless power transmission system topologies. By closing or closing the switch, different compensation networks can be switched to achieve constant current / constant voltage output modes.

[0137] 3) In the forward power transmission mode, the present invention charges the battery at high power when the battery is lightly loaded, at medium power when the battery is medium loaded, and at low power when the battery is heavily loaded. In the reverse power transmission mode, the battery discharges at high power when the battery is at high voltage, thus realizing a charging mode of high power under light load, medium power under medium load, and low power under heavy load. It can also achieve reverse high power discharge, so it is suitable for bidirectional charging and discharging scenarios of electric vehicles.

[0138] 4) The system provided by this invention transmits energy efficiently over a wide power operating range. It boasts a strong maximum output capability and high transmission efficiency over a wide operating range.

[0139] 5) Compared with common wireless power transmission systems based on LCC-LCC compensation, this invention does not add any extra inductors or capacitors. It only adds some switches to the branches to complete the switching of constant current and constant voltage modes.

[0140] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0141] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A two-way wireless power transfer system for electric vehicles, characterized in that, include: PFC module, first high-frequency conversion unit, ground-end compensation network, magnetic coupling coil, vehicle-mounted compensation network and second high-frequency conversion unit; The PFC module is connected to the power grid and the first high-frequency conversion unit respectively; the first high-frequency conversion unit is connected to the ground-side compensation network; the ground-side compensation network resonates with the vehicle-side compensation network through the magnetic coupling coil; the vehicle-side compensation network is connected to the second high-frequency conversion unit; the second high-frequency conversion unit is connected to the electric vehicle battery; Both the first high-frequency conversion unit and the second high-frequency conversion unit are full-bridge converters; a switch is provided on the connection branch between the first high-frequency conversion unit and the ground-side compensation network; a switch is also provided on the connection branch between the second high-frequency conversion unit and the vehicle-mounted compensation network. Using orthogonal decoupling coils as the magnetic coupling coils, the three coil design schemes are as follows: ① The main inductor L is a DD coil, and the auxiliary inductor L... f ① The main inductor L is a rectangular coil; ② The auxiliary inductor L is a rectangular coil. f For DD coils; main inductance L and auxiliary inductance L f All are DD coils, but their directions differ by 90°; the coils on the same side are placed symmetrically about the center line to achieve decoupling; For electric vehicle applications, the compensation networks are SS, S-LCC, LCC-S, and LCC-LCC. (1) When the vehicle battery voltage is low, the power is transmitted in the forward direction to charge the battery. The ground-end compensation network and the vehicle-end compensation network form the SS compensation network. The first high-frequency conversion unit operates in full-bridge inverter mode, and the second high-frequency conversion unit operates in full-bridge rectification mode. When the bus voltage and battery voltage increase, the transmitted power increases accordingly. In SS mode, constant current charging is achieved. Due to the small self-inductance and mutual inductance of the auxiliary coil, the system transmits a large power, thereby achieving high power transmission under light load. Among them, the low vehicle battery voltage means that it is lower than a certain set value. (2) When the vehicle battery voltage rises to a certain level, the power is transmitted in the forward direction to charge the battery. It still maintains the constant current mode but the required current decreases. Then, the ground-end compensation network and the vehicle-end compensation network form a dual-coupled LCC-LCC compensation network. The first high-frequency conversion unit works in full-bridge inverter mode, and the second high-frequency conversion unit works in full-bridge rectification mode. When the bus voltage and battery voltage increase, the transmitted power increases accordingly. In the dual-coupled LCC-LCC mode, constant current charging is achieved. The mutual inductance parameters are designed so that the system transmission power is within the target range, thereby achieving medium-load medium-power transmission. (3) When the vehicle battery voltage rises to a large value, the power forward transmission is to charge the battery, and the constant voltage mode charging is switched to charging. The charging current continues to decrease. The ground-end compensation network and the vehicle-end compensation network form an LCC-S compensation network. In the LCC-S mode, constant voltage charging is achieved. The first high-frequency conversion unit works in full-bridge inverter mode. The second high-frequency conversion unit works in half-bridge rectification mode. The excitation voltage of the converter port becomes 1 / 2 of that in the full-bridge mode, which limits the output capability and is suitable for low power transmission under heavy load. Among them, the vehicle battery voltage rises to a large value means that the vehicle battery voltage value rises to a set value. (4) When the vehicle battery voltage is high, the power is transmitted in reverse to discharge to the grid. The ground-side compensation network and the vehicle-side compensation network form an S-LCC compensation network. In S-LCC mode, constant voltage discharge is achieved. The second high-frequency conversion unit operates in full-bridge inverter mode, and the first high-frequency conversion unit operates in full-bridge rectification mode. Therefore, reverse high-power transmission is achieved. Among them, the vehicle battery voltage is high, which means higher than the set value.

2. The electric vehicle bidirectional wireless power transmission system according to claim 1, characterized in that, The first high-frequency conversion unit includes: a power switch S 1. Power switch S 2. Power switch S 3 and power switch S 4; The power switch S One end of 1 and the power switch S One end of each of the three is connected to the positive terminal of the ground DC bus; the power switch S 2 and power switch S One end of each of the four switches is connected to the negative terminal of the ground DC bus; the power switch S The other end of 1 is connected to the power switch. S The other end of 2 is connected; the power switch S The other end of 3 is connected to the power switch. S Connect the other end of 4.

3. The electric vehicle bidirectional wireless power transmission system according to claim 2, characterized in that, The second high-frequency conversion unit includes: a power switch Q 1. Power switch Q 2. Power switch Q 3 and power switch Q 4; The power switch Q One end of 1 and the power switch Q One end of each of the three terminals is connected to the positive terminal of the electric vehicle battery; the power switch Q 2 and power switch Q One end of each of the four terminals is connected to the negative terminal of the electric vehicle battery; the power switch Q The other end of 1 is connected to the power switch. Q The other end of 2 is connected; the power switch Q The other end of 3 is connected to the power switch. Q Connect the other end of 4.

4. The electric vehicle bidirectional wireless power transmission system according to claim 3, characterized in that, The ground-end compensation network includes: a main inductor. L 1. Compensation capacitor C 1. Compensation capacitor C f1 and compensating inductor L f1 ; The main inductor L One end of 1 is connected to a switch K 3 Connected to the power switch S 1 and the power switch S 2. Connection branch; the main inductor L One end of 1 is also connected to a switch K 2 Connect to power switch S 3 and the power switch S On the connecting branch of 4; The main inductor L The other end of 1 is connected to the compensation capacitor. C One end of 1 is connected; the compensation capacitor C The other end of 1 is connected to the compensation capacitor. C f1 One end and the compensation inductor L f1 One end is connected; the compensation inductor L f1 The other end is connected to a switch K 1 connected to the power switch S 1 and the power switch S On the connecting branch of 2; the compensation capacitor C f1 The other end is connected to the switch K 2. On the connection branch with the first high-frequency conversion unit.

5. The electric vehicle bidirectional wireless power transfer system according to claim 4, characterized in that, The on-board compensation network includes: a main inductor. L 2. Compensation capacitor C 2. Compensation capacitor C f2 and compensating inductor L f2 ; The main inductor L One end of 2 is connected to a switch K 5 connected to the power switch Q 3 and the power switch Q 4. Connection branch; the main inductor L One end of 2 is also connected to a switch K 6 Connect to power switch Q 2. On the branch connecting to the negative terminal of the electric vehicle battery; The main inductor L The other end of 2 is connected to the compensation capacitor. C One end of 2 is connected; the compensation capacitor C The other end of 2 is connected to the compensation capacitor. C f2 One end and the compensation inductor L f2 One end is connected; the compensation inductor L f2 The other end is connected to a switch K 4 connected to the power switch Q 1 and the power switch Q On the connecting branch of 2; the compensation capacitor C f2 The other end is connected to the connection branch between the switch K5 and the first high-frequency conversion unit.

6. The electric vehicle bidirectional wireless power transfer system according to claim 3, characterized in that, The ground-end compensation network includes: a main inductor. L 1. Compensation capacitor C 1. Compensation capacitor C f1 and compensating inductor L f1 ; The main inductor L One end of 1 is connected to a switch K 3 Connected to the power switch S 1 and the connection branch of the power switch S2; the main inductor L One end of 1 is also connected to a switch K 2 Connect to power switch S 3 and the power switch S 4. On the connecting branch; the main inductor L One end of 1 is connected to a switch K 4 connected to the power switch S 4. On the branch connecting to the negative terminal of the ground DC bus; The main inductor L The other end of 1 is connected to the compensation capacitor. C One end of 1 is connected; the compensation capacitor C The other end of 1 is connected to the compensation capacitor. C f1 One end and the compensation inductor L f1 One end is connected; the compensation inductor L f1 The other end is connected to a switch K 1 connected to the power switch S 1 and the power switch S On the connecting branch of 2; the compensation capacitor C f1 The other end is connected to the switch K 2. On the connection branch with the first high-frequency conversion unit.

7. The electric vehicle bidirectional wireless power transfer system according to claim 6, characterized in that, The on-board compensation network includes: a main inductor. L 2. Compensation capacitor C 2. Compensation capacitor C f2 and compensating inductor L f2 ; The main inductor L One end of 2 is connected to a switch K 5 connected to the power switch Q 3 and the power switch Q 4 connecting branches; The main inductor L The other end of 2 is connected to the compensation capacitor. C One end of 2 is connected; the compensation capacitor C The other end of 2 is connected to the compensation capacitor. C f2 One end and the compensation inductor L f2 One end is connected; the compensation inductor L f2 The other end is connected to the power switch Q 1 and the power switch Q On the connecting branch of 2; the compensation capacitor C f2 The other end is connected to the connection branch between the switch K5 and the first high-frequency conversion unit.

8. The electric vehicle bidirectional wireless power transfer system according to claim 1, characterized in that, The magnetically coupled coil includes a unipolar coil and a bipolar coil; Both the unipolar coil and the bipolar coil are symmetrically arranged about the center line.

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