High-power dynamic wireless charging system

Abstract

The invention discloses a high-power dynamic wireless charging system. The system comprises a direct current input end, an inverter module, a transmitting coil module, a receiving coil module, a rectifier module, a DC / DC converter module and a direct current output end. According to the invention, the size of the system is reduced, the optimal balance between power density and thermal management is realized, meanwhile, high-frequency interference is effectively filtered, and the requirement of high-power transmission is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless charging, and in particular relates to a high-power dynamic wireless charging system. Background Art

[0002] With the rapid development of science and technology, electric vehicles are becoming more and more popular in society. However, the increasing number of electric vehicles poses a huge challenge to traditional charging methods. Traditional charging methods are inflexible and cannot effectively reduce the range anxiety of electric vehicles.

[0003] In this context, dynamic wireless power transfer (DWPT) came into being. It is a technology that can wirelessly transmit power while the vehicle is driving, mainly using magnetic coupling resonant wireless power transmission. Specifically, the transmitting coil is buried under the road, and the receiving coil on the vehicle continuously forms magnetic coupling resonance with the transmitting coil during driving, thereby obtaining electrical energy for the electric vehicle. This method can provide energy for the electric vehicle while it is driving, extend the driving range in an economical and effective way, and significantly reduce mileage anxiety. At the same time, dynamic charging can also reduce the required on-board battery capacity, reduce the weight, volume and cost of electric vehicles. However, the existing wireless power transmission devices have low power, low efficiency, and a very short transmission distance. They are mainly used in electronic equipment charging occasions. This technology is difficult to use in high-power occasions. The application of wireless power transmission in high-power occasions (such as electric vehicle charging) is of great significance, but this application requires that the wireless power transmission power must reach at least the KW level. This level of power transmission must require a high transmission efficiency, otherwise not only will there be huge energy losses, but the heat dissipation of the device is also a difficult problem to solve. The existing wireless power transmission solution cannot meet such high-power occasions. In addition, in existing wireless power transmission devices, coils mostly use circular coupling topology, but the disadvantage of circular coupling is that when the shielding effect of the vehicle chassis is added, the power transmission efficiency of circular coupling will drop significantly, and the drop can exceed 50%. Therefore, circular coupling cannot effectively maintain efficient energy transmission in dynamic wireless charging scenarios, especially when electric vehicles are driving.

[0004] In order to make DWPT technology feasible, the charging power needs to be increased to 200KW level. This can reduce the coverage area on the road that needs to be electrified, and avoid the high cost of electronic equipment on the vehicle side. High-power DWPT systems rely on power electronics to regulate power transmission and ensure operation under the premise of efficiency and reliability.

[0005] The high-power wireless power transmission system uses the principle of magnetic coupling resonant wireless power transfer (MCR-WPT) to achieve power transmission through the transmitter and receiver. In recent years, high-power wireless power transmission technology has developed rapidly, which can meet the efficient transmission within tens of centimeters to several meters, and is suitable for application scenarios with large power demand. However, in the pursuit of high power, the system requires a more complex design to handle higher voltages and currents, which may require advanced circuit topologies and more control and regulation circuits to optimize efficiency and stability. At the same time, in order to reduce power loss, the system usually requires more sophisticated matching and compensation designs, which further increases the difficulty of design and implementation. The increase in system power means that more heat will be generated. Since the losses during transmission and conversion are dissipated in the form of heat, the system may heat up quickly. High-power transmission generates high currents and high voltages, which generate strong magnetic fields. This will not only generate electromagnetic interference (EMI) to surrounding equipment, but may also affect sensitive circuits inside the system. As the power of the system increases, the losses in conductors and switching elements will also increase accordingly. In summary, high-power systems have problems such as high complexity, difficult thermal management, electromagnetic interference, and increased power loss. Summary of the invention

[0006] The purpose of the present invention is to provide a high-power dynamic wireless charging system that can reduce the volume of the wireless charging system, achieve an optimal balance between power density and thermal management, effectively filter out high-frequency interference, and meet the needs of high-power transmission.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A high-power dynamic wireless charging system includes a DC input terminal, an inverter module, a transmitting coil module, a receiving coil module, a rectifier module, a DC / DC converter module and a DC output terminal; the voltage of the DC input terminal is 800V, and the voltage of the DC output terminal is 300-400V; the inverter module includes two groups of SiC full-bridge modules, a drive circuit, a cooling system and a decoupling capacitor, and the inverter module is responsible for converting the 800V DC input voltage into high-frequency AC power to power the transmitting coil module; the transmitting coil module includes an LCC resonant network, a transmitting coil and related tuning capacitors, the transmitting coil transmits power to the receiving coil wirelessly, and the LCC resonant network is used to keep the main coil current constant, thereby achieving stable wireless energy transmission; the receiving coil module includes a vehicle bottom The receiving coil module receives the AC power from the transmitting coil and transmits it to the rectifier module, which is then provided to the vehicle battery; both the transmitting coil and the receiving coil adopt a "DD" coil topology structure, and the "DD" coil topology structure consists of two adjacent D-shaped coils to form a larger planar magnetic field area; the rectifier module includes a four-phase SiC rectifier bridge, a cooling system and a decoupling capacitor; the AC power transmitted by the receiving coil is converted into DC power, and an input voltage is provided for the DC / DC converter module; the DC / DC converter module includes a four-phase step-down circuit, a filter, a power module and a cooling system, which further reduces the rectified DC voltage to 300-400V; a plurality of DC / DC converter modules are arranged, and the plurality of DC / DC converter modules are multi-phase staggered in parallel.

[0009] Furthermore, there are two ways to supply the voltage of the DC input terminal: one is the DC power output after rectification from the AC power grid; the other is the DC power directly taken from the local DC power grid.

[0010] Furthermore, the mutual inductance coefficient of the transmitting coil and the receiving coil is:

[0011]

[0012] Where P is the transmission power, I pri is the primary coil current, I sec is the secondary coil current, ω0 is the angular velocity.

[0013] Furthermore, the transmitting coil and the receiving coil constitute an LCC-S compensation network, the primary side adopts an LCC tuning method, and the secondary side adopts a series tuning method. In order to achieve decoupling of the output voltage and the load, the primary side circuit should meet the following resonance conditions:

[0014]

[0015] In the formula, C fis the primary side capacitance, L f is the primary side inductance, ω is the angular velocity, L p is the transmitting coil;

[0016] The secondary side circuit should meet the following resonance conditions:

[0017]

[0018] In the formula, C s is the secondary side capacitance, L s For the receiving coil.

[0019] Furthermore, the specific manner of multi-phase staggered parallel connection between the multiple DC / DC converter modules is that the input ends of the multiple DC / DC converter modules are connected in parallel to the output end of the rectifier module to receive a unified DC power input.

[0020] Furthermore, in the SiC full-bridge module of the inverter module and the SiC rectifier bridge of the rectifier module, wide bandgap devices made of SiC material are selected as high-frequency switches.

[0021] Furthermore, the decoupling capacitors of the rectifier module and the inverter module are lead lanthanum zirconium titanium oxide (PLZT) capacitors, and the decoupling capacitors are closely placed on the DC bus of each SiC wide bandgap device and close to the pins of the SiC wide bandgap device; in addition, the decoupling capacitors are staggered on the PCB bus.

[0022] Furthermore, the specific layout of the decoupling capacitor is as follows: the PCB bus adopts V dc+ and V dc- In a design where copper layers are tightly stacked, the decoupling capacitors are placed in the middle area between the two layers of copper conductors.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The transmitting coil and receiving coil of this system adopt the "DD" coil topology structure, which can generate parallel magnetic flux components and has a high offset tolerance. In the direction of the car's travel, by reasonably changing the spacing of the energy transmitting coil and the size of the energy receiving coil, the change amplitude of the overall mutual inductance value of the energy transmitting end during the movement of the car can be effectively reduced, thereby making the output power of the system more stable, and ultimately achieving the purpose of improving the power transmission efficiency and alignment tolerance of the system. In addition, the double D-type coil has the characteristics of bidirectional symmetry in structure, so that the magnetic field can effectively maintain a relatively consistent state at different positions. Even in the presence of a certain degree of metal shielding, the magnetic field will not be significantly weakened due to shielding in a single direction, so the shielding effect caused by the shielding of the chassis is relatively small for its transmission efficiency, and can even be ignored.

[0025] The system has multiple DC / DC converter modules, and multiple DC / DC converter modules are multi-phase interleaved and connected in parallel, thereby increasing the switching frequency, optimizing the power distribution, and reducing the component temperature. It also reduces the system volume and achieves the best balance between power density and thermal management.

[0026] Furthermore, the present invention selects wide bandgap devices of SiC material as high-frequency switches in both the inverter module and the rectifier module, so as to use small passive components, including inductors, capacitors and smaller heat sinks, thereby making the overall system more compact and meeting the needs of high power transmission. At the same time, a decoupling capacitor is set, and a lead lanthanum zirconium titanium oxide (PLZT) capacitor is selected as a decoupling capacitor. The decoupling capacitor is placed closely on the DC bus of each SiC wide bandgap device and close to the pins of the SiC wide bandgap device. By shortening the distance between the capacitor and the power module, the parasitic inductance in the switch loop can be effectively reduced, thereby reducing voltage overshoot and switching noise. In addition, the decoupling capacitors are staggered on the PCB bus. This staggered arrangement makes the current distribution more symmetrical, which can further reduce the inductance and improve the electrical balance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a block diagram of the architecture principle of the present invention;

[0028] Figure 2 is a circuit diagram of a power supply architecture of the present invention;

[0029] Figure 3 Schematic diagram of the transmitting coil;

[0030] Figure 4 Schematic diagram of the receiving end coil;

[0031] Figure 5 It is a schematic diagram of the LCC-S compensation topology structure of the present invention. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] like Figure 1 , 2 As shown, a high-power dynamic wireless charging system described in this embodiment includes a DC input terminal, an inverter module, a transmitting coil module, a receiving coil module, a rectifier module, a DC / DC converter module and a DC output terminal.

[0034] The voltage of the DC input terminal of the whole system is 800V. There are two ways to supply the voltage of the DC input terminal: one is the DC power output after rectification from the AC power grid; the other is the DC power directly taken from the local DC power grid. After the system processing and conversion, the final voltage of the DC output terminal is 300-400V, which can meet the operating requirements for charging light batteries.

[0035] The inverter module includes two sets of SiC full-bridge modules, drive circuits, cooling systems, and decoupling capacitors. The module is responsible for converting the 800V DC input voltage into high-frequency AC power to power the transmitting coil module. Power transmission is controlled by adjusting the phase and duty cycle of the AC output.

[0036] The transmitting coil module includes an LCC resonant network, a transmitting coil and related tuning capacitors. The transmitting coil transmits power to the receiving coil wirelessly. The LCC resonant network is used to keep the main coil current constant, thereby achieving stable wireless energy transmission.

[0037] The receiving coil module consists of a receiving coil and a series resonant network at the bottom of the vehicle. This module receives the AC power from the transmitting coil and transmits it to the rectifier module, which then supplies it to the vehicle battery.

[0038] like Figure 3 , 4 As shown in the figure, both the transmitting coil and the receiving coil adopt the "DD" coil topology, which consists of two adjacent D-shaped coils to form a larger planar magnetic field area. In the double D topology, multiple Litz wires are cleverly arranged between the two loops of the double D coil, so that better inductance effect and current balance between the wires can be achieved.

[0039] The double D-type coil is a bipolar coil that can generate parallel magnetic flux components and has a high tolerance for offset. Although the coil has a coupling zero point in the direction of the connection between the two poles of the coil, it does not affect its energy transmission capability when aligned. At the same time, in the direction of the car's travel, by reasonably changing the spacing of the energy transmitting coil and the size of the energy receiving coil, the change in the overall mutual inductance value of the energy transmitting end during the movement of the car can be effectively reduced, thereby making the system's output power more stable, and ultimately achieving the purpose of improving the system's power transmission efficiency and alignment tolerance.

[0040] The double D-type coil has a bidirectional symmetry in structure, which enables the magnetic field to effectively maintain a relatively consistent state at different positions. Even in the presence of a certain degree of metal shielding, the magnetic field will not be significantly weakened due to shielding in a single direction, so the shielding effect caused by the chassis shielding is relatively small and even negligible for its transmission efficiency.

[0041] In the dynamic wireless power transmission system, the determination of the mutual inductance coefficient M is very important. It directly affects the transmission efficiency, compensation network design and the stability of system power transmission. The formula is as follows:

[0042]

[0043] Where P is the transmission power, I pri is the primary coil current, I sec is the secondary coil current, ω0 is the angular velocity.

[0044] LCC resonant network and series resonant network have been widely used in WPT systems and can be applied to both the transmitting end and the receiving end. The transmitting coil and the receiving coil of the present invention constitute an LCC-S compensation network, such as Figure 5 As shown in the figure, the LCC-S compensation network provides a constant current source at the transmitting end, ensuring that the current of the transmitting coil will not fluctuate significantly due to changes in the load and coupling coefficient when the vehicle is moving. The compensation network can effectively balance the reactive power in the system, ensuring that the power transmission between the transmitting coil and the receiving coil is mainly active power, thereby reducing the loss of reactive power. At the same time, the LCC-S compensation topology can maintain a high transmission efficiency under different transmission distances and coupling coefficient changes. LCC compensation provides a stable magnetic field distribution at the transmitting end, and S compensation stabilizes the voltage at the receiving end, so that the system can still maintain good performance when the vehicle position is offset.

[0045] The primary side uses LCC tuning, which makes the primary side coil show the characteristics of a constant current source in the resonant state, that is, the coil current will not be affected by load changes and coupling coefficient changes. This constant coupler current behavior of LCC tuning is quite advantageous for dynamic wireless power transmission DWPT applications. Because in this tuning mode, even if there is no load (such as a vehicle), the coil can still be energized, thereby ensuring that when the vehicle is connected to the system, it can obtain the maximum energy from the system. However, this tuning method also has certain disadvantages. If the power demand at the output end is reduced (for example, the battery management system is disconnected), the LCC tuning on the secondary side may quickly cause the capacitor at the output of the rectifier to overcharge, thereby causing overvoltage faults in the rectifier module and the DC / DC converter module.

[0046] In contrast, the series tuning method exhibits voltage source-like behavior at resonance. When using series tuning, the output voltage of the rectifier module is limited to a value range that is far lower than the 1200V SiC semiconductor and the rated voltage of the DC capacitor. Therefore, after comprehensive consideration, series tuning was selected on the secondary side.

[0047] In order to achieve decoupling of the output voltage and the load, the primary side circuit should meet the following resonance conditions:

[0048]

[0049] In the formula, C f is the primary side capacitance, L f is the primary side inductance, ω is the angular velocity, L p is the transmitting coil;

[0050] The secondary side circuit should meet the following resonance conditions:

[0051]

[0052] In the formula, C s is the secondary side capacitance, L s is the receiving coil;

[0053] LCC-S compensation network output voltage and input voltage U s The relationship is as follows:

[0054]

[0055] LCC-S compensation network output power P out It is expressed as:

[0056]

[0057] In the formula, R L is the load resistance.

[0058] In order to explore the current stress of the LCC-S compensation network and design appropriate compensation components, the line impedance is equivalent. In the resonant circuit, the impedance mainly comes from the inductor component. Assuming L f , L p and L s The equivalent impedances are R1, R2 and R3 respectively, so:

[0059]

[0060] Where i1, i2 and i3 are the currents flowing through R1, R2 and R3 respectively, and L1 is the resonant inductor.

[0061] LCC-S compensation network equivalent impedance Z in for:

[0062]

[0063] The rectifier module includes a four-phase SiC rectifier bridge, a cooling system and a decoupling capacitor. It converts the AC power transmitted by the receiving coil into DC power and provides input voltage for the DC / DC converter module.

[0064] In order to achieve a lightweight and compact design, wide bandgap devices made of SiC materials are selected as high-frequency switches in the SiC full-bridge module of the inverter module and the SiC rectifier bridge of the rectifier module, so that small passive components, including inductors, capacitors and smaller heat sinks can be used, making the overall system more compact while meeting the needs of high power transmission.

[0065] Wide bandgap devices use SiC materials. Compared with other wide bandgap semiconductor materials, the manufacturing process of SiC devices is more mature. Relatively speaking, the manufacturing process of GaN and ZnO devices is still developing in the high-power field, and the cost and supply chain maturity are not as good as SiC. In addition, SiC devices can withstand higher breakdown voltages and are often used in voltage applications above 600V or even up to several thousand volts, while GaN and ZnO have lower breakdown voltages and are usually suitable for low to medium voltage (below 600V) applications. DWPT systems usually require high voltages of hundreds to kilovolts, so SiC is more suitable for such high-power scenarios.

[0066] In order to deal with the current ripple and voltage overshoot problems caused by high-frequency switching operations, decoupling capacitors are set in the inverter module and rectifier module. In the system, the self-resonant frequency is the critical point where the capacitor exhibits inductive behavior in the frequency response. When the operating frequency is close to or higher than the self-resonant frequency of the capacitor, the impedance of the capacitor will increase significantly, and it will not be able to effectively decouple high-frequency noise. Therefore, it is necessary to select a suitable decoupling capacitor to ensure that the capacitor effectively filters out high-frequency interference within the operating frequency band and maintains the stability and efficiency of power transmission. The equivalent series inductance is a parasitic inductance in the capacitor, which affects its performance at high frequencies. Higher ESL will reduce the high-frequency filtering ability of the capacitor, making it difficult for the capacitor to decouple high-frequency ripple; in the DWPT system, higher ripple currents may be generated during power transmission, and these currents will generate heat when passing through the capacitor, affecting the life and stability of the capacitor. Capacitors with high ripple current tolerance can handle larger ripple currents without overheating or failure, thereby improving the reliability and stability of the system. This is particularly important in high-power DWPT applications.

[0067] Therefore, according to the above three electrical characteristics, lead lanthanum zirconium titanium oxide (PLZT) capacitors are selected as decoupling capacitors. In order to reduce the electrical impedance between the capacitor and the power module, the decoupling capacitors are placed closely on the DC bus bar of each SiC wide bandgap device, as close to the pins of the SiC wide bandgap device as possible. By shortening the distance between the capacitor and the power module, the parasitic inductance in the switching loop can be effectively reduced, thereby reducing voltage overshoot and switching noise. In addition, the decoupling capacitors are staggered on the PCB busbar. The PCB busbar adopts the V dc+ and V dc- The copper layers are stacked closely together, and the decoupling capacitors are placed in the middle area between the two layers of copper conductors. This staggered arrangement makes the current distribution more symmetrical, which can further reduce the inductance and improve the electrical balance of the system.

[0068] The DC / DC converter module includes a four-phase step-down circuit, filter, power module and cooling system, which further reduces the rectified DC voltage to 300-400V to charge the vehicle battery and ensure that the charging voltage meets the battery requirements.

[0069] The system has multiple DC / DC converter modules, and the multiple DC / DC converter modules are multi-phase interleaved and connected in parallel. That is, the input ends of the multiple DC / DC converter modules are connected in parallel to the output end of the rectifier module to receive a unified DC power input. Driven by the controller, the multiple DC / DC converter modules work in an interleaved manner with a phase difference of 90 degrees.

[0070] Through multi-phase interleaved parallel technology, the system distributes the total power to multiple phase modules, and each module only bears part of the power, thereby reducing the heat load of a single module. Moreover, since the interleaved parallel technology increases the equivalent switching frequency of the system, the dynamic response speed of the system is also improved, which is particularly important in scenarios with rapid load changes, helping the system to quickly respond to load fluctuations and maintain stable output. Interleaved parallel technology achieves higher total power output by connecting multiple phase modules in parallel. At the same time, the power density of the entire system is improved by reducing current ripple and power loss of a single module. This multi-phase design not only improves system efficiency, but also reduces system size, achieving the best balance between power density and thermal management.

[0071] Working principle: The DC input terminal first obtains a DC input voltage of 800V from a DC power source (such as DC power after grid rectification or a local DC grid). This DC power is converted into high-frequency AC power by the inverter module, and the high-frequency AC power is transmitted to the LCC resonant network of the transmitting coil module to convert electrical energy into magnetic field energy. When the part of the vehicle with the receiving coil moves above the transmitting coil, the alternating magnetic field generated by the transmitting coil induces an electromotive force in the receiving coil, and the energy is transferred to the receiving end of the vehicle in a non-contact manner. The received high-frequency AC power is converted into DC power by the rectifier module, and then the rectified DC voltage is reduced to 300-400V by the DC / DC converter module, and the vehicle battery is charged through the DC output terminal.

Claims

1. A high-power dynamic wireless charging system, characterized in that: It includes a DC input terminal, an inverter module, a transmitting coil module, a receiving coil module, a rectifier module, a DC / DC converter module and a DC output terminal; The voltage of the DC input terminal is 800V, and the voltage of the DC output terminal is 300-400V; The inverter module includes two sets of SiC full-bridge modules, a drive circuit, a cooling system and a decoupling capacitor. The inverter module is responsible for converting the 800V DC input voltage into high-frequency AC power to power the transmitting coil module. The transmitting coil module includes an LCC resonant network, a transmitting coil and related tuning capacitors. The transmitting coil transmits power to the receiving coil wirelessly. The LCC resonant network is used to keep the main coil current constant, thereby achieving stable wireless energy transmission. The receiving coil module comprises a receiving coil and a series resonant network at the bottom of the vehicle, the receiving coil module receives the alternating current from the transmitting coil and transmits it to the rectifier module, which is subsequently provided to the vehicle battery; The transmitting coil and the receiving coil both adopt a "DD" coil topology structure, which is composed of two adjacent D-shaped coils to form a larger planar magnetic field area; The rectifier module includes a four-phase SiC rectifier bridge, a cooling system and a decoupling capacitor; it converts the AC power transmitted by the receiving coil into DC power and provides input voltage for the DC / DC converter module; The DC / DC converter module includes a four-phase step-down circuit, a filter, a power module and a cooling system, which further reduces the rectified DC voltage to 300-400V; multiple DC / DC converter modules are provided, and multiple DC / DC converter modules are multi-phase staggered and paralleled.

2. A high-power dynamic wireless charging system according to claim 1, characterized in that: The voltage supply of the DC input terminal can be provided in two ways: one is the DC power outputted from the AC power grid after rectification; the other is the DC power directly taken from the local DC power grid.

3. A high-power dynamic wireless charging system according to claim 1, characterized in that: The mutual inductance coefficient of the transmitting coil and the receiving coil is: Where P is the transmission power, I pri is the primary coil current, I sec is the secondary coil current, ω0 is the angular velocity.

4. A high-power dynamic wireless charging system according to claim 3, characterized in that: The transmitting coil and the receiving coil constitute an LCC-S compensation network. The primary side adopts LCC tuning and the secondary side adopts series tuning. To achieve decoupling of the output voltage and the load, the primary side circuit should meet the following resonance conditions: In the formula, C f is the primary side capacitance, L f is the primary side inductance, ω is the angular velocity, L p is the transmitting coil; The secondary side circuit should meet the following resonance conditions: In the formula, C s is the secondary side capacitance, L s For the receiving coil.

5. A high-power dynamic wireless charging system according to claim 1, characterized in that: The specific manner of multi-phase staggered parallel connection between the multiple DC / DC converter modules is that the input ends of the multiple DC / DC converter modules are connected in parallel to the output end of the rectifier module to receive a unified DC power input.

6. A high-power dynamic wireless charging system according to claim 1, characterized in that: In the SiC full-bridge module of the inverter module and the SiC rectifier bridge of the rectifier module, wide bandgap devices made of SiC material are selected as high-frequency switches.

7. A high-power dynamic wireless charging system according to claim 6, characterized in that: The decoupling capacitors of the rectifier module and the inverter module are lead lanthanum zirconium titanium oxide (PLZT) capacitors, and the decoupling capacitors are closely placed on the DC bus of each SiC wide bandgap device and close to the pins of the SiC wide bandgap device; in addition, the decoupling capacitors are staggered on the PCB bus.

8. A high-power dynamic wireless charging system according to claim 7, characterized in that: The specific layout of the decoupling capacitor is as follows: the PCB busbar adopts V dc+ and V dc- In a design where copper layers are tightly stacked, the decoupling capacitors are placed in the middle area between the two layers of copper conductors.

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