Wireless electric energy transmission system with repeating coil

Abstract

The invention discloses a wireless electric energy transmission system with a repeating coil, and belongs to the technical field of wireless electric energy transmission. A relay coil is added, and the relay coil is composed of a power frequency alternating current power supply input part, a rectification part, an inversion part, a transmitting part, a relay part, a receiving part, a high-frequency rectification part and a load part. A coil is wound by a plurality of strands of enameled wires, parameters are designed according to a 85kHz frequency band, and a specific resonant capacitor is matched. An SQL50A rectifier module is adopted at the transmitting end, IRFP32N50K serves as an inverter switch tube, an MDQ60A rectifier module is adopted at the load end, and a constant-voltage control module is designed at the load end. Through system construction, TMS320F28335 is adopted as a control core, and a corresponding peripheral circuit, a driving circuit and a sampling module are matched. In a low-power verification test, the alternating current input of the system is 24V, the distance between the three-stage coils is 100mm, an expected waveform is output through inversion, the voltage after rectification conforms to the design, 40V constant voltage output of a load end is achieved by controlling the conduction ratio of a full-control device to be 0.463, and the feasibility and effectiveness of the system are verified.

Description

Technical Field

[0001] The invention relates to the technical field of wireless power transmission, and in particular to a wireless power transmission system with a relay coil. Background Art

[0002] Under the background of the global promotion of sustainable development, the new energy vehicle industry has flourished and become an important development direction of the automotive industry. Many countries have introduced policies to encourage the research and development, production and consumption of new energy vehicles. China has also put electric vehicles on the agenda to replace traditional fuel vehicles, which has led to a rapid expansion of the electric vehicle market. With this comes a huge demand for electric vehicle charging facilities, and the charging pile market has ushered in unprecedented development opportunities.

[0003] At present, there are two main charging methods for electric vehicles: wired plug-in charging and wireless charging. Wired plug-in charging is the most widely used charging method, but it has many disadvantages. On the one hand, frequent plugging and unplugging of charging cables will cause mechanical wear, which not only reduces the service life of the charging cable, but may also cause safety hazards; on the other hand, this charging method requires a larger charging station site, has high requirements for site space, and is not convenient to operate, making it difficult to meet people's needs for smart life.

[0004] As an emerging charging method, wireless charging technology has the advantages of avoiding mechanical wear, small footprint, and convenient charging, and has received widespread attention. In wireless charging technology, magnetic coupling resonance wireless energy transmission technology has become a research hotspot in the field of wireless charging of electric vehicles due to its high efficiency, low loss, and high safety. This technology sets a transmitting coil and a receiving coil on the power side and the load side respectively, and uses matching capacitors to make the two reach the same natural frequency. When the excitation power frequency is consistent with the system natural frequency, strong magnetic coupling resonance occurs, thereby achieving efficient wireless energy transmission.

[0005] However, the existing magnetically coupled resonant wireless energy transmission system still faces some challenges in practical applications. In terms of transmission efficiency, when the distance between the transmitting coil and the receiving coil is far, the mutual inductance value will decrease, resulting in reduced transmission efficiency, which cannot meet the charging needs of electric vehicles in different usage scenarios. In terms of transmission distance, the traditional two-pole magnetically coupled wireless energy transmission method has obvious limitations, making it difficult to achieve efficient energy transmission over long distances. In addition, when the existing system responds to load changes, the output voltage stability is poor, and it is impossible to ensure that the load end always obtains a stable charging voltage, which affects the charging effect and equipment life.

[0006] In summary, during the development of current electric vehicle charging technologies, the deficiencies of traditional wired charging methods and the limitations of existing wireless charging technologies urgently require a more efficient, stable, and adaptable wireless power transmission system to meet the rapid development needs of the electric vehicle industry, which also provides an opportunity and direction for the research of this invention. Summary of the Invention

[0007] The object of the present invention is to provide a wireless power transmission system with a relay coil to improve the efficiency and distance of wireless power transmission, while achieving constant voltage charging at the load end and enhancing the stability and practicality of the system.

[0008] To achieve the above object, the present invention provides a wireless power transmission system with a relay coil, including a power frequency AC power input module, a power frequency rectification module, a high-frequency inversion module, a wireless energy transmitting coil, a relay coil, an energy receiving coil, a high-frequency rectification module, and a load part; the wireless energy transmitting coil, the relay coil, and the energy receiving coil are respectively combined with resonant capacitors to form resonators, and the relay coil is arranged between the wireless energy transmitting coil and the energy receiving coil.

[0009] Preferably, the design parameters of each coil are determined according to the 85 kHz frequency band (81.39k - 90 kHz), and the coil wire is made of stranded multi-strand enameled wire to reduce the influence of the skin effect.

[0010] Preferably, the number of turns of the spiral coil is 8, the coil radius is 0.2 m, and the calculated resonant capacitance value is 4.31559×10 -8 F, and the actually used capacitor is a DTR5000K0.047 model capacitor with a capacitance value of 47 nF.

[0011] Preferably, the transmitting end frequency conversion circuit includes a three-phase full-bridge rectification module, a high-frequency inversion module, and an RCD absorption circuit; the three-phase full-bridge rectification module is of the SQL50A model, the high-frequency inversion module uses an N-channel MOSFET of the IRFP32N50K model as the power switching tube, and the absorption resistance of the RCD absorption circuit is 200 Ω and the absorption capacitance is 2200 pF.

[0012] Preferably, the load end circuit includes a high-frequency rectification module and a constant voltage control module; the high-frequency rectification module uses an MDQ60A single-phase rectification module, and the constant voltage control module uses an N-channel MOSFET of the IRFP32N50K model as a fully controlled device to achieve constant voltage charging on the load side by adjusting the conduction ratio of the fully controlled device.

[0013] Preferably, the wireless energy transmitting coil, the relay coil, and the energy receiving coil all adopt an RLC series resonance network. When all the resonators are in resonance, the system is in an efficient transmission state. At this time, the resonance frequencies of the coils satisfy ω = 1 / √(L1C1) = 1 / √(L2C2) = 1 / √(L3C3), where L1, L2, and L3 are the inductance values of the transmitting coil, the relay coil, and the receiving coil respectively, and C1, C2, and C3 are the resonance capacitance values matching them.

[0014] Preferably, it further includes a signal sampling module. The signal sampling module is used to collect the current signals in the transmitting coil, the relay coil, and the receiving coil. This module includes a Hall closed-loop current sensor HA2020 - 100A, an AD7658 A / D conversion chip, and a signal conditioning circuit composed of a TL084 operational amplifier.

[0015] Preferably, the system is controlled by a digital signal processor (DSP). The DSP selects the 32-bit floating-point digital signal processor TMS320F28335 of Texas Instruments, which is responsible for controlling the AC voltage, current value, and resonance frequency on the high-frequency side of the wireless energy transmission.

[0016] Preferably, using the near-field theory, by artificially creating an LC resonance alternating magnetic field emission source, wireless energy transmission is realized, and the electric field is suppressed within the capacitor, with less electromagnetic wave radiation outward.

[0017] Preferably, the driving circuit of the system includes a power amplification device IR2110 and a fast optocoupler 6N137. By reasonably selecting the bootstrap capacitor and the bootstrap diode, effective driving and electrical isolation of the MOSFET are achieved. Among them, the bootstrap capacitor is 47uF, and the bootstrap diode is FR107.

[0018] Therefore, the wireless power transmission system with a relay coil adopting the above structure in the present invention has the following beneficial effects:

[0019] (1) By adding a relay coil in the present invention, the distance between adjacent coils is shortened, the mutual inductance value is increased, and the transmission efficiency and transmission distance of the wireless power transmission system are improved. Through simulation analysis, after adding the relay coil, the maximum transmission efficiency of the system is above 0.8, and the change is more gentle, showing significant advantages compared with the traditional two-pole coil structure.

[0020] (2) The present invention adopts reasonable coil design and parameter selection, including coil wire, number of turns, radius, and resonance capacitance, etc., ensuring the stable operation of the system within the 85kHz frequency band and improving the efficiency and stability of energy transmission.

[0021] (3) The present invention designs a constant voltage control module, which realizes constant voltage charging at the load end, avoids the influence of power supply voltage and load changes on the load side voltage, and improves the practicability and safety of the system.

[0022] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of a wireless power transmission system with a relay coil according to the present invention;

[0024] Figure 2 It is a schematic structural diagram of the constant voltage control module of a wireless power transmission system with a relay coil according to the present invention;

[0025] Figure 3 It is a schematic structural diagram of the load end circuit of a wireless power transmission system with a relay coil according to the present invention;

[0026] Figure 4 It is a schematic structural diagram of the RCD absorption circuit of a wireless power transmission system with a relay coil according to the present invention;

[0027] Figure 5 It is a schematic structural diagram of the transmitter side frequency conversion circuit of a wireless power transmission system with a relay coil according to the present invention. Detailed Embodiments

[0028] The technical solution of the present invention will be further described below with reference to the drawings and embodiments.

[0029] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left", "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0030] Embodiment

[0031] As Figures 1-5As shown in the figure, the present invention provides a wireless power transmission system with a relay coil, including a power frequency AC power input module, a power frequency rectification module, a high-frequency inversion module, a wireless energy transmitting coil, a relay coil, an energy receiving coil, a high-frequency rectification module, and a load part; the wireless energy transmitting coil, the relay coil, and the energy receiving coil are respectively combined with resonant capacitors to form resonators, and the relay coil is arranged between the wireless energy transmitting coil and the energy receiving coil.

[0032] Select the 32-bit floating-point digital signal processor TMS320F28335 of Texas Instruments as the control core of the entire wireless power transmission system. It is responsible for precisely controlling the AC voltage, current value, and resonant frequency on the high-frequency side of wireless energy transmission to ensure the stable operation of the system.

[0033] Power supply circuit: The GPIO port of TMS320F28335 requires 3.3V power supply, and the core requires 1.9V power supply. Therefore, a special power supply circuit is designed to stably output these two voltages through specific power conversion chips and circuit layouts, providing stable power support for the normal operation of the DSP.

[0034] Clock oscillation circuit: A 30M active external crystal oscillator is used to provide a clock signal for the DSP. The clock signal generated by this crystal oscillator is multiplied by the PLL, and the internal clock of DSP28335 can reach up to 150MHz at most. Then, through configuration of the DSP for frequency division, each peripheral device can obtain an appropriate operating frequency, ensuring both the operation speed and accuracy while taking into account energy consumption.

[0035] Reset circuit: The reset circuit is designed based on the principle of capacitor charge and discharge. At the moment when DSP28335 is powered on, the capacitor is equivalent to a short circuit, and the reset pin is grounded to achieve reset; after the capacitor is fully charged, it is open, and the reset pin is connected to a high level through a pull-up resistor. When the button is pressed, the reset pin is grounded for reset, and after releasing the button, it returns to the pull-up state, thus ensuring the stability and reliability of the DSP during startup and operation.

[0036] Driver circuit: The main function of the driver circuit is to provide a driving signal with sufficient power for the MOSFET and achieve electrical isolation between the signal side and the power side.

[0037] Power amplification and electrical isolation: The power amplification device IR2110 and the fast optocoupler 6N137 are adopted. The PWM signal generated by the DSP has a small power. After being amplified by IR2110, it can effectively drive the MOSFET. The fast optocoupler 6N137 establishes electrical isolation between the power side and the signal side, improves the anti-interference ability of the system, and ensures the safe and stable operation of the system.

[0038] Bootstrap capacitor and bootstrap diode selection: Reasonable selection of the bootstrap capacitor and bootstrap diode is the key to the normal operation of the drive circuit. The bootstrap capacitor needs to provide sufficient charge to maintain the stability of the gate voltage of the high-side device. According to the formula calculation, when the switching frequency is about 100K, a 47uF bootstrap capacitor is selected. The bootstrap diode uses a fast-recovery diode FR107, which has the characteristic of fast recovery speed and can meet the requirements of rapid switching of the circuit.

[0039] Sampling module: The sampling module is used to collect the current signal in the system and provide data support for control and monitoring.

[0040] Current signal acquisition: Use the Hall closed-loop current sensor HA2020-100A to collect the current signals in the transmitting, relay, and receiving coils. This sensor can operate in the frequency band of 0Hz - 150kHz, with a current rise rate greater than 50A / s and a response time less than 1us, and can quickly and accurately sense current changes. Its rated current is 100A, the maximum measurement range is 0 - ±150A, the internal turns ratio is 1:1000, and the rated output current is 100mA, which can meet the measurement requirements of this system.

[0041] A / D conversion: The collected analog current signal needs to be converted into a digital signal before it can be processed by the DSP. Therefore, the AD7658 chip is used for A / D conversion. It is a high-precision 14-bit analog-to-digital conversion chip with 6 conversion channels, and 4 channels are used in this system. It only takes 3.8us for all conversion channels to complete the conversion, which is much less than the sampling period, ensuring the real-time and accuracy of data acquisition.

[0042] Signal conditioning: The TL084 operational amplifier is used for signal conditioning. The collected voltage and current signals are AC signals. TL084 is a commonly used four-input operational amplifier, which has the characteristics of high conversion rate, low input offset and bias current, and low offset voltage temperature coefficient. And its common-mode input resistance is as high as 1012Ω, and the common-mode input capacitance is 6.25pF, which can meet the requirements of the operational amplifier input resistance and capacitance for voltage acquisition, and effectively filter, isolate, and amplify the signal.

[0043] Under the laboratory environment, a low-power verification test is carried out. The AC input of the system is set to 24V, and the distances between the three-stage coils (transmitting coil, relay coil, receiving coil) are all set to 100mm to simulate a working condition in the actual application scenario.

[0044] High-frequency inverter waveform: The full-controlled device mosfet of the full-bridge high-frequency inverter uses square-wave drive, and the duty cycle is set to 50%. Under this drive condition, the inverter output voltage is a square wave. When this square-wave signal is input into the RLC series resonance circuit, the current waveform is a sine wave with the same frequency as the drive signal, which conforms to the characteristics of the RLC series resonance circuit, indicating that the inverter circuit and the resonance circuit are working normally.

[0045] Voltage after rectification: After passing through the high-frequency rectification circuit of wireless energy transmission without adding filter capacitors, the rectified voltage can be regarded as an alternating DC voltage with a waveform of |sin(ωt)|. Through measurement, its voltage amplitude is 34V and the effective value is 24V, which provides an input basis for subsequent constant voltage control.

[0046] Verification of constant voltage output: Through theoretical calculation, it is obtained that when the conduction ratio of the fully controlled device is 0.463, a constant voltage output of 40V can be achieved at the load end. In the experiment, by collecting the input voltage of the constant voltage module, comparing the relationship with the set output voltage through the processor, and adjusting the duty cycle of the fully controlled device, a stable output of 40V constant voltage at the load end is finally successfully achieved. This result verifies the feasibility and effectiveness of the system in the constant voltage output function, indicating that the entire wireless power transmission system can work stably according to the design requirements, providing a strong experimental basis for practical applications.

[0047] Therefore, the present invention adopts the above-mentioned wireless power transmission system with a relay coil, adding a relay coil, which consists of a power frequency AC power input, rectification, inversion, transmission, relay, reception, high-frequency rectification, and load parts. Multistrand enameled wire is selected to wind the coil, and the parameters are designed according to the 85kHz frequency band, and specific resonant capacitors are matched. The SQL50A rectification module and IRFP32N50K are used as the inversion switching tubes at the transmitting end, and the MDQ60A rectification module and a constant voltage control module are designed at the load end. After the system is built, TMS320F28335 is used as the control core, with corresponding peripheral circuits, drive circuits, and sampling modules. In the small-power verification test, the AC input of the system is 24V, the distance between the three-stage coils is 100mm, the expected waveform of the inversion output is achieved, the voltage after rectification meets the design, and a constant voltage output of 40V is achieved at the load end by controlling the conduction ratio of the fully controlled device to 0.463, verifying the feasibility and effectiveness of the system.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A wireless power transmission system with a relay coil, characterized in that: It includes an industrial frequency AC power input module, an industrial frequency rectification module, a high-frequency inverter module, a wireless energy transmitting coil, a relay coil, an energy receiving coil, a high-frequency rectification module and a load part; the wireless energy transmitting coil, the relay coil, the energy receiving coil and the resonant capacitor respectively form a resonant body, and the relay coil is arranged between the wireless energy transmitting coil and the energy receiving coil.

2. A wireless power transmission system with a relay coil according to claim 1, characterized in that: The design parameters of each level of coils are determined based on the 85kHz frequency band, which ranges from 81.39k to 90kHz. The coil conductors are made of multiple strands of enameled wire twisted together to reduce the impact of the skin effect.

3. A wireless power transmission system with a relay coil according to claim 1, characterized in that: The spiral coil has 8 turns and a coil radius of 0.2 m. The matching resonant capacitance value is calculated to be 4.31559×10 -8 F, the actual capacitance used is DTR5000K0.047 capacitor with a capacitance of 47nF.

4. A wireless power transmission system with a relay coil according to claim 1, characterized in that: The transmitter frequency conversion circuit includes a three-phase full-bridge rectifier module, a high-frequency inverter module and an RCD absorption circuit; the three-phase full-bridge rectifier module uses the SQL50A model, the high-frequency inverter module uses the IRFP32N50K model N-channel MOSFET as the power switch tube, and the absorption resistance of the RCD absorption circuit is 200Ω and the absorption capacitance is 2200pF.

5. A wireless power transmission system with a relay coil according to claim 1, characterized in that: The load-side circuit includes a high-frequency rectifier module and a constant voltage control module; the high-frequency rectifier module adopts the MDQ60A single-phase rectifier module, and the constant voltage control module adopts the IRFP32N50K model N-channel MOSFET as a fully controlled device, and realizes constant voltage charging on the load side by adjusting the conduction ratio of the fully controlled device.

6. A wireless power transmission system with a relay coil according to claim 1, characterized in that: The wireless energy transmitting coil, relay coil and energy receiving coil all use RLC series resonant networks. When the resonant bodies resonate, the system is in an efficient transmission state. At this time, the resonant frequency of each coil satisfies ω=1 / √(L1C1)=1 / √(L2C2)=1 / √(L3C3), where L1, L2, L3 are the inductance values ​​of the transmitting coil, relay coil and receiving coil respectively, and C1, C2, C3 are the resonant capacitance values ​​matching them respectively.

7. A wireless power transmission system with a relay coil according to claim 1, characterized in that: It also includes a signal sampling module, which is used to collect current signals in the transmitting coil, relay coil and receiving coil. The module contains a Hall closed-loop current sensor HA2020-100A, an AD7658A / D conversion chip and a signal conditioning circuit composed of a TL084 operational amplifier.

8. A wireless power transmission system with a relay coil according to claim 1, characterized in that: The system is controlled by a digital signal processor (DSP). The DSP uses a 32-bit floating-point digital signal processor TMS320F28335 from Texas Instruments, which is responsible for controlling the AC voltage, current value and resonant frequency on the high-frequency side of wireless energy transmission.

9. A wireless power transmission system with a relay coil according to claim 1, characterized in that: By utilizing the near-field theory and artificially creating an LC resonant alternating magnetic field emission source, wireless energy transmission can be achieved. The electric field is suppressed within the capacitor, and the electromagnetic waves radiated outward are relatively small.

10. A wireless power transmission system with a relay coil according to claim 1, characterized in that: The driving circuit includes the power amplifier device IR2110 and the fast optocoupler 6N137. By properly selecting the bootstrap capacitor and bootstrap diode, effective driving and electrical isolation of the MOSFET can be achieved. The bootstrap capacitor is 47uF and the bootstrap diode is FR107.

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