Disclosure of Invention
The invention aims to provide a strong-coupling unmanned aerial vehicle wireless power transmission and magnetic shielding system, which can shield electromagnetic interference generated by electronic equipment and sensors in an unmanned aerial vehicle in the wireless power transmission process and supply electric energy with high efficiency under the offset condition.
It is another object of the present invention to provide a transmission and magnetic shielding method based on a strongly coupled unmanned aerial vehicle wireless power transmission and magnetic shielding system.
The first technical scheme adopted by the invention is based on a strong-coupling unmanned aerial vehicle wireless power transmission and magnetic shielding system, which is formed by sequentially connecting a high-frequency inversion network, a primary side resonance compensation network, a coupling mechanism, a secondary side resonance compensation network and a rectifying and filtering circuit, wherein the primary side resonance compensation network, the coupling mechanism and the secondary side resonance compensation network form an LCC-S compensation network.
The first aspect of the present invention is also characterized in that,
The high-frequency inverter network is a full-bridge inverter circuit consisting of a switching tube Q1, a switching tube Q2, a switching tube Q3 and a switching tube Q4, the input end of the full-bridge inverter circuit is connected with a direct-current power supply Uin, and the switching tube Q1 and the switching tube Q4 of the full-bridge inverter circuit are connected with the primary resonance compensation network.
The primary resonance compensation network comprises an inductor LR, one end of the inductor LR is connected with a switch tube Q1, the other end of the inductor LR is connected with one end of a capacitor Cp, the other end of the capacitor Cp is connected with an inductor Lp and then is connected with a switch tube Q4 of the primary resonance compensation network, one end of a capacitor CR is further connected between the inductor LR and the capacitor Cp, the other end of the capacitor CR is connected with the switch tube Q4, the inductor Lp and the inductor Ls form the coupling mechanism, the inductor Lp is a transmitting coil inductor, the inductor Ls is a receiving coil inductor, and the inductor Ls of the coupling mechanism is connected with the secondary resonance compensation network.
The secondary side resonance compensation network comprises a capacitor Cs, one end of the capacitor Cs is connected with one end of the inductor Ls, the other end of the capacitor Cs is connected with the rectifying and filtering circuit, and the other end of the inductor Ls is connected with the rectifying and filtering circuit.
The rectifying and filtering circuit comprises a rectifying bridge formed by a diode D1, a diode D2, a diode D3 and a diode D4, wherein the diode D1 is connected with the diode D3 in series, the diode D2 and the diode D4 are connected in parallel with a capacitor Co after being connected in series, the diode D1 is connected with a capacitor Cs of the secondary side resonance compensation network, the diode D4 is connected with an inductor Ls of the coupling mechanism, and a capacitor Co is also connected with a load Ro.
The second technical scheme adopted by the invention is a method based on strong coupling unmanned aerial vehicle wireless power transmission and magnetic shielding, which comprises the following steps:
writing a KVL equation in columns to obtain;
ensuring that the system is in a resonance state needs to meet the following conditions:
Substituting equation (2) into equation (1), the corresponding current vector in the circuit is reduced to:
The output power is expressed as:
Uin inverts the output voltage, I1 is the invertion output current, IP is the primary resonance current, LR is the primary resonance inductance, CR is the primary parallel resonance capacitance, CP is the primary series resonance capacitance, LP is the primary coil self inductance, Rp is the primary coil parasitic resistance, LS is the secondary coil self inductance, RS is the secondary coil parasitic resistance, CS is the secondary series resonance capacitance, IS is the secondary resonance current, RL is the equivalent load, ω is the resonance angular frequency, M is the mutual inductance, j is the imaginary part representation, and P is the output power.
The second aspect of the present invention is also characterized in that,
The magnetic shielding structure design is that a magnetic field generated by eddy current loss on a shielding aluminum plate is expressed as:
Wherein H Aluminum (Al) is a reverse magnetic field generated by eddy currents in the coil;
h is the magnitude of the source magnetic field near the shielding aluminum plate:
L Aluminum (Al) is the equivalent inductance of the shielding aluminum plate;
An aluminum-ferrite composite shield composed of two types of materials is employed.
And (3) miniaturization design of a receiving end:
the expression of the output efficiency of the system is obtained as follows:
η is the system transmission efficiency;
The mutual inductance expression with the highest efficiency is:
Mmax is the highest efficiency mutual inductance value of the system;
The mutual inductance value under the optimal efficiency expression is obtained through the formula (7), the self-inductance value of the transmitting end coil is increased by utilizing ferrite under the condition that the mutual inductance value is kept unchanged, the self-inductance value of the receiving end coil is further reduced, the volume of the receiving end coil carried by the unmanned aerial vehicle can be reduced, and the transmitting coil and the receiving coil are combined with aluminum-ferrite to design to avoid external leakage and internal loss of a magnetic field to a great extent.
The aluminum-ferrite composite shielding structure has the beneficial effects that based on the strong-coupling unmanned aerial vehicle wireless power transmission and magnetic shielding system and method, the aluminum plate structure can shield electromagnetic radiation outside the system, and meanwhile, the ferrite structure can reduce the influence of eddy currents on the aluminum plate on the electrical parameters of the system. The problem of system output power and efficiency fluctuation caused by external metal interference is solved. The magnetic coupling resonant wireless power transmission mode adopts the LCC-S compensation topological structure, can improve the power transmission efficiency by optimizing the compensation network parameters, has good stability, is beneficial to realizing stable wireless power transmission, and is beneficial to reducing the energy loss. According to the wireless power transmission system, the transmitting coil is combined with ferrite in the shielding device, so that strong magnetic coupling is realized, meanwhile, the weight of a receiving end coil carried by the unmanned aerial vehicle can be reduced, and the navigation working time and the cruising mileage of the unmanned aerial vehicle are prolonged.
Detailed Description
The invention will be described in detail below with reference to the drawings and the detailed description.
The invention is based on a strong coupling unmanned aerial vehicle wireless power transmission and magnetic shielding system, and is formed by sequentially connecting a high-frequency inversion network, a primary side resonance compensation network, a coupling mechanism, a secondary side resonance compensation network and a rectification filter circuit, wherein the primary side resonance compensation network, the coupling mechanism and the secondary side resonance compensation network form an LCC-S compensation network.
The high-frequency inverter network is a full-bridge inverter circuit consisting of a switching tube Q1, a switching tube Q2, a switching tube Q3 and a switching tube Q4, the input end of the full-bridge inverter circuit is connected with a direct-current power supply Uin, and the switching tube Q1 and the switching tube Q4 of the full-bridge inverter circuit are connected with the primary resonance compensation network.
The primary resonance compensation network comprises an inductor LR, one end of the inductor LR is connected with a switch tube Q1, the other end of the inductor LR is connected with one end of a capacitor Cp, the other end of the capacitor Cp is connected with an inductor Lp and then is connected with a switch tube Q4 of the primary resonance compensation network, one end of a capacitor CR is further connected between the inductor LR and the capacitor Cp, the other end of the capacitor CR is connected with the switch tube Q4, the inductor Lp and the inductor Ls form the coupling mechanism, the inductor Lp is a transmitting coil inductor, the inductor Ls is a receiving coil inductor, and the inductor Ls of the coupling mechanism is connected with the secondary resonance compensation network.
The secondary side resonance compensation network comprises a capacitor Cs, one end of the capacitor Cs is connected with one end of the inductor Ls, the other end of the capacitor Cs is connected with the rectifying and filtering circuit, and the other end of the inductor Ls is connected with the rectifying and filtering circuit.
The rectifying and filtering circuit comprises a rectifying bridge formed by a diode D1, a diode D2, a diode D3 and a diode D4, wherein the diode D1 is connected with the diode D3 in series, the diode D2 and the diode D4 are connected in parallel with a capacitor Co after being connected in series, the diode D1 is connected with a capacitor Cs of the secondary side resonance compensation network, the diode D4 is connected with an inductor Ls of the coupling mechanism, and a capacitor Co is also connected with a load Ro.
Fig. 1 shows a topology structure diagram of a wireless power transmission system of the invention, which consists of a high-frequency inversion network, a primary side resonance compensation network, a coupling mechanism, a secondary side resonance compensation network and a rectifying and filtering circuit.
In fig. 1, Uin is a dc power supply, Q1, Q2, Q3, and Q4 are switching transistors required for a full-bridge inverter circuit, a primary side compensation network formed by Lr、Cr and Cp, and inductors Lp and Ls are a transmitting coil and a receiving coil respectively, and Cs forms a secondary side compensation circuit. The rectifier bridge and the Co form a rectifier filter circuit to realize stable direct current output.
The invention discloses a method based on strong coupling unmanned aerial vehicle wireless power transmission and magnetic shielding, which specifically comprises the following steps:
writing a KVL equation according to the column of figure 2;
ensuring that the system is in a resonance state needs to meet the following conditions:
Substituting equation (2) into equation (1), the corresponding current vector in the circuit is reduced to:
The output power is expressed as:
As shown in fig. 2: Uin inverts the output voltage, I1 is the invertion output current, IP is the primary resonance current, LR is the primary resonance inductance, CR is the primary parallel resonance capacitance, CP is the primary series resonance capacitance, LP is the primary coil self inductance, Rp is the primary coil parasitic resistance, LS is the secondary coil self inductance, RS is the secondary coil parasitic resistance, CS is the secondary series resonance capacitance, IS is the secondary resonance current, RL is the equivalent load, ω is the resonance angular frequency, M is the mutual inductance, j is the imaginary part representation, and P is the output power.
In the process of power transmission, gaps always exist between the receiving coils, and the occurrence of magnetic leakage is increased due to the existence of the gaps. The leakage of the magnetic field can not only affect the surrounding working electrical equipment, but also cause harm to staff. By adopting effective electromagnetic protection, on one hand, the damage of the electromagnetic field to the human body can be reduced, the safe and reliable operation of the equipment is ensured, and on the other hand, the electromagnetic shielding structure used for inhibiting and protecting the influence of the electromagnetic field not only reduces electromagnetic leakage, but also improves the transmission efficiency of the system.
The aluminum-ferrite magnetic shielding structure is adopted to reduce the leakage of an external magnetic field and reduce the internal eddy current loss. The magnetic permeability of ferromagnetic metal materials is large, and the existence of hysteresis effects complicates the magnetic field distribution. The material with high magnetic conductivity can form a good magnetic flux channel to form a good magnetization vector and an induction magnetic field, and the magnetic field around the wireless power supply pile is converged to reduce the leakage of the magnetic field. But the introduction of the magnetic strip increases the self inductance and mutual inductance of the coil. The self-inductance is increased, the compensation capacitance is unchanged, the resonance frequency point of the system moves leftwards, and the efficiency of wireless power transmission is affected. However, the increase of mutual inductance can compensate the influence caused by the left shift of the resonance frequency to a certain extent;
The presence of non-ferromagnetic metallic materials can cause an alternating electromagnetic field to be generated in the coil and induce eddy currents in the metallic surface, causing serious interference with the original magnetic field generated by the coil. The self-inductance of the coil becomes smaller, and at this time, if the compensation capacitance is not changed, the system resonant frequency shifts to the right, which also reduces the system transmission efficiency.
With reference to fig. 3 and 4, the magnetic shielding structure is designed in such a way that a magnetic field generated by eddy current loss on a shielding aluminum plate is expressed as:
Wherein H Aluminum (Al) is a reverse magnetic field generated by eddy currents in the coil;
h is the magnitude of the source magnetic field near the shielding aluminum plate:
l Aluminum (Al) is the equivalent inductance of the shielding aluminum plate.
As can be seen from the above formula, when the frequency of the system increases, a larger eddy current loss is formed inside the shielding aluminum plate, but the shielding effect is improved. The shielding aluminum plates are different in position in space, and the magnetic fields are different in size. The larger the magnetic field in the space, the higher the eddy current voltage on the shielding aluminum plate, and the generated eddy current magnetic field opposite to the original magnetic field increases. The eddy currents generated on the shielding aluminum plate can be equivalent to a plurality of small inductances. If a shielding aluminum plate is also added at the receiving end, the equivalent small inductance in the shielding aluminum plate will also inductively couple with the receiving end.
From the analysis, the addition of the ferromagnetic material and the non-ferromagnetic material can reduce the magnetic flux leakage of the receiving and transmitting coil in the transmission process to different degrees, and the output characteristic of the system is improved. But the introduction of both types of shielding materials will have different directional effects on the original system. Specifically, the two materials have different effects on self inductance and mutual inductance of the original coupler, the nonferromagnetic material has a good shielding effect, but can greatly change the electrical parameters of the system to reduce the output performance of the system, and the ferromagnetic material has a good magnetic gathering effect, can gather a magnetic field, reduce magnetic leakage, further reduce eddy current loss generated by an aluminum plate, and can improve the electrical parameters of the system. An aluminum-ferrite composite shield composed of two types of materials is therefore employed.
And (3) miniaturization design of a receiving end:
through simulation and calculation of a magnetic coupler model, the addition of ferrite at the transmitting end is determined to reduce the coil at the receiving end and maintain the mutual inductance value required by the optimal efficiency. The invention realizes miniaturization and light weight of the receiving end coil and is convenient for carrying and sailing of unmanned aerial vehicles.
The system output efficiency expression is derived from fig. 2 as:
η is the system transmission efficiency;
The mutual inductance expression with the highest efficiency is:
Mmax is the highest efficiency mutual inductance value of the system;
the mutual inductance value under the optimal efficiency expression is obtained through the formula (7), and under the condition that the mutual inductance value is kept unchanged, the ferrite is utilized to increase the self-inductance value of the transmitting end coil, so that the self-inductance value of the receiving end coil is reduced, and the volume of the receiving end coil carried by the unmanned aerial vehicle can be reduced.
Example 1
The invention is based on a strong coupling unmanned aerial vehicle wireless power transmission and magnetic shielding system, and is formed by sequentially connecting a high-frequency inversion network, a primary side resonance compensation network, a coupling mechanism, a secondary side resonance compensation network and a rectification filter circuit, wherein the primary side resonance compensation network, the coupling mechanism and the secondary side resonance compensation network form an LCC-S compensation network.
The high-frequency inverter network is a full-bridge inverter circuit consisting of a switching tube Q1, a switching tube Q2, a switching tube Q3 and a switching tube Q4, the input end of the full-bridge inverter circuit is connected with a direct-current power supply Uin, and the switching tube Q1 and the switching tube Q4 of the full-bridge inverter circuit are connected with the primary resonance compensation network.
Example 2
The invention is based on a strong coupling unmanned aerial vehicle wireless power transmission and magnetic shielding system, and is formed by sequentially connecting a high-frequency inversion network, a primary side resonance compensation network, a coupling mechanism, a secondary side resonance compensation network and a rectification filter circuit, wherein the primary side resonance compensation network, the coupling mechanism and the secondary side resonance compensation network form an LCC-S compensation network.
The high-frequency inverter network is a full-bridge inverter circuit consisting of a switching tube Q1, a switching tube Q2, a switching tube Q3 and a switching tube Q4, the input end of the full-bridge inverter circuit is connected with a direct-current power supply Uin, and the switching tube Q1 and the switching tube Q4 of the full-bridge inverter circuit are connected with the primary resonance compensation network.
Example 3
The invention discloses a method based on strong coupling unmanned aerial vehicle wireless power transmission and magnetic shielding, which specifically comprises the following steps:
writing a KVL equation according to the column of figure 2;
ensuring that the system is in a resonance state needs to meet the following conditions:
Substituting equation (2) into equation (1), the corresponding current vector in the circuit is reduced to:
The output power is expressed as:
As shown in fig. 2: Uin inverts the output voltage, I1 is the invertion output current, IP is the primary resonance current, LR is the primary resonance inductance, CR is the primary parallel resonance capacitance, CP is the primary series resonance capacitance, LP is the primary coil self inductance, Rp is the primary coil parasitic resistance, LS is the secondary coil self inductance, RS is the secondary coil parasitic resistance, CS is the secondary series resonance capacitance, IS is the secondary resonance current, RL is the equivalent load, ω is the resonance angular frequency, M is the mutual inductance, j is the imaginary part representation, and P is the output power.
In the process of power transmission, gaps always exist between the receiving coils, and the occurrence of magnetic leakage is increased due to the existence of the gaps. The leakage of the magnetic field can not only affect the surrounding working electrical equipment, but also cause harm to staff. By adopting effective electromagnetic protection, on one hand, the damage of the electromagnetic field to the human body can be reduced, the safe and reliable operation of the equipment is ensured, and on the other hand, the electromagnetic shielding structure used for inhibiting and protecting the influence of the electromagnetic field not only reduces electromagnetic leakage, but also improves the transmission efficiency of the system.
The aluminum-ferrite magnetic shielding structure is adopted to reduce the leakage of an external magnetic field and reduce the internal eddy current loss. The magnetic permeability of ferromagnetic metal materials is large, and the existence of hysteresis effects complicates the magnetic field distribution. The material with high magnetic conductivity can form a good magnetic flux channel to form a good magnetization vector and an induction magnetic field, and the magnetic field around the wireless power supply pile is converged to reduce the leakage of the magnetic field. But the introduction of the magnetic strip increases the self inductance and mutual inductance of the coil. The self-inductance is increased, the compensation capacitance is unchanged, the resonance frequency point of the system moves leftwards, and the efficiency of wireless power transmission is affected. However, the increase of mutual inductance can compensate the influence caused by the left shift of the resonance frequency to a certain extent;
The presence of non-ferromagnetic metallic materials can cause an alternating electromagnetic field to be generated in the coil and induce eddy currents in the metallic surface, causing serious interference with the original magnetic field generated by the coil. The self-inductance of the coil becomes smaller, and at this time, if the compensation capacitance is not changed, the system resonant frequency shifts to the right, which also reduces the system transmission efficiency.
The magnetic shielding structure design is that a magnetic field generated by eddy current loss on a shielding aluminum plate is expressed as:
Wherein H Aluminum (Al) is a reverse magnetic field generated by eddy currents in the coil;
h is the magnitude of the source magnetic field near the shielding aluminum plate:
l Aluminum (Al) is the equivalent inductance of the shielding aluminum plate.
As can be seen from the above formula, when the frequency of the system increases, a larger eddy current loss is formed inside the shielding aluminum plate, but the shielding effect is improved. The shielding aluminum plates are different in position in space, and the magnetic fields are different in size. The larger the magnetic field in the space, the higher the eddy current voltage on the shielding aluminum plate, and the generated eddy current magnetic field opposite to the original magnetic field increases. The eddy currents generated on the shielding aluminum plate can be equivalent to a plurality of small inductances. If a shielding aluminum plate is also added at the receiving end, the equivalent small inductance in the shielding aluminum plate will also inductively couple with the receiving end.
From the analysis, the addition of the ferromagnetic material and the non-ferromagnetic material can reduce the magnetic flux leakage of the receiving and transmitting coil in the transmission process to different degrees, and the output characteristic of the system is improved. But the introduction of both types of shielding materials will have different directional effects on the original system. Specifically, the two materials have different effects on self inductance and mutual inductance of the original coupler, the nonferromagnetic material has a good shielding effect, but can greatly change the electrical parameters of the system to reduce the output performance of the system, and the ferromagnetic material has a good magnetic gathering effect, can gather a magnetic field, reduce magnetic leakage, further reduce eddy current loss generated by an aluminum plate, and can improve the electrical parameters of the system. An aluminum-ferrite composite shield composed of two types of materials is therefore employed.
And (3) miniaturization design of a receiving end:
through simulation and calculation of a magnetic coupler model, the addition of ferrite at the transmitting end is determined to reduce the coil at the receiving end and maintain the mutual inductance value required by the optimal efficiency. The invention realizes miniaturization and light weight of the receiving end coil and is convenient for carrying and sailing of unmanned aerial vehicles.
The system output efficiency expression is derived from fig. 2 as:
η is the system transmission efficiency;
The mutual inductance expression with the highest efficiency is:
Mmax is the highest efficiency mutual inductance value of the system;
the mutual inductance value under the optimal efficiency expression is obtained through the formula (7), and under the condition that the mutual inductance value is kept unchanged, the ferrite is utilized to increase the self-inductance value of the transmitting end coil, so that the self-inductance value of the receiving end coil is reduced, and the volume of the receiving end coil carried by the unmanned aerial vehicle can be reduced.
The invention adds shielding devices on both sides of the transmitting coil and the receiving coil and the coil with strong coupling capability to form a magnetic resonance type wireless electric energy transmission system. In addition, the magnetic resonance type wireless power transmission system uses the LCC-S type compensation network, can supply energy for a load battery by constant voltage output, on one hand, ensures that the unmanned aerial vehicle avoids the influence of electromagnetic interference, and on the other hand, improves the reliability of battery charging. The main embodiment is as follows:
(1) Aluminum-ferrite composite magnetic shielding structure:
The invention provides a magnetic shielding structure based on aluminum-ferrite. The magnetic gathering effect of the ferromagnetic material and the shielding effect of the non-ferromagnetic material combine to reduce the external leakage and the internal loss of the magnetic field. And establishing a magnetic field eddy current loss mathematical expression, and analyzing the influence of the eddy current loss on the electrical parameters of the shielding device system.
(2) Main circuit topology structure of magnetic resonance type wireless power transmission system:
in the wireless power transmission system, a transmitting end needs to form a compensation network of LCC-S by using a compensation inductance, two compensation capacitors and a compensation capacitor connected in series with a receiving end. And analyzing the input and output expressions of the LCC-S compensation network by using the main circuit equivalent model.
(3) Wireless power transfer coil with strong coupling capability:
The coupling coils of the transmitting end and the receiving end are designed by combining ferrite, and the magnetic field is gathered through ferrite so as to enhance the coupling strength. Based on the theory of high-frequency alternating electromagnetic field, a coupling coil model of the strong coupling mechanism is constructed, and the required coupling magnetic field intensity is analyzed and determined.
Be applied to unmanned aerial vehicle's wireless power transmission system can continue unmanned aerial vehicle outdoor work duration. The magnetic coupling coil can radiate high-frequency alternating magnetic field in the wireless power transmission process to interfere normal work of electronic equipment and sensors in the unmanned aerial vehicle, and the power transmission efficiency that the unmanned aerial vehicle can lead to when stopping at wireless charging platform's position deviation is lower. The magnetic resonance type wireless power transmission system based on magnetic shielding and strong coupling capability can meet the requirements, and becomes a key for solving the wireless power supply technology of an unmanned aerial vehicle.
Aiming at the requirements of the wireless power transmission system of the current unmanned aerial vehicle, the invention relates to a magnetic resonance type wireless power transmission system based on magnetic shielding and strong coupling capability. The aluminum-ferrite composite shielding device is utilized to improve the influence of a high-frequency alternating magnetic field on electronic equipment and sensors in the unmanned aerial vehicle in the wireless power transmission process. Meanwhile, a wireless power transmission system with strong coupling capacity is realized by combining a ferrite optimization design method, and a receiving side device carried by the unmanned aerial vehicle is reduced.
The invention has the advantages of simple circuit, low cost, high reliability and the like. The transmitting coil and the receiving coil are combined with aluminum-ferrite design, so that external leakage and internal loss of a magnetic field are avoided to a great extent. And moreover, the design of combining the ferrite at the transmitting end not only realizes the degree of strong coupling of the magnetic field, but also reduces the volume of the charging coil required to be carried by the unmanned aerial vehicle. The LCC-S compensation network is used for achieving the aim of pure resistance of input impedance and achieving the characteristic of maximizing output power.