A targeted energy transmission method for WPT system based on mutual inductance identification and phase shift angle optimization

Abstract

The invention belongs to the technical field of electric energy transmission, and specifically relates to a WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization, the method comprising: constructing a wireless power transmission system, the system comprising an electric energy transmitting mechanism and an electric energy receiving mechanism; the wireless power transmission system is powered on, and system parameters are obtained; the mutual inductance of a composite planar coil is calculated according to the system parameters; an optimization objective function based on the phase shift angle of a receiving coil is constructed according to the mutual inductance, and an optimal phase shift angle of the optimization objective function is calculated by using a ternary function extreme value method; the synthetic magnetic field generated by the electric energy transmitting mechanism is azimuthally controlled according to the optimal phase shift angle; the invention adopts a composite planar coil with omnidirectional magnetic energy transmission capability as a transmitting mechanism, establishes a system model based on three independent inverters and an LCC resonance compensation network, and derives the relationship between the efficiency of a coupling mechanism and the mutual inductance and the phase shift angle; and obtains an excitation current required for targeted energy transmission by optimizing the phase shift angle.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric energy transmission, and in particular relates to a WPT system targeted energy transmission method based on mutual inductance recognition and phase shift angle optimization. Background Art

[0002] Magnetic coupling wireless power transfer (WPT) technology refers to the technology that uses the comprehensive application of electrical theory, power electronics technology, and control theory to realize the transmission of electrical energy from the power grid or battery to the electrical equipment in a non-electrical contact manner by using magnetic fields; this technology is safe, reliable, flexible, and convenient, and is widely used in electric vehicles, underwater equipment, medical implants, industrial robots, consumer electronics, and other fields. Traditional WPT technology usually only allows one-way energy transmission and has weak resistance to position displacement or angle rotation; therefore, omnidirectional WPT technology came into being. This technology is a new technology that can use electrical equipment to wirelessly transmit electrical energy at any position and angle within a certain spatial area. It can effectively make up for the shortcomings of traditional WPT technology such as weak resistance to displacement and single transmission angle, and has good position and angle adaptability.

[0003] Regarding the magnetic field direction control of omnidirectional WPT technology, rotating magnetic field and targeted magnetic field control are the main ways to achieve omnidirectional magnetic field; rotating magnetic field refers to a magnetic field in which the magnetic field vector rotates at a fixed frequency, and its magnetic field direction scans and points to any direction over time; targeted magnetic field refers to a magnetic field in which the magnetic field vector points to the receiving coil, and its magnetic field direction changes with the change of the receiving coil's orientation; among them, the use of rotating magnetic field to achieve omnidirectional wireless energy transmission has problems such as large magnetic field leakage and low energy transmission efficiency; the targeted energy transmission method can make the synthetic magnetic field vector generated by the transmitting mechanism point to the receiving coil, which can effectively reduce the magnetic leakage of the coupling mechanism and improve efficiency. In the existing targeted energy transmission method, three orthogonal rectangular coils are used as the transmitting mechanism, and the magnetic field direction control method based on the excitation current amplitude and phase control is used to reduce the magnetic leakage of the coupling mechanism and improve efficiency; however, the above method cannot effectively identify the orientation of the receiving coil, which makes the accuracy of the excitation current low, which is not conducive to power transmission. Summary of the invention

[0004] In order to solve the problems existing in the above prior art, the present invention proposes a WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization, the method comprising: constructing a wireless power transmission system, the system comprising a controller, three full-bridge inverters, three LCC resonant compensation networks, a composite planar coil, a receiving coil and a load, wherein the controller, the three full-bridge inverters, the three LCC resonant compensation networks and the composite planar coil constitute an electric power transmitting mechanism, and the receiving coil and the load constitute an electric power receiving mechanism; the wireless power transmission system is powered on and system parameters are obtained; the mutual inductance of the composite planar coil is calculated according to the system parameters; an optimization objective function based on the phase shift angle of the receiving coil is constructed according to the mutual inductance, and the optimal phase shift angle of the optimization objective function is calculated by using a ternary function extreme value method; the direction of the synthetic magnetic field generated by the electric power transmitting mechanism is azimuthally controlled according to the optimal phase shift angle, so that the electric power transmitting mechanism generates a synthetic magnetic field pointing to the electric power receiving mechanism; a current threshold domain is set, and the difference between the input current of the current system and the input current at the previous moment is calculated. If the difference is within the current threshold domain, the current phase shift angle is kept unchanged, otherwise the current phase shift angle is optimized again.

[0005] Preferably, the composite planar coil comprises three coils, the first coil and the second coil are mutually crossed figure-8 coils, the third coil is a ring coil, and the first coil and the second coil are located inside the third coil.

[0006] Preferably, each full-bridge inverter in the electric energy transmitting mechanism is connected to a corresponding LCC resonant compensation network and then connected in parallel with each other, and an output end of each LCC resonant compensation network is connected to a coil in the composite planar coil.

[0007] Preferably, the acquired system parameters include the system input voltage U dc , working angular frequency ω, compensation inductance L f , Transmitting coil internal resistance R i 、Internal resistance of receiving coil R s And the load resistance R L ; The compensation inductance is the inductance value in the LCC resonant compensation network.

[0008] Preferably, calculating the mutual inductance of the composite planar coil includes: operating the three inverters in turn, that is, only one inverter works at a time, and recording the system DC input current I when each inverter works. dci , according to the system DC input current and system parameters, the mutual inductance calculation formula is used to calculate the mutual inductance of each coil in the composite planar coil.

[0009] Preferably, establishing an optimization objective function based on the phase shift angle of the receiving coil includes: constructing a coupling mechanism efficiency function according to system parameters; solving the coupling mechanism efficiency function according to the mutual inductance of the composite planar coil to obtain a target optimization function; and constructing constraints for the target optimization function.

[0010] Beneficial effects of the present invention:

[0011] The present invention adopts a composite planar coil with omnidirectional magnetic energy emission capability as a transmitting mechanism, establishes a system model based on three independent inverters and an LCC resonant compensation network, and derives the relationship between the efficiency of the coupling mechanism and the mutual inductance and the phase shift angle; on this basis, the orientation of the "target" (i.e., the receiving coil) is indirectly determined through mutual inductance identification, and the excitation current required for targeted energy transmission is obtained through phase shift angle optimization; the present invention can make the coupling mechanism always work in a state of maximum efficiency, and the method does not require direct detection of the receiving coil posture, nor does it require a communication link. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram of the composite planar coil and its coupling mechanism of the present invention;

[0013] Figure 2 The system circuit topology of the present invention;

[0014] Figure 3 A flow chart of mutual inductance identification and phase shift angle optimization of the present invention;

[0015] Figure 4 is a relationship diagram between the efficiency and the phase shift angle of the present invention;

[0016] Figure 5 It is the overall flow chart of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] A targeted energy transmission method for WPT system based on mutual inductance identification and phase shift angle optimization, such as Figure 5As shown, the method includes: constructing a wireless power transmission system, the system includes a controller, three full-bridge inverters, three LCC resonant compensation networks, a composite planar coil, a receiving coil and a load, wherein the controller, the three full-bridge inverters, the three LCC resonant compensation networks and the composite planar coil constitute an electric power transmitting mechanism, and the receiving coil and the load constitute an electric power receiving mechanism; the wireless power transmission system is powered on and system parameters are obtained; the mutual inductance of the composite planar coil is calculated according to the system parameters; an optimization objective function based on the phase shift angle of the receiving coil is constructed according to the mutual inductance, and the optimal phase shift angle of the optimization objective function is calculated by using a ternary function extreme value method; the direction of the synthetic magnetic field generated by the electric power transmitting mechanism is azimuthally controlled according to the optimal phase shift angle, so that the electric power transmitting mechanism generates a synthetic magnetic field pointing to the electric power receiving mechanism; a current threshold domain is set, and the difference between the input current of the current system and the input current at the previous moment is calculated. If the difference is within the current threshold domain, the current phase shift angle is kept unchanged, otherwise the current phase shift angle is re-optimized.

[0019] In this embodiment, the composite planar coil includes three coils, the first coil and the second coil are mutually crossed 8-shaped coils, the third coil is a ring coil, and the first coil and the second coil are located inside the third coil. Figure 1 As shown, the composite planar coil consists of two crossed 8-shaped coils (coil-1 and coil-2) and a ring coil (coil-3). The present invention selects a disc-shaped coil as a receiving mechanism, and lays a magnetic core under the composite planar coil to shield the magnetic field. In the central area above the composite planar coil, coil-1, coil-2 and coil-3 mainly generate magnetic fields in the x-direction, y-direction and z-direction respectively. Through a reasonable excitation current control strategy, the synthetic magnetic field generated by the composite planar coil can point to any direction, thereby realizing all-round wireless energy transmission.

[0020] A circuit structure of a WPT system, such as Figure 2 As shown in FIG. 1 , the circuit structure includes an LCC resonant compensation network on the primary side, which can make the excitation current of the transmitting coil only controlled by the inverter output voltage and has nothing to do with the mutual inductance and load. fi , C fi and C i are the resonant compensation inductor, parallel compensation capacitor and series compensation capacitor in the i-th LCC resonant compensation network, respectively. i and R i are the self-inductance and equivalent series resistance of coil-i, L s and R s are the self-inductance and equivalent series resistance of the receiving coil, M i is the mutual inductance between the transmitting coil-i and the receiving coil, C s is the series compensation capacitor of the receiving coil, the diode in the D1-D4 rectifier bridge, C ois the filter capacitor, R L is the load. dc and I dc The DC input voltage and current of the system, U i and I fi are the output voltage and current of inverter-i, I i is the excitation current of coil-i, I s is the current of the receiving coil, U s is the input voltage before the rectifier bridge, U o is the output voltage of the system.

[0021] In this embodiment, a full-bridge inverter phase-shift control method is used to control the excitation current of the transmitting coil. Compared with the DC-DC method, this method does not add additional hardware circuits. fi and C fi The higher harmonics can be filtered out, so this paper adopts the fundamental wave approximation method for analysis. The output voltage U of inverter-i i It can be expressed as:

[0022]

[0023] Among them, θ i is the phase shift angle of inverter i.

[0024] In this embodiment, the driving timing of the three inverters is adjusted to always keep U1, U2 and U3 in phase or in reverse phase, and the phase shift angle θ i The adjustment range is [-180°, 180°]. If the phase shift angles of the three inverters have the same positive and negative signs, they are in phase. If the phase shift angles have different positive and negative signs, they are in opposite phases.

[0025] Since the three coils in the composite planar coil are decoupled from each other, the phase mutual inductance between the three transmitting coils is not considered. In order to make the system work in a resonant state, the operating angular frequency of the system should satisfy the following relationship:

[0026]

[0027] Among them, ω=2πf, f is the operating frequency of the system.

[0028] According to the circuit structure diagram of the WPT system, the KVL equation is constructed and its expression is:

[0029]

[0030] Among them, R eq is the equivalent resistance before the rectifier bridge, R eq =8R L / π 2 ; represents the output voltage of the ith inverter, represents the output current of the ith inverter, represents the excitation current of the i-th transmitting coil, Represents the current in the receiving coil.

[0031] Simplify the KVL equation, that is, let L f =L fi , C f =C f , then the expressions of each current are obtained, which are:

[0032]

[0033]

[0034]

[0035] Calculate the output impedance Z of each inverter based on each current i , whose expression is:

[0036]

[0037] The output power expression of the calculation system is:

[0038]

[0039] The change of the receiving coil's orientation will cause the mutual inductance between the receiving coil and each transmitting coil to change. The orientation of the receiving coil can be indirectly determined by mutual inductance identification. On the other hand, the purpose of achieving targeted energy transmission is to reduce the magnetic leakage of the magnetic coupling mechanism and enable the receiving coil to efficiently capture magnetic energy in any orientation, thereby achieving the maximum efficiency transmission of the magnetic coupling mechanism. Therefore, this paper takes the efficiency of the magnetic coupling mechanism as the starting point, first identifies the mutual inductance, and optimizes the phase shift angle with the maximum efficiency of the magnetic coupling mechanism as the optimization target to obtain the excitation current required for targeted energy transmission.

[0040] When only one coil is excited by current, that is, only one inverter is running, the output current of the inverter in the running state can be expressed as:

[0041]

[0042] Among them, I dci is the DC input current of the system when inverter-i works alone. When the loss of the inverter is ignored, I dci It can be expressed as:

[0043]

[0044] According to the above expression, the mutual inductance calculation formula is solved as follows:

[0045]

[0046] Among them, M i represents the mutual inductance between the i-th transmitting coil and the receiving coil, ω represents the operating angular frequency, and L f Represents the compensation inductance, R s Represents the internal resistance of the receiving coil, R L Represents the load resistance, I dci It represents the DC input current of the system when the ith inverter works alone, U dc Represents the system input voltage, θ i represents the phase shift angle of the ith inverter. The positive and negative signs in the expression represent the direction of the mutual inductance.

[0047] The above mutual inductance identification method can only identify the size of the mutual inductance, but cannot identify the positive and negative signs of the mutual inductance. When the signs of the mutual inductance of the three transmitting coils and the receiving coil are different, if the excitation currents of the three transmitting coils are in phase, the induced voltages in the receiving coils will cancel each other out, causing a sharp drop in output power and efficiency. Therefore, the positive and negative signs of the mutual inductance should match the positive and negative signs of the excitation current. Specifically, first determine the maximum absolute value of the three mutual inductances M1, M2 and M3, and use the maximum absolute value of the three mutual inductances to correspond to the phase shift angle θ of the branch x (x=1,2,3) as reference, change the remaining two phase shift angles θ according to the four combinations shown in Table 1 y (y≠x) and θ z (z≠x,z≠y) sign, detect and record the DC input current I of the system in each mode dc -1, I dc -2.I dc -3 and I dc -4, the sign of the phase shift angle corresponding to the maximum DC current is used as the sign of the mutual inductance. For example, when it is identified that the absolute value of M1 is the largest, θ1 is used as a reference, and θ2 and θ3 change their signs in turn according to the four ways shown in Table 1, and the DC input current corresponding to each way is recorded. If the DC input current I dc -2 is the largest, which means that the sign of the phase shift angle of mode 2 matches the sign of the mutual inductance, the sign of M2 is the same as the sign of M1, and the sign of M3 is opposite to the sign of M1.

[0048] Table 1 Four combinations of phase shift angle symbols

[0049] Tab.1 Four combinations of phase-shift angles symbols

[0050]

[0051] The above mutual inductance identification mainly includes two steps: single excitation and combined excitation. When single excitation is used, the three inverters are put into operation in turn, and the DC input current of the system is detected three times to identify the size of the three mutual inductances. When combined excitation is used, the phase shift angle of the branch corresponding to the maximum absolute value of the mutual inductance is selected as a reference, and the signs of the remaining two phase shift angles are changed four times, and the DC input current of the system is detected four times to identify the signs of the three mutual inductances.

[0052] like Figure 3 As shown, the process of optimizing the phase shift angle includes: establishing an optimization objective function based on the phase shift angle of the receiving coil, including: constructing a coupling mechanism efficiency function according to system parameters; solving the coupling mechanism efficiency function according to the mutual inductance of the composite planar coil to obtain a target optimization function; and constructing constraints for the target optimization function.

[0053] The expression of the coupling mechanism efficiency function is:

[0054]

[0055] Among them, P o Indicates the system output power, I i represents the excitation current of the i-th transmitting coil, R i represents the internal resistance of the i-th transmitting coil, I s represents the current in the receiving coil, R s Represents the internal resistance of the receiving coil, R L Represents the load resistance, M i represents the mutual inductance between the i-th transmitting coil and the receiving coil, θ i represents the phase shift angle of the i-th inverter, and ω represents the operating angular frequency.

[0056] After the mutual inductance of the three transmitting coils to the receiving coils is identified, the phase shift angles of the three inverters need to be optimized to achieve maximum efficiency. According to the coupling mechanism efficiency function, when the mutual inductances M1, M2, and M3 are determined, the efficiency is a function of the phase shift angles θ1, θ2, and θ3, and the optimization objective function can be expressed as

[0057] maxη=f(θ1,θ2,θ3)

[0058]

[0059] For this optimization problem, genetic algorithm, particle swarm algorithm, simulated annealing and other intelligent algorithms can be used to solve it. To simplify the calculation, the optimal phase shift angle corresponding to the maximum efficiency is solved by solving the extreme value of the ternary function. Optimize the maximum efficiency θ i (i=1,2,3) should satisfy the following relationship:

[0060]

[0061] Among them, M2, M3≠0, θ2, θ3≠0.

[0062] In this embodiment, two sets of mutual inductance parameters are selected as representatives for verification, wherein the relevant parameters are as follows: f = 100 kHz, R L =10Ω, R1=0.1Ω, R2=0.1Ω, R3=0.2Ω, R s =0.5Ω. When (M1, M2, M3) = (3, 4, 5) μH, the optimal phase shift angle satisfies the relationship condition formula and calculates that sinθ1 / sinθ2 = 0.75 and sinθ2 / sinθ3 = 0.75. When (M1, M2, M3) = (-6, 7, 8) μH, inθ1 / sinθ2 = -0.8571 and sinθ2 / sinθ3 = 1.75. The relationship between the efficiency η and the phase shift angle under the two sets of mutual inductance parameters is calculated as follows: Figure 4 As shown, Figure 4 The maximum efficiency point scanned under the two sets of mutual inductance parameters is consistent with the calculated value of the above expression, which indicates the correctness of the phase shift angle.

[0063] In this embodiment, the three angle offset states of the receiving coil are used to further illustrate the operation mechanism of targeted energy transmission. The relevant data of the mutual inductance identification and phase shift angle optimization process of the receiving coil in the three angle offset states are shown in Table 2, where I dci (i=1,2,3) is the system DC input current measured when the i-th inverter works alone, I dcj (j=1,2,3,4) is the system DC input current measured under the jth combination of inverter phase shift angle, M i (i=1,2,3) is the mutual inductance of the transmitting coil-i to the receiving coil, θ i (i=1,2,3) is the phase shift angle of the i-th inverter, P o is the received power and η is the system DC-DC efficiency.

[0064] Table 2 Related parameters in the process of mutual inductance identification and phase shift angle optimization

[0065]

[0066]

[0067] When the receiving coil is at angle #1, the three inverters detect I dc1 ,I dc2 and I dc3 They are 0.05A, 0.06A and 2A respectively. dc1 and I dc2is almost zero, indicating that the coupling between the receiving coil and coil-1 and coil-2 is very weak. dc1 ,I dc2 and I dc3 , according to the mutual inductance calculation formula, M1, M2 and M3 are calculated to be 0μH, 0μH and 9.8μH respectively. Since there are two mutual inductance values ​​of zero, there is no need to determine the signs of the three mutual inductances. Since M1 and M2 are zero and M3 is the largest, inverter-1 and inverter-2 are not working to avoid the loss of coil-1 and coil-2, and the phase shift angle of inverter-3 is kept at 180°.

[0068] When the receiving coil is at angle #2, the three inverters detect I dc1 ,I dc2 and I dc3 They are 1.06A, 0.59A and 0.07A respectively. dc3 is almost zero, indicating that the coupling between the receiving coil and coil-3 is very weak. dc1 ,I dc2 and I dc3 , and then combined with the mutual inductance calculation formula, the values ​​of M1, M2 and M3 are calculated to be 7.1μH, 5.1μH and 0μH respectively. Since M3 is zero, it is only necessary to determine the signs of M1 and M2. Since M1 is the largest, θ1 is selected as the reference, and the sign of θ2 is changed twice. When θ2 is "+", I is measured. dc -1 is 3.17A, θ2 is measured under the symbol "-" dc -2 is 0.35A, from which we can judge that M1 and M2 have the same sign. Since M1 is the largest and M3 is zero, θ1 is 180° and θ3 is 0. According to the optimal phase shift angle, θ2 is calculated to be 89°.

[0069] When the receiving coil is at angle #3, the three inverters detect I dc1 ,I dc2 and I dc3 They are 0.41A, 0.1A and 0.75A respectively. dc1 ,I dc2 and I dc3 , and then combined with the mutual inductance calculation formula, the values ​​of M1, M2 and M3 are calculated to be 4.1μH, 2.3μH and 5.8μH respectively. Since M3 is the largest, θ3 is selected as the reference. According to the four combinations of phase shift angle signs in Table 1, the phases of θ1 and θ2 are changed in turn. I is measured under the four combinations of excitation. dc -1, I dc -2.I dc -3 and I dc-4 are 0.26A, 0.58A, 1.38A and 3.18A respectively. Since the DC input current under the fourth combination excitation mode is the largest, it means that the signs of M1 and M3 are opposite, and the signs of M2 and M3 are also opposite. Since M3 is the largest, θ3 is 180°. According to the formula for satisfying the conditions of the optimal phase shift angle, θ1 and θ2 are calculated to be -130° and -59° respectively.

[0070] The number of detection and calculation times (7 times) of the targeted energy transfer method proposed in this paper is much lower than the number of detection and calculation times (200 times) required to achieve targeted energy transfer based on current amplitude scanning. In the proposed targeted energy transfer method, usually only 3-7 detections and calculations are required to identify the mutual inductance and calculate the phase shift angle. When only one transmitting coil is coupled with the receiving coil, it is not necessary to identify the sign of the mutual inductance, and only 3 detections are required. When all three transmitting coils are coupled with the receiving coil, the size and sign of the mutual inductance need to be identified, and a total of 7 detections are required. The sampling time set in the experiment is 5μs, and the average value of 10 samples is taken as the detection value. In the 7 detections, the working states of the three inverters changed a total of 7 times. It takes 10ms for the circuit to switch from one working state to another to allow the circuit to enter a steady state before starting the detection. The system takes about 71ms from startup to working in the targeted energy transfer mode.

[0071] The above embodiments further illustrate the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above embodiments are only preferred implementation modes of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization, characterized in that: The method comprises: constructing a wireless power transmission system, the system comprising a controller, three full-bridge inverters, three LCC resonant compensation networks, a composite planar coil, a receiving coil and a load, wherein the controller, the three full-bridge inverters, the three LCC resonant compensation networks and the composite planar coil constitute an electric power transmitting mechanism, and the receiving coil and the load constitute an electric power receiving mechanism; the wireless power transmission system is powered on, and system parameters are obtained; the mutual inductance of the composite planar coil is calculated according to the system parameters; an optimization objective function based on the phase shift angle of the receiving coil is constructed according to the mutual inductance, and an optimal phase shift angle of the optimization objective function is calculated by using a ternary function extreme value method; and the direction of the synthetic magnetic field generated by the electric power transmitting mechanism is azimuthally controlled according to the optimal phase shift angle, so that the electric power transmitting mechanism generates a synthetic magnetic field pointing to the electric power receiving mechanism; The current threshold domain is set, and the difference between the current system input current and the input current at the previous moment is calculated. If the difference is within the current threshold domain, the current phase shift angle is kept unchanged, otherwise the current phase shift angle is re-optimized.

2. According to claim 1, a WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization is characterized in that: The composite planar coil comprises three coils, the first coil and the second coil are mutually crossed 8-shaped coils, the third coil is a ring coil, and the first coil and the second coil are located inside the third coil.

3. According to claim 1, a WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization is characterized in that: Each full-bridge inverter in the electric energy transmitting mechanism is connected to a corresponding LCC resonant compensation network and then connected in parallel with each other, and the output end of each LCC resonant compensation network is connected to a coil in the composite planar coil.

4. According to claim 1, a WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization is characterized in that: The system parameters obtained include the system input voltage U dc , working angular frequency ω, compensation inductance L f , Transmitting coil internal resistance R i 、Internal resistance of receiving coil R s And the load resistance R L ; The compensation inductance is the inductance value in the LCC resonant compensation network.

5. According to claim 1, a WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization is characterized in that: Calculating the mutual inductance of the composite planar coil includes: the three inverters operate in turn, that is, only one inverter works at a time, and recording the system DC input current I when each inverter works dci , according to the system DC input current and system parameters, the mutual inductance calculation formula is used to calculate the mutual inductance of each coil in the composite planar coil.

6. A WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization according to claim 5, characterized in that: The mutual inductance calculation formula is: Among them, M i represents the mutual inductance between the i-th transmitting coil and the receiving coil, ω represents the operating angular frequency, and L f Represents the compensation inductance, R s Represents the internal resistance of the receiving coil, R L Represents the load resistance, I dci It represents the DC input current of the system when the ith inverter works alone, U dc Represents the system input voltage, θ i represents the phase shift angle of the i-th inverter.

7. The WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization according to claim 1 is characterized in that: Constructing an optimization objective function based on the phase shift angle of the receiving coil includes: constructing a coupling mechanism efficiency function according to system parameters; solving the coupling mechanism efficiency function according to the mutual inductance of the composite planar coil to obtain a target optimization function; and constructing constraint conditions for the target optimization function.

8. A WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization according to claim 7, characterized in that: The expression of the coupling mechanism efficiency function is: Among them, P o Indicates the system output power, I i represents the excitation current of the ith coil, R i represents the internal resistance of the i-th transmitting coil, I s represents the current in the receiving coil, R s Represents the internal resistance of the receiving coil, R L Represents the load resistance, M i represents the mutual inductance between the i-th transmitting coil and the receiving coil, θ i represents the phase shift angle of the i-th inverter, and ω represents the operating angular frequency.

9. The WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization according to claim 7 is characterized in that: The expression of the optimized objective function is: max η=f(θ1,θ2,θ3) Among them, M max Represents the maximum value of the mutual inductance of the coil, θ x Represents the angle of the xth coil.

10. The WPT system targeted energy transmission method based on mutual inductance identification and phase shift angle optimization according to claim 7, characterized in that: The process of calculating the optimal phase shift angle of the optimization objective function using the ternary function extreme value method includes: taking the partial derivative of the objective optimization function, setting the partial derivative to 0, and obtaining the optimal phase shift angle when the efficiency is maximum; the optimal phase shift angle satisfies: Among them, θ1 represents the phase shift angle of the first inverter, θ2 represents the phase shift angle of the second inverter, θ3 represents the phase shift angle of the third inverter, M1 represents the mutual inductance between the first transmitting coil and the receiving coil, M2 represents the mutual inductance between the second transmitting coil and the receiving coil, M3 represents the mutual inductance between the third transmitting coil and the receiving coil, R1 represents the internal resistance of the first transmitting coil, R2 represents the internal resistance of the second transmitting coil, and R3 represents the internal resistance of the third transmitting coil.

Images