CN115566814B - A targeted energy transmission method for WPT system based on mutual inductance identification and phase shift angle optimization - Google Patents
A targeted energy transmission method for WPT system based on mutual inductance identification and phase shift angle optimization Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
- H02J50/12—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling of the resonant type
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/005—Mechanical details of housing or structure aiming to accommodate the power transfer means, e.g. mechanical integration of coils, antennas or transducers into emitting or receiving devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/40—Circuit arrangements or systems for wireless supply or distribution of electric power using two or more transmitting or receiving devices
- H02J50/402—Circuit arrangements or systems for wireless supply or distribution of electric power using two or more transmitting or receiving devices the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/90—Circuit arrangements or systems for wireless supply or distribution of electric power involving detection or optimisation of position, e.g. alignment
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- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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Abstract
本发明属于电能传输技术领域，具体涉及一种基于互感识别和移相角优化的WPT系统靶向传能方法，该方法包括：构建无线电能传输系统，该系统包括电能发射机构和电能接收机构；无线电能传输系统通电，并获取系统参数；根据系统参数计算复合平面线圈的互感大小；根据互感大小构建基于接收线圈的移相角的优化目标函数，采用三元函数极值法计算优化目标函数的最优移相角；根据最优移相角对电能发射机构产生的合成磁场进行方位控制；本发明采用具备全方位磁能发射能力的复合平面线圈作为发射机构，基于三个独立逆变器及LCC谐振补偿网络建立系统模型，推导耦合机构效率与互感及移相角的关系；通过移相角优化以获得靶向传能所需的激励电流。
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
The invention belongs to the technical field of electric energy transmission, and particularly relates to a WPT system targeting energy transfer method based on mutual inductance identification and phase shift angle optimization.
Background
The magnetic coupling wireless power transmission (Wireless Power Transfer, WPT) technology refers to a technology for comprehensively applying an electrician theory, a power electronic technology and a control theory and utilizing a magnetic field to realize that electric energy is transmitted from a power grid or a battery to electric equipment in a non-electric contact mode, and has the characteristics of safety, reliability, flexibility, convenience and the like, and has wide application in the fields of electric automobiles, underwater equipment, medical implantation equipment, industrial robots, consumer electronics and the like. The traditional WPT technology generally only allows unidirectional energy transmission and has weak position deviation resistance or angle rotation resistance, so the omnibearing WPT technology is generated, and the technology is a novel technology capable of enabling electric equipment to wirelessly transmit electric energy at any position and angle in a certain space area, can effectively overcome the defects of weak deviation resistance, single transmission angle and the like of the traditional WPT technology, and has good position and angle adaptability.
The magnetic field direction regulation and control method aims at the magnetic field direction regulation and control of the omnibearing WPT technology, the rotating magnetic field and the targeting magnetic field regulation and control are main modes for realizing the omnibearing magnetic field, the rotating magnetic field refers to a magnetic field with a magnetic field vector rotating at a fixed frequency, the magnetic field direction of the rotating magnetic field scans along with time and points to any direction, the targeting magnetic field refers to a magnetic field with a magnetic field vector pointing to a receiving coil, the magnetic field direction of the magnetic field vector changes along with the change of the direction of the receiving coil, the omnibearing wireless energy transmission is realized by adopting the rotating magnetic field mode, the problems of large magnetic field leakage, low energy transmission efficiency and the like exist, the targeting energy transmission mode can enable a composite magnetic field vector generated by a transmitting mechanism to point to the receiving coil, and the magnetic leakage of a coupling mechanism can be effectively reduced and the efficiency can be improved. In the existing targeting energy transmission mode, three orthogonal rectangular coils are adopted as a transmitting mechanism, and the magnetic field direction regulating and controlling method based on excitation current amplitude and phase control is adopted, so that magnetic leakage of a coupling mechanism is reduced, and efficiency is improved.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a WPT system targeting energy transmission method based on mutual inductance identification and phase shift angle optimization, which comprises the steps of constructing a wireless electric energy transmission system, wherein the system comprises a controller, three full-bridge inverters, three LCC resonance compensation networks, a composite plane coil, a receiving coil and a load, the controller, the three full-bridge inverters, the three LCC resonance compensation networks and the composite plane coil form an electric energy transmitting mechanism, and the receiving coil and the load form an electric energy receiving mechanism; the wireless power transmission system is electrified, system parameters are acquired, 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, the optimal phase shift angle of the optimization objective function is calculated by adopting a ternary function extremum method, the direction of a synthesized magnetic field generated by the power transmission mechanism is controlled according to the optimal phase shift angle, the power transmission mechanism generates the synthesized magnetic field pointing to the power receiving mechanism, a set current threshold value field is used for calculating the difference value between the input current of the current system and the input current at the last moment, if the difference value is in the current threshold value field, the current phase shift angle is kept unchanged, and otherwise, the current phase shift angle is optimized again.
Preferably, the composite planar coil comprises three coils, the first coil and the second coil are crossed 8-shaped coils, the third coil is an annular coil, and the first coil and the second coil are positioned in the third coil.
Preferably, each full-bridge inverter in the electric energy transmitting mechanism is connected with the corresponding LCC resonance compensation network and then connected in parallel, and the output end of each LCC resonance compensation network is connected with one coil in the composite plane coil.
Preferably, the acquired system parameters include a voltage U dc input by the system, an operating angular frequency omega, a compensation inductance L f, a transmitting coil internal resistance R i, a receiving coil internal resistance R s and a load resistance R L, wherein the compensation inductance is an inductance value in an LCC resonance compensation network.
Preferably, calculating the mutual inductance of the composite planar coil comprises alternately operating three inverters, namely only one inverter works at a time, recording the system direct current input current I dci when each inverter works, and calculating the mutual inductance of each coil in the composite planar coil by adopting a mutual inductance calculation formula according to the system direct current input current and system parameters.
Preferably, establishing the optimized objective function based on the phase shift angle of the receiving coil comprises the steps of 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 an objective optimized function, and constructing constraint conditions for the objective optimized function.
The invention has the beneficial effects that:
the invention adopts a composite plane coil with omnibearing magnetic energy transmitting capability as a transmitting mechanism, establishes a system model based on three independent inverters and an LCC resonance compensation network, deduces the relation between the efficiency of a coupling mechanism and mutual inductance and phase shift angle, indirectly judges the azimuth of a target (namely a receiving coil) through mutual inductance identification on the basis, and obtains exciting current required by targeted energy transmission through phase shift angle optimization.
Drawings
FIG. 1 is a schematic diagram of a composite planar coil and a coupling mechanism thereof according to the present invention;
FIG. 2 is a system circuit topology of the present invention;
FIG. 3 is a flow chart of mutual inductance identification and phase shift angle optimization of the present invention;
FIG. 4 is a graph of efficiency versus phase shift angle for the present invention;
Fig. 5 is an overall flow chart of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
A WPT system targeting energy transfer method based on mutual inductance identification and phase shift angle optimization is shown in fig. 5, and comprises the steps of constructing a wireless electric energy transmission system, wherein the system comprises a controller, three full-bridge inverters, three LCC resonance compensation networks, a composite planar coil, a receiving coil and a load, the controller, the three full-bridge inverters, the three LCC resonance compensation networks and the composite planar coil form an electric energy transmitting mechanism, the receiving coil and the load form an electric energy receiving mechanism, the wireless electric energy transmission system is electrified and acquires system parameters, the mutual inductance of the composite planar coil is calculated according to the system parameters, an optimized objective function based on the phase shift angle of the receiving coil is constructed according to the mutual inductance, an optimal phase shift angle of the optimized objective function is calculated by adopting a ternary function extremum method, the direction of a synthesized magnetic field generated by the electric energy transmitting mechanism is controlled according to the optimal phase shift angle, the electric energy transmitting mechanism generates a synthesized magnetic field pointing to the electric energy receiving mechanism, a set current threshold value domain is calculated, if the difference between the input current of the current system and the input current at the previous moment is in the current threshold value domain, otherwise, the current phase shift angle is unchanged, and the current phase shift angle is optimized again.
In this embodiment, the composite planar coil includes three coils, the first coil and the second coil are 8-shaped coils intersecting each other, the third coil is a loop coil, and the first coil and the second coil are located in the third coil. Specifically, as shown in fig. 1, the composite planar coil is composed of two crossed 8-shaped coils (coil-1 and coil-2) and one annular coil (coil-3). The invention selects a disc-type coil as a receiving mechanism, and a magnetic core is paved below the composite plane coil to shield a magnetic field. In the central area above the composite plane coil, the coil-1, the coil-2 and the coil-3 mainly generate magnetic fields in the x direction, the y direction and the z direction respectively, and the composite magnetic field generated by the composite plane coil can point to any direction through a reasonable excitation current regulation strategy, so that omnibearing wireless energy transmission is realized.
A circuit structure of a WPT system is shown in figure 2, and comprises a primary side adopting an LCC resonance compensation network, so that the excitation current of a transmitting coil is controlled by the output voltage of an inverter only, and is irrelevant to mutual inductance and load. L fi、Cfi and C i are respectively the resonance compensation inductance in the ith LCC resonance compensation network, The parallel compensation capacitor and the series compensation capacitor are respectively L i and R i which are self inductance and equivalent series resistance of the coil-i, L s and R s which are self inductance and equivalent series resistance of the receiving coil, M i which is mutual inductance of the transmitting coil-i and the receiving coil, C s which is series compensation capacitor of the receiving coil, a diode in the D 1-D4 rectifier bridge, C o which is filter capacitor, and R L which is load. U dc and I dc are respectively direct current input voltage and current of the system, U i and I fi are respectively output voltage and current of the inverter-I, I i is excitation current of the coil-I, I s is current of the receiving coil, U s is input voltage before a rectifier bridge, and U o is output voltage of the system.
In this embodiment, a full-bridge inversion phase-shift control mode is used to control the excitation current of the transmitting coil, and no additional hardware circuit is added compared with a DC-DC mode. Since L fi and C fi in the LCC resonant compensation network can filter out higher harmonics, the fundamental approximation is used herein for analysis, and the output voltage U i of inverter-i can be expressed as:
Wherein θ i is the phase shift angle of the inverter i.
In this embodiment, by adjusting the driving timings of the three inverters, U 1、U2 and U 3 are always kept in phase or in opposite phase, the adjustment range of the phase shift angle θ i belongs to [ -180 °,180 ° ], the positive and negative signs of the phase shift angles of the three inverters are the same and are in phase, and the positive and negative signs of the phase shift angles are different and are in opposite phase.
Since the three coils in the composite planar coil are decoupled from each other, the inter-phase mutual inductance between the three transmit coils is not considered. In order for the system to operate in a resonant state, the operating angular frequency of the system should satisfy the following relationship:
where ω=2pi f, f is the operating frequency of the system.
Constructing a KVL equation according to a circuit structure diagram of the WPT system, wherein the KVL equation has the following expression:
Wherein R eq is the equivalent resistance before the rectifier bridge, R eq＝8RL/π2; representing the output voltage of the i-th inverter, Representing the output current of the i-th inverter,Representing the excitation current of the ith transmit coil,Representing the current in the receive coil.
Simplifying the KVL equation, namely letting L f＝Lfi,Cf＝Cf, obtaining the expression of each current, namely:
the output impedance Z i of each inverter is calculated according to each current, and the expression is as follows:
the output power expression of the computing system is:
The change of the azimuth of the receiving coil can cause the mutual inductance change of the receiving coil and each transmitting coil, and the azimuth of the receiving coil can be indirectly judged through mutual inductance identification. On the other hand, the aim of realizing the targeted energy transmission is to reduce the magnetic leakage of the magnetic coupling mechanism, and enable the receiving coil to capture the magnetic energy in any direction with high efficiency, thereby realizing the maximum efficiency transmission of the magnetic coupling mechanism. Therefore, the efficiency of the magnetic coupling mechanism is taken as an entry point, mutual inductance is firstly identified, and the maximum efficiency of the magnetic coupling mechanism is taken as an optimization target to optimize the phase shift angle, so that excitation current required by targeted energy transmission can be obtained.
When only one coil is energized, i.e., only one inverter is operating, the inverter output current in the operating state can be expressed as:
Where I dci is the dc input current of the system when the inverter-I is operating alone, when the loss of the inverter is ignored, I dci can be expressed as:
Solving a mutual inductance calculation formula according to the expression, namely:
Wherein M i represents the mutual inductance of the ith transmitting coil and the receiving coil, ω represents the operating angular frequency, L f represents the compensating inductance, R s represents the internal resistance of the receiving coil, R L represents the load resistance, I dci represents the direct current input current of the system when the ith inverter operates independently, U dc represents the voltage input by the system, and θ i represents the phase shift angle of the ith inverter. The sign in the expression indicates the direction of mutual inductance.
The 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 mutual inductances of the three transmitting coils and the receiving coils are different, if the exciting currents of the three transmitting coils are in phase, the induced voltages in the receiving coils can cancel each other, and the output power and the efficiency can be reduced sharply. Therefore, the sign of the mutual inductance should match the sign of the excitation current. Specifically, the maximum value of the absolute values in the three mutual inductances M 1、M2 and M 3 is firstly determined, the phase shift angle θ x (x=1, 2, 3) of the branch corresponding to the maximum value of the three mutual inductances is taken as a reference, the signs of the remaining two phase shift angles θ y (y+.x) and θ z (z+.x, z+.y) are changed according to four combination modes shown in table 1, and the direct current input currents I dc-1、Idc-2、Idc -3 and I dc -4 of the system in each mode are detected and recorded, and the phase shift angle sign corresponding to the maximum direct current is taken as the sign of the mutual inductance. for example, when it is recognized that the absolute value of M 1 is maximum, θ 1 is used as a reference, and θ 2 and θ 3 are sequentially changed in sign in four ways as shown in table 1, and the dc input current corresponding to each way is recorded. If the maximum DC input current I dc -2 is detected, the phase shift angle sign of description 2 matches the mutual inductance sign, the sign of M 2 is the same as that of M 1, and the signs of M 3 and M 1 are opposite.
Table 1 four combinations of phase angle symbols
Tab.1 Four combinations of phase-shift angles symbols
The mutual inductance identification mainly comprises two steps of independent excitation and combined excitation, wherein three inverters are sequentially in an operating state during independent excitation, and the three mutual inductances can be identified by detecting the direct current input current of the system for three times. And when combined excitation is performed, selecting the phase shift angle of the branch corresponding to the maximum value of the mutual inductance absolute value as a reference, changing the signs of the remaining two phase shift angles four times, and detecting the direct current input current of the system four times to identify the signs of three mutual inductances.
The process of optimizing the phase shift angle comprises the steps of constructing an optimized objective function based on the phase shift angle of the receiving coil, wherein the optimized objective function comprises the steps of 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 an objective optimized function, and constructing constraint conditions for the objective optimized function.
The expression of the coupling mechanism efficiency function is:
Wherein, P o represents the output power of the system, I i represents the excitation current of the ith transmitting coil, R i represents the internal resistance of the ith 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 ith transmitting coil and the receiving coil, θ i represents the phase shift angle of the ith inverter, and ω represents the working angular frequency.
When the mutual inductance of the three transmitting coils to the receiving coils is identified, the phase shift angles of the three inverters are optimized to achieve maximum efficiency. From the coupling mechanism efficiency function, when the mutual inductances M 1、M2 and M 3 are determined, the efficiency is a function of the phase shift angles θ 1、θ2 and θ 3, and the optimized objective function can be expressed as
maxη=f(θ1,θ2,θ3)
For the optimization problem, intelligent algorithms such as genetic algorithm, particle swarm algorithm, simulated annealing and the like can be adopted for solving. In order to simplify the calculation, the optimal phase shift angle corresponding to the maximum efficiency is solved by solving the ternary function extremum mode. Order of the gameΘ i (i=1, 2, 3) should satisfy the following relationship when the optimized out efficiency is maximum:
wherein M 2,M3≠0,θ2,θ3 is not equal to 0.
In this embodiment, two sets of mutual inductance parameters are chosen as representative for verification, where the relevant parameters are f=100 khz and r L＝10Ω,R1＝0.1Ω,R2＝0.1Ω,R3＝0.2Ω,Rs =0.5Ω. When (M 1,M2,M3) = (3, 4, 5) μh, sin θ 1/sinθ2 =0.75 and sin θ 2/sinθ3 =0.75 are calculated from the relation condition equation satisfied by the optimal phase shift angle. When (M 1,M2,M3) = (-6, 7, 8) μh, in θ 1/sinθ2 = -0.8571 and sin θ 2/sinθ3 = 1.75. The relation between the efficiency eta and the phase shift angle under the two groups of mutual inductance parameters is shown in fig. 4, and the calculated value of the maximum efficiency point scanned under the two groups of mutual inductance parameters in fig. 4 is identical with the calculated value of the expression, so that the accuracy of the phase shift angle is indicated.
In this embodiment, the three angularly offset states of the receive coil are used to further illustrate the operating mechanism of the targeted transduction. The related data of the receiving coil in the mutual inductance identification and phase shift angle optimization process under three angle offset states are shown in table 2, wherein I dci (i=1, 2, 3) is a system direct current input current measured when the ith inverter works independently, I dcj (j=1, 2,3, 4) is a system direct current input current measured in the j-th combination mode of the phase shift angle of the inverter, M i (i=1, 2, 3) is the mutual inductance of the receiving coil of the transmitting coil-I, θ i (i=1, 2, 3) is the phase shift angle of the ith inverter, P o is the receiving power, and η is the system direct current-direct current efficiency.
TABLE 2 mutual inductance identification and related parameters in phase shift angle optimization
When the receiving coil is at angle #1, the three inverters are operated individually to detect that I dc1、Idc2 and I dc3 are 0.05A, 0.06A, and 2A, respectively. I dc1 and I dc2 are almost zero, indicating that the coupling of the receive coil to coil-1 and coil-2 is weak. M 1、M2 and M 3 were calculated to be 0 μH, 0 μH and 9.8 μH, respectively, according to I dc1、Idc2 and I dc3, according to the mutual inductance calculation formula. Since there are two mutual inductance values of zero, it is not necessary to judge the signs of three mutual inductances. Since M 1 and M 2 are zero and M 3 is maximum, inverter-1 and inverter-2 are disabled to avoid losses in coil-1 and coil-2, leaving the phase shift angle of inverter-3 at 180.
When the receiving coil is at angle #2, the three inverters are operated individually to detect I dc1、Idc2 and I dc3 as 1.06A, 0.59A, and 0.07A, respectively. I dc3 is almost zero, indicating that the coupling of the receive coil to coil-3 is weak. According to I dc1、Idc2 and I dc3, the numerical values of M 1、M2 and M 3 are calculated to be 7.1 mu H respectively by combining a mutual inductance calculation formula, 5.1. Mu.H and 0. Mu.H. Since M 3 is zero, only the symbols of M 1 and M 2 need to be determined. since M 1 is the largest, the symbols of θ 2 are changed twice by selecting θ 1 as a reference, and θ 2 measures I dc -1 as 3.17A with the symbol "+" and θ 2 measures I dc -2 as 0.35A with the symbol "-" to determine that M 1 is the same as M 2. Since M 1 is maximum and M 3 is zero, θ 1 is 180 °, and θ 3 is 0. And calculating the theta 2 to be 89 degrees according to the optimal phase shift angle meeting condition.
When the receiving coil is at angle #3, the three inverters are operated individually to detect I dc1、Idc2 and I dc3 as 0.41A, 0.1A, and 0.75A, respectively. According to I dc1、Idc2 and I dc3, the numerical values of M 1、M2 and M 3 are calculated to be 4.1 mu H respectively by combining a mutual inductance calculation formula, 2.3. Mu.H and 5.8. Mu.H. Because M 3 is maximum, θ 3 is selected as a reference, the phases of θ 1 and θ 2 are sequentially changed according to four combination modes of phase shift angle symbols in Table 1, and I dc-1、Idc-2、Idc -3 and I dc -4 are respectively 0.26A, 0.58A, 1.38A and 3.18A. Since the dc input current is the greatest in the fourth combined excitation, it is indicated that the signs of M 1 and M 3 are opposite, and that the signs of M 2 and M 3 are also opposite. Since M 3 is maximum, θ 3 is 180 °, and θ 1 and θ 2 are calculated to be-130 ° and-59 °, respectively, according to the optimal phase shift angle satisfying conditional formula.
The detection and calculation times (7 times) of the targeted energy transfer method are far lower than the detection and calculation times (200 times) required for realizing the targeted energy transfer based on current amplitude scanning. In the proposed targeted energy transfer method, the mutual inductance can be identified and the phase shift angle can be calculated usually only by 3-7 times of detection and calculation. When only one transmitting coil is coupled with the receiving coil, the mutual inductance symbol is not required to be identified, and only 3 times of detection are required. When the three transmitting coils are coupled with the receiving coils, the size and the sign of mutual inductance need to be identified, and the total detection is required to be performed for 7 times. The sampling time set in the experiment is 5 mu s, and the average value is taken as a detection value by sampling 10 times. The working states of the three inverters are changed for 7 times in7 times of detection, the circuit needs to wait 10ms to start detection after the circuit enters a steady state when being switched from one working state to the other working state, and the total time from starting to working in a target energy transfer mode is about 71ms.
While the foregoing is directed to embodiments, aspects and advantages of the present invention, other and further details of the invention may be had by the foregoing description, it will be understood that the foregoing embodiments are merely exemplary of the invention, and that any changes, substitutions, alterations, etc. which may be made herein without departing from the spirit and principles of the invention.
Claims (10)
1. A WPT system targeting energy transfer method based on mutual inductance identification and phase shift angle optimization is characterized by comprising the steps of constructing a wireless electric energy transmission system, carrying out azimuth control on a synthetic magnetic field direction generated by an electric energy transmission mechanism according to the optimal phase shift angle, enabling the electric energy transmission mechanism to generate a synthetic magnetic field pointing to the electric energy reception mechanism, calculating a difference value between an input current of a current system and an input current at the previous moment, keeping the current phase shift angle unchanged if the difference value is in the current threshold, and optimizing the current phase shift angle again if the difference value is in the current threshold, and calculating the current phase shift angle.
2. The WPT system targeting energy transfer method based on mutual inductance identification and phase shift angle optimization of claim 1, wherein the composite planar coil includes three coils, the first coil and the second coil are 8-shaped coils intersecting each other, the third coil is a loop coil, and the first coil and the second coil are located in the third coil.
3. The WPT system targeting energy transfer method based on mutual inductance identification and phase shift angle optimization according to claim 1, wherein each full-bridge inverter in the electric energy transmitting mechanism is connected with a corresponding LCC resonance compensation network and then connected in parallel, and the output end of each LCC resonance compensation network is connected with one coil in the composite plane coil.
4. The WPT system targeting energy transfer method based on mutual inductance identification and phase shift angle optimization according to claim 1, wherein the acquired system parameters comprise a voltage U dc input by a system, an operating angular frequency omega, a compensation inductance L f, a transmitting coil internal resistance R i, a receiving coil internal resistance R s and a load resistance R L, wherein the compensation inductance is an inductance value in an LCC resonance compensation network.
5. The WPT system targeting energy transfer method based on mutual inductance identification and phase shift angle optimization according to claim 1 is characterized in that calculating the mutual inductance of the composite planar coil comprises the steps of running three inverters in turn, namely only one inverter works at a time, recording system direct current input current I dci when each inverter works, and calculating the mutual inductance of each coil in the composite planar coil by adopting a mutual inductance calculation formula according to the system direct current input current and system parameters.
6. The WPT system targeting energy transfer method based on mutual inductance identification and phase shift angle optimization as set forth in claim 5, wherein the expression of the mutual inductance calculation formula is:
Wherein M i represents the mutual inductance of the ith transmitting coil and the receiving coil, ω represents the operating angular frequency, L f represents the compensating inductance, R s represents the internal resistance of the receiving coil, R L represents the load resistance, I dci represents the direct current input current of the system when the ith inverter operates independently, U dc represents the voltage input by the system, and θ i represents the phase shift angle of the ith inverter.
7. The WPT system targeting energy transfer method based on mutual inductance identification and phase shift angle optimization, which is characterized by comprising the steps of constructing a coupling mechanism efficiency function according to system parameters, solving the coupling mechanism efficiency function according to the mutual inductance of a composite planar coil to obtain a target optimization function, and constructing constraint conditions for the target optimization function.
8. The WPT system targeting energy transmission method based on mutual inductance identification and phase shift angle optimization according to claim 7, wherein the expression of the coupling mechanism efficiency function is:
Wherein, P o represents the output power of the system, I i represents the excitation current of the ith coil, R i represents the internal resistance of the ith 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 of the ith transmitting coil and the receiving coil, θ i represents the phase shift angle of the ith inverter, and ω represents the working angular frequency.
9. The WPT system targeted energy transfer method based on mutual inductance identification and phase shift angle optimization of claim 7, wherein the expression of the optimized objective function is:
max η=f(θ1,θ2,θ3)
Where M max represents the maximum value of the mutual inductance of the coils, and θ x represents the angle of the x-th coil.
10. The WPT system targeting energy transfer method based on mutual inductance identification and phase shift angle optimization according to claim 7, wherein the process of calculating the optimal phase shift angle of the optimization objective function by adopting the ternary function extremum method comprises the steps of performing partial derivative on the objective optimization function to enable the partial derivative to be 0, and obtaining the optimal phase shift angle when the efficiency is maximum, wherein the optimal phase shift angle meets the following conditions:
Wherein, θ 1 represents the phase shift angle of the first inverter, θ 2 represents the phase shift angle of the second inverter, θ 3 represents the phase shift angle of the third inverter, M 1 represents the mutual inductance of the 1 st transmitting coil and the receiving coil, M 2 represents the mutual inductance of the 2 nd transmitting coil and the receiving coil, M 3 represents the mutual inductance of the 3 rd transmitting coil and the receiving coil, R 1 represents the internal resistance of the first transmitting coil, R 2 represents the internal resistance of the second transmitting coil, and R 3 represents the internal resistance of the third transmitting coil.
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