CN115441593A - Double-solenoid type coupling mechanism and parameter design method thereof - Google Patents

Double-solenoid type coupling mechanism and parameter design method thereof Download PDF

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CN115441593A
CN115441593A CN202210850859.6A CN202210850859A CN115441593A CN 115441593 A CN115441593 A CN 115441593A CN 202210850859 A CN202210850859 A CN 202210850859A CN 115441593 A CN115441593 A CN 115441593A
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coil
solenoid
coupling mechanism
magnetic core
double
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CN115441593B (en
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吴晓锐
孙跃
李小飞
肖静
陈绍南
左月
周远钊
韩帅
莫宇鸿
吴宁
龚文兰
陈卫东
郭敏
郭小璇
唐春森
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Chongqing University
Electric Power Research Institute of Guangxi Power Grid Co Ltd
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Electric Power Research Institute of Guangxi Power Grid Co Ltd
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
    • B60L53/10—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles characterised by the energy transfer between the charging station and the vehicle
    • B60L53/12—Inductive energy transfer
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/24—Magnetic cores
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
    • H01F38/14—Inductive couplings
    • 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
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Theoretical Computer Science (AREA)
  • Physics & Mathematics (AREA)
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  • General Physics & Mathematics (AREA)
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Abstract

The invention relates to the technical field of wireless power transmission, and particularly discloses a double-solenoid type coupling mechanism and a parameter design method thereof. The invention ensures that the transmission power of the system has good stability when large-range deviation occurs, and improves the deviation resistance of the system. By matching with a corresponding parameter design method, the transverse anti-offset capability of the magnetic coupling mechanism can be exerted to a higher level. Further, the multi-section double-solenoid type transmitting guide rail is applied to dynamic wireless charging, and no obvious power drop exists in a guide rail switching domain.

Description

Double-solenoid type coupling mechanism and parameter design method thereof
Technical Field
The invention relates to the technical field of wireless power transmission, in particular to a double-solenoid type coupling mechanism and a parameter design method thereof.
Background
Wireless Power Transfer (WPT) technology can complete contactless Power Transfer between an electric device and a Power supply facility without depending on physical carriers such as plugs, wires and the like, thereby greatly increasing the safety and reliability of Power Transfer. Wireless Power transmission has various transmission modes, which can be roughly classified into microwave mode, laser mode, magnetic field Coupling mode, electric field Coupling mode, etc., wherein the Magnetic Coupling based Wireless Power transmission (MC-WPT) technology is the technology that is most developed and widely applied in the WPT field, and has the advantages of simple system structure, long transmission distance, high transmission Power and efficiency, etc. The WPT technology is one of ten new technologies which have the greatest influence on the world, provides an optimal solution for the technical bottlenecks of various industries, provides a new solution for global energy challenges, and further promotes the rapid development of related industries.
The traditional electric energy supply mode of an Electric Vehicle (EV) adopts a wired charging mode, the charging process of the EV needs to be completed under the cooperation of people, and meanwhile, the safety and reliability of power supply of equipment are greatly reduced due to inevitable system line aging, short circuit risk during charging in rainy days and the like. The MC-WPT technology can well solve the problems, and is widely researched and applied in recent years. When the MC-WPT technology is applied to the field of electric automobiles, the MC-WPT technology can be mainly divided into two modes of static Wireless Power transmission and dynamic Wireless Power transmission, wherein the static Wireless Power transmission (EV-SWPT) means that electric automobiles are supplied with electric energy when parked in parking spaces or special parking stations, and the electric automobiles are relatively static in the whole charging process; and the electric automobile Dynamic Wireless Power Transfer (EV-DWPT) is wirelessly charged in the driving process of the electric automobile, and the electric automobile does not need to carry a large-capacity energy storage battery in the mode, so that the whole automobile space is saved, and the automobile weight and the automobile cost can be reduced.
The power supply guide rail of the EV-DWPT system has two modes of long guide rail power supply and distributed short guide rail power supply. The long guide rail mode system is generally composed of a set of primary side electric energy conversion device, a long guide rail, an energy receiving coil and a secondary side electric energy conversion device, and is simple in structure and control strategy and low in engineering construction cost. However, the length of the guide rail is generally tens of meters, the equivalent Series impedance (ESR) of the guide rail is very large, and a large magnetic flux leakage condition exists in a road section where no vehicle runs, so that the system coupling coefficient and the transmission efficiency are reduced, serious electromagnetic pollution is caused, and the harm is brought to the health of pedestrians and animals and plants on the road. In practical engineering application, an EV-DWPT system usually adopts a distributed short-rail power supply mode, which is different from a long-rail power supply mode, a system primary side is composed of a plurality of sets of primary-side electric energy conversion devices and a plurality of sections of distributed short rails, the working state of each section of rail is controlled by a set of independent electric energy conversion device, when a vehicle runs above a certain section of rail, the corresponding section or sections of short rails are started to work, and other rails are in a dormant or standby state. The coupling coefficient and the system transmission efficiency of the distributed short guide rail power supply mode are high, the electromagnetic radiation is small, but the engineering construction cost is high, and in addition, the switching control method of the distributed short guide rail is relatively more complex. More importantly, the distributed short guide rails have serious mutual inductance drop in the guide rail switching domain, so that the drop of transmission power is caused, the efficient and reliable electric energy supply of the electric automobile in the driving process is not facilitated, and the service life of a vehicle-mounted battery is seriously influenced.
Relevant scholars and teams at home and abroad carry out a great deal of research on the dynamic wireless power supply of the electric automobile with the distributed short guide rails, but the following problems still exist: firstly, the extra detection circuit and control circuit increase the complexity of the system; secondly, a complex control strategy is difficult to meet the control requirement of the EV-DWPT system in high-speed motion; thirdly, the EV-DWPT system with multiple channels can generate cross coupling when the system is laterally offset, so that the system is detuned and cannot work normally.
Disclosure of Invention
The invention provides a double-solenoid type coupling mechanism and a parameter design method thereof, and solves the technical problems that: how to design a magnetic coupling mechanism with stronger anti-offset capability.
In order to solve the technical problems, the invention provides a double-solenoid type coupling mechanism, which comprises a transmitting structure and a receiving structure, wherein the transmitting mechanism comprises a double-solenoid type transmitting guide rail, the double-solenoid type transmitting guide rail comprises a square tubular magnetic core vertical to a road surface, and an internal energy transmitting solenoid and an external energy transmitting solenoid which are respectively wound on the inner wall and the outer wall of the square tubular magnetic core in a solenoid type, and the internal energy transmitting solenoid and the external energy transmitting solenoid are wound by using the same litz wire and have opposite winding directions;
the receiving structure comprises a pickup coil, a receiving end magnetic core and a metal shielding plate which are arranged in a hierarchical mode, and the pickup coil is of a square annular structure.
Preferably, the square tubular magnetic core comprises an inner layer square tubular magnetic core, a middle layer square tubular magnetic core and an outer layer square tubular magnetic core which are separated, the inner energy emission solenoid is wound on the inner wall of the inner layer square tubular magnetic core, and the outer energy emission solenoid is wound on the outer wall of the outer layer square tubular magnetic core.
Preferably, a central position of the receiving-end magnetic core is provided with a square protrusion, and the square protrusion is embedded with a square gap in the center of the pickup coil.
Preferably, the double-solenoid type launching guide rails are arranged in a plurality and are arranged at equal intervals along the road direction.
Preferably, the inner energy emitting solenoid, the outer energy emitting solenoid emitting coil and the pick-up coil are all wound by litz wires with 0.1mm × 1000 strands and 5mm outer diameter.
Preferably, the square tubular magnetic core and the receiving end magnetic core are made of manganese zinc ferrite made of PC95 materials.
The invention also provides a parameter design method of the double-solenoid type coupling mechanism, and the number of turns of the external energy transmitting solenoid is recorded as n 1 The number of turns of the pick-up coil is n 2 Determining n by 1 、n 2 ：
A1, target mutual inductance value M of given design min A transmission distance h;
a2, determining n by combining the sizes of the outer layer square tubular magnetic core and the receiving end magnetic core 1 Maximum value of (n) 1 ) max 、n 2 Maximum value of (n) 2 ) max ；
A3, order n 1 ＝n 2 =1, calculating the mutual inductance M of the magnetic coupling mechanism by means of COMSOL finite element simulation software;
a4, judging whether M is larger than M min If yes, recording the current n 1 、n 2 If not, entering the next step;
A5、n 2 plus 1, i.e. n 2 ＝n 2 +1；
A6, judging the current n 2 Whether or not greater than (n) 2 ) max If not, returning to the step A4, and if so, entering the next step;
a7, order n 2 ＝1，n 1 Plus 1, i.e. n 1 ＝n 1 +1；
A8, judging the current n 1 Whether or not greater than (n) 1 ) max Otherwise, returning to the step A4, if so, failing to design.
Further, after n is determined 1 、n 2 Thereafter, the coil size of the internal energy emitting solenoid is determined by:
b1, setting the number of turns of a coil in a transmitting guide rail and the maximum dropping delta M of mutual inductance when the coil is deviated according to the power grade of a system max Giving a coilA size initial value;
b2, simulating the anti-offset characteristic of the system;
b3, analyzing whether the mutual inductance falling delta M is smaller than delta M or not during deviation max If yes, recording the current coil size, otherwise, adjusting the coil size and returning to the step B2.
The invention provides a magnetic coupling mechanism with a double-solenoid structure and a parameter design method thereof.A transmitting mechanism adopts a double-solenoid transmitting guide rail and comprises an internal energy transmitting solenoid and an external energy transmitting solenoid which are wound on the inner wall and the outer wall of a square tubular magnetic core in a solenoid way. By matching with a corresponding parameter design method, the transverse anti-offset capability of the magnetic coupling mechanism can be exerted to a higher level. Further, the multi-section double-solenoid type transmitting guide rail is applied to dynamic wireless charging, no obvious power drop exists in a guide rail switching domain, and the stability of output power in the dynamic charging process is realized.
Drawings
FIG. 1 is a schematic diagram of a launch EV-DWPT system provided by an embodiment of the present invention;
FIG. 2 is a voltage-mode full-bridge inverter topology according to an embodiment of the present invention;
FIG. 3 is a circuit topology diagram of a T-type resonance compensation network provided by an embodiment of the invention;
FIG. 4 is a diagram of a mutual inductance model of a magnetic coupling mechanism of a single-launch EV-DWPT system according to an embodiment of the present invention;
FIG. 5 is a decoupling equivalent circuit diagram of a magnetic coupling mechanism provided by an embodiment of the invention;
FIG. 6 is an overall structure diagram of a distributed short-guideway EV-DWPT system provided by an embodiment of the present invention;
FIG. 7 is a logic diagram of a rail switch sequence provided by an embodiment of the present invention;
FIG. 8 is a schematic diagram of a planar rectangular magnetic coupling mechanism provided by an embodiment of the present invention;
FIG. 9 is a schematic diagram of a rectangular coordinate system of a coil of a dual-emitting magnetic coupling mechanism according to an embodiment of the present invention;
FIG. 10 is a diagram illustrating the trend of mutual inductance fluctuation of a system according to an embodiment of the present invention;
FIG. 11 is a schematic view of a double solenoid type magnetic coupling mechanism provided by an embodiment of the present invention;
FIG. 12 is a block diagram of a planar rectangular magnetic coupling mechanism provided by an embodiment of the present invention;
FIG. 13 is a cloud of magnetic field distributions for a planar rectangular magnetic coupling mechanism according to an embodiment of the present invention;
FIG. 14 is a magnetic field distribution cloud diagram of a double-solenoid coupling mechanism according to an embodiment of the present invention;
FIG. 15 is a graph illustrating the variation in mutual inductance between two coupling mechanisms provided by an embodiment of the present invention;
FIG. 16 is a y-z cross-sectional self-coupling region and mutual-coupling region layout provided by an embodiment of the present invention;
FIG. 17 is a y-z sectional equivalent magnetic circuit model diagram provided in the embodiment of the present invention;
FIG. 18 is a flow chart illustrating design optimization of a magnetic core structure according to an embodiment of the present invention;
FIG. 19 is a block diagram of a magnetic coupling mechanism having an optimized magnetic core according to an embodiment of the present invention;
FIG. 20 is a graph comparing coupling coefficients for two core configurations provided by embodiments of the present invention;
FIG. 21 is a flow chart of an optimized design of a coil according to an embodiment of the present invention;
FIG. 22 is a graph of mutual inductance versus number of coil turns provided by an embodiment of the present invention;
FIG. 23 is a graph of coupling coefficient versus number of coil turns provided by an embodiment of the present invention;
FIG. 24 is a graph illustrating the variation of mutual inductance at different widths L according to an embodiment of the present invention;
figure 25 is a three-dimensional graph of mutual inductance for two magnetic coupling mechanisms provided by embodiments of the present invention.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, which are given solely for the purpose of illustration and are not to be construed as limitations of the invention, including the drawings which are incorporated herein by reference and for illustration only and are not to be construed as limitations of the invention, since many variations thereof are possible without departing from the spirit and scope of the invention.
This embodiment will be described by taking an EV-DWPT system as an example.
The EV-DWPT system mainly comprises an AC/DC converter, a DC/DC converter, a high-frequency inverter, a resonance compensation network, a magnetic coupling mechanism, a rectification filter circuit and the like, and is shown in figure 1. The power frequency alternating current of the power grid is sent into a high-frequency inverter after being rectified and filtered by an AC/DC converter and boosted and converted by a DC/DC converter, high-frequency inverter voltage with specific frequency is generated and acts on a resonance compensation network and a transmitting guide rail to generate a high-frequency alternating magnetic field with the same frequency, an energy pickup coil is arranged in the high-frequency alternating magnetic field to generate high-frequency induced current, and the high-frequency induced current is converted into direct current voltage and current required by charging of the electric automobile through a series of electric energy conversion links such as resonance compensation, rectification and filtering and the like to charge a vehicle-mounted battery pack of the electric automobile, so that wireless transmission of electric energy is realized. The design of the invention adopts the direct current power supply as the input of the high-frequency inverter, omits an AC/DC converter and a DC/DC converter, and simplifies the system model. Several key elements of the high frequency inverter, the resonance compensation network, and the magnetic coupling mechanism will be described below.
The EV-DWPT system based on the magnetic coupling resonance mode has the advantages of large system power density, long energy transmission distance, high overall efficiency and the like. In order to make the EV-DWPT system in a resonance state and raise the power factor of the system, the self-inductance of the coupling coil is generally compensated by using series-parallel capacitors, and the value of the compensation capacitor can be determined by formula (0.1).
ω 2 LC＝1(0.1)
In order to reduce the volume of the resonant element, the value of the compensation capacitor should be as small as possible while ensuring the resonance of the system. It can be seen from the formula (0.1) that the higher the system operating frequency is, the smaller the value of the compensation capacitor C is when the resonant state is reached under the same condition, so that the energy transmission level and the power density of the system can be improved by increasing the system operating frequency, and therefore, the high-frequency inverter circuit is very important for the EV-DWPT system.
The circuit topology of the high-frequency inverter circuit has various forms, wherein the voltage type full-bridge inverter circuit overcomes the defects of a half-bridge type inverter circuit and a push-pull type inverter circuit, and has the advantages of simple structure, strong output capacity, high power density, high transmission efficiency, simple control strategy and the like, so the EV-DWPT system designed by the method adopts the voltage type full-bridge inverter circuit, and is shown in figure 2, by considering the aspects of circuit complexity, input and output voltage level, power capacity requirement and the like of the EV-DWPT system. The voltage type full-bridge high-frequency inverter circuit consists of a voltage-stabilizing capacitor and four switching tubes which are connected in parallel, wherein every two of the four switching tubes are combined to form a bridge structure of the inverter circuit, and S 1 、S 3 Form a set of bridge arms, S 2 、S 4 And another group of bridge arms is formed, and the switching tubes on the same bridge arm are alternately and complementarily conducted, so that the system short circuit is avoided. The switching tube usually adopts a MOSFET with high switching speed, small conduction loss and high power grade, and the switching tube is controlled to be switched on and off by a driving signal so as to realize the conversion from direct current to high-frequency alternating current.
In an EV-DWPT system, a large air gap exists between a transmitting guide rail and a pickup coil of a magnetic coupling mechanism, the system is in a loose coupling state, and the transmitting guide rail is inductive, so that a resonance compensation link needs to be added. The resonance compensation network is an important ring formed by the wireless power transmission system, and the characteristics of the resonance compensation network have important influence on the overall performance of the system. The resonance compensation network in the system is generally composed of compensation inductance and capacitance, and mainly has the following basic functions: (1) a system resonance loop is formed, the equivalent impedance of the system is reduced, and a magnetic field with high-frequency change is generated; (2) the self-inductance of the transmitting guide rail is compensated, the reactive power of the system is reduced, and the power factor of the system and the grade and efficiency of power transmission are improved; (3) higher harmonics in the inverted voltage are filtered, soft switching is facilitated, and electromagnetic interference of the system is reduced. The most basic resonance compensation topology of the WPT system comprises two types of series compensation (S) and parallel compensation (P), and four basic compensation structures can be obtained through different combinations of the two types of compensation at two ends of a transmitting guide rail and a pick-up coil: the resonance conditions and output characteristics of the four resonance compensation networks, series-series (SS), parallel-series (PS), series-parallel (SP), and parallel-parallel (PP), are shown in table 1.
TABLE 1 resonance condition and output characteristics of four basic compensation structures
Figure BDA0003754593030000071
As can be seen from Table 1, the compensation capacitor C of the SS topology among the four compensation topologies s Only with omega and L p Related to, and compensation capacitance C of PS, SP, PP topology s Except for the sum of ω and L p In addition, M, L s And R L It is related. In EV-DWPT system applications, the energy pick-up coil at the bottom of the vehicle is offset from (i.e., changes relative position to) the single transmit rail, so the mutual inductance M varies with vehicle position. Capacitance values of SP, PP and PS in topological resonance states can change along with changes of M, so that the EV-DWPT system can be in a detuning state in the running process of a vehicle, the energy efficiency characteristic of the system is greatly reduced, and the PS, SP and PP topologies are not suitable for the EV-DWPT system. In addition, the change of the secondary side impedance of the SS topology has obvious influence on the primary side current, and the primary side short circuit can be caused under the no-load condition, so that an inverter and other devices are damaged, and the SS structure is not suitable for an EV-DWPT system.
Besides the four basic compensation structures, the resonance compensation network also comprises composite compensation networks such as LCL (lower control limit) and LCC (lower control limit). The LCC is an optimized form of the LCL compensation network, the parameter design of the compensation network is more flexible by adding a compensation capacitor, and the LCC has wider application scenes. The LCC resonance compensation network is analyzed by adopting a T-shaped network, and the equivalent circuit topology is shown in figure 3.
The left bridge arm and the right bridge arm of the T-shaped network are inductive, the impedance is jX, the lower bridge arm perpendicular to the two inductive bridge arms is capacitive, the impedance is-jX, and the left bridge arm, the right bridge arm and the lower bridge arm are in a resonance state. If the impedance of the load is known as Z o The equivalent impedance Z of the T-network i Comprises the following steps:
Figure BDA0003754593030000081
when the input is known as U i Then, the current flows through the resistor Z o Current of (I) o Comprises the following steps:
Figure BDA0003754593030000082
from the formula (0.3), it can be seen that when the LCC resonance compensation topology is used for primary side resonance compensation, the current of the transmission guide rail is only equal to the input voltage U i The system is related to compensation inductance, is unrelated to mutual inductance M, has the characteristic of constant current, cannot be influenced by a secondary side pickup coil, ensures that the system has good stability, and is suitable for an EV-DWPT system with frequent switching control of a guide rail. When the LCC resonance compensation topology is used for secondary side resonance compensation, the system output also has constant current characteristics, and the output power can be adjusted by matching with a vehicle Battery Management System (BMS). Therefore, the EV-DWPT system designed by the method adopts an LCC-LCC resonance compensation topology.
The electromagnetic coupling mechanism is a core component of the EV-DWPT system, and the shape structure, the winding mode and the energy efficiency characteristic of the electromagnetic coupling mechanism are important contents of the research and design of the EV-DWPT system. The mutual inductance equivalent model of the single-emission EV-DWPT system is shown in FIG. 4, where u 1 For transmitting the input voltage of the rail, i p For transmitting coil current of guide rail u 2 For the output voltage of the energy pick-up coil, i s To pick up the induced current of the coil, L p 、L s Respectively the self-inductance of the emitting rail and the energy pick-up coil.
The transmitting guide rail generates a high-frequency alternating magnetic field under the action of high-frequency inversion voltage, and the energy pickup coil is arranged in the high-frequency alternating magnetic field to generate induced electromotive force u s And simultaneously, induced electromotive force u is also generated in the primary transmission guide rail p The decoupling equivalent circuit of the electromagnetic coupling mechanism is shown in fig. 5, in which the self-inductance and resistance value of the transmission rail is L p 、R p Indicating the self-inductance and resistance of the energy-receiving coil by L s 、R s Express, equivalentR for load L And (4) showing.
Induced electromotive force u of primary transmission guide rail p Comprises the following steps:
u p ＝jωMi s (0.4)
induced electromotive force u of energy pickup line s Comprises the following steps:
u s ＝jωMi p (0.5)
according to kirchhoff's law, the equivalent circuit of the magnetic coupling mechanism can be represented by the following equation:
Figure BDA0003754593030000091
let the input impedance of the energy pick-up end be Z s And then:
Figure BDA0003754593030000092
then the equivalent reflected impedance Z from the energy pick-up to the primary transmission rail r Comprises the following steps:
Figure BDA0003754593030000093
therefore, the transmission power P of the electromagnetic coupling mechanism of the EV-DWPT system is as follows:
Figure BDA0003754593030000094
according to the formula (0.9), the transmission power of the electromagnetic coupling mechanism, the angular frequency omega of the system work, the mutual inductance M and the primary side emission guide rail current i p Internal resistance R of energy receiving coil s Energy receiving coil self-inductance L s And an equivalent load R L It is relevant. Where the angular frequency ω of system operation affects the system tuning, L s 、R s Determined by the pickup coil structure and the number of turns of the winding, i p The wire diameter should not be too large and will increase the system loss when it is increased,equivalent load R L Depending on the equivalent internal resistance of the on-board battery, the optimal way to raise the power transmission level of the electromagnetic coupling mechanism is to increase the mutual inductance M. In addition, the angular frequency omega of the system and the internal resistance R of the coil in the running process of the electric automobile s Coil self-inductance L s And an equivalent load R L Remains unchanged, emits a guide rail current i p From the formula (0.3), it is known that the EV-DWPT system has a constant current characteristic, and therefore, the stability of the transmission power of the EV-DWPT system depends on whether the mutual inductance M is stable.
The EV-DWPT system based on the distributed short guide rail adopts a multi-emission parallel structure, in order to reduce the system construction cost and reduce the number of inverters, a mode that two groups of resonance compensation networks and guide rails are driven by the same inverter is adopted in the design, and the overall structure of the EV-DWPT system is shown in fig. 6. It should be noted that, due to the limitation of the highest operating frequency of the electronic switching device, the switching speed of the guideway can only reach the level of μ s, and considering that the detection of the vehicle position and the control of the guideway switching require a certain response time, the length of the transmitting guideway should be much longer than that of the pickup coil.
From the foregoing analysis, it can be seen that the output power of the system is closely related to the mutual inductance M. In order to obtain stable mutual inductance M, ensure that an electric automobile continuously and stably picks up electric energy in the driving process, reduce the overall loss of a system and reduce electromagnetic radiation, sectional time-sharing switching control must be carried out on the states of guide rails according to the positions of pickup coils, namely, one group or a few groups of guide rails positioned below the electric automobile at a certain moment are ensured to be in an open state, and the rest guide rails are in a standby state. The specific switching control sequence is shown in fig. 7:
the area directly above the rails is defined herein as the center area of the rails, and the transition area between the rails is defined as the rail switch area. The working mode of the guide rail switching can be divided into the following 4 stages according to time:
stage 1: at the present moment, the electric automobile is in an nth section of guide rail charging area, the inverter with the number of n controls the corresponding guide rail to start to work, the rest guide rails are in standby, and the pickup coil is powered by the transmitting guide rail n;
and (2) stage: the electric automobile is about to enter a (n + 1) th section guide rail charging area, an inverter with the number of (n + 1) receives a vehicle position detection signal to start working, at the moment, a pickup coil is still positioned in the area where the transmitting guide rail n is positioned, and the transmitting guide rail n provides electric energy;
and (3) stage: at the moment, the magnetic field of the guide rail (n + 1) is completely established, the electric automobile runs to the switching area of the guide rail n and the guide rail (n + 1), and the pick-up coil is powered by the transmitting guide rail n and the transmitting guide rail (n + 1) together;
and (4) stage: when the electric automobile exits from the guide rail n, the inverter with the number n receives a vehicle exiting signal, the state of the corresponding guide rail is switched to standby, and the pick-up coil is powered by the transmitting guide rail (n + 1).
By analogy, the corresponding transmitting guide rail is controlled to be opened and closed according to the real-time position of the electric automobile, a magnetic field is established before the automobile enters the next section of transmitting guide rail, the stability of the mutual inductance M is maintained to the maximum extent, the electric automobile is ensured to continuously and stably pick up electric energy in the driving process, the influence of electromagnetic radiation on the surrounding environment is reduced, and the overall efficiency of the system is improved.
The analysis shows that the segmented time-sharing switching control is carried out on the states of the transmitting guide rails, so that the energy can be provided by the adjacent multiple sections of transmitting guide rails when the pickup coils are positioned in the guide rail switching domain, and the stability of system power transmission is improved to a certain extent. It has been found that when the relative position of the energy pick-up coil and the transmitting guide rail is changed, the mutual inductance of the rectangular coil is more stable than that of the circular coil structure, and the system transmission power is also more stable, i.e. the magnetic coupling mechanism with the rectangular-rectangular structure is more advantageous in terms of output stability, so the coil of the magnetic coupling mechanism of the EV-DWPT system usually adopts a planar rectangular structure, as shown in fig. 8.
Because the length of the transmitting guide rail is far longer than that of the energy pickup coil, the pickup coil is coupled with at most two transmitting guide rails in the running process of the electric automobile, so that the mutual inductance change rule of the pickup coil at different positions of the guide rails is researched by taking the double-transmitting magnetic coupling mechanism as a minimum unit, and a rectangular coordinate system of the coil of the double-transmitting EV-DWPT system magnetic coupling mechanism is established as shown in fig. 9.
Hypothesis transmit guideThe length of the coil at the outermost part of the rail is L, the width of the coil is W, and the number of turns of the coil is N 1 (ii) a The length of the outermost coil of the pick-up coil is l, the width of the outermost coil is w, and the number of turns of the outermost coil of the pick-up coil is N 2 And the turn-to-turn distance of each coil is d. Establishing a space rectangular coordinate system by taking the middle position of the two emitting guide rails (namely the centers of the guide rail switching domains) as an original point O, and assuming that the center coordinate of the pickup coil at the moment is O', the emitting guide rail 1 is the ith (i =1,2, …, N) from outside to inside 1 ) The vertexes of the turn coils are respectively A i 、B i 、C i 、D i The emitting guide rail 2 is the ith (i =1,2, …, N) from outside to inside 1 ) The apexes of the turns are E i 、F i 、G i 、H i The j (j =1,2, …, N) of the pickup coil from the outside to the inside 2 ) The vertexes of the turn coils are respectively a i 、b i 、c i 、d i The coordinates of the various vertices of the emitting guideway 1 can then be listed as:
Figure BDA0003754593030000111
similarly, the coordinates of each vertex of the launching guide rail 2 are:
Figure BDA0003754593030000121
assuming that the coordinates of the center position of the pickup coil are O' (x, y, z), a i 、b i 、c i 、d i Can be expressed as:
Figure BDA0003754593030000122
given the respective vertex coordinates in equations (0.10), (0.11), the loops of the ith turn of the emitter rail 1 and emitter rail 2 can be respectively denoted as l p1 (i)、l p2 (i)：
Figure BDA0003754593030000123
Figure BDA0003754593030000124
The j-th loop/of the pick-up coil is known for each vertex coordinate in equation (0.12) s (j) Can be expressed as:
Figure BDA0003754593030000125
according to the calculation formula of the Noumann mutual inductance, the ith turn loop l of the transmitting guide rail 1 and the transmitting guide rail 2 p1 (i)、l p2 (i) Loop of j turn with pick-up coil s (j) The mutual inductance between them is:
Figure BDA0003754593030000126
Figure BDA0003754593030000127
in the formula of 0 ＝4π×10 -7 N/A 2 Is a vacuum permeability, mu r For relative permeability, R ij Loop of loop i for transmitting guide rail p1 (i)、l p2 (i) And j loop of pick-up coil s (j) The infinitesimal distance of (1). The mutual inductance of the transmitting guide rail 1 and the transmitting guide rail 2 and the pickup coil can be respectively expressed as follows:
Figure BDA0003754593030000128
Figure BDA0003754593030000131
therefore, the total mutual inductance M of the magnetic coupling mechanism of the dual-emission EV-DWPT system can be expressed as follows:
M＝M 1 +M 2 (0.20)
taking the length of the transmitting guide rail as 0.6m, the width as 0.25m, the number of turns as 8 turns, the length of the energy pickup coil as 0.3m, the width as 0.3m, the number of turns as 15 turns and the coupling distance as 0.1m as an example, the system mutual inductance characteristic of the planar rectangular magnetic coupling mechanism is researched, and the mutual inductance change rule between the energy pickup coil and the primary transmitting guide rail in the driving process of the electric automobile is mainly considered. Defining the running direction of the electric automobile as an x direction, the transverse deviation direction as a y direction, introducing high-frequency alternating current with the same frequency, the same phase and the same amplitude into the two energy transmitting guide rails at the same moment, moving the energy pickup coil from the center dead-center position (x = -0.325) of one transmitting guide rail to the center dead-center position (x = 0.325) of the next transmitting guide rail along the x direction, and obtaining the mutual inductance M between the transmitting guide rails 1 and 2 at different positions and the energy pickup coil through calculation 1 、M 2 And the sum M of the mutual inductance between the two transmitting guide rails and the energy pickup coil, and drawing the mutual inductance M 1 、M 2 And M as the energy pick-up coil moves in the x direction is shown in FIG. 10 (a) (where the line starting point is M at the highest 1 )。
As can be seen from fig. 10 (a), when the coupling distance is constant, the mutual inductance M is generated during the process that the energy pick-up coil moves from the center of the transmission rail 1 to the center of the transmission rail 2 1 Gradually decreasing, mutual inductance M 2 The mutual inductance M gradually increases, and the mutual inductance M is gradually decreased and then increased, is maximum when being positioned above the center of the transmitting guide rail, is minimum in the switching domain of the transmitting guide rail, and is symmetrically distributed by taking the switching domain of the guide rail as the axial center, and the result shows that the mutual inductance of the system in the switching domain of the guide rail obviously falls. Further, in the actual running process of the electric vehicle, the lateral shift inevitably occurs due to environmental and human factors, and a curve for fitting the mutual inductance M when the pickup coil is laterally shifted over the center of the transmission rail is plotted by calculation as shown in (b) of fig. 10. As can be seen from the figure, the mutual inductance M gradually decreases with the left-right offset of the pickup coil, and the mutual inductance M of the magnetic coupling mechanism is maximized at the position directly opposite to the center of the transmission rail.
Therefore, when the relative position of the energy pick-up coil and the transmitting guide rail is changed, the mutual inductance of the planar rectangular magnetic coupling mechanism obviously fluctuates, and particularly, when the guide rail switching domain and the large-range transverse offset occur, the mutual inductance greatly falls. It should be noted that, in order to enhance the magnitude of the mutual inductance, a ferrite core is usually added to the magnetic coupling mechanism, and the mutual inductance variation rule of the system after the magnetic core is added is consistent with the above analysis, and serious mutual inductance drop occurs in the switching region of the guide rail and when a large offset occurs. In conclusion, mutual inductance fluctuation of the EV-DWPT system in the dynamic operation process causes the fluctuation of the output power of the system. The magnitude of the mutual inductance depends on the geometry, size, turns, coupling distance of the electromagnetic coupling mechanism and magnetic field distribution around the pickup coil under the action of the magnetic core, and in order to maintain the stability of the mutual inductance in the dynamic operation process of the system and improve the stability of output power in the dynamic operation process of the EV-DWPT system, a magnetic coupling mechanism with a double-solenoid structure is proposed, and a schematic diagram of the magnetic coupling mechanism is shown in fig. 11. The magnetic coupling mechanism comprises a transmitting structure and a receiving structure, wherein the transmitting mechanism comprises a plurality of double-solenoid transmitting guide rails which are arranged at equal intervals along the road direction, each double-solenoid transmitting guide rail comprises a square tubular magnetic core perpendicular to the road surface, an inner energy transmitting solenoid (an energy transmitting solenoid 2) and an outer energy transmitting solenoid (an energy transmitting solenoid 1) which are respectively wound on the inner wall and the outer wall of the square tubular magnetic core in a spiral mode, and the inner energy transmitting solenoid and the outer energy transmitting solenoid are wound by using the same litz wire and are opposite in winding direction. The receiving structure comprises an energy pickup coil, a receiving end magnetic core and a metal shielding plate (aluminum plate), wherein the energy pickup coil, the receiving end magnetic core and the metal shielding plate are arranged in a hierarchical mode, and the pickup coil is of a square annular structure.
For a magnetic field coupling wireless power transmission system, the higher the working frequency is in a certain range, the higher the power transmission grade and efficiency of a magnetic coupling mechanism is, but the larger the system loss caused by skin effect and proximity effect generated by a high-frequency alternating magnetic field is, the more serious the heating of a lead can cause the melting of an insulating layer of the lead, and the dangers of ignition, short circuit, fire and the like are caused. The magnitude of the skin effect is expressed in terms of skin depth δ, i.e.:
Figure BDA0003754593030000141
where ρ represents the resistivity of the conductor, and the value thereof at room temperature is 1.72 × 10 -8 Omega.m; f represents the frequency of the current flowing through the coil in Hz; mu.s o Is the magnetic permeability in vacuum, the value is 4 pi multiplied by 10 -7 H/m；μ r The relative permeability of the copper wire is 1. As can be seen from the equation (0.21), the skin effect is stronger as the skin depth δ is smaller as the frequency is increased, and table 2 shows the skin depth values of copper at different frequencies.
TABLE 2 skin depth values of copper at different frequencies
Figure BDA0003754593030000142
Figure BDA0003754593030000151
The wireless power transmission system usually works in a high-frequency state, and in order to reduce the negative influence of the skin effect on the system, the magnetic coupling mechanism must select litz wires as coil materials. The EV-DWPT system designed by the method adopts the working frequency of 85kHz, and determines to select litz wires with the single wire diameter of 0.1mm as the coil material by combining with the common litz wire specification on the market. In addition, the rated current value of the litz wire is also an important parameter for type selection, and the following table 3 gives the corresponding relationship between different specifications of the litz wire and the current resistance value thereof. The current endurance capacity of the litz wire is comprehensively considered, and the transmitting coil and the pick-up coil are wound by 0.1mm 1000 strands of litz wires with the specification of 5mm of outer diameter.
TABLE 3 reference specification table for litz wire selection
Figure BDA0003754593030000152
In order to increase the coupling coefficient of the system and reduce the magnetic leakage of the coupling mechanism, a magnetic core is usually required to be added to the magnetic coupling mechanism. The ferrite magnetic core is mostly applied to a wireless power transmission system and mainly comprises a manganese zinc base material and a nickel zinc base material, the manganese zinc base ferrite has high magnetic conductivity and saturation magnetic flux density, the magnetic core loss is low when the frequency is less than 1MHz, and compared with the nickel zinc base ferrite, the ferrite magnetic core is more suitable for the wireless power transmission system. The manganese-zinc-based ferrite magnetic core applied to high-power occasions mainly comprises types of PE22, PC40, PC95 and the like, the material characteristics of the magnetic cores of the three types are listed in Table 4, the parameters of magnetic core loss, magnetic conductivity, saturation magnetic flux density and the like are comprehensively considered, and the manganese-zinc-based ferrite made of the PC95 material is selected as the magnetic core material in the design.
TABLE 4 Material Properties of three types of magnetic cores
Figure BDA0003754593030000153
In EV-DWPT systems, the magnetic coupling mechanism often adopts a planar rectangular structure, as shown in fig. 12. The structure has the advantages of high coupling coefficient, long transmission distance and the like, but the analysis in the previous chapter shows that the transmission power of the pickup coil obviously drops when the guide rail switches over a domain and generates transverse offset.
In order to stabilize the output power of the electric automobile in the rail switching domain and improve the anti-offset capability of the system, the structure of the magnetic coupling mechanism is optimally designed. Since the energy pick-up coil of the EV-DWPT system is usually installed at the bottom of the car, the size and weight of the energy pick-up coil are severely limited, and especially, the thickness of the energy pick-up coil should be as thin as possible, the energy pick-up coil still adopts a planar rectangular structure, and the focus of the research is the transmitting end guide rail structure.
The double solenoid type emitter end guide structure proposed herein is shown in fig. 13. The structure is different from a coil structure of a planar rectangular transmitting guide rail, is similar to a solenoid winding mode, the coil is wound on a magnetic core in a spiral upward mode, an inner coil and an outer coil are wound by a litz wire, and the winding directions of the inner coil and the outer coil are opposite. The double-solenoid type transmitting guide rail changes the magnetic field distribution of the planar rectangular transmitting guide rail, so that the transmission power of the coupling mechanism has good stability when the pickup coil is in a guide rail switching domain and generates large-range transverse deviation. Simulation models of the double-emitting-plane rectangular coupling mechanism and the double-solenoid type coupling mechanism are set up by utilizing COMSOL finite element simulation software to analyze the mutual inductance fluctuation trend of the coupling mechanism, and the parameters of the simulated coupling mechanism are shown in a table 5.
Table 5 two kinds of guide rail structure simulation parameter table
Figure BDA0003754593030000161
Fig. 13 and 14 are respectively magnetic field distribution cloud charts of two coupling mechanisms, it can be seen by comparison that in the traveling direction of the electric vehicle, i.e. the x direction, the magnetic field strength of the planar rectangular coupling mechanism is obviously weakened in the guide rail switching region, so as to cause mutual inductance drop, while the magnetic field strength of the double-solenoid type coupling mechanism is uniformly distributed in the x direction, and no obvious mutual inductance drop region exists; in the transverse deviation direction, namely the y direction, the magnetic field intensity of the planar rectangular coupling mechanism is strong in the center area of the transmitting guide rail, the magnetic field intensity on two sides is gradually weakened, the magnetic field intensity of the double-solenoid type coupling mechanism is weak in the center area of the transmitting guide rail, the magnetic field intensity on two sides is strong, the mutual inductance falling of the double-solenoid type coupling mechanism is slow when the electric automobile is subjected to transverse deviation, and the deviation resistance performance is better. The mutual inductance changes in the x-direction and the y-direction of the planar rectangular coupling mechanism and the double solenoid type coupling mechanism are plotted as shown in fig. 15.
Comparing the mutual inductance change of the two coupling mechanisms in different directions in fig. 15, it can be found that the mutual inductance of the planar rectangular coupling mechanism at the position opposite to the transmitting guide rail is slightly larger than that of the double-solenoid coupling mechanism, but the mutual inductance stability of the double-solenoid coupling mechanism is obviously better when the guide rail is switched and laterally deviates, the coupling mechanism provided by the invention has better performance in the aspect of power drop resistance, and the coupling mechanism is continuously optimized in the aspects of the magnetic core structure and the number of turns of the coil.
A large air gap exists between a transmitting guide rail and an energy pick-up coil of the wireless power transmission system, and the magnetic coupling mechanism is in a loose coupling state, so that magnetic lines of force of the system not only pass through the inside of the magnetic core, but also must pass through the air gap. The magnetic permeability of the magnetic core is far larger than that of the air gap, and the magnetic field distribution around the magnetic coupling mechanism is qualitatively analyzed by establishing an equivalent magnetic circuit model of the magnetic coupling mechanism, so that the magnetic resistance of a magnetic flux path can be effectively reduced, and the optimal design of the magnetic core is guided. A cross-sectional view in the y-z plane of the coupling mechanism is established when the pick-up coil is located in the central region of the emitter rail as shown in fig. 16.
Neglecting the magnetic resistance of the ferrite magnetic core, the magnetic force lines can be divided into two parts of self-coupling and mutual coupling according to whether the transmitting coil is coupled with the pick-up coil, because the double-solenoid type magnetic coupling mechanism is symmetrically distributed along the central plane of the x direction and the y direction, the magnetic field is also symmetrically distributed along the central axis, the magnetic field characteristics of the system can be analyzed by approximately using the magnetic field distribution of the cross section, and the two-dimensional cross-section magnetic field distribution and the self-coupling and mutual coupling areas of the double-solenoid type magnetic coupling mechanism are shown in fig. 16. Let the magnetic resistances of the self-coupling region 1 and the self-coupling region 2 be R s1 And R s2 The mutual coupling region 1 and the mutual coupling region 2 have magnetic resistances of R m1 And R m2 The system magnetomotive force is F, and an equivalent magnetic circuit model is established as shown in FIG. 17.
Analyzing the equivalent magnetic circuit model of the y-z section by
Figure BDA0003754593030000171
The total magnetic flux on one side of the cross section is shown,
Figure BDA0003754593030000172
the self-coupling and mutual-coupling fluxes at one side of the cross section are respectively shown, and the relationship among the fluxes is as follows:
Figure BDA0003754593030000173
the magnetic circuit expression for the coupling coefficient K can be expressed as:
Figure BDA0003754593030000181
simplifying to obtain:
Figure BDA0003754593030000182
from the formula (0.24), the magnetic resistance R of the mutual coupling region m1 、R m2 The smaller, the reluctance R of the self-coupling region s1 、R s2 The larger the system coupling coefficient K. Therefore, the magnetic resistance of the mutual coupling region can be reduced and the magnetic resistance of the self-coupling region can be increased by changing the shape structure and the position arrangement of the magnetic core, so that the coupling coefficient of the system is improved, and the design flow of the magnetic core structure is shown in fig. 18.
According to the design optimization process of the magnetic core, the magnetic cores on the mutual coupling magnetic circuit are added, the optimized magnetic core structure of the energy pickup mechanism is shown in fig. 19 (a), the designed convex parts of the magnetic cores are designed according to the trend of magnetic lines in fig. 16, the magnetic resistance of the mutual coupling area is reduced by adding the magnetic cores on the mutual coupling magnetic circuit, and the coupling coefficient is improved to a certain extent. In addition, the greater the number of magnetic cores in the magnetic coupling mechanism in a certain range, the stronger the coupling capability of the system. However, the weight and cost of the system are proportional to the number of magnetic cores, and the amount of magnetic cores should be reduced as much as possible while ensuring the power transmission capability of the system, so as to reduce the amount of magnetic cores used for the transmission rail, as shown in fig. 19 (b).
It can be seen that the square tubular magnetic core comprises an inner layer square tubular magnetic core, a middle layer square tubular magnetic core and an outer layer square tubular magnetic core which are separated, the inner energy emission solenoid is wound on the inner wall of the inner layer square tubular magnetic core, and the outer energy emission solenoid is wound on the outer wall of the outer layer square tubular magnetic core;
the central position of the receiving end magnetic core is provided with a square bulge, and the square bulge is embedded with a square gap at the center of the pickup coil.
To verify the above conclusions, the sizes and changes of the coupling coefficients of the system at different positions before and after optimization are compared through COMSOL simulation analysis, the coupling coefficients of the magnetic core before and after optimization are shown in FIG. 20, and the simulation parameters are shown in Table 5.
As can be seen from fig. 20, the coupling coefficient is significantly improved after the optimization of the magnetic core, and the coupling coefficients at different offset distances are all larger than the magnetic core structure before the optimization. The magnetic field distribution of the double-solenoid type coupling mechanism is analyzed, a magnetic circuit expression of the coupling coefficient is deduced by establishing an equivalent magnetic circuit model, and the magnetic core structure is optimally designed, so that the coupling coefficient of the system is effectively improved, and the charging efficiency of the system is further improved.
In practical engineering applications, the size of the electromagnetic coupling mechanism is strictly limited by practical application scenarios, and therefore, after the magnetic core structure and the coil winding shape are determined, the number of turns of the coil needs to be considered in an important manner. Aiming at the proposed double-solenoid type coupling mechanism, the invention also provides a parameter design method of the double-solenoid type coupling mechanism, firstly, on the basis of the given target mutual inductance, the optimal design is carried out on the number of turns of a coil by combining the size of a magnetic core so as to obtain the sufficient mutual inductance M; secondly, the size of the coil in the transmitting guide rail is designed, the stability of mutual inductance M under the conditions of guide rail switching domain and offset is further improved, the specific optimization design flow is shown in figure 21, and the method comprises the following steps:
a1, target mutual inductance value M of given design min A transmission distance h;
a2, determining n by combining the sizes of the outer layer square tubular magnetic core and the receiving end magnetic core 1 Maximum value of (n) 1 ) max 、n 2 Maximum value of (n) 2 ) max ；
A3, making n 1 ＝n 2 =1, calculating the mutual inductance M of the magnetic coupling mechanism by means of COMSOL finite element simulation software;
a4, judging whether M is larger than M min If yes, recording the current n 1 、n 2 If not, entering the next step;
A5、n 2 by addition of 1, i.e. n 2 ＝n 2 +1；
A6, judging the current n 2 Whether or not greater than (n) 2 ) max If not, returning to the step A4, and if so, entering the next step;
a7, order n 2 ＝1，n 1 By addition of 1, i.e. n 1 ＝n 1 +1；
A8, judging the current n 1 Whether or not greater than (n) 1 ) max Otherwise, returning to the step A4, if so, failing to design.
In determining n 1 、n 2 Thereafter, the coil size of the internal energy emitting solenoid is determined by:
b1, setting the number of turns of a coil in a transmitting guide rail and the maximum dropping delta M of mutual inductance when the coil is deviated according to the power grade of a system max Giving an initial value of the coil size;
b2, simulating the anti-offset characteristic of the system;
b3, analyzing whether the falling delta M of mutual inductance is smaller than delta M during deviation max If yes, recording the current coil size, otherwise, adjusting the coil size and returning to the step B2.
According to the calculation formula of the Noeman mutual inductance, the mutual inductance of the coil is in direct proportion to the number of turns. Simulation analysis shows that the mutual inductance of the double-solenoid type magnetic coupling mechanism mainly depends on the number of turns of the outer coil of the transmitting guide rail and the number of turns of the pickup coil, and the number of turns of the inner coil has little influence on the mutual inductance. The main function of the coil in the launching guide rail is to change the direction and distribution of magnetic lines of force, so that the coil has an important influence on the anti-deflection performance of the system. Therefore, the number of turns of the outer coil of the emitting guide rail and the number of turns of the pickup coil are mainly considered when the number of turns of the coil is designed, and when the number of turns of the coil in the emitting guide rail is 0, the change of the mutual inductance M of the system along with the number of turns of the outer coil of the emitting guide rail when the number of turns of the pickup coil is different is shown in fig. 22. Analyzing fig. 22, it can be seen that when the number of turns of the pickup coil is fixed, the mutual inductance of the coupling mechanism is proportional to the number of turns of the coil outside the transmission rail; the greater the number of turns of the pick-up coil, the greater the mutual inductance of the coupling mechanism. However, as the number of turns increases, the weight and cost of the magnetic coupling mechanism also increases, and the system loss increases, the amount of wire used should be minimized while ensuring the magnitude of the mutual inductance. According to the design flow shown in fig. 11, with 10 μ H as the target mutual inductance value, the optimal number of turns of the transmitting guide rail outer coil and the pickup coil is 8 turns and 15 turns, respectively.
Fig. 23 plots the variation of the coupling coefficient K with the number of turns of the outer coil of the launching guide rail and the number of turns of the pickup coil, and with the increase of the number of turns of the outer coil of the launching guide rail, the coupling coefficient of the system tends to be stable after being reduced, and when the number of turns of the outer coil of the launching guide rail is greater than 5 turns, the coupling coefficient is basically kept unchanged. Although the coupling coefficient of the system is larger when the number of turns of the coil outside the transmitting guide rail is smaller, the mutual inductance M at the moment is too small to meet the power transmission requirement of the system. Comparing the coupling coefficients of the pickup coils with different numbers of turns can find that the number of turns of the pickup coil has almost no influence on the coupling coefficient of the system.
In order to improve the anti-offset performance of the system, the size of the coil in the transmitting guide rail is designed in a simulation mode on the basis that the number of the coils outside the transmitting guide rail is 8 and the number of the coils of the pickup coil is 15. The optimal size of the inner coil is not unique, but the width of the inner coil has an optimal design value when the length of the inner coil is determined. Combining the size of the magnetic core, the width L of the inner coil is simulated and optimized on the premise that the length of the inner coil is 400mm, and the mutual inductance M between the transmitting guide rail 1 and the transmitting guide rail 2 and the pickup coil is drawn p1s 、M p2s And the variation curve of the total equivalent mutual inductance M is shown in fig. 24.
In FIG. 24 (a), the mutual inductance M at different widths L is shown p1s 、M p2s Along with the variation trend that the pickup coil moves along the x direction, the influence of the width of the coil in the transmitting guide rail on the mutual inductance is mainly concentrated at the center of the guide rail, and the larger the width L of the inner coil is, the smaller the mutual inductance M of the system is. After crossing the center position of the rail switching field, the mutual inductance of the pick-up coil with the previous transmit rail is almost no longer affected by the inner coil width. Fig. 24 (b) shows the fluctuation characteristic of the total equivalent mutual inductance M in relation to the change of the inner coil width L, and when L =50mm, the fluctuation of M is the smallest, so that the size of the coil in the transmission rail is designed to be 400mm × 50mm. In summary, specific parameters of the dual solenoid type coupling mechanism designed herein are shown in table 6.
Table 6 design parameter table of double solenoid type coupling mechanism
Figure BDA0003754593030000211
Three-dimensional curves of the mutual inductance of the planar rectangular magnetic coupling mechanism and the double solenoid type magnetic coupling mechanism under different offsets are plotted as shown in fig. 25.
As can be seen from the figure, the double-solenoid type magnetic coupling mechanism designed in the invention greatly improves the mutual inductance drop problem of the planar rectangular magnetic coupling mechanism in the guide rail switching domain, and simultaneously improves the anti-offset capability of the system to a certain extent.
It should be further noted that, in the present embodiment, a dual-solenoid coupling mechanism is applied to dynamic charging of an electric vehicle as an example, but the implementation of the present invention is not limited to the field of electric vehicles and is not limited to dynamic charging, and when the coupling mechanism only has one segment of dual-solenoid transmitting guide rail and one segment of dual-solenoid receiving mechanism (i.e., static charging), the offset resistance of the system can be improved, and the stability of the output power during the charging process is achieved.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (8)

1. Double solenoid type coupling mechanism, including transmission structure and receiving structure, its characterized in that:
the transmitting mechanism comprises a double-solenoid transmitting guide rail, the double-solenoid transmitting guide rail comprises a square tubular magnetic core perpendicular to the road surface, and an internal energy transmitting solenoid and an external energy transmitting solenoid which are respectively wound on the inner wall and the outer wall of the square tubular magnetic core in a solenoid manner, and the internal energy transmitting solenoid and the external energy transmitting solenoid are wound by using the same litz wire but in opposite winding directions;
the receiving structure comprises a pickup coil, a receiving end magnetic core and a metal shielding plate which are arranged in a hierarchical mode, and the pickup coil is of a square annular structure.
2. The double-solenoid type coupling mechanism of claim 1, wherein:
the square tubular magnetic core comprises an inner layer square tubular magnetic core, a middle layer square tubular magnetic core and an outer layer square tubular magnetic core which are separated, the inner energy emission solenoid is wound on the inner wall of the inner layer square tubular magnetic core, and the outer energy emission solenoid is wound on the outer wall of the outer layer square tubular magnetic core.
3. The double-solenoid type coupling mechanism according to claim 2, wherein:
the central position of the receiving end magnetic core is provided with a square bulge, and the square bulge is embedded with a square gap at the center of the pickup coil.
4. The double-solenoid type coupling mechanism according to claim 1, wherein:
the double-solenoid type launching guide rail is provided with a plurality of double-solenoid type launching guide rails which are arranged at equal intervals along the road direction.
5. The double-solenoid type coupling mechanism according to claim 1, wherein: the inner energy emission solenoid, the outer energy emission solenoid emission coil and the pick-up coil are all wound by litz wires with the specification of 0.1mm × 1000 strands and the outer diameter of 5 mm.
6. The double-solenoid type coupling mechanism according to claim 1, wherein: the square tubular magnetic core and the receiving end magnetic core are made of manganese zinc ferrite made of PC95 materials.
7. The method for designing parameters of a double-solenoid type coupling mechanism according to any one of claims 1 to 6, wherein the number of turns of said external energy emitting solenoid is recorded as n 1 The number of turns of the pick-up coil is n 2 Determining n by 1 、n 2 ：
A1, target mutual inductance value M of given design min A transmission distance h;
a2, determining n by combining the sizes of the outer layer square tubular magnetic core and the receiving end magnetic core 1 Maximum value of (n) 1 ) max 、n 2 Maximum value of (n) 2 ) max ；
A3, order n 1 ＝n 2 =1, calculating the mutual inductance M of the magnetic coupling mechanism by means of COMSOL finite element simulation software;
a4, judging whether M is larger than M min If yes, recording the current n 1 、n 2 If not, entering the next step;
A5、n 2 plus 1, i.e. n 2 ＝n 2 +1；
A6, judging the current n 2 Whether or not greater than (n) 2 ) max If not, returning to the step A4, and if so, entering the next step;
a7, order n 2 ＝1，n 1 Plus 1, i.e. n 1 ＝n 1 +1；
A8, judging the current n 1 Whether or not greater than (n) 1 ) max Otherwise, returning to the step A4, if so, failing to design.
8. The method for designing parameters of a double-solenoid type coupling mechanism according to claim 7, wherein n is determined 1 、n 2 Thereafter, the coil size of the internal energy emitting solenoid is determined by:
b1, setting the number of turns of a coil in a transmitting guide rail and the maximum dropping delta M of mutual inductance when the coil is deviated according to the power grade of a system max Giving an initial value of the coil size;
b2, simulating the anti-offset characteristic of the system;
b3, analyzing whether the mutual inductance falling delta M is smaller than delta M or not during deviation max If yes, recording the current coil size, otherwise, adjusting the coil size and returning to the step B2.
CN202210850859.6A 2022-07-20 2022-07-20 Double-solenoid type coupling mechanism and parameter design method thereof Active CN115441593B (en)

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