Magnetic energy harvesting system based on current transformer and its parameter design method

Abstract

The present invention provides a magnetic energy collection system based on a current transformer and a parameter design method thereof. The energy collection part of the magnetic energy collection system includes a magnetic core and a coil winding, and is characterized in that: the magnetic core is formed by snapping together two split magnetic ring structures, the coil winding is wound on one section of the magnetic ring structure, and a through hole is reserved in the middle of the magnetic core for the transmission cable to pass through. The effect is that the system can operate at the maximum power point by optimizing the cross-sectional area of ​​the magnetic core and the number of turns of the winding, meet the power demand, improve the power density of the system, and reduce the weight and volume of the system. By performing parameter design according to the parameter design method proposed in the present invention, it is possible to quickly optimize the parameters under specific working environment requirements and improve the power supply power.

Description

Technical Field

[0001] The present invention relates to a magnetic induction energy harvesting technology, and in particular to a magnetic energy harvesting system based on a current transformer and a parameter design method thereof. Background Art

[0002] Magnetic induction energy harvesting technology is based on Faraday's law of electromagnetic induction. It collects magnetic energy in the environment and induces alternating current through magnetoelectric conversion, thereby realizing self-powering of sensor equipment or other power loads. In recent years, smart grids have developed rapidly, among which real-time monitoring of transmission line status is an important foundation for the development of smart grids. Wireless sensor networks can monitor the operating status of transmission lines and equipment in real time. Therefore, how to achieve continuous and stable power supply for sensors has gradually become a research hotspot at home and abroad.

[0003] With the continuous increase in the total mileage of transmission lines and the rapid development of sensor detection equipment, equipment such as climbing robots and visual cameras have been widely used, which has led to an increasing demand for self-powered magnetic energy collectors. In order to meet the safety issues of transmission lines, the size and weight of the magnetic energy collector should not be too large. Therefore, it is necessary to reasonably optimize and design the energy extraction parameters or energy extraction circuits to increase their power density as much as possible.

[0004] In order to increase power output, some scholars use additional windings to control the magnetic field to delay the saturation of the magnetic core, use energy-taking CT (current transformer) and battery to jointly supply power, or increase the cross-sectional area of ​​the magnetic core or optimize the control of the energy-taking circuit to increase power output. However, these methods bring additional devices, which will increase the size and weight of the energy-taking equipment, posing a hidden danger to the safe operation of the transmission line.

[0005] In some application scenarios, there are restrictions on the volume and weight requirements of the magnetic energy collector. In order to meet the energy extraction needs, the front end of the magnetic energy collector needs to be reasonably optimized so that the magnetic energy collector can achieve the required power requirements with the smallest volume. Summary of the invention

[0006] Based on the above needs, the primary purpose of the present invention is to propose a magnetic energy collection system based on a current transformer. The magnetic energy collection system has a simple structure, and the number of winding turns and the cross-sectional area of ​​the magnetic core can be quickly adjusted according to different application scenarios, so that it can operate at the maximum power point, thereby improving the power density of the energy collection equipment and achieving the self-power supply requirements of the sensor equipment with the smallest volume.

[0007] In order to achieve the above object, the specific technical solution adopted by the present invention is as follows:

[0008] A magnetic energy collection system based on a current transformer, the energy collection part includes a magnetic core and a coil winding, the key of which is that the magnetic core is formed by snapping together two split magnetic ring structures, the coil winding is wound on one section of the magnetic ring structure, and a through hole is reserved in the middle of the magnetic core for the transmission cable to pass through.

[0009] Optionally, a power conversion circuit is provided at the end of the coil winding.

[0010] Optionally, the power conversion circuit includes a rectifier circuit and a DC / DC conversion module.

[0011] Optionally, a load is connected to the output end of the power conversion circuit.

[0012] Optionally, the load is a pure resistive load.

[0013] Optionally, a pair of semi-arc-shaped insulating magnetic conductive containing grooves are arranged on the outer side of the magnetic core, and the upper and lower semi-arc-shaped magnetic cores in the two-split magnetic ring structure are respectively clamped in the insulating magnetic conductive containing grooves.

[0014] Based on the above structure, another object of the present invention is to provide an optimal power parameter design method for a magnetic energy collection system based on a current transformer, the key of which is to include the following steps:

[0015] S1: Consider the transmission line current as an ideal sinusoidal current source and determine the transmission line current amplitude I P , current angular frequency ω, required output power P L and saturation magnetic induction intensity B s ;

[0016] S2: Determine the energy extraction time t at maximum power output s ;

[0017] S3: Follow Determine the number of turns N of the coil winding;

[0018] S4: According to Determine the core cross-sectional area A core .

[0019] Optionally, the energy acquisition time t in step S2 s Designed for 6.81ms.

[0020] Optionally, according to the core cross-sectional area A determined in step S4 core The length and thickness of the core are determined by the thickness of the magnetic field and the transmission line.

[0021] The effects of the present invention are:

[0022] (1) The magnetic energy collection system based on current transformer provided by the present invention can make the system operate at the maximum power point by optimizing the design of the core cross-sectional area and the number of winding turns, thereby meeting the power demand, improving the power density of the system, and reducing the weight and volume of the system.

[0023] (2) The optimal power parameter design method of the magnetic energy collection system based on current transformer provided by the present invention can quickly optimize its parameters under specific working environment requirements and improve the system output power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific implementation of the present invention or the technical solution in the prior art, the drawings required for use in the specific implementation or the description of the prior art are briefly introduced below.

[0025] Figure 1 is an overall structural diagram of an embodiment of the present invention;

[0026] Figure 2 Schematic diagram of the structure of the magnetic energy collection system in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0028] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0029] like Figure 1 and Figure 2 As shown, this embodiment provides a magnetic energy collection system based on a current transformer, and the energy collection part includes a magnetic core and a coil winding. The magnetic core is formed by snapping together two split magnetic ring structures, and the coil winding is wound on one section of the magnetic ring structure. A through hole is reserved in the middle of the magnetic core for the transmission cable to pass through.

[0030] pass Figure 1 It can be seen that a power conversion circuit is provided at the end of the coil winding, the power conversion circuit includes a rectifier circuit and a DC / DC conversion module, and a load is connected to the output end of the power conversion circuit, and the load is a pure resistive load.

[0031] In order to facilitate the installation of the magnetic core, in a specific implementation, a pair of semi-arc-shaped insulating magnetic conductive grooves can be further provided on the outside of the magnetic core, and the upper and lower semi-arc-shaped magnetic cores in the two-split magnetic ring structure are respectively clamped in the insulating magnetic conductive grooves.

[0032] Through the above structural design, the number of turns of the coil can be easily adjusted in different application scenarios, and the cross-sectional area of ​​the magnetic core can also be easily changed by selecting magnetic cores of different sizes, so that the required power output can be achieved with the smallest volume.

[0033] In combination with the above structure, this embodiment also discloses a parameter design method for a magnetic energy collection system based on a current transformer, comprising the following steps:

[0034] S1: Consider the transmission line current as an ideal sinusoidal current source and determine the transmission line current amplitude I P , current angular frequency ω, required output power P L and saturation magnetic induction intensity B s ;

[0035] S2: Determine the energy extraction time t at maximum power output s ;

[0036] S3: Follow Determine the number of turns N of the coil winding;

[0037] S4: According to Determine the core cross-sectional area A core .

[0038] In order to better understand the technical effects of the above method, the design principle is further described below:

[0039] Since the power line is equivalent to the current flowing through one turn of the primary winding, the primary leakage inductance and the winding internal resistance can be ignored; when the magnetic core has a high magnetic permeability, the secondary leakage inductance can also be ignored compared to the excitation inductance; the excitation resistance reflects the active loss of the magnetic core, which is usually divided into eddy current loss and hysteresis loss. At present, most magnetic cores are made of laminated steel plates to ensure effective insulation between layers, effectively block eddy current channels, and have low eddy current losses; hysteresis loss is mainly related to the hysteresis loop of different materials. For magnetic core materials with low hysteresis loss, hysteresis loss can be ignored; since the secondary equivalent current is often at the microampere level, the loss of the secondary winding internal resistance is ignored. Therefore, the working environment and circuit of the magnetic energy collector are in an ideal state, the power line is an ideal sinusoidal current source, the working circuit does not consider losses, and the load can be regarded as purely resistive.

[0040] In the core cross-sectional area (A core ), when optimizing the design of the number of winding turns (N), it is necessary to consider designing a suitable cross-sectional area to meet the power output requirements without causing material waste and volume increase due to an excessively large cross-sectional area; a reasonably designed number of turns can make the magnetic energy harvester operate at the optimal power point of the PR curve under specific load conditions.

[0041] The transmission line current is denoted as iP , assuming it is an ideal sinusoidal current source, it can be expressed as:

[0042] i P =I P sin(ωt) (1)

[0043] Assume that the magnetic saturation characteristics of the magnetic core are in an ideal state when it is working, that is, when the magnetic core is not saturated, the excitation inductance is very large, the excitation branch is approximately in an open circuit state, and an AC voltage is induced on the secondary side; when the magnetic flux accumulates to the saturation value, the magnetic flux value does not change, the excitation inductance value quickly decreases to zero, the secondary side voltage is zero, and the energy harvesting device only transmits energy when it is not saturated:

[0044]

[0045] The load power equivalent is the load in each energy extraction cycle (R L ) is the average value of the instantaneous power integral, that is, P L It is expressed as:

[0046]

[0047] Among them, t s The energy extraction time of the magnetic core, that is, the unsaturated time, that is, the primary current, load resistance, number of winding turns and energy extraction time determine the power transmission capacity of the energy extraction device.

[0048] The magnetic energy harvesting system based on current transformer performs magnetoelectric conversion. Its output power is limited by the saturation time. The saturation time is closely related to the maximum magnetic flux that the magnetic energy harvester can carry. According to the Faraday electromagnetic relationship, the accumulated magnetic flux of the magnetic core is equal to the integral of the secondary side voltage over time, which is expressed as:

[0049]

[0050] Among them, "2" represents the magnetic flux accumulation from -B s To B s , B s A is the saturation magnetic induction intensity of the energy-taking CT, core is the cross-sectional area of ​​the magnetic core. The energy extraction time t can be obtained from formula (4): s , t s The expression is:

[0051]

[0052] Because the saturation time and B s , A core , N, therefore, the output power can be controlled by properly designing the cross-sectional area and number of turns of the magnetic core. Substituting equation (5) into equation (3), we can obtain the relationship between the output power and the design parameters of each energy-taking CT, namely:

[0053]

[0054] It can be seen from equation (6) that under different transmission line currents and loads, by reasonably selecting the core material and designing the corresponding cross-sectional area and number of turns, the corresponding engineering requirements can be met. According to equations (5) and (6), MATLAB can be used to derive the influence of each parameter on the output power, that is, under the same conditions, the change in the number of turns only affects the change in the maximum power point, while the maximum output power will not change; the change in the core cross-sectional area affects the maximum output power of the energy-taking CT, and the maximum power point also changes; in addition, it can be found that no matter how the parameters of the energy-taking CT change, the energy-taking time at maximum power output is the same, that is, the energy-taking time t in step S2 s It is 6.81ms.

[0055] The design of the energy-harvesting CT core follows the premise of meeting the power output requirements under certain current and load conditions and reducing the core volume as much as possible. Under the conditions of known power, primary current and load, according to the conclusions drawn above, when the energy-harvesting section ωt s When it is 2.14, the energy-taking CT works at the maximum power point. According to formula (3), the number of turns designed should be:

[0056]

[0057] According to equations (4) and (7), the designed core cross-sectional area can be obtained as:

[0058]

[0059] The energy extraction parameters (core cross-sectional area, number of winding turns) designed according to the above process are the optimal parameters for the maximum power that the load can pick up.

[0060] In specific implementation, the core cross-sectional area A determined in step S4 may also be used. core The length and thickness of the core are determined by the thickness of the magnetic field and the transmission line.

[0061] In summary, it can be seen that the magnetic energy collection system based on current transformer and the parameter design method thereof proposed in the present invention can put the load in the maximum power point state and achieve the required power demand with the smallest volume.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and such changes should be included in the scope of the claims and description of the present invention.

Claims

1. A parameter design method for a magnetic energy collection system based on a current transformer, wherein the energy collection part of the system includes a magnetic core and a coil winding, wherein the magnetic core is formed by snapping together two split magnetic ring structures, wherein the coil winding is wound on one section of the magnetic ring structure, and a through hole is reserved in the middle of the magnetic core for a transmission cable to pass through, wherein: The parameter design method of the system includes the following steps: S1: Consider the transmission line current as an ideal sinusoidal current source and determine the transmission line current amplitude I P , current angular frequency ω, required output power P L and saturation magnetic induction intensity B s ; S2: Determine the energy extraction time t at maximum power output s ; S3: Follow Determine the number of turns N of the coil winding; S4: According to Determine the core cross-sectional area A core .

2. The parameter design method of the magnetic energy collection system based on current transformer according to claim 1 is characterized in that: Energy extraction time t in step S2 s Designed for 6.81ms.

3. The parameter design method of the magnetic energy collection system based on current transformer according to claim 1 or 2, characterized in that: According to the core cross-sectional area A determined in step S4 core The length and thickness of the core are determined by the thickness of the magnetic field and the transmission line.

4. The parameter design method of the magnetic energy collection system based on current transformer according to claim 1 is characterized in that: A power conversion circuit is arranged at the end of the coil winding.

5. The parameter design method of the magnetic energy collection system based on current transformer according to claim 4 is characterized in that: The power conversion circuit includes a rectifier circuit and a DC / DC conversion module.

6. The parameter design method of the magnetic energy collection system based on current transformer according to claim 4 or 5, characterized in that: A load is connected to the output end of the power conversion circuit.

7. The parameter design method of the magnetic energy collection system based on current transformer according to claim 6 is characterized in that: The load is a pure resistive load.

8. The parameter design method of the magnetic energy collection system based on current transformer according to claim 1 is characterized in that: A pair of semi-arc-shaped insulating magnetic conductive containing grooves are arranged outside the magnetic core, and the upper and lower semi-arc-shaped magnetic cores in the two-split magnetic ring structure are respectively clamped in the insulating magnetic conductive containing grooves.

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