Maximum power acquisition method for non-intrusive power line energy harvesting system considering magnetic saturation

Abstract

The application discloses a maximum power acquisition method of a non-intrusive power line energy extraction system considering magnetic saturation, and comprises the following steps: firstly, a circuit model of energy extraction on the secondary side of a split magnetic core is established; then, in a half cycle of alternating current, the magnetic core model parameters are determined from the start time to the end time of the half cycle according to the circuit model of energy extraction on the secondary side of the split magnetic core and the magnetic core parameters; finally, the constraint relationship between the energy extraction power of the energy extraction system and the number of turns of the magnetic core is established under the determined magnetic core model parameters, and the optimal number of turns under the consideration of magnetic saturation is determined, so that the maximum power of the energy extraction system is acquired.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power line energy extraction, and more specifically relates to a maximum power acquisition method for a non-intrusive power line energy extraction system considering magnetic saturation. BACKGROUND

[0002] Power line energy extraction technology is a technology for self-power supply of sensing devices and the like based on electromagnetic induction principle from the magnetic field generated by the alternating current of the power line. Compared with the whole magnetic core without air gap used in the intrusive power line energy extraction system, the split magnetic core with air gap used in the non-intrusive power line energy extraction system has the characteristics of convenient installation, and has better application prospect in the scene where the power line cannot be powered off.

[0003] Although the split magnetic core has the characteristics of strong environmental adaptability and convenient installation for magnetic energy collection, there are still some problems. Due to the inevitable air gap of the split magnetic core, the effective permeability of the magnetic core is reduced, thereby reducing the energy extraction power of the magnetic core. At the same time, the complete saturation of the magnetic core will limit the improvement of the energy extraction power, so in order to avoid the saturation of the magnetic core and obtain relatively higher power, a larger magnetic core must be used, which is not conducive to the miniaturization of the power line energy extraction system, and cannot meet the requirements of the power line in terms of sag and the like, so improving the power density of the magnetic core becomes the key to solving the problem.

[0004] In order to solve the above problems, relevant personnel have proposed some improvement methods for the magnetic core, for example: Li Ping team of Chongqing University proposed to change the air gap contact surface of the split magnetic core into a tooth shape as shown in Figure 1 , so as to improve the distribution of the magnetic force line of the magnetic core, so that the magnetic flux leakage is reduced, and the magnetic induction intensity of the magnetic core is increased by 2 times compared with the split magnetic core without tooth shape, and the system energy extraction power is increased by 2 times when the primary side current is 10 Arms, the power line radius is 2.5 mm, and the load is 400Ω. It is proved that the more the number of teeth is, the better the improvement effect is.

[0005] Although the above method reduces the problem of reduction of the effective permeability of the split magnetic core caused by the introduction of air gap to a certain extent, in order to avoid the easy saturation of the magnetic core, only 2 teeth are selected in the article, and the number of turns of the coil is increased to 2000 turns, which limits the increase of the magnetic induction intensity of the magnetic core, and greatly increases the weight of the magnetic core. In addition, the design of the tooth surface of the split magnetic core increases the processing difficulty of the magnetic core and the manufacturing cost.

[0006] The above method avoids the saturation of the magnetic core by sacrificing part of the performance of the magnetic core, such as the effective permeability and the weight of the magnetic core, which leads to the fact that the energy extraction power density of the energy extraction system cannot be fully improved. SUMMARY

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for obtaining the maximum power of a non-intrusive power line energy harvesting system that takes into account magnetic saturation. This method harvests the maximum power when the magnetic core is magnetically saturated, which can effectively improve the energy harvesting capacity of the power line energy harvesting system and broaden its application scenarios.

[0008] To achieve the above-mentioned objective, the present invention provides a method for obtaining maximum power in a non-intrusive power line energy harvesting system considering magnetic saturation, characterized by comprising the following steps:

[0009] (1) Establish a circuit model for energy extraction from the secondary side of the split magnetic core using simulation software;

[0010] (2) Determine the excitation inductance L in the circuit model μ The possible values ​​of:

[0011]

[0012] Among them, l FLUX μ represents the perimeter of the magnetic core's magnetic circuit. eff The value represents the effective permeability of the magnetic core, μ0 represents the initial permeability of air, A represents the cross-sectional area of ​​the magnetic core, and N represents the number of turns of the coil.

[0013] Among them, the effective permeability μ of the magnetic core eff for:

[0014]

[0015] Where, μ core The relative permeability of the magnetic core, l gap Indicates the perimeter of the magnetic core air gap magnetic circuit;

[0016] (3) When the load is a constant voltage load, determine the time t for the magnetic core to reach full saturation. SAT for:

[0017]

[0018] Among them, B SAT V represents the maximum saturation magnetic flux density, T represents the period of the alternating current on the primary side of the magnetic core, and V represents the maximum saturation magnetic flux density. Load This indicates the voltage of a constant voltage load;

[0019] (4) Establish the constraint relationship between the energy harvesting power and the number of coil turns;

[0020] When the magnetic core does not reach saturation within half a cycle of the alternating current on the primary side of the magnetic core, that is... At this time, the energy harvesting power P of the non-intrusive power line energy harvesting system unsat-OUT for:

[0021]

[0022] Among them, I P ω represents the maximum value of the alternating current on the primary side of the magnetic core, and i represents the angular frequency of the current on the primary side of the magnetic core. μ (t) represents the current value of the magnetizing inductor at time t, T S The starting moment when the magnetic core begins to accumulate magnetic flux is determined by the following formula:

[0023]

[0024] When the magnetic core reaches saturation within half a cycle of the alternating current on the primary side of the core, that is... At this time, the energy harvesting power P of the non-intrusive power line energy harvesting system sat-OUT for:

[0025]

[0026] (5) Establish optimization constraints for the number of coil turns N based on the energy harvesting power under unsaturated and fully saturated magnetic core conditions:

[0027]

[0028] Among them, P OUT-max This represents the maximum power of the energy harvesting system.

[0029] (6) Based on the optimization constraint of the number of coil turns N, the optimal number of coil turns N of the magnetic core is determined by circuit simulation software, thereby simulating and obtaining the maximum power of the energy harvesting system.

[0030] The objective of this invention is achieved as follows:

[0031] This invention discloses a method for maximizing the power of a non-intrusive power line energy harvesting system considering magnetic saturation. First, a circuit model for secondary-side energy harvesting from a separate magnetic core is established. Then, within half a cycle of the alternating current, from the beginning to the end of the half-cycle, the parameters of the magnetic core model are determined based on the circuit model and the magnetic core parameters. Finally, under the determined magnetic core model parameters, a constraint relationship is established between the harvested power of the energy harvesting system and the number of coil turns of the magnetic core, thereby determining the optimal number of coil turns considering magnetic saturation, thus enabling the energy harvesting system to acquire maximum power.

[0032] Meanwhile, the maximum power acquisition method of the non-intrusive power line energy harvesting system considering magnetic saturation of the present invention also has the following beneficial effects:

[0033] (1) By determining the excitation inductance and effective permeability parameters of the split magnetic core, the secondary side energy harvesting circuit model of the split magnetic core can be quickly built, breaking through the traditional mode of requiring a large amount of experimental data analysis to determine the effective permeability of the split magnetic core and then build the circuit model.

[0034] (2) The non-intrusive energy harvesting system can operate in the saturation region to harvest energy, which improves the system's energy harvesting capability compared with the traditional method of using a split magnetic core to harvest power lines in the unsaturation region.

[0035] (3) The magnetic core operates in the saturation region to obtain energy. A magnetic core with higher initial permeability can be used, and fewer coil turns can be used to effectively reduce the volume and weight of the energy harvesting system. It can be effectively applied to scenarios where the energy harvesting bus has requirements such as sag, thus broadening the scope of application. Attached Figure Description

[0036] Figure 1 This is a picture of a magnetic core with a toothed air gap contact surface;

[0037] Figure 2 This is a flowchart of a method for obtaining maximum power in a non-intrusive power line energy harvesting system considering magnetic saturation, according to the present invention.

[0038] Figure 3 This is a schematic diagram of a split magnetic core;

[0039] Figure 4 It is an equivalent model of the secondary side circuit of a split magnetic core;

[0040] Figure 5 It is a simplified equivalent model of the secondary side circuit of the split magnetic core;

[0041] Figure 6 It is the system power extracted under the optimal number of coil turns. Detailed Implementation

[0042] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0043] Example

[0044] Figure 2 This is a flowchart of a method for obtaining maximum power in a non-intrusive power line energy harvesting system considering magnetic saturation, according to the present invention.

[0045] In this embodiment, as Figure 2 As shown, the present invention provides a method for obtaining maximum power in a non-intrusive power line energy harvesting system considering magnetic saturation, comprising the following steps:

[0046] S1. Establish a circuit model for energy extraction from the secondary side of the split magnetic core using simulation software;

[0047] In this embodiment, the split magnetic core is cut from a toroidal magnetic core, specifically as follows: Figure 3 As shown, the coil is wound around the magnetic core. Considering the effect of the number of coil turns on the core saturation, the maximum power can be obtained by adjusting the number of coil turns to make the core operate in the saturation region. However, this invention is not limited to split magnetic cores made by cutting toroidal magnetic cores; other split magnetic cores, such as those made by cutting rectangular coils, are also possible.

[0048] like Figure 3 For the split magnetic core shown, we first establish a circuit model of the secondary side energy extraction of the split magnetic core using simulation software, such as... Figure 4 As shown, the model includes an alternating current source I. s ,Magnetic core excitation inductance L μ Magnetic core leakage inductance L leak impedance R CORE impedance R wire Load R Load Among them, AC current source I s Simulate the secondary current of the magnetic core. The secondary current of the magnetic core is obtained from the magnetic core winding, which includes wires and the magnetic core. The wires are wound around the magnetic core.

[0049] Magnetizing Inductance L μ The voltage across the two sides is v CORE (t), flowing through the leakage inductance L of the magnetic core leak The excitation inductor current is i μ (t), the resistance of the series connection of the magnetic reluctance of the split core material and the magnetic reluctance caused by the air gap of the split core, and the parallel connection of the magnetic reluctance caused by the leakage inductance of the core, is R. CORE The impedance value of the line is R wire AC power supply I s Magnetizing inductance L μ and core impedance R CORE Connected in parallel with the core leakage inductance L leak and line impedance R wire The series connection is followed by the parallel connection of the load R. Load .

[0050] It should be noted that this model is for a constant voltage load. Due to the small leakage inductance, the line impedance is relatively small compared to the actual effective impedance of the load in the circuit, and is therefore negligible in the actual parameter calculation. The impedance R of the magnetic core... CORE The current flowing through it is relatively large, so it is negligible. The energy extraction current on the secondary side of the magnetic core flows through the magnetizing inductor of the magnetic core and the constant voltage load. The equivalent simplified model of the secondary side circuit of the magnetic core is as follows:Figure 5 As shown;

[0051] S2. Determine the excitation inductance L in the circuit model. μ The possible values ​​of:

[0052] Magnetizing Inductance L μ It is positively correlated with the effective permeability of the magnetic core, the effective cross-sectional area of ​​the magnetic core, and the number of coil turns, and negatively correlated with the effective magnetic loop perimeter of the magnetic core, determined by the following formula:

[0053]

[0054] Among them, l FLUX μ represents the perimeter of the magnetic core's magnetic circuit. eff The value represents the effective permeability of the magnetic core, μ0 represents the initial permeability of air, A represents the cross-sectional area of ​​the magnetic core, and N represents the number of turns of the coil.

[0055] Among them, the effective permeability μ of the magnetic core eff for:

[0056]

[0057] Where, μ core l represents the initial permeability of the magnetic core. gap Indicates the perimeter of the magnetic core air gap magnetic circuit;

[0058] S3. When the load is a constant voltage load, determine the time t for the magnetic core to reach full saturation. SAT for:

[0059]

[0060] Among them, B SAT V represents the maximum saturation magnetic flux density, T represents the period of the alternating current on the primary side of the magnetic core, and V represents the maximum saturation magnetic flux density. Load This indicates the voltage of a constant voltage load;

[0061] In this embodiment, it can be seen from formulas (1)-(3) that as long as the effective cross-sectional area A of the magnetic core and the initial permeability μ of the magnetic core are given, core Magnetic core air gap magnetic circuit perimeter l gap Circumference of magnetic core and magnetic circuit l FLUX Initial permeability of air μ0, number of coil turns N, and maximum saturation magnetic induction B SAT Then, the core excitation inductance L can be determined. μ The saturation time t required for the magnetic core to reach magnetic saturation SAT .

[0062] In this embodiment, as Figure 3As shown, the outer diameter of the split toroidal core is φB = 43 mm, the inner diameter is φC = 23 mm, the height is φD = 18 mm, and the initial permeability is μ. core =64000, maximum saturation magnetic induction intensity B SAT =1T, voltage V of constant voltage load Load =5V, magnetic core air gap magnetic circuit perimeter l gap =5.6um, primary side current I of the magnetic core p =20A;

[0063] Therefore, the effective permeability μ of the magnetic core can be determined. eff =9700, Magnetizing inductance L μ =2.1×10 -5 ·N 2 ;

[0064] S4. Establish the constraint relationship between the energy harvesting power and the number of coil turns;

[0065] When the magnetic core does not reach saturation within half a cycle of the alternating current on the primary side of the magnetic core, that is... At this time, the energy harvesting power P of the non-intrusive power line energy harvesting system unsat-OUT for:

[0066]

[0067] Among them, I P ω represents the maximum value of the alternating current on the primary side of the magnetic core, and i represents the angular frequency of the current on the primary side of the magnetic core. μ (t) represents the current value of the magnetizing inductor at time t, T S The starting moment when the magnetic core begins to accumulate magnetic flux is determined by the following formula:

[0068]

[0069] When the magnetic core reaches saturation within half a cycle of the alternating current on the primary side of the core, that is... At this time, the energy harvesting power P of the non-intrusive power line energy harvesting system sat-OUT for:

[0070]

[0071] S5. Establish optimization constraints for the number of coil turns N based on the energy harvesting power under unsaturated and fully saturated magnetic core conditions:

[0072]

[0073] Among them, P OUT-max This represents the maximum power of the energy harvesting system.

[0074] S6. Based on the optimization constraint of the number of coil turns N, the optimal number of coil turns N of the magnetic core is determined by simulation using the simulation software LTspice, thereby simulating and obtaining the maximum power of the energy harvesting system.

[0075] In this embodiment, the simulation yields the following relationship between the system's harvested power and the number of coil turns: Figure 6 As shown, the optimal number of coil turns N is 245, corresponding to the magnetic core operating in the saturation region, and the system achieves a maximum power of 216mW.

[0076] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A method for obtaining maximum power in a non-intrusive power line energy harvesting system considering magnetic saturation, characterized in that, Includes the following steps: (1) Establish a circuit model for energy extraction from the secondary side of the split magnetic core using simulation software; (2) Determine the magnetizing inductance in the circuit model The possible values ​​of: ； in, Indicates the perimeter of the magnetic core's magnetic circuit. Indicates the effective permeability of the magnetic core. Indicates the initial magnetic permeability of air. Indicates the cross-sectional area of ​​the magnetic core. Indicates the number of coil turns; Among them, the effective permeability of the magnetic core for: ； in, This indicates the relative permeability of the magnetic core. Indicates the perimeter of the magnetic core air gap magnetic circuit; (3) When the load is a constant voltage load, determine the time when the magnetic core reaches full saturation. for: ； in, Indicates the maximum saturation magnetic flux density. This indicates the period of the alternating current on the primary side of the magnetic core. This indicates the voltage of a constant voltage load; (4) Establish the constraint relationship between the energy extraction power and the number of coil turns; When the magnetic core does not reach saturation within half a cycle of the alternating current on the primary side of the magnetic core, that is... At this time, the energy harvesting power of the non-intrusive power line energy harvesting system for: ； in, This indicates the maximum value of the alternating current on the primary side of the magnetic core. This represents the angular frequency of the current on the primary side of the magnetic core. express The current value of the magnetizing inductor at any given time. The starting moment when the magnetic core begins to accumulate magnetic flux is determined by the following formula: ； When the magnetic core reaches saturation within half a cycle of the alternating current on the primary side of the core, that is... At this time, the energy harvesting power of the non-intrusive power line energy harvesting system for: ； (5) Determine the number of coil turns based on the energy harvesting power under unsaturated and fully saturated magnetic core conditions. Optimization constraints: ； in, This represents the maximum power of the energy harvesting system. (6) Based on the number of coil turns The optimal number of coil turns for the magnetic core is determined through circuit simulation software based on the optimization constraints. This allows for the simulation to obtain the maximum power of the energy harvesting system.

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