CN111817303A - A circuit and method for improving power quality of power grid - Google Patents

Abstract

The invention discloses a circuit and a method for improving the electric energy quality of a power grid, and the circuit comprises a power grid input terminal, a rectifying circuit, a power factor correction circuit, a high-frequency inverter circuit and an output terminal which are connected in sequence, wherein a control circuit is in control connection with the rectifying circuit, the power factor correction circuit and the high-frequency inverter circuit, the high-frequency inverter circuit comprises a magnetic core and a coil which are used for magnetic coupling, the coil is wound on an insulating structure, and one part of the magnetic core is arranged in a hollow channel of the insulating structure; the core and coil arrangement is such that a portion of the magnetic flux cuts the coil and a portion of the shunt magnetic cuts the coil within the core window to reduce eddy current losses. Under the condition that the number of turns of the coil is not changed, the magnetic flux leakage utilization rate of the magnetic core is improved, the distance between the coil and the magnetic core is increased, or the width of an air gap on the magnetic core is reduced, so that the magnetic flux leakage reduction device can be applied to the fields of photovoltaic grid connection, switching power supplies and the like, and the harmonic wave of a power grid is reduced, or the ripple is adjusted, the reactive power is adjusted, and.

Description

A circuit and method for improving power quality of power grid

technical field

The present invention relates to a circuit and method for improving power quality of power grid, in particular, the present invention relates to a circuit and method for improving power quality of power grid with low harmonic current and less pollution to power grid, which can be applied to photovoltaic grid-connected, switch Power supply and other fields, reduce grid harmonics or adjust ripple, adjust reactive power, etc.

Background technique

With the development of the national economy, power converters have been more and more widely used, and the capacity and quantity of inverter devices and rectifier devices used in equipment have become larger and larger. Large-capacity nonlinear load equipment produces a large number of High-order harmonic currents are injected into the power grid, causing waveform distortion of the power supply grid, reducing the quality and reliability of power supply, and threatening the economic operation of power supply and electrical equipment.

Large-capacity nonlinear load equipment mainly includes: thyristor rectifier power supplies widely used in metallurgy, chemical industry, and mining departments; frequency conversion speed regulation devices widely used in industry; locomotives using AC single-phase rectification power supply in electrified railways; household appliances (TV, refrigerators, washing machines, electronic energy-saving lamps), etc. The capacity of electric arc furnaces for steelmaking is constantly expanding, and electric arc furnaces and contact welding equipment widely used in production, as well as submerged arc furnaces, ferrosilicon furnaces, intermediate frequency and high frequency furnaces, are also nonlinear power loads. The commissioning and use of these equipments make more and more harmonics in the power grid, and the harmonics will form radiation and conduction along the lines, pollute the power grid, and affect the application of electronic equipment.

In the operation of power distribution network, the problem of reactive power compensation is a very important and typical problem. Taking lighting as an example, high-pressure sodium lamps are the main light source for road lighting. In modern agriculture, there are many needs for supplementary light. Generally, high-power supplementary light special lamps are characterized by bulbs with a tube voltage range of 175-330V and an operating frequency range of 100-200KHZ. The dimming range is required to be within the range of 50-110%. The standard of electromagnetic compatibility requires that it meet the standard of civil FCC, the efficiency is up to 96%, and the output power can be adjusted.

The ballast is an indispensable control element for the normal operation of loads such as fill light and lighting. It is used in series in the circuit to limit the lamp current and avoid burning out the bulb. The effective form of the inductive ballast is inductive in nature, and its inherent power factor is very low, about 0.06, and when connected in series with a sodium lamp, the series circuit power factor is about 0.45. Such a low power factor will increase the power loss and voltage drop of the power supply line, affecting the luminous efficiency of the light source. Increasing inductance results in larger device size, increased harmonics, and increased cost.

Generally, the load can only be used under a certain rated voltage. Due to the different voltages in different countries and regions in the world, the power supply needs to be converted when connecting the load to adapt to different loads. Usually, the power conversion device also needs to be used at a certain rated voltage. When the power supply voltage is high, a lot of energy consumption will be generated, especially when the power supply voltage is too high, the energy consumption will be even greater. Generally, one type of power conversion device cannot meet different requirements. National voltage requirements; this usually requires different conversion devices for different voltages, increasing production costs. Due to the different power quality in different regions, too high or too low voltage also affects the efficiency of the power conversion device, affects the normal operation of the load, and further deteriorates the quality of the power grid. Therefore, manufacturing switching power supplies that can be connected to different power supply voltages can reduce costs, Improve the power quality of the power grid, and users do not need to choose when using it.

In a word, magnetic components are a very important part of power electronic technology, which undertakes many functions such as energy transfer, energy storage, filtering, isolation and so on. As a key component that accounts for 30%-50% of the total loss of the circuit, the research work such as loss test, loss calculation and optimization design of magnetic components is particularly important. The general switching power supply circuit includes an inductor, and its coil and iron core have losses during the power conversion process, which reduces the conversion efficiency. Increasing the number of coil turns or switching to a more expensive magnetic core can reduce energy loss and improve conversion rate, but lead to volume change. large and increased cost.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a circuit for improving the power quality of the power grid, which minimizes losses and has high power conversion efficiency and low harmonics without increasing the volume. The wave current can improve the power quality of the grid.

Another object of the present invention is to provide a method for improving the power quality of a power grid. The method improves the leakage flux utilization rate of the magnetic core, reduces the magnetic inductance and the leakage inductance loss, and makes the unit winding and the number of turns unchanged without changing the coil winding and the number of turns. The volume energy conversion efficiency is greatly improved and the harmonics are reduced.

In order to solve the above-mentioned technical problems, the basic conception of the technical scheme adopted in the present invention is:

The present invention includes grid input terminal, rectifier circuit, power factor correction circuit, high frequency inverter circuit and output terminal connected in sequence, and the control circuit is controlled and connected with rectifier circuit, power factor correction circuit and high frequency inverter circuit. The inverter circuit includes a magnetic core and a coil for magnetic coupling, the coil is wound on the insulating structure, and a part of the magnetic core is arranged in the hollow channel of the insulating structure; the magnetic core and the coil are arranged as part of the magnetic flux to cut the coil and bypass A portion of the magnet cuts the coil within the core window to reduce eddy current losses.

In the present invention, the leakage flux cuts the coil in the magnetic core window to reduce the eddy current loss.

In the present invention, there is a first distance between at least part of the coil and the end face of the window of the magnetic core.

In the present invention, there is a first distance between the channel wall of the hollow channel through which the partial coil passes through the insulating structure and the end face of the window of the magnetic core.

In the present invention, there is a first distance between the opposite first and second walls of the hollow channel through which the coil passes through the insulating structure and the two end faces of the magnetic core window, respectively.

In the present invention, a second distance is set between the opposite third and fourth walls of the hollow channel of the insulating structure and the corresponding left and right end faces of the middle magnetic column respectively.

In the present invention, there is a first distance between the opposite first wall and the second wall of the hollow channel of the insulating structure and the two end faces of the window of the magnetic core, and the first distance is 1 of the height of the magnetic core. /3-1/6.

In the present invention, the air gaps in the magnetic core are n spaced air gaps, n is greater than or equal to 2, and the sum of the widths of the n air gaps is equal to the width of the air gaps when the magnetic core has one air gap, so as to reduce eddy current loss.

In the present invention, the described magnetic core and coil for magnetic coupling satisfy the following formula:

In the formula, r is the radius of the magnetic core or the radius of the central column of the magnetic core, δ is the width of the air gap, d is the distance between the coil and the magnetic core, K is the converted value of the magnetic flux of the magnetic core, and γ is the edge magnetic Pass loss conversion value, M is the effective conversion value of magnetic flux.

The present invention also includes a method for improving the power quality of the power grid by using the above circuit, including: rectifying, filtering, and correcting the power factor of the input high-voltage power from the power grid to obtain direct current, and performing high-frequency inversion on the direct current to obtain alternating current. In the high-frequency inverter circuit, the magnetic core and the coil are set to bypass the magnetic flux to cut a part of the winding to reduce the eddy current loss.

After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

The invention increases the inductance by reducing the eddy current loss without changing the number of turns of the coil, without increasing the volume and cost, and only needs to select the inductor according to the minimum inductance, and the same number of turns of the coil can greatly improve the inductance to harmonics. Suppression, reduce power grid harmonics, improve the quality of power grid power.

By reducing the loss of the coil and the loss of the magnetic core during the power conversion process, the inductance of the inductor is greatly improved, and the energy conversion efficiency per unit volume is greatly improved. The input end of the power conversion device can adapt to different ranges of input voltage without affecting the use of the inductor. ; Since there is no need to increase the number of coil turns or switch to a more expensive magnetic core, the cost of the same volume is greatly reduced.

In the case of the same number of turns as the prior art, the inductor of the present invention increases the inductance by reducing the magnetic loss, reduces the reactive power according to the relationship between the power factor, reactive power and apparent power, and reduces the voltage drop of the power grid . The compensation requirements for reactive power by the grid are reduced.

The simulation results of MATLAB show that the technology is effective and feasible.

The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

Description of drawings

The accompanying drawings, as a part of the present invention, are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings in the following description are only some embodiments, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

FIG. 1 is a schematic structural diagram of a power conversion device provided by an embodiment of the present invention;

2 is a cross-sectional view of a power conversion device provided by an embodiment of the present invention;

3 is a schematic structural diagram of a skeleton provided by an embodiment of the present invention;

4 is a schematic structural diagram of a magnetic core structure provided by an embodiment of the present invention;

5 is a schematic diagram of the distribution of main magnetic flux and leakage magnetic flux on a magnetic core structure provided by an embodiment of the present invention;

6 is a schematic structural diagram of a magnetic core structure provided by another embodiment of the present invention;

7 is a schematic structural diagram of a magnetic core structure with an insulating member inserted in an air gap according to an embodiment of the present invention;

Figure 8 is a schematic diagram of the circuit of the present invention.

In the figure: 1-skeleton; 11-winding part; 111-hollow channel; 12-coil pin; 2-magnetic core; 21-sub-magnetic core; 211-outer ring core; 212-center column; 22-magnetic Column; 23-intermediate magnetic column; 231-sub-intermediate magnetic column; 3-spacing; 31-first spacing; 32-second spacing; 4-first bump; 41-first extension; 5-second Bump; 51-Second extending part; 6-Limiting groove; 7-Air gap; 71-Intermediate air gap; 72-Side air gap; 8-Insulator; 81-First plastic sheet; 9-Heat sink ; 91 - Glue layer.

It should be noted that these drawings and written descriptions are not intended to limit the scope of the present invention in any way, but to illustrate the concept of the present invention to those skilled in the art by referring to specific embodiments.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and the following embodiments are used to illustrate the present invention , but are not intended to limit the scope of the present invention.

In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation or a specific orientation. construction and operation, and therefore should not be construed as limiting the invention.

In the description of the present invention, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense, unless otherwise expressly specified and limited, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; it can be mechanical connection or electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

Example

Referring to FIG. 8, the circuit for improving the power quality of the power grid of the present invention includes a rectifier and filter circuit connected to the input terminal of the power grid, a power factor correction circuit, a high-frequency inverter circuit, a control circuit and an output terminal. It includes a magnetic core for magnetic coupling and a coil, the coil is wound on the insulating structure, and a part of the magnetic core is arranged in the hollow channel of the insulating structure.

In an embodiment of the present invention, the magnetic core and the coil are magnetically coupled as an inductance, and the circuit for improving the power quality of the grid is a switching power supply circuit of a power conversion device.

As shown in FIG. 5, FIG. 5 is a magnetic core structure according to an embodiment of the present invention, and FIG. 5 shows the distribution of the main magnetic flux and leakage magnetic flux on the magnetic core structure; the magnetic core structure includes a magnetic core and a part of the magnetic core The coil set on the upper part of the magnetic core is provided with an air gap. After the coil is energized, a current flows through the coil. When there is current in the coil, a magnetic field will be formed in the space around the coil. Due to the magnetic permeability of the magnetic core It is better than air, so most of the magnetic flux forms a loop along the iron core and the air gap. This part of the magnetic flux becomes the main magnetic flux, and the main magnetic flux forms a circulation loop in the magnetic core, which stores most of the energy and has nothing to do with the eddy current loss. The inductor also includes leakage flux, which includes diffused flux and bypass flux. The diffused magnetic flux is the diffused magnetic flux at the edge of the air gap, which is caused by the magnetic pressure drop on the upper and lower end faces of the air gap. This part of the magnetic flux enters the magnetic core window, so it will cause eddy current losses to the windings near the air gap. The bypass flux is the leakage flux that traverses the core window, and the magnetic field lines cut the windings to generate eddy current losses. In fact, there is still a part of the magnetic flux that does not pass through the air gap, but forms a loop through the air. This part is also a leakage magnetic flux. Generally, the magnetic flux that does not pass through the magnetic core to form a closed loop is called "leakage magnetic flux".

In the prior art, most or all of the leakage flux of the magnetic core is cut by the coil of the inductance, resulting in eddy current loss in the coil, which increases the coil loss of the inductance, thereby reducing the inductance. The leakage flux of the coil is partially cut, that is, the cutting of the leakage flux of the magnetic core by the coil is reduced to reduce the eddy current loss of the coil, thereby increasing the inductance of the power conversion device under the condition that the number of turns of the coil remains unchanged.

In the embodiment of the present invention, at least some of the coils and the magnetic core are arranged with a distance.

As shown in FIG. 2 , in the embodiment of the present invention, the insulating structure includes a skeleton 1 on which a winding portion 11 is arranged, the interior of the skeleton is a hollow channel 111 , the magnetic core has a magnetic core window, and part of the magnetic core 2 is provided with air The magnetic core is formed with leakage magnetic flux at the air gap. By setting at least part of the coil and the magnetic core with a distance of 3, the coil can be far away from the leakage magnetic flux of the magnetic core, and the leakage magnetic flux of the coil to the magnetic core is minimized as much as possible. Cutting of leakage flux. Reduce the eddy current loss and improve the inductance of the power conversion device; do not increase the number of coil turns or use a more expensive magnetic core to reduce the eddy current loss of the coil and reduce the cost; as shown in Figure 1 and Figure 2, the insulating structure includes a skeleton 1. The bobbin 1 has a winding portion 11 for winding the coil. The winding portion 11 is provided with a hollow channel 111 in the axial direction. At least part of the outer wall of the magnetic core in the hollow channel 111 is provided with a gap 3 between the hollow channel 111 and the coil. Due to the existence of the gap 3, the cutting of the leakage magnetic flux of the magnetic core by the coil, especially the bypass magnetic flux cutting The coil inside the magnetic core window can reduce the eddy current loss, and the coil arranged outside the magnetic core window is far away from the air gap and the bypass magnetic flux, which reduces the cutting of the coil by the bypass magnet and minimizes the eddy current loss. Under the condition of high inductance, the inductance is greatly improved, which reduces the production cost. The insulating structure has no effect on cutting, and the insulating structure has a thickness. The spacing 3 of the present invention is to provide a spacing between the coil and the magnetic core. Increasing the thickness of the insulating structure will lead to a decrease in the spacing 3 and even the inner wall of the insulating structure and the magnetic core. contact, but still maintain a spaced arrangement between at least part of the coil and the core.

It should be noted that there is a distance 3 between at least part of the magnetic core and the hollow channel 111, and the distance 3 refers to the distance 3 between each part of the magnetic core 2 and the wall passing through the hollow channel 111 and the coil. Part of the coil protrudes from the core window of the magnetic core 2. In a preferred embodiment, the wall of the hollow channel 111 protrudes from the magnetic core window of the magnetic core 2, so that the inner wall of the hollow channel 111 is between the inner wall of the hollow channel 111 and the magnetic core window of the magnetic core 2. With spacing 3.

As shown in FIG. 2 , in the embodiment of the present invention, two magnetic columns 22 are arranged on opposite sides of the magnetic core 2 , a middle magnetic column 23 is arranged on the magnetic core between the two magnetic columns 22 , and the middle magnetic column 23 is inserted into the hollow core In the channel 111 , a distance 3 is set between the middle magnetic column 23 and the hollow channel 111 , or a distance 3 is set between the middle magnetic column 23 passing through the wall of the hollow channel 111 and the coil.

In one embodiment of the present invention, the middle of the magnetic core 2 is provided with an intermediate magnetic column 23 , the intermediate magnetic column 23 is inserted into the hollow channel 111 , and an air gap 7 is opened on the intermediate magnetic column 23 , and the air gap 7 is opened in the magnetic core 2 . The role of the air gap 7 is to reduce the magnetic permeability, so that the coil characteristics are less dependent on the initial magnetic permeability of the magnetic core material, and the air gap can avoid the phenomenon of magnetic saturation under large AC signals or DC bias. , to better control the inductance, in addition, there is a distance 3 between the entire outer wall of the middle magnetic column 23 and the inner wall of the hollow channel, which can reduce the cutting of the coil by the leakage magnetic flux of the air gap 7.

As shown in FIG. 2 , FIG. 3 and FIG. 4 , in the embodiment of the present invention, the magnetic core 2 includes two sub-magnetic cores 21 , and the sub-magnetic cores 21 include an outer ring magnetic core 211 and a middle Posts 212; the two outer ring magnetic cores 211 are opposite and contact to form two magnetic posts and magnetic core windows, and the two central posts 212 are inserted into the hollow channel 111 opposite and spaced apart to form the central magnetic post 23 and the air gap 7.

In the embodiment of the present invention, the magnetic core 2 includes two sub-magnetic cores 21, and the sub-magnetic cores 21 each include an outer ring magnetic core 211 and a central column 212 disposed inside the outer ring magnetic core 211; the two outer ring magnetic cores 211 are opposite to each other. And contact to form two magnetic columns, the two middle columns 212 are opposite and spaced apart to form a middle magnetic column, an air gap in the middle magnetic column is formed between the axial end faces of the two middle columns 212, and the other air gaps are respectively opened in the middle magnetic column. On the two central pillars 212; the two sub-magnetic cores 21 are both open on one side, so that the outer ring magnetic core 211 is a semi-ring structure, and the semi-ring structure can be a circular half-ring or a square half-ring; A middle column 212 is arranged inside the outer ring magnetic core 211 , and the two middle columns 212 are opposite to each other and spaced apart to form a middle magnetic column 23 ; There is a distance, so that there is a distance between the air gap and the space channel 111 , so that the leakage magnetic flux on the magnetic core 2 can be kept away from the coil.

Specifically, the two sub-magnetic cores have the same size and are both E-shaped. The outer ring magnetic core includes two sub-magnetic columns disposed on both sides of the central column and a connecting magnetic column connecting the two sub-magnetic columns. The central column 212 is inserted into the hollow core. In the channel 111, one side wall of the winding portion is clamped between one sub-magnetic column and the middle column and abuts against the connecting magnetic column, and the opposite side wall of the winding portion is clamped between the other sub-magnetic column and the central column and is in contact with the connecting magnetic column. The outer ring magnetic core 211 is a semi-ring structure, and the semi-ring structure is a square half ring. The outer ring magnetic core 211 includes sub-magnetic columns arranged on both sides of the central column 212 and a magnetic column connecting the two sub-magnetic columns. The connecting magnetic column, the two sub-magnetic columns and the connecting magnetic column are both perpendicular to the connecting magnetic column; one sub-magnetic column, the middle column 212 and the connecting magnetic column form a clamping space, and the other sub-magnetic column, the middle column 212 and the connecting magnetic column form a clamping space. The column is surrounded by another holding space, and the above-mentioned two clamping spaces are used to cooperate with the skeleton 1 of the power conversion device; the two sub-magnetic cores 21 are both E-shaped, so that the length of the middle column 212 of the sub-magnetic core 21 is smaller than the length of the sub-magnetic column. Therefore, when the outer ring magnetic cores 211 face each other and are in contact with each other, an air gap can be formed between the two central pillars 212 at intervals.

As shown in FIG. 2 , in the embodiment of the present invention, the central column 23 is a rectangular parallelepiped column, the distances between the upper and lower end surfaces of the central column and the corresponding hollow channels are equal, and the distances between the left and right end surfaces of the central column and the hollow channels are equal. The center pillar 23 may also be in other shapes. The upper and lower end faces of the middle column are basically on the same plane as the window end face of the magnetic core, and each end face is a horizontal plane; due to the different shapes of the hollow channel 111 and the different insertion methods of the middle magnetic column 23, the upper and lower end faces of the middle magnetic column 23 are in the same plane. A first distance 31 is set between the end face, that is, the end face of the window of the magnetic core and the wall of the hollow channel 111. The opposite walls of the hollow channel 111 include a first wall and a second wall, which are respectively between the two end faces of the window of the magnetic core. Each has a first spacing 31 , and it can be understood that the first spacing 31 is substantially the spacing between the two end faces of the magnetic core window and the coils wound on the outer wall of the hollow channel 111 . A second distance 32 is set between the left end face and the right end face of the middle magnetic column 23 through the hollow channel 111 opposite the third wall and the fourth wall and the coil; the two first distances 31 may be equal or unequal, and the two second distances 32 can be equal or unequal, preferably, the two first spacings 31 are equal, and the two second spacings 32 are equal, the first spacing is 1/3-1/6 of the height of the magnetic core, preferably the first spacing The spacing between the two is larger than the diameter of the coil and smaller than the width of the central column. The leakage magnetic flux of the coil to the magnetic core 2, mainly the cutting of the bypass magnetic flux, is greatly reduced. The first spacing and the second spacing substantially ensure the distance between the coil and the magnetic core, which may be the spacing formed between the inner wall of the hollow channel 111 and the magnetic core, or may be formed by increasing the thickness of the hollow channel 111. In the present invention, the magnetic core The coil in the window should be as close as possible to the inner wall of the magnetic core window but keep a gap. Generally, insulating tape is wrapped around the coil, and the distance between the coil and the magnetic core can be adjusted by adjusting the thickness of the hollow channel.

In the embodiment of the present invention, as shown in FIG. 6 and FIG. 7 , n air gaps may be provided on the magnetic core, that is, the n air gaps divide the magnetic core into multiple sections, so that the magnetic core intermittently generates magnetic flux leakage It is mainly diffused magnetic flux, wherein the sum of the widths of n air gaps is equal to the width of the air gaps when the magnetic core has one air gap, so that the air gap width when the magnetic core is provided with n air gaps is relative to the width of the air gaps when the magnetic core is provided with n air gaps. When there is an air gap, the width of the air gap is reduced, so that the leakage flux through the air loop is reduced. When the leakage flux is reduced, the magnetic loss of the magnetic core is reduced, and when the leakage flux is reduced, the magnetic loss of the core is reduced. The leakage magnetic flux of the coil to the magnetic core is cut, and the eddy current loss of the coil is reduced. Combined with the setting of the second spacing described above, the distance between the diffused magnetic flux and the coil is increased, and it is difficult for the diffused magnetic flux to carry out the coil in the magnetic core window. Cutting, the eddy current loss is greatly reduced, and the setting of the air gap 7 can also prevent magnetic saturation.

For the existing magnetic core structure, only one air gap is provided on the magnetic core 2. In the magnetic core structure of the present invention shown in FIG. 6 and FIG. 7, the magnetic core 2 is provided with at least two air gaps 7. The widths of all air gaps 7 are equal to the width of the air gaps when one air gap 7 is opened on the magnetic core 2 . For example, the width of one air gap in the prior art is 8 mm, then the sum of the widths of multiple air gaps in the present application is 8 mm.

In the embodiment of the present invention, a plurality of air gaps 7 are provided on the magnetic core 2 to reduce the relative width of the air gaps 7 to reduce the leakage magnetic flux, thereby reducing the magnetic loss of the magnetic core structure. Therefore, it can reduce the cutting of the leakage flux of the coil to the magnetic core, reduce the eddy current loss of the coil, and achieve the purpose of increasing the inductance under the condition of the same number of coil turns; and, on the basis of the purpose of increasing the inductance The material of the magnetic core is not changed, so the production cost is reduced; two magnetic columns 22 are arranged on opposite sides of the magnetic core, and a middle magnetic column 23 is arranged on the magnetic core between the two magnetic columns 22. The magnetic column and the middle magnetic column 23 are both provided with at least two air gaps, and the widths of all the air gaps are equal to the width of the air gap when one air gap is opened on the middle magnetic column. The two magnetic columns 22 and the middle magnetic column 23 are cuboid magnetic columns; in other embodiments, the shape of the magnetic columns 22 can also be changed to a cylinder, a polygonal prism or an irregular column according to actual needs; specifically, At least two air gaps are provided on the two magnetic columns 22 and the middle magnetic column 23, and an appropriate number can be opened according to actual needs; The space between the magnetic columns 22 forms the air gap 7 , and the width of the air gap 7 generally refers to the size of the air gap in the axial direction of the magnetic column 22 .

As shown in FIG. 6 and FIG. 7 , in the embodiment of the present invention, at least two air gaps are opened on the middle magnetic column 23 , the at least two air gaps are arranged at intervals along the axial direction of the middle magnetic column, and each air gap is along the middle magnetic column. The axial widths of the columns 23 are of equal or unequal dimension. As a preferred embodiment, only the middle magnetic column 23 is provided with at least two air gaps. For example, the middle magnetic column is provided with three air gaps, and the three air gaps are arranged at intervals along the axial direction of the magnetic column 22. Preferably, The three are uniformly arranged along the axial direction of the magnetic column; the widths of the air gaps on the middle magnetic column 23 are equal, or, according to actual needs, the widths of the air gaps on the middle magnetic column 23 can be set to be unequal.

In the embodiment of the present invention, the magnetic core includes two sub-magnetic cores 21, and the sub-magnetic cores 21 each include an outer ring magnetic core 211 and a central column 212 disposed inside the outer ring magnetic core 211; the two outer ring magnetic cores 211 are opposite to each other and Contact to form two magnetic columns, the two middle columns 212 are opposite and spaced apart to form a middle magnetic column 23, an air gap in the middle magnetic column 23 is formed between the axial end faces of the two middle columns 212, and the other air gaps are opened respectively On the two center pillars 212 .

In the embodiment of the present invention, the magnetic core is composed of two sub-magnetic cores 21 . The sub-magnetic cores 21 include an outer ring magnetic core 211 and a central column 212 disposed inside the outer ring magnetic core 211 . One side of the two sub-magnetic cores 21 is open, so that the outer ring magnetic core 211 is a semi-ring structure, and the semi-ring structure can be a circular half ring or a square half ring; The columns 212 are opposite and spaced apart to form the middle magnetic column 23 , and the axial end faces of the two middle columns 212 form one air gap in the middle magnetic column, and the other air gaps on the middle magnetic column 23 are opened in the two middle columns 212 For example, three air gaps are opened on the middle magnetic column, the axial end faces of the two middle columns 212 form one of the three air gaps, and one middle column 212 is provided with the other of the three air gaps. , and the other center column 212 is provided with another air gap among the three air gaps.

As shown in FIG. 6 and FIG. 7 , in the embodiment of the present invention, the two sub-magnetic cores 21 have the same size and are both E-shaped, and the middle air gap of the middle magnetic column 23 is formed between the axial end faces of the two middle columns 212 71. The air gaps opened on each center column 212 are side air gaps 72.

In the embodiment of the present invention, the two sub-magnetic cores 21 are both E-shaped, the outer ring magnetic core 211 is a semi-ring structure, the semi-ring structure is a square half ring, the outer ring magnetic core 211 includes a center column 212 The sub-magnetic column on both sides and the connecting magnetic column connecting the two sub-magnetic columns, the two sub-magnetic columns and the connecting magnetic column are both perpendicular to the connecting magnetic column; a sub-magnetic column, the middle column 212 and the connecting magnetic column form a plug space , the other sub-magnetic column, the middle column 212 and the connecting magnetic column form another plug-in space, and the above-mentioned two plug-in spaces are used to cooperate with the skeleton of the power conversion device; the two sub-magnetic cores 21 are both E-shaped, so that the The length of the central column 212 of the magnetic core 21 is smaller than the length of the sub-magnetic column, so that when the outer ring magnetic cores 211 are opposite and in contact, an air gap can be formed between the two central columns 212; specifically, the width of the middle air gap 71 It is greater than or equal to the width of the side air gaps 72, and the distances between the air gaps are equal; preferably, the width of the middle air gap 71 is greater than the width of the side air gaps 72 to avoid being close to the magnetic core 2 due to the large width of the side air gaps 72 both sides of the magnetic core 2, resulting in increased damage to the magnetic core 2.

Several air gaps are set at intervals in the magnetic core window, and there is only a large magnetic potential difference in the center column, which can reduce the scattered magnetic flux. Due to the pulsating magnetic field, the scattered magnetic flux couples noise and EMI to the external space, causing interference to external circuits and even power grids. Further, in the present invention, in the window of the magnetic core, the left end face and the right end face of the middle magnetic column 23 are provided with a second distance 32 between the opposite third and fourth walls of the hollow channel 111 and the coil; the diffusion magnetic flux and the coil are increased. The distance between them increases, the scattered magnetic flux and the diffused magnetic flux attenuate along this distance, or the swing of the magnetic flux is small or it is difficult to cut the coil in the magnetic core window, which greatly reduces the eddy current loss and avoids the scattered magnetic flux from reducing noise and noise. EMI is coupled to the external space, causing interference to external circuits and even power grids.

Wherein, the inductance of the present invention, that is, the power conversion device, satisfies the following formula:

In the formula, r is the radius of the magnetic core, or half of the radius of the central column of the magnetic core or the width of the central column, δ is the total width of the air gap, d is the distance between the coil and the magnetic core, and K is the conversion of the magnetic flux of the magnetic core. value, γ is the converted value of the edge magnetic flux loss, M is the effective converted value of the magnetic flux, and the effective value of the magnetic flux is positively related to the magnetic flux; there are at least n air gaps on the magnetic core, and the width of each air gap is δ1 , δ2...δn, and satisfy δ1+δ2+...+δn=δ.

It should be noted that, in the embodiment of the present invention, the coil is equivalent to being sleeved on the middle magnetic column, and n air gaps are opened on the middle magnetic column, and d can be considered as the average value between the middle magnetic column and the hollow flow channel. distance;

The power conversion device designed with the above relational formula, under the condition of adjusting δ, d and the number of turns of the coil, produces lower losses, and the resulting increase in the effective value of the inductance magnetic flux φ can be obtained at the same number of turns N In the case of , the inductance L is larger. It can also be understood that when other parameters of the inductance remain unchanged, the same inductance L can be obtained when the number of turns N of the inductance is lower than that of the usual inductance, thereby further reducing the loss caused by the inductance coil.

It can be understood that increasing the value of d reduces the eddy current loss of the coil and increases the effective converted value M of the magnetic flux. To increase the value of d, different methods such as thickening the insulating layer 12 and changing the skeleton 1 can be adopted (but not limited to).

The data in Table 1 uses a magnetic core with a central column radius of r=5mm, a coil of 50 turns, and the total length of the winding portion 11 is 42mm. According to different δ values and d values, it is divided into 4 groups, and the corresponding power conversion is measured. The inductance of the device is calculated, and the eddy current loss of the coil is calculated. The measurement results are compared with the control groups 1 and 2. The results are shown in Table 1. The data of Examples 1-3 are directly listed in Table 1, and the magnetic cores are EE4220 and EE425.

Example 4

This embodiment is basically the same as Embodiment 1, and the difference is:

Referring to FIG. 3 , there are five air gaps, and the widths of each air gap are δ1, δ2, δ3, δ4, and δ5 respectively, and satisfy δ1+δ2+δ3+δ4+δ5=8mm.

In this embodiment, δ1=δ2=δ3=δ4=1 mm, and δ5=4 mm.

It should be noted that, among the 5 air gaps, each magnetic core 2 is provided with 2 air gaps, that is, the part of the magnetic core 2 extending into the core slot 11 is divided into 3 sections, and each section is connected in turn by an insulating pad, then each section The magnetic cores 2 are separated from each other to form an air gap.

In actual production, a single magnetic core 2 is segmented, and the segmented magnetic core 2 is tightly pressed together with an insulating pad to form a magnetic core with an air gap.

Comparative Example 1

This comparative example is basically the same as Example 1, the difference is:

The values of δ and d are randomly selected, in this control example, δ=8mm, d=2mm.

Comparative Example 2

This comparative example is basically the same as Example 1, the difference is:

The values of δ and d are randomly selected, in this control example, δ=8mm, d=1mm.

Table 1

grouping δ(mm) d (mm) Inductance (μH) Eddy current loss (W) 1 8 4 89 1.8 2 5 2.5 85 2.15 3 15 7.5 81 2.85 4 - 4 92 1.5 Control 1 8 2 72 3.5 Control 2 8 1 70 4.5

As can be seen from Table 1, Group 1, Group 2 and Group 3 all achieved good results, and Group 1 had the best effect. In addition, it can be seen from Group 4 that when multiple air gaps were used, the reduction of The influence of the diffused magnetic flux on the winding can further increase the inductance and further reduce the eddy current loss.

It can be seen from the control group 1 and the control group 2 that when the values of δ and d are randomly selected, the effect achieved is obviously lower than that of the examples of the present application.

Referring to FIG. 8, it is a schematic diagram of the apparatus and method for improving the power quality of the power grid according to the present invention. Among them, the rectifier circuit is used to realize the electrical isolation function, so as to ensure the safety of the power supply equipment and avoid the danger from the high-voltage feeder. The power factor correction circuit is used to force the line current to follow the line voltage, make the line current sinusoidal, improve the power factor and reduce the harmonic content. The time ratio enables the frequency and amplitude of the output voltage or current of the inverter to be flexibly changed according to people's wishes or the requirements of equipment work. The above circuit may also include a filter circuit, or the rectification and filter circuits may be combined into one circuit.

Among the above switching power supplies, a large number of magnetic material components are used, such as high-frequency transformers, pulse transformers, commutation and resonant inductors, power inductors, filter inductors, transformers, etc. current, causing serious harmonic pollution, reducing the power factor of the input end, causing huge waste and serious harm. Although the circuit shown in Figure 8 is used in modern inverter systems to suppress harmonics, the reliability of the circuit is reduced because the electric energy of this circuit needs to undergo three-stage transformation; the efficiency generally does not exceed 80%.

Improving circuit design and control methods to provide high-quality power and improve conversion rates is a hot topic in the field of power electronics, but it has been found that circuit improvements usually lead to the number of devices and the complexity of the control circuit, in exchange for increased efficiency. The existing technology has also been trying to improve the structure and manufacturing process of magnetic material components, reduce magnetic flux leakage, leakage inductance, and reduce losses to fundamentally solve the problem.

In the present invention, the inductance core and coil in the above circuit are set as bypass magnetic flux to partially cut the windings to reduce leakage flux and leakage inductance losses; further, the present invention sets the magnetic core and coil as bypass magnetic flux to partially cut the magnetic core The winding in the window can reduce the loss of magnetic leakage and leakage inductance. The specific method of the present invention is to set the coil part outside the window of the magnetic core to increase the distance between the coil and the magnetic core, and the coil inside the magnetic core window is set close to The inner wall of the magnetic core window is far away from the central column of the magnetic core to reduce the interference and loss of the leakage inductance. Further, the present invention further reduces the interference and loss of magnetic flux leakage inductance and increases heat dissipation by setting the central column as multiple spaced air gaps, thereby fundamentally solving the problem of inductance loss. Designed to reduce harmonics and voltage fluctuations to improve power factor and improve power quality.

Generally, the inductance corresponding to the "leakage flux" in an inductive device is the "leakage inductance". The existence of the leakage inductance causes the leakage inductance energy storage to be released when the switch tube is turned off, and a voltage spike appears on the switch tube, increasing the switch tube. The turn-off loss is easy to damage the switch tube. Moreover, the leakage inductance is also easy to resonate with the distributed capacitance, causing electromagnetic interference. At the same time, since the leakage inductance is equivalent in the form of series connection in the circuit, when the voltage is constant, the larger the leakage inductance, the lower the effective value of the current, the lower the output power, the lower the energy conversion efficiency of the high-frequency transformer, the doubled resonance, and the lower the output power. The electromagnetic interference of the circuit and the power grid increases. Therefore, reducing the leakage inductance is very important to reduce the power loss, protect the performance of the switching tube and switching power supply, and reduce the impact on the power grid. By setting the spacing and the air gap, the invention keeps the coil away from the leakage magnetic flux of the magnetic core, avoids interference, has high output, high energy conversion efficiency of the high-frequency transformer, reduces resonance, and reduces electromagnetic interference to circuits and power grids.

The magnitude of the current harmonics is related to the inductance used. The larger the inductance, the more fully suppressed the harmonics. In the prior art, the inductance is generally increased by increasing the diameter of the coil, which often causes problems such as poor power supply adaptability and inductance. A series of problems such as heat generation, volume and cost increase. The invention increases the inductance by reducing the eddy current loss without changing the number of turns of the coil, without increasing the volume and cost, and only needs to select the inductor according to the minimum inductance, and the same number of turns of the coil can greatly improve the inductance to harmonics. Suppression, reduce power grid harmonics, improve the quality of power grid power.

Since the inductance of the inductor is greatly improved by reducing the loss of the coil and the loss of the magnetic core during the power conversion process under the condition that the number of turns of the coil remains unchanged, the input end of the power conversion device can adapt to different ranges of input. voltage without affecting the use of the inductor; since there is no need to increase the number of coil turns or switch to a more expensive magnetic core, the cost of the same volume is greatly reduced.

In the prior art, under normal circumstances, the input end of the coil of the power conversion device can be connected to a certain rated voltage, and high-end products can be connected to any input voltage between 170-380 V. For different voltages, it is necessary to select and Adapting to different models, the turbine loss of the inductor structure in the circuit of this application is reduced by nearly 40%, and the inductance is increased by 20%. The loss can enable the input end of the coil of the power conversion device to be connected to a wide range of input voltages, such as 1000 watts In the power output state, the input voltage can adapt to the voltage between 110-600V; the best input voltage is between 200 and 500V, and there is no need to replace different models. The inductance of the present invention can withstand voltage fluctuations, and also improves adaptability to transmission lines with unstable voltages, and will not cause power grid fluctuations because the voltage is too low to be turned on or output normally, and the voltage is too high to cause burnout.

The frequency, voltage and power supply reliability of the power grid are important indicators to measure the quality of the power grid. The harm of reactive power to the power grid includes: reducing the output of generator active power, reducing the power supply capacity of transmission and substation equipment, resulting in increased line voltage loss and electrical energy. The increase of loss causes low power factor operation and voltage drop, so that the capacity of electrical equipment cannot be fully utilized. In the case of the same number of turns as the prior art, the inductance of the present invention increases the inductance by reducing the magnetic loss, improves the inductance, and reduces the reactive power according to the relationship between the power factor, reactive power and apparent power. The voltage drop of the power grid is reduced, and the compensation requirements for the reactive power of the power grid are reduced.

The inductance of the present invention can be the prior art EE, EI, EF, EEL, PEEPEL, ER, ETD, EQ/EQI, EP, EP, EFD, EPC, POT, PQ, RM, etc. specifications.

As shown in FIG. 7 , in the embodiment of the present invention, at least two air gaps divide the middle magnetic column into several sub-intermediate magnetic columns 231 , and an air gap is formed between the axial end faces of two adjacent sub-intermediate magnetic columns 231 . An insulating member 8 is provided in each air gap, and the insulating member 8 is attached and connected to the axial end faces of the two sub-middle magnetic columns 231 respectively.

In the embodiment of the present invention, the insulating member 8 is inserted into the air gap to realize the connection between two adjacent sub-intermediate magnetic columns 231, and the insulating member 8 has insulating properties, which does not have a cutting effect on the main magnetic flux; The arrangement of multiple air gaps and multiple insulating members 8 enables the saturation value of the magnetic core to be raised higher and the distribution of the magnetic circuit to be more balanced; wherein, the insulating members 8 can be completely inserted into the air gap or partially inserted into the air gap. In addition, the material and shape of the insulating member 8 can be various, as long as there is no cutting effect on the magnetic field lines.

As shown in FIG. 7, in the embodiment of the present invention, the insulating member 8 is a first plastic sheet 81, the first plastic sheet 81 is inserted into the corresponding air gap, and the opposite sides of the first plastic sheet 81 are respectively connected to the two sub-intermediate magnetic The axial end surfaces of the pillars 231 are attached and connected, and the area of the side surface of the first plastic sheet 81 is smaller than or equal to the area of the axial end surfaces of the sub-middle magnetic pillars 231 .

In the embodiment of the present invention, the insulating member 8 is made of plastic, and its shape is sheet-like. The first plastic sheet 81 is inserted into the air gap. Fitting connection, the opposite side is connected with the axial end face of the adjacent sub-middle magnetic column 231 to realize the connection of two adjacent sub-middle magnetic columns 231; when the insulating member 8 is completely inserted into the air gap, the side surface of the first plastic sheet 81 The area may be smaller than the area of the axial end surface of the sub-middle magnetic column 231, or equal to the area of the axial end surface of the middle magnetic column, as long as it is ensured that two adjacent sub-intermediate magnetic columns 231 can be connected, preferably, the side surface of the first plastic sheet 81 The area is equal to the area of the axial end face of the middle magnetic column, which increases the connection strength between the two adjacent sub-intermediate magnetic columns 231 .

Further, the middle magnetic column is provided with a second plastic sheet extending along the axial direction of the middle magnetic column. The first plastic sheet is arranged on the same side of the second plastic sheet, and the second plastic sheet integrates several first plastic sheets 81, so as to avoid the situation that several first plastic sheets 81 are easily lost, and can realize the integration of several first plastic sheets 81. The sheets 81 are simultaneously inserted into their corresponding air gaps to improve the insertion efficiency.

As shown in FIG. 7 , in the embodiment of the present invention, heat sinks 9 are provided on opposite sides of the first plastic sheet 81 . One side of the heat sink 9 is connected to the axial end face of the middle magnetic column 231 , and the other side is connected to the axial end surface of the middle magnetic column 231 . One side of the first plastic sheet 81 is connected.

In the embodiment of the present invention, the disposition of the heat sink 9 enables the first plastic sheet 81 to be connected to the sub-middle magnetic columns 231 to realize the connection of two adjacent sub-middle magnetic columns 231, and at the same time, the heat sink 9 can reduce the temperature of the magnetic core , which is conducive to heat dissipation and further improves the saturation value.

As shown in FIG. 7 , in the embodiment of the present invention, the heat sink 9 is a glue layer 91 for pasting the first plastic sheet 81 on the axial end faces of the two sub-middle magnetic columns 231 .

In the embodiment of the present invention, the glue layer 91 is epoxy resin glue. Of course, it can also be other types of materials that can play a bonding role. At the same time, this material cannot have the function of magnetic permeability, and needs to have the function of heat dissipation; the glue layer The area of the side surface of 91 may be smaller than the area of the side surface of the plastic sheet 81 and the area of the axial end surface of the sub-middle magnetic column 231, or it may be equal to the area of the side surface of the plastic sheet 81 and the area of the axial end surface of the sub-middle magnetic column 231. Preferably, the side surface of the glue layer 91 The area is equal to the area of the side surface of the plastic sheet 81 and the area of the axial end face of the sub-middle magnetic column 231 , which improves the connection strength between two adjacent sub-middle magnetic columns 231 .

As shown in FIG. 3 , in the embodiment of the present invention, first bumps 4 protruding axially relative to the winding portion 11 are provided on opposite sides of the top of the winding portion 11 , and opposite sides of the bottom of the winding portion 11 are provided with first bumps 4 . A second bump 5 protruding axially relative to the winding portion 11 is provided, and a part of the connecting magnetic core is sandwiched between the first bump 4 and the second bump 5 .

In the embodiment of the present invention, when the upper and lower end surfaces and the left and right end surfaces of the center column are spaced with the inner wall of the hollow channel 111 , in order to realize that the magnetic core 2 is mounted on the bobbin 1 , the opposite sides of the top of the winding portion 11 are arranged with distances. A first protrusion 4 protruding in the axial direction is provided on the side, and a second protrusion 5 protruding in the axial direction is provided on the opposite sides of the bottom of the winding portion 11 , between the first protrusion 4 and the second protrusion 5 A clamping space is formed, and part of the connected magnetic core is clamped in the clamping space, so as to realize the assembly of the magnetic core 2 and the bobbin 1 and improve the stability of the magnetic core 2 on the bobbin 1 .

As shown in FIG. 3 , in the embodiment of the present invention, the left and right sides of the first bump 4 are radially protruded relative to the winding portion 11 to form two first extending portions 41 . Two second extending portions 51 protrude radially relative to the winding portion 11 to form two second extending portions 51 .

In the embodiment of the present invention, in order to further enhance the assembly strength between the magnetic core 2 and the bobbin 1 , first extending portions 41 are provided on the left and right sides of the first bump 4 , and the left and right sides of the second bump 5 are provided with first extending portions 41 . Each side is provided with a second extending portion 51 , a clamping space is formed between the first extending portion 41 and the second extending portion 51 , and the sub-magnetic column and the remaining part of the connecting magnetic core are arranged in the clamping space.

As shown in FIG. 3 , in the embodiment of the present invention, two first protrusions radially protrude relative to the winding portion 11 to form a first groove body, and two second protrusions radially protrude relative to the winding portion 11 to form a first groove body. In the second groove body, the winding portion 11 located between the first protrusion and the second protrusion is provided with four third protrusions radially protruding relative to the winding portion 11, and one of the two opposite third protrusions A third groove body is formed between the groove bodies, and each groove body is connected in sequence to form a continuous limit groove 6 .

In the embodiment of the present invention, the first protrusions radially protrude upward relative to the winding portion 11 , so that a first groove body is formed between two opposite first protrusions, and the second protrusions face downward relative to the winding portion 11 . The radial protrusions form a second groove body between the two opposite second protrusions, and the winding portion 11 between the first protrusion and the second protrusion is also provided with an opposite diameter of the winding portion 11. The four third protrusions protruding toward each other, the third groove body is formed between the two opposite third protrusions, and the pair of the first groove body, the second groove body, the third groove body and the fourth groove body are formed. The limit slot 6 in which the coil is limited, so that the coil is wound in the limit slot 6, so as to avoid the situation of winding confusion when the coil is wound.

As shown in FIG. 3 , in the embodiment of the present invention, a plurality of coil pins 12 are arranged on the second protrusion at intervals along the left-right direction.

In the embodiment of the present invention, the second protrusion is provided with a coil pin 12, the coil wound on the winding portion 11 has an input end and an output end, and both the input end of the coil and the output end of the coil are set on the coil pin 12 on.

The present invention also provides a power conversion method, using the power conversion device provided by the above technical solution, under the condition that the number of turns of the coil remains unchanged, by increasing the distance between at least part of the coil and the magnetic core or reducing the air on the magnetic core The width of the gap widens the range of the input voltage connected to the input end of the coil.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Within the scope of the technical solution of the present invention, personnel can make some changes or modifications to equivalent examples of equivalent changes by using the above-mentioned technical content, but any content that does not depart from the technical solution of the present invention is based on the technical solution of the present invention. Substantially any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the solutions of the present invention.

Claims (10)

1. A circuit for improving the electric energy quality of a power grid is characterized by comprising a power grid input terminal, a rectifying circuit, a power factor correction circuit, a high-frequency inverter circuit and an output terminal which are sequentially connected, wherein a control circuit is in control connection with the rectifying circuit, the power factor correction circuit and the high-frequency inverter circuit, the high-frequency inverter circuit comprises a magnetic core and a coil which are used for magnetic coupling, the coil is wound on an insulating structure, and one part of the magnetic core is arranged in a hollow channel of the insulating structure; the core and coil arrangement is such that a portion of the flux cuts the coil and a portion of the bypass flux cuts the coil within the core window to reduce eddy current losses.

2. A circuit for improving power quality of a power grid as claimed in claim 1, wherein the leakage flux cuts the coil within the core window to reduce eddy current losses.

3. A circuit for improving power quality of a power grid as claimed in claim 2, wherein at least some of the windings are spaced from the window end of the core by a first distance.

4. A circuit for improving power quality of a power grid according to claim 3, wherein the partial coil is spaced from the window end of the core by a first distance through the wall of the hollow channel of the insulating structure.

5. A circuit for improving the power quality of a power grid according to claim 4, wherein the coil is spaced from the two end faces of the core window by a first distance through the first and second opposite walls of the hollow passage of the insulating structure.

6. A circuit for improving the power quality of a power grid according to any one of claims 1 to 5, wherein the coil is provided with a second distance between the left end face and the right end face of the middle magnetic column respectively corresponding to the third wall and the fourth wall which are opposite to each other and pass through the hollow channel of the insulating structure.

7. A circuit for improving the power quality of a power grid according to any one of claims 1 to 5, wherein the first and second opposite walls of the hollow channel of the insulating structure are spaced from the two end faces of the window of the magnetic core by a first distance, and the first distance is 1/3-1/6 of the height of the magnetic core.

8. A circuit for improving the power quality of a power grid according to any one of claims 1-5, wherein the air gaps in the magnetic core are n spaced air gaps, n is greater than or equal to 2, and the sum of the widths of the n air gaps is equal to the width of the air gap when the magnetic core has one air gap, so as to reduce the eddy current loss.

9. A circuit for improving power quality of a power grid according to claim 8, wherein said magnetic core and said coil for magnetic coupling satisfy the following equation:

where r is a radius of the core or a radius of a center pillar of the core, and is a width of the air gap, d is a distance between the coil and the core, K is a reduced value of a magnetic flux of the core, γ is a reduced value of a fringe magnetic flux loss, and M is an effective reduced value of the magnetic flux.

10. A method of improving the power quality of a power grid using the circuit of any one of claims 1 to 9, comprising: the high-frequency inverter circuit is characterized in that a magnetic core and a coil in the high-frequency inverter circuit are arranged as a part of a bypass magnetic flux cutting winding to reduce eddy current loss.

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