JP2021100055A - Transformer and power converter using the same - Google Patents

Abstract

To suppress a potential difference between components that make up a transformer, shorten a distance between the components, and downsizes the transformer while ensuring insulation.SOLUTION: A transformer includes a primary winding, a first core with the primary winding installed, a secondary winding, a second core with the secondary winding installed, and an insulating plate sandwiched between the first core and the second core, and a voltage dividing electrode is provided inside the insulating plate, a core contact electrode is provided outside the insulating plate, and the voltage dividing electrode and the core contact electrode are electrically connected to each other, and the core contact electrode is electrically connected to at least one of the first core and the second core.SELECTED DRAWING: Figure 3

Description

The present invention relates to a transformer and a power conversion device using the transformer.

In recent years, electrification has been accelerating in various fields. In particular, the progress of electrification of mobile objects (automobiles, aircraft, construction machinery, ships, etc.) and the introduction of renewable energy is remarkable, and the demand for power conversion devices used in these power supply systems is increasing. In this trend, the level of specifications required for power converters is rapidly increasing.

Specifications required for power converters include not only basic performance of AC / DC input / output and high efficiency, but also miniaturization, high reliability, multiple inputs / outputs, high voltage, and addition of storage function. ..

Further, in applications where the installation space is limited, it is particularly required to miniaturize the transformer which is a part of the configuration of the power conversion device.

As a technique for realizing this, Solid State Transformer (hereinafter referred to as "SST") has been proposed. This SST generates a voltage of an arbitrary frequency and amplitude from a converter 1 that converts a commercial frequency voltage into a high frequency voltage of several kHz to several hundred kHz, a transformer that is driven by the converter 1 at a high frequency, and a transformer output. It is composed of a converter 2. High-frequency driven transformers can be significantly smaller and lighter than conventional commercial transformers.

When SST is applied to high-voltage equipment such as for grid interconnection, a high voltage of several kV is superimposed on the winding connected to the high-voltage side (hereinafter referred to as "primary winding") with respect to the ground potential. Therefore, it is necessary to ensure insulation between the winding connected to the low voltage side (hereinafter referred to as "secondary winding") and the primary winding on the high voltage side.

Patent Document 1 has a shielding device for electrically shielding the first core portion from the second core portion, in a state where the conductive pattern faces the primary winding and the first core portion. A transformer is disclosed that includes an electrostatic shield placed between the two cores and between the primary and secondary windings.

Japanese Unexamined Patent Publication No. 2003-86436

Since the electrostatic shield described in Patent Document 1 is provided with a thin conductive layer on the surface of the insulating material, the potential difference between the first core portion and the second core portion is large, and the electrostatic shield and the core portion Partial discharges can occur in the small gaps between them.

An object of the present invention is to suppress a potential difference between each component constituting a transformer, shorten the distance between the components, and reduce the size of the transformer while ensuring insulation.

The transformer of the present invention includes a primary winding, a first core in which the primary winding is installed, a secondary winding, a second core in which the secondary winding is installed, and a first core. An insulating plate sandwiched between the second core is provided, a voltage dividing electrode is provided inside the insulating plate, and a core contact electrode is provided outside the insulating plate. The core contact electrode is electrically connected, and the core contact electrode is electrically connected to at least one of the first core and the second core.

According to the present invention, it is possible to suppress the potential difference between each component constituting the transformer, shorten the distance between the components, and miniaturize the transformer while ensuring insulation.

It is an oblique projection drawing which shows the transformer of Example 1. FIG. It is an exploded oblique projection drawing of the transformer of FIG. It is a vertical cross-sectional view of the transformer of FIG. It is a horizontal cross-sectional view which shows the example of the insulating plate which comprises the transformer of FIG. It is a horizontal cross-sectional view which shows the insulating plate of Example 2. FIG. It is a horizontal cross-sectional view which shows the insulating plate of Example 3. FIG. It is a schematic cross-sectional view which shows the transformer of Example 1. FIG. It is a circuit block diagram which shows the equivalent circuit of the transformer of FIG. 5A. FIG. 5 is an enlarged cross-sectional view showing a gap portion of the transformer of FIG. 5A. It is a schematic cross-sectional view which shows the conventional transformer. It is a circuit block diagram which shows the equivalent circuit of the transformer of FIG. 6A. FIG. 6 is an enlarged cross-sectional view showing a gap portion of the transformer of FIG. 6A. It is a block diagram which shows the power conversion apparatus of this invention.

Although the transformer is mainly described in the present specification, the transformer can be a component of the power conversion device, and the power conversion device can be a component of the power supply system.

First, a conventional transformer will be described.

FIG. 6A is a schematic cross-sectional view showing a conventional transformer not provided with an electrostatic shield or the like.

In this figure, the transformer 60 includes a first core 612a, a second core 612b, an insulating plate 622 arranged between them, a primary winding 14 installed on the first core 612a, and the like. It includes a secondary winding 16 installed on the second core 612b.

The voltage dividing electrode described later is not provided inside the insulating plate 622.

The magnetic flux 61 is generated by the current flowing through the primary winding 14.

Further, the broken line ZZ'shown in the figure corresponds to a part of the circuit configuration of FIG. 6B described below.

FIG. 6B is a circuit configuration diagram showing an equivalent circuit of the transformer of FIG. 6A.

Z and Z'shown in FIG. 6B correspond to the dashed lines ZZ'in FIG. 6A. That is, the first core, the primary winding, the insulator, the secondary winding and the second core are electrically connected in this order. Further, Z and Z'are electrically connected by a convex portion of the first core, an insulator and a convex portion of the second core, forming a closed circuit as a whole.

In FIG. 6B, the potential of the primary winding is 11 kV and the potential of the secondary winding is 0 V (ground potential). Between the primary winding and the secondary winding, there is a bobbin and a gap between the bobbin and the insulator. As a result, the potentials on the two surfaces (upper and lower surfaces in the drawing) of the insulator located in the region sandwiched between the primary winding and the secondary winding are 7 kV and 4 kV, respectively.

Further, the outer surface of the primary winding (the upper surface of the primary winding in the drawing) is in electrical contact with the first core (the concave portion thereof) via the bobbin to form a capacitor. Similarly, the outer surface of the secondary winding (the lower surface of the secondary winding in the figure) is in electrical contact with the second core (its recess) via the bobbin to form a capacitor. ..

Since the first core and the second core have lower electrical resistance than the resin used for the insulator, at the end of the convex portion of the first core and the second core (the portion close to the insulator). Also has the same potential as each recess. In this example, it is 8.5 kV and 2.5 kV, respectively. Therefore, the potential difference is 6 kV.

In this way, a capacitor is formed between each member to form a circuit as a whole.

FIG. 6C is an enlarged cross-sectional view showing a gap portion of the transformer of FIG. 6A.

A gap 63 is microscopically large between the insulating plate 622 and the first core 612a in the vicinity thereof due to surface roughness, tolerance, or other reasons, unless the structure is intentionally brought into close contact with the insulating plate 622. It occurs less.

As shown in FIG. 6B, the potential difference of 6 kV between the first core and the second core is large. Further, since the insulating plate 622 is a dielectric material, an electric field larger than the electric field of the insulating plate 622 may be generated in the gap 63 (called electric field concentration). Therefore, in the gap 63 of FIG. 6C, a partial discharge 65 may occur, depending on the size of the gap 63.

In order to make the partial discharge 65 less likely to occur, it is necessary to reduce the potential difference between the first core and the second core and relax the electric field. It is possible to increase the distance between parts or add parts to alleviate the electric field, but the problem is that the size of the transformer becomes large, and the magnetic flux generated in the core becomes small, which reduces the performance of the transformer. Problems can occur.

Hereinafter, examples of the present invention will be described with reference to the drawings. In addition, substantially the same or similar configurations are designated by the same reference numerals, and when the explanations are duplicated, the explanations may be omitted.

FIG. 1 is an oblique projection drawing showing a state in which the components constituting the transformer of this embodiment are incorporated.

In this figure, the transformer 10 includes a first core 12a, a second core 12b, an insulating plate 22 arranged between them, a primary winding 14 installed in the first core 12a, and the like. It includes a secondary winding 16 installed on the second core 12b.

The primary winding 14 is fixed to the bobbin 24a (primary side bobbin). The secondary winding 16 is fixed to the bobbin 24b (secondary bobbin). The primary winding 14 is installed together with the bobbin 24a on a convex portion formed in the central portion of the first core 12a. The secondary winding 16 is installed together with the bobbin 24b in a convex portion formed in the central portion of the second core 12b.

The first core 12a and the second core 12b are made of ferrite having a high magnetic permeability. In addition, these materials are not limited to ferrite, and other magnetic materials can also be applied.

The bobbins 24a and 24b are installed so as not to be completely in close contact with the first core 12a or the second core 12b, and a gap is provided between the bobbins 24a and 24b and the first core 12a or the second core 12b. It is desirable to secure it.

The voids provided in this way function as an electric field relaxation layer for preventing partial discharge. The void also has a function of cooling the primary winding 14 and the secondary winding 16 as an air passage. Further, the primary winding 14 and the first core 12a can be separated from each other by a gap, and the heat generated by these can be prevented from being tilted. The relationship between the secondary winding 16 and the second core 12b is the same.

The insulating plate 22 electrically insulates the primary winding 14 from the secondary winding 16 and electrically insulates the first core 12a from the second core 12b. Details of the insulating plate 22 will be described later.

FIG. 2 is an exploded oblique projection drawing of the transformer of FIG.

As shown in this figure, the first core 12a and the second core 12b are blocks having an "E" -shaped cross section. The shapes of the first core 12a and the second core 12b may be other shapes such as a "C" shape, a half ring, and the like.

Further, a core contact electrode 28 is installed on the insulating plate 22.

FIG. 3 is a vertical cross-sectional view of the transformer of FIG.

As shown in FIG. 3, the insulating plate 22 has a configuration in which the voltage dividing electrode 29 is embedded inside the substrate 26 made of resin. The voltage dividing electrodes 29 are provided in two layers (two) at positions facing the bottom surfaces of the bobbins 24a and 24b, respectively. It is desirable that the voltage dividing electrode 29 is parallel to the bottom surfaces of the bobbins 24a and 24b. The voltage dividing electrode 29 may be a metal plate or thin film such as copper, or may be a resin or other material as long as it is conductive.

In this figure, the voltage dividing electrode 29 has two layers, but it may be one layer or three or more layers depending on the application.

The core contact electrode 28 is provided on both the surfaces of the insulating plate 22 on the primary winding 14 side and the secondary winding 16 side. The core contact electrode 28 is arranged so as to be in contact with the first core 12a and the second core 12b. The core contact electrode 28 is made of a conductive material such as copper.

Further, the core contact electrode 28 is connected to the voltage dividing electrode 29 by a conductive connecting wire 32. The connecting line 32 is also embedded in the substrate 26.

It is desirable that the core contact electrode 28, the voltage dividing electrode 29, and the connecting line 32 be arranged in a region where the magnetic flux generated in the first core 12a and the second core 12b does not pass. This is because eddy currents are likely to occur. In particular, since the voltage dividing electrode 29 has a large area, its arrangement is important. It is desirable that the voltage dividing electrode 29 is arranged in a region sandwiched between the primary winding 14 and the secondary winding 16.

It is desirable that the core contact electrode 28 is arranged on the primary winding 14 side and the secondary winding 16 side. In particular, it is desirable to arrange the first core 12a and the second core 12b on the side surface portions (primary winding 14 side and secondary winding 16 side) of the convex portions (ends thereof). This position is also desirable from the viewpoint of installing the core contact electrode 28 at a position as far as possible from the primary winding 14 and the secondary winding 16.

FIG. 4A is a horizontal cross-sectional view showing an example of an insulating plate constituting the transformer of FIG.

FIG. 4A shows a cross section of the insulating plate 22 including the voltage dividing electrode 29 (one of the layers when a plurality of layers are embedded).

The voltage dividing electrode 29 has a rectangular shape. The voltage dividing electrode 29 is arranged in a part of the region where the primary winding 14 and the secondary winding 16 are projected on the horizontal cross section. The voltage dividing electrode 29 becomes an intermediate potential between these two potentials in an electric field generated by the difference in potentials of the primary winding 14 and the secondary winding 16.

In manufacturing the insulating plate 22 provided with the voltage dividing electrode 29, it is desirable to embed the insulating plate 22 by vacuum defoaming in order to arrange the voltage dividing electrode 29 while preventing air from remaining in the substrate 26. Alternatively, it can be manufactured so that a metal foil having an arbitrary shape is formed between the resin plates in the same manner as when a printed circuit board having two or more layers is manufactured.

Further, regarding the connecting wire 32, in addition to the method of embedding by resin molding, a conductor in contact with the voltage dividing electrode 29 may be installed in advance on the resin layer located on the outside in the same manner as in producing a printed circuit board. Further, even if a through hole such as a through hole is provided in the resin layer located on the outside so that a part of the voltage dividing electrode 29 is exposed, and the core contact electrode 28 is connected, it may be connected by solder or the like. Good.

FIG. 5A is a schematic cross-sectional view showing the transformer of the embodiment.

In this figure, the transformer 10 includes a first core 12a, a second core 12b, an insulating plate 22 arranged between them, a primary winding 14 installed in the first core 12a, and the like. It includes a secondary winding 16 installed on the second core 12b.

A voltage dividing electrode 29 is provided inside the insulating plate 22, and is connected to the core contact electrode 28 by a conductive connecting wire. The core contact electrode 28 is in contact with the first core 12a and the second core 12b.

The magnetic flux 51 is generated by the current flowing through the primary winding 14.

Further, the broken lines ZZ'shown in the figure correspond to a part of the circuit configuration of FIG. 5B described below.

FIG. 5B is a circuit configuration diagram showing an equivalent circuit of the transformer of FIG. 5A.

Z and Z'shown in FIG. 5B correspond to the dashed lines ZZ'in FIG. 5A. That is, the first core, the primary winding, the insulator, the secondary winding and the second core are electrically connected in this order. Further, Z and Z'are electrically connected by a convex portion of the first core, an insulator and a convex portion of the second core, forming a closed circuit as a whole. In FIG. 5B, the two voltage dividing electrodes inside the insulator shown on the right side are electrically connected to the convex portion of the first core and the convex portion of the second core shown on the left side, respectively.

In FIG. 5B, the potential of the primary winding is 11 kV and the potential of the secondary winding is 0 V (ground potential). Between the primary winding and the secondary winding, there is a bobbin and a gap between the bobbin and the insulator. Further, two voltage dividing electrodes are provided inside the insulator. As a result, the potentials of the two voltage dividing electrodes are 7 kV and 4 kV, respectively. Since the two voltage dividing electrodes are electrically connected to the first core and the second core by the respective core contact electrodes, the end of the convex portion of the first core and the second core (insulator). In the portion close to), the potentials of the respective voltage dividing electrodes are 7 kV and 4 kV. Therefore, the potential difference is 3 kV.

The potentials on the two surfaces (upper and lower surfaces in the drawing) of the insulator located in the region sandwiched between the primary winding and the secondary winding are 8 kV and 3 kV, respectively.

Since the first core and the second core have lower electrical resistance than the resin constituting the insulator, even at the end of the recess of the first core and the second core (the part close to the insulator). , The potential is the same as each convex part. In this example, it is 7 kV and 4 kV, respectively.

In this way, a capacitor is formed between each member to form a circuit as a whole.

FIG. 5C is an enlarged cross-sectional view showing a gap portion of the transformer of FIG. 5A.

There is a large gap 53 microscopically between the insulating plate 22 and the first core 12a adjacent to the insulating plate 22 due to surface roughness, tolerances, and other reasons, unless a structure is intentionally brought into close contact with the insulating plate 22. It occurs less or less.

As shown in FIG. 5B, the potential difference between the first core and the second core is 3 kV, which is smaller than that of the conventional example of FIG. 6B. Therefore, in the gap 53 of FIG. 5C, partial discharge is less likely to occur, although it depends on the size of the gap 53.

FIG. 4B is a horizontal cross-sectional view showing the insulating plate of the second embodiment.

The configuration of other parts of the transformer is the same as in the first embodiment.

In this figure, the voltage dividing electrode 29 is not a simple rectangular shape but a comb shape. In other words, the voltage dividing electrode 29 has a configuration in which a plurality of elongated electrodes are arranged in parallel and one end of the electrodes is conductive. As a result, it is possible to prevent the generation of eddy currents due to the magnetic fields generated by the first core 12a and the second core 12b (FIG. 3) as much as possible. In other words, by subdividing the voltage dividing electrode 29, it is possible to prevent the generation of an eddy current having a large diameter.

The number, width, spacing, etc. of parallel electrodes constituting the comb shape are not limited to the example of FIG. 4B. The thickness and conductivity of the voltage dividing electrode 29 are also important factors. These factors are designed according to the frequency and intensity of the magnetic field penetrating the voltage dividing electrode 29.

FIG. 4C is a horizontal cross-sectional view showing the insulating plate of the third embodiment.

The configuration of other parts of the transformer is the same as in the first embodiment.

In this figure, the voltage dividing electrode 29 has a fold shape. In other words, the voltage dividing electrode 29 has a configuration in which a plurality of elongated electrodes are arranged in parallel and their ends are alternately conducted. In other words, the voltage dividing electrode 29 shown in this figure has a meandering shape such as an elongated conductive film. The meandering shape may be not only a fold shape, which is a regular reciprocating wiring as shown in this figure, but also an arbitrary complicated bending shape.

As a result, it is possible to prevent the generation of an eddy current having a large diameter, as in the second embodiment.

Further, in the present invention, instead of the voltage dividing electrode used in the above embodiment, three capacitors connected in series (generally used ones may be used) are used, and the primary winding and the secondary winding are used. It may be configured to electrically connect the wire. In this case, the positions where the capacitors are connected in the primary winding and the secondary winding can be set arbitrarily. Then, as in the above embodiment, a core contact electrode is provided outside the insulating plate, and the end of the three capacitors located at the center (middle) of the series connection is electrically connected to the core contact electrode. Connect to.

The number of capacitors connected in series may be three or more. In that case, the core contact electrode is electrically connected to the terminal of the capacitor located at other than both ends of the series connection.

According to the above embodiment, the insulating property is improved and the partial discharge is suppressed, so that the spatial distance and the creepage distance of the transformer can be reduced.

As a result, the SST type power conversion device that combines the transformer and the semiconductor element of the embodiment can be miniaturized, which is particularly effective in applications where the installation space of the power conversion device is limited.

Hereinafter, the power conversion device including the transformer of the above embodiment will be described with reference to the drawings.

FIG. 7 is a block diagram showing a power conversion device.

In this figure, the power converter 701 has N converter cells 720-1 to 720-N (N is a natural number of 2 or more). Then, each converter cell 720-k (where k is a stage number and 1 ≦ k ≦ N) is directly connected to a pair of primary side terminals 725 and 726 and a pair of secondary side terminals 727 and 728. Converter 711 (first AC / DC converter, primary side converter), AC / DC converter 712 (second AC / DC converter, primary side converter), AC / DC converter 713 (third AC / DC converter) , Secondary side converter), AC / DC converter 714 (fourth AC / DC converter, secondary side converter), transformer 715 (high frequency transformer), and capacitors 717 and 718. ..

The primary side terminals 725 and 726 of the converter cells 720-1 to 720-N are sequentially connected in series, and the primary side power supply system 731 is connected to these series circuits. Further, the secondary side terminals 727 and 728 of the converter cells 720-1 to 720-N are sequentially connected in series, and the secondary side power supply system 732 is connected to these series circuits. Each converter cell 720-1 to 720-N transmits power in both directions or in one direction between the primary terminals 725 and 726 and the secondary terminals 727 and 728. The primary power supply system 731 and the secondary power supply system 732 include an inductive impedance or a filter reactor. Further, as the primary side power supply system 731 and the secondary side power supply system 732, various power generation facilities and power receiving facilities such as a commercial power generation system, a photovoltaic power generation system, and a motor can be adopted. The voltage of the primary side power supply system 731 is the primary side system voltage VS1, and the voltage of the secondary side power supply system 732 is the secondary side system voltage VS2. The primary side system voltage VS1 and the secondary side system voltage VS2 are independent of each other in amplitude and frequency, and the power conversion device 701 is bidirectional between the primary side power supply system 731 and the secondary side power supply system 732. Or transmit power in one direction.

Of the pair of terminals of the primary power system 731, one is called the primary reference terminal 733 and the other is called the terminal 735. Similarly, of the pair of terminals of the secondary power system 732, one is referred to as a secondary reference terminal 734 and the other is referred to as a terminal 736. The primary side reference terminal 733 is a terminal on which the primary side reference potential appears, and the secondary side reference terminal 734 is a terminal on which the secondary side reference potential appears. The primary side and secondary side reference potentials are, for example, ground potentials. The reference potential does not necessarily have to be the ground potential, but the primary side reference terminal 733 is preferably a terminal on the side where the maximum value (absolute value) of the ground potential is lower than that of the other terminal 735, and the secondary side. The reference terminal 734 is preferably a terminal on the side where the maximum value (absolute value) of the ground potential is lower than that of the other terminal 736.

The primary side reference terminal 733 is connected to the primary side terminal 725 of the converter cell 720-1, and the secondary side reference terminal 734 is connected to the secondary side terminal 728 of the converter cell 720-N. That is, the larger the stage number k, the higher the absolute value of the ground voltage of the primary side terminals 725 and 726, and the lower the absolute value of the ground voltage of the secondary side terminals 727 and 728.

In this figure, the case where the power conversion device has two or more converter cells is shown, but the present invention is not limited to this, and the power conversion device including only one converter cell is provided. Also includes.

The present invention is not limited to the above examples, but includes various modifications. For example, the examples have been described in detail for the sake of comprehension of the present invention, and are not necessarily limited to those having all the configurations described. It is possible to delete a part of the configuration of the embodiment, add another configuration, or replace it with another configuration.

10: Transformer, 12a: First core, 12b: Second core, 14: Primary winding, 16: Secondary winding, 22: Insulation plate, 24a, 24b: Bobbin, 26: Substrate, 28: Core Contact electrode, 29: Pressure dividing electrode, 32: Connection line, 701: Power converter, 711: AC / DC converter, 712: AC / DC converter, 713: AC / DC converter, 714: AC / DC converter, 715: Transformer, 717 , 718: Capacitor, 720-1 to 720-N: Converter cell, 725, 726: 1 primary side terminal, 727, 728: Secondary side terminal, 731: 1 primary side power supply system, 732: Secondary side power supply system.

Claims (8)

With the primary winding,
The first core on which the primary winding is installed and
With the secondary winding
With the second core in which the secondary winding is installed,
An insulating plate sandwiched between the first core and the second core is provided.
A voltage dividing electrode is provided inside the insulating plate.
A core contact electrode is provided on the outside of the insulating plate.
The voltage dividing electrode and the core contact electrode are electrically connected to each other.
A transformer in which the core contact electrode is electrically connected to at least one of the first core and the second core. The transformer according to claim 1, wherein the voltage dividing electrode has a flat plate shape. The transformer according to claim 1, wherein the voltage dividing electrode is arranged in a region sandwiched between the primary winding and the secondary winding. The transformer according to claim 2, wherein the voltage dividing electrodes are arranged so that the two layers face each other in parallel. The transformer according to claim 2, wherein the voltage dividing electrode has a rectangular shape, a comb shape, a fold shape, or a bent shape. With the primary winding,
The first core on which the primary winding is installed and
With the secondary winding
With the second core in which the secondary winding is installed,
An insulating plate sandwiched between the first core and the second core,
Equipped with three or more capacitors,
At least three of the capacitors are connected in series
The primary winding and the secondary winding are electrically connected by the three capacitors.
A core contact electrode is provided on the outside of the insulating plate.
The end of the three capacitors located in the center of the series connection is electrically connected to the core contact electrode.
A transformer in which the core contact electrode is electrically connected to at least one of the first core and the second core. A power conversion device including the transformer according to claim 1. A power conversion device including the transformer according to claim 6.

Images