JP2016111794A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device of which the downsizing is attained by shortening a spatial insulation distance.SOLUTION: A unit cell of a power converter comprises a switching element 201 of IGBT or the like, a smoothing capacitor 204 and a control board. In the switching element 201, a radiation fin 202 for cooling is provided. In order to electrically connect the switching element 201 and the smoothing capacitor 204, a conductor called bus bar 203 is present. Since a geometrical shape of a board housing end 93 of a board housing 91 forming a part of a unit support housing is sharp and field concentration is high, a metal cover 3 (metal body to be insulated) which is fixed while being insulated by a paint insulator 4 is fitted to a side of the unit cell after the unit cell is assembled and completed, thereby preventing local discharge occurrence.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a power conversion device.

  One of the important technologies for realizing an environmentally harmonious society is the effective use of electrical energy. To that end, power electronics technology that can change the shape of electricity optimally is indispensable.

  In power electronics, power converters are an important key component, and improving the conversion efficiency is an important issue. In addition, in large power converters such as electric power, railways, and industries, miniaturization of the power converter panel is an important issue from the viewpoint of space saving and direct material cost reduction.

  Power converters such as inverters, converters, and power conditioners exceeding the rated voltage of 500 V are usually configured in units called unit cells. The inverter panel is structured to store a plurality of unit cells.

  It is necessary to provide a space and a creeping insulation distance between the casing of the inverter panel and the unit cell or between the units to maintain different potentials. If insulation cannot be maintained, not only the function as a power converter is lost, but also the converter panel itself may be seriously damaged by arc discharge at the time of short circuit.

  If the space insulation distance is insulated with air, it is necessary to increase the insulation distance, and it is difficult to reduce the size of the panel. Therefore, a solid-air composite insulation structure with excellent insulation that has been put to practical use in busbars and switch gears. By applying, the insulation distance of the converter panel can be shortened.

  Therefore, for example, a technique for shortening the space insulation distance by preventing a local discharge by attaching a solid-insulated metal as an insulated metal body to the electric field emphasizing part is known. Such a technique is described in, for example, WO 2014/038000.

WO2014 / 038000 Publication

  In the prior art described above, a solid-insulated metal plate is applied at least partially so as to cover the electric field concentration part of the converter panel such as the sharp end of the unit cell. When the unit cell is covered with the applied metal plate, the solid insulating metal plate is folded and attached to the unit cell, and there are paint bulges at the corners where the solid insulating metal plate is bent. Exists. This paint bulge makes it difficult to fix, and there is a possibility that the structural strength cannot be maintained when an earthquake or the like occurs. As a result, the insulation system may be deformed and insulation reliability may be reduced.

  An object of the present invention is to provide a power conversion device that can easily be positioned between a unit cell and an insulated metal plate formed so as to be bent, and that can prevent a decrease in insulation reliability caused by deformation of the insulation system. There is to do.

  In order to achieve the above object, the present invention has a unit cell, and the unit cell includes a switching element, a capacitor connected to the switching element, and a cooling fin for cooling the switching element. A composite insulator configured by applying powder coating on both surfaces of metal to cover the unit cell, and a distance between the unit cell generated by the coating bulge related to the powder coating and the composite insulator is maintained. The holding member is provided.

  According to the present invention, the positioning between the unit cell and the metal object to be insulated is facilitated, the insulation reliability and the mountability are improved, and further, the insulation mounting is simplified while the yield rate of the composite insulator of the high voltage converter is improved. It becomes possible.

It is a figure showing the whole power converter concerning an embodiment. The side view in the unit periphery of the power converter is shown in 1st embodiment. The unit sectional view of the power converter concerning a first embodiment is shown. The unit sectional view of the power converter concerning a second embodiment is shown. The unit sectional view of the power converter concerning a second embodiment is shown. The system configuration figure of the power converter concerning an embodiment is shown.

  Hereinafter, a specific example of a power converter unit according to a mode for carrying out the present invention (hereinafter, referred to as “this embodiment” as appropriate) will be described in detail with reference to the drawings. However, the present invention is not limited to the above-described contents, and can be arbitrarily changed and implemented without departing from the scope of the invention.

  FIG. 6 shows an example in which the power converter according to this embodiment is used as a high-voltage direct inverter. Specifically, it is a circuit diagram of a multiple power conversion device in which cell units are connected in series. The three-phase AC power supply from the commercial power supply 101 is divided into 3 × 3 three-phase AC by the multiple transformer 122. In the figure, n = 3 three-stage multiplexing is shown. Three alternating currents for each phase are the cell units 2-1u, 2-2u, 2-3u (for U-phase output), 2-1v, 2-2v, 2-3v (for V-phase output), 2-1w, 2 Input to -2w, 2-3w (for W-phase output). The cell unit 2 (2-1u, 2-2u, 2-3u, 2-1v, 2-2v, 2-3v, 2-1w, 2-2w, and 2-3) is configured as a rectifier, for example. Switching element 201a, smoothing capacitor section 204, and switching element 201b configured as an inverter section. Cell unit 2-1u, 2-2u, 2-3u U phase output, 2-1v, 2-2v, 2-3v V phase output, 2-1w, 2-2w, 2-3w W phase output , Converted to alternating current of arbitrary amplitude and frequency and output. An AC signal is input to the motor 104 by multiplex connection of those obtained by converting these.

  FIG. 1 is a diagram showing an overall external view of the circuit of the multiple power conversion device shown in FIG. As shown in FIG. 1, power converters such as inverters, converters, and power conditioners are configured as unit cells 2 in units.

  The converter panel 1 includes a plurality of unit cells 2, a ventilation duct 8 for air-cooling the unit cells 2, a unit cell support housing 9 that supports the unit cells 2, and an insulating plate 7. An insulating plate 7 is arranged on the unit cell support housing 9 so as to be spread over, and a beam 92 is provided on the lower surface of the unit cell support housing 9 in order to maintain strength. Although not shown because it is described in a perspective view, the unit cell support housing 9 (the insulating plate 7 is arranged on the upper surface and the lower surface is also provided on the cell units 2-1u, 2-1v, 2-1w. Is provided with a beam 92).

  In FIG. 1, since a high voltage is applied to the unit cell 2 or the components inside the unit cell 2, it is necessary to insulate from the ground region, and it is necessary to secure a space and a creeping insulation distance. Similarly, since the potentials and phases of the unit cells 2 are also different, it is necessary to secure a space and a creeping insulation distance between the unit cells 2.

  In this inverter, it is recommended that the insulation distance determined by the standard is secured because the phase differs in each stage. In this structure, an insulating plate 7 is laid under the unit cell 2, and a unit support housing 9 (ground metal housing) is formed under the insulating plate 7. That is, the space insulation distance between the upper surface of the unit cell and the ground metal casing above it is required. According to the standard, the distance is as large as 60 mm in the 6 kV class.

  In order to secure the above-mentioned space insulation space distance, it is not enough to secure insulation only with air, so the insulation distance can be shortened by applying a composite insulation structure of solid and air here Is possible. Moreover, even if a conductive atmosphere derived from the switching element is generated in the insulating space, a short circuit between different potentials can be prevented and explosion prevention can be achieved.

  In order to describe the above-described composite insulating structure, FIG. 2 shows a side view around the unit of the power converter in one embodiment (viewed from the “direction A” defined in FIG. 1). As shown in the figure, there is a beam 92 for maintaining the structural strength of the panel casing as the casing of the converter panel 1 (inverter panel casing). Since the upper portion of the unit cell 2 has a high potential, in such a configuration, the highest electric field is generated between the unit cell 2 and the beam, and in order to shorten the space insulation distance, it is necessary to improve insulation.

  Therefore, as shown in FIG. 2, the upper surface of the unit cell 2 and the high electric field portion by the beam 92 are covered with a metal having an insulator applied to the surface. This is referred to as an insulated metal body 5. Although details of the insulated metal body 5 will be described later, by preventing the occurrence of local discharge by attaching the insulated metal body 5, the space insulation distance can be shortened and the power converter can be miniaturized. . At the same time, by inserting the insulator 4 inside the metal cover 3, the coating thickness is made uniform and the coating insulating portion is not processed, thereby improving the insulation reliability and improving the mounting efficiency. It will improve. In addition, the degree of freedom in design of the insulated metal body 5 is improved, and it is possible to prevent explosion from a short circuit caused by the conductive gas derived from the switching element. This makes it possible to reduce the size and improve the reliability of the power converter at low cost. It becomes possible to shorten the space insulation distance between the beam 92 and the unit cell 2. In other words, even if the space insulation distance is shortened by about 50 to 90% by applying the composite insulation, it is possible to have an insulation characteristic equal to or higher than that of the conventional air insulation.

  The region where the metal insulator is installed can be adjusted so that sufficient insulation can be maintained even when a conductive atmosphere derived from the failure of the switching element 201 occurs.

  Specifically, the distance between the tip of the beam 92 and the uninsulated portion of the unit cell 2 is the spatial insulation distance. By making this distance 1.5 times or more of the space insulation distance defined in the standard, insulation is maintained even if a conductive atmosphere occurs.

  FIG. 3 is a cross-sectional view seen from the “B direction” defined in FIG. 1 showing a unit cross-sectional view of the power converter according to the first embodiment. The cross section is a dotted line portion in FIG. Usually, a switching element 201 such as an insulated gate bipolar transistor (hereinafter referred to as “IGBT” as appropriate), a smoothing capacitor 204 electrically connected to the switching element 201, and a control board (not shown). have. The switching element 201 (IGBT or the like) is often provided with a cooling fin for cooling. In order to electrically connect between the switching element 201 and the smoothing capacitor 204, a conductor called a bus bar 203 exists. Bus bars are mainly made of materials such as copper and aluminum.

  Details of the insulated structure will be described with reference to the cross-sectional view of FIG. A beam 92 is provided on the lower surface of the panel casing 91 that forms part of the unit support casing 9. The thickness of the beam 92 is about several millimeters, and its angle R is about 0.5 mm. Iron, SUS, molten plated steel, aluminum, etc. are applied.

  The thickness of the coating insulating part 4 is about 0.1 to 1 mm for a 6 kV class inverter and about 0.1 to 2 mm for an 11 kV class. Thus, the insulation can be sufficiently improved as compared with air alone. As the coating insulating part 4, pressure molding with epoxy resin, powder coating, spray insulation, and the like can be applied. However, the powder coating method is most appropriately applied in the sense of shortening the manufacturing time while preventing minute discharge by improving the adhesion with the metal part.

  On the other hand, the panel casing 91 is made of a metal plate of about several mm, and its corner R is sharp and 1 mm or less. That is, the board casing end 93 is sharper in geometry than the beam 92 and the electric field concentration is higher, so that the unit cell side is solid-insulated. This is because the unit housing side is about 2 mm and is difficult to round structurally. It is easy to ease the electric field concentration by rounding the corner R. Iron, SUS, molten plated steel, aluminum, etc. are applied.

  As a unit in which the composite insulation is applied and the space insulation distance from the ground plane is shortened, the unit is assembled and then covered with the metal 5 to be insulated. This eliminates the need for solid insulation on the entire surface of the unit cell. Moreover, since the metal is used as an intermediary, the structural strength of the insulated metal body can be maintained.

  In this structure, it is possible to fix screws (bolts) (not shown; arranged around reference numeral 32 in the figure) to the unit housing by exposing the metal without exposing the end of the metal 5 to be insulated without applying composite insulation. Thus, the metal cover (also referred to as a metal body) 3 inside the insulated metal body 5 and the unit cell can be set to the same potential. However, even if the exposed portion is not made, the same potential may be obtained by removing the insulating portion and conducting between the units by wiring. The metal cover 3 is made of iron, SUS, molten plated steel plate, aluminum, copper or the like.

  Further, the coating insulator 4 (also simply referred to as an insulator) on both the front and back surfaces of the metal cover 3 eliminates the need for a masking process for preventing the insulator from adhering. The masking process is costly because it requires an artificial process. Therefore, it is possible to reduce the cost and simplify the processing process by insulating both surfaces.

  At this time, the insulated metal 5 is fitted into the unit cell 2, but there is a paint bulge at the inner corner of the metal body 3. Therefore, a plate-like insulator 61 is separately installed in a region where there is no swelling in order to position the units. The thickness of the insulator 61 is equal to or greater than that of the paint bulge.

  With the above structure, there is only one bent portion of the metal body, so it is easy to ensure uniformity during painting. As a result, even when the coating area is enlarged, pinholes and coating are less likely to be thin, and production efficiency can be increased. Moreover, it is not necessary to process the intermediary metal. Thus, manufacturability can be simplified and insulation reliability can be enhanced.

  Without the insulator 61, it is difficult to fix the metal body to be insulated, and there is a possibility that the structural strength cannot be maintained when an earthquake or the like occurs. As a result, the insulation system may be deformed and insulation reliability may be reduced.

  As the material of the insulator 61, application of a plate-like epoxy resin, bakelite, FRP or the like is effective, but there is no particular limitation as long as the insulator is general. In terms of positioning enhancement, an insulative insulator is also good.

  This embodiment shows an example in which composite insulation is provided between the ground casing of the converter panel and the unit. However, the present invention is not limited to the above. For example, the cooling fin and unit casing inside the unit, the switching element and unit casing, etc. It is also applicable to the space insulation distance. Applicable to general space insulation between different potentials on transformer panel.

  As described above, to summarize this embodiment, a metal plate subjected to solid insulation is applied at least partially so as to cover the electric field concentration portion of the converter panel such as a sharp unit end. It is possible to facilitate positioning by arranging an insulator inside the metal body to be insulated, and to improve insulation reliability and mountability. In addition, by applying a composite-insulated metal body, the space insulation distance can be shortened, and a short circuit due to the conductive gas derived from the switching element can be prevented. In addition, it is possible to improve the yield rate of the composite insulator of the high-voltage converter and simplify the insulation mounting.

  FIG. 4 is a diagram illustrating an overall view of the power converter according to the second embodiment. Unlike the first embodiment, the insulated metal 5 is provided with a portion 62 (also referred to as a region to be coated twice) in the painted insulator 4.

  This eliminates the necessity of providing the metal cover 3 with the insulator provided in the first embodiment when the metal object 5 is attached to or detached from the metal cover 3 of the casing of the unit cell 2. The area to be painted twice should be as wide as possible.

  However, in this structure, it is necessary to locally mask the portion to be bolted. Therefore, in general, Example 1 is more practical.

  FIG. 5 is a diagram illustrating an overall view of a power converter according to the third embodiment. In this structure, a metal plate 63 is disposed instead of the insulator 61.

In this structure, since the metal plate 63 and the intermediate metal cover 3 are at the same potential, no discharge or the like occurs between the insulators, and insulation deterioration does not occur. This structure is also an effective mounting method.

DESCRIPTION OF SYMBOLS 1 Power converter 2 Unit cell 3 Metal cover 4 Insulator 5 Insulated metal body 41 Paint swelling 201 Switching element 202 Radiation fin 203 Bus bar 204 Smoothing capacitor

Claims (9)

  The unit cell includes a switching element, a capacitor connected to the switching element, and a cooling fin for cooling the switching element, and is configured by applying powder coating on both surfaces of the metal. A composite insulator covering the unit cell, and a holding member provided so as to maintain a distance between the unit cell generated by the coating bulge relating to the powder coating and the composite insulator. Power conversion device.   The power conversion device according to claim 1, wherein the holding unit is an insulator.   3. The power conversion device according to claim 2, wherein the holding portion is an insulator having a thickness equivalent to or greater than a bulge formed in a bent portion of the composite insulator.   4. The power conversion device according to claim 3, wherein the holding portion is provided between the high voltage portion of the unit cell and the composite insulator.   The power conversion device according to claim 1, wherein the holding portion is formed by coating a region other than the bulge portion of the composite member a plurality of times.   The power conversion device according to claim 1, wherein the holding unit relatively positions the unit cell and the composite member.   The power conversion device according to claim 1, wherein the holding member is provided as a metal plate having a thickness equal to or greater than or equal to a coating bulge of the composite member.   2. The power converter according to claim 1, wherein the capacitor is plural, and a bus bar connecting the capacitor and the switching element is stored in the unit cell.   9. The power conversion device according to claim 8, wherein there are a plurality of the switching elements, and a predetermined switching element among the plurality of switching elements is opposed to another switching element across the bus bar.