Power conversion unit and power conversion device

Abstract

To provide a multistage conversion type power conversion device configured by storing a plurality of power conversion units in a common metallic housing and connecting the power conversion units in series, wherein the power conversion device can be downsized while ensuring an insulation property between power conversion units and between each power conversion unit and a housing frame.SOLUTION: A power conversion unit is used for a multistage conversion type power conversion device configured by storing a plurality of power conversion units in a common metallic housing and connecting the power conversion units in series. The power conversion unit comprises: a power conversion substrate 301 on which a power semiconductor device 302 is mounted; a unit housing 309 including the power conversion substrate; an insulation filler 303 filling the space inside the unit housing in which the power conversion substrate is disposed; and an insulator plate 307 disposed between a housing frame of the metallic housing and the power conversion substrate. The insulator plate includes an air layer 314 equal to or more than a fixed thickness inside.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a structure of a power conversion device, and more particularly to a technique that is effective when applied to a power conversion device of a multi-stage conversion type configured by connecting a plurality of power conversion units in series. [Background technology]

[0002] In recent years, power converters have achieved faster switching operations and reduced losses from the power semiconductors thanks to technological innovations in the power semiconductor modules that are their main components. This makes it possible to miniaturize the coolers, and as a result, the power converters themselves. In addition, reducing losses in the power semiconductors can improve the efficiency of the power converters.

[0003] For example, wide band gap devices such as SiC and GaN have an electron saturation velocity that is approximately twice as fast as that of Si, which enables high-speed SW (Switching) operation to reduce SW losses and also enables high-frequency inverter SW operation.

[0004] Additionally, in industrial power converters, the system voltage is becoming higher in order to improve the system efficiency. By increasing the system voltage, it is possible to reduce current and conduction losses at the same power, and to improve the system efficiency. However, since there is a limit to the withstand voltage of power semiconductor modules, a power converter configuration has been proposed in which multiple power conversion units including power semiconductor devices are connected in series to increase the withstand voltage of the power converter's system voltage.

[0005] Background art in this technical field includes, for example, a technology such as Patent Document 1. Patent Document 1 discloses a power conversion device having a housing that forms a first compartment in which a first main circuit board is housed, a second compartment having a ventilation path for cooling air to pass through, and a third compartment in which a second main circuit board is housed, the electrical terminals of a first capacitor and the electrical terminals of a first semiconductor element are housed in the first compartment, at least a part of the first capacitor and at least a part of the first heat sink are exposed in the second compartment, the electrical terminals of a second capacitor and the electrical terminals of a second semiconductor element are housed in the third compartment, and at least a part of the second capacitor and at least a part of the second heat sink are exposed in the second compartment. (Summary of Patent Document 1, etc.) Furthermore, Patent Document 1 describes that an exhaust passage is formed behind each power conversion device, and cooling air is taken in from the front of each power conversion device (paragraph

[0041] of Patent Document 1). Furthermore, in order to increase the withstand voltage of a power converter, it is necessary to ensure insulation distances between each component and unit within the power conversion units that make up the power converter, which poses the problem of the power converter becoming larger.

[0006] Therefore, as a technology for shortening the insulation distance, for example, there is a technology as described in Patent Document 2. In Patent Document 2, in order to ensure the insulation characteristics between the multiple power semiconductor devices inside the module, the inside of the module is filled with an insulating material such as silicon gel and sealed with a case. With this configuration, it is possible to ensure the insulation characteristics between the multiple power semiconductor devices. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018 / 173379 [Patent Document 2] JP 2008-125240 A Summary of the Invention [Problem to be solved by the invention]

[0008] Conventional high-voltage power converters that use multiple isolation transformers have the problem of large weight and volume due to the multiple transformers. Multi-stage converters (MSCs) that use high-frequency isolation transformers make it possible to miniaturize the isolation transformers. In MSCs, high-voltage power converters that include multiple power conversion units handle high-voltage input by connecting multiple power conversion units with built-in power semiconductor devices in series.

[0009] When placing multiple power conversion units inside a converter panel, it is necessary to ensure insulation between the units and between the units and the panel frame. To ensure insulation between the power conversion units, air gaps and space for insulating materials are required. The challenge in miniaturizing converters is to achieve high-density packaging that minimizes the required insulating space.

[0010] As with the technology of Patent Document 2, when filling insulating material such as silicon gel between parts that require an insulating distance, it is essential to manage tiny air layers (voids). If tiny air layers exist inside the insulating material or between parts separated by the insulating material, an electric field will concentrate in the tiny air layer, causing a corona discharge in the air layer.

[0011] When corona discharge occurs in a tiny air layer, the insulating material carbonizes over time, the insulating properties between parts deteriorate, and ultimately there is a problem of dielectric breakdown between the parts. To avoid corona discharge caused by the combination of this insulating layer and tiny air layer, it is necessary to either eliminate the tiny air layer or to create a structure that can manage the thickness of the air layer above a certain value.

[0012] Therefore, an object of the present invention is to provide a power conversion device that uses a multi-stage conversion method in which multiple power conversion units are housed in a common metal housing and connected in series, and that can be made compact while maintaining insulation characteristics between each power conversion unit and between each power conversion unit and the housing frame. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention provides a power conversion unit for use in a multi-stage conversion type power conversion device in which a plurality of power conversion units are housed in a common metal housing and the power conversion units are connected in series, the power conversion unit comprising: a plurality of power conversion boards on which power semiconductor devices are mounted; Multiple A unit housing containing a power conversion board; Multiple An insulating filler is filled in the space inside the unit housing in which the power conversion board is arranged, and the unit housing is sealed. Multiple An insulating plate, The plurality of power conversion boards include a primary side power conversion board and a secondary side power conversion board, the plurality of insulating plates include a first insulating plate and a second insulating plate, the primary side power conversion board and the secondary side power conversion board are disposed between the first insulating plate and the second insulating plate, and each of the first insulating plate and the second insulating plate is characterized by having voids of a certain thickness or more inside.

[0014] The present invention also provides a power conversion device comprising the above-mentioned power conversion unit and a metal housing in which a plurality of the power conversion units are housed. Effect of the Invention

[0015] According to the present invention, in a power conversion device using a multi-stage conversion method in which multiple power conversion units are housed in a common metal housing and each power conversion unit is connected in series, it is possible to realize a power conversion device that can be made compact while ensuring insulation characteristics between each power conversion unit and between each power conversion unit and the housing frame.

[0016] This makes it possible to improve the reliability and reduce the size of a multi-stage conversion type power conversion device.

[0017] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0018] [Figure 1] 1 is a circuit diagram showing a schematic configuration of a power conversion device according to a first embodiment of the present invention. [Diagram 2] 1 is an equivalent circuit diagram of a power conversion unit (converter cell) according to a first embodiment of the present invention. [Diagram 3] 1 is a system configuration diagram of a power conversion device according to a first embodiment of the present invention. [Figure 4] FIG. 3 is a diagram showing an example of operational waveforms of the power conversion device according to the first embodiment of the present invention. [Diagram 5] 1 is an external view of a power conversion device (converter board) according to a first embodiment of the present invention. [Figure 6] 1 is a cross-sectional view showing a configuration of a power conversion unit (converter cell) according to a first embodiment of the present invention. [Figure 7] FIG. 11 is a side view of a power conversion unit (converter cell) according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a cross-sectional view of a power conversion unit (converter cell) according to a third embodiment of the present invention. [Figure 9] FIG. 11 is a perspective view showing an insulating plate of a power conversion unit (converter cell) according to Example 4 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and detailed description of overlapping parts will be omitted. EXAMPLES

[0020] A power conversion device according to a first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 6. Fig. 1 is a circuit diagram (block diagram) showing a schematic configuration of the power conversion device of this embodiment.

[0021] 1, the power conversion device 1 has N converter cells (power conversion units) 20-1 to 20-N. Each converter cell 20-k (where k is a stage number, 1≦k≦N) includes a pair of primary side terminals 25, 26, a pair of secondary side terminals 27, 28, an AC / DC converter 11 (a first AC / DC converter, primary side converter, that converts an AC voltage, which is the primary side system voltage, into a DC voltage), an AC / DC converter 12 (a second AC / DC converter, primary side converter, that converts a DC voltage converted by the first AC / DC converter into an AC voltage), and an AC / DC converter 13 (a second AC / DC converter, primary side converter). The power supply system includes a third AC / DC converter, a secondary converter that converts the AC voltage converted by the third AC / DC converter into a DC voltage, AC / DC converter 14 (a fourth AC / DC converter, secondary converter that converts the DC voltage converted by the third AC / DC converter into an AC voltage and supplies it to the secondary power supply system), a high-frequency transformer 15 (transformer) connected between AC / DC converter 12 and AC / DC converter 13, a capacitor 17 (first capacitor), and a capacitor 18 (second capacitor).

[0022] The AC / DC converters 11 to 14 are configured with power semiconductor devices such as metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), bipolar transistors, and diodes, which will be described later.

[0023] Capacitor 17 is connected between AC / DC converters 11 and 12, and capacitor 18 is connected between AC / DC converters 13 and 14.

[0024] The primary side terminals 25, 26 of the converter cells 20-1 to 20-N are sequentially connected to each other in series, and this series circuit is connected to a primary side power supply system 31. The secondary side terminals 27, 28 of the converter cells 20-1 to 20-N are sequentially connected to each other in series, and this series circuit is connected to a secondary side power supply system 32. Each of the converter cells 20-1 to 20-N transmits power bidirectionally or unidirectionally between the primary side terminals 25, 26 and the secondary side terminals 27, 28.

[0025] The primary power supply system 31 and the secondary power supply system 32 include an inductive impedance or a filter reactor. As the primary power supply system 31 and the secondary power supply system 32, various power generation equipment and power receiving equipment such as a commercial power supply system, a solar power generation system, a motor, etc. can be used.

[0026] The voltage of the primary power supply system 31 is a primary system voltage VS1, and the voltage of the secondary power supply system 32 is a secondary system voltage VS2. The primary system voltage VS1 and the secondary system voltage VS2 are independent of each other in amplitude and frequency, and the power conversion device 1 transmits power between the primary power supply system 31 and the secondary power supply system 32 in either a bidirectional or unidirectional manner.

[0027] As shown in Fig. 1, one of a pair of terminals of the primary power supply system 31 is called a primary reference terminal 33, and the other is called a terminal 35. Similarly, one of a pair of terminals of the secondary power supply system 32 is called a secondary reference terminal 36, and the other is called a terminal 34. The primary reference terminal 33 is a terminal where a primary reference potential appears, and the secondary reference terminal 36 is a terminal where a secondary reference potential appears. The primary and secondary reference potentials are, for example, ground potentials. However, the reference potential does not necessarily have to be ground potential.

[0028] The primary side reference terminal 33 is connected to the primary side terminal 25 of the converter cell 20-1, and the terminal 35 is connected to the primary side terminal 26 of the converter cell 20-N. The secondary side reference terminal 36 is connected to the secondary side terminal 27 of the converter cell 20-1, and the terminal 34 is connected to the secondary side terminal 28 of the converter cell 20-N.

[0029] FIG. 2 is a circuit diagram (block diagram) showing an equivalent circuit of converter cell 20-k (20-1 to 20-N) of FIG.

[0030] As shown in FIG. 2, each of the AC / DC converters 11 to 14 is composed of four switching elements connected in an H-bridge configuration, and an FWD (Free Wheeling Diode) connected in inverse parallel to these switching elements.

[0031] As described above, these switching elements use power semiconductor devices such as MOSFETs, IGBTs, bipolar transistors, and diodes.

[0032] The voltage appearing across the capacitor 17 is the primary DC link voltage V dc1 (primary DC voltage). The voltage appearing between the primary terminals 25 and 26 is called the primary AC terminal voltage V U1k The AC / DC converter 11 is called the primary side AC terminal voltage V U1k and the primary DC link voltage V dc1 The power is transmitted while converting the current into electricity in one direction or two directions.

[0033] High frequency transformer 15 has a primary winding 15a and a secondary winding 15b, and transmits power at a predetermined frequency between primary winding 15a and secondary winding 15b.

[0034] The currents input and output between the primary side AC / DC converter 12 and the secondary side AC / DC converter 13 and the high frequency transformer 15 are high frequency. Here, the high frequency is, for example, a frequency of 100 Hz or higher, but it is preferable to adopt a frequency of 1 kHz or higher, and it is more preferable to adopt a frequency of 10 kHz or higher.

[0035] The primary side AC / DC converter 12 converts the primary side DC link voltage V dc1 The power is transmitted while bidirectionally or unidirectionally converting the voltage appearing in the primary winding 15a and the voltage appearing in the secondary winding 15b.

[0036] The voltage appearing across the capacitor 18 is the secondary DC link voltage V dc2 (secondary DC voltage).

[0037] The secondary side AC / DC converter 13 converts the secondary side DC link voltage V dc2 The power is transmitted while converting the voltage appearing in the secondary winding 15b bidirectionally or unidirectionally.

[0038] The voltage appearing between the secondary terminals 27 and 28 is called the secondary AC terminal voltage V u2k The secondary side AC / DC converter 14 is called the secondary side AC terminal voltage V u2k and the secondary DC link voltage V dc2 The power is transmitted while converting the current into electricity in one direction or two directions.

[0039] In Figure 1, the amplitude value of the primary side system voltage VS1 is V max and the primary DC link voltage V of each converter cell 20-k dc1 is the amplitude value V max If we assume that the primary AC terminal voltage V U1k is ±V max The voltage will be either / N or 0. The secondary side is similar, so the explanation will be omitted.

[0040] In Figure 2, the power converter section including AC / DC converter 11, capacitor 17, and AC / DC converter 12 is referred to as primary side power conversion unit 101, and the power converter section consisting of AC / DC converter 13, capacitor 18, and AC / DC converter 14 is referred to as secondary side power conversion unit 102.

[0041] FIG. 3 is a system configuration diagram (block diagram) showing the three-phase AC system of this embodiment, which is composed of the converter cells 20-1 to 20-N shown in FIGS.

[0042] In Fig. 3, the terminals of the U-phase, V-phase, and W-phase of the primary three-phase power supply system are designated as U1, V1, and W1, respectively, the terminals of the U-phase, V-phase, and W-phase of the secondary three-phase power supply system are designated as U2, V2, and W2, respectively, and their neutral points are designated as N1 and N2. In the three-phase AC system shown in Fig. 3, the neutral points N1 and N2 are the reference terminals of the primary and secondary sides.

[0043] Between the primary side terminal U1 and the neutral point N1, the primary side terminals 25, 26 (see FIGS. 1 and 2) of the converter cells 20-1 to 20-N are sequentially connected in series. In addition, between the secondary side neutral point N2 and the terminal U2, the secondary side terminals 27, 28 (see FIGS. 1 and 2) are sequentially connected in series.

[0044] Although illustration is omitted for the V-phase and W-phase, the power conversion device 1 is connected to them in the same manner as the U-phase.

[0045] Figure 4 shows an example of the waveforms of the primary system voltage VS1 and the secondary system voltage VS2. As shown in Figure 3, the input and output of each converter cell are connected in series, and the series-connected converter cells are controlled to support AC input and AC output.

[0046] Fig. 5 shows a configuration diagram of a converter board of the power conversion device 1. A primary side power conversion unit 101 constituting the AC / DC converter shown in Fig. 2, a high frequency transformer 15, and a secondary side power conversion unit 102 constituting the DC / AC inverter are built into each power conversion unit 20 (converter cells 20-1 to 20-N).

[0047] A plurality of power conversion units (converter cells) 20 constituting the power conversion device 1 are arranged (housed) in a converter board (metallic housing) 201. A frame (housing frame 310 in FIG. 6 described later) inside the converter board (metallic housing) 201 is fixed to a specific potential such as GND. At this time, insulation is required between the frame (housing frame) inside the converter board (metallic housing) 201 and the primary side power conversion unit 101, secondary side power conversion unit 102, and high frequency transformer 15 of each power conversion unit (converter cell).

[0048] 6 shows a cross-sectional view of a power conversion unit (converter cell) 20. The power conversion unit (converter cell) 20 includes a primary side power conversion board 301, a power semiconductor device 302, a conductor (metal plate) 305 below the power semiconductor device 302, a cooling medium path 304, a conductor (metal wall) 306 constituting the cooling medium path 304, and a secondary side power conversion board 308, which are covered by a unit housing 309 made of resin or the like (are enclosed in the unit housing 309).

[0049] Similar to the primary side power conversion board 301 side, the secondary side power conversion board 308 side also has a power semiconductor device, a conductor (metal plate) above the power semiconductor device, and a conductor (metal wall) constituting the cooling medium path 304 arranged thereon.

[0050] Furthermore, the spaces inside the power conversion unit (converter cell) 20 in which the primary side power conversion board 301 and the secondary side power conversion board 308 are mounted are filled with an insulating filler 303 such as gel, resin, oil, or the like.

[0051] In the case of a water-cooling system, a cooling medium such as cooled water flows through the cooling medium path 304, and in the case of an air-cooling system, a cooling medium such as air flows through the cooling medium path 304, and heat generated by the switching operation of the power semiconductor device 302 is cooled by heat exchange.

[0052] The upper and lower covers that seal the power conversion unit (converter cell) are provided with insulating plates 307 made of, for example, resin, and an air layer 314 is provided inside the insulating plate 307 to improve the insulation resistance between the primary side power conversion board 301 and the converter panel inner frame (housing frame) 310. The power conversion unit (converter cell) sealed with the above-mentioned structure is mounted (stored) in a metal converter panel (metal housing) 201.

[0053] 6 shows an example of an insulating plate with an air layer built in, in which air layer 314 is sealed inside insulating plate 307. By completely sealing air layer 314 inside insulating plate 307, the plate is less susceptible to the effects of humidity and particles such as metal powder that enter from the outside, and stable insulating performance can be ensured.

[0054] However, the shape of the insulating plate 307 is not necessarily limited to this as long as the required insulation resistance can be obtained between the primary side power conversion board 301 or the secondary side power conversion board 308 and the converter board inner frame (housing frame) 310. For example, the insulating plate 307 may have a small hole or slit in a part thereof so that the internal space of the insulating plate 307 communicates with the outside. In other words, regardless of whether it is sealed or not, it is sufficient that a gap of a certain thickness (distance) or more is provided inside the insulating plate 307.

[0055] In addition, instead of the air layer 314, a vacuum space may be provided inside the insulating plate 307, or the space may be filled with an insulating material such as an inert gas such as nitrogen gas (N2) or argon gas (Ar), sulfur hexafluoride (SF6), insulating oil, water, or a fluorine-based inert liquid, and then sealed.

[0056] Moreover, it is desirable that the air layer 314 or gap provided in the insulating plate 307 is provided larger than the size of the primary side power conversion board 301 and the secondary side power conversion board 308 so as to cover the entire surfaces of the primary side power conversion board 301 and the secondary side power conversion board 308 when the power conversion unit (converter cell) is viewed in a plan view (top view). This is to reliably improve the insulation resistance between the primary side power conversion board 301 and the secondary side power conversion board 308 and the converter panel inner frame (housing frame) 310.

[0057] Considering moldability and strength, the insulating plate 307 may be made of PPS resin (Poly Phenylene Sulfide) or epoxy resin. In addition, by providing a gap such as an air layer 314 having a certain thickness (distance) or more inside the insulating plate 307 as in this embodiment, the insulating plate 307 can be made lighter by using a foaming material such as foamable urethane resin. Since the insulating plate 307 is foamed, many air bubbles are present in the insulating plate 307 itself, but since a gap such as the air layer 314 having a thickness controlled to a certain value or more is provided inside the insulating plate 307, it is possible to ensure insulation resistance between the primary side power conversion board 301 or the secondary side power conversion board 308 and the converter board inner frame (housing frame) 310.

[0058] The material of unit housing 309 may be the same as that of insulating plate 307, or different resins may be used for each.

[0059] As described above, according to the power conversion device of this embodiment, gaps such as air layers 314 are arranged at a specific thickness between the primary side power conversion board 301 and the secondary side power conversion board 308 and the metal converter panel inner frame (housing frame) 310. Therefore, even if tiny air layers (voids) exist in the insulating filler 303 such as silicone gel, electric field concentration in the tiny air layers (voids) can be avoided, making it possible to achieve high voltage resistance.

[0060] Although there is a small air layer 330 between the insulating filler 303 and the insulating plate 307, it is difficult to control the thickness of this air layer 330 because it is formed when filling with gel. Although this air layer 330 somewhat alleviates the discharge of the minute air layers (voids) in the insulating filler 303, the thickness of the air layer 330 cannot be controlled when filling with gel, so the discharge problem cannot be fully solved. In contrast, by providing a gap inside the insulating plate 307 as in this embodiment, it is possible to control the thickness of the gap and reliably solve the discharge problem.

[0061] Furthermore, by providing a gap such as a sealed air layer 314 inside the insulating plate 307, it is possible to take measures against dust particles such as metal powder that may invade from the outside. In addition, it is possible to increase the pressure resistance of the air layer 314 by reducing the temperature rise.

[0062] This makes it possible to minimize the thickness of the resin frame and the filling material inside the power conversion unit required for insulation, which is advantageous for miniaturizing the power conversion device. It also reduces thermal interference between each power conversion unit and between each power conversion unit and the high-frequency transformer, making it possible to miniaturize the cooling fins and the power conversion device. EXAMPLES

[0063] Second Embodiment A power conversion device according to a second embodiment of the present invention will be described with reference to Fig. 7. Fig. 7 is a side view of a power conversion unit (converter cell) of this embodiment.

[0064] 7, in the power conversion unit (converter cell) of this embodiment, the cooling medium input / output terminal 313 is disposed on the right end (one end) side of the unit housing 309, and the primary side input terminal 311 which is an input terminal to the primary side power conversion board 301 and the secondary side output terminal 312 which is an output terminal from the secondary side power conversion board 308 are disposed on the left end (the other end) side of the unit housing 309. In other words, the cooling medium input / output terminal 313, the primary side input terminal 311, and the secondary side output terminal 312 are disposed at opposing positions on the unit housing 309.

[0065] 5, the cooling medium input / output terminals 313 of each power conversion unit are wired (connected) on the front side of the converter board (metallic housing) 201. On the other hand, the primary side input terminals 311 and secondary side output terminals 312 of each power conversion unit are wired (connected) on the rear side of the converter board (metallic housing) 201.

[0066] The converter panel internal frame (housing frame) 310 is at GND potential, the conductor 306 constituting the cooling medium path 304 and the converter panel internal frame (housing frame) 310 are connected to the same potential (GND potential), and the primary side power conversion board 301 and the secondary side power conversion board 308 are connected to a potential different from the potential of the converter panel internal frame (housing frame) 310 (GND potential).

[0067] According to this embodiment, the primary side input terminal 311 and the secondary side output terminal 312, which have different potentials, and the cooling medium input / output terminal 313, which is at GND potential, are arranged facing each other in the longitudinal direction of the power conversion unit, thereby making it possible to ensure an insulation distance, which is advantageous for miniaturizing the power conversion device. EXAMPLES

[0068] Third Embodiment A power conversion device according to a third embodiment of the present invention will be described with reference to Fig. 8. Fig. 8 is a side view (cross-sectional view) of the inside of a power conversion unit (converter cell) of this embodiment.

[0069] As shown in FIG. 8, inside the power conversion unit (converter cell) of this embodiment, a high-frequency transformer 15 is arranged on the cooling medium input / output terminal 313 side, and a primary side power conversion board 301 and a secondary side power conversion board 308 are arranged on the primary side input terminal 311 and secondary side output terminal 312 sides.

[0070] Inside the power conversion unit, a cooling medium path formed by a cooling medium path casing 320 is disposed from the right end (one end) to the left end (the other end) of the power conversion unit. The power semiconductor device 302 and the high frequency transformer 15 are configured to be in contact with the cooling medium path casing 320. As in Fig. 6, the cooling medium path casing 320 constituting the cooling medium path 304 is composed of a conductor (metal wall) 306 and a unit casing 309 formed of an insulating material such as resin.

[0071] According to this embodiment, the primary side power conversion board 301 and the secondary side power conversion board 308 are arranged facing each other across a cooling medium path case 320 provided in a unit case 309. Therefore, the primary side power conversion board 301 and the primary side power semiconductor device 302, the secondary side power conversion board 308 and the secondary side power semiconductor element are insulated by the cooling medium path case 320 formed of an insulating material.

[0072] Furthermore, similar to the first embodiment, an air layer 314 is formed in the insulating plate 307, which can shorten the required insulation distance when mounting the device in a metal converter panel (metal housing) 201, which is advantageous for miniaturizing the power conversion device. EXAMPLES

[0073] Fourth embodiment A power converter according to the present invention will be described with reference to Fig. 9. Fig. 9 shows another embodiment of the insulating plate 307 mounted on the power conversion unit (converter cell) of this embodiment.

[0074] As described above, so long as the necessary insulation resistance can be obtained between the primary side power conversion board 301 or the secondary side power conversion board 308 and the converter panel inner frame (housing frame) 310, it is not necessary to seal the air layer 314 inside the insulating plate 307.

[0075] As shown in FIG. 9, it is also possible to provide an opening in the side of insulating plate 307 to form a gap (air layer communicating with the outside) inside insulating plate 307 whose thickness is controlled to a certain value or more.

[0076] According to this embodiment, it is possible to reduce the amount of material required to form the insulating plate 307 having the air layer, which is advantageous for reducing the weight of the power conversion device.

[0077] Although FIG. 9 shows a case where the opening is disposed on the side surface, the opening may be disposed in a location other than the side surface.

[0078] The present invention is not limited to the above-mentioned embodiment, but includes various modified examples. For example, the above-mentioned embodiment has been described in detail to aid in understanding the present invention, and is not necessarily limited to those including all of the configurations described. Also, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Also, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0079] 1...Power conversion device 11...Power semiconductor device (first AC / DC converter, primary converter) 12...Power semiconductor device (second AC / DC converter, primary converter) 13...Power semiconductor device (third AC / DC converter, secondary converter) 14...Power semiconductor device (fourth AC / DC converter, secondary converter) 15...High frequency transformer (transformer) 15a…Primary winding 15b...Secondary winding 17, 18…Capacitor 20, 20-1 to 20-N, 20-k… Converter cells (power conversion units) 25,26…Primary side terminal 27,28…Secondary side terminal 31…Primary side power supply system 32…Secondary side power system 33...Primary side reference terminal 34...(The other terminal of the secondary power supply system 32) 35...(The other terminal of the primary power supply system 31) 36...Secondary side reference terminal 101...Primary power conversion unit 102...Secondary power conversion unit 201... Converter board (metal case) 301...Primary power conversion board 302...Power semiconductor devices 303...Insulating filler 304...Cooling medium path 305...Conductor (metal plate) 306...Conductor (metal wall) 307...(Air layer built-in) insulating plate 308...Secondary power conversion board 309...Unit housing 310... Converter panel inner frame (housing frame) 311...Primary input terminal 312...Secondary output terminal 313…Cooling medium input / output terminal 314…Air layer 320...cooling medium passage housing 330…Air layer V dc1 …Primary side DC link voltage (primary side DC voltage) V dc2 …Secondary DC link voltage (secondary DC voltage)

Claims

1. A power conversion unit used in a multi-stage power conversion device configured by storing a plurality of power conversion units in a common metal housing and connecting the respective power conversion units in series, A plurality of power conversion boards on which power semiconductor devices are mounted; a unit housing containing the plurality of power conversion boards; an insulating filler material filled in a space within the unit housing in which the plurality of power conversion boards are arranged; a plurality of insulating plates that seal the unit housing; The plurality of power conversion boards include a primary side power conversion board and a secondary side power conversion board, the plurality of insulating plates include a first insulating plate and a second insulating plate, the primary side power conversion board and the secondary side power conversion board are disposed between the first insulating plate and the second insulating plate, A power conversion unit, wherein each of the first insulating plate and the second insulating plate has a gap therein of at least a certain thickness.

2. 2. The power conversion unit according to claim 1, A power conversion unit characterized in that, when the power conversion unit is viewed in a plane, the gap of the first insulating plate is larger than that of the primary power conversion board so as to cover the entire surface of the primary power conversion board, and the gap of the second insulating plate is larger than that of the secondary power conversion board so as to cover the entire surface of the secondary power conversion board.

3. 2. The power conversion unit according to claim 1, the gap is a sealed space inside each of the first insulating plate and the second insulating plate, A power conversion unit characterized in that it is filled with an insulating material selected from the group consisting of air, nitrogen gas, argon gas, sulfur hexafluoride, insulating oil, water, and a fluorine-based inert liquid.

4. 2. The power conversion unit according to claim 1, the gap is a sealed space inside each of the first insulating plate and the second insulating plate, A power conversion unit maintained in a vacuum.

5. 2. The power conversion unit according to claim 1, each of the first insulating plate and the second insulating plate has an opening; A power conversion unit, comprising: a first insulating plate and a second insulating plate; a first insulating plate and a second insulating plate;

6. 2. The power conversion unit according to claim 1, a power conversion unit characterized in that the primary side power conversion board and the secondary side power conversion board are arranged opposite each other across a cooling medium path provided within the unit housing, a metal wall on the primary side power conversion board side and a metal wall on the secondary side power conversion board side that constitute the cooling medium path, a power semiconductor device mounted on the primary side power conversion board and a metal plate below it, and a power semiconductor device mounted on the secondary side power conversion board and a metal plate above it.

7. 7. The power conversion unit according to claim 6, A power conversion unit, characterized in that it is either a water-cooled type in which cooling water flows through the cooling medium path, or an air-cooled type in which air flows through the cooling medium path.

8. 7. The power conversion unit according to claim 6, an input / output terminal of the cooling medium path disposed on one end side of the power conversion unit; a power conversion unit comprising: an input terminal of the primary side power conversion board and an output terminal of the secondary side power conversion board, the input terminal and the output terminal of the secondary side power conversion board being disposed on the other end side of the power conversion unit.

9. 9. The power conversion unit according to claim 8, a high-frequency transformer that electrically couples the primary-side power conversion board and the secondary-side power conversion board; the high-frequency transformer is disposed on an input / output terminal side of the cooling medium path, A power conversion unit characterized in that the primary side power conversion board and the secondary side power conversion board are arranged on the input terminal side of the primary side power conversion board and the output terminal side of the secondary side power conversion board.

10. 7. The power conversion unit according to claim 6, each of the unit housing, the first insulating plate, and the second insulating plate is made of resin; 11. A power conversion unit, comprising: a first insulating filler material that is a silicone gel;

11. 7. The power conversion unit according to claim 6, a cooling medium path case forming the cooling medium path and a case frame of the metal case are connected to the same potential; A power conversion unit, characterized in that the primary side power conversion board and the secondary side power conversion board are connected to a potential different from a potential of the housing frame.

12. A power conversion unit according to any one of claims 1 to 11; and a metal housing in which a plurality of the power conversion units are housed.

Images