JP2019187128A - Electric power conversion system - Google Patents

Abstract

To provide an electric power conversion system capable of enhancing the performance of a converter by adjusting the characteristics.SOLUTION: An electric power conversion system according to the embodiment is provided with a power converter including a main circuit including a switching element, a capacitor, and a wiring member that electrically connects the switching element and the capacitor to flow a main current. The wiring member includes a first conductive plate and a second conductive plate that are plate members of a conductor, and an insulating plate being a plate member of an insulator that electrically insulates the first conductive plate and the second conductive plate between the first conductive plate and the second conductive plate. The shapes of the first conductive plate, the second conductive plate, and the insulating plate are set so that each of the main currents has a desired waveform.SELECTED DRAWING: Figure 3

Description

  Embodiments described herein relate generally to a power conversion apparatus.

  A number of circuit systems have been proposed as power conversion systems capable of realizing a large capacity while achieving miniaturization by using a self-extinguishing semiconductor switching element. In the multi-level output power converter, since the harmonic component of the AC voltage waveform can be reduced, the harmonic filter can be simplified and reduced, and the size can be reduced. For example, a modular multilevel converter (hereinafter referred to as MMC) has been put into practical use.

  The MMC is provided with a large number of unit converters, and in order to improve the performance of the MMC itself, it is necessary to match the performance of each unit converter as much as possible. There are variations in the parts constituting the unit converter, and it is often impractical to limit the variations inherent in the components in view of cost effectiveness.

Japanese Unexamined Patent Publication No. 2016-220356

  Embodiments provide a power conversion device that can adjust the characteristics to improve the performance of the converter.

  A power conversion device according to an embodiment includes a power converter including a plurality of main circuits each including a switching element, a capacitor, and a wiring member that electrically connects the switching element and the capacitor to flow a main current. . The wiring member is a first conductive plate and a second conductive plate, which are plate members of a conductor, and a plate member of an insulator, and the first conductive plate and the second conductive plate between the first conductive plate and the second conductive plate. And an insulating plate for electrically insulating the first conductive plate and the second conductive plate. The shapes of the first conductive plate, the second conductive plate, and the insulating plate are set so that each of the main currents has a desired waveform.

  In the present embodiment, since the first conductive plate, the second conductive plate, and the insulating plate are provided with the wiring member in which the main current flowing through each main circuit is set to have a desired waveform, the characteristics are adjusted. The performance of the transducer is improved.

It is a block diagram which illustrates the power converter concerning an embodiment. It is a typical circuit diagram which shows the structural example of a unit converter. FIG. 3A is a plan view illustrating a part of the unit converter. FIG. 3B is a bottom view illustrating a part of the unit converter. FIG. 3C is a cross-sectional view taken along the line AA ′ of FIG. FIGS. 4A to 4D are views corresponding to the cross section taken along the line AA ′ of FIG. 3A, and are cross-sectional views illustrating a modification of a part of the unit converter. It is a top view corresponding to Drawing 3 (a), and is a figure which illustrates some modifications of a unit converter.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. Further, even when the same part is represented, the dimensions and ratios may be represented differently depending on the drawings.
In the present specification and drawings, the same elements as those described above with reference to the previous drawings are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

FIG. 1 is a block diagram illustrating a power conversion apparatus according to the embodiment.
As shown in FIG. 1, the power conversion device 10 of this embodiment includes a power converter 20. The power converter 20 is a modular multilevel converter (hereinafter referred to as MMC). The power converter 20 is connected to the AC power system 1 via AC terminals 21a to 21c. As in this example, the power converter 20 may be connected to the power system 1 via the transformer 2. For example, the electric power system 1 can be configured to include a three-phase or single-phase 50 Hz or 60 Hz power source, a load, and an AC power transmission line. The power conversion apparatus 10 is connected to the DC circuit 3 through DC terminals 21d and 21e. DC circuit 3 includes, for example, a DC transmission line. In the following, it is assumed that the power converter 20 is linked to the three-phase power system 1.

  The power converter 20 includes an arm 22 corresponding to each phase of the three-phase alternating current. The arm 22 is connected in series between the DC terminals 21d and 21e.

  A buffer reactor 24 is connected in series to each of the arms 22 connected in series between the DC terminals 21d and 21e. The buffer reactor 24 prevents an instantaneous short-circuit current from flowing between the upper and lower arms 22.

  The taps of the buffer reactor 24 are connected to the AC terminals 21a to 21c, respectively.

  The arm 22 includes unit converters 30 connected in cascade.

FIG. 2 is a schematic circuit diagram illustrating a configuration example of the unit converter.
As shown in FIG. 2, the unit converter 30 includes terminals 31a and 31b. Unit converter 30 includes a switching element 32a, a diode 32b, and a capacitor 32c. The two switching elements 32a are connected in series. The two diodes 32b are connected in antiparallel to the two switching elements 32a, respectively. The capacitor 32c is connected in parallel to the series circuit of the switching element 32a.

  The capacitor 32 c is electrically connected to the switching element 32 a and the diode 32 b by the wiring member 40. The main current of the unit converter 30 flows through the wiring member 40. Although the wiring member 40 will be described in detail later, the inductance is determined according to the length and width, the distance when the wiring members 40 are overlapped via an insulator, and the dimensions of the overlapping. The switching element 32a is a self-extinguishing type semiconductor switch such as an IGBT (Insulated Gate Bipolar Transistor). The switching element 32a is driven by a drive signal to charge / discharge the capacitor 32c. Therefore, the waveform of the switching current (main current) varies depending on the inductance value of the wiring member 40. When the switching current changes, for example, the conversion efficiency of the unit converter 30 changes, which affects the conversion efficiency of the entire power conversion device. In the power converter 10 of the embodiment, by adjusting the inductance value of the wiring member 40, the waveform of the switching current can be optimized and the conversion efficiency of the unit converter 30 can be set to an appropriate value.

FIG. 3A is a plan view illustrating a part of the unit converter. FIG. 3B is a bottom view illustrating a part of the unit converter. FIG.3 (c) is sectional drawing in the AA 'line of Fig.3 (a).
As shown in FIGS. 3A to 3C, the wiring member 40 includes conductive plates 42 a and 42 b and an insulating plate 43. The conductive plates 42a and 42b are made of a highly conductive material such as a metal such as a copper alloy. The insulating plate 43 is made of an insulating material, is provided between the conductive plates 42a and 42b, and electrically insulates the conductive plates 42a and 42b. As will be described in detail later, the insulating plate 43 is also provided for setting the distance between the conductive plates 42a and 42b. The conductive plate 42a, the insulating plate 43, and the conductive plate 42b are stacked and constitute an integrated wiring member 40.

  The conductive plates (first and second conductive plates) 42a and 42b have two end portions through which current can flow in and out. Connection portions 44a and 44b are provided at one end of the conductive plates 42a and 42b, respectively, and connection portions 45a and 45b are provided at the other end, respectively. The conductive plate 42a is electrically connected to an external circuit through the connection portions 44a and 45a. The conductive plate 42b is electrically connected to an external circuit through the connection portions 44b and 45b.

  Specifically, the high potential side terminal of the capacitor 32c is connected to the conductive plate 42a by the connection portion 44a. The conductive plate 42a is connected to the collector terminal of the switching element 32a by the connecting portion 45a. The terminal on the low potential side of the capacitor 32c is connected to the conductive plate 42b by the connecting portion 44b. The conductive plate 42b is connected to the emitter terminal of the switching element 32a by the connecting portion 45b.

  The conductive plates 42a and 42b are conductive plates having substantially the same shape, and the shape of the conductive plates 42a and 42b is not limited, but is substantially rectangular, for example. The connecting portions 44a and 44b are provided to extend along the direction in which current flows from one end of the conductive plates 42a and 42b. The connection parts 45a and 45b are provided at the end part which is the other side opposite to the side provided with the end part provided with the connection parts 44a and 44b of the conductive plates 42a and 42b. In this example, the connecting portions 44a and 45a are provided at positions offset in one direction along the respective edges from the center of the respective edges of the conductive plate 42a provided with the connecting portions 44a and 45a. The connecting portions 44b and 45b are also provided at positions offset from the centers of the respective edges where the connecting portions 44b and 45b are provided along the respective edges to the side opposite to the connecting portions 44a and 45a. The position of the connecting portion can be arbitrarily set to an appropriate position depending on the arrangement of circuit elements connected by the wiring member 40. In the case of this example, the conductive plate 42a and the connecting portions 44a and 45a, and the conductive plate 42b and the connecting portions 44b and 45b have a shape that is a line object with respect to the center line.

  The wiring member 40 has an inductance value determined by the shape of the conductive plates 42a and 42b, the distance between the conductive plates 42a and 42b, and the direction of the current flowing through each of the conductive plates 42a and 42b. The longer the length of the conductive plates 42a and 42b along the direction in which the current flows (hereinafter simply referred to as the length), the greater the self-inductance of the conductive plates 42a and 42b. The longer the length of the conductive plates 42a and 42b in the direction perpendicular to the direction in which the current flows (hereinafter referred to as the width), the smaller the self-inductance of the conductive plates 42a and 42b.

  The distance between the conductive plates 42a and 42b can be set by the thickness of the insulating plate 43. The thicker the insulating plate 43, the longer the distance between the conductive plates 42a and 42b. The mutual inductance between the conductive plates 42a and 42b differs depending on the direction of the current flowing through the conductive plates 42a and 42b and the separation distance between the conductive plates 24a and 42b. When the directions of the currents flowing through the conductive plates 42a and 42b are the same, the magnetic field generated by the currents is weakened, so that the inductance value decreases as the separation distance between the conductive plates 42a and 42b decreases. When the directions of the currents flowing through the conductive plates 42a and 42b are different, the magnetic fields generated by the currents are strengthened, so that the inductance value increases as the distance between the conductive plates 42a and 42b decreases. Hereinafter, a specific example will be described in the case where the directions of the currents flowing through the conductive plates 42a and 42b are different, but the case where the directions of the currents flowing through the conductive plates 42a and 42b are the same is applied as described above. Is possible.

  The inductance value of the wiring member 40 is determined by the magnitudes of the self-inductance and the mutual inductance of the conductive plates 42a and 42b.

4A to 4D are views corresponding to the cross section taken along the line AA ′ of FIG. 3A, and are cross-sectional views illustrating a modification of the unit converter.
FIG. 4A is a diagram reprinted as a comparison target, and is the same diagram as FIG. The insulating plate 43 has a thickness t0. As described above, in the wiring member, the separation distance between the two conductive plates can be adjusted by changing the thickness of the insulating member. As shown in FIG. 4B, the wiring member 140 includes an insulating member 143 having a thickness different from that of the wiring member 40. The insulating member 143 has a thickness t1. In the case of t1> t0, the distance between the conductive plates 42a and 42b becomes long, and the strengthening of the magnetic field between the conductive plates 42a and 42b decreases. It becomes smaller than the case of.

  As shown in FIG. 4C, the wiring member 240 includes conductive plates 242a and 242b different from the case of the wiring member 40 of FIG. The width W2 of the conductive plates 242a and 242b is set wider than the width W0 of the conductive plates 42a and 42b of the wiring member 40. Therefore, since the self-inductance of the conductive plates 242a and 242b is reduced, the overall inductance of the wiring member 240 is smaller than that in the case of FIG.

  As shown in FIG. 4D, the wiring member 340 is different from the wiring member 40 in FIG. 4A in the overlapping length L3 of the conductive plates 42a and 42b. In the wiring member 340, the length L3 in which the conductive plates 42a and 42b overlap via the insulating plate 43 is shorter than the width W0 of the conductive plate. Accordingly, the strength of the magnetic field is reduced, so that the inductance of the entire wiring member 340 is reduced as compared with the case of FIG.

FIG. 5 is a plan view corresponding to FIG. 3A and illustrates a modification of a part of the unit converter.
The left figure of FIG. 5 is the same figure as FIG. 3 (a) reproduced as a comparison object. As shown in the right diagram of FIG. 5, the wiring member 440 includes a conductive plate 442a having a length L4 different from the length L0 in the case of the wiring member 40 of FIG. Although not shown, an electric plate having the same dimensions as the conductive plate 442a is provided at the position of the conductive plate 42b via an insulating plate 443. In this example, the length L4 of the conductive plate 442a is set shorter than the length L0 in the case of FIG. Therefore, the self-inductance of the conductive plate 442a is smaller than in the case of FIG. 3A, and the inductance of the entire wiring member 440 can be reduced.

The effect of the power converter of this embodiment is demonstrated.
As described above, the power conversion device according to the embodiment includes the wiring member 40. In the wiring member 40, the length and width of the conductive plate are changed, or the separation distance of the conductive plate is changed to thereby change the wiring member. Can be adjusted. Since the wiring member 40 is used to connect the capacitor 32c and the switching element 32a of the unit converter 30, by adjusting the inductance value of the wiring member 40, the waveform of the charge / discharge current to the capacitor is adjusted, and unit conversion is performed. The conversion efficiency of the device 30 can be adjusted to an appropriate value.

  In a power converter including a large number of unit converters 30 such as an MMC, various characteristics such as conversion efficiency and noise emission of the power converter are achieved in order to achieve appropriate values such as target values and specification values. It is necessary to align various characteristics such as the conversion efficiency and noise radiation of the unit converter 30 to optimum values. The performance can be adjusted to some extent by adjusting the driving conditions of the switching element 32a. However, if the characteristics of the parasitic circuit parameters caused by the wiring through which the main current flows can be adjusted, more appropriate performance can be realized. can do. In the present embodiment, as described above, the inductance value of the wiring member can be adjusted, so that an appropriate value can be set more easily.

  It is also possible to prepare in advance a plurality of types of wiring members in which the dimensions of the conductive plate, the thickness of the insulating plate, and the like are variously changed. By measuring the characteristics for each unit converter 30 and selecting a wiring member having an appropriate parameter, the characteristics of the unit converter 30 can be optimally adjusted for each unit converter 30 and the performance of the entire power converter Can be adjusted to an appropriate value.

  According to the embodiment described above, it is possible to realize a separately excited power conversion device that simplifies the structure of the converter while reducing the installation space.

  As mentioned above, although several embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and the equivalents thereof. Further, the above-described embodiments can be implemented in combination with each other.

  1 AC system, 2 transformer, 3 DC system, 20 power converter, 22 unit arm, 24 transformer, 30 unit converter, 32a switching element, 32b diode, 32c capacitor, 40, 140, 240, 340, 440 wiring Member, 42a, 42b, 242a, 242b, 442a Conductive plate, 43, 143, 443 Insulating plate

Claims (6)

A power converter including a plurality of main circuits each including a switching element, a capacitor, and a wiring member that electrically connects the switching element and the capacitor to flow a main current;
The wiring member is
A first conductive plate and a second conductive plate which are plate-like bodies of a conductor;
An insulating plate, and an insulating plate that electrically insulates the first conductive plate and the second conductive plate between the first conductive plate and the second conductive plate;
Including
The shape of the said 1st conductive plate, the said 2nd conductive plate, and the said insulating plate is a power converter device set so that each of the said main current may become a desired waveform.   The power converter according to claim 1, wherein the first conductive plate and the second conductive plate have the same shape.   The power conversion device according to claim 2, wherein the first conductive plate and the second conductive plate are provided at positions facing each other.   The power conversion device according to claim 2, wherein the first conductive plate and the second conductive plate are provided at positions offset from positions facing each other in a direction intersecting a direction in which the main current flows.   The power converter according to claim 1, wherein the insulating plate has a uniform thickness.   The power converter according to any one of claims 1 to 5, wherein the power converter is a modular multilevel converter.

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