JP2019176566A - Power conversion device - Google Patents

Abstract

To provide a power conversion device which has high efficiency by reduction of loss in a DC circuit.SOLUTION: The power conversion device according to an embodiment includes a plurality of converters that have switching elements, perform conversion from AC power to DC power and/or conversion from AC power to DC power by switching of the switching elements, and are connected, on a DC side, in parallel so as to be arranged in one line, a first common line connected to the DC side of the plurality of converters, a second common line connected to the DC side of the plurality of converters and set so as to have a potential lower than that of the first common line, and a power storage unit connected between the first common line and the second common line. The power storage unit is set adjacent to a converter at an end among the plurality of converters.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a power conversion apparatus.

  There is a parallel multiplex type power converter in which a plurality of converters are connected in parallel. Each converter includes a switching element, and performs at least one of conversion from AC power to DC power and conversion from DC power to AC power by switching of the switching element. A capacitor, which is a charge storage element, is provided on the DC side of each converter. Each capacitor is connected in parallel with the converter via a DC bus bar.

  In the parallel multiplex type power conversion device, a plurality of converters are connected in parallel to one line of AC power, and thus it is possible to cope with an increase in capacity while suppressing a high breakdown voltage of the switching element.

  When a plurality of converters are connected in parallel, a harmonic current having a frequency twice the fundamental frequency of the AC voltage flows between the converters. Since this harmonic current flows through the DC bus bar, if the current path becomes longer, the loss at the DC bus bar increases. Therefore, it is necessary to set the current capacity of the DC bus bar to be larger than necessary, and this is also a cause of reducing the conversion efficiency of the power converter.

JP 2005-102444 A

  Embodiments of the present invention provide a highly efficient power conversion device by reducing the loss of a DC circuit.

  According to an embodiment of the present invention, a switching element is provided, and at least one of conversion from AC power to DC power and conversion from DC power to AC power is performed by switching the switching element, and parallel on the DC side. A plurality of converters connected and arranged in a row, a first common line connected to the DC side of the plurality of converters, and connected to a DC side of the plurality of converters, than the first common line A second common line set at a low potential; and a power storage unit connected between the first common line and the second common line. The power storage unit is disposed adjacent to a converter at an end of the plurality of converters.

  A highly efficient power converter is provided by reducing the loss of the DC circuit.

It is a block diagram which illustrates the power converter concerning an embodiment. It is a block diagram which illustrates the converter concerning an embodiment. FIG. 3A and FIG. 3B are schematic views illustrating the arrangement of the converter and the power storage unit. It is a block diagram which represents typically the power converter device of a comparative example.

Each embodiment will be described below 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.
Note that, in the present specification and each drawing, 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 schematically illustrating a power conversion device according to the embodiment.
As illustrated in FIG. 1, the power conversion device 10 includes a plurality of converters 20, a first common line 31, a second common line 32, a plurality of first wirings 41, and a plurality of second wirings 42. , And wirings 43 to 46 and power storage units 62a and 62b.

  Moreover, the power converter device 10 has the 1st alternating current terminal 60u, the 2nd alternating current terminal 60v, and the 3rd alternating current terminal 60w. The power conversion device 10 is connected to the AC circuit 1 via each AC terminal 60u, 60v, 60w. The AC circuit 1 can include a power system, an AC power supply, an AC power transmission line, an AC load, and the like. In this example, the AC circuit 1 is an AC power system, and the AC power is three-phase AC power. Each AC terminal 60u, 60v, 60w is connected to each phase line of the power system.

  Each converter 20 is connected to one of the AC terminals 60u, 60v, 60w via an inductor 64. Each converter 20 converts AC power supplied from each AC terminal 60u, 60v, 60w into DC power.

  The power storage units 62 a and 62 b are provided on the DC side of each converter 20. The power storage units 62a and 62b store the DC power converted by each converter 20. For example, a charge storage element or a secondary battery is used for the power storage units 62a and 62b. Each converter 20 converts the DC power stored in power storage units 62a and 62b into AC power, and supplies the converted AC power to the AC power system.

  Thus, each converter 20 performs conversion from AC power to DC power, and conversion from DC power to AC power. Thereby, the power converter device 10 suppresses the fluctuation | variation of an alternating current power grid | system, for example. Each converter 20 is not limited to the one that performs bidirectional conversion, and may be one that performs only one of conversion from AC power to DC power and conversion from DC power to AC power.

  Each converter 20 has a first DC terminal 20a, a second DC terminal 20b, and an AC terminal 20c. The potential of the second DC terminal 20b is lower than the potential of the first DC terminal 20a. The first DC terminal 20a is a high potential side terminal and the second DC terminal 20b is a low potential side DC power input to each converter 20 or DC power output from each converter 20. Terminal.

  Each converter 20 is connected to one of the inductor 64 and each AC terminal 60u, 60v, 60w via the AC terminal 20c.

  The plurality of converters 20 are converters 21 to 23. The converter 21 is connected to the first AC terminal 60u. The converter 22 is connected to the second AC terminal 60v. The converter 23 is connected to the third AC terminal 60w.

  The first common line 31 is provided on the DC side of each converter 21 to 23. The second common line 32 is provided on the direct current side of each of the converters 21 to 23 and is set at a lower potential than the first common line 31.

  The first common line 31 and the second common line 32 are DC bus bars, for example, are formed of the same conductive material and have substantially the same width and thickness over the respective length directions. That is, the first common line 31 and the second common line 32 have a substantially constant resistance value (resistivity) per unit length.

  The converters 21 to 23 are arranged almost in a line. It is not necessary for the converters 21 to 23 to be arranged in a line, and it means that other converters are arranged adjacent to one converter. More specifically, the converters arranged in a line are arranged so that the converter 22 is arranged adjacent to the converter 21 and the converter 23 is arranged adjacent to the converter 22. It is included.

  The converters 21 to 23 are electrically connected to the first wiring 41 and the second wiring 42 in the central portion (first portion) C of the DC bus bar. The DC bus bar has end portions (second portions) Ta and Tb at both ends. The end portions Ta and Tb are not limited to the physical ends of the central portion C, and are adjacent to the central portion C connected to the first wiring 41 and the second wiring 42 as described in detail later. Including a portion provided outside C.

  One end portion Ta includes connection portions 31a and 32a. The other end Tb includes connection portions 31b and 32b. The first common line 31 and the second common line 32 are electrically connected to the power storage unit 62a via the wirings 43 and 44 at one connection unit 31a and 32a. The first common line 31 and the second common line 32 are electrically connected to the power storage unit 62b via the wirings 45 and 46 at the other connection portions 31b and 32b. That is, the converters 21 to 23 arranged in approximately one row are arranged between the power storage units 62a and 62b.

  For convenience of explanation, the first wiring 41, the second wiring 42, and the wirings 43 to 46 are distinguished from each other by using different symbols from the first common line 31 and the second common line 32. Of course, the portion may be formed of substantially the same member, for example, integrally.

  Each first wiring 41 connects the converters 21 to 23 and the first common line 31. Each second wiring 42 connects the converters 21 to 23 and the second common line 32. More specifically, each first wiring 41 connects the first DC terminal 20 a of the converters 21 to 23 and the first common line 31. Each second wiring 42 connects the second DC terminal 20 b of the converters 21 to 23 and the second common line 32.

  Each charge storage element 50 is connected between the first wiring 41 and the second wiring 42 on the DC side of the converters 21 to 23. In other words, each charge storage element 50 is connected between the first DC terminal 20a and the second DC terminal 20b of each converter 21-23.

  Thus, the power converter device 10 is a power converter device in which the DC sides of the plurality of converters 21 to 23 are connected in parallel.

  Each first resistor 51 is provided on the first common line 31 so as to be disposed between each first wiring 41. Further, the first resistor 51 is arranged between the first wiring 41 and the wiring 43 connected to the converter 21 arranged at the position closest to the connection portion 31a, so that the first common line 31 is arranged. Is provided. The first resistor 51 is provided on the first common line 31 so as to be disposed between the first wiring 41 and the wiring 45 connected to the converter 23 disposed at a position closest to the connection portion 31b. It has been. Each first resistor 51 is provided in series with the first common line 31.

  Each second resistor 52 is provided on the second common line 32 so as to be disposed between each second wiring 42. Further, the second resistor 52 is arranged between the second wiring 42 and the wiring 44 connected to the converter 21 arranged at the position closest to the connection portion 32a, so that the second common line 32 is arranged. Is provided. The second resistor 52 is provided on the second common line 32 so as to be disposed between the second wiring 42 and the wiring 46 connected to the converter 23 disposed at a position closest to the connection portion 32b. It has been. Each second resistor 52 is provided in series with the second common line 32.

  For each of the first resistor 51 and the second resistor 52, for example, a water-cooled resistor having a flow path for flowing cooling water therein is used. The resistance value of each first resistor 51 and the resistance value of each second resistor 52 are, for example, several mΩ (1 mΩ or more and 10 mΩ or less). The resistance value of each first resistor 51 may be substantially the same or different in each of the first resistors 51. The resistance value of each second resistor 52 may be substantially the same or different in each of the second resistors 52.

  Since the current flowing through the ends Ta and Tb does not include a harmonic current having a frequency twice the fundamental frequency of the AC voltage, the first resistor 51 and the second resistor on the ends Ta and Tb side The current capacity and the allowable loss may be set smaller than those of the first resistor 51 and the second resistor 52.

  All three converters 21 to 23 are arranged between power storage units 62a and 62b. In the central part C of the first common line 31 and the second common line 32 to which the converters 21 to 23 are connected, harmonic currents having a frequency twice as high as the fundamental frequency of the AC voltage flow mutually. At the ends Ta and Tb of the first common line 31 and the second common line 32, a harmonic current having a frequency twice the basic frequency of the AC voltage does not flow. By arranging in this way, the length of the central portion C (a length along the direction in which the current flows) through which the harmonic current having a frequency twice the fundamental frequency of the AC voltage flows can be relatively shortened. Therefore, the lengths of the first common line 31 and the second common line 32 can be suppressed, and loss in the first common line 31 and the second common line 32 can be reduced.

  The power storage unit may be one power storage unit instead of being divided into two as in this example. In that case, the power storage unit is electrically connected at either end Ta or Tb of the first common line 31 or the second common line 32. Thus, when setting it as one electrical storage part, Preferably, an electrical storage part is arrange | positioned adjacent to the one converter 21 or the converter 23 arrange | positioned at the edge part among the several converters 21-23. .

FIG. 2 is a block diagram schematically illustrating the converter according to the embodiment.
As shown in FIG. 2, the converter 20 includes two switching elements 101 and 102 connected in series and two rectifying elements 111 and 112 connected in antiparallel to the two switching elements 101 and 102. And having. For the switching elements 101 and 102, for example, a power semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) or a power MOSFET is used. The rectifying elements 111 and 112 are so-called reflux diodes.

  One main terminal (for example, collector) of the switching element 101 is connected to the first DC terminal 20a. The other main terminal (for example, emitter) of the switching element 101 is electrically connected to one main terminal of the switching element 102. The other main terminal of the switching element 102 is connected to the second DC terminal 20b. The connection point of the switching elements 101 and 102 is connected to the AC terminal 20c.

  In this way, the converter 20 is a half bridge circuit in which both ends of the two switching elements 101 and 102 are connected to the DC terminals 20a and 20b, and a connection point of the two switching elements 101 and 102 is connected to the AC terminal 20c. It is. In other words, the converter 20 is a bidirectional chopper circuit. As a result, conversion from AC power to DC power and conversion from DC power to AC power can be performed by switching the switching elements 101 and 102 of each converter 20 as described above.

  In the power conversion device 10 according to the present embodiment, each first resistor 51 and each second resistor 52 are provided on the DC side of the converters 21 to 23. In each of the converters 21 to 23 connected in parallel, LC resonance may occur on the DC side, and a resonance current may flow through the first common line 31 and the second common line 32. Even in such a case, the resonance current can be attenuated by providing the first resistor 51 and the second resistor.

FIG. 3A and FIG. 3B are schematic views illustrating the arrangement of the converter and the power storage unit.
FIG. 3A is a simplified diagram of the above-described power conversion device 10 in order to show the arrangement of the converter 20 and the power storage units 62a and 62b.
As shown in FIG. 3A, one set of converters 20 is electrically connected between the AC circuit 1 and the DC circuit. The DC circuit includes first common line 31 and second common line 32, and power storage units 62a and 62b.

  The set of converters 20 is disposed between power storage units 62a and 62b. In order to achieve such an arrangement, the set of converters 20 is electrically connected at the center C of the first common line 31 and the second common line 32, and the power storage units 62 a and 62 b are connected to the first common line 31. And the end portions Ta and Tb of the second common line 32 are electrically connected.

The set of converters 20 is not limited to one set and may be a plurality of sets.
As shown in FIG.3 (b), the power converter device 110 is provided with the sets P1 and P2 of the converter 20, and electrical storage part 62a-62c. The set P1 of the converter 20 is disposed between the power storage units 62a and 62b. The set P2 of the converter 20 is disposed between the power storage units 62b and 62c.

  On the AC side of the pairs P1 and P2 of the converter 20, the converters 20 connected to the U phase, the V phase, and the W phase of the AC circuit 1 are connected in parallel. That is, the converter 20 connected to the U phase of the set P1 of the converter 20 and the converter 20 connected to the U phase of the set P2 of the converter 20 are connected to the U phase of the AC circuit 1. . The same applies to the V phase and the W phase.

  The DC side of the set P <b> 1 of the converter 20 is electrically connected by the first portion C <b> 1 of the first common line 31 and the second common line 32. The power storage units 62a and 62b are electrically connected at the second portions T1 and T2 of the first common line 31 and the second common line 32. The first portion C1 is provided between the second portions T1 and T2.

  The DC side of the set P <b> 2 of the converter 20 is electrically connected by the first portion C <b> 2 of the first common line 31 and the second common line 32. The power storage units 62b and 62c are electrically connected at the second portions T2 and T3 of the first common line 31 and the second common line 32. The first portion C2 is provided between the second portions T2 and T3.

  In the example of the power conversion device described above, one set of converters 20 is realized by a two-level half-bridge configuration (FIG. 2), but may be a multi-level half-bridge such as a neutral point clamp method, Other single-ended conversion circuits may be used.

The effects of the power conversion device 10 of the embodiment will be described in comparison with the power conversion device 210 of the comparative example.
FIG. 4 is a block diagram schematically showing a power conversion device of a comparative example.
As illustrated in FIG. 4, the power conversion device 210 of the comparative example includes a plurality of converters 21 to 23 and a plurality of power storage units 62a and 62b. One power storage unit 62 a is disposed between the converters 21 and 22. The other power storage unit 62 b is disposed between the converters 22 and 23. As shown in this example, the number of converters and the number of power storage units are the same as in the case of the power conversion device 10 of the embodiment, and both the case of the comparative example and the case of the embodiment have the same output capacity. And

  The first common line 131 and the second common line 132 are provided on the DC side of the plurality of converters 21 to 23.

  Each first wiring 41 connects each of the converters 21 to 23 to the first common line 131. Each second wiring 42 connects each of the converters 21 to 23 to the second common line 132.

  The power storage unit 62a is connected to each of the first common line 131 and the second common line 132 via wirings 143 and 144. The power storage unit 62 b is connected to each of the first common line 131 and the second common line 132 via wirings 144 and 145.

  The wiring 143 is connected to the first common line 131 between the connection positions of the adjacent first wirings 41 to the first common line 131. The wiring 144 is connected to the second common line 132 between the connection positions of the adjacent second wiring 42 and the second common line 132.

  The wiring 145 is connected to the first common line 131 between the connection positions of the adjacent first wiring 41 and the first common line 131. The wiring 146 is connected to the second common line 132 between the connection positions of the adjacent second wirings 42 to the second common line 132.

  In the power conversion device 210 of the comparative example configured as described above, the converter 20 is disposed between the power storage units 62a to 62b. Alternatively, power storage units 62 a and 62 b are arranged between converters 20. Therefore, a harmonic current having a frequency twice the fundamental frequency of the AC voltage flows between adjacent converters across the power storage unit and is superimposed on a direct current flowing into and out of the power storage units 62a and 62b. Therefore, since a large current flows over the entire length L of the first common line 131 and the second common line 132, the loss of the first common line 132 and the second common line 132 increases. In addition, since the power storage units 62a and 62b are arranged between the converters 20, the total length L of the first common line 131 and the second common line 132 becomes long, and the first common line 131 and the second common line 132 The loss due to the increased resistance value also increases. Therefore, the conversion efficiency of the power conversion device 210 decreases.

  On the other hand, since all the converters 20 are arrange | positioned between the electrical storage parts 62a and 62b in the power converter device 10 of embodiment, the distance between the converters 20 arrange | positioned adjacently becomes short. Therefore, since the length of the central portion C of the first common line 31 and the second common line 32 can be shortened, the resistance value in the length direction of the first common line 31 and the second common line 32 can be reduced. , Loss can be suppressed.

  At the end portions Ta and Tb of the first common line 31 and the second common line 32, a harmonic current having a frequency twice the basic frequency of the AC voltage does not flow, so that the first common line 31 and the second common line 32 The flowing current value itself becomes small. Therefore, the loss at the end portions Ta and Tb of the first common line 31 and the second common line 32 can be reduced.

  As described above, the conversion efficiency of the power converter 10 can be improved by reducing the loss in the first common line 31 and the second common line 32.

  Furthermore, since the value of the flowing current is small at the end portions Ta and Tb of the first common line 31 and the second common line 32, the first common line 41 and the wiring 43 of the converter 20 adjacent to the power storage unit 62a are between them. The current capacity and allowable loss of the connected first resistor 51 and the first resistor 51 connected between the first wiring 41 and the wiring 45 of the converter 20 adjacent to the power storage unit 62b are also different from each other. The current capacity and allowable loss of the first resistor 51 can be made smaller.

  Similarly, the second resistor 52 connected between the second wiring 42 and the wiring 44 of the converter 20 adjacent to the power storage unit 62a, and the second wiring 42 of the converter 20 adjacent to the power storage unit 62b The current capacity and allowable loss of the second resistor 52 connected to the wiring 46 can be made smaller than the current capacity and allowable loss of the other second resistors 52.

  From the above, it is possible to reduce the loss of the DC circuit and realize a highly efficient power converter.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... AC circuit 10, 110, 210 ... Power converter, 20-23 ... Converter, 31 ... 1st common line, 32 ... 2nd common line, 41 ... 1st wiring, 42 ... 2nd wiring, 43- 46 ... wiring, 50 ... charge storage element, 51 ... first resistor, 52 ... second resistor, 60u ... first AC terminal, 60v ... second AC terminal, 60w ... third AC terminal, 62a, 62b ... electricity storage 64, inductor, 101-106, switching element, 111-116, rectifying element

Claims (6)

A plurality of switching elements that are connected in parallel on the direct current side and arranged in a row, having at least one of conversion from AC power to DC power and conversion from DC power to AC power by switching of the switching elements A converter of
A first common line connected to the DC side of the plurality of converters;
A second common line connected to the DC side of the plurality of converters and set at a lower potential than the first common line;
A power storage unit connected between the first common line and the second common line;
With
The power storage unit is a power conversion device arranged adjacent to an end converter among the plurality of converters. The power storage unit includes a first power storage unit and a second power storage unit,
The power converter according to claim 1, wherein the plurality of converters are disposed between the first power storage unit and the second power storage unit. The plurality of converters are respectively connected to the first common line via a first wiring,
The plurality of converters are respectively connected to the second common line via a second wiring,
All the first wirings are connected at the first part of the first common line, and all the second wirings are connected at the second part of the second common line,
3. The power conversion device according to claim 1, wherein the power storage unit is electrically connected at a third portion closer to the end than the first portion and the second portion. A plurality of first wirings provided between the first wiring and the power storage unit provided between the first wirings and connected to a converter adjacent to the power storage unit among the plurality of converters. One resistor,
A plurality of second wirings provided between the second wiring and the power storage unit provided between the second wirings and connected to a converter adjacent to the power storage unit among the plurality of converters. Two resistors,
The power converter according to any one of claims 1 to 3, further comprising:   The power converter according to any one of claims 1 to 4, wherein the plurality of converters are provided according to each phase of alternating current. The plurality of converters are connected in parallel on the AC side,
The power conversion device according to claim 5, wherein the power storage unit is arranged between the plurality of sets arranged adjacent to each other.

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