JP6788940B2 - Power converter - Google Patents

Description

Embodiments of the present invention relate to a power converter.

There is a parallel multiplex type power converter in which a plurality of converters are connected in parallel. Each converter has a switching element, and by switching the switching element, at least one of conversion from AC power to DC power and conversion from DC power to AC power is performed. A charge storage element (DC capacitor) is provided on the DC side of each converter. Each charge storage element is connected in parallel.

In the parallel multiplexing type power converter, by connecting a plurality of converters in parallel to one line of AC power, it is possible to cope with a large capacity while suppressing a high withstand voltage of the switching element.

On the other hand, when a plurality of converters are connected in parallel, the switching timing of the switching element in each converter becomes a problem. In each converter, the switching timing of the switching element varies due to the influence of individual differences of the switching element, wiring resistance, wiring inductance, and the like. If this timing difference becomes relatively large, current imbalance will occur in each of the converters connected in parallel. For example, a large current may transiently flow through a converter having a fast timing, or a current may flow from a converter having a fast timing to a converter having a slow timing, which may damage the switching element.

It is common to insert a reactor on the AC output side in order to suppress a transient large current generated by a shift in switching timing. However, the unbalanced current between parallels increases with each switching. On the other hand, there is a method of suppressing the expansion of the unbalanced current by attenuating the unbalanced current generated by the timing shift of switching by installing a resistor on the AC output side. However, in this case, a relatively large alternating current flows through the resistor, resulting in a large resistance loss. Therefore, in a parallel multiplex type power converter, it is desired to be able to suppress current imbalance in a plurality of converters connected in parallel while suppressing loss.

Japanese Unexamined Patent Publication No. 2005-102444

An embodiment of the present invention provides a power converter capable of suppressing current imbalance in a plurality of converters connected in parallel while suppressing loss.

According to an embodiment of the present invention, a plurality of converters having a switching element and performing at least one of conversion from AC power to DC power and conversion from DC power to AC power by switching the switching element. A first common line provided on the DC side of the plurality of converters, and a second common line provided on the DC side of the plurality of converters and set to a lower potential than the first common line. A plurality of first wires connecting each of the plurality of converters and the first common line, a plurality of second wires connecting each of the plurality of converters and the second common line, and the plurality of second wires. On each DC side of the converter, a plurality of charge storage elements provided between the first wiring and the second wiring are arranged between the plurality of first wirings, and are arranged in series as a whole. a first resistor, a power conversion apparatus having a are provided a plurality of provided in the first common line so that make up the resistor string.

A power converter capable of suppressing current imbalance in a plurality of converters connected in parallel while suppressing loss is provided.

It is a block diagram which shows typically the power conversion apparatus which concerns on embodiment. It is a block diagram which shows typically the converter which concerns on embodiment. It is a block diagram which shows typically the modification of the power conversion apparatus which concerns on embodiment. It is a block diagram which shows typically the modification of the power conversion apparatus which concerns on embodiment. It is a block diagram which shows typically the converter which concerns on embodiment.

Hereinafter, each embodiment 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 ratio of the sizes between the parts, and the like are not necessarily the same as the actual ones. Further, even when the same parts are represented, the dimensions and ratios may be different from each other depending on the drawings.
In addition, in the present specification and each figure, the same elements as those described above with respect to the above-mentioned figures are designated by the same reference numerals, and detailed description thereof will be omitted as appropriate.

FIG. 1 is a block diagram schematically showing a power conversion device according to an embodiment.
As shown 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. , A charge storage element 50, a plurality of first resistors 51, and a plurality of second resistors 52.

Further, the power conversion device 10 has a first AC terminal 60u, a second AC terminal 60v, a third AC terminal 60w, and a power storage unit 62. The power conversion device 10 is connected to the AC power system via, for example, the AC terminals 60u, 60v, and 60w. In this example, the AC power of the AC power system is three-phase AC power. The AC terminals 60u, 60v, and 60w are connected to the lines of each phase of the AC power system.

Each converter 20 is connected to any of the AC terminals 60u, 60v, and 60w via an inductor 64. Each converter 20 converts the AC power supplied from the AC terminals 60u, 60v, 60w into DC power. The power storage unit 62 is provided on the DC side of each converter 20. The power storage unit 62 stores the DC power converted by each converter 20. For the power storage unit 62, for example, a charge storage element, a secondary battery, or the like is used. Each converter 20 converts the DC power stored in the power storage unit 62 into AC power, and supplies the converted AC power to the AC power system.

In this way, each converter 20 performs conversion from AC power to DC power and conversion from DC power to AC power. As a result, the power conversion device 10 suppresses fluctuations in the AC power system, for example. The converter 20 is not limited to the one that performs both conversions, and may be one that performs only one of the conversion from AC power to DC power and the 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. With respect to the DC power input to each converter 20 or the DC power output from each converter 20, the first DC terminal 20a is a terminal on the high potential side, and the second DC terminal 20b is a terminal on the low potential side. It is a terminal.

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

The plurality of converters 20 include a plurality of first converters 21, a plurality of second converters 22, and a plurality of third converters 23. Each first converter 21 is connected to the first AC terminal 60u. Each second converter 22 is connected to a second AC terminal 60v. Each third converter 23 is connected to the third AC terminal 60w.

The first common line 31 is provided on the DC side of each converter 20. The second common line 32 is provided on the DC side of each converter 20 and is set to a lower potential than the first common line 31.

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

In this example, the DC side of each converter 20 is connected to the first common line 31 and the second common line 32 so as to be repeatedly arranged in the order of the first converter 21, the second converter 22, and the third converter 23. Has been done.

Further, in this example, one end of the power storage unit 62 is connected to the first common line 31 via the wiring 43, and the other end of the power storage unit 62 is connected to the second common line 32 via the wiring 44. .. The common lines 31, 32 and the wirings 41 to 44 are, for example, parallel flat plate-shaped busbars.

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

In this way, the power converter 10 is a parallel multiplexing type in which a plurality of converters 20 are connected in parallel to each AC terminal 60u, 60v, 60w and the DC sides of the plurality of converters 20 are connected in parallel. There is a power converter. In such a parallel multiplex type power conversion device, it is possible to relatively easily increase the capacity by increasing the number of converters 20 connected in parallel. In this example, two converters 20 are connected in parallel to each of the AC terminals 60u, 60v, and 60w. The number of parallel connections of each converter 20 is not limited to two, and may be three or more. The number of parallel connections of each converter 20 may be any number.

Each of the first resistors 51 is provided on the first common line 31 so as to be arranged between the first wirings 41. Each first resistor 51 is provided so as to be connected in series to the first common line 31. Further, in this example, the first resistor 51 is also provided between the first wiring 41 and the wiring 43.

Each second resistor 52 is provided on the second common line 32 so as to be arranged between each of the second wirings 42. Each second resistor 52 is provided so as to be connected in series to the second common line 32. Further, in this example, a second resistor 52 is also provided between the second wiring 42 and the wiring 44.

For each of the first resistor 51 and each second resistor 52, for example, a water-cooled resistor provided with a flow path for flowing cooling water inside 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 of the second resistors 52 may be substantially the same or different in each of the second resistors 52.

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

One main terminal (for example, a collector) of the switching element 101 is connected to the first DC terminal 20a. The other main terminal (for example, an 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 points of the switching elements 101 and 102 are 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 the connection points of the two switching elements 101 and 102 are connected to the AC terminal 20c. Is. In other words, the converter 20 is a bidirectional chopper circuit. As a result, as described above, the conversion from AC power to DC power and the 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 each converter 20. As a result, for example, in the converters 21, 22, 23, etc. connected in parallel, when a difference occurs in the switching timing of the switching elements 101, 102 and an unbalanced current is generated, the unbalanced current is attenuated. It is possible to suppress the expansion of the unbalanced current generated at each switching by accelerating. Therefore, in the converters 21, 22, 23, etc. connected in parallel, it is possible to suppress the expansion of the unbalanced current even when there is a difference in the switching timing of the switching elements 101, 102. it can.

For example, it has been proposed to provide a resistor on the AC side of each converter 20 by connecting it in series with the inductor 64. However, when a resistor is provided on the AC side, a relatively large AC current flows through the resistor, so that the resistance loss becomes large.

On the other hand, when each of the first resistor 51 and each of the second resistors 52 is provided on the DC side, only the unbalanced current flows through each of the first resistor 51 and each of the second resistors 52. Therefore, the loss can be suppressed as compared with the case where the resistor is provided on the AC side. Therefore, it is possible to suppress the current imbalance in the plurality of converters 20 connected in parallel while suppressing the loss.

Further, the capacitance of each of the first resistor 51 and each of the second resistors 52 can be reduced as the loss is suppressed. For example, even when a water-cooled resistor is used for each of the first resistor 51 and each of the second resistors 52, it is possible to suppress the enlargement of each of the first resistor 51 and each of the second resistors 52. it can. Therefore, the power conversion device 10 can be downsized.

Further, a resonance current is generated on the DC side of each converter 20 due to the influence of each charge storage element 50, wiring inductance, and the like. At this time, as described above, by providing each of the first resistors 51 and each of the second resistors 52 on the DC side, the resonance current generated on the DC side can be suppressed.

Further, in the power converter 10, the first common line 31 and the second common line 31 and the second common line so that the DC side of each converter 20 is repeatedly arranged in the order of the first converter 21, the second converter 22, and the third converter 23. It is connected to 32. As a result, the number of resistors provided between the converters 20 connected in parallel can be increased. For example, resistors 51 and 52 of the second converter 22 and the third converter 23 may be provided between the first converters 21 connected in parallel. Thereby, the imbalance of the current can be suppressed more appropriately.

FIG. 3 is a block diagram schematically showing a modified example of the power conversion device according to the embodiment.
The same reference numerals are given to those having substantially the same functions and configurations as those of the above-described embodiment, and detailed description thereof will be omitted.
As shown in FIG. 3, in the power converter 10a of this example, the third AC terminal 60w and the plurality of third converters 23 are omitted. In this example, the AC power of the AC power system is single-phase AC power. The AC terminals 60u and 60v are connected to each of a pair of single-phase AC power lines of the AC power system.

Then, in the power converter 10a, the DC side of each converter 20 is connected to the first common line 31 and the second common line 32 so that the first converter 21 and the second converter 22 are arranged alternately. There is.

As described above, the AC power converted by the power conversion device 10a may be single-phase AC power. Then, when converting the single-phase AC power, the first common line 31 and the second common line 31 and the second common line are arranged on the DC side of each converter 20 so that the first converter 21 and the second converter 22 are arranged alternately. Connect to 32. As a result, the number of resistors provided between the converters 20 connected in parallel can be increased, and the current imbalance can be suppressed more appropriately.

FIG. 4 is a block diagram schematically showing a modified example of the power conversion device according to the embodiment.
As shown in FIG. 4, in the power converter 10b, each converter 20 has a first DC terminal 20a, a second DC terminal 20b, a first AC terminal 20c, a second AC terminal 20d, and a third. It has an AC terminal 20e and.

The first AC terminal 20c is connected to the first AC terminal 60u via an inductor 64u. The second AC terminal 20d is connected to the second AC terminal 60v via an inductor 64v. The third AC terminal 20e is connected to the first AC terminal 60w via an inductor 64w. In this way, each of the converters 20 may be connected to each of the AC terminals 60u, 60v, and 60w.

FIG. 5 is a block diagram schematically showing the converter according to the embodiment.
In the power converter 10b, each converter 20 has six switching elements 101-106 and six rectifying elements 111-116. Each converter 20 is a 3-leg full-bridge circuit in which six switching elements 101 to 106 are fully bridge-connected.

One end of the switching elements 101 and 102 connected in series is electrically connected to the first DC terminal 20a. The other ends of the switching elements 101 and 102 are electrically connected to the second DC terminal 20b. The connection point between the switching element 101 and the switching element 102 is electrically connected to the first AC terminal 20c.

One end of the switching elements 103 and 104 connected in series is electrically connected to the first DC terminal 20a. The other ends of the switching elements 103 and 104 are electrically connected to the second DC terminal 20b. The connection point between the switching element 103 and the switching element 104 is electrically connected to the second AC terminal 20d.

One end of the switching elements 105 and 106 connected in series is electrically connected to the first DC terminal 20a. The other ends of the switching elements 105 and 106 are electrically connected to the second DC terminal 20b. The connection point between the switching element 105 and the switching element 106 is electrically connected to the third AC terminal 20e.

The rectifying elements 111 to 116 are connected to the switching elements 101 to 106 in antiparallel.

Also in the power converter 10b configured in this way, by providing each first resistor 51 and each second resistor 52 on the DC side, they are connected in parallel while suppressing loss as in the above embodiment. It is possible to suppress the imbalance of current in the plurality of converters 20.

Further, in the power conversion device 10b, the case where the AC power of the AC power system is a three-phase AC power is illustrated. When the AC power of the AC power system is single-phase AC power and each converter 20 is connected to each of the AC terminals 60u and 60v, each converter 20 is connected to a 2-leg full bridge circuit. do it.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

10, 10a, 10b ... Power converter, 20-23 ... Converter, 31 ... 1st common line, 32 ... 2nd common line, 41 ... 1st wiring, 42 ... 2nd wiring, 43, 44 ... Wiring, 50 ... Charge storage element, 51 ... 1st resistor, 52 ... 2nd resistor, 60u ... 1st AC terminal, 60v ... 2nd AC terminal, 60w ... 3rd AC terminal, 62 ... Power storage unit, 64 ... inductor, 101 ~ 106 ... Switching element, 111-116 ... Rectifying element

Claims (4)

A plurality of converters having a switching element and performing at least one of conversion from AC power to DC power and conversion from DC power to AC power by switching the switching element.
The first common line provided on the DC side of the plurality of converters and
A second common line provided on the DC side of the plurality of converters and set to a lower potential than the first common line,
A plurality of first wirings connecting each of the plurality of converters and the first common line, and
A plurality of second wirings connecting each of the plurality of converters and the second common line, and
On the DC side of each of the plurality of converters, a plurality of charge storage elements provided between the first wiring and the second wiring, and
Wherein disposed respectively between the plurality of first wirings, a plurality of first resistors provided on the first common line so that make up the series resistor string as a whole,
Power converter equipped with. Disposed between each of the plurality of second wiring as a whole a plurality of second resistors provided on the second common line so that make up the series resistor string further claim 1, further comprising Power converter. The AC power is a three-phase AC power.
Further provided with a first AC terminal, a second AC terminal, and a third AC terminal,
The plurality of converters
A plurality of first converters connected to the first AC terminal,
A plurality of second converters connected to the second AC terminal,
A plurality of third converters connected to the third AC terminal,
Have,
The DC side of the plurality of converters is connected to the first common line and the second common line so as to be repeatedly arranged in the order of the first converter, the second converter, and the third converter. The power converter according to claim 1 or 2. The AC power is single-phase AC power, and is
Further equipped with a first AC terminal and a second AC terminal,
The plurality of converters
A plurality of first converters connected to the first AC terminal,
A plurality of second converters connected to the second AC terminal,
Have,
Claim 1 or 2 in which the DC side of the plurality of converters is connected to the first common line and the second common line so that the first converter and the second converter are arranged alternately. The power converter described in.

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