WO2019102839A1

WO2019102839A1 - Power conversion device and method of connecting power conversion devices

Info

Publication number: WO2019102839A1
Application number: PCT/JP2018/041106
Authority: WO
Inventors: 公久古川; 叶田　玲彦; 瑞紀中原; 馬淵　雄一
Original assignee: 株式会社日立製作所
Priority date: 2017-11-24
Filing date: 2018-11-06
Publication date: 2019-05-31
Also published as: JP2019097322A; CN111108676A; JP6931595B2; CN111108676B

Abstract

Provided is a power conversion device which is small and can be configured inexpensively. The power conversion device (100) is provided with first to third power conversion cells (20-1 to 20-6) connected between a primary-side system (60) and a secondary-side system (70) which is an N-phase (N is a natural number of 3 or more) alternating-current system, each of the cells having a pair of primary-side terminals (25, 26) and a pair of secondary-side terminals (27, 28). The primary-side terminals of the first to third power conversion cells (20-1 to 20-6) are connected in series and connected to the primary-side system (60). The secondary-side terminals of the first power conversion cells (20-1, 20-2) are connected to portions relating to the secondary-side first phase (secondary-side V phase). The secondary-side terminals of the second power conversion cells (20-3, 20-4) are connected to portions relating to the secondary-side second phase (secondary-side U phase). The secondary-side terminals of the third power conversion cells (20-5, 20-6) are connected to portions relating to the secondary-side third phase (secondary-side W phase).

Description

Power converter and connection method of power converter

The present invention relates to a power converter and a method of connecting the power converter.

As background art of the present technical field, as described in “Patent Document 1 below,“ a plurality of converter cells 20-1, 20-2,..., 20-N in the first aspect of the present invention as shown in In the power converter 1 having N is a natural number of 2 or more, the AC sides of the first AC / DC converters 11 of the plurality of converter cells 20-1, 20-2, ..., 20-N are connected in series, And, the AC sides of the fourth AC / DC converter 14 of each of the plurality of converter cells are connected in series with each other The AC voltage is multileveled (multilevel) as the number of stages of converter cells connected in series increases. (See paragraph 0019 of the specification).

JP 2005-73362 A

The converter cell described in Patent Document 1, for example, converts an alternating voltage on one of the primary side or the secondary side to a direct voltage, and converts the direct voltage to the other alternating voltage. Here, a pulsating current component fluctuating at the primary side frequency or the secondary side frequency is superimposed on the DC voltage. If this pulsating flow component is large, there arises a problem that the voltage fluctuation on the primary side or the secondary side becomes large. Therefore, in order to suppress the pulsating current component, it is necessary to enlarge the parts such as the capacitor included in the converter cell, and as a result, there is a problem that the power converter and the converter cell become large and expensive.
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a power converter and a method of connecting the power converter which can be compact and inexpensive.

In order to solve the above problems, in the power converter of the present invention, it is connected between the primary side system and the secondary side system which is an AC system of N phases (N is a natural number of 3 or more). Includes first to third power conversion cells each having a pair of primary side terminals and a pair of secondary side terminals, and the primary side terminals of the first to third power conversion cells are connected in series. And the secondary side terminal of the first power conversion cell is connected to the portion related to the secondary side first phase, and the secondary side terminal of the second power conversion cell is connected to the primary side system. The side terminal is connected to a part related to the secondary side second phase, and the secondary side terminal of the third power conversion cell is connected to the part related to the secondary side third phase.

According to the present invention, the power converter can be configured compactly and inexpensively.

1 is a connection diagram of a power conversion device according to a first embodiment of the present invention. It is a block diagram of a converter cell. It is a connection diagram of the power converter by a comparative example. It is a wiring diagram of the power converter by a 2nd embodiment of the present invention. It is a wiring diagram of the power converter by a 3rd embodiment of the present invention. It is a wiring diagram of the power converter by a 4th embodiment of the present invention. It is a block diagram of the modification of a converter cell. It is a circuit diagram of a high frequency transformer periphery applied to other modifications. It is a circuit diagram of a high frequency transformer periphery applied to another modification. It is a circuit diagram of a high frequency transformer periphery applied to another modification.

First Embodiment
<Configuration of First Embodiment>
First, the configuration of the power conversion device 100 according to the first embodiment of the present invention will be described.
FIG. 1 is a connection diagram of the power conversion device 100. As illustrated, power converter 100 has eighteen converter cells 20-1 to 20-18. The converter cell 20-1 includes the primary side circuit 21, the secondary side circuit 22, and the high frequency transformer 15. The configuration of converter cells 20-2 to 20-18 is also similar to that of converter cell 20-1. Hereinafter, converter cells 20-1 to 20-18 may be collectively referred to as "converter cell 20".

The power conversion device 100 performs bidirectional or unidirectional power conversion between the primary side system 60, which is a three-phase alternating current system, and the secondary side system 70. Here, the primary side system 60 has a neutral wire 60N, an R phase wire 60R, an S phase wire 60S, and a T phase wire 60T in which R phase, S phase, and T phase voltages appear. In addition, the secondary side system 70 has a neutral wire 70N, a U-phase wire 70U in which U-phase, V-phase, and W-phase voltages appear, a V-phase wire 70V, and a W-phase wire 70W.

Further, voltage amplitude, frequency and phase of the primary side system 60 and the secondary side system 70 are mutually independent. The R-phase, S-phase, and T-phase voltages have a phase difference of 2π / 3 at the primary side frequency, and the U-phase, V-phase, and W-phase voltages mutually change at the secondary side frequency. It has a phase difference of "2π / 3". As the primary side and

secondary side systems

60 and 70, various power generation facilities and power reception facilities such as a commercial power supply system, a solar power generation system, a motor, etc. can be adopted.

FIG. 2 is a block diagram of converter cell 20.
The primary side circuit 21 described above includes AC /

DC converters

11 and 12 and a capacitor 17. Further, the secondary side circuit 22 includes AC /

DC converters

13 and 14 and a capacitor 18. The AC / DC converters 11 to 14 each have four switching elements connected in an H-bridge shape and FWD (Free Wheeling Diode) connected in anti-parallel to these switching elements (both without reference numeral) . In the present embodiment, these switching elements are, for example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). The voltage appearing between both ends of the capacitor 17 is called a primary side DC link voltage Vdc1 (primary side DC voltage). Further, a voltage appearing between the

primary side terminals

25 and 26 is referred to as a primary side AC terminal voltage V1. Then, the AC / DC converter 11 transmits power while converting the voltage V1 between the primary side AC terminals and the primary side DC link voltage Vdc1 in both directions or in one direction.

The high frequency transformer 15 has a primary winding 15a and a secondary winding 15b, and transmits power at a predetermined frequency between the primary winding 15a and the secondary winding 15b. The current that the AC /

DC converters

12 and 13 input to and output from the high frequency transformer 15 is a high frequency. Here, the high frequency is, for example, a frequency of 100 Hz or more, but it is preferable to adopt a frequency of 1 kHz or more, and it is more preferable to adopt a frequency of 10 kHz or more. The AC / DC converter 12 transmits power while converting the primary side DC link voltage Vdc1 and the voltage appearing in the primary winding 15a in two directions or one direction.

Further, a voltage appearing between both ends of the capacitor 18 is called a secondary side DC link voltage Vdc2 (secondary side DC voltage). The AC / DC converter 13 transmits power while converting the secondary side DC link voltage Vdc2 and the voltage appearing in the secondary winding 15b in two directions or one direction. Further, a voltage appearing between the

secondary side terminals

27 and 28 is referred to as a secondary side AC terminal voltage V2. Then, the AC / DC converter 14 transmits power while converting the voltage between the secondary side AC terminals V2 and the secondary side DC link voltage Vdc2 in two directions or one direction.

Returning to FIG. 1, the

primary side terminals

25 and 26 and the

secondary side terminals

27 and 28 of the converter cell 20-1 are illustrated, but illustration is omitted for the other converter cells 20-2 to 20-18. Do.

Primary terminals

25 and 26 of converter cells 20-1 to 20-6 are sequentially connected in series between R-phase wire 60R and neutral wire 60N. Similarly,

primary terminals

25 and 26 of converter cells 20-7 to 20-12 are sequentially connected in series between T-phase wire 60T and neutral wire 60N. Similarly,

primary terminals

25 and 26 of converter cells 20-13 to 20-18 are sequentially connected in series between S-phase wire 60S and neutral wire 60N.

In FIG. 1, among the secondary side circuits 22, those connected between the U-phase line 70U and the neutral line 70N are dotted. That is, between U-phase line 70U and neutral line 70N, converter cells 20-17 and 20-18 (ninth power conversion cell) and 20-3 and 20-4 (second power conversion cell) And 20-7, 20-8 (fourth power conversion cells) are connected in series.

Further, among the secondary side circuits 22, those connected between the V-phase wire 70V and the neutral wire 70N are hatched. That is, converter cells 20-11 and 20-12 (sixth power conversion cells) and 20-15 and 20-16 (eighth power conversion cells are provided between V-phase line 70V and neutral line 70N). And 20-1 and 20-2 (first power conversion cells) are connected in series.

Further, among the secondary side circuits 22, those connected between the W-phase wire 70W and the neutral wire 70N are white circles. That is, converter cells 20-5 and 20-6 (third power conversion cells) and 20-9 and 20-10 (fifth power conversion cells) are disposed between W-phase line 70W and neutral line 70N. And converter cells 20-13 and 20-14 (seventh power conversion cells) are connected in series. As described above, the power conversion apparatus 100 connects the primary system 60 and the secondary system 70 by YY connection.

<Operation of First Embodiment>
Next, the operation of converter cell 20-1 will be described with reference to FIG. 2 again.
When converter cell 20 shown in FIG. 2 is converter cell 20-1 in FIG. 1, voltage V1 on the primary side AC terminal is a voltage obtained by dividing the R phase voltage on the primary side, and secondary side AC The inter-terminal voltage V2 is a voltage obtained by dividing the V-phase voltage on the secondary side. Assuming that the power flow is flowing from the primary side to the secondary side, the voltage V1 across the primary side AC terminals is rectified by the AC / DC converter 11 and smoothed by the capacitor 17. That is, the smoothed primary side DC link voltage Vdc1 appears at both ends of the capacitor 17.

However, the primary side DC link voltage Vdc1 is not a complete direct current, but has a pulsating current component of the primary side frequency, that is, a pulsating current component synchronized with the R-phase voltage. The AC / DC converter 12 modulates the primary side DC link voltage Vdc1 at a high frequency, and the modulated wave is rectified by the AC / DC converter 13 via the high frequency transformer 15. The capacitor 18 is charged by the rectified power, and the secondary side DC link voltage Vdc2 appears at its both ends. The secondary side DC link voltage Vdc2 also has a pulsating current component of the primary side frequency, that is, a pulsating current component synchronized with the R-phase voltage. The AC / DC converter 14 switches the secondary side DC link voltage Vdc2 including the pulsating current component, and outputs a secondary side AC terminal voltage V2 alternating at the secondary side frequency.

As a result, the voltage V2 between the secondary side AC terminals includes a fluctuation component that pulsates at the primary side frequency. The smaller the capacitances of the

capacitors

17 and 18, the larger the fluctuation component. If the capacitances of the

capacitors

17 and 18 are increased, this fluctuation component can be suppressed, but this causes a problem that the converter cell 20 becomes large and expensive.

Returning to FIG. 1, each converter cell relating to the V phase, that is, each of the converter cells 20-1, 20-2, 20-11, 20-12, 20-15, 20-16 hatched in the secondary side circuit 22. The secondary voltages appearing at the

secondary terminals

27 and 28 both include fluctuating components that pulsate at the primary frequency. Here, fluctuation components appearing in the secondary side voltages of the converter cells 20-1 and 20-2 are synchronized with the primary side R phase voltage. Further, fluctuation components appearing in the secondary side voltages of the converter cells 20-11 and 20-12 are synchronized with the primary side T-phase voltage. Further, fluctuation components appearing in the secondary side voltages of the converter cells 20-15 and 20-16 are synchronized with the primary side S phase voltage.

The individual fluctuation components synchronized with the R-phase voltage, the S-phase voltage, and the T-phase voltage are waveforms having substantially the same shape, and have a phase difference of “2π / 3”. When six converter cells relating to these V phases are connected in series, individual fluctuation components synchronized with the R phase voltage, the S phase voltage, and the T phase voltage in the V phase voltage are canceled out, and the level thereof is suppressed. Thereby, the voltage fluctuation rate of the V-phase voltage can be lowered compared to the voltage fluctuation rate of the secondary side voltage in each converter cell. Although the V-phase voltage has been described above, the voltage variation rate can be made lower for the U-phase voltage and the W-phase voltage as well as for individual converter cells. Further, the voltage fluctuation rate can be lowered similarly for the R-phase voltage, the S-phase voltage and the T-phase voltage on the primary side.

As described above, according to the present embodiment, even when the capacitances of the

capacitors

17 and 18 are small, it is possible to suppress the voltage fluctuation rate of the primary side voltage and the secondary side voltage. A small one can be applied, and a small and inexpensive power converter 100 can be realized.

Here, the primary side potential and the secondary side potential of each converter cell 20 will be examined. First, the potential of the neutral wire 60N is referred to as a primary reference potential, and the potential of the neutral wire 70N is referred to as a secondary reference potential. The primary side and secondary side reference potentials are, for example, the ground potential, but may not necessarily be the ground potential. Hereinafter, although the primary side and secondary side electric potential of each converter cell 20 is examined, these are potentials on the basis of the primary side and secondary side reference electric potential of each.

In FIG. 1, the potential (absolute value) of the primary side circuit 21 with respect to the primary side reference potential (potential of the neutral wire 60N) of each converter cell 20 is referred to as "primary side potential". The potential (absolute value) of the secondary circuit 22 with respect to the secondary reference potential (potential of the neutral wire 70N) is referred to as “secondary potential”. The primary side potential increases with distance from the neutral wire 60N (as approaching the R phase wire 60R, the S phase wire 60S, and the T phase wire 60T). Similarly, the potential on the secondary side increases with distance from the neutral wire 70N (as approaching the U-phase wire 70U, the V-phase wire 70V, and the W-phase wire 70W).

For example, considering converter cells related to the V phase in which the secondary side circuit 22 is hatched, these primary side potentials are 20-12, 20-11, 20-16, 20-15, 20-2 , 20-1 in order. Also, these secondary side potentials increase in the order of 20-1, 20-2, 20-16, 20-15, 20-11, and 20-12. Thus, the secondary side voltage tends to be lower as the converter cell 20 has a higher primary side potential. The same applies to the converter cells 20 related to the U-phase and the W-phase.

The voltage between the primary winding 15a and the secondary winding 15b of the high frequency transformer 15 (see FIG. 2) is referred to as a "transformer potential difference". According to this embodiment, the transformer potential difference of each converter cell 20 can be equalized, and the maximum value of the transformer potential difference can be made relatively low. As a result, the withstand voltage of the high frequency transformer 15 can be reduced, a small and inexpensive high frequency transformer can be applied, and the power conversion device 100 can be configured to be smaller and less expensive.

Comparative Example
Next, in order to clarify the effect of the present embodiment, the configuration of the comparative example will be described.
FIG. 3 is a connection diagram of the power conversion device in the comparative example. The power conversion device 101 of the present comparative example has P converter cells 20-1 to 20-P. The configuration of each converter cell 20 is the same as that of the first embodiment (see FIG. 2). In this comparative example, primary side terminals 25 and 26 (see FIG. 2) of converter cells 20-1 to 20-P are sequentially connected in series between primary side R-phase wire 60R and neutral wire 60N. It is done. The secondary terminals 27, 28 (see FIG. 2) are sequentially connected in series between the U-phase wire 70U and the neutral wire 70N on the secondary side. Although illustration is omitted about primary side S phase, T phase and secondary side V phase, and W phase, power conversion device 101 is connected like primary side R phase.

In this comparative example, all the converter cells 20-1 to 20-P related to the R phase on the primary side are converter cells related to the U phase on the secondary side. As in the first embodiment, in the primary side DC link voltage Vdc1 appearing at both ends of the capacitor 17 in the converter cell 20, a pulsating current component synchronized with the R phase voltage is generated. Therefore, the voltage fluctuation rate of the secondary side voltage in each converter cell and the voltage fluctuation rate of the U-phase voltage become equal values. The same applies to the V-phase voltage and the W-phase voltage. Therefore, in the present comparative example, in order to suppress the voltage fluctuation rate of the secondary side voltage, the capacity of the capacitors 17 and 18 (see FIG. 2) has to be increased, and compared to the first embodiment, the power conversion The apparatus 101 becomes large and expensive.

Further, in the present comparative example, when the primary voltage E1 has a positive peak value and the secondary voltage E2 has a negative peak value, or the primary voltage E1 has a negative peak value, When the secondary voltage E2 has a positive peak value, the transformer potential difference of the converter cell 20-1 is maximized. That is, the transformer potential difference of the converter cell 20-1 is substantially equal to the sum of the amplitude values of the primary side voltage E1 and the secondary side voltage E2, and is higher than that of the first embodiment. Conversely, the transformer potential difference of converter cell 20-P is approximately equal to "1 / P" of the sum of the amplitude values of primary side voltage E1 and secondary side voltage E2, and is lower than that in the first embodiment. be able to.

However, in order to apply the same specification as converter cells 20-1 to 20-P, the specification must be determined in accordance with the highest transformer potential difference. As a result, the converter cell 20 of the present comparative example is compelled to apply a high frequency transformer 15 having a high withstand voltage as compared with that of the first embodiment, whereby the high frequency transformer 15 and the power conversion device 101 are further enhanced. It becomes large and expensive.

<Effect of First Embodiment>
As described above, according to the present embodiment, it is connected between the primary side system (60) and the secondary side system (70) which is an AC system of N phase (N is a natural number of 3 or more), The first to third power conversion cells (20-1 to 20-6) each having a pair of primary terminals (25, 26) and a pair of secondary terminals (27, 28), The primary side terminals of the first to third power conversion cells (20-1 to 20-6) are connected in series and connected to the primary side system (60), and the first power conversion cell (20-) is connected. The secondary side terminal of 1, 20-2) is connected to the place related to the secondary side first phase (secondary side V phase), and the secondary side of the second power conversion cell (20-3, 20-4) The side terminal is connected to the part related to the secondary side second phase (secondary side U phase), and the secondary side terminal of the third power conversion cell (20-5, 20-6) is the secondary side third phase (Secondary W phase) It is connected to a portion of. As a result, it is possible to suppress the fluctuation component of the secondary voltage based on the primary voltage or the fluctuation component of the primary voltage based on the secondary voltage with small parts, and the power converter (100) can be miniaturized. And it can be configured inexpensively.

Also, the first to third power conversion cells (20-1 to 20-6) respectively have a primary winding (15a) and a secondary winding isolated from the primary winding (15a) And a transformer (15) having the following. Thereby, the primary side and the secondary side can be properly insulated.

Further, according to the present embodiment, the primary side system (60) is an AC system of M phase (M is a natural number of 3 or more), and the power conversion device (100) has a pair of primary side terminals. It further comprises fourth to ninth power conversion cells (20-7 to 20-18) having (25, 26) and a pair of secondary terminals (27, 28), and the first to third powers The primary side terminals of the conversion cells (20-1 to 20-6) are connected in series and connected to a portion related to the primary side first phase (primary side R phase), and the fourth to sixth electric powers The primary side terminals of the conversion cells (20-7 to 20-12) are connected in series and connected to a portion related to the primary side second phase (primary side T phase), and the seventh to ninth electric powers The primary side terminals of the conversion cells (20-13 to 20-18) are connected in series and connected to a portion related to the primary side third phase (primary side S phase), Power conversion cell (20-1, 20-2), sixth power conversion cell (20-11, 20-12), and secondary side terminal of eighth power conversion cell (20-15, 20-16) Are connected in series and connected to a point related to the secondary side first phase (secondary side V phase), the second power conversion cell (20-3, 20-4), the fourth power conversion cell The secondary side terminals of 20-7, 20-8) and the ninth power conversion cell (20-17, 20-18) are connected in series, and the secondary side second phase (secondary side U phase) Connected to the third power conversion cell (20-5, 20-6), the fifth power conversion cell (20-9, 20-10), and the seventh power conversion cell (20-13). , 20-14) are connected in series and connected to a point related to the secondary side third phase (secondary W phase)
Thereby, even when converting multi-phase alternating current, it is possible to suppress the fluctuation component of the secondary voltage based on the primary voltage or the fluctuation component of the primary voltage based on the secondary voltage with a small component. The power converter (100) can be small and inexpensive.

The transformer (15) transmits power at a frequency of 100 Hz or more between the primary winding (15a) and the secondary winding (15b), and the first to third power conversion cells (20 -1 to 20-6) includes a primary side circuit (21) for transmitting power between the primary side terminals (25, 26) and the primary winding (15a), and a secondary side terminal And 28, a secondary side circuit (22) transmitting power between the secondary winding (15b). Thus, power can be properly converted in the primary side circuit (21) and the secondary side circuit (22).

In addition, the primary side circuit (21) is a first AC / DC converter (11) that transmits power between the pair of primary side terminals (25, 26) and the primary side DC voltage (Vdc1); A second AC / DC converter (12) for transmitting power between the primary side DC voltage (Vdc1) and the primary winding (15a), and the secondary side circuit (22) Third AC-DC converter (13) for transmitting power between the DC voltage (Vdc2) on the side and the secondary winding (15b), a pair of secondary terminals (27, 28) and a DC voltage on the secondary side And (d) a fourth AC / DC converter (14) for transmitting power between the power supply and the (Vdc2). Thereby, power can be stably converted via the DC voltage.

Further, in the present embodiment, among the first to third power conversion cells (20-1 to 20-6), the power conversion in which the absolute value of the ground potential at the primary side terminals (25, 26) is the highest. The fourth to sixth power conversion cells (20-1) are different from the power conversion cell (20-6) in which the absolute value of the ground potential at the secondary terminal (27, 28) is the highest. In 20-7 to 20-12), the power conversion cell (20-7) in which the absolute value of the ground potential at the primary terminal (25, 26) is the highest, and the secondary terminal (27, 28) The power conversion cell (20-12) in which the absolute value of the ground potential is the highest is different, and the primary side terminal (25,) of the seventh to ninth power conversion cells (20-13 to 20-18) is different. Power conversion cell (20-13) in which the absolute value of ground potential in 26) is the highest , Each secondary side terminal to the secondary side system (70) so that the power conversion cell (20-18) where the absolute value of the ground potential at the secondary side terminal (27, 28) becomes the highest is different. Connected
Thereby, the variation in the transformer potential difference of the power conversion cell can be reduced, and the transformer (15) having a low withstand voltage can be applied. As a result, the power converter (100) can be made smaller and less expensive.

Second Embodiment
Next, a configuration of a power conversion device 120 according to a second embodiment of the present invention will be described. In the following description, parts corresponding to those in FIGS. 1 to 3 may be denoted by the same reference numerals, and the description thereof may be omitted.
FIG. 4 is a connection diagram of the power conversion device 120. The power conversion device 120 has eighteen converter cells 20-1 to 20-18 as in the first embodiment (see FIG. 1). The configuration of each converter cell 20 is the same as that of the first embodiment (see FIG. 2). The power conversion device 120 performs bidirectional or unidirectional power conversion between the primary side system 62, which is a three-phase AC system, and the secondary side system 70.

Here, the primary side system 62 has an R phase line 62R, an S phase line 62S, and a T phase line 62T in which R phase, S phase, and T phase voltages appear. The configuration of the secondary system 70 is the same as that of the first embodiment. The primary side terminals 25 and 26 (see FIG. 2) of the converter cells 20-1 to 20-6 are sequentially connected in series between the R phase line 62R and the T phase line 62T. Similarly, the

primary side terminals

25 and 26 of the converter cells 20-7 to 20-12 are sequentially connected in series between the T phase line 62T and the S phase line 62S. Similarly,

primary side terminals

25 and 26 of converter cells 20-13 to 20-18 are sequentially connected in series between S phase line 62S and R phase line 62R.

Further, the connection relationship between the

secondary side terminals

27 and 28 of each converter cell 20 and the secondary side system 70 is the same as that of the first embodiment. Thus, the power conversion device 120 connects the primary side system 62 and the secondary side system 70 by Δ-Y connection. According to the present embodiment, the same effects as those of the first embodiment can be obtained, and the application range can be expanded in that the present embodiment can be applied to a three-phase three-wire primary side system 62 without a neutral wire.
In the example described above, the primary side is Y-connected and the secondary side is Δ-connected, but the primary side may be Δ-connected and the secondary side may be Y-connected.

Third Embodiment
Next, a configuration of a power conversion device 130 according to a third embodiment of the present invention will be described. In the following description, parts corresponding to those in FIGS. 1 to 4 may be denoted by the same reference numerals, and the description thereof may be omitted.
FIG. 5 is a connection diagram of the power conversion device 130. The power converter 130 has eighteen converter cells 20-1 to 20-18, as in the second embodiment (see FIG. 4). The configuration of each converter cell 20 is the same as that of the first embodiment (see FIG. 2). The power conversion device 130 performs bidirectional or unidirectional power conversion between the primary side system 62, which is a three-phase alternating current system, and the secondary side system 72.

Here, the configuration of the primary side system 62 is the same as that of the second embodiment (see FIG. 4). Further, the connection relationship between the

primary side terminals

25 and 26 of the converter cells 20-1 to 20-18 and the primary side system 62 is also similar to that of the second embodiment. On the other hand, the secondary side system 72 has a U-phase line 72U, a V-phase line 72V and a W-phase line 72W in which U-phase, V-phase and W-phase voltages appear.

Here, each

secondary side terminal

27 and 28 of converter cells 20-1, 20-2, 20-16, 20-15, 20-11, and 20-12 whose hatched secondary side circuit 22 is U It is sequentially connected in series between the phase line 72U and the V-phase line 72V. Further, each

secondary side terminal

27, 28 of converter cells 20-13, 20-14, 20-10, 20-9, 20-5, 20-6 in which secondary side circuit 22 is white is a V phase The line 72V and the W-phase line 72W are sequentially connected in series. Further, each of the

secondary terminals

27 and 28 of the converter cells 20-7, 20-8, 20-4, 20-3, 20-17, and 20-18 in which the secondary circuit 22 is dot-dotted, The W-phase wire 72W and the U-phase wire 72U are sequentially connected in series.

As described above, the power conversion device 130 connects the primary side system 62 and the secondary side system 72 by Δ-Δ connection. According to the present embodiment, the same effects as those of the first embodiment can be obtained, and even if the primary side system 62 and the secondary side system 72 are both three-phase three-wire systems without neutral wires. The scope of application can be further expanded in terms of

Fourth Embodiment
Next, a configuration of a power conversion device 140 according to a fourth embodiment of the present invention will be described. In the following description, parts corresponding to those in FIGS. 1 to 5 may be denoted by the same reference numerals, and the description thereof may be omitted.
FIG. 6 is a connection diagram of the power conversion device 140. Power converter 140 has three converter cells 20-101 to 20-103 (first to third power conversion cells). The configuration of each converter cell 20 is the same as that of the first embodiment (see FIG. 2). The power conversion device 140 performs bidirectional or unidirectional power conversion between the primary side system 64 which is a single phase alternating current system and the secondary side system 74 which is a three phase alternating current system.

Here, the primary side system 64 has a pair of

lines

64P and 64N. Further, the secondary side system 74 has a neutral wire 74N, a U-phase wire 74U in which U-phase, V-phase, and W-phase voltages appear, a V-phase wire 74V, and a W-phase wire 74W.

Primary terminals

25 and 26 of converter cells 20-101 to 20-103 are sequentially connected in series between

lines

64P and 64N.

Further,

secondary terminals

27, 28 of converter cell 20-101 are connected to V-phase wire 74V and neutral wire 74N, respectively. Similarly,

secondary terminals

27, 28 of converter cell 20-102 are connected to U-phase wire 74U and neutral wire 74N, respectively. Similarly,

secondary terminals

27, 28 of converter cells 20-103 are connected to W-phase wire 74W and neutral wire 74N, respectively.

In FIG. 6, assuming that power flow is flowing from the secondary side to the primary side, the terminal voltage of capacitors 17 and 18 (see FIG. 2) included in converter cell 20-101 is V phase voltage. It has a pulsating flow component synchronized. Thereby, the fluctuation component appearing in the primary side voltage of converter cell 20-101 is synchronized with the secondary side V phase voltage. Similarly, the fluctuation component appearing in the primary side voltage of converter cell 20-102 is synchronized with the secondary side U-phase voltage. Similarly, fluctuation components appearing in the primary side voltage of converter cells 20-103 are synchronized with the secondary side W-phase voltage.

The individual fluctuation components synchronized with these V-phase voltage, U-phase voltage and W-phase voltage are waveforms of substantially the same shape, and have a phase difference of "2π / 3". When the

primary side terminals

25 and 26 of these converter cells 20-101 to 20-103 are connected in series, individual fluctuation components synchronized with the V phase voltage, U phase voltage and W phase voltage in the primary side voltage cancel each other out. And their level is suppressed.

Thus, this embodiment is connected between the primary side system (64) and the secondary side system (74) of the N phase (N is a natural number of 3 or more), each of which is a pair of primary side First to third power conversion cells (20-101 to 20-103) each having a terminal (25, 26) and a pair of secondary terminals (27, 28); The primary side terminals of the conversion cells (20-101 to 20-103) are connected in series and connected to the primary side system (64), and the secondary side terminals of the first power conversion cell (20-101) Is connected to a point related to the secondary side first phase (secondary side V phase), and the secondary side terminal of the second power conversion cell (20-102) is a secondary side second phase (secondary side U phase) Connected to the point related to the second power conversion cell (20-103) connected to the point related to the second side third phase (secondary W phase) That the point is the same as the first to third embodiments.

Therefore, in the present embodiment, as in the first to third embodiments, the voltage fluctuation rate can be suppressed even when the capacitances of the capacitors 17 and 18 (see FIG. 2) are small. A small-capacity one can be applied as 18 and a small and inexpensive power converter 140 can be realized.

[Modification]
The present invention is not limited to the embodiments described above, and various modifications are possible. The embodiments described above are illustrated to facilitate understanding of the present invention, and are not necessarily limited to those having all the described configurations. Also, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. In addition, it is possible to delete part of the configuration of each embodiment or to add / replace other configuration. Further, control lines and information lines shown in the drawing indicate those which are considered to be necessary for explanation, and not all the control lines and information lines necessary on the product are shown. In practice, almost all configurations may be considered to be mutually connected. Possible modifications to the above embodiment are, for example, as follows.

(1) In each of the above embodiments, an example in which a MOSFET is applied as a switching element has been described. However, as a switching element, an IGBT (Insulated Gate Bipolar Transistor), a bipolar transistor, a thyristor, a GTO (Gate Turn-Off Thyristor), an IEGT A vacuum tube type element such as (Injection Enhanced Gate Transistor) or a thyratron may be applied. Moreover, when applying a semiconductor, the material can apply arbitrary things, such as Si, SiC, and GaN.

(2) FIG. 7 is a block diagram of a modification of converter cell 20. Referring to FIG. The AC-DC converters 11 to 14 shown in FIG. 2 use the H-bridge using switching elements so as to convert power in two directions. However, if it is sufficient to convert power in one direction, the AC-DC converters 11 to In part of 14, an H bridge using a rectifying element may be applied. As an example, the configuration shown in FIG. 7 is obtained by replacing the AC / DC converter 13 in FIG. 2 with an AC / DC converter 13a to which four rectifying elements (without reference numerals) are applied. Also in this modification, since the transformer potential difference of the high frequency transformer 15 is the same as that in each of the above embodiments, the power conversion device can be configured in a small size and at low cost. The four rectifying elements in the AC / DC converter 13a may be semiconductor diodes or vacuum tube mercury rectifiers. Moreover, when applying a semiconductor, the material can apply arbitrary things, such as Si, SiC, and GaN.

(3) In the first embodiment described above, the converter cells 20-1 to 20-18 are connected such that the secondary side voltage tends to be lower as the converter cell 20 with the higher primary side potential. More specifically, converter cell 20 in which the absolute value of ground potential at

primary side terminals

25 and 26 is the highest, and converter cell 20 cells in which the absolute value of ground potential at

secondary side terminals

27 and 28 is the highest; Converter cells 20-1 to 20-18 are connected in such a manner as to be different.
However, when the high frequency transformer 15 can cope with a high transformer potential difference, it is not necessary to necessarily adopt such a connection method. That is, converter cell 20 in which the absolute value of ground potential at

primary side terminals

25 and 26 is the highest, and converter cell 20 at which the absolute value of ground potential at

secondary terminals

27 and 28 is the highest are the same. It may be.

Further, in FIG. 1, the converter cells 20-1 to 20-61 are listed in descending order of the potential on the secondary side: converter cells 20-1 and 20-2 (V phase), converter cells 20-3 and 20-4 (U phase) , Converter cells 20-5, 20-6 (W phase), and so on. However, if the high frequency transformer 15 can handle this order, (U, V, W), (U, W, V), (V, U, W), (V, W, U), (W , U, V) and (W, V, U) may be in any of the six orders.

(4) Further, in each of the above embodiments, a capacitor may be inserted between the AC /

DC converters

12 and 13 shown in FIG. 2 and the high frequency transformer 15. FIG. 8A shows an example in which the capacitor 51 is inserted between the AC / DC converter 12 and the primary winding 15a, and the capacitor 52 is inserted between the AC / DC converter 13 and the secondary winding 15b. . 8B shows an example in which the capacitor 51 is inserted between the AC / DC converter 12 and the primary winding 15a, and FIG. 8C shows the AC / DC converter 13 and the secondary winding 15b. The capacitor 52 is inserted between them. In addition, the high frequency transformer 15 applied to each of the above embodiments may be designed to intentionally generate a leakage inductance.

(5) In the fourth embodiment, the primary side system 64 is a single-phase alternating current system, and the secondary side system 74 is a three-phase alternating current system, but the primary side is a three-phase alternating current system; The next side may be a single phase AC system. In addition, the side of the three-phase alternating current system may be Δ-connected.

Furthermore, the primary side system 64 may be a DC system. In this case, the AC / DC converter 11 (see FIG. 2) in the converter cell 20 may be eliminated and both ends of the capacitor 17 may be connected to the

primary side terminals

25 and 26. In other words, in this modification, the primary side circuit (21) transmits power between the pair of primary side terminals (25, 26) and the primary winding (15a). A third AC / DC converter (13) having a power supply (12), the secondary side circuit (22) transmitting power between the secondary side DC voltage (Vdc2) and the secondary winding (15b) And a fourth AC / DC converter (14) for transmitting power between the pair of secondary terminals (27, 28) and the secondary DC voltage (Vdc2).

(6) Moreover, in each said embodiment, the structure of the converter cell 20 can apply various structures other than what was shown to FIG. 2 and FIG. That is, a fluctuation component corresponding to the primary side AC terminal voltage V1 appears in the secondary side AC terminal voltage V2, or a fluctuation component corresponding to the secondary side AC terminal voltage V2 is the primary side AC terminal voltage If it is a converter cell which appears in V1, the same effect as each above-mentioned embodiment can be produced regardless of the composition.

(7) In the first to third embodiments described above, the number of phases M in the primary side system and the number N of phases in the secondary side system are both “3”. May be “4” or more, and the number of phases M may be a value different from the number of phases N. In each of the above embodiments, the number of converter cells 20 is “18”, but the number of converter cells 20 is arbitrary. However, in order to make the specifications of each converter cell 20 identical, the number of converter cells 20 is preferably a natural number multiple of “N × M”.

11 AC / DC converter (1st AC / DC converter)
12 AC / DC converter (2nd AC / DC converter)
13 AC / DC converter (3rd AC / DC converter)
14 AC / DC converter (the fourth AC / DC converter)
15 High frequency transformer (transformer)
15a Primary winding 15b Secondary winding 20 Converter cell (power conversion cell)
20-1, 20-2 converter cell (first power conversion cell)
20-3, 20-4 converter cell (second power conversion cell)
20-5, 20-6 converter cell (third power conversion cell)
20-7, 20-8 converter cell (fourth power conversion cell)
20-9, 20-10 converter cell (fifth power conversion cell)
20-11, 20-12 converter cell (sixth power conversion cell)
20-13, 20-14 converter cell (seventh power conversion cell)
20-15, 20-16 converter cell (eighth power conversion cell)
20-17, 20-18 converter cell (9th power conversion cell)
20-101 converter cell (first power conversion cell)
20-102 converter cell (second power conversion cell)
20-103 Converter Cell (Third Power Conversion Cell)
21 primary side circuit 22

secondary side circuit

25, 26

primary side terminal

27, 28

secondary side terminal

60, 62, 64

primary side system

70, 72, 74

secondary side system

100, 120, 130, 140 electric power Converter Vdc1 (Primary side DC voltage)
Vdc2 (Secondary DC voltage)

Claims

It is connected between the primary side system and the secondary side system which is an AC system of N phase (N is a natural number of 3 or more), each of which comprises a pair of primary side terminals and a pair of secondary side terminals Comprising first to third power conversion cells,
The primary side terminals of the first to third power conversion cells are connected in series and connected to the primary side system,
The secondary side terminal of the first power conversion cell is connected to a point related to the secondary side first phase,
The secondary side terminal of the second power conversion cell is connected to a location related to the secondary side second phase,
The power conversion device, wherein the secondary side terminal of the third power conversion cell is connected to a portion related to a secondary side third phase.
Each of the first to third power conversion cells is
The power converter according to claim 1, further comprising a transformer having a primary winding and a secondary winding isolated with respect to the primary winding.
The primary side system is an AC system of M phase (M is a natural number of 3 or more),
The power conversion cell further includes fourth to ninth power conversion cells each having a pair of the primary side terminals and a pair of the secondary side terminals.
The primary side terminals of the first to third power conversion cells are connected in series, and are connected to a point related to the primary side first phase,
The primary side terminals of the fourth to sixth power conversion cells are connected in series and connected to a point related to the primary side second phase,
The primary side terminals of the seventh to ninth power conversion cells are connected in series and connected to a point related to the primary side third phase,
The secondary side terminals of the first power conversion cell, the sixth power conversion cell, and the eighth power conversion cell are connected in series, and are connected to a point related to the secondary side first phase ,
The second power conversion cell, the fourth power conversion cell, and the secondary side terminal of the ninth power conversion cell are connected in series, and are connected to a location related to the secondary side second phase ,
The second power conversion cell, the fifth power conversion cell, and the secondary side terminal of the seventh power conversion cell are connected in series and connected to a portion related to the second phase of the secondary side. The power converter according to claim 1, characterized in that:
The transformer transmits power at a frequency of 100 Hz or more between the primary winding and the secondary winding,
Each of the first to third power conversion cells is
A primary side circuit for transferring power between the primary side terminal and the primary winding;
The power converter according to claim 2, further comprising: a secondary side circuit that transmits power between the secondary side terminal and the secondary winding.
The primary side circuit includes: a first AC / DC converter for transmitting power between a pair of the primary side terminals and a primary side DC voltage; a primary side DC voltage; and the primary winding And a second AC / DC converter for transferring power between the
The secondary circuit includes a third AC / DC converter for transmitting power between a secondary DC voltage and the secondary winding, and a pair of the secondary terminals and the secondary DC voltage. The 4th AC / DC converter which transmits electric power between, The power converter device of Claim 4 characterized by the above-mentioned.
The primary side circuit has a second AC / DC converter for transmitting power between a pair of the primary side terminals and the primary winding,
The secondary circuit includes a third AC / DC converter for transmitting power between a secondary DC voltage and the secondary winding, and a pair of the secondary terminals and the secondary DC voltage. The 4th AC / DC converter which transmits electric power between, The power converter device of Claim 4 characterized by the above-mentioned.
Among the first to third power conversion cells, the power conversion cell in which the absolute value of the ground potential at the primary side terminal is the highest, and the power conversion in which the absolute value of the ground potential at the secondary side terminal is the highest The power conversion device according to claim 3, wherein the cell is a different power conversion cell.
A power conversion device comprising first to ninth power conversion cells each having a pair of primary side terminals and a pair of secondary side terminals, an M phase (M is a natural number of 3 or more) primary side system And a method of connecting a power conversion apparatus connected between an N-phase (N is a natural number of 3 or more) secondary side system,
The primary side terminals of the first to third power conversion cells are connected in series, and connected to a point related to the primary side first phase,
The primary side terminals of the fourth to sixth power conversion cells are connected in series, and connected to a point related to the primary side second phase,
The primary side terminals of the seventh to ninth power conversion cells are connected in series, and connected to a location related to the primary side third phase,
The secondary terminals of the first power conversion cell, the sixth power conversion cell, and the eighth power conversion cell are connected in series, and connected to a location related to the secondary first phase,
The second power conversion cell, the fourth power conversion cell, and the secondary side terminal of the ninth power conversion cell are connected in series, and connected to a location related to the secondary side second phase,
The second power conversion cell, the fifth power conversion cell, and the secondary side terminal of the seventh power conversion cell are connected in series, and connected to a portion related to the second phase of the secondary side, and ,
Among the first to third power conversion cells, the power conversion cell in which the absolute value of the ground potential at the primary side terminal is the highest, and the power conversion in which the absolute value of the ground potential at the secondary side terminal is the highest Among the fourth to sixth power conversion cells, the power conversion cell having the highest absolute value of the ground potential at the primary side terminal, and the absolute value of the ground potential at the secondary side terminal, are different from the cells. Power conversion cell having the highest value of the power conversion cell, and among the seventh to ninth power conversion cells, the power conversion cell having the highest absolute value of ground potential at the primary side terminal, and the secondary side terminal The method of connecting a power conversion device, wherein each of the secondary side terminals is connected to the secondary side system so that the power conversion cell in which the absolute value of the ground potential is the highest is different.