JP2017054889A - Transformer unit and power conversion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve miniaturization of a transformer and restraint of total iron loss.SOLUTION: The transformer unit includes: a plurality of primary windings which forms a transformer different from each other and has a serial star connection; a plurality of secondary windings which is arranged to be electromagnetically coupled to the corresponding primary winding and can connect respective power conversion apparatuses; a plurality of tertiary windings which is arranged to be electromagnetically coupled to the corresponding primary winding and are delta-connected to form a reflux path astride all the transformers.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a transformer unit and a power converter.

In recent years, power electronics have made great strides, and large-scale converters with various configurations have come to be used in power systems.
As an example of such a large-scale conversion device, a large-scale conversion device provided with a plurality of transformers in which primary windings are connected in a series star connection is known.

In this type of large-scale converter, the zero-phase current cannot be recirculated because the primary side is star-connected.
For this reason, it is known that a delta winding type tertiary winding is provided independently for each transformer for the purpose of reducing distortion of the secondary output voltage waveform.

JP 2000-269044 A JP-A-7-264857 JP 2001-196244 A

By the way, converters such as converters and inverters are connected to the secondary winding, and when each converter is controlled independently, the voltage sharing between the primary windings connected in series is not uniform. Thus, the magnetic flux density in the iron core of the transformer that becomes unbalanced and becomes larger becomes higher, and the magnetic flux density in the iron core of other transformers becomes lower.
It is necessary to design the transformer in accordance with the higher magnetic flux density, and there is a risk of increasing the size of the transformer when a usage that causes a large difference in the magnetic flux density is assumed.

In addition, there is a possibility that the transformer may be increased in size by using the transformer so that a large difference occurs in the current flowing through the transformer.
Furthermore, there is a possibility that the total iron loss may increase due to an imbalance of the magnetic flux density for each transformer.

  This invention is made | formed in view of the above, Comprising: While aiming at size reduction of a transformer, it aims at providing the transformer unit and power converter device which can also suppress a total iron loss.

  Each of the transformer units of the embodiment constitutes a transformer different from each other, and is arranged so as to be electromagnetically coupled with a plurality of primary windings connected in series and a corresponding primary winding. A plurality of connectable secondary windings and a plurality of tertiary windings arranged to be electromagnetically coupled to the corresponding primary winding and delta-connected to form a return path across all transformers; .

FIG. 1 is an explanatory diagram of a connection state of the power conversion device. FIG. 2 is an explanatory diagram of a connection state of a conventional power converter. FIG. 3 is an explanatory diagram of an analysis example of the zero-phase magnetic flux density of the conventional first transformer. FIG. 4 is an explanatory diagram of an analysis example of the zero-phase magnetic flux density of the conventional second transformer. FIG. 5 is an explanatory diagram of an analysis example of the transformer DC winding zero-phase current in the conventional first transformer and second transformer. FIG. 6 is an explanatory diagram of an analysis example of the zero-phase magnetic flux density of the first transformer according to the embodiment. Drawing 7 is an explanatory view of the example of analysis of the zero phase magnetic flux density of the 2nd transformer of an embodiment. FIG. 8 is an explanatory diagram of an analysis example of the transformer DC winding zero-phase current in the first transformer and the second transformer of the embodiment.

Next, embodiments will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram of a connection state of the power conversion device.
The power converter 10 includes a first transformer 15 and a second transformer 16 that are electrically connected to a power source.

  Here, the first transformer 15 and the second transformer 16 are connected in series, and the first transformer 15 and the second transformer 16 are configured as, for example, a transformer having a three-phase five-leg iron core. ing. Here, the three phases are the U phase, the V phase, and the W phase, and the five legs are the U phase iron core, the V phase iron core, the W phase iron core, the left leg (first side leg), and the right leg (second leg). Side leg).

  One end of the U-phase primary winding U1 of the first transformer 15, one end of the V-phase primary winding V1 of the first transformer 15 and one end of the W-phase primary winding W1 of the first transformer are connected to the high potential side connection point. Commonly connected to PH and in a star connection state.

  The other end of the U-phase primary winding U1 of the first transformer 15 is connected in series to one end of the U-phase primary winding U2 of the second transformer 16 via the connection line LU, and the V-phase primary of the first transformer 15 is connected. The other end of the winding V1 is connected in series to one end of the V-phase primary winding V2 of the second transformer 16 via a connection line LV, and the other end of the W-phase primary winding W1 of the first transformer 15 is The two transformers 16 are connected in series to one end of the W-phase primary winding W2 via a connection line LW.

  The other end of the U-phase primary winding U2 of the second transformer 16, the other end of the V-phase primary winding V2 of the second transformer 16, and the other end of the W-phase primary winding W2 of the second transformer 16 are The low-potential side connection point PL is commonly connected and is in a star connection state.

A first power conversion unit 23-1 is connected to the U-phase secondary winding u <b> 1 of the first transformer 15.
A second power conversion unit 23-2 is connected to the V-phase secondary winding v1 of the first transformer 15.
A third power converter 23-3 is connected to the W-phase secondary winding w1 of the first transformer 15.

Similarly, the first power conversion unit 25-1 is connected to the U-phase secondary winding u <b> 2 of the second transformer 16.
A second power conversion unit 25-2 is connected to the V-phase secondary winding v <b> 2 of the second transformer 16. A third power converter 25-3 is connected to the W-phase secondary winding w2 of the second transformer 16.

  The first tertiary winding a1 of the first transformer 15 → the first tertiary winding a2 of the second transformer 16 → the second tertiary winding b1 of the first transformer 15 → the second tertiary of the second transformer 16 In all the transformers, the winding b2 → the third tertiary winding c1 of the first transformer 15 → the third tertiary winding c2 of the second transformer 16 → the first tertiary winding a1 of the first transformer 15 In order to form a return path across the first transformer 15 and the second transformer 16, delta connection is made through connection lines La 1, La 2, Lb 1, Lb 2, Lc 1, Lc 2, and a loop circuit (reflux circuit) is formed. It is composed.

When the first transformer 15 and the second transformer 16 described above are configured as transformers having a three-phase five-leg iron core, the first tertiary winding a1 of the first transformer 15 is included in a part of the U-phase iron core. Is wound on the first tertiary winding a1, and the U-phase secondary winding u1 of the first transformer 15 is wound on the first tertiary winding a1, and the first transformer 15 is wound on the U-phase secondary winding u1. The U-phase primary winding U1 is wound.
Similarly, the first tertiary winding a2 of the second transformer 16 is wound on the other portion where the winding of the first transformer 15 of the U-phase iron core is not wound, and on the first tertiary winding a2. The U-phase secondary winding u2 of the second transformer 16 is wound, and the U-phase primary winding U2 of the second transformer 16 is wound on the U-phase secondary winding u2.

The second tertiary winding b1 of the first transformer 15 is wound around a part of the V-phase iron core, and the V-phase secondary winding of the first transformer 15 is placed on the second tertiary winding b1. v1 is wound, and the V-phase primary winding V1 of the first transformer 15 is wound on the V-phase secondary winding v1.
Similarly, the second tertiary winding b2 of the second transformer 16 is wound on the other portion where the winding of the first transformer 15 of the V-phase iron core is not wound, and is placed on the second tertiary winding b2. The V-phase secondary winding v2 of the second transformer 16 is wound, and the V-phase primary winding V2 of the second transformer 16 is wound on the V-phase secondary winding v2.

Further, the third tertiary winding c1 of the first transformer 15 is wound around a part of the W-phase iron core, and the W-phase secondary winding of the first transformer 15 is placed on the third tertiary winding c1. W1 is wound, and the W-phase primary winding W1 of the first transformer 15 is wound on the W-phase secondary winding w1.
Similarly, the third tertiary winding c2 of the second transformer 16 is wound around the other portion where the winding of the first transformer 15 of the W-phase iron core is not wound, and is placed on the third tertiary winding c2. The W-phase secondary winding w2 of the second transformer 16 is wound, and the W-phase primary winding W2 of the second transformer 16 is wound on the W-phase secondary winding w2.

Here, the connection state and operation | movement of the conventional power converter device are demonstrated for a comparison.
FIG. 3 is a connection state explanatory diagram of a conventional power converter.
In FIG. 3, for the sake of easy understanding, the same parts as those in the embodiment are denoted by the same reference numerals.
The difference from the power conversion device 10 of the embodiment of FIG. 2 is that the tertiary winding is delta-connected for each transformer to form a loop circuit for each transformer.

  In the secondary windings u1, v1, and w1 of the conventional first transformer 15P, the first power converter 23-1, the second power converter 23-2, and the third, which are connected single-phase converters. The magnetic flux in the iron core is distorted because it is affected by the switching operation of the converter and inverter constituting the power converter 23-3.

Moreover, when the 1st power converter 23-1, the 2nd power converter 23-2, and the 3rd power converter 23-3 are each controlled independently, between the primary windings connected in series ( The shared voltage between the U-phase windings, between the V-phase windings, and between the W-phase windings is not uniform, and is unevenly distributed.
For this reason, the magnetic flux density in the iron core of the transformer with the increased shared voltage is high, and the magnetic flux density in the iron core of the other transformer is low.

  In the following, when the first transformer 15P has a relatively higher shared voltage and the second transformer 16P has a lower shared voltage, the first transformer 15P and the second transformer The case where 16P is comprised as a transformer of 3 phase 5 leg iron core structure is demonstrated.

FIG. 4 is an explanatory diagram of an analysis example of the zero-phase magnetic flux density of the conventional first transformer.
FIG. 5 is an explanatory diagram of an analysis example of the zero-phase magnetic flux density of the conventional second transformer.
As shown in FIGS. 4 and 5, the magnetic flux density in the iron core of the first transformer 15P is low (maximum magnetic flux density = ± 0.7 Tesla [T]), and the magnetic flux density in the iron core of the second transformer 16P. Is higher (maximum magnetic flux density = ± 0.9 Tesla).

  By the way, in the design of a transformer, it is necessary to design according to the one where magnetic flux density is higher. Therefore, if a large difference in magnetic flux density appears as shown in FIGS. 4 and 5, it may lead to an increase in size of the transformer.

Further, since the iron loss of the transformer core increases in proportion to about 1.8 power of the magnetic flux density, the total iron loss of all the transformers increases when the magnetic flux density becomes unbalanced.
Thus, if the magnetic flux density in the iron core in a transformer is not balanced, a difference will arise in the electric current which flows into each converter.

FIG. 6 is an explanatory diagram of an analysis example of the transformer DC winding zero-phase current in the conventional first transformer and second transformer.
As shown in FIG. 6, there is a large difference between the zero-phase current flowing through the conventional first transformer 15P and the zero-phase current flowing through the conventional second transformer 16P.

Specifically, in the analysis example of FIG. 6, the zero-phase current flowing through the first transformer 15P is ± 1000A, and the zero-phase current flowing through the second transformer 16P is ± 2700A.
Therefore, the control of the first power conversion unit 23-1 to the third power conversion unit 23-3 and the first power conversion unit 25-1 to the third power conversion unit 25-3 may become unstable.

  Moreover, since it is necessary to design according to the one where the zero-phase current is larger, there is a possibility that the first transformer 15P and the second transformer 16P may be increased in size.

FIG. 6 is an explanatory diagram of an analysis example of the zero-phase magnetic flux density of the first transformer according to the embodiment.
Drawing 7 is an explanatory view of the example of analysis of the zero phase magnetic flux density of the 2nd transformer of an embodiment.
Unlike the conventional first transformer 15P and second transformer 16P, according to the first transformer 15 and the second transformer 16 of the embodiment, as shown in FIG. 6 and FIG. It is the same and it turns out that the difference has not arisen.

  In addition, the maximum value of the magnetic flux density in the first transformer 15 and the second transformer 16 of the embodiment is greater than the maximum magnetic flux density of the conventional first transformer 15P and the second transformer 16P = about ± 0.9 Tesla. Since it is a low value of about ± 0.8 Tesla, the possibility of an increase in size can be reduced.

FIG. 8 is an explanatory diagram of an analysis example of the transformer DC winding zero-phase current in the first transformer and the second transformer of the embodiment.
As shown in FIG. 8, the zero-phase current flowing through the first transformer 15 of the embodiment and the zero-phase current flowing through the second transformer 16 of the embodiment are ± 1900 A, and the first power conversion unit 23- The currents flowing through the first to third power conversion units 23-3 and the first power conversion unit 25-1 to the third power conversion unit 25-3 are the same, and the control is stable. Furthermore, since the zero-phase maximum current is also smaller than that of the conventional first transformer 15P and second transformer 16P, there is no possibility of increasing the size.

As described above, according to this embodiment, two transformers, that is, all the tertiary windings constituting the first transformer 15 and the second transformer 16 are all connected in series, and one set The built-in delta winding (one loop circuit) is formed, so in a plurality of series-connected transformers adopting the conventional built-in delta winding configuration, the magnetic flux density of each transformer is uneven and the power conversion unit It is possible to suppress unevenness of the current supplied to
As a result, according to this embodiment, the enlargement of the transformer can be suppressed, and consequently, the enlargement of the power converter can be suppressed.
Furthermore, according to this embodiment, an iron loss can be suppressed and the efficiency of a power converter device can be improved.

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 scope 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.
For example, in the above description, two transformers are connected in series by star connection, but it is also possible to configure a power conversion device in which three or more transformers are connected in series by star connection. is there.

DESCRIPTION OF SYMBOLS 10 Power converter 11 Overhead line 12 Pantograph 13 Line 14 Wheel 15 1st transformer (transformer unit)
16 Second transformer (transformer unit)
21 Converter 22 Inverter 23-1 to 23-3 First power conversion unit to third power conversion unit 24 Power motor 25-1 to 25-3 First power conversion unit to third power conversion unit PH High potential side connection point PL Low-potential side connection point U1, U2 U-phase primary winding V1, V2 V-phase primary winding W1, W2 W-phase primary winding a1, a2 First tertiary winding b1, b2 Second tertiary winding c1, c2 First 3 tertiary winding u1, u2 U phase secondary winding v1, v2 V phase secondary winding w1, w2 W phase secondary winding

Claims (5)

Each constitutes a different transformer, a plurality of primary windings connected in series star connection,
A plurality of secondary windings arranged so as to be electromagnetically connectable to the corresponding primary windings and capable of being connected to the respective power converters;
A plurality of tertiary windings arranged to be electromagnetically coupled to the corresponding primary winding and delta-connected to form a return path across all the transformers;
Transformer unit with The secondary winding is the tertiary winding wound on an iron core, and the corresponding primary winding is wound on the same tertiary winding,
The primary winding is wound on the corresponding secondary winding,
The transformer unit according to claim 1. The primary winding includes a U-phase primary winding, a V-phase primary winding, and a W-phase primary winding corresponding to the U-phase, V-phase, and W-phase, respectively.
The secondary winding includes a U-phase secondary winding, a V-phase secondary winding, and a W-phase secondary winding corresponding to the U-phase primary winding, the V-phase primary winding, or the W-phase primary winding, respectively. Equipped with a line,
The transformer unit according to claim 1 or 2. A plurality of primary windings each constituting a different transformer and connected in series star connection, a plurality of secondary windings arranged to be electromagnetically coupled to the corresponding primary winding, and the corresponding primary A transformer unit comprising a plurality of tertiary windings arranged electromagnetically coupled to the windings and delta-connected to form a return path across all the transformers;
A plurality of power converters connected to each of the plurality of secondary windings to perform power conversion and supply the connected loads;
The power converter provided with. The plurality of power conversion units are independently controlled,
The power conversion device according to claim 4.

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