JP2018190763A - Transformer and power conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transformer capable of suppressing an increase in an electrostatic capacitance between a primary winding and a secondary winding while suppressing an increase in wiring loss caused by a proximity effect and capable of achieving size and weight reductions.SOLUTION: A transformer 10 includes: an iron core 20; a primary winding 21 surrounding the iron core 20 and formed from a sheet-like conductor wound around the iron core; and a secondary winding 22 surrounding the iron core 20 and formed from a sheet-like conductor wound around the iron core. At least either one of the primary winding 21 and the secondary winding 22 has at least one through hole 23.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a transformer and a power conversion system using the same, and more particularly to a technique effective for reducing the size and weight of a transformer.

  In order to contribute to the reduction of carbon dioxide emissions, grid connection of large-scale wind power generation system (wind farm) is expected. Such large-scale wind power generation systems are often installed on the ocean, and there are many cases where the transmission distance exceeds 100 km. When the power transmission distance is long, DC power transmission is more preferable than AC power transmission from the viewpoint of power transmission efficiency.

  In general, wind farm power is collected by alternating current, boosted by a transformer mounted on the offshore platform, converted from alternating current to direct current by a power conversion system, and transmitted to land. However, since the step-up transformer is large and heavy, and the offshore platform on which it is mounted is inevitably large, the construction and transportation of the offshore platform involves enormous costs.

  In view of this, a system for collecting the generated power of the wind farm with direct current, boosting the direct-current power with a power conversion system, and transmitting it to the land has been studied. The power conversion system for such a use is also called a DC / DC converter, and includes an inverter circuit that converts direct current into high frequency alternating current, a high frequency transformer, and a rectifier circuit that converts high frequency alternating current into direct current. Although it is known that the transformer can be miniaturized by increasing the drive frequency, there is a problem that the winding loss increases due to the influence of the proximity effect.

  As a background art in this technical field, for example, there is a technique such as Patent Document 1. In Patent Document 1, “a spiral coil pattern formed on an insulating substrate is provided with slits and a plurality of holes to prevent generation of a large eddy current in the coil pattern. A “coil device with a core that relaxes the concentration of the distribution” is disclosed.

  Further, Non-Patent Document 1 discloses a “method of reducing winding loss by suppressing proximity effect by alternately superimposing primary and secondary windings of a high-frequency transformer on a layer-by-layer basis and winding them simultaneously”. Is disclosed.

JP-A-8-203736

H. Tanaka, K. Nakamura, and O. Ichinokura, “Winding Arrangement of High-frequency Amorphous Transformers for MW-class DC-DC Converters”, Journal of the Magnetics Society of Japan, Vol. 40, (2016), No. 2, p.35-38

  The structure in which the primary winding and the secondary winding are alternately overlapped for each layer and wound simultaneously like the transformer described in Non-Patent Document 1 is advantageous for reducing the size and weight of the transformer. As is clear from FIG. 10B and the like in the literature, since the facing area between the primary winding and the secondary winding is large, the capacitance between the primary winding and the secondary winding increases. As a result, the transient insulation between the input side and the output side of the transformer is lost, and there is a concern that a surge may pass or unexpected electrical resonance may occur.

  On the other hand, in Patent Document 1, in a coil device with a core such as a planar type inductor or transformer, the problem is coil conduction loss due to eddy current generated in the spiral coil pattern itself formed on the substrate. The winding loss due to the electrostatic capacitance between the primary winding and the secondary winding is not described.

  Accordingly, the present invention suppresses an increase in winding loss due to the proximity effect, while suppressing an increase in capacitance between the primary winding and the secondary winding, and a transformer that can be reduced in size and weight. An object is to provide a power conversion system used.

  In order to solve the above problems, the present invention provides an iron core, a primary winding made of a thin plate-like conductor wound around the iron core and surrounding the iron core, and surrounding the iron core around the iron core. A secondary winding made of a wound thin plate-like conductor, and at least one of the primary winding and the secondary winding has one or more through holes. .

  According to the present invention, it is possible to provide a transformer that has both surge resistance and high efficiency and is small and light.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a figure which shows the structure of the transformer 9 of a comparative example. It is a figure which shows a part of primary winding 21 and the secondary winding 22 of the transformer 9 of a comparative example. The correlation of the opposing area of the primary winding 21 and the secondary winding 22 which concerns on the transformer 9 of a comparative example, and the capacity | capacitance between the primary winding 21 and the secondary winding 22, a proximity effect, and a leakage inductance is shown. FIG. 1 is a horizontal sectional view showing a structure of a transformer 10 according to Example 1. FIG. FIG. 3 is a diagram illustrating a part of the primary winding 21 and the secondary winding 22 of the transformer 10 according to the first embodiment. It is a part of secondary winding 22 of the transformer 10 which concerns on the modification of Example 1, and its enlarged view. FIG. 6 is a diagram illustrating a part of a primary winding 21 and a secondary winding 22 of a transformer 10 according to a second embodiment. It is a horizontal sectional view showing the structure of the transformer 10 according to the second embodiment. FIG. 6 is a diagram illustrating a part of a primary winding 21 and a secondary winding 22 of a transformer 10 according to a modification of the second embodiment. FIG. 6 is a diagram illustrating a part of a primary winding 21 and a secondary winding 22 of a transformer 10 according to another modification of the second embodiment. It is a figure which shows the periphery of the through-hole 23b given to the secondary winding 22 of the transformer 10 which concerns on Example 2. FIG. It is a figure which illustrates notionally the effect which through-hole 23 in transformer 10 concerning Example 2 brings to transformer 10. It is a figure which shows the structure of the power conversion system 11 which concerns on Example 3. FIG. It is a figure which shows the structure of the power conversion system 11 which concerns on the modification of Example 3. FIG. It is a figure which shows the structure of the power conversion system 11 which concerns on another modification of Example 3. FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and detailed description of the overlapping portions is omitted.

  The transformer of Example 1 is demonstrated with reference to FIGS. FIG. 1 shows a comparative transformer 9 in which a primary winding and a secondary winding are overlapped and wound simultaneously. 1A and 1B are a front view and a horizontal sectional view of the transformer 9, respectively. The transformer 9 includes an iron core 20, a primary winding 21, and a secondary winding 22 as main components. The primary winding 21 and the secondary winding 22 are thin plate conductors, respectively. The primary winding 21 and the secondary winding 22 are stacked in a state of facing each other and wound around both legs of the iron core 20. For the purpose of improving the insulation strength and mechanical strength, between the primary winding 21 and the secondary winding 22, an insulating paper, an epoxy resin laminated board, or all or a part of the air gap, not shown, is included. There is a case.

  One end portion of the primary winding 21 wound around the left and right legs of the iron core 20 is electrically connected by a primary-side inter-leg wire 31. Similarly, one end portion of the secondary winding 22 wound around the left and right legs of the iron core 20 is electrically connected to each other by a secondary-side leg wiring 32. The remaining one end portion of the primary winding 21 wound around the left and right legs of the iron core 20 is connected to the primary winding connection terminal 33, respectively. Similarly, the remaining terminal portions of the secondary windings 22 wound around the left and right legs of the iron core 20 are connected to the secondary winding connection terminals 34, respectively.

FIG. 2 shows a part of the primary winding 21 and the secondary winding 22. The primary winding 21 and the secondary winding 22 in FIG. 2 are in a state before being wound around the iron core 20. In general, the capacitance C ₁ between the primary winding 21 and the secondary winding 22 is expressed by the following equation (1).

Here, ε ₀ is the dielectric constant of vacuum, ε _s is the relative permittivity of the insulator sandwiched between the primary winding 21 and the secondary winding 22, and S is the opposite of the primary winding 21 and the secondary winding 22. The area d is the distance between the primary winding 21 and the secondary winding 22. According to the equation (1), the capacitance C ₁ between the primary winding 21 and the secondary winding 22 in the transformer 9 of the comparative example is equal to the opposing area of the primary winding 21 and the secondary winding 22. Proportional. In the transformer 9 of the comparative example shown in FIG. 1, the primary winding 21 and the secondary winding 22 are wound while being overlapped with each other, so the primary winding 21 and the secondary winding 22 are wound. The capacitance between is large.

  FIG. 3 is a diagram for explaining the influence of the opposing area of the primary winding 21 and the secondary winding 22 on the transformer 9. As described above, the larger the facing area between the primary winding 21 and the secondary winding 22, the larger the capacitance between the primary winding 21 and the secondary winding 22. On the other hand, the proximity effect that increases the winding resistance at high frequency and the leakage inductance tend to decrease as the opposing area of the primary winding 21 and the secondary winding 22 increases. That is, it can be said that the capacitance between the primary winding 21 and the secondary winding 22, the proximity effect, and the leakage inductance are in a trade-off relationship.

  In FIG. 3, the proximity effect and the leakage inductance have linear characteristics with respect to the opposing area of the primary winding 21 and the secondary winding 22, but this is a measure for simplifying the explanation, Proximity effects and leakage inductance are actually determined by various factors.

  FIG. 4 is a horizontal sectional view of the transformer 10 according to the first embodiment. The same parts as those of the transformer 9 in FIG. The secondary winding 22 of the transformer 10 of this embodiment has at least one or more through holes 23. The role and effect of the through hole 23 are as follows.

FIG. 5 is a diagram illustrating the capacitance between the primary winding 21 and the secondary winding 22 of the transformer 10 according to the present embodiment. The facing area between the primary winding 21 and the secondary winding 22 is reduced by the area of the through hole 23 provided in the secondary winding 22. In other words, it puts the sum of the areas of all the through-hole 23 and S _h, the electrostatic capacitance C ₂ between the primary winding 21 of the transformer 10 according to the present embodiment and the secondary winding 22 following formula It is represented by (2).

Equation (1), the comparison of (2), it is clear _{that C 2} is smaller than _{C 1.} In other words, the capacitance between the primary winding 21 and the secondary winding 22 of the transformer 10 according to this embodiment is smaller than that of the transformer 9 of the comparative example. Thereby, it is possible to provide the transformer 10 that suppresses an increase in the capacitance between the primary winding and the secondary winding while suppressing an increase in winding loss and leakage inductance due to the proximity effect.

  In designing the transformer 10, if the primary purpose is to reduce the capacitance between the primary winding 21 and the secondary winding 22, the number of through-holes 23 should be at least two. These through holes 23 are preferably distributed over a wide range of the secondary winding 22. In order to greatly reduce the capacitance between the primary winding 21 and the secondary winding 22 with one through hole 23, the area of the through hole 23 must be increased, and the mechanical structure of the transformer 10 is increased. This is because there is a concern about insufficient strength and it may be difficult to design the electrical characteristics of the transformer 10.

  A modification of the present embodiment will be described with reference to FIG. FIG. 6 shows a part of the secondary winding 22 of the transformer 10 according to a modification of the present embodiment and an enlarged view thereof. The secondary winding 22 in FIG. 6 is in a state before being wound around the iron core 20. The secondary winding 22 is provided with at least one or more through holes 23, and the shape of the through holes 23 is a rhombus (square). In FIG. 6, it is assumed that a current flows in the secondary winding 22 from the left to the right.

  As shown in the partially enlarged view of FIG. 6, when the through hole 23 is provided in the secondary winding 22, the current at point A is shunted by the end of the through hole 23. Further, the current is shunted by another through hole 23 beyond that. As a result, since the path of the current flowing through the secondary winding 22 is zigzag-shaped, the net DC resistance of the secondary winding 22 with the through hole 23 is increased as compared with the case where the through hole 23 is not provided. To do. Therefore, compared with the case where the through hole 23 is not provided, there is a concern that the loss of the secondary winding 22 provided with the through hole 23 increases.

  In order to avoid this, the net conductive area of the secondary winding 22 reduced due to the presence of the through hole 23 may be increased. More specifically, the width and thickness of the secondary winding 22 may be increased. However, when the width of the secondary winding 22 is increased, the height of the iron core 20 is increased, and when the thickness of the secondary winding 22 is increased, the lateral width of the iron core 20 is increased. On the other hand, when a high-frequency current flows through a conductor, it is known that the resistance value at the center of the conductor increases due to the influence of the skin effect. That is, when the transformer 10 is driven at a high frequency, the desired effect may not be obtained even if the thickness of the secondary winding 22 is increased.

  Therefore, attention is paid to the shape of the through hole 23. Various shapes of the through hole 23 are conceivable. If the shape of the through hole 23 is a rhombus (square), the current flowing through the secondary winding 22 is smoothly divided in a zigzag shape as shown in FIG. The current path in the secondary winding 22 can be shortened. As a result, an increase in DC resistance due to the application of the through hole 23 can be suppressed. The same effect can be expected even if the shape of the through hole 23 is a hexagon. Further, regarding the shape of the through hole 23, if the length in the direction parallel to the current of the through hole 23 is X, the length in the direction perpendicular to the current direction is Y, and X / Y is increased, the zigzag path is more linear. Therefore, an increase in DC resistance can be further suppressed.

  On the other hand, there is a concern that the electric field concentrates at the end of the polygonal through hole and the insulation performance deteriorates during a long-term operation. Therefore, by making the shape of the through hole 23 a circle or an ellipse, the electric field concentration at the end in the through hole 23 can be relaxed, and the influence on the insulation performance can be wiped out. Even if the shape of the through-hole 23 is an ellipse, the secondary winding 22 can be obtained by shortening the shape of the through-hole 23 in the direction parallel to the current flowing through the secondary winding 22 and shortening it in the vertical direction. The increase in direct current resistance can be suppressed.

  In FIG. 4, the transformer 10 having a turns ratio of 1 is shown as an example, but the turns ratio may be larger than 1. 4 shows a structure in which the primary winding 21 and the secondary winding 22 are overlapped with each other facing each other and wound around both legs of the iron core 20, but the present invention is not limited to this structure. For example, when the primary winding 21 and the secondary winding 22 are overlapped and wound around only one leg of the iron core 20, or the primary winding 21 and the secondary winding are wound around one leg of the iron core 20. Even when the primary winding 21 is wound around the other leg of the iron core 20 and the secondary winding 22 is wound on the other leg of the iron core 20, the wires 22 are wound in an opposing state. The effect brought about by the through hole 23 is the same.

  From the above, it is important to comprehensively consider the winding thickness, width, through-hole shape, number, total area, and winding method according to the design purpose of the transformer 10. Accordingly, it is possible to provide the transformer 10 in which the increase in winding loss due to the proximity effect, the leakage inductance, and the capacitance between the primary winding and the secondary winding are appropriately designed with a minimum manufacturing cost.

  Although the case where the through hole 23 is provided in the secondary winding 22 has been described above, it is obvious that the same effect can be obtained when the through hole 23 is provided in the primary winding 21. Further, when the through holes 23 are provided in both the primary winding 21 and the secondary winding 22, further effects may be expected, which will be described in detail below.

  The transformer of Example 2 is demonstrated with reference to FIG. 7 and FIG. FIG. 7 shows a part of the primary winding 21 and the secondary winding 22 of the transformer 10 according to the present embodiment. The primary winding 21 and the secondary winding 22 in FIG. 7 are in a state before being wound around the iron core 20. In the present embodiment, the through hole 23 is provided in both the primary winding 21 and the secondary winding 22 as through holes 23a and 23b, respectively. Furthermore, the primary winding 21 and the secondary winding 22 are overlapped so that the through-hole 23a provided in the primary winding 21 and the through-hole 23b provided in the secondary winding 22 do not overlap as much as possible. It is wound around the iron core 20. By setting it as such a structure, the transformer 10 which further suppressed the increase in the electrostatic capacitance between a primary winding and a secondary winding can be provided.

  From FIG. 4, it can be seen that as the number of turns of the winding increases, the length of the winding required to form a rounded corner portion increases. Further, since the secondary winding 22 is wound outside the primary winding 21, the length per turn of the secondary winding 22 is longer than that of the primary winding 21. From this, as the number of turns increases, the degree of overlap between the through hole 23a and the through hole 23b gradually changes, and the electrostatic capacity between the primary winding 21 and the secondary winding 22 is designed to a desired value. Difficult to do. Therefore, as shown in FIG. 8, if the through-hole 23a and the through-hole 23b are formed only in the portion excluding the rounded corner portion of the winding, that is, in the straight portion, the through-hole 23a and the through-hole are formed. Since the degree of overlap with the hole 23b can be brought close to the design value, the capacitance between the primary winding and the secondary winding can be designed with high accuracy.

  A modification of this embodiment will be described with reference to FIG. FIG. 9 shows a part of the primary winding 21 and the secondary winding 22 of the transformer 10 according to the present embodiment. The primary winding 21 and the secondary winding 22 in FIG. 9 are in a state before being wound around the iron core 20. In the present embodiment, a through hole 23a is provided in the primary winding 21 excluding the primary winding upper side region 24a and the primary winding lower side region 25a. Similarly, a through hole 23b is provided in the secondary winding 22 except for the secondary winding upper side region 24b and the secondary winding lower side region 25b. Further, the primary winding 21 and the secondary winding 22 are overlapped and wound around the iron core 20 so that the through hole 23a and the through hole 23b do not overlap as much as possible.

  Generally, in the primary winding 21 and the secondary winding 22 that are opposed to each other, in the central region of the winding, they are opposed to each other, thereby canceling out the magnetic fields generated by the primary winding 21 and the secondary winding 22, respectively. Although it is large, the action is relatively small in the upper winding region and the lower winding region, and it can be said that most of the leakage inductance occurs in the upper winding region and the lower winding region. If the through holes 23 are provided in the upper side region and the lower side region of the winding, the effect of canceling the magnetic fields generated by the primary winding 21 and the secondary winding 22 is weakened, so that the leakage inductance is greatly increased.

  Further, since mechanical stress concentrates in the upper side region of the winding and the lower side region of the winding, if the through hole 23 is provided in the upper side region of the winding and the lower side region of the winding, the primary winding 21, the secondary winding It is easy to reduce the overall mechanical strength of 22.

  Therefore, by providing the through hole 23 only in the winding central region excluding the winding upper side region and the winding lower side region, the deterioration of the mechanical strength of the primary winding 21 and the secondary winding 22 is prevented, and leakage is prevented. It is possible to provide the transformer 10 in which the electrostatic capacitance between the primary winding 21 and the secondary winding 22 is reduced while suppressing an increase in inductance as much as possible. In other words, a forbidden region in which no through hole is provided is set at an end in the short direction of the winding in which the through hole 23 is provided.

  With reference to FIG. 10, another modification of the present embodiment will be described. FIG. 10 shows both ends of the primary winding 21 and the secondary winding 22 of the transformer 10 according to the present embodiment. The primary winding 21 and the secondary winding 22 in FIG. 10 are in a state before being wound around the iron core 20, respectively. In FIG. 10, the inner peripheral side end region 26 a and the outer peripheral side end region 26 b of the secondary winding 22 are shown, but the primary winding 21 hidden behind the secondary winding 22 is also similar. An inner peripheral side end region and an outer peripheral side end region are set. Hereinafter, the inner peripheral side end region 26a and the outer peripheral side end region 26b of the secondary winding 22 will be described, but the same applies to the inner peripheral side end region and the outer peripheral side end region of the primary winding 21.

  A predetermined mechanical strength may be required to mechanically wind both the inner peripheral side end region 26 a and the outer peripheral side end region 26 b of the secondary winding 22. In view of this, a through hole 23b is provided in a portion of the secondary winding 22 excluding the inner peripheral side end region 26a and the outer peripheral side end region 26b. In other words, a forbidden area in which no through hole is provided is set at the end in the longitudinal direction of the winding in which the through hole 23 is provided.

  By adopting such a configuration, the transformer 10 is provided in which the electrostatic capacity between the primary winding 21 and the secondary winding 22 is reduced as much as possible while maintaining the mechanical strength necessary for manufacturing the transformer 10. it can.

  The outer peripheral side end region 26b is often required to have a higher mechanical strength than the inner peripheral side end region 26a. Therefore, a region wider than the inner peripheral side end region 26a is set to the outer peripheral side end portion 26a. It is preferable to set the area 26b.

  The shape of the through hole 23 will be described in detail with reference to FIG. FIG. 11 shows a rhomboid (left figure) or elliptical (right figure) through-hole 23b applied to the secondary winding 22 and a vertical sectional view thereof. When the shape of the through hole 23b is a rhombus, the lengths of the two diagonal lines are designed to decrease from both surfaces of the secondary winding 22 to the center in the vertical cross section of the through hole 23b. In addition, when the shape is an ellipse, the major axis and the minor axis are designed to decrease from both surfaces of the secondary winding 22 to the central part. That is, the cross section of the through hole 23b has a so-called taper shape.

  With such a configuration, when the through hole 23b is formed in the secondary winding 22, it is possible to suppress the occurrence of unnecessary protrusions, that is, so-called burrs that are generated on the processing end face. If burrs remain on the surface of the secondary winding 22, the insulation distance between the primary winding 21 and the secondary winding 22 becomes shorter than the design, and the expected insulation performance cannot be obtained. During operation, burrs come off and cause unexpected failures such as electrical shorts. Therefore, by forming the cross-section of the through hole 23b into a tapered shape, it is possible to suppress the generation of burrs and provide the highly reliable transformer 10. Even when the through hole 23a is provided in the primary winding 21, the same effect can be expected by the same method.

  With reference to FIG. 12, another effect which the through-hole 23 of a present Example brings to the transformer 10 is demonstrated. The transformer 10 is, for example, an oil immersion transformer, and the insulating oil circulates naturally or forcibly, and cools the iron core 20, the primary winding 21, and the secondary winding 22. Usually, the insulating oil penetrates from the lower part of the transformer between the iron core 20 and the primary winding 21 or between the primary winding 21 and the secondary winding 22, drains to the upper part of the transformer, and is installed in the transformer tank. It is cooled by the radiator that is used, and it goes around to the lower part of the transformer again.

  When the primary winding 21 and the secondary winding 22 do not have the through hole 23, the flow path from the lower part to the upper part of the transformer is linear, and the iron core 20, the primary winding 21, and the secondary winding 22 are connected to each other. Temperature distribution is likely to occur. In particular, when the transformer 10 is driven at a high frequency, the iron core 20 generates a large amount of heat because the iron loss is large, the oil temperature between the iron core 20 and the primary winding 21 is the highest, and the outermost winding is wound. The difference with the nearby temperature becomes large.

  In the insulation class “class A insulation” applied to the oil immersion transformer, when the reference ambient temperature is 40 ° C., the temperature rise limit is set to 65K. For this reason, it is necessary to design the location where the maximum temperature is within 65K, and it is preferable to reduce the temperature distribution in the transformer 10.

  Therefore, as shown in FIG. 12, if the through hole 23 is provided in the primary winding 21 and the secondary winding 22, the oil flow 40 can enter the adjacent flow path through the through hole 23, and the iron core. The oil temperature between 20 and the primary winding 21 and the oil temperature between the primary winding 21 and the secondary winding 22 are leveled.

  By adopting such a configuration, it is possible to make a natural circulation of a transformer that has been required to forcibly circulate oil until now. Further, since the cooling performance of the iron core 20, the primary winding 21, and the secondary winding 22 is increased, further downsizing can be achieved.

  With reference to FIG. 13, the power conversion system of Example 3 is demonstrated. FIG. 13 is a diagram illustrating a configuration example of the power conversion system 11 in which the transformer 10 according to the present embodiment is mounted. The power conversion system 11 mainly includes a first conversion unit 12, a second conversion unit 13, a transformer 10, and a control device 19.

The first conversion unit 12 is intended for converting the input DC voltage V _in the alternating voltage. The transformer 10 boosts or steps down the AC voltage output from the first conversion unit 12 according to the turns ratio. The second conversion unit 13 rectifies the AC voltage boosted or stepped down by the transformer 10 and outputs the DC voltage _Vout .

  Here, the connection of each component in the power conversion system 11 is demonstrated. The primary winding 21 of the transformer 10 is connected to the output terminal of the first conversion unit 12, and the secondary winding 22 is connected to the input terminal of the second conversion unit 13. The control device 19 performs calculation processing necessary for controlling the operation of the power conversion system 11 and performs data exchange with the first conversion unit 12 and the second conversion unit 13. The data sent from the first conversion unit 12 and the second conversion unit 13 to the control device 19 are, for example, instantaneous values of voltage and current. The data sent from the control device 19 to the first conversion unit 12 and the second conversion unit 13 is, for example, a gate signal for driving the semiconductor switching element.

  Next, configuration examples of the first conversion unit 12 and the second conversion unit 13 will be described. The first conversion unit 12 is a two-level full-bridge type inverter circuit mainly composed of a bridge circuit composed of four semiconductor switching elements 15 such as IGBTs and four diodes 16 and a capacitor 17. Specifically, the bridge circuit included here includes a series connection circuit in which a diode 16 is connected in antiparallel to each of two semiconductor switching elements 15 connected in series, and the output terminals of both circuits are transformed. It is connected to both ends of the primary winding 21 of the vessel 10.

  On the other hand, the second conversion unit 13 includes a bridge circuit configured by four diodes 16, a reactor 18, and a capacitor 17, for example. Specifically, in this bridge circuit, a series connection circuit of two diodes 16 is installed in parallel, and input terminals of both circuits are connected to both ends of the secondary winding 22 of the transformer 10. Since the diode 16 is lower in cost than the semiconductor switching element 15 and is a passive component, a driving circuit can be eliminated, so that the second converter unit 13 can be configured at low cost.

  When the semiconductor switching element 15 is turned off, a surge voltage determined by a time change of the interrupted current and an inductance component included in the current path is generated. This surge voltage may destroy the insulation of the semiconductor switching element 15 and the transformer 10. However, it is not easy to reduce the inductance component included in the interrupted current path, and in many cases, the cost tends to increase. On the other hand, there is a case where a snubber capacitor is connected in parallel to the semiconductor switching element 15 in order to alleviate the time change of the interrupted current. In this case, additional cost is generated, and the power conversion system 11 is large. Invite

  As described in the first embodiment or the second embodiment, the transformer 10 of the present invention has the leakage inductance, the primary by providing the through hole 23 in one or both of the primary winding 21 and the secondary winding 22. It is possible to appropriately design the capacitance between the winding 21 and the secondary winding 22. The leakage inductance of the transformer 10 is included in the inductance component of the interrupted current path described above. Therefore, by applying the transformer 10 in which the size and the number of the through holes 23 are reduced so that the leakage inductance is reduced in the power conversion system 11, the generation of the surge voltage due to the turn-off operation of the semiconductor switching element 15 is suppressed. it can.

  Thereby, the operation reliability of the semiconductor switching element 15 and the transformer 10 can be improved. Further, the capacity of the snubber capacitor connected in parallel to the semiconductor switching element 15 can be reduced and omitted, and the power conversion system 11 can be provided at low cost and with high reliability.

  In addition, when the rated power of the power conversion system 11 is 100 kW or more, for example, the drive frequency of the transformer 10 is preferably excited at a high frequency higher than the commercial frequency, for example, 1 kHz. By doing in this way, the cross-sectional area of the iron core 20 can be made small, and the volume of the transformer 10 can be made small. Furthermore, by making the iron core 20 a wound iron core formed by winding a plurality of thin strip-shaped magnetic materials, it is possible to suppress the occurrence of eddy current loss that becomes noticeable in the high frequency region, and to further reduce the volume of the transformer 10. As such a wound iron core, a ribbon-like alloy having an amorphous structure or a fine crystal structure mainly composed of iron is preferable, but not limited thereto.

  A modification of this embodiment will be described with reference to FIG. FIG. 14 shows another configuration example of the second conversion unit 13 of FIG. The first conversion unit 12 shown here is the same as that shown in FIG.

  The second conversion unit 13 in FIG. 14 is a two-level full-bridge converter circuit including a bridge circuit including four semiconductor switching elements 15 such as IGBTs and four diodes 16 and a capacitor 17. Specifically, the bridge circuit included here includes a series connection circuit in which a diode 16 is connected in antiparallel to each of two semiconductor switching elements 15 connected in series, and the input terminals of both circuits are transformed. It is connected to both ends of the secondary winding of the vessel 10.

With such a configuration, the power conversion system 11 can be flexible and DC voltages V ₁ side, power bidirectionally between a direct current voltage V ₂ side. In addition, when power is to be accommodated from the DC voltage V ₁ side to the DC voltage V ₂ side, the semiconductor switching element 15 of the second conversion unit 13 is driven by the synchronous rectification method, so that the four types shown in FIG. The conduction loss can be reduced as compared with the case where rectification is performed by a bridge circuit composed of diodes. Similarly, when interchange power from the DC voltage V ₂ side to the DC voltages V ₁ side, if driving the semiconductor switching element 15 of the first conversion unit 12 in the synchronous rectification, the same effect can be obtained.

  With reference to FIG. 15, another modification of the present embodiment will be described. FIG. 15 shows another configuration example of the power conversion system 11. In addition, the part already demonstrated is attached | subjected the same code | symbol and the description is abbreviate | omitted. The transformer 10 is a multi-winding transformer having two secondary windings 22, and the power conversion system 11 has two second conversion units 13. Each secondary winding 22 of the transformer 10 is connected to an input terminal of each second conversion unit 13. With such a configuration, the power conversion system 11 can have two outputs. If two outputs are connected in series, twice the output voltage can be obtained. Further, if the two outputs are connected in parallel, twice the output current can be obtained, and the application range of the power conversion system 11 can be widened.

  Specific examples of the first conversion unit 12 and the second conversion unit 13 of the present embodiment have been shown in FIGS. 13 to 15, but the combination of the conversion units is not limited to these. For example, the same effect as that of the present embodiment can be obtained by any combination of a three-level half-bridge type, three-level full-bridge type inverter circuit, converter circuit, and rectifier circuit.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a 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. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  For example, the semiconductor switching element 15 shown in FIG. 13 includes a semiconductor switching element group configured by connecting a plurality of semiconductor switching elements in series and in parallel. The same applies to other components.

  In each embodiment, control lines and information lines indicate what is considered necessary for the description, and not all control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  In addition, as described at the beginning, the present specification has been described on the premise of the transformer and the power conversion system used in the offshore wind farm, but the scope of the present invention is not limited to this, and the onshore wind farm Needless to say, the present invention can also be applied to power conversion systems (DC / DC converters) such as DC solar power distribution systems.

DESCRIPTION OF SYMBOLS 9,10 ... Transformer 11 ... Power conversion system 12 ... 1st conversion unit 13 ... 2nd conversion unit 15 ... Semiconductor switching element 16 ... Diode 17 ... Capacitor 18 ... Reactor 19 ... Controller 20 ... Iron core 21 ... Primary volume Wire 22 ... Secondary winding 23, 23a, 23b ... Through hole 24a ... Primary winding upper side region 24b ... Secondary winding upper side region 25a ... Primary winding lower side region 25b ... Secondary winding lower side region 26a ... secondary winding inner peripheral side end region 26b ... secondary winding outer peripheral side end region 31 ... primary side leg wiring 32 ... secondary side leg wiring 33 ... primary winding connection terminal 34 ... secondary winding Connection terminal 40 ... oil flow.

Claims (14)

Iron core,
A primary winding made of a thin plate-like conductor wound around the iron core and surrounding the iron core;
A secondary winding made of a thin plate-like conductor that surrounds the iron core and is wound around the iron core, and
At least one of the primary winding and the secondary winding has one or more through holes. The transformer of claim 1,
The transformer, wherein the primary winding and the secondary winding are wound around each other around the iron core. The transformer according to claim 1 or 2,
The whole or part of the through hole is a quadrangle, a polygon including a hexagon, or a circle or an ellipse. The transformer according to any one of claims 1 to 3,
The transformer is excited at a frequency higher than the commercial frequency,
The said iron core is a wound iron core comprised by winding several sheets of thin strip-shaped magnetic materials, The transformer characterized by the above-mentioned. The transformer according to claim 4,
The said iron core is comprised with the thin strip-shaped alloy which has the amorphous structure which has iron as a main component, or a fine crystal structure. The transformer according to any one of claims 1 to 5,
The transformer is an oil immersion transformer in which insulating oil flows between the iron core and the primary winding and between the primary winding and the secondary winding. The transformer according to any one of claims 1 to 6,
The through hole is provided in both the primary winding and the secondary winding,
The transformer is characterized in that the through hole is provided so that the center of the through hole of the primary winding and the center of the through hole of the secondary winding do not overlap each other. The transformer according to any one of claims 1 to 7,
A transformer having a forbidden region in which a through hole is not provided at an end portion in a short direction of a winding in which the through hole is provided among the primary winding and the secondary winding. The transformer according to any one of claims 1 to 8,
A transformer having a forbidden region in which a through hole is not provided at an end in a longitudinal direction of a winding in which the through hole is provided among the primary winding and the secondary winding. The transformer according to any one of claims 1 to 9,
The transformer is characterized in that the opening area of the through hole decreases from the surface to the center in the cross section of the primary winding or the secondary winding. A first conversion unit that converts an input DC voltage into an AC voltage and outputs the AC voltage;
A transformer for stepping up or stepping down the AC voltage output from the first conversion unit;
A second conversion unit that converts the AC voltage stepped up or down by the transformer into a DC voltage and outputs the DC voltage;
A control device for controlling the first conversion unit and the second conversion unit;
The said transformer is a transformer of any one of Claim 1 to 10, The power conversion system characterized by the above-mentioned. The power conversion system according to claim 11, wherein
The first conversion unit includes a two-level full-bridge inverter circuit having a bridge circuit including four semiconductor switching elements and four diodes, and one capacitor.
The second conversion unit includes a bridge circuit including four diodes, one reactor, and one capacitor. The power conversion system according to claim 11, wherein
Each of the first conversion unit and the second conversion unit is configured by a two-level full-bridge inverter circuit having a bridge circuit including four semiconductor switching elements and four diodes and one capacitor. A featured power conversion system. The power conversion system according to claim 11, wherein
The power conversion system includes one first conversion unit and two second conversion units,
The transformer comprises one primary winding and two secondary windings,
An output terminal of the first conversion unit is connected to the primary winding;
An input terminal of each of the two second conversion units is a multi-winding transformer connected to the two secondary windings, respectively.

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