Three-winding transformer connected with different power grids and adaptive to energy flow multi-working mode and working method

Abstract

The three-winding transformer comprises an iron core, a primary winding and split windings, the split windings comprise the first split winding and the second split winding which are distributed around the iron core in the radial direction, the first split winding and the second split winding are axially divided into three sections and then are distributed in a crossed series connection mode, and the first split winding and the second split winding are connected in series. The axial structures of the split windings are symmetrical, that is, the number of turns of the upper end of the first split winding is consistent with the number of turns of the lower end of the first split winding, and the number of turns of the upper end of the second split winding is also identical with the number of turns of the lower end of the second split winding. Due to the radial split structure, split impedance is smaller, when energy flow is transmitted in the split winding, a leakage magnetic field still takes axial leakage flux as a main part, and higher power transformation quality and efficiency are ensured; by adjusting the ratio of the number of turns of the middle section winding, balance of energy distribution and voltage distribution can be ensured when energy flow is transmitted between the primary winding and the split winding; the structure satisfies axial symmetry, and the anti-short-circuit capability is strong.

Description

Technical Field

[0001] The present invention relates to the field of transformers, and in particular to a three-winding transformer capable of connecting different power grids and adapting to multiple working modes of energy flow and a working method thereof. Background Art

[0002] In a power system, a three-winding transformer is mainly used to connect three transmission systems with different voltages. Compared with using two ordinary transformers, it is more economical, occupies less land, and is more convenient for maintenance and management; a multi-winding split transformer used for new energy grid connection can ensure that when a fault occurs in a certain low-voltage winding of the transformer, the remaining low-voltage windings can still work normally, reducing the power generation and grid connection losses caused by transformer faults. The existing transformers mainly adopt an axial split form in structure. Although the Chinese Utility Model Patent No. 202321589319.3 also adds a radial arrangement of split windings, it cannot overcome the imbalance between the impedances of the two axially split windings and the impedances of the radially split windings, which is not conducive to realizing the energy flow transfer between the split windings. In addition, when a short-circuit fault occurs in any split winding, the short-circuit resultant force in the axial direction of the winding is relatively large, which poses a major challenge to the operation of the transformer. Summary of the Invention

[0003] Object of the Invention: The object of the present invention is to provide a three-winding transformer capable of connecting different power grids and adapting to multiple working modes of energy flow, with controllable split impedance, balanced through impedance, and strong short-circuit resistance. Another object of the present invention is to provide a working method for connecting different power grids based on the above three-winding transformer.

[0004] Technical Solution: A three-winding transformer capable of connecting different power grids and adapting to multiple working modes of energy flow according to the present invention includes an iron core 1, a primary winding 2, and a split winding 3. The split winding includes a first split winding 4 and a second split winding 5 that are radially distributed around the iron core. The first split winding and the second split winding are axially divided into three sections and then cross-connected in series, and the axial structure of the split winding is symmetrical.

[0005] Furthermore, the first split winding includes a first-stage winding 41 that is radially internal and axially upper-end, a second-stage winding 42 that is radially external and axially middle-end, and a third-stage winding 43 that is radially internal and axially lower-end. The first-stage winding, the second-stage winding, and the third-stage winding are connected in series, and the number of turns of the first-stage winding and the third-stage winding is the same. The second split winding includes a fourth-stage winding 51 that is radially external and axially upper-end, a fifth-stage winding 52 that is radially internal and axially middle-end, and a sixth-stage winding 53 that is radially external and axially lower-end. The fourth-stage winding, the fifth-stage winding, and the sixth-stage winding are connected in series, and the number of turns of the fourth-stage winding and the sixth-stage winding is the same. The split winding adopts a structural form of radial splitting and axial three-stage staggered arrangement, making the design of split, full-through, and half-through impedances more flexible and controllable. When operating in split mode, the axial leakage magnetic field is the main one. By adjusting the radial spacing and the number of turns between the first split winding and the second split winding, the lower limit value of the split impedance between the two windings can be made as small as possible. With such a setting, the leakage magnetic field of the transformer is more uniform, suppressing the magnitude of the short-circuit current.

[0006] Moreover, the number of turns of the second-stage winding and the fifth-stage winding is adjustable. During design, by changing the turns ratio between the two end windings of the first split winding and the second-stage winding, and changing the turns ratio between the two end windings of the second split winding and the fifth-stage winding, the half-through impedance of the primary winding to the first split winding, the half-through impedance of the primary winding to the second split winding, and the full-through impedance of the primary winding to the first split winding and the second split winding can be adjusted to reduce the deviation among the three.

[0007] Preferably, by combining three-winding transformers, a three-phase three-column structure or a three-phase five-column structure can be formed, and the technical effect can also be achieved.

[0008] A working method for connecting different power grids to adapt to multiple working modes of energy flow according to the present invention adopts the three-winding transformer defined by the above conditions, which can achieve magnetic coupling connection of three power grids, realize multiple combinations of energy flow modes, and has controllable split impedance, balanced through impedance, and strong short-circuit resistance.

[0009] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: (1) The split winding adopts a radial split structure form, and the split impedance can be made to have a smaller value. When the transformer operates in a split mode, the leakage magnetic field is still mainly axial leakage magnetic field, which can ensure higher power conversion quality and efficiency; (2) The split winding adopts an axial three-section staggered series structure form. By adjusting the turn ratios of the second winding and the fifth winding, the through impedance balance can be achieved, and the balance of energy distribution and voltage distribution can be ensured; (3) The structure of the split winding is symmetric up and down. Therefore, when a short circuit occurs at the outlet, the electrodynamic force distribution of any split winding is also symmetric up and down and cancels each other out. The overall electrodynamic force on the winding is small, and the short-circuit resistance ability is greatly improved. Brief Description of the Drawings

[0010] Figure 1 It is a schematic structural diagram of the present invention. Detailed Embodiment

[0011] The technical solution of the present invention will be further described below with reference to the drawings.

[0012] A three-winding transformer for connecting different power grids and adapting to multi-operation modes of energy flow according to the present invention includes an iron core 1, a primary winding 2, and a split winding 3. The split winding is composed of a first split winding 4 and a second split winding 5 that are radially distributed around the iron core. The first split winding 4 is divided into three sections from top to bottom, namely a first section winding 41 inside the radial direction, a second section winding 42 outside the radial direction, and a third section winding 43 inside the radial direction. The number of turns of the first section winding 41 is exactly the same as that of the third section winding 43; the second split winding 5 is also divided into three sections from top to bottom, namely a fourth section winding 51 outside the radial direction, a fifth section winding 52 inside the radial direction, and a sixth section winding 53 outside the radial direction. The split winding adopts a radial split structure form. Compared with the axial split structure, the split impedance can be made to have a smaller value to achieve controllability of the split impedance. When the energy flow is transmitted in the first split winding and the second split winding, because the magnitude of the impedance is inversely proportional to the height in the direction of the leakage magnetic field of the winding area and directly proportional to the width of the leakage magnetic field, this arrangement form can make the split impedance very small. That is, when the transformer operates in a split mode, the leakage magnetic field is still mainly axial leakage magnetic field, which can ensure higher power conversion quality and efficiency.

[0013] In addition, the connection mode between different windings of the same split winding is in series, and after series connection, they are axially cross-distributed. Coils are wound on both the primary winding and the split winding. The actual conductor height of the coil is called the reactance height. The reactance heights of the first split winding and the second split winding are exactly the same, and the central axes of the reactance heights also coincide. The number of turns of the two windings in the same axial direction is the same, that is, the number of turns of the first winding 41 is the same as that of the third winding 43, and the number of turns of the fourth winding 51 is the same as that of the sixth winding 53. The split winding of the present invention is completely symmetrical in axial structure. The advantage of this design is that during short-circuit tests or any form of outlet short-circuit, the overall axial short-circuit resultant force on the split winding is very small, further improving the short-circuit resistance ability of the transformer.

[0014] The number of turns of the second winding 42 and the fifth winding 52 can be adjusted and always remain the same. When designing the transformer, the number of turns is set according to needs. By adjusting the turn ratio of the second winding 42 to the first winding 41 and the third winding 43, the half-transfer impedance of the primary winding to the first split winding, the half-transfer impedance of the primary winding to the second split winding, and the full-transfer impedance of the primary winding to the first split winding and the second split winding can be made to reduce the deviation among the three; due to the complete axial symmetry of the structure, the turn ratio setting of the fifth winding 52 to the fourth winding 51 and the sixth winding 53 only needs to be the same as that of the first split winding. When the energy flow is transferred between the primary winding and the split winding, that is, when the transformer operates in a through mode, the balance of energy distribution and voltage distribution can be ensured, and the through impedance balance can be achieved.

[0015] Combine the three-winding transformers shown in the three groups Figure 1 The three core columns form a magnetic flux circuit through the upper yoke and the lower yoke. The three groups of windings respectively correspond to the three phases of the three-phase windings, and the line ends of the three groups of windings are led out, thus forming a three-phase three-winding transformer. The three-phase core can adopt a three-column structure or a five-column structure, and both can achieve the technical effect.

[0016] A working method for connecting different power grids to adapt to multiple working modes of energy flow according to the present invention adopts the three-winding transformer defined by the above conditions, and can realize the magnetic coupling connection of three power grids, enabling multiple energy flows to be realized between power grids with different voltages, greatly improving the practicability.

Claims

1. A three-winding transformer for connecting different power grids and adapting to multiple working modes of energy flow, comprising an iron core (1), a primary winding (2), and a split winding (3), characterized in that, The split winding includes a first split winding (4) and a second split winding (5) that are radially distributed around the iron core. The axial directions of the first split winding and the second split winding are divided into three segments and then cross-connected in series, and the axial structure of the split winding is symmetrical.

2. The three-winding transformer according to claim 1, wherein, The first split winding (4) includes a first-segment winding (41) at the upper axial end and inside the radial direction, a second-segment winding (42) at the middle axial position and outside the radial direction, and a third-segment winding (43) at the lower axial end and inside the radial direction.

3. The three-winding transformer according to claim 2, characterized in that, The number of turns of the second-segment winding (42) is adjustable.

4. The three-winding transformer according to claim 2, wherein, The first-segment winding, the second-segment winding, and the third-segment winding are connected in series, and the number of turns of the first-segment winding and the third-segment winding is the same.

5. The three-winding transformer according to claim 1, characterized in that, The second split winding (5) includes a fourth-segment winding (51) at the upper axial end and outside the radial direction, a fifth-segment winding (52) at the middle axial position and inside the radial direction, and a sixth-segment winding (53) at the lower axial end and outside the radial direction.

6. The three-winding transformer according to claim 5, characterized in that, The number of turns of the fifth-segment winding (52) is adjustable.

7. The three-winding transformer according to claim 5, characterized in that, The fourth-segment winding, the fifth-segment winding, and the sixth-segment winding are connected in series, and the number of turns of the fourth-segment winding and the sixth-segment winding is the same.

8. The three-winding transformer according to claim 1, characterized in that It can be set into a three-phase three-column structure.

9. The three-winding transformer according to claim 1, characterized in that, It can be set into a three-phase five-column structure.

10. A working method for connecting different power grids to adapt to multiple working modes of energy flow, characterized in that, A three-winding transformer defined in claims 1-7 is adopted.

Images