New-energy high-capacity corner-junction-free 400kV split transformer

Abstract

The invention relates to a new energy high-capacity corner-junction-free 400kV split transformer, a low-voltage side of a split transformer body is connected with a new energy system line, a high-voltage side of the split transformer body is connected with a power grid line, a plurality of inversion load transformers are arranged on the new energy system line, each inversion load transformer is connected with a corresponding front-end inverter, and the front-end inverters are connected with the front-end inverters. The harmonic wave of the front-end inverter and the harmonic wave of the inversion load transformer are both smaller than 3%, the split transformer body comprises an iron core, the iron core is of a three-phase five-column structure, and each core column of the iron core is sequentially provided with a low-voltage winding, a high-voltage winding and a voltage regulating winding from inside to outside. Wherein the low-voltage winding comprises a first low-voltage coil and a second low-voltage coil, an electrostatic plate assembly is arranged between the first low-voltage coil and the second low-voltage coil, and the first low-voltage coil and the second low-voltage coil are both U-shaped coils. A voltage stabilizing coil structure in the new energy split transformer is omitted, and operation is stable and reliable.

Description

Technical Field

[0001] This invention relates to the field of transformer technology, specifically a new energy large-capacity 400kV split transformer without corner joints. Background Technology

[0002] Traditional large-capacity split transformers generally adopt a three-phase five-limb structure with a voltage-stabilizing delta coil. The delta coil provides a current path for the odd harmonic generation to control the output voltage phase of the transformer, thereby improving the stability and performance of the system. In addition, the delta coil can help adjust the voltage phase, so that the transformer can maintain a stable output voltage under different load conditions. For example, the patent with authorization announcement number CN103051236B discloses a CHB cascaded photovoltaic inverter circuit based on a three-phase multi-split transformer. The three-phase multi-split transformer used includes a core, coils and other structures. Each phase coil includes multiple windings. Each winding has a primary side coil, a secondary side coil and a stabilizing winding coil arranged from the outside to the inside. The stabilizing winding coil adopts a delta connection.

[0003] However, as the new energy market grows larger, the demand for large-capacity split transformers is increasing. Furthermore, split transformers typically have overload requirements, while transformers with voltage-stabilizing corner coil structures are relatively expensive and can no longer meet market needs. Against this backdrop, research into the operating conditions of new energy photovoltaic systems has revealed that not all three-phase five-limb transformers require corner coils; some applications do not. This provides a direction for achieving the voltage regulation and stabilization required by split transformers through other methods. Summary of the Invention

[0004] The purpose of this invention is to provide a new energy high-capacity 400kV split transformer without corner joints, which eliminates the need for a voltage stabilizing coil structure and operates stably and reliably.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A new energy high-capacity, junctionless 400kV split transformer includes a split transformer body, wherein the low-voltage side of the split transformer body is connected to the new energy system line and the high-voltage side is connected to the power grid line. Multiple inverter load transformers are installed on the new energy system line, and each inverter load transformer is connected to a corresponding front-end inverter. The harmonics of the front-end inverter and the inverter load transformer are both less than 3%. The split transformer body includes a core, which is a three-phase, five-limb structure. Each limb of the core has a low-voltage winding, a high-voltage winding, and a voltage regulating winding arranged sequentially from the inside to the outside. The low-voltage winding includes a first low-voltage coil and a second low-voltage coil, and an electrostatic plate assembly is provided between the first and second low-voltage coils. Both the first and second low-voltage coils are U-shaped coils.

[0007] The upper end of the electrostatic plate assembly is separated from the first low-voltage coil by an upper coil oil passage spacer, and the lower end of the electrostatic plate assembly is separated from the second low-voltage coil by a lower coil oil passage spacer. The upper end of the electrostatic plate assembly is provided with an upper electrostatic plate and an upper insulating end ring, and the lower end is provided with a lower electrostatic plate and a lower insulating end ring. The position of the upper electrostatic plate corresponds to the outer layer of the first low-voltage coil, and the remaining part of the upper end of the electrostatic plate assembly is covered by the upper insulating end ring. The position of the lower electrostatic plate corresponds to the outer layer of the second low-voltage coil, and the remaining part of the lower end of the electrostatic plate assembly is covered by the lower insulating end ring.

[0008] The electrostatic plate assembly has an intermediate insulating end ring in the middle, and the upper end of the intermediate insulating end ring is separated from the upper electrostatic plate and the upper insulating end ring, and the lower end of the intermediate insulating end ring is separated from the lower electrostatic plate and the lower insulating end ring by an intermediate coil oil passage spacer.

[0009] The inverter load transformer includes an inverter load core, and the outer side of the core column of the inverter load core is provided with an inverter load low-voltage winding and an inverter load high-voltage winding from the inside to the outside, and a copper shield is provided between the inverter load low-voltage winding and the inverter load high-voltage winding.

[0010] The front-end inverter is connected to the corresponding solar panel.

[0011] The core column of the iron core is provided with a slotted non-magnetic pull plate. The slotted non-magnetic pull plate has multiple slots along its length, and the upper and lower ends of the slotted non-magnetic pull plate are provided with connecting webs.

[0012] The advantages and positive effects of this invention are as follows:

[0013] 1. This invention first controls the typical harmonic content to below 3% through harmonic suppression measures at the front end (front-end inverter and inverter load transformer). Then, the low-voltage, high-voltage, and voltage-regulating arrangement structure of the transformer body meets the requirements for transformer use. The low-voltage winding includes a first low-voltage coil and a second low-voltage coil, and both the first and second low-voltage coils are U-shaped coils with a strong anti-short-circuit electrostatic plate assembly in between. The transformer core connection group is YN,yn0-yn0 and low magnetic density material is used. The neutral point on the high-voltage side and the neutral point on the low-voltage side are reliably fixed grounded. This serves as a path for zero-sequence current, and the system harmonic current content is low, so it will not affect the transformer. Thus, this invention can eliminate the need for a voltage-stabilizing coil structure.

[0014] 2. This invention takes into account the large short-circuit force of the electrostatic plate assembly in the middle of the two low-voltage coils, and the fact that the inner and outer layers of the two low-voltage coils are separate coils, while also taking into account the electrical strength of the high-voltage winding. Therefore, the electrostatic plate assembly has been specially designed to resist short circuits, thereby further ensuring the operation of the equipment. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the transformer body structure of the present invention.

[0016] Figure 2 for Figure 1 A schematic diagram of the electrostatic plate assembly structure in the diagram.

[0017] Figure 3 This is a schematic diagram of the full-pass test of the transformer YN,yn0-yn0 connection of the present invention.

[0018] Figure 4 This is a schematic diagram of the semi-crossing test of the transformer YN,yn0-yn0 connection of the present invention.

[0019] Figure 5 This is a schematic diagram of a solar power generation system using the present invention.

[0020] Figure 6 for Figure 5 Schematic diagram of the transformer body structure for a medium-voltage inverter load transformer.

[0021] Figure 7 for Figure 1 Installation diagram of China Railway core.

[0022] Among them, 1 is the split transformer body, 2 is the inverter load transformer, 3 is the front-end inverter, 4 is the solar power generation panel, 5 is the iron core, 6 is the first low-voltage coil, 601 is the outer layer of the first low-voltage coil, 602 is the inner layer of the first low-voltage coil, 7 is the second low-voltage coil, 701 is the outer layer of the second low-voltage coil, 702 is the inner layer of the second low-voltage coil, 8 is the electrostatic plate assembly, 801 is the upper coil oil passage pad, 802 is the upper electrostatic plate, 803 is the upper insulating end ring, 804 is the middle coil oil passage pad, 805 is the middle insulating end ring, 806 is the lower electrostatic plate, 807 is the lower insulating end ring, 808 is the lower coil oil passage pad, 9 is the high-voltage winding, 10 is the voltage regulating winding, 11 is the new energy system line, 12 is the connecting web plate, and 13 is the slotted non-magnetic pull plate. Detailed Implementation

[0023] The invention will now be described in further detail with reference to the accompanying drawings.

[0024] like Figures 1-5 As shown, the present invention includes a split transformer body 1, and as... Figure 5 As shown, the low-voltage side of the split transformer body 1 is connected to the new energy system line 11, and the high-voltage side is connected to the power grid line. Multiple inverter load transformers 2 are installed on the new energy system line 11, and each inverter load transformer 2 is connected to a corresponding front-end inverter 3. The harmonics of both the front-end inverter 3 and the inverter load transformer 2 are less than 3%. Figures 1-4 As shown, the split transformer body 1 includes a core 5, and the core 5 has a three-phase five-limb structure. Each limb of the core 5 is provided with a low-voltage winding, a high-voltage winding 9, and a voltage regulating winding 10 sequentially from the inside out. For example... Figure 1 As shown, the low-voltage winding includes a first low-voltage coil 6 and a second low-voltage coil 7, and an electrostatic plate assembly 8 is provided between the first low-voltage coil 6 and the second low-voltage coil 7. Both the first low-voltage coil 6 and the second low-voltage coil 7 are U-shaped coils.

[0025] The coil arrangement on the core column 5 of this invention adopts a low-voltage, high-voltage, and voltage-regulating structure. Simultaneously, the high-voltage winding 9 achieves on-load voltage regulation through the voltage-regulating winding 10. This winding arrangement is well-known in the art; for example, see the patent with authorization publication number CN102543397B. However, this invention is used for new energy power generation, and in order to eliminate the stabilizing winding coil in existing new energy split transformers to reduce costs, such as… Figure 5 As shown, this invention first controls the typical harmonic content to below 3% through harmonic suppression measures taken at the front end (i.e., the front-end inverter 3 and the inverter load transformer 2), and then as... Figures 1-4As shown, the low-voltage winding of this invention includes a first low-voltage coil 6 and a second low-voltage coil 7. Both the first low-voltage coil 6 and the second low-voltage coil 7 are U-shaped coils with a high short-circuit withstand electrostatic plate assembly 8 in between. The core 5 of the transformer has a connection group of YN,yn0-yn0 and uses a low magnetic flux density (1.69 Tesla in this embodiment) material. The neutral point on the high-voltage side and the neutral point on the low-voltage side are reliably and fixedly grounded. This serves as a path for zero-sequence current, resulting in low harmonic current content in the system, thus having no impact on the transformer. Consequently, this invention can control the output voltage phase of the transformer without providing a current path for odd-order harmonics through the corner junction coil, thereby eliminating the need for a voltage stabilizing coil structure. The split transformer body 1 of this invention has a capacity of 330MVA and a voltage combination of 400 / 33-33kV.

[0026] Furthermore, since both the first low-voltage coil 6 and the second low-voltage coil 7 are U-shaped coils, considering the large short-circuit force of the electrostatic plate assembly in the middle of the two low-voltage coils, and that the inner and outer layers of the two low-voltage coils are separate coils, while also taking into account the electrical strength for the high-voltage winding 9, this invention incorporates a special short-circuit protection design for the electrostatic plate assembly 8, such as... Figure 2 As shown, the electrostatic plate assembly 8 of the present invention has independent electrostatic plates designed at both ends for the outer layer of the low-voltage coil, and the remaining parts are provided with insulating end rings, specifically as follows: Figure 2 As shown, the upper end of the electrostatic plate assembly 8 is separated from the first low-voltage coil 6 by an upper coil oil passage spacer 801, and the lower end of the electrostatic plate assembly 8 is separated from the second low-voltage coil 7 by a lower coil oil passage spacer 808. The upper end of the electrostatic plate assembly 8 is provided with an upper electrostatic plate 802 and an upper insulating end ring 803, and the lower end is provided with a lower electrostatic plate 806 and a lower insulating end ring 807. The position of the upper electrostatic plate 802 corresponds to the outer layer 601 of the first low-voltage coil. The remaining part of the upper end of the electrostatic plate assembly 8 is covered by the upper insulating end ring 803. The position of the lower electrostatic plate 806 corresponds to the outer layer 701 of the second low-voltage coil. The remaining part of the lower end of the electrostatic plate assembly 8 is covered by the lower insulating end ring 807.

[0027] like Figure 2 As shown, in this embodiment, the electrostatic plate assembly 8 has an intermediate insulating end ring 805 in the middle, and the upper end of the intermediate insulating end ring 805 is separated from the upper electrostatic plate 802 and the upper insulating end ring 803, and the lower end of the intermediate insulating end ring 805 is separated from the lower electrostatic plate 806 and the lower insulating end ring 807 by an intermediate coil oil passage spacer 804.

[0028] This invention requires a 120% load, and its connection diagram for full-crossing and half-crossing tests is shown below. Figures 3-4As shown, this test is a well-known technique in the field. In addition, the present invention does not have magnetic shielding for the body, but uses magnetic shielding for the oil tank, which meets the requirements of oil surface temperature rise ≤35K, winding temperature rise ≤45K, hot spot temperature rise ≤66K, and structural component temperature rise ≤60K.

[0029] The front-end inverter 3 of this invention is a commercially available product, and its harmonic control of less than 3% is a well-known technology in the field. However, as... Figure 6 As shown, in this embodiment, the inverter load transformer 2 includes an inverter load core 201, and an inverter load low-voltage winding 202 and an inverter load high-voltage winding 203 are arranged sequentially from the inside to the outside of the core column of the inverter load core 201. A copper shield 204 is provided between the inverter load low-voltage winding 202 and the inverter load high-voltage winding 203 to achieve harmonics less than 3%. The inverter load transformer 2 is connected to group D,yn+yn+yn+yn.

[0030] like Figure 7 As shown in this embodiment, the core column of the iron core 5 is provided with a slotted non-magnetic pull plate 13. The slotted non-magnetic pull plate 13 has multiple slots along its length. In addition, the upper and lower ends of the slotted non-magnetic pull plate 13 are provided with connecting web plates 12, which are correspondingly connected to the upper and lower connecting parts of the transformer body. The slotted non-magnetic pull plate 13 is made of non-magnetic steel plate, the purpose of which is to reduce eddy current losses caused by leakage magnetic field, thereby reducing temperature rise.

[0031] The working principle of this invention is as follows:

[0032] This invention aims to eliminate the need for a stabilizing winding coil in existing renewable energy split transformers, thereby reducing costs. Figure 5 As shown, this invention first controls the typical harmonic content to below 3% through harmonic suppression measures taken at the front end (i.e., the front-end inverter 3 and the inverter load transformer 2), and then as... Figures 1-4 As shown, the first low-voltage coil 6 and the second low-voltage coil 7 of the low-voltage winding of this invention are both U-shaped coils with a strong short-circuit withstand electrostatic plate assembly 8 in the middle. The transformer core 5 is connected in group YN,yn0-yn0 and uses a low magnetic flux density (1.69 Tesla in this embodiment) material. The neutral point on the high-voltage side and the neutral point on the low-voltage side are reliably fixed grounded. This serves as a path for zero-sequence current, resulting in low harmonic current content in the system, thus having no impact on the transformer. Consequently, this invention can control the output voltage phase of the transformer without providing a current path for odd-order harmonics through the corner junction coil, thereby eliminating the need for a voltage regulator coil structure. Furthermore, as... Figure 2As shown, considering the large short-circuit force of the electrostatic plate assembly in the middle of the two low-voltage coils, and that the inner and outer layers of the two low-voltage coils are separate coils, while also taking into account the electrical strength of the high-voltage winding 9, the present invention has carried out a special short-circuit protection design for the electrostatic plate assembly 8. The two ends of the electrostatic plate assembly 8 are designed with independent electrostatic plates for the outer layer of the low-voltage coils, and the rest of the parts are provided with insulating end rings.

[0033] like Figure 5 As shown, one application example of the present invention is a solar power generation project, wherein the front-end inverter 3 is connected to the corresponding solar power panels 4.

Claims

1. A new energy, high-capacity, junctionless 400kV split transformer, characterized in that: The system includes a split transformer body (1), and the low-voltage side of the split transformer body (1) is connected to the new energy system line (11), and the high-voltage side is connected to the power grid line. The new energy system line (11) is equipped with multiple inverter load transformers (2), and each inverter load transformer (2) is connected to a corresponding front-end inverter (3). The harmonics of the front-end inverter (3) and the inverter load transformer (2) are both less than 3%. The split transformer body (1) includes an iron core (5), and the iron core (5) is a three-phase five-column structure. Each column of the iron core (5) is provided with a low-voltage winding, a high-voltage winding (9) and a voltage regulating winding (10) from the inside to the outside. The low-voltage winding includes a first low-voltage coil (6) and a second low-voltage coil (7), and an electrostatic plate assembly (8) is provided between the first low-voltage coil (6) and the second low-voltage coil (7). The first low-voltage coil (6) and the second low-voltage coil (7) are both U-shaped coils.

2. The new energy large-capacity junctionless 400kV split transformer according to claim 1, characterized in that: The upper end of the electrostatic plate assembly (8) is separated from the first low-voltage coil (6) by an upper coil oil passage spacer (801), and the lower end of the electrostatic plate assembly (8) is separated from the second low-voltage coil (7) by a lower coil oil passage spacer (808). The upper end of the electrostatic plate assembly (8) is provided with an upper electrostatic plate (802) and an upper insulating end ring (803), and the lower end is provided with a lower electrostatic plate (806) and a lower insulating end ring (807). The position of the upper electrostatic plate (802) corresponds to the outer layer (601) of the first low-voltage coil. The remaining part of the upper end of the electrostatic plate assembly (8) is covered by the upper insulating end ring (803). The position of the lower electrostatic plate (806) corresponds to the outer layer (701) of the second low-voltage coil. The remaining part of the lower end of the electrostatic plate assembly (8) is covered by the lower insulating end ring (807).

3. The new energy large-capacity junctionless 400kV split transformer according to claim 2, characterized in that: The electrostatic plate assembly (8) has an intermediate insulating end ring (805) in the middle, and the upper end of the intermediate insulating end ring (805) is separated from the upper electrostatic plate (802) and the upper insulating end ring (803) and the lower end of the intermediate insulating end ring (805) is separated from the lower electrostatic plate (806) and the lower insulating end ring (807) by an intermediate coil oil passage pad (804).

4. The new energy large-capacity junctionless 400kV split transformer according to claim 1, characterized in that: The inverter load transformer (2) includes an inverter load core (201), and the inverter load core (201) has an inverter load low voltage winding (202) and an inverter load high voltage winding (203) arranged sequentially from the inside to the outside on the outer side of the core column. A copper shield (204) is provided between the inverter load low voltage winding (202) and the inverter load high voltage winding (203).

5. The new energy large-capacity junctionless 400kV split transformer according to claim 1, characterized in that: The front-end inverter (3) is connected to the corresponding solar panel (4).

6. The new energy large-capacity junctionless 400kV split transformer according to claim 1, characterized in that: The core (5) has a slotted non-magnetic pull plate (13) inside the core column. The slotted non-magnetic pull plate (13) has multiple slots along its length, and the upper and lower ends of the slotted non-magnetic pull plate (13) are provided with connecting web plates (12).

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