An oil-insulated three-phase integrated converter transformer system

Abstract

The application provides an oil insulation three-phase integrated converter transformer system, which comprises a converter valve provided with a diode valve and DC side outgoing lines and AC side outgoing lines, three-phase winding structures, three-phase three-winding transformers each comprising a grid side outgoing line, a valve Y side outgoing line and a valve D side outgoing line; a converter oil tank provided with a DC bushing on the top and a valve side bushing on the side wall; a transformer oil tank provided with a grid side bushing on the top and a valve Y side bushing and a valve D side bushing on the side wall; a plurality of converter valve side bushings are connected to a plurality of valve Y side bushings and a plurality of valve D side bushings in a butt joint mode; and the AC side outgoing lines are connected to the valve Y side outgoing lines and the valve D side outgoing lines. The system provided by the application solves the problems of low integration, large number of devices, large volume, complex structure and complex electrical connection of the converter transformer system.

Description

Technical Field

[0001] This application relates to the field of high voltage direct current transmission technology, and in particular to an oil-insulated three-phase integrated converter transformer system. Background Technology

[0002] In traditional high-voltage direct current (HVDC) transmission projects, the converter transformer system typically consists of a three-phase, three-winding converter transformer, converter valves, and a valve hall. In modern converter transformer systems, thyristor converter valves are often arranged in a suspended structure within the air-insulated valve hall. The air-insulated valve hall relies on air as the insulating medium and employs a centralized cooling scheme, resulting in problems such as large operating area, low equipment integration, large electrical spacing, complex structure, difficult transportation, and high operating energy consumption. Simultaneously, the three-phase, three-winding converter transformers are arranged in multiple units and are specifically designed to accommodate air-insulated valve halls, generally resulting in a large number of devices, large equipment size, low integration, complex system construction, and high cost.

[0003] Meanwhile, the three-phase, three-winding converter transformer and the converter valves are arranged separately. Each three-phase, three-winding converter transformer needs to first use a long bushing to span the large space, tilting through the side wall of the valve hall and extending into the valve hall, before connecting to multiple converter valves via high-voltage leads, cables, or busbars. This split-type converter transformer system results in a lengthy electrical structure, complex energy transmission paths, and increases the possibility of interphase interference and energy loss. It also makes efficient coordination in electrical parameter matching and structural layout difficult, affecting the response efficiency and system coordination of the entire converter transformer system.

[0004] As the converter transformer system of modern DC transmission projects is evolving towards smaller equipment size and higher integration, a comprehensive technical solution that integrates the valve hall, converter valve and three-phase three-winding converter transformer has not yet emerged. Utility Model Content

[0005] To address the aforementioned problems, this utility model provides an oil-insulated three-phase integrated converter transformer system, which solves the problems of low integration, large number and size of equipment, complex structure and complex electrical connections in current converter transformer systems.

[0006] This utility model provides an oil-insulated three-phase integrated converter transformer system, and the technical solution adopted is as follows: An oil-insulated three-phase integrated converter transformer system includes: The converter valve includes multiple connected diode valves as well as DC-side and AC-side outputs; A three-phase, three-winding converter transformer, including a three-phase winding structure, wherein each phase winding structure includes a grid-side output line, a valve Y-side output line, and a valve D-side output line; The converter oil tank is filled with oil and the converter valve. A DC bushing is installed on the top, and the DC side line is led out from the DC bushing. The side wall is connected to the converter transformer side bushing, and the AC side line is led out from the converter transformer side bushing. The transformer tank is filled with oil and the three-phase three-winding converter transformer. The grid-side bushing leads out the grid-side output line. The side wall is connected to the valve Y-side bushing and the valve D-side bushing. The valve Y-side bushing leads out the valve Y-side output line, and the valve D-side bushing leads out the valve D-side output line. The converter valve is located inside the converter oil tank, and the three-phase three-winding converter transformer is located inside the transformer oil tank. The first part of the converter transformer valve-side bushing on the converter oil tank is connected to the valve Y-side bushing on the transformer oil tank, and the second part of the converter transformer valve-side bushing is connected to the valve D-side bushing on the transformer oil tank. The AC side output line is connected to the valve Y-side output line and the valve D-side output line in a one-to-one correspondence.

[0007] As one of the preferred embodiments, the converter valve includes twelve diode valves, which are connected in a three-phase six-pulse pseudo-bipolar topology and form two sets of three-phase six-pulse bridges. The valve Y-side output of the three-phase winding structure is connected to the AC-side output of the first group of three-phase six-pulse bridges using a Y-connection; the valve D-side output of the three-phase winding structure is connected to the AC-side output of the second group of three-phase six-pulse bridges using a Δ-connection.

[0008] As one of the preferred solutions, there are three DC bushings and six converter valve side bushings. The six converter valve side bushings are arranged in two rows at intervals in the height direction of the converter oil tank. The number of converter valve side bushings in each row is the same and they are aligned one by one. There are three grid-side bushings, three valve Y-side bushings, and three valve D-side bushings. The three valve Y-side bushings and the three valve D-side bushings are aligned one-to-one in the height direction of the transformer tank. The three converter transformer valve side bushings in the first row are aligned with the three valve Y side bushings, and the three AC side outgoing lines of the first group of three-phase six-pulse bridges are led out. The three converter valve side bushings in the second row are aligned with the three valve D side bushings, and the three AC side outgoing lines of the second group of three-phase six-pulse bridges are led out.

[0009] As one preferred embodiment, the three DC bushings extend vertically from the top of the converter oil tank; the six converter valve side bushings extend horizontally from the side wall of the converter oil tank. The three grid-side bushings extend vertically from the top of the transformer tank; the three valve Y-side bushings and the three valve D-side bushings extend horizontally from the side wall of the transformer tank. In this configuration, each converter transformer valve-side bushing in the first row is horizontally aligned with each valve Y-side bushing; and each converter transformer valve-side bushing in the second row is horizontally aligned with each valve D-side bushing.

[0010] As one of the preferred embodiments, the three converter valve side bushings in the same row are arranged at intervals along the length of the converter oil tank, and the arrangement direction of the three DC bushings is parallel to the arrangement direction of the plurality of converter valve side bushings. The three valve Y-side bushings are arranged at intervals along the length of the transformer tank, and the arrangement direction of the three grid-side bushings is parallel to the arrangement direction of the three valve Y-side bushings.

[0011] As one preferred embodiment, each diode valve includes multiple diodes, with adjacent diodes connected in series via crimping; wherein, twelve diode valves are arranged in an array, with four diode valves in each row.

[0012] As one preferred embodiment, the top of each diode valve is suspended from the top wall of the converter oil tank by insulating cardboard, and the bottom of each diode valve is fixed to the bottom wall of the converter oil tank by insulating cardboard.

[0013] As one of the preferred solutions, the three-phase winding structure includes three iron core main columns, two iron core side columns, and three-phase windings; Each of the iron core main columns is wound with corresponding phase windings, and each phase winding includes a grid-side winding, a voltage regulating winding, a valve Y-side winding, and a valve D-side winding. The valve Y-side winding, the mesh-side winding, the voltage regulating winding, and the valve D-side winding are wound sequentially from the radial inside to the radial outside around the outer periphery of each iron core body.

[0014] As one of the preferred solutions, both the converter oil tank and / or the transformer oil tank are equipped with: A passive cooling oil passage extends in a spiral shape, with its ends connected and communicating with a corresponding oil tank, allowing the oil to flow naturally between the corresponding oil tank and the passive cooling oil passage. An active cooling oil passage is located on the outside of the corresponding oil tank, and an oil pump and a radiator are installed on the active cooling oil passage.

[0015] As one preferred embodiment, the converter oil tank is equipped with an active flow guiding mechanism, which includes a guide baffle and multiple fuel injectors; wherein... The fuel injector is connected to the active cooling oil passage and is located above the diode valve; Each of the guide baffles is disposed between two adjacent diode valves, and the guide baffles are at a distance from at least one side of the converter oil tank to allow the oil to flow within the converter oil tank.

[0016] Compared with the prior art, this application has the following advantages: Firstly, this utility model embodiment technically modifies the converter valve and valve chamber, eliminating the traditional independent valve chamber design and directly integrating multiple high-voltage diode groups inside the converter oil tank through modular design, thus constructing a compact rectifier system. This structure fully utilizes the oil tank body as a supporting platform for the converter valve, achieving integrated design in terms of insulation, electrical connection, and heat dissipation path, significantly simplifying the system architecture and improving overall integration and engineering deployment efficiency.

[0017] Secondly, this utility model embodiment integrates the three-phase, three-winding functions by unifying the transformer tank structure and outgoing bushing arrangement, effectively simplifying the wiring structure and on-site construction, and improving the overall system integrity and coordination. A single three-phase, three-winding converter transformer achieves simultaneous three-phase conversion, reducing the workload of operation and maintenance. The previous multi-unit operation and maintenance has been reduced to a single unit, lowering the risk of operation and maintenance and improving the efficiency of substation operation and maintenance. Adopting an integrated three-phase, three-winding structure, the three-phase, three-winding converter transformer is led out horizontally from the transformer tank on the valve side, making it more suitable for scenarios with height restrictions. This reduces the overall installation height of the transformer, significantly reducing the site layout area and effectively facilitating the connection and installation of the converter tank. Attached Figure Description

[0018] To more clearly illustrate the technical solution of this application, the drawings used in the description of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is an assembly diagram of an oil-insulated three-phase integrated converter transformer system provided in one embodiment of this application; Figure 2 This is an internal structural diagram of an oil-insulated three-phase integrated converter transformer system provided in an embodiment of this application; Figure 3 This is a front view of an embodiment of the oil-insulated three-phase integrated converter transformer system provided in this application; Figure 4 This is a schematic diagram of the outlet structure of a converter valve provided in one embodiment of this application; Figure 5This is an electrical schematic diagram of a three-phase three-winding converter transformer and converter valve provided in one embodiment of this application; Figure 6 This is a schematic diagram of the wiring structure of a three-phase three-winding converter transformer and converter valve provided in one embodiment of this application.

[0020] Explanation of reference numerals in the attached figures: 1. Converter oil tank; 2. Transformer oil tank; 11. DC bushing; 12. Converter transformer valve side bushing; 13. Diode valve; 21. Grid side bushing; 22. Valve Y side bushing; 23. Valve D side bushing. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] It is understandable that in high-voltage direct current (HVDC) transmission projects, the converter system mainly consists of converter transformers, converter valves, and valve halls. In long-distance, high-power HVDC transmission, the converter valve towers primarily adopt suspended or supported structures. Taking a ±800kV HVDC transmission system as an example, each pole's converter valve consists of six double valve towers, achieving twelve-pulse converter operation through twelve single-phase, double-winding converter transformers. Each single-phase, double-winding converter transformer includes a primary winding connecting to the AC system and a secondary winding connecting to the converter, emphasizing high capacity. In this converter system, the overall height of the converter valve is close to 22 meters, occupying a large space, resulting in a long construction period and high costs. Furthermore, the converter valve arrangement requires a dedicated valve hall, which uses an air-insulated system. This system is bulky, has high civil engineering costs, and is sensitive to humidity, temperature, and environmental electric field interference, limiting its reliability. Due to the large spacing required for the air-insulated structure, the overall structure cannot be further compressed, hindering the miniaturization of highly integrated and reliable equipment.

[0023] Converter transformers also rely on the large space of the air-insulated valve hall. A twelve-pulse converter is achieved by combining multiple units, thus not constrained by the volume of the valve hall. Consequently, the equipment is also relatively large, with significant electrical spacing between units. Because multiple converter transformers are combined into a single system, firewalls and separate fire protection systems are required between each transformer. This results in a large number of devices, massive size, low integration, and the highest construction and maintenance costs.

[0024] Furthermore, the existing converter valves and converter transformers are arranged separately and need to be connected via busbars, resulting in a lengthy electrical structure, complex energy transmission paths, and an increased possibility of interphase interference and energy loss. Efficient coordination in electrical parameter matching and structural layout is also difficult to achieve. Meanwhile, the air-insulated valve hall and transformer tank 2 operate independently, and their cooling and insulation systems are independent of each other, further complicating the overall system structure and reducing integration.

[0025] It is evident that the three core components of traditional converter systems—converter valves, converter transformers, and valve halls—all suffer from numerous problems, including large size, complex structure, low integration, low heat dissipation efficiency, large footprint, difficult maintenance, and high construction costs. Therefore, referring to... Figure 1 and Figure 2 , Figure 1 This is an assembly diagram of the oil-insulated three-phase integrated converter system shown in this utility model; Figure 2 This diagram illustrates the internal structure of the oil-insulated three-phase integrated converter system of this invention, showing the arrangement of the diode valve 13 inside the converter valve. Figure 1 and Figure 2 As shown, this utility model provides an oil-insulated three-phase integrated converter system, including: a converter valve, comprising multiple connected diode valves 13 and DC side output lines and AC side output lines; a three-phase three-winding converter transformer, comprising a three-phase winding structure, each phase winding structure including a grid-side output line, a valve Y-side output line and a valve D-side output line; a converter valve oil tank 1, with a DC bushing 11 installed on the top, the DC bushing 11 leading out a DC side output line; a converter transformer valve-side bushing 12 connected to the side wall, the converter transformer valve-side bushing 12 leading out an AC side output line; a transformer oil tank 2, with a grid-side bushing 21 installed on the top, the grid-side bushing 21 leading out a grid-side output line; a valve Y-side bushing 22 and a valve D-side bushing 23 connected to the side wall, the valve Y... The valve Y-side outlet is led out from bushing 22, and the valve D-side outlet is led out from bushing 23. The converter valve is installed in the converter valve tank 1, and the three-phase three-winding converter transformer is installed in the transformer tank 2. The first part of the converter transformer valve side bushing 12 on the converter valve tank 1 is connected to the valve Y-side bushing 22 on the transformer tank 2, and the second part of the converter transformer valve side bushing 12 is connected to the valve D-side bushing 23 on the transformer tank 2. The AC side outlet is connected to the valve Y-side outlet and the valve D-side outlet in a one-to-one correspondence. Oil fills the space between the converter valve tank 1, the transformer tank 2, the converter transformer valve side bushing 12, the valve Y-side bushing 22, and the valve D-side bushing 23, forming a shared oil insulation path.

[0026] As an illustration of this embodiment, for the converter valve, an independent and enclosed converter valve tank 1 is used as the basic platform. Multiple diode valves 13 are vertically arranged inside the tank according to electrical and mechanical stability requirements. Each diode valve 13 includes multiple diodes. Depending on the required target voltage level, dozens, hundreds, or even thousands of diodes can be configured. After the multiple diode valves 13 are electrically connected inside the converter valve tank 1, they exit from inside the tank and connect to the valve-side winding output of the three-phase three-winding converter transformer, forming a complete three-phase six-pulse rectifier circuit. The diode converter valves are integrated into the converter valve tank 1, which is filled with oil, such as transformer oil, mineral oil, or synthetic ester insulating liquid. The converter valves are in contact with the oil, utilizing its insulating and heat dissipation characteristics to cool and insulate the converter, ensuring stable equipment operation and achieving a compact and integrated high-voltage rectification function. Meanwhile, since the converter valve oil tank 1 and the converter valve are integrated into one structure, the equipment is assembled at the factory and can be put into operation on site with only simple wiring, which significantly shortens the construction period.

[0027] Specifically, the DC and AC output lines of diode valve 13 are led out of converter valve tank 1 through corresponding bushings. The DC output line is led out from inside converter valve tank 1 and passes through the top DC bushing 11, connecting to a DC transmission line or DC load system to output rectified DC power. The AC output line is led out from inside converter valve tank 1 and passes through the converter transformer side bushing 12 on the side wall, connecting to the three-phase three-winding converter transformer in transformer tank 2 to input transformed AC power to diode valve 13.

[0028] For example, in the wiring process of the converter valve, the principles of insulation priority, short and straight path, heat dissipation adaptation, mechanical stability, and convenient maintenance are followed. Priority is given to the "short and straight route." The AC side outgoing line uses a new type of oil-filled bushing to be horizontally led out from the same side of the converter valve tank 1, and horizontally connected to the three-phase three-winding converter transformer. The DC side outgoing line is led out vertically from the top of the converter valve tank 1 via a DC bushing 11, reducing the number of bends. The distance between the AC side outgoing line and the tank wall of the converter valve tank 1 meets the insulation requirements; if necessary, it can be isolated by an insulating bracket. An insulating bracket can be used for fixing, or additional support points can be added. The DC side outgoing line uses a pillar-type insulating bracket, which is vertically fixed to the top inner wall of the converter valve tank 1 or below the DC bushing 11. A slot is opened at the top, and the upper end of the diode valve 13 passes through the slot and is fixed with insulating bolts to ensure verticality. The AC side output cable adopts a frame-type bracket, which is fixed to the inner wall of the side of the converter valve oil tank 1. The diode valve 13 is supported by multiple horizontal plates. The frame-type bracket can surround the conductor to form an insulation channel and enhance the creepage distance.

[0029] For a three-phase, three-winding converter transformer, this embodiment is a three-phase, three-winding converter transformer for DC transmission. The main improvement is achieved through technical modifications to the tank structure, electrical wiring, and winding arrangement strategy. This transforms the AC system voltage to the commutation voltage required by the connected converter valves, while simultaneously achieving high performance, miniaturization, low cost, and engineering friendliness of the converter transformer equipment within the converter system. Therefore, other components of the converter transformer that are not detailed herein should be readily available from known technologies, including but not limited to cooling devices, bushing structures, insulation support structures, pressure relief valves, gas relays, temperature and oil level monitoring devices, grounding and sampling accessories, etc. For clarity and brevity, these will not be elaborated upon further in this document.

[0030] Specifically, in terms of tank structure, transformer tank 2 is filled with oil for insulation and cooling. To adapt to the AC / DC conversion requirements of the converter system, the three-phase winding structure of each phase is designed based on the electromagnetic relationship of the three-phase three-winding (multi-phase multi-winding phase coupling, DC bias model, harmonic loss model), engineering practice (insulation loss, protection mechanism), and operating characteristics (short-circuit impedance, wiring method, voltage regulation range). Each phase winding structure corresponds to the grid-side output line, valve Y-side output line, and valve D-side output line. The valve Y-side output line and valve D-side output line are connected to the AC-side output line of the converter valve. The three grid-side output lines of the three-phase three-winding converter transformer are located at the top of transformer tank 2 and are directly connected to the substation overhead line or high-voltage cable through grid-side bushing 21. The top grid-side output lines are structurally far away from the ground control cabinet and secondary system, effectively reducing electromagnetic interference and improving the electrical safety of the system. The outlets of valve Y-side and valve D-side corresponding to each phase winding are respectively set on the side wall of transformer tank 2, and connected to the AC side outlets by side outlet method.

[0031] Therefore, in the grid-side layout, the top-entry method matches the insulation layout requirements of the high-voltage system. Simultaneously, the top-entry grid-side wiring is structurally far from the ground control cabinet and secondary systems, effectively reducing electromagnetic interference and improving the system's electrical safety. Combined with a lifting maintenance platform, the operation and maintenance process is simplified, and maintenance efficiency is improved. In the valve-side layout, the outgoing lines of valve Y-side bushing 22 and valve D-side bushing 23 are respectively located on the side wall of transformer tank 2, using a side-outgoing method to connect to the rectifier valve group. The valve-side outgoing lines on the same side wall not only facilitate symmetrical arrangement of the converter transformer, shortening cable length and reducing wiring inductance, but also provide a suitable installation and maintenance height, improving the safety and efficiency of human-machine operation.

[0032] For the converter system, both the converter valve tank 1 and the transformer tank 2 have side-outlet wiring. The valve-side bushings (valve Y-side bushing 22 and valve D-side bushing 23) are aligned with the converter transformer valve-side bushing 12. Each AC-side outgoing line is drawn from each converter transformer valve-side bushing 12, each valve Y-side outgoing line is drawn from each valve Y-side bushing 22, and each valve D-side outgoing line is drawn from each valve D-side bushing 23. This electrically connects each valve-side winding outgoing line in each bushing to each AC outgoing line, creating an oil-to-oil direct connection mode, meeting the maximum integration requirements of the new generation of integrated oil-to-oil converter stations. The side-outgoing wiring structure of both the converter valve tank 1 and the transformer tank 2 allows for a compact fit, outputting DC voltages from ±50kV to ±500kV, meeting the high-efficiency, low-cost, and high-reliability requirements of the high-voltage DC transmission system for new energy transmission.

[0033] The valve-side bushing also adopts a new type of oil-oil bushing. The new type of oil-oil bushing is an insulating connection device used between oil-immersed equipment and external equipment. It is immersed in oil and can play the role of electrical connection and insulation isolation.

[0034] In this embodiment, the oil circuit of the converter transformer valve-side bushing 12 is connected to the converter valve oil tank 1, and the valve-side bushing is connected to the transformer oil tank 2. The converter transformer valve-side bushing 12 and the valve-side bushing are also connected, forming a continuous shared oil insulation path. The same type of oil provides oil insulation for the entire converter system. The continuous oil path formed by the converter valve oil tank 1 and the transformer oil tank 2 enables a reliable electrical connection between the diode valve 13 and the external three-phase three-winding converter transformer. Using oil as a uniform insulating medium avoids the large electrical spacing required by traditional air insulation methods, significantly improving insulation performance. Simultaneously, the continuous oil path makes the system structure more compact.

[0035] Therefore, in the first aspect, this utility model embodiment has made technical modifications to the converter valve and valve chamber, eliminating the traditional independent valve chamber design and directly integrating multiple high-voltage diode valves 13 into the converter valve oil tank 1 through modular design, thus constructing a compact rectification system. This structure makes full use of the oil tank body as the carrier platform for the converter valve, achieving integrated design in terms of insulation, electrical connection, and heat dissipation path, greatly simplifying the system architecture and improving the overall integration and engineering deployment efficiency.

[0036] Secondly, by unifying the structure of transformer tank 2 and the arrangement of outgoing bushings, the three-phase, three-winding functions are integrated, effectively simplifying the wiring structure and on-site construction, and improving the overall system integrity and coordination. A single three-phase, three-winding converter transformer achieves simultaneous three-phase conversion, reducing the workload of operation and maintenance. The previous multi-unit operation and maintenance has been reduced to a single unit, lowering the risk of operation and maintenance and improving the efficiency of substation operation and maintenance. Adopting an integrated three-phase, three-winding structure, the three-phase, three-winding converter transformer is led out horizontally from transformer tank 2 on the valve side, making it more suitable for scenarios with height restrictions. This reduces the overall installation height of the transformer, significantly reducing the site layout area, and effectively aligns with the connection and installation of the modified converter valve tank 1.

[0037] Thirdly, the continuous oil insulation path allows the converter valve and the three-phase three-winding converter transformer to share the oil cooling circuit. The shared oil circulation system can simultaneously remove the heat generated by both the converter valve and the three-phase three-winding converter transformer, improving heat dissipation efficiency. This also avoids the need for separate cooling systems, improving energy utilization and reducing equipment operating energy consumption, thereby significantly improving the system's reliability and economy.

[0038] In this way, the converter valve and the three-phase three-winding converter transformer are connected as one unit and share the oil passage. Most of the connections can be completed at the factory, eliminating the need for additional long-distance bushings and conductors. This reduces the number of connection links, shortens the electrical connections, reduces the overall equipment size, and saves station area.

[0039] In some embodiments, the power device may also be a thyristor. This invention can be used in combination with other commutation devices to construct a hybrid rectifier system of thyristors and diodes for redundancy backup or commutation assistance, further improving system reliability and flexibility.

[0040] In further technical solutions, such as Figure 4 As shown, Figure 4 This is a schematic diagram of the outgoing line structure of the converter valve provided in this embodiment. The converter valve includes twelve diode valves 13, which are connected in a three-phase six-pulse pseudo-bipolar topology and form two sets of three-phase six-pulse bridges. The Y-side outgoing line of the three-phase winding structure valve is connected to the AC-side outgoing line of the first set of three-phase six-pulse bridges in a Y-connection. The D-side outgoing line of the three-phase winding structure valve is connected to the AC-side outgoing line of the second set of three-phase six-pulse bridges in a delta connection.

[0041] In this scheme, the twelve-pulse converter, as the mainstream converter circuit form in current converter systems, can significantly improve the output power quality and enhance the stability and economy of system operation while ensuring structural simplicity. Each group of three-phase six-pulse rectifier circuits of the converter valve requires six diode valves 13. Twelve diode valves 13 are used to form two groups of six-pulse rectifier circuits, which are connected in parallel or series to form a twelve-pulse rectifier. The electrical connection of the converter valve adopts a three-phase six-pulse pseudo-bipolar topology. Specifically, inside the converter valve tank 1, the twelve diode valves 13 are symmetrically arranged in a positive and negative polarity manner, and together with six rectifier arms, they form two groups of three-phase rectifier circuits.

[0042] Please see Figure 5 and Figure 6 , Figure 5 The electrical schematic diagram of the three-phase three-winding converter transformer and converter valve of this utility model is shown. Figure 6 The diagram illustrates the wiring structure of the three-phase three-winding converter transformer and converter valves of this invention. One set of three-phase six-pulse bridge AC side outputs is Y-connected to the valve Y-side output (A1B1C1) of the three-phase three-winding converter transformer. The other set of three-phase six-pulse bridge AC side outputs is D-connected to the valve D-side output (A2B2C2) of the three-phase three-winding converter transformer. The DC sides of the two sets of converter valves are connected in parallel, ultimately outputting a superimposed twelve-pulse DC voltage. Therefore, based on the wiring method of the three-phase six-pulse pseudo-bipolar topology and the bushing output structure in the oil, a Y / D secondary-side combination is used to achieve six-pulse DC rectification. This output method has a compact structure, short path, and low magnetic field interference, which is beneficial for improving the system's EMC performance and energy efficiency.

[0043] Correspondingly, in terms of converter circuit topology, the electrical connection of the three-phase three-winding converter transformer adopts a YY / D structure. The valve-side outputs are divided into upper and lower groups, corresponding to the input terminals of the two groups of six-pulse converter valves with Y-connection and Δ-connection, respectively. The three valve Y-side outputs (A1B1C1) are connected to the input terminals of the first group of three-phase six-pulse converter valves with Y-connection, and the three valve D-side outputs (A2B2C2) are connected to the input terminals of the second group of three-phase six-pulse converter valves with Δ-connection, respectively supplying power to the two groups of three-phase six-pulse converter bridges to meet the requirements of twelve-pulse converter. Since the valve-side windings of the converter transformer need to eliminate the third harmonic generated by the converter through special wiring (to avoid grid-side pollution), they need to be strictly matched with the symmetry of the three-phase system. The valve-side windings use Δ-connection to ensure that the three-phase phase difference is strictly 120°. Therefore, the wiring method in this embodiment effectively reduces the harmonic content of the six-pulse rectification, making the DC system operation more reliable, greatly simplifying the filter system design, and reducing the investment cost of the converter station.

[0044] In a twelve-pulse converter system, the total cost of connecting six single-phase dual-winding three-phase three-winding converter transformers or three single-phase three-winding three-phase three-winding converter transformers is prohibitively high. This requires more bushings, tap changers, and a matching transformer tank, significantly increasing the overall system investment. This embodiment of the invention places the valve-side Y winding and valve-side D winding of the AC ABC three-phase windings within the same three-phase three-winding converter transformer. Only a single three-phase three-winding converter transformer is needed to achieve twelve-pulse converter operation, maximizing the reduction in the number of devices required. The number of bushings, voltage regulators, tanks, and other components is also significantly reduced, resulting in a substantial optimization of overall manufacturing, transportation, and installation costs.

[0045] For further technical solutions, please refer to Figure 3 , Figure 3 This is a front view of an oil-insulated three-phase integrated converter system. Three DC bushings 11 are provided, and six converter transformer valve-side bushings 12 are provided. The six converter transformer valve-side bushings 12 are arranged in two rows at intervals along the height of the converter valve tank 1, with the same number of bushings 12 in each row and aligned one by one. Three grid-side bushings 21 are provided, three valve Y-side bushings 22 are provided, and three valve D-side bushings 23 are provided. The three valve Y-side bushings 22 and three valve D-side bushings 23 are aligned one by one along the height of the transformer tank 2. The three converter transformer valve-side bushings 12 in the first row are aligned with the three valve Y-side bushings 22, and three AC output lines of the first group of three-phase six-pulse bridges are led out. The three converter transformer valve-side bushings 12 in the second row are aligned with the three valve D-side bushings 23, and three AC output lines of the second group of three-phase six-pulse bridges are led out.

[0046] In this design, each bushing corresponds to one outgoing line. Specifically, the two rows of converter transformer side bushings 12 on the converter valve tank 1 correspond to two sets of three-phase six-pulse bridges, and the three converter transformer side bushings 12 in the same row lead out one set of three-phase three-phase lines. To reduce the usable area on the outside of the converter valve tank 1, the two rows of converter transformer side bushings 12 are located on one side of the converter valve tank 1, and the three converter transformer side bushings 12 in the same row are horizontally spaced apart. Two of the converter transformer side bushings 12 in the two rows are aligned vertically, maximizing the use of external space in the converter valve tank 1.

[0047] The three valve Y-side outgoing lines and three valve D-side outgoing lines each correspond to a set of three phases, and are led out through three valve Y-side bushings 22 and three valve D-side bushings 23, respectively. In order to reduce the usable area on the outside of the transformer tank 2, the valve Y-side bushings 22 and valve D-side bushings 23 corresponding to the Y and D secondary winding outgoing lines of the three-phase three-winding converter transformer are aligned in the height direction of the transformer tank 2, and the three valve Y-side bushings 22 or three valve D-side bushings 23 are spaced apart along the length or width direction of the transformer tank 2. Each corresponding valve Y-side bushing 22 and valve D-side bushing 23 are arranged side by side, maximizing the saving of external space of the transformer tank 2.

[0048] Therefore, the six converter transformer valve-side bushings 12 are arranged in two rows and three columns, and the six valve-side bushings (three valve Y-side bushings 22 and three valve D-side bushings 23) are also arranged in two rows and three columns. The row spacing and column spacing of the converter transformer valve-side bushings 12 are equal to those of the valve-side bushings. The three converter transformer valve-side bushings 12 in the first row are horizontally aligned and connected to the three valve Y-side bushings 22, and the three converter transformer valve-side bushings 12 in the second row are horizontally aligned and connected to the three valve D-side bushings 23. The three-phase three-winding converter transformer and the diode converter valve form an integrated compact structure, eliminating the need for high-voltage leads, cables, or busbars for connection. This avoids a lengthy electrical structure, complex energy transmission paths, and reduces the possibility of interphase interference and energy loss. High efficiency and coordination are achieved in electrical parameter matching and structural layout, improving the response efficiency and system coordination of the entire rectifier unit.

[0049] Preferably, three DC bushings 11 extend vertically from the top of the converter valve tank 1; six converter transformer valve-side bushings 12 extend horizontally from the side wall of the converter valve tank 1; three grid-side bushings 21 extend vertically from the top of the transformer tank 2; and three valve Y-side bushings 22 and three valve D-side bushings 23 extend horizontally from the side wall of the transformer tank 2. In this embodiment, both the DC bushings 11 and the grid-side bushings 21 are vertical bushings, while the converter transformer valve-side bushings 12 and the valve-side bushings are horizontal bushings. The top exit of the grid side can adapt to the vertical space configuration requirements of the ultra-high voltage bushings, enabling the high-voltage leads to connect to the external system via the shortest path and reducing the risk of electric field concentration in the leads. The converter transformer valve-side bushings 12 and the valve-side bushings all extend horizontally and side-by-side from the same side wall of the corresponding tank, which can accommodate the most compact interface and achieve the shortest connection path.

[0050] Furthermore, the three converter valve side bushings 12 in the same row are arranged at intervals along the length of the converter valve tank 1, and the arrangement direction of the three DC bushings 11 is parallel to the arrangement direction of the multiple converter valve side bushings 12; the three valve Y side bushings 22 are arranged at intervals along the length of the transformer tank 2, and the arrangement direction of the three grid side bushings 21 is parallel to the arrangement direction of the three valve Y side bushings 22. In this embodiment, the converter valve tank 1 and the transformer tank 2 can be set as rectangular boxes, and the horizontal bushings (converter valve side bushings 12 and valve side bushings) are set on the side wall of the box along the length of the box, and the converter valve side bushings 12 and valve side bushings are arranged along the length direction, so that the installation space can be fully utilized within the limited tank volume.

[0051] Correspondingly, the vertical bushings (DC bushing 11 and grid-side bushing 21) are arranged parallel to the horizontal bushings, meaning they are also arranged along the length of the top wall of the enclosure. This maximizes the use of the enclosure wall's installation space and allows for the design of appropriate electrical spacing. Simultaneously, the bushings extend horizontally from the side wall in a double-row, three-column arrangement, resulting in higher installation efficiency for the converter valve and converter transformer when horizontally aligned. This compresses the phase-to-phase insulation distance to the height of the tank, preventing excessive tank width and simultaneously meeting the road transport width and height restrictions for both the converter valve tank 1 and the transformer tank 2.

[0052] It is worth mentioning that the six valve-side bushings of the converter transformer in this embodiment can also be arranged in a single row of six columns, three rows of double columns, or six rows of single columns on the side wall of the transformer tank 2, integrating the Y-connected and Δ-connected valve-side windings into one unit, and completing twelve-pulse commutation with a single unit. Compared with the traditional structure of the converter transformer, this can still be considered an optimized solution, resulting in a smaller footprint, fewer bushings, and the highest system integration. In actual design, the arrangement of the valve-side bushings of the converter transformer directly affects the safety, reliability, and economy of the equipment. This embodiment is based on multiple dimensions of design goals, including space optimization, mechanical strength, converter valve connection, insulation performance, balancing cost, and engineering implementation difficulty. Through dedicated simulation tools, it optimizes from scratch and designs a double-row parallel arrangement, achieving multiple goals.

[0053] Specifically, in the actual implementation process: In terms of mechanical strength: Transformer tank 2 has a box-type structure with vertical plane structures on its sides (side walls). It primarily bears the radial load (horizontal outward force generated by its own weight) and short-circuit electrodynamic force (horizontal impact force) of the bushings. Its stress logic differs from that of the top (which primarily bears vertical loads). This embodiment uses this design to distribute the radial load across two height ranges of the side walls, reducing the load per row by 50%. Therefore, two rows of support structures can be installed on the inner side wall of transformer tank 2, with the support structures and valve-side bushing assemblies located on the same side wall of transformer tank 2. The two rows of support structures are spaced apart along the height direction of transformer tank 2, and valve Y-side bushing 22 is fixed to the upper side wall of transformer tank 2 via the upper row of support structures, while valve D-side bushing 23 is fixed to the lower side wall of transformer tank 2 via the lower row of support structures. This adapts to the stress characteristics of the side walls and reduces the risk of deformation. Thus, the support structures (such as reinforcing ribs) can be arranged in a distributed manner (each row of bushings corresponds to an independent small reinforcing frame), resulting in a more uniform stress distribution in the overall structure.

[0054] Regarding the connection with the converter valve: The converter valve is located on the side of the converter transformer (on the same side as the bushing). The connection between the valve-side bushing and the converter valve is mainly a horizontal rigid busbar (copper busbar or aluminum tube). The path length and direction directly affect the electrical performance. In this embodiment, through this design, it can be directly connected to the converter valve (the upper row valve Y-side bushing 22 connects to the upper row converter transformer valve-side bushing 12, and the lower row valve D-side bushing 23 connects to the lower row converter transformer valve-side bushing 12). The busbar path is shortened to 2-3m (straight horizontal connection), stray inductance can be controlled within 10-15μH, and overvoltage amplitude is reduced by 20%-30%. In addition, the shorter busbar has better rigidity, does not require intermediate support, and reduces electric field distortion points; at the same time, the thermal expansion and contraction of the horizontal busbar can be easily compensated by the end expansion joints (a single row of long busbars requires multi-stage compensation), resulting in higher connection reliability.

[0055] Regarding transportation: The transportation of converter transformers must meet width, height, and weight restrictions. The arrangement of the side bushings directly affects the equipment's "outline dimensions" and weight distribution. This embodiment utilizes a design where the double-row valve-side bushings are staggered in the height direction, with the lateral protrusion width determined only by the diameter of a single valve-side bushing (0.8-1.2m). This eliminates the need to exceed transportation width restrictions, enabling "integrated transportation" (bushing pre-installation) and saving on-site installation time. Simultaneously, the distributed load distribution between the upper and lower rows makes the tank's center of gravity more central, resulting in more even stress on the vehicle during transportation and reducing the risk of overturning. Furthermore, the distributed support structure (such as independent upper and lower row reinforcing frames) is 8%-12% lighter than a single-row / single-column concentrated "heavy-duty frame," making it easier to meet weight restrictions.

[0056] Regarding insulation: The side-mounted valve bushings are directly exposed to the external environment (rain, snow, dust, dirt), and the electric field distribution is affected by the three-dimensional space of "sidewall-bushing-air," making the arrangement more significant to insulation reliability. This embodiment utilizes this design to effectively increase the phase-to-phase distance between the upper and lower rows, reducing electric field coupling. The root field strength can be reduced to 25-30 kV / cm (no need for ultra-large equalizing rings; a diameter of 1.5m-2m is sufficient). The upper row valve Y-side bushing 22 provides some shielding for the lower row valve D-side bushing 23, reducing direct rainwater erosion of the lower row valve side bushing surface. Since the angle of sunlight on the side (such as direct sunlight at noon in summer) can cause the bushing temperature to rise, the vertical spacing between the upper and lower rows increases air convection space, reducing local temperature rise (measured temperature difference can reach 5-8℃), and preventing high temperatures from accelerating insulation aging.

[0057] In terms of cost: the cost of side bushing arrangement needs to be evaluated in conjunction with the entire process of "manufacturing-transportation-operation and maintenance". The advantage of double-row arrangement is reflected in long-term economic efficiency. In this embodiment, this design eliminates the need for detachable structures. Therefore, the grid-side bushing, valve Y-side bushing 22, and valve D-side bushing 23 are all fixed to the transformer tank 2. Distributed support results in lower material consumption (reduced by 8%-12%); overall transportation saves on-site disassembly and assembly costs; improved insulation reliability extends the operation and maintenance cycle (from 3 years to 5 years), and the total life cycle cost can be reduced by 15%-20%.

[0058] To take into account the above-mentioned advantages, the specific structural form of the transformer tank 2 is as follows: height 12.6m, length 7.5m, and width 5.9m; the spacing between two adjacent valve Y-side bushings 22 is greater than 1.5m; the spacing between each pair of valve Y-side bushings 22 and valve D-side bushings 23 aligned vertically is 1.5m-2m. Furthermore, this design avoids problems such as insulation failure due to excessively small horizontal spacing of bushings in the same row, creepage and flashover due to insufficient vertical spacing of bushings in the same column, and excessive stress on bushings, structural damage, insufficient maintenance space, and accelerated dirt accumulation due to excessively small bushing spacing in the same row and column. It also avoids situations where excessively large horizontal and / or vertical spacing exceeds the installation space of the transformer tank 2, preventing further reduction of the converter system volume. Correspondingly, the converter valve tank 1 is set up in a similar manner to ensure direct alignment between the two.

[0059] In summary, compared to single-row centralized arrangement, which is only suitable for low-voltage, small-capacity scenarios due to transportation limitations, concentrated stress, and insulation risks, three-row two-by-two arrangement increases the tank height (potentially exceeding transportation height limits) and the connection path of the middle row bushings is complex, resulting in very few engineering applications. The three-phase three-winding converter transformer structure provided in this embodiment has advantages in multiple dimensions, including space optimization, mechanical strength, converter valve connection, insulation performance, cost balancing, and engineering implementation difficulty, and can adapt to space-constrained converter station scenarios. Similarly, the converter valve should also have similar effects.

[0060] In another technical solution, each diode valve 13 includes multiple diodes, with adjacent diodes connected in series via press-fit. Twelve diode valves 13 are arranged in an array, with four diode valves 13 in each row. In this embodiment, each diode valve 13 consists of two series-connected diode groups, each group containing thirty diodes, for a total of sixty series-connected units. The diodes are connected via a press-fit structure, which enables a high-density, shock-resistant, and integrated insulating structural arrangement. Each diode can be equipped with a damping resistor, a capacitor, and a voltage-equalizing resistor to form a standardized submodule. This standardized diode module ensures voltage equalization and surge absorption performance, thereby improving overall operational stability. This design optimizes the coordinated operation performance between modules and enhances the system's anti-interference capability and long-term operational stability.

[0061] Specifically, multiple diode valves 13 are arranged in a matrix array within the converter valve tank 1, saving tank volume compared to a distributed arrangement. The rows are aligned with the width of the converter valve tank 1, the columns with the length, and the vertical arrangement with the height. In some alternative embodiments, twelve diode valves 13 can be arranged in a single row of twelve columns within the converter valve tank 1. Alternatively, twelve diode valves 13 can be arranged in a double row of six columns within the converter valve tank 1. Alternatively, twelve diode valves 13 can be arranged vertically in multiple layers within the converter valve tank 1. However, this design can lead to excessive width, length, or height in the tank design, resulting in transportation difficulties and challenges in minimizing the usable area.

[0062] Preferably, to meet the size restrictions of highway transportation and fully consider the width and height restrictions of domestic highway transportation, the width of the converter valve tank 1 should be controlled at 4.5m and the height should not exceed 4.9m, so as to achieve overall transportation and on-site immediate use. To meet the size restrictions of highway transportation and fully consider the width and height restrictions of domestic highway transportation, the twelve diodes are arranged in three rows and four columns in the converter valve tank 1. In the three-row, four-column structure of this embodiment, the distance between rows and columns is equal, and each row and two columns correspond to two valve arms of a phase group. The array-arranged diode valves 13 are set in the middle area of ​​the converter valve tank 1, with a reserved gap between the valves. Therefore, the converter valve structure design of this utility model embodiment can achieve compact installation of the diode valves 13 within the limited volume of the converter valve tank 1, and ensure electrical symmetry and uniform heat dissipation. Moreover, the reasonable insulation design can ensure the dielectric safety of the system under high voltage operation. Combined with the novel electrical connection method, the structure is compact and the heat dissipation path is reasonable, effectively reducing power loss and thermal stress concentration.

[0063] To further improve the space utilization of the converter valve oil tank 1 and minimize its usable area, the top of each diode valve 13 is suspended from the top wall of the converter valve oil tank 1 by insulating cardboard, and the bottom of each diode valve 13 is fixed to the bottom wall of the converter valve oil tank 1 by insulating cardboard. Therefore, by optimizing the internal space layout of the converter valve oil tank 1, a multi-column suspension arrangement between diode valves 13 is supported, taking into account electrical insulation, safety clearance, and oil convection heat dissipation requirements.

[0064] In another technical solution, a monitoring element is provided inside the converter valve oil tank 1, and the monitoring line of the monitoring element extends out of the converter valve oil tank 1 along the edge of at least one side wall of the converter valve oil tank 1; the monitoring line is fixed to the corresponding side wall of the converter valve oil tank 1 by an insulating clip.

[0065] In this embodiment, monitoring elements can be installed inside the converter valve oil tank 1. These monitoring elements may include temperature sensors, oil level gauges, and pressure sensors, used to monitor signals such as temperature, oil level, and pressure within the converter valve oil tank 1, and transmit these signals to the external converter station via corresponding auxiliary lines. After completing the wiring of the AC and DC side outgoing lines, the auxiliary lines are designed to run away from the main leads within the converter valve oil tank 1, preferentially following the inner wall edge or corners of the converter valve oil tank 1. After the auxiliary lines are led out from the monitoring elements (e.g., the temperature sensor at the bottom of the converter valve oil tank 1, the oil level gauge at the top of the converter valve oil tank 1), they are centrally inserted into an insulating protective tube (such as a PTFE tube) and then led to the terminal box outside the converter valve oil tank 1.

[0066] Furthermore, insulating clips (spaced ≤ 50cm) can be used to fix the transformer to the inner wall of the converter valve tank 1 to prevent sagging and vibration wear. The wiring connections are sealed with waterproof terminals to prevent transformer oil from seeping in and causing a short circuit.

[0067] Thus, this application ensures that the insulation distance between leads of different voltage levels and between leads and grounding components (such as the tank wall) meets design standards through reasonable wiring, avoiding partial discharge or short circuits. Lead length is reduced to lower impedance loss, while redundant bending is avoided (to prevent corona or mechanical wear). Simultaneously, AC side outgoing lines, DC side outgoing lines, and auxiliary lines do not obstruct the oil circulation path inside the converter valve tank 1, preventing localized overheating. Furthermore, it resists the effects of short-circuit electrodynamics, vibration (transportation / operation), and its own weight, ensuring reliable fixation. The wiring path is clear and free of hidden dead corners, facilitating inspection of insulation status and joint tightness.

[0068] As a further explanation of this embodiment, the three-phase winding structure includes three iron core main columns, two iron core side columns, and three-phase windings; wherein, each iron core main column is wound with corresponding phase windings, each phase winding including a grid-side winding, a voltage regulating winding, a valve Y-side winding, and a valve D-side winding; the valve Y-side winding, grid-side winding, voltage regulating winding, and valve D-side winding are wound sequentially from the radial inside to the radial outside around the outer periphery of each iron core body.

[0069] In this embodiment, a five-column core design is adopted, with three main columns and two side columns. Three main yokes are wound around each phase winding. Each phase valve Y-side winding corresponds to a corresponding valve Y-side lead-out line, and each phase valve D-side winding corresponds to a corresponding valve D-side lead-out line. Two side yokes are used for flux closure. The voltage regulating winding compensates for grid-side voltage fluctuations (e.g., within ±10%) in real time to ensure stable valve-side commutation voltage. The voltage regulation speed of the three-phase, three-winding converter transformer can complete ±1% adjustment within 200ms. Its voltage regulation speed and range are optimized through co-simulation based on the control algorithm of the external converter valve.

[0070] The windings, from the inside out, are: valve Y-side winding, grid-side winding, voltage regulating winding, and valve D-side winding. This arrangement considers both heat dissipation balance and insulation coordination, and rationally distributes the internal windings. It employs a winding structure with an internal valve-side Y-winding, a centrally located AC winding, and an externally located valve-side D-winding, achieving effective electromagnetic shielding and mechanical balance within the five-limb core. In particular, the AC winding acts as a magnetic barrier layer, significantly reducing electromagnetic interference between the valve-side windings. The symmetrical arrangement also facilitates self-balancing of axial and radial forces, improving short-circuit withstand capability and mechanical stability. In terms of manufacturing and maintenance, the standardized winding structure reduces manufacturing errors and the complexity of spare parts management, offering significant advantages in engineering implementation.

[0071] In another embodiment, both the converter valve tank 1 and / or the transformer tank 2 are equipped with: The passive cooling oil channel extends in a spiral shape, with its ends connected and linked to the corresponding oil tank, allowing for natural flow of oil between the tank and the channel. The active cooling oil channel is located outside the corresponding oil tank and is equipped with an oil pump and radiator. In this embodiment, the oil channel arrangement can employ a natural oil circulation method, passively cooling the diode valve 13 in the converter valve tank 1 and the three-phase winding structure in the transformer tank 2 through natural oil circulation. During passive cooling, the heat-generating elements (the diode valve 13 body and the three-phase winding structure) are directly placed inside the corresponding oil tank. Therefore, the heat-generating elements, the gaps between elements, and the internal space of the tank naturally form a cooling space. The heat-generating elements generate heat during operation, and the oil envelops them. There is no forced power device inside the tank; the oil flows axially from the bottom to the top of the heat-generating elements, carrying away their heat. Specifically, within the formed cooling space, hot oil rises to the top of the oil tank or the external radiator, cools down, and sinks back into the coolant, forming a closed loop of heat rise and cool fall. By reducing flow resistance, this ensures that the oil flow covers all heat-generating areas. A spiral-shaped passive cooling oil channel is installed inside the oil tank. The spiral extends parallel to the height of the oil tank and is a tubular structure with openings at both the top and bottom, connecting to the top area of ​​the oil tank and the bottom area, further guiding the oil to form a heat rise and cool fall flow path.

[0072] Furthermore, the converter valve tank 1 and / or transformer tank 2 are equipped with an active cooling oil channel located on the outside of the corresponding tank. An oil pump and a radiator are installed on the active cooling oil channel. In this embodiment, the oil channel arrangement can also be designed as a forced oil circulation method, using power to drive the oil flow for active cooling of the heat-generating components. In this embodiment, the active cooling oil channel is connected to the outside of the converter valve tank 1 and / or transformer tank 2, and an oil pump and an air-cooled or water-cooled radiator are installed on the active cooling oil channel. In this embodiment, an oil inlet is provided at the top of the side wall of the converter valve tank 1 and / or transformer tank 2, and an oil outlet is provided at the bottom of the side wall, communicating with the active cooling oil channel to form an external cooling circulation loop. The oil pump provides external driving force, and the radiator releases the heat in the oil to the air cooling medium, reducing the return oil temperature. Therefore, under high load, high ambient temperature, or when the natural oil cooling cycle is inefficient, the active cooling oil passages, oil pump, and radiator can form a directional forced flow, optimize the oil flow velocity (1m / s-2m / s) and path, and enhance heat dissipation efficiency.

[0073] In some embodiments, multiple heat sinks can be provided on the surface of the diode valve 13 to provide directional cooling for each diode valve 13. Further, a spiral oil passage of 30mm-100mm is provided between the inner wall of the converter valve oil tank 1 and the heat sink of the valve string. This size can be varied according to the heat dissipation to ensure that cold oil can enter the bottom of the valve string from the bottom of the oil tank, and hot oil overflows from the top to the upper part of the oil tank or the external heat sink.

[0074] To further guide the oil from the top down to the bottom of the valve, a flow guide ramp is provided on the bottom wall of the converter valve tank 1; the bottom of the flow guide ramp is aligned with the bottom of each diode valve 13. In this embodiment, the inclined bottom end of the flow guide ramp is aligned with the bottom of the diode valve 13, allowing the cold oil to naturally converge to the bottom of the diode valve 13, avoiding oil stagnation or the formation of dead zones at the bottom. The flow guide ramp can be formed by changing the geometry of the bottom wall of the converter valve tank 1, or it can be an inclined structural component provided on the bottom wall of the converter valve tank 1.

[0075] In a further technical solution, an active flow guiding mechanism is provided inside the converter valve oil tank 1. This mechanism includes guide baffles and multiple oil nozzles. The oil nozzles are connected to the active cooling oil passages and are located above the diode valves 13. Each guide baffle is positioned between two adjacent diode valves 13, and the guide baffles are spaced apart from at least one side of the converter valve oil tank 1 to allow oil to flow within the tank. This embodiment provides a forced flow guiding mechanism, including guide baffles and oil nozzles, within the converter valve oil tank 1 to ensure the effective cooling of the active cooling system.

[0076] Specifically, the oil injector is positioned at the top of the converter valve oil tank 1, above the diode valve 13. Cooled oil, after being cooled by the radiator, is evenly sprayed onto the valve body, flushing the diode valve 13 and quickly removing heat from the upper hot oil. In this embodiment, guide baffles are installed between the valves to enhance the adhesion and flushing of the oil onto the valve surface of the diode valve. Simultaneously, a gap is maintained between the guide baffles and the tank wall, establishing a semi-enclosed flow channel. This guides most of the oil to flush the valve body and prevents oil isolation, ensuring that the oil flows uniformly from the outlet to the active cooling oil passage.

[0077] Therefore, the compact design of the converter valve and the three-phase three-winding converter transformer require higher heat dissipation. This embodiment can combine natural oil circulation and forced oil circulation design, so that the insulating oil can efficiently absorb heat and release it quickly through the oil tank wall, radiator and other heat dissipation surfaces, thereby reducing the average oil temperature. This solves the problem of insufficient heat dissipation efficiency in the traditional single oil channel design and ensures the operational reliability and thermal stability of the converter system under high voltage and high current conditions.

[0078] In conjunction with the above embodiments, the design of the cooling space, passive cooling oil channels, and guide ramps specifically guides the oil flow through the diode's heating area, eliminating hot spots and preventing oil flow turbulence (such as localized eddies) caused by excessive temperature differences, or stress deformation caused by uneven heating of the oil tank structure. Furthermore, the guide baffles reduce oil flow resistance (e.g., avoiding sharp turns and narrow channels), minimizing energy loss during oil circulation, improving oil flow efficiency, and avoiding dead zones.

[0079] In summary, oil-immersed converter valve halls represent the future trend. This application achieves structural reconstruction and system upgrade of the converter valve, designs an oil-immersed converter valve hall, and integrates a press-fit diode converter valve into the converter valve tank 1. The overall equipment structure height is reduced to less than 5m, and the volume is significantly reduced, meeting transportation specifications and reducing the station's footprint requirements. For the designed oil-insulated converter valve hall, the tank space is extremely small. To achieve twelve-pulse converter operation, multiple converter transformers need to be connected from multiple sides or the same side of the tank. The bushings of multiple converter transformers are dispersed, and the span between them is large. Therefore, the bushings need to be distributed on different side walls of the converter valve tank or interfere with each other on the same side. The space between the bushings conflicts, making it difficult to completely align with the new valve hall, and may even prevent them from extending into the converter valve tank due to excessive span. This application further designs a three-phase, three-winding converter transformer, integrating the six valve-side bushings of the three-phase, three-winding converter transformer in double rows onto the same side of the transformer tank 2. These bushings extend horizontally and connect quickly to the six valve-side bushings 12 of the converter valve tank 1, eliminating the need for busbar connections and achieving the shortest connection path. This converter system is applicable to high-voltage direct current transmission projects (such as LCC-HVDC) and meets the development requirements of next-generation high-voltage transmission systems in terms of compactness, low cost, and high reliability.

[0080] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0081] It should also be noted that, in this document, the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations, nor should they be construed as indicating or implying relative importance. Moreover, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device.

Claims

1. An oil-insulated three-phase integrated converter transformer system, characterized in that, include: The converter valve includes multiple connected diode valves as well as DC-side and AC-side outputs; A three-phase, three-winding converter transformer, including a three-phase winding structure, wherein each phase winding structure includes a grid-side output line, a valve Y-side output line, and a valve D-side output line; The converter oil tank is filled with oil and the converter valve. A DC bushing is installed on the top, and the DC side line is led out from the DC bushing. The side wall is connected to the converter transformer side bushing, and the AC side line is led out from the converter transformer side bushing. The transformer tank is filled with oil and the three-phase three-winding converter transformer. A grid-side bushing is installed on the top, and the grid-side output line is led out from the grid-side bushing. A valve Y-side bushing and a valve D-side bushing are connected to the side wall. The valve Y-side bushing leads out from the valve Y-side output line, and the valve D-side bushing leads out from the valve D-side output line. Specifically, the first part of the converter transformer valve-side bushing on the converter oil tank is connected to the valve Y-side bushing on the transformer oil tank, and the second part of the converter transformer valve-side bushing is connected to the valve D-side bushing on the transformer oil tank; and the AC side output line is connected to the valve Y-side output line and the valve D-side output line in a one-to-one correspondence.

2. The oil-insulated three-phase integrated converter transformer system according to claim 1, characterized in that, The converter valve includes twelve diode valves, which are connected in a three-phase six-pulse pseudo-bipolar topology and form two sets of three-phase six-pulse bridges. The valve Y-side output of the three-phase winding structure is connected to the AC-side output of the first group of three-phase six-pulse bridges using a Y-connection; the valve D-side output of the three-phase winding structure is connected to the AC-side output of the second group of three-phase six-pulse bridges using a Δ-connection.

3. The oil-insulated three-phase integrated converter transformer system according to claim 2, characterized in that, There are three DC bushings and six converter valve side bushings. The six converter valve side bushings are arranged in two rows at intervals along the height direction of the converter oil tank. The number of converter valve side bushings in each row is the same and they are aligned one by one. There are three grid-side bushings, three valve Y-side bushings, and three valve D-side bushings. The three valve Y-side bushings and the three valve D-side bushings are aligned one-to-one in the height direction of the transformer tank. The three converter transformer valve side bushings in the first row are aligned with the three valve Y side bushings, and the three AC side outgoing lines of the first group of three-phase six-pulse bridges are led out. The three converter valve side bushings in the second row are aligned with the three valve D side bushings, and the three AC side outgoing lines of the second group of three-phase six-pulse bridges are led out.

4. The oil-insulated three-phase integrated converter transformer system according to claim 3, characterized in that, Three of the DC bushings extend vertically from the top of the converter oil tank; six of the converter valve side bushings extend horizontally from the side wall of the converter oil tank. The three grid-side bushings extend vertically from the top of the transformer tank; the three valve Y-side bushings and the three valve D-side bushings extend horizontally from the side wall of the transformer tank. In this configuration, each converter transformer valve-side bushing in the first row is horizontally aligned with each valve Y-side bushing; and each converter transformer valve-side bushing in the second row is horizontally aligned with each valve D-side bushing.

5. The oil-insulated three-phase integrated converter transformer system according to claim 3, characterized in that, The three converter valve side bushings in the same row are arranged at intervals along the length of the converter oil tank, and the arrangement direction of the three DC bushings is parallel to the arrangement direction of the plurality of converter valve side bushings. The three valve Y-side bushings are arranged at intervals along the length of the transformer tank, and the arrangement direction of the three grid-side bushings is parallel to the arrangement direction of the three valve Y-side bushings.

6. The oil-insulated three-phase integrated converter transformer system according to claim 2, characterized in that, Each of the diode valves includes multiple diodes, with adjacent diodes connected in series by crimping; wherein, twelve of the diode valves are arranged in an array, with four diode valves in each row.

7. The oil-insulated three-phase integrated converter transformer system according to claim 2, characterized in that, The top of each diode valve is suspended from the top wall of the converter oil tank by insulating cardboard, and the bottom of each diode valve is fixed to the bottom wall of the converter oil tank by insulating cardboard.

8. The oil-insulated three-phase integrated converter transformer system according to claim 1, characterized in that, The three-phase winding structure includes three iron core main columns, two iron core side columns, and three-phase windings; Each of the iron core main columns is wound with corresponding phase windings, and each phase winding includes a grid-side winding, a voltage regulating winding, a valve Y-side winding, and a valve D-side winding. The valve Y-side winding, the mesh-side winding, the voltage regulating winding, and the valve D-side winding are wound sequentially from the radial inside to the radial outside around the outer periphery of each iron core main column.

9. The oil-insulated three-phase integrated converter transformer system according to claim 1, characterized in that, The converter oil tank and / or the transformer oil tank are each equipped with: The passive cooling oil passage extends in a spiral shape, with its ends connected and communicating with the corresponding oil tank, allowing the oil to flow naturally between the corresponding oil tank and the passive cooling oil passage.

10. The oil-insulated three-phase integrated converter transformer system according to claim 9, characterized in that, The converter oil tank and / or the transformer oil tank are equipped with: An active cooling oil passage is located on the outside of the corresponding oil tank, and an oil pump and a radiator are installed on the active cooling oil passage.

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