A high power four quadrant converter system

Abstract

This invention discloses a high-power four-quadrant converter system, comprising a dual-secondary-side oil-immersed rectifier transformer whose output is connected to four three-phase bridge thyristor rectifiers. Each pair of rectifier bridges shares a set of secondary windings of the rectifier transformer. Two rectifier bridges sharing the same set of secondary windings are connected in anti-parallel, with one bridge providing forward output and the other providing reverse output. Two sets of rectifier bridges providing output in the same direction can operate independently or in parallel. When two sets of rectifier bridges operate in parallel, current sharing is achieved through parallel reactors. The forward and reverse output rectifier bridges transition smoothly under the control of a controller, thus achieving four-quadrant operation of the output current. The integration method of this invention results in a centrally symmetrical system layout and strong electromagnetic compatibility of sensitive components during system operation. The output busbars of two rectifier bridges within the same rectifier unit can be very close, saving installation space and improving the stability of the supporting structure.

Description

Technical Field

[0001] This invention relates to the field of current rectifier system integration technology, specifically to a high-power four-quadrant converter system. Background Technology

[0002] Currently, the methods for integrating high-current rectifier systems all follow the traditional in-phase anti-parallel rectifier system integration technology. This technology mainly requires the parallel integration of all rectifiers and smoothing reactors. Therefore, this system design has a large footprint and poor electromagnetic compatibility.

[0003] To meet the requirements of the ITER poloidal field converter, a major international collaborative scientific project, a high-power rectifier capable of outputting a maximum voltage of 1kV and a DC current of 60kA while simultaneously operating in all four quadrants is required. This rectifier system needs to integrate all subsystems within a limited space; traditional methods cannot satisfy the system integration requirements. Therefore, a novel method was designed for system integration, and its correctness was verified by installing a prototype rectifier system. Summary of the Invention

[0004] The present invention proposes a high-power four-quadrant converter system that can solve at least one of the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A high-power four-quadrant converter system includes a dual-secondary-side oil-immersed rectifier transformer whose output is connected to four three-phase bridge thyristor rectifiers, wherein each pair of rectifier bridges shares a set of rectifier transformer secondary sides.

[0007] Two rectifier bridges sharing the same set of rectifier transformer secondary sides are connected in anti-parallel. If one of these two rectifier bridges achieves forward output, the other will achieve reverse output.

[0008] The two sets of rectifier bridges with the same output direction can operate independently or in parallel; when the two sets of rectifier bridges are operating in parallel, current sharing is achieved through parallel reactors.

[0009] The rectifier bridges for forward and reverse outputs achieve a smooth transition under the control of the controller, thus enabling four-quadrant operation of the output current.

[0010] Furthermore, it includes both AC and DC components. The AC component includes high-voltage cable terminals, AC disconnect switches, surge arresters, rectifier transformers, AC busbars, and high-voltage busbars that connect the equipment to each other.

[0011] The AC high-voltage cable is connected to the rectifier transformer via cable terminals, AC disconnect switches, surge arresters, and surge arresters; the cable terminals, AC disconnect switches, and surge arresters are installed on the same steel structure support, which is required to be reliably grounded at multiple points.

[0012] The DC section includes a rectifier bridge, bypass, reactor, controller, and DC bus for interconnecting the equipment.

[0013] The four rectifier bridges are connected to the input of the reactors via a DC water-cooled bus, and the outputs of the reactors are connected in parallel and then output through a DC disconnect switch.

[0014] Furthermore, the three-phase AC busbars in the AC section must adopt a closed structure;

[0015] The AC busbar requires a reliable electrical connection between the three phase shielding layers and a single-point grounding.

[0016] Furthermore, it also includes reserved interfaces at both ends to meet the scalable connection mode, serving as the connection medium between the AC and DC parts.

[0017] Furthermore, a bypass cabinet is also included for system protection. One end of the bypass cabinet is connected to the rectifier bridge via a flexible connection, and the other end is connected to the rectifier bridge via a flexible connection. It is positioned in the middle of the four rectifier bridges, with a clearance of not less than 800mm from the rectifier bridges.

[0018] Furthermore, the rectifier bridge includes two rectifier bridges sharing the secondary side of the rectifier transformer. One rectifier bridge has a positive output and is named the positive bridge, while the other has a negative output and is named the negative bridge. The positive bridge and the negative bridge together form a rectifier unit. The positive bridge and the negative bridge sharing the secondary side of the rectifier transformer cannot work at the same time, and the clearance distance between the two sets of rectifier units cannot be less than 2 meters.

[0019] Furthermore, the reactor comprises two reactors arranged one above the other with a clearance of not less than 800 mm. The taller reactor is fixed to the surface of the other reactor using a non-magnetic material.

[0020] Furthermore, the DC disconnect switches are arranged vertically with a clearance distance of not less than 1.5m; the DC disconnect switches are fixed with a steel structure.

[0021] Furthermore, the DC busbar is an aluminum busbar with a cross-section of 200×60mm and a water passage hole diameter of 20mm in the middle. The aluminum busbar is fixed to the suspension beam by insulators, and the suspension beam is connected to the main steel structure by bolts.

[0022] Furthermore, the clearance between each control cabinet and the rectifier bridge is not less than 1m; a 200mm channel steel is installed under the control cabinet as a support to facilitate the electrical connection between each control cabinet.

[0023] As can be seen from the above technical solution, the high-power four-quadrant converter system of the present invention, especially the system integration design of non-in-phase anti-parallel rectifiers with a single unit current exceeding 30kA and a total current exceeding 100kA, is particularly applicable to four-quadrant current operation scenarios. The present invention avoids the defects of traditional system integration methods, saves installation space, and makes the system more compact and aesthetically pleasing. It effectively fills the gap in high-power rectifier system integration methods based on non-in-phase anti-parallel structures and can be effectively applied in fields such as electrolytic aluminum, metallurgy, and nuclear fusion experimental devices. The integration method of the present invention makes the system equipment layout symmetrical along the central axis, making installation more convenient. The integration method of the present invention allows all connections between system equipment to be made by bolting with flexible connections, avoiding severe localized overheating at equipment joints caused by poor welding processes. Since all joints are bolted, the system can be easily disassembled and assembled, facilitating necessary return-to-factory maintenance and repair.

[0024] This invention achieves its goal by interconnecting devices via flexible connections, allowing for appropriate amplification of positioning deviations in key components. The integration method of this invention ensures a centrally symmetrical system layout, resulting in a centrally symmetrical magnetic field distribution during system operation. Charged conductors located along the centerline experience equal and opposite magnetic forces. This reduces the difficulty of designing, processing, and manufacturing subsequent support structures. Furthermore, the integration method ensures a centrally symmetrical system layout and strong electromagnetic compatibility for sensitive components during system operation. The output busbars of the two rectifier bridges within the same rectifier unit can be very close together, saving installation space and improving the stability of the support structure. Attached Figure Description

[0025] Figure 1 This is the electrical schematic diagram of the present invention;

[0026] Figure 2 This is a schematic diagram of the overall top view structure of the present invention;

[0027] Figure 3 This is a schematic diagram of the AC side main view angle according to an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the DC side main view angle according to an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of the DC side from a top view according to an embodiment of the present invention;

[0030] 1. Converter; 2. Bypass cabinet; 3. DC reactor; 4. DC disconnect switch; 5. Control cabinet; 6. Water distributor; 7. DC busbar; 8. Cable trough; 9. AC disconnect switch; 10. Rectifier transformer; 11. Enclosed AC busbar. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0032] like Figure 1 As shown, the high-power four-quadrant converter system described in this embodiment includes a dual-secondary-side oil-immersed rectifier transformer 10 (hereinafter referred to as the rectifier transformer) whose output is connected to four three-phase bridge thyristor rectifiers (hereinafter referred to as the rectifier bridge). Figure 1 The rectifier bridges (CU1-C1, CU1-C2, CU2-C1, and CU2-C2) share a common set of secondary windings. (CU1-C1 and CU2-C2 share one set of secondary windings, while CU2-C1 and CU2-C2 share another set.) To achieve four-quadrant operation, the two rectifier bridges sharing the same set of secondary windings need to be connected in anti-parallel. One of these two rectifier bridges (e.g., CU1-C1 and CU2-C1) outputs in the forward direction, while the other outputs in the reverse direction (e.g., CU1-C2 and CU2-C2). Two sets of rectifier bridges outputting in the same direction (e.g., CU1-C1 and CU2-C1 or CU1-C2 and CU2-C2) can operate independently or in parallel. When two sets of rectifier bridges are operating in parallel, current sharing must be achieved through parallel connection of reactors (200uH) to ensure reliable parallel operation. The rectifier bridge with forward and reverse output (hereinafter referred to as the positive bridge or the reverse bridge) can achieve a smooth transition under the control of the controller, thus enabling four-quadrant operation of the output current.

[0033] The following details the specific implementation method as follows: Figure 2 As shown:

[0034] The main components of this invention can be divided into two parts: AC and DC. The main components of the AC part include high-voltage cable terminals, AC disconnect switches 9, surge arresters, rectifier transformers, AC busbars 11, and high-voltage busbars connecting the equipment. The main components of the DC part include rectifier bridges, bypass cabinets 2, DC reactors 3, controllers, and DC busbars connecting the equipment.

[0035] The system integration method of the communication section is as follows: Figure 3 As shown, the AC high-voltage cable is connected to the rectifier transformer via cable terminations, AC disconnect switches, surge arresters, and surge arresters. The cable terminations, AC disconnect switches, and surge arresters are all mounted on the same steel structural support, which requires reliable multi-point grounding.

[0036] Because the high-power four-quadrant rectifier system is a non-in-phase reverse parallel system and needs to pass through the wall from outdoors to indoors, the three-phase AC busbar must adopt a closed structure. Simultaneously, the AC busbar requires reliable electrical connection between the three-phase shielding layers and single-point grounding. Furthermore, interfaces must be reserved at both ends to accommodate a retractable connection mode, serving as the connection medium between the AC and DC sections.

[0037] The system integration method of the DC section is as follows: Figure 3 As shown. The four rectifier bridges are connected to the reactor input via a DC water-cooled bus, and the reactor outputs are connected in parallel and output through a DC disconnect switch 4. Since the load of the high-power four-quadrant rectifier system in this embodiment of the invention is a large inductive load, a bypass cabinet 2 is added to the system for system protection.

[0038] The bypass cabinet 2 is connected to the rectifier bridges (CU1-C1) at one end via a flexible connector, and to the rectifier bridges (CU2-C1) at the other end via a flexible connector. It is positioned in the middle of the four rectifier bridges, with a clearance of at least 800mm between it and the rectifier bridges.

[0039] The rectifier bridge layout is as follows: Figure 4 As shown, the rectifier transformer shares a secondary side with two rectifier bridges. One rectifier bridge provides forward output and is named the positive bridge, while the other provides reverse output and is named the reverse bridge (the positive and reverse bridges together form a rectifier unit). The positive and reverse bridges sharing the secondary side of the rectifier transformer cannot operate simultaneously. The clearance between the two sets of rectifier units must not be less than 2 meters.

[0040] The reactor layout is as follows Figure 4 As shown, the two reactors are arranged vertically, with a clearance of no less than 800mm. The taller reactor is fixed to the surface of the other reactor using non-magnetic material. The DC disconnect switches are also arranged vertically, with a clearance of no less than 1.5m. The DC disconnect switches need to be fixed with a steel structure to improve their stability.

[0041] The DC busbar is an aluminum busbar with a cross-section of 200×60mm (the diameter of the water passage hole in the middle is 20mm). The aluminum busbar is fixed to the suspension beam by insulators, and the suspension beam is connected to the main steel structure by bolts.

[0042] The layout of the controller 5 is as follows: Figure 5 As shown, the clearance between each control cabinet and the rectifier bridge must not be less than 1 meter. A 200mm channel steel support is required under each control cabinet to facilitate electrical connections between them.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-power four-quadrant converter system, comprising a dual-secondary-side oil-immersed rectifier transformer output connected to four three-phase bridge thyristor rectifiers, wherein the three-phase bridge thyristor rectifiers constitute the rectifier bridges, and each pair of rectifier bridges shares a set of secondary sides of the dual-secondary-side oil-immersed rectifier transformer; characterized in that, Two rectifier bridges sharing the secondary side of a dual-secondary oil-immersed rectifier transformer are connected in anti-parallel. If one of these two rectifier bridges achieves forward output, the other will achieve reverse output. The two sets of rectifier bridges with the same output direction can operate independently or in parallel; when the two sets of rectifier bridges are operating in parallel, current sharing is achieved through parallel reactors. The rectifier bridges for forward and reverse outputs achieve a smooth transition under the control of the controller, thus enabling four-quadrant operation of the output current. The high-power four-quadrant converter system consists of two parts: AC and DC. The AC part includes high-voltage cable terminals, AC disconnect switches, surge arresters, double-side oil-immersed rectifier transformers, AC busbars, and high-voltage busbars connecting the equipment. The AC high-voltage cable is connected to the double-side oil-immersed rectifier transformer via cable terminals, AC disconnect switches, surge arresters, and the cable terminals, AC disconnect switches, and surge arresters are installed on the same steel structure support, which is required to be reliably grounded at multiple points. The DC section includes a rectifier bridge, reactors, controllers, and DC buses that connect the devices. The four rectifier bridges are connected to the input of the reactors via a DC water-cooled bus, and the outputs of the reactors are connected in parallel and then output through a DC disconnect switch. The high-power four-quadrant converter system also includes reserved interfaces at both ends of the AC bus to meet the scalable connection mode. The AC bus is the connection medium between the AC part and the DC part.

2. The high-power four-quadrant converter system according to claim 1, characterized in that: The three-phase AC busbars in the AC section adopt a closed structure; The three-phase shielding layers of the AC busbar are reliably electrically connected and grounded at a single point.

3. The high-power four-quadrant converter system according to claim 1, characterized in that: It also includes a bypass cabinet for system protection. One end of the bypass cabinet is connected to the rectifier bridge CU1-C1 via a flexible connection, and the other end is connected to the rectifier bridge CU2-C1 via a flexible connection. The rectifier bridges CU1-C1 and CU2-C1 share a set of secondary sides. Its position is placed in the middle of the four rectifier bridges, and the clearance between it and the rectifier bridges is not less than 800mm.

4. The high-power four-quadrant converter system according to claim 1, characterized in that: The two rectifier bridges sharing the secondary side of the dual-secondary-side oil-immersed rectifier transformer are named as follows: one rectifier bridge has a forward output and is called the positive bridge, and the other has a reverse output and is called the reverse bridge. The positive bridge and the reverse bridge together form a rectifier unit. The positive bridge and the reverse bridge sharing the secondary side of the dual-secondary-side oil-immersed rectifier transformer cannot work at the same time, and the clearance distance between the two sets of rectifier units cannot be less than 2 meters.

5. The high-power four-quadrant converter system according to claim 1, characterized in that: The reactor comprises two reactors, arranged one above the other with a clearance of not less than 800 mm. The taller reactor is fixed to the surface of the other reactor using a non-magnetic material.

6. The high-power four-quadrant converter system according to claim 1, characterized in that: The DC disconnect switches are arranged vertically with a clearance distance of not less than 1.5m; the DC disconnect switches are fixed with a steel structure.

7. The high-power four-quadrant converter system according to claim 1, characterized in that: The DC busbar is an aluminum busbar with a water passage hole diameter of 20mm in the middle. The aluminum busbar is fixed to the suspension beam by insulators, and the suspension beam is connected to the main steel structure by bolts.

8. The high-power four-quadrant converter system according to claim 1, characterized in that: The clearance between each control cabinet and the rectifier bridge is no less than 1m; a 200mm channel steel is installed under the control cabinet as a support to facilitate the electrical connection between each control cabinet.

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