WO2024098381A1

WO2024098381A1 - Alternating current power transmission system

Info

Publication number: WO2024098381A1
Application number: PCT/CN2022/131388
Authority: WO
Inventors: 赵国亮; 邓占锋; 徐云飞; 陆振纲; 李卫国; 乔光尧; 周丁
Original assignee: 国网智能电网研究院有限公司; 国家电网有限公司
Priority date: 2022-11-11
Filing date: 2022-11-11
Publication date: 2024-05-16

Abstract

Disclosed in embodiments of the present disclosure is an alternating current power transmission system, comprising: a converter. The converter comprises a plurality of converter valve groups, one end of each converter valve group is connected to a first alternating current system, each bridge arm of the other end of each converter valve group is connected to a winding at one side of a first transformer in series, and a winding at the other side of the first transformer is connected to a second alternating current system. According to the present disclosure, a winding at one side of a transformer is connected to each bridge arm of a converter, so that the winding can be used for simultaneously inhibiting an interphase circulating current and improving the utilization rate of an IGBT switching device in the converter, the reactance of the bridge arms of the converter is omitted while the normal work of a converter valve is ensured, and thus the impedance of the system can be reduced, and the transmission capability of the system is improved.

Description

An AC power transmission system

Technical Field

The present disclosure relates to the field of power electronics technology, and in particular to an alternating current power transmission system.

Background technique

The flexible low-frequency AC transmission system uses the frequency conversion and grid control technology of electronic power to flexibly select the appropriate frequency from 0 to 50HZ, enhance the flexible control capability of the grid, improve the transmission capacity of the grid, and make up for the shortcomings of industrial frequency AC and DC transmission methods. The AC-AC converter in the flexible low-frequency AC transmission system generally adopts a modular multi-level matrix converter (hereinafter referred to as the converter), which can perform flexible control of the grid such as power flow control and voltage regulation while realizing frequency conversion, and is the core equipment of the AC transmission.

In the related art, when the converter is working, a series reactor is usually connected to each bridge arm of each converter to suppress the circulating current caused by energy imbalance between phases, and a transformer needs to be installed at both ends of the converter to improve the utilization rate of the IGBT switching device in the converter. However, installing the series reactor and the transformer at the same time will increase the impedance of the system and reduce the transmission capacity of the system.

Summary of the invention

Therefore, the technical problem to be solved by the present disclosure is to overcome the defect in the prior art that the simultaneous installation of a series reactor and a transformer will increase the impedance of the system and reduce the transmission capacity of the system, thereby providing an AC power transmission system.

The disclosed embodiment of the present invention discloses an AC power transmission system, including: a converter, wherein the converter includes: a plurality of converter valve groups, one end of each of the converter valve groups is connected to a first AC system, each bridge arm at the other end of each of the converter valve groups is connected in series with a side winding of a first transformer, and the other side winding of the first transformer is connected to a second AC system.

In some embodiments, a second transformer is provided between the first AC system and the converter.

In some embodiments, the first transformer comprises: a plurality of three-phase transformers, and the number of the three-phase transformers is the same as the number of the converter valve groups.

In some embodiments, the first transformer includes: a plurality of single-phase transformer groups, the number of the single-phase transformer groups is the same as the number of the converter valve groups, each of the single-phase transformer groups includes: a plurality of single-phase transformers, the number of the single-phase transformers is the same as the number of bridge arms of each of the converter valve groups, and the other side windings of the plurality of single-phase transformers are connected in parallel and connected to the second AC system.

In some embodiments, the first transformer includes: a plurality of single-phase transformer groups, the number of the single-phase transformer groups is the same as the number of the converter valve groups, each of the single-phase transformer groups includes: a plurality of single-phase transformers, the number of the single-phase transformers is the same as the number of bridge arms of each of the converter valve groups, and the other side windings of the plurality of single-phase transformers are connected in series and then connected to the second AC system.

In some embodiments, the second transformer includes: a plurality of three-phase transformers or a plurality of single-phase transformer groups, and the number of the three-phase transformers and the number of the single-phase transformer groups are the same as the number of the converter valve groups.

In some embodiments, one side winding of the first transformer adopts a Y-type connection.

In some embodiments, one end of a winding on one side of the first transformer is connected in series with a bridge arm of the converter valve group in a one-to-one correspondence, and the other end of a winding on one side of the first transformer is connected in series with another bridge arm to form a series circuit.

In some embodiments, a winding on one side of the second transformer connected to the first AC system adopts a Y-type connection.

The AC power transmission system provided by the present disclosure includes: a converter, the converter includes: a plurality of converter valve groups, one end of each converter valve group is connected to a first AC system, each bridge arm at the other end of each converter valve group is connected in series with a winding on one side of a first transformer, and the winding on the other side of the first transformer is connected to a second AC system; the present disclosure connects a winding on one side of the transformer to each bridge arm of the converter, and can utilize the winding to simultaneously suppress interphase circulating current and improve the utilization rate of IGBT switching devices in the converter, thereby eliminating the reactance of the converter bridge arm while ensuring the normal operation of the converter valve, thereby reducing the system impedance and improving the transmission capacity of the system.

The technical solution provided by the embodiments of the present disclosure is described in detail below through the accompanying drawings and examples.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the specific embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the specific embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

FIG1 is a specific example diagram of an AC power transmission system in an embodiment of the present disclosure;

FIG2 is a principle block diagram of a partial example in which the first transformer is a single-phase transformer in the embodiment of the present disclosure;

FIG3 is another partial example diagram of the first transformer in the embodiment of the present disclosure where the first transformer is a single-phase transformer;

FIG4 is a principle block diagram of another partial example in which the first transformer is a single-phase transformer in the embodiment of the present disclosure;

FIG. 5 is another specific example diagram of the AC power transmission system in the embodiment of the present disclosure.

Detailed ways

The technical solution of the present disclosure will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.

In the description of the present disclosure, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present disclosure. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

In the description of the present disclosure, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two elements, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

In addition, the technical features involved in the different embodiments of the present disclosure described below can be combined with each other as long as they do not conflict with each other.

The present disclosure discloses an AC power transmission system, as shown in FIG1 , including:

The converter 10 includes: a plurality of converter valve groups 101, one end of each of the converter valve groups 101 is connected to the first AC system 20, each bridge arm at the other end of each of the converter valve groups is connected in series with one side winding of the first transformer 30, and the other side winding of the first transformer 30 is connected to the second AC system 40.

Exemplarily, the first AC system 20 can be an industrial frequency system (i.e., an AC power with a frequency of 50 Hz) or a low frequency system (i.e., a low frequency AC power with a frequency of 0 to 49 Hz). The second AC system 40 can also be an industrial frequency system or a low frequency system. When the first AC system 20 is an industrial frequency system, the second AC system 40 is a low frequency system; when the first AC system 20 is a low frequency system, the second AC system 40 is an industrial frequency system. The embodiments of the present disclosure do not specifically limit the specific frequency values of the first AC system 20, the second AC system 40, and the low frequency AC power, and those skilled in the art can determine them according to actual needs.

As shown in FIG. 1 , in the embodiment of the present disclosure, each converter 10 includes three converter valve groups 101 , each converter valve group 101 includes three bridge arms, and each bridge arm includes a plurality of full-bridge sub-modules, which may be H-bridge sub-modules.

One end of the converter 10 is connected to the first AC system 20, and the other end of the converter 10 is connected to the first transformer 30. The first transformer 30 may include multiple three-phase transformers, or multiple single-phase transformer groups. The number of three-phase transformers and the number of single-phase transformer groups are the same as the number of converter valve groups 101. In the embodiment of the present disclosure, the number of three-phase transformers and the number of single-phase transformer groups are both three. When the first transformer 30 includes multiple single-phase transformer groups, each single-phase transformer group includes: multiple single-phase transformers, the number of single-phase transformers is the same as the number of bridge arms of each converter valve group 101. In the embodiment of the present disclosure, the number of single-phase transformers in each single-phase transformer group is three, and one side winding of the three single-phase transformers is connected in series with the bridge arm of the converter valve group 101. As shown in Figures 2 and 4, after one bridge arm of each converter valve group 101 is connected in series with one end of a winding on one side of the first transformer 30, the other end of each winding on one side of the first transformer 30 is connected in a Y-type connection, or as shown in Figure 3, after one bridge arm of each converter valve group 101 is connected in series with one winding on one side of the first transformer 30 in a one-to-one correspondence, the three bridge arms are connected in series to form a series circuit, and the other side windings are connected in parallel (as shown in Figure 2) or in series (as shown in Figure 4) and connected to the second AC system 40.

When the other end of each of the above windings is connected in a Y-type connection, one end of each winding can be directly connected together, or can be connected together and then grounded.

The AC power transmission system provided by the present disclosure includes: a converter, the converter includes: a plurality of converter valve groups, one end of each converter valve group is connected to a first AC system, each bridge arm at the other end of each converter valve group is connected in series with a winding on one side of a first transformer, and the winding on the other side of the first transformer is connected to a second AC system; thus, the present disclosure connects a winding on one side of the transformer to each bridge arm of the converter, and can utilize the winding to simultaneously suppress interphase circulating current and improve the utilization rate of IGBT switching devices in the converter, thereby eliminating the reactance of the converter bridge arm while ensuring the normal operation of the converter valve, reducing the system impedance, and improving the transmission capacity of the system.

As an optional implementation of the embodiment of the present disclosure, one side winding of the first transformer 30 adopts a Y-type connection.

As an optional implementation of the embodiment of the present disclosure, in order to improve the protection of the other side of the converter 10, as shown in Figure 4, a second transformer 50 is provided between the first AC system 20 and the converter 10. The second transformer 50 may include multiple three-phase transformers or multiple single-phase transformer groups. The number of three-phase transformers and the number of single-phase transformer groups are the same as the number of converter valve groups 101. In the embodiment of the present disclosure, the number of three-phase transformers and the number of single-phase transformer groups are both 3. The embodiment of the present disclosure does not specifically limit the second transformer 50, and those skilled in the art can determine it according to actual conditions. Similarly, the winding on one side of the second transformer 50 connected to the first AC system 20 also adopts a Y-type connection. Like the first transformer 30, when the winding on one side adopts a Y-type connection, one end of each winding can be directly connected together, or it can be connected together and then grounded.

Although the embodiments of the present disclosure have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present disclosure, and such modifications and variations are all within the scope defined by the appended claims.

Industrial Applicability

The embodiment of the present disclosure discloses an AC power transmission system, including: a converter, the converter including: a plurality of converter valve groups, one end of each of the converter valve groups is connected to a first AC system, each bridge arm at the other end of each of the converter valve groups is connected in series with a winding on one side of a first transformer, and the winding on the other side of the first transformer is connected to a second AC system. The present disclosure connects a winding on one side of the transformer to each bridge arm of the converter, and can utilize the winding to simultaneously suppress interphase circulating current and improve the utilization rate of IGBT switching devices in the converter, while ensuring the normal operation of the converter valve, eliminating the reactance of the converter bridge arm, thereby reducing the system impedance and improving the transmission capacity of the system.

Claims

An alternating current power transmission system, comprising:

A converter, the converter comprising: a plurality of converter valve groups, one end of each of the converter valve groups being connected to a first AC system, each bridge arm at the other end of each of the converter valve groups being connected in series to a winding on one side of a first transformer, and the winding on the other side of the first transformer being connected to a second AC system.
According to the AC power transmission system of claim 1, a second transformer is provided between the first AC system and the converter.
According to the AC power transmission system of claim 1, the first transformer comprises: a plurality of three-phase transformers, and the number of the three-phase transformers is the same as the number of the converter valve groups.
According to the AC power transmission system of claim 1, the first transformer comprises: a plurality of single-phase transformer groups, the number of the single-phase transformer groups is the same as the number of the converter valve groups, each of the single-phase transformer groups comprises: a plurality of single-phase transformers, the number of the single-phase transformers is the same as the number of bridge arms of each of the converter valve groups, and the other side windings of the plurality of single-phase transformers are connected in parallel and then connected to the second AC system.
According to the AC power transmission system of claim 1, the first transformer comprises: a plurality of single-phase transformer groups, the number of the single-phase transformer groups is the same as the number of the converter valve groups, each of the single-phase transformer groups comprises: a plurality of single-phase transformers, the number of the single-phase transformers is the same as the number of bridge arms of each of the converter valve groups, and the other side windings of the plurality of single-phase transformers are connected in series and then connected to the second AC system.
According to the AC power transmission system of claim 2, the second transformer comprises: a plurality of three-phase transformers or a plurality of single-phase transformer groups, and the number of the three-phase transformers and the number of the single-phase transformer groups are the same as the number of the converter valve groups.
According to the AC power transmission system of claim 1, one side winding of the first transformer adopts a Y-type connection.
According to the AC power transmission system of claim 1, one end of the winding on one side of the first transformer is connected in series with the bridge arm of the converter valve group in a one-to-one correspondence, and the other end of the winding on one side of the first transformer is connected in series with the other bridge arm to form a series circuit.
According to the AC power transmission system of claim 2, a winding on one side of the second transformer connected to the first AC system adopts a Y-type connection.