WO2022222950A1

WO2022222950A1 - Series-type multi-winding converter, direct current transformer, and control method

Info

Publication number: WO2022222950A1
Application number: PCT/CN2022/087881
Authority: WO
Inventors: 杨晨; 谢晔源; 姜田贵; 张中锋; 葛健; 苟建民; 马道源
Original assignee: 南京南瑞继保电气有限公司; 南京南瑞继保工程技术有限公司
Priority date: 2021-04-23
Filing date: 2022-04-20
Publication date: 2022-10-27
Also published as: CN114696648A

Abstract

Provided are a series-type multi-winding converter, a direct current transformer, and a control method. The series-type multi-winding converter comprises M converter chains (101, 102, ..., 10M) and a first isolation transformer (10c), wherein the M converter chains (101, 102, ..., 10M) are connected in series, a positive terminal of the first converter chain (101) and a negative terminal of the Mth converter chain (10M) constitute a first direct current port (10b) of the series-type multi-winding converter, and M is a positive integer greater than or equal to 2. The first isolation transformer (10c) comprises M first-type windings (10c1) and at least one second-type winding (10c2), and all the first-type windings (10c1) are isolated from each other. All the first-type windings (10c1) are isolated from the second-type windings (10c2), wherein each first-type winding (10c1) is connected to an alternating current port of each converter chain respectively, and the second-type windings (10c2) are connected in combination to form an alternating current port of the series-type multi-winding converter.

Description

Series-type multi-winding converter, DC transformer and control method

technical field

The present application relates to the technical field of power electronic applications, in particular to a series-type multi-winding converter, a DC transformer and a control method.

Background technique

As an important component of the voltage conversion equipment in the DC power grid, the DC transformer has received more and more attention from scholars in the field of DC power grids. In order to realize the conversion from medium/high voltage to low voltage, due to the influence of the stress and cost of the switching tube device, when the isolation function is required, the DC transformer for this type of application generally adopts the structure of multiple modules input in series and output in parallel (ISOP), or The scheme of step-down and rectification of MMC plus centralized transformer is adopted. In comparison, the ISOP structure places the isolation transformer in each module, which puts forward higher requirements for the isolation voltage level, while the MMC plus centralized transformer step-down and rectification scheme places the isolation voltage level requirements on the centralized transformer. On the other hand, the highest voltage level that its solution is easy to implement is higher than that of the ISOP solution.

However, the MMC scheme usually requires six bridge arms when carrying out inverse transformation, and the system has a large number of modules and a high cost. In terms of cost saving, many literatures propose non-isolation methods, but non-isolation methods have hidden dangers for fault isolation and system security. Therefore, it is necessary to propose a DC transformer that can reduce the cost and has an isolation function.

SUMMARY OF THE INVENTION

An embodiment of the present application provides a series-type multi-winding converter, including M commutator chains and a first isolation transformer, wherein the M commutator chains are connected in series, and the positive end of the first commutator chain and the Mth commutator chain are connected in series. The negative end of the commutation chain constitutes the first DC port of the series-type multi-winding converter, and M is a positive integer greater than or equal to 2; the first isolation transformer includes M first-type windings and at least one first-type winding. Class II windings, all the first class windings are isolated from each other; all the first class windings and the second class windings are isolated from each other, wherein each first class winding is respectively connected to the AC port of each commutation chain, the second class winding The quasi-windings are connected in combination to form an AC port of the series-type multi-winding converter.

According to some embodiments, the M first type windings of the first isolation transformer have different insulation to ground.

According to some embodiments, when there are at least three windings of the second type of the first isolation transformer, the combined connection of the windings of the second type includes a delta connection or a star connection.

According to some embodiments, the converter chain includes two groups of AC-DC converter sub-chains connected in parallel, and the AC-DC converter sub-chain includes at least one valve arm reactor and N AC-DC converter sub-modules, where N is a positive value greater than or equal to 2 Integer, a capacitor is connected in parallel with the DC port of each AC-DC conversion sub-module, and the AC ports of the N AC-DC conversion sub-modules are connected in series in sequence, and are connected in series with the valve arm reactor.

According to some embodiments, the first terminals of the AC ports of the first AC-DC conversion sub-modules of the two groups of AC-DC conversion sub-chains are connected to form the positive end of the converter chain, and the Nth AC-DC converter of the two groups of AC-DC conversion sub-chains is connected. The second terminal of the AC port of the sub-module is connected to form the negative end of the commutation chain. In each group of AC-DC conversion sub-chains, the connection points of any two AC-DC conversion sub-modules lead to one end each, which is used as the AC port of the commutation chain. .

According to some embodiments, the AC-DC conversion sub-module includes at least one of a half-bridge converter, a full-bridge converter, and a three-level converter.

Embodiments of the present application further provide the above-mentioned control method for a series-type multi-winding converter, which is used to complete the startup and power operation from the DC port to the AC port of the series-type multi-winding converter, and the control method The method includes: unlocking all AC-DC conversion sub-modules of the M converter chains; collecting and controlling the voltage or power of the AC port of the series-type multi-winding converter.

The embodiment of the present application also provides a control method for a series-type multi-winding converter as described above, which is used to complete the startup and power operation from the AC port to the DC port of the DC transformer, and the control method includes: unlocking the M All AC-DC conversion sub-modules of a converter chain; collecting and controlling the voltage or power of the DC port of the series-type multi-winding converter.

An embodiment of the present application further provides a DC transformer, comprising: the series-type multi-winding converter and the second converter as described above, wherein the DC port of the series-type multi-winding converter constitutes the DC port of the DC transformer. a first DC port; the AC port of the second converter is connected to the second type winding of the first isolation transformer of the series-type multi-winding converter, and the DC port of the second converter constitutes the The second DC port of the DC transformer.

According to some embodiments, the second converter includes at least one of a modular multi-level converter, a full-bridge converter, a three-level converter, and the series-type multi-winding converter.

The embodiments of the present application further provide the above-mentioned control method for a DC transformer, which is used to complete the startup and power operation of the DC port to the AC port of the DC transformer, including: unlocking all AC-DC converters of the M converter chains module; collecting and controlling the voltage or power of the AC port of the series-type multi-winding inverter; unlocking the second inverter, and collecting and controlling the DC port voltage or power of the second inverter through the second inverter.

Embodiments of the present application further provide the above-mentioned control method for a DC transformer, which is used to complete startup and power operation from an AC port to a DC port of the DC transformer, including: unlocking the second converter, The converter collects and controls the AC port voltage or power of the second converter; unlocks all AC-DC conversion sub-modules of the M converter chains; collects and controls the DC port voltage or power of the series-type multi-winding converter.

Compared with the ISOP solution, the technical solutions provided by the embodiments of the present application still use centralized transformer isolation, and the highest voltage level that can be achieved by the equipment is higher; compared with the MMC solution, the solution of the present application requires only two strings of replacements on the high-voltage side. The flow chain reduces the number of modules and reduces the system cost under the condition of the same voltage level. Compared with some existing patented solutions, this patented solution avoids the need to use high-voltage capacitors, which is more convenient for the complete design of the system.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present application more clearly, the following briefly introduces the drawings that are used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

FIG. 1 is a schematic diagram of a series-type multi-winding converter provided by an embodiment of the present application.

FIG. 2 is a schematic diagram of a converter chain provided by an embodiment of the present application.

FIG. 3 is a schematic diagram (M=3) of a typical series-connected multi-winding converter provided by an embodiment of the present application.

FIG. 4 is a schematic diagram of a half-bridge converter provided by an embodiment of the present application.

FIG. 5 is a schematic diagram 1 of a full-bridge converter provided by an embodiment of the present application.

FIG. 6 is a second schematic diagram of a full-bridge converter provided by an embodiment of the present application.

FIG. 7 is a third schematic diagram of a full-bridge converter provided by an embodiment of the present application.

FIG. 8 is a schematic diagram of a three-level converter provided by an embodiment of the present application.

FIG. 9 is a schematic diagram (M=3) of a DC transformer composed of a typical series-connected multi-winding converter provided in an embodiment of the present application.

FIG. 10 is a schematic flowchart of a control method for starting a DC port of a DC transformer to an AC port according to an embodiment of the present application.

11 is a schematic flowchart of a control method for starting an AC port of a DC transformer to a DC port according to an embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of this application.

It should be understood that the terms "first", "second" and the like in the claims, description and drawings of the present application are used to distinguish different objects, rather than to describe a specific order. The terms "comprising" and "comprising" as used in the specification and claims of this application indicate the presence of the described feature, integer, step, operation, element and/or component, but do not exclude one or more other features, integers , step, operation, element, component and/or the presence or addition of a collection thereof.

As shown in FIG. 1 , the series-type multi-winding converter includes

M commutation chains

101 , 102 , . . . 10M and a first isolation transformer 10c , where M is a positive integer greater than or equal to 2.

The M commutator chains are connected in series, and the positive end 101a of the first commutator chain 101 and the negative end 10Mb of the Mth commutator chain 10M constitute the first DC port 10b of the series-type multi-winding converter.

The first isolation transformer 10c includes M first type windings 10c1 and at least one second type winding 10c2. All first-type windings 10c1 are isolated from each other, and all first-type windings 10c1 and second-type windings 10c2 are isolated from each other, wherein each first-type winding 10c1 is respectively connected to the AC port of each commutation chain, and the second-type winding 10c2 is connected in combination to form the AC port 10a of the series-type multi-winding inverter.

Optionally, the M first-type windings 10c1 of the first isolation transformer 10c have different insulation to ground, which can meet the requirements of different voltage levels.

Optionally, when there are at least three second-type windings 10c2 of the first isolation transformer 10c, the combined connection of the second-type windings 10c2 includes angular connection or star connection. As shown in FIG. 3 , the combined connection of the second type windings 10c2 is a star connection.

Among them, the converter chain includes two groups of AC-DC converter sub-chains connected in parallel, as shown in FIG. 2 .

The AC-DC conversion sub-chain includes at least one valve arm reactor and N AC-DC conversion sub-modules, where N is a positive integer greater than or equal to 2. A capacitor is connected in parallel with the DC port of each AC-DC conversion sub-module, and the AC ports of the N AC-DC conversion sub-modules are sequentially connected in series, and are connected in series with the valve arm reactor.

As shown in Fig. 2, the converter chain includes two groups of AC-DC converter sub-chains connected in parallel, and one AC-DC converter sub-chain includes a valve arm reactor 30c and N AC-

DC converter sub-modules

301, 302, ... 30N, where N is a positive integer greater than or equal to 2. Another AC-DC conversion sub-chain includes a valve arm reactor 30d and N AC-DC conversion sub-modules 30(N+1), 30(N+2), . . . 30(2N).

A capacitor is connected in parallel with the DC port of each AC-DC conversion sub-module, and the AC ports of the N AC-DC conversion sub-modules are sequentially connected in series, and are connected in series with the valve arm reactor.

The first terminal of the AC port of the first AC-DC conversion submodule of the two sets of AC-DC conversion sub-chains is connected to form the positive terminal 30a of the converter chain, and the second terminal of the AC port of the N-th AC-DC conversion sub-module of the two sets of AC-DC conversion sub-chains is connected. The negative terminal 30b is connected to form the converter chain. In each group of AC-DC conversion sub-chains, the connection points of any two AC-DC conversion sub-modules lead to one end each, which is used as the AC port of the converter chain.

Optionally, the AC-DC conversion sub-module includes at least one of a half-bridge converter, a full-bridge converter, and a three-level converter.

As shown in FIG. 4 , the half-bridge converter includes two series-connected fully-controlled switching devices or fully-controlled switching device groups.

As shown in FIG. 5 , the full-bridge converter includes four fully-controlled switching devices or groups of fully-controlled switching devices connected in series in pairs.

As shown in FIG. 6 , the full-bridge converter includes two series-connected fully-controlled switching devices or fully-controlled switching device groups and two series-connected capacitors or capacitor banks.

As shown in FIG. 7 , the full-bridge converter includes six fully-controlled switching devices or fully-controlled switching device groups connected in series in pairs.

As shown in FIG. 8, the three-level converter includes four fully-controlled switching devices or groups of fully-controlled switching devices connected in series in sequence.

FIG. 9 is a schematic diagram of a typical series-type multi-winding converter forming a DC transformer (M=3).

The DC transformer includes the series-type multi-winding inverter and the second inverter 80 as described in the above embodiments.

As shown in FIG. 9 , the series-type multi-winding converter is a typical series-type multi-winding converter, and the second-type windings of the first isolation transformer of the series-type multi-winding converter are three (M=3). The secondary windings 10c2 are connected in a star connection.

The DC port of the series-type multi-winding converter constitutes the first DC port of the DC transformer. The AC port of the second converter 80 is connected to the second type winding of the first isolation transformer of the series-type multi-winding converter, and the DC port of the second converter 80 constitutes the second DC port of the DC transformer.

Optionally, the second converter includes at least one of a modular multi-level converter, a full-bridge converter, a three-level converter, and the above-mentioned series-type multi-winding converter.

In FIG. 9, the second converter is a three-level converter.

As shown in FIG. 10 , when the startup and power operation from the DC port of the DC transformer to the AC port are completed, the following control flow is included.

In S11, unlock all the AC-DC conversion submodules of the M commutator chains.

In S12, the voltage or power of the AC port of the series-type multi-winding converter is collected and controlled.

In S13, unlock the second inverter, and collect and control the DC port voltage or power of the second inverter through the second inverter.

As shown in FIG. 11 , when the startup and power operation from the AC port of the DC transformer to the DC port are completed, the following control flow is included.

In S21, the second inverter is unlocked, and the AC port voltage or power of the second inverter is collected and controlled through the second inverter.

In S22, unlock all the AC-DC conversion submodules of the M converter chains.

In S23, the voltage or power of the DC port of the series-type multi-winding converter is collected and controlled.

The embodiments of the present application are described in detail above, and specific examples are used herein to illustrate the principles and implementations of the present application. The descriptions of the above embodiments are only used to help understand the methods and core ideas of the present application. Meanwhile, any changes or deformations made by those skilled in the art based on the ideas of the present application and the specific embodiments and application scope of the present application fall within the protection scope of the present application. In conclusion, the content of this specification should not be construed as a limitation on the present application.

Claims

A DC transformer, comprising:

a series-type multi-winding converter, the DC port of the series-type multi-winding converter constitutes the first DC port of the DC transformer;

The second converter, the AC port of the second converter is connected to the second type winding of the first isolation transformer of the series-type multi-winding converter, and the DC port of the second converter constitutes the the second DC port of the DC transformer; wherein,

The series-type multi-winding converter includes:

M commutator chains, the M commutator chains are connected in series, and the positive end of the first commutator chain and the negative end of the Mth commutator chain constitute the first DC of the series-type multi-winding converter port, M is a positive integer greater than or equal to 2;

The first isolation transformer includes M first-type windings and at least one second-type winding, and all first-type windings are isolated from each other; all first-type windings and second-type windings are isolated from each other, wherein each first-type winding is The windings are respectively connected to the AC ports of each converter chain, and the second type of windings are connected in combination to form the AC ports of the series-type multi-winding converter.
The DC transformer of claim 1, wherein the second converter comprises a modular multi-level converter, a full-bridge converter, a three-level converter, the series multi-winding converter at least one.
The DC transformer of claim 1, wherein the M first type windings of the first isolation transformer have different insulations to ground.
The DC transformer according to claim 1, wherein, when the number of the second type of windings of the first isolation transformer is at least three, the combined connection of the second type of windings includes angular connection or star connection.
The DC transformer according to claim 1, wherein the commutation chain comprises two sets of AC-DC conversion sub-chains connected in parallel, the AC-DC conversion sub-chains comprising:

At least 1 arm reactor;

N AC-DC conversion sub-modules, N is a positive integer greater than or equal to 2, the DC port of each AC-DC conversion sub-module is connected in parallel with a capacitor, and the AC ports of the N AC-DC conversion sub-modules are sequentially connected in series, and are connected in series with the valve arm reactor.
The DC transformer according to claim 5, wherein the first terminals of the AC ports of the first AC-DC converter sub-modules of the two groups of the AC-DC converter sub-chains are connected to form the positive terminal of the converter chain, and the two groups of AC-DC converter sub-chains are connected to form the positive terminal of the converter chain. The second terminal of the AC port of the Nth AC-DC conversion sub-module of the chain is connected to form the negative end of the converter chain. In each group of AC-DC conversion sub-chains, the connection points of any two AC-DC conversion sub-modules lead to one end each. As the AC port of the commutation chain.
The DC transformer of claim 5, wherein the AC-DC conversion sub-module comprises at least one of a half-bridge converter, a full-bridge converter, and a three-level converter.
A control method for a DC transformer according to any one of claims 1 to 7, used to complete the startup and power operation from a DC port to an AC port of the DC transformer, the control method comprising:

Unlock all AC/DC converter sub-modules of M converter chains;

collecting and controlling the voltage or power of the AC port of the series-type multi-winding converter;

The second inverter is unlocked, and the DC port voltage or power of the second inverter is collected and controlled through the second inverter.
A control method for a DC transformer according to any one of claims 1 to 7, for completing the startup and power operation from an AC port to a DC port of the DC transformer, the control method comprising:

unlocking the second inverter, collecting and controlling the AC port voltage or power of the second inverter through the second inverter;

Unlock all AC/DC converter sub-modules of M converter chains;

The voltage or power of the DC port of the series-type multi-winding converter is collected and controlled.
A series-type multi-winding converter, comprising:

M commutator chains, the M commutator chains are connected in series, and the positive end of the first commutator chain and the negative end of the Mth commutator chain constitute the first DC of the series-type multi-winding converter port, M is a positive integer greater than or equal to 2;

The first isolation transformer includes M first-type windings and at least one second-type winding, and all first-type windings are isolated from each other; all first-type windings and second-type windings are isolated from each other, wherein each first-type winding is The windings are respectively connected to the AC ports of each converter chain, and the second type of windings are connected in combination to form the AC ports of the series-type multi-winding converter.
A control method for a series-type multi-winding converter as claimed in claim 10, which is used to complete the startup and power operation from the DC port to the AC port of the series-type multi-winding converter, the control method comprising:

Unlock all AC/DC converter sub-modules of M converter chains;

The voltage or power of the AC port of the series-type multi-winding converter is collected and controlled.
A control method for a series-type multi-winding converter as claimed in claim 10, used for completing the start-up and power operation from the AC port to the DC port of the DC transformer, the control method comprising:

Unlock all AC/DC converter sub-modules of M converter chains;

The voltage or power of the DC port of the series-type multi-winding converter is collected and controlled.