Arrangement method of bridge arm and bridge arm reactor of modular multi-level matrix converter

Abstract

The present invention discloses a method for arranging bridge arms and bridge arm reactors of a modular multi-level matrix converter. The present invention proposes a method for arranging the positions of bridge arms and bridge arm reactors based on two combinations of sub-converters in a modular multi-level matrix converter; and determines the arrangement of three bridge arm positions inside the sub-converter based on three position relationships between the sub-converters. The present invention can effectively prevent direct short-circuit faults caused by parallel connection of bridge arms without passing through bridge arm reactors, transformers and other components, thereby improving the operating safety of flexible low-frequency power transmission frequency conversion valves.

Description

Technical Field

[0001] The invention belongs to the technical field of power transmission and distribution of electric power systems, and relates to a method for arranging the positions of bridge arms and bridge arm reactors of a modular multi-level matrix converter. Background Art

[0002] Flexible low-frequency transmission is a new type of AC transmission technology, and its transmission frequency is between industrial frequency and DC. Due to the reduction in frequency, flexible low-frequency transmission combines the technical characteristics of industrial frequency and DC transmission, and has broad application prospects in the fields of urban power grid interconnection, new energy grid connection, and long-distance power supply. The advantages of flexible low-frequency transmission are mainly reflected in: 1) Compared with industrial frequency AC solutions, it has a longer effective transmission distance and a larger transmission capacity; 2) Wind turbines can directly generate low-frequency electricity and boost it for transmission, without the need to build offshore converter stations, effectively reducing construction and operation costs; 3) AC switches and transformers can be used to build multi-terminal systems, which have stronger networking capabilities and lower networking costs than flexible DC.

[0003] When used in high-voltage and high-capacity applications, the low-frequency transmission system based on modular multi-level matrix converters is the mainstream solution. In this solution, the layout position of the bridge arm reactor and the relative position between the bridge arms have an important impact on the safe operation of the modular multi-level converter. When a short circuit fault occurs between adjacent bridge arms, if the layout position of the bridge arm reactor and the relative position between the bridge arms are unreasonable, it is very easy for the bridge arms to be connected in parallel without connecting the bridge arm reactors, transformers and other components. At this time, the cascaded sub-module capacitors in the two bridge arms form a short circuit through the IGBT device, and the short-circuit current quickly rises to more than 10kA within 1ms, which will cause damage to the IGBT device.

[0004] Since the development of flexible low-frequency transmission technology based on modular multi-level matrix converter is in its infancy, so far, most of the published literature has basically only studied the networking mode, modeling and control strategy of low-frequency transmission system, and there is no research on the layout method of the internal bridge arm and bridge arm reactor of the converter.

[0005] In order to avoid the direct short-circuit fault between bridge arms and improve the operation safety of flexible low-frequency power transmission frequency conversion valve, it is necessary to study the layout method of bridge arms and bridge arm reactors. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the above-mentioned prior art and provide a method for arranging the positions of bridge arms and bridge arm reactors of a modular multi-level matrix converter. The method aims at the modular multi-level matrix converter and effectively prevents the direct short circuit fault caused by the bridge arms being connected in parallel without passing through components such as bridge arm reactors and transformers through the arrangement of the positions of bridge arm reactors and bridge arms.

[0007] To this end, the present invention adopts the following technical solution: a method for arranging bridge arms and bridge arm reactors of a modular multi-level matrix converter, which comprises the following steps:

[0008] Firstly, the combination mode of sub-converters in modular multi-level matrix converter is determined;

[0009] Then, determine the arrangement position of the bridge arm reactor in the bridge arm;

[0010] Then, the relative position relationship between the sub-converters is determined;

[0011] Finally, the relative positions of the bridge arms in each sub-converter are determined.

[0012] Furthermore, the modular multi-level matrix converter is connected between the first AC system and the second AC system, the first AC system outputs first frequency electric energy, and the output side is the first frequency side; the second AC system outputs second frequency electric energy, and the output side is the second frequency side; the modular multi-level matrix converter is used to realize the mutual conversion of the first frequency electric energy and the second frequency electric energy, and comprises a total of 9 bridge arms, each bridge arm comprises more than one full-bridge sub-module and 1 bridge arm reactor, wherein every 3 bridge arms constitute a sub-converter.

[0013] Furthermore, the sub-converters have two combinations:

[0014] The first combination mode: the three bridge arms in the sub-converter are respectively connected to the A, B, and C phases of the first AC system on the first frequency side, and the three bridge arms are connected in parallel on the second frequency side to form one phase of the second AC system;

[0015] The second combination mode: the three bridge arms in the sub-converter are connected in parallel on the first frequency side to form one phase of the first AC system, and are respectively connected to the A, B, and C phases of the second AC system on the second frequency side.

[0016] Furthermore, when the sub-converter adopts the first combination mode, the bridge arm inductor is arranged on the side of the bridge arm close to the second frequency.

[0017] Furthermore, when the sub-converter adopts the second combination mode, the bridge arm reactor is arranged on the side of the bridge arm close to the first frequency.

[0018] Furthermore, the three bridge arms of each sub-converter are arranged from left to right in space.

[0019] Furthermore, the three sub-converters are spatially arranged in three ways:

[0020] The first layout is the "one" shape layout: the 3 sub-converters are arranged in a row from left to right, which are the first sub-converter, the second sub-converter and the third sub-converter from left to right respectively, and the 9 arms are arranged in a "1×9" pattern;

[0021] The second layout is the "square" shape layout: the 3 sub-converters are arranged in a column from top to bottom, which are the first sub-converter, the second sub-converter and the third sub-converter from top to bottom respectively, and the 9 arms are arranged in a "3×3" pattern;

[0022] The third layout is the "triangle" shape layout: the first sub-converter, the second sub-converter and the third sub-converter are arranged at the three vertex positions of the triangle.

[0023] Furthermore, when the "one" shape layout is adopted among the three sub-converters: the 2 adjacent arms on the left and right of the first sub-converter and the second sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side; the 2 adjacent arms on the left and right of the second sub-converter and the third sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side.

[0024] Furthermore, when the "square" shape layout is adopted among the three sub-converters: the 3 adjacent arms on the top and bottom of the first sub-converter and the second sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side; the 3 adjacent arms on the top and bottom of the second sub-converter and the third sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side.

[0025] Furthermore, when the "triangle" shape layout is adopted among the three sub-converters: the two closest arms between the sub-converters are not connected to the same AC phase on the first frequency side and the second frequency side, and the sub-converters connected to the same AC phase on the first frequency side or the second frequency side should be arranged as far apart as possible.

[0026] The beneficial effects of the present invention are as follows: for the modular multilevel matrix converter, through the arm reactors and the position layout of the arms, it can effectively prevent the through short-circuit fault caused by the parallel connection of the arms without passing through components such as arm reactance and transformers, improve the operation safety of the flexible low-frequency power transmission frequency conversion valve, and has important value for guiding the actual engineering design. Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of a flexible low-frequency power transmission frequency conversion station based on a modular multilevel matrix converter in the prior art;

[0028] Figure 2 is Figure 1 a schematic structural diagram of the modular multilevel matrix converter in

[0029] Figure 3Schematic diagram of a combination mode of the sub-converters of the present invention;

[0030] Figure 4 Schematic diagram of another combination mode of the sub-converters of the present invention;

[0031] Figure 5 Schematic diagram of a through short-circuit fault between existing bridge arms;

[0032] Figure 6 Schematic diagram of the "one"-shaped arrangement mode of the sub-converters of the present invention;

[0033] Figure 7 Schematic diagram of the "square"-shaped arrangement mode of the sub-converters of the present invention;

[0034] Figure 8 Schematic diagram of the "triangle"-shaped arrangement mode of the sub-converters of the present invention;

[0035] Fig. 9 Schematic diagram of an arrangement mode of the internal bridge arms when the "one"-shaped arrangement is adopted between the sub-converters of the present invention;

[0036] Fig.10 Schematic diagram of another arrangement mode of the internal bridge arms when the "one"-shaped arrangement is adopted between the sub-converters of the present invention;

[0037] Fig.11 Schematic diagram of an arrangement mode of the internal bridge arms when the "square"-shaped arrangement is adopted between the sub-converters of the present invention;

[0038] Fig.12 Schematic diagram of another arrangement mode of the internal bridge arms when the "square"-shaped arrangement is adopted between the sub-converters of the present invention;

[0039] Fig.13 Schematic diagram of an arrangement mode of the internal bridge arms when the "triangle"-shaped arrangement is adopted between the sub-converters of the present invention;

[0040] Fig.14 Schematic diagram of another arrangement mode of the internal bridge arms when the "triangle"-shaped arrangement is adopted between the sub-converters of the present invention. Specific implementation manner

[0041] In order to describe the present invention more specifically, the technical solution of the present invention will be described in detail below in conjunction with the drawings and specific implementation manners.

[0042] This embodiment provides a method for arranging the positions of the bridge arms and bridge arm reactors of a modular multilevel matrix converter, including the following steps:

[0043] First, determine the combination mode of the sub-converters in the modular multilevel matrix converter.

[0044] The topology of modular multi-level matrix converter is as follows: Figure 1 As shown, the modular multi-level matrix converter is connected between the first AC system and the second AC system. The first AC system outputs the first frequency electric energy through the industrial frequency transformer, and the output side is the first frequency side; the second AC system outputs the second frequency electric energy through the low-frequency transformer, and the output side is the second frequency side. The modular multi-level matrix converter is used to realize the mutual conversion between the first frequency electric energy and the second frequency electric energy, and includes a total of 9 bridge arms, each bridge arm includes more than one full-bridge sub-module and 1 bridge arm reactor, and every 3 bridge arms constitute a sub-converter. The structure of the full-bridge sub-module is shown in Figure 2 shown.

[0045] There are two ways to combine sub-converters. The first way is as follows: Figure 3 As shown, the three bridge arms in the sub-converter are connected to the A, B, and C phases of the first AC system on the first frequency side, and the three bridge arms are connected in parallel on the second frequency side to form one phase of the second AC system; the second combination mode is as follows Figure 4 As shown, the three bridge arms in the sub-converter are connected in parallel on the first frequency side to form one phase of the first AC system, and are respectively connected to the A, B, and C phases of the second AC system on the second frequency side.

[0046] Then, the arrangement position of the bridge arm reactor in the bridge arm is determined according to different combinations of the sub-converters. When the sub-converters adopt the first combination mode, the bridge arm reactor is arranged on the side of the bridge arm close to the second frequency, such as Figure 3 When the sub-converter adopts the second combination mode, the bridge arm reactor is arranged on the side of the bridge arm close to the first frequency, as shown in FIG. Figure 4 The advantage of the above arrangement is that when two adjacent bridge arms are short-circuited, the fault circuit will always contain bridge arm reactors or AC system impedance of equivalent value, and the following will not occur: Figure 5 The two bridge arms shown in the figure do not pass through the bridge arm reactor, transformer and other components in parallel to cause a direct short circuit fault, thereby avoiding the IGBT device from being damaged due to excessive current stress.

[0047] Then, determine the relative position between the sub-converters. The three sub-converters can be arranged in three ways in space: The first arrangement adopts a "one" shape arrangement, and the three sub-converters are arranged from left to right in sequence, from left to right are the first sub-converter, the second sub-converter and the third sub-converter, and the 9 bridge arms are arranged in a "1×9" manner, such as Figure 6 As shown; the second arrangement adopts a "mouth" shape arrangement, and the three sub-converters are arranged in sequence from top to bottom, namely the first sub-converter, the second sub-converter and the third sub-converter from top to bottom, and the 9 bridge arms are arranged in a "3×3" manner, as shown Figure 7The third arrangement is a "△"-shaped arrangement, where the first sub-converter, the second sub-converter and the third sub-converter are arranged according to the three vertices of the triangle, as shown in FIG. Figure 8 shown. Figure 8 This is only a specific example of a triangular arrangement. All examples of arrangements that form a triangle with the locations of the three sub-inverters as vertices are within the scope of protection of the claims.

[0048] Finally, the relative positions of the bridge arms in each sub-converter are determined, and the three bridge arms of each sub-converter are arranged from left to right in space.

[0049] When the sub-converters are arranged in a straight line, the two adjacent bridge arms of the first sub-converter and the second sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side; the two adjacent bridge arms of the second sub-converter and the third sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side. Figure 9-10 Two examples of the arrangement of internal bridge arms when the sub-converters are arranged in a straight line are provided. Fig. 9 As shown, taking the "I"-shaped arrangement of the sub-converter using the first combination as an example, the two adjacent bridge arms of the first sub-converter and the second sub-converter are the C-phase bridge arm of the first sub-converter and the A-phase bridge arm of the second sub-converter. The two bridge arms are respectively connected to the C-phase and the A-phase of the first AC system on the first frequency side, and are respectively connected to the A-phase and the B-phase of the second AC system on the second frequency side, which conforms to the arrangement mode in which the two adjacent bridge arms are not connected to the same AC phase on the first frequency side and the second frequency side; the two adjacent bridge arms of the second sub-converter and the third sub-converter are the C-phase bridge arm of the second sub-converter and the A-phase bridge arm of the third sub-converter. The two bridge arms are respectively connected to the C-phase and the A-phase of the first AC system on the first frequency side, and are respectively connected to the B-phase and the C-phase of the second AC system on the second frequency side, which conforms to the arrangement mode in which the two adjacent bridge arms are not connected to the same AC phase on the first frequency side and the second frequency side. The above two arrangements are only specific examples of the arrangement of the bridge arms inside the two sub-converters. Other arrangement examples that satisfy "the two adjacent bridge arms of the first sub-converter and the second sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side; the two adjacent bridge arms of the second sub-converter and the third sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side" are all within the scope of protection of the claims.

[0050] When the sub-converters are arranged in a "mouth" shape, the three adjacent bridge arms of the first sub-converter and the second sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side; the three adjacent bridge arms of the second sub-converter and the third sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side. Figure 11-12 Two examples of the arrangement of the internal bridge arms when the sub-converters are arranged in a "mouth" shape are provided: Fig.11 As shown in the figure, taking the "mouth" - shaped arrangement where the sub - converters adopt the first combination method as an example, the three pairs of adjacent arms between the first sub - converter and the second sub - converter are respectively "the A - arm of the first sub - converter and the B - arm of the second sub - converter", "the B - arm of the first sub - converter and the C - arm of the second sub - converter", "the C - arm of the first sub - converter and the A - arm of the second sub - converter". Among them, "the A - arm of the first sub - converter and the B - arm of the second sub - converter" are respectively connected to the A - phase and B - phase of the first AC system on the first - frequency side and to the A - phase and B - phase of the second AC system on the second - frequency side. "The B - arm of the first sub - converter and the C - arm of the second sub - converter" are respectively connected to the B - phase and C - phase of the first AC system on the first - frequency side and to the A - phase and B - phase of the second AC system on the second - frequency side. "The C - arm of the first sub - converter and the A - arm of the second sub - converter" are respectively connected to the C - phase and A - phase of the first AC system on the first - frequency side and to the A - phase and B - phase of the second AC system on the second - frequency side, meeting the arrangement method that the three adjacent arms of the first sub - converter and the second sub - converter do not connect to the same AC phase on both the first - frequency side and the second - frequency side. The three pairs of adjacent arms between the second sub - converter and the third sub - converter are respectively "the B - arm of the second sub - converter and the C - arm of the third sub - converter", "the C - arm of the second sub - converter and the A - arm of the third sub - converter", "the A - arm of the second sub - converter and the B - arm of the third sub - converter". Among them, "the B - arm of the second sub - converter and the C - arm of the third sub - converter" are respectively connected to the B - phase and C - phase of the first AC system on the first - frequency side and to the B - phase and C - phase of the second AC system on the second - frequency side. "The C - arm of the second sub - converter and the A - arm of the third sub - converter" are respectively connected to the C - phase and A - phase of the first AC system on the first - frequency side and to the B - phase and C - phase of the second AC system on the second - frequency side. "The A - arm of the second sub - converter and the B - arm of the third sub - converter" are respectively connected to the A - phase and B - phase of the first AC system on the first - frequency side and to the B - phase and C - phase of the second AC system on the second - frequency side, meeting the arrangement method that the three adjacent arms of the second sub - converter and the third sub - converter do not connect to the same AC phase on both the first - frequency side and the second - frequency side.

[0051] When the sub - converters adopt a "△" - shaped arrangement, the two closest arms between the sub - converters do not connect to the same AC phase on both the first - frequency side and the second - frequency side. Sub - converters that connect to the same AC phase on the first - frequency side or the second - frequency side should be arranged as far apart as possible. For example Figure 13-14 Two examples of the internal arm arrangements when the sub - converters adopt a "pin" - shaped arrangement are provided: For example Fig.13As shown, taking the "△"-shaped arrangement of the sub-converters in the first combination mode as an example: the two closest bridge arms between the first sub-converter and the second sub-converter are "the A bridge arm of the first sub-converter and the C bridge arm of the second sub-converter", the two closest bridge arms between the first sub-converter and the third sub-converter are "the C bridge arm of the first sub-converter and the A bridge arm of the third sub-converter", and the two closest bridge arms between the second sub-converter and the third sub-converter are "the C bridge arm of the second sub-converter and the A bridge arm of the third sub-converter", where "the A bridge arm of the first sub-converter and the C bridge arm of the second sub-converter" are the closest bridge arms to the first sub-converter and the C bridge arm of the second sub-converter. The "bridge arm" is connected to the A phase and C phase of the first AC system on the first frequency side, and is connected to the A phase and B phase of the second AC system on the second frequency side; the "C bridge arm of the first sub-converter and the A bridge arm of the third sub-converter" are connected to the C phase and A phase of the first AC system on the first frequency side, and are connected to the A phase and C phase of the second AC system on the second frequency side; the "C bridge arm of the second sub-converter and the A bridge arm of the third sub-converter" are connected to the C phase and A phase of the first AC system on the first frequency side, and are connected to the B phase and C phase of the second AC system on the second frequency side. It conforms to the arrangement mode that the two bridge arms closest to the sub-converters are not connected to the same AC phase on the first frequency side and the second frequency side.

[0052] The present specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for arranging bridge arms and bridge arm reactors of a modular multi-level matrix converter, characterized in that: It includes the following steps: First, determine the combination mode of the sub-converters in the modular multilevel matrix converter; Then, determine the arrangement position of the arm reactor in the arm; Then, determine the relative position relationship between the sub-converters; Finally, determine the relative position between the arms in each sub-converter; The modular multilevel matrix converter is connected between the first AC system and the second AC system. The first AC system outputs electric energy with a first frequency, and this output side is the first frequency side; the second AC system outputs electric energy with a second frequency, and this output side is the second frequency side. The modular multilevel matrix converter is used to realize the mutual conversion of electric energy with the first frequency and electric energy with the second frequency, and it includes a total of 9 arms. Each arm includes more than one full-bridge sub-module and 1 arm reactor, and every 3 arms form a sub-converter; There are two combination modes for the sub-converters: The first combination mode: The 3 arms in the sub-converter are respectively connected to the A, B, and C phases of the first AC system on the first frequency side, and the 3 arms are connected in parallel on the second frequency side to form one phase of the second AC system; The second combination mode: The 3 arms in the sub-converter are connected in parallel on the first frequency side to form one phase of the first AC system, and are respectively connected to the A, B, and C phases of the second AC system on the second frequency side; The 3 arms of each sub-converter are arranged from left to right in space, and the three sub-converters adopt three arrangement modes in space: The first arrangement mode is the "one"-shaped arrangement: The 3 sub-converters are arranged in sequence from left to right, which are the first sub-converter, the second sub-converter, and the third sub-converter from left to right, and the 9 arms are arranged in a "1×9" arrangement; The second arrangement mode is the "square"-shaped arrangement: The 3 sub-converters are arranged in sequence from top to bottom, which are the first sub-converter, the second sub-converter, and the third sub-converter from top to bottom, and the 9 arms are arranged in a "3×3" arrangement; The third arrangement mode is the "triangle"-shaped arrangement: The first sub-converter, the second sub-converter, and the third sub-converter are arranged according to the three vertex positions of the triangle.

2. The method for arranging bridge arms and bridge arm reactors of a modular multi-level matrix converter according to claim 1, characterized in that: For the arm reactor, when the sub-converter adopts the first combination mode, the arm reactor is arranged near the second frequency side of the arm.

3. The method for arranging bridge arms and bridge arm reactors of a modular multi-level matrix converter according to claim 1, characterized in that: For the arm reactor, when the sub-converter adopts the second combination mode, the arm reactor is arranged near the first frequency side of the arm.

4. The method for arranging bridge arms and bridge arm reactors of a modular multi-level matrix converter according to claim 1, characterized in that: When the "one"-shaped arrangement is adopted between the three sub-converters: The 2 adjacent arms on the left and right of the first sub-converter and the second sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side; The 2 adjacent arms on the left and right of the second sub-converter and the third sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side.

5. The method for arranging bridge arms and bridge arm reactors of a modular multi-level matrix converter according to claim 1, characterized in that: When the "square"-shaped arrangement is adopted between the three sub-converters: The 3 adjacent arms on the top and bottom of the first sub-converter and the second sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side; The 3 adjacent arms on the top and bottom of the second sub-converter and the third sub-converter are not connected to the same AC phase on the first frequency side and the second frequency side.

6. The method for arranging bridge arms and bridge arm reactors of a modular multi-level matrix converter according to claim 1, characterized in that: When the three sub-converters are arranged in a "△" shape: the two closest bridge arms between the sub-converters are not connected to the same AC phase on the first frequency side and the second frequency side, and different sub-converters connected to the same AC phase on the first frequency side or the second frequency side should be arranged as far away as possible.

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