CN119995367B - An AC/DC solid-state transformer and mixing modulation method based on MMC embedded module - Google Patents
An AC/DC solid-state transformer and mixing modulation method based on MMC embedded moduleInfo
- Publication number
- CN119995367B CN119995367B CN202510485381.5A CN202510485381A CN119995367B CN 119995367 B CN119995367 B CN 119995367B CN 202510485381 A CN202510485381 A CN 202510485381A CN 119995367 B CN119995367 B CN 119995367B
- Authority
- CN
- China
- Prior art keywords
- switch tube
- bridge arm
- ports
- voltage
- embedded module
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Landscapes
- Inverter Devices (AREA)
Abstract
The application provides an alternating current-direct current solid-state transformer based on an MMC embedded module, which comprises a low-voltage direct current port, a three-phase DC/AC converter, a three-phase circuit topology and a medium-voltage alternating current port, wherein the three-phase circuit topology comprises three identical single-phase circuits, each single-phase circuit comprises an upper bridge arm, an upper bridge arm inductor, an embedded module, a lower bridge arm inductor and a lower bridge arm inductor, and the embedded module comprises a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube and a sixth switching tube, a direct current capacitor and a high-frequency transformer. The application reduces the number of the high-frequency transformers of the traditional solid-state transformer to only 1 by introducing one embedded module, greatly reduces the volume of the solid-state transformer, and eliminates the high-frequency pulse voltage generated by the embedded module because the upper bridge arm and the lower bridge arm generate high-frequency voltage pulses. Therefore, the high-frequency pulse voltage output by the embedded module does not deteriorate the bridge arm circulating current.
Description
Technical Field
The application relates to the technical field of power systems, in particular to a compact medium/low voltage alternating current/direct current solid-state transformer based on an MMC middle point embedded sub-module and a mixing modulation method.
Background
The solid state transformer (solid state transformer, SST) is typically composed of a power electronic circuit and a high frequency transformer, and is a novel power electronic device with the voltage class conversion and electrical isolation functions of a conventional power frequency transformer. By increasing the operating frequency of the isolation transformer, SST significantly reduces the volume and weight of the transformer. Compared with the traditional power frequency transformer, the SST has higher flexibility, and can conveniently realize multiple functions such as fault tolerance, electric energy quality adjustment, direct current access of renewable energy sources and energy storage equipment, multiport operation and the like.
SST is used as an electric energy conversion device, and the topological structure and the control method of the SST are closely related to specific application scenes. In early studies, the input side of SSTs was typically connected to a medium voltage or medium voltage ac distribution network. Cascaded H-bridges (CASCADED H-Bridge, CHB) and modular multilevel converters (Modular Multilevel Converter, MMC) are the most common two input stage topologies. In the SST (CHB-SST) adopting the CHB structure, the direct current side of each CHB sub-module is connected with a bidirectional active bridge (Dual Active Bridge, DAB) based on a high-frequency isolation transformer, and the other sides of the DAB units are connected on a low-voltage direct current bus in parallel, so that high-current output is realized. In the SST (MMC-SST) adopting an MMC structure, the direct current side of each sub-module is also connected with a DAB unit, and the output ends are connected in parallel to form a low-voltage direct current port.
Compared with CHB-SST, MMC-SST can directly realize the output of Medium Voltage Alternating Current (MVAC) and Medium Voltage Direct Current (MVDC) ports, so the conversion stage number is smaller. Because each MMC sub-module in the MMC-SST is provided with a Double Active Bridge (DAB) conversion unit, the number of DAB units required by a seed topology structure is consistent with that of the MMC sub-modules, so that the number of transformers is excessive, the insulation grade requirement is high, and the problems of huge volume and high cost are caused.
Disclosure of Invention
In order to overcome the technical defects, the application provides an alternating current-direct current solid-state transformer based on an MMC embedded module and a mixing modulation method, and the application is realized according to the following technical scheme:
The application provides an alternating current-direct current solid-state transformer based on an MMC embedded module, which is characterized by comprising a low-voltage direct current port, a three-phase DC/AC converter, a three-phase circuit topology and a medium-voltage alternating current port;
The three-phase circuit topology comprises three same single-phase circuits, wherein each single-phase circuit comprises an upper bridge arm, an upper bridge arm inductor, an embedded module, a lower bridge arm and a lower bridge arm inductor;
The embedded module comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube and a sixth switch tube, a direct current capacitor and a high-frequency transformer, wherein the collector node of the first switch tube and the emitter node of the second switch tube are connected with one end of a primary side winding of the high-frequency transformer and one end of an upper bridge arm inductor to form a node m, the emitter node of the fourth switch tube and the collector node of the third switch tube are connected with one end of a primary side winding of the high-frequency transformer and one end of a lower bridge arm inductor to form a node n, the emitter nodes of the first switch tube, the third switch tube and the sixth switch tube are connected with the negative end of the direct current capacitor, the collector nodes of the second switch tube, the fourth switch tube and the fifth switch tube are connected with the positive end of the direct current capacitor, one end of a secondary side winding of the high-frequency transformer is connected with the three-phase DC/AC converter, and one end of a secondary side winding of the high-frequency transformer is connected with one end of the high-phase DC/AC converter and one end of the secondary winding is connected with the low-voltage side winding of the high-frequency transformer;
the upper bridge arm and the lower bridge arm comprise a plurality of half-bridge sub-modules, and the half-bridge sub-modules are connected in series;
One end of the last half-bridge submodule in the upper bridge arm is connected with the other end of the upper bridge arm inductor, and one end of the first half-bridge submodule in the lower bridge arm is connected with the other end of the lower bridge arm inductor;
the positive electrode end and the negative electrode end of the low-voltage direct current port are respectively connected with the three-phase DC/AC converter;
the medium-voltage alternating current port is formed by three ports respectively led out from connecting lines between the fifth switching tube and the sixth switching tube, wherein the connecting lines are included by the three single-phase line embedded modules.
Optionally, the method comprises:
one end of the first half-bridge sub-module in the upper bridge arm is connected with one end of the first half-bridge sub-module in the upper bridge arm in the other two phases, and one end of the last half-bridge sub-module in the lower bridge arm is connected with the last half-bridge sub-module in the lower bridge arm in the other two phases.
In a second aspect, the present application provides a mixing modulation method, for the compact medium/low voltage ac/dc solid-state transformer based on the MMC midpoint embedded sub-module according to the first aspect, comprising:
an embedded module is arranged between an upper bridge arm and a lower bridge arm of a single-phase line, and upper and lower ports of the embedded module respectively generate first high-frequency voltage pulses as input voltages on the primary side of a high-frequency transformer;
The upper bridge arm and the lower bridge arm respectively generate second high-frequency voltage pulses, wherein the first high-frequency voltage pulses and the second high-frequency voltage pulses are equal in size and opposite in direction.
Optionally, when the upper and lower ports of the embedded module respectively generate the first high-frequency voltage, the embedded module comprises a first working state, a second working state, a third working state and a fourth working state;
the first working state is that the first switching tube, the fourth switching tube and the fifth switching tube are conducted, the second switching tube and the third switching tube are turned off, the direct-current capacitor is reversely put into the working state, the output voltages U mn of m and n ports are-U c, the output voltages U mx of m and x ports are-U c, and the output voltages U mx of x and n ports are 0.
Optionally, the second working state is that the first switching tube, the fourth switching tube and the sixth switching tube are turned on, the second switching tube, the third switching tube and the fifth switching tube are turned off, the direct-current capacitors are reversely put into the working state, the m and n port output voltages U mn are-U c, the m and x port output voltages U mx are 0, and the x and n port output voltages U mx are-U c.
Optionally, the third working state is that the second switching tube, the third switching tube and the fifth switching tube are turned on, the first switching tube, the fourth switching tube and the sixth switching tube are turned off, the direct-current capacitor is thrown in forward direction, the output voltages U mn of m and n ports are U c, the output voltages U mx of m and x ports are 0, and the output voltage U mx of x and n ports is U c.
Optionally, the fourth working state is that the second switching tube, the third switching tube and the sixth switching tube are turned on, the first switching tube, the fourth switching tube and the fifth switching tube are turned off, the direct-current capacitor is thrown in the forward direction, the m and n port output voltages U mn are U c, the m and x port output voltages U mx are U c, and the x and n port output voltages U mx are 0.
The application has the following beneficial effects:
The CMMC-SST topology provided by the application reduces the number of high-frequency transformers of the traditional solid-state transformer to only 1 by introducing one embedded module, so that the volume of the solid-state transformer is greatly reduced, and in addition, the high-frequency pulse voltage generated by the embedded module can be eliminated because the upper bridge arm and the lower bridge arm generate high-frequency voltage pulses, so that the high-frequency pulse voltage output by the embedded module does not deteriorate bridge arm circulating current.
In addition to the objects, features and advantages described above, the present application has other objects, features and advantages. The application will be described in further detail with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
fig. 1 is a schematic diagram of an ac/dc solid-state transformer topology based on an MMC embedded module according to an embodiment of the present application;
FIG. 2 is a schematic diagram of high-frequency pulse voltages of m and n ports of an embedded module according to an embodiment of the present application;
Fig. 3 (a) is an equivalent circuit diagram of the embedded module provided in the embodiment of the present application in the first working state;
Fig. 3 (b) is an equivalent circuit diagram of the embedded module provided in the embodiment of the present application in the second working state;
fig. 3 (c) is an equivalent circuit diagram of the embedded module provided in the embodiment of the present application in a third working state;
fig. 3 (d) is an equivalent circuit diagram of the embedded module provided in the embodiment of the present application in a fourth operating state;
fig. 4 is a schematic diagram of an upper and lower bridge arm modulation principle provided by an embodiment of the present application;
FIG. 5 (a) is a schematic diagram of u mx when the embedded module provided in the embodiment of the present application is in the second working state and the fourth working state;
Fig. 5 (b) is a schematic diagram of u xn when the embedded module provided in the embodiment of the present application is in the first working state and the third working state;
FIG. 6 (a) is a schematic diagram of u mx when the embedded module provided in the embodiment of the present application is in the second operating state and the fourth operating state;
Fig. 6 (b) is a schematic diagram of u mx when the embedded module provided in the embodiment of the present application is in the second operating state and the fourth operating state.
Detailed Description
Embodiments of the application are described in detail below with reference to the attached drawings, but the application can be implemented in a number of different ways, which are defined and covered by the claims.
In order to solve the problems in the background art, as shown in FIG. 1, the application provides an alternating-direct current solid-state transformer (CMMC-SST) based on an MMC embedded module, which comprises a low-voltage direct current port, a three-phase DC/AC converter, a three-phase circuit topology and a medium-voltage alternating current port;
the three-phase circuit topology comprises three identical single-phase circuits, namely an A phase, a B phase and a C phase, wherein each single-phase circuit comprises an upper bridge arm, an upper bridge arm inductor L 1, an embedded module, a lower bridge arm and a lower bridge arm inductor L 2;
The embedded module comprises a first switch tube S 1, a second switch tube S 2, a third switch tube S 3, a fourth switch tube S 4, a fifth switch tube S 5 and a sixth switch tube S 6, a direct-current capacitor C and a high-frequency transformer T 1, six uplink switch tubes, mainly 6 switch devices based on silicon-based insulated gate bipolar transistors (Insulated Gate Bipolar Transistor, IGBT), wherein the embedded module realizes the construction of a direct-current port of a CMMC-SST, and the specific connection mode is as follows:
The collector node of the first switching tube S 1, the emitter node of the second switching tube S 2, the node formed by connecting the primary winding side end of the high-frequency transformer T 1 and one end of the upper bridge arm inductor L 1 is m, the emitter node of the fourth switching tube S 4, the collector node of the third switching tube S 3, the node formed by connecting the other end of the primary winding of the high-frequency transformer T 1 and one end of the lower bridge arm inductor L 2 is n, the emitter nodes of the first switching tube S 1, the third switching tube S 3 and the sixth switching tube S 6 are connected to the negative end of the direct-current capacitor, the collector nodes of the second switching tube S 2, the fourth switching tube S 4 and the fifth switching tube S 5 are connected to the positive end of the direct-current capacitor C, the secondary winding end of the high-frequency transformer T 1 is connected to the three-phase DC/AC converter, and the secondary winding end of the high-frequency transformer T 1 is connected to the low-voltage medium-current node;
the upper bridge arm and the lower bridge arm comprise a plurality of half-bridge sub-modules HSM, the plurality of half-bridge sub-modules are connected in series, one end of the last half-bridge sub-module in the upper bridge arm is connected with the other end of the upper bridge arm inductor, and one end of the first half-bridge sub-module in the lower bridge arm is connected with the other end of the lower bridge arm inductor;
the positive electrode end and the negative electrode end of the low-voltage direct current port are respectively connected with the three-phase DC/AC converter;
The medium-voltage alternating current port is formed by three ports respectively led out from connecting lines between a fifth switching tube and a sixth switching tube which are included in the embedded module on the three single-phase lines.
The CMMC-SST comprises a low-voltage direct current port and a medium-voltage alternating current port, and each phase only comprises one high-frequency transformer (T 1) for realizing energy exchange and electrical isolation.
The embedded module of CMMC-SST topology can lead out the direct current port through only one high-frequency transformer, and compared with the mode that the MVDC port adopts a capacitor series voltage division structure, the number of the high-frequency transformers can be greatly reduced, and the volume of the device is reduced.
The application provides a mixing modulation strategy aiming at the CMMC-SST topology, wherein an embedded module is arranged between an upper bridge arm and a lower bridge arm of a single-phase line, and m and n ports of the embedded module generate a first high-frequency pulse voltage as an input voltage of a primary side of a high-frequency transformer by controlling the closing of a switching tube of the embedded module. In addition, the upper bridge arm and the lower bridge arm respectively generate opposite second high-frequency pulse voltages to counteract the influence of the high-frequency pulse voltages at the m port and the n port on the circulating current, and the specific analysis is as follows:
(1) Modulation principle of middle embedded module
The m and n ports of the embedded module can generate two levels of U c、-Uc, and the specific switching mode is shown in table 1.
Table 1 in-line module switch mode
,
Note that "1" represents device on and "0" represents device off
The modulation principle of the modulation voltage of the m and n ports is shown in figure 2 by controlling the switch device of the embedded module.
As can be seen from table 1, according to the different on states of the switching tube, the 4 operating states of the embedded module are as shown in fig. 3 (a) -3 (d):
In the first working state (a), the first switching tube S 1, the fourth switching tube S 4 and the fifth switching tube S 5 are turned on, the second switching tube S 2, the third switching tube S 3 and the sixth switching tube S 6 are turned off, the direct-current capacitors are reversely put into operation, the m and n-port output voltages U mn are-U c, the m and x-port output voltages U mx are-U c, and the x and n-port output voltages U mx are 0.
In the second working state (b), the first switching tube S 1, the fourth switching tube S 4 and the sixth switching tube S 6 are turned on, the second switching tube S 2, the third switching tube S 3 and the fifth switching tube S 5 are turned off, the direct-current capacitors are reversely put into operation, the m and n-port output voltages U mn are-U c, the m and x-port output voltages U mx are 0, and the x and n-port output voltages U mx are-U c.
In the third working state (c), the second switching tube S 2, the third switching tube S 3 and the fifth switching tube S 5 are turned on, the first switching tube S 1, the fourth switching tube S 4 and the sixth switching tube S 6 are turned off, the direct-current capacitors are positively input, the m and n-port output voltages U mn are U c, the m and x-port output voltages U mx are 0, and the x and n-port output voltages U mx are U c.
In the fourth operating state (d), the second switching tube S 2、S3 and the sixth switching tube S 6 are turned on, the first switching tube S 1, the fourth switching tube S 4 and the fifth switching tube S 5 are turned off, the direct-current capacitors are positively charged, the m-port output voltage U mn is U c, the m-port output voltage U mx is U c, and the x-port output voltage U mx is 0.
2) Upper and lower bridge arm modulation principle
According to the working state analysis of the embedded module, the sum of the direct-current voltages of the MMC can be changed by the high-frequency pulse voltages of the m and n ports, and if the upper bridge arm and the lower bridge arm are not controlled, the pulse voltages can be superimposed to the bridge arm inductance, so that the circulating current of the system is increased. In order to eliminate the influence of the high-frequency pulse voltages of the m and n ports on the total voltage of the MMC bridge arm. The upper and lower legs need to output an additional high frequency voltage-u mx and-u xn, respectively, in opposite directions, as shown in fig. 4.
As can be seen from fig. 2, the high-frequency pulse voltages of the m and n ports can be decomposed into two high-frequency voltages u mx and u xn of the m and x ports and the x and n ports, as shown in fig. 5 (a) -5 (b) and fig. 6 (a) -6 (b). According to the working state of the middle embedded module, the working states of the upper bridge arm and the lower bridge arm can be divided into the following two cases:
When the embedded module operates in the second working state (b) and the fourth working state (d), the m and x ports equivalently output pulse voltage of +U c level, and the x and n ports equivalently output pulse voltage of-U c. When the output voltages of the m and the x ports are +U c, the upper bridge arm needs to input 1 sub-module, and when the output voltages of the x and the n ports are-U c, the lower bridge arm needs to input 1 sub-module.
When the embedded module operates in the first working state (a) and the third working state (c), the m and x ports equivalently output pulse voltages of-U c level, and the x and n ports equivalently output pulse voltages of +U c. When the output voltages of the m and the x ports are-U c, the upper bridge arm needs to input more than 1 sub-module, and when the output voltages of the x and the n ports are +U c, the lower bridge arm needs to input less than 1 sub-module.
In summary, the middle embedded module and the upper bridge arm submodule and the lower bridge arm submodule are cooperatively matched in the MMC-SST operation principle, so that the influence of high-frequency pulse voltages of m and n ports of the middle embedded module on the bridge arm voltage can be eliminated.
In summary, the CMMC-SST topology provided by the application reduces the number of high-frequency transformers of the traditional solid-state transformer to only 1 per phase by introducing an embedded module, so that the volume of the solid-state transformer is greatly reduced, and in addition, the bridge arm circulating current is not deteriorated due to the high-frequency pulse voltage output by the embedded module.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (7)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202510485381.5A CN119995367B (en) | 2025-04-17 | 2025-04-17 | An AC/DC solid-state transformer and mixing modulation method based on MMC embedded module |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202510485381.5A CN119995367B (en) | 2025-04-17 | 2025-04-17 | An AC/DC solid-state transformer and mixing modulation method based on MMC embedded module |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN119995367A CN119995367A (en) | 2025-05-13 |
| CN119995367B true CN119995367B (en) | 2025-07-18 |
Family
ID=95625005
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202510485381.5A Active CN119995367B (en) | 2025-04-17 | 2025-04-17 | An AC/DC solid-state transformer and mixing modulation method based on MMC embedded module |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN119995367B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN120262936B (en) * | 2025-06-04 | 2025-09-02 | 湖南大学 | A hybrid MMC and its operation strategy based on dual-end sharing of Si/SiC intensive redundant modules |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017128499A1 (en) * | 2016-01-27 | 2017-08-03 | 东南大学 | Four-port power electronic transformer based on hybrid modular multilevel converter |
| CN111817599A (en) * | 2020-07-16 | 2020-10-23 | 哈尔滨工业大学 | Multiport power router and control method thereof |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118117905A (en) * | 2024-03-04 | 2024-05-31 | 南京师范大学 | Hexagonal solid-state transformer topology, control method and device |
| CN119482763B (en) * | 2024-11-14 | 2025-10-03 | 南京师范大学 | Solid-state transformer topology based on MMC lightweight submodule and its mixing frequency modulation method |
-
2025
- 2025-04-17 CN CN202510485381.5A patent/CN119995367B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017128499A1 (en) * | 2016-01-27 | 2017-08-03 | 东南大学 | Four-port power electronic transformer based on hybrid modular multilevel converter |
| CN111817599A (en) * | 2020-07-16 | 2020-10-23 | 哈尔滨工业大学 | Multiport power router and control method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN119995367A (en) | 2025-05-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US20190052177A1 (en) | Power electronic conversion unit and system | |
| EP2946464B1 (en) | A multilevel converter with hybrid full-bridge cells | |
| CN109067218B (en) | A solid-state transformer topology construction method based on multi-level sub-modules | |
| CN108173442B (en) | Isolated modular multilevel converter based on high-frequency chain technology | |
| CN107863884A (en) | A kind of multiple module commutator transformer | |
| CN107834854A (en) | A kind of high-voltage large-capacity commutator transformer | |
| CN112910302B (en) | A power router and a power router control method | |
| CN110311381A (en) | A kind of alternating current-direct current mixing grid power electronic transformer passing through DC Line Fault | |
| CN102097967B (en) | Cascaded multi-level converter | |
| CN107070249A (en) | A kind of electric power electric transformer applied to alternating current-direct current power distribution network | |
| US10873254B2 (en) | Electrical circuit for zero-voltage soft-switching in DC-DC converter under all load conditions | |
| CN119995367B (en) | An AC/DC solid-state transformer and mixing modulation method based on MMC embedded module | |
| CN108199586A (en) | A kind of high potential high voltage direct current draw-out power supply device | |
| CN108471250B (en) | Five-level topological structure for power conversion system | |
| CN101834451A (en) | High voltage back-to-back converter | |
| CN106100361A (en) | A kind of ac-dc conversion circuit and electric power electric transformer | |
| CN115940649A (en) | SST topology and fault ride-through method based on bridge arm multiplexing of MMC submodules | |
| CN113489359A (en) | Submodule topology with direct-current fault clearing capability | |
| CN209562411U (en) | High-frequency-chain bidirectional direct-current transformer connected with bidirectional switch | |
| CN108494229B (en) | A universal AC/DC power router topology and control method thereof | |
| CN111049389A (en) | Direct current transformer | |
| CN116345550A (en) | True Bipolar Low Voltage DC System Based on Isolated Modular Multilevel Converter | |
| CN112968612A (en) | Modular high-transformation-ratio isolated DC-DC converter | |
| CN113726162A (en) | Series network type transformer based on voltage reduction type public direct current bus | |
| CN113014086A (en) | Direct-current transformer topological structure with high voltage transmission ratio and control method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |