CN212183139U - Symmetrical single-pole flexible direct current converter station - Google Patents

Symmetrical single-pole flexible direct current converter station Download PDF

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Publication number
CN212183139U
CN212183139U CN202020347430.1U CN202020347430U CN212183139U CN 212183139 U CN212183139 U CN 212183139U CN 202020347430 U CN202020347430 U CN 202020347430U CN 212183139 U CN212183139 U CN 212183139U
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transformer
direct current
converter station
flexible direct
winding
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CN202020347430.1U
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Inventor
周月宾
曹婉钰
许树楷
张楠
朱喆
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CSG Electric Power Research Institute
Maintenance and Test Center of Extra High Voltage Power Transmission Co
Research Institute of Southern Power Grid Co Ltd
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Maintenance and Test Center of Extra High Voltage Power Transmission Co
Research Institute of Southern Power Grid Co Ltd
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Abstract

The utility model relates to the technical field of flexible direct current transmission, and discloses a symmetrical unipolar flexible direct current converter station, which comprises a modular multilevel converter, a transformer and a grounding module, wherein the input end of the transformer is used for being connected with an alternating current power grid, the output end of the transformer is connected with the input end of the modular multilevel converter, a neutral point of a valve side winding of the transformer is grounded through the grounding module, and a neutral point of a network side winding of the transformer is grounded or ungrounded; the grounding module comprises a large resistance unit and a large inductance unit which are connected in series. The utility model discloses a symmetrical unipolar type flexible direct current converter station can adopt optimization system design methods such as zero sequence injection to reduce equipment investment; and the number of used equipment is relatively small, so that the structure of the symmetrical unipolar flexible direct current converter station is simpler, and the cost is reduced. Furthermore, the utility model discloses a flexible direct current converter station of symmetry unipolar type's ground connection is respond well, can provide effectual ground potential reference for total station equipment.

Description

Symmetrical single-pole flexible direct current converter station
Technical Field
The utility model relates to a flexible direct current transmission of electricity technical field especially relates to a flexible direct current converter station of symmetry unipolar type.
Background
Compared with alternating current transmission and conventional direct current transmission, the flexible direct current transmission is used as a new generation of direct current transmission technology, can flexibly adjust the voltage of an alternating current system connected with the flexible direct current transmission while transmitting energy, has the remarkable advantages of better controllability, flexible operation mode and the like, and is widely applied to scenes of wind power integration, passive network power supply, asynchronous interconnection of power grids and the like.
At present, the existing flexible direct current converter station generally comprises a converter, a converter transformer device and the like. The flexible direct current converter station is mainly grounded in the following two ways; the first mode is as follows: the neutral point position of a winding at the side of a transformer valve in the flexible direct current converter station is grounded through a large resistor, as shown in figure 1; the second way is: the transformer valve side position in the flexible dc converter station is grounded via a star connection reactor as shown in fig. 2. However, in the process of implementing the present invention, the present inventors found that the prior art has at least the following technical problems: when the flexible direct current converter station is grounded in the first mode, although the grounding effect is good, the flexible direct current converter station cannot adopt optimized system design methods such as zero sequence injection and the like, so that the equipment investment is reduced; and when the flexible direct current converter station adopts the second middle mode grounding, the number of used equipment is large, and the cost of the flexible direct current converter station is increased.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a flexible direct current converter station of symmetry unipolar type can adopt the system design method of optimizing such as zero sequence injection to reduce equipment investment, the equipment quantity that uses moreover is less relatively.
In order to solve the technical problem, the utility model provides a flexible direct current converter station of symmetrical unipolar type, including modularization multilevel converter, transformer and ground connection module, the input of transformer is used for being connected with the alternating current electric wire netting, the output of transformer with the input of modularization multilevel converter is connected, the neutral point of the valve side winding of transformer passes through ground connection module ground connection; the grounding module comprises a large resistance unit and a large inductance unit which are connected in series.
As a preferred scheme, a neutral point of a valve side winding of the transformer is grounded through the grounding module, specifically:
the neutral point of the valve side winding of the transformer is connected with the first end of the large resistance unit, the second end of the large resistance unit is connected with the first end of the large inductance unit, and the second end of the large inductance unit is grounded.
As a preferred scheme, a neutral point of a valve side winding of the transformer is grounded through the grounding module, specifically:
the neutral point of the valve side winding of the transformer is connected with the first end of the large inductance unit, the second end of the large inductance unit is connected with the first end of the large resistance unit, and the second end of the large resistance unit is grounded.
Preferably, the large resistance unit is a resistor.
Preferably, the large inductance unit is a dry air core reactor or a voltage transformer.
Compared with the prior art, the utility model provides a flexible direct current converter station of symmetrical unipolar type, through making the neutral point of the valve side winding of the transformer in the flexible direct current converter station of symmetrical unipolar type through the big resistance unit and the big inductance unit ground connection of establishing ties, make the flexible direct current converter station of symmetrical unipolar type can adopt the system design method of optimizing such as zero sequence injection, in order to reduce the equipment investment; and the number of used equipment is relatively small, so that the structure of the symmetrical unipolar flexible direct current converter station is simpler, and the cost is reduced. Furthermore, the utility model discloses the flexible direct current converter station of symmetry unipolar type's ground connection is respond well, can provide effectual ground potential reference for total station equipment.
Drawings
Fig. 1 is a schematic diagram of a grounding mode of a symmetrical unipolar type flexible dc converter station in the prior art;
fig. 2 is a schematic diagram of another grounding method of a symmetrical unipolar type flexible dc converter station in the prior art;
fig. 3 is a schematic structural diagram of a symmetrical unipolar flexible dc converter station according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a modular multilevel converter according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a power unit according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of another power unit according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
Referring to fig. 3, it is a schematic structural diagram of a symmetric unipolar type flexible dc converter station provided in an embodiment of the present invention.
In the embodiment of the present invention, the symmetrical unipolar type flexible dc converter station includes a modular multilevel converter 1, a transformer 2 and a grounding module 3, an input end of the transformer 2 is used for being connected to an ac power grid, an output end of the transformer 2 is connected to an input end of the modular multilevel converter 1, and a neutral point of a valve side winding of the transformer 2 is grounded through the grounding module 3; the grounding module 3 comprises a large resistance unit 31 and a large inductance unit 32 connected in series.
The input end of the transformer 2 is connected with the alternating current power grid through an alternating current bus; the neutral point of the valve side winding of the transformer 2 is grounded through the grounding module 3, which is embodied as follows: the neutral point of the valve side winding of the transformer 2 is connected with one end of the grounding module 3, and the other end of the grounding module 3 is grounded.
The embodiment of the utility model provides an in, the theory of operation of the flexible direct current converter station of symmetry unipolar type specifically is: alternating current output by the alternating current power grid is input through the alternating current bus, flows through the transformer 2, is converted into direct current through the modular multilevel converter 1 and is output.
In the embodiment of the present invention, the neutral point of the valve side winding of the transformer 2 in the symmetrical unipolar type flexible dc converter station is grounded through the series connection of the large resistance unit 31 and the large inductance unit 32, so that the symmetrical unipolar type flexible dc converter station can adopt the optimized system design method such as zero sequence injection to reduce the equipment investment; and the number of used equipment is relatively small, so that the structure of the symmetrical unipolar flexible direct current converter station is simpler, and the cost is reduced. Furthermore, the utility model discloses the flexible direct current converter station of symmetry unipolar type's ground connection is respond well, can provide effectual ground potential reference for total station equipment.
It should be noted that the zero sequence injection design method specifically includes: certain zero sequence component (generally third harmonic) is injected into the output voltage of the flexible direct current converter station, so that a higher line voltage peak value is obtained under the condition of the same phase voltage peak value, and the direct current voltage utilization rate is improved.
In a preferred embodiment, the neutral point of the valve-side winding of the transformer 2 is grounded via the grounding module 3, specifically:
the neutral point of the valve side winding of the transformer 2 is connected to the first end of the large resistance unit 31, the second end of the large resistance unit 31 is connected to the first end of the large inductance unit 32, and the second end of the large inductance unit 32 is grounded.
In another preferred embodiment, a neutral point of a valve side winding of the transformer 2 is grounded through the grounding module 3, specifically:
the neutral point of the valve side winding of the transformer 2 is connected to the first end of the large inductance unit 32, the second end of the large inductance unit 32 is connected to the first end of the large resistance unit 31, and the second end of the large resistance unit 31 is grounded.
In the embodiment of the present invention, the type of the large resistance unit 31 can be set according to the actual use condition, and it is only necessary to ensure that the large resistance unit 31 has a larger resistance value; the resistance value of the large resistance unit 31 is generally in the kilo-ohm range in engineering experience. In order to simplify the structure and reduce the cost, it is preferable that the large resistance unit 31 is a resistor in the present embodiment.
In addition, the type of the large inductance unit 32 may also be set according to the actual use condition, and it is only necessary to ensure that the large inductance unit 32 has a larger inductance value; the inductance value of the large inductance unit 32 is typically of the order of kilohents in engineering experience. In order to simplify the structure and reduce the cost, it is preferable that the large inductance unit 32 in this embodiment is a dry air core reactor or other devices capable of being equivalent to an inductance, such as a voltage transformer.
The embodiment of the utility model provides an in, there is the zero sequence passageway in flexible direct current converter station, adopts transformer valve side winding neutral point position under the condition of the mode of big resistance ground connection at flexible direct current converter station, after flexible direct current converter station took zero sequence injection design method, ground resistance's consumption is great, leads to the consumption increase of flexible direct current converter station, and then has increased the equipment investment. The embodiment of the utility model provides a through making in the flexible direct current convertor station of symmetry unipolar type the neutral point of transformer 2's valve side winding is through establishing ties big resistance unit 31 and big inductance unit 32 ground connection have avoided the flexible direct current convertor station of symmetry unipolar type to take the zero sequence to pour into the design method after, the problem of equipment investment increase effectively, promptly the flexible direct current convertor station of symmetry unipolar type can adopt the system design method of optimizing such as zero sequence injection to reduce the equipment investment.
In a preferred embodiment, the grid-side winding of the transformer 2 may select a corresponding grounding mode according to an ac bus voltage input to the symmetrical unipolar type flexible dc converter station;
specifically, when the alternating-current bus voltage of the symmetrical unipolar flexible direct-current converter station is greater than or equal to 220V, the neutral point of the grid-side winding of the transformer 2 is grounded;
when the alternating-current bus voltage of the symmetrical unipolar flexible direct-current converter station is less than or equal to 110V, the neutral point of the grid-side winding of the transformer 2 is grounded through the arc suppression coil, or the neutral point of the grid-side winding of the transformer 2 is not grounded.
The embodiment of the present invention provides a method for grounding a network side winding of a transformer 2, which comprises the steps of, when the ac bus voltage of a symmetrical unipolar type flexible dc converter station is greater than or equal to 220V, making the neutral point of the network side winding of the transformer 2 is directly grounded, and when the ac bus voltage of the symmetrical unipolar type flexible dc converter station is less than or equal to 110V, making the neutral point of the network side winding of the transformer 2 is grounded through an arc suppression coil, or making the neutral point of the network side winding of the transformer 2 is ungrounded, so that under different ac bus voltages, the symmetrical unipolar type flexible dc converter station has a good grounding effect, and further ensures the safety of the symmetrical unipolar type flexible dc converter station.
In a preferred embodiment, as shown in fig. 4, the modular multilevel converter 1 comprises three legs 11, a first end of the leg 11 is a first output end of the modular multilevel converter 1, a second end of the leg 11 is a second output end of the modular multilevel converter 1, and a midpoint of the leg 11 is an input end of the modular multilevel converter 1;
the bridge arm 11 comprises two power modules 111 and a first bridge arm reactor L1And a second bridge arm reactor L2The first end of one power module 111 is the first end of the bridge arm 11, and the second end of the power module 111 and the first bridge arm reactor L1Is connected to the first end of the first leg reactor L1The second end of (a) is the midpoint of the bridge arm 11; the first bridge arm reactor L1And said second leg reactor L2Is connected to the first end of the second leg reactor L2Is connected to a first end of another power module 111, and a second end of the power module 111 is a second end of the bridge arm 11.
It can be understood that a first end of each of the bridge arms 11 is connected, a second end of each of the bridge arms 11 is connected, and a midpoint of one of the bridge arms 11 is correspondingly connected to an output end of the transformer 2.
Further, as shown in fig. 4 and 5, in a preferred embodiment, the power module 111 includes a plurality of power units, and the second terminal of one of the power units is connected to the first terminal of another one of the power units;
the power unit comprises a first insulated gate bipolar transistor VT1, a second insulated gate bipolar transistor VT2, a third insulated gate bipolar transistor VT3, a fourth insulated gate bipolar transistor VT4, a first capacitor C1, a first resistor R1 and a first switch W1, wherein a collector of the first insulated gate bipolar transistor VT1 is the first end of the power unit, a collector of the first insulated gate bipolar transistor VT1 is respectively connected with a collector of the third insulated gate bipolar transistor VT3, a first end of the first capacitor C1 and a first end of the first resistor R1, an emitter of the first insulated gate bipolar transistor VT1 is respectively connected with a collector of the second insulated gate bipolar transistor VT2 and a first end of the first switch W1, a second end of the first switch W1 is respectively connected with a collector of the second insulated gate bipolar transistor VT2 and a collector of the fourth insulated gate bipolar transistor VT4, an emitter of the second igbt VT2 is a second end of the power unit, an emitter of the second igbt VT2 is connected to an emitter of the fourth igbt VT4, a second end of the first capacitor C2, and a second end of the first resistor R2, respectively, and an emitter of the third igbt VT3 is connected to a collector of the fourth igbt VT 4.
It can be understood that, in the plurality of power units, the plurality of power units are connected in sequence, that is, the second end of one power unit is only connected to the first end of another power unit, and in the connected plurality of power units, the first end of the first power unit is the first end of the power module 111, and the second end of the last power unit is the second end of the power module 111.
In addition, the types of the first resistor R1 and the first capacitor C1 can be set according to actual use conditions; preferably, in this embodiment, the first resistor R1 is a voltage-sharing resistor; the first capacitor C1 is a power module capacitor.
In another preferred embodiment, as shown in fig. 4 and fig. 6, the power module 111 includes a plurality of power units, and the second terminal of one power unit is connected to the first terminal of another power unit;
the power unit comprises a fifth insulated gate bipolar transistor VT5, a sixth insulated gate bipolar transistor VT6, a second capacitor C2, a second resistor R2 and a second switch W2, the collector of the fifth igbt VT5 is the first terminal of the power cell, the collector of the fifth igbt VT5 is connected to the first terminal of the second capacitor C2 and the first terminal of the second resistor R2, the emitter of the fifth insulated gate bipolar transistor VT5 is connected to the collector of the sixth insulated gate bipolar transistor VT6 and to the first terminal of the second switch W2, the emitter of the sixth igbt VT6 is the second terminal of the power unit, an emitter of the sixth igbt VT6 is connected to the second terminal of the second switch W2, the second terminal of the second capacitor C2, and the second terminal of the second resistor R2, respectively.
It should be noted that the types of the second resistor R2 and the second capacitor C2 may be set according to actual use cases; preferably, in this embodiment, the second resistor R2 is a voltage-sharing resistor; the second capacitor C2 is a power module capacitor.
Furthermore, in the embodiment of the present invention, the symmetrical unipolar type flexible dc converter station further includes related devices for measurement and protection.
To sum up, the utility model provides a flexible direct current converter station of symmetrical unipolar type, including modularization multilevel converter, transformer and ground connection module, the input of transformer is connected with alternating current bus, the output of transformer with the input of modularization multilevel converter is connected, the neutral point of the valve side winding of transformer passes through ground connection module ground connection; the grounding module comprises a large resistance unit and a large inductance unit which are connected in series. The neutral point of the valve side winding of the transformer 2 in the symmetrical unipolar type flexible direct current converter station is grounded through the large resistance unit 31 and the large inductance unit 32 which are connected in series, so that the symmetrical unipolar type flexible direct current converter station can adopt an optimized system design method such as zero sequence injection and the like, and the equipment investment is reduced; and the number of used equipment is relatively small, so that the structure of the symmetrical unipolar flexible direct current converter station is simpler, and the cost is reduced. Furthermore, the utility model discloses the flexible direct current converter station of symmetry unipolar type's ground connection is respond well, can provide effectual ground potential reference for total station equipment.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and replacements can be made without departing from the technical principle of the present invention, and these modifications and replacements should also be regarded as the protection scope of the present invention.

Claims (5)

1. The symmetrical unipolar flexible direct-current converter station is characterized by comprising a modular multilevel converter, a transformer and a grounding module, wherein the input end of the transformer is used for being connected with an alternating-current power grid, the output end of the transformer is connected with the input end of the modular multilevel converter, and a neutral point of a valve side winding of the transformer is grounded through the grounding module; the grounding module comprises a large resistance unit and a large inductance unit which are connected in series.
2. The symmetrical unipolar flexible dc converter station according to claim 1, wherein a neutral point of a valve-side winding of the transformer is grounded through the grounding module, specifically:
the neutral point of the valve side winding of the transformer is connected with the first end of the large resistance unit, the second end of the large resistance unit is connected with the first end of the large inductance unit, and the second end of the large inductance unit is grounded.
3. The symmetrical unipolar flexible dc converter station according to claim 1, wherein a neutral point of a valve-side winding of the transformer is grounded through the grounding module, specifically:
the neutral point of the valve side winding of the transformer is connected with the first end of the large inductance unit, the second end of the large inductance unit is connected with the first end of the large resistance unit, and the second end of the large resistance unit is grounded.
4. The symmetrical unipolar flexible direct current converter station according to any one of claims 1-3, wherein said high resistance units are resistors.
5. A symmetrical unipolar flexible dc converter station according to any one of claims 1 to 3, characterized in that said large inductance unit is a dry air reactor or a voltage transformer.
CN202020347430.1U 2020-03-18 2020-03-18 Symmetrical single-pole flexible direct current converter station Active CN212183139U (en)

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Application Number Priority Date Filing Date Title
CN202020347430.1U CN212183139U (en) 2020-03-18 2020-03-18 Symmetrical single-pole flexible direct current converter station

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202020347430.1U CN212183139U (en) 2020-03-18 2020-03-18 Symmetrical single-pole flexible direct current converter station

Publications (1)

Publication Number Publication Date
CN212183139U true CN212183139U (en) 2020-12-18

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Country Status (1)

Country Link
CN (1) CN212183139U (en)

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