CN110544580A - Main transformer and boosting system of offshore wind power plant boosting station - Google Patents
Main transformer and boosting system of offshore wind power plant boosting station Download PDFInfo
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- CN110544580A CN110544580A CN201811287591.XA CN201811287591A CN110544580A CN 110544580 A CN110544580 A CN 110544580A CN 201811287591 A CN201811287591 A CN 201811287591A CN 110544580 A CN110544580 A CN 110544580A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/28—Coils; Windings; Conductive connections
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/40—Structural association with built-in electric component, e.g. fuse
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F29/00—Variable transformers or inductances not covered by group H01F21/00
- H01F29/02—Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings
- H01F29/04—Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings having provision for tap-changing without interrupting the load current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
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Abstract
the application relates to an offshore wind farm booster station and a booster system. Wherein, offshore wind power plant booster station owner transformer includes: the high-voltage side winding is connected with the first submarine cable, and the low-voltage side winding is connected with the second submarine cable. The high-voltage side winding, the low-voltage side winding and the additional winding are wound on the iron core. The high-voltage side winding and the low-voltage side winding are both star-connected windings; the additional windings are delta-connected windings. The neutral point of the low-voltage side winding is grounded through a grounding resistor. Based on the structure, the neutral point grounding mode of a low-voltage side system in the traditional offshore wind farm booster station can be changed, the probability of cable faults can be reduced when a single-phase grounding fault occurs in the offshore wind farm, and the safe operation of the whole booster station is guaranteed. Meanwhile, when the low-voltage side of the main transformer has single-phase earth fault, the high-voltage side switch of the main transformer is prevented from tripping, the running reliability of the wind power plant is improved, and the generated energy of the wind power plant is ensured to be sent out.
Description
Technical Field
The application relates to the technical field of offshore wind power generation, in particular to a main transformer and a boosting system of a boosting station of an offshore wind farm.
Background
According to the latest data, wind power generation is only second to hydroelectric power generation and accounts for 16% of the power generation amount of global renewable resources. Under the environment of global high concern on developing low-carbon economy, offshore wind power has become the dominant force of renewable energy power. In a coastal region with dense population, a gigawatt-level offshore wind farm can be quickly established, so that offshore wind power can become one of important technologies for reducing carbon emission in the energy production link in an economic and effective mode. Although the offshore wind power starts late, the offshore wind power is rapidly developed all over the world in recent years by virtue of the characteristics of stability of sea wind resources and large power generation power, has the characteristic of high dependence on technical drive, and has the condition of serving as a core power supply to promote the development of global low-carbon economy. Therefore, with the development of offshore wind power, the related technology will be changed day by day.
In the implementation process, the inventor finds that at least the following problems exist in the conventional technology: when a single-phase earth fault occurs on the low-voltage side of the main transformer, the protection of the cable and the reliability of the power generation of the transformer cannot be considered.
Disclosure of Invention
therefore, it is necessary to provide a main transformer and a boosting system for an offshore wind farm booster station, which are used for solving the problem that safety and reliability cannot be both considered when a single-phase ground fault occurs on the low-voltage side of the main transformer in the conventional technology.
In order to achieve the above object, in one aspect, an embodiment of the present application provides a main transformer of an offshore wind farm booster station, including: the device comprises an iron core, an additional winding, a grounding resistor, a high-voltage side winding used for being connected with a first submarine cable, and a low-voltage side winding used for being connected with a second submarine cable.
The high-voltage side winding, the low-voltage side winding and the additional winding are wound on the iron core. The high-voltage side winding is a star-connected winding; the low-voltage side winding is a star-connected winding; the additional windings are delta-connected windings. The neutral point of the low-voltage side winding is grounded through a grounding resistor.
in one embodiment, the additional winding is a winding with a preset capacity; the value range of the preset capacity is 33% to 30% of the rated capacity of the main transformer.
In one embodiment, the first submarine cable is a 220kV (kilovolt) bus.
the second submarine cable is a 35kV bus.
In one embodiment, the low voltage side winding comprises a first low voltage side winding, a second low voltage side winding for connecting to a second sea cable. The ground resistor includes a first ground resistor and a second ground resistor. The neutral point of the first low-voltage side winding is grounded through a first grounding resistor; the neutral point of the second low-voltage side winding is grounded through a second grounding resistor.
In one embodiment, the device further comprises a switch circuit; the high-voltage side winding is grounded through the switching circuit.
On the other hand, the embodiment of the application also provides an offshore wind farm booster system, which comprises a first submarine cable used for connecting an onshore booster station, a second submarine cable used for connecting an offshore wind turbine, and the offshore wind farm booster station main transformer. A high-voltage side winding of the main transformer is connected with a first submarine cable; and a low-voltage side winding of the main transformer is connected with the second submarine cable.
In one embodiment, the number of main transformers is two; the first submarine cable comprises two 220kV buses; the second submarine cable comprises at least two 35kV busbars. The high-voltage side winding is connected with a corresponding 220kV bus; and the low-voltage side winding is connected with a corresponding 35kV bus.
In one embodiment, the system further comprises a station transformer. And the low-voltage side winding is connected with the transformer for the station through a corresponding 35kV bus.
In one embodiment, the station transformer is a Z-connected transformer.
In one embodiment, the station transformer comprises an in-station transformer core, a first winding in triangular connection, and a second winding in star connection; the first winding is wound on the transformer iron core in the station; the second winding is wound on the transformer core in the station. The first winding is connected with a corresponding 35kV bus.
one of the above technical solutions has the following advantages and beneficial effects:
Marine wind power plant booster station main transformer includes: the device comprises an iron core, an additional winding, a grounding resistor, a high-voltage side winding used for being connected with a first submarine cable, and a low-voltage side winding used for being connected with a second submarine cable. The high-voltage side winding, the low-voltage side winding and the additional winding are wound on the iron core. The high-voltage side winding is a star-connected winding; the low-voltage side winding is a star-connected winding; the additional windings are delta-connected windings. The neutral point of the low-voltage side winding is grounded through a grounding resistor. Based on the structure, the neutral point grounding mode of a low-voltage side system in the traditional offshore wind farm booster station can be changed, the probability of cable faults can be reduced when a single-phase grounding fault occurs in the offshore wind farm, and the safe operation of the whole booster station is guaranteed. Meanwhile, when the low-voltage side of the main transformer has single-phase earth fault, the high-voltage side switch of the main transformer is prevented from tripping, the running reliability of the wind power plant is improved, and the generated energy of the wind power plant is ensured to be sent out.
Drawings
The foregoing and other objects, features and advantages of the application will be apparent from the following more particular description of preferred embodiments of the application, as illustrated in the accompanying drawings. Like reference numerals refer to like parts throughout the drawings, and the drawings are not intended to be drawn to scale in actual dimensions, emphasis instead being placed upon illustrating the subject matter of the present application.
FIG. 1 is a first schematic block diagram of a conventional offshore wind farm booster station;
FIG. 2 is a second schematic block diagram of a conventional offshore wind farm booster station;
FIG. 3 is a schematic external view of a split transformer of a conventional offshore wind farm booster station;
FIG. 4 is a schematic diagram of a conventional 35kV system wiring of a booster station of an offshore wind farm;
FIG. 5 is a third schematic block diagram of a conventional offshore wind farm booster station;
FIG. 6 is a first schematic block diagram of a main transformer of a booster station of an offshore wind farm in one embodiment;
FIG. 7 is a second schematic block diagram of a main transformer of a booster station of an offshore wind farm in one embodiment;
FIG. 8 is a third schematic block diagram of a main transformer of a booster station of an offshore wind farm in one embodiment;
FIG. 9 is a first schematic block diagram of an offshore wind farm boost system in one embodiment;
FIG. 10 is a second schematic block diagram of an offshore wind farm boost system in one embodiment.
Detailed Description
to facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are shown in the drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element and be integral therewith, or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
A conventional offshore wind farm booster station can be as shown in fig. 1, where fig. 1 is a first schematic structural diagram of the conventional offshore wind farm booster station, and two 220/35/35kV three-phase and copper winding with a capacity of 240MVA (megavolt ampere), natural oil circulation, self-cooling, oil-immersed, low-loss, low-voltage double-split on-load voltage regulation power transformers are arranged in one 220kV offshore booster station. 2-in 2-out inner bridge type wiring is adopted at the 220kV side; the 35kV side adopts 4 sections of single buses to connect, and buses among different main transformers (main transformers) are communicated. 2-circuit 220kV three-core 3X 500mm2 (square millimeter) and XLPE (cross-linked polyethylene) insulated submarine cables (called submarine cables for short) are adopted to be transmitted to an onshore centralized control center.
The 35kV system of the offshore booster station is connected with the fan through a 35kV submarine cable, the number of cables is large, the current of a single-phase grounding capacitor is large, and arc light overvoltage is prevented from occurring when the 35kV system is grounded in a single phase, so that electric equipment is damaged, even insulation breakdown to the ground is caused.
According to the requirement of the measure of a power grid company, the single-phase fault of a wind power plant collection line system is required to be quickly removed, meanwhile, all the collection lines of the offshore wind power plant adopt submarine cables, the capacitance current is large, a proper grounding mode is recommended to be adopted so as to limit the overvoltage level, and the single-phase grounding fault can be quickly removed through corresponding protection. The neutral point grounding mode of the offshore wind power plant is considered as follows: the grounding mode of the neutral point at the high-voltage side of the main transformer is determined according to the short-circuit current level in the power grid, and because the capacitance current level of the submarine cable is very high, the grounding mode of the neutral point at the low-voltage side of the main transformer adopts resistance grounding, so that faults can be quickly removed; when no neutral point is led out from the low-voltage side of the main transformer, it can be considered that each section of bus or low-voltage outlet of the low-voltage side of the main transformer is provided with a set of grounding transformer and grounding resistor.
in a conventional offshore wind farm project, the offshore booster station may be as shown in fig. 2 to 4, and fig. 2 is a second schematic structural diagram of the conventional offshore wind farm booster station; FIG. 3 is a schematic external view of a split transformer of a conventional offshore wind farm booster station; FIG. 4 is a schematic diagram of a conventional 35kV system wiring of a booster station of an offshore wind farm. In an offshore wind power project, a winding connection group wiring scheme of a main transformer of an offshore booster station is YN, d11-d11 or YN, d11, namely, the wiring type of a winding at the low-voltage side of 35kV is triangular connection, and a neutral point cannot be led out. Therefore, a neutral point grounding transformer can be arranged on a 35kV bus at a 35kV neutral point, and is used as grounding equipment of a 35kV system, namely, a mode of grounding and small-resistance grounding is adopted, a set of grounding transformer (grounding transformer for short) and a resistance cabinet is arranged on each section of 35kV bus, and a station transformer (station transformer for short) is also used as the grounding transformer. When the wind power plant is in single-phase grounding, a fault loop is quickly tripped, and the electrical equipment of the wind power plant is protected.
The above conventional techniques have the following disadvantages:
1. If the grounding transformer on the 35kV bus fails, namely, the incoming switch on the 35kV bus is tripped at the moment. Because in this scheme, the 35kV cable between main transformer low-voltage side to 35kV generating line service switch can't set up the protection, if this department takes place single-phase earth fault this moment, this section cable can not break off because do not dispose corresponding protection, then can lead to the trouble to enlarge, and then takes place the cable fault, causes serious accident such as cable conflagration even, influences the safe operation of whole booster station.
2. Because the low voltage side of the main transformer is in triangular connection, a neutral point cannot be led out, and only 4 grounding transformers can be considered to be arranged on each section of 35kV bus, the 35kV bus of the offshore booster station platform has 4 sections, each section of bus needs to be provided with the grounding transformers, and 4 grounding transformers need to be arranged, wherein two grounding transformers are used as station transformers, as shown in figure 4. The area of the grounding transformer room is correspondingly increased to about 280m2 (square meter), meanwhile, the load of each grounding transformer is 10 tons, the basis weight of the offshore booster station platform is inevitably increased, the civil engineering quantity is greatly increased, and the engineering cost is improved.
The conventional offshore booster station can also be shown in fig. 5, fig. 5 is a third schematic structural diagram of the conventional offshore wind farm booster station, the winding wiring scheme of a main transformer of the offshore booster station is YN, d11-d11 or YN, d11, a grounding transformer is led out from the low-voltage side of the main transformer, four low-voltage side lead-out points of the two main transformers are totally provided, the grounding transformer is not arranged on a 35kV bus, 4 grounding transformers are required to be arranged totally, 2 station transformers are used, the room size needs to reach 336m2, the basis weight of the offshore booster station platform is increased, the civil engineering amount is greatly increased, the engineering cost is increased, and the economy of offshore wind power is reduced. And if the cable that main transformer low voltage side and 35kV distribution device are connected takes place single-phase ground connection, can directly lead to the switch of main transformer high voltage side to take place the tripping operation, and at this moment, one main transformer stops the operation, has reduced the seeing off of wind-powered electricity generation field electric quantity.
The grounding mode of the grounding transformer is connected to the low-voltage side T of the main transformer, if the operation mode of a booster station with a large island needs to be considered in the sea area where the wind power plant is located, the diesel engine needs to be started in the island operation state, at the moment, the grounding transformer needs to be added at the outlet of the diesel generator, and the arrangement of the grounding transformer of the diesel generator and the area of the booster station need to be increased.
based on the method, the offshore wind farm booster station can perform model selection adjustment on the main transformer. The basic principle of the selection of the transformer winding connection group is as follows:
A main transformer of a traditional offshore wind power booster station adopts YNd11-d11 or YNd11, and a neutral point cannot be led out; however, if a transformer with the connection group YNyn0-yn0 or YNyn0 is selected, the influence of the harmonic wave of the transformer needs to be considered. The three-phase voltage symmetry, the voltage harmonic component and the current harmonic component in the operation of the transformer depend on the connection mode of the three-phase transformer. The magnetic connection of the cores determines whether the transformer can obtain all the higher harmonics of the excitation current required for the flux density variation corresponding to the grid voltage variation.
If the primary windings of the three-phase transformer are star-connected and the secondary windings are delta-connected, the higher harmonics 3N (N ═ 1, 2, 3 …) of the transformer can flow through the delta-windings on the secondary side. If the three-phase transformer windings are all star-connected, the neutral point is connected with the neutral point of a three-phase power supply grid, zero-sequence current flows only on the primary side, and the transformer is in a free state, current harmonics of 3N (N is 1, 2, 3 …) cannot pass through the primary winding, and at the moment, a balance winding needs to be additionally arranged on the transformer.
The balance winding is used as a delta connection winding and can provide a path for 3N (N is 1, 2, 3 …) subharmonic current, induced electromotive force waveform is improved, output voltage of the transformer is further ensured to be close to sine wave, power supply quality is ensured, relay protection misoperation in a power system is prevented, and unnecessary loss is avoided. In the transformer test process, the correctness of the measurement result can be ensured.
Specifically, the oil-immersed transformer with star-shaped connection at the low-voltage side and an additional winding is characterized by comprising: the connection group of the high-low voltage side of the main transformer of the offshore wind power is YNyn0-yn0d11 or YNyn0d11, and the capacity of the additional winding of the transformer is 30% of the total capacity of the transformer. The equipment of the neutral point of the 35kV system is formed by a star winding on the low-voltage side of a main transformer. In combination with the parameters of the balance winding in the operation of the transformer, the operation mode and the structural form of the balance winding, under the condition of ensuring that the transformer can meet the use requirement, when the additional winding only serves as the balance winding, the design is generally in the 10kV level, and the capacity is about 1/3 or 30 percent of the rated capacity of the transformer.
The arrangement of the additional winding can improve the power supply quality of the transformer and reduce the local overheating phenomenon of zero-sequence leakage magnetic flux in the structural part of the transformer; the transformer can be operated economically, safely and reliably while the manufacturing cost of the transformer is saved. Because the voltage output by the balanced winding side is non-sinusoidal voltage, the higher harmonic component (mainly 3 Nth order) in the non-sinusoidal voltage has the same direction in the three-phase winding at the same time, and the triangular winding is a closed loop, the non-sinusoidal current containing the higher harmonic component (mainly 3 Nth order) is generated, so that the higher harmonic component current can flow in the windings connected in a triangular shape. In addition, according to the principle of magnetic potential balance, harmonic magnetic fluxes are generated in the transformer core, and the magnetic fluxes can cancel a large amount of harmonic magnetic fluxes generated at the moment of power transmission, so that the magnetic fluxes in the core approach a sine wave, and the induced magnetic potential has a sine wave shape. And because the fundamental frequency of the magnetostriction of the silicon steel sheets of the transformer is twice of the rated frequency of the transformer, the noise of the transformer determined by the magnetostriction is reduced, and the balance winding which is used as the additional winding plays an important role in reducing the environmental pollution.
For this reason, the application of an additional delta (d) winding inside a transformer (especially in a large-capacity transformer) is necessary to provide a higher harmonic path for improving the induced electromotive force waveform. The embodiment of the application provides a novel offshore wind power offshore booster station, which comprises a wiring scheme of a low-voltage side system (such as a 35kV system). Wherein, the connection group of the main transformer is YNyn0-yn0, d11 or YNyn0, d 11; by introducing a neutral point to the star winding on the low-voltage side of the main transformer and connecting a resistor to the neutral point, a grounding transformer does not need to be provided on the bus side (for example, 35kV bus side) connected to the low-voltage side.
In an embodiment, an offshore wind farm booster main transformer is provided, as shown in fig. 6 and 7, where fig. 6 is a first schematic structural diagram of an offshore wind farm booster main transformer in an embodiment, and fig. 7 is a second schematic structural diagram of the offshore wind farm booster main transformer in an embodiment, and includes: the device comprises an iron core, an additional winding, a grounding resistor, a high-voltage side winding used for being connected with a first submarine cable, and a low-voltage side winding used for being connected with a second submarine cable.
The high-voltage side winding, the low-voltage side winding and the additional winding are wound on the iron core. The high-voltage side winding is a star-connected winding; the low-voltage side winding is a star-connected winding; the additional windings are delta-connected windings. The neutral point of the low-voltage side winding is grounded through a grounding resistor.
Specifically, the offshore booster station main transformer includes a high side winding, a low side winding, and an additional winding wound on a core. The high-voltage side winding and the low-voltage side winding are both star windings, and the additional winding is a triangular winding. The low-voltage side winding leads out a neutral point, and the neutral point is grounded through a grounding resistor.
The high-voltage side winding is used for connecting a first submarine cable; the low-voltage side winding is used for connecting the second submarine cable.
The high-voltage side winding may be connected to an onshore booster station, an offshore high-voltage switchyard, or an onshore centralized control center, etc. through a first sea cable, and is used for transmitting the electric energy generated by the offshore wind farm to the onshore. The low-voltage side winding can be connected with the offshore wind turbine through a second submarine cable and can be used for receiving electric energy generated by the offshore wind turbine. Through the induction of the high-voltage side winding and the low-voltage side winding, the main transformer of the booster station can boost the electric energy generated by the offshore wind turbine and transmit the electric energy to the onshore station.
The additional winding can be used as a balance winding and used for providing a higher harmonic channel so as to improve the waveform of the induced electromotive force; meanwhile, the star winding on the low-voltage side of the main transformer can be connected with a neutral point. The neutral point is used for grounding through a grounding resistor.
The first submarine cable and the second submarine cable are submarine cables and can be used for power transmission on the seabed. Wherein, first submarine cable can be used to connect the onshore center, and the second submarine cable can be used to connect offshore wind turbine.
The embodiment of the application changes the neutral point grounding mode of a low-voltage side system in the traditional booster station of the offshore wind farm, can reduce the probability of cable faults when a single-phase grounding fault occurs in the offshore wind farm, and ensures the safe operation of the whole booster station. Meanwhile, when the low-voltage side of the main transformer has single-phase earth fault, the high-voltage side switch of the main transformer is prevented from tripping, the running reliability of the wind power plant is improved, and the generated energy of the wind power plant is ensured to be sent out. Based on this, the embodiment of the application simplifies the wiring of the low-voltage side system of the offshore booster station, improves the reliability, reduces the equipment investment, simplifies the arrangement of the platform, reduces the load of the offshore booster station, and reduces the overall cost of the platform.
In one embodiment, the additional winding is a winding of a predetermined capacity; the value range of the preset capacity is 33% to 30% of the rated capacity of the main transformer.
Specifically, the capacity of the additional winding can be designed according to actual needs; in particular, the capacity of the additional winding may be less than one third of the main transformer capacity, which may range from 33% to 30% of the rated capacity of the main transformer.
In one embodiment, the first submarine cable is a 220kV bus.
The second submarine cable is a 35kV bus.
Specifically, the high voltage side of the main transformer may be used to output a voltage of 220kV standard, and accordingly, the first submarine cable may be matched using a 220kV bus or the like.
The low voltage side of the main transformer may be adapted to receive a voltage of the 35kV standard and correspondingly the second submarine cable may be adapted with a 35kV busbar or the like.
In the offshore booster station, a high-voltage side system and a low-voltage side system related to a main transformer can be set with different voltage standards according to actual needs; accordingly, the transmission specification of the submarine cable connected to the main transformer needs to match the voltage standard, and is not limited herein.
In one embodiment, the low voltage side winding comprises a first low voltage side winding, a second low voltage side winding for connecting to a second sea cable. The ground resistor includes a first ground resistor and a second ground resistor. The neutral point of the first low-voltage side winding is grounded through a first grounding resistor; the neutral point of the second low-voltage side winding is grounded through a second grounding resistor.
In particular, the low voltage side may comprise two windings, the neutral points of which are grounded by corresponding ground resistances.
The main transformer comprises two low-voltage side windings, and when one low-voltage side winding has a single-phase ground fault, the other low-voltage side winding and the high-voltage side winding can still keep running, so that the power generation efficiency of the offshore wind farm is guaranteed, and the reliability of the booster station is improved.
In one embodiment, as shown in FIG. 8, FIG. 8 is a third schematic block diagram of a main transformer of a booster station of an offshore wind farm in one embodiment, further comprising a switching circuit; the high-voltage side winding is grounded through the switching circuit.
Specifically, the main transformer further comprises a switching circuit for grounding the high-side winding. The switching circuit can be grounded in time when a high-voltage side system fails, so that fault expansion is avoided.
In a specific example, a comparison between the main transformer provided by the embodiment of the present application and the conventional main transformer is shown in table 1.
TABLE 1 comparison of the technical and economic properties of two transformers
The scheme that traditional technique will become ground connection and set up in the main low voltage side of becoming includes:
1) For selecting YN, d11-d11 main transformers (low-voltage side double-branch operation), when 35kV buses are adopted for grounding, 4Z-type wiring transformers are generally arranged on (4 sections of buses) 35kV buses. If the primary transformer secondary head end hanging ground transformer mode is adopted, two grounding transformers (4 grounding transformers and 2 station transformers) are added compared with the bus hanging mode.
2) For selecting a main transformer (low-voltage side double-branch operation) of YN and d11, when a 35kV bus is adopted to be hung and grounded, 4Z-type wiring transformers are generally arranged on the (4-section bus) 35kV bus. If the mode of hanging the primary transformer secondary head end on the ground is adopted, the number of the transformer units is the same as that of the bus hanging mode, namely 2 grounding transformers are adopted, and 2 station transformers are adopted.
in the above-mentioned technical scheme of the conventional art, when the earth becomes trouble, will jump the switch of the main transformer high-voltage side, namely 220kV side of GIS (gas insulated metal enclosed switchgear) side, will have a considerable amount of fans to stop the operation this moment, lead to the reduction of output power, influence the economic nature of whole project.
According to the main transformer of the offshore booster station, the connection group adopts Y/Y or Y/Y/Y (Y refers to star connection); the additional winding capacity of the main transformer can be 30% of the total capacity of the main transformer; the neutral point is led out from the star winding at the low-voltage side and is grounded through a neutral point and a grounding resistor. Based on the structure, when the main transformer is in single-phase earth fault in an offshore wind farm, the probability of cable fault is reduced, and the safe operation of the whole booster station is guaranteed. Meanwhile, when the low-voltage side of the main transformer has single-phase earth fault, the high-voltage side switch of the main transformer is prevented from tripping, the operation reliability of the offshore wind farm is improved, and the generated energy of the offshore wind farm is guaranteed to be sent out. Based on this, the embodiment of the application simplifies the wiring of the low-voltage side system of the offshore booster station, improves the reliability, reduces the equipment investment, simplifies the arrangement of the platform, reduces the load of the offshore booster station, and reduces the overall cost of the platform.
In one embodiment, an offshore wind farm booster system is also provided, as shown in fig. 9, and fig. 9 is a first schematic block diagram of an offshore wind farm booster system in one embodiment, including a first submarine cable for connecting to an onshore booster station, a second submarine cable for connecting to an offshore wind turbine, and an offshore wind farm booster station main transformer as described above. A high-voltage side winding of the main transformer is connected with a first submarine cable; and a low-voltage side winding of the main transformer is connected with the second submarine cable.
Specifically, the offshore wind farm boosting system comprises a main transformer of an offshore wind farm boosting station, a first submarine cable and a second submarine cable; the high-voltage side winding of the main transformer is connected with the onshore power station through a first submarine cable, and the low-voltage side winding is connected with the offshore wind turbine through a second submarine cable.
In the embodiment of the application, the main transformer adopted by the offshore wind farm boosting system is Y/Y or Y/Y in the connection group, the additional winding capacity of the main transformer can be 30% of the total capacity of the main transformer, a neutral point is led out from a star winding at the low-voltage side, and the neutral point is grounded with a grounding resistor. Based on this, offshore wind farm voltage boost system can reduce the probability of taking place the cable fault when offshore wind farm takes place single-phase earth fault, ensures whole voltage boost system's safe operation. Meanwhile, when the low-voltage side of the main transformer has single-phase earth fault, the high-voltage side switch of the main transformer is prevented from tripping, the operation reliability of the offshore wind farm is improved, and the output of the generated energy of the offshore wind farm is ensured. According to the embodiment of the application, the wiring of the offshore wind power station boosting system is simplified, the reliability is improved, the equipment investment is reduced, the arrangement of the boosting system is simplified, the load of the offshore boosting system is reduced, and the overall cost of the boosting system is reduced.
in one embodiment, as shown in fig. 9, the number of main transformers is two; the first submarine cable comprises two 220kV buses; the second submarine cable comprises at least two 35kV busbars. The high-voltage side winding is connected with a corresponding 220kV bus; and the low-voltage side winding is connected with a corresponding 35kV bus.
specifically, the offshore wind farm boosting system comprises two main transformers, namely a first main transformer and a second main transformer; the first submarine cable comprises a first 220kV bus and a second 220kV bus; the second submarine cable comprises a first 35kV bus and a second 35kV bus. The first main transformer is respectively connected with a first 220kV bus and a first 35kV bus, and the second main transformer is respectively connected with a second 220kV bus and a second 35kV bus.
It should be noted that, the number of the main transformers in the offshore wind farm voltage boosting system may be set according to actual design requirements, and is not limited herein. Accordingly, the number of the first sea cables and the second sea cables is not limited.
In one embodiment, as shown in fig. 10, fig. 10 is a second schematic structural diagram of the offshore wind farm voltage boosting system in one embodiment, and further includes a station transformer. And the low-voltage side winding is connected with the transformer for the station through a corresponding 35kV bus.
Specifically, the offshore wind farm boosting system further comprises a station transformer. And a low-voltage side winding of the main transformer is connected with the transformer for the station through a corresponding 35kV bus.
In one embodiment, the station transformer is a Z-connected transformer.
Specifically, the offshore wind farm voltage boosting system may employ a Z-connected transformer as a station transformer.
In one embodiment, the station transformer shown in fig. 10 includes an intra-station transformer core, delta-connected first windings, and star-connected second windings; the first winding is wound on the transformer iron core in the station; the second winding is wound on the transformer core in the station. The first winding is connected with a corresponding 35kV bus.
Specifically, the station transformer may include an in-station transformer core, a first winding and a second winding wound around the in-station transformer core; the first winding is a winding in triangular connection, and the second winding is a winding in star connection. The first winding is connected with a corresponding 35kV bus.
In one example, as shown in fig. 10, an offshore wind farm boost system includes a first in-station transformer and a second in-station transformer. The second submarine cable further comprises a third 35kV bus and a fourth 35kV bus. The first main transformer is connected with the first transformer in the station through a first 35kV bus, and is connected with the second transformer in the station through a third 35kV bus. The second main transformer is connected with the first transformer in the station through a second 35kV bus, and is connected with the second transformer in the station through a fourth 35kV bus.
the technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present application. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.
Claims (10)
1. the utility model provides an offshore wind farm booster station main transformer which characterized in that includes: the device comprises an iron core, an additional winding, a grounding resistor, a high-voltage side winding and a low-voltage side winding, wherein the high-voltage side winding is used for being connected with a first submarine cable, and the low-voltage side winding is used for being connected with a second submarine cable;
The high-voltage side winding, the low-voltage side winding and the additional winding are wound on the iron core;
The high-voltage side winding is a star-connected winding; the low-voltage side winding is a star-connected winding; the additional winding is a winding in triangular connection; the neutral point of the low-voltage side winding is grounded through the grounding resistor.
2. the offshore wind farm booster station main transformer according to claim 1, wherein the additional winding is a winding of a preset capacity; the value range of the preset capacity is 33% to 30% of the rated capacity of the main transformer.
3. The offshore wind farm booster station main transformer of claim 1, wherein the first submarine cable is a 220kV bus; the second submarine cable is a 35kV bus.
4. The offshore wind farm booster station main transformer of claim 1, wherein the low voltage side winding comprises a first low voltage side winding, a second low voltage side winding for connecting the second sea cable;
The grounding resistor comprises a first grounding resistor and a second grounding resistor; the neutral point of the first low-voltage side winding is grounded through the first grounding resistor; the neutral point of the second low-voltage side winding is grounded through the second grounding resistor.
5. The offshore wind farm booster station main transformer according to any one of claims 1 to 4, further comprising a switching circuit; the high-voltage side winding is grounded through the switch circuit.
6. An offshore wind farm booster system comprising a first sea cable for connection to a land based booster station, a second sea cable for connection to an offshore wind turbine, and an offshore wind farm booster station main transformer according to any one of claims 1 to 5;
The high-voltage side winding of the main transformer is connected with the first submarine cable; and a low-voltage side winding of the main transformer is connected with the second submarine cable.
7. the offshore wind farm voltage boosting system according to claim 6, wherein the number of the main transformers is two; the first submarine cable comprises two 220kV buses; the second submarine cable comprises at least two 35kV buses;
the high-voltage side winding is connected with the corresponding 220kV bus; and the low-voltage side winding is connected with the corresponding 35kV bus.
8. The offshore wind farm boost system of claim 6 or 7, further comprising a station transformer;
And the low-voltage side winding is connected with the station transformer through the corresponding 35kV bus.
9. Offshore wind farm voltage boosting system according to claim 8, wherein the station transformer is a Z-connected transformer.
10. The offshore wind farm voltage boosting system according to claim 8, wherein the station transformer comprises an intra-station transformer core, a delta-connected first winding, and a star-connected second winding; the first winding is wound on the transformer iron core in the station; the second winding is wound on the transformer iron core in the station;
The first winding is connected with the corresponding 35kV bus.
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| CN201811287591.XA CN110544580A (en) | 2018-10-31 | 2018-10-31 | Main transformer and boosting system of offshore wind power plant boosting station |
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| CN201811287591.XA CN110544580A (en) | 2018-10-31 | 2018-10-31 | Main transformer and boosting system of offshore wind power plant boosting station |
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Application publication date: 20191206 |