CN113659612B - Wind generating set operation method based on offshore wind power bus type system - Google Patents
Wind generating set operation method based on offshore wind power bus type system Download PDFInfo
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- CN113659612B CN113659612B CN202110751790.7A CN202110751790A CN113659612B CN 113659612 B CN113659612 B CN 113659612B CN 202110751790 A CN202110751790 A CN 202110751790A CN 113659612 B CN113659612 B CN 113659612B
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- 238000000034 method Methods 0.000 title claims abstract description 26
- 230000005540 biological transmission Effects 0.000 claims abstract description 57
- 238000010248 power generation Methods 0.000 abstract description 68
- 230000005611 electricity Effects 0.000 abstract description 7
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- 238000010586 diagram Methods 0.000 description 2
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- 230000005284 excitation Effects 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
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Classifications
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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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
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/28—The renewable source being wind energy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/76—Power conversion electric or electronic aspects
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
Abstract
The invention discloses a wind generating set operation method based on an offshore wind power bus system, which comprises the following steps: the method comprises the steps that when the rated frequency of an offshore frequency division/low-frequency power grid in an offshore wind power bus system is 50/3+/-5% Hz, a medium-voltage direct-drive type doubly-fed generator is adopted, and when the rated frequency of the offshore frequency division/low-frequency power grid is 10+/-17% Hz, the medium-voltage direct-drive type doubly-fed generator is adopted. The problems of safe and reliable operation, investment cost efficiency and life cycle electricity cost of offshore long-distance and large-range power transmission in the process of transmitting the wind power generation with the 5-20GW level above deep open sea to the shore are solved, and the problem that the invasion of typhoons, fire disasters, salt mist and the like of expensive high-power electronic equipment and large-scale heavy mechanical power transformation equipment on the sea cannot be effectively prevented and reduced are avoided.
Description
Technical Field
The invention belongs to the technical field of offshore deep sea wind power generation, and particularly relates to an operation method of a medium-voltage direct-matching double-fed wind power generator set based on an offshore wind power bus system (frequency division/low-frequency power grid).
Background
Wind energy is used as clean renewable new energy and is an important energy source. At present, the large-scale development of offshore wind farms has resulted in a long-term development. The wind power resources to be developed in deep open sea are quite rich; how to improve the benefit and the expected return rate of the development of the deep-sea wind power resources and reduce the full life cycle electricity cost of the wind power plant is an urgent need for an advanced technology for effectively developing the deep-sea wind power resources, which is a very urgent need for solving the problem at present.
The offshore conventional high-voltage alternating-current booster station and the submarine high-voltage cable are used for long-distance (more than 70 km) landing on the network for power transmission, the load moment is small, the power transmission cost is high, the offshore conventional high-voltage booster station has high requirements on resisting the offshore severe environment, and the offshore conventional high-voltage booster station can not be used for rescuing at all when encountering an irresistible fire disaster; main equipment on a single loop landing high-voltage alternating current transmission loop fails, and a wind turbine generator system which needs to be on the net cannot normally generate electricity and run in the loop, so that the safety of the wind turbine generator system is at great risk if the wind turbine generator system meets typhoon.
The offshore conventional high-voltage direct-current converter station and the submarine high-voltage direct-current cable are used for logging on the network for transmission at a long distance (more than 70 km), the load moment is high, the offshore conventional high-voltage direct-current converter station has high cost, the offshore conventional high-voltage direct-current converter station has high requirements on resisting the offshore severe environment, and the offshore conventional high-voltage direct-current converter station cannot be saved at all when an irresistible fire disaster occurs; main equipment on the network high-voltage direct current transmission loop is gone into to the shore on single circuit is trouble, and wind turbine generator system on this circuit can't normally generate electricity and move, if meet typhoon wind turbine generator system's safety face very big risk.
Disclosure of Invention
The invention aims at solving the problems of safety, reliability, efficiency, cost performance and the like in the deep open sea offshore wind power generation and remote power transmission by adopting the conventional power frequency alternating current high voltage power transmission and direct current high voltage power transmission landing scheme. Therefore, for deep sea offshore wind power generation and remote power transmission, a wind generating set operation method based on an offshore wind power bus system is provided.
The aim of the invention is achieved by the following technical scheme:
a method of operating a wind turbine generator system based on an offshore wind power bus system, the method of operating a wind turbine generator system comprising: the method comprises the steps that when the rated frequency of an offshore frequency division/low-frequency power grid in an offshore wind power bus system is 50/3+/-5% Hz, a medium-voltage direct-drive type doubly-fed generator is adopted, and when the rated frequency of the offshore frequency division/low-frequency power grid is 10+/-17% Hz, the medium-voltage direct-drive type doubly-fed generator is adopted.
According to a preferred embodiment, wind farm virtual generators of a plurality of adjacent wind farms at sea are longitudinally wired through the hub double bus bars thereof; and the upper bus and the lower bus of the plurality of adjacent hub double buses are respectively connected by transverse connection lines among the hub double buses, so that the offshore wind power bus type system of the offshore frequency division/low frequency power grid is formed.
According to a preferred embodiment, the offshore frequency division/low frequency power grid comprises: a virtual generator cluster, a frequency division/low frequency power transmission network and a VSC cluster frequency division/low frequency power network side of the offshore wind farm; the ring network two-way longitudinal outgoing line output of each wind power plant virtual generator in the offshore wind power plant virtual generator cluster is connected with the network from the side of the VSC cluster frequency division/low frequency power grid through the offshore frequency division/low frequency power grid.
According to a preferred embodiment, the offshore frequency division/low frequency power transmission network comprises two longitudinal output lines of each wind farm virtual generator ring network. The device is characterized by comprising a longitudinal input line of a corresponding double bus of a hub in a longitudinal output section of the offshore wind farm, a longitudinal output line of the corresponding double bus of the hub in the longitudinal output section of the offshore wind farm, and transverse connection lines between the double buses of the hubs and the double buses of the hubs in the bus system of the offshore wind farm.
According to a preferred embodiment, the offshore wind farm virtual generator cluster comprises a plurality of wind farm virtual generators, each wind farm virtual generator comprises a plurality of power generation units and a plurality of step-up high-impedance transformers, and each power generation unit comprises a plurality of medium-voltage direct-matching double-fed wind turbines.
According to a preferred embodiment, the wind power generation unit adopts a step-up high-impedance transformer to regulate the Internet voltage deviation of the medium-voltage direct-matching double-fed wind power generator set in cooperation with the output reactive power of the medium-voltage direct-matching double-fed wind power generator set. Meanwhile, the short-time operation range of high voltage ride through and low voltage ride through can be improved; the rated voltage range and the high voltage ride through range can be dynamically and stably widened. Selecting u as the impedance voltage percentage value of the step-up high-impedance transformer dT ％＝12～36。
The foregoing inventive subject matter and various further alternatives thereof may be freely combined to form a plurality of alternatives, all of which are employable and claimed herein; and the invention can be freely combined between the (non-conflicting choices) choices and between the choices and other choices. Various combinations will be apparent to those skilled in the art from a review of the present disclosure, and are not intended to be exhaustive or all of the present disclosure.
The invention has the beneficial effects that: the invention adopts a wind generating set operation method based on an offshore wind power bus system, solves the problems that one of the processes of power generation and power transmission of wind power above 5-20GW level in deep open sea to shore is the operation problem of offshore long-distance and large-range power transmission, the other is the problem of whole input cost efficiency and life cycle electricity cost, and the other is the problem of incapacity of effectively resisting and reducing disasters caused by the invasion of typhoons, fires, salt fog and the like of expensive high-power electronic equipment and large-scale heavy mechanical power transformation equipment at sea.
After the offshore wind power bus type system based on the offshore frequency division/low-frequency power grid is used, the power transmission and transformation equipment capacity of each wind power station on-line channel can be reduced by 40% p.u., the cost can be saved by 40%, and the power transmission investment cost is greatly reduced.
The medium-voltage direct-matching doubly-fed wind generating set is obtained by adopting the offshore frequency division/low-frequency power grid interconnection, the capacities of a single-machine main loop boost converter and a converter are greatly reduced, the cost of the wind generating set is greatly reduced, the capacity of a primary boost transformer is reduced by 80-90%, the efficiency of 0.8% is improved, and the cost of the whole wind generating set can be reduced by 5-10%. The total investment of each 1GW class virtual generator (wind farm) is estimated to be reduced by about 8-10 percent; the cost performance of the whole offshore wind farm operation is greatly improved, and the full life cycle electricity cost of the wind farm is reduced. The power transmission and transformation system of the offshore wind farm adopts a redundant structure, and truly has the power generation operation of 'N-1' safety standard; the safe and reliable operation performance is maximized, the daily operation and maintenance workload and the time window are minimized, and the availability and maintainability of the whole offshore and onshore wind power generation and transmission equipment are improved.
Drawings
FIG. 1 is a schematic diagram of a cluster power generation flow of a wind farm virtual generator for an offshore frequency division/low frequency grid of the present invention;
FIG. 2 is an offshore wind power bus system of the present invention;
FIG. 3 is an offshore frequency division/low frequency power grid of the present invention;
FIG. 4 is a wind farm virtual generator of the present invention;
FIG. 5 is a section A of a wind farm virtual generator according to the present invention;
FIG. 6 is a section B of a wind farm virtual generator according to the present invention;
FIG. 7 is a section C of a wind farm virtual generator of the present invention;
FIG. 8 is a section D of a wind farm virtual generator of the present invention;
FIG. 9 is a schematic diagram of a P-n curve of the medium voltage direct-coupled doubly-fed wind turbine generator system of the present invention;
the system comprises a 1-50Hz power grid, a 2-VSC cluster, a 3-VSC cluster frequency division/low frequency power grid side, a 4-longitudinal output u section, a 5-offshore wind power bus system, a 6-longitudinal output d section, a 7-virtual generator cluster, an 8-VSC (left circuit and right circuit), a 9-frequency division/low frequency power transmission grid, a 10-hub double-bus transverse connection line, a 11-hub double-bus longitudinal outgoing line, a 12-hub double-bus, a 13-hub double-bus longitudinal incoming line, a 14-virtual generator, a 15-frequency division/low frequency power grid, a 16-high voltage collecting cable, a 17-medium voltage collecting ring main unit, a 18-medium voltage collecting cable, a 19-boosting high-impedance transformer, a 20-high voltage collecting ring main unit, a 21-medium voltage direct-distribution double-feed unit, a 22-double-feed converter, a 23-direct-drive double-feed generator, a 24-half direct-drive double-feed generator, a 25-gearbox, a 26-hub, 27-blades, a 28-rotor loop transformer and a 29-power generation unit.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict.
It should be noted that, for the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments.
Thus, the following detailed description of the embodiments of the invention is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In addition, in the present invention, if a specific structure, connection relationship, position relationship, power source relationship, etc. are not specifically written, the structure, connection relationship, position relationship, power source relationship, etc. related to the present invention can be known by those skilled in the art without any creative effort.
Examples:
referring to fig. 1 to 9, the invention discloses a wind generating set operation method based on an offshore wind power bus system. When the rated frequency of the offshore frequency division/low frequency power grid is 50/3+/-5% Hz, a semi-direct-drive double-fed generator is adopted, and a primary or secondary gear box is arranged; the rated frequency of the offshore frequency division/low frequency power grid is 10+/-17% Hz of the low frequency, and a direct-drive double-fed generator is adopted without a gear box. The rated voltage of the rotor ranges from 0.69kV to 10kV, the rated voltage of the stator ranges from 0.69kV to 35kV, and the capacity of the generator set ranges from 5MW to 50MW.
The wind power plant virtual generators of a plurality of adjacent wind power plants on the sea are longitudinally wired through the double buses of the hinges; and the upper bus and the lower bus of the plurality of adjacent hub double buses are respectively connected by transverse connection lines among the hub double buses, so that the offshore wind power bus type system of the offshore frequency division/low frequency power grid is formed.
The offshore frequency division/low frequency power grid comprises an offshore wind farm virtual generator cluster, a frequency division/low frequency power transmission grid and a VSC cluster frequency division/low frequency power grid side; wherein: the two paths of output of each wind power plant virtual generator in the longitudinal direction correspond to the longitudinal incoming line of the double buses of the hinges in the longitudinal outgoing line d section of the offshore wind power plant, correspond to the double buses of the hinges in the bus type system of the offshore wind power plant, correspond to the longitudinal outgoing line of the double buses of the hinges in the longitudinal output u section of the offshore wind power plant, and correspond to the VSC side (left path and right path) in the VSC cluster frequency division/low-frequency power grid side. The two paths of output of each wind power plant virtual generator in the transverse direction correspond to the upper bus and the lower bus of the hub double bus in the offshore wind power bus type system, and the upper bus and the lower bus of the hub double bus are respectively connected by transverse connection lines (hot standby connection between each double bus).
The wind power plant virtual generator is required to longitudinally enter through a hinge double bus of the wind power plant virtual generator, and the upper bus and the lower bus of the plurality of adjacent hinge double buses are respectively connected by transverse connection lines between the hinge double buses (hot standby connection between each double bus), so that an offshore wind power bus type system of an offshore frequency division/low frequency power transmission network is formed.
Offshore frequency division/low frequency power transmission network comprising: two paths of output of each wind power plant virtual generator in the longitudinal direction correspond to a longitudinal incoming line of a double bus of a junction in a longitudinal outgoing line d section of the offshore wind power plant, correspond to a double bus of a junction in a bus system of the offshore wind power plant, correspond to a longitudinal outgoing line of the double bus of the junction in a longitudinal output u section of the offshore wind power plant, and correspond to VSC (left path and right path) sides in a VSC cluster frequency division/low-frequency power grid side; the two paths of output of each wind power plant virtual generator in the transverse direction correspond to the upper bus and the lower bus of the hub double bus in the offshore wind power bus type system, and the upper bus and the lower bus of the hub double bus are respectively connected by transverse connection lines (hot standby connection between each double bus).
The double-bus longitudinal line of the offshore wind farm hub faces the high-voltage collecting ring network cable, the high-voltage collecting ring network cabinet and the wind farm power generation unit and can be equivalently used as a virtual wind farm generator.
The input side of the high-voltage collecting ring main unit in the offshore wind farm virtual generator faces to the boosting high-impedance transformer and the medium-voltage collecting ring main cable, the medium-voltage collecting ring main unit and the medium-voltage direct-matching double-fed wind turbine generator, and is equivalent to a wind farm power generation unit.
The rated frequency of the offshore frequency division/low-frequency power grid adopts the conventional frequency division 16/3 Hz, the 80% p.u. cable capacity can be used for transmitting 270km of power, and the offshore wind power transmission of deep open sea of 200-120km in the longitudinal direction of an offshore area can be satisfied. The rated frequency of the offshore frequency division/low frequency power grid adopts low frequency 10Hz, and the low frequency power transmission distance of 80% of the p.u. cable capacity is 440km, so that the offshore wind power transmission of deep open sea in the longitudinal direction 70-200km and the transverse direction 370-240km of the offshore area can be satisfied. Therefore, by adopting an offshore frequency division/low-frequency power grid (an offshore wind power bus system), the offshore or onshore longitudinal and transverse power transmission distance can be further expanded, and the deep sea wind power can be effectively transmitted to a load center for a long distance.
The running method of the wind generating set based on the offshore wind power bus system is equivalent to basically and equivalently moving a large-sized high-voltage direct current converter station of an offshore flexible direct current scheme to the land, and dispersing the large-sized high-voltage alternating current booster station of the offshore high-voltage alternating current scheme to each wind power plant generating unit which is miniaturized in capacity and connected with a ring network, so that the safety is greatly improved; meanwhile, a high-voltage collecting ring network double-path and medium-voltage collecting ring network two-layer structure with high cost performance and high reliability of the wind power plant is adopted; the hot standby connection of the doubly-fed wind generating sets at the tail ends of the same class of different wind generating units is safe and reliable to operate; the doubly-fed wind generating set of the wind power generating unit has a network access loop fault, so that island micro-grid connection operation can be realized; the power transmission and transformation system of the offshore wind farm adopts a redundant structure, and truly has the power generation operation of 'N-1' safety standard; the problems of serious safety, reliability and usability of the HVDC marine converter station and the HVAC booster station caused by severe marine environment are avoided, equipment maintenance time is shortened, and the situation that a fire disaster occurs to a marine large-scale main station equipment cannot be rescued at all is avoided.
The offshore frequency division/low frequency power grid comprises an offshore wind farm virtual generator cluster, a frequency division/low frequency power transmission grid and a VSC cluster frequency division, and the low frequency power grid side really has the operating requirement of N-1 safety standard.
Compared with the conventional power frequency high-voltage alternating current and high-voltage direct current transmission, the operation method of the wind generating set based on the offshore wind power bus type system has the advantages that the operation method is connected with a power grid in a landing mode, and the operation safety reliability and efficiency, the generating capacity, the cost performance and the dynamic and static stability of the voltage of the offshore wind power plant wind generating set are improved on the aspects of return on investment and full life cycle electricity cost.
Specifically:
fig. 1 shows the flow of power generation, transmission, VSC commutation to a 50Hz grid 1 for an offshore frequency division/low frequency grid 15. The wind power plant virtual generator cluster 7 is provided with n wind power plant virtual generators 14, and any wind power plant virtual generatorThe wind power plant longitudinally outputs a section d 6, the net surfing power through a section 1 is less than or equal to 85% pu (corresponding to the i wind power plant see capacity), the net surfing power through a section 2 is less than or equal to 50% pu after the net surfing power is input to a junction double bus i (net surfing power) in an offshore wind power bus system 5, and then two paths of the section u 4 are longitudinally output to an onshore VSC through the wind power plant i1 /VSC i2 Frequency division/low frequency grid side commutation to VSC i1 /VSC i2 The total power of the section 3 on the 50Hz power grid side is less than or equal to 50% pu, and the power of the section 1 entering the 50Hz power grid is less than or equal to 50% pu (1 pu. The capacity is found for the corresponding i wind power plant); or the total power of the net surfing is smaller than or equal to 35% pu (1 pu. The corresponding i wind power plant see capacity) through the left side and the right side of the hub double buses i, the total power of the net surfing is smaller than 50% pu. The longitudinal channel (section 2) through other hub double buses 12 and the longitudinal output u section 4 of the other wind power plant is input, then the net surfing is converted to the 50Hz power grid side (section 3, figure 1) of the VSC (left and right) 8 through the frequency division of the VSC (left and right) 8/the low frequency power grid side, and finally the net surfing enters the 50Hz power grid 1.
A plurality of wind farm virtual generators 14 of adjacent wind farms on the sea are longitudinally connected to the corresponding hub double bus bars 12 through the hub double bus bars 13; the offshore wind power bus type system 5 (figure 2) of the offshore frequency division/low frequency power grid 15 is formed by connecting upper buses and lower buses (hot standby connection exists between the upper buses and the lower buses of each hub double bus) of a plurality of adjacent hub double buses 12 through cables respectively by transverse connecting wires 10 between the hub double buses.
For any ith wind farm virtual generator 14, the ith hub double bus 12 in the offshore wind power bus system 5 (figure 2) corresponding to the longitudinal internet access is provided with an upper bus and a lower bus, and the upper bus left hub double bus longitudinal incoming line 13 inputs power P' i1 Output power P' of right-hinge double-bus longitudinal outgoing line 11 i2 The lower bus right hinge double bus longitudinal incoming line 13 inputs power P' i2 Output power P' of left hub double-bus longitudinal outgoing line 11 i1 Longitudinal input total power (P 'of the ith hinge double bus longitudinal 12' i1 +P′ i2 Less than or equal to 85% pu.), item ii the total power (P') of the longitudinal output of the pivot double bus 12 i1 +P″ i2 Less than or equal to 50% pu); input or output power ΔP 'of transverse connection 10 between upper bus and left hub dual bus of ith pivot dual bus 12' (i-1)1-i1 The right hinge double bus transverse connection 10 inputs or outputs power deltap' i1-(i+1)1 While the lower bus left hinge double bus transverse connection 10 inputs or outputs power ΔP' (i-1)2-i2 The right hinge double bus transverse connection 10 inputs or outputs power deltap' i2-(i+1)2 The method comprises the steps of carrying out a first treatment on the surface of the The i-th pivot double bus 12 the right pivot upper double/lower bus transverse link 10 inputs or outputs power (|ΔP' (i-1)1-i1 +ΔP′ (i-1)2-i2 More than or equal to 35% pu.) and input or output power (|delta P 'of transverse connection 10 between upper bus and lower bus of left hub' i1-(i+1)1 +ΔP′ i2-(i+1)2 And (3) the content of the pure water is more than or equal to 35% pu). The upper and lower bus bars of the ith pivot double bus bar 12 are connected by tie switches for hot standby.
Offshore frequency division/low frequency power grid 15 (fig. 3), comprising: an offshore wind farm virtual generator cluster 7, a frequency division/low frequency power transmission network 9 and a VSC cluster frequency division/low frequency power network side 3; each wind farm virtual generator 14 has two paths of ring network longitudinal outgoing lines, namely a corresponding hub double-bus longitudinal incoming line 13 in a sea wind farm longitudinal output d section 6, a corresponding hub double-bus 12 in a sea wind farm bus system 5, a corresponding hub double-bus longitudinal outgoing line 11 in a sea wind farm longitudinal output u section 4, and a corresponding VSC (left path and right path) 8 in a VSC cluster frequency division/low frequency power grid side 3. The two paths of output of the ring network of each adjacent wind power plant virtual generator 14 are mutually connected in the transverse direction of the pivot double bus 12 in the corresponding offshore wind power bus type system 5, and are connected by cables of the pivot double bus transverse connection 10 (hot standby connection between each double bus) between the upper bus and between the lower bus.
Offshore frequency division/low frequency power transmission network 9 (fig. 3), comprising: each wind power plant virtual generator 14 is looped network two-path longitudinal output line which is respectively a corresponding hub double-bus longitudinal incoming line 13 in a sea wind power plant longitudinal output d section 6, a corresponding hub double-bus longitudinal outgoing line 11 in a sea wind power plant longitudinal output u section 4, and a plurality of hub double-buses 12 and a plurality of inter-hub double-bus transverse connection lines 10 in a sea wind power bus system 5; the adjacent hub double buses 12 in the offshore wind power bus system 5 are connected with each other in the transverse direction, and the upper buses and the lower buses of the adjacent hub double buses 12 are respectively connected with each other by transverse connecting cables 10 (hot standby connection between each double buses) between the hub double buses.
The offshore frequency division/low frequency power transmission network 9 (figure 3), the offshore wind power bus system 5 (figure 2) and the wind power plant virtual generator 14 (figure 4) adopt conventional frequency division 16/3 Hz based on the rated frequency of the offshore frequency division/low frequency power transmission network 15, and the power transmission distance of 80% p.u. cable capacity can be 270km, so that the offshore region longitudinal 70-150km and the offshore wind power transmission of 200-120km deep open sea can be satisfied. The rated frequency based on the offshore frequency division/low frequency power grid 15 adopts low frequency 10Hz and low frequency power transmission distance of 80% of p.u. cable capacity of 440km, and can meet the requirement of offshore area longitudinal 70-200km and transverse 370-240km deep open sea offshore wind power transmission. Therefore, by utilizing the characteristic of frequency division/low-frequency alternating current long-distance transmission, the medium-voltage direct-matching doubly-fed wind generating set 21 is obtained by adopting the interconnection of the offshore frequency division/low-frequency power grid 15, the offshore or onshore longitudinal and transverse transmission distances can be further expanded, and the deep-sea wind power can be effectively transmitted to the load center of the onshore 50Hz power grid 1 in a long distance.
Each wind farm virtual generator 14 in the offshore frequency division/low frequency transmission network 9 has the maximum power less than or equal to 85% pu capacity (1 pu wind farm installation capacity), is connected to the hub double bus 12 in the offshore wind power bus system 5 of the corresponding frequency division/low frequency transmission network 9 through a ring network double-output hub double bus longitudinal incoming line 13, is then outputted through a hub double bus longitudinal outgoing line 11, has the double-channel longitudinal incoming line less than or equal to 50% p.u. capacity, and is respectively outputted to the on-shore VSC (left and right) 8 frequency division/low frequency power network side, and has the double-channel transverse output power at both sides of the re-hub double bus 12 greater than or equal to 35% p.u. capacity, and is respectively outputted to the on-shore VSC (left and right) 8 frequency division/low frequency power network side through the hub double bus 12 corresponding to other wind farms and the double-channel hub double bus longitudinal outgoing line 11 (total less than or equal to 50% p.u.); the cost of the power transmission and transformation equipment of the internet surfing channel above the offshore wind power bus system 5 (frequency division/low frequency power grid 15) can be saved by 40 percent. The on-shore VSC (left and right) 8 frequency division/low frequency power grid side can cooperate with the frequency and the same voltage to adjust, and the 50Hz power grid side of the VSC (left and right) 8 cooperates with the land 50Hz power grid 1 to adjust the frequency and the voltage, participate in the active power and reactive power adjustment, and cooperate with the primary frequency adjustment. Based on the frequency division/low-frequency power transmission network 9 and the wind farm virtual generator 14, the two-layer high-voltage power collection ring network and medium-voltage power collection ring network structure with high cost performance and high safety and reliability are provided; the medium-voltage direct-matching double-fed wind generating set 21 at the tail end of the same class of adjacent wind generating units 29 in the wind farm virtual generator 14 is connected for hot standby; the wind power generation unit 29 is in medium-voltage direct-matching double-fed wind power generation unit 21, and the fault of the head-tail outlet circuit can realize island micro-grid connection operation.
Offshore wind farm virtual generator cluster 7 comprising: each wind farm virtual generator 14 is provided with a plurality of generating units 29 and a plurality of boosting high-impedance transformers 19, and each generating unit 29 is provided with a plurality of medium-voltage direct-matching double-fed wind power generation units 21.
The offshore wind farm hub double-bus longitudinal incoming line 13 faces a plurality of high-voltage collecting ring main units 20, high-voltage collecting cables 16 and wind farm power generation units 29, and can be equivalently one wind farm virtual generator 14.
The wind farm power generation unit 29 inside the wind farm virtual generator 14 is connected with one medium voltage direct-matching double-fed wind turbine generator 21 through a medium voltage collecting cable 18 and a medium voltage collecting ring main unit 17 in two paths, the generated power is boosted to a high voltage collecting ring main unit 20 through the medium voltage collecting cable 18, the medium voltage collecting ring main unit 17 and a boosting high-impedance transformer 19, and is output to a ring main double-path high voltage collecting cable 16 through the high voltage collecting ring main unit 20 in two paths. After the power generated by the wind farm virtual generator 14 is sent out by the plurality of wind farm power generation units 29, the power is output to the upper bus and the lower bus of the hub double bus 12 in the offshore wind power bus type system 5 through the ring network double-path high-voltage collecting ring network cabinet 20 and the high-voltage collecting cable 16.
The input side of the high-voltage collecting ring main unit 20 in the offshore wind farm virtual generator 14 faces the boosting high-impedance transformer 19 and the plurality of medium-voltage collecting cables 18, the medium-voltage collecting ring main unit 17 and the medium-voltage direct-matching double-fed wind turbine 21, which are equivalent to a wind farm power generation unit 29 (fig. 8).
The wind power generation unit 29 of the wind power plant can also adopt a two-mode operation mode to realize the operation of the medium-voltage direct-matching double-fed wind turbine generator set 21 in a wide rotating speed range.
The medium-voltage direct-matching doubly-fed wind turbine generator 21 is composed of a doubly-fed converter 22, a direct-driven doubly-fed generator 23 (the rated frequency of a power transmission network is low frequency), a semi-direct-driven doubly-fed generator 24, a gear box 25 (the rated frequency of the power transmission network is frequency division), a hub 26, blades 27, a rotor loop transformer 28 and a power generation unit 29.
When the rated frequency of the offshore frequency division/low-frequency power grid 15 is frequency division, the generator of the medium-voltage direct-matching doubly-fed wind generating set 21 adopts a semi-direct-drive doubly-fed generator 24, and when the rated frequency of the offshore frequency division/low-frequency power grid 15 is low frequency, the generator of the medium-voltage direct-matching doubly-fed wind generating set 21 adopts a direct-drive doubly-fed generator 23.
VSC (left and right) 8-divide/low frequency grid side synchronous f/V and/or P/V regulation of the VSC cluster 2. Referring to fig. 3, in a method for operating a medium voltage direct-coupled doubly-fed wind generator set 21 by interconnecting an offshore frequency division/low frequency grid 15, a VSC cluster 2 is composed of n groups of VSCs (left and right) 8, each group of VSCs (left and right) 8 is composed of a left VSC and a right VSC, each VSC (left and right) frequency division/low frequency grid side 3 corresponds to an offshore frequency division/low frequency grid 9, a 50Hz grid side of each VSC (left and right) 8 corresponds to a 50Hz grid 1, and direct current conversion links are formed between the interiors of the VSCs (left and right) 8.
According to the wind power generation tide distribution requirement of the offshore frequency division/low frequency power transmission network 9, the end voltage of the VSC cluster 2 at the side of the frequency division/low frequency power transmission network of n groups of VSCs (left and right paths) 8 can be regulated singly or in a cluster mode, namely, the synchronous f/V or P/V regulation and control of the medium-voltage direct-matching double-fed wind turbine generator in the virtual generator cluster of the wind power plant are realized; according to the wind power generation tide distribution of the offshore frequency division/low frequency power transmission network 9 and the requirement of the on-line 50Hz power transmission network 1, the 50Hz power transmission network side terminal voltage of the VSC (left path and right path) 8 can be regulated singly or in a cluster; when it comes to, each VSC (left, right) 8 divide/low frequency grid side power input and VSC (left, right) 8 50Hz grid side power output must ensure power balance.
According to the operation method, the operation curves of the medium-voltage direct-matching doubly-fed wind turbine generator system 21 (for the VSC cluster frequency division/low-frequency power grid side 3, the hub double-bus longitudinal outgoing line 11, the offshore wind power bus system 5, the hub double-bus longitudinal incoming line 13 and the wind power plant virtual generator cluster 7) are utilized, and the 2n VSCs (left and right circuits) 8 frequency division/low-frequency power grid sides in the VSC cluster frequency division/low-frequency power grid side 3 are utilized to complete the interconnection of the offshore frequency division/low-frequency power grid 15 to obtain the synchronous frequency cluster adjustment, the synchronous voltage single or cluster adjustment of the medium-voltage direct-matching doubly-fed wind turbine generator system 21.
As shown in fig. 9, according to wind conditions of the wind farm in the offshore area, VSC (left and right paths) 8-frequency division/low-frequency grid side synchronous f/V regulation is implemented at low wind speed in a small wind period; at a frequency division/low frequency nominal frequency f L/F Under the condition, the medium-voltage direct-matching double-fed wind turbine generator system 21 runs below the point 5, namely synchronous rotation speedBelow, the generator speed n as at point 3 m3 Can reduce the rated frequency f of the offshore frequency division/low-frequency power grid L/F To->So that the synchronous speed decreases from point 5 to point 4, at which point the synchronous speed is from +.>Become->The electric slip is reduced, the power generation output power of the stator loop is relatively improved, the feedback power of the rotor loop is relatively reduced, meanwhile, the system voltage can be reduced, namely, the outlet voltage of the doubly-fed generator, the voltage and the excitation loss of the excitation loop are reduced, the efficiency and the high voltage ride through capability in the low wind stage and the low wind speed are improved, and the power generation working range in the low wind speed area is widened.
As shown in fig. 9, according to wind conditions of the wind farm in the offshore area, VSC (left and right paths) 8-frequency division/low-frequency grid side synchronous f/V regulation is implemented at low wind speed in a small wind period; at frequency division/low frequencyRated frequency f L/F Under the condition, the medium-voltage direct-matching double-fed wind turbine generator system 21 runs above the point 5, namely synchronous rotation speedAbove, generator speed n as at point 7 m7 Can adjust the rated frequency f L/F To->So that the synchronous speed increases from point 5 to point 6, at which point the synchronous speed is from +.>Become->The electric slip is reduced, the power generation output power of the stator loop is relatively improved, and the feedback power of the rotor loop is relatively reduced.
As shown in FIG. 9, according to the wind condition of the wind farm in the offshore area, the medium-voltage direct-matching doubly-fed wind turbine 21 operates between the point 8 and the rated operation point 9 at the high wind speed in the high wind period, and the rotating speed n m8 And n m9 (n m.n ) The synchronous P/V regulation of the VSC (left and right) 8 frequency division/low frequency power grid side can be realized; at 9 points, which are rated operation points 9, the medium-voltage direct-matching double-fed wind turbine generator system 21 is at rated rotation speed n m.n (n m9 ) 100% p.u. rated power, 100% p.u. rated voltage, and rated frequency f L/F And (5) running downwards.
The offshore frequency division/low frequency power grid 15 is interconnected to obtain a medium-voltage direct-matching doubly-fed wind generating set 21, and the offshore frequency division/low frequency power grid 15 comprises a VSC cluster frequency division/low frequency power grid side 3 and an offshore frequency division/low frequency power transmission grid 9, and any wind farm virtual generator i in the wind farm virtual generator cluster 7 can meet the safety criterion of a power grid 'N-1'.
Any one of the input/output lines of the VSC cluster 2 in the offshore frequency division/low frequency grid 15 (fig. 3) fails or the left VSC or the right VSC in the VSC (left, right) 8 fails, and the fault loop can be cut off through the on-shore high-voltage cabinet output switch; if the operation capacity is overloaded, the corresponding wind power plant medium-voltage direct-matching double-fed wind power generation set 21 needs to be subjected to unified load shedding operation, or the offshore frequency division/low-frequency wind power transmission network 9 (the offshore wind power bus system 5) is coordinated, the redundant power generation load is transferred to the double-channel internet surfing hub double-bus longitudinal outgoing line 11 with lighter loop load, and finally the redundant power is surfing through other light-load VSCs (left road and right road) 8.
Any one of the i/o line failures and switch failures in the offshore crossover/low frequency grid 15 may be incorporated into another normally operating loop or bus by cutting off the failed loop or switch and by its hot or cold backup tie switch.
As shown in fig. 2, 3 and 4, any loop cable of the two-way junction double-bus longitudinal incoming line 13 or the two-way junction double-bus longitudinal outgoing line 11 fails, a fault cable loop is cut off through a switch on an onshore high-voltage cabinet or the junction double-bus 12, or an offshore frequency division/low-frequency wind power transmission network 9 (an offshore wind power bus type system 5) is coordinated, redundant power generation load is transferred to the other loop load light double-way network double-bus longitudinal outgoing line 11, and finally the redundant power is accessed to the internet through other light-load VSCs (left and right circuits) 8.
Any fault of the vertical incoming line 13 of the double buses of the hub is removed through the switch on the double buses 12 of the hub in the offshore wind power bus system 5 and the bus switch of the high-voltage collecting ring main unit 20, redundant power generation load of the double-channel outgoing high-voltage collecting cable 16 of the ring network is transferred to the other double-channel outgoing high-voltage collecting cable 16 which normally operates, and when the power generation load of the outgoing high-voltage collecting cable 16 of the virtual generator 14 of the wind power plant is overloaded, unified load shedding allowance operation is needed.
As in fig. 4, 5, 6, 7, 8, in the wind farm virtual generator 14,
1) The bus or switch fault of the high-voltage collecting ring main unit 20, the upper, lower, left and right switches are cut off, the two paths of medium-voltage direct-matching double-fed wind turbine generator sets 21 in the wind power generation unit 29 of the current high-voltage collecting ring main unit 20 output power load, the tail section of the double-fed wind turbine generator set is connected with the tail sections of other wind power generation units 29 which are in the same transformer group in the wind power plant, and then the output is transferred, so that when the power generation load of the wind power generation unit 29 is overloaded, unified load shedding limit operation is required; the wind farm virtual generator 14 generates power load, and transfers redundant power generation load through disconnecting two paths or one path of the ring network double-path hinge double-bus longitudinal incoming line 13, and when overload occurs, the load is required to be operated under unified load shedding limit.
2) The high-voltage collecting cable 16 fails, input and output switches of the high-voltage collecting ring main unit 20 connected before and after cutting off are not influenced, and the operation of the wind power generation units 29 on two sides of the ring main unit double-path high-voltage collecting cable 16 is not influenced, and if other high-voltage collecting cables 16 are overloaded, the corresponding wind power generation units 29 are required to be subjected to unified load shedding limit operation.
3) The step-up high-impedance transformer 19 in the wind power generation unit 29 is failed, the power generation load output by the two paths of medium-voltage direct-matching double-fed wind power generation units 21 in the current wind power generation unit 29 is transferred and output after the tail section is connected with the tail sections of other internal transformers of the same group of wind power generation units 29, and when the power generation load is overloaded, the wind power generation units 29 are required to uniformly perform load shedding limit operation.
4) The medium-voltage collecting cable 18 in the wind power generation unit 29 is in fault, the power generation load output by the medium-voltage direct-matching double-fed wind power generation unit 21 in the current wind power generation unit 29 in the link is transferred and output through connection between the tail section and the tail sections of other wind power generation units 29 by cutting off the upper, lower, left and right switches, and when the power generation load is overloaded, the medium-voltage direct-matching double-fed wind power generation unit 21 in the link is required to perform unified load shedding limit operation.
5) The medium voltage collecting ring main unit 17 in the wind power generation unit 29 fails, the upper, lower, left and right switches are cut off, the other medium voltage direct-matching double-fed wind power generation units 21 which cannot be output by the medium voltage circuit in the ring main unit are output with power generation load, the tail sections are connected with the tail sections of the other wind power generation units 29 and transferred to output, and when the power generation load is overloaded, the medium voltage direct-matching double-fed wind power generation units 21 need to be operated in a unified load shedding limit mode. The medium-voltage direct-matching double-fed wind turbine generator system 21 output by the corresponding fault medium-voltage current collection ring main unit 17 can only be operated by turning to the island below.
As shown in fig. 4, 5, 6, 7 and 8, the single medium-voltage direct-coupled double-fed wind turbine 21 in the wind farm virtual generator 14 operates in island.
If the internal failure of the medium-voltage collecting ring main unit 17 occurs, the normal output channel of the power generation is disconnected and the normal operation cannot be performed, and the medium-voltage direct-matching double-fed wind turbine 21 can adopt an internal low-power isolated grid operation mode, and the medium-voltage direct-matching double-fed wind turbine 21 performs low-power generation operation island operation under the condition that the dynamic and static stability of a voltage range and a frequency range is met.
Therefore, the offshore frequency division/low frequency power grid 15, that is, the offshore frequency division/low frequency power grid 9 and the virtual generator cluster 7, the VSC cluster frequency division/low frequency power grid side 3, any left VSC and right VSC of the onshore VSC (left and right) 8, the hub double-bus longitudinal outgoing line 11 cable, the hub double-bus 12, the hub double-bus longitudinal incoming line 13 cable, the hub double-bus transverse connection 10 cable, the high-voltage collecting cable 16, the high-voltage collecting ring main unit 20, the boosting high-impedance transformer 19, the medium-voltage collecting cable 18 and the medium-voltage collecting ring main unit 17 are failed, after the failed equipment is cut off, the wind power generation power is transmitted to the internet through the hot or cold standby line, so that the offshore frequency division/low frequency power grid 9 and the virtual generator cluster 7 and the VSC cluster frequency division/low frequency power grid side 3 can normally generate power. The power generated by a wind power generation unit 29 in a wind power plant virtual generator 14 is connected with the other wind power generation units 29 in a hot or cold standby way by adopting a ring network two-way medium-voltage current collection ring main unit 17 and a medium-voltage current collection cable 18, and a ring network two-way hinge double-bus longitudinal incoming line 13 is connected with the network through a high-voltage current collection ring main unit 20; the adjacent offshore hub double buses 12 in the offshore wind power bus system 5 are transversely connected through an upper bus/an upper bus and a lower bus/a lower bus, and a hot standby connecting line is arranged in the hub double buses 12, and the longitudinal double upper banks are respectively connected with a left-way VSC and a right-way VSC frequency division/low-frequency power grid side in VSC (left-way and right-way) 8; the offshore frequency division/low frequency grid 15, comprising the offshore wind farm virtual generator cluster 7, the frequency division/low frequency power transmission grid 9 and the VSC cluster frequency division/low frequency power grid side 3, really has the "N-1" safety guidelines operating requirements.
The wind power generation unit 29 of the wind power plant adopts the step-up high-impedance transformer 19, and cooperates with the output reactive power of the medium-voltage direct-matching double-fed wind power generator set 21 to adjust the on-line power of the medium-voltage direct-matching double-fed wind power generator set 21The voltage deviation participates in steady-state and dynamic operation in a wide rated voltage range, high voltage ride through and low voltage ride through range; meanwhile, the rated voltage range, the high voltage ride through range and the low voltage ride through range can be widened. The impedance voltage percentage value of the step-up high impedance transformer 19 is selected as u dT ％＝12～36。
According to the running method of the wind generating set based on the offshore wind power bus system, when the rated frequency of the offshore frequency division/low-frequency power grid 15 is 50/3+/-5% Hz, a semi-direct-drive doubly-fed generator 24 is adopted, and a primary or secondary gear box 25 is arranged; the rated frequency of the offshore crossover/low frequency power grid 15 is 10 + -17% Hz at low frequency, and a direct drive doubly fed generator 23 is used without a gearbox 25. The rated voltage of the rotor ranges from 0.69kV to 10kV, the rated voltage of the stator ranges from 0.69kV to 35kV, and the capacity of the generator set ranges from 5MW to 50MW.
The foregoing basic embodiments of the invention, as well as other embodiments of the invention, can be freely combined to form numerous embodiments, all of which are contemplated and claimed. In the scheme of the invention, each selection example can be arbitrarily combined with any other basic example and selection example. Numerous combinations will be apparent to those skilled in the art.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (5)
1. The operation method of the wind generating set based on the offshore wind power bus system is characterized by comprising the following steps of:
the wind power plant virtual generators of a plurality of adjacent wind power plants on the sea are longitudinally wired through the double buses of the hinges; the upper bus and the lower bus of the plurality of adjacent hub double buses are respectively connected by transverse connection lines between the hub double buses, so that an offshore wind power bus type system of an offshore frequency division/low frequency power grid is formed;
the method comprises the steps that when the rated frequency of an offshore frequency division/low-frequency power grid in an offshore wind power bus system is 50/3+/-5% Hz, a medium-voltage direct-drive type doubly-fed generator is adopted, and when the rated frequency of the offshore frequency division/low-frequency power grid is 10+/-17% Hz, a medium-voltage direct-drive type doubly-fed generator or a medium-voltage direct-drive type doubly-fed generator is adopted.
2. A method of operating a wind power generator set based on an offshore wind power bus system as claimed in claim 1, wherein the offshore frequency division/low frequency power grid comprises: a virtual generator cluster, a frequency division/low frequency power transmission network and a VSC cluster frequency division/low frequency power network side of the offshore wind farm;
the two-way longitudinal outgoing line output of the ring network of each wind power plant virtual generator in the offshore wind power plant virtual generator cluster is connected with the network from the frequency division/low frequency power grid side of the VSC cluster through the offshore frequency division/low frequency power grid.
3. A method of operating a wind park based on an offshore wind park bus system according to claim 2, wherein the offshore frequency division/low frequency power transmission network comprises two longitudinal output lines of each wind park virtual generator ring network.
4. The method for operating the wind generating set based on the offshore wind power bus system according to claim 3, wherein the offshore wind farm virtual generator cluster comprises a plurality of wind farm virtual generators, each wind farm virtual generator comprises a plurality of power generating units and a plurality of step-up high-impedance transformers, and each power generating unit comprises a plurality of medium-voltage direct-matching double-fed wind generating sets.
5. The method for operating a wind generating set based on an offshore wind power bus system according to claim 4, wherein the generating unit adopts a step-up high-impedance transformer to regulate the on-line voltage deviation of the medium-voltage direct-coupled doubly-fed wind generating set in cooperation with the output reactive power of the medium-voltage direct-coupled doubly-fed wind generating set.
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