AU2020102600A4 - A system and method of DC voltage droop control for grid connection of offshore wind farms - Google Patents

A system and method of DC voltage droop control for grid connection of offshore wind farms Download PDF

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Publication number
AU2020102600A4
AU2020102600A4 AU2020102600A AU2020102600A AU2020102600A4 AU 2020102600 A4 AU2020102600 A4 AU 2020102600A4 AU 2020102600 A AU2020102600 A AU 2020102600A AU 2020102600 A AU2020102600 A AU 2020102600A AU 2020102600 A4 AU2020102600 A4 AU 2020102600A4
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offshore wind
voltage
cable
grid
igbt
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AU2020102600A
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Sipeng HAO
Haitao Liu
Peng Zhang
Xiaolian Zhang
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Nanjing Institute of Technology
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Nanjing Institute of Technology
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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
    • H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
    • H02J3/00125—Transmission line or load transient problems, e.g. overvoltage, resonance or self-excitation of inductive loads
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
    • F03D7/028—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor controlling wind motor output power
    • F03D7/0284—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor controlling wind motor output power in relation to the state of the electric grid
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
    • F03D7/04—Automatic control; Regulation
    • F03D7/042—Automatic control; Regulation by means of an electrical or electronic controller
    • F03D7/048—Automatic control; Regulation by means of an electrical or electronic controller controlling wind farms
    • 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
    • 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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/22—Arrangements for adjusting, eliminating or compensating reactive power in networks in cables
    • 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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02J3/40—Synchronising a generator for connection to a network or to another generator
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
    • H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
    • H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
    • H02M5/443—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M5/45—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/10—Purpose of the control system
    • F05B2270/107—Purpose of the control system to cope with emergencies
    • F05B2270/1071—Purpose of the control system to cope with emergencies in particular sudden load loss
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/30—Control parameters, e.g. input parameters
    • F05B2270/337—Electrical grid status parameters, e.g. voltage, frequency or power demand
    • 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
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
    • H02J13/00007—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using the power network as support for the transmission
    • H02J13/00009—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using the power network as support for the transmission using pulsed signals
    • 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
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H02J13/00032—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for
    • H02J13/00036—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers
    • H02J13/0004—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers involved in a protection system
    • 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
    • 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
    • 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
    • Y02E10/72—Wind turbines with rotation axis in wind direction
    • 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
    • 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
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
    • Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
    • Y04S40/121—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment using the power network as support for the transmission

Abstract

The invention discloses a direct current voltage droop control system and a method suitable for grid connection of offshore wind farms. When the offshore wind farms are merged into a power grid through a direct current link and then through inversion, connect the IGBT in power electronic equipment in parallel to the line of a direct current cable by using the capability of being randomly turned on and off at each moment of IGBT in power electronic equipment, so as to adjust the resistance value of the direct current cable flexibly, thus improving the performance of the direct current voltage sag curve. The invention has the following beneficial effects: the system does not need to adjust the DC voltage by adjusting the pulse width modulation index of the grid-side inverter, thus avoiding the power fluctuation on the AC grid side and a series of subsequent problems might be caused by it; In the invention, the IGBT starts to turn on when the DC voltage fluctuates, and it turns off when the DC voltage is stable, which can avoid the problem of cable failure caused by long-time use of a small-capacity cable after voltage adjustment by such a flexible control. 1 /3 FIG, 1

Description

1 /3
FIG, 1
A system and method of DC voltage droop control for grid connection of offshore wind farms
TECHNICAL FIELD
[01] The invention relates to a direct current voltage droop control system suitable for grid connection of offshore wind farms and a method thereof.
BACKGROUND
[02] With the upcoming energy crisis, people have gradually turned to new energy resources. The wind energy at sea has attracted more and more people's attention because of its more constant and higher speed than that on land. When the capacity of offshore wind farm is larger, it is an economical choice to input offshore wind energy into inland power grid through DC link, considering the distance between offshore wind farm and land. With the increasing capacity of offshore wind energy integrated into the grid, the fluctuation of the output of wind turbine caused by the randomness of wind speed often causes the voltage fluctuation of grid-side inverter. It has become the current study focus as to how to maintain the DC voltage stability of grid-side when the output of wind turbine fluctuates.
[03] The traditional voltage droop control is limited by the fixed resistance of DC cable, so it can not easily improve the performance of regulated voltage as shown in Figure 2. When the resistance of DC cable is relatively large, once the output of offshore wind farm fluctuates, the DC voltage on the grid side will fluctuate seriously. Therefore, it is very important to study a better method of adjusting voltage.
SUMMARY
[04] To solve the shortcomings of the prior art, the purpose of the present invention is to provide a DC voltage droop control system and method suitable for grid connection of offshore wind farms, and to solve the problem that once the output of offshore wind farms fluctuates in the prior art, the DC voltage on the grid side will fluctuate seriously.
[05] In order to achieve the above objectives, the invention adopts the following technical scheme:
[06] A system and method of DC voltage droop control for grid connection of offshore wind farms is connected from the offshore wind farm to the rectifier and converter station via transformer, then connected to the onshore inverse converter station via DC cable, and finally connected to the onshore AC power grid. The feature of such a system is a number of IGBTs are uniformly connected in parallel on the DC cable line, and all IGBTs are independent of each other.
[07] A system and method of DC voltage droop control for grid connection of offshore wind farms, according to claim 1, is characterized in that when the power generated by offshore wind farms changes randomly with the wind speed, the current Idc input to the DC cable changes, and the number k of IGBT conduction is controlled according to the real-time quantity of current Ide to keep the stability of capacitor voltage of the offshore wind farms connected to the DC side rectifier, wherein UWF_dc is the capacitor voltage of DC side rectifier connected to offshore wind farm, and UGS_dc is the DC capacitor voltage of inverter connected to grid side after offshore wind farm is input to grid through DC cable, R is the resistance of DC cable connected to system, and K is the number of IGBT connected to system.
[08]
UGS dc k- UWF dc RO Idc
[09] Furthermore, the way of turning on IGBT is accomplished by controlling the pulse trigger signal of each IGBT.
[010] The system has the beneficial effects that it does not need to adjust the DC voltage by adjusting the pulse width modulation index of the grid-side inverter, thus avoiding the power fluctuation on the AC grid side and a series of problems caused by the fluctuation; In the invention, the IGBT starts to turn on when the DC voltage fluctuates and turns off when the DC voltage is stable, so that the control is flexible, and the problem of cable failure caused by long-time use of a small-capacity cable after voltage adjustment is avoided.
BRIEF DESCRIPTION OF THE FIGURES
[011] FIG. 1 is a schematic diagram of controlling DC cable resistance with IGBT;
[012] FIG. 2 shows various voltage droop curves after changing the resistance of DC cable.
[013] FIG. 3 is an overall schematic diagram of an offshore wind farm imported into the mainland through DC link.
[014] The meaning of reference numerals in the drawings:
[015] 1-IGBT, 2- offshore wind farm, 3- transformer, 4- rectifier side converter station, 5- DC cable, 6- inverter side converter station and 7- onshore equivalent power supply.
DESCRIPTION OF THE INVENTION
[016] The present invention will be further described with reference to the accompanying drawings. The following examples are only used to illustrate the technical scheme of the present invention more clearly, but cannot be used to limit the protection scope of the present invention.
[017] The overall schematic diagram of the system is shown in fig. 3. The system is connected from offshore wind farm to a rectifier and converter station via transformer, then it is connected to an onshore inverse converter station via DC cable, and then it is connected to an onshore AC power grid. The specific operation mode of the intermediate DC loop is shown in fig. 1. When the wind speed of offshore wind field hardly changes, the active power generated by the wind farm hardly fluctuates, and the capacitor voltage on the grid-side inverter can be kept constant without adjustment. At this time, under each section of resistance, the IGBT is connected in parallel. This system makes use of the ability of IGBT in power electronic equipment to be turned on and off at any time, and connects IGBT in parallel to the line of DC cable, so as to flexibly adjust the resistance value of DC cable, thus improving the performance of DC voltage droop curve.
[018] When the wind speed at sea changes greatly, the active power generated by the wind farm will fluctuate accordingly. Meanwhile, a certain number of IGBT's are turned on by controlling the pulse trigger signal of each IGBT, and the resistance connected in parallel with it will be short-circuited, thus the total resistance value of the DC cable will become smaller, and the corresponding DC voltage droop curve will gradually change from @ to @ in Figure 2.
[019] The number of IGBT represented by K in the following equation that need to be turned on is roughly determined. According to the active power generated by the wind farm changes with the wind speed, the change of current Idc caused by it will not cause a large change of UGSdc.
[020]
kW dc -UGSdc k= R Idc
[021] This invention provides an improved DC voltage droop control method applied to the grid connection of offshore wind farms that can well inhibit the fluctuation of the DC voltage of the grid-side inverter capacitor when the active power generated by the wind farms fluctuates. When the DC voltage is adjusted, because the resistance of the DC cable becomes smaller, the current on the cable will increase accordingly, and the cable will be adversely affected if it is operated in this way for a long time. Therefore, when the DC voltage is adjusted to a reasonable range, the turn off signal will be sent to those IGBT's which are conducted to the system, restoring the DC cable to the level when the power does not fluctuate.
[022] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms, in keeping with the broad principles and the spirit of the invention described herein.
[023] The present invention and the described embodiments specifically include the best method known to the applicant of performing the invention. The present invention and the described preferred embodiments specifically include at least one feature that is industrially applicable

Claims (3)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:
1. A system and method of DC voltage droop control for grid connection of offshore wind farms is connected to a rectifier converter station via a voltage transformer, then connected to an onshore reverse converter station via a DC cable, and finally connected to an onshore alternating current network. It is characterized in that a number of IGBTs are uniformly connected in parallel on the DC cable line, and all IGBTs are independent of each other.
2. A system and method of DC voltage droop control for grid connection of offshore wind farms, according to claim 1, is characterized in that when the power generated by offshore wind farms changes randomly with the wind speed, the current Idc input to the DC cable changes, and the number k of IGBT conduction is controlled according to the real-time quantity of current Idc to keep the stability of capacitor voltage of the offshore wind farms connected to the DC side rectifier, wherein UWF_dc is the capacitor voltage of DC side rectifier connected to offshore wind farm, and UGS_dc is the DC capacitor voltage of inverter connected to grid side after offshore wind farm is input to grid through DC cable, R is the resistance of DC cable connected to system, and K is the number of IGBT connected to system.
UWFdc UGS dc Ro Id
3. A system and method of DC voltage droop control for grid connection of offshore wind farms according to claim 2 is characterized in that the way of turning on IGBT is completed by controlling the pulse trigger signal of each IGBT.
AU2020102600A 2020-10-05 2020-10-05 A system and method of DC voltage droop control for grid connection of offshore wind farms Active AU2020102600A4 (en)

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Application Number Priority Date Filing Date Title
AU2020102600A AU2020102600A4 (en) 2020-10-05 2020-10-05 A system and method of DC voltage droop control for grid connection of offshore wind farms

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