WO2016115662A1 - Method for operating wind farm in islanding mode and control system therefor - Google Patents

Method for operating wind farm in islanding mode and control system therefor Download PDF

Info

Publication number
WO2016115662A1
WO2016115662A1 PCT/CN2015/071012 CN2015071012W WO2016115662A1 WO 2016115662 A1 WO2016115662 A1 WO 2016115662A1 CN 2015071012 W CN2015071012 W CN 2015071012W WO 2016115662 A1 WO2016115662 A1 WO 2016115662A1
Authority
WO
WIPO (PCT)
Prior art keywords
wind turbine
auxiliary equipment
wind
power source
collection network
Prior art date
Application number
PCT/CN2015/071012
Other languages
French (fr)
Inventor
Yao Chen
Xing Huang
Original Assignee
Abb Technology Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Abb Technology Ltd filed Critical Abb Technology Ltd
Priority to PCT/CN2015/071012 priority Critical patent/WO2016115662A1/en
Publication of WO2016115662A1 publication Critical patent/WO2016115662A1/en

Links

Images

Classifications

    • 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
    • F03D9/00—Adaptations of wind motors for special use; Combinations of wind motors with apparatus driven thereby; Wind motors specially adapted for installation in particular locations
    • F03D9/20—Wind motors characterised by the driven apparatus
    • F03D9/25—Wind motors characterised by the driven apparatus the apparatus being an electrical generator
    • F03D9/255—Wind motors characterised by the driven apparatus the apparatus being an electrical generator connected to electrical distribution networks; Arrangements therefor
    • F03D9/257—Wind motors characterised by the driven apparatus the apparatus being an electrical generator connected to electrical distribution networks; Arrangements therefor the wind motor being part of a wind farm
    • 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
    • F03D9/00—Adaptations of wind motors for special use; Combinations of wind motors with apparatus driven thereby; Wind motors specially adapted for installation in particular locations
    • F03D9/10—Combinations of wind motors with apparatus storing energy
    • F03D9/11—Combinations of wind motors with apparatus storing energy storing electrical energy
    • 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
    • H02J3/381—Dispersed generators
    • 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
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • 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
    • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
    • 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
    • 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
    • Y02E70/00—Other energy conversion or management systems reducing GHG emissions
    • Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin

Definitions

  • the invention relates to a method for operating wind farm in islanding mode and control system therefor, and more particularly to a method for operating in islanding mode, the wind farm including a DC connection network and the control system therefor.
  • Offshore wind farm is one typical offshore application which is expected to grow in a steady pace and the installed power is expected to increase.
  • DC connection strategies could be extended from high voltage DC to the wind turbine generator outputs.
  • Such a configuration and the resulting DC collection network could potentially reduce the total cost of the power converters and improve the overall system efficiency and performance.
  • Patent US 20130197704 discloses a system having a power generation system that is provided with generator-rectifier subsystems.
  • a medium voltage DC collection network is provided with pole cables connected to DC outputs of rectifier.
  • An offshore substation is provided with bus bars connected to pole cables.
  • Main DC-DC converters are provided with modules having positive and negative outputs that are connected to one another.
  • the control system of the wind farm and/or the control system in each wind turbine of the wind farm should be able to take measure when problems occur during operation.
  • Islanding is a situation which may occur ifthe wind fann or part of the wind turbines of the wind farm becomes disconnected from the electrical grid, e.g. because of planned switching action or protective switching of a circuit breaker in the grid.
  • circuit breakers may automatically disconnect one or more turbines from the DC connection system and thus from the grid.
  • each disconnected wind turbine sets itself to a parking or standby state by stopping rotation of the blades by pitching the blades in the vane position.
  • the standby state will last until the islanded wind farm can be reconnected to the grid.
  • auxiliary equipment of the wind turbine e. g. the wind turbine controller controlling the wind turbine to stay within the requested limits, the wind turbine navigation light, the wind turbine sensor and communication apparatus, ventilation and heating equipment etc. , may be supplied with power from an independent emergency power source.
  • patent EP 2236821 teaches a method involving configuring an AC collection network and a main grid in island operation.
  • One of a set of deactivated wind turbine is activated, where the activated wind turbine and one of the remaining deactivated wind turbines are coupled to the AC collection network.
  • the activated wind turbine is configured to act as a power supply for the deactivated wind turbine via the AC collection network, rather than a DC collection network.
  • the wind farm includes a plurality of wind turbines, a DC collection network, and a substation, each the wind turbine including a generator with a rectifier, and wind turbine auxiliary equipment, the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier, and the DC input of the wind turbine auxiliary equipment of each the wind turbine, the substation including substation auxiliary equipment and a DC power source whose DC output is electrically connectable to the positive pole cable and the negative pole cable of the DC collection network, a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment, the method including: selecting a group of the plurality of wind turbines; choosing the DC power source as a first power source; choosing the selected wind turbine group as a second power source; activating the selected wind turbine; closing the electrical connection between the DC collection network and the DC input of the wind farm auxiliary equipment;
  • the wind farm includes a plurality of wind turbines, a DC collection network, and a substation, each the wind turbine including a generator with a rectifier, and wind turbine auxiliary equipment, the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier, and the DC input of the wind turbine auxiliary equipment of each the wind turbine, a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment, the method including: selecting a first group and a second group of the plurality of wind turbines; choosing the first wind turbine group as a first power source; choosing the second wind turbine group as a second power source; activating the selected wind turbine; closing the electrical connection between the DC collection network and the DC input of the wind farm auxiliary equipment; closing the electrical connection between the DC collection network and the DC output of the rectifier
  • the wind farm includes a plurality of wind turbines, a DC collection network, and a substation, each the wind turbine including a generator with a rectifier, and wind turbine auxiliary equipment, the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier, and the DC input of the wind turbine auxiliary equipment of each the wind turbine, the substation including substation auxiliary equipment and a DC power source whose DC output is electrically connectable to the positive pole cable and the negative pole cable of the DC collection network, a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment, the control system including: a first switch, for electrically connecting the DC collection network and the DC input of the wind farm auxiliary equipment; a second switch, for electrically connecting the DC collection network and the DC output of the rectifier of the wind turbine; and a third switch, for electrically connecting the DC collection
  • the wind farm includes a plurality of wind turbines, a DC collection network, and a substation, each the wind turbine including a generator with a rectifier, and wind turbine auxiliary equipment, the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier, and the DC input of the wind turbine auxiliary equipment of each the wind turbine, a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment, the control system including: a first switch, for electrically connecting the DC collection network and the DC input of the wind farm auxiliary equipment; a second switch, for electrically connecting the DC collection network and the DC output of the rectifier of the wind turbine of a first group; a third switch, for electrically connecting the DC collection network and the DC output of the rectifier of the wind turbine of a second group; wherein: one of the wind turbine of the first group and the second group is
  • the method and control system according to the invention thus provides an efficient and cheap way of separating power control and voltage control to two sorts of emergency power sources so that both of active power balancing among the emergency power source and power consumers and DC voltage stabilization at the DC collection network are achieved.
  • Figure 1 schematically illustrates a wind farm according to an embodiment of present invention
  • FIG. 1 shows the principle of voltage reference calculation under V control mode
  • Figure 3 shows the principle of active power reference calculation under P control mode.
  • FIG. 1 schematically illustrates a wind farm according to an embodiment of present invention.
  • the wind farm 1 includes a plurality of wind turbines 10-15,20-25, 30-35, a substation 4, DC collection network 50, 51, 52 and a control system 6.
  • the DC collection network 50, 51, 52 is electrically connectable to a utility grid via a first switch 7, for example a circuit breaker.
  • the first switch 7 can be opened when a fault in the utility grid occurred.
  • the wind turbines are arranged in three groups, where group G1 consists of the wind turbines 10-15, group G2 consists of the wind turbines 20-25, and group G3 consists of the wind turbines 30-35.
  • Each of the wind turbines 10-15 of group G1 is electrically connectable to the DC collection network 50 via respective one of second switches 800-805
  • each of the wind turbines 20-25 of group G2 is electrically connectable to the DC collection network 51 via respective one of second switches 810-815
  • each of the wind turbines 30-35 of group G3 is electrically connectable to the DC collection network 52 via respective one of second switches 820-825.
  • the skilled person shall understand that the number of DC collection network can be equal or above one, and the wind turbines can be arranged in one or more groups to deliver energy to the one or more DC collection networks.
  • the wind farm 1 can include a bus bar 8 arranged between the first switch 7 and the respective DC collection network 50, 51, 52 and electrically connecting the first switch 7 and the respective DC collection network 50, 51,52.
  • Each of wind turbines 10-15, 20-25, 30-35 includes a generator 100-150, 200-250, 300-350, with a rectifier 101-151, 201-251, 301-351, wind turbine auxiliary equipment 102-152, 202-252, 302-352.
  • Each generator is associated with the rectifier which provides a positive voltage output and a negative voltage output.
  • the each DC collection network 50, 51, 52 includes a positive pole cable 50p, 51p, 52p and a negative pole cable 50n, 51n, 52n which are electrically connectable to an DC output of the rectifier 101-151, 201-251, 301-351 of the wind turbine 10-15, 20-25, 30-35 via a third switch 104-154, 204-254, 304-354.
  • the each DC collection network 50, 51, 52 are electrically connectable to DC input of the wind turbine auxiliary equipment 102-152, 202-252, 302-352 of each the wind turbine 10-15, 20-25, 30-35 via a fourth switch 105-155, 205-255, 305-355.
  • the substation 4 includes substation auxiliary equipment 3 and a DC power source 9 whose DC output is electrically connectable to the positive pole cable and the negative pole cable of the DC collection network 50, 51, 52 respectively via a seventh switch 5 and a fifth switch 2.
  • the so-called wind farm auxiliary equipment includes the substation auxiliary equipment 3 and/or the wind turbine auxiliary equipment 102-152, 202-252, 302-352.
  • the substation auxiliary equipment 3 can be located inside the substation 4, which can be electrically connectable to the DC collection network 50, 51, 52 via the fifth switch 2 and the respective bus bar 8. By closing the fifth switch 2, energy can be delivered to and consumed by the substation auxiliary equipment 3 from some of or all of the generators 100-150, 200-250, 300-350 of the wind turbines 10-15, 20-25, 30-35.
  • the each wind turbines 10-15, 20-25, 30-35 includes an energy storage system 106-156, 206-256, 306-356 which is electrically connectable to the DC collection network 50, 51, 52 via a sixth switch 103-153, 203-253, 303-353.
  • the control system 6 can control to switch the on/off state of the second switch 800-805, 810-815, 820-825, the third switch 104-154, 204-254, 304-354, the fourth switch 105-155, 205-255, 305-355, the fifth switch 2, and the sixth switch 103-153, 203-253, 303-353.
  • the control system 6 can send command to the switches so that they act switch accordingly, either from on to off or vice versa.
  • the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch can be for example circuit breaker.
  • energy can be delivered from the respective one of the wind turbines 10-15, 20-25, 30-35 to the utility grid via the respective closed second switch 800-805, 810-815, 820-825, the respective closed third switch 104-154, 204-254, and the DC collection network 50, 51, 52, and the closed first switch 7.
  • the control system 6 can contain two layers of controller: central level controller which is located in the offshore platform, and distributed level controller which is located in the individual wind turbine. The functionality of the two layers of controller is introduced below.
  • Central controller determines the control references for the DC power source and the wind turbines.
  • the control references can be consist of connection mode, control mode and operation command; besides, the central controller determines the on/off commands for DC circuit breakers located inside the offshore substation.
  • Distributed controller determines the control references for the generator inside individual wind turbine; if the energy storage system of the wind turbine will be used for providing power, such control references shall involve the energy storage system as well.
  • the control references can be consist of connection mode, control mode and operation command; besides, the distributed controller determines the on/off commands for DC circuit breakers located inside the wind turbine.
  • the DC power source 9 there are two types of connection mode, and two types of control mode, as listed in Table I.
  • V control mode voltage control mode
  • P control mode power control mode
  • V control the power source acts as a voltage source, which mainly focus on the control of its output DC voltage value.
  • P control the power source acts as a current source, which mainly focus on the control of its output DC current value.
  • connection mode and the control mode are a bit more complicated.
  • the possible connection mode is shown in Table II, the corresponding on/off commands for the circuit breakers are also given.
  • the possible connection mode can be reduced from 8 to 4 types.
  • control mode of the wind turbine can be listed in Table III, totally four possible combinations are given. If the wind turbine is in V control mode, then at least one out of energy storage system and the generator of it should be able to work in V control mode; if the wind turbine is in P control mode, then both of energy storage system and the generator of it should be operated under P control mode.
  • a distributed level controller and/or the central level controller may disconnect-as a protective measure-one or more wind turbines from local grid by opening the first switch 7, the second switch 800-805, 810-815, 820-825.
  • further switches e.g. the third switch 104-154, 204-254, 304-354, the fourth switch 105-155, 205-255, 305-355, and the sixth switch 103-153, 203-253, 303-353 may be opened providing further electrical isolation of the wind turbine from the grid.
  • Each of the of the (high voltage) switches and/or high speed circuit breakers may be controlled (opened/closed) by the distributed level controller, central level controller and/or protective devices.
  • wind turbines 10-15, 20-25, 30-35 may have been deactivated after a power fault or a controlled shut down (either autonomously by one or more distributed level controllers or by the central level controller) .
  • a controlled shut down either autonomously by one or more distributed level controllers or by the central level controller.
  • Each deactivated wind turbine is isolated from the grid and each deactivated wind turbine is kept in standby operation by using its energy storage system, which is switchable connected to the wind turbine.
  • the wind turbine controller may set the wind turbine in a standby mode by stopping the rotation of the turbine by pitching the wind blades in the vane position.
  • a wind turbine in the standby mode (hereafter referred to as a ′′deactivated′′ wind turbine) is disconnected from the main grid.
  • the substation auxiliary equipment 3 and/or the wind turbine auxiliary equipment 102-152, 202-252, 302-352 may be connected to the DC collection network 50, 51, 52 to consume the power fed from the generator of the activated wind turbine and the DC power source 9.
  • even the ESS based DC power source 9, and distributed ESS in each wind turbine can change their operation from discharging power state into charging power state, and act as power consumer.
  • the central controller can collect information e. g. wind condition, DC power source capabilities (incl. available capacity and control model, threshold for stable/safety operation if any) and measurements (incl. voltage, current, power, etc. ) , wind turbine capabilities (incl. available capacity and control mode of both wind generators and energy storage system if installed, threshold for stable/safety operation if any) and measurements (incl. voltage, current, power, etc. ) , and circuit breaker status, etc.
  • the central controller can judge whether the DC power source or the selected wind turbines are put into V control or P control.
  • Figure 2 shows the principle of voltage reference calculation under V control mode.
  • the voltage references for this power source will be calculated according to a pre-defined operating point (V0, P0) , the measured active power output P, and the droop factor KP. By doing this, we can protect this power source from running out of capacity.
  • the V/P characteristic can be further illustrated in Figure 2 (b).
  • Figure 3 shows the principle of active power reference calculation under P control mode.
  • the active power reference will be calculated according to a pre-defined operating point (P 0 , V 0 ) , the measured voltage V, and the droop factor Kv.
  • the control system 6 can select a group of the plurality of wind turbines. It can select part or all of the wind turbines 10-15, 20-25, 30-35 in the wind farm, for example selecting the wind turbine 10, 20, 30.
  • the control system 6 chooses the DC power source 9 as a first power source and the selected wind turbine group 10, 20, 30 as a second power source.
  • the control system 6 instrusts to close the electrical connection between the DC collection network and the selected wind turbine 10, 20, 30 by switching the second switch 800, 810, 820.
  • the control system 6 instructs to close the electrical connection between the DC collection network 50, 51, 52 and the DC input of the wind farm auxiliary equipment 102-152, 202-252, 302-352 by switching on the fourth swtiches 105-155, 205-255, 305-355, and the second switch 800-805, 810-815, 820-815, close the electrical connection between the DC collection network and the DC output of the rectifier 101, 201, 301 of each the selected wind turbine 10, 20, 30 by switching on the third swiches 104, 204, 304, and close the electrical connection between the DC collection network 50, 51, 52 and the DC power source 9 of the substation 4 by switching on the seventh switch 5 and the fifth switch 2.
  • an islanded local grid is formed by interconnected the DC collection netwwork 50, 51, 52, wherein the local grid is disconnected from the main grid by the first switch 7.
  • the first power source as of the DC power source 9 supplies DC power in V control mode so that the DC voltage between the positive pole cable 50p, 51p, 52p and the negative pole cable 50n, 51n, 52n of the DC collection network 50, 51, 52 is kept in a predetermined voltage range, and the second power source as of the selected wind turbines 10, 20, 30 supplies DC power in P control to the wind farm auxiliary equipment via the DC connection network.
  • the method according to the invention thus provides an efficient and cheap way of separating power control and voltage control to two sorts of emergency power sources so that both of active power balancing among the emergency power source and power consumers and DC voltage stabilization at the DC collection network are achieved.
  • control system may decide that activation of one or more wind turbines is necessary.
  • the control system may select for example two operational wind turbines, wherein each of the wind turbines is located such that the power load of the two operative wind turbines are shared.
  • Wind turbine number for the selected wind turbine group is calculated in consideration of a first value for DC power deliverable by the first power source, a second value for DC power deliverable by the second power, and a third value for power consumable by the wind farm auxiliary
  • the central controller can calculate the desired power output from the DC power source by considering factors e.g. capacity, efficiency, safety limits, etc., and based on which to calculate the desired power output from the connected wind turbines in order to realize the power balance between the power sources and the auxiliary loads.
  • the central controller can judge whether the connected wind turbines are able to meet the desired power output or not based on a set of factors as well, e.g. the measured or forecasted wind conditions, wind turbine conditions, capacity, efficiency and safety limits etc. If not, then the central controller will adjust the number of connected wind turbines and put more connected wind turbines in P control mode.
  • the central controller can allocate the desired power output to each of the connected wind turbine.
  • the control system 6 may select a group of the plurality of wind turbines. It can select part or all of the wind turbines 10-15, 20-25, 30-35 in the wind farm, for example selecting the wind turbine 10, 20, 30.
  • the control system 6 chooses the DC power source 9 as a first power source and the selected wind turbine group 10, 20, 30 as a second power source.
  • the control system 6 instrusts to close the electrical connection between the DC collection network and the selected wind turbine 10, 20,30 by switching the second switch 800, 810, 820.
  • the control system 6 instructs to close the electrical connection between the DC collection network 50, 51, 52 and the DC input of the wind farm auxiliary equipment 102-152, 202-252, 302-352 by switching on the fourth swtiches 105-155, 205-255, 305-355, and the second switch 800-805, 810-815, 820-815, close the electrical connection between the DC collection network and the DC output of the rectifier 101, 201, 301 of each the selected wind turbine 10, 20, 30 by switching on the third swiches 104, 204, 304, and close the electrical connection between the DC collection network 50, 51, 52 and the DC power source 9 of the substation 4 by switching on the seventh switch 5 and the fifth switch 2.
  • an islanded local grid is formed by interconnected the DC collection netwwork 50, 51, 52, wherein the local grid is disconnected from the main grid by the first switch 7.
  • the second power source as of the selected wind turbines 10, 20, 30 supplies DC power in V control mode so that the DC voltage between the positive pole cable 50p, 51p, 52p and the negative pole cable 50n, 51n, 52n of the DC collection network 50, 51, 52 is kept in a predetermined voltage range, and the first power source as of the DC power source 9 supplies DC power in P control to the wind farm auxiliary equipment via the DC connection network.
  • the method according to the invention thus provides an efficient and cheap way of separating power control and voltage control to two sorts of emergency power sources so that both of active power balancing among the emergency power source and power consumers and DC voltage stabilization at the DC collection network are achieved.
  • the control system may decide that activation of one or more wind turbines is necessary.
  • the control system may select for example two operational wind turbines, wherein each of the wind turbines is located such that the power load of the two operative wind turbines are shared.
  • Wind turbine number for the selected wind turbine group is calculated in consideration of a first value for DC power deliverable by the first power source, a second value for DC power deliverable by the second power, and a third value for power consumable by the wind farm auxiliary equipment.
  • the central controller may calculate the desired power output from the connected wind turbines for power balance between the sources and loads, and then judge whether the connected wind turbines are able to meet such power output or not by considering factors e.g.
  • the central controller will adjust the number of connected wind turbines and put more connected wind turbines in.
  • the central controller can allocate the desired power output to each of the connected wind turbine.
  • the control system 6 selecting a first group and a second group of the plurality of wind turbines 10-15, 20-25, 30-35. It can select part or all of the wind turbines 10-15, 20-25, 30-35 in the wind farm, for example selecting the wind turbine 10, 20, 30 as the first group, and wind turbines 11, 21, 31 as the second group.
  • the control system 6 may choose the first wind turbine group as a first power source and the second wind turbine group as a second power source.
  • the control system 6 instrusts to close the electrical connection between the DC collection network and the selected wind turbine 10, 20, 30, 11, 21, 31 by switching the second switch 800, 810, 820, 801, 811, 821.
  • the control system 6 may instruct to close the electrical connection between the DC collection network 50, 51, 52 and the DC input of the wind farm auxiliary equipment 102-152, 202-252, 302-352 by switching on the fourth swtiches 105-155, 205-255, 305-355, close the electrical connection between the DC collection network and the DC output of the rectifier 101, 111, 201, 211, 301, 311 of each the selected wind turbine 10, 11, 20, 21, 30, 31 by switching on the third swiches 104, 114, 204, 214, 304.
  • an islanded local grid is formed by interconnected the DC collection netwwork 50, 51, 52, wherein the local grid is disconnected from the main grid by the first switch 7.
  • the first power source supplying DC power in V control mode so that the DC voltage between the positive pole cable and the negative pole cable of the DC collection network is kept in a predetermined voltage range; and the second power source supplying DC power in P control to the wind farm auxiliary equipment via the DC connection network.
  • the method according to the invention thus provides an efficient and cheap way of separating power control and voltage control to two sorts of emergency power sources so that both of active power balancing among the emergency power source and power consumers and DC voltage stabilization at the DC collection network are achieved.
  • the control system may decide that activation of one or more wind turbines is necessary.
  • the control system may select for example two operational wind turbines, wherein each of the wind turbines is located such that the power load of the two operative wind turbines are shared.
  • Wind turbine number for the selected wind turbine group is calculated in consideration of a first value for DC power deliverable by the first power source, a second value for DC power deliverable by the second power source in consideration of its electrical parameters and wind condition, and a third value for power consumable by the wind farm auxiliary equipment.
  • the method further including: closing the electrical connection between the DC collection network and the DC power source of the substation by switching on the seventh switch 5.
  • the DC power source 9 may supply DC power in P control to the wind farm auxiliary equipment via the DC connection network 50, 51, 52.
  • the calculation of the wind turbine number for the second wind turbine group further takes into account a third value for DC power deliverable by the DC power source of the substation.
  • the central controller will calculate the desired power output from the connected wind turbines for power balance between the sources and loads, and then judge whether the connected wind turbines are able to meet such power output or not by considering factors e.g. the measured or forecasted wind conditions, wind turbine conditions, capacity, efficiency and safety limits etc.
  • the central controller will optionally disconnect the DC power source if connected depending on the capacity, efficiency and safety limits of the DC power source, or furthermore, even change the operation state of the ESS based DC power source 9 from power generation state into charging power state, and act as power consumer; otherwise, the central controller will judge whether there are disconnected wind turbines available that can be connected and contribute for power supply.
  • the central controller will adjust the number of connected wind turbines accordingly, and calculate the acceptable power output range for each connected wind turbine based on their condition, capacity, efficiency and safety limits etc.; if there is no other wind turbine available, the central controller will connected the DC power source and put it in P control with acceptable power output range calculated based on its condition, capacity, efficiency and safety limits etc.
  • the method according to present invention further includes: closing the electrical connection between the DC collection network and the DC output of the energy storage system of each the selected wind turbine. If the wind turbine operates in V control mode: at least one of its rectifier and energy storage system operate in V control mode; and at most one of its rectifier and energy storage system operate in P control mode.

Abstract

A method and a control system thereof for operating a wind farm in islanding mode are provided, wherein: the wind farm (1) includes a plurality of wind turbines (10-15, 20-25, 30-35), a DC collection network (50, 51, 52) and a substation (4); each the wind turbine (10-15, 20-25, 30-35) includes a generator (100-150, 200-250, 300-350) with a rectifier (101-151, 201-251, 301-351) and a wind turbine auxiliary equipment (102-152, 202-252, 302-352); the DC collection network (50, 51, 52) includes a positive pole cable (50p, 51p, 52p) and a negative pole cable (50n, 51n, 52n) which are electrically connectable to an DC output of the rectifier (101-151, 201-251, 301-351) and the DC input of the wind turbine auxiliary equipment (102-152, 202-252, 302-352) of each the wind turbine(10-15, 20-25, 30-35); the substation (4) includes a substation auxiliary equipment (3) and a DC power source (9) whose DC output is electrically connectable to the positive pole cable (50p, 51p, 52p) and the negative pole cable (50n, 51n, 52n) of the DC collection network (50, 51, 52); a wind farm auxiliary equipment includes the substation auxiliary equipment (3) and/or the wind turbine auxiliary equipment (102-152, 202-252, 302-352). The method includes: selecting a group of the plurality of wind turbines (10-15, 20-25, 30-35); choosing the DC power source (9) as a first power source; choosing the selected wind turbine group as a second power source; activating the selected wind turbine; closing the electrical connection between the DC collection network (50, 51, 52) and the DC input of the wind farm auxiliary equipment; closing the electrical connection between the DC collection network (50, 51, 52) and the DC output of the rectifier (101-151, 201-251, 301-351) of each the selected wind turbine; closing the electrical connection between the DC collection network (50, 51, 52) and the DC power source (9) of the substation (4); one of the first power source and the second power source supply DC power in V control mode so that the DC voltage between the positive pole cable (50p, 51p, 52p) and the negative pole cable (50n, 51n, 52n) of the DC collection network (50, 51, 52) is kept in a predetermined voltage range and the other of the first power source and the second power source supply DC power in P control to the wind farm auxiliary equipment via the DC connection network (50, 51, 52). The method and control system according to the invention thus provide an efficient and cheap way of separating power control and voltage control to two sorts of emergency power sources so that both of active power balancing among the emergency power source and power consumers, and DC voltage stabilization at the DC collection network (50, 51, 52) are achieved.

Description

METHOD FOR OPERATING WIND FARM IN ISLANDING MODE AND CONTROL SYSTEM THEREFOR Technical Field
The invention relates to a method for operating wind farm in islanding mode and control system therefor， and more particularly to a method for operating in islanding mode， the wind farm including a DC connection network and the control system therefor.
Background Art
Offshore wind farm is one typical offshore application which is expected to grow in a steady pace and the installed power is expected to increase. In a desire to improve system efficiency from wind turbine generators to grid connection points， it is believed that DC connection strategies could be extended from high voltage DC to the wind turbine generator outputs. Such a configuration and the resulting DC collection network could potentially reduce the total cost of the power converters and improve the overall system efficiency and performance. Patent US 20130197704 discloses a system having a power generation system that is provided with generator-rectifier subsystems. A medium voltage DC collection network is provided with pole cables connected to DC outputs of rectifier. An offshore substation is provided with bus bars connected to pole cables. Main DC-DC converters are provided with modules having positive and negative outputs that are connected to one another. The control system of the wind farm and/or the control system in each wind turbine of the wind farm should be able to take measure when problems occur during operation.
One of the problems faced in the wind farm operations relates to so-called islanding. Islanding is a situation which may occur ifthe wind fann or part of the wind turbines of the wind farm becomes disconnected from the electrical grid， e.g. because of planned switching action or protective switching of a circuit breaker in the grid. For example after detection of a power failure， circuit breakers may automatically disconnect one or more turbines from the DC connection system and thus from the grid. Thereafter， each disconnected wind turbine sets itself to a parking or standby state by stopping rotation of the blades by pitching the blades in the vane position. The standby state will last until the islanded wind farm can be reconnected to the grid. During this state， auxiliary equipment of the wind turbine， e. g. the wind turbine controller controlling the wind turbine to stay within the requested limits， the wind turbine navigation light， the wind turbine sensor and communication apparatus， ventilation and heating equipment etc. ， may be supplied with power from an independent emergency power source.
In addressing a technical problem of inefficient and expensive way of supplying power to an islanded group of wind turbines， patent EP 2236821 teaches a method involving configuring an AC collection network and a main grid in island operation. One of a set of deactivated wind turbine is activated， where the activated wind turbine and one of the remaining deactivated wind turbines are coupled to the AC collection network. The activated wind turbine is configured to act as a power supply for the deactivated wind turbine via the AC collection network， rather than a DC collection network.
Therefore， there is a technical problem with the DC connection strategy in consideration of active power balancing among the emergency power source and power consumers， and DC voltage stabilization at the DC collection network.
Brief Summary of the Invention
It is therefore an objective of the invention to provide a method for operating a wind farm in islanding mode， wherein： the wind farm includes a plurality of wind turbines， a DC collection network， and a substation， each the wind turbine including a generator with a rectifier， and wind turbine auxiliary equipment， the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier， and the DC input of the wind turbine auxiliary equipment of each the wind turbine， the substation including substation auxiliary equipment and a DC power source whose DC output is electrically connectable to the positive pole cable and the negative pole cable of the DC collection network， a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment， the method including： selecting a group of the plurality of wind turbines； choosing the DC power source as a first power source； choosing the selected wind turbine group as a second power source； activating the selected wind turbine； closing the electrical connection between the DC collection network and the DC input of the wind farm auxiliary equipment； closing the electrical connection between the DC collection network and the DC output of the rectifier of each the selected wind turbine； closing the electrical connection between the DC collection network and the DC power source of the substation； one of the first power source and the second power source supplying DC power in V control mode so that the DC voltage between the positive pole cable and the negative pole cable of the DC collection network is kept in a predetermined voltage range； and the other of the first power source and the second power source supplying DC power in P control to the wind farm auxiliary equipment via the DC connection network.
According to another aspect of present invention， it provides a method for operating a wind farm during a fault in a utility grid to which power is to be delivered from the wind farm， wherein： the wind farm includes a plurality of wind turbines， a DC collection network， and a substation， each the wind turbine including a generator with a rectifier， and wind turbine auxiliary equipment， the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier， and the DC input of the wind turbine auxiliary equipment of each the wind turbine， a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment， the method including： selecting a first group and a second group of the plurality of wind turbines； choosing the first wind turbine group as a first power source； choosing the second wind turbine group as a second power source； activating the selected wind turbine； closing the electrical connection between the DC collection network and the DC input of the wind farm auxiliary equipment； closing the electrical connection between the DC collection network and the DC output of the rectifier of each the selected wind turbine of the first group and the second group； the first power source supplying DC power in V control mode so that the DC voltage between the positive pole cable and the negative pole cable of the DC collection network is kept in a predetermined voltage range； and the second power source supplying DC power in P control to the wind farm auxiliary equipment via the DC connection network.
According to another aspect of present invention， it provides a control system for operating a wind farm in islanding mode， wherein： the wind farm includes a plurality of wind  turbines， a DC collection network， and a substation， each the wind turbine including a generator with a rectifier， and wind turbine auxiliary equipment， the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier， and the DC input of the wind turbine auxiliary equipment of each the wind turbine， the substation including substation auxiliary equipment and a DC power source whose DC output is electrically connectable to the positive pole cable and the negative pole cable of the DC collection network， a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment， the control system including： a first switch， for electrically connecting the DC collection network and the DC input of the wind farm auxiliary equipment； a second switch， for electrically connecting the DC collection network and the DC output of the rectifier of the wind turbine； and a third switch， for electrically connecting the DC collection network and the DC power source of the substation； wherein： one the DC power source of the substation and the rectifier of the wind turbine is adapted for supplying DC power in V control mode so that the DC voltage between the positive pole cable and the negative pole cable of the DC collection network is kept in a predetermined voltage range； and the other of the DC power source of the substation and the rectifier of the wind turbine is adapted for supplying DC power in P control to the wind farm auxiliary equipment via the DC connection network.
According to another aspect of present invention， it provides a control system for operating a wind farm in islanding mode， wherein： the wind farm includes a plurality of wind turbines， a DC collection network， and a substation， each the wind turbine including a generator with a rectifier， and wind turbine auxiliary equipment， the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier， and the DC input of the wind turbine auxiliary equipment of each the wind turbine， a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment， the control system including： a first switch， for electrically connecting the DC collection network and the DC input of the wind farm auxiliary equipment； a second switch， for electrically connecting the DC collection network and the DC output of the rectifier of the wind turbine of a first group； a third switch， for electrically connecting the DC collection network and the DC output of the rectifier of the wind turbine of a second group； wherein： one of the wind turbine of the first group and the second group is adapted for supplying DC power in V control mode so that the DC voltage between the positive pole cable and the negative pole cable of the DC collection network is kept in a predetermined voltage range； and the other of the wind turbine of the first group and the second group is adapted for supplying DC power in P control to the wind farm auxiliary equipment via the DC connection.
Provided that suitable wind conditions are available， the method and control system according to the invention thus provides an efficient and cheap way of separating power control and voltage control to two sorts of emergency power sources so that both of active power balancing among the emergency power source and power consumers and DC voltage stabilization at the DC collection network are achieved.
Brief Description of the Drawings
The subject matter of the invention will be explained in more detail in the following text with reference to preferred exemplary embodiments which are illustrated in the drawings， in which：
Figure 1 schematically illustrates a wind farm according to an embodiment of present invention；
Figure 2 shows the principle of voltage reference calculation under V control mode； and
Figure 3 shows the principle of active power reference calculation under P control mode.
Preferred Embodiments of the Invention
Figure 1 schematically illustrates a wind farm according to an embodiment of present invention. As shown in figure 1， the wind farm 1 includes a plurality of wind turbines 10-15，20-25， 30-35， a substation 4， DC collection network 50， 51， 52 and a control system 6. The DC collection network 50， 51， 52 is electrically connectable to a utility grid via a first switch 7， for example a circuit breaker. The first switch 7 can be opened when a fault in the utility grid occurred. The wind turbines are arranged in three groups， where group G1 consists of the wind turbines 10-15， group G2 consists of the wind turbines 20-25， and group G3 consists of the wind turbines 30-35.
Each of the wind turbines 10-15 of group G1 is electrically connectable to the DC collection network 50 via respective one of second switches 800-805， each of the wind turbines 20-25 of group G2 is electrically connectable to the DC collection network 51 via respective one of second switches 810-815， and each of the wind turbines 30-35 of group G3 is electrically connectable to the DC collection network 52 via respective one of second switches 820-825. The skilled person shall understand that the number of DC collection network can be equal or above one， and the wind turbines can be arranged in one or more groups to deliver energy to the one or more DC collection networks. Where there is more than one DC collection network 50， 51， 52， the wind farm 1 can include a bus bar 8 arranged between the first switch 7 and the respective DC collection network 50， 51， 52 and electrically connecting the first switch 7 and the respective DC collection network 50， 51，52.
Each of wind turbines 10-15， 20-25， 30-35 includes a generator 100-150， 200-250， 300-350， with a rectifier 101-151， 201-251， 301-351， wind turbine auxiliary equipment 102-152， 202-252， 302-352. Each generator is associated with the rectifier which provides a positive voltage output and a negative voltage output. The each DC collection network 50， 51， 52 includes a positive pole cable 50p， 51p， 52p and a negative pole cable 50n， 51n， 52n which are electrically connectable to an DC output of the rectifier 101-151， 201-251， 301-351 of the wind turbine 10-15， 20-25， 30-35 via a third switch 104-154， 204-254， 304-354. The each DC collection network 50， 51， 52 are electrically connectable to DC input of the wind turbine auxiliary equipment 102-152， 202-252， 302-352 of each the wind turbine 10-15， 20-25， 30-35 via a fourth switch 105-155， 205-255， 305-355. The substation 4 includes substation auxiliary equipment 3 and a DC power source 9 whose DC output is electrically connectable to the positive pole cable and the negative pole cable of the DC collection network 50， 51， 52 respectively via a seventh switch 5 and a fifth switch 2. The so-called wind farm auxiliary equipment includes the substation auxiliary equipment 3 and/or the wind turbine auxiliary equipment 102-152， 202-252， 302-352. The substation auxiliary equipment 3 can be located inside the substation 4， which can be electrically connectable to the DC collection network 50， 51， 52 via the fifth switch 2 and the respective bus bar 8. By closing the fifth switch 2， energy can be delivered to and consumed by the substation auxiliary equipment 3 from some of or all of the generators 100-150， 200-250， 300-350 of the wind turbines 10-15， 20-25， 30-35.
Preferably， the each wind turbines 10-15， 20-25， 30-35 includes an energy storage system 106-156， 206-256， 306-356 which is electrically connectable to the DC collection network 50， 51， 52 via a sixth switch 103-153， 203-253， 303-353.
The control system 6 can control to switch the on/off state of the second switch 800-805， 810-815， 820-825， the third switch 104-154， 204-254， 304-354， the fourth switch 105-155， 205-255， 305-355， the fifth switch 2， and the sixth switch 103-153， 203-253， 303-353. For example， the control system 6 can send command to the switches so that they act switch accordingly， either from on to off or vice versa. The second switch， the third switch， the fourth switch， the fifth switch and the sixth switch can be for example circuit breaker. During normal operation， energy can be delivered from the respective one of the wind turbines 10-15， 20-25， 30-35 to the utility grid via the respective closed second switch 800-805， 810-815， 820-825， the respective closed third switch 104-154， 204-254， and the DC collection network 50， 51， 52， and the closed first switch 7.
The control system 6 can contain two layers of controller： central level controller which is located in the offshore platform， and distributed level controller which is located in the individual wind turbine. The functionality of the two layers of controller is introduced below. Central controller determines the control references for the DC power source and the wind turbines. The control references can be consist of connection mode， control mode and operation command； besides， the central controller determines the on/off commands for DC circuit breakers located inside the offshore substation. Distributed controller determines the control references for the generator inside individual wind turbine； if the energy storage system of the wind turbine will be used for providing power， such control references shall involve the energy storage system as well. Similarly， the control references can be consist of connection mode， control mode and operation command； besides， the distributed controller determines the on/off commands for DC circuit breakers located inside the wind turbine.
For the DC power source 9， there are two types of connection mode， and two types of control mode， as listed in Table I. When the DC power source is connected， i.e. the seventh switch 5 and the fifth switch 2 are closed， it can choose to use V control mode (voltage control mode) or P control mode (power control mode) according to its capability. By using V control， the power source acts as a voltage source， which mainly focus on the control of its output DC voltage value. By using P control， the power source acts as a current source， which mainly focus on the control of its output DC current value. When it is disconnected， i.e. the seventh switch 5 or the fifth switch 2 is open， most likely V control mode will be chosen to operate the DC power source 9 as a standby power source.
Figure PCTCN2015071012-appb-000001
Table I
For the wind turbines， and the energy storage system and the wind generator located inside the wind turbine， the connection mode and the control mode are a bit more complicated. Take the wind turbine 10 for example， the possible connection mode is shown in Table II， the corresponding on/off commands for the circuit breakers are also given. Of course， if  there is no energy storage system installed in the wind turbine， then the possible connection mode can be reduced from 8 to 4 types.
Figure PCTCN2015071012-appb-000002
Table II
Correspondingly， the control mode of the wind turbine can be listed in Table III， totally four possible combinations are given. If the wind turbine is in V control mode， then at least one out of energy storage system and the generator of it should be able to work in V control mode； if the wind turbine is in P control mode， then both of energy storage system and the generator of it should be operated under P control mode.
To make the whole system work under islanding operation， it is a precondition that either DC power source or at least one wind turbine is capable of doing DC voltage control.
Figure PCTCN2015071012-appb-000003
Figure PCTCN2015071012-appb-000004
Table III
If a distributed level controller and/or the central level controller detects a power fault， it may disconnect-as a protective measure-one or more wind turbines from local grid by opening the first switch 7， the second switch 800-805， 810-815， 820-825. During disconnection， further switches e.g. the third switch 104-154， 204-254， 304-354， the fourth switch 105-155， 205-255， 305-355， and the sixth switch 103-153， 203-253， 303-353 may be opened providing further electrical isolation of the wind turbine from the grid. Each of the of the (high voltage) switches and/or high speed circuit breakers may be controlled (opened/closed) by the distributed level controller， central level controller and/or protective devices. As shown in Figure 1， wind turbines 10-15， 20-25， 30-35 may have been deactivated after a power fault or a controlled shut down (either autonomously by one or more distributed level controllers or by the central level controller) . Each deactivated wind turbine is isolated from the grid and each deactivated wind turbine is kept in standby operation by using its energy storage system， which is switchable connected to the wind turbine.
When the circuit breakers are opened， the wind turbine controller may set the wind turbine in a standby mode by stopping the rotation of the turbine by pitching the wind blades in the vane position. A wind turbine in the standby mode (hereafter referred to as a ″deactivated″ wind turbine) is disconnected from the main grid. Hence in order to ensure continuous standby operation of the wind turbine， the substation auxiliary equipment 3 and/or the wind turbine auxiliary equipment 102-152， 202-252， 302-352 may be connected to the DC collection network 50， 51， 52 to consume the power fed from the generator of the activated wind turbine and the DC power source 9. Or furthermore， under some conditions with high speed of wind， even the ESS based DC power source 9， and distributed ESS in each wind turbine can change their operation from discharging power state into charging power state， and act as power consumer.
The central controller can collect information e. g. wind condition， DC power source capabilities (incl. available capacity and control model， threshold for stable/safety operation if any) and measurements (incl. voltage， current， power， etc. ) ， wind turbine capabilities (incl. available capacity and control mode of both wind generators and energy storage system if installed， threshold for stable/safety operation if any) and measurements (incl. voltage， current， power， etc. ) ， and circuit breaker status， etc. In order to balance active power among the emergency power source (e. g. the generator of the activated wind turbine and the DC power source 9) and power consumers， and stabilize DC voltage at the DC collection network 9， the central controller can judge whether the DC power source or the selected wind turbines are put into V control or P control.
Figure 2 shows the principle of voltage reference calculation under V control mode. For example， if the DC power source (or the selected wind turbines) is selected to work in V control mode， as illustrated in Figure 2 (a) ， the voltage references for this power source  will be calculated according to a pre-defined operating point (V0， P0) ， the measured active power output P， and the droop factor KP. By doing this， we can protect this power source from running out of capacity. The V/P characteristic can be further illustrated in Figure 2 (b).
Figure 3 shows the principle of active power reference calculation under P control mode. On the other hand， if the DC power source (or the selected wind turbines) is selected to work in P control mode， as illustrated in Figure 3 (a) ， the active power reference will be calculated according to a pre-defined operating point (P0， V0) ， the measured voltage V， and the droop factor Kv. By doing this， we can ensure the stable operation of the system with multiple power sources operated together in an autonomous way. The P/V characteristic can be further illustrated in Figure 3 (b) .
Scenario A：
If the DC power source 9 is in V control， the control system 6 can select a group of the plurality of wind turbines. It can select part or all of the wind turbines 10-15， 20-25， 30-35 in the wind farm， for example selecting the  wind turbine  10， 20， 30. The control system 6 chooses the DC power source 9 as a first power source and the selected  wind turbine group  10， 20， 30 as a second power source. The control system 6 instrusts to close the electrical connection between the DC collection network and the selected  wind turbine  10， 20， 30 by switching the  second switch  800， 810， 820. In order to power the wind turbine auxiliary equipment 102-152， 202-252， 302-352， the control system 6 instructs to close the electrical connection between the DC collection network 50， 51， 52 and the DC input of the wind farm auxiliary equipment 102-152， 202-252， 302-352 by switching on the fourth swtiches 105-155， 205-255， 305-355， and the second switch 800-805， 810-815， 820-815， close the electrical connection between the DC collection network and the DC output of the rectifier 101， 201， 301 of each the selected  wind turbine  10， 20， 30 by switching on the third swiches 104， 204， 304， and close the electrical connection between the DC collection network 50， 51， 52 and the DC power source 9 of the substation 4 by switching on the seventh switch 5 and the fifth switch 2. After closing said switches an islanded local grid is formed by interconnected the DC collection netwwork 50， 51， 52， wherein the local grid is disconnected from the main grid by the first switch 7. The first power source as of the DC power source 9 supplies DC power in V control mode so that the DC voltage between the positive pole cable 50p， 51p， 52p and the negative pole cable 50n， 51n， 52n of the DC collection network 50， 51， 52 is kept in a predetermined voltage range， and the second power source as of the selected  wind turbines  10， 20， 30 supplies DC power in P control to the wind farm auxiliary equipment via the DC connection network.
Provided that suitable wind conditions are available， the method according to the invention thus provides an efficient and cheap way of separating power control and voltage control to two sorts of emergency power sources so that both of active power balancing among the emergency power source and power consumers and DC voltage stabilization at the DC collection network are achieved.
In case of a large group of deactivated wind turbines the control system may decide that activation of one or more wind turbines is necessary. The control system may select for example two operational wind turbines， wherein each of the wind turbines is located such that the power load of the two operative wind turbines are shared. Wind turbine number for the selected wind turbine group is calculated in consideration of a first value for DC power deliverable by the first power source， a second value for DC power deliverable by the second power， and a third value for power consumable by the wind farm auxiliary 
equipment. For example， the central controller can calculate the desired power output from the DC power source by considering factors e.g. capacity， efficiency， safety limits， etc.， and based on which to calculate the desired power output from the connected wind turbines in order to realize the power balance between the power sources and the auxiliary loads. The central controller can judge whether the connected wind turbines are able to meet the desired power output or not based on a set of factors as well， e.g. the measured or forecasted wind conditions， wind turbine conditions， capacity， efficiency and safety limits etc. If not， then the central controller will adjust the number of connected wind turbines and put more connected wind turbines in P control mode. The central controller can allocate the desired power output to each of the connected wind turbine.
Senario B：
If the DC power source 9 is not in V control， the control system 6 may select a group of the plurality of wind turbines. It can select part or all of the wind turbines 10-15， 20-25， 30-35 in the wind farm， for example selecting the  wind turbine  10， 20， 30. The control system 6 chooses the DC power source 9 as a first power source and the selected  wind turbine group  10， 20， 30 as a second power source. The control system 6 instrusts to close the electrical connection between the DC collection network and the selected  wind turbine  10， 20，30 by switching the  second switch  800， 810， 820. In order to power the wind turbine auxiliary equipment 102-152， 202-252， 302-352， the control system 6 instructs to close the electrical connection between the DC collection network 50， 51， 52 and the DC input of the wind farm auxiliary equipment 102-152， 202-252， 302-352 by switching on the fourth swtiches 105-155， 205-255， 305-355， and the second switch 800-805， 810-815， 820-815， close the electrical connection between the DC collection network and the DC output of the rectifier 101， 201， 301 of each the selected  wind turbine  10， 20， 30 by switching on the third swiches 104， 204， 304， and close the electrical connection between the DC collection network 50， 51， 52 and the DC power source 9 of the substation 4 by switching on the seventh switch 5 and the fifth switch 2. After closing said switches an islanded local grid is formed by interconnected the DC collection netwwork 50， 51， 52， wherein the local grid is disconnected from the main grid by the first switch 7. The second power source as of the selected  wind turbines  10， 20， 30 supplies DC power in V control mode so that the DC voltage between the positive pole cable 50p， 51p， 52p and the negative pole cable 50n， 51n， 52n of the DC collection network 50， 51， 52 is kept in a predetermined voltage range， and the first power source as of the DC power source 9 supplies DC power in P control to the wind farm auxiliary equipment via the DC connection network.
Provided that suitable wind conditions are available， the method according to the invention thus provides an efficient and cheap way of separating power control and voltage control to two sorts of emergency power sources so that both of active power balancing among the emergency power source and power consumers and DC voltage stabilization at the DC collection network are achieved.
In case of a large group of deactivated wind turbines the control system may decide that activation of one or more wind turbines is necessary. The control system may select for example two operational wind turbines， wherein each of the wind turbines is located such that the power load of the two operative wind turbines are shared. Wind turbine number for the selected wind turbine group is calculated in consideration of a first value for DC power deliverable by the first power source， a second value for DC power deliverable by the second power， and a third value for power consumable by the wind farm auxiliary equipment. For example， the central controller may calculate the desired power output from the connected wind turbines for power balance between the sources and loads， and  then judge whether the connected wind turbines are able to meet such power output or not by considering factors e.g. the measured or forecasted wind conditions， wind turbine conditions， capacity， efficiency and safety limits etc. If the connected wind turbines are not able to meet such desired power output， then the central controller will adjust the number of connected wind turbines and put more connected wind turbines in. The central controller can allocate the desired power output to each of the connected wind turbine.
Scenario C：
If the DC power source 9 is not in V control， as an alternative to scenario A， the control system 6 selecting a first group and a second group of the plurality of wind turbines 10-15， 20-25， 30-35. It can select part or all of the wind turbines 10-15， 20-25， 30-35 in the wind farm， for example selecting the  wind turbine  10， 20， 30 as the first group， and  wind turbines  11， 21， 31 as the second group. The control system 6 may choose the first wind turbine group as a first power source and the second wind turbine group as a second power source. The control system 6 instrusts to close the electrical connection between the DC collection network and the selected  wind turbine  10， 20， 30， 11， 21， 31 by switching the  second switch  800， 810， 820， 801， 811， 821. In order to power the wind turbine auxiliary equipment 102-152， 202-252， 302-352， and the second switch 800-805， 810-815， 820-815， the control system 6 may instruct to close the electrical connection between the DC collection network 50， 51， 52 and the DC input of the wind farm auxiliary equipment 102-152， 202-252， 302-352 by switching on the fourth swtiches 105-155， 205-255， 305-355， close the electrical connection between the DC collection network and the DC output of the rectifier 101， 111， 201， 211， 301， 311 of each the selected  wind turbine  10， 11， 20， 21， 30， 31 by switching on the third swiches 104， 114， 204， 214， 304. After closing said switches an islanded local grid is formed by interconnected the DC collection netwwork 50， 51， 52， wherein the local grid is disconnected from the main grid by the first switch 7. The first power source supplying DC power in V control mode so that the DC voltage between the positive pole cable and the negative pole cable of the DC collection network is kept in a predetermined voltage range； and the second power source supplying DC power in P control to the wind farm auxiliary equipment via the DC connection network.
Provided that suitable wind conditions are available， the method according to the invention thus provides an efficient and cheap way of separating power control and voltage control to two sorts of emergency power sources so that both of active power balancing among the emergency power source and power consumers and DC voltage stabilization at the DC collection network are achieved.
In case of a large group of deactivated wind turbines， the control system may decide that activation of one or more wind turbines is necessary. The control system may select for example two operational wind turbines， wherein each of the wind turbines is located such that the power load of the two operative wind turbines are shared. Wind turbine number for the selected wind turbine group is calculated in consideration of a first value for DC power deliverable by the first power source， a second value for DC power deliverable by the second power source in consideration of its electrical parameters and wind condition， and a third value for power consumable by the wind farm auxiliary equipment.
Preferably， the method further including： closing the electrical connection between the DC collection network and the DC power source of the substation by switching on the seventh switch 5. The DC power source 9 may supply DC power in P control to the wind farm auxiliary equipment via the DC connection network 50， 51， 52. The calculation of the wind turbine number for the second wind turbine group further takes into account a third value for DC power deliverable by the DC power source of the substation. For example， the  central controller will calculate the desired power output from the connected wind turbines for power balance between the sources and loads， and then judge whether the connected wind turbines are able to meet such power output or not by considering factors e.g. the measured or forecasted wind conditions， wind turbine conditions， capacity， efficiency and safety limits etc. Ifthe connected wind turbines are able to meet such desired power output， the central controller will optionally disconnect the DC power source if connected depending on the capacity， efficiency and safety limits of the DC power source， or furthermore， even change the operation state of the ESS based DC power source 9 from power generation state into charging power state， and act as power consumer； otherwise， the central controller will judge whether there are disconnected wind turbines available that can be connected and contribute for power supply. If there are disconnected wind turbines available， the central controller will adjust the number of connected wind turbines accordingly， and calculate the acceptable power output range for each connected wind turbine based on their condition， capacity， efficiency and safety limits etc.； if there is no other wind turbine available， the central controller will connected the DC power source and put it in P control with acceptable power output range calculated based on its condition， capacity， efficiency and safety limits etc.
Preferably， the method according to present invention further includes： closing the electrical connection between the DC collection network and the DC output of the energy storage system of each the selected wind turbine. If the wind turbine operates in V control mode： at least one of its rectifier and energy storage system operate in V control mode； and at most one of its rectifier and energy storage system operate in P control mode.
Though the present invention has been described on the basis of some preferred embodiments， those skilled in the art should appreciate that those embodiments should by no way limit the scope of the present invention. Without departing from the spirit and concept of the present invention， any variations and modifications to the embodiments should be within the apprehension of those with ordinary knowledge and skills in the art， and therefore fall in the scope of the present invention which is defined by the accompanied claims.

Claims (10)

  1. A method for operating a wind farm in islanding mode， wherein： the wind farm includes a plurality of wind turbines， a DC collection network， and a substation， each the wind turbine including a generator with a rectifier， and wind turbine auxiliary equipment， the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier， and the DC input of the wind turbine auxiliary equipment of each the wind turbine， the substation including substation auxiliary equipment and a DC power source whose DC output is electrically connectable to the positive pole cable and the negative pole cable of the DC collection network， a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment，
    the method including：
    selecting a group of the plurality of wind turbines；
    choosing the DC power source as a first power source；
    choosing the selected wind turbine group as a second power source；
    activating the selected wind turbine；
    closing the electrical connection between the DC collection network and the DC input of the wind farm auxiliary equipment；
    closing the electrical connection between the DC collection network and the DC output of the rectifier of each the selected wind turbine；
    closing the electrical connection between the DC collection network and the DC power source of the substation；
    one of the first power source and the second power source supplying DC power in V control mode so that the DC voltage between the positive pole cable and the negative pole cable of the DC collection network is kept in a predetermined voltage range； and the other of the first power source and the second power source supplying DC power in P control to the wind farm auxiliary equipment via the DC connection network.
  2. A method for operating a wind farm during a fault in a utility grid to which power is to be delivered from the wind farm， wherein： the wind farm includes a plurality of wind turbines， a DC collection network， and a substation， each the wind turbine including a generator with a rectifier， and wind turbine auxiliary equipment， the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier， and the DC input of the wind turbine auxiliary equipment of each the wind turbine， a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment，
    the method including：
    selecting a first group and a second group of the plurality of wind turbines；
    choosing the first wind turbine group as a first power source；
    choosing the second wind turbine group as a second power source；
    activating the selected wind turbine；
    closing the electrical connection between the DC collection network and the DC input of the wind farm auxiliary equipment；
    closing the electrical connection between the DC collection network and the DC output of the rectifier of each the selected wind turbine of the first group and the second group；
    the first power source supplying DC power in V control mode so that the DC voltage between the positive pole cable and the negative pole cable of the DC collection network is kept in a predetermined voltage range； and
    the second power source supplying DC power in P control to the wind farm auxiliary equipment via the DC connection network.
  3. The method according to claim 1， wherein：
    wind turbine number for the selected wind turbine group is calculated in consideration of a first value for DC power deliverable by the first power source， a second value for DC power deliverable by the second power source， and a third value for power consumable by the wind farm auxiliary equipment.
  4. The method according to claim 2， wherein：
    wind turbine number for the selected wind turbine group is calculated in consideration of a first value for DC power deliverable by the first power source， a second value for DC power deliverable by the second power source in consideration of its electrical parameters and wind condition， and a third value fos power consumable by the wind farm auxiliary equipment.
  5. The method according to claim 4， wherein： the substation of the wind farm further includes a DC power source whose DC output is electrically connectable to the positive pole cable and the negative pole cable of the DC collection network； the method further including：
    closing the electrical connection between the DC collection network and the DC power source of the substation；
    the DC power source supplying DC power in P control to the wind farm auxiliary equipment via the DC connection network.
  6. The method according to claim 5， wherein：
    the calculation of the wind turbine number for the selected wind turbine group further takes into account a third value for DC power deliverable by the DC power source of the substation.
  7. The method according to any of claims 1-4， wherein： each the wind turbine further includes an energy storage system， an DC output of the energy storage system of each the wind turbine being electrically connectable to the positive pole cable and the negative pole cable；
    the method further including：
    closing the electrical connection between the DC collection network and the DC output of the energy storage system of each the selected wind turbine.
  8. The method according to claim 7， wherein：
    if the wind turbine operates in V control mode：
    at least one of its rectifier and energy storage system operate in V control mode；
    and
    at most one of its rectifier and energy storage system operate in P control mode.
  9. A control system for operating a wind farm in islanding mode， wherein： the wind farm includes a plurality of wind turbines， a DC collection network， and a substation， each the wind turbine including a generator with a rectifier， and wind turbine auxiliary equipment， the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier， and the DC input of the wind turbine auxiliary equipment of each the wind turbine， the substation including substation auxiliary equipment and a DC power source whose DC output is electrically connectable to the positive pole cable and the negative pole cable of the DC collection network， a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment， the control system including：
    a first switch， for electrically connecting the DC collection network and the DC input of the wind farm auxiliary equipment；
    a second switch， for electrically connecting the DC collection network and the DC output of the rectifier of the wind turbine； and
    a third switch， for electrically connecting the DC collection network and the DC power source of the substation；
    wherein：
    one the DC power source of the substation and the rectifier of the wind turbine is adapted for supplying DC power in V control mode so that the DC voltage between the positive pole cable and the negative pole cable of the DC collection network is kept in a predetermined voltage range； and
    the other of the DC power source of the substation and the rectifier of the wind turbine is adapted for supplying DC power in P control to the wind farm auxiliary equipment via the DC connection network.
  10. A control system for operating a wind farm in islanding mode， wherein： the wind fann includes a plurality of wind turbines， a DC collection network， and a substation， each the wind turbine including a generator with a rectifier， and wind turbine auxiliary equipment， the DC collection network including a positive pole cable and a negative pole cable which are electrically connectable to an DC output of the rectifier， and the DC input of the wind turbine auxiliary equipment of each the wind turbine， a wind farm auxiliary equipment including the substation auxiliary equipment and/or the wind turbine auxiliary equipment，
    the control system including：
    a first switch， for electrically connecting the DC collection network and the DC input of the wind farm auxiliary equipment；
    a second switch， for electrically connecting the DC collection network and the DC output of the rectifier of the wind turbine of a first group；
    a third switch， for electrically connecting the DC collection network and the DC output of the rectifier of the wind turbine of a second group；
    wherein：
    one of the wind turbine of the first group and the second group is adapted for supplying DC power in V control mode so that the DC voltage between the positive pole cable and the negative pole cable of the DC collection network is kept in a predetermined voltage range； and
    the other of the wind turbine of the first group and the second group is adapted for supplying DC power in P control to the wind farm auxiliary equipment via the DC connection.
PCT/CN2015/071012 2015-01-19 2015-01-19 Method for operating wind farm in islanding mode and control system therefor WO2016115662A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/CN2015/071012 WO2016115662A1 (en) 2015-01-19 2015-01-19 Method for operating wind farm in islanding mode and control system therefor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2015/071012 WO2016115662A1 (en) 2015-01-19 2015-01-19 Method for operating wind farm in islanding mode and control system therefor

Publications (1)

Publication Number Publication Date
WO2016115662A1 true WO2016115662A1 (en) 2016-07-28

Family

ID=56416248

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2015/071012 WO2016115662A1 (en) 2015-01-19 2015-01-19 Method for operating wind farm in islanding mode and control system therefor

Country Status (1)

Country Link
WO (1) WO2016115662A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110192317A (en) * 2016-10-26 2019-08-30 菱重维斯塔斯海上风力有限公司 The exchange of electric power of control and self-commutation converter

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2236821A1 (en) * 2009-04-03 2010-10-06 XEMC Darwind B.V. Wind farm island operation
CN103140670A (en) * 2010-12-29 2013-06-05 再生动力系统欧洲股份公司 Wind farm and method for operating a wind farm
CN103890385A (en) * 2011-09-05 2014-06-25 湘电达尔文有限责任公司 Generating auxiliary power for a wind turbine
CN104137376A (en) * 2012-02-01 2014-11-05 Abb研究有限公司 DC connection scheme for windfarm with internal mvdc collection grid

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2236821A1 (en) * 2009-04-03 2010-10-06 XEMC Darwind B.V. Wind farm island operation
CN103140670A (en) * 2010-12-29 2013-06-05 再生动力系统欧洲股份公司 Wind farm and method for operating a wind farm
CN103890385A (en) * 2011-09-05 2014-06-25 湘电达尔文有限责任公司 Generating auxiliary power for a wind turbine
CN104137376A (en) * 2012-02-01 2014-11-05 Abb研究有限公司 DC connection scheme for windfarm with internal mvdc collection grid

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110192317A (en) * 2016-10-26 2019-08-30 菱重维斯塔斯海上风力有限公司 The exchange of electric power of control and self-commutation converter
CN110192317B (en) * 2016-10-26 2023-02-14 维斯塔斯风力系统集团公司 Controlling power exchange with a self-commutated converter

Similar Documents

Publication Publication Date Title
EP3238316B1 (en) Method and controller for coordinating control of wind farm during disconnection to utility grid
EP3487035B1 (en) Power supply system and method
EP2876768B1 (en) Method of operating a wind park
US8247917B2 (en) Storage battery output power control method for wind turbine generator
CN107394829B (en) Direct current power supply system coordination control system and method based on non-interconnection communication
WO2016082070A1 (en) Method for black starting wind turbine, wind farm, and restoring wind farm and wind turbine, wind farm using the same
JP6261866B2 (en) Power generation system including power generation facility and power storage device, control method thereof, and program
JP5945594B2 (en) Power supply system
JP2008099527A (en) Storage battery system in non-utility generation equipment connected to electric power system and driving method therefor
US20130002027A1 (en) Uninterruptible power supply
CN102460899A (en) Emergency power supply device
EP3821129B1 (en) Wind turbine power consumption control
US9257859B2 (en) Dynamic battery control based on demand
CN107980194A (en) Redundancy residential power
Morais et al. Interlink Converters in DC nanogrids and its effect in power sharing using distributed control
KR20180136177A (en) An energy storage system
CN110571906A (en) Working state self-adaptive control method for power station with multiple working modes
WO2016115662A1 (en) Method for operating wind farm in islanding mode and control system therefor
CN203707801U (en) Energy-saving high-power positioning capability ship hybrid electric propulsion system
WO2016070319A1 (en) Method for coordinating control of wind farm during black start of islanding operation
WO2016033769A1 (en) Method and system for coordinating control of wind farm during disconnection to utility grid
JP2021526786A (en) Energy storage unit Separate current transformer and its application system, control method
JP2021197823A (en) Dc microgrid system and control method thereof
WO2020161766A1 (en) Direct-current power supply system
CN111130138A (en) Multi-energy complementary microgrid off-grid stable operation control method and system

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15878340

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15878340

Country of ref document: EP

Kind code of ref document: A1