CN116316785A - Offshore wind power direct current sending-out system based on onshore crossbar switch and control method - Google Patents
Offshore wind power direct current sending-out system based on onshore crossbar switch and control method Download PDFInfo
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- CN116316785A CN116316785A CN202310531871.5A CN202310531871A CN116316785A CN 116316785 A CN116316785 A CN 116316785A CN 202310531871 A CN202310531871 A CN 202310531871A CN 116316785 A CN116316785 A CN 116316785A
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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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/28—The renewable source being wind energy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
The invention provides a offshore wind power direct current sending-out system based on an onshore crossbar and a control method, wherein the system comprises the following components: the shore cross switch comprises a first switch, a second switch, a third switch and a fourth switch, wherein the first switch and the second switch are connected with the third switch and the fourth switch in a cross manner and then are connected with a submarine cable, and the first switch and the second switch are interlocked with the third switch and the fourth switch in a switch state so as to realize the positive-negative conversion of the voltage at the direct current side; the power grid is connected with the onshore converter valve through a low-voltage winding and a fifth switch of a transformer in the three-winding transformer, and is connected with the onshore converter valve through a high-voltage winding and a sixth switch of the transformer in the three-winding transformer; the on-shore converter valve adopts a half-bridge modularized multi-level converter, and the direct current side of the on-shore converter valve is connected with the direct current side of the on-shore converter valve through an on-shore cross switch and a sea cable; the alternating current side of the offshore converter valve is connected with an offshore wind farm. The system reduces the cost and ensures the stable operation of the offshore wind power direct current delivery system.
Description
Technical Field
The invention relates to the technical field of offshore wind power, in particular to an offshore wind power direct current sending-out system based on an onshore crossbar and a control method.
Background
The remote offshore wind power transmission generally adopts a high-voltage direct current transmission technology, after the offshore wind turbine generates electricity and is converged through an alternating current cable, an offshore converter station converts alternating current into direct current, and then the direct current sea cable is used for transmitting the electric energy to the offshore converter station. At present, all the converter valves of the offshore converter stations in the offshore wind power direct current transmission project adopt MMC structures, but the MMC converter valves are high in cost and large in volume and weight. For this reason, various offshore converter valve topology schemes with diode valves (DR) and MMC valves connected in series are proposed in the prior art, but DR-MMC series valves have a problem that it is difficult to start black in an offshore wind farm in practical application.
Aiming at the problem of black start of the DR-MMC series valve of the offshore wind power plant, the existing solution is to lead an alternating current line to an offshore converter station from the shore for supplying energy required for black start of the offshore wind power plant, but the method adds extra cost and loss. In addition, black start of the offshore wind farm can be realized by utilizing the MMC part of the offshore DR-MMC series valve, the scheme is that a bypass switch is connected in parallel to the direct current side of the diode valve in the offshore DR-MMC series valve, when the offshore wind farm needs black start, the bypass switch is firstly closed, so that the offshore converter station can directly transmit electric energy to the MMC part of the DR-MMC series valve, and then the MMC provides alternating current for the offshore wind farm to realize black start. In another scheme of the offshore wind power DR-MMC series valve, the onshore converter station MMC converter valve adopts a full-bridge module topology, so that the onshore converter valve can output negative voltage, a diode of the offshore DR-MMC series valve is conducted forward, and at the moment, an MMC part of the offshore DR-MMC series valve can transmit electric energy to an offshore wind farm to realize black start.
Disclosure of Invention
Therefore, the technical scheme of the invention mainly solves the defect of high cost of the existing offshore wind power direct current delivery system, thereby providing the offshore wind power direct current delivery system based on the onshore crossbar and the control method.
In a first aspect, an embodiment of the present invention provides an offshore wind power dc delivery system based on an onshore crossbar, including: the system comprises a power grid, an onshore converter valve, an onshore cross switch, a submarine cable, an offshore converter valve and an offshore wind farm; wherein,,
the shore cross switch comprises a first switch, a second switch, a third switch and a fourth switch, wherein the first switch and the second switch are connected with the sea cable after being cross-connected with the third switch and the fourth switch, and the first switch and the second switch are interlocked with the switch states of the third switch and the fourth switch so as to realize the positive-negative conversion of the direct-current side voltage;
the power grid is connected with the onshore converter valve through a transformer low-voltage winding and a fifth switch in the three-winding transformer, and is connected with the onshore converter valve through a transformer high-voltage winding and a sixth switch in the three-winding transformer; the on-shore converter valve adopts a half-bridge modularized multi-level converter, and the direct current side of the on-shore converter valve is connected with the direct current side of the on-shore converter valve through the on-shore cross switch and the submarine cable; the alternating current side of the offshore converter valve is connected with the offshore wind farm.
According to the offshore wind power direct current delivery system and the control method based on the onshore crossbar switch, the onshore crossbar switch is used for conducting positive-negative electrode conversion, the onshore converter valve does not need to output negative pressure, a full-bridge submodule is not needed, cost of the onshore converter valve is saved, the onshore converter valve and the offshore wind power plant are matched with interaction, and starting and stable operation of the offshore wind power direct current delivery system are achieved with low cost and high reliability.
With reference to the first aspect, in one possible implementation manner, the offshore converter valve includes: a first diode valve, a second diode valve and a full-bridge modular multilevel converter, wherein,
the alternating current sides of the first diode valve and the second diode valve are respectively connected with the alternating current side of the full-bridge modularized multi-level converter in parallel, the direct current side of the first diode valve, the direct current side of the second diode valve and the direct current side of the full-bridge modularized multi-level converter are connected in series, the first diode valve is connected with an offshore wind farm through a seventh switch and a first transformer, the second diode valve is connected with the offshore wind farm through an eighth switch and a second transformer, and the full-bridge modularized multi-level converter is connected with the offshore wind farm through a ninth switch and a third transformer.
With reference to the first aspect, in another possible implementation manner, the full-bridge modular multilevel converter is formed by cascading a plurality of full-bridge submodules.
With reference to the first aspect, in another possible implementation manner, the method further includes: an energy storage device;
the energy storage device is connected with the offshore wind farm through a tenth switch and a step-up transformer.
With reference to the first aspect, in another possible implementation manner, the first switch, the second switch, the third switch and the fourth switch adopt a high-voltage direct-current circuit breaker.
In a second aspect, the embodiment of the invention further provides a control method of an offshore wind power direct current transmission system based on an onshore crossbar, which is applied to the offshore wind power direct current transmission system based on the onshore crossbar, and the method comprises the following steps:
acquiring a starting instruction, and based on the starting instruction, establishing negative voltage by using an on-shore converter valve and an on-shore cross switch, wherein the negative voltage supplies power to an offshore wind farm through the offshore converter valve so as to finish black starting of the offshore wind farm;
disconnecting the onshore cross switch by limiting fan output of the offshore wind farm to disconnect the connection between the onshore converter valve and the offshore converter valve;
and lifting the direct current side voltage of the on-shore converter valve, and controlling the on-shore cross switch to be closed until the direct current side voltage of the on-shore converter valve is higher than the rated direct current voltage, wherein connection is established between the on-shore converter valve and the on-shore converter valve so as to finish starting of the on-shore wind power direct current delivery system.
With reference to the second aspect, in another possible implementation manner, the establishing, based on the start command, a negative voltage with an on-shore converter valve and an on-shore crossbar, the negative voltage supplying power to an offshore wind farm via the offshore converter valve to complete a black start of the offshore wind farm includes:
a first opening instruction is sent to a first switch, a second switch and a fifth switch based on the starting instruction, a first closing instruction is sent to a third switch, a fourth switch and a sixth switch Guan Fasong, the first opening instruction is used for controlling the first switch, the second switch and the fifth switch to be opened, the first closing instruction is used for controlling the third switch, the fourth switch and the sixth switch to be closed, and after the third switch, the fourth switch and the sixth switch are closed, a first working voltage output by a power grid is charged to an onshore converter valve through a transformer low-voltage winding;
acquiring direct-current side voltage of an on-shore converter valve, and sending an unlocking instruction to the on-shore converter valve when the direct-current side voltage of the on-shore converter valve accords with a preset voltage, wherein after the on-shore converter valve is unlocked based on the unlocking instruction, the direct-current side voltage of the on-shore converter valve establishes the negative voltage through an on-shore cross switch, and the negative voltage is used for charging the offshore converter valve;
and when the direct-current side voltage of the offshore converter valve accords with the preset voltage, sending a second closing instruction to a ninth switch, wherein the second closing instruction is used for controlling the closing of the ninth switch, and after the ninth switch is closed, the offshore converter valve establishes the voltage of the offshore wind farm in a zero-starting mode so as to finish black start of the offshore wind farm.
With reference to the second aspect, in another possible implementation manner, the disconnecting the onshore crossbar by limiting a fan output of the offshore wind farm to disconnect the onshore converter valve from the offshore converter valve includes:
acquiring alternating current collection voltage of an offshore wind farm, and sending a first control instruction to the offshore wind farm based on the alternating current collection voltage of the offshore wind farm, wherein the first control instruction is used for limiting fan output of an offshore fan;
and acquiring the current of a third switch and the current of a fourth switch, and when the current of the third switch and the current of the fourth switch pass through zero points, giving a second disconnection instruction to the third switch and the fourth switch Guan Fasong, wherein the second disconnection instruction is used for controlling the disconnection of the third switch and the fourth switch so as to disconnect the connection between the onshore converter valve and the offshore converter valve.
With reference to the second aspect, in another possible implementation manner, the lifting the dc side voltage of the onshore converter valve until the dc side voltage of the onshore converter valve is higher than the rated dc voltage, controlling the onshore crossbar to be closed, and establishing a connection between the offshore converter valve and the onshore converter valve to complete starting of the offshore wind power dc output system includes:
after the disconnection states of the third switch and the fourth switch are obtained, a second control instruction is sent to the full-bridge modularized multi-level converter, and the second control instruction is used for controlling the direct-current side voltage of the full-bridge modularized multi-level converter to be converted into a forward rated voltage;
when the direct-current side voltage of the full-bridge modularized multi-level converter is the forward rated voltage, a third opening instruction is sent to the sixth opening Guan Fasong, and a second closing instruction is sent to the fifth switch, wherein when the fifth switch is closed based on the second closing instruction, a second working voltage output by a power grid charges the onshore converter valve through a transformer high-voltage winding;
and when the direct-current side voltage of the shore-based converter valve is higher than the rated direct-current voltage, a third closing instruction is given to the first switch, the second switch, the seventh switch and the eighth switch Guan Fasong, wherein after the first switch, the second switch, the seventh switch and the eighth switch are closed, the offshore wind farm operates in a maximum power point tracking mode, and the first diode valve, the second diode valve and the full-bridge modularized multi-level converter are put into offshore wind power transmission, and an offshore wind power direct-current delivery system is started.
With reference to the second aspect, in another possible implementation manner, the method further includes:
and the direct current side total voltage of the full-bridge sub-modules is obtained, the energy storage device is controlled to charge when the direct current side total voltage of the full-bridge sub-modules is increased, and the energy storage device is controlled to discharge when the direct current side total voltage of the full-bridge sub-modules is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a circuit diagram of an offshore wind power direct current transmission system based on an onshore crossbar provided by an embodiment of the invention;
FIG. 2 is a flowchart of a control method of an offshore wind power DC output system based on an onshore crossbar according to an embodiment of the present invention;
fig. 3 is a flowchart of S201 provided in an embodiment of the present invention;
fig. 4 is a flowchart of S202 provided in an embodiment of the present invention;
fig. 5 is a flowchart of S203 provided in an embodiment of the present invention;
fig. 6 is a diagram illustrating an embodiment of an electronic device according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, unless explicitly stated or limited otherwise, the terms "mounted," "connected," "coupled," and "connected" are to be construed broadly, and may be, for example, fixedly connected, mechanically connected, or electrically connected; or can be directly connected, or can be indirectly connected through an intermediate medium, or can be communication between the two elements, or can be wireless connection or wired connection. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
The embodiment of the invention provides an offshore wind power direct current transmission system based on an onshore crossbar, which is shown in fig. 1 and comprises the following components: the system comprises a power grid 1, an onshore converter valve 2, an onshore cross switch 3, a submarine cable 4, an offshore converter valve 5 and an offshore wind farm 6; wherein,,
the shore cross switch 3 comprises a first switch 7, a second switch 8, a third switch 9 and a fourth switch 10, wherein the first switch 7 and the second switch 8 are connected with the third switch 9 and the fourth switch 10 in a cross connection mode and then are connected with the submarine cable 4, and the first switch 7 and the second switch 8 are interlocked with the third switch 9 and the fourth switch 10 in a switch state so as to realize positive-negative conversion of direct-current side voltage.
The power grid 1 is connected with the onshore converter valve 2 through a transformer low-voltage winding 11 and a fifth switch 12 in a three-winding transformer, and is connected with the onshore converter valve 2 through a transformer high-voltage winding 13 and a sixth switch 14 in the three-winding transformer; the on-shore converter valve 2 adopts a half-bridge modularized multi-level converter (half-bridge MMC for short), and the direct current side of the on-shore converter valve 2 is connected with the direct current side of the on-shore converter valve 5 through the on-shore cross switch 3 and the submarine cable 4; the ac side of the offshore converter valve 5 is connected to the offshore wind farm 6.
Specifically, the first switch 7, the second switch 8, the third switch 9, and the fourth switch 10 are high-voltage dc breakers.
Further, the first switch 7 and the second switch 8 are interlocked with the third switch 9 and the fourth switch 10 in a switch state, that is, the first switch 7 and the second switch 8 are opened or closed at the same time, the third switch 9 and the fourth switch 10 are opened or closed at the same time, and the onshore crossbar 3 can realize the positive-negative conversion of the output voltage of the onshore converter valve 2.
According to the offshore wind power direct current delivery system based on the onshore crossbar switch, positive and negative electrode conversion is carried out through the onshore crossbar switch, the onshore converter valve does not need to output negative pressure, a full-bridge submodule is not needed, cost of the onshore converter valve is saved, the onshore converter valve and the onshore converter valve are matched with interaction between the onshore crossbar switch and an offshore wind power plant, and starting and stable operation of the offshore wind power direct current delivery system are realized with low cost and high reliability.
As an alternative embodiment of the present invention, the above-mentioned marine converter valve 5 includes: a first diode valve 15, a second diode valve 16 and a full-bridge modular multilevel converter 17 (abbreviated as full-bridge MMC), wherein,
the ac side of the first diode valve 15 and the ac side of the second diode valve 16 are connected in parallel with the ac side of the full-bridge modular multilevel converter 17, the dc side of the first diode valve 15, the dc side of the second diode valve 16 and the dc side of the full-bridge modular multilevel converter 17 are connected in series, the first diode valve 15 is connected to the offshore wind farm 6 via a seventh switch 18 and a first transformer 19, the second diode valve 16 is connected to the offshore wind farm 6 via an eighth switch 20 and a second transformer 21, and the full-bridge modular multilevel converter 17 is connected to the offshore wind farm 6 via a ninth switch 22 and a third transformer 23.
Specifically, the full-bridge modular multilevel converter 17 is formed by cascading a plurality of full-bridge submodules.
Further, the offshore wind turbines in the offshore wind farm 6 are collected to the offshore converter valve 5 by medium voltage ac cables, which are connected to the first diode valve 15, the second diode valve 16 and the full bridge modular multilevel converter 17 of the offshore converter valve 5 by transformers (including a first transformer 19, a second transformer 21 and a third transformer 23) and switches (including a seventh switch 18, an eighth switch 20 and a ninth switch 22), respectively.
Further, the ratio of the direct current rated voltage of the first diode valve 15 and the second diode valve 16 to the direct current side rated voltage of the full-bridge modular multilevel converter 17 is 3:1.
in the alternative implementation mode, the offshore converter valve adopts a structure that the direct current side of the first diode valve, the direct current side of the second diode valve and the direct current side of the full-bridge modularized multi-level converter are connected in series, the offshore converter valve adopts a common half-bridge MMC form, and is matched with an onshore cross switch and the offshore wind power collection side to store energy, so that the volume and the cost of the offshore converter valve are reduced, the stable operation of a low-cost high-reliability offshore wind power direct current delivery system is realized, the alternating current voltage on the collection side of an offshore wind turbine is continuously stable, and the offshore wind turbine is ensured to stably operate in a network following mode.
As an alternative embodiment of the present invention, further comprising: an energy storage device 24;
the energy storage device 24 is connected to the offshore wind farm 6 via a tenth switch 25 and a step-up transformer 26.
The embodiment of the invention also discloses a control method of the offshore wind power direct current transmission system based on the onshore crossbar, which is applied to the offshore wind power direct current transmission system based on the onshore crossbar, as shown in fig. 2, and comprises the following steps:
s201, acquiring a starting instruction, and based on the starting instruction, establishing negative voltage by using an on-shore converter valve and an on-shore cross switch, wherein the negative voltage supplies power to the offshore wind farm through the offshore converter valve so as to complete black starting of the offshore wind farm.
S202, disconnecting the onshore cross switch by limiting the fan output of the offshore wind farm so as to disconnect the onshore converter valve from the offshore converter valve.
And S203, lifting the direct current side voltage of the on-shore converter valve, and controlling the on-shore cross switch to be closed until the direct current side voltage of the on-shore converter valve is higher than the rated direct current voltage, and establishing connection between the on-shore converter valve and the on-shore converter valve so as to finish starting of the offshore wind power direct current delivery system.
According to the control method of the offshore wind power direct current delivery system based on the onshore crossbar, the onshore crossbar is used for conducting positive-negative electrode conversion, the onshore converter valve does not need to output negative pressure, a full-bridge submodule is not needed, cost of the onshore converter valve is saved, the onshore converter valve and the offshore wind power plant are matched with interaction, and starting and stable operation of the offshore wind power direct current delivery system are achieved with low cost and high reliability.
As an alternative embodiment of the present invention, as shown in fig. 3, the step S201 of establishing a negative voltage by using an onshore converter valve and an onshore crossbar based on the start command, where the negative voltage supplies power to the offshore wind farm via the offshore converter valve to complete black start of the offshore wind farm includes:
and S2011, sending a first opening instruction to a first switch, a second switch and a fifth switch based on the starting instruction, and sending a first closing instruction to a third switch, a fourth switch and a sixth switch Guan Fasong, wherein the first opening instruction is used for controlling the first switch, the second switch and the fifth switch to be opened, and the first closing instruction is used for controlling the third switch, the fourth switch and the sixth switch to be closed, wherein after the third switch, the fourth switch and the sixth switch are closed, the first working voltage output by the power grid is charged to an onshore converter valve through a transformer low-voltage winding.
S2012, acquiring direct current side voltage of the on-shore converter valve, and sending an unlocking command to the on-shore converter valve when the direct current side voltage of the on-shore converter valve accords with a preset voltage, wherein after the on-shore converter valve is unlocked based on the unlocking command, the direct current side voltage of the on-shore converter valve establishes the negative voltage through an on-shore cross switch, and the off-shore converter valve is charged by using the negative voltage.
Specifically, the power grid charges a direct-current side capacitor of the on-shore converter valve through soft start, and when the voltage of the direct-current side capacitor of the on-shore converter valve reaches 80% of rated voltage, the on-shore converter valve is unlocked.
Further, after the on-shore converter valve is unlocked, the half-bridge modularized multi-level converter in the on-shore converter valve adopts a voltage drop operation mode, the direct current side voltage of the half-bridge module of each bridge arm of the half-bridge modularized multi-level converter adopts a voltage drop operation mode, the direct current side voltage of the on-shore converter valve establishes negative voltage through the on-shore cross switch, the on-shore converter valve is charged by utilizing the negative voltage, and then stable negative voltage is established on the direct current side of the full-bridge modularized multi-level converter in the on-shore converter valve, and the direct current side of the full-bridge modularized multi-level converter of the on-shore converter valve is charged at the same time, and at the moment, the direct current sides of the first diode valve and the second diode valve of the on-shore converter valve are in a short circuit state.
S2013, acquiring direct-current side voltage of the offshore converter valve, and sending a second closing instruction to a ninth switch when the direct-current side voltage of the offshore converter valve accords with a preset voltage, wherein the second closing instruction is used for controlling the closing of the ninth switch, and after the closing of the ninth switch, the offshore converter valve establishes the voltage of the offshore wind farm in a zero-starting mode so as to finish black start of the offshore wind farm.
Specifically, a full-bridge modularized multi-level converter in the offshore converter valve adopts a V/F voltage source operation mode (a mode of ensuring that output voltage is in direct proportion to frequency) and completes starting and unlocking, alternating-current voltage is established for the offshore wind farm, and in order to prevent the transformer on the alternating-current side of the offshore converter valve from starting impact current, the full-bridge modularized multi-level converter of the offshore converter valve adopts a zero-starting mode to establish the voltage of the offshore wind farm.
As an alternative embodiment of the present invention, as shown in fig. 4, the step S202 of opening the onshore crossbar by limiting the fan output of the offshore wind farm to disconnect the onshore converter valve from the offshore converter valve includes:
s2021, acquiring alternating current collection voltage of the offshore wind farm, and sending a first control instruction to the offshore wind farm based on the alternating current collection voltage of the offshore wind farm, wherein the first control instruction is used for limiting fan output of an offshore fan.
Specifically, the offshore wind turbine is started in sequence and operated in a grid following mode, meanwhile, based on a first control instruction, the wind turbine output is close to zero in a mode of adjusting equal power limitation through a blade paddle of the wind turbine, the current flowing through the third switch and the fourth switch is ensured to flow from an onshore converter valve to an offshore converter valve, the wind turbine output is gradually lifted subsequently, zero can be generated on the current flowing through the third switch and the fourth switch, and normal disconnection of the third switch and the fourth switch is ensured.
And S2022, acquiring the current of a third switch and the current of a fourth switch, and when the current of the third switch and the current of the fourth switch pass through zero points, giving a second disconnection instruction to the third switch and the fourth switch Guan Fasong, wherein the second disconnection instruction is used for controlling the third switch and the fourth switch to be disconnected so as to disconnect the onshore converter valve and the offshore converter valve.
Specifically, the fan output limit of the offshore wind farm is gradually raised until the current flowing through the third and fourth switches drops to 0, at which time the third and fourth switches are opened and the connection between the land and sea converter valves is broken.
As an alternative embodiment of the present invention, as shown in fig. 5, S203, that is, lifting the dc side voltage of the on-shore converter valve until the dc side voltage of the on-shore converter valve is higher than the rated dc voltage, controls the on-shore cross switch to be closed, and establishes a connection between the on-shore converter valve and the on-shore converter valve to complete the startup of the on-shore wind power dc delivery system, includes:
s2031, after the disconnection state of the third switch and the fourth switch is obtained, sending a second control instruction to the full-bridge modular multilevel converter, where the second control instruction is used to control the direct-current side voltage of the full-bridge modular multilevel converter to be converted into a forward rated voltage.
Specifically, the direct-current side voltage control function of the full-bridge modularized multi-level converter is utilized to raise the direct-current side total voltage of the full-bridge modularized multi-level converter, the negative voltage is adjusted to the positive rated voltage, and at the moment, the alternating-current voltage of the offshore wind farm is provided by the full-bridge modularized multi-level converter.
And S2032, when the direct-current side voltage of the full-bridge modularized multi-level converter is the positive rated voltage, sending a second closing instruction to the fifth switch by a third opening instruction to the sixth opening Guan Fasong, wherein when the fifth switch is closed based on the second closing instruction, the second working voltage output by the power grid charges the onshore converter valve through the high-voltage winding of the transformer.
And S2033, when the direct-current side voltage of the shore-based converter valve is higher than the rated direct-current voltage, a third closing instruction is given to the first switch, the second switch, the seventh switch and the eighth switch Guan Fasong, wherein after the first switch, the second switch, the seventh switch and the eighth switch are closed, the offshore wind farm operates in a maximum power point tracking mode (namely an MPPT mode), the first diode valve, the second diode valve and the full-bridge modularized multi-level converter are put into offshore wind power transmission (namely the offshore converter valve operates in a full-power transmission operation mode), and an offshore wind power direct-current delivery system is started.
Specifically, the direct-current side voltage of the shore converter valve is higher than the rated direct-current voltage, so that the first diode valve and the second diode valve are prevented from being conducted after the marine converter valve is started.
In the alternative implementation mode, the offshore converter valve adopts a structure that the direct current side of the first diode valve, the direct current side of the second diode valve and the direct current side of the full-bridge modularized multi-level converter are connected in series, the offshore converter valve adopts a common half-bridge MMC form, and is matched with an onshore cross switch and the offshore wind power collection side to store energy, so that the volume and the cost of the offshore converter valve are reduced, the stable operation of a low-cost high-reliability offshore wind power direct current delivery system is realized, the alternating current voltage on the collection side of an offshore wind turbine is continuously stable, and the offshore wind turbine is ensured to stably operate in a network following mode.
As an alternative embodiment of the present invention, further comprising:
s204, obtaining the total voltage of the direct current sides of the full-bridge sub-modules, controlling the energy storage device to charge when the total voltage of the direct current sides of the full-bridge sub-modules is increased, and controlling the energy storage device to discharge when the total voltage of the direct current sides of the full-bridge sub-modules is reduced.
Specifically, after the collected alternating voltage of the offshore wind power plant is established, a tenth switch is closed, the energy storage device is put into operation, the energy storage device is operated in a current source mode, and the full-bridge modularized multi-level converter in the offshore converter valve charges the energy storage device until the SOC of the energy storage device reaches about 80%.
Further, when the fan output of the offshore wind farm is close to zero, the energy storage control target is changed to keep the direct-current side voltage of the full-bridge submodule unchanged, if the direct-current side voltage of the full-bridge submodule is increased, the energy storage is charged, and if the direct-current side voltage of the full-bridge submodule is reduced, the energy storage is discharged.
As shown in fig. 1, a control method of the offshore wind power dc delivery system based on the onshore crossbar is described below by way of a specific embodiment.
Example 1:
k1 and K2 in the onshore crossbar are opened, and K3 and K4 are closed.
And closing a switch K6 connected with a low-voltage winding of the transformer in the three-winding transformer, and charging a capacitor on the direct current side of the offshore converter valve through a soft start circuit, wherein the full-bridge MMC direct current side of the offshore converter valve is charged at the same time, and the direct current side part of the diode valve of the offshore converter valve is in a short circuit state.
The on-shore converter valve is unlocked, stable negative voltage is established on the direct current side of the full-bridge MMC in the offshore converter valve, a voltage drop running mode is adopted in the control method of the half-bridge MMC in the on-shore converter valve in the step, and a voltage reduction running mode is adopted in the direct current side voltage of the half-bridge module of each bridge arm of the half-bridge MMC.
And closing a switch K9, then adopting a V/F voltage source operation mode by the full-bridge MMC in the offshore converter valve, completing starting and unlocking, and establishing alternating current voltage for the offshore wind farm, wherein in order to prevent the transformer on the alternating current side of the offshore converter valve from starting impact current, the full-bridge MMC of the offshore converter valve adopts a zero-starting mode to establish the voltage of the offshore wind farm.
After the collection alternating voltage of the offshore wind farm is established, the switch K10 is closed, the energy storage device is put into operation, the energy storage device is operated in a current source mode, and the energy storage device is charged until the SOC (state of charge), namely the residual electric quantity, of the energy storage device reaches about 80%.
The offshore wind turbine is started in sequence and operated in a grid following mode, meanwhile, the output of the wind turbine is close to zero in a mode of adjusting equal power limitation through blades and paddles of the wind turbine, after that, the energy storage control target is changed to keep the direct-current side voltage of the full-bridge submodule in the full-bridge MMC unchanged, if the direct-current side voltage of the full-bridge submodule is increased, the energy storage device is charged, and if the direct-current side voltage of the full-bridge MMC converter valve submodule is reduced, the energy storage device is discharged.
Gradually lifting the output limit of the fan until the current flowing through the switches K3 and K4 is reduced to 0, and at the moment, disconnecting the switches K3 and K4; then lifting the total voltage of the direct current side of the full-bridge MMC, adjusting the total voltage from negative rated voltage to positive rated voltage, and at the moment, the alternating current voltage of the offshore wind farm is still provided by the full-bridge MMC, and the energy storage device is responsible for maintaining the power balance of the offshore wind farm.
And closing a switch K5, starting a high-voltage winding of the onshore coupling transformer, starting and unlocking an onshore converter valve, and establishing a direct-current side rated voltage value, wherein the direct-current side rated voltage value needs to ensure that the offshore diode valve is not conducted after being started.
And closing K1 and K2, then sequentially closing K7 and K8, sequentially operating the offshore wind turbine in an MPPT mode, and converting a control target of the energy storage device into controlling the SOC of the energy storage device to reach about 80% when the switches K1 and K2 flow current, wherein the offshore full-bridge MMC works in a normal operation mode, and completing a starting control process by the whole offshore wind power direct current delivery system.
In addition, an electronic device is provided in an embodiment of the present invention, as shown in fig. 6, where the electronic device may include a processor 110 and a memory 120, where the processor 110 and the memory 120 may be connected by a bus or other manner, and in fig. 6, the connection is exemplified by a bus. In addition, the electronic device further includes at least one interface 130, where the at least one interface 130 may be a communication interface or other interfaces, and the embodiment is not limited thereto.
The processor 110 may be a central processing unit (Central Processing Unit, CPU). The processor 110 may also be other general purpose processors, digital signal processors (Digital Signal Processor, DSPs), application specific integrated circuits (Application Specific Integrated Circuit, ASICs), field programmable gate arrays (Field-Programmable Gate Array, FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or a combination of the above.
The memory 120 is used as a non-transitory computer readable storage medium for storing non-transitory software programs, non-transitory computer executable programs, and modules, such as program instructions/modules corresponding to the video compositing method according to the embodiments of the present invention. The processor 110 executes various functional applications and data processing of the processor by running non-transitory software programs, instructions and modules stored in the memory 120, i.e. implementing the control method of the offshore wind turbine dc output system based on an onshore crossbar in the above-described method embodiment.
In addition, at least one interface 130 is used for communication of the electronic device with external devices, such as with a server or the like. Optionally, at least one interface 130 may also be used to connect peripheral input, output devices, such as a keyboard, display screen, etc.
The one or more modules are stored in the memory 120, which when executed by the processor 110, performs the method of controlling an offshore wind turbine dc output system based on an onshore crossbar in the embodiment shown in fig. 2.
The details of the electronic device may be understood correspondingly with respect to the corresponding relevant descriptions and effects in the embodiment shown in fig. 2, which are not repeated herein.
It will be appreciated by those skilled in the art that implementing all or part of the above-described embodiment method may be implemented by a computer program to instruct related hardware, where the program may be stored in a computer readable storage medium, and the program may include the above-described embodiment method when executed. The storage medium may be a magnetic Disk, an optical disc, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), a Flash Memory (Flash Memory), a Hard Disk (HDD), a Solid State Drive (SSD), or the like; the storage medium may also comprise a combination of memories of the kind described above.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (10)
1. Offshore wind power direct current delivery system based on onshore crossbar switch, characterized by comprising: the system comprises a power grid, an onshore converter valve, an onshore cross switch, a submarine cable, an offshore converter valve and an offshore wind farm; wherein,,
the shore cross switch comprises a first switch, a second switch, a third switch and a fourth switch, wherein the first switch and the second switch are connected with the sea cable after being cross-connected with the third switch and the fourth switch, and the first switch and the second switch are interlocked with the switch states of the third switch and the fourth switch so as to realize the positive-negative conversion of the direct-current side voltage;
the power grid is connected with the onshore converter valve through a transformer low-voltage winding and a fifth switch in the three-winding transformer, and is connected with the onshore converter valve through a transformer high-voltage winding and a sixth switch in the three-winding transformer; the on-shore converter valve adopts a half-bridge modularized multi-level converter, and the direct current side of the on-shore converter valve is connected with the direct current side of the on-shore converter valve through the on-shore cross switch and the submarine cable; the alternating current side of the offshore converter valve is connected with the offshore wind farm.
2. Offshore wind power direct current delivery system based on an onshore crossbar according to claim 1, characterized in that the offshore converter valve comprises: a first diode valve, a second diode valve and a full-bridge modular multilevel converter, wherein,
the alternating current sides of the first diode valve and the second diode valve are respectively connected with the alternating current side of the full-bridge modularized multi-level converter in parallel, the direct current side of the first diode valve, the direct current side of the second diode valve and the direct current side of the full-bridge modularized multi-level converter are connected in series, the first diode valve is connected with an offshore wind farm through a seventh switch and a first transformer, the second diode valve is connected with the offshore wind farm through an eighth switch and a second transformer, and the full-bridge modularized multi-level converter is connected with the offshore wind farm through a ninth switch and a third transformer.
3. Offshore wind power direct current delivery system based on an onshore crossbar according to claim 2, characterized in that the full-bridge modular multilevel converter is composed of a cascade of a plurality of full-bridge sub-modules.
4. Offshore wind power direct current delivery system based on an onshore crossbar according to claim 1, further comprising: an energy storage device;
the energy storage device is connected with the offshore wind farm through a tenth switch and a step-up transformer.
5. Offshore wind power direct current delivery system based on an onshore crossbar according to claim 1, characterized in that the first switch, the second switch, the third switch and the fourth switch are high voltage direct current breakers.
6. Method for controlling an offshore wind power dc delivery system based on an onshore crossbar, applied to an offshore wind power dc delivery system based on an onshore crossbar according to any of claims 1 to 5, the method comprising:
acquiring a starting instruction, and based on the starting instruction, establishing negative voltage by using an on-shore converter valve and an on-shore cross switch, wherein the negative voltage supplies power to an offshore wind farm through the offshore converter valve so as to finish black starting of the offshore wind farm;
disconnecting the onshore cross switch by limiting fan output of the offshore wind farm to disconnect the connection between the onshore converter valve and the offshore converter valve;
and lifting the direct current side voltage of the on-shore converter valve, and controlling the on-shore cross switch to be closed until the direct current side voltage of the on-shore converter valve is higher than the rated direct current voltage, wherein connection is established between the on-shore converter valve and the on-shore converter valve so as to finish starting of the on-shore wind power direct current delivery system.
7. The method for controlling an offshore wind farm direct current delivery system based on an onshore crossbar according to claim 6, wherein the establishing a negative voltage using an onshore converter valve and an onshore crossbar based on the start command, the negative voltage supplying power to an offshore wind farm via the onshore converter valve to complete a black start of the offshore wind farm, comprises:
a first opening instruction is sent to a first switch, a second switch and a fifth switch based on the starting instruction, a first closing instruction is sent to a third switch, a fourth switch and a sixth switch Guan Fasong, the first opening instruction is used for controlling the first switch, the second switch and the fifth switch to be opened, the first closing instruction is used for controlling the third switch, the fourth switch and the sixth switch to be closed, and after the third switch, the fourth switch and the sixth switch are closed, a first working voltage output by a power grid is charged to an onshore converter valve through a transformer low-voltage winding;
acquiring direct-current side voltage of an on-shore converter valve, and sending an unlocking instruction to the on-shore converter valve when the direct-current side voltage of the on-shore converter valve accords with a preset voltage, wherein after the on-shore converter valve is unlocked based on the unlocking instruction, the direct-current side voltage of the on-shore converter valve establishes the negative voltage through an on-shore cross switch, and the negative voltage is used for charging the offshore converter valve;
and when the direct-current side voltage of the offshore converter valve accords with the preset voltage, sending a second closing instruction to a ninth switch, wherein the second closing instruction is used for controlling the closing of the ninth switch, and after the ninth switch is closed, the offshore converter valve establishes the voltage of the offshore wind farm in a zero-starting mode so as to finish black start of the offshore wind farm.
8. The method of controlling an offshore wind power direct current delivery system based on an onshore crossbar of claim 7, wherein the opening of the onshore crossbar by limiting a fan output of the offshore wind farm to disconnect the onshore converter valve from the offshore converter valve comprises:
acquiring alternating current collection voltage of an offshore wind farm, and sending a first control instruction to the offshore wind farm based on the alternating current collection voltage of the offshore wind farm, wherein the first control instruction is used for limiting fan output of an offshore fan;
and acquiring the current of a third switch and the current of a fourth switch, and when the current of the third switch and the current of the fourth switch pass through zero points, giving a second disconnection instruction to the third switch and the fourth switch Guan Fasong, wherein the second disconnection instruction is used for controlling the disconnection of the third switch and the fourth switch so as to disconnect the connection between the onshore converter valve and the offshore converter valve.
9. The method for controlling an offshore wind power direct current delivery system based on an onshore crossbar according to claim 8, wherein the step of raising the onshore converter valve direct current side voltage until the onshore converter valve direct current side voltage is higher than a rated direct current voltage, controlling the onshore crossbar to be closed, and establishing a connection between the onshore converter valve and the onshore converter valve to complete startup of the offshore wind power direct current delivery system comprises:
after the disconnection states of the third switch and the fourth switch are obtained, a second control instruction is sent to the full-bridge modularized multi-level converter, and the second control instruction is used for controlling the direct-current side voltage of the full-bridge modularized multi-level converter to be converted into a forward rated voltage;
when the direct-current side voltage of the full-bridge modularized multi-level converter is the forward rated voltage, a third opening instruction is sent to the sixth opening Guan Fasong, and a second closing instruction is sent to the fifth switch, wherein when the fifth switch is closed based on the second closing instruction, a second working voltage output by a power grid charges the onshore converter valve through a transformer high-voltage winding;
and when the direct-current side voltage of the shore-based converter valve is higher than the rated direct-current voltage, a third closing instruction is given to the first switch, the second switch, the seventh switch and the eighth switch Guan Fasong, wherein after the first switch, the second switch, the seventh switch and the eighth switch are closed, the offshore wind farm operates in a maximum power point tracking mode, and the first diode valve, the second diode valve and the full-bridge modularized multi-level converter are put into offshore wind power transmission, and an offshore wind power direct-current delivery system is started.
10. The method for controlling an offshore wind power direct current delivery system based on an onshore crossbar of claim 6, further comprising:
and the direct current side total voltage of the full-bridge sub-modules is obtained, the energy storage device is controlled to charge when the direct current side total voltage of the full-bridge sub-modules is increased, and the energy storage device is controlled to discharge when the direct current side total voltage of the full-bridge sub-modules is reduced.
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