CN115001011A - Offshore distributed direct-current transmission system topological structure and direct-current protection control method - Google Patents

Offshore distributed direct-current transmission system topological structure and direct-current protection control method Download PDF

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Publication number
CN115001011A
CN115001011A CN202210584257.0A CN202210584257A CN115001011A CN 115001011 A CN115001011 A CN 115001011A CN 202210584257 A CN202210584257 A CN 202210584257A CN 115001011 A CN115001011 A CN 115001011A
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China
Prior art keywords
current
offshore
direct current
boosting
output end
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Pending
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CN202210584257.0A
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Chinese (zh)
Inventor
卢章辉
彭国平
周治国
张�浩
史奔
王红占
李立冬
宋海军
刘会民
徐元龙
白代兵
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Guangdong Mingyang Longyuan Power Electronics Co Ltd
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Guangdong Mingyang Longyuan Power Electronics Co Ltd
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Priority to CN202210584257.0A priority Critical patent/CN115001011A/en
Publication of CN115001011A publication Critical patent/CN115001011A/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • 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
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H02J13/00002—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by monitoring
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
    • H02J13/00016—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using a wired telecommunication network or a data transmission bus
    • H02J13/00017—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using a wired telecommunication network or a data transmission bus using optical fiber
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H02J13/00032—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for
    • H02J13/00036—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers
    • H02J13/0004—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers involved in a protection system
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • 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
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The marine distributed direct-current transmission system topological structure comprises the following components: a plurality of offshore fan sets; the device comprises a plurality of boosting and current converting platforms which correspond to a plurality of offshore fan sets one by one, wherein each boosting and current converting platform is provided with a boosting and current converting module, each boosting and current converting module is used for boosting alternating current input by the offshore fan sets and converting the alternating current into direct current, and the plurality of boosting and current converting modules are sequentially connected in series to form a series structure; the shore current conversion module is used for converting the direct current into alternating current and transmitting the alternating current to an external alternating current power grid through an alternating current output end; the direct current protection module is used for collecting the voltage value and the current value of the offshore direct current cable, generating a locking signal according to the voltage value and the current value and sending the locking signal to the control unit of each offshore wind driven generator, so that each control unit controls the corresponding offshore wind driven generator to stop outputting after receiving the locking signal, and the problems of large size and high cost of the existing offshore converter station are solved.

Description

Offshore distributed direct-current transmission system topological structure and direct-current protection control method
Technical Field
The invention belongs to the field of offshore power transmission, and particularly relates to a topological structure of an offshore distributed direct-current power transmission system and a direct-current protection control method.
Background
The existing large-scale and long-distance offshore wind power transmission basically adopts a flexible direct current power transmission mode. All fans of the offshore wind power plant are divided into N offshore fan groups, and each offshore fan group is connected with a medium-voltage alternating current cable bus in parallel and then connected with an offshore booster station. Each offshore booster station is provided with a booster transformer for converting medium-voltage alternating current into high-voltage alternating current and then outputting the high-voltage alternating current, and the high-voltage alternating current output ends of the N offshore booster stations are connected in parallel and then connected to the offshore converter station. The offshore converter station converts high-voltage alternating current into high-voltage direct current and then transmits the high-voltage direct current to the onshore converter station through the offshore direct current cable, and the onshore converter station converts the direct current transmitted by the offshore converter station into alternating current and transmits the alternating current to an external alternating current power grid. The offshore converter station consists of six groups of MMC converter valves, bridge arm reactors and positive and negative direct-current circuit breakers. When the offshore direct-current cable has a short-circuit fault, the direct-current circuit breaker is disconnected to ensure that the system can remove the fault.
The MMC converter valve adopts a half-bridge structure and/or a full-bridge structure, so that the system structure is complex and large in size; the direct current circuit breaker is also composed of a full-control power electronic switch device, and has a complex structure and large floor area; the offshore converter station comprises high-voltage equipment such as an MMC converter valve, a direct-current breaker and the like, and the requirement on high-voltage insulation strength is also met, so that the offshore converter station is large in size and high in cost. Therefore, the existing flexible direct current transmission system structure cannot be completely suitable for large-scale and long-distance offshore wind power grid connection.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a topological structure of an offshore distributed direct current transmission system, which solves the problems of large size and high cost of the existing offshore converter station.
The invention also provides a direct current protection control method.
According to the embodiment of the first aspect of the invention, the offshore decentralized direct current transmission system topology structure comprises:
the system comprises a plurality of offshore wind turbine sets, a plurality of offshore wind turbine generators and a plurality of offshore wind turbine generators, wherein each offshore wind turbine set comprises a plurality of offshore wind turbine generators;
the offshore wind turbine generator set comprises a plurality of offshore wind turbine generator sets, a plurality of boosting and current converting platforms and a plurality of voltage boosting and current converting platforms, wherein the plurality of boosting and current converting platforms are in one-to-one correspondence with the plurality of offshore wind turbine generator sets, each boosting and current converting platform is provided with a boosting and current converting module, each boosting and current converting module is used for boosting alternating current input by the offshore wind turbine generator sets and converting the alternating current input by the offshore wind turbine generator sets into direct current, the plurality of boosting and current converting modules are sequentially connected in series to form a series structure, and the series structure is provided with a positive output end and a negative output end;
the shore-based current conversion module is provided with a direct current positive input end, a direct current negative input end and an alternating current output end, wherein the direct current positive input end is used for being connected with the positive output end through an offshore direct current cable, the direct current negative input end is used for being connected with the negative output end through the offshore direct current cable, and the shore-based current conversion module is used for converting direct current into alternating current and transmitting the alternating current to an external alternating current power grid through the alternating current output end;
the direct current protection module is arranged on the boosting and current converting platform connected to the offshore direct current cable and used for acquiring the voltage value and the current value of the offshore direct current cable, generating a locking signal according to the voltage value and the current value and sending the locking signal to the control unit of each offshore wind driven generator, so that each control unit controls the corresponding offshore wind driven generator to stop outputting after receiving the locking signal.
The offshore distributed direct-current transmission system topological structure provided by the embodiment of the invention at least has the following technical effects: the alternating current input by the offshore fan sets can be boosted and converted into direct current through the boosting converter modules, and the direct current is transmitted to the onshore converter module through the offshore direct current cable, and the boosting converter module integrates the functions of the existing offshore booster station and the existing offshore converter station, so that the existing offshore converter station is omitted, and the equipment volume is reduced. The voltage value and the current value of the offshore direct-current cable can be collected through the direct-current protection module, a locking signal is generated and sent to the control unit of each offshore wind driven generator, and each control unit can control the corresponding offshore wind driven generator to stop outputting after receiving the locking signal, so that direct-current fault current isolation is guaranteed, a direct-current breaker is omitted, the size of equipment is reduced, and the power transmission efficiency is improved. The direct current can be converted into alternating current through the onshore converter module and transmitted to an external alternating current power grid. The offshore distributed direct current transmission system topological structure solves the problems of large size and high cost of the existing offshore converter station.
According to some embodiments of the invention, the dc protection module comprises:
the sensor group is used for acquiring the voltage value and the current value of the offshore direct current cable;
the first comparator is used for comparing a voltage preset value with the voltage value;
the second comparator is used for comparing a current preset value with the magnitude of the current value;
the logic judgment assembly is provided with a first comparison input end, a second comparison input end and a locking signal output end, the first comparison input end is connected with the first comparator, the second comparison input end is connected with the second comparator, and the logic judgment assembly is used for generating the locking signal and sending the locking signal to each control unit of the offshore wind turbine.
According to some embodiments of the invention, each offshore wind turbine is further provided with a signal receiving module connected with the control unit, the direct current protection module further comprises a signal sending module connected with the blocking signal output end, and the blocking signal is subjected to electro-optical conversion by the signal sending module, then sent to the signal receiving module of each offshore wind turbine through an optical cable, subjected to photoelectric conversion, and then sent to the control unit.
According to some embodiments of the invention, each of the boost converter modules comprises:
the booster transformer is provided with a boosting input end, a first boosting output end and a second boosting output end, the boosting input end is used for being connected with the offshore fan set through an alternating current cable bus, and the booster transformer is used for boosting alternating current input by the offshore fan set;
the diode converter valve is provided with a first converter input end connected with the first boosting output end, a second converter input end connected with the second boosting output end, a first converter output end and a second converter output end, and is used for converting the boosted alternating current into direct current and outputting the direct current through the first converter output end and the second converter output end;
and the bypass switch is connected between the first commutation output end and the second commutation output end in parallel.
According to some embodiments of the invention, the onshore converter module comprises:
the MMC converter valve is provided with a first input end, a second input end and a first output end, wherein the first input end is used for being connected with the positive output end through the offshore direct current cable, and the second input end is used for being connected with the negative output end through the offshore direct current cable;
and the onshore transformer is provided with a transformation input end connected with the first output end and a transformation output end used for connecting the external alternating current power grid.
According to some embodiments of the invention, the onshore inversion module further comprises a dc energy consumer connected in parallel between the first input and the second input, the dc energy consumer being configured to consume excess energy of the dc power.
According to some embodiments of the invention, the onshore converter module further comprises:
a first onshore direct current breaker connected in series between one end of the direct current energy consumption device and the first input end;
the second onshore direct current breaker is connected in series between the other end of the direct current energy consumption device and the second input end;
and the shore alternating current circuit breaker is connected between the first output end and the transformation input end in series.
According to the embodiment of the second aspect of the invention, the direct current protection control method comprises the following steps:
acquiring a voltage value and a current value of the offshore direct current cable;
determining a locking signal according to the voltage value, the current value and the fault alarm parameter group, and sending the locking signal to a control unit of each offshore wind turbine; each control unit is used for stopping the output of the offshore wind turbine after receiving the locking signal; the fault alarm parameter group comprises a current preset value and a voltage preset value.
The direct current protection control method provided by the embodiment of the invention at least has the following technical effects: in the offshore direct-current transmission process, the voltage value and the current value of the offshore direct-current cable are obtained, the locking signal is determined according to the voltage value and the current value and the fault alarm parameter group, the locking signal is sent to the control unit of each offshore wind driven generator, and each control unit stops outputting of the offshore wind driven generator after receiving the locking signal, so that isolation of direct-current fault current can be guaranteed, and transmission efficiency is improved.
According to some embodiments of the invention, said determining a blocking signal from said voltage and current values and a set of fault warning parameters comprises the steps of:
and if the current value is greater than the current preset value and the voltage value is less than the voltage preset value, generating the locking signal.
According to some embodiments of the invention, each offshore wind turbine is provided with a signal receiving module connected with the control unit, and the signal receiving module is used for converting an electric signal into an optical signal and sending the optical signal to the control unit;
the step of sending the blocking signal to a control unit of each offshore wind turbine comprises the following steps:
and carrying out electro-optical conversion on the blocking signal and then sending the blocking signal to the signal receiving module of each offshore wind turbine through an optical cable.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic structural diagram of a conventional offshore direct current transmission system;
FIG. 2 is a schematic structural diagram of a conventional offshore booster station;
FIG. 3 is a schematic structural diagram of a conventional offshore converter station;
fig. 4 is a schematic structural diagram of an offshore decentralized dc power transmission system topology according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a plurality of boost converter modules according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of an onshore converter module according to an embodiment of the invention;
fig. 7 is a schematic structural diagram of a dc protection module according to an embodiment of the present invention;
fig. 8 is a flowchart of a dc protection control method according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention and are not to be construed as limiting the present invention.
In the description of the present invention, it is to be understood that the directional descriptions, such as the directions of upper, lower, front, rear, left, right, etc., are referred to only for convenience of describing the present invention and for simplicity of description, and are not intended to indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.
In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present invention, unless otherwise specifically limited, terms such as set, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention by combining the specific contents of the technical solutions.
In order to better explain the specific structure and function of the topology structure of the offshore decentralized direct current transmission system according to the embodiment of the present invention, a brief explanation is first made on the conventional offshore direct current transmission system. Fig. 1 is a schematic structural diagram of a conventional offshore direct current transmission system, each offshore fan set is connected in parallel to a medium voltage alternating current cable bus, and then connected to an offshore booster station (as shown in fig. 2), each offshore booster station is provided with a booster transformer for converting medium voltage alternating current into high voltage alternating current and outputting the high voltage alternating current, high voltage alternating current output ends of N offshore booster stations are connected in parallel and then connected to an offshore converter station, the offshore converter station converts high voltage alternating current into high voltage direct current and then transmits the high voltage direct current to an onshore converter station through an offshore direct current cable, and the onshore converter station converts direct current transmitted by the offshore converter station into alternating current and transmits the alternating current to an external alternating current power grid. The offshore converter station comprises six groups of MMC converter valves, a bridge arm reactor and positive and negative direct-current circuit breakers, and when the offshore direct-current cable has a short-circuit fault, the direct-current circuit breakers are disconnected to ensure that the system can remove the fault (as shown in figure 3).
The MMC converter valve adopts a half-bridge structure and/or a full-bridge structure, the system structure is complex, and the equipment volume is large. The direct current circuit breaker is composed of a full-control power electronic switch device, and is complex in structure and large in occupied area. The MMC converter valve and the direct current breaker in the offshore converter station are high-voltage equipment, and the requirement for high-voltage insulation strength is also required to be met, so that the offshore converter station is large in size and high in cost, and therefore the existing flexible direct current transmission system structure cannot be completely suitable for large-scale and long-distance offshore wind power grid connection.
An offshore decentralized direct current transmission system topology according to an embodiment of the first aspect of the invention is described below with reference to fig. 1 to 8.
The offshore distributed direct-current transmission system topological structure comprises a plurality of offshore fan sets, a plurality of boosting current conversion platforms, an onshore current conversion module and a direct-current protection module. The system comprises a plurality of offshore wind turbine sets, a plurality of offshore wind turbine generators and a plurality of offshore wind turbine generators, wherein each offshore wind turbine set comprises a plurality of offshore wind turbine generators; the device comprises a plurality of boosting and current converting platforms which correspond to a plurality of offshore fan sets one by one, wherein each boosting and current converting platform is provided with a boosting and current converting module, each boosting and current converting module is used for boosting alternating current input by the offshore fan sets and converting the alternating current into direct current, the boosting and current converting modules are sequentially connected in series to form a series structure, and the series structure is provided with a positive output end and a negative output end; the shore-based converter module is provided with a direct current positive input end, a direct current negative input end and an alternating current output end, wherein the direct current positive input end is used for being connected with the positive output end through an offshore direct current cable, the direct current negative input end is used for being connected with the negative output end through an offshore direct current cable, and the shore-based converter module is used for converting direct current into alternating current and transmitting the alternating current to an external alternating current power grid through the alternating current output end; the direct current protection module is arranged on a boosting and current converting platform connected to the offshore direct current cable and used for acquiring the voltage value and the current value of the offshore direct current cable, generating a locking signal according to the voltage value and the current value and sending the locking signal to the control unit of each offshore wind driven generator, so that each control unit controls the corresponding offshore wind driven generator to stop outputting after receiving the locking signal.
As shown in fig. 4, the boost converter module boosts and converts alternating current input by the offshore fan set into direct current, the direct current is input to the onshore converter module through the offshore direct current cable, the onshore converter module converts the direct current into alternating current and transmits the alternating current to an external alternating current power grid, so that an offshore direct current transmission process of the offshore wind farm is realized, the existing offshore booster station and the offshore converter station are integrated by the boost converter module, the existing offshore converter station is omitted, and the overall equipment volume is reduced.
The direct current protection module is arranged on a boosting and current converting platform corresponding to the boosting and current converting module connected with the offshore direct current cable and used for acquiring the voltage value and the current value of the offshore direct current cable in real time and generating a locking signal according to the voltage value and the current value, the locking signal represents that the offshore direct current cable has a fault and needs to cut off the power supply of an offshore wind power plant, the locking signal is sent to the control unit of each offshore wind driven generator, each control unit controls the corresponding offshore wind driven generator to stop outputting after receiving the locking signal, a direct current breaker in a traditional offshore current converting station is cancelled, the isolation of direct current fault current is ensured, the size of equipment is reduced, and the power transmission efficiency is improved.
According to the topological structure of the offshore distributed direct current transmission system, the alternating current input by the offshore fan sets can be boosted and converted into the direct current through the plurality of boosting current conversion modules, and the direct current is transmitted to the onshore current conversion module through the offshore direct current cable, the functions of the existing offshore boosting station and the existing offshore current conversion station are integrated through the boosting current conversion module, the existing offshore current conversion station is omitted, and the equipment size is reduced. The voltage value and the current value of the offshore direct-current cable can be collected through the direct-current protection module, a locking signal is generated and sent to the control unit of each offshore wind driven generator, and each control unit can control the corresponding offshore wind driven generator to stop outputting after receiving the locking signal, so that direct-current fault current isolation is guaranteed, a direct-current breaker is omitted, the size of equipment is reduced, and the power transmission efficiency is improved. The direct current can be converted into alternating current through the onshore converter module and transmitted to an external alternating current power grid. The offshore distributed direct current transmission system topological structure solves the problems of large size and high cost of the existing offshore converter station.
In some embodiments of the present invention, referring to fig. 7, the dc protection module includes a sensor group, a first comparator, a second comparator, and a logic determination component. The sensor group is used for acquiring a voltage value U _ DC and a current value I _ DC of the offshore direct current cable; the first comparator is used for comparing the voltage preset value U _ DC0 with the voltage value U _ DC; the second comparator is used for comparing the current preset value I _ DC0 with the current value I _ DC; and the logic judgment assembly is provided with a first comparison input end, a second comparison input end and a locking signal output end, the first comparison input end is connected with the first comparator, the second comparison input end is connected with the second comparator, and the logic judgment assembly is used for generating a locking signal and sending the locking signal to the control unit of each offshore wind turbine.
The sensor group comprises a first sensor and a second sensor, the first sensor acquires a voltage value U _ DC of the offshore direct-current cable, the second sensor acquires a current value I _ DC of the offshore direct-current cable, after the acquisition is finished, the voltage value U _ DC of the offshore direct-current cable is input to an input end A of a first comparator, an input end B of the first comparator is used for inputting a voltage preset value U _ DC0, and an output end of the first comparator is connected to a first comparison input end of the logic judgment component; and inputting the current value I _ DC of the offshore direct current cable to an input end A of a second comparator, wherein an input end B of the second comparator is used for inputting a current preset value I _ DC0, and the output end of the second comparator is connected to a second comparison input end of the logic judgment component. If the current value I _ DC is larger than the current preset value I _ DC0 and the voltage value U _ DC is smaller than the voltage preset value U _ DC0, the direct current short circuit phenomenon is indicated, the blocking signal output end of the logic judgment assembly outputs a high level, namely a blocking signal, and the blocking signal is sent to the control unit of each offshore wind turbine to control the offshore wind turbines to stop outputting. And after the fault disappears, the latching signal output end of the logic judgment assembly outputs a low level, and the offshore wind driven generator recovers to the initial state. When the direct current is in a normal state, the latching signal output end of the logic judgment component outputs a low level.
In some embodiments, if the value input by the input terminal a of the first comparator is greater than the value input by the input terminal B of the first comparator, the output terminal of the first comparator outputs a high level, the value input by the input terminal a of the second comparator is greater than the value input by the input terminal B of the second comparator, and the output terminal of the second comparator outputs a high level, the logic determination component uses an and gate device. It should be noted that the specific configurations of the first comparator, the second comparator and the logic determining component can be changed, and the above-mentioned case is only an example and should not be construed as a limitation to the present invention.
In some embodiments, the DC protection module further includes a first low pass filter and a second low pass filter, as shown in fig. 7, the first sensor collects the voltage value U _ DC of the offshore DC cable, and then performs low pass filtering processing on the voltage value U _ DC through the first low pass filter, and transmits the voltage value U _ DC to the input end a of the first comparator. And the second sensor acquires the current value I _ DC of the offshore direct current cable, performs low-pass filtering processing on the current value I _ DC through a second low-pass filter, and transmits the current value I _ DC to the input end A of the second comparator.
In some embodiments of the present invention, referring to fig. 4, each offshore wind turbine is further provided with a signal receiving module connected to the control unit, the dc protection module further includes a signal sending module connected to the blocking signal output end, and the blocking signal is subjected to electro-optical conversion by the signal sending module, sent to the signal receiving module of each offshore wind turbine through an optical cable, subjected to photoelectric conversion, and sent to the control unit.
The signal sending module receives the blocking signal, converts the blocking signal from an electric signal into an optical signal and transmits the optical signal to the signal receiving module through an optical cable, the signal receiving module converts the optical signal back into the electric signal and then transmits the electric signal to the control unit of the offshore wind driven generator, and the control unit controls the offshore wind driven generator to stop outputting. Because the blocking signal is transmitted through the cable, the blocking signal and alternating current input by the offshore fan unit can be influenced mutually, and signal interference is caused, so that the problem is avoided by adopting an optical signal transmission mode.
In some embodiments of the invention, referring to fig. 5, each boost converter module comprises a step-up transformer, a diode converter valve and a bypass switch. The booster transformer is provided with a boosting input end, a first boosting output end and a second boosting output end, the boosting input end is used for being connected with the offshore fan set through an alternating current cable bus, and the booster transformer is used for boosting alternating current input by the offshore fan set; the diode converter valve is provided with a first converter input end connected with the first boosting output end, a second converter input end connected with the second boosting output end, a first converter output end and a second converter output end, and is used for converting the boosted alternating current into direct current and outputting the direct current through the first converter output end and the second converter output end; and the bypass switch is connected between the first commutation output end and the second commutation output end in parallel.
The offshore fan set inputs alternating current to a boosting input end of a boosting transformer, and the boosting transformer boosts the alternating current and transmits the boosted alternating current to a diode converter valve to convert the alternating current into direct current. The diode converter valve adopts a converter series structure formed by connecting two groups of six-pulse bridge rectifier diodes in series, replaces an MMC converter valve and a bridge arm reactor adopted by the existing offshore converter station, reduces the cost and reduces the equipment volume. The bypass switch can stop the operation of the boost commutation module when the boost commutation module fails, so that each boost commutation module can be controlled independently. It should be noted that the number of secondary sides of the step-up transformer and the number of groups of six-pulse bridge rectifier diodes are not to be considered as limitations of the present invention, and the diode converter valve may have another rectifier structure and may not be considered as limitations of the present invention.
In some embodiments of the invention, referring to fig. 6, the onshore converter module comprises an MMC converter valve and an onshore transformer. The MMC converter valve is provided with a first input end, a second input end and a first output end, wherein the first input end is used for being connected with the positive output end through an offshore direct current cable, and the second input end is used for being connected with the negative output end through an offshore direct current cable; the shore transformer is provided with a transformation input end connected with the first output end and a transformation output end used for connecting an external alternating current power grid;
as shown in fig. 6, the MMC converter valve includes 6 bridge arms, which are divided into 3 MMC positive converter valves and 3 MMC negative converter valves, each bridge arm is connected with a bridge arm smoothing reactor and a power module, each power module adopts a half-bridge structure and/or a full-bridge structure for converting direct current to alternating current, and the alternating current is transmitted to an external power grid through an onshore transformer. It should be noted that the operation principle of the MMC converter valve and the on-shore transformer is the prior art known to those skilled in the art, and will not be described herein.
In some embodiments of the present invention, referring to fig. 6, the onshore inversion module further comprises a dc energy consumption device connected in parallel between the first input terminal and the second input terminal, the dc energy consumption device being configured to consume excess energy of the dc power. After the shore current conversion module receives direct current, the direct current firstly passes through the direct current energy consumption device and then is input into the MMC current conversion valve to convert the direct current into alternating current, redundant energy of the direct current is consumed, and the total direct current voltage is prevented from being overhigh.
In some embodiments of the invention, referring to fig. 6, the onshore commutation module further comprises a first onshore dc breaker, a second onshore dc breaker and an onshore ac breaker. The first shore direct current circuit breaker is connected between one end of the direct current energy consumption device and the first input end in series; the second shore direct current circuit breaker is connected between the other end of the direct current energy consumption device and the second input end in series; and the shore AC circuit breaker is connected between the first output end and the transformation input end in series. The arrangement of the first shore direct current breaker, the second shore direct current breaker and the shore alternating current breaker can control the breaking at multiple points so as to eliminate circuit faults.
A dc protection control method according to an embodiment of the second aspect of the present invention is described below with reference to fig. 7 and 8.
The direct current protection control method provided by the embodiment of the invention comprises the following steps of:
acquiring a voltage value and a current value of the offshore direct current cable;
determining a locking signal according to the voltage value, the current value and the fault alarm parameter group, and sending the locking signal to a control unit of each offshore wind turbine; each control unit is used for stopping the output of the offshore wind driven generator after receiving the locking signal; the fault alarm parameter group comprises a current preset value and a voltage preset value.
The method comprises the steps of collecting a voltage value and a current value of the offshore direct current cable, comparing the current value with a current preset value and the voltage value with a voltage preset value after collection is finished, if the current value is larger than the current preset value and the voltage value is smaller than the voltage preset value, indicating that a direct current short circuit phenomenon occurs, generating a locking signal, and sending the locking signal to a control unit of each offshore wind driven generator to control the offshore wind driven generators to stop outputting. And after the fault disappears, the offshore wind driven generator restores to the initial state. The direct-current protection control method provided by the embodiment of the invention can ensure that the direct-current fault current is isolated, and meanwhile, the power transmission efficiency is improved.
According to the direct current protection control method provided by the embodiment of the invention, in the process of offshore direct current transmission, the voltage value and the current value of the offshore direct current cable are obtained, the locking signal is determined according to the voltage value, the current value and the fault alarm parameter group, and is sent to the control unit of each offshore wind driven generator, and each control unit stops outputting the offshore wind driven generator after receiving the locking signal, so that the isolation of direct current fault current can be ensured, and the transmission efficiency is improved.
In some embodiments of the present invention, referring to FIG. 7, determining a lockout signal based on voltage and current values and a set of fault alarm parameters includes the steps of: and if the current value is greater than the current preset value and the voltage value is less than the voltage preset value, generating a locking signal. The method comprises the steps of collecting a voltage value and a current value of the offshore direct current cable, comparing the current value with a current preset value and the voltage value with a voltage preset value after collection is finished, if the current value is larger than the current preset value and the voltage value is smaller than the voltage preset value, indicating that a direct current short circuit phenomenon occurs, generating a locking signal, and sending the locking signal to a control unit of each offshore wind driven generator to control the offshore wind driven generators to stop outputting. After the fault disappears, the offshore wind driven generator recovers to the initial state, the direct current fault current can be guaranteed to be isolated, and meanwhile, the power transmission efficiency is improved.
In some embodiments of the present invention, each offshore wind turbine is provided with a signal receiving module connected to the control unit, and the signal receiving module is configured to convert an electrical signal into an optical signal and send the optical signal to the control unit; sending the blocking signal to the control unit of each offshore wind turbine, comprising the steps of: and the blocking signals are subjected to electro-optical conversion and then are sent to the signal receiving module of each offshore wind driven generator through the optical cable.
After the blocking signal is generated, the blocking signal is converted into an optical signal from an electric signal and then transmitted to the signal receiving module through the optical cable, the optical signal is converted back to the electric signal by the signal receiving module and then transmitted to the control unit of the offshore wind driven generator, and the control unit controls the offshore wind driven generator to stop outputting. Because the blocking signal is transmitted through the cable, the blocking signal and alternating current input by the offshore fan unit can be influenced mutually, and signal interference is caused, so that the problem is avoided by adopting an optical signal transmission mode.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to the embodiments, and those skilled in the art will understand that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims (10)

1. Offshore distributed direct current transmission system topological structure, its characterized in that includes:
the system comprises a plurality of offshore wind power generators, a plurality of offshore wind power generators and a plurality of offshore wind power generators, wherein each offshore wind power generator comprises a wind power generator unit and a wind power generator unit;
the offshore wind turbine generator set comprises a plurality of offshore wind turbine generator sets, a plurality of boosting and current converting platforms and a plurality of voltage boosting and current converting platforms, wherein the plurality of boosting and current converting platforms are in one-to-one correspondence with the plurality of offshore wind turbine generator sets, each boosting and current converting platform is provided with a boosting and current converting module, each boosting and current converting module is used for boosting alternating current input by the offshore wind turbine generator sets and converting the alternating current input by the offshore wind turbine generator sets into direct current, the plurality of boosting and current converting modules are sequentially connected in series to form a series structure, and the series structure is provided with a positive output end and a negative output end;
the shore-based current conversion module is provided with a direct current positive input end, a direct current negative input end and an alternating current output end, wherein the direct current positive input end is used for being connected with the positive output end through an offshore direct current cable, the direct current negative input end is used for being connected with the negative output end through the offshore direct current cable, and the shore-based current conversion module is used for converting direct current into alternating current and transmitting the alternating current to an external alternating current power grid through the alternating current output end;
the direct current protection module is arranged on the boosting and current converting platform connected to the offshore direct current cable and used for acquiring the voltage value and the current value of the offshore direct current cable, generating a locking signal according to the voltage value and the current value and sending the locking signal to the control unit of each offshore wind driven generator, so that each control unit controls the corresponding offshore wind driven generator to stop outputting after receiving the locking signal.
2. The offshore decentralized direct current transmission system topology according to claim 1, wherein said direct current protection module comprises:
the sensor group is used for acquiring the voltage value and the current value of the offshore direct current cable;
the first comparator is used for comparing a preset voltage value with the voltage value;
the second comparator is used for comparing a current preset value with the current value;
the logic judgment assembly is provided with a first comparison input end, a second comparison input end and a locking signal output end, the first comparison input end is connected with the first comparator, the second comparison input end is connected with the second comparator, and the logic judgment assembly is used for generating the locking signal and sending the locking signal to each control unit of the offshore wind turbine.
3. The offshore decentralized direct current transmission system topology structure of claim 2, wherein each offshore wind turbine is further provided with a signal receiving module connected to the control unit, the direct current protection module further comprises a signal sending module connected to the blocking signal output end, and the blocking signal is subjected to electro-optical conversion by the signal sending module, sent to the signal receiving module of each offshore wind turbine through an optical cable, subjected to photoelectric conversion, and sent to the control unit.
4. The offshore decentralized dc power transmission system topology according to claim 1, wherein each of the boost converter modules comprises:
the booster transformer is provided with a boosting input end, a first boosting output end and a second boosting output end, the boosting input end is used for being connected with the offshore fan set through an alternating current cable bus, and the booster transformer is used for boosting alternating current input by the offshore fan set;
the diode converter valve is provided with a first converter input end connected with the first boosting output end, a second converter input end connected with the second boosting output end, a first converter output end and a second converter output end, and is used for converting the boosted alternating current into direct current and outputting the direct current through the first converter output end and the second converter output end;
and the bypass switch is connected between the first commutation output end and the second commutation output end in parallel.
5. The offshore decentralized direct current transmission system topology according to claim 1, wherein the onshore converter module comprises:
the MMC converter valve is provided with a first input end, a second input end and a first output end, wherein the first input end is used for being connected with the positive output end through the offshore direct current cable, and the second input end is used for being connected with the negative output end through the offshore direct current cable;
and the onshore transformer is provided with a transformation input end connected with the first output end and a transformation output end used for connecting the external alternating current power grid.
6. The offshore decentralized direct current transmission system topology according to claim 5, wherein the onshore converter module further comprises a direct current energy consuming device connected in parallel between the first input and the second input, the direct current energy consuming device being configured to consume excess energy of the direct current.
7. The offshore decentralized direct current transmission system topology according to claim 6, characterized in that the onshore converter module further comprises:
a first onshore direct current breaker connected in series between one end of the direct current energy consumption device and the first input end;
the second onshore direct current breaker is connected in series between the other end of the direct current energy consumption device and the second input end;
and the shore alternating current circuit breaker is connected between the first output end and the transformation input end in series.
8. A direct current protection control method is characterized by comprising the following steps:
acquiring a voltage value and a current value of the offshore direct current cable;
determining a locking signal according to the voltage value, the current value and the fault alarm parameter group, and sending the locking signal to a control unit of each offshore wind turbine; each control unit is used for stopping the output of the offshore wind turbine after receiving the locking signal; the fault alarm parameter group comprises a current preset value and a voltage preset value.
9. The dc protection control method of claim 8, wherein the determining a blocking signal according to the voltage value and the current value and the set of fault alarm parameters comprises the steps of:
and if the current value is greater than the current preset value and the voltage value is less than the voltage preset value, generating the locking signal.
10. The direct-current protection control method according to claim 8, wherein each offshore wind turbine is provided with a signal receiving module connected with the control unit, and the signal receiving module is used for converting an electric signal into an optical signal and sending the optical signal to the control unit;
the step of sending the blocking signal to a control unit of each offshore wind turbine comprises the following steps:
and carrying out electro-optical conversion on the blocking signal and then sending the blocking signal to the signal receiving module of each offshore wind turbine through an optical cable.
CN202210584257.0A 2022-05-26 2022-05-26 Offshore distributed direct-current transmission system topological structure and direct-current protection control method Pending CN115001011A (en)

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