CN119401538B - An onshore wind power transmission system - Google Patents
An onshore wind power transmission systemInfo
- Publication number
- CN119401538B CN119401538B CN202411692535.XA CN202411692535A CN119401538B CN 119401538 B CN119401538 B CN 119401538B CN 202411692535 A CN202411692535 A CN 202411692535A CN 119401538 B CN119401538 B CN 119401538B
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- Prior art keywords
- direct current
- wind power
- pole
- transformer
- power transmission
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
- H02J3/36—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
- 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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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
本发明公开了一种陆上风电输电系统，用于解决相关技术存在的谐波谐振、无功传输等交流汇集和送出的问题。陆上风电输电系统采用双极拓扑结构，每一极均包括风电送端单元及风电受端单元；风电送端单元包括直流变压器、两台以上风电机组；每台风电机组的内部设置机侧变流器且对应一个低压断路器；直流变压器安装一台送端直流断路器；对于每台风电机组，其发出的电能经机侧变流器整流为第一直流电，并经过低压断路器并联接入直流变压器，以升压为第二直流电，经直流变压器的送端直流断路器送入风电受端单元；风电受端单元包括受端换流站、联接变压器及启动回路；第二直流电经过受端换流站换流之后，经联接变压器及启动回路接入交流电网。
The present invention discloses an onshore wind power transmission system, which is used to solve the problems of AC collection and transmission, such as harmonic resonance and reactive power transmission, existing in related technologies. The onshore wind power transmission system adopts a bipolar topology structure, with each pole including a wind power sending unit and a wind power receiving unit. The wind power sending unit includes a DC transformer and two or more wind turbines. Each wind turbine is internally provided with a machine-side converter and corresponds to a low-voltage circuit breaker. The DC transformer is equipped with a sending-end DC circuit breaker. For each wind turbine, the electric energy generated by it is rectified into a first DC power by the machine-side converter, and then connected in parallel to the DC transformer through the low-voltage circuit breaker to be stepped up to a second DC power. The second DC power is then sent to the wind power receiving unit through the sending-end DC circuit breaker of the DC transformer. The wind power receiving unit includes a receiving-end converter station, a connecting transformer, and a starting circuit. After the second DC power is converted by the receiving-end converter station, it is connected to the AC power grid through the connecting transformer and the starting circuit.
Description
Technical Field
The invention relates to the technical field of wind power transmission, in particular to a land wind power transmission system.
Background
The wind power generation base gathers dominant resources, can fully exert scale effect, reduces power generation cost, and is an important direction of large-scale development of wind power generation. Currently, wind power generation systems mainly include two modes of ac collection-ac delivery and ac collection-dc delivery. However, if the ac collection-ac delivery system is adopted, problems such as harmonic resonance and reactive power transmission are prominent. If the alternating current collecting-direct current sending mode is adopted, the problems of more electric energy conversion links and high system cost exist.
Disclosure of Invention
The invention provides a land wind power transmission system which is used for solving or partially solving the problems of AC collection and sending out such as harmonic resonance, reactive power transmission and the like in the prior art.
The invention provides a land wind power transmission system which adopts a bipolar topological structure, wherein the land wind power transmission system comprises a first pole power transmission unit and a second pole power transmission unit, each pole power transmission unit comprises a wind power transmitting end unit and a wind power receiving end unit,
Each wind power transmitting end unit comprises a direct current transformer and more than two wind power units, wherein a machine side converter is arranged in each wind power unit, and each wind power unit corresponds to a low-voltage circuit breaker;
for each wind turbine generator, the electric energy generated by the wind turbine generator is rectified into first direct current through the machine side converter, and is connected into the direct current transformer in parallel through the low-voltage circuit breaker;
The first direct current is boosted into second direct current through the direct current transformer, and the second direct current is sent into the wind power receiving end unit through the sending end direct current breaker;
each wind power receiving end unit comprises a receiving end converter station, a connecting transformer and a starting loop;
After the second direct current is subjected to current conversion through the receiving-end converter station, the second direct current is subjected to voltage calibration through the connecting transformer, then passes through the starting loop and finally is connected into an alternating current power grid.
Optionally, the mechanical part of each wind turbine generator is 690V alternating current, and the electric energy generated by the wind turbine generator is rectified into first direct current of +/-550V through the machine side converter.
Optionally, a first direct current of +/-550V obtained after rectification of the machine side converter is connected in parallel to the input end of the direct current transformer through the low-voltage circuit breaker, wherein the input end of the direct current transformer corresponds to a low-voltage side, and the output end of the direct current transformer corresponds to a high-voltage side;
The low-voltage side of the DC transformer boosts a first DC power of +/-550V to a second DC power of high voltage class, which represents a voltage with a voltage capacity of +/-100 kV and above, and outputs the second DC power through the high-voltage side of the DC transformer.
Optionally, the dc transformer is composed of a plurality of dc converter units, and the plurality of dc converter units are connected in series-parallel connection;
Boosting and rectifying the first direct current of +/-550V through each direct current converter unit, and outputting medium-voltage direct current;
And carrying out voltage summation according to each medium-voltage direct current to obtain a second direct current with high voltage class.
Optionally, each direct current transformer unit is composed of an IGBT module, a high-frequency transformer and a rectifying and filtering output;
in each direct current transformer unit, the first direct current of +/-550V is firstly subjected to alternating current inversion through the IGBT module, then is boosted through the high-frequency transformer, and then is subjected to rectification and filtering through the rectification filtering output to output medium-voltage direct current.
Optionally, the receiving-end converter station comprises a full-bridge half-bridge hybrid MMC converter with direct-current fault clearing capability;
And after the second direct current with the high voltage level is subjected to current conversion through the full-bridge half-bridge hybrid MMC converter, voltage calibration is performed through the connecting transformer, the calibrated alternating current with the high voltage level is obtained, and then the alternating current is connected into an alternating current power grid through the starting loop.
Optionally, the transmitting end direct current breaker of each pole of the transmitting end is connected to the full-bridge half-bridge hybrid MMC converter of the homopolar of the receiving end through a direct current overhead line of a high voltage grade;
when any direct current overhead line with extremely high voltage level fails, the full-bridge half-bridge hybrid MMC converter with the same polarity is matched with the transmitting end direct current breaker together, so that the direct current line failure is cleared, and the line operation of the non-failed one pole is not affected in the period.
Optionally, when a direct current overhead line of any one extremely high voltage class fails, for the failed pole:
the line protection of the wind power transmitting end unit of the fault pole and the line protection of the wind power receiving end unit of the fault pole detect faults and execute fault clearing actions respectively to realize the common cooperation of the homopolar transmitting end and the receiving end direct current line fault clearing, wherein,
The line protection of the wind power transmitting end unit of the fault pole generates a tripping instruction, and the tripping instruction is issued to the transmitting end direct current breaker of the fault pole so as to control the tripping of the transmitting end direct current breaker of the fault pole;
And generating a voltage control instruction by line protection of the wind power receiving end unit of the fault pole, and transmitting the voltage control instruction to the full-bridge half-bridge hybrid MMC converter of the fault pole so that the full-bridge half-bridge hybrid MMC converter of the fault pole can control the direct-current side voltage of the receiving end of the fault pole to be below 0.
Optionally, when the sending end and the receiving end of the fault pole execute fault clearing action, after the preset recovery time is spent, the full-bridge half-bridge hybrid MMC converter of the fault pole controls and recovers the direct current side voltage of the receiving end of the fault pole, the sending end direct current breaker of the fault pole is reclosed, and the onshore wind power transmission system recovers operation.
Optionally, the receiving-end converter station comprises a receiving-end direct current breaker and a half-bridge MMC converter, wherein the receiving-end direct current breaker is positioned between the half-bridge MMC converter and the homopolar sending-end direct current breaker;
And the second direct current with the high voltage level passes through the receiving end direct current breaker, passes through the half-bridge MMC converter to be converted, and then passes through the connecting transformer to be subjected to voltage calibration, so as to obtain the alternating current with the high voltage level after calibration, and then passes through the starting loop and finally is connected into an alternating current power grid.
Optionally, the transmitting end direct current breaker of each pole of the transmitting end is connected to the receiving end direct current breaker of the same pole of the receiving end through a direct current overhead line of a high voltage grade;
When any direct current overhead line with extremely high voltage level fails, the receiving end direct current breaker and the sending end direct current breaker which are in the same polarity are matched together, so that the direct current line failure is cleared, and the line operation of the non-failed one pole is not affected in the period.
Optionally, when a direct current overhead line of any one extremely high voltage class fails, for the failed pole:
the line protection of the wind power transmitting end unit of the fault pole and the line protection of the wind power receiving end unit of the fault pole detect faults and execute fault clearing actions respectively to realize the common cooperation of the homopolar transmitting end and the receiving end direct current line fault clearing, wherein,
Generating a transmitting end tripping instruction by line protection of a wind power transmitting end unit of the fault pole, and transmitting the transmitting end tripping instruction to a transmitting end direct current breaker of the fault pole so as to control the transmitting end direct current breaker of the fault pole to be tripped;
and generating a receiving-end tripping instruction by line protection of the wind power receiving-end unit of the fault pole, and sending the receiving-end tripping instruction to the receiving-end direct current breaker of the fault pole so as to control the tripping of the receiving-end direct current breaker of the fault pole.
Optionally, when the sending end and the receiving end of the fault pole execute fault clearing actions, after the preset recovery time is removed, the sending end direct current breaker and the receiving end direct current breaker of the fault pole are reclosed again, and the onshore wind power transmission system resumes operation.
Optionally, the land wind power transmission system further comprises a positive direct current overhead line and a negative direct current overhead line;
the neutral line area between the positive direct current overhead line and the negative direct current overhead line adopts an overhead line metal neutral line, and the receiving end is grounded for clamping;
Or alternatively, the first and second heat exchangers may be,
And the neutral line area between the positive direct current overhead line and the negative direct current overhead line is respectively grounded at a transmitting end and a receiving end through a grounding electrode.
From the above technical scheme, the invention has the following advantages:
An onshore wind power transmission system is provided. The land wind power transmission system adopts a bipolar topological structure, each pole comprises a wind power transmitting end unit and a wind power receiving end unit, each wind power transmitting end unit comprises a direct current transformer and more than two wind power units, a machine side converter is arranged in each wind power unit and corresponds to one low-voltage circuit breaker, the direct current transformer is provided with one transmitting end direct current circuit breaker, electric energy generated by each wind power unit is rectified into first direct current through the machine side converter and is connected into the direct current transformer in parallel through the low-voltage circuit breaker to be boosted into second direct current, the second direct current is transmitted into the wind power receiving end unit through the transmitting end direct current circuit breaker of the direct current transformer, and the wind power receiving end unit comprises a receiving end converter station, a connecting transformer and a starting circuit. The output of the fan is direct current, the direct current is boosted to medium-high grade direct current voltage, and the direct current is finally sent out through a long-distance overhead line, so that the middle alternating current-direct current conversion link can be reduced, the problems of traditional alternating current collection and sending out such as harmonic resonance and reactive power transmission can be effectively solved, and the power generation cost can be reduced. The full DC discharge mode has higher discharge efficiency and reliability. Meanwhile, the bipolar system can realize high-capacity power transmission, and compared with a symmetrical monopole system, the bipolar system adopted by the invention can avoid bipolar outage after monopole faults occur, and the system has higher operation reliability.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings can be obtained according to these drawings without inventive effort to a person skilled in the art.
FIG. 1 is a schematic diagram of a schematic circuit configuration of a land wind power transmission system;
FIG. 2 is a schematic diagram of a circuit principle structure of wind turbine side rectification;
Fig. 3 is a schematic circuit schematic diagram of a dc transformer unit for step-up rectification;
FIG. 4 is a schematic circuit schematic diagram of a pole receiving-end converter unit;
FIG. 5 is a schematic diagram of a schematic circuit configuration of another land wind power transmission system;
FIG. 6 is a schematic diagram of a schematic circuit configuration of another land wind power transmission system;
Fig. 7 is a schematic diagram of a basic topology of a converter station comprising only one half-bridge sub-module.
Detailed Description
The embodiment of the invention provides a land wind power transmission system, which is used for solving or partially solving the problems of AC collection and transmission such as harmonic resonance, reactive power transmission and the like in the prior art.
In order to make the objects, features and advantages of the present invention more comprehensible, the technical solutions in the embodiments of the present invention are described in detail below with reference to the accompanying drawings, and it is apparent that the embodiments described below are only some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As an example, the wind power generation base gathers dominant resources, can fully exert scale effect, reduce power generation cost, and is an important direction of large-scale development of wind power generation. Currently, wind power generation systems mainly include two modes of ac collection-ac delivery and ac collection-dc delivery. However, if the ac collection-ac delivery system is adopted, problems such as harmonic resonance and reactive power transmission are prominent. If the alternating current collecting-direct current sending mode is adopted, the problems of more electric energy conversion links and high system cost exist.
In order to effectively solve the problems of harmonic resonance, reactive power transmission and other alternating current collection and delivery existing in the current land wind power transmission, and realize efficient grid connection, a novel land wind power delivery topological structure is required to be provided, so that the overall cost of a land wind power delivery system is reduced on the basis of stable delivery of land wind power.
Through further analysis, the invention adopts a full direct current output mode, and can reduce intermediate conversion links. However, if a system architecture with a symmetrical single main is adopted, the operation flexibility and reliability are low, and the requirement of high-capacity power transmission cannot be met.
Therefore, one of the key points of the embodiment of the invention is to organically combine the direct-current transmission technology with the direct-current wind turbine generator and provide a land wind power full direct-current transmission system with a bipolar topological structure. Each pole transmitting end of the land wind power transmission system can comprise a plurality of wind turbine generators and a machine side converter. And the low-voltage direct current output by the direct current wind turbine generator is boosted and collected by a direct current converter, and then is connected into a flexible direct current converter station at a receiving end by a long-distance overhead line provided with a direct current breaker. The receiving-end flexible direct-current converter station adopts a full-bridge half-bridge hybrid MMC (ModularMultilevel Converter, modularized multi-level converter) converter with direct-current fault clearing capability, or adopts a combined framework of combining a receiving-end direct-current breaker with a half-bridge MMC converter. The output of the fan is direct current, the direct current is boosted to medium-high grade direct current voltage, and the direct current is finally sent out through a long-distance overhead line, so that the middle alternating current-direct current conversion link can be reduced, the problems of traditional alternating current collection and sending out such as harmonic resonance and reactive power transmission can be effectively solved, and the power generation cost can be reduced. The full DC discharge mode has higher discharge efficiency and reliability. Meanwhile, the bipolar system can realize high-capacity power transmission, and compared with a symmetrical monopole system, the bipolar system adopted by the invention can avoid bipolar outage after monopole faults occur, and the system has higher operation reliability.
Referring to fig. 1, a schematic circuit principle structure diagram of a land wind power transmission system according to an embodiment of the present invention is shown.
The onshore wind power transmission system in the embodiment of the invention adopts a bipolar topological structure. To better distinguish between the dipoles, it is provided that the onshore wind power transmission system specifically comprises a first pole power transmission unit (corresponding to the upper half in fig. 1) and a second pole power transmission unit (corresponding to the lower half in fig. 1). Each pole of power transmission unit comprises a wind power transmitting end unit (corresponding to a transmitting end) and a wind power receiving end unit (corresponding to a receiving end).
One of the poles in fig. 1 is taken as an example for illustration. Each wind power transmitting end unit comprises a DC/DC (Direct Currentto Direct Current Converter, direct current to direct current) transformer and more than two wind power units (for simplifying the schematic diagram, only two permanent magnet direct drive generators of a fan 1 and a fan n are shown in fig. 1). Each wind turbine is internally provided with a machine side converter (which is shown detached from the wind turbine in fig. 1 for ease of illustration). Each wind motor group corresponds to a low-voltage circuit breaker.
For each wind turbine, electric energy generated by the wind turbine is rectified into first direct current through a machine side converter, and is connected in parallel to a direct current transformer through a low-voltage circuit breaker. The first direct current is boosted into the second direct current through the direct current transformer, and the second direct current is sent into the wind power receiving end unit through the sending end direct current breaker.
With reference to fig. 1, fig. 2 shows a schematic circuit schematic structure of wind turbine generator side rectification. Taking the fan 1 with one pole as an example in fig. 1, the mechanical part of each wind turbine generator set is 690V alternating current, and the electric energy generated by the wind turbine generator set is rectified into first direct current of +/-550V through a machine side converter.
And then, the first direct current of +/-550V obtained after rectification of the plurality of machine side converters in a plurality of application scenes is connected in parallel to the input end of the direct current transformer through the low-voltage circuit breaker, namely, the input end corresponds to the low-voltage side. The low-voltage side of the dc transformer boosts the first dc power of ±550v to the second dc power of the high-voltage class and outputs (which may also be understood as the second dc power boosted to the high-voltage class) via the high-voltage side of the dc transformer. The high voltage class means a voltage having a voltage capacity of + -100 kV and above. And the output end (namely the corresponding high-voltage side) of each pole of direct-current transformer is provided with a transmitting end direct-current breaker. And then the wind power receiving end unit is connected into a receiving end converter station of the wind power receiving end unit through a long-distance overhead line.
As can be seen from fig. 1, the dc transformer is composed of a plurality of dc converter units (e.g. modules 1 to n) connected in series-parallel.
When boosting, the first direct current of +/-550V is subjected to boosting rectification treatment through each direct current converter unit, medium-voltage direct current is output, and then voltage summation is carried out according to each medium-voltage direct current, so that the second direct current with high voltage class (such as +/-100 kV or +/-110 kV) is obtained.
More specifically, fig. 3 shows a schematic circuit principle structure of boost rectification of a dc transformer unit.
As can be seen in connection with fig. 3, each dc transformer unit is mainly composed of an IGBT (Insulated Gate Bipolar Transistor ) module, a high-frequency transformer, and a rectifying and filtering output.
In each direct current transformer unit, first direct current of +/-550V is subjected to alternating current inversion through an IGBT module, then is boosted through a high-frequency transformer, and then is subjected to rectification and filtering through rectification and filtering output to output medium-voltage direct current.
More specifically, the input of the direct current transformer unit is +/-550V direct current, and the input end of the direct current transformer unit is composed of an IGBT module. The first direct current of +/-550V is inverted into low-voltage alternating current of high frequency through an IGBT module, the low-voltage alternating current is boosted to high-voltage alternating current of high frequency through a high-frequency transformer, and then the high-voltage alternating current is rectified and filtered to output (a diode rectifier), and medium-voltage direct current of +/-2.5 kV is formed after rectification and filtering.
A medium voltage direct current of + -2.5 kV after boosting can be obtained by each direct current transformer unit. The n DC/DC converter units are connected in series and parallel, and finally can output second direct current corresponding to high voltage level. For example, for the second direct current of +/-110 kV, 44 DC/DC converter units are required to be connected in series-parallel connection and combined to form a DC transformer.
It is understood that the number of dc transformer units is not necessarily 44 for the second dc power of ±110kV, as long as the final output dc voltage is ±110kV. 44 are used here because the high side output of a single dc transformer unit is + -2.5 kV and the summation is + -110 kV. For example, a dc power of 550V is assumed to be processed by a single dc converter unit to output a dc power of 5kV, and the dc transformer can obtain a total dc power of 110kV by using only 22 dc converter units. It will be appreciated that the invention is not limited in this regard.
Fig. 4 is a schematic circuit diagram of a current converting unit with one pole receiving end according to an embodiment of the present invention.
In connection with fig. 4, each wind power receiving unit may comprise a receiving converter station, a coupling transformer and a starting circuit. After the second direct current with high voltage level is subjected to current conversion through the receiving end current conversion station, the voltage calibration is performed through the connecting transformer, then the second direct current is subjected to the starting loop, and finally the second direct current is connected into an alternating current power grid.
Specifically, in the embodiment of the invention, the receiving end converter station of each pole adopts a full-bridge half-bridge hybrid MMC topological structure with direct-current fault clearing capability, namely a full-bridge half-bridge hybrid MMC converter.
Wherein the MMC is composed of a plurality of Sub-Modules (SM). Each sub-module typically contains a half-bridge or full-bridge inverter and an energy storage capacitor. The sub-modules are connected in series to form a phase arm. A typical MMC includes three phase arms, each corresponding to A, B, C three phases in a three-phase ac system.
The Full-bridge Half-bridge hybrid MMC converter provided by the embodiment of the invention mainly comprises HBSM (Half-Bridge Submodule ) and FBSM (Full-Bridge Submodule, full-bridge submodule). Wherein HBSM is composed of two IGBTs and an energy storage capacitor. The FBSM is composed of four IGBTs and one storage capacitor.
In other words, the full-bridge half-bridge hybrid MMC converter basic topology of the receiving end mainly may include two sub-modules, namely a full-bridge sub-module and a half-bridge sub-module. Therefore, when the fault occurs, the full-bridge submodule can output negative level, and the full-bridge submodule is matched with the half-bridge submodule to jointly control the voltage of the direct current side to be below 0. The topological structure part of the full-bridge half-bridge hybrid MMC converter adopts half-bridge submodules, so that compared with the full-bridge submodules, the number of power devices can be reduced and the investment cost of equipment can be reduced while the fault ride-through of the direct current side is realized.
The direct current side of the full-bridge half-bridge mixed MMC converter is connected with a sending-out direct current breaker of a homopolar sending end, receives a second direct current of +/-110 kV, and the alternating current side is connected with a connecting transformer and a starting loop and then is connected into a large power grid through 110kV power frequency alternating current transmission. The second direct current with the high voltage level of +/-110 kV is subjected to converter conversion through a full-bridge half-bridge hybrid MMC converter, voltage calibration is performed through a connecting transformer, and the high-voltage-level alternating current (namely the alternating current meeting the standard voltage level) after calibration is obtained, then the alternating current passes through a starting loop, and finally is connected into an alternating current power grid through 110kV power frequency alternating current transmission.
The connection transformer (also called as connection transformer or coupling transformer) can further boost the voltage transmitted by the transmitting end, so as to realize voltage conversion and reduce line loss during long-distance transmission.
The Start-Up loop (Start-Up Circuit) may enable a smooth, reliable Start-Up of the system after power-Up or reset.
Wherein, the voltage class of the network side alternating current is 110kV and above. The voltage class of the + -110 kV direct current obtained after the boost of the receiving end is taken as an example for illustration, and in practical application, the voltage class of the network side alternating current can be 220kV/500kV/750kV/1000kV. Similarly, the high voltage class obtained after the voltage boosting of the transmitting end can be 220kV/500kV/750kV/1000kV.
Voltage calibration is set because the voltage on the input side of the coupling transformer is generally not a standard voltage level. That is, although the embodiment of the present invention is described with a high voltage level of 110kV, there may be a deviation in practical application, and the high voltage level voltage received by the receiving end needs to be converted into a standard voltage level after the conversion, so that the receiving end can be connected to an external power grid.
The transmitting end direct current circuit breaker of each pole of the transmitting end is connected to the full-bridge half-bridge hybrid MMC converter of the homopolar of the receiving end through a direct current overhead line of a high voltage grade (such as +/-110 kV).
When the direct current overhead line with any extremely high voltage level (+ -110 kV) fails, the full-bridge half-bridge hybrid MMC converter with the same poles is matched with the transmitting-end direct current breaker together, so that the direct current line failure is cleared. Wherein the line operation of the non-faulty one of the poles is not affected during this time.
In a specific implementation, when a direct current overhead line with any extremely high voltage level (+ -110 kV) fails, for the failed fault pole, the line protection of the wind power transmitting end unit of the failed pole and the line protection of the wind power receiving end unit of the failed pole detect the fault and execute fault clearing actions respectively so as to realize the joint coordination of the homopolar transmitting end and the receiving end direct current line fault clearing.
The method comprises the steps of generating a tripping instruction by line protection of a wind power transmitting end unit of a fault pole, and transmitting the tripping instruction to a transmitting end direct current breaker of the fault pole so as to control the tripping of the transmitting end direct current breaker of the fault pole.
The line protection of the wind power receiving end unit of the fault pole generates a voltage control instruction, and the voltage control instruction is issued to the full-bridge half-bridge hybrid MMC converter of the fault pole, so that the full-bridge half-bridge hybrid MMC converter of the fault pole controls the voltage of the direct current side of the receiving end of the fault pole to be below 0.
Further, when the sending end and the receiving end of the fault pole execute fault clearing action, after the preset recovery time (such as hundreds of milliseconds) is spent, the full-bridge half-bridge hybrid MMC converter of the fault pole is controlled to recover the direct-current side voltage of the receiving end of the fault pole. The sending end direct current breaker of the fault pole is reclosed. And recovering the operation of the land wind power transmission system.
As can be seen in fig. 1, the land wind power transmission system further comprises a positive dc overhead line and a negative dc overhead line of high voltage.
The neutral line region between the positive and negative dc overhead lines may be a metallic neutral line of the overhead line as shown in fig. 1, and the connection is made by clamping (dc-isolating blade) at the ground of the end.
Alternatively, as for the (low voltage) neutral line region between the positive dc overhead line and the negative dc overhead line, a connection method may be adopted in which the positive dc overhead line and the negative dc overhead line are grounded via a grounding electrode, respectively, at the transmitting end and the receiving end as shown in fig. 5.
In the embodiment of the invention, a land wind power full direct current transmission system with a bipolar topological structure is provided. Each pole transmitting end of the land wind power transmission system can comprise a plurality of wind turbine generators and a machine side converter. And the low-voltage direct current output by the direct current wind turbine generator is boosted and collected by a direct current converter, and then is connected into a flexible direct current converter station at a receiving end by a long-distance overhead line provided with a direct current breaker. The flexible direct-current converter station at the receiving end adopts a full-bridge half-bridge hybrid MMC converter with direct-current fault clearing capacity. The output of the fan is direct current, the direct current is boosted to medium-high grade direct current voltage, and the direct current is finally sent out through a long-distance overhead line, so that the middle alternating current-direct current conversion link can be reduced, the problems of traditional alternating current collection and sending out such as harmonic resonance and reactive power transmission can be effectively solved, and the power generation cost can be reduced. The full DC discharge mode has higher discharge efficiency and reliability. Meanwhile, the bipolar system can realize high-capacity power transmission, and compared with a symmetrical monopole system, the bipolar system adopted by the invention can avoid bipolar outage after monopole faults occur, and the system has higher operation reliability.
Referring to fig. 6, a schematic circuit schematic structure of another land wind power transmission system according to an embodiment of the present invention is shown.
The onshore wind power transmission system in the embodiment of the invention adopts a bipolar topological structure. To better distinguish between the dipoles, it is provided that the onshore wind power transmission system specifically comprises a first pole power transmission unit (corresponding to the upper half in fig. 6) and a second pole power transmission unit (corresponding to the lower half in fig. 6). Each pole of power transmission unit comprises a wind power transmitting end unit (corresponding to a transmitting end) and a wind power receiving end unit (corresponding to a receiving end).
The detailed description of the wind power transmission unit is only required to refer to the foregoing embodiments, and will not be repeated here.
Each wind power receiving unit may comprise a receiving converter station, a coupling transformer and a starting circuit. After the second direct current with high voltage level is subjected to current conversion through the receiving end current conversion station, the voltage calibration is performed through the connecting transformer, then the second direct current is subjected to the starting loop, and finally the second direct current is connected into an alternating current power grid.
Specifically, in the embodiment of the present invention, the receiving-end converter station of each pole includes a receiving-end dc breaker and a half-bridge MMC converter. As can be seen from fig. 6, the receiving end dc breaker is located between the half-bridge MMC converter and the homopolar transmitting end dc breaker.
The basic topology of a half-bridge MMC converter for each pole is shown in fig. 7. As can be seen in fig. 7, the half-bridge MMC converter comprises only half-bridge sub-modules, and no full-bridge sub-modules are provided.
For any pole, the second direct current with high voltage class (such as +/-110 kV) is subjected to end direct current breaker, after the converter is carried out through the half-bridge MMC converter, voltage calibration is carried out through the connecting transformer, the high-voltage class alternating current after calibration is obtained, then the alternating current is connected into an alternating current power grid through a starting loop and finally (110 kV) power frequency alternating current transmission.
The transmitting-end direct current circuit breaker of each pole of the transmitting end is connected to the receiving-end homopolar receiving-end direct current circuit breaker through a direct current overhead line with a high voltage level (+ -110 kV).
When the direct current overhead line with any extremely high voltage level (+ -110 kV) fails, the receiving end direct current breaker and the transmitting end direct current breaker which are in the same polarity are matched together, so that the direct current line failure is cleared, and the line operation of the non-failed one pole is not affected in the period.
In a specific implementation, when a direct current overhead line with any extremely high voltage level (+ -110 kV) fails, for the failed fault pole, the line protection of the wind power transmitting end unit of the failed pole and the line protection of the wind power receiving end unit of the failed pole detect the fault and execute fault clearing actions respectively so as to realize the joint coordination of the homopolar transmitting end and the receiving end direct current line fault clearing.
The line protection of the wind power transmitting end unit of the fault pole generates a transmitting end tripping instruction, and the transmitting end tripping instruction is issued to the transmitting end direct current breaker of the fault pole so as to control the transmitting end direct current breaker of the fault pole to be tripped.
And generating a receiving-end tripping instruction by line protection of the wind power receiving-end unit of the fault pole, and sending the receiving-end tripping instruction to the receiving-end direct current breaker of the fault pole so as to control the tripping of the receiving-end direct current breaker of the fault pole.
Further, when the sending end and the receiving end of the fault pole execute fault clearing action, after the preset recovery time (such as hundreds of milliseconds) is removed, the sending end direct current breaker and the receiving end direct current breaker of the fault pole are reclosed. And recovering the operation of the land wind power transmission system.
Similar to the previous embodiments, the onshore wind power transmission system of the embodiments of the invention also includes a high voltage positive dc overhead line and a negative dc overhead line.
The neutral line region (low voltage) between the positive dc overhead line and the negative dc overhead line can be referred to as an overhead line metal neutral line as shown in fig. 1, and the connection mode of clamping (dc-blocking) is performed at the ground of the end.
Alternatively, as for the (low voltage) neutral line region between the positive dc overhead line and the negative dc overhead line, a connection method may be adopted in which the positive dc overhead line and the negative dc overhead line are grounded via a grounding electrode, respectively, at the transmitting end and the receiving end as shown in fig. 6.
In the embodiment of the invention, a land wind power full direct current transmission system with a bipolar topological structure is provided. Each pole transmitting end of the land wind power transmission system can comprise a plurality of wind turbine generators and a machine side converter. And the low-voltage direct current output by the direct current wind turbine generator is boosted and collected by a direct current converter, and then is connected into a flexible direct current converter station at a receiving end by a long-distance overhead line provided with a direct current breaker. The receiving-end flexible direct-current converter station adopts a combined framework of a receiving-end direct-current breaker and a half-bridge MMC converter. The output of the fan is direct current, the direct current is boosted to medium-high grade direct current voltage, and the direct current is finally sent out through a long-distance overhead line, so that the middle alternating current-direct current conversion link can be reduced, the problems of traditional alternating current collection and sending out such as harmonic resonance and reactive power transmission can be effectively solved, and the power generation cost can be reduced. The full DC discharge mode has higher discharge efficiency and reliability. Meanwhile, the bipolar system can realize high-capacity power transmission, and compared with a symmetrical monopole system, the bipolar system adopted by the invention can avoid bipolar outage after monopole faults occur, and the system has higher operation reliability.
It should be noted that, in order to enable those skilled in the art to better distinguish data with the same type but different actual directions, in the embodiment of the present invention, the first and second distinguishing descriptions are adopted for part of technical features, and the first and second distinguishing uses only as data, and there is no other special meaning, so that it is to be understood that the present invention is not limited thereto.
In the embodiments provided by the present invention, it should be understood that the disclosed system may be implemented in other manners. For example, the apparatus embodiments described above are merely illustrative, e.g., the division of the units is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional unit in the embodiments of the present invention may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in software functional units.
The integrated units, if implemented in the form of software functional units and sold or used as stand-alone products, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied essentially or in part or all of the technical solution or in part in the form of a software product stored in a storage medium, including instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. The storage medium includes a U disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RandomAccess Memory, RAM), a magnetic disk, an optical disk, or other various media capable of storing program codes.
While the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that the foregoing embodiments may be modified or equivalents may be substituted for some of the features thereof, and that the modifications or substitutions do not depart from the spirit and scope of the embodiments of the invention.
Claims (13)
1. A land wind power transmission system is characterized in that the land wind power transmission system adopts a bipolar topological structure and comprises a first pole power transmission unit and a second pole power transmission unit, each pole power transmission unit comprises a wind power transmitting end unit and a wind power receiving end unit, wherein,
Each wind power transmitting end unit comprises a direct current transformer and more than two wind power units, wherein a machine side converter is arranged in each wind power unit, and each wind power unit corresponds to a low-voltage circuit breaker;
for each wind turbine generator, the electric energy generated by the wind turbine generator is rectified into first direct current through the machine side converter, and is connected into the direct current transformer in parallel through the low-voltage circuit breaker;
The first direct current is boosted into second direct current through the direct current transformer, and the second direct current is sent into the wind power receiving end unit through the sending end direct current breaker;
each wind power receiving end unit comprises a receiving end converter station, a connecting transformer and a starting loop;
after the second direct current is subjected to current conversion through the receiving-end converter station, the second direct current is subjected to voltage calibration through the connecting transformer, then passes through the starting loop and finally is connected into an alternating current power grid;
The receiving end converter station comprises a full-bridge half-bridge hybrid MMC converter with direct-current fault clearing capacity, wherein the transmitting end direct-current circuit breaker of each pole of a transmitting end is connected to the full-bridge half-bridge hybrid MMC converter with the same pole of the receiving end through a direct-current overhead line with high voltage level;
When the direct current overhead line with any extremely high voltage level breaks down, for the broken down pole, the line protection of the wind power transmitting end unit of the broken down pole and the line protection of the wind power receiving end unit of the broken down pole detect the faults and execute fault clearing actions respectively so as to realize the joint coordination of the homopolar transmitting end and the receiving end direct current line fault clearing,
The line protection of the wind power transmitting end unit of the fault pole generates a tripping instruction, and the tripping instruction is issued to the transmitting end direct current breaker of the fault pole so as to control the tripping of the transmitting end direct current breaker of the fault pole;
And generating a voltage control instruction by line protection of the wind power receiving end unit of the fault pole, and transmitting the voltage control instruction to the full-bridge half-bridge hybrid MMC converter of the fault pole so that the full-bridge half-bridge hybrid MMC converter of the fault pole can control the direct-current side voltage of the receiving end of the fault pole to be below 0.
2. The land wind power transmission system of claim 1, wherein the mechanical part of each wind turbine generator is 690V ac, and the electric energy generated by the wind turbine generator is rectified to a first dc power of ±550V by the machine side converter.
3. The land wind power transmission system according to claim 2, wherein the first direct current of +/-550V obtained by rectification of the machine side converter is connected in parallel to the input end of the direct current transformer through the low voltage circuit breaker, wherein the input end of the direct current transformer corresponds to a low voltage side, and the output end corresponds to a high voltage side;
The low-voltage side of the DC transformer boosts a first DC power of +/-550V to a second DC power of high voltage class, which represents a voltage with a voltage capacity of +/-100 kV and above, and outputs the second DC power through the high-voltage side of the DC transformer.
4. A land wind power transmission system according to claim 3, wherein said dc transformer is constituted by a plurality of dc converter units, said plurality of dc converter units being coupled in series-parallel combination;
boosting the first direct current of +/-550V through each direct current converter unit, and outputting medium-voltage direct current;
And carrying out voltage summation according to each medium-voltage direct current to obtain a second direct current with high voltage class.
5. The land wind power transmission system of claim 4, wherein each of said dc transformer units is comprised of an IGBT module, a high frequency transformer, and a rectifying and filtering output;
in each direct current transformer unit, the first direct current of +/-550V is firstly subjected to alternating current inversion through the IGBT module, then is boosted through the high-frequency transformer, and then is subjected to rectification and filtering through the rectification filtering output to output medium-voltage direct current.
6. The land wind power transmission system according to any one of claims 3 to 5, wherein said second direct current of high voltage level is converted by said full-bridge half-bridge hybrid MMC converter, voltage calibrated by said coupling transformer to obtain an ac power of calibrated high voltage level, and then passed through said starting circuit to be finally connected to an ac power grid.
7. The land wind power transmission system of claim 6, wherein when any one of the extremely high voltage levels of the dc overhead lines fails, the full-bridge half-bridge hybrid MMC converter in homopolarity cooperates with the feed dc breaker to effect removal of dc line faults, during which line operation of the non-failed one of the poles is unaffected.
8. The land wind power transmission system of claim 7, wherein when said transmitting and receiving ends of said fault pole have performed fault clearing actions, said full-bridge half-bridge hybrid MMC converter of said fault pole is controlled to restore a direct current side voltage of said receiving end of said fault pole after a predetermined restore time has elapsed, said transmitting end direct current breaker of said fault pole is reclosed, and said land wind power transmission system is restored to operation.
9. The land wind power transmission system of any one of claims 3 to 5, wherein said receiving end converter station comprises a receiving end dc breaker and a half-bridge MMC converter, said receiving end dc breaker being located between said half-bridge MMC converter and said transmitting end dc breaker of homopolarity;
And the second direct current with the high voltage level passes through the receiving end direct current breaker, passes through the half-bridge MMC converter to be converted, and then passes through the connecting transformer to be subjected to voltage calibration, so as to obtain the alternating current with the high voltage level after calibration, and then passes through the starting loop and finally is connected into an alternating current power grid.
10. The land wind power transmission system of claim 9, wherein said send-side dc breaker of each pole of a send-side is connected to said receive-side dc breakers of the same polarity of a receive-side by a high voltage class dc overhead line;
When any direct current overhead line with extremely high voltage level fails, the receiving end direct current breaker and the sending end direct current breaker which are in the same polarity are matched together, so that the direct current line failure is cleared, and the line operation of the non-failed one pole is not affected in the period.
11. The land wind power transmission system of claim 10, wherein when a dc overhead line of any extremely high voltage class fails, for the failed pole:
the line protection of the wind power transmitting end unit of the fault pole and the line protection of the wind power receiving end unit of the fault pole detect faults and execute fault clearing actions respectively to realize the common cooperation of the homopolar transmitting end and the receiving end direct current line fault clearing, wherein,
Generating a transmitting end tripping instruction by line protection of a wind power transmitting end unit of the fault pole, and transmitting the transmitting end tripping instruction to a transmitting end direct current breaker of the fault pole so as to control the transmitting end direct current breaker of the fault pole to be tripped;
and generating a receiving-end tripping instruction by line protection of the wind power receiving-end unit of the fault pole, and sending the receiving-end tripping instruction to the receiving-end direct current breaker of the fault pole so as to control the tripping of the receiving-end direct current breaker of the fault pole.
12. The land wind power transmission system of claim 11, wherein when the transmitting end and the receiving end of the fault pole perform fault clearing actions, after a preset recovery time is set free, the transmitting end direct current circuit breaker and the receiving end direct current circuit breaker of the fault pole are reclosed, and the land wind power transmission system resumes operation.
13. The land wind power transmission system of claim 1, further comprising a positive dc overhead line and a negative dc overhead line;
the neutral line area between the positive direct current overhead line and the negative direct current overhead line adopts an overhead line metal neutral line, and the receiving end is grounded for clamping;
Or alternatively, the first and second heat exchangers may be,
And the neutral line area between the positive direct current overhead line and the negative direct current overhead line is respectively grounded at a transmitting end and a receiving end through a grounding electrode.
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| CN116131325A (en) * | 2022-12-29 | 2023-05-16 | 西安交通大学 | A solid-state transformer for direct current collection and transmission in long-distance offshore wind farms |
| CN117318129A (en) * | 2023-09-27 | 2023-12-29 | 国网智能电网研究院有限公司 | Offshore wind power full DC collection and delivery system and its start-up control method and device |
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| CN116131325A (en) * | 2022-12-29 | 2023-05-16 | 西安交通大学 | A solid-state transformer for direct current collection and transmission in long-distance offshore wind farms |
| CN117318129A (en) * | 2023-09-27 | 2023-12-29 | 国网智能电网研究院有限公司 | Offshore wind power full DC collection and delivery system and its start-up control method and device |
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