CN114094617A - Hybrid direct-current power transmission system and receiving-end alternating-current fault ride-through method thereof - Google Patents

Hybrid direct-current power transmission system and receiving-end alternating-current fault ride-through method thereof Download PDF

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CN114094617A
CN114094617A CN202111402061.7A CN202111402061A CN114094617A CN 114094617 A CN114094617 A CN 114094617A CN 202111402061 A CN202111402061 A CN 202111402061A CN 114094617 A CN114094617 A CN 114094617A
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station
type
current
voltage
lcc
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CN114094617B (en
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彭茂兰
王海军
甘宗跃
吴健颖
刘航
冯雷
黄炟超
廖芳群
张沛然
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Maintenance and Test Center of Extra High Voltage Power Transmission Co
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Maintenance and Test Center of Extra High Voltage Power Transmission Co
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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
    • 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
    • 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
    • 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)
  • Direct Current Feeding And Distribution (AREA)

Abstract

The application relates to a hybrid direct-current power transmission system and a receiving end alternating-current fault ride-through method thereof. The sending end of the hybrid direct-current transmission system comprises an LCC type rectifying station, the receiving end of the hybrid direct-current transmission system comprises an MMC type inverting station, and the method comprises the following steps: if the hybrid direct-current power transmission system has a receiving-end alternating-current fault, acquiring a receiving-end alternating-current fault type; if the type of the alternating current fault at the receiving end is a serious fault and the maximum value of the average value of the capacitor voltage of each submodule of the MMC type inverter station is larger than a first preset voltage, the MMC type inverter station is locked and the LCC type rectifier station is controlled to stop transmitting electric energy until the direct current between the LCC type rectifier station and the MMC type inverter station is smaller than the preset current, the MMC type inverter station is unlocked and the LCC type rectifier station is recovered to transmit electric energy; and if the receiving end alternating current fault type is a non-serious fault, reducing the electric energy transmitted by the LCC type rectifying station according to the direct current voltage rising degree of the LCC type rectifying station. The method effectively inhibits the MMC inverter station from continuously charging, and avoids the problem of direct-current overvoltage tripping of the MMC inverter station.

Description

Hybrid direct-current power transmission system and receiving-end alternating-current fault ride-through method thereof
Technical Field
The present disclosure relates to the field of dc power transmission technologies, and in particular, to a hybrid dc power transmission system, a receiving-end ac fault ride-through method thereof, a control device, and a computer-readable storage medium.
Background
Conventional direct current Converter stations, such as LCC (Line Commutated Converter) Converter stations, have the advantages of high voltage level, large capacity, strong device tolerance capability and the like, and related engineering technologies are quite mature. Compared with a conventional direct current Converter station, a flexible direct current Converter station, such as an MMC (Modular Multilevel Converter), has the advantages of independence on an alternating current system, active and reactive independent control, no problem of commutation failure and the like. Therefore, the hybrid direct-current transmission system which integrates the advantages of the LCC converter station and the MMC converter station and takes the LCC converter station as a sending-end rectifying station and the MMC converter station as a receiving-end inverting station has wider application prospect.
For the occurrence of receiving end alternating current faults of a hybrid direct current transmission system, a control strategy is not refined according to the receiving end alternating current fault degree in the traditional technology, and the problem of overvoltage tripping of a receiving end inverter station is easily caused.
Disclosure of Invention
In view of the above, it is necessary to provide a hybrid dc power transmission system capable of solving the overvoltage trip of a receiving-end inverter station, a receiving-end ac fault ride-through method thereof, a control device, and a computer readable storage medium.
In one aspect, an embodiment of the present invention provides a receiving-end ac fault ride-through method for a hybrid dc power transmission system, where a sending end of the hybrid dc power transmission system includes an LCC-type rectifier station, a receiving end of the hybrid dc power transmission system includes an MMC-type inverter station, and the receiving-end ac fault ride-through method includes: if the hybrid direct-current power transmission system has a receiving end alternating-current fault, acquiring a receiving end alternating-current fault type; if the type of the alternating current fault at the receiving end is a serious fault and the maximum value of the average value of the capacitor voltage of each submodule of the MMC type inverter station is larger than a first preset voltage, the MMC type inverter station is locked and the LCC type rectifier station is controlled to stop transmitting electric energy until the direct current between the LCC type rectifier station and the MMC type inverter station is smaller than the preset current, the MMC type inverter station is unlocked and the LCC type rectifier station is recovered to transmit electric energy; and if the receiving end alternating current fault type is a non-serious fault, reducing the electric energy transmitted by the LCC type rectifying station according to the direct current voltage rising degree of the LCC type rectifying station.
In one embodiment, if a receiving-end ac fault occurs in the hybrid dc power transmission system, the step of obtaining the type of the receiving-end ac fault includes: acquiring three-phase positive sequence voltage at the alternating current side of the hybrid direct current transmission system; if at least one phase positive sequence voltage is lower than a second preset voltage, judging that a receiving end alternating current fault occurs in the hybrid direct current power transmission system; if at least two phases of positive sequence voltage are lower than a third preset voltage, judging that the type of the receiving end alternating current fault is a serious fault, otherwise, judging that the type of the receiving end alternating current fault is a non-serious fault; the third preset voltage is less than the second preset voltage.
In one embodiment, the step of reducing the electric energy delivered by the LCC-type rectification station according to the dc voltage increase level of the LCC-type rectification station comprises: if the direct-current voltage of the LCC type rectifying station is greater than the fourth preset voltage, determining the direct-current voltage range of the direct-current voltage of the LCC type rectifying station; setting a direct current target value of the LCC type rectifier station as a preset target value according to the direct voltage range so as to reduce the electric energy transmitted by the LCC type rectifier station; the preset target value corresponds to a direct current voltage range, and the preset target value corresponding to the direct current voltage range with high voltage is lower than the preset target value corresponding to the direct current voltage range with low voltage.
In one embodiment, the step of setting the dc target value of the LCC-type rectifier station to a preset target value according to the dc voltage range to reduce the power delivered by the LCC-type rectifier station comprises: if the direct current voltage range is the first direct current voltage range, setting the direct current target value of the LCC type rectifier station as a first preset target value; if the direct-current voltage range is the second direct-current voltage range, setting the direct-current target value of the LCC type rectifying station as a second preset target value; the voltage in the first direct current voltage range is higher than the voltage in the second direct current voltage range, and the first preset target value is lower than the second preset target value.
In one embodiment, the step of controlling the LCC-type rectification station to stop supplying electric power comprises: and increasing the trigger angle of the LCC type rectifying station to 90 degrees so as to stop transmitting the electric energy by the LCC type rectifying station.
In one embodiment, the step of unlocking the MMC inverter station and recovering the LCC-type rectifier station from transmitting electric energy until the dc current between the LCC-type rectifier station and the MMC inverter station is less than the predetermined current comprises: and unlocking the MMC type inverter station and recovering the LCC type rectifier station to transmit electric energy until the duration that the direct current between the LCC type rectifier station and the MMC type inverter station is smaller than the preset current is longer than the preset duration.
On the other hand, an embodiment of the present invention provides a hybrid dc power transmission system, where a sending end of the hybrid dc power transmission system includes an LCC-type rectification station, a receiving end of the hybrid dc power transmission system includes an MMC-type inversion station, and the hybrid dc power transmission system further includes a control module, where the control module includes a memory and a processor, where the memory stores a computer program, and the processor implements the steps of the ac fault ride-through method when executing the computer program.
In another aspect, an embodiment of the present invention provides a control device for a hybrid dc power transmission system, where a transmitting end of the hybrid dc power transmission system includes an LCC-type rectifier station, a receiving end of the hybrid dc power transmission system includes an MMC-type inverter station, and the control device includes: the receiving end alternating current fault type obtaining module is used for obtaining a receiving end alternating current fault type if a receiving end alternating current fault occurs in the hybrid direct current power transmission system; the serious fault processing module is used for locking the MMC type inverter station and controlling the LCC type rectifier station to stop transmitting electric energy if the type of the alternating-current fault of the receiving end is a serious fault and the maximum value of the average value of the capacitor voltage of each submodule of the MMC type inverter station is larger than a first preset voltage until the direct current between the LCC type rectifier station and the MMC type inverter station is smaller than a preset current, unlocking the MMC type inverter station and recovering the LCC type rectifier station to transmit the electric energy; and the non-serious fault processing module is used for reducing the electric energy transmitted by the LCC type rectifying station according to the rising degree of the direct current voltage of the LCC type rectifying station if the receiving end alternating current fault type is a non-serious fault.
In one embodiment, the receiving-end alternating current fault type acquiring module comprises a voltage acquiring unit, a first judging unit and a second judging unit; the voltage acquisition unit is used for acquiring three-phase positive sequence voltage of an alternating current side of the hybrid direct current power transmission system; the first judging unit is used for judging that a receiving end alternating current fault occurs if at least one phase positive sequence voltage is lower than a second preset voltage; the second judging unit is used for judging the type of the receiving end alternating current fault as a serious fault if at least two phases of positive sequence voltages are lower than a third preset voltage, and otherwise, judging the type of the receiving end alternating current fault as a non-serious fault; the third preset voltage is less than the second preset voltage.
In another aspect, an embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements the steps of the ac fault ride-through method described above.
Based on any one of the embodiments, the control strategy is refined according to the receiving end alternating current fault degree, and for the mixed direct current power transmission system with non-serious faults, certain power transmission is kept while the fault is successfully passed through. To mixed direct current transmission system serious fault appearing, receive end MMC type contravariant station adopts temporary shutting, and send end LCC type rectifier station stops power transmission, can effectively restrain MMC type contravariant station and continuously charge, avoids MMC type contravariant station direct current overvoltage tripping operation problem to appear.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic diagram of a hybrid dc power transmission system according to an embodiment;
FIG. 2 is a schematic flow diagram of a fault ride-through method for a hybrid DC power transmission system in accordance with an embodiment;
FIG. 3 is a schematic diagram illustrating a process for obtaining a type of a receive-side ac fault according to an embodiment;
FIG. 4 is a schematic flow chart of a computer for reducing the transmission of an LCC type rectification station in another embodiment;
fig. 5 is a block diagram of a control device of the hybrid dc power transmission system according to an embodiment.
Detailed Description
To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another.
Spatial relational terms, such as "under," "below," "under," "over," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "under" can encompass both an orientation of above and below. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations) and the spatial descriptors used herein interpreted accordingly.
It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or be connected to the other element through intervening elements. Further, "connection" in the following embodiments is understood to mean "electrical connection", "communication connection", or the like, if there is a transfer of electrical signals or data between the connected objects.
As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, as used in this specification, the term "and/or" includes any and all combinations of the associated listed items.
Fig. 1 is a schematic diagram of a hybrid dc power transmission system to which the present invention is directed, a transmitting end of the hybrid dc power transmission system includes an LCC type rectification station, and a receiving end of the hybrid dc power transmission system includes an MMC type inversion station. The sending end of the hybrid direct-current transmission system is connected with power generation facilities such as a power station and a wind power plant, alternating current generated by the power generation facilities is rectified by the LCC type rectifier station to be converted into direct current, the direct current is transmitted to the receiving end of the hybrid direct-current transmission system through a direct-current cable between the sending end of the hybrid direct-current transmission system and the receiving end of the hybrid direct-current transmission system, and the MMC type inverter station inverts the received direct current to be converted into alternating current and transmits the alternating current to an alternating-current power grid.
As shown in fig. 2, a receiving ac fault ride-through method for a hybrid dc power transmission system according to an embodiment of the present invention includes steps S202 to S206.
S202, if the hybrid direct current power transmission system has a receiving end alternating current fault, obtaining a receiving end alternating current fault type.
Specifically, a receiving-end alternating-current fault refers to that an alternating-current power grid connected with a receiving end of a hybrid direct-current power transmission system fails, which causes that electric energy transmitted to the alternating-current power grid by the receiving end of the hybrid direct-current power transmission system is limited, at the moment, a transmitting end of the hybrid direct-current power transmission system still continuously transmits electric energy to the receiving end of the hybrid direct-current power transmission system, unbalanced power which cannot be transmitted can cause an overvoltage problem to occur to an MMC (modular multilevel converter) inversion station, even the MMC inversion station can be tripped, and then the whole hybrid direct-current power transmission system is broken down. When receiving-end ac faults of different severity are encountered, a specific fault ride-through strategy should be adopted, so the present embodiment classifies the types of receiving-end ac faults into severe faults and non-severe faults according to the severity of the receiving-end ac faults.
And S204, if the alternating current fault type of the receiving end is a serious fault and the maximum value of the mean value of the capacitor voltage of each sub-module of the MMC type inverter station is larger than a first preset voltage, the MMC type inverter station is locked and the LCC type rectifier station is controlled to stop transmitting electric energy until the direct current between the LCC type rectifier station and the MMC type inverter station is smaller than the preset current, the MMC type inverter station is unlocked and the transmission power of the LCC type rectifier station is recovered.
It can be understood that the MMC inverter station includes a plurality of sub-modules, each sub-module includes a capacitor, a power electronic power device, and the like, and the capacitors in the sub-modules are charged and discharged when the hybrid dc power transmission system normally transmits electric energy to the ac power grid. The average value of the sub-module capacitance voltage can be used for evaluating whether the capacitance and the power electronic power device in the sub-module are damaged by high voltage. Under the condition that the type of the receiving-end alternating current fault is a serious fault, the sending end of the hybrid direct current transmission system cannot transmit electric energy to an alternating current power grid, and the voltage of a submodule of the MMC type inverter station can rise rapidly. Therefore, under the condition that the receiving end alternating current fault type is judged to be a serious fault, the average value of the capacitor voltage of each sub-module of the MMC type inverter station is obtained, and the fact that the maximum value of the average value of the capacitor voltage of each sub-module is larger than the first preset voltage means that the voltage of the sub-module is too high, and damage to the MMC inverter station can be caused.
This embodiment is through shutting MMC type contravariant station for the charging channel of submodule piece electric capacity in MMC contravariant station is closed, prevents that submodule piece electric capacity voltage from continuing to rise. The first preset voltage may be selected according to a withstand voltage of a device in the sub-module, for example, a rated voltage of an IGBT device in the sub-module is 4.5kV, and the first preset voltage may be selected to be 3 kV. Meanwhile, as the MMC inverter station at the receiving end of the hybrid direct-current transmission system is locked, the receiving end of the hybrid direct-current transmission system cannot receive electric energy, the LCC rectifier station is controlled to stop transmitting the electric energy by the embodiment, so that the electric energy source of the receiving end of the hybrid direct-current transmission system is cut off, and the safety of the hybrid direct-current transmission system is protected. The fact that the direct current between the LCC type rectifying station and the MMC type inverter station is smaller than the preset current means that alternating current faults are eliminated, the hybrid direct current transmission system can recover normal transmission, and therefore the MMC type inverter station is unlocked and the LCC type rectifying station is controlled to recover transmission power.
And S206, if the receiving end alternating current fault type is a non-serious fault, reducing the electric energy transmitted by the LCC type rectifying station according to the direct current voltage increasing degree of the LCC type rectifying station.
Under the condition that the type of the alternating current fault at the receiving end is a non-serious fault, the sending end of the hybrid direct current transmission system can still output certain electric energy to the alternating current power grid, so that the rising speed of the voltage of the sub-modules of the MMC type inversion station is slower than that of the voltage when the type of the alternating current fault at the receiving end is a serious fault, and the rising of the voltage of the sub-modules of the MMC type inversion station can be restrained only by reducing the electric energy transmitted by the LCC type rectification station. Specifically, the more the direct-current voltage of the LCC type rectifier station exceeds the direct-current voltage during normal operation, the more the power that the MMC type inverter station cannot deliver in the power output by the LCC type rectifier station, the more the LCC type rectifier station should be controlled to correspondingly reduce the power delivered to the MMC type inverter station.
Based on the receiving end alternating current fault ride-through method of the hybrid direct current transmission system in the embodiment, the control strategy is refined according to the receiving end alternating current fault degree, and for the hybrid direct current transmission system with non-serious faults, certain power is kept to be sent out while the fault successful ride-through is ensured. To mixed direct current transmission system serious fault appearing, receive end MMC type contravariant station adopts temporary shutting, and send end LCC type rectifier station stops power transmission, can effectively restrain MMC type contravariant station and continuously charge, avoids MMC type contravariant station direct current overvoltage tripping operation problem to appear.
In one embodiment, as shown in fig. 3, step S202 includes steps S302 to S306.
And S302, acquiring three-phase positive sequence voltage of the alternating current side of the hybrid direct current transmission system.
It is understood that the ac side of the hybrid dc transmission system refers to the ac grid to which the hybrid dc transmission system is connected. When the alternating current power grid fails, the three-phase positive sequence voltage obtained by decomposing the three-phase voltage of the alternating current power grid according to the symmetrical component method is abnormal, and the severity of the receiving end alternating current fault is related to the abnormality of the three-phase positive sequence voltage on the alternating current side. Therefore, the receiving end alternating current fault condition can be judged according to the three-phase positive sequence voltage on the alternating current side.
And S304, if the voltage of at least one phase positive sequence is lower than a second preset voltage, judging that the hybrid direct current power transmission system has a receiving end alternating current fault.
It can be understood that when any phase of the ac power grid fails, such as a short circuit, the voltage drop phenomenon occurs in the phase voltage of the failed phase line, so that when the positive sequence voltage of at least one phase is lower than the second preset voltage, it can be determined that the receiving end ac fault occurs in the hybrid dc power transmission system. The second predetermined voltage may be set according to a nominal voltage of the ac power grid, for example, the second predetermined voltage is selected to be 0.9 times the nominal voltage of the ac power grid.
And S306, if at least two phases of positive sequence voltage are lower than the third preset voltage, judging that the type of the receiving end alternating current fault is a serious fault, and otherwise, judging that the type of the receiving end alternating current fault is a non-serious fault.
And the third preset voltage is smaller than the second preset voltage. After the hybrid direct current power transmission system is determined to have the receiving end alternating current fault according to the conditions in the step S304, the type of the receiving end alternating current fault is further determined. The fact that the positive sequence voltage of any phase line is lower than the second preset voltage reflects that the phase line has a serious voltage drop phenomenon, and the fact that at least two phases of the alternating current power grid have the serious voltage drop phenomenon reflects that the type of the alternating current fault at the receiving end is a serious fault. The remaining receive ac faults may be determined to be non-critical faults. The third predetermined voltage may also be set according to the nominal voltage of the ac power supply system, for example, the third predetermined voltage is selected to be 0.2 times the nominal voltage of the ac power supply system.
In one embodiment, as shown in fig. 4, the step of reducing the power supplied by the LCC type rectification station according to the dc voltage increase degree of the LCC type rectification station in step S204 includes step S402 and step S404.
And S402, if the direct-current voltage of the LCC type rectifying station is greater than the fourth preset voltage, determining the direct-current voltage range of the direct-current voltage of the LCC type rectifying station.
It can be understood that the fact that the direct-current voltage of the LCC type rectifying station is greater than the fourth preset voltage reflects that the direct-current voltage of the LCC type rectifying station exceeds the direct-current voltage during normal operation more. The fourth preset voltage may be determined according to a rated voltage of the dc cable of the hybrid dc transmission system, for example, the fourth preset voltage is selected to be 1.03 times the rated voltage of the dc cable of the hybrid dc transmission system.
And S404, setting the direct current target value of the LCC type rectifying station as a preset target value according to the direct current voltage range so as to reduce the electric energy transmitted by the LCC type rectifying station.
The preset target value corresponds to a dc voltage range, that is, each dc voltage range corresponds to a preset target value. The preset target value corresponding to the direct current voltage range with high voltage is lower than the preset target value corresponding to the direct current voltage range with low voltage. Specifically, any dc voltage value in the dc voltage range with a high voltage will be greater than the dc voltage value in the dc voltage range with a low voltage. The power is the product of direct current voltage and direct current, and a lower direct current target value is selected when the direct current voltage is higher, so that the electric energy transmitted by the LCC type rectifier station can be reduced.
In one embodiment, step S404 includes step S404A and step S404B.
S404A, if the dc voltage range is the first dc voltage range, setting the dc target value of the LCC-type rectifying station as a first preset target value.
The first preset target value is a preset target value corresponding to the first direct current voltage range.
S404B, if the dc voltage range is the second dc voltage range, setting the dc target value of the LCC-type rectifier station as the second preset target value.
The voltage in the first direct current voltage range is higher than the voltage in the second direct current voltage range, and the first preset target value is lower than the second preset target value. The second preset target value is a preset target value corresponding to the second direct-current voltage range. In one embodiment, if the DC cable of the hybrid DC power transmission system has a rated voltage of UNThe rated direct current target value of the LCC type rectifier station is INThe first DC voltage range is 1.03UNTo 1.1UNThe second DC voltage range is greater than 1.1UNThe first preset target value is 0.5INThe second preset target value is 0.1IN。
In one embodiment, the step of controlling the LCC-type rectifier station to stop supplying power in step S204 includes: and the trigger angle of the LCC type rectifying station is increased to 90 degrees, so that the LCC type rectifying station stops transmitting electric energy. According to the working principle of the LCC type rectifying station, the trigger angle of the LCC type rectifying station can affect the working state and the output power of the LCC type rectifying station, and when the trigger angle of the LCC type rectifying station is increased to 90 degrees, the LCC type rectifying station rapidly shifts the phase to interrupt the output electric energy to the MMC type inverter station. When the output power of the LCC type rectifying station needs to be recovered subsequently, the trigger angle is changed according to the working mode of the LCC type rectifying station.
In one embodiment, the step of unlocking the MMC inverter station and recovering the power delivered by the LCC-type rectifier station until the dc current between the LCC-type rectifier station and the MMC inverter station is less than the preset current comprises: and unlocking the MMC type inverter station and recovering the power transmitted by the LCC type rectifier station until the duration that the direct current between the LCC type rectifier station and the MMC type inverter station is smaller than the preset current is longer than the preset duration. It can be understood that, in order to prevent the occurrence of misjudgment caused by the fluctuation of the direct current, the present embodiment unlocks the MMC inverter station and recovers the power delivered by the LCC rectifier station only when the direct current is less than the preset current for a period of time. In one embodiment, the predetermined time period is 10 ms.
It should be understood that although the various steps in the flowcharts of fig. 2-4 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 2-4 may include multiple steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of performing the steps or stages is not necessarily sequential, but may be performed alternately or alternatively with other steps or at least some of the other steps or stages.
Referring to fig. 1, a sending end of the hybrid dc power transmission system includes an LCC-type rectifier station, a receiving end of the hybrid dc power transmission system includes an MMC-type inverter station, and the hybrid dc power transmission system further includes a control module, the control module includes a memory and a processor, the memory stores a computer program, and the processor implements the steps of the ac fault ride-through method in any of the embodiments when executing the computer program.
In one embodiment, the control module comprises a receiving end controller and a sending end controller, wherein the sending end controller comprises a first memory and a first processor, the first memory stores a first computer program, the receiving end controller comprises a second memory and a second processor, and the second memory stores a second computer program. The sending end controller is in communication connection with the receiving end controller, the sending end controller is used for controlling the LCC rectifier, and the first processor realizes the following when executing a first computer program: under the condition of receiving a first control instruction, controlling the LCC rectifier to stop transmitting electric energy until the direct current between the LCC rectifier station and the MMC inverter station is smaller than the preset current to recover the LCC rectifier to transmit electric energy; and when receiving a second control instruction, reducing the electric energy transmitted by the LCC type rectifying station according to the DC voltage increasing degree of the LCC type rectifying station.
The receiving end controller is used for controlling the MMC type inverter station, and the second processor executes a second computer program to realize the following steps: if the hybrid direct-current power transmission system has a receiving end alternating-current fault, acquiring a receiving end alternating-current fault type; if the type of the alternating current fault at the receiving end is a serious fault and the maximum value of the average value of the capacitor voltage of each submodule of the MMC type inverter station is greater than a first preset voltage, the MMC type inverter station is locked and a first control instruction is sent to a sending end controller until the direct current between the LCC type rectifying station and the MMC type inverter station is smaller than the preset current to unlock the MMC type inverter station; and if the type of the receiving end alternating current fault is a non-serious fault, sending a second control instruction to the first controller.
In one embodiment, the second processor, when executing the second computer program, implements: acquiring three-phase positive sequence voltage of an alternating current side of the hybrid direct current power transmission system; if at least one phase positive sequence voltage is lower than a second preset voltage, judging that a receiving end alternating current fault occurs in the hybrid direct current power transmission system; if at least two phases of positive sequence voltage are lower than a third preset voltage, judging that the type of the receiving end alternating current fault is a serious fault, otherwise, judging that the type of the receiving end alternating current fault is a non-serious fault; the third preset voltage is less than the second preset voltage.
In one embodiment, the second processor, when executing the second computer program, implements: and unlocking the MMC type inverter station and recovering the LCC type rectifier station to transmit electric energy until the duration that the direct current between the LCC type rectifier station and the MMC type inverter station is smaller than the preset current is longer than the preset duration.
In one embodiment, the first processor, when executing the first computer program, implements: if the direct-current voltage of the LCC type rectifying station is greater than the fourth preset voltage, determining the direct-current voltage range of the direct-current voltage of the LCC type rectifying station; setting a direct current target value of the LCC type rectifier station as a preset target value according to the direct voltage range so as to reduce the electric energy transmitted by the LCC type rectifier station; the preset target value corresponds to a direct current voltage range, and the preset target value corresponding to the direct current voltage range with high voltage is lower than the preset target value corresponding to the direct current voltage range with low voltage.
In one embodiment, the first processor, when executing the first computer program, implements: if the direct current voltage range is the first direct current voltage range, setting the direct current target value of the LCC type rectifier station as a first preset target value; if the direct-current voltage range is the second direct-current voltage range, setting the direct-current target value of the LCC type rectifier station as a second preset target value; the voltage in the first direct current voltage range is higher than the voltage in the second direct current voltage range, and the first preset target value is lower than the second preset target value.
In one embodiment, the first processor, when executing the first computer program, implements: and the trigger angle of the LCC type rectifying station is increased to 90 degrees, so that the LCC type rectifying station stops transmitting electric energy.
Referring to fig. 1 and fig. 5, an embodiment of the present invention provides a control apparatus for a hybrid dc power transmission system, where a transmitting end of the hybrid dc power transmission system includes an LCC-type rectifying station, a receiving end of the hybrid dc power transmission system includes an MMC-type inverting station, and the control apparatus includes a receiving end ac fault type obtaining module 10, a severe fault processing module 30, and a non-severe fault processing module 50. The receiving-end ac fault type obtaining module 10 is configured to obtain a receiving-end ac fault type if a receiving-end ac fault occurs in the hybrid dc power transmission system. The major fault processing module 30 is configured to, if the receiving-end ac fault type is a major fault and the maximum value of the average value of the capacitor voltages of the sub-modules of the MMC inverter station is greater than a first preset voltage, lock the MMC inverter station and control the LCC rectifier station to stop transmitting electric energy until the dc current between the LCC rectifier station and the MMC inverter station is less than a preset current, unlock the MMC inverter station, and recover the transmission power of the LCC rectifier station. The non-critical fault processing module 50 is configured to reduce the electric energy transmitted by the LCC-type rectification station according to the dc voltage increase degree of the LCC-type rectification station if the receiving-end ac fault type is a non-critical fault.
In one embodiment, the receiving-end alternating current fault type acquiring module comprises a voltage acquiring unit, a first judging unit and a second judging unit. The voltage acquisition unit is used for acquiring three-phase positive sequence voltage on the alternating current side of the hybrid direct current power transmission system. The first judging unit is used for judging that the receiving end alternating current fault occurs if at least one phase positive sequence voltage is lower than a second preset voltage. The second judging unit is used for judging the type of the receiving end alternating current fault as a serious fault if at least two phases of positive sequence voltages are lower than a third preset voltage, and otherwise, judging the type of the receiving end alternating current fault as a non-serious fault. The third preset voltage is less than the second preset voltage.
In one embodiment, the critical fault handling module includes a direct voltage range determination unit and a direct current target value setting unit. The direct-current voltage range determining unit is used for determining the direct-current voltage range of the direct-current voltage of the LCC type rectifying station if the direct-current voltage of the LCC type rectifying station is larger than the fourth preset voltage. The direct current target value setting unit is used for setting the direct current target value of the LCC type rectifying station as a preset target value according to the direct voltage range so as to reduce the electric energy transmitted by the LCC type rectifying station. The preset target value corresponds to a direct current voltage range, and the preset target value corresponding to the direct current voltage range with high voltage is lower than the preset target value corresponding to the direct current voltage range with low voltage.
In an embodiment, the dc current target value setting unit is configured to set the dc current target value of the LCC-type rectifying station to a first preset target value if the dc voltage range is the first dc voltage range. And if the direct current voltage range is the second direct current voltage range, setting the direct current target value of the LCC type rectifying station as a second preset target value. The voltage in the first direct current voltage range is higher than the voltage in the second direct current voltage range, and the first preset target value is lower than the second preset target value.
In one embodiment, the non-critical fault handling module comprises a firing angle setting unit. The trigger angle setting unit is used for increasing the trigger angle of the LCC type rectifying station to 90 degrees so as to stop the LCC type rectifying station from transmitting electric energy.
In one embodiment, the critical fault handling module is configured to unlock the MMC inverter station and restore the LCC rectifier station to deliver electrical energy until a duration of the dc current between the LCC rectifier station and the MMC inverter station being less than a predetermined current is greater than a predetermined duration.
For specific limitations of the control device of the hybrid dc power transmission system, reference may be made to the above limitations of the fault ride-through method of the hybrid dc power transmission system, which are not described herein again. All or part of each module in the control device of the hybrid direct current power transmission system can be realized by software, hardware and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules. It should be noted that, in the embodiment of the present application, the division of the module is schematic, and is only one logic function division, and there may be another division manner in actual implementation.
Embodiments of the present invention provide a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements the steps of the ac fault ride-through method in any of the above embodiments.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware related to instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in the embodiments provided herein can include at least one of non-volatile and volatile memory. Non-volatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical storage, or the like. Volatile Memory can include Random Access Memory (RAM) or external cache Memory. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), among others.
In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., 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, schematic depictions of the above terms do not necessarily refer to the same embodiment or example.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above examples only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. A receiving end alternating current fault ride-through method of a hybrid direct current transmission system is disclosed, wherein a sending end of the hybrid direct current transmission system comprises an LCC type rectifier station, and a receiving end of the hybrid direct current transmission system comprises an MMC type inverter station, and the receiving end alternating current fault ride-through method comprises the following steps:
if the hybrid direct-current power transmission system has a receiving end alternating-current fault, acquiring a receiving end alternating-current fault type;
if the type of the receiving-end alternating-current fault is a serious fault and the maximum value of the mean value of the capacitor voltage of each sub-module of the MMC type inverter station is larger than a first preset voltage, the MMC type inverter station is locked and the LCC type rectifier station is controlled to stop transmitting electric energy until the direct current between the LCC type rectifier station and the MMC type inverter station is smaller than a preset current, the MMC type inverter station is unlocked and the LCC type rectifier station is recovered to transmit electric energy;
and if the receiving end alternating current fault type is a non-serious fault, reducing the electric energy transmitted by the LCC type rectifying station according to the direct current voltage increasing degree of the LCC type rectifying station.
2. The receiving end alternating current fault ride-through method according to claim 1, wherein the step of obtaining a receiving end alternating current fault type if the hybrid direct current power transmission system has a receiving end alternating current fault comprises:
acquiring three-phase positive sequence voltage of an alternating current side of the hybrid direct current power transmission system;
if at least one phase positive sequence voltage is lower than a second preset voltage, judging that the receiving end alternating current fault occurs in the hybrid direct current power transmission system;
if at least two phases of positive sequence voltages are lower than a third preset voltage, judging that the type of the receiving end alternating current fault is a serious fault, otherwise, judging that the type of the receiving end alternating current fault is a non-serious fault; the third preset voltage is less than the second preset voltage.
3. The method for fault ride-through according to claim 1, wherein the step of reducing the power delivered by the LCC-type rectifier station according to the dc voltage boost level of the LCC-type rectifier station comprises:
if the direct-current voltage of the LCC type rectifying station is greater than a fourth preset voltage, determining the direct-current voltage range of the direct-current voltage of the LCC type rectifying station;
setting a direct current target value of the LCC type rectifier station as a preset target value according to the direct voltage range so as to reduce the electric energy transmitted by the LCC type rectifier station; the preset target value corresponds to the direct-current voltage range, and the preset target value corresponding to the direct-current voltage range with high voltage is lower than the preset target value corresponding to the direct-current voltage range with low voltage.
4. The method for receiving ac fault ride-through according to claim 3, wherein the step of setting the dc target value of the LCC-type rectification station to a preset target value according to the dc voltage range to reduce the power transmitted by the LCC-type rectification station comprises:
if the direct-current voltage range is the first direct-current voltage range, setting the direct-current target value of the LCC type rectifying station as a first preset target value;
if the direct-current voltage range is a second direct-current voltage range, setting the direct-current target value of the LCC type rectifying station as a second preset target value; wherein the voltage in the first direct voltage range is higher than the voltage in the second direct voltage range, and the first preset target value is lower than the second preset target value.
5. The terminated ac fault ride-through method of claim 1, wherein the step of controlling the LCC-type rectification station to stop delivering power comprises:
and increasing the trigger angle of the LCC type rectifying station to 90 degrees so as to stop the LCC type rectifying station from transmitting electric energy.
6. The receiving-end alternating current fault ride-through method according to claim 1, wherein the step of unlocking the MMC inverter station and recovering the LCC rectifier station from transmitting electric energy until the direct current between the LCC rectifier station and the MMC inverter station is less than a preset current comprises:
and until the duration that the direct current between the LCC type rectifier station and the MMC type inverter station is less than the preset current is longer than the preset duration, unlocking the MMC type inverter station and recovering the LCC type rectifier station to transmit electric energy.
7. A hybrid dc power transmission system, the transmitting end of which comprises an LCC-type rectifying station and the receiving end of which comprises an MMC inverter station, characterized by a control module comprising a memory and a processor, the memory storing a computer program, the processor implementing the steps of the ac fault ride-through method of any one of claims 1 to 6 when executing the computer program.
8. The utility model provides a controlling means of hybrid direct current transmission system, hybrid direct current transmission system's send end includes LCC type rectifier station, hybrid direct current transmission system's receive end includes MMC type inverter station, its characterized in that, controlling means includes:
a receiving end alternating current fault type obtaining module, configured to obtain a receiving end alternating current fault type if a receiving end alternating current fault occurs in the hybrid direct current power transmission system;
the serious fault processing module is used for locking the MMC type inverter station and controlling the LCC type rectifier station to stop transmitting electric energy if the receiving end alternating current fault type is a serious fault and the maximum value of the average value of the capacitor voltage of each submodule of the MMC type inverter station is larger than a first preset voltage until the direct current between the LCC type rectifier station and the MMC type inverter station is smaller than a preset current, unlocking the MMC type inverter station and recovering the LCC type rectifier station to transmit electric energy;
and the non-serious fault processing module is used for reducing the electric energy transmitted by the LCC type rectifying station according to the rising degree of the direct-current voltage of the LCC type rectifying station if the receiving end alternating-current fault type is a non-serious fault.
9. The control device according to claim 8, wherein the receiving-end ac fault type acquisition module includes a voltage acquisition unit, a first determination unit, and a second determination unit;
the voltage acquisition unit is used for acquiring an alternating-current side three-phase positive sequence voltage of the hybrid direct-current power transmission system;
the first judging unit is used for judging that the receiving end alternating current fault occurs in the hybrid direct current power transmission system if at least one phase positive sequence voltage is lower than a second preset voltage;
the second judging unit is used for judging that the type of the receiving end alternating current fault is a serious fault if at least two phases of positive sequence voltages are lower than a third preset voltage, and otherwise, judging that the type of the receiving end alternating current fault is a non-serious fault; the third preset voltage is less than the second preset voltage.
10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the ac fault ride-through method of any one of claims 1 to 6.
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CN106058826A (en) * 2016-06-03 2016-10-26 南京南瑞继保电气有限公司 Method for handling failure of alternating current side of invertor side of mixed-type direct current transmission system
CN109066759A (en) * 2018-08-16 2018-12-21 重庆大学 Take into account the continuous commutation failure control method of mixing double feed-in d. c. power transmission system of electric network active balance
CN110571840A (en) * 2019-09-04 2019-12-13 中国电力科学研究院有限公司 Sending end fault ride-through control method and device for LCC-MMC power transmission system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106058826A (en) * 2016-06-03 2016-10-26 南京南瑞继保电气有限公司 Method for handling failure of alternating current side of invertor side of mixed-type direct current transmission system
CN109066759A (en) * 2018-08-16 2018-12-21 重庆大学 Take into account the continuous commutation failure control method of mixing double feed-in d. c. power transmission system of electric network active balance
CN110571840A (en) * 2019-09-04 2019-12-13 中国电力科学研究院有限公司 Sending end fault ride-through control method and device for LCC-MMC power transmission system

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