CN111654050B - Direct current transmission system starting method and device - Google Patents
Direct current transmission system starting method and device Download PDFInfo
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- CN111654050B CN111654050B CN202010360372.0A CN202010360372A CN111654050B CN 111654050 B CN111654050 B CN 111654050B CN 202010360372 A CN202010360372 A CN 202010360372A CN 111654050 B CN111654050 B CN 111654050B
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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
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
The invention discloses a method for starting a direct current transmission system, which is suitable for a strength judging device of a direct current transmission converter station access system, and comprises the following steps: monitoring the running state of the alternating current system in real time; the running state comprises the running state of a short-circuit current element at the side of the alternating current system, a grid structure of a near-zone alternating current system of the direct current transmission converter station, the switching of a generator and the change of the capacity; determining the system strength of the alternating current system according to the running state of the alternating current system; according to the system strength, the starting power and the starting control strategy of the direct current system are selected, and a corresponding starting control strategy type instruction is sent to the control system of the direct current transmission converter station, so that the control system responds to the starting control strategy type instruction to start the direct current transmission system, the direct current transmission system can be started in a targeted manner, the impact on the alternating current system when the direct current transmission system is started is avoided, and the stability of the alternating current system is greatly improved. The invention also discloses a starting device of the direct current transmission system.
Description
Technical Field
The invention relates to the technical field of direct current transmission, in particular to a method and a device for starting a direct current transmission system.
Background
In recent years, high-voltage power transmission technology is rapidly developed, and the high-voltage power transmission plays more and more important roles in the fields of long-distance and large-capacity power transmission and urban central area power transmission. When a weak alternating current system is connected by high-voltage direct current transmission, such as an island alternating current power grid, a typical 'large direct current and small alternating current' situation is formed because the load proportion of the power transmitted by a direct current system to the weak alternating current power grid is higher, and the frequency stability of the weak alternating current power grid is directly influenced by the operation of the direct current system.
At present, most of conventional high-voltage direct-current power transmission is connected to a stronger alternating-current system, and the direct-current system is started by adopting 10% rated power. When starting, the rated direct current voltage and 10% rated current are adopted, then the direct current is gradually increased to the rated value according to a certain speed, and the starting process is completed. For a stronger alternating current system, when the direct current system is started by adopting 10% rated power, the frequency fluctuation of the alternating current system is smaller. However, for a weak alternating current system, the direct current system is started by adopting 10% of rated power, so that huge impact is generated on the alternating current system, the requirement of alternating current power grid frequency fluctuation limitation is difficult to meet, and the alternating current power grid is unstable. Therefore, in order to maintain the weak ac system stable, the start-up power of the dc system should be reduced. Meanwhile, in order to prevent the interruption of the dc current, the dc current is generally not less than 10%, so the starting power of the dc system needs to be reduced by reducing the dc voltage.
In addition, the strength of the alternating current system is constantly changed according to the grid structure and the change of the switching state of the generator. When most alternating current inlet wires are connected and the generator is put in, the alternating current system is strong, the short circuit ratio is large, and large starting power can be selected at the moment. When part of the alternating current inlet wires are not connected and the generator is not switched in, the alternating current system is weak, the short-circuit ratio is small, and if a large starting power is still selected, the system may be unstable. Therefore, the adaptive starting power and starting method of the direct current transmission system need to be researched according to the change of the intensity of the alternating current system, so that the requirement of safe and stable operation of a power grid is met in the starting process of the direct current system.
Disclosure of Invention
The embodiment of the invention provides a method and a device for starting a direct current power transmission system, which can realize the targeted starting of the direct current power transmission system, avoid the impact on an alternating current system when the direct current power transmission system is started, and greatly improve the stability of the alternating current system.
An embodiment of the present invention provides a method for starting a dc power transmission system, which is applicable to a strength determination device for an access system of a dc power transmission converter station, and the method includes:
monitoring the running state of the alternating current system in real time; the running state of the alternating current system comprises the running state of a short-circuit current element on the alternating current system side, a grid structure of a near-zone alternating current system of the direct current transmission converter station, switching of a generator and change of capacity;
determining the system strength of the communication system according to the running state of the communication system;
and selecting the starting power and the starting control strategy of the direct current system according to the system strength of the alternating current system, and sending a corresponding starting control strategy type instruction to the control system of the direct current transmission converter station so that the control system responds to the starting control strategy type instruction to start the direct current transmission system.
As an improvement of the above scheme, the determining the system strength of the communication system according to the operation state of the communication system specifically includes:
when the fact that the connected alternating current inlet wire does not exceed a first inlet wire connection threshold or the input generator does not exceed a first generator input threshold is detected, the alternating current system is judged to be an extremely weak system;
when detecting that the connected alternating current incoming line exceeds the first incoming line connection threshold and does not exceed a second incoming line connection threshold, or the input generator exceeds the first generator input threshold and does not exceed a second generator input threshold, judging that the alternating current system is a weak system;
and when the connected alternating current inlet wire is detected to exceed the second inlet wire connection threshold value and the input generator exceeds the second generator input threshold value, judging that the alternating current system is a strong system.
As an improvement of the above scheme, the selecting, according to the system strength of the ac system, a dc system startup power and a startup control strategy, and sending a corresponding startup control strategy type instruction to the control system of the dc transmission converter station, so that the control system starts the dc transmission system in response to the startup control strategy type instruction, includes:
when the alternating current system is a strong system, selecting the starting power of the direct current system as a first power, generating a first control instruction, sending the first control instruction to the control system, so that the control system responds to the first control instruction, starts the direct current transmission system according to a first direct current voltage and a first direct current corresponding to the first power, and then gradually increases the first direct current to a preset rated direct current; the first direct current voltage is a preset rated direct current voltage, and the first power is smaller than a preset rated power.
As an improvement of the above scheme, the selecting, according to the system strength of the ac system, a dc system startup power and a startup control strategy, and sending a corresponding startup control strategy type instruction to the control system of the dc transmission converter station, so that the control system starts the dc transmission system in response to the startup control strategy type instruction, further includes:
when the alternating current system is a weak system, selecting the starting power of the direct current system as a second power, generating a second control instruction, sending the second control instruction to the control system, so that the control system responds to the second control instruction, starting the direct current power transmission system according to a second direct current voltage and a second direct current corresponding to the second power, keeping the second direct current voltage within a first preset time period after starting, further increasing the second direct current voltage to the rated direct current voltage, and gradually increasing the second direct current to the rated direct current; wherein the second power is less than the first power.
As an improvement of the above scheme, the selecting, according to the system strength of the ac system, a dc system startup power and a startup control strategy, and sending a corresponding startup control strategy type instruction to the control system of the dc transmission converter station, so that the control system starts the dc transmission system in response to the startup control strategy type instruction, further includes:
when the alternating current system is an extremely weak system, selecting the starting power of the direct current system as a third power, generating a third control instruction, sending the third control instruction to the control system, so that the control system responds to the third control instruction, starting the direct current power transmission system according to a third direct current voltage and a third direct current corresponding to the third power, keeping the third direct current voltage for a second preset time after starting, further increasing the third direct current voltage to the rated direct current voltage, and gradually increasing the third direct current to the rated direct current; wherein the third power is less than the second power.
The invention correspondingly provides a direct current transmission system starting device, which comprises a strength judging device and a control system of a direct current transmission converter station access system;
the intensity judging device comprises a real-time monitoring module, a system intensity judging module and a starting control strategy selecting module;
the real-time monitoring module is used for monitoring the running state of the alternating current system in real time; the running state of the alternating current system comprises the running state of a short-circuit current element on the alternating current system side, a grid structure of a near-zone alternating current system of the direct current transmission converter station, switching of a generator and change of capacity;
the system intensity judging module is used for determining the system intensity of the alternating current system according to the running state of the alternating current system;
the starting control strategy selection module is used for selecting the starting power and the starting control strategy of the direct current system according to the system strength of the alternating current system and sending a corresponding starting control strategy type instruction to the control system of the direct current transmission converter station;
the control system comprises a control module; and the control module is used for responding to the control strategy type starting instruction and starting the direct current power transmission system.
As an improvement of the above scheme, the system strength determination module includes an extremely weak system determination unit, a weak system determination unit, and a strong system determination unit;
the weak system judging unit is used for judging that the alternating current system is a weak system when the fact that the connected alternating current inlet wire does not exceed a first inlet wire connection threshold or the input generator does not exceed a first generator input threshold is detected;
the weak system judging unit is used for judging that the alternating current system is a weak system when detecting that the connected alternating current inlet wire exceeds the first inlet wire connection threshold and does not exceed a second inlet wire connection threshold or the input generator exceeds the first generator input threshold and does not exceed a second generator input threshold;
and the strong system judging unit is used for judging that the alternating current system is a strong system when the connected alternating current inlet wire is detected to exceed the second inlet wire connection threshold and the input generator exceeds the second generator input threshold.
As an improvement of the above scheme, the start control strategy selection module includes a first start control strategy selection unit; the first starting control strategy selecting unit is used for selecting the starting power of the direct current system as a first power when the alternating current system is a strong system, generating a first control instruction and sending the first control instruction to the control system;
the control module comprises a first starting control unit; the first starting control unit is used for responding to the first control instruction, starting the direct current power transmission system according to a first direct current voltage and a first direct current corresponding to the first power, and gradually increasing the first direct current to a preset rated direct current; the first direct current voltage is a preset rated direct current voltage, and the first power is smaller than a preset rated power.
As an improvement of the above scheme, the start control strategy selection module includes a second start control strategy selection unit; the second starting control strategy selecting unit is used for selecting the starting power of the direct current system as a second power when the alternating current system is a weak system, generating a second control instruction and sending the second control instruction to the control system;
the control module comprises a second starting control unit; the second start control unit is configured to start the dc power transmission system according to a second dc voltage and a second dc current corresponding to the second power in response to the second control instruction, maintain the second dc voltage for a first preset time period after the start, further increase the second dc voltage to the rated dc voltage, and gradually increase the second dc current to the rated dc current; wherein the second power is less than the first power.
As an improvement of the above scheme, the start control strategy selection module includes a third start control strategy selection unit; the third start control strategy selecting unit is used for selecting the start power of the direct current system as a third power when the alternating current system is an extremely weak system, generating a third control instruction and sending the third control instruction to the control system;
the control module comprises a third starting control unit; the third start control unit is configured to start the dc power transmission system according to a third dc voltage and a third dc current corresponding to the third power in response to the third control instruction, maintain the third dc voltage for a second preset time period after the start, further increase the third dc voltage to the rated dc voltage, and gradually increase the third dc current to the rated dc current; wherein the third power is less than the second power.
Compared with the prior art, the embodiment of the invention discloses a method and a device for starting a direct current transmission system, which have the following beneficial effects:
by monitoring the running state of an alternating current system in real time, wherein the running state of the alternating current system comprises the running state of a short-circuit current element at the side of the alternating current system, the grid structure of an alternating current system in the vicinity of a direct current transmission converter station, the switching of a generator and the change of the capacity, the system strength of the alternating current system is determined according to the running state of the alternating current system, the starting power and the starting control strategy of the direct current system are selected according to the system strength of the alternating current system, and then a corresponding starting control strategy type instruction is sent to a control system of the direct current transmission converter station, so that the control system responds to the starting control strategy type instruction to start the direct current transmission system, different starting powers and strategies can be selected according to the strength of the alternating current system when the running mode of the alternating current system changes, and the targeted starting of the direct current transmission system is realized, the impact on the alternating current system when the direct current transmission system is started is avoided, and the stability of the alternating current system is greatly improved.
Drawings
Fig. 1 is a schematic flowchart of a dc power transmission system starting method according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a dc power transmission system connected to an ac power grid according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a dc power transmission system starting apparatus according to a second embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
Fig. 1 is a schematic flow chart of a method for starting a dc power transmission system according to an embodiment of the present invention, where the method is applied to a strength determination device of an access system of a dc power transmission converter station. The method comprises steps S101 to S103.
S101, monitoring the running state of the alternating current system in real time; the running state of the alternating current system comprises the running state of a short-circuit current element on the alternating current system side, the grid structure of the direct current transmission converter station near-zone alternating current system, the switching of a generator and the change of the capacity.
It should be noted that, referring to fig. 2, a schematic structural diagram of a dc transmission system connected to an ac power grid according to an embodiment of the present invention is provided, where the dc transmission system connected to the ac power grid includes a dc transmission system including two converter stations, and a hydroelectric power plant, a thermal power plant, and a transformer substation, where the converter stations are connected through an ac line. In order to ensure the safe operation of the alternating current system, the intensity discrimination device monitors the current, the voltage and the switch state information of an alternating current line and a generator port in the alternating current system in real time. The intensity judging device can be connected to the near-zone alternating current system of the converter station to detect information, so that the intensity of the alternating current system can be conveniently acquired before the direct current transmission system is started.
S102, determining the system intensity of the alternating current system according to the running state of the alternating current system.
Specifically, step S102 includes:
when the fact that the connected alternating current inlet wire does not exceed a first inlet wire connection threshold or the input generator does not exceed a first generator input threshold is detected, the alternating current system is judged to be an extremely weak system;
when detecting that the connected alternating current incoming line exceeds the first incoming line connection threshold and does not exceed a second incoming line connection threshold, or the input generator exceeds the first generator input threshold and does not exceed a second generator input threshold, judging that the alternating current system is a weak system;
and when the connected alternating current inlet wire is detected to exceed the second inlet wire connection threshold value and the input generator exceeds the second generator input threshold value, judging that the alternating current system is a strong system.
More specifically, if most of the alternating current inlet wires are normally connected and most of the generators are normally put into use, the alternating current system strength judging device judges that the alternating current system is a strong system; if a part of alternating current inlet wires are not connected or a part of generators are not put into use, the alternating current system strength judging device judges that the alternating current system is a weak system; if most of the alternating current inlet wires are not connected or most of the generators are not put into use, the alternating current system strength judging device judges that the alternating current system is an extremely weak system.
S103, selecting a direct current system starting power and a starting control strategy according to the system strength of the alternating current system, and sending a corresponding starting control strategy type instruction to a control system of the direct current transmission converter station so that the control system responds to the starting control strategy type instruction to start the direct current transmission system.
In a preferred embodiment, when the ac system is a strong system, selecting the dc system starting power as a first power, generating a first control instruction, sending the first control instruction to the control system, so that the control system responds to the first control instruction, starts the dc power transmission system according to a first dc voltage and a first dc current corresponding to the first power, and then gradually increases the first dc current to a preset rated dc current; the first direct current voltage is a preset rated direct current voltage, and the first power is smaller than a preset rated power.
Illustratively, the first power is 10% of rated power, and accordingly the first dc voltage is set to the rated dc voltage and the first dc current is set to 10% of rated current. The intensity judging device selects the starting power to be 10% of rated power, namely the starting control strategy corresponding to the first control instruction is started by adopting rated direct current voltage and 10% of rated current, and then the direct current is gradually increased to the rated direct current.
In a preferred embodiment, when the ac system is a weak system, selecting the dc system starting power as a second power, generating a second control instruction, sending the second control instruction to the control system, so that the control system starts the dc power transmission system according to a second dc voltage and a second dc current corresponding to the second power in response to the second control instruction, after starting, keeping the second dc voltage for a first preset time, further increasing the second dc voltage to the rated dc voltage, and then gradually increasing the second dc current to the rated dc current; wherein the second power is less than the first power.
In this embodiment, to prevent the interruption of the dc current, the dc current is generally not less than 10%, so the starting power of the dc system needs to be reduced by reducing the dc voltage. Preferably, the second power for starting the weak system is smaller than the first power for starting the strong system, and then the second dc voltage is smaller than the first dc voltage. Similarly, the third power for starting the very weak system is smaller than the second power, and the third dc voltage is smaller than the second dc voltage.
Illustratively, the second power is 7% of rated power, and accordingly the second dc voltage is set to 70% of rated dc voltage and the second dc current is set to 10% of rated current. The strength judging device selects the starting power to be 7% of rated power, namely the starting control strategy corresponding to the second control instruction is started by adopting 70% of rated direct current voltage and 10% of rated direct current, and the trigger angle during starting is increased. After starting, the rated power of 7% is maintained within 2min, then the trigger angle is gradually reduced, the direct current voltage is increased to the rated direct current voltage, and finally the direct current is gradually increased to the rated direct current.
In another preferred embodiment, when the ac system is an extremely weak system, selecting the starting power of the dc system as a third power, generating a third control instruction, sending the third control instruction to the control system, so that the control system responds to the third control instruction, starting the dc power transmission system according to a third dc voltage and a third dc current corresponding to the third power, keeping the third dc voltage for a second preset time period after starting, further increasing the third dc voltage to the rated dc voltage, and then gradually increasing the third dc current to the rated dc current; wherein the third power is less than the second power.
Illustratively, the third power is 2.5% of the rated power, and accordingly the third dc voltage is set to 25% of the rated dc voltage and the third dc current is set to 10% of the rated current. The strength judging device selects the starting power to be 2.5% of rated power, namely, the starting control strategy corresponding to the third control instruction is started by adopting 25% of rated direct current voltage and 10% of rated direct current, and the trigger angle during starting is continuously increased. After starting, the 2.5 percent rated power is maintained within 2min, then the trigger angle is gradually reduced, the direct current voltage is increased to the rated direct current voltage, and finally the direct current is gradually increased to the rated direct current.
The method for starting the direct current transmission system provided by the embodiment of the invention monitors the running state of the alternating current system in real time, wherein the running state of the alternating current system comprises the running state of a short-circuit current element at the side of the alternating current system, the grid structure of the alternating current system in the vicinity of the direct current transmission converter station, the switching of a generator and the change of the capacity, the system strength of the alternating current system is determined according to the running state of the alternating current system, the starting power and the starting control strategy of the direct current system are selected according to the system strength of the alternating current system, a corresponding starting control strategy type instruction is sent to the control system of the direct current transmission converter station, so that the control system responds to the starting control strategy type instruction to start the direct current transmission system, and different starting powers and strategies can be selected according to the strength of the alternating current system when the running mode of the alternating current system changes, the direct-current power transmission system is started in a targeted manner, so that the impact on the alternating-current system when the direct-current power transmission system is started is avoided, and the stability of the alternating-current system is greatly improved.
Example two
Referring to fig. 3, which is a schematic structural diagram of a dc power transmission system starting apparatus according to a second embodiment of the present invention, the dc power transmission system starting apparatus 20 includes a strength determining apparatus 21 and a control system 22 of a dc power transmission converter station access system;
the intensity discriminating device 21 comprises a real-time monitoring module 211, a system intensity discriminating module 212 and a start control strategy selecting module 213;
the real-time monitoring module 211 is configured to monitor an operating state of the ac system in real time; the running state of the alternating current system comprises the running state of a short-circuit current element on the alternating current system side, a grid structure of a near-zone alternating current system of the direct current transmission converter station, switching of a generator and change of capacity;
the system strength determination module 212 is configured to determine the system strength of the ac system according to the operating state of the ac system;
the start control strategy selection module 213 is configured to select a dc system start power and a start control strategy according to the system strength of the ac system, and send a corresponding start control strategy type instruction to the control system of the dc transmission converter station;
the control system 22 includes a control module 221; the control module 221 is configured to respond to the start control policy type instruction and start the dc power transmission system.
Preferably, the system strength determination module 212 includes an extremely weak system determination unit, a weak system determination unit, and a strong system determination unit;
the weak system judging unit is used for judging that the alternating current system is a weak system when the fact that the connected alternating current inlet wire does not exceed a first inlet wire connection threshold or the input generator does not exceed a first generator input threshold is detected;
the weak system judging unit is used for judging that the alternating current system is a weak system when detecting that the connected alternating current inlet wire exceeds the first inlet wire connection threshold and does not exceed a second inlet wire connection threshold or the input generator exceeds the first generator input threshold and does not exceed a second generator input threshold;
and the strong system judging unit is used for judging that the alternating current system is a strong system when the connected alternating current inlet wire is detected to exceed the second inlet wire connection threshold and the input generator exceeds the second generator input threshold.
Preferably, the start control policy selecting module 213 includes a first start control policy selecting unit; the first starting control strategy selecting unit is used for selecting the starting power of the direct current system as a first power when the alternating current system is a strong system, generating a first control instruction and sending the first control instruction to the control system;
the control module 221 includes a first start control unit; the first starting control unit is used for responding to the first control instruction, starting the direct current power transmission system according to a first direct current voltage and a first direct current corresponding to the first power, and gradually increasing the first direct current to a preset rated direct current; the first direct current voltage is a preset rated direct current voltage, and the first power is smaller than a preset rated power.
Preferably, the start control policy selecting module 213 includes a second start control policy selecting unit; the second starting control strategy selecting unit is used for selecting the starting power of the direct current system as a second power when the alternating current system is a weak system, generating a second control instruction and sending the second control instruction to the control system;
the control module 221 includes a second start control unit; the second start control unit is configured to start the dc power transmission system according to a second dc voltage and a second dc current corresponding to the second power in response to the second control instruction, maintain the second dc voltage for a first preset time period after the start, further increase the second dc voltage to the rated dc voltage, and gradually increase the second dc current to the rated dc current; wherein the second power is less than the first power.
Preferably, the start control policy selecting module 213 includes a third start control policy selecting unit; the third start control strategy selecting unit is used for selecting the start power of the direct current system as a third power when the alternating current system is an extremely weak system, generating a third control instruction and sending the third control instruction to the control system;
the control module 221 includes a third start-up control unit; the third start control unit is configured to start the dc power transmission system according to a third dc voltage and a third dc current corresponding to the third power in response to the third control instruction, maintain the third dc voltage for a second preset time period after the start, further increase the third dc voltage to the rated dc voltage, and gradually increase the third dc current to the rated dc current; wherein the third power is less than the second power.
The dc power transmission system starting apparatus provided in the second embodiment of the present invention monitors the operating state of an ac system in real time, wherein the operating state of the ac system includes the operating state of a short-circuit current element on the ac system side, a grid structure of an ac system in a vicinity of the dc power transmission converter station, switching of a generator, and a change in capacity, determines the system strength of the ac system according to the operating state of the ac system, selects a starting power and a starting control strategy of the dc system according to the system strength of the ac system, and sends a corresponding starting control strategy type instruction to a control system of the dc power transmission converter station, so that the control system can start the dc power transmission system in response to the starting control strategy type instruction, thereby enabling different starting powers and strategies to be selected according to the strength of the ac system when the operating mode of the ac system changes, the direct-current power transmission system is started in a targeted manner, so that the impact on the alternating-current system when the direct-current power transmission system is started is avoided, and the stability of the alternating-current system is greatly improved.
It should be noted that the above-described device embodiments are merely illustrative, where the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. In addition, in the drawings of the embodiment of the apparatus provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, and may be specifically implemented as one or more communication buses or signal lines. One of ordinary skill in the art can understand and implement it without inventive effort.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (6)
1. A starting method of a direct current transmission system is characterized by being applicable to a strength judging device of a direct current transmission converter station access system, and comprises the following steps:
monitoring the running state of the alternating current system in real time; the running state of the alternating current system comprises the running state of a short-circuit current element on the alternating current system side, a grid structure of a near-zone alternating current system of the direct current transmission converter station, switching of a generator and change of capacity;
determining the system strength of the communication system according to the running state of the communication system, which specifically comprises the following steps:
when the fact that the connected alternating current inlet wire does not exceed a first inlet wire connection threshold or the input generator does not exceed a first generator input threshold is detected, the alternating current system is judged to be an extremely weak system;
when detecting that the connected alternating current incoming line exceeds the first incoming line connection threshold and does not exceed a second incoming line connection threshold, or the input generator exceeds the first generator input threshold and does not exceed a second generator input threshold, judging that the alternating current system is a weak system;
when the connected alternating current inlet wire is detected to exceed the second inlet wire connection threshold value and the input generator exceeds the second generator input threshold value, judging that the alternating current system is a strong system;
selecting a direct current system starting power and a starting control strategy according to the system strength of the alternating current system, and sending a corresponding starting control strategy type instruction to a control system of the direct current transmission converter station so that the control system responds to the starting control strategy type instruction to start the direct current transmission system, and the method specifically comprises the following steps:
when the alternating current system is a strong system, selecting the starting power of the direct current system as a first power, generating a first control instruction, sending the first control instruction to the control system, so that the control system responds to the first control instruction, starts the direct current transmission system according to a first direct current voltage and a first direct current corresponding to the first power, and then gradually increases the first direct current to a preset rated direct current; the first direct-current voltage is a preset rated direct-current voltage, and the first power is smaller than a preset rated power;
when the alternating current system is a weak system, selecting the starting power of the direct current system as a second power, generating a second control instruction, sending the second control instruction to the control system, so that the control system responds to the second control instruction, starting the direct current power transmission system according to a second direct current voltage and a second direct current corresponding to the second power, keeping the second direct current voltage within a first preset time period after starting, further increasing the second direct current voltage to the rated direct current voltage, and gradually increasing the second direct current to the rated direct current; wherein the second power is less than the first power;
when the alternating current system is an extremely weak system, selecting the starting power of the direct current system as a third power, generating a third control instruction, sending the third control instruction to the control system, so that the control system responds to the third control instruction, starting the direct current power transmission system according to a third direct current voltage and a third direct current corresponding to the third power, keeping the third direct current voltage for a second preset time after starting, further increasing the third direct current voltage to the rated direct current voltage, and gradually increasing the third direct current to the rated direct current; wherein the third power is less than the second power.
2. A dc power transmission system starting device based on the dc power transmission system starting method according to claim 1, comprising a strength determination device and a control system of a dc power transmission converter station access system;
the intensity judging device comprises a real-time monitoring module, a system intensity judging module and a starting control strategy selecting module;
the real-time monitoring module is used for monitoring the running state of the alternating current system in real time; the running state of the alternating current system comprises the running state of a short-circuit current element on the alternating current system side, a grid structure of a near-zone alternating current system of the direct current transmission converter station, switching of a generator and change of capacity;
the system intensity judging module is used for determining the system intensity of the alternating current system according to the running state of the alternating current system;
the starting control strategy selection module is used for selecting the starting power and the starting control strategy of the direct current system according to the system strength of the alternating current system and sending a corresponding starting control strategy type instruction to the control system of the direct current transmission converter station;
the control system comprises a control module; and the control module is used for responding to the control strategy type starting instruction and starting the direct current power transmission system.
3. The direct-current transmission system startup device according to claim 2, wherein the system strength determination module includes an extremely weak system determination unit, a weak system determination unit, and a strong system determination unit;
the weak system judging unit is used for judging that the alternating current system is a weak system when the fact that the connected alternating current inlet wire does not exceed a first inlet wire connection threshold or the input generator does not exceed a first generator input threshold is detected;
the weak system judging unit is used for judging that the alternating current system is a weak system when detecting that the connected alternating current inlet wire exceeds the first inlet wire connection threshold and does not exceed a second inlet wire connection threshold or the input generator exceeds the first generator input threshold and does not exceed a second generator input threshold;
and the strong system judging unit is used for judging that the alternating current system is a strong system when the connected alternating current inlet wire is detected to exceed the second inlet wire connection threshold and the input generator exceeds the second generator input threshold.
4. A dc transmission system starting apparatus according to claim 3, wherein the starting control strategy selection module comprises a first starting control strategy selection unit; the first starting control strategy selecting unit is used for selecting the starting power of the direct current system as a first power when the alternating current system is a strong system, generating a first control instruction and sending the first control instruction to the control system;
the control module comprises a first starting control unit; the first starting control unit is used for responding to the first control instruction, starting the direct current power transmission system according to a first direct current voltage and a first direct current corresponding to the first power, and gradually increasing the first direct current to a preset rated direct current; the first direct current voltage is a preset rated direct current voltage, and the first power is smaller than a preset rated power.
5. The direct current transmission system startup device of claim 4, wherein the startup control strategy selection module comprises a second startup control strategy selection unit; the second starting control strategy selecting unit is used for selecting the starting power of the direct current system as a second power when the alternating current system is a weak system, generating a second control instruction and sending the second control instruction to the control system;
the control module comprises a second starting control unit; the second start control unit is configured to start the dc power transmission system according to a second dc voltage and a second dc current corresponding to the second power in response to the second control instruction, maintain the second dc voltage for a first preset time period after the start, further increase the second dc voltage to the rated dc voltage, and gradually increase the second dc current to the rated dc current; wherein the second power is less than the first power.
6. The direct current transmission system startup device of claim 5, wherein the startup control strategy selection module comprises a third startup control strategy selection unit; the third start control strategy selecting unit is used for selecting the start power of the direct current system as a third power when the alternating current system is an extremely weak system, generating a third control instruction and sending the third control instruction to the control system;
the control module comprises a third starting control unit; the third start control unit is configured to start the dc power transmission system according to a third dc voltage and a third dc current corresponding to the third power in response to the third control instruction, maintain the third dc voltage for a second preset time period after the start, further increase the third dc voltage to the rated dc voltage, and gradually increase the third dc current to the rated dc current; wherein the third power is less than the second power.
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| CN101969206A (en) * | 2010-09-03 | 2011-02-09 | 中国电力科学研究院 | Evaluation method for judging influence of grid structure on alternating current/direct current (AC/DC) system |
| CN109193734A (en) * | 2018-09-20 | 2019-01-11 | 国网山东省电力公司电力科学研究院 | The adaptability teaching method and system that alternating current-direct current power grid restores direct current system |
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| CN101359828A (en) * | 2008-09-28 | 2009-02-04 | 华北电力大学（保定） | High-voltage DC transmission starting and operating method |
| CN101969206A (en) * | 2010-09-03 | 2011-02-09 | 中国电力科学研究院 | Evaluation method for judging influence of grid structure on alternating current/direct current (AC/DC) system |
| CN109193734A (en) * | 2018-09-20 | 2019-01-11 | 国网山东省电力公司电力科学研究院 | The adaptability teaching method and system that alternating current-direct current power grid restores direct current system |
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