CN111416378B - Switching control method, device, terminal and medium for converting metal return wire into earth return wire - Google Patents

Switching control method, device, terminal and medium for converting metal return wire into earth return wire Download PDF

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CN111416378B
CN111416378B CN202010316160.2A CN202010316160A CN111416378B CN 111416378 B CN111416378 B CN 111416378B CN 202010316160 A CN202010316160 A CN 202010316160A CN 111416378 B CN111416378 B CN 111416378B
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current value
converter station
station
current
ertb
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CN111416378A (en
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陈怡静
黄伟煌
刘涛
李岩
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China South Power Grid International Co ltd
China Southern Power Grid Co Ltd
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China South Power Grid International Co ltd
China Southern Power Grid Co Ltd
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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
    • 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 application provides a method, a device, a terminal and a medium for controlling switching of a metal return wire to a ground return wire, wherein the method comprises the following steps: responding to the closing of an MRTB switch of the converter station to be switched, and detecting a first current value of a ground return wire of the converter station to be switched; and calculating the duration time that the first current value is not greater than a preset ERTB switch disconnection threshold value, and adjusting the first current value by adjusting the output of a converter station of the multi-terminal direct current transmission system when the duration time exceeds the preset duration time threshold value, so that the adjusted first current value is greater than the ERTB switch disconnection threshold value. According to the method and the device, after an ERTB switch of the converter station to be switched is closed, when the fact that the first current value flowing through the metal return wire does not meet the switching condition is detected, the first current value is adjusted to meet the switching condition and the switching action is completed, and the technical problem that the converter station of the existing multi-terminal direct current transmission system is prone to falling into a coexisting state of the earth metal double return wires in the process of switching the metal return wires is solved.

Description

Switching control method, device, terminal and medium for converting metal return wire into earth return wire
Technical Field
The present invention relates to the field of multi-terminal dc power transmission technologies, and in particular, to a method, an apparatus, a terminal, and a medium for controlling switching from a metal return line to a ground return line.
Background
With the increase of the power demand and the improvement of the direct current transmission technology, compared with a conventional two-end direct current transmission system, the multi-end direct current transmission system comprising three or more converter stations has stronger transmission capability, can better adapt to the current and future power environments, and has greater potential.
For a multi-terminal dc transmission system with a bipolar structure, when the system operates in a single pole, there are two operation modes of ground return and metal return, and in order to operate, the two operation modes need to be switched with each other, taking the three-terminal system shown in fig. 1 as an example, two converter stations usually need to be configured with a ground return breaker (ERTB) and a metal return breaker (MRTB) to complete the process of ground metal return mutual rotation, and when the system operates in a metal return, the MRTB is in an open state, and the ERTB is in a closed state. If the system is required to go from the metallic return to the earth return, then MRTB is required to go from open to closed and ERTB is required to go from closed to open. For ERTB, the ERTB will not perform the disconnect operation until MRTB has a current flow. However, in the research process, it is found that under some working conditions, even though the MRTB is closed, the ground loop in the system is already established but the current flowing through the MRTB is still zero or still less than the minimum current threshold of the ERTB opening operation due to the effect of the resistance shunt, in this case, the ERTB does not perform the opening operation, and then the system is in a state of coexisting ground metal loops for a long time.
Moreover, due to the increase of the number of the converter stations, the loop conversion mode becomes more complex, so that the converter stations of the existing multi-terminal direct current transmission system are more likely to fall into the coexistence state of the earth metal double loops in the process of converting the earth loops.
Disclosure of Invention
The application provides a switching control method, a switching control device, a switching control terminal and a switching control medium for converting a metal return wire into a ground return wire, which are used for solving the technical problem that a converter station of an existing multi-terminal direct current transmission system is easy to fall into a coexisting state of a ground metal double return wire in the process of converting the metal return wire.
The first aspect of the present application provides a method for controlling switching of a metal return wire to a ground return wire, including:
responding to the closing of an MRTB switch of the converter station to be switched, and detecting a first current value of a ground return wire of the converter station to be switched;
and calculating the duration time that the first current value is not greater than a preset ERTB switch disconnection threshold value, and adjusting the first current value by adjusting the output of a converter station of the multi-terminal direct-current transmission system when the duration time exceeds the preset duration threshold value, so that the adjusted first current value is greater than the ERTB switch disconnection threshold value.
Optionally, the adjusting the first current value so that the adjusted first current value is greater than the ERTB switch off threshold specifically includes:
determining a source end converter station corresponding to the first current value according to the topology of the multi-terminal direct current transmission system;
and adjusting the first current value by adjusting the output current value of at least one source end converter station according to the difference value between the first current value and the ERTB switch disconnection threshold value, so that the adjusted first current value is larger than the ERTB switch disconnection threshold value.
Optionally, after the first current value is not greater than a preset ERTB switch off threshold, the method further includes:
and calculating the duration of the first current value not greater than a preset ERTB switch off threshold, and adjusting the first current value when the duration exceeds a preset duration threshold.
The second aspect of the present application provides a switching control device for a metal return wire to a ground return wire, comprising:
the current value acquisition unit is used for responding to the closing of an MRTB switch of the converter station to be switched and detecting a first current value of a ground loop of the converter station to be switched;
and the current adjusting unit is used for calculating the duration time that the first current value is not greater than a preset ERTB switch disconnection threshold value, and when the duration time exceeds the preset duration time threshold value, adjusting the first current value by adjusting the output of a converter station of the multi-terminal direct current transmission system, so that the adjusted first current value is greater than the ERTB switch disconnection threshold value.
Optionally, the current adjusting unit specifically includes:
the timing subunit is used for calculating the duration that the first current value is not greater than a preset ERTB switch disconnection threshold value, and triggering the source end converter station to determine the subunit when the duration exceeds a preset duration threshold value;
a source end converter station determining subunit, configured to determine, according to the topology of the multi-terminal direct current transmission system, a source end converter station corresponding to the first current value;
and the current adjusting subunit is configured to adjust the first current value by adjusting an output current value of at least one source-end converter station according to a difference between the first current value and the ERTB switch disconnection threshold value, so that the adjusted first current value is greater than the ERTB switch disconnection threshold value.
A third aspect of the present application provides a terminal, comprising: a memory and a processor;
the memory is used for storing program codes corresponding to the ground loop switching control method of the multi-terminal direct current power transmission system in the first aspect of the application;
the processor is configured to execute the program code.
A fourth aspect of the present application provides a storage medium having stored therein program code corresponding to the method for controlling ground return switching in a multi-terminal dc power transmission system according to the first aspect of the present application.
According to the technical scheme, the embodiment of the application has the following advantages:
the application provides a switching control method for converting a metal return wire into a ground return wire, which comprises the following steps: responding to the closing of an MRTB switch of the converter station to be switched, and detecting a first current value of a ground return wire of the converter station to be switched; and calculating the duration time that the first current value is not greater than a preset ERTB switch disconnection threshold value, and adjusting the first current value by adjusting the output of a converter station of the multi-terminal direct-current transmission system when the duration time exceeds the preset duration threshold value, so that the adjusted first current value is greater than the ERTB switch disconnection threshold value.
According to the method and the device, after an ERTB switch of the converter station to be switched is closed, the first current value of the earth return wire of the converter station to be switched is detected, when the first current value flowing through the metal return wire is detected to be not satisfied with the switching condition, the first current value is adjusted through adjusting the output of the converter station of the multi-terminal direct current transmission system, so that the switching condition is satisfied and the switching action is completed, and the technical problem that the converter station of the existing multi-terminal direct current transmission system is easy to fall into the coexisting state of the earth return wires in the process of metal return wire switching is solved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a schematic structural diagram of a conventional three-terminal dc power transmission system;
fig. 2 is a schematic flowchart of a first embodiment of a method for controlling switching of a metallic return line to a ground return line provided in the present application;
fig. 3 is a schematic flowchart of a second embodiment of a method for controlling switching of a metallic return line to a ground return line according to the present application;
fig. 4 is a schematic structural diagram of a switching control device for converting a metal return wire into a ground return wire according to the present application;
fig. 5 is a schematic diagram of the relationship between the converter station conversion dead zone and the source side converter station current level.
Detailed Description
For a multi-terminal dc transmission system with a bipolar structure, when performing unipolar operation, there are two operation modes of a ground return and a metal return, taking a three-terminal system shown in fig. 1 as an example, generally two converter stations need to be configured with a ground return breaker (ERTB) and a metal return breaker (MRTB) to complete a process of mutual rotation of the ground metal returns, a specific conversion mode is to close the ERTB of each converter station one by one, and then disconnect the MRTB switch when a current flowing through the metal return meets a preset requirement, so that the converter station completes the process of ground-to-metal return operation.
Taking the system shown in fig. 1 as an example, the power transmission direction in normal operation of the three-terminal system is that station 1 transmits power to stations 2 and 3. The sequence of operations for turning metal to earth for the three-terminal system of fig. 1 is as follows:
initial state: the three stations are in a metal loop state, and the currents flowing through the three stations are respectively
Figure GDA0003215331420000041
Wherein InAnd n-represents (1,2, 3.) the total output current of station n. Wherein, the physical meaning of each parameter in fig. 1 is as follows: r1: station 1 earth lead and earth resistance, R2: station 2 earth lead and earth resistance, R3: station 3 earth lead and earth resistance, RL1: resistance of DC line between station 1 and station 2, RL2: direct current line resistance between station 2 and station 3;
operation 1: the station 3 closes the MRTB switch, the station 3 is in a state of coexistence of the earth and the metal return wire, and the station 2 is in a state of the metal return wire;
operation 2: detecting current flowing through ground return of station 3
Figure GDA0003215331420000042
Satisfy the requirement of
Figure GDA0003215331420000043
When the station 3ERTB switch is pulled open, the station 3 is in the ground loop state, the station 2 is in the metal loop state, wherein IminIs the ERTB switch off threshold;
operation 3: the station 2 closes the MRTB switch, the station 2 is in a state of coexistence of earth and a metal return wire, and the station 3 is in an earth return wire state;
and operation 4: detecting current flowing through the station 2 metallic return
Figure GDA0003215331420000051
Satisfy the requirement of
Figure GDA0003215331420000052
When the station 2ERTB switch is opened, the station 2 is in a ground loop state;
and (3) final state: the three-terminal system stably operates in the ground loop state.
In practical application, however, the inventor finds that the flow of electric energy between the converter stations becomes more complicated due to the increase of the number of the converter stations, and due to the effect of resistance shunt, when MRTB is closed, the possibility of the return current flowing through the earth being less than IminIn this case, the converter station of the multi-terminal dc power transmission system is more likely to be in the coexisting state of the earth metal double-circuit line in the process of converting the earth metal double-circuit line, and if the converter station is in the coexisting state of the earth metal double-circuit line for a long time, a large earth current will seriously affect the underground substances near the earth electrode, so how to avoid the harm caused by the fact that the dc power transmission system is in the coexisting state of the earth metal double-circuit line becomes a technical problem that needs to be solved urgently by those skilled in the art.
In view of this, embodiments of the present application provide a method, an apparatus, a terminal, and a medium for controlling switching of a metal return line to a ground return line, so as to solve a technical problem that a converter station of an existing multi-terminal dc power transmission system is likely to fall into a coexisting state of a ground metal double return line in a process of converting the ground return line.
In order to make the objects, features and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the embodiments described below are only a part of the embodiments of the present application, 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 application.
Referring to fig. 2, a first aspect of the present application provides a method for controlling switching of a metal return to a ground return, including:
step 101, responding to the closing of an MRTB switch of a converter station to be switched, and detecting a first current value of a ground return wire of the converter station to be switched;
and 102, calculating the duration time that the first current value is not greater than a preset ERTB switch disconnection threshold value, and adjusting the first current value by adjusting the output of a converter station of the multi-terminal direct current transmission system when the duration time exceeds the preset duration time threshold value, so that the adjusted first current value is greater than the ERTB switch disconnection threshold value.
It should be noted that, taking the MRTB of the station 3 closed first as an example, after detecting that the first current value does not satisfy the ERTB switch opening threshold for opening the MRTB, and before adjusting the first current value, the duration that the first current value is not greater than the ERTB switch opening threshold may be accumulated first, and if the first current value reaches the normal level within the preset duration threshold, the first current value is not adjusted.
When the three-terminal system performs operation 1, with station 3 in earth and metallic return coexistence and station 2 in earth return operation, the current flowing through the earth return of station 3 in this case can be seen from the system topology shown in fig. 1
Figure GDA0003215331420000061
And current flowing through the metallic return
Figure GDA0003215331420000062
The following were used:
Figure GDA0003215331420000063
Figure GDA0003215331420000064
Figure GDA0003215331420000065
when in use
Figure GDA0003215331420000066
In this case, the station 3 will always be in the condition that the earth and the metal return wire exist at the same time, and if not, the station 3 can normally complete the process of turning the metal return wire to the earth return wire.
After the station 3 completes the earth return line conversion, the MRTB of the station 2 is closed, and at this time, the station 2 is in the state of the earth return line coexistence, and the current flowing through the earth return line of the station 2 can be known from the system topology shown in fig. 1
Figure GDA0003215331420000067
And current flowing through the metallic return
Figure GDA0003215331420000068
The following were used:
Figure GDA0003215331420000069
Figure GDA00032153314200000610
Figure GDA00032153314200000611
if the current flows through the station 2 metallic return
Figure GDA00032153314200000612
The following conditions are satisfied:
Figure GDA00032153314200000613
then, the station 2 will not have the running condition of being in the ground and having two metal loops coexisting for a long time, otherwise the station 2 will have the running condition of being in the ground and having two metal loops coexisting for a long time.
When the current flowing through the metal loop in the target converter station is determined to be less than the ERTB switch disconnection threshold IminBased onThe parameter relationship shown in the formula (2) or the formula (5) is that the first current value is adjusted by adjusting the output of a converter station (station 2 and/or station 3) of the multi-terminal direct current transmission system, so that the adjusted first current value is larger than the ERTB switch-off threshold value.
It can be understood that the formulas (1), (2), (4), and (5) in this embodiment are obtained based on the system topology shown in fig. 1, and a user can adaptively adjust the forms of the four formulas according to the actual topology structure of the multi-terminal dc power transmission system to which the method is applied, which is not described herein again.
According to the embodiment of the application, after an MRTB switch of a converter station to be switched is closed, a first current value of a ground return wire of the converter station to be switched is detected, and after ts time elapses after the MRTB switch is closed, an ERTB switch is still in a closed state, which indicates that the first current value is not larger than a preset ERTB switch disconnection threshold value possibly due to a resistance shunt effect, and the first current value is adjusted by adjusting the output of a converter station of a multi-terminal direct-current transmission system to meet a switching condition and complete a switching action, so that the technical problem that the converter station of the existing multi-terminal direct-current transmission system is easily trapped in a ground metal double-return wire coexisting state in the process of converting the ground return wire is solved.
The above is a detailed description of a first embodiment of a method for controlling switching from a metallic return line to an earth return line provided by the present application, and the following is a detailed description of a second embodiment of a method for controlling switching from a metallic return line to an earth return line provided by the present application.
Referring to fig. 3, on the basis of the first embodiment, a second embodiment of the present application provides a method for controlling switching of a metallic return line to a ground return line,
further, step 102 specifically includes:
step 1020, calculating and judging whether the duration time that the first current value is not greater than the preset ERTB switch off threshold exceeds a preset duration time threshold, if so, executing step 1021.
Step 1021, determining a source end converter station corresponding to the first current value according to the topology of the multi-terminal direct current transmission system;
and 1022, adjusting the first current value by adjusting the output current value of at least one source end converter station according to the difference value between the first current value and the cut-off threshold value of the ERTB switch, so that the adjusted first current value is greater than the cut-off threshold value of the ERTB switch.
Please refer to fig. 5, fig. 5 is a schematic diagram illustrating a relationship between a dead zone of a converter station conversion and a current level of a source converter station. Taking station 3 as an example, if the return current of the ground metal is less than 20A when station 3 is in the process of converting the ground metal return, station 3 is in the condition of coexistence of two loops of ground metal for a long time. When this occurs, the following three schemes can be adopted to make the system jump out of the dead zone where the earth metal return wires of the station 3 coexist for a long time.
Scheme 1: the total output current level of the first source side converter station (station 2) is adjusted.
Taking the system operating at 20 ℃ as an example, the dead zone where the earth metal return wires of station 2 coexist for a long time is the shaded area in the figure. When the system initial value is at
Figure GDA0003215331420000071
When a point is run on the straight line represented, it moves dis to the left or rightxWhere isxFor a unit adjustment value of the output current level of the converter station, and
Figure GDA0003215331420000081
for example, generally, for an operating point that may be in a dead zone, it is not possible to accurately determine that the operating point is in a straight line because the line resistance changes with temperature and the accurate value of the line resistance at any one time cannot be measured
Figure GDA0003215331420000082
The upper half or the lower half of the area. In order to ensure that this point can jump out of the dead zone of the long-term operation of the earth return of the station 2, it is therefore proposed to offset this operating point by 2dis to the left or to the rightxSince the station 2 controls the voltage and the stations 1 and 3 are power control stations in the three-terminal system, the current of the station 3 is increased or decreased and the current of the station 1 needs to be increased or decreased synchronouslyThe method comprises the following steps:
step 1: the initial state of the system is at point a0＝(I2,I3) The system is operated by the switch sequence control operation, so that the station 2 operates for a metal return wire, and the station 3 operates for an earth return wire. The station 2MRTB switching system access station 2 is in earth, metallic return operation, the station 3 is in earth return operation, if the current flowing through the earth return of the station 2 is less than IminThe station 2ERTB cannot perform the opening operation of the switch according to the criterion, in which case step 2 is performed.
Step 21: maintaining the station 3 initial current constant, increasing the station 1 and station 2 currents 2disxAnd satisfy I2+2disx≤Irated2If I is2+2disx＞Irated2Then the station 1 and station 2 currents 2dis are reducedx。
Step 22: maintaining the initial current of station 3 constant, reducing station 1 and station 2 currents 2disxAnd satisfy I2-2disx≥0.1Irated2(ii) a If I2-2disx＜0.1Irated2Then, the station 1 and station 2 currents 2dis are increasedx。
When all resistance values change along with the temperature, the R is calculated1,R2Taking a maximum temperature value, RL1When taking the minimum value, there is 2disx88.7777, it is recommended to reduce or increase (by a factor of 1.2) the station 1 and station 2 current levels 110A when the system may be in station 2 station earth metal operating dead zone, taking into account certain margins.
When all resistance values vary with temperature, it is advisable to reduce or increase (by a factor of 1.2) the station 2, 1 current level 170A when the system may appear in the large metal operating dead zone of station 3, taking into account certain margins.
When solution 1 is adopted, the system power level changes by the following values for different voltage operating conditions (full voltage assumed to be 800 kV):
table 1 embodiment 1 power level changes of each station under different voltage operation conditions
Full pressure operation Reduced pressure 80% operation
Station
1 ±88MW ±70.4MW
Station
2 ±88MW ±70.4MW
Station 3 0MW 0MW
Scheme 2: the total output current level of the second source side converter station (station 3) is adjusted.
When the system initial value is at
Figure GDA0003215331420000091
When a point is run on the straight line represented, the point is moved dis up or downyTime of flight
Figure GDA0003215331420000092
The system can jump out of the dead zone where the earth metal of the station 2 coexists for a long time.
Generally, for an operating point which may be located in a dead zone, since the line resistance cannot measure an accurate value of the line resistance at any time along with the temperature change, it cannot be accurately determined that the operating point is located in a straight line
Figure GDA0003215331420000093
The upper half or the lower half of the area. In order to ensure that this point can jump out of the dead zone of the long-term operation of the earth return of the station 2, it is therefore proposed to offset this operating point by 2dis to the left or to the rightyIn the three-terminal system, the station 3 controls the voltage, and the stations 1 and 2 are power control stations, so that the current of the station 2 is increased or decreased, and the current of the station 1 needs to be increased or decreased synchronously, specifically as follows:
step 1: the initial state of the system is at point a0＝(I2，I3) And the station 2 operates for a metal return wire and the station 3 operates for a ground return wire when the system is in the intermediate state through the sequential control operation of the switch. And (3) the closing station 2MRTB switching system enters an intermediate state, the station 2 is in ground and metal loop operation, the station 3 is in ground loop operation, if the current flowing through the ground loop of the station 2 is less than Imin in, the station 2ERTB can not perform the switching-off operation according to the criterion, and the step 2 is performed under the condition.
Step 21: keeping the initial current of station 2 constant and increasing the current 2dis of station 1yAnd satisfy I3+2disy≤Irated3If I is3+2disy＞Irated3Then the station 1 current 2dis is reducedyWherein, IratedRepresenting the rated current of the converter station.
Step 22: maintaining the station 2 initial current constant, reducing the station 1 current 2disyAnd satisfy I3-2disy≥0.1Irated3(ii) a If I3-2disy＜0.1Irated3Then, the station 1 current 2dis is increasedy。
When all resistance values vary with temperature, it is advisable to reduce or increase the station 1 current level 730A (by a factor of 1.2) when the system may appear in the heavy metal operating dead zone of the station 3, taking into account certain margins.
When solution 2 is adopted, the system power level changes by the following values for different voltage operating conditions:
table 2 power level changes of each station under different voltage operation conditions in embodiment 2
Full pressure operation Reduced pressure 80% operation
Station
1 ±584MW ±467.2MW
Station
2 0MW 0MW
Station 3 ±584MW ±467.2MW
Scheme 3: the total output current level of all source side converter stations (station 2, station 3) is adjusted.
When the system initial value is at
Figure GDA0003215331420000101
When a point is moved upward or downward in a direction perpendicular to the straight line, the point is moved on the straight line as shown by
Figure GDA0003215331420000102
If the point moves down L along the vertical, then station 3 needs to be reduced
Figure GDA0003215331420000103
Station 2 needs to be increased
Figure GDA0003215331420000104
If the point moves up along the vertical line by L, then station 3 needs to be increased
Figure GDA0003215331420000105
Station 2 needs to be reduced
Figure GDA0003215331420000106
In this case, the total change level of the current of the system of the present embodiment is
Figure GDA0003215331420000107
Wherein,
Figure GDA0003215331420000108
the dead zone of the earth metal coexisting in the station 2 for a long time can be jumped out by the operating system.
Generally, for an operating point which may be located in a dead zone, since the line resistance cannot measure an accurate value of the line resistance at any time along with the temperature change, it cannot be accurately and definitely determined that the operating point is located in a straight line
Figure GDA0003215331420000109
So to ensure that this point can jump out of the dead zone of long-term operation of the earth return of station 2, it is advisable to offset this point upwards or downwards by 2 dis. When all resistance values vary with temperature, (2dis)max87.1733 (2 Δ x)max＝84.8098,(2Δy)max＝18.3443。
And considering certain margins, when the system is operating in a station 2 station earth metal operating dead zone, station 3 current 25A may be increased (1.2 times) by increasing station 2 current 105A (1.2 times), decreasing station 3 current 25A (1.2 times), or decreasing station 2 current 105A, increasing station 3 current 25A to jump out of the dead zone.
When the station 2 current 105A is selected to be increased and the station 3 current 25A is selected to be decreased, the system power level change values for different voltage operating conditions are shown in table 3:
TABLE 3 Power level Change for each station under different Voltage operating conditions
Figure GDA0003215331420000111
When the station 2 current 105A is selected to be decreased and the station 3 current 25A is selected to be increased, the system power level change values for different voltage operating conditions are shown in table 4:
TABLE 4 Power level changes for various stations under different Voltage operating conditions
Figure GDA0003215331420000112
In order to facilitate understanding and verifying the technical solution of the present embodiment, the present embodiment further provides resistance reference values of the resistors in the structure shown in fig. 1, as shown in table 5.
TABLE 5 System resistance variation with temperature Range (0 ℃ C. to 60 ℃ C.)
Figure GDA0003215331420000121
The above is a detailed description of the second embodiment of the method for controlling switching of metallic return to ground return provided by the present application, and the following is a detailed description of the first embodiment of the device for controlling switching of metallic return to ground return provided by the present application.
Referring to fig. 4, a third embodiment of the present application provides a switching control device for a metal return to ground return, including:
the current value obtaining unit 201 is configured to detect a first current value of a ground return wire of the converter station to be switched in response to the MRTB switch of the converter station to be switched being turned on;
the current adjusting unit 202 is configured to calculate a duration time that the first current value is not greater than a preset ERTB switch off threshold, and adjust the first current value by adjusting an output of a converter station of the multi-terminal dc power transmission system when the duration time exceeds the preset duration threshold, so that the adjusted first current value is greater than the ERTB switch off threshold.
More specifically, the current adjusting unit 202 specifically includes:
the timing subunit 2020 is configured to calculate a duration that the first current value is not greater than a preset ERTB switch off threshold, and when the duration exceeds a preset duration threshold, trigger the source-end converter station determining subunit 2021;
the source-end converter station determining subunit 2021 is configured to determine, according to the topology of the multi-terminal direct current transmission system, a source-end converter station corresponding to the first current value;
the current adjusting subunit 2022 is configured to adjust the first current value by adjusting the output current value of the at least one source end converter station according to a difference between the first current value and the ERTB switch disconnection threshold, so that the adjusted first current value is greater than the ERTB switch disconnection threshold.
More specifically, the method further comprises the following steps:
the above is a detailed description of a first embodiment of a device for controlling switching of a metallic return wire to an earth return wire provided by the present application, and in addition, the present application also provides embodiments of a terminal and a storage medium, and the following is a detailed description of an embodiment of a terminal and a storage medium provided by the present application.
A fourth embodiment of the present application provides a terminal, including: a memory and a processor;
the memory is used for storing program codes corresponding to the ground loop switching control method of the multi-terminal direct-current power transmission system mentioned in the first embodiment or the second embodiment of the application;
the processor is used for executing the program codes.
A fifth embodiment of the present application provides a storage medium, in which program codes corresponding to the ground return switching control method of the multi-terminal dc power transmission system according to the first embodiment or the second embodiment of the present application are stored.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, a division of a unit is merely a logical division, and an actual implementation may have another division, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The terms "first," "second," "third," "fourth," and the like in the description of the application and the above-described figures, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.

Claims (4)

1. A switching control method for converting a metal return wire into a ground return wire is applied to a multi-terminal direct-current power transmission system and is characterized by comprising the following steps:
responding to the closing of an MRTB switch of the converter station to be switched, and detecting a first current value of a ground return wire of the converter station to be switched;
calculating the duration time that the first current value is not greater than a preset ERTB switch disconnection threshold value, and when the duration time exceeds the preset duration time threshold value, adjusting the first current value by adjusting the output of a converter station of the multi-terminal direct-current transmission system, so that the adjusted first current value is greater than the ERTB switch disconnection threshold value, wherein the output adjustment amount of the converter station is 1.2 times of the output amount of the converter station;
the adjusting the output of the converter station of the multi-terminal direct current transmission system and the adjusting the first current value so that the adjusted first current value is greater than the ERTB switch disconnection threshold specifically includes:
determining a source end converter station corresponding to the first current value according to the topology of the multi-terminal direct current transmission system;
and adjusting the first current value by adjusting the output current value of at least one source end converter station according to the difference value between the first current value and the ERTB switch disconnection threshold value, so that the adjusted first current value is larger than the ERTB switch disconnection threshold value.
2. A switching control device for converting a metal return wire into an earth return wire is characterized by comprising:
the current value acquisition unit is used for responding to the closing of an MRTB switch of the converter station to be switched and detecting a first current value of a ground loop of the converter station to be switched;
the current adjusting unit is used for calculating the duration time that the first current value is not greater than a preset ERTB switch disconnection threshold value, and when the duration time exceeds the preset duration time threshold value, adjusting the first current value by adjusting the output of a converter station of the multi-terminal direct current transmission system, so that the adjusted first current value is greater than the ERTB switch disconnection threshold value, wherein the output adjustment amount of the converter station is 1.2 times of the output amount of the converter station;
the current adjusting unit specifically includes:
the timing subunit is used for calculating the duration that the first current value is not greater than a preset ERTB switch disconnection threshold value, and triggering the source end converter station to determine the subunit when the duration exceeds a preset duration threshold value;
a source end converter station determining subunit, configured to determine, according to the topology of the multi-terminal direct current transmission system, a source end converter station corresponding to the first current value;
and the current adjusting subunit is configured to adjust the first current value by adjusting an output current value of at least one source-end converter station according to a difference between the first current value and the ERTB switch disconnection threshold value, so that the adjusted first current value is greater than the ERTB switch disconnection threshold value.
3. A terminal, characterized in that it comprises: a memory and a processor;
the memory is used for storing program codes corresponding to the switching control method of the metallic return wire to ground return wire of claim 1;
the processor is configured to execute the program code.
4. A storage medium characterized in that a program code corresponding to the method for controlling switching of a metallic return wire to a ground return wire according to claim 1 is stored in the storage medium.
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