CN114640107A - Out-of-step oscillation multi-oscillation center positioning method considering RX ratio - Google Patents

Out-of-step oscillation multi-oscillation center positioning method considering RX ratio Download PDF

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CN114640107A
CN114640107A CN202210245804.2A CN202210245804A CN114640107A CN 114640107 A CN114640107 A CN 114640107A CN 202210245804 A CN202210245804 A CN 202210245804A CN 114640107 A CN114640107 A CN 114640107A
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oscillation
voltage
ratio
line
bus
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南东亮
王维庆
赵启
张路
张陵
刘志
韩连山
谭金龙
程志江
杨帅
王畅
马健
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NR Electric Co Ltd
Xinjiang University
Electric Power Research Institute of State Grid Xinjiang Electric Power Co Ltd
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NR Electric Co Ltd
Xinjiang University
Electric Power Research Institute of State Grid Xinjiang Electric Power 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
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • 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
    • H02J3/002—Flicker reduction, e.g. compensation of flicker introduced by non-linear load
    • 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
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2113/00—Details relating to the application field
    • G06F2113/04—Power grid distribution networks
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]

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Abstract

The invention discloses an out-of-step oscillation multi-oscillation center positioning method considering an RX ratio, which includes the steps of equating power grids on two sides of a power transmission line to obtain a simplified double-machine equivalent system, dividing a power transmission channel into 2 sections according to different R/X ratios, analyzing the electrical distance between the out-of-step oscillation center and equivalent generators on two sides aiming at the 2 sections of power transmission channels respectively, further obtaining the positions of the out-of-step oscillation centers of the 2 sections of power transmission channels under different R/X ratios, and obtaining which power transmission section the oscillation centers of the 2 sections of power transmission channels are respectively positioned on through reverse analysis. The invention can guide the formulation of the out-of-step oscillation out-of-step disconnection device configuration scheme, avoids the grid instability caused by the disconnection of the grid into a plurality of pieces, and is beneficial to the practical engineering application.

Description

Out-of-step oscillation multi-oscillation center positioning method considering RX ratio
Technical Field
The invention relates to the field of safety and stability of power systems, in particular to an out-of-step oscillation multi-oscillation center positioning method considering an RX ratio.
Background
In recent years, large-scale construction and operation of ultrahigh voltage direct current projects in China include sequential production of ultrahigh voltage direct current transmission projects of northwest power grids, Sichuan-Tibet networking projects and the like, and the power transmission scale of each power transmission channel is further improved. With the large-scale production of new energy in China and the promotion of relevant national policies on improving the utilization rate of the new energy, reducing the limitation of the new energy and the like, the proportion of the new energy output in large-scale new energy bases such as northwest, inner Mongolia and the like to the conventional energy output is gradually improved, and the utilization rate of the power transmission capacity of each power transmission section is operated in a long-term pressure limit manner. Under the conditions of high-capacity direct-current line locking and important section alternating-current line N-2 fault, out-of-step oscillation among different areas of a power grid is easily caused, safe and stable operation of the power grid is influenced, and reasonable countermeasures need to be taken.
Currently, the out-of-step separation research mainly focuses on the directions of positioning of an oscillation center, out-of-step separation criterion, active separation based on wide area measurement information and the like. In the existing research on the oscillation center, the oscillation center is usually located by measuring the minimum value of the apparent impedance or the minimum value of the voltage. The existing out-of-step disconnection criteria applied to domestic power systems in large quantity mainly comprise 3 types, impedance type out-of-step disconnection criteria,
Figure BDA0003544423610000011
the 3 types of criteria are mainly applied to single splitting devices at present, the splitting devices are not matched with each other, and the conditions that the wiring of a power grid is complicated and the operation mode is variable are difficult to adapt.
Currently, the research aiming at the out-of-step oscillation center does not consider the influence of different RX ratios of lines on the number of the out-of-step oscillation centers and a positioning method, but along with the development of a distributed power grid, a microgrid and the like, the RX ratio of a low-voltage-level line is obviously different from that of a high-voltage-level line, the influence of different RX ratios on the out-of-step oscillation center of the power grid is gradually highlighted, and important attention needs to be paid.
Disclosure of Invention
The purpose of the invention is as follows: the invention provides an out-of-step oscillation multi-oscillation center positioning method considering RX ratios, which solves the problem of corresponding oscillation center positioning under the condition of multiple oscillation centers caused by different RX ratios of a power transmission line.
An out-of-step oscillation multi-oscillation center positioning method taking RX ratio into account comprises the following steps:
(1) performing equivalence processing on power grids on two sides of a power transmission line based on simulation software to obtain a simplified power grid model, wherein in the simplified power grid model, if the impedance ratio of two lines is basically the same, a segmentation point is selected at any time, if the impedance ratio of the two lines is greatly different, the segmentation point is selected according to the difference of the impedance RX ratio, and the power grid model also comprises a generator-side equivalent BUS GEN and a system-side equivalent BUS BUS;
(2) selecting segmentation points based on the step (1), and obtaining electrical parameters E & lt 0 & gt and E & lt 1 for a generator-side equivalent BUS GEN1 and a system-side equivalent BUS BUS11∠δ1、Z1＝R1+jX1、X2Calculating the lowest voltage point of the first section of line and the electrical distance to the system side equivalent BUS 1;
(3) calculating the voltage lowest point of the second section of line, and calculating the electrical distance from the point to the generator-side equivalent bus GEN 1;
(4) to the station BUS of the side of the analyzed power transmission line routing systemnOne station BUS extends to the system siden+1Equating the system side outside the plant again to obtain equivalent impedance Z1′；
(5) Judgment of Z1′/Z1Whether or not it is greater than k1If yes, returning to the step (4); if not, the station BUS of the step (4) with the system side oscillation center can be obtainedn、BUSn+1Ending the positioning of the system side oscillation center, and jumping to the step (6);
(6) to analyzed power transmission line route generator side station GENnExtending a plant GEN to the system siden+1Equating the generator side outside the plant again to obtain equivalent impedance X2′；
(7) Judgment of X2′/X2Whether or not it is greater than k2If yes, returning to the step (6); if not, the available starting motor oscillation center is positioned in the plant station GEN in the step (6)n、GENn+1And the positioning of the oscillation center on the generator side is finished.
Further, the step (2) includes the following calculation process:
(21) defining the electrical distance between the lowest point of the first section of line voltage and a system side bus as Z1minRatio k to the first section line impedance1＝|Z1min|/|R+jX1I, voltage amplitude E at junction of two sections of lines2＝k*E；
(22) Calculating the first segment lineCurrent of the current path
Figure BDA0003544423610000031
Further calculating to obtain a voltage value corresponding to the voltage lowest point of the first section of line
Figure BDA0003544423610000032
(23) Voltage value to lowest point
Figure BDA0003544423610000033
Performing a squaring operation and performing a pair k1The derivation operation of (1) is performed according to the result of the voltage lowest point derivation operation
Figure BDA0003544423610000034
Considering, further obtaining the ratio k of the electrical distance from the voltage lowest point to the system side bus and the impedance of the first section of line1。
Wherein, the lowest point voltage value in the step (23)
Figure BDA0003544423610000035
The computational expression for performing the squaring operation is as follows:
Figure BDA0003544423610000036
obtaining an impedance ratio k1：
Figure BDA0003544423610000037
Further, step (22) is for the first segment line current
Figure BDA0003544423610000038
Voltage value corresponding to the lowest voltage point of the first section of line
Figure BDA0003544423610000039
The calculation expression of (a) is as follows:
current:
Figure BDA00035444236100000310
minimum point voltage:
Figure BDA00035444236100000311
in the above method, the step (3) includes the following calculation process:
(31) defining the ratio of the electrical distance from the lowest point of the second section of line voltage to the generator side bus to the second section of line impedance as k2；
(32) Calculating the second line current
Figure BDA00035444236100000312
Further calculating to obtain a voltage value corresponding to the voltage lowest point of the second section of line
Figure BDA00035444236100000313
Wherein, take E1＝E；
(33) To lowest point voltage value
Figure BDA0003544423610000041
Performing a square operation and applying k2The derivation operation of (1) is performed according to the result of the voltage lowest point derivation operation
Figure BDA0003544423610000042
Considering, the ratio k of the electrical distance from the voltage lowest point to the generator side bus to the impedance of the second section of line is further obtained2。
Wherein the step (33) is to the lowest point voltage value
Figure BDA0003544423610000043
The computational expression for performing the squaring operation is as follows:
Figure BDA0003544423610000044
calculating the impedance ratio k2：
Figure BDA0003544423610000045
Step (32) for the second section of line current
Figure BDA0003544423610000046
Voltage value corresponding to the lowest voltage point of the second line section
Figure BDA0003544423610000047
The calculation expression of (a) is as follows:
current:
Figure BDA0003544423610000048
minimum point voltage:
Figure BDA0003544423610000049
in the above method, wherein:
GEN1 is an equivalent bus at the side close to the generator;
BUS1 is an equivalent BUS near the system side;
Z1＝R+jX1the impedance is the equivalent impedance of the near system side, namely the impedance of the first section of line;
X2the impedance is equivalent impedance at the side close to the generator, namely the impedance of the second section of line, and the impedance ratio is approximately considered to be lower due to the side close to the generator, and the impedance is equivalent to pure reactance;
e & lt 0 DEG is the equivalent voltage and the corresponding power angle of the system side, and the default power angle of the system side is 0 DEG;
E1∠δ1for generator side equivalent voltage and corresponding power angle delta1；
E2∠δ2For equivalent voltage and corresponding angle delta at the junction of two end lines2。
Has the advantages that: compared with the prior art, the out-of-step oscillation multi-oscillation center positioning method considering the RX ratio can guide the positioning of the out-of-step oscillation center and the configuration of the out-of-step separation device, can avoid the disordered action of the out-of-step separation device under the out-of-step condition by locking the positions of a plurality of oscillation centers in advance, and reduces the power grid stability risk; on the other hand, the positioning method of the oscillation center provided by the invention is simple in calculation and beneficial to practical engineering application.
Drawings
FIG. 1 is a general flow diagram of the process of the present invention;
FIG. 2 is a schematic diagram of an equivalent grid according to the method of the present invention;
FIG. 3 is a schematic diagram of a simulation of a power grid in an embodiment;
FIG. 4 is a graph of voltage angle difference between different nodes during out-of-step oscillation in the embodiment;
FIG. 5 shows different node voltages during the out-of-step oscillation in the embodiment.
Detailed Description
The invention is described in further detail below with reference to the drawings and the detailed description.
The invention provides an out-of-step oscillation multi-oscillation center positioning method considering an RX ratio, which is characterized in that a simplified double-machine equivalent system is obtained by equating power grids on two sides of a power transmission line, power transmission channels are divided into 2 sections according to different R/X ratios, the electrical distance between the out-of-step oscillation center and equivalent generators on two sides is analyzed respectively aiming at the 2 sections of the power transmission channels, the positions of the out-of-step oscillation centers of the 2 sections of the power transmission channels under different R/X ratios are further obtained, and which power transmission section the oscillation centers of the 2 sections of the power transmission channels are respectively positioned in is obtained through reverse analysis.
Specifically, first, as shown in fig. 1, a general flow chart of the present invention includes the following steps:
step 1, equivalence is carried out on power grids on two sides of a power transmission line to be analyzed based on power system simulation software and corresponding basic data containing power grid parameters, and a simplified power grid model shown in figure 2 is obtained.
In combination with the prior art, including the definition and terminology of the electrical parameters in the power grid system and the definition of the parameters in the existing simulation system software, the part of the electrical parameters used for calculation in this embodiment are described as follows:
GEN1 is an equivalent bus at the side close to the generator;
BUS1 is an equivalent BUS near the system side;
Z1＝R+jX1the equivalent impedance of the near system side, namely the impedance of the first section of the line in the embodiment;
X2the impedance is equivalent impedance at the side close to the generator, namely, the impedance of the second segment of the circuit in the embodiment, and the impedance ratio can be approximately considered to be lower at the side close to the generator, and the impedance is equivalent to pure reactance;
e & lt 0 DEG is the equivalent voltage and the corresponding power angle of the system side, and the default power angle of the system side is 0 DEG;
E1∠δ1for generator side equivalent voltage and corresponding power angle delta1；
E2∠δ2For equivalent voltage and corresponding angle delta at the junction of two end lines2。
Step 2, according to the electrical parameters E & lt 0 & gt and E obtained in the step 11∠δ1、Z1＝R1+jX1、X2The voltage lowest point of the first leg of the line and the electrical distance to the system side equivalent BUS1 are calculated.
For the step (2), the specific calculation process and implementation process are as follows:
(21) defining the electrical distance between the lowest point of the first section of line voltage and a system side bus as Z1minRatio k to the first section line impedance1＝|Z1min|/|R+jX1I, voltage amplitude E at junction of two sections of lines2＝k*E；
(22) Calculating the first section line current
Figure BDA0003544423610000061
Further calculating to obtain a voltage value corresponding to the voltage lowest point of the first section of line
Figure BDA0003544423610000062
The calculation formula is shown in formulas (1) to (2).
Current:
Figure BDA0003544423610000063
minimum point voltage:
Figure BDA0003544423610000064
(23) voltage value to lowest point
Figure BDA0003544423610000065
Performing a squaring operation, as shown in formula (3), and performing a pair k on formula (3)1The derivation operation of (1) is performed according to the result of the voltage lowest point derivation operation
Figure BDA0003544423610000066
Considering, further obtaining the ratio k of the electrical distance from the voltage lowest point to the system side bus and the impedance of the first section of line1The final result of (3) is shown in formula (4).
And (3) square operation of the lowest point voltage:
Figure BDA0003544423610000071
impedance ratio k1：
Figure BDA0003544423610000072
And 3, further calculating the voltage lowest point of the second section of line and the electric distance from the generator-side equivalent bus GEN1 according to the calculation mode in the step 2.
For the step (3), the implementation process and the calculation method are specifically as follows:
(31) defining the ratio of the electrical distance from the lowest point of the second section of line voltage to the generator side bus to the second section of line impedance as k2；
(32) Calculating the second line current
Figure BDA0003544423610000073
Further calculating to obtain a voltage value corresponding to the voltage lowest point of the second section of line
Figure BDA0003544423610000074
The calculation formula is shown in formulas (5) to (6), wherein, for simplification, E is taken1＝E，
Current:
Figure BDA0003544423610000075
minimum point voltage:
Figure BDA0003544423610000076
(33) voltage value to lowest point
Figure BDA0003544423610000077
Performing a squaring operation, as shown in equation (7), and performing a pair k on equation (7)2The derivation operation of (1) is performed according to the result of the voltage lowest point derivation operation
Figure BDA0003544423610000078
Considering, the ratio k of the electrical distance from the voltage lowest point to the generator side bus to the impedance of the second section of line is further obtained2The final result of (2) is shown in formula (8).
Wherein, the operation of the square of the lowest point voltage in the step (33) is as follows:
Figure BDA0003544423610000081
impedance ratio k2：
Figure BDA0003544423610000082
Step 4, analyzing the power transmission line routing system side station BUSnOne station BUS extends to the system siden+1Equating the system side outside the plant again to obtain equivalent impedance Z1′。
Step 5, judging Z1′/Z1Whether or not it is greater than k1If yes, returning to the step (4); if not, the station BUS with the system side oscillation center positioned in the step 4 can be obtainedn、BUSn+1And finally, positioning the system side oscillation center is finished, and the step 6 is skipped.
Step 6, analyzing the GEN of the power transmission line route generator side stationnExtending a plant GEN to the system siden+1Equating the generator side outside the plant again to obtain equivalent impedance X2′。
Step 7, judging X2′/X2Whether or not it is greater than k2If yes, returning to the step (6); if not, the available starting motor oscillation center is positioned in the plant station GEN in the step (6)n、GENn+1And the positioning of the oscillation center on the generator side is finished.
Still further, according to the general flow chart in fig. 1, taking the power system shown in fig. 3 as an example, the specific steps of the present invention are described as follows:
under the mode that the impedance angle of the line Z1 is 60 degrees, the impedance value of the line is taken to be 0.5+ j0.866 p.u., and the reactance of the generator is fixed to be j1.0 p.u. At this time, in the case of a single transient fault on the line, the system is subjected to out-of-step oscillation.
By observing the phase angle difference curve of the bus between the nodes, as shown in fig. 4, it is found that the phase angle difference between the nodes 7 and 8 and between the nodes 8 and 9 varies between 0 ° and 360 °, and the angle variation trends are the same. Further, the voltages of the nodes in the first period of the step-out oscillation, i.e., 2.6s to 2.9s, are selected for comparison, as shown in fig. 5, and the lowest points of the voltages are approximately located at the nodes 7 and 9 on both sides of the node 8 in the step-out oscillation process.

Claims (7)

1. An out-of-step oscillation multi-oscillation center positioning method considering RX ratio is characterized by comprising the following steps of: the method comprises the following steps:
(1) performing equivalence processing on power grids on two sides of a power transmission line based on simulation software to obtain a simplified power grid model, wherein in the simplified power grid model, if the impedance ratio of two lines is basically the same, a segmentation point is selected at any time, if the impedance ratio of the two lines is greatly different, the segmentation point is selected according to the difference of the impedance RX ratio, and the power grid model also comprises a generator-side equivalent BUS GEN and a system-side equivalent BUS BUS;
(2) selecting segmentation points based on the step (1), and obtaining electrical parameters E & lt 0 & gt and E & lt 1 for a generator-side equivalent BUS GEN1 and a system-side equivalent BUS BUS11∠δ1、Z1＝R1+jX1、X2Calculating the lowest voltage point of the first section of line and the electrical distance to the system side equivalent BUS 1;
(3) calculating the voltage lowest point of the second section of line, and calculating the electrical distance from the point to the generator-side equivalent bus GEN 1;
(4) to the station BUS of the side of the analyzed power transmission line routing systemnOne station BUS extends to the system siden+1Equating the system side outside the plant again to obtain equivalent impedance Z1′；
(5) Judgment of Z1′/Z1Whether or not it is greater than k1If yes, returning to the step (4); if not, the station BUS of the step (4) with the system side oscillation center can be obtainedn、BUSn+1Ending the positioning of the system side oscillation center, and jumping to the step (6);
(6) to analyzed transmission line route generator side station GENnExtending a plant GEN to the system siden+1Equating the generator side outside the plant again to obtain equivalent impedance X2′；
(7) Judgment of X2′/X2Whether or not it is greater than k2If yes, returning to the step (6); if not, the available starting motor oscillation center is positioned in the plant station GEN in the step (6)n、GENn+1And the positioning of the oscillation center on the generator side is finished.
2. The out-of-step oscillation multi-oscillation centering method taking into account RX ratio of claim 1, wherein said step (2) comprises the calculation process of:
(21) defining the first section line voltageThe low point is at an electrical distance Z from the side bus of the system1minRatio k to the first section line impedance1＝|Z1min|/|R+jX1I, voltage amplitude E at junction of two sections of lines2＝k*E；
(22) Calculating the first section line current
Figure FDA0003544423600000021
Then the voltage value corresponding to the voltage lowest point of the first section of line is calculated and obtained
Figure FDA0003544423600000022
(23) Voltage value to lowest point
Figure FDA0003544423600000023
Performing a squaring operation and performing a pair k1The derivation operation of (1) is performed according to the result of the voltage lowest point derivation operation
Figure FDA0003544423600000024
Considering, further obtaining the ratio k of the electrical distance from the voltage lowest point to the system side bus and the impedance of the first section of line1。
3. Out-of-sync oscillation multi-oscillation centering method taking into account RX ratio as claimed in claim 2, wherein the voltage value to the lowest point in step (23)
Figure FDA0003544423600000025
The computational expression for performing the squaring operation is as follows:
Figure FDA0003544423600000026
obtaining an impedance ratio k1：
Figure FDA0003544423600000027
4. Out-of-sync oscillatory multi-oscillation centering method taking RX ratio into account as claimed in claim 2, wherein step (22) is for the first section line current
Figure FDA0003544423600000028
Voltage value corresponding to the lowest voltage point of the first section of line
Figure FDA0003544423600000029
The calculation expression of (a) is as follows:
current:
Figure FDA00035444236000000210
minimum point voltage:
Figure FDA00035444236000000211
5. out-of-sync oscillation multi-oscillation centering method taking into account RX ratio according to claim 1, wherein said step (3) comprises the calculation procedure of:
(31) defining the ratio of the electrical distance from the lowest point of the second section of line voltage to the generator side bus to the second section of line impedance as k2；
(32) Calculating the second line current
Figure FDA0003544423600000031
Further calculating to obtain a voltage value corresponding to the voltage lowest point of the second section of line
Figure FDA0003544423600000032
Wherein, take E1＝E；
(33) To lowest point voltage value
Figure FDA0003544423600000033
The square operation is carried out to carry out the square operation,and pair k2The derivation operation of (1) is performed according to the result of the voltage lowest point derivation operation
Figure FDA0003544423600000034
Considering, the ratio k of the electrical distance from the voltage lowest point to the generator side bus to the impedance of the second section of line is further obtained2。
6. The out-of-step oscillation multi-oscillation centering method taking into account RX ratio of claim 5, wherein step (33) is to locate the lowest point voltage value
Figure FDA0003544423600000035
The computational expression for performing the squaring operation is as follows:
Figure FDA0003544423600000036
calculating the impedance ratio k2：
Figure FDA0003544423600000037
7. The out-of-step oscillation multi-oscillation centering method taking into account RX ratio of claim 5, wherein step (32) is performed for a second segment of line current
Figure FDA0003544423600000038
Voltage value corresponding to the lowest voltage point of the second line section
Figure FDA0003544423600000039
The calculation expression of (a) is as follows:
current:
Figure FDA00035444236000000310
minimum point voltage:
Figure FDA00035444236000000311
CN202210245804.2A 2022-03-14 2022-03-14 Out-of-step oscillation multi-oscillation center positioning method considering RX ratio Pending CN114640107A (en)

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