Accurate calculation method for distribution characteristics of voltage along line aiming at series charging of ultrahigh-voltage power transmission line

Abstract

The invention provides a method for accurately calculating distribution characteristics of voltage along a line aiming at series charging of an ultrahigh-voltage transmission line, which comprises the following steps of: firstly, calculating line wave impedance and propagation constants based on line power frequency lumped parameters or distribution parameters; calling a voltage load flow calculation result of any one of the head end, the series charging point and the tail end of the series charging line in the load flow simulation result of the power system; secondly, considering the position of a line parallel high-voltage reactor, and calculating voltage distribution and head end current along a second section of line according to a voltage reading result; then, calculating the tail end current of the first section of line and the voltage distribution along the first section of line; and finally, drawing a voltage distribution curve along the series charging line, and returning the highest value of the voltage along the line and the corresponding position. The method can quickly and accurately calculate the voltage distribution curve along the series charging line of the ultrahigh-voltage transmission line when the parallel high-voltage reactor of the line is located at different positions of the series charging line, and can effectively avoid the damage of overvoltage along the line to the insulation of power equipment during debugging.

Description

Technical Field

[0001] The present invention relates to a steady-state voltage calculation scenario for startup and commissioning of a new power transmission project in an electric power system, and specifically to an accurate calculation method for voltage distribution characteristics along a series charging of an ultra-high voltage transmission line. Background Art

[0002] Before the new ultra-high voltage transmission project of the power system is put into operation and power transmission, the startup and commissioning of the new equipment must be completed. The startup and commissioning work includes switch protection verification, phase verification test, bus phase verification test, new line switching test, synchronous closing test, etc. The line is facing the risk of voltage exceeding the maximum working voltage along the line when it is empty and charging, which will cause damage to the insulation of power equipment. When a line parallel high-voltage reactor is installed at the head or end of the new line, the highest voltage along the line when it is empty and charging may not appear at the charging end. It is related to the side where the charging power source is located, the capacity of the line parallel high-voltage reactor, and the electrical parameters of the line. When the new transmission project involves line π connection or there are new lines at adjacent sites, there are often two lines in series charging during the startup and commissioning process. At this time, the highest voltage along the line of the line series charging and the location are related to the electrical parameters of the two lines, and the voltage distribution characteristics are more complicated. However, the current power system simulation software, typified by the Power System Analysis Comprehensive Program (PSASP), can only calculate the voltage at the head and end of the line, and cannot calculate the voltage along the series charging line, nor can it give the highest voltage along the series charging line and the location. When the series charging line is segmented, only the voltage simulation results of the nodes in the segment can be obtained, and the voltage distribution characteristics along the series charging line cannot be accurately described.

[0003] Therefore, for the ultra-high voltage transmission long line series charging scenario including line shunt high-voltage reactors, it is urgent to study the fast and accurate calculation method of the voltage distribution characteristics along the series charging line under different installation positions of the line shunt high-voltage reactors, so as to meet the calculation requirements of the maximum steady-state voltage along the line during the startup and commissioning of new transmission projects. Summary of the invention

[0004] The technical problem to be solved by the present invention is a method for calculating the voltage distribution characteristics along the series charging line of a transmission line. The method is based on the voltage simulation results of the nodes at either end of the series charging line, considers the different installation positions of the line parallel high-voltage reactors, calculates the voltage distribution along the series charging line in sequence, and finally returns the voltage distribution curve and the maximum value information along the line. The method can be applied to the steady-state voltage calculation scenario of the startup and commissioning of a new transmission project, thereby avoiding damage to power equipment caused by overvoltage along the line during commissioning, and ensuring the safe and stable operation of the power grid.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A method for accurately calculating voltage distribution characteristics along a series charge of an ultra-high voltage transmission line comprises the following steps:

[0007] (1) Calculating line electrical parameters based on line power frequency concentrated parameters or distributed parameters, the line electrical parameters including line wave impedance and propagation constant, and retrieving voltage flow calculation results of any node at the head end, the string charging point and the end of the series charging line in the power system flow simulation results;

[0008] (2) Based on the line electrical parameters and node voltage flow calculation results obtained in step (1), considering the situation where the line shunt high-voltage reactor is located at different positions of the series charging line, calculate the voltage distribution along the second section of the series charging line and the head-end current;

[0009] (3) obtaining the voltage and current information at the first end of the second line segment according to the calculation result of step (2), and calculating the current at the end of the first line segment and the voltage distribution along the first line segment;

[0010] (4) According to the voltage distribution along the second section of the line calculated in step (2) and the voltage distribution along the first section of the line calculated in step (3), the highest voltage point and position along the line are identified, and a voltage distribution curve along the series charging line is drawn.

[0011] Furthermore, in the step (1), the line power frequency centralized parameters or distributed parameters are obtained based on the basic database of the power system simulation software PSASP, wherein the centralized parameters include π-type equivalent impedance, susceptance, rated capacity and rated voltage of the line parallel high-voltage reactor, and line length; and the distributed parameters include impedance per unit length, susceptance, rated capacity and rated voltage of the line parallel high-voltage reactor, and line length.

[0012] Furthermore, the step (2) calculates the voltage distribution along the line and the head-end current of the second section of the series charging line based on the voltage flow calculation results of the head end, the series charging point, and any node at the end of the series charging line read from the flow simulation results according to the line electrical parameters obtained in step (1), for the three situations where the line shunt high-voltage reactor is located at the end of the first section of the line, the beginning of the second section of the line, and the end of the second section of the line, wherein the series charging point is the end of the first section of the line or the beginning of the second section of the line.

[0013] Furthermore, when the line shunt high-voltage reactor is located at the end of the first line or the beginning of the second line, assuming that the parameters of each line section are evenly distributed along the line, the voltage and current at any position of the second line section are as follows:

[0014]

[0015]

[0016] In the formula, They represent the voltage and current of the node at a distance of n from the end of the line respectively; is the voltage at the end of the second line; γ2, Z C2 They represent the line propagation constant and wave impedance of the second line segment respectively; n is the line length at any position from the end of the second line segment;

[0017] The voltage and current along the second section of the line are calculated based on the voltage flow calculation results of any node at the head end, the series charging point and the end of the series charging line obtained by the PSASP power flow simulation:

[0018] 1) Known series charging point voltage

[0019]

[0020]

[0021] 2) Known line end voltage

[0022]

[0023]

[0024] 3) Known line head voltage

[0025]

[0026]

[0027] In the formula, γ1, Z C1 They represent the line propagation constant and wave impedance of the second line segment respectively; Indicates the voltage at the end of the first line segment; is the current at the beginning of the second line; is the voltage at the end of the second line; L2 is the length of the second line; X L It is the reactance value of the line shunt high-voltage reactor located at the end of the first line section or the beginning of the second line section, calculated based on the rated capacity and rated voltage.

[0028] Furthermore, when the line shunt high-voltage reactor is located at the end of the second line section, assuming that the parameters of each line section are evenly distributed along the line, the voltage and current at any position of the second line section are as follows:

[0029]

[0030]

[0031] Where, X L2is the reactance value of the line shunt high-voltage reactor at the end of the second line section, calculated based on the rated capacity and rated voltage;

[0032] The voltage and current along the second section of the line are calculated based on the voltage flow calculation results of any node at the head end, the series charging point and the end of the series charging line obtained by the PSASP power flow simulation:

[0033] 1) Known series charging point voltage

[0034]

[0035]

[0036] 2) Known line end voltage

[0037]

[0038]

[0039] 3) Known line head voltage

[0040]

[0041]

[0042] In the formula, γ2, Z C2 They represent the line propagation constant and wave impedance of the second line segment respectively; n is the line length at any position from the end of the second line segment; They represent the voltage and current of the node at a distance of n from the end of the line respectively; is the voltage at the end of the second line segment.

[0043] Furthermore, the step (3) obtains the voltage and current at the first end of the second line segment according to the calculation result of step (2), calculates the current at the end of the first line segment and the voltage distribution along the first line segment, and specifically includes:

[0044] 1) When the line shunt high-voltage reactor is located at the end of the first line or the beginning of the second line, the current at the end of the first line and the voltage at any position are as follows:

[0045]

[0046]

[0047] In the formula, is the current at the end of the first line section; is the current at the beginning of the second line; Indicates the voltage at the first end of the second line; X L The reactance value of the line shunt high-voltage reactor located at the end of the first line section or the beginning of the second line section is calculated based on the rated capacity and rated voltage; It represents the voltage of the node at the first line section where the line length is m from the end of the line; Indicates the voltage at the beginning of the second line; γ1, Z C1 They represent the line propagation constant and wave impedance of the first line segment respectively; m is the line length at any position from the end of the first line segment;

[0048] 2) When the line shunt high-voltage reactor is located at the end of the second line, the current at the end of the first line and the voltage at any position are as follows:

[0049]

[0050]

[0051] The beneficial effects of the present invention are as follows: the present invention explores a method for accurately calculating the voltage distribution characteristics along the ultra-high voltage transmission line during series charging, and can quickly and accurately calculate the voltage distribution curve along the ultra-high voltage transmission line when the line parallel high-voltage reactor is located at different positions of the series charging line, effectively making up for the limitation that the existing power system simulation software can only calculate the voltage at the beginning and end of the line, and can provide the maximum value and position information of the voltage along the series charging line when the maximum value is not at the charging end, which is superior to the traditional segmented simulation or segmented iteration method, and is suitable for the steady-state voltage calculation scenario of the startup and commissioning of a new transmission project, and has important guiding significance for the boundary conditions of engineering commissioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A schematic flow chart of a method for accurately calculating voltage distribution characteristics along a series charge of an ultra-high voltage transmission line according to an embodiment of the present invention;

[0053] Figure 2 It is a voltage distribution curve diagram along the series charging line AB and line BC of the present invention;

[0054] Figure 3 It is a curve diagram of voltage distribution along the series charging lines DE and EF of the present invention. DETAILED DESCRIPTION

[0055] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0056] like Figure 1As shown, an embodiment of the present invention provides a method and program for accurately calculating the voltage distribution characteristics along the series charging of an ultra-high voltage transmission line. First, the line wave impedance and propagation constant are calculated based on the concentrated parameters or distributed parameters of the line power frequency, and the voltage flow calculation results of any node at the beginning, charging point and end of the series charging line in the power system flow simulation results are retrieved; secondly, considering the location of the line parallel high-voltage reactor, the voltage distribution along the second section of the line and the head end current are calculated according to the voltage reading results; then, the end current of the first section of the line and the voltage distribution along the first section of the line are calculated; finally, the voltage distribution curve along the series charging line is drawn, and the maximum voltage value along the line and the corresponding position are returned.

[0057] The power frequency centralized parameters or distributed parameters of each section of the line are obtained based on the basic database of the power system simulation software PSASP: 1) centralized parameters: π-type equivalent impedance, susceptance, rated capacity and rated voltage of the line parallel high-voltage reactor, and line length; 2) distributed parameters: impedance and susceptance per unit length, rated capacity and rated voltage of the line parallel high-voltage reactor, and line length. Then, the wave impedance and propagation constant of each section of the series charging line are calculated based on the centralized parameters / distributed parameters of the line.

[0058] The voltage distribution along the second section of the line and the calculation of the head-end current will be carried out based on the voltage flow calculation results of the head end of the series charging line, the series charging point (the end of the first section of the line / the beginning of the second section of the line), and any node at the end read from the flow simulation results, for different situations where the line shunt high-voltage reactor is located at the end of the first section of the line, the beginning of the second section of the line, and the end of the second section of the line. The voltage distribution along the second section of the series charging line and the head-end current will be calculated.

[0059] When the line shunt high-voltage reactor is located at the end of the first line or the beginning of the second line, the voltage distribution along the second line and the current at the beginning are calculated as follows:

[0060] Assuming that the parameters of each section of the line are evenly distributed along the line, the voltage and current at any position of the second section of the line are as follows:

[0061]

[0062]

[0063] In the formula, γ2, Z C2 They represent the line propagation constant and wave impedance of the second line segment respectively; n is the line length at any position from the end of the second line segment; They represent the voltage and current of the node at a distance of n from the end of the line respectively; is the voltage at the end of the second line segment.

[0064] The voltage and current along the second section of the line are calculated based on the voltage flow calculation results of any node at the head end, the series charging point and the end of the series charging line retrieved from the PSASP power flow simulation.

[0065] 1) Known series charging point voltage

[0066]

[0067]

[0068] 2) Known line end voltage

[0069]

[0070]

[0071] 3) Known line head voltage

[0072]

[0073]

[0074] In the formula, γ1, Z C1 They represent the line propagation constant and wave impedance of the second line segment respectively; Indicates the voltage at the end of the first line segment; is the current at the beginning of the second line; is the voltage at the end of the second line; L2 is the length of the second line; X L It is the reactance value of the line shunt high-voltage reactor located at the end of the first line section or the beginning of the second line section, which can be calculated based on the rated capacity and rated voltage.

[0075] When the line shunt high-voltage reactor is located at the end of the second line, the voltage distribution along the second line and the head-end current calculation are as follows:

[0076] Assuming that the parameters of each section of the line are evenly distributed along the line, the voltage and current at any position of the second section of the line are as follows:

[0077]

[0078]

[0079] Where, X L2 It is the reactance value of the line shunt high-voltage reactor located at the end of the second section of the line, which is calculated based on the rated capacity and rated voltage.

[0080] The voltage and current along the second section of the line are calculated based on the voltage flow calculation results of any node at the head end, the series charging point and the end of the series charging line retrieved from the PSASP power flow simulation.

[0081] 1) Known series charging point voltage

[0082]

[0083]

[0084] 2) Known line end voltage

[0085]

[0086]

[0087] 3) Known line head voltage

[0088]

[0089]

[0090] The method for calculating the voltage distribution along the first section of the line is as follows:

[0091] Based on the above calculation, the voltage and current at the first end of the second line section are obtained, and the current at the end of the first line section and the voltage distribution along the first line section are further calculated.

[0092] 1) When the line shunt high-voltage reactor is located at the end of the first line or the beginning of the second line, the current at the end of the first line and the voltage at any position are as follows:

[0093]

[0094]

[0095] Where m is the length of the line at any position from the end of the first line segment; It represents the voltage of the node at the first line section where the line length is m from the end of the line; is the current at the end of the first line section; Indicates the voltage at the beginning of the second line.

[0096] 2) When the line shunt high-voltage reactor is located at the end of the second line, the current at the end of the first line and the voltage at any position are as follows:

[0097]

[0098]

[0099] Example verification analysis 1:

[0100] Taking the line series charging during the startup and commissioning of a new power transmission and transformation project as an example, the precise calculation method of the voltage distribution characteristics along the line for series charging of ultra-high voltage transmission lines is verified and analyzed on the MATLAB 2018a simulation platform.

[0101] First, the centralized parameters of the power frequency of the series charging line obtained based on the basic database of the power system simulation software PSASP are as follows:

[0102] The length of the ultra-high voltage line AB is 179.586 km, and the length of the ultra-high voltage line BC is 44.7 km. The line parameters are shown in Table 1 below. The B side of line AB has a line parallel high-voltage reactor with a rated capacity of 150 Mvar and a rated voltage of 550 kV.

[0103] Table 1 500kV line AB, BC power frequency centralized parameter standard value reference value: U b =525kV, S b =100MVA

[0104] Line Name <![CDATA[R1]]> <![CDATA[X1]]> <![CDATA[B1 / 2]]> <![CDATA[R0]]> <![CDATA[X0]]> <![CDATA[B0 / 2]]> BC 0.000230 0.004296 0.266711 0.002944 0.012127 0.151395 AB 0.001162 0.017533 1.056712 0.012132 0.047886 0.688674

[0105] The stations on both sides of line AB are substation A and substation B, and the stations on both sides of line BC are substation B and substation C. Considering the scenario of charging line AB in series with line BC (operating with line parallel high-voltage reactors) with substation A as the power source, the electrical parameters of the line and the location of the parallel high-voltage reactor are known. Based on PSASP, the node voltage at the head end of the series line is obtained as 531.53∠-25.68°kV. The proposed precise calculation method and program for the voltage distribution characteristics along the series charging line are used to calculate the voltage distribution characteristics along the line of line AB and line BC. Starting from the A side of line AB, the voltage distribution curves along line AB and line BC are as follows Figure 2 The highest voltage along the line is 535.17 kV, located at 108.7 km from the A side of line AB; the voltage at the B side of line AB is 533.63 kV; the voltage at the C side of line BC is 534.24 kV.

[0106] Example verification analysis 2:

[0107] Taking the line series charging during the startup and commissioning of a new power transmission and transformation project as an example, the precise calculation method of the voltage distribution characteristics along the line for series charging of ultra-high voltage transmission lines is verified and analyzed on the MATLAB 2018a simulation platform.

[0108] First, the centralized parameters of the power frequency of the series charging line obtained based on the basic database of the power system simulation software PSASP are as follows:

[0109] The length of the ultra-high voltage line DE is 62.98 km, and the length of the ultra-high voltage line EF is 162.68 km. The line parameters are shown in Table 2 below. The F side of line EF has a line parallel high-voltage reactor with a rated capacity of 150 Mvar and a rated voltage of 550 kV.

[0110] Table 2 500kV line DE, EF power frequency centralized parameter standard value reference value: U b =525kV, S b =100MVA

[0111] Line Name <![CDATA[R1]]> <![CDATA[X1]]> <![CDATA[B1 / 2]]> <![CDATA[R0]]> <![CDATA[X0]]> <![CDATA[B0 / 2]]> DE 0.000217 0.006138 0.396357 0.004623 0.020431 0.218591 EF 0.000561 0.015853 1.023769 0.011940 0.052771 0.564608

[0112] The stations on both sides of line DE are substation D and substation E, and the stations on both sides of line EF are substation E and substation F. Considering the scenario of charging line DE in series with line EF (operating with line parallel high-voltage reactors) with substation D as the power source, the electrical parameters of the line and the position of the parallel high-voltage reactor are known. Based on PSASP, the series node voltage of the series line is obtained as 527.25∠-6.82°kV. The proposed accurate calculation method and program for the voltage distribution characteristics along the series charging line are used to calculate the voltage distribution characteristics along the line of line DE and line EF. Starting from the D side of line DE, the voltage distribution curves along line DE and line EF are as follows Figure 3 The highest voltage along the line is 528.21 kV, located at 54.3 km from the E side of line EF; the voltage at the F side of the end of line EF is 524.40 kV.

[0113] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for accurately calculating the voltage distribution characteristics along the ultra-high voltage transmission line series charging, characterized in that: The following steps are involved: (1) Calculating line electrical parameters based on line power frequency concentrated parameters or distributed parameters, the line electrical parameters including line wave impedance and propagation constant, and retrieving voltage flow calculation results of any node at the head end, the string charging point and the end of the series charging line in the power system flow simulation results; (2) Based on the line electrical parameters and node voltage flow calculation results obtained in step (1), considering the situation where the line shunt high-voltage reactor is located at different positions of the series charging line, calculate the voltage distribution along the second section of the series charging line and the head-end current; (3) obtaining the voltage and current information at the first end of the second line segment according to the calculation result of step (2), and calculating the current at the end of the first line segment and the voltage distribution along the first line segment; (4) According to the voltage distribution along the second section of the line calculated in step (2) and the voltage distribution along the first section of the line calculated in step (3), the highest voltage point and position along the line are identified, and a voltage distribution curve along the series charging line is drawn.

2. According to claim 1, a method for accurately calculating the voltage distribution characteristics along the ultra-high voltage transmission line series charging is characterized in that: In the step (1), the power frequency concentrated parameters or distributed parameters of the line are obtained based on the basic database of the power system simulation software PSASP, wherein the concentrated parameters include π-type equivalent impedance, susceptance, rated capacity and rated voltage of the line parallel high-voltage reactor, and line length; the distributed parameters include impedance and susceptance per unit length, rated capacity and rated voltage of the line parallel high-voltage reactor, and line length.

3. According to claim 1, a method for accurately calculating the voltage distribution characteristics along the ultra-high voltage transmission line series charging is characterized in that: The step (2) calculates the voltage distribution along the line and the head-end current of the second section of the series charging line based on the voltage flow calculation results of the head end, the series charging point, and any node at the end of the series charging line read from the flow simulation results according to the line electrical parameters obtained in step (1), for the three situations where the line shunt high-voltage inductor is located at the end of the first section of the line, the beginning of the second section of the line, and the end of the second section of the line, wherein the series charging point is the end of the first section of the line or the beginning of the second section of the line.

4. According to claim 3, a method for accurately calculating the voltage distribution characteristics along the ultra-high voltage transmission line series charging is characterized in that: When the line shunt high-voltage reactor is located at the end of the first line or the beginning of the second line, assuming that the parameters of each line section are evenly distributed along the line, the voltage and current at any position of the second line section are as follows: In the formula, They represent the voltage and current of the node at a distance of n from the end of the line respectively; is the voltage at the end of the second line; γ2, Z C2 They represent the line propagation constant and wave impedance of the second line segment respectively; n is the line length at any position from the end of the second line segment; The voltage and current along the second section of the line are calculated based on the voltage flow calculation results of any node at the head end, the series charging point and the end of the series charging line obtained by the PSASP power flow simulation: 1) Known series charging point voltage 2) Known line end voltage 3) Known line head voltage In the formula, γ1, Z C1 They represent the line propagation constant and wave impedance of the second line segment respectively; Indicates the voltage at the end of the first line segment; is the current at the beginning of the second line; is the voltage at the end of the second line; L2 is the length of the second line; X L It is the reactance value of the line shunt high-voltage reactor located at the end of the first line section or the beginning of the second line section, calculated based on the rated capacity and rated voltage.

5. According to claim 3, a method for accurately calculating the voltage distribution characteristics along the ultra-high voltage transmission line series charging is characterized in that: When the line shunt high-voltage reactor is located at the end of the second section of the line, assuming that the parameters of each section of the line are evenly distributed along the line, the voltage and current at any position of the second section of the line are as follows: Where, X L2 is the reactance value of the line shunt high-voltage reactor at the end of the second line section, calculated based on the rated capacity and rated voltage; The voltage and current along the second section of the line are calculated based on the voltage flow calculation results of any node at the head end, the series charging point and the end of the series charging line obtained by the PSASP power flow simulation: 1) Known series charging point voltage 2) Known line end voltage 3) Known line head voltage In the formula, γ2, Z C2 They represent the line propagation constant and wave impedance of the second line segment respectively; n is the line length at any position from the end of the second line segment; They represent the voltage and current of the node at a distance of n from the end of the line respectively; is the voltage at the end of the second line segment.

6. The method for accurately calculating the voltage distribution characteristics along the ultra-high voltage transmission line series charging according to claim 1 is characterized in that: The step (3) obtains the voltage and current at the first end of the second line segment according to the calculation result of the step (2), calculates the current at the end of the first line segment and the voltage distribution along the first line segment, and specifically includes: 1) When the line shunt high-voltage reactor is located at the end of the first line or the beginning of the second line, the current at the end of the first line and the voltage at any position are as follows: In the formula, is the current at the end of the first line section; is the current at the beginning of the second line; Indicates the voltage at the first end of the second line; X L The reactance value of the line shunt high-voltage reactor located at the end of the first line section or the beginning of the second line section is calculated based on the rated capacity and rated voltage; It represents the voltage of the node at the end of the first line where the line length is m; Indicates the voltage at the beginning of the second line; γ1, Z C1 They represent the line propagation constant and wave impedance of the first section of the line respectively; m is the length of the line at any position from the end of the first line segment; 2) When the line shunt high-voltage reactor is located at the end of the second line, the current at the end of the first line and the voltage at any position are as follows:

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