CN111130069B - Method and system for calculating direct current power grid line operation overvoltage - Google Patents
Method and system for calculating direct current power grid line operation overvoltage Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention discloses a method and a system for calculating the operation overvoltage of a direct current power grid line, which are used for obtaining the initial parameter of the calculation of the monopolar earth fault operation overvoltage of the direct current power grid line; establishing an electromagnetic simulation calculation analysis model of the operation overvoltage during the monopolar grounding fault; segmenting a direct-current power grid line, and setting a single-pole grounding fault point at each segment; determining influence factors and setting levels of direct current power grid line operation overvoltage; designing an orthogonal table containing influence factors according to an orthogonal test method, and respectively calculating the maximum line operation overvoltage generated by the direct-current power grid line when the unipolar ground fault occurs at different fault points on the direct-current power grid line under the scheme of different setting levels of the influence factors to obtain the maximum value of the direct-current line operation overvoltage; and carrying out variance analysis on the maximum value of the direct current line operating overvoltage, determining the setting level of each influence factor, and calculating the maximum value of the direct current power grid line operating overvoltage according to the setting level of each influence factor.
Description
Technical Field
The invention relates to the technical field of high-voltage direct-current transmission, in particular to a method and a system for calculating over-voltage of a direct-current network circuit operation.
Background
When the direct current power grid operates, because the operating overvoltage generated by the single-pole grounding fault on the healthy pole is one of the faults with higher probability of the direct current transmission line, the method plays a very key role in the insulation coordination of the direct current transmission line. The method can accurately calculate and analyze the operation overvoltage of the direct current circuit on a healthy pole due to the single-pole grounding fault, reasonably determine the operation air gap of the direct current circuit, and is an important basis for making the matching of the overvoltage and the insulation of the direct current circuit.
The operation overvoltage of the direct current line generated on the sound pole by the single pole earth fault of the direct current system has complicated electromagnetic induction and coupling processes, and the maximum value of the overvoltage is obtained by generally processing the line in sections and calculating and counting the maximum operation overvoltage value on the line. Meanwhile, the input power, the grounding resistance, the action of the circuit breaker and other conditions of the direct current system have certain influence on the operation overvoltage. In the initial stage of the insulation fit design of the direct current system, various working conditions need to be considered comprehensively, and the magnitude of the operation overvoltage of the direct current system needs to be analyzed. Due to the presence of multiple factors considered, coupled with the line segmentation process, each case doubles the amount of simulation computation after permutation and combination. In the prior art (application number: 201810995013.5), an orthogonal test method using range analysis is proposed, a representative part of the dc line operation overvoltage influence factors is selected for comprehensive processing, so as to reduce the number of calculation times, and the maximum influence factor of the dc line operation overvoltage is analyzed by using the obtained data on the basis of less calculation, and then the maximum operation overvoltage value is obtained. The orthogonal test method based on the range analysis is simple, feasible, intuitive and understandable, but the range analysis cannot distinguish data fluctuation caused by the change of test conditions (the change of factor levels) in the test process from data fluctuation caused by test errors, and cannot give accurate quantitative estimation on the importance (significance) of the factor influence. Therefore, a technique is needed to overcome this deficiency and to calculate the dc network line operating overvoltage.
Disclosure of Invention
The technical scheme of the invention provides a method and a system for calculating the direct current power grid line operation overvoltage, which aim to solve the problem of how to calculate the direct current power grid line operation overvoltage.
In order to solve the above problem, the present invention provides a method for calculating a dc grid line operation overvoltage, the method comprising:
acquiring initial parameters of direct current power grid line monopole earth fault operation overvoltage calculation;
establishing an electromagnetic simulation calculation analysis model of the operation overvoltage during the monopolar earth fault of the direct-current power grid line based on the initial parameters;
segmenting the direct-current power grid line, and setting a single-pole grounding fault point on each segment of the direct-current power grid line;
determining influence factors of the direct-current power grid line operation overvoltage and setting levels of the influence factors;
designing an orthogonal table containing the influence factors, and respectively calculating the maximum line operation overvoltage generated by the direct-current power grid line under the scheme of different setting levels of the influence factors when different fault points on the direct-current power grid line have unipolar ground faults based on the segmented direct-current power grid line through the electromagnetic simulation calculation analysis model to obtain the maximum value of the direct-current line operation overvoltage;
carrying out variance analysis on the maximum value of the direct current line operation overvoltage to obtain a variance analysis result;
determining a setting level of each influencing factor when the direct current line operates an overvoltage maximum value according to the analysis of variance result; and calculating the maximum value of the operating overvoltage of the direct-current power grid line according to the set level of each influence factor.
Preferably, the initial parameters include: system parameters, converter station parameters, and equipment parameters.
Preferably, the influencing factors include: input power, ground resistance and direct current breaker operating time.
Preferably, the determining the influence factors of the overvoltage operation of the dc power grid line and the setting levels of the influence factors includes:
the set levels of input power are: full power input, half power input, and low power input;
the setting level of the grounding resistor is as follows: 15 ohms, 10 ohms, and 5 ohms;
the setting level of the action time of the direct current breaker is as follows: the circuit breaker at the sending end acts firstly, the circuit breakers at the two ends act simultaneously, and the circuit breaker at the receiving end acts firstly.
Preferably, the segmenting the dc power grid line includes:
and equally dividing the direct current power grid line into sections according to the length.
According to another aspect of the present invention, there is provided a system for calculating a dc grid line operation overvoltage, the system comprising:
the initial unit is used for acquiring initial parameters of the direct current power grid line monopole grounding fault operation overvoltage calculation;
the establishing unit is used for establishing an electromagnetic simulation calculation analysis model of the operating overvoltage when the direct-current power grid line is in the monopole grounding fault based on the initial parameters;
the dividing unit is used for segmenting the direct current power grid line and setting a single-pole ground fault point on each segment of the direct current power grid line;
the setting unit is used for determining influence factors of the direct-current power grid line operation overvoltage and setting levels of the influence factors;
an obtaining unit, configured to design an orthogonal table including the influence factor, and based on the segmented dc power grid line, respectively calculate, through the electromagnetic simulation calculation analysis model, a maximum line operation overvoltage generated by the dc power grid line when a unipolar ground fault occurs at different fault points on the dc power grid line under a scheme of different setting levels of the influence factor, so as to obtain a maximum value of the dc line operation overvoltage;
the analysis unit is used for carrying out variance analysis on the maximum value of the direct-current line operation overvoltage to obtain a variance analysis result;
a calculation unit for determining a setting level of each influence factor when the direct current line operates an overvoltage maximum value, based on the analysis of variance result; and calculating the maximum value of the operating overvoltage of the direct-current power grid line according to the set level of each influence factor.
Preferably, the initial parameters include: system parameters, converter station parameters, and equipment parameters.
Preferably, the influencing factors include: input power, ground resistance and direct current breaker operating time.
Preferably, the setting unit is configured to determine influencing factors of the overvoltage operation of the dc power grid line and setting levels of the influencing factors, and is further configured to:
the set levels of input power are: full power input, half power input, and low power input;
the setting level of the grounding resistor is as follows: 15 ohms, 10 ohms, and 5 ohms;
the setting level of the action time of the direct current breaker is as follows: the sending-end circuit breaker acts first, the circuit breakers at both ends act simultaneously, and the receiving-end circuit breaker acts first.
Preferably, the dividing unit is configured to segment the dc power grid line, and includes:
and equally dividing the direct current power grid line into sections according to the length.
The technical scheme of the invention provides a method and a system for calculating the direct current power grid line operation overvoltage, wherein the method comprises the following steps: acquiring initial parameters of direct current power grid line monopole earth fault operation overvoltage calculation; establishing an electromagnetic simulation calculation analysis model of the operation overvoltage during the monopolar earth fault of the direct-current power grid line based on the initial parameters; segmenting a direct-current power grid line, and setting a single-pole grounding fault point on each segment of the direct-current power grid line; determining influence factors of direct-current power grid line operation overvoltage and setting levels of the influence factors; designing an orthogonal table containing influence factors according to an orthogonal test method, respectively calculating the maximum line operation overvoltage generated by the direct-current power grid line under the scheme of different setting levels of the influence factors when different fault points on the direct-current power grid line have unipolar ground faults through an electromagnetic simulation calculation analysis model based on the segmented direct-current power grid line, and obtaining the maximum value of the direct-current line operation overvoltage; carrying out variance analysis on the maximum value of the direct current line operation overvoltage by using an orthogonal test method to obtain a variance analysis result; and determining the setting level of each influence factor when the direct current power grid line operates the overvoltage maximum value according to the analysis result of the variance, determining the setting level of each influence factor, and calculating the direct current power grid line operates the overvoltage maximum value according to the setting level of each influence factor. The technical scheme of the invention makes up the defects of extreme difference analysis, and analyzes the data obtained by the orthogonal test method by using variance analysis, accurately judges the influence degree of each factor, and calculates to obtain the operating overvoltage value.
Drawings
Exemplary embodiments of the invention may be more completely understood in consideration of the following drawings:
fig. 1 is a flow chart of a method for calculating a dc grid line operating overvoltage, according to a preferred embodiment of the present invention; and
fig. 2 is a block diagram of a system for calculating dc power grid line operating overvoltage, according to a preferred embodiment of the present invention.
Detailed Description
Example embodiments of the present invention will now be described with reference to the accompanying drawings, however, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, which are provided for a complete and complete disclosure of the invention and to fully convey the scope of the invention to those skilled in the art. The terms used in the exemplary embodiments shown in the drawings are not intended to limit the present invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In addition, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their context in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Fig. 1 is a flow chart of a method for calculating an overvoltage of a dc power network line operation according to a preferred embodiment of the present invention. In the simulation calculation of the line operation overvoltage of the direct-current transmission system, in order to fully consider the influence of various factors such as input power, grounding resistance, action time sequence of a direct-current breaker and the like, the simulation under various combination modes caused by different influence factors is added on the basis of the original sectional calculation, and the calculation amount is multiplied. The embodiment of the application provides a direct current line operation overvoltage analysis and calculation method based on an orthogonal test. The method is based on a wave process propagation mechanism and theory of the direct current transmission line operation overvoltage, determines influence factors of the operation overvoltage generated on a sound pole when the direct current line has the unipolar earth fault, selects the horizontal range of each influence factor, adopts an orthogonal test method to arrange simulation calculation by using an orthogonal table, selects a representative part from all combinations of the influence factors to carry out comprehensive treatment so as to reduce the calculation times, obtains the importance degree of each influence factor by using the obtained data through variance analysis on the basis of less calculation, and determines the maximum value of the direct current line operation overvoltage. Aiming at the defects that various influence factors need to be considered in the calculation of the direct-current power grid line operation overvoltage, the comprehensive combination condition is more, and the calculation amount is larger, the application provides the direct-current line operation overvoltage maximum value simulation calculation method based on the orthogonal test. According to the method, based on related parameters and data of the direct-current line provided by a direct-current transmission engineering design and operation unit, a PSCAD calculation program is adopted to segment the direct-current line, a simulation calculation analysis model is built, influence factors of the direct-current power grid line operation overvoltage and the horizontal range of the influence factors are determined, an orthogonal test table is designed to carry out simulation analysis calculation, variance analysis processing is carried out on data, the maximum influence factor of the direct-current power grid line operation overvoltage is determined, and then the maximum value of the operation overvoltage is obtained through calculation. As shown in fig. 1, a method for calculating a dc grid line operation overvoltage, the method comprising:
preferably, in step 101: and acquiring initial parameters of the direct current power grid line monopole earth fault operation overvoltage calculation. Preferably, the initial parameters include: system parameters, converter station parameters, and equipment parameters. The method adopts a computer to collect and arrange the operating overvoltage calculation parameters of the single-pole grounding faults of the direct-current power grid lines. When the monopolar earth fault occurs in the direct current line, the operation overvoltage generated on the sound electrode is calculated, and the relevant engineering parameters are provided by an engineering design or an operation unit and are sorted by adopting a computer. The method comprises the following steps: system parameters, converter station and main equipment parameters, direct current line and tower parameters and the like.
Preferably, at step 102: and establishing an electromagnetic simulation calculation analysis model of the operation overvoltage during the monopolar earth fault of the direct-current power grid line based on the initial parameters. The method utilizes a PSCAD program to establish an electromagnetic transient simulation calculation analysis model of the direct current line operation overvoltage under the condition of the single-pole ground fault through a computer. According to data provided by engineering design and operation units, PSCAD programs are utilized, parameters of an alternating current system, a converter station and equipment are respectively input through a computer, and electromagnetic transient simulation calculation analysis models of direct current line operation overvoltage under the condition of single-pole ground fault are respectively built, wherein the electromagnetic transient simulation calculation analysis models comprise an alternating current-direct current system model, a converter model, a direct current line and tower model, a direct current breaker model and the like.
Preferably, in step 103: and segmenting the direct-current power grid line, and setting a single-pole grounding fault point on each segment of the direct-current power grid line. The method and the device have the advantages that the direct-current line is segmented according to the line length, and the single-pole grounding fault points are respectively arranged according to the number of the segments. And equally dividing the direct current line according to the line length by a certain amount in a PSCAD model, uniformly marking the direct current line in sequence, and setting a single-pole ground fault point.
Preferably, at step 104: and determining the influence factors of the direct-current power grid line operation overvoltage and the setting level of each influence factor. Preferably, the influencing factors include: input power, ground resistance and direct current breaker operating time. Preferably, determining the influencing factors of the direct current power grid line operation overvoltage and the setting levels of the influencing factors comprises: the set levels of input power are: full power input, half power input, and low power input; the setting level of the grounding resistor is as follows: 15 ohms, 10 ohms, and 5 ohms; the setting level of the action time of the direct current breaker is as follows: the circuit breaker at the sending end acts firstly, the circuit breakers at the two ends act simultaneously, and the circuit breaker at the receiving end acts firstly. The method and the device determine the influence factors of the direct-current power grid line operation overvoltage and the horizontal range of each influence factor. When a single-pole ground fault occurs in a direct-current line, the line operation overvoltage generated on a healthy pole is mainly influenced by factors such as the input power, the grounding resistance value, the action time sequence of a direct-current breaker and the like, and the levels of the three influencing factors are determined.
Preferably, at step 105: designing an orthogonal table containing influence factors according to an orthogonal test method, respectively calculating the maximum line operation overvoltage generated by the direct-current power grid line under the scheme of different setting levels of the influence factors when different fault points on the direct-current power grid line have unipolar ground faults through an electromagnetic simulation calculation analysis model based on the segmented direct-current power grid line, and obtaining the maximum value of the direct-current line operation overvoltage. Preferably, the dc grid line is segmented, further comprising: and (3) equally dividing the direct-current power grid line into sections according to the length. According to the influence factors and levels determined in the step 104 and an orthogonal test method, an orthogonal test table is designed, and according to the direct current line sections and the direct current line labels determined in the step 103, a PSCAD calculation program is adopted to respectively calculate the maximum line operation overvoltage generated on a sound polar line when the single-pole grounding faults occur at different positions on the direct current line under each calculation scheme.
Preferably, at step 106: and carrying out variance analysis on the maximum value of the direct current line operation overvoltage by using an orthogonal test method to obtain a variance analysis result.
Preferably, in step 107: determining the setting level of each influence factor when the direct current power grid line is operated at the maximum voltage according to the analysis of variance result, determining the setting level of each influence factor, and calculating the maximum voltage of the direct current power grid line according to the setting level of each influence factor. According to the method, the calculation result is analyzed according to the variance analysis method of the orthogonal test, the influence degree of each influencing factor on the direct current line operation overvoltage and the operation condition of the maximum direct current line operation overvoltage are determined when the direct current power grid has the unipolar ground fault, and therefore the maximum value of the direct current power grid line operation overvoltage is obtained.
According to the method, when a single-pole grounding fault occurs to a direct-current power grid line, the propagation mechanism and the physical process of the operation overvoltage generated on the line determine the influence factors of the operation overvoltage of the direct-current line, and the method comprises the following steps: input power, grounding resistance and action time of the direct current circuit breaker. According to the method and the device, the horizontal ranges of three influence factors, namely input power, grounding resistance and action time sequence of the direct current breaker, are determined according to the actual operation condition of the line. The method is based on an orthogonal test method, an orthogonal table is designed according to the determined influence factors and levels, and the maximum operation overvoltage generated on a robust polar line is calculated according to the segmentation of the direct current line when the single-pole ground fault occurs at different positions of the direct current line under different calculation schemes. According to the method, the influence degree of each influencing factor on the direct current line operation overvoltage and the operation condition of generating the maximum direct current line operation overvoltage are determined when the direct current power grid has a single-pole ground fault through data analysis and processing according to an orthogonal test variance analysis method, and therefore the maximum value of the direct current power grid line operation overvoltage is obtained.
The application exemplifies a direct current power grid line operation overvoltage calculation and analysis method based on an orthogonal test. Firstly, collecting and organizing system parameters, converter station and main equipment parameters, direct current line parameters and the like of a project by a computer for project design data of a direct current power grid with 500kV at two ends provided by a design unit. The system parameters comprise direct current rated voltage, converter station capacity, short circuit current level and the like; the converter station and main equipment parameters comprise equipment parameters such as a converter, a converter transformer, a bridge arm reactor, a current limiting reactor, a starting resistor, a direct current breaker, a lightning arrester and the like; the parameters of the direct current line and the tower comprise line length, span length, tower type, structure parameters of a conducting wire and a metal return wire and the like.
And secondly, according to data provided by engineering design and operation units, adopting a PSCAD program, respectively inputting parameters of an alternating current system, a converter station and equipment through a computer, and building an electromagnetic transient simulation calculation analysis model of the direct current line operation overvoltage under the condition of the single-pole ground fault, wherein the electromagnetic transient simulation calculation analysis model comprises an alternating current-direct current system model, a converter model, a direct current line and tower model, a direct current breaker model and the like.
And thirdly, equally dividing the direct-current line into 10 sections according to the line length in a PSCAD model, numbering the lines in sequence, and setting 11 single-pole ground fault points.
And fourthly, determining influence factors of the direct current power grid line operation overvoltage and the horizontal range of each influence factor. When a single-pole ground fault occurs in a direct-current line, the line operation overvoltage generated on a healthy electrode is mainly influenced by three factors, namely the input power, the grounding resistance and the action time sequence of a direct-current breaker, and the three factors are set as follows according to the actual production operation of a direct-current power grid:
input power: full power input, half power input, low power input;
grounding resistance: 15 ohms, 10 ohms, 5 ohms;
action time sequence of the direct current breaker: the circuit breaker at the sending end acts firstly, the circuit breakers at the two ends act simultaneously, and the circuit breaker at the receiving end acts firstly.
Based on the above, the factor levels are shown in Table 1
TABLE 1 factor level table
And fifthly, designing an orthogonal test table according to the influence factors and the levels determined in the fourth step and an orthogonal test method. In this example, L is selected 9 (3 4 ) Orthogonal table, see Table 2, L 9 (3 4 ) The orthogonal table has 4 columns and 9 rows except the head, wherein the head of the row is arranged in the table3 factors of input power, grounding resistance and action time sequence of the direct current breaker are listed, and head row test numbers are listed as 1-9; the corresponding horizontal numbers "1", "2", and "3" in each column occupied by 3 factors are filled in the corresponding positions of each test number in the table.
Next, according to the number of segments and labels of the dc line determined in the third step, the maximum line operating overvoltage generated on the robust line when the unipolar ground fault occurs at different positions on the dc line under the 9 test schemes is calculated by using a PSCAD calculation program, as shown in table 2.
TABLE 2 orthogonal design Table
Three-level influencing factors in the application, namely 3 multiplied by 3 which is 27 times of experiments are needed for comprehensive experiments, and an orthogonal table L is used at present 9 (3 4 ) The experimental protocol was designed such that 9 runs resulted in 2/3 reductions in workload, which in a sense represented 27 trials.
And sixthly, analyzing the calculation result according to an analysis of variance method of the orthogonal test.
TABLE 3 analysis of orthogonal experiments
Calculating the sum T of the same level test indexes of all factors:
level 1 of factor a: t1 ═ Y1+ Y2+ Y3 ═ 2179.37;
level 2 of factor a: t2 ═ Y4+ Y5+ Y6 ═ 2155.3;
level 3 of a factor: t3 ═ Y7+ Y8+ Y9 ═ 2149.15;
level 1 of factor B: t1 ═ Y1+ Y4+ Y7 ═ 2168.33;
level 2 of factor B: t2 ═ Y2+ Y5+ Y8 ═ 2144.29;
level 3 of factor B: t3 ═ Y3+ Y6+ Y9 ═ 2171.2;
level 1 of factor C: t1 ═ Y1+ Y6+ Y8 ═ 2100.72;
level 2 of factor C: t2 ═ Y2+ Y4+ Y9 ═ 2232.83;
level 3 of factor C: t3 ═ Y3+ Y5+ Y7 ═ 2150.27;
and then calculating the average t of the same level test indexes of all factors:
level 1 of factor a: t 1-2179.37/3-726.46;
level 2 of a factor: t 2-2155.3/3-718.43;
level 3 of a factor: t 3-2149.15/3-716.38;
the average of the test indexes of B, C factors at each level can be obtained in the same way, and the specific results are shown in Table 3.
Sum of all factors of the test indices:
T＝Y1+Y2+Y3+Y4+Y5+Y6+Y7+Y8+Y9＝6483.82；
correction number C ═ T 2 /n＝4671102.421；
Sum of squares of T ＝Y1 2 +Y2 2 +Y3 2 +……+Y7 2 +Y8 2 +Y9 2 -C
＝4675169.528-4671102.421＝4067.107；
Sum of squares of A factor SS A ＝(2179.37 2 +2155.3 2 +2149.15 2 )/3-C＝170.0488；
Sum of squares of B factors SS B ＝(2168.33 2 +2144.29 2 +2171.2 2 )/3-C＝145.59；
Sum of squares of C factor SS C ＝(2100.72 2 +2232.83 2 +2150.27 2 )/3-C＝2969.379067；
Sum of squares error SSE ═ SS T -SS A -SS B -SS C ＝782.089133；
Total degree of freedom: df is a T 9-1-8; a factor degree of freedom df A B factor degree of freedom df B C factor degree of freedom df C Each is 3-1 ═ 2; degree of freedom of error: df is a compound of formula e ＝df T -df A -df B -df C ＝8-2-2-2＝2。
An analysis of variance table for this set of orthogonal experimental designs was thus obtained, see table 4.
TABLE 4 analysis of variance results
| Factors of the design | SS | Df | MS | F |
| A | 170.0488 | 2 | 85.0244 | 0.2174 |
| B | 145.59 | 2 | 72.795 | 0.186 |
| C | 2969.379067 | 2 | 1484.69 | 3.797 |
| Error of the measurement | 782.089133 | 2 | 391.045 | |
| Sum of | 4067.107 | 8 |
A, B, C comparing the F values of the three factors and referring to the F distribution table, F 0.1 (2,2)＝9；F 0.05 (2,2)＝19；F 0.01 (2,2) ═ 99, compare the F value with F 0.1 、F 0.05 、F 0.01 Of (c) is used.
The MS value is less than F due to A, B, C three factors 0.1 、F 0.05 、F 0.01 Therefore, the three factors have little influence on the calculation value of the operation overvoltage; in contrast, since Fc is greater than F A Greater than F B Therefore, the factor of the direct current breaker operation timing C has the largest influence on the calculation result, and the ground resistance B is the smallest.
Meanwhile, it can be seen from the calculation results of the T value in table 3 that in the combination A1B3C2, when a single-pole ground fault occurs in the dc line, the operating overvoltage generated in the robust pole line is the largest, that is, when the dc line is in full power operation, the ground resistance is 5 ohms, and when the circuit breakers at both ends are simultaneously operated, the operating overvoltage on the dc line is the largest when a single-pole ground fault occurs in the dc line.
In a PSCAD software program, under a working condition corresponding to A1B3C2, when a direct-current line is divided into 10 sections, unipolar ground faults occur at different positions, the maximum line operation overvoltage generated on a sound polar line is 764.59kV, and the value is the maximum operation overvoltage generated on the line when the direct-current line unipolar ground fault occurs in the direct-current engineering.
By means of the thought of orthogonal test design, when a single-pole ground fault occurs on a direct current circuit, the electromagnetic coupling and wave process of operating overvoltage is generated on a healthy pole, influence factors and levels of the direct current circuit operating overvoltage are determined, an orthogonal test table is designed, an orthogonal test scheme is arranged, the influence degree of each factor on the maximum value of the direct current circuit operating overvoltage is obtained according to an analysis of variance method, accurate quantitative estimation is given to the importance degree (significance) of the influence of the factors, the operation working condition of generating the maximum direct current circuit operating overvoltage is analyzed, and therefore the maximum value of the direct current power grid circuit operating overvoltage is determined.
The method fully considers the influence factors of the direct-current power grid line operation overvoltage, selects a representative part of design orthogonal table from all combinations of the influence factors and levels based on the idea of orthogonal test design, carries out comprehensive processing to reflect the result of comprehensive calculation and analysis, and analyzes the correct conclusion capable of guiding the actual production by using the obtained data on the basis of less calculation amount. The whole analysis process is simple, the accuracy is high, the calculation workload is reduced, the working efficiency is improved, and the obtained conclusion provides an important reference basis for the direct-current power grid engineering design and operation.
According to the embodiment of the application, the influence factors of the direct current line operation overvoltage are determined according to the propagation mechanism and the physical process of the operation overvoltage generated on the direct current power grid line when the single-pole grounding fault occurs on the direct current power grid line. According to the method and the device, the horizontal range of each influence factor of the direct current line operation overvoltage is determined according to the actual operation condition of the line. The method is based on an orthogonal test method, an orthogonal test table is designed by combining determined influence factors and levels, the direct current line is processed in a segmented mode, and the maximum operation overvoltage generated on a sound polar line is calculated when the single-pole ground faults occur at different positions under different schemes. According to the method, the influence degree of each influence factor on the direct current circuit operation overvoltage when the direct current power grid has the unipolar ground fault is determined according to a variance analysis method of an orthogonal test, accurate quantitative estimation is given to the importance degree and significance of the influence of each influence factor on the direct current circuit operation overvoltage, and the operation working condition of the generated maximum direct current circuit operation overvoltage is analyzed, so that the maximum value of the direct current power grid circuit operation overvoltage is obtained.
Fig. 2 is a block diagram of a system for calculating an overvoltage of a dc power grid line operation according to a preferred embodiment of the present invention. As shown in fig. 2, the present application provides a system for calculating a dc grid line operating overvoltage, the system comprising:
an initial unit 201, configured to obtain initial parameters of the dc grid line unipolar ground fault operation overvoltage calculation. Preferably, the initial parameters include: system parameters, converter station parameters, and equipment parameters.
The establishing unit 202 is configured to establish an electromagnetic simulation calculation analysis model of the operating overvoltage during the unipolar ground fault of the direct current power grid line based on the initial parameters.
And the dividing unit 203 is used for segmenting the direct current power grid line and setting a single-pole ground fault point on each segment of the direct current power grid line. Preferably, the dividing unit is configured to segment the dc power grid line, and includes: and (4) dividing the direct-current power grid line into sections according to the length.
The setting unit 204 is configured to determine influencing factors of the dc power grid line operation overvoltage and setting levels of the influencing factors. Preferably, the influencing factors include: input power, ground resistance and direct current breaker action time. Preferably, the setting unit is configured to determine the influencing factors of the overvoltage operation of the dc power grid line and the setting levels of the influencing factors, and is further configured to: the set levels of input power are: full power input, half power input, and low power input; the setting level of the grounding resistor is as follows: 15 ohms, 10 ohms, and 5 ohms; the setting level of the action time of the direct current breaker is as follows: the sending-end circuit breaker acts first, the circuit breakers at both ends act simultaneously, and the receiving-end circuit breaker acts first.
An obtaining unit 205, configured to design an orthogonal table containing influence factors according to an orthogonal test method, based on the segmented dc power grid line, respectively calculate, through an electromagnetic simulation calculation analysis model, a maximum line operation overvoltage generated by the dc power grid line when a unipolar ground fault occurs at different fault points on the dc power grid line under a scheme of different setting levels of the influence factors, and obtain a maximum value of the dc line operation overvoltage.
And the analysis unit 206 is configured to perform analysis of variance on the maximum dc line operating overvoltage value by using an orthogonal test method, so as to obtain an analysis of variance result.
And the calculating unit 207 is used for determining the setting level of each influence factor when the direct current power grid line operates the overvoltage maximum value according to the analysis result of the variance, determining the setting level of each influence factor, and calculating the direct current power grid line operates the overvoltage maximum value according to the setting level of each influence factor.
A system 200 for calculating an overvoltage of a dc power grid line according to the preferred embodiment of the present invention corresponds to the method 100 for calculating an overvoltage of a dc power grid line according to the preferred embodiment of the present invention, and will not be described herein again.
The invention has been described with reference to a few embodiments. However, other embodiments of the invention than the ones disclosed above are equally possible within the scope of these appended patent claims, as these are known to those skilled in the art.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a// the [ device, component, etc ]" are to be interpreted openly as referring to at least one instance of said device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
Claims (10)
1. A method for calculating a dc grid line operating overvoltage, the method comprising:
acquiring initial parameters of direct current power grid line monopole earth fault operation overvoltage calculation;
establishing an electromagnetic simulation calculation analysis model of the operation overvoltage during the monopolar earth fault of the direct-current power grid line based on the initial parameters; the electromagnetic transient simulation calculation analysis model comprises an alternating current and direct current system model, a current converter model, a direct current line and tower model and a direct current breaker model;
segmenting the direct-current power grid line, and setting a single-pole ground fault point on each segment of direct-current power grid line;
determining influence factors of the direct-current power grid line operation overvoltage and setting levels of the influence factors;
designing an orthogonal table containing the influence factors, and respectively calculating the maximum line operation overvoltage generated by the direct-current power grid line under the scheme of different setting levels of the influence factors when different fault points on the direct-current power grid line have unipolar ground faults based on the segmented direct-current power grid line through the electromagnetic simulation calculation analysis model to obtain the maximum value of the direct-current power grid line operation overvoltage; adopting a PSCAD calculation program to respectively calculate the maximum line operation overvoltage Y1-Y9 generated on a sound polar line when the single-pole ground faults occur at different positions on a direct current network line under 9 test schemes;
and carrying out variance analysis on the maximum value of the direct current power grid line operation overvoltage to obtain a variance analysis result, wherein the variance analysis result comprises the following calculation steps:
sum of all factors of the test indices: t ═ Y1+ Y2+ Y3+ Y4+ Y5+ Y6+ Y7+ Y8+ Y9, and the correction amount C ═ T 2 N, total square and SS T ＝Y1 2 +Y2 2 +Y3 2 +……+Y7 2 +Y8 2 +Y9 2 -C，
Sum of squares of A influence factor SS A ＝((Y1+Y2+Y3) 2 +(Y4+Y5+Y6) 2 +(Y7+Y8+Y9) 2 ))/3-C，
B sum of squares of influence factors SS B ＝((Y1+Y4+Y7) 2 +(Y2+Y5+Y8) 2 +(Y3+Y6+Y9) 2 ))/3-C，
Sum of squares of C-influential factors SS C ＝((Y1+Y6+Y8) 2 +(Y2+Y4+Y9) 2 +(Y3+Y5+Y7) 2 ))/3-C，
Sum of squares error SSE SS T -SS A -SS B -SS C ，
Degree of freedom of error: df is a e ＝df T -df A -df B -df C ，
Wherein df is T For total degree of freedom, df A Is A degree of freedom of influence, df B Is the degree of freedom of the B influencing factor, df C C influence factor degree of freedom;
determining a setting level of each influencing factor when the direct current power grid line operates an overvoltage maximum value according to the analysis of variance result; and calculating the maximum value of the operating overvoltage of the direct-current power grid line according to the setting level of each influence factor.
2. The method of claim 1, the initial parameters comprising: system parameters, converter station parameters, and equipment parameters.
3. The method of claim 1, the influencing factors comprising: input power, ground resistance and direct current breaker action time.
4. The method of claim 3, the determining the influencing factors and the setting levels of the influencing factors of the direct current power grid line operating overvoltage comprises:
the set levels of input power are: full power input, half power input, and low power input;
the setting level of the grounding resistor is as follows: 15 ohms, 10 ohms, and 5 ohms;
the setting level of the action time of the direct current breaker is as follows: the circuit breaker at the sending end acts firstly, the circuit breakers at the two ends act simultaneously, and the circuit breaker at the receiving end acts firstly.
5. The method of claim 1, the segmenting the direct current grid line, comprising:
and equally dividing the direct-current power grid line into sections according to the length.
6. A system for calculating a dc grid line operating overvoltage, the system comprising:
the initial unit is used for acquiring initial parameters of the direct current power grid line single-pole earth fault operation overvoltage calculation;
the establishing unit is used for establishing an electromagnetic simulation calculation analysis model of the operation overvoltage during the monopolar earth fault of the direct-current power grid line based on the initial parameters; the electromagnetic transient simulation calculation analysis model comprises an alternating current/direct current system model, a current converter model, a direct current line and tower model and a direct current breaker model;
the dividing unit is used for segmenting the direct current power grid line and setting a single-pole ground fault point on each segment of the direct current power grid line;
the setting unit is used for determining influence factors of the direct-current power grid line operation overvoltage and setting levels of the influence factors;
an obtaining unit, configured to design an orthogonal table including the influencing factor, and based on the segmented direct-current power grid line, respectively calculate, through the electromagnetic simulation calculation analysis model, a maximum line operation overvoltage generated by the direct-current power grid line when a unipolar ground fault occurs at different fault points on the direct-current power grid line under a scheme of different setting levels of the influencing factor, so as to obtain a maximum value of the direct-current power grid line operation overvoltage; adopting a PSCAD calculation program to respectively calculate the maximum line operation overvoltage Y1-Y9 generated on a sound polar line when the single-pole ground faults occur at different positions on a direct current network line under 9 test schemes;
the analysis unit is used for carrying out variance analysis on the maximum value of the direct-current power grid line operation overvoltage to obtain a variance analysis result, and comprises the following steps:
sum of all factors of the test indices: t ═ Y1+ Y2+ Y3+ Y4+ Y5+ Y6+ Y7+ Y8+ Y9, and the correction amount C ═ T 2 N, total square and SS T ＝Y1 2 +Y2 2 +Y3 2 +……+Y7 2 +Y8 2 +Y9 2 -C，
Sum of squares of A influence SS A ＝((Y1+Y2+Y3) 2 +(Y4+Y5+Y6) 2 +(Y7+Y8+Y9) 2 ))/3-C，
B sum of squared influence of SS B ＝((Y1+Y4+Y7) 2 +(Y2+Y5+Y8) 2 +(Y3+Y6+Y9) 2 ))/3-C，
Sum of squares of C-influencing factors SS C ＝((Y1+Y6+Y8) 2 +(Y2+Y4+Y9) 2 +(Y3+Y5+Y7) 2 ))/3-C，
Sum of squares error SSE SS T -SS A -SS B -SS C ，
Error degree of freedom: df is a e ＝df T -df A -df B -df C ，
Wherein df is T To total degree of freedom, df A Is a degree of freedom of influence of A, df B Is the degree of freedom of the B influencing factor, df C C influence factor degree of freedom; the calculation unit is used for determining the setting level of each influence factor when the direct current power grid line operates the maximum overvoltage according to the variance analysis result; and calculating the maximum value of the operating overvoltage of the direct-current power grid line according to the setting level of each influence factor.
7. The system of claim 6, the initial parameters comprising: system parameters, converter station parameters, and equipment parameters.
8. The system of claim 6, the influencing factors comprising: input power, ground resistance and direct current breaker action time.
9. The system of claim 8, the setting unit configured to determine the influencing factors of the dc grid line operating overvoltage and the setting levels of the influencing factors, and further configured to:
the set levels of input power are: full power input, half power input, and low power input;
the setting level of the grounding resistor is as follows: 15 ohms, 10 ohms, and 5 ohms;
the setting level of the action time of the direct current breaker is as follows: the sending-end circuit breaker acts first, the circuit breakers at both ends act simultaneously, and the receiving-end circuit breaker acts first.
10. The system of claim 6, the partitioning unit to segment the direct current grid line, comprising:
and equally dividing the direct current power grid line into sections according to the length.
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