A method and system for reliability evaluation of a flexible direct current power transmission system

Abstract

The application discloses a kind of flexible direct current transmission system reliability evaluation method and system.According to the correlation between reliability evaluation indexes in the historical operation data of the transmission system to be evaluated, the first weight of each evaluation index is obtained;According to the historical operation data of each evaluation index of a plurality of other transmission systems related to the transmission system to be evaluated, the second weight of each evaluation index is calculated;According to the first weight and the second weight, the comprehensive weight of each reliability evaluation index is calculated;According to the comprehensive weight, the final evaluation result of the reliability of the flexible direct current transmission system is obtained by using the fuzzy comprehensive evaluation method.The first weight is calculated by using the minimum information discrimination principle, which avoids the weight deviation caused by the large deviation of bias differentiation;The second weight is calculated to avoid the weight deviation caused by information overlap;The comprehensive weight is calculated based on game theory to ensure the scientificity of the weight;The use of fuzzy comprehensive evaluation enhances the correlation between reliability evaluation indexes, making the evaluation result more accurate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of reliability evaluation of power transmission system, and particularly relates to a flexible direct current power transmission system reliability evaluation method and system. BACKGROUND

[0002] Due to the spatial imbalance between supply and demand of power resources in China, long-distance and large-capacity power energy needs to be allocated. The flexible direct current power transmission technology has been widely applied in long-distance and large-capacity power transmission, long-distance transmission of offshore wind power and the like due to its advantages of flexible power regulation, less harmonic and no need for large amount of reactive power compensation. As an important component of long-distance power transmission, the reliability evaluation of power transmission system safety and stability power transmission capacity based on the historical operation data of the flexible direct current power transmission system can provide suggestions for operation control and optimized maintenance of the power transmission system sending end and receiving end system, and therefore, the accurate evaluation of the reliability of the flexible direct current power transmission system has great significance for the safe and stable operation of the power system.

[0003] At present, the reliability evaluation methods for the flexible direct current power transmission system are mostly aimed at evaluating single subsystems or devices such as converter stations and power transmission lines, and lack evaluation methods for summarizing and analyzing the overall reliability of the flexible direct current power transmission system. Secondly, the complex fault tree method, the Delphi method, the method based on the characteristic parameter matrix and the like adopted by the existing evaluation methods need a large amount of data support. Due to the complex structure of the flexible direct current power transmission system and the large number of influencing factors, it is difficult to obtain specific data. The analytic hierarchy process adopted by the traditional comprehensive evaluation method is prone to bias, and the entropy weight method and the like are difficult to distinguish the correlation between indexes, which is prone to information overlap and affects the scientificity of the weight. SUMMARY

[0004] In order to make the evaluation result more reliable, the application provides a flexible direct current power transmission system reliability evaluation method and system.

[0005] The flexible direct current power transmission system reliability evaluation method for achieving one of the purposes of the application comprises the following steps:

[0006] According to the correlation between the reliability evaluation indexes in the historical operation data of the flexible direct current power transmission system to be evaluated, the first weight of each reliability evaluation index is obtained;

[0007] According to the historical operation data of each reliability evaluation index of a plurality of flexible direct current power transmission systems related to the flexible direct current power transmission system to be evaluated, the second weight of each reliability evaluation index is calculated;

[0008] According to the first weight and the second weight of each reliability evaluation index, the comprehensive weight of each reliability evaluation index of the flexible direct current power transmission system is calculated;

[0009] The final evaluation result of the reliability of the flexible direct current transmission system is obtained by adopting a fuzzy comprehensive evaluation method according to the comprehensive weight.

[0010] The correlation between the reliability evaluation indicators is the positive or negative correlation between any two indicators. If the correlation is very high, there will be information overlap when calculating the weight of each reliability evaluation indicator. Therefore, it is necessary to calculate the correlation between any two indicators to avoid the influence of information overlap, thereby avoiding unreasonable weights of the reliability evaluation indicators.

[0011] The reliability evaluation indicators are directly or indirectly derived from the historical operation data of the flexible DC transmission system, including: number of outages, number of derating operations, forced energy unavailability rate, derating equivalent outage hours, energy availability rate, energy utilization rate, and average recovery time.

[0012] In the above method, the method for calculating the first weight of each reliability evaluation indicator includes:

[0013] Score the correlation between each reliability evaluation indicator and construct a reliability judgment matrix A based on the score k , (k=1,2,…,l), l is the number of scoring rounds; the purpose of multiple rounds of scoring is to make the calculated weights better reflect the importance attached to the reliability assessment indicators from different angles or different rules, and to effectively reduce the weight deviation caused by the bias of the scoring of some rules; the scoring can come from a machine scoring according to certain rules or algorithms, or from the scoring of multiple experts.

[0014]

[0015] a k,ij is the score value of the k-th round of correlation between the i-th reliability evaluation index and the j-th reliability evaluation index;

[0016] According to the reliability judgment matrix A k Get the first score weight ω′ of the k-th round of scoring k ;

[0017] According to the weight of the first score of each round of scoring ω′ k Get the first weight of each reliability evaluation indicator.

[0018] Furthermore, the reliability judgment matrix A k Get the first score weight ω′ of each round of scoring k The methods include:

[0019]

[0020] Where:

[0021] n is the number of reliability evaluation indicators;

[0022] ω′ k is the first score weight of the k-th round of scoring, (k=1,2,…,l), l is the number of scoring rounds;

[0023] ω′ kn It represents the score of the nth reliability evaluation indicator in the kth round of scoring.

[0024] Furthermore, the first score weight ω′ of each round of scoring k Methods for obtaining the first weight of each reliability evaluation indicator include:

[0025]

[0026] ω′ k =[ω′ k1 ,ω′ k2 ,…,ω′ kn ]

[0027] Where:

[0028] n is the number of reliability evaluation indicators;

[0029] ω j represents the first weight of the j-th reliability evaluation index;

[0030] ω′ kn represents the score of the nth reliability evaluation indicator in the kth round of scoring;

[0031] ω′ lj It represents the score of the jth reliability evaluation indicator in the lth round of scoring.

[0032] Furthermore, according to the reliability judgment matrix A k Before calculating the first weight of each scoring round, a consistency check is performed. The consistency check includes:

[0033] The consistency ratio CR of each round of scoring is calculated according to the following formula: k :

[0034]

[0035] Where:

[0036] n is the number of reliability evaluation indicators;

[0037] λ maxk The reliability judgment matrix A is formed by the pairwise comparison scores of each reliability evaluation index in the kth round of scoring. k The maximum eigenvalue of

[0038] CI k is the consistency indicator;

[0039] RI is the average random consistency index related to the number of reliability evaluation indicators;

[0040] If CR k If it is greater than or equal to the set value, the judgment matrix A needs to be rebuilt. k .

[0041] In the above method, the method for calculating the second weight of each reliability evaluation indicator based on historical operation data includes:

[0042] Calculate the coefficient of variation v of each reliability evaluation indicator based on historical operating data j ;

[0043] Calculate the conflict quantification value D of each reliability evaluation indicator according to the correlation coefficient between the reliability evaluation indicators j ;

[0044] According to the coefficient of variation v of each reliability evaluation indicator j and conflict quantification value D j A second weight of each reliability evaluation indicator is calculated.

[0045] Furthermore, the coefficient of variation v of each reliability evaluation index is j The calculation methods include:

[0046]

[0047] Where:

[0048] y ij is the measured value of the historical operating data of the jth reliability evaluation indicator of the i-th Flexible HVDC transmission system; i=1,…,m,j=1,…,n, m is the number of Flexible HVDC transmission systems;

[0049] The average value of the standardized data for the jth reliability evaluation indicator.

[0050] Furthermore, the conflict quantification value D of each reliability evaluation indicator is calculated based on the correlation coefficient between the reliability evaluation indicators. j The calculation methods include:

[0051]

[0052] Where:

[0053] r ij According to the standardized data matrix Y=[y ij ] m×nCalculate the correlation coefficient between the reliability evaluation indexes of the i-th and j-th flexible DC transmission systems; standardize the data matrix Y = [y ij ] m×n is a matrix obtained by dimensionlessly processing the historical operation data of each reliability evaluation indicator in the reliability evaluation indicator set U obtained from the historical operation data of multiple DC transmission systems, where y ij is the dimensionalized value of the measured value of the historical operation data of the j-th reliability evaluation indicator of the i-th flexible DC transmission system.

[0054] Furthermore, according to the coefficient of variation v of each reliability evaluation indicator j and conflict quantification value D j The calculation method of the second weight of each reliability evaluation indicator includes:

[0055] E j =v j ×D j

[0056]

[0057] In the above method, the method for calculating the comprehensive weight λ of each reliability assessment indicator of the flexible direct current transmission system according to the first weight and the second weight includes:

[0058] λ=[λ1 λ2 λ3,…,λ n ]

[0059] λ j =αω j +βθ j

[0060] in:

[0061] λ represents the comprehensive weight of the reliability assessment index of the flexible DC transmission system;

[0062] α and β are weight coefficients of the first weight and the second weight, respectively. The calculation method includes solving and normalizing according to the following formula to obtain the optimal solution of α and β:

[0063]

[0064] Furthermore, a method for obtaining a final evaluation result Z of the reliability of the flexible HVDC system using a fuzzy comprehensive evaluation method according to the comprehensive weight λ includes:

[0065]

[0066] B=[b(V k )] H×1=[b(V1)b(V2)…b(V H )]

[0067]

[0068] A reliability assessment system for a flexible direct current transmission system to achieve the second objective of the present invention includes a first weight calculation module, a second weight calculation module, a comprehensive weight calculation module, and an assessment result calculation module;

[0069] The first weight calculation module is used to obtain a first weight of each reliability evaluation indicator based on the correlation between the reliability evaluation indicators in the historical operation data of the flexible direct current transmission system to be evaluated;

[0070] The second weight calculation module is used to calculate the second weight of each reliability evaluation indicator based on the historical operation data of each reliability evaluation indicator of multiple flexible direct current transmission systems related to the flexible direct current transmission system to be evaluated;

[0071] The comprehensive weight calculation module is used to calculate the comprehensive weight of the reliability evaluation index of the flexible direct current transmission system according to the first weight and the second weight of each reliability evaluation index;

[0072] The evaluation result calculation module is used to obtain the final evaluation result of the reliability of the flexible direct current transmission system by adopting a fuzzy comprehensive evaluation method according to the comprehensive weight.

[0073] The beneficial effects of the present invention include:

[0074] 1. To address the complex nature of the HVDC Flexible system, which presents numerous fault types and is difficult to analyze in detail, a results-oriented reliability evaluation system is proposed, encompassing the number of outages, number of derating operations, forced energy unavailability rate, derating equivalent outage hours, energy availability rate, energy utilization rate, and mean recovery time. This ensures that the evaluation indicators are more aligned with the economic benefits of line operation and user requirements.

[0075] 2. Use the improved analytic hierarchy process to calculate the first weight, comprehensively consider multiple rounds of judgment, adopt the minimum information identification principle, comprehensively calculate the first weight, and conduct multiple rounds of scoring to avoid bias in the first weight caused by excessive bias. Use the CRITIC method to calculate the second weight to avoid bias caused by information overlap;

[0076] 3. Calculate comprehensive weights based on game theory to ensure the scientific nature of the weights;

[0077] 4. The present invention fully utilizes the inherent correlation between the historical operating data of the flexible DC transmission system and uses the comparison results between the historical operating data to reduce the impact of information data errors in the evaluation and improve the accuracy of the evaluation;

[0078] 5. The use of fuzzy comprehensive evaluation enhances the correlation between reliability assessment indicators, making the assessment results more accurate. The assessment results can provide reference information and decision-making basis for optimizing maintenance arrangements, and to a certain extent improve the reliability level of the flexible DC transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 is a schematic flow chart of an embodiment of the method of the present invention;

[0080] Figure 2 1 is a schematic diagram of a process for calculating a first weight based on an improved analytic hierarchy process in an embodiment of the method of the present invention;

[0081] Figure 3 1 is a flow chart of calculating the second weight using the CRITIC method in an embodiment of the method of the present invention. DETAILED DESCRIPTION

[0082] The following detailed description is intended to explain the technical solutions of the present invention claims, so that those skilled in the art can understand the present claims. The scope of protection of the present invention is not limited to the specific implementation structures described below. Any implementation schemes created by those skilled in the art that incorporate the technical solutions of the present invention claims but differ from the following detailed descriptions are also within the scope of protection of the present invention.

[0083] S1. Proposing an evaluation index system based on the structural characteristics of the flexible direct current transmission system to be evaluated, wherein the evaluation index system includes an evaluation index set U and a comment set V for reliability evaluation;

[0084] Analysis of the structure and fault types of the flexible DC transmission system shows that the flexible DC transmission system has a complex structure and numerous fault types, making detailed analysis difficult. Therefore, based on a result-oriented approach, an evaluation index system for reliability assessment is constructed according to the system transmission performance, the impact after a fault occurs, and the recovery situation.

[0085] The result-oriented evaluation index set U for the reliability assessment of the flexible HVDC transmission system includes: outage times, derating times, forced energy unavailability rate, derating equivalent outage hours, energy availability rate, energy utilization rate, and average restoration time.

[0086] The number of outages refers to the number of outages of the flexible HVDC system within a period of time;

[0087] The number of derating operations refers to the number of derating operations of the flexible DC transmission system within a period of time;

[0088] The forced energy unavailability rate refers to the rate of reduction in the transmission capacity of the DC transmission system caused by forced outages and derating operations;

[0089] The derating equivalent outage hours refer to the number of hours of unit output reduction converted into the outage hours calculated based on rated capacity;

[0090] The energy availability rate is the ability of the AC / DC transmission system to deliver energy within a given time interval, that is, how much energy the system can deliver under ideal conditions;

[0091] The energy utilization rate refers to the percentage of the total electric energy transmitted by the power transmission system during the statistical period to the rated electric energy transmitted by the power transmission system during the period;

[0092] The mean restoration time refers to the average repair time for the HVDC Flexible system to return from a fault state to a working state;

[0093] The reliability of the flexible DC transmission system is divided into five different levels, forming a five-level evaluation set V: {V1 (high reliability), V2 (relatively high reliability), V3 (average reliability), V4 (relatively low reliability), V5 (low reliability)};

[0094] Each comment V i The corresponding scoring intervals are: (85,100], (75,85], (60,75], (50,60], (0,50], and the quantitative score of the reliability assessment of the flexible DC transmission system is for: As shown in Table 1 below:

[0095] Table 1 Quantitative classification of reliability assessment results of HVDC flexible transmission system

[0096]

[0097] S2. acquiring historical operating data of multiple flexible HVDC transmission systems related to the HVDC flexible transmission system to be evaluated;

[0098] The historical operation data include: transmission capacity, transmission power, energy availability, energy utilization, number of system unipolar forced outages, number of system bipolar forced outages, derating equivalent outage hours, number of planned outages, number of forced outages, and outage time.

[0099] S3. Calculate a first weight ω of the reliability evaluation index of the flexible DC transmission system to be evaluated; and calculate a second weight θ based on historical operation data;

[0100] Since the AHP can form a judgment matrix from each round of scoring and use it to calculate weights, the weighted results are more consistent with the actual situation. To avoid the problem of excessive bias in a certain round of scoring, which leads to the first weight being inconsistent with the actual situation, this embodiment uses an improved AHP to calculate the first weight of the reliability assessment index of the flexible DC transmission system. The specific steps include:

[0101] S311: Construct a judgment matrix A for pairwise comparison of the importance of reliability evaluation indicators of the flexible DC transmission system. In each round of scoring, the nine-scale method is used to score each evaluation indicator in the reliability evaluation indicator set U and construct a judgment matrix for each. The reliability judgment matrix formed by the k-th round of scoring is recorded as A k ;

[0102]

[0103] Where: a k,ij is the nine-scale score of the k-th round of correlation between the i-th reliability evaluation indicator and the j-th reliability evaluation indicator, and n is the number of evaluation indicators.

[0104] S312: Calculate the first score weight of each round of scoring. The judgment matrix A formed by the k-th round of scoring k Normalize by column, then use the arithmetic mean method to calculate the weight to obtain the first score weight ω of the k-th round of scoring k ';

[0105]

[0106] Where: ω′ kj The evaluation weight value of the jth indicator in the kth round of scoring.

[0107] S313: Consistency check. Use the following formula to calculate the first weight ω′ of each round of scoring. k The consistency ratio CR k , to determine the consistency of each round of scoring:

[0108]

[0109] Where:

[0110] n is the number of evaluation indicators;

[0111] λ maxk The reliability judgment matrix A given for the k-th round of scoring k The maximum eigenvalue of

[0112] CI k is the consistency indicator;

[0113] RI is the average random consistency index related to the number of evaluation indicators. As shown in Table 2 below, when the number of evaluation indicators is 7, the RI value is 1.36.

[0114] Table 2 Average random consistency index values

[0115]

[0116] If the ratio of CI to RI, i.e., the consistency ratio CR, satisfies CR<0.1, the consistency test is passed, and the first weight ω′ k Reasonable, otherwise it is necessary to re-score and construct a new reliability judgment matrix A k , until the consistency check passes.

[0117] S314: Determine the first weight. To avoid excessive bias in scoring, which would lead to excessive deviation in the weight of the same indicator, the analytic hierarchy process (AHP) is improved, and the following formula is used to determine the first weight ω′1, …, ω′ obtained from the first round of scoring: l Perform synthesis and obtain the first weight ω:

[0118]

[0119] For multi-indicator and multi-object evaluation problems such as the reliability assessment of a flexible DC transmission system, the CRITIC method can eliminate information overlap between highly correlated reliability assessment indicators, thereby obtaining a second weight that is more consistent with the actual situation of the flexible DC transmission system. Therefore, this embodiment calculates the second weight of the reliability assessment indicator of the flexible DC transmission system based on the CRITIC method. The specific steps are as follows:

[0120] S321: Data standardization: The historical operation data matrix X = [x ij ] m×n Perform dimensionless processing, and use the following formula to process the two indicators of positive index (the larger the better) and reverse index (the smaller the better), and then obtain the standardized data matrix Y=[y ij ] m×n :

[0121]

[0122] Where:

[0123] x ij is the measured value of the historical operating data of the jth reliability assessment indicator of the i-th evaluation object (the evaluation object is the Flexible DC transmission system); when evaluating the reliability of a Flexible DC transmission system, the historical operating data of multiple Flexible DC transmission systems are collected for reliability analysis to make the analysis result more accurate;

[0124] y ij is x ij The data value after normalization processing; i = 1, ..., m, j = 1, ..., n, m is the number of evaluation objects;

[0125] n is the number of indicators in the evaluation indicator set U for reliability assessment of HVDC flexible system;

[0126] max(x j ), min(x j ) are the maximum and minimum values ​​of the same evaluation index data for different evaluation objects.

[0127] S322: Calculate the coefficient of variation of the indicator, which is used to quantify the comparison strength of the evaluation indicator. The coefficient of variation v j The calculation formula is:

[0128]

[0129] Where: Normalize the data mean for the j-th evaluation metric.

[0130] S323: Calculation of index conflict: Calculate the correlation coefficient r between the i-th and j-th VDC system reliability assessment indicators based on the standardized data matrix Y. ij , according to r ij Calculate the conflict quantification value D of each evaluation indicator j :

[0131]

[0132] S324: Information calculation: According to the coefficient of variation v of each indicator j and conflict quantification value D j Calculate the amount of information E j :

[0133] E j =v j ×D j

[0134] S325: Second weight calculation: For the information amount E j Normalize and get the second weight θ=[θ j ] 1×n .

[0135]

[0136] S4. Calculating the comprehensive weight λ of the reliability assessment index of the flexible DC transmission system according to the first weight ω and the second weight θ, specifically including:

[0137] λ=[λ1λ2λ3,…,λ n ]

[0138] λ j =αω j +βθ j

[0139] Where: α and β are the weight coefficients of the first weight and the second weight respectively. The calculation method based on the game theory equilibrium algorithm is as follows:

[0140]

[0141] The optimal weight coefficients α and β are obtained by solving and normalizing the coefficients so that the sum of the deviations between the first and second weights and the comprehensive weight is minimized, and the comprehensive weight λ is then calculated.

[0142] S5. Fuzzy comprehensive evaluation of the reliability of the flexible DC transmission system is performed based on fuzzy comprehensive evaluation and comprehensive weight λ, specifically including:

[0143] S51, membership function construction: constructing Gauss-type membership functions of five evaluation levels according to the five-level comment set V selected in step S1;

[0144] S52, calculate the evaluation matrix: the evaluation data y in the standardized data matrix Y in step S321 ij Substitute them into the Gauss-type membership functions of H (5 in this embodiment as shown in Table 1) evaluation levels, and obtain the evaluation matrix F of each evaluation index = [f Vk (y ij )] H×n Right now:

[0145]

[0146] The standardized data value y of the jth indicator of the i-th flexible DC transmission system ij Comments V k The degree of membership; H is the number of comments;

[0147] S53, adopt The operator is combined with the comprehensive weight λ of the HVDC Flexible system reliability assessment index to obtain the overall assessment value B of each evaluation index of the HVDC Flexible system reliability assessment system, which is calculated as follows:

[0148] B=[b(V k )] H×1 =[b(V1)b(V2)…b(V H )]

[0149]

[0150] Where: b(V k ) represents the relative reliability evaluation of the flexible DC transmission system V k The degree of membership;

[0151] S54. Quantitative score based on the reliability assessment of the flexible DC transmission system Calculate the comprehensive reliability assessment result Z of the flexible DC transmission system:

[0152]

[0153] The calculated reliability assessment result Z of the flexible DC transmission system is matched with the scoring range shown in Table 1, which is the final assessment result, i.e., high, relatively high, average, poor, or bad.

[0154] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0155] The embodiment of the present application also includes a reliability assessment system for a flexible direct current transmission system, including a first weight calculation module, a second weight calculation module, a comprehensive weight calculation module, and an assessment result calculation module;

[0156] The first weight calculation module is used to obtain a first weight of each reliability evaluation indicator based on the correlation between the reliability evaluation indicators in the historical operation data of the flexible direct current transmission system to be evaluated;

[0157] The second weight calculation module is used to calculate a second weight of each reliability evaluation indicator according to historical operation data of each reliability evaluation indicator of a plurality of flexible direct current transmission systems related to the flexible direct current transmission system to be evaluated;

[0158] The comprehensive weight calculation module is used to calculate the comprehensive weight of the reliability evaluation index of the flexible direct current transmission system according to the first weight and the second weight of each reliability evaluation index;

[0159] The evaluation result calculation module is used to obtain the final evaluation result of the reliability of the flexible direct current transmission system by adopting a fuzzy comprehensive evaluation method according to the comprehensive weight.

[0160] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A method for evaluating the reliability of a flexible direct current transmission system, characterized in that: include: Obtaining a first weight of each reliability evaluation indicator according to correlations between reliability evaluation indicators in historical operation data of the flexible direct current transmission system to be evaluated; calculating a second weight of each reliability evaluation indicator based on historical operation data of each reliability evaluation indicator of a plurality of flexible direct current transmission systems related to the flexible direct current transmission system to be evaluated; Calculating a comprehensive weight of the reliability assessment index of the flexible direct current transmission system according to the first weight and the second weight of each reliability assessment index; A fuzzy comprehensive evaluation method is used according to the comprehensive weight to obtain a final evaluation result of the reliability of the flexible DC transmission system; The calculation method of the first weight of each reliability evaluation indicator includes: Score the correlation between each reliability evaluation indicator and construct a reliability judgment matrix A based on the score k , k=1,2,…,l, l is the number of scoring rounds; a k,ij is the score value of the k-th round of correlation between the i-th reliability evaluation index and the j-th reliability evaluation index; According to the reliability judgment matrix A k Get the first score weight ω′ of the k-th round of scoring k ; The first weight of each reliability evaluation indicator is obtained according to the first weight of each round of scoring; According to the reliability judgment matrix A k Get the first score weight ω′ of the k-th round of scoring k The methods include: Where: n is the number of reliability evaluation indicators; ω′ k is the weight of the first score in the k-th round of scoring, k = 1, 2, ..., l, l is the number of scoring rounds, l is greater than 1; ω′ kn It represents the evaluation weight value of the k-th round of scoring on the n-th reliability evaluation index; The method for obtaining the first weight of each reliability evaluation indicator according to the first weight of each round of scoring includes: ω=[ω1···ω j ···oh n ] oh' k =[ω′ k1 Oh, oh k2 ,…,oh' kn ] Where: n is the number of reliability evaluation indicators; ω j represents the first weight of the j-th reliability evaluation index; ω′ kn Represents the evaluation weight value of the nth reliability evaluation indicator in the kth round of scoring; ω′ lj Represents the evaluation weight value of the jth reliability evaluation indicator in the lth round of scoring.

2. The method for evaluating the reliability of a flexible DC transmission system according to claim 1, wherein: Before calculating the first weight of each scoring round, a consistency check is performed. The consistency check includes: The consistency ratio CR of each round of scoring is calculated according to the following formula: k : Where: n is the number of reliability evaluation indicators; λ maxk The reliability judgment matrix A is formed by the pairwise comparison scores of each reliability evaluation index in the kth round of scoring. k The maximum eigenvalue of CI k is the consistency indicator; RI is the average random consistency index related to the number of reliability evaluation indicators; If CR k If it is greater than or equal to the set value, the judgment matrix A needs to be rebuilt. k .

3. The method for evaluating the reliability of a flexible DC transmission system according to claim 1, wherein: The method for calculating the second weight of each reliability evaluation indicator based on historical operation data includes: Calculate the coefficient of variation v of each reliability evaluation indicator based on historical operating data j ; Calculate the conflict quantification value D of each reliability evaluation indicator according to the correlation coefficient between the reliability evaluation indicators j ; According to the coefficient of variation v of each reliability evaluation indicator j and conflict quantification value D j A second weight of each reliability evaluation indicator is calculated.

4. The method for evaluating the reliability of a flexible DC transmission system according to claim 3, wherein: According to the coefficient of variation v of each reliability evaluation indicator j and conflict quantification value D j The calculation method of the second weight of each reliability evaluation indicator includes: Calculate the coefficient of variation v of each reliability evaluation indicator according to the following formula: j : The conflict quantification value D of each reliability evaluation indicator is calculated according to the following formula: j : The second weight θ of each reliability evaluation index is calculated according to the following formula j : E j =v j ×D j Where: θ j represents the second weight of the j-th reliability evaluation index; y ij is the measured value of the historical operating data of the jth reliability evaluation indicator of the i-th Flexible HVDC transmission system; i=1,…,m,j=1,…,n, m is the number of Flexible HVDC transmission systems; The average value of the standardized data for the jth reliability evaluation index; r ij According to the data matrix Y=[y ij ] m×n Calculate the correlation coefficient between the reliability evaluation indexes of the i-th and j-th flexible DC transmission systems; standardize the data matrix Y = [y ij ] m×n is the matrix obtained by dimensionlessly processing the historical operation data of each reliability evaluation indicator in the historical operation data of multiple DC transmission systems, where y ij is the dimensionalized value of the measured value of the historical operation data of the j-th reliability evaluation indicator of the i-th flexible DC transmission system.

5. The method for evaluating the reliability of a flexible DC transmission system according to claim 4, wherein: The method for calculating the comprehensive weight of the reliability evaluation index of the flexible direct current transmission system according to the first weight and the second weight of each reliability evaluation index includes: λ=[λ1λ2λ3,…,λ n ] l j =oh j +βθ j Where: λ represents the comprehensive weight of the reliability assessment index of the flexible DC transmission system; α and β are weight coefficients of the first weight and the second weight, respectively. The calculation method includes solving and normalizing according to the following formula to obtain the optimal solution of α and β:

6. The method for evaluating the reliability of a flexible DC transmission system according to claim 5, wherein: The method for obtaining the final evaluation result Z of the reliability of the flexible DC transmission system by using the fuzzy comprehensive evaluation method according to the comprehensive weight includes: in: Z represents the final evaluation result of the reliability of the HVDC flexible system; represents the quantitative score of the k-th VDC system reliability assessment; The standardized data value y of the jth reliability index of the i-th flexible DC transmission system ij Comments V k The degree of membership; H is the number of comments.

7. A VSD system reliability assessment system using the VSD system reliability assessment method according to any one of claims 1 to 6, characterized in that: It includes a first weight calculation module, a second weight calculation module, a comprehensive weight calculation module and an evaluation result calculation module; The first weight calculation module is used to obtain a first weight of each reliability evaluation indicator according to the correlation between the reliability evaluation indicators in the historical operation data of the flexible direct current transmission system to be evaluated; The second weight calculation module is used to calculate the second weight of each reliability evaluation indicator based on the historical operation data of each reliability evaluation indicator of multiple flexible direct current transmission systems related to the flexible direct current transmission system to be evaluated; The comprehensive weight calculation module is used to calculate the comprehensive weight of the reliability evaluation index of the flexible direct current transmission system according to the first weight and the second weight of each reliability evaluation index; The evaluation result calculation module is used to obtain the final evaluation result of the reliability of the flexible direct current transmission system by adopting a fuzzy comprehensive evaluation method according to the comprehensive weight.

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