Ultra-high voltage direct current transmission technology optimization method and system based on variable weight optimization

Abstract

This application relates to the field of power system technology, specifically to a method and system for optimizing ultra-high voltage direct current (UHVDC) transmission technology based on variable weight optimization. The method includes: constructing multiple evaluation indicators covering three dimensions: power supply structure, stability level, and economic benefits; obtaining the actual values ​​of each evaluation indicator, standardizing the actual values ​​to obtain a standard state vector; dynamically weighting the key constraint indicators in the standard state vector based on a state-weighted penalty function to form a state-weighted vector; calculating a weighted composite vector by combining the initial weight vector and the state-weighted vector; performing a weighted summation of the standard state vector and the weighted composite vector to obtain a comprehensive score; and determining the recommended transmission technology route based on the preset interval of the comprehensive score. By constructing a scientific evaluation indicator system and introducing variable weight theory to dynamically adjust the indicator weights, the method effectively reflects the constraint effect of key indicators, improving the scientificity and accuracy of technology route selection.

Description

Technical Field

[0001] This application relates to the field of power system technology, specifically to a method and system for optimizing ultra-high voltage direct current transmission technology based on variable weight optimization. Background Technology

[0002] Ultra-high voltage direct current (UHVDC) transmission technology, with its advantages of large transmission capacity, long transmission distance, flexible power regulation, and low line loss, has become a core means of optimizing the allocation of large-scale energy resources across regions. Currently, the mainstream UHVDC transmission technologies include two types: conventional direct current (LCC-HVDC) and flexible direct current (VSC-HVDC). The former is technologically mature and relatively inexpensive, while the latter performs better in terms of power supply adaptability and low inertia support. Different technical routes differ significantly in terms of project cost, land area, system stability support capability, and adaptability to power supply structures. The choice of technical route directly affects the project's investment efficiency and operational reliability, and is a core decision-making step in the planning and design of UHVDC projects.

[0003] In existing practices for optimizing technical routes, the engineering design phase typically involves researchers conducting qualitative analysis and techno-economic comparisons based on engineering experience and expert opinions, combined with existing engineering cases. Alternatively, a weighted scoring method is used, assigning fixed weights to each evaluation dimension. This approach is suitable when the evaluation objects are relatively similar and the indicators are relatively balanced. However, when certain indicators are at critical or extreme levels, the evaluation conclusions are prone to bias. For example, in scenarios with a high proportion of renewable energy power transmission, conventional DC power is insufficiently adaptable due to minimum operating power constraints; in scenarios with weak receiving-end grid strength, the risk of commutation failure in conventional DC power transmission increases significantly. In these cases, the constraints of certain key factors on the technical route far exceed the impact that can be reflected in a fixed-weight model.

[0004] With the accelerated transformation of the energy structure, power sources at the sending end are becoming more diversified and have a higher proportion of new energy sources, while the power grid structure at the receiving end is becoming increasingly complex. The importance of various evaluation dimensions varies significantly under different engineering scenarios, and evaluation methods relying on fixed weights are difficult to adapt to these dynamically changing needs. Therefore, existing methods for selecting UHVDC transmission technology routes have the following shortcomings: they lack a systematic quantitative evaluation framework, making it difficult to conduct a comprehensive and objective quantitative comparison of the applicability of technology routes; at the same time, fixed-weight evaluation models cannot dynamically reflect the changes in the strength of constraints of various factors based on the actual level of indicators, resulting in insufficient accuracy of evaluation conclusions when individual factors are at an unfavorable level. Summary of the Invention

[0005] In view of this, the embodiments of this application provide a method and system for optimizing ultra-high voltage direct current transmission technology based on variable weight optimization. By constructing a scientific evaluation index system and introducing variable weight theory to dynamically adjust the index weights, the constraint effect of key indicators is effectively reflected, and the scientificity and accuracy of technology route selection are improved.

[0006] The first aspect of this application provides a method for optimizing ultra-high voltage direct current (UHVDC) transmission technology based on variable weight optimization, comprising: Construct multiple evaluation indicators covering three dimensions: power supply structure, stability level, and economic benefits; Obtain the actual values ​​of each evaluation index, and standardize the actual values ​​to obtain a standard state vector; Based on the state-weighted penalty function, the key constraint indicators in the standard state vector are dynamically weighted to form a state-weighted vector. The combined weight vector is calculated by combining the initial weight vector and the state-adjusted weight vector. The comprehensive score is obtained by weighted summation of the standard state vector and the variable weighted comprehensive vector. Based on the preset range in which the comprehensive score falls, a recommended power transmission route is determined.

[0007] A second aspect of this application provides a variable-weight optimization-based ultra-high voltage direct current transmission technology optimization system, comprising: The indicator system construction module is used to construct multiple evaluation indicators covering three dimensions: power supply structure, stability level, and economic benefits. The standardization processing module is used to obtain the actual values ​​of each of the evaluation indicators, and to standardize the actual values ​​to obtain a standard state vector. The variable weighting processing module is used to dynamically change the weights of key constraint indicators in the standard state vector based on the state variable weighting penalty function to form a state variable weighting vector. The comprehensive vector calculation module is used to calculate the variable weight comprehensive vector by combining the initial weight vector and the state variable weight vector; The comprehensive scoring module is used to perform a weighted summation based on the standard state vector and the variable weight comprehensive vector to obtain a comprehensive score. The route recommendation module is used to determine the recommended power transmission route based on the preset interval in which the comprehensive score is located.

[0008] The first aspect of this application provides a method for optimizing ultra-high voltage direct current (UHVDC) transmission technology based on variable weight optimization. This method constructs multiple evaluation indicators covering three dimensions: power structure, stability level, and economic benefits. It obtains the actual values ​​of each evaluation indicator and standardizes them to obtain a standard state vector. Based on a state-variable weight penalty function, it dynamically weights key constraint indicators to form a state-variable weight vector. Combining the initial weight vector and the state-variable weight vector, it calculates a variable weight comprehensive vector. A comprehensive score is obtained by weighted summation of the standard state vector and the variable weight comprehensive vector. Based on the preset interval where the comprehensive score falls, a recommended transmission technology route is determined. This method fully considers the impact of dynamic changes in indicators on the evaluation results, especially strengthening the constraint effect of key indicators. It significantly improves the scientificity, accuracy, and practicality of UHVDC transmission technology route selection, providing reliable and systematic decision support for UHVDC project planning and design.

[0009] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a flowchart illustrating an embodiment of the preferred method for ultra-high voltage direct current transmission technology based on variable weight optimization provided in this application. Figure 2 This is a schematic diagram of the structure of the UHVDC transmission technology optimization system based on variable weight optimization provided in the embodiments of this application. Detailed Implementation

[0012] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0013] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0014] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0015] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0016] like Figure 1 As shown, the method for optimizing ultra-high voltage direct current (UHVDC) transmission technology based on variable weight optimization provided in this embodiment of the invention is applicable to the planning and design stage of various UHVDC projects, and is particularly suitable for the comprehensive comparison and selection of conventional DC and flexible DC technologies. It includes the following steps S1 to S6: Step S1: Construct multiple evaluation indicators covering three dimensions: power supply structure, stability level, and economic benefits.

[0017] Step S2: Obtain the actual values ​​of each evaluation index, and standardize the actual values ​​to obtain a standard state vector.

[0018] Step S3: Based on the state-weighted penalty function, the key constraint indicators in the standard state vector are dynamically weighted to form a state-weighted vector.

[0019] Step S4: Combine the initial weight vector and the state-change weight vector to calculate the combined weight vector.

[0020] Step S5: Perform a weighted summation based on the standard state vector and the variable weighted composite vector to obtain the comprehensive score.

[0021] Step S6: Determine the recommended power transmission route based on the preset range in which the comprehensive score is located.

[0022] In step S1, combining the application characteristics and engineering experience of UHVDC transmission technology, an evaluation index system covering three core dimensions—power supply structure, stability level, and economic benefits—is constructed. This evaluation index system refers to a set of quantitative indicators used to compare and analyze the advantages and disadvantages of different UHVDC transmission technology routes. Its purpose is to transform the various factors involved in technology route selection into quantifiable and comparable numerical indicators, thereby providing a data foundation for subsequent comprehensive evaluation. The power supply structure dimension focuses on the composition of the power supply at the sending end and its adaptability to DC transmission technology; the stability level dimension focuses on the receiving end grid's support capacity for DC feedin; and the economic benefits dimension focuses on the differences in engineering cost and land area among different technology routes.

[0023] In step S2, obtaining the actual values ​​of each evaluation indicator refers to determining the values ​​of each evaluation indicator under a specific engineering scenario based on engineering design data, operational data, system simulation calculation results, and investment calculation reports. Standardization processing refers to the process of uniformly converting the actual values ​​of indicators with different dimensions and numerical ranges to the same scale. Its purpose is to eliminate dimensional differences caused by different physical meanings and units of measurement, making the indicators comparable. The standard state vector is a vector composed of the standard values ​​of each indicator after standardization processing.

[0024] In step S3, the state-variable penalty function is a mathematical function that automatically adjusts the weights based on the current state value of the indicator. When the actual level of a key indicator is lower than a set benchmark value, the function increases its weight percentage by increasing the corresponding variable weight factor, thereby strengthening the constraint effect of the indicator. When the actual level of a key indicator is higher than the benchmark value, the variable weight factor remains at 1, and the weight is not adjusted further. Here, the key constraint indicator refers to an indicator that plays a decisive role in the selection of the technical route; when its value is at an unfavorable level, its impact on the selection of the technical route will significantly increase. Dynamic variable weight processing refers to the process of automatically adjusting the weights according to different indicator state values, which is different from the fixed weight method. The state-variable weight vector is a vector composed of the variable weight factors of each indicator.

[0025] In step S4, the initial weight vector refers to the basic weight allocation scheme for each evaluation index under normal scenarios. Its determination is based on recent research experience, expert opinions, and industry standard requirements for multiple UHVDC transmission projects. The variable weight composite vector is the final weight vector obtained by normalizing the initial weight vector and the state variable weight vector; the sum of its elements is 1, satisfying the basic mathematical properties of weights.

[0026] In step S5, the comprehensive score refers to the sum of the values ​​obtained by multiplying the standard values ​​of each indicator by their corresponding dynamic weights. This score can comprehensively and quantitatively reflect the overall advantages and disadvantages of different technical approaches in a specific engineering scenario. The weighted summation refers to the operation of multiplying the standard state vector and the variable weight comprehensive vector element by element and then accumulating the results.

[0027] In step S6, the preset interval refers to a pre-determined comprehensive scoring standard. This standard is determined based on the analysis and summary of numerous UHVDC engineering cases, engineering practice experience, and a trade-off between technology and economy. Based on the different intervals in which the comprehensive score falls, corresponding recommendations for power transmission technology routes are given.

[0028] The above embodiments construct multiple evaluation indicators covering three dimensions—power structure, stability level, and economic benefits—transforming various factors involved in technology route selection into quantifiable numerical indicators. Standardization eliminates dimensional differences, enabling unified comparison of different indicators. A state-variable penalty function dynamically adjusts indicator weights, automatically increasing the weight of key indicators when they are at unfavorable levels, highlighting their constraining effect. Finally, a weighted summation yields a comprehensive score, which is used to recommend a technology route. The entire evaluation process is scientific, systematic, and repeatable. The technical advantages of this solution are: compared to traditional fixed-weight evaluation methods, the variable-weight mechanism can dynamically adapt to changes in the importance of each indicator under different engineering scenarios. Especially when individual key indicators are at critical or extreme levels, it effectively reflects their dominant constraining effect on technology route selection, thereby improving the accuracy and reliability of the evaluation conclusions.

[0029] In one embodiment, the multiple evaluation indicators include: the proportion of reliable output of supporting power sources in the power structure dimension; the ratio of multi-infeed DC short circuits in the stability level dimension; and the ratio of converter station floor area and converter station construction investment in the economic benefit dimension.

[0030] In this embodiment, the reliable output ratio of supporting power sources refers to the ratio of the reliable output of supporting power sources (such as coal-fired power and hydropower) with reliable regulation capabilities in the sending-end power supply to the rated DC transmission power. Supporting power sources refer to conventional power sources capable of providing stable active power support for the DC transmission system, as opposed to intermittent renewable energy sources such as wind power and photovoltaics. This indicator effectively reflects the adaptability of the sending-end power source to DC transmission technology: conventional DC transmission technology is limited by a minimum operating power (generally 10% of the rated power), requiring a certain scale of supporting power sources to maintain stable system operation under low-power conditions; while flexible DC transmission technology has no minimum power limit and can adapt to weak system scenarios with a high proportion of renewable energy transmission. Therefore, the reliable output ratio of supporting power sources is one of the key indicators for distinguishing the applicable scenarios of the two types of technical routes.

[0031] The short-circuit ratio of multiple-infeed DC transmission lines is a core indicator for measuring the receiving-end grid's ability to support multiple DC feeds. A higher value indicates a stronger grid, a lower risk of commutation failure in the DC transmission system, and better system stability. According to the "Specification for Calculation of Power System Security and Stability" (GB / T 40581-2021), a short-circuit ratio greater than 3 indicates a strong system, between 2 and 3 indicates a medium-strength system, and less than 2 indicates a weak system. Conventional DC transmission requires a high grid strength and generally needs to be connected to a strong system with a short-circuit ratio greater than 3; while flexible DC transmission has no strict limit on the short-circuit ratio of the connected system and can still maintain stable operation in weak system scenarios.

[0032] The ratio of converter station floor space (flexible DC / conventional DC) and the ratio of converter station construction investment (flexible DC / conventional DC) are two evaluation indicators in the economic efficiency dimension. As a core component of UHVDC projects, the land area and construction investment of converter stations directly affect the economic efficiency of the projects. Flexible DC converter stations, due to the use of fully controlled power electronic devices, can save on AC filters, synchronous condensers, and some reactive power compensation equipment, giving them a certain advantage in terms of land area; however, the manufacturing cost of key equipment for flexible DC is still higher than that of conventional DC equipment, resulting in a relatively higher construction investment. By comparing the land area and construction investment of converter stations under the two technical routes, their economic differences can be comprehensively reflected.

[0033] The above embodiments selected four indicators across three dimensions—power structure, stability level, and economic benefits—to construct an evaluation system. These four indicators differentiate and quantify the two technical routes from three aspects: power supply adaptability at the sending end, grid support capability at the receiving end, and engineering economics. This covers the most critical influencing factors in the selection of technical routes, making the evaluation system both comprehensive and concise, avoiding the increased computational complexity caused by too many indicators and the one-sidedness of the evaluation caused by too few indicators.

[0034] In one embodiment, the actual values ​​of each of the evaluation indicators are calculated using the following formula: ; ; ; ; in, To support the reliable output ratio of the power supply, For the installed capacity of Class t supporting power supplies, Let be the reliability output coefficient of the type t supported power source. This is the rated DC transmission power. The short-circuit ratio is the ratio of multiple-infeed DC lines, where i and j are the converter bus numbers. The short-circuit capacity of DC-fed converter bus i. To account for the equivalent DC power of converter bus i after considering the influence of other DC circuits, Let i be the voltage of the converter bus i. , For the DC power of converter buses i and j, The equivalent nodal impedance matrix as seen from each DC converter bus The element in the i-th row and i-th column, The equivalent nodal impedance matrix as seen from each DC converter bus The element in the i-th row and j-th column, , These represent the ratio of the land area occupied by converter stations and the ratio of construction investment under different technical routes. , These correspond to the land area of ​​converter stations under flexible DC and conventional DC schemes, respectively. , These correspond to the total investment in converter station construction under the flexible DC and conventional DC schemes, respectively.

[0035] In this embodiment, the reliable output ratio of the supporting power supply is... The calculation process is as follows: multiply the installed capacity of each type of supporting power source at the sending end by its corresponding reliability output coefficient, sum the results, and then divide by the rated DC transmission power. The reliability output coefficient reflects the reliable output level of each type of power source. For coal-fired power, because its output is stable and controllable, its reliability output coefficient is taken as 1. Hydropower output is affected by many factors such as water inflow, flood control, navigation, and water supply; therefore, its reliability output coefficient needs to be determined comprehensively based on the characteristics of the hydropower output at the sending end.

[0036] Multi-infeed DC short-circuit ratio The calculation process involves parameters such as the short-circuit capacity of the receiving-end power grid, converter bus voltage, DC power, and equivalent node impedance matrix. This index comprehensively considers the mutual influence between multiple DC feeds and more accurately reflects the actual support capacity of the receiving-end power grid than a single short-circuit ratio index. Among these parameters, the equivalent node impedance matrix... This is the system equivalent impedance matrix viewed from each DC converter bus, and its diagonal elements are... Represents self-impedance, off-diagonal elements The mutual impedance represents the electrical coupling relationship between the converter buses.

[0037] The ratio of the area occupied by the converter station Ratio of construction investment The calculation is relatively intuitive, showing the ratio of converter station footprint and construction investment for flexible DC schemes and conventional DC schemes, respectively. When When the value is less than 1, it indicates that the flexible DC transmission scheme has a greater advantage in terms of floor space; when... A value greater than 1 indicates that the construction investment for the flexible DC scheme is higher than that for the conventional DC scheme.

[0038] The above embodiments, by clarifying the specific calculation formulas for each evaluation indicator, enable the evaluation system to have clear mathematical definitions and operable quantitative calculation methods, avoiding the subjectivity and ambiguity of qualitative evaluation, and providing accurate numerical basis for the objective comparison of technical routes.

[0039] In one embodiment, the standardization of the actual values ​​includes: standardizing the actual values ​​of each evaluation index on a percentage basis to obtain a standard state vector. The formula for the standardization process is: ; in, To support the reliable output ratio of the power supply, For multi-feed DC short-circuit ratio, This represents the ratio of the area occupied by the converter station. The investment ratio for converter station construction, This is the standard value for the proportion of reliable output of the supporting power source. This is the standard value for the multi-infeed DC short-circuit ratio. This is the standard value for the ratio of the converter station's floor area to its total floor area. This is the standard value for the investment ratio in converter station construction.

[0040] In this embodiment, the standardization process adopts a percentage-based standardization method. The purpose is to convert the actual values ​​of each indicator into standardized scores on a unified scale, making indicators with different dimensions comparable. The coefficients of the standardization formula are determined based on the reasonable range of each indicator, engineering design experience, and relevant standards and specifications. The physical meaning of each indicator's standard value is clear: a standard value of 0 points corresponds to extreme scenarios in UHVDC projects, namely, a reliable output ratio of supporting power sources of 0 (pure new energy DC transmission), a multi-infeed DC short-circuit ratio of 1 (extremely weak system), a converter station footprint ratio of 0.7 (flexible DC has a footprint only 70% of conventional DC), and a converter station construction investment ratio of 1 (equal investment for the two technical routes). A standard value of 60 points corresponds to a normal and reasonable scenario in engineering design, namely, a reliable output ratio of supporting power sources of 0.5, a multi-infeed DC short-circuit ratio of 3 (strong system threshold), a converter station footprint ratio of 0.9, and a converter station construction investment ratio of 1.25. This classification method conforms to the current actual design level and technological development status of UHVDC projects.

[0041] The above embodiments, by reasonably setting the coefficients of the standardized formula, distribute the standard values ​​of each indicator within the range of 0 to 100 percentiles, and make 60 points correspond to conventional and reasonable scenarios. This ensures both the intuitiveness and interpretability of the standardized results, as well as the sensitivity of the evaluation under different engineering scenarios, providing a reliable data foundation for subsequent weighted processing and comprehensive scoring.

[0042] In one embodiment, the state-change penalty function The expression is: ; in, Let k be the variable-weight penalty factor for the k-th indicator. These are the standardized state variables; This is the baseline value of the corresponding state variable.

[0043] In this embodiment, the state-varying penalty function adopts a piecewise form: when the standard value of the k-th index... Lower than or equal to its benchmark value At that time, variable factor Take the value of the exponential function ,because and Therefore, the power of the exponent term is non-positive, the variable weight factor is greater than or equal to 1, and the lower the index value is than the benchmark value, the larger the variable weight factor is. The weight of this index increases more during subsequent normalization, thus highlighting its constraining effect; when the standard value of the k-th index... Higher than its benchmark value At this time, the variable weighting factor is set to 1, and the weight remains unchanged. This avoids the situation where excessively high indicator values ​​lead to weight decay and consequently a decrease in the overall score, thus ensuring the monotonicity between the indicator value and the overall score. Among these, the variable weighting penalty factor... What is being controlled is the sensitivity to changes in weights. The larger the value, the more significant the increase in weight when the indicator is below the benchmark value. (Benchmark value for state variables) It is the dividing point for judging whether an indicator has triggered a weighted adjustment, and its setting is based on the current planning practice experience of UHVDC projects.

[0044] The above embodiment realizes the automatic dynamic adjustment of indicator weights through a piecewise continuous state-varying penalty function. When the key indicator is at an unfavorable level, its weight can be automatically increased to highlight the constraint effect. When the key indicator is at a favorable level, the weight remains unchanged to ensure the stability and monotonicity of the evaluation, thus taking into account both the requirements of sensitivity and stability.

[0045] In one embodiment, the key constraint indicators are the reliable output ratio of the supporting power source and the multi-infeed DC short-circuit ratio; the variable weighting penalty factor for each indicator. The values ​​are [0.05, 0.07, 0, 0], which correspond to the reliable output ratio of the supporting power source, the short-circuit ratio of multiple infeed DC, the ratio of the converter station's land area, and the ratio of the converter station's construction investment, respectively. Among the state variable benchmark values, the benchmark value corresponding to the reliable output ratio of the supporting power source is 0.5, and the benchmark value corresponding to the short-circuit ratio of multiple infeed DC is 3.

[0046] In this embodiment, the value of the variable weight penalty factor is determined based on a systematic analysis of recently commissioned, approved under construction, and planned UHVDC transmission technology routes. Only the reliable output ratio of supporting power sources and the multi-infeed DC short-circuit ratio are given effective variable weight penalty factors (0.05 and 0.07, respectively), while the variable weight penalty factors for the ratio of converter station land area and the ratio of converter station construction investment are both set to 0. This means that only the first two indicators are subject to variable weight penalty functions, reflecting the decisive constraint role of these two indicators in technology route selection: the reliable output ratio of supporting power sources directly relates to the feasibility of conventional DC transmission, and the multi-infeed DC short-circuit ratio directly relates to the stability of system operation. While the two indicators in the economic benefit dimension are important, they do not possess similar rigid constraint characteristics; their role is reflected in the initial allocation of fixed weights.

[0047] The variable weighting penalty factor (0.07) for the multi-infeed DC short-circuit ratio is greater than that for the reliable output ratio of the supporting power source (0.05), indicating that when the multi-infeed DC short-circuit ratio decreases, its weight increases more significantly, reflecting that the multi-infeed DC short-circuit ratio has a stronger constraint on the selection of technical routes.

[0048] The benchmark value corresponding to the reliable output ratio of the supporting power source is 0.5 (equivalent to 60 points after standardization), which is determined based on the design experience of the current UHVDC planning scheme; the benchmark value corresponding to the short-circuit ratio of multiple infeed DC sources is 3 (equivalent to 60 points after standardization), which is consistent with the threshold value of strong systems in the "Power System Safety and Stability Calculation Specification".

[0049] The above embodiments, by setting different variable weighting penalty factors and benchmark values ​​for each indicator, enable the variable weighting mechanism to accurately match the actual constraint characteristics of each indicator in the selection of technical routes. This avoids over-adjustment caused by applying variable weighting to all indicators equally, and ensures that the dominant position of key constraint indicators can be fully reflected in the evaluation results.

[0050] In one embodiment, calculating the weighted composite vector by combining the initial weight vector and the state-weighted vector includes: setting the initial weight vector. ; The combined weighted vector is calculated by combining the initial weight vector and the state weighted vector. The calculation formula is: ; in, The k-th element in the initial weight vector. It is the k-th element in the state change weight vector.

[0051] In this embodiment, the initial weight vector The determination was based on recent research experience, expert opinions, and industry standard requirements for multiple UHVDC transmission schemes. The initial weights for the reliable output ratio of supporting power sources and the short-circuit ratio of multi-infeed DC systems were both 0.3, reflecting the core importance of these two indicators in conventional scenarios. The initial weights for the ratio of converter station floor area and construction investment were both 0.2, reflecting the auxiliary decision-making role of economic benefits.

[0052] Variable weight composite vector The calculation process is as follows: The initial weight vector... With state change weight vector Multiply corresponding elements (i.e.) (This represents element-wise product), then divide by the sum of all element-wise products (i.e., ... This normalization process ensures that the sum of all elements in the variable weight composite vector is 1, satisfying the basic mathematical properties of weight.

[0053] The calculation process of the variable-weighted composite vector enables dynamic weight adaptation: when the standard value of the reliable output ratio of the supporting power source or the multi-infeed DC short-circuit ratio is lower than the reference value, the corresponding state-weighted value is adjusted. This leads to an increase in the proportion of their weights in the variable-weighted composite vector, highlighting their constraining effect; when the standard values ​​of these two indicators are higher than the benchmark values... The weights are kept in the same proportional relationship as the initial values ​​to ensure the rationality of the evaluation in normal scenarios.

[0054] The above embodiments achieve an organic combination of initial weights and dynamic variable weight factors through normalized variable weight comprehensive vector calculation. This not only preserves the conventional importance ranking of each indicator reflected by the initial weights, but also automatically adjusts the weight allocation when key indicators are at an unfavorable level, so that the weight allocation scheme can dynamically adapt to the actual situation of different engineering scenarios.

[0055] In one embodiment, the formula for calculating the comprehensive score is: ;in, For comprehensive scoring, For the standard state vector, This is the variable weighted composite vector.

[0056] In this embodiment, the comprehensive score The calculation is essentially the standard state vector. With variable weight composite vector The inner product operation, i.e. ,in , , , These are the variable weighted composite vectors. The formula combines four elements. By multiplying each standardized index value with its corresponding dynamic weight and then summing the results, it integrates multi-dimensional evaluation information into a single scalar score, facilitating intuitive quantitative comparison and interval judgment.

[0057] The above embodiments compress multi-dimensional evaluation information into a single comprehensive score through weighted inner product operations, realizing a comprehensive quantitative expression of the advantages and disadvantages of technical routes. The calculation process is simple and clear, and the evaluation results have good interpretability.

[0058] In one embodiment, determining the recommended power transmission route based on the preset interval where the comprehensive score falls includes: when Flexible DC transmission is recommended at this time; when At that time, flexible DC or conventional DC transmission is recommended; when At that time, conventional DC transmission is recommended.

[0059] In this embodiment, the criteria for dividing the preset intervals are determined based on the analysis and summary of numerous UHVDC engineering cases and a trade-off between technology and economy. When the comprehensive score is below 50, it indicates that there are significant constraints in the engineering scenario (such as insufficient supporting power or weak grid strength), highlighting the adaptability advantages of flexible DC transmission technology, and recommending the flexible DC transmission technology route. When the comprehensive score is between 50 and 70, it indicates that the constraints in the engineering scenario are not significant, and both technical routes have certain applicability and economy. It is recommended to further evaluate the project based on specific electrical calculation results (such as system stability simulation, fault ride-through capability analysis, etc.), actual site conditions (such as terrain, land use restrictions, etc.), and subsequent operation and maintenance needs (such as operation and maintenance technical level, spare parts supply, etc.) to select the most suitable technical route. When the comprehensive score is above 70, it indicates that there are no obvious constraints in the engineering scenario, and conventional DC transmission technology has advantages in terms of economy and maturity, recommending the conventional DC transmission technology route.

[0060] The above embodiment uses a three-stage comprehensive scoring interval division to map continuous comprehensive scores into clear technical route recommendations. The setting of the scoring interval takes into account both the clarity of decision-making (clear recommendations are given in the low and high score segments) and the flexibility of the middle zone (the middle segment suggests further analysis based on specific conditions), which meets the actual needs of engineering decision-making.

[0061] To further verify the scientific validity and practicality of the method of the present invention, the following are application examples of four different types of ultra-high voltage direct current projects.

[0062] In one embodiment, the specific application process of the method of the present invention is illustrated using DC project A (already in operation, conventional DC scenario) as an example.

[0063] Project A is an ultra-high voltage direct current (UHVDC) project that has been put into operation, with a rated transmission capacity of 8 million kilowatts. The power supply at the sending end includes 4.64 million kilowatts of coal-fired power, 4 million kilowatts of wind power, 9 million kilowatts of photovoltaic power, and 1.3 million kilowatts of energy storage (2 hours). The receiving end is connected to the strong power grid. The project actually adopts the conventional DC transmission technology route.

[0064] Step S1-1: Obtain the actual values ​​of each evaluation indicator. Based on engineering design data, operational data, and calculation results, obtain the actual values ​​of each evaluation indicator: Reliable output ratio of supporting power source. The reliable output coefficient of the coal-fired power plant at the sending end is taken as 1. There is no supporting hydropower. Calculations show that... Multi-infeed DC short-circuit ratio The receiving-end power grid is strong, as calculated by short-circuit capacity. The ratio of the area occupied by the converter station The conventional DC solution requires two 300MVar synchronous condensers at the receiving end, with an area of ​​approximately 20 hectares within the walled enclosure. The flexible DC solution, due to the immaturity of 5kA IGBT devices at the design stage, uses 3kA IGBT devices, with an area of ​​approximately 26.5 hectares within the walled enclosure. Calculations show... The ratio of investment in converter station construction The conventional DC power supply with added synchronous condensers requires an investment of approximately 5.81 billion yuan, while the flexible DC power supply requires an investment of approximately 7.95 billion yuan. .

[0065] Step S1-2: Standardization. Substitute the actual values ​​of each indicator into the standardization formula to calculate the standard state vector: ; ; ; Standard state vector .

[0066] Step S1-3: Calculation of the state-weighted vector. The standard value of the reliable output ratio of the supporting power source (69.6%) is greater than the reference value of 60%, and the standard value of the multi-infeed DC short-circuit ratio (73.5%) is also greater than the reference value of 60%. Neither of these triggers the penalty function, and the state-weighted vector... .

[0067] Step S1-4: Calculate the variable weight composite vector. Substitute the initial weight vector... and state change weight vector Calculate the denominator Variable weight composite vector .

[0068] Steps S1-5: Calculation of comprehensive score. .

[0069] Steps S1-6: Technical Route Recommendation. With a comprehensive score of 98.1 (greater than 70), the conventional DC transmission technology route is recommended. This is completely consistent with the technical route used in actual engineering projects, verifying the accuracy of this method in conventional DC application scenarios.

[0070] In one embodiment, the application process of the method of the present invention in a flexible DC application scenario is illustrated by taking the B DC project (approved and under construction, flexible DC scenario) as an example.

[0071] The B DC project is an approved ultra-high voltage DC project under construction, with a rated transmission capacity of 8 million kilowatts. The power supply at the sending end includes 4 million kilowatts of coal-fired power, 4 million kilowatts of wind power, 7 million kilowatts of photovoltaic power, 200,000 kilowatts of solar thermal power, and 2 million kilowatts of energy storage (2 hours). The grid strength at the receiving end is relatively weak, and the project actually adopts the flexible DC (sending and receiving end) technology route.

[0072] Step S2-1: Obtain the actual values ​​of each evaluation indicator. Based on engineering design data, system stability calculation results, and investment calculation report, obtain the actual values ​​of each evaluation indicator: the proportion of reliable output of supporting power source. Multi-infeed DC short-circuit ratio Without the synchronous condenser, the value is 1.85; after installing three 300MVar synchronous condensers, it increases to 2.05. The ratio of the area occupied by the converter station The conventional DC system with added synchronous condenser has an enclosed area of ​​approximately 27.4 hectares, while the flexible DC system using 5kA IGBT devices has an enclosed area of ​​approximately 24.4 hectares. Calculations show... The ratio of investment in converter station construction The conventional DC power supply with added synchronous condensers requires an investment of approximately 5.95 billion yuan, while the flexible DC power supply requires an investment of approximately 7.14 billion yuan. .

[0073] Step S2-2: Standardization process. ; ; ; Standard state vector .

[0074] Step S2-3: Calculation of state-weighted vector. The standard value of 60% for the reliable output ratio of the supporting power source is equal to the baseline value of 60%, triggering the penalty function, but... The standard value of the multi-infeed DC short-circuit ratio, 31.5, is less than the reference value of 60, triggering the penalty function. The penalty factor for the ratio of converter station land area to construction investment is 0. , State-variable weight vector .

[0075] Step S2-4: Calculation of the variable weight composite vector. Denominator . ; ; ; Variable weighted composite vector .

[0076] Step S2-5: Calculate the overall score. .

[0077] Step S2-6: Technical Route Recommendation. With a comprehensive score of 37.4 (less than 50), the flexible DC transmission technology route is recommended, consistent with the actual engineering approach. In this embodiment, the standard value of the multi-infeed DC short-circuit ratio is only 31.5, far lower than the benchmark value of 60, triggering the variable-weight penalty function. This significantly increases the weight of the multi-infeed DC short-circuit ratio from the initial 0.3 to 0.76, giving it a dominant position in the weight allocation. This effectively highlights the constraint effect of insufficient receiving-end grid strength on the technical route selection and verifies the method's responsiveness to key indicator constraints.

[0078] In one embodiment, the application process of the method of the present invention in an intermediate scenario is illustrated by taking a C-DC project (which has been included in the regulations and can be implemented using either technical route) as an example.

[0079] The C-type DC project is an ultra-high voltage DC project that has been included in the planning. The rated transmission capacity is 8 million kilowatts. The power supply at the sending end includes 4 million kilowatts of coal-fired power, 4 million kilowatts of wind power, 7 million kilowatts of photovoltaic power, and 2.2 million kilowatts of energy storage (2 hours). The grid strength at the receiving end is moderate. The initial feasibility study of the project considered to adopt a conventional DC scheme, but it was later adjusted to a flexible DC scheme after demonstration.

[0080] Step S3-1: Obtain the actual values ​​of each evaluation indicator. ; ; ; .

[0081] Step S3-2: Standardization process. ; ; ; Standard state vector .

[0082] Step S3-3: Calculation of the state-weighted vector. The standard values ​​of all key indicators are not lower than the benchmark values. The state-weighted vector... .

[0083] Step S3-4: Calculation of the variable weight composite vector. Variable weight composite vector. .

[0084] Step S3-5: Calculate the overall score. .

[0085] Step S3-6, Technical Route Recommendation. With a comprehensive score of 55.4, falling between 50 and 70, both flexible DC and conventional DC are recommended. Considering the actual project conditions (flexible DC has a better footprint and aligns with the trend of new energy consumption), the flexible DC technical route is preferred, consistent with the results of the actual project demonstration and adjustment.

[0086] In one embodiment, the application process of the method of the present invention is illustrated using a D-type DC project (already included in the regulations, leaning towards flexible DC scenarios) as an example.

[0087] The D DC project is an ultra-high voltage DC project that has been included in the planning. The rated transmission capacity is 8 million kilowatts. The power supply at the sending end includes 4 million kilowatts of coal power, 4 million kilowatts of wind power, 8 million kilowatts of photovoltaic power, and 2.5 million kilowatts of energy storage (2 hours). The grid conditions at the receiving end are relatively good. However, conventional DC schemes require a large number of synchronous condensers. At this stage, the project has basically decided to adopt the flexible DC (receiving end) technology route.

[0088] Step S4-1: Obtain the actual values ​​of each evaluation indicator. ; ; ; .

[0089] Step S4-2: Standardization process. ; ; ; Standard state vector .

[0090] Step S4-3: Calculation of the state-weighted vector. The standard values ​​of all key indicators are not lower than the benchmark values. The state-weighted vector... .

[0091] Step S4-4: Calculation of the variable weight composite vector. Variable weight composite vector. .

[0092] Step S4-5: Calculate the overall score. .

[0093] Steps S4-6: Recommended Technical Approach. With a comprehensive score of 53.1, falling between 50 and 70, both flexible DC and conventional DC are recommended. Considering the significant advantage of flexible DC in terms of land area (only 72% of conventional DC) and the relatively small difference in construction investment (only 1.109 times that of conventional DC), the flexible DC technical approach is preferred, consistent with the current project plan.

[0094] The above four embodiments cover UHVDC projects at different stages, such as those already in operation, approved for construction, and included in regulations, as well as in different scenarios such as conventional DC, flexible DC, and projects using both technical routes. The recommended results of the method of this invention are highly consistent with the actual engineering schemes or demonstration conclusions, which fully verify the scientific nature, accuracy, and practicality of the method.

[0095] This application also provides a variable-weight optimization-based UHVDC transmission technology optimization system for executing the steps in the above-described variable-weight optimization-based UHVDC transmission technology optimization method embodiments. The variable-weight optimization-based UHVDC transmission technology optimization system can be a virtual appliance in an electronic device, run by the electronic device's processor, or it can be the electronic device itself.

[0096] In one embodiment, such as Figure 2 As shown, an ultra-high voltage direct current (UHVDC) transmission technology optimization system 100 based on variable weight optimization includes: The indicator system construction module 101 is used to construct multiple evaluation indicators covering three dimensions: power supply structure, stability level, and economic benefits. The standardization processing module 102 is used to obtain the actual values ​​of each of the evaluation indicators, and to standardize the actual values ​​to obtain a standard state vector. The variable weighting processing module 103 is used to perform dynamic variable weighting processing on the key constraint indicators in the standard state vector based on the state variable weighting penalty function to form a state variable weighting vector. The comprehensive vector calculation module 104 is used to calculate the variable weight comprehensive vector by combining the initial weight vector and the state variable weight vector; The comprehensive scoring module 105 is used to perform a weighted summation based on the standard state vector and the variable weight comprehensive vector to obtain a comprehensive score. The route recommendation module 106 is used to determine a recommended power transmission route based on the preset interval in which the comprehensive score is located.

[0097] In application, the indicator system construction module is used to construct multiple evaluation indicators covering three dimensions: power supply structure, stability level, and economic benefits. Specifically, these include the proportion of reliable output of supporting power supply in the power supply structure dimension, the ratio of multi-infeed DC short circuit in the stability level dimension, and the ratio of converter station land area and converter station construction investment in the economic benefits dimension.

[0098] The standardization module is used to obtain the actual values ​​of each evaluation indicator and standardize them on a percentage basis to obtain a standard state vector. .

[0099] The variable weighting module is used to dynamically weight two key constraint indicators, namely the reliable output ratio of the supporting power source and the short-circuit ratio of multiple infeed DC, based on the state-variable weighting penalty function, to form a state-variable weighting vector. .

[0100] The integrated vector calculation module is used to combine the initial weight vector. and state change weight vector The variable weighted composite vector is obtained through normalization calculation. .

[0101] The comprehensive scoring module is used to score based on the standard state vector. and variable weighted composite vector The comprehensive score is calculated by weighted summation. .

[0102] The route recommendation module is used to recommend routes based on a comprehensive score. The recommended power transmission route is determined based on the preset interval.

[0103] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps described in the various method embodiments above.

[0104] This application provides a computer program product, including a computer program, which, when run on an electronic device, enables the electronic device to perform the steps described in the various method embodiments above.

[0105] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments of this application can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. A computer-readable medium can include at least: any entity or device capable of carrying computer program code to a device / electronic device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium. Examples include USB flash drives, portable hard drives, magnetic disks, or optical disks. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electrical carrier signals or telecommunication signals.

[0106] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0107] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0108] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0109] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0110] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for optimizing ultra-high voltage direct current (UHVDC) transmission technology based on variable weight optimization, characterized in that, include: Construct multiple evaluation indicators covering three dimensions: power supply structure, stability level, and economic benefits; Obtain the actual values ​​of each evaluation index, and standardize the actual values ​​to obtain a standard state vector; Based on the state-weighted penalty function, the key constraint indicators in the standard state vector are dynamically weighted to form a state-weighted vector. The combined weight vector is calculated by combining the initial weight vector and the state-adjusted weight vector. The comprehensive score is obtained by weighted summation of the standard state vector and the variable weighted comprehensive vector. Based on the preset range in which the comprehensive score falls, a recommended power transmission route is determined.

2. The method for optimizing UHVDC transmission technology based on variable weight optimization as described in claim 1, characterized in that, The aforementioned evaluation indicators include: The proportion of reliable power output supported by the power supply structure. Stable horizontal dimension of multi-infeed DC short-circuit ratio; The ratio of converter station land area to converter station construction investment ratio in terms of economic benefits.

3. The method for optimizing UHVDC transmission technology based on variable weight optimization as described in claim 2, characterized in that, The actual values ​​of each of the aforementioned evaluation indicators are calculated using the following formula: ； ； ； ； in, To support the reliable output ratio of the power supply, For the installed capacity of Class t supporting power supplies, Let be the reliability output coefficient of the type t supported power source. This is the rated DC transmission power. For multi-feed DC short-circuit ratio, For the converter bus numbering, The short-circuit capacity of DC-fed converter bus i. To account for the equivalent DC power of converter bus i after considering the influence of other DC circuits, Let i be the voltage of the converter bus i. For the DC power of converter buses i and j, The equivalent nodal impedance matrix as seen from each DC converter bus The element in the i-th row and i-th column, The equivalent nodal impedance matrix as seen from each DC converter bus The element in the i-th row and j-th column, , These represent the ratio of the land area occupied by converter stations and the ratio of construction investment under different technical routes. , These correspond to the land area of ​​converter stations under flexible DC and conventional DC schemes, respectively. , These correspond to the total investment in converter station construction under the flexible DC and conventional DC schemes, respectively.

4. The method for optimizing UHVDC transmission technology based on variable weight optimization as described in claim 2, characterized in that, The standardization process for the actual value includes: The actual values ​​of each evaluation indicator are standardized on a percentage basis to obtain a standard state vector. ; The formula for the standardization process is: ； in, To support the reliable output ratio of the power supply, For multi-feed DC short-circuit ratio, This represents the ratio of the area occupied by the converter station. The investment ratio for converter station construction, This is the standard value for the proportion of reliable output of the supporting power source. This is the standard value for the multi-infeed DC short-circuit ratio. This is the standard value for the ratio of the converter station's floor area to its total floor area. This is the standard value for the investment ratio in converter station construction.

5. The method for optimizing UHVDC transmission technology based on variable weight optimization as described in claim 1, characterized in that, The state-change penalty function The expression is: ； in, Let k be the variable-weight penalty factor for the k-th indicator. These are the standardized state variables; This is the baseline value of the corresponding state variable.

6. The method for optimizing UHVDC transmission technology based on variable weight optimization as described in claim 5, characterized in that, The key constraints are the reliable output ratio of the supporting power source and the short-circuit ratio of multi-infeed DC; the variable weighting penalty factor for each indicator. The values ​​are [0.05, 0.07, 0, 0], which correspond to the reliable output ratio of the supporting power source, the short-circuit ratio of multiple infeed DC, the ratio of the converter station's land area, and the ratio of the converter station's construction investment, respectively. Among the state variable benchmark values, the benchmark value corresponding to the reliable output ratio of the supporting power source is 0.5, and the benchmark value corresponding to the short-circuit ratio of multiple infeed DC is 3.

7. The method for optimizing UHVDC transmission technology based on variable weight optimization as described in claim 1, characterized in that, The calculation of the weighted composite vector by combining the initial weight vector and the state-weighted vector includes: Set the initial weight vector ; The combined weighted vector is calculated by combining the initial weight vector and the state weighted vector. The calculation formula is: ； in, The first weight in the initial weight vector k One element, The first in the state-change weight vector k Each element.

8. The method for optimizing UHVDC transmission technology based on variable weight optimization as described in claim 1, characterized in that, The formula for calculating the comprehensive score is as follows: ; in, For comprehensive scoring, For the standard state vector, This is the variable weighted composite vector.

9. The method for optimizing ultra-high voltage direct current transmission technology based on variable weight optimization as described in claim 8, characterized in that, The step of determining the recommended power transmission route based on the preset interval of the comprehensive score includes: when Flexible DC transmission is recommended at this time; when At that time, flexible DC or conventional DC transmission is recommended; when At that time, conventional DC transmission is recommended.

10. A variable-weight optimization-based ultra-high voltage direct current transmission technology optimization system, characterized in that, include: The indicator system construction module is used to construct multiple evaluation indicators covering three dimensions: power supply structure, stability level, and economic benefits. The standardization processing module is used to obtain the actual values ​​of each of the evaluation indicators, and to standardize the actual values ​​to obtain a standard state vector. The variable weighting processing module is used to dynamically change the weights of key constraint indicators in the standard state vector based on the state variable weighting penalty function to form a state variable weighting vector. The comprehensive vector calculation module is used to calculate the variable weight comprehensive vector by combining the initial weight vector and the state variable weight vector; The comprehensive scoring module is used to perform a weighted summation based on the standard state vector and the variable weight comprehensive vector to obtain a comprehensive score. The route recommendation module is used to determine the recommended power transmission route based on the preset interval in which the comprehensive score is located.

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