Variable-speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS

Abstract

The invention discloses a variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS, and the method comprises the steps: collecting the configuration parameters of a variable speed pumped storage power station and the operation parameters of the variable speed pumped storage power station during operation, and carrying out the calculation to obtain the operation benefit generated after the transformation of the variable speed pumped storage power station; dividing different benefit indexes for operation benefits based on benefit sources to construct a comprehensive benefit evaluation index system, and layering the indexes by adopting an improved analytic hierarchy process to determine the weight of each index; and then a comprehensive benefit evaluation model based on TOPSIS is constructed to comprehensively analyze the operation benefit and the index weight to obtain a benefit evaluation score, and the constructed index system is more comprehensive by comprehensively considering the economic benefit, the social benefit and the environmental benefit, so that the obtained benefit score is more in line with the actual situation, and the economic benefit evaluation efficiency is improved. And the reliability and the accuracy of benefit scoring are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of benefit evaluation of energy storage power stations, and in particular to a variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS. Background Art

[0002] Small and medium-sized pumped storage power stations have the advantages of small regulating storage capacity, relatively low water head, good adaptability to water source and topographic geological conditions, rich site resources and flexible layout, low investment, quick results, and low requirements for transmission lines, which can cooperate with the development of urban distributed energy supply systems. According to local conditions and giving full play to resource advantages, small hydropower will be transformed into variable speed pumped storage, so that the development and utilization of hydropower will be more in line with new needs. The benefit evaluation of the transformation is one of the important indicators for the feasibility of the transformation, which directly reflects the rationality of the transformation. Therefore, how to conduct efficient and accurate quantitative evaluation of the comprehensive benefits of the transformation of variable speed pumped storage power stations has become a research hotspot. At present, the evaluation method for the transformation benefits of variable speed pumped storage power stations is mainly based on the economic perspective. The evaluation of other benefits (such as social benefits and environmental benefits) is basically in the form of text description, which is highly subjective. Therefore, how to select or improve the existing evaluation method to objectively evaluate the comprehensive benefits of the transformation of variable speed pumped storage power station units is an urgent problem to be solved.

[0003] Chinese patent, publication number: CN112926851A, publication date: June 8, 2021, discloses a method for calculating the benefits of a pumped-storage power station, by determining at least one indicator type characterizing the benefits of the pumped-storage power station, and at least one indicator contained in each indicator type; based on the determined indicator, the corresponding indicator value is calculated; based on the indicator type, the first weight of each indicator is calculated; based on the entropy weight method, the second weight of each indicator is calculated; combining the first weight and the second weight to determine the third weight corresponding to each indicator; combining the indicator value corresponding to each indicator and the third weight to determine the score characterizing the benefits of the pumped-storage power station, but it only considers the economy of the pumped-storage power station, and does not consider other benefits, and the reliability of the comprehensive benefits of the pumped-storage power station obtained is low. Summary of the invention

[0004] In view of the problem that it is difficult to take social benefits and environmental benefits into consideration when evaluating the benefits of variable-speed pumped-storage power station transformation, resulting in large limitations and low reliability of the benefits, the present invention provides a variable-speed pumped-storage power station transformation benefit evaluation method based on improved AHP-TOPSIS. The method collects the configuration parameters of the variable-speed pumped-storage power station itself and the operating parameters during operation, calculates the operating benefits generated when the variable-speed pumped-storage power station is transformed, and then divides the operating benefits into different benefit indicators based on the benefit sources to construct a comprehensive benefit evaluation index system, and uses an improved hierarchical analysis method to hierarchically determine the weight of each indicator for the indicators, and then constructs a comprehensive benefit evaluation model based on the TOPSIS method to comprehensively analyze the operating benefits and indicator weights to obtain a benefit evaluation score. By comprehensively considering the economic benefits, social benefits and environmental benefits, the constructed index system is more comprehensive, so that the obtained benefit score is more in line with the actual situation, and the reliability and accuracy of the benefit score are improved.

[0005] In a first aspect, a technical solution provided in an embodiment of the present invention is: a variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS, comprising the following steps: S1. Collect configuration parameters and operation parameters of variable speed pumped storage power station based on data collection principles; S2. Benefit accounting principle: The operation benefit of the variable speed pumped storage power station transformation is obtained in response to the configuration parameters and operation parameters, and a comprehensive benefit evaluation index system is constructed based on the operation benefit; S3. Based on the improved analytic hierarchy process, the various indicators in the comprehensive benefit evaluation index system are layered, and the indicators at the same level are compared to obtain the indicator weights; S4. Based on the TOPSIS method, a comprehensive benefit evaluation model is constructed, and the indicator weights and operating benefits are input into the comprehensive benefit evaluation model to obtain the benefit evaluation score of the variable speed pumped storage power station.

[0006] In this scheme, through the principle of benefit accounting, not only the direct economic benefits of the variable speed pumped storage power station (such as power generation income, fuel cost savings, etc.) are considered, but also environmental benefits (such as reducing greenhouse gas emissions) and social benefits (such as improving grid stability and promoting local economic development, etc.), which is helpful to build a comprehensive and multi-dimensional comprehensive benefit evaluation index system to more accurately reflect the overall value of the power station; the various indicators in the comprehensive benefit evaluation index system are layered and weighted by adopting the improved hierarchical analysis method. This method can systematically deal with complex problems, and obtain relatively objective weights by comparing the importance of indicators at the same level, thereby ensuring the accuracy and fairness of the evaluation results; by constructing a comprehensive benefit evaluation model, after inputting the indicator weights and operating benefits into the model, the benefit evaluation score of the variable speed pumped storage power station transformation can be quantitatively calculated, which not only provides a clear evaluation of the current operating status of the power station, but also provides a basis for future continuous improvement and optimization. Through regular evaluation, potential problems can be discovered and solved in a timely manner, promoting the continuous improvement of power station benefits.

[0007] Preferably, in S2, the benefit accounting principle obtains the operating benefit of the variable speed pumped storage power station transformation in response to the configuration parameters and the operating parameters, including the following steps: The economic benefits of the variable speed pumped storage power station transformation are obtained based on the investment cost, operating cost and unit capacity of various equipment in the variable speed pumped storage power station transformation; the social benefits of the variable speed pumped storage power station transformation are obtained based on the influence of the variable speed pumped storage power station on energy dispatch; the environmental benefits of the variable speed pumped storage power station transformation are obtained based on the utilization degree of clean energy by the variable speed pumped storage power station; the economic benefits, social benefits and environmental benefits are taken as the operating benefits of the variable speed pumped storage power station transformation.

[0008] In this plan, environmental benefits are incorporated into the evaluation system, and the degree of utilization of clean energy by variable-speed pumped-storage power stations is emphasized, which helps promote the sustainable development of power stations. By improving the utilization rate of clean energy, it can reduce dependence on fossil energy and reduce greenhouse gas emissions, thereby protecting the environment and responding to climate change. The impact of variable-speed pumped-storage power stations on energy scheduling is taken into account through the evaluation of social benefits, which helps to enhance the social recognition of power stations. When power stations can provide stable power supply, improve grid reliability and promote local economic development, their social image will be more positive, which will help win the support of the masses. By comprehensively considering economic benefits, social benefits and environmental benefits, the overall value of variable-speed pumped-storage power stations can be comprehensively evaluated, and comprehensive evaluations can help decision makers understand the overall performance of power stations more accurately, thereby making more informed decisions.

[0009] Preferably, the economic benefits include investment cost, operating cost, net present value, internal rate of return, payback period and total investment rate of return; the social benefits include frequency regulation benefit, phase regulation benefit, black start benefit and employment benefit; the environmental benefits include new energy consumption rate, emission reduction benefit and water resource utilization coefficient.

[0010] In this plan, the investment cost includes construction cost, equipment purchase cost, installation cost, commissioning cost and possible indirect cost; the operating cost includes various expenses required for the operation of the units in the variable speed pumped storage power station transformation within one year; the net present value is the present value difference between the cash inflow and expenditure expected to be achieved by the project. The larger the difference, the better the plan; the internal rate of return is the discount rate when the net present value is zero during the entire calculation period. When the internal rate of return is greater than or equal to the benchmark rate, it means that the plan is feasible; the investment payback period is the number of years required to recover the total investment through capital return after the project is put into production; the total investment rate of return is the ratio of the average annual total profit of the project during the production and operation period to the total funds of the construction period (the sum of fixed asset investment and all working capital); the social benefits are mainly reflected in the benefits generated by replacing phase-modulating and frequency-modulating units with variable speed pumped storage units of a certain capacity; the environmental benefits are mainly reflected in the benefits generated by improving the utilization of resources.

[0011] As a preferred embodiment, in S2, a comprehensive benefit evaluation index system is constructed based on the operation benefit, including the following steps: Taking economic benefits, social benefits and environmental benefits as the primary indicators, and investment cost, operating cost, net present value, internal rate of return, payback period, total investment rate of return, frequency regulation benefit, phase regulation benefit, black start benefit, employment benefit, new energy consumption rate, emission reduction benefit and water resource utilization coefficient as the secondary indicators, a comprehensive benefit evaluation index system is obtained.

[0012] In this plan, the benefits are considered from three main aspects: economy, society and environment, to ensure the comprehensiveness and accuracy of the evaluation. The refinement of secondary indicators can more specifically reflect the performance of the project in various aspects, avoid one-sided evaluation, and thus improve the reliability of the subsequent benefit evaluation scores. By further refining the analysis of the three main aspects of economy, society and environment, the number of considered factors is increased, making the comprehensive benefit evaluation of the transformation of variable speed pumped storage power stations more comprehensive, thereby reducing the probability of problems such as the large proportion of certain indicators having too much influence on the final results and thus affecting the effectiveness of the results.

[0013] As a preferred embodiment, in S3, the various indicators in the comprehensive benefit evaluation index system are layered based on the improved hierarchical analysis method, including the following steps: The indicators in the secondary indicators are divided into the scheme level, and the indicators in the primary indicators are divided into the criterion level; The comprehensive benefit index of the variable speed pumped storage power station transformation is obtained by comprehensive analysis of economic benefits, social benefits and environmental benefits, and the comprehensive benefit index is taken as the target layer.

[0014] In this plan, by dividing the indicators into the program layer, the criterion layer and the target layer, a clear evaluation framework is formed, making the evaluation process more intuitive and easy to understand, and the hierarchical structure helps to better manage and organize information during the evaluation process to ensure the accuracy and efficiency of the evaluation; by incorporating various indicators into a unified evaluation framework, comparison between different projects or plans becomes possible, providing strong support for decision-making, and the target layer (comprehensive benefit indicators) as the final result of the evaluation provides decision makers with an intuitive and quantitative basis, which helps to make more scientific and reasonable decisions.

[0015] Preferably, in S3, the indicators at the same level are compared to obtain the indicator weights, including the following steps: assigning values ​​to the indicators at each level based on the importance of each indicator and using an improved proportional scaling method to obtain corresponding indicator values, then comparing the indicator values ​​corresponding to the indicators at each level in pairs to obtain the proportions of each indicator, and constructing a judgment matrix corresponding to each level based on the proportions of each indicator; The judgment matrix is ​​checked for consistency. If the consistency is passed, the m-th power of the product of each row of the judgment matrix is ​​calculated to obtain an m-dimensional vector, where m is the order of the judgment matrix. The m-dimensional vector is then standardized to obtain the weights of each indicator at each level.

[0016] In this scheme, a judgment matrix is ​​constructed through the hierarchical analysis method, and qualitative analysis is converted into quantitative analysis, making the decision-making process more scientific and objective. Calculating the indicator weights according to the judgment matrix can convert the decision-maker's subjective judgment and experience accumulation into specific values, thereby reducing the impact of subjective factors on the decision-making results; and by calculating the indicator weights, it can ensure that each factor is properly considered in the decision-making process, avoiding decision-making errors caused by personal preferences or prejudices; by decomposing complex problems into multiple levels and factors, the decision-making process can be further simplified, thereby improving the efficiency of obtaining benefit evaluation scores; by calculating the indicator weights, the relative importance of each factor can be reflected, providing decision-makers with a more accurate decision-making basis, which helps decision-makers choose the best option when faced with multiple options.

[0017] Preferably, the consistency check of the judgment matrix includes the following steps: Calculate the maximum eigenvalue of the judgment matrix, and obtain the consistency index value based on the maximum eigenvalue and order of the judgment matrix; Based on the order of the judgment matrix, the corresponding random consistency index value is searched from the set random consistency index table; The consistency index value is compared with the random consistency index value to obtain the consistency ratio. If the consistency ratio is less than the set threshold, the matrix is ​​judged to be consistent.

[0018] In this scheme, by performing a consistency check on the judgment matrix, it can be ensured that the relationship between the elements in the judgment matrix is ​​logically consistent, that is, if A is more important than B, and B is more important than C, then A should be more important than C, avoiding logical contradictions that may occur in the decision-making process; and through consistency testing, those logically unreasonable judgments can be screened out, thereby improving the credibility and scientificity of the decision.

[0019] As a preferred embodiment, in S4, a comprehensive benefit evaluation model is constructed based on the TOPSIS method, and the indicator weights and operating benefits are input into the comprehensive benefit evaluation model to obtain the benefit evaluation score of the variable speed pumped storage power station transformation, including the following steps: The operation benefit is converted into a matrix form to obtain an operation benefit matrix, the operation benefit matrix is ​​forward processed to obtain a forward matrix; the forward matrix is ​​normalized to obtain a normalized matrix; Based on the order of each level in the comprehensive benefit evaluation index system, the index weights are comprehensively calculated to obtain the comprehensive weights, the comprehensive weights are converted into a matrix form to obtain a comprehensive weight matrix, and the comprehensive weight matrix is ​​multiplied with the standardized matrix to obtain a weighted evaluation matrix; The benefit evaluation score of the variable speed pumped storage power station is obtained based on the distance between each unit in the weighted evaluation matrix and the set positive standard value and negative standard value.

[0020] In this scheme, an operation benefit matrix is ​​constructed based on actual operation data, and after positive and standardized processing, the influence of different dimensions and indicator directions (positive or negative) is eliminated, so that each indicator is comparable in the evaluation. The indicator weight is calculated by the entropy weight method, which avoids the bias of subjective assignment and improves the objectivity of the evaluation. Due to the use of intuitive matrix form and distance calculation, the evaluation process and results are easy to understand, and the contribution of each indicator to the evaluation results and the differences between different power stations can be clearly seen. The final benefit evaluation score is obtained by calculating the distance between each unit in the weighted evaluation matrix and the set positive standard value and negative standard value. The higher the benefit evaluation score, the more reasonable the transformation of the variable speed pumped storage power station is.

[0021] As a preferred method, based on the order of each level in the comprehensive benefit evaluation index system, the index weights are comprehensively calculated to obtain the comprehensive weights, including the following steps: The indicator weight corresponding to the criterion layer in the comprehensive benefit evaluation index system is multiplied by the indicator weight corresponding to the scheme layer to obtain the intermediate weight of each indicator in the scheme layer; the intermediate weight is used as the comprehensive weight.

[0022] In this scheme, the comprehensive weight is obtained by comprehensively analyzing the indicator weights corresponding to the two levels in the comprehensive benefit evaluation index system, which fully considers the relationship between the indicators at the two levels, thereby improving the reliability of the benefit evaluation score.

[0023] Preferably, the order of the levels in the comprehensive benefit evaluation index system from top to bottom is target level, criterion level and program level.

[0024] In this scheme, in the comprehensive benefit evaluation index system, low-level indicators will affect high-level indicators, and high-level indicators are the calculation targets of low-level indicators, which link each individual indicator and improve the correlation between the indicators.

[0025] Beneficial effects of the present invention: The present invention analyzes the feasibility of the transformation of variable speed pumped storage units in combination with economic benefits, social benefits and environmental benefits, and establishes a comprehensive benefit evaluation index system for the three, and the proposed index system is more comprehensive; then the weight acquisition method of AHP is improved, and combined with TOPSIS to score the variable speed pumped storage transformation project, which reduces the subjectivity of the evaluation method while also improving the accuracy and reliability of the evaluation results, and can also provide standards and methods for measuring the effectiveness of the transformation of variable speed pumped storage units.

[0026] The above invention content is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings. The drawings are only for the purpose of illustrating preferred embodiments and are not to be considered as limiting the present invention. Also, the same reference symbols are used throughout the drawings to represent the same parts.

[0028] Figure 1 This is a flow chart of a variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS of the present invention; Figure 2 It is a schematic diagram of the comprehensive benefit evaluation index system of the present invention. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation method described herein is only an optimal embodiment of the present invention, which is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flow charts. Although the flow charts describe the operations (or steps) as sequential processes, many of the operations (or steps) therein can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but can also have additional steps not included in the drawings; the process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0031] Example: Figure 1 As shown, in order to solve the problem that it is difficult to take social benefits and environmental benefits into consideration when evaluating the benefits of variable-speed pumped storage power stations, resulting in large benefits limitations and low reliability, this embodiment provides a variable-speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS, including the following steps: S1: Collect configuration parameters and operating parameters of variable speed pumped storage power station based on data acquisition principles.

[0032] S2: Benefit accounting principles The operating benefits of the variable speed pumped storage power station transformation are obtained in response to the configuration parameters and operating parameters, and a comprehensive benefit evaluation index system is constructed based on the operating benefits.

[0033] In this embodiment, the benefit accounting principle obtains the operating benefit of the variable speed pumped storage power station transformation in response to the configuration parameters and the operating parameters, including the following steps: The economic benefits of the variable speed pumped storage power station transformation are obtained based on the investment cost, operating cost and unit capacity of various equipment in the variable speed pumped storage power station transformation; the social benefits of the variable speed pumped storage power station transformation are obtained based on the influence of the variable speed pumped storage power station on energy dispatch; the environmental benefits of the variable speed pumped storage power station transformation are obtained based on the utilization degree of clean energy by the variable speed pumped storage power station; the economic benefits, social benefits and environmental benefits are taken as the operating benefits of the variable speed pumped storage power station transformation.

[0034] This embodiment incorporates environmental benefits into the evaluation system and emphasizes the degree of utilization of clean energy by variable speed pumped storage power stations, which helps to promote the sustainable development of power stations. By improving the utilization rate of clean energy, it can reduce dependence on fossil energy and reduce greenhouse gas emissions, thereby protecting the environment and responding to climate change. The impact of variable speed pumped storage power stations on energy scheduling is taken into account through the evaluation of social benefits, which helps to enhance the social recognition of power stations. When the power station can provide stable power supply, improve grid reliability and promote local economic development, its social image will be more positive, which will help to win the support of the masses. By comprehensively considering economic benefits, social benefits and environmental benefits, the overall value of the transformation of variable speed pumped storage power stations can be comprehensively evaluated, and a comprehensive evaluation can help decision makers understand the overall performance of the power station more accurately, thereby making more informed decisions.

[0035] In this embodiment, the economic benefits include investment cost, operating cost, net present value, internal rate of return, payback period and total investment rate of return; the social benefits include frequency regulation benefit, phase regulation benefit, black start benefit and employment benefit; the environmental benefits include new energy consumption rate, emission reduction benefit and water resource utilization coefficient.

[0036] The investment cost of this embodiment includes construction cost, equipment purchase cost, installation cost, commissioning cost and possible indirect cost, and the formula is as follows: C invest =C B +C D +C S +C M In the formula, C B is the construction cost, including civil engineering, hydraulic engineering, mechanical and electrical engineering, etc., RMB 10,000; C D is the equipment purchase cost, mainly refers to the purchase cost of variable speed pumped storage units and their supporting equipment, RMB 10,000; C S The installation and commissioning cost includes the cost of equipment installation, commissioning, trial operation, etc., RMB 10,000; C M Indirect costs include management fees, financial costs (such as loan interest), taxes, design fees, supervision fees, insurance costs and other unforeseen expenses that may arise, totaling RMB 10,000.

[0037] The operating cost includes various expenses required for the operation of the units in the variable speed pumped storage power station transformation within one year. The formula is as follows: C year =C E +C R +C P +C O In the formula, C E is the energy consumption cost, 10,000 yuan; C Ris the maintenance cost, 10,000 yuan; C P is personnel cost, 10,000 yuan; C O For other operating costs, RMB 10,000.

[0038] More specifically, energy cost is the electricity or fuel cost consumed by the unit during operation. For variable speed pumped storage power stations, the main energy consumption comes from the pumping process and the hydropower generation process, but usually more attention is paid to the energy consumption of the pumping process (because the power generation process generates income). The energy cost can be calculated based on the unit's operating efficiency, annual pumping hours and electricity price. The formula is as follows: In the formula, Q v is the annual water pumping volume, m 3 ; Unit pumping energy consumption, kWh / m 3 ; C i is the electricity price, Yuan / kWh.

[0039] More specifically, based on the unit power and pumping time: C E =P i ×m×C i Where P i is the unit power, kW; m is the annual pumping hours.

[0040] More specifically, maintenance costs are the expenses required to keep the unit in good operating condition, including regular maintenance, troubleshooting, parts replacement, etc. Maintenance costs can be estimated based on historical data, equipment aging, maintenance plans, etc., and can usually be expressed as the sum of fixed costs and variable costs that are proportional to the unit's operating time or power generation: In the formula, C inv is the fixed maintenance cost, ten thousand yuan; is the maintenance cost per unit time, ten thousand yuan; h is the annual operating hours.

[0041] If it is estimated based on power generation, then: In the formula, is the maintenance cost per unit power generation, ten thousand yuan; W is the annual power generation, kWh.

[0042] More specifically, personnel costs are the salaries and related benefits paid to employees responsible for the operation, maintenance and management of the unit. This can be calculated based on factors such as the number of employees, average salary level and benefit expenditures: C P =(r×p)×(1+η w ) In the formula, r is the number of employees; p is the average salary; η w The welfare rate.

[0043] More specifically, other operating costs may include administrative expenses, insurance costs, taxes (non-energy consumption taxes), rental costs, etc. These costs are usually estimated based on actual incurred situations and added to the three main costs mentioned above.

[0044] The net present value is the present value difference between the cash inflow and expenditure expected to be achieved by the project. The larger the difference, the better the plan. The formula is as follows: In the formula, FNPV is the financial net present value, ten thousand yuan; i c is the benchmark rate of return for power industry projects; t is the number of years t = 1, 2, …, n; n is the calculation period; CI is the actual cash inflow or recalculated cash inflow during the calculation period, RMB 10,000; CO is the actual cash outflow or recalculated cash outflow during the calculation period, RMB 10,000.

[0045] The internal rate of return is the discount rate when the net present value is zero during the entire calculation period. When the internal rate of return is greater than or equal to the benchmark rate, it means that the plan is feasible. The formula is as follows: Where FIRR is the financial internal rate of return.

[0046] The payback period is the number of years required to recover the total investment through capital return after the project is put into production. t ) and the industry's benchmark payback period (P c ) compared to P t <P c When , it indicates that the daily investment can be recovered within the specified time. The formula is as follows: P t =[P k -1]+(I k-1 / I k ) Where P k The number of years in which the cumulative net cash flow appears positive; I k-1 is the absolute value of the cumulative net cash flow in the previous year; k The net cash flow for the year.

[0047] The total investment rate of return is the ratio of the average annual total profit of the project during the production and operation period to the total funds during the construction period (the sum of fixed asset investment and all working capital). If the investment profit rate is greater than or equal to the standard investment profit rate or the average investment profit rate, it indicates that the transformation is feasible.

[0048] The social benefits are mainly reflected in the income generated by replacing phase-modulation and frequency-modulation units with variable-speed pumped storage units of a certain capacity. The frequency-modulation benefits mainly include the fuel costs of starting and stopping thermal power units or low-load frequency modulation, the energy loss of frequent start-stop frequency modulation of hydropower, and the economic losses caused by the lag in thermal power adjustment speed. The calculation formula is as follows: In the formula, F f is the frequency regulation benefit of the variable speed pumped storage power station; b2 is the fuel consumption rate of the gas turbine startup or the coal consumption rate of the thermal power unit from the minimum technical output to full load, g / kW; n2 is the number of daily startups or load increases, times; b is the standard coal consumption of the unit during power generation, g / kWh; T is the total operating hours of a unit with unplanned load in a period of time, h; N0 is the capacity of a unit, 10,000 kW; m T is the number of corresponding units, units; f is the coal price, yuan / t; V is the no-load water consumption of the turbine startup, m3 / S; H is the average water head of the hydropower station; η is the efficiency of the turbine generator set; n H is the number of turbine starts during this period, times; m H is the number of corresponding turbines, units; f1 is the electricity price, yuan / kWh; R is the increase in maintenance costs during this period under the frequency regulation of thermal power units.

[0049] More specifically, the phase adjustment benefit refers to the variable speed pumped storage unit providing reactive power regulation for the power grid under the conditions of power generation, pumping and phase adjustment. According to the idea of ​​equivalent substitution, a variable speed pumped storage unit of a certain capacity is used to replace a phase adjustment unit of the corresponding capacity. The reduced fixed asset investment can actually reflect the benefits brought by the phase adjustment of the variable speed pumped storage unit. The formula is as follows: F x =K·A P (e,a)+C0 In the formula, F x is the phase modulation benefit; K is the reduced phase modulation equipment investment; A P (e, a) is the capital recovery factor, where a is the useful life of the unit equipment and e is the annual interest rate; C0 is the reduced annual cost of the phase-shifting unit.

[0050] More specifically, the black start benefit comes from the variable speed pumped storage unit. Compared with thermal power and nuclear power units, the turbine generator has a simple structure, no complex auxiliary system, less plant power consumption, and fast startup speed, so it is an ideal and convenient black start power source. In order to achieve the black start function, the variable speed pumped storage unit needs to compensate for the following main costs: the minimum power compensation cost required for the self-start of the generator, the minimum power compensation cost required for the operation of basic plant equipment, black start electricity billing, black start annual test cost (or experimental cost), black start unit annual maintenance cost, social and economic loss recovery reward, dynamic reward, and the calculation process is as follows: Minimum power compensation cost F required for a single generator min : P min =U min ×I min Where P min The minimum power required for a single machine to start; U min The minimum voltage required for single machine braking; I min It is the minimum current required for single machine braking.

[0051] The calculation formula for the minimum power compensation cost required for a single machine is as follows: F min =μ×P min Where μ is the unit power compensation price.

[0052] Minimum power compensation cost F0 required for the operation of basic plant equipment: P0=∑S0 F0=μ×P0 Where P0 is the minimum power required for the operation of basic plant equipment; S0 is the minimum power required for the operation of a single basic equipment.

[0053] Black start electricity billing F b : The variable speed pumped storage power station is used as a black start unit. From the time when the target substations or loads and units without self-starting function are connected to the grid or when the entire network resumes stable operation, the power it provides is considered black start power.

[0054] Fb=∫0t 1 P(t)μ(t)dt In the formula, t1 is the time taken for the system to recover; P(t) is the amount of electricity provided by the variable speed pumped storage power station at each moment during the system recovery period; μ(t) is the unit price of the electricity provided by the variable speed pumped storage power station at each moment during the system recovery period. The unit price of black start electricity during the system recovery period should not be regarded as ordinary electricity, so its pricing should also reflect the value it embodies. In theory, μ(t) should be a decreasing function as the number of grid-connected units gradually increases. When the system is fully restored at time t0, μ(t) returns to the peak load grid-connected electricity price.

[0055] Black start annual test cost (or experimental cost) F t : In order to ensure that the unit can respond promptly and quickly when the system fails, the selected black start power supply must undergo black start testing at regular intervals. The testing process will inevitably lead to a reduction in the daily online power generation of the black start power supply, and will also generate additional management costs and energy consumption. All losses incurred at that time should be reasonably compensated.

[0056] Annual maintenance cost of black start unit F k Reward for recovering social and economic losses s : As a black start power source, variable speed pumped storage units have a significant advantage of shorter start-up time compared with conventional thermal power units. Therefore, they will greatly reduce the economic losses caused by power grid failure to the whole society.

[0057] F s =M s ×α Where M s is the total socio-economic recovery; α is the reward percentage.

[0058] Dynamic RewardsF e : For the crew that undertakes the black start mission, the system often stipulates that it will be rewarded a certain amount after it successfully completes the black start mission. In order to make this reward more motivating, the system can adjust the reward according to the response time of the crew in completing the black start mission.

[0059] Where M e is the agreed reward value, t0 is the actual time of the unit connected to the grid during the black start process, and t t It is the minimum time value of the unit’s grid-connected power generation during all previous experiments.

[0060] In summary, when the variable speed pumped storage unit serves as the black start power source, its black start benefit amount F h Should be: F h =F min+F0+F b +F t +F k +F s +F e .

[0061] More specifically, it also includes employment benefits. After the hydropower transformation project is completed, additional management personnel and workers will be needed during the management and operation period. Therefore, the transformation of the power station creates a certain employment effect. The direct employment effect D is used to represent the employment benefit, and the formula is as follows: Where d is the number of direct jobs provided by the project (persons).

[0062] Environmental benefits are mainly reflected in the benefits generated by improving resource utilization, specifically, including the new energy consumption rate, and the formula is as follows: In the formula, E grid E is the actual amount of clean energy connected to the grid during the statistical period; gen It is the actual power generation of renewable energy.

[0063] More specifically, it also includes emission reduction benefits. Variable-speed pumped storage units reduce dependence on traditional fossil energy through efficient energy storage and power generation processes, thereby reducing emissions of greenhouse gases such as carbon dioxide. In addition, compared with fossil energy power generation methods such as coal-fired power plants, variable-speed pumped storage power stations do not produce harmful gases such as sulfur dioxide and nitrogen oxides during operation, which significantly reduces the emissions of these pollutants and helps improve air quality. At present, the emission reductions of new energy systems such as pumped storage wind and light are calculated by replacing coal-fired power with an equal amount, and then using the pollutant emission factor of coal. Reducing coal use reduces pollutant emissions, and monetizing the emission reductions to quantify the emission reduction benefits. The formula is as follows: In the formula, F t is the emission reduction benefit, 10,000 yuan; m is the type of pollutant, P t For the electricity from pumpable storage units replacing coal-fired power, A j is the emission of pollutant type j, B j The cost of treating pollutant type j is shown in Table 1, taking the main pollutants emitted by burning 1 t of coal and their treatment costs as an example: Table 1. Major pollutants emitted by burning 1 ton of coal and their treatment costs Pollutants Emission A / kg <![CDATA[Governance cost B / yuan·kg -1 > CO2 1731.00 0.13 CO 0.26 1.00 SO2 1.25 6.00 NOX 8.00 8.00 TSP (Total Suspended Particulate Matter) 0.41 2.20 Ash 110.00 0.12 Slag 30.00 0.10 More specifically, it also includes the water resource utilization coefficient, and the formula is as follows: Where, E is the water resource utilization coefficient; e before is the water resource utilization rate before transformation; e after It is the water resource utilization rate after transformation.

[0064] In this embodiment, a comprehensive benefit evaluation index system is constructed based on the operation benefit, including the following steps: Will be like Figure 2 As shown, economic benefits, social benefits and environmental benefits are taken as the primary indicators, and investment cost, operating cost, net present value, internal rate of return, investment payback period, total investment rate of return, frequency regulation benefit, phase regulation benefit, black start benefit, employment benefit, new energy consumption rate, emission reduction benefit and water resource utilization coefficient are taken as secondary indicators to obtain a comprehensive benefit evaluation index system.

[0065] This embodiment ensures the comprehensiveness and accuracy of the evaluation by considering the benefits from three main aspects: economy, society and environment. By refining the secondary indicators, it can more specifically reflect the performance of the project in various aspects, avoid one-sided evaluation, and thus improve the reliability of the subsequent benefit evaluation scores. By further refining the analysis of the three main aspects of economy, society and environment, the number of considered factors is increased, thereby making the comprehensive benefit evaluation of the transformation of the variable speed pumped storage power station more comprehensive, thereby reducing the probability of the problem that the final result is too greatly affected by the large proportion of certain indicators, thereby affecting the effectiveness of the results.

[0066] S3: Based on the improved hierarchical analysis method, the various indicators in the comprehensive benefit evaluation index system are stratified, and the indicators at the same level are compared to obtain the indicator weights.

[0067] In this embodiment, the various indicators in the comprehensive benefit evaluation index system are layered based on the improved analytic hierarchy process, including the following steps: The indicators in the secondary indicators are divided into the scheme level, and the indicators in the primary indicators are divided into the criterion level; The comprehensive benefit index of the variable speed pumped storage power station transformation is obtained by comprehensive analysis of economic benefits, social benefits and environmental benefits, and the comprehensive benefit index is taken as the target layer.

[0068] This embodiment forms a clear evaluation framework by dividing the indicators into the program layer, the criterion layer and the target layer, making the evaluation process more intuitive and easy to understand, and the hierarchical structure helps to better manage and organize information during the evaluation process to ensure the accuracy and efficiency of the evaluation; by incorporating various indicators into a unified evaluation framework, comparison between different projects or programs becomes possible, providing strong support for decision-making, and the target layer (comprehensive benefit index) as the final result of the evaluation provides decision makers with an intuitive and quantitative basis, which helps to make more scientific and reasonable decisions.

[0069] In this embodiment, comparing the indicators at the same level to obtain the indicator weights includes the following steps: Based on the importance of each indicator, the improved proportional scaling method is used to assign values ​​to each indicator at each level to obtain corresponding indicator values. The improved proportional scaling method is shown in Table 2: Table 2. Improved ratio scaling method 1~4 scale meaning 1 / 4 Compared with the two indicators, indicator b is more important than indicator a. 1 / 3 Compared with the two indicators, indicator b is more important than indicator a. 1 / 2 Compared with the two indicators, indicator b is slightly more important than indicator a. 1 Compared with the two indicators, indicators a and b are equally important. 2 Compared with the two indicators, indicator a is slightly more important than indicator b. 3 Compared with the two indicators, indicator a is more important than indicator b. 4 Compared with the two indicators, indicator a is more important than indicator b. Then, the indicator values ​​corresponding to the indicators of each layer are compared pairwise to obtain the proportion of each indicator, and the judgment matrix corresponding to each layer is constructed based on the proportion of each indicator; The judgment matrix is ​​checked for consistency. If the consistency is passed, the m-th power of the product of each row of the judgment matrix is ​​calculated to obtain an m-dimensional vector. The formula is as follows: Where m is the order of the judgment matrix, a ij is the object in the i-th row and j-th column of the judgment matrix.

[0070] Then standardize the m-dimensional vector to obtain the weights of each indicator in each level. The formula is as follows: Among them, w i is the weight of each indicator in each level.

[0071] This embodiment constructs a judgment matrix through the hierarchical analysis method, converts qualitative analysis into quantitative analysis, and makes the decision-making process more scientific and objective. The subjective judgment and experience accumulation of the decision maker can be converted into specific numerical values ​​by calculating the indicator weights according to the judgment matrix, thereby reducing the influence of subjective factors on the decision results; and by calculating the indicator weights, it can be ensured that each factor is properly considered in the decision-making process, avoiding decision-making errors caused by personal preferences or prejudices; by decomposing complex problems into multiple levels and factors, the decision-making process can be further simplified, thereby improving the efficiency of obtaining benefit evaluation scores; by calculating the indicator weights, the relative importance of each factor can be reflected, providing decision makers with a more accurate decision-making basis, which helps decision makers to select the best solution when faced with multiple options.

[0072] In this embodiment, the consistency check of the judgment matrix includes the following steps: The maximum eigenvalue of the judgment matrix is ​​calculated and recorded as λ max , based on the maximum eigenvalue and order of the judgment matrix, the consistency index value is obtained, and the formula is as follows: Where n is the order of the matrix. The closer CI is to 0, the more satisfactory the consistency is. When CI = 0, it has complete consistency. The larger the CI is, the more serious the inconsistency of the judgment matrix is.

[0073] In order to balance the size of CI, a random consistency index is introduced, denoted as RI. Based on the order of the judgment matrix, the corresponding random consistency index value is found from the set random consistency index table. The formula is as follows: The random consistency index is related to the order n of the judgment matrix, and the corresponding relationship is shown in Table 3 below: Table 3. Standard values ​​of random consistency index RI n 1 2 3 4 5 6 7 8 9 10 RI 0 0 0.85 0.90 1.12 1.24 1.32 1.41 1.45 1.49 The consistency index value is compared with the random consistency index value to obtain the consistency ratio. If the consistency ratio is less than the set threshold, the judgment matrix is ​​consistent. The formula is as follows: If CR<0.1, the judgment matrix passes the consistency test, otherwise it does not have satisfactory consistency and the weights need to be redetermined.

[0074] This embodiment can ensure that the element relationship in the judgment matrix is ​​logically consistent by performing a consistency check on the judgment matrix, that is, if A is more important than B, and B is more important than C, then A should be more important than C, thereby avoiding logical contradictions that may occur in the decision-making process; and through the consistency check, those logically unreasonable judgments can be screened out, thereby improving the credibility and scientificity of the decision.

[0075] S4: A comprehensive benefit evaluation model is constructed based on the TOPSIS method, and the indicator weights and operating benefits are input into the comprehensive benefit evaluation model to obtain the benefit evaluation score of the variable speed pumped storage power station transformation.

[0076] In this embodiment, a comprehensive benefit evaluation model is constructed based on the TOPSIS method, and the indicator weights and operating benefits are input into the comprehensive benefit evaluation model to obtain the benefit evaluation score of the variable speed pumped storage power station transformation, including the following steps: The operating benefit is converted into a matrix form to obtain the operating benefit matrix M, and the operating benefit matrix M is forward processed to obtain the forward matrix X, which is expressed as follows: The normalized matrix X is normalized to obtain the normalized matrix Y, which is expressed as follows: In the formula, x ij is the value of the jth evaluation factor of the i-th evaluation unit after positive processing; y ij is the value in the i-th row and j-th column of matrix Y.

[0077] Based on the order of each level in the comprehensive benefit evaluation index system, the index weights are comprehensively calculated to obtain the comprehensive weights, and the comprehensive weights are converted into a matrix form to obtain a comprehensive weight matrix. The comprehensive weight matrix is ​​multiplied by the standardized matrix to obtain a weighted evaluation matrix. The formula is as follows: Z=αY Where α is the comprehensive weight matrix calculated by the AHP method.

[0078] Based on the distance between each unit in the weighted evaluation matrix and the set positive standard value and negative standard value, the benefit evaluation score of the variable speed pumped storage power station transformation is obtained. The formula is as follows: In the formula, is the Euclidean distance between the evaluation object and the positive standard value; is the Euclidean distance between the evaluation object and the negative standard value.

[0079] In the formula, S i is the benefit evaluation score of the ith evaluation object, and its value is [0,1]. The higher the final score, the more reasonable the variable speed pumped storage transformation is.

[0080] This embodiment constructs an operation benefit matrix based on actual operation data, and after positive and standardized processing, eliminates the influence of different dimensions and indicator directions (positive or negative), so that each indicator is comparable in the evaluation, and then calculates the indicator weight by the entropy weight method, avoiding the deviation of subjective assignment and improving the objectivity of the evaluation; due to the use of intuitive matrix form and distance calculation, the evaluation process and results are easy to understand, and the contribution of each indicator to the evaluation results and the differences between different power stations can be clearly seen; the final benefit evaluation score is obtained by calculating the distance between each unit in the weighted evaluation matrix and the set positive standard value and negative standard value, wherein the higher the benefit evaluation score, the higher the rationality of the transformation of the variable speed pumped storage power station.

[0081] In this embodiment, based on the order of each level in the comprehensive benefit evaluation index system, the index weights are comprehensively calculated to obtain the comprehensive weights, including the following steps: The indicator weight corresponding to the criterion layer in the comprehensive benefit evaluation index system is multiplied by the indicator weight corresponding to the scheme layer to obtain the intermediate weight of each indicator in the scheme layer; the intermediate weight is used as the comprehensive weight.

[0082] This embodiment obtains a comprehensive weight by comprehensively analyzing the indicator weights corresponding to the two levels in the comprehensive benefit evaluation indicator system, and fully considers the relationship between the indicators at the two levels, thereby improving the reliability of the benefit evaluation score.

[0083] In this embodiment, the order of the levels in the comprehensive benefit evaluation index system from top to bottom is the target level, the criterion level and the solution level.

[0084] In the comprehensive benefit evaluation index system of this embodiment, low-level indicators will affect high-level indicators, and high-level indicators are the calculation targets of low-level indicators. Each individual indicator is linked together to improve the degree of correlation between the indicators.

[0085] This embodiment not only considers the direct economic benefits of the variable speed pumped storage power station (such as power generation income, fuel cost savings, etc.) through the principle of benefit accounting, but also may include environmental benefits (such as reducing greenhouse gas emissions) and social benefits (such as improving grid stability, promoting local economic development, etc.), which helps to build a comprehensive and multi-dimensional comprehensive benefit evaluation index system to more accurately reflect the overall value of the power station; the various indicators in the comprehensive benefit evaluation index system are layered and weighted by adopting the improved analytic hierarchy process. This method can systematically deal with complex problems, and by comparing the importance of indicators at the same level, relatively objective weights are obtained to ensure the accuracy and fairness of the evaluation results; by constructing a comprehensive benefit evaluation model, after inputting the indicator weights and operating benefits into the model, the benefit evaluation score of the variable speed pumped storage power station can be quantitatively calculated, which not only provides a clear evaluation of the current operating status of the power station, but also provides a basis for future continuous improvement and optimization. Through regular evaluation, potential problems can be discovered and solved in a timely manner, promoting the continuous improvement of power station benefits.

[0086] As a further supplement to this embodiment, the following scenario is taken as an example to further illustrate this solution: based on the specific parameters of the transformation of the three variable speed pumped storage power stations in region X, region Y, and region Z, the comprehensive benefits of the transformation of the three variable speed pumped storage power stations in region X, region Y, and region Z are scored by the improved AHP-TOPSIS method, so as to judge the rationality of the variable speed pumped storage transformation plan. The specific process is as follows: Step 1: Construct the judgment matrix of each indicator, determine the single-level weight, and perform consistency test: According to the comprehensive benefit evaluation index system, the first-level indicators are economic benefit A1, social benefit A2, and environmental benefit A3. The judgment matrix and single-level weights are shown in Table 4. CR = 0.0088 < 1, passing the consistency test. Table 4. First-level indicator judgment matrix and single-level weights According to the above method, the judgment matrix of economic benefit A1, social benefit A2 and environmental benefit A3 is constructed internally to obtain the weight of each level and conduct consistency test. All levels pass the consistency test. The specific judgment matrix and weight of each level are shown in Tables 5 to 7 below: Table 5. (Economic Benefit A1) Index Judgment Matrix and Single-Level Weights Table 6. (Social Benefit A2) Index Judgment Matrix and Single-Level Weights Table 7. (Environmental benefit A3) indicator judgment matrix and single-level weights Step 2: Obtain the comprehensive weight through the total ranking of the levels in the comprehensive benefit evaluation index system: The weight of the last layer of indicators is equal to the weight ratio of the layer where the indicator is located multiplied by the weights of the previous layer. The weights of various benefit evaluation indicators of the variable speed pumped storage renovation project are summarized as shown in Table 8 below: Table 8. Summary of weights of benefit evaluation indicators for variable speed pumped storage renovation projects According to the comprehensive weights of each indicator in Table 8, the comprehensive weight matrix α can be obtained as follows: α=[0.05780.05780.10510.17950.10510.03430.03900.03900.07090.01450.16030.08820.0485] Step 3: Obtain comprehensive benefit evaluation results: The benefits of the transformation of variable speed pumped storage power stations in regions X, Y and Z are calculated according to the formula, as shown in Table 9: Table 9. Summary of benefits of transformation of variable speed pumped storage power stations in regions X, Y and Z The benefits of the transformation of the variable speed pumped storage power stations in regions X, Y and Z in Table 9 are written in matrix form, and the operating benefit matrix M is: The operation benefit matrix M is processed forward, and all indicator types are uniformly converted into extremely large indicators to obtain the forward matrix X: Then normalize the forward matrix X to get the normalized matrix Y: Introducing the indicator weight matrix α, we get the weighted evaluation matrix Z: Calculate the benefit assessment score: According to the formula, the final scores of the various benefit evaluations of the three variable speed pumped storage power station renovations in Region X, Region Y, and Region Z are calculated as shown in Table 10: Table 10. Benefit evaluation scores of variable speed pumped storage power stations in regions X, Y and Z Variable speed pumped storage power station Region X Area Y Region Z Benefit evaluation score 0.5868 0.4709 0.2938 It can be seen that the variable speed pumped storage power station transformation in area X has the highest comprehensive benefit score, followed by area Y and finally area Z, that is, the variable speed pumped storage power station transformation in area X is the most reasonable.

[0087] It can be seen from the above embodiments that at least the following substantial effects are achieved: The feasibility of the transformation of variable speed pumped storage units is analyzed by combining economic benefits, social benefits and environmental benefits, and a comprehensive benefit evaluation index system of the three is established. The proposed index system is more comprehensive. Then, the weight acquisition method of AHP is improved, and the variable speed pumped storage transformation project is scored in combination with TOPSIS. While reducing the subjectivity of the evaluation method, the accuracy and reliability of the evaluation results are also improved, and standards and methods can be provided for measuring the effectiveness of the transformation of variable speed pumped storage units.

[0088] The specific implementation described above is a preferred implementation of the variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS of the present invention, and is not intended to limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to this specific implementation. All equivalent changes made in accordance with the shape and structure of the present invention are within the protection scope of the present invention.

Claims

1. A variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS, characterized by: The following steps are involved: S1. Collect configuration parameters and operation parameters of variable speed pumped storage power station based on data collection principles; S2. Benefit accounting principle: The operation benefit of the variable speed pumped storage power station transformation is obtained in response to the configuration parameters and operation parameters, and a comprehensive benefit evaluation index system is constructed based on the operation benefit; S3. Based on the improved analytic hierarchy process, the various indicators in the comprehensive benefit evaluation index system are layered, and the indicators at the same level are compared to obtain the indicator weights; S4. Based on the TOPSIS method, a comprehensive benefit evaluation model is constructed, and the indicator weights and operating benefits are input into the comprehensive benefit evaluation model to obtain the benefit evaluation score of the variable speed pumped storage power station transformation.

2. The variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS according to claim 1 is characterized by: In S2, the benefit accounting principle obtains the operating benefit of the variable speed pumped storage power station in response to the configuration parameters and the operating parameters, including the following steps: The economic benefits of the variable speed pumped storage power station transformation are obtained based on the investment cost, operating cost and unit capacity of each equipment in the variable speed pumped storage power station transformation; the social benefits of the variable speed pumped storage power station transformation are obtained based on the influence of the variable speed pumped storage power station on energy dispatch; the environmental benefits of the variable speed pumped storage power station transformation are obtained based on the utilization degree of clean energy by the variable speed pumped storage power station; Economic benefits, social benefits and environmental benefits are taken as the operating benefits of the variable speed pumped storage power station transformation.

3. The variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS according to claim 2 is characterized by: The economic benefits include investment cost, operating cost, net present value, internal rate of return, payback period and total investment rate of return; the social benefits include frequency regulation benefit, phase regulation benefit, black start benefit and employment benefit; the environmental benefits include new energy consumption rate, emission reduction benefit and water resource utilization coefficient.

4. The variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS according to claim 3 is characterized by: In S2, a comprehensive benefit evaluation index system is constructed based on the operational benefits, including the following steps: Taking economic benefits, social benefits and environmental benefits as the primary indicators, and investment cost, operating cost, net present value, internal rate of return, payback period, total investment rate of return, frequency regulation benefit, phase regulation benefit, black start benefit, employment benefit, new energy consumption rate, emission reduction benefit and water resource utilization coefficient as the secondary indicators, a comprehensive benefit evaluation index system is obtained.

5. The variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS according to claim 4 is characterized by: In S3, the various indicators in the comprehensive benefit evaluation index system are layered based on the improved hierarchical analysis method, including the following steps: The indicators in the secondary indicators are divided into the scheme level, and the indicators in the primary indicators are divided into the criterion level; The comprehensive benefit index of the variable speed pumped storage power station transformation is obtained by comprehensive analysis of economic benefits, social benefits and environmental benefits, and the comprehensive benefit index is taken as the target layer.

6. The variable speed pumped storage power station transformation benefit evaluation method based on improved AHP-TOPSIS according to claim 1 is characterized by: In S3, the indicators at the same level are compared to obtain the indicator weights, including the following steps: Based on the importance of each indicator, the improved proportional scaling method is used to assign corresponding indicator values ​​to each indicator at each level, and then the indicator values ​​corresponding to each level are compared pairwise to obtain the proportion of each indicator. Based on the proportion of each indicator, the judgment matrix corresponding to each level is constructed; The judgment matrix is ​​checked for consistency. If the consistency is passed, the m-th power of the product of each row of the judgment matrix is ​​calculated to obtain an m-dimensional vector, where m is the order of the judgment matrix. The m-dimensional vector is then standardized to obtain the weights of each indicator at each level.

7. The variable speed pumped storage power station reconstruction benefit evaluation method based on improved AHP-TOPSIS according to claim 6 is characterized by: The consistency check of the judgment matrix includes the following steps: Calculate the maximum eigenvalue of the judgment matrix, and obtain the consistency index value based on the maximum eigenvalue and order of the judgment matrix; Based on the order of the judgment matrix, the corresponding random consistency index value is searched from the set random consistency index table; The consistency index value is compared with the random consistency index value to obtain the consistency ratio. If the consistency ratio is less than the set threshold, the matrix is ​​judged to be consistent.

8. The variable speed pumped storage power station reconstruction benefit evaluation method based on improved AHP-TOPSIS according to claim 1 is characterized by: In S4, a comprehensive benefit evaluation model is constructed based on the TOPSIS method, and the indicator weights and operating benefits are input into the comprehensive benefit evaluation model to obtain the benefit evaluation score of the variable speed pumped storage power station transformation, including the following steps: The operation benefit is converted into a matrix form to obtain an operation benefit matrix, the operation benefit matrix is ​​forward processed to obtain a forward matrix; the forward matrix is ​​normalized to obtain a normalized matrix; Based on the order of each level in the comprehensive benefit evaluation index system, the index weights are comprehensively calculated to obtain the comprehensive weights, the comprehensive weights are converted into a matrix form to obtain a comprehensive weight matrix, and the comprehensive weight matrix is ​​multiplied with the standardized matrix to obtain a weighted evaluation matrix; The benefit evaluation score of the variable speed pumped storage power station transformation is obtained based on the distance between each unit in the weighted evaluation matrix and the set positive standard value and negative standard value.

9. The variable speed pumped storage power station reconstruction benefit evaluation method based on improved AHP-TOPSIS according to claim 7 is characterized by: Based on the order of each level in the comprehensive benefit evaluation index system, the index weights are calculated comprehensively to obtain the comprehensive weights, including the following steps: The indicator weight corresponding to the criterion layer in the comprehensive benefit evaluation index system is multiplied by the indicator weight corresponding to the scheme layer to obtain the intermediate weight of each indicator in the scheme layer; the intermediate weight is used as the comprehensive weight.

10. The variable speed pumped storage power station reconstruction benefit evaluation method based on improved AHP-TOPSIS according to claim 7 is characterized by: The order of the levels in the comprehensive benefit evaluation index system from top to bottom is the target level, the criterion level and the program level.

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