Power system power transmission network line planning method and system

Abstract

The invention relates to the technical field of electricity, and relates to a power system power transmission network line planning method and system. The method comprises the steps that all extensible power transmission lines in a power grid planning area are acquired, a multi-objective optimization model is constructed, and the multi-objective optimization model comprises an economical efficiency objective function, a reliability objective function, an environmental protection objective function and constraint conditions; solving the multi-objective optimization model by using a genetic algorithm to obtain an optimal extension scheme; the solving process comprises the steps of randomly generating an initial population, calculating a fitness value of each individual in the population, iteratively selecting, crossing and mutating the population, calculating a fitness value of each individual in a new population, and stopping iteration and outputting an optimal solution until the fitness values of the individuals in the population converge. By adopting the method provided by the invention, the expanded power transmission network can meet the performance requirements in the aspects of economy, reliability and environmental protection, and the comprehensive performance is relatively excellent.

Description

Technical Field

[0001] The present invention relates to the field of electrical technology, and more specifically, to a method and system for planning a power transmission network line. Background Art

[0002] The power grid consists of nodes (i.e., intersections of electricity demand, including substations, load centers, and power supply points) and lines. Lines are physical channels connecting nodes and are responsible for transmitting electricity from power supply nodes to load nodes. With the development of science and technology, people's electricity consumption in daily life and work continues to increase, resulting in an increase in the load of the power system network year by year. Therefore, it is necessary to expand the power system transmission network to deliver more electricity to users. Before expanding the power system transmission network, it is necessary to plan the power grid so that the transmission lines can be constructed according to the planning results.

[0003] Grid planning is a process of systematically designing and optimizing power generation, transmission, and distribution in the power system, aiming to meet future power demand in an economical, safe, reliable, and environmentally friendly way. Its core is to achieve a dynamic balance between power supply and demand through scientific analysis and prediction, coordinated resource allocation, technology selection, facility layout, and investment timing. The process of grid planning is usually as follows: first determine the nodes of the existing power grid, then preliminarily plan all expandable transmission lines based on the node locations, and select the better lines for expansion; the way to select transmission lines is to construct an objective function and solve the objective function to select the better lines, but because the constructed objective function is too single, the transmission lines to be expanded cannot take into account reliability, economy, and environmental protection.

[0004] In summary, the existing power system transmission network line planning method has the problem of not being able to take into account reliability, economy and environmental protection. Summary of the invention

[0005] In order to solve the problems that the existing power system transmission network line planning method has low efficiency and cannot take into account reliability, economy and environmental protection, the present invention provides solutions in the following aspects.

[0006] In a first aspect, the present invention provides a method for planning a power transmission network line in a power system, comprising: obtaining all expandable transmission lines in a power grid planning area, and constructing a multi-objective optimization model, wherein the multi-objective optimization model comprises: an economic objective function, a reliability objective function, an environmental objective function, and constraint conditions; and solving the multi-objective optimization model using a genetic algorithm to obtain an optimal expansion plan; the solution process comprises: randomly generating an initial population, wherein individuals in the population represent expansion plans, and the expansion plans are used to characterize whether each expandable transmission line is used as a transmission line to be expanded; Calculate the fitness value for each individual in the population. The calculation expression of the fitness value is as follows: ; In the formula, , and respectively represent the economic objective function, the reliability objective function, and the environmental protection objective function. , and are the weights of the economic objective function, the reliability objective function, and the environmental protection objective function respectively. represents the exponential function with base e, S represents the range corresponding to the economic objective function value, the reliability objective function value, and the environmental protection objective function value; represents the over-limit amount of the m-th constraint, represents the constraint violation penalty factor; Iteratively select, crossover, mutate the population, and calculate the fitness value of each individual in the new population until the fitness value of the individuals in the population converges, then stop the iteration and output the optimal solution.

[0007] The beneficial effects of the present invention are as follows: The method of the present invention solves the multi-objective optimization model including the economic objective function, the reliability objective function, and the environmental protection objective function, so that the expanded transmission network takes into account the performance requirements in terms of economy, reliability, and environmental protection, and has relatively excellent comprehensive performance; By using the genetic algorithm to solve the multi-objective optimization model, the global optimal solution can be quickly generated, improving the efficiency of transmission network planning.

[0008] Preferably, the calculation expression of the economic objective function is: ; In the formula, N represents the total number of transmission lines to be expanded, represents the unit length investment cost of the i-th transmission line to be expanded, and respectively represent the operation and maintenance cost and the power loss cost of the i-th transmission line to be expanded in the t-th year; T represents the planning period, r is the discount rate, represents the total building area of the target power supply area of the i-th transmission line to be expanded, and a represents the total area of the power grid planning area.

[0009] Its beneficial effect is that when calculating the economic objective function value, it comprehensively considers the investment cost, operation and maintenance cost, power loss cost of the transmission line to be expanded, and the influence of the ratio of the total building area of the target power supply area of the transmission line to be expanded to the total area of the power grid planning area on the power consumption load of the transmission line to be expanded, thereby improving the accuracy of the calculation result of the economic objective function.

[0010] Preferably, the calculation expression of the reliability objective function is: ; In the formula, represents the load loss caused by the failure of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , respectively represent the frequencies of rain, wind, and lightning strikes in the target power supply area of the i-th line to be expanded in the past year, represents the influence range of geological disasters, and a represents the total area of the power grid planning area.

[0011] Preferably, the calculation expression of the reliability objective function is: ; In the formula, represents the load loss caused by the failure of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , and respectively represent the frequencies of rain, wind, lightning strikes, and geological disasters in the target power supply area of the i-th line to be expanded in the past year, represents the influence range of geological disasters, and a represents the total area of the power grid planning area.

[0012] Preferably, the calculation expression of the reliability objective function is: ; In the formula, represents the load loss caused by the failure of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , and respectively represent the frequencies of rain, wind, lightning strikes, and geological disasters in the target power supply area of the i-th line to be expanded in the past year, represents the influence range of geological disasters, a represents the total area of the power grid planning area, represents the proportion of the special terrain area in the target power supply area of the i-th line to be expanded.

[0013] Preferably, the special terrain includes mountains, forests, canyons, and swamps.

[0014] Preferably, the calculation expression of the reliability objective function is: ; In the formula, respectively represent the load losses caused by the faults of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , and respectively represent the frequencies of rain, wind, lightning strikes, and geological disasters in the past year in the target power supply area of the i-th line to be expanded, represents the influence range of geological disasters, a represents the total area of the power grid planning area, represents the proportion of the special terrain area in the target power supply area of the i-th line to be expanded, represents the altitude change of the area through which the i-th line to be expanded passes.

[0015] Preferably, obtain the total number of ecological sensitive periods in the power grid planning area and set the avoidance priority weights for each ecological sensitive period, and then construct an environmental protection objective function, and its expression is: ; In the formula, represents the exponential function with e as the base, N represents the total number of transmission lines to be expanded, represents the total number of ecological sensitive areas in the power grid planning area, represents the avoidance priority weight of the j-th ecological sensitive area, represents the overlapping degree of the i-th line to be expanded and the j-th ecological sensitive area, represents the length of the i-th transmission line to be expanded, represents the penalty index, which is used for non-linear penalty of high-overlap areas.

[0016] Preferably, update the weights of each objective function once every time a population is generated. After a certain population is generated, the calculation method of the weight of the i-th objective function includes: Obtain the economic objective function values, reliability objective function values, and environmental protection objective function values corresponding to each individual in the population, and perform maximum-minimum normalization on them to obtain the normalized economic objective function values, normalized reliability objective function values, and normalized environmental protection objective function values; Calculate the standard deviation corresponding to the normalized economic objective function value, the standard deviation of the reliability objective function value, and the standard deviation of the environmental protection objective function value .

[0017] In a second aspect, the present invention further provides a power system transmission grid line planning system, including a processor and a memory. The memory stores computer program instructions, and when the computer program instructions are executed by the processor, the power system transmission grid line planning method of the present invention is implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] By referring to the accompanying drawings and reading the following detailed description, the above and other objects, features, and advantages of the exemplary embodiments of the present invention will become readily understandable. In the drawings, several embodiments of the present invention are shown in an exemplary rather than restrictive manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein: Figure 1 is a schematic flowchart showing the power system transmission grid line planning method according to an embodiment of the present invention; Figure 2 is a schematic structural diagram showing the power system transmission grid line planning system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] Next, the specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0021] Embodiment of the power system transmission grid line planning method: As Figure 1 shown, the power system transmission grid line planning method of the present invention includes: obtaining all expandable transmission lines in the grid planning area and constructing a multi-objective optimization model, where the multi-objective optimization model includes: an economic objective function, a reliability objective function, an environmental protection objective function, and constraint conditions; and using a genetic algorithm to solve the multi-objective optimization model to obtain an optimal expansion plan; The economic objective function is used to evaluate the economy of the expansion plan; the reliability objective function is used to evaluate the power supply reliability of the planned transmission grid lines; the environmental protection objective function is used to evaluate the environmental protection of the planned transmission grid lines, that is, the degree of impact on the environment.

[0022] The constraint conditions include power balance constraints, line capacity constraints, voltage security constraints, and electromagnetic radiation constraints.

[0023] Among them, the power balance constraint is: ; In the formula, represents the generator output, represents the external input power, represents the network loss, represents the load demand in the power grid supply area, represents the charge and discharge power of the energy storage device connected to the power grid, represents the reserve capacity of the power grid.

[0024] The line capacity constraint is: The voltage security constraint is: ; In the formula, and are the maximum voltage and the minimum voltage respectively, represents the predicted value of the line voltage of the i-th line to be expanded; The electromagnetic radiation constraint is:

[0025] In the formula, is the predicted value of the electromagnetic radiation intensity of the i-th line to be expanded, is the electromagnetic radiation intensity threshold.

[0026] The solution process includes: S101. Generate an initial population, specifically: randomly generate an initial population, and the individuals in the population represent expansion plans, where the expansion plans are used to characterize whether each expandable transmission line is used as a transmission line to be expanded; For example: Suppose there are 5 expandable lines. The selected lines can be marked as 1, and the unselected ones as 0. If the first three lines are selected and the last two are not, then the chromosome of an individual can be represented as X = [1, 1, 1, 0, 0].

[0027] S102. Calculate the fitness value of the individuals in the population, specifically: calculate the fitness value for each individual in the population, and the calculation expression of the fitness value is: ; In the formula, , and represent the economic objective function, the reliability objective function, and the environmental protection objective function respectively, , and are the weights of the economic objective function, the reliability objective function, and the environmental protection objective function respectively, represents the exponential function with base e, and S represents the range corresponding to the economic objective function value, the reliability objective function value, and the environmental protection objective function value; Represents the over-limitation amount of the m-th constraint, Represents the penalty factor for violating the constraint; The greater the range of the economic objective function value, the reliability objective function value, and the environmental protection objective function value, the better the expansion plan performs in one aspect and the worse in another, and it cannot balance economy, reliability, and environmental protection. Therefore, the fitness value is made inversely proportional to the range, so that the expansion plan corresponding to the selected excellent individuals can balance economy, reliability, and environmental protection as much as possible.

[0028] S103. Obtain the optimal solution, specifically: iteratively perform selection, crossover, mutation on the population, and calculate the fitness value of each individual in the new population; until the fitness value of the individuals in the population converges or reaches the maximum number of iterations, stop the iteration, and output the optimal solution.

[0029] Traditional transmission network planning methods usually aim at the lowest cost or the highest reliability, resulting in the expanded transmission network only meeting the performance requirements in terms of economy or reliability, and unable to balance the performance requirements in all aspects. The transmission network line planning method of the power system of the present invention constructs a multi-objective optimization model including an economic objective function, a reliability objective function, and an environmental protection objective function, and solves it, so as to ensure that the expanded transmission network balances the requirements in terms of economy, reliability, and environmental protection. By using the genetic algorithm to solve the multi-objective optimization model, the global optimal solution can be quickly generated, improving the efficiency of transmission network planning; in addition, when calculating the fitness value of an individual, the fitness value is made inversely proportional to the range corresponding to the three objective function values, so as to further ensure that the generated expansion plan balances economy, reliability, and environmental protection.

[0030] And use the genetic algorithm for solution, so that In one embodiment, the calculation expression of the economic objective function is: ; In the formula, N represents the total number of transmission lines to be expanded, Represents the unit length investment cost of the i-th transmission line to be expanded, And respectively represent the operation and maintenance cost and the power loss cost of the i-th transmission line to be expanded in the t-th year; T represents the planning period, r is the discount rate, Represents the total building area of the target power supply area of the i-th transmission line to be expanded, and a represents the total area of the power grid planning area. The greater the ratio of the total building area of the target power supply area of the i-th transmission line to be expanded to the total area of the power grid planning area, the higher the importance of the transmission line to be expanded, the greater the power consumption load after completion, and the higher the income brought by the transmission line to be expanded. Therefore, the economic objective function value is made proportional to this ratio.

[0031] By introducing a discount rate into the economic objective function, the time value of funds is quantified, making the costs and benefits at different time points comparable, and thus more scientifically evaluating the economic benefits of transmission lines.

[0032] The expression of the economic objective function in this embodiment not only takes into account the investment cost, operation and maintenance cost, and line loss cost of the transmission line to be expanded when calculating the value of the economic objective function, but also considers the relationship between the ratio of the total building area of the target power supply area of the transmission line to be expanded to the total area of the power grid planning area and the power consumption load of the transmission line to be expanded, making the value of the economic objective function proportional to this ratio, thereby improving the accuracy of the calculation result of the economic objective function.

[0033] In one embodiment, the calculation expression of the reliability objective function is: ; In the formula, represents the load loss caused by the failure of the i-th transmission line to be expanded, represents the total load of the power system in the power grid planning area, , , respectively represent the frequency of rain, the frequency of wind, and the lightning strike frequency in the past year in the target power supply area of the i-th transmission line to be expanded, represents the influence range of geological disasters, and a represents the total area of the power grid planning area.

[0034] The calculation method of the frequency of rain in the past year in the target power supply area can be: count the number of rainy days in the past year in the target power supply area and divide it by the total number of days in the past year to obtain the frequency of rain in the past year in the target power supply area. The frequency of wind and the frequency of being struck by lightning can both be determined in this way.

[0035] Generally, the load loss caused by the failure of the transmission line to be expanded will have a negative impact on the power supply reliability of the power grid. Therefore, the value of the reliability objective function is inversely proportional to the load loss caused by the failure of the transmission line to be expanded; when there are bad weather conditions such as rain, wind, or thunder in the power supply area of the transmission line, it will cause faults such as short circuits or open circuits in the transmission line. Therefore, the greater the frequency of rain, the frequency of wind, and the frequency of thunder in the past year in the target power supply area of the transmission line to be expanded, the lower the power supply reliability of the power grid. The reliability objective function is inversely proportional to the frequency of rain, the frequency of wind, and the frequency of thunder, thereby further improving the accuracy of the value of the reliability objective function.

[0036] When calculating the reliability objective function value in this embodiment, the relationship between the load loss caused by the failure of the line to be expanded and the power grid power supply reliability, as well as the relationship between the frequency of severe weather in the target power supply area of the transmission line and the power grid power supply reliability are considered, so that the obtained reliability objective function value is more accurate.

[0037] In another embodiment, the calculation expression of the reliability objective function is: ; In the formula, respectively represent the load loss caused by the failure of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , and respectively represent the frequencies of rain, wind, lightning strikes, and geological disasters in the target power supply area of the i-th line to be expanded in the past year, represents the influence range of geological disasters, and a represents the total area of the power grid planning area.

[0038] When geological disasters such as debris flows and earthquakes occur in the target power supply area, it may cause the wire poles of the transmission line to collapse, resulting in the fracture of the transmission line. Moreover, the greater the influence range of the geological disaster, the greater the negative impact on the transmission line. Therefore, the reliability objective function value is made proportional to both the frequency of geological disasters and the influence range of geological disasters.

[0039] In yet another embodiment, the calculation expression of the reliability objective function is: ; In the formula, respectively represent the load loss caused by the failure of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , and respectively represent the frequencies of rain, wind, lightning strikes, and geological disasters in the target power supply area of the i-th line to be expanded in the past year, represents the influence range of geological disasters, a represents the total area of the power grid planning area, represents the proportion of the special terrain area in the target power supply area of the i-th line to be expanded, and the special terrain includes mountains, forests, canyons, and swamps.

[0040] The terrain of the target power supply area can be obtained through GIS data.

[0041] For transmission lines in mountainous, forested, canyon, and swamp areas, the inspection difficulty is often high, and the transmission lines are prone to being damaged. In this embodiment, when calculating the reliability objective function value, the influence of the special terrain of the area through which the line to be expanded passes on the reliability of the power supply line is further considered, thereby further improving the accuracy of the reliability objective function value.

[0042] In one embodiment, the calculation expression of the reliability objective function is: ; In the formula, respectively represent the load loss caused by the failure of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , and respectively represent the frequencies of rain, wind, lightning strikes, and geological disasters in the target power supply area of the i-th line to be expanded in the past year, represents the influence range of geological disasters, a represents the total area of the power grid planning area, represents the proportion of the special terrain area in the target power supply area of the i-th line to be expanded, represents the altitude change in the target power supply area of the i-th line to be expanded.

[0043] The greater the altitude change in the target power supply area, the more uneven the ground in the target power supply area, which will have a negative impact on the overall stability of the transmission line. Therefore, in this embodiment, the reliability objective function value is negatively correlated with the altitude change in the target power supply area of the transmission line, which can further improve the accuracy of the reliability objective function value.

[0044] In one embodiment, the total number of ecological sensitive periods in the power grid planning area is obtained, and the avoidance priority weights of each ecological sensitive period are set, and then an environmental protection objective function is constructed, and the expression is: ; In the formula, represents the exponential function with base e, N represents the total number of transmission lines to be expanded, represents the total number of ecological sensitive areas in the power grid planning area, represents the avoidance priority weight of the j-th ecological sensitive area, represents the overlap degree between the i-th line to be expanded and the j-th ecological sensitive area, represents the length of the i-th transmission line to be expanded, represents the penalty index, which is used for non-linear penalty of high overlap areas.

[0045] The method for determining the overlapping degree between the line to be expanded and the ecological sensitive area is as follows: Multiply the line length of the line to be expanded by the corridor width to obtain the occupied area of the line to be expanded, and divide the occupied area of the line to be expanded by the area of the ecological sensitive area to obtain the overlapping degree.

[0046] The corridor width refers to the occupied space required within the ground projection range of the line. In this embodiment, the corridor width is calculated based on the electrical distance of the line , the half-width of the tower foundation , the width of the operation and maintenance passage and the width of the safety buffer zone for calculation. The expression is: .

[0047] An ecological sensitive area refers to an area with a fragile ecological environment, special ecological value or vulnerable to human activities. In this embodiment, the ecological sensitive areas include nature reserves (such as forests, wetlands, habitats of rare species), water source protection areas (river sources, areas around reservoirs), ecological corridors (animal and plant migration paths), and scenic spots or cultural relics.

[0048] In this embodiment, the environmental friendliness of the expanded transmission line is measured based on the overlapping degree between the transmission line to be expanded and various ecological sensitive areas, so as to make the calculation of the environmental friendliness objective function value more accurate.

[0049] In one embodiment, the weights of each objective function are updated once every time a population is generated. After a certain population is generated, the calculation method of the weight of the i-th objective function includes: Obtain the economic objective function values, reliability objective function values, and environmental friendliness objective function values corresponding to each individual in the population, and perform maximum-minimum normalization on them to obtain the normalized economic objective function values, normalized reliability objective function values, and normalized environmental friendliness objective function values; Calculate the standard deviation corresponding to the normalized economic objective function value , the standard deviation of the reliability objective function value and the standard deviation of the environmental friendliness objective function value , and then calculate the weight of the i-th objective function. The calculation expression is: .

[0050] Since the objective function values with a larger dispersion have a more significant impact on the differences in solutions, larger weights are assigned to the objective functions with a larger standard deviation, thereby improving the efficiency of multi-objective optimization; by dynamically updating the weights with the iteration of the population, the dynamic importance of the objectives can be reflected, enhancing the self-adaptability and robustness of multi-objective optimization.

[0051] Embodiment of the Transmission Grid Line Planning System of the Power System: The present invention also provides a transmission grid line planning system of the power system. As Figure 2 shown, the transmission grid line planning system of the power system includes a processor and a memory, and the memory stores computer program instructions. When the computer program instructions are executed by the processor, a transmission grid line planning method of the power system described in the above embodiments of the present invention is implemented.

[0052] The transmission grid line planning system of the power system further includes other components well known to those skilled in the art such as a communication bus and a communication interface. Their settings and functions are known in the art, and thus will not be described in detail herein.

[0053] In the description of this specification, the meanings of "a plurality of" and "several" are at least two, such as two, three or more, etc., unless otherwise specifically defined.

[0054] Although this specification has shown and described multiple embodiments of the present invention, it is obvious to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art will think of many changes, alterations and alternative ways without departing from the spirit and idea of the present invention. It should be understood that various alternative solutions to the embodiments of the present invention described herein can be adopted in the process of practicing the present invention.

Claims

1. A method for power system transmission network line planning, characterized in that Including: Obtain all the expandable transmission lines in the power grid planning area and construct a multi-objective optimization model, where the multi-objective optimization model includes: an economic objective function, a reliability objective function, an environmental protection objective function, and constraint conditions; and use the genetic algorithm to solve the multi-objective optimization model to obtain the optimal expansion plan; the solution process includes: randomly generating an initial population, where the individuals in the population represent expansion plans, and the expansion plans are used to characterize whether each expandable transmission line is to be an expanded transmission line; Calculate the fitness value for each individual in the population, and the calculation expression of the fitness value is: ； In the formula, , and respectively represent the economic objective function, the reliability objective function, and the environmental protection objective function. , and are respectively the weights of the economic objective function, the reliability objective function, and the environmental protection objective function. represents the exponential function with base e, and S represents the range corresponding to the values of the economic objective function, the reliability objective function, and the environmental protection objective function. represents the amount of violation of the m-th constraint. represents the penalty factor for violating the constraint. Iteratively select, cross, mutate the population and calculate the fitness value of each individual in the new population until the fitness value of the individuals in the population converges, stop the iteration and output the optimal solution.

2. The power system transmission network line planning method according to claim 1, wherein The calculation expression of the economic objective function is: ; where N represents the total number of transmission lines to be expanded, represents the investment cost per unit length of the i-th transmission line to be expanded, and represent the operation and maintenance cost and the power loss cost of the i-th transmission line to be expanded in the t-th year respectively; T represents the planning period, r is the discount rate, represents the total building area of the target power supply area of the i-th transmission line to be expanded, and a represents the total area of the power grid planning area.

3. The power system transmission network line planning method according to claim 1, wherein, The calculation expression of the reliability objective function is: ； In the formula, represents the load loss caused by the fault of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , respectively represent the frequencies of rain, wind, and lightning strikes in the past year in the target power supply area of the i-th line to be expanded, represents the influence range of geological disasters, and a represents the total area of the power grid planning area.

4. The power system transmission network line planning method according to claim 1, wherein The calculation expression of the reliability objective function is: ； In the formula, represents the load loss caused by the failure of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , and respectively represent the frequencies of rain, wind, lightning strikes, and geological disasters in the past year in the target power supply area of the i-th line to be expanded, represents the influence range of geological disasters, and a represents the total area of the power grid planning area.

5. The power system transmission network line planning method according to claim 1, characterized in that, The calculation expression of the reliability objective function is: ； In the formula, represents the load loss caused by the fault of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , and respectively represent the frequencies of rain, wind, lightning strikes, and geological disasters in the past year in the target power supply area of the i-th line to be expanded, represents the influence range of geological disasters, a represents the total area of the power grid planning area, represents the proportion of the special terrain area in the target power supply area of the i-th line to be expanded.

6. The power system transmission network line planning method according to claim 5, characterized in that, The special terrains include mountains, forests, canyons, and swamps.

7. The power system transmission network line planning method according to claim 1, characterized in that The calculation expression of the reliability objective function is: ； In the formula, respectively represent the load loss caused by the fault of the i-th line to be expanded, represents the total load of the power system in the power grid planning area, , , and respectively represent the frequencies of rain, wind, lightning strikes, and geological disasters in the past year in the target power supply area of the i-th line to be expanded, represents the influence range of geological disasters, a represents the total area of the power grid planning area, represents the proportion of the special terrain area in the target power supply area of the i-th line to be expanded, represents the altitude change of the area through which the i-th line to be expanded passes.

8. The power system transmission network line planning method according to claim 1, wherein Obtain the total number of ecological sensitive periods in the power grid planning area and set the avoidance priority weights for each ecological sensitive period, and then construct an environmental protection objective function, and its expression is: ; In the formula, represents the exponential function with base e, N represents the total number of transmission lines to be expanded, represents the total number of ecological sensitive areas in the power grid planning area, represents the avoidance priority weight of the j-th ecological sensitive area, represents the overlapping degree between the i-th transmission line to be expanded and the j-th ecological sensitive area, represents the length of the i-th transmission line to be expanded, represents the penalty exponent, which is used for non-linear penalty of high-overlap areas.

9. The power system transmission network line planning method according to claim 1, characterized in that, Update the weights of each objective function once every time a population is generated. After a certain population is generated, the calculation method of the weight of the i-th objective function includes: Obtain the economic objective function values, reliability objective function values, and environmental protection objective function values corresponding to each individual in the population, and perform maximum-minimum normalization on them to obtain the normalized economic objective function values, normalized reliability objective function values, and normalized environmental protection objective function values; calculate the standard deviation corresponding to the normalized economic objective function value , the standard deviation of the reliability objective function value and the standard deviation of the environmental protection objective function value , and then calculate the weight of the economic objective function. The calculation expression is: 。 10. A power system transmission network line planning system, comprising a processor and a memory, characterized in that, The memory stores computer program instructions, and when the computer program instructions are executed by the processor, the power system transmission grid line planning method described in any one of claims 1 to 9 is implemented.

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