A method and system for analyzing the safety carrying capacity of the main grid of a megacity power grid

Abstract

The present invention discloses a method and system for analyzing the safe carrying capacity of the main grid of a megacity power grid, including: evaluating the load demand of each substation in the area during the high-load period of winter and summer, and evaluating the peak power generation capacity of each power source and energy storage facility; establishing the topological relationship between low-voltage substations, power sources, energy storage and high-voltage substations based on the load demand and peak power generation capacity of the area, and dividing the power supply area under the safety and stability constraints of short-circuit current, voltage and grid risk management to form a standard operation mode; according to the standard operation mode, identifying the main grid safe carrying capacity and checkpoints under the standard operation mode of each area, and forming the main grid safe carrying capacity and power supply checkpoints under the standard operation mode of the megacity power grid. The present invention can accurately identify the load demand of the power grid, the safe carrying capacity of the main grid, the checkpoints, and the commissioning efficiency of the transmission and transformation project.

Description

Technical Field

[0001] The present invention relates to the field of power grid power supply security and development planning decision-making, and in particular to a method and system for analyzing the safe carrying capacity of a main grid of a megacity power grid. Background Art

[0002] In subsequent grid planning and construction, the impact of transmission and transformation projects on the main grid's safe carrying capacity is the primary consideration and a key factor in determining the feasibility of each grid construction and renovation project. A correspondingly strong main grid safe carrying capacity can also serve to attract investment for major projects, preventing users from being left without electricity after investing substantial capital.

[0003] Existing domestic safety capacity assessment methods primarily focus on provincial power grids and local distribution networks. Provincial power grid assessment methods prioritize grid-wide power balance and optimization, with less consideration given to the electricity demands of local governments and consumers. Algorithms prioritize maximizing grid safety margins. However, assessments of the safety capacity of megacities do not require consideration of interprovincial power transactions, simplifying power balance algorithms. However, they do require prioritizing consumer power demand, verifying power-rich areas, and implementing emergency measures to eliminate bottlenecks, aiming to meet the power supply needs of local governments and consumers as much as possible while meeting safety constraints.

[0004] The safety load-carrying capacity verification method for local distribution networks differs significantly from that for the main grid. Distribution networks operate entirely in open-loop mode, resulting in a temporary loss of load after a distribution equipment failure. Compliance with safety constraints in accordance with the "Guidelines for Safety and Stability of Electric Power Systems" (GB 38755-2019) is not required. The main grid primarily operates in closed-loop mode, with local open-loop mode. Failures can result in power flow shifts, voltage, and frequency fluctuations, requiring compliance with the safety constraints in the "Guidelines for Safety and Stability of Electric Power Systems" (GB 38755-2019).

[0005] At the same time, various parties now use various methods and standards to evaluate the performance of power transmission and transformation projects, resulting in some projects producing results less than expected after they are put into operation; the importance of some key projects has not received sufficient attention, and human, financial and material resources have not received strong support, resulting in the inability to put them into production on schedule. It is necessary to reasonably evaluate the performance of power transmission and transformation projects to guide the planning and construction of projects.

[0006] In view of this, this application is hereby filed. Summary of the Invention

[0007] The technical problem to be solved by the present invention is that the existing technical methods have the problems of being unable to accurately identify the safe carrying capacity and checkpoints of the main network of the urban power grid, and being unable to accurately evaluate the effectiveness of the power transmission and transformation project. The purpose of the present invention is to provide a method and system for analyzing the safe carrying capacity of the main network of the power grid in a megacity. The present invention mainly evaluates the safe carrying capacity of the power grid in a megacity through the power supply checkpoint identification technology. The obtained safe carrying capacity data effectively quantifies the safe carrying capacity of the main network of the power grid, and is the most core data for the preparation and implementation of power supply guarantee work plans for the urban power grid to meet the peak summer and winter demand, and for major decision-making. On this basis, the calculated power transmission and transformation project effectiveness evaluation method quantitatively evaluates the effect of the power transmission and transformation project commissioning, and provides a quantitative data basis for the feasibility study of power grid planning and construction, and the allocation of human, financial and material resources.

[0008] The present invention is achieved through the following technical solutions:

[0009] In a first aspect, the present invention provides a method for analyzing the safe carrying capacity of a main grid of a megacity power grid, the method comprising:

[0010] Based on the historical load of each substation and the list of newly connected users, the regional load demand of each substation during the peak load periods of winter and summer is evaluated; based on the installed capacity of existing grid-connected power sources, energy storage, and newly connected power sources and energy storage, the peak power generation capacity of each power source and energy storage facility is evaluated;

[0011] Based on the load demand of the area and the peak power generation capacity, a topological relationship between low-voltage substations, power sources, energy storage and high-voltage substations is established. The power supply area is divided under the safety and stability constraints of short-circuit current, voltage and grid risk management to form a standard operation mode.

[0012] According to the standard operation mode, the main grid safety carrying capacity and checkpoints under the standard operation mode of each area are identified, and the main grid safety carrying capacity and power supply checkpoints under the standard operation mode of the super-large city power grid are formed.

[0013] Furthermore, the method further comprises:

[0014] According to the main grid's safe carrying capacity and power supply checkpoints under the standard operation mode of each area, if a load checkpoint exists in an area, the area has no grid surplus capacity; if a load checkpoint does not exist in an area, the grid surplus carrying capacity of the area is verified;

[0015] Based on the main grid's safe carrying capacity, power supply checkpoint, and surplus carrying capacity, the impact of the power transmission and transformation project's non-operation or operation on the grid's carrying capacity, power supply checkpoint, and surplus carrying capacity is evaluated to obtain the magnitude of the impact; the magnitude of the impact is the commissioning efficiency of the power transmission and transformation project.

[0016] Furthermore, based on the historical load of each substation and the list of newly connected users, the regional load demand of each substation during the peak load periods of winter and summer was evaluated. Based on the installed capacity of existing grid-connected power sources, energy storage, and newly connected power sources and energy storage, the peak power generation capacity of each power source and energy storage facility was evaluated, including:

[0017] S101: Based on the new user access system list and the reported load demand, the new user load is attributed to the corresponding substation connected in the planning and design, and the new power load is calculated;

[0018] S102: Calculate the load growth rate of each substation. The natural growth rate of the load at a single site = 30% / average operating life of the substation switch interval. If the operating life is less than 1 year, it will be included in the new user load increase in S101.

[0019] S103: Calculate the substation's winter and summer loads: Substation's winter and summer loads = historical maximum load × natural load growth rate + user's newly added power load. The natural load growth rate is not calculated for newly commissioned stations; only the newly added power load is calculated.

[0020] S104: Obtain historical data through the SCADA system to calculate the average daily maximum power generation of grid-connected power sources and energy storage during the summer and winter periods of previous years. This data is added to the declared power generation capacity of new grid-connected power sources and energy storage, and then attributed to the corresponding substations according to the grid connection point to obtain the peak power generation capacity of each substation.

[0021] Furthermore, the power supply area is divided and a standard operation mode is formed, including:

[0022] S201: The line connecting the 110kV substation to the upper 220kV substation is considered a 110kV power line, and the lines between 110kV substations are considered 110kV interconnection lines. If there is only one 110kV power line, close that line directly. If there are ≥2 110kV power lines, close only the line with the smallest impedance, and keep the other lines disconnected. If the 110kV substation has only interconnection lines but no power lines, close the interconnection line with the smallest impedance, and keep the other lines disconnected.

[0023] S202: The lines connecting the 220kV substation to the upper 500kV substation are considered 220kV power lines, and the lines between 220kV substations are considered 220kV interconnection lines. All 220kV power lines and interconnection lines are closed; all 500kV lines are closed.

[0024] S203: Traverse all 220kV busbar short-circuit currents in the entire network, identify all 220kV busbars with short-circuit currents exceeding 50kA, and sort them from largest to smallest. 220kV power lines or tie lines with more severe excess short-circuit currents on both sides of the 220kV busbars are disconnected first, followed by 220kV power lines or tie lines with even more severe excess short-circuit currents on one side of the 220kV busbars.

[0025] S204: After each line is disconnected, all 220kV busbar short-circuit currents in the entire network are traversed once, and the 220kV buses that exceed the standard are re-sorted, and step S203 is executed until the short-circuit currents of all 220kV busbars in the entire network do not exceed 50kA. After this step is completed, the entire network forms a 500kV line closed operation; the 220kV substation is divided into areas, and the lines within the area are all in a closed state, and the lines between areas are in a disconnected state; the 110kV substation has only one power line, and the 110kV substation without a power line has only one connecting line, and the remaining lines are all in a disconnected state, realizing open-loop operation.

[0026] Furthermore, the division of power supply areas and the formation of standard operation modes also include:

[0027] S205: After short-circuit current verification, conduct fault verification on all power grid equipment, including 500kV and 220kV main transformers N-1, 500kV and 220kV lines N-1, 500kV and 220kV lines on the same tower N-2, and 220kV / 110kV busbar N-1. Record the substations where the voltage drops by more than 10% under each fault condition.

[0028] S206: During the voltage verification period, synchronously record the power angle change trends of the generator sets in each 500kV area of the synchronous system and the designated large generator sets in the province after the failure of 500kV and 220kV main transformers N-1, 500kV and 220kV lines N-1, 500kV and 220kV lines on the same tower N-2, and 220kV / 110kV busbar N-1. If the power angle oscillation angle gradually decreases, the power angle stability verification is considered to have passed;

[0029] S207: After the short-circuit current, voltage, and power angle verification are passed, the current grid risk control mode is manually verified, and the 220kV substation with single-line and double-circuit power supply on the same tower is operated separately, and supplied by two different 500kV areas respectively. If the 220kV substation cannot be separated, it will be skipped.

[0030] Furthermore, the step S205 of recording the substations where the voltage drops by more than 10% under each fault condition includes:

[0031] For 500kV substations where the busbar voltage drops by more than 10%, the 220kV substations supplied will be adjusted to other 500kV substations in descending order of electrical distance from the 500kV substation. If a 220kV substation cannot be adjusted due to network topology issues, it will be skipped. After each substation is adjusted, the nearby lines and buses will be repeatedly checked for faults until the voltage requirements are met.

[0032] For 220kV substations with voltage drops exceeding 10%, priority will be given to adjusting the supply from the 110kV substation to other 220kV substations according to the load from small to large. If the 110kV substation cannot be adjusted due to network topology not meeting the requirements, it will be skipped until the voltage requirements are met.

[0033] For 110kV substations where the voltage drops by more than 10%, disconnect the current power line or tie line, close another power line or tie line, and adjust the power supply to other 220kV substations;

[0034] If the 110kV substation still does not meet the voltage verification conditions after adjustment, the load supplied by the station will be deducted, and the deducted load will be included in the voltage constraint power supply card port.

[0035] Furthermore, according to the standard operation mode, the main grid safety carrying capacity and checkpoints under the standard operation mode of each area are identified, and the main grid safety carrying capacity and power supply checkpoints under the standard operation mode of the super-large city power grid are formed, including:

[0036] S301: According to the standard operation mode, all 500kV and 220kV main transformers N-1, 500kV and 220kV lines N-1, 500kV and 220kV lines on the same tower N-2, and 220kV / 110kV busbar N-1 are checked for faults, and lines whose post-fault current exceeds the current carrying capacity and main transformers whose load exceeds the rated capacity of the main transformer * the overload factor are recorded;

[0037] S302: Calculate the overload line fault power flow / rated load, which is recorded as the thermal overload coefficient; calculate the overload main transformer fault power flow / (rated capacity*overload coefficient), which is recorded as the thermal overload coefficient;

[0038] S303: Considering that there may be no equipment thermally overloaded within a single 500kV area, or there may be one or more equipment thermally overloaded, the one with the largest thermal overload coefficient is selected, and the thermal stability constraint main grid safe carrying capacity = off-grid load under standard operation mode / maximum thermal overload coefficient. The load within the area that exceeds the thermal stability constraint main grid safe carrying capacity is included in the thermal stability constraint power supply card;

[0039] S304: The power supply port for a single 500kV area is the maximum value of the thermal stability constraint power supply port, voltage constraint power supply port, and power angle constraint power supply port.

[0040] S305: Safe carrying capacity of a single 500kV area main grid = area load in standard operation mode - area power supply port;

[0041] S306: According to steps S303-S305, the safe carrying capacity and power supply port of the 220kV site main grid are calculated.

[0042] Furthermore, based on the main grid's safe carrying capacity and power supply checkpoints under the standard operating mode of each area, if a load checkpoint exists in an area, the area has no grid surplus capacity; if a load checkpoint does not exist in an area, the grid surplus carrying capacity of the area is verified, including:

[0043] S401: Read the fault verification results of the 500kV and 220kV main transformer N-1, 500kV and 220kV line N-1, 500kV and 220kV line N-2 on the same tower, and 220kV / 110kV busbar N-1 in the non-overloaded 500kV area, and select the device with the highest load rate among them: the 500kV main transformer, 220kV line, and 220kV main transformer.

[0044] S402: The load of the area is increased in the same proportion until the load rate of the 500 kV main transformer and the 220 kV line reaches 100% for the first time after the fault verification is completed in the area. The load of the area at this time is recorded as the maximum load that can be carried by the area under the thermal stability constraint condition.

[0045] S403: Based on the maximum load that the area can carry under the thermal stability constraint conditions, the short-circuit current, voltage, and power angle are re-checked under fault conditions. If all checks pass, the maximum load that can be carried under the current thermal stability constraint conditions becomes the maximum load that the area can carry. If one or more checks fail, the load of the area is reduced until all constraints are met. The load at this point becomes the maximum load that the area can carry, and the maximum load that the area can carry is not less than the safe carrying capacity of the area main grid.

[0046] S404: The surplus carrying capacity of the 500kV main transformer and 220kV line = the maximum load that can be carried in the area - the safe carrying capacity of the main grid in the area;

[0047] S405: According to steps S402-S404, the surplus carrying capacity of the 220 kV main transformer is calculated.

[0048] In a second aspect, the present invention provides a system for analyzing the safety carrying capacity of a main grid of a megacity power grid, the system comprising:

[0049] The source-grid-load-storage assessment unit is used to assess the regional load demand of each substation during the peak winter and summer load periods based on the historical load of each substation and the list of newly connected users. It also assesses the peak power generation capacity of each power source and energy storage facility based on the installed capacity of existing grid-connected power sources, energy storage, and newly connected power sources and energy storage facilities.

[0050] A standard mode generation unit is used to establish a topological relationship between low-voltage substations, power sources, energy storage, and high-voltage substations based on the load demand of the area and the peak power generation capacity, and to divide the power supply area under the safety and stability constraints of short-circuit current, voltage, and grid risk management to form a standard operation mode;

[0051] The carrying capacity analysis unit is used to identify the main network safety carrying capacity and checkpoints under the standard operating mode of each area according to the standard operating mode, and form the main network safety carrying capacity and power supply checkpoints under the standard operating mode of the super-large city power grid.

[0052] In a third aspect, the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the computer program implements the above-mentioned method for analyzing the safe carrying capacity of the main network of a megacity power grid.

[0053] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0054] 1. The present invention provides a method and system for analyzing the safe carrying capacity of the main grid of a megacity power grid. The method mainly uses power supply bayonet identification technology to evaluate the safe carrying capacity of the megacity power grid. The obtained safe carrying capacity data effectively quantifies the safe carrying capacity of the main grid of the power grid. It is the most core data for the formulation and implementation of power supply guarantee work plans for urban power grids to meet peak summer and winter power supply needs and for major decision-making. It is also the most important reference factor for power grid planning and construction.

[0055] 2. The present invention provides a method and system for analyzing the safe carrying capacity of the main grid of a megacity power grid, which accurately identifies the load demand of the power grid, the safe carrying capacity of the main grid, the power supply checkpoints, and the commissioning efficiency of the transmission and transformation project. It provides a core basis for the distribution of electric power and power supply, as well as for the major decisions of the power grid company. It is also a key feasibility basis for subsequent power grid planning and construction, and optimizes the service level of attracting investment for major projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0057] Figure 1 This is a flow chart of a method for analyzing the safe carrying capacity of a main grid of a megacity power grid according to embodiment 1 of the present invention;

[0058] Figure 2 This is a structural block diagram of a system for analyzing the safe carrying capacity of a main grid of a megacity power grid according to embodiment 2 of the present invention. DETAILED DESCRIPTION

[0059] 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 examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0060] Example 1

[0061] like Figure 1 As shown, the present invention provides a method for analyzing the safe carrying capacity of a main grid of a megacity power grid, the method comprising:

[0062] S1: Based on the historical load of each substation and the list of newly connected users, evaluate the regional load demand of each substation during the peak load periods of winter and summer. Based on the installed capacity of existing grid-connected power sources, energy storage, and newly connected power sources and energy storage, evaluate the peak power generation capacity of each power source and energy storage facility.

[0063] Step S1 mainly performs load assessment and peak power generation capacity assessment. Step S1 specifically includes:

[0064] S101: Based on the new user access system list and the reported load demand, the new user load is attributed to the corresponding substation connected in the planning and design, and the new power load is calculated;

[0065] S102: Calculate the load growth rate of each substation. The natural growth rate of the load at a single site = 30% / average operating life of the substation switch interval. If the operating life is less than 1 year, it will be included in the new user load increase in S101.

[0066] S103: Calculate the substation's winter and summer loads: Substation's winter and summer loads = historical maximum load × natural load growth rate + user's newly added power load. The natural load growth rate is not calculated for newly commissioned stations; only the newly added power load is calculated.

[0067] S104: Obtain historical data through the SCADA system to calculate the average daily maximum power generation of grid-connected power sources and energy storage during the summer and winter periods of previous years. This data is added to the declared power generation capacity of new grid-connected power sources and energy storage, and then attributed to the corresponding substations according to the grid connection point to obtain the peak power generation capacity of each substation.

[0068] S2: Based on the load demand and peak power generation capacity of the area, a topological relationship between low-voltage substations, power sources, energy storage, and high-voltage substations is established. The power supply area is divided under the safety and stability constraints of short-circuit current, voltage, and grid risk management to form a standard operation mode.

[0069] Step 2 specifically includes:

[0070] S201: The line connecting the 110kV substation to the upper 220kV substation is considered a 110kV power line, and the lines between 110kV substations are considered 110kV interconnection lines. If there is only one 110kV power line, close that line directly. If there are ≥2 110kV power lines, close only the line with the smallest impedance, and keep the other lines disconnected. If the 110kV substation has only interconnection lines but no power lines, close the interconnection line with the smallest impedance, and keep the other lines disconnected.

[0071] S202: The lines connecting the 220kV substation to the upper 500kV substation are considered 220kV power lines, and the lines between 220kV substations are considered 220kV interconnection lines. All 220kV power lines and interconnection lines are closed; all 500kV lines are closed.

[0072] S203: Traverse all 220kV busbar short-circuit currents in the entire network, identify all 220kV busbars with short-circuit currents exceeding 50kA, and sort them from largest to smallest. 220kV power lines or tie lines with more severe excess short-circuit currents on both sides of the 220kV busbars are disconnected first, followed by 220kV power lines or tie lines with even more severe excess short-circuit currents on one side of the 220kV busbars.

[0073] S204: After each line is disconnected, all 220kV busbar short-circuit currents in the entire network are traversed once, and the 220kV buses that exceed the standard are reordered, and step S203 is executed until the short-circuit current of all 220kV busbars in the entire network does not exceed 50kA. After this step is completed, the entire network forms a 500kV line closed operation; 220kV substations are divided into sections, and the lines within the sections are all in a closed state, and the lines between sections are in a disconnected state; 110kV substations have only one power supply line, and 110kV substations without power supply lines have only one interconnection line, and the remaining lines are all in a disconnected state, realizing open-loop operation;

[0074] S205: After the short-circuit current is verified, all power grid equipment is checked for faults of 500kV and 220kV main transformers N-1, 500kV and 220kV lines N-1, 500kV and 220kV lines on the same tower N-2, and 220kV / 110kV busbar N-1, and the substations where the voltage drops by more than 10% under each fault are recorded, including: (1) For 500kV substations where the busbar voltage drops by more than 10%, the supplied 220kV substations are adjusted to other 500kV substations in order of electrical distance from the 500kV substation from far to near. If the 220kV substation cannot be adjusted because the network topology does not meet the requirements, it will be skipped. After each substation is adjusted, the nearby lines are checked again. , conduct a fault check on the busbar until the voltage requirements are met; (2) For 220kV substations with a voltage drop of more than 10%, the 110kV substations supplied shall be adjusted to other 220kV substations according to the load from small to large. If the 110kV substation cannot be adjusted due to network topology failure, it shall be skipped until the voltage requirements are met; (3) For 110kV substations with a voltage drop of more than 10%, disconnect the current power line or interconnection line, close another power line or interconnection line, and adjust the power supply to other 220kV substations; (4) If the 110kV substation still does not meet the voltage check conditions after adjustment, the load supplied by the station shall be deducted, and the deducted load shall be included in the voltage constraint power supply card.

[0075] S206: During the voltage verification, synchronously record the power angle change trends of the generator sets in each 500kV area of the synchronous system and the designated large-scale generator sets in the province after the fault of 500kV and 220kV main transformers N-1, 500kV and 220kV lines N-1, 500kV and 220kV same-tower lines N-2, and 220kV / 110kV busbar N-1. If the power angle oscillation angle meets the requirement of gradually reducing, it is deemed that the power angle stability verification has passed; if the units in the 500kV area do not meet the requirement of gradually reducing the power angle oscillation angle, the 220kV substations supplied will be adjusted to other 500kV substations in order of electrical distance from the 500kV substation from far to near. If the 220kV substation that cannot be adjusted due to network topology not meeting the requirements is skipped, and each time a substation is adjusted, the fault verification of the nearby lines and buses is repeated until the power angle stability requirements are met. If there are still areas that do not meet the power angle stability verification conditions after adjustment, the load supplied by the 110kV substation in the area will be deducted, and the deducted load will be included in the power angle constraint power supply card.

[0076] S207: After the short-circuit current, voltage, and power angle verification are passed, the current grid risk control mode is manually verified, and the 220kV substation with single-line and double-circuit power supply on the same tower is operated separately, and supplied by two different 500kV areas respectively. If the 220kV substation cannot be separated, it will be skipped.

[0077] S3: Based on the standard operation mode, identify the main grid safety carrying capacity and checkpoints under the standard operation mode of each area, and form the main grid safety carrying capacity and power supply checkpoints under the standard operation mode of the super-large city power grid;

[0078] Step S3 specifically includes:

[0079] S301: According to the standard operation mode, all 500kV and 220kV main transformers N-1, 500kV and 220kV lines N-1, 500kV and 220kV lines on the same tower N-2, and 220kV / 110kV busbar N-1 are checked for faults, and lines whose post-fault current exceeds the current carrying capacity and main transformers whose load exceeds the rated capacity of the main transformer * the overload factor are recorded;

[0080] S302: Calculate the overload line fault power flow / rated load, which is recorded as the thermal overload coefficient; calculate the overload main transformer fault power flow / (rated capacity*overload coefficient), which is recorded as the thermal overload coefficient;

[0081] S303: Within a single 500kV area, there may be no equipment with thermal overload, or one or more equipment with thermal overload. The area with the largest thermal overload coefficient is selected, and the thermal stability constraint main grid safe carrying capacity = off-grid load under standard operation mode / maximum thermal overload coefficient. Loads within the area that exceed the thermal stability constraint main grid safe carrying capacity are included in the thermal stability constraint power supply checkpoint.

[0082] S304: The power supply port for a single 500kV area is the maximum value of the thermal stability constraint power supply port, voltage constraint power supply port, and power angle constraint power supply port.

[0083] S305: Safe carrying capacity of a single 500kV area main grid = area load in standard operation mode - area power supply port;

[0084] S306: According to steps S303-S305, the safe carrying capacity and power supply port of the 220kV site main grid are calculated.

[0085] It should be noted that steps 2 and 3 are mutually optimized and do not pursue global optimality.

[0086] S4: Based on the main grid's safe carrying capacity and power supply checkpoints under the standard operating mode of each area, if a load checkpoint exists in an area, the area has no grid surplus capacity; if a load checkpoint does not exist in an area, the grid surplus carrying capacity of the area is verified;

[0087] Step S4 specifically includes:

[0088] S401: Read the fault verification results of the 500kV and 220kV main transformer N-1, 500kV and 220kV line N-1, 500kV and 220kV line N-2 on the same tower, and 220kV / 110kV busbar N-1 in the non-overloaded 500kV area, and select the device with the highest load rate among them: the 500kV main transformer, 220kV line, and 220kV main transformer.

[0089] S402: The load of the area is increased in the same proportion until the load rate of the 500 kV main transformer and the 220 kV line reaches 100% for the first time after the fault verification is completed in the area. The load of the area at this time is recorded as the maximum load that can be carried by the area under the thermal stability constraint condition.

[0090] S403: Based on the maximum load that the area can carry under the thermal stability constraint conditions, the short-circuit current, voltage, and power angle are re-checked under fault conditions. If all checks pass, the maximum load that can be carried under the current thermal stability constraint conditions becomes the maximum load that the area can carry. If one or more checks fail, the load of the area is reduced until all constraints are met. The load at this point becomes the maximum load that the area can carry, and the maximum load that the area can carry is not less than the safe carrying capacity of the area main grid.

[0091] S404: The surplus carrying capacity of the 500kV main transformer and 220kV line = the maximum load that can be carried in the area - the safe carrying capacity of the main grid in the area;

[0092] S405: According to steps S402-S404, the surplus carrying capacity of the 220 kV main transformer is calculated.

[0093] It should be noted that in step S4, the surplus capacity is divided into 500kV surplus capacity and 220kV surplus capacity, which are used to guide large customers' access; for areas with insufficient surplus capacity, grid planning, construction and transformation goals must be formulated.

[0094] S5: Based on the main grid's safe carrying capacity, power supply checkpoint, and surplus carrying capacity, evaluate the impact of the power transmission and transformation project's non-operation or operation on the grid's carrying capacity, power supply checkpoint, and surplus carrying capacity, and obtain the magnitude of the impact; the magnitude of the impact is the commissioning efficiency of the power transmission and transformation project.

[0095] Step S5 specifically includes:

[0096] S501: Record the safe carrying capacity, power supply checkpoints and surplus carrying capacity of the power grid in the area before the power transmission and transformation project is put into operation.

[0097] S502: After the power transmission and transformation project is put into operation, a standard operation mode of the power transmission and transformation project is formed with reference to steps S201 to S207.

[0098] S503: According to the standard operation mode after the power transmission and transformation project is put into operation, refer to steps S301-306 and S401-S405 to obtain the increase in the safe carrying capacity of the power grid in each area, the reduction in the power supply checkpoint, and the increase in the surplus carrying capacity. Among them, the increase in the safe carrying capacity of the power grid and the reduction in the power supply checkpoint are the efficiency values of improving the safe carrying capacity of the power grid of the project. The efficiency values of improving the safe carrying capacity of the power grid and improving the surplus carrying capacity respectively represent the quality and efficiency of the power supply and the reserved power potential for economic development.

[0099] In the specific implementation, the 2024 Chengdu power grid 500 kV TX, Shiling high-speed area main network safety carrying capacity, and 500 kV Shiling transmission and transformation project performance evaluation are taken as examples:

[0100] The first step is to assess the load demand and peak power generation capacity of the area. The historical maximum loads of all substations across the grid from September 2023 to July 2024 were collected. The maximum load demand in the 500 kV TX area was 3.3 million kilowatts. After collecting a list of new customers and commissioning a new 220 kV substation, the total customer load in the area was 265,000 kilowatts. The average operating age of the substations in the area is 4.24 years, resulting in a natural growth rate of 7.07%. No new power sources or energy storage were added. Therefore, the load demand in the TX area in 2024 = 330 * 107.07% + 26.5 = 3.7983 million kilowatts, approximately 3.8 million kilowatts.

[0101] The second step is to establish a topological relationship and establish a standard operating mode. The 110kV substation is topologically connected to the upstream 220kV station in a "one primary, one backup" configuration. All 220kV station lines are closed, and all 220kV busbars with short-circuit currents exceeding 50kA are identified. These lines are sorted from highest to lowest, and the 220kV lines are disconnected sequentially until the short-circuit current on all 220kV busbars does not exceed 50kA. After short-circuit current verification, the TX area includes the 220kV SL, DM, BH, HS, SS, RP, SQZ, MHC, CC, YL, and JY substations, as well as the corresponding 110kV substations they supply. Based on this operating mode, voltage and power angle verification are carried out. If both pass, a standard operating mode is established, with no voltage or power angle constraint checkpoints.

[0102] The third step was to verify the safe carrying capacity of the power grid and the power supply threshold. Fault verification was performed on all 500kV and 220kV main transformers N-1, 500kV and 220kV lines N-1, 500kV and 220kV co-tower lines N-2, and 220kV / 110kV busbar N-1 in the 500kV TX area. Calculations revealed that the TX main transformer had the highest thermal overload factor, reaching 1.49. Therefore, the safe carrying capacity of the main grid under thermal stability constraints in the TX area was 380 / 1.49 = 2.55 million kilowatts, and the thermal stability threshold was 380-255 = 1.25 million kilowatts. Since there were no voltage or power angle constraint thresholds, the threshold for the 500kV TX area was 1.25 million kilowatts.

[0103] The fourth step is to check the surplus capacity of the power grid in this area. Due to the existence of power supply bottlenecks, the surplus capacity of the power grid in this area is 0.

[0104] The fifth step is to verify the effectiveness of key power supply guarantee projects. If the 500kV Shiling High-voltage Transmission and Transformation Project is commissioned, after establishing topological relationships and standard operating modes, the 500kV Shiling High-voltage and TX sub-areas cannot operate as a group due to short-circuit current limitations and must operate independently. The 220kV SL, DM, BH, and HS loads in the 500kV TX sub-area, totaling 1.2 million kilowatts, will be transferred to the 500kV Shiling High-voltage sub-area. The load in the 500kV TX sub-area will decrease from 3.8 million kilowatts to 2.6 million kilowatts. The thermal overload factor of the main transformer remains the highest, but has dropped to 1.02. The thermal stability constraint for the 500kV TX sub-area is 260 / 1.02 = 2.55 million kilowatts, reducing the thermal stability constraint to 50,000 kilowatts, a reduction of 1.2 million kilowatts in the sub-area. After the load of the 500 kV Shiling High-voltage area was proportionally amplified, fault verification was carried out. The 500 kV main transformer was overloaded first. At this time, the maximum load-bearing capacity of the area was 1.7 million kilowatts. Since the current load was 1.2 million kilowatts, the grid's surplus carrying capacity was 170-120=500,000 kilowatts.

[0105] Therefore, after evaluation, the grid's safe carrying capacity improvement efficiency value of the key summer power supply project, the 500kV Shiling high-speed transmission and transformation project, is 1.2 million kilowatts, and the grid's surplus carrying capacity is 500,000 kilowatts.

[0106] After obtaining accurate evaluation and analysis using this method, the 500 kV Shiling transmission and transformation project received high attention from all parties, ensuring that the project was put into operation on schedule.

[0107] Using the method provided by this paper, we obtained that the power supply capacity of a certain power grid in 2024 is 20.4 million kilowatts, which provides the core basis for the summer power supply guarantee work in 2024.

[0108] Example 2

[0109] like Figure 2As shown, the difference between this embodiment and embodiment 1 is that this embodiment provides a system for analyzing the safe carrying capacity of a main network of a megacity power grid, which corresponds in function to the method for analyzing the safe carrying capacity of a main network of a megacity power grid in embodiment 1; the system includes:

[0110] The source-grid-load-storage assessment unit is used to assess the regional load demand of each substation during the peak winter and summer load periods based on the historical load of each substation and the list of newly connected users. It also assesses the peak power generation capacity of each power source and energy storage facility based on the installed capacity of existing grid-connected power sources, energy storage, and newly connected power sources and energy storage facilities.

[0111] A standard mode generation unit is used to establish a topological relationship between low-voltage substations, power sources, energy storage, and high-voltage substations based on the load demand of the area and the peak power generation capacity, and to divide the power supply area under the safety and stability constraints of short-circuit current, voltage, and grid risk management to form a standard operation mode;

[0112] The carrying capacity analysis unit is used to identify the main network safety carrying capacity and checkpoints under the standard operating mode of each area according to the standard operating mode, and form the main network safety carrying capacity and power supply checkpoints under the standard operating mode of the super-large city power grid.

[0113] As a further implementation, the system further includes:

[0114] The verification unit is used to verify the main grid's safe carrying capacity and power supply checkpoints under the standard operating mode of each area. If a load checkpoint exists in an area, the area has no surplus power grid capacity; if a load checkpoint does not exist in an area, the surplus power grid carrying capacity of the area is verified.

[0115] The commissioning efficiency evaluation unit is used to evaluate the impact of the non-commissioning or commissioning of the transmission and transformation project on the grid carrying capacity, power supply checkpoint and surplus carrying capacity based on the main grid's safe carrying capacity, power supply checkpoint and surplus carrying capacity, and obtain the magnitude of the impact; the magnitude of the impact is the commissioning efficiency of the transmission and transformation project.

[0116] Among them, the execution process of each unit can be executed according to the process steps of the method for analyzing the safe carrying capacity of the main network of a super-large city power grid in Example 1, and will not be repeated in this embodiment.

[0117] At the same time, the present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the above-mentioned method for analyzing the safe carrying capacity of the main network of a super-large city power grid.

[0118] The present invention mainly evaluates the safe carrying capacity of the power grid in megacities through power supply identification technology. The obtained safe carrying capacity data effectively quantifies the safe carrying capacity of the main power grid. It is the most core data for the formulation and implementation of power supply guarantee plans for urban power grids during peak summer and winter, and for major decision-making. It is also the most important reference factor for power grid planning and construction.

[0119] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0120] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0121] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0122] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0123] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for analyzing the safe carrying capacity of a metropolitan power grid main network, characterized in that: The method includes: Based on the historical load of each substation and the list of newly connected users, the regional load demand of each substation during the peak load periods of winter and summer is evaluated. Based on the installed capacity of existing grid-connected power sources and energy storage, as well as newly connected power sources and energy storage, the peak power generation capacity of each power source and energy storage facility is evaluated. Based on the load demand and peak power generation capacity of the area, a topological relationship between low-voltage substations, power sources and energy storage, and high-voltage substations is established. The power supply area is divided under the safety and stability constraints of short-circuit current, voltage, and grid risk management to form a standard operation mode. According to the standard operation mode, identify the main grid safety carrying capacity and checkpoints under the standard operation mode of each area, and form the main grid safety carrying capacity and power supply checkpoints under the standard operation mode of the super-large city power grid; According to the main grid's safe carrying capacity and power supply checkpoints under the standard operation mode of each area, if a load checkpoint exists in an area, the area has no surplus power grid carrying capacity; if a load checkpoint does not exist in an area, the surplus power grid carrying capacity of the area is verified; Based on the historical load of each substation and the list of newly connected users, the regional load demand of each substation during the peak load periods of winter and summer is evaluated. Based on the installed capacity of existing grid-connected power sources and energy storage, as well as newly connected power sources and energy storage, the peak power generation capacity of each power source and energy storage facility is evaluated, including: S101: Based on the list of newly connected users and the reported load demand, the newly added user load is attributed to the corresponding substation connected in the planning and design, and the newly added power load is calculated; S102: Calculate the natural growth rate of load at each substation. The natural growth rate of load at a single station = 30% / average operating life of the substation switch interval. If the operating life is less than one year, it will be included in the new power load in S101. S103: Calculate the substation's winter and summer loads. The substation's winter and summer loads = historical maximum load × natural load growth rate + user-added power load. The natural load growth rate is not calculated for newly commissioned sites; only the newly added power load is calculated. S104: Obtain historical data through the SCADA system to calculate the average daily maximum power generation of grid-connected power sources and energy storage during the summer and winter periods of previous years. This data is added to the declared power generation capacity of new grid-connected power sources and energy storage, and then attributed to the corresponding substations according to the grid connection point to obtain the peak power generation capacity of each substation.

2. A method for analyzing the safe carrying capacity of a metropolitan power grid main network according to claim 1, characterized in that: The method further includes: Based on the main grid's safe carrying capacity, power supply checkpoint, and surplus carrying capacity, the impact of the power transmission and transformation project's non-operation or operation on the grid's carrying capacity, power supply checkpoint, and surplus carrying capacity is evaluated to obtain the magnitude of the impact; the magnitude of the impact is the commissioning efficiency of the power transmission and transformation project.

3. The method for analyzing the safe carrying capacity of a metropolitan power grid main network according to claim 1, characterized in that: Divide the power supply area and form a standard operation mode, including: S201: The line connecting the 110kV substation to the upper 220kV substation is considered a 110kV power line, and the lines between 110kV substations are considered 110kV interconnection lines. If there is only one 110kV power line, close that line directly. If there are ≥2 110kV power lines, close only the line with the smallest impedance, and keep the other lines disconnected. If the 110kV substation has only interconnection lines but no power lines, close the interconnection line with the smallest impedance, and keep the other lines disconnected. S202: The lines connecting the 220kV substation to the upper 500kV substation are considered 220kV power lines, and the lines between 220kV substations are considered 220kV interconnection lines. All 220kV power lines and interconnection lines are closed; all 500kV lines are closed. S203: Traverse all 220kV busbar short-circuit currents in the entire network, identify all 220kV busbars with short-circuit currents exceeding 50kA, and sort them from largest to smallest. 220kV power lines or tie lines with the largest excess short-circuit currents on both sides of the 220kV busbars are disconnected first, followed by the 220kV power lines or tie lines with the largest excess short-circuit currents on one side of the 220kV busbars. S204: After each line is disconnected, all 220kV busbar short-circuit currents in the entire network are traversed once, and the 220kV buses that exceed the standard are re-sorted, and step S203 is executed until the short-circuit currents of all 220kV busbars in the entire network do not exceed 50kA, and the entire network forms a 500kV line closed operation; the 220kV substation is divided into areas, and the lines within the area are all in a closed state, and the lines between areas are in a disconnected state; the 110kV substation has only one power line, and the 110kV substation without a power line has only one connecting line, and the remaining lines are all in a disconnected state, realizing open-loop operation.

4. A method for analyzing the safe carrying capacity of a metropolitan power grid main network according to claim 3, characterized in that: Divide the power supply area and form a standard operation mode, which also includes: S205: After short-circuit current verification, conduct fault verification on all power grid equipment, including 500kV and 220kV main transformers N-1, 500kV and 220kV lines N-1, 500kV and 220kV lines on the same tower N-2, and 220kV / 110kV busbar N-1. Record the substations where the voltage drops by more than 10% under each fault condition. S206: During the voltage verification period, synchronously record the power angle change trends of the generator sets in each 500kV area of the synchronous system and the designated large generator sets in the province after the failure of 500kV and 220kV main transformers N-1, 500kV and 220kV lines N-1, 500kV and 220kV lines on the same tower N-2, and 220kV / 110kV busbar N-1. If the power angle oscillation angle gradually decreases, the power angle stability verification is considered to have passed; S207: After the short-circuit current, voltage, and power angle verification are passed, the current grid risk control mode is manually verified, and the 220kV substation with single-line and double-circuit power supply on the same tower is operated separately, and supplied by two different 500kV areas respectively. If the 220kV substation cannot be separated, it will be skipped.

5. A method for analyzing the safe carrying capacity of a metropolitan power grid main network according to claim 4, characterized in that: The step S205 of recording the substations where the voltage drops by more than 10% under each fault condition includes: For 500kV substations where the busbar voltage drops by more than 10%, the 220kV substations supplied will be adjusted to other 500kV substations in descending order of electrical distance from the 500kV substation. If a 220kV substation cannot be adjusted due to network topology issues, it will be skipped. After each substation is adjusted, the nearby lines and buses will be repeatedly checked for faults until the voltage requirements are met. For 220kV substations with voltage drops exceeding 10%, the supply will be adjusted from the 110kV substations to other 220kV substations according to the load from small to large. If the 110kV substation cannot be adjusted due to network topology not being met, it will be skipped until the voltage requirements are met. For 110kV substations where the voltage drops by more than 10%, disconnect the current power line or tie line, close another power line or tie line, and adjust the power supply to other 220kV substations; If the 110kV substation still does not meet the voltage verification conditions after adjustment, the load supplied by the station will be deducted, and the deducted load will be included in the voltage constraint power supply card port.

6. A method for analyzing the safe carrying capacity of a metropolitan power grid main network according to claim 1, characterized in that: According to the standard operation mode, the main grid safety carrying capacity and checkpoints under the standard operation mode of each area are identified, and the main grid safety carrying capacity and power supply checkpoints under the standard operation mode of the super-large city power grid are formed, including: S301: According to the standard operation mode, all 500kV and 220kV main transformers N-1, 500kV and 220kV lines N-1, 500kV and 220kV lines on the same tower N-2, and 220kV / 110kV busbar N-1 are checked for faults, and lines whose post-fault current exceeds the current carrying capacity and main transformers whose load exceeds the rated capacity of the main transformer * the overload factor are recorded; S302: Calculate the overload line fault power flow / rated load, which is recorded as the thermal overload coefficient; calculate the overload main transformer fault power flow / (rated capacity*overload coefficient), which is recorded as the thermal overload coefficient; S303: The largest thermal overload coefficient is selected, and the thermal stability constraint main grid safe carrying capacity = the off-grid load under the standard operation mode / the maximum thermal overload coefficient. The load in the area that exceeds the thermal stability constraint main grid safe carrying capacity is included in the thermal stability constraint power supply card; S304: The power supply port for a single 500kV area is the maximum value of the thermal stability constraint power supply port, voltage constraint power supply port, and power angle constraint power supply port. S305: Single 500kV area main grid safe carrying capacity = standard operation mode area load - area power supply card port; S306: According to steps S303-S305, the safe carrying capacity and power supply port of the 220kV site main grid are calculated.

7. A method for analyzing the safe carrying capacity of a metropolitan power grid main network according to claim 2, characterized in that: According to the main grid's safe carrying capacity and power supply checkpoints under the standard operation mode of each area, if a load checkpoint exists in an area, the area has no surplus power grid carrying capacity; if a load checkpoint does not exist in an area, the surplus power grid carrying capacity of the area is verified, including: S401: Read the fault verification results of the 500kV and 220kV main transformer N-1, 500kV and 220kV line N-1, 500kV and 220kV line N-2 on the same tower, and 220kV / 110kV busbar N-1 in the non-overloaded 500kV area, and select the device with the highest load rate among them: the 500kV main transformer, 220kV line, and 220kV main transformer. S402: The load of the area is increased in the same proportion until the load rate of the 500kV main transformer and the 220kV line reaches 100% for the first time after the fault verification is completed in the area. The load of the area at this time is recorded as the maximum load that can be carried by the area under the thermal stability constraint condition. S403: Based on the maximum load that the area can carry under the thermal stability constraint conditions, the short-circuit current, voltage, and power angle are re-checked under fault conditions. If all checks pass, the maximum load that can be carried under the current thermal stability constraint conditions becomes the maximum load that the area can carry. If one or more checks fail, the load of the area is reduced until all constraints are met. The load at this point becomes the maximum load that the area can carry, and the maximum load that the area can carry is not less than the safe carrying capacity of the area main grid. S404: The surplus carrying capacity of the 500kV main transformer and 220kV line = the maximum load that can be carried in the area - the safe carrying capacity of the main grid in the area; S405: According to steps S402-S404, the surplus carrying capacity of the 220 kV main transformer is calculated.

8. A system for analyzing the safety carrying capacity of a megacity power grid main network, characterized in that: The system includes: The source-grid-load-storage assessment unit is used to assess the regional load demand of each substation during the peak winter and summer load periods based on the historical load of each substation and the list of newly connected users. It also assesses the peak power generation capacity of each power source and energy storage facility based on the installed capacity of existing grid-connected power sources and energy storage, as well as newly connected power sources and energy storage facilities. A standard mode generation unit is used to establish a topological relationship between low-voltage substations, power sources and energy storage, and high-voltage substations based on the load demand of the area and the peak power generation capacity, and to divide the power supply area under the safety and stability constraints of short-circuit current, voltage, and grid risk management to form a standard operation mode; A carrying capacity analysis unit is used to identify the main grid safety carrying capacity and checkpoints under the standard operating mode of each area according to the standard operating mode, and to form the main grid safety carrying capacity and power supply checkpoints under the standard operating mode of the super-large city power grid; The verification unit is used to check the main grid's safe carrying capacity and power supply checkpoints under the standard operation mode of each area. If a load checkpoint exists in an area, the area has no surplus power grid carrying capacity; if a load checkpoint does not exist in an area, the surplus power grid carrying capacity of the area is verified; Based on the historical load of each substation and the list of newly connected users, the regional load demand of each substation during the peak load periods of winter and summer is evaluated. Based on the installed capacity of existing grid-connected power sources and energy storage, as well as newly connected power sources and energy storage, the peak power generation capacity of each power source and energy storage facility is evaluated, including: S101: Based on the list of newly connected users and the reported load demand, the newly added user load is attributed to the corresponding substation connected in the planning and design, and the newly added power load is calculated; S102: Calculate the natural growth rate of load at each substation. The natural growth rate of load at a single station = 30% / average operating life of the substation switch interval. If the operating life is less than one year, it will be included in the new power load in S101. S103: Calculate the substation's winter and summer loads. The substation's winter and summer loads = historical maximum load × natural load growth rate + user-added power load. The natural load growth rate is not calculated for newly commissioned sites; only the newly added power load is calculated. S104: Obtain historical data through the SCADA system to calculate the average daily maximum power generation of grid-connected power sources and energy storage during the summer and winter periods of previous years. This data is added to the declared power generation capacity of new grid-connected power sources and energy storage, and then attributed to the corresponding substations according to the grid connection point to obtain the peak power generation capacity of each substation.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for analyzing the safe carrying capacity of a main grid of a megacity power grid according to any one of claims 1 to 7 is implemented.

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