Method and system for analyzing safety bearing capacity of major grid of power grid in extra-large city

Abstract

The invention discloses a method and system for analyzing the safety bearing capacity of a main power grid of an extra-large city, and the method comprises the steps: evaluating the load demands of all transformer substations in a heavy-load period in winter and summer, and evaluating the peak power generation capacity of all power supplies and energy storage facilities; establishing a topological relation among a low-voltage-class transformer substation, a power supply, energy storage and a high-voltage-class transformer substation according to the load demand and the peak power generation capacity of the district, and dividing power supply districts under the safe and stable constraint conditions of short-circuit current, voltage and power grid risk management and control to form a standard operation mode; and according to the standard operation mode, identifying the main network safety bearing capacity and the bayonet of each district in the standard operation mode, and forming the main network safety bearing capacity and the power supply bayonet of the extra-large city power grid in the standard operation mode. According to the method, the power grid load requirement, the main grid safety bearing capacity, the bayonet and the production efficiency of the power transmission and transformation project can be accurately identified.

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 the subsequent planning and construction of power grids, the effect of transmission and transformation projects on improving the safety carrying capacity of the main grid is the most important reference factor and the key basis for the feasibility of various power grid construction and transformation projects. The corresponding main grid's abundant safety carrying capacity can also serve to attract investment for major projects, avoiding the dilemma of users being unable to use electricity after investing a large amount of money.

[0003] The existing domestic safety carrying capacity assessment methods are mainly concentrated on provincial power grids and local distribution networks. The provincial power grid assessment method focuses on the balance and optimization of power and electricity in the entire network, and pays less attention to the power demand of local governments and users. The algorithm focuses on reserving as much power grid safety margin as possible. When assessing the safety carrying capacity of megacities, it is not necessary to consider inter-provincial power transactions, which simplifies the power balance algorithm. However, it is necessary to focus on user power demand, verify power-rich areas, and use emergency methods to eliminate bottlenecks, so as to meet the power supply needs of local governments and users as much as possible under safety constraints.

[0004] The verification method of the safety carrying capacity of the local distribution network is very different from that of the main network. The distribution network is open-loop operation. After the distribution network equipment fails, the load will be lost for a short time. There is no need to verify whether the safety constraints are met in accordance with the "Guidelines for Safety and Stability of Power Systems" (GB 38755-2019). The main network mainly operates in a closed loop and partially in an open loop. After a failure, there will be flow transfer, voltage, and frequency fluctuations. The safety constraints in the "Guidelines for Safety and Stability of Power Systems" (GB 38755-2019) must be met.

[0005] At the same time, various methods and standards are used to evaluate the performance of power transmission and transformation projects, resulting in some projects not producing results as 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 be put into operation on schedule. It is necessary to reasonably evaluate the performance of power transmission and transformation projects to guide project planning and construction.

[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 cannot accurately identify the safe carrying capacity and checkpoints of the main network of the urban power grid, and cannot accurately evaluate the effectiveness of the commissioning of power transmission and transformation projects. 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, which is the most core data for the preparation and implementation of power supply guarantee work plans for urban power grids during the peak summer and winter, and major decisions. On this basis, the calculated power transmission and transformation project efficiency evaluation method quantitatively evaluates the role of the commissioning of power transmission and transformation projects, 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, evaluate the load demand of each substation in the area during the high-load period of winter and summer; based on the installed capacity of the grid-connected power source, energy storage and the newly connected power source and energy storage, evaluate the peak power generation capacity of each power source and energy storage facility;

[0011] According to the load demand of the area and the peak power generation capacity, the topological relationship between low-voltage substations, power sources, energy storage and high-voltage substations is established, and 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 safety carrying capacity and power supply checkpoints under the standard operation mode of each area, when there is a load checkpoint in the area, the area has no surplus power grid capacity; when there is no load checkpoint in the area, the surplus carrying capacity of the power grid in the area is checked;

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

[0016] Furthermore, based on the historical load of each substation and the list of newly connected users, the load demand of each substation in the winter and summer high-load period is evaluated; based on the installed capacity of the grid-connected power source, energy storage and the newly connected power source and energy storage, the peak power generation capacity of each power source and energy storage facility is evaluated, including:

[0017] S101: According to 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 of 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's additional load in S101;

[0019] S103: Calculate the winter and summer load of the substation, which is the winter and summer load of the substation = historical maximum load × natural growth rate of load + new power load added by users; and the natural growth rate of load is not calculated for new sites, only the new power load is calculated;

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

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

[0022] S201: The line connecting the 110kV substation to the upper 220kV substation is regarded as a 110kV power line, and the line between 110kV substations is regarded as a 110kV interconnection line; if there is only one 110kV power line, the line is directly closed; if there are ≥2 110kV power lines, only the line with the smallest impedance is closed, and the other lines remain disconnected; if the 110kV substation has only interconnection lines but no power lines, the interconnection line with the smallest impedance is closed, and the other lines remain disconnected;

[0023] S202: The lines connecting the 220kV substation to the upper 500kV substation are regarded as 220kV power lines, and the lines between 220kV substations are regarded as 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 large to small; the 220kV power lines or tie lines with more serious 220kV busbar short-circuit currents on both sides will be disconnected first, followed by the 220kV power lines or tie lines with more serious 220kV busbar short-circuit currents on one side;

[0025] S204: After each line is disconnected, all 220kV bus short-circuit currents in the entire network are traversed once, and the 220kV bus that exceeds the standard is reordered, and step S203 is executed until the short-circuit current of all 220kV bus in the entire network does not exceed 50kA. After this step is completed, the entire network forms a 500kV line closed operation; the 220kV substation is divided into sections, and the lines within the section are all in a closed state, and the lines between sections are in an open 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 power supply area is divided to form a standard operation mode, which also includes:

[0027] S205: After the short-circuit current is checked, the fault check of 500kV and 220kV main transformer N-1, 500kV and 220kV line N-1, 500kV and 220kV same-tower line N-2, and 220kV / 110kV bus N-1 is carried out on all power grid equipment, and the substations with voltage drops exceeding 10% under each fault are recorded;

[0028] S206: During the voltage verification, synchronously record the power angle change trend 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 bus N-1. If the power angle oscillation angle gradually decreases, it is regarded as passing the power angle stability verification;

[0029] S207: After the short-circuit current, voltage and power angle verification are passed, the current mode is manually verified for grid risk control. The 220kV substation with single-line and double-circuit power supply on the same tower is operated separately, and is supplied by two different 500kV areas respectively. If the 220kV substation cannot be divided, 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 bus voltage drops by more than 10%, 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 cannot be adjusted due to network topology not being met, it will be skipped. For each substation adjusted, the nearby lines and busbars will be repeatedly checked for faults until the voltage requirements are met.

[0032] For 220kV substations with voltage drops exceeding 10%, the 110kV substations supplied will be adjusted to other 220kV substations according to load from small to large. If the 110kV substation cannot be adjusted due to network topology, 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.

[0035] Furthermore, according to the standard operation mode, the main network safety carrying capacity and the checkpoint under the standard operation mode of each area are identified, and the main network safety carrying capacity and the power supply checkpoint under the standard operation mode of the megacity 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 current exceeds the current carrying capacity after the fault, and main transformers whose load exceeds the rated capacity of the main transformer * 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 thermal overload in a single 500kV area, or there may be one or more equipment thermal overload. Select the one with the largest thermal overload coefficient, then the thermal stability constraint main grid safety carrying capacity = off-grid load under standard operation mode / maximum thermal overload coefficient, and the load in the area that exceeds the thermal stability constraint main grid safety 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: Single 500kV area main grid safe carrying capacity = standard operation mode area load - 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, according to the main grid safety carrying capacity and power supply checkpoints under the standard operation mode of each area, when there is a load checkpoint in the area, the area has no grid surplus capacity; when there is no load checkpoint in the area, the grid surplus carrying capacity of the area is checked, including:

[0043] S401: Read the fault verification results of 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 bus N-1 in the non-overload 500kV area, and select the equipment with the highest load rate among them, namely, 500kV main transformer, 220kV line, and 220kV main transformer;

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

[0045] S403: Based on the maximum load that can be carried by the area under the thermal stability constraint conditions, the short-circuit current, voltage, and power angle under the fault condition are checked again; if all the checks are passed, the maximum load that can be carried under the current thermal stability constraint conditions is the maximum load that can be carried by the area; if one or several checks fail, the area load is reduced until all the constraint conditions are met. At this time, the area load is the maximum load that can be carried by the area, and the maximum load that can be carried by the area is not less than the safe carrying capacity of the main grid of the area;

[0046] S404: The surplus carrying capacity of 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 220kV 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 load demand of each substation during the winter and summer high-load period based on the historical load of each substation and the list of newly connected users; and to assess the peak power generation capacity of each power source and energy storage facility based on the installed capacity of the grid-connected power source, energy storage and the newly connected power source and energy storage;

[0050] A standard mode generating unit is used to establish a topological relationship between low-voltage substations, power sources, energy storage and high-voltage substations according to the load demand of the area and the peak power generation capacity, and 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 network of a megacity power grid. The safe carrying capacity data obtained effectively quantifies the safe carrying capacity of the main network of the power grid. It is the most core data for the preparation and implementation of power supply guarantee plans for the city power grid during the peak summer and winter, 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, providing a core basis for the distribution of electric power and power supply and even 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 investment promotion 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 embodiments and drawings. The exemplary embodiments of the present invention and their description 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: Evaluate the load demand of each substation in the winter and summer high-load period based on the historical load of each substation and the list of newly connected users; evaluate the peak power generation capacity of each power source and energy storage facility based on the installed capacity of the existing grid-connected power source, energy storage and the newly connected power source and energy storage;

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

[0064] S101: According to 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 of 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's additional load in S101;

[0066] S103: Calculate the winter and summer load of the substation, which is the winter and summer load of the substation = historical maximum load × natural growth rate of load + new power load added by users; and the natural growth rate of load is not calculated for new sites, only the new power load is calculated;

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

[0068] S2: According to the load demand of the area and the peak power generation capacity, the topological relationship between low-voltage substation, power supply, energy storage and high-voltage substation is established, and 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 regarded as a 110kV power line, and the line between 110kV substations is regarded as a 110kV interconnection line; if there is only one 110kV power line, the line is directly closed; if there are ≥2 110kV power lines, only the line with the smallest impedance is closed, and the other lines remain disconnected; if the 110kV substation has only interconnection lines but no power lines, the interconnection line with the smallest impedance is closed, and the other lines remain disconnected;

[0071] S202: The lines connecting the 220kV substation to the upper 500kV substation are regarded as 220kV power lines, and the lines between 220kV substations are regarded as 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 large to small; the 220kV power lines or tie lines with more serious 220kV busbar short-circuit currents on both sides will be disconnected first, followed by the 220kV power lines or tie lines with more serious 220kV busbar short-circuit currents on one side;

[0073] S204: After each line is disconnected, all 220kV bus short-circuit currents in the entire network are traversed once, and the 220kV bus that exceeds the standard is reordered, and step S203 is executed until all 220kV bus short-circuit currents in the entire network do 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 an open state; 110kV substations have and only have one power line, and 110kV substations without power lines have and only have one contact line, and the remaining lines are all in an open state, realizing open-loop operation;

[0074] S205: After the short-circuit current is verified, all power grid equipment is verified for faults 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. 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 a 220kV substation cannot be adjusted because the network topology is not satisfied, it will be skipped. After each substation is adjusted, the nearby lines are checked repeatedly. , conduct a busbar fault check until the voltage requirements are met; (2) For 220kV substations with a voltage drop of more than 10%, the 110kV substations supplied will 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, it will 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 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.

[0075] S206: During the voltage verification, synchronously record the power angle change trends of the generator sets in each 500kV area in the synchronous system and the designated large-scale 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 bus 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 supplied 220kV substations 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 failure 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 mode is manually verified for grid risk control. The 220kV substation with single-line and double-circuit power supply on the same tower is operated separately, and is supplied by two different 500kV areas respectively. If the 220kV substation cannot be divided, it will be skipped.

[0077] S3: 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;

[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 current exceeds the current carrying capacity after the fault, and main transformers whose load exceeds the rated capacity of the main transformer * 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: There may be no equipment thermal overload in a single 500kV area, or there may be one or more equipment thermal overload. Select the one with the largest thermal overload coefficient, then the thermal stability constraint main grid safety carrying capacity = off-grid load under standard operation mode / maximum thermal overload coefficient, and the load in the area that exceeds the thermal stability constraint main grid safety carrying capacity is included in the thermal stability constraint power supply card;

[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: Single 500kV area main grid safe carrying capacity = standard operation mode area load - 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 step 2 and step 3 are mutually optimized and do not pursue the global optimum.

[0086] S4: According to the main grid safety carrying capacity and power supply checkpoints under the standard operation mode of each area, when there is a load checkpoint in the area, the area has no grid surplus capacity; when there is no load checkpoint in the area, check the grid surplus carrying capacity of the area;

[0087] Step S4 specifically includes:

[0088] S401: Read the fault verification results of 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 bus N-1 in the non-overload 500kV area, and select the equipment with the highest load rate among them, namely, 500kV main transformer, 220kV line, and 220kV main transformer;

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

[0090] S403: Based on the maximum load that can be carried by the area under the thermal stability constraint conditions, the short-circuit current, voltage, and power angle under the fault condition are checked again; if all the checks are passed, the maximum load that can be carried under the current thermal stability constraint conditions is the maximum load that can be carried by the area; if one or several checks fail, the area load is reduced until all the constraint conditions are met. At this time, the area load is the maximum load that can be carried by the area, and the maximum load that can be carried by the area is not less than the safe carrying capacity of the main grid of the area;

[0091] S404: The surplus carrying capacity of 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 220kV 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 to 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 checkpoints and surplus carrying capacity, evaluate the impact of the non-operation or operation of the transmission and transformation project on the grid's carrying capacity, power supply checkpoints and surplus carrying capacity, and obtain the magnitude of the impact; the magnitude of the impact is the production efficiency of the 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 where the power transmission and transformation project is located before it is put into operation.

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

[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 which 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 the efficiency values ​​of improving the surplus carrying capacity respectively represent the quality and efficiency of power supply guarantee and the reserved power potential for economic development.

[0099] In the specific implementation, take 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 as an example:

[0100] The first step is to evaluate the load demand and peak power generation capacity of the area. The historical maximum load of each substation in the entire network from September 2023 to July 2024 was collected, among which the maximum load demand of the 500 kV TX area was 3.3 million kilowatts; after collecting the list of new users and the newly invested 220 kV substation, the total load of users connected to the area was 265,000 kilowatts; the average operating life of the switch intervals of each substation in the area was 4.24 years, so the natural growth rate was 7.07%; there was no new power supply or energy storage. Therefore, the load demand of the TX area in 2024 = 330*107.07%+26.5 = 3.7983 million kilowatts ≈ 3.8 million kilowatts.

[0101] The second step is to establish a topological relationship and form a standard operation mode. The 110kV substation is topologically connected with the upper 220kV station in the form of "one main and one backup", and all 220kV station lines are closed. All 220kV busbars with short-circuit currents exceeding 50kA are identified and sorted from large to small, and the 220kV lines are disconnected in sequence until the short-circuit current of all 220kV busbars does not exceed 50kA. After the short-circuit current is verified, the TX area includes 220kV SL, DM, BH, HS, SS, RP, SQZ, MHC, CC, YL, JY substations and the corresponding 110kV substations. Based on this operation mode, voltage verification and power angle verification are carried out, and all pass, that is, a standard operation mode is formed, without voltage constraint checkpoints and power angle constraint checkpoints.

[0102] The third step is to check the safe carrying capacity of the power grid and the power supply checkpoint. In the 500kV TX area, all 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 fault checks were carried out. After calculation, it was found that the thermal overload coefficient of the TX main transformer was the highest, reaching 1.49. Therefore, the safe carrying capacity of the thermal stability constraint main grid in the TX area = 380 / 1.49 = 2.55 million kilowatts, and the thermal stability constraint checkpoint = 380-255 = 1.25 million kilowatts. Since there is no voltage constraint checkpoint and power angle constraint checkpoint, the checkpoint of the 500kV TX area is 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 checkpoints, the surplus capacity of the power grid in this area is 0.

[0104] The fifth step is to verify the effectiveness of key supply guarantee projects. If the 500kV Shiling high-speed transmission and transformation project can be put into operation, after establishing the topological relationship and forming the standard operation mode, due to the short-circuit current limitation, the 500kV Shiling high-speed and TX areas cannot be operated as a group, and need to be operated independently. The 220kV SL, DM, BH, and HS in the 500kV TX area with a total load of 1.2 million kilowatts are transferred to the 500kV Shiling high-speed area. The load of the 500kV TX area has dropped from 3.8 million kilowatts to 2.6 million kilowatts. The thermal overload coefficient of the main transformer is still the highest, but it has dropped to 1.02. The thermal stability constraint of the 500kV TX area main network safety carrying capacity = 260 / 1.02 = 2.55 million kilowatts, and the thermal stability constraint checkpoint is reduced to 50,000 kilowatts, that is, the area checkpoint is reduced by 1.2 million kilowatts. The load of the 500 kV Shiling High-voltage area was proportionally amplified for fault verification. 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 load-bearing capacity was 170-120=500,000 kilowatts.

[0105] Therefore, after evaluation, the grid's safe carrying capacity improvement efficiency value of the key summer supply guarantee 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 party, it is 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, and the system corresponds to the function of a 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 load demand of each substation during the winter and summer high-load period based on the historical load of each substation and the list of newly connected users; and to assess the peak power generation capacity of each power source and energy storage facility based on the installed capacity of the grid-connected power source, energy storage and the newly connected power source and energy storage;

[0111] A standard mode generating unit is used to establish a topological relationship between low-voltage substations, power sources, energy storage and high-voltage substations according to the load demand of the area and the peak power generation capacity, and 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 also includes:

[0114] The verification unit is used to verify the safe carrying capacity of the main grid and the power supply checkpoints under the standard operation mode of each area. When there is a load checkpoint in the area, the area has no surplus power grid capacity; when there is no load checkpoint in the area, the surplus carrying capacity of the power grid in the area is verified;

[0115] The production efficiency evaluation unit is used to evaluate the impact of the non-production or production 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 production 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 a method for analyzing the safe carrying capacity of a main grid of a megacity power grid in Example 1, and will not be described one by one 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 the power supply bayonet 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 preparation 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 may be provided as methods, systems, or computer program products. Therefore, the present application may 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 may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include 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 generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes 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 capable of directing a computer or other programmable data processing device to operate 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 A 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 operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified 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 main grid of a megacity power grid, characterized in that: The method includes: Based on the historical load of each substation and the list of newly connected users, evaluate the load demand of each substation in the area during the high-load period of winter and summer; based on the installed capacity of the grid-connected power source, energy storage and the newly connected power source and energy storage, evaluate the peak power generation capacity of each power source and energy storage facility; According to the load demand of the area and the peak power generation capacity, the topological relationship between low-voltage substations, power sources, energy storage and high-voltage substations is established, and 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, 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.

2. A method for analyzing the safe carrying capacity of a main grid of a megacity power grid according to claim 1, characterized in that: The method further includes: According to the main grid safety carrying capacity and power supply checkpoints under the standard operation mode of each area, when there is a load checkpoint in the area, the area has no surplus power grid capacity; when there is no load checkpoint in the area, the surplus carrying capacity of the power grid in the area is checked; Based on the main grid's safe carrying capacity, power supply checkpoints and surplus carrying capacity, the impact of the non-operation or operation of the transmission and transformation project on the grid's carrying capacity, power supply checkpoints and surplus carrying capacity are evaluated respectively to obtain the magnitude of the impact; the magnitude of the impact is the production efficiency of the transmission and transformation project.

3. A method for analyzing the safe carrying capacity of a main grid of a megacity power grid according to claim 1, characterized in that: According to the historical load of each substation and the list of newly connected users, the load demand of each substation in the area during the high load period of winter and summer is evaluated; Based on the installed capacity of existing grid-connected power sources, energy storage and new grid-connected power sources and energy storage, the peak power generation capacity of each power source and energy storage facility is evaluated, including: S101: According to 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; S102: Calculate the load growth rate of each substation, the natural growth rate of the load of 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's additional load in S101; S103: Calculate the winter and summer load of the substation, which is the winter and summer load of the substation = historical maximum load × natural growth rate of load + new power load added by users; The natural growth rate of load is not calculated for newly invested sites, only the newly added power load is calculated; S104: Obtain historical data through the SCADA system, calculate the average daily maximum power generation of grid-connected power sources and energy storage during the summer and winter periods of previous years, add it to the declared power generation capacity of new grid-connected power sources and energy storage, and return it to the corresponding substation according to the grid connection point to obtain the peak power generation capacity of each substation.

4. A method for analyzing the safe carrying capacity of a main grid of a megacity power grid 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 regarded as a 110kV power line, and the line between 110kV substations is regarded as a 110kV interconnection line; if there is only one 110kV power line, the line is directly closed; if there are ≥2 110kV power lines, only the line with the smallest impedance is closed, and the other lines remain disconnected; if the 110kV substation has only interconnection lines but no power lines, the interconnection line with the smallest impedance is closed, and the other lines remain disconnected; S202: The lines connecting the 220kV substation to the upper 500kV substation are regarded as 220kV power lines, and the lines between 220kV substations are regarded as 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 large to small; the 220kV power lines or tie lines with the larger excess short-circuit currents of the 220kV busbars on both sides will be disconnected first, followed by the 220kV power lines or tie lines with the larger excess short-circuit currents of the 220kV busbars on one side; S204: After each line is disconnected, all 220kV bus short-circuit currents in the entire network are traversed once, and the 220kV bus that exceeds the standard is reordered, and step S203 is executed until the short-circuit current of all 220kV bus in the entire network does not exceed 50kA, and the entire network forms a 500kV line closed operation; the 220kV substation is divided into sections, and the lines within the sections are all in a closed state, and the lines between sections are in an open 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.

5. A method for analyzing the safe carrying capacity of a main grid of a megacity power grid according to claim 4, characterized in that: Divide the power supply area and form a standard operation mode, which also includes: S205: After the short-circuit current is checked, the fault check of 500kV and 220kV main transformer N-1, 500kV and 220kV line N-1, 500kV and 220kV same-tower line N-2, and 220kV / 110kV bus N-1 is carried out on all power grid equipment, and the substations with voltage drops exceeding 10% under each fault are recorded; S206: During the voltage verification, synchronously record the power angle change trend 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 bus N-1. If the power angle oscillation angle gradually decreases, it is regarded as passing the power angle stability verification; S207: After the short-circuit current, voltage and power angle verification are passed, the current mode is manually verified for grid risk control. The 220kV substation with single-line and double-circuit power supply on the same tower is operated separately, and is supplied by two different 500kV areas respectively. If the 220kV substation cannot be divided, it will be skipped.

6. A method for analyzing the safe carrying capacity of a main grid of a megacity power grid according to claim 5, characterized in that: The step S205 records the substations where the voltage drops by more than 10% under each fault, including: For 500kV substations where the bus voltage drops by more than 10%, 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 cannot be adjusted due to network topology not being met, it will be skipped. For each substation adjusted, the nearby lines and busbars will be repeatedly checked for faults until the voltage requirements are met. For 220kV substations with voltage drops exceeding 10%, the 110kV substations supplied will be adjusted to other 220kV substations according to load from small to large. If the 110kV substation cannot be adjusted due to network topology, 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.

7. A method for analyzing the safe carrying capacity of a main grid of a megacity power grid 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 current exceeds the current carrying capacity after the fault, and main transformers whose load exceeds the rated capacity of the main transformer * 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 safety 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 safety carrying capacity is included in the thermal stability constraint power supply card port; 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 port; S306: According to steps S303-S305, the safe carrying capacity and power supply port of the 220kV site main grid are calculated.

8. A method for analyzing the safe carrying capacity of a main grid of a megacity power grid according to claim 2, characterized in that: According to the main grid safety carrying capacity and power supply checkpoints under the standard operation mode of each area, when there is a load checkpoint in the area, the area has no grid surplus capacity; when there is no load checkpoint in the area, the grid surplus carrying capacity of the area is checked, including: S401: Read the fault verification results of 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 bus N-1 in the non-overload 500kV area, and select the equipment with the highest load rate among them, namely, 500kV main transformer, 220kV line, and 220kV main transformer; S402: the load of the area is enlarged in the same proportion until the load rate of the 500 kV main transformer and the 220 kV line in the area reaches 100% for the first time after the fault verification is completed, and the load of the area at this time is recorded as the maximum load that can be carried by the area under the condition of thermal stability constraint; S403: Based on the maximum load that can be carried by the area under the thermal stability constraint conditions, the short-circuit current, voltage, and power angle under the fault condition are checked again; if all the checks are passed, the maximum load that can be carried under the current thermal stability constraint conditions is the maximum load that can be carried by the area; if one or several checks fail, the area load is reduced until all the constraint conditions are met. At this time, the area load is the maximum load that can be carried by the area, and the maximum load that can be carried by the area is not less than the safe carrying capacity of the main grid of the area; S404: The surplus carrying capacity of 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 220kV main transformer is calculated.

9. A system for analyzing the safety carrying capacity of a main grid of a megacity power grid, characterized in that: The system includes: The source-grid-load-storage assessment unit is used to assess the load demand of each substation during the winter and summer high-load period based on the historical load of each substation and the list of newly connected users; and to assess the peak power generation capacity of each power source and energy storage facility based on the installed capacity of the grid-connected power source, energy storage and the newly connected power source and energy storage; A standard mode generating unit is used to establish a topological relationship between low-voltage substations, power sources, energy storage and high-voltage substations according to the load demand of the area and the peak power generation capacity, and 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; 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.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, a method for analyzing the safe carrying capacity of a main grid of a megacity power grid as claimed in any one of claims 1 to 8 is implemented.

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