Power transmission section transmission capacity analysis method and system considering multi-resource coupling relationship

Abstract

The invention provides a power transmission section transmission capacity analysis method and system considering a multi-resource coupling relationship, and the method comprises the steps: carrying out the three-permanent fault testing of a transmission line in a full wiring state and a maintenance state, and dividing a transmission section cut set based on the voltage stability and power angle stability sensitivity; in a normal operation state, carrying out on-off operation on the restricted fault line, and checking and obtaining a power transmission limit of a sending-out section in a static and stable state; in a normal operation state and a maintenance state, through adjusting a coupling relation among a load, new energy and starting-up, checking and obtaining a sending-out section power transmission limit of a restricted fault line under transient stability; and according to the power transmission limits of the sending-out section under static stability and transient stability, an operation rule is formulated. According to the method, the coupling relation of multiple resources is adjusted, and the power transmission limit which restricts the fault line to be transmitted out of the section under static and transient stability is checked and obtained, so that the accuracy and reliability of analyzing the transmission capacity of the power transmission section are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system analysis, and in particular to a method and system for analyzing transmission capacity of a power transmission section taking into account a multi-resource coupling relationship. Background Art

[0002] The research on transmission capacity of power transmission sections plays a very important role in social production and life. If the transmission power exceeds the transmission limit capacity, once the power angle and voltage of the system become unstable due to improper handling of internal faults or external force majeure factors, it will have a very serious adverse impact on the entire social production and people's lives.

[0003] At present, traditional power transmission capacity analysis issues mostly consider the transmission of thermal power units in the transmission area or wind-fire, wind-water bundled transmission, and believe that the power angle stability under this transmission form is the dominant factor restricting the power transmission capacity. However, with the access of new energy and the growth of load, the transmission of multiple resources such as thermal power, pumped storage, and new energy is becoming more and more common. With the access of a high proportion of new energy and the growth of load groups, the traditional power angle stability constraint will gradually transform into a dual constraint of power angle and voltage stability on power transmission capacity. However, the existing transmission capacity analysis rarely involves the problem of weak voltage support in this case. Summary of the invention

[0004] In order to solve the problems of weak voltage support and limited power transmission capacity under the condition of multi-resource transmission, the present invention proposes a transmission section transmission capacity analysis method and system considering the multi-resource coupling relationship. The method first divides the transmission section cut set, determines the power transmission capacity restriction fault through simulation verification, and performs static stability verification and transient stability verification under the restriction fault. In the transient stability verification, the control variable method is adopted to comprehensively analyze the transmission section capacity of the new energy, load, and startup coupling relationship, thereby realizing a more comprehensive power transmission capacity evaluation.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for analyzing transmission capacity of a transmission section considering a multi-resource coupling relationship, comprising:

[0007] In the full connection state and the maintenance state, the three permanent fault tests are carried out on the transmission line respectively, and the transmission section cut sets are divided based on the sensitivity of voltage stability and power angle stability; the line with the greatest sensitivity to voltage stability and power angle stability in the transmission section cut set is taken as the restraining fault line;

[0008] Under normal operating conditions, the control fault line is disconnected to check and obtain the power transmission limit of the sending section under static stability;

[0009] In normal operation and maintenance status, the coupling relationship between load, new energy and startup is adjusted to check and obtain the transmission limit of the section that restricts the fault line under transient stability.

[0010] The operating regulations are determined based on the extreme limiting conditions of the sending section under static stability and transient stability.

[0011] Preferably, the normal operating state refers to the operating state of the power system without any faults or abnormalities;

[0012] The fully connected state refers to a state in which all devices in the power system are in normal operation and are all connected together according to preset requirements;

[0013] The overhaul status refers to a state in which the power system needs to temporarily stop operating due to overhaul, maintenance or fault handling.

[0014] Preferably, the three-permanent fault test is performed on the transmission line, and the transmission section cut sets are divided based on the sensitivity of voltage stability and power angle stability, specifically:

[0015] Perform three permanent fault simulations on the transmission line, gradually start the sending-end units to increase the line power until the transmission line becomes unstable, and calculate the maximum power transmission capacity of the transmission line; the maximum power transmission capacity is the power transmission capacity at critical stability;

[0016] The maximum power transmission capacity of each transmission line is sorted from small to large, and based on the set maximum power transmission capacity value, the transmission lines that are sensitive to voltage stability and power angle stability are screened out;

[0017] The sensitive outgoing transmission lines obtained in the full connection state and the maintenance state are combined to obtain the outgoing section cut set.

[0018] Preferably, the sending-end unit includes all sending-out units and new energy power generation equipment.

[0019] Preferably, the interruption operation on the constrained fault line is performed to check and obtain the power transmission limit of the sending section under static stability, which specifically includes: gradually increasing the power of the sending-end unit, reducing the power of the receiving-end unit by the same amount or increasing the load of the receiving-end unit by the same amount, solving the maximum transmission power of the constrained fault line, and obtaining the static power angle stability limit.

[0020] Preferably, the method of adjusting the coupling relationship among load, new energy and startup to check and obtain the transmission limit of the section that restricts the fault line from transmitting under transient stability specifically includes:

[0021] Set the load, new energy, and startup to different gears, fix any gear, and gradually increase the transmission power of the transmission section until the critical point of transient instability under the restraining fault is reached;

[0022] Gradually change the load gear and repeat the above process of increasing the transmission power of the transmission section until instability occurs, so as to obtain the projection of the relationship surface between load, new energy and startup on the load axis;

[0023] Based on the projection, the relationship between any two variables is obtained, and finally the critical stability plane is determined to obtain the power transmission limit of the transmission section.

[0024] Preferably, the operation regulations for determining the maximum transmission limit of the transmission section under static stability and transient stability specifically include:

[0025] Determine the minimum section power according to the transmission limit of the transmission section under static stability and transient stability respectively, compare the minimum section powers, and take the smaller value as the comprehensive minimum section power;

[0026] The startup and new energy output of the transmission area are regulated according to the comprehensive minimum section power, or the section power is controlled according to different startup gears.

[0027] In a second aspect, the present invention provides a transmission section transmission capacity analysis system considering multi-resource coupling relationships, comprising:

[0028] The cut set division module is used to perform three-permanent fault tests on the transmission line in the full connection state and the maintenance state, and divide the transmission section cut sets based on the sensitivity of voltage stability and power angle stability; the line with the greatest sensitivity to voltage stability and power angle stability in the transmission section cut set is taken as the restraining fault line;

[0029] A static stability checking module is used to perform a disconnection operation on the constrained fault line, check and obtain the power transmission limit of the sending section under static stability;

[0030] The transient stability verification module is used to verify and obtain the transmission limit of the section that restricts the fault line under transient stability by adjusting the coupling relationship between load, new energy and startup in normal operation and maintenance status;

[0031] The regulation formulation module is used to determine the operating regulations based on the transmission limit of the transmission section under static stability and transient stability.

[0032] In a third aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in a method for analyzing the transmission capacity of a transmission section taking into account the coupling relationship of multiple resources as described in the first aspect.

[0033] In a fourth aspect, the present invention provides a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps in a method for analyzing the transmission capacity of a transmission section taking into account the coupling relationship of multiple resources as described in the first aspect are implemented.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention comprehensively considers the coupling relationship between thermal power, pumped storage, new energy and other resources in the full connection state, maintenance state and normal operation state, conducts three permanent fault tests, voltage stability and power angle stability sensitivity analysis, and checks the power transmission limit of the fault-constrained line under static stability and transient stability. It effectively solves the problem that the traditional power transmission capacity analysis only considers thermal power units or wind-fire, wind-water bundled transmission, and ignores the weak voltage support caused by the high proportion of new energy access and the growth of load groups, realizes a comprehensive and accurate assessment of the transmission capacity of the transmission section, and provides a scientific basis for the formulation of operation regulations.

[0036] (2) The present invention uses simulation to check the transmission limit of the line to determine the relationship between the line and the stability sensitivity, selects a line set with high sensitivity and containing the sending-end unit as a section cut set, and by dividing the transmission section cut set, it can accurately identify the transmission lines that are most sensitive to voltage stability and power angle stability. These lines constitute the key connection points between the sending-end and receiving-end power grids. This effectively distinguishes the sending-end and receiving-end power grids, providing an important basis for power grid planning, operation and dispatching.

[0037] (3) The present invention proposes both static stability check and transient stability check, which can comprehensively evaluate the transmission capacity of the transmission section under different operating conditions and ensure that the power grid can maintain stable operation when facing various faults and abnormal conditions. Static stability check focuses on the stability of the system in long-term operation, while transient stability check focuses on the system's ability to respond quickly to emergencies. The combination of the two provides a scientific basis for formulating more accurate and effective operating regulations, thereby improving the overall safety and reliability of the power grid.

[0038] (4) In the analysis of power transmission capacity, the present invention studies the relationship between thermal power, load and renewable energy through the control variable method, and finally generates a three-dimensional graph, which intuitively and effectively shows the impact of each variable on the transmission capacity. It not only helps to deeply understand the coupling effect of various resources in the power grid, but also provides strong support for the formulation of targeted operation strategies and scheduling plans, thereby ensuring the stable operation of the power grid and efficient power transmission.

[0039] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention but do not constitute a limitation of the present invention.

[0041] Figure 1 A main flow chart of a method for analyzing transmission capacity of a power transmission section considering multi-resource coupling relationships provided by an embodiment of the present invention;

[0042] Figure 2 A schematic diagram of the 500kV grid in the Yantai-Weihai area and the main supply area provided by the embodiment of the present invention;

[0043] Figure 3 The static stability limit verification curve provided by the embodiment of the present invention;

[0044] Figure 4 The PV relationship curve of the light-life double power outage mode provided in the embodiment of the present invention;

[0045] Figure 5 A simplified schematic diagram of a smoke delivery system provided in an embodiment of the present invention;

[0046] Figure 6 A comparison diagram of the power angles of the units of the Laizhou Power Plant in the delivery area and the Qingdao Power Plant in the delivery point area provided by the embodiment of the present invention;

[0047] Figure 7 A schematic diagram of the power output section provided by the embodiment of the present invention in addition to the optical life double;

[0048] Figure 8 A comparison diagram of motor load slip between Zhongqiao Station in the delivery area and Lishan Station in the landing area provided by an embodiment of the present invention;

[0049] Fig. 9 A schematic diagram of a 500kV substation voltage curve in a transmission area and a landing area provided in an embodiment of the present invention;

[0050] Fig.10 A schematic diagram of a critical stability plane under the coupling relationship between new energy, startup, and load provided in an embodiment of the present invention;

[0051] Fig.11 A schematic diagram of the power angle of Laizhou Power Plant in different cross-section power critical instability modes provided by an embodiment of the present invention;

[0052] Fig.12 A schematic diagram of Laoshan bus voltage in different cross-section power critical instability modes provided by an embodiment of the present invention;

[0053] Fig.13 A three-dimensional schematic diagram of the relationship between new energy and startup provided by an embodiment of the present invention;

[0054] Fig.14 A schematic diagram of a curve of correlation between new energy and startup provided in an embodiment of the present invention;

[0055] Fig.15A three-dimensional schematic diagram of the load and startup relationship projection provided by an embodiment of the present invention;

[0056] Fig.16 A schematic diagram of a load and startup correlation curve provided in an embodiment of the present invention;

[0057] Fig.17 A three-dimensional schematic diagram of the relationship between new energy and load provided in an embodiment of the present invention;

[0058] Fig.18 A schematic diagram of a new energy and load correlation curve provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0059] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0060] Technical term explanation

[0061] 1. Transmission capacity of power transmission section: refers to the maximum power that can be safely and stably transmitted in a specific area or line in the power system.

[0062] 2. Power angle stability: Power angle stability refers to the ability of all synchronous motors in the power system to maintain synchronous operation after being disturbed. It is the basis for the safe and stable operation of the power system and is of great significance for ensuring the reliability, economy and safety of the power system. According to the nature and size of the disturbance, power angle stability can be divided into the following three categories:

[0063] (1) Static stability: refers to the ability of a system to maintain synchronous operation after being subjected to small disturbances.

[0064] (2) Transient stability: refers to the ability of a system to recover to a synchronous operating state within a period of time after being subjected to a large disturbance.

[0065] (3) Dynamic stability: refers to the ability of a system to maintain or return to a synchronous operating state after being subjected to periodic or non-periodic disturbances.

[0066] 3. Voltage stability: Voltage stability refers to the ability of the power system to maintain or restore the system voltage to the allowable range without voltage collapse after the power system is disturbed. It is one of the important conditions for the normal operation of the power system. Voltage stability depends on the support of reactive power. Reactive power establishes and maintains the electromagnetic field in electrical equipment, completes the mutual conversion of electromagnetic energy, and provides voltage support for the system.

[0067] 4. Cut set: also called cut set or cut-off set, is a basic concept in graph theory and network analysis. In power systems, a cut set usually refers to a set of edges that can divide the power grid into two independent parts under certain conditions. If all the edges in the edge set are removed, the power grid will be separated into two and only two subgraphs that are separated from each other but connected to each other; if any edge in the edge set is retained and not removed, the power grid is still connected.

[0068] Embodiment 1

[0069] like Figure 1 As shown, this embodiment discloses a method for analyzing transmission capacity of a transmission section considering a multi-resource coupling relationship, including:

[0070] S1: In the full connection state and the maintenance state, the three permanent fault tests are performed on the transmission line respectively, and the transmission section cut sets are divided based on the sensitivity of voltage stability and power angle stability; the line with the highest sensitivity to voltage stability and power angle stability in the transmission section cut set is taken as the restraining fault line.

[0071] S1 specifically includes:

[0072] S101: in the full connection state and the maintenance state, three permanent fault simulations are respectively performed on the transmission line, and the sending end units are gradually turned on to increase the line power until the transmission line becomes unstable, and the maximum power transmission capacity of the transmission line is calculated; the maximum power transmission capacity is the power transmission capacity at critical stability;

[0073] S102: sorting the maximum power transmission capacity of each transmission line from small to large, and selecting the transmission line that is sensitive to voltage stability and power angle stability based on the set maximum power transmission capacity value;

[0074] S103: Taking a union set of the sensitive outgoing transmission lines obtained in the full connection state and the maintenance state, respectively, to obtain an outgoing section cut set.

[0075] Among them, the fully connected state refers to the state in which all equipment in the power system is in normal operation and is all connected together according to preset requirements; the normal operation state refers to the operation state of the power system without any faults and abnormal conditions; the maintenance state refers to the state in which the power system needs to temporarily exit operation due to overhaul, maintenance or fault handling.

[0076] The sending-end unit includes all sending units and new energy power generation equipment.

[0077] The sensitive transmission line has a low margin in power transmission. When the power system is disturbed (such as a three-phase fault), it can quickly and significantly affect the voltage stability or power angle stability of the system, and when it is close to its maximum power transmission capacity, it is more likely to become a key factor causing system instability.

[0078] The smaller the power transmission capacity, the more sensitive the line maintenance is to stability, and the final cut set should include sensitive lines.

[0079] It should be understood that the three permanent faults refer to permanent three-phase short circuit faults, which are a serious fault type used to evaluate the stability of the system under extreme conditions and the reliability of protection actions.

[0080] As a specific implementation method, this example simulates the actual power grid system in Yantai and Weihai, Shandong power transmission areas, to illustrate the research method flow of the transmission area transmission limit. The total installed capacity of thermal power, pumped storage, nuclear power, onshore and offshore renewable energy in Yantai and Weihai is about 15,160MW, and the units are connected to 220kV and 500kV power grids respectively. The power grid structure diagram is as follows Figure 2 shown.

[0081] As a specific implementation method, three permanent faults are set for each transmission line for simulation. Different transmission limits under line faults are shown in Table 1. By checking the 500kV grid full connection mode and the fault-constraining Guangshou double-line tower N-2 under the maintenance mode, including the sensitive group, the transmission section is determined to be the Guangzhou-Shouguang double-circuit line, Dengzhou-Daze one-circuit line, Dengzhou-Laiyang one-circuit line, National Nuclear Demonstration-Laiyang one-circuit line, and three 220kV main transformers in Laiyang station send 500kV power, forming a complete cut set of Yantai-Weihai transmission sections. The transmission capacity of Yantai-Weihai area under full connection and maintenance modes is shown in the following table.

[0082] Table 1 Verification of maximum power transmission capacity under different line maintenance conditions

[0083]

[0084] Furthermore, the line with the greatest sensitivity to voltage stability and power angle stability in the transmission section is cut and concentrated as the restrained fault line.

[0085] In this specific embodiment, the faults that minimize the power transmission capacity are all the three-permanent faults of the Guangshou double line N-2, so this fault is preferably used as the restricting fault, and the line under this restricting fault is the restricting fault line.

[0086] S2: Under normal operating conditions, the constrained fault line is disconnected to check and obtain the power transmission limit of the sending section under static stability.

[0087] S2 specifically includes: gradually increasing the power of the sending-end unit, reducing the power of the receiving-end unit by the same amount or increasing the load of the receiving-end unit by the same amount, solving the maximum transmission power of the fault-constrained line, and obtaining the static power angle stability limit.

[0088] Static stability verification should be carried out in accordance with the Technical Specifications for Safety and Stability Calculation of Power Systems. The power of the sending-end units should be gradually increased, and the power of the receiving-end units should be reduced by the same amount or the load on the receiving end should be increased. The maximum transmission power of the transmission line or section is the static power angle stability limit. During the calculation process, the frequency and voltage of the system should be kept within the normal range as much as possible.

[0089] As the power of the transmission section increases, the load characteristic curve and the network characteristic curve gradually no longer have intersections, the solutions of the power system network equation decrease, and the minimum static stability limit appears in the Guangshou double-line power outage mode. The section power transmission rate reaches 8.37 million kWh, reaching the static stability limit. By checking the curve ( Figure 3 As shown in the figure, the PV curve of the delivery point is as follows: Figure 4 shown.

[0090] The static stability verification principle formula (PV curve) is as follows:

[0091]

[0092] Among them, P R and Q R is the active and reactive power consumed by the receiving end, V R is the receiving end voltage, is the receiving end voltage vector, is the voltage vector transpose of the receiving end, is the load current vector transpose, E S is the sending end voltage, Z L is the load impedance, X L is the transmission line reactance, θ R It is the angle between the real and imaginary parts of the voltage after quantization.

[0093] From the above formula, we can get:

[0094]

[0095]

[0096] Where:

[0097]

[0098] Obviously, p, q, and v are dimensionless, eliminating θ from the equation R The relationship between variables can be obtained:

[0099]

[0100] The relationship curve between variables is a nose-shaped curve, and the vertex is the critical static stability point.

[0101] S3: Under normal operation and maintenance conditions, the coupling relationship between load, new energy and startup is adjusted to check and obtain the transmission limit of the section under transient stability of the fault line. Specifically, it includes:

[0102] S301: In normal operation and maintenance states, the load, new energy, and startup are set to different gears respectively, any gear is fixed, and the transmission power of the transmission section is gradually increased until the critical point of transient instability under the restraining fault is reached;

[0103] S302: gradually changing the load gear and repeating the above process of increasing the transmission power of the transmission section until instability occurs, so as to obtain the projection of the relationship surface between the load, the new energy, and the startup on the load axis;

[0104] S303: Based on the projection, the relationship between any two variables is obtained, and finally a critical stability plane is determined to obtain the power transmission limit of the transmission section.

[0105] S304: Compare the power transmission limits of the outgoing section under transient stability obtained in the normal operation state and the maintenance state respectively, and take the minimum value as the final power transmission limit of the outgoing section under transient stability.

[0106] The startup refers to power generation output, which refers to the state that, in order to ensure the robustness of the calculation, all units are running without reserving additional spare capacity or power. In other words, the units are running at their maximum or full load output state, without reserving any power reserves for possible emergencies or uncertainties. It should be understood that under full load, setting different gears for startup is actually simulating different power system states by adjusting the load and the level of new energy output.

[0107] Transient verification is performed on the controlled faults in normal and maintenance modes. First, the load, new energy, and startup are divided into different gears (usually the operating regulations will adopt the form of grading to deal with and cover the uncertainty of the power system). When studying the relationship between new energy and startup, a certain load gear is fixed, and the transmission power of the transmission section is gradually increased until transient instability occurs under the controlled fault. At this time, the load, new energy, and startup are critical points. The load gear is gradually changed and this process is repeated. Finally, the projection of the relationship surface of the three on the load axis can be obtained. The relationship between the two variables is studied, and finally the critical stability plane can be obtained.

[0108] As a specific implementation method, assume that in a certain power system, the fixed load is 100MW, and then gradually increase the access amount of renewable energy power generation (such as wind power), and at the same time adjust the startup status (such as increasing or decreasing the output of the generator set) until the system reaches the critical point of transient instability. Record the renewable energy power generation and startup status at this time. Then, increase the load to 150MW and repeat the above process. Through multiple such experiments, a series of data points can be obtained, which can be plotted into a three-dimensional surface graph to show the relationship between load, renewable energy, and startup.

[0109] Among them, the data of new energy and startup status when the system reaches the critical point of transient instability at different load levels are collected. These data points can be plotted into a three-dimensional surface graph, where the x-axis represents the load, the y-axis represents the new energy, and the z-axis represents the startup status.

[0110] In order to study the relationship between any two variables (such as the relationship between renewable energy and startup), this three-dimensional surface graph can be projected along the load axis. This means fixing a load level (such as 100MW) and then observing the relationship between renewable energy and startup status at this load level. By changing the load level and repeating this process, a series of relationship curves between renewable energy and startup at different load levels can be obtained. By analyzing these curves, the critical stability plane of the system can be determined. This plane is the boundary at which the system remains stable under different loads, renewable energy, and startup states. When the state of the system exceeds this boundary, the system will experience transient instability.

[0111] In this specific implementation, the Yanwei area is used as a delivery area and the stability mechanism of the delivery limit situation is as follows:

[0112] The Yanwei transmission grid can be divided into three parts. The first part is the Yanwei thermal power and new energy transmission group, the second part is the Weifang and Qingdao load centers, and the third part is the external grid, which can be regarded as an infinite busbar. The three parts are in series relationship, as shown in the schematic diagram. Figure 5 As shown, T1 is the generator node, T2 is the new energy node, T3 is the load node, and T4 is the infinite bus node.

[0113] The study pointed out that by adding load nodes between the unit and the infinite bus, as the load capacity increases, the system will transform from power angle stability to a complex problem where transient power angle stability and voltage stability coexist. Taking the full wiring method as an example, considering the 50% simultaneous rate of new energy in the Yanwei area, after the Guangshou Shuangguangzhou side fault occurs, the comparison of electrical quantities in the transmission and landing areas is shown in the figure.

[0114] After the fault occurs, the group in the sending area enters the acceleration phase more quickly than the group in the landing area due to the closer electrical distance to the fault point ( Figure 6), and at the same time, the reactive power consumed by the two-wire power transfer of Guangshou ( Figure 7 ) and after the motor load is blocked in the landing area ( Figure 8 ) absorbs reactive power, and the voltage recovery in the transmission point area is slow ( Fig. 9 ), the UHV interconnection also affects the voltage recovery in the transmission area, further reducing the power angle stability margin of the unit. A serious fault in the section may cause instability in the transmission and landing area with transient voltage and power angle coexisting.

[0115] The stability of Yantai-Weihai transmission is related to the power of the transmission section. The startup capacity, load capacity, and low penetration of new energy in the Yantai-Weihai area cannot be ignored in terms of the transient stability of the transmission in the Yantai-Weihai area. By checking various faults such as single-phase, three-phase, and different-phase on the same tower in the transmission section, it is determined that the restrictive fault with the widest impact range and the greatest stability destructiveness is the Guangshou double-line Sanyong N-2 fault. The coupling relationship between load, startup, and new energy under critical stability is shown in the following table:

[0116] Table 2 Coupling relationship between critical stable load, startup and new energy

[0117]

[0118] Draw the three-dimensional critical stability surface according to the table ( Fig.10 ), the surface is composed of the intersection of two planes, Plane 1 and Plane 2, which divides the three-dimensional area into two. The red on the left is the stable area, and the light orange on the right is the unstable area. The darker the color of the critical stable plane, the higher the cross-sectional power.

[0119] Fig.10 In plane 1, as the new energy grows, the power of the transmission section continues to grow. In plane 2, as the new energy grows, the power of the transmission section reaches the transient stability limit and remains unchanged at 7.94 million kilowatts. At the intersection of the two planes, the stability characteristics of the power grid change. Taking the critical instability mode of the transmission sections of 7.6 million kilowatts and 8.1 million kilowatts as an example, the power angle of the units in the Yanwei area ( Fig.11 ) and the output drop point voltage curve ( Fig.12 )Comparison situation.

[0120] After the fault occurs, the units on both sides of the section accelerate and swing away in opposite directions under low section power (green curve), and the power angle becomes unstable as soon as it swings, while the power angle does not become unstable under high section power (blue curve). In the right figure, the voltage cannot be restored under low section power and oscillates with the instability of the power angle. When the section power is high, the voltage recovers slowly and cannot recover to 0.9pu, which does not meet the voltage stability requirements after large disturbances in the power system safety and stability guidelines.

[0121] In order to study the impact of load, startup and new energy on the transmission stability in Yantai and Weihai areas, one of the variables is kept constant and the relationship between the other two variables is studied.

[0122] (1) The load in Yantai and Weihai regions remains unchanged at 7 million. The relationship between new energy and startup is shown in Table 3 below:

[0123] Table 3 Relationship between new energy and startup

[0124]

[0125] The relationship curve between new energy and startup is as follows Fig.13 , 14 As shown in the figure on the right, the yellow dotted line is the projection of the equal power line of different transmission sections, and its intersection with the relationship curve is shown in Fig.14 exhibit.

[0126] When the transmission section power is less than the transient stability power limit, for every 500,000 kilowatts of new energy output, the unit output in the Yantai-Weihai area needs to be reduced by 160,000 kilowatts to ensure transient stability. This is because as the simultaneous rate of new energy increases, the section power increases, and the power flow transfer after the fault intensifies. Since the active power shortage will also increase during the low penetration of new energy, the transient energy injected into the system by the unit power angle acceleration is dispersed to a certain extent, which is conducive to the unit transmission and has a certain positive effect on the power angle stability.

[0127] The section power reaches the transient stable power limit of 7.94 million kilowatts. For every 500,000 kilowatt increase in new energy output, the unit output needs to be reduced by 500,000 kilowatts to ensure that the section power does not increase further. Although the increase in the simultaneous rate of new energy still has a positive effect on the stability of the power angle in the Yantai-Weihai area, the increased power transfer pressure of the transmission channel and the stalling of the motor in the load center have aggravated the contradiction of insufficient reactive support capacity. Although the system has a stable operating point after the fault, it is constrained by the channel transmission capacity and voltage support capacity, and the stable operating point cannot meet the actual operation requirements.

[0128] (2) The output of new energy in Yantai and Weihai remained unchanged at 4 million. The relationship between load and startup is shown in Table 4 below:

[0129] Table 4 Relationship between load and startup

[0130]

[0131] The relationship curve between new energy and startup is as follows Fig.15 , 16 As shown in the figure on the right, the yellow dotted line is the projection of the equal power line of different transmission sections, and its intersection with the relationship curve is shown in Fig.16 exhibit.

[0132] New energy remains unchanged, and for every 500,000 load capacity increase, the unit output can be increased by the same amount, and the cross-sectional power remains unchanged. The increase in load in the sending area is not only conducive to the unit power delivery, but also can reduce the sending cross-sectional power, which has a positive effect on stability.

[0133] (3) The unit output in Yantai and Weihai regions remains unchanged at 10.26 million kW, and the relationship between load and new energy is shown in Table 5 below:

[0134] Table 5 Relationship between load and new energy

[0135]

[0136] The relationship curve between new energy and startup is as follows Fig.17 , 18 As shown in the figure on the right, the yellow dotted line is the projection of the equal power line of different transmission sections, and its intersection with the relationship curve is shown in Fig.18 As displayed.

[0137] When the transmission section power is less than the transient stability power limit, the load needs to increase by 160,000 kilowatts for every 500,000 kilowatts of new energy output. When the section power reaches the transient stability power limit, the load needs to increase by 500,000 kilowatts for every 500,000 kilowatts of new energy output to ensure that the section power does not increase further.

[0138] Through the above analysis, reducing the startup and increasing the same capacity load have almost the same impact on system stability.

[0139] Through the study of the relationship between new energy, startup and load coupling in Yantai-Weihai area under the control fault, the impact of its transient characteristics on the transmission capacity and stability in Yantai-Weihai area is analyzed, and the following conclusions are preliminarily summarized:

[0140] (1) With the continuous growth of installed capacity in the Yantai-Weihai area, the power of the transmission section continues to increase. If a three-phase grounding fault occurs in the channel, it may cause a large-scale power flow transfer. At the same time, the transmission landing area is the load center of the province, and the influence of the motor load characteristics on the voltage cannot be ignored. Therefore, the occurrence of a restraining fault on the section will cause a complex problem of coexistence of power angle stability and voltage stability.

[0141] Through simulation verification under normal and maintenance scenarios, it was determined that the controlling fault was the Guangshou double-line Sanyong N-2 fault. The minimum static stability limit of the transmission section was 8.37 million kilowatts, and the maximum temporary stability limit was 7.94 million kilowatts. The temporary stability limit was smaller than the static stability limit.

[0142] (2) When the power of the section sent out in the Yantai-Weihai area is less than the transient stability limit power, the increase in the simultaneous rate of renewable energy requires a slight reduction in the unit output to ensure system stability. The low penetration characteristics of renewable energy are conducive to the power delivery of the unit and have a positive effect on stability, but the increase in the simultaneous rate will increase the section power delivery and intensify the power flow transfer after the fault, which has a negative impact on stability;

[0143] When the transmission section power in the Yantai-Weihai area is equal to the transient stability limit power, subject to the transmission capacity and reactive power support capacity, the increase in the simultaneous rate of renewable energy requires the reduction of the output of an equal number of units to ensure that the section power does not exceed the transient limit power;

[0144] Reducing the startup and increasing the load in the Yanwei area with the same capacity have almost the same impact on stability.

[0145] (3) After the commissioning of the Phase II of the National Nuclear Demonstration Project and the Phase II of Penglai, the installed capacity in the Yantai-Weihai area has further increased, and the transmission capacity of the Yantai-Weihai area needs to be improved urgently. With the commissioning of power transmission and transformation projects such as Zhaoyuan and Rushan, the transmission channels in the Yantai-Weihai area have been further strengthened, which is conducive to improving the stability of the Yantai-Weihai area.

[0146] S4, according to the operation regulations of the extreme limit of the sending section under static stability and transient stability.

[0147] S401: determining the minimum section power according to the transmission limits of the transmission sections under static stability and transient stability respectively, comparing the minimum section powers, and taking the smaller value as the comprehensive minimum section power;

[0148] S402: Regulate the power-on and renewable energy output in the transmission area according to the comprehensive minimum section power, or control the section power according to different start-up gears.

[0149] In S402, according to the determined minimum section power, the startup and new energy output of the transmission area are regulated. Specifically, when the actual transmission power is lower than the minimum section power, it is necessary to increase the number of startups or increase the output of new energy power generation equipment to increase the transmission power of the transmission section to a safe range; conversely, when the actual transmission power is higher than the minimum section power but close to or reaches the transmission limit, it is necessary to reduce the number of startups or reduce the output of new energy power generation equipment to prevent overload of the transmission section and ensure the stable operation of the power system.

[0150] In addition, the section power can be flexibly adjusted according to the different startup gears of the power system. By presetting the section power limit under different startup gears, the appropriate startup gear is selected according to the real-time operation status and dispatching requirements to achieve refined control of the transmission section power. In this process, it is necessary to comprehensively consider factors such as load demand, new energy power generation forecast, and system stability to ensure that the adjusted section power not only meets the requirements of safe and stable operation of the power grid, but also maximizes the use of new energy resources to achieve dual optimization of economic and environmental benefits.

[0151] It should be understood that the formulation of the control or operation regulations can be set by those skilled in the art according to actual conditions.

[0152] As a specific implementation method, the transmission section in Yantai and Weihai areas is designated according to the relationship between new energy, startup and load coupling in Yantai and Weihai areas. The transmission power can be pre-controlled to not exceed 6 million kilowatts according to the minimum transmission section; or it can be graded according to the unit, with a startup of less than 10.5 million kilowatts and a section transmission power of no more than 6 million kilowatts, a startup of less than 1150 and greater than 1050 and a transmission power of no more than 7 million kilowatts, and a startup of greater than 1150 and a transmission power of no more than 8 million kilowatts.

[0153] In the power system, changes in load will directly affect the supply and demand balance of the power system, while the power generation and stability of new energy (such as wind power, photovoltaics, etc.) are affected by natural factors such as weather, and the number and status of startups determine the power generation capacity of the power system. The interaction and mutual influence between these three constitute the "coupling" relationship in the power system.

[0154] In this embodiment, by adjusting the coupling relationship between load, new energy and startup, the transmission limit of the transmission section under transient stability of the faulty line can be checked and obtained, which can characterize the transmission capacity of the transmission section to a certain extent. In this embodiment, three permanent fault tests are performed on the transmission line in the full connection state and the maintenance state, and the transmission section cut set is divided based on the sensitivity of voltage stability and power angle stability. On this basis, under different operating states (normal, full connection, maintenance), by adjusting the coupling relationship between load, new energy and startup, the transmission limit of the transmission section under static stability and transient stability is checked respectively, so as to fully consider the coupling relationship in the power system to improve the accuracy and reliability of analyzing the transmission capacity of the transmission section. Not only a variety of operating states and fault conditions are considered, but also by adjusting the resource coupling relationship, the ultimate transmission capacity of the transmission section is deeply explored, which provides strong support for the safe and stable operation of the power system.

[0155] Embodiment 2

[0156] This embodiment provides a transmission section transmission capacity analysis system considering multi-resource coupling relationships, including:

[0157] The cut set division module is used to perform three-permanent fault tests on the transmission line in the full connection state and the maintenance state, and divide the transmission section cut sets based on the sensitivity of voltage stability and power angle stability; the line with the greatest sensitivity to voltage stability and power angle stability in the transmission section cut set is taken as the restraining fault line;

[0158] A static stability checking module is used to perform a disconnection operation on the constrained fault line, check and obtain the power transmission limit of the sending section under static stability;

[0159] The transient stability verification module is used to verify and obtain the transmission limit of the section that restricts the fault line under transient stability by adjusting the coupling relationship between load, new energy and startup in normal operation and maintenance status;

[0160] The regulation formulation module is used to determine the operating regulations according to the transmission limit of the transmission section under static stability and transient stability

[0161] Embodiment 3

[0162] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps in the method for analyzing the transmission capacity of a transmission section considering the coupling relationship of multiple resources as described in the first embodiment above are implemented.

[0163] Embodiment 4

[0164] This embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps in the method for analyzing the transmission capacity of a transmission section taking into account the coupling relationship of multiple resources as described in the first embodiment above are implemented.

[0165] The steps or modules involved in the above embodiments 2 to 4 correspond to those in embodiment 1. For the specific implementation, please refer to the relevant description of embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood to include any medium that can store, encode or carry an instruction set for execution by a processor and enable the processor to execute any method in the present invention.

[0166] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for analyzing the transmission capacity of a transmission section considering the coupling relationship of multiple resources, characterized in that: include: In the full connection state and maintenance state, the three permanent fault tests are carried out on the transmission line respectively, and the transmission section cut sets are divided based on the sensitivity of voltage stability and power angle stability; The line with the greatest sensitivity to voltage stability and power angle stability in the transmission section cut concentration is taken as the restraining fault line; Under normal operating conditions, the constrained fault line is disconnected to check and obtain the power transmission limit of the sending section under static stability; In normal operation and maintenance status, the coupling relationship between load, new energy and startup is adjusted to check and obtain the transmission limit of the section that restricts the fault line under transient stability. The operating regulations are determined based on the extreme limiting conditions of the sending section under static stability and transient stability.

2. A method for analyzing transmission section transmission capacity considering multi-resource coupling relationship according to claim 1, characterized in that: The normal operating state refers to the operating state of the power system without any faults or abnormalities; The fully wired state refers to a state in which all devices in the power system are in normal operation and are all connected together according to preset requirements; The overhaul status refers to a state in which the power system needs to temporarily stop operating due to overhaul, maintenance or fault handling.

3. A method for analyzing transmission section transmission capacity considering multi-resource coupling relationship according to claim 1, characterized in that: The three-permanent fault test is performed on the transmission line, and the transmission section cut sets are divided based on the sensitivity of voltage stability and power angle stability, specifically: Perform three permanent fault simulations on the transmission line, gradually start the sending-end units to increase the line power until the transmission line becomes unstable, and calculate the maximum power transmission capacity of the transmission line; the maximum power transmission capacity is the power transmission capacity at critical stability; The maximum power transmission capacity of each transmission line is sorted from small to large, and based on the set maximum power transmission capacity value, the transmission lines that are sensitive to voltage stability and power angle stability are screened out; The sensitive outgoing transmission lines obtained in the full connection state and the maintenance state are combined to obtain the outgoing section cut set.

4. A method for analyzing transmission capacity of a transmission section considering multi-resource coupling relationships as claimed in claim 3, characterized in that: The sending-end unit includes all sending units and new energy power generation equipment.

5. The method for analyzing transmission capacity of a power transmission section considering the coupling relationship of multiple resources according to claim 1, characterized in that: The interrupting operation of the constrained fault line is performed to check and obtain the power transmission limit of the sending section under static stability, specifically including: gradually increasing the power of the sending-end unit, reducing the power of the receiving-end unit by the same amount or increasing the load of the receiving-end unit by the same amount, solving the maximum transmission power of the constrained fault line, and obtaining the static power angle stability limit.

6. A method for analyzing transmission capacity of a transmission section considering multi-resource coupling relationships according to claim 1, characterized in that: The above-mentioned method of adjusting the coupling relationship between load, new energy and startup to check and obtain the transmission limit of the section under transient stability of the fault line is specifically as follows: Set the load, new energy, and startup to different gears, fix any gear, and gradually increase the transmission power of the transmission section until the critical point of transient instability under the restraining fault is reached; Gradually change the load gear and repeat the above process of increasing the transmission power of the transmission section until instability occurs, so as to obtain the projection of the relationship surface between load, new energy and startup on the load axis; Based on the projection, the relationship between any two variables is obtained, and finally the critical stability plane is determined to obtain the power transmission limit of the transmission section.

7. A method for analyzing transmission section transmission capacity considering multi-resource coupling relationship according to claim 1, characterized in that: The above-mentioned operation regulations based on the transmission section transmission limit under static stability and transient stability specifically include: Determine the minimum section power according to the transmission limit of the transmission section under static stability and transient stability respectively, compare the minimum section powers, and take the smaller value as the comprehensive minimum section power; The startup and new energy output of the transmission area are regulated according to the comprehensive minimum section power, or the section power is controlled according to different startup gears.

8. A transmission section transmission capacity analysis system considering multi-resource coupling relationships, characterized in that: include: The cut set division module is used to perform three-permanent fault tests on the transmission line in the full connection state and the maintenance state, and divide the transmission section cut sets based on the sensitivity of voltage stability and power angle stability; the line with the greatest sensitivity to voltage stability and power angle stability in the transmission section cut set is taken as the restraining fault line; A static stability checking module is used to perform a disconnection operation on the constrained fault line, check and obtain the power transmission limit of the sending section under static stability; The transient stability verification module is used to verify and obtain the transmission limit of the section that restricts the fault line under transient stability by adjusting the coupling relationship between load, new energy and startup in normal operation and maintenance status; The regulation formulation module is used to formulate operating regulations based on the transmission limit of the transmission section under static stability and transient stability.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps in a method for analyzing transmission capacity of a power transmission section taking into account multi-resource coupling relationships as described in any one of claims 1 to 7 are implemented.

10. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps in the method for analyzing the transmission capacity of a power transmission section considering the coupling relationship of multiple resources as described in any one of claims 1-7 are implemented.

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