Operation control method and system suitable for limit survival of urban strong local power grid

Abstract

The invention relates to an operation control method and system suitable for limit survival of an urban strong local power grid, and the method comprises the steps: setting at least two paths of power supplies for supplying power for important users in the strong local power grid, the total construction capacity of the indemnificatory power supply is not lower than the load of important users in the strong local power grid; each strong local power grid is provided with at least one black-start power supply; a backbone network frame in a strong local power grid is provided with an overhead line and a cable, important lines in the backbone network frame adopt a single-loop erection mode, and a plurality of important lines are arranged on a plurality of corridors in a safe geographic area; the transmission power of the tie line channel in the strong local power grid cannot be larger than the maximum power shortage which can be borne by the power grid system in the minimum starting mode meeting the important load power supply requirement. Compared with the prior art, the method can achieve the purpose of the limit survival of the urban firm local power grid, and guarantees the continuous and stable power supply of the power grid in an extreme environment.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid dispatching, and in particular to an operation control method and system applicable to the extreme survival of a strong local power grid in a city. Background Art

[0002] Currently, the research objects and scopes of the urban power grid resilience theory in China are basically the same as those of foreign related research. There are many related researches in the aspects of urban power grid resilience theory, resilience assessment and risk analysis. For example, the invention with the application number CN202410765123.8 and the publication number CN118333410A discloses a power grid risk transfer analysis, determination, prevention and control method, system, equipment and medium, which realizes the accurate identification of the risk transfer path and key nodes of the power grid system, improves the dimension and efficiency of risk transfer analysis, and enhances the resilience and security of the power grid.

[0003] The existing research on the resilience analysis and assessment of the strong local power grid in extra-large cities mainly explores at the level of resilience theory, but does not further expand the resilience theory from the perspective of the continuous survival of the power grid, explore the extreme survival principle mechanism of the strong local power grid in the city, and further put forward requirements for the planning and operation control of the power grid.

[0004] Among them, the extreme survival of the power grid is a partial extension of the concept of power grid resilience, which means that after the superior power grid fails due to extreme faults or becomes unstable, the strong local power grid in the important area of the city coordinates the internal resources of the power grid and quickly switches to the island state, and realizes uninterrupted power supply to important loads while maintaining frequency stability. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art and provide an operation control method and system applicable to the extreme survival of a strong local power grid in a city, so that the strong local power grid in the city can realize uninterrupted power supply to important loads while maintaining frequency stability after the superior power grid fails due to extreme faults or becomes unstable.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] An operation control method applicable to the extreme survival of a strong local power grid in a city includes the following steps:

[0008] At least two power supplies are set for important users in the strong local power grid for power supply, one of which is a guarantee power supply, and the total construction capacity of the guarantee power supply is not less than the load of important users in the strong local power grid. The power supply types of the guarantee power supply include at least two types; each strong local power grid has at least one black start power supply, and the guarantee power supply cooperates with energy storage for frequency modulation to ensure that the frequency drop value of the power grid under extreme disasters is not less than the requirements of the power grid;

[0009] For the backbone grid in a strong local power grid, overhead lines and cables are set up in two forms. The important lines in the backbone grid are erected in a single-circuit manner. Multiple important lines are arranged on multiple corridors in a safe geographical area. When a single important line crosses over a non-important line, the construction standards of both the important line and the non-important line are raised above those of other important lines.

[0010] The transmission power of the tie-line channel in a strong local power grid shall not be greater than the maximum power deficit that the power grid system can withstand under the minimum operating mode that meets the power supply requirements for important loads. When the urban power grid is off-grid, the unit operating mode and primary frequency regulation reserve can meet the peak shaving and frequency regulation requirements of the local power grid.

[0011] Furthermore, the power source types of the guaranteed power sources include coal-fired units and gas-fired units.

[0012] Furthermore, the backbone grid is the key lines and important network structures necessary to maintain the extreme survival of a strong urban local power grid. The conditions that the backbone grid meets include:

[0013] Meet the constraints of the safe operation of the power grid;

[0014] Meet the constraints of network topology connectivity;

[0015] Ensure continuous power supply to important users;

[0016] Under the premise of meeting the above conditions, the number of occupied branches is the least.

[0017] Furthermore, the backbone grid of the urban power grid is identified through a pre-established identification model for the backbone grid of the urban power grid. The identification model for the backbone grid of the urban power grid searches for the minimum-scale grid through a mathematical model based on the conditions for establishing the minimum-scale grid. With the goal of minimizing the number of occupied branches in the urban power grid and with the constraints of the safe operation of the power grid, topological connectivity, and continuous power supply to important users, a minimum-scale grid identification model for a strong urban local power grid that guarantees the uninterrupted power supply of first-class and second-class loads is constructed.

[0018] Furthermore, the objective function expression of the identification model for the backbone grid of the urban power grid is:

[0019] min N sk

[0020] In the formula, N sk is the number of backbone grid lines;

[0021] The constraint conditions of the identification model for the backbone grid of the urban power grid include:

[0022] Node power balance:

[0023]

[0024] Line power flow constraint;

[0025] Line capacity constraint:

[0026]

[0027] Output constraint of security power supply:

[0028]

[0029] Ramp constraint of security power supply:

[0030]

[0031] Output constraint of flexible power supply:

[0032]

[0033] Ramp constraint of flexible power supply:

[0034]

[0035] Minimum start-stop time constraint of flexible power supply:

[0036]

[0037] Continuous power supply guarantee constraint for Class I loads:

[0038]

[0039] Power supply scope constraint for various loads:

[0040]

[0041] Output range constraint of new energy:

[0042]

[0043] Energy storage operation constraint:

[0044]

[0045]

[0046] Line operation status statistic constraint:

[0047]

[0048] Wherein, and represent the output of security power supply and flexible power supply respectively; is the output of the new energy power plant; and are the charging power and discharging power of the energy storage; f l,t represents the line power flow; respectively represent the supply powers of Class I load, Class II load, and Class III load, where Class I load represents special-grade, some first-class, and second-class important electricity users, Class II load represents some first-class and second-class users with relatively low electricity consumption grades, and Class III load is the remaining electricity users; z l is the line status 0-1 variable, whose value of 1 represents the line is in operation and 0 represents the line is disconnected; f l max represents the line capacity; and respectively represent the maximum and minimum outputs of the guaranteed power supply; is the maximum ramping rate of the guaranteed power supply; and respectively represent the maximum and minimum outputs of the flexible power supply; is the flexible power supply operation 0-1 status variable, whose value of 1 represents the unit is in operation and 0 represents the unit is not in operation; is the maximum ramping rate of the flexible power supply; and T g are the minimum start-up and shutdown times of the flexible unit; are the original power loads of Class I, Class II, and Class III electricity users respectively; is the predicted output of the new energy power plant; is the curtailment power of the new energy power plant; is the rated power of the energy storage; and are the energy storage charge-discharge 0-1 status variables respectively, whose value of 1 represents the energy storage is charging and discharging and 0 represents no charge-discharge; and are the maximum and minimum capacity limits of the energy storage; E e,t is the capacity status of the energy storage at a certain moment, E e,1 is the capacity status of the energy storage at the initial moment, E e,T is the capacity status of the energy storage at the end moment; and represent the charge-discharge efficiency of the energy storage; Δt is the time step of 1h; is the initial capacity of the energy storage.

[0049] Furthermore, if the corridor is in a congested state, the number of important lines arranged in each safe area corridor does not exceed 2.

[0050] Furthermore, two or more important lines do not cross each other between adjacent poles.

[0051] Furthermore, the objective function expression of the calculation model for the minimum startup mode that meets the important load power supply requirements is as follows:

[0052]

[0053] In the formula, u s and u f are the startup states of the security power supply and the flexible power supply respectively. When the value is 1, it means startup; when the value is 0, it means shutdown; Ω Gs and Ω Gf are the security power supply set and the flexible power supply set respectively;

[0054] The constraint conditions of the calculation model for the minimum startup mode that meets the important load power supply requirements include: node balance constraint, line power flow constraint, line capacity constraint, wind curtailment constraint, balance node phase angle constraint, generator output constraint, and load shedding constraint;

[0055] The load shedding constraint includes:

[0056] During the process of the strong local power grid going off the grid, to ensure the uninterrupted power supply of the security load in the important user load, the corresponding calculation expression is:

[0057] ΔD d,ξ = 0, ξ = 1, 2

[0058] 0 ≤ ΔD d,3 ≤ ΔD max

[0059] In the formula, ΔD d,ξ is the load shedding size at the ξ level, and ΔD d,max is the maximum load shedding amount of the third-level load;

[0060] After the strong local power grid goes off the grid in the minimum startup mode, the power of the connection line between the strong local power grid and the superior power grid does not exceed the following constraint:

[0061]

[0062] In the formula, ΔP max is the maximum transmission power of the connection line, H g is the inertia time constant of the synchronous generator set g; S g is the rated capacity of the synchronous generator set g; u g is the startup and shutdown state of the synchronous generator set g; ROCOF max is the maximum frequency change rate; f0 is the rated frequency, and f is the frequency.

[0063] Furthermore, during the adjustment process of the transmission power of the connection line channels within the strong local power grid, considering the frequency-voltage coupling interaction effect, the voltage and frequency drops or rises are controlled within the safe range.

[0064] The present invention also provides an operation control device suitable for the extreme survival of a strong local urban power grid, including a memory and a processor. The memory stores a computer program, and the processor calls the computer program to execute the steps of the method described above.

[0065] Compared with the prior art, the present invention has the following advantages:

[0066] (1) The present invention optimizes operation control from three aspects: guaranteed power supply and flexible power supply, toughness of transmission channels, and rapid off-grid control under sudden large power deficits, meets the demand for uninterrupted power supply to important user loads, achieves the purpose of extreme survival of a strong local urban power grid, and can ensure the continuous and stable power supply of the power grid in extreme environments.

[0067] (2) The present invention is configured such that at least two power sources supply power to important users of the urban power grid, and one of them is a guaranteed power supply. This design not only improves the stability of power supply but also provides strong support for the normal operation of the city;

[0068] The total construction capacity of the guaranteed power supply is set not to be lower than the load of important users in the strong local power grid, which helps to ensure the reliability and safety of power supply and enhance the toughness and adaptability of the power system in extreme disaster situations;

[0069] The types of guaranteed power supply are set to include at least two types, such as coal-fired units and gas-fired units. This diversified power structure can effectively cope with various risks that may occur under extreme weather conditions;

[0070] By configuring a black start power source, the urban power grid can be quickly started and restored to power in the event of natural disasters, ensuring the normal operation of society and the safety of residents' lives;

[0071] The guaranteed power supply in the strong local urban power grid is configured to be able to cooperate with energy storage for frequency modulation, ensuring that the frequency drop value of the power grid under extreme disasters is not lower than the requirements of the power grid, enhancing the stability and safety of the power system, and providing reliable power protection for important users.

[0072] (3) The present invention conducts an overall differential design of the power grid, divides important substations and lines among all substations and lines, constructs the minimum backbone grid for disaster resistance and disaster tolerance, and comprehensively adopts two transmission forms of overhead lines and cables, which can effectively enhance the risk resistance ability of the power system and improve the power supply guarantee for important loads;

[0073] Define the key lines and important network structures necessary to maintain the extreme survival of the strong local urban power grid as the backbone grid, and propose an identification model for the backbone grid of the urban power grid, which can quickly obtain the key branches that meet the conditions for establishing the backbone grid of the urban power grid, and realize the rapid and efficient optimization and adjustment of the network structure;

[0074] It is advisable to adopt a single-circuit erection method for important lines. Multiple important lines need to be arranged on multiple corridors in a safe geographical area. When the corridors are crowded, no more than 2 important lines are arranged on each corridor in the safe area, which can reduce various risks brought by the concentrated arrangement of lines and ensure the safe operation of the power system;

[0075] It is not advisable to set two or more important lines to cross each other within one span (between adjacent poles and towers), to avoid multiple important lines being damaged simultaneously in the same area in case of extreme natural disasters or equipment failures;

[0076] When setting important lines to cross non-important lines, the construction standards of both important lines and non-important lines are raised above the construction standards of other important lines to ensure the anti-risk ability of the system and the operability of maintenance, thus ensuring the safe power supply of important loads.

[0077] (4) The transmission power of the tie-line channel set in the present invention shall not be greater than the maximum power shortage that the system can withstand under the minimum unit startup mode that meets the power supply requirements for important loads. And a model for the minimum unit startup mode that meets the power supply requirements for important loads is proposed for rapid optimization calculation. By strictly restricting the transmission power of the tie-line channel, the power grid can maintain the frequency stability when encountering faults, and avoid system collapse or protective shutdown of power generation equipment;

[0078] When formulating the frequency control decision-making method, consider the frequency-voltage coupling interaction, and control the voltage and frequency drops or rises within a safe range, which can ensure the safe and stable operation of the strong local power grid after being off-grid;

[0079] When the urban power grid is off-grid, ensuring that the unit startup mode and primary frequency modulation reserve can meet the peak shaving and frequency modulation requirements of the local power grid is not only a necessary condition for ensuring the stable operation of the power system, but also an important measure to cope with extreme weather events and ensure social safety and economic stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 It is a schematic flow chart of an operation control method applicable to the extreme survival of a strong local urban power grid provided in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0081] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Components of the embodiments of the present invention usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0082] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0083] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0084] Embodiment 1

[0085] As Figure 1 shown, this embodiment provides an operation control method applicable to the extreme survival of a strong local urban power grid, including the following steps:

[0086] S1: At least two power supplies are set for important users in the strong local power grid for power supply, one of which is a guarantee power supply. The total construction capacity of the guarantee power supply is not less than the load of important users in the strong local power grid, and the power supply types of the guarantee power supply include at least two types; each strong local power grid has at least one black start power supply, and the guarantee power supply cooperates with energy storage for frequency modulation to ensure that the frequency drop value of the power grid under extreme disasters is not less than the requirements of the power grid.

[0087] S2: For the backbone grid in the strong local power grid, overhead lines and cables are adopted. The important lines in the backbone grid are erected in a single-circuit manner, and multiple important lines are arranged on multiple corridors in a safe geographical area. When a single important line drills through a non-important line, the construction standards of both the important line and the non-important line are increased to above the construction standards of other important lines.

[0088] S3: The transmission power of the tie line channel in the strong local power grid shall not be greater than the maximum power deficit that the power grid system can withstand under the minimum unit starting mode that meets the power supply requirements of important loads; when the urban power grid is off-grid, the unit starting mode and primary frequency modulation reserve can meet the peak shaving and frequency modulation requirements of the local power grid.

[0089] The following is a specific description of each step:

[0090] 1. Requirements for guarantee power sources and flexible power sources for the extreme survival of a strong local power grid

[0091] 1.1 Requirements for the number of power supply circuits for important users

[0092] In the urban power grid, the design concept of providing at least two power sources for important users (such as hospitals, data centers, public facilities, etc.) is based on the comprehensive consideration of power supply reliability and security. Important users have extremely high requirements for power supply. Any power outage event may lead to serious consequences, including economic losses, life safety, and social order chaos. Therefore, the design of a single power source is difficult to meet the power needs of urban operation and public safety.

[0093] The dual power source configuration can significantly reduce the risk of power outages caused by power source failures. When one power source fails or malfunctions, the other power source can quickly take over the power supply task, thus ensuring the normal power consumption of users. This redundant design provides an additional safety layer for the power system, ensuring stable power supply under various emergency situations.

[0094] Therefore, in the context of frequent extreme disasters, there should be at least two power sources supplying power to important users in the urban power grid, with one being a guarantee power source. This design not only improves the stability of power supply but also provides strong support for the normal operation of the city, ensuring that important users can obtain continuous and stable power supply under extreme conditions.

[0095] 1.2 Requirements for the capacity of guarantee power sources

[0096] In the urban power grid, the total construction capacity of guarantee power sources should not be lower than the load of important users in a strong local power grid. This principle is of great significance for improving the reliability and security of power supply, especially in the context of facing extreme disasters (such as typhoons, heavy rains, ice disasters, etc.). It helps to ensure the reliability and security of power supply, as well as enhance the resilience and adaptability of the power system under extreme disaster situations. By constructing sufficient guarantee power source capacity, it can provide strong support for the stable operation of the urban power grid and help important users obtain continuous and reliable power supply.

[0097] 1.3 Requirements for the types of guarantee power sources

[0098] To ensure that important users (such as hospitals, data centers, and public facilities) can obtain stable power supply during extreme disasters (such as typhoons, heavy rains, ice disasters, etc.), the construction of guarantee power sources is crucial. The types of guarantee power sources should include at least two, such as coal-fired units and gas-fired units. This diversified power structure can effectively cope with various risks that may occur under extreme weather conditions.

[0099] (1) Extreme weather events may lead to the failure and outage of gas pipelines. Under extreme disasters, floods, foundation collapses, etc. may cause damage or leakage of gas pipelines, thus affecting the normal operation of gas turbine units. If the urban power grid mainly relies on a single gas turbine unit, then once a pipeline failure occurs, the entire power supply system will be impacted, and important users may face the risk of power supply interruption. However, if coal-fired units are also configured in the power grid, although the gas turbine units may be affected, the coal-fired units can continue to provide power supply to ensure that important users receive the necessary power support in emergencies. This design of power source diversification provides redundancy for the power system and enhances its risk resistance ability.

[0100] (2) The stability of fuel supply is also an important factor that must be considered in the design of backup power sources. Under extreme weather conditions, the transportation of coal or gas may be disrupted. For example, in ice disasters, low temperatures may cause transportation delays, or in heavy rains, damaged roads may make it difficult to transport fuel to power plants in a timely manner. If the power grid only relies on a certain type of fuel, any unexpected situation may lead to fuel shortages, thus affecting power generation. However, by using multiple backup power sources (such as coal-fired units and gas turbine units), when the supply of a certain fuel is insufficient, it can quickly switch to another type of power source to ensure that the power supply needs of important users are not affected.

[0101] (3) The diversified design of backup power sources is particularly important when dealing with emergencies. Under extreme climate conditions, the power system must have the ability to respond quickly to adapt to changing power supply demands and sudden equipment failures. By configuring multiple types of backup power sources, the urban power grid can quickly adjust its power supply strategy in the face of risks such as gas pipeline failures and fuel shortages, ensuring that important users can obtain stable power support under any circumstances.

[0102] In summary, the types of backup power sources in a strong local power grid should be at least two. Through a diversified power source structure, the reliability of power supply is enhanced, the response ability to emergencies is improved, and it is ensured that important users can still receive continuous and stable power supply during a crisis to cope with various risks that may occur under extreme weather conditions.

[0103] 1.4 Requirements for black start power sources

[0104] After a local power grid encounters extreme disasters (such as typhoons, heavy rains, ice disasters, etc.), it may experience large-scale power outages or complete power outages, and a black start power source is needed to quickly restore power supply. The safety and stability requirements of the local power grid also make the black start power source an indispensable component. With climate change leading to frequent extreme weather events, the power system must have the ability to respond to various emergencies. By configuring a black start power source, the urban power grid can quickly start and restore power supply when encountering natural disasters, ensuring the normal operation of society and the safety of residents' lives. A black start power source refers to an important power source that can operate independently and provide initial power when a large-scale power outage occurs in the entire power grid, and then drive other power facilities to gradually restore normal power supply.

[0105] Therefore, each strong local power grid needs to have at least one black start power source. This is not only to quickly restore power supply after extreme disasters occur, but also to enhance the resilience and stability of the power system. The independence, flexibility, and diversity of the black start power source enable the urban power grid to quickly and effectively respond to various risks when facing challenges, ensuring that important users and residents can obtain reliable power supply in times of crisis. This design concept will lay a solid foundation for the sustainable development of the urban strong local power grid and enhance the safety and stability of the entire society.

[0106] 1.5. Requirements for power frequency regulation of power sources

[0107] Coordinating energy storage systems for frequency regulation by the backup power source is an important measure to ensure that the frequency drop value of the power grid does not fall below the requirements of the power grid after encountering extreme disasters (such as typhoons, heavy rains, ice disasters, etc.). This strategy is related to the stability and safety of the power system and directly affects the power consumption needs of important users and the normal operation of society.

[0108] In summary, the backup power source in the urban strong local power grid should be able to coordinate with energy storage for frequency regulation to ensure that the frequency drop value of the power grid does not fall below the requirements of the power grid under extreme disasters. The backup power source can coordinate with energy storage for frequency regulation, enhancing the stability and safety of the power system and providing reliable power protection for important users. In the face of increasingly frequent extreme weather events, this coordination ability will provide strong support for the resilience and off-grid safe operation of the urban strong local power grid.

[0109] 2. Requirements for the resilience of transmission channels for the urban strong local power grid to achieve extreme survival

[0110] As a key link in power transmission, the stability and disaster resistance ability of the transmission channel directly affect the overall operation safety of the power grid and the load supply guarantee ability.

[0111] 2.1. Requirements for differential design of the backbone grid

[0112] The basic idea of differential design for the power grid is as follows: On the basis of generally improving the design standards of the transmission grid, the method of differential planning is adopted to study how to maximize the overall fortification standard by enhancing the disaster prevention standards of some substations and lines, identify a batch of important substations and transmission lines, improve their ability to withstand severe natural disasters, ensure the continuous power supply to important loads under natural disasters, and at the same time strive for economic rationality. Through the differential planning and design of the transmission grid, if a disaster beyond the disaster prevention standard during the design of general lines occurs, the safe and stable operation of important lines such as the minimum core backbone grid of each voltage level, strategic transmission channels, and power supply lines for important loads can be maintained, ensuring the continuous and reliable power supply to high-risk users, important users, and users closely related to post-disaster rescue and emergency repair.

[0113] To sum up, the minimum-scale grid for ensuring the power supply to special-class, some first-class, and second-class important users needs differential design to ensure the uninterrupted power supply to important load users.

[0114] In the power system, to ensure the reliability of power supply to important loads, multiple lifeline channels should comprehensively consider two forms: overhead lines and cables. This diversified design can enhance the overall reliability of the system and avoid the system instability and load loss that may be brought by a single power transmission method.

[0115] Comprehensively adopting two power transmission forms of overhead lines and cables can effectively enhance the risk resistance ability of the power system and improve the power supply guarantee for important loads. The combined layout of overhead lines and cables can make full use of their respective advantages to form a redundant system that complements each other. When the overhead line is damaged due to the external environment, the cable line can continue to maintain power supply; conversely, when the cable system fails, the overhead line can undertake the power supply task. In this way, the power system can maintain power supply stability under a wider range of disaster or accident scenarios. Through the decentralized layout of overhead lines and cables, the power system can effectively avoid the systematic instability caused by single-point failures. For example, important loads can be powered through multiple paths. When one path fails, the system can quickly switch to the standby path, reducing load loss and the time of power supply interruption. This layout method can reduce the risk of cascading failures and improve the overall resilience of the power system. Reduce the operation and maintenance difficulty and improve the emergency repair efficiency: When a fault occurs in the system, the combination of overhead lines and cables can provide more options to quickly restore power supply. The faults of overhead lines are easy to be detected and handled, while the robustness of the cable system can provide long-term power supply guarantee. This diversified layout method not only reduces the complexity of long-term system maintenance but also can restore the power supply to important loads faster after an accident.

[0116] In summary, there are respective risks in solely adopting overhead lines or cables for power supply, which may lead to system instability and power loss of important loads. Therefore, the requirements can be summarized as follows: for multiple lifeline channels to ensure the power supply of important loads, two forms, namely overhead lines and cables, should be considered. Achieve high reliability of the system through diversified layout, reduce the impact of faults and accidents, and ensure that important loads can obtain stable power supply under any circumstances.

[0117] Here, the key lines and important network structures necessary to maintain the extreme survival of a strong local urban power grid under specific operating modes and initial fault conditions are defined as the backbone grid. To quantitatively describe the backbone grid mathematically, the specific conditions that the backbone grid satisfies are further given:

[0118] a) Meet the constraints of the safe operation of the power grid;

[0119] b) Meet the constraints of network topological connectivity;

[0120] c) Ensure continuous power supply to important users;

[0121] d) The number of branches occupied is the least under the premise of meeting the above conditions.

[0122] According to the above conditions, a recognition model of the backbone grid of the urban power grid can be established through network structure adjustment and optimization.

[0123] According to the conditions for establishing the minimum-scale grid, search for the minimum-scale grid through a mathematical model. Taking the least number of branches occupied in the urban power grid as the goal and the safe operation of the power grid, topological connectivity, and continuous power supply to important users as the constraint conditions, a recognition model of the minimum-scale grid of a strong local urban power grid to ensure the uninterrupted power supply of first-class and second-class loads is constructed as follows:

[0124] Objective function:

[0125] min N sk Constraint conditions:

[0126] a) Node power balance

[0127]

[0128] b) Line power flow

[0129]

[0130] c) Line capacity constraint

[0131]

[0132] d) Output constraint of the security power supply

[0133]

[0134] e) Security power ramp constraint

[0135]

[0136] f) Flexible power output constraint

[0137]

[0138] g) Flexible power ramp constraint

[0139]

[0140] h) Minimum start - stop time constraint of flexible power

[0141]

[0142] i) Continuous power supply constraint for Class - I loads

[0143]

[0144] j) Power supply scope constraint for various loads

[0145]

[0146] k) New - energy output scope constraint

[0147]

[0148] l) Energy - storage operation constraint

[0149]

[0150] m) Constraint on line operation state statistic

[0151]

[0152] In the above formula, N sk represents the number of backbone grid lines; and represent the power outputs of security power and flexible power respectively; is the power output of the new - energy power plant; and are the charging power and discharging power of the energy storage; f l,t represents the line power flow; represent the supply powers of Class - I, Class - II, and Class - III loads respectively, where Class - I loads represent special - grade, some first - level, and second - level important electricity users, Class - II loads represent some first - level and second - level users with relatively low electricity consumption levels, and Class - III loads are the remaining electricity users; B l is the line reactance; θ fr(l),tand θ to(l),t are the voltage phase angles at both ends of the line; z l is the line status 0-1 variable, with a value of 1 representing the line is in operation and 0 representing the line is disconnected; f l max represents the line capacity; and represent the maximum and minimum outputs of the guaranteed power supply respectively; is the maximum ramping rate of the guaranteed power supply; and represent the maximum and minimum outputs of the flexible power supply respectively; is the flexible power supply operation 0-1 state variable, with a value of 1 representing the unit is in operation and 0 representing the unit is not in operation; is the maximum ramping rate of the flexible power supply; and T g are the minimum start-up and shut-down times of the flexible unit; are the original power loads of the first-class, second-class, and third-class electricity users respectively; is the predicted output of the new energy power plant; is the curtailment power of the new energy power plant; is the rated power of the energy storage; and are the energy storage charge and discharge 0-1 state variables respectively, with a value of 1 representing energy storage charging and discharging and 0 representing no charging and discharging; and are the maximum and minimum capacity limits of the energy storage; E e,t is the capacity state of the energy storage at a certain moment; and represent the charge and discharge efficiency of the energy storage; Δt is the time step of 1h; is the initial capacity of the energy storage.

[0153] By solving the identification model of the backbone grid of the urban power grid, the key branches that meet the conditions for establishing the backbone grid of the urban power grid can be obtained. These branches form the backbone grid of the strong local urban power grid, laying a foundation for the subsequent solution of the optimal operation of the extreme survival of the strong local urban power grid and the clarification of the principle mechanism.

[0154] 2.2. Requirements for the Number of Important Lines in the Corridor

[0155] In the planning and design of the power system, the safety of line layout is directly related to the stability and reliability of the system. Therefore, important lines should preferably be arranged in a single-circuit manner. Multiple important lines need to be arranged on multiple corridors in a safe geographical area. When the corridors are crowded, the number of important lines arranged on each corridor in the safe area should not exceed 2. This design principle is to reduce various risks brought by the concentrated layout of lines and ensure the safe operation of the power system.

[0156] 2.3 Requirements for Crossing of Important Lines

[0157] The crossing of lines, that is, the spatial intersection or overlap of different power lines, will increase the vulnerability of the system in the event of an accident. To ensure the continuous and stable power supply to important loads, the following requirements need to be particularly concerned about in the design:

[0158] 1. Two or more important lines should not cross each other within one span (between adjacent poles and towers).

[0159] When two or more important lines cross each other within the same span (between adjacent poles and towers), the failure of any one line will affect the safe operation of other lines. Especially in the face of extreme natural disasters or equipment failures, if multiple important lines are damaged simultaneously in the same area, more serious consequences may occur, such as cascading failure reactions, reduced power supply redundancy, and increased difficulty of maintenance and emergency repair.

[0160] 2. When an important line crosses a non-important line, the construction standards of both the important line and the non-important line should be raised above the construction standards of other important lines.

[0161] In the power system, there are differences in the construction standards of important lines and non-important lines. The design of important lines usually requires higher reliability to ensure their safe operation under various extreme conditions. However, when an important line crosses a non-important line, if the construction standard of the non-important line is low, there is a potential risk that the failure of the non-important line may spread to the important line and even affect the safety of the entire power grid. Therefore, in this case, it is required that the construction standard of the non-important line must be raised to reach the construction level of the important line, and the construction level of the important line needs to reach a higher standard.

[0162] Non-important lines usually carry lighter loads, and their designs have lower anti-risk capabilities and maintenance requirements. However, when they cross an important line, the failure of a non-important line (such as insulation damage, pole collapse, etc.) may affect the important line and cause the power supply to important loads to be interrupted. Therefore, it is required that when a non-important line crosses an important line, it should be constructed according to the standards of important lines, and its design redundancy, structural strength, durability and other indicators should be improved to ensure that its failure will not harm the important line.

[0163] By enhancing the construction standards of non-essential lines, the overall risk resistance of the system can be significantly strengthened. For example, in wind-resistant design, non-essential lines usually have lower requirements for extreme wind forces. However, when drilling through important lines, their wind resistance level must be raised to the same level as that of important lines to ensure that non-essential lines will not cause the failure of important lines due to insufficient structural strength during typhoon or strong wind weather. In addition, for the geological conditions in the crossing areas, infrastructure construction needs to be strengthened to prevent line damage caused by unstable foundations or other geological disasters.

[0164] To sum up, it is not advisable for two or more important lines to drill through each other within one span (between adjacent poles and towers); when an important line drills through a non-essential line, the construction standards of both the important line and the non-essential line should be raised above those of other important lines. Ensure the risk resistance ability of the system and the operability of maintenance, so as to guarantee the safe power supply of important loads.

[0165] 3. Requirements for rapid off-grid control for the ultimate survival of a strong local power grid under sudden large power deficits

[0166] Regarding the requirement for uninterrupted power supply guarantee for important load users, analyze the impact of off-grid power deficits on the local strong power grid from aspects such as power deficit range, frequency-voltage interaction, starting mode, and primary frequency regulation reserve, and summarize the requirements for off-grid control for the ultimate survival of a strong local power grid.

[0167] 3.1. Power deficit requirements

[0168] In the operation and dispatching of the power system, the transmission power of the tie-line channel directly affects the stability and power supply safety of the system. Especially when the system is dealing with emergency faults or sudden accidents, reasonably controlling the transmission power of the tie-line can effectively prevent large-scale collapse of the system. To ensure the stable operation of the power system under different conditions, the transmission power of the tie-line must be strictly restricted, especially in terms of power deficits.

[0169] System inertia is the kinetic energy stored in the rotating machinery of generator sets in the power system, which determines the response ability of the power grid to sudden power deficits. In the minimum starting mode, the system inertia is small, and the ability to adjust power imbalance is relatively weak. If the transmission power of the tie-line is too high, once a fault occurs (such as a tie-line trip), the resulting power deficit will quickly cause the system frequency to drop, and even lead to frequency collapse. The sharp fluctuation of the system frequency will cause power equipment to fail, and ultimately may trigger a large-scale power outage.

[0170] The transmission power of the tie-line channel shall not exceed the maximum power deficit that the system inertia can withstand. If the power deficit is too large and the system inertia cannot respond in time, it may cause the frequency of the entire power grid to fail to be maintained within the normal range, resulting in a series of cascading failures. Under extreme weather conditions or natural disasters, the power grid is prone to major failures such as tie-line breaks. In this case, if the transmission power of the tie-line is too large, the system needs to make up for the power deficit caused by the tie-line tripping within an extremely short time. When the system inertia is low, the buffering capacity is limited, and the frequency fluctuation is difficult to control. In severe cases, it will cause important loads to be unable to be continuously and stably powered.

[0171] To further ensure the safe operation of the power system, in addition to relying on system inertia, another important constraint on the transmission power of tie-lines comes from the starting capacity of local units. Usually, when a tie-line undertakes excessive power transmission, if the tie-line fails or trips suddenly, the power grid requires local generating units to quickly make up for this power deficit. In the power system, the size of the power deficit is not only related to the transmission power of the tie-line, but also closely related to factors such as the system load, the distribution of generating units, and the reserve capacity. If the power deficit is too large, the adjustment ability of the power system will be difficult to maintain, affecting the operation safety of the entire power grid. By reasonably restricting the transmission power of the tie-line channel, the power deficit can be effectively reduced, ensuring that the system can maintain stable operation when facing sudden tie-line failures.

[0172] In case of a failure, the power supply priority of important loads is extremely high. If the transmission power of the tie-line exceeds the limit, the power deficit will directly affect the power supply stability of important loads. Controlling the power deficit within the adjustable range of system inertia and local units can ensure that even in extreme cases, important loads can still obtain continuous and reliable power supply. A too large power deficit will cause the system frequency to drop rapidly, and frequency stability is one of the cores of the safe operation of the power system. By strictly restricting the transmission power of the tie-line channel, the power grid can maintain frequency stability when encountering failures, avoiding system collapse or protective shutdown of generating equipment.

[0173] In summary, the transmission power of the tie-line channel shall not be greater than the maximum power deficit that the system can withstand under the minimum starting mode that meets the power supply requirements of important loads.

[0174] The model of the minimum starting mode that meets the power supply requirements of important loads is as follows:

[0175] ① Objective function:

[0176] In the minimum starting mode model, the objective function is the minimum number of starts:

[0177]

[0178] In the formula: u s And uf They are the starting states of the security power supply and the flexible power supply respectively. When the value is 1, it means starting up; when the value is 0, it means shutting down; Ω Gs and Ω Gf They are the sets of the security power supply and the flexible power supply respectively.

[0179] ② Constraint conditions

[0180] (1) Node balance constraint

[0181]

[0182] In the formula: P s s and They are the outputs of the security power supply s and the flexible power supply f respectively; Ω W is the set of wind farms; Ω L is the set of lines; f mn is the power flow of line mn.

[0183] (2) Line power flow constraint

[0184]

[0185] In the formula: θ m and θ n They are the voltage phase angles at both ends of line mn respectively.

[0186] (3) Line capacity constraint

[0187]

[0188] (4) Wind curtailment constraint

[0189]

[0190] (5) Slack node phase angle constraint

[0191] θ ref = 0

[0192] (6) Generator output constraint

[0193]

[0194] (7) Load shedding constraint

[0195] During the process of the strong local power grid going off the grid, it is necessary to ensure the uninterrupted power supply of the security loads in the important user loads:

[0196] ΔD d,ξ = 0, ξ = 1, 2

[0197] 0 ≤ ΔD d,3 ≤ ΔDmax

[0198] In the formula: ΔD d,ξ is the magnitude of the ξ-level load shedding, and ΔD d,max is the maximum shedding amount of the tertiary load.

[0199] When the strong local power grid is islanded, it causes power imbalance. Under the minimum generation mode, the power of the connection line between the strong local power grid and the superior power grid does not exceed:

[0200]

[0201] In the formula: ΔP max is the maximum transmission power of the connection line; in the formula, H g is the inertia time constant of the synchronous generator set g; S g is the rated capacity of the synchronous generator set g; u g is the on / off state of the synchronous generator set g; ROCOF max is the maximum rate of frequency change; f0 is the rated frequency.

[0202] 3.2. Requirements for Voltage and Frequency

[0203] In the power system, voltage and frequency are two key parameters for the stable operation of the system, and there is a close coupling relationship between them. This coupling effect is particularly significant in the fault handling and emergency control processes of industrial enterprise power grids. The active power consumption of the load in the power grid is not only affected by voltage but also affects the system frequency conversely. Therefore, the mutual coupling effect of voltage and frequency has become an important issue in power system regulation.

[0204] When a fault occurs in the power grid, the coupling effect of voltage and frequency causes various problems in system operation. For example, low voltage and high frequency problems and high voltage and low frequency problems are common phenomena. When the voltage in the power grid drops, the active power absorption of the load decreases, which may cause the system frequency to rise; conversely, when some loads are shed, the voltage may increase while the system frequency may decrease. The existence of this coupling effect means that controlling the voltage fluctuation in the power grid will inevitably affect the frequency fluctuation of the system. Especially in the scenarios of islanded operation or large-scale load fluctuations, the coordinated control of voltage and frequency is particularly important.

[0205] To ensure the stable operation of the power grid, the regulation of voltage and frequency must be coordinated. Emergency control measures need to avoid steady-state overvoltage while restoring the transient voltage to ensure the long-term stable operation of the system. The rapid restoration of voltage helps to maintain the stable power supply to the load, while the steady-state voltage control prevents the system from overloading or equipment damage. Therefore, the influence of voltage-frequency coupling cannot be ignored and must be considered comprehensively in the control strategy.

[0206] In emergency control measures, the coupling effect of voltage and frequency affects the core elements of control decisions, including the control moment, control object, and control quantity. For example, in the power grid of industrial enterprises with large-scale power reception, the voltage instability problem after the failure of the connection section often preferentially cuts off the induction motor load. The induction motor load has a large reactive power demand, and its removal can quickly reduce the reactive power burden on the power grid and help the transient voltage to recover. However, excessive load shedding will cause the system frequency to rise, which will further lead to the problems of light load flow and steady-state overvoltage. Therefore, the steady-state overvoltage phenomenon after over-shedding of loads is exactly caused by light load flow and excessive reactive power compensation provided by capacitor banks.

[0207] In addition, the frequency will also fluctuate during the voltage recovery process, especially in an isolated power grid system where the system frequency regulation ability is limited and it is difficult to quickly recover through primary frequency modulation. Therefore, shortening the control time and accelerating the recovery of transient voltage and frequency must be considered in control measures. However, during the recovery of transient voltage, the reactive power compensation of capacitor banks is still a key factor for voltage stability. Due to the increased demand for reactive power absorption by induction motor loads, the inductive reactive power of capacitor banks is particularly important at this stage. If the capacitor banks and loads are removed simultaneously, it may delay the recovery of transient voltage and even lead to voltage instability. The coupling effect of voltage and frequency reflects the complexity in the operation of the power system. The voltage change of the power grid directly affects the active power consumption of the load, which in turn affects the fluctuation of the system frequency. And the frequency fluctuation will further affect the output of the generating unit, making voltage regulation more difficult. Therefore, in the dispatching and control of the power grid, the changes in both voltage and frequency must be considered simultaneously to ensure the stable operation of the system under dynamic conditions. The core of voltage-frequency coupling lies in its interactivity. Disturbances and load changes in the power grid will affect both voltage and frequency simultaneously. If not coordinated and controlled, it may lead to the overall instability of the system. Therefore, any emergency control measure must fully consider the interactive influence between voltage and frequency and cannot solely control one parameter while ignoring the other. This interactive influence needs to be emphasized in the control strategy to ensure that the power system has sufficient response capabilities when dealing with emergencies and to avoid system collapse and large-scale power outages.

[0208] To sum up, when formulating the frequency control decision-making method, it is necessary to consider the interactive influence of frequency-voltage coupling and control the voltage and frequency drops or rises within a safe range. Ensure that the strong local power grid can operate safely and stably after being separated from the grid.

[0209] 2.3, Startup method and primary frequency modulation reserve requirements

[0210] In the case of the urban power grid being off-grid, it is crucial to ensure that the unit startup mode and primary frequency regulation reserve can meet the peak shaving and frequency regulation requirements of the local power grid. This requirement is not only related to the stability and security of the power system but also directly affects the power supply reliability under extreme disasters (such as typhoons, heavy rains, ice disasters, etc.).

[0211] When the urban power grid is off-grid, it is necessary to ensure that the unit startup mode and primary frequency regulation reserve can meet the peak shaving and frequency regulation requirements of the local power grid. This is not only a necessary condition for ensuring the stable operation of the power system but also an important measure to cope with extreme weather events and ensure social safety and economic stability. In an increasingly complex power environment, flexible power generation methods and sufficient frequency regulation reserves will provide strong support for the sustainable development of the urban power grid.

[0212] Embodiment 2

[0213] This embodiment provides an operation control device applicable to the extreme survival of a strong local urban power grid, including a memory and a processor. The memory stores a computer program, and the processor calls the computer program to execute the steps of the operation control method applicable to the extreme survival of a strong local urban power grid as described above.

[0214] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention through logical analysis, reasoning, or limited experiments based on the concept of the present invention on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. An operation control method applicable to the extreme survival of a strong local power grid in a city, characterized in that, Including: At least two power supplies are set for important users within the strong local power grid, one of which is a guarantee power supply, and the total construction capacity of the guarantee power supply is not less than the load of important users in the strong local power grid; each strong local power grid has at least one black start power supply, and the guarantee power supply collaborates with energy storage for frequency regulation to ensure that the frequency drop value of the power grid under extreme disasters is not lower than the requirements of the power grid; for the backbone grid in the strong local power grid, two forms of overhead lines and cables are set, and the important lines in the backbone grid are erected in a single-circuit manner, and the important lines are arranged on the corridors of safe geographical areas. When a single important line drills through unimportant lines, the construction standards of both the important line and the unimportant line are above the construction standards of other important lines; The transmission power of the tie-line channel within the strong local power grid is not greater than the maximum power deficit that the power grid system can withstand under the minimum unit startup mode that meets the power supply requirements of important loads; when the urban power grid is off-grid, the unit startup mode and primary frequency regulation reserve meet the peak shaving and frequency regulation requirements of the local power grid.

2. The operation control method applicable to the extreme survival of a strong local urban power grid according to claim 1, wherein The power supply types of the guarantee power supply include at least two types, and the power supply types of the guarantee power supply include coal-fired units and gas-fired units.

3. The operation control method applicable to the extreme survival of a strong local urban power grid according to claim 1, wherein The backbone grid is the key lines and important network structures necessary to maintain the extreme survival of the urban strong local power grid, and the conditions met by the backbone grid include: Meeting the constraints of power grid safe operation; Meeting the constraints of network topology connectivity; Ensuring continuous power supply to important users; With the fewest number of occupied branches on the premise of meeting the above conditions.

4. The operation control method applicable to the extreme survival of a strong urban local power grid according to claim 3, wherein The backbone grid is identified through a pre-established urban power grid backbone grid identification model. The urban power grid backbone grid identification model searches for the minimum-scale grid through a mathematical model according to the minimum-scale grid establishment conditions, with the goal of the fewest number of occupied branches in the urban power grid, and with the power grid safe operation, topology connectivity, and continuous power supply to important users as the constraint conditions, to construct a minimum-scale grid identification model for the urban strong local power grid to ensure uninterrupted power supply for first-class and second-class loads.

5. The operation control method applicable to the extreme survival of a strong local urban power grid according to claim 4, wherein, The objective function expression of the urban power grid backbone grid identification model is: min N sk Where N sk is the number of backbone grid lines; The constraint conditions of the urban power grid backbone grid identification model include: Node power balance: Line power flow constraint; Line capacity constraint: Guarantee power supply output constraint: Guarantee power supply ramp constraint: Flexible power supply output constraint: Flexible power supply ramp constraint: Flexible power supply minimum start-stop time constraint: Continuous power supply guarantee constraint for first-class loads: Power supply range constraints for various loads: New energy output range constraint: Energy storage operation constraint: Line operation status statistic constraint: Wherein, and respectively represent the output of the security power supply and the flexible power supply; is the output of the new energy power plant; and are the charging power and discharging power of the energy storage; f l,t represents the line power flow; respectively represent the supply powers of the first-class load, the second-class load, and the third-class load. Among them, the first-class load represents special-class, some first-class, and second-class important electricity users; the second-class load represents some first-class and second-class users with lower electricity consumption levels; the third-class load is the remaining electricity users; z l is the line state 0-1 variable, whose value is 1 representing the line is in operation and 0 representing the line is disconnected; represents the line capacity; and respectively represent the maximum and minimum outputs of the security power supply; is the maximum ramping rate of the security power supply; and respectively represent the maximum and minimum outputs of the flexible power supply; is the flexible power supply operation 0-1 state variable, whose value is 1 representing the unit is in operation and 0 representing the unit is not in operation; is the maximum ramping rate of the flexible power supply; and T g are the minimum start-up and shutdown times of the flexible unit; are respectively the original power loads of the first-class, second-class, and third-class electricity users; is the predicted output of the new energy power plant; is the curtailment power of the new energy power plant; is the rated power of the energy storage; and are respectively the energy storage charge-discharge 0-1 state variables, whose value is 1 representing the energy storage is charging and discharging and 0 representing no charge and discharge; and are the maximum and minimum capacity limits of the energy storage; E e,t is the capacity state of the energy storage at a certain moment, E e,1 is the capacity state of the energy storage at the initial moment, E e,T is the capacity state of the energy storage at the end moment; and represent the charge-discharge efficiency of the energy storage; Δt is the time step of 1h; is the initial capacity of the energy storage.

6. The operation control method applicable to the extreme survival of a strong urban local power grid according to claim 1, characterized in that If the corridor is in a congested state, the number of important lines arranged on each safe area corridor does not exceed 2.

7. The operation control method applicable to the extreme survival of a strong local urban power grid according to claim 1, wherein Two or more important lines do not drill through each other between adjacent poles.

8. The operation control method for extreme survival of a strong local urban power grid according to claim 1, characterized in that, The objective function expression of the calculation model for the minimum startup mode that meets the power supply requirements of important loads is: where, u s and u f are the startup states of the security power supply and the flexible power supply respectively. When the value is 1, it indicates startup; when the value is 0, it indicates shutdown; Ω Gs and Ω Gf are the sets of the security power supply and the flexible power supply respectively; The constraint conditions of the calculation model for the minimum startup mode that meets the power supply requirements of important loads include: node balance constraint, line power flow constraint, line capacity constraint, wind curtailment constraint, balance node phase angle constraint, generator output constraint, and load shedding constraint; The load shedding constraint includes: During the off-grid process of a strong local power grid, to ensure uninterrupted power supply to the security loads in the important user loads, the corresponding calculation expression is as follows: ΔD d,ξ = 0, ξ = 1, 2 0 ≤ ΔD d,3 ≤ ΔD max where ΔD d,ξ is the magnitude of the ξ-level load shedding, and ΔD d,max is the maximum shedding amount of the tertiary load; After the strong local power grid goes off-grid and operates in the minimum generation mode, the power of the connection line between the strong local power grid and the superior power grid shall not exceed the following constraints: Where, ΔP max is the maximum transmission power of the tie line, H g is the inertia time constant of the synchronous unit g; S g is the rated capacity of the synchronous unit g; u g is the start / stop state of the synchronous unit g; ROCOF max is the maximum rate of frequency change; f0 is the rated frequency, and f is the frequency.

9. The operation control method applicable to the extreme survival of a strong local urban power grid according to claim 1, wherein During the adjustment process of the transmission power of the connection line channels within the strong local power grid, considering the frequency-voltage coupling interaction effects, the voltage and frequency drops or rises are controlled within the safe range.

10. An operation control device applicable to the extreme survival of a strong local power grid in a city, characterized in that, It includes a memory and a processor. The memory stores a computer program, and the processor calls the computer program to execute the steps of the method according to any one of claims 1 to 9.

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