Emergency frequency control optimization decision method and system for off-grid process of distribution system

Abstract

The present invention provides an optimization decision method and system for emergency frequency control during the off-grid process of a power distribution system, which belongs to the technical field of frequency control of a power distribution network system. An average system frequency response model of the power distribution system is established. Based on the reasonable assumption that the additional active power of the system increases approximately linearly with time, the frequency deviation is approximated as a quadratic function, and open-loop processing of the frequency response model is implemented. The obtained open-loop model makes decisions on the control amount of fast power control resources in the power distribution system, establishes an optimization model for emergency frequency control of the power distribution system, and solves and obtains a decision-making emergency control scheme under the condition of the lowest cost of emergency control measures. The present invention implements open-loop processing of the frequency response model, obtains an expression of the lowest frequency point and the additional active power of the system, makes decisions on the control amount of fast power control resources in the power distribution system, and ensures that the system frequency safety index and the like meet the requirements under the condition of the lowest cost of emergency control measures.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency control of power distribution network systems, and in particular to an optimization decision method and system for emergency frequency control during an off-grid process of a power distribution system. Background Art

[0002] The distribution system usually has the characteristics of a high proportion of external power supply, multi-voltage level operation, and coexistence of multiple heterogeneous power sources. When extreme events cause the destruction of key transmission paths, the loss of voltage in the entire substation, and the instability of the upper power grid, the distribution system may be disconnected from the upper power grid. The large active power shortage at the moment of disconnection can easily cause a large frequency fluctuation, making off-grid control difficult. Therefore, by coordinating multiple types of resources such as sources, loads, and storage within the distribution system to participate in emergency frequency control, the distribution system can smoothly transition to the island operation mode, which is of great significance to ensure uninterrupted power supply to important power loads.

[0003] Accurately establishing a system frequency response model is the basis for emergency frequency control during the off-grid process. The classic frequency response models of the power system include the average system frequency (ASF) model and the system frequency response (SFR) model. The ASF model retains the dynamic characteristics of all units and applies the output power aggregation to the equivalent rotor to obtain the dynamics of the average system frequency. The SFR model uses a reheating link speed control system to be equivalent to all generator speed control systems, converting the power grid into a single-machine model. The large-scale access of new energy sources has brought new characteristics to the frequency response of the power system, which mainly uses technologies such as fast power control or virtual inertia control to participate in system frequency control. In order to reflect the impact of new energy on the system frequency response characteristics, corresponding branches or modules can be added to the frequency response model.

[0004] In terms of emergency frequency control methods, the formulation of off-grid control strategies in existing studies is usually based on solving emergency control optimization decision models, and more focus is on how to construct frequency security constraints based on frequency response models. Reference [“Ke Deping, Feng Shuaishuai, Liu Fusuo, et al. Rapid optimization of emergency frequency control strategy for DC blocking of sending-end power grid with participation of renewable energy generation regulation [J]. Transactions of China Electrotechnical Society, 2022, 37(05): 1204-1218.”] proposes an optimization model for emergency frequency control strategy of renewable energy stations in coordination with conventional units, and discretizes the SFR model using the difference method to convert the model into a standard mixed integer linear programming problem. Reference [“Wei Jiuming, Li Zhaowei, Li Bijun, et al. Energy storage emergency control strategy for improving transient frequency safety under short-term power shocks of renewable energy [J]. Automation of Electric Power Systems, 2024, 48(08): 152-161.”] By simplifying the frequency response model, the time domain expression of system frequency response taking into account energy storage emergency power control is obtained. The literature [“Zheng Shi, Yin Xu, Ying Wang, Jinghan He, et al. Coordinating Multiple Resources for Emergency Frequency Control in the Energy Receiving-End Power System with HVDCs[J]. IEEE Transactions on Power Systems, 2023, 38(5): 4708-4723.”] reduces the order of the system frequency response model considering multiple resources based on the parameter aggregation method, and derives the time domain approximate analytical expression of the system frequency extreme points. The frequency response expressions in the above studies are mostly derived based on simplified models, and the control delay and resource aggregation issues are rarely considered. The frequency response model of the distribution system is complex and high-order, and there are multiple fast power control resources with different delay times. Traditional emergency frequency control research results are difficult to apply, and it is urgent to explore emergency frequency control strategies suitable for distribution systems. Summary of the invention

[0005] The object of the present invention is to provide a method and system for optimizing decision-making of emergency frequency control during off-grid operation of a power distribution system, so as to solve at least one technical problem existing in the above-mentioned background technology.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides an optimization decision method for emergency frequency control during an off-grid process of a power distribution system, comprising:

[0008] Obtain the frequency regulation parameters and load disturbance size of the unit, and establish an average system frequency response model of the distribution system based on the average system frequency response model;

[0009] Based on the average system frequency response model of the power distribution system and the reasonable assumption that the system's additional active power increases approximately linearly with time, the frequency deviation is approximated as a quadratic function to implement open-loop processing of the frequency response model, thereby obtaining an open-loop model;

[0010] Based on the open-loop model, a decision is made on the control amount of the fast power control resources in the power distribution system, and an optimization model for emergency frequency control of the power distribution system is established;

[0011] The optimization model of emergency frequency control of distribution system is solved to obtain the decision-making emergency control scheme with the lowest cost of emergency control measures.

[0012] Furthermore, an average system frequency response model of the distribution system is established, including: obtaining the frequency regulation parameters of wind turbines and traditional units and the size of load disturbances; deriving the wind power-frequency transfer function taking into account the operating point offset based on the small signal analysis method according to the frequency regulation parameters of the wind turbine units; obtaining the frequency response transfer function of the traditional units based on the frequency regulation parameters of the traditional units; and constructing the average system frequency response model of the distribution system based on the load disturbances, combining the wind power-frequency transfer function and the frequency response transfer function of the traditional units.

[0013] Furthermore, based on the average system frequency response model of the distribution system and the reasonable assumption that the additional active power generated by the system increases approximately linearly with time, the frequency deviation is approximated as a quadratic function to implement open-loop processing of the frequency response model. The resulting open-loop model includes: after a power system disturbance occurs, the additional active power generated by the system increases approximately linearly with time, so a linear function is used to simulate the additional active power generated by the system; when the frequency reaches the lowest point, the additional active power generated by the system is equal to the power deficit; after a disturbance occurs, the frequency response process of the power system is described by the rotor motion equation; the rotor motion equation is integrated to obtain a time domain expression of the frequency.

[0014] Furthermore, the obtained time domain expression of the system frequency is Laplace transformed to determine the additional active power of the system after the disturbance; the additional active power of the system after the disturbance is inversely Laplace transformed to obtain the time domain expression of the additional active power of the system after the disturbance. When t=t nadir When , the unbalanced power of the system is 0, and the optimization model of emergency frequency control of the distribution system is established.

[0015] In a second aspect, the present invention provides an optimization decision system for emergency frequency control during off-grid operation of a power distribution system, comprising:

[0016] The first establishment module is used to obtain the frequency regulation parameters and load disturbance size of the unit, and establish an average system frequency response model of the distribution system based on the average system frequency response model;

[0017] An open-loop module is used to approximate the frequency deviation as a quadratic function based on the average system frequency response model of the power distribution system and the reasonable assumption that the active power generated by the system increases approximately linearly with time, so as to implement open-loop processing of the frequency response model and obtain an open-loop model;

[0018] A second establishment module is used to make decisions on the control amount of the fast power control resources in the power distribution system based on the open-loop model, and establish an emergency frequency control optimization model for the power distribution system;

[0019] The solution module is used to solve the optimization model of emergency frequency control of the distribution system and obtain the decision-making emergency control plan with the lowest cost of emergency control measures.

[0020] In a third aspect, the present invention provides a non-transitory computer-readable storage medium, which is used to store computer instructions. When the computer instructions are executed by a processor, the emergency frequency control optimization decision method for the distribution system off-grid process as described in the first aspect is implemented.

[0021] In a fourth aspect, the present invention provides a computer device comprising a memory and a processor, wherein the processor and the memory communicate with each other, the memory stores program instructions executable by the processor, and the processor calls the program instructions to execute the emergency frequency control optimization decision method for the off-grid process of the distribution system as described in the first aspect.

[0022] In a fifth aspect, the present invention provides an electronic device, comprising: a processor, a memory and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory so that the electronic device executes instructions for implementing the emergency frequency control optimization decision method for the off-grid process of the distribution system as described in the first aspect.

[0023] The beneficial effects of the present invention are as follows: based on the reasonable assumption that the system's additional active power increases approximately linearly with time, the frequency deviation is approximated as a quadratic function, open-loop processing of the frequency response model is achieved, and based on the open-loop model, an expression for the lowest frequency point and the system's additional active power is obtained; a decision is made on the control amount of the fast power control resources in the distribution system, and an emergency control plan is decided to ensure that the system frequency safety indicators and the like meet the requirements when the cost of the emergency control measures is the lowest.

[0024] Additional advantages of the present invention will be more clearly given in the following description or learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0026] Figure 1 It is a schematic diagram of a process for realizing emergency frequency control during off-grid operation of a power distribution system according to an embodiment of the present invention.

[0027] Figure 2 This is an example information diagram of a power distribution system according to an embodiment of the present invention.

[0028] Figure 3 Schematic diagram of a frequency response model of a power distribution system according to an embodiment of the present invention.

[0029] Figure 4 This is a diagram showing the emergency frequency control effect of a power distribution system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below by the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0031] It should be understood by those skilled in the art that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs.

[0032] It should also be understood that terms, such as those defined in commonly used dictionaries, should be understood to have a meaning consistent with that in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless as defined herein.

[0033] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements and / or groups thereof.

[0034] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. Different embodiments or examples described in this specification and features of different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

[0035] To facilitate understanding of the present invention, the present invention is further explained below with reference to specific embodiments in conjunction with the accompanying drawings, and the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0036] Those skilled in the art should understand that the drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily necessary for implementing the present invention.

[0037] Example 1

[0038] In this embodiment 1, firstly, an optimization decision system for emergency frequency control during the off-grid process of a distribution system is provided, and the system comprises: a first establishment module, used to obtain the frequency regulation parameters and load disturbance size of the unit, and establish an average system frequency response model of the distribution system based on the average system frequency response model; an open-loop module, used to approximate the frequency deviation as a quadratic function based on the average system frequency response model of the distribution system and a reasonable assumption that the system's additional active power increases approximately linearly with time, to implement open-loop processing of the frequency response model and obtain an open-loop model; a second establishment module, used to make decisions on the control amount of the fast power control resources in the distribution system based on the open-loop model, and establish an optimization model for emergency frequency control of the distribution system; a solution module, used to solve the optimization model for emergency frequency control of the distribution system, and obtain a decision-making emergency control plan with the lowest cost of emergency control measures.

[0039] In this embodiment, the above-mentioned system can be used to implement an optimization decision method for emergency frequency control during the off-grid process of the distribution system, including: obtaining the frequency regulation parameters and load disturbance size of the unit, and establishing an average system frequency response model of the distribution system based on the average system frequency response model; based on the average system frequency response model of the distribution system, and based on the reasonable assumption that the system's additional active power increases approximately linearly with time, the frequency deviation is approximated as a quadratic function, and open-loop processing of the frequency response model is implemented to obtain an open-loop model; based on the open-loop model, a decision is made on the control amount of the fast power control resources in the distribution system, and an optimization model for emergency frequency control of the distribution system is established; the optimization model for emergency frequency control of the distribution system is solved to obtain a decision-making emergency control plan with the lowest cost of emergency control measures.

[0040] An average system frequency response model of the distribution system is established, including: obtaining the frequency regulation parameters of wind turbines and traditional units and the size of load disturbances; deriving the wind power frequency transfer function taking into account the working point offset based on the small signal analysis method according to the frequency regulation parameters of the wind turbine units; obtaining the frequency response transfer function of the traditional units based on the frequency regulation parameters of the traditional units; and constructing the average system frequency response model of the distribution system based on the load disturbance, combining the wind power frequency transfer function and the frequency response transfer function of the traditional units.

[0041] Based on the average system frequency response model of the distribution system and the reasonable assumption that the additional active power of the system increases approximately linearly with time, the frequency deviation is approximated as a quadratic function to implement open-loop processing of the frequency response model. The obtained open-loop model includes: after a power system disturbance occurs, the additional active power of the system increases approximately linearly with time, so a linear function is used to simulate the additional active power of the system; when the frequency reaches the lowest point, the additional active power of the system is equal to the power deficit; after a disturbance occurs, the frequency response process of the power system is described by a rotor motion equation; the rotor motion equation is integrated to obtain a time domain expression of the frequency.

[0042] The obtained time domain expression of the system frequency is Laplace transformed to determine the additional active power of the system after the disturbance; the additional active power of the system after the disturbance is inversely Laplace transformed to obtain the time domain expression of the additional active power of the system after the disturbance. When t = t nadir When , the unbalanced power of the system is 0, and the optimization model of emergency frequency control of the distribution system is established.

[0043] Example 2

[0044] like Figures 1 to 4 As shown, in this embodiment 2, an optimization decision method for emergency frequency control during off-grid operation of a distribution system is provided to improve the resilience of the distribution system, and the following technical solutions are adopted:

[0045] S1: Collect frequency modulation parameters and load disturbance size of synchronous units, wind power and other resources, and establish an average system frequency response model of the distribution system based on the average system frequency response model; this step may include the following steps:

[0046] Obtain the frequency regulation parameters of wind turbines and traditional turbines and the size of load disturbances, and derive the wind power-frequency transfer function taking into account the working point offset based on the small signal analysis method:

[0047]

[0048] In the formula, ΔP we1 is the output power increment of the wind turbine when participating in frequency regulation; s is the Laplace operator; k P is the droop coefficient; Δf is the frequency change; T W Indicates the fan control response time constant.

[0049] Get the frequency modulation parameters of the traditional unit, the frequency response transfer function expression of the traditional unit:

[0050]

[0051] In the formula, F H , T R , T ch , T g and R are the work ratio of the high-pressure cylinder of the thermal power unit steam turbine, the time constant of the reheater, the volume effect constant of the steam turbine, the time constant of the governor and the adjustment coefficient; ΔP SG It is the output increment of the traditional unit during frequency regulation; Δf(s) is the change in system frequency.

[0052] The disturbance magnitude is obtained and the average system frequency response model of the distribution system is constructed.

[0053] S2: Based on the average system frequency response model of the power distribution system described in S1, and based on the reasonable assumption that the system's additional active power increases approximately linearly with time, the frequency deviation is approximated as a quadratic function, and open-loop processing of the frequency response model is implemented. Based on the open-loop model, an expression of the lowest frequency point and the system's additional active power is obtained; this step may include the following steps:

[0054] After the power system disturbance occurs, the additional active power of the system increases approximately linearly with time. Therefore, a linear function can be used to simulate the additional active power of the system. When the frequency reaches the lowest point, the additional active power of the system is equal to the power deficit. That is:

[0055]

[0056] After the disturbance occurs, the frequency response process of the power system can be described by the rotor motion equation:

[0057]

[0058] Where ΔP is the active power added by the system when the frequency reaches the lowest point; H is the equivalent inertia time constant of the system; ΔP m (t) is the change of system active power over time; ΔP e (t) is the change of system electromagnetic power over time; t d1 ,t d2 ,...,t dn Represents the delay time corresponding to each fast power control resource; t nadir Indicates the time when the frequency reaches the lowest point.

[0059] u(tt di ) is the unit delay step function, as shown in the following equation.

[0060]

[0061] For equation (4) at t∈[0,t nadir ], the time domain expression of the frequency can be obtained as follows:

[0062]

[0063] Therefore, the frequency response model of the open-loop distribution system is as follows: Figure 1 shown.

[0064] S3: Based on the open-loop model described in S2, a decision is made on the control amount of the fast power control resources in the power distribution system, and an emergency control solution is decided to ensure that the system frequency safety index and other requirements are met when the cost of the emergency control measures is the lowest. This step may include the following steps:

[0065] Perform Laplace transform on the time domain expression of the system frequency obtained from equation (6):

[0066]

[0067] At this time, the active power ΔP generated by the system after the disturbance m (s) is:

[0068]

[0069] Where: G sys The transfer function of the system

[0070] ΔP m (s) Perform an inverse Laplace transform to obtain the time domain expression of the additional active power of the system after the disturbance: ΔP m (t). When t=t nadirWhen , the unbalanced power of the system is 0, so:

[0071]

[0072] Therefore, the optimization model of emergency frequency control of distribution system can be established:

[0073]

[0074] In the formula, Δf m is the maximum frequency deviation allowed by the system. The first constraint indicates that the maximum frequency variation of the system is less than the maximum frequency deviation allowed by the system. The second constraint indicates that when t=t nadir When , the unbalanced power of the system is 0; x 1, x 2,..., x n and are the upper and lower limits of the adjustable amount of each fast power control resource. c1,c2,...,c n is the cost corresponding to each fast power control resource.

[0075] By solving the above optimization model, the control amount of each fast power control resource can be obtained, so that the maximum frequency deviation after the emergency control action is within a reasonable range under the lowest cost.

[0076] In this embodiment, a method for emergency frequency control during the off-grid process of a distribution system is provided. Based on the reasonable assumption that the system's additional active power increases approximately linearly with time, the frequency deviation is approximated as a quadratic function, open-loop processing of the frequency response model is implemented, and based on the open-loop model, an expression for the lowest frequency point and the system's additional active power is obtained; a decision is made on the control amount of the fast power control resources in the distribution system, and an emergency control plan is decided to ensure that the system frequency safety indicators and other requirements are met when the cost of emergency control measures is minimized.

[0077] Example 3

[0078] This embodiment 3 provides a non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by a processor, the above-mentioned method for optimizing decision-making for emergency frequency control during off-grid operation of a power distribution system is implemented. The method includes:

[0079] Obtain the frequency regulation parameters and load disturbance size of the unit, and establish an average system frequency response model of the distribution system based on the average system frequency response model;

[0080] Based on the average system frequency response model of the power distribution system and the reasonable assumption that the system's additional active power increases approximately linearly with time, the frequency deviation is approximated as a quadratic function to implement open-loop processing of the frequency response model, thereby obtaining an open-loop model;

[0081] Based on the open-loop model, a decision is made on the control amount of the fast power control resources in the power distribution system, and an optimization model for emergency frequency control of the power distribution system is established;

[0082] The optimization model of emergency frequency control of distribution system is solved to obtain the decision-making emergency control scheme with the lowest cost of emergency control measures.

[0083] Example 4

[0084] This embodiment 4 provides a computer device, including a memory and a processor, the processor and the memory communicate with each other, the memory stores program instructions executable by the processor, the processor calls the program instructions to execute the above-mentioned distribution system off-grid emergency frequency control optimization decision method, the method comprising:

[0085] Obtain the frequency regulation parameters and load disturbance size of the unit, and establish an average system frequency response model of the distribution system based on the average system frequency response model;

[0086] Based on the average system frequency response model of the power distribution system and the reasonable assumption that the system's additional active power increases approximately linearly with time, the frequency deviation is approximated as a quadratic function to implement open-loop processing of the frequency response model, thereby obtaining an open-loop model;

[0087] Based on the open-loop model, a decision is made on the control amount of the fast power control resources in the power distribution system, and an optimization model for emergency frequency control of the power distribution system is established;

[0088] The optimization model of emergency frequency control of distribution system is solved to obtain the decision-making emergency control scheme with the lowest cost of emergency control measures.

[0089] Example 5

[0090] This embodiment 5 provides an electronic device, including: a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory, so that the electronic device executes instructions for implementing the above-mentioned method for optimizing decision-making of emergency frequency control during off-grid operation of a distribution system, the method including:

[0091] Obtain the frequency regulation parameters and load disturbance size of the unit, and establish an average system frequency response model of the distribution system based on the average system frequency response model;

[0092] Based on the average system frequency response model of the power distribution system and the reasonable assumption that the system's additional active power increases approximately linearly with time, the frequency deviation is approximated as a quadratic function to implement open-loop processing of the frequency response model, thereby obtaining an open-loop model;

[0093] Based on the open-loop model, a decision is made on the control amount of the fast power control resources in the power distribution system, and an optimization model for emergency frequency control of the power distribution system is established;

[0094] The optimization model of emergency frequency control of distribution system is solved to obtain the decision-making emergency control scheme with the lowest cost of emergency control measures.

[0095] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0096] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0097] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0098] These computer program instructions can also be loaded onto a computer or other programmable data processing device, and a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0099] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative work on the basis of the technical solution disclosed in the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for optimizing decision-making of emergency frequency control during off-grid process of power distribution system, characterized in that: include: Obtain the frequency regulation parameters and load disturbance size of the unit, and establish an average system frequency response model of the distribution system based on the average system frequency response model; Based on the average system frequency response model of the power distribution system and the reasonable assumption that the system's additional active power increases approximately linearly with time, the frequency deviation is approximated as a quadratic function to implement open-loop processing of the frequency response model, thereby obtaining an open-loop model; including: A linear function is used to simulate the additional active power of the system. When the frequency reaches the lowest point, the additional active power of the system is equal to the power deficit, that is: After the disturbance occurs, the frequency response process of the power system is described by the rotor motion equation as follows: Where ΔP is the active power value generated by the system when the frequency reaches the lowest point; H sys is the system equivalent inertia time constant; ΔP m (t) is the change of system active power over time; ΔP e (t) is the change of system electromagnetic power over time; t d1 ,t d2 ,...,t dn Represents the delay time corresponding to each fast power control resource; t nadir Indicates the time when the frequency reaches the lowest point; u(tt di ) is a unit delay step function: The rotor motion equation is nadir ] to obtain the time domain expression of frequency: Among them, a, b, c are constants; Based on the open-loop model, a decision is made on the control amount of the fast power control resource in the distribution system, and an optimization model for emergency frequency control of the distribution system is established; including: performing Laplace transform on the time domain expression of the frequency: The additional active power ΔP of the system after the disturbance m (s) is: Where: G sys is the transfer function of the system; ΔP m (s) Perform inverse Laplace transform to obtain the time domain expression of the additional active power of the system after the disturbance ΔP m (t), when t = t nadir When the unbalanced power of the system is 0, then: The optimization model of emergency frequency control of distribution system is established as: Where Δf m is the maximum frequency deviation allowed by the system. The first constraint indicates that the maximum frequency variation of the system is less than the maximum frequency deviation allowed by the system. The second constraint indicates that when t=t nadir When x1,x2,...,x n and are the upper and lower limits of the adjustable amount of each fast power control resource; c1, c2, ..., c n is the cost corresponding to each fast power control resource; x i represents the i-th fast power control resource, i∈1,2,...,n; The optimization model of emergency frequency control of distribution system is solved to obtain the decision-making emergency control scheme with the lowest cost of emergency control measures.

2. The method for optimizing decision-making for emergency frequency control during off-grid operation of a power distribution system according to claim 1, characterized in that: An average system frequency response model of the distribution system is established, including: obtaining the frequency regulation parameters of wind turbines and traditional units and the size of load disturbances; deriving the wind power frequency transfer function taking into account the working point offset based on the small signal analysis method according to the frequency regulation parameters of the wind turbine units; obtaining the frequency response transfer function of the traditional units based on the frequency regulation parameters of the traditional units; and constructing the average system frequency response model of the distribution system based on the load disturbance, combining the wind power frequency transfer function and the frequency response transfer function of the traditional units.

3. The method for optimizing decision-making for emergency frequency control during off-grid operation of a power distribution system according to claim 2, characterized in that: Based on the small signal analysis method, the wind power frequency transfer function taking into account the working point offset is derived as follows: In the formula, ΔP we1 It is the output power increment of wind turbines when participating in frequency regulation; s is the Laplace operator; k P is the droop coefficient; Δf is the frequency change; T W Indicates the fan control response time constant; The frequency response transfer function expression of the traditional unit is: In the formula, F h 、T R 、T ch 、T g and R are the work ratio of the high-pressure cylinder of the thermal power unit steam turbine, the time constant of the reheater, the volume effect constant of the steam turbine, the time constant of the governor and the adjustment coefficient; ΔP SG It is the output increment of the traditional unit during frequency regulation; Δf(s) is the change in system frequency.

4. An emergency frequency control optimization decision system for off-grid process of power distribution system, characterized in that: include: The first establishment module is used to obtain the frequency regulation parameters and load disturbance size of the unit, and establish an average system frequency response model of the distribution system based on the average system frequency response model; An open-loop module is used to approximate the frequency deviation as a quadratic function based on the average system frequency response model of the power distribution system and the reasonable assumption that the additional active power of the system increases approximately linearly with time, so as to implement open-loop processing of the frequency response model and obtain an open-loop model; including: A linear function is used to simulate the additional active power of the system. When the frequency reaches the lowest point, the additional active power of the system is equal to the power deficit, that is: After the disturbance occurs, the frequency response process of the power system is described by the rotor motion equation as follows: Where ΔP is the active power value generated by the system when the frequency reaches the lowest point; H sys is the system equivalent inertia time constant; ΔP m (t) is the change of system active power over time; ΔP e (t) is the change of system electromagnetic power over time; t d1 ,t d2 ,...,t dn Represents the delay time corresponding to each fast power control resource; t nadir Indicates the time when the frequency reaches the lowest point; u(tt di ) is a unit delay step function: The rotor motion equation is nadir ] to obtain the time domain expression of frequency: Among them, a, b, c are constants; The second establishment module is used to make decisions on the control amount of the fast power control resources in the distribution system based on the open-loop model and establish an emergency frequency control optimization model for the distribution system; including: performing Laplace transform on the time domain expression of the frequency: The additional active power ΔP of the system after the disturbance m (s) is: Where: G sys is the transfer function of the system; ΔP m (s) Perform inverse Laplace transform to obtain the time domain expression of the additional active power of the system after the disturbance ΔP m (t), when t = t nadir When the unbalanced power of the system is 0, then: The optimization model of emergency frequency control of distribution system is established as: Where Δf m is the maximum frequency deviation allowed by the system. The first constraint indicates that the maximum frequency variation of the system is less than the maximum frequency deviation allowed by the system. The second constraint indicates that when t=t nadir When , the unbalanced power of the system is 0; x 1, x 2,..., x n and are the upper and lower limits of the adjustable amount of each fast power control resource; c1, c2, ..., c n is the cost corresponding to each fast power control resource; x i represents the i-th fast power control resource, i∈1,2,...,n; The solution module is used to solve the optimization model of emergency frequency control of the distribution system and obtain the decision-making emergency control plan with the lowest cost of emergency control measures.

5. A computer device, characterized in that: It includes a memory and a processor, the processor and the memory communicate with each other, the memory stores program instructions that can be executed by the processor, and the processor calls the program instructions to execute the emergency frequency control optimization decision method for the off-grid process of the distribution system as described in any one of claims 1-3.

6. An electronic device, characterized in that: include: A processor, a memory and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory so that the electronic device executes instructions for implementing the method for optimizing decision-making for emergency frequency control during off-grid operation of a power distribution system as described in any one of claims 1 to 3.

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