Method and System for Evaluating Power System Frequency Stability Margin Considering Network-Forming Energy Storage

Abstract

A method and system for evaluating the frequency stability margin of a power system considering network-forming energy storage. The total inertia of the power generation resources on the power generation resource side of the system is taken as the total inertia of the system, and the system inertia time constant is determined. The minimum inertia time constant requirement of the system is determined by using the N-1 inertia disturbance power and the system frequency change rate. The inertia stability margin of the system is determined by using the system inertia time constant and the minimum inertia time constant requirement of the system. The frequency modulation power stability margin in the system load increase direction and the frequency modulation power stability margin in the system load decrease direction are respectively determined by using the total up and down frequency modulation powers of the power generation resource side of the system and the minimum values of the system up and down frequency modulation power requirements. The frequency stability margin of the power system is evaluated by using the inertia stability margin of the system, the frequency modulation power stability margin in the system load increase direction and the frequency modulation power stability margin in the system load decrease direction, so as to ensure the safe and stable operation of the new power system.

Description

Technical Field

[0001] The present invention relates to the technical field of power system stability assessment and control, and particularly to a new method and system for evaluating the frequency stability margin of a power system based on a network-forming energy storage system. Background Art

[0002] The frequency stability of a new power system with a high proportion of new energy is facing severe challenges. On the one hand, the power generation of wind and solar renewable energy has characteristics such as strong randomness, volatility, and intermittency, making it increasingly difficult to balance the active power of the system. On the other hand, the power system with a high proportion of new energy has a low inertia level, poor frequency regulation ability, and weak anti-interference ability. The main reasons for this characteristic include: power electronic devices such as wind and solar renewable energy often adopt a grid-following control mode and operate in the maximum power point tracking (MPPT) state, do not participate in the frequency coupling process of the power grid, hardly show inertia response to the power grid, and have no primary frequency regulation ability; improper operation control strategies of power electronic devices may deteriorate the frequency oscillation mode of the system, reduce the self-stabilization of the system, and the tolerance ability (overvoltage, overcurrent, frequency crossing) of power electronic devices is poor, and frequency disturbances are likely to cause them to trip off the grid, which in turn has an adverse impact on the frequency stability of the system. In recent years, frequency stability accidents have occurred frequently, and their internal reasons are mainly related to factors such as low inertia level and insufficient frequency regulation reserve.

[0003] With the promotion of the "dual carbon" goal, the construction of a new power system has accelerated, and the proportion of new energy and power electronic devices in the power system has been increasing continuously. In this development process, problems such as system strength reduction and stability reduction are also faced. The emergence of network-forming control technology can greatly avoid such situations. In the "dual high" new power system, it has the control characteristics of active inertia support and can participate in primary and secondary frequency regulation, thereby maintaining the frequency stability of the power system. While having the network-forming characteristics, the network-forming energy storage system has the ability of bidirectional power deep regulation, can provide stable frequency support for the system, can also operate in island mode and grid-connected mode and provide black start, and can achieve 100% new energy access, playing an increasingly important role in the field of new power systems and having a very broad application prospect. Summary of the Invention

[0004] To address the deficiencies in the existing system frequency stability assessment method that do not consider network-forming devices, the present invention provides a method and system for assessing the frequency stability margin of a power system considering network-forming energy storage. Aiming at the problems of high new energy proportion, decreasing inertia level, and insufficient frequency regulation capacity in the new power system, the supporting role of network-forming energy storage devices in power grid frequency stability is considered. The frequency stability operation level of the new power system is evaluated from two dimensions: the system inertia stability margin and the primary frequency regulation power stability margin, enhancing the awareness of the frequency stability operation situation of the new power system, which is of great significance for ensuring the safe and stable operation of the new power system.

[0005] The present invention adopts the following technical solutions.

[0006] The present invention proposes a method for assessing the frequency stability margin of a power system considering network-forming energy storage. The power generation resources of the power system include conventional units, network-forming energy storage power stations, and new energy power stations, and it includes:

[0007] Obtain the stability constraint parameters of the power generation resources and the system fault data. Based on the N-1 principle, calculate the N-1 inertia disturbance power, N-1 upward frequency regulation disturbance power, and the minimum value of the system upward frequency regulation power demand, N-1 downward frequency regulation disturbance power, and the minimum value of the system downward frequency regulation power demand of the system;

[0008] Take the sum of the total inertias of different types of power generation resources as the total inertia on the power generation resource side of the system, so as to determine the system inertia time constant; use the N-1 inertia disturbance power and the system frequency change rate to determine the minimum inertia time constant demand of the system; use the system inertia time constant and the minimum inertia time constant demand of the system to determine the system inertia stability margin;

[0009] Use the total upward frequency regulation power on the power generation resource side of the system and the minimum value of the system upward frequency regulation power demand to determine the frequency regulation power stability margin in the system load increase direction; use the total downward frequency regulation power on the power generation resource side of the system and the minimum value of the system downward frequency regulation power demand to determine the frequency regulation power stability margin in the system load decrease direction;

[0010] Use the system inertia stability margin, the frequency regulation power stability margin in the system load increase direction, and the frequency regulation power stability margin in the system load decrease direction to evaluate the frequency stability margin of the power system.

[0011] Preferably, obtain the system fault data. Based on the N-1 principle, calculate the inertia disturbance power, upward frequency regulation disturbance power, and downward frequency regulation disturbance power of the system, including:

[0012] Obtain the power loss and power surplus amount when a single or double pole blockage occurs in the system's external DC connection line and the power loss amount when large-scale new energy bases in the system have cascading faults and trip off the network Power loss due to large unit tripping within the system Power surplus due to large load disconnecting from the grid

[0013] Based on the N - 1 principle, calculate the real - time inertia disturbance power, upward frequency regulation disturbance power, and downward frequency regulation disturbance power of the system as follows:

[0014] Take and The maximum value in as the N - 1 upward frequency regulation disturbance power

[0015] Take and The maximum value in as the N - 1 downward frequency regulation disturbance power

[0016] Take and The maximum value in as the N - 1 inertia disturbance power ΔP H .

[0017] Preferably, according to the stable constraint parameters of power generation resources, the real - time N - 1 inertia disturbance power, N - 1 upward frequency regulation disturbance power, and N - 1 downward frequency regulation disturbance power of the system, based on the system transient power - frequency response model, simulate the dynamic process of the system frequency response after a fault to solve the maximum value of the frequency difference and the maximum value of the system frequency change rate when the system fails.

[0018] Preferably, under the system frequency deviation constraint conditions, determine the minimum value of the system power - side frequency regulation characteristic coefficient according to the maximum value of the frequency difference by the following relational expression:

[0019]

[0020] In the formula, M1 is the proportional coefficient; α1 is the adjustable exponent of time; t m1 , t OB Are the moment of the maximum frequency and the moment of the reference frequency respectively; ω1 is the angular frequency; Is the phase angle; ΔP L Is the real - time N - 1 maximum active power disturbance or N - 2 maximum active power disturbance of the system, including the maximum upward frequency regulation disturbance And the maximum downward frequency regulation disturbance Covering large - disturbance fault scenarios such as DC blocking and new - energy base disconnecting from the grid; K g Is the system power - side frequency regulation characteristic coefficient; K L Is the system active power - frequency characteristic coefficient;

[0021] Among them, the system frequency deviation constraint conditions include the low - frequency load - shedding threshold value and the high - frequency generator - tripping threshold value; the minimum value of the system power - side frequency regulation characteristic coefficient includes: corresponding to the system low - frequency load - shedding threshold value The minimum value of the frequency regulation characteristic coefficient on the system power supply side Corresponding to the system high-frequency generator tripping threshold The minimum value of the frequency regulation characteristic coefficient on the system power supply side for frequency reduction

[0022] Preferably, using the minimum value of the frequency regulation characteristic coefficient on the system power supply side, calculate the minimum value of the system frequency regulation power demand according to the following relational expression:

[0023]

[0024] In the formula, is the minimum value of the system frequency regulation power demand for frequency increase; is the minimum value of the system frequency regulation power demand for frequency reduction.

[0025] Preferably, use the sum of the total inertias of different types of power generation resources as the total inertia on the system power generation resource side, so as to determine the system inertia time constant; use the N-1 inertia disturbance power and the system frequency change rate to determine the system minimum inertia time constant demand; use the system inertia time constant and the system minimum inertia time constant demand to determine the system inertia stability margin, including:

[0026] Calculate the total inertia of conventional units, grid-forming energy storage power stations and new energy power stations respectively;

[0027] Use the sum of the total inertias of different types of power generation resources as the total inertia on the system power generation resource side, and calculate the system inertia time constant according to the following relational expression:

[0028] H sys =(E gΣ +E wΣ +E SΣ ) / P Lsys

[0029] In the formula, P Lsys is the system total load;

[0030] Use the N-1 inertia disturbance power ΔP H and the system frequency change rate to calculate the system minimum inertia time constant demand H min :

[0031] H min =ΔP H / (df / dt) max

[0032] In the formula, (df / dt) max is the maximum value of the system frequency change rate;

[0033] Calculate the system inertia stability margin according to the following relational expression:

[0034]

[0035] Wherein, H marg is the system inertia stability margin.

[0036] Preferably, the total inertia of the conventional unit is calculated by the following relational expression:

[0037]

[0038] Wherein, E gΣ is the total inertia of the conventional unit; ζ gi is the operating state of the conventional unit i. When the conventional unit is connected to the grid, ζ gi takes 1, otherwise ζ gi takes 0; H gi is the inertia time constant of the conventional unit i; S Ni is the rated capacity of the conventional unit i; n g is the number of conventional units;

[0039] The total inertia of the grid-forming energy storage power station is calculated by the following relational expression:

[0040]

[0041] Wherein, E SΣ is the total inertia of the grid-forming energy storage power station; ζ Sj is the flag bit indicating whether the energy storage power station j operates in the grid-forming mode. When the energy storage power station j operates in the grid-forming mode, ζ Sj takes 1, otherwise ζ Sj takes 0; H Sj is the virtual inertia time constant set for the grid-forming energy storage power station j; S Sj is the rated capacity of the grid-forming energy storage power station j; n S is the number of grid-forming energy storage power stations;

[0042] The total inertia of the new energy power station is calculated by the following relational expression:

[0043]

[0044] Wherein, E wΣ is the total inertia of the new energy power station; ζ wj is the flag bit indicating whether the new energy power station j has the virtual inertia response ability. When the new energy power station j has the virtual inertia response ability, ζ wj takes 1, otherwise ζ wj takes 0; H wj is the virtual inertia time constant of the new energy power station j; P wj is the active power of the new energy power station j; n w is the number of new energy power stations;

[0045] For the same energy storage power station j, the following constraint conditions are introduced:

[0046] ζ Sj +ζ wj = 1

[0047] When the energy storage power station j operates in the grid-forming mode, ζ Sj takes 1, and ζ wj takes 0; conversely, when the energy storage power station j operates in the non-grid-forming mode, ζ Sj takes 0, and ζ wj takes 1.

[0048] Preferably, the frequency modulation power stability margin in the system load increase direction is determined by using the total upward frequency modulation power on the system power generation resource side and the minimum value of the system upward frequency modulation power demand; the frequency modulation power stability margin in the system load decrease direction is determined by using the total downward frequency modulation power on the system power generation resource side and the minimum value of the system downward frequency modulation power demand, including:

[0049] Calculate the upward and downward frequency modulation powers of conventional units, new energy power stations, and energy storage power stations respectively;

[0050] Take the sum of the upward frequency modulation powers of different types of power generation resources as the total upward frequency modulation power ΔP + of the system power generation resource side; take the sum of the downward frequency modulation powers of different types of power generation resources as the total downward frequency modulation power ΔP - of the system power generation resource side;

[0051] Calculate the system frequency modulation power stability margin according to the following relational expression:

[0052]

[0053] In the formula, is the frequency modulation power stability margin in the system load increase direction, is the frequency modulation power stability margin in the system load decrease direction; are respectively the minimum value of the system upward frequency modulation power demand and the minimum value of the system downward frequency modulation power demand.

[0054] Preferably, calculate the upward frequency modulation power and the downward frequency modulation power

[0055]

[0056] In the formula, ζ j is the operating state of the thermal power unit or nuclear power unit j. When the unit is connected to the grid, ζ j takes 1, and conversely ζ j takes 0; χ jIt is the required value of the minimum frequency regulation power for thermal power and nuclear power units with different installed capacities in GB / T 40595-2021 "Technical Regulations and Test Guidelines for Primary Frequency Regulation of Grid-Connected Power Sources"; P Nj It is the rated active power of unit j; P min It is the allowable minimum technical output of thermal power units or nuclear power units;

[0057] The upward frequency regulation power of hydropower units is calculated by the following relational expression and the downward frequency regulation power

[0058] In the formula, ζ h is the operating state of hydropower unit h. When the unit is connected to the grid, ζ h takes 1, otherwise ζ h takes 0; χ h is the required value of the minimum frequency regulation power for hydropower units with different outputs in GB / T40595-2021 "Technical Regulations and Test Guidelines for Primary Frequency Regulation of Grid-Connected Power Sources"; P Nh is the rated power of the hydropower unit, P h is the actual active output of the unit; if there is a unit vibration operation area in the load increase direction of the operating point of hydropower unit h, then P oh takes the lower threshold power value of the unit vibration operation area. If there is no unit vibration operation area in the load increase direction of hydropower unit h, then P oh takes (1 + χ h )P Nh ; if there is a unit vibration operation area in the load decrease direction of hydropower unit h, then P qh takes the upper threshold power value of the unit vibration operation area. If there is no unit vibration operation area in the load decrease direction of hydropower unit h, then P qh takes 0;

[0059] The upward frequency regulation power of new energy power stations is calculated by the following relational expression and the downward frequency regulation power

[0060]

[0061] In the formula, χ g is the flag bit indicating whether the new energy power station g is equipped with the primary frequency regulation function. When the primary frequency regulation function is equipped, χ g takes 1, otherwise χ g takes 0; P g is the active power of the new energy power station g, P g_pred is the ultra-short-term predicted power of the new energy power station g;

[0062] The upward frequency regulation power of energy storage power stations is calculated by the following relational expression and the down-regulation frequency power

[0063] where χ m is the flag bit indicating whether the energy storage power station m is configured with the primary frequency regulation function. When the primary frequency regulation function is configured, χ m takes 1, and vice versa, χ m takes 0; P m is the active power of the power station collected in real time, is the maximum allowable regulation power in the load increase direction of the energy storage power station m; is the maximum allowable regulation power in the load decrease direction of the energy storage power station m.

[0064] Preferably, the total up-regulation frequency power ΔP on the power generation resource side of the system is calculated by the following relational expression + :

[0065]

[0066] The total down-regulation frequency power ΔP on the power generation resource side of the system is calculated by the following relational expression - :

[0067]

[0068] Preferably, the frequency stability margin of the power system is evaluated by using the system inertia stability margin, the frequency regulation power stability margin in the system load increase direction, and the frequency regulation power stability margin in the system load decrease direction, including:

[0069] The real-time frequency stability margin F of the system is calculated by the following relational expression marg :

[0070]

[0071] where H marg is the system inertia stability margin; is the frequency regulation power stability margin in the system load increase direction, is the frequency regulation power stability margin in the system load decrease direction; λ1, λ2, and λ3 are all evaluation factors, and satisfy λ1 + λ2 + λ3 = 1.

[0072] Preferably, the objective function minF for optimizing the evaluation factors is established, satisfying the following relational expression:

[0073]

[0074] where C(H marg ≤1) is the number of times that H marg is less than or equal to 100%, is The number of times less than or equal to 100%, is The number of times less than or equal to 100%.

[0075] Taking the evaluation factor corresponding to the minimum value of the objective function minF as the optimal value, calculate the real-time frequency stability margin of the system based on the optimal value.

[0076] The present invention also proposes a power system frequency stability margin evaluation system considering network-forming energy storage, including:

[0077] A parameter calculation module, an inertia margin calculation module, a frequency regulation power margin calculation module, and a frequency stability margin evaluation module;

[0078] The parameter calculation module is used to obtain the stable constraint parameters of the power generation resources and the system fault data, and calculate the N-1 inertia disturbance power, N-1 upward frequency regulation disturbance power and the minimum value of the system upward frequency regulation power demand, N-1 downward frequency regulation disturbance power and the minimum value of the system downward frequency regulation power demand of the system based on the N-1 principle;

[0079] The inertia margin calculation module is used to take the sum of the total inertias of different types of power generation resources as the total inertia on the power generation resource side of the system, so as to determine the system inertia time constant; use the N-1 inertia disturbance power and the system frequency change rate to determine the minimum inertia time constant demand of the system; use the system inertia time constant and the minimum inertia time constant demand of the system to determine the system inertia stability margin;

[0080] The frequency regulation power margin calculation module is used to use the total upward frequency regulation power on the power generation resource side of the system and the minimum value of the system upward frequency regulation power demand to determine the frequency regulation power stability margin in the system load increase direction; use the total downward frequency regulation power on the power generation resource side of the system and the minimum value of the system downward frequency regulation power demand to determine the frequency regulation power stability margin in the system load decrease direction;

[0081] The frequency stability margin evaluation module is used to evaluate the frequency stability margin of the power system by using the system inertia stability margin, the frequency regulation power stability margin in the system load increase direction and the frequency regulation power stability margin in the system load decrease direction.

[0082] A terminal includes a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method.

[0083] A computer-readable storage medium stores a computer program thereon, and when the program is executed by a processor, the steps of the method are implemented.

[0084] The beneficial effects of the present invention are at least as follows compared with the prior art:

[0085] 1) Consider the network-forming energy storage device, classify the main body of in-network power generation resources by region and category, conduct grouped evaluations of inertia level and frequency regulation power according to the characteristics of various resources, and conduct zonal statistics and display of frequency stability support capabilities according to dispatching agencies. When the system's frequency regulation capacity is insufficient, the frequency regulation resources can be flexibly adjusted according to the evaluation results of the frequency regulation capabilities of each region.

[0086] 2) Conduct real-time analysis of the system's anticipated disturbance forms. For the transient power-frequency response process after the system's anticipated disturbance, considering the constraints of the system frequency change rate and the boundary conditions of high and low frequency operation stability, simulate the system's frequency operation characteristics to obtain the evaluation results of the system's inertia stability margin and frequency regulation power stability margin.

[0087] 3) Comprehensively consider the two influencing factors of the system's inertia stability level and frequency regulation power level that determine the system's frequency stability, introduce a weighted evaluation factor, and conduct an evaluation of the system's frequency stability margin. The evaluation scheme is more comprehensive than a single inertia evaluation, and the evaluation results can better reflect the true frequency stability boundary conditions of the system. Description of the Drawings

[0088] Figure 1 It is a flowchart of a new method and system for evaluating the frequency stability margin of a power system considering network-forming energy storage proposed by the present invention. Detailed Embodiment

[0089] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only a part of the embodiments of the present invention, not all embodiments. Based on the spirit of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0090] The present invention proposes a method for evaluating the frequency stability margin of a power system considering network-forming energy storage, as Figure 1 shown, including:

[0091] Step 1: Obtain the stability constraint parameters of power generation resources and system fault data, and calculate the N-1 inertia disturbance power, N-1 upward frequency regulation disturbance power, and N-1 downward frequency regulation disturbance power of the system based on the N-1 principle.

[0092] Specifically, Step 1 includes:

[0093] Step 1.1: Divide the power grid into regions and then groups according to the dispatching agencies to which the power generation resources belong and the types of power generation resources.

[0094] In a non-limiting preferred embodiment, the power generation resources belonging to the same dispatching agency are divided into the same partition, and the entire network is divided into m partitions, where m is a positive integer. Within the same partition, the power generation resources are divided into a thermal power group, a hydropower group, a nuclear power group, a wind power group, a photovoltaic group, a conventional energy storage group, and a network-forming energy storage group according to the type of power generation resources.

[0095] Partition according to the affiliated dispatching agency, so that each power generation resource is directly dispatched and controlled by its affiliated dispatching agency. After the actual inertia and frequency regulation power of the power generation resources in each region are evaluated subsequently, the inertia and frequency regulation power of the power generation resources managed by each dispatching agency can be intuitively displayed. At the same time, when the inertia and frequency regulation power of the power generation resources are insufficient, the dispatching agency can take targeted measures such as controlling the start-up and output to improve the frequency stability.

[0096] After partitioning the entire network according to the affiliated dispatching agency of the power generation-side resources in the network, then group the power generation resources within the region according to the type of power generation-side resources in the network. Within the same partition, it is divided into a thermal power group, a hydropower group, a nuclear power group, a wind power group, a photovoltaic group, a conventional energy storage group, and a network-forming energy storage group according to the resource type. By grouping the resources, different types of resources have different inertia and frequency regulation power evaluation methods, different adjustment priorities, and different adjustable limits.

[0097] Step 1.2, obtain the stability constraint parameters of all power generation resources, including but not limited to: rated capacity.

[0098] Furthermore, the stability constraint parameters obtained for thermal power units include but are not limited to: the minimum allowable technical output; the stability constraint parameters obtained for hydropower units include but are not limited to: the non-vibration allowable operating output range.

[0099] Step 1.3, obtain the operating status of the power generation resources and the operating status of the AC and DC tie lines.

[0100] Specifically, real-time monitor the operating status information of each power generation resource entity, including but not limited to start-stop information and active power information; real-time monitor the operating status information of the system's external AC tie lines, including but not limited to start-stop information and active power information; real-time monitor the operating status information of the system's external DC tie lines, including but not limited to the start-stop information and active power information of the high- and low-voltage converter poles; real-time monitor the load information of the entire network; and real-time obtain the ultra-short-term power prediction curve of each new energy power station.

[0101] Obtain the information such as the rated capacity of all power generation resources, the allowable minimum technical output parameters of thermal power units, the non-vibration allowable operating output range of hydropower units, and the ultra-short-term power prediction curves of new energy power plants successively through Step 1.2 and Step 1.3. On the one hand, it is for the per-unitization processing of various parameters when constructing the system transient power-frequency response model subsequently, and on the other hand, it is for parameter preparation for the inertia assessment and frequency regulation power assessment of various power generation resources subsequently.

[0102] Step 1.4: Obtain system fault data, and calculate the real-time inertia disturbance power, upward frequency regulation disturbance power, and downward frequency regulation disturbance power of the system based on the N-1 principle.

[0103] Specifically, Step 1.4 includes:

[0104] Step 1.4.1: Obtain the power loss and power surplus amounts caused by the single-pole or double-pole blocking of the system's external DC connection lines. and the power surplus amount the power loss amount caused by the cascading faults and disconnections of large-scale new energy bases within the system the power loss amount caused by the tripping of large units within the system the power surplus amount caused by the disconnection of large loads

[0105] In a non-restrictive preferred embodiment, the fault scenarios include but are not limited to: the single-pole or double-pole blocking of the system's external DC connection lines, the cascading faults and disconnections of large-scale new energy bases within the system, and the tripping of large units within the system.

[0106] Step 1.4.2: Calculate the real-time N-1 inertia disturbance power, N-1 upward frequency regulation disturbance power, and N-1 downward frequency regulation disturbance power of the system based on the N-1 principle.

[0107] The N-1 principle, also known as the single-fault safety inspection rule, is a technical requirement proposed from the perspective of the safe operation of the power grid. In a power system under normal operating conditions, when any component (such as a line, generator, transformer, DC monopole, etc.) fails or is disconnected due to a fault, the power system should be able to maintain stable operation and normal power supply, and other components should not be overloaded, and the voltage and frequency should be within the allowable range.

[0108] Specifically, Step 1.4.2 includes:

[0109] 1), Take the maximum value of and as the N-1 upward frequency regulation disturbance power

[0110] 2), Take the maximum value of and as the N-1 downward frequency regulation disturbance power

[0111] 3), take the maximum value of and as the N-1 inertia disturbance power ΔP H .

[0112] Step 1.4.3, based on the stability constraint parameters of the power generation resources, the real-time N-1 inertia disturbance power, N-1 up-frequency regulation disturbance power, and N-1 down-frequency regulation disturbance power of the system, and based on the system transient power-frequency response model, simulate the dynamic process of the system frequency response after a fault to solve the maximum value of the frequency difference Δf max and the maximum value of the system frequency change rate (df / dt) max .

[0113] In a non-limiting preferred embodiment, the system transient power-frequency response model adopted includes but is not limited to: the classical SFR model; the stability constraint parameters of the power generation resources and the real-time N-1 inertia disturbance power, N-1 up-frequency regulation disturbance power, and N-1 down-frequency regulation disturbance power of the system are all input into the SFR model, and the dynamic process of the system frequency response after a fault is calculated and simulated to solve the maximum value of the frequency difference Δf max and the maximum value of the system frequency change rate (df / dt) max .

[0114] Step 1.4.5, based on the dynamic process of the system frequency response, under the system frequency offset constraint condition, determine the minimum value K of the system power supply side frequency modulation characteristic coefficient according to the maximum value of the frequency difference by the following relational expression gmin :

[0115]

[0116] In the formula, M1 is a proportional coefficient; α1 is an adjustable exponent of time; t m1 , t OB are the time of the maximum frequency and the reference frequency time respectively; ω1 is the angular frequency; is the phase angle; ΔP L is the real-time N-1 maximum active power disturbance or N-2 maximum active power disturbance of the system, including the maximum up-frequency regulation disturbance and the maximum down-frequency regulation disturbance covering large disturbance fault scenarios such as DC blocking and new energy base disconnection from the grid; K g is the system power supply side frequency modulation characteristic coefficient; K L is the system active power frequency characteristic coefficient.

[0117] The maximum frequency difference is constrained according to the system frequency offset constraint conditions. In a non-limiting preferred embodiment, the system frequency offset constraint conditions include, but are not limited to, the frequency allowable deviation value, the low-frequency load shedding threshold value, and the high-frequency generator tripping threshold value; Δf is constrained according to the system frequency offset allowable value max to obtain the minimum value K of the frequency regulation characteristic coefficient on the system power supply side gmin , including the minimum value of the upward frequency regulation characteristic coefficient on the system power supply side corresponding to the system low-frequency load shedding threshold value the minimum value of the downward frequency regulation characteristic coefficient on the system power supply side corresponding to the system high-frequency generator tripping threshold value

[0118] Step 1.4.6, using the minimum value of the frequency regulation characteristic coefficient on the system power supply side, calculate the minimum value of the system frequency regulation power demand according to the following relational expression:

[0119]

[0120] In the formula, is the minimum value of the system upward frequency regulation power demand; is the minimum value of the system downward frequency regulation power demand.

[0121] Step 2, determine the system minimum inertia time constant demand based on the N-1 inertia disturbance power and the system frequency change rate; use the comprehensive inertia time constant of the system and the minimum inertia time constant demand to determine the system inertia stability margin.

[0122] Specifically, Step 2 includes:

[0123] Step 2.1, calculate the total inertia of conventional units, grid-forming energy storage power stations, and new energy power stations respectively;

[0124] In a non-limiting preferred embodiment, based on the operating status information of each power generation resource entity, calculate the total inertia of each power generation resource; the power generation resources of the power system include, but are not limited to, conventional units, grid-forming energy storage power stations, and new energy power stations, where the new energy power stations include non-grid-forming energy storage power stations and grid-forming energy storage power stations.

[0125] 1), taking thermal power units, hydropower units, and nuclear power units as conventional units, calculate the total inertia of conventional units according to the following relational expression:

[0126]

[0127] In the formula, E gΣ is the total inertia of the conventional units; ζ gi is the operating status of the conventional unit i. When the conventional unit is connected to the grid, ζ gi takes 1, otherwise ζ gi takes 0; H​​gi is the inertia time constant of the conventional unit i; S Ni is the rated capacity of the conventional unit i; n g is the number of conventional units.

[0128] 2), The network-forming energy storage power station is also a new energy power station. The total inertia of the network-forming energy storage power station is calculated by the following relationship:

[0129]

[0130] In the formula, E SΣ is the total inertia of the network-forming energy storage power station; ζ Sj is the flag bit indicating whether the energy storage power station j is operating in the network-forming mode. When the energy storage power station j is operating in the network-forming mode, ζ Sj takes 1, otherwise ζ Sj takes 0; H Sj is the virtual inertia time constant set for the network-forming energy storage power station j; S Sj is the rated capacity of the network-forming energy storage power station j; n S is the number of network-forming energy storage power stations.

[0131] 3), Taking the wind farm, photovoltaic power station and energy storage power station as new energy power stations, according to whether virtual inertia control is applied and the set virtual inertia control parameters, the total inertia of the new energy power station is calculated by the following relationship:

[0132]

[0133] In the formula, E wΣ is the total inertia of the new energy power station; ζ wj is the flag bit indicating whether the new energy power station j has the ability of virtual inertia response. When the new energy power station j has the ability of virtual inertia response, ζ wj takes 1, otherwise ζ wj takes 0; H wj is the virtual inertia time constant of the new energy power station j; P wj is the active power of the new energy power station j; n w is the number of new energy power stations.

[0134] Step 2.2, Taking the sum of the total inertias of different types of power generation resources as the total inertia on the power generation resource side of the system, the system inertia time constant is calculated by the following relationship:

[0135] H sys =(E gΣ +E wΣ +E SΣ ) / P Lsys

[0136] In the formula, P Lsys is the total system load.

[0137] The present invention divides the power generation resources of the power system into conventional units, network-forming energy storage power stations, and new energy power stations. Among them, the new energy power stations include non-network-forming energy storage power stations, so as to ensure that when evaluating the frequency stability of a power system including network-forming energy storage, the active inertia support and the control characteristics that can participate in primary and secondary frequency modulation of the network-forming energy storage are accurately considered, thereby avoiding system instability caused by over-evaluation or waste of system construction caused by under-evaluation.

[0138] Moreover, the following constraint conditions are introduced for the flag bit of the same energy storage power station j:

[0139] ζ Sj +ζ wj = 1

[0140] When the above constraint conditions are met and the energy storage power station j operates in the network-forming mode, ζ Sj takes 1 and ζ wj takes 0; on the contrary, when the energy storage power station j operates in the non-network-forming mode, ζ Sj takes 0 and ζ wj takes 1; the above constraint conditions not only realize the distinction of inertia according to whether the energy storage power station operates in the network-forming mode, but also facilitate digital implementation and avoid double counting of the inertia of the network-forming energy storage power station.

[0141] Step 2.3: Use the N-1 inertia disturbance power ΔP H and the system frequency change rate to calculate the system minimum inertia time constant requirement H min by the following relational expression:

[0142] H min = ΔP H / (df / dt) max

[0143] In the formula, (df / dt) max is the maximum value of the system frequency change rate, and this fixed value is set according to the actual frequency requirements of each regional power grid.

[0144] Step 2.4: Calculate the system inertia stability margin H sys according to the system inertia time constant H min and the system minimum inertia time constant requirement H marg , and satisfy the following relational expression:

[0145]

[0146] Step 3: Determine the frequency modulation power stability margin in the system load increase direction by using the total upward frequency modulation power on the system power generation resource side and the minimum value of the system upward frequency modulation power demand; determine the frequency modulation power stability margin in the system load decrease direction by using the total downward frequency modulation power on the system power generation resource side and the minimum value of the system downward frequency modulation power demand.

[0147] Specifically, Step 3 includes:

[0148] Step 3.1: Calculate the upward frequency modulation power and downward frequency modulation power of conventional units, new energy power stations, and energy storage power stations respectively.

[0149] In a non-restrictive and preferred embodiment, based on the operation status information of each power generation resource entity, calculate the frequency modulation power of each power generation resource, including:

[0150] 1) Calculate the upward frequency modulation power of thermal power units and nuclear power units according to the following relational expression

[0151] In the formula, ζ j is the operation status of thermal power unit or nuclear power unit j. When the unit is connected to the grid, ζ j takes 1, otherwise ζ j takes 0; χ j is the reserved requirement for the minimum frequency modulation power of thermal power and nuclear power units with different installed capacities in GB / T 40595-2021 "Technical Regulations and Test Guidelines for Primary Frequency Modulation of Grid-connected Power Supplies". For example, for thermal power units with a capacity less than 350MW, when connected to the grid, the upward frequency modulation power needs to be greater than 10% of the rated capacity, then χ j takes 0.1; P Nj is the rated active power of unit j.

[0152] Calculate the downward frequency modulation power of thermal power units and nuclear power units according to the following relational expression

[0153]

[0154] In the formula, P min is the allowable minimum technical output of thermal power unit or nuclear power unit.

[0155] 2) Calculate the upward frequency modulation power of hydroelectric units according to the following relational expression

[0156]

[0157] In the formula, ζ h is the operation status of hydroelectric unit h. When the unit is connected to the grid, ζ h takes 1, otherwise ζ h takes 0; χ hFor the reserve requirements of the minimum frequency modulation power of hydropower units with different output levels in GB / T 40595-2021 "Technical Regulations and Test Guidelines for Primary Frequency Modulation of Grid-connected Power Sources", for hydropower units operating under non-rated active power conditions, when grid-connected, the upward frequency modulation power needs to be greater than 10% of the rated capacity, then χ h Take 0.1; P Nh is the rated power of the hydropower unit, P h is the actual active power output of the unit; if there is a unit vibration operation area in the load increase direction of the h operating point of the hydropower unit, then P oh Take the lower threshold power value of the unit vibration operation area. If there is no unit vibration operation area in the load increase direction of the h operating point of the hydropower unit, then P oh Take (1 + χ h )P Nh ;

[0158] Calculate the downward frequency modulation power of the hydropower unit with the following relational expression

[0159]

[0160] In the formula, if there is a unit vibration operation area in the load decrease direction of the h operating point of the hydropower unit, then P qh Take the upper threshold power value of the unit vibration operation area. If there is no unit vibration operation area in the load decrease direction of the h operating point of the hydropower unit, then P qh Take 0.

[0161] 3), For wind farms and PV power plants as new energy power stations, determine the upward frequency modulation power and downward frequency modulation power according to whether they are equipped with primary frequency modulation function, real-time active power output and ultra-short-term power prediction curve.

[0162] Calculate the upward frequency modulation power of the new energy power station with the following relational expression

[0163]

[0164] In the formula, χ g is the flag bit indicating whether the new energy power station g is equipped with primary frequency modulation function. When equipped with primary frequency modulation function, χ g Take 1, otherwise χ g Take 0; P g is the active power of the new energy power station g, P g_pred is the ultra-short-term predicted power of the new energy power station g;

[0165] Calculate the downward frequency modulation power of the new energy power station with the following relational expression

[0166]

[0167] 4) Determine the upward frequency regulation power and downward frequency regulation power according to whether the energy storage power station is equipped with the primary frequency regulation function and its operating conditions.

[0168] Calculate the upward frequency regulation power of the energy storage power station using the following relational expression

[0169]

[0170] In the formula, χ m is the flag bit indicating whether the energy storage power station m is equipped with the primary frequency regulation function. When equipped with the primary frequency regulation function, χ m takes 1; otherwise, χ m takes 0; P m is the active power of the power station collected in real time, is the maximum allowable regulation power in the load increase direction of the energy storage power station m;

[0171] Calculate the downward frequency regulation power of the energy storage power station using the following relational expression

[0172]

[0173] In the formula, is the maximum allowable regulation power in the load decrease direction of the energy storage power station m.

[0174] Step 3.2: Use the sum of the upward frequency regulation powers of different types of power generation resources as the total upward frequency regulation power on the power generation resource side of the system; use the sum of the downward frequency regulation powers of different types of power generation resources as the total downward frequency regulation power on the power generation resource side of the system.

[0175] Calculate the total upward frequency regulation power ΔP on the power generation resource side of the system using the following relational expression + :

[0176]

[0177] Calculate the total downward frequency regulation power ΔP on the power generation resource side of the system using the following relational expression - :

[0178]

[0179] Step 3.3: Calculate the frequency regulation power stability margin of the system using the following relational expression:

[0180]

[0181] In the formula, is the frequency regulation power stability margin in the load increase direction of the system, is the frequency regulation power stability margin in the load decrease direction of the system; are the minimum values of the system's upward frequency regulation power demand and downward frequency regulation power demand respectively.

[0182] Step 4: Evaluate the frequency stability margin of the power system by using the system inertia stability margin, the frequency modulation power stability margin in the system load increase direction, and the frequency modulation power stability margin in the system load decrease direction.

[0183] In a preferred non-restricted embodiment, based on the system real-time inertia stability margin and the system real-time frequency modulation power stability margin, estimate and judge the system frequency operation trend after a presupposed disturbance, determine the system frequency stable operation state, introduce a weighted evaluation factor, and obtain the system frequency stability margin.

[0184] Specifically, calculate the system real-time frequency stability margin F with the following relational expression marg :

[0185]

[0186] where H marg is the system inertia stability margin; is the frequency modulation power stability margin in the system load increase direction, is the frequency modulation power stability margin in the system load decrease direction; λ1, λ2, and λ3 are all evaluation factors, and satisfy λ1 + λ2 + λ3 = 1.

[0187] Establish an objective function minF for optimizing the evaluation factor, which satisfies the following relational expression:

[0188]

[0189] where C(H marg ≤1) is the number of times that H marg is less than or equal to 100%, is the number of times less than or equal to 100%, is the number of times less than or equal to 100%.

[0190] Take the evaluation factor corresponding to the minimum value of the objective function minF as the optimal value, and calculate the system real-time frequency stability margin based on the optimal value.

[0191] The evaluation factors λ1, λ2, and λ3 with the minimum value of the objective function minF not only ensure the optimality of the system inertia stability margin, the frequency modulation power stability margin in the system load increase direction, and the frequency modulation power stability margin in the system load decrease direction, but also avoid misjudging the system stability evaluation in the case of a decrease in the system damping performance due to an excessive system inertia stability margin.

[0192] Introduce the weighted evaluation factor of the system frequency stability margin, determine the system frequency stable operation state, and obtain the system frequency stability margin F marg, if the system frequency stability margin is insufficient, adjust the unit startup mode or the power transmitted by AC / DC tie lines according to the inertia and frequency regulation power resources assessment of each region and the actual adjustable capacity, so as to improve the system frequency stable operation margin.

[0193] Aiming at the problems of high proportion of new energy, decreasing inertia level and insufficient frequency regulation capacity in the new power system, the present invention proposes a method and system for evaluating the frequency stability margin of a new power system considering network-forming energy storage: on the one hand, considering network-forming energy storage, according to the frequency regulation response characteristics and requirements of each type of power source, the primary frequency regulation power of the whole network's power generation side is evaluated in real time, and considering the real-time contingency disturbance information and the constraint of the system operation frequency extreme value condition, the primary frequency regulation power margin of the system is obtained; on the other hand, considering the participation of new energy power plants in the system inertia support, the inertia of the whole network's conventional synchronous units and new energy power plants is quantitatively evaluated, considering the inertia support effect of the network-forming energy storage power station in the network-forming control mode, mastering the inertia contribution of the new energy storage power station to the large power grid, and considering the real-time contingency disturbance information and the system ROCOF condition constraint, the system inertia stability margin is obtained. By introducing a weighted evaluation factor for the system frequency stability margin, the frequency stable operation level of the new power system is determined from two dimensions of the system inertia stability margin and the primary frequency regulation power stability margin, improving the situation awareness ability of the frequency stable operation of the new power system, which is of great significance for ensuring the safe and stable operation of the new power system.

[0194] The present invention also proposes a power system frequency stability margin evaluation system considering network-forming energy storage, including:

[0195] A parameter calculation module, an inertia margin calculation module, a frequency regulation power margin calculation module, and a frequency stability margin evaluation module;

[0196] The parameter calculation module is used to obtain the stable constraint parameters of power generation resources and system fault data, and calculate the N-1 inertia disturbance power, N-1 upward frequency regulation disturbance power and the minimum value of the system upward frequency regulation power demand, N-1 downward frequency regulation disturbance power and the minimum value of the system downward frequency regulation power demand of the system based on the N-1 principle.

[0197] The inertia margin calculation module is used to take the sum of the total inertias of different types of power generation resources as the total inertia on the power generation resource side of the system, so as to determine the system inertia time constant; use the N-1 inertia disturbance power and the system frequency change rate to determine the minimum inertia time constant demand of the system; use the system inertia time constant and the minimum inertia time constant demand of the system to determine the system inertia stability margin.

[0198] A frequency modulation power margin calculation module is used to determine the frequency modulation power stability margin in the system load increase direction by using the total upward frequency modulation power on the system power generation resource side and the minimum value of the system upward frequency modulation power demand; and determine the frequency modulation power stability margin in the system load decrease direction by using the total downward frequency modulation power on the system power generation resource side and the minimum value of the system downward frequency modulation power demand.

[0199] A frequency stability margin evaluation module is used to evaluate the frequency stability margin of the power system by using the system inertia stability margin, the frequency modulation power stability margin in the system load increase direction, and the frequency modulation power stability margin in the system load decrease direction.

[0200] The present disclosure may be a system, a method, and / or a computer program product. The computer program product may include a computer-readable storage medium having thereon computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0201] The computer-readable storage medium may be a tangible device that can retain and store instructions for use by an instruction execution device. The computer-readable storage medium may be, for example, but is not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), a memory stick, a floppy disk, a mechanically encoded device such as a punch card or raised structures in a groove having instructions stored thereon, and any suitable combination of the foregoing. The computer-readable storage medium as used herein is not construed as being a transitory signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., an optical pulse through an optical fiber cable), or an electrical signal transmitted through a wire.

[0202] The computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to various computing / processing devices, or downloaded to an external computer or external storage device through a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include a copper transmission cable, an optical fiber transmission, a wireless transmission, a router, a firewall, a switch, a gateway computer, and / or an edge server. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in each computing / processing device.

[0203] Computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state-setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages such as Smalltalk, C++, etc., and conventional procedural programming languages such as the "C" language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, executed as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., through the Internet using an Internet service provider). In some embodiments, by using the state information of the computer-readable program instructions to customize an electronic circuit, such as a programmable logic circuit, a field-programmable gate array (FPGA), or a programmable logic array (PLA), the electronic circuit can execute the computer-readable program instructions to implement various aspects of the present disclosure.

[0204] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific embodiments of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered by the protection scope of the claims of the present invention.

Claims

1. A method for evaluating the frequency stability margin of a power system considering network-forming energy storage. The power generation resources of the power system include conventional units, network-forming energy storage power stations, and new energy power stations, and it is characterized in that Including: Obtain the stable constraint parameters of power generation resources and system fault data. Based on the N-1 principle, calculate the N-1 inertia disturbance power, N-1 upward frequency regulation disturbance power, minimum value of system upward frequency regulation power demand, N-1 downward frequency regulation disturbance power, and minimum value of system downward frequency regulation power demand of the system. Take the sum of the total inertias of different types of power generation resources as the total inertia on the power generation resource side of the system, thereby determining the system inertia time constant; use the N-1 inertia disturbance power and the system frequency change rate to determine the minimum system inertia time constant requirement; use the system inertia time constant and the minimum system inertia time constant requirement to determine the system inertia stability margin. Use the total upward frequency regulation power on the power generation resource side of the system and the minimum value of the system upward frequency regulation power demand to determine the frequency regulation power stability margin in the system load increase direction. Use the total downward frequency regulation power on the power generation resource side of the system and the minimum value of the system downward frequency regulation power demand to determine the frequency regulation power stability margin in the system load decrease direction. Use the system inertia stability margin, the frequency regulation power stability margin in the system load increase direction, and the frequency regulation power stability margin in the system load decrease direction to evaluate the frequency stability margin of the power system.

2. The method for evaluating the frequency stability margin of a power system considering network-forming energy storage according to claim 1, wherein Obtain system fault data. Based on the N-1 principle, calculate the inertia disturbance power, upward frequency regulation disturbance power, and downward frequency regulation disturbance power of the system, including: Obtain the power loss and power surplus caused by the single - pole or double - pole blocking of the external DC connection line of the system and the power surplus The power loss caused by the cascading faults and disconnection of large - scale new - energy bases within the system The power loss caused by the tripping of large - scale units within the system The power surplus caused by the disconnection of large loads Based on the N-1 principle, calculate the real-time inertia disturbance power, upward frequency regulation disturbance power, and downward frequency regulation disturbance power of the system as follows: Take and the maximum value in as the N-1 up-frequency modulation disturbance power Take and the maximum value in as the N-1 down-frequency modulation disturbance power Take and the maximum value in as the N-1 inertia disturbance power ΔP H .

3. The method for evaluating the frequency stability margin of a power system considering network-forming energy storage according to claim 2, wherein According to the stable constraint parameters of power generation resources, the real-time N-1 inertia disturbance power, N-1 upward frequency regulation disturbance power, and N-1 downward frequency regulation disturbance power of the system, based on the system transient power-frequency response model, simulate the dynamic process of the system frequency response after a fault to solve the maximum frequency difference and the maximum system frequency change rate when the system fails.

4. The method for evaluating the frequency stability margin of a power system considering network-forming energy storage according to claim 3, wherein Under the system frequency offset constraint condition, determine the minimum value of the system power source side frequency regulation characteristic coefficient according to the following relationship with the maximum frequency difference: Wherein, M1 is a proportionality coefficient; α1 is an adjustable exponent of time; t m1 , t OB are respectively the moment of maximum frequency and the moment of reference frequency; ω1 is the angular frequency; is the phase angle; ΔP L is the real-time N-1 maximum active power disturbance or N-2 maximum active power disturbance of the system, including the maximum up-frequency regulation disturbance and the maximum down-frequency regulation disturbance K g is the frequency regulation characteristic coefficient of the system power supply side; K L is the active power frequency characteristic coefficient of the system; Among them, the system frequency offset constraint conditions include the low-frequency load shedding threshold value and the high-frequency generator tripping threshold value; the minimum value of the system power supply side frequency modulation characteristic coefficient includes: the minimum value of the upward frequency modulation characteristic coefficient of the system power supply side corresponding to the system low-frequency load shedding threshold value of the system power supply side upward frequency modulation characteristic coefficient corresponding to the system high-frequency generator tripping threshold value of the system power supply side downward frequency modulation characteristic coefficient 5. The method for evaluating the frequency stability margin of a power system considering network-forming energy storage according to claim 4, wherein Use the minimum value of the system power source side frequency regulation characteristic coefficient to calculate the minimum value of the system frequency regulation power demand according to the following relationship: wherein, is the minimum value of the frequency regulation power demand in the system for upward regulation; is the minimum value of the frequency regulation power demand in the system for downward regulation.

6. The method for evaluating the frequency stability margin of a power system considering network-forming energy storage according to claim 3, wherein Take the sum of the total inertias of different types of power generation resources as the total inertia on the power generation resource side of the system, thereby determining the system inertia time constant; use the N-1 inertia disturbance power and the system frequency change rate to determine the minimum system inertia time constant requirement; Use the system inertia time constant and the minimum system inertia time constant requirement to determine the system inertia stability margin, including: Calculate the total inertia of conventional units, network-forming energy storage power stations, and new energy power stations respectively. The sum of the total inertias of different types of power generation resources is used as the total inertia on the power generation resource side of the system, and the system inertia time constant is calculated by the following relational expression: H sys = (E gΣ + E wΣ + E SΣ ) P Lsys Wherein, P Lsys is the total system load; H sys is the system inertia time constant, E gΣ is the total inertia of conventional units, E SΣ is the total inertia of the grid-forming energy storage power station, E wΣ is the total inertia of the new energy power station; Using the N-1 inertia disturbance power ΔP H and the system frequency change rate, calculate the system minimum inertia time constant requirement H with the following relational expression min : H min = ΔP H (df / dt) max where (df / dt) max is the maximum value of the system frequency change rate; The system inertia stability margin is calculated by the following relational expression: Wherein, H marg is the system inertia stability margin.

7. The power system frequency stability margin evaluation method considering network-forming energy storage according to claim 6, characterized in that The total inertia of conventional units is calculated by the following relational expression: where, E gΣ is the total inertia of the conventional unit; ζ gi is the operating state of the conventional unit i. When the conventional unit is connected to the grid, ζ gi takes 1, otherwise ζ gi takes 0; H gi is the inertia time constant of the conventional unit i; S Ni is the rated capacity of the conventional unit i; n g is the number of conventional units. The total inertia of a network-forming energy storage power station is calculated by the following relational expression: Where, E SΣ is the total inertia of the grid-forming energy storage power station; ζ Sj is the flag indicating whether the energy storage power station j operates in the grid-forming mode. When the energy storage power station j operates in the grid-forming mode, ζ Sj takes 1, otherwise ζ Sj takes 0; H Sj is the virtual inertia time constant set for the grid-forming energy storage power station j; S Sj is the rated capacity of the grid-forming energy storage power station j; n S is the number of grid-forming energy storage power stations; The total inertia of a new energy power station is calculated by the following relational expression: Where, E wΣ is the total inertia of the new energy power station; ζ wj is the flag bit indicating whether the new energy power station j has the virtual inertia response ability. When the new energy power station j has the virtual inertia response ability, ζ wj takes 1, otherwise ζ wj takes 0; H wj is the virtual inertia time constant of the new energy power station j; P wj is the active power of the new energy power station j; n w is the number of new energy power stations. For the same energy storage power station j, the following constraint conditions are introduced: ζ Sj +ζ wj = 1 When the energy storage power station j operates in the grid-forming mode Sj Take 1, wj Take 0; conversely, when the energy storage power station j operates in the non-grid-forming mode Sj Take 0, wj Take 1.

8. The power system frequency stability margin evaluation method considering network-forming energy storage according to claim 3, characterized in that The frequency modulation power stability margin in the system load increase direction is determined by using the total upward frequency modulation power on the power generation resource side of the system and the minimum value of the system upward frequency modulation power demand; The frequency modulation power stability margin in the system load decrease direction is determined by using the total downward frequency modulation power on the power generation resource side of the system and the minimum value of the system downward frequency modulation power demand, including: The upward and downward frequency modulation powers of conventional units, new energy power stations and energy storage power stations are calculated respectively; The sum of the upward frequency regulation powers of different types of power generation resources is used as the total upward frequency regulation power ΔP on the power generation resource side of the system + ; The sum of the downward frequency regulation powers of different types of power generation resources is used as the total downward frequency regulation power ΔP on the power generation resource side of the system - ; The system frequency modulation power stability margin is calculated by the following relational expression: In the formula, is the frequency modulation power stability margin in the direction of increasing load of the system, is the frequency modulation power stability margin in the direction of decreasing load of the system; are respectively the minimum value of the upward frequency modulation power demand and the minimum value of the downward frequency modulation power demand of the system.

9. The power system frequency stability margin evaluation method considering network-forming energy storage according to claim 8, characterized in that Calculate the up-regulation frequency power and down-regulation frequency power of thermal power units and nuclear power units according to the following relationship and down-regulation frequency power where ζ j is the operating status of thermal power unit or nuclear power unit j. When the unit is connected to the grid, ζ j takes 1, otherwise ζ j takes 0; χ j is the required value of the minimum frequency regulation power for thermal power and nuclear power units with different installed capacities in GB / T 40595-2021 "Technical Regulations and Test Guidelines for Primary Frequency Regulation of Grid-connected Power Sources"; P Nj is the rated active power of unit j; P min is the allowable minimum technical output of thermal power units or nuclear power units. Calculate the up - frequency regulation power of the hydropower unit according to the following relationship and the down - frequency regulation power Where ζ h is the operating state of the hydropower unit h. When the unit is connected to the grid, ζ h takes 1; otherwise, ζ h takes 0; χ h is the required value of the minimum frequency modulation power for hydropower units with different outputs in the "Technical Regulations and Test Guidelines for Primary Frequency Modulation of Grid-connected Power Sources" (GB / T 40595-2021); P Nh is the rated power of the hydropower unit, and P h is the actual active power output of the unit. If there is a unit vibration operation area in the load increase direction of the operating point of hydropower unit h, then P oh takes the lower threshold power value of the unit vibration operation area. If there is no unit vibration operation area in the load increase direction of the operating point of hydropower unit h, then P oh takes (1 + χ h )P Nh ; if there is a unit vibration operation area in the load decrease direction of the operating point of hydropower unit h, then P qh takes the upper threshold power value of the unit vibration operation area. If there is no unit vibration operation area in the load decrease direction of the operating point of hydropower unit h, then P qh takes 0. Calculate the upward frequency regulation power of the new energy power station according to the following relationship and the downward frequency regulation power where χ g is the flag bit indicating whether the new energy power station g is configured with primary frequency regulation function. When the primary frequency regulation function is configured, χ g takes 1, otherwise χ g takes 0; P g is the active power of the new energy power station g, and P g_pred is the ultra-short-term predicted power of the new energy power station g; Calculate the upward frequency regulation power of the energy storage power station according to the following relationship and the downward frequency regulation power where χ m is the flag bit indicating whether the energy storage power station m is configured with the primary frequency regulation function. When it is configured with the primary frequency regulation function, χ m takes 1, and vice versa, χ m takes 0; P m is the active power of the power station collected in real time, is the maximum allowable regulation power in the load increase direction of the energy storage power station m; is the maximum allowable regulation power in the load decrease direction of the energy storage power station m.

10. The power system frequency stability margin evaluation method considering network-forming energy storage according to claim 1, characterized in that The power system frequency stability margin is evaluated by using the system inertia stability margin, the frequency modulation power stability margin in the system load increase direction and the frequency modulation power stability margin in the system load decrease direction, including: Calculate the real-time frequency stability margin F of the system using the following relationship marg : Where H marg is the system inertia stability margin; is the frequency modulation power stability margin in the system load increase direction, is the frequency modulation power stability margin in the system load decrease direction; λ1, λ2, and λ3 are all evaluation factors, and satisfy λ1 + λ2 + λ3 = 1.

11. The power system frequency stability margin evaluation method considering network-forming energy storage according to claim 10, characterized in that An objective function minF for optimizing the evaluation factor is established, satisfying the following relational expression: Wherein, C(H marg ≤1) is the number of times H marg is less than or equal to 100%, is the number of times less than or equal to 100%, is the number of times less than or equal to 100%; The evaluation factor corresponding to the minimum value of the objective function minF is used as the optimal value, and the real-time frequency stability margin of the system is calculated based on the optimal value.

12. A power system frequency stability margin evaluation system considering network-forming energy storage, characterized in that, Including: A parameter calculation module, an inertia margin calculation module, a frequency modulation power margin calculation module, and a frequency stability margin evaluation module; The parameter calculation module is used to obtain the stable constraint parameters of power generation resources and system fault data, and calculate the N-1 inertia disturbance power, N-1 upward frequency modulation disturbance power and the minimum value of the system upward frequency modulation power demand, N-1 downward frequency modulation disturbance power and the minimum value of the system downward frequency modulation power demand of the system based on the N-1 principle; The inertia margin calculation module is used to use the sum of the total inertias of different types of power generation resources as the total inertia on the power generation resource side of the system, so as to determine the system inertia time constant; the minimum inertia time constant demand of the system is determined by using the N-1 inertia disturbance power and the system frequency change rate; the system inertia stability margin is determined by using the system inertia time constant and the minimum inertia time constant demand of the system; The frequency modulation power margin calculation module is used to determine the frequency modulation power stability margin in the system load increase direction by using the total upward frequency modulation power on the power generation resource side of the system and the minimum value of the system upward frequency modulation power demand; Determine the frequency modulation power stability margin in the system load shedding direction by using the total downward frequency modulation power on the power generation resource side of the system and the minimum value of the system downward frequency modulation power demand; A frequency stability margin evaluation module is used to evaluate the frequency stability margin of the power system by using the system inertia stability margin, the frequency modulation power stability margin in the system load increase direction, and the frequency modulation power stability margin in the system load shedding direction.

13. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is used to operate according to the instructions to execute the steps of the method described in any one of claims 1-11.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, the steps of the method described in any one of claims 1-11 are implemented.

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