Method for identifying weak link of safe and low-carbon electrical coupling integrated energy system

Abstract

The present application relates to a kind of weak link identification method of electrical coupling integrated energy system considering safe low carbon, comprising the following steps: step 1, construct IEGS continuous multi-energy flow model to locate the critical state of gas pressure stability;Step 2, based on the critical state of gas pressure stability positioned in step 1, construct the gas pressure-total load sensitivity index of natural gas system at the time of gas pressure stability critical state;Step 3, calculate the gas pressure-total load sensitivity index of natural gas system at the time of gas pressure stability critical state constructed in step 2, locate the node with maximum system sensitivity, i.e. the weakest link of IEGS gas pressure.The present application can solve the technical problems of system realization weak link positioning and stable safety control under the condition of load fluctuation and renewable energy output uncertainty.

Description

Technical Field

[0001] This invention belongs to the technical field of load control and safety stability analysis of electrically coupled integrated energy systems, and relates to a method for identifying weak links in electrically coupled integrated energy systems, particularly a method for identifying weak links in electrically coupled integrated energy systems that considers safety and low carbon emissions. Background Technology

[0002] With the increasing depletion of fossil fuels and the continuous deterioration of the ecological environment, it is imperative to thoroughly implement the concept of sustainable development and actively promote energy transformation. Natural gas produces relatively low pollution during its production and transportation, making it a low-carbon energy source. Furthermore, natural gas can be coupled with various other energy sources to achieve multi-energy complementarity, thus promoting sustainable development.

[0003] To mitigate power output fluctuations from renewable energy sources such as solar and wind power, natural gas-fired generator units (NGUs) are widely used in power systems. Integrated Electricity-Gas Systems (IEGS) couple the power and natural gas systems through NGUs, improving multi-energy utilization efficiency. However, IEGS operation presents numerous safety risks. When the power and natural gas systems are deeply coupled within an IEGS, any internal disturbance in either system can spread from a point to a surface through the coupling equipment, threatening the safe operation of the entire IEGS. For example, during significant load fluctuations, the NGU unit needs to frequently adjust its output, causing continuous changes in the natural gas system's state and pressure fluctuations, which can easily lead to power outages.

[0004] In power systems, vulnerability identification based on sensitivity analysis can effectively locate voltage-weak nodes in the power grid, allowing operators to implement targeted safety measures to prevent such accidents. In IEGS (Interconnected Energy Systems), numerous studies have incorporated this analytical approach, analyzing the safety and stability of coupled IEGS systems and providing control strategies. Some studies, based on the sensitivity matrix between subsystems of an electro-gas interconnected integrated energy system, explore the interaction coupling mechanism between electro-gas energy subsystems and propose measures to improve the operational safety of the integrated energy system by deploying gas storage devices at weak nodes. Other research proposes a static sensitivity analysis method based on a unified power flow model for typical electro-gas coupled integrated energy systems, analyzing the interaction mechanism between electricity and natural gas supply systems, and verifying through numerical examples that the reasonable configuration of gas storage devices effectively improves system safety. Still other studies define a comprehensive sensitivity matrix and use it to seek and adjust the parameters with the highest controllability at unsafe points to achieve safe system control.

[0005] The above literature all use sensitivity analysis of the current operating state to locate the weak link in the system that may first become unstable, without considering the impact of the simultaneous increase of electrical and gas loads in IEGS on the location of the weak link.

[0006] The sensitivity index is derived based on the Jacobian matrix and has strong nonlinearity. The sensitivity index of each node may change significantly during the growth of electric and gas loads. Therefore, it is not possible to accurately determine the node where the gas pressure is most prone to instability using only the current sensitivity index.

[0007] In power systems, continuous power flow is often used to solve the static voltage stability critical state. By performing sensitivity analysis on the system under the critical state, the node most prone to voltage collapse can be located and measures can be taken for the weak link. However, this method has not been widely adopted in IEGS, especially in natural gas systems.

[0008] To improve IEGS pressure stability, it is necessary to simultaneously consider the load changes and their coupling effects of the natural gas system and the power system, and to construct an IEGS sensitivity index under the critical state of static pressure stability.

[0009] A search revealed no patent documents of the same or similar prior art as this invention. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and propose a method for identifying weak links in an electrically coupled integrated energy system that considers safety and low carbon emissions. This method can solve the technical problem of locating weak links and achieving stable and safe control of the system under load fluctuations and uncertainties in renewable energy output.

[0011] The present invention solves its practical problem by adopting the following technical solution:

[0012] A method for identifying weak links in an electrically coupled integrated energy system that considers safety and low carbon emissions includes the following steps:

[0013] Step 1: Construct an IEGGS continuous multi-energy flow model to locate the critical state of pressure stability;

[0014] Step 2: Based on the critical state of gas pressure stability identified in Step 1, construct the gas pressure-total load sensitivity index of the natural gas system at the critical state of gas pressure stability.

[0015] Step 3: Calculate the gas pressure-total load sensitivity index of the natural gas system under the critical state of gas pressure stability constructed in Step 2, and locate the node with the highest system sensitivity, which is the weakest link in IEGS gas pressure.

[0016] Furthermore, the specific steps of step 1 include:

[0017] The IEGGS Continuous Multi-Energy Flow Model (CMEF) is a generalization of the Continuous Power Flow Algorithm (CPF) in power system static voltage stability analysis.

[0018] The CPF model introduces a growth factor λ. e The growth trend of the power system is shown in equations (1)-(3):

[0019]

[0020]

[0021]

[0022] In the formula, P g,i0 P l,i0 and Q l,i0 These represent the initial active power, initial active load, and initial reactive load of the generator at node i in the power system, respectively. and These are the unit step increments of the active power, active load, and reactive load of the generator at node i in the power system, respectively.

[0023] This invention assumes that all NGU units fully respond to the increase in active power of the power system;

[0024] Based on this, the CMEF model further introduces the gas network growth factor λ. e The correlation coefficient r reflects the growth of the gas network load, as shown in equations (4)-(5):

[0025]

[0026] λ g =rλ e (5)

[0027] In the formula, L l,m0 The initial flow load on node m of the natural gas system; Let be the unit step increment; r represents the proportional relationship between the increase in electricity and gas load. For ease of analysis, the gas-to-electricity conversion coefficient η of the NGU is used. ge The increase in natural gas load is converted into an equivalent increase in electricity load to maintain dimensional consistency.

[0028] At the same time, the IEGGS static pressure stability index is introduced to determine whether the IEGGS has reached the static pressure stability critical state through CMEF operation.

[0029] The static stability index of air pressure is the minimum nodal pressure p. min Auxiliary judgment, namely:

[0030] p min≥0 (6)

[0031] When p min When p < 0, the natural gas pipeline cannot output a stable flow rate, the natural gas system collapses, therefore p min The point at which the value equals 0 represents the static, stable, critical operating state of the natural gas system.

[0032] Moreover, the specific method of step 2 is as follows: construct the natural gas system pressure-gas load sensitivity matrix and the natural gas system pressure-active load sensitivity matrix respectively, and combine the two to construct the natural gas system pressure-total load sensitivity index.

[0033] The gas pressure-load sensitivity matrix of the natural gas system is as follows:

[0034] Sensitivity matrix of air pressure to air load It can be calculated from equation (7):

[0035]

[0036] In the IEGS multi-energy flow unified solution algorithm, the submodule J of the unified Jacobian matrix J gg It can be represented as:

[0037]

[0038] In the formula:

[0039]

[0040] J gg This is calculated in each iteration, therefore J can be used in the CMEF process. gg Continuously locate the weak points in IEGS pressure under load growth.

[0041] From equation (9), the relationship between Π and p can be expressed as:

[0042]

[0043] Combining (8) and (10), the sensitivity matrix of air pressure to air load It can be written as:

[0044]

[0045] In the formula, diag is a diagonal matrix; The element in the i-th row and j-th column of the matrix reflects the magnitude of the influence of the increase in air load at node j on the air pressure at node i.

[0046] Specifically, the natural gas system pressure-active load sensitivity matrix is ​​as follows:

[0047] Considering the load growth of a single load node i in the power system, the impact on the gas pressure of node m in the natural gas system via a coupling device NGU; the gas pressure-electric load sensitivity matrix of the natural gas system. It can be represented as:

[0048]

[0049] Equation (12) can be transformed into:

[0050]

[0051] If both matrices use the same units, then:

[0052]

[0053] Specifically, the natural gas system pressure-to-total-load sensitivity index is as follows:

[0054] First, for the multi-node load growth of the natural gas system itself, let G be the set of all nodes with load growth, and L be the load growth of each node. k , where k∈G;

[0055] make:

[0056]

[0057] α k =L k / L sum ,k∈G (16)

[0058] In the formula, α k The proportion of the load increase at each natural gas system node k to the total system load increase;

[0059] definition:

[0060]

[0061] This indicates the sensitivity of the gas pressure at node m to the load growth of multiple nodes in the natural gas system in this scenario.

[0062] Similarly, the load increase of the power system can be equivalent to the load increase at the nodes of the coupled natural gas system; therefore, for an IEGS with multiple coupled NGU units, let the total active power load increase of the power grid be P. sum Assume there are w NGU units responding to an increase in active power load. The nodes of the natural gas system connected to the NGUs are set E, and the increase in active power output of each unit is denoted as P. t , where t∈G; Let:

[0063]

[0064] β t =P t / P sum ,t∈E (19)

[0065] In the formula, β t Let t be the proportion of the increase in active power of each NGU unit to the total increase in active power of all NGU units; then, according to equation (13), let the set E be the natural gas system nodes connected to w NGU units. G Then we can define:

[0066]

[0067] If we comprehensively consider the random growth of electricity and gas loads in IEGS, according to equation (5), the gas pressure-to-total load sensitivity index of the natural gas system is derived as follows:

[0068]

[0069] Moreover, the specific method of step 3 is as follows: under a certain load growth trend, calculate the gas pressure-to-total load sensitivity index of each node in the natural gas system, sort the index, and select the node with the largest gas pressure-to-total load sensitivity index. This node is the gas pressure weak link of the system under the current load growth trend.

[0070] Advantages and beneficial effects of the present invention:

[0071] 1. This invention proposes a method for identifying weak links in an electrically coupled integrated energy system (IEGS) that considers safety and low carbon emissions. This method considers the network state of the IEGS, uses a continuous multi-energy flow method to determine the critical state of IEGS pressure stability, constructs sensitivity indices to analyze the sensitivity of each IEGS node's pressure to increases in electrical and gas loads, and thereby locates the weak links in the IEGS under the critical state of static pressure stability. This invention considers the impact of simultaneous increases in electrical and gas loads in the IEGS on the location of system weak links, enabling more accurate location of system weak links even under continuous load increases.

[0072] 2. This invention introduces the power system sensitivity analysis method into the electrical coupling integrated energy system, fully considers the deep coupling between electrical systems, and derives the magnitude of the impact of gas pressure on electricity and gas load growth at each node in the natural gas system.

[0073] 3. This invention introduces a continuous multi-energy flow method, which considers not only the random growth of electrical load but also the random change process of natural gas load. That is, it simulates the random growth process of both electrical and gas loads in an electrical-coupled integrated energy system to locate the weak link node of the system.

[0074] 4. The sensitivity index proposed in this invention is based on the critical system of electrical and integrated energy systems. It obtains the system's stable critical state parameters through continuous multi-energy flow, fully considers the static stability factors of the electrically coupled integrated energy system, locates the most vulnerable collapse node in the system's stable critical state, and provides technical support for the formulation of subsequent system stability recovery strategies. Attached Figure Description

[0075] Figure 1 This is a specific embodiment of the IEGS topology diagram.

[0076] Figure 2 This is a schematic diagram of the air pressure-to-total-load sensitivity index and initial air pressure value of each node in the IEGS according to a specific embodiment of the present invention.

[0077] Figure 3 This is a specific embodiment of the present invention, showing the sensitivity index of air pressure-to-total load at each node of the IEGS under the critical state of static air pressure stability.

[0078] Figure 4 This is a specific embodiment of the present invention showing the sensitivity index of air pressure-total load at each node of the IEGS under the static stable critical state of air pressure in scenario two, and a schematic diagram of air pressure.

[0079] Figure 5 This is a graph showing the relationship between the Sg (ratio) of each node in the IEGS and the growth factor in a specific embodiment of the present invention. Detailed Implementation

[0080] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings:

[0081] This invention proposes a method for analyzing the gas pressure weak links in an Integrated Electricity-Gas System (IEGS) under statically stable critical conditions. This method considers the network state of the IEGS, analyzes the differential relationship between the gas pressure at each node and the electrical and gas loads, as well as the functional relationship with the load growth direction, using sensitivity indices. The sensitivity indices for the critical state are then obtained using the continuous multi-energy flow method, thus locating the gas pressure weak links under the statically stable critical conditions of the IEGS.

[0082] The specific steps include:

[0083] Step 1: Construct an IEGGS continuous multi-energy flow model to locate the critical state of pressure stability;

[0084] The specific steps of step 1 include:

[0085] The IEGS Continuation Multi-Energy Flow (CMEF) model is a generalization of the Continuation Power Flow (CPF) algorithm used in power system static voltage stability analysis.

[0086] The CPF model introduces a growth factor λ. e The growth trend of the power system is shown in equations (1)-(3):

[0087]

[0088]

[0089]

[0090] In the formula, P g,i0 P l,i0 and Q l,i0 These represent the initial active power, initial active load, and initial reactive load of the generator at node i in the power system, respectively. and These represent the unit step increments of the active power, active load, and reactive load of the generator at node i of the power system. This invention assumes that all NGU units fully respond to the increase in active power of the power system.

[0091] Based on this, the CMEF model further introduces the gas network growth factor λ. e The correlation coefficient r reflects the growth of the gas network load, as shown in equations (4)-(5):

[0092]

[0093] λ g =rλ e (5)

[0094] In the formula, L l,m0 The initial flow load on node m of the natural gas system; Let be the unit step increment; r represents the proportional relationship between the increase in electricity and gas load. For ease of analysis, the gas-to-electricity conversion coefficient η of the NGU is used. ge The increase in natural gas load is converted into an equivalent increase in electricity load to maintain dimensional consistency.

[0095] Meanwhile, an IEGGS static pressure stability index is introduced to determine whether the IEGGS has reached the critical state of static pressure stability through CMEF operation.

[0096] The static stability index of air pressure is the minimum nodal pressure p. min Auxiliary judgment, namely:

[0097] p min ≥0 (6)

[0098] When p min When p < 0, the natural gas pipeline cannot output a stable flow rate, the natural gas system collapses, therefore p min The point at which the value equals 0 represents the static, stable, critical operating state of the natural gas system.

[0099] This invention focuses on the impact of electricity and gas load growth on gas pressure, therefore neglecting the limitation of voltage static stability limit during the analysis. The calculation of the CMEF model consists of two parts: prediction and correction. The prediction part is based on the current operating point to predict the estimated value of the next equilibrium point; the correction part uses the estimated value as the initial value for iteration, uses the Newton-Raphson method to solve for the next equilibrium point, and determines whether the gas pressure static stability index (6) is met. Through repeated prediction and correction parts, the system continues to operate until it reaches the static stability critical operating state.

[0100] Step 2: Based on the critical state of gas pressure stability identified in Step 1, construct the gas pressure-total load sensitivity index of the natural gas system at the critical state of gas pressure stability.

[0101] The specific method of step 2 is as follows: construct the natural gas system pressure-gas load sensitivity matrix and the natural gas system pressure-active load sensitivity matrix respectively, and combine the two to construct the natural gas system pressure-total load sensitivity index.

[0102] The gas pressure-load sensitivity matrix of the natural gas system is as follows:

[0103] The gas pressure level of a natural gas system directly reflects its current operating status. As node load increases, node gas pressure continuously decreases, and excessively low pressure poses a significant threat to the safe operation of the system. This invention employs a sensitivity method to analyze the changing trend of node gas pressure with increasing gas load.

[0104] Sensitivity matrix of air pressure to air load It can be calculated from equation (7):

[0105]

[0106] In the IEGS multi-energy flow unified solution algorithm, the submodule J of the unified Jacobian matrix J gg It can be represented as:

[0107]

[0108] In the formula:

[0109]

[0110] J gg This is calculated in each iteration, therefore J can be used in the CMEF process. gg Continuously locate the weak points in IEGS pressure under load growth.

[0111] From equation (9), the relationship between Π and p can be expressed as:

[0112]

[0113] Combining (8) and (10), the sensitivity matrix of air pressure to air load It can be written as:

[0114]

[0115] In the formula, diag is a diagonal matrix; The element in the i-th row and j-th column of the matrix reflects the magnitude of the influence of the increase in air load at node j on the air pressure at node i.

[0116] Specifically, the natural gas system pressure-active load sensitivity matrix is ​​as follows:

[0117] In IEGS, the natural gas system and the power system are connected through coupling devices. This invention takes the NGU unit as an example for analysis.

[0118] Consider the impact of load growth at a single load node i in the power system on the gas pressure at natural gas system node m via a coupling device NGU (connected to a natural gas system node n). Natural gas system pressure-electric load sensitivity matrix. It can be represented as:

[0119]

[0120] Since only one unit is responding, for the natural gas system, the load increase at node i of the power system can be considered equivalent to the increase in the active power output of the NGU unit. Therefore, equation (12) can be transformed into:

[0121]

[0122] This means that the impact of power system load growth on the gas pressure at node m of the natural gas system can be considered equivalent to the impact of load growth at the corresponding coupled natural gas system node n on the gas pressure at node m. If both matrices use the same dimensions (i.e., the gas-to-electricity conversion coefficient η through the NGU)... ge Converting the gas load to an equivalent electrical load, we have:

[0123]

[0124] Specifically, the natural gas system pressure-to-total-load sensitivity index is as follows:

[0125] In practice, the growth of electricity and gas loads often exhibits strong randomness. The sensitivity value of a single node cannot reflect the impact of simultaneous load increases at multiple electricity and gas load nodes in the IEGS on the node gas pressure. Therefore, this invention defines a gas pressure-total load growth sensitivity index S for natural gas systems. g It is used to characterize the sensitivity of IEGS pressure to load under the simultaneous increase of multiple electrical and gas load nodes, and thereby locate the weak link of IEGS pressure.

[0126] First, for the multi-node load growth of the natural gas system itself, let G be the set of all nodes with load growth (a total of s nodes), and let L be the load growth of each node. k , where k∈G. Let:

[0127]

[0128] α k =L k / L sum ,k∈G (16)

[0129] In the formula, α k This represents the proportion of the load increase at each node k in the natural gas system to the total system load increase. Definition:

[0130]

[0131] This indicates the sensitivity of the gas pressure at node m to the load growth of multiple nodes in the natural gas system in this scenario.

[0132] Similarly, the load increase in the power system can be equivalent to the load increase at coupled natural gas system nodes. Therefore, for an IEGS with multiple coupled NGU units, let the total active power load increase of the grid be P. sum Assume there are w NGU units responding to an increase in active power load (the natural gas system nodes connected to the NGUs are set E, and the increase in active power output of each unit is denoted as P). t , where t∈G. Let:

[0133]

[0134] β t =P t / P sum ,t∈E (19)

[0135] In the formula, β tLet t be the proportion of the increase in active power of each NGU unit to the total increase in active power of all NGU units (i.e., the active power output ratio). Then, according to equation (13), let the set E be the natural gas system nodes connected to w NGU units. G Then we can define:

[0136]

[0137] If we comprehensively consider the random growth of electricity and gas loads in IEGS, according to equation (5), the gas pressure-to-total load sensitivity index of the natural gas system is derived as follows:

[0138]

[0139] This indicator reflects the sensitivity of the gas pressure at node m of the natural gas system to the random increase in the total electricity and gas load. The larger the indicator, the greater the influence of external load on the gas pressure at that node under the current load change trend, meaning the weaker the gas pressure at that node, which can further identify the weak points in the system's gas pressure.

[0140] Step 3: Calculate the gas pressure-total load sensitivity index of the natural gas system under the critical state of gas pressure stability constructed in Step 2, and locate the node with the highest system sensitivity, which is the weakest link in IEGS gas pressure.

[0141] The specific method of step 3 is as follows: Under a certain load growth trend, calculate the gas pressure-to-total load sensitivity index of each node in the natural gas system, sort the index, and select the node with the largest gas pressure-to-total load sensitivity index. This node is the gas pressure weak link of the system under the current load growth trend.

[0142] The invention will be further illustrated below with specific examples:

[0143] This invention selects a typical IEGS example as its example. The IEGS load includes electrical load and gas load, and the energy equipment includes two CHP units.

[0144] The IEGS topology constructed in this invention is as follows: Figure 1 As shown, this IEGS consists of an IEEE 9-node system coupled to an improved 6-node natural gas system via two NGU units. NGU1 couples the power system EN2 and the natural gas system GN2 nodes, and NGU1 couples the power system EN3 and the natural gas system GN3 nodes. GN1 is the natural gas system balancing node, with its gas source pressure set at 10 bar. The parameters of the 6-node natural gas system are shown in Tables 1 and 2.

[0145] Table 1 Flow Load of Natural Gas System Nodes

[0146]

[0147] Table 2 Natural Gas System Pipeline Parameters

[0148]

[0149] The total active power load and total natural gas load within the IEGS are set to increase simultaneously and by the same amount, i.e., r = 1, and the unit increment K of both power and gas loads is set to 1 MW. The active power load at nodes EN5, EN7, and EN9 increases proportionally in a 1:1:1 ratio, and the corresponding reactive power load increases proportionally with a power factor of 0.9. The natural gas load at nodes GN4, GN5, and GN6 also increases proportionally in a 1:1:1 ratio.

[0150] To investigate the impact of different load growth patterns under electrical coupling on the identification of weak links in IEGS gas pressure, this invention sets up the following two scenarios with different active power output ratios of NGU units.

[0151] Scenario 1: The active power output ratio of the two NGU units is 1:1;

[0152] Scenario 2: The active power output ratio of the two NGU units is 2:1;

[0153] In scenario one, when the total load increment is 0, the pressure-to-total load sensitivity index S of each node in the initial coupling state of IEGS is first solved using equation (21). g,0 With air pressure Figure 2 As shown in the figure, it can be seen that the pressure-to-total-load sensitivity index of node GN3 is the highest in the initial operating state. If the initial state sensitivity is used for identification, then GN3 is the weak link in the IEGS pressure.

[0154] By using CMEF and judging whether equation (6) is satisfied, the static stability critical state of IEGS gas pressure can be solved. It can be seen that when λ = 304, the gas pressure at node GN3 of the natural gas system reaches the static pressure stability boundary first. Therefore, the critical operating point is λ = 303. At this time, the gas pressure-total load sensitivity index S of each node of IEGS under the static stability critical state can be calculated by using equation (21). g,max air pressure Figure 3 As shown.

[0155] Depend on Figure 2 and Figure 3 It can be seen that S in both states g The largest nodes all reach the static pressure stability boundary first, and can effectively identify the weak nodes in the system pressure. As the pressure decreases, the sensitivity values ​​of all nodes increase, meaning that when the pressure decreases, the pressure of all nodes is affected by the increase in load.

[0156] The active power output ratio of the two NGU units was adjusted to 2:1, and the static pressure stability critical state of the IEGS was solved using CMEF. When λ = 310, the gas pressure at node GN6 of the natural gas system met the critical discrimination condition of equation (6), and reached the static pressure stability boundary first, which is the current weak point of the IEGS. Therefore, the critical operating point is λ = 309. The pressure-to-total load sensitivity index S of each node of the IEGS at this time was calculated using equation (21). g,max air pressure Figure 4 As shown.

[0157] from Figure 4 As can be seen, node GN6 has the largest S g,max Ultimately, it also approaches the static pressure stability limit, proving that the pressure-total load sensitivity index calculated under the critical pressure stability state can accurately identify the weak pressure link.

[0158] And S g,0 The identified pressure-weak node GN3 did not reach the static pressure stability limit first in this scenario because the change in the way electricity and gas loads grow altered the sensitivity of each node's pressure to the load. In Scenario 1, the initial and ultimate state assessments of the weak point were consistent because node GN3, which initially had higher sensitivity, also had the largest load increase, ultimately reaching the static stability limit first. However, in Scenario 2, the NGU's active power output ratio was adjusted to 2:1, reducing the load increase ratio of gas network node GN3. As the total load increase increased, the pressure-weak point gradually shifted towards GN6, causing a deviation in the initial sensitivity index for identifying the pressure-weak point. To track the changes in the IEGS pressure-weak point under load growth, the following... Figure 5 S is based on natural gas node GN6 as each growth factor. g Value benchmark, other nodes S under the same growth factor g The ratio of the value to the GN6 value.

[0159] As shown in the figure, except for node GN3, the gas pressure-to-total load sensitivity index S of all other natural gas system nodes is... gThe pressure at GN3 is consistently lower than that at GN6, meaning that node GN6 is weaker than GN2, GN4, and GN5 throughout the load growth process. The curves for GN3 and GN6 intersect at a growth factor λ ≈ 40.5, where the lowest gas pressure in the natural gas system occurs at node GN3 at 8.94 bar. Before this point, GN3 is the weakest point, followed by GN6. Therefore, it can be concluded that the weakest point in the IEGS (Integrated Energy System) pressure distribution is not static during continuous load growth. Planning and scheduling require not only assessing the current weakest point in the IEGS pressure distribution but also identifying the weakest nodes most prone to pressure instability during electricity and gas load growth and providing necessary safety measures to ensure the stable and safe operation of the entire IEGS.

[0160] It should be emphasized that the embodiments described in this invention are illustrative rather than limiting. Therefore, this invention includes, but is not limited to, the embodiments described in the specific implementation. Any other implementations derived by those skilled in the art based on the technical solutions of this invention are also within the scope of protection of this invention.

Claims

1. A method for identifying weak links in an electrically coupled integrated energy system that considers safety and low carbon emissions, characterized in that: Includes the following steps: Step 1: Construct an IEGGS continuous multi-energy flow model to locate the critical state of pressure stability; Step 2: Based on the critical state of gas pressure stability identified in Step 1, construct the gas pressure-total load sensitivity index of the natural gas system at the critical state of gas pressure stability. Step 3: Calculate the gas pressure-total load sensitivity index of the natural gas system under the critical state of gas pressure stability constructed in Step 2, and locate the node with the highest system sensitivity, which is the weakest link in IEGS gas pressure. The specific steps of step 1 include: The IEGGS Continuous Multi-Energy Flow Model (CMEF) is a generalization of the Continuous Power Flow Algorithm (CPF) in power system static voltage stability analysis. The CPF model introduces a growth factor. λ e The growth trend of the power system is shown in equations (1)-(3): (1) (2) (3) In the formula, , and Power system nodes i The initial active power, initial active load, and initial reactive load of the generator; 、 and Power system nodes i The unit step increment of the generator's active power, active load, and reactive load; Assume that all NGU units fully respond to the increase in active power of the power system; Based on this, the CMEF model further incorporates the gas network growth factor. and correlation coefficient r The growth of the gas grid load is reflected in equations (4)-(5): (4) (5) In the formula, For natural gas system nodes m Initial flow load; Its unit step increment; r This indicates the proportional relationship between the increase in electricity and gas load; it utilizes the gas-to-electricity conversion coefficient of the NGU. η ge The increase in natural gas load is converted into an equivalent increase in electricity load to maintain dimensional consistency. At the same time, the IEGGS static pressure stability index is introduced to determine whether the IEGGS has reached the static pressure stability critical state through CMEF operation. The static stability index of air pressure is the minimum air pressure at the node. p min Auxiliary judgment, namely: (6) when At that time, the natural gas pipeline could not output a stable flow, causing the natural gas system to collapse. The time is the static, stable, critical operating state of the natural gas system.

2. The method for identifying weak links in an electrically coupled integrated energy system considering safety and low carbon emissions, as described in claim 1, is characterized in that: The specific method of step 2 is as follows: construct the natural gas system pressure-gas load sensitivity matrix and the natural gas system pressure-active load sensitivity matrix respectively, and combine the two to construct the natural gas system pressure-total load sensitivity index; The gas pressure-load sensitivity matrix of the natural gas system is as follows: Sensitivity matrix of air pressure to air load It can be calculated from equation (7): (7) In the IEGS multi-energy flow unified solution algorithm, the unified Jacobian matrix is ​​used. J submodules J gg It can be represented as: (8) In the formula: (9) J gg This is calculated in each iteration, therefore the CMEF process can be utilized. J gg Continuously locate the weak points in IEGS pressure under load growth; From equation (9), Π and p The relationship can be represented as: (10) Combining (8) and (10), the sensitivity matrix of air pressure to air load It can be written as: (11) In the formula, diag is a diagonal matrix; The first in the matrix i Line number j Column elements reflect the nodes i The air pressure is affected by the node j The magnitude of the impact of the increase in gas load; Specifically, the gas pressure-active load sensitivity matrix of the natural gas system is as follows: Considering a single load node in the power system i Load growth is achieved by using a coupling device NGU to connect natural gas system nodes. m The influence of gas pressure; Gas pressure-electric load sensitivity matrix of natural gas system It can be represented as: (12) Equation (12) can be transformed into: (13) If both matrices use the same units, then: (14) Specifically, the natural gas system pressure-to-total-load sensitivity index is as follows: First, for the multi-node load growth of the natural gas system itself, let the set of all nodes with increasing load be denoted as . G The load increase at each node is L k ,in ; make: (15) (16) In the formula, For each natural gas system node k The proportion of load growth to total system load growth; definition: (17) This indicates that in this scenario, the node m The sensitivity of gas pressure to the load growth at multiple nodes of a natural gas system; Similarly, the load increase in the power system can be equivalent to the load increase at coupled natural gas system nodes; therefore, for an IEGS with multiple coupled NGU units, the total active power load increase of the power grid is denoted as... P sum Suppose there is w The NGU unit responds to the increase in active power load. The natural gas system nodes connected to the NGU are a set. E The increase in active power output of each unit is recorded as follows: P t ,in ;make: (18) (19) In the formula, For each NGU unit t The proportion of the increase in active power to the total increase in active power of all NGU units; then, according to equation (13), denoted as . w The natural gas system nodes connected to the NGU units are a set. E G Then we can define: (20) If we comprehensively consider the random growth of electricity and gas loads in IEGS, according to equation (5), the gas pressure-to-total load sensitivity index of the natural gas system is derived as follows: (21)。 3. The method for identifying weak links in an electrically coupled integrated energy system considering safety and low carbon emissions, as described in claim 1, is characterized in that: The specific method of step 3 is as follows: Under a certain load growth trend, calculate the gas pressure-to-total load sensitivity index of each node in the natural gas system, sort the index, and select the node with the largest gas pressure-to-total load sensitivity index. This node is the gas pressure weak link of the system under the current load growth trend.

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