Power and gas integrated energy system failure evolution analysis method under extreme typhoon disaster

Abstract

The application provides a kind of power transmission and distribution-gas integrated energy system fault evolution analysis method under extreme typhoon disaster, based on the mechanical stress model of typhoon wind-rain load, the time-varying failure probability of power transmission and distribution network element is calculated, and the initial opening set is generated by Monte Carlo sampling;Through the affine power flow calculation of power transmission and distribution network coupling, the seriously overloaded line caused by power flow transfer is identified and protection is removed;The dynamic affine model is used to analyze the power transmission and distribution-gas load shedding strategy, the influence of power line opening on natural gas system pressure fluctuation and pipe storage change is quantified combined with natural gas pipe storage equation and electric-gas coupled equipment operation constraint, and the overload power of general overload line is balanced;Handle bilinear term, and use rotating second-order cone relaxation to transform non-convex constraint;Combined with the coupled operation constraints of electric-driven compressor, gas turbine and electric-to-gas equipment, the natural gas system failure propagation risk caused by power line opening and power transmission and distribution-gas load shedding is quantified.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power system disaster prevention and mitigation and intelligent dispatching, and particularly relates to a fault evolution analysis method for an integrated electricity-gas system under an extreme typhoon disaster. BACKGROUND

[0002] In recent years, extreme typhoon disasters with small probability and high loss have occurred frequently, seriously affecting the safe operation of an integrated electricity-gas system (IEGS). With the continuous development of the path and wind circle, the high wind speed and heavy load of the typhoon will bring strong mechanical stress, causing the initial fault breaking of the power elements of the ground transmission and distribution network. In reality, due to the deepening of energy interaction, the fault induced by the extreme typhoon disaster will further evolve, aggravating the risk of the expansion of the disaster scale of the system. However, in the existing research on the fault of the energy system under the typhoon disaster, the propagation of the fault in the power system and between the electricity-gas coupling is often ignored, the fault evolution process of the integrated electricity-gas system under the typhoon disaster is not clear, and the real fault caused by the typhoon disaster to the IEGS cannot be accurately grasped. In addition, in the new integrated energy system, there is a high proportion of new energy connected to the grid, the output of which has intermittency and volatility, and the system load demand has fluctuations. The load shortage caused by the system fault induced by the typhoon disaster will be greatly affected. The existing fault research under the typhoon disaster often ignores the above-mentioned source and load uncertainty, which will lead to deviation in the development of subsequent recovery strategies, causing additional energy and economic losses.

[0003] At present, the research on the fault of the energy system caused by the typhoon disaster mainly focuses on the mechanical stress impact brought by the typhoon. This kind of research method is based on the calculation of the failure probability of the power line caused by the typhoon, but this method ignores the fault evolution process induced by the typhoon disaster to the integrated electricity-gas system, and it is difficult to accurately grasp the system fault caused by the typhoon disaster. In reality, after the typhoon causes the initial fault of the power element, the fault will further evolve in the power system and between the electricity-gas system, inducing power line overload and electricity-gas coupling fault. A few studies have analyzed the cascading failure process in the power system, but they have not subdivided the power system into the transmission network and the distribution network, ignoring the power flow transfer relationship between the two when the fault evolves, resulting in deviation in the simulation results.

[0004] In addition, in the current research on energy system failure under typhoon disaster, the modeling of new energy output and load demand often relies on prediction information, and the influence of uncertainty on typhoon-induced failure is rarely considered. In practice, the prediction accuracy of new energy output and load demand under typhoon disaster is lower than that in normal conditions, which leads to increased uncertainty and has a significant impact on the failure and its evolution process. In traditional methods for handling uncertainty, the robust method may lead to an enlarged failure scenario due to its over-conservatism; the interval method is difficult to reflect the influence of uncertain variables on the evolution results of the failure; and the random optimization method requires variable distribution information which is difficult to obtain in extreme scenarios.

[0005] Furthermore, the current research does not consider the actual situation that the failure under typhoon disaster spreads from the power system to the natural gas system, ignores the process of electric-gas coupling failure, and leads to a failure scenario limited to the power system, making it difficult to quantitatively reflect the actual impact of surface typhoon disaster on deep underground natural gas networks, resulting in additional energy and economic losses.

[0006] Finally, in the existing research on energy system failure under typhoon disaster, the difference in transmission speed of different energy flows of electricity and gas is often not considered, and the time scale problem in the research of integrated energy system failure is ignored. In practice, the flow rate of natural gas is much slower than the power flow, so the steady-state model used in traditional failure analysis methods is not completely accurate. Moreover, for the integrated energy system of transmission and distribution networks and gas transmission networks, there is no research that can clearly show the failure evolution process under typhoon disaster. SUMMARY

[0007] In view of the defects and deficiencies of the prior art, especially the difficulty in quantifying the failure evolution process of electric integrated energy system under extreme typhoon disaster, the unclearness of cross-system failure propagation mechanism, and the inaccuracy of recovery strategy caused by source and load uncertainty, the present application provides a method and system for analyzing the failure evolution of integrated energy system of transmission and distribution networks and gas transmission networks. The innovative design realizes full-chain failure tracking through a dual-layer architecture decoupled in time and space: on the millisecond time scale, based on the affine power flow calculation of the coordinated transmission and distribution network, the line overload state caused by power flow transfer is accurately captured, and the system collapse is prevented through the protection removal mechanism; on the minute time scale, combined with the slow dynamic characteristics of natural gas, the failure propagation effect of power load reduction strategy on deep buried pipe network is quantified.

[0008] Innovatively integrate physical mechanism and uncertainty handling: through the normal distribution model of tower mechanical stress and the Markov process model of overhead lines, an initial opening probability system under typhoon load is established; the affine form of "center value + noise element" is used to analyze the fluctuations of new energy output and load demand disturbances, so that the power flow calculation truly reflects the uncertainty of source and load; for electric-gas coupling equipment (gas turbine, electric-gas conversion device, electric-driven compressor), energy conversion constraints are established to reveal the cross-system propagation path of gas pressure instability caused by power load reduction.

[0009] Break the non-linear bottleneck at the solution level: use McCormick linear envelope method to deal with the bilinear term in the load shedding model, and through the rotation of the second-order cone relaxation to transform the gas pressure constraint of the natural gas network, the complex non-convex problem is transformed into a convex optimization model which can be solved efficiently. This scheme realizes the closed-loop tracking of "initial opening → overload protection → load shedding propagation → coupling analysis" during the typhoon passage for the first time, and provides core technical support for the disaster prevention and dispatch of integrated energy system.

[0010] The technical scheme specifically adopted by the present application to solve its technical problems is:

[0011] A fault evolution analysis method of power transmission and distribution-gas integrated energy system under extreme typhoon disaster:

[0012] Based on the mechanical stress model of typhoon wind and rain load, the time-varying failure probability of power transmission and distribution network elements is calculated, and the initial opening set is generated through Monte Carlo sampling;

[0013] Based on the updated system topology, the serious overload line caused by power flow transfer is identified and protection is removed through the affine power flow calculation of power transmission and distribution network coupling;

[0014] The dynamic affine model is used to analyze the power transmission and distribution-gas load shedding strategy, the influence of power line opening on the pressure fluctuation and pipe storage change of the natural gas system is quantified combined with the natural gas pipe storage equation and the operation constraint of electric-gas coupling equipment, and the overload power of general overload line is balanced; the bilinear term is processed by McCormick linear envelope method, and the non-convex constraint is transformed by rotation of the second-order cone relaxation;

[0015] Combined with the coupling operation constraints of electric-driven compressor, gas turbine and electric-gas equipment, the fault propagation risk of natural gas system caused by power load shedding is quantified.

[0016] Further, the calculation of the time-varying failure probability is based on:

[0017] The tower failure rate is modeled as a normal distribution function of equivalent wind speed;

[0018] The failure rate of overhead line is modeled as a Markov process of wind speed and rainfall.

[0019] Further, the affine power flow calculation includes:

[0020] The power flow equations of power transmission network and distribution network are solved by master-slave splitting method;

[0021] The influence of source and load uncertainty on power flow distribution is represented based on affine arithmetic.

[0022] Further, the dynamic affine model includes:

[0023] An affine optimization model based on linearized AC power flow is established for load shedding of transmission network.

[0024] An affine constraint model based on DistFlow equation is established for load shedding of distribution network.

[0025] A slow dynamic affine model combined with Weymouth equation is established for load shedding of natural gas network.

[0026] Further, the rotation second-order cone relaxation comprises:

[0027] The Weymouth equation is decomposed into bidirectional conduction constraints;

[0028] The square term of gas pressure is transformed by an auxiliary variable.

[0029] Further, the fault propagation path comprises:

[0030] The exit of the electrically driven compressor from operation triggers an unstable state in which the node pressure is lower than the operating threshold;

[0031] The gas load and the interruption of gas turbine power supply triggered by gas network pressure fluctuation.

[0032] Further, the electric-gas coupling device operation constraint comprises:

[0033] The affine consumption characteristic equation of the gas turbine;

[0034] The affine energy conversion equation of the electric-to-gas device;

[0035] The affine power equation of the electrically driven compressor.

[0036] And a power transmission and distribution-gas integrated energy system fault evolution analysis system under extreme typhoon disasters comprises:

[0037] An initial opening generation module is configured to calculate the time-varying failure probability of power transmission and distribution network elements based on a mechanical stress model of typhoon wind and rain load, and to generate an initial opening set through Monte Carlo sampling;

[0038] An overload protection control module is configured to identify serious overload lines caused by power flow transfer and execute protection removal instructions through affine power flow calculation of power transmission-distribution network coupling based on the updated system topology;

[0039] A load shedding propagation analysis module is configured to analyze power transmission and distribution-gas load shedding strategies using a dynamic affine model, to quantify the influence of power line opening on natural gas system pressure fluctuation and pipe storage change in combination with natural gas pipe storage equation and electric-gas coupling device operation constraint, and to balance the overload power of general overload lines;

[0040] A fault risk quantification module configured to quantify the risk of natural gas system failure propagation caused by power line opening and transmission-distribution gas load shedding in conjunction with electro-gas coupling device constraints.

[0041] A nonlinear solving engine configured to handle bilinear terms by McCormick linear envelope method and to transform non-convex constraints by rotated second-order cone relaxation.

[0042] Further, the nonlinear solving engine comprises:

[0043] A gas network constraint transformation unit configured to decompose Weymouth equation into bidirectional conduction constraints.

[0044] An auxiliary variable processing unit configured to transform gas pressure square terms by auxiliary variables.

[0045] A second-order cone relaxation unit configured to construct a rotated second-order cone constraint set.

[0046] Further, the load shedding propagation analysis module is communicatively connected with a SCADA system to obtain in real time:

[0047] Power grid node voltage data;

[0048] Gas network pipeline pressure data.

[0049] And a computer device comprising a memory, a processor and a computer program stored in the memory, wherein the processor implements the method as described above when executing the computer program.

[0050] A non-transitory computer readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the method as described above.

[0051] Compared with the prior art, the present application and its preferred schemes at least include the following beneficial effects:

[0052] 1. Breakthrough in the ability to track the evolution of electro-gas system failures

[0053] The double-layered space-time decoupling architecture is created to accurately capture line overload caused by power flow transfer at the millisecond time scale, and to quantify the slow dynamic response of the gas network at the minute scale. This mechanism overcomes the technical blind spot of traditional methods that ignore the difference in energy flow transmission speed (electricity propagates at nearly the speed of light, while natural gas flows at about 10 m / s).

[0054] 2. Improved accuracy in analyzing extreme scenario uncertainty

[0055] Based on affine arithmetic, a "center value + noise element" model is constructed to embed new energy output fluctuation and load demand disturbance into the whole process of fault evolution. Compared with traditional robust optimization or stochastic programming methods, the influence of source and load prediction deviation on the analysis results under typhoon disaster is significantly reduced.

[0056] 3. Visualization of cross-system fault propagation path

[0057] By modeling the operation constraints of coupling devices such as electrically driven compressors and gas turbines, the influence path of surface typhoon disasters on deep buried gas pipes is revealed for the first time. For example, the withdrawal of electrically driven compressors triggers a chain reaction of pressure instability, providing a clear intervention target for cutting off fault propagation.

[0058] 4. Optimization of solving efficiency of complex model

[0059] McCormick envelope method and second-order cone relaxation technology are used to effectively handle the bilinear terms in the reduced load model and the non-convex constraints of the gas network. Through actual testing, the solving speed of large-scale systems is improved under the premise of ensuring accuracy.

[0060] 5. Enhanced compatibility of high proportion of new energy

[0061] The affine model adaptively handles the high fluctuation characteristics of wind and light output, filling the gap in disaster analysis of integrated energy systems containing high penetration rate of new energy, and supporting accurate modeling of new energy penetration scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0062] The application will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0063] Figure 1 The IEGS fault evolution process under typhoon disaster modeled for the embodiments of the application is shown in the figure;

[0064] Figure 2 The overall flowchart for the embodiments of the application is shown in the figure. DETAILED DESCRIPTION

[0065] In order to make the features and advantages of the application more obvious and easy to understand, the following embodiments are described in detail as follows:

[0066] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0067] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0068] The present application aims at the problem of inducing power line overload and electro-gas coupling failure after the initial failure of power elements caused by typhoon, and proposes a fault evolution analysis method of power transmission and distribution-gas integrated energy system under extreme typhoon disaster. The influence of wind and rain load stress of typhoon is comprehensively considered to identify the initial failure of system power elements. Then, the coupling connection between power transmission and distribution networks is considered, and the affine power flow calculation model of the constructed power transmission and distribution network under typhoon disaster is solved based on the master-slave split power flow calculation method. The power flow transfer under the fluctuation of source and load is considered to analyze the serious overload line protection opening caused by power flow transfer in a very short time scale. Then, load shedding measures are taken on the power transmission and distribution-gas integrated energy system to eliminate the safety hazards of general overload lines and balance the system power. The assistance of new energy and the influence of load demand fluctuation in the load shedding process are analyzed based on affine arithmetic. In addition, the disturbance influence of gas network is considered in a longer time scale, and the model is established based on the slow dynamic characteristics of gas network and the steady-state characteristics of power system to master the process of electro-gas coupling failure. The method simulates the fault evolution process of power transmission and distribution-gas integrated energy system under typhoon disaster, and can effectively track the influence of source and load fluctuation on the system failure, providing reference for the development of recovery strategy.

[0069] The main design points include:

[0070] (1) A double-layer affine fault evolution model of power transmission and distribution-gas integrated energy system under typhoon disaster is constructed. The power system is divided into power transmission network and power distribution network. The evolution of faults in the power system and between the electro-gas system is considered to induce the process of power line overload and electro-gas coupling failure. Affine arithmetic is used to process the source and load uncertainty in the fault evolution process induced by typhoon disaster;

[0071] (2) The upper layer constructs an affine line overload protection opening model of power transmission and distribution network under typhoon disaster. The coupling connection between power transmission and distribution networks is considered, and the affine power flow calculation model of the constructed power transmission and distribution network under typhoon disaster is solved based on the master-slave split power flow calculation method. The power flow transfer under the fluctuation of source and load is considered to analyze the serious overload line protection opening caused by power flow transfer in a very short time scale. In this process, due to the difference in transmission speed of different energy flows of electro-gas, the state of natural gas network is almost unchanged;

[0072] (3) Lower layer construction affine load shedding model of power transmission and distribution-gas integrated energy system under typhoon disaster: In order to eliminate the safety hazard of general overload line in the upper layer model and maintain the power balance of the system, load shedding measures are implemented on the power transmission and distribution-gas integrated energy system. The assistance of new energy and the influence of load demand fluctuation in the load shedding process are analyzed based on affine arithmetic. The implementation of load shedding measures consumes a certain amount of time, and the disturbance of the gas network should be considered in a long time scale. Therefore, the invention considers the actual situation that the fault spreads from the power system to the natural gas system under the typhoon disaster, and models based on the slow dynamic characteristics of the gas network and the steady-state characteristics of the power system to master the process of electric-gas coupling fault. Among them, McCormick envelope and rotating second-order cone method are used to convex the affine non-convex terms in the model.

[0073] The implementation process of the above scheme of the present application is introduced below through specific examples:

[0074] 1 Fault evolution process of power transmission and distribution-gas integrated energy system under typhoon disaster

[0075] With the continuous development of the path and the wind circle, the high wind speed and heavy load of the typhoon will bring strong mechanical stress, causing the initial fault opening of the power elements of the ground power transmission and distribution network. Such a fault is the initial disturbance of the typhoon to the IEGS, which is the "initial opening".

[0076] Then, further fault evolution will occur in the IEGS: the system topology change caused by the "initial opening" will cause power flow transfer, which will lead to the overload of part of the line power flow. The line power flow overload is divided into serious overload and general overload, and the system will protect and open the seriously overloaded line in a very short time, further changing the system topology. Because the transmission speed of electric energy is close to the speed of light, and the natural gas is only about 10 m / s. Therefore, in the instantaneous process of the serious overload of the power line and the protection opening, the state of the natural gas network almost has no big change. After the protection opening of the seriously overloaded line, in order to eliminate the safety hazard of the general overloaded line and maintain the power balance, the system needs to take load shedding measures.

[0077] Compared with the protection opening of the seriously overloaded line in a short time scale, the system needs to consume a certain amount of time to implement load shedding control, and the disturbance of the natural gas network should be considered. After the line opening and system load shedding, the electrically driven coupling equipment may exit operation, causing electric-gas coupling fault. Therefore, even if the typhoon is a ground disaster, it can still affect the natural gas network buried deep in the ground. For example, when the electrically driven compressor exits operation, it will cause serious pressure loss of the natural gas pipeline, causing gas flow blockage and affecting the natural gas supply of the gas load node. Further, the natural gas network may reduce the energy support to the power system, affecting the resilience mutual aid between subsystems.

[0078] In summary, the fault evolution process of the IEGS under the typhoon disaster constructed in this embodiment is as followsFigure 1 The power element initial opening, power line overload and electro-mechanical coupling failure are shown.

[0079] 2Power element initial opening model under typhoon disaster

[0080] The coordinate system is established based on the geographical location of the system, and the typhoon related moving path is obtained through weather forecast information. The moving path is described with the typhoon center eye position as the center, as shown in the formula .

[0081]

[0082] In the formula: x t and y t represent the typhoon center coordinates at time t; x t-1 and y t-1 represent the typhoon center coordinates at time t-1; represents the direction angle of typhoon movement; v t is the moving speed; and Δt is the time interval.

[0083] The Batts model is used to model the symmetric wind field of the typhoon, as shown in the formula .

[0084]

[0085]

[0086]

[0087]

[0088]

[0089] In the formula: R max is the maximum radius of the wind circle of the typhoon; ΔP t is the pressure difference (hPa) between the periphery and the center of the typhoon at time t; v gx is the vertical moving speed of the typhoon; θ is an empirical coefficient; f is the Coriolis force coefficient of the earth rotation; v Rmax is the maximum wind speed of the typhoon; v t is the horizontal moving speed of the typhoon; V rin and V rout are respectively the distances between the line and the typhoon eye not greater than and greater than R max ​​The instantaneous wind speed at time t; r is the distance between the line and the eye of the typhoon; x is the typhoon intensity attenuation parameter; ΔP0 is the pressure difference (hPa) between the outer periphery and center of the typhoon at the initial moment; γ is the angle between the typhoon and the coastline when it makes landfall; t is the time elapsed since the initial moment.

[0090] In addition to strong wind loads, typhoon rain loads also exert stress on the system towers. The stress impact of the load can be measured by calculating the equivalent wind speed, as shown in the formula. As shown.

[0091]

[0092] In the formula: V is the equivalent wind speed of the tower at a height of 10 m at time t; 10,z,t H represents the average wind speed at time t, 10 m above the tower, one moment before time z. z,t Let a be the average rainfall at tower z one moment before time t; equ b equ c equ d equ e equ This is the equivalent coefficient.

[0093] Assuming the vulnerability of the tower follows a normal distribution, calculate the failure rate R of the tower at time t using the equivalent wind speed. z,t As shown in the formula As shown.

[0094]

[0095] In the formula: R z,t Let z be the failure rate of the tower at time t; z,t and μ z,t Let x be the standard deviation and average of the equivalent wind speed of tower z at time t; let x be the ln( ).

[0096] In addition to power towers, overhead power lines will also be directly affected by typhoons. The time-varying failure rate λ of overhead power lines can be calculated. ij,t As shown in the formula As shown.

[0097]

[0098] In the formula: λ ij,t L represents the time-varying fault rate of the overhead line at time t. ij α is the line length; ij β ij and γ ij The correlation coefficient; Vij,t and V des are the average wind speed and the wind speed design value of line ij in the previous period before time t; H ij,t and H des are the average rainfall and the rainfall design value of line ij in the previous period before time t.

[0099] The failure rate R of overhead line is solved according to Markov process ij,t as shown in formula .

[0100]

[0101] In the formula: R ij,t is the failure rate of overhead line at time t; R ij,t-1 is the failure rate of overhead line at t-1.

[0102] The collapse of tower will cause the failure of the whole line. The total line failure probability R of the system is calculated comprehensively in combination with the failure probability of tower and overhead line. all,ij,t as shown in formula .

[0103]

[0104] In the formula: R all,ij,t is the total line failure probability of the system at time t.

[0105] Finally, the failure state of power elements is determined in combination with Monte Carlo sampling and the method of system information entropy, and the system "initial opening and closing" condition is obtained. As shown in formula .

[0106]

[0107] In the formula: W s is the system information entropy value; Ω B represents the total line set of transmission and distribution network; g i,t represents whether line ij fails at time t, 1 if it fails, otherwise 0.

[0108] The reasonable entropy value cannot be too large or too small, as shown in formula .

[0109]

[0110] In the formula: W min and W max are the minimum and maximum values of information entropy value, respectively.

[0111] 3Two-layer affine fault evolution model of power-gas integrated energy system under typhoon disaster

[0112] (1) Affine modeling of uncertain variables

[0113] To take into account the influence of uncertain fluctuations of sources and loads on fault evolution analysis of power-gas system, the present invention represents uncertain variables as a combination of central values and noise elements based on affine theory, as shown in formula .

[0114]

[0115] In the formula: P DG,i,t is the noise element coefficient of active power output of distributed new energy i at t time; is the affine analytical expression of active power output of distributed new energy i at t time; P DG,i,t,0 is the central value of active power output of distributed new energy i at t time; ε DG,i,t is the noise element of active power output of distributed new energy i at t time; P T,i,t , P D,m,t and F L,p,t are noise element coefficients of active load i of power transmission network, active load m of power distribution network and gas load p at t time, respectively; , and are affine analytical expressions of active load i of power transmission network, active load m of power distribution network and gas load p at t time, respectively; P T,i,t,0 , P D,m,t,0 and F L,p,t,0 are central values of active load i of power transmission network, active load m of power distribution network and gas load p at t time, respectively; ε T,i,t , ε D,m,t and ε L,p,t are noise elements of active load i of power transmission network, active load m of power distribution network and gas load p at t time, respectively.

[0116] (2) Affine line overload protection tripping model of power transmission-distribution network under upper-layer typhoon disaster

[0117] Under typhoon disaster, to consider the influence of source and load fluctuations on system power flow transfer, power and node voltage are represented as affine analytical expressions, and then according to power balance equation of power system, an affine power flow calculation model of power transmission-distribution network can be constructed as shown in formula .

[0118]

[0119] In the formula: superscript " * " represents conjugate; I PQ, I PV and I PH are PQ, PV and set of slack nodes respectively; N e is the number of system nodes; Y ik is the (i, k)th element of the node admittance matrix; is the affine voltage of node k; is the conjugate of the affine injected power of node i; is the conjugate of the affine voltage of node i; and are the affine injected active and reactive power of node i; j is the imaginary unit; is the affine voltage of node i; is the given voltage value of the slack node; is the given voltage magnitude of the PV node.

[0120] The basic iteration form based on master-slave splitting is used to calculate the power flow of the transmission-distribution network, and the specific steps are as follows:

[0121] Step 1: Set the power interaction nodes between the networks and assign the initial voltage values, and set the iteration number to 0.

[0122] Step 2: Calculate the distribution network power flow equation based on the boundary node voltage updated in the last iteration, or calculate it with the initial value if it is the first iteration.

[0123] Step 3: Calculate the transmission network power flow equation using the boundary node voltage obtained in step 2. After the distribution and transmission network power flow calculation, update the boundary node voltage and the iteration number.

[0124] Step 4: Determine whether the difference between the boundary node voltages of the adjacent two iterations is less than the convergence threshold value. If yes, stop the iteration and output the power flow calculation result, otherwise go back to step 2.

[0125] After the initial opening, the power flow is transferred, and the line may be overloaded due to a large change in transmission power. The overloaded line is divided into a serious overload line and a general overload line. The transmission power of the serious overload line exceeds the critical limit value, which will trigger the protection device action to remove in a very short time, while the general overload line can be eliminated by load reduction. The present application constructs the affine expression of the serious overload line protection opening, as shown in formula (16).

[0126]

[0127] In the formula: is the affine active power flow of line ij; is the affine overload removal probability of line ij; p0 is the probability of line protection occurring hidden fault, which is very small; and These are the normal limit and the critical limit of the transmission power of line ij, respectively.

[0128] (2) Affine load reduction model of power transmission and distribution-gas integrated energy system under lower-level typhoon disaster

[0129] After severe overload line protection is disconnected, overloaded lines can generally be relieved of overload through load reduction measures. Furthermore, load reduction measures are urgently needed to address the unbalanced power generated by line fault interruptions. Considering the difference in transmission speed between electrical energy and gas flow, a steady-state model is used for transmission and distribution networks, while a dynamic model is used for natural gas networks. The affine objective function of the IEGS load reduction model is shown in the equation... As shown.

[0130]

[0131] In the formula: , and The affine analytical expressions for load losses in transmission, distribution, and gas networks are respectively; C T C D and C L These are the load loss cost coefficients for transmission, distribution, and gas networks, respectively. , and Let Ω be the affine analytical expressions for the remaining rates of the active power load i of the transmission network, the active power load m of the distribution network, and the gas load p at time t, respectively, reflecting the load surplus situation; TE Ω DE and Ω G These are the node sets for the transmission and distribution networks and the gas network, respectively.

[0132] Affine load shedding modeling on the transmission network side: To account for the reactive power impact of transmission-distribution network interaction, a linearized AC power flow model is adopted. In addition, constraints also include: unit output constraints. Unit ramping constraints Power balance constraints and safety constraints .

[0133]

[0134]

[0135]

[0136]

[0137]

[0138] where , are affine equality and less than or equal to operator respectively; M is a large enough positive number; Z T,ij,t is a binary variable representing the operating state of transmission line ij at time t, 1 for normal operation, otherwise 0; and are the affine active and reactive power of line ij at time t; B ij and G ij are the mutual susceptance and mutual conductance between node i and node j; and are the affine phase angle of node i and node j at time t; and are the affine voltage of node i and node j at time t; and are the upper and lower limit of active power output of thermal generator i; and are the upper and lower limit of reactive power output of thermal generator i; and are the affine active and reactive power output of thermal generator i at time t; and are the affine active and reactive power output of thermal generator i at time t-1; and are the upper limit of ramp down and ramp up rate of active power output of thermal generator i; and are the upper limit of ramp down and ramp up rate of reactive power output of thermal generator i; is the affine active power output of gas turbine i at time t; is the affine power consumption of electric-gas equipment i at time t; is the affine power consumption of electric-driven compressor i at time t; is the affine surplus rate of transmission network reactive load i at time t; is the magnitude of transmission network affine reactive load i at time t; is the upper limit of transmission power of branch ij; and are the upper and lower limit of phase angle difference of node i and j; and are the upper and lower limit of voltage of node i; U ref,t and θ ref,t are the voltage and phase angle of slack bus at time t; U0 is the voltage value of slack bus.

[0139] Distribution network side affine load shedding modeling: model with DistFlow power flow model, constraints include: active and reactive power balance constraints , load shedding constraints , branch voltage drop constraints , branch power flow equation , node voltage constraints , branch current constraints and branch power flow constraints .

[0140]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146]

[0147] In the formula: , respectively, the affine active and reactive power from node n to node m at time t; is the affine current from node n to node m at time t; r mk and x mk are the resistance and reactance of branch mk, respectively; , respectively, the affine active and reactive power from node m to node k at time t; b1 and b2 are the initial node set of the branch with terminal node m and the terminal node set of the branch with initial node m, respectively; Z D,mk,t is a binary variable representing the operating state of line mk at time t, 1 for normal operation, and 0 otherwise; and are the affine voltages of node m and node k at time t, respectively; is the affine current from node m to node k at time t; y m,t is a binary variable representing the operating state of node m at time t, 1 for normal operation, and 0 otherwise; and upper and lower limits of voltage of node m, respectively; and kupper and lower limits of current of node m flowing to node k, respectively; and Pmkupper and lower limits of active power of node m flowing to node k, respectively; and Qmkupper and lower limits of reactive power of node m flowing to node k, respectively.

[0148] wherein, the formula is nonlinear. In order to reduce the complexity of model solving, the embodiment respectively replaces and with variables and , and then further processes the affine analytic formula of formula into formula .

[0149]

[0150] In the formula: is an auxiliary variable of affine voltage of node m at time t; is an auxiliary variable of affine current of node m flowing to node k at time t.

[0151] In formula , the affine equation is expanded to obtain the central value equation , the first-order constraint formula and the second-order constraint formula after second-order cone relaxation .

[0152]

[0153]

[0154]

[0155] In the formula: P mk,t,0 , Q mk,t,0 are central values of affine active and reactive power flowing from node m to node k at time t; P mk,t , Q mk,t are noise element coefficients of affine active and reactive power flowing from node m to node k at time t; u m,t,0 is a central value of auxiliary variable of affine voltage of node m at time t; l mk,t,0 is a central value of auxiliary variable of affine current of node m flowing to node k at time t; u m,t is a noise element coefficient of auxiliary variable of affine voltage of node m at time t; lmk,t is the auxiliary variable noise element coefficient of the affine current from node m to node k at time t.

[0156] where the first order constraint The bilinear term contained in the affine first order constraint will increase the difficulty of solving, the present application utilizes McCormick envelope to process the bilinear term in the affine first order constraint, introduces an auxiliary variable s, and , then the McCormick envelope processing is utilized to introduce the formula .

[0157]

[0158] In the formula, l max and l min are the maximum and minimum values of l mk,t respectively; u max and u min are the maximum and minimum values of u m,t respectively.

[0159] Then the formula can be approximated as the following formula.

[0160]

[0161] Natural gas network side affine load shedding modeling: the constraints include Weymouth equation constraint , node gas pressure constraint , pipeline flow constraint , gas source output constraint , gas compressor constraint , node flow balance constraint and load reduction constraint and pipe storage constraint.

[0162]

[0163]

[0164]

[0165]

[0166]

[0167]

[0168]

[0169]

[0170] where Ωe p, Ωs p and Ω C,p are the set of head nodes with node p as the tail node, the set of tail nodes with node p as the head node and the set of compressors with node p as the inlet, respectively; is the affine average flow of pipe pq at time t; sgn() is the sign function; W pq is the pipe constant of pipe pq; and are the affine pressure of node p and q at time t, respectively; is the affine output of gas source p at time t; is the affine flow of compressor pipe h at time t; is the affine gas consumption of gas turbine p at time t; is the affine gas production of electric-gas conversion equipment p at time t; is the affine head flow of pipe pq at time t; is the affine tail flow of pipe lp at time t; is the affine tail flow of pipe pq at time t; and are the upper and lower limits of pressure of node p, respectively; and are the upper and lower limits of output of gas source p, respectively; is the upper limit of flow of compressor h; and are the upper and lower limits of compression factor of compressor, respectively; and are the upper limits of flow of pipe pq and the upper limit of flow of compressor pipe h, respectively; is the affine pipe storage of pipe pq at time t; is the affine pipe storage of pipe pq at time t-1; S pq is the pipe storage constant of pipe pq; Ω GA is the set of pipes; is the affine pipe storage of pipe pq at the initial time.

[0171] In addition, the non-convex and nonlinear equation Weymouth equation is processed by combining the big M method and the second-order cone relaxation method. Unlike the fixed pipe flow direction in the day-ahead scheduling, the bidirectional conduction pipe model meets the demand at different time periods. Therefore, the state variable pq,t is introduced instead of the sign function sgn( ), pq,t =1 represents ≥ 0, otherwise pq,t = 0 represents ≤ 0, formula is equivalent to formula - .

[0172]

[0173]

[0174] In the formula: pq,t is a state variable representing the flow direction of the pipeline pq at time t.

[0175] An auxiliary variable u p,t and v q,t is introduced, and formula is converted to formula - .

[0176]

[0177]

[0178] In the formula: u p,t and v q,t are auxiliary variables representing the gas pressure of nodes p and q at time t.

[0179] Finally, the non-convex formula is converted into a rotating second-order cone constraint, as shown in formula .

[0180]

[0181] The affine coupling constraints between subsystems include: the consumption characteristic equation of the gas turbine , the energy conversion equation of the electric-gas conversion device , the power equation of the electric-driven compressor , and the power transmission node equation between the transmission and distribution networks .

[0182]

[0183]

[0184]

[0185]

[0186] In the formula: η gt and η p2g These are the conversion efficiencies of the gas turbine and the electro-gas conversion equipment, respectively; H HV It has a high calorific value for natural gas; K represents the upper limit of power consumption for the electro-gas conversion device i; c,1 and K c,2 For compressor parameters; k cp This refers to the compression ratio; and These are the affine active and reactive load reduction rates of the transmission network at transmission-distribution interaction node i at time t, respectively. and Let i be the affine active and reactive loads of the transmission network at the transmission-distribution interaction node i at time t; and Let be the total injected affine active and reactive power of the distribution network at node i of the transmission-distribution interaction at time t.

[0187] like Figure 2 As shown, based on the above design, the specific steps of the fault evolution analysis method for the integrated power transmission and distribution-gas energy system under extreme typhoon disasters proposed in this invention are as follows:

[0188] Step 1: Input typhoon forecast information and network parameters and coupling equipment parameters of the integrated power transmission and distribution-gas energy system;

[0189] Step 2: Based on the proposed initial interruption model of power components under typhoon disaster, calculate the fault probability of power transmission and distribution lines according to equations (1)-(11), obtain the fault set of power lines through Monte Carlo sampling, and then calculate the fault probability of power transmission and distribution lines according to equation (1)-(11). Calculate the system information entropy under different sampling results, according to the formula Once the power line fault status is obtained, determine whether the system has experienced an initial power line interruption. If so, output the result and execute step 3; otherwise, execute step 5.

[0190] Step 3: Update the system topology based on the fault conditions of the power lines. Based on the proposed simulated linear overload protection interruption model of the transmission-distribution network under upper-level typhoon disasters, and according to the formula... The power flow transfer distribution of the transmission and distribution network under the influence of source load fluctuations is calculated by combining the iterative form of master-slave splitting. The specific iterative steps are as follows:

[0191] (1) Set up power interaction nodes between networks and assign initial voltage values, and set the number of iterations to 0;

[0192] (2) Calculate the power flow equation of the distribution network using the updated boundary node voltage from the previous iteration, or the initial value if it is the first iteration;

[0193] (3) Calculate the power flow equation of the transmission network using the boundary node voltage obtained in (2). After the power flow calculation of the distribution and transmission networks, update the boundary node voltage and the iteration number;

[0194] (4) Determine whether the difference between the boundary node voltages of the adjacent two iterations is less than the convergence threshold. If yes, stop the iteration and output the power flow calculation results. Otherwise, go back to (2).

[0195] According to the output power flow calculation results of the transmission and distribution networks, determine whether the transmission power of any line exceeds its critical limit value, i.e., determine whether there is a severely overloaded line. If there is, perform protective removal and update the system topology, and re-execute step 3 to further consider the subsequent possible power flow transfer. If there is not, execute step 4;

[0196] Step 4: To eliminate the safety hazards of general overloaded lines and balance the system power, based on the proposed affine load shedding model of the transmission-distribution-gas integrated energy system under typhoon disasters, according to the formula - Implement system load shedding measures considering source and load uncertainty, with the objective function Output the affine load shedding distribution of the transmission-distribution-gas integrated energy system, and then execute step 5;

[0197] Step 5: According to the formula - Obtain the operating state of the electric-gas coupling device and the interactive node of the transmission-distribution network, combine the affine load shedding distribution and the operating state of the system, and obtain the electric-gas coupling fault result, and then execute step 6;

[0198] Step 6: According to the formula - Determine whether the typhoon has passed the system according to the typhoon model, if yes, end the process, otherwise, return to step 2.

[0199] ​Based on the same inventive concept, the present application further provides a computer device, comprising: one or more processors, and a memory for storing one or more computer programs; the program comprises program instructions, and the processor is configured to execute the program instructions stored in the memory. The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, and are configured to implement one or more instructions, and are specifically configured to load and execute one or more instructions in the computer storage medium to implement the above method.

[0200] It needs to be further explained that, based on the same inventive concept, the present application further provides a computer storage medium, which stores a computer program, and the computer program is executed by the processor to perform the above method. The storage medium can adopt any combination of one or more computer readable media. The computer readable medium can be a computer readable signal medium or a computer readable storage medium. The computer readable storage medium can be, but is not limited to, an electrical, magnetic, optical, infrared, or semiconductor system, device or component, or any combination thereof. More specific examples (non-exhaustive list) of the computer readable storage medium include: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present application, the computer readable storage medium can be any tangible medium containing or storing a program, which can be used by or in combination with an instruction execution system, device or component.

[0201] It should be noted that, unless otherwise defined, technical terms or scientific terms used in the present application shall have the common meaning understood by one of ordinary skill in the art to which the present application pertains. The terms "first", "second", and similar terms used in the present application do not denote any order, quantity, or importance, but are used to distinguish different components. The terms "comprise", "include", and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like are used only to indicate relative positional relationships, and when the absolute positions of the described objects are changed, the relative positional relationships can also be changed accordingly.

[0202] The above description is only the preferred embodiments of the present application, and is not intended to limit the present application in other forms. Any person skilled in the art can modify or change the above-mentioned disclosed technology into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change, and modification of the above-mentioned embodiments made without departing from the technical solution of the present application and in accordance with the technical essence of the present application shall still fall within the protection scope of the present application.

[0203] The present application is not limited to the above-mentioned preferred embodiments, and anyone can derive other various forms of extreme typhoon disaster under the inspiration of the present application. Any equivalent change and modification made in accordance with the scope of the present application shall fall within the scope of the present application.

Claims

1. A method for fault evolution analysis of an integrated power transmission and distribution-gas energy system under extreme typhoon disasters, characterized in that: Based on the mechanical stress model of typhoon wind-rain load, the time-varying failure probability of power transmission and distribution network components is calculated, and the initial interruption set is generated by Monte Carlo sampling. Based on the updated system topology, affine power flow calculations of the transmission-distribution network coupling are used to identify severely overloaded lines caused by power flow transfer and to perform protection disconnection. A dynamic affine model is used to analyze the load reduction strategy of power transmission and distribution and gas transmission. Combining the natural gas pipeline storage equation and the operating constraints of the electric-gas coupling equipment, the impact of power line interruption on the pressure fluctuation and pipeline storage change of the natural gas system is quantified, and the overload power of general overloaded lines is balanced. The bilinear terms are handled by McCormick's linear envelope method, and the non-convex constraints are transformed by rotating second-order cone relaxation. By combining the coupled operation constraints of electric compressors, gas turbines, and electric-to-gas equipment, the risk of natural gas system fault propagation caused by power line interruption and power-to-gas load reduction is quantified.

2. The fault evolution analysis method for integrated power transmission and distribution-gas energy systems under extreme typhoon disasters as described in claim 1, characterized in that: The calculation of the time-varying fault probability is based on: The tower failure rate is modeled as a normal distribution function of the equivalent wind speed; The failure rate of overhead lines is modeled as a Markov process of wind speed and rainfall.

3. The fault evolution analysis method for integrated power transmission and distribution-gas energy systems under extreme typhoon disasters according to claim 1, characterized in that: The affine current calculation includes: The power flow equations of the transmission and distribution networks are solved iteratively using the master-slave splitting method. The impact of source load uncertainty on power flow distribution is represented by affine arithmetic.

4. The method for fault evolution analysis of integrated power transmission and distribution-gas energy systems under extreme typhoon disasters as described in claim 1, characterized in that: The dynamic affine model includes: An affine optimization model based on linearized AC power flow is established for load reduction in the power transmission network; An affine constraint model based on the DistFlow equation is established for load shedding in the distribution network. A slow dynamic affine model combining pipeline storage equations is established for natural gas network load shedding.

5. The fault evolution analysis method for integrated power transmission and distribution-gas energy systems under extreme typhoon disasters according to claim 1, characterized in that: The rotational second-order cone relaxation includes: Decompose the Weymouth equation into bidirectional conduction constraints; Transform the squared term of air pressure using auxiliary variables.

6. The fault evolution analysis method for integrated power transmission and distribution-gas energy systems under extreme typhoon disasters according to claim 1, characterized in that: The fault propagation path includes: The shutdown of the electrically driven compressor caused an unstable state in which the node pressure fell below the operating threshold. Gas load and gas turbine power supply interruption triggered by gas network pressure fluctuations.

7. The fault evolution analysis method for integrated power transmission and distribution-gas energy systems under extreme typhoon disasters according to claim 1, characterized in that: The operational constraints of the electro-pneumatic coupling device include: Affine consumption characteristic equation of a gas turbine; Affine energy conversion equation for electro-gas conversion equipment; Affine power equation for an electrically driven compressor.

8. A fault evolution analysis system for an integrated power transmission and distribution-gas energy system under extreme typhoon disasters, characterized in that, include: Initial interruption generation module: configured to calculate the time-varying failure probability of power transmission and distribution network components based on the mechanical stress model of typhoon wind-rain load, and generate the initial interruption set through Monte Carlo sampling; Overload protection control module: configured to identify severely overloaded lines caused by power flow transfer and execute protection disconnection commands based on the updated system topology and through affine power flow calculation of the transmission-distribution network coupling; Load shedding propagation analysis module: configured to use a dynamic affine model to analyze the load shedding strategy of power transmission and distribution, combined with the natural gas pipeline storage equation and the operating constraints of the electric-gas coupling equipment, to quantify the impact of power line interruption on pressure fluctuations and pipeline storage changes in the natural gas system, and to balance the overload power of general overloaded lines; Fault Risk Quantification Module: Configured to combine constraints of electro-gas coupling equipment to quantify the risk of natural gas system fault propagation caused by power line interruption and power-gas transmission and distribution load reduction; Nonlinear solution engine: configured to handle bilinear terms using the McCormick linear envelope method and transform non-convex constraints by rotating a second-order cone relaxation.

9. The fault evolution analysis system for integrated power transmission and distribution-gas energy system under extreme typhoon disasters as described in claim 8, characterized in that: The nonlinear solution engine includes: Gas network constraint conversion unit: configured to decompose the Weymouth equation into bidirectional conduction constraints; Auxiliary variable processing unit: configured to transform the square term of air pressure through auxiliary variables; Second-order cone relaxation element: configured to construct a rotational second-order cone constraint group.

10. The fault evolution analysis system for integrated power transmission and distribution-gas energy system under extreme typhoon disasters according to claim 8, characterized in that: The load reduction propagation analysis module is connected to the SCADA system and acquires data in real time: Transmission network node voltage data; Gas pipeline pressure data.

Images