A modeling method for hierarchical collaborative restoration of electric-gas interconnected systems

Abstract

The present invention relates to a method for modeling a hierarchical collaborative restoration model for an interconnected power-gas system. The method comprises: establishing a hierarchical collaborative restoration framework model for an interconnected power-gas system; establishing the interconnected power-gas system collaborative restoration model; adding power-gas network coupling constraints to the interconnected power-gas system collaborative restoration model, including transmission-gas system coupling constraints, distribution-gas system coupling constraints, and boundary connection constraints between the transmission-gas system and the distribution-gas system; and finally establishing the interconnected power-gas system collaborative restoration model. Compared with existing technologies, the present invention offers advantages such as faster collaborative restoration and full consideration of the coupling characteristics of the power-gas network.

Description

Technical Field

[0001] The present invention relates to the technical field of power network restoration, and in particular to a modeling method for a hierarchical collaborative restoration model of an electricity-gas interconnected system. Background Art

[0002] Traditional power system restoration refers to the process of gradually restoring the system's backbone grid and load after a local or large-scale power outage, using gas-fired units, hydropower units, and other units with black start capabilities within the system, or external power supplies, to provide starting power to other units within the system that do not have self-starting capabilities, thereby safely and effectively restoring the system to a new normal operating state.

[0003] However, traditional power system restoration models have the following defects: ① They focus on transmission network restoration, but rarely consider the recovery capacity of the distribution network itself. The distribution network needs to be restored after the main units are connected to the grid and the trunk transmission network is restored, which affects the continuous power supply of important loads; ② After a large-scale energy supply interruption accident, the restoration of electricity and natural gas energy networks is closely interdependent. The traditional power network black start model fails to consider the impact of the power-natural gas network coupling characteristics on power network restoration, resulting in low efficiency and slow speed of power network black start.

[0004] During large-scale power outages, the black start time becomes the most important consideration for the black start problem, because there is an urgent need for a power system collaborative restoration model that can take into account the coupling characteristics of the power-gas network. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a modeling method for a hierarchical collaborative restoration model of an electric-gas interconnected system with fast collaborative restoration speed and full consideration of the coupling characteristics of the electric-gas network.

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

[0007] A modeling method for a hierarchical collaborative restoration model of an electric-gas interconnected system, the modeling method comprising:

[0008] Step 1: Establish a hierarchical collaborative recovery framework model for the electricity-gas interconnection system;

[0009] Step 2: Establish a collaborative restoration model for the electricity-gas interconnected system based on the framework model in step 1;

[0010] Step 3: Add power-gas network coupling constraints to the electricity-gas interconnected system collaborative restoration model, including transmission-gas system coupling constraints, distribution-gas system coupling constraints, and boundary connection constraints between the transmission-gas system and the distribution-gas system.

[0011] Step 4: Complete the establishment of the collaborative recovery model of the electricity-gas interconnection system.

[0012] Preferably, the step 1 is specifically as follows:

[0013] Assume that the energy supply interruption accident occurs at time t0. k From that moment on, the electricity and gas loads at the transmission and gas transmission system level will be restored, and at the same time, the loads of the distribution and gas distribution system will be restored on a large scale.

[0014] Hierarchical collaborative recovery of the electricity-gas interconnection system k At the beginning of the moment, the restoration preparation phase has been completed, the power supply and gas source within the power transmission and gas transmission system have been started, and the power transmission lines, gas transmission channels, distribution network substations and gas distribution network pressure regulating stations have been put into operation;

[0015] Based on the current electricity-gas interconnection system, a hierarchical collaborative recovery framework model of the electricity-gas interconnection system is established.

[0016] Preferably, the electric-gas interconnected system collaborative recovery model is specifically:

[0017] The objective function of the model is to maximize the weighted supply of electricity load and gas load in the transmission-gas transmission system and the distribution-gas distribution system, specifically:

[0018]

[0019] Among them, the superscript T of each variable represents the transmission network or gas transmission network, the superscript D represents the distribution network or gas distribution network; the subscript E represents the power system, the subscript G represents the natural gas system; the superscript L represents the load; the subscript t represents the restoration time, T R represents the set of restoration moments; subscript m represents the node number of the transmission network, subscript n represents the node number of the gas transmission network, subscript i represents the node number of the distribution network, and subscript j represents the node number of the gas distribution network; and Represents the set of all nodes of the transmission network, gas transmission network, distribution network and gas distribution network respectively; and Respectively represent the weight coefficients of each node of the corresponding system; are the loads restored by each system at each moment.

[0020] Preferably, the hierarchical collaborative restoration model of the electricity-gas interconnection system is provided with a power transmission-gas transmission system restoration constraint and a power distribution-gas distribution system restoration constraint;

[0021] The power transmission-gas transmission system restoration constraints include power transmission network flow constraints and safety constraints, gas transmission network flow constraints and safety constraints, and power transmission-gas transmission system load restoration constraints;

[0022] The power distribution-gas distribution system recovery constraints include power distribution network flow constraints and safety constraints, gas distribution network flow constraints and safety constraints, and power distribution-gas distribution system load recovery constraints.

[0023] More preferably, the power flow constraint of the transmission network is specifically:

[0024] Active and reactive balance constraints at transmission system nodes:

[0025]

[0026] Among them, the superscript G of each variable represents the power source; m′ is the node adjacent to m, K T is the set of transmission lines connected to node m; are the active power injected into node m and the active power flowing through line mm′ respectively; are the reactive power injection of node m, reactive load and reactive power flowing through line mm′ respectively;

[0027] The right side of the equation and They represent the total active and reactive losses on the transmission line connected to node m;

[0028] Active and reactive power balance constraints of transmission system lines:

[0029]

[0030] in, are the conductance and susceptance of line mm′ respectively; are the voltage amplitudes at nodes m and m′ respectively; is the phase difference of the voltage at both ends of line mm′; among them, the voltage amplitude and cosine term and the sine term The cross product term is processed by quadratic relaxation technique, and the voltage amplitude square term An improved piecewise linearization method is used to obtain a convex expression of the line power flow constraint, thus achieving convex relaxation of the constraint.

[0031] Transmission grid restoration security constraints:

[0032] Including voltage amplitude constraint, power supply active and reactive output upper and lower limit constraints and climbing constraints, which are:

[0033]

[0034] in, and They are the upper and lower limits of the active output of the power supply respectively; and are the upper and lower limits of the reactive power output of the power supply, The upper limit of the power supply's ramping capability within adjacent recovery periods;

[0035] Constraints between the change in the total amount of system active load restored between adjacent restoration moments and the maximum total amount of active load restored:

[0036]

[0037] More preferably, the gas transmission network flow constraints and safety constraints are specifically:

[0038] The airflow balance constraint at node n in the gas transmission network system is:

[0039]

[0040] in, and are the natural gas flow rate injected by the gas source and the natural gas flow rate consumed by the gas load at node n at time t, is the natural gas flow rate flowing through the gas pipeline nn′;

[0041] Constraints on the relationship between gas flow rate in a gas transmission pipeline and the pressure difference between the two ends of the pipeline:

[0042]

[0043] in, are the air pressures at nodes n and n′, respectively, is the Weymouth constant of the pipeline nn′;

[0044] The expression of the sign function of the pressure difference between the two ends of the pipeline is:

[0045]

[0046] For the nonlinear terms in the above constraints, an improved piecewise linearization method is used;

[0047] Gas transmission network restoration safety constraints:

[0048] It includes upper and lower limit constraints of pipeline airflow, upper and lower limit constraints of node air pressure, upper and lower limit constraints of gas source output and climbing constraints, which are:

[0049]

[0050] More preferably, the load recovery constraints of the power transmission-gas transmission system are specifically:

[0051] Active load recovery constraints:

[0052]

[0053] Reactive load recovery constraints:

[0054]

[0055] Transmission grid load upper limit constraints:

[0056]

[0057] Constraints on safe operation of gas source:

[0058]

[0059] More preferably, the distribution network power flow constraints and safety constraints are specifically:

[0060] The active and reactive power balance constraints at node i in the mth distribution network at time t are:

[0061]

[0062] in, and are the active power flow and reactive power flow through line ii′ connected to node i, respectively; is the square of the current amplitude flowing through line ii′; and are the active power and reactive power injected into node i, and are respectively the active load and reactive load actually restored at node i;

[0063] The relationship constraint between the square of the voltage amplitude between node i and node i′ is:

[0064]

[0065] Among them, r ii′ and x ii′ are the resistance and reactance of line ii′ respectively; is the square of the line impedance modulus;

[0066] Constraints on the relationship between node voltage amplitude and corresponding line current amplitude, active and reactive power flow values:

[0067]

[0068] This constraint is a non-convex constraint. For the cross product term McCormick convex relaxation method is used to deal with the square term of the variable The piecewise linearization method is used for processing;

[0069] Distribution network security constraints:

[0070] It includes voltage amplitude, upper and lower limit constraints of power supply active and reactive output, and climbing constraints, specifically:

[0071]

[0072] More preferably, the load recovery constraints of the power distribution-gas distribution system are specifically:

[0073] Active load recovery constraints:

[0074]

[0075] Reactive load recovery constraints:

[0076]

[0077] Terminal power load restoration continuity constraints:

[0078]

[0079] Active and reactive power constraints accepted by the distribution substation:

[0080]

[0081] Restoration constraints of terminal gas load in the gas distribution network:

[0082]

[0083] Gas distribution and pressure regulating stations are subject to natural gas flow constraints:

[0084]

[0085] Preferably, the power transmission-gas transmission system coupling constraints and the power distribution-gas distribution system coupling constraints in step 3 are specifically:

[0086] Energy conversion relationship constraints of gas units:

[0087]

[0088] in, is the natural gas consumption of the gas generating unit connected between the distribution network node i and the gas distribution network node j at time t; Provides active power for the gas generator set; is the power generation efficiency; G is the lower calorific value of natural gas;

[0089] Energy conversion constraints for gas-fired units connected to the transmission grid and gas grid;

[0090] P2G facility energy conversion relationship constraints:

[0091]

[0092] in, The active power consumed by the P2G facility as an electrical load; is the corresponding natural gas flow rate, is the gas production efficiency;

[0093] Constraints on the relationship between the natural gas flow rate transmitted by the power-driven pressure regulating station in the gas transmission network and the power consumed:

[0094]

[0095] in, is the natural gas flow rate flowing through the power-driven pressure regulating station between the gas transmission network node n and the gas distribution network node j; The electric power consumed by the power-driven voltage regulating station as an electric load; β reg,T is the energy consumption coefficient;

[0096] The boundary connection constraints of the power distribution-gas distribution system are specifically:

[0097]

[0098] The above constraints represent the power and voltage relationships of the power transmission system and the gas transmission system at the substation, where V t D,m,sub,sqr represents the square of the voltage amplitude of the substation connected to the transmission network node m;

[0099] The boundary connection constraints of the gas transmission-distribution system are:

[0100]

[0101] and is the boundary connection constraint of the gas transmission-distribution system, Indicates the gas pressure on the boost side of the gas distribution and pressure regulating station connected to the gas transmission network node n, represents the pressure on the step-down side, Γ c is the step-up ratio;

[0102] Will and Set as the boundary connection variable of the transmission-gas transmission system and the distribution-gas distribution system during the restoration process.

[0103] Compared with the prior art, the present invention has the following beneficial effects:

[0104] 1. Faster collaborative recovery speed: The modeling method of the hierarchical collaborative recovery model of the electric-gas interconnected system in the present invention takes into account the impact of the coupling characteristics of the electric power-natural gas network on the restoration of the electric power network. The model incorporates electric power-natural gas network coupling constraints, including the coupling constraints of the transmission-gas transmission system, the coupling constraints of the distribution-gas distribution system, and the boundary connection constraints of the transmission-gas transmission system and the distribution-gas distribution system. It fully utilizes the close interdependence of the restoration of the electric power and natural gas energy networks, making the recovery speed faster when using the model for collaborative restoration of the electric power system.

[0105] 2. Fully consider the coupling characteristics of the power-gas network: The modeling method of the hierarchical collaborative recovery model of the power-gas interconnected system in the present invention proposes a hierarchical collaborative recovery framework model of the power-gas interconnected system before formal modeling, fully considers the impact of the power-gas network coupling characteristics on the power network restoration, and models according to the power-gas network coupling characteristics, and the model has high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0106] Figure 1 Schematic diagram of the flow of the modeling method of the hierarchical collaborative recovery model of the electric-gas interconnected system in the present invention;

[0107] Figure 2 Schematic diagram of the overall framework mechanism for hierarchical collaborative recovery of an electricity-gas interconnection system according to an embodiment of the present invention;

[0108] Figure 3 Schematic diagram of the interaction between the power system and the natural gas system in an embodiment of the present invention;

[0109] Figure 4 Schematic diagram of energy conversion and information interaction during the collaborative recovery process of the model in an embodiment of the present invention. DETAILED DESCRIPTION

[0110] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0111] This embodiment relates to a modeling method for a hierarchical collaborative recovery model of an electric-gas interconnected system, and its process is as follows: Figure 1 As shown, including:

[0112] Step 1: Establish a hierarchical collaborative recovery framework model for the electricity-gas interconnection system;

[0113] Step 2: Establish a collaborative restoration model for the electricity-gas interconnected system based on the framework model in step 1;

[0114] Step 3: Add power-gas network coupling constraints to the electricity-gas interconnected system collaborative restoration model, including transmission-gas system coupling constraints, distribution-gas system coupling constraints, and boundary connection constraints between the transmission-gas system and the distribution-gas system.

[0115] The following describes each step in detail:

[0116] 1. Establish a hierarchical collaborative recovery framework for the electricity-gas interconnection system

[0117] The restoration of the interconnected power-gas system can be broken down into the restoration of the transmission-gas system and the restoration of the distribution-gas system. The main tasks of restoring the transmission-gas system include: 1) starting the energy source (blackout start of generators and restoration of gas supply); 2) restoring the transmission and gas grids; and 3) restoring the electrical load at distribution substations and the gas load at distribution substations. The restoration of the distribution-gas system typically begins with the load restoration phase of the transmission-gas system. Its main tasks include: 1) optimizing the order and size of load input based on the importance of electricity and gas loads; and 2) determining the scheduling decisions for distributed power sources and gas sources (including distributed gas storage facilities and P2G devices) within the distribution-gas system.

[0118] The overall framework mechanism of hierarchical coordinated recovery of the electricity-gas interconnection system is as follows: Figure 2 As shown. Assuming that a large-scale energy supply interruption accident occurs at time t0, from time t1, the power-gas interconnection system enters the recovery preparation stage, and the power transmission-gas transmission system starts to restore the energy source and the power transmission and gas transmission grid. At this time, the distribution-gas distribution system grid and load nodes begin to recover, and can accept part of the power from the power transmission-gas transmission system to start the internal power supply and P2G device and restore part of the terminal load, and balance the output of the units in the power transmission-gas transmission system; if there is a faster starting energy source in the distribution-gas distribution system, electricity or natural gas can also be injected into the power transmission-gas transmission system to start the energy source therein. k At this moment, the electricity and gas loads at the power transmission and gas transmission system level are restored (the substations and pressure regulating stations of the power distribution and gas distribution system are the electricity and gas load nodes), and at the same time, the loads of the power distribution and gas distribution system are officially restored on a large scale. The hierarchical coordinated restoration of the power-gas interconnected system in this embodiment starts from t k At the beginning of the moment, the restoration preparation phase has been completed, the power supply and gas source within the power transmission and gas transmission system have been started, the transmission lines, gas transmission channels, distribution network substations and gas distribution network pressure regulating stations have been put into operation, and the focus is on t kThe physical process and mechanism model of information interaction and mutual support between the power transmission-gas transmission system and the power distribution-gas distribution system during the load recovery process after the moment.

[0119] The framework mechanism for hierarchical coordinated restoration of the electricity-gas interconnected system includes the following implementation steps:

[0120] (1) Solve the load recovery problem of the power transmission-gas transmission system.

[0121] Determine the output of each power source and gas source in the power transmission and gas transmission system at each moment, the node voltage and gas pressure of each distribution transformer station and gas distribution pressure regulating station, as well as the load recovery supply capacity.

[0122] (2) Solve the load recovery problem of the power distribution-gas distribution system.

[0123] Since k At this moment, the order and size of load recovery in the power distribution and gas distribution system, the scheduling decisions of each distributed power source and gas source, and the boundary connection variables such as voltage, gas pressure, active and reactive power flow and air flow of the distribution transformer station and gas distribution pressure regulating station are determined.

[0124] (3) Information interaction and update.

[0125] Based on the load recovery problem of the power transmission-gas transmission system and the load recovery problem of the power distribution-gas distribution system solved in the above two steps, k The results at each moment after the moment, the corresponding boundary connection variable information of the interactive power transmission-gas transmission system and the power distribution-gas distribution system, and the iterative update of the corresponding Lagrange multipliers.

[0126] In summary, through the mechanism of hierarchical coordinated restoration of the electricity-gas interconnection system, the solution to the original centralized electricity-gas interconnection system restoration problem can be decomposed into solving a transmission-gas transmission system load restoration sub-problem and several distribution-gas distribution system load restoration sub-problems. After each solution, information interaction is carried out through limited boundary connection variables to ensure the global optimality of the solution.

[0127] 2. Establishing a Collaborative Restoration Model for Electricity-Gas Interconnected Systems

[0128] The objective function is defined as maximizing the weighted supply of electricity and gas loads in the transmission-gas system and the distribution-gas system:

[0129]

[0130] Among them, the superscript T of each variable represents the transmission network or gas transmission network (transmission level), the superscript D represents the distribution network or gas distribution network (distribution level); the subscript E represents the power system, the subscript G represents the natural gas system; the superscript L represents the load. The subscript t represents the restoration time, T Rrepresents the set of restoration times; subscript m represents the transmission network node number, subscript n represents the gas transmission network node number, subscript i represents the distribution network node number, and subscript j represents the gas distribution network node number. This embodiment assumes that all load nodes in the transmission network are connected to the distribution network and not to the terminal power loads. The same applies to the gas transmission network. and Represents the set of all nodes of the transmission network, gas transmission network, distribution network and gas distribution network respectively; and Represent the weight coefficients of each node in the corresponding system. are the loads restored by each system at each moment.

[0131] It should be noted that the electricity load and natural gas load in the above objective function are both normalized. That is, in the objective function, the restored electricity and natural gas loads are the percentages of the restored loads to the original total load. For ease of expression in this embodiment, the objective function is still written in the above form.

[0132] The hierarchical coordinated restoration model for the power-gas interconnected system also includes power flow and security constraints for the transmission network, as well as restoration constraints for the power-gas distribution system. These are described below:

[0133] 1. Restoration constraints of the power and gas transmission system

[0134] (1) Transmission network power flow constraints and safety constraints

[0135] The restoration of the power system requires consideration of both reactive power and voltage, thus necessitating the establishment of an AC power flow model for the transmission system. Electromechanical transients in the power system can last for seconds, while electromagnetic transients can last for milliseconds or even microseconds. This embodiment focuses on the restoration of the power and natural gas systems, with a 15-minute interval for restoration optimization and control. Therefore, it can be assumed that the transients in the power system are complete within the interval between adjacent restoration moments. Therefore, this embodiment does not consider transients in the power system during the restoration process. Transmission network power flow constraints can be established based on the steady-state power system algebraic power flow equations.

[0136] Active and reactive balance constraints at transmission system nodes:

[0137]

[0138] Among them, the superscript G of each variable represents the power source. m′ is the node adjacent to m, K T is the set of transmission lines connected to node m. are the active power injected into node m and the active power flowing through line mm′ respectively; are the reactive power injection of node m, reactive load and reactive power flowing through line mm′ respectively. and They represent the total active and reactive losses on the transmission line connected to node m.

[0139] Active and reactive power balance constraints of transmission system lines:

[0140]

[0141] in, are the conductance and susceptance of line mm′ respectively; are the voltage amplitudes at nodes m and m′ respectively; is the phase angle difference of the voltage at both ends of line mm′. Among them, the voltage amplitude and cosine term and the sine term The cross product term is processed by quadratic relaxation technique, and the voltage amplitude square term An improved piecewise linearization method is used to obtain a convex expression of the line power flow constraint and achieve convex relaxation of the constraint.

[0142] Transmission grid restoration security constraints:

[0143] Including voltage amplitude constraint, power supply active and reactive output upper and lower limit constraints and climbing constraints, which are:

[0144]

[0145] in, and They are the upper and lower limits of the active output of the power supply respectively; and are the upper and lower limits of the reactive power output of the power supply, It is the upper limit of the power supply's ramping capability within adjacent recovery periods.

[0146] At the same time, to ensure the frequency stability of the transmission system during the restoration process, the change in the total amount of system active load restored between adjacent restoration moments should be lower than the maximum total amount of active load restored:

[0147]

[0148] (2) Gas transmission network flow constraints and safety constraints

[0149] This embodiment mainly studies the physical process and mechanism model of information interaction and mutual support between the power transmission-gas transmission system and the power distribution-gas distribution system during the restoration process. The steady-state Weymouth flow equation that ignores dynamic characteristics is used to model the flow constraints of the gas transmission network and the gas distribution network.

[0150] The airflow balance constraint at node n in the gas transmission network system is:

[0151]

[0152] in, and are the natural gas flow rate injected by the gas source and the natural gas flow rate consumed by the gas load at node n at time t, is the natural gas flow rate flowing through the gas pipeline nn′.

[0153] Constraints on the relationship between gas flow rate in a gas transmission pipeline and the pressure difference between the two ends of the pipeline:

[0154]

[0155] in, are the air pressures at nodes n and n′, respectively, is the Weymouth constant of the pipeline nn′.

[0156] The expression of the sign function of the pressure difference between the two ends of the pipeline is:

[0157]

[0158] For the nonlinear terms in the above constraints, an improved piecewise linearization method is used.

[0159] Gas transmission network restoration safety constraints:

[0160] It includes upper and lower limit constraints of pipeline airflow, upper and lower limit constraints of node air pressure, upper and lower limit constraints of gas source output and climbing constraints, which are:

[0161]

[0162] (3) Load recovery constraints of power and gas transmission systems

[0163] It includes active load recovery constraints, reactive load recovery constraints, transmission network load upper limit constraints, and gas source safe operation constraints of the gas transmission system, which are:

[0164]

[0165] in, and are the maximum active and reactive loads to be restored at node m, respectively. The restoration of the active load of the transmission network should be capped at the maximum load of the node, while the reactive load should be restored in proportion to the active load according to a specific power factor.

[0166] Since this embodiment assumes that the transmission network load node is the distribution network substation node, the transmission network load upper limit is the distribution network substation capacity:

[0167]

[0168] Similar to the power transmission system, the gas source safe operation constraints of the gas transmission system are:

[0169]

[0170] 2. Power distribution and gas distribution system recovery constraints

[0171] (1) Distribution network flow constraints and safety constraints

[0172] This embodiment ignores the impact of unbalanced three-phase loads on the distribution network and assumes a three-phase balanced system. A single-phase closed-form branch flow model is used to model the distribution network power flow constraints. For the mth distribution network (the distribution network number is the same as the load node number of the transmission network; for simplicity, the superscript m is omitted here), the mathematical expression of the power flow constraint is as follows:

[0173] The active and reactive power balance constraints at node i in the mth distribution network at time t are:

[0174]

[0175] in, and are the active power flow and reactive power flow through line ii′ connected to node i, respectively; is the square of the current amplitude flowing through line ii′; and are the active power and reactive power injected into node i, and are respectively the active load and reactive load actually restored at node i;

[0176] The relationship constraint between the square of the voltage amplitude between node i and node i′ is:

[0177]

[0178] Among them, r ii′ and x ii′ are the resistance and reactance of line ii′ respectively; is the square of the line impedance modulus. Similarly, the voltage amplitude only appears in the form of a square term, so it is considered as an independent variable.

[0179] Constraints on the relationship between node voltage amplitude and corresponding line current amplitude, active and reactive power flow values:

[0180]

[0181] This constraint is a non-convex constraint. For the cross product term McCormick convex relaxation method is used to deal with the square term of the variable The piecewise linearization method is used.

[0182] Distribution network security constraints:

[0183] It includes voltage amplitude, upper and lower limit constraints of power supply active and reactive output, and climbing constraints, specifically:

[0184]

[0185] (2) Gas distribution network flow constraints and safety constraints

[0186] The mathematical expressions of the flow constraints and safety constraints of the gas distribution network are the same as those of the gas transmission network.

[0187] (3) Load recovery constraints

[0188] The load restoration constraints of the distribution network are similar to those of the transmission network:

[0189]

[0190] To ensure the restoration effect, the restoration of terminal power load should be continuous, that is, the load restored at the subsequent moment must not be less than the previous moment:

[0191]

[0192] In addition, the active / reactive power received by the distribution substation should not exceed the power flowing out of the transmission grid node to which it is connected:

[0193]

[0194] Similarly, the terminal gas load recovery constraints of the gas distribution network are as follows:

[0195]

[0196] The natural gas flow rate received by the gas distribution and pressure regulating station should also meet the following constraints:

[0197]

[0198] 3. Transmission-Gas Transmission System Coupling Constraints and Distribution-Gas Distribution System Coupling Constraints

[0199] It includes transmission-gas transmission system coupling constraints, distribution-gas distribution system coupling constraints, and boundary connection constraints between transmission-gas transmission system and distribution-gas distribution system.

[0200] Figure 3This diagram illustrates the interaction between the power and natural gas systems. As can be seen, the power system's operation requires the natural gas system to supply fuel to the gas-fired units and micro-turbines; while the natural gas pipeline transmission system requires the power system to supply electricity to the electrically driven pressure regulating stations. Therefore, the gas-fired units within the transmission system and the electrically driven pressure regulating stations within the gas transmission system are the primary coupling points between the power transmission and gas transmission systems. The distribution system, including the micro-turbines, power-to-gas facilities, and the gas distribution system's step-down and pressure regulating stations, are the primary coupling points between the power transmission and gas distribution systems.

[0201] The transmission-gas transmission system coupling constraints and the distribution-gas distribution system coupling constraints include:

[0202] Energy conversion relationship constraints of gas units:

[0203]

[0204] in, is the natural gas consumption of the gas generating unit connected between the distribution network node i and the gas distribution network node j at time t; Provides active power for the gas generator set; is the power generation efficiency; G is the lower calorific value of natural gas, which is 35590kJ / m 3 .

[0205] The energy conversion relationship constraint of the gas-fired unit connected to the transmission grid and the gas transmission grid is the same as the expression of the energy conversion relationship constraint of the gas-fired unit, with only the variable symbols and superscripts being different, which are omitted here.

[0206] P2G facility energy conversion relationship constraints:

[0207]

[0208] in, The active power consumed by the P2G facility as an electrical load; is the corresponding natural gas flow rate, is the gas production efficiency;

[0209] After an extreme event, if the electric-powered pressure regulating stations lose power, the remaining available natural gas-powered pressure regulating stations can maintain basic network operations, but the gas transmission network's delivery capacity will be severely impacted. Therefore, the goal of gas transmission network restoration is to quickly restore the network's delivery capacity and the ability to supply the gas distribution network.

[0210] Constraints on the relationship between the natural gas flow rate transmitted by the power-driven pressure regulating station in the gas transmission network and the power consumed:

[0211]

[0212] in, is the natural gas flow rate flowing through the power-driven pressure regulating station between the gas transmission network node n and the gas distribution network node j; The electric power consumed by the power-driven voltage regulating station as an electric load; β reg,T is the energy consumption coefficient.

[0213] The boundary connection constraints of the power transmission-gas transmission system and the power distribution-gas distribution system are as follows:

[0214] Substations and gas distribution and pressure regulating stations are key hubs connecting the power transmission and distribution systems, and the gas transmission and distribution systems, respectively. Substations can be considered loads for the transmission network and power sources for the distribution network. The same applies to gas distribution and pressure regulating stations. The boundary constraints for the power transmission and gas transmission systems and the power distribution and gas distribution systems are defined as follows:

[0215]

[0216] The above constraints represent the power and voltage relationships of the power transmission system and the gas transmission system at the substation, where V t D,m,sub,sqr represents the square of the voltage amplitude of the substation connected to the transmission network node m; it should be noted that, in this embodiment, all voltage values are normalized values.

[0217] At the same time, considering that the boost ratio of the gas distribution and pressure regulating station is fixed and the natural gas flow rate on both sides is the same, the boundary connection constraint of the gas transmission-distribution system can be obtained:

[0218]

[0219] and is the boundary connection constraint of the gas transmission-distribution system, Indicates the gas pressure on the boost side of the gas distribution and pressure regulating station connected to the gas transmission network node n, represents the pressure on the step-down side, Γ c is the step-up ratio.

[0220] In this embodiment, P t sub,D,m 、 V t D,m,sub,sqr 、 and Set as the boundary connection variable of the transmission-gas transmission system and the distribution-gas distribution system during the restoration process.

[0221] At this point, the collaborative restoration model of the power transmission-gas transmission system and the power distribution-gas distribution system can be established. The energy conversion and information interaction relationship in the collaborative restoration process of the model can be summarized as follows: Figure 4 shown.

[0222] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A modeling method for a hierarchical collaborative recovery model of an electric-gas interconnected system, characterized in that: The modeling method includes: Step 1: Establish a hierarchical collaborative recovery framework model for the electricity-gas interconnection system; Step 2: Establish a collaborative restoration model for the electricity-gas interconnected system based on the framework model in step 1; Step 3: Add power-gas network coupling constraints to the electricity-gas interconnected system collaborative restoration model, including transmission-gas system coupling constraints, distribution-gas system coupling constraints, and boundary connection constraints between the transmission-gas system and the distribution-gas system. Step 4: Complete the establishment of the coordinated restoration model of the electricity-gas interconnection system; The step 1 is specifically as follows: Assume that the energy supply interruption accident occurs at time t0. k From the moment of t, the electricity and gas loads at the transmission-gas transmission system level were restored, and at the same time, the loads of the distribution-gas distribution system officially began to be restored on a large scale; the layered coordinated restoration of the electricity-gas interconnection system started from t k At the beginning of the moment, the restoration preparation phase has been completed, the power supply and gas source within the power transmission and gas transmission system have been started, and the power transmission lines, gas transmission channels, distribution network substations and gas distribution network pressure regulating stations have been put into operation; Based on the current electricity-gas interconnection system, a hierarchical collaborative recovery framework model for the electricity-gas interconnection system is established; the hierarchical collaborative recovery framework model for the electricity-gas interconnection system includes: (1) Solve the load recovery problem of the power transmission and gas transmission system: determine the output of each power source and gas source in the power transmission and gas transmission system at each moment, the node voltage and gas pressure of each distribution transformer station and gas distribution and regulating station, and the load recovery supply; (2) Solve the load recovery problem of the power distribution-gas distribution system: k At this moment, determine the order and size of load recovery in the power distribution and gas distribution system, the scheduling decisions of each distributed power source and gas source, and the boundary connection variables of the voltage, gas pressure, active and reactive power flow and air flow of the distribution transformer station and gas distribution pressure regulating station; (3) Information interaction and update: Based on the load recovery problem of the power transmission-gas transmission system and the load recovery problem of the power distribution-gas distribution system solved in the above two steps (1) and (2), the load recovery problem of the power transmission-gas transmission system is solved in t k The results of each moment after the moment, the corresponding boundary connection variable information of the interactive power transmission-gas transmission system and the power distribution-gas distribution system, and the iterative update of the corresponding Lagrange multipliers; The electric-gas interconnected system collaborative recovery model is specifically as follows: The objective function of the model is to maximize the weighted supply of electricity load and gas load in the transmission-gas transmission system and the distribution-gas distribution system, specifically: Among them, the superscript T of each variable represents the transmission network or gas transmission network, the superscript D represents the distribution network or gas distribution network; the subscript E represents the power system, the subscript G represents the natural gas system; the superscript L represents the load; the subscript t represents the restoration time, T R represents the set of restoration moments; subscript m represents the node number of the transmission network, subscript n represents the node number of the gas transmission network, subscript i represents the node number of the distribution network, and subscript j represents the node number of the gas distribution network; and Represents the set of all nodes of the transmission network, gas transmission network, distribution network and gas distribution network respectively; and Respectively represent the weight coefficients of each node of the corresponding system; are the loads restored by each system at each moment.

2. The method for modeling a hierarchical collaborative recovery model for an electrical-gas interconnected system according to claim 1, characterized in that: The hierarchical collaborative restoration model of the electricity-gas interconnected system is provided with restoration constraints of the power transmission-gas transmission system and the power distribution-gas distribution system; The power transmission-gas transmission system restoration constraints include power transmission network flow constraints and safety constraints, gas transmission network flow constraints and safety constraints, and power transmission-gas transmission system load restoration constraints; The power distribution-gas distribution system recovery constraints include power distribution network flow constraints and safety constraints, gas distribution network flow constraints and safety constraints, and power distribution-gas distribution system load recovery constraints.

3. The method for modeling a hierarchical collaborative recovery model for an electrical-gas interconnected system according to claim 2, characterized in that: The transmission network power flow constraints are specifically: Active and reactive balance constraints at transmission system nodes: Among them, the superscript G of each variable represents the power source; m′ is the node adjacent to m, K T is the set of transmission lines connected to node m; are the active power injected into node m and the active power flowing through line mm′ respectively; are the reactive power injection of node m, reactive load and reactive power flowing through line mm′ respectively; The right side of the equation and They represent the total active and reactive losses on the transmission line connected to node m; Active and reactive power balance constraints of transmission system lines: in, are the conductance and susceptance of line mm′ respectively; are the voltage amplitudes at nodes m and m′ respectively; is the phase difference of the voltage at both ends of line mm′; among them, the voltage amplitude and cosine term and the sine term The cross product term is processed by quadratic relaxation technique, and the voltage amplitude square term An improved piecewise linearization method is used to obtain a convex expression of the line power flow constraint, thus achieving convex relaxation of the constraint. Transmission grid restoration security constraints: Including voltage amplitude constraint, power supply active and reactive output upper and lower limit constraints and climbing constraints, which are: in, and They are the upper and lower limits of the active output of the power supply respectively; and are the upper and lower limits of the reactive power output of the power supply, The upper limit of the power supply's ramping capability within adjacent recovery periods; Constraints between the change in the total amount of system active load restored between adjacent restoration moments and the maximum total amount of active load restored:

4. The method for modeling a hierarchical collaborative recovery model for an electrical-gas interconnected system according to claim 2, characterized in that: The gas transmission network flow constraints and safety constraints are specifically: The airflow balance constraint at node n in the gas transmission network system is: in, and are the natural gas flow rate injected by the gas source and the natural gas flow rate consumed by the gas load at node n at time t, is the natural gas flow rate flowing through the gas pipeline nn′; the relationship between the gas flow rate of the gas pipeline and the pressure difference between the two ends of the pipeline is constrained: in, are the air pressures at nodes n and n′, respectively, is the Weymouth constant of the pipeline nn′; The expression of the sign function of the pressure difference between the two ends of the pipeline is: For the nonlinear terms in the above constraints, an improved piecewise linearization method is used; Gas transmission network restoration safety constraints: It includes upper and lower limit constraints of pipeline airflow, upper and lower limit constraints of node air pressure, upper and lower limit constraints of gas source output and climbing constraints, which are:

5. The method for modeling a hierarchical collaborative recovery model for an electrical-gas interconnected system according to claim 2, characterized in that: The load recovery constraints of the power transmission and gas transmission system are specifically: Active load recovery constraints: Reactive load recovery constraints: Transmission grid load upper limit constraints: Constraints on safe operation of gas source:

6. The method for modeling a hierarchical collaborative recovery model for an electrical-gas interconnected system according to claim 2, characterized in that: The distribution network power flow constraints and safety constraints are specifically: The active and reactive power balance constraints at node i in the mth distribution network at time t are: in, and are the active power flow and reactive power flow through line ii′ connected to node i, respectively; is the square of the current amplitude flowing through line ii′; and are the active power and reactive power injected into node i, and are respectively the active load and reactive load actually restored at node i; The relationship constraint between the square of the voltage amplitude between node i and node i′ is: Among them, r ii′ and x ii′ are the resistance and reactance of line ii′ respectively; is the square of the line impedance modulus; the relationship constraints between the node voltage amplitude and the corresponding line current amplitude, active and reactive power flow values are: This constraint is a non-convex constraint. For the cross product term McCormick convex relaxation method is used to deal with the square term of the variable The piecewise linearization method is used for processing; Distribution network security constraints: It includes voltage amplitude, upper and lower limit constraints of power supply active and reactive output, and climbing constraints, specifically:

7. The method for modeling a hierarchical collaborative restoration model for an electrical-gas interconnected system according to claim 2, characterized in that: The load recovery constraints of the power distribution-gas distribution system are specifically: Active load recovery constraints: Reactive load recovery constraints: Terminal power load restoration continuity constraints: Active and reactive power constraints accepted by the distribution substation: Restoration constraints of terminal gas load in the gas distribution network: Gas distribution and pressure regulating stations are subject to natural gas flow constraints:

8. The method for modeling a hierarchical collaborative restoration model for an electrical-gas interconnected system according to claim 1, characterized in that: The power transmission-gas transmission system coupling constraints and the power distribution-gas distribution system coupling constraints in step 3 are specifically: Energy conversion relationship constraints of gas units: in, is the natural gas consumption of the gas generating unit connected between the distribution network node i and the gas distribution network node j at time t; Provides active power for the gas generator set; is the power generation efficiency; G is the lower calorific value of natural gas; Energy conversion constraints for gas-fired units connected to the transmission grid and gas grid; P2G facility energy conversion relationship constraints: in, The active power consumed by the P2G facility as an electrical load; is the corresponding natural gas flow rate, is the gas production efficiency; Constraints on the relationship between the natural gas flow rate transmitted by the power-driven pressure regulating station in the gas transmission network and the power consumed: in, is the natural gas flow rate flowing through the power-driven pressure regulating station between the gas transmission network node n and the gas distribution network node j; The electric power consumed by the power-driven voltage regulating station as an electric load; β reg,T is the energy consumption coefficient; The boundary connection constraints of the power distribution-gas distribution system are specifically: The above constraints represent the power and voltage relationships of the power transmission system and the gas transmission system at the substation, where V t D ,m,sub,sqr represents the square of the voltage amplitude of the substation connected to the transmission network node m; the boundary connection constraint of the gas transmission-distribution system is: and is the boundary connection constraint of the gas transmission-distribution system, Indicates the gas pressure on the boost side of the gas distribution and pressure regulating station connected to the gas transmission network node n, represents the pressure on the step-down side, Γ c is the step-up ratio; P t sub,D,m 、 V t D,m,sub,sqr 、 and Set as the boundary connection variable of the transmission-gas transmission system and the distribution-gas distribution system during the restoration process.

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