An analysis method and system based on the energy flow exchange model of the electric-gas coupling system

Abstract

The present invention belongs to the field of electric power technology, and discloses an analysis method based on an interval energy flow exchange model of an electric-gas coupling system. By establishing an interval energy flow exchange model, and based on the established interval energy flow exchange model, a natural gas system branch and an electric system node state quantity solution model is established, and then the natural gas system branch and the electric system node state quantity are solved and analyzed, and at the same time, combined with constraint conditions, the natural gas system branch parameter interval and the electric system node state quantity parameter interval in the interval energy flow exchange model are obtained. The present invention takes into account the uncertainty of renewable energy injection that cannot be ignored, and through the establishment of an interval energy flow exchange model, the modeling and calculation of uncertain energy flows of an electric-gas coupling system with high penetration renewable energy are realized. The present invention also discloses an analysis system based on the interval energy flow exchange model of an electric-gas coupling system.

Description

Technical Field

[0001] The present invention belongs to the field of electric power technology, and in particular relates to an analysis method and system based on an interval energy flow exchange model of an electric-gas coupling system. Background Art

[0002] As the coupling between the power system and the natural gas system gradually deepens, electricity-gas coupling has become an important form of multi-energy coupling. The failure of a single system is transmitted to another system through coupling, and accidents causing serious safety problems have occurred frequently, and safety issues have become more prominent.

[0003] The uncertainty of renewable energy not only affects the operating state of the power system, but also affects the operating state of the natural gas system through the output change of the coupling element gas unit. The unpredictable reduction of renewable energy output will increase the gas consumption of the gas unit, causing the operating pressure of the pipeline network to drop. Since the load in the natural gas system often requires a certain pressure head, there will be a risk of load loss when the operating pressure is too low. When the inlet pressure of the gas unit is lower than the minimum pressure limit, it will cause it to trip and shut down, causing the power system to further lose power, thereby causing a chain failure of the power system and even a power outage; the unpredictable increase in its output will reduce the gas consumption of the gas unit, causing the operating pressure of the pipeline network to increase, and excessive pressure will bring the risk of damage to natural gas equipment such as pipelines and valves. The failure of natural gas equipment will in turn affect the gas supply of the gas unit, thereby limiting the output of the gas unit, and then affecting the safe operation of the power system. Therefore, it is very important to calculate the uncertain energy flow of the electric-gas coupling system with high penetration of renewable energy.

[0004] At present, device-level modeling and single energy flow system modeling have become very mature, and multi-energy flow microgrid models that do not consider network characteristic constraints have also been widely used. Although initial results have been achieved in multi-energy flow coupling modeling considering network constraints, how to consider the multi-time scale characteristics and distributed parameter characteristics of the coupled network and establish a fast energy flow analysis method suitable for fault scenarios is still a difficult problem to be solved. Summary of the invention

[0005] The purpose of the embodiment of the present invention is to provide a method for analyzing the natural gas branch airflow and the power system state variable parameters based on the electric-gas coupling system interval energy flow exchange model, by establishing an energy flow exchange model and solving the model, and then analyzing the natural gas branch airflow change interval and the power system node state parameter interval.

[0006] To achieve the above objectives, the present invention provides an analysis method and system based on an energy flow exchange model of an electric-gas coupling system.

[0007] The first is an analysis method based on the energy flow exchange model of the electric-gas coupling system, which includes the following steps:

[0008] Establish an interval energy flow AC model, which includes an AC power flow model of the power system and a steady-state hydraulic nonlinear model of the natural gas system;

[0009] Based on the established interval energy flow exchange model, a state quantity solution model for natural gas system branches and power system nodes is established;

[0010] The established natural gas system branch and power system node state quantity solution models are analyzed, and combined with the constraint conditions, the natural gas system branch parameter interval and the power system node state quantity parameter interval in the interval energy flow exchange model are obtained.

[0011] Preferably, the process of establishing the interval energy flow communication model includes:

[0012] The AC power flow model of the power system in the electric-gas coupled multi-energy flow system is established, where the model is as follows:

[0013]

[0014] in, represents the active power injected into node i, Inject reactive power into node i, V i 、V j is the voltage amplitude at nodes i and j, G ij and B ij are the mutual conductance and mutual susceptance between nodes i and j, respectively, θ i ,θ j is the phase angle between nodes i and j, θ ij is the voltage phase difference between nodes i and j, θ ij =θ i -θ j ;

[0015] Considering the changes of pipeline parameters with flow rate, a steady-state hydraulic nonlinear model of the natural gas system is established, where the model is as follows:

[0016]

[0017] Where p is the node pressure, P i represents the pressure at node i, P j represents the pressure at node j, m is the pipe flow rate, m ij represents the pipe flow rate between node i and node j, where c is the sound velocity in the medium, l is the pipe length, d is the pipe diameter, λ is the friction coefficient, π is the parameter symbol, let π = P 2 To simplify the calculation;

[0018] The gas base group model is established. According to the heat rate curve, the gas unit model of the gas unit can be obtained. The quadratic function is constructed as follows:

[0019]

[0020] Where P Gg It represents the active power output of the gas unit, HR represents the natural gas combustion heat rate, and α, β, δ are the heat rate coefficients of the gas turbine;

[0021] Establish the natural gas combustion heat rate HR and gas mass flow rate m Gg The relationship equation is as follows:

[0022]

[0023] Where ρ0 is the density of natural gas under standard conditions, which is 0.7174 kg / Nm 3 GHV is the calorific value of natural gas combustion, in MJ / Nm 3 ;

[0024] The functional relationship between the active output of the gas unit and the inlet mass flow rate is obtained, and the analysis is simplified. The gas unit model equation is simplified to a linear equation, α and δ are taken as zero, and β depends on the efficiency coefficient of the gas turbine. The conversion relationship equation of the constructed gas unit model is obtained as follows:

[0025] T Gg ·P Gg =η·m gG (5)

[0026] Where P Gg is the active power output vector of the node gas generator set, m gG is the mass flow vector of the gas consumption of the node gas generator set, T Gg is the connection matrix between the gas unit nodes of the power system and the gas unit load nodes of the natural gas system, η is the gas unit efficiency parameter vector;

[0027] In view of the rapid response characteristics of the gas-fired unit, the regulation equation of the gas-fired unit to the uncertainty of renewable energy is established, namely, P Gg Follow P RE The model equation of the change is as follows:

[0028]

[0029] Among them, P RE is the active power output vector of the node renewable energy, is the initial dispatch output of the gas unit under the predicted value of renewable energy, G is the allocation ratio factor, To predict the active output vector of renewable energy at the node;

[0030] Based on equations (1)-(6), the interval AC energy flow exchange model is established, and the model is as follows:

[0031]

[0032]

[0033] T Gg · <P Gg > = η· <m gG > (9),

[0034]

[0035] Among them, equation (7) is the adjustment equation of the gas unit to the uncertainty of renewable energy, <P Gg > represents the active output vector interval of the node gas unit, <P RE >Indicates the active output vector interval of renewable energy sources at the node;

[0036] Equation (8) is the AC power flow model of the power system, F e represents the power system function, Represents the injected active power vector interval of the PV node and PQ node, <P Gg > represents the active output vector interval of the node gas unit, <P RE > represents the active output vector interval of renewable energy in the node, represents the active output vector of other thermal power units at the node under the predicted value of renewable energy, P ed is the node active load vector, Indicates the reactive power vector injected by the PQ node, Q Gg is the reactive power output vector of the node gas generator set, Q Go is the reactive power output vector of other thermal power units at the node, Q ed is the node reactive load vector, v represents the node voltage, and θ represents the phase angle;

[0037] Equation (9) is the coupling equation for the conversion between the gas turbine inlet mass flow and active output. <P Gg > represents the active output vector interval of the node gas unit, <m gG > is the mass flow vector interval of gas consumption of the node gas generator set;

[0038] Equation (10) is the steady-state nonlinear hydraulic model of the natural gas system, let Π = p 2 To simplify the calculation of assumed variables, K is the pipeline transmission parameter vector, <m sp >Node injection natural gas mass flow vector interval, <m gs > is the node gas source output mass flow vector interval, mgd is the mass flow vector of other natural gas loads at the node, A g The node-branch association matrix of the natural gas network topology, <m b > is the branch natural gas flow vector interval, Π i =P i 2 , <Π> is the node pressure square vector interval.

[0039] Preferably, a natural gas branch and power system node state quantity solution model is obtained based on the established interval energy flow exchange model, which is characterized as a non-convex nonlinear optimization model, as follows:

[0040]

[0041]

[0042]

[0043] T Gg ·P Gg =η·m gG (14)

[0044]

[0045] Formula (11) indicates that the constraint condition is the active output vector interval of the node renewable energy, P RE Indicates the active output quality of renewable energy at the node, P RE Represents the minimum value of the interval of the active power output vector of renewable energy, Represents the active power output vector P of renewable energy RE The maximum value of the interval;

[0046] Formula (12) is the regulation equation of the gas unit to the uncertainty of renewable energy, P RE is the active power output vector of the node renewable energy, is the initial dispatch output of the gas unit under the predicted value of renewable energy, G is the allocation ratio factor, To predict the active output vector of renewable energy at the node;

[0047] Formula (13) is the AC power flow model equation of the power system, F e represents the power system function, represents the injected active power vector of the PV node and the PQ node, P Gg is the active power output vector of the node gas generator set, P RE Represents the active output vector of renewable energy in the node, represents the active output vector of other thermal power units at the node under the predicted value of renewable energy, P ed is the node active load vector, Indicates the reactive power vector injected by the PQ node, Q Gg is the reactive power output vector of the node gas generator set, Q Go is the reactive power output vector of other thermal power units at the node, Q ed is the node reactive load vector, V represents the node voltage, and θ represents the phase angle;

[0048] Formula (14) is the gas turbine model conversion equation, P Gg is the active power output vector of the node gas generator set, m gG is the mass flow vector of the gas consumption of the node gas generator set, T Gg is the connection matrix between the gas unit nodes of the power system and the gas unit load nodes of the natural gas system, η is the gas unit efficiency parameter vector;

[0049] Formula (15) is the steady-state nonlinear hydraulic model equation of the natural gas system, K is the pipeline transmission parameter vector, m sp Node injected natural gas mass flow vector, m gs is the node gas source output mass flow vector; m gd is the mass flow vector of other natural gas loads at the node, A g The node-branch association matrix of the natural gas network topology, m b is the branch natural gas flow vector, Π i =P i 2 , ∏ is the squared node pressure vector.

[0050] Preferably, based on the established solution model, the natural gas system branch flow solution is analyzed:

[0051] Based on equation (14) and equation (12), the following equation is obtained:

[0052]

[0053] Wherein, equation (16) represents the mass flow vector interval of the gas consumption of the node gas unit: <m gG >Renewable energy active output vector interval <P RE >Relationship;

[0054] Mass flow vector interval based on gas consumption of node gas generator set <m gG >, the branch gas flow interval solution equation of the natural gas system is calculated as:

[0055]

[0056] Among them, min / maxm b，k Indicates the solution of the equation for m b，k Solve for the maximum and minimum values, m b，k is the natural gas branch flow quality of pipeline k, k = 1, 2, ..., NB g , N.B. g is the number of natural gas pipelines;

[0057] m gG Indicates the minimum value of the mass flow vector interval of the gas consumption of the node gas unit, Indicates the maximum value of the mass flow vector interval of the gas consumption of the node gas unit, Represents the constraint condition of the mass flow vector of the gas consumption of the gas unit at the node of this equation;

[0058] Preferably, based on the established solution model, the power system node voltage amplitude interval solution equation includes:

[0059] Based on equations (12) and (13), the active power vector interval of the injection node is obtained: <P SP >Interval of active output vector of renewable energy sources at the node <P RE >Relation equation:

[0060]

[0061] Combining equation (18) and equation (13), we get the node voltage interval calculation equation:

[0062]

[0063] Among them, i=1, 2,...,NN e , N.N. e is the number of buses in the power system. According to the model equation (19), the node voltage vector interval can be obtained.

[0064] Preferably, based on establishing the solution model, an analysis method for node state variables other than node voltage in the power system AC model and branch interval state variables other than branch flow in the natural gas system can also be obtained.

[0065] The present invention also provides an analysis system based on an energy flow exchange model between electric and gas coupling systems, comprising a first establishment unit, a second establishment unit, and an analysis unit, wherein:

[0066] The first establishing unit is used to establish an interval energy flow AC model according to the AC power flow model of the power system and the steady-state hydraulic model of the natural gas system;

[0067] The second establishing unit is used to establish a state quantity solution model for a natural gas system branch and a power system node according to the interval energy flow exchange model established by the first establishing unit;

[0068] The analysis unit is used to analyze the electromechanical state parameters of the natural gas branch and the power system according to the solution model established by the second establishment unit.

[0069] The present invention has the following beneficial effects: considering the boundary information of uncertain variables in the electric-gas coupling system, an interval energy flow "communication" model is proposed for the steady-state model of the electric-gas coupling system. For the proposed interval energy flow model, a corresponding interval energy flow calculation method is proposed, which can be solved separately in the management center of each subject by exchanging a small number of variables. Thus, the modeling and calculation of the uncertain energy flow state variables of the electric-gas coupling system with high penetration renewable energy are realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0071] Figure 1 A flow chart of the analysis method based on the energy flow exchange model of the electric-gas coupling system is shown. DETAILED DESCRIPTION

[0072] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0073] This embodiment provides an analysis method based on an interval energy flow AC model of an electric-gas coupling system, by establishing an interval energy flow AC model of an electric-gas coupling system, and a solution model for the state quantity of a natural gas branch and an electrical system node established based on the interval energy flow AC model, and further, by decomposing and calculating the model, the relationship between the node voltage interval in the electric power system and the branch mass flow rate in the natural gas system and the active output of the node renewable energy is obtained, and then the change of the node voltage of the electrical system and the change of the branch mass flow rate in the natural gas system are obtained through the change of the active output of the renewable energy, such as Figure 1 As shown, the specific steps include:

[0074] 1. Establish an interval energy flow exchange model, which includes an AC power flow model for the power system and a steady-state hydraulic nonlinear model for the natural gas system;

[0075] 2. Based on the interval energy flow exchange model established in 1, a state quantity solution model for natural gas system branches and power system nodes is established;

[0076] 3. Analyze the node state quantity solution model of the natural gas system branch and the power system established in 2, and combine the constraints to obtain the natural gas system branch parameter interval and the power system node state quantity parameter interval in the interval energy flow exchange model.

[0077] The present invention is explained by two embodiments based on establishing an electric-gas coupling system interval energy flow exchange model to obtain a node voltage range in an electric power system and a branch mass flow range in a natural gas system.

[0078] Furthermore, the establishment of the interval energy flow communication model includes the following steps:

[0079] 1.1. Establish the AC power flow model in the electric-gas coupled multi-energy flow power system, where the model is as follows:

[0080]

[0081] in, represents the active power injected into node i, Inject reactive power into node i, V i 、V j is the voltage amplitude at nodes i and j, G ij and B ij are the mutual conductance and mutual susceptance between nodes i and j, respectively, θ i ,θ j is the phase angle between nodes i and j, θ ij is the voltage phase difference between nodes i and j, θ ij =θ i -θ j ;

[0082] The model equation (1) is established to relate the active power injected into the node to the voltage and phase angle;

[0083] 1.2. Establish a steady-state hydraulic model of the natural gas system. The "quasi-circuit" model of the natural gas system is a linear model that can be solved directly. However, this model ignores the change of the gas resistance parameter R0 with the system operation state. In the embodiment of the present invention, the natural gas system considers the change of pipeline parameters with flow rate and adopts a nonlinear hydraulic equation as the "AC" model (2), that is, the Weymouth formula commonly used in the steady-state hydraulic calculation of the natural gas system, where the equation is as follows:

[0084]

[0085] Among them, the nonlinear model is a set of nonlinear equations, p is the node pressure, P i represents the pressure at node i, P j represents the pressure at node j, m is the pipe flow rate, and m ij represents the pipeline flow between node i and node j, where c is the sound velocity in the medium, l is the pipeline length, d is the pipeline diameter, and λ is the friction coefficient. The model equation can be solved using the Newton method similar to the above-mentioned power system AC power flow analysis. π is the parameter symbol. In the solution process, π=P 2 To simplify the calculation;

[0086] 1.3. According to the heat rate curve, the output active power P of the gas unit can be obtained Gg The relationship between the heat consumption rate HR can be approximately expressed by a quadratic function without loss of generality, as shown below:

[0087]

[0088] Where P Gg It represents the output active power of the gas unit, HR represents the relationship between the consumed heat rates, and α, β, and δ are the heat rate coefficients of the gas turbine;

[0089] 1.4. Establish the natural gas combustion heat rate HR and natural gas mass flow rate m Gg The model equation is as follows,

[0090]

[0091] Where ρ0 is the density of natural gas under standard conditions (273.15K, 101kPa), usually 0.7174kg / Nm 3 GHV is the calorific value of natural gas combustion, in MJ / Nm 3 ;

[0092] 1.5. According to the model equations in 1.3 and 1.4, the parameters in the equations are replaced with vectors to obtain the functional relationship between the active output of the gas unit and the inlet mass flow rate. In order to simplify the analysis, the gas unit model equation in step 1.3 is simplified to a linear equation, α and δ are taken as zero, and β depends on the efficiency coefficient of the gas turbine. The conversion relationship equation for constructing the gas unit model is obtained as follows:

[0093] T Gg ·P Gg =η·m gG (5)

[0094] Where P Ggis the active power output vector of the node gas unit (the vector value corresponding to the node without gas unit is zero, and the following power vectors are processed in the same way), m gG is the mass flow vector of gas consumption of the node gas generator set; T Gg is the connection matrix between the gas unit nodes of the power system and the gas unit load nodes of the natural gas system, η is the gas unit efficiency parameter vector;

[0095] 1.6. In view of the rapid response characteristics of gas-fired units, it is assumed that when renewable energy fluctuates, the gas-fired units are mainly responsible for the ramp-up task, and their increased / decreased output is distributed according to a certain ratio. The regulation equation (7) of the gas-fired units to the uncertainty of renewable energy is established, that is, P Gg Follow P RE The equation of change is as follows:

[0096]

[0097] Among them, P RE is the active power output vector of the node renewable energy, is the initial dispatch output of the gas unit under the predicted value of renewable energy, is the active output vector of renewable energy in the predicted node, G is the allocation proportional factor, and it is assumed that the i-th row and j-th column of the matrix G are G ij , which means that when the output of the renewable energy unit at node j is short of a unit MW, the output change of the gas unit at node i, the sum of the elements in the jth column of the matrix G should be 1. This factor is the same as the proportional factor of the unbalanced power of the generator automatic control AGC to adjust the distribution unit. Generally, it is always hoped that G ij ≥0, that is, when the fluctuation of renewable energy causes a power shortage in the system, the output of the units will increase to avoid a further decrease in the system's power generation;

[0098] The establishment of this model equation can obtain the change of the active output of the gas unit node through the change of the active output of the renewable energy at the node;

[0099] 1.7. Based on equations (1)-(6), an interval energy flow exchange model can be established. The model is as follows:

[0100]

[0101]

[0102] T Gg · <P Gg > = η· <m gG > (9),

[0103]

[0104] Among them, equation (7) is the adjustment equation of the gas unit to the uncertainty of renewable energy, which is the active power vector of the node into the active power vector interval model equation according to model equation (6). <P Gg > represents the active output vector interval of the node gas unit, <P RE >Indicates the active output vector interval of renewable energy sources at the node;

[0105] Equation (8) is the AC power flow model of the power system, which can be obtained by transforming the model equation (1). At the same time, the active power vector and the injected active power vector are transformed into interval vectors, F e Represents the power system function. Combined with this, it means that the active power vector injected at the node and the reactive power vector injected at the node are functions of the voltage and phase angle at the node. Represents the injected active power vector interval of the PV node and PQ node, <P Gg > represents the active output vector interval of the node gas unit, <P RE > represents the active output vector interval of renewable energy in the node, represents the active output vector of other thermal power units at the node under the predicted value of renewable energy, P ed is the node active load vector, Indicates the reactive power vector injected by the PQ node, Q Gg is the reactive power output vector of the node gas generator set, Q Go is the reactive power output vector of other thermal power units at the node, Q ed is the node reactive load vector, V represents the node voltage, and θ represents the phase angle;

[0106] Equation (9) is the coupling equation for the conversion between the inlet mass flow rate and active power output of the gas turbine unit. According to the interval vector equation obtained by model equation (5), <P Gg > represents the active output vector interval of the node gas unit, <m gG > is the mass flow vector interval of gas consumption of the node gas generator set;

[0107] Equation (10) is the steady-state nonlinear hydraulic model of the natural gas system, which is obtained by transforming the model equation (2), where Π=P 2 To simplify the calculation of assumed variables, K is the pipeline transmission parameter vector, <m sp >Node injection natural gas mass flow vector interval, <m gs > is the node gas source output mass flow vector interval, m gd is the mass flow vector of other natural gas loads at the node, A g The node-branch association matrix of the natural gas network topology, <m b > is the branch natural gas flow vector interval, <Π> is the node pressure square vector interval.

[0108] Based on the established interval energy flow exchange model of the electric-gas coupling system, a model for solving the state quantity of the natural gas branch and the power system node is established. The maximum and minimum values ​​of the state quantity of each node and branch are solved one by one to obtain its operating range, which is characterized as a non-convex nonlinear optimization model, as follows:

[0109]

[0110]

[0111]

[0112] T Gg ·P Gg =η·m gG (14)

[0113]

[0114] Among them, formula (11) represents the constraint condition as the active output vector interval of the node renewable energy, P RE Indicates the active output quality of renewable energy at the node, P RE Represents the minimum value of the interval of the active power output vector of renewable energy, Indicates the interval maximum value of the active power output vector of renewable energy;

[0115] Formula (12) is the regulation equation of the gas unit to the uncertainty of renewable energy, P RE is the active power output vector of the node renewable energy, is the initial dispatch output of the gas unit under the predicted value of renewable energy, G is the allocation ratio factor, To predict the active output vector of renewable energy at the node;

[0116] Formula (13) is the AC power flow model equation of the power system, F e represents the power system function, represents the injected active power vector of the PV node and the PQ node, P Gg is the active power output vector of the node gas generator set, P RE Represents the active output vector of renewable energy in the node, represents the active output vector of other thermal power units at the node under the predicted value of renewable energy, P ed is the node active load vector, Indicates the reactive power vector injected by the PQ node, Q Gg is the reactive power output vector of the node gas generator set, Q Go is the reactive power output vector of other thermal power units at the node, Q edis the node reactive load vector; V represents the node voltage, θ represents the phase angle;

[0117] Formula (14) is the gas turbine model conversion equation, P Gg is the active power output vector of the node gas unit (the vector value corresponding to the node without gas unit is zero, and the following power vectors are processed in the same way), m gG is the mass flow vector of the gas consumption of the node gas generator set, T Gg is the connection matrix between the gas unit nodes of the power system and the gas unit load nodes of the natural gas system, η is the gas unit efficiency parameter vector;

[0118] Formula (15) is the steady-state nonlinear hydraulic model equation of the natural gas system, K is the pipeline transmission parameter vector, m sp Node injected natural gas mass flow vector, m gs is the node gas source output mass flow vector; m gd is the mass flow vector of other natural gas loads at the node, A g The node-branch association matrix of the natural gas network topology, m b is the branch natural gas flow vector, Π i =P i 2 , Π is the node pressure square vector interval;

[0119] For large-scale electric-gas coupled systems, the amount of computation required to solve the interval values ​​of all state variables in sequence is huge. Considering that the power system and the natural gas system often belong to different management departments, and the coupling between the electric and gas coupled systems is mainly achieved through coupling elements, the interval "AC" energy flow can be decomposed and solved, which not only protects the data privacy of each management center to a greater extent, but also reduces the amount of computation.

[0120] For example, the interval "AC" energy flow solution model is analyzed. First, the natural gas system is still taken as an example of branch air flow. The interval value of the gas consumption of the gas unit is directly and quickly calculated. The interval value can be transmitted from the power system to the natural gas system. Based on equation (14) and equation (12), the following equation is obtained:

[0121]

[0122] Wherein, equation (16) represents the active output vector interval of renewable energy at the node: <P RE >, get the mass flow vector interval of gas consumption of node gas unit <m gG >

[0123] The mass flow vector interval of gas consumption of gas generator sets passing through the node <m gG>, the branch gas flow interval solution equation of the natural gas system is calculated as:

[0124]

[0125] Among them, min / maxm b，k Indicates the solution of the equation for m b，k Solve for the maximum and minimum values, m b，k is the natural gas branch flow quality of pipeline k, k = 1, 2, ..., NB g , N.B. g is the number of natural gas pipelines;

[0126] m gG Indicates the minimum value of the mass flow vector interval of the gas consumption of the node gas unit, Indicates the maximum value of the mass flow vector interval of the gas consumption of the node gas unit, Represents the constraint condition of the mass flow vector of the gas consumption of the gas unit at the node of this equation;

[0127] For example, based on the established solution model, the equations for solving the voltage amplitude interval of the power system node include:

[0128] Based on equations (12) and (13), the active power vector interval of the injection node is obtained: <P SP >Interval of active output vector of renewable energy sources at the node <P RE >Relation equation:

[0129]

[0130] Combining equation (18) and equation (13), we get the node voltage interval calculation equation:

[0131]

[0132] Among them, i=1, 2,...,NN e , NN e is the number of buses in the power system. According to equation (19), the node voltage vector interval can be obtained.

[0133] Other methods for solving the state variables of power system nodes and natural gas system branches are completely similar to the above two embodiments, such as the analysis method of the interval value of node injected active power and the interval value of gas consumption of gas units in the power system AC power flow model. Only the objective function of the optimization model is different, and the solution of each variable is independent of each other, so multiple optimizers can be used for parallel solution.

[0134] The embodiment of the present invention further provides an analysis system based on an energy flow exchange model between electric and gas coupling systems, comprising a first establishing unit, a second establishing unit, and an analyzing unit, wherein:

[0135] The first establishing unit is used to establish an interval energy flow AC model according to the AC power flow model of the power system and the steady-state hydraulic model of the natural gas system;

[0136] The second establishing unit is used to establish a state quantity solution model for a natural gas system branch and a power system node according to the interval energy flow exchange model established by the first establishing unit;

[0137] The analyzing unit is used to analyze the natural gas branch flow parameter and the power system state parameter interval according to the solution model established by the second establishing unit.

[0138] Through the implementation of the embodiment of the present invention, considering the boundary information of uncertain variables in the electric-gas coupling system, an interval energy flow "communication" model is proposed for the steady-state model of the electric-gas coupling system. For the proposed interval energy flow model, a corresponding interval energy flow calculation method is proposed. On the basis of protecting the data privacy of each subject, a small amount of variable exchange can be exchanged and solved separately in the management center of each subject. Thereby, the modeling and calculation of the uncertain energy flow of the electric-gas coupling system with high penetration of renewable energy is realized.

[0139] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art can still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. An analysis method based on the energy flow exchange model of the electric-gas coupling system, characterized in that: The steps include: S1: Establish an interval energy flow AC model, where the interval energy flow AC model includes an AC power flow model of the power system and a steady-state hydraulic nonlinear model of the natural gas system; S2: Based on the interval energy flow exchange model established in S1, a state quantity solution model for natural gas system branches and power system nodes is established; S3: Analyze the node state quantity solution model of the natural gas system branch and the power system established in S2, and obtain the flow parameter interval of the natural gas system branch and the node state quantity parameter interval of the power system in the interval energy flow exchange model in combination with the constraint conditions; The step S2 specifically includes: Based on the established interval energy flow exchange model, the state quantity solution model of the natural gas branch and power system node is obtained, which is characterized as a non-convex nonlinear optimization model, as follows: T Gg ·P Gg =η·m gG (14), Formula (11) indicates that the constraint condition is the active output vector interval of the node renewable energy, P RE Represents the active output quality of renewable energy at the node, P RE Represents the minimum value of the interval of the active power output vector of renewable energy, Indicates the interval maximum value of the active power output vector of renewable energy; Formula (12) is the regulation equation of the gas unit to the uncertainty of renewable energy, P RE is the active power output vector of the node renewable energy, is the initial dispatch output of the gas unit under the predicted value of renewable energy, G is the allocation ratio factor, To predict the active output vector of renewable energy at the node; Formula (13) is the AC power flow model equation of the power system, F e represents the power system function, represents the injected active power vector of the PV node and the PQ node, P Gg is the active power output vector of the node gas generator set, P RE Represents the active output vector of renewable energy in the node, represents the active output vector of other thermal power units at the node under the predicted value of renewable energy, P ed is the node active load vector, Indicates the reactive power vector injected by the PQ node, Q Gg is the reactive power output vector of the node gas generator set, Q Go is the reactive power output vector of other thermal power units at the node, Q ed is the node reactive load vector, V represents the node voltage, and θ represents the phase angle; Formula (14) is the gas turbine model conversion equation, P Gg is the active power output vector of the node gas generator set, m gG is the mass flow vector of the gas consumption of the node gas generator set, T Gg is the connection matrix between the gas unit nodes of the power system and the gas unit load nodes of the natural gas system, η is the gas unit efficiency parameter vector; Formula (15) is the steady-state nonlinear hydraulic model equation of the natural gas system, K is the pipeline transmission parameter vector, m sp Node injected natural gas mass flow vector, m gs is the node gas source output mass flow vector, m gd is the mass flow vector of other natural gas loads at the node, A g The node-branch association matrix of the natural gas network topology, m b is the branch natural gas flow vector, and ∏ is the node pressure square vector.

2. The analysis method based on the energy flow exchange model of the electric-gas coupling system according to claim 1 is characterized in that: The step S1 specifically includes: S1.

1. Establish the AC power flow model of the power system in the electric-gas coupled multi-energy flow system, where the model is as follows: in, represents the active power injected into node i, Inject reactive power into node i, V i 、V j is the voltage amplitude at nodes i and j, G ij and B ij are the mutual conductance and mutual susceptance between nodes i and j, respectively, θ i ,θ j is the phase angle between nodes i and j, θ ij is the voltage phase difference between nodes i and j, θ ij =θ i -θ j ; S1.

2. Considering the changes of pipeline parameters with flow rate, a steady-state hydraulic nonlinear model of the natural gas system is established, where the model is as follows: Where p is the node pressure, P i represents the pressure at node i, P j represents the pressure at node j, m is the pipe flow rate, m ij represents the pipe flow rate between node i and node j, where c is the sound velocity in the medium, l is the pipe length, d is the pipe diameter, λ is the friction coefficient, π is the parameter symbol, let π = P 2 To simplify the calculation; S1.

3. Establish a gas base group model. According to the heat rate curve, the gas unit model of the gas unit can be obtained. The quadratic function is constructed as follows: Where P Gg It represents the active power output of the gas turbine unit, HR represents the natural gas combustion heat rate, and α, β, δ are the heat rate coefficients of the gas turbine; S1.

4. Establish the natural gas combustion heat rate HR and gas mass flow rate m Gg The relationship equation is as follows: Where ρ0 is the density of natural gas under standard conditions, which is 0.7174 kg / Nm 3 GHV is the calorific value of natural gas combustion, in MJ / Nm 3 ; S1.

5. According to the equations in S1.3 and S1.4, the functional relationship between the active output of the gas unit and the inlet mass flow rate is obtained. The gas unit model equation in step S1.3 is simplified into a linear equation, α and δ are taken as zero, and β depends on the efficiency coefficient of the gas turbine. The conversion relationship equation for constructing the gas unit model is obtained as follows: T Gg ·P Gg =η·m gG (5), Where P Gg is the active power output vector of the node gas generator set, m gG is the mass flow vector of the gas consumption of the node gas generator set, T Gg is the connection matrix between the gas unit nodes of the power system and the gas unit load nodes of the natural gas system, η is the gas unit efficiency parameter vector; S1.

6. In view of the rapid response characteristics of the gas-fired unit, the regulation equation of the gas-fired unit to the uncertainty of renewable energy is established, namely, P Gg Follow P RE The model equation of the change is as follows: Among them, P RE is the active power output vector of the node renewable energy, is the initial dispatch output of the gas unit under the predicted value of renewable energy, G is the allocation ratio factor, To predict the active output vector of renewable energy at the node; S1.

7. Based on equations (1)-(6), an interval AC energy flow model is established. The model is as follows: T Gg · <P Gg >=η· <m gG > (9), Among them, equation (7) is the adjustment equation of the gas unit to the uncertainty of renewable energy, <P Gg > represents the active output vector interval of the node gas unit, <P RE >Indicates the active output vector interval of renewable energy sources at the node; Equation (8) is the AC power flow model of the power system, F e represents the power system function, Represents the injected active power vector interval of the PV node and PQ node, <P Gg > represents the active output vector interval of the node gas unit, <P RE > represents the active output vector interval of renewable energy in the node, represents the active output vector of other thermal power units at the node under the predicted value of renewable energy, P ed is the node active load vector, Indicates the reactive power vector injected by the PQ node, Q Gg is the reactive power output vector of the node gas generator set, Q Go is the reactive power output vector of other thermal power units at the node, Q ed is the node reactive load vector, V represents the node voltage, and θ represents the phase angle; Equation (9) is the coupling equation for the conversion between the gas turbine inlet mass flow and active output. <P Gg > represents the active output vector interval of the node gas generator set, < mg G> is the mass flow vector interval of gas consumption of the node gas generator set; Equation (10) is the steady-state nonlinear hydraulic model of the natural gas system, let Π = P 2 To simplify the calculation of assumed variables, K is the pipeline transmission parameter vector, <m sp >Node injection natural gas mass flow vector interval, <m gs > is the node gas source output mass flow vector interval, m gd is the mass flow vector of other natural gas loads at the node, A g The node-branch association matrix of the natural gas network topology, <m b > is the branch natural gas flow vector interval, ∏ i =P i 2 , <Π> is the node pressure square vector interval.

3. The analysis method based on the energy flow exchange model of the electric-gas coupling system according to claim 1 is characterized in that: The step S3 specifically includes: S3.

1. Based on the established solution model, analyze the natural gas system branches: Based on equation (14) and equation (12), the following equation is obtained: Wherein, equation (16) represents the mass flow vector interval of the node gas unit gas consumption <m gG >Renewable energy active output vector interval <P RE >Relationship; Mass flow vector interval based on gas consumption of node gas generator set <m gG >, the branch gas flow interval solution equation of the natural gas system is calculated as: Where min / max m b,k Indicates the solution of the equation for m b,k Solve for the maximum and minimum values, m b,k is the natural gas branch flow quality of pipeline k, k = 1, 2, ..., NB g , N.B. g is the number of natural gas pipelines; m gG Indicates the minimum value of the mass flow vector interval of the gas consumption of the node gas unit, Indicates the maximum value of the mass flow vector interval of the gas consumption of the node gas unit, Represents the constraint condition of the mass flow vector of the gas consumption of the gas unit at the node of this equation; S3.

2. Based on the established solution model, the equations for solving the voltage amplitude interval of the power system nodes include: Based on equations (12) and (13), the active power vector interval of the injection node is obtained: <P SP >Interval of active output vector of renewable energy sources at the node <P RE >Relation equation: Combining equation (18) and equation (13), we get the node voltage interval calculation equation: Among them, i=1,2,…,NN e , N.N. e is the number of buses in the power system. According to the model equation (19), the node voltage vector interval can be obtained.

4. The analysis method based on the energy flow exchange model of the electric-gas coupling system according to claim 1 is characterized in that: Based on the established solution model, the analysis method of node state variables other than node voltage in the power system AC model and branch interval state variables other than branch flow in the natural gas system can also be obtained.

5. An analysis system based on an electric-gas coupling system interval energy flow exchange model, used to execute the method of claim 1, comprising a first establishment unit, a second establishment unit, and an analysis unit, characterized in that: The first establishing unit is used to establish an interval energy flow AC model according to the AC power flow model of the power system and the steady-state hydraulic model of the natural gas system; The second establishing unit is used to establish a state quantity solution model for a natural gas system branch and a power system node according to the interval energy flow exchange model established by the first establishing unit; The analyzing unit is used to analyze the natural gas branch flow parameters and the power system node state parameters according to the solution model established by the second establishing unit.

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