CN108416507B - Static Sensitivity Analysis Method for Electric-Pneumatic Coupled Integrated Energy System - Google Patents

Abstract

The invention discloses a static sensitivity analysis method for an electric-gas coupling integrated energy system, which is used for analyzing the interaction mechanism between the electric power and the gas energy supply system. First, the present invention provides a unified power flow model of the electric-gas coupled integrated energy system; on this basis, the gas pressure-node injection power sensitivity of the electric-gas coupled integrated energy system is defined; finally, combined with the integrated energy system in a typical scenario Sensitivity index, analyze the influence of the injected power of grid nodes on the gas pressure, and locate the weak link of the integrated energy system. The calculation example shows that the invention can provide auxiliary information for the safe and stable operation of the regional comprehensive energy system, and effectively improve the safety of the system.

Description

Static Sensitivity Analysis Method for Electric-Pneumatic Coupled Integrated Energy System

technical field

The invention relates to the field of electric-pneumatic coupled integrated energy systems, in particular to a static sensitivity analysis method of an electric-pneumatic coupled integrated energy system based on a unified power flow model.

Background technique

With the increasing scarcity of fossil energy and the continuous deterioration of the environment, energy transformation has become the only way to achieve sustainable economic and social development. Breaking the existing mode of separate planning and independent operation of each energy supply system, and realizing the energy system towards a new energy system with multi-energy integration, integration and complementation, is an important way to promote the above process. To this end, the "Thirteenth Five-Year Plan for Energy Development" clearly proposes to "implement multi-energy complementary integration and optimization projects" and "overall planning for infrastructure such as electricity, gas, heating, cooling, water supply pipe gallery, etc., and build an integrated integrated supply energy system”, which promotes the development of comprehensive utilization of multiple energy sources at the national level ^[1] .

Integrated Energy Systems (IES) is known as one of the main ways to realize the comprehensive utilization of multiple energy sources. dispatch, improve the efficiency of energy efficient utilization, and realize the full consumption of renewable energy ^[2] . However, while IES achieves the above goals, it also brings the overall risk of the safe operation of the system. In the face of the tight coupling of multiple energy sources, different energy supply systems are "connected to the whole body", and the interaction between them should be closely watched. On the one hand, the failure of the gas system will be transmitted to the power system and directly lead to power outages, such as the 8.15 blackout accident in Taiwan, China in 2017, when 6 units were disconnected from the grid caused by the interruption of natural gas supply, causing 6.68 million households User power outage, the affected population exceeds 85% of the total population in Taiwan, China ^[3] . Similar incidents also appeared in the United States. In 2015, in Southern California, the Aliso Canyon natural gas leakage caused a shortage of natural gas supply in gas-fired power plants, which seriously affected the normal operation of the local power system ^[4] . On the other hand, the adverse effects of the power system are also transmitted to the natural gas system and endanger the safe operation of the natural gas system. With the increase in the penetration rate of renewable energy in the United States, the frequent adjustment of gas-fired power plants as the main peak-shaving resources has led to large fluctuations in the pressure of the gas pipeline network, which directly affects the gas transmission safety of the natural gas system ^[5] . At the same time, the power link of the IES often contains Distributed Generation (DG), and the intermittent fluctuation of its output will be transmitted to the entire IES through the coupling link between the two (such as gas generating units), causing adverse effects on the entire system ^{[6] ]} . In view of this, the influence of the unfavorable factors of each energy supply system on the safe operation of Integrated Electricity and Gas Systems (IEGS) must be paid great attention. Without loss of generality, the influence of unfavorable factors on the safe operation of the system often depends on the safe operation margin of the weak links of the system. Therefore, quickly locating the weak links of IEGS has become an urgent problem to be solved.

Reference [7] established a steady-state analysis model of an electrical-pneumatic coupled system, considering the interaction between the two systems from the perspective of energy flow; further, reference [8] proposed an optimal electrical-pneumatic coupled system based on network operation constraints. The energy flow model provides a decision-making aid for the optimal scheduling of the system; Reference [9] uses the point-by-point method to analyze the influence of the increase of the heat network load on the voltage of the grid nodes and the heating temperature of the heating network nodes based on the power flow calculation; Reference [10] Based on the energy hub model, the literature [11] uses the hybrid power flow algorithm to analyze the interaction characteristics of each electric-gas energy supply network in steady state.

However, the above research focuses on the power flow calculation of IEGS, and does not fully consider the influence of different energy supply network states (such as network topology, pipeline structure, load level, etc.) on the interaction between different energy sources in the integrated energy system, and how to determine the weak links of IEGS .

SUMMARY OF THE INVENTION

The invention provides a static sensitivity analysis method for an electric-gas coupled integrated energy system. The invention defines the gas pressure-node injection power sensitivity index of the electric-gas coupled integrated energy system; combined with the sensitivity of the integrated energy system in a typical scenario The index analyzes the influence of the injected power of the grid nodes on the gas pressure; locates the weak links of the integrated energy system, and provides a decision-making basis for the operation control of the integrated energy system (especially the location of the gas storage device), as described below:

A static sensitivity analysis method for an electric-pneumatic coupling integrated energy system, the static sensitivity analysis method comprises the following steps:

Establish an IEGS unified power flow model consisting of a gas system model, a power distribution system model and an energy coupling link model;

According to the IEGS unified power flow model, obtain the current stable operating point and the Jacobian matrix of the current operating point;

Calculate the gas pressure-node injection power sensitivity according to the Jacobian matrix; sort the gas pressure-node injection power sensitivity, and the node set with high sensitivity is the weak link of IEGS.

The IEGS unified power flow model is specifically:

为电网节点电压；Y为节点导纳矩阵，^*为复数共轭；A^NGS为燃气网络的节点-支路关联矩阵；

为轻型燃气轮机的输出电功率；c_ge为转化系数。In the formula, x = [θ, V, p] represents the state variables of IEGS, which are the phase angle of each node of the distribution network except the balance node, the voltage of the electric load node, and the gas pressure of the gas load node; u = [P ^PDS , Q ^PDS , L ^NGS ] represents the disturbance variable of IEGS, which injects active power, reactive power and gas load into nodes respectively; a represents independent parameters; P ^PDS injects active power into nodes;

is the grid node voltage; Y is the node admittance matrix, ^* is the complex conjugate; A ^NGS is the node-branch correlation matrix of the gas network;

is the output electric power of the light gas turbine; c _ge is the conversion coefficient.

The calculation of the gas pressure-node injection power sensitivity according to the Jacobian matrix is specifically:

According to the Jacobian matrix, the gas pressure-gas load sensitivity and the output-node injection power sensitivity of the light-duty gas turbine are calculated respectively;

The gas pressure-node injection power sensitivity is calculated from the gas pressure-gas load sensitivity and the output of the light gas turbine-node injection power sensitivity.

The gas pressure-node injection power sensitivity is specifically:

代表了MT的输出电功率；

为MT的燃气消耗。Among them, P ^PDS is the active power injected at the node; p is the gas pressure at the gas node; L ^NGS is the gas load;

Represents the output power of MT;

Gas consumption for MT.

Further, the gas pressure-gas load sensitivity S ^gg is equal to the negative number of the inverse of the Jacobian matrix J _gg in the power flow solution of the natural gas system:

In the formula, A ^NGS is the node-branch correlation matrix of the gas network; f _i is the flow rate of pipe i; ∏ _i is the pressure difference of pipe i; n _p is the number of pipes; T is the matrix transpose; diag() represents the construction diagonal array.

发生变化，对于配电网有：In specific implementation, if a certain node i injects power

Changes occur, for the distribution network there are:

为配电网网损，对

求偏导有：In the formula,

is the network loss of the distribution network, for

The partial derivatives are:

In the formula, the second term on the right side of the equation is the network loss slight increase rate, which represents the change relationship between the network loss and the injected power of the node.

The beneficial effects of the technical scheme provided by the present invention are:

1. This method defines the pressure safety index of the integrated energy system and locates the weak links of the integrated energy system;

2. This method analyzes the mechanism of the instability of the operating air pressure in the power system due to the fluctuation of the load power or the fluctuation of the new energy power generation output in the integrated energy system in a typical scenario;

3. This method provides corresponding guidance for the selection of the gas storage location of the integrated energy system.

Description of drawings

Fig. 1 is a flow chart of a static sensitivity analysis method for an electric-pneumatic coupled integrated energy system;

Figure 2 is a schematic diagram of an electric-pneumatic coupling integrated energy system;

Figure 3 is a schematic diagram of an IEGS calculation example;

Figure 4 is a schematic diagram of the ^See of each node of the distribution network;

Figure 5 is a schematic diagram of S ^gg of each node of the gas network;

Figure 6 is a schematic diagram of gas pressure-node injection power sensitivity;

Figure 7 is a schematic diagram of air pressure under different load growth levels;

Figure 8 is a schematic diagram of air pressure under different schemes.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention are further described in detail below.

Sensitivity analysis technology has been widely used in power system operation optimization. The static analysis method based on the power flow equation can analyze the change situation between the two through the differential relationship between different physical quantities, so as to determine the weak nodes and key branches of the system. information ^[12] .

To this end, the embodiment of the present invention expects to propose a static sensitivity analysis method for an electric-pneumatic coupled integrated energy system for IEGS with the help of a mature sensitivity analysis method in the power system. The method considers the network state of the power-gas system, analyzes the interaction law between the gas pipeline pressure and the electric power injection space, and deeply explores the interaction between different energy supply networks in IEGS, and determines the weak areas that affect the safe operation of the system. The example shows that This method can quickly and directly obtain the weak areas of IEGS, which can provide decision-making basis for IEGS operation control (especially the location of gas storage devices).

Example 1

A static sensitivity analysis method for an electrical-pneumatic coupled integrated energy system is shown in Figure 1. The static sensitivity analysis method includes the following steps:

101: Establish an IEGS unified power flow model consisting of a gas system model, a power distribution system model and an energy coupling link model;

102: Obtain the current stable operating point and the Jacobian matrix of the current operating point according to the IEGS unified power flow model;

103: Calculate the gas pressure-gas load sensitivity and the light-duty gas turbine output-node injection power sensitivity according to the Jacobian matrix, so as to calculate the gas pressure-node injection power sensitivity;

104: Sort the gas pressure-node injection power sensitivity, and the node set with greater sensitivity is the weak link of the IEGS.

To sum up, in the embodiment of the present invention, the network state of the power-gas system is considered through the above steps 101 to 104, and the interaction law between the gas pipeline pressure and the electric power injection space is analyzed. This method can quickly and directly obtain the weak area of IEGS, Provide decision-making basis for the operation control of IEGS.

Example 2

The scheme in Embodiment 1 is further introduced below in conjunction with the specific calculation formula, Fig. 2, and specific examples, and is described in detail below:

201: IEGS modeling;

In the embodiment of the present invention, an IEGS including a natural gas network (Natural Gas System, NGS), a power distribution network (Power Distribution System, PDS) and a coupling link is taken as an example to verify the effectiveness of the method.

Among them, NGS consists of gas source, gas pipeline, gas load, compressor, valve, etc. The valve is used to control the flow or cut-off of gas in the pipeline. It is assumed that the valve is only in two states of fully open or fully closed, so the network topology of NGS is determined. IEGS is connected to the large grid through distribution transformers and assumes that IEGS has signed a power supply contract with the upstream grid. The energy coupling link is a key link in the interaction of various energy supply systems in IEGS, and has the characteristics of various coupling devices. For example, the light gas turbine (Micro-turbines, MT) realizes the coupling of the gas system with the power grid; through the power to gas technology (Power to Gas, P2G), electrical energy can be converted into natural gas energy. Considering that the MT is widely used in the IEGS, the embodiment of the present invention sets the MT as the coupling link of the IEGS. The electric-pneumatic coupling integrated energy system studied in the embodiment of the present invention is shown in FIG. 2 .

The embodiment of the present invention assumes that IEGS has signed a power supply contract with an external large power grid, and the contract specifies the amount of electricity that the distribution network interacts with the large power grid at different time periods. Therefore, the unbalanced power caused by various unfavorable factors during the operation process is borne by the MT , that is, MT acts as a balancing unit of the distribution network.

A typical conduction scenario considering the unfavorable factors of IEGS: the surge in electrical load caused by the extensive use of air conditioners and other refrigeration equipment in summer, the power shortage in the system is made up by MT, which causes changes in gas load and further changes in gas pressure; Or due to short-term output fluctuations of DG represented by wind power or photovoltaics, the output of MT fluctuates, which in turn causes changes in gas pressure in the gas network. In short, the change of the injected power at any node of the distribution network will affect the gas pressure level of the gas network through the coupling link. In some extreme scenarios, it may even cause operation problems of the gas system, such as large fluctuations in gas pressure and gas pressure exceeding the limit.

Therefore, the gas network pressure level can be regarded as one of the important indicators for the safe operation of IEGS, and it is considered that the area where the pressure drops rapidly in the IEGS is the weak link of the IEGS when unfavorable factors act on the system. Obtaining the weak links of the system and installing gas storage equipment in the weak links is a preventive control measure to improve the safety margin of IEGS air pressure.

1) Gas system model

The model of the gas system is mainly the steady-state flow equation of the pipeline, which can be divided into pipelines with compressors and pipelines without compressors. There is a pressure drop at both ends of the pipeline, especially in long-distance and large-capacity medium and high pressure gas transmission networks, it is necessary to configure a compressor to increase the pressure of the gas transmission pipeline. Considering that the IEGS studied in the embodiment of the present invention belongs to the category of low-pressure gas distribution network (0-75 mbar), the embodiment of the present invention does not consider the influence of the compressor for the time being ^[13] .

The node variables of the gas system include the injected gas flow and the node air pressure. Following the node classification of the power system, the nodes can be divided into nodes with known pressure and nodes with known injection flow according to the known variables. In the gas system, the gas source is the balance node, the gas pressure is known but the injection flow rate is unknown, the gas pressure of the gas load is unknown and the gas demand is known. If the gas system has n _g nodes and n _p pipelines, node 1 is the gas source node, and the rest are gas load nodes. For gas line k connecting nodes i, j (i,j=1,2,...,n _g ), steady state flow f _k (k=1,2,・··,n _p ) can be described by the following formula ^[10,13] :

Π=-(A ^NGS ) ^T p (3)

In the formula, λ _k is the friction coefficient of the pipeline k; Π _k represents the pressure difference between the two ends of the pipeline k; D _k and L _k represent the diameter and length of the pipeline k; G is the relative density of the gas; p represents the gas node pressure; A ^NGS is the node-branch association matrix of the gas network. When Π _k >0, _sk =1; when Π _k <0, _sk =-1.

Analogous to Kirchhoff's first and second laws, the flow of gas in the network should satisfy the following two conditions: the gas flow injected into a node is equal to the gas flow out of the node; for any loop of the network, the gas flows The sum of the pressure drops in the process is zero. Therefore, the flow behavior of gas in the network can be described by the following equation:

A ^NGS f = L ^NGS (4)

In the formula, f is the steady-state flow column vector of the pipeline; L ^NGS is the gas load.

2) Distribution system model

The embodiment of the present invention assumes that the three-phase unbalance problem of the distribution network has been effectively solved by commutation ^[14] , so the embodiment of the present invention ignores the influence of the three-phase unbalance on the power flow calculation. If the distribution network has n _e nodes, node 1 is a balanced node, node 2 to node 1+n _pv are PV nodes (nodes with given active power P and voltage V), and the rest are PQ nodes (with given active power P and reactive power Q nodes). The model of the distribution network is the node power equation that reflects the relationship between node power, node voltage and phase angle ^[14] :

为节点i上发电机发出的有功，无功功率；

为节点i上负荷的有功，无功功率；V_i，V_j为节点i，j的电压；G_ij，B_ij为节点i，j之间导纳Y_ij的实部，虚部；θ_ij为节点i同节点j之间的相角差(i,j＝1,2,···,n_e)。In the formula, Pi is the injected active power of node _{i; Q i is} the injected reactive power of node i;

is the active and reactive power emitted by the generator on node i;

are the active and reactive power of the load on node i; V _i , V _j are the voltages of nodes i, j; G _ij , B _ij are the real and imaginary parts of the admittance Y _ij between nodes i and j; θ _ij is the phase angle difference between node i and node j (i,j=1,2,..., _ne ).

3) Energy coupling link model

The embodiment of the present invention assumes that the output adjustment of the MT is at the second level ^[15] . When considering the interaction between different energy supply networks, the dynamic characteristics of the MT are ignored, and the network interaction is considered from the perspective of energy interaction. The input of MT is gas, and the high-temperature gas generated by gas combustion is used to expand to do work and then output electricity. Therefore, the model of MT is a static model that characterizes its steady-state input and output characteristics. The MT model is as follows:

代表了MT的输出电功率；

代表了MT的燃气消耗；c_ge代表了MT的转化系数。In the formula,

Represents the output power of MT;

represents the gas consumption of MT; c _ge represents the conversion coefficient of MT.

202: IEGS static sensitivity analysis method; the IEGS power flow solution model can be divided into a unified power flow model and a discrete solution model ^[10] , both of which have no effect on the derivation of the sensitivity analysis. The embodiment of the present invention is based on the unified power flow model, and further defines Gas pressure-node injection power sensitivity index, and locate the weak link of the system through static sensitivity analysis.

The embodiment of the present invention further defines the gas pressure-node injection power sensitivity index on the basis of the IEGS unified power flow model, and locates the weak link of the system through static sensitivity analysis.

1) IEGS unified power flow model;

For IEGS, the essence of power flow calculation is the process of finding the stable operating point of the system under a given series of conditions. The unified power flow model can be described as:

为电网节点电压；Y为节点导纳矩阵，这在公式(5)-(8)里面已说明，^*为复数共轭的数学运算符号。In the formula, x = [θ, V, p] represents the state variables of IEGS, which are the phase angle of each node of the distribution network except the balance node, the voltage of the electric load node, and the gas pressure of the gas load node; u = [P ^PDS , Q ^PDS , L ^NGS ] represents the disturbance variables of the IEGS, which are the active power injected into the node, the reactive power and the gas load, and the gas load, respectively; a represents the independent parameters, such as the power system node admittance, the gas system network topology, and the pipeline parameters. P ^PDS injects active power into the node;

is the grid node voltage; Y is the node admittance matrix, which has been explained in formulas (5)-(8), and ^* is the mathematical operation symbol of complex conjugate.

The unified power flow model is solved by the Newton-Raphson method, and its iterative form is as follows:

In the formula, Δx ^(k+1) is the change of the state variable of the IEGS in the k+1 iteration; x ^(k+1) is the state variable of the IEGS in the k+1 iteration; ΔF is the power flow equation. Deviation value; J is the Jacobian matrix, which can be expressed as ^[7] :

According to the given initial conditions of the system, the simultaneous equations (10)-(12) are solved to obtain the current stable operating point of the system.

The meanings of the elements in the Jacobian matrix J are well known to those skilled in the art, and details are not described in this embodiment of the present invention.

2) Gas pressure-node injection power sensitivity matrix

Clarifying the influence of unfavorable factors on different energy supply networks is equivalent to analyzing the changes of system operating state of IEGS under the action of unfavorable factors (such as changes in node injection power). Unfavorable factors can generally be characterized by the disturbance variables of the system, so the static sensitivity of IEGS The general expression for analysis is:

According to the changing relationship of different physical quantities in different energy supply networks, various forms of sensitivity indicators can be constructed. The interaction between the two energy supply networks is conducted through the MT. According to the scenario in Section 1, the MT is set as the balance machine of the distribution network and connected to the node h in the gas network. Considering the typical conduction scenario of unfavorable factors, in this embodiment of the present invention, the fluctuation of the injected power of the grid node is used as the unfavorable factor of the IEGS, and the gas pressure is used as the state variable of the IEGS. According to formula (13), the gas pressure-node injection power sensitivity matrix S ^ge is defined as follows:

是矩阵S^ge中的元素，代表配电网节点i注入功率的变化(i＝1,2,···,n_e)对燃气节点j(j＝1,2,···,n_g)气压的影响。in,

is an element in the matrix S ^ge , representing the change of the injected power of the distribution network node i (i=1,2,...,n _e ) to the gas node j (j=1,2,...,n _g ) influence of air pressure.

为c_eg，则S^ge为这三者的乘积。Define S ^gg as the gas pressure-gas load sensitivity, S ^ee as the MT output-node injection power sensitivity as follows, according to equation (9)

is c _eg , then S ^ge is the product of these three.

是矩阵S^gg中的元素，代表MT燃气需求变化对于燃气节点j气压变化的影响(j＝1,2,···,n_g)；

是矩阵S^ee的元素，代表配电网节点i注入电功率变化对于MT出力变化的影响。

is an element in the matrix S ^gg , which represents the influence of MT gas demand change on the gas pressure change of gas node j (j=1,2,...,n _g );

is the element of the matrix ^See , which represents the influence of the change of the electric power injected by the node i of the distribution network on the change of the MT output.

For the gas network, it can be seen from the analysis of equations (1)-(4) that S ^gg is equal to the negative number of the inverse of the Jacobian matrix J _gg in the power flow solution of the natural gas system:

In the formula, the function diag() represents the construction of a diagonal matrix.

发生变化，对于配电网有：For the distribution network, if a node i injects power

Changes occur, for the distribution network there are:

为配电网网损，考虑到其它节点注入功率不变，式(19)对节点注入功率

求偏导有：In the formula,

For the network loss of the distribution network, considering that the injected power of other nodes remains unchanged, formula (19) injects power to the node

The partial derivatives are:

In the formula, the second term on the right side of the equation is the network loss slight increase rate, which represents the change relationship between the network loss and the injected power of the node. Intuitively, for a lossless network, the MT output is the same as the node injected power. However, for an actual power grid, its network topology and load level will affect the network loss micro-increase rate of the network, thereby affecting the energy interaction between the energy supply networks. The network loss is determined by the voltage and phase angle of each node ^[16] , and the net loss micro-increase rate is further derived as follows:

Note that the inversion of the grid Jacobian matrix J _ee in equation (12) can be expressed as:

Comparing equations (20) and (22), it can be seen that the Jacobian matrix J _ee can provide corresponding information for solving S ^ee , and the simultaneous equations (20)-(22) can solve S ^ee .

203: Implementation steps of gas pressure-node injection power sensitivity analysis.

值越大的表明燃气节点j(j＝1,2,···,n_g)气压变化对配电网节点i(i＝1,2,···,n_e)电功率注入变化敏感。可见当不利因素作用于IEGS时，灵敏度大的节点气压变化幅度最大，将最先到达燃气网络气压约束边界，可将其视为系统安全运行的短板。S^ge考虑了不同供能网络的状态，反映了电功率注入空间的扰动对天然气气压水平的影响，可为运行和控制提供重要信息。

A larger value indicates that the gas pressure change of the gas node j (j=1,2,...,n _g ) is sensitive to the electric power injection change of the distribution network node i (i=1,2,...,n _e ). It can be seen that when the unfavorable factors act on the IEGS, the pressure change of the node with high sensitivity is the largest, and it will reach the pressure constraint boundary of the gas network first, which can be regarded as the short board for the safe operation of the system. S ^ge considers the states of different energy supply networks, reflects the influence of the disturbance of electric power injection space on the gas pressure level, and can provide important information for operation and control.

It is worth noting that the different MT access locations will affect the power flow distribution of the IEGS. Therefore, before calculating the sensitivity matrix, it is necessary to specify the deployment position of the MT, change the initial conditions of the power flow calculation, and form different stable operating points. The steps of the sensitivity analysis method are:

1) Read natural gas network status information, including: natural gas pipeline parameters, pipeline topology information, form A ^NGS , read distribution network network information, form Y;

2) Solve the power flow equations according to equations (10) to (12) to obtain the current stable operating point of the IEGS and the Jacobian matrix J of the current operating point;

3) According to the Jacobian matrix J, calculate S ^gg and ^See respectively according to formulas (16), (17), (20)-(22);

4) Calculate the gas pressure-node injection power sensitivity S ^ge according to formula (14);

5) Sort the sensitivity of the gas pressure-node injection power sensitivity S ^ge , and the node with a larger sensitivity value (the specific value is selected and set according to the needs of the actual application, generally takes the first 30% of the sensitivity value, the present invention The embodiment does not limit this) the set is the weak link of the IEGS.

To sum up, in this embodiment of the present invention, the network state of the power-gas system is considered through the above steps 201 to 203, and the interaction law between the gas pipeline pressure and the electric power injection space is analyzed. This method quickly and directly obtains the weak area of the IEGS, Provide decision-making basis for IEGS operation control (such as the location of gas storage device).

Example 3

The feasibility of the solutions in Embodiments 1 and 2 is verified below with a specific calculation example in conjunction with Figures 3 to 8, as described in the following:

In order to verify the effectiveness of this method, a typical IEGS is taken as an example to illustrate the simulation. As shown in Figure 3, the IEGS calculation example of the embodiment of the present invention is composed of an IEEE-33 node power distribution system and a modified 11-node gas network coupled through MT ^[13,17] , where EBi and GBi represent grid nodes and gas nodes, respectively .

The distribution network is connected to the external large power grid through EB1. It is assumed that the electric power obtained by the distribution network and the external large power grid is 3500kW, and EB1 is the PV node at this time. The MT connects GB11 of the gas network and EB2 of the distribution network as a balance unit, so EB2 is the balance node of the distribution network. Assume that the warning air pressure for the safe operation of the load nodes (GB2-GB11) in the gas network is 20mbar, the air pressure of the gas source node GB1 is 75mbar, and the c _ge is 6.1kW/m ³ . See Table A1 and A2 for gas network data.

Table A1 Gas Pipeline Data

Table A2 Gas Load Data

1) Sensitivity calculation and weak link analysis First, the operating point and Jacobian matrix J of the system are calculated according to the initial conditions of IEGS. The results of calculating S ^ee according to formulas (20) to (22) are shown in Figure 4. The size of the histogram in the figure represents the sensitivity of the change of MT output to the change of the injected power of the grid node. It can be seen from Figure 4 that the farther the electrical distance is from the MT, the more obvious the fluctuation of the MT output caused by the change of the injected power of the node. As shown in Figure 3, EB18 is far away from EB2 where the MT is located. Therefore, when the load in the EB18 node increases by 1 unit of load demand, the MT should increase the active power output by 1.1404 units accordingly. In Figure 3, the electrical distance between EB19 and MT is relatively close. After the load demand is increased by 1 unit, the MT only needs to increase the active power output by 1.0007 units. The different positions of the node injected power in the distribution network have different effects on the output of the MT. The reason is that in the process of active power rebalancing in the distribution network, the size of the network loss is different due to the distance of the electrical distance.

The calculation of S ^gg according to equations (16) and (17) is shown in Figure 5. The size of the bar graph in the figure represents the sensitivity of the gas network pressure change to the gas load change. It should be noted that the calculation result in FIG. 5 is the result when the MT is connected to GB11 of the gas system.

When the gas load demand of MT increases by 1 unit, the air pressure of GB11 decreases correspondingly by 0.3175 units, and the air pressure of GB2 near the gas source decreases correspondingly by 0.1155 units. According to formula (1), it can be seen that with the increase of the flow rate in the gas pipeline, the pressure difference between the two ends of the pipeline will increase. When the newly added 1 unit of gas is transported to GB11 through the gas network, the pipeline in the network will increase the air pressure difference due to the increase in flow rate. GB2 air pressure drop is not obvious.

Combining S ^ee and S ^gg to further calculate S ^ge according to formula (14), as shown in Figure 6, for a point (x, y, z) determined in the figure, it represents the air pressure of the gas grid node y to the power grid node x Sensitivity size z to fluctuations. According to Figure 6, it can be seen that the sensitivity values corresponding to the gas grid nodes 8, 9, and 11 are relatively large, and the air pressure change speed caused by the power fluctuation of the grid nodes is faster than that of other nodes. The nodes with the top 30% of the sensitivity value are taken as the weak nodes of the IEGS. At this time, the weak nodes of the gas network are {GB8, GB9, GB11}.

In order to verify the effectiveness of this method, the pressure changes under different injection power growth levels are simulated by power flow calculation, as shown in Figure 7. The active power growth rate of each load node (compared to the original node load level) is 2%. When the load growth rate of the node is 10%, the GB11 air pressure exceeds the limit (the circle in the figure). From the data in Figure 6, it can be seen that the MT output will increase due to the increase of the load, and the corresponding air pressure will decrease, and the air pressure of the weak node will first reach the boundary of safe operation. On the other hand, starting from the actual physical system, GB11 in Figure 3 is at the end of the line and is heavily loaded, and its gas load variation has the greatest impact on the system air pressure. It can be seen that the sensitivity analysis results are in line with the actual situation of the network.

2) Optimal location of gas storage

Setting gas storage devices at weak nodes of the system is an effective means to improve the gas pressure level and ensure the safe operation of the system. During the peak period of gas consumption in a short period of time, the gas storage device can stabilize the air pressure level by injecting gas into the system and ensure the continuous and stable airflow. However, it is not economical to set up gas storage devices for all nodes. In the embodiment of the present invention, according to the sensitivity calculation result, gas storage is set at the weak nodes of the system.

Taking a load increase of 10% as an example, a gas storage device with a capacity of ^20m3 is set up. There are three options for the selection of gas storage locations:

1) No gas storage

2) Set up gas storage in non-weak links such as GB4;

3) Set up gas storage at the weak node GB11 of the system.

In the power flow calculation, the gas storage equipment can be approximately used to reduce the corresponding gas load for processing. Figure 8 shows the air pressure levels of the system at different access locations through the power flow calculation. Although connecting the gas storage device at the GB4 node can effectively raise the overall air pressure level, compared with Scheme 2 and Scheme 3, setting up the gas storage device at the weak node is more effective in raising the system pressure, and the safe operation margin of the system is significantly improved. The embodiment of the present invention is based on the static sensitivity analysis method of the unified power flow model, and based on the unified power flow model of the power system and the gas system, the IEGS gas pressure-node injection power sensitivity matrix is studied, the influence of the grid node injection power on the gas pressure is analyzed, and the positioning The weak link of the regional integrated energy system provides auxiliary information for the safe and stable operation of the integrated energy system and effectively improves the security of the system. Through the example analysis, the following conclusions can be drawn:

1) The gas pressure of the node - the sensitivity of the injected power of the node can effectively reflect the safe operation margin of the gas pressure at each load node of the gas network;

2) The sensitivity index can be used to quickly locate the weak links of the system, accurately determine the nodes in the system where the gas pressure is most likely to cross the boundary, and avoid a large number of calculations by the point-by-point method; 3) The gas pressure-node injection power sensitivity truly and effectively reflects the load node injection space The degree of influence of the fluctuation of the gas network on the air pressure level of the gas network, the installation of gas storage equipment in the weak link of the system can effectively improve the safety operation margin of air pressure and improve the safety of the system.

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In the embodiment of the present invention, the models of each device are not limited unless otherwise specified, as long as the device can perform the above functions.

Those skilled in the art can understand that the accompanying drawing is only a schematic diagram of a preferred embodiment, and the above-mentioned serial numbers of the embodiments of the present invention are only for description, and do not represent the advantages or disadvantages of the embodiments.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (5)

1. a static sensitivity analysis method oriented to electric-pneumatic coupling integrated energy system, is characterized in that, described static sensitivity analysis method comprises the following steps: Establish an IEGS unified power flow model consisting of a gas system model, a power distribution system model and an energy coupling link model; According to the IEGS unified power flow model, obtain the current stable operating point and the Jacobian matrix of the current operating point; Calculate the gas pressure-node injection power sensitivity according to the Jacobian matrix; sort the gas pressure-node injection power sensitivity, and the node set with high sensitivity is the weak link of IEGS; The IEGS unified power flow model is specifically:

In the formula, x = [θ, V, p] represents the state variables of IEGS, which are the phase angle of each node of the distribution network except the balance node, the voltage of the electric load node, and the gas pressure of the gas load node; u = [P ^PDS , Q ^PDS , L ^NGS ] represents the disturbance variable of IEGS, which injects active power, reactive power and gas load into nodes respectively; a represents independent parameters; P ^PDS injects active power into nodes;

is the grid node voltage; Y is the node admittance matrix, ^* is the complex conjugate; A ^NGS is the node-branch correlation matrix of the gas network;

is the output electric power of the light gas turbine; c _ge is the conversion coefficient. 2. a kind of static sensitivity analysis method oriented to electricity-pneumatic coupling integrated energy system according to claim 1, is characterized in that, described according to Jacobian matrix to calculate gas pressure-node injection power sensitivity is specifically: According to the Jacobian matrix, the gas pressure-gas load sensitivity and the output-node injection power sensitivity of the light-duty gas turbine are calculated respectively; The gas pressure-node injection power sensitivity is calculated from the gas pressure-gas load sensitivity and the output of the light gas turbine-node injection power sensitivity. 3. A kind of static sensitivity analysis method for electric-gas coupling integrated energy system according to claim 2, is characterized in that, described gas pressure-node injection power sensitivity is specifically:

Among them, P ^PDS is the active power injected at the node; p is the gas pressure at the gas node; L ^NGS is the gas load;

Represents the output power of MT;

Gas consumption for MT. 4. A kind of static sensitivity analysis method for electric-pneumatic coupling integrated energy system according to claim 2, is characterized in that, The gas pressure-gas load sensitivity S ^gg is equal to the negative number of the inversion of the Jacobian matrix J _gg in the power flow solution of the natural gas system:

In the formula, A ^NGS is the node-branch correlation matrix of the gas network; f _i is the flow of the pipeline i; Π _i is the gas pressure difference of the pipeline i; n _p is the number of gas pipelines; T is the matrix transpose; diag( ) means constructing a diagonal matrix. 5. A kind of static sensitivity analysis method oriented to electric-pneumatic coupling integrated energy system according to any one of claims 1-4, it is characterized in that, If a node i injects power

Changes occur, for the distribution network there are:

In the formula,

is the network loss of the distribution network, for

The partial derivative is:

In the formula, the second term on the right side of the equation is the network loss slight increase rate, which represents the change relationship between the network loss and the injected power of the node.

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