Optimal load shedding method and device, system and storage medium of integrated energy system

Abstract

The application discloses an optimal load shedding method and device of a comprehensive energy system, a system and a storage medium, and comprises the following steps: constructing a city electrical coupling network model; according to the topological connection relationship of the city electrical network of the city electrical coupling network model, the sensitivity of the gas power plant node is calculated, the fragile node is iteratively cut off, the equal consumption micro-increase rate after cutting off the node is calculated as a cycle termination condition, and the optimal load shedding scheme is found out. By adopting the technical scheme of the application, the optimal load shedding of the city-level electrical comprehensive energy system is realized, and the decision maker can be helped to allocate emergency resources to realize more effective post-disaster recovery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy management, and particularly relates to an optimal load shedding method and device, system and storage medium of an integrated energy system. BACKGROUND

[0002] With the transformation and optimization of global energy structure, an integrated energy system (IES) as a new type of energy ecosystem integrates multiple energy links such as electricity, natural gas, heat / cold power, etc., aiming to realize efficient coordination and optimization of the energy supply chain. IES realizes interconnection and interworking through energy networks, not only improves energy conversion capacity, but also effectively makes up for power fluctuation and uncertainty of renewable energy, which has important significance for building an efficient and stable energy system and sustainable development of society. In order to improve the flexibility of the electrically coupled network, it is necessary to study the cross-domain propagation model of IEGS, and provide theoretical guidance for safe and reliable operation of IEGS and effective power and gas supply after extreme events.

[0003] At present, most of the researches only consider the park-level electrically coupled system, and the research on the city-level electrically coupled network is very few, ignoring the multi-level characteristics of the electrically integrated energy system, without the optimal load shedding scheme of the city-level electrically integrated energy system, and cannot provide theoretical guidance for large-scale electrically integrated energy system. SUMMARY

[0004] The technical problem to be solved by the application is to provide an optimal load shedding method and device, system and storage medium of an integrated energy system, which realizes optimal load shedding of a city-level electrically integrated energy system based on iterative search of a fault propagation model and evaluation index of an electrically coupled network, and helps decision makers to allocate emergency resources to realize more effective post-disaster recovery.

[0005] To achieve the above purpose, the application adopts the following technical solution:

[0006] An optimal load shedding method of an integrated energy system comprises the following steps:

[0007] Constructing a city electrically coupled network model;

[0008] According to the topological connection relationship of the city electric network of the city electrically coupled network model, the sensitivity of the gas power plant node is calculated, the weak node is iteratively cut off, and the equal consumption increment rate after cutting off the node is calculated as a loop termination condition to find the optimal load shedding scheme.

[0009] The application further provides an optimal load shedding method of an integrated energy system, comprising the following steps:

[0010] Step 1: Obtain the network topology structure, line flow, node injection power and sensitivity data of the target area power grid and gas network;

[0011] Step two, calculate the initial operating point and initial gas power plant gas pressure and change node operating state;

[0012] Step three, calculate the operating state of the high-voltage transmission and distribution network;

[0013] Step four, calculate the state of the electric-gas coupling element;

[0014] Step five, calculate the operating state of each node of the gas network;

[0015] Step six, cycle termination condition is calculated by the same amount of increase rate Is less than zero, if less than zero, proceed to step eight, if greater than zero, proceed to step seven;

[0016] Step seven, output the node with the highest sensitivity in the remaining nodes of the gas network, and return to step two;

[0017] Step eight, import the city power grid data to calculate the state of the low-voltage distribution network and the gas distribution network;

[0018] Step nine, calculate the number of affected users of the electric-gas coupling network.

[0019] The present application also provides an optimal load shedding device for a comprehensive energy system, comprising:

[0020] The first processing module is used for constructing a city electric coupling network model;

[0021] The second processing module is used for calculating the sensitivity of the gas power plant node according to the topological connection relationship of the city electric coupling network model of the city electric network, iteratively cutting off the weak node, calculating the same amount of increase rate after cutting off the node as the cycle termination condition, and finding the optimal load shedding scheme.

[0022] The present application also provides an optimal load shedding system for a comprehensive energy system, comprising: a memory and a processor, the memory stores a computer program run by the processor, and the computer program executes the optimal load shedding method for a comprehensive energy system when run by the processor.

[0023] The present application also provides a storage medium, which stores a computer program that executes the optimal load shedding method for a comprehensive energy system when run.

[0024] The present application is based on the topological connection relationship of the city electric coupling network model, calculates the sensitivity of the gas power plant node, iteratively cuts off the weak node, calculates the same amount of increase rate after cutting off the node as the cycle termination condition, and finds the optimal load shedding scheme, which improves the stability of the gas power plant node; and provides a reference for the post-disaster emergency disposal of the city electric comprehensive energy system. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description only constitute a part of the embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings.

[0026] Figure 1 The flow chart of the optimal load shedding method of the comprehensive energy system in the embodiment of the present application; DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute a part of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0028] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0029] Embodiment 1:

[0030] The embodiment of the present application provides an optimal load shedding method of a comprehensive energy system, comprising:

[0031] Constructing a city electrical coupling network model;

[0032] According to the topological connection relationship of the city electrical network of the city electrical coupling network model, the sensitivity of the gas power plant node is calculated, the weak node is iteratively cut off, the equal consumption micro-increment rate after cutting off the node is calculated as the cycle termination condition, and the optimal load shedding scheme is found out.

[0033] The present application is based on the topological connection relationship of the city electrical coupling network model, the sensitivity of the gas power plant node is calculated, the weak node is iteratively cut off, and the optimal load shedding scheme is found out, so as to improve the stability of the gas power plant node; and the present application provides a reference for the post-disaster emergency disposal of the city electrical comprehensive energy system.

[0034] Embodiment 2:

[0035] A model is adopted to represent the impact of N-k contingencies on load loss and pump operation (function fF2P). Generally, UPN is partially served by internal thermal power plants, gas power plants, and partially by external transmission systems. Load loss is determined by four factors, including economic dispatch of thermal power plants, stable operation of gas power plants, network reconfiguration, and optimal load shedding. The modeling of UPN consists of meshed HVT networks, substations, and HVD networks. Based on the input parameters of line fault status and gas power plant operation, the simplified economic dispatch model is given by equations (1.1)-(1.10).

[0036]

[0037] θ ref = 0 (5)

[0038]

[0039] z g = 0, ij e Ω EBF (9)

[0040]

[0041] Objective function (1) minimizes the total cost of generators and load shedding. Constraint (2) enforces the output limit of generating units. Load shedding limits are given by (3-4). The DC power flow equations are adopted to model the power flow under N-k contingency scenarios, as shown in (5)-(8). Equation (5) specifies the voltage angle of the reference bus. Constraint (6) represents the bus power balance. Note that only a small fraction of nodes are equipped with generating units; if no generator is available, PG j,t is set to 0. (7) represents the branch power flow, which is relaxed if the branch is open. Equation (8) limits the upper bound of branch power flow. If branch (i,j) is faulted, then Pij,t = 0. (9) limits the status of faulted branches. Equation (10) indicates that the HVD network maintains a radial structure by opening switches in loop k. Optimal load shedding is converted to the number of affected customers, given by (11).

[0042]

[0043] If a substation is not served by the upstream system, including gas power plants, then the substation will be de-energized. In addition, if a substation is de-energized or the local power source is below the WTP load, then the substation is identified as unable to support the WTP, as shown in (12).

[0044]

[0045] To show the relationship between the output of the gas generator and the natural gas injection quantity more clearly, based on the precise model of the gas generator, it is assumed that the influence of the surrounding environment change on the operation of the gas generator is negligible, and it is considered that the internal circulation of the gas generator is completely ideal, and thus a multi-state output reliability model of the gas generator is established. The overall energy conversion process of the gas generator can be described by equations (1.13)-(1.16):

[0046] -W×C pa (T2-T1)+W×C pc (T3-T4)=P (13)

[0047]

[0048] Wherein W is the total flow of natural gas W f and air W a , W=W f +W a ; C pa , C pc are the heat capacities of air and natural gas respectively; T i is the temperature at different points in the gas generator, and the subscripts 1, 2, 3 and 4 are the temperatures at the inlet and outlet of the air compressor, the inlet and outlet of the combustion chamber respectively; H u is the low heat value of natural gas; P is the power generation of the gas generator, wherein p i is the pressure at different points in the gas generator; ηc ,η t are the efficiencies of the air compressor and the turbine respectively; σ is a constant, and the embodiment of the present application takes 1.4. Since it is assumed that the internal circulation of the gas generator is completely ideal, the pressure of each part of the gas generator remains unchanged, and (1.17) and (1.18) can be written as:

[0049]

[0050] T3-T4=T3×η t ×K2 (18)

[0051] The relationship between the output of the gas generator and the injection natural gas flow can be obtained by combining equations (1.13)-(1.16):

[0052]

[0053] The function fP2H is based on the comprehensive water power modeling of GDN. The pipeline network has the dual functions of natural gas transmission and storage, which can buffer and adjust the uncertainty of gas load demand or new energy grid output to reduce the harm to the operation of the natural gas system. In addition, as the core equipment of pipeline transportation, the compressor can effectively improve the energy supply reliability of the natural gas system. During long-distance gas transmission, the pipeline will generate pressure loss due to pipeline friction, so the gas in the pipeline may face the problem of slow flow or even stagnation. For actual natural gas network, the use of compressors is limited, only in drainage gas recovery, gas gathering and treatment, pipeline transportation, and gas storage. In the urban natural gas pipeline network, the use of compressors is limited, only in natural gas compressor stations, automobile gas stations and gas storage. In the urban natural gas pipeline network, a large number of pressure regulating stations and pressure regulators are used, so that the urban gas network and the urban power grid also have a multi-level network. Because the gas has different physical properties at different pressure levels, a multi-level gas network calculation model is established to better simulate the gas network failure.

[0054] Basic formula for hydraulic calculation of low-pressure gas pipeline:

[0055]

[0056] If the conventional units are used and considering that the pressure of urban gas pipeline is generally below 1.6 MPa, Z0=1, then the basic calculation formula for high and medium pressure gas pipeline is:

[0057]

[0058] p1 is the starting pressure of the pipeline (Pa), p2 is the ending pressure of the pipeline (Pa), L is the calculation length of the pipeline (m), Q0 is the calculation flow rate of the gas pipeline (Nm 3 / h), d is the inner diameter of the pipeline (mm), p0 is the density of the gas (kg / Nm 3) , l is the friction resistance coefficient of the gas pipeline, T is the standard temperature of the gas (K), and T0 is the absolute temperature of the standard state (273.15 K).

[0059] Basic calculation formula for low-pressure pipeline

[0060]

[0061] Due to the multi-pressure level characteristics of the natural gas system, each pressure level is connected by a pressure regulator and a pressure regulating station. The urban gas network has a radial network and a ring network, and the physical state of different pressure gas is different, so different pressure levels require different calculation models. Through multi-level constraints

[0062] The high-pressure gas network includes node flow balance constraints, pipeline flow upper and lower limit constraints, gas load reduction constraints, and element operation constraints. Its model can be represented as:

[0063]

[0064] f mr = V lcak + f rn (25)

[0065] π i,min ≤ π i ≤ π i, max (26)

[0066] f ij,min ≤ f ij ≤ f ij, max (27)

[0067] W s,min ≤ W s ≤ W s, max (28)

[0068] 0 ≤ ΔW g ≤ W g (29)

[0069] wherein: Ψ GS , Ψ GT , Ψ GC , Ψ j are gas source, gas turbine unit, compressor, natural gas pipeline set respectively; W s , f c are gas output of gas source, gas flow of branch where compressor is located respectively.

[0070] Constraint conditions of medium pressure and low pressure gas network

[0071]

[0072] f mr = V lcak + f rn (31)

[0073] π i,min ≤ π i ≤ π i, max (32)

[0074] f ij,min ≤ f ij ≤ f ij, max (33)

[0075] Y s,min ≤ Y s ≤ Y s, max(34)

[0076] 0≤ΔW g ≤W g (35)wherein:Ψ TS 、Ψ j are respectively a pressure regulator, a natural gas pipeline set;Y s are respectively a pressure regulator gas output.

[0077] Due to the multiple gas pressure grade characteristics of the urban natural gas system, different gas pressure grade networks are connected by pressure regulators and pressure regulating stations. There is a very mature system for the optimal load shedding scheme of the power grid. However, the optimal load shedding scheme of the urban gas network has not been proposed. Natural gas has slow dynamic characteristics. During the transmission of natural gas, part of the gas exists in the form of pipe storage in the pipeline, so that the change of the pipeline flow is a slow change process. By using the slow dynamic characteristics of natural gas, through the optimal load shedding scheme of the urban gas network, the gas pressure of the gas power plant node can be controlled to be stable. The embodiment of the present application combines the electrical coupling weak point identification method, and proposes an optimal load shedding scheme of the urban gas network considering the operating state of the gas turbine. Since the urban gas network has radial networks and ring networks, and the physical states of different gas pressure grades are different, the calculation methods are different. Through analysis of the natural gas network topology graph, the number of low-pressure gas network nodes is large and the distance from the gas turbine node is far, and the influence on the gas turbine node is small, so as to simplify the operation, the load shedding range is controlled in the medium-pressure and high-pressure gas network.

[0078] The embodiment of the present application defines Q i The natural gas node pressure-gas turbine node pressure growth sensitivity matrix R L , the influence of different nodes on the gas turbine node, the gas turbine is an important coupling element of the IEGS, and the operating state of the gas turbine is equivalent to the operating state of the IEGS system, and the weak link of the IEGS gas pressure is located.

[0079] Definition:

[0080]

[0081] This index reflects the sensitivity of the gas pressure of the gas turbine node m of the natural gas system to the load growth of node L. The larger the index is, the greater the influence of the change node on the gas turbine node is, and thus the weak link of the system gas pressure can be further identified. Through the electrical coupling important coupling node, the weak link of the IEGS gas pressure of the gas network node is found out.

[0082] First, the natural gas node pressure-gas turbine node pressure growth sensitivity matrix R L p is calculated, and then the sensitivity is iteratively operated from high to low, and the calculation of the incremental rate of the equal consumption is iterated:

[0083]

[0084] Wherein, S is the multi-output power of the gas turbine, and AL is the output flow change value of the low-pressure gas network pressure regulator before and after load shedding

[0085] When D=0, the iteration is stopped, the removed node is output, and the final affected users are calculated.

[0086] As Figure 1 shown, the optimal load shedding method of the integrated energy system according to the embodiment of the application comprises the following steps:

[0087] Step one, obtaining the network topology, line flow, node injection power and sensitivity data of the target area power grid and gas network; wherein the sensitivity data is calculated by formula (36);

[0088] Step two, calculating the initial operating point, initial gas pressure of the gas power plant and the operating state of the change node by formula (20)-(35);

[0089] Step three, calculating the operating state of the high-voltage transmission and distribution network by formula (1)-(13);

[0090] Step four, calculating the state of the electric-gas coupling element by formula (13)-(29);

[0091] Step five, calculating the operating state of each node of the gas network by formula (20)-(35);

[0092]

[0093] If it is less than zero, proceed to step eight, and if it is greater than zero, proceed to step seven;

[0094] Step seven, outputting the node with the highest sensitivity among the remaining nodes of the gas network and returning to step two;

[0095] Step eight, importing the city power grid data to calculate the state of the low-voltage distribution network and gas distribution network;

[0096] Step nine, calculating the number of affected users of the electric-gas coupling network.

[0097] Embodiment 3:

[0098] The embodiment of the application further provides an optimal load shedding device for an integrated energy system, comprising:

[0099] A first processing module is configured to construct a city electric-gas coupling network model;

[0100] The second processing module is configured to calculate the sensitivity of the gas power plant node according to a topological connection relationship of a city electrical network of the city electrical coupling network model, iteratively remove a fragile node, calculate an equal consumption micro-increase rate after the removal of the node as a loop termination condition, and find an optimal load shedding scheme.

[0101] Embodiment 4:

[0102] The embodiment of the present application also provides an optimal load shedding system of a comprehensive energy system, comprising a memory and a processor, the memory has a computer program run by the processor stored thereon, and the computer program executes the optimal load shedding method of the comprehensive energy system when run by the processor.

[0103] Embodiment 5:

[0104] The embodiment of the present application also provides a storage medium, and the storage medium has a computer program stored thereon, and the computer program executes the optimal load shedding method of the comprehensive energy system when run.

[0105] The above-described embodiments are only descriptions of the preferred modes of the present application, and do not limit the scope of the present application, and various modifications and improvements to the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope of the present application defined by the claims.

Claims

1. An optimal load shedding method for an integrated energy system, characterized in that, Comprising: Step one, obtain the network topology, line flow, node injection power, and sensitivity data of the target regional power grid and gas grid; wherein, the gas pressure-gas turbine node pressure growth sensitivity matrix is defined as , The influence of different nodes on the gas turbine node is that the gas turbine is an important coupling element of the integrated energy grid system (IEGS), the operation state of the gas turbine is equivalent to the operation state of the IEGS, and the weak link of the IEGS gas pressure is located, that is, wherein, P is the pipe pressure, is the pipe length; Step two, calculate the initial operating point and initial gas power plant gas pressure and change node operating state; Step three, calculate the operating state of the high-voltage transmission and distribution network; Step four, calculate the state of the electric-gas coupling element; Step five, calculate the operating state of each node of the gas network; Step six, cycle termination condition is equal to the amount of micro-increase rate calculation Is less than zero, if less than zero, step eight, if greater than zero, step seven; wherein, S is the gas turbine multi-output power, Is the low-pressure gas network pressure regulator before and after the load shedding output flow change value; when D = 0, stop iteration, output cut node, and calculate the final impact user; Step seven, output the node with the highest sensitivity in the remaining nodes of the gas network, and return to step two; Step eight, import the city power grid data to calculate the state of the low-voltage distribution network and the gas distribution network; Step nine, calculate the number of affected users of the electric-gas coupling network.

2. An optimal load shedding device of an integrated energy system for implementing the optimal load shedding method of claim 1, characterized in that, Comprising: A first processing module for constructing a city electric-gas coupling network model; A second processing module for calculating the sensitivity of the gas power plant node according to the topological connection relationship of the city electric-gas network of the city electric-gas coupling network model, iteratively cutting off the weak node, taking the equal consumption micro-increment rate after cutting off the node as the loop termination condition, and finding the optimal load shedding scheme.

3. An optimal load shedding system of an integrated energy system, characterized in that, Comprising: A memory and a processor, the memory has a computer program executed by the processor stored thereon, and the computer program, when executed by the processor, performs the optimal load shedding method of the integrated energy system as claimed in claim 1.

4. A storage medium, characterized by The storage medium has a computer program stored thereon, and the computer program, when executed, performs the optimal load shedding method of the integrated energy system as claimed in claim 1.

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