Topology planning model of sending-end power system and construction method
By constructing a topology planning model for the sending-end power system based on analytical embedding of security and stability constraints, the problem of topology optimization in power grid planning under high-proportion renewable energy access is solved, realizing the coordinated optimization of the economy and security of power grid planning, and improving computational efficiency and power grid stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- STATE GRID JIBEI ELECTRIC POWER COMPANY LIMITED CHENGDE POWER SUPPLY
- Filing Date
- 2026-01-27
- Publication Date
- 2026-05-01
AI Technical Summary
Existing power grid planning methods struggle to effectively embed complex, time-varying, and strongly coupled security and stability constraints in scenarios with high proportions of renewable energy integration and power electronic equipment applications, leading to difficulties in topology optimization. This is especially true in environments with ultra-long time spans and massive equipment combinations, where traditional methods are difficult to solve.
By constructing a topology planning model for the sending-end power system based on analytical embedding of security and stability constraints, multiple types of security and stability problems are transformed into mixed integer linear constraints, and deeply integrated with the backbone topology planning model, a new power grid planning decision-making system adapted to scenarios with a high proportion of new energy access is constructed.
It achieves synergistic optimization of the planning scheme's economy and operational safety, significantly improves the feasibility and computational efficiency of the planning scheme, and enhances the structural strength and safety stability of the sending-end power grid.
Smart Images
Figure CN121965830A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of distributed energy system planning technology, specifically to a power system topology planning model and construction method at the sending end. Background Technology
[0002] The "three highs" typically refer to a high proportion of renewable energy integration, a high proportion of power electronic equipment application, and a high proportion of distributed power source penetration. Under the "three highs" background, the transformation of power source characteristics and the massive integration of equipment lead to significant changes in system security and stability. Large-scale power flow shifts occur frequently, the growth trend of short-circuit current becomes ambiguous, frequency and voltage issues become prominent, and system security and stability problems become increasingly serious. The security and stability constraints of the sending-end power grid exhibit new characteristics of "high dimension and strong coupling." Ultra-long-term topology planning faces massive equipment, and the huge search space makes topology optimization difficult. It is necessary to guide the topology with form, reduce the topology optimization search space, and improve the topology planning and optimization capabilities of the sending-end power grid. Form and topology must jointly satisfy the power grid security and stability constraints, but the abstract form makes it difficult to quantify the impact of power grid security and stability, resulting in no starting point for form optimization. Meanwhile, the specific topology structure is coupled with ultra-high-dimensional security and stability constraints, making topology planning under these constraints difficult to solve.
[0003] The problems are as follows: Existing power grid planning methods mainly rely on deterministic scenarios or traditional security verification processes, making it difficult to effectively embed and quantify the aforementioned complex, time-varying, and strongly coupled security and stability constraints during the planning stage. Especially in planning environments with ultra-long time spans and massive equipment combinations, the search space for topology optimization is enormous, and traditional methods are difficult to solve, requiring the introduction of morphological guidance to reduce the search range and improve optimization efficiency. However, as a macroscopic structural feature, the impact of morphology on power grid security and stability lacks analytical and quantifiable expression, resulting in a lack of clear basis for morphological optimization; while the specific topology structure is tightly coupled with ultra-high-dimensional security and stability constraints, making it extremely difficult to perform refined topology planning modeling and solving under multiple security constraints. Summary of the Invention
[0004] This invention addresses the problems existing in the prior art by providing a topology planning model and construction method for the sending-end power system based on analytical embedding of security and stability constraints. Through the theory of analytical embedding of security and stability constraints, it provides a complete mathematical modeling tool for systematically embedding "high-dimensional, strongly coupled" security and stability requirements at the source of power grid planning, facilitating the synergistic optimization of planning scheme economy and operational safety. By transforming various security and stability problems such as short-circuit current stability, static voltage stability, and frequency stability into mixed-integer linear constraints and deeply integrating them with the backbone topology planning model, a new power grid planning decision-making system is constructed that is compatible with traditional security verification requirements and adaptable to scenarios with high proportions of renewable energy integration.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, embodiments of the present invention propose a method for constructing a topology planning model for a power system at the sending end, comprising: Obtain planning parameters and operational data; An initial model is constructed based on planning parameters and operational data; The planning model is constructed based on the initial model. The planning model includes an objective function and constraints. The objective function is to minimize the sum of the first cost and the second cost. The first cost is the total cost of line investment in the planning stage, and the second cost is the short-term operating cost. The constraints include line investment and life constraints, line operation constraints, short-circuit current stability constraints, static voltage stability constraints, and frequency stability constraints. The short-circuit current stability constraints are constructed based on the node admittance matrix and the node impedance matrix. The static voltage stability constraints are constructed based on the multi-infeed short-circuit ratio, DC loop transmission power, and line impedance. The frequency stability constraints are constructed based on node voltage, node disturbance power, generator, and battery energy storage system.
[0006] In some embodiments, the node admittance matrix includes a first admittance matrix, a second admittance matrix, and a third admittance matrix. The first admittance matrix is the original admittance matrix of the short-circuit node, the second admittance matrix is the admittance matrix of the short-circuit node after the line is put into operation, and the third admittance matrix is the admittance matrix of the short-circuit node after the unit is put into operation. Short-circuit current stability constraints are constructed based on the nodal admittance matrix and the nodal impedance matrix, including: The first expression is constructed based on the first admittance matrix and the nodal impedance matrix; Obtain information on power line construction and generating unit construction; The first change matrix is obtained based on the first expression, the first admittance matrix, the second admittance matrix, and the line construction information; The second change matrix is obtained based on the first expression, the first admittance matrix, the third admittance matrix, and the unit construction information; The second expression is obtained based on the first transformation matrix and the node impedance matrix; The third expression is obtained based on the second transformation matrix and the node impedance matrix; The short-circuit current stability constraint is obtained based on the first, second, and third expressions.
[0007] In some embodiments, static voltage stability constraints are constructed based on the multi-infeed short-circuit ratio, DC loop transmission power, and line impedance, including: Obtain the fourth expression, which is the multi-infeed short-circuit ratio expression that takes into account the AC system short-circuit capacity, the capacity of multiple DC transmission lines, and the electrical coupling relationship between converter stations. The fifth expression is derived from the fourth expression. The fifth expression is a multi-feed short-circuit ratio expression based on DC loop transmission power and line impedance. The static voltage stability constraint is obtained by linearizing the fifth expression.
[0008] In some embodiments, based on the pure inductive nature of the circuit's node voltage amplitude, the fifth expression is obtained according to the fourth expression, ignoring value differences and angle differences.
[0009] In some embodiments, static voltage stability constraints are obtained by linearizing the fifth expression based on Kirchhoff's voltage law.
[0010] In some embodiments, frequency stability constraints are constructed based on node voltage, node disturbance power, generators, and battery energy storage systems, including: The node inertia is obtained based on the seventh, eighth, and ninth expressions. The seventh expression is the expression for the relationship between node inertia and node disturbance power. The eighth expression is the expression for the relationship between node frequency, node voltage, and generator internal potential. The ninth expression is the expression for the relationship between generator frequency change rate, node disturbance power, and generator internal potential. Based on the total primary frequency regulation power of the generator and the battery energy storage system, a quasi-steady-state frequency safety constraint is constructed. Frequency stability constraints are obtained based on the node inertia and quasi-steady-state frequency security constraints.
[0011] In some embodiments, the planning parameters include generator rated power and line parameters.
[0012] In some embodiments, the runtime data includes load data.
[0013] Secondly, embodiments of this application propose a topology planning model for a power system at the sending end, including a planning module, a first constraint module, and a second constraint module; The planning module is used to construct the objective function and plan the sending-end power system based on the first constraint module and the second constraint module; the objective function is to minimize the sum of the first cost and the second cost. The first constraint module is used to construct line investment and life constraints and line operation constraints; The second constraint module is used to construct short-circuit current stability constraints, static voltage stability constraints, and frequency stability constraints. The short-circuit current stability constraints are constructed based on the node admittance matrix and the node impedance matrix. The static voltage stability constraints are constructed based on the multi-infeed short-circuit ratio, DC loop transmission power, and line impedance. The frequency stability constraints are constructed based on node voltage, node disturbance power, generator, and battery energy storage system.
[0014] In some embodiments, the Benders decomposition algorithm is used, and the sending-end power system is planned based on the first constraint module and the second constraint module.
[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This application embeds multiple types of safety and stability constraints, such as line investment and life constraints, line operation constraints, short-circuit current stability constraints, static voltage stability constraints, and frequency stability constraints, into the planning model. When using this planning model to plan the sending-end power system, simultaneous decision-making for planning and safety verification can be achieved, which significantly improves the feasibility and computational efficiency of the planning scheme.
[0016] 2. This application constructs short-circuit current stability constraints based on nodal admittance matrices and nodal impedance matrices, and constructs static voltage stability constraints based on multi-infeed short-circuit ratios, DC loop transmission power, and line impedance. It transforms complex nonlinear stability problems into linear constraints that can be embedded in planning models, thus overcoming the technical bottleneck that safety constraints are difficult to quantify directly.
[0017] 3. This application proposes a method for constructing a power system planning model for sending-end power grids with multiple DC transmission lines, providing a customized planning tool for scenarios with high proportions of renewable energy transmission, and effectively enhancing the structural strength and safety stability of the sending-end power grid. This application provides systematic theoretical and methodological support for the safe, economical, and efficient planning of new sending-end power grids. Attached Figure Description
[0018] Figure 1 This is a flowchart illustrating the method for constructing the power system topology planning model at the sending end of this application. Figure 2 This is a schematic diagram of the improved IEEE 24-node distribution network structure used in the examples of this application. Figure 3 This is a per-unit diagram showing the initial short-circuit current levels at each node in the example of this application; Figure 4 This is a per-unit diagram showing the initial static voltage levels of each node in the example of this application; Figure 5 This is a diagram showing the initial inertia level per unit value of each node in the example of this application; Figure 6 This is a comparison diagram of the node short-circuit current levels under different methods in the examples of this application. Detailed Implementation
[0019] To clearly illustrate the technical features of this solution, the implementation methods of this application will be described in detail below with reference to the accompanying drawings and embodiments. This will allow for a full understanding and implementation of how this application uses technical means to solve technical problems and achieve corresponding technical effects. The embodiments of this application and the various features within them can be combined with each other without conflict, and the resulting technical solutions are all within the protection scope of this application.
[0020] See Figure 1 In a first aspect, embodiments of the present invention propose a method for constructing a topology planning model for a power system at the sending end, comprising: acquiring planning parameters and operating data; in some embodiments, the planning parameters include generator rated power and line parameters, and in some embodiments, the operating data includes load data.
[0021] An initial model is constructed based on planning parameters and operational data; The planning model is constructed based on the initial model. The planning model includes an objective function and constraints. The objective function is to minimize the sum of the first cost and the second cost. The first cost is the total cost of line investment in the planning stage, and the second cost is the short-term operating cost. The constraints include line investment and life constraints, line operation constraints, short-circuit current stability constraints, static voltage stability constraints, and frequency stability constraints. The short-circuit current stability constraints are constructed based on the node admittance matrix and the node impedance matrix. The static voltage stability constraints are constructed based on the multi-infeed short-circuit ratio, DC loop transmission power, and line impedance. The frequency stability constraints are constructed based on node voltage, node disturbance power, generator, and battery energy storage system.
[0022] Beneficially, this application embeds multiple types of safety and stability constraints, such as line investment and lifespan constraints, line operation constraints, short-circuit current stability constraints, static voltage stability constraints, and frequency stability constraints, into the planning model. Using this model to plan the sending-end power system enables simultaneous decision-making for planning and safety verification, significantly improving the feasibility and computational efficiency of the planning scheme. Simultaneously, this application constructs short-circuit current stability constraints based on node admittance and node impedance matrices, and static voltage stability constraints based on multi-infeed short-circuit ratios, DC loop transmission power, and line impedance. This transforms complex nonlinear stability problems into linear constraints that can be embedded in the planning model, overcoming the technical bottleneck of directly quantifying safety constraints. This application proposes a method for constructing a planning model for sending-end power systems with multiple DC transmission problems, providing a customized planning tool for scenarios with high proportions of renewable energy transmission, effectively enhancing the structural strength and safety stability of the sending-end power grid.
[0023] Rapid economic development has led to a surge in electricity demand, resulting in a rapid increase in power supply capacity and consequently, increasingly higher levels of short-circuit current in the power system. This has made the problem of excessive short-circuit current more prominent. Therefore, limiting short-circuit current has become a crucial issue that power grid planning, dispatching, and operation must address.
[0024] In some embodiments, the node admittance matrix includes a first admittance matrix, a second admittance matrix, and a third admittance matrix. The first admittance matrix is the original admittance matrix of the short-circuit node, the second admittance matrix is the admittance matrix of the short-circuit node after the line is put into operation, and the third admittance matrix is the admittance matrix of the short-circuit node after the unit is put into operation. Short-circuit current stability constraints are constructed based on the nodal admittance matrix and the nodal impedance matrix, including: The first expression is constructed based on the first admittance matrix and the nodal impedance matrix; Compared to other short-circuit faults, three-phase short circuits have more serious consequences. Therefore, three-phase short-circuit current is often used to determine the breaking capacity of system circuit breakers. When a three-phase short-circuit fault occurs at a node in the system, according to the superposition principle, the faulty nodes have the following relationship: ; In the formula, Short-circuit node The voltage before the fault, Short-circuit node The short-circuit current, This is the node number where the short-circuited node is located. Short-circuit node Self-impedance.
[0025] Before a three-phase short-circuit fault occurs, the system node voltage can be considered as 1.0 pu. Therefore, the node short-circuit current can be obtained by calculating the node self-impedance. The three-phase short-circuit current is as follows: .
[0026] Therefore, when discussing short-circuit current, we only need to focus on the self-impedance of the node associated with the short-circuit current, combined with the node admittance matrix. and node impedance matrix Relationship ,in The identity matrix is taken from the column vectors corresponding to the impedances in the nodal impedance matrix and the identity matrix, and includes... A short-circuit node in a node system that experiences a short-circuit fault The relationship between column vectors and nodal admittance matrices is discussed below, for example: ; In the formula, Let be the self-admittance of node 1. For node 1 and short-circuited node Mutual admittance between them For node 1 and node Mutual admittance between them Short-circuit node Mutual admittance with node 1 Short-circuit node Self-guided absorbance, Short-circuit node With nodes Mutual admittance between them For nodes Mutual admittance with node 1 For nodes With short-circuit nodes Mutual admittance between them For nodes Self-guided absorbance, For node 1 and short-circuited node mutual impedance between For nodes With short-circuit nodes Mutual impedance between them; For ease of subsequent discussion, the above formula will be written in matrix and vector form, i.e., the first expression is: ; In the formula, is Short-circuit node The original admittance matrix, also known as the first admittance matrix, Short-circuit node The impedance vector, i.e., the impedance vector in the nodal impedance matrix. The column vector, T Indicates transpose. The first in the identity matrix The column vector of a column. 1 in the middle represents the short-circuit node. The element at the corresponding position.
[0027] Obtain information on power line construction and generating unit construction; The first change matrix is obtained based on the first expression, the first admittance matrix, the second admittance matrix, and the line construction information; The second change matrix is obtained based on the first expression, the first admittance matrix, the third admittance matrix, and the unit construction information; Assume the initial state of the system is that all generating units are operational and all transmission lines are in operation. Since the construction of transmission lines alters the system's original admittance matrix... Instead of introducing new elements, the corresponding elements in the code can be used to define the lines. Admittance matrix after construction Decomposed into the original admittance matrix With the first transformation matrix The sum of these matrices, and the first change matrix, characterizes the change in the original admittance matrix due to the line disconnection. Thus, we can obtain the following, considering the short-circuit node after the construction of a single line. Admittance matrix and short-circuit node The relationship between the impedance vectors is as follows: ; In the formula, This refers to the line number where the constructed line is located. When the line... When considering a potential power line, neglecting the line-to-ground capacitance, the first transformation matrix... It is represented as shown below.
[0028] ; In the formula, For the collection of lines that can be built, For the line Admittance, For the line In the The construction status at each planning stage. This is the planning phase number. For 0-1 variables, Indicates the line In the Construction will be carried out in each planning phase. Indicates the line In the No construction was carried out during the planning phase. For the line The position vector of coordinates, where 1 represents the starting node and -1 represents the ending node.
[0029] Similar to the derivation of power line construction, when the unit When a generating unit is considered ready for construction, the unit refers to a generator set, and the original admittance matrix is changed according to the unit's outage status. The corresponding element in the data can be used to connect the generator set. The admittance matrix after construction is decomposed into the original admittance matrix. With the second change matrix The sum of the two, the second change matrix represents the change matrix caused by the shutdown of the unit, which alters the original admittance matrix. for: ; In the formula, For the construction of units, This refers to the unit number of the unit under construction. For the unit Subtransient reactance, For the unit In the The construction status at each planning stage. For 0-1 variables, Indicates the unit In the Construction will be carried out in each planning phase. Indicates the unit In the No construction was carried out during the planning phase. For the unit The node location vector, where 1 represents the node where the unit is located. Consider the short-circuit node after a single unit is put into operation. Admittance matrix and short-circuit node The relationship between the impedance vectors is as follows: ; Based on this, consider Line ,…, investment and construction Taiwanese unit ,…, The investment and construction This indicates the first line to be constructed. Indicates the first One line to be built, The total number of lines to be constructed. This indicates the first generating unit to be put into operation. Indicates the first Taiwan invests in building units, Given the total number of generating units under construction, the first change matrix is... Second transformation matrix Expanded to: ; ; in, For the line The position vector of the coordinates, For the line The position vector of the coordinates, For the line Admittance, For the line In the Phase of construction status For the line Admittance, For the line In the The construction status at each planning stage. For the unit The node position vector, For the unit The node position vector, For the unit Subtransient reactance, For the unit In the first Phase of construction status For the unit Subtransient reactance, For the unit In the The construction status of each planning stage.
[0030] Based on the above explanation, the disconnection of different power lines and the shutdown of generating units do not affect the elements in the original admittance matrix, and the corresponding change matrices can be linearly added. Therefore, the change matrices of multiple power line disconnections and multiple unit shutdowns are independent. It can be written as the following formula: ; In summary, considering the impact of multiple line disconnections and multiple unit shutdowns on the original admittance matrix, and considering the short-circuit nodes after multiple line disconnections and multiple unit shutdowns... Admittance matrix and short-circuit node The relationship between the impedance vectors is as follows: .
[0031] The second expression is obtained based on the first transformation matrix and the node impedance matrix; The third expression is obtained based on the second transformation matrix and the node impedance matrix; For single-line construction and single-unit construction scenarios. It is a highly sparse matrix containing only 4 non-zero elements. It is a highly sparse matrix containing only one non-zero element, therefore and as follows: ; ; In the formula, for Central and Line The element corresponding to the first endpoint, for Central and Line The element corresponding to the endpoint, for Central and Line The index of the element corresponding to the first endpoint. In order to connect with the line The index of the element corresponding to the end point, corresponding to, In order to connect with the line The node number corresponding to the first endpoint, In order to connect with the line The node number corresponding to the end point, , for In and the unit The element corresponding to the node; due to the formula and Both are 0-1 variables, while Since the variables are continuous, the problem arises when multiplying a 0-1 variable with a continuous variable. To solve this problem, intermediate variables are introduced as follows: ; In the formula, As the first intermediate variable, As the second intermediate variable, It is the third intermediate variable; With the first intermediate variable For example, the product of 0-1 variables and continuous variables is linearized, that is, the first intermediate variable is represented by the Big M method. With 0-1 variables and continuous variables The relationship is as follows: ; ; In the formula, The values of the parameters for the Big M method are given.
[0032] The short-circuit current stability constraint is obtained based on the first, second, and third expressions; based on the expressions for the above intermediate variables, the short-circuit node is considered after multiple lines are disconnected and multiple generating units are shut down. Admittance matrix and short-circuit node The relationship between impedance vectors can be transformed into: ; In summary, the explicit expression of the short-circuit current, i.e., the short-circuit current stability constraint, considering the construction of multiple lines and multiple generating units, is as follows: .
[0033] In summary, optimization is performed for all possible three-phase short-circuit faults in the power grid. This is achieved by calculating the self-impedance of the short-circuit current nodes and then converting the self-impedance into a short-circuit current constraint based on the relationship between the node self-impedance and the short-circuit current, as shown in the equation: ; In the formula, This is the short-circuit current limit. If the short-circuit current breaking capacity of the circuit breaker is considered when setting this limit, then the influence of the non-periodic component on the breaking capacity of the circuit breaker should be considered in addition to the steady-state value of the short-circuit current.
[0034] In some embodiments, static voltage stability constraints are constructed based on the multi-infeed short-circuit ratio, DC loop transmission power, and line impedance, including: The fourth expression is obtained, which is the multiple input short circuit ratio (MISCR) expression that takes into account the short-circuit capacity of the AC system, the capacity of multiple DC transmission lines, and the electrical coupling relationship between converter stations; the fourth expression is: ; In the formula, For the first DC-DC MISCR This is the DC circuit number. For the first Short-circuit capacity of DC return, For the first Equivalent DC power of DC return As a multi-feedback interactive influencing factor, Indicates the first DC return to the first The degree of influence of DC voltage. This is the DC circuit number. For the first Rated transmission power of DC, For the first Rated transmission power of DC, This represents the total number of DC circuits.
[0035] The fifth expression is derived from the fourth expression. The fifth expression is a multi-feed short-circuit ratio expression based on DC loop transmission power and line impedance. In some embodiments, based on the purely inductive nature of the circuit's node voltage amplitude, and ignoring value differences and angle differences, the fifth expression is derived from the fourth expression. The fifth expression is: ; In the formula, For the first Per-unit value of DC transmission power. For the first Returning DC transmission power per unit value, The first node in the equivalent nodal impedance matrix The self-impedance of the bus return line The first node in the equivalent nodal impedance matrix DC return and the first The mutual impedance between DC and DC is the first... DC return and the first Equivalent mutual impedance between the DC and DC converter buses; The static voltage stability constraint is obtained by linearizing the fifth expression. From the relationship between MISCR and converter bus node impedance, it can be seen that if the topology of the receiving-end grid is adjusted during system planning or operation, the MISCR may increase or decrease. This uncertainty indicates that changes in the grid topology will expose the system to potential safety risks. Therefore, it is necessary to introduce MISCR constraints into the relevant optimization model. Since this invention uses a single-source multi-network model, it is based on a typical three-infeed receiving-end system. First, its accompanying network is extracted, and the mutual influence of impedance factors within the accompanying network is studied. Second, it is deduced that when the grid contains multiple DC feeds, a corresponding accompanying network needs to be constructed for each DC feed point to extract the impedance elements of each node related to MISCR. Because the above method requires constructing multiple accompanying networks according to the number of DC feeds, and each network is supplemented with a unit current source, it is called a single-source multi-network model. The accompanying networks constructed to extract MISCR constraints are parallel to each other and jointly assist the main grid in grid topology decision optimization. In some embodiments, the static voltage stability constraint is obtained by linearizing the fifth expression based on Kirchhoff's voltage law: ; ; ; ; ; ; ; In the formula, For the first Return DC direction The current flowing through the lines in the network during DC-DC conversion. For the first Return DC direction The current flowing through the lines in the network during DC-DC conversion. For the accompanying network by the first The magnitude of the current source returning to the DC injection node. For accompanying networks, It is the set of DC landing points for a multi-infeed system. A set of system nodes. , To accompany different combinations of nodes in the network, For the set of accompanying network nodes, For the first Return DC direction The impedance of the corresponding lines in the network accompanying the DC-DC converter. To feed the first into the accompanying network DC voltage For the time of feeding into the accompanying network DC voltage For the first DC return and the first The construction status of the branch lines between the DC and DC lines. Indicates the first DC return and the first The branch between the DC and DC lines is disconnected. Indicates the first DC return and the first The branch line between the DC and DC lines has been put into operation. For parameters, Let represent a very large number used to relax related inequality constraints. The ideal MISCR threshold is typically set to 3; The generator set includes a generator, and in some embodiments, frequency stability constraints are constructed based on node voltage, node disturbance power, the generator, and the battery energy storage system, including: The nodal inertia is obtained based on expressions seven, eight, and nine. Expression seven is the expression relating nodal inertia to nodal disturbance power. ; In the formula, For nodes inertia, For node sequence number, For nodes The disturbance power at that location For nodes Frequency deviation at that location For time.
[0036] The eighth expression is the expression relating node frequency, node voltage, and generator internal potential; the eighth expression is derived from the power system network equations: ; In the formula, For nodes frequency amplitude, for The middle corresponds to the node and generator Elements relating to voltage. This is the correlation matrix between network node voltages and generator internal potential node voltages. This refers to the node number where the generator is located. For generator The amplitude of the internal potential, For generator The frequency amplitude.
[0037] The ninth expression is the expression for the relationship between the generator's frequency change rate, nodal disturbance power, and generator internal electromotive force; nodal Disturbance power appears at [location] At that time, the unbalanced power is distributed to the nodes where each generator is located according to the synchronization power coefficient. Based on the generator rotor motion equation and the unbalanced power borne by the generator, the frequency change rate of the generator is obtained as follows: ; In the formula, For generator Corresponding node Synchronous power coefficient, , For nodes voltage amplitude, To shrink to the generator Internal potential nodes and nodes The susceptance between them For generator and nodes The initial phase angle difference between the voltages, For generator The disturbance power at the node. For generator inertia; The default system voltage is near the rated value. Based on the above, the node can be obtained. The calculated inertia, i.e.: ; In the formula, For nodes The computational inertia. Visible nodes. The calculated inertia depends on the synchronizing machine (inertia source), i.e., the generator. The magnitude of inertia and its relationship with the generator electrical distance .
[0038] Based on the total primary frequency regulation power of the generator and the battery energy storage system, a quasi-steady-state frequency security constraint is constructed. Power system frequency security indicators include: 1) RoCoF (Rate of Change of Frequency); 2) Quasi-steady-state frequency; and 3) Frequency minimum point. Dynamic frequency security of the system can be ensured by co-optimizing the operating state of the synchronous machine and the FFR (Frequency Fast Response) of the energy storage system, providing a reference for energy storage planning. This invention mainly studies quasi-steady-state frequency indicators. Frequency deviation under quasi-steady-state conditions depends on the total PFR (Primary Frequency Regulation Power) of the generator and the FFR (Frequency Fast Response) of the BES (Battery Energy Storage System).
[0039] By assuming RoCoF is 0 in the quasi-steady state, we can obtain the constraint that ensures the safety of the quasi-steady-state frequency (QSSF), that is, the quasi-steady-state frequency safety constraint is: ; In the formula, For the frequency deviation under quasi-steady state, The power imbalance under quasi-steady-state conditions. For the generator governor response power, For fast frequency response power, The damping coefficient is... For mechanical power, This represents the maximum permissible deviation under quasi-steady-state conditions.
[0040] Frequency stability constraints are obtained based on the node computational inertia and quasi-steady-state frequency security constraints. The frequency stability constraints include the node computational inertia and quasi-steady-state frequency security constraints.
[0041] The analytical and integrated modeling of the short-circuit current stability constraints, steady-state voltage stability constraints, and frequency stability constraints proposed above forms a framework for planning models, which can provide new solutions for research topics such as transmission network expansion planning, distribution network reconfiguration, multi-energy network collaborative planning, and power system security domain analysis.
[0042] The objective function of the planning model is: ; In the formula, To minimize the function, For total cost, This represents the total number in the planning phase. For line number, The total number of lines, For the first Each planning stage of the route The construction cost, For the first Each planning stage of the route The construction status, For 0-1 variables, Indicates the first Each planning stage of the route Investment and construction Indicates the first Each planning stage of the route No construction has been carried out. The discount rate is... This refers to the node number where the generator unit is located. The set of nodes where the generator sets are located. For the first Units in the planning phase The cost of output, For the first Units in the planning phase of efforts, For node sequence number, A set of system nodes. To incur penalties for load loss, For the first Each planning stage node The load gap at the location is expressed in MW. The line investment and lifespan constraints are: ; ; ; In the formula, The maximum number of lines to be constructed in each planning phase. The maximum cost of constructing lines at each planning stage. For the first Each planning stage of the route retirement variables, For the entire life cycle of the line, For the first The planning phase preceding the planning phase, For the first Each planning stage of the route The retirement variable; The line operation constraints are: ; In the formula, For the first The node where the planning phase unit is located The generator output, For the first Each planning stage node With nodes The active power flow of the existing lines between them, For the first Each planning stage node With nodes The active power flow of the lines to be built between them, For the first Each planning stage node The load size, For the first Each planning stage node Loss of load, For node sequence number, , For nodes With nodes The route between, The set of nodes where the generator is located. For existing line sets, For the collection of lines to be built, A collection of system nodes; ; ; In the formula, For the first The existing lines in the planning stage The meritorious trend, For the first Lines under planning phase The meritorious trend, For the line Admittance, For the first Each planning stage node phase angle, For the first Each planning stage node phase angle, For the first The existing lines in the planning stage Running state parameters related to scenario N-1 Indicates component failure. It is an infinite constant. For the decision variables of newly built lines, the above two sets of formulas indicate that the node power balance constraint should be satisfied in both normal operation and N-1 scenario. ; ; In the formula, For the line The maximum power; the above two sets of formulas describe the active power flow and power upper and lower limit constraints of existing lines and the active power flow and power upper and lower limit constraints of newly built lines. ; In the formula, For the unit Maximum output For the first Units in the planning phase Running state parameters related to scenario N-1 This indicates a unit malfunction. For the first Units in the planning phase The switching state; this formula limits the unit's output in normal and N-1 scenarios.
[0043] ; ; In the formula, The minimum node phase angle, For the first Each planning stage node The phase angle at the point, The two formulas above limit the range of variation of the node phase angle, which represents the maximum node phase angle.
[0044] Secondly, embodiments of this application propose a topology planning model for a power system at the sending end, including a planning module, a first constraint module, and a second constraint module; The planning module is used to construct the objective function and plan the sending-end power system based on the first constraint module and the second constraint module; the objective function is to minimize the sum of the first cost and the second cost. The first constraint module is used to construct line investment and life constraints and line operation constraints; The second constraint module is used to construct short-circuit current stability constraints, static voltage stability constraints, and frequency stability constraints. The short-circuit current stability constraints are constructed based on the node admittance matrix and the node impedance matrix. The static voltage stability constraints are constructed based on the multi-infeed short-circuit ratio, DC loop transmission power, and line impedance. The frequency stability constraints are constructed based on node voltage, node disturbance power, generator, and battery energy storage system.
[0045] In some embodiments, the Benders decomposition algorithm is used, and the sending-end power system is planned based on the first constraint module and the second constraint module.
[0046] Calculation example: The effectiveness of the topology model construction method proposed in this patent was verified using an improved IEEE 24-node distribution network. The IEEE 24-node distribution network structure is shown below. Figure 2The initial planning level sets the maximum daily load at 2500MW, with an annual load growth rate of 5%, a planning period of 1 year, and a planning timeframe of 3 years. The topology short-circuit current limit is set at 35kA.
[0047] The problems with short-circuit current, static voltage, and frequency under the initial operating conditions of the system are analyzed using the initial power flow calculation results, as follows: Figure 2 As shown.
[0048] from Figure 3-5 As can be seen, the safety and stability issues of each node are different, but the problem of excessive short-circuit current is the most serious. This is because the short-circuit current is most significantly affected by the line topology. The switching and decommissioning of the line will cause changes in the node impedance matrix, and according to the analysis of the short-circuit current, its magnitude is directly related to the elements of the node impedance matrix. The system was planned using the topology planning model construction method with multiple embedded safety and stability constraints proposed in this patent and the traditional planning method. The results of the new line construction at different planning stages and the comparison are shown in Table 1.
[0049] Table 1 Comparison of results from different planning methods As can be seen from Table 1, the planning results using the model proposed in this patent result in more newly built lines, and the newly built lines have more obvious constraints on the safety and stability of nodes, thus better controlling the safety and stability indicators of nodes to prevent them from exceeding the limits.
[0050] As mentioned above, the short-circuit current level changes most significantly during the system planning process. Therefore, a comparison chart of short-circuit currents after adopting the model construction method of this patent is provided. Figure 6 As shown. By Figure 6 It can be seen that, with 35kA as the short-circuit current limit, the short-circuit current level of the system decreased significantly after the embedded safety and stability constraints were implemented. Furthermore, the short-circuit current exceeding the limit at nodes that previously occurred was significantly improved. This indicates that safety and stability constraints have a guiding role in topology construction, which can effectively reduce the number of safety and stability problems that occur in the system after topology planning and improve the system stability.
[0051] In summary, the comparison shows that the power system topology planning model and construction method proposed in this invention are accurate and effective, and have practical application potential.
[0052] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.
Claims
1. A method for constructing a topology planning model for a power system at the sending end, characterized in that, include: Obtain planning parameters and operational data; An initial model is constructed based on the planning parameters and the operational data; A planning model is constructed based on the initial model. The planning model includes an objective function and constraints. The objective function is to minimize the sum of a first cost and a second cost. The first cost is the total cost of line investment during the planning stage, and the second cost is the short-term operating cost. The constraints include line investment and lifespan constraints, line operation constraints, short-circuit current stability constraints, static voltage stability constraints, and frequency stability constraints. The short-circuit current stability constraints are constructed based on the node admittance matrix and the node impedance matrix. The static voltage stability constraints are constructed based on the multi-infeed short-circuit ratio, DC loop transmission power, and line impedance. The frequency stability constraints are constructed based on node voltage, node disturbance power, generators, and battery energy storage systems.
2. The method for constructing a topology planning model for a power system at the sending end according to claim 1, characterized in that, The node admittance matrix includes a first admittance matrix, a second admittance matrix, and a third admittance matrix. The first admittance matrix is the original admittance matrix of the short-circuit node, the second admittance matrix is the admittance matrix of the short-circuit node after the line is put into operation, and the third admittance matrix is the admittance matrix of the short-circuit node after the unit is put into operation. The short-circuit current stability constraints are constructed based on the nodal admittance matrix and the nodal impedance matrix, including: A first expression is constructed based on the first admittance matrix and the nodal impedance matrix; Obtain information on power line construction and generating unit construction; The first change matrix is obtained based on the first expression, the first admittance matrix, the second admittance matrix, and the line construction information; The second change matrix is obtained based on the first expression, the first admittance matrix, the third admittance matrix, and the unit construction information; The second expression is obtained based on the first change matrix and the node impedance matrix; The third expression is obtained based on the second transformation matrix and the node impedance matrix; The short-circuit current stability constraint is obtained based on the first expression, the second expression, and the third expression.
3. The method for constructing a topology planning model for a power system at the sending end according to claim 1, characterized in that, The static voltage stability constraints are constructed based on the multi-infeed short-circuit ratio, DC loop transmission power, and line impedance, including: Obtain the fourth expression, which is a multi-infeed short-circuit ratio expression that takes into account the AC system short-circuit capacity, the capacity of multiple DC transmission lines, and the electrical coupling relationship between converter stations; The fifth expression is obtained from the fourth expression, and the fifth expression is a multi-feed short-circuit ratio expression based on DC loop transmission power and line impedance. The static voltage stability constraint is obtained by linearizing the fifth expression.
4. The method for constructing a topology planning model for a power system at the sending end according to claim 3, characterized in that, Based on the pure inductive nature of the circuit's node voltage amplitude, and ignoring value and angle differences, the fifth expression is obtained according to the fourth expression.
5. The method for constructing a topology planning model for a power system at the sending end according to claim 3, characterized in that, The static voltage stability constraint is obtained by linearizing the fifth expression based on Kirchhoff's voltage law.
6. The method for constructing a topology planning model for a power system at the sending end according to claim 1, characterized in that, The frequency stability constraints are constructed based on node voltage, node disturbance power, generators, and battery energy storage systems, including: The node inertia is obtained according to the seventh, eighth and ninth expressions. The seventh expression is the expression for the relationship between the node inertia and the node disturbance power. The eighth expression is the expression for the relationship between the node frequency and the node voltage and the generator internal potential. The ninth expression is the expression for the relationship between the generator frequency change rate and the node disturbance power and the generator internal potential. Based on the total primary frequency regulation power of the generator and the battery energy storage system, a quasi-steady-state frequency safety constraint is constructed. The frequency stability constraint is obtained based on the node's calculated inertia and the quasi-steady-state frequency security constraint.
7. The method for constructing a topology planning model for a power system at the sending end according to claim 1, characterized in that, The planning parameters include the generator's rated power and line parameters.
8. The method for constructing a topology planning model for a power system at the sending end according to claim 1, characterized in that, The operational data includes load data.
9. A topology planning model for a power system at the sending end, characterized in that, It includes a planning module, a first constraint module, and a second constraint module; The planning module is used to construct an objective function and plan the sending-end power system based on the first constraint module and the second constraint module; the objective function is to minimize the sum of the first cost and the second cost. The first constraint module is used to construct line investment and life constraints and line operation constraints; The second constraint module is used to construct short-circuit current stability constraints, static voltage stability constraints, and frequency stability constraints. The short-circuit current stability constraints are constructed based on the node admittance matrix and the node impedance matrix. The static voltage stability constraints are constructed based on the multi-infeed short-circuit ratio, DC loop transmission power, and line impedance. The frequency stability constraints are constructed based on node voltage, node disturbance power, generator, and battery energy storage system.
10. The power system topology planning model at the sending end according to claim 9, characterized in that, The Benders decomposition algorithm is used to plan the sending-end power system based on the first constraint module and the second constraint module.