A power flow convergence adjustment method based on high-dimensional space similarity

Abstract

The application is a power flow convergence adjustment method based on high-dimensional space similarity, which has the following characteristics: firstly, the key non-convergent nodes are extracted according to the geometric relationship between the intermediate power flow injection space and the initial power flow injection space, and the key factors of system power flow non-convergence are quickly identified; secondly, the dichotomy is used to adjust the variable, and the minimum adjustment amount most similar to the initial power flow space is determined; finally, the adjusted power flow is calculated to obtain the power flow most similar to the initial power flow injection space, and the characteristics of the initial injection space are retained. The method has the advantages of scientific rationality, simplicity and practicality, fast calculation speed and high engineering application value.

Description

Technical Field

[0001] This invention belongs to the application field of power flow convergence adjustment in large-scale interconnected power grids, and specifically involves a power flow adjustment method based on high-dimensional spatial similarity. Background Technology

[0002] With the continuous expansion of power grid interconnection and the scale of new energy power generation, the high penetration rate of renewable energy and the high proportion of power electronics are becoming increasingly prominent, making the power grid a high-dimensional time-varying nonlinear power cyber-physical system with multi-source information interaction. Power flow calculation is the foundation of power system analysis, and it is indispensable in power grid planning and design, security assessment, and online operation and dispatch analysis. The function of power flow calculation is to robustly and efficiently calculate the solutions to nonlinear equations by solving them. In the operation of large-scale interconnected power grids, it can effectively solve complex problems caused by the imbalance of energy resources and load distribution between regions. However, in engineering, due to insufficient knowledge of power flow non-convergence in power flow calculation and a lack of understanding of the causes of power flow non-convergence, engineers cannot systematically solve the power flow non-convergence problems encountered in actual engineering.

[0003] Currently, the adjustments made by operators of large-scale interconnected power grids to address power flow non-convergence are still largely based on trial and error, relying on experience. This trial-and-error approach is inefficient and labor-intensive. There is a significant lack of expertise in diagnosing the causes of power flow non-convergence, and a complete procedure for power flow diagnosis and adjustment has not yet been established. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a scientific, reasonable and highly applicable power flow adjustment method based on high-dimensional spatial similarity. This method is widely used for adaptive adjustment of power flow non-convergence in large-scale interconnected power grids. It can solve the power flow non-convergence problem caused by high complexity, variability and random load and power generation changes, and is not limited by the influence of model establishment. It has the advantages of being simple and practical, fast in calculation and high in engineering application value.

[0005] The solution to this technical problem is a power flow adjustment method based on high-dimensional spatial similarity, characterized by the following: 1) Establish an intermediate power flow model: that is, a model of injected power and voltage. Considering the uncertainty of the voltage at the load nodes, the power at the load nodes is established as an equation of injected power and node voltage. Therefore, the model for an n-node system is: (1) (2) In the formula, G ij Represents the mutual conductance between nodes. Bij Represents the mutual susceptance between nodes. δ ij Let be the voltage phase angle difference between node i and node j. U i Let be the voltage magnitude of node i; 2) Based on whether the power flow equation has a solution or not, convergent power flow and non-convergent power flow are divided into two regions. The set of convergent power flow is called the convergence region, and the set of non-convergent power flow is called the external power flow. The intersection of the power flow in the convergence region and the external power flow is the convergence boundary. 3) According to the power flow model, the convergence region of the power flow must exist. A similarity relationship is established between the power flows within the convergence region and those outside the convergence region using the L2 norm of the injected power:

[0006] In the formula: S represents the initial non-convergent power flow injection power, S' represents the intermediate power flow injection power, the intermediate power flow is calculated and output based on the power flow, and the power flow with the smallest L2 norm between the intermediate power flow and the initial power flow is found; 4) Identify the intermediate tidal current with the smallest L2 norm relative to the initial tidal current. Use this intermediate tidal current as the reference vector for tidal current adjustment. Combined with the iterative convergence trend of the intermediate tidal current, perform dimensionality reduction on the adjustment variables and determine the tidal current adjustment variables. The adjustment variables are determined based on the difference in injection power between the initial tidal current and the intermediate tidal current in each dimension, satisfying given indices.

[0007] Where: ε is the convergence radius of the node power of the given intermediate power flow. If the intermediate power flow is known to be within the convergence region, that is, the injected power of each node is within the convergence region, then if the distance between the injected power of each node in the initial power flow and the injected power of each node in the initial power flow is within the convergence radius, it can be determined that the power of that node is within the convergence region. If it is greater, it can be determined that it is outside the convergence region. At this time, the adjustment variable of the initial power flow can be reduced in dimension according to the degree of convergence, and then the adjustment variable can be selected.

[0008] 5) Based on the selected adjustment variables, establish the initial current flow adjustment channel. The adjustment direction of the variables is determined by the relative position of the intermediate current flow and the initial current flow. In order to minimize the impact on the initial current flow, the variables of the initial current flow are adjusted using the dichotomy method to obtain the minimum adjustment amount.

[0009] This invention addresses the convergence problem in power flow calculations for large-scale power systems by proposing a method based on intermediate power flow similarity to adjust the initial power flow space. This effectively meets the speed requirement of power flow calculation algorithms for large power grids, and specifically includes the following effects: 1) A mathematical model for intermediate power flow was constructed, which was slightly modified based on the existing Newton-Raphson algorithm without increasing the complexity of the algorithm, while retaining the characteristics of good and fast convergence of Newton's method, so as to meet the convergence adjustment of large-scale power grids and realize real-time online adjustment. 2) Starting from data-driven approach, the power flow convergence space is divided into convergence and non-convergence domains based on the concept of domains. This overcomes the difficulties in building and solving physical models, and can intuitively depict the degree of power flow convergence. It provides a visual interface for operators, making it convenient for engineering technicians to fully grasp the global state of the power flow. 3) By introducing intermediate current flow as a reference, the dimensionality of the adjustment variable is reduced by iterating the convergence trend of the intermediate current flow, and the adjustment amount is explored and solved by the bisection method. The initial current flow convergence space is not significantly changed, and the adjusted current flow is closer to the initial current flow.

[0010] 4) The proposed power flow adjustment method based on high-dimensional spatial similarity can effectively adjust the non-convergent power flow caused by load and generation changes in a highly complex, variable, and stochastic power grid. This method is scientific and reasonable, not limited by the influence of model establishment, has a fast calculation speed, simple adjustment method, strong applicability, meets the requirements of real-time online adjustment, and has great engineering application value. Attached Figure Description

[0011] Figure 1 A block diagram of a non-convergent adjustment system for power flow calculation; Figure 2 A schematic diagram representing the adjustment of the direction of a variable; Figure 3 This is a topology diagram of the IEEE-118 node system. Figure 4 A graph showing the incremental active power data for intermediate power flow; Figure 5 This is a graph showing the incremental reactive power data of the intermediate power flow. Figure 6 Graph showing the results of adjusting variables for initial power flow; Figure 7 The result diagram shows the adjustment variables for the initial power flow reactive power. Detailed Implementation

[0012] Reference Figure 1 This invention discloses a power flow convergence adjustment method based on high-dimensional spatial similarity, which can break free from the constraints of physical models through data-driven approaches, achieve dimensionality reduction of adjustment variables, avoid complex calculation processes, and ensure the effectiveness and accuracy of the adjustment strategy. It includes the following: 1) Establish an intermediate power flow model: that is, a model of injected power and voltage. Considering the uncertainty of the voltage at the load nodes, the power at the load nodes is established as an equation of injected power and node voltage. Therefore, the model for an n-node system is: (1) (2) In the formula, G ij Represents the mutual conductance between nodes. B ij Represents the mutual susceptance between nodes. δ ij Let be the voltage phase angle difference between node i and node j. U i Let be the voltage magnitude of node i; 2) Based on whether the power flow equation has a solution or not, convergent power flow and non-convergent power flow are divided into two regions. The set of convergent power flow is called the convergence region, and the set of non-convergent power flow is called the external power flow. The intersection of the power flow in the convergence region and the external power flow is the convergence boundary. 3) According to the power flow model, the convergence region of the power flow must exist. A similarity relationship is established between the power flows within the convergence region and those outside the convergence region using the L2 norm of the injected power:

[0013] In the formula: S represents the initial non-convergent power flow injection power, S' represents the intermediate power flow injection power, the intermediate power flow is calculated and output based on the power flow, and the power flow with the smallest L2 norm between the intermediate power flow and the initial power flow is found; 4) Identify the intermediate tidal current with the smallest L2 norm relative to the initial tidal current. Use this intermediate tidal current as the reference vector for tidal current adjustment. Combined with the iterative convergence trend of the intermediate tidal current, perform dimensionality reduction on the adjustment variables and determine the tidal current adjustment variables. The adjustment variables are determined based on the difference in injection power between the initial tidal current and the intermediate tidal current in each dimension, satisfying given indices.

[0014] Where: ε is the convergence radius of the node power of the given intermediate power flow. If the intermediate power flow is known to be within the convergence region (the target to be adjusted), that is, the injected power of each node is within the convergence region, then if the distance between the injected power of each node in the initial power flow and the injected power of each node in the initial power flow is within the convergence radius, it can be determined that the power of that node is within the convergence region. If it is greater, it can be determined that it is outside the convergence region. At this time, the adjustment variables of the initial power flow can be reduced in dimensionality according to the degree of convergence, and then the adjustment variables can be selected.

[0015] 5) Based on the selected adjustment variables, establish the initial current flow adjustment channel. The adjustment direction of the variables is determined by the relative position of the intermediate current flow and the initial current flow. In order to minimize the impact on the initial current flow, the variables of the initial current flow are adjusted using the dichotomy method to obtain the minimum adjustment amount.

[0016] This invention addresses the convergence problem in power flow calculations for large-scale power systems by proposing a method based on intermediate power flow similarity to adjust the initial power flow space. This effectively meets the speed requirement of power flow calculation algorithms for large power grids, and specifically includes the following effects: 1) A mathematical model for intermediate power flow was constructed, which was slightly modified based on the existing Newton-Raphson algorithm without increasing the complexity of the algorithm, while retaining the characteristics of good and fast convergence of Newton's method, so as to meet the convergence adjustment of large-scale power grids and realize real-time online adjustment. 2) Starting from data-driven approach, the power flow convergence space is divided into convergence and non-convergence domains based on the concept of domains. This overcomes the difficulties in building and solving physical models, and can intuitively depict the degree of power flow convergence. It provides a visual interface for operators, making it convenient for engineering technicians to fully grasp the global state of the power flow. 3) By introducing intermediate current as a reference, the dimensionality of the adjustment variable is reduced by iterating the convergence trend of the intermediate current, and the adjustment amount is explored and solved by the bisection method. The initial current convergence space is not significantly changed, and the adjusted current is closer to the initial current.

[0017] 4) The proposed power flow adjustment method based on high-dimensional spatial similarity can effectively adjust the non-convergent power flow caused by load and generation changes in a highly complex, variable, and stochastic power grid. This method is not limited by the influence of model establishment, has a fast calculation speed, simple adjustment method, strong applicability, meets the requirements of real-time online adjustment, and has great engineering application value.

[0018] To more clearly illustrate the embodiments of the present invention, a further detailed description is provided in conjunction with the accompanying drawings: 1) Targeting Figure 2 The 118-node network topology shown first models the intermediate power flow. Initial power flow injection data is input, and power flow calculations are performed. The norm of the intermediate power flow is calculated, as shown in Table 1, to determine... Figure 3 The spatial distribution relationship between the intermediate tidal current and the initial tidal current is shown.

[0019]

[0020] 2) Based on the calculated norm, the 18th power flow is determined to be most similar to the initial injection space. Figure 4 and Figure 5 The dimensional injection power distance of each injection node is used to determine the dominant active non-convergence node, as shown in Table 2.

[0021] 3) Adjust variables for the identified dominant node. Adjust the relative positions of the identified dominant node and the initial power flow, and finally determine the specific values ​​of the adjustment variables, such as... Figure 6 and Figure 7 As shown, the convergent power flow is obtained by recalculating the power flow.

Claims

1. A power flow adjustment method based on high-dimensional spatial similarity, characterized in that, It includes the following: 1) Establish an intermediate power flow model: that is, a model of injected power and voltage. Considering the uncertainty of the voltage at the load nodes, the power at the load nodes is established as an equation of injected power and node voltage. Therefore, the model for an n-node system is: （1） （2） In the formula, G ij Represents the mutual conductance between nodes. B ij Represents the mutual susceptance between nodes. δ ij Let be the voltage phase angle difference between node i and node j. U i Let be the voltage magnitude of node i; 2) Based on whether the power flow equation has a solution or not, convergent power flow and non-convergent power flow are divided into two regions. The set of convergent power flow is called the convergence region, and the set of non-convergent power flow is called the external power flow. The intersection of the power flow in the convergence region and the external power flow is the convergence boundary. 3) According to the power flow model, the convergence region of the power flow must exist. A similarity relationship is established between the power flows within the convergence region and those outside the convergence region using the L2 norm of the injected power: ； In the formula: S represents the initial non-convergent power flow injection power, S' represents the intermediate power flow injection power, the intermediate power flow is calculated and output based on the power flow, and the power flow with the smallest L2 norm between the intermediate power flow and the initial power flow is found; 4) Identify the intermediate tidal current with the smallest L2 norm relative to the initial tidal current. Use this intermediate tidal current as the reference vector for tidal current adjustment. Combined with the iterative convergence trend of the intermediate tidal current, perform dimensionality reduction on the adjustment variables and determine the tidal current adjustment variables. The adjustment variables are determined based on the difference in injection power between the initial tidal current and the intermediate tidal current in each dimension, satisfying given indices. ； Where: ε is the convergence radius of the node power of the given intermediate power flow. It is known that the intermediate power flow is within the convergence region, that is, the injected power of each node is within the convergence region. At this time, if the distance between the injected power of each node of the initial power flow and the injected power of each node of the initial power flow is within the convergence radius, it can be determined that the power of that node is within the convergence region. If it is greater, it can be determined that it is outside the convergence region. At this time, the adjustment variable of the initial power flow can be reduced in dimension according to the degree of convergence, and then the adjustment variable can be selected. 5) Based on the selected adjustment variables, establish the initial current flow adjustment channel. The adjustment direction of the variables is determined by the relative position of the intermediate current flow and the initial current flow. In order to minimize the impact on the initial current flow, the variables of the initial current flow are adjusted using the dichotomy method to obtain the minimum adjustment amount.

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