Node partitioning method and system considering load transient coupling and voltage similarity

Abstract

The present invention proposes a node partitioning method and system considering load transient coupling and voltage similarity, and relates to the technical field of power grid stability assessment. It includes constructing an improved load transient model taking into account node coupling; determining the improved transient characteristic equation of each load node, and determining the dominant mode and its corresponding characteristic root of the improved transient characteristic equation to achieve preliminary partitioning of each node; obtaining the voltage disturbance trajectory of the load node after the disturbance, defining the similarity distance of the node voltage transient, and achieving secondary partitioning of each node; using the result of the secondary partitioning to update the result of the preliminary partitioning, and obtaining the final voltage partitioning result. The present invention performs voltage partitioning from two perspectives, namely, load transient coupling and voltage fluctuation similarity, to construct a more accurate partitioning method, and then selects the key bus to represent the transient voltage stability of the entire partition, and achieves the dimensionality reduction of transient voltage stability judgment in time and space.

Description

Technical Field

[0001] The present invention belongs to the technical field of power grid stability assessment, and in particular relates to a node partitioning method and system considering load transient coupling and voltage similarity. Background Art

[0002] With the transformation of energy structure, a new pattern of power system is gradually emerging, and the problem of transient voltage stability is becoming increasingly prominent. The demand for non-plan emergency control technology in new power systems is increasing. Correspondingly, it is imperative to judge transient voltage instability based on measurable response electrical quantities. Unlike power angle instability, voltage instability can show regional characteristics, and local nodes may have similar voltage transient characteristics and voltage stability. Considering the increasing scale of the system and the increasingly complex operation mode, it is neither necessary nor difficult to measure all nodes in the power grid when judging transient voltage instability. Therefore, it is of great significance to reasonably partition the power grid nodes according to the similarity of voltage transients and select a few key nodes in the same partition to represent the entire partition, which is of great significance for realizing non-plan control and transient voltage stability judgment based on response.

[0003] At present, the transient voltage instability process in the power grid is dominated by the transient voltage instability mechanism of positive feedback on the load side. Therefore, the division of voltage partitions should fully consider the transient characteristics of the load. However, most traditional voltage partitioning methods start from the control range of the node voltage by the reactive power emitted by the generator, define the electrical distance between nodes, and combine hierarchical clustering, graph theory, and complex network theory to divide the area. The goal is only to better control the voltage quality, not to reduce the dimension in the process of voltage stability judgment. Some scholars define the electrical distance between nodes according to the voltage-reactive sensitivity, and propose a reactive voltage partition based on DS evidence theory. Some scholars have proposed a reactive voltage partition method based on reactive source control space clustering analysis. The above voltage method only considers the reactive voltage coupling characteristics of the generator, and does not divide according to the load characteristics after the disturbance occurs.

[0004] In addition, the existing partitioning method based on load transient characteristics only starts from a single load transient characteristic equation, ignores the electrical relationship of nodes in the network, and does not consider the coupling relationship between the transient characteristics of nodes.

[0005] On the other hand, existing methods for voltage zoning are mostly based on steady-state electrical quantities of the power system: some scholars calculate the partition based on the Jacobian matrix of the power flow calculation, and then modify the partition results by considering the changes in various network topologies; some scholars also define multiple indicators related to the system steady-state information and propose a method for voltage zone division based on fuzzy clustering.

[0006] The above methods only consider steady-state information and ignore the transient process under fault disturbance, which may cause the regional division results to be inconsistent with the actual partition results under the transient process.

[0007] In summary, although the above studies have considered the influencing factors of the power system voltage zoning method to a certain extent, these zoning methods have not comprehensively considered the transient characteristics of the load and the coupling relationship of the transient characteristics, and have also ignored the transient process under fault disturbances. They are one-sided and there is still room for improvement in the accuracy of the final voltage zoning results. Summary of the invention

[0008] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a node partitioning method and system considering load transient coupling and voltage similarity, performs voltage partitioning from the two perspectives of load transient coupling and voltage fluctuation similarity, constructs a more accurate partitioning method, and then selects key buses to represent the transient voltage stability of the entire partition, thereby realizing dimensionality reduction of transient voltage stability judgment in time and space.

[0009] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0010] A first aspect of the present invention provides a node partitioning method considering load transient coupling and voltage similarity.

[0011] The node partitioning method considering load transient coupling and voltage similarity includes the following steps:

[0012] Identify the dominant mechanism of transient voltage instability on the load side, and build an improved load transient model taking into account node coupling based on the electrical relationship of the nodes in the network;

[0013] Based on the load transient improvement model taking into account node coupling, the improved transient characteristic equation of each load node is determined, and the dominant mode and corresponding characteristic root of the improved transient characteristic equation are determined, and the preliminary partition of each node is realized according to the characteristic root distance;

[0014] Obtain the voltage disturbance trajectory of the load node after the disturbance, define the similarity distance of the node voltage transient, and realize the secondary partition of each node according to the similarity distance of the node voltage transient;

[0015] The results of the secondary partitioning are used to update the results of the preliminary partitioning to obtain the final voltage partitioning results.

[0016] Furthermore, the dominant mechanism of transient voltage instability on the load side is identified, and an improved load transient model taking into account node coupling is constructed based on the electrical relationship of the nodes in the network. Specifically:

[0017] Based on the load-side transient voltage instability mechanism, considering the transient process dominated by the induction motor rotor motion, the characteristic equation of the load-side transient voltage instability is determined as follows:

[0018]

[0019] Where s is the slip rate (state variable), T J is the inertia time constant, T m is the mechanical torque; T e is the electromagnetic torque;

[0020] Based on the multi-time scale theory, since the electromagnetic transient process between network nodes is much faster than the mechanical transient process of the induction motor rotor, the electrical coupling relationship between nodes is determined to be expressed as the node voltage equation in the steady state, specifically:

[0021]

[0022] In the formula, is the current between the load node and the neutral point, Y is the node admittance matrix, is the node voltage;

[0023] Based on the dominant mechanism of voltage instability on the load side and the electrical relationship of network nodes, the load transient characteristic equation is rewritten using the node voltage equation, and an improved load transient model taking into account node coupling is constructed, specifically:

[0024]

[0025] Where α is the proportion of the mechanical load torque that is not related to the speed of the induction motor; p m is an index related to the mechanical load characteristics; k is the load rate of the motor; s is the slip rate of the induction motor; R r / s is the equivalent resistance of the rotor; ω is the angular velocity of the stator magnetic field.

[0026] Furthermore, based on the dominant mode of the transient characteristics of the loads at each node after improvement, the preliminary partitioning of each node is realized according to the characteristic root distance, specifically:

[0027] Based on the stability analysis theory, since the transient characteristic equation of the load node is a first-order differential equation, the transient characteristics of the load node are determined to be dominated by the characteristic roots of the linearized characteristic equation, specifically:

[0028]

[0029] Where, λ is the characteristic root of the transient characteristic equation of the load node after linearization;

[0030] Cluster analysis was performed based on the characteristic root and square sum of deviations method for each node, and the initial partitioning result considering load transient coupling was obtained.

[0031] Furthermore, based on the disturbed trajectory of the load voltage after the disturbance, the similarity distance of the node voltage transient is defined, and the secondary partitioning of each node is realized according to the similarity distance of the node voltage transient, specifically:

[0032] Based on the voltage disturbance trajectory of the load node after the disturbance, the node voltage fluctuation characteristics are analyzed and the similarity distance of the node voltage transient is defined, which is specifically:

[0033]

[0034] Where, d ij is the similarity distance of voltage transient between node i and node j, K is the number of sampling points after disturbance; U ib (m) and U jb (m) is the voltage fluctuation value between node i and node j at the sampling time;

[0035] Clustering is performed using a hierarchical clustering algorithm based on the similarity distance of node voltage transients, and a secondary partitioning result based on voltage similarity is obtained.

[0036] Furthermore, the result of the secondary partitioning is used to update the result of the preliminary partitioning, specifically:

[0037] The intersection of the secondary partitioning result and the preliminary partitioning result is divided into one zone, and the remaining nodes are divided into their respective areas, so as to update the preliminary partitioning result and obtain the final voltage partitioning result.

[0038] A second aspect of the present invention provides a node partitioning system that considers load transient coupling and voltage similarity.

[0039] A node partitioning system considering load transient coupling and voltage similarity, including:

[0040] The model improvement module is configured to: identify the dominant mechanism of transient voltage instability on the load side, and build a load transient improvement model taking into account node coupling based on the electrical relationship of the nodes in the network;

[0041] The preliminary partitioning module is configured to: determine the improved transient characteristic equation of each load node based on the load transient improvement model taking into account node coupling, determine the dominant mode of the improved transient characteristic equation and its corresponding characteristic root, and realize the preliminary partitioning of each node according to the characteristic root distance;

[0042] The secondary partitioning module is configured to: obtain the voltage disturbance trajectory of the load node after the disturbance, define the similarity distance of the node voltage transient, and realize the secondary partitioning of each node according to the similarity distance of the node voltage transient;

[0043] The updating module is configured to update the result of the preliminary partitioning by using the result of the secondary partitioning to obtain the final voltage partitioning result.

[0044] A third aspect of the present invention provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the steps in the node partitioning method considering load transient coupling and voltage similarity as described in the first aspect of the present invention.

[0045] The fourth aspect of the present invention provides an electronic device, comprising a memory, a processor, and a program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps in the node partitioning method considering load transient coupling and voltage similarity as described in the first aspect of the present invention are implemented.

[0046] One or more of the above technical solutions have the following beneficial effects:

[0047] The present invention provides a node partitioning method and system considering load transient coupling and voltage similarity. Based on the transient voltage instability mechanism on the load side and the electrical relationship of the nodes on the network side, an improved load transient model considering node coupling is constructed, and then the improved transient characteristic equation of each load node is determined, and the dominant mode and the corresponding characteristic root of the improved transient characteristic equation are determined. The preliminary partitioning of each node is realized according to the characteristic root distance, and the transient characteristics and coupling relationship of the load in the power grid are fully considered, avoiding the one-sided consideration of a single load transient process and the one-sided analysis from the perspective of reactive voltage coupling characteristics.

[0048] The present invention performs voltage partitioning based on voltage similarity. On the basis of considering the transient coupling characteristics of load nodes, the disturbed fluctuation trajectory of node voltage after disturbance is utilized, and the transient voltage fluctuation characteristics of nodes are combined to realize the update of voltage partitioning results. This avoids the problem that the partitioning results are inconsistent with the actual results due to the voltage area being divided only based on the steady-state electrical quantities of the power system, and can achieve the purpose of voltage partitioning more accurately.

[0049] The present invention focuses on solving the problem of voltage area division in transient voltage stability assessment, and can be used as an important basis for selecting key nodes to represent the voltage level of the partition, thereby achieving dimensionality reduction in transient voltage stability assessment in time and space.

[0050] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0052] Figure 1 This is a flow chart of a node partitioning method considering load transient coupling and voltage similarity in the first embodiment of the present invention.

[0053] Figure 2 This is a load model considering the mechanical transient process of the induction motor in the first embodiment of the present invention.

[0054] Figure 3 This is a load power-slip curve diagram in the first embodiment of the present invention.

[0055] Figure 4 This is a structural diagram of a new energy AC / DC power system in Embodiment 1 of the present invention.

[0056] Figure 5 This is the partition result considering load transient coupling in the first embodiment of the present invention.

[0057] Figure 6 This is the partitioning result considering the node voltage similarity in the first embodiment of the present invention.

[0058] Figure 7 This is the disturbed trajectory of some node voltages after the disturbance in the first embodiment of the present invention. DETAILED DESCRIPTION

[0059] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0060] It should be noted that the terms used herein are for describing specific embodiments only and are not intended to be limiting of exemplary embodiments according to the present invention.

[0061] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0062] Embodiment 1

[0063] The essence of the voltage area partition problem is to select key buses to analyze their voltage transient process within a certain period of time, so as to represent the transient voltage stability of the entire partition. Therefore, it is advisable to construct a more accurate partitioning method based on measurable response electrical quantities, taking into account the transient characteristics of the load while combining the electrical relationship of the nodes in the network. This embodiment provides a node partitioning method that considers load transient coupling and voltage similarity, by performing voltage partitioning from the two perspectives of load transient coupling and voltage fluctuation similarity, and then selecting key buses to analyze their voltage transient process within a certain period of time, so as to represent the transient voltage stability of the entire partition, and realize the dimensionality reduction of transient voltage judgment in time and space.

[0064] like Figure 1 As shown, the node partitioning method considering load transient coupling and voltage similarity in this embodiment includes:

[0065] Identify the dominant mechanism of transient voltage instability on the load side, and build an improved load transient model taking into account node coupling based on the electrical relationship of the nodes in the network;

[0066] Based on the load transient improvement model taking into account node coupling, the improved transient characteristic equation of each load node is determined, and the dominant mode and corresponding characteristic root of the improved transient characteristic equation are determined, and the preliminary partitioning of each node voltage is realized according to the characteristic root distance;

[0067] Obtain the voltage disturbance trajectory of the load node after the disturbance, define the similarity distance of the node voltage transient, and realize the secondary partition of each node voltage according to the similarity distance of the node voltage transient;

[0068] The results of the secondary partitioning are used to update the results of the preliminary partitioning to obtain the final voltage partitioning results.

[0069] The main implementation steps of this embodiment are as follows:

[0070] Step 1: Construct an improved load transient model taking into account node coupling

[0071] The voltage stability of the power system is the result of the combined effect of system characteristics and load characteristics. Therefore, the voltage area division problem should consider both the transient characteristics of the load side and the electrical relationship of the nodes on the network side. The mathematical model of the analysis can be expressed by a differential-algebraic equation system as shown in (1):

[0072]

[0073] Where x is the state variable of the system; V is the node voltage vector; I is the node injection current vector; and Y is the node admittance matrix of the system. The differential and algebraic equations in the above model are used to reflect the impact of the load side and the network side respectively.

[0074] There are many types of loads, but the largest share is induction motors. Therefore, the transient characteristics of the load are mainly determined by the transient behavior of the induction motor in the load. This embodiment selects a load model that considers the mechanical transient process of the induction motor for analysis. The specific model is as follows: Figure 2 As shown, X s and X r are the leakage reactance of the stator and rotor respectively; R r / s is the rotor equivalent resistance, R μ and X μ is the mutual impedance between the stator and the rotor.

[0075] Ignore R μ , taking the induction motor slip rate as the state variable, the load model can be described as shown in formula (2):

[0076]

[0077] Therefore, the relationship between the active power absorbed by the load and the slip rate s can be plotted according to formula (2), as follows: Figure 3 As shown. Figure 3 Analysis shows that as the slip rate s increases, the active power absorbed by the load shows a trend of increasing first and then decreasing. Taking the case where the load mechanical power remains unchanged as an example, there are two intersection points between the mechanical power and active power curves. The intersection point on the left is a stable equilibrium point and the intersection point on the right is an unstable equilibrium point. When the load runs to the right of the right intersection point, the load mechanical power is greater than the active power, resulting in an increase in the slip rate s. The increase in the slip rate s will cause the active power absorbed by the load to further decrease, that is, it enters a positive feedback vicious cycle mode.

[0078] Therefore, the mechanism of transient voltage instability on the load side can be analyzed: when the balance between the power demand of the load and the power supply capacity of the system to the load is broken, the unbalanced state of power causes the change of system state variables to further destroy the unbalanced state, and the system enters a vicious cycle of positive feedback, causing transient voltage instability on the load side.

[0079] Based on the above analysis, the dominant equation of load transient characteristics can be obtained, as shown in formula (3):

[0080]

[0081] Where, T J is the inertia time constant, T m is the mechanical torque; T e is the electromagnetic torque.

[0082] The mechanical torque calculation formula in the equation is shown in formula (4):

[0083]

[0084] Where: α is the proportion of the mechanical load torque that is not related to the speed of the induction motor; p m is an index related to the mechanical load characteristics; k is the load rate of the motor; s is the slip rate of the induction motor.

[0085] The electromagnetic torque in the equation can be calculated with the help of the electromagnetic power on the rotor resistance. Since the mutual impedance between the rotor and the stator is large, the influence of this branch can be ignored, and the current on the rotor can be approximately considered to be the load port current. Therefore, the electromagnetic torque calculation formula is shown in formula (5):

[0086]

[0087] Where I is the load node current; ω is the stator magnetic field angular velocity.

[0088] Based on the dominant equation of load transient characteristics, it can be seen that load transient is an electromechanical transient process with a time scale of seconds, while the electromagnetic transient process of electric and magnetic fields and corresponding voltage and current changes in various components of the power system has a time scale of milliseconds. Therefore, based on the multi-time scale theory, it can be seen that at the time scale of analyzing load transient characteristics, the electromagnetic transient process can be considered to have been completed. Therefore, the electrical relationship between nodes in the network at this time is a static algebraic equation in steady state, which can be expressed by the node voltage equation, as shown in formula (6):

[0089]

[0090] In the formula, is the load node current, Y is the node admittance matrix, is the node voltage

[0091] Based on the above analysis, according to the dominant mechanism of voltage instability on the load side and the electrical relationship of network nodes, the load transient characteristic equation can be rewritten using the node voltage equation to construct an improved load transient model taking into account node coupling, as shown in formula (7):

[0092]

[0093] Step 2: Implement preliminary voltage partitioning considering load transient coupling

[0094] Based on the constructed load transient improved model taking into account node coupling, according to the stability analysis theory, the transient characteristic equation of the load node is a first-order differential equation, and its transient characteristics are dominated by the characteristic roots of the linearized equation. Therefore, the transient characteristic equation of the load node is linearized, as shown in formula (8):

[0095]

[0096] According to the linearized transient characteristic equation of the load node, the characteristic root of the equation can be obtained, as shown in formula (9):

[0097]

[0098] Based on the structural parameters of the power system, the output of each generator in the system and the load operation status, the system operation status is determined, the characteristic root of the transient characteristic equation of each node is calculated, and the voltage partition is performed by the square sum method. The calculation formula is shown in formula (10):

[0099]

[0100] In the formula, is the square distance between the two categories p and q, and are the centroids of the two categories p and q, n p 、n q and n r They are the number of samples in categories p and q and the total number of samples.

[0101] Clustering is performed using a hierarchical clustering algorithm based on characteristic root distances, and preliminary voltage partitioning results considering load transient coupling are obtained.

[0102] Step 3: Implement secondary voltage partitioning by considering node voltage similarity

[0103] Based on simulation / actual measurement, the voltage disturbance trajectory of the load node after the disturbance is obtained, and the node voltage fluctuation characteristics are analyzed. The voltage of a load node i after the disturbance is expressed as follows:

[0104] U i (t) = U is +U ib (t) (11)

[0105] Where U is is the steady-state voltage of the node before the disturbance, U ib (t) is the voltage fluctuation value after disturbance.

[0106] According to the voltage fluctuation characteristics of the node after the disturbance, the similarity distance of the node voltage transient can be defined as shown in formula (12):

[0107]

[0108] Where, d ij is the similarity distance of voltage transient between node i and node j, K is the number of sampling points after disturbance, U ib (m) and U jb (m) is the voltage fluctuation value at the sampling moment of node i and node j.

[0109] According to the similarity distance of node voltage transients, voltage partitioning is performed using the class average method, and its calculation formula is shown in formula (13):

[0110]

[0111] Where D MN Represents the distance between categories M and N, n M and n N Represents the number of samples in the two categories M and N.

[0112] Clustering is performed based on the similarity distance of node voltage transients using a hierarchical clustering algorithm to obtain the second voltage partitioning result based on node voltage similarity.

[0113] Step 4: Use the results of the secondary partitioning to update the results of the preliminary partitioning

[0114] The intersection of the two partition results is divided into one area, and the remaining nodes are divided into their respective areas, so as to update the preliminary partition result and obtain the final partition result.

[0115] Example analysis: In this embodiment, the transient voltage collapse standard example test system of China Electric Power Research Institute is taken as an example to verify the effectiveness of the voltage partitioning method proposed in this embodiment that considers load transient coupling and node voltage similarity. This example describes a DC feed-in system with a high proportion of new energy. There are a total of 100 nodes, of which the 500kV main grid has a total of 48 nodes. The main grid wiring diagram is as follows: Figure 4 This example sets the installed capacity of new energy to 2.4 million kilowatts and the installed capacity of conventional power to 6.3 million kilowatts. The basic operation mode is that the new energy units generate 1.8 million kilowatts of electricity and the conventional units generate 3.86 million kilowatts of electricity. A DC loop is fed into the system, and the power of the DC fed into the receiving AC power system is 800,000 kilowatts.

[0116] Based on the dominant mechanism of transient voltage instability on the load side and the electrical relationship of nodes on the network side, an improved load transient model taking into account node coupling is constructed, and the node voltage equation is introduced to improve the transient characteristic equation of the load node. The node transient characteristic equation is linearized, and the system operation state is determined according to the grid structure parameters, generator output and load operation conditions in the example system. The characteristic root of the equation is calculated, and the first voltage partition is performed by the sum of squares method. The partition results are as follows: Figure 5 As shown. Figure 5 According to the clustering results, the 21 load nodes can be divided into two areas, namely {1, 2, 3, 4, 5, 14, 18, 21} and {6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 19, 20}.

[0117] A three-phase ground short circuit fault is set on the AC line connecting bus1A-12 node and bus1A-13 node. The fault point is located at bus1A-12 node. The fault line is removed 0.1s after the short circuit fault occurs. According to the voltage disturbance trajectory of the load node after the disturbance is set, the similarity distance of the node voltage transient is defined, and the second voltage partition is performed by the class average method. The partition results are shown as follows: Figure 6 As shown. Figure 6 The clustering results can divide the 21 load nodes into two areas, namely {1, 2, 3, 4, 5, 7} and {6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21}.

[0118] The intersection of the two partition results is divided into one area, and the remaining nodes are divided into their respective areas, and it is ensured that there are at least two nodes in each area, so as to update the preliminary partition result and obtain the final partition result, which is specifically three areas {1,2,3,4,5,7}, {14,18,21} and {6,8,9,10,11,12,13,15,16,17,19,20}.

[0119] To verify the feasibility of the proposed method, the voltage disturbance trajectory of nodes {1, 14, 10, 21} is obtained by simulation under the same disturbance as above, as shown in Figure 7 As shown. Figure 7 It can be seen that the voltage trajectories of the four nodes can be divided into three categories, and the voltage disturbed trajectories of nodes 14 and 21 almost overlap. The above results are consistent with the partition results.

[0120] Through simulation analysis, the effectiveness of the partitioning method proposed in the present invention that takes into account load transient coupling and node voltage similarity in power grid area division is verified.

[0121] Embodiment 2

[0122] This embodiment discloses a node partitioning system that considers load transient coupling and voltage similarity.

[0123] A node partitioning system considering load transient coupling and voltage similarity, including:

[0124] The model improvement module is configured to: identify the dominant mechanism of transient voltage instability on the load side, and build a load transient improvement model taking into account node coupling based on the electrical relationship of the nodes in the network;

[0125] The preliminary partitioning module is configured to: determine the improved transient characteristic equation of each load node based on the load transient improvement model taking into account node coupling, determine the dominant mode of the improved transient characteristic equation and its corresponding characteristic root, and realize the preliminary partitioning of each node according to the characteristic root distance;

[0126] The secondary partitioning module is configured to: obtain the voltage disturbance trajectory of the load node after the disturbance, define the similarity distance of the node voltage transient, and realize the secondary partitioning of each node according to the similarity distance of the node voltage transient;

[0127] The updating module is configured to update the result of the preliminary partitioning by using the result of the secondary partitioning to obtain the final voltage partitioning result.

[0128] Embodiment 3

[0129] The purpose of this embodiment is to provide a computer-readable storage medium.

[0130] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the node partitioning method considering load transient coupling and voltage similarity as described in Embodiment 1 of the present disclosure.

[0131] Embodiment 4

[0132] The purpose of this embodiment is to provide an electronic device.

[0133] An electronic device includes a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, the steps in the node partitioning method considering load transient coupling and voltage similarity as described in Example 1 of the present disclosure are implemented.

[0134] The steps involved in the apparatuses of the above embodiments 2, 3 and 4 correspond to the method embodiment 1, and the specific implementation methods can refer to the relevant description part of embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood to include any medium that can store, encode or carry an instruction set for execution by a processor and enable the processor to execute any method in the present invention.

[0135] Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0136] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A node partitioning method considering load transient coupling and voltage similarity, characterized in that: The following steps are involved: Identify the dominant mechanism of transient voltage instability on the load side, and build an improved load transient model taking into account node coupling based on the electrical relationship of the nodes in the network. Specifically: Considering the transient process dominated by the induction motor rotor motion, the characteristic equation of transient voltage instability on the load side is determined; Based on the multi-time scale theory, the electrical coupling relationship between nodes is determined to be expressed as the node voltage equation in steady state; The characteristic equation of transient voltage instability on the load side is rewritten using the node voltage equation, and an improved load transient model taking into account node coupling is constructed. Based on the load transient improvement model taking into account node coupling, the improved transient characteristic equation of each load node is determined, and the dominant mode and corresponding characteristic root of the improved transient characteristic equation are determined, and the preliminary partition of each node is realized according to the characteristic root distance; The improved load transient model considering node coupling is as follows: Where α is the proportion of the mechanical load torque that is not related to the speed of the induction motor; p m is an index related to the mechanical load characteristics; k is the load rate of the motor; s is the slip rate of the induction motor; R r / s is the equivalent resistance of the rotor; ω is the angular velocity of the stator magnetic field; T J is the inertia time constant; is the node voltage; Obtain the voltage disturbance trajectory of the load node after the disturbance, define the similarity distance of the node voltage transient, and realize the secondary partition of each node according to the similarity distance of the node voltage transient; The results of the secondary partitioning are used to update the results of the preliminary partitioning to obtain the final voltage partitioning results.

2. The node partitioning method considering load transient coupling and voltage similarity according to claim 1, characterized in that: Since the electromagnetic transient process between network nodes is much faster than the mechanical transient process of the induction motor rotor, the electrical coupling relationship between nodes is determined to be expressed as the node voltage equation in steady state, specifically: In the formula, is the current between the load node and the neutral point, Y is the node admittance matrix, is the node voltage.

3. The node partitioning method considering load transient coupling and voltage similarity according to claim 1, characterized in that: The characteristic roots of the improved transient characteristic equation are: The characteristic root of the improved transient characteristic equation of each node is calculated, and the nodes are clustered according to the characteristic root of each node and the sum of squares of deviation method to obtain the preliminary partitioning results considering load transient coupling.

4. The node partitioning method considering load transient coupling and voltage similarity according to claim 1, characterized in that: Based on the voltage disturbance trajectory of the load node after the disturbance, the node voltage fluctuation characteristics are analyzed; According to the voltage fluctuation characteristics of the node after the disturbance, the similarity distance of the node voltage transient is defined as: Where, d ij is the similarity distance of voltage transient between node i and node j, K is the number of sampling points after disturbance, U ib (m) and U jb (m) is the voltage fluctuation value between node i and node j at the sampling time; According to the similarity distance of node voltage transients, nodes are clustered using a hierarchical clustering algorithm, and a secondary partitioning result based on voltage similarity is obtained.

5. The node partitioning method considering load transient coupling and voltage similarity according to claim 1, characterized in that: The results of the secondary partitioning are used to update the results of the preliminary partitioning, specifically: The intersection of the secondary partitioning result and the preliminary partitioning result is divided into one zone, and the remaining nodes are divided into their respective areas, so as to update the preliminary partitioning result and obtain the final voltage partitioning result.

6. A node partitioning system considering load transient coupling and voltage similarity, characterized in that: include: The model improvement module is configured to: identify the dominant mechanism of transient voltage instability on the load side, combine the electrical relationship of the nodes in the network, and construct a load transient improvement model taking into account node coupling; specifically: Considering the transient process dominated by the induction motor rotor motion, the characteristic equation of transient voltage instability on the load side is determined; Based on the multi-time scale theory, the electrical coupling relationship between nodes is determined to be expressed as the node voltage equation in steady state; The characteristic equation of transient voltage instability on the load side is rewritten using the node voltage equation, and an improved load transient model taking into account node coupling is constructed. The preliminary partitioning module is configured as follows: based on the load transient improvement model taking into account node coupling, determine the improved transient characteristic equation of each load node, determine the dominant mode of the improved transient characteristic equation and its corresponding characteristic root, and realize the preliminary partitioning of each node according to the characteristic root distance; the load transient improvement model taking into account node coupling is specifically: Where α is the proportion of the mechanical load torque that is not related to the speed of the induction motor; p m is an index related to the mechanical load characteristics; k is the load rate of the motor; s is the slip rate of the induction motor; R r / s is the equivalent resistance of the rotor; ω is the angular velocity of the stator magnetic field; T J is the inertia time constant; is the node voltage; The secondary partitioning module is configured to: obtain the voltage disturbance trajectory of the load node after the disturbance, define the similarity distance of the node voltage transient, and realize the secondary partitioning of each node according to the similarity distance of the node voltage transient; The updating module is configured to update the result of the preliminary partitioning by using the result of the secondary partitioning to obtain the final voltage partitioning result.

7. A computer-readable storage medium having a program stored thereon, characterized in that: When the program is executed by a processor, the steps of the node partitioning method considering load transient coupling and voltage similarity as described in any one of claims 1 to 5 are implemented.

8. An electronic device comprising a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps in the node partitioning method considering load transient coupling and voltage similarity as described in any one of claims 1 to 5 are implemented.

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