A method and system for evaluating static voltage stability of a power grid

Abstract

The present invention discloses a method, system, electronic device, and computer-readable storage medium for evaluating the static voltage stability of power grids, belonging to the technical field of power system static voltage stability evaluation. This method visualizes the grid voltage support topology, where reactive power regulation is generated from a voltage source and transmitted to loads via lines after a power disturbance. This helps operators and dispatchers gain an intuitive understanding of the overall structure of the current grid voltage support and facilitates intuitive judgment of the current grid static voltage stability situation and key factors.

Description

Technical Field

[0001] The present application relates to the technical field of static voltage stability assessment of power systems, and in particular to a method and system for evaluating static voltage stability of power grids. Background Art

[0002] The statements in this section merely mention the background technology related to this application and do not necessarily constitute the prior art.

[0003] With the widespread and high-proportion integration of renewable energy generation and the gradual decline of coal-fired power generation in power systems, voltage regulation and stability will become increasingly prominent issues. As renewable energy generation gradually becomes dominant, the voltage support role of thermal synchronous generators, the most important dynamic reactive power source in traditional power grids, needs to be replaced by other resources and methods, such as static var compensators (SVCs) or static var generators (SVGs); and by leveraging the inherent reactive power and voltage regulation capabilities of some wind and solar power generation equipment. Compared with synchronous generators, these new dynamic reactive power sources differ significantly in their distribution within the grid, dynamic reactive power capacity, operational control methods, and market player characteristics. Furthermore, the development of intermittent and distributed power sources has increased the variability and uncertainty of network flows. When power fluctuations occur in the power system, reactive power regulation is generated by voltage sources (dynamic reactive power sources) and transmitted via lines to the voltage supported points (load nodes receiving the reactive power regulation), thus forming a voltage support topology for power grids that are subject to power fluctuations. Compared with the traditional relatively fixed topology, due to the change in dynamic reactive source characteristics, the probabilistic and bidirectional characteristics of power grid flow have emerged. The new power grid voltage support topology will become complex and changeable. The power grid voltage support topology has a significant impact on the voltage distribution, static voltage stability and voltage regulation characteristics of the power grid. Therefore, with the current development of the power grid, real-time power grid voltage support topology information has become an important component of static voltage stability assessment.

[0004] The existing methods for evaluating the static voltage stability of power grids mainly include the continuous power flow method, the power flow Jacobian matrix analysis method, the sensitivity method, the direct method, the bifurcation theory analysis method, the Thevenin equivalent method, etc.

[0005] (1) The continuous power flow method solves the ill-conditioned power flow problem near the voltage collapse point by constructing parametric equations and extending the power flow Jacobian matrix. The method gradually increases the load power through prediction, correction, and step-size control, calculates the power flow state changes, and then solves the PV or QV curve. Due to its clear and well-defined concepts, it has been widely used in engineering practice. However, the determination of the load growth method and the large computational burden hinder its online application in complex power grids.

[0006] (2) The power flow Jacobian matrix analysis method is to perform eigenvalue analysis, singular value analysis or modal analysis on the power flow Jacobian matrix to reveal the characteristics of the power grid, analyze voltage stability, identify instability characteristics, etc. The eigenvalue method and the singular value method are both based on the characteristics that the power flow Jacobian matrix is singular at the power grid limit power point, and its minimum eigenvalue and minimum singular value are 0 to evaluate voltage stability. The biggest problem of the two methods is that the eigenvalues and singular values of the power flow Jacobian matrix have highly nonlinear characteristics, and the minimum eigenvalue and minimum singular value will suddenly change when the reactive power of the voltage source exceeds the limit, so their predictability of voltage instability is relatively poor. Based on the preset power growth direction, the modal law calculates the degree of participation of each node in the most dangerous mode based on the eigenvector corresponding to the minimum eigenvalue, thereby identifying key power sources, key branches, weak nodes, etc. that affect voltage stability.

[0007] (3) The sensitivity method is a method for evaluating voltage stability by constructing different sensitivity indicators based on the differential relationship between variables in the power grid. It has the advantages of clear physical concepts and small computational complexity. However, the sensitivity method based on power flow has problems such as difficulty in convergence at critical points, sensitivity indicators can only reflect the current power grid state, and node voltage sensitivity is highly nonlinear, making it difficult to accurately provide safety margins.

[0008] (4) The direct method is a method of obtaining the voltage instability operating point by constructing and solving a set of equations. It expresses the critical point characteristics, such as the Jacobian matrix determinant being 0, using a set of nonlinear equations. For actual complex systems, the dimension of the nonlinear equation set formed by its construction is often high, which is difficult to solve, and has disadvantages such as the inability to consider the reactive power output limit of the generator. On this basis, the nonlinear programming method defines the objective function as the maximum total load of the system, uses the power flow equation as a constraint condition, and solves the critical point through nonlinear programming. Although the nonlinear programming solution is more complicated than the nonlinear equation solution, the nonlinear programming method can easily add various operation and safety constraints, and any nonlinear programming solution method can be selected.

[0009] (5) Bifurcation theory studies the bifurcation phenomenon, which occurs when certain system parameters in a dynamic system undergo continuous changes, leading to sudden changes in certain essential characteristics or topological structures of the dynamic system. The bifurcation phenomenon is very consistent with the phenomenon of grid voltage instability, and it connects some of the results of static voltage stability analysis and dynamic voltage stability analysis.

[0010] (6) Thevenin's theorem states that a port containing an independent power supply, a linear resistor, and a controlled source can be replaced with a series combination of a voltage source and a resistor for external circuits. For AC power grids, a Thevenin equivalent circuit exists at any node at any operating moment. The Thevenin equivalent-based grid static voltage stability assessment method essentially analyzes the relationship between the equivalent load impedance in the current state and the critical equivalent load impedance as shown by the maximum power transmission principle.

[0011] Existing technologies fail to visualize the grid voltage support topology and instead assess voltage stability using only node or comprehensive stability indicators. Voltage support topology information is hidden within these indicators. When the grid voltage support topology changes, these indicators also undergo sudden changes, but there is a lack of methods to predict and analyze the causes and processes. If only the impact of topology changes on stability is observed, preventive control measures cannot be implemented, and the window for emergency control may be very short. Summary of the Invention

[0012] In order to address the deficiencies of the prior art, the present application provides a method, system, electronic device and computer-readable storage medium for evaluating the static voltage stability of a power grid, which utilizes real-time measurement data of the power grid to realize a static voltage stability evaluation of the power grid with visualization of the power grid voltage support topology.

[0013] In a first aspect, the present application provides a method for evaluating the static voltage stability of a power grid;

[0014] A method for evaluating static voltage stability of a power grid, comprising:

[0015] Obtain real-time grid measurement data and power flow data. Based on the real-time grid measurement data, obtain the line reactive power-voltage stiffness index and the reactive power regulation power transmission direction of each line;

[0016] Starting from each voltage source, the power transmission direction and the plane grid are adjusted according to reactive power, and the grid nodes are traversed through depth-first search to obtain the vertical network of the grid voltage support topology space;

[0017] Visualize the vertical network of the grid voltage support topology space to obtain a grid voltage support topology visualization module, and display corresponding line reactive power-voltage stiffness indicators on the lines of the grid voltage support topology visualization module;

[0018] According to the system static voltage stability safety margin requirements, the reactive power regulation power transmission capacity warning value and the voltage support island warning value of each line are set; according to the reactive power regulation power transmission capacity warning value and the voltage support island warning value of each line, a visual warning is issued in the vertical network of the visualized power grid voltage support topology space.

[0019] In a second aspect, the present application provides a system for evaluating the static voltage stability of a power grid;

[0020] A power grid static voltage stability assessment system, comprising:

[0021] The line parameter calculation module is configured to: obtain real-time grid measurement data and power flow data, and based on the real-time grid measurement data, obtain the line reactive power-voltage stiffness index and the reactive power regulation power transmission direction of each line;

[0022] The grid voltage support topology mapping module is configured to: start from each voltage source, adjust the power transmission direction and the plane grid according to reactive power, traverse the grid nodes through depth-first search, and obtain the vertical network of the grid voltage support topology space;

[0023] The grid voltage support topology visualization module is configured to: visualize the grid voltage support topology space longitudinal network, obtain the grid voltage support topology visualization module, and display the corresponding line reactive power-voltage stiffness index on the line of the grid voltage support topology visualization module;

[0024] The static voltage stability assessment and early warning module is configured to: set the reactive power regulation power transmission capacity warning value and voltage support island warning value of each line according to the system static voltage stability safety margin requirements; and issue a visual early warning in the vertical network of the visualized power grid voltage support topology space based on the reactive power regulation power transmission capacity warning value and voltage support island warning value of each line.

[0025] In a third aspect, the present application provides an electronic device;

[0026] An electronic device includes a memory and a processor, and computer instructions stored in the memory and running on the processor. When the computer instructions are run by the processor, the steps of the above-mentioned power grid static voltage stability assessment method are completed.

[0027] In a fourth aspect, the present application provides a computer-readable storage medium;

[0028] A computer-readable storage medium is used to store computer instructions, which, when executed by a processor, complete the steps of the above-mentioned power grid static voltage stability assessment method.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. This application first establishes the line reactive-voltage stiffness index according to the line power transmission characteristics, and then, on the basis of retaining the complete structural information of the power grid, maps the planar power grid distributed by geographical location into a spatial longitudinal network distributed according to the power grid voltage support topology based on the reactive power regulation transmission path of the power grid, and visualizes the power grid voltage support topology. On this basis, based on the line reactive-voltage stiffness index, the mechanism explanation and judgment of the static voltage instability of the power grid under the visualization analysis of the power grid voltage support topology are given. After the power disturbance, the reactive regulation power is generated from the voltage source, and the power grid voltage support topology transmitted to the load through the line is visualized, which helps the operation and dispatching personnel to form an intuitive understanding of the overall structure of the current power grid voltage support, and facilitates the dispatching personnel to intuitively judge the current power grid static voltage stability situation and key points.

[0031] 2. With the current development trend of power grids, small-capacity, distributed power electronic dynamic reactive power sources are becoming increasingly prevalent. Simultaneously, the proportion of distributed renewable energy generation on the load side is rapidly increasing. The transformation of load nodes into generation nodes, leading to power flow reversals, is becoming increasingly common, and the grid voltage support topology is becoming increasingly complex and variable. A static voltage stability assessment method based on the grid voltage support topology can clearly and visually demonstrate the impact of structural changes such as node nature transformation and grid power flow reversals on static voltage stability. It can also provide early warning and preventive control of voltage instability risks caused by changes in the grid voltage support topology. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings in the specification, which constitute a part of this application, are used to provide further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute improper limitations on this application.

[0033] Figure 1 A schematic diagram of a process flow provided for an embodiment of the present application;

[0034] Figure 2 Schematic diagram of the AC line Π circuit model provided in an embodiment of the present application;

[0035] Figure 3 Schematic diagram of a visualization module for the grid voltage support topology of a 7-node system provided in an embodiment of the present application;

[0036] Figure 4 A schematic diagram illustrating the voltage stability criteria provided in the embodiment of the present application, wherein: Figure 4 (a) is a schematic diagram of the voltage support topology of a 7-bus system when the reactive-voltage stiffness of line 1-3 is 0 (voltage stability). Figure 4 (b) Schematic diagram of the voltage support topology of the 7-bus system when the reactive-voltage stiffness of lines 1-3, 2-4, and 5-4 is 0 (voltage instability);

[0037] Figure 5 A schematic diagram of a visualization module for the voltage support topology of the power grid in the initial state of the IEEE-39 node system provided in an embodiment of the present application;

[0038] Figure 6 A schematic diagram of a visualization module for the grid voltage support topology when the IEEE-39 node system load increases by 160% provided in an embodiment of the present application;

[0039] Figure 7 Schematic diagram of the grid voltage support topology visualization module when the IEEE-39 node system load increases by 163% provided in an embodiment of the present application. DETAILED DESCRIPTION

[0040] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which this application belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0042] In the absence of conflict, the embodiments of the present invention and the features thereof may be combined with each other.

[0043] Explanation of terms:

[0044] SVC: Static VAR Compensation Equipment

[0045] SNB: Saddle Node Bifurcation

[0046] LIB: Limit Induced Bifurcation

[0047] Example 1

[0048] In the existing technology, only node or comprehensive stability indicators are used to evaluate voltage stability. The impact of voltage support topology information on stability is hidden in these indicators. Only the impact of topology changes on stability can be observed, and prediction, analysis and preventive control cannot be performed; therefore, the present application provides a method for evaluating the static voltage stability of a power grid.

[0049] A method for evaluating static voltage stability of a power grid, comprising:

[0050] Obtain real-time grid measurement data and power flow data, and based on the real-time grid measurement data, obtain the line reactive power-voltage stiffness index; obtain the reactive power regulation power transmission direction of each line based on the real-time grid measurement data or power flow data;

[0051] Starting from each voltage source, the power transmission direction and the plane grid are adjusted according to reactive power, and the grid nodes are traversed through depth-first search to obtain the vertical network of the grid voltage support topology space;

[0052] Visualize the vertical network of the grid voltage support topology space to obtain a grid voltage support topology visualization module, and display corresponding line reactive power-voltage stiffness indicators on the lines of the grid voltage support topology visualization module;

[0053] According to the system static voltage stability safety margin requirements, the reactive power regulation power transmission capacity warning value and the voltage support island warning value of each line are set; according to the reactive power regulation power transmission capacity warning value and the voltage support island warning value of each line, a visual warning is issued in the vertical network of the visualized power grid voltage support topology space.

[0054] Furthermore, based on the voltage amplitude and phase angle difference at both ends of the line, the line reactive-voltage stiffness index is calculated:

[0055] H jk =β jk,1 -(α jk,1 / α jk,3 )

[0056] α jk,1 =2V j (g jk +g j0 )-V k (g jk cosθ jk -b jk sinθ jk )

[0057] α jk,3 =V j V k (g jk sinθ jk +b jk cosθ jk )

[0058] β jk,1 =2V j (b jk -c j0 )-V k (g jk sinθjk +b jk cosθ jk )

[0059] Among them, H jk is the reactive-voltage stiffness of line jk, V j and V k are the voltage amplitudes at nodes j and k respectively; θ jk is the voltage phase angle difference between nodes j and k, g jk is the line conductance; b jk is the absolute value of line susceptance; c j0 、c k0 g is the earth susceptance at both ends of the line; j0 、g k0 The conductivity of the line from both ends to the ground.

[0060] Furthermore, the reactive regulation power transmission direction of each line is obtained based on the reactive transmission power of each line at the current moment and the previous moment.

[0061] Furthermore, based on the predicted data, the reactive transmission power of each line at the current moment and the next moment is compared to obtain the reactive regulation power transmission flow direction of each line.

[0062] Furthermore, based on the predicted data, the reactive transmission power of each line at the current moment and the next moment is compared to obtain the reactive regulation power transmission flow direction of each line.

[0063] Furthermore, the voltage source that generates reactive regulation power is mapped as a fixed point, the load is mapped as a load, and the line is mapped as a longitudinal spring, visually presenting the longitudinal network of the grid voltage support topology space.

[0064] Furthermore, when the reactive-voltage stiffness index of a line is less than the reactive regulation power transmission capacity warning value, the line is presented in a different color or brightness in the grid voltage support topology visualization module to remind the dispatcher that the reactive regulation power transmission capacity of the line is too low.

[0065] Furthermore, when the sum of the reactive-voltage stiffness of all directly connected lines of a certain load node or a certain set of load nodes is less than the voltage support island warning value, the corresponding load node will be presented in a different color or brightness in the grid voltage support topology visualization module to remind the dispatcher that the load node or the set of load nodes may become a voltage support island and the system faces the risk of static voltage instability.

[0066] Next, combine Figure 1-5 A method for evaluating the static voltage stability of a power grid disclosed in this embodiment is described in detail.

[0067] This embodiment provides a method for evaluating the static voltage stability of a power grid.

[0068] A method for evaluating static voltage stability of a power grid, comprising:

[0069] S01. Obtain real-time measurement data and power flow data of the power grid, and calculate the line reactive-voltage stiffness index based on the real-time measurement data of the power grid; compare the reactive transmission power of each line at the current moment and the previous moment based on the measurement data or power flow calculation data, and obtain the reactive regulation power transmission direction of each line; wherein the reactive transmission power is the reactive power transmitted by the line, and the reactive regulation power is the change value of the reactive power transmitted by the line.

[0070] This example aims to assess the static voltage stability of a power grid by analyzing its voltage support topology. Grid lines serve as the grid's voltage support channels, and the reactive power regulation provided by voltage sources must be transmitted to corresponding load nodes through these lines. The state of these lines affects their ability to transmit reactive power regulation, and thus, the grid's voltage stability. Therefore, a line reactive-voltage stiffness indicator is proposed to reflect the line's ability to transmit reactive power regulation to nodes.

[0071] For example, a schematic diagram of a general AC line π circuit model is shown as follows: Figure 2 As shown in Figure 2, assuming that the nodes at the beginning and end of the AC line L are j and k, and the reactive power regulation power transmission direction of the line is from j to k, the steps for obtaining the line reactive-voltage stiffness index are as follows:

[0072] The active and reactive power delivered to terminal k through line L is:

[0073] P jk =V j 2 (g jk +g j0 )-V j V k (g jk cosθ jk -b jk sinθ jk ) (1)

[0074] Among them, P jk is the active power transmitted from line jk to terminal k, V j is the voltage amplitude at node j, V k is the voltage amplitude of node k, g jk is the conductance of line jk, g j0 is the conductance of line end j to ground, θ jk is the voltage phase angle difference between nodes j and k, b jk is the absolute value of line jk susceptance.

[0075] Q jk=V j 2 (b jk -c j0 )-V j V k (g jk sinθ jk +b jk cosθ jk ) (2)

[0076] Among them, Q jk is the reactive power transmitted from line jk to terminal k, V j is the voltage amplitude at node j, V k is the voltage amplitude of node k, b jk is the absolute value of line jk susceptance, c j0 is the line j end to ground susceptance, g jk is the conductance of circuit jk, θ jk is the voltage phase angle difference between nodes j and k.

[0077] Through equations (1) and (2), we can get the first-order incremental value of active power and reactive power delivered to terminal k by line L:

[0078] ΔP jk =α jk,1 ΔV j +α jk,2 ΔV k +α jk,3 Δθ jk (3)

[0079] ΔQ jk =β jk,1 ΔV j +β jk,2 ΔV k +β jk,3 Δθ jk (4)

[0080] The coefficients in formula (3) and formula (4) are the corresponding partial derivatives, and their specific expressions are shown as follows:

[0081] α jk,1 =2V j (g jk +g j0 )-V k (g jk cosθ jk -b jk sinθ jk )

[0082] α jk,2 =-V j (g jk cosθjk -b jk sinθ jk )

[0083] α jk,3 =V j V k (g jk sinθ jk +b jk cosθ jk )

[0084] β jk,1 =2V j (b jk -c j0 )-V k (g jk sinθ jk +b jk cosθ jk )

[0085] β jk,2 =-V j (g jk sinθ jk +b jk cosθ jk )

[0086] β jk,3 =-V j V k (g jk cosθ jk -b jk sinθ jk ) (5)

[0087] The condition for system balance is that both active power and reactive power are in a balanced state. Here, we assume that the system active power is balanced and examine whether the system reactive power can be balanced. If it cannot be balanced, the assumption is not established, which means that the grid reactive power-voltage cannot support the assumed active power balance. According to the assumption, let the active power micro-increment in formula (3) be equal to 0, and combine it with formula (4), eliminating the phase angle difference micro-increment, and we can get

[0088] ΔQ jk =H jk ΔV j -K jk ΔV k (6)

[0089] In formula (6), H jk , K jk are the sensitivities of the reactive power transmitted by line L to node k to the voltage amplitudes at the sending end and the receiving end under the assumption of active power balance of the system, respectively. The expressions are:

[0090] H jk =β jk,1 -(α jk,1 / α jk,3 ) (7)

[0091] K jk =(α jk,2 / α jk,3 )-β jk,2 (8)

[0092] K jk It is the reactive-voltage stiffness index of the line, which represents the ability of line L to transmit reactive regulation power to node k under this state. The smaller the stiffness, the greater the change in node voltage amplitude when transmitting the same reactive regulation power.

[0093] According to formula (8) and grid measurement data or power flow data, the reactive power-voltage stiffness index of the relevant line can be calculated.

[0094] Furthermore, as an implementation method, the reactive transmission power of each line at the current moment and the next moment is compared according to the prediction data to obtain the reactive regulation power transmission direction of each line.

[0095] S02. Obtain a reactive power regulation transmission path based on the reactive power transmission direction of each line. Starting from each voltage source, traverse the grid nodes along the reactive power regulation transmission path using a depth-first search, and vertically arrange the subsequent lines and nodes in the search order. Map the planar grid distributed by geographical location into a spatial longitudinal network distributed according to the grid voltage support topology. The specific steps are as follows:

[0096] S021. Select an unvisited voltage source node as a starting point, and perform a depth-first search along the reactive power transmission path, starting from each unvisited adjacent node of the starting point that obtains reactive power from the starting point, to traverse the grid node graph.

[0097] S022. Repeat step S021 until all nodes in the power grid are searched;

[0098] S023. Distribute the nodes and lines in the power grid vertically in a search order.

[0099] S03. Map the voltage source that generates reactive regulation power as a fixed point (support point), map the load as a load, and map the line as a longitudinal spring, visualize the longitudinal network of the grid voltage support topology space, obtain the grid voltage support topology visualization module, and display the line reactive-voltage stiffness index obtained by real-time calculation on the corresponding line of the grid voltage support topology visualization module.

[0100] S04. According to the static voltage stability safety margin requirements of the system, set a warning value for the reactive power regulation transmission capacity of each line. When the reactive-voltage stiffness index of a line is less than the warning value, it will be presented in different colors or brightness in the grid voltage support topology visualization module, prompting the dispatcher that the reactive power regulation transmission capacity of the line is too low; set a voltage support island warning value. When the sum of the reactive-voltage stiffness of all directly connected lines of a certain load node or a certain set of load nodes is less than the set warning value, the corresponding load node will be presented in different colors or brightness in the grid voltage support topology visualization module, prompting the dispatcher that the load node (set) may become a voltage support island and the system faces the risk of static voltage instability.

[0101] For example, Figure 3 As shown, a seven-node grid is mapped into a vertical network with a voltage support topology. In this seven-node system, nodes 1 and 5 are generator nodes, and node 2 is connected to a wind farm and SVC. Assuming that all three nodes have voltage support capabilities, the load power at nodes 4 and 7 increases, and the direction of reactive power transmission is indicated on the line. The specific display may vary depending on the usage scenario and software design, but the basic structural features are similar.

[0102] Based on the intuitive display of the grid voltage support topology, this embodiment further provides a mechanism explanation and a determination method for grid static voltage instability.

[0103] When the reactive-voltage stiffness of the line grid is close to or equal to 0, it indicates that the line can no longer transmit reactive regulation power, and it is equivalent to being disconnected in the grid voltage support topology.

[0104] like Figure 4 As shown, if Figure 4 In the grid voltage support topology visualization module shown in (a), the reactive-voltage stiffness of line 1-3 is 0, so the reactive regulation power of the load node can only come from voltage source nodes 2 and 5. At this time, the grid can still maintain static voltage stability, that is, it can support changes in active power balance. If the load power of nodes 3 and 4 increases further, the reactive-voltage stiffness of lines 2-4 and 5-4 gradually decreases to 0, and the two lines are also in a disconnected state in the voltage support topology, then a load node area that cannot obtain reactive regulation power will appear in the voltage support topology, which is called a voltage support island. There is no voltage source in the voltage support island, such as Figure 4 (b) shown.

[0105] When the static voltage characteristics of the load are not considered, the load nodes in the voltage support island will experience static voltage instability due to the inability to obtain reactive power regulation. This situation is caused by the grid reaching its power transmission limit and is therefore classified as SNB voltage instability. In another case, if the voltage source output power reaches its capacity limit, resulting in the formation of a voltage support island and instability, it is classified as LIB voltage instability, such as Figure 4 In the grid voltage support topology shown in (a), if the voltage source nodes 2 and 5 lose their voltage support capabilities, LIB voltage instability will occur.

[0106] In summary, under the visualization analysis of the grid voltage support topology, the criterion for grid static voltage instability is:

[0107] 1) If a voltage support island appears in the grid voltage support topology, that is, the sum of the reactive power-voltage stiffness of all directly connected lines of a load node or a group of load nodes is zero, the load nodes in the voltage support island will experience static voltage instability;

[0108] 2) If the reactive-voltage stiffness drops to zero due to increased line power transmission, leading to the appearance of voltage support islands, this is considered SNB static voltage instability;

[0109] 3) If the voltage source loses its voltage support capability due to power exceeding the limit, resulting in the appearance of a voltage support island, it is considered LIB static voltage instability.

[0110] It is worth noting that in the actual operation of the power system, due to the influence of factors such as model error, measurement error and dynamic characteristics of the load, the static voltage stability boundary of the power grid is difficult to accurately determine and obtain. At the same time, voltage instability is something that needs to be avoided as much as possible during the operation of the power system. Therefore, it is necessary to set a certain warning value for the occurrence of voltage support islands in the power grid according to the different static voltage stability safety margin requirements of each system. When the sum of the reactive power-voltage stiffness of all directly connected lines of a load node (or a set of load nodes) is less than the set warning value, there is a risk of becoming a voltage support island, and the dispatcher needs to carry out corresponding preventive control.

[0111] The method of this embodiment is applied to the IEEE-39 node system, such as Figure 5-7 As shown, all loads in the IEEE-39 node system are gradually increased according to the constant power factor in equal proportion, and each generator node participates in the active power balance according to the initial output power ratio. Figure 5 、 Figure 6 、 Figure 7 Schematic diagrams of the IEEE-39 bus system voltage support topology visualization module for the initial state, when the load increases by 160%, and when the load increases by 163%. Line reactive power-voltage stiffness indicators that are less than the warning value are displayed in red. Figure 6 and Figure 7 The load area below the middle curve is at risk of becoming a voltage support island. The reactive power-voltage stiffness provided by only one line is greater than the warning value, which requires the dispatcher's attention.

[0112] Example 2

[0113] This embodiment discloses a system for evaluating the static voltage stability of a power grid, including:

[0114] The line parameter calculation module is configured to: obtain real-time grid measurement data and power flow data, obtain the line reactive power-voltage stiffness index based on the real-time grid measurement data; and obtain the reactive power regulation power transmission direction of each line based on the real-time grid measurement data or power flow data;

[0115] The grid voltage support topology mapping module is configured to: start from each voltage source, adjust the power transmission direction and the plane grid according to reactive power, traverse the grid nodes through depth-first search, and obtain the vertical network of the grid voltage support topology space;

[0116] The grid voltage support topology visualization module is configured to: visualize the grid voltage support topology space longitudinal network, and display corresponding line reactive power-voltage stiffness indicators on the lines of the grid voltage support topology space longitudinal network;

[0117] The static voltage stability assessment and early warning module is configured to: set the reactive power regulation power transmission capacity warning value and voltage support island warning value of each line according to the system static voltage stability safety margin requirements; and issue a visual early warning in the vertical network of the visualized power grid voltage support topology space based on the reactive power regulation power transmission capacity warning value and voltage support island warning value of each line.

[0118] It should be noted that the aforementioned line parameter calculation module, grid voltage support topology mapping module, grid voltage support topology visualization module, and static voltage stability assessment and early warning module correspond to the steps in Example 1. The examples and application scenarios implemented by these modules and the corresponding steps are the same, but are not limited to the contents disclosed in Example 1. It should be noted that the aforementioned modules, as part of the system, can be executed in a computer system, such as a set of computer-executable instructions.

[0119] Example 3

[0120] A third embodiment of the present invention provides an electronic device, including a memory and a processor, and computer instructions stored in the memory and executed on the processor. When the computer instructions are executed by the processor, the steps of the above-mentioned grid static voltage stability assessment method are completed.

[0121] Example 4

[0122] A fourth embodiment of the present invention provides a computer-readable storage medium for storing computer instructions. When the computer instructions are executed by a processor, the steps of the above-mentioned method for evaluating the static voltage stability of a power grid are completed.

[0123] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0124] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0125] These computer program instructions can also be loaded onto a computer or other programmable data processing device, and a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide the functions for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0126] The description of each embodiment in the above embodiments has different emphases. For parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0127] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for evaluating the static voltage stability of a power grid, characterized in that: include: Obtain real-time grid measurement data and power flow data. Based on the real-time grid measurement data, obtain the line reactive power-voltage stiffness index and the reactive power regulation power transmission direction of each line; Taking each voltage source as the starting point, the power transmission direction and the plane grid are adjusted according to the reactive power, and the grid nodes are traversed through the depth-first search to obtain the vertical network of the grid voltage support topology space; The voltage source that generates reactive power regulation is mapped as a fixed point, the load is mapped as a load, and the line is mapped as a longitudinal spring, visualizing the longitudinal network of the grid voltage support topology space; Visualize the vertical network of the grid voltage support topology space to obtain a grid voltage support topology visualization module, and display corresponding line reactive power-voltage stiffness indicators on the lines of the grid voltage support topology visualization module; Based on the voltage amplitude and phase angle difference at both ends of the line, the line reactive-voltage stiffness index is calculated: Among them, H jk is the reactive-voltage stiffness of line jk, V j and V k are the voltage amplitudes at nodes j and k respectively; θ jk is the voltage phase angle difference between nodes j and k, g jk is the line conductance; b jk is the absolute value of line susceptance; c j0 、c k0 g is the earth susceptance at both ends of the line; j0 、g k0 The conductivity of the two ends of the line to the ground; According to the system static voltage stability safety margin requirements, the reactive power regulation power transmission capacity warning value and the voltage support island warning value of each line are set; according to the reactive power regulation power transmission capacity warning value and the voltage support island warning value of each line, a visual warning is issued in the power grid voltage support topology visualization module.

2. The method for evaluating the static voltage stability of a power grid according to claim 1, wherein: According to the reactive transmission power of each line at the current moment and the previous moment, the reactive regulation power transmission flow direction of each line is obtained.

3. The method for evaluating the static voltage stability of a power grid according to claim 1, wherein: According to the predicted data, the reactive transmission power of each line at the current moment and the next moment is compared to obtain the reactive regulation power transmission direction of each line.

4. The method for evaluating the static voltage stability of a power grid according to claim 1, wherein: When the reactive-voltage stiffness index of a line is lower than the reactive regulation power transmission capacity warning value, the line will be displayed in a different color or brightness in the grid voltage support topology visualization module to remind the dispatcher that the reactive regulation power transmission capacity of the line is too low.

5. The method for evaluating the static voltage stability of a power grid according to claim 1, wherein: When the sum of the reactive power-voltage stiffness of all directly connected lines of a load node or a set of load nodes is less than the voltage support island warning value, the corresponding load node will be presented with different colors or brightness in the grid voltage support topology visualization module to remind the dispatcher that the load node or the set of load nodes may become a voltage support island and the system faces the risk of static voltage instability.

6. A grid static voltage stability assessment system, characterized in that: include: The line parameter calculation module is configured to: obtain real-time grid measurement data and power flow data, and based on the real-time grid measurement data, obtain the line reactive power-voltage stiffness index and the reactive power regulation power transmission direction of each line; The grid voltage support topology mapping module is configured to: take each voltage source as the starting point, adjust the power transmission flow direction and the plane grid according to the reactive power, traverse the grid nodes through depth-first search, and obtain the vertical network of the grid voltage support topology space; The voltage source that generates reactive power regulation is mapped as a fixed point, the load is mapped as a load, and the line is mapped as a longitudinal spring, visualizing the longitudinal network of the grid voltage support topology space; The grid voltage support topology visualization module is configured to: visualize the grid voltage support topology space longitudinal network, obtain the grid voltage support topology visualization module, and display the corresponding line reactive power-voltage stiffness index on the line of the grid voltage support topology visualization module; Based on the voltage amplitude and phase angle difference at both ends of the line, the line reactive-voltage stiffness index is calculated: Among them, H jk is the reactive-voltage stiffness of line jk, V j and V k are the voltage amplitudes at nodes j and k respectively; θ jk is the voltage phase angle difference between nodes j and k, g jk is the line conductance; b jk is the absolute value of line susceptance; c j0 、c k0 g is the earth susceptance at both ends of the line; j0 、g k0 The conductivity of the two ends of the line to the ground; The static voltage stability assessment and early warning module is configured to: set the reactive power regulation power transmission capacity warning value and voltage support island warning value of each line according to the system static voltage stability safety margin requirements; and issue a visual warning in the power grid voltage support topology visualization module based on the reactive power regulation power transmission capacity warning value and voltage support island warning value of each line.

7. An electronic device, characterized in that: The method comprises a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein the steps described in any one of claims 1 to 5 are completed when the computer instructions are executed by the processor.

8. A computer-readable storage medium, characterized in that Used to store computer instructions, which, when executed by a processor, complete the steps described in any one of claims 1 to 5.

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